Overview of Spintronic Sensors, Internet of Things, and Smart Living
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paper_title: Sensing as a Service Model for Smart Cities Supported by Internet of Things

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The world population is growing at a rapid pace. Towns and cities are accommodating half of the world's population thereby creating tremendous pressure on every aspect of urban living. Cities are known to have large concentration of resources and facilities. Such environments attract people from rural areas. However, unprecedented attraction has now become an overwhelming issue for city governance and politics. The enormous pressure towards efficient city management has triggered various Smart City initiatives by both government and private sector businesses to invest in ICT to find sustainable solutions to the growing issues. The Internet of Things (IoT) has also gained significant attention over the past decade. IoT envisions to connect billions of sensors to the Internet and expects to use them for efficient and effective resource management in Smart Cities. Today infrastructure, platforms, and software applications are offered as services using cloud technologies. In this paper, we explore the concept of sensing as a service and how it fits with the Internet of Things. Our objective is to investigate the concept of sensing as a service model in technological, economical, and social perspectives and identify the major open challenges and issues.
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paper_title: Towards the trillion sensors market

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Purpose ::: ::: ::: ::: – This article aims to provide an insight into recent deliberations on the possibility of a global sensor market reaching one trillion units per annum within the next decade. ::: ::: ::: ::: ::: Design/methodology/approach ::: ::: ::: ::: – Following an introduction, which includes details of the TSensors Summit, this article discusses existing high volume sensor applications with multi-billion unit growth prospects. It then considers certain new and emerging applications, including the Internet of Things. This is followed by technological considerations and a brief discussion. ::: ::: ::: ::: ::: Findings ::: ::: ::: ::: – The possibility of a global sensor market reaching one trillion units per annum within the next decade is the topic of serious debate. Several applications representing multi-billion levels have been identified and the ongoing TSensors Summit activities seek to identify further high volume, high growth uses and the factors that will stimulate them. While MEMS will play a central role, other, often new sensor technologies will be vital to achieving the trillion unit level. ::: ::: ::: ::: ::: Originality/value ::: ::: ::: ::: – This article provides a timely review of recent deliberations surrounding the feasibility of achieving a global, trillion sensor market.
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paper_title: Challenges in healthcare and welfare intercloud

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In this paper, we introduce healthcare and welfare provisioning intercloud on an example of Aging in Place platform. We relate it to earlier work both in healthcare and intercloud domain. We describe goals and architecture of the platform and demonstrate benefits of applying Cloud Computing solutions to previously identified challenges. Subsequently, we list and analyze challenges that seem to be unique to such setting and identify risk factors.
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paper_title: Wireless sensor networks in intelligent transportation systems

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Wireless sensor networks (WSNs) offer the potential to significantly improve the efficiency of existing transportation systems. Currently, collecting traffic data for traffic planning and management is achieved mostly through wired sensors. The equipment and maintenance cost and time-consuming installations of existing sensing systems prevent large-scale deployment of real-time traffic monitoring and control. Small wireless sensors with integrated sensing, computing, and wireless communication capabilities offer tremendous advantages in low cost and easy installation. In this paper, we first survey existing WSN technologies for intelligent transportation systems (ITSs), including sensor technologies, energy-efficient networking protocols, and applications of sensor networks for parking lot monitoring, traffic monitoring, and traffic control. Then, we present new methods on applying WSNs in traffic modeling and estimation and traffic control, and show their improved performance over existing solutions. Copyright © 2008 John Wiley & Sons, Ltd.
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paper_title: New challenges to power system planning and operation of smart grid development in China

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The future development trend of electric power grid is smart grid, which includes such features as secure and reliable, efficient and economical, clean and green, flexible and compatible, open and interactive, integrated and so on. The concept and characteristics of smart grid are introduced in this paper. On the basis of practical national situation, the development plans of smart grid in china with Chinese characteristics are proposed. Smart grid development in china is bases on information technology, communication technology, computer technology with the high integration with infrastructure of generating, transmission and distribution power system. Besides, smart grid development in china brings forward many new challenge and requirements for power system planning and operation in 9 key technologies as below: 1. Planning and construction of strong ultra high voltage (UHV) power grid 2. Large-scale thermal power, hydropower and nuclear power bases integration of power grid 3. Large-scale renewable energy sources integration of power grid 4. Distributed generation and coordinated development of the grids of various voltage ratings 5. Study on smart grid planning and developing strategy 6. Improve the controllability of the power grid based on power electronics technology. 7. Superconductivity, energy storage and other new technologies widely used in power system 8. Power system security monitoring, fast simulation, intelligent decision-making and comprehensive defense technology 9. The application of emergency and restoration control technology in power system In response to the challenge, this paper presents the main research contents, detailed implementation plan and anticipated goals of above 9 key technologies. Some measures and suggestions for power system planning and operation of smart grid development in China are given in this paper.
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paper_title: Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing

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The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications.
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paper_title: An Internet of Things Framework for Smart Energy in Buildings: Designs, Prototype, and Experiments

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Smart energy in buildings is an important research area of Internet of Things (IoT). As important parts of the smart grids, the energy efficiency of buildings is vital for the environment and global sustainability. Using a LEED-gold-certificated green office building, we built a unique IoT experimental testbed for our energy efficiency and building intelligence research. We first monitor and collect 1-year-long building energy usage data and then systematically evaluate and analyze them. The results show that due to the centralized and static building controls, the actual running of green buildings may not be energy efficient even though they may be “green” by design. Inspired by “energy proportional computing” in modern computers, we propose an IoT framework with smart location-based automated and networked energy control, which uses smartphone platform and cloud-computing technologies to enable multiscale energy proportionality including building-, user-, and organizational-level energy proportionality. We further build a proof-of-concept IoT network and control system prototype and carried out real-world experiments, which demonstrate the effectiveness of the proposed solution. We envision that the broad application of the proposed solution has not only led to significant economic benefits in term of energy saving, improving home/office network intelligence, but also bought in a huge social implication in terms of global sustainability.
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paper_title: Internet of Things for Smart Cities

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The Internet of Things (IoT) shall be able to incorporate transparently and seamlessly a large number of different and heterogeneous end systems, while providing open access to selected subsets of data for the development of a plethora of digital services. Building a general architecture for the IoT is hence a very complex task, mainly because of the extremely large variety of devices, link layer technologies, and services that may be involved in such a system. In this paper, we focus specifically to an urban IoT system that, while still being quite a broad category, are characterized by their specific application domain. Urban IoTs, in fact, are designed to support the Smart City vision, which aims at exploiting the most advanced communication technologies to support added-value services for the administration of the city and for the citizens. This paper hence provides a comprehensive survey of the enabling technologies, protocols, and architecture for an urban IoT. Furthermore, the paper will present and discuss the technical solutions and best-practice guidelines adopted in the Padova Smart City project, a proof-of-concept deployment of an IoT island in the city of Padova, Italy, performed in collaboration with the city municipality.
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paper_title: Internet of Things: A Survey on Enabling Technologies, Protocols, and Applications

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This paper provides an overview of the Internet of Things (IoT) with emphasis on enabling technologies, protocols, and application issues. The IoT is enabled by the latest developments in RFID, smart sensors, communication technologies, and Internet protocols. The basic premise is to have smart sensors collaborate directly without human involvement to deliver a new class of applications. The current revolution in Internet, mobile, and machine-to-machine (M2M) technologies can be seen as the first phase of the IoT. In the coming years, the IoT is expected to bridge diverse technologies to enable new applications by connecting physical objects together in support of intelligent decision making. This paper starts by providing a horizontal overview of the IoT. Then, we give an overview of some technical details that pertain to the IoT enabling technologies, protocols, and applications. Compared to other survey papers in the field, our objective is to provide a more thorough summary of the most relevant protocols and application issues to enable researchers and application developers to get up to speed quickly on how the different protocols fit together to deliver desired functionalities without having to go through RFCs and the standards specifications. We also provide an overview of some of the key IoT challenges presented in the recent literature and provide a summary of related research work. Moreover, we explore the relation between the IoT and other emerging technologies including big data analytics and cloud and fog computing. We also present the need for better horizontal integration among IoT services. Finally, we present detailed service use-cases to illustrate how the different protocols presented in the paper fit together to deliver desired IoT services.
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paper_title: A Study on the Sensitivity of a Spin Valve with Conetic-Based Free Layers

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An exchange-biased spin valve with Conetic-based free layers of Co90Fe10, Co90Fe10/Conetic and Conetic was investigated. The spin valve with the Co90Fe10 free layer showed the highest giant magnetoresistance (GMR) ratio of 4% but showed the lowest normalized sensitivity of 0.02 Oe-1. The GMR ratio of 3% and the normalized sensitivity of 0.07 Oe-1 were obtained for the spin valve with the Co90Fe10/Conetic free layer after annealing. The spin valve having the Conetic free layer showed softer magnetic properties and well-defined smaller anisotropy than the other spin valves. Though the spin valve showed the lowest GMR of 0.4% after annealing, it showed the highest normalized sensitivity of 0.14 Oe-1. Our study shows that further improvement in MR response of spin valves with Conetic-based free layers can make a spin valve sensor promising for detecting extremely low fields.
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paper_title: Nobel Lecture: Origin, development, and future of spintronics

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Electrons have a charge and a spin, but until recently, charges and spins have been considered separately. In conventional electronics, the charges are manipulated by electric fields but the spins are ignored. Other classical technologies, magnetic recording, for example, are using the spin but only through its macroscopic manifestation, the magnetization of a ferromagnet. This picture started to change in 1988 when the discovery Baibich et al., 1988; Binash et al., 1989 of the giant magnetoresistance GMR of the magnetic multilayers opened the way to an efficient control of the motion of the electrons by acting on their spin through the orientation of a magnetization. This rapidly triggered the development of a new field of research and technology, today called spintronics and, like the GMR, exploiting the influence of the spin on the mobility of the electrons in ferromagnetic materials. Actually, the influence of the spin on the mobility of the electrons in ferromagnetic metals, first suggested by Mott 1936 , had been experimentally demonstrated and theoretically described in my Ph.D. thesis almost 20 years before the discovery of 1988. The GMR was the first step on the road of the exploitation of this influence to control an electrical current. Its application to the read heads of hard disks greatly contributed to the fast rise in the density of stored information and led to the extension of the hard disk technology to consumer’s electronics. Then, the development of spintronics revealed many other phenomena related to the control and manipulation of spin currents. Today this field of research is expanding considerably, with very promising new axes like the phenomena of spin transfer, spintronics with semiconductors, molecular spintronics, or single-electron spintronics.
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paper_title: Magnetoresistance of FeCo Nanocontacts With Current-Perpendicular-to-Plane Spin-Valve Structure

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We have achieved a magnetoresistance (MR) ratio of 7%-10% at a resistance area product (RA) of 0.5-1.5 Omegamum2 by ferromagnetic FeCo nanocontacts in Al nano-oxide-layer (NOL) with current-perpendicular-to-plane spin-valve (CPP-SV) structure. Conductive atomic-force-microscopy shows clear current-path regions of a few nanometers in size surrounded by the Al-NOL. The MR dependence on resistance area product (RA) is well explained by the current-confined-path model assuming that the spin-dependent scattering has an FeCo nanocontact origin, different from tunnel magnetoresistance (TMR). Resistance increases with increasing bias voltage, indicating joule heating by high-current density in nanocontacts, in contrast to TMR. The MR origin is mainly interpreted as spin-dependent scattering due to domain wall formed at ferromagnetic nanocontact
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paper_title: MR ratio enhancement by NOL current-confined-path structures in CPP spin valves

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We have compared the magnetoresistance (MR) performance of current-confined-path (CCP) current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) spin valve films with a nano-oxide-layer (NOL), made between natural oxidation (NO) and ion-assisted oxidation (IAO). For the NO, an MR ratio was only 1.5% at an RA of 370 m/spl Omega//spl mu/m/sup 2/, whereas for the IAO, an MR ratio was greatly increased to 5.4% at an RA of 500 m/spl Omega//spl mu/m/sup 2/. Fitted data by the Valet-Fert model showing larger MR enhancement effect by the IAO is explained by the improvement of the metal-purity of the Cu inside the CCP structure. By further improvement of metal-purity of the Cu, a large MR ratio of more than 30% can be expected at a small RA of 300 m/spl Omega//spl mu/m/sup 2/. The CCP-CPP spin valve film is a promising candidate for realizing high-density recording heads for 200 to 400-Gbpsi recording.
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paper_title: Enhancement of giant magnetoresistance by L21 ordering in Co2Fe(Ge0.5Ga0.5) Heusler alloy current-perpendicular-to-plane pseudo spin valves

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We report large magnetoresistance (MR) output in fully epitaxial Co2Fe(Ge0.5Ga0.5)/Ag/Co2Fe(Ge0.5Ga0.5) current-perpendicular-to-plane pseudo spin valves. The resistance-area product change (ΔRA) of 12 mΩμm2 at room temperature (RT), equivalent to MR ratio of 57%, and ΔRA = 33 mΩμm2 at 10 K, equivalent to MR ratio of 183%, were obtained by using L21-ordered Co2Fe(Ge0.5Ga0.5) ferromagnetic electrodes. The bulk spin scattering asymmetry (β) were estimated to be ∼0.83 at RT and ∼0.93 at 10 K for the L21-ordered Co2Fe(Ge0.5Ga0.5) films by the Valet-Fert model, indicating that the L21-ordered Co2FeGe0.5Ga0.5 Heusler alloy is virtually half-metal at 10 K, but its half-metallicity is degraded at RT.
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paper_title: Nobel Lecture: From spin waves to giant magnetoresistance and beyond

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The “Institute for Magnetism” within the department for solid-state physics at the research center in Julich, Germany, which I joined in 1972, was founded in 1971 by Professor W. Zinn. The main research topic was the exploration of the model magnetic semiconductors EuO and EuS with Curie temperatures Tc=60 K and Tc =17 K, respectively. As I had been working with light scattering LS techniques before I came to Julich, I was very much interested in the observation of spin waves in magnetic materials by means of LS. LS can be performed with grating spectrometers, which is called Raman spectroscopy, and alternatively by Brillouin light scattering BLS spectroscopy. In the latter case, a Fabry-Perot FP interferometer is used for the frequency analysis of the scattered light see righthand side of Fig. 1 . The central part consists of two FP mirrors whose distance is scanned during operation. BLS spectroscopy is used when the frequency shift of the scattered light is small below 100 GHz , as expected for spin waves in ferromagnets. In the early 1970s, an interesting instrumental development took place in BLS, namely, the invention of the multipass operation, and later, the combination of two multipass interferometers in tandem. The inventor was Dr. J. A. Sandercock in Zurich. Since we had the opportunity to install a new laboratory, we decided in favor of BLS, initially using a single three-pass instrument as displayed on the righthand side of Fig. 1. With this, we started investigating spin waves in EuO. We indeed were able to find and identify the expected spin waves as shown by the peaks in Fig. 1 marked green . Different intensities on the Stokes S and antiStokes aS side were known from other work to be due to the magneto-optic interaction of light with the spin waves. The peaks marked red remained a puzzle for some time until good luck came to help us. Good luck in this case was a breakdown of the system, a repair and unintentional interchange of the leads when reconnecting the magnet to the power supply. To our surprise S and aS side were now reversed. To understand what this means, one has to know that classically S and aS scattering is related to the propagation direction of the observed mode, which is opposite for the two cases. This can be understood from the corresponding Doppler shift, which is to higher frequencies when the wave travels towards the observer and down when away from him. The position of the observer here would be the same as of the viewer in Fig. 1. The appearance of the red peak in the spectra on only either the S or the aS side can be explained by an unidirectional propagation of the corresponding spin wave along the surface of the sample. It can be reversed by reversing B0 and M. The unidirectional behavior of the wave can be understood on the basis of symmetry. For this, one has to know that axial vectors which appear in nature, such as B and M on the left-hand side of Fig. 1, reverse their sign under time inversion and so does the sense of the propagation of the surface wave as indicated. The upper and lower parts of Fig. 1, on the left-hand side therefore are linked by time inversion symmetry, which is valid without damping. Hence, the unidirectional behavior reflects the symmetry of the underlying system. Finally, the observed wave could be identified as the DamonEshbach DE surface mode known from theory and from microwave experiments. From the magnetic parameters of EuO, one predicts in the present case that the penetration depth of the DE mode will be a few 100 A. Sample thickness d is of the order of mm. Therefore, for the present purpose, EuO is opaque. In this case, the wave traveling on the backside of the sample in the opposite direction to the wave on the front side cannot be seen in this experiment. BLS is then either S or aS but not both at the same time. Due to all of these unique features, the results of Fig. 1 have also been chosen as examples for current research in magnetism in a textbook on “Solid State Physics” Ibach and Luth, 1995, p. 186 .
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paper_title: Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing

paper_content:

The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications.
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paper_title: Spin Valve Devices With Synthetic-Ferrimagnet Free-Layer Displaying Enhanced Sensitivity for Nanometric Sensors

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Spin valves (SVs) with synthetic-antiferromagnet (SAF) pinned layers and synthetic-ferrimagnet (SF) free-layers deposited by ion beam deposition are optimized for incorporation in nanometric sensors. The results on combined SAF-SF structures indicate a reduced saturation and offset fields when compared with the simple top-pinned or SAF structure. Therefore, SAF-SF SV display sensitivities of ~0.025%/Oe (200 nm sensor), ~0.1%/Oe (500 nm sensor), and ~0.2%/Oe (1 μm sensor), which correspond to an improvement of 2x, 4.5x, and 7x, respectively, when compared with all other SV stacks tested. The results are relevant for geometries where nanometric SVs are incorporated within very narrow gaps of magnetic flux concentrators leading to superior and competitive gains in sensitivity. These geometries have the unique feature of submicrometric spatial resolution, and have high impact on surface scanning applications.
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paper_title: Comparison of the soft magnetic properties of permalloy and conetic thin films

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Abstract The soft magnetic properties of the substrate/[non-buffer or buffer Ta]/[permalloy (Ni 80 Fe 20 ) or conetic (Ni 77 Fe 14 Cu 5 Mo 4 )]/Ta prepared by ion beam sputter deposition are investigated. The value of the surface resistance of the conetic film is twice as high as that of the permalloy film. The value of the coercivity and magnetic susceptibility of the conetic film decreased by 25% and doubled relative to that of the permalloy film. The coercivity, with a value of 0.12 Oe, and the magnetic susceptibility, with a value of 1.2×10 4 for the conetic film, are suitable for soft magnetic biosensor applications.
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paper_title: Fabrication of Fully-Epitaxial Co$_{{{2}}}$MnSi/Ag/Co$_{{{2}}}$MnSi Giant Magnetoresistive Devices by Elevated Temperature Deposition

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(001)-oriented epitaxial Co2MnSi (CMS) films were grown by elevating the substrate temperature during deposition instead of a conventional post-annealing process. The CMS film deposited at 250°C showed a very flat surface morphology, large saturation magnetization, and a highly L21-ordered crystal structure. A CMS/Ag/CMS giant-magnetoresistive device with CMS layers grown at 250°C showed the high magnetoresistance ratio (33%) at room temperature. This ratio was close to that realized in the case of samples fabricated using post-annealing at 500-550°C. The elevated temperature deposition for the Heusler electrodes is a promising method to fabricate a practical magnetic read sensor for next generation hard disc drives without high temperature annealing process over 300°C.
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paper_title: Giant tunneling magnetoresistance up to 330% at room temperature in sputter deposited Co2FeAl/MgO/CoFe magnetic tunnel junctions

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Magnetoresistance ratio up to 330% at room temperature (700% at 10 K) has been obtained in a spin-valve-type magnetic tunnel junction (MTJ) consisting of a full-Heusler alloy Co2FeAl electrode and a MgO tunnel barrier fabricated on a single crystal MgO (001) substrate by sputtering method. The output voltage of the MTJ at one-half of the zero-bias value was found to be as high as 425 mV, which is the largest reported to date in MTJs using Heusler alloy electrodes. The present finding suggests that Co2FeAl may be one of the most promising candidates for future spintronics devices applications.
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paper_title: Improvement of the low-frequency sensitivity of MgO-based magnetic tunnel junctions by annealing

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Magnetic tunnel junctions can serve as ultrasensitive low-frequency magnetic sensors, however, their low-frequency performance is limited by low-frequency noise, i.e., 1/f noise. In this paper, we investigate the 1/f noise in MgO magnetic tunnel junctions (MTJs) with a tunneling magnetoresistance (TMR) of 160%, and examine the influence of annealing and MTJ size. The results show that the annealing process can not only dramatically improve the TMR, but can also strongly decrease the MTJ noise. The effect is discussed in terms of the structure of MgO barriers and tunneling probabilities. Increasing the MTJ area to 6400 μm2 yields a voltage spectral density as low as 11 nV/Hz1/2 at 1000 Hz. The possible reasons for the area dependence are discussed.
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paper_title: Effect of electrode composition on the tunnel magnetoresistance of pseudo-spin-valve magnetic tunnel junction with a MgO tunnel barrier

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The authors investigate the effect of electrode composition on the tunnel magnetoresistance (TMR) ratio of (CoxFe100−x)80B20∕MgO∕(CoxFe100−x)80B20 pseudo-spin-valve magnetic tunnel junctions (MTJs). TMR ratio is found to strongly depend on the composition and thicknesses of CoFeB. High resolution transmission electron microscopy shows that the crystallization process of CoFeB during annealing depends on the composition and the thicknesses of the CoFeB film, resulting in different TMR ratios. A TMR ratio of 500% at room temperature and of 1010% at 5K are observed in a MTJ having 4.3nm and 4-nm-thick (Co25Fe75)80B20 electrodes with a 2.1-nm-thick MgO barrier annealed at 475°C.
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paper_title: Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers

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Magnetically engineered magnetic tunnel junctions (MTJs) show promise as non-volatile storage cells in high-performance solid-state magnetic random access memories (MRAM)1. The performance of these devices is currently limited by the modest (<∼70%) room-temperature tunnelling magnetoresistance (TMR) of technologically relevant MTJs. Much higher TMR values have been theoretically predicted for perfectly ordered (100) oriented single-crystalline Fe/MgO/Fe MTJs. Here we show that sputter-deposited polycrystalline MTJs grown on an amorphous underlayer, but with highly oriented (100) MgO tunnel barriers and CoFe electrodes, exhibit TMR values of up to ∼220% at room temperature and ∼300% at low temperatures. Consistent with these high TMR values, superconducting tunnelling spectroscopy experiments indicate that the tunnelling current has a very high spin polarization of ∼85%, which rivals that previously observed only using half-metallic ferromagnets2. Such high values of spin polarization and TMR in readily manufactureable and highly thermally stable devices (up to 400 °C) will accelerate the development of new families of spintronic devices.
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paper_title: Improved tunnel magnetoresistance of magnetic tunnel junctions with Heusler Co2FeAl0.5Si0.5 electrodes fabricated by molecular beam epitaxy

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The authors have developed a magnetic tunnel junction of Co2FeAl0.5Si0.5 electrodes and a MgO barrier fabricated by molecular beam epitaxy and observed that this device had a tunnel magnetoresistance ratio of 386% at approximately 300 K and 832% at 9 K. The lower Co2FeAl0.5Si0.5 electrode was annealed during and after deposition resulting in a highly ordered structure with small roughness. This highly ordered structure could be obtained by annealing treatment even at low temperatures. Furthermore, a weak temperature dependence of the tunnel magnetoresistance ratio was observed for the developed magnetic tunnel junction.
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paper_title: Influence of growth and annealing conditions on low-frequency magnetic 1/f noise in MgO magnetic tunnel junctions

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Magnetic 1/f noise is compared in magnetic tunnel junctions with electron-beam evaporated and sputtered MgO tunnel barriers in the annealing temperature range 350 - 425 °C. The variation of the magnetic noise parameter (αmag) of the reference layer with annealing temperature mainly reflects the variation of the pinning effect of the exchange-bias layer. A reduction in αmag with bias is associated with the bias dependence of the tunneling magnetoresistance. The related magnetic losses are parameterized by a phase lag e, which is nearly independent of bias especially below 100 mV. The similar changes in magnetic noise with annealing temperature and barrier thickness for two types of MgO magnetic tunnel junctions indicate that the barrier layer quality does not affect the magnetic losses in the reference layer.
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paper_title: Giant magnetic tunneling effect in Fe/Al2O3/Fe junction

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Abstract A giant magnetoresistance ratio of 30% at 4.2 K and 18% at 300 K was observed for the first time in an Fe/Al 2 O 3 /Fe junction. The conductance at room temperature was expressed well by G =96.2 (1 + 0.09 cos θ)(Ω -1 ), where θ is the angle between the magnetizations of two iron electrodes. The dependence of the magnetoresistance ratio, saturated resistance and also the tunneling current on temperature were measured in the range 4.2–300 K. The results support the claim that the giant magnetoresistance is due to the magnetic tunneling of electrons between the electrodes through the thin Al 2 O 3 insulator.
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paper_title: Shot Noise in Magnetic Tunnel Junctions: Evidence for Sequential Tunneling

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We report the experimental observation of sub-Poissonian shot noise in single magnetic tunnel junctions, indicating the importance of tunneling via impurity levels inside the tunnel barrier. For junctions with weak zero-bias anomaly in conductance, the Fano factor (normalized shot noise) depends on the magnetic configuration being enhanced for antiparallel alignment of the ferromagnetic electrodes. We propose a model of sequential tunneling through nonmagnetic and paramagnetic impurity levels inside the tunnel barrier to qualitatively explain the observations.
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paper_title: Breakdown mechanisms in MgO based magnetic tunnel junctions and correlation with low frequency noise

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Magnetic tunnel junctions (MTJs) are very attractive for magnetic random access memories (MRAMs), thanks to their combination of non-volatility, speed, low power and endurance. In particular spin transfer torque (STT) RAMs based on STT writing show a very good downsize scalability. However, an issue is that at each write event, the MTJ is submitted to an important electrical stress due to write voltage of the order of half of the electrical breakdown voltage. Here we present a study of breakdown mechanisms in MgO based MTJ performed under pulsed conditions. We developed a model of charge trapping/detrapping on barrier defects to explain and predict device endurance. We also show that endurance is correlated to low frequency 1/f noise and that such noise measurement could thus be used as a non destructive and predictive tool for the reliability of the devices.
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paper_title: Sub-Poissonian shot noise in CoFeB/MgO/CoFeB-based magnetic tunneling junctions

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We measured the shot noise in the CoFeB/MgO/CoFeB-based magnetic tunneling junctions with a high tunneling magnetoresistance ratio (over 200% at 3 K). Although the Fano factor in the anti-parallel configuration is close to unity, it is observed to be typically 0.91\pm0.01 in the parallel configuration. It indicates the sub-Poissonian process of the electron tunneling in the parallel configuration due to the relevance of the spin-dependent coherent transport in the low bias regime.
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paper_title: 60% magnetoresistance at room temperature in Co–Fe/Al–O/Co–Fe tunnel junctions oxidized with Kr–O2 plasma

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The influence of the mixed inert gas species for plasma oxidization process of a metallic Al layer on the tunnel magnetoresistance (TMR) was investigated for a magnetic tunnel junction (MTJ), Ta 50 A/Cu 200 A/Ta 200 A/Ni–Fe 50 A/Cu 50 A/Mn75Ir25 100 A/Co70Fe30 25 A/Al–O/Co70Fe30 25 A/Ni–Fe 100 A/Cu 200 A/Ta 50 A. Using Kr–O2 plasma, a 58.8% of TMR ratio was obtained at room temperature after annealing the junction at 300 °C, while the achieved TMR ratio of the MTJ fabricated with usual Ar–O2 plasma remained 48.6%. A faster oxidization rate of the Al layer by using Kr–O2 plasma is a possible cause to prevent the over oxidization of the Al layer, which depolarizes the surface of the underlaid ferromagnetic electrode, and to realize a large magnetoresistance.
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paper_title: Dilute ferromagnetic semiconductors: Physics and spintronic structures

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This review compiles results of experimental and theoretical studies on thin films and quantum structures of semiconductors with randomly distributed Mn ions, which exhibit spintronic functionalities associated with collective ferromagnetic spin ordering. Properties of p-type Mn-containing III-V as well as II-VI, V_2-VI_3, IV-VI, I-II-V, and elemental group IV semiconductors are described paying particular attention to the most thoroughly investigated system (Ga,Mn)As that supports the hole-mediated ferromagnetic order up to 190 K for the net concentration of Mn spins below 10%. Multilayer structures showing efficient spin injection and spin-related magnetotransport properties as well as enabling magnetization manipulation by strain, light, electric fields, and spin currents are presented together with their impact on metal spintronics. The challenging interplay between magnetic and electronic properties in topologically trivial and non-trivial systems is described, emphasizing the entangled roles of disorder and correlation at the carrier localization boundary. Finally, the case of dilute magnetic insulators is considered, such as (Ga,Mn)N, where low temperature spin ordering is driven by short-ranged superexchange that is ferromagnetic for certain charge states of magnetic impurities.
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paper_title: Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunnelling junctions

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Epitaxial thin films of the theoretically predicted half metal Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different substrates and buffer layers. The samples were characterized by x-ray and electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler compound with only a small fraction of disorder on the Co sites. Magnetic tunnelling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter electrode were prepared. From the Julliere model a spin polarization of Co2Cr0.6Fe0.4Al of 54% at T = 4 K was deduced. The relation between the annealing temperature of the Heusler electrodes and the magnitude of the tunnelling magnetoresistance effect was investigated and the results are discussed in the framework of morphology and surface order based on in situ scanning tunnelling microscopy (STM) and RHEED investigations.
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paper_title: Experimental investigations of SiO2 based ferrite magnetic tunnel junction

paper_content:

We report experimental results of ferrite based magnetic tunnel junction. Ferrite junction and spin transport through SiO2 were interesting since they can readily replace the conventional electronics. We fabricated a cobalt ferrite/SiO2/cobalt nickel ferrite based magnetic tunnel junction over a copper coated n-silicon substrate using a RF/DC magnetron sputtering. The tunneling magnetoresistance shows a very good response to applied field and we achieved a TMR of about 16%. Although theoretically it was predicted infinite TMR for half metallic ferromagnetic junction, the deviation was explained on the basis of incoherent scattering along the interfaces.
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paper_title: Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature

paper_content:

The authors observed tunnel magnetoresistance (TMR) ratio of 604% at 300K in Ta∕Co20Fe60B20∕MgO∕Co20Fe60B20∕Ta pseudo-spin-valve magnetic tunnel junction annealed at 525°C. To obtain high TMR ratio, it was found critical to anneal the structure at high temperature above 500°C, while suppressing the Ta diffusion into CoFeB electrodes and in particular to the CoFeB∕MgO interface. X-ray diffraction measurement of MgO on SiO2 or Co20Fe60B20 shows that an improvement of MgO barrier quality, in terms of the degree of the (001) orientation and stress relaxation, takes place at annealing temperatures above 450°C. The highest TMR ratio observed at 5K was 1144%.
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paper_title: 230% room temperature magnetoresistance in CoFeB/MgO/CoFeB magnetic tunnel junctions

paper_content:

The magnetoresistance ratio of 230% at room temperature is reported. This was achieved in spin-valve type magnetic tunnel junctions using MgO barrier layer and amorphous CoFeB ferromagnetic electrodes fabricated on thermally oxidized Si substrates. The amorphous CoFeB electrodes are of great advantage to the polycrystalline FeCo electrodes in achieving a high homogeneity in small 100 nm-sized MTJs.
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paper_title: Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions

paper_content:

The tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs)1,2 is the key to developing magnetoresistive random-access-memory (MRAM), magnetic sensors and novel programmable logic devices3,4,5. Conventional MTJs with an amorphous aluminium oxide tunnel barrier, which have been extensively studied for device applications, exhibit a magnetoresistance ratio up to 70% at room temperature6. This low magnetoresistance seriously limits the feasibility of spintronics devices. Here, we report a giant MR ratio up to 180% at room temperature in single-crystal Fe/MgO/Fe MTJs. The origin of this enormous TMR effect is coherent spin-polarized tunnelling, where the symmetry of electron wave functions plays an important role. Moreover, we observed that their tunnel magnetoresistance oscillates as a function of tunnel barrier thickness, indicating that coherency of wave functions is conserved across the tunnel barrier. The coherent TMR effect is a key to making spintronic devices with novel quantum-mechanical functions, and to developing gigabit-scale MRAM.
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paper_title: Band overlap via chemical pressure control in double perovskite (Sr2−xCax)FeMoO6 (0 ⩽ x ⩽ 2.0) with TMR effect

paper_content:

Abstract The chemical pressure control in (Sr 2− x Ca x )FeMoO 6 (0 ⩽ x ⩽ 2.0) with double perovskite structure has been investigated systematically. We have performed first-principles total energy and electronic structure calculations for x = 0 and x = 2.0. The increasing Ca content in (Sr 2− x Ca x )FeMoO 6 samples increases the magnetic moment close to the theoretical value due to reduction of Fe/Mo anti-site disorder. An increasing Ca content results in increasing (Fe 2+ + Mo 6+ )/(Fe 3+ + Mo 5+ ) band overlap rather than bandwidth changes. This is explained from simple ionic size arguments and is supported by X-ray absorption near edge structure (XANES) spectra and band structure calculations.
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paper_title: Dependence of magnetoresistance on temperature and applied voltage in a 82Ni-Fe/Al-Al2O3/Co tunneling junction

paper_content:

Abstract The dependence of magnetoresistance on temperature T and on the applied voltage V in a 82Ni-Fe/Al-Al 2 O 3 /Co tunneling junction has been studied. The magnetoresistance Δ R / R increased rapidly at T ⩽ 30 K and V ⩽2.5 mV. The result is discussed by taking into account the tunneling conductance due to ferromagnetic tunneling and nonferromagnetic tunneling causing the zero-bias anomaly.
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paper_title: 70% TMR at room temperature for SDT sandwich junctions with CoFeB as free and reference Layers

paper_content:

Spin dependent tunneling (SDT) wafers were deposited using dc magnetron sputtering. SDT junctions were patterned and connected with one layer of metal lines using photolithography techniques. These junctions have a typical stack structure of Si(100)-Si/sub 3/N/sub 4/-Ru-CoFeB-Al/sub 2/O/sub 3/-CoFeB-Ru-FeCo-CrMnPt with the antiferromagnet CrMnPt layers for pinning at the top. High-resolution transmission electron microscopy (HRTEM) reveals that the CoFeB has an amorphous structure and a smooth interface with the Al/sub 2/O/sub 3/ tunnel barrier. Although it is difficult to pin the amorphous CoFeB directly from the top, the use of a synthetic antiferromagnet (SAF) pinned layer structure allows sufficient rigidity of the reference CoFeB layer. The tunnel junctions were annealed at 250/spl deg/C for 1 h and tested for magneto-transport properties with tunnel magnetoresistive (TMR) values as high as 70.4% at room temperature, which is the highest value ever reported for such a sandwich structure. This TMR value translates to a spin polarization of 51% for CoFeB, which is likely to be higher at lower temperatures. These junctions also have a low coercivity (Hc) and a low parallel coupling field (Hcoupl). The combination of a high TMR, a low Hc, and a low Hcoupl is ideal for magnetic field sensor applications.
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paper_title: Spin-tunnel-junction thermal stability and interface interdiffusion above 300 °C

paper_content:

Spin tunnel junctions (CoFe/Al2O3/CoFe/MnIr) were fabricated with tunneling magnetoresistance (TMR) of 39%–41% after anneal at 300 °C, decreasing to 4%–6% after anneal at 410 °C. Junction resistance decreases from (0.8–1.6) to (0.5–0.8) M Ω μm2 during anneal. The pinned-layer moment decreases by 44% after anneal at 435 °C, but the free-layer moment does not change. The current–voltage characteristics change significantly and become asymmetric above 300 °C. Rutherford backscattering analysis (RBS) shows that above 300 °C, strong interdiffusion starts at the CoFe/MnIr interface with Mn moving into CoFe, causing the electrode moment to decrease. Mn eventually reaches the Al2O3/CoFe interface contributing to the TMR decrease. RBS analysis of a separate CoFe/Al2O3/CoFe structure shows only minor structural changes at the CoFe/Al2O3 interfaces after anneal at 435 °C, possibly leading to a second mechanism for the loss of interface polarization and TMR.
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paper_title: Spin dependent electron tunneling between ferromagnetic films

paper_content:

Abstract The hysteresis of tunneling resistance in Gd/GdO x / Fe and Fe / GdO x / Fe junctions in the external magnetic field has been observed. The relative changes of tunneling resistance were of order 2.5–7.7%. The domain structures and magnetization reversal processes in the area of tunneling junctions were investigated by defocused electron microscopy. We found that the ferromagnetic coupling between electrodes of the junction strongly modified the domain structures and magnetization reversal processes in the area of tunnel junction. The hysteresis of tunneling resistance was closely connected with magnetization processes in the junction area. We estimated the polarization of tunneling densities of states for Fe electrodes to be not lower than 17% and the change of barrier height corresponding to the barrier spin filtering effect to be of order 1 meV.
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paper_title: Giant tunneling magnetoresistance up to 410% at room temperature in fully epitaxial Co∕MgO∕Co magnetic tunnel junctions with bcc Co(001) electrodes

paper_content:

Fully epitaxial Co(001)∕MgO(001)∕Co(001) magnetic tunnel junctions (MTJs) with metastable bcc Co(001) electrodes were fabricated with molecular beam epitaxy. The MTJs exhibited giant magnetoresistance (MR) ratios up to 410% at room temperature, the highest value reported to date. Temperature dependence of the MR ratio was observed to be very small compared with fully epitaxial Fe∕MgO∕Fe and textured CoFeB∕MgO∕CoFeB MTJs. The MR ratio of the Co∕MgO∕Co MTJ showed larger bias voltage dependence than that of the epitaxial Fe∕MgO∕Fe MTJs, which probably reflects the band structures of bcc Co and Fe for the k‖=0 direction.
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paper_title: Fabrication of fully epitaxial Co2MnSi∕MgO∕Co2MnSi magnetic tunnel junctions

paper_content:

Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with full-Heusler alloy Co2MnSi thin films as both lower and upper electrodes and with a MgO tunnel barrier. The fabricated MTJs showed clear exchange-biased tunnel magnetoresistance (TMR) characteristics with high TMR ratios of 179% at room temperature (RT) and 683% at 4.2K. In addition, the TMR ratio exhibited oscillations as a function of the MgO tunnel barrier thickness (tMgO) at RT, having a period of 0.28nm, for tMgO ranging from 1.8to3.0nm.
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paper_title: Low frequency noise peak near magnon emission energy in magnetic tunnel junctions

paper_content:

We report on the low frequency (LF) noise measurements in magnetic tunnel junctions (MTJs) below 4 K and at low bias, where the transport is strongly affected by scattering with magnons emitted by hot tunnelling electrons, as thermal activation of magnons from the environment is suppressed. For both CoFeB/MgO/CoFeB and CoFeB/AlOx/CoFeB MTJs, enhanced LF noise is observed at bias voltage around magnon emission energy, forming a peak in the bias dependence of noise power spectra density, independent of magnetic configurations. The noise peak is much higher and broader for unannealed AlOx-based MTJ, and besides Lorentzian shape noise spectra in the frequency domain, random telegraph noise (RTN) is visible in the time traces. During repeated measurements the noise peak reduces and the RTN becomes difficult to resolve, suggesting defects being annealed. The Lorentzian shape noise spectra can be fitted with bias-dependent activation of RTN, with the attempt frequency in the MHz range, consistent with magnon dyn...
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paper_title: Co2FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

paper_content:

We succeed to integrate BaO as a tunneling barrier into Co2FeAl based magnetic tunnel junctions (MTJs). By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR) ratio of -10% is found for Co2FeAl (24 nm) / BaO (5 nm) / Fe (7 nm) MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM), it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double lay...
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paper_title: Very low 1/f barrier noise in sputtered MgO magnetic tunnel junctions with high tunneling magnetoresistance

paper_content:

Low frequency 1/f barrier noise has been investigated in sputtered MgO magnetic tunnel junctions (MTJs) with a tunneling magnetoresistance ratio of up to 330% at room temperature. The lowest normalized noise parameter α of the tunnel barrier reaches 2.5 × 10−12–2.1 × 10−11 μm2, which is comparable to that found in MTJs with the MgO barrier grown by MBE or electron–beam evaporation. This normalized barrier noise is almost bias independent in the voltage range of up to ±1.2 V. The low noise level and high voltage stability may reflect the high quality of the sputtered MgO with a uniform distribution of defects in the MgO layer.
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paper_title: 1/f noise in MgO double-barrier magnetic tunnel junctions

paper_content:

Low frequency noise has been investigated in MgO double-barrier magnetic tunnel junctions (DMTJs) with tunneling magnetoresistance (TMR) ratios up to 250% at room temperature. The noise shows a 1/f frequency spectrum and the minimum of the noise magnitude parameter is 1.2×10−10 μm2 in the parallel state for DMTJs annealed at 375 °C. The bias dependence of noise and TMR suggests that DMTJs with MgO barriers can be useful for magnetic field sensor applications.
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paper_title: Optimized thickness of superconducting aluminum electrodes for measurement of spin polarization with MgO tunnel barriers

paper_content:

Superconducting tunneling spectroscopy (STS) is one of the most useful techniques for measuring the tunneling spin polarization of magnetic materials, typically carried out using aluminum electrodes. Recent studies using MgO barriers have shown the extreme sensitivity of the spin polarization to annealing at temperatures up to ∼400°C. Here the authors show that by optimizing the thickness of aluminum superconducting electrodes, STS measurements can be carried out even for such high annealing temperatures.
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paper_title: Linearization and Field Detectivity in Magnetic Tunnel Junction Sensors Connected in Series Incorporating 16 nm-Thick NiFe Free Layers

paper_content:

In this work, arrays of MgO-based magnetic tunnel junction elements (5×20 μm2) connected in series are studied for sensor applications. Linearization is obtained by combining shape anisotropy with a longitudinal hard bias field set by CoCrPt permanent magnets integrated on the sides of the array. We show that this architecture has the drawback of a large footprint in the chip, but is largely compensated by the weak bias voltage dependence and huge electric robustness, when comparing with individual magnetic tunnel junctions.
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paper_title: MEMS approach for making a low cost, high sensitivity magnetic sensor

paper_content:

An approach based on electromechanical systems (MEMS) technology will be presented that essentially eliminates the problem of 1/f noise in small magnetic sensors. The sensor based on this approach, the MEMS flux concentrator sensor, should outperform all other high sensitivity vector magnetometers in terms of cost, power consumption, and sensitivity. The method for achieving this improvement is to employ flux concentrators on MEMS structures that are near the magnetic sense element. The motion of the flux concentrators modulates the magnetic field and shifts the operating frequency of the sensor to higher frequencies where 1/f noise is unimportant. The data presented here provides our first evidence that the MEMS flux concentrator improves the signal to noise ratio at low frequencies.
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paper_title: MgO based picotesla field sensors

paper_content:

MgO magnetic tunnel junctions with RA=150Ωμm2 and tunnel magnetic resistance=100% were patterned into pillars with different geometries with areas up to 2000μm2. Sensors were incorporated in 500nm thick Co94Zr3Nb4 flux guides with different shapes and free layer stabilization was achieved through internal (Co66Cr16Pt18 pads) and external longitudinal bias fields (3.5mT). Sensitivities of 870%∕mT were obtained in the center of the transfer curve. Noise levels of 97pT∕Hz0.5 at 10Hz, 51pT∕Hz0.5 at 30Hz, and 2pT∕Hz0.5 at 500kHz were measured in the linear region of the transfer curve.
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paper_title: Low frequency picotesla field detection using hybrid MgO based tunnel sensors

paper_content:

Low frequency ultrasensitive magnetic sensors are required for magnetocardiography (1pT at 10Hz) applications. MgO based magnetic tunnel junctions with RA=100–150Ωμm2 and tunnel magnetic resistance=100% were patterned into rectangular pillars with side up to 50μm. Sensors were incorporated in 500nm thick Co94Zr3Nb4 flux guides. Sensor linearization was achieved through internal (Co66Cr16Pt18 pads) and external (3.5mT) longitudinal bias fields resulting in sensitivities of 720%∕mT. Noise levels of 97pT∕Hz0.5 at 10Hz, 51pT∕Hz0.5 at 30Hz, and 2pT∕Hz0.5 at 500kHz were measured in the linear region of the transfer curve.
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paper_title: Magnetic tunnel junction sensors with pTesla sensitivity for biomedical imaging

paper_content:

Ultrasensitive magnetic field sensors at low frequencies are necessary for several biomedical applications. Suitable devices can be achieved by using large area magnetic tunnel junction sensors combined with permanent magnets to stabilize the magnetic configuration of the free layer and improve linearity. However, further increase in sensitivity and consequently detectivity are achieved by incorporating also soft ferromagnetic flux guides. A detailed study of tunnel junction sensors with variable areas and aspect ratios is presented in this work. In addition, the effect in the sensors transfer curve, namely in their coercivity and sensitivity, as a consequence of the incorporation of permanent magnets and flux guides is also thoroughly discussed. Using sensors with a tunnel magnetoresistance of ~200 %, incorporating both permanent magnets and flux guides sensitivities of 220-260 %/mT were obtained for high aspect ratio sensors, increasing to values larger than ~2000%/mT for large areas and low aspect ratio sensors. Measured noise levels of the final device at 10 Hz yield 3.9×10 -17 V 2 /Hz, leading to an improved lowest detectable field of ~ 94 pT/ Hz 0.5 .
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paper_title: Linearization strategies for high sensitivity magnetoresistive sensors

paper_content:

Ultrasensitive magnetic field sensors envisaged for applications on biomedical imaging require the detection of low-intensity and low-frequency signals. Therefore linear magnetic sensors with enhanced sensitivity low noise levels and improved field detection at low operating frequencies are necessary. Suitable devices can be designed using magnetoresistive sensors, with room temperature operation, adjustable detected field range, CMOS compatibility and cost-effective production. The advent of spintronics set the path to the technological revolution boosted by the storage industry, in particular by the development of read heads using magnetoresistive devices. New multilayered structures were engineered to yield devices with linear output. We present a detailed study of the key factors influencing MR sensor performance (materials, geometries and layout strategies) with focus on different linearization strategies available. Furthermore strategies to improve sensor detection levels are also addressed with best reported values of ∼40 pT/√Hz at 30 Hz, representing a step forward the low field detection at room temperature.
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paper_title: Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing

paper_content:

The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications.
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paper_title: Iddq testing for CMOS VLSI

paper_content:

It is little more than 15-years since the idea of Iddq testing was first proposed. Many semiconductor companies now consider Iddq testing as an integral part of the overall testing for all IC's. This paper describes the present status of Iddq testing along with the essential items and necessary data related to Iddq testing. As part of the introduction, a historical background and discussion is given on why this test method has drawn attention. A section on physical defects with in-depth discussion and examples is used to illustrate why a test method outside the voltage environment is required. Data with additional information from case studies is used to explain the effectiveness of Iddq testing. In Section IV, design issues, design styles, Iddq test vector generation and simulation methods are discussed. The concern of whether Iddq testing will remain useful in deep submicron technologies is addressed (Section V). The use of Iddq testing for reliability screening is described (Section VI). The current measurement methods for Iddq testing are given (Section VII) followed by comments on the economics of Iddq testing (Section VIII). In Section IX pointers to some recent research are given and finally, concluding remarks are given in Section X.
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paper_title: Power pin testing: making the test coverage complete

paper_content:

Most modern ICs have multiple power and ground pins. It becomes necessary that all these pins are indeed connected to the board. In this paper a structural test method is presented for testing the connections of power and ground pins to the board. This on-chip test method is based on supply current detection between a bonding pad and its connection to the IC power distribution network. The method has been implemented and evaluated on a CMOS IC, using IEEE Std. 1149.1 to control and observe the embedded current sensors.
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paper_title: Non-contact electric-coupling-based and magnetic-field-sensing-assisted technique for monitoring voltage of overhead power transmission lines

paper_content:

Adopting non-contact electric coupling for voltage monitoring avoids electrical connection to high-voltage transmission lines, making installation of the sensing platforms easier and enabling wide-area deployment. However, coupled transformation matrix is difficult to determine in practice as the exact spatial positions of the transmission lines are typically unknown and dynamic. This problem can be overcome by integrating magnetic field sensing with stochastic optimization algorithm. In this technique, magnetic signals emanated from the overhead transmission lines are measured by magnetic sensor arrays to determine the coupling coefficients so that the high voltage of the transmission lines can be deduced from the induced voltage in the copper bars on the ground. This proposed technique can be potentially implemented with low-cost copper induction bars and magnetoresistive (MR) sensors. Thus sectional and wide-area deployment may become possible and Ferranti effect and travelling lightning waves can then be monitored. Its enhanced sensing ability over potential transformers (PTs) can largely improve transient-fault identification and save cost for transmission-network inspection.
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paper_title: Nonintrusive Current Sensor for the Two-Wire Power Cords

paper_content:

This paper presents a nonintrusive current sensor for the two-wire power cords connected to household and commercial appliances. The sensor uses a gapped magnetic core surrounding the power cord to constrain the distribution of the magnetic field induced by the current. The magnetic fields in four air gaps of the magnetic core are respectively measured by four magnetoresistive (MR) sensors. The current in the power cord and the rotation angle of the power cord around its central axis are calculated together by the output voltages of the four MR sensors. The current sensor encircles the power cord without any alignment process and can detect the current nonintrusively in the two-wire power cords of any type, such as zip-cord or nonmetallic sheathed cable. The experimental results show that the nonlinearity of the sensor is ±1.5% for the current range from 0 to 20 A with the maximum error limited to ±1.8%, this sensor is ideally suited for measuring the end use of electric power in residential and commercial areas.
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paper_title: Design, installation, and field experience with an overhead transmission dynamic line rating system

paper_content:

Dynamic line rating (DLR) systems for high voltage overhead transmission lines have been installed by three utilities over the past five years. These DLR systems utilize the Power Donut/sup TM/ to measure load and conductor temperature at several locations over the length of the circuit. The effective wind acting on the conductor at each site is determined in real-time by a dynamic heat balance and used to compute the normal, LTE and STE ratings each minute. The lowest ratings of all locations define the circuit's ratings and are sent to SCADA as analog signals. This method is known as the conductor temperature model (CTM) as opposed to the weather model (WM) which calculates ratings using weather data only. These first DLR installations have also measured weather parameters at each ground station location to allow a comparison of the two methods. Data from the latest of these systems is presented and the behavior of the real time ratings are discussed.
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paper_title: A vehicle detection algorithm based on wireless magnetic sensor networks

paper_content:

At present, the research of parking management system based on Wireless Sensor Networks (WSN) and Anisotropic Magneto Resistive (AMR) sensors have made great progress. However, due to the diversity of the vehicle magnetic signal and the interference caused by the adjacent parking spaces, vehicle detection technique using wireless magnetic sensor networks is still immature. For accurately detecting a parking vehicle in a parking lot, we propose a detection algorithm named Relative Extremum Algorithm (REA). On the parking lot at Shenzhen Institutes of Advanced Technology (SIAT), 82 sensor devices are deployed to evaluate the performance of REA. By running the system for more than half a year, we observe that the vehicle detection accuracy of the REA is above 98.8%.
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paper_title: A Parking Occupancy Detection Algorithm Based on AMR Sensor

paper_content:

Recently, with the explosive increase of automobiles in cities, parking problems are serious and even worsen in many cities. This paper proposes a new algorithm for parking occupancy detection based on the use of anisotropic magnetoresistive sensors. Parking occupancy detection is abstracted as binary pattern recognition problem. According to the status of the parking space, the recognition result contains two categories: vacant and occupied. The feature extraction method of the parking magnetic signal is proposed. In addition, the classification criteria are derived based on the distance discriminate analysis method. Eighty-two sensor nodes are deployed on the roadside parking spaces. By running the system for six months, we observed that the accuracy rate of the proposed parking occupancy detection algorithm is better than 98%.
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paper_title: Traffic measurement and vehicle classification with a single magnetic sensor

paper_content:

Wireless magnetic sensor networks offer a very attractive, low-cost alternative to inductive loops for traffic measurement in freeways and at intersections. In addition to vehicle count, occupancy and speed, the sensors yield traffic information (such as vehicle classification) that cannot be obtained from loop data. Because such networks can be deployed in a very short time, they can also be used (and reused) for temporary traffic measurement. This paper reports the detection capabilities of magnetic sensors, based on two field experiments. The first experiment collected a two-hour trace of measurements on Hearst Avenue in Berkeley. The vehicle detection rate is better than 99 percent (100 percent for vehicles other than motorcycles); and estimates of vehicle length and speed appear to be better than 90 percent. Moreover, the measurements also give inter-vehicle spacing or headways, which reveal such interesting phenomena as platoon formation downstream of a traffic signal. Results of the second experiment are preliminary. Sensor data from 37 passing vehicles at the same site are processed and classified into 6 types. Sixty percent of the vehicles are classified correctly, when length is not used as a feature. The classification algorithm can be implemented in real time by the sensor node itself, in contrast to other methods based on high scan-rate inductive loop signals, which require extensive offline computation. We believe that when length is used as a feature, 80-90 percent of vehicles will be correctly classified.
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paper_title: A Cross-Correlation Technique for Vehicle Detections in Wireless Magnetic Sensor Network

paper_content:

Vehicle detections are an important research field and attract many researchers. Most research efforts have been focused on vehicle parking detection (VPD) in indoor parking lot. For on-street parking, strong noise disturbances affect detection accuracy. To deal with vehicle detections in on-street environment, we propose two vehicle detection algorithms based on a cross-correlation technique in wireless magnetic sensor networks. One is for VPD, and the other one is for vehicle speed estimation (VSE). The proposed VPD algorithm combines the state-machine detection and the cross-correlation detection. In the VSE, speed estimation is based on the calculation of the normalized cross correlation between the signals of two sensors along the road with a certain spacing. Experimental results show that the VPD has an accuracy of 99.65% for arrival and 99.44% for departure, while the VSE has an accuracy of 92%.
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paper_title: The Development of Vehicle Position Estimation Algorithms Based on the Use of AMR Sensors

paper_content:

This paper focuses on the use of anisotropic magnetoresistive (AMR) sensors for imminent crash detection in cars. The AMR sensors are used to measure the magnetic field from another vehicle in close proximity to estimate relative position and velocity from the measurement. An analytical formulation for the relationship between magnetic field and vehicle position is developed. The challenges in the use of the AMR sensors include their nonlinear behavior, limited range, and magnetic signature levels that vary with each type of car. An adaptive filter based on the iterated extended Kalman filter (IEKF) is developed to automatically tune filter parameters for each encountered car and to reliably estimate relative car position. The utilization of an additional sonar sensor during the initial detection of the encountered vehicle is shown to highly speed up the parameter convergence of the filter. Experimental results are presented from a number of tests with various vehicles to show that the proposed sensor system is viable.
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paper_title: Vehicle detection using a magnetic field sensor

paper_content:

The measurement of vehicle magnetic moments and the results from use of a fluxgate magnetic sensor to actuate a lighting system from the magnetic fields of passing vehicles is reported. A typical U.S. automobile has a magnetic moment of about 200 A-m2(Ampere-meters2), while for a school bus it is about 2000 A-m2. When the vehicle is modeled as an ideal magnetic dipole with a moment of 200 A-m2, the predicted results from an analysis of the sensor-vehicle geometry agree closely with observations of the system response to automobiles.
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paper_title: VEHICLE DETECTION AND COMPASS APPLICATIONS USING AMR MAGNETIC SENSORS

paper_content:

This paper presents a review of magnetic sensing and discusses applications for magnetic sensors. Focus is on magnetic sensing in vehicle detection and navigation that is based on magnetic fields.
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paper_title: Portable Roadside Sensors for Vehicle Counting, Classification, and Speed Measurement

paper_content:

This paper focuses on the development of a portable roadside magnetic sensor system for vehicle counting, classification, and speed measurement. The sensor system consists of wireless anisotropic magnetic devices that do not require to be embedded in the roadway-the devices are placed next to the roadway and measure traffic in the immediately adjacent lane. An algorithm based on a magnetic field model is proposed to make the system robust to the errors created by larger vehicles driving in the nonadjacent lane. These false calls cause an 8% error if uncorrected. The use of the proposed algorithm reduces this error to only 1%. Speed measurement is based on the calculation of the cross correlation between longitudinally spaced sensors. Fast computation of the cross correlation is enabled by using frequency-domain signal processing techniques. An algorithm for automatically correcting for any small misalignment of the sensors is utilized. A high-accuracy differential Global Positioning System is used as a reference to measure vehicle speeds to evaluate the accuracy of the speed measurement from the new sensor system. The results show that the maximum error of the speed estimates is less than 2.5% over the entire range of 5-27 m/s (11-60 mi/h). Vehicle classification is done based on the magnetic length and an estimate of the average vertical magnetic height of the vehicle. Vehicle length is estimated from the product of occupancy and estimated speed. The average vertical magnetic height is estimated using two magnetic sensors that are vertically spaced by 0.25 m. Finally, it is shown that the sensor system can be used to reliably count the number of right turns at an intersection, with an accuracy of 95%. The developed sensor system is compact, portable, wireless, and inexpensive. Data are presented from a large number of vehicles on a regular busy urban road in the Twin Cities, MN, USA.
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paper_title: Vehicle Detection and Classification for Low-Speed Congested Traffic With Anisotropic Magnetoresistive Sensor

paper_content:

A vehicle detection and classification system has been developed based on a low-cost triaxial anisotropic magnetoresistive sensor. Considering the characteristics of vehicle magnetic detection signals, especially the signals for low-speed congested traffic in large cities, a novel fixed threshold state machine algorithm based on signal variance is proposed to detect vehicles within a single lane and segment the vehicle signals effectively according to the time information of vehicles entering and leaving the sensor monitoring area. In our experiments, five signal features are extracted, including the signal duration, signal energy, average energy of the signal, ratio of positive and negative energy of x-axis signal, and ratio of positive and negative energy of y-axis signal. Furthermore, the detected vehicles are classified into motorcycles, two-box cars, saloon cars, buses, and Sport Utility Vehicle commercial vehicles based on a classification tree model. The experimental results have shown that the detection accuracy of the proposed algorithm can reach up to 99.05% and the average classification accuracy is 93.66%, which verify the effectiveness of our algorithm for low-speed congested traffic.
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paper_title: Wireless magnetic sensors for traffic surveillance

paper_content:

Sensys Networks' VDS240 vehicle detection system is a wireless sensor network composed of a collection of 3'' by 3'' by 2'' sensor nodes put in the center of a lane and a 6'' by 4'' by 4'' access point (AP) box placed 15' high on the side of the road. A node measures changes in the earth's magnetic field induced by a vehicle, processes the measurements to detect the vehicle, and transfers the processed data via radio to the AP. The AP combines data from the nodes into information for the local controller or the Traffic Management Center (TMC). An AP communicates via radio directly with up to 96 nodes within a range of 150'; a Repeater extends the range to 1000'. This range makes it suitable to deploy VDS240 networks for traffic counts, stop-bar and advance detection, and measurement of queue lengths on ramps and at intersections, as well as parking guidance and enforcement. VDS240 is self-calibrating, IP-addressable and remotely monitored. Data are not lost because unacknowledged data packets are retransmitted. The accuracy of VDS240 for vehicle counts, speed and occupancy is comparable to that of well-tuned loops. Because the nodes report individual vehicle events, the AP also calculates individual vehicle lengths, speeds and inter-vehicle headways--measurements that can be used for new traffic applications. In July 2007, VDS240 systems were deployed in arterials and freeways in several cities and states, and 30 customer trials were underway in the US, Australia, Europe and South Africa.
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paper_title: Experimental study of a vehicle detector with an AMR sensor

paper_content:

Abstract This paper proposes a vehicle detector with an anisotropic magnetoresistive (AMR) sensor and addresses experimental study carried out to show the detector's characteristics and performance. The detector consists of an AMR sensor and mechanical and electronic apparatuses. Composed of four magnetoresistors, the AMR sensor senses disturbance of the earth's magnetic field caused by a moving vehicle over the sensor itself and then produces an output indicative of the moving vehicle. Experiments have been carried out with three stages. At the first stage, the outputs of the sensor have been analyzed to show the validity of the detector's circuit and the detecting method. At the second stage, the detector has been tested on a local highway in Korea. Through the field tests, the outputs of the detector in response to various kinds of moving vehicles have been collected and analyzed. At the final stage, to verify the performance of the detector, traffic volumes on the highway have been measured with the detector and compared with the exact traffic volumes in a highly congested traffic.
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paper_title: Wireless sensor networks in intelligent transportation systems

paper_content:

Wireless sensor networks (WSNs) offer the potential to significantly improve the efficiency of existing transportation systems. Currently, collecting traffic data for traffic planning and management is achieved mostly through wired sensors. The equipment and maintenance cost and time-consuming installations of existing sensing systems prevent large-scale deployment of real-time traffic monitoring and control. Small wireless sensors with integrated sensing, computing, and wireless communication capabilities offer tremendous advantages in low cost and easy installation. In this paper, we first survey existing WSN technologies for intelligent transportation systems (ITSs), including sensor technologies, energy-efficient networking protocols, and applications of sensor networks for parking lot monitoring, traffic monitoring, and traffic control. Then, we present new methods on applying WSNs in traffic modeling and estimation and traffic control, and show their improved performance over existing solutions. Copyright © 2008 John Wiley & Sons, Ltd.
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paper_title: A Cross-Correlation Technique for Vehicle Detections in Wireless Magnetic Sensor Network

paper_content:

Vehicle detections are an important research field and attract many researchers. Most research efforts have been focused on vehicle parking detection (VPD) in indoor parking lot. For on-street parking, strong noise disturbances affect detection accuracy. To deal with vehicle detections in on-street environment, we propose two vehicle detection algorithms based on a cross-correlation technique in wireless magnetic sensor networks. One is for VPD, and the other one is for vehicle speed estimation (VSE). The proposed VPD algorithm combines the state-machine detection and the cross-correlation detection. In the VSE, speed estimation is based on the calculation of the normalized cross correlation between the signals of two sensors along the road with a certain spacing. Experimental results show that the VPD has an accuracy of 99.65% for arrival and 99.44% for departure, while the VSE has an accuracy of 92%.
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paper_title: Automatic vehicle classification using wireless magnetic sensor

paper_content:

This paper proposes an extension to our previous work on an automatic low-computed vehicle classification using embedded wireless magnetic sensor. A realization of our vehicle classification on embedded wireless magnetic sensor is studied in this work. The implementation allows real-time vehicle classification based on vehicle magnetic length, averaged energy, and Hill-pattern peaks. The system automatically detects vehicles, extracts features, and classifies them. The three features are of low-computation. We classify vehicles into 4 types: motorcycle, car, pickup and van. The classification shows a promising result. It can classify motorcycle with 95% accuracy. The classification rates between 70%-80% are achieved with car, pickup and van due to their similarity in these extracted features. The results obtained are comparable to our implementation using PC in our previous work and demonstrate that the algorithm can be realized on the embedded wireless magnetic sensor.
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paper_title: Portable Roadside Sensors for Vehicle Counting, Classification, and Speed Measurement

paper_content:

This paper focuses on the development of a portable roadside magnetic sensor system for vehicle counting, classification, and speed measurement. The sensor system consists of wireless anisotropic magnetic devices that do not require to be embedded in the roadway-the devices are placed next to the roadway and measure traffic in the immediately adjacent lane. An algorithm based on a magnetic field model is proposed to make the system robust to the errors created by larger vehicles driving in the nonadjacent lane. These false calls cause an 8% error if uncorrected. The use of the proposed algorithm reduces this error to only 1%. Speed measurement is based on the calculation of the cross correlation between longitudinally spaced sensors. Fast computation of the cross correlation is enabled by using frequency-domain signal processing techniques. An algorithm for automatically correcting for any small misalignment of the sensors is utilized. A high-accuracy differential Global Positioning System is used as a reference to measure vehicle speeds to evaluate the accuracy of the speed measurement from the new sensor system. The results show that the maximum error of the speed estimates is less than 2.5% over the entire range of 5-27 m/s (11-60 mi/h). Vehicle classification is done based on the magnetic length and an estimate of the average vertical magnetic height of the vehicle. Vehicle length is estimated from the product of occupancy and estimated speed. The average vertical magnetic height is estimated using two magnetic sensors that are vertically spaced by 0.25 m. Finally, it is shown that the sensor system can be used to reliably count the number of right turns at an intersection, with an accuracy of 95%. The developed sensor system is compact, portable, wireless, and inexpensive. Data are presented from a large number of vehicles on a regular busy urban road in the Twin Cities, MN, USA.
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paper_title: Vehicle Detection and Classification for Low-Speed Congested Traffic With Anisotropic Magnetoresistive Sensor

paper_content:

A vehicle detection and classification system has been developed based on a low-cost triaxial anisotropic magnetoresistive sensor. Considering the characteristics of vehicle magnetic detection signals, especially the signals for low-speed congested traffic in large cities, a novel fixed threshold state machine algorithm based on signal variance is proposed to detect vehicles within a single lane and segment the vehicle signals effectively according to the time information of vehicles entering and leaving the sensor monitoring area. In our experiments, five signal features are extracted, including the signal duration, signal energy, average energy of the signal, ratio of positive and negative energy of x-axis signal, and ratio of positive and negative energy of y-axis signal. Furthermore, the detected vehicles are classified into motorcycles, two-box cars, saloon cars, buses, and Sport Utility Vehicle commercial vehicles based on a classification tree model. The experimental results have shown that the detection accuracy of the proposed algorithm can reach up to 99.05% and the average classification accuracy is 93.66%, which verify the effectiveness of our algorithm for low-speed congested traffic.
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paper_title: Magnetoresistive-based biosensors and biochips.

paper_content:

Over the past five years, magnetoelectronics has emerged as a promising new platform technology for biosensor and biochip development. The techniques are based on the detection of the magnetic fringe field of a magnetically labeled biomolecule interacting with a complementary biomolecule bound to a magnetic-field sensor. Magnetoresistive-based sensors, conventionally used as read heads in hard disk drives, have been used in combination with biologically functionalized magnetic labels to demonstrate the detection of molecular recognition. Real-world bio-applications are now being investigated, enabling tailored device design, based on sensor and label characteristics. This detection platform provides a robust, inexpensive sensing technique with high sensitivity and considerable scope for quantitative signal data, enabling magnetoresistive biochips to meet specific diagnostic needs that are not met by existing technologies.
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paper_title: Detection of 10-nm Superparamagnetic Iron Oxide Nanoparticles Using Exchange-Biased GMR Sensors in Wheatstone Bridge

paper_content:

We demonstrated the use of exchange-biased giant magnetoresistance (GMR) sensors in Wheatstone bridge for the detection of 10-nm superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs were synthesized via coprecipitation method, exhibiting a superparamagnetic behavior with saturation magnetization of 57 emu/g. The output voltage signal of the Wheatstone bridge exhibits log-linear function of the concentration of SPIONs (from 10 ng/ml to 0.1 mg/ml), making the sensors suitable for use as a SPION concentration detector. Thus the combination of 10 nm SPIONs and the exchange-biased GMR sensors has potential to be used in the bio-detection applications where ultra-small bio-labels are needed.
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paper_title: Matrix-insensitive protein assays push the limits of biosensors in medicine

paper_content:

Advances in biosensor technologies for in vitro diagnostics have the potential to transform the practice of medicine. Despite considerable work in the biosensor field, there is still no general sensing platform that can be ubiquitously applied to detect the constellation of biomolecules in diverse clinical samples (for example, serum, urine, cell lysates or saliva) with high sensitivity and large linear dynamic range. A major limitation confounding other technologies is signal distortion that occurs in various matrices due to heterogeneity in ionic strength, pH, temperature and autofluorescence. Here we present a magnetic nanosensor technology that is matrix insensitive yet still capable of rapid, multiplex protein detection with resolution down to attomolar concentrations and extensive linear dynamic range. The matrix insensitivity of our platform to various media demonstrates that our magnetic nanosensor technology can be directly applied to a variety of settings such as molecular biology, clinical diagnostics and biodefense.
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paper_title: Magnetic Nanoparticle Sensors

paper_content:

Many types of biosensors employ magnetic nanoparticles (diameter = 5–300 nm) or magnetic particles (diameter = 300–5,000 nm) which have been surface functionalized to recognize specific molecular targets. Here we cover three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation. The first type consists of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates. The second type consists of magnetic particle relaxation sensors, which determine the relaxation of the magnetic moment within the magnetic particle. The third type is magnetoresistive sensors, which detect the presence of magnetic particles on the surface of electronic devices that are sensitive to changes in magnetic fields on their surface. Recent improvements in the design of magnetic nanoparticles (and magnetic particles), together with improvements in instrumentation, suggest that magnetic material-based biosensors may become widely used in the future.
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paper_title: Magnetoresistive-based biosensors and biochips.

paper_content:

Over the past five years, magnetoelectronics has emerged as a promising new platform technology for biosensor and biochip development. The techniques are based on the detection of the magnetic fringe field of a magnetically labeled biomolecule interacting with a complementary biomolecule bound to a magnetic-field sensor. Magnetoresistive-based sensors, conventionally used as read heads in hard disk drives, have been used in combination with biologically functionalized magnetic labels to demonstrate the detection of molecular recognition. Real-world bio-applications are now being investigated, enabling tailored device design, based on sensor and label characteristics. This detection platform provides a robust, inexpensive sensing technique with high sensitivity and considerable scope for quantitative signal data, enabling magnetoresistive biochips to meet specific diagnostic needs that are not met by existing technologies.
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paper_title: Integration of Magnetoresistive Biochips on a CMOS Circuit

paper_content:

Since 2006, fully scalable matrix-based magnetoresistive biochips have been proposed. This integration was initially achieved with thin film switching devices and moved to complementary metal-oxide-semiconductor (CMOS) switching devices and electronics. In this paper, a new microfabrication process is proposed to integrate magnetoresistive sensors on a small CMOS chip (4 mm2). This chip includes a current generator, multiplexers, and a diode in series with a spin valve as matrix element. In this configuration, it is shown that the fabricated spin-valves have similar magnetic characteristics when compared to standalone spin valves. This validates the successfulness of the developed microfabrication process. The noise of each matrix element is further characterized and compared to the noise of a standalone spin valve and a portable electronic platform designed to perform biological assays. Although the noise is still higher, the spin valve integrated on the CMOS chip enables an increase in density and compactness of the measuring electronics.
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paper_title: Magnetic Nanoparticles for Magnetoresistance-Based Biodetection

paper_content:

Magnetic nanoparticles (MNPs) have been studied widely as a powerful diagnostic probe and therapeutic agent for biomedical applications. In recent years, they are also found to be sensitive to magnetoresistive (MR) devices and MNP-MR biochips are predicted to be more affordable, portable and sensitive than the conventional optical detection methods. In this MNP-MR biochip design, MNP probes are required to have high magnetic moment, high susceptibility, and be target-specific. This review summarizes recent advances in chemical syntheses and functionalization of MNPs with controlled magnetic properties for sensitive MR detection and for bio-sensing applications.
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paper_title: Biological applications of magnetic nanoparticles.

paper_content:

In this review an overview about biological applications of magnetic colloidal nanoparticles will be given, which comprises their synthesis, characterization, and in vitro and in vivo applications. The potential future role of magnetic nanoparticles compared to other functional nanoparticles will be discussed by highlighting the possibility of integration with other nanostructures and with existing biotechnology as well as by pointing out the specific properties of magnetic colloids. Current limitations in the fabrication process and issues related with the outcome of the particles in the body will be also pointed out in order to address the remaining challenges for an extended application of magnetic nanoparticles in medicine.
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paper_title: Detection of Magnetically Labelled Microcarriers for Suspension Based Bioassay Technologies

paper_content:

Microarrays and suspension-based assay technologies have attracted significant interest over the past decade with applications ranging from medical diagnostics to high throughput molecular biology. The throughput and sensitivity of a microarray will always be limited by the array density and slow reaction kinetics. Suspension (or bead) based technologies offer a conceptually different approach, improving detection by substituting a fixed plane of operation with millions of microcarriers. However, these technologies are currently limited by the number of unique labels that can be generated in order to identify the molecular probes on the surface. We have proposed a novel suspension-based technology that utilizes patterned magnetic films for the purpose of generating a writable label. The microcarriers consist of an SU-8 substrate that can be functionalized with various chemical or biological probes and magnetic elements, which are individually addressable by a magnetic sensor. The magnetization of each element is aligned in one of two stable directions, thereby acting as a magnetic bit. In order to detect the stray field and identify the magnetic labels, we have developed a microfluidic device with an integrated tunneling magnetoresistive (TMR) sensor, sourced from Micro Magnetics Inc. We present the TMR embedding architecture as well as detection results demonstrating the feasibility of magnetic labeling for lab-on-a-chip applications.
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paper_title: Giant magnetoresistive biochip for DNA detection and HPV genotyping.

paper_content:

A giant magnetoresistive (GMR) biochip based on spin valve sensor array and magnetic nanoparticle labels was developed for inexpensive, sensitive and reliable DNA detection. The DNA targets detected in this experiment were PCR products amplified from Human Papillomavirus (HPV) plasmids. The concentrations of the target DNA after PCR were around 10 nM in most cases, but concentrations of 10 pM were also detectable, which is demonstrated by experiments with synthetic DNA samples. A mild but highly specific surface chemistry was used for probe oligonucleotide immobilization. Double modulation technique was used for signal detection in order to reduce the 1/f noise in the sensor. Twelve assays were performed with an accuracy of approximately 90%. Magnetic signals were consistent with particle coverage data measured with Scanning Electron Microscopy (SEM). More recent research on microfluidics showed the potential of reducing the assay time below one hour. This is the first demonstration of magnetic DNA detection using plasmid-derived samples. This study provides a direct proof that GMR sensors can be used for biomedical applications.
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paper_title: Magnetoresistive performance and comparison of supermagnetic nanoparticles on giant magnetoresistive sensor-based detection system

paper_content:

Giant magnetoresistive (GMR) biosensors have emerged as powerful tools for ultrasensitive, multiplexed, real-time electrical readout, and rapid biological/chemical detection while combining with magnetic particles. Finding appropriate magnetic nanoparticles (MNPs) and its influences on the detection signal is a vital aspect to the GMR bio-sensing technology. Here, we report a GMR sensor based detection system capable of stable and convenient connection, and real-time measurement. Five different types of MNPs with sizes ranging from 10 to 100 nm were investigated for GMR biosensing. The experiments were accomplished with the aid of DNA hybridization and detection architecture on GMR sensor surface. We found that different MNPs markedly affected the final detection signal, depending on their characteristics of magnetic moment, size, and surface-based binding ability, etc. This work may provide a useful guidance in selecting or preparing MNPs to enhance the sensitivity of GMR biosensors, and eventually lead to a versatile and portable device for molecular diagnostics.
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paper_title: Quantitative detection of DNA labeled with magnetic nanoparticles using arrays of MgO-based magnetic tunnel junction sensors

paper_content:

We have demonstrated the detection of 2.5μM target DNA labeled with 16nm Fe3O4 nanoparticles (NPs) using arrays of magnetic tunnel junction sensors with (001)-oriented MgO barrier layers. A MTJ sensor bridge was designed to detect the presence of magnetic NPs bonded with target DNA. A raw signal of 72μV was obtained using complementary target DNA, as compared with a nonspecific bonding signal of 25μV from noncomplementary control DNA. Our results indicate that the current system’s detection limit for analyte DNA is better than 100nM.
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paper_title: Advances in Giant Magnetoresistance Biosensors With Magnetic Nanoparticle Tags: Review and Outlook

paper_content:

We present a review of giant magnetoresistance (GMR) spin valve sensors designed for detection of magnetic nanoparticles as biomolecular labels (nanotags) in magneto-nano biodetection technology. We discuss the intricacy of magneto-nano biosensor design and show that as few as approximately 14 monodisperse 16-nm superparamagnetic nanoparticles can be detected by submicron spin valve sensors at room temperature without resorting to lock-in (narrow band) detection. GMR biosensors and biochips have been successfully applied to the detection of biological events in the form of both protein and DNA assays with great speed, sensitivity, selectivity, and economy. The limit of molecular detection is well below 10 pM in concentration, and the protein or DNA assay time can be under two hours. The technology is highly scalable to deep multiplex detection of biomarkers in a complex disease, and amenable to integration of microfluidics and CMOS electronics for portable applications. On-chip CMOS circuitry makes a sensor density of 0.1-1 million sensors per square centimeter feasible and affordable. The theoretical and experimental results thus far suggest that magneto-nano biochip-based GMR sensor arrays and nanotags hold great promise in biomedicine, particularly for point-of-care molecular diagnostics of cancer, infectious diseases, radiation injury, cardiac diseases, and other diseases.
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paper_title: Internet of Things (IoT): A Vision, Architectural Elements, and Future Directions

paper_content:

Ubiquitous sensing enabled by Wireless Sensor Network (WSN) technologies cuts across many areas of modern day living. This offers the ability to measure, infer and understand environmental indicators, from delicate ecologies and natural resources to urban environments. The proliferation of these devices in a communicating-actuating network creates the Internet of Things (IoT), wherein sensors and actuators blend seamlessly with the environment around us, and the information is shared across platforms in order to develop a common operating picture (COP). Fueled by the recent adaptation of a variety of enabling wireless technologies such as RFID tags and embedded sensor and actuator nodes, the IoT has stepped out of its infancy and is the next revolutionary technology in transforming the Internet into a fully integrated Future Internet. As we move from www (static pages web) to web2 (social networking web) to web3 (ubiquitous computing web), the need for data-on-demand using sophisticated intuitive queries increases significantly. This paper presents a Cloud centric vision for worldwide implementation of Internet of Things. The key enabling technologies and application domains that are likely to drive IoT research in the near future are discussed. A Cloud implementation using Aneka, which is based on interaction of private and public Clouds is presented. We conclude our IoT vision by expanding on the need for convergence of WSN, the Internet and distributed computing directed at technological research community.
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paper_title: The History of WiMAX: A Complete Survey of the Evolution in Certification and Standardization for IEEE 802.16 and WiMAX

paper_content:

Most researchers are familiar with the technical features of WiMAX technology but the evolution that WiMAX went through, in terms of standardization and certification, is missing and unknown to most people. Knowledge of this historical process would however aid to understand how WiMAX has become the widespread technology that it is today. Furthermore, it would give insight in the steps to undertake for anyone aiming at introducing a new wireless technology on a worldwide scale. Therefore, this article presents a survey on all relevant activities that took place within three important organizations: the 802.16 Working Group of the IEEE (Institute of Electrical and Electronics Engineers) for technology development and standardization, the WiMAX Forum for product certification and the ITU (International Telecommunication Union) for international recognition. An elaborated and comprehensive overview of all those activities is given, which reveals the importance of the willingness to innovate and to continuously incorporate new ideas in the IEEE standardization process and the importance of the WiMAX Forum certification label granting process to ensure interoperability. We also emphasize the steps that were taken in cooperating with the ITU to improve the international esteem of the technology. Finally, a WiMAX trend analysis is made. We showed how industry interest has fluctuated over time and quantified the evolution in WiMAX product certification and deployments. It is shown that most interest went to the 2.5 GHz and 3.5 GHz frequencies, that most deployments are in geographic regions with a lot of developing countries and that the highest people coverage is achieved in Asia Pacific. This elaborated description of all standardization and certification activities, from the very start up to now, will make the reader comprehend how past and future steps are taken in the development process of new WiMAX features.
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paper_title: Future internet: The Internet of Things

paper_content:

Nowadays, the main communication form on the Internet is human-human. But it is foreseeable that in a near soon that any object will have a unique way of identification and can be addressed so that every object can be connected. The Internet will become to the Internet of Things. The communicate forms will expand from human-human to human-human, human-thing and thing-thing (also called M2M).This will bring a new ubiquitous computing and communication era and change people's life extremely. Radio Frequency Identification techniques (RFID) and related identification technologies will be the cornerstones of the upcoming Internet of Things (IOT).This paper aims to show a skeleton of the Internet of Things and we try to address some essential issues of the Internet of Things like its architecture and the interoperability, etc. At the beginning we describe an overview of the Internet of Things. Then we give our architecture design proposal of the Internet of Things and then we design a specific the Internet of Things application model which can apply to automatic facilities management in the smart campus. At last, we discuss some open questions about the Internet of Things.
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paper_title: Research on the architecture of Internet of Things

paper_content:

The Internet of Things is a technological revolution that represents the future of computing and communications. It is not the simple extension of the Internet or the Telecommunications Network. It has the features of both the Internet and the Telecommunications Network, and also has its own distinguishing feature. Through analysing the current accepted three-layer structure of the Internet of things, we suggest that the three-layer structure can't express the whole features and connotation of the Internet of Things. After reanalysing the technical framework of the Internet and the Logical Layered Architecture of the Telecommunication Management Network, we establish new five-layer architecture of the Internet of Things. We believe this architecture is more helpful to understand the essence of the Internet of Things, and we hope it is helpful to develop the Internet of Things.
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paper_title: The Internet of Things: A survey

paper_content:

This paper addresses the Internet of Things. Main enabling factor of this promising paradigm is the integration of several technologies and communications solutions. Identification and tracking technologies, wired and wireless sensor and actuator networks, enhanced communication protocols (shared with the Next Generation Internet), and distributed intelligence for smart objects are just the most relevant. As one can easily imagine, any serious contribution to the advance of the Internet of Things must necessarily be the result of synergetic activities conducted in different fields of knowledge, such as telecommunications, informatics, electronics and social science. In such a complex scenario, this survey is directed to those who want to approach this complex discipline and contribute to its development. Different visions of this Internet of Things paradigm are reported and enabling technologies reviewed. What emerges is that still major issues shall be faced by the research community. The most relevant among them are addressed in details.
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paper_title: Wireless sensor networks: a survey

paper_content:

This paper describes the concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics. First, the sensing tasks and the potential sensor networks applications are explored, and a review of factors influencing the design of sensor networks is provided. Then, the communication architecture for sensor networks is outlined, and the algorithms and protocols developed for each layer in the literature are explored. Open research issues for the realization of sensor networks are also discussed.
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paper_title: Future Internet: The Internet of Things Architecture, Possible Applications and Key Challenges

paper_content:

The Internet is continuously changing and evolving. The main communication form of present Internet is human-human. The Internet of Things (IoT) can be considered as the future evaluation of the Internet that realizes machine-to-machine (M2M) learning. Thus, IoT provides connectivity for everyone and everything. The IoT embeds some intelligence in Internet-connected objects to communicate, exchange information, take decisions, invoke actions and provide amazing services. This paper addresses the existing development trends, the generic architecture of IoT, its distinguishing features and possible future applications. This paper also forecast the key challenges associated with the development of IoT. The IoT is getting increasing popularity for academia, industry as well as government that has the potential to bring significant personal, professional and economic benefits.
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paper_title: Study and application on the architecture and key technologies for IOT

paper_content:

IOT refers to the third scientific and economic tide after computer, Internet in the global information industry, having attracted highly attention of governments, enterprises, and academia, and brought a huge new market for the communication industry. At present, global main operators and equipment suppliers begin to provide M2M business and solution. Here mainly introduces the concept of IOT, analyses the structure of IOT: perception layer, network layer, application layer. Sets forth the key technologies of IOT: RFID, network communication, etc. At length, it proposes the future development and reform trend of IOT.
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paper_title: Internet of Things (IoT): A Vision, Architectural Elements, and Future Directions

paper_content:

Ubiquitous sensing enabled by Wireless Sensor Network (WSN) technologies cuts across many areas of modern day living. This offers the ability to measure, infer and understand environmental indicators, from delicate ecologies and natural resources to urban environments. The proliferation of these devices in a communicating-actuating network creates the Internet of Things (IoT), wherein sensors and actuators blend seamlessly with the environment around us, and the information is shared across platforms in order to develop a common operating picture (COP). Fueled by the recent adaptation of a variety of enabling wireless technologies such as RFID tags and embedded sensor and actuator nodes, the IoT has stepped out of its infancy and is the next revolutionary technology in transforming the Internet into a fully integrated Future Internet. As we move from www (static pages web) to web2 (social networking web) to web3 (ubiquitous computing web), the need for data-on-demand using sophisticated intuitive queries increases significantly. This paper presents a Cloud centric vision for worldwide implementation of Internet of Things. The key enabling technologies and application domains that are likely to drive IoT research in the near future are discussed. A Cloud implementation using Aneka, which is based on interaction of private and public Clouds is presented. We conclude our IoT vision by expanding on the need for convergence of WSN, the Internet and distributed computing directed at technological research community.
---
paper_title: The Internet of Things: A survey

paper_content:

This paper addresses the Internet of Things. Main enabling factor of this promising paradigm is the integration of several technologies and communications solutions. Identification and tracking technologies, wired and wireless sensor and actuator networks, enhanced communication protocols (shared with the Next Generation Internet), and distributed intelligence for smart objects are just the most relevant. As one can easily imagine, any serious contribution to the advance of the Internet of Things must necessarily be the result of synergetic activities conducted in different fields of knowledge, such as telecommunications, informatics, electronics and social science. In such a complex scenario, this survey is directed to those who want to approach this complex discipline and contribute to its development. Different visions of this Internet of Things paradigm are reported and enabling technologies reviewed. What emerges is that still major issues shall be faced by the research community. The most relevant among them are addressed in details.
---
paper_title: Perpetual and low-cost power meter for monitoring residential and industrial appliances

paper_content:

The recent research efforts in smart grids and residential power management are oriented to monitor pervasively the power consumption of appliances in domestic and non-domestic buildings. Knowing the status of a residential grid is fundamental to keep high reliability levels while real time monitoring of electric appliances is important to minimize power waste in buildings and to lower the overall energy cost. Wireless Sensor Networks (WSNs) are a key enabling technology for this application field because they consist of low-power, non-invasive and cost-effective intelligent sensor devices. We present a wireless current sensor node (WCSN) for measuring the current drawn by single appliances. The node can self-sustain its operations by harvesting energy from the monitored current. Two AAA batteries are used only as secondary power supply to guarantee a fast start-up of the system. An active ORing subsystem selects automatically the suitable power source, minimizing power losses typical of the classic diode configuration. The node harvests energy when the power consumed by the device under measurement is in the range 10W÷10kW, which also corresponds to the range of current 50mA÷50A drawn directly from the main. Finally the node features a low-power, 32-bit microcontroller for data processing and a wireless transceiver to send data via the IEEE 802.15.4 standard protocol.
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paper_title: Wireless sensor networks: a survey

paper_content:

This paper describes the concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics. First, the sensing tasks and the potential sensor networks applications are explored, and a review of factors influencing the design of sensor networks is provided. Then, the communication architecture for sensor networks is outlined, and the algorithms and protocols developed for each layer in the literature are explored. Open research issues for the realization of sensor networks are also discussed.
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paper_title: Energy conservation in wireless sensor networks: A survey

paper_content:

In the last years, wireless sensor networks (WSNs) have gained increasing attention from both the research community and actual users. As sensor nodes are generally battery-powered devices, the critical aspects to face concern how to reduce the energy consumption of nodes, so that the network lifetime can be extended to reasonable times. In this paper we first break down the energy consumption for the components of a typical sensor node, and discuss the main directions to energy conservation in WSNs. Then, we present a systematic and comprehensive taxonomy of the energy conservation schemes, which are subsequently discussed in depth. Special attention has been devoted to promising solutions which have not yet obtained a wide attention in the literature, such as techniques for energy efficient data acquisition. Finally we conclude the paper with insights for research directions about energy conservation in WSNs.
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paper_title: A Nonintrusive Power Supply Design for Self-Powered Sensor Networks in the Smart Grid by Scavenging Energy From AC Power Line

paper_content:

An advanced metering and monitoring system based on autonomous, ubiquitous and maintenance-free wireless sensor networks is of great significance to the smart grid. However, the power supply for sensor nodes (especially those installed on high-voltage side) remains one of the most challenging issues. To date, miniaturized, reliable, low-cost and flexible designs catering the massive application of self-powered sensor nodes in the smart grid are still limited. This paper presents a nonintrusive design of power supply to support the sensor network applied in the smart grid. Using a cantilever-structured magnetoelectric (ME) composite, the energy harvester is able to scavenge energy from the power-frequency (50 Hz) magnetic field distributed around the transmission line. Design considerations for this specific type of scavenger have been discussed, and optimized energy harvester prototypes have been fabricated, which are further tested on a power line platform. Experimental results show that the single-cell and double-cell energy harvesters are capable of producing 0.62 mW and 1.12 mW at 10 A, respectively, while corresponding power outputs are enhanced to 4.11 mW and 9.40 mW at 40 A. The good energy harvesting ability of this particular ME composite indicates its great potential to make a nonintrusive, miniaturized, flexible and cost-effective power supply, which possesses great application prospects in the smart grid.
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paper_title: Routing Techniques in Wireless Sensor Networks: A Survey

paper_content:

Wireless sensor networks consist of small nodes with sensing, computation, and wireless communications capabilities. Many routing, power management, and data dissemination protocols have been specifically designed for WSNs where energy awareness is an essential design issue. Routing protocols in WSNs might differ depending on the application and network architecture. In this article we present a survey of state-of-the-art routing techniques in WSNs. We first outline the design challenges for routing protocols in WSNs followed by a comprehensive survey of routing techniques. Overall, the routing techniques are classified into three categories based on the underlying network structure: flit, hierarchical, and location-based routing. Furthermore, these protocols can be classified into multipath-based, query-based, negotiation-based, QoS-based, and coherent-based depending on the protocol operation. We study the design trade-offs between energy and communication overhead savings in every routing paradigm. We also highlight the advantages and performance issues of each routing technique. The article concludes with possible future research areas.
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paper_title: Minimum-energy mobile wireless networks revisited

paper_content:

We propose a protocol that, given a communication network, computes a subnetwork such that, for every pair $(u,v)$ of nodes connected in the original network, there is a minimum-energy path between $u$ and $v$ in the subnetwork (where a minimum-energy path is one that allows messages to be transmitted with a minimum use of energy). The network computed by our protocol is in general a subnetwork of the one computed by the protocol given in [13]. Moreover, our protocol is computationally simpler. We demonstrate the performance improvements obtained by using the subnetwork computed by our protocol through simulation.
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paper_title: Integration of plug-in hybrid electric vehicles into energy and comfort management for smart building

paper_content:

Abstract The smart building and plug-in hybrid electric vehicle (PHEV) are two promising technologies. The integration of these two emerging technologies holds great promises in improving the power supply reliability and the flexibility of building energy and comfort management. The overall control goal of the smart building is to maximize the customer comfort with minimum power consumption. In this study, multi-agent technology coupled with particle swarm optimization (PSO) is proposed to address the control challenge. The proper aggregation of a number of PHEVs turns out to be able to provide both capacity and energy to make the building more economical and more reliable by impacting the building energy flow. Case studies and simulation results are presented and discussed in the paper.
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paper_title: Multi-port topology for composite energy storage and its control strategy in micro-grid

paper_content:

Energy storage system (ESS) plays a significant role in micro-grid, but single energy storage can't meet the comprehensive requirements of micro-grid applications. Due to technical and economic reasons, composite energy storage is a better choice nowadays, which can combine all the suitable energy storages together, take the best of their positives to meet customer's demand. So the topology for composite energy storage is very important. Typical topology can be used for composite energy storage is compared, upon which, a novel multi-port port based on DC-link interfacing and magnetic coupling method is proposed for composite energy storage application. The multi-port topology allows different kinds of energy storage and/or micro-sources to get in, where energy can be controlled to flow bi-directionally, in and out of energy storage. And a novel Economical inverter based on three phase four switch topology is introduced for micro-grid interface of composite energy storage, which have features of low cost, easy to control and suitable for energy storage application. A double layer control strategy is designed for composite energy storage, the upper layer is responsible for energy management, and a knowledge based energy management method is utilized to separate different energy storage. In the lower layer, a phase shift PWM method is utilized to control energy flow between different ports. Simulation experiments testified their feasibility
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paper_title: Noncontact Power Meter

paper_content:

Energy metering is increasingly important in today's power grid. With real-time power meters, utilities can efficiently incorporate renewables and consumers can tailor their demand accordingly. Several high-profile attempts at delivering realtime energy analytics to users, including Google Power Meter and Microsoft Hohm, have essentially failed because of a lack of sufficient richness and access to data at adequate bandwidth for reasonable cost. High performance meters can provide adequate data, but require custom installation at prohibitive expense, e.g., requiring an electrician for installation. This paper presents hardware and signal processing algorithms that enable high bandwidth measurements of voltage, current, harmonics, and power on an aggregate electrical service (such as a residential powerline) for nonintrusive analysis with hardware that requires no special skill or safety considerations for installation.
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paper_title: Photovoltaic and wind energy systems monitoring and building/home energy management using ZigBee devices within a smart grid

paper_content:

The actual electric grid was developed to offer electricity to the clients from centralized generation, so with large-scale distributed renewable generation there is an urgent need for a more flexible, reliable and smarter grid. The wireless technologies are becoming an important asset in the smart grid, particularly the ZigBee devices. These smart devices are gaining increased acceptance, not only for building and home automation, but also for energy management, efficiency optimization and metering services, being able to operate for long periods of time without maintenance needs. In this context, this paper provides new comprehensive field tests using open source tools with ZigBee technologies for monitoring photovoltaic and wind energy systems, and also for building and home energy management. Our experimental results demonstrate the proficiency of ZigBee devices applied in distributed renewable generation and smart metering systems.
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paper_title: A review on optimized control systems for building energy and comfort management of smart sustainable buildings

paper_content:

Buildings all around the world consume a significant amount of energy, which is more or less one-third of the total primary energy resources. This has raised concerns over energy supplies, rapid energy resource depletion, rising building service demands, improved comfort life styles along with the increased time spent in buildings; consequently, this has shown a rising energy demand in the near future. However, contemporary buildings’ energy efficiency has been fast tracked solution to cope/limit the rising energy demand of this sector. Building energy efficiency has turned out to be a multi-faceted problem, when provided with the limitation for the satisfaction of the indoor comfort index. However, the comfort level for occupants and their behavior have a significant effect on the energy consumption pattern. It is generally perceived that energy unaware activities can also add one-third to the building’s energy performance. Researchers and investigators have been working with this issue for over a decade; yet it remains a challenge. This review paper presents a comprehensive and significant research conducted on state-of-the-art intelligent control systems for energy and comfort management in smart energy buildings (SEB’s). It also aims at providing a building research community for better understanding and up-to-date knowledge for energy and comfort related trends and future directions. The main table summarizes 121 works closely related to the mentioned issue. Key areas focused on include comfort parameters, control systems, intelligent computational methods, simulation tools, occupants’ behavior and preferences, building types, supply source considerations and countries research interest in this sector. Trends for future developments and existing research in this area have been broadly studied and depicted in a graphical layout. In addition, prospective future advancements and gaps have also been discussed comprehensively.
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paper_title: A novel current sensor for home energy use monitoring

paper_content:

This paper presents a novel magnetic sensor array based technique for measuring currents in a group of enclosed conductors. It is designed specifically for monitoring the real-time power consumptions of North American homes. The technique consists of three key components: magnetic field sensors deployed in close proximity of the power conductors to be measured; algorithms to compute the conductor currents based on the magnetic fields measured; a simple, integrated sensor calibration and communication scheme. Prototype devices have been developed based on the technique. Extensive lab and field tests have demonstrated that the technique can provide adequate current measurements for residential homes. Combining with the non-intrusive load monitoring methods, the proposed measurement technique represents an attractive platform to create a complete home energy use tracking system.
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paper_title: Demand Side Management: Demand Response, Intelligent Energy Systems, and Smart Loads

paper_content:

Energy management means to optimize one of the most complex and important technical creations that we know: the energy system. While there is plenty of experience in optimizing energy generation and distribution, it is the demand side that receives increasing attention by research and industry. Demand Side Management (DSM) is a portfolio of measures to improve the energy system at the side of consumption. It ranges from improving energy efficiency by using better materials, over smart energy tariffs with incentives for certain consumption patterns, up to sophisticated real-time control of distributed energy resources. This paper gives an overview and a taxonomy for DSM, analyzes the various types of DSM, and gives an outlook on the latest demonstration projects in this domain.
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paper_title: Getting to green: understanding resource consumption in the home

paper_content:

Rising global energy demands, increasing costs and limited natural resources mean that householders are more conscious about managing their domestic resource consumption. Yet, the question of what tools Ubicomp researchers can create for residential resource management remains open. To begin to address this omission, we present a qualitative study of 15 households and their current management practices around the water, electricity and natural gas systems in the home. We find that in-the-moment resource consumption is mostly invisible to householders and that they desire more real-time information to help them save money, keep their homes comfortable and be environmentally friendly. Designing for domestic sustainability therefore turns on improving the visibility of resource production and consumption costs as well as supporting both individuals and collectives in behavior change. Domestic sustainability also highlights the caveat of potentially creating a green divide by making resource management available only to those who can afford the technologies to support being green. Finally, we suggest that the Ubicomp community can contribute to the domestic and broader sustainability agenda by incorporating green values in designs and highlight the challenge of collecting data on being green.
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paper_title: Towards a zero-configuration wireless sensor network architecture for smart buildings

paper_content:

Today's buildings account for a large fraction of our energy consumption. In an effort to economize scarce fossil fuels on earth, sensor networks are a valuable tool to increase the energy efficiency of buildings without severely reducing our quality of life. Within a smart building many sensors and actuators are interconnected to form a control system. Nowadays, the deployment of a building control system is complicated because of different communication standards. In this paper, we present a web services-based approach to integrate resource constrained sensor and actuator nodes into IP-based networks. A key feature of our approach is its capability for automatic service discovery. For this purpose, we implemented an API to access services on sensor nodes following the architectural style of representational state transfer (REST). We implemented a prototype application based on TinyOS 2.1 on a custom sensor node platform with 8 Kbytes of RAM and an IEEE 802.15.4 compliant radio transceiver.
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paper_title: Development of an energy monitoring system for large public buildings

paper_content:

Abstract Building energy consumption is an important component of the total social energy consumption, especially for large public buildings in China. Building energy conservation is one valid method for increasing energy efficiency. In order to locate the status of energy consumption for large public buildings, such as supermarket, government office buildings, hospital and campus buildings, an Internet-based energy monitoring system was developed. The implementation of this system was introduced in detail, including the principle of selecting monitoring points at the bottom layer, the design of a data collector with storage function avoiding data loss caused by network faults, and the development of database and application software at the top layer. The monitoring platform releases the energy consumption data on the web, so the authorized users can access the data any time and anywhere through Internet. In addition, the data display system is given in form of graph-charts or tables, so users can choose any kind of data they want to see, either instant values uploaded every 5 min or historic data uploaded every hour, day and month. The platform has been used in some large public buildings in Liaoning Province in China over two years, and the results confirm its feasibility and validity.
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paper_title: Intelligent Management Systems for Energy Efficiency in Buildings: A Survey

paper_content:

In recent years, reduction of energy consumption in buildings has increasingly gained interest among researchers mainly due to practical reasons, such as economic advantages and long-term environmental sustainability. Many solutions have been proposed in the literature to address this important issue from complementary perspectives, which are often hard to capture in a comprehensive manner. This survey article aims at providing a structured and unifying treatment of the existing literature on intelligent energy management systems in buildings, with a distinct focus on available architectures and methodology supporting a vision transcending the well-established smart home vision, in favor of the novel Ambient Intelligence paradigm. Our exposition will cover the main architectural components of such systems, beginning with the basic sensory infrastructure, moving on to the data processing engine where energy-saving strategies may be enacted, to the user interaction interface subsystem, and finally to the actuation infrastructure necessary to transfer the planned modifications to the environment. For each component, we will analyze different solutions, and we will provide qualitative comparisons, also highlighting the impact that a single design choice can have on the rest of the system.
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paper_title: Sensors in Intelligent Buildings

paper_content:

We've all heard of `sick-building' syndrome and the misery this can inflict in the workplace in terms of poor health and lost production. The notion of the Intelligent Building is the modern civil engineer's Big Idea in tackling these and other such deficiencies. The intelligent building can adapt itself to maintain an optimized environment. This ability relies on sensors as a front-line technology - the subject of this volume. Gassmann and Meixner tackle the subject matter by using five categories of intelligent building technology: energy and HVAC (heating, ventilation and air conditioning), information and transportation, safety and security, maintenance, and facility management. These categories of home and building technology are intended to encompass domestic as well as workplace and public environments, but as the introduction states, the breakthrough into the domestic market is not quite here yet. They have targeted, successfully in this reviewer's opinion, the researcher and designer in the field who has his or her own specific interest in sensor issues. Each section of the book contains a number of articles contributed from predominantly European, particularly German and Swiss, research institutions. They cover subjects as diverse as inflatable buildings and a combination of a sensing chair and sensing floor that allows the exact interaction of a human user with his/her immediate surroundings to be integrated within an information system. A fascinating item on biometric access security systems brings to life the `spy-thriller' world of automatic iris and fingerprint scanners as a means of secure access to key-less buildings. The discussion extends to threats to such systems whereby `replay' attacks, for example presenting a face recognition system with a photograph of an individual, reveal the necessary further steps if the technology is to be considered safe. Inevitably though, it is the massive strides in communications and processing technology that are visible in the contributions to this volume that point to where most of the advances will come. The massive interconnection issue of numerous sensors, the `nervous system' of the building is approached in items covering the complexities of fieldbus systems and the use of `wireless' in-building networks. This well presented volume with good quality illustration ends in an investigation of system technologies for the automated home of the near future. Presence-controlled heating and air-conditioning, telemonitoring of the sick or elderly, gas and fire detection and of course a high data rate communication backbone to link everything: all these could feature in the future household. We shall see. Peter Foote
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paper_title: Current and Voltage Reconstruction From Non-Contact Field Measurements

paper_content:

Non-contact electromagnetic field sensors can monitor voltage and current in multiple-conductor cables from a distance. Knowledge of the cable and sensor geometry is generally required to determine the transformation that recovers voltages and currents from the sensed electromagnetic fields. This paper presents a new calibration technique that enables the use of non-contact sensors without the prior knowledge of conductor geometry. Calibration of the sensors is accomplished with a reference load or through observation of in situ loads.
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paper_title: An integrated system for buildings’ energy-efficient automation: Application in the tertiary sector

paper_content:

Although integrated building automation systems have become increasingly popular, an integrated system which includes remote control technology to enable real-time monitoring of the energy consumption by energy end-users, as well as optimization functions is required. To respond to this common interest, the main aim of the paper is to present an integrated system for buildings’ energy-efficient automation. The proposed system is based on a prototype software tool for the simulation and optimization of energy consumption in the building sector, enhancing the interactivity of building automation systems. The system can incorporate energy-efficient automation functions for heating, cooling and/or lighting based on recent guidance and decisions of the National Law, energy efficiency requirements of EN 15232 and ISO 50001 Energy Management Standard among others. The presented system was applied to a supermarket building in Greece and focused on the remote control of active systems.
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paper_title: A WSN-based testbed for energy efficiency in buildings

paper_content:

Residential and business buildings account for a large fraction of the overall world energy consumption. Despite the high energy costs and the raising awareness about the impact on climate changes, a significant part of energy consumption in buildings is still due to an improper use of electrical appliances. In this paper we propose GreenBuilding, a sensor-based system for automated power management of electrical appliances in a building. We implemented GreenBuilding as a prototype system and deployed it in a real household scenario to perform a prolonged experimental analysis. The obtained results show that GreenBuilding is able to provide significant energy savings by using appropriate energy conservation strategies tailored to specific appliances.
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paper_title: A Novel Approach for Fault Location of Overhead Transmission Line With Noncontact Magnetic-Field Measurement

paper_content:

Prompt and accurate location of faults in a large-scale transmission system can accelerate system restoration, reduce outage time, and improve system reliability. Traditional approaches are categorized into traveling-wave-based and impedance-based measurement techniques. The traveling-wave-based approach requires detection devices to connect to the high-voltage transmission line, making the solution complex and costly. And the impedance-measurement-based approach is highly dependent on the quality of the signal and affected by fault resistance, ground resistance and non-homogeneity in line configuration. Hence, these approaches may cause a location error that is unacceptable in certain operation cases. In this paper, a novel approach based on noncontact magnetic-field measurement is proposed. With the magnetic field measured along the transmission line by using highly sensitive, broadband, and a low-cost magnetoresistive magnetic sensor, the fault span can be located. The collected data can be further used for identifying the fault type and location within the fault span. The overall system was designed and numerical simulations were performed on typical tower configurations. The simulated results verify the validity of the proposed scheme.
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paper_title: Challenges in reliability, security, efficiency, and resilience of energy infrastructure: Toward smart self-healing electric power grid

paper_content:

This article deals with the challenges in reliability, security, efficiency, and resilience of energy infrastructure for a smart self-healing electric power grid. The electricity grid faces three looming challenges: its organization, its technical ability to meet 25 year and 50 year electricity needs, and its ability to increase its efficiency without diminishing its reliability and security. These three are not unrelated, as the grid's present organization reflects an earlier time when electrification was developing, objectives and needs were simpler, and today's technology was still over the horizon. Given economic, societal, and quality-of-life issues and the ever-increasing interdependencies among infrastructures, a key challenge before us is whether the electricity infrastructure will evolve to become the primary support for the 21st century's digital society a smart grid with self-healing capabilities or be left behind as an 20th century industrial relic.
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paper_title: Effect of sag on transmission line

paper_content:

This paper looks into the factors affecting sag in conductors while erecting an overhead line, it is very important that conductors are under safe tension. If the conductors are too much stretched between supports, the stress in the conductor may reach unsafe value and in certain cases the conductors may break due to excessive tension. The conductor sag should be kept to a minimum in order to reduce the conductor material required and to avoid extra pole height for sufficient clearance above ground level. It is also desirable that tension in the conductor should be low to avoid the mechanical failure of conductor and to permit the use of less strong supports. The effects of sag on electrical construction were examined. Also, a look into the solution to effect of sag were examined. The meaning sag was not left out. This write up suggested ways to reduce the effect of sag on overhead line conductors.
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paper_title: Design, installation, and field experience with an overhead transmission dynamic line rating system

paper_content:

Dynamic line rating (DLR) systems for high voltage overhead transmission lines have been installed by three utilities over the past five years. These DLR systems utilize the Power Donut/sup TM/ to measure load and conductor temperature at several locations over the length of the circuit. The effective wind acting on the conductor at each site is determined in real-time by a dynamic heat balance and used to compute the normal, LTE and STE ratings each minute. The lowest ratings of all locations define the circuit's ratings and are sent to SCADA as analog signals. This method is known as the conductor temperature model (CTM) as opposed to the weather model (WM) which calculates ratings using weather data only. These first DLR installations have also measured weather parameters at each ground station location to allow a comparison of the two methods. Data from the latest of these systems is presented and the behavior of the real time ratings are discussed.
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paper_title: A vehicle detection algorithm based on wireless magnetic sensor networks

paper_content:

At present, the research of parking management system based on Wireless Sensor Networks (WSN) and Anisotropic Magneto Resistive (AMR) sensors have made great progress. However, due to the diversity of the vehicle magnetic signal and the interference caused by the adjacent parking spaces, vehicle detection technique using wireless magnetic sensor networks is still immature. For accurately detecting a parking vehicle in a parking lot, we propose a detection algorithm named Relative Extremum Algorithm (REA). On the parking lot at Shenzhen Institutes of Advanced Technology (SIAT), 82 sensor devices are deployed to evaluate the performance of REA. By running the system for more than half a year, we observe that the vehicle detection accuracy of the REA is above 98.8%.
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paper_title: Reducing emergency services response time in smart cities: An advanced adaptive and fuzzy approach

paper_content:

Nowadays, the unprecedented increase in road traffic congestion has led to severe consequences on individuals, economy and environment, especially in urban areas in most of big cities worldwide. The most critical among the above consequences is the delay of emergency vehicles, such as ambulances and police cars, leading to increased deaths on roads and substantial financial losses. To alleviate the impact of this problem, we design an advanced adaptive traffic control system that enables faster emergency services response in smart cities while maintaining a minimal increase in congestion level around the route of the emergency vehicle. This can be achieved with a Traffic Management System (TMS) capable of implementing changes to the road network's control and driving policies following an appropriate and well-tuned adaptation strategy. This latter is determined based on the severity of the emergency situation and current traffic conditions estimated using a fuzzy logic-based scheme. The obtained simulation results, using a set of typical road networks, have demonstrated the effectiveness of our approach in terms of the significant reduction of emergency vehicles' response time and the negligible disruption caused to the non-emergency vehicles travelling on the same road network.
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paper_title: Green Transport System: A Technology Demonstration of Adaptive Road Lighting with Giant Magnetoresistive Sensor Network for Energy Efficiency and Reducing Light Pollution

paper_content:

To enhance energy efficiency and reduce light pollution of overnight road lighting in suburban traffic, we propose a novel green transport system based on giant magnetoresistive (GMR) sensors. The basic principle is to detect the perturbation to the earth magnetic field by a ferrous vehicle with GMR sensors. This system can switch on the road lighting to full illumination gradually before the motor vehicle arrives and dim it out after the vehicle leaves without the driver noticing. Based on a sparse suburban road in the countryside of Hong Kong, a demonstration model was constructed to illustrate its feasibility. GMR sensors and the associated electrical energy control components including signal processors, relays, and dimmers were integrated into a complete system. The experimental result indicates that the sensing principle is feasible and the whole system can function together coherently to achieve over 90% energy saving. Such system can be scaled up to be implemented in real road conditions.
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paper_title: Train Detection by Magnetic Field Measurement with Giant Magnetoresistive Sensors for High-Speed Railway

paper_content:

Train detection, as part of the railway signaling system, is important for safe operation of high-speed railway. The recent flourishing development of high-speed railway stimulates the research need of train detection technology to enhance the safety and reliability of train operation. This paper proposes a new technique for train detection through magnetic field measurement by giant magnetoresistive sensors. This technology was studied by the analysis of magnetic field distribution in the high-speed rail system obtained from modeling and simulation. The results verify the feasibility for detection of train presence, number of rolling stocks, speed, and length. It can overcome the limitations of track circuits and provide additional measurement capabilities to the signaling system. This detection system can be built with low cost and minimal maintenance load as well as compacted construction. Therefore, it may serve as a new train detection system to help improve the current systems, enhancing and promoting the safety and reliability of high-speed rail system.
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paper_title: Wireless sensor networks for traffic management and road safety

paper_content:

Wireless sensor networks (WSN) employ self-powered sensing devices that are mutually interconnected through wireless ad-hoc technologies. This study illustrates the basics of WSN-based traffic monitoring and summarises the possible benefits in Intelligent Transport Systems (ITS) applications for the improvement of quality and safety of mobility. Compared with conventional infrastructure-based monitoring systems, this technology facilitates a denser deployment of sensors along the road, resulting in a higher spatial resolution of traffic parameter sampling. An experimental data analysis reported in this study shows how the high spatial resolution can enhance the reliability of traffic modelling as well as the accuracy of short-term traffic state prediction. The analysis uses the data published by the freeway performance measurement system of the University of California-Berkeley and the California Department of Transportation. A microscopic cellular automata model is used to estimate traffic flow and occupancy over time on a road segment in which a relevant traffic-flow anomaly is detected. The analysis shows that the estimate accuracy improves for increasing number of active sensors, as feasible in the case of WSN-based monitoring systems.
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paper_title: A Communications-Oriented Perspective on Traffic Management Systems for Smart Cities: Challenges and Innovative Approaches

paper_content:

The growing size of cities and increasing population mobility have determined a rapid increase in the number of vehicles on the roads, which has resulted in many challenges for road traffic management authorities in relation to traffic congestion, accidents, and air pollution. Over the recent years, researchers from both industry and academia have been focusing their efforts on exploiting the advances in sensing, communication, and dynamic adaptive technologies to make the existing road traffic management systems (TMSs) more efficient to cope with the aforementioned issues in future smart cities. However, these efforts are still insufficient to build a reliable and secure TMS that can handle the foreseeable rise of population and vehicles in smart cities. In this survey, we present an up-to-date review of the different technologies used in the different phases involved in a TMS and discuss the potential use of smart cars and social media to enable fast and more accurate traffic congestion detection and mitigation. We also provide a thorough study of the security threats that may jeopardize the efficiency of the TMS and endanger drivers' lives. Furthermore, the most significant and recent European and worldwide projects dealing with traffic congestion issues are briefly discussed to highlight their contribution to the advancement of smart transportation. Finally, we discuss some open challenges and present our own vision to develop robust TMSs for future smart cities.
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paper_title: Wireless sensor networks for healthcare: A survey

paper_content:

Becoming mature enough to be used for improving the quality of life, wireless sensor network technologies are considered as one of the key research areas in computer science and healthcare application industries. The pervasive healthcare systems provide rich contextual information and alerting mechanisms against odd conditions with continuous monitoring. This minimizes the need for caregivers and helps the chronically ill and elderly to survive an independent life, besides provides quality care for the babies and little children whose both parents have to work. Although having significant benefits, the area has still major challenges which are investigated in this paper. We provide several state of the art examples together with the design considerations like unobtrusiveness, scalability, energy efficiency, security and also provide a comprehensive analysis of the benefits and challenges of these systems.
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paper_title: Cloud-enabled wireless body area networks for pervasive healthcare

paper_content:

With the support of mobile cloud computing, wireless body area networks can be significantly enhanced for massive deployment of pervasive healthcare applications. However, several technical issues and challenges are associated with the integration of WBANs and MCC. In this article, we study a cloud-enabled WBAN architecture and its applications in pervasive healthcare systems. We highlight the methodologies for transmitting vital sign data to the cloud by using energy-efficient routing, cloud resource allocation, semantic interactions, and data security mechanisms.
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paper_title: nanoLAB: An ultraportable, handheld diagnostic laboratory for global health

paper_content:

Driven by scientific progress and economic stimulus, medical diagnostics will move to a stage in which straightforward medical diagnoses are independent of physician visits and large centralized laboratories. The future of basic diagnostic medicine will lie in the hands of private individuals. We have taken significant strides towards achieving this goal by developing an autoassembly assay for disease biomarker detection which obviates the need for washing steps and is run on a handheld sensing platform. By coupling magnetic nanotechnology with an array of magnetically responsive nanosensors, we demonstrate a rapid, multiplex immunoassay that eliminates the need for trained technicians to run molecular diagnostic tests. Furthermore, the platform is battery-powered and ultraportable, allowing the assay to be run anywhere in the world by any individual.
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paper_title: Point of Care Diagnostics: Status and Future

paper_content:

Introduction A Why POC Diagnostics? B Time B Patient Responsibility and Compliance B Cost B Diagnostic Targets C Proteins C Metabolites and Other Small Molecules C Nucleic Acids C Human Cells D Microbes/Pathogens D Drugs and Food Safety D Current Context of POC Assays E POC Glucose Assays E Lateral Flow Assays E Limitations of “Traditional” POC Approaches F Enabling Technologies G Printing and Laminating G Microfluidic Technologies and Approaches: “Unit Operations” for POC Devices G Pumping and Valving H Mixing I Separation I Reagent Storage J Sample Preparation K Surface Chemistry and Device Substrates L Physical Adsorption L Bioaffinity Attachment L Covalent Attachment M Substrate Materials M Detection M Electrochemical Detection N Optical Detection N Magnetic Detection N Label-Free Methods O Enabling Multiplexed Assays O Recent Innovation O Lateral Flow Assay Technologies O Proteins P Antibodies P Protein Expression and Purification Q Nucleic Acids Q Aptamers R Infectious Diseases and Food/Water Safety R Blood Chemistry S Coagulation Markers S Whole Cells S Trends, Unmet Needs, Perspectives T Glucose T Global Health and the Developing World T Personalized Medicine and Home Testing U Technology Trends U Multiplexing V Author Information V Biographies V Acknowledgment W References W
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paper_title: Improving Healthcare Accessibility through Point-of-Care Technologies

paper_content:

Background: The NIH is committed to improving healthcare quality in the US and has set up initiatives to address problems such as the fragmented nature of healthcare provision. A hypothesis has been developed that testing closer to the point at which care is delivered may reduce fragmentation of care and improve outcomes. Methods: The National Institute of Biomedical Imaging and Bioengineering (NIBIB), the NIH’s National Heart, Lung, and Blood Institute, and the National Science Foundation sponsored a workshop, “Improving Health Care Accessibility through Point-of-Care Technologies,” in April 2006. The workshop assessed the clinical needs and opportunities for point-of-care (POC) technologies in primary care, the home, and emergency medical services and reviewed minimally invasive and noninvasive testing, including imaging, and conventional testing based on sensor and lab-on-a-chip technologies. Emerging needs of informatics and telehealth and healthcare systems engineering were considered in the POC testing context. Additionally, implications of evidence-based decision-making were reviewed, particularly as it related to the challenges in producing reliable evidence, undertaking regulation, implementing evidence responsibly, and integrating evidence into health policy. Results: Many testing procedures were considered to be valuable in the clinical settings discussed. Technological solutions were proposed to meet these needs, as well as the practical requirements around clinical process change and regulation. From these considerations, a series of recommendations was formulated for development of POC technologies based on input from the symposium attendees. Conclusion: NIBIB has developed a funding initiative to establish a Point-of-Care Technologies Research Network that will work to bridge the technology/clinical gap and provide the partnerships necessary for the application of technologies to pressing clinical needs in POC testing.
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<format>
Title: Overview of Spintronic Sensors, Internet of Things, and Smart Living

Section 1: Introduction
Description 1: Introduce the concept of smart living and the role of IoT and spintronic sensors in achieving it.

Section 2: Spintronic sensors
Description 2: Explain the basic principles and different types of spintronic sensors, along with their fabrication and sensing capabilities.

Section 3: Winning combination: IoT and spintronic sensors
Description 3: Provide a brief introduction to the concept and architecture of IoT, and discuss how wireless spintronic sensor networks (WSSNs) can be integrated into the IoT platform.

Section 4: IoT and spintronic sensors enabling smart living
Description 4: Discuss how WSSN-based solutions can support smart building, smart grid, smart transport, and smart healthcare applications.

Section 5: Conclusion and outlook
Description 5: Summarize the paper and provide future directions for the development and integration of spintronic sensors and IoT for smart living.
</format>
