Hello everyone welcome to this session I am Priyanka Bansore and today we are going to study about working of TACO generator. These are the learning outcomes of this video lecture at the end of this session students will be able to explain construction principle and operation of TACO generator and explain types of TACO generator. These are the contents we will be covering in this session. Before moving towards pause this video for few seconds and you have to think and write the difference. Do you know the difference between TACO meter and TACO generator? Let us see the difference between TACO meter and TACO generator. So first TACO meter consist of TACO generator and TACO generator is usually referred as permanent magnet DC brush generator. Then next a TACO meter is just a display for human readings and a TACO generator can be a part of control loop. Then next a TACO meter is an instrument that measures and displays rotational speed. But TACO generator is an electric generator that generates a voltage that is accurately proportional to the speed of the shaft. Now we will see in detail about TACO generator. The word TACO generator comes from the Greek word TACO. So TACO generator consist of two words that is TACO plus generator. In Greek TACO means speed and the generator means an instrument which generate power. So here the figure shows the TACO generator and shaft. TACO generator is a device which is used for measuring the speed of shaft and converting this speed into a voltage so that it can be measured. So voltage is measured through this voltmeter. Common voltage signal used with TACO generators is 0 to 10 volts. We see the types of TACO generator. There are two types of TACO generator. So first AC TACO generator and second DC TACO generator. First we see about AC TACO generator. The AC TACO generator is a small brushless alternator with a rotating multiple permanent magnet. In AC TACO generator the armature is provided with an AC winding either single phase or three phase winding and the output voltage is measured by a voltmeter although the varying frequency will affect the accuracy of this instrument. Now we see the construction and working of AC TACO generator. So here the AC TACO generator consists of permanent magnet then rectifier for converting AC output into the DC then smoothing circuit moving coil voltmeter and the rotor where the speed is to be measured. When the rotor is stationary no AMF is induced in the output winding and primary winding excited by an AC input voltage. The induced voltage in secondary is 0 due to relative position of two windings being placed at 90 degrees to each other. Then as the rotor rotates a voltage is induced in the secondary winding whose magnitude is proportional to the rotor speed and then EMF is induced in the quadrature coil and this EMF is directly proportional to the rotor speed. So here the equation is VT is equal to kT phi of T where VT is the voltage and phi of T is the rotor speed and kT is nothing but it is the TACO generator constant and is in phase with applied voltage to the reference coil. We see about DC TACO generator. A DC TACO generator is a small DC generator which has to generate electrical voltage corresponding to the speed of rotating machine. Then the produced voltage is dynamically induced EMF. Dynamically induced EMF means what? When the conductor is in motion and the field is in stationary and EMF is induced in the conductor and this type of EMF is called dynamically induced EMF. The requirement of this EMF is to establish necessary flux in the field and also system of conductors is required so that a relative motion between the flux and the conductor create rate of change of flux linkage and generate the DC voltage. So the field system may be in the form of electromagnet or permanent magnet and it is stationary part of the DC TACO generator. So now we see the construction and working of DC TACO generator. So here the DC TACO generator consists of permanent magnet, moving coil voltmeter and shaft for speed measuring. Same as the AC TACO generator but here no need of rectifier because already output is in DC form. Then the series resistance is used to limit the current under output short circuit condition. Then the polarity of output voltage indicates the direction of rotation. Then the commutator collects the current from the armature conductors and converts internally induced AC EMF into the DC EMF. Then brushes are used to collect current from commutator and make it available to external circuitry of the DC TACO generator. So this is the construction about the DC TACO generator actually DC TACO generator is based on the principle of Faraday's law of electromagnetic induction. According to the law when a conductor move in a magnetic field it cut the magnetic lines of force due to which an EMF is induced in the conductor. We know that the magnitude of induced EMF depends upon the rate of change of magnetic flux linkage with the conductor. Now we see the working principle of DC TACO generator. So first the armature of DC TACO generator is kept in a permanent magnetic field and the armature of TACO generator is coupled to the machine whose speed is to be measured. When the shaft of the machine revolves the armature of the TACO generator also revolves in the magnetic field producing EMF which is proportional to the product of flux and speed to be measured. As the field of permanent magnet is fixed the EMF generated is proportional to the speed directly. And this generator EMF is measured using moving coil rule meter. We see the difference between AC and the DC TACO generator. So first difference is in AC TACO generator speed is measured only in one direction and in DC TACO generator speed is measured in both direction. Then next in AC TACO generator rectifier is needed because here we have to convert AC output into the DC but in DC TACO generator already output is in DC form. So no need of rectifier. Then next here ripples are reduced in AC TACO generator and small ripples are appearing at the output in DC TACO generator. And then the last one maintenance is difficult in AC TACO generator and maintenance is easy in DC TACO generator. So these are the some points between the AC TACO generator and the DC TACO generator. Now we see the advantages of TACO generator. First it is simple in construction and design then it is not expensive. It has a linear relationship between output and the rotational speed. It requires less maintenance and temperature compensation is also simple. It is advantages of TACO generator. So first it is limited to low speed and tachometers are hard to calibrate. These are the applications of TACO generator. So first is majoring rotating speed of disk or shaft. This is the main application of TACO generator. Then it is used in automobile speedometer. It is used in industries and rail for controlling motor and speed respectively. These are the some references of this video lecture. Thank you.


The researchers have discovered two-dimensional, 2D, porphyrin frameworks with giant magnetic and isotropy energies, MAEs, which could be used as promising candidates for future spintronic applications. They replaced the hydrogen atoms on the edges of the re-based 2D porphyrin framework with hydroxyl and amino radicals, resulting in an increase of MAE from 24 MeV to 60 MeV. This was due to the charge redistributions and energy shifts of the Re5D orbitals caused by the functional radicals. These results suggest that the incorporation of functional radicals into 2D porphyrins may provide a viable route towards the development of magnetic organic materials with tunable MAE for use in spintronic applications. This article was authored by Peng Wang, Xue Jiang, Jun Hu, and others.


Hi, this is Neil Oliver and this is Sinura Gaddam. We are architects in the network platforms group at Intel. Our topic is edge computing platform architecture. Intel has worked in this domain for several years contributing to standards, open source code and products, and we are seeing strong growth in the market and among our ecosystem partners. The topic we are presenting here is the architectural style of cloud native computing as applied to edge computing. While we started originally by implementing an edge computing platform, we are devoting significant attention to the development of microservices, which are one of the fundamental features of cloud native computing. We will describe our cloud native architecture and draw attention to the areas where the cloud native style is impacted by deployment on the edge, and then talk about a few interesting microservices which emerged from our investigation into these use cases. Cloud native computing is an approach to building systems that run in the cloud. In the cloud, the number of users of a system is not only large, but may increase or decrease over orders of magnitude. And so the system itself must be able to scale over orders of magnitude. Because the user base is large, the system must be always on. The cloud has no downtime. But since no computing components, hardware or software are infinitely reliable, a system in the cloud must be reliable even when built from unreliable components. The cloud native approach has had considerable success in creating scalable resilient systems. So cloud applications are everywhere, providing services to consumers and businesses. Edge computing at a high level can be thought of as cloud computing where the physical location of the cloud matters. An edge computing network can be thought of as a cloud with special constraints. And so cloud native techniques ought to be applicable to edge networks. We will call this an edge native system and we'll talk about it for a few minutes. We will then move from theory to practice and talk about the Open Network Edge Services Software, OpenNES project, and its approach to edge native computing, covering both the platform architecture that enables it and the microservices which it employs. Cloud native computing does not have a precise rigorous definition. It is partly a class of computer network architecture, partly a style of software engineering, and partly an organizational style and mindset for IT. Over the last few years of widespread use, however, there is a consensus on its basic tenets. Stateless processing means that components of a system should not own their states such as user information databases, but should retrieve it from external data sources where necessary. This is needed for resilience and scalability. New components can be started in a uniform manner, whether to increase capacity or to recover from a crash. Statelessness allows applications to scale out by increasing the number of compute components. Microservices follow from the tenet of statelessness. Microservice is a much overloaded term, particularly the micro part, but it is basically a function that does a particular set of tightly related actions efficiently and is networked to other microservices. Applications and complex systems are expected to be built by composition, connecting microservices together. The connection method is usually a REST, a representational state transfer API, which is also a way that a microservice can remain stateless. Strictly speaking, open source software is not a fundamental tenet of cloud native computing, but historically cloud native computing came from organizations with a habit of contributing software to open source. These organizations, however, often take themselves take a hybrid approach, releasing community editions of software to open source, but retaining a highly maintained high performance version for their mission critical and proprietary requirements. Finally, the deployment of cloud native software is carried out by a standard building blocks and run by standard processes. Virtual machines and containers are widely used and orchestration frameworks and tools built on them, such as helm charts and operators, formalize deployment and make them easier to debug and maintain. There are various definitions of edge. Some definitions place the edge in an embedded system, such as a cabinet or enclosure in an outdoor environment. Others consider it to be a server cluster located at a telco central office or even a regional data center. The variations are determined by use cases, but what they all have in common is that they are responding to the laws of physics and sometimes the laws of nations, for example data sovereignty. Edge native computing makes some important changes in the cloud native tenets. The most obvious differences come from the physical constraints of an edge cluster. It is safe to say they are more constrained in size and power and therefore compute in network capacity than a data center. The number of distinct edge cluster locations, like separated by wide area networks, is larger as well. Thus, the scale out approach of cloud native orchestration is no longer homogeneous. Past a certain capacity, the scale out reaches out to other edge clusters. But time sensitive applications must be located close enough to their data sources to work, so an orchestrator will ultimately have to optimize for compute capacity and density in an edge cloud. Depending on the workloads, optimizing for compute density will require the use of accelerators such as GPUs, NPUs, or FPGAs. Orchestrators must take these additional constraints into account. Finally, data sources reach the edge application via access networks. For many important use cases, these are mobile networks which have control and data plane separation and full sets of protocols and APIs which must be used to steer data plane traffic to edge applications. The net effect is that an edge native system has more moving parts, more heterogeneity, and more constraints in operation than a cloud native system. Well, that was all somewhat theoretical. We will now move toward an example of an edge native system, specifically the Open Network Edge Services Software or OpenNES Toolkit. OpenNES is a software toolkit that enables the construction of high-performance edge platforms. It is designed to provide cloud features to edge clusters within the edge native constraints described in the previous slide. The features listed in this slide depict the range of features supported, which enables commercial deployments. Implicit in this list is that the microservice approach to creating features enables real-world deployments. Now let's look at the OpenNES platform level architecture. Depicted here are a representative edge node on which edge applications execute and a controller which is used to deploy and manage edge nodes. An edge cluster consists of one or more edge nodes. Multiple edge nodes may be associated with one controller. Note that I said representative. The green and blue blocks in the diagram are microservices. Not all OpenNES microservices are shown here because not all microservices of an OpenNES distribution need be in a given configuration. The platform is based on Kubernetes. Thus, many of the microservices shown here are containers grouped together in pods so that they can be deployed together. OpenNES supports virtual machines for applications, but does so via KubeVert rather than natively. The color coding and stacking of various subsystems suggests a certain layer cake design, but this is more for ease of explanation. The microservices actually interact with each other via a container network. Cloud native design allows for elements to be deployed in a coordinated manner, and we follow that rule too. The color coding does indicate where the building blocks come from. Blue blocks are standard open source ingredients. On the left side of the figure, we see CentOS, the host operating system, and Docker for low-level container management. Elsewhere, you can see the standard Kubernetes components, KubeProxy, KubeNet, KubeCTL, etc., that comprise a working Kubernetes cluster. This is a stock Kubernetes distribution, although with optimizations it until is upstreamed into open source. The green blocks are OpenNES components. Most of them are microservices, although some of them might be more accurately called ingredients or enhancements or plugins. The first pod we will look at is the Container Networking Interface, C&I pod. This platform uses KubeOVN as a default C&I, but can support other C&Is as well, such as Weave or Calico. Because many edge applications require multiple ports, OpenNES uses the Multis C&I to support this functionality. We will now move to the system pods. These microservices enable time-sensitive applications and other tenant-of-edge native computing. Time-sensitive applications need to have fine control over app deployment, over sequestered cores, a selection of numinodes, availability of special instructions, or other features. These microservices enable the controller microservices to control app deployment. The platform pods exist for a similar reason. In this case, rather than fine-grain control of the CPUs, these microservices are used to support computing and network accelerators. When an application is deployed, in addition to selecting a destination with enough computing headroom, it can also select a candidate cluster with required special purpose hardware and control the hardware as they are configured. These microservices are specialized for certain families of hardware and work with other microservices in the controller. Moving over to the controller, the OpenNES microservices work with the edge node microservices, harvesting information from edge nodes and making orchestration decisions based on that information. The information received includes capabilities and attributes, as well as telemetry information. The remaining blocks to mention here have to do with the access network. The OpenNES configuration shown here assumes a connection to a mobile network, either 4G or 5G. The blocks along the bottom of the diagram are radio access network and core network. The mobile network and the edge platform must cooperate to steer traffic from the network to edge applications. OpenNES provides reference implementations of the core network building blocks, as well as a special controller microservice, the core network configuration agent, CNCA, to accomplish this. We will explain this in more detail later in the talk. Before moving on to microservices, a few more comments about CNI networks. Edge applications are often very time sensitive. They have requirements on latency and or jitter in order to function properly, such as gaming apps which need to minimize lag or public safety applications which need to be able to respond to signals raised by algorithms in a timely manner. Networking between microservices must be able to support these requirements. The CNCF community accepted a project, the CNI project, to develop specifications for container network interfaces for Linux containers. Today, there is a growing list of CNI implementations, such as Calico, Veev or SRIOV. OpenNES works with many of these, and the installation charts provides procedures for installing them when configuring on OpenNES system. For time sensitive application support, OpenNES in particular adopts OVN or OVS virtual networking. The cube OVN CNI may be used as well as enhanced CNI based on the data plane development DPDK. This is OVS DPDK. The multis CNI is configured by default, as many edge applications require multi-port for their functionality. A key microservice included in OpenNES is Topology Manager. This microservice, which is now supported in Kubernetes, makes the orchestrator NUMA aware for optimum deployment of time sensitive net edge applications. With the multi-core and multi-socket CAUTH system, which provide a variety of memory and IO features, an application whose CPU memory and IO are not located on the same socket or NUMA node will have degraded performance. The Topology Manager microservice allows resources to be inventoried and tagged. When the container containing an application is deployed, the same Kubernetes mechanisms, CPU manager and device manager that uses the labels to select a platform can also select for appropriate hardware on the same NUMA node. An example of this might be a video analytics application that must run on the same NUMA node where the network card supplying its input stream is located. The next microservice we will discuss is the Node Feature Discovery or NFT. CAUTH's platforms used for edge deployment come with many hardware features to provide better performance and meet the SLA. The features may be intrinsic to the CPU, such as special instruction sets, or maybe external, such as GPUs, TPUs, FPGA, non-volatile memory, et cetera. For these features to be used, they must be discovered and tracked within the controller. Let's take an example. A container network function or CNF, such as 5G G node B, that implements the layer one of base station. This CNF needs to have hardware that includes FPGA acceleration for forward error correction, vector instructions in the CPU to implement the math functions, and a real-time host operating system, and so on. The NFT microservice, which is implemented in Kubernetes as an add-on, provides this feature. There is an NFT worker component that inspects the edge platforms for hardware and software capabilities. An NFT worker puts this information in an ETCD database where the NFT control uses it to perform scheduling. Our G node B would therefore be automatically scheduled on a node that has the hardware capabilities that it requires. The next microservice to discuss is telemetry aware scheduler. It enables the user to make Kubernetes scheduling and scheduling decisions using telemetry information. The telemetry allows the scheduler to observe metrics such as CPU or network utilization and react to performance bottlenecks by moving applications to different nodes. Like node feature discovery, this is an add-on to the Kubernetes scheduler developed by Intel and used by OpenNAS. The app developer is able to create a set of policies defining the rules to which port placement must adhere. The Kubernetes scheduler has the ability to trigger an action if the policy is violated. Policies can be applied on a workload-by-workload basis, allowing the right indicators to be used to place the port. The TAS may collect metrics from many sources, but in particular supports metrics received from the Intel Resource Director Technology, RGT, and Reliability, Availability, and Serviceability Metrics provided by Intel on CPUs. The final topic we will consider is the integration of OpenNAS with a mobile network. This talk is not the place to discuss all of mobile network architecture. The standards run to thousands of pages and are different for LTE and 5G networks. The important part for this talk is that the mobile network routes data from the user equipment, or UE, I think, phone or tablet to the endpoint where it is connected to the Edge platform. We will restrict ourselves to the 5G network and will only cover a few of the network functions of 5G. The white boxes depict the primary 5G network functions. There are numerous other functions that we are not going to cover. This description is not specific to Edge computing. It is a way that any 5G network operates. In this diagram, the UE is user equipment, the phone or tablet are similar equipment. The genode B is the base station and other functions that deal with the radio signal and turn it into an IP stream. The application function, or AF, provides services relating to applications. For example, applications need to steer traffic from the UE to the application and configure various mobile network configurations. The network exposure function, or NEF, provides an interface so that untrusted third parties such as, for example, an Edge native platform can request the mobile network to steer traffic. The NEF is already designed as a service by the 3GPP standards. It provides its own API used by other services and the openness framework will also use it. The UPF performs routing and filtering functions for data flows. It receives traffic from the genode B and from data networks and forwards it based on policies and filtering rules that are set up by the functions of the control plane. In general, multiple UPFs exist in a 5G network and they may forward user data between each other. Data routing from one UPF to another might happen in order to make sure that a data flow reaches a selected Edge node. Finally, the data network, or DN, is the opposite end of data sessions with the UE. For us, the DN is the Edge platform. Now we move back to the openness platform architecture you see in the upper left-hand corner focusing on the mobile network blocks, the main part of the diagram. The gray blocks in this diagram come from the previous slide. The green blocks are provided by openness as before. The NEF is a reference implementation provided by openness. It interacts with the rest of a 5G network following the 3GPP standard. The AF, or application function, is a reference implementation that interacts with the NEF via the standard 3GPP APIs and also provides application interfaces that allow it to talk to other network functions, in particular to the CNCA. The CNCA, or core network configuration agent, is a microservice that is part of the controller. It is a function that knows both where the Edge platform is in terms of IP addresses and where the NEF is. It can therefore steer data flows from a particular UE to a particular Edge application. It provides an API to allow it to be used by a telco operation support system and also a user interface so it can be controlled by a system operator. In other words, the AF and NEF are reference implementation microservices that implement 3GPP network functions on the one hand and provide APIs that allow the controller microservices to steer data flows on the other hand. There is an equivalent set of network functions for LTE, but we won't go into them here and they work somewhat similarly. Because of the complexity of mobile networks and because telco networks configure and operate their networks in many different ways, these microservices are only reference implementations. But they provide a starting point for an operator wanting to use the OpenNES toolkit to add Edge computing services to their network. The previous two slides talked about enabling a mobile network to steer traffic to an Edge application. But Edge platforms can also host mobile network components. In the previous slides, the AXIS network or Gnode B was just a single box. In reality, it is a very complex function requiring very demanding real-time processing. It is often implemented with special purpose hardware. But one configuration of OpenNES Edge platform consists of implementation of Gnode B. The RAM architecture in the diagram comes from the ORAN reference architecture published by the OpenRadio AXIS Network Alliance. In the configuration shown here, the application consists of distributed unit or DU functions following the ORAN reference architecture. The DU is deployed as a pod in which various physical and link-level functions execute. The 5G code can also be hosted by OpenNES Edge nodes. In this case, two different Edge nodes are employed. One is for the user plane in which UPF network functions are run and the other for the control plane in which AF and NEF functions are run. The advantage of running 5G RAM and co-functions in an Edge platform is that the network functions can be moved closer to one another than if they were in discrete components, which improves performance. It also allows functions of a mobile network to be converged into a single server, which can then be deployed with much more flexibility. We have covered a lot of ground in the last 30 minutes. We discussed the concept of cloud-native computing and how it applies to Edge computing. After this theory, we then took a specific example, the OpenNES toolkit, which provides both a platform for executing Edge microservices and also a growing catalog of microservices. We discussed the CNI network, the topology manager, node feature discovery, telemetry aware scheduling microservices and building blocks. We talked about why they are implemented and how they are used. This talk only scratched the surface of a very large topic. We invite you to visit the OpenNES website, www.openness.org to browse through our engineering white papers and to download and evaluate the toolkit yourself. We hope you have found this talk interesting and informative. Thank you for your attention and have a nice conference. Bye. Bye.


So you probably know that vinyl beats are important for lucid dreaming or at least you know they help you do it They really do So you're probably wondering also Which ones do you listen to right because there are so many vinyl beats on YouTube? There are you know thousands probably millions of videos Which you know are free to listen to of course But do they actually work okay, and that's the question I want to just explain today So you know you might be considering trying to use one of these YouTube video by neural beats to have a lucid dream And yes, they do work, but in my opinion I just found that they aren't as good quality as the ones you buy And that's because you know one of two reasons firstly the people that made them Want to put more effort into the things they're selling because you know they're getting money for it as opposed to just giving it out for free Which is fine by the way giving stuff out for free But you know people want some sort of compensation if they put a lot of effort into something And secondly, you know they just by by having something that they can sell They're able to invest more in sound quality better microphones better sound mixing studios better sound editing software that sort of stuff So you know in a nutshell the most generally with vinyl beats the more expensive and sort of luxury They are the better. They'll work because more effort has gone into producing them To bang out a YouTube video, you know, you can make by neural beats that do work And that are you know, they do give a binary or frequency and you can sort of get some results from them I mean, I've made two of them Which I have posted for free on YouTube, but they're not as good as the ones you can buy And when I say the ones you can buy I mean the ones which they usually come in like a sort of package where you download or have access to Several by no beats and they're sort of like an album So from my experience personally The best by no beats or isochronic tones That I've that I've tried and tested are the ones from in aura From the unexplainable store and and this isn't by no beats or this isn't brainwave entrainment But from bliss coded sound now, but let me just explain a bit about all of those So in aura is generally by no beats packages for lucid dreaming for things like, you know Meditation improved awareness cognitive function that sort of stuff. They're like you or sort of your basic Binary beats Producers or company as if you will Then you've got the unexplainable store, which is focused slightly more towards the spiritual side of things So you've got things for astral projection. You've got things for spirituality for third eye awakening that sort of stuff Which it was is great, you know, depending on sort of where you are on the spiritual spectrum and where what you sort of believe in and I mean, some people don't believe in astral projection Some people don't believe in the whole third eye chakras that sort of stuff, which you know, everyone's entitled to believe what they want But anyway, unexplainable store is more for that sort of stuff and they've got a lot of products But I'd say probably the most said at the biggest selection of by no beats is on the unexplainable store And as I said Nora is for sort of basic lucid dreaming meditation, you know, simple things which are proven And that you can just get started with right away and then you've got bliss coded sound Okay, now bliss coded sound is like in a new in its own sort of league. It's a different type of player They produce sounds based on sacred geometry, which if for those of you who don't know sacred geometry is the idea that there's this one sort of sequence of numbers or one number that Appears again and again, you know in nature In the law fit laws of physics the laws of mathematics And it's sort of in theory governs the whole universe. It's sort of like the universal code or the not like the matrix, but sort of a Code or number that keeps reappearing in various different areas and they've bliss coded sound have actually made soundtracks that incorporate that and They're not by no beats. They're not isochronic tones as such there They're sort of a mixture of both but also neither And you sort of have to try it out to believe it and to sort of see how they work But I would say of the three that I've mentioned Bliss coded sound is the one that you'll listen to it and you'll instantly think wow, okay, you know, you'll feel the effect instantly within a minute or so Which is why they have sample, you know, free samples to listen to on their website now Yes, bliss coded sound is more expensive than the other two because it does more for you in my opinion It it lets you access different brainwave states, you know, very quickly Not to mention the fact that they have a whole range of Subliminal learning products which can help you, you know master things and improve at skills, you know While you sleep much like lucid dreaming but sort of the whole for the whole night as opposed to just in your REM sleep When you're having a dream So I know this has gone on a bit. This is a bit of a rant, but I just wanted to make sure that you understand Yeah, you can get free by normal beats videos on YouTube. Okay, there's thousands of them And yes, they sound great and they'll probably work But they won't work as well as the ones you pay for because as I said more time has gone into the ones you pay for Bliss coded sound, however, I don't think you can find any for free because it's it's a very like specialist Audio entrainment program, whatever you want to call it. It's a very specialist product It's expensive for that reason because it works Now I think there is actually one video of Of bliss coded sound for free on YouTube and it's got several million views Simply because it's just so good, you know the people commenting are not lying. It does work Anyway, if you would like to get some sort of discount and a good deal on bliss coded sound or in aura or the unexplainable store I'll leave some links in the description below which you can check out right here if not do your own research obviously make sure that you Read testimonials There's a lot of companies out there that don't produce very good by normal beats, but they still still try and sell them Okay, so in my opinion and I've tried sort of I would say I've tried 90% of the ones out there of the companies that produces I would say those three In my opinion are the best so so that's it guys if you enjoy this, please leave a like leave a comment And I'll see you next time


So we're going to get started. I'm very excited to be here today to talk to you about Xerox. This project has been a long time in the coming. And I hope that we can get some people excited about it today. So just to outline this presentation, I'm going to quickly give a little bit of background and timeline on Xerox protocol, motivate the problem we are trying to solve, talk a little bit about the existing work. Then we'll go into Xerox protocol. We'll talk about the benefits of an open standard. We'll cover the developer ecosystem that we see developing today. And we'll quickly discuss the need for governance for open protocols. Then we'll go into DAP integrations and something that we like to call token abstraction. So my co-founder Amir and I started working on Xerox just over a year ago. We released our white paper in February of this year. And since then have put together a really talented and awesome team. All eight of us are here at the conference. We love chatting with people. So feel free to come up and say hello. And we're happy to answer any questions. So really the motivation behind creating Xerox protocol was this long-term theme that we see coming into existence where anything that can be assigned to value in the world is going to eventually be tokenized and moved onto an open financial network like the Ethereum blockchain. So this can be things like traditional assets like fiat currencies, stocks and bonds, debt assets, all the way to scarce digital goods like video game items and loyalty points and airline miles, and even things that are more abstract like attention. So naturally, with all of these different tokens that are going to eventually find their way onto the Ethereum blockchain, there needs to be a very low friction way to exchange these tokens. So just taking a quick look at the exchange ecosystem on the Ethereum blockchain, kind of, this is kind of the state of the Ethereum blockchain back when we started. There's been quite a few developments recently as well. But there's a handful of existing decentralized exchanges and there's a lot of decentralized applications that require exchange functionality in order to operate. So things like prediction markets or stable coins or decentralized fund management platforms, all of these things require exchange functionality. So the problem that we identified in the ecosystem was that every single one of these exchanges and dApps was creating their own proprietary and custom smart contracts from scratch. And what this meant is that not only would each exchange have to bootstrap liquidity from scratch, but it would also expose end users to a bunch of different smart contracts that have varying levels of security and efficiency, and they all do the exact same thing. So that's not a very efficient approach. Another issue with having a bunch of different implementations of exchange smart contracts is that there's no interoperability between any of them. So it fractures the ecosystem and it kind of results in less liquidity for everyone. So in our view, smart contracts should really behave like modular building blocks that can be assembled and reconfigured. And we also believe that open standards tend to win out in the long run. So I'm just gonna briefly talk about the different approaches to decentralized exchange that exist and give like a high level view of the pros and cons. So the very first decentralized exchanges that were created on the Ethereum blockchain kind of took the same functionality of a centralized exchange and pulled it into an Ethereum smart contract. So the Ethereum smart contract would store an order book within the contract. So what this means is that every time someone wants to post, modify, or cancel an order, they must pay gas costs and create an Ethereum transaction. And this becomes completely unrealistically expensive for any sort of market maker to create liquidity using an on-chain order book. Not only is it really expensive, but you also bloat the blockchain with tons of unnecessary transactions that aren't necessarily moving any value. They're also high latency. A second class of decentralized exchanges are automated market makers. And automated market makers, instead of having two parties on either side of a market trading directly, both parties trade with a smart contract. And the exchange rate that is offered by that smart contract is modified deterministically according to how strong the market forces are on either side of the market. Auger spent a long time working on finding working implementations of automated market makers and found that they're really subject to front running, they can be gameable. And they're really low throughput.  So it's really inefficient. The third approach to decentralized exchange, and we haven't seen any examples in production yet, but we will soon, I'm sure, are state channels. And so state channels are amazing for reducing latency and increasing throughput because with state channels, transactions occur off of the blockchain. And you can sort of accumulate a series of intermediate state changes, aggregate them and settle them all in the blockchain in a single transaction. The issue with state channels is that they're great if you wanna do day trading, but if you wanna just do one block trade, you just wanna buy a big chunk of tokens and immediately use them, there's a lot of friction around using a state channel. You have to move your funds into the channel. You have to place down a security deposit to ensure that everyone is behaving honestly within that channel. And then when you want to move your funds out of the state channel, there's a challenge period which is required also to ensure people are behaving honestly. Another downside to state channels is that when you move into a state channel off of the blockchain, you isolate yourself from all of the cool and interesting smart contracts that exist on the Ethereum blockchain. Yep. So Zach pioneered the off-chain order book with on-chain settlement approach. Around a little while after, we came up with a similar approach, but it's really a protocol instead of an on-chain order book. So Xerox Protocol really is comprised of a standard order schema that represents the different parameters associated with a given order. So the two assets that are being exchanged, the exchange rate, the expiration time for this order, and a cryptographic signature of the above parameters. And that is coupled with a smart contract system that is responsible for settling these trades directly on the blockchain. What's really makes Xerox a protocol is that there really aren't any rules about how you choose to pass these cryptographically signed chunks of data around off of the blockchain. So the transport layer is arbitrary. You can generate one of these cryptographically signed orders and you can send it to a counterparty in an email or over Facebook, or you can write it down on a piece of paper and send it to them using a carrier pigeon. It doesn't matter. The cryptographic signature just needs to be valid. Another thing that is different is that the message passing semantics are arbitrary and you can choose to use a variety of different strategies. So if I wanted to trade directly with a counterparty in a peer-to-peer fashion, like an over-the-counter trade, I can just create this order that specifies the parameters I am interested in trading at and I can cryptographically sign it and I can send it to my counterparty and we can settle that trade directly on the blockchain, completely free. There's no fees involved other than the gas costs. But naturally, people need to go to a location where a bunch of different parties are interested in trading and where these orders are aggregated in a single location. And we call these relayers or they're very similar to decentralized exchanges. What's really cool about 0x is that anyone can be a relayer. Anyone can create a decentralized exchange and charge trading fees on all the volume that they create. They keep 100% of the fees that they charge. There's also a variety of different relayer strategies that a relayer can decide to use. So you can use an open order book strategy, kind of like Ether Delta, where there's a public post-it board and people can put their orders up and anyone can take them down. You can also do a centralized matching strategy where a relayer will only accept orders onto their order book if they are specified as the only entity able to fill those orders. And when they find two orders on either side of the market, they can batch fill them simultaneously and synchronously on the blockchain and you can eliminate things like front running. A third option is a shape shift type exchange where someone essentially acts as a reserve manager and they just post a bid and ask for a single trading pair. So why create an open standard? Why? Well, one of the reasons is because if you have an open standard, you can create really robust developer tools. So things like Xerox.js, our JavaScript library, and things like our standard relayer API. And with these tools, you massively lower the barrier to entry for new people and developers that wanna create decentralized exchanges. And so what you end up getting are a variety of different decentralized exchanges that are highly competitive on fees as well as user experience. They also find and target different market niches and you end up with a diversity of different decentralized exchanges. A second reason to create an open standard is that if every single decentralized exchange is speaking the exact same language, it creates these network effects around liquidity where each relayer isn't necessarily competing with the others, they could actually benefit from a new relayer entering the ecosystem as arbitrages are taken advantage of across different exchanges risk-free and atomically. Decentralized applications can also be a source of customers for these decentralized exchanges or relayers. So since deploying Xerox protocol on the Ethereum mainnet in August 15th, we've seen just a crazy explosion of development activity. There are upwards of 10 different completely independent developer teams creating relayers on top of Xerox protocol. So I'm just gonna give you a closer look at a few of these. So the first relayer to go live on the Ethereum mainnet is Kin Alpha. And this was created by a single developer in their spare time over the course of a few weeks. You can see that it leaves a little bit to be desired in terms of the user experience, but we just thought it was pretty amazing that someone could go and create this on their own in a matter of weeks. Another really cool relayer that's worth checking out is Radar Relay. They're live on the mainnet today. You can go to radarrelay.com and check them out. They're doing a little bit of volume, but their API should be up soon. And third is Paradex. Paradex has created this beautiful user interface and they're expecting to launch their beta on the mainnet this month. And they're using a centralized matching strategy. So we're really excited to see all this development activity going on. And I think that we will see a dent put into the centralized exchange industry. Some other interesting development that we've seen are just independent developers out there creating trade explorers that allow you to view and explore the various trading activity going on on top of ZeroX protocol. And you can sort of sort trades by different relayers and by different trading pairs, et cetera. It's been really exciting for us to see people building things completely independently on top of the protocol and just finding out about it on Reddit. So now I wanna talk about something that is a little bit different that ZeroX protocol enables. And I think this is something that's pretty unique compared to the other approaches and implementations that are out there today. So ZeroX protocol allows smart contracts to natively execute trades in a single line of smart contract code. And this is really powerful because this essentially allows ZeroX protocol to act as an exchange module that exists natively within the EVM. And this allows ZeroX to be treated as a sort of fundamental building block that can be combined and built upon by other developers creating their own protocols. And to date we've seen two examples of completely independent protocols being created on top of ZeroX, DYDX and Dharma. I would encourage you to go check them out. There are also a variety of other decentralized applications that have decided to either right now or some point in the future integrate ZeroX protocol because it will allow them to get the functionality they need without having to write any code from scratch. So now I wanna talk a little bit about governance. So ZeroX is an open system and there are a variety of stakeholders and they each have their own motives and their own desires that they need out of the protocol. But they all benefit from the network effects of building on top of the same shared standard. And at the same time, ZeroX protocol is a system of Ethereum smart contracts that are immutable, but they must remain future proof over time. So how do you decide on protocol upgrades? You can either allow a small group of developers to make all the decisions about the future direction of the protocol, or you can allow all of the stakeholders in the system to have this fair say. So what we decided to do is to create a decentralized governance mechanism that uses token voting for future upgrades to the protocol. So I understand that everyone here is probably a little bit sick of all the tokens that are out there today and they might not wanna deal with another token. So I'm gonna just briefly talk about something called token abstraction that ZeroX enables and I think is really exciting, but we're gonna have to think about five or 10 years out from now. So when we think about decentralized applications, we used to think of them as sort of these vertically integrated monoliths that might've been built on the Bitcoin blockchain or the Ethereum blockchain, but I think what we're starting to see is an unbundling where there's many layers in the decentralized application stack and they're all specialized networks with distinct incentives and tokens. So you might imagine that a decentralized application requires a consensus layer, it might require some file storage and some computation and it might require some oracle to inject external data into that DAP. So if we have all of these different layers in the decentralized application stack and you're the end user of this DAP, it's going to require you to have a bunch of these different tokens for each layer of the stack and that's something that I don't think very many people are excited about. So in this example you can see there's some sort of decentralized application and what it wants to do is it wants to take a data set from say IPFS, it wants to run some computations on that data set using something like Trubit and the result of that computation is going to be injected into a smart contract which makes some sort of decision depending upon the result. Something that just would not be feasible within the EVM. In order to power some sort of sophisticated decentralized application like this, you might be required to have a handful of different tokens and that's not a very good user experience. So something that we're really excited about that we think ZeroX will play a role in in the future is something called token abstraction. So as the end user of a decentralized application, instead of having to hold a variety of different tokens that you may not know or care about or really have any vested interest in, you can just hold on to some tokenized fiat and you can pass in this fiat along with a thick stack of ZeroX orders into the decentralized application that you want to use into the smart contract. It will forward those fiat tokens and the ZeroX orders onto the ZeroX smart contracts and the smart contract will synchronously and immediately receive the variety of tokens that it needs to power that decentralized application. The smart contract will immediately go on its merry way using them as it needs to. So you can imagine that the takeaway from this is that instead of having to have a bunch of different tokens as an end user in the future, you might just go to a decentralized application and see that it's gonna cost you $3.50 in fiat tokens in order to access some of its functionality. So lastly, we're working on version two of ZeroX protocol today and we would love to get some community involvement and feedback. Some of the things that we're really excited about, including in our ZeroX improvement proposals are things like support for non-fungible tokens, atomic order matching, order generation by smart contracts, and a variety of other things as well. So we welcome you to come and contribute to the protocol and shape its future. So thank you very much, I appreciate the attention. Thank you.


Ladies and gentlemen, here we are back on the air again. As you probably know, Jack recently returned from a U.S.O. tour in the Far East. So now let's go back and show you what happened the day our little star arrived home. Well, Mary, Jack will be here pretty soon. Yeah, and I'll sure be glad to see him, Don. I'll bet Jack will be glad to get home where you'll be able to step into a hot tub again. You're not kidding. What are you laughing at, Mary? Jack sent me a picture of himself taking a bath and a barrel. Here it is. See? Yeah. Oh, wait a minute. That doesn't look like Jack. Where's his hair? He's using it for a wash rag. Well, that's Jack getting his back scrubbed in a shampoo at the same time. Next plane is supposed to pull up at gate four. Let's push in a little closer. Okay. You see, Chloe, I told you there'd be lots of excitement here at the airport. Oh, you're right, Clem. Why, I haven't seen so many people since MacArthur came through Calabasas. Is that Clem? Who is this fellow you dragged me down here to see today? Jack Binney. Who? Jack Binney, the star of stage, screen, radio and television. You ought to know him. He played the violin at your Aunt Poodie's wedding. Oh, yes, I remember. Instead of, oh, promise me, he played the hot canary. That's the boy. The plane is coming in now. Control tower to pilot. Pilot to control tower. Pilot to control tower. Pan-American special flight from Tokyo coming in for a landing. Mr. Benny, you can take your head out of my lap now. Thank you. This trip wasn't half as rough as I thought it would be. Oh, this was a very smooth flight. And in just a moment, we'll be landing at the International Airport in Los Angeles. Control tower to pilot. Control tower to pilot. Here are your landing instructions. Go ahead. Weather clear. Well, of course it's Los Angeles. Gee, I can recognize all those landmarks. Oh, yes, there's the Hollywood Bowl. And there's the California Bank. There's the Coliseum. Look, and there's the Bank of America. There's Westlake Park. And there's the Security Bank. Look, there's where they're building the Amalgamated First National. Oh, a new one. Isn't this exciting?  I see him. Come on, Mary. Let's push through the crowd. Oh, Jack. Jack. Oh, boy, it's good to see it. It's good to be back. Come here up, Mary. I'm going to give you a great big kiss. Oh, Jack, not in front of your friend. My friend? Yes, that man standing right behind you. He came off the plane with you. All these people who follow celebrities. Oh, look, Mr., will you please beat it? I can. What? Remember when the pilot told you to sit down and fasten your safety belt? You sat on me and tied my suspenders around you. Oh, I'm sorry. I'll untie them.  Thank you. Jack, I'm going out the main gate and hold a cab for you. Okay. Gosh, Mary, look at all these people at the airport. I wonder how many of them came down to see me. After all, I am a celebrity. Hi, Rube. Oh, yes, yes. How are you? Fine, fine.  How do you do? She ain't no Jane Russell, but she's my kind of woman. Certainly nice meeting. Jack, Don is waving at us. He's got a taxi. Okay, let's go. So long, Rube. So long, so long. Goodbye, Miss Russell. Right over here, Jack. The cab's right here. Oh, here we are. Thanks, Don. Ah, I'll be glad to get home. Where to, folks? 366 North Camden Drive. Yes, sir. Just think. Ten hours ago, I was in Honolulu, and now I'm almost home. Well, Jack, don't you feel tired and worn out after that long trip? Yes, Don, but it was quite an experience doing those shows in Korea. We had a great show, too. There was Marjorie Reynolds, Vinay Vanuda, Frank Remly, June Bruner, Harry Kahn, Dolores Gay, and Errol Flynn. He was our chaperone. And, Don, one incident that happened in Korea I'll never forget. This was so exciting. We were just about 10 miles above the 38th parallel. Say, mister, do you want me to go up Sepulveda to Sunset or cut across the Santa Monica Boulevard? Either way, either way. Anyway, kids, we were above the 38th parallel, and we stayed with this battalion for three days. I'll get this. We marched right with them. For three days and nights until we finally reached the outskirts of Yangdong, Seoul. Now, to enter this village, we had to cross a little stream, and we were so tired, so dirty and grimy, we jumped right into the water. And, Mary, you'll never guess what. You were the only one with a wash rag. I was not. Now, Mary, listen, that night, get this, that night we were tamped on the outskirts of the town, you know, just a few miles from the front lines. There was a dark night, no moon, when all of a sudden... It's shorter by Santa Monica, but there ain't so much traffic on Sunset.  All right, I'll go by Pico. Go, Pico, go, go. Anyway, kids, look at that night. Kids, I don't want you to get the impression, look at that I was braver than the others, but it was about two o'clock in the morning when I was awakened by a rustle in the bushes near my tent. I didn't have a gun, but never the land. You mind if I turn on the radio?  Thanks. Anyway, kids, look at when I heard this noise, I went out to investigate. I got down on all fours, was crawling along the ground, and all of a sudden... Anyway, I crawled around to the side of the brush, and there in a gully were four snipers. I had to think fast. I knew I could get a hand grenade, but then I found that it was protected by a barbed wire which had a high voltage of electricity running through it. Just turned from Correa, where he spent several weeks entertaining our boys. Wait a minute, wait a minute, he's talking about me. Driver, driver. No, no, don't turn it off, turn it on, turn it on loud. He's talking about me. What? Your radio, turn it on. Okay. It's 366 North Canada Drive. Gosh, Mary, I can't get over it. Here I am home, and only 36 hours ago I was in Tokyo, Japan. Watch your step, Mary. I'll take care of the cab. Here you are, driver. 75 yen. Keep the change there. yen? They're no good here. Look, if you can get them changed at the bank. Now, come on, kids, let's go in the house.  The house. You really miss me, huh, Rochester? Yeah. All the way to your way, this old house was so lonely. I'd go into the living room and see a big easy chair sitting there with no one in it. I'd feel like crying. Geez. Trees outside were in bloom, but they didn't mean nothing to me. Oh, Rochester. Words were singing, but I never could seem to hear them. The sun was shining, but I never saw it. Really, Rochester? Yeah, I never got up to eight o'clock at night. That's what I thought. Say, look, hey, the Coleman's had their house painted, didn't they? Yeah. Jack, there's Benita at the kitchen window, and Ronnie's looking out of the upstairs window. Oh, yeah. Ronnie! If they're going to give a party for my homecoming. Could be they gave a dilly when you went away. Well, that was nice. Oh, gosh. Home. Home, sweet home. Ah, the house sure looked good. Everything is just like I left it. Yeah. Diana was in the corner, my easy chair by the lamp, and Rochester, that picture on the wall. Who is it? Shall we dust it and find out? Never mind. Look, kids, let's all sit down for a while. I just want to relax. All say, Jack, I've been meaning to ask you. I presume that on your trip there were various times when you had the opportunity to meet some very important people. Don, I'm glad you brought that up. Now, I was in Tokyo when General Ridgway and his wife gave a big reception at the embassy. It was a thrilling occasion. Say, Jack, I've seen so many pictures of Mrs. Ridgway in the papers, and she seems so charming. How was she to talk to? Well... You see, I didn't get a chance to meet Mrs. Ridgway because she was so busy with all the women there, but the general, General Ridgway, what a guy. He was so friendly, so congenial. Really, you've never met anyone like him. Oh, then you met General Ridgway. Well... You see, a funny thing happened, Don. Just as I was about to be introduced to him, General Van Fleet arrived. So naturally, we had a rush over and shake hands with him. Oh, then you shook hands with General Van Fleet. Well, almost. What do you mean, almost? I stuck out my hand and he handed me his hat. I was so embarrassed I didn't know what to do with it. If you had to put it on, maybe you'd have met somebody. Met somebody? What are you talking about? Before the evening was over, I met a lot of people. Why talk for nearly 30 minutes to Corporal Peterson? Corporal Peterson. He was the one who married Aunt Poodie, but they drafted him anyway. Anyway, kids, this is one trip I'll never forget if I live to be a... Oh, boss, boss! Yes, Rochester? It's your sponsor. On the phone? No, the picture I just dusted in. Oh, good, good. Now, what was I talking about? About not meeting any generals. Oh, yes, but that was in Japan. Now, Mary, when we got to Korea... Come in. Well, hello, everybody. Dennis! Hi, Mr. Penny. Welcome home. Well, thanks, kid. Thanks. Gee, you look wonderful. Well, thanks. Turn around. Okay. Gee, you look even better that way. Dennis, look, why can't you just walk? Well, never mind. Tell me, Dennis, did you go...  Oh, sure. I went to Hawaii. Well, Hawaii. Well, did you take the boat? No. Oh. Then you went by plane, huh? No. Dennis, I'd like to hear the song you're going to do on the first program. Wait a minute, Jack. Aren't you going to ask him how he got to Hawaii? Not for a million dollars. This love... Great. It'll be nice for our opening show. Mahalo nui loa. O kule maluna mahi mahi e o loa hapa hala kamehameha kui moi. Sad, Dennis. Hawaiian. Oh, did you learn to speak Hawaiian while you were there? Mahalo nui loa. Kule maluna mahi mahi e o loa hapa hali kamehameha kui moi. What does that mean? I don't know, but if you say it to a Hawaiian girl, you get your face slapped. A peng heng tesu mingan kuli gu wao man. What's that? It's the same thing in Korea. You know, it's a funny thing, but when you go to a foreign country... Well, goodbye. It was nice being with you. Finally got the suspenders unfastened. Being that close behind me. Oh, Rochester. Yes, boss? Would you make us some sandwiches, please?  Rochester, what happened to the money I left you when I went overseas? I'm sorry, boss, but that only lasted for three weeks. You know, a dollar doesn't go as far as it used to.  A dollar. Looking at me. He was supposed to buy seeds and grow things. I think that means... Oh, Mary, I'm tired. Answer the door, will you please? Oh, sure, Jack. Oh, my truly, truly bad. Thanks. Let me look at you, Liv. Turn around. Let me put the ray on you. You ain't changed a bit. You haven't changed either, Phil. Just set your glass on the table and come on in. Welcome home. Thanks, Phil. Before I forget it, I want to thank you for letting Remli come to Korea with me. Oh, that's all right, Jackson. He was very handy. Every time we did a show for the soldiers, he accompanied us on the guitar. Good, good. And I want you to know that I brought him back to you safe and sound. That's all right. No hard feelings. Anyway, Phil, it was a good idea. I mean, it was worth a try. All right, so we weren't lucky. Listen, the kid. Oh, that's fine. You want to know something, Liv? Alice got herself a new car yesterday. Ooh, that's nice. What kind? Oh, one of them foreign cars, a Dagmar. That's Jaguar. Well, Dagmar is a girl on television. I've changed it. What? Mahalo nui loa kula ma luna meneo. Now, how does Dennis behave yourself? Hey, Don C. I didn't see you. How are you, Don? Well, hello, Phil. All set for the first program? Yeah, ready to go for another season. Jack. What? I've waited long enough. I've got to ask him. What? Dennis, how in the world did you get to Hawaii if you didn't take the boat or the plane? No, no, wait. No, you don't. Well, it's the first time we've been together in months.  Wait a minute. What's so silly about it? If he didn't take the boat to Hawaii and he didn't fly, maybe he took the train. Well, he took the train, eh? And how, pray tell, can anybody go by train from here to Hawaii? You can go into a pulmon and get a loa. But this morning, I told you that old man had...  I'm going. I'm going. Hey, so long, Jackson. I'm gonna see you later. I'm going too, Phil.  So long, kids. Thanks for coming on. So long, Jack. Aloha. All right. So I bid on it. At least I have sense enough not to ask Dennis why he was wearing that grass skirt. Boss, would you like me to fill the bath up for you? Oh, not yet, Rochester. I think I'll just turn on the radio and relax a while. Okay. Yeah, go ahead, Rochester. See, that's a pretty song. You know, boss, considering how far you traveled, your clothes didn't get very wrinkled. So I'll just hang them up and... Boss. What's the matter, Rochester? What thing? Ain't that a hand grenade? Yes, but don't get frightened, Rochester. Just pick it up. Who, me? Rochester, believe me, it's all right. Pick it up and shake it. I know. It's the safest little piggy bank in the world. What are you laughing at? Boss, you haven't changed a bit, but it's sure good to have you home. Thanks. This is the United States Armed Forces Radio Service.


Hey there lads and ladies, it is Petrifying Pumpkins here and today I want to talk to you about Firewall Ultra Stardene, it's very first competitive league thanks to the support of GSPL, Game and Synergy Pro League and I'm here to give you all the details about that if you would so be interested. There's a small child in the background so please ignore any noises he may make during the creation of this video if you can. So let me tell you everything you need to know. The league is now open for registration. Registration can be done by the captain of a squad joining GSPL's Discord which I will have a link to in the description of this video you're watching right now and they have to write the team's name in the registration channel. Registration will close at the end of January. Each team will play one match every week consisting of four maps, each team will pick two maps, one to start defending on and one to start attacking on. All four maps must be different. The league will start about two weeks after registration closes. Each squad is required to have at least one person streaming every match. Some of the matches will even be covered by commentators from AHC, which is amateur hour commentary. GSPL will be organizing fixtures, updating and posting the scores and be there to answer any questions players have. There will obviously be varying levels of skill seen as this is the very first Ultra League. The following season will however be seeded if there are enough teams joining. Players of varying skill levels are encouraged to join and more than welcome to join and players will be able to learn new tactics by watching these other top level teams streams as well.  GSPL have run 13 league seasons on firewall zero hour and are a very professional outfit.  I hope to see you out there on the battlefield. GG's. GG.


Let us start with a brief review of last class. So for the last couple of classes, we have been looking at optoelectronic devices. So these are devices where there is interaction between incident light and the electrical properties of the material or you have a situation where electrons and holes recombine in order to give you a light output. Last class, we looked at LEDs or light emitting diodes. The case of LEDs, we saw that we could model them as a simple p-n junction where we inject carriers. So we inject electrons from the n side and holes from the p side so that these electrons and holes recombine in order to give you light. Now depending upon the band gap of the material, that determines the wavelength of the light. So if you have a material like gallium arsenide, then the light output is produced in the IR region. If you want light in the visible region, you choose a material with the corresponding band gap. So we talked about LEDs and LEDs are an example of spontaneous emission which means typically the radiation is emitted in any direction and is not necessarily in phase. Today we are going to look at lasers. So lasers is another example of an optoelectronic device where we have incident current introduced into the material. So usually you have current that is injected which produces light. Now lasers stand for light amplification by stimulated emission of radiation. So the first letter in each of this comes together to give you your acronym that is the laser.  For example you can have a gas based laser, you can have a gas based laser. Typical example would be a helium neon laser. You could also have a solid state laser but based on a material that is not a semiconductor. For example you have Ruby lasers. In today's lecture you are going to focus on lasers but you are going to focus specifically on semiconductor based lasers. So what are some of the important properties of lasers that you must keep in mind? Lasers are highly monochromatic which means the line width is really small. Last class we saw that the line width is nothing but the spread in the wavelength of the output radiation that is delta lambda and this line width is very small. Laser radiation is also spatially coherent and it is also temporarily coherent which means the radiation is highly in phase. For laser the primary thing we need is population inversion. So what population inversion means is that we must have more number of particles in the excited state as compared to the ground state. When we achieve population inversion we have an incident radiation that strikes your material. This is the stimulated emission part. This incident radiation causes the particles to go from the excited state to the ground state and when they do they emit an output radiation which is in phase with the incident radiation. So this leads to stimulated emission and basically is responsible for the laser action. So we need to create a population inversion in the system before laser action occurs. In the case of semiconductor lasers the structure is very similar to the LEDs that we saw before but there are some important points to keep in mind when we talk about semiconductor lasers. So the structure of these lasers is very similar to LEDs but when we compare semiconductor lasers to lasers produced by other means for example a gas based laser there are some important differences. The first case here the transition is between energy bands. So one of the important criteria of lasers is that they should be highly monochromatic which means the line width should be extremely small. In the case of a gas based laser say a helium neon laser the transition occurs between atomic states and these atomic states are very sharp which gives rise to the high monochromaticity. On the case of a semiconductor laser though the transition is usually from a conduction band to a valence band. So these are energy bands. So there is some spread in the energy and this can affect the monochromatic nature of the light. If you remember when we talk about LEDs we also had a similar problem where we had an energy band because of the energy band there was a spread in energy of both the electrons and the holes so that there was a line width and the line width increased with increase in temperature and also with a decrease in the wavelength. So when we talk about semiconductor lasers we have to be aware that because you are using energy bands there is a potential for a line width issue. The active region in these lasers is usually very narrow. We will define an active region later when we look at the structure of these lasers but the active region is narrow is usually of the order of nanometers so it is usually less than 1 micrometer. The advantage of this is that you can have a laser device that is very compact. So think of the optical pointers that you have but the disadvantage is that it can lead to a high beam divergence. Lasering action is usually controlled by the current so the lasing action depends upon the current because the current controls the number of carriers that are injected into the material. So this means it is easy to modulate these devices especially at high frequencies, easy to modulate at high frequencies. So we said that the structure of a laser is very similar to that of an LED. So if you remember in the case of an LED we had electrons in the conduction band and holes in the valence band and these two recombined in order to give you radiation. So if I were to show that schematically I have two energy bands we call one E2 the other E1. In a generalized sense we can also think as E1 as the ground state and E2 as the excited state. So I have an electron in the excited state which basically relaxes back to the ground state. We saw that this can happen either by releasing light or by releasing heat in the case of an LED or a laser. This process leads to light and the wavelength or the frequency of light depends upon the band gap. So this is basically a spontaneous emission which occurs in an LED. You can also have stimulated emission once again I have a ground state E1 and an excited state E2. I have an electron in the excited state. In this particular case I have some incident radiation H mu and the energy of the radiation coincides with the energy of this gap. When this happens the electron falls back down. This emits another photon which is in phase with the photon that is incident on your sample. The output is now essentially two photons that are in phase. This is an example of stimulated emission. So in the case of a laser you can have both spontaneous emission and stimulated emission. So both of these are essentially competing processes. The reverse process can also occur when we have an incident light instead of causing an electron to fall back from the excited to the ground. This light can be absorbed by an electron in the ground state and also take it to the excited state. So absorption process can also occur. So in the case of a laser material we have a number of competing processes. We have stimulated emission, we have a spontaneous emission and we have absorption. So for an ideal laser material we want to suppress the spontaneous emission and absorption at the same time promote stimulated emission. If r s t denotes the rate of stimulated emission and r a b is your rate of absorption and phi is the incident photon intensity then we can write r s t minus, so the rate of stimulated emission minus the rate of absorption depends on the number of electrons that are there in the excited state minus number of electrons in the ground state times the incident photon intensity times a constant that is called the Einstein coefficient. So n 2 and n 1 is the population in the excited and ground state. The excited state is e 2 and the ground state is e 1, b 2 1 is called the Einstein coefficient. It depends upon the material and also upon the transition. So it depends upon what the states 2 and 1 are. This is material and transition dependent. In this particular formula we have ignored the fact that spontaneous emission occurs. We make sure that the spontaneous emission rate is much smaller than the stimulated emission. So the only competition is between emission and absorption. In order for r s t to be greater than r a b, we essentially want n 2 to be greater than n 1. This is the reason why you want population inversion in the case of a laser. So let me just rewrite that equation it is nothing but n 2 minus n 1. We said that if you want r s t to be greater than r absorbed possible only when you have n 2 greater than n 1. So this population inversion is usually achieved by external means. So the simple idea being if you had a p n junction you could apply a forward bias. We saw earlier that when you apply a forward bias you inject carriers into your p n junction. So these carriers basically create the population inversion. Inject carriers I will link that to here which means that this creates your population inversion. So we have seen earlier that a semiconductor laser structure is similar to an LED. But we also have other optical components to the device. So typically a laser will have optical resonators we will see those in a minute. So optical resonators the function of these resonators is to reflect the light. So that a certain intensity of laser is build up. They usually are used to build up laser intensity. So usually two resonators are used one on either side. One of these is totally reflecting and the other one is partially reflecting. So that the laser output comes from one side. Now if you look at materials that we use for lasers these are very similar to the materials that we saw earlier for LEDs. They have to be direct band gap materials usually some sort of a graded hetero structure is used and depending upon the band gap the wavelength of the laser will be determined. So some examples of laser materials I will just draw a graph to show you some of the materials used in different wavelength regions. So I have wavelength on my x axis the units is micrometers 0.1 micrometers is 100 nanometers. So that is the UV region 0.5 is in the middle of the visible region 1. This is essentially a log scale. So if you want laser light in the case of visible region you want a material whose band gap lies in the visible these are usually the two sixes. So you can have cadmium zinc sulfide we saw that in the case of LEDs a lot of material was based upon gallium arsenide which is a direct band gap semiconductor. Most of these materials can also be used for lasers. So you have aluminum gallium arsenide can also have gallium arsenic and phosphorus for the higher wavelengths or the lower band gaps can again have indium arsenide based materials cadmium and mercury. So this is not a complete list there are a whole bunch of other materials that can be used but this sort of gives the operating wavelengths of some of the common materials. Usually heterostructures are used we saw earlier in the case of LEDs heterostructure junctions are used in order to concentrate the carriers near the depletion region and something similar is used here and we also usually end up having graded compositions. Graded compositions are used so that you can have an epitaxial growth if you have a huge lattice mismatch that leads to defects at the interfaces if you want to grow epitaxial layers we want to have lattice parameters as close as possible. So graded compositions help to achieve that because they give you the wave the change in the band gap well at the same time allowing you to grow epitaxial layers. As we mentioned earlier usually a double heterostructure model is used for lasers. So consider the case of a laser material of length L there are two reflecting mirrors on either sides so these are your mirrors and they have reflectivity values of R1 and R2. So you have light or laser light that is generated within the material these light this light gets reflected from both the reflecting mirrors and finally some of the light will also escape. So in this particular material you have both emission which is your stimulated emission and we saw that for lasing action this emission must be more than the absorption. So if I define alpha as a loss due to absorption and G as the gain due to emission alpha must be G must be greater than alpha your gain must be more than your loss and then we define the net gain at a particular position Z the net gain depends upon the reflectivity of the two layers times exponential G minus alpha over Z. Now if L is the length of your laser and I have a light that originates at one corner it travels a length L gets reflected from the second mirror and travels a length L back which means the total distance traveled is 2 L. So your net gain occurs you write it here so you have a net gain when phi is more than 1 or you have R1 times R2 exponential G minus alpha now the total distance traveled is 2 L because it travels from one mirror to the next and then gets reflected and comes back this should be greater than 1. Usually we like to define something called a threshold gain which tells you how much current you need to supply in order for lasing action to occur. Once again you must supply enough current so that the emission is more than the absorption. So we define a threshold gain is equal to alpha plus 1 over 2 L ln of 1 over R1 and R2. So this in turn helps you to define the minimum current define the minimum current that is required for lasing action. So in this particular example the two reflectors help to confine the laser in the plane of the device but we also need to confine the light within the active layer so that light does not escape from the top or the bottom. So this is done by usually choosing a graded structure with different refractive indices so that you have total internal reflection and the light is kept within the active region. So let me include that as well and draw a schematic of the laser structure. So we want to confine the beam in the lateral direction done by using reflectors and we also want to confine the beam in the vertical direction this is called wave guiding. So this is usually done by choosing materials with different refractive index. So these are my two mirrors I have an active region so the length is L there is an active region of width D the active region is the region where your electrons and holes recombine in order to produce the laser light there are also two inactive regions. So these can be used in order to confine the electrons and holes within the active region but we also want materials in such a way in order to provide for wave guiding. For example you can have an active region there is made of gallium arsenide and your inactive regions could be P type aluminum gallium arsenide on one side and N type aluminum gallium arsenide on the other.  For total internal reflection we want N R 2 to be greater N R 1 N R 3 so when this happens light can just get reflected within the active layer and will not escape outside. So we can define this angle theta and the critical angle theta for total internal reflection is given by theta c is your critical angle for total internal reflection which is nothing but sin inverse over N 2. So consider the case of your gallium arsenide aluminum gallium arsenide material. So aluminum gallium arsenide can be written as aluminum x gallium 1 minus x AS. So this is a structure that is formed by combining aluminum arsenide and gallium arsenide and the property depends upon the value of x. For example the band gap E g as a function of x is nothing but 1.43 plus similarly the refractive index also depends upon the value of x. So this gives a refractive index that is lower than that of gallium arsenide so that you can have total internal reflection. For a particular value of x say 0.3 your band gap E g calculate is 1.8 which is greater than the band gap of gallium arsenide which is 1.43. You can calculate the refractive index for x is equal to 0.3 which is 3.38 which is less than 3.59 which is the value of gallium arsenide. So we can calculate the critical angle for total internal reflection so theta c comes out to be 70.3 degrees. So if your incident radiation has angle greater than theta c then we will have total internal reflection if it is less than theta c it will be partially reflective. So by using both optical reflectors at the edges and also by wave guiding so by using a graded structure with different refractive indexes can basically have lacing action. So this action is similar to that of an LED but in the case of an LED we do not have these optical resonators or these wave guiding structures. So consider the band structure of a simple p-n junction laser. We want to achieve population inversion so we want excess carriers or excess electrons in the conduction band, excess holes in the balance band. So we start with heavily doped p and n type materials and we usually use degenerate semiconductors. So these are heavily doped. We saw degenerate semiconductors earlier where we said that the doping level was so high that the impurity levels form a band which can combine with the balance or the conduction band. In this particular case the Fermi level will lie within the band. So we can have a p side this is E c E v and the Fermi level lies within the balance band. Similarly we can have a conduction side we can have the n side where the Fermi level lies within the conduction band. So in this particular case if we form a p-n junction with these two so these are the excess holes that are there on the p side these are the excess electrons on the n side. The depletion region is also very narrow because we have heavy doping. So when we apply a forward bias the electrons are injected from the n side to the depletion region the holes are injected from the p side these electrons and holes combined within the active region which is the depletion region and that gives you your laser. Have recombination in the active region and the active region is nothing but the depletion region. We can modify the structure in this particular case it is a simple p-n junction based upon the same material just like in the case of LEDs we can use hetero junctions or we can also go for a double hetero structure. So let us look at an example of that. So we already saw earlier that we had a gallium arsenide aluminum gallium arsenide based system. So the advantage of that in the case of wave guiding was that total internal reflection is also possible. But aluminum gallium arsenide also has a higher band gap than gallium arsenide so this helps to confine the carriers within the active region which is the gallium arsenide region. So if I have an aluminum gallium arsenide gallium arsenide based structure n type and then p-type aluminum gallium arsenide so when we forward bias this double hetero structure junction once again we can inject electrons from the n side on to gallium arsenide and inject holes from the p side on to gallium arsenide and these then recombine to give you your laser light. So if I were to draw a very basic band picture just draw the extra lines so that this central region is your active region you have electrons and holes these can recombine to give you light. So this kind of a structure can then be incorporated with mirrors in order to produce the lasing action. The intensity of the output light depends upon the intensity depends upon the number of electron hole pairs or the current. So if I were to plot the light intensity versus the bias current so the bias current defines how many electron hole pairs are injected. There is a threshold value below which the material behaves as an LED and above which behaves as a laser. Design an I threshold below which it is an LED and above which it is a laser. We saw earlier that this threshold current depends upon the threshold gain which says that you must have emission greater than absorption. This threshold value not only depends upon the material but also depends upon the design so it depends upon alpha the reflectivity of your mirrors and also the dimensions of the sample. So this is just a simple double heterostructure based laser can also have speciality lasers for example you can have quantum confinement within this active region in order to give you quantum well based lasers. In the case of a double heterostructure laser like the one we just saw with gallium arsenide and aluminum gallium arsenide the active region is the gallium arsenide region. If the width of the active region is comparable to the de Broglie wavelength in that particular case you can get quantum confinement within the active region. Now the de Broglie wavelength is usually of the order of few nanometers. So one can do a simple calculation relating the thermal energy to the momentum and from which we can calculate the wavelength. If you do that is usually of the order of a few nanometers. So the active region is only a few nanometers thick whether it is in 1D, 2D or 3D you can get different orders of quantum confinement. So if your active region is in the form of a thin film if it is a thin film then only the thickness is of the order of the de Broglie wavelength. So the thickness is comparable to lambda in this case you have 1D quantum confinement this is called quantum well. On the other hand if it is in the form of a wire where your radius of the wire is of the order of lambda that is a case of 2D quantum confinement that is a quantum wire and if it is in the form of a dot then all three dimensions. So you can just say for all three dimensions are of the order of lambda. So now you have 3D quantum confinement so you have a dot whenever you have quantum confinement you have discrete energy levels. So that when you make quantum lasers because you have discrete energy levels it also leads to a much narrower line width. So you have looked at two optoelectronic devices where we have an input electric current giving you an output light both LEDs and lasers. In next class we are going to look at the reverse problem where we shine light onto a material and look at the output electrical current. We will look at photo detectors in next class and after that we will look at solar cells.


Hello, this is Watika Smith, Safety Compliance Manager with the City of Columbia. This is your monthly safety message for the City of Columbia employees and for the public. I'm here today to discuss with you the monthly safety tips of hurricane safety. Before we get started, let's remember that the city has built our teamwork. What you see or if you see anything, please let us know. We're here to assist and to prevent bad things from happening. So let's just do that together. Hurricane Safety Tips is first in hand. Hurricane season we're going to go over is what to do before, doing, and after hurricane. Doing a hurricane season, which is from June the 1st to November the 30th, we must be prepared. I always have a first day kit with you. All for each person that's in your family. Make sure you have at least a gallon of water per person, per day. Have some non-perishable items. Some meat in a can. Have some crackers, some peanut butter and jelly, some bread. Make sure you have some batteries for your flashlight. Always remember to keep your cell phones charged. And I hope you can have a cordless cell phone charger to have with you, just for backup. Always stay tuned to your local radio station and your local news channels. That's why it's always important to be informed. You will now hear from H. Demetrius Rump. He will provide and guide and give you information to follow during this hurricane season. And by the way, always remain safe, and let's keep in our prayers out of the ones that infected with this hurricane. Thank you and have a great day. Hello, my name is Demetrius Rump, the Director of Safety and Risk Management for the City of Columbia. This is your monthly safety message for the City of Columbia employees. As our safety compliance manager, Ms. Watika Smith, stated earlier, the topic of discussion today will be about hurricane safety. As she stated earlier, hurricane activity has already begun, and the United States has already been touched by Mother Nature. It is so important that you abide by the recommendations and suggestions that we suggest to you during hurricane season or in hurricane safety. Today, I will be talking about what needs to be done to be safe before a hurricane, during a hurricane, and after a hurricane. Before a hurricane, you need to make sure you have a plan, a plan with you and your family, just in case if you get separated, then you will know what to do in order to be able to reunite with your family. One of the things you also need to do is fill up all your cars with gasoline, because gasoline is typically one of the products that will run out during a hurricane very quickly.   You also too, you don't want to use any electrical equipment during that time. If your home becomes flooded, turn off your main breaker to any electrical appliances in the home. Do not use your computer while doing a hurricane. You just want to make sure that your personal safety and your family safety is protected at all times. And after a hurricane, you want to make sure that you don't go outside because nine times out of ten more people have a fatality going outside because the area is not safe. You want to make sure that area has been cleared by an official before you go outside. I know everybody wants to go and assess the damages, but that's the time you have low hanging power lines, you have wires, so you really do not know whether that area has it free.  If you're staying in a shelter and typically your public shelters would be in schools, make sure you listen to any news stations or broadcasting stations, and they will give you direction on what to do after the hurricane. And just remember, we're still in a pandemic crisis, so it's important that we also maintain and adhere by protecting our families by supplying masks, hand sanitizer, and disinfecting wipes because during a hurricane, if power goes out, we may not have access to water. We just want to make sure that you have those applicable items based on what the CDC recommends.  This is your shot. Remember, safety starts with an S, but it begins with you.