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Thursday, June 20, 2013

Electrophoretic image display (EPID)

The motion of charged particles of pigments suspended in a liquid under the influence of an electric field is known as Electrophoresis. Electrophoretic image displays use this phenomenon. The main parts of this display are dc voltage source, base plate, electrode segments, coloured liquid, transparent electrode and electrophoretic pigment particles. A liquid suspension consists of pigment particles are sandwiched between a pair of electrodes. One among the two electrodes is transparent and made as common electrode. On the application of dc electric field, pigment particles move electrophoretically towards electrodes and this motion is dependent on the polarity of the charge on the particles. The transparent electrode is preferably maintained at ground potential and segment electrodes at different potentials. Colour combinations of both the pigment particles and the suspending liquid can be used to achieve a desired colour display. Electrophoretic image displays are characterized by large character size, low power dissipation and internal memory. 

Tuesday, May 7, 2013

Cryptography techniques

Cryptography is an art of codifying messages to avoid possible attacks. Sniffing, Spoofing and phishing are some common internet attacks. Attacks can be classified into two- Passive attack where attacker does not modify the contents of a message and Active attack where attacker modifies the content of the message. Cryptography is an efficient method to increase the security of messages where some codes are used to make message non-readable. The message in the non-readable format can be decoded by a technique, Cryptanalysis. The combination of Cryptography and Cryptanalysis is known as Cryptology. In the first step, plain text is converted into Cipher text, a codified text. For this we can employ two techniques- substitution techniques and transposition techniques. Caesar cipher, modified version of Caesar cipher, mono-alphabetic cipher, homophonic substitution cipher, polygram substitution cipher, poly-alphabetic substitution cipher, playfair cipher and hill cipher are examples for substitution techniques. Example for transposition techniques are Rail fence.

Tuesday, December 18, 2012

Computer vision

Computer vision is an emerging technology. Here the reconstruction of explicit and meaningful descriptions of physical objects from images is carried out using some innovative techniques. Computer vision which is also known as machine vision finds applications in many areas like military, medicine and manufacturing. Computer aided tomographic scan (CT scan or CAT scan), a diagnostic tool used in medicine is based on computer vision. Computer vision finds its military application in aerial photography which helps to locate enemy naval vessels. In manufacturing field, computer vision is applied in locating and modifying different machine components such as conveyer belts, robotic mechanical parts etc. Computer vision systems are classified into three. They are two-dimensional system, stereo vision and structured light system. Two dimensional system is just like an optical comparator. Stereo vision system uses two cameras. A laser system is employed in structured light system.