Santhi Ani, Joseph; Gaurav, Sharma; Misha, Hari; Mathew, S; Radhakrishnan, P; Nampoori, V P N(Optical Society of America, 2010)
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Abstract:
We demonstrate the possibility of realizing, all-optical switching in gold nanosol. Two overlapping laser beams are used for this purpose, due to which a low-power beam passing collinear to a high-power beam will undergo cross phase modulation and thereby distort the spatial profile. This is taken to advantage for performing logic operations. We have also measured the threshold pump power to obtain a NOT gate and the minimum response time of the device. Contrary to the general notion that the response time of thermal effects used in this application is of the order of milliseconds, we prove that short pump pulses can result in fast switching. Different combinations of beam splitters and combiners will lead to the formation of other logic functions too.
Cryptosystem using linear codes was developed in 1978 by Mc-Eliece.
Later in 1985 Niederreiter and others developed a modified version of cryptosystem using concepts of
linear codes. But these systems were not used frequently because of its larger key size. In this study we
were designing a cryptosystem using the concepts of algebraic geometric codes with smaller key size.
Error detection and correction can be done efficiently by simple decoding methods using the
cryptosystem developed. Approach: Algebraic geometric codes are codes, generated using curves.
The cryptosystem use basic concepts of elliptic curves cryptography and generator matrix. Decrypted
information takes the form of a repetition code. Due to this complexity of decoding procedure is
reduced. Error detection and correction can be carried out efficiently by solving a simple system of
linear equations, there by imposing the concepts of security along with error detection and correction.
Results: Implementation of the algorithm is done on MATLAB and comparative analysis is also done
on various parameters of the system. Attacks are common to all cryptosystems. But by securely
choosing curve, field and representation of elements in field, we can overcome the attacks and a stable
system can be generated. Conclusion: The algorithm defined here protects the information from an
intruder and also from the error in communication channel by efficient error correction methods.
We define a new graph operator called the P3 intersection graph,
P3(G)- the intersection graph of all induced 3-paths in G. A characterization
of graphs G for which P-3 (G) is bipartite is given . Forbidden
subgraph characterization for P3 (G) having properties of being
chordal , H-free, complete are also obtained . For integers a and b
with a > 1 and b > a - 1, it is shown that there exists a graph G
such that X(G) = a, X(P3( G)) = b, where X is the chromatic number
of G. For the domination number -y(G), we construct graphs G such
that -y(G) = a and -y (P3(G)) = b for any two positive numbers a > 1
and b. Similar construction for the independence number and radius,
diameter relations are also discussed.
In this note,the (t) properties of five class are studied. We proved that the classes of cographs and clique perfect graphs without isolated vertices satisfy the (2) property and the (3) property, but do not satisfy the (t) property for tis greater than equal to 4. The (t) properties of the planar graphs and the perfect graphss are also studied . we obtain a necessary and suffieient conditions for the trestled graph of index K to satisfy the (2) property
Babita Roslind, Jose; Dr.Mythili, P(Cochin University of Science & Technology, January , 2010)
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Abstract:
Analog-to digital Converters (ADC) have an important impact on the overall performance of signal processing system. This research is to explore efficient techniques for the design of sigma-delta ADC,specially for multi-standard wireless tranceivers. In particular, the aim is to develop novel models and algorithms to address this problem and to implement software tools which are avle to assist the designer's decisions in the system-level exploration phase. To this end, this thesis presents a framework of techniques to design sigma-delta analog to digital converters.A2-2-2 reconfigurable sigma-delta modulator is proposed which can meet the design specifications of the three wireless communication standards namely GSM,WCDMA and WLAN. A sigma-delta modulator design tool is developed using the Graphical User Interface Development Environment (GUIDE) In MATLAB.Genetic Algorithm(GA) based search method is introduced to find the optimum value of the scaling coefficients and to maximize the dynamic range in a sigma-delta modulator.
Description:
School of Engineering, Cochin University of Science and Technology
Usha, Nair; Bindu M, Krishna; Namboothiri, V N N; Nampoori, V P N(Springer, 2010)
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Abstract:
Machine tool chatter is an unfavorable phenomenon during metal cutting, which results in heavy vibration of cutting tool. With increase in depth of cut, the cutting regime changes from chatter-free cutting to one with chatter. In this paper, we propose the use of permutation entropy (PE), a conceptually simple and computationally fast measurement to detect the onset of chatter from the time series using sound signal recorded with a unidirectional microphone. PE can efficiently distinguish the regular and complex nature of any signal and extract information about the dynamics of the process by indicating sudden change in its value. Under situations where the data sets are huge and there is no time for preprocessing and fine-tuning, PE can effectively detect dynamical changes of the system. This makes PE an ideal choice for online detection of chatter, which is not possible with other conventional nonlinear methods. In the present study, the variation of PE under two cutting conditions is analyzed. Abrupt variation in the value of PE with increase in depth of cut indicates the onset of chatter vibrations. The results are verified using frequency spectra of the signals and the nonlinear measure, normalized coarse-grained information rate (NCIR).