Zero knowledge one time digital signature scheme

In many applications, when communicating with a host, we may or may not be concerned about the privacy of the data but are mainly concerned about the integrity of data being transmitted. This paper presents a simple algorithm based on zero knowledge proof by which the receiver can confirm the integrity of data without the sender having to send the digital signature of the message directly. Also, if the same document is sent across by the same user multiple times, this scheme results in different digital signature each time thus making it a practical one-time signature scheme.

Electrical switching in amorphous Si-Te-Ge thin films: Impact of input energy on crystallization process and switching parameters

Electrical switching studies on amorphous Si15Te74Ge11 thin film devices show interesting changes in the switching behavior with changes in the input energy supplied; the input energy determines the extent of crystallization in the active volume, which is reflected in the value of SET resistances. This in turn, determines the trend exhibited by switching voltage (V-t) for different input conditions. The results obtained are analyzed on the basis of the amount of Joule heat generated, which determines the temperature of the active volume. Depending on the final temperature, devices are rendered either in the intermediate state with a resistance of 5*10(2) Omega or the ON state with a resistance of 5*10(1) Omega. (C) 2013 Elsevier B.V. All rights reserved.

Numerical simulations of bubble formation from submerged needles under non-uniform direct current electric field

In several chemical and space industries, small bubbles are desired for efficient interaction between the liquid and gas phases. In the present study, we show that non-uniform electric field with appropriate electrode configurations can reduce the volume of the bubbles forming at submerged needles by up to three orders of magnitude. We show that localized high electric stresses at the base of the bubbles result in slipping of the contact line on the inner surface of the needle and subsequent bubble formation occurs with contact line inside the needle. We also show that for bubble formation in the presence of highly non-uniform electric field, due to high detachment frequency, the bubbles go through multiple coalescences and thus increase the apparent volume of the detached bubbles. (C) 2013 AIP Publishing LLC.

Delay optimized zero-forcing channel shortening algorithm for wireless communication

In Orthogonal Frequency Division Multiplexing and Discrete Multitone transceivers, a guard interval called Cyclic Prefix (CP) is inserted to avoid inter-symbol interference. The length of the CP is usually greater than the impulse response of the channel resulting in a loss of useful data carriers. In order to avoid long CP, a time domain equalizer is used to shorten the channel. In this paper, we propose a method to include a delay in the zero-forcing equalizer and obtain an optimal value of the delay, based on the location of zeros of the channel. The performance of the algorithms is studied using numerical simulations.

CHARACTERIZATION AND HARDNESS OF Co-P COATINGS OBTAINED FROM DIRECT CURRENT ELECTRODEPOSITION USING GLUCONATE BATH

Direct current electrodeposition of Co-P alloy coatings were carried out using gluconate bath and they were characterized by employing techniques like XRD, FESEM, DSC and XPS. Broad XRD lines demonstrate the amorphous nature of Co-P coatings. Spherical and rough nodules are observed on the surface of coatings as seen from FESEM images. Three exothermic peaks around 290, 342 and 390 degrees C in DSC profiles of Co-P coatings could be attributed to the crystallization and formation of Co2P phase in the coatings. As-deposited coatings consist of Co metal and oxidized Co species as revealed by XPS studies. Bulk alloy P (P delta-) as well as oxidized P (P5+) are present on the surface of coatings. Concentrations of Co metal and P delta- increase with successive sputtering of the coating. Observed microhardness value is 1005 HK when Co-P coating obtained from 10 g L-1 NaH2PO2 is heated at 400 degrees C that is comparable with hard chromium coatings.

Switching and release dynamics of an electrostatically actuated MEMS switch under the influence of squeeze-film damping

This paper reports analytical modeling, simulation and experimental validation for switching and release times of an electrostatically actuated micromachined switch. Presented work is an extension of our earlier work [1] that analytically argued, and numerically and experimentally demonstrated, why pull-in time is larger that pull-up time when the actuation voltage is less than twice of the pull-in voltage. In this paper, switching dynamics is investigated under the influence of squeeze-film damping. Tests were performed on SOI (silicon-on-insulator) based parallel beams structures.Typical voltage requirement for actuation is in the range of 10-30 V. All the experiments were performed in normal atmospheric pressure. Measurement results confirm that the quality factor Q has appreciable effect on the release time compared to the switching time. The quality factor Q is extracted from the response measurement and compared with the ANSYS simulation result. In addition, the dynamic pull-in effect has also been studied and reported in this paper. A contribution of this work includes the effect of various phenomena such as squeeze-film damping, dynamic pull-in, and frequency pull-in effects on the switching dynamics of a MEMS switch.

Design of double toggle switching mechanisms

Toggle mechanisms are ubiquitous in electrical switches. However, literature for their mechanical design is scarce. This paper defines and classifies the toggle phenomena observed during switching. The concept of double toggle introduced in this paper enables a systematic screening of kinematic structure for the suitability in high performance switches. Seven structural and three kinematic criteria are identified for this purpose. It is also demonstrated that each such feasible kinematic structure lends itself to multiple physical embodiments. Therefore, the theory and procedure presented in this work can be used for design of numerous kinematically distinct mechanisms. One representative mechanical embodiment for a novel double toggle switch, including mass and geometric shape of links has been included in the paper. The switching behavior of the design is validated using Pro/Mechanism (TM). (C) 2013 Elsevier Ltd. All rights reserved.

Compensator Design for Closed Loop Hall-Effect Current Sensors

Closed loop current sensors used in power electronics applications are expected to have high bandwidth and minimal measurement transients. In this paper, a closed loop compensated Hall-effect current sensor is modeled. The model is used to tune the sensor's compensator. Analytical expression of step response is used to evaluate the performance of the PI compensator in the current sensor. This analysis is used to devise a procedure to design parameters of the PI compensator for fast dynamic response and for small dynamic error. A prototype current sensor is built in the laboratory. Simulations using the model are compared with experimental results to validate the model and to study the variation in performance with compensator parameters. The performance of the designed PI compensator for the sensor is compared with a commercial current sensor. The measured bandwidth of the designed current sensor is above 200 kHz, which is comparable to commercial standards. Implementation issues of PI compensator using operational amplifiers are also addressed.

Harmonic Analysis of DC-Link Capacitor Current in Sinusoidally Modulated Neutral-Point-Clamped Inverter

The voltage ripple and power loss in the DC-capacitor of a voltage source inverter depend on the harmonic currents flowing through the capacitor. This paper presents double Fourier series based harmonic analysis of DC capacitor current in a three-level neutral point clamped inverter, modulated with sine-triangle PWM. The analytical results are validated experimentally on a 5-kVA three-level inverter prototype. The results of the analysis are used for predicting the power loss in the DC capacitor.

Comparative Evaluation of Switching and Average Models of a DC-DC Boost Converter for Real-Time Simulation

This paper presents a comparative evaluation of the average and switching models of a dc-dc boost converter from the point of view of real-time simulation. Both the models are used to simulate the converter in real-time on a Field Programmable Gate Array (FPGA) platform. The converter is considered to function over a wide range of operating conditions, and could do transition between continuous conduction mode (CCM) and discontinuous conduction mode (DCM). While the average model is known to be computationally efficient from the perspective of off-line simulation, the same is shown here to consume more logical resources than the switching model for real-time simulation of the dc-dc converter. Further, evaluation of the boundary condition between CCM and DCM is found to be the main reason for the increased consumption of resources by the average model.

On the nature of meandering of the springtime western boundary current in the Bay of Bengal

We present evidence that the springtime western boundary current (WBC) in the Bay of Bengal is a continuous northward-flowing current from about 12 degrees N to 17 degrees N, which then separates from the coast at around 18 degrees N. We first revisit a hydrographic data set collected in 1987 from a potential vorticity perspective, and then analyze absolute dynamic height maps from satellite altimeters during the period 2000-2010. The altimetric maps suggest that the mean configuration of the WBC is that of an intense current with two anticyclonic eddies on the offshore side, which are part of the basin-wide anticyclonic circulation. The WBC consistently separates from the coast at around 18 degrees N in all years between 2000 and 2010. The path of the eastward-flowing mean stream after separation appears to be consistent with isolines of f/H and with Ertel's potential vorticity, based on an analysis of the hydrographic data from 1987.

Study on Rotor Current Waveforms in an Inverter-fed Induction Motor Drive During Overmodulation

Overmodulation introduces low-order harmonics in the output voltage of a voltage source inverter. This paper presents the effects of low-order harmonics in the stator voltage on the rotor currents of an induction motor. Rotor current waveforms are presented for various operating zones in overmodulation, including six-step mode. Harmonic spectra of stator and rotor currents are compared in six-step mode of operation. Pulsating torque is evaluated at various depths of modulation during overmodulation.

Chemical vapor detection using nonlinear electrical properties of carbon nanotube bundles

We demonstrate the electrical transport behavior of carbon nanotubes (CNTs) upon exposure to organic analytes (namely ethanol, benzene, acetone and toluene). The resulting nonlinear current-voltage characteristics revealed a power law dependence of the differential conductivity on the applied bias voltage. Moreover, suppression of differential conductivity at zero bias is found to be dependent on different selective analytes. The power law exponent values have been monitored before, during and after exposure to the chemicals, which revealed a reversible change in the number of electron conducting channels. Therefore, the reduction in the number of conductive paths can be attributed to the interaction of the chemical analyte on the CNT surfaces, which causes a decrease in the differential conductivity of the CNT sample. These results demonstrate chemical selectivity of CNTs due to varying electronic interaction with different chemical analytes.