Fracture mechanisms during fiber pull-out for carbon-fiber-reinforced thermosetting composites

We have investigated the mechanism of fiber/resin debonding in three untreated and three corresponding plasma-treated carbon-fiber-reinforced thermosetting micro-composites by examining the fiber/resin fracture surfaces with the aid of wetting force scanning. The wettability of a debonded microdroplet resin site (50–150 μm long) on a fiber was compared with that of the original fiber surface by scanning with ethylene glycol. Wetting force scans show that, for most fiber/resin combinations, the original location of the interface had a distinctly different wetting force as compared with adjacent non-bonded fiber surfaces. This suggested either the removal of a layer of carbon fiber along with the resin or a sub-microscopic cohesive failure in the resin leaving a thin residual layer of the resin on the fiber. For only a few specimens, no change in wetting force at the resin site was observed, suggesting adhesive failure of the interface. The different failure mechanisms proposed for various fiber/resin systems are explained on the basis of the morphological structures of the carbon fibers, cohesive shear strengths of the resins and the measured bond strengths.     

Some integrals involving the Q/sub m/(a/spl radic/x,b/spl radic/x) with application to error probability analysis of diversity receivers

This paper derives closed-form formulas for two integrals involving the generalized Marcum Q-function with linear arguments Q/sub m/(a/spl radic/x,b/spl radic/x). These integrals are known to arise in the analysis of multichannel diversity reception of differentially coherent and noncoherent digital communications in Rayleigh and Nakagami-m channels. Applications of the results for efficient performance evaluation of the average bit error rates of dual branch selection diversity combining and postdetection equal gain combining over independent and correlated fading channels are also presented.     

The relativistic theory of weak discontinuities in high temperature phenomena

A relativistic theory of the propagation of weak discontinuities in an optically thick medium at temperature 10⁵⁰K or higher is presented. The effects of radiation pressure and radiation energy density have been taken into account, while the profiles structured by radiant heat transfer are assumed imbedded in the discontinuities. The velocity of propagation of a relativistic weak discontinuity has been determined. The fundamental growth equation governing the growth and decay of a relativistic weak wave has been obtained and solved. The relativistic results are shown to be in full agreement with the earlier results of classical gasdynamics. The problem of breakdown of weak waves and the consequent formation of shock waves has also been studied and a finite critical time $\text{t}{}_{\mathrm{c}}$ is determined when a weak wave will terminate into a shock wave due to nonlinear steepening. A critical wave amplitude is determined, which provides a critical line for the decay and growth of a weak discontinuity in a relativistic flow referred to an instantaneous rest frame. The local and global behaviour of the wave amplitude is also examined.     

Avalanche-multiplication-region operation of n-p-n?-n+ power transistors

Internal behaviour of an n-p-n?-n+ high-voltage power transistor for the avalanche-multiplication-region operating conditions is presented as obtained by a mathematical model. This model incorporates the avalanche generation of carriers due to electric field and current density and the resulting semiconductor transport equations are solved in two dimensions by numerical methods.     

Conductivity of highly concentrated aqueous electrolyte solutions III: H2O+NH4NO3+RbNO3 system

Conductivity of H₂O+NH₄NO₃+RbNO₃ system containing up to 5.15 stoichiometric mol percent of RbNO₃ and water/ammonium nitrate mol ratio varying between 1 and 6 have been measured at temperatures ranging between 275–345 K. At all compositions, variation of conductivity with temperature deviated slightly from Arrhenius behaviour. Conductivity-composition isotherms pass through a maximum at c0.18 mol fraction of electrolyte concentration; these have been discussed using the free volume model, cooperative rearrangement theory and environmental relaxation model of liquid transport.     

Hybrid buffers based coarse-grained power gated network on chip router microarchitecture

ABSTRACT

With the failure of Dennard’s Scaling, we cannot power on all the transistors of an circuit simultaneously for a given thermal design power. In this paper, we propose coarse-grained power gated hybrid buffer based Network on Chip router microarchitecture which a large amount of Network on Chip router power and area is consumed by the FIFO buffers. State of the art NoC router buffers is composed of SRAM, which is neither power efficient nor area efficient. We have proposed hybrid buffers based coarse-grained power gated Network on Chip router microarchitecture. As STT-MRAM (Spin Transfer Torque Magneto-resistive Random Access Memory) provides an improved solution having near zero leakage power and higher package density. Our proposed router microarchitecture improves 12.3% average packet latency as compared to state of the art power gated SRAM based router and 4.90% as compared to the fine-grained power gated hybrid buffer based router respectively for PARSEC benchmarks. We have achieved 65% and 21.34% total network energy saving for PARSEC benchmarks as compared with one without power gating and state of the art power gated SRAM based router respectively. Our hybrid router is 35.10% area efficient as compare to pure SRAM based power gated router at 32nm technology node.     

ATMAC: adaptive token‐based medium access control protocol for cognitive radio wireless mesh network

In next generation wireless communication, cognitive radio technology facilitates to utilize underutilized licensed frequency bands that help to enhance the spectrum utilization. Cognitive radio wireless mesh network (CRWMN) is a promising and reliable technology to experience high throughput with low cost. Existing IEEE 802.11 based medium access control (MAC) protocols offer high data rates with decreasing efficiency at the MAC layer. Hence, most of the researchers applied aggregation mechanisms to provide the solution to bandwidth craving applications. In CRWMN, MAC design is significant because stability, efficient resource utilization, and scalability are predominating problems; however, the specified MAC issues are not yet resolved. The proposed MAC is novel, which aims to ensure reliability and scalability for CRWMN. The common control channel is used to exchange handshaking frames between the transmitter and receiver. It helps us to schedule the data transmission as well as reserve the channel in a discrete time interval. It introduces a token‐based channel accessing mechanism with resource‐aware channel assignment, which resolves the problems of efficiency and stability. The proposed MAC simulated using the network simulator (ns‐2), and the simulation results demonstrate that the proposed protocol improved the performance compared with the existing protocols.     

An improved circuit model for polymer solar cells

Authenticity of conventional circuit model, to interpret the characteristics of polymer solar cells (PSCs) is examined. Conventional circuit model is found to be quite limited, and various assumptions used there are not valid for PSCs. By understanding the nature of photovoltaic characteristics, through detailed investigations, we developed an improved circuit model, which explains correctly the behavior of PSCs under different environmental conditions. Investigations are carried out on the solar cells, made of the blend of regioregular poly(3‐hexylethiophene) (P3HT) and phenyl [6,6] C₆₁ butyric acid methyl ester (PCBM). The model is developed by treating both the dark and illuminated characteristics separately, even the characteristics were dealt with separately in reverse and forward biases. The formulated equivalent circuit model helps us in explaining many other important features, observed in the characteristics of PSCs. Copyright © 2013 John Wiley & Sons, Ltd.