Vulcanization characteristics and mechanical properties of nitrile rubber filled with short leather fibres

Leather shavings have been used as filler in short fibre form for nitrile rubber reinforcement. Shavings neutralized with sodium bicarbonate and ammonia showed improved vulcanization characteristics and mechanical properties, whereas sodium hydroxide neutralized shavings exhibited poor properties. Swelling of the vulcanizates in water and 1% NaOH was found to increase with leather loading, whereas in MEK a reversed trend was observed. Thermogravimetric analysis indicates that the thermal stabilities of the vulcanizates fall between those of pure leather and gum nitrile rubber vulcanizate.     

Tensile Deformation of a Nickel-base Alloy at Elevated Temperatures

The results of tensile testing involving Waspaloy indicate that the failure strain was gradually reduced at temperatures ranging between ambient and 300 °C. Further, serrations were observed in the engineering stress versus strain diagrams in the temperature range of 300-600 °C. The reduced failure strain and the formation of serrations in these temperature regimes could be the result of dynamic strain aging of this alloy. The extent of work hardening due to plastic deformation was reduced at temperatures above 300 °C. A combination of ductile and intergranular brittle failures was seen at temperatures above 600 °C. γ′ was detected at all tested temperatures.     

A traveling-wave high electron mobility transistor

A traveling-wave high electron mobility transistor (THEMT) is proposed. The device is unique in that it includes an integral distributed load resistor and uses a HEMT as the active device. A rigorous analysis of the device is carried out, using a small-signal equivalent circuit model for an incremental section of the device. Losses and reflected waves are not neglected, as has been done in other work. Treating the device as a four-port network, closed-form expressions for S-parameters are derived. Theoretical calculations, using equivalent circuit parameter values for a HEMT reported in the literature, show that the proposed device is capable of exponential increase in gain with device width. Power gain of more than 10 dB at 50 GHz and remarkably flat response in the frequency range 10-100 GHz are shown to be achievable for a 1-mm-wide device     

Vector representation of Moiré fringes

Moiré fringes are represented as vectors and their characteristics established using vector algebra. It is shown that the Moiré fringe vector of deformation is the vector sum of those due to extension and rotation.>     

Performance analysis of voice/data cellular CDMA with SIR-based admission control

In this paper, we analyze the performance of a signal-to-interference ratio (SIR)-based admission control strategy on the uplink in cellular code-division multiple-access (CDMA) systems with voice and data traffic. Most studies in the current literature to estimate CDMA system capacity with both voice and data traffic do not take into account admission control based on SIR constraints. Here, we present an analytical approach to evaluate the outage probability for voice traffic, the average system throughput, and the mean delay for data traffic in a voice/data CDMA system, which employs an SIR-based admission control. We make two main approximations in the voice call outage analysis-one based on the central limit theorem (CLT) and the other based on the Fenton's method. We apply the Fenton's method approximation to compute the retransmission probability and the mean delay for data traffic, and the average system throughput. We show that for a voice-only system, a capacity improvement of about 30% is achieved with the SIR-based admission control as compared with the code availability-based admission control. For a mixed voice/data system with 10 Erlangs of voice traffic, an improvement of about 40% in the mean delay for data is shown to be achieved. Also, for a mean delay of 50 ms with 10 Erlangs of voice traffic, the data Erlang capacity improves by about 50%.     

Rapid increase of NGF, BDNF and NT-3 mRNAs in inflamed bladder

Nerve growth factor (NGF) is a mediator of hyperalgesia and has been previously associated with sensory and reflex changes after inflammation of the urinary bladder. A sensitive assay was developed to examine neurotrophin gene expression after bladder inflammation by turpentine, which causes a short-lived inflammatory response. Two hours, but not 6 or 24 h after induction of inflammation, there were significant increases in levels of NGF, brain-derived neurotrophic factor and neurotrophin-3 mRNAs. NGF immunoreactivity was elevated with a similar time course to its mRNA. Our results suggest that during bladder inflammation, endogenous NGF is rapidly up-regulated and released to mediating sensory and reflex changes. Brain-derived neurotrophic factor and neurotrophin-3 may also have a role in the inflammatory response.     

The tensile response and fracture behavior of an Al-Zn-Mg-Cu alloy: Influence of temperature

A high-performance, high-strength, and novel AI-Zn-Mg-Cu alloy in the T7751 condition was deformed to failure in laboratory air environment at ambient and elevated temperatures. Temperature influenced the tensile response of the alloy for both the longitudinal and transverse orientations. Strength decreased with an increase in test temperature, with a concomitant improvement in ductility. Test results indicate the alloy response to be the same for both the longitudinal and transverse orientations. No major change in the macroscopic fracture mode was observed with the direction of testing. Tensile fracture, on a microscopic scale, revealed features reminiscent of both ductile and brittle mechanisms. The microscopic fracture behavior was a function of test temperature. The mechanisms and intrinsic micromechanisms governing the tensile fracture process are discussed in terms of mutually interactive influences of microstructural effects, matrix deformation characteristics, test temperature, and grain boundary failure.     

Fully implanted GaAs millimetre-wave mixer diode using high energy implantation

Fully implanted GaAs millimetre-wave planar mixer diodes, suitable for monolithic integration, have been fabricated and tested. Multiple energy implantation, having a maximum energy of 6 MeV, was used to form the 3 ?m-thick active layer. The DC and RF characteristics were comparable to state-of-the-art GaAs mixer diodes fabricated on epitaxial layers.