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.     

Resonant frequencies of shielded rectangular and circular microstrip resonators

Resonant frequencies of shielded rectangular and circular microstrip patches have been determined using the modified Wolff model (MWM). The model determines effect of top-shield, side-walls, and end-walls on the resonant frequency. Results of the MWM have been compared to those of SDA and FEM. The MWM has an accuracy of 0.2% compared with experimental results. Numerically, the MWM is fast even on a desktop computer. The model is suitable for CAD applications. © 1995 John Wiley & Sons, Inc.     

Thermal aspects of shear localization in microporous viscoplastic solids

A set of phenomenological state variable constitutive equations for large deformations of isotropic, thermo-elasto-viscoplastic, porous materials is considered, and a new semi-implicit, incrementally objective time-integration procedure for these constitutive equations is developed. The constitutive equations and the time-integration procedure are implemented in a finite element program, and used to study the shear band formation and ductile fracture initiation triggered by flow softening due to the combined effects of void growth and deformation heating, in a plane strain tension test.     

Vibrational Technique for Stress Measurement in Films: I, Ideal Membrane Behavior

A vibrational technique for the measurement of stress in films has been developed, based on the theory of membranes. Specimens for vibrational analysis are prepared by removing a circular or square piece of the substrate. It is shown that the error introduced due to substrate removal is negligible except for thin metallic films. The resulting specimen, a film stretched across a hole in the substrate, behaves as a membrane. Since its natural frequencies increase with the square root of in-plane stress, these can be measured to compute the in-plane stress. The only material parameter needed is the density of the film. Because a number of natural frequencies can be measured, each of which can be used to compute the stress, this method has a strong check for internal consistency. Two different techniques have been used to measure natural frequencies: (1) sinusoidal excitation and holographic imaging of the vibration modes, and (2) random excitation and Fourier analysis of measured vibrations. In this, the first part of the study, we discuss cases when ideal membrane behavior is obtained. Three applications of the method are presented: measurement of stress in a filled-glass layer bonded to an aluminum substrate, a study of the effect of temperature and humidity on stress in a thermoset polymer coating, and stress in a silver film during heat treatment. The second part of the study¹ deals with extensions of the technique when complicating effects, such as air loading, bending stiffness, and an aniso-tropic state of stress, are important. In the third part of the study,² the method is used to identify the orthotropic axes and all nine elasticity coefficients of a commercially made film.