Games to induce specified equilibria

Media access protocols in wireless networks require each contending node to wait for a backoff time, chosen randomly from a fixed range, before attempting to transmit on a shared channel. However, nodes acting in their own selfish interest may not follow the protocol. In this paper, a static version of the problem is modeled as a strategic game played by non-cooperating, rational players (the nodes). The objective is to design a game which exhibits a unique, a priori mixed-strategy Nash equilibrium. In the context of the media access problem, the equilibrium of the game would correspond to nodes choosing backoff times randomly from a given range of values, according to the given distribution. We consider natural variations of the problems concerning the number of actions available to the players and show that it is possible to design such a game when there are at least two players that each have the largest number of possible actions among all players. In contrast, we show that if there are exactly two players with different number of actions available to them, then it becomes impossible to design a strategic game with a unique such Nash equilibrium.     

Estimation of unknown speaker’s height from speech

In the present study, we propose a regression-based scheme for the direct estimation of the height of unknown speakers from their speech. In this scheme every speech input is decomposed via the openSMILE audio parameterization to a single feature vector that is fed to a regression model, which provides a direct estimation of the persons’ height. The focus in this study is on the evaluation of the appropriateness of several linear and non-linear regression algorithms on the task of automatic height estimation from speech. The performance of the proposed scheme is evaluated on the TIMIT database, and the experimental results show an accuracy of 0.053 meters, in terms of mean absolute error, for the best performing Bagging regression algorithm. This accuracy corresponds to an averaged relative error of approximately 3%. We deem that the direct estimation of the height of unknown people from speech provides an important additional feature for improving the performance of various surveillance, profiling and access authorization applications.     

Particle Swarm Optimization for Sorted Adapted Gaussian Mixture Models

Recently, we introduced the sorted Gaussian mixture models (SGMMs) algorithm providing the means to tradeoff performance for operational speed and thus permitting the speed-up of GMM-based classification schemes. The performance of the SGMM algorithm depends on the proper choice of the sorting function, and the proper adjustment of its parameters. In the present work, we employ particle swarm optimization (PSO) and an appropriate fitness function to find the most advantageous parameters of the sorting function. We evaluate the practical significance of our approach on the text-independent speaker verification task utilizing the NIST 2002 speaker recognition evaluation (SRE) database while following the NIST SRE experimental protocol. The experimental results demonstrate a superior performance of the SGMM algorithm using PSO when compared to the original SGMM. For comprehensiveness we also compared these results with those from a baseline Gaussian mixture model-universal background model (GMM-UBM) system. The experimental results suggest that the performance loss due to speed-up is partially mitigated using PSO-derived weights in a sorted GMM-based scheme.     

A novel numerical technique for dielectric measurement of generallylossy dielectrics

A method for determining the dielectric properties of infinite half-space of generally lossy dielectric materials is described. This method utilizes the measurement of the admittance of a rectangular waveguide radiating into such dielectrics. It is shown that the real part of the admittance is relatively insensitive to the variations of the imaginary part of the dielectric constant. A numerical procedure is initiated which provides a simple and fast-converging approach for calculating the dielectric properties. This numerical procedure lends itself to implementation by personal computers. The theoretical formulation for the expression of the admittance of an open-ended waveguide and the numerical procedure are discussed in detail. Results of several measurements of freespace and lossy dielectric samples (rubber with carbon black) to verify the theory and the numerical scheme are given. The results give good agreement with other measurement schemes. Comments on the accuracy of the results are also provided     

Open-ended rectangular waveguide for nondestructive thicknessmeasurement and variation detection of lossy dielectric slabs backed bya conducting plate

Solutions for fields inside a slab of a generally lossy dielectric medium backed by a conducting plate, placed outside a waveguide-fed rectangular aperture, are used for the microwave nondestructive thickness measurement of such dielectric slabs. Upon construction of the waveguide terminating admittance expression from its variational form, an inverse problem is solved to extract the slab thickness form the conductance and susceptance in a recursive manner. A comparison between the experimental and theoretical results showed that the significance of higher order modes is minimal; hence, the dominant mode assumption is, in general, valid for describing the aperture field distribution. The validity of this assumption has led to the construction of a simple integral solution which is fast converging for generally lossy dielectric slabs, and may easily be implemented for real-time applications. Good agreement was obtained between the theoretical and experimental results. Multiple thicknesses of two different dielectric samples were estimated in this way     

Microwave diagnosis of rubber compounds

The results of a study investigating the dielectric properties of rubber compounds and their constituents in the frequency range of 5 to 24 GHz are presented. A completely filled short circuited waveguide technique was used to conduct these dielectric measurements. The influence of carbon black content in rubber was investigated for carefully prepared rubber samples. The results showed that for all frequencies, the dielectric constant increases as a function of increasing carbon black content. The variation of dielectric constant values decreases as frequency increases. The presence of curatives in uncured rubber samples was also detected, which indicates the sensitivity of microwaves to the chemical reaction triggered by curatives     

Experimental study of hydrodynamic and heat-transfer processes in the downward motion of a two-phase flow under annular and dispersed-annular conditions

Relationships are derived for determining the average thickness of a liquid film and the predominant frequency of the wave motion on its surface under conditions of two-phase flow; relationships are also derived for calculating the hydraulic resistance and the rate of heat transfer to the film under these conditions.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.31, No.1, pp. 13–20, July, 1976.     

Investigation of the electrodeposition process in the Cu-In-Se system

The electrodeposition process of the ternary Cu-In-Se system was investigated. The abilities of complexing agents to bring closer the deposition potentials of individual elements are analyzed. The results obtained show that thiocyanate ions (CNS^- can be used as a suitable complexing agent for electrodeposition of CuInSe₂ thin films from aqueous solution. The potentiodynamic measurements point out identical behavior of Cu and In species in the potential range of -0.7 V to -1 V. X-ray diffraction and EDAX were used for structural and compositional characterization of the electrodeposited thin films.     

Microwave Diagnosis of Low-Density Fiberglass Composites with Resin Binder

Abstract

Dielectric properties of low-density fiberglass composites are studied at microwave frequencies and are related to the resin binder content and state of cure. A completely filled short-circuited waveguide method is used to study the dielectric properties of fresh and slightly cured resin binder (used in the production of low-density fiberglass composite materials) in the frequency range of 4–18 GHz. The preliminary results indicate that the dielectric properties of resin binder may be used to determine its state of cure. The same measurement approach is used to determine the dielectric properties of fiberglass materials containing uncured resin binder, no resin binder, and three different levels of resin binder. It is found that the dielectric properties of these low-permittivity and low-loss materials are very similar. Consequently, to distinguish among real fiberglass products with different resin binder levels, an open-ended rectangular waveguide measurement approach is used. This technique allows for noncontact and on-line inspection. The standoff distance is utilized as an optimization parameter increasing the sensitivity of detection to slight dielectric property variations. Two microwave images at 24 and 10 GHz of a panel containing five different fiberglass specimens are presented.