On the Theory of Electrical Phenomena in Combustion of Heterogeneous Systems with Condensed Products

The effect of the electromotive force arising in combustion of heterogeneous systems with condensed products is explained. A convective mechanism of arising regions with different charge densities due to charge transfer by the gas filtered in the pores is formulated on the basis of the developed physical concepts, estimates, and analysis of experimental data. Key words: combustion, electron emission, filtration, electromotive force.     

Optical dot gain on newsprint determined with the Lund nuclear microprobe

A technique for measuring optical dot gain, i.e. the relative difference between the actual screen dot and the optically perceived one, is presented. By combining measurements from the non-optical nuclear microprobe with data from image analyzing technique the optical dot gain can be determined. The procedure to reach pixel by pixel correlation on a micrometer scale is discussed. In the newsprint sample studied in this investigation a typical optical dot gain between 15 and 20% was deduced. The variation in the optical dot gain was correlated with other characteristic parameters of the print and newsprint and especially a positive correlation to the mass density of the newsprint was observed.     

Solution and applications of the Lyapunov equation for controlsystems

Recent advances in control systems analysis and design have implied new uses for the Lyapunov equation of the form AX+XA^T+Q=0. Implementation requirements for the incorporation of the use of Lyapunov equations in practical design, however, point out the need for a set of specialized numerical procedures. This special set of numerical procedures must efficiently solve large, sparse Lyapunov equations, solve sets of Lyapunov equations that differ only in the coefficient matrix Q, and provide good low rank estimates of the Lyapunov equation solution X in the case where low rank approximations are applicable. Discussions of the motivations for the solution of these problems and of candidate solution approaches are provided     

Low-temperature interface reaction in aluminium-silicon carbide particulate composites produced by mechanical alloying

An experimental investigation has been carried out on the reaction that takes place between 3 and 20 μm SiC particles and the aluminium alloy 1050 matrix of composite materials prepared by a mechanical alloying process. The work is different from that undertaken by other researchers in that the SiC-Al interface reaction has been studied in the temperature range 853–933 K, i.e., with the matrix initially in the solid state. Differential thermal analysis, X-ray diffraction and scanning electron microscopy all show that the SiC-Al reaction initiates in the solid state at temperatures as low as 883 K. The reaction produces Al4C3 and Si, the latter entering into solid solution in the aluminium matrix. At temperatures exceeding 903 K, the reaction produces a liquid phase and at this stage the speed of the interface reaction increases significantly. The results are discussed in terms of Al-Si-C metastable equilibrium and the kinetics of the reaction. This revised version was published online in November 2006 with corrections to the Cover Date.     

Electrochromic properties of tungsten-molybdenum oxide electrodes

Tungsten oxide and molybdenum doped tungsten oxide electrochromic films have been electrochemically prepared from a metal peroxide bath and experimentally tested. They were characterized by electrical and optical methods, using cyclic voltammograms and calculating the charge capacity as a function of the number of deposition cycles.The color of the electrochromic WO₃ film is strongly altered by doping it with molybdenum. Electrochromic W---Mo oxide films were fabricated by adding different percentages of molybdenum to tungsten oxide, ranging from 0.5% to 7% weight of deposition solution. Normal optical transmittance was also measured and evidence is given of different behavior if the switching for oxidation and reduction cycle, so that coloration occurs in a shorter time than the bleaching. The time constant of the process tends to increase as a function of the molybdenum oxide doping concentration.     

A new SPICE model of power P-I-N diode based on asymptotic waveformevaluation

A new SPICE subcircuit model for power p-i-n diodes is proposed in this paper. The model is based on a moment-matching approximation of the ambipolar diffusion equation. It is shown that both the quasistatic model and the lumped charge model can be obtained as ion-order moment-matching approximations while new and more accurate models can be obtained from higher-order solutions. The proposed model takes into account emitter recombination in the highly doped end regions, conductivity modulation in the base and the moving-boundaries effect during reverse-recovery, showing good convergence properties and fast simulation times. Comparisons between the results of the SPICE model and both numerical device simulations and experimental results are presented     

The probability density and autocorrelation of short-term global and beam irradiance

For individual hours, a characteristic bimodal pattern of short-term global and beam irradiance is frequently observed, with modes at high and low irradiances and with low probabilities near the hourly averages. For such hours, averaging over the hour will imply smoothing of quite significant variations within the hour. Models for the probability density distributions of short-term (5 min or less) irradiances are presented in this paper. These distributions are not unique functions of the hourly averages, but depend heavily also on the irradiance variability within the hour. This intrahour variability is found to depend on the averaging time and also on the interhour variability among three hourly averages, namely, the hour in question, the preceding and the deceding hour. The distribution differences between 5 min averages and instantaneous values are, however, negligible for most practical purposes. The lag one autocorrelation is evaluated as a function of averaging time, and a first order autoregressive model is presented. With hourly averages as the only input the probability density and autoregressive model in combination produce time series of short-term intrahour averages having realistic distributions and autocorrelation structure.