Investigation and simulation of foam aluminum obtained from secondary aluminum raw materials by mechanical doping

The structure and phase composition of the samples of foam aluminum based on the AMg6 alloy (Al-6%Mg-0.7%Mn) obtained in a high-energy planetary mill are investigated. Mechanical doping provides high dispersity and homogeneity of all structural components including particles of the foam agent TiH₂, which allows one to obtain foam aluminum with a pore size of 1–5 mm at a density of 1.20–0.80 g/cm³. Mechanical properties of foam aluminum were estimated based on the results of compression tests. Based on preliminary investigations, an imitation model of foam formation is suggested that well describes the process of foam formation.     

Effect of the particle size ratio on the conductivity of conductor-insulator powder composites: Numerical simulation

A theoretical method for determining the percolation limit and effective conductivity of composites based on polydisperse mixtures of insulator and conductor powders is proposed. The effect of the particle size ratio between the insulator and conductor on the percolation limit and effective conductivity is studied. Numerical simulation of the microstructure, effective properties, and percolation limit in composites is discussed. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 31–40, 2007.     

Fast algorithms for single frequency estimation

In this paper, some new estimators of the frequency of a single complex sinusoid are presented. The rotate-add-decimate (RAD) method of Crozier is first refined to more closely approach the Cramer-Rao Bound (CRB). An additional modification yields an unbiased estimator (ERAD) that essentially achieves the CRB above a signal-to-noise ratio (SNR) threshold comparable to that of RAD. In addition, this estimator is proven to achieve the CRB for high SNR. The ERAD method requires approximately 2N complex multiply-adds and log/sub 2/N arctangents. A modified ERAD (MERAD) is proposed that matches the SNR threshold and computational complexity of the RAD method (approximately 3N complex multiply-adds and log/sub 2/N arctangents) but achieves the CRB for high SNR.     

Low-threshold single-quantum-well InGaAs/GaAs lasers grown bymetal-organic chemical vapor deposition on structure substrates

Low-threshold current (as low as 3.0 mA) and high-external efficiency (≈88%) InGaAs/GaAs lasers emitting at 1 μm under a stable fundamental transverse mode were obtained by using the temperature engineered growth technique for the growth on prepatterned substrates     

Currents induced on multiconductor transmission lines by radiationand injection

Multiconductor transmission line theory is used to compare current induced on individual wires within a bundle by injection and radiated excitation. Calculations show that the two types of excitation generally induce significantly different current distributions, but the differences are much smaller for electrically short lines. The results are relevant to the validity of using current injection testing to replace radiated immunity testing