Enhanced antenna-pattern measurements for Satellite systems

This paper describes an enhanced measurement technique for earth-station antennas in a satellite communication system. A new data-acquisition algorithm improves the dynamic range of the measurements by increasing the signal-to-noise ratio in the test setup. The resolution limitation of conventional techniques is eliminated without any modifications to the ground station setup. The proposed approach improves the conventional measurement techniques by utilizing pulse modulation of the test-signal amplitude and its synchronous detection. The noise floor in the pattern is reduced by biasing out the average noise power calculated during the OFF cycle of the pulse. In addition, a randomly fluctuating local mean in the receiver output is reduced. Experimental results show improvements of as much as 25 dB in the noise variance and over 11 dB in the dynamic range of the antenna pattern.     

Mixture of probability distributions as a basic component in simulating measurement accuracy

A stochastic model is proposed for a basic mechanism in the formation of uncertainties in physical quantity measurements. __________ Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–17, January, 2006.     

(BETS)2[RuX5NO] (X = Cl, Br): An Explanation of Different Conductive Properties Through Structural and Spectroscopic Studies

For the development of new crystal and electronic structures in molecular conductors, dimeric tetrathiafulvalene (TTF) and tetraselenafulvalenes (TSFs)1–3 linked by single or double methyl antimony bridge(s) have been prepared and their neutral crystal structures have been investigated. The donor2 (cis-2) forms a metallic cation radical salt with tetracyanoquinodimethane (TCNQ) containing one-dimensional array interactions.     

Cyclic strength of parts with overlapping zones formed by roller burnishing

The authors study residual stresses in and cyclic strength of shaft with overlapping zones formed during roller burnishing. The most significant decrease in fatigue strength is shown to occur in the presence of an overlapping zone with the areas arising due to a lowered roller burnishing pressure in the second pass. __________ Translated from Problemy Prochnosti, No. 3, pp. 144–148, May–June, 2006.     

New Ideas on the Mechanism of Structure Formation in Nitrided Steels

The main laws of formation of structure and properties of nitrided structural steels are studied depending on their composition, parameters of preliminary heat treatment, and nitriding modes. New factors controlling the structure and operational properties based on new concepts of the mechanism of formation of nitride particles in the nitriding process are determined.     

Procedure for the evaluation of the accumulation of defects in metallic structural materials under complex elastoplastic loading

Within framework of the continual fracture mechanics, we describe the engineering approach to the assessment of scattered microdamage accumulation kinetics in metallic materials under elastoplastic loading conditions in case of plane stressed state. Automatized experimental stand and the respective investigation technique are discussed. The stand has been developed based on modification of the UMé-10T electromechanic test machine. State-of-the-art computer technologies and microprocessing hardware are incorporated in the stand automation. We present the technique of experimental assessment of damage accumulation kinetics in metallic structural materials under complex elastoplastic loading conditions with account of two different fracture (cleavage and shear) processes, which technique is based on measuring the specific electric resistance of the specimen. __________ Translated from Problemy Prochnosti, No. 1, pp. 128–137, January–February, 2006.     

Transformations in machining. Part 1. enhancement of wavelet transformation neural network (WT-NN) combination with a preprocessor

Properly selected transformation methods obtain the most significant characteristics of metal cutting data efficiently and simplify the classification. Wavelet Transformation (WT) and Neural Networks (NN) combination was used to classify the experimental cutting force data of milling operations previously. Preprocessing (PreP) of the approximation coefficients of the WT is proposed just before the classification by using the Adaptive Resonance Theory (ART2) type NNs. Genetic Algorithm (GA) was used to estimate the weights of each coefficient of the PreP. The WT-PreP-NN (ART2) combination worked at lower vigilances by creating only a few meaningful categories without any errors. The WT-NN (ART2) combination could obtain the same error rate only if very high vigilances are used and many categories are allowed.     

Functional characteristics of Bi2Sr2Ca2Cu3O10 + δ/ZrN composites

We present the results of investigation of the magnetic, transport, structural, and mechanical properties of composites obtained by introducing finely dispersed zirconium nitride into a matrix of a Bi₂Sr₂Ca₂Cu₃O_{10 + δ} (Bi2223) high-temperature superconductor. It is established that the introduction of ZrN particles in the range of very small concentrations (0.1–0.3 wt %) leads to a significant (more than threefold) increase in the critical current density of Bi2223 and increases the density of the composite, while the microhardness of the superconducting phase remains unchanged.     

Mössbauer study of the Ge two-electron donor centers in PbSe

Mössbauer emission spectroscopy at ⁷³As(⁷³Ge) is used to show that the charge state of the ⁷³Ge antisite defect formed in the anion sublattice after the radioactive transformation of ⁷³As is independent of the position of the Fermi level. In contrast, the ⁷³Ge center in the cation sublattice of PbSe is an electrically active substitutional impurity. For the n-type samples, the spectrum corresponds to the neutral state of the donor center (⁷³Ge²⁺), and for the p-type samples, the spectrum corresponds to the doubly ionized state (⁷³Ge⁴⁺) of this center.