Research on Clay-Cement Concrete in Anti-Filtration Elements of Earth Dams at Freeze-Thaw Temperatures

Power Technology and Engineering - This article presents and analyzes the results of a study on the frost resistance of clay-cement concrete used for repairing the anti-filtration element of the...     

Processing a Sn–Pb Alloy to Produce Tin

Russian Journal of Non-Ferrous Metals - The aim of the work is to develop an optimal method for processing Sn–Pb alloy to obtain a marketable product-branded O1?O3 tin (Sn ≥...     

Configurational statistics of copolymers prepared by complex-radical polymerization

Radical copolymerization is considered theoretically taking into account the effect of complexing on the configurational statistics of macromolecules formed. Akinetic model has been developed that considers, apart from the ordinary addition of single monomer units to a propagating chain, the possible addition of monomer unit pairs along with a complexing agent in the form of a ternary complex. Within the framework of this model, the problem of calculating the probabilities of formation of any sequences of monomer units (taking into account their microtacticity) in a macromolecule has been rigorously solved as well as the problem of finding the composition distribution of the copolymer formed. It has been shown that this distribution is described by a conventional Gauss law and the appropriate parameters are given. Possible generalizations of the suggested approach are indicated.     

Effect of vanadium and chromium on the microstructural features of V–Cr–Mn–Ni spheroidal carbide cast irons

The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys＇ microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic（based on M7C3）, pearlite, martensite, and austenite. Their combinations and area fraction（AF） ratios are reported to be influenced by the alloys＇ chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic（γ-Fe ＋ М7С3）, preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.     

Adjustment Dynamics in a Network Game with Stochastic Parameters

Automation and Remote Control - In this paper, stochastic parameters are introduced into the network games model with production and externalities of knowledge. This model was formulated by V....     

Mechanisms of neuronal calcium homeostasis destabilization caused by hyperstimulation of glutamate receptors

The present paper summarizes the data obtained in studying the mechanisms of glutamate-induced deterioration of neuronal Ca2+ homeostasis. In the cultured mammalian central neurons, a short-term (< 1 min) glutamate (GLU, 100 mu) challenge is known to induce a readily reversible (transient) neuronal [Ca2+]i increase. In contrast, a long-term (15-30 min) GLU exposure leads to the appearance of high [Ca2+]i plateau or to the partial recovery of the increased [Ca2+]i. Experiments show that impaired [Ca2+]i recovery in the postglutamate period cannot be explained by the increased [Ca2+]i permeability of the neuronal membrane, as earlier considered. Moreover, a sustained elevation of [Ca2+]i during and after chronic GLU application is associated with a progressive decrease in Ca2+ permeability. The major cause of GLU-induced Ca2+ overload is the mitochondrial depolarization resulted from excessive Ca2+ influx into the mitochondria, the generation of free radicals and the opening of a "giant pore" in the inner mitochondrial membrane. This in turn suppresses both ATP synthesis and Ca2+ electrophoretic uptake into the mitochondrial matrix. In combination with [Ca2+]i-dependent acidification, this leads to the suppression of Ca2+ release from the cell via Na+/Ca2+ exchanger and Ca2+/H+ pump of the neuronal membrane. Therefore, [Ca2+]i recovery following a long-term GLU treatment becomes strongly or even irreversibly compromised.     

Managing complex orthodontic problems: the use of implants for anchorage

In congestive heart failure captopril modifies the left ventricular filling pattern mainly by unloading the heart. We investigated whether the structural characteristics of the left ventricle may influence the acute effects of captopril on this pattern in patients with untreated hypertensive (H group, 6 patients) or idiopathic (I group, 14 patients) cardiomyopathy. We evaluated changes of pulsed Doppler mitral flow, of systemic arterial and wedge pulmonary pressures 40 min after 25 mg captopril administered sublingually, and correlated these changes with the M-mode echocardiographic relative wall thickness index (h/r). Baseline mean arterial pressure (H = 137 +/- 20 mm Hg, mean +/- SD, I = 95 +/- 19 mm Hg; p < 0.001), and h/r (H = 0.38 +/- 0.03, I = 0.28 +/- 0.09; p < 0.05) were greater in the high blood pressure group; wedge pressure, echocardiographic biplane ejection fraction, and Doppler indexes of the left ventricular filling were similar in the two populations. After captopril, ejection fraction did not change significantly, mean arterial pressure decreased significantly in hypertensive patients (H group, baseline = 137 +/- 20, captopril = 119 +/- 10, p = 0.02; I group, baseline = 95 +/- 19, captopril = 90 +/- 24, p = nonsignificant), and the wedge pressure was reduced by the same extent in both groups (H group, baseline = 27.7 +/- 3, captopril = 21 +/- 7, p < 0.05; I group, baseline = 20 +/- 12, captopril = 15 +/- 8, p < 0.05). In the H group early mitral flow increased [(E wave integral) x (mitral annulus area)] by 38 +/- 15%, and was almost steady in the I group (-1.3 +/- 30%; group H vs. I = p < 0.01); late mitral flow [(A wave integral) x (mitral annulus area)] showed a pattern exactly opposite to this (H = +0.4 +/- 40%, I = +38 +/- 19; p < 0.01). In the whole population there was a significant correlation between the early/late flow ratio variations and baseline h/r (r = 0.6, p < 0.05). In chronic congestive heart failure, changes in left ventricular filling with captopril are related to h/r: a higher index, as recorded in the H group, is associated with "true normalization' of the filling pattern after captopril; a lower index, as recorded in the I group, is associated with "pseudonormalization' despite a similar decrease of left ventricular filling pressure.     

Adaptive control system for car parking

In the paper, the first results of the work on the development and implementation of an adaptive control system for car parking are presented. The proposed approach to construction of a car control system differs from the commonly accepted approach [1–3] and is based on the autonomous adaptive control method [4] developed by the research team headed by A.A. Zhdanov. In the framework of this method, car control and training and retraining of the control system are implemented in one process with satisfaction of all necessary conditions and constraints. This allows the control system to adjust to parameters of a particular car and to automatically readjust if these parameters vary in the course of the car usage. In the paper, a program modeling car parking based on the principles developed in this study is described. Examples of parking a car for some particular cases of mutual location of obstacles and the desired slot in the parking place are presented.     

Accuracy of a Bellows vacuum meter with an LC-generator

Errors of pressure measurement are considered. The error as a function of the pressure for a vacuum gauge rated at up to 1000 Pa is calculated as an example. It is 0.15 ≤ δp/p ≤ 0.2% over a pressure range of 14 ≤ p ≤ 1000 Pa and it increases hyperbolically up to 100% with p = 0.01 Pa. The parametric reliability of the instrument and its immunity to an accidental increase in pressure the atmospheric level is substantiated. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 37–41, September, 2006.