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211.
Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Sumy Branch, Khar'kov Polytechnic Institute. Translated from Problemy Prochnosti, No. 8, pp. 102–104, August, 1989. 相似文献
212.
A numerical solution of the inverse problem of the gravitational field at a single point is obtained using six field elements
for a point, a spherical cap, a differential spherical sector and a vertical segment. In the system of six equations obtained,
the unknowns are the mass of the body, the depth of its center, and the second, third, and fourth degree moments. The accuracy
of the solution of this system is ten times higher than when using three field elements.
__________
Translated from Izmeritel’naya Tekhnika, No. 5, pp. 3–8, May, 2007. 相似文献
213.
Indoor body-area channel model for narrowband communications 总被引:1,自引:0,他引:1
Fort A. Desset C. Wambacq P. Biesen L.V. 《Microwaves, Antennas & Propagation, IET》2007,1(6):1197-1203
Using wireless sensors placed on a person to continuously monitor health information is a promising new application. At the same time, new low-power wireless standards such as Bluetooth and Zigbee have been proposed for short range, low data-rate communication matching the requirements of these bio-medical applications. However, there are currently few measurements or models describing propagation around the body. To address this problem, electromagnetic waves near the torso are measured and a statistical model is derived for communication in the 915 MHz and 2.45 GHz industrial, scientific and medical bands associated with Zigbee and Bluetooth. Measurement setup and statistical analysis are described. 相似文献
214.
The paper is devoted to the effect of compressibility of the avalanche snow impacting an obstacle. Compression shocks generated by obstacle cause high pressure peaks at first instants of impact. That is why the account of compressibility is essential for the understanding of measurements and the design of structures. The main problem in calculation compression shocks in avalanches is to formulate an equation of state for moving snow in impact. Two different types of equations of state are proposed depending on the type of the avalanche (low-density and high-density flows). The approach is not totally new. It was earlier proposed mainly in Russian literature. Here a brief review of the previous work is given with discussion of some gaps in it. The theory is reformulated and further developed to account thermodynamical equations. The simplest case of a normal compression shock in an avalanche flow is studied. Examples of estimations of pressure and density behind a shock are given. It is important to emphasize that the Mach number plays an important role in the theory of compressible flows so it should be taken into account (together with the Froude number) in calculation and modelling an avalanche impact pressure. 相似文献
215.
The polycrystalline samples of Dy
x
Bi1−x
FeO3 (x = 1, 0.8, 0.6, 0.4 and 0.2) were synthesized by standard solid state reaction technique. The samples synthesized were characterized
by X-ray diffraction (XRD) technique. Further the samples were characterized by infrared (IR) spectroscopic technique. The
dielectric measurements were carried out as a function of frequency in the range 100 Hz to 1 MHz at room temperature. Also
the dielectric measurements were carried out as a function of temperature at certain fixed frequencies. The ac and dc resistivity
measurements were carried out using two probe method. Also temperature dependence of ac and dc resistivity was noted. These
measurements suggest polaron conduction in the samples. Finally, the data from XRD, IR, dielectric measurements were correlated. 相似文献
216.
V. Thomas Paul S. Saroja P. Hariharan A. Rajadurai M. Vijayalakshmi 《Journal of Materials Science》2007,42(14):5700-5713
This paper presents the results of a study on the microstructural and microchemical variations in a multipass Gas Tungsten
Arc weld (GTAW) of modified 9Cr-1Mo steel. The changes brought about in the steel due to the heating and cooling cycles during
welding and the subsequent effects due to reheating effects during multipass welding are described. Detailed analytical transmission
electron microscopy has been carried to study the type and composition of the primary and secondary phases in this steel.
The systematic changes in microstructural parameters such as Prior Austenite Grain Size, martensite lath size, number density,
size and microchemistry of carbides, have been understood based on the different transformations that the steel undergoes
during the heating and cooling process. Based on the observed microstructure, an attempt has been made to identify distinct
microstructural zones and possible thermal cycles experienced by different regions of the weldment. 相似文献
217.
Dielectric relaxation behaviour of (1 − x)PMN − xPZ, for x = 0.10, 0.30 and 0.40 have been studied. The nature of relaxational behaviour was found to change with PZ concentration.
A crossover from a static freezing to critical slowing down like behaviour is observed with increase in Zr4+ concentration. We have used Glazounov and Tangastev criterion to distinguish freezing and critical slowing down like behaviour. 相似文献
218.
We propose a method of fabricating surface barrier diodes with overlapped metal junction, which provides for a significant decrease in the reverse currents and an increase in the breakdown voltage. 相似文献
219.
A consistent analytical model of nonlinear ion drift spectrometry for modern gas analyzers is developed. A procedure for determining the field dependence of the ion mobility using the experimental data is described. An ionogram is calculated for the case of a flat drift chamber and polynomial character of the field dependence of the ion mobility. 相似文献
220.