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《工程热物理学报》2017,(3)
本文介绍了由VM型热压缩机驱动的脉冲管制冷机基本结构、数值模拟与实验研究。热压缩机借鉴VM制冷机产生压力波动的方式,即依靠室温与冷源之间的温度差产生压力波动,驱动低温级脉冲管制冷机。利用液氮温区制冷机为热压缩机提供所需要的冷量,避免使用低温液体带来的不便。低温级脉冲管制冷机的回热器与脉管采用U型布置,调相机构采用小孔气库加双向进气方式。这种结构不使用有阀压缩机,可以产生低频压力波动,保证回热器在低温区高效工作。在原有结构的基础上,改造热压缩机回热器尺寸与填料,使用Sage软件进行了整机模拟,对调相机构进行优化,考察其在不同的运行频率、平均压力、排出器位移下的制冷性能。对改造后的脉冲管制冷机进行了初步的实验研究,获得14.4K无负荷制冷温度。 相似文献
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《Journal of Electrostatics》2007,65(1):21-29
The electrostatic problem of a hollow, conducting tube of finite length held at a fixed potential is solved using two methods. A two-term Galerkin solution is constructed for the surface distribution of induced charge. The sum of a uniform component and a simple edge-condition term provides a variational solution to the dual integral equations that are the equations-of-motion for the mixed boundary value problem. Comparisons are made with the numerical results of an independent boundary element or moment method. The numerical solution uses collocation or point matching and a piecewise constant basis for the charge density. 相似文献
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The diffusion of particles in confining walls forming a tube is discussed. Such a transport phenomenon is observed in biological cells and porous media. We consider the case in which the tube is winding with curvature and torsion, and the thickness of the tube is sufficiently small compared with its curvature radius. We discuss how geometrical quantities appear in a quasi-one-dimensional diffusion equation. 相似文献
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A common mechanism for intracellular transport is the use of controlled deformations of the membrane to create spherical or tubular buds. While the basic physical properties of homogeneous membranes are relatively well known, the effects of inhomogeneities within membranes are very much an active field of study. Membrane domains enriched in certain lipids, in particular, are attracting much attention, and in this Letter we investigate the effect of such domains on the shape and fate of membrane tubes. Recent experiments have demonstrated that forced lipid phase separation can trigger tube fission, and we demonstrate how this can be understood purely from the difference in elastic constants between the domains. Moreover, the proposed model predicts time scales for fission that agree well with experimental findings. 相似文献
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Experimental investigations of acoustically induced turbulence in a resonance tube have been performed. Frequency (f) and sound pressure level (Ip) effects have been studied. Measurements were made at various spatial locations on loops and nodes. Sampled data were processed to estimate the characteristics of turbulence. It is found that the acoustically induced turbulence appears when Ip exceeds 160 dB under the experimental conditions of f = 680–2740 Hz and Ip = 160–166 dB. The turbulent spectrum (F) and the wave number (κ) are found to satisfy a power law F ∝ Ks with . The r.m.s. turbulent velocity () is experimentally found to have an dependence, yet is relatively insensitive to the variation of f. Throughout the whole measuring range of f and Ip, the rate of energy dissipation per unit mass (ε) is estimated to be in the order of 106–107cm2/s3. 相似文献
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We present a re-analysis of the decaybs in the Minimal Supersymmetric Standard Model with radiatively induced breaking of the gauge groupSU(2)×U(1). We extend this analysis to regions of the supersymmetric parameter space wider than those previously studied. Results are explicitly presented form
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=150 GeV. We discuss the consequences of a measurement of this decay at the Standard Model level for future searches of charged Higgs and charginos. In spite of the strong sensitivity of this decay to the effects of supersymmetry, we find that, at the moment, no lower limit on the mass of these particles can be obtained. The large chargino contribution to the branching ratio forbs obtained at large values of tan is effectively reduced by pushing the lightest eigenvalue of the up-squark mass matrix closer to the electroweak scale, i.e. by increasing the degree of degeneracy among the up-squarks.Supported by the Bundesministerium für Forschung und Technologie, 05 5 HH 91P(8), Bonn, Germany 相似文献
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N. S. Ginzburg N. I. Zaitsev E. V. Ilyakov I. S. Kulagin Yu. V. Novozhilova R. M. Rozental’ A. S. Sergeev 《Technical Physics》2001,46(11):1420-1427
Experimental and theoretical studies on the self-modulation mode of generation in a high-power BWT with the electrodynamic system representing a slightly corrugated waveguide are presented. The BWT is fed by an electron beam with the energy 150 keV and the current 150 A. The system operates at the E 01 mode with the mean frequency 8.7 GHz. Dynamic chaos is obtained by a three-fold increase in the length of the interaction space in comparison with the prototype exhibiting stationary generation. The stationary generation was changed to periodic sinusoidal self-modulation and then to chaotic self-modulation as the current increases from 6 to 60 A. The generation mode is simplified when the current ranges from 70 to 90 A and becomes complicated again for the current exceeding 100 A. Experimental observations are in good agreement with the results of simulation predicting a certain simplification of the self-modulation mode at the currents 70–90 A owing to the effect of high-frequency space charge. Under the conditions of chaotic generation, the mean power was as high as 2 MW at the relative spectral width of the signal 4% and the total duration of the microwave pulse 10 μs. 相似文献