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991.
992.
李章成 《武汉大学学报(工学版)》1998,(3)
在解析法的基础上,利用应力与温度、比载和挡距的函数关系,求解架空送电线路导线力学计算的有效临界档距和判断控制气象条件,对其原理、应用作了分析介绍.这种方法简明、直观,在架空线路设计中有实用价值. 相似文献
993.
在满足机构许用压力角条件下,采用0.618法最优确定盘状摆动凸轮机械的最小基圆半径。 相似文献
994.
C. Boned M. Moha-Ouchane A. Allal M. Benseddik 《International Journal of Thermophysics》1998,19(5):1325-1341
The dynamic viscosity and the density of the associative ternary mixture water+diacetone alcohol+2-propanol have been measured as a function of temperature T (303.15, 323.15, and 343.15 K) and pressure P (100 MPa). The experimental results correspond to 698 values of and . With reference to the 54 values previously published on pure substances and 486 values for three corresponding binaries, the system is globally described by 1188 experimental values for various values of P, T and composition. The results for are discussed in terms of excess activation energy of viscous flow. 相似文献
995.
双股射流壁面脉动压强与近壁紊动流速相关与频谱特性 总被引:2,自引:0,他引:2
本文用多通道动态压力检测系统和二维激光测速仪对在单股和双股射流作用下,水垫塘底板脉动压强与近壁脉动流速的相关,功率谱和紊动比尺进行了测试研究。实测表明,双股射流形成的动水扩建在塘底水平方向的脉动使得双股射流在第二冲击点下游的脉动量特性与单股射流不同:前者的水平脉动速度与脉动压强的互相关系数较后者明显增大,且水平脉动速度和脉动压强的功率谱具有大致相同的优势频率。单股和双股射流塘底脉动压强系数与近壁紊 相似文献
996.
I. M. Abdulagatov S. B. Kiselev L. N. Levina Z. R. Zakaryaev O. N. Mamchenkova 《International Journal of Thermophysics》1996,17(2):423-440
The specific heat at constant volume, Cv, of propane, and mixture with a concentration ofx=0.0081 cool fraction of propane was measured along the critical isochores at temperatures between 290 and 400 K. The measurements were performed with a high-temperature constant-volume adiabatic calorimeter. The uncertainty of most of the measurements is estimated to be less than 1.5%. Measurements have been carried out in both the one- and two-phase regions. The results for the pure components are compared with earlier measurements. Crossover equations forC, obtained on the basis of the renormalization-group method and -expansion are applied to represent our experimental specific heat data for ethane, propane. and its mixture along the critical isochores. 相似文献
997.
L. A. Bulavin A. V. Oleinikova A. V. Petrovitskij 《International Journal of Thermophysics》1996,17(1):137-145
The lower critical point of stratification of a 3-methylpyridine (MP)+heavy water (D2O) mixture in the presence of Na+ and CI– ions has been studied by the Toepler shadow method. Addition of 0.3% ions lowered the critical temperature and reduced the equilibration time and the gradient of the refractive index (compressibillity). The analysis of the form of the near-critical isotherm demonstrated the ionic mixture to be described by the index = 3.05 ± 0.15. which corresponds to the classical mean-field theory. The results obtained provide evidence that even small admixtures of charged particles result in a substantial suppression of fluctuations near the critical point by the long-range Coulomb interaction.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
998.
L. P. Cook W. Wong-Ng P. Paranthaman 《Journal of research of the National Institute of Standards and Technology》1996,101(5):675-689
The melting and vaporization of the 1223 [(Tl,Pb):(Ba,Sr):Ca:Cu] oxide phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O) have been investigated using a combination of dynamic methods (differential thermal analysis, thermogravimetry, effusion) and post-quenching characterization techniques (powder x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry). Vaporization rates, thermal events, and melt compositions were followed as a function of thallia loss from a 1223 stoichiometry. Melting and vaporization equilibria of the 1223 phase are complex, with as many as seven phases participating simultaneously. At a total pressure of 0.1 MPa the 1223 phase was found to melt completely at (980 ± 5) °C in oxygen, at a thallia partial pressure (pTl2O) of (4.6 ± 0.5) kPa, where the quoted uncertainties are standard uncertainties, i.e., 1 estimated standard deviation. The melting reaction involves five other solids and a liquid, nominally as follows:
Stoichiometries of the participating phases have been determined from microchemical analysis, and substantial elemental substitution on the 1212 and 1223 crystallographic sites is indicated. The 1223 phase occurs in equilibrium with liquids from its melting point down to at least 935 °C. The composition of the lowest melting liquid detected for the bulk compositions of this study has been measured using microchemical analysis. Applications to the processing of superconducting wires and tapes are discussed. 相似文献
999.
1000.
以羊场湾煤矿120204综采工作面为例,介绍了一种工作面压力实时监测系统的设计。该系统根据压力监测单元采集的各支架前柱、后柱、前梁压力参数,由地面主机中的分析软件给出量化分析结果,即支架前后柱及前梁压力变化、支架立柱的工作特性、支架立柱循环阻力的频率分布、顶板压力分布;并可根据支架立柱的工作特性分析结果分析支架压力变化与顶煤破碎效果之间的关系,从而为提高放顶煤效率提供依据。实际应用表明,该系统功能完善,能有效地反映工作面压力变化的全过程。 相似文献