共查询到19条相似文献,搜索用时 140 毫秒
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在血管壁施加第三类边界条件是计算血液与组织间对流换热的一种近似计算方法.为分析其可行性,用有限元数值模拟方法计算血管分支结构中血液与组织的对流换热,得到不同流速和半径下分支血管内血液的截面平均Nu数沿管长的变化曲线.结果表明,血管树中分支血管的Nu数变化幅度不大,且趋于稳定值的速度很快.以相同边界条件下包含简单血管系统的舌体为例,分别用近似方法和完全耦合计算方法,进行血液流场和舌体温度场模拟.通过比较计算结果,得出两种方法得到的温度场分布趋势基本相同;用完全耦合计算方法得到的舌体温度略高于用近似方法得到的舌体温度,两者差值小于0.2℃. 相似文献
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运用热分析软件Icepak对望远镜LAMOST的圆顶围挡通道进行了热计算与分析,重点分析了围挡壁面的热辐射和热传导对整个温度场的影响。在通风管道冷却方案的基础上,分别建立了壁面辐射和传导的热模型,描述了壁面的传热结构。仿真计算了增加壁面热辐射和热传导时主光学组件——焦面的温度场分布,并对此作了对比分析。数值计算与仿真结果表明:壁面传热对其内部温度场的影响不大;利用通风管道的冷却措施可将焦面的最大温度梯度控制在0.4℃/m;围挡的特性结构对传热有效。 相似文献
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A spin-1 transverse Ising model with longitudinal crystal field in a longitudinal magnetic field is examined by introducing an effective field approximation (IEFT) which includes the correlations between different spins that emerge when expanding the identities. The effects of the crystal field as well as the transverse and longitudinal magnetic fields on the thermal and magnetic properties of the spin system are discussed in detail. The order parameters, Helmholtz free energy, entropy and specific heat curves are calculated numerically as functions of the temperature and Hamiltonian parameters. A number of interesting phenomena such as reentrant phenomena originating from the temperature, crystal field, transverse and longitudinal magnetic fields have been found. 相似文献
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Magnetic and thermodynamic properties of the anisotropic XYZ spin-1/2 finite chain under both homogeneous and inhomogeneous magnetic fields are theoretically studied at low temperature. Using exact diagonalization method (ED), we study the magnetization, magnetic susceptibility, and specific heat of the model characterized in terms of the finite correlation length in the presence of three different magnetic fields including longitudinal, transverse, and transverse staggered magnetic fields. The magnetization, susceptibility, and the specific heat of the model are investigated under two conditions separately: (i) When the model is putted in the presence of homogeneous magnetic fields. (ii) When finite inhomogeneities are considered for all applied magnetic fields in the Hamiltonian. We show that for the finite-size XYZ chains at low temperature, the evident magnetization plateaus gradually convert to their counterpart quasi-plateaus when the transverse magnetic field increases. Moreover, the influence of the transverse and staggered transverse magnetic fields, and their corresponding inhomogeneities on the magnetization process, magnetic susceptibility, and specific heat are reported in detail. Our exact results illustrate that by altering the inhomogeneity parameters, magnetization plateaus gradually convert to their counterpart quasi-plateaus. The specific heat manifests Schottky-type maximum, double-peak, and triple-peak, as well as, transformation between them by varying considered inhomogeneity parameters in the Hamiltonian. 相似文献
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Measurements of the Kapitza conductance by the ac technique are reported for oriented gallium and copper single crystal discs. The data show convincing evidence that conduction electrons participate in the transmission of heat across the metal-He II interfaces for both metals. Measurements of the Kapitza conductance as a function of transverse and longitudinal fields and the influence of temperature, sample thickness and impurities allow a qualitative understanding of the total heat transfer across the sample. 相似文献
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基于矢量瑞利-索末菲衍射积分,研究了矢量空心高斯光束横向光场和纵向光场在自由空间中的传输特性.研究结果表明,空心高斯光束的横向光场与纵向光场在传输过程中光强分布情况并不相同,横向光场的光强分布具有旋转对称性,并且保持空心特性的距离受光束阶数的影响,而纵向光场不再具有旋转对称性,并且在理想状态下纵向光场可以一直保持空心特... 相似文献
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采用放电等离子烧结技术,在相同的温度(1 473 K)及压力(30 MPa)下,制备出不同配比的致密的W-Mo系复合材料样品。采用高精度超声波脉冲回波重合方法,精确测量了超声波在样品中传播的横、纵波声速,并由此得到样品的特性波阻抗值。对样品的相组成分析及电子探针分析的结果表明,W-Mo系复合材料主要是以W、Mo机械混合的形式通过粘结相获得致密化的。因此,选用混合物模型对其特性波阻抗值进行了理论预测,与实测值的比较表明该模型能对W-Mo系复合材料的特性波阻抗作出比较准确的预测。 相似文献
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P. V. Gorskii 《Russian Physics Journal》2006,49(5):489-499
In the present paper, oscillations of the longitudinal component of the electrical conductivity of layered crystals are examined
in electric and quantizing magnetic fields perpendicular to the layers. It is demonstrated that frequencies and amplitudes
of longitudinal conductivity oscillations can be determined with sufficient accuracy through the chemical potential of the
electron gas and effective width of the miniband caused by the charge ordering. In addition, based on an analysis of formulas
for the transverse conductivity, it is established that the applicability limits for the transverse conductivity in the semiclassical
approximation (for the magnetic field induction) in the field perpendicular to the layers are much wider than for the longitudinal
conductivity. An immediate reason for this is the zero longitudinal velocity of current carriers in the extreme cross sections,
which leads to the field dependence of the amplitudes of longitudinal conductivity oscillations stronger than of transverse
ones. Calculated results are used to interpret experimental data obtained for the β-(ET)2IBr2 synthetic metals.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 34–43, May, 2006. 相似文献
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Photoelastic and shadowgraph imaging techniques were used to visualize the propagation and evolution of stress waves, and the resultant transient stress fields in solids during shock wave lithotripsy. In parallel, theoretical analysis of the wavefront evolution inside the solids was performed using a ray-tracing method. Excellent agreement between the theoretical prediction and experimental results was observed. Both the sample size and geometry were found to have a significant influence on the wave evolution and associated stress field produced inside the solid. In particular, characteristic patterns of spalling damage (i.e., transverse and longitudinal crack formation) were observed using plaster-of-Paris cylindrical phantoms of rectangular and circular cross sections. It was found that the leading tensile pulse of the reflected longitudinal wave is responsible for the initiation of microcracks in regions inside the phantom where high tensile stresses are produced. In addition, the transmitted shear wave was found to play a critical role in facilitating the extension and propagation of the microcrack. 相似文献