Unstructured Adaptive Grid Flow Simulations of Inert and Reactive Gas Mixtures

Unstructured adaptive grid flow simulation is applied to the calculation of high-speed compressible flows of inert and reactive gas mixtures. In the present case, the flowfield is simulated using the 2-D Euler equations, which are discretized in a cell-centered finite volume procedure on unstructured triangular meshes. Interface fluxes are calculated by a Liou flux vector splitting scheme which has been adapted to an unstructured grid context by the authors. Physicochemical properties are functions of the local mixture composition, temperature, and pressure, which are computed using the CHEMKIN-II subroutines. Computational results are presented for the case of premixed hydrogen–air supersonic flow over a 2-D wedge. In such a configuration, combustion may be triggered behind the oblique shock wave and transition to an oblique detonation wave is eventually obtained. It is shown that the solution adaptive procedure implemented is able to correctly define the important wave fronts. A parametric analysis of the influence of the adaptation parameters on the computed solution is performed.     

体全息子波关联记忆器

基于子波匹配相关理论和光折变晶体的体全息关联存储特性,提出并实现了一个关联记忆的新构思。中根据缺损特征实现原始图像的记忆和恢复,其中光折变晶体兼作图像识别时的运算单元和图像恢复时的存储单元,文中以人脸为研究对象,给出了实验结果。     

基于智能手机和Matlab的居家悬滴法表面张力测量实验

本文基于智能手机和Matlab软件设计了一种居家环境下可实现的悬滴法水滴表面张力测量实验.借助智能手机拍照功能获得水滴图像,利用Matlab进行边缘检测及计算,从而得出表面张力系数.对于不同清晰度的情况提出了对应的分析和处理方法,实验结果表明该方法稳定可靠.为后疫情时代开展居家大学物理实验教学提供了一个典型案例.     

双稀土氧化物LnEuO3的Mossbauer效应研究

 本文首次利用高温高压方法合成了双稀土氧化物LaEuO₃、PrEuO₃、NdEuO₃和SmEuO₃。此外，还合成了CeEuO_3.5。X射线衍射分析表明LaEuO₃属A型（六方）结构，PrEuO₃、NdEuO₃和SmEuO₃属B型（单斜）结构，CeEuO_3.5属F型（萤石）结构。室温下用¹⁵¹Eu的21.6 eV γ射线测量了它们的Mossbauer谱，观察到了¹⁵¹Eu同质异能移位和四极劈裂强烈地依赖于Eu离子配位体体积而呈线性关系。超精细相互作用的这种体积效应，主要原因是由于Eu离子5s壳层的重叠畸变所引起。     

垂直并联管内高压汽水两相流压力降型脉动的研究

本文在宽广的参数范围内,对垂直并联管内高压汽水两相流压力降型脉动特性进行了试验研究,得出了系统参数对脉动起始点、周期和振幅的影响。根据两相流的均相模型,对压力降型脉动的周期和振幅进行了数值计算。此方法考虑了系统非线性的影响,与试验结果符合较好。     

Proof of gridlock in a polymer model

It has been suggested that some lattice models of polymers, especially ones that incorporate more realistic excluded volume interactions extending to further neighbors, may be subject to gridlock. A model is defined to have the property of gridlock if it cannot melt at any temperature unless a density decrease is allowed. Classical theories of polymer melting are incompatible with the property of gridlock. This paper proves rigorously that a two-dimensional square-lattice model of polymer chains that have nearest-neighbor excluded volume interactions (called the X1S model) has the gridlock property. The proof uses elementary concepts from graph theory. Also, different interpretations of the X1S model are given in terms of real polymers. This leads to a discussion of a number of different classes of melting depending upon whether the intramolecular rotameric energies and the attractive intermolecular energies are antagonistic to or supportive of the melting transition.     

利用有效液滴模型对超重元素α衰变半衰期的研究

利用有效液滴模型计算了偶偶超重核的α衰变半衰期,计算过程中采用了保持碎片体积守恒的不对称形状描述以及有效惯性系数计算Gamow势垒穿透因子.首先在质子数Z为88—98的区域检验了有效液滴模型,发现计算结果与实验符合得比较好.随后将此模型推广到Z≥100的情况,虽然只用了两个模型参数,计算结果与实验数据符合,说明有效液滴模型是计算偶偶超重核素α衰变半衰期的一个成功模型.     

On the Capability of the Generalized Gamma Function to Represent Spray Drop‐Size Distribution

The three‐parameter, Generalized Gamma function solution of a recent MEF formulation used to derive liquid spray drop‐size distribution, is applied to sprays resulting from three different atomization processes. The objectives of these applications are to determine the sign of the parameters for which this function reports a more reliable fit and to further understand the parameter stability problem reported elsewhere. It is found that the lack of stability of the parameters is related to a characteristic feature of the mathematical function and appears for a series of spray drop‐size distributions with constant shape. For each situation analyzed in the present study, the Generalized Gamma function provides a very good fit with parameters that are either constant or correlated to the working conditions. As far as the sign of the parameters is concerned, the results show that the best formulation is a function of the spray and that it is impossible to know, a priori, which parameter sign will report the best fit. Finally, for one situation, it is found that the Generalized Gamma function allows extrapolation of drop sizes outside the measured values. All of the results converge to conclude that the three‐parameter Generalized Gamma function, which is identical to the well‐known Nukiyama‐Tanasawa distribution, accumulates valuable attributes to represent liquid spray drop‐size distributions.     

大块金属玻璃Zr41Ti14Cu12.5Ni10Be22.5的流变行为研究

采用静态拉伸方法在连续升温条件下动态地测量了大块金属玻璃Zr41Ti14Cu12.5Ni10Be22.5（Vit1）的黏度随温度的变化关系.在应变速率与温度的关系曲线中，观测到了与玻璃转变和晶化过程相联系的多个应变速率峰.在玻璃转变温度Tg以上，大块金属玻璃Zr41Ti14Cu12.5Ni10Be22.5的过冷液体呈现Newton流体特征，其黏度与温度的关系符合Vogel Fulcher-Tammann (VFT)关系式，拟合得到脆度D*＝36，VFT温度T0＝319K，脆度参数m＝30，这说明Zr41T 关键词： 大块金属玻璃 应变速率 剪切黏度 自由体积     

COIL压力恢复系统气流主动冷却技术数值模拟

 引射式压力恢复系统是化学激光系统应用中的一个重要组成部分,为了提高引射器引射效率,减小整个系统尺寸,可以采用主动降低光腔出口气流温度的方法。通过数值模拟,开展了用热交换器降低光腔出口气流温度的研究。给出了混合气体的热物理性质、热交换器建模方法及数值模拟条件,比较了不同条件下热交换器性能的差异,发现由于出口气流密度很低,热交换器的总传热系数、压力损失比常规条件下有较大幅度的减小。此时适当增大椭圆管尺寸,采用高翅片换热管,可以有效地提高热交换器的换热能力。