双轴压缩下颗粒物质剪切带的形成与发展

本文采用离散元方法,研究了双轴压缩的颗粒体系在刚性边界约束下,局部剪切带的形成和发展过程,注重分析了细观的体积分数、配位数、颗粒旋转角度等参数以及力链结构形态的演变.并从颗粒体系jamming 相图中J点附近的边壁压强和配位数随体积分数的标度规律出发,分析了剪切带内外的体积分数和配位数的变化.结果表明:剪切带形成于颗粒体系的塑性变形开始阶段,此时体系发生剪胀,颗粒体积分数减小,颗粒体系抵抗旋转的能力降低,开始出现细小剪切带,随着轴向应变的继续,细小剪切带发生连接,最终导致贯穿性优势剪切带形成 关键词： 颗粒物质 力链 双轴压缩 剪切带     

Thermodynamic parameters of N-(p-n-alkoxybenzylidene)-p-n-(butyloxyanilines), (nO.O4) liquid crystal compounds — A dilatometric study

Different thermodynamic parameters are estimated from volume expansion coefficient, α for a number of N-(p-n-alkoxybenzylidene)-p-n-butyloxyanilines, nO.O4 compounds in isotropic phase (at T_IN + 5 °C) and in liquid crystalline phases. The variation of different thermodynamic parameters with the alkoxy chain length in nO.O4 series and their variation with the temperature in individual liquid crystal compounds are discussed. The parameters like available volume (V_a), inter molecular free length (L_f) and molecular radius (M_r) are also computed from density, and refractive index for these nO.O4 compounds and the nature of molecular free length and molecular radius are analyzed and discussed.     

Template-free synthesis of TS-1 zeolite film on tubular mullite support

The TS-1 film on tubular mullite support was prepared by secondary growth via template-free route using tetraethyl orthosilicate (TEOS) and tetrabutyl orthotitanate (TBOT) as silica and titanium sources. The as-made films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV-vis). Continuous TS-1 seed layer was bonded tightly to the mullite substrates. After secondary growth in the template-free synthesis solution, intergrown TS-1 zeolite film with the typical MFI-type structure was formed on the outer surface of support. The Si atoms in zeolitic lattice were found to be isomorphously substituted by Ti atoms which existed only in tetrahedral coordination. The thickness of the obtained TS-1 zeolite film was less than 20 μm.     

黎开管热声振荡的主动控制研究

本文以黎开管内的热声耦合振荡为研究对象,设计基于主动补偿的适应性控制器抑制黎开管内的不稳定燃烧。试验以扬声器为执行机构来改变黎开管的边界条件,从而抑制黎开管内的热声耦合振荡。实时控制效果表明,本文所采用的适应性控制算法能够有效抑制因热声耦合产生的燃烧振荡,为实际动力系统燃烧振荡抑制提供了思路。     

弯管和文丘里管组合燃烧器的颗粒分布特性

本文给出一种弯管和文丘里管组合结构的新型浓淡煤粉燃烧器,并分别对弯管、文丘里管和这种弯管和文丘里管组合结构燃烧器内的气固两相流动进行了数值模拟。采用Euler-Lagrange方法和离散相模型（DPM）研究气固两相流动,气相湍流采用分离涡（DES）模拟方法,固相湍流采用离散随机游动（DRW）模型。结果表明,这三种结构对...     

椭圆管矩形翅片间空气流动的扰流特征

针对椭圆管矩形翅片间的空气流动特性,将应用于直接空冷电站椭圆管矩形翅片的几何中心相对于椭圆管的几何中心偏置.针对不同偏心距离x,以及不同入口风速u,得到空气侧对流换热系数h和压差P随u的变化规律.模拟结果表明翅片的偏置会对着空气侧的流动与换热产生不同影响:翅片向前偏置,低速尾流区对翅片表面换热的影响减小,空气侧总的表面...     

高效同轴脉冲管制冷机性能的实验研究

同轴式脉冲管制冷机具有结构紧凑、与器件耦合简单的优点,在实际应用中得到了越来越广泛的采用.本文对一台经理论优化设计的高频同轴脉冲管制冷机进行了实验研究,采用自制的直线压缩机驱动,惯性管/气库作为调相机构,在输入电功150 W、冷端温度为77 K时得到了9.86 W的制冷量,相对卡诺效率达到18.4%,这是目前同轴脉冲管...     

Computational performance of Free Mesh Method applied to continuum mechanics problems

The free mesh method (FMM) is a kind of the meshless methods intended for particle-like finite element analysis of problems that are difficult to handle using global mesh generation, or a node-based finite element method that employs a local mesh generation technique and a node-by-node algorithm. The aim of the present paper is to review some unique numerical solutions of fluid and solid mechanics by employing FMM as well as the Enriched Free Mesh Method (EFMM), which is a new version of FMM, including compressible flow and sounding mechanism in air-reed instruments as applications to fluid mechanics, and automatic remeshing for slow crack growth, dynamic behavior of solid as well as large-scale Eigen-frequency of engine block as applications to solid mechanics.     

三元Co-Cu-Pb偏晶合金的快速凝固组织形成规律研究

在自由落体条件下实现了三元Co-Cu-Pb合金的液相分离与快速凝固. 实验发现,随液滴直径减小,Co₅₁Cu₄₇Pb₂合金液滴发生由枝晶→两层壳核→枝晶组织的转变,Co₄₇Cu₄₄Pb₉合金液滴的组织形态由壳核组织演化为均匀组织. 两种合金的快速凝固组织均由α(Co),(Cu)和(Pb)固溶体三相组成,α(Co)和(Cu)相主要以枝晶方式生长,(Pb)相分布在(Cu)枝晶间. 关键词： 液相分离 偏晶合金 快速凝固 自由落体     

求解非线性方程的最优8阶史蒂芬森方法

本文研究了非线性方程求根问题.利用权函数方法,获得了一种三步8阶收敛的史蒂芬森型方法.实验结果表明本文提出的方法计算时间少于其它同阶的最优方法.