稀相气粒两相流中亚网格尺度涡对颗粒扩散影响的LES／FDF模拟

本文基于颗粒扩散率这一参数,应用LES／FDF模型对稀相气粒两相流中亚网格尺度涡对颗粒湍流扩散的影响进行了数值模拟研究．通过将使用LES／FDF模型得到的模拟结果与不使用LES／FDF模型得出的结果进行对比后,得出：对于小颗粒（小Stokes数颗粒）,大涡结构是影响颗粒空间扩散的主要因素;但是对于中等粒径颗粒和大颗粒,亚网格尺度涡对于颗粒扩散率的影响与大涡处于同一数量级．亚网格尺度涡在大多数情况下会使颗粒扩散率增大,但有时也会降低颗粒扩散率．亚网格尺度下颗粒的扩散率不仅仅取决于亚网格尺度涡的强度和Stokes数,还与流场中的大尺度涡结构有关;对于各向同性湍流中的颗粒,在亚网格尺度涡的作用下,其扩散率随粒径增大而降低．     

颗粒惯性对气固两相各向同性湍流中温度统计特性的影响

颗粒运动轨迹上流体的温度统计特性对于理解非等温/反应气粒两相湍流的机理, 特别是对于检验非等温气粒两相湍流Lagrangian模型是十分重要的. 对带有平均标量梯度的气固两相各向同性湍流中颗粒及颗粒所见流体温度的统计行为进行了直接数值模拟研究, 讨论了颗粒惯性对于颗粒温度以及颗粒所见流体温度的Lagrangian统计特性的影响. 结果显示, 对于τ_p/τ_k<1的颗粒, 颗粒所见流体温度的脉动强度随τ_p/τ_k的增大而减小; 而对于τ_p/τ_k>1的颗粒, 其趋势相反. 小颗粒(τ_p/τ_k<5)温度的Lagrangian自相关系数R_p^T也随颗粒惯性(τ_p/τ_k)的增大而减小, 对于大颗粒这一趋势也相反. 颗粒运动轨迹上流体温度的自相关系数 都随颗粒惯性的增加而减弱, 而且随颗粒惯性的增加, 颗粒运动轨迹上流体温度的自相关比颗粒温度的自关联下降得快. 平均温度梯度的存在使得在沿平均温度梯度的方向上颗粒速度和温度有很强的关联性. 当τ_p/τ_k<1时, 其关联系数随颗粒惯性的增加而增大; 当τ_p/τ_k>1时, 这一系数的值与颗粒惯性无关.     

多维虚内键模型(VMIB)及其在岩体数值模拟中的应用

多维虚内键模型(VMIB, virtual multi-dimensional internal bonds)是在虚内键(VIB, virtual internal bond)理论基础上发展起来的一个多尺度力学模型. VIB理论认为固体材料在微观尺度上由随机分布的材料微粒(material particle)组成, 微粒之间由单一法向键连结; 而VMIB模型则在原VIB模型单一法向键基础上又引入了切向键用以约束微粒点对之间的相对转动自由度. 材料的宏观本构方程则由两种虚内键的刚度系数导出, 并在理论上证明了微观两种虚内键的刚度系数与宏观材料常数之间存在一一对应关系, 表明了在VMIB模型中增加切向键的充分性和必要性. 由于材料的断裂准则直接嵌入到本构方程中, 这使得VIB和VMIB模型在模拟材料断裂破坏方面有着较大的优越性. 岩体由于受到分布裂纹的切割作用, 宏观上表现为各向异性力学特征. 在岩体损伤模型中, 岩体裂纹的分布特征通常由损伤张量描述. 岩体在某一方向上的相对刚度大小决定于该方向上损伤值的大小. 在VMIB模型中, 微观虚内键的空间分布密度决定着材料宏观各方向上相对刚度的大小, 这与岩体损伤对岩体力学性能的影响是一致的. 文中在损伤张量与虚内键分布密度之间建立了定量关系, 将岩体等效为VMIB固体. 理论与试验结果表明, 这种等效的VMIB固体可以再现分布裂纹对岩体力学性能的影响, 这为进一步应用VMIB模型对岩体破坏行为进行数值模拟奠定了基础, 同时也为其他多裂纹体的数值计算提供一种新思路.     

基于平面距离的模糊数之间差异的度量及其在优化调度问题中的应用

利用平面上的距离函数及水平重要性函数, 建立了衡量模糊数之间差异的UID度量和LPID度量, 讨论了UID度量和LPID度量的基本性质, 证明了模糊数空间关于UID度量和LPID度量成为度量空间的充分必要条件是水平重要性函数在区间[0,1]上几乎处处不为零. 进而讨论了由平面上的范数确定的UID度量和LPID度量的收敛性、可分性和完备性问题. 最后通过实例进一步分析了UID度量和LPID度量的特性.     

耦合多水动力过程的二维山坡产汇流数值模型及其在壤中流模拟中的应用

基于物理性水分运动方程的山坡产汇流数值模型是进行降雨产流机制和规律研究的重要工具,当前还缺乏耦合地表水、土壤水和地下水多水动力过程的、具有较高计算效率和稳定性的二维山坡产汇流数值模型．本研究耦合地表水流动的圣维南方程组、变饱和土壤水分运动的Richards方程,采用有限差分法,对边界条件进行了改进,建立了THRM模型,对实验山坡实测壤中流过程有很好的模拟效果,通过数值试验揭示了边界条件、网格大小、初始含水率等对计算稳定性和计算效果的影响规律,所建模型对于山坡产流研究有应用价值,分析结论对壤中流数值模拟有参考意义．     

An apparatus for investigation of heterogeneous reactions in a flow system

Zusammenfassung Es wird eine Apparatur zum Studium heterogener und pyrolytischer Reaktionen in Fliess-Systemen beschrieben, die für flüssige und gasförmige Ausgangsstoffe, Reaktionsprodukte sowie für deren Mischungen geeignet ist.     

The crystalline phase of cellulose changes under developmental control in a marine chordate

The native form of cellulose is a fibrillar composite of two crystalline phases, the triclinic I_α and monoclinic I_β allomorphs. Allomorph ratios are species-specific, and this gives rise to natural structural variations in cellulose crystals. However, the mechanisms contributing to crystal formation remain unknown. We show that the two crystalline phases of cellulose are tailored to distinct structures during different developmental stages of the tunicate chordate Oikopleura dioica. Larval cellulose consisting of I_α allomorph constitutes the body cuticle fin, whereas adult cellulose consisting of I_β allomorph frames a mucous filter-feeding device, the “house.” Both structures are secreted from the epidermis in accordance with the mutually exclusive expression patterns of two distinct putative cellulose synthase genes. We discuss a possible linkage between structural variations of the crystalline phases of cellulose and the underlying evolutionary genetics of cellulose biosynthesis.     

Inflammation and repeated infections in CGD: two sides of a coin

Chronic granulomatous disease (CGD) is an uncommon congenital immunodeficiency seen approximately in 1 of 250,000 individuals. It is caused by a profound defect in a burst of oxygen consumption that normally accompanies phagocytosis in all myeloid cells (neutrophils, eosinophils, monocytes, and macrophages). This “respiratory burst” involves the catalytic conversion of molecular oxygen to the oxygen free-radical superoxide, which in turn gives rise to hydrogen peroxide, hypochlorous acid, and hydroxyl radicals. These oxygen derivatives play a critical role in the killing of pathogenic bacteria and fungi. As a result of the failure to activate the respiratory burst in their phagocytes, the majority of CGD patients suffer from severe recurrent infections and rather unexplained prolonged inflammatory reactions that may result in granulomatous lesions. Both may cause severe organ dysfunction depending on the tissues involved. Preventive measures as well as rapid (invasive) diagnostic procedures are required to successfully treat CGD. Hematopoietic stem cell transplantation may be a serious option in some of the patients.     

Arousal threshold in the cat as a function of sleep phase and stimulus significance

Résumé Chez le Chat éveillé après conditionnement au moyen de clicks et de lait, les clicks déclenchent le réveil de manière plus efficace qu'en l'absence de conditionnement. Le seuil d'éveil s'est avéré plus bas lors d'un sommeil accompagné d'ondes lentes de haut voltage que pendant le sommeil paradoxal.

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Supported by NSF Grant No. GB 1965.     

Identification of organ-specific glycosylation of a membrane protein in two tissues using lectins

Since glycosylation of proteins is performed by the host cell, and variable sugar groupings can confer heterogeneity on the same polypeptide, we wished to see whether membrane proteins, in particular the ubiquitous transmembrane Na, K-ATPase, could be glycosylated differently in different organs. Using a highly sensitive enzyme-linked antibody detection system of bound digoxigenin-labelled lectins on nitrocellulose sheets containing electroblotted and subunits of kidney and brain Na,K-ATPase, isolated from various rat strains, in combination with isoform-specific immunoblots, we discovered that brain Na,K-ATPase was highly mannosylated in contrast to renal Na,K-ATPase. Thus, we describe the existence of organ-related glycoforms of an integral ubiquitous membrane protein, i.e. diversification of the same polypeptide by organ-typical sugars. At the same time, the presence of the same glycosylation pattern can make distinct protein isoforms occurring in a same organ more homogeneous. Such organ-related glycoforms may serve for tissue identification and as tissue-specific receptors.     

K252a: A new blocker of the cell-cycle at G1 phase in a human hepatoma cell line

The administration of 200 nM K252a to HuH7 suppressed the proliferation of the cells almost completely. The uptake of [³H]thymidine was inhibited, and flow cytometry revealed only one peak at 2C on day 3 after treatment with 100 nM K252a. The expression of proto-oncogene c-myc was not reduced. Despite the blockage at G1, both the size of the cells and the amount of cell protein had increased by 4 times by day 3 after treatment with K252a, while the cells secreted albumin and -fetoprotein into the medium as usual. These results show that K252a can increase the cell size of HuH7 without losing its function by blocking the cell cycle at G1 phase.