基于NPLS技术的可压缩湍流机理实验研究新进展

可压缩湍流机理的实验研究是一件难度很大的工作, 其主要的难度在于高时空分辨率的可压缩湍流结构非接触精细测试技术和低噪声的高速风洞设备技术. 近几年来, 由于在低噪声的超声速、高超声速风洞研究和可压缩流动精细结构测量技术研究方面取得的重要进展及其在可压缩湍流机理研究方面的应用, 超声速流动转捩与湍流的机理研究取得了较大的进展. 本文介绍了最近几年高速流动非接触精细测试技术, 尤其是基于纳米粒子的平面激光散射技术(nano-tracer planar laser scattering, NPLS)、背景导向纹影技术(background oriented schlieren, BOS) 和超声速流场的粒子图像测速技术(particle image velocimetry, PIV)的研究进展和发展前景, 以及基于这些技术, 在可压缩湍流机理实验研究方面的进展和发展前景, 其中包括在超声速混合层转捩、超声速绕流与尾流结构、超声速边界层转捩、激波边界层干扰等典型流场的机理研究方面, 以及气动光学机理研究方面的研究进展. 最后, 展望了目前湍流机理实验研究对湍流工程模型研究的可能贡献.      

泥沙输运模拟综述——现状及其发展趋势

随着流体力学中数值方法的飞速发展,计算模型已经成为研究流体运动,泥沙输运和不同环境(诸如河流,湖泊及沿海地区)中相应污染物归趋过程等方面非常有吸引力的工具,在过去的30多年里,发展了许多计算水动力学/泥沙输运模型.文章追溯当前具有代表性的(一维、二维、三维)模型的发展历程,描述他们各自的特点,优势及局限,力图作为对模型方面感兴趣读者的第一指南,同时也为大家讨论模型的局限性,未来的发展趋势和研究需求方面搭建一个平台.给出了模型的表达,时空特性,水动力学和沉积物的耦合方式,处理非恒定流,推移质和悬移质,泥沙交换过程,泥沙类型(粘性或非粘性)及非均匀泥沙输运的能力.总结了不同模型的应用实例,读者可以运用这些例子作为研究模型设置,模型率定及模型验证的参考.给出了选择泥沙输运模型应遵循的原则,模型输入及率定方面存在的问题及改进的途径.探讨了现有水动力学/泥沙输运模型在处理复杂湍流,泥沙携带,流动与输沙耦合,非均匀泥沙,离散和扩散系数,河岸来沙处理等方面的局限性及改进的方向.最后,对基于多相流思想的泥沙输运模型及其它一些交叉性问题作了评述与展望.     

Extraction and Anti-diabetic Activity on Alloxan-induced Diabetic Mice of Polysaccharides from Huidouba

The polysaccharide extracted from Huidouba(PEH) exihibited a significant anti-diabetic activity. The polysaccharide contained glucose, mannose and galactose in a content ratio of 1.00:0.34:0.32. After administration with 50―200 mg/kg body weight of PEH to type Ⅱ diabetic mice induced by alloxan for four weeks, the blood glucose level of mice was decreased significantly. Moreover, the SOD activity increased at the same time(p<0.01). PEH showed a significant anti-diabetic and anti-oxidation activity. In addit...     

Synthesis,Characterization and Biological Activities of Novel Acrylamide Compounds

With dimethomorph and flumorph as the leading compounds, four novel acrylamide compounds with two types of structure were designed and synthesized by means of the method of ＂me too chemistry＂. The target compounds were characterized by 1H NMR, IR, MS, and elemental analysis. The influences of solvent and raw material on the yield were investigated and optimum processing conditions were determined. The results of preliminary biological tests show that all those compounds exhibit certain antifungal activities.     

重视对数据通信集团用户的服务

在河北省数据通信用户中,集团用户只占２４％,但９４．７％的业务收入却来自这些用户。本文针对目前对集团用户重视不够的问题提出了一些建议,主要包括：建立集团用户档案,定期走访,提高维护质量,实行优惠政策,加大宣传力度和加强对营销人员的培训等。     

冷轧低碳钢高压相变组织的透射电镜分析

 对冷轧低碳钢在高压下进行再结晶,用透射电子显微镜（TEM）分析高压相变组织,发现压力可以使再结晶晶粒细化;压力升高,具有体心立方结构的普通低碳钢可形成ε-马氏体,并根据电子衍射花样的计算确定ε-马氏体的晶格参数。     

聚甲基丙烯酸甲酯-氯化银复合纳米微球的制备及其摩擦学性能

采用原位种子乳液聚合法合成了聚甲基丙烯酸甲酯 氯化银(PMMA AgCl)核壳结构复合纳米微球,通过透射电镜(TEM),红外光谱(IR),热分析(TG DTA)和X射线粉末衍射(XRD)等测试手段对其结构及性能进行了表征.在四球试验机上对其摩擦学行为进行了考察,研究结果表明,PMMA AgCl核壳结构复合纳米微球用作润滑油添加剂具有良好的抗磨性能,能显著提高基础油的失效负荷.     

关于整数n的k次补数

设n为正整数,a(n)表示n的k次补数.本文的主要目的是研究a(n)的某些分布性质,并给出一个有趣的渐近公式.     

The new interpretation of support vector machines on statistical learning theory

This paper is concerned with the theoretical foundation of support vector machines (SVMs). The purpose is to develop further an exact relationship between SVMs and the statistical learning theory (SLT). As a representative, the standard C-support vector classification (C-SVC) is considered here. More precisely, we show that the decision function obtained by C-SVC is just one of the decision functions obtained by solving the optimization problem derived directly from the structural risk minimization principl...     

Isospin dependence of nuclear multifragmentation in statistical model

The evolution of nuclear disintegration mechanisms with increasing excitation energy, from compound nucleus to multifragmentation, has been studied by using the Statistical Multifragmentation Model (SMM) within a micro-canonical ensemble. We discuss the observable characteristics as functions of excitation energy in multifragmentation, concentrating on the isospin dependence of the model in its decaying mechanism and break-up fragment configuration by comparing the A₀=200, Z₀=78 and A₀=200, Z₀=100 systems. The calculations indicate that the neutron-rich system (Z₀=78) translates to a fission-like process from evaporation later than the symmetric nucleus at a lower excitation energy, but gets a larger average multiplicity as the excitation energy increases above 1.0 MeV/u.