Non-hydrostatic versus hydrostatic modelings of free surface flows

The hydrodynamics of geophysical flows in oceanic shelves, estuaries, and rivers are often studied by solving shallow water equations under either hydrostatic or non-hydrostatic assumptions. Although the hydrostatic models are quite accurate and cost-efficient for many practical applications, there are situations when the fully hydrodynamic models are preferred despite a larger cost for computations. The present numerical model is implemented by the finite volume method (FVM) based on unstructured grids. The model can be efficiently switched between hydrostatic and non-hydrostatic modules. The case study shows that for waves pro-pagating along the bar a criterion with respect to the shallowness alone, the ratio between the depth and the wave length, is insufficient to warrant the performance of shallow flow equations with a hydrostatic approach and the nonlinearity in wave dynamics can be better accounted with a hydrodynamic approach. Besides the prediction of the flows over complex bathymetries, for instance, over asymmetrical dunes, by a hydrodynamic approach is shown to be superior in accuracy to the hydrostatic simulation.     

模拟汗液中铜币的腐蚀行为（英文）

采用电化学方法以及扫描电子显微镜、X-射线电子能谱表面分析技术,研究铜币在模拟汗液中的腐蚀行为。结果表明,模拟汗液中的氯离子能加剧黄铜的阳极活性溶解反应,是发生孔蚀和脱锌腐蚀的主要原因,氨水和乳酸的存在对其阳极反应过程有一定促进作用,而尿素的存在对腐蚀过程影响不大。黄铜表面形成的腐蚀产物主要由氯化铜、氧化亚铜、尿素与铜形成的配合物以及少量的乳酸离子组成。黄铜在模拟汗液中蚀孔发展的动力学过程遵循方程J0=0.3735(t+185.93)-1/2,该过程受孔表面盐膜溶解控制。     

基于电压电荷法的静电放电能量检测方法

传统的静电放电能量检测方法多依赖于经验公式,方法简单,计算误差较大。根据电压电荷法计算静电放电能量的原理,设计并搭建了实验系统,开发了基于MATLAB APP Designer的静电放电能量计算软件,并结合静电火灾事故调查实例验证其的科学性,为静电事故的预防与调查提供技术手段。     

Experimental study on mechanical properties and failure behaviour of the pre-cracked coal-rock combination

Bulletin of Engineering Geology and the Environment - The mechanical property of roof is critically important for underground coal mining activities. The existence of hard roof that cannot cave...     

Genetic Differentiation between Natural and Hatchery Stocks of Japanese Scallop (Mizuhopecten yessoensis) as Revealed by AFLP Analysis

Japanese scallop (Mizuhopecten yessoensis) is a cold-tolerant bivalve that was introduced to China for aquaculture in 1982. In this study, amplified fragment length polymorphism (AFLP) markers were used to investigate levels of genetic diversity within M. yessoensis cultured stocks and compare them with wild populations. Six pairs of primer combinations generated 368 loci among 332 individuals, in four cultured and three wild populations. High polymorphism at AFLP markers was found within both cultured and wild M. yessoensis populations. The percentage of polymorphic loci ranged from 61.04% to 72.08%, while the mean heterozygosity ranged from 0.2116 to 0.2596. Compared with wild populations, the four hatchery populations showed significant genetic changes, such as lower expected heterozygosity and percentage of polymorphic loci, and smaller frequency of private alleles, all indicative of a reduction in genetic diversity. Some genetic structures were associated with the geographical distribution of samples; with all samples from Dalian and Japan being closely related, while the population from Russia fell into a distinct clade in the phylogenetic analysis. The genetic information derived from this study indicated that intentional or accidental release of selected Japanese scallops into natural sea areas might result in disturbance of local gene pools and loss of genetic variability. We recommend monitoring the genetic variability of selected hatchery populations to enhance conservation of natural Japanese scallop resources.     

Hardware design of motion data decoding process for H.264/AVC

In H.264/AVC, motion data can be basically derived by the following two schemes: one is a typical spatial prediction scheme based on the DPCM and the other is a sophisticated spatiotemporal prediction scheme for the skipped motion data, formally referred to as a direct mode. We verified through instruction level profiling that when these schemes are combined with various H.264/AVC coding techniques, the computational burden to derive the motion data could be considerably aggravated. Specifically, its computational complexity amounts to maximally 55% of that of the overall syntax parsing process. In this paper, we aim at an efficient hardware design of the motion data decoding process for H.264/AVC, for which all the key design considerations are addressed in detail and respective rational answers are presented. As comparing the resulting hardware design with the processor-based solution, its effectiveness was clearly demonstrated. The proposed design was implemented with 43.2 K logic gates and three on-chip memories of 3584 bits using Samsung Semiconductor’s Standard Cell Library in 65 nm L6LP process technology (SS65LP), and was capable of operating the H.264/AVC high-profile video bitstream of 1080p@60fps at 100 MHz consuming 843 μW.     

乳酸杆菌表层蛋白基因结构及功能研究进展

乳酸杆菌对宿主的黏附性是其发挥益生作用的基础,而其黏附性与自身的表层蛋白密切相关。乳酸杆菌表层蛋白具有相对分子质量低、高等电点、结构和基因的多样性等特点。国内外学者对于乳酸杆菌的表层蛋白进行了深入的研究。作者从乳酸杆菌表层蛋白的基因结构和特性、和生物学功能几个方面对乳酸杆菌表层蛋白进行了综述。     

冷库用空气冷却器的经济性计算模型

为了优化结霜工况下翅片管式空气冷却器的结构设计,提出经济性分析计算模型。综合考虑换热性能、材料成本及运行费用,以单位制冷量的费用年值为目标函数,以费用年值最小为优化目标求解经济模型得到合理的空气冷却器的结构参数,分析了翅片间距、换热管管径、管排数变化对目标函数的影响,并通过一冷库案例进行实际测试验证。计算及试验结果表明:随着翅片间距的增大,目标函数先减小后增大,翅片间距为10时目标函数取极小值;在相同翅片间距的情况下管径越大,其目标函数值也越大;综合考虑换热管直径、翅片间距和管排数的影响,翅片间距为10,换热管外径为9.52,管排数为6时,目标函数取极小值。     

Ti-6Al-4V合金氮离子注入后在Tyrode’s体液中的耐蚀耐磨性能

Ti-6Al-4V合金注入氮离子后,生物相容性、抗磨损性、抗疲劳性及抗腐蚀性均有所提高,其植入人体后在体液中的耐蚀耐磨性能尤为重要,目前对此研究较少。对Ti-6Al-4V合金进行氮离子注入,并在人工模拟体液Tyrode’s溶液中进行摩擦磨损和电化学试验,研究了注氮Ti-6Al-4V合金的耐蚀耐磨性能。采用扫描电镜观察腐蚀形貌,用其自带的能谱仪分析注氮层的元素组成,采用X射线衍射仪分析注氮层的结构。结果表明:Ti-6Al-4V氮离子注入后表面形成主要由TiC,Ti及少量TiO2组成的膜层,硬度提高,在Tyrode’s溶液中的腐蚀电位升高、极化电阻增大,阳极极极化电流密度降低;在Tyrode’s溶液中摩擦后的注氮Ti-6Al-4V合金的阳极极化电流密度大于未摩擦的,极化电阻减小;Ti-6Al-4V合金氮离子注入后的摩擦系数明显降低,比磨损率减少。     

复合材料四结点四边形多层退化壳单元

本文提出了一个复合材料四结点四边形多层退化壳单元。单元从修正的Hu-Washizu变分原理导出,独立假设位移场、每层内部应变场和应力场。文中给出了几个复合材料板和壳静力线性问题实例。计算结果表明本文的单元是准确和有效的。