Effect of liquid-solid ratio on the morphology,structure, conductivity,and electromagnetic characteristics of iron particles

Using a ball-milling technique, polymorphous iron particles were prepared by changing only the liquid-solid ratio λ. Effects of λ on their morphology, structure, conductivity, and electromagnetic properties were studied. The results show that an increase of λ from 0 to 0.25 causes a nonlinear decrease of the conductivity in the ranges of 88.50–2.25 S cm^?1 and a regular variation of the electromagnetic parameters, corresponding to the as-obtained iron particles. This is ascribed to a combination of the increased shape anisotropy and the decreased fresh surface with active atoms deriving from the weakened welding-on action and the enhanced micro-malleation action in the ball-milling process. Hereinto, the iron flakes formed at wet-milling with λ=0.08?0.25 have lower conductivity, higher permittivity and permeability, and more excellent absorption property compared with the irregular iron particles obtained at dry-milling with λ=0. It is a consequence of the synergistic effect of dielectric relaxation loss, exchange energy and conductance loss originating from the flake-shape structures. This indicates that the morphology, structure, conductivity, and electromagnetic properties of the products can be effectively controlled by changing λ.

     

鳗弧菌油乳化二价口服疫苗免疫养殖大菱鲆的免疫应答及免疫效果的研究

以鳗弧菌M3和SMP1为细菌抗原制备了油乳化二价疫苗,用饵料包埋后连续7天口服免疫大菱鲆鱼,评价鱼的免疫应答和疫苗的保护效果.结果显示,乳化疫苗在鱼后肠刺激产生的溶菌酶和抗蛋白酶活性以及抗体水平均高于未乳化疫苗(P＜0.05);并且在乳化疫苗免疫的鱼血清检测到明显升高的M3抗体效价(P＜0.05).原位杂交结果显示,乳化疫苗免疫鱼的后肠IgM的产生水平高于未乳化疫苗免疫鱼.攻毒实验显示,乳化疫苗免疫的鱼对M3和SMP1的感染分别获得100%和50%的免疫保护率,而未乳化疫苗获得的免疫保护率分别为57.9%和0%.结果表明,鳗弧菌油乳化二价口服疫苗能引起大菱鲆后肠的非特异性和特异性免疫应答并有效地抵抗鳗弧菌的感染,适合用作水产口服鱼用疫苗.     

T194型组合机床液压系统爬行现象的诊断与排除

首先介绍液压系统爬行现象,然后详细分析液压系统爬行现象的各种因素及排除方法.     

计算挠性转子动平衡量的摄动最小二乘法

给出影响系数法平衡挠性转子及其轴系时一种平衡量的计算方法——摄动最小二乘法,该方法既可以有效抑制测振点最大残余振动,又可以维持整体残余振动较小即各测振点的残余振动平方和最接近最小二乘法的水平。通过算例将该方法与目前常用的最小二乘法、加权最小二乘法和极小化最大残振法进行比较,结果表明,摄动最小二乘法是对最小二乘法的有效修正,在一些场合可以取得比加权最小二乘法和极小化最大残振法更好的平衡效果。     

4种山野菜及4种特种蔬菜营养物质含量分析

对4种山野菜和4种特种蔬菜的营养物质含量进行分析,并与普通蔬菜的文献值进行比较。结果表明：山野菜和特种蔬菜的碳水化合物、蛋白质、维生素C及微量元素钙、铁、锌含量较丰富,而胡萝卜素、脂肪、硒含量与普通蔬菜相比无明显差异。     

Integrated Risk Management of Flood Disasters in Metropolitan Areas of China

A review of flood disasters in China during the past five decades has shown a steady increase in the disaster toll due to rapid urbanization, especially through landscape urbanization in metropolitan areas. This paper illustrates the relationship and the interactions between urbanization in the metropolis and the process of flood disaster changes. Furthermore, a solution is proposed to alleviate fluctuations in flood disasters through the adjustment of the land use structure and pattern in metropolitan areas. Based on the solution, the authors conclude that the proportion of ‘ecological land’ in metropolitan areas should not be lower than 40%. The proportion of water and wetlands in ecological land should not be lower than their area in the years of average precipitation and water level. This means that in the Pearl River Metropolitan Area and the Yangtze River Delta Metropolitan Area, the proportion of water and wetlands in ecological land should be more than 25%. Moreover, the authors propose constituting a regional management mode which combines government, society, and insurance companies for controlling flood risk in metropolitan areas.     

Haptic rendering for dental training system

Immersion and interaction are two key features of virtual reality systems, which are especially important for medical applications. Based on the requirement of motor skill training in dental surgery, haptic rendering method based on triangle model is investigated in this paper. Multi-rate haptic rendering architecture is proposed to solve the contradiction between fidelity and efficiency requirements. Realtime collision detection algorithm based on spatial partition and time coherence is utilized to enable fast contact determination. Proxy-based collision response algorithm is proposed to compute surface contact point. Cutting force model based on piecewise contact transition model is proposed for dental drilling simulation during tooth preparation. Velocity-driven levels of detail haptic rendering algorithm is proposed to maintain high update rate for complex scenes with a large number of triangles. Hapticvisual collocated dental training prototype is established using half-mirror solution. Typical dental operations have been realized including dental caries exploration, detection of boundary within dental cross-section plane, and dental drilling during tooth preparation. The haptic rendering method is a fundamental technology to improve immersion and interaction of virtual reality training systems, which is useful not only in dental training, but also in other surgical training systems. Supported by National Natural Science Foundation of China (Grant Nos. 60605027, 50575011), National High-Tech Research & Development Program of China (Grant No. 2007AA01Z310)