Comparative Study Of The Influence Of Natural Convection On Directional Solidification Of Al-3.5 Wt% Ni And Al-7 Wt% Si Alloys

We present numerical simulations of thermosolutal convection for directional solidification of Al-3.5 wt% Ni and Al-7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al-7 wt% Si, but not in Al-3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

爆炸法处理软土地基的回弹模量研究

简要介绍了自洽方法和爆炸法处理软土地基的工作原理,并用自洽方法计算爆炸法处理的软土地基的回弹模量,计算结果和试验结果符合较好.试验证明了用自洽方法计算爆炸法处理软土地基的回弹模量是可行的.

Characteristics of polypyrrole (PPy) nano-tubules made by templated ac electropolymerization

Electrochemical alternating current (ac) method designed for the synthesis of polypyrrole (PPy) nano-tubule arrays is the topic of this paper. Two-step anodic aluminum oxide (AAO) membrane is used as a template. The morphology of PPy nano-tubules is observed by SEM and discussed. FTIR spectra exhibit that the peaks of PPy nano-tubules shift compared to conventional PPy film. (c) 2005 Elsevier Ltd. All rights reserved.

Construction and characterization of bacterial artificial chromosome library of black-handed spider monkey (Ateles geoffroyi)

The large-insert genomic DNA library is a critical resource for genome-wide genetic dissection of target species. We constructed a high-redundancy bacterial artificial chromosome (BAC) library of a New World monkey species, the black-handed spider monkey

一种基于性能模型的中间件自配置框架

高动态的计算环境使得QoS(quality of service)保障对于基于组件的分布式系统越来越重要,软件系统需要具备自我调整的能力以适应外部环境的变化.给出一种自适应的中间件配置框架,能够动态感知负载变化,并自动调整系统参数配置以保持用户所要求的服务质量.该框架的核心是一个基于分层排队网络的性能预测模型,用于指导搜索最优的资源配置,使性能需求得到最大的满足.在OnceAS应用服务器上进行原型实现,并以StockOnline应用做实验,比较了在使用和不使用该框架时的性能需求的满足情况.结果显示,在负载增加时,通过自配置框架的调控,应用性能需求的保障程度得到了较大的提升.

高超声速流动研究进展

<正>高超声速的英文名称hypersonic,是钱学森先生1946年命名的。由于洲际导弹、卫星、飞船、航天飞机以及当前国际上十分关心的各种高超声速飞行器的研制需要,过去的半个多世纪,世界大国纷纷投入力量开展高超声速流动研究,使其成为最为活跃的力学研究领域之一。

兰州储存环上小丸内靶的速度分析

小丸内靶是在兰州储存环主环上进行强子物理实验的主要候选内靶之一.小丸速度是该内靶的一个重要物理参数.大的靶丸速度可以缩短单个靶丸与束流的接触时间,从而使靶丸有较小的温度变化和质量损失,保证内靶系统工作稳定.从流体力学方面对小丸内靶的速度进行了分析,优化了影响小丸靶速度的各种实验条件,并指出靶丸的速度上限在100m/s左右.