Effect of synthetic fibers on resisting scour caused by horizontal jet

Given that the development of scour downstream of hydraulic structures increases the risk of structural damage, it is important to find cost-effective and environmental approaches to reduce this risk. This study aimed to experimentally evaluate the effect of synthetic fibers on the scour profile downstream of a sluice gate with a rigid apron. Experiments were performed with the same Froude number and with different weight percentages of synthetic fibers on both non-cohesive and cohesive sediments. One uniform sand was used as the non-cohesive sediment, and three different cohesive sediments were prepared by mixing different percentages of kaolinite soil with the used sand. The scouring experiments showed that the presence of synthetic fibers did not considerably affect the scour hole dimension in non-cohesive sediments. Evaluation of the scour in the cohesive sediments in silty sand (SM) texture found that an increase in the percentage of silt reduced the scour hole dimensions. The effect of synthetic fibers on scour of SM-texture-based sediments was also investigated, and the results showed that increasing the percentage of synthetic fibers decreased the scour hole dimensions. In addition, the cohesive sediments in SM texture did not have a similar non-dimensional scour profile, and the presence of synthetic fibers did not significantly affect the scour hole.     

一种自适应混合粒子群优化算法及其应用*

为提高粒子群算法的寻优精度,提出一种将单纯形法(SM)和粒子群(PSO)算法相结合的自适应混合粒子群优化(AHPSO)算法,该算法根据进化需要动态调整粒子的惯性权重,并在进化停滞时使用SM优化。通过仿真实验证明了AHPSO的寻优性能优于SPSO和SMPSO。将AHPSO用于某航空发动机的PID参数优化,其整定性能优于现有的工业方法和其他PSO算法。     

A Social Media framework to support Engineering Design Communication

Engineering Design Communication (EDC) is fundamental to almost all Engineering Design activities as it provides the ability for knowledge and information to be shared between engineers. It is part of ‘what we do’. This communication contains a great deal of rationale relating to the evolution of Product Development and is essential for understanding ‘why the product is the way it is’. The need to support EDC is becoming more important due to the fact that Product Development is becoming more distributed, multi-disciplinary and involving greater re-use of past designs. With the advent of Social Media (SM), it is argued that there is the technical capability to provide more effective support for EDC within a computer-mediated environment. In order to explore this potential, this paper defines the requirements for the effective support of EDC through an extensive review of the literature. It then discusses the suitability of a SM approach and then presents the theoretical foundations of a SM framework to support EDC.     

SM6000型空压机的故障分析与维护

介绍了4300mm宽厚板SM6000型空压机的结构和组成，论述了空压机常见的故障和解决方法。经过改进后，SM6000型空压机运行平稳，故障明显减少，保证了生产的顺利进行。     

Comments on the IPC Surface Mount Attachment Reliability Guidelines

The Institute for Interconnecting and Packaging Electronic Circuits (IPC) has published guidelines and standards related to surface mount solder attachments. The latest standard IPC‐9701 was published in 2002. In this paper, the general methodology for creating the aforementioned documents and the related qualification requirements are reviewed and discussed. Also, corrections to the standards and guidelines are proposed. The corrections are related both to the use of formulas and to inaccuracies in the units used. Copyright © 2005 John Wiley & Sons, Ltd.     

热处理工艺对SM570钢叉车横梁力学性能的影响

通过试验对比了正火和调质热处理工艺对SM570钢叉车横梁力学性能的影响。结果表明,有效厚度为40 mm的横梁在900 ℃×3 h水淬+550 ℃×4 h回火的调质处理后才能完全满足力学性能的要求。而正火后试样的抗拉强度和屈服强度都较低,尤其屈服强度比技术要求低很多。SM570钢叉车横梁若要在正火态下交货,除了Si、Mn的固溶强化,还必须通过微合金化进行细晶强化,从而提高正火态下的屈服强度,提升屈强比。     

基于CM300和SM79164的基站监控系统

介绍了一种采用高性能8位单片机SM79164作为主要控制芯片的通信基站环境和动力监控系统的设计,该系统使用各种高性能传感器采集基站里的环境和动力参数,利用串口摄像头获取基站里的图像,在初步分析和处理数据后,通过CDMA2000-1X模块CM300与中心机房建立TCP/IP连接,把所有数据传送回主机,主机将信息进一步处理后通知相关维护人员,从而实现了对基站的实时监控,提高了基站动力设备和通信设备运行的可靠性.     

Large-eddy simulation of turbulent flow in a stirred tank driven by a Rushton turbine

Large-eddy simulation (LES) of mixing process in a baffled tank was presented. The impeller rotation was modeled using the sliding mesh technique. In this study the CFD code was used for simulation of a standard vessel agitated by a 6-blade Rushton turbine and results were evaluated in terms of the predicted flow field, power number, mean velocity components, mixing time, turbulent kinetic energy and turbulent dissipation rate using published experimental data. Subsequently, the effects of varying injection position of the passive scalar have been investigated. The results show that LES is a reliable tool to investigate the unsteady behavior of the turbulent flow in stirred tank.     

基于SM9的CCA安全广播加密方案

选择密文安全模型能有效刻画主动攻击,更接近现实环境.现有抵抗选择密文攻击的密码算法以国外算法为主,缺乏我国自主设计且能抵抗选择密文攻击的密码算法.虽然实现选择密文安全存在通用转化方法,代价是同时增加计算开销和通信开销.基于国密SM9标识加密算法,提出一种具有选择密文安全的标识广播加密方案.方案的设计继承了SM9标识加密算法结构,用户密钥和密文的大小都是固定的,其中用户密钥由一个群元素组成,密文由3个元素组成,与实际参与加密的接收者数量无关.借助随机谕言器,基于GDDHE困难问题可证明方案满足CCA安全.加密算法的设计引入虚设标识,通过该标识可成功回复密文解密询问,实现CCA的安全性.分析表明,所提方案与现有高效标识广播加密方案在计算效率和存储效率上相当.