Superplasticity of fine-grained 7475 Al alloy and a proposed new deformation mechanism

A study has been made to investigate the superplastic deformation mechanisms of 7475 Al alloy in relation to the variation of grain size ranging between 5.5 μm and 13 μm. The strain-rate sensitivity (m) was increased with decreasing grain size in the superplastic deformation regime. Microstructural investigation after tension tests revealed that the dispersoid free zones were produced mostly at the grain boundaries normal to the tensile direction. A new model for describing the deformation behavior of the 7475 Al alloy has been proposed based on the assumption that the grain boundary sliding was accommodated by both diffusional flow and slip. This new model well predicts many aspects of experimental results.     

The form error prediction in side wall machining considering tool deflection

In this research, an effective method for the form error prediction in side wall machining with a flat end mill is suggested. The form error is predicted directly from the tool deflection without surface generation by cutting edge locus with time simulation. The developed model can predict the surface form error accurately about 300 times faster than the previous method. Cutting forces and tool deflection are calculated considering tool geometry, tool setting error and machine tool stiffness. The characteristics and the difference of generated surface shape in up milling and down milling are discussed. The usefulness of the presented method is verified from a set of experiments under various cutting conditions generally used in die and mold manufacturing. This study contributes to real time surface shape estimation and cutting process planning for the improvement of form accuracy.     

中厚板在线30通道超声波探伤方法及应用

介绍了柳钢公司在生产锅炉板、压力容器板过程中，曾试用了６种探伤方法；而研制的３０通道在线超声波探伤法不仅可满足国家标准要求，而且能适应生产节奏，并具有快速、准确、简便的特点。     

Microstructure of reactive sintered Al bonded Si3N4-SiC ceramics

Aluminium nitride-silicon nitride-silicon carbide （AIN-Si3N4-SiC） composite ceramics were prepared to increase the bending strength and improve the phase structure of Si3N4-based ceramics. The ceramics were made by reactive sintering in N2 atmosphere at 1 360 ℃, using Al as sintering additive. The phase composing of ceramics was identified with an X-ray diffractometer and the microstructure of the materials was studied by scanning electron microscopy. The results indicate that the phase structure is affected remarkably and the interface modality is changed. The interface between Si3N4 and SiC becomes blurry and that between SiC and AlN matches more better at the same time. But the liquid-phase appears during the reactive sintering along with the addition of AI by which the melting point of Si is decreased. The appearance of liquid Si decreases the bending strength of the ceramics. Lower temperature nitrification technic was introduced to avoid the appearance of liquid-phase Si. The optimum addition of Al was investigated by XRD and SEM analysis in order to obtain the maximal bending strength of materials.     

用于交流自动埋弧焊机的SCR—D调节系统

本文阐述了用SCR-D调节系统代替F-D调节系统的交流自动埋弧焊机的工作原理和电路分析,同时也对该焊机自动引弧提出见解。     

基于速龙码的WSNs传输功率控制重编程协议

为了降低节点能耗,提高能量的利用率,提出了一种高效节能的基于速龙码（ RC）的传输功率控制（ RC-TPC）重编程协议。该协议分两个阶段完成数据传输,第一阶段各个节点更新自己的位置信息,形成最优化的拓扑结构。进入第二阶段后,根据优化的拓扑结构通过调整发送节点的传输功率和中继节点的累计选择次数,Sink节点选择适当的中继节点,使中继节点的传输功率和RC的开销达到最优化。此外,RC的编码方式使传输数据包发生的错误概率更小,减少了重编程过程中的冗余以保证网络负载的均匀分布,有效地实现了高效节能,从而提高整个网络的生存周期。理论分析与实验结果表明：与MNP协议和ATPC协议相比,RC-TPC协议用于传输的平均能量消耗降低17.2%。     

基于GPU的原油液体仿真效率优化研究

针对有杆抽油系统的采油过程,原油液体在油管内受力而不断运动。为了将此过程形象、逼真的展现出来以便于相关工作人员观察和分析,需建立一个高精度、高效率、易使用的可视化环境。本文在VC++6.0环境下,运用粒子系统技术模拟原油液体的运动过程,并采用通过GPU加速和非GPU加速对比的方式优化了系统效率。通过数据对比表明：随着粒子数的增加,通过采用GPU加速运算方式的系统效率大大提高。     

基于 Activiti 流程管理关键技术设计与实现

Activiti 是用于管理业务流程的工作流引擎,它的使用降低了复杂业务流程开发与维护的难度。但在实际应用中,流程节点无法自由跳转,给管理和使用带来诸多不便。本文研究了 Activiti 中的系统框架和接口,基于现有接口设计实现了流程节点自由跳转功能,并进行了框架整合。测试结果表明,该功能满足各项既定功能需求,具有一般性,可满足实际工作中相关要求。     

国际水协会河流水质模型1号(RWQM1)述评

剖析河流水质模型1号(RWQM1)的建模背景、设计思路、基本框架与建模方法,认为RWQM1从技术层面和建模方法上对当前水质模型进行了重大调整,提供了全新的水质模型框架,作为未来水质建模的科学标准,RWQM1的标准化设计思路包括:1较全面地划分水质组分,统一水质组分的表述方式;2基于严格的化学计量方程实现对水质转化过程及其动力学的数学描述,确保反应物、产物的物质守恒;3将各种水质过程通过化学计量矩阵的形式实现模型的结构化表达。结构化的思路使得RWQM1水质模型具有灵活、适用性广等特点,但过于复杂的状态变量、缺乏强大的软件平台等问题,在一定程度上限制了RWQM1水质模型的推广。