等通道挤压后镁合金的微观结构研究

对Mg-6Zn-IGd-0．6Zr合金在预热温度为350、400、450℃下进行了2、4、6道次的挤压。采用光学显锻镜和透射电子显微镜分析了试样ECAP变形前后的显微组织变化，采用显维硬度计对Mg-6Zn-1Gd-0．6Zr合金ECAP变形前后进行了硬度测试，采用X-射线分析法分析了ECAP变形过程中晶面的转动。结果表明：ECAP不仅能够将晶粒细化到纳米级，而且能够提高材料的硬度；Mg-6Zn-IGd-0．6Zr合金ECAP变形后晶粒内部出现高密度位错．促进动态再结晶，对细化晶粒起着重要的作用。     

等通道转角挤压对L2工业纯铝力学性能的影响

利用等通道转角挤压(ECAP)技术挤压工业纯铝L2，探讨了挤压次数对其力学性能的影响。结果表明，随挤压次数的增加，L2的抗拉强度和硬度得到显著提高，抗拉强度可提高95％，硬度提高70％。挤压1次后，其伸长率由40％下降至15％，此后伸长率基本保持稳定。     

Hydropower development on rivers in Scotland

This paper reviews the development of Britain's limited hydropower resources, most of which is concentrated in Scotland producing on average some 4000 GWh per year. The Scottish schemes are dominated by the reservoir storage type although pumped storage plants have been constructed since the 1960s. These latter also occur at two sites in Wales. The performance of existing schemes is examined, with particular reference to environmental aspects, and the potential and prospects for future hydropower development are considered.     

无线数据传输系统在气田的研究与应用

本文首先对我厂陕141井区以前的数据采集方式进行了简要分析,指出存在的不足,并对MDS2710A教传电台进行了介绍。提出了利用无线数据传输系统解决陕141井区各集气站和天然气井井口生产数据的远程传输问题,实现对陕141井区各集气站和天然气井井口生产数据的远程实时监控。并结合实际经验,对该系统实施过程和功能进行了详细介绍。同时指出系统在安装过程中需要注意的问题,并进行了经济效益评价。     

棒材厂改造后大规格螺纹钢的生产实践

介绍了棒材生产工艺改造后大规格螺纹钢的开发与轧制,主要进行了孔型设计和相关设备改进,取得较好的生产指标,力学性能检测优良.     

环境友好的近自然型鱼道

鱼道是帮助鱼类顺利通过闸坝等障碍物的专用设施,在维系河流连续性与生物种群交流方面具有不可替代的作用。近自然型鱼道是目前国际上十分流行的鱼道布置形式,其典型特点是利用漂石与天然河道床沙质构建尽可能接近于天然河流的水流流态。与传统的工程鱼道相比,近自然型鱼道由于构建了鱼类更为熟悉的水流流态,因而往往具有更高的过鱼效率。本文全面介绍了近自然型鱼道的设计理念、类型、构造布置特点、设计原则、以及水力计算方法,并对我国鱼道技术的进一步发展提出了若干建议。     

扫描次数对钢板激光弯曲成形影响的模拟

研究了6 mm和9 mm两种厚度的钢板在不同激光工艺参数下扫描次数对激光弯曲成形过程的影响.利用三维热力耦合有限元(FEM)模型模拟计算了激光多次扫描弯曲成形过程的温度场、应力场和弯曲角度的变化.测忖量了成形过程中温度和弯曲角度的变化,模拟结果与实验结果符合较好.模拟结果表明,每次扫描过程中温度场变化基本相同,残余应力和钢板弯曲角度随激光扫描次数的增加而增大.随着扫描次数的增加,6 mm厚钢板的弯曲角度增量减小,而9 mm厚钢板的弯曲角度呈线性增大.激光工艺参数影响钢板下表面的应变强化程度,在不同的激光工艺参数下不同厚度钢板的弯曲角度随扫描次数的增加变化规律不同.     

粗轧机R2主传动轴损坏原因的分析及改进

粗轧机R2主传动轴是十分重要的部件,当主传动轴较长时其自重、平衡力、扭矩及附加弯矩会显著影响使用状态及寿命。通过对传动轴静态和动态两种情况的强度校核计算,分析出了R2主传动轴断裂的原因,并确定了接轴中间部位支撑力的大小,使传动轴的工作状态达到最佳。     

Performance analysis of finned tube and unbaffled shell-and-tube heat exchangers

This work considers an optimum design problem for the different constraints involved in the designing of a shell-and-tube heat exchanger consisting of longitudinally finned tubes. A Matlab simulation has been employed using the Kern's method of design of extended surface heat exchanger to determine the behavior on varying the values of the constraints and studying the overall behavior of the heat exchanger with their variation for both cases of triangular and square pitch arrangements, along with the values of pressure drop. It was found out that an optimum fin height existed for particular values of shell and tube diameters when the heat transfer rate was the maximum. Moreover it was found out that the optimum fin height increased linearly with the increase in tube outer diameter. Further studies were also performed with the variation of other important heat exchanger design features and their effects were studied on the behavior of overall performance of the shell-and-tube heat exchanger. The results were thereby summarized which would proclaim to the best performance of the heat exchanger and therefore capable of giving a good idea to the designer about the dimensional characteristics to be used for designing of a particular shell and tube heat exchanger.     

A new method to evaluate polydisperse kaolinite clay particle removal in roughing filtration using colloid filtration theory

Previous application of colloid filtration theory to roughing filtration has not considered a reliable method for determining a representative attachment factor for a polydisperse suspension (of constant particle density). Establishment of such a method would broaden the application of trajectory modelling in roughing filtration, and progress the development of a comprehensive database of attachment factors and surface charge potentials for various particle and fluid types. This study establishes a methodology for the application of colloid filtration theory to roughing filtration and incorporates recent advancements in theoretical single-collector efficiency. A polydisperse kaolinite clay suspension was passed through a series of four gravel upflow roughing filters and removal efficiencies were calculated. Both the classical and Tufenkji and Elimelech's more recent correlation equations were used to calculate theoretical single-collector efficiencies and associated attachment factors for three different filter media sizes, flow rates, and suspended solids concentrations (0.137+/-0.023). The use of Tufenkji and Elimelech's modified correlation equation resulted in reduced variability in the estimation of theoretical single-collector efficiencies.