跌坎消力池脉动压强试验

为了对跌坎消力池的水动力特性作更深入的研究,为跌坎消力池的设计防护提供参考,基于模型试验对跌坎消力池脉动压强的分布规律、幅值特性和频谱特性进行了系统研究。结果表明:水流条件是影响脉动压强的主要因素,跌坎消力池底板脉动压强系数沿程呈先增大后减小并逐渐趋于稳定的趋势;跌坎消力池底板中线和靠近边墙的脉动压强相当,脉动压强最大达到总水头的5.1%;跌坎消力池前端位于泄槽边墙延长线附近区域的脉动压强最大,最大达到总水头的11.5%;跌坎消力池前端中线的脉动压强比传统消力池有明显降低,最大降幅达55.2%。     

6001B燃气轮机MAVR自动电压调节器功能介绍及故障分析

MAVR自动电压调节装置,在实用运行操作过程中,由于慢建压回路故障,超调量过 大而导致过压、灭磁故障,经研究、分析,采取欠频保护建压的方法后,长期以来建压稳定,效果 明显 。     

乌井水库坝体防渗墙对坝坡稳定的影响研究

增建防渗墙是一种常见的土石坝加固手段,目前,关于土石坝除险加固工程中增建混凝土防渗墙后是否对坝坡稳定产生影响的研究较少,工程设计上也很少考虑.为分析增建防渗墙对坝体的影响,采用有限元法建立数值计算模型,分析增建防渗墙前后坝体渗流、应力场变化规律,对比计算不同运行工况条件下的坝坡稳定情况.计算结果表明:增设防渗墙后,上游坝坡浸润线有所抬高,下游坝坡浸润线明显降低;墙前土体孔隙水压力大于墙后土体,墙后土体的有效应力大于墙前土体;增建防渗墙后上游坝坡的稳定安全系数减小,但减小的幅度不大,相比上游坝坡,增建防渗墙对于下游坝坡的稳定安全系数影响更显著,安全系数提升了近10％;水位骤降速度越大,上游坝坡稳定安全系数下降越快,骤降达到的最小坝坡稳定安全系数越小,对于坝坡的稳定越不利.     

Energy Loss at a Drop Structure with a Step at the Base

Abstract

The flow over a drop structure placed in a rectangular channel was investigated through an experimental program. It was noted that the downstream depth of flow was crucial to the formulation of the problem. Two procedures were developed for the estimation of the downstream depth. The first procedure was physically based with an empirical component for the estimation of the depth of the pool formed at the base of the drop. The second was a purely empirical procedure, which resulted in an equation for the direct estimation of the downstream depth. The parameters of the equation were determined by least-squares techniques. Both procedures resulted in reasonably accurate estimates of the downstream depth. The energy loss at the drop was then calculated and compared with the results of previous studies. The investigations were repeated with a single step placed at the base of the drop. It was observed that the step significantly increased the energy loss at the drop.     

Parametric instability of a liquid metal sessile drop under the action of low-frequency alternating magnetic fields

A 2-D mathematical model is developed in order to simulate a parametric electromagnetic instability oscillation process of a liquid metal droplet under the action of low frequency magnetic field. The Arbitrary Lagrangian-Eulerian (ALE) method and weak form constraint boundary condition are introduced in this model for implementation of the surface tension and electromagnetic force on liquid droplet free surface. The results of the numerical calculations indicate the appearance of various regimes of oscillation. It is found that according to the magnetic field frequency various types of oscillation modes may be found. The oscillation is originated from an instability phenomenon. The stability diagram of liquid metal droplet in the parameter space of magnetic frequency and magnetic flux density is determined numerically. The diagram is very similar to that found in the so-called parametric instability.     

阶梯式跌水与微孔曝气一体化氧化沟性能研究

为解决我国丘陵地带中小城镇生活污水处理厂的建设和运行费用偏高等实际问题,利用丘陵地势条件,将阶梯式跌水曝气装置、微孔曝气器、潜水推进器等节能技术应用到一体化氧化沟工艺中,设计出一种新型污水处理工艺。小试和中试结果均表明:该工艺具有良好的充氧性能,在处理污水能达标排放的同时取得了很好的节能效果。结合混合液流态和阶梯式跌水装置复氧过程等方面的节能机理分析,导出的阶梯式跌水曝气装置复氧过程中氧亏比的数学计算模型为该工艺指导实践提供了理论依据。     

上市公司净资产收益率波动的影响因素

对我国深圳股票市场2001年度净资产收益率大幅下降的原因进行的实证研究表明:已处于亏损境地企业的净资产收益率变动,是深圳股票市场净资产收益率大幅下降的最主要因素;其他因素虽有一定影响,但不够显著。     

中压配电网规划中馈线电气计算的估算方法

针对中压配电网规划的特点，介绍并推导了用于估算馈线主干线有功损耗的方法———损失系数法，提出了不同典型负荷分布情况下对馈线主干线电压损耗的估算公式及其电压损失系数表。结合电网实际情况，提出了有效考虑配电变压器损耗的配电网线损估算方法，并基于电压损失系数表提出了在各种典型负荷分布情况下对馈线低电压问题的快速判断法，为配电网规划工作提供实用性参考。     

页岩气水平井最优长度研究

页岩气作为一种新兴能源,得到国家与各个能源公司的重视。我国页岩气资源十分丰富,但是我国的页岩气勘探开发刚刚起步。目前广泛采用水平井开发页岩气藏,采用较大的水平段长度可以获得较高的采收率和较大的采油速度,但成本必然相应地增加,采用较小的水平段长度,可以降低成本,但会影响采油速度和最终采收率。由此看来,对于某一具体的水平井,必然存在一个合理水平段长度。本文从采油工程的角度研究页岩气水平井段最优长度的确定方法。     

基于蓝色经济区甩挂运输结成战略联盟研究

从战略联盟理论分析入手,通过对山东半岛蓝色经济区甩挂运输的发展现状的研究,认真分析甩挂运输的内涵,探讨山东半岛蓝色经济区甩挂运输企业联盟的可行性分析、风险及防范措施,从而得出甩挂运输企业建立联盟,并在山东半岛蓝色经济区进行实施迎来了机遇,又迎来了挑战。