五坐标数控快锻机的液压系统设计

对63MN五坐标数控快锻机在自由锻和恒温锻不同的工艺过程进行分析,根据压机设备压力高、流量大的特点,进行系统的优化设计。并对降低噪声、抗污染、保证系统可靠性、实现系统的高精度、高响应等要求,提出了合理的设计方案。     

Rolling and swaying motion estimation for a mobile robot by using omnidirectional optical flows

Described here is a method for estimating rolling and swaying motions of a mobile robot using optical flow. We have proposed an image sensor with a hyperboloidal mirror for the vision-based navigation of a mobile robot. Its name is HyperOmni Vision. The radial component of optical flow in HyperOmni Vision has a periodic characteristic. The circumferential component of optical flow has a symmetric characteristic. The proposed method makes use of these characteristic to estimate robustly the rolling and swaying motion of the mobile robot. Correspondence to: Y. Yagi e-mail: y-yagi@sys.es.osaka-u.ac.jp     

平面绕流泥沙磨损试验及水轮机磨损预估

本文介绍室内平面绕流磨损试验结果和应用于真机的磨损预估，与刘家峡、葛洲坝机组实测磨损量核算结果差别不大。在此基础上对在建的小浪底机组做了估算，并提出了一些看法。     

PID控制技术在砌块养护窑中的应用

本文介绍了一种利用S7-200型PLC的PID控制技术来实现砌块养护窑的自动控制系统，详细介绍了系统的硬件配置以及软件设计流程图，并根据模拟实验的编程经验．介绍了编程中的关键问题。     

Flow boiling in small diameter channels

Many studies have been carried out on two-phase flow heat transfer in channels with hydraulic diameter bigger than 6 mm, but relatively little work has been done for small diameter channels in the meso and compact range (diameter from 0.1 to 3 mm). The use of exchangers with small channels in refrigeration units, which are very numerous besides, could bring a significant reduction of the internal volume of the exchanger, and therefore diminish the refrigerant charge of the whole refrigerating system. One can imagine the interest to widen knowledge on the flow and the heat transfer in small-diameter tubes. This paper examine the thermal behavior of refrigerants boiling in small pipes. The correlations available for in-tube evaporation heat transfer coefficient are discussed and evaluated, when possible, and new research areas of relevance than can contribute to expand the use of small-diameter channels evaporators in refrigeration units are suggested.     

全钒液流电池隔膜在钒溶液中的性能

考察了Nafion、日-160、日-80、FYM(日本产Nafion膜)和均相膜5种离子交换膜的两个关键性能(渗透性和面电阻)及其影响因素,对均相膜的化学稳定性进行了初步研究,并对两种膜进行了改性。实验发现:均相膜的钒扩散系数最小,但面电阻较大,化学稳定性不好;用二乙烯苯(DVB)对均相膜改性,综合性能较好;减小电场可降低钒离子扩散,提高钒溶液中氢离子浓度可减小面电阻。     

Velocity Distribution in the Roughness Layer of Rough-Bed Flows

Several models for the vertical distribution of the double-averaged (in time and in the plane parallel to the mean bed) longitudinal velocity in the flow region between roughness troughs and roughness tops are suggested. We found that the same model for velocity distribution may be applicable to a range of flow conditions and roughness types, which share some common features. The suggested models for velocity distribution in the near-bed region are: (1) Constant velocity; (2) exponential velocity distribution; and (3) linear velocity distribution. The measured velocity distributions may be approximated by a single model or by a combination of models depending on roughness geometry and flow conditions. The validity of these models for velocity distribution is supported by laboratory data.     

High order finite difference methods for unsteady incompressible flows in multi-connected domains

Using the vorticity and stream function variables is an effective way to compute 2-D incompressible flow due to the facts that the incompressibility constraint for the velocity is automatically satisfied, the pressure variable is eliminated, and high order schemes can be efficiently implemented. However, a difficulty arises in a multi-connected computational domain in determining the constants for the stream function on the boundary of the “holes”. This is an especially challenging task for the calculation of unsteady flows, since these constants vary with time to reflect the total fluxes of the flow in each sub-channel. In this paper, we propose an efficient method in a finite difference setting to solve this problem and present some numerical experiments, including an accuracy check of a Taylor vortex-type flow, flow past a non-symmetric square, and flow in a heat exchanger.     

网络等值与互联电网潮流分析

基于互联电网解合环潮流分析的现实需求。开发了一个应用软件。它采用潮流网络等值算法进行电网解合环分析。介绍了该算法的基本思路。并以实际算例阐明其计算精度高。具有普遍应用意义。在等值模式的选择中,通过分析端口模式和局部网络模式的优缺点。认为在可获得较多主网数据的情况下应优先采用局部网络模式。同时还指出。在软件的实现中应注意操作界面的图形化、数据对接的自动化和数据传送的信息化等问题。     

经济评价方法中内部收益率的分析与研究

内部收益率是经济评价中的一项重要指标,反映项目收回投资时间的快慢,可用试差法计算,也可近似等于偿还期的倒数.