The effects of gravity on the features of the interfacial waves in annular two-phase flow

A physical model of interfacial waves in annular two-phase flow was studied in both microgravity and normal gravity. The wave structure was obtained for local film thickness and velocity measurements using a conductance probe technique. It was found that the wave height, and not its width, is strongly affected by changing the gravity level. In fact, the wave height in normal gravity is more than twice that in microgravity. Using an analogous approach to a turbulent, single-phase flow in a rough tube, a preliminary mathematical model was proposed to calculate the wave amplitude. The model fits well with the experimental data and shows that the wave height in normal gravity is approximately 1.7 times the combined thickness of the viscous sublayer and transition zones in the turbulent gas stream. The wave height in microgravity was estimated to be approximately 80% of the total thickness.     

Effect of synthesis temperature on density and microstructure of MgB2 superconductor at ambient pressure

The experimental thermodynamic of MgB₂ synthesis process and phase compositions have been investigated by diffraction thermal analysis (DTA) technology and X-ray diffraction. The fabrication of MgB₂ bulks and superconducting properties at the temperatures range from 600 to 800°C were reported. And microstructure of MgB₂ bulks were observed by scanning electron microscope (SEM). A method was developed to determine the porosity of MgB₂ and the highest density can be obtained in MgB₂ prepared at 650°C at ambient pressure. It is found that the vapor pressure of Mg increases remarkably at high temperature, leading to the high porosity in MgB₂ samples. MgB₂ bulk with good superconducting property and fine microstructure was synthesized at 750°C.     

Baseline Models for Bridge Performance Monitoring

A baseline model is essential for long-term structural performance monitoring and evaluation. This study represents the first effort in applying a neural network-based system identification technique to establish and update a baseline finite element model of an instrumented highway bridge based on the measurement of its traffic-induced vibrations. The neural network approach is particularly effective in dealing with measurement of a large-scale structure by a limited number of sensors. In this study, sensor systems were installed on two highway bridges and extensive vibration data were collected, based on which modal parameters including natural frequencies and mode shapes of the bridges were extracted using the frequency domain decomposition method as well as the conventional peak picking method. Then an innovative neural network is designed with the input being the modal parameters and the output being the structural parameters of a three-dimensional finite element model of the bridge such as the mass and stiffness elements. After extensively training and testing through finite element analysis, the neural network became capable to identify, with a high level of accuracy, the structural parameter values based on the measured modal parameters, and thus the finite element model of the bridge was successfully updated to a baseline. The neural network developed in this study can be used for future baseline updates as the bridge being monitored periodically over its lifetime.     

ZrO_2汽车氧传感器烧结工艺研究

采用注射成型方法制备汽车氧传感器。通过分析得知,烧结制品好的力学性能和高导电率往往是矛盾的,要获得四方相ZrO2须保证烧结过程中材料的晶粒尺寸要控制在1μm以内。综合考虑,烧结温度在1550℃左右比较合适。     

TCPDUMP简介

介绍Tcpdump特点、所支持的参数和安装方法.     

分布式控制系统在气相法白炭黑生产过程中的应用

本文介绍了SIEMENS公司的分布式控制系统SIMAT-IC DCS在白炭黑生产过程中的应用。阐述了系统的工艺流程、硬件配置、软件配置和控制系统完成的主要功能。     

CAN总线在仿人机器人运动控制系统中的应用

文章先对CAN总线进行了介绍，然后把CAN总线应用到仿人机器人中，设计出一种适合仿人机器人的分布式运动控制系统，并给出了详细的设计过程。整个控制系统层次清晰，结构灵活，对仿人机器人的进一步发展具有积极的作用，同时为现场总线在仿人机器人中的应用提供了重要的参考。     

中国科学院广州分院、广东省科学院科技成果专利信息系统

文章阐述了建设网上科技成果信息系统的目的和必要性，结合中科院广州分院、广东省科学院成果管理的经验提出网上科技成果信息以及交易应有的功能摸块及关键技术，开发了一套实用管理系统信息模型，在实际中应用效果良好。     

Effect of Rare Earths on Corrosion Resisting Properties of Carbon-Manganese Clean Steels

Rareearthelementshavesignificantactionsinsteels ,includingwipingoffimpurityelements ,trans modifyinginclusions ,andimprovingmicrostructureetal,soaddingappropriaterareearthsintosteelscanef fectivelyimprovetheircorrosionresistingproper ties[1,2 ] .Todaypuri…     

主从式小型集散系统设计

集散型控制系统是一种昂贵的先进自动化装置,作者设计一套经济、实用的主从式小型集散系统,用于仪器开发领域,不仅能节省开发资金,还能提高仪器系统的利用率、可靠性、稳定性。该文构建了小型集散系统的框架,并为此设计一套完善的通讯协议,克服了通用的通讯协议中存在的安全隐患。以此理论为基础,开发了自动生化分析仪系统。