Flux Jumps and H-T Diagram of Instability for MgB2

We present a study of magneto-thermal instabilities in polycrystalline MgB₂ superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated.     

Research on the Handover of a Novel Cellular Architecture in Wireless Personal Communication Systems

1　IntroductionHandoverbetweencellsisplayinganimportantroleincellularcommunicationsystems[1～ 1 2 ] .Thehandoverprocedureanditseffectivenessareseriouslylimitedbythecellulararchitectureasaresultofmar ketplanning .Basedonthehexagonalcellulararchi tecture,manyhandoverprocedureshavebeendis cussedandevaluated ,andmostoftheimprovementproposedonthemleadstotheintroductionofsector ingcellularorlayeredcellularmodel.Otherwise ,abetterhandoverprocedureisessentialinmaintainingacallinprogressbutitreflectshi…     

变频调速技术在济钢焦化厂高压氨水泵上的应用

济钢焦化厂高压氨水泵变频调速系统采用变频器和PLC相结合的方式 ,具有调速精度高、节能等多种功能 ,保证氨水泵正常工作。全年可增加经济效益 77.3万元。     

共青团员要担当历史重任

青年只有在党的领导下 ,积极投身于建设祖国的伟大实践 ,才能为祖国和人民建功立业 ,才能有所作为。青年是推动历史发展和社会进步的重要力量。     

关于项目管理中施工进度控制的研究

阐述了项目管理中施工进度控制的地位与作用，分析了影响工程进度的因素，提出项目进度控制需做好的工作，以提高进度控制水平，确保合同工期的实现。     

用φ20mm离心萃取器两步法制取高纯钇

本文研究了中钇富镧稀土的氧化物溶液在环烷酸中的萃取行为，测定了镧钇组成、温度变化与分离系数的关系；在Ｐ＿（５０７）体系中研究了ｐＨ值与分配比的关系；提出用环烷酸、Ｐ＿（５０７）两种萃取剂制备高纯钇的工艺流程。用８４台φ２０ｍｍ离心萃取器进行了一个月的台架试验，结果证明两种萃取剂有很好的互补性，在满足钇的纯度要求下有较高收率。离心萃取器具有易分相、体系存留量少、液流密闭性好等优点，它更适宜于粘度大、级数多、产品纯度要求高的体系。     

轻水堆发展规划的核燃料循环模型及优化

一、前言提高核燃料循环的经济性是增进核动力经济性极为重要的一环。国外有人提出利用动态线性规划方法,依据燃料循环中各环节内在的物理和化工过程,建立起一系列线性方     

钇铁石榴石薄膜材料的光吸收谱及Bi,Al掺入对谱的影响研究

采用单离子晶场跃迁模型，拟合出钇铁石榴石（ＹＩＧ）薄膜材料的光吸收谱，与实验谱吻合得较好。从实验和理论上分析了（ＢＩＡＩ）ＹＩＧ 薄膜材料的光吸收谱，结果表明，Ａｌ３＋离子的作用如同稀释剂一样，减小了光吸收，Ｂｉ３＋离子由于其强的自旋轨道耦合作用，增大了跃迁振子强度和跃迁线宽，从而增大了光吸收损耗，在此基础上所作的（ＢｉＡｌ）ＹＩＧ的理论谱与实验谱符合得较好。     

Observation of atomic steps on CaCO3 crystal surface

By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed.     

步进式加热炉炉温优化设定模型及软件开发

针对线材厂步进式加热炉实际工况，提出了基于经验规则的炉温优化设定模型和在线自学习获取知识的思想，并以炉温优化设定模型为核心，开发出加热炉计算机控制系统的优化运行软件。