Thermal flow simulation of twin-roll casting magnesium alloy

In order to better understand twin-roll casting process, a 3D finite element method (FEM) simulation was carried out, based on the conditions of the pilot vertical twin-roll caster, to study the thermal flow and solidification behavior in the twin-roll casting process. The simulation results show that non-uniform temperature and velocity distribution near the side dam region are the main reason for causing non-uniform solidification and non-uniform deformation along the cast sheet width. Therefore, it is necessary to preheat the side dams or improve the design of nozzle to compensate the effect of side dams on the casting process. High quality magnesium sheets have been cast after improved the casting devices.     

隧道瞬变电磁法地电参数敏感度分析

为探讨瞬变电磁法用于隧道超前预报时瞬变电磁场的特点,用ANSYS模拟了层状半空间和地下全空间瞬变电磁场的传播特性．通过改变低阻异常体的埋深、半径、电阻率及高阻围岩的电阻率,得到了瞬变电磁场探测结果对各参数的敏感程度,并对探测结果进行拟合,得到了相应的函数特性．结果表明：地下全空间瞬变涡流场的传播表现为“水波效应”,而非层状半空间的“烟圈效应”;隧道中低阻体地电参数变化将显著改变二次场的时域特性．是隧道电磁法的敏感参数：高阻围岩电导率变化对二次场时域特性的影响不大．是不敏感参数．     

Numerical simulation of macrosegregation during steel ingot solidification using continuum model

A continuum model is adopted to study the macrosegregation phenomena during solidification of large steel ingots. Evolution of temperature, melt velocity, and compositional concentration field during a 22 t steel ingot solidification are illustrated by using the finite volume method. Numerical results of temperature distribution are validated by experiments. The influence of local permeability relates to the friction that the melt experienced in mushy region is investigated. It is shown that the continuum model is able to predict the temperature field, and the variation of permeability obviously affects the melt flowing behavior and the final compositional distribution.     

分层媒质中极低频水平电偶极子在绝缘介质半空间中产生的电磁场

推导出分层导电媒质中顶层极低频时谐电偶极子在绝缘介质半空间中产生的电磁场分布的索末非积分表达式;以海床-海水-空气三层模型为例,水平交流电偶极子位于海水中,采用汉克尔变换及快速傅里叶变换,数值计算了空气半空间中的电磁场分布.结果表明极低频时谐电偶极子在空气中产生的电磁场有可测量的量级.     

320kA预焙铝电解槽电磁场分布计算与优化

利用ANSYS电磁场有限元法,建立了320 kA预焙铝电解槽三维电磁场有限元模型,计算了铝电解槽内的电场分布及磁场分布,计算结果与实测结果相吻合,验证了该模型的正确性.在此基础上提出了一种新型电解槽结构,并应用参数化设计语言（APDL）建立该结构的电磁场计算模型,以磁场为目标对该结构进行了整体优化.最终优化后电磁场分布表明：该结构铝电解槽能减小铝液层水平电流,磁场分布对称性好,有利于改善槽内铝液的流动状态,具备较大的节能潜力.     

Numerical implementation of meshless method for electromagnetic field governing equations

For electromagnetic governing equations formulated by magnetic vector potential and electric scalar potential, its detailed numerical implementation is achieved by using meshless method and Galerkin approach. And essential boundary and interface condition of electromagnetic field are imposed by means of Lagrange multiplier method. Furthermore, the influences of interpolation point number at essential boundary and interface on computational results are also discussed. Examples are given to validate the effects of meshless method and Lagrange multiplier approach for electromagnetic field.     

铁路道碴瞬态电磁散射特性分析

引用离散随机媒质结构来模拟铁路道碴的分布情况，采用在ＦＤＴＤ法的差分网格中进行随机填充来实现铁路道碴的计算模拟模型，并求解其瞬态电磁散射场。通过对该散射场的处理，提取出道碴的非相关散射场，然后再对该非相关场进行分析，得出了可描述道碴分布状况的电磁参量。数值分析结果显示，该参量与道碴空隙率之间在一定范围内具有指数关系。这表明，用电磁方法来探测铁路道碴的空隙率是可能的。     

采用压电微泵散热的超磁致精密驱动器

针对超磁致精密驱动器(GMA)工作时因电磁线圈发热而导致GMA定位精度差的问题,采用体积小、噪声低、无电磁干扰的压电微泵驱动水流进行散热,以控制超磁致伸棒的温度.制作了一台GMA样机,设计了一个热变形测试系统,进行了GMA在无水冷和有水冷条件下的热变形对比实验.结果表明,提出的温控措施是有效的.     

电磁波在光子晶体中介质界面的传输矩阵

为探讨电磁波在光子晶体中两介质界面的传播特点,利用电磁场的边界条件,导出了电磁波在介质交界面传播的传输矩阵,并用此矩阵讨论了透射波和反射波的相位和偏振特征;得到了反射波相位发生突变的条件和布儒斯特定律。     

Numerical Simulation and Optimization Design of Electromagnetic Fields in the Electromagnetic Casting of Copper Round Billet

IntroductionInrecentyOars,e1eCtrOmngneticcontinuouscashngtechnologyhasbeenexPerimentngandusinginmostcoUntris,WhichgainedwideaPPicathasinnon-ferrOUsmetalichstry.Atthesamehme,anUmerofsCholarshavecalculatedandmeasuredelectromagneticfields.MapnehqfieldmodelsofmpOREandMSlllhasgainedwideaPPlicationsinthesemodels.Someolsemodels,suchasH-offormula,alsohaVdescribeddistributingofelectromapneticfieldinelectromngneticcontinuouscashngwellandttuly.Electromapneticcontinuouscashngwithsofucontactmoldha…     

Corrections to the Casimir Force Due to Interactions of Plasmons and Electromagnetic Field

IntroductionThe phenomenon that an attractive force ex-ists between two uncharged conducting parallelplates is the so-called Casimir effect. Casimir cal-culated the sum of the zero-point energies of thenormal modes of the electromagnetic (EM) fieldsconfined in between the two conducting plates andshowed that the sum and the Casimir force (perplate area A) depend only on the distance d be-tween the two plates and on the fundamental con-stants (Planck constant) and c (light speed)[1]. Due to t…     

上限单元技术中建立速度场的基元体法

本文采用在基本单元内截取基元体的方法,建立了轴对称变形和平面变形问题的速度场,从而为建立速度场找到了一个简捷的新方法。     

基于磁悬浮技术的建筑隔震研究进展

隔震是在强烈地震中保护建筑物最有效的技术之一,采用磁悬浮技术对建筑结构进行隔震是结构工程的前沿研究领域,与采用传统橡胶隔震支座的技术相比,磁悬浮技术可以同时实现对隔震结构水平振动和竖向振动的主动控制,但基于磁悬浮技术的建筑隔震研究还相对比较薄弱. 简要回顾了磁悬浮技术的发展历程,详细介绍了磁悬浮隔震的基本原理和工作过程,系统阐述了永磁体轨道-电磁铁、衔铁-电磁铁两种磁悬浮隔震体系的理论研究进展与隔震装置研发情况,指出了磁悬浮隔震技术在建筑结构的实际应用中还有待解决的关键问题,并对今后基于磁悬浮技术的建筑结构隔震研究提出了一些建议.      

考虑相变作用的冻土路基应力与变形分析模型

基于冻土路基温度场的控制方程,考虑水分转化为冰的相变作用对土体瞬时变形和蠕变变形的影响,建立路基应力和变形的二维数值方程,并通过1月份的路基冻胀力学模型,分析冻胀带内水分相变引起的路基应力和变形的分布规律.研究发现,在冻胀区域一定的情况下,冻胀率的大小决定了路基表面应力和变形的极值大小;竖向位移的最大值在坡脚处产生,并向路基中部和左侧边界逐渐递减;随着冻胀率的增加,路基表面裂缝有从坡脚向路中发展的趋势;路基表面产生最大拉应力的位置与最大竖向位移的位置基本吻合;路中所承受的拉应力主要发生在水分集聚的相变带范围内.结果表明,相变作用是引起路基发生冻胀病害的直接因素,分析路基应力与变形的分布规律是研究多年冻土路基破坏机理的有效方法.     

粗粒硫酸盐渍土区高速铁路水泥固化级配碎石变形特性

为了探究粗粒硫酸盐渍土区高速铁路路涵、桥梁等过渡段的水泥固化级配碎石在不同工况下的变形特征及其机理，基于固化路基填料的材料特点，采用0~2.5%含盐量的级配碎石，掺加不同种类及含量的水泥，开展常温下有(无)毛细水上升的变形特性试验；针对固化路基段的基床，开展基础冻融循环模拟试验，同时结合XRD试验分析变形机理；在试验的基础上，选取典型试验材料，开展冻融循环工况下的路基-构筑物模拟试验。试验结果表明:在无毛细水上升工况中，普通水泥配制的含盐级配碎石试样产生的变形可达5%特种水泥掺配试样变形的4.2倍；在有毛细水上升工况中，普通水泥配制试样产生的变形最高可达5%特种水泥掺配试样变形的33.0倍；在不同含盐量条件下，3%~5%特种水泥固化级配碎石对相应普通水泥工况产生变形(毛细水上升导致)的最低抑制率为60%~80%；在6次基础冻融循环条件下，添加普通硅酸盐水泥试样产生的最终变形是添加特种水泥试样最终变形的16.0倍；路基-构筑物冻融循环模拟试验中特种水泥固化级配碎石的最大膨胀变形率仅为0.2%；在粗粒硫酸盐渍土地区，虽然水泥固化路基填料可以减少路基其他变形，但是对于高速铁路等对变形控制要求较严格的工程，周围介质中的盐分因素较难避免，普通水泥无法满足盐渍土地区的路基工程需求，需要采取特种水泥固化等工程措施。      

Establishment of particular methods in casting simulation

Casting simulation tool ADSTEFAN is useful to design casting technology of complicated iron castings. Based on the function of solidification analysis, special methods were taken to carry out the prediction and optimization of shake-out timing for large sized iron castings. It has been proved that these analyses are effective to iron casting production. During the research of cast iron semi-solid process, to predict and control the influence of inclined cooling plate on flow and heat transmission of molten iron, the basis of analysis model has been built in this study. Flow field simulation considering temperature field was carried out for further research and satisfied with the practical production.     

改性脲醛树脂加固基床土质的研究

在脲醛树脂中加入其它高分子材料,降低其脆性和收缩性,提高其耐水性。将改性脲醛树酯以液态的形式掺入土中,使聚合物在土中进行交链固化,从而实现对土体的加固。对改良土样的抗水性及强度室内试验表明,改性脲醛树脂能够显著提高土体的强度及抗水性,对翻浆冒泥路基基床的现场灌浆试验表明,改性脲醛树酯能够明显减少基床的翻浆冒泥病害。     

海排灰基层结合料中氯离子固化特性的研究

分析普通水泥、石灰等结合料对海排灰中氯离子固化能力的影响,揭示水泥海排灰、水泥石灰海排灰混合料结合氯离子的固化特性。采用测定氯离子固化含量的水溶盐化学分析法、氯离子的固化理论方法,对水泥海排灰和水泥石灰海排灰固化氯离子特性进行深入研究。试验结果表明,对于水泥海排灰结合料,当氯离子含量超过混合料中海排灰含量2%时,各个龄期的氯离子固化率不再增加。而水泥石灰海排灰结合料,氯离子含量越多,固化率越高。对海排灰基层结合料中氯离子固化研究表明,含适量的氯盐的海排灰可以用做道路基层材料。     

Feasibility of localizing in vivo micro-devices with electromagnetic methods

In order to measure the location of medical micro-devices in the gastrointestinal tract, electromagnetic methods were developed considering the magnetic permeability of human bodies. Two varieties of electromagnetic localization methods have been implemented： one uses direct current（DC） to generate the electromagnetic field, and the other uses alternating current （AC）. The two varieties of the localization principle were analyzed and relevant experiments were made. The experiments show that the alternating electromagnetic method acquires higher accuracy, higher stability and wider measurement range.     

Fe—21Ni—4Mn合金磁场诱发马氏体形貌和惯习面

本文采用强脉冲磁场、光学显微镜和 H.R.Pak 等提出的惯习面确定方法研究了 Fc-21Ni-4Mn 合金中磁场诱发马氏体形貌和惯习面.结果表明,Fe-21Nj-4Mn 合金冷却形成板条马氏体,而在 Ms 温度以上,磁场诱发形成多片状而少板条马氏体,且随温度升高,磁场诱发马氏体形貌为蝶状.磁场诱发马氏体惯习面与冷却形成的马氏体相同,均为(225),对于蝶状马氏体发现了一种新的对称面(110).