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Singularities of noncompact charged objects

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Chinese Physics B 2013年第3期22卷 192-195页

作者： M.Sharif G.Abbas Department of Mathematics University of the PunjabQuaid-e-Azam CampusLahore-54590Pakistan

We formulate a model for noncompact spherical charged objects in the framework of noncommutative field *** Einstein-Maxwell field equations are solved with charged anisotropic *** choose matter and charge densities as functions of the two parameters,instead of defining these quantities in terms of the Gaussian distribution *** is found that the corresponding densities and the Ricci scalar are singular in origin,whereas the metric is nonsingular,indicating a spacelike *** numerical solution of the horizon equation implies that there are two or one or no horizon（s）,depending on the *** also evaluate the Hawking temperature and find that a black hole with two horizons is evaporated to an extremal black hole with one horizon.

关键词： noncommutative geometry electromagnetic field spacetime singularity

Structure and mechanical properties of AZ31 magnesium alloy billets by different hot-top semi-continuous casting technology

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Rare Metals 2011年第4期30卷 414-418页

作者： ZHANG Zhiqiang LE Qichi CUI Jianzhong The Key Laboratory of electromagnetic Processing of Materials （Ministry of Education of China） Northeastern University Shenyang 110004 China

AZ31 alloy billets of 200 mm in diameter were produced by three different processes of conventional direct chill （DC） casting, low-frequency electromagnetic casting （LFEC） and low-frequency electromagnetic vibration casting （LFEVC）, respectively. The effect of LFEC and LFEVC on the microstructures, macmsegregation and mechanical properties of AZ31 alloy billets was investigated. In conventional DC casting, the AZ31 alloy billets exhibited coarse grains （about 370 μa） and severe segregation of A1 and Zn. In the presence of a solo low-frequency alternating magnetic field or a low-frequency electromagnetic vibration field applied during DC casting of Ф200 mm AZ31 billets, grains in the AZ31 alloy billets were effectively reffmed （about 210 μa） and the macrosegregation of A1 and Zn in the billets was greatly decreased. Furthermore, the tensile strength, fracture elongation and hardness of the as-cast AZ31 alloy billets were improved by the processes of LFEC and LFEVC relative to that cast by the process of conventional DC casting.

关键词： magnesium alloys electromagnetic field microstructure macrosegregation mechanical properties casting

Numerical Simulation of Two Types of electromagnetic Edge Dam Used in Twin Roll Strip Casting

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Journal of Materials Science & Technology 2005年第4期21卷 526-530页

作者： Peiwei BAO Peijie LI Hongshuang DI Xianghua LIU Guodong WANG Key Laboratory for Advanced Manufacturing by Materials Processing Technology Department of Mechanical Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 China

Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, the eddy current intensity and the magnetic force were obtained from the computing. The differences in these fields were explained according to the two types of electromagnetic dam, and characters of their application in twin roll casting were also discussed.

关键词： Twin roll casting electromagnetic field electromagnetic containment Numerical simulation Finite element

Two Dimension Finite Element Simulations on the electromagnetic Containment in Twin-Roll Strip Casting

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Journal of Materials Science & Technology 2003年第1期19卷 9-12页

作者： Peiwei BAO, Hongshuang DI, Xiaoming ZHANG, Guodong WANG and Xianghua LIUState Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110004, China Lab. of Rolling and Automat. Northeastern Univ. Shenyang 110004 China

Distribution of magnetic field and electromagnetic force in twin-roll casting of steels was studied by the method of numericalsimulation in this paper. Two-dimension finite element model, which includes the regions of melt, stainless collar, coil andmagnetic core, has been constructed. By solving magnetic vector potential formulations of quasi-static electromagnetic field,distribution of magnetic flux density and magnetic force at different molten height is determined. Calculated results showedthat intensity of the distribution of magnetic flux density increased linearly with the increased coil current; and the magneticforce in the melt increased as a quadratic cure with creased coil current. More attention was given to the distribution of eddycurrent and magnetic force in the melt, the confine effect at different molten height was also discussed.

关键词： Twin roll casting electromagnetic field electromagnetic containment Simulation Finite element

Micron-sized fiber diamond probe for quantum precision measurement of microwave magnetic field

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Chinese Physics B 2024年第8期33卷 186-190页

作者：卢文韬夏圣开陈爱庆何康浩许增博陈艺涵汪洋葛仕宇安思瀚吴建飞马艺菡杜关祥 Portland Institute Nanjing University of Posts and TelecommunicationsNanjing 210023China School of Computer Science Nanjing University of Posts and TelecommunicationsNanjing 210023China College of Telecommunication and Information Engineering Nanjing University of Posts and TelecommunicationsNanjing 210003China School of Economics Nanjing University of Posts and TelecommunicationsNanjing 210023China School of Electronic and Optical Engineering Nanjing University of Posts and TelecommunicationsNanjing 210023China School of Science Nanjing University of Posts and TelecommunicationsNanjing 210023China College of Electronic Science and Technology National University of Defense TechnologyChangsha 410000China

We present a quantitative measurement of the horizontal component of the microwave magnetic field of a coplanar waveguide using a quantum diamond probe in fiber *** measurement results are compared in detail with simulation,showing a good *** simulation shows fiber diamond probe brings negligible disturbance to the field under measurement compared to bulk *** method will find important applications ranging from electromagnetic compatibility test and failure analysis of high frequency and high complexity integrated circuits.

关键词： quantum precision measurement electromagnetic field diamond NV center quantum metrology

Numerical prediction of the incremental melting and solidification process

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Journal of University of Science and Technology Beijing 2003年第4期10卷 50-54页

作者： Jun Wang, Chengchang Jia, and Sheng YinMaterials Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China Mat. Sci. and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

A mathematical formulation is applied to represent the phenomena in theincremental melting and solidification process (IMSP), and the temperature and electromagneticfields and the depth of steel liquid phase are calculated by a finite difference technique using thecontrol volume method. The result shows that the predicted values are in good agreement with theobservations. In accordance with the calculated values for different kinds of materials anddifferent size of molds, the technological parameter of the IMS process such as the power supply andthe descending speed rate can be determined.

关键词： incremental melting and solidification process (IMSP) numerical prediction electromagnetic field temperature field technological parameter

Simulation of electron behavior in PIG ion source for 9 MeV cyclotron

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Chinese Physics C 2014年第12期38卷 70-76页

作者： X.J.Mu M.Ghergherehchi Y.H.Yeon J.W.Kim J.S.Chai College of Information & communication Engineering School of Electronic and Electrical EngineeringSungkyunkwan University Department of Energy Science Sungkyunkwan University

In this paper, we focus on a PIG source for producing intense H-ions inside a 9 MeV cyclotron. The properties of the PIG ion source were simulated for a variety of electric field distributions and magnetic field strengths using a CST particle studio. After analyzing the secondary electron emission（SEE） as a function of both magnetic and electric field strengths, we found that for the modeled PIG geometry, a magnetic field strength of 0.2 T provided the best results in terms of the number of secondary electrons. Furthermore, at 0.2 T, the number of secondary electrons proved to be greatest regardless of the cathode potential. Also, the modified PIG ion source with quartz insulation tubes was tested in a KIRAMS-13 cyclotron by varying the gas flow rate and arc current, *** capacity of the designed ion source was also demonstrated by producing plasma inside the constructed 9 MeV cyclotron. As a result, the ion source is verified as being capable of producing an intense H-beam and high ion beam current for the desired 9 MeV cyclotron. The simulation results provide experimental constraints for optimizing the strength of the plasma and final ion beam current at a target inside a cyclotron.

关键词： PIG ion source CST particle studio electromagnetic field secondary electron gas flow rate arc

Effect of electromagnetic fields on Proliferation and Differentiation of Cultured Mouse Bone Marrow Mesenchymal Stem Cells

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Journal of Huazhong University of Science and Technology(Medical Sciences) 2005年第2期25卷 185-187页

作者：吴华任凯赵文春葛保剑彭松林 Department of Orthopedics Tongji Hospital Tongji Medical College Huazhong Universityof Science and Technology Wuhan 430030 China

Summary: In order to study the effects of electromagnetic fields (EMFs) on proliferation, differentiation and intercellular cyclic AMP (cAMP) in mouse bone marrow mesenchymal stem cells (MSCs) in vitro, the mouse bone MSCs were isolated and cultured in vitro. The third passage MSCs were divided into 4 groups and stimulated with EMFs. The cellular proliferation (MTT), the cellular differentiation (alkaline phosphatase activity, ALP), and the intercellular cAMP level were investigated at different time points. The results showed that EMF (50Hz pulse burst 2 mT peak) inhibited the cellular proliferation (P<0.05), enhanced the cellular differentiation (P<0.05), and increased the intercellular cAMP level (P<0.01) in the early time of the stimulation (1-3 days), but the intercellular cAMP level did not increased further in the later days. We are led to conclude that the cAMP may be involved in the mediation of the growth inhibitory and differentiation-inducing signals of specific EMFs in vitro.

关键词： electromagnetic field cyclic AMP alkaline phosphatase marrow mesenchymal stem cells

Calculating the transient behavior of grounding systems using inverse Laplace transform

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第3期12卷 250-262页

作者： Nabiollah RAMEZANI Seyed Mohammad SHAHRTASH Behshahr Branch Iran University of Science and TechnologyBehshahr 47137Iran Center of Excellence for Power Systems Automation and Operation Department of Electrical EngineeringIran University of Science and TechnologyTehran 16844Iran

This paper deals with a unified and novel approach for analyzing the frequency and time domain performance of grounding *** proposed procedure is based on solving the full set of Maxwell's equations in the frequency domain,and enables the exact computation of very near fields at the surface of the grounding grid,as well as far fields,by simple and accurate closed-form expressions for solving Sommerfeld *** addition,the soil ionization is easily considered in the proposed *** frequency domain responses are converted to the time domain by fast inverse Laplace *** results are validated and have shown acceptable accuracy.

关键词： electromagnetic field Near-field computation High frequency performance Soil ionization Grounding system Fast inverse Laplace transform