Effect of Stable Magnetic Field on the Phase Transformation of Sr3 Steel

The experimental equipment designed by the author was used to carry out quenching treatments on Sr3 steel, with and without magnet it field in different quenching mediums. The effect of steady magnetic field on the phase transformation of Sr3 steel was studied by metallographic microscope and scanning electron microscope. The result shows: the application of magnetic field can obviously increase the volume fraction of ferrite during the austenite to ferrite transformation of Sr3 steel, promote the ferrite grains refining and homogenization, and get the pearlite beam much homogeneously and much compact, when Sr3 steel is quenched in the water.

Effect of antenna helicity on discharge characteristics of helicon plasma under a divergent magnetic field

The characteristics of the blue core phenomenon observed in a divergent magnetic field helicon plasma are investigated using two different helical antennas, namely right-handed and lefthanded helical antennas. The mode transition, discharge image, spatial profiles of plasma density and electron temperature are diagnosed using a Langmuir probe, a Nikon D90 camera,an intensified charge-coupled device camera and an optical emission spectrometer, respectively.The results demonstrated that the blue core phenomenon appeared in the upstream region of the discharge tube at a fixed magnetic field under both helical antennas. However, it is more likely to appear in a right-handed helical antenna, in which the plasma density and ionization rate of the helicon plasma are higher. The spatial profiles of the plasma density and electron temperature are also different in both axial and radial directions for these two kinds of helical antenna. The wavelength calculated based on the dispersion relation of the bounded whistler wave is consistent with the order of magnitude of plasma length. It is proved that the helicon plasma is part of the wave mode discharge mechanism.

Effect of non-uniform temperature gradient and magnetic field on onset of Marangoni convection heated from below by a constant heat flux

This paper investigates the effect of non-uniform temperature gradient and magnetic field on Marangoni convection in a horizontal fluid layer heated from below and cooled from above with a constant heat flux. A linear stability analysis is performed. The influence of various parameters on the convection onset is analyzed. Six non-uniform basic temperature profiles are considered, and some general conclusions about their desta- bilizing effects are presented.

On the heating mechanism of electron cyclotron resonance thruster immerged in a non-uniform magnetic field

To study the heating mechanism of electron cyclotron resonance thruster(ECRT)immersed in a non-uniform magnetic field,experiments and simulations are performed based on an electron cyclotron resonance plasma source at ASIPP.It is found that the first harmonic of electron cyclotron resonance is essential for plasma ignition at high magnetic field(0.0875 T),while the plasma can sustain without the first and second harmonics of electron cyclotron resonance at low magnetic field(till 0.0170 T).Evidence of radial hollow density profile indicates that upper hybrid resonance,which has strong edge heating effect,is the heating mechanism of low-field ECRT.The heating mode transition from electron cyclotron resonance to upper hybrid resonance is also revealed.Interestingly,the evolutions of electron temperature and electron density with input power experience a‘delayed’jump,which may be correlated with the different power levels required for cyclotron and ionization.Moreover,when the field strength decreased,the variation of electron density behaves in an opposite trend with that of electron temperature,implying a possible competition of power deposition between them.The present work is of great interest for understanding the plasma discharge in ECRT especially immersed in a non-uniform magnetic field,and designing efficient ECRT using low magnetic field for economic space applications.

Magnetic Field and Operating Performance Analysisof Conical-rotor Permanent Magnet Synchronous Motor

In order to accurately analyze the magnetic field of conical-rotor permanent magnet synchronous motor(CR-PMSM),the effectiveness of two methods was studied on handling of problems concerned with non-uniform distribution of magnetic field along axial direction in CR-PMSM,which were sectional calculation(SC)method and three-dimensional finite element(3-D FE)method.On this basis,the influence of the axial displacement and dq-axis currents on the operating characteristics of axial magnetic force and torque is analyzed by using the 3-D FE model.Analysis results show that the axial magnetic force and torque decrease with the increase of axial displacement of the rotor,and the amplitude regularity of the axial magnetic force is affected by the d-axis current.A prototype machine is fabricated and tested,in order to validate the design theory.

Bi System Superconducting Fibres by the Laser-heated Pedestal Growth Method in Stable Magnetic Field

1 Introduction The technology of the laser-heated pedestal growth (LHPG) in making single crystalsand fibres is based on the Czochralski technique, which makes use of a laser as heaterto produce all kinds of high melting temperature oxide single crystal materials. Inthe early 1980s, the Bell Laboratory in USA produeed some kinds of single cryatalsand fibres having special properties by using this technique. Since 1986, high-T_csuperconducing fibres have been produced in many laboratories of LHPG insome countries, and the Institute of Metal Research, Academia Sinica,also built an experimental apparatus financially supported by the NationalSuperconducting Centre specially to study the superconducor.

Effect of non-uniform magnetic field on crystal growth by floating-zone method in microgravity

The magnetic damping effect of the non-uniform magnetic field on the floating-zone crystal growth process in microgravity is studied by numerical simulation. The results show that the non-uni-form magnetic field with designed configuration can effectively reduce the flow near the free surface and then in the melt zone. At the same time, the designed magnetic field can improve the impurity concen-tration non-uniformity along the solidification interface. The primary principles of the magnetic field con-figuration design are also discussed.

The Landau-level structure of a single polaron in a nanorod under a non-uniform magnetic field

Nanorod is a unique low-dimensional nanometer structure in which the Landau level arrangement of polaron is essential for understanding its quasiparticle system. However, the stability of the polaron level is susceptible to external factors, such as changing magnetic fields.In this manuscript, the Pekar variational method is employed to calculate the external magnetic field's effect on the nanorod's polaron Landau level. It was found that different magnetic fields have different effects on the polaron energy levels of the nanorod, which demonstrated that the external environment had critical effects on the polaron energy levels. This study provides a theoretical basis for regulating the interaction between electrons and phonons in low-dimensional nanomaterials.

Numerical analysis of a magnetohydrodynamic duct flow with flow channel insert under a non-uniform magnetic field

This study performs a numerical analysis of three-dimensional liquid metal(LM) magnetohydrodynamic(MHD) flows in a square duct with an FCI in a non-uniform magnetic field. The current study predicts detailed information on flow velocity, Lorentz force, pressure, current and electric potential of MHD duct flows for different Hartmann numbers. Also, the effect of the electric conductivity of FCI on the pressure drop along the main flow direction in a non-uniform magnetic field is examined. The present study investigates the features of LM MHD flows in consideration of the interdependency among the flow variables.

面向渗漏探测的堤防磁场分布特性分析

快速确定堤防渗漏隐患的位置信息,对堤防的治理具有重要意义。然而在渗漏通道弱磁数据处理过程中,堤防正常场计算往往需要花费较长时间,严重制约着渗漏隐患的定位效率。为解决上述问题,本文基于有限单元法开展了磁电阻率法探测堤防渗漏的建模仿真工作,探究了不同尺寸堤防内稳定电流场及其外部磁场的分布特性,并构建了一定数量的模型数据库。研究结果表明,磁感应强度y分量在测域中部的整体波动相较于x分量和z分量更大,其值随堤防上宽的增加呈下降趋势,而随斜坡角度的增大或堤防主体高度的增加呈上升趋势。依据本文总结的分布特性,可以预测数据库中缺失的堤防正常场,堤防模型的预测平均相对误差为9.63%。

磁场下液体乙醇微尺度扩散火焰的实验研究

通过实验研究了液体乙醇微尺度扩散火焰的高度、温度以及火焰稳定燃烧的流量范围随磁场强度的变化.结果表明:固定磁场的作用下,液体乙醇微尺度扩散火焰的高度降低,火焰的温度有所升高,火焰稳定燃烧的流量范围扩大.这是固定磁场对火焰中没有完全燃烧的离子和离子团作用的结果.

稳恒磁场对马氏体转变的影响

利用自制的磁场热处理设备对中、高碳钢进行了施加磁场与不施加磁场的淬火处理,研究了奥氏体在NaCl溶液中冷却时的组织转变,观察了相变后的组织变化。结果表明,在中、高碳钢发生奥氏体向马氏体转变时,稳恒磁场可使马氏体的形核率增加,提高马氏体的转变开始温度,使相变在更宽的温度区间进行,促进了奥氏体向板条马氏体的转变。

稳恒磁场在金属相变过程中的应用

稳恒磁场在材料科学中的应用越来越受到关注。本文从稳恒磁场作用下生成的磁化力和洛伦兹力两个角度归纳了稳恒磁场对金属材料的固态相变和液态相变的影响。其中磁化力可以影响固态相变过程,形成取向,引起磁对流,进行磁性分离。而洛伦兹力可以抑制熔体的流动和波动,提高溶质离子在基体中的固溶度,另外,利用洛伦兹力还可以在电磁离心铸造中获得均匀的凝固组织。

水下焊接稳弧装置的磁场及其双流道流场

为了解决水下焊接焊缝质量差的问题,提高水下焊接自动化,设计了一种用于水下湿法焊接稳弧装置,可为水环境中的电弧制造半干环境和进行磁力约束,达到稳定水中焊接电弧的目的。采用有限元方法对该装置的磁场进行分析。运用流体力学仿真方法对该装置的高压气道和保护气道进行了仿真分析,分析了在水下高压环境下,不同气压对高压气道流场的影响和不同进气口速度对保护气道流场的影响,验证了高压气道的排水效果和保护气道的保护效果。

稳恒磁场下CuCo颗粒膜电沉积制备与巨磁电阻效应

在稳恒磁场下电沉积制备了CuCo功能膜材料.用SEM和XRD对镀层组分、微观结构进行观察和分析,并测量了膜层的巨磁电阻效应.颗粒膜的组成随磁场强度变化而改变,0.6～0.8T下沉积的膜层中Co含量较高,更强磁场反而抑制了Co的沉积.施加磁场能使膜层晶粒更加致密,0.6T磁场下制备的膜层晶粒较小,并使膜层(111)晶面择优取向增强.磁阻测试表明,0.6T磁场下制备的CuCo颗粒膜经真空退火处理后,巨磁电阻较无磁场下提高约25%.

稳态强磁场中直流有源滤波器连接电感的计算

针对国外稳态强磁场实验装置有源滤波器的不足,结合PWM技术及并联型的优点,采用并联型PWM有源滤波在直流侧的滤波方案。介绍了并联型PWM有源滤波器的结构及其工作原理,对其断续电流工作模式下的电感参数及最大输出电流进行分析设计,同时分析了其控制模型。最后研制样机对所提方案进行实验验证,实验结果表明,该滤波器具有良好的滤波效果,为稳态强磁场实验装置电源系统的有源滤波提供了参考依据。

稳态强磁场电源直流有源滤波技术方案的分析

为了满足强磁场装置电源供电极低的电流纹波要求,设计了一种直流有源滤波器。分析比较了目前国际上现有的强磁场装置电源所需的直流有源滤波器,对稳态强磁场电源采用利用并联有源滤波技术的滤波方案并给出了系统结构并对其工作原理进行了说明,论述了该系统的设计方法。根据其实际负载特性,通过检测负载端纹波电压,进而控制有源滤波器产生所需电流;通过对负载侧的滤波电容进行充、放电来调整负载端电压,实现负载电流的低纹波。基于传递函数建立该系统的数学模型并对控制系统进行详细的分析表明,该系统具有良好的快速跟踪性能及对谐波很好的抑制效果。仿真及实验结果验证了该有源滤波器的良好性能,尤其对低次谐波的抑制更为明显,为以后强磁场电源有源滤波装置提供了理论和设计依据。

永磁同步电机直接转矩和矢量控制运行稳定性对比研究

目前永磁同步电机的主流控制方式主要有直接转矩控制和矢量控制,而系统能否稳定运行是这些电机控制算法的基础.分别基于两种控制算法的基本原理,从实际运行工作点出发,结合转矩角、磁链、电流角限幅和系统的单调性等理论,分析了永磁同步电机直接转矩控制和矢量控制的稳定运行区间,并运用仿真实验对理论分析进行了验证,对比分析了两种控制算法稳定运行规律的异同点.

低稳恒磁场对锡锌基合金液与铜片界面反应的影响

利用SEM、XRD等方法研究了0.1 T低稳恒磁场对锡锌合金液/铜片和锡锌铜合金液/铜片的界面反应过程中金属间化合物(IMC)层的生长、晶体取向以及形貌的影响。结果表明:界面IMC层的厚度随反应时间的延长而增加;在0.1 T磁场下,锡锌合金液/铜片和锡锌铜合金液/铜片的界面IMC层的生长均受到抑制;同时磁场抑制了IMC晶粒的粗化,使IMC颗粒更加细小致密;0.1 T磁场抑制了锡锌合金液/铜片界面处Cu5Zn8(330)的取向度,但对锡锌铜合金液/铜片的界面晶粒取向度影响并不很明显。

恒定磁场杀菌作用的研究

目的:探讨恒定磁场的杀菌作用及其影响因素。方法:选用大肠杆菌8099标准株为 试验菌株,配制成一定菌密度的模拟水样,分别控温在5℃、15℃、35℃3个水平。以滤膜荧光法定量 检测:菌密度随时间的自然变化及经磁处理水样菌密度随时间的变化。结果:无磁处理,3种温度下 菌密度随时间延长均呈下降趋势,符合负指数函数关系:y=ae-bt。5℃下磁场的杀菌作用不显著, 15℃及35℃下,恒定磁场有较显著的杀菌作用。结论:恒定磁场的杀菌作用与菌株特征、环境温度及 处理时间关系密切。