Diffusion Equations of the Electric Charges and Magnetic Flux

Innovative definitions of the electric and magnetic diffusivities through conducting mediums and innovative diffusion equations of the electric charges and magnetic flux are verified in this article. Such innovations depend on the analogy of the governing laws of diffusion of the thermal, electrical, and magnetic energies and newly defined natures of the electric charges and magnetic flux as energy, or as electromagnetic waves, that have electric and magnetic potentials. The introduced diffusion equations of the electric charges and magnetic flux involve Laplacian operator and the introduced diffusivities. Both equations are applied to determine the electric and magnetic fields in conductors as the heat diffusion equation which is applied to determine the thermal field in steady and unsteady heat diffusion conditions. The use of electric networks for experimental modeling of thermal networks represents sufficient proof of similarity of the diffusion equations of both fields. By analysis of the diffusion phenomena of the three considered modes of energy transfer;the rates of flow of these energies are found to be directly proportional to the gradient of their volumetric concentration, or density, and the proportionality constants in such relations are the diffusivity of each energy. Such analysis leads also to find proportionality relations between the potentials of such energies and their volumetric concentrations. Validity of the introduced diffusion equations is verified by correspondence their solutions to the measurement results of the electric and magnetic fields in microwave ovens.

Influence of Temperature and Frequency on Minority Carrier Diffusion Coefficient in a Silicon Solar Cell under Magnetic Field

In this study, the effects of temperature and frequency on minority carrier diffusion coefficient in silicon solar cell under a magnetic field are presented. Using two methods (analytic and graphical), the optimum temperature corresponding to maximum diffusion coefficient is determined versus cyclotronic frequency and magnetic field.

Friction Coefficient Displayed by the Scratch of Epoxy Composites Filled by Metallic Particles under the Influence of Magnetic Field

The wide use of epoxy composites as bearing materials in electronic appliances necessitates studying their frictional behaviour under the influence of magnetic field. Experiments were carried out to investigate the effect of magnetic field on the friction coefficient displayed by the scratch of epoxy composites filled by iron, copper and aluminium particles at different concentrations. It was observed that, for epoxy filled by the metallic fillers (iron, copper and aluminium), under the effect of the magnetic field, friction coefficient showed relative decrease then significantly increased with further increase of the intensity of the magnetic field. Besides, friction coefficient increased with increasing the content of the metallic fillers due to the decrease of the strength of the epoxy matrix. The values of friction coefficient displayed by epoxy filled by copper were lower than those observed for epoxy filled by iron. Filling epoxy by aluminium displayed lower friction coefficient than that observed for epoxy composites filled by iron and copper. This can be attributed to the charging of aluminium by positive charge when slid against steel. The resultant charge on the sliding surfaces was lower than that generated when epoxy was filled by iron and copper. In that condition, the adhesion of epoxy composites would be relatively weaker leading to the decrease of friction coefficient.

Sliding wear behavior of magnetorheological fluid for brass with and without magnetic field

A pin-on-disc wear apparatus was used to carry out the tribological experiment of brass to investigate the effect of a magnetorheological （MR） fluid on the interfacial surface with and without magnetic field. A series of tests were performed at the loads of 20-100 N and rotating speeds of 127-425 r/min for 2 h. The friction coefficient and wear rate were monitored by the wear apparatus, while the microstructures of the worn surfaces were observed by scanning electron microscope （SEM）. In addition, the chemical composition of worn surfaces was analyzed by energy dispersive X-ray spectroscopy （EDS）. Test results show different friction and wear performance of the MR fluid with and without magnetic field. At the same time, the effects of various normal loads and rotating speeds on the tribological behavior were investigated. Through the investigation of the morphologies of the wom surfaces under the magnetic field, it is found that the MR particles are clearly evident on the wom surface and the plastic flow of ridges causes the lateral extrusion. This directly indicates that abrasive wear is the predominant wear mechanism observed with MR fluid.

Design and implementation of square Helmholtz coil for uniform magnetic field generation

In order to calibrate electrical instruments and generate a constant magnetic field, a novel design method for square Helmholtz coil is proposed. According to the superposition principle in electromagnetics, the theory of the square Helmholtz coil is established, and the design method is verified by Matlab calculation. Compared with conventional circular Helmholtz coil, the novel square one is with a larger uniform region. Simulation work is conducted in Maxwell, and the distribution of the magnetic field is obtained. The results demonstrate the validation of the applied calculation method of the proposed Helmholtz model. The space utilization rate η is used to make a comparison between the square and circular coils for the uniform region. The square Helmholtz coil is fabricated, the length of a single square coil is 1.5 m, and the amplitude of the magnetic field is controlled by the current. The GSM-19 T proton magnetometer is used to measure the amplitude of the magnetic field generated by the square Helmholtz coil. Experimental results indicate that a wide-range variable uniform magnetic field from 0 to 120 μT is generated in the center of Helmholtz coils.

Configuration of propagator method for calculation of electron velocity distribution function in gas under crossed electric and magnetic fields

This paper presents a self-contained description on the configuration of propagator method(PM)to calculate the electron velocity distribution function(EVDF) of electron swarms in gases under DC electric and magnetic fields crossed at a right angle. Velocity space is divided into cells with respect to three polar coordinates v,θ and f. The number of electrons in each cell is stored in three-dimensional arrays. The changes of electron velocity due to acceleration by the electric and magnetic fields and scattering by gas molecules are treated as intercellular electron transfers on the basis of the Boltzmann equation and are represented using operators called the propagators or Green’s functions. The collision propagator, assuming isotropic scattering, is basically unchanged from conventional PMs performed under electric fields without magnetic fields. On the other hand, the acceleration propagator is customized for rotational acceleration under the action of the Lorentz force. The acceleration propagator specific to the present cell configuration is analytically derived. The mean electron energy and average electron velocity vector in a model gas and SF6 were derived from the EVDF as a demonstration of the PM under the Hall deflection and they were in a fine agreement with those obtained by Monte Carlo simulations. A strategy for fast relaxation is discussed, and extension of the PM for the EVDF under AC electric and DC/AC magnetic fields is outlined as well.

Electronic transport of Lorentz plasma with collision and magnetic field effects

The electronic transverse transport of Lorentz plasma with collision and magnetic field effects is studied by solving the Boltzmann equation for different electron density distributions. For the Maxwellian distribution, it is shown that transport coefficients decrease as ? increases, ? is the ratio of an electron’s magneto-cyclotron frequency to plasma collision frequency. It means that the electrons are possible to be highly collimated by a strong magnetic field. For the quasimonoenergetic distribution with different widths, it is found that the transport coefficients decrease greatly as εˉ decreases.In particular when the width approaches to zero the transverse transport coefficients are hardly affected by the magnetic field and the minimal one is obtained. Results imply that the strong magnetic field and quasi-monoenergetic distribution are both beneficial to reduce the electronic transverse transport. This study is also helpful to understand the relevant problems of plasma transport in the background of the inertial confinement fusion.

Effect of Rotation, Magnetic Field and Initial Stresses on Propagation of Plane Waves in Transversely Isotropic Dissipative Half Space

The problem regarding the reflection of plane waves in a transversely isotropic dissipative medium is considered, in which we are studying about the reflection of incidence waves in initially stressed dissipative half space. After solving the governing equations, we find the two complex quasi-P (qP) and quasi-SV (qSV) waves. The occurrence of reflected waves is studied to calculate the reflection coefficient and the energy partition of incidence wave at the plane boundary of the dissipative medium. Numerical example is considered for the reflection coefficient and the partition of incident energy, in which we study about the effect of rotation, initial stresses and magnetic field.

Minority Carrier Diffusion Coefficient <i>D</i>*(<i>B,T</i>): Study in Temperature on a Silicon Solar Cell under Magnetic Field

This work deals with minority carrier diffusion coefficient study in silicon solar cell, under both temperature and applied magnetic field. New expressions of diffusion coefficient are pointed out, which gives attention to thermal behavior of minority carrier that is better understood with Umklapp process. This study allowed to determine an optimum temperature which led to maximum diffusion coefficient value while magnetic field remained constant.

Diffusion Coefficient in Silicon Solar Cell with Applied Magnetic Field and under Frequency: Electric Equivalent Circuits

In this paper, a theory on the determination of the diffusion coefficient of excess minority carriers in the base of a silicon solar cell is presented. The diffusion coefficient expression has been established and is related to both frequency modulation and applied magnetic field;the study is then carried out using the impedance spectroscopy method and Bode diagrams. From the diffusion coefficient, we deduced the diffusion length and the minority carriers’ mobility. Electric parameters were derived from the diffusion coefficient equivalent circuits.

Relation between stabilization energy, crystal field coefficient and the magnetic exchange interaction for Tb^(3+) ion

Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coefficient B20 and the magnetic exchange interaction was studied as temperature approaches to 0 K. The results show that the stabilization energy contributed by Tb3+ is linear with crystal field coefficient B20 approximately, but it is insensitive to the change of magnetic exchange interaction for the strong magnetic substances such as TbCo5, Tb2Co17 and Tb2Fe14B compounds.

Magnetic Field Enhancement in Ammonia-Water Absorption Refrigeration Systems

Absorption enhancement has been considered as an effective way of improving coefficient of performance (COP) of refrigeration systems and magnetic enhancement is one of these methods. A model of magnetic field enhancement in ammonia-water absorption systems is presented in this paper. A numerical model using finite difference scheme was developed based on the conservation equations and mass transport relationship. Macroscopic magnetic field force was introduced in the momentum equation. The model was validated using data obtained from the literature. Changes in the physical properties of ammonia solution while absorbing both in the direction of falling film and across its thickness were investigated. The magnetic field was found to have some positive effect on the ammonia-water falling film absorption. The results indicate that absorption performance enhancement increased with magnetic intensity. The COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectively.

基于多场耦合提升逸散性颗粒与磁种碰撞系数动力学研究

以多场耦合提升逸散性颗粒与磁种碰撞系数为研究对象,基于计算流体力学-离散相模型(DPM),通过用户自定义函数(UDF)添加逸散性颗粒与磁种之间的库仑力和磁偶极子力,数值计算电场和磁场构成的多场中逸散性颗粒与磁种之间的碰撞系数,获得提升磁凝并程度的方法.结果表明,当流体速度u=0.5m/s,颗粒粒径0.5μm≤d_(p)<2.0μm,库仑力和磁偶极子力均可提高逸散性颗粒与磁种之间的碰撞系数,且库仑力可弥补弱磁性颗粒与磁种之间磁偶极子力较小的问题.若荷电场强E_(0)=0.5kV/cm,逸散性颗粒饱和磁化强度M_(j)=500A/m,磁种饱和磁化强度M_(i)=40000A/m,逸散性颗粒与磁种之间的碰撞系数比未荷电时提高了13.50%,若荷电场强E_(0)=1.0kV/cm,碰撞系数提高了23.60%.

Magnetic field stabilization system designed for the cold-atom coherent population-trapping clock

Accurate control of magnetic fields is crucial for cold-atom experiments,often necessitating custom-designed control systems due to limitations in commercially available power supplies.Here,we demonstrate precise and flexible control of a static magnetic field by employing a field-programmable gate array and a feedback loop.This setup enables us to maintain exceptionally stable current with a fractional stability of 1 ppm within 30 s.The error signal of the feedback loop exhibited a noise level of 10^(-5)A·Hz^(-1/2)for control bandwidths below 10 k Hz.Utilizing this precise magnetic field control system,we investigate the second-order Zeeman shift in the context of cold-atom coherent population-trapping (CPT)clocks.Our analysis reveals the second-order Zeeman coefficient to be 574.21 Hz/G^(2),with an uncertainty of 1.36 Hz/G^(2).Consequently,the magnetic field stabilization system we developed allows us to achieve a second-order Zeeman shift below10^(-14),surpassing the long-term stability of current cold-atom CPT clocks.

高比例磁精粉烧结试验研究

为提高本地自产矿粉的使用,优化原料资源配置,降低烧结原料成本,首钢股份进行了高比例磁精粉配加不同种类进口富矿的烧结杯实验,分别探索了高比例磁精粉条件下不同富矿粉种类、熔剂结构和料厚参数的变化,并对烧结矿各项经济技术指标进行了分析。结果表明:高比例磁精粉搭配褐铁矿时,烧结矿强度和粒度质量较好,但利用系数偏低;烧结矿品位偏低;搭配赤铁矿和半褐铁矿的烧结利用系数较高,成品率偏低,返矿产生量较大,强度和粒度指标也偏低,但烧结矿品位较高;配加少量灰石后,强度和平均粒径略有改善,但烧结机利用系数和烧结速度降低;低料厚实验在利用系数和转鼓强度指标方面有所下降,燃耗有所升高,但返矿量减少,平均粒径增加,成品率和转鼓强度有所提高。因此,首钢股份烧结厂采用60%自产矿粉进行高比例磁精粉烧结时,水分应控制在8%左右,熔剂结构采用白灰和少量灰石搭配使用能够获得较好的烧结矿强度和粒度,改善料层透气性,进口矿方面可采用褐铁矿(杨迪)搭配赤铁矿(巴卡)或半褐铁矿(PB、麦克)的方式来平衡利用系数和质量指标,料层厚度控制在800 mm。

Effects of Pulsed Magnetic Field on Microsegregation of Solute Elements in a Ni-Based Single Crystal Superalloy

The effects of a pulsed magnetic field （PMF） on the microsegregation of solute elements during directional solidification of a Ni-based single crystal superalloy were experimentally investigated, and the results show that the PMF significantly affects the microsegregation of Al, Ti, Co, Mo and W elements in the alloy. However, the distribution behavior differs for both positive and negative segregation elements. With the PMF, the microsegregation of negative segregation elements, Co and W, was restrained effectively, while that of positive segregation elements, A1, Ti and Mo, was aggravated. A segregation model was estab- lished to reveal the distribution mechanism of the elements with PME It is considered that, under the action of PME the jumping of solute atoms from the liquid phase to solid phase is hindered, but the jumping of solute atoms from the solid phase into liquid phase is promoted during solidification. As a result, the effective distribution coefficient of the solute atoms is reduced, which leads to the reduction of microsegregation of negative segregation elements and aggravation of microsegregation of positive segregation elements.

Revealing the influence of high magnetic field on the solute distribution during directional solidification of Al-Cu alloy

The effect of the high magnetic field(MF)on the distribution of solute concentration during directional solidification of Al-Cu alloy under low growth speed was experimentally investigated.The amount of nonequilibrium eutectic is quantified via X-ray computed tomography(XCT)and demonstrated to reduce with the application of MF.Further,experimental results reveal that the MF alleviates the microsegregation and increases the average Cu concentration in solid solution,leading to the increases of the effective partition coefficient ke.It was also found that Cu concentration in solid solution increases continuously with the increasing intensity of MF,following the strengthening of micro-hardness.The change of ke under the MF is demonstrated to attribute to the thermoelectric magnetic convection(TEMC)in the mushy zone and the thermoelectric magnetic force(TEMF)acting on the solid.The TEMC is supposed to cause secondary convection owing to the inequality in flow velocities of circulation in different positions of dendrite stem.And the vacancies created by the proliferation and movement of dislocations induced by TEMF in the matrix is supposed to be able to capture solute atoms and thus enhance the solute concentration in the solid solution.

Thomson and rotation effects during photothermal excitation process in magnetic semiconductor medium using variable thermal conductivity

This study investigates a strong magnetic field acting over an elastic rotator semiconductor medium.The Thomson effect due to the magnetic field during the photothermal transport process is studied,and the thermoelectricity theory is used to explain the behavior of waves in the homogenous and isotropic medium under the effect of variable thermal conductivity.The variable thermal conductivity is considered as a linear function of the temperature.The two-dimensional deformation equations are used to describe the overlaps among plasma,electrical,thermal,and magneto-elastic waves.The charge density of inertia-particles is considered as a function of time for studying the induced electric current.The normal mode analysis is used to obtain the exact solutions of the physical field distributions as part of this phenomenon.To obtain the complete solutions of the physical field quantities,the certain mechanical loads,electromagnetic effects,thermal effects,and plasma recombination process are applied herein.The results of the physical distributions are graphically depicted and discussed in consideration of the internal heat source,rotation,and Peltier coefficient.

Diffusion Coefficient at Double Resonances in Frequency and Temperature, Applied to (n+/p/p+) Silicon Solar Cell Base Thickness Optimization under Long Wavelength Illumination

The diffusion coefficient of the minority charge carriers in the base of a silicon solar cell under temperature and subjected to a magnetic field, passes in reso-nance at temperature (Topt). For this same magnetic field, the diffusion coeffi-cient of the photogenerated carriers by a monochromatic light in frequency modulation enters into resonance, at the frequency (ωc). Under this double resonance in temperature and frequency, the diffusion coefficient is used in the expression of the recombination velocity of the minority charge carriers on the back side of the base of the solar cell (n+/p/p+), to obtain, by a graphical method, the optimum thickness. A modeling of the results obtained shows a material saving (Si), in the development of the solar cell.

磁场下黏弹性基中输流纳米管的颤振失稳分析

基于非局部欧拉-伯努利梁模型,研究了外部轴向磁场作用下黏弹性基体中悬臂输流单层碳纳米管系统的动态失稳特性。黏弹性基体采用线性Kelvin-Voigt弹性基模型,利用哈密顿原理,建立该系统的振动微分方程及其边界条件。应用微分变换法求解该振动方程,着重研究不同质量比下,黏弹性基体、轴向磁场与小尺度效应共同影响时,该系统的颤振失稳特性。数值计算结果表明:黏弹性基体的弹性参数与外加轴向磁场的增加均能提高悬臂输流碳纳米管系统的稳定性,而小尺度系数的增加则降低系统稳定性。不同质量比下,黏弹性基体的阻尼系数对系统动态稳定性的影响不同。进一步研究表明,随着轴向磁场与基体弹性参数的共同增加,系统稳定性的提升并未呈现“协力效应”,而是各自的提升效果均有所减弱。