Exploration of magnetic field generation of H_(3)^(2+)by direct ionization and coherent resonant excitation

Coherent electronic dynamics are of great significance in photo-induced processes and molecular magnetism.We theoretically investigate electronic dynamics of triatomic molecule H_(3)^(2+) by circularly polarized pulses,including electron density distributions,induced electronic currents,and ultrafast magnetic field generation.By comparing the results of the coherent resonant excitation and direct ionization,we found that for the coherent resonant excitation,the electron is localized and the coherent electron wave packet moves periodically between three protons,which can be attributed to the coherent superposition of the ground A′state and excited E+state.Whereas,for the direct single-photon ionization,the induced electronic currents mainly come from the free electron in the continuum state.It is found that there are differences in the intensity,phase,and frequency of the induced current and the generated magnetic field.The scheme allows one to control the induced electronic current and the ultrafast magnetic field generation.

Phase diagram and collective modes in Rashba spin–orbit coupled BEC: Effect of in-plane magnetic field

We studied the system of pure Rashba spin–orbit coupled Bose gas with an in-plane magnetic field. Based on the mean field theory, we obtained the zero temperature phase diagram of the system which exhibits three phases, plane wave（PW） phase, striped wave（SW） phase, and zero momentum（ZM） phase. It was shown that with a growing in-plane field,both SW and ZM phases will eventually turn into the PW phase. Furthermore, we adopted the Bogoliubov theory to study the excitation spectrum as well as the sound speed.

Effective Lifetime Experimental Measurement under External Magnetic Field in Transient Dynamic State by Open Circuit Voltage Decay Method

In this work, we present an experimental transient 3-Dimensionnal study for the minority charge carriers’ effective lifetime measurement under magnetic field in transient dynamic state. The magnitude of the magnetic field B is varied from 0 mT to 0.03 mT. The method used is mainly based on the open circuit voltage decay method. The solar cell is injected by a low electrical excitation which protects against capacitance effects. Our approach is based on the open circuit voltage decay response analysis. From an experimental set-up, we get the transient voltage data on a digital scope. The data are used for plotting transient voltage decay curves. The curves obtained and analyzed are fitted in their linear zone. This zone presents an ideal decay which permits to get good values of lifetime. The slope of the linear decay is inversely proportional to effective lifetime. The results of fitting permit determinate the effective charge carriers’ lifetime directly. The results obtained are then presented and analyzed. The observations indicate that the charge carriers effective lifetime decrease when the magnetic field increases.

Isotope effects of plasma chemical carbon oxidation in a magnetic field

The influence of different factors on the plasma chemical reactions is widely studied today. However, insufficient consideration is given to the research of paramagnetic phenomena which takes place in plasma systems. The results of modeling the process of redistribution carbon isotopes between different phases while oxidizing it in high-frequency low-temperature plasma in an external magnetic field are shown in the article. The equilibrium concentrations of components involved in the oxidation process in a plasma system are defined. A principle possibility of isotope-selective plasma chemical reactions in a magnetic field was experimentally determined. The increase of concentration of 13C in the gas phase up to 1.3 times relative to natural abundance was obtained. It was found that the content of the carbon heavy isotope in the gas phase depends on the magnetic field action area. The best results were achieved with the combination of magnetic field impact area and the priority area of the appearance of plasma chemical reactions products.

Mossbauer study of martensitic transformation andcollective magnetic excitations in Fe_9Ni．1 fine particles

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Electrokinetic energy conversion of electro-magneto-hydro-dynamic nanofluids through a microannulus under the time-periodic excitation

In this work,the effects of externally applied axial pressure gradients and transverse magnetic fields on the electrokinetic energy conversion(EKEC)efficiency and the streaming potential of nanofluids through a microannulus are studied.The analytical solution for electro-magneto-hydro-dynamic(EMHD)flow is obtained under the condition of the Debye-Huuckel linearization.Especially,Green’s function method is used to obtain the analytical solutions of the velocity field.The result shows that the velocity distribution is characterized by the dimensionless frequency?,the Hartmann number Ha,the volume fraction of the nanoparticlesφ,the geometric radius ratio a,and the wallζpotential ratio b.Moreover,the effects of three kinds of periodic excitations are compared and discussed.The results also show that the periodic excitation of the square waveform is more effective in increasing the streaming potential and the EKEC efficiency.It is worth noting that adjusting the wallζpotential ratio and the geometric radius ratio can affect the streaming potential and the EKEC efficiency.

多变运行工况下混合励磁轴向磁场永磁电机自适应模型预测电流控制

针对多变运行工况下混合励磁轴向磁场永磁(hybrid excited axial field permanent magnet,HE-AFPM)电机中电励磁磁场与电枢磁场之间矢量耦合、端部漏磁等导致的电机参数非线性变化问题,该文提出一种混合励磁轴向磁场永磁电机自适应模型预测电流控制方法。详细分析HE-AFPM电机拓扑结构及参数变化特性;引入多矢量模型预测电流控制,理论推导分析HE-AFPM电机参数对控制系统的敏感性。在此基础上,将多矢量预测模型作为自适应控制的可调模型,降低了控制算法的复杂度和控制系统的计算负荷,提高了控制系统响应速度;依据波波夫(Popov)超稳定理论,引入3个不等式稳定判据设计各参数的自适应律,可实现多变运行工况下的HE-AFPM电机磁链、自感、互感等参数的有效识别,提高了控制模型的准确性和电流跟踪性能。最后,通过实验验证所提出的自适应模型预测电流控制的有效性。

机械设备用感应电机电磁力动态特性计算与研究

机械设备用感应电机的动态性能是不可忽略的设计要求。为抑制电机动态电磁振动和噪声水平,展开了对电机电磁力动态特性分析及相应削弱措施的研究。首先利用经典气隙谐波磁场理论,确定磁场中的谐波磁势和谐波磁导来源,由此再通过张量法计算电机径向电磁力,并对比主要谐波分量的幅值、极对数和频率特征。然后采用有限元仿真和傅里叶分解法,确定电磁力时空行波的基本特征,推断主要力波的谐波磁场产生来源。结果表明谐波径向力绝对幅值的变化很难影响其占基波的相对比值。最后建立磁性槽楔理想模型对比仿真,谐波电磁力的削弱程度与槽楔磁导率正相关,样机振动测试试验间接验证了磁性槽楔的优越性,为电机动态特性研究及优化设计提供理论依据。

真空干泵用永磁-磁阻复合式同步电机设计与分析

针对真空干泵用驱动电机在真空环境中转子散热难的问题,设计了一种混合励磁永磁-磁阻复合式同步电机。该电机转子永磁体励磁结构由钕铁硼与铁氧体两种磁体组成,旨在改变永磁体的排布方式,降低电机的损耗。首先,构建电机转子的拓扑结构,并设计两种方案来研究永磁体的排列方式对电机性能的影响;其次,分析转子参数对电机空载反电动势和电磁转矩的影响,并对电机转子的尺寸进行调整;然后,对比两种方案的损耗大小,选择损耗更低的电机方案;最后,通过有限元计算对目标电机进行了温度场分析,结果表明,所设计方案的电机温度分布合理,因此通过改变永磁体的排布方式能有效提升电机效率,降低电机损耗,确保电机稳定运行。

基于Magnet的无刷交流励磁机瞬态特性仿真研究

对于航空交流电源中交流励磁机的旋转电枢式结构,有限元电磁分析的研究较少。文章以此为研究对象,阐述应用M agnet软件建立二维瞬态运动场仿真模型的原理和步骤,并仿真了交流励磁机在空载工况下的磁场空间分布、电磁参数、电路参数,通过实测对比,证明了模型的实用性,该模型可指导该类型电机的结构优化设计和其它工况瞬态特性研究。

电磁式线-角振动激振器气隙磁场特性分析

针对传统单轴激振器无法复现线-角空间耦合运动的问题,提出了一种可实现复合振动的电磁式线-角振动激振器磁路结构,并对其气隙磁场特性进行分析。首先构建了激振器的磁路和线圈结构,基于等效电流法,建立了气隙磁场的解析模型,与有限元分析结果的最大相对误差为1.25%,验证了解析模型的正确性;接着研究了各磁路参数对气隙磁场分布特性的影响规律,以及线圈电流产生的磁场与原磁场的耦合效应,并分析了线圈在运动过程中的受力情况;最后研制了激振器磁路拓扑结构样机,分别对线、角振动气隙磁场进行了实验测量,测得结果与有限元计算结果的最大相对误差小于5%,进一步验证了所提出磁路结构的有效性。

感应子电机二维磁场计算模型的对比研究

感应子电机因其转子结构简单,具有非常高的可靠性,特别适用于高速场合,在脉冲电源、储能系统、航空发电、船舶推进系统等领域有着广泛的应用。感应子电机的磁场为三维磁场,但三维磁场分析所需计算资源和时间太多。因此,对感应子电机的磁场分析一般采用简化二维模型。目前,感应子电机二维磁场计算模型主要有:标量磁位法、矢量磁位法、等效励磁绕组法和改进等效励磁绕组法四种模型。标量磁位法、矢量磁位法、等效励磁绕组法和改进等效励磁绕组法各有优缺点,本文对以上四种二维磁场计算模型进行了对比研究,分析了各自的优缺点,对其适用性进行了讨论。

轨道车辆铝合金长大薄壁脉冲复合磁控高效弧焊工艺研究

利用外加磁场改善电弧焊焊接工艺,具有成本低、附加耗能少、易操作等优点,已成为当今研究的热点之一。针对高速MIG焊时焊缝成形不良及焊接接头质量差等问题,在焊枪上装配一紧凑型脉冲复合磁场发生器,同时调控电弧和熔滴的左右摆动及前倾行为;并开展不同焊接参数下的铝合金车体长大薄壁型材对接接头焊接工艺试验,以研究高速焊条件下的最佳焊接工艺。研究发现,对于铝合金车体焊缝,励磁参数为8A、120 Hz,焊接参数为265A、23.5 V、1.2 m/min时,焊缝成形质量最佳。利用金相显微镜以及背向散射电子衍射(EBSD)技术表征了不同焊接参数下焊接接头的微观组织,分析了外加脉冲复合磁场对焊接接头组织的影响。结果表明,在高速焊接条件下(>1.0 m/min),焊接接头的晶粒相较于常规焊速时明显粗化,且熔合区宽度有所增加。然而,引入脉冲复合磁场后,晶粒尺寸和熔合区宽度均降低至与常规焊速相当的水平。开展不同焊接参数下的焊接接头力学性能测试,结果表明,外加脉冲复合磁场对焊接接头的机械性能具有显著的改善作用,焊缝区的平均硬度提高了21.37%,而接头的平均抗拉强度达到187 MPa,与传统焊接速度时的193 MPa相当接近。在保证焊缝成形质量和接头机械性能的前提下,最终将焊接速度从0.75 m/min提高到1.2 m/min,实现了优质高效的焊接过程。

二极三相感应电机转子轴向通风孔对功率因数的影响研究

文章对某400 kW三相异步感应电机的设计开发经验进行了总结,针对初始电磁方案试验结果不符合设计要求的情况,经理论分析和电磁仿真分析,得出初始方案不合格的原因是轴向通风孔的尺寸太小。通过增大轴向通风孔的尺寸,有效改善了电机的功率因数,最终形成了满足要求的电磁方案。

非晶合金平面卷铁心模型仿真分析及验证

针对目前非晶合金卷铁心配电变压器设计存在的问题,利用有限元软件对非晶合金平面卷铁心进行建模及仿真分析,以掌握不同磁密状态下铁心磁场分布特征及规律,并通过实验验证该仿真模型的可行性、有效性,探索非晶配电变压器精细化设计的可实现途径。

基于嵌入式神经网络的电梯钢丝绳弱磁检测系统

为实时监测和排查电梯钢丝绳运行中存在的安全问题,提出了剩余磁场激励的弱磁检测方法。该方法采用开环永磁体磁化方式将被测钢丝绳充分磁激励,励磁后的钢丝绳缺陷部位会产生微弱漏磁场,采用霍尔传感器可将被测钢丝绳周围空间中磁感应强度的变化情况转化为电信号。检测系统采用多传感器融合的RBF-BP组合神经网络算法结合RT-Thread实时操作系统在单片机上运行。结果显示,钢丝绳各类损伤判断准确率达到了80%以上,检测效果良好,为电梯的安全运行提供了一条解决路径。

一种感应式角度传感器的激励信号产生方法

针对基于印制板谐振感应式角位移传感器感应信号弱,现有感应式角度传感器单端、低压高频方波激励信号强度低,抗干扰能力差的问题,提出一种感应式角度传感器的激励信号产生方法。通过反向电路、自举升压电路和驱动电路等硬件电路设计和优化,将单端、低压的高频方波激磁信号转换为高频、高压的差分正弦激磁信号,有效解决感应式角度传感器谐振信号强度低、高次谐波占比大的问题。此方法不仅可以提高感应式角度传感器磁场的强度,减小高次谐波占比,提升模拟信号的抗干扰能力,还可以提升感应式角度传感器的输出精度。

Design of Braunbeck Coil for Nuclear Magnetic Resonance Gyro Magnetic Field Excitation

For generating a uniform and steady magnetic field, Helmholtz coil is extensively used in nuclear magnetic resonance gyro(NMRG). Unfortunately, the volume of Helmholtz coil makes it inconvenient to miniaturize NMRG. This study introduces Braunbeck coil that can be used in magnetic field excitation system. Braunbeck coil can produce homogeneous magnetic field within a limit space, and occupy a small volume. In addition, this study presents mathematical expressions that can be used to calculate the area of uniform magnetic field. Experimental test verifies the effectiveness of the proposed design, and the results accord closely with the actual simulation.

Development of High Torque and High Power Density Hybrid Excitation Flux Switching Motor for Traction Drive in Hybrid Electric Vehicles

This paper presents design feasibility study and development of a new hybrid excitation flux switching motor (HEFSM) as a contender for traction drives in hybrid electric vehicles (HEVs). Initially, the motor general construction, the basic working principle and the design concept of the proposed HEFSM are outlined. Then, the initial drive performances of the proposed HEFSM are evaluated based on 2D-FEA, in which the design restrictions, specifications and target performances are similar with conventional interior permanent magnet synchronous motor (IPMSM) used in HEV. Since the initial results fail to achieve the target performances, deterministic design optimization approach is used to treat several design parameters. After several cycles of optimization, the proposed motor makes it possible to obtain the target torque and power of 333 Nm and 123 kW, respectively. In addition, due to definite advantage of robust rotor structure of HEFSM, rotor mechanical stress prediction at maximum speed of 12,400 r/min is much lower than the mechanical stress in conventional IPMSM. Finally, the maximum torque and power density of the final design HEFSM are approximately 11.41 Nm/kg and 5.55 kW/kg, respectively, which is 19.98% and 58.12% more than the torque and power density in existing IPMSM for Lexus RX400h.

Movement of Self-Organizing Solitons in Ferromagnet

Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition induced by a magnetic field directed along the axis of anisotropy, while the additional action of high-frequency field perpendicular to the main magnetic field, are analyzed. It is shown that the spatial motion of solitons, associated with thermal fluctuations in the crystal, does not destroy the equilibrium of self-organized PBS.