共查询到20条相似文献,搜索用时 15 毫秒
1.
Amaresh Chandra Mishra 《Physica B: Condensed Matter》2012,407(6):923-934
Magnetic thin films of NiFe and CoNiFe alloys were electrodeposited from three different deposition baths onto copper wires of 100-μm diameter. The magnetic and magnetoimpedance (MI) properties of the samples along with their microstructure were investigated as a function of thiourea additive concentrations (CT) in the plating bath. For all intermediate frequencies, the MI ratio increased with thiourea concentration in plating bath up to a critical concentration of 80 mg/l and then decreased considerably. The change in MI with thiourea concentration in electrodeposition bath was attributed to the grain size reducing action of thiourea, which in turn enhances the soft magnetic properties of the films. At higher concentration of thiourea, the sulfur inclusion increased the magnetic softness and MI value enhanced considerably. The origin of MI lies in the combined effect of domain wall motion and spin rotation, which contributes to permeability. Inductance spectroscopy (IS) was used to evaluate the magnetic characteristic of the samples by modeling coated wires in terms of equivalent electrical circuit; namely parallel LR (inductance and resistance) circuit in series with series LR circuit. The domain wall motion was found to be greatly affected by thiourea addition in the bath, which was revealed through the study of variation of these circuit parameters. The domain wall motion thereby affects the magnetic softness of samples, which is reflected in the MI enhancement. 相似文献
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Lumped modeling with circuit elements for nonreciprocal magnetoelectric tunable band-pass filter 下载免费PDF全文
This paper presents a lumped equivalent circuit model of the nonreciprocal magnetoelectric tunable microwave bandpass filter.The reciprocal coupled-line circuit is based on the converse magnetoelectric effect of magnetoelectric composites,includes the electrical tunable equivalent factor of the piezoelectric layer,and is established by the introduced lumped elements,such as radiation capacitance,radiation inductance,and coupling inductance,according to the transmission characteristics of the electromagnetic wave and magnetostatic wave in an inverted-L-shaped microstrip line and ferrite slab.The nonreciprocal transmission property of the filter is described by the introduced T-shaped circuit containing controlled sources.Finally,the lumped equivalent circuit of a nonreciprocal magnetoelectric tunable microwave band-pass filter is given and the lumped parameters are also expressed.When the deviation angles of the ferrite slab are respectively 0° and45°,the corresponding magnetoelectric devices are respectively a reciprocal device and a nonreciprocal device.The curves of S parameter obtained by the lumped equivalent circuit model and electromagnetic simulation are in good agreement with the experimental results.When the deviation angle is between 0° and 45°,the maximum value of the S parameter predicted by the lumped equivalent circuit model is in good agreement with the experimental result.The comparison results of the paper show that the lumped equivalent circuit model is valid.Further,the effect of some key material parameters on the performance of devices is predicted by the lumped equivalent circuit model.The research can provide the theoretical basis for the design and application of nonreciprocal magnetoelectric tunable devices. 相似文献
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Extrinsic equivalent circuit modeling of InP HEMTs based on full-wave electromagnetic simulation 下载免费PDF全文
Shi-Yu Feng 《中国物理 B》2022,31(4):47303-047303
With the widespread utilization of indium-phosphide-based high-electron-mobility transistors (InP HEMTs) in the millimeter-wave (mmW) band, the distributed and high-frequency parasitic coupling behavior of the device is particularly prominent. We present an InP HEMT extrinsic parasitic equivalent circuit, in which the conductance between the device electrodes and a new gate-drain mutual inductance term Lmgd are taken into account for the high-frequency magnetic field coupling between device electrodes. Based on the suggested parasitic equivalent circuit, through HFSS and advanced design system (ADS) co-simulation, the equivalent circuit parameters are directly extracted in the multi-step system. The HFSS simulation prediction, measurement data, and modeled frequency response are compared with each other to verify the feasibility of the extraction method and the accuracy of the equivalent circuit. The proposed model demonstrates the distributed and radio-frequency behavior of the device and solves the problem that the equivalent circuit parameters of the conventional InP HEMTs device are limited by the device model and inaccurate at high frequencies when being extracted. 相似文献
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现有的“E”型平衡电枢等效磁路模型仿真研究通常不考虑金属外壳磁阻带来的影响。为了解决平衡电枢换能器中因金属外壳和平衡电枢紧密接触带来的非线性磁阻问题,在现有的平衡电枢换能器等效磁路模型上加入了外壳磁阻影响。分析等效磁路模型磁通部分和力学部分的状态空间方程在不同参数条件下的仿真结果,总结不同参数对该模型阻抗和振膜位移的影响情况。通过仿真对比,外壳磁阻对平衡电枢换能器位移频率响应曲线的影响为1~3 dB。对于组装后包含金属外壳的平衡电枢耳机、助听器产品降低频率响应曲线偏差具有一定的指导意义。 相似文献
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V. V. Vasil'ev I. I. Vintizenko A. S. Sulakshin N. M. Filipenko G. P. Fomenko 《Russian Physics Journal》2003,46(10):968-978
The physical processes in a system relativistic microwave generator - power supply unit with a strong feedback are investigated. A computer model is constructed to calculate the output parameters of these systems substituted by equivalent circuits. A model is constructed for a linear induction accelerator based on magnetic elements intended for operation with relativistic magnetrons the nonlinear units of the equivalent circuit of which are calculated in the context of the theory of average motion. 相似文献
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针对深水、低频、宽带换能器的技术需求,结合Janus-Helmholtz换能器的结构特点和铁镓单晶材料低场应变大及机械强度高的特性,提出了铁镓单晶Janus-Helmholtz换能器设计方案。采用永磁偏磁场和环形闭合磁路,建立了一系列铁镓单晶磁致伸缩换能器理论分析模型,包括对磁致伸缩材料参数进行线性化处理,设计了换能器最佳工作点,结合静态磁场和动态磁场分布情况分段细化换能器驱动等效参数,以及利用全阻抗模型通过电感损耗等效计算换能器静态阻抗,然后通过二维有限元分析等效模型,优化分析了换能器的结构参数与电声性能。最后制作了换能器样机,并进行了测试与分析。对比仿真和测试结果表明:全阻抗模型得到的阻抗曲线与样机测试结果相一致,有限元等效模型计算的发送电流响应与样机测试结果良好吻合。换能器样机水中谐振基频为1000 Hz,谐振频率下发送电流响应176.4 dB;在875~2300 Hz频率范围内,发送电流响应起伏不大于6 dB;增加驱动电流有效值到16.2 A,最大声源级可以达到196.2 dB。 相似文献
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针对长片型磁电层状复合材料,提出了一种适用于准静态和动态磁场激励的引入界面耦合系数的等效电路模型,旨在为基于长片型磁电层状复合材料的传感器、换能器等器件的设计、制作和应用提供理论指导.考虑到磁电层状复合材料实际工作过程中磁致伸缩层和压电层的应变并不相同,首先利用运动方程分别对磁致伸缩层和压电层进行建模,提出了一个从物理上反映相间应变传递的界面耦合系数表达式,然后利用一个变比恰为界面耦合系数的理想变压器将两层材料的等效电路耦合,构成改进的磁电层状复合材料的等效电路模型,得到包含界面耦合系数的磁电电压系数和最佳层合比的表达式.对12个具有不同尺寸和负载条件的样品进行实验,制作过程中承受500g砝码负载的样品的界面耦合系数为0.15,最佳层合比为0.57;承受100g砝码负载的样品的界面耦合系数为0.10,最佳层合比为0.50.磁电电压系数和最佳层合比的实验值与各自包含界面耦合系数的理论值基本符合,证明了改进的等效电路模型的合理性和正确性. 相似文献
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Two Mechanisms for Extracting Energy and Angular Momentum from a Rotating Black Hole 总被引:1,自引:0,他引:1
Two mechanisms of extracting energy and angular momentum from a rotating black hole, the Blandford-Znajek (BZ) process and magnetic coupling (MC) of a rotating black hole (BH) with the surrounding accretion disk, are discussed in detail by using a modified equivalent circuit. We obtain the same value for the BZ power as given by Lee. The strength of the power and torque produced by the rotating BH in the BZ process are compared with those in MC process. In addition, entropy production on the BH horizon due to the BZ process and that due to MC process are compared and discussed also by using the modified equivalent circuit. 相似文献
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设计了外Q值较小,工作于高阶横磁TM310模的X波段速调管单间隙同轴输出谐振腔。用微波等效电路理论计算了高阶横磁TM310模情形六个漂移管的等效间隙中心位置,由此计算腔内等效间隙中心到输出波导内横向膜片的等效长度。以MATLAB编程计算得到同轴谐振腔TM310模式加载矩形波导滤波器输出回路的间隙阻抗,其结果与传统冷测模拟法计算结果吻合。验证了等效长度计算方法的正确性,用于圆柱腔基模的传统微波等效电路理论能用于分析同轴谐振腔高阶横磁模式输出回路,且比传统的冷测模拟法及场分析法更为快捷。 相似文献
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Equivalent magnetic dipole method used to design gradient coil for unilateral magnetic resonance imaging 下载免费PDF全文
The conventional magnetic resonance imaging(MRI) equipment cannot measure large volume samples nondestructively in the engineering site for its heavy weight and closed structure. In order to realize the mobile MRI, this study focuses on the design of gradient coil of unilateral magnet. The unilateral MRI system is used to image the local area above the magnet. The current density distribution of the gradient coil cannot be used as a series of superconducting nuclear magnetic resonance gradient coils, because the region of interest(ROI) and the wiring area of the unilateral magnet are both cylindrical side arc surfaces. Therefore, the equivalent magnetic dipole method is used to design the gradient coil, and the algorithm is improved for the special case of the wiring area and the ROI, so the X and Y gradient coils are designed.Finally, a flexible printed circuit board(PCB) is used to fabricate the gradient coil, and the magnetic field distribution of the ROI is measured by a Gauss meter, and the measured results match with the simulation results. The gradient linearities of x and y coils are 2.82% and 3.56%, respectively, less than 5% of the commercial gradient coil requirement. 相似文献
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Transfer functions determined from the component values of an equivalent circuit are used to calculate the relative signal-to-noise ratio of rf coils for magnetic resonance imaging. Experimental verification of the method is obtained by directly measuring signals from three solenoidal coils and by measuring the signal-to-noise ratio of these solenoids. The transfer functions separate the total noise voltage into contributions from the coil resistance and contributions from magnetic and electric field interactions with the sample. The use of this technique in understanding and improving coil design is discussed. 相似文献
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In this paper, a planar Schottky varistor diode is studied and modeled by equivalent circuit method and three dimensional full wave electromagnetic (3D-EM) method, respectively. The diode's equivalent circuit is extracted from millimeter-wave small-signal S-parameter measurements. Since the package of the diode influences the electromagnetic field distribution at millimeter and sub-millimeter wavelengths, a 3D-EM model and an improved equivalent circuit model is applied to describe the field precisely. The simulated results of equivalent circuit, improved equivalent circuit and 3D-EM model are compared with the measured results. In addition, the effects caused by silver paste conductive adhesive are considered in 3D-EM model and improved equivalent circuit model. The results show that both the 3D-EM model and improved equivalent circuit model have good S-parameter consistency with measured results. 相似文献
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从层流模型出发,根据线电压和线电流,给出了磁绝缘稳态时传输线极间的电磁场分布的解析表达式。在此基础上,计算了考虑空间电子效应后处于磁绝缘稳态的传输线等效分布电感和电容,以改进磁绝缘稳态的电路单元模型。利用该方法,模拟计算了Z加速器的MITL-A在磁绝缘稳态时的等效分布电感和电容。结果表明,等效分布电容随空间电子效应的增强而变大,而等效分布电感随空间电子效应的增强而变小;且线电压越低,等效分布电感和电容随空间电子效应的增强变化越快。 相似文献
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《Photonics and Nanostructures》2014,12(2):114-121
Magnetic response of a planar dielectric ring to an axially applied time-harmonic magnetic field is analyzed. We find the self-consistent distribution of the polarization current in the ring and its magnetic moment. It is shown that the magnetic moment exhibits multiple resonances corresponding to the excitation of different eigenmodes in the ring. The properties of the fundamental eigenmode are used to analyze the performance and limitations of an equivalent LCR circuit model. 相似文献
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Equivalent circuit with complex physical constants and equivalent-parameters-expressed dissipation factors of piezoelectric materials 下载免费PDF全文
The equivalent circuit with complex physical constants for a piezoelectric
ceramic in thickness mode is established. In the equivalent circuit,
electric components (equivalent circuit parameters) are connected to real
and imaginary parts of complex physical coefficients of piezoelectric
materials. Based on definitions of dissipation factors, three of them
(dielectric, elastic and piezoelectric dissipation factors) are represented
by equivalent circuit parameters. Since the equivalent circuit parameters
are detectable, the dissipation factors can be easily obtained. In the
experiments, the temperature and the stress responses of the three
dissipation factors are measured. 相似文献