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111.
Microwave propagation parameters in magnetic fluids 总被引:1,自引:0,他引:1
P. C. Fannin I. Malaescu C. N. Marin N. Stefu 《The European physical journal. E, Soft matter》2009,29(3):299-303
Complex dielectric permittivity and complex magnetic permeability measurements of two magnetic fluids (as microwave propagation
media), in the approximate range 0.2-5GHz were performed. The two samples consisted of magnetite nanoparticles, dispersed
in kerosene and in water, respectively. Based on the dielectric and magnetic measurements, the frequency (f ) dependence of the attenuation parameter, , the phase constant, , the propagation constant, , the intrinsic impedance, Zm, the refractive index, n , the reflection coefficient, R , the wavelength, and the skin depth, , of the investigated samples were determined. 相似文献
112.
C. P. Yin T.-B. Wang J.-W. Dong Y. H. Chen H. Z. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(3):357-361
By means of transfer matrix method, we investigate the transmittance and
reflectance of Thue-Morse (T-M) structure composed of negative-permittivity
and negative-permeability materials. It is shown that the width and location
of an omnidirectional reflectance band remain invariant with the change of
generation order, and that the omnidirectional reflectance band is
determined by both TE and TM polarization, which different completely from
that in dielectric T-M structure. Moreover, a flat-top total transmission
band occurs around the same frequency in which the general zero average
permittivity and permeability are both satisfied in T-M structure. The basis
for these phenomena are presented and discussed. 相似文献
113.
Y.X. Gong L. Zhen J.T. Jiang C.Y. Xu W.Z. Shao 《Journal of magnetism and magnetic materials》2009,321(22):3702-3705
CoFe alloy nanoparticles with different particle sizes were successfully prepared by hydrogen-thermal reduction of CoFe2O4 microspheres at different temperatures. It was found that the real part of the permeability of the CoFe alloy nanoparticles increased with the decrease of the particle size, and accordingly the reflection loss (RL) peak moved towards the low-frequency region. The maximum RL of the coating based on CoFe alloy nanoparticles exceeded −23 dB, and a wide effective absorption band width (RL≤−10 dB) of about 6 GHz was simultaneously achieved. The EMA performance was confirmed to be tunable by the control of the absorber's particle size, and thus a new clue for the design of the EMA applications was supplied. 相似文献
114.
An analysis is done of a relativistic paradox posed in the Feynman Lectures of Physics involving two interacting charges.
The physical system presented is compared with similar systems that also lead to relativistic paradoxes. The momentum conservation
problem for these systems is presented. The relation between the presented analysis and the ongoing debates on momentum conservation
in the Aharonov-Bohm problem is discussed. 相似文献
115.
David N. Smithe John R. Cary Johan A. Carlsson 《Journal of computational physics》2009,228(19):7289-7299
The recent advances in alternating direct implicit (ADI) methods promise important new capability for time domain plasma simulations, namely the elimination of numerical stability limits on the time step. But the utility of these methods in simulations with charge and current sources, such as in electromagnetic particle-in-cell (EMPIC) computations, has been uncertain, as the methods introduced so far do not have the property of divergence preservation. This property is related to charge conservation and self-consistency, and is critical for accurate and robust EMPIC simulation. This paper contains a complete study of these ADI methods in the presence of charge and current sources. It is shown that there are four significantly distinct cases, with four more related by duality. Of those, only one preserves divergence and, thus, is guaranteed to be stable in the presence of moving charged particles. Computational verification of this property is accomplished by implementation in existing 3D-EMPIC simulation software. Of the other three cases, two are verified unstable, as expected, and one remains stable, despite the lack of divergence preservation. This other stable algorithm is shown to be related to the divergence preserving case by a similarity transformation, effectively providing the complement of the divergence preserving field in the finite-difference energy quantity. 相似文献
116.
117.
We consider two player electromagnetic evasion-pursuit games where each player must incorporate
significant uncertainty into their design strategies to disguise
their intension and confuse their opponent. In this paper, the
evader is allowed to make dynamic changes to his strategies in
response to the dynamic input with uncertainty from the
interrogator. The problem is formulated in two different ways. One
is based on the evolution of the probability density function of
the intensity of reflected signal and leads to a controlled forward Kolmogorov or Fokker-Planck equation. The other formulation is based on the
evolution of expected value of the intensity of reflected signal and leads to controlled backward Kolmogorov equations.
In addition, a number of numerical results are presented to
illustrate the usefulness of the proposed approach in exploring
problems of control in a general dynamic game setting. 相似文献
118.
为了分析EAST装置电磁测量系统中70m双绞线给测量信号带来的影响,建立了电磁线圈和双绞线的等效电路模型。设计了有双绞线模型和没有双绞线模型的两种电路模型,并对这两种模型在simolorer6.0软件中进行了仿真,通过分析这两种模型的传递函数和仿真输出的电压峰峰值,证明了70m双绞线对EAST中电磁测量系统的影响是可以忽略的。 相似文献
119.
We set up a correspondence between solutions of the Yang–Mills equations on and in Minkowski spacetime via de Sitter space. Some known Abelian and non-Abelian exact solutions are rederived. For the Maxwell case we present a straightforward algorithm to generate an infinite number of explicit solutions, with fields and potentials in Minkowski coordinates given by rational functions of increasing complexity. We illustrate our method with a nontrivial example. 相似文献
120.
YU Bingwen JIN Wei ZHU Dan YING Yangwei YU Haixiang SHAN Jin XU Chen LIU Wenlong JIN Qinhan 《高等学校化学研究》2016,32(4):549-555
In order to obtain a stable plasma and improve the performance of the torch for atomic emission spectroscopy(AES), the structure of microwave plasma torch(MPT) was analyzed. The transmission and distribution characteristics of the electromagnetic field of the torch configuration with two or three concentric tubes, as well as the metal spacer between inner and intermediate tubes with different depths were simulated with electromagnetic simulation software and verified by experiments. The results indicate that the inner tube of MPT plays an important role in strengthening the electric field intensity at the opening end of the MPT and redistributing the electromagnetic field in the whole torch by forming a double resonance configuration, and contributes to enhancing the macroscopic stability and the self-sustainment of the plasma. The stability of the plasma is proved to be excellent when the metal spacer between the inner and intermediate tubes is located at a place 20—30 mm away from the top opening of the torch. A proper location of the spacer can also avoid the formation of a static filament plasma or a rotating plasma rooted from the outer wall of the inner tube. With the help of morphological analysis, the underlying reason why MPT possesses a great tolerance to wet aerosols and air introduction was clearly made, that is, the formation region of the plasma formed with MPT is apparently separated from the reaction zone of it. 相似文献