Singularity-free Green's function for EM sources embedded in a stratified medium

We present a method to unify the calculation of Green＇s functions for an electromagnetic（EM） transmitting source embedded in a homogeneous stratified medium.A virtual interface parallel to layer interfaces is introduced through the source location.The potentials for Green＇s function are derived by decomposing the partial wave solutions to Helmholtz＇s equations into upward and downward within boundaries.The amplitudes of the potentials in each stratum are obtained recursively from the initial amplitudes at the source level.The initial amplitudes are derived by coupling with the transmitting sources and following the discontinuity of the tangential electric and magnetic fields at the source interface.Only the initial terms are related to the transmitting sources and thus need to be modified for different transmitters,whereas the kernel connected with the stratified media stays unchanged.Hence,the present method can be easily applied to EM transmitting sources with little modification.The application of the proposed method to the marine controlled-source electromagnetic method（MCSEM） demonstrates its simplicity and flexibility.

Spin-Dependent Transport and Densities of States in Non-collinear Magnetic Barriers

The spin-dependent transport properties in the non-collinear pattern of series of δ-magnetic barriers are studied by using scattering theory and Green＇s function methods. The Green＇s function is obtained by using distorted wave approach and the scattering matrix is related by Fisher-Lee relationship. In addition to reproducing the results of Papp＇s and Xu＇s in parallel and antiparallel configurations, we also obtain further results, where arbitrary orientations of the magnetic barriers and arbitrary number of barriers are included. The main finding of our results is that the signs of polarizations can be switched around some ＂geometric unpolarized windows＂. The well-known antiparallel configuration has no such characteristics. Furthermore, we discuss spin-related partial densities of states in both polarized and unpolarized structures.

Solving Electromagnetism Differential Equations Based on Random Walk

An approach of solving the finite difference equations with Monte Carlo method was presented. The accuracy of algorithm is guaranteed by the Central Limit Theorem. The computation of the value on each single node is independent of each other, which makes it easy to realize the algorithm in parallel processing and greatly improves the efficiency while dealing with local area computation. As long as different kinds of boundary conditions are statistics modeled,wide applications can the be made where the finite difference method is of competence.

PERIODIC DYADIC GREEN’S FUNCTION FOR FIELD ANALYSIS IN EMC CHAMBER

Herein a novel Dyadic Green’s Function (DGF) is presented to calculate the field in ElectroMag-netic Compatibility (EMC) chamber. Due to the difficulty of simulating the whole chamber environment, the analysis combines the DGF formulation and the FEM method, with the latter deals with the reflection from absorbers. With DGF formulation for infinite periodic array structures, this paper investigates electromagnetic field in chamber with truncated arrays. The reflection from the absorber serves as the virtual source contribut-ing to the total field. Hence the whole chamber field calculation can be separated from the work of absorber model set-up. Practically the field homogeneity test and Normal Site Attenuation (NSA) test are carried out to evaluate the chamber performance. Based on the method in this paper, the simulation results agree well with the test, and predict successfully the victim frequency points of the chamber.

Transport Through a Precessing Spin Coupled to Noncollinearly Polarized Ferromagnetic Leads

The quantum electronic transport through a precessing magnetic spin coupled to noncollinearly polarized ferromagnetic leads （F-MS-F） has been studied in this paper. The nonequilibrium Green function approach is used to calculate local density of states （LDOS） and current in the presence of external bias. The characters of LDOS and the electronic current are obtained. The tunneling current is investigated for different precessing angle and different configurations of the magnetization of the leads. The investigation revea/s that when the precessing angle takes θ 〈 π /2 and negative bias is applied, the resonant tunneling current appears, otherwise, it appears when positive bias is applied. When the leads are totally polarized and the precessing angel takes O, the tunneling current changes with the configuration of two leads; and it becomes zero when the two leads are antiparallel.

Magnetic Properties of One-Dimensional Ferromagnetic Mixed-Spin Model within Tyablikov Decoupling Approximation

In this paper, we apply the two-time Green's function method, and provide a simple way to study themagnetic properties of one-dimensional spin-(S, s) Heisenberg ferromagnets.The magnetic susceptibility and correlationfunctions are obtained by using the Tyablikov decoupling approximation.Our results show that the magnetic susceptibilityand correlation length are a monotonically decreasing function of temperature regardless of the mixed spins.It isfound that in the case of S = s, our results of one-dimensional mixed-spin model is reduced to be those of the isotropicferromagnetic Heisenberg chain in the whole temperature region.Our results for the susceptibility are in agreement withthose obtained by other theoretical approaches.

Magnetic Properties of Spin-1／2 Quantum Heisenberg Ferromagnet with Spatially Anisotropy

The spin-1/2 quantum Heisenberg ferromagnet with anisotropic spin exchange interactions in three dimensions are investigated by means of the Green's function method. In the Tyablikov approximation, the correlation function s, the magnetization, and the susceptibilities are computed. The magnetic properties of this model are found to be dependent of anisotropy.

Statistical Average of Spin Operators for Calculation of Three-Component Magnetization

When one wants to calculate all the three components of magnetization of Heisenberg model under random phase approximation, at least one of the components should be the solution of an ordinary differential equation. In this paper such an equation is established. It is argued that the general expressions of magnetization for any spin quantum number S suggested before are the solution of the ordinary differential equation.

用高真空管激发雷达脉冲

最初,产生雷达中磁控管的激发脉冲,曾经用过高真空管。所需功率大,因此激发管要用很高的屏压(当时还没有脉冲变压器)和栅极激动电功率。这使激发管线路庞大,而效率甚低。但其优点是被激发的磁控管工作稳定。随后,发现了用氢闸流管及传输线元件构成的体积小而效率高的激发器。但所输出电压在到达峯值时变化率极大,结果容易使磁控管内有飞(?)。

Effect of cilostazol on cerebral arteries in secondary prevention of ischemic stroke

Objective To compare the effects of cilostazol on cerebral arteries and cerebrovascular blood flow in secondary prevention of ischemic stroke, with those of aspirin. Methods Sixty-eight patients who had ischemic stroke during the recent 1-6 months were recruited and randomized into cilostazol or aspirin group. Cerebrovascular condition was assessed by magnetic resonance angiography （MRA） and transcranial doppler ultrasonography （TCD） at the beginning of the study and after 12-month medication. Results During the clinical follow-up, ischemic stroke recurred in 2 patients in cilostazol group, while in aspirin group, one case of ischemic stroke recurrence and one case of acute myocardial infarction were found. MRA revealed that in aspirin group, the percentages of patients experiencing aggravation and attenuation of cerebrovascular condition were 3.3% and 6.7%, respectively, while in aspirin group, they were 3.3% and 10%, respectively. Moreover, TCD revealed that 26.9% of the patients in aspirin group and 14.3% of the patients in cilostazol group experienced aggravation of cerebrovascular condition. However, the systolic peak flow velocity of the previously abnormal arteries increased by 42.9% after 12-month medication of cilostazol, which was significantly higher than that after aspirin medication （27.5%） （P = 0.04）. Furthermore, as a major side effect of antiplatelet therapy, the frequrency of bleeding was much less in cilostazol group （0 case in cilostazol group vs 5 in aspirin, P 〈 0.05）. Conclusion Cilostazol is as effective as aspirin in preventing the aggravation of cerebral arteries in secondary prevention of ischemic stroke. Besides, it is more safe. Cilostazol can increase the systolic peak flow velocity of cerebral arteries, which may improve the blood supply of focal ischemia.

Solid-State 13C Nuclear Magnetic Resonance Spectroscopic Characterization of Soil Organic Matter Fractions in a Forest Ecosystem Subjected to Prescribed Burning and Thinning

Forest management practices such as prescribed burning and thinning in forest ecosystems may alter the properties of soil organic matter （SOM）. In this study, surface softs from field plots in the Bankhead National Forest, Alabama, USA, were used to investigate possible SOM transformations induced by thinning and burning. Elemental analysis and solid-state 13C cross polarization magic angle spinning nuclear magnetic resonance （13C CPMAS NMR） spectroscopy were used to characterize SOM fractions in whole soils, humic substances, and density fractions. Our data revealed that the changes in SOM fractions due to the repeated burning carried out in the forest ecosystem studied were involved mainly with alkyl C, O-alkyl C, and carbohydrate functional groups, implying that most prominent reactions that occurred involved dehydrogenation, de-oxygenation, and decarboxylation. In addition, burning and thinning might have also affected the distribution and composition of free and occluded particulate SOM fractions. The limited structural changes in SOM fractions suggested that low-intensity prescribed fire in the forest ecosystem studied will not create major structural changes in SOM fractions.

Organic-ferromagnetic hetero-structures with spin transport properties and fundamental physical effects

Organic spintronics refers to control spin dependent transport through organic materials.In the last two decades,extraordinary development has been achieved for organic-spintronics.A series of theoretical and experimental studies have been done to reveal the mechanisms of spin dependent transport properties.The theoretical analysis is based on the non-equilibrium Green's function formalism provides a mathematical framework for solving the transmission coefficients in the Landauer formula from atomistic first principles without any phenomenological parameters.In this article,we provide a brief theoretical review on organic spintronics devices and device physics therein.

Review on Application of Electromagnetic Theory and Technology to Forest Pests Control

Many domestic and international scholars have done a wide range of researches on electromagnetic and technology and have made some achievements. Electromagnetic technology has been used in forest pests control as a convenient and high-efficient physics means. This article summaries the current study of the electromagnetic biological effect and introduces the appfication of microwave, pulsed electromagnetic field and electrostatic field to forest pests control. The research direction and prospect of the application of electromagnetic theory and technology to forest pests control arc also discussed.