Volt-ampere characteristics of a nitrogen DC plasma arc with anode melting

The characteristics of a nitrogen arc using a graphite cathode and a melting anode in a pilot-scale plasma furnace are investigated. The voltage is examined as a function of current and apparent plasma length. The voltage increases non-linearly with the increase of apparent plasma length, with the current fixed. The experimental data so obtained are compared with the predictions of the Bowman model for the electric arc, and with numerical simulations as well. The level of agreement between the experimental data at the melting anode and the numerical predictions confirms the suitability of the proposed the Bowman model. These characteristics are relevant to the engineering design and evaluation of a DC plasma furnace and reactor for the treatment of hazardous fly ash waste.     

Improved layer peeling algorithm for strongly reflecting fiber gratings

An improved algorithm based on the layer peeling (LP) method is proposed and demonstrated. The new method is shown to be effective for mitigating the impact of numerical errors on reconstruction of coupling function for strongly reflecting Bragg gratings. As examples, a flat-top dispersion-free fiber grating and a fiber-grating dispersion compensator are designed by the improved LP method. For a chirp grating, more accurate results are demonstrated in comparison with those obtained by the integral layer peeling (ILP) method.     

Improved layer peeling algorithm for strongly reflecting fiber gratings

An improved algorithm based on the layer peeling (LP) method is proposed and demonstrated.The new method is shown to be effective for mitigating the impact of numerical errors on reconstruction of coupling function for strongly reflecting Bragg gratings.As examples,a flat-top dispersion-free fiber grating and a fiber-grating dispersion compensator are designed by the improved LP method.For a chirp grating,more accurate results are demonstrated in comparison with those obtained by the integral layer peeling (ILP) method.     

Landau damping in a bounded magnetized plasma column

The damping decrement of Landau damping and the effect of thermal velocity on the frequency spectrum of a propagating wave in a bounded plasma column are investigated.The magnetized plasma column partially filling a cylindrical metallic tube is considered to be collisionless and non-degenerate.The Landau damping is due to the thermal motion of charge carriers and appears whenever the phase velocity of the plasma waves exceeds the thermal velocity of carriers.The analysis is based on a self-consistent kinetic theory and the solutions of the wave equation in a cylindrical plasma waveguide are presented using Vlasov and Maxwell equations.The hybrid mode dispersion equation for the cylindrical plasma waveguide is obtained through the application of appropriate boundary conditions to the plasma-vacuum interface.The dependence of Landau damping on plasma parameters and the effects of the metallic tube boundary on the dispersion characteristics of plasma and waveguide modes are investigated in detail through numerical calculations.     

Theoretical study on the band structure and optical properties of 4H-SiC

We have studied the band structure and optical properties of 4H-SiC by using a full potential linearized augmented plane waves (FPLAPW) method. The density of states (DOS) and band structure are presented. The imaginary part of the dielectric function has been obtained directly from the band structure calculation. With band gap correction, the real part of the dielectric function has been derived from the imaginary part by the Kramers－Kronig (KK) dispersion relationship. The values of reflectivity for normal incidence as a function of photon energy have also been calculated. We found the theoretical results are in good agreement with the experimental data.     

Approximate direct reduction method: infinite series reductions to the perturbed mKdV equation

The approximate direct reduction method is applied to the perturbed mKdV equation with weak fourth order dispersion and weak dissipation. The similarity reduction solutions of different orders conform to formal coherence, accounting for infinite series reduction solutions to the original equation and general formulas of similarity reduction equations. Painlevé II type equations, hyperbolic secant and Jacobi elliptic function solutions are obtained for zero-order similarity reduction equations. Higher order similarity reduction equations are linear variable coefficient ordinary differential equations.     

The complex variable reproducing kernel particle method for two-dimensional elastodynamics

On the basis of the reproducing kernel particle method (RKPM), a new meshless method, which is called the complex variable reproducing kernel particle method (CVRKPM), for two-dimensional elastodynamics is presented in this paper. The advantages of the CVRKPM are that the correction function of a two-dimensional problem is formed with one-dimensional basis function when the shape function is obtained. The Galerkin weak form is employed to obtain the discretised system equations, and implicit time integration method, which is the Newmark method, is used for time history analysis. And the penalty method is employed to apply the essential boundary conditions. Then the corresponding formulae of the CVRKPM for two-dimensional elastodynamics are obtained. Three numerical examples of two-dimensional elastodynamics are presented, and the CVRKPM results are compared with the ones of the RKPM and analytical solutions. It is evident that the numerical results of the CVRKPM are in excellent agreement with the analytical solution, and that the CVRKPM has greater precision than the RKPM.     

Electric ignition energy evaluation and the energy distribution structure of energy released in electrostatic discharge process

Ignition energy is one of the important parameters of flammable materials, and evaluating ignition energy precisely is essential to the safety of process industry and combustion science and technology. By using electric spark discharge test system, a series of electric spark discharge experiments were conducted with the capacitor-stored energy in the range of 10 J, 100 J, and 1000 J, respectively. The evaluation method for energy consumed by electric spark, wire, and switch during capacitor discharge process has been studied respectively. The resistance of wire, switch, and plasma between electrodes has been evaluated by different methods and an optimized evaluation method has been obtained. The electric energy consumed by wire, electric switch, and electric spark-induced plasma between electrodes were obtained and the energy structure of capacitor-released energy was analyzed. The dynamic process and the characteristic parameters(the maximum power, duration of discharge process) of electric spark discharge process have been analyzed. Experimental results showed that, electric spark-consumed energy only accounts for 8%–14% of the capacitor-released energy. With the increase of capacitor-released energy, the duration of discharge process becomes longer, and the energy of plasma accounts for more in the capacitor-released energy. The power of electric spark varies with time as a damped sinusoids function and the period and the maximum value increase with the capacitor-released energy.     

Detailed Radiative Opacity Studies of a High-Temperature Gold Plasma

The radiative opacity of a gold plasma at a temperature of 360eV and a density of 0.01 g/cm^3 has been studied using a detailed level accounting （DLA） method. Under this plasma condition, the average ionization degree is 50.2. Dominant ion types in the plasma are Au^＋49, Au^＋50 and Au^＋51, which account for 18.3%, 33.1% and 32.6%, respectively. The spectrally resolved opacity shows complex fine structures. The result obtained by the DLA method is compared with that of the average atom model. Detailed analyses are carried out to study the strongest absorption peaks caused by 3d- 4 f transitions near the photon energy of 2600 e V. To better understand the value of the Rosseland mean opacity, the radiative opacity around the energy region of the maximal Rosseland weighting function is also discussed in detail.     

Landau damping of longitudinal oscillation in ultra- relativistic plasmas with nonextensive distribution

The generalized dispersion equation for longitudinal oscillation in an unmagnetized, collisionless, isotropic and relativistic plasma is derived in the context of nonextensive q-distribution. An analytical expression for the Landau damping is obtained in an ultra-relativistic regime, which is related to q-parameter. In the limit q → 1, the result based on the relativistic Maxwellian distribution is recovered. It is shown that the interactions between the wave and particles are stronger and the waves are more strongly damped for lower values of q-parameter. The results are explained by the increased number of superthermal particles or low velocity particles contained in the plasma with the nonextensive distribution.     

Quantum and geometric effects on the symmetric and anti-symmetric modes of the surface plasma wave

The propagation of the surface quantum plasma waves is investigated in a thin quantum plasma slab. The symmetric and anti-symmetric dispersion modes of the quantum surface wave are obtained by the plasma dielectric function with the kinetic dispersion model for the slab geometry. The quantum mechanical and slab geometric effects on the symmetric and anti-symmetric modes are also discussed.     

Some results in the theory of interacting electron systems

The expressions for the longitudinal dielectric function, spin and orbital susceptibilities in the static, long wavelength limit are evaluated by solving the corresponding linearized vertex functions exactly in this limit. The plasma dispersion relation to leading order in the long wave limit is similarly obtained. These are compared with the corresponding results obtained previoulsy by us by a variational solution to the same vertex equations. It is established that the variational method gives the exact results in the static, zero wave vector limit, involving the proper renormalizations. The plasma dispersion relation is found to be the same as in the exact calculation whereas the coefficient of q² in the static density correlation function has an important additional contribution to the variational result. Applications of these results are briefly discussed.     

线性偏振激光在相对论等离子体中的调制不稳定性

 从相对论等离体中电磁波的非线性色散方程出发,利用Karpman方法获得了线性偏振波模所满足的非线性控制方程,在非线性色散方程和非线性控制方程的基础上对线性偏振激光在相对论等离体中传播的调制不稳定性进行分析,给出了调制不稳定的时间增长率与扰动态波数之间的函数关系。     

Relativistic Linear Theory in the Absence of External Fields

The dielectric tensor for a multi-component, homogeneous, field-free relativistic plasma is derived in manifestly covariant form. From the dielectric tensor, linear dispersion relations are obtained explicitly when each component of the plasma is isotropic in its rest frame. If the components are relativistic Maxwellians, these dispersion relations are expressible in terms of the relativistic plasma dispersion function. Special attention is given to the Weible and two-stream instabilities and to the normal modes of a quiescent, hot electron gas. For the last case the dispersion relations are solved numerically and compared against computer simulation data. An appendix applies the formalism to cold plasmas.     

等离子体加载耦合腔慢波结构色散分析

利用磁化等离子体介电张量和纵向场分量法对任意大小轴向磁场中等离子体填充耦合腔慢波结构进行场分析，得到磁化等离子体填充电子注通道电磁波场分量的轴对称精确解.在此基础上，建立耦合腔分区模型、采用场匹配方法建立色散方程，并数值计算得出不同等离子体密度及磁场下的耦合腔色散曲线.对不同密度等离子体填充情况下的耦合腔色散特性、混合模式的形成机理以及等离子体空间电荷波进行了分析讨论. 关键词： 耦合腔慢波结构 等离子体 混合模式 色散特性     

Dispersion characteristics of distorted circular doubly clad optical fibers having plasma in inner cladding

The theoretical analysis of two distorted doubly clad optical waveguides having plasma in inner cladding region have been presented. By matching the electric field and its derivative on the various interfaces, the dispersion characteristic equations have been derived and hence the cutoff frequencies are obtained. It is observed that the cutoff frequency of both considered cases are the function of plasma frequency and plasma width. Also, the plasma in the inner cladding region provides the extra degree of freedom to control the dispersion characteristics and one can trail the cutoff frequencies dynamically in time by playing with the discharge parameters associated with the plasma.     

平面火花隙三电极开关研制及性能测试

研制了一种适用于平行板传输连接的平面火花隙三电极开关，开关正负电极为半圆形状，触发电极为细条状。将之替代立体式（半球形电极）火花隙三电极开关并应用于爆炸箔起爆装置中，装置回路参数将得以优化。实验测试了空气间隙为4.12， 3.14和2.2 mm的平面火花隙三电极开关的性能。结果表明，在开关间隙间距一定的情况下，随着电压的升高，开关间隙的放电时延和分散时间呈指数降低，开关电感小于15 nH；对于不同范围内的应用电压，使用不同间隙间距的开关，其分散时间不大于10 ns。该开关应用于较低充电电压（小于10 kV）的脉冲功率装置中，与立体式火花隙三电极开关相比，回路电感降低了约50 nH，放电周期缩短近1/3，峰值电流增加约1/3。     

Surface plasmons on corrugated metal films

The dispersion relation for a surface plasmon, propagating across a corrugated metal film on a dielectric substrate, is obtained by the method of reduced Rayleigh equations. It is found that the surface plasmon dispersion curve has an infinite number of branches. Numerical solutions of the dispersion relation are obtained for a film, characterized by a free-electron metal dielectric function and a sinusoidal profile function.     

Energy relations of plasma waves in planar two-dimensional electron-ion plasmas

A derivation of the energy densities and power flows of plasma waves in a planar two-dimensional electron-ion plasma is presented through a simple approach. In this method, the response of an external current density introduced into the system is determined by a so-called dispersion function. The advantage of the dispersion function is that it yields not only the dispersion relations of both plasmon (high-frequency) and ion-acoustic (low-frequency) waves of the system, but expressions for the energy relations as well.     

����������β¡�ֲ�����µ�ɫɢ�����о�

当同时使用离子(或电子)回旋及中性束注入方式加热等离子体时,高能量粒子的能量分布函数一般应为尾部隆起(简称尾隆)分布。这种具有正能量梯度区域的分布函数更容易激发不稳定性,同时由于分布函数尾部隆起,在色散关系中引入了新的色散函数。主要研究了这种新色散函数的计算方法,结果表明:色散函数实部是关于原点对称的奇函数;而虚部则是关于纵轴对称的偶函数。色散函数的实部有2~4个极值点且极值点的位置与尾隆分布函数的能量梯度⊿有关、虚部有1~3个极值点但极值点位置与⊿无关。当其宗量趋于无穷大时,色散函数的值趋于零。当尾隆分布趋近于麦克斯韦分布时,用该方法计算的结果与色散函数表中给出的结果非常吻合。