Effect of sheaths on the capacitance of a plane grid capacitor in a plasma

An experimental investigation of the capacitance of a grid capacitor shows that the minimum sheath occurs for the grids biased to space potential. Above space potential, the sheath is attributed to electron acceleration, and a simple calculation shows that this effect is of the right magnitude.     

Radiation through an inhomogeneous plasma covering a ground plane

Electromagnetic radiation from a slot-excited ground plane covered by a plasma layer with exponentially decreasing electron density is considered. It is found that the far-field radiation pattern is simply related to that found for the case where the layer is absent.     

Radiation from a slot antenna in a ground plane coated with a moving plasma sheath

The electromagnetic radiation from a slot antenna in a conducting plane coated with a moving isotropic cold plasma layer is considered. It is assumed that the direction of motion of the layer is across the slot, which is taken to be infinitely long. An integral representation for the field radiated through the plasma layer is obtained and evaluated asymptotically in the far zone by the method of steepest descents. The migration of the poles in the integrand of this integral representation as the speed of the slab is varied is discussed and related to several calculated radiation patterns. It is found that the motion of the plasma layer has the greatest effect on the radiation pattern when the wave frequency and plasma frequency are nearly equal.     

Adrenaline for the grid [superconducting synchronous condenser]

This paper presents a novel superconducting device that provides essential voltage support. A superconducting synchronous condenser is basically an electric generator that is optimized and operated to act like a capacitor or inductor, providing the grid with reactive power, an abstruse but absolutely vital element in any power system relying on alternating current. The condenser quickly provides large quantities of reactive power to support grid voltage - as much as double the rating for up to a minute from a single unit and to supply controllable continuous-duty reactive compensation for optimizing grid-transmission effectiveness. It promises to do the job more effectively, and possibly more economically, than other solution, especially for industrial voltage flicker applications and voltage regulation of transmission lines with large isolated nodes.     

Wave propagation in a moving plasma

This letter comments on previous work by Scarf on wave propagation in a moving plasma and also adds new results.     

Probability distributions of randomly moving objects on a plane (Corresp.)

An object is moving on a piecewise linear random path with a constant speed. Given the initial location and direction, the probability distribution of the object's location is calculated as a function of time, and the result is presented graphically. Then the probability of detecting such an object is calculated by using circular and line sensors.     

Scattering of a dipole field by a moving plasma column

The problem of scattering of a dipole field by a plasma column moving uniformly in the axial direction is treated. In order to know the effect of the motion of the plasma on the scattering pattern, first the scattering properties of the dipole field by a stationary plasma with the aid of numerical examples are discussed. In this case two kinds of scattering patterns are illustrated: one in a cross section of the column and the other in the longitudinal section of the column. Then the scattering pattern of the dipole field by the moving plasma is investigated. From the numerical examples for the stationary plasma it is found that the scattering patterns are well-classified into three typical patterns by investigating the ratio of the backward scattering to the forward scattering with respect to the parameters which govern the scattering properties. In the case of moving plasma, it is shown that the scattering pattern in the longitudinal section will have a characteristic directional pattern, which does not appear in the case of stationary plasma, at a frequency lower than the plasma frequency.     

Measurements of microwaves scattered from a moving density-modulated plasma

Measurements of the absolute intensity and the angular distribution of the microwaves scattered from an oscillating plasma column of a finite length are presented. These measurements show that the scattered wave produces diffraction patterns and frequency shifts. The results substantiate quantitatively the theory of nonlinear microwave scattering.     

动态平板周视反射式全息图

介绍一种新的周视平板反射全息图制作原理与拍摄方法。它具有白光反射显示、重现活动图像、３６０°可视、立体感强的特点,有很高艺术欣尝价值与商业价值。     

Ion current to a plane probe in a flowing plasma

An expression is developed for the ion current to a plane probe in a flowing plasma, for the probe surface parallel to the ion flow, and neglecting ion thermal motion. The application of the result to the measurement of plasma density of a plasma torch is considered.     

Electrostatic potential through a circular aperture in a thickconducting plane

The Hankel transform is applied to express the scattered potential in the spectral domain and the boundary conditions are enforced to obtain simultaneous equations for the transmitted potential inside the thick conducting plane. The simultaneous equations are solved to represent the transmitted and scattered potentials in series forms. Numerical computations are performed to illustrate the behavior of polarizability in terms of the aperture size. The numerical comparisons to other available data show excellent agreement. The presented series solution is fast convergent so that it is very efficient for numerical computation     

Resonance of a plane capacitor containing inhomogeneous and anisotropic plasma

The quasistatic approximate resonance of a plane capacitor partially filled with an inhomogeneous and anisotropic plasma is found using the calculus of variations.     

雷达表盘图像移动目标的快速识别与跟踪

针对以往对机载雷达表盘的图像移动目标的识别与跟踪速度较慢,缺乏实时性的问题,提出一种快速识别和跟踪移动目标的方法。分析和总结了关于移动物体连续两帧图像的特点,并根据它们在图像对比中的空间位移上的相对变化关系,运用OTSU算法、差影法、直方图统计特征分析法,对移动目标进行识别与跟踪。该方法处理一帧图像的时间不超过40ms,具有识别速度快、跟踪准确、抗干扰能力强等特点。     

Measurement of ion density in a plasma torch using a plane probe

The plasma density of the flame of a plasma torch has been determined from the current to a plane probe using two theories. One includes only the ion flow motion; the other includes only the ion thermal motion. Comparison with spectroscopic results suggests that both motions should be included.     

Quasi-static analysis of a microstrip via through a hole in aground plane

The equivalent circuit of a via connecting two semi-infinitely long transmission lines through a circular hole in a ground plane is found. The π-type equivalent circuit consists of two excess capacitances and an excess inductance. These are quasistatic quantities and thus are computed statically by the method of moments from integral equations. The integral equations are established by introducing a sheet of magnetic current in the electrostatic case and a layer of magnetic charge in the magnetostatic case. Parametric plots of the excess capacitances, the excess inductance, and the characteristic admittance of the via are given     

Radiation resistance of an oscillating dipole in a moving compressible plasma

The radiation resistance of an electric dipole located in a moving compressible plasma is treated. First, the wave equations for a uniformly moving compressible plasma in the presence of a current source without any restriction upon the magnitude of the velocity are derived. Then, using these wave equations the radiation resistance of the present problem is obtained and its characteristics are investigated numerically. It is shown that if the moving velocity of plasmaupsilon_{0}exceeds the thermal velocity of the electronupsilon_{t}, a region appears in which the plasma wave component of the radiation resistance becomes negative. In this case, the numerical calculation shows that there is a range ofupsilon_{0}where the radiation efficiency of the electromagnetic wave is much improved. The cutoff frequency of the plasma wave in a moving compressible plasma becomes lower than that of the plasma wave in the rest frame of the plasma.     

Impedance of plane capacitor in a plasma with a resonance velocity distribution function

The RF impedance characteristics of a plane capacitor, which is immersed in a warm isotropic plasma, are investigated with a kinetic theory. An analytical solution is derived by assuming that the plasma has a resonance velocity distribution function which approximates a Maxwellian one. It is found that the results agree fairly well with those obtained numerically from the Maxwellian velocity distribution function.     

Reflection of a transient plane wave obliquely incident on compressible plasma half-space

The expression for the reflected transient pulses from the sharp surface of a compressible plasma half-space are obtained in a series form with the first perturbation order explicitely evaluated and valid for small to moderate compressibility (α = u/C0≤ 0.3, u is the electron acoustic velocity and C0is the velocity of light in free space). The reflected waveform are close to the waveform of cold plasma (α = 0) with noticeable change of amplitude and time delay of the first maxima.     

Magnetostatic potential distribution through a circular aperture ina thick conducting plane

The magnetostatic potential distribution through a circular aperture in a thick conducting plane is studied. The Hankel transform and mode-matching technique are utilized to obtain simultaneous equations for the modal coefficients inside the thick conducting plane. The simultaneous equations are solved to illustrate the behavior of the susceptibility in terms of the aperture size. Our solution is numerically very efficient in that it is represented in a rapidly converging series form