弓网系统降弓电弧电气特性仿真研究

基于Mayr电弧电路模型和Cassie电弧电路模型,考虑纵向气流吹弧效应,对电弧电压梯度U和电弧耗散功率P0进行修正,建立降弓电弧电路分析模型。研究降弓速度、降弓时刻以及降弓电弧电流对降弓电弧电压的影响。发现降弓电弧电压呈现近似线性的增长关系,降弓速度越高,降弓电弧电压增长得越快。降弓时刻对于电弧电压的影响主要体现在电弧电压出现的时刻差异,降弓电弧电压的波形基本一致。不同电弧电流情况下,电弧电压基本一致。文中的研究对于指导降弓操作、减轻弓网材料损失具有重要意义。     

Structural and electrical resistivity characteristics of vacuum arc ion deposited zirconium nitride thin films

Zirconium nitride (ZrN) thin films were grown on glass and aluminum substrates using a dual cathodic arc ion deposition technique. The effects of various negative bias voltages and flow ratios of N₂/Ar on the stoichiometric ratio of nitrogen to zirconium (N/Zr), deposition rate, structure, surface morphology and electrical resistivity of the ZrN layer were investigated. Rutherford backscattering spectroscopy measurements indicated a drop in the deposition rate and a slight increase in stoichiometric ratio (N/Zr) with the increase of bias voltage up to −400 V, although the latter still remained slightly less than unity (~0.92). Deposition rate of the film showed an increase with the argon addition. X-ray diffraction patterns depicted mostly polycrystalline nature of the films, with preferential orientation of (2 0 0) planes in the −100 V to −300 V bias voltage range. For 70–50% nitrogen and at a bias voltage of −400 V, the (1 1 1) orientation of ZrN film predominated. The films were smoother at a lower bias of −100 V, while the roughness increased slightly at a higher bias voltage possibly due to (increased) preferential re-sputtering of zirconium-rich clusters/islands. Changes in the resistivity of the films were correlated with stoichiometry, crystallographic orientation and crystalline quality.     

Electrodynamic characteristics of two-mirror open waveguides with periodic irregularities

A brief analysis of electrodynamic characteristics of two-mirror open waveguides with periodic irregularities of different geometry has been presented. It was established that plane-parallel quasi-optical systems were characterized by big losses caused by energy radiation into the ambient space. These losses can be reduced by using the phase correction of mirrors and by introducing metal-dielectric structures into their volume. Recommendations are provided on the use of the specified type of open waveguides in practical circuits of electronic and microwave devices.     

Electrodynamic characteristics of a strip antenna in a magnetoplasma

The problem of the distribution of a current in an antenna that is an infinitesimally thin, perfectly conducting narrow strip is considered. The antenna is embedded in an anisotropic plasma medium, oriented perpendicularly to an external magnetic field, and excited by an external electromotive force. The problem is reduced to a system of singular integral equations. On the basis of these equations, expressions for the distribution of the current and the antenna impedance are derived and analyzed.     

A research on the characteristics of an interleaver with a symmetrical resonator

In order to improve the transmission performance of the conventional Mach-Zehnder interferometer (MZI), a novel interleaver combining an "8"form ring resonator with a planar 3×3 single fiber coupler is proposed. Based on the phase modulation provided by the ring resonator, a flat filtering response is obtained by optimizing the coupling angle of resonator. The output expression is derived and numerical simulation is performed. The simulation indicates that the 0.5 dB passband and 25 dB stopband of the proposed interleaver are simultaneously improved remarkably, which are much wider than those of the single-stage MZI and the two-stage MZI interleavers, and the filtering performance of the proposed interleaver, which achieves a nearly square spectrum response, is also much better. Compared with the interleaver based on an asymmetrical MZI with a resonator in one arm, there is no difference between the intensities of two coherent beams in the condition of considering the influence of the propagation loss. Theoretical analysis shows that the influence of the propagation loss on extinction ratio can be effectively reduced.     

Electrodynamic characteristics of submillimeter waveband surface wave prismal resonator. Part I

Theory of Surface Wave Prismal Resonator (SWPR) is presented. It is shown that SWPR may be used as selective transformer of plane submillimeter radiation into the surface waves. Results of preliminary experiments are discussed.     

基于机器视觉的多圆弧对称零件测量方法研究

在实际工业生产中,对具有多圆弧对称特性零件的尺寸测量需求越来越多。而传统接触式测量方法大多存在测量精度不稳定、容易损伤零件和效率低等缺点。因此,本文基于机器视觉的非接触式测量原理,首先搭建一套双远心机器视觉测量系统,采集有效的零件图像。然后,利用亚像素边缘检测算法提取图像的亚像素边缘,并结合最小二乘法及多圆弧拟合内切圆的自定义Halcon算子,最终实现多圆弧对称零件的精密测量。为了验证所设计系统的有效性,本文对某球笼联轴器内套进行了稳定性和重复性测量实验。实验结果表明:该系统测量精度可达到001mm,且测量过程快速、稳定。     

十例电焊工尘肺的超微结构观察

10例电焊工尘肺病人经支气管肺活检的样品进行电镜观察。在肺泡隔、肺泡腔内见有活跃的巨噬细胞,其细胞内含电子致密颗粒的异噬体,肺泡隔中有大量胶原纤维、弹性纤维和成纤维细胞。据此说明,长期吸入电焊烟尘可引起肺纤维化,超微结构观察有助于电焊工尘肺的诊断。     

Electrodynamic simulation of transformation of wave modes in an H-plane waveguide transition

Electrodynamic simulation of transformation of wave modes in an H-plane waveguide transition is performed. The influence of different design versions of such a junction on the magnitude of excitation of higher-order modes is analyzed. Variation in the attenuation level of higher-order modes as a function of the chosen length of the transition is shown.     

电弧炉电气系统的建模与谐波电流研究

电弧炉是一种不平衡、非线性、时变负载,给电网带来了严重的电能质量问题。基于电弧弧长随机特性和电弧炉电气系统实际运行环境,使用简化的电弧电流电压特性得到了交流电弧的等效电阻数学模型,应用Matlab/Simulink软件仿真验证了该模型的正确性。然后建立了三相非线性时变电弧炉电气系统的仿真模型,并且对电弧炉电气系统进行谐波分析,采用无源滤波器抑制谐波,仿真结果表明该模型能有效地减小谐波总失真率、改善电能质量。     

Directional and polarization radiation characteristics of a horizontal impedance vibrator located above a rectangular screen

An algorithm of calculation of the directivity, energy, and polarization radiation characteristics of an arbitrarily oriented thin impedance vibrator located above a rectangular screen is developed on the basis of the asymptotic solution to the 3D problem of diffraction of the field of the electric vibrator by a perfectly conducting rectangular screen. The asymptotic expressions for the current of an impedance vibrator having the electric length 0.4 ≤2l/λ ≤ 0.6 are applied. The asymptotic solution is obtained on the basis of the method of the uniform geometric diffraction theory. The aforementioned characteristics are studied in the whole observation space in the far zone. The effects of the thickness and length of the vibrators and the effects of the distances from the screen on the resonance values of the distributed surface impedance and the corresponding radiation characteristics are shown. The resonance vibrator’s radiation characteristics that depend on the screen dimensions are analyzed. The amplitude and polarization patterns of a horizontal vibrator located above a square screen having optimal dimensions are calculated.     

Electrodynamic Theory of Sagnac Effect

Using the strict solution of the problem on the possibility that there exists an electric-type wave in rotating cylindrical waveguide analysis of electromagnetic phenomena is performed. Dependence effects of wavelength, phase and group velocity of propagating partial harmonics and independence effects of phase and group velocities of re-reflecting in the cross section partial harmonics on the waveguide’s rotation speed are revealed.Astrictly applicable formula for estimating experimental results in Sagnac effect for partial harmonics’ phase difference (phase difference due to path length difference) is obtained     

利用数字存储示波器测量特殊信号

随着数字化技术、集成电路的高速发展,数字存储示波器以其强大的测试能力、稳定的性能和更快捷的数据处理方式越来越多的应用于科研生产中,已成为检测电子线路最有效的工具之一.     

Frequency-dependent electrical characteristics of GaAs MESFETs

Output resistance and transconductance of GaAs MESFETs have been observed to change significantly at very low frequencies. Extensive measurements of these characteristics as a function of device bias are reported. Direct measurements of the dispersive behavior between DC and 100 kHz and over a broad temperature range have been made on ion-implanted monolithic microwave IC (MMIC) devices. Conductance deep level transient spectroscopy (DLTS) and microwave S-parameter measurements have also been made to investigate this behavior. These measurements reveal that surface or channel-substrate interface traps in the material are most likely to be responsible for the observed behavior. A new equivalent-circuit model which accounts for many of the observed characteristics is developed. Unlike previously proposed equivalent circuits, the model does not rely on physically unrealistic circuit element values in order to obtain accurate performance predictions. The bias dependence of circuit element values is computed for one device. Effects not described by the model are also discussed     

The electrical characteristics of cermet-silicon contacts

The conductance and capacitance of metal/cermet/n-Si sandwiches has been found to be strongly dependent on the metal content of the cermet. Conductive cermets behave essentially as series resistors. Insulating cermets give rise to some Si surface inversion, and the surface minority carrier density varies with bias. This and the cermet capacitance results in a large dispersion of the measured capacitance with frequency and bias. In addition, metal particles in the cermet were found to trap charges, which then induced minority carrier charges at the interface and gave rise to a memory effect.     

Electrodynamic analysis of a Pendry lens

Excitation of a magnetodielectric plate with the parameters ? → ?1 and μ → ?1 by an elementary electric dipole is considered. The behavior of the wave field is investigated in the case when the values of the constitutive parameters approach the singular point ? = μ = ?1 along the curve ?μ = 1. A condition is established under which the transverse dimension of the field in the focal plane of the lens is smaller than the diffraction limit. The dimension of the spot is expressed in an explicit form. It is shown, that, in the situation considered, the effect of longitudinal focusing is absent.     

Transition from the anodic arc phase to the cathodic metallic arc phase in vacuum at low DC electrical level

Contact material transfer during arcing in relays has been described in several papers. Transfer from the anode to the cathode has been attributed to the anodic arc phase, and opposite transfer from the cathode to the anode has been attributed to the cathodic arc phase. In a previous paper we showed that the transition from the anodic to the cathodic arc occurs when a break arc becomes longer than a critical arc length, independently from electrical and mechanical parameters. In this paper, we completed our work by using the same breaking apparatus (14 VDC, 40 A) equipped with an arc length control device. We showed that the transition from the anodic to the cathodic arc occurs always at the same critical arc length, independently from the opening speed and the ambient pressure. Through measurements of material transfer in vacuum, we have shown that a cathodic arc in the metallic phase can occur, i.e., that material transfer direction is independent of metallic and gaseous phases. Finally, we showed that it was possible to distinguish the transition from the anodic to the cathodic arc by observing the evolution of the arc spots on the rivets.     

感应式电动振动台特性计算

通过对感应式电动振动台和传统的电动振动台的结构原理进行比较，利用传统的电动振动台比较成熟的计算方法，对感应式电动振动台的计算方法进行了研究，提出了利用类似变压器模型来模拟感应式电动振动台的新型计算方法，引入变流比的参数来建立感应式电动振动台的电路方程。并在40kg传统的电动振动台的基础上设计制造出一台感应式电动振动台原理样机，通过对这台感应式电动振动台原理样机和传统的40kg电动振动台的特性测试进行比较，验证感应式电动振动台的理论计算公式，并总结感应式电动振动台的优缺点，为今后大型感应式振动台的设计提供理论依据。     

电动式扬声器单元中的降低失真问题

探讨了在电动式低音扬声器单元中非线性失真的原因,并且提出了减少偶次谐波的带对称磁路的电动式扬声器单元的某些结构方案.介绍了已进行的降低偶次谐波的方法即应用双低频扬声器单元,该方法还能减小声系统箱体的容积.