瞬态抑制二极管电磁脉冲响应建模

针对目前浪涌保护器件性能分析方法不完善、缺乏准确数学模型的问题,提出了一种基于NARX神经网络的电磁脉冲响应时域建模方法,并给出NARX神经网络建模的理论基础及设计步骤。通过组建传输线脉冲测试平台及静电放电实验平台,对NUP2105L型瞬态抑制二极管进行注入实验,采集输入输出实验数据并建立NARX神经网络模型。对建模效果进行分析,所建模型可以较为准确地预测输入脉冲为方波脉冲、人体金属模型及机器模型静电放电电磁脉冲时,响应电压曲线趋势、响应时间、脉冲峰值、箝位时间及箝位电压等性能指标,验证了模型的正确性。     

单稳系统的脉冲响应研究

针对单稳系统检测脉冲信号的参数调节方法很难达到理想随机共振效果的难点, 本文提出了脉冲序列整体平移的方法. 该方法不采用系统参数调节, 而是通过偏移量的设置来实现并达到增强单稳随机共振的目的. 为了减小单稳脉冲响应波形的失真, 探讨了该方法减小脉冲响应失真的机理. 在噪声存在的情况下, 揭示了该平移方法调节噪声使噪声产生积极作用从而改善单稳随机共振的机理, 表明所提方法有利于含噪脉冲信号的检测.     

Time-domain split-step method with variable step-sizes in vectorial pulse propagation by using digital filters

Finite impulse response (FIR) and infinite impulse response (IIR) digital filters are proposed to allow for time-domain simulation of optical pulse propagation by using the operator-splitting technique. These filters simulate polarization mode dispersion and chromatic dispersion effects with acceptable accuracy in time-domain. An analytical relation between the coefficients of these filters and the simulation step-size is established to accommodate the possibility of carrying out the time-domain split-step method with variable split-step length at virtually no computational burden. The superiority of the proposed method over the conventional frequency-domain technique is particularly demonstrated in wavelength-division multiplexing (WDM) applications.     

垂直极化平行板有界波电磁脉冲模拟器辐射近场的快速估算方法

为快速估算出垂直极化平行板有界波电磁脉冲(EMP)模拟器的时域近场,将散射传递函数法应用于该类型模拟器近场的时域计算中,即对于给定的脉冲源,先寻找有效频谱范围能覆盖该源的高斯脉冲源,并应用时域有限差分(FDTD)方法计算该高斯脉冲源激励时模拟器中测试点场的时域响应,再利用傅里叶变换、系统的传递函数及傅里叶逆变换计算得到给定脉冲源激励时各测试点场的瞬态响应。所得计算结果与直接使用给定脉冲源激励时FDTD方法的计算结果符合较好。所述方法可用于同一模拟器在不同脉冲源激励时辐射近场的快速估算,能大大减少FDTD模拟计算的次数,尤其对于中大型模拟器能有效减少计算时间和内存。     

Unipolar characteristics of ZnO ceramics

The paper presents research on unipolar characteristics of ZnO ceramics. Dielectric response analysis is generally known method to characterize electrical properties of materials. It becomes important method for non-destructive testing. Recently, the possibilities and limitations of this method to reflect the deterioration processes due to thermal and electrical stress were investigated. The method is based on measuring the conduction and dielectric or polarization response. Present investigations are bringing extension to this research by high-energy pulse loading of samples that are used e.g. in production of gapless overvoltage protections. Moreover, the variations of characteristics due to pulse energy stress of samples are investigated.     

600kV高压大电流脉冲变压器的研制

 介绍了工作于低阻抗负载下的高压大电流快响应脉冲变压器的一种设计方法。设计了一台用于调制器型加速器的标称电压为600kV的脉冲变压器, 其设计值与实验值基本一致。     

耦合环形腔马赫-曾德尔干涉仪瞬态响应及应用

对耦合环形腔马赫-曾德尔干涉仪光脉冲瞬态响应进行了理论和数值研究.利用光束追迹法推导了脉冲传输的解析关系，并数值模拟了传输光场随时间的演化.输出脉冲形状可通过控制损耗进行调解，响应速度为皮秒量级.由于马赫-曾德尔干涉仪两输出端口的互补性，在输出端可同时实现光脉冲微分和积分操作.利用损耗控制机制，可实现单通道脉冲微分和积分操作转换.引入增益补偿损耗，可实现脉冲压缩及产生可调单一触发光脉冲.     

Time shift and superposition method for solving transient radiative transfer equation

Due to the long-time transient response of pulse irradiation, the computational time required for solving transient radiative transfer (TRT) is often very long, especially for the case in which the boundary is subjected to continuous pulse train and the geometry is complicated. In addition, sometimes, before actual experiments are carried out, a suitable pulse shape or type often needs to be selected by numerical simulation and comparison. Because the numerical solution of TRT needs to be repeated many times, the selection processes is very time-consuming. In this paper, by considering that the TRT equation and its initial and boundary conditions are linear, a time shift and superposition method is developed for solving TRT equation in non-emitting media, in which only the transient response of a short square pulse needs to be solved, and the solution of TRT under any pulse shape can be constructed by time shift and then superposition using the basis solution of the short square pulse. Three numerical examples are studied to illustrate the peformance of the superposition method in solving TRT problems. The results show that the superposition is effective, accurate and very suitable for solving TRT in the medium subjected to a series of pulse train.     

Transient response analysis of photoconductive detector under ultra-short laser pulse radiation

The transient response characteristics of HgCdTe photoconductive detector under the radiation of ultra-short laser pulse have been discussed in detail. Specifically, the transient effect of pulse width to the temperature of electronics and crystal lattice, and corresponding resistance changes of detector are mainly discussed. Based on traditional drift-diffusion model, considering that the temperature of electronics and crystal lattice are different under the ultra-short laser pulse, the double-temperature equation is joined to describe the semiconductor carriers’ dynamics features. Using the numerical method, the transient response characteristics of detector in the case of ultra-short pulse have been worked out. The calculation results show that: When the pulse width is greater than nanosecond pulse, the temperature of electronics will be equal to which of crystal lattice. If the pulse width is less than nanosecond pulse, the temperature of electronics is higher than which of the latter. After the end of a pulse, the rebound resistance of detector will be higher than the dark resistance because of the thermal effect. The heat effect is more obvious when a pulse with narrower width and higher energy density incident to the detector.     

激光脉冲在各向异性散射介质内的瞬态热效应

本文考察了激光脉冲在吸收、发射、各向异性散射介质内引起的瞬态热效应。将激光脉冲辐射在介质内的传递过程分为两个子过程：发射－衰减－反射过程和吸收－散射过程。用光线踪迹法结合节点分析导出辐射传递系数和辐射源项,用控制容积法解瞬态能量方程。检验结果表明,本文的计算方法准确。在此基础上,考察了散射特性、初始温度对激光脉冲响应的影响。     

提高RZ码偏振度椭球对偏振模色散响应范围的方法

提出了使用适当带宽的光带通滤波器和选择合适的脉冲宽度两种方法来增加RZ码光纤通信系统中偏振度椭球对偏振模色散的响应范围,模拟计算得到了40 Gb/s的 RZ码在不同脉冲宽度以及同一脉冲宽度下不同的滤波器带宽两种情况下偏振度椭球的短轴随偏振模色散的变化情况. 结果表明, 采用这二种方法可以明显地提高偏振度椭球的短轴对偏振模色散的响应范围. 另外, 数值模拟结果还表明对于40 Gb/s的系统滤波器带宽应大于50 Hz, 光源脉宽应在4 ps~10 ps较为合适. 通过实验证明了这二种方案是可行的.     

Frequency-domain Hadamard spectroscopy

A new technique is proposed for multichannel excitation and detection of NMR signals in the frequency domain, an alternative to the widely used pulse-excited Fourier transform method. An extensive array of N radiofrequency irradiation channels covers the spectrum of interest. A selective radiofrequency pulse sequence is applied to each channel, generating a steady-state NMR response acquired one-point-at-a-time in the intervals between pulses. The excitation pattern is repeated N times, phase-encoded according to a Hadamard matrix, and the corresponding N composite responses are decoded by reference to the same matrix. This multiplex technique offers the same sensitivity advantage as conventional Fourier transform spectroscopy. The irradiation pattern may be tailored to concentrate on interesting spectral regions, to facilitate homonuclear double resonance, or to avoid exciting strong solvent peaks. As no free induction decay is involved, the new method avoids problems of pulse breakthrough or lineshape distortion by premature termination of the time-domain signal.     

The chemical shift interaction under weak radio frequency pulses

The chemical shift anisotropy of a nuclear spin system in a strong magnetic field can be comparable to the strength of the rf pulse (weak pulse condition). In this case, the commonly used assumption that the chemical shift interaction Hamiltonian in the duration of a rf pulse can be neglected is no longer effective. The rf response characteristics of a spin-1/2 system under a weak pulse condition is studied in detail. The relationships between the distortion of the chemical shift powder spectrum and the relative rf field amplitude under various conditions are given. The suppression of sidebands of a MAS spectrum is analysed as an example of solid multiple pulse experiments. The experimental results are in good agreement with computer simulations.     

Multi-objective optimisation of laser beam cutting process

This paper presents a hybrid Taguchi method and response surface method (TMRSM) for the multi-response optimisation of a laser beam cutting process. The approach first uses the Taguchi quality loss function to find the optimum level of input cutting parameters such as assist gas pressure, pulse width, pulse frequency and cutting speed. The optimum input parameter values are further used as the central values in the response surface method to develop and optimise the second-order response model. The two quality characteristics Kerf width (KW), and material removal rate (MRR), that are of different nature (KW is of the smaller-the-better type, while MRR is of the higher the better type), have been selected for simultaneous optimisation. The results show considerable improvement in both the quality characteristics when the hybrid approach is used, as compared the results of a single approach.     

光电倍增管对14 MeV脉冲中子的直照响应

 采用ING-103型DPF脉冲中子源产生的14.1 MeV脉冲中子对EMI两个不同型号的光电倍增管EMI-9815B和EMI-9850B进行了直照实验。针对DPF脉冲中子源产生中子脉冲的同时也会产生X射线脉冲的特点，采取了飞行时间法及吸收衰减法来消除X射线对中子脉冲的干扰。利用中子及X射线速度的差异，将光电倍增管放置在离源较远的测点位置，测得了X射线脉冲和中子脉冲时间上错开的双峰波形。通过在辐射通道内添加5 cm厚的铅吸收体有效地抑制了X射线峰，在离源较近的测量位置测到了干净的脉冲中子波形。根据实测波形，得到的光电倍增管EMI-9815B和EMI-9850B中子直照灵敏度分别为10^-13与10^-15量级，该结果与理论计算结果在量级上一致。     

The absorption coefficient measurement of underwater materials in a water tube by using the wide-band pulse method

The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is proposed.After obtaining the response of the entire system,the transducer is excited with wide-band,short-duration signals.Then,the received signals are processed with inverse filters and the "blurred" reflective signals of standard reflector and test sample are recovered respectively,finally,the reflection coefficient and absorption coefficient are calculated.Simulation work is implemented to verify the advantage of postprocessing inverse filter over pre-processing inverse filter in terms of low frequency measurement.To verify the proposed method,two different wide-band pulses in the separate frequency ranges are adopted to measure the same rubber material.The experimental results indicate that the wide-band pulse method and CW(Continuous Wave) pulse method have good agreement in both low frequency range and high frequency range.Wide-band pulse method is of high efficiency,and the low frequency reaches 350 Hz,which is able to extend the low frequency range.     

导体板上单极天线对电磁脉冲响应特性的矩量法分析

 针对应用广泛的单极天线,基于矩量法分析了天线对高空电磁脉冲和高功率微波、超宽带非核电磁脉冲的响应,计算了三类电磁脉冲通过天线耦合产生感应电流频谱响应和时域瞬态响应,窄带脉冲的响应曲线与入射脉冲有较大相似性,电流响应峰值依次为100,60和10.3 A,对现有大功率限幅器的功率容限提出了更高的要求。     

Analysis of conditions for determining the thermophysical characteristics of energetic materials by the laser pulse method

An analysis of conditions for determining the thermophysical characteristics of energetic materials by the laser pulse method is performed. Based on the results of numerical solution of the heat conduction problems for a sample of a material irradiated with a short heating laser pulse corresponding to actual experimental conditions, the time dependences on the sample surface temperature are determined. The heat pulse duration required to determine the thermophysical properties of materials and the ignition delay time are compared. It is shown that the determination of the thermophysical characteristics of a typical energetic material by the laser pulse method is possible at pulse durations of no longer than 0.24 s.     

铝基薄膜忆阻器作为感觉神经系统的习惯化特性

感觉神经系统可在外界刺激与生物体反应之间建立联系.感觉神经系统中的最小单位神经元可直接将外界刺激传递至中枢神经,再由中枢神经通过控制和调节生物体对外界刺激作出反应.神经突触连接了相邻神经元进行脉冲信息传递功能.习惯化是神经突触在信息传递中过滤外界无关信息时的一个基本特性,可以让感觉神经系统更快速地适应外界环境变化.忆阻器模拟神经突触功能在近年获得进展,然而针对以忆阻器为基础的具有习惯化特性的神经突触以及完整神经系统的研究相对匮乏.本文利用磁控溅射技术制备了厚度约为40 nm且含铝纳米颗粒的氮化铝薄膜忆阻器,并发现这种结构忆阻器对于重复的外界刺激有明显的习惯化行为,该行为与感觉神经系统的习惯化特性极为相似.若将这种具有习惯化的神经突触与感觉神经元串联,可形成LIF(leaky integrate-and-fire)生物模型模拟完整的神经系统行为,也为忆阻器在第三代神经网络(脉冲神经网络)中的应用提供理论参考.     

The measurement of the free field impulse response of microphones in a laboratory environment

A method is presented of measuring the free field frequency and impulse response of microphones by using a pulse technique in an ordinary laboratory environment. The pressure transient generated by exciting a loudspeaker with a narrow pulse is detected at some point in the loudspeaker's far field by a “reference” microphone whose response is assumed flat over the frequency range of interest. The microphone to be tested is then substituted in exactly the same position and its response to the transient measured. The outputs of the two microphones are accurately sampled and deconvolved by using a discrete Fourier transform technique to give the magnitude and phase parts of the “test” microphone's frequency response, and hence, via the discrete Fourier transform, its response to a delta function of pressure propagating in the free field. The computed impulse responses are presented and the accuracy of the method discussed.To illustrate the use of the method, the free field frequency response and free field correction curves of a one inch instrumentation microphone are measured. The method is then used to measure the pressure which occurs at the centre of the flat end-face of a long a cylinder when excited by an impulse of acoustic pressure propagating in the free field from various angles of incidence.