基于磁致伸缩导波的尖轨缺陷检测技术研究

尖轨在其周期性载荷作用下易发生断裂,引发列车事故。为对尖轨缺陷进行检测,文章基于磁致伸缩效应研制了导波检测系统,研究导波在尖轨中的传播特性、导波对尖轨附属件的检测能力以及缺陷的识别能力。采用ABAQUS/Explicit有限元方法研究了不同频率导波在尖轨中的传播特性。所研发的磁致伸缩导波检测系统在尖轨上的检测是可行有效的。使用导波检测系统在尖轨底面激励的水平剪切导波在基本轨和尖轨上可传播的有效距离至少为12 m,在空轨中至少能传播16 m。而且低频导波主要沿轨底传播,高频导波主要沿轨腰和轨头传播,多频导波结合能更加准确地对尖轨的检(监)测。     

Determining characteristics of a microsecond plasma opening switch at the moment of current interruption

A new approach to determining characteristics of a microsecond plasma opening switch at the moment of current interruption is proposed. Dependences of the switch voltage and resistance on the current and geometric parameters are presented, and the calculated values of the resistance are compared to the experimental data.     

Terahertz wave switch based on silicon photonic crystals

A compact and integrated terahertz (THz) wave photonic crystal switch is proposed in silicon. The switch operates based on a dynamic shift of the photonic bandgap by using an external applied electric field. The plane wave expansion method and the finite-difference time-domain method are used to verify and analyze the characteristics of the proposed THz wave switch. Numerical simulation results show that the THz wave switch has a high extinction ratio of 29.9 dB.     

Optical bandwidth in coupling: the multicore photonic switch

In the present study, the bandwidth of a photonic switch described previously [Appl. Opt. 37,2296 (1998); 38, 3239 (1999)] is evaluated. First the optical bandwidth is evaluated for coupling between two fiber-core waveguides, in which the cores are embedded within the same cladding. Then the coupling bandwidth is determined for a fiber-core-to-slab-core waveguide, in which the cores are embedded within the same cladding. These bandwidths are then compared and contrasted with the bandwidths of the photonic switch, which consists of two fiber cores and a control waveguide. Two configurations of the photonic switch are considered: one in which the control waveguide is a fiber core and one in which the control waveguide is a slab core. For the photonic switch, the bandwidth characteristics are more complicated than for the coupled pairs, and these characteristics are discussed in detail.     

An Optoelectronic Switch for Low-Level Analog Applications

This paper discusses characteristics and applications of an analog switch based upon the back-to-back connection of two light-emitter/phototransistor assemblies, with an original method of zeroing the offset voltage. The resulting device is thoroughly analyzed, and it is shown how this solid-state switch is comparable in accuracy with electromechanical relays, but it has much higher repetition-rate capabilities. Two applications are then introduced, namely an analog commutator and a low-level multiplexer, where the performances of the switch find their best exploitation.     

Integrated liquid crystal optical switch based on double teeth-shaped structure at telecom wavelengths

The characteristics of a double teeth-shaped plasmonic optical switch are analyzed. Based on the metal–insulator–metal waveguide consisting of double rectangular teeth, a nanoscale liquid crystal optical switch is proposed and numerically simulated by using the finite difference time domain method with a perfectly matched layer absorbing boundary condition. It is found that the double teeth-shaped structure filled with liquid crystal can realize the function of a switch. The modulation depth of the double teeth-shaped structure is larger than 50?dB.     

Advances in opening switch technology at IAP research

The author describes some advances in opening switch technology and their demonstration in the megampere advanced switch technology (MAST) hardware. After describing the MAST concept, he examines the efficiency, weight, and life characteristics of the switch. He concludes that the MAST switch demonstrates the feasibility of large-bore rapid-fire railgun systems based on inductive energy storage     

Replicate/transfer bubble switch

A replicate/transfer switch compatible with the gap tolerant structure has been developed. The switch characteristics are superior to that of the existing switches both at the the 8-μm and 16-μm periods. The switch offers the advantages of good bias and phase margins, ease of fabrication, and reduced drive field requirements. In the 8-μm version the device requires a substantially lower drive field than the pickax design by virtue of reduced bubble-bubble interaction in the minor loops.     

Comparative analysis of chopper voltage regulators with LC filter

The chopper voltage regulators using a diode and an LC filter for output rectification and filtering are widely used in dc-to-dc conversion. Three possible configurations are 1) a series connection of the filter choke and switch with the load, 2) a series connection of the choke and the parallel connection of the switch with the load, and 3) a series connection of a chopper and the parallel connection of a choke with the load. Static characteristics of the regulators vary considerably among the aforementioned circuits. The output-to-input voltage ratios and the output characteristics of the circuits listed above are defined in the continuous and discontinuous current domains. An estimate and a comparison of the regulator performances are given.     

开关特性测试仪校准装置的速度发生器设计

在对开关特性测试仪各速度参量进行校准时,需要有一个能够满足校准需要的速度发生装置。本文介绍了一种在高压开关特性测试仪校准时提供速度信号的速度发生器的总体设计方案,详细讨论了其设计过程。该速度发生器应用STM32F407作为主控芯片;设计了一套提供真实位移过程的位移机构;设计了信号输出电路以输出可自定义脉宽与幅值的脉冲信号。校准时可以根据被校准仪器的需要选用不同的速度信号源,以解决开关特性测试仪速度参数校准的速度源问题。     

飞机驾驶舱话音记录器中开关声的三尺度小波分析

国内目前主要采用基于计算机音频原理的译码系统对飞机驾驶舱话音记录器记录的舱音信号进行“辨听”分析,这种舱音分析方法存在不易获得准确的舱音信号特征的缺点。根据这一问题,针对某一真实舱音中的瞬态开关声信号,提出了利用一维离散小波函数进行三尺度分解小波方法,得到了基于传统“辨听”方法得不到的、更多、更准确的舱音声频特征,为识别分析瞬态、非平稳飞机舱音信号提供了一种较好的参考依据。     

气隙式热开关的特性研究及压力调节

论述了气隙式热开关的原理，结构形式及参数特性，讨论了它的结构尺寸对性能参数的影响。给出了导热管的直径，长度，壁厚与导通热导之间的关系曲线以及气体压强，外壳厚度与关断热导之间的关系曲线。建立了气隙式热开关的数学模型，求出了导通热流的瞬态响应特性，并给出了特性曲线有压力调节系统图。     

Study on the new control scheme of class-E inverter for IH-jar application with clamped voltage characteristics using pulse frequency modulation

A new control scheme of Class-E inverter for induction heating jar applications with clamped voltage characteristics using pulse frequency modulation (PFM) is introduced. To reduce the voltage stress of a switch, the proposed PFM control scheme does not need any auxiliary circuit. It can decrease the voltage stress of a switch through the modulation of switching frequency. The Class-E inverter using the proposed control scheme has the advantages of not only the same output power when it is compared with an active clamped class-E (ACCE) inverter, but also zero-voltage-switching, which are characteristics of conventional Class-E and ACCE inverter. The control principles of the proposed method are explained in detail and its validity is verified through experimental results     

A Guided Wave Approach to Defect Detection in Switch Rail

An approach to detect switch rail defect based on ultrasonic guided wave technology is studied. Eight typical cross-sections are chosen from the switch rail, and each cross-section's theoretical dispersion curves and wave structures are derived using the semianalytical finite-element method. The dispersion curve of eight sections has 262 modes at 60 kHz. Based on k-means clustering analysis algorithm, 25 kinds of classification results are obtained from 262 modes. According to the mean and variance of energy, an optimal set of modes with uniform amplitude over the entire section of the switch rail is selected. The optimal excitation point is determined based on the vibration energy. The defect echo signal is obtained by excitation of these guided wave modes. Field experiment results show that by comparing the sum of the differences between the collected and basic data and setting a certain threshold, the internal defect detection of the switch guide rail can be realized. The research results herein are valuable for analyzing the dispersion characteristics and realizing the nondestructive testing of the variable cross-section waveguide.     

新型控制与保护开关闭合过程动态特性探究

基于KB0系列产品的结构,以其动态数学模型为理论基础,设计一套基于单片机和高速图像处理技术的新型控制与保护开关动态测试系统。该系统可测试保护开关的铁芯及触头的位移,并在空载条件下验证了位移测试的准确性。开展了新型控制与保护开关闭合过程的动态特性研究,在不同的线圈工作电压、工作频率和合闸相角工况下,分别测试开关的闭合动作时间。研究了新型控制与保护开关闭合过程产生的触头弹跳现象,分析了一次弹跳和二次弹跳产生的原因,探究其与铁芯和触头闭合末速度的内在联系机理;通过试验结果的数据统计与图表分析,综合考虑动作时间、触头弹跳、铁芯末速度和触头末速度等特性参数,得出最佳合闸相角在30°左右。     

Effect of spectral correlations on spectral switches in the diffraction of partially coherent light

The subject is the spectral characteristics of partially coherent light whose spectral degree of coherence satisfies or violates the scaling law in diffraction by a circular aperture. Three kinds of spectral correlations of the incident light are considered. It is shown that no matter whether the partially coherent light satisfies or violates the scaling law, a spectral switch defined as a rapid transition of spectral shifts is always found in the diffraction field. Different spectral correlations of the incident field in the aperture result in different points at which the spectral switch occurs. With an increment in the correlations, the position at which the spectral switch takes place moves toward the point at which the phase of the center frequency component omega0 becomes singular for illumination by spatially fully coherent light. For light that satisfies the scaling law, the spectral switch is attributed to the diffraction-induced spectral changes; for partially coherent light that violates the scaling law, the spectral switch is attributed to both the diffraction-induced spectral changes and the correlation-induced spectral changes.     

Photonic highway switches based on ring resonators used as frequency-selective components

A new concept for a highway switch, which can be used to connect different optical wavelength division multiplexing data highways for data exchange, is proposed and the system relevant properties are outlined. For the required add-drop filter elements we used ring resonators. Typical characteristics of channel bandwidth, channel spacing, free spectral range, amplification, and cross-talk behavior of a highway switch with double-cavity ring resonators are basically examined and to some extent compared with solutions that were obtained with standard single-ring resonators. A signal flow chart transformation for evaluating filter transfer functions is presented.     

Study of scattering parameters of RFMEMS shunt switch with high-K dielectrics

This paper discussed about the effect of using high-k materials on scattering parameters of RFMEMS shunt switch. The effect of variation of dielectric constant (k: 3–70) of the dielectric layer of thickness 0.16 µm was studied first. In the upstate, no noticeable change is observed in insertion loss and return loss due to the variation of dielectric constants. In the down-state, both the isolation and return loss are found to be strongly dependent on the dielectric constants of the dielectric layer. Resonant frequency of the switch is decreasing exponentially with the increasing dielectric constant. In order to get resonant frequency of 35 GHz, optimum dielectric layer thicknesses for each dielectric constant are found by parametric analysis of the switch structure. With the optimum dielectric layer thicknesses, all the isolation and return loss behavior are found to be almost identical. However, now the up-state characteristics of the switch are found to be affected. Thus for Ka band applications, the insulating layer with dielectric constant 20–30, with corresponding layer thickness 0.4–0.6 μm, may be suitable for the RFMEMS switch applications. This will lead to return loss 相似文献   

基于CPCIE的高速数据交换中心的设计

针对高速图像处理的需求,本文设计实现了一种混合结构的CPCIE交换板.根据高速串行通信的电气特性及CPCIE系统规范要求,将PCIE链路信号和高速串行图像信号合成一组,按照CPCIE交换板信号的拓扑关系,传到各个下游槽位.在标准的CPCIE机箱中,本系统单板实现了PCI Express系统扩展功能和高速光纤图像的动态交...     

All-optical switching in Pharaonis phoborhodopsin protein molecules

Low-power all-optical switching with pharaonis phoborhodopsin (ppR) protein is demonstrated based on nonlinear excited-state absorption at different wavelengths. A modulating pulsed 532-nm laser beam is shown to switch the transmission of a continuous-wave signal light beam at: 1) 390 nm; 2) 500 nm; 3) 560 nm; and 4) 600 nm, respectively. Simulations based on the rate equation approach considering all seven states in the ppR photocycle are in good agreement with experimental results. It is shown that the switching characteristics at 560 and 600 nm, respectively, can exhibit negative to positive switching. The switching characteristics at 500 nm can be inverted by increasing the signal beam intensity. The profile of switched signal beam is also sensitive to the modulating pulse frequency and signal beam intensity and wavelength. The switching characteristics are also shown to be sensitive to the lifetimes of$mmb pbf pR_bf M$and$mmb pbf pR_bf O$intermediates. The results show the applicability of ppR as a low-power wavelength tunable all-optical switch.