应用于磁光开关的纳秒脉冲发生器设计

探讨了一种可用于磁光开关的基于雪崩晶体管的纳秒脉冲发生器,对其电路及雪崩晶体管的工作原理进行了具体分析,并对纳秒脉冲发生器电路进行计算机仿真和实验验证.测试结果表明:这种纳秒脉冲发生器能够输出上升沿2～5ns、脉宽6～20ns和上升幅度30～100V的脉冲,很适合用于全光通信网络中的磁光开关.     

用于纳秒级窄脉冲工作的大功率半导体激光器模块

介绍了一种将脉冲半导体激光器发射应用系统中脉冲整形电路、驱动电路、激光器保护电路、激光器集成封装成一个激光器模块的方式。当激光器工作于纳秒级窄脉冲状态下时,激光器封装引腿所产生电抗会使得耦合进激光器的脉冲波形劣化,能量损失。为得到上升时间短,波形半宽窄,峰值功率大的光输出,改进激光器管芯的结构并采用混合光电子集成的方式将驱动电路和激光器管芯封装在一个模块内,使得窄脉冲电信号高效地耦合进半导体管芯。分析验证了改进后的激光器模块的各项输出参数均得到改善。同等条件下,改进后的模块在光脉冲宽度为4.5ns时,峰值功率比单独封装激光器提高6倍多。此激光器模块可以得到宽度7ns左右,峰值光功率176W的光脉冲输出。测试了该模块在脉冲宽度为7ns左右的U-P曲线。     

新型纳秒级探地雷达脉冲源设计

针对超宽带探地雷达脉冲源的要求,提出并验证了一种利用FPGA触发来合成彼此有任意延迟的窄脉冲波形合成方法.研究和实际设计了一种提高脉冲源性能的新型宽范围输入输出的线性直流电源,并利用此电源制成了适用于多种雪崩管为核心的宽范围纳秒级脉冲源,给出了脉冲源各个单元的设计、及雪崩三极管的筛选及老化处理方法.在50 Ω负载上得到了脉宽在2 ～ 50 ns、幅度在20～180 V的多种超宽带窄脉冲,并对多种雪崩管的雪崩性能进行了对比,给出了集电极充电电容与脉冲幅度和宽度的关系.     

基于FPGA的脉冲信号发生器设计

基于FPGA并运用DDS技术的相关理论,通过模块化设计,使标准脉冲信号发生器达到较高的性能指标,能够产生1~100kHz线性可调的脉冲,脉冲分辨率达100Hz,上升沿及下降沿为2.5ns,脉冲宽度从200ns~5μs可调,脉宽分辨率50ns,满足集成电路的脉冲驱动要求。     

基于雪崩三极管的高压方波脉冲发生器研究

测试与测量领域对快前沿脉冲发生器的需求越来越高,特别是要求产生高重复频率和高电压的快脉冲。本文使用串行雪崩三极管开发了一种低成本的便携式高重复频率高压纳秒方波脉冲发生器。通过优化设计串行晶体管电路和PCB,有效降低杂散电感和电压反射,使输出方波脉冲获得2.5ns的上升时间,幅度输出脉冲2.5kV,脉冲宽度为12.5ns。高压脉冲发生器在10kHz的高重复频率工作模式下,脉冲时间抖动小于100ps。     

高频窄脉宽微细电火花加工用微能脉冲电源的研究

分析了微能脉冲电源的实现途径。采用开关管推挽工作原理设计出了具有高频窄脉宽的微细电火花加工用微能脉冲电源。并对具有陡上升沿和下降沿的高频脉冲电源工作时产生的电磁振荡现象的原因进行了深入的研究。在此基础上设计出的脉冲电源最小脉宽可达100ns，较好地满足了微细电火花加工的需要。     

智能变电站中OTDR系统激光脉冲电路的设计及应用

针对智能变电站的光纤通信延时测量问题,对智能变电站中OTDR的工作原理和光源器件进行了研究,分析了激光脉冲频率和脉宽对系统性能的影响。根据激光二极管的发光机理与特点设计出了一套基于STM32控制单元的适合智能变电站中OTDR工作的激光驱动电路,重点分析了驱动电路中的调制电流,考虑了驱动电路对激光器的保护,并利用所设计的激光驱动电路搭建了简易OTDR观察光纤的损耗特性。研究结果表明,该电路可扩大激光脉冲频率和脉宽的调整范围,实现激光脉冲宽度最小可达300 ns,脉冲频率最大为50 KHz,激光发射功率为3 MW;通过实验,验证了光在光纤中的衰减特性,证实了该电路能满足实际智能变电站中OTDR工作所需,具有一定的参考价值。     

脉冲电化学光整加工电源的设计

根据脉冲电化学光整加工PECM工艺需要大功率、窄脉宽、高频率电源的这一特殊要求,以绝缘栅极双极晶体管IGBT为主控元件设计了一种高频脉冲加工电源.重点介绍了其主电路以及IGBT的驱动保护电路的设计方法.实验结果表明,这种高频脉冲电源在高频、窄脉宽、大功率等方面均能满足该工艺的要求.     

基于FPGA平台的窄脉冲大电流LED频闪光源设计

针对高频信号的特点,利用FPGA,设计了一种窄脉宽、大电流的LED频闪光源。通过FPGA平台上的编程控制,实现了满足频闪光源控制时序要求的窄脉宽信号。最后,将窄脉宽信号进行电流放大,获得脉宽为ns级,电流最大可达30A的LED驱动脉冲信号。     

微型大电流窄脉宽半导体激光器电源的研究

针对激光探测和目标识别设计了微型大电流窄脉宽半导体激光器电源 ,并对其中电源电路的脉宽、峰值电流、上升时间及小体积进行了分析。根据驱动电路的需要设计了 DC- DC变换器     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.