LD端面泵浦的1.57μm内腔式OPO

1.57 μm波长激光为人眼安全波长激光。将KTP晶体置于一个由LD端面泵浦、声光调Q的Nd:YVO4晶体双凹谐振腔内,利用KTP表面镀膜建立了内腔式OPO,实现了重复率在5～40 kHz范围内1.57 μm脉冲激光的稳定输出。实验结果表明,激光的阈值将随声光调Q器重复率的增加而升高,重复率为5 kHz时得到最低阈值1.52 W。重复率为15 kHz、泵浦功率为3.7 W时,输出光平均功率为305 mW,脉冲宽度50 ns,峰值功率400 W。     

激光-MIG复合焊接工艺参数对焊缝形状的影响

本文以激光-MIG复合焊焊接工艺参数对焊缝形状的影响为出发点,对复合焊进行了初步的研究。实验研究了激光与电弧之间的距离、离焦量、焊接速度、送丝速度、电弧的类型以及激光的倾斜角度等工艺参数对复合焊焊缝的熔深熔宽的影响。实验表明,激光与电弧之间的距离(DL A)对复合焊的熔深影响较大,在DL A为2mm时,熔深达到最大。离焦量主要是通过影响能量密度来影响熔深和熔宽,在离焦量为+2mm时熔深达到最大,不同于单独激光焊负离焦时熔深最大。焊接速度有一个合适的范围,在这个范围内随着焊接速度的增加,熔深熔宽减少。送丝速度对复合焊的焊缝形状影响最大,送丝丝度较小时焊缝形状类似于单独激光焊;送丝速度过大电弧等离子体屏蔽激光,焊缝形状类似于MIG。激光的倾斜角度对复合焊的焊缝熔深熔宽也有一定的影响,当激光的倾斜角度为10oC时,熔深达到最大熔宽最小。     

太阳电池掩膜窗口宽度与电极宽度比对光生电流性能的影响

提出了一个有效工艺设计参数——选择性扩散掩膜窗口宽度与电极宽度的比值T。研究结果表明,对不同的衬底浓度和掺杂浓度均存在一个最佳T值可以获得最大短路电流。选择性扩散浓度为1×1018~1×10-3cm-3时,其最佳T值为1;选择性扩散浓度为1×10-3cm-3时,最佳T值小于0.5。电极宽度的增加减小了光生电流,但对最佳T值影响较小。选择性掺杂浓度的增加会使得最佳T值减小。     

脉宽调制转换器的电压跟踪性能仿真

给出了脉宽调制转换器的数学模型,介绍了脉宽调制矢量脉宽调制算法,设计了脉宽调制转换器控制系统,实现了良好的电压跟踪性能。使用Matlab/Simulink对其进行了建立仿真模型,仿真结果验证了良好的电压跟踪性能。     

一种可展宽频带的U型切角天线

设计了一种可展宽频带的U型切角天线。将U型贴片天线进行切角处理,改变天线的结构与电流路径,可以有效展宽天线频带,并使其具有良好的阻抗匹配特性。采用HFSS15.0软件对天线模型进行仿真分析,对切角的长度、宽度进行优化,给出了天线的反射系数S11与U型槽尺寸和切角尺寸间的关系。结果表明,优化后的U型切角天线覆盖了整个2.4~2.5 GHz频带范围,电压驻波比VSWR≤2的相对带宽为19%,天线增益达到7 dB,波束宽度为83o左右。     

Dynamically scalable dual-core pipelined processor

This article proposes design and architecture of a dynamically scalable dual-core pipelined processor. Methodology of the design is the core fusion of two processors where two independent cores can dynamically morph into a larger processing unit, or they can be used as distinct processing elements to achieve high sequential performance and high parallel performance. Processor provides two execution modes. Mode1 is multiprogramming mode for execution of streams of instruction of lower data width, i.e., each core can perform 16-bit operations individually. Performance is improved in this mode due to the parallel execution of instructions in both the cores at the cost of area. In mode2, both the processing cores are coupled and behave like single, high data width processing unit, i.e., can perform 32-bit operation. Additional core-to-core communication is needed to realise this mode. The mode can switch dynamically; therefore, this processor can provide multifunction with single design. Design and verification of processor has been done successfully using Verilog on Xilinx 14.1 platform. The processor is verified in both simulation and synthesis with the help of test programs. This design aimed to be implemented on Xilinx Spartan 3E XC3S500E FPGA.     

Transmission of 160-Gb/s Modified Manchester modulation over WDM system

The paper examines the performance of Modified Manchester (MM) modulation scheme over wavelength division multiplexing (WDM) in high-speed optical communication links. The MM as a new modulation technique has a narrow spectral width compared to conventional Manchester coding, which allows its implementation in WDM systems beneficial. In this study, the performance characteristics of MM and conventional Manchester modulation formats are assessed in WDM system at 10 Gb/s bitrate for each channel, for the least allowable channel spacing as well as tolerance to chromatic dispersion (CD). It is revealed from the results of simulation that MM performs meaningfully well in comparison with conventional Manchester in terms of tolerance against narrow optical filtering, spectral efficiency, which is improved by 32% and CD tolerance, which is improved by +100 ps/nm. Sixteen wavelength channels (16 × 10 Gb/s) are modulated to provide 160 Gb/s data capacity, which was transmitted successfully over 224 km standard single mode fibre (SSMF) using MM while the conventional Manchester only covered about 157 km.     

雷达发射机阳极电源的原理分析

地波雷达是从事海洋环境研究以及电波传播相关理论探索的关键设备,设备安装和使用条件恶劣,并且处于连续运行状态,如何通过良好的维护来保证地波雷达的可靠运行,尤其是雷达的大功率发射设备,已成为使用和保障部门的重要课题。文中主要介绍了一种地波雷达微波管发射机的电源系统的组成,重点分析了阳极高压开关电源的电路原理,提出了变形脉宽调制控制的概念。 经过仿真和稳态工作波形分解,得出了该电源高可靠性和高效率的结论,给出了电源的主要工作电流、电压波形,希望为设备的使用和维护提供参考。     

未焊透焊缝疲劳强度分析及工程应用

本文针对工程中焊接结构大量采用单面焊对接焊缝这一事实,对含有未焊透缺陷的单面焊对接焊缝试件进行了疲劳试验,得到了疲劳强度曲线。由于单面焊对接焊缝中的未焊透缺陷位于试件根部表面,在缺陷率相同的条件下,其疲劳强度损失比双面焊未焊透焊缝更严重。试件母材为低碳钢钢板(σ_b≥450MPa)。本试验结果应用于钢瓶焊缝的缺陷容限分析,为制订我国民用在役液化石油气钢瓶判废标准提供了实验依据。     

迭代学习控制在GTAW焊接过程中的应用研究

针对相同工件的批量焊接,并且焊接轨迹相同的情况下,焊接过程具有极高的重复性。提出了基于迭代学习控制(ILC)的脉冲气体钨极氩弧焊(GTAW)焊接过程跟踪控制方法。根据GTAW焊接的动态过程模型,设计了GTAW焊接过程控制的ILC算法,并对算法的收敛性进行了证明。研究结果表明,ILC可以有效地利用焊接过程中的重复信息,经过60次迭代学习后,焊接系统输出可以较好的达到期望轨迹,并获得较高的控制精度,验证了方法的有效性。与PID控制相比ILC控制器不但可以获得较好的跟踪效果,而且还能有效抑制外部扰动的作用,具有较强的鲁棒性。