一种舰载测量雷达伺服回路分析和设计

波束稳定是舰载测量雷达区别于岸基测量雷达的主要特点和要求,伺服系统需要克服船摇保持波束稳定.在工程设计中,回路参数设计是伺服系统设计的重要环节.详细阐述根据船摇隔离度、回路带宽等指标要求,重点分析位置跟踪回路、船摇稳定跟踪回路的参数设计方法和过程.理论计算和工程实践证明,雷达能较好地克服船摇影响,稳定跟踪快速目标.     

封闭式喷雾冷却系统启动时间

 以蒸馏水为冷却工质,对冷凝器内置的封闭式光滑表面喷雾冷却系统进行了启动时间变化规律的实验研究,结果表明喷雾系统不同模块最优启动顺序为冷凝器、泵和加热器。采取6种不同的启动顺序,启动后加热表面的温度不均匀度均小于0.25 ℃。在最优启动顺序下,研究了冷却水流量、泵高度、加热功率和喷雾流量对启动时间的影响。随冷却水流量和喷雾流量增加启动时间缩短,随泵高度增加启动时间略微增大,随加热功率增大启动时间先增大后减小。启动时间影响程度由大到小的因素依次为喷雾流量、冷却水流量、加热功率及泵相对于加热表面的高度。喷雾工质流量由10 mL/min增大到35 mL/min时,封闭式喷雾系统的启动时间缩短了5 000 s。同样操作条件下,封闭式系统的启动时间比开放式系统延长15%~20%。     

一般情况下两共轴圆线圈间互感系数的简便计算

采用级数展开的方法,得到了一般情况下两共轴圆线圈间互感系数的严格无穷级数表达式,所得结果在除两线圈重合之外的所有情况下均是收敛的.并且在计算过程中利用磁矢势而非磁感应强度求出磁通量,使得该方法较为简便.     

基于点缺陷扩散理论与离散位错动力学耦合的位错攀移模型研究

位错的攀移运动对高温下晶体材料的塑性行为有重要影响,为了能够有效揭示攀移的物理本质及其对塑性行为的作用,本文基于点缺陷扩散理论,通过将体扩散和管扩散机理的共同作用与三维离散位错动力学耦合,建立了适用条件更广的位错攀移模型. 利用此模型我们模拟了单个及多个棱柱型位错环的收缩变形过程,发现影响位错攀移速率的决定因素不是传统理论认为的机械攀移力,而是位错周围(体扩散)及位错段上(管扩散)的空位浓度梯度. 该模型也能够完全重现棱柱型位错环群的粗化过程中不同位错环半径及晶体内平均空位浓度随时间变化的三个阶段. 关键词： 位错攀移 点缺陷扩散理论 位错动力学 棱柱位错环     

非线性光纤环镜在受激布里渊散射慢光级联系统中的可行性研究

基于非线性光纤环镜(NOLM)的脉冲压缩特性,分析了NOLM在基于受激布里渊散射(SBS)慢光级联系统中对延迟脉冲的影响.利用环形结构来模拟多次级联,有效地降低了系统的复杂度,得到了在不同抽运光功率和级联次数下脉冲的延迟输出特性.理论分析表明,NOLM可以有效地抑制SBS慢光级联系统中延迟脉冲的展宽,抽运光功率决定了展宽因子的变化趋势及最终稳定值的大小,展宽因子在级联4次时趋于稳定值,恰当选取抽运光功率可实现脉冲的零展宽延迟;改变抽运光功率和级联次数可以实现延迟量的连续可调,且延迟量理论上不受限制;增大抽 关键词： 慢光 脉冲压缩 非线性光纤环镜 受激布里渊散射     

Synthesis of Multi‐substituted Benzamide Derivatives under Microwave Irradiation Conditions

A facile microwave‐assisted synthesis of N‐[(Z)‐1‐(substituted carbamoyl)‐2‐arylvinyl] benzamide derivatives is accomplished via reactions of 4‐arylmethylene‐2‐phenyloxazol‐5(4H)‐ones with different amines (for example methylamine, cyclopropylamine, para‐toluidine, phenylamine) in ethylene glycol. This protocol broadens the scope of the reaction for the synthesis of N‐benzamide derivatives.     

PV-reduction of sunset topology with auxiliary vector

The Passarino–Veltman (PV) reduction method has proven to be very useful for the computation of general one-loop integrals. However, not much progress has been made when it is applied to higher loops. Recently, we have improved the PV-reduction method by introducing an auxiliary vector. In this paper, we apply our new method to the simplest two-loop integrals, i.e., the sunset topology. We show how to use differential operators to establish algebraic recursion relations for reduction coefficients. Our algorithm can be easily applied to the reduction of integrals with arbitrary high-rank tensor structures. We demonstrate the efficiency of our algorithm by computing the reduction with the total tensor rank up to four.     

All polarization-maintaining Er:fiber-based optical frequency comb for frequency comparison of optical clocks

We demonstrate an optical frequency comb (OFC) based on a turnkey mode-locked laser with a figure-9-shape structure and polarization-maintaining fibers, for the comparison of frequency among optical clocks with wavelengths of 698 nm, 729 nm, 1068 nm, and 1156 nm. We adopt a multi-branch approach in order to produce high power OFC signals at these specific wavelengths, enabling the signal-to-noise ratio of the beatnotes between the OFC and the clock lasers to exceed 30 dB at a resolution bandwidth of 300 kHz. This approach makes the supercontinuum spectra much easier to be generated than a single branch OFC. However, more out-of-loop fibers degrade the long-term frequency instability due to thermal drift. To minimize the thermal drift effect, we set the fiber lengths of different branches to be similar, and we stabilize the temperature as well. The out-of-loop frequency instability of the OFC due to the incoherence of the multi-branch is about 5.5×10^-19 for 4000 s, while the in-loop frequency instability of f_ceo and that of f_beat are 7.5×10^-18 for 1 s and 8.5×10^-18 for 1 s, respectively. The turnkey OFC meets the requirement for the comparison of frequency between the best optical clocks.     

单脉冲雷达导引头角度跟踪环路建模及抗干扰仿真分析

以对单脉冲雷达导引头目标检测跟踪过程建立信号级仿真模型为出发点,介绍了振幅和差式单脉冲雷达导引头角度跟踪环路建模仿真的实现思路,然后结合具体实例对单脉冲雷达导引头的角度跟踪性能进行了仿真试验分析,最后对单脉冲雷达导引头抗自卫式单点源干扰能力进行了总结。     

应用于配电网单相接地在线故障指示器电源

配电网单向接地故障指示器在配电网自动化方面应用广泛,但其在线故障诊断所需的能量不能靠低压侧供给,只能在高压端获取,因此文中设计了特殊的取电电路和控制电路,根据故障指示器各个元器件的需求,此取能电源可以为故障指示器提供5V、-4V和3．2V3路电压,以满足故障指示器信号采集和处理以及无线通信的需要。整机实验结果表明,该取能电源在15—800A的变化范围内,能提供不少于1．5W的功率,可满足故障指示器的需要。