SVC电压控制对提高大型自并励机组运行稳定性作用

针对大型互联电网部分极端工况下自并励机组难于维持机端电压稳定,以及对维持发电机机端电压稳定较重要的自动电压调节器综合放大倍数整定过大时易弱化系统阻尼等问题,提出在机端添加静止无功发生器(staticvar compensator,SVC)的协调控制措施。该措施利用SVC的电压控制及其与自动电压调节器(automatic volt-age regulator,AVR)的协调配合,可以提高多工况下自并励机组的运行稳定性,避免AVR高增益弱化系统阻尼;同时,SVC的电压控制也能有效防止发电机的进相运行。仿真结果表明了该控制措施的良好效果。     

Analysis of inverse synthetic aperture radar imaging in the presence of time-varying plasma sheath

The plasma sheath can induce radar signal modulation, causing not only ineffective target detection, but also defocusing in inverse synthetic aperture radar (ISAR) imaging. In this paper, through establishing radar echo models of the reentry object enveloped with time-varying plasma sheath, we simulated the defocusing of ISAR images in typical environment. Simulation results suggested that the ISAR defocusing is caused by false scatterings, upon which the false scatterings’ formation mechanism and distribution property are analyzed and studied. The range of false scattering correlates with the electron density fluctuation frequency. The combined value of the electron density fluctuation and the pulse repetition frequency jointly determines the Doppler of false scattering. Two measurement metrics including peak signal-to-noise ratio and structural similarity are used to evaluate the influence of ISAR imaging     

Wideband radar cross-section reduction using plasma-based checkerboard metasurface

For stealth technology, in order to overcome the limitations of thin-layer plasma for electromagnetic waves attenuation and further broaden the radar cross-section (RCS) reduction (RCSR) band of the metasurface, the plasma-based checkerboard metasurface composed of plasma and checkerboard metasurface is investigated to achieve better RCSR. We designed a checkerboard metasurface which can achieve abnormal reflection to reduce RCS and whose −10 dB RCSR bandwidth is from 8.1 to 14.5 GHz, the RCSR principle of it lies in the backscattering cancellation, which depends on the phase difference of artificial magnetic conductor (AMC) units. The designed plasma-based checkerboard metasurface is a thin composite structure, including a checkerboard metasurface, a plasma layer, and an air gap which is between them. Full wave simulations confirm that the plasma-based checkerboard metasurface's ‒10 dB RCS reduction bandwidth and RCS reduction amplitude, are both increased under different polarized waves compared with the only single plasma or the only metasurface. We also introduced the reason and mechanism of the interaction between plasma and the checkerboard metasurface to improve the RCSR effect in detail. As plasma-based checkerboard metasurface does not need the plasma to be too thick for plasma stealth, its application in practical scenarios is easier to implement.     

Inverse synthetic aperture radar range profile compensation of plasma-sheath-enveloped reentry object

The scattering points in a plasma sheath characterized with coupled velocities can cause pulse compression mismatching, which results in displacement and energy diffusion in the one-dimension range profile. To solve this problem, we deduce the echo model of the plasma-sheath-enveloped reentry object. By estimating the coupled velocities, we propose a compensation method to correct the defocus of an inverse synthetic aperture radar (ISAR) image in range dimension to improve the quality of the ISAR images. The simulation results suggest that the echoes from different regions of the surface of the reentry object have various coupling velocities, and the higher the coupled velocity, the more serious the displacement and energy diffusion in the range dimension. Our proposed method can correct the range dimension aberration. Two measurement metrics were used to evaluate the improvement of the compensation method.     

磨溪天然气净化厂中水回用可行性探讨

文章对磨溪天然气净化厂外排废水的来源、水量、水质、处理工艺和达标情况进行了研究，探讨了工厂外排废水处理的中水回用的可行性，证明磨溪净化厂中水可用于厂内绿化，既可减少污染物排放，降低能耗，又可增加新鲜水资源，经济和环境效益明显。     

高阶类型化软件体系结构建模和验证及案例

根据权威统计数据，软件测试中发现的70%以上的错误由需求获取或体系结构设计引起.因此，应用软件体系结构在设计阶段的正确性验证非常重要.现有的软件体系结构设计方法不支持需求满足验证，需求满足验证需要其他验证工具的支持.面向主流Web应用软件的体系结构设计及其需求满足验证，提出了一种高阶类型化软件体系结构建模和验证语言（SAML）与软件体系结构建模和验证方法（SAMM）.SAML语言通过定义类型和项的语法及语义，描述软件体系结构中类型和对象的构造，通过定义类型规则及其类型检查算法来判定Γ|-t：T和Γ|-R（T₁，T₂）是否成立.SAMM给出了软件体系结构建模范式，包括构建接口类型M_cls（type interface）、组件M_cmpt（component）、容器M_cont（container）、框M_frm（frame）和框架M_frwk（framework）这5层建模过程，以及生成层内与层间类型之间关系对应的类型规则，同时定义了接口类型方法调用图（G_SA）用以刻画软件体系结构设计要求，定义了类型序列及其正确性用以刻画需求期望的性质，并给出了相应的验证算法.设计实现了基于该方法的原型工具系统SAMVS，其中，模型编辑环境支持应用软件的设计过程，验证环境支持设计满足需求的自动化验证.通过一个实际案例，完成了一个较大规模"互联网+"应用软件系统的体系结构建模和验证.     

BGA红外植球技术

BGA(Ball Grid Array)，即球栅阵列封装，是在封装体基板的底部制作阵列焊球作为电路的I/O端与印刷线路板(PCB)互联，广泛应用于各类PCBA中。采用田口方法开展试验设计，对一类球栅阵列封装器件植球方法进行了研究，通过评估焊点推力和焊接界面金属间化合物厚度等参数响应，获得了组装工艺参数对BGA器件植球特征的影响规律。     

Multilevel hierarchical production planning architecture for engineer-to-order enterprises

0　ＩＮＴＲＯＤＵＣＴＩＯＮＥｎｇｉｎｅｅｒ ｔｏ ｏｒｄｅｒ ,ａｎｉｍｐｏｒｔａｎｔｐｒｏｄｕｃｔｉｏｎｔｙｐｅｉｎｌａｒｇｅａｎｄｍｅｄｉｕｍｅｎｔｅｒｐｒｉｓｅｓ ,ｉｓａｔｙｐｉｃａｌｍｏｄｅｄｒｉｖｅｎｂｙｕｓｅｒｗｉｔｈｃｏｍｐｌｅｘｐｒｏｄｕｃｔｉｏｎｐｌａｎｎｉｎｇａｎｄｃｏｎｔｒｏｌ (ＰＰＣｆｏｒｓｈｏｒｔ) [1] .Ｉｎｐｒａｃｔｉｃｅ ,ｔｈａｔＰＰＣｏｆＥＴＯｃａｎｎｏｔｂｅｅｆ ｆｅｃｔｉｖｅｌｙｉｍｐｌｅｍｅｎｔｅｄｏｒｃｏｎｔｒｏｌｌｅｄｆｏｒｔｈｅｒｅａｓｏｎｓｓｕｃｈａｓｌ…     

重力小车的结构设计与功能测试

设计了一款能够利用砝码的重力势能自主绕过固定障碍物完成8字往复运动的重力无碳小车。叙述了该无碳重力小车的能量转换、支撑、行走、转向等结构的设计思路和功能实现的原理。重点介绍了凸轮的设计方法：先借助MATLAB迭代计算出凸轮的形状，然后将计算所得数据导入SolidWorks软件进行建模仿真，验证重力小车的行动轨迹。在仿真轨迹和预设轨迹基本一致的基础上，完成实物制作和实验测试，进一步验证设计的正确性，为无碳能源的利用提供思路和参考。     

7075与ER5356铝合金焊丝用于7075铝合金MIG焊接头性能对比研究

采用MIG焊的方式使用自制7075铝合金焊丝与市面购进的ER5356焊丝进行3mm厚7075铝合金对接焊，对比分析两种焊丝焊接接头的显微组织与力学性能。经过光学显微镜(OM)、X射线衍射(XRD)、扫描电镜(SEM)与能谱仪(EDS)结合室温拉伸与显微硬度测试，结果表明：两种接头焊缝组织均为枝晶网状组织，但由于合金元素含量与热导量增大，7075接头焊缝组织相对细小且枝晶特征更为明显。SEM和XRD检测分析得出，由于焊接时金属流动作用将部分母材合金元素带至焊缝，两者焊缝析出相均主要为η相(MgZn₂)、S相(CuMgAl₂)或T相(AlZnMgCu)，同时存在Al₁₃Fe₄金属化合物。7075焊缝平均硬度为120HV，相较于5356焊缝更为优异；两者拉伸力学性能较为接近，断裂机制相同。