变压器内部故障在线检测方法仿真及误差分析

为研究变压器内部故障在线检测方法的有效性及抗干扰性,搭建实际变压器的非线性三维有限元模型.对变压器常见几种类型的内部故障进行详细的结构仿真,通过"场-路耦合法"构建各类型故障的ΔV-I1轨迹.同时,通过对正常绕组的测量信号设置一定的误差,构建了考虑测量误差时的误差轨迹.在此基础上,将正常时的标准轨迹、误差轨迹和各种类型的故障轨迹进行对比分析,通过对ΔV-I1轨迹特征差异的定性分析与定量计算,验证该方法在实际应用中的有效性,总结判断各类型故障的规则,同时针对测量误差所造成的干扰提出了建议.     

广东早期砖薄壳结构的建构技术研究——1957-1958年新会的"逼拱"实验

揭示1957-1958年华南工学院土木系薄壳结构研究小组在新会的砖薄壳结构实验图景.以田野调查、文献分析、三维图示、超声波检测等方法发现、确认此研究小组在新会的6处薄壳建筑及其遗存情况.它们是广东地区推广砖薄壳建筑的起点,其中的回旋砖薄壳实验是从结构角度探索中国建筑民族形式的重要案例,弥补国内结构工程史学研究的薄弱点,也是共和国早期节约"三材"约束下的薄壳建造技术自主创新设计的重要内容.     

基于SCAE⁃ACGAN的直升机行星齿轮裂纹故障诊断

直升机行星传动轮系结构复杂、工况多变,其振动信号受工况影响大,在故障样本较少的情况下导致行星齿轮箱故障诊断准确率不高,早期故障诊断困难。针对上述问题,提出将堆栈收缩自动编码网络(stacked contractive autoencoder,简称SCAE)与辅助分类生成式对抗网络(auxiliary classifier generative adversarial networks,简称ACGAN)相结合的SCAE-ACGAN故障诊断方法。ACGAN的生成器产生与真实样本具有类似分布的生成样本,扩展训练样本集,并与真实样本一起输入至判别器进行训练。ACGAN采用SCAE作为判别器,利用SCAE良好的抗数据波动能力,从扩展样本集中挖掘出有效的深度特征,并实现样本的真伪与类别的判定。ACGAN的判别器和生成器在对抗学习训练机制下交替优化,提高方法的样本生成质量与故障判定能力。将SCAE-ACGAN应用于直升机行星轮裂纹故障诊断,结果表明,SCAE-ACGAN的故障诊断性能好,在样本数量少与工况变化情况下具有较好的健壮性和适应性。     

用于疏浚工程泥浆密度测量的电阻层析成像技术

江河湖海疏浚工程对于拓展和保障航运安全、促进生态恢复、维护/改善远海岛礁环境具有不可或缺的作用.目前,在绞吸和耙吸疏浚船上,多采用射线密度计及电磁流量计对输泥密度、产量等进行在线计量,并作为实现疏浚系统自动控制的重要参量.由于射线密度计潜在的人员健康、公共安全和环保风险,在一些国家和地区已建立了放射源的有序退出机制.电阻层析成像使用安装于管壁的电极阵列获得管道内流体的电导率分布,进而推导出管道内的泥浆密度,具有无辐射、全场测量及实时可视化的优点.电阻层析成像测量系统经过特殊设计,可适应从内陆淡水到海水的巨大电导率变化.初步测试表明,电阻层析成像测量数据与射线密度计具有良好一致性,具备了作为在线泥浆密度测量的可行性.此外,ERT可提供实时的流动成像,对于提高对疏浚管道监测能力和降低堵管概率具有重要意义.     

回字形环山地建筑结构设计

中央美院青岛创业中心项目为角部重叠的回字形山地建筑,采用了框架-剪力墙结构体系.主体建筑结构总高度为54m,坐落在三个台地上,每两个相邻台地高差10m左右.掉层处采用"掉层脱开式且有拉梁"的方式进行结构布置.结合山地建筑结构的基本概念和受力特点,介绍了本项目的结构处理方式和设计难点,采用PKPM,MIDAS Building,SAUSAGE软件对结构进行了弹性反应谱法分析、弹性时程分析、动力弹塑性时程分析和抗震性能设计,同时针对各种不利因素采取了相应的加强措施,确保了结构安全.     

Robust Control of Permanent Magnet Synchronous Motors

In this paper, permanent magnet synchronous motors (PMSMs) are investigated. According to the feature of PMSMs, a novel state equation of PMSMs is obtained by choosing suitable state variables. Based on the state equation, robust controllers are designed via interval matrix and PI control idea. In terms of bilinear matrix inequations, sufficient conditions for the existence of the robust controller are derived. In order to reduce the conservation and the dependence on parameter, the control inputs of PMSMs are divided into two parts, a feedforward control input and a feedback control input, and relevant sufficient conditions for the existence of the controller are obtained. Because of the suitable choice of state variables, the proposed control strategies can cope with the load uncertainty and have robustness for disturbance. Finally, simulations are carried out via Matlab/Simulink soft to verify the effectiveness of the proposed control strategies. The performance of the proposed control strategies are demonstrated by the simulation results.      

High‐performance thermosets with tailored properties derived from methacrylated eugenol and epoxy‐based vinyl ester

A renewable chemical, eugenol, is methacrylated to produce methacrylated eugenol (ME) employing the Steglich esterification reaction without any solvent. The resulting ME is used as a low‐viscosity co‐monomer to replace styrene in a commercial epoxy‐based vinyl ester resin (VE). The volatility and viscosity of ME and styrene are compared. The effect of ME loading and temperature on the viscosity of the VE–ME resin is investigated. Moreover, the thermomechanical properties, curing extent and thermal stability of the fully cured VE–ME thermosets are systematically examined. The results indicate that ME is a monomer with low volatility and low viscosity, and therefore the incorporation of ME monomer in VE resins allows significant reduction of viscosity. Moreover, the viscosity of the VE–ME resin can be tailored by adjusting the ME loadings and processing temperature to meet commercial liquid molding technology requirements. The glass transition temperatures of VE–ME thermosets range from 139 to 199 °C. In addition, more than 95% of the monomer is incorporated and fixed in the crosslinked network structure of VE–ME thermosets. Overall, the developed ME monomer exhibits promising potential for replacing styrene as an effective low‐viscosity co‐monomer. The VE–ME resins show great advantages for use in polymer matrices for high‐performance fiber‐reinforced composites. This work is of great significance to the vinyl ester industry by providing detailed experimental support. © 2018 Society of Chemical Industry