单相五电平逆变器3次谐波自消除SHMPAM

为提升低开关频率单相五电平电压源型逆变器的输出电能质量,设计了一种改进的特定谐波缓解脉冲幅值调制(SHMPAM)策略.为单相五电平级联H桥逆变器的两个开关角建立了约束条件,从而推导出谐波幅值表达式,达到使3倍频谐波自消除的目标,同时还可以降低5次和7次谐波含量.利用一台单相五电平级联H桥逆变器样机开展了实验测试,结果表明新调制算法具有理想的3倍频谐波自消除能力,可作为单相多电平逆变器带线性和非线性负载的优化配置方案.     

配电变压器低压隔离开关柜内母线短路监测研究

开关柜的故障会造成整个电力系统的不稳定,通过监控开关柜内的母线短路情况,可以有效降低故障的发生概率.采用红外测温的方式,对开关柜内的母线进行检测,在不影响系统稳定的前提下,提高了温度测量的准确性.采用LSTM算法结合小波变换的算法,在母线短路的判断上综合考虑了历史数据的影响,提高了判断的精准度.通过试验对算法进行验证,结果证明了方法的优越性.     

遗传算法优化BP神经网络的非接触式血压估计方法

血压是人体重要的生理参数,能够反应心脏泵血功能、外周血管阻力、血容,对其进行非接触连续测量在日常生活和诸多应用场合中具有很重要的意义。从面部视频中获取相关脉搏波信号,然后提取信号中与血压相关性高的特征参数,从而利用这些参数建立血压估计的神经网络模型,并采用遗传算法对其进行优化。通过验证得出遗传算法优化BP神经网络(GA-BP)模型估计能力和拟合精度明显提高,且其估计结果满足相应血压测量标准并能实现血压非接触连续估计,其收缩压估计准确率为93.1%,舒张压估计准确率为96.6%。故通过脉搏波特征参数建立GA-BP模型是一种有效非接触式血压估计方法。     

数控焊接变位机示教再现控制系统

叙述了数控焊接变位机示教再现控制系统的实现过程。利用工业控制计算机和单片机实现了示教盒、操纵杆和计算机键盘等三种示教装置，同时设计了一套包括程序控制指令、轨迹描述指令和I／O通讯指夸的数控焊接变位机控制指令系统。变位机工作时首先通过示教装置完成所有焊接位置的示教并存储各示教点的坐标。然后通过指令系统描述各示教点之问的运动关系和运动顺序，并通过指令控制I/O通讯接口协调变位机与自动焊设备或焊接机器人的配合，从而实现复杂焊件的变位和焊接。     

喷射成形1.8C-1.6Al超高碳钢快速凝固组织研究

铸造1．8C-1．6Al超高碳钢(UHCS)由于冷速较低，晶粒粗大，珠光体片间距也较大，品界形成了粗大的碳化物网络，同时合金元素产生偏析，品内生成了大块的合金渗碳体，使得它在室温下为脆性，机加工性能极差。喷射成形1．8C—1．6Al超高碳钢则利用喷射成形工艺冷却速度大的特点细化了晶粒，减小了珠光体的片间距，提高了硬度与强度，同时降低了元素偏析程度。同时发现：在铸态1．8C-1．6Al超高碳钢中和在喷射成形1．8C-1．6Al超高碳钢中Al在晶内的分布情况正好相反，由反偏析转变为正偏析。     

Improvement of SiC_p Reinforced Cast AluminiumComposites by the ROC Method

ＩｍｐｒｏｖｅｍｅｎｔｏｆＳｉＣ＿ｐＲｅｉｎｆｏｒｃｅｄＣａｓｔＡｌｕｍｉｎｉｕｍＣｏｍｐｏｓｉｔｅｓｂｙｔｈｅＲＯＣＭｅｔｈｏｄＺｈｅｎｇＱｉｆｅｉ，ＸｉｅＳｈｕｉｓｈｅｎｇ，ＹｕａｎＧｕａｎｓｅｎ，ＳｈｉＬｉｋａｉ（郑弃非）（谢水生）（袁冠森）（...     

用稀土钇提高离子镀TiN膜层与基体结合力的研究

研究了不同含量稀土钇对离子镀ＴｉＮ膜与基体结合力的影响，结果表明，加入稀土钇后，大大提高ＴｉＮ膜与基体的结合力，并使膜层内ＴｉＮ相增加，此外，稀土钇能明显提高镀膜过程中钛料蒸发率，在相同镀膜内，能使ＴｉＮ膜层加厚。     

富钛BaO-TiO2(Ti/Ba=4～4.5)系微波介质陶瓷

采用固相反应法制备了富钛BaTi4+xO9+2x(x=0.0-0.50)微波介质陶瓷,探讨了TiO2含量以及烧结温度对物相组成和介电性能的影响.在1300～1350 ℃烧结BaTi4+xO9+2x陶瓷即可达到约98%的相对密度.当x≤0.28时,BaTi4+xO9+2x陶瓷为BaTi4O9单相.随TiO2含量的增加,BaTi4+xO9+2x陶瓷从BaTi4O9单相逐渐转变成以BaTi4O9为主相,同时出现TiO2和Ba2Ti9O20相,并且随烧结温度提高,TiO2含量较多的试样中出现更多的Ba2Ti9O20相.随TiO2含量的增加介电常数逐渐增大,而Qf值呈下降趋势.Qf值从x=0.0时的约40 000 GHz逐渐降低至x=0.50时的15 000 GHz.     

Resistance of Mo-bearing stainless steels and Mo-bearing stainless-steel coating to naphthenic acid corrosion and erosion-corrosion

Naphthenic acid corrosion (NAC) and erosion-corrosion (NAEC) behavior of Mo-bearing (0-7.0 wt.%) stainless steels have been investigated in laboratory to evaluate the essential role of Mo on their NAC and NAEC resistance. The NAC and NAEC resistance of a high-velocity-oxygen-fuel (HVOF) thermal sprayed Mo-bearing stainless-steel coating was also investigated in both laboratory and an oil refinery. It was found that increasing the Mo content remarkably enhanced the NAC and NAEC resistance of stainless steels. The Mo-rich areas or phases in the steels played an importance role in resisting the NAEC. The HVOF coating showed excellent NAC and NAEC resistance in laboratory tests. The 700-day field test in an oil refinery revealed that the coating can effectively prevent the carbon-steel substrate from erosion-corrosion during long-term exposure in oil-refining environment. The corresponding NAC and NAEC mechanisms of the stainless steels and the beneficial role of Mo were discussed by taking account of inherent susceptibility of metal elements to corrosion, possible effects of Mo on surface films, and Mo-induced change in microstructure and microhardness.     

Numerical simulation of gas metal arc welding temperature field

The infrared camera is used to investigate the temperature field of gas metal arc welding.The results show that the temperature distribution of weld pool and adjacent area appears cone shape.A new heat source model combined by Gaussian distribution heat source of the arc and conical distribution heat source of the droplet is set up based on the experimental results, and with the combined boundary conditions,the temperature field of gas metal arc welding is simulated using finite element method.According to the comparison between the results of experiment and simulation in temperature field shows that the new combined heat source model is more accurate and effective than the Gauss heat source model.