基于GPRS的电力系统远程监控设计与研究

以电力远程监测系统领域现阶段的技术为参考,提出了一种基于GPRS无线通信技术和以ARM为内核的高性能的嵌入式微处理器的电力远程监测系统。首先简述了GPRS无线业务特点及其嵌入式系统技术,然后重点介绍了基于GPRS的电力线路监控系统的组成、原理,给出了硬件原理图,对具体的软硬件设计过程进行了简要的阐述。实践证明GPRS技术非常适用于要求实时性的、大数据量传送的应用场合。     

加厚膜片带通滤波器的仿真设计

随着频率应用的提高,传统的电感膜片耦合波导式带通滤波器已经不能适应机加工的现有能力和精度要求.通过增加膜片的厚度可以降低对机加工能力的要求,同时也易于满足设计精度的要求.本文通过CAD仿真设计,由传统的薄电感膜片带通滤波器设计原理演绎出加厚膜片带通滤波器的设计原理,并且通过对单节电感膜片和多级电感膜片级连滤波器电路特性的分析,得出了它们在滤波器中级联时对电性能贡献的共性.本文采用高频电磁场仿真进行计算,优化具体的电尺寸,给出了具体的设计实例.实测的结果和理论设计仿真的结果一致性较高.这种加厚膜片的滤波器能够扩展到毫米波频段应用,而且易于加工;运用S参数的等效性和高频电磁场仿真软件可以方便、准确地设计出易于加工、性能良好的滤波器件.这种设计方法同样适用于其他微波器件的设计(如电感销钉滤波器等).     

基于D-S证据理论的直流电机故障诊断研究

通过分析直流电机的故障机理,得到在不同信号(如电流、转速、转矩等)中所表现的故障特征,提出了一种神经网络和D-S证据理论的多传感器数据融合技术的直流电机故障诊断方法。利用多源信息间的冗余性和互补性,有效提取故障特征信息,提高了诊断的可靠性和灵敏度。     

750kV电网在甘肃电网中的降损作用分析

750 kV电网已逐渐成为我国西北地区的主力电网,分析了西北地区750 kV电网的发展概况和750 kV线路的电气特性,分析了750 kV线路投运前后甘肃电网网损及网损率、甘肃电网330 kV线损和省际联络线线损,分析结果表明750 kV线路的投运明显降低了甘肃电网损耗。     

有机硅/聚氨酯共聚物的制备研究与应用

有机硅改性聚氨酯结合了聚氨酯材料及有机硅材料的优异性能,具有广泛的应用前景.共聚法是制备有机硅改性聚氨酯的最佳方法.本文综述了有机硅/聚氨酯共聚物的制备方法,对其相关应用进行了介绍,并对这类材料的发展前景进行了展望.     

舰艇水下腐蚀静电场计算及影响因素仿真分析

为了进一步分析影响舰船电场的不同因素,提高舰艇水下静电场仿真分析中电偶极子建模方法的准确性,研究产生舰艇水下腐蚀静电场的腐蚀电化学原理和特性,从腐蚀电流密度的角度推导船体-螺旋桨电偶腐蚀电流表达式,并利用镜像法求解出了空气海水二层模型下水平和垂直电偶极子电场解析式。建立基于舰艇腐蚀电流电偶极子的电场解析模型,在此基础上利用数值仿真对一中型舰艇水下50 m测线上的电场进行分析。结果表明:在设定变化范围内,船体腐蚀电位、螺旋桨腐蚀电位、船体浸水面积、螺旋桨浸水面积、海水温度、海水电导率对舰艇水下腐蚀静电场的影响程度分别约为29%、23%、53%、82%、30%和67%。仿真结果和电场解析模型可以为进一步研究舰艇水下腐蚀静电场特征及防护方法提供有力的理论支撑。     

Effects of clearance flow on the characteristics of centrifugal pump under low flow rate

Journal of Mechanical Science and Technology - The Reynolds averaged Navier-Stokes equations and the shear stress transport k-w turbulence model are employed to simulate the centrifugal pump with...     

入射光椭圆度对晶体微粒旋转角速度的影响

光致旋转技术在微机械和微生物等领域的应用越来越广泛。利用光束自旋角动量可以导致晶体微粒光致旋转的机理,从理论上分析了入射光椭圆度对晶体微粒旋转角速度的影响。通过MATLAB对不同激光功率下,光束的椭圆度与晶体微粒旋转角速度的关系进行数值模拟。结果表明:在实际对晶体微粒光致旋转操作中,晶体微粒能否旋转起来取决于光束椭圆度与微粒厚度之间的关系;在同一激光功率下,光束椭圆度与晶体微粒旋转角速度呈正旋曲线变化。因此,通过调节光束的椭圆度和较高的激光功率可以提高晶体微粒的旋转角速度。该结论对光驱动微机械马达的优化设计有一定的指导意义。     

Moisture Sensitive Smart Yarns and Textiles from Self‐Balanced Silk Fiber Muscles

Smart textiles that sense, interact, and adapt to environmental stimuli have provided exciting new opportunities for a variety of applications. However, current advances have largely remained at the research stage due to the high cost, complexity of manufacturing, and uncomfortableness of environment‐sensitive materials. In contrast, natural textile materials are more attractive for smart textiles due to their merits in terms of low cost and comfortability. Here, water fog and humidity‐driven torsional and tensile actuation of thermally set twisted, coiled, plied silk fibers, and weave textiles from these silk fibers are reported. When exposed to water fog, the torsional silk fiber provides a fully reversible torsional stroke of 547° mm^?1. Coiled‐and‐thermoset silk yarns provide a 70% contraction when the relative humidity is changed from 20% to 80%. Such an excellent actuation behavior originates from water absorption‐induced loss of hydrogen bonds within the silk proteins and the associated structural transformation, which are corroborated by atomistic and macroscopic characterization of silk and molecular dynamics simulations. With its large abundance, cost‐effectiveness, and comfortability for wearing, the silk muscles will open up additional possibilities in industrial applications, such as smart textiles and soft robotics.     

Nanostructured Metal Chalcogenides for Energy Storage and Electrocatalysis

Energy storage and conversion technologies are vital to the efficient utilization of sustainable renewable energy sources. Rechargeable lithium‐ion batteries (LIBs) and the emerging sodium‐ion batteries (SIBs) are considered as two of the most promising energy storage devices, and electrocatalysis processes play critical roles in energy conversion techniques that achieve mutual transformation between renewable electricity and chemical energies. It has been demonstrated that nanostructured metal chalcogenides including metal sulfides and metal selenides show great potential for efficient energy storage and conversion due to their unique physicochemical properties. In this feature article, the recent research progress on nanostructured metal sulfides and metal selenides for application in SIBs/LIBs and hydrogen/oxygen electrocatalysis (hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction) is summarized and discussed. The corresponding electrochemical mechanisms, critical issues, and effective strategies towards performance improvement are presented. Finally, the remaining challenges and perspectives for the future development of metal chalcogenides in the energy research field are proposed.