电机转速和转子位置数字测量方法的研究

电机转速和转子位置的测量在电机交直流调速控制系统中占有重要的位置,为提高测量的精度和避免噪声影响,多采用数字式测量方法.基于常规的M/T法,提出了电机转速和转子位置测量的综合M/T法,该方法是利用测量电路对光电编码器信号进行预处理,以确定采样信号脉冲与码盘信号脉冲之间的相对位置,并将这个相对位置表示为含有小数的码盘脉冲个数,由此不仅可以测量出电机在采样时刻的转速,同时还可以测量出该时刻电机的转子位置.与常规的M/T法相比,该方法提高了测量的精度,扩展了M/T法的应用范围.     

Milling process simulation for the variable pitch cutter based on an integrated process-machine model

Milling process simulations provide a useful way to design and adjust the technical parameters of milling process. As the milling process involves coupling     

炸药冲击波激励氩气闪光实验研究

建立了对可见光和近红外的瞬态测试记录系统。用实验方法研究了氩气在炸药冲击小励下产生的可见光光强。测得了不同压力下氩气的辐射强度,分析了气体压力对光强的影响。     

分布式实时数据库在输变电系统中的应用

本论文主要对分布式实时数据在输变电系统中各项事务管理和数据汇总处理等应用进行阐述.首先介绍了分布式实时数据库及其特点,接着,详细介绍了分布式实时数据库在输变电系统中的应用.分布式实时数据库的建立可以实现对国网山西省电力公司检修公司所有事务的处理和对所运营的各地区的变电站实时数据进行汇总和处理,同时为智能变电站网络管理系统的建立提供知识库数据和专家经验.为变电站的联网运行奠定基础.     

频扫天线波瓣指向角的温度修正方法分析

介绍了几种常用的温度影响频扫天线测角误差的消除方法，由于实验设备、条件的限制以及制作频扫天线等效慢波线的材料、形状有别，这些方法在工程应用中都难以采用。本文提出了一种工程上较易实现的慢波线膨胀系数测量修正法，该方法简单实用，且能满足雷达测角精度的要求。     

建筑师应博学

前辈梁思成先生在上世纪四十年代于清华大学教导学生：“建筑师的知识领域要很广,要有哲学家的头脑、社会学家的眼光、工程师的精确与实践、心理学家的敏感、文学家的洞察力……但是最本质的,他应当是一位有文化修养的综合艺术家”.     

Effects of Tearing Conditions on the Crack Propagation in a Monolayer Graphene Sheet

The path of crack propagation in a graphene sheet is significant for graphene patterning via the tearing approach. In this study, we evaluate the fracture properties of pre-cracked graphene during the tearing process, with consideration of the effects of the aspect ratio, loading speed, loading direction, and ambient temperatures on the crack propagation in the monolayer sheet. Some remarkable conclusions are drawn based on the molecular dynamic simulation results, i.e., a higher loading speed may result in a complicated path of crack propagation, and the propagation of an armchair crack may be accompanied by sp carbon links at high temperatures. The reason for this is that the stronger thermal vibration reduces the load stress difference near the crack tip and, therefore, the crack tip can pass through the sp link. A crack propagates more easily along the zigzag direction than along the armchair direction. The out-of-plane tearing is more suitable than the in-plane tearing for graphene patterning. The path of crack propagation can be adjusted by changing the loading direction, e.g., a rectangular graphene ribbon can be produced by oblique tearing. This new understanding will benefit the application of graphene patterning via the tearing approach.     

High-pseudocapacitance of porous and square NiO@NC nanosheets for high-performance lithium-ion batteries

Layered nickel oxides have been focused with intense research interests as high-performance lithium-ion batterie(LIB) anode.However,it is hard to obtain few layered nickel oxides material directly as it easily forms bulk material with the strong interaction between the interlayer.In this work,two-dimensional(2 D) nickel-based coordination polymers were successfully prepared according to aqueous phase copolymerization approach.And then uniform carbondoped NiO nanosheets were successfully obtained from facile solution assembly and post-thermal treatment.The detailed electrochemical testing shows that the uniform NiO nanocrystals encapsulated into porous N-doped carbon(NiO@NC) nanosheets present much higher rate capability with the discharge specific capacity of 782.7 mAh·g~(-1) at high current density of 2.0 A·g~(-1) than pure NiO(690 mAh·g~(-1)).It also shows long-term cycling performance with 91 % retention after 50 cycles at 1.0 A·g~(-1).The high rate capability,cycling stability and the easy synthesis make NiO@NC nanosheets as a promising candidate for LIB anode and build up new way for the fabrication of metal oxides anode materials.     

Strength,strain capacity and toughness of five dual-phase pipeline steels

The effect of microstructures on strength, strain capacity and low temperature toughness of a micro-alloyed pipeline steel was elucidated. Five various dual-pha...     

摩擦改进剂对改善燃油经济性的影响研究

采用四球机试验,考察了钼胺化合物、二烷基二硫代氨基甲酸钼、无灰型摩擦改进剂与摩擦因数的关系以及它们之间的复配作用。结果表明：摩擦改进剂（FM）降低摩擦因数的效果与其化学结构有关;加入量提高,摩擦因数的改善效果明显;不同化学结构的摩擦改进剂复配使用,可以减低整个温度区的摩擦因数。