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  • 基于PLC和变频技术的中央空调控制系统改造设计

    基于节能减排的目的,对中央空调控制系统实施改造.首先分析了中央空调系统的运行现状,阐述了中央空调系统的构成和变频节能原理,继而采用PLC和变频控制相结合的温差法控制方案对原有系统进行改造,给出了设计方案,进行了变频器的参数设置,并进行了节能分析.最后指出了中央空调采用变频调速控制具有较好的实用价值和发展前景.
    张涛,张丽,尚希 - 电机与控制应用
    文章来源: 万方数据
  • 脉搏信号调理电路设计

    脉搏作为人体重要的生理及病理指标之一,具有重要的医学研究价值.针对其信号微弱、频率低且易受干扰的特点,提出了信号调理电路设计的要求;针对性地选择元器件并设计硬件电路,其中包括:一级放大电路、调零电路、50 Hz限波电路、带通滤波电路及二级放大电路;最后对所设计的硬件电路进行实际测试.测试结果表明,该调理电路具有输出波形稳定、噪声小和共模抑制比高的特点,提高了脉搏信号采集的精度.
    张金榜,刘军,齐华 - 电子技术应用
    文章来源: 万方数据
  • 铝-空气电池铝合金阳极的研究进展

    从铝活化-钝化机理、添加合金元素(镓、铟、镁、锡、锰、铋及铅等)对铝阳极性能的影响等方面,综述了铝-空气电池铝合金阳极的发展、研究及应用概况.
    鲁火清,卢周广,沈冬,唐有根 - 电池
    文章来源: 万方数据
  • DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics(CFD) and computational aerodynamic acoustics(CAA) simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures(i.e. the heat sink, the bell-mouth type shroud and the outlet grille) upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring's size and throat's depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %(i.e. 100 m3·h-1) at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.
     - 中国机械工程学报
    文章来源: 万方数据
  • Corrole和Corrolazine的结构及其内氢迁移反应的理论研究

    采用B3LYP/6.31G**方法在Gaussian03程序下,对Corrole(CH3)和Corrolazine(C2H3)体系进行结构优化和振动分析.结果显示,CH3和C2H3的不同构型稳定性差异可忽略不计,结构参数的变化则说明中心空穴的大小顺序为PH2〉CH3〉PzH2〉C2H3.优化不同构型间相互转化的IHAT反应的过渡态,并进行相关的比较计算,发现CH3和C2H3的正反应速率都明显大于PH2和P2H2;同时CH3和C2H3的非平面构型的电子效应远大于PH2和P2H2的平面离域体系的平均化电子效应.
    廖玉婷,饶火瑜,王秋月,胡宝群 - 计算机与应用化学
    文章来源: 万方数据
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