脉冲电流在金属凝固过程中的作用及研究进展

综述了国内外关于脉冲电流处理对金属凝固组织和对合金性能影响的研究概况,根据电磁学和金属凝固原理,分析了电脉冲细化金属晶粒和改善合金性能的原因,揭示了电脉冲影响金属凝固的主要机制,并对其影响规律进行了理论推测。     

转角不对中转子系统的电机电流特性

为了通过监测电机电流以实现转子系统故障的识别与诊断,建立偏角不对中转子系统动力学模型,推导出转子系统的转角不对中力矩,并以电机的电磁扭矩为纽带,在MATLAB/Simulink环境下建立三相异步电动机—转子系统机电耦合仿真模型,应用傅里叶变换对定子电流信号进行频谱分析,研究偏角不对中故障激励下电机电流信号的耦合特性。仿真结果表明:正常状态下,电流信号会产生工频分量和奇数次倍频的谐波分量。当转子系统存在转角不对中故障时,三次谐波分量会出现明显的增强,而且其峰值会随着转角不对中量的增加而变大。     

中国高校博物馆建筑发展与设计初探

高校博物馆是已知最早的博物馆建筑,其工作内容及运营模式都不同于社会博物馆。我国高校博物馆发展较晚,从现状上来看仍存在一些问题,本文从我国高校博物馆的发展历史和现状出发,发掘现有的问题和局限,并对其未来发展模式和建筑设计提出建议并进行展望。     

电流密度和润湿剂对Ni镀层组织与形貌的影响

采用普通型瓦特液,按照不同的工艺参数在铜材表面电镀镍,通过SEM对镀层表面进行扫描观察和使用XRD测试对镀层表面进行检测,并且对不同样品数据进行对比和分析,从而达到研究电流密度及润湿剂对镀层沉积速度、表面显微形貌和晶粒尺寸的影响的目的.实验结果表明,电流密度的影响非常显著,不同电流密度下的镀层表面形貌和晶粒尺寸存在相应的差别.适量的润湿剂对镀层的沉积具有促进作用,对防止针孔的生成及细化晶粒具有明显的效果.     

The metastable pitting behaviors of mild steel in bicarbonate and nitrite solutions containing Cl

The metastable pitting behaviors of mild steel in NaHCO₃ + NaCl and NaNO₂ + NaCl solutions were studied with electrochemical methods. In NaHCO₃ + NaCl solution the potential range between metastable pitting potential E_m and pitting potential E_b is relatively large, and most of the current fluctuations are individual. While in NaNO₂ + NaCl solution the E_m and E_b values are much higher and the potential range between them is very narrow, leading to overlapped current peaks. The changes of E_m and E_b with chloride concentration follow similar tendency. In both testing solutions, the repassivated metastable pitting sites are prone to become preferential sites for following metastable pits to nucleate, leading to accumulated corrosion damages on the surface. Mild steel shows stronger passivity in NaNO₂ + NaCl solution than in NaHCO₃ + NaCl solution, which explains the higher pitting resistance of the steel in the former. In addition, the competitive adsorption of anions also plays an important role in the increase of E_m and E_b, especially in inhibiting nucleation of metastable pits.     

Current efficiency in electro-winning of lanthanum and cerium metals from molten chloride electrolytes

The objective of this study is to prepare lanthanum and cerium metals by fused salt electrolysis of their anhydrous chloride in molten media such as LiCl-KCl, NaCl-KCl, KCl, NaCl, and LiCl and to characterize the metal deposit by X-ray diffraction, energy dispersive X-ray fluorescence, and inductive coupled plasma-atomic emission spectroscopy. Deposit metal of purity more than 99 % was obtained in each of the experiments. The entire process starting from preparation of anhydrous lanthanum/cerium chloride to electrolysis yielding of metal deposits has been described. The effect of process parameters such as temperature, electrolyte composition, and current density on the current efficiency was studied. All these parameters were varied to get the highest current efficiency and metal yield. The major non-rare earth impurities with the deposit are found to be Fe, Cr, and Ni along with ～1×10-3 of total gaseous impurities.     

新型铂族金属抗肿瘤药物赛特铂的研究现状

铂族金属抗肿瘤药物顺铂和卡铂已广泛应用于临床，它们对治疗睾丸肿瘤、卵巢癌和肺癌等十几种肿瘤有显著的疗效。近年来又有奈达铂、 到铂和乐铂等获批准进入临床应用。但目前这些临床应用的铂族金属抗肿瘤药口服活性低，都是静脉途径给药。本文介绍了已进入Ⅲ期临床试验的第一个口服活性铂抗肿瘤药物赛特铂及其合成、化学特点、临床前和临床研究情况。     

基于电涡流传感器的转速测量方法研究

研究了一种利用电涡流传感器和PCI-9118DG数据采集卡测量转速的方法。该方法利用电涡流传感器测量转子测速圆盘上均匀分布小孔产生的周期信号，再对测量信号进行Bunerworth低通滤波处理，然后进行0、1转换，得到一系列脉冲信号，便于对信号周期数进行计数。由于采样时间可通过采样频率和采样点数计算得到，因而可根据这一时间间隔内信号的周期数来计算转速。中文详细论述了该方法的硬件组成、测量原理和软件实现，分析了该方法的误差来源以及相应的改进措施，在小型转子试验台的测量结果表明，该方法在测量平稳转速时，准确度高，简单实用。     

基于电动机电流的数控机床主轴状态监测系统研究

提出了一种基于主轴电动机电流的数控机床主轴状态监测系统,建立了主轴交流电动机转矩输出模型,深入研究了主轴组件故障诊断和主轴当前运行能力评估原理,搭建了主轴状态监测系统;实验证明提出的主轴状态监测方法简单、准确、有效,具有很高的性价比,从而为数控机床状态在线监测提供了技术支撑.     

脉冲涡流无损检测技术应用研究

脉冲涡流与传统涡流不同，脉冲涡流通过测量磁场最大值出现的时间来确定缺陷的位置。对脉冲涡流的检测原理进行了分析，设计了脉冲波形发生器和垂直磁场检测电路，并通过试验对此方法进行了验证。