论光与眼睛及色彩的关系

“花开红树乱莺啼．草上平湖白鹭飞。”试想．如果没有太阳，你会感知到花开鸟飞的美景吗？也不会有什么蓝天、白云、青山、绿水、红色的苹果、黄色的柑橘、金首饰、银餐具、宽阔的马路、高大的楼房、美丽的脸蛋、华丽的时装等等。如果是在一片漆黑的夜晚里，再好看的一切，也都会失去它的魅力。     

Dynamic modelling and robust current control of wind-turbine driven DFIG during external AC voltage dip

INTRODUCTION Due to concerns about emissions from fossil fuels and the depletion of fossil fuel resources, re- newable energy systems are becoming a topic of great interest and investment in the world. In particular, wind energy has been the subject of much recent research and development. In order to overcome the problems associated with fixed-speed wind-turbine system and to maximize the wind energy capture, many new wind farms will employ wind turbines based on Doubly-Fed Induction Ge…     

测试双向可控硅输出电压波形对称性的简便方法

重点介绍使用万用表测量双向可控硅输出电压波形对称性的简单方法.     

Induction of diabetes by Streptozotocin in rats

The objective of this study is to induce experimental diabetes mellitus by Streptozotocin in normal adult Wistar rats via comparison of changes in body weight, consumption of food and water, volume of urine and levels of glucose, insulin and C-peptide in serum, between normal and diabetic rats. Intra-venous injection of 60mg/kg dose of Streptozotocin in adult wistar rats, makes pancreas swell and at last causes degeneration in Langerhans islet beta cells and induces experimental diabetes mellitus in the 2–4 days. Induction of experimental diabetes mellitus is indeed the first step in the plan of purification of pancreatic Langerhans islet cells of normal rats for transplanting under the testis subcutaneous of experimentally induced diabetic rats. Streptozotocin induces one type of diabetes which is similar to diabetes mellitus with non-ketosis hyperglycemia in some animal species. For induction of experimental diabetes in male adult rats weighted 250–300 grams (75–90 days), 60mg/kg of Streptozotocin was injected intravenously. Three days after degeneration of beta cells, diabetes was induced in all animals. The diabetic and normal animals were kept in the metabolic cages separately and their body weight, consumption of food and water, urine volume, the levels of serum glucose, insulin and C-peptide quantities in all animals were measured and then these quantities were compared. For a microscopic study of degeneration of Langerhans islet beta cells of diabetic rats, sampling from pancreas tissue of diabetic and normal rats, staining and comparison between them, were done. Induction of diabetes with Streptozotocin decreases Nicotinamide-adenine dinucleotide (NAD) in pancreas islet beta cells and causes histopathological effects in beta cells which probably intermediates induction of diabetes. In this study, we used Streptozotocin for our experiments in induction of experimental diabetes mellitus. After Induction of diabetes, consumption of food and water, volume of urine and glucose increased in the diabetic animals in comparison with normal animals, but the weight of body and the volume of insulin and C-peptide decreased in the diabetic animals. Sampling and staining of pancreas tissue of diabetic and normal rats showed that the Langerhans islet beta cells of diabetic rats have been clearly degenerated. In three days, Streptozotocin makes pancreas swell and at last causes degeneration in Langerhans islet beta cells and induces experimental diabetes. It also changes normal metabolism in diabetic rats in comparison with normal rats. Consumption of water and food, volume of urine, serum glucose increases in diabetic animals in comparison with normal rats but the levels of serum insulin, C-peptide and body weight decreases.     

电力系统机电暂态-电磁暂态混合仿真的研究

随着电网规模的日趋扩大,传统的机电暂态或者电磁暂态仿真软件在分析电网的运行特性时,已开始显露出各自的局限性。将两者联合起来进行混合仿真,可以较好的解决仿真的规模、速度和精度的协调问题。在分析机电暂态和电磁暂态各自的特点的基础上,文中介绍了两者接口的原理和所涉及的问题。最后,对现有的三种混合仿真的接口时序方法进行了对比分析。     

Feature extraction related to bearing damage in electric motors by wavelet analysis

The purpose of this paper is to extract features from vibration signals measured from motors subjected to accelerated bearing fluting aging and to detect the effects of bearing fluting at each aging cycle of induction motors. This trending of bearing degradation is achieved by monitoring the changes in the vibration signals at various sub-band levels. This is accomplished by the application of wavelet transforms and multi-resolution analysis in order to extract information from selected frequency bands with minimum signal distortion.     

探地雷达在实际应用中的几个问题

文中对探地雷达在实际应用中的五个方面问题进行了试验和探讨,给出了试验的结果。试验结果表明这五个方面要从不同角度引起注意,这对使用探地雷达具有一定的参考价值。     

基于光电编码器的双馈调速系统中数字信号的检测

光电编码器是电气传动系统中用来测量电动机转速和转子位置的核心部件。本文介绍了其工作原理和主要特点,并给出了电机双馈调速系统中基于增量式光电编码器的电机转速、转子位置及转子感应电势相位的检测方法。     

汽车内部线束网络电磁模型数值求解的子波谱法

本文针对汽车内部线束网络电磁干扰问题建立了线束网络的电磁模型,并引入了子波分析的方法对该模型的数值求解进行了研究。我们首先构造了针对控制方程的二维正交区间的子波,并将其代入球坐标系下的电磁积分方程,得到了模型数值求解过程所需要的系数矩阵的具体形式。该方法利用子波具有紧支撑和消失矩的特性,能使积分方程数值求解中的满秩矩阵变为稀疏矩阵从而提高求解速度。     

交流异步电机状态变量观测及其优化控制

采用维持磁通始终恒定的方法对电机转矩直接控制，可解决交流异步电机控制精度和系统复杂性之间的矛盾，在电机状态变量观测及位置控制中应用了现代控制理论，和传统的矢量控制方法相比，在相同的性能指标下，该系统便于用微机来完成实时控制。