Diagnosis of stator faults in induction motor based on zero sequence voltage after switch-off

To improve the accuracy of the stator winding fault diagnosis in induction motor, a new diagnostic method based on the Hilbert-Huang transform （HHT） was proposed. The ratio of fundamental zero sequence voltage to positive sequence voltage after switch-off was selected as the stator fault characteristic, which could effectively avoid the influence of the supply unbalance and the load fluctuation, and directly represent the asymmetry in the stator. Using the empirical mode decomposition （EMD） based on HHT, the zero sequence voltage after switch-off was decomposed and the fundamental component was extracted. Then, the fault characteristic can be acquired. Experimental results on a 4-kW induction motor demonstrate the feasibility and effectiveness of this method.     

影响跨国公司在武汉直接投资因素实证研究

英国学邓宁认为东道国或地区的区位优势是跨国公司对外直接投资的必要条件。章以武汉这个地区作为研究对象，借鉴一般区位理论和国际直接投资相关理论的基本方法和思路来探讨影响跨国公司在武汉直接投资因素。     

发挥专属经济区基本功能的法律思考

创设专属经济区的目的和立法意图在于为建立国际海洋新秩序奠定基石,将沿海国的资源利益同国际社会的航海利益结合在一起,保证沿海国对其自然资源的有效控制,为沿海国政治上的独立和军事上的安全提供法律保障。要将专属经济区的＂主权权利＂实现＂国家政治主权＂和＂国家经济主权＂的有机统一。沿海国的主权权利在两个＂适当顾及＂中处于优先地位。＂和平目的＂原则是《联合国海洋法公约》的基本宗旨,也是确认专属经济区的法理依据。     

X70管线钢焊接接头断裂韧度试验

采用裂纹尖端张开位移(CTOD)测试技术和金相显微组织分析,设计2种三点弯曲试样,测试了X70管线钢埋弧焊焊接接头低温-10℃的断裂韧性,比较接头焊缝、热影响不同区域金属断裂韧性,分析组织结构对力学性能的影响。结果显示,焊缝中心金属性能均匀,裂纹尖端张开位移平均值为0.346 mm,断裂韧性小于热影响区稳定裂纹扩展的CTOD值。热影响区组织不均匀,包括稳定裂纹扩展和中途失稳断裂,出现不同特征的CTOD值。热影响细晶区组织为细小的多边形铁素体和珠光体,在-10℃环境下仍有良好的低温韧性。热影响粗晶区组织主要是板条状贝氏体和粒状贝氏体,而且晶粒尺寸粗大,该区域在-10℃时容易失稳断裂,呈现低温脆性。     

Recognition of the major scattering sources on complex targets based on the high frequency radar cross section integrated calculation technique

Based on the high frequency (HF) integrated radar cross section (RCS) calculation approach, a technique of detecting major scattering source is developed by using an appropriate arithmetic for scattering distribution and scattering source detection. For the perfect adaptability to targets and the HF of the HF integrated RCS calculation platform, this technique is suitable to solve large complex targets and has lower requirement to the target modeling. A comparison with the result of 2-D radar imaging confirms the accuracy and reliability of this technique in recognition of the major scattering source on complex targets. This technique provides the foundation for rapid integrated evaluation of the scattering performance and 3-D scattering model reconstruction of large complex targets. Project supported by the National Natural Science Foundation of China (Grant No.90305026)