Calculation of Circumferential Modal Frequencies of Permanent Magnet Synchronous Motor

Accurate calculation of the natural frequencies of permanent magnet synchronous motors( PMSMs) is essential to the prediction of vibration and noise of PMSMs. The analytical and numerical methods are respectively used to calculate natural frequencies of stator yoke,stator core,stator core with windings,motor casing and stator system. It is found that the relative errors between calculated results with traditional analytical formulas and numerical results are very large. For the sake of reducing relative errors,novel analytical formulas of calculating circumferential modal frequencies of stator core,stator core with windings,motor casing and stator system are proposed. Compared with the results of numerical and experimental modal analysis,the effectiveness of novel analytical formulas is verified.

不同致泻性大肠杆菌感染调控细胞信号通路的研究进展

腹泻性大肠杆菌是在全世界引起人类和动物疾病的主要病原之一,也给社会经济带来巨大损失。根据致病机理的不同,可将腹泻性大肠杆菌分为6种:肠致病性大肠杆菌、肠出血性大肠杆菌、肠凝集性大肠杆菌、产肠毒素大肠杆菌、扩散黏附性大肠杆菌和肠侵袭性大肠杆菌。不同致病型大肠杆菌侵入宿主的方式及引起的炎症反应有所不同。文章综合分析了致病机制不同的大肠杆菌在调控宿主细胞信号通路方式上的不同,从炎症级联反应方面阐述了不同致病类型大肠杆菌的感染特征,并探讨了炎症信号通路与病原感染、预防和治疗的关系,以期为腹泻性大肠杆菌致病机制及治疗方案的研究提供帮助。