静态纵向边端效应是直线电机铁心和绕组开断所致的固有特性之一,对于多段长初级双边直线感应电动机(double-sided linear induction motor,DLIM),其分段供电方式导致电机铁心长度大于通电绕组长度。针对上述特点,该文从理论分析、数字...静态纵向边端效应是直线电机铁心和绕组开断所致的固有特性之一,对于多段长初级双边直线感应电动机(double-sided linear induction motor,DLIM),其分段供电方式导致电机铁心长度大于通电绕组长度。针对上述特点,该文从理论分析、数字仿真的角度研究了电机极数及边端铁心对电机静态纵向边端效应的影响机理同时得到了阻抗矩阵规律。研究结果表明,边端铁心的存在对静态纵向边端效应影响很大,且该效应随着边端铁心长度的增加而作用显著,随着极数的增加,该效应作用减弱;电机阻抗矩阵不再是循环对称矩阵,但可以通过测量三相端口电压电流的幅值和相位方便求解。上述规律的正确性通过峰值功率400kW,最大出力14000N的长初级双边直线感应电动机实验系统进行了验证,为电机数学模型的准确描述和参数的精确提取提供了参考。展开更多
Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun,Guizhou Province. They generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,...Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun,Guizhou Province. They generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,and are evenly scattered in micritic matrix. Their abundance makes the rock as-signed to microbialites. The accompanied organisms include ostracods and algal mat,but no gastro-pods or bivalves. Presence of small (<7 μm) pyrite framboids indicates that this bed formed in anoxic conditions. In some sections,this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small burrows. Occurrence only in deposits on reef top indicates that the micro-bial organism was benthic,and needed sunlight in life. The size of the microbial fossil exceeds that of any bacteria or cyanobacteria. Thus,it does not belong to these two phyla. It may belong to lower green algae,and is assigned to a new species in a new genus,Ziyunosphaeridium sinensis gen. et sp. nov. Up to now,the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima (1997),(2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann (1999),(3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al. (1999),(4) spherical microbial limestone adapted to anoxic environments described from Ziyun,Guizhou reported in this paper,(5) limestone with cyanobacterial fossils such as that described by Wang et al. (2005),and (6) stromatolites. All these microbialites are not reefs in the proper sense,and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.展开更多
Endoscopic retrograde cholangiopancreatography(ERCP) has become an important therapeutic modality for biliary and pancreatic disorders. Perforation is one of the most feared complications of ERCP and endoscopic sphinc...Endoscopic retrograde cholangiopancreatography(ERCP) has become an important therapeutic modality for biliary and pancreatic disorders. Perforation is one of the most feared complications of ERCP and endoscopic sphincterotomy. A MEDLINE search was performedfrom 2000-2014 using the keywords "perforation", "ERCP" and "endoscopic sphincterotomy". All articles including more than nine cases were reviewed. The incidence of ERCP-related perforations was low(0.39%, 95%CI: 0.34-0.69) with an associated mortality of 7.8%(95%CI: 3.80-13.07). Endoscopic sphincterotomy was responsible for 41% of perforations, insertion and manipulations of the endoscope for 26%, guidewires for 15%, dilation of strictures for 3%, other instruments for 4%, stent insertion or migration for 2% and in 7% of cases the etiology was unknown. The diagnosis was made during ERCP in 73% of cases. The mechanism, site and extent of injury, suggested by clinical and radiographic findings, should guide towards operative or non-operative management. In type I perforations early surgical repair is indicated, unless endoscopic closure can be achieved. Patients with type II perforations should be treated initially non-operatively. Non-operative treatment includes biliary stenting, fasting, intravenous fluid resuscitation, nasogastric drainage, broad spectrum antibiotics, percutaneous drainage of fluid collections. Non-operative treatment was successful in 79% of patients with type II injuries, with an overall mortality of 9.4%. Non-operative treatment was sufficient in all patients with type III injuries. Surgical technique depends on timing, site and size of defect and clinical condition of the patient. In conclusion, diagnosis is based on clinical suspicion and clinical and radiographic findings. Whilst surgery is usually indicated in patients with type I injuries, patients with type II or III injuries should be treated initially non-operatively. A minority of them will finally require surgical intervention.展开更多
文摘静态纵向边端效应是直线电机铁心和绕组开断所致的固有特性之一,对于多段长初级双边直线感应电动机(double-sided linear induction motor,DLIM),其分段供电方式导致电机铁心长度大于通电绕组长度。针对上述特点,该文从理论分析、数字仿真的角度研究了电机极数及边端铁心对电机静态纵向边端效应的影响机理同时得到了阻抗矩阵规律。研究结果表明,边端铁心的存在对静态纵向边端效应影响很大,且该效应随着边端铁心长度的增加而作用显著,随着极数的增加,该效应作用减弱;电机阻抗矩阵不再是循环对称矩阵,但可以通过测量三相端口电压电流的幅值和相位方便求解。上述规律的正确性通过峰值功率400kW,最大出力14000N的长初级双边直线感应电动机实验系统进行了验证,为电机数学模型的准确描述和参数的精确提取提供了参考。
基金Supported by the National Natural Science Foundation of China (Grant No. 40472015)the State Key Laboratory of Modern Paleontology and Stratigraphy (Grant No. 053102)as well as the Key Laboratory for Minerals and Resources, the Chinese Academy of Sciences
文摘Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun,Guizhou Province. They generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,and are evenly scattered in micritic matrix. Their abundance makes the rock as-signed to microbialites. The accompanied organisms include ostracods and algal mat,but no gastro-pods or bivalves. Presence of small (<7 μm) pyrite framboids indicates that this bed formed in anoxic conditions. In some sections,this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small burrows. Occurrence only in deposits on reef top indicates that the micro-bial organism was benthic,and needed sunlight in life. The size of the microbial fossil exceeds that of any bacteria or cyanobacteria. Thus,it does not belong to these two phyla. It may belong to lower green algae,and is assigned to a new species in a new genus,Ziyunosphaeridium sinensis gen. et sp. nov. Up to now,the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima (1997),(2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann (1999),(3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al. (1999),(4) spherical microbial limestone adapted to anoxic environments described from Ziyun,Guizhou reported in this paper,(5) limestone with cyanobacterial fossils such as that described by Wang et al. (2005),and (6) stromatolites. All these microbialites are not reefs in the proper sense,and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.
文摘Endoscopic retrograde cholangiopancreatography(ERCP) has become an important therapeutic modality for biliary and pancreatic disorders. Perforation is one of the most feared complications of ERCP and endoscopic sphincterotomy. A MEDLINE search was performedfrom 2000-2014 using the keywords "perforation", "ERCP" and "endoscopic sphincterotomy". All articles including more than nine cases were reviewed. The incidence of ERCP-related perforations was low(0.39%, 95%CI: 0.34-0.69) with an associated mortality of 7.8%(95%CI: 3.80-13.07). Endoscopic sphincterotomy was responsible for 41% of perforations, insertion and manipulations of the endoscope for 26%, guidewires for 15%, dilation of strictures for 3%, other instruments for 4%, stent insertion or migration for 2% and in 7% of cases the etiology was unknown. The diagnosis was made during ERCP in 73% of cases. The mechanism, site and extent of injury, suggested by clinical and radiographic findings, should guide towards operative or non-operative management. In type I perforations early surgical repair is indicated, unless endoscopic closure can be achieved. Patients with type II perforations should be treated initially non-operatively. Non-operative treatment includes biliary stenting, fasting, intravenous fluid resuscitation, nasogastric drainage, broad spectrum antibiotics, percutaneous drainage of fluid collections. Non-operative treatment was successful in 79% of patients with type II injuries, with an overall mortality of 9.4%. Non-operative treatment was sufficient in all patients with type III injuries. Surgical technique depends on timing, site and size of defect and clinical condition of the patient. In conclusion, diagnosis is based on clinical suspicion and clinical and radiographic findings. Whilst surgery is usually indicated in patients with type I injuries, patients with type II or III injuries should be treated initially non-operatively. A minority of them will finally require surgical intervention.
