A hot primary-air pipe system is the bridge connecting an air-preheater with a coal mill in power generation stations.The effective geometrical configuration of the pipe network greatly affects the air flow distributi...A hot primary-air pipe system is the bridge connecting an air-preheater with a coal mill in power generation stations.The effective geometrical configuration of the pipe network greatly affects the air flow distribution and consequently influences the safe and economic operation of milling systems in power stations.In order to improve the properties of the air flow,in the present work the SIMPLEC method is used to simulate numerically the flow field for the original layout of the system.As a result,the internal mechanisms influencing the uneven pressure drop in each branch are explored and three optimization schemes are proposed accordingly.The numerical results indicate that,for the original layout,the local pressure drop of the tee section accounts for approximately 74%of the total drop of the system,with other pressure drops depending on the specific branch considered.It is shown that after optimization,a roughly balanced flow resistance and flow rate can be obtained.Compared with the original layout,the pressure drop relating to different branches is significantly reduced.展开更多
In the present work, the microstructures of A356 feedstock cast via a pipe consisting of partial inclined and partial vertical sections were investigated. The experimental results indicate that semisolid feedstock wit...In the present work, the microstructures of A356 feedstock cast via a pipe consisting of partial inclined and partial vertical sections were investigated. The experimental results indicate that semisolid feedstock with ideal microstructures can be obtained at higher temperatures 645℃ and above by the proposed process, and the solid shell inside the pipe can be avoided at the optimum pouring temperature. Thus the process is attractive for industrial applications. The slanted angle of inclined section has an influence on the optimum pouring temperature. That is, the bigger the slanted angle, the higher the optimum pouring temperature, but accordingly, the greater the possibility of solid shell occurring inside the pipe. Therefore, small slanted angle should be considered first on the premise of ensuring a certain nucleation. The formation of semisolid feedstock is owed to the coactions of wall nucleation and stirring resulting from fluid flow. The inclined section greatly affects nucleation, and the vertical section has an important effect on both nucleation and generating stirring.展开更多
目的:研究原发性肝癌患者治疗期间经外周静脉穿刺置入中心静脉导管(peripherally inserted central catheter,PICC)堵管的相关因素并提出有效护理对策。方法:选取2010年3月1日至2015年12月1日无锡市第二人民医院收治的原发性肝癌患者1 ...目的:研究原发性肝癌患者治疗期间经外周静脉穿刺置入中心静脉导管(peripherally inserted central catheter,PICC)堵管的相关因素并提出有效护理对策。方法:选取2010年3月1日至2015年12月1日无锡市第二人民医院收治的原发性肝癌患者1 026例为研究对象,记录患者性别、年龄、家族史、吸烟史、基础疾病等基本信息,PICC过程中对患者进行严密观察,记录穿刺部位、有无血液反流、冲管或封管、导管尖端移位及导管折叠等情况,并回顾性分析原发性肝癌患者治疗期间PICC堵管的相关因素。结果:原发性肝癌患者治疗期间PICC堵管26例,占2.6%;影响PICC堵管的危险因素中基础疾病(OR=1.978,P<0.05)、血液返流(OR=2.237,P<0.05)、导管维护不当(OR=2.161,P<0.05)、机械因素(OR=2.643,P<0.05)。结论:原发性肝癌患者治疗期间PICC堵管与患者基础疾病、血液反流、导管维护不当、机械性因素等密切相关,因此临床护理中应加强对导管的维护,及时有效冲管、封管,避免血液反流,做到早发现、早处理,从而减少堵管对患者不良影响。展开更多
文摘A hot primary-air pipe system is the bridge connecting an air-preheater with a coal mill in power generation stations.The effective geometrical configuration of the pipe network greatly affects the air flow distribution and consequently influences the safe and economic operation of milling systems in power stations.In order to improve the properties of the air flow,in the present work the SIMPLEC method is used to simulate numerically the flow field for the original layout of the system.As a result,the internal mechanisms influencing the uneven pressure drop in each branch are explored and three optimization schemes are proposed accordingly.The numerical results indicate that,for the original layout,the local pressure drop of the tee section accounts for approximately 74%of the total drop of the system,with other pressure drops depending on the specific branch considered.It is shown that after optimization,a roughly balanced flow resistance and flow rate can be obtained.Compared with the original layout,the pressure drop relating to different branches is significantly reduced.
基金supported by the National KeyBasic Research Foundation of China under grant No.2006CB605203the National Hi-Tech Research Founda-tion of China under grant No. 2006AA03Z115 the National Natural Science Foundation of China under grantNo.50774007.
文摘In the present work, the microstructures of A356 feedstock cast via a pipe consisting of partial inclined and partial vertical sections were investigated. The experimental results indicate that semisolid feedstock with ideal microstructures can be obtained at higher temperatures 645℃ and above by the proposed process, and the solid shell inside the pipe can be avoided at the optimum pouring temperature. Thus the process is attractive for industrial applications. The slanted angle of inclined section has an influence on the optimum pouring temperature. That is, the bigger the slanted angle, the higher the optimum pouring temperature, but accordingly, the greater the possibility of solid shell occurring inside the pipe. Therefore, small slanted angle should be considered first on the premise of ensuring a certain nucleation. The formation of semisolid feedstock is owed to the coactions of wall nucleation and stirring resulting from fluid flow. The inclined section greatly affects nucleation, and the vertical section has an important effect on both nucleation and generating stirring.
文摘目的:研究原发性肝癌患者治疗期间经外周静脉穿刺置入中心静脉导管(peripherally inserted central catheter,PICC)堵管的相关因素并提出有效护理对策。方法:选取2010年3月1日至2015年12月1日无锡市第二人民医院收治的原发性肝癌患者1 026例为研究对象,记录患者性别、年龄、家族史、吸烟史、基础疾病等基本信息,PICC过程中对患者进行严密观察,记录穿刺部位、有无血液反流、冲管或封管、导管尖端移位及导管折叠等情况,并回顾性分析原发性肝癌患者治疗期间PICC堵管的相关因素。结果:原发性肝癌患者治疗期间PICC堵管26例,占2.6%;影响PICC堵管的危险因素中基础疾病(OR=1.978,P<0.05)、血液返流(OR=2.237,P<0.05)、导管维护不当(OR=2.161,P<0.05)、机械因素(OR=2.643,P<0.05)。结论:原发性肝癌患者治疗期间PICC堵管与患者基础疾病、血液反流、导管维护不当、机械性因素等密切相关,因此临床护理中应加强对导管的维护,及时有效冲管、封管,避免血液反流,做到早发现、早处理,从而减少堵管对患者不良影响。
