The microstructure, precipitate type, precipitate distribution and tensile strength of a ZL205 alloy, beforeand after ageing treatment, have been studied by means of optical microscopy and transmission electron micros...The microstructure, precipitate type, precipitate distribution and tensile strength of a ZL205 alloy, beforeand after ageing treatment, have been studied by means of optical microscopy and transmission electron microscopy.The results showed that the as-cast microstructure of the alloy was made up of α-Al and eutectic phase distributedat the grain boundaries. During ageing treatment, the tensile strength increased at first and then reduced with time,and the highest ultimate tensile strength was found to be around 488.2 MPa.展开更多
A unified numerical model for simulating solidification transport phenomena (STP) of steel slab in electromagnetic continuous casting (EMCC) process was developed. In order to solve the multi-physics fields coupled pr...A unified numerical model for simulating solidification transport phenomena (STP) of steel slab in electromagnetic continuous casting (EMCC) process was developed. In order to solve the multi-physics fields coupled problem conveniently, the complicated bidirectional coupled process between EM and STP was simplified as a unidirectional one, and a FEM/FVM-combined numerical simulation technique was adopted. The traveling magnetic fields (TMFs) applied to the EMCC process were calculated using the ANSYS11.0 software, and then the EM-data output by ANSYS were converted to FVM-format using a data-format conversion program developed previously. Thereafter, the governing equations were solved using a pressure-based Direct-SIMPLE algorithm. The simulation results of the STP in CC-process show that, due to the influences of Lorentz force and Joule heat, the two strong circulating flows and the temperature field can be obviously damped and changed once TMF with one pair of poles (1-POPs) or 2-POPs is applied, which would accordingly improve the quality of casting. It was found in the present research that the integrated actions of 2-POPs TMF are superior to 1-POPs. All the computations indicate that the present numerical model of EM-STP as well as the FEM/FVM-combined technique is successful.展开更多
目的系统评价预防性应用抗生素对重症急性胰腺炎患者的有效性与安全性。方法检索PubMed、EMbase、Web of Science、Cochrane Library、CNKI以及万方数据库,并辅以手工检索关于预防性应用抗生素治疗重症急性胰腺炎的随机对照试验,检索时...目的系统评价预防性应用抗生素对重症急性胰腺炎患者的有效性与安全性。方法检索PubMed、EMbase、Web of Science、Cochrane Library、CNKI以及万方数据库,并辅以手工检索关于预防性应用抗生素治疗重症急性胰腺炎的随机对照试验,检索时间为数据库建库至2017年12月。采用RevMan 5.3统计软件进行meta分析。结果共纳入16项RCT研究,共计999例研究对象,其中预防性应用抗生素者(干预组)501例,接受安慰剂或对照治疗(对照组)498例。meta分析结果显示,干预组的胰腺感染率[OR=0.68,95%CI为(0.50,0.93),P=0.02]和胰外感染率[OR=0.63,95%CI为(0.45,0.88),P=0.007]均低于对照组,但2组的手术干预率[OR=0.79,95%CI为(0.57,1.08),P=0.14]和死亡率[OR=0.81,95%CI为(0.56,1.15),P=0.24]比较差异均无统计学意义。结论预防性应用抗生素有益于降低重症急性胰腺炎患者的胰腺感染率和胰外感染率,但在手术干预率及死亡率方面不具有保护性作用。展开更多
文摘The microstructure, precipitate type, precipitate distribution and tensile strength of a ZL205 alloy, beforeand after ageing treatment, have been studied by means of optical microscopy and transmission electron microscopy.The results showed that the as-cast microstructure of the alloy was made up of α-Al and eutectic phase distributedat the grain boundaries. During ageing treatment, the tensile strength increased at first and then reduced with time,and the highest ultimate tensile strength was found to be around 488.2 MPa.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50801019 and 51071062)the State Key Lab of Advanced Metals Materials (Grant No. 2009ZD-06)the National Key Basic Research and Development Program (973) of China (Grant No. 2011CB605504)
文摘A unified numerical model for simulating solidification transport phenomena (STP) of steel slab in electromagnetic continuous casting (EMCC) process was developed. In order to solve the multi-physics fields coupled problem conveniently, the complicated bidirectional coupled process between EM and STP was simplified as a unidirectional one, and a FEM/FVM-combined numerical simulation technique was adopted. The traveling magnetic fields (TMFs) applied to the EMCC process were calculated using the ANSYS11.0 software, and then the EM-data output by ANSYS were converted to FVM-format using a data-format conversion program developed previously. Thereafter, the governing equations were solved using a pressure-based Direct-SIMPLE algorithm. The simulation results of the STP in CC-process show that, due to the influences of Lorentz force and Joule heat, the two strong circulating flows and the temperature field can be obviously damped and changed once TMF with one pair of poles (1-POPs) or 2-POPs is applied, which would accordingly improve the quality of casting. It was found in the present research that the integrated actions of 2-POPs TMF are superior to 1-POPs. All the computations indicate that the present numerical model of EM-STP as well as the FEM/FVM-combined technique is successful.
文摘目的系统评价预防性应用抗生素对重症急性胰腺炎患者的有效性与安全性。方法检索PubMed、EMbase、Web of Science、Cochrane Library、CNKI以及万方数据库,并辅以手工检索关于预防性应用抗生素治疗重症急性胰腺炎的随机对照试验,检索时间为数据库建库至2017年12月。采用RevMan 5.3统计软件进行meta分析。结果共纳入16项RCT研究,共计999例研究对象,其中预防性应用抗生素者(干预组)501例,接受安慰剂或对照治疗(对照组)498例。meta分析结果显示,干预组的胰腺感染率[OR=0.68,95%CI为(0.50,0.93),P=0.02]和胰外感染率[OR=0.63,95%CI为(0.45,0.88),P=0.007]均低于对照组,但2组的手术干预率[OR=0.79,95%CI为(0.57,1.08),P=0.14]和死亡率[OR=0.81,95%CI为(0.56,1.15),P=0.24]比较差异均无统计学意义。结论预防性应用抗生素有益于降低重症急性胰腺炎患者的胰腺感染率和胰外感染率,但在手术干预率及死亡率方面不具有保护性作用。
