This paper aims at studying the influence mechanism of gas temperatures(300 K,400 K,500 K,and 600 K)on gas atomization by simulating the integral atomization process of the close-coupled nozzle in vacuum induction gas...This paper aims at studying the influence mechanism of gas temperatures(300 K,400 K,500 K,and 600 K)on gas atomization by simulating the integral atomization process of the close-coupled nozzle in vacuum induction gas atomization(VIGA).The primary atomization is simulated by the volume of fluid(VOF)approach,and the second atomization is studied by the discrete phase model(DPM)combined with the instability breakage model.The results show that,at an increased gas temperature,the influences of gas-liquid contact angle and gas temperature in the recirculation zone on the primary atomization are virtually negligible.However,increasing the gas temperature will increase the gas-liquid relative velocity near the recirculation zone and decrease the melt film thickness,which are the main reasons for the reduced mass median diameter(MMD,d50)of primary atomized droplets.During the secondary atomization,increasing the gas temperature from 300 K to 600 K results in an increase in the droplet dispersion angle,which is beneficial to the formation of spherical metal powder.In addition,increasing the gas temperature,the positive effect of gas-liquid relative velocity increase on droplets refinement overweighs the negative influence of the GMR decrease,resulting in the reduced MMD and diameter distribution interval.From the analysis of the atomization mechanism,the increase in atomization efficiency caused by increasing the temperature of the atomizing gas,including primary atomization and secondary atomization,is mainly due to the increase in the gas drag force difference between the inner and outer sides of the annular liquid film.展开更多
研究采用真空感应气雾化(Vacuum Induction Gas Atomization,VIGA)技术制备GH4169合金粉末,系统探究气体温度对粉末特性的影响规律。结果表明,随着气体温度从100℃升高到600℃,粉末的粒度分布明显向左移动,D50由75μm减小到42μm。扫描...研究采用真空感应气雾化(Vacuum Induction Gas Atomization,VIGA)技术制备GH4169合金粉末,系统探究气体温度对粉末特性的影响规律。结果表明,随着气体温度从100℃升高到600℃,粉末的粒度分布明显向左移动,D50由75μm减小到42μm。扫描电子显微镜(Scanning Electron Microscope,SEM)分析表明,较高气体温度有助于提高粉末的球形度,减少卫星粉的生成。X射线衍射(X-Ray Diffraction,XRD)分析揭示,气体温度对粉末的物相组成影响不大,但是较高温度下粉末具有更高的结晶度和更大的晶粒尺寸。此外,粉末的流动性随气体温度的升高而显著改善。展开更多
目的探讨IgA肾病(IgAN)患者转化生长因子-β(TGF-β)的启动子-509C/T位点多态性及铁皮石斛处方的疗效。方法采用PCR-RFLP和直接测序法鉴定118例桂西壮族IgA肾病患者,按TGF-β1基因测序情况,分为CC、CT和TT三种类型,每种类型随机分为试...目的探讨IgA肾病(IgAN)患者转化生长因子-β(TGF-β)的启动子-509C/T位点多态性及铁皮石斛处方的疗效。方法采用PCR-RFLP和直接测序法鉴定118例桂西壮族IgA肾病患者,按TGF-β1基因测序情况,分为CC、CT和TT三种类型,每种类型随机分为试验组和观察组。另外选取入选患者的兄弟姐妹118例作为家系对照组,采用传递不平衡检验和HRR分析的方法观察TGFβ1-509 C/T在患病子代的不平衡传递。随机抽取具有至少1名健康的兄弟姐妹同胞的壮族IgA N患者,检测患者和核心家系成员的TGF-β基因型,在激素联合ACEI/ARB基础上观察铁皮石斛处方的干预效果,并检测患者尿蛋白定量(24 h Upr)、血清白蛋白(ALB)、肌酐(Scr)、尿素氮(BUN)水平的变化情况。结果桂西壮族IgA N患者TGF-β1启动子-509C/T位点基因CC型32例(占27.1%),CT型58例(占49.2%),TT型28例(占23.7%)。而IgAN患者核心家系人群为CC型33例(占28.4%),CT型55例(占46.6%),TT型30例(占25.0%)。治疗前试验组与观察组差异无统计学意义(P>0.05),治疗后,CC型:试验组24h Upr、Scr、BUN水平降低的幅度较观察组高(P<0.01或P<0.05)。ALB水平升高的幅度较观察组高,但其差异无统计学意义(P>0.05);CT型:24 h Upr和BUN水平降低的幅度较观察组高(P<0.01)。Scr水平降低的幅度较观察组高,ALB水平降低的幅度较观察组高,但其差异无统计学意义(P>0.05);TT型:24 h Upr、BUN水平降低的幅度较观察组高(P<0.01或P<0.05)。ALB水平升高的幅度较观察组高(P<0.01)。Scr水平降低的幅度较观察组高,但差异无统计学意义(P>0.05)。结论桂西壮族居民TGF-β启动子-509C/T位点多态性与IgA N患病无关联性;西药联合铁皮石斛处方治疗可有效提高IgA N的临床疗效;携带TGF-β启动子-509基因位点CC型的患者,不仅对西医治疗敏感,对铁皮石斛处方联合干预效果更敏感。展开更多
基金the Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment(Grant No.SKL2019006)the National Natural Science Foundation of China(Grant No.51975240).
文摘This paper aims at studying the influence mechanism of gas temperatures(300 K,400 K,500 K,and 600 K)on gas atomization by simulating the integral atomization process of the close-coupled nozzle in vacuum induction gas atomization(VIGA).The primary atomization is simulated by the volume of fluid(VOF)approach,and the second atomization is studied by the discrete phase model(DPM)combined with the instability breakage model.The results show that,at an increased gas temperature,the influences of gas-liquid contact angle and gas temperature in the recirculation zone on the primary atomization are virtually negligible.However,increasing the gas temperature will increase the gas-liquid relative velocity near the recirculation zone and decrease the melt film thickness,which are the main reasons for the reduced mass median diameter(MMD,d50)of primary atomized droplets.During the secondary atomization,increasing the gas temperature from 300 K to 600 K results in an increase in the droplet dispersion angle,which is beneficial to the formation of spherical metal powder.In addition,increasing the gas temperature,the positive effect of gas-liquid relative velocity increase on droplets refinement overweighs the negative influence of the GMR decrease,resulting in the reduced MMD and diameter distribution interval.From the analysis of the atomization mechanism,the increase in atomization efficiency caused by increasing the temperature of the atomizing gas,including primary atomization and secondary atomization,is mainly due to the increase in the gas drag force difference between the inner and outer sides of the annular liquid film.
文摘研究采用真空感应气雾化(Vacuum Induction Gas Atomization,VIGA)技术制备GH4169合金粉末,系统探究气体温度对粉末特性的影响规律。结果表明,随着气体温度从100℃升高到600℃,粉末的粒度分布明显向左移动,D50由75μm减小到42μm。扫描电子显微镜(Scanning Electron Microscope,SEM)分析表明,较高气体温度有助于提高粉末的球形度,减少卫星粉的生成。X射线衍射(X-Ray Diffraction,XRD)分析揭示,气体温度对粉末的物相组成影响不大,但是较高温度下粉末具有更高的结晶度和更大的晶粒尺寸。此外,粉末的流动性随气体温度的升高而显著改善。
文摘目的探讨IgA肾病(IgAN)患者转化生长因子-β(TGF-β)的启动子-509C/T位点多态性及铁皮石斛处方的疗效。方法采用PCR-RFLP和直接测序法鉴定118例桂西壮族IgA肾病患者,按TGF-β1基因测序情况,分为CC、CT和TT三种类型,每种类型随机分为试验组和观察组。另外选取入选患者的兄弟姐妹118例作为家系对照组,采用传递不平衡检验和HRR分析的方法观察TGFβ1-509 C/T在患病子代的不平衡传递。随机抽取具有至少1名健康的兄弟姐妹同胞的壮族IgA N患者,检测患者和核心家系成员的TGF-β基因型,在激素联合ACEI/ARB基础上观察铁皮石斛处方的干预效果,并检测患者尿蛋白定量(24 h Upr)、血清白蛋白(ALB)、肌酐(Scr)、尿素氮(BUN)水平的变化情况。结果桂西壮族IgA N患者TGF-β1启动子-509C/T位点基因CC型32例(占27.1%),CT型58例(占49.2%),TT型28例(占23.7%)。而IgAN患者核心家系人群为CC型33例(占28.4%),CT型55例(占46.6%),TT型30例(占25.0%)。治疗前试验组与观察组差异无统计学意义(P>0.05),治疗后,CC型:试验组24h Upr、Scr、BUN水平降低的幅度较观察组高(P<0.01或P<0.05)。ALB水平升高的幅度较观察组高,但其差异无统计学意义(P>0.05);CT型:24 h Upr和BUN水平降低的幅度较观察组高(P<0.01)。Scr水平降低的幅度较观察组高,ALB水平降低的幅度较观察组高,但其差异无统计学意义(P>0.05);TT型:24 h Upr、BUN水平降低的幅度较观察组高(P<0.01或P<0.05)。ALB水平升高的幅度较观察组高(P<0.01)。Scr水平降低的幅度较观察组高,但差异无统计学意义(P>0.05)。结论桂西壮族居民TGF-β启动子-509C/T位点多态性与IgA N患病无关联性;西药联合铁皮石斛处方治疗可有效提高IgA N的临床疗效;携带TGF-β启动子-509基因位点CC型的患者,不仅对西医治疗敏感,对铁皮石斛处方联合干预效果更敏感。
