The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 1...The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 13.56-MHz power source in 0.35-Pa argon environment. The peak of the external non-uniform magnetic field （Bex） along the axis is observed in a range from 0 Gs to 250 Gs （1 Gs=10^-4 T）, where the electron density varies from 0.5×10^16 m^-3 to 9×10^16 m^-3. When Bex is located near the tube upper end sealed by a dielectric plate, or near the tube bottom end connected with a diffusion chamber, the plasmas are centralized in the tube in the former case while the strong luminance appears between the edge of the tube and the axial line in the latter case. When Bex is located in the middle of the antenna, moreover, an effective resistance （Reff） peak appears apparently with increasing magnetic field. The glow moves toward first the edge of the tube and then the two antenna legs as the magnetic field increases. The discharge in this case is caused by the absorption of Trivelpiece-Gould （TG） wave. It is suggested that Bex is located in the middle of the antenna to obtain a higher efficiency of power transfer.展开更多
A series of three-dimensional numerical simulations is carried out to investigate the effect of inclined angle on flow behavior behind two side-by-side inclined cylinders at low Reynolds number Re=100 and small spacin...A series of three-dimensional numerical simulations is carried out to investigate the effect of inclined angle on flow behavior behind two side-by-side inclined cylinders at low Reynolds number Re=100 and small spacing ratio T/D=1.5 (T is the center-to-center distance between two side-by-side cylinders, D is the diameter of cylinder). The instantaneous and time-averaged flow fields, force coefficients and Strouhal numbers are analyzed. Special attention is focused on the axial flow characteristics with variation of the inclined angle. The results show that the inclined angle has a significant effect on the gap flow behaviors behind two inclined cylinders. The vortex shedding behind two cylinders is suppressed with the increase of the inclined angle as well as the flip-flop gap flow. Moreover, the mean drag coefficient, root-mean-square lift coefficient and Strouhal numbers decrease monotonously with the increase of the inclined angle, which follows the independent principle at small inclined angles.展开更多
目的:评价配戴基弧非球面设计角膜塑形镜控制近视的临床效果。方法:前瞻性研究。选取2020-01/2021-07于我院验配角膜塑形镜的8~13岁近视患者94例94眼(单眼接受角膜塑形镜治疗者,选取该眼作为观察眼,双眼均接受角膜塑形镜治疗的患者则以...目的:评价配戴基弧非球面设计角膜塑形镜控制近视的临床效果。方法:前瞻性研究。选取2020-01/2021-07于我院验配角膜塑形镜的8~13岁近视患者94例94眼(单眼接受角膜塑形镜治疗者,选取该眼作为观察眼,双眼均接受角膜塑形镜治疗的患者则以右眼作为观察眼),根据患者所配戴的角膜塑形镜基弧区的设计不同分为观察组:配戴基弧非球面设计的角膜塑形镜患者46例;对照组:配戴基弧球面设计的角膜塑形镜患者48例。根据两组患者戴镜前等效球镜(SE)不同进一步分为低度近视组(-3.00D<SE≤-0.75D)52例52眼和中度近视组(-6.00D<SE≤-3.00D)中度近视组42例42眼。评估戴镜后1d,1wk,1、3、6、9mo,1a裸眼视力,并于戴镜后6mo,1a分别测量眼轴。结果:所有患者均完成随访,戴镜1mo后观察组裸眼视力(LogMAR)-0.12±0.08与对照组(-0.17±0.07)比较无差异(P>0.05);两组患者戴镜后6mo,1a眼轴增长平均值均无差异(均P>0.05)。低度近视组中,观察组戴镜1a眼轴增长值为0.19±0.17mm,明显低于对照组(0.31±0.18mm)(P<0.05);中度近视组中,观察组戴镜1a眼轴增长值为0.22±0.18mm,与对照组(0.19±0.12mm)比较无差异(P>0.05)。戴镜后6mo,1a观察组低度近视组与中度近视组眼轴增长值无差异(P>0.05),而对照组低度近视与中度近视组戴镜后6mo(0.15±0.13 vs 0.05±0.12mm)、1a(0.31±0.18 vs 0.19±0.12mm)眼轴增长值均有差异(均P<0.05)。结论:配戴基弧非球面设计角膜塑形镜可以有效提高裸眼视力,延缓眼轴增长。对于低度近视患者,基弧非球面设计角膜塑形镜延缓眼轴增长的效果优于基弧球面设计。展开更多
针对高压大口径轴流式止回阀超低温工况密封失效,特别是经过高压试验或者高压下开关动作后密封面损坏,阀门无法满足长周期稳定运行问题,设计了一种具有特殊阀内密封结构的高压轴流式止回阀。使用有限元软件对改进后的阀体结构进行强度...针对高压大口径轴流式止回阀超低温工况密封失效,特别是经过高压试验或者高压下开关动作后密封面损坏,阀门无法满足长周期稳定运行问题,设计了一种具有特殊阀内密封结构的高压轴流式止回阀。使用有限元软件对改进后的阀体结构进行强度分析校核;以相关型式试验论证,将阀门置于-196℃试验温度下,进行2 000次的阀门整机低温疲劳寿命试验,试验全过程中最大泄漏率为1 700 m L/min,远远低于标准规定上限值3 600 m L/min;经江苏LNG现场使用,结果表明通过结构优化,低温大口径高压轴流式止回阀性能完全满足LNG装置及超低温工况要求,主要性能和技术指标达到了国际上同类阀门的水平。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11175024,11375031,and 11505013)the Beijing Natural Science Foundation of China(Grant No.KZ201510015014)the Beijing Municipal Natural Science Foundation,China(Grant No.4162024)
文摘The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 13.56-MHz power source in 0.35-Pa argon environment. The peak of the external non-uniform magnetic field （Bex） along the axis is observed in a range from 0 Gs to 250 Gs （1 Gs=10^-4 T）, where the electron density varies from 0.5×10^16 m^-3 to 9×10^16 m^-3. When Bex is located near the tube upper end sealed by a dielectric plate, or near the tube bottom end connected with a diffusion chamber, the plasmas are centralized in the tube in the former case while the strong luminance appears between the edge of the tube and the axial line in the latter case. When Bex is located in the middle of the antenna, moreover, an effective resistance （Reff） peak appears apparently with increasing magnetic field. The glow moves toward first the edge of the tube and then the two antenna legs as the magnetic field increases. The discharge in this case is caused by the absorption of Trivelpiece-Gould （TG） wave. It is suggested that Bex is located in the middle of the antenna to obtain a higher efficiency of power transfer.
基金financially supported by Joint Key Funds of Zhejiang Provincial Natural Science Foundation of China and Powerchina Huadong Engineering Corporation Limited(Grant No.LHZ19E090004)the National Key R&D Program of China(Grant No.2018YFD0900901)
文摘A series of three-dimensional numerical simulations is carried out to investigate the effect of inclined angle on flow behavior behind two side-by-side inclined cylinders at low Reynolds number Re=100 and small spacing ratio T/D=1.5 (T is the center-to-center distance between two side-by-side cylinders, D is the diameter of cylinder). The instantaneous and time-averaged flow fields, force coefficients and Strouhal numbers are analyzed. Special attention is focused on the axial flow characteristics with variation of the inclined angle. The results show that the inclined angle has a significant effect on the gap flow behaviors behind two inclined cylinders. The vortex shedding behind two cylinders is suppressed with the increase of the inclined angle as well as the flip-flop gap flow. Moreover, the mean drag coefficient, root-mean-square lift coefficient and Strouhal numbers decrease monotonously with the increase of the inclined angle, which follows the independent principle at small inclined angles.
文摘目的:评价配戴基弧非球面设计角膜塑形镜控制近视的临床效果。方法:前瞻性研究。选取2020-01/2021-07于我院验配角膜塑形镜的8~13岁近视患者94例94眼(单眼接受角膜塑形镜治疗者,选取该眼作为观察眼,双眼均接受角膜塑形镜治疗的患者则以右眼作为观察眼),根据患者所配戴的角膜塑形镜基弧区的设计不同分为观察组:配戴基弧非球面设计的角膜塑形镜患者46例;对照组:配戴基弧球面设计的角膜塑形镜患者48例。根据两组患者戴镜前等效球镜(SE)不同进一步分为低度近视组(-3.00D<SE≤-0.75D)52例52眼和中度近视组(-6.00D<SE≤-3.00D)中度近视组42例42眼。评估戴镜后1d,1wk,1、3、6、9mo,1a裸眼视力,并于戴镜后6mo,1a分别测量眼轴。结果:所有患者均完成随访,戴镜1mo后观察组裸眼视力(LogMAR)-0.12±0.08与对照组(-0.17±0.07)比较无差异(P>0.05);两组患者戴镜后6mo,1a眼轴增长平均值均无差异(均P>0.05)。低度近视组中,观察组戴镜1a眼轴增长值为0.19±0.17mm,明显低于对照组(0.31±0.18mm)(P<0.05);中度近视组中,观察组戴镜1a眼轴增长值为0.22±0.18mm,与对照组(0.19±0.12mm)比较无差异(P>0.05)。戴镜后6mo,1a观察组低度近视组与中度近视组眼轴增长值无差异(P>0.05),而对照组低度近视与中度近视组戴镜后6mo(0.15±0.13 vs 0.05±0.12mm)、1a(0.31±0.18 vs 0.19±0.12mm)眼轴增长值均有差异(均P<0.05)。结论:配戴基弧非球面设计角膜塑形镜可以有效提高裸眼视力,延缓眼轴增长。对于低度近视患者,基弧非球面设计角膜塑形镜延缓眼轴增长的效果优于基弧球面设计。
文摘针对高压大口径轴流式止回阀超低温工况密封失效,特别是经过高压试验或者高压下开关动作后密封面损坏,阀门无法满足长周期稳定运行问题,设计了一种具有特殊阀内密封结构的高压轴流式止回阀。使用有限元软件对改进后的阀体结构进行强度分析校核;以相关型式试验论证,将阀门置于-196℃试验温度下,进行2 000次的阀门整机低温疲劳寿命试验,试验全过程中最大泄漏率为1 700 m L/min,远远低于标准规定上限值3 600 m L/min;经江苏LNG现场使用,结果表明通过结构优化,低温大口径高压轴流式止回阀性能完全满足LNG装置及超低温工况要求,主要性能和技术指标达到了国际上同类阀门的水平。
