Particle mixing and segregation are common phenomena in rotary drums,which are challenging to be controlled and driven artificially in powder technology.In this work,the discrete element method(DEM)was applied to cons...Particle mixing and segregation are common phenomena in rotary drums,which are challenging to be controlled and driven artificially in powder technology.In this work,the discrete element method(DEM)was applied to construct the novel rotary drum composed of different shaped curved sidewalls.By varying the operation parameters of particle and sidewall shapes as well as the length-to-diameter(L/D)ratio of drums,the axial mixing and segregation processes of binary size-induced particles were investigated.The results show that the axial flow velocity of the particle mixtures is noticeably weakened once the particle angularity increases,making the non-spherical particles to mix better in rotary drums compared to the spherical particles.Besides,in the short drums with size-induced spherical particles,the axial segregation characteristics are significantly enhanced by the convex sidewalls while suppressed by the concave sidewalls.However,for size-induced non-spherical particles,the axial segregation structure can be present in rotary drums with plane and concave sidewalls while not in drums with convex sidewalls.Moreover,the axial segregation band structure of spherical particles eventually increases proportionally with the increased drum L/D ratios.In contrast,the non-spherical particles cannot form obvious multi-proportional segregation bands.展开更多
Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak...Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions.The complete stress-displacement surface(CSDS)model was developed to describe analytically the pre-and post-peak behavior of rock interfaces under differential loads.Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools.The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stressdisplacement behavior of rock interfaces under differential loads.The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations.Barton’s concepts of joint roughness coefficient(JRC)and joint compressive strength(JCS)are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations.Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method.The results illustrate that the revised model successfully predicts the post-peak and complete axial stressestrain and shear stressedisplacement curves for rock joints.展开更多
为研究沙漠砂对再生混凝土力学性能的影响,以再生骨料为粗骨料,分别采用0%、20%、40%和60%的沙漠砂取代普通河砂制备沙漠砂再生骨料混凝土圆柱体试件并开展轴心受压试验。采用试件表面粘贴应变片和外夹式LVDT位移传感器分别采集荷载峰...为研究沙漠砂对再生混凝土力学性能的影响,以再生骨料为粗骨料,分别采用0%、20%、40%和60%的沙漠砂取代普通河砂制备沙漠砂再生骨料混凝土圆柱体试件并开展轴心受压试验。采用试件表面粘贴应变片和外夹式LVDT位移传感器分别采集荷载峰前和峰后应变,消除试件开裂以及加载板间隙等因素对测量精度的影响,从而更准确地测得轴压应力-应变全曲线。研究结果表明:随着沙漠砂替代率的增加,沙漠砂再生骨料混凝土抗压强度、弹性模量和横向变形系数呈现先增大后降低的趋势,其中抗压强度和横向变形系数在沙漠砂掺量为20%时最大,弹性模量在沙漠砂掺量为40%时最大。沙漠砂再生骨料混凝土应力-应变全过程曲线的形状与普通混凝土相似,基于Carrerira D J模型和过镇海模型建立了沙漠砂再生骨料混凝土应力-应变本构方程,计算结果与试验结果吻合较好。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
基金support from the National Natural Science Foundation of China (grant No.51775109)Natural Science Foundation of Jiangsu Province (grant No.BK20221465)the Jiangsu Province Elevator Intelligent Safety Key Construction Laboratory Open Project (grant No.JSKLESS202105).
文摘Particle mixing and segregation are common phenomena in rotary drums,which are challenging to be controlled and driven artificially in powder technology.In this work,the discrete element method(DEM)was applied to construct the novel rotary drum composed of different shaped curved sidewalls.By varying the operation parameters of particle and sidewall shapes as well as the length-to-diameter(L/D)ratio of drums,the axial mixing and segregation processes of binary size-induced particles were investigated.The results show that the axial flow velocity of the particle mixtures is noticeably weakened once the particle angularity increases,making the non-spherical particles to mix better in rotary drums compared to the spherical particles.Besides,in the short drums with size-induced spherical particles,the axial segregation characteristics are significantly enhanced by the convex sidewalls while suppressed by the concave sidewalls.However,for size-induced non-spherical particles,the axial segregation structure can be present in rotary drums with plane and concave sidewalls while not in drums with convex sidewalls.Moreover,the axial segregation band structure of spherical particles eventually increases proportionally with the increased drum L/D ratios.In contrast,the non-spherical particles cannot form obvious multi-proportional segregation bands.
基金The authors acknowledge the financial support from Natural Sciences and Engineering Research Council of Canada through its Discovery Grant program(RGPIN-2022-03893)École de Technologie Supérieure(ÉTS)construction engineering research funding.
文摘Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions.The complete stress-displacement surface(CSDS)model was developed to describe analytically the pre-and post-peak behavior of rock interfaces under differential loads.Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools.The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stressdisplacement behavior of rock interfaces under differential loads.The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations.Barton’s concepts of joint roughness coefficient(JRC)and joint compressive strength(JCS)are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations.Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method.The results illustrate that the revised model successfully predicts the post-peak and complete axial stressestrain and shear stressedisplacement curves for rock joints.
文摘为研究沙漠砂对再生混凝土力学性能的影响,以再生骨料为粗骨料,分别采用0%、20%、40%和60%的沙漠砂取代普通河砂制备沙漠砂再生骨料混凝土圆柱体试件并开展轴心受压试验。采用试件表面粘贴应变片和外夹式LVDT位移传感器分别采集荷载峰前和峰后应变,消除试件开裂以及加载板间隙等因素对测量精度的影响,从而更准确地测得轴压应力-应变全曲线。研究结果表明:随着沙漠砂替代率的增加,沙漠砂再生骨料混凝土抗压强度、弹性模量和横向变形系数呈现先增大后降低的趋势,其中抗压强度和横向变形系数在沙漠砂掺量为20%时最大,弹性模量在沙漠砂掺量为40%时最大。沙漠砂再生骨料混凝土应力-应变全过程曲线的形状与普通混凝土相似,基于Carrerira D J模型和过镇海模型建立了沙漠砂再生骨料混凝土应力-应变本构方程,计算结果与试验结果吻合较好。
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。
