Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was...Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was established. Using parametric programming language, finite element calculation modules considering climate conditions, bridge site, structure dimension and material thermophysical properties were compiled. Six standard day cycles with the strongest yearly radiation among the bridge sites were selected for sectional solar temperature field calculation and temperature distributions under different temperature-sensitive parameters were compared. The results show that under the influence of sunshine, U-shape section of the beam shows obvious nonlinear distribution characteristics and the maximum cross-section temperature difference is more than 21℃; the ballast significantly reduces sunshine temperature difference of the beam and temperature peak of the bottom margin lags with the increase of ballast thickness; the maximum cross-section vertical temperature gradient appears in summer while large transverse temperature difference appears in winter.展开更多
In this work,we report a novel octa-nuclear uranyl(U8)motif[(UO2)8O4(μ3-OH)2(μ2-OH)2]4+embedded in a uranyl-oxalate coordination polymer(compound 1)based on a U-shaped linker with extra-long xylylene chains for stab...In this work,we report a novel octa-nuclear uranyl(U8)motif[(UO2)8O4(μ3-OH)2(μ2-OH)2]4+embedded in a uranyl-oxalate coordination polymer(compound 1)based on a U-shaped linker with extra-long xylylene chains for stabilizing the resulting high-nuclear motif through additional cross-linking connectivity.A comparison with dimeric and monomeric uranyl compounds obtained at different pH value from the same hydrothermal system reveals that,solution pH plays a vital role in formation of this octa-nuclear uranyl motif by promoting hydrolysis of uranyl source.Since high similarity of eight uranium centers in this nearly planar U8 motif here,overlapping and broadening of signals in fluorescence,infra-red(IR)and Raman spectra can be found.展开更多
目的探讨维持性血液透析(maintenance hemodialysis,MHD)患者计时站立行走测试(time up and go test,TUG)时间延长的影响因素。方法采用横断面调查法,选取2023年6月1日至2024年1月31日于首都医科大学附属北京潞河医院规律血液透析、数...目的探讨维持性血液透析(maintenance hemodialysis,MHD)患者计时站立行走测试(time up and go test,TUG)时间延长的影响因素。方法采用横断面调查法,选取2023年6月1日至2024年1月31日于首都医科大学附属北京潞河医院规律血液透析、数据完整且可配合的患者,分别采用简易精神状态检查表(Minimum Mental State Examination,MMSE)、5次起坐试验(5 times sit to stand,STS-5)、TUG量表评估患者认知功能、下肢肌肉力量、平衡及步态功能;根据TUG结果进行分组,即TUG≤12 s,判定为TUG正常组;TUG>12 s判定为TUG延长组,采用多因素Logistic回归法分析患者TUG延长组的影响因素,以受试者工作特征(receiver operating characteristic,ROC)曲线分析影响因素对TUG延长患者的预测价值。结果本研究共纳入146例MHD患者,TUG延长组86例,TUG正常组60例,两组的性别、年龄、合并高血压、合并糖尿病、血糖、教育水平、MMSE评分、C反应蛋白、血白蛋白、血肌酐、血钠、全段甲状旁腺素、低密度脂蛋白胆固醇、血尿酸、STS-5、单次尿素氮清除指数(urea clearance index,Kt/V)差异具有统计学意义(P<0.05);进一步行多因素Logistic回归分析显示,高龄、女性、低MMSE评分、低Kt/V以及STS-5时间延长是发生TUG延长的独立危险因素(P<0.05);ROC曲线显示,年龄、性别、MMSE总分、STS-5时间预测MHD患者发生TUG延长的曲线下面积(area under the curve,AUC)分别为0.825、0.678、0.777、0.836(P<0.01),具有较高的预测价值,Kt/V预测患者发生TUG延长的AUC为0.602(P=0.037),有一定的预测价值;以上5项指标作为整体模型预测MHD患者发生TUG延长的AUC为0.923(P<0.01)结论MHD患者的年龄、性别、MMSE评分、STS-5时间延长、Kt/V的水平与合并TUG延长相关,是发生TUG延长的独立危险因素,可能成为预测TUG延长的生物学指标。展开更多
巷道断面成形是煤矿掘进过程中的重要工序,但目前的巷道断面成形作业多为人工控制掘进机进行往复式截割,制约了煤矿掘进工作面的智能化发展。为此,针对断面成形轨迹规划未考虑煤岩特征、优化目标单一的问题,提出了一种基于改进灰狼优化(...巷道断面成形是煤矿掘进过程中的重要工序,但目前的巷道断面成形作业多为人工控制掘进机进行往复式截割,制约了煤矿掘进工作面的智能化发展。为此,针对断面成形轨迹规划未考虑煤岩特征、优化目标单一的问题,提出了一种基于改进灰狼优化(grey wolf optimizer, GWO)算法的掘进机断面成形轨迹规划方法。首先,根据夹矸位置将待截割断面环境分为4种情况,对相应断面进行栅格化处理并建立栅格地图,同时采用二值膨胀法对不规则夹矸进行膨胀化处理。然后,对GWO算法进行了改进,以提升其寻优性能和收敛速度。接着,开展了仿真实验,利用改进GWO算法实现了4种环境下掘进机断面成形轨迹的规划。最后,利用掘进机样机开展了断面截割实验。仿真结果表明:相较于传统的GWO算法,改进GWO算法的收敛速度更快且收敛精度更高;在4种断面环境下,基于改进GWO算法规划的断面成形轨迹长度最短,欠挖面积最小,转向次数最少,更容易实现高精度、高效率的轨迹跟踪控制,保证了巷道断面的成形质量。实验结果表明,基于改进GWO算法规划的断面成形轨迹既能提高掘进机的截割效率,又能满足巷道断面成形的质量要求。研究结果可为煤矿井下智能掘进技术的发展提供新的思路和方法。展开更多
基金Project(51378503)supported by the National Natural Science Foundation of ChinaProject(2010G018-A-3)supported by Technology Research and Development Program of the Ministry of Railways,China
文摘Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was established. Using parametric programming language, finite element calculation modules considering climate conditions, bridge site, structure dimension and material thermophysical properties were compiled. Six standard day cycles with the strongest yearly radiation among the bridge sites were selected for sectional solar temperature field calculation and temperature distributions under different temperature-sensitive parameters were compared. The results show that under the influence of sunshine, U-shape section of the beam shows obvious nonlinear distribution characteristics and the maximum cross-section temperature difference is more than 21℃; the ballast significantly reduces sunshine temperature difference of the beam and temperature peak of the bottom margin lags with the increase of ballast thickness; the maximum cross-section vertical temperature gradient appears in summer while large transverse temperature difference appears in winter.
基金National Natural Science Foundation of China(21671191,21577144,11405186)。
文摘In this work,we report a novel octa-nuclear uranyl(U8)motif[(UO2)8O4(μ3-OH)2(μ2-OH)2]4+embedded in a uranyl-oxalate coordination polymer(compound 1)based on a U-shaped linker with extra-long xylylene chains for stabilizing the resulting high-nuclear motif through additional cross-linking connectivity.A comparison with dimeric and monomeric uranyl compounds obtained at different pH value from the same hydrothermal system reveals that,solution pH plays a vital role in formation of this octa-nuclear uranyl motif by promoting hydrolysis of uranyl source.Since high similarity of eight uranium centers in this nearly planar U8 motif here,overlapping and broadening of signals in fluorescence,infra-red(IR)and Raman spectra can be found.
文摘目的探讨维持性血液透析(maintenance hemodialysis,MHD)患者计时站立行走测试(time up and go test,TUG)时间延长的影响因素。方法采用横断面调查法,选取2023年6月1日至2024年1月31日于首都医科大学附属北京潞河医院规律血液透析、数据完整且可配合的患者,分别采用简易精神状态检查表(Minimum Mental State Examination,MMSE)、5次起坐试验(5 times sit to stand,STS-5)、TUG量表评估患者认知功能、下肢肌肉力量、平衡及步态功能;根据TUG结果进行分组,即TUG≤12 s,判定为TUG正常组;TUG>12 s判定为TUG延长组,采用多因素Logistic回归法分析患者TUG延长组的影响因素,以受试者工作特征(receiver operating characteristic,ROC)曲线分析影响因素对TUG延长患者的预测价值。结果本研究共纳入146例MHD患者,TUG延长组86例,TUG正常组60例,两组的性别、年龄、合并高血压、合并糖尿病、血糖、教育水平、MMSE评分、C反应蛋白、血白蛋白、血肌酐、血钠、全段甲状旁腺素、低密度脂蛋白胆固醇、血尿酸、STS-5、单次尿素氮清除指数(urea clearance index,Kt/V)差异具有统计学意义(P<0.05);进一步行多因素Logistic回归分析显示,高龄、女性、低MMSE评分、低Kt/V以及STS-5时间延长是发生TUG延长的独立危险因素(P<0.05);ROC曲线显示,年龄、性别、MMSE总分、STS-5时间预测MHD患者发生TUG延长的曲线下面积(area under the curve,AUC)分别为0.825、0.678、0.777、0.836(P<0.01),具有较高的预测价值,Kt/V预测患者发生TUG延长的AUC为0.602(P=0.037),有一定的预测价值;以上5项指标作为整体模型预测MHD患者发生TUG延长的AUC为0.923(P<0.01)结论MHD患者的年龄、性别、MMSE评分、STS-5时间延长、Kt/V的水平与合并TUG延长相关,是发生TUG延长的独立危险因素,可能成为预测TUG延长的生物学指标。
文摘巷道断面成形是煤矿掘进过程中的重要工序,但目前的巷道断面成形作业多为人工控制掘进机进行往复式截割,制约了煤矿掘进工作面的智能化发展。为此,针对断面成形轨迹规划未考虑煤岩特征、优化目标单一的问题,提出了一种基于改进灰狼优化(grey wolf optimizer, GWO)算法的掘进机断面成形轨迹规划方法。首先,根据夹矸位置将待截割断面环境分为4种情况,对相应断面进行栅格化处理并建立栅格地图,同时采用二值膨胀法对不规则夹矸进行膨胀化处理。然后,对GWO算法进行了改进,以提升其寻优性能和收敛速度。接着,开展了仿真实验,利用改进GWO算法实现了4种环境下掘进机断面成形轨迹的规划。最后,利用掘进机样机开展了断面截割实验。仿真结果表明:相较于传统的GWO算法,改进GWO算法的收敛速度更快且收敛精度更高;在4种断面环境下,基于改进GWO算法规划的断面成形轨迹长度最短,欠挖面积最小,转向次数最少,更容易实现高精度、高效率的轨迹跟踪控制,保证了巷道断面的成形质量。实验结果表明,基于改进GWO算法规划的断面成形轨迹既能提高掘进机的截割效率,又能满足巷道断面成形的质量要求。研究结果可为煤矿井下智能掘进技术的发展提供新的思路和方法。
