The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(ID...The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.展开更多
In the United States, the costs of health care have become a major burden for the health care system. In order to address this problem, the hospitals of Syracuse, New York, developed programs to provide subacute and c...In the United States, the costs of health care have become a major burden for the health care system. In order to address this problem, the hospitals of Syracuse, New York, developed programs to provide subacute and complex care. The Subacute programs provided patient transportation services for dialysis and other types of care outside hospitals. They also developed programs for services such as intravenous therapy in nursing homes. The Complex Care Programs, such as intravenous therapy and mental health services, have provided alternatives to extended care in hospitals. During the past five years, utilization of these programs has varied, declining between 2019 and 2022, and then increasing between 2022 and 2024. The programs have avoided the need for 1530 - 2974 patient days in hospitals. The programs saved the Syracuse hospitals approximately $600 per inpatient day. This amounted to savings of $918,000 - $1,784,400 per year. These programs demonstrated how relatively small mechanisms can save large amounts of health care resources.展开更多
利用昆明站1991-2020年近30年逐日降水数据计算昆明雨季(5-10月)的起止时期,进一步确定昆明市雨季的长短。又基于云南省和昆明市的统计年鉴数据,使用年末总人口、城市建成区面积、城镇化率、人均GDP等城市发展因子确定昆明的城市发展进...利用昆明站1991-2020年近30年逐日降水数据计算昆明雨季(5-10月)的起止时期,进一步确定昆明市雨季的长短。又基于云南省和昆明市的统计年鉴数据,使用年末总人口、城市建成区面积、城镇化率、人均GDP等城市发展因子确定昆明的城市发展进程,将昆明市的城市发展进程划分为缓慢发展期(1991-2003年)和快速发展期(2004-2020年),进而分析比较两段时期中昆明市雨季长短的特征和差异,采用统计分析、小波分析和M-K突变检验等综合分析方法,系统分析了昆明市雨季长短的时间变化特征,并用灰色关联度分析方法分析了昆明市雨季长短与城市发展的关联性。结果表明,1991-2020年昆明市的雨季开始日呈逐渐偏晚的趋势,而雨季结束日呈逐渐偏早的趋势,总体上雨季长度呈逐渐缩短的趋势;小波系数分析结果显示,在8年以下的时间尺度上,昆明市雨季长短变化的周期不存在明显的规律性,在17年时间尺度上的周期变化明显,呈偏短-偏长-偏短-偏长-偏短的5个循环交替,2003-2008年、 2014-2017年雨季增长,1991-2002年、 2009-2012年、 2018-2020年雨季缩短,2018-2020年等值线未闭合说明还有进一步缩短的趋势。通过M-K检验表明昆明市的雨季长短在1991-2020年间出现4次突变,分别发生在2002年、 2008年、 2012年和2017年。从昆明城市发展与雨季长短的关系来看,昆明城市发展缓慢期的雨季长短的变化趋势较为平稳,而城市发展快速期2004年以后,昆明市雨季长度缩短的变化明显,并随着城市发展进程的加快其极端波动性更加明显。运用SPSS(Statistical Product and Service Solutions)软件对未来10年昆明的雨季长短进行预测,结果显示未来10年昆明雨季长短将持续偏短的趋势。在灰色关联度分辨率为0.5时,表征城市发展进程的4个因子对昆明雨季长短变化均产生不同程度影响,其关联度系数都在0.70以上,表明昆明城市发展与雨季长短显著关联性,其中影响最大的因子是年末总人口,最小为人均GDP,灰色关联度分别为0.88和0.70,属于高度关联和显著关联。对4个因子的关联系数进行排序为:年末总人口>城镇化率>城市建成区面积>人均GDP。展开更多
目的探讨影响单侧髋膝关节置换术后住院时间(length of stay,LOS)的围术期因素。方法通过筛选纳入我院行单侧髋或膝关节置换术的患者1490例;记录术前一般情况、合并症、药物使用、手术方式、手术医生、麻醉方式、麻醉用药、手术时间、...目的探讨影响单侧髋膝关节置换术后住院时间(length of stay,LOS)的围术期因素。方法通过筛选纳入我院行单侧髋或膝关节置换术的患者1490例;记录术前一般情况、合并症、药物使用、手术方式、手术医生、麻醉方式、麻醉用药、手术时间、液体出入量和种类等相关参数;采用单因素、多因素线性回归模型,分析患者关节置换术后影响LOS的因素。结果术后LOS为(9.63±5.13)d;THA、TKA和股骨头置换术后LOS分别为(8.80±4.70)d、(10.25±4.41)d和(11.94±7.09)d;手术时长(97.00±43.00)min;术后情况有急性肾功能损伤(AKI)80例(5.4%)、转入ICU病房99例(6.6%)、死亡5例(0.3%);其中年龄(P<0.001)、术前合并肺部感染(P=0.004)、手术医生的手术量和工作年限(P<0.001)、术中异体红细胞输注(P=0.028)、手术时长(P<0.001)、术后进入ICU(P<0.001)及术后发生AKI(P=0.047)与LOS的变化有显著相关性;术中异体红细胞输注患者LOS增加2 d;术后入住ICU比未入住者LOS延长4 d;术后发生AKI的患者LOS增加3 d。结论年龄>70岁、术前合并肺部感染、手术时间>120 min、工作年限短和年手术量少的手术医生、术中输注红细胞、术后转入ICU以及发生AKI是髋膝关节置换术后LOS增加的独立风险因素。展开更多
为研究进排气门正时角度和进气歧管长度对于柴油机综合性能的影响,利用发动机仿真软件GT-Power对某款国产柴油发电机的柴油机部分进行建模,并基于台架实验验证其模型准确性。在额定转速为1500 r/min、负载为90%的工况下,应用实验设计(de...为研究进排气门正时角度和进气歧管长度对于柴油机综合性能的影响,利用发动机仿真软件GT-Power对某款国产柴油发电机的柴油机部分进行建模,并基于台架实验验证其模型准确性。在额定转速为1500 r/min、负载为90%的工况下,应用实验设计(design of experiments,DOE)工具,以发动机进排气门正时角度和进气歧管长度作为自变量,柴油机功率、比油耗和碳烟(soot)排放率为因变量,进行了最大功率、最小比油耗和最低碳烟排放量的多目标优化。结果表明:适当缩短进气歧管长度可以提高发动机进气压力和进气效率,提高发动机动力性和燃油经济性,增大气门重叠角可以有效降低气缸的泵气损失,提升柴油机做功效率,同时降低气缸内温度,从而降低碳烟的排放率。最终,各个目标值分别实现了1.3%、1.0%和2.6%的优化。展开更多
基金supported by Wuyi University Hong Kong and Macao Joint Research and Development Fund(GrantsNos.2021WGALH15,2019WGALH17,2019WGALH15)the National Natural Science Foundation of China-Guangdong Joint Fund(GrantsNo.2019A1515111052)+2 种基金the National Natural Science Foundation of China(Grant No.52202426)a grant from the Research Grants Council(RGC)of the Hong Kong Special Administrative Region(SAR),China(Grants No.15205723)a grant from the Hong Kong Polytechnic University(Grant No.P0045325).
文摘The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.
文摘In the United States, the costs of health care have become a major burden for the health care system. In order to address this problem, the hospitals of Syracuse, New York, developed programs to provide subacute and complex care. The Subacute programs provided patient transportation services for dialysis and other types of care outside hospitals. They also developed programs for services such as intravenous therapy in nursing homes. The Complex Care Programs, such as intravenous therapy and mental health services, have provided alternatives to extended care in hospitals. During the past five years, utilization of these programs has varied, declining between 2019 and 2022, and then increasing between 2022 and 2024. The programs have avoided the need for 1530 - 2974 patient days in hospitals. The programs saved the Syracuse hospitals approximately $600 per inpatient day. This amounted to savings of $918,000 - $1,784,400 per year. These programs demonstrated how relatively small mechanisms can save large amounts of health care resources.
文摘利用昆明站1991-2020年近30年逐日降水数据计算昆明雨季(5-10月)的起止时期,进一步确定昆明市雨季的长短。又基于云南省和昆明市的统计年鉴数据,使用年末总人口、城市建成区面积、城镇化率、人均GDP等城市发展因子确定昆明的城市发展进程,将昆明市的城市发展进程划分为缓慢发展期(1991-2003年)和快速发展期(2004-2020年),进而分析比较两段时期中昆明市雨季长短的特征和差异,采用统计分析、小波分析和M-K突变检验等综合分析方法,系统分析了昆明市雨季长短的时间变化特征,并用灰色关联度分析方法分析了昆明市雨季长短与城市发展的关联性。结果表明,1991-2020年昆明市的雨季开始日呈逐渐偏晚的趋势,而雨季结束日呈逐渐偏早的趋势,总体上雨季长度呈逐渐缩短的趋势;小波系数分析结果显示,在8年以下的时间尺度上,昆明市雨季长短变化的周期不存在明显的规律性,在17年时间尺度上的周期变化明显,呈偏短-偏长-偏短-偏长-偏短的5个循环交替,2003-2008年、 2014-2017年雨季增长,1991-2002年、 2009-2012年、 2018-2020年雨季缩短,2018-2020年等值线未闭合说明还有进一步缩短的趋势。通过M-K检验表明昆明市的雨季长短在1991-2020年间出现4次突变,分别发生在2002年、 2008年、 2012年和2017年。从昆明城市发展与雨季长短的关系来看,昆明城市发展缓慢期的雨季长短的变化趋势较为平稳,而城市发展快速期2004年以后,昆明市雨季长度缩短的变化明显,并随着城市发展进程的加快其极端波动性更加明显。运用SPSS(Statistical Product and Service Solutions)软件对未来10年昆明的雨季长短进行预测,结果显示未来10年昆明雨季长短将持续偏短的趋势。在灰色关联度分辨率为0.5时,表征城市发展进程的4个因子对昆明雨季长短变化均产生不同程度影响,其关联度系数都在0.70以上,表明昆明城市发展与雨季长短显著关联性,其中影响最大的因子是年末总人口,最小为人均GDP,灰色关联度分别为0.88和0.70,属于高度关联和显著关联。对4个因子的关联系数进行排序为:年末总人口>城镇化率>城市建成区面积>人均GDP。
文摘为研究进排气门正时角度和进气歧管长度对于柴油机综合性能的影响,利用发动机仿真软件GT-Power对某款国产柴油发电机的柴油机部分进行建模,并基于台架实验验证其模型准确性。在额定转速为1500 r/min、负载为90%的工况下,应用实验设计(design of experiments,DOE)工具,以发动机进排气门正时角度和进气歧管长度作为自变量,柴油机功率、比油耗和碳烟(soot)排放率为因变量,进行了最大功率、最小比油耗和最低碳烟排放量的多目标优化。结果表明:适当缩短进气歧管长度可以提高发动机进气压力和进气效率,提高发动机动力性和燃油经济性,增大气门重叠角可以有效降低气缸的泵气损失,提升柴油机做功效率,同时降低气缸内温度,从而降低碳烟的排放率。最终,各个目标值分别实现了1.3%、1.0%和2.6%的优化。
