This paper studies the wall-bounded flow around a cylindrical at a high Reynolds numbers body in a determined computational domain, with simulations of the 3-D, turbulent concentric annulus flow in a straight pipe. Nu...This paper studies the wall-bounded flow around a cylindrical at a high Reynolds numbers body in a determined computational domain, with simulations of the 3-D, turbulent concentric annulus flow in a straight pipe. Numerical results show that a reversing zone, appearing as a tongue zone with nested velocities higher than the surrounding area, exists behind the cylindrical body. The annulus space is a region of high velocity and low pressure. The zero velocity, of combined the X- velocity and the Y- velocity, exists in the cross sections and no vortex shedding is formed behind the attaching cylinders. Among all investigated effecting factors, the diameters of the attaching and the main cylinders affect the wake feature behind the cylindrical body while the main cylinder length does not affect the distribution tendency of the flow field. The diameters of the main cylinder and the pipe affect the pressure values and the distribution tendencies on the main cylinder surface. Obviously, the increase of the pipe diameter reduces the drag coefficient of the cylindrical body and the increase of the diameter of the main cylinder increases the drag coefficient greatly. The numerical investigation of the concentric annulus flow provides foundations for further improvements of the intricate flow studies.展开更多
目的分析新生儿肺炎(NP)患儿经加温湿化高流量鼻导管通气(HHFNC)治疗失败的危险因素,构建预测模型并评估其预测效能。方法选取2023年2月至2024年10月南阳市中心医院收治的130例NP患儿,均采用HHFNC作为主要呼吸支持治疗方式。依据HHFNC...目的分析新生儿肺炎(NP)患儿经加温湿化高流量鼻导管通气(HHFNC)治疗失败的危险因素,构建预测模型并评估其预测效能。方法选取2023年2月至2024年10月南阳市中心医院收治的130例NP患儿,均采用HHFNC作为主要呼吸支持治疗方式。依据HHFNC治疗效果分为治疗成功组、治疗失败组,单因素、多因素logistic回归分析法筛选NP患儿HHFNC治疗失败的影响因素。基于上述影响因素构建NP患儿HHFNC治疗失败风险列线图模型,并评估列线图模型预测效能。结果采用HHFNC作为主要呼吸支持治疗方式的130例NP患儿中,22例(16.92%)患儿HHFNC治疗失败,108例(83.08%)患儿HHFNC治疗成功。治疗成功组、治疗失败组咽喉分泌物清理不及时比例、出生后5 min Apgar评分、HHFNC治疗前降钙素原(PCT)、25羟维生素D(25-OH-D)、呼吸评分(RS)、氧合指数(OI)及HHFNC初始吸入氧浓度(FiO_(2))差异有统计学意义(P<0.05)。多因素logistic回归分析,结果显示,咽喉分泌物清理不及时(OR=1.352)、HHFNC治疗前PCT(OR=1.329)、HHFNC治疗前RS(OR=1.124)、HHFNC初始FiO_(2)(OR=1.042)是NP患儿HHFNC治疗失败的危险因素(P<0.05),出生后5 min Apgar评分(OR=0.742)、HHFNC治疗前25-OH-D(OR=0.710)、HHFNC治疗前OI(OR=0.804)是NP患儿HHFNC治疗失败的保护因素(P<0.05)。基于上述影响因素构建NP患儿HHFNC治疗失败风险列线图模型,结果显示,该列线图模型预测值与实测值差异无统计学意义(χ^(2)=2.025,P=0.228),预测NP患儿HHFNC治疗失败的敏感度、特异度、曲线下面积分别为90.00%、78.00%、0.889(95%CI:0.752~0.945),且当预测概率阈值0.20~0.75时,对NP患儿采取干预措施,患儿净获益情况最佳。结论NP患儿HHFNC治疗失败受咽喉分泌物清理不及时、出生后5 min Apgar评分、HHFNC治疗前PCT、25-OH-D、RS、OI及HHFNC初始FiO_(2)的影响。本研究构建的列线图模型预测NP患儿HHFNC治疗失败的准确度、区分度均较高。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51179116,51109155)
文摘This paper studies the wall-bounded flow around a cylindrical at a high Reynolds numbers body in a determined computational domain, with simulations of the 3-D, turbulent concentric annulus flow in a straight pipe. Numerical results show that a reversing zone, appearing as a tongue zone with nested velocities higher than the surrounding area, exists behind the cylindrical body. The annulus space is a region of high velocity and low pressure. The zero velocity, of combined the X- velocity and the Y- velocity, exists in the cross sections and no vortex shedding is formed behind the attaching cylinders. Among all investigated effecting factors, the diameters of the attaching and the main cylinders affect the wake feature behind the cylindrical body while the main cylinder length does not affect the distribution tendency of the flow field. The diameters of the main cylinder and the pipe affect the pressure values and the distribution tendencies on the main cylinder surface. Obviously, the increase of the pipe diameter reduces the drag coefficient of the cylindrical body and the increase of the diameter of the main cylinder increases the drag coefficient greatly. The numerical investigation of the concentric annulus flow provides foundations for further improvements of the intricate flow studies.
文摘目的分析新生儿肺炎(NP)患儿经加温湿化高流量鼻导管通气(HHFNC)治疗失败的危险因素,构建预测模型并评估其预测效能。方法选取2023年2月至2024年10月南阳市中心医院收治的130例NP患儿,均采用HHFNC作为主要呼吸支持治疗方式。依据HHFNC治疗效果分为治疗成功组、治疗失败组,单因素、多因素logistic回归分析法筛选NP患儿HHFNC治疗失败的影响因素。基于上述影响因素构建NP患儿HHFNC治疗失败风险列线图模型,并评估列线图模型预测效能。结果采用HHFNC作为主要呼吸支持治疗方式的130例NP患儿中,22例(16.92%)患儿HHFNC治疗失败,108例(83.08%)患儿HHFNC治疗成功。治疗成功组、治疗失败组咽喉分泌物清理不及时比例、出生后5 min Apgar评分、HHFNC治疗前降钙素原(PCT)、25羟维生素D(25-OH-D)、呼吸评分(RS)、氧合指数(OI)及HHFNC初始吸入氧浓度(FiO_(2))差异有统计学意义(P<0.05)。多因素logistic回归分析,结果显示,咽喉分泌物清理不及时(OR=1.352)、HHFNC治疗前PCT(OR=1.329)、HHFNC治疗前RS(OR=1.124)、HHFNC初始FiO_(2)(OR=1.042)是NP患儿HHFNC治疗失败的危险因素(P<0.05),出生后5 min Apgar评分(OR=0.742)、HHFNC治疗前25-OH-D(OR=0.710)、HHFNC治疗前OI(OR=0.804)是NP患儿HHFNC治疗失败的保护因素(P<0.05)。基于上述影响因素构建NP患儿HHFNC治疗失败风险列线图模型,结果显示,该列线图模型预测值与实测值差异无统计学意义(χ^(2)=2.025,P=0.228),预测NP患儿HHFNC治疗失败的敏感度、特异度、曲线下面积分别为90.00%、78.00%、0.889(95%CI:0.752~0.945),且当预测概率阈值0.20~0.75时,对NP患儿采取干预措施,患儿净获益情况最佳。结论NP患儿HHFNC治疗失败受咽喉分泌物清理不及时、出生后5 min Apgar评分、HHFNC治疗前PCT、25-OH-D、RS、OI及HHFNC初始FiO_(2)的影响。本研究构建的列线图模型预测NP患儿HHFNC治疗失败的准确度、区分度均较高。
