In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(...In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.展开更多
We investigate the onset and the decay of Taylor-Couette flow in finite cylinders, and we report the estimated time scales in the azimuthal section of the flow state transition between the super-critical state and the...We investigate the onset and the decay of Taylor-Couette flow in finite cylinders, and we report the estimated time scales in the azimuthal section of the flow state transition between the super-critical state and the sub-critical state by fitting the numerical result to the solution of the Stuart-Landau equation. The inner cylinder rotates, and the outer cylinder and both end walls of the cylinders are stationary. Near the end walls of the cylinders, the value of the time scale is small. In the inner region, the radial velocity component has a large time scale near the center of the vortices, while the axial velocity component has a large time scale between the vortices.展开更多
Installation of refractory castables depend not only on flow , but also on how soon the flow is lost because of setting. The loss of flow (flow decay) has always been one of the main problems of refractory castable ma...Installation of refractory castables depend not only on flow , but also on how soon the flow is lost because of setting. The loss of flow (flow decay) has always been one of the main problems of refractory castable manufacturers , a problem that has not been too well described in literature . The flow decay has been studied for a castable system based on alumina , pointing out some general trends . The flow decay was found very temperature sensitive, being strongly accelerated by temperature increases. To compensate for excessive flow loss, a retarder like citric acid may be used. Thus flow decay was measured as a function of citric acid ( retarder) addition at 35℃.展开更多
The decay of weakly swirling flows in a type of cross-section-varying pipes was discussed analytically. For laminar swirling flow, the feature of exponential decay was demonstrated. For turbulent swirling flow, in spi...The decay of weakly swirling flows in a type of cross-section-varying pipes was discussed analytically. For laminar swirling flow, the feature of exponential decay was demonstrated. For turbulent swirling flow, in spite of the decay of circulation flux, a necessary condition for local circulation to amplify along downstream was obtained under the Boussinesq's hypothesis.展开更多
A prototype cleanroom for hazardous testing and handling of satellites prior to launcher encapsulation,satisfying the ISO8 standard has been designed and analyzed in terms of performances.Unsteady Reynolds Averaged Na...A prototype cleanroom for hazardous testing and handling of satellites prior to launcher encapsulation,satisfying the ISO8 standard has been designed and analyzed in terms of performances.Unsteady Reynolds Averaged Navier-Stokes(URANS)models have been used to study the related flow field and particulate matter(PM)dispersion.The outcomes of the URANS models have been validated through comparison with equivalent large-eddy simulations.Special attention has been paid to the location and shape of the air intakes and their orientation in space,in order to balance the PM convection and diffusion inside the cleanroom.Forming a cyclone-type flow pattern inside the cleanroom is a key to maintaining a high ventilation efficiency.展开更多
Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The su...Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.展开更多
This paper investigates the asymptotic behavior of end effects for a Stokes flow defined on a three-dimensional semi-infinite cylinder. With homogeneous Dirichlet conditions of the velocity on the lateral surface of t...This paper investigates the asymptotic behavior of end effects for a Stokes flow defined on a three-dimensional semi-infinite cylinder. With homogeneous Dirichlet conditions of the velocity on the lateral surface of the cylinder, solutions either grow or decay exponentially in the distance from the finite end of the cylinder. In the case of decay, the effect of perturbing the equation parameters is also investigated.展开更多
Direct numerical simulation of decaying homogeneous isotropic turbulence （DHIT） of a polymer solution is performed. In order to understand the polymer effect on turbulence or additive-turbulence interaction, we dire...Direct numerical simulation of decaying homogeneous isotropic turbulence （DHIT） of a polymer solution is performed. In order to understand the polymer effect on turbulence or additive-turbulence interaction, we directly investigate the influence of polymers on velocity gradient tensor including vorticity and strain. By visualizing vortex tubes and sheets, we observe a remarkable inhibition of vortex structures in an intermediate-scale field and a small-scale field but not for a large scale field in DHIT with polymers. The geometric study indicates a strong relevance among the vorticity vector, rate-of-strain tensor, and polymer conformation tensor. Joint probability density functions show that the polymer effect can increase ＂strain generation resistance＂ and ＂vorticity generation resistance＂, i.e., inhibit the generation of vortex sheets and tubes, ultimately leading to turbulence inhibition effects.展开更多
The boundary layer integral method is used to investigate the development of the turbulent swirling flow at the entrance region of a conical nozzle. The governing equations in the spherical coordinate system are simpl...The boundary layer integral method is used to investigate the development of the turbulent swirling flow at the entrance region of a conical nozzle. The governing equations in the spherical coordinate system are simplified with the boundary layer as- sumptions and integrated through the boundary layer. The resulting sets of differential equations are then solved by the fourth-order Adams predictor-corrector method. The free vortex and uniform velocity profiles are applied for the tangential and axial velocities at the inlet region, respectively. Due to the lack of experimental data for swirling flows in converging nozzles, the developed model is validated against the numerical simulations. The results of numerical simulations demonstrate the capability of the analytical model in predicting boundary layer parameters such as the boundary layer growth, the shear rate, the boundary layer thickness, and the swirl intensity decay rate for different cone angles. The proposed method introduces a simple and robust procedure to investigate the boundary layer parameters inside the converging geometries.展开更多
We report a fresh and simpler approach to the modelling of the kinetics of the polymerization of Hb SS in sickle cell patients that couples the kinetics and the hydrodynamics of blood flow in mechanistic understanding...We report a fresh and simpler approach to the modelling of the kinetics of the polymerization of Hb SS in sickle cell patients that couples the kinetics and the hydrodynamics of blood flow in mechanistic understanding of the process. The well-known two-step autocatalytic reaction scheme was used for the polymerization reaction with the assumption of simpler first-order reaction scheme for each stage. In addition, the forces acting on a particle in motion were also introduced to account for compelling settling of the red cells that lead to vessel occlusion (vaso-occlusion). A first attempt on the prediction of vessel blockage was made using this novel model. The time for the onset of the polymerization reaction was derived from hydrodynamic considerations and kinetics while the kinetic rate constants were obtained from the autocatalytic nature of the reaction. Experimental data for model validation were obtained from recruited SS patients and in vitro data of Hofrichter. Over 100 volunteers were recruited for participation in this work but less than 40% met the inclusion criteria. Participants were of age range 13 - 43 (with a mean of 26 ± 8 years) for SCD patients and 18 - 43 (with a mean of 28 ± 7 years) for control participants. Blood indices and Transcranial Doppler (TCD) test parameters of all participants were the principal parameters used for model validation. Constant k2/k1 ratios was obtained for individual in vivo/in vitro system. This ratio is unique for any individual, independent on protein sequence and also suggests the degree of expression of the symptoms of Sickle Cell Disease (SCD) with higher values reflecting greater propensity to pain crisis. Delay time, tD, was found to have an inverse relationship with the kinetic constant for the residual reaction, k1. Therefore, long delay times calculated, offer insight on why SCD patients are not in perpetual crises because enough time is provided the cells to escape microcirculation while keeping the residual reaction at the minimum. Sensitivity analysis was carried out to obviate the limitations encountered in the course of the work. Results showed the onset of occlusion to be most sensitive to the diameter of the blood vessel. 展开更多
目的研究早发型胎儿生长受限(FGR)合并血流异常对围产结局的影响。方法回顾性分析2018年1月至2021年12月在西北妇女儿童医院产科分娩的158例FGR孕妇的临床资料。按照胎儿是否存在血流异常将孕妇分为研究组108例(胎儿血流异常)和对照组50...目的研究早发型胎儿生长受限(FGR)合并血流异常对围产结局的影响。方法回顾性分析2018年1月至2021年12月在西北妇女儿童医院产科分娩的158例FGR孕妇的临床资料。按照胎儿是否存在血流异常将孕妇分为研究组108例(胎儿血流异常)和对照组50例(胎儿血流正常)。比较两组孕妇的围产结局和新生儿结局。结果研究组孕妇合并妊娠期高血压(HDP)和应用糖皮质激素的比例分别为43.52%、54.63%,明显高于对照组的26.00%、28.00%,差异均有统计学意义(P<0.05);但两组孕妇的孕前BMI、年龄、经产妇、孕期增重、诊断孕周、孕次≥2次、合并免疫系统疾病比例比较,差异均无统计学意义(P>0.05);研究组孕妇合并羊水过少占比、剖宫产率、选择剖宫产率分别为34.26%、80.56%、22.22%,明显高于对照组的18.00%、64.00%、6.00%,差异均有统计学意义(P<0.05);研究组孕妇胎盘重量、胎盘体积、分娩孕周分别为(405.68±101.82)g、(493.76±108.52)cm3、(34.92±2.58)周,明显低于对照组的(473.52±80.31)g、(628.35±201.74)cm3、(37.11±2.60)周,差异均有统计学意义(P<0.05);研究组新生儿出生体质量为(1753.26±481.35)g,明显低于对照组的(2207.59±356.42)g,新生儿早产、脑室出血、1 min Apgar评分≤7分占比、入住NICU率分别为60.19%、10.19%、32.41%、83.33%,明显高于对照组的26.00%、0、4.00%、54.00%,差异均有统计学意义(P<0.05)。结论FGR合并血流异常会影响围产结局,应加强FGR合并血流异常孕妇妊娠期间监测,尽可能延长孕周。如出现胎儿宫内窘迫及较为严重并发症时,应及时终止妊娠。展开更多
基金partly supported by the National Natural Science Foundation of China (Nos. U2032145 and 11875125)the National Key Research and Development Program of China (No. 2020YFE0202002)。
文摘In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.
文摘We investigate the onset and the decay of Taylor-Couette flow in finite cylinders, and we report the estimated time scales in the azimuthal section of the flow state transition between the super-critical state and the sub-critical state by fitting the numerical result to the solution of the Stuart-Landau equation. The inner cylinder rotates, and the outer cylinder and both end walls of the cylinders are stationary. Near the end walls of the cylinders, the value of the time scale is small. In the inner region, the radial velocity component has a large time scale near the center of the vortices, while the axial velocity component has a large time scale between the vortices.
文摘Installation of refractory castables depend not only on flow , but also on how soon the flow is lost because of setting. The loss of flow (flow decay) has always been one of the main problems of refractory castable manufacturers , a problem that has not been too well described in literature . The flow decay has been studied for a castable system based on alumina , pointing out some general trends . The flow decay was found very temperature sensitive, being strongly accelerated by temperature increases. To compensate for excessive flow loss, a retarder like citric acid may be used. Thus flow decay was measured as a function of citric acid ( retarder) addition at 35℃.
文摘The decay of weakly swirling flows in a type of cross-section-varying pipes was discussed analytically. For laminar swirling flow, the feature of exponential decay was demonstrated. For turbulent swirling flow, in spite of the decay of circulation flux, a necessary condition for local circulation to amplify along downstream was obtained under the Boussinesq's hypothesis.
基金funded by Space Research and Innovation Network (www.sprint.ac.uk)for Technology Grants (OW131743P4V4M,OW131797P4V2B,ZX and CY)grateful to NERC (www.nerc.ac.uk)for the Grant (NE/W002841/1,ZX)to complete the writing of the paper。
文摘A prototype cleanroom for hazardous testing and handling of satellites prior to launcher encapsulation,satisfying the ISO8 standard has been designed and analyzed in terms of performances.Unsteady Reynolds Averaged Navier-Stokes(URANS)models have been used to study the related flow field and particulate matter(PM)dispersion.The outcomes of the URANS models have been validated through comparison with equivalent large-eddy simulations.Special attention has been paid to the location and shape of the air intakes and their orientation in space,in order to balance the PM convection and diffusion inside the cleanroom.Forming a cyclone-type flow pattern inside the cleanroom is a key to maintaining a high ventilation efficiency.
基金National Key Basic Research and Development Planning Program of China(Program 973)(2013CB430202)Basic Research Program of Jiangsu Province,China(BK20130997)+1 种基金National Natural Science Fund of China(91337109)Project Funded by the Priority Academic program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Global gridded daily mean data from the NCEP/NCAR Reanalysis(1948-2012) are used to obtain the onset date,retreat date and duration time series of the South China Sea summer monsoon(SCSSM) for the past 65 years.The summer monsoon onset(retreat) date is defined as the time when the mean zonal wind at 850 hPa shifts steadily from easterly(westerly) to westerly(easterly) and the pseudo-equivalent potential temperature at the same level remains steady at greater than 335 K(less than 335 K) in the South China Sea area[110-120°E(10-20°N)].The clockwise vortex of the equatorial Indian Ocean region,together with the cross-equatorial flow and the subtropical high,plays a decisive role in the burst of the SCSSM.The onset date of the SCSSM is closely related to its intensity.With late(early) onset of the summer monsoon,its intensity is relatively strong(weak),and the zonal wind undergoes an early(late) abrupt change in the upper troposphere.Climate warming significantly affects the onset and retreat dates of the SCSSM and its intensity.With climate warming,the number of early-onset(-retreat) years of the SCSSM is clearly greater(less),and the SCSSM is clearly weakened.
基金supported by the National Research Foundation of Korea (NRF) (No.2010-0012215)
文摘This paper investigates the asymptotic behavior of end effects for a Stokes flow defined on a three-dimensional semi-infinite cylinder. With homogeneous Dirichlet conditions of the velocity on the lateral surface of the cylinder, solutions either grow or decay exponentially in the distance from the finite end of the cylinder. In the case of decay, the effect of perturbing the equation parameters is also investigated.
基金supported by the National Natural Science Foundation of China (Grant No. 10872060)the Fundamental Research Funds for the Central Universities (Grant No. HIT.BRET2.2010008)
文摘Direct numerical simulation of decaying homogeneous isotropic turbulence （DHIT） of a polymer solution is performed. In order to understand the polymer effect on turbulence or additive-turbulence interaction, we directly investigate the influence of polymers on velocity gradient tensor including vorticity and strain. By visualizing vortex tubes and sheets, we observe a remarkable inhibition of vortex structures in an intermediate-scale field and a small-scale field but not for a large scale field in DHIT with polymers. The geometric study indicates a strong relevance among the vorticity vector, rate-of-strain tensor, and polymer conformation tensor. Joint probability density functions show that the polymer effect can increase ＂strain generation resistance＂ and ＂vorticity generation resistance＂, i.e., inhibit the generation of vortex sheets and tubes, ultimately leading to turbulence inhibition effects.
文摘The boundary layer integral method is used to investigate the development of the turbulent swirling flow at the entrance region of a conical nozzle. The governing equations in the spherical coordinate system are simplified with the boundary layer as- sumptions and integrated through the boundary layer. The resulting sets of differential equations are then solved by the fourth-order Adams predictor-corrector method. The free vortex and uniform velocity profiles are applied for the tangential and axial velocities at the inlet region, respectively. Due to the lack of experimental data for swirling flows in converging nozzles, the developed model is validated against the numerical simulations. The results of numerical simulations demonstrate the capability of the analytical model in predicting boundary layer parameters such as the boundary layer growth, the shear rate, the boundary layer thickness, and the swirl intensity decay rate for different cone angles. The proposed method introduces a simple and robust procedure to investigate the boundary layer parameters inside the converging geometries.
文摘We report a fresh and simpler approach to the modelling of the kinetics of the polymerization of Hb SS in sickle cell patients that couples the kinetics and the hydrodynamics of blood flow in mechanistic understanding of the process. The well-known two-step autocatalytic reaction scheme was used for the polymerization reaction with the assumption of simpler first-order reaction scheme for each stage. In addition, the forces acting on a particle in motion were also introduced to account for compelling settling of the red cells that lead to vessel occlusion (vaso-occlusion). A first attempt on the prediction of vessel blockage was made using this novel model. The time for the onset of the polymerization reaction was derived from hydrodynamic considerations and kinetics while the kinetic rate constants were obtained from the autocatalytic nature of the reaction. Experimental data for model validation were obtained from recruited SS patients and in vitro data of Hofrichter. Over 100 volunteers were recruited for participation in this work but less than 40% met the inclusion criteria. Participants were of age range 13 - 43 (with a mean of 26 ± 8 years) for SCD patients and 18 - 43 (with a mean of 28 ± 7 years) for control participants. Blood indices and Transcranial Doppler (TCD) test parameters of all participants were the principal parameters used for model validation. Constant k2/k1 ratios was obtained for individual in vivo/in vitro system. This ratio is unique for any individual, independent on protein sequence and also suggests the degree of expression of the symptoms of Sickle Cell Disease (SCD) with higher values reflecting greater propensity to pain crisis. Delay time, tD, was found to have an inverse relationship with the kinetic constant for the residual reaction, k1. Therefore, long delay times calculated, offer insight on why SCD patients are not in perpetual crises because enough time is provided the cells to escape microcirculation while keeping the residual reaction at the minimum. Sensitivity analysis was carried out to obviate the limitations encountered in the course of the work. Results showed the onset of occlusion to be most sensitive to the diameter of the blood vessel.
文摘目的研究早发型胎儿生长受限(FGR)合并血流异常对围产结局的影响。方法回顾性分析2018年1月至2021年12月在西北妇女儿童医院产科分娩的158例FGR孕妇的临床资料。按照胎儿是否存在血流异常将孕妇分为研究组108例(胎儿血流异常)和对照组50例(胎儿血流正常)。比较两组孕妇的围产结局和新生儿结局。结果研究组孕妇合并妊娠期高血压(HDP)和应用糖皮质激素的比例分别为43.52%、54.63%,明显高于对照组的26.00%、28.00%,差异均有统计学意义(P<0.05);但两组孕妇的孕前BMI、年龄、经产妇、孕期增重、诊断孕周、孕次≥2次、合并免疫系统疾病比例比较,差异均无统计学意义(P>0.05);研究组孕妇合并羊水过少占比、剖宫产率、选择剖宫产率分别为34.26%、80.56%、22.22%,明显高于对照组的18.00%、64.00%、6.00%,差异均有统计学意义(P<0.05);研究组孕妇胎盘重量、胎盘体积、分娩孕周分别为(405.68±101.82)g、(493.76±108.52)cm3、(34.92±2.58)周,明显低于对照组的(473.52±80.31)g、(628.35±201.74)cm3、(37.11±2.60)周,差异均有统计学意义(P<0.05);研究组新生儿出生体质量为(1753.26±481.35)g,明显低于对照组的(2207.59±356.42)g,新生儿早产、脑室出血、1 min Apgar评分≤7分占比、入住NICU率分别为60.19%、10.19%、32.41%、83.33%,明显高于对照组的26.00%、0、4.00%、54.00%,差异均有统计学意义(P<0.05)。结论FGR合并血流异常会影响围产结局,应加强FGR合并血流异常孕妇妊娠期间监测,尽可能延长孕周。如出现胎儿宫内窘迫及较为严重并发症时,应及时终止妊娠。
