The grid drop concept is introduced and used to develop a micromechanism-based methodology for calculating watershed flow concentration. The flow path and distance traveled by a grid drop to the outlet of the watershe...The grid drop concept is introduced and used to develop a micromechanism-based methodology for calculating watershed flow concentration. The flow path and distance traveled by a grid drop to the outlet of the watershed are obtained using a digital elevation model （DEM）. Regarding the slope as an uneven carpet through which the grid drop passes, a formula for overland flow velocity differing from Manning＇s formula for stream flow as welt as Darcy＇s formula for pore flow is proposed. Compared with the commonly used unit hydrograph and isochronal methods, this new methodology has outstanding advantages in that it considers the influences of the slope velocity field and the heterogeneity of spatial distribution of rainfall on the flow concentration process, and includes only one parameter that needs to be calibrated. This method can also be effectively applied to the prediction of hydrologic processes in un-gauged basins.展开更多
To calculate the flow resistance of a main cable dehumidification system,this study considers the air flow in the main cable as the flow in a porous medium,and adopts the Hagen–Poiseuille equation by using average hy...To calculate the flow resistance of a main cable dehumidification system,this study considers the air flow in the main cable as the flow in a porous medium,and adopts the Hagen–Poiseuille equation by using average hydraulic radius and capillary bundle models.A mathematical derivation is combined with an experimental study to obtain a semi-empirical flow resistance formula.Additionally,Fluent software is used to simulate the flow resistance across the main cable relative to the experimental values.Based on the actual measured results for a Yangtze River bridge,this study verifies the semi-empirical formula,and indicates that it can be applied in actual engineering.展开更多
Velocity of debris flow is one of the most important characteristics for the protective construction design. Since debris flows are rare events, and observations are conducted only on stations in Russia, Ukraine, Ital...Velocity of debris flow is one of the most important characteristics for the protective construction design. Since debris flows are rare events, and observations are conducted only on stations in Russia, Ukraine, Italy, Switzerland, USA, China, Japan and New Zealand, the velocity is calculated rather than measured. Nowadays, a large number of videos with passing debris flows have appeared on the Internet. Scientists can use such video materials to obtain qualitative and quantitative characteristics of the debris flow. Therefore, the aim of our research is an attempt to measure the debris flow velocity using video materials and compare the obtained results with the calculated values using various methods. The debris flow that came down in Firgen, Austria on August 4, 2012 was chosen as the object of our study. The video was carried out from several angles, so it was possible to select a section of the channel, through which we could measure the debris flows waves velocity. In addition, we calculated the velocities of waves by formulas adopted in the regulatory documents and compared with the measured by video values. During the video analysis, debris flow velocities at different sites were observed: minimum—7.2 m/s and maximum—10 m/s. The calculated values varied from 4.5 m/s to 11.4 m/s. Moreover, we applied model of the transport-shear process of debris flow formation developed by Yu. B. Vinogradov. When we were comparing the obtained debris flow discharges with results from Austrian colleagues, we found out that the values were similar to each other. However, internal scatter in the model changed from 151 to 190 m3/s, while in the report of Austrian colleagues the discharges were from 80 to 250 m3/s.展开更多
On the basis of hypothesis of replacement and the vector formula of Newton’s law for a viscous fluid the way of a finding of resistance a slow flow by an incompressible fluid of bodies of the various form is represen...On the basis of hypothesis of replacement and the vector formula of Newton’s law for a viscous fluid the way of a finding of resistance a slow flow by an incompressible fluid of bodies of the various form is represented. Application of an offered way to calculation of a flow of various bodies is shown: a sphere, a cylinder, a oblong ellipsoid, a flat plate. Comparison with results of other authors is given.展开更多
Flow characteristics of thermally stratified shear flow in braided rivers are particularly complicated and poorly understood. In this study, a series of typical flow patterns was examined and their critical criteria w...Flow characteristics of thermally stratified shear flow in braided rivers are particularly complicated and poorly understood. In this study, a series of typical flow patterns was examined and their critical criteria were determined. Four flow patterns were identified: mixed, locally unstable, continuously stratified, and two-layer flow. Temperature distributions of the four types of flow patterns were analyzed and compared.The critical Froude numbers for unstable flow, FDcr1, and stable flow, FDcr2, were determined to be 6 and 1, respectively, and comparison of FDcr1 and FDcr2 to the peak Froude numbers, FD1 at the outer bank and FD2 at the inner bank along the anabranch, allowed the flow patterns to be assessed. Then, a discriminant based on initial Jeffreys-Keulegan stability parameters was established to distinguish the flow stages from twolayer flow to completely mixed flow. It is indicated that the three critical Jeffreys-Keulegan parameters increased with the diversion angle of braided rivers. Results also show that, compared to the stratified flow in straight and curved channels, it was more difficult for braided stratified flow to maintain as two-layer flow, and it more easily became mixed flow. Consequently, empirical expressions for stability criteria of the thermally stratified shear flow in braided rivers are presented.展开更多
目的探讨化瘀解痉方联合尼莫地平治疗动脉瘤性蛛网膜下腔出血(Subarachnoid hemorrhage,SAH)后脑血管痉挛患者的疗效及对其血管内皮功能的影响。方法选取2022年1月-2023年1月期间保定市第一中心医院收治的SAH后脑血管痉挛患者90例,按随...目的探讨化瘀解痉方联合尼莫地平治疗动脉瘤性蛛网膜下腔出血(Subarachnoid hemorrhage,SAH)后脑血管痉挛患者的疗效及对其血管内皮功能的影响。方法选取2022年1月-2023年1月期间保定市第一中心医院收治的SAH后脑血管痉挛患者90例,按随机数字表法分为对照组和观察组,每组各45例。对照组给予尼莫地平治疗,观察组在对照组基础上联合化瘀解痉方治疗,均连续治疗15 d。观察两组患者治疗前后神经功能缺损评分(National institute of health stroke scale,NIHSS)、Hunt-Hess分级评分、意识障碍程度评分(Glasgow coma scale,GCS)、血管内皮功能指标[内皮素-1(Endothelin-1,ET-1)、血管内皮生长因子(Vascular endothelial growth factor,VEGF)]、脑血流指标[大脑中动脉平均流速(Mean flow velocity of middle cerebral artery,MCA-Vm)、颈内动脉颅外段平均流速(Mean extracranial velocity of internal carotid artery,VICA-Vm)、脑血管痉挛(Cerebral vasospasm,CAS)指数]改善情况,临床总有效率及不良反应情况。结果治疗后两组患者NIHSS、Hunt-Hess评分均较治疗前降低,GCS评分均较治疗前升高,差异有统计学意义(P<0.05);且观察组NIHSS、Hunt-Hess评分均明显低于对照组,GCS评分明显高于对照组,差异有统计学意义(P<0.05)。治疗后两组患者ET-1、VEGF水平均较治疗前降低,差异有统计学意义(P<0.05);且观察组ET-1、VEGF水平均明显低于对照组,差异有统计学意义(P<0.05)。治疗后两组患者MCA-Vm、VICA-Vm及CAS指数均较治疗前降低,差异有统计学意义(P<0.05);且观察组MCA-Vm、VICA-Vm及CAS指数均明显低于对照组,差异有统计学意义(P<0.05)。治疗后观察组临床总有效率91.11%(41/45)明显高于对照组73.33%(33/45),差异有统计学意义(P<0.05)。治疗期间,两组患者均未发生不良反应,也未出现死亡病例。结论化瘀解痉方联合尼莫地平能够改善SAH后脑血管痉挛患者的血管内皮功能,增加脑血流灌注,减轻神经功能损伤,控制病情发展,疗效显著,安全性高。展开更多
基金supported by the National Nature Science Foundation of China (Grant No. 50609005)the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China (Grant No. 101075)
文摘The grid drop concept is introduced and used to develop a micromechanism-based methodology for calculating watershed flow concentration. The flow path and distance traveled by a grid drop to the outlet of the watershed are obtained using a digital elevation model （DEM）. Regarding the slope as an uneven carpet through which the grid drop passes, a formula for overland flow velocity differing from Manning＇s formula for stream flow as welt as Darcy＇s formula for pore flow is proposed. Compared with the commonly used unit hydrograph and isochronal methods, this new methodology has outstanding advantages in that it considers the influences of the slope velocity field and the heterogeneity of spatial distribution of rainfall on the flow concentration process, and includes only one parameter that needs to be calibrated. This method can also be effectively applied to the prediction of hydrologic processes in un-gauged basins.
基金Ministry of Communications and Provincial and Joint Research Project[2008-353-332-170].
文摘To calculate the flow resistance of a main cable dehumidification system,this study considers the air flow in the main cable as the flow in a porous medium,and adopts the Hagen–Poiseuille equation by using average hydraulic radius and capillary bundle models.A mathematical derivation is combined with an experimental study to obtain a semi-empirical flow resistance formula.Additionally,Fluent software is used to simulate the flow resistance across the main cable relative to the experimental values.Based on the actual measured results for a Yangtze River bridge,this study verifies the semi-empirical formula,and indicates that it can be applied in actual engineering.
文摘Velocity of debris flow is one of the most important characteristics for the protective construction design. Since debris flows are rare events, and observations are conducted only on stations in Russia, Ukraine, Italy, Switzerland, USA, China, Japan and New Zealand, the velocity is calculated rather than measured. Nowadays, a large number of videos with passing debris flows have appeared on the Internet. Scientists can use such video materials to obtain qualitative and quantitative characteristics of the debris flow. Therefore, the aim of our research is an attempt to measure the debris flow velocity using video materials and compare the obtained results with the calculated values using various methods. The debris flow that came down in Firgen, Austria on August 4, 2012 was chosen as the object of our study. The video was carried out from several angles, so it was possible to select a section of the channel, through which we could measure the debris flows waves velocity. In addition, we calculated the velocities of waves by formulas adopted in the regulatory documents and compared with the measured by video values. During the video analysis, debris flow velocities at different sites were observed: minimum—7.2 m/s and maximum—10 m/s. The calculated values varied from 4.5 m/s to 11.4 m/s. Moreover, we applied model of the transport-shear process of debris flow formation developed by Yu. B. Vinogradov. When we were comparing the obtained debris flow discharges with results from Austrian colleagues, we found out that the values were similar to each other. However, internal scatter in the model changed from 151 to 190 m3/s, while in the report of Austrian colleagues the discharges were from 80 to 250 m3/s.
文摘On the basis of hypothesis of replacement and the vector formula of Newton’s law for a viscous fluid the way of a finding of resistance a slow flow by an incompressible fluid of bodies of the various form is represented. Application of an offered way to calculation of a flow of various bodies is shown: a sphere, a cylinder, a oblong ellipsoid, a flat plate. Comparison with results of other authors is given.
基金supported by the National Natural Science Foundation of China(Grants No.51379058,51379060,and 51479064)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD Project)the Fundamental Research Funds for the Central Universities(Grants No.2016B06714 and 2014B07814)
文摘Flow characteristics of thermally stratified shear flow in braided rivers are particularly complicated and poorly understood. In this study, a series of typical flow patterns was examined and their critical criteria were determined. Four flow patterns were identified: mixed, locally unstable, continuously stratified, and two-layer flow. Temperature distributions of the four types of flow patterns were analyzed and compared.The critical Froude numbers for unstable flow, FDcr1, and stable flow, FDcr2, were determined to be 6 and 1, respectively, and comparison of FDcr1 and FDcr2 to the peak Froude numbers, FD1 at the outer bank and FD2 at the inner bank along the anabranch, allowed the flow patterns to be assessed. Then, a discriminant based on initial Jeffreys-Keulegan stability parameters was established to distinguish the flow stages from twolayer flow to completely mixed flow. It is indicated that the three critical Jeffreys-Keulegan parameters increased with the diversion angle of braided rivers. Results also show that, compared to the stratified flow in straight and curved channels, it was more difficult for braided stratified flow to maintain as two-layer flow, and it more easily became mixed flow. Consequently, empirical expressions for stability criteria of the thermally stratified shear flow in braided rivers are presented.
文摘目的探讨化瘀解痉方联合尼莫地平治疗动脉瘤性蛛网膜下腔出血(Subarachnoid hemorrhage,SAH)后脑血管痉挛患者的疗效及对其血管内皮功能的影响。方法选取2022年1月-2023年1月期间保定市第一中心医院收治的SAH后脑血管痉挛患者90例,按随机数字表法分为对照组和观察组,每组各45例。对照组给予尼莫地平治疗,观察组在对照组基础上联合化瘀解痉方治疗,均连续治疗15 d。观察两组患者治疗前后神经功能缺损评分(National institute of health stroke scale,NIHSS)、Hunt-Hess分级评分、意识障碍程度评分(Glasgow coma scale,GCS)、血管内皮功能指标[内皮素-1(Endothelin-1,ET-1)、血管内皮生长因子(Vascular endothelial growth factor,VEGF)]、脑血流指标[大脑中动脉平均流速(Mean flow velocity of middle cerebral artery,MCA-Vm)、颈内动脉颅外段平均流速(Mean extracranial velocity of internal carotid artery,VICA-Vm)、脑血管痉挛(Cerebral vasospasm,CAS)指数]改善情况,临床总有效率及不良反应情况。结果治疗后两组患者NIHSS、Hunt-Hess评分均较治疗前降低,GCS评分均较治疗前升高,差异有统计学意义(P<0.05);且观察组NIHSS、Hunt-Hess评分均明显低于对照组,GCS评分明显高于对照组,差异有统计学意义(P<0.05)。治疗后两组患者ET-1、VEGF水平均较治疗前降低,差异有统计学意义(P<0.05);且观察组ET-1、VEGF水平均明显低于对照组,差异有统计学意义(P<0.05)。治疗后两组患者MCA-Vm、VICA-Vm及CAS指数均较治疗前降低,差异有统计学意义(P<0.05);且观察组MCA-Vm、VICA-Vm及CAS指数均明显低于对照组,差异有统计学意义(P<0.05)。治疗后观察组临床总有效率91.11%(41/45)明显高于对照组73.33%(33/45),差异有统计学意义(P<0.05)。治疗期间,两组患者均未发生不良反应,也未出现死亡病例。结论化瘀解痉方联合尼莫地平能够改善SAH后脑血管痉挛患者的血管内皮功能,增加脑血流灌注,减轻神经功能损伤,控制病情发展,疗效显著,安全性高。
