The breakage and bending of ducts result in a difficulty to cope with ventilation issues in bidirectional excavation tunnels with a long inclined shaft using a single ventilation method based on ducts.To discuss the h...The breakage and bending of ducts result in a difficulty to cope with ventilation issues in bidirectional excavation tunnels with a long inclined shaft using a single ventilation method based on ducts.To discuss the hybrid ventilation system applied in bidirectional excavation tunnels with a long inclined shaft,this study has established a full-scale computational fluid dynamics model based on field tests,the Poly-Hexcore method,and the sliding mesh technique.The distribution of wind speed,temperature field,and CO in the tunnel are taken as indices to compare the ventilation efficiency of three ventilation systems(duct,duct-ventilation shaft,duct–ventilated shaft-axial fan).The results show that the hybrid ventilation scheme based on duct-ventilation shaft–axial fan performs the best among the three ventilation systems.Compared to the duct,the wind speed and cooling rate in the tunnel are enhanced by 7.5%–30.6%and 14.1%–17.7%,respectively,for the duct-vent shaft-axial fan condition,and the volume fractions of CO are reduced by 26.9%–73.9%.This contributes to the effective design of combined ventilation for bidirectional excavation tunnels with an inclined shaft,ultimately improving the air quality within the tunnel.展开更多
Twelve steroids, including eight ergostane-type sterols and four mono-glucosides of ergostane-type sterols, were isolated from the ethyl acetate soluble fraction of the fungus Pleurotus ostreatus ( Jacq. : Fr.) Kummer...Twelve steroids, including eight ergostane-type sterols and four mono-glucosides of ergostane-type sterols, were isolated from the ethyl acetate soluble fraction of the fungus Pleurotus ostreatus ( Jacq. : Fr.) Kummer. A new compound 3-O-beta-D-glucopyranosyl-22E, 24R-ergosta-7, 22-diene-5alpha, 6beta, 9alpha-triol, was structurally elucidated by spectroscopic and chemical methods. The eleven known compounds were 22E, 24R-ergosta-7, 22-diene-3beta, 5alpha, 6beta, 9alpha-tetraol; 3-O-beta-D-glucopyranosyl-22E, 24R-ergosta-7, 22-diene-5alpha, 6beta-diol; 22E, 24R-ergosta-7, 22-diene-3beta, 5alpha, 6beta-triol; 22E, 24R-ergosta-5, 7, 22-trien-3beta-ol 3-O-beta-D-glucopyranoside; ergosterol; 22E, 24R-ergosta-7, 22-dien-3beta-ol 3-O-beta-D-glucopyranoside; 22E, 24R-ergosta-7, 22-diene-3beta-ol; 22E, 24R-ergosta-4, 6, 8, 22-tetraen-3-one; 22E, 24R-ergosta-7, 22-diene-3beta, 5alpha, 6alpha-triol; ergosterol peroxide; 22E, 24R-ergosta-7, 22-diene-3beta, 5alpha-diol-6-one.展开更多
To study the draft sensation distribution of an air jet supply system in a large space building in summer,experiments are conducted in a large laboratory.The temperature,velocity and draft sensation distributions at a...To study the draft sensation distribution of an air jet supply system in a large space building in summer,experiments are conducted in a large laboratory.The temperature,velocity and draft sensation distributions at a nozzle height of 4 m in the occupied zone are obtained.Then,the numerical simulation under the test condition is carried out by the computational fluid dynamics(CFD)method.The calculation results of the indoor vertical temperature and the draft sensation distribution are validated by the test data.Simulations with different nozzle heights are conducted.The satisfactory air supply condition is determined by analyzing the draft sensations and the temperatures in the occupied zone under three conditions.The simulation results show that the optimal draft sensation distribution and the uniform temperature and velocity fields can be obtained at a nozzle height of 5 m.展开更多
A new process for utilization of hazardous lead-bearing wastes and iron-rich wastes by reducing-matting smelting has been developed.The slag(SG) and the iron-rich matte(IRM) are the main by-products from reducing-...A new process for utilization of hazardous lead-bearing wastes and iron-rich wastes by reducing-matting smelting has been developed.The slag(SG) and the iron-rich matte(IRM) are the main by-products from reducing-matting smelting of lead-bearing wastes and iron-rich wastes.The environmental risk of heavy metals(Cd,Zn,Pb and As) in the main by-products versus the charging material for reducing-matting smelting(CM) has been systematically assessed using leaching toxicity test,the three-stage sequential extraction procedure of European Community Bureau of Reference(BCR) and Hakanson Potential Ecological Risk Index Method(PERI).The results demonstrate that the ecological risk level of heavy metals for SG and IRM is significantly reduced after the reducing-matting smelting process compared with that for CM.展开更多
Objective: To explore the pituitary function of acute pituitary apoplexy and its effect by transsphenoidal surgery. Methods: The clinical data and endocrine hormones level of 25 patients with acute pituitary apoplex...Objective: To explore the pituitary function of acute pituitary apoplexy and its effect by transsphenoidal surgery. Methods: The clinical data and endocrine hormones level of 25 patients with acute pituitary apoplexy who underwent transsphenoidal surgery from Jan. 2002 to June 2004 were retrospectively analyzed. Results: 13 cases underwent surgery within 3 days after admission and 22 cases within 1 week. Of the 25 cases, 9 patients suffered the impairment of pituitary-thyroidal function, 14 cases of pituitary-adrenal function and 11 cases of pituitary-gonadal function before surgery. After surgery, 5/9, 8/14 and 7/11 were recovered from the corresponding hypopituitarism. Conclusion: Hypopituitarism is a major manifestation of acute pituitary apoplexy. Urgent surgery decompression contributed to the improvement of pituitary function. Patients with hypopituitarism after surgery required the corresponding hormones replacement therapy.展开更多
This paper analyzes the applications of four air terminal device(ATD)models(i.e.,the basic model,the box model,the N-point momentum model,the jet main region specification model)in computational fluid dynamics(CF...This paper analyzes the applications of four air terminal device(ATD)models(i.e.,the basic model,the box model,the N-point momentum model,the jet main region specification model)in computational fluid dynamics(CFD)simulation and their performance in case study.A full-scale experiment is performed in an environment chamber,and the measured air velocity and temperature fields are compared with the simulation results by using four ATD models.The velocity and temperature fields are measured by an omni-directional thermo-anemometer system.It demonstrates that the basic model and the box model are not applicable to complicated air terminal devices.At the occupant area,the relative errors between simulated and measured air velocities are less than 20% based on the N-point momentum model and the jet main region specification model.Around the ATD zone,the relative error between the numerical and measured air velocity based on the jet main region specification model is less than 15%.The jet main region specification model is proved to be an applicable approach and a more accurate way to study the airflow pattern around the ATD with complicated geometry.展开更多
An analytical study of the flow and pressure fields inside a small-diameter dense-media cyclone is presented.The simulations were done with the help of the CFD software FLUENT.The following conclusions were reached:th...An analytical study of the flow and pressure fields inside a small-diameter dense-media cyclone is presented.The simulations were done with the help of the CFD software FLUENT.The following conclusions were reached:the tangential velocity tends to increase when moving from the center toward the exterior.The velocity then begins to decrease when the maximum velocity point is reached.The velocity field divides into two different sections;an inner swirling zone and an outer swirling zone.The axial velocity points down at the wall and gradually decreases toward the bottom.Continuing toward the bottom,the axial velocity passes through zero and then gradually increases in the opposite direction.In the cyclone's central zone,the pressure is negative and the suction of air allows an air column to be formed therein.At the center of the radial negative zone the pressure drops to its lowest value—phenomenon that has been verified by theoretical analysis.Some discrepancies between the observed data and the simulated data are noted when an analysis in made on a cyclone operating with either fresh water only or with water with added heavy particles.展开更多
The 13th Five-year Plan period (2016-2020) is a crucial period for environmental protection in China and represents the last chance for the achievement of the environmental objective under the goal of building a wel...The 13th Five-year Plan period (2016-2020) is a crucial period for environmental protection in China and represents the last chance for the achievement of the environmental objective under the goal of building a well-off society in an all-round manner. During this period of time, China' s environment is confronted with the following major risks: risks of environmental quality, human health, ecological security, balanced regional development and international influence. The overall conclusion is that the tendencies of changing eco-environment are complex, problems remain outstanding, and some risks have abated while others have intensified with possible improvements in the future. Future prospects mainly depend on the intensity of actions taken. It is suggested that environmental protection strategy of"overall optimization" be adopted for the 13th Five-year Plan period, i.e. environmental protection requirements should be incorporated into political, economic, social and cultural spheres, so that these areas with major influence on the natural environment will improve and transform towards an environmentally friendly direction and ultimately help achieve the objective of improving eco-environment and people's welfare. In order to fundamentally reverse mainstream understanding on environmental protection, it is suggested to define the "contradiction between environmental pressures arising from growing economic development and China ' s limited and fragile environmental capacity" as a major contradiction of Chinese society.展开更多
Based on measurements at the Beijing 325-m Meteorological Tower,this study reports an analysis of atmospheric stability conditions and turbulent exchange during consecutive episodes of particle air pollution in Beijin...Based on measurements at the Beijing 325-m Meteorological Tower,this study reports an analysis of atmospheric stability conditions and turbulent exchange during consecutive episodes of particle air pollution in Beijing(China),primarily due to haze and dust events(15–30 April 2012).Of particular interest were relevant vertical variations within the lower urban boundary layer(UBL).First,the haze and dust events were characterized by different atmospheric conditions,as quite low wind speed and high humidity are typically observed during haze events.In addition,for the description of stability conditions,the bulk Richardson number(RiB) was calculated for three different height intervals: 8–47,47–140,and 140–280 m.The values of RiB indicated an apparent increase in the occurrence frequency of stably-stratified air layers in the upper height interval—for the 140–280-m height interval,positive values of RiB occurred for about 85% of the time.The downward turbulent exchange of sensible heat was observed at 280 m for the full diurnal cycle,which,by contrast,was rarely seen at 140 m during daytime.These results reinforce the importance of implementing high-resolution UBL profile observations and addressing issues related to stably-stratified flows.展开更多
The computational fluid dynamics (CFD) method is used to investigate the aerodynamic characteristics of the seat/occupant with windblast protection devices. The upwind Osher scheme is used for the spatial discretisa...The computational fluid dynamics (CFD) method is used to investigate the aerodynamic characteristics of the seat/occupant with windblast protection devices. The upwind Osher scheme is used for the spatial discretisation. The detached-eddy simulation (DES) based on the Spalart-Allmaras one-equation turbulence model is ap- plied to the detached viscous flow simulation behind the seat/occupant, with Mach numbers 0.6 and 1.2 at attack angles between --10 and 30°, and at two sideslip angles of 0 and 15°, respectively. The aerodynamic characteristics of seat/occupants with and without windblast protection devices are calculated in cases of the freestream Mach numbers 0. 8 and 1.6, attack angles from 5 to 30°, and three sideslip angles of 0, --20 and --50°, respectively. Results show that simulation results agree well with experimental data. And the occupant is efficiently protected by windblast protection devices.展开更多
Breast cancer (BC) is diagnosed in 〉 65 year old women in about half of cases. Experts currently recommend that systemic therapy is offered to elderly patients with BC, if, based on their overall conditions and lif...Breast cancer (BC) is diagnosed in 〉 65 year old women in about half of cases. Experts currently recommend that systemic therapy is offered to elderly patients with BC, if, based on their overall conditions and life expectancy, it can be reasonably anticipated that the benefits will outweigh the risks of treatment. Like for young subjects, the monoclonal antibody against human epidermal growth factor receptor-2 (HER-2), trastuzumab, represents a valid therapeutic option when BC over-expresses this receptor. Unforttmately, administration of trastu- zumab is associated with the occurrence of left ventricular dysfunction and chronic heart failure (CHF), possibly because of interference with the homeostatic functions of HER-2 in the heart. Registry-based, retrospective analyses have reported an incidence of CHF around 25% in elderly women receiving trastuzumab compared with 10%-15% in those not given any therapy for BC, and the risk of CHF has been estimated to be two-fold higher in 〉 60455 year old trastuzumab users vs. non-users. Extremely advanced age and preexisting cardiac disease have been shown to predispose to trastuzumab cardiotoxicity. Therefore, selection of older patients for treatment with trastuzumab should be primarily based on their general status and the presence of comorbidities; previous chemotherapy, especially with anthracyclines, should be also taken into account. Once therapy has started, efforts should be made to ensure regular cardiac surveillance. The role of selected biomarkers, such as cardiac troponin, or new imaging techniques (three-dimension, tissue Doppler echocardiography, magnetic resonance imaging) is promising, but must be further investigated especially in the elderly. Moreover, additional studies are needed in order to better understand the mechanisms by which trastuzumab affects the old heart.展开更多
According to fluid dynamics analysis during the fire, the criteria k-ε two-equation model for solving three-dimensional turbulence was determined, the pollutants generated in the fire disaster were set by adopting Mi...According to fluid dynamics analysis during the fire, the criteria k-ε two-equation model for solving three-dimensional turbulence was determined, the pollutants generated in the fire disaster were set by adopting Mixture multiphase flow, and the SIMPLE algorithm was used for solving on the basis of comprehensive consideration on the heat radia- tion and components transmission during fire. By simulating the airflow flowing state inside the tunnel during fire disaster of downward ventilation, drift ventilation, and ascensional ventilation, respectively, with regard to the actual situation of No.l, No.3, and No.5 belt roadway in Kongzhuang Coal Mine, the velocity vector distributions of pollutants under different inlet air volumes were obtained, and the damage degree and influential factors of disaster were also clear, which is helpful to control and avoid disaster during belt roadway fire.展开更多
In this paper we generalize the aggregated premium income process from a constant rate process to a poisson process for the classical compound Poinsson risk model,then for the generalized model and the classical compo...In this paper we generalize the aggregated premium income process from a constant rate process to a poisson process for the classical compound Poinsson risk model,then for the generalized model and the classical compound poisson risk model ,we respectively get its survival probability in finite time period in case of exponential claim amounts.展开更多
Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especia...Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine.展开更多
This paper presents a study on the gravityinduced rock slope deformation observed along the Nujiang River in China. We performed a comprehensive field investigation and analysis to identify the deformation pattern of ...This paper presents a study on the gravityinduced rock slope deformation observed along the Nujiang River in China. We performed a comprehensive field investigation and analysis to identify the deformation pattern of the slope and its triggering factors. Moreover, a geologicalevolutionary model was developed, and it considers the effects of river incision and rock mass degradation caused by weathering and simulates the mechanisms underlying the initiation and progression of the slope deformation. The results support the proposed failure mechanism in which fractures within the slope are induced by rock mass degradation caused by weathering. Importantly, the modeling reveals that compressional deformation at the toe of the slope results in a tensile failure in the upper portion of the slope, demonstrating that the rock mass in the slope toe is the key factor inducing slope deformation. This analysis of slope deformation and its spatial and temporal correlations with rock weathering and river incision reveal the main triggering factors that control the evolution of the studied slope and provide insights into the deformation process.展开更多
Outsourcing software development has many advantages as well as inevitable risks. Of these risks, outsourcee se-lection is one of the most important. A wrong outsourcee selection may have severe adverse influence on t...Outsourcing software development has many advantages as well as inevitable risks. Of these risks, outsourcee se-lection is one of the most important. A wrong outsourcee selection may have severe adverse influence on the expected outcome of the project. We analyzed the risks involved in outsourcee selection and also provided methods to identify these risks. Using the principles of Analytical Hierarchy Process (AHP) and Cluster Analysis based on Group Decision Making, we established an index evaluation system to evaluate and select outsourcees. Real world applications of this system demonstrated its effectiveness in evaluating and selecting qualified outsourcees.展开更多
In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buri...In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buried sand and a paleo-weathered rock mass was investigated in the laboratory by direct shear testing. A DRS-1 high pressure soil shear testing machine and orthogonal design method were used in the direct shear tests. Variance and range methods were applied to analyze the sensitivity of each factor that has an influence on the mechanical characters of the interface. The test results show that the normal pressure is the main influencing factor for mechanical characteristics of the interface, while the lithological characters and roughness are minor factors; the shear stress against shear displacement curve for the interface shows an overall hyperbola relationship, no obvious peak stress and dilatancy was observed.When the normal pressure is 6 MPa, the shear strengths of interfaces with different roughness are basically the same, and when the normal pressure is more than 8 MPa, the larger the roughness of the interface, the larger will be the shear strength; the shear strength has a better linear relationship with the normal pressure, which can be described by a linear Mohr–Coulomb criterion.展开更多
基金Project(N2022G031)supported by the Science and Technology Research and Development Program Project of China RailwayProjects(2022-Key-23,2021-Special-01A)supported by the Science and Technology Research and Development Program Project of China Railway Group LimitedProject(52308419)supported by the National Natural Science Foundation of China。
文摘The breakage and bending of ducts result in a difficulty to cope with ventilation issues in bidirectional excavation tunnels with a long inclined shaft using a single ventilation method based on ducts.To discuss the hybrid ventilation system applied in bidirectional excavation tunnels with a long inclined shaft,this study has established a full-scale computational fluid dynamics model based on field tests,the Poly-Hexcore method,and the sliding mesh technique.The distribution of wind speed,temperature field,and CO in the tunnel are taken as indices to compare the ventilation efficiency of three ventilation systems(duct,duct-ventilation shaft,duct–ventilated shaft-axial fan).The results show that the hybrid ventilation scheme based on duct-ventilation shaft–axial fan performs the best among the three ventilation systems.Compared to the duct,the wind speed and cooling rate in the tunnel are enhanced by 7.5%–30.6%and 14.1%–17.7%,respectively,for the duct-vent shaft-axial fan condition,and the volume fractions of CO are reduced by 26.9%–73.9%.This contributes to the effective design of combined ventilation for bidirectional excavation tunnels with an inclined shaft,ultimately improving the air quality within the tunnel.
基金The National Natural Science Foundation of China(No.50478113)the Leading Academic Discipline Project of Shanghai Municipal Education Commission(No.J50502)
文摘To study the draft sensation distribution of an air jet supply system in a large space building in summer,experiments are conducted in a large laboratory.The temperature,velocity and draft sensation distributions at a nozzle height of 4 m in the occupied zone are obtained.Then,the numerical simulation under the test condition is carried out by the computational fluid dynamics(CFD)method.The calculation results of the indoor vertical temperature and the draft sensation distribution are validated by the test data.Simulations with different nozzle heights are conducted.The satisfactory air supply condition is determined by analyzing the draft sensations and the temperatures in the occupied zone under three conditions.The simulation results show that the optimal draft sensation distribution and the uniform temperature and velocity fields can be obtained at a nozzle height of 5 m.
基金Project(2012BAC12B02)supported by the National Key Technology R&D Program of ChinaProject(2014FJ1011)supported by the Key Projects of Science and Technology of Hunan Province,ChinaProject(2011AA061001)supported by the National High-tech Research and Development Program of China
文摘A new process for utilization of hazardous lead-bearing wastes and iron-rich wastes by reducing-matting smelting has been developed.The slag(SG) and the iron-rich matte(IRM) are the main by-products from reducing-matting smelting of lead-bearing wastes and iron-rich wastes.The environmental risk of heavy metals(Cd,Zn,Pb and As) in the main by-products versus the charging material for reducing-matting smelting(CM) has been systematically assessed using leaching toxicity test,the three-stage sequential extraction procedure of European Community Bureau of Reference(BCR) and Hakanson Potential Ecological Risk Index Method(PERI).The results demonstrate that the ecological risk level of heavy metals for SG and IRM is significantly reduced after the reducing-matting smelting process compared with that for CM.
基金This project was supported by a grant from the National Natural Science Foundation of China (No. 39670736).
文摘Objective: To explore the pituitary function of acute pituitary apoplexy and its effect by transsphenoidal surgery. Methods: The clinical data and endocrine hormones level of 25 patients with acute pituitary apoplexy who underwent transsphenoidal surgery from Jan. 2002 to June 2004 were retrospectively analyzed. Results: 13 cases underwent surgery within 3 days after admission and 22 cases within 1 week. Of the 25 cases, 9 patients suffered the impairment of pituitary-thyroidal function, 14 cases of pituitary-adrenal function and 11 cases of pituitary-gonadal function before surgery. After surgery, 5/9, 8/14 and 7/11 were recovered from the corresponding hypopituitarism. Conclusion: Hypopituitarism is a major manifestation of acute pituitary apoplexy. Urgent surgery decompression contributed to the improvement of pituitary function. Patients with hypopituitarism after surgery required the corresponding hormones replacement therapy.
文摘This paper analyzes the applications of four air terminal device(ATD)models(i.e.,the basic model,the box model,the N-point momentum model,the jet main region specification model)in computational fluid dynamics(CFD)simulation and their performance in case study.A full-scale experiment is performed in an environment chamber,and the measured air velocity and temperature fields are compared with the simulation results by using four ATD models.The velocity and temperature fields are measured by an omni-directional thermo-anemometer system.It demonstrates that the basic model and the box model are not applicable to complicated air terminal devices.At the occupant area,the relative errors between simulated and measured air velocities are less than 20% based on the N-point momentum model and the jet main region specification model.Around the ATD zone,the relative error between the numerical and measured air velocity based on the jet main region specification model is less than 15%.The jet main region specification model is proved to be an applicable approach and a more accurate way to study the airflow pattern around the ATD with complicated geometry.
基金Projects 2007AA05Z339 supported by the Hi-tech Research and Development Program of ChinaCPEUKF08-10 by the Key Laboratory Opening Fund of Coal Processing & Efficient Utilization,Ministry of Education of China
文摘An analytical study of the flow and pressure fields inside a small-diameter dense-media cyclone is presented.The simulations were done with the help of the CFD software FLUENT.The following conclusions were reached:the tangential velocity tends to increase when moving from the center toward the exterior.The velocity then begins to decrease when the maximum velocity point is reached.The velocity field divides into two different sections;an inner swirling zone and an outer swirling zone.The axial velocity points down at the wall and gradually decreases toward the bottom.Continuing toward the bottom,the axial velocity passes through zero and then gradually increases in the opposite direction.In the cyclone's central zone,the pressure is negative and the suction of air allows an air column to be formed therein.At the center of the radial negative zone the pressure drops to its lowest value—phenomenon that has been verified by theoretical analysis.Some discrepancies between the observed data and the simulated data are noted when an analysis in made on a cyclone operating with either fresh water only or with water with added heavy particles.
文摘The 13th Five-year Plan period (2016-2020) is a crucial period for environmental protection in China and represents the last chance for the achievement of the environmental objective under the goal of building a well-off society in an all-round manner. During this period of time, China' s environment is confronted with the following major risks: risks of environmental quality, human health, ecological security, balanced regional development and international influence. The overall conclusion is that the tendencies of changing eco-environment are complex, problems remain outstanding, and some risks have abated while others have intensified with possible improvements in the future. Future prospects mainly depend on the intensity of actions taken. It is suggested that environmental protection strategy of"overall optimization" be adopted for the 13th Five-year Plan period, i.e. environmental protection requirements should be incorporated into political, economic, social and cultural spheres, so that these areas with major influence on the natural environment will improve and transform towards an environmentally friendly direction and ultimately help achieve the objective of improving eco-environment and people's welfare. In order to fundamentally reverse mainstream understanding on environmental protection, it is suggested to define the "contradiction between environmental pressures arising from growing economic development and China ' s limited and fragile environmental capacity" as a major contradiction of Chinese society.
基金funded by the National Basic Research Program of China (Grant No.2014CB447900)Xiaofeng GUO acknowledges the support of the State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chinese Academy of Sciences (Grant No.LAPC-KF-2009-02)
文摘Based on measurements at the Beijing 325-m Meteorological Tower,this study reports an analysis of atmospheric stability conditions and turbulent exchange during consecutive episodes of particle air pollution in Beijing(China),primarily due to haze and dust events(15–30 April 2012).Of particular interest were relevant vertical variations within the lower urban boundary layer(UBL).First,the haze and dust events were characterized by different atmospheric conditions,as quite low wind speed and high humidity are typically observed during haze events.In addition,for the description of stability conditions,the bulk Richardson number(RiB) was calculated for three different height intervals: 8–47,47–140,and 140–280 m.The values of RiB indicated an apparent increase in the occurrence frequency of stably-stratified air layers in the upper height interval—for the 140–280-m height interval,positive values of RiB occurred for about 85% of the time.The downward turbulent exchange of sensible heat was observed at 280 m for the full diurnal cycle,which,by contrast,was rarely seen at 140 m during daytime.These results reinforce the importance of implementing high-resolution UBL profile observations and addressing issues related to stably-stratified flows.
基金Supported by the Aeronautical Science Foundation of China(2008ZC52039)~~
文摘The computational fluid dynamics (CFD) method is used to investigate the aerodynamic characteristics of the seat/occupant with windblast protection devices. The upwind Osher scheme is used for the spatial discretisation. The detached-eddy simulation (DES) based on the Spalart-Allmaras one-equation turbulence model is ap- plied to the detached viscous flow simulation behind the seat/occupant, with Mach numbers 0.6 and 1.2 at attack angles between --10 and 30°, and at two sideslip angles of 0 and 15°, respectively. The aerodynamic characteristics of seat/occupants with and without windblast protection devices are calculated in cases of the freestream Mach numbers 0. 8 and 1.6, attack angles from 5 to 30°, and three sideslip angles of 0, --20 and --50°, respectively. Results show that simulation results agree well with experimental data. And the occupant is efficiently protected by windblast protection devices.
文摘Breast cancer (BC) is diagnosed in 〉 65 year old women in about half of cases. Experts currently recommend that systemic therapy is offered to elderly patients with BC, if, based on their overall conditions and life expectancy, it can be reasonably anticipated that the benefits will outweigh the risks of treatment. Like for young subjects, the monoclonal antibody against human epidermal growth factor receptor-2 (HER-2), trastuzumab, represents a valid therapeutic option when BC over-expresses this receptor. Unforttmately, administration of trastu- zumab is associated with the occurrence of left ventricular dysfunction and chronic heart failure (CHF), possibly because of interference with the homeostatic functions of HER-2 in the heart. Registry-based, retrospective analyses have reported an incidence of CHF around 25% in elderly women receiving trastuzumab compared with 10%-15% in those not given any therapy for BC, and the risk of CHF has been estimated to be two-fold higher in 〉 60455 year old trastuzumab users vs. non-users. Extremely advanced age and preexisting cardiac disease have been shown to predispose to trastuzumab cardiotoxicity. Therefore, selection of older patients for treatment with trastuzumab should be primarily based on their general status and the presence of comorbidities; previous chemotherapy, especially with anthracyclines, should be also taken into account. Once therapy has started, efforts should be made to ensure regular cardiac surveillance. The role of selected biomarkers, such as cardiac troponin, or new imaging techniques (three-dimension, tissue Doppler echocardiography, magnetic resonance imaging) is promising, but must be further investigated especially in the elderly. Moreover, additional studies are needed in order to better understand the mechanisms by which trastuzumab affects the old heart.
基金Supported by the International Science and Technology Cooperation Projects(2009DFA71840)Basic Research Business Projects of China Academy of Safety Science and Technology(2009JBKY07)
文摘According to fluid dynamics analysis during the fire, the criteria k-ε two-equation model for solving three-dimensional turbulence was determined, the pollutants generated in the fire disaster were set by adopting Mixture multiphase flow, and the SIMPLE algorithm was used for solving on the basis of comprehensive consideration on the heat radia- tion and components transmission during fire. By simulating the airflow flowing state inside the tunnel during fire disaster of downward ventilation, drift ventilation, and ascensional ventilation, respectively, with regard to the actual situation of No.l, No.3, and No.5 belt roadway in Kongzhuang Coal Mine, the velocity vector distributions of pollutants under different inlet air volumes were obtained, and the damage degree and influential factors of disaster were also clear, which is helpful to control and avoid disaster during belt roadway fire.
基金Supported by the Natural Science Foundation of China(10071019)
文摘In this paper we generalize the aggregated premium income process from a constant rate process to a poisson process for the classical compound Poinsson risk model,then for the generalized model and the classical compound poisson risk model ,we respectively get its survival probability in finite time period in case of exponential claim amounts.
文摘Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine.
基金Supported by the National Natural Science Foundation of China(Grant Nos. 41521002,41572283 and 41130745)supported by the Funding of Science and Technology Office of Sichuan Province (Grant Nos. 2015JQ0020)
文摘This paper presents a study on the gravityinduced rock slope deformation observed along the Nujiang River in China. We performed a comprehensive field investigation and analysis to identify the deformation pattern of the slope and its triggering factors. Moreover, a geologicalevolutionary model was developed, and it considers the effects of river incision and rock mass degradation caused by weathering and simulates the mechanisms underlying the initiation and progression of the slope deformation. The results support the proposed failure mechanism in which fractures within the slope are induced by rock mass degradation caused by weathering. Importantly, the modeling reveals that compressional deformation at the toe of the slope results in a tensile failure in the upper portion of the slope, demonstrating that the rock mass in the slope toe is the key factor inducing slope deformation. This analysis of slope deformation and its spatial and temporal correlations with rock weathering and river incision reveal the main triggering factors that control the evolution of the studied slope and provide insights into the deformation process.
基金Project supported by the National Natural Science Foundation of China (No. 70571025), and Modern Information Management Re-search Center of Hubei Key Station for Humanities and Social Sci-ence (No. 200603), China
文摘Outsourcing software development has many advantages as well as inevitable risks. Of these risks, outsourcee se-lection is one of the most important. A wrong outsourcee selection may have severe adverse influence on the expected outcome of the project. We analyzed the risks involved in outsourcee selection and also provided methods to identify these risks. Using the principles of Analytical Hierarchy Process (AHP) and Cluster Analysis based on Group Decision Making, we established an index evaluation system to evaluate and select outsourcees. Real world applications of this system demonstrated its effectiveness in evaluating and selecting qualified outsourcees.
基金the National Natural Science Foundation of China(Nos.41172290 and40572160)
文摘In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buried sand and a paleo-weathered rock mass was investigated in the laboratory by direct shear testing. A DRS-1 high pressure soil shear testing machine and orthogonal design method were used in the direct shear tests. Variance and range methods were applied to analyze the sensitivity of each factor that has an influence on the mechanical characters of the interface. The test results show that the normal pressure is the main influencing factor for mechanical characteristics of the interface, while the lithological characters and roughness are minor factors; the shear stress against shear displacement curve for the interface shows an overall hyperbola relationship, no obvious peak stress and dilatancy was observed.When the normal pressure is 6 MPa, the shear strengths of interfaces with different roughness are basically the same, and when the normal pressure is more than 8 MPa, the larger the roughness of the interface, the larger will be the shear strength; the shear strength has a better linear relationship with the normal pressure, which can be described by a linear Mohr–Coulomb criterion.