The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corr...The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.展开更多
In this paper, we present measurements of velocity, temperature, salinity, and turbulence collected in Prydz Bay, Antarctica, during February, 2005. The dissipation rates of turbulent kinetic energy （e） and diapycna...In this paper, we present measurements of velocity, temperature, salinity, and turbulence collected in Prydz Bay, Antarctica, during February, 2005. The dissipation rates of turbulent kinetic energy （e） and diapycnal diffusivities （Ks） were estimated along a section in front of the Amery Ice Shelf. The dissipation rates and diapycnal diffusivities were spatially non-uniform, with higher values found in the western half of the section where E reached 10.7 W/kg and Kz reached 10.2 mVs, about two and three orders of magnitude higher than those in the open ocean, respectively. In the western half of the section both the dissipation rates and diffusivities showed a high-low-high vertical structure. This vertical structure may have been determined by internal waves in the upper layer, where the ice shelf draft acts as a possible energy source, and by bottom-generated internal waves in the lower layer, where both tides and geostrophic currents are possible energy sources. The intense diapycnal mixing revealed in our observations could contribute to the production of Antarctic Bottom Water in Prydz Bay.展开更多
In China,gravity retaining walls are widely used as protection structures against rockfalls,debris flows and debris avalanches along the roads in mountainous areas.In this paper,the Discrete Element Method(DEM) has be...In China,gravity retaining walls are widely used as protection structures against rockfalls,debris flows and debris avalanches along the roads in mountainous areas.In this paper,the Discrete Element Method(DEM) has been used to investigate the impact of granular avalanches and debris flows on retaining walls.The debris is modeled as two dimensional circular disks that interact through frictional sliding contacts.The basic equations that control the deformation and motion of the particles are introduced.A series of numerical experiments were conducted on an idealized debris slide impacting a retaining wall.The parametric study has been performed to examine the influences of slope geometry,travel distance of the sliding mass,wall position,and surface friction on the impact force exerted on the wall.Results show that:1) the force achieves its maximum value when slope angle is equal to 60°,as it varies from 30° to 75°;2) an approximate linear relationship between the impact force and the storage area length is determined.展开更多
The article deals with the experimental studies of atmosphere indistinct radiation structure. The information extraction background of dot size thermal object presence in atmosphere is reasonable. Indistinct generaliz...The article deals with the experimental studies of atmosphere indistinct radiation structure. The information extraction background of dot size thermal object presence in atmosphere is reasonable. Indistinct generalization of experimental study regularities technique of space-time irregularity radiation structure in infrared wave range is offered. The approach to dot size thermal object detection in atmosphere is proved with a help of threshold method in the thermodynamic and turbulent process conditions, based on the indistinct statement return task solution.展开更多
The paper evaluates the evolvement of coherent structures and penetration height of gaseous transverse jet penetration into a supersonic turbulent flow.The high spatiotemporal resolution coherent structures of the jet...The paper evaluates the evolvement of coherent structures and penetration height of gaseous transverse jet penetration into a supersonic turbulent flow.The high spatiotemporal resolution coherent structures of the jet plume are obtained by utilizing the nanoparticle-based planar laser scattering technique(NPLS).The evolving pattern of the coherent structures generated on the upwind surface of the transverse jet is analyzed based on the NPLS images.The shedding eddies from the jet near-field have lower convection velocity along freestream direction,while vortex growth rate is apparently higher than the far-field.Farther downstream,the large-scale eddies have less deformation and translate at velocities near the freestream velocity.Thus the near-field determines the scale of eddies in the far-field and affects the whole mixing process.The effect of injection stagnation pressure on the coherent structures is discussed and a modified penetration correlation is proposed based on an edge approximation definition and least square method with various injection pressures.展开更多
This paper aims at probing the flow characteristics of a jet in supersonic crossflow(JISC)by installing a vortex generator(VG)upstream of the jet orifice.Nanoparticle planar laser scattering(NPLS)and stereo-particle i...This paper aims at probing the flow characteristics of a jet in supersonic crossflow(JISC)by installing a vortex generator(VG)upstream of the jet orifice.Nanoparticle planar laser scattering(NPLS)and stereo-particle image velocimetry(SPIV)technologies were employed to observe the flowfield,and three cases were designed for comparison.CASE0 stands for JISC without passive VG.In CASE1 and CASE2,VG is installed at 20 mm and 80 mm upstream away from the jet orifice,respectively.Transient flow structures show that two flow modes exist when the VG wake interacts with the JISC.In CASE1,vortices are induced from both sides of the jet plume because of the VG wake.This leads to a complex streamwise vortex system.Penetration and lateral diffusion are enhanced.In CASE2,intermittent large-scale eddies in the VG wake cause large streamwise vortices at the windward side of the jet.The penetration depth is also enhanced while the lateral diffusion is restrained.In addition,experimental results show that the penetration depth is approximately 8.5%higher in CASE1 than that in CASE0,and the lateral diffusion is larger by about 17.0%.In CASE2,the penetration is increased by about 26.2%,while the lateral diffusion is enhanced by just 0.5%.展开更多
A Lagrangian modeling approach is applied to the numerical simulation of the temporal dynamics of a stage-structured population. The growth dynamics is determined only by the main biological processes： development of...A Lagrangian modeling approach is applied to the numerical simulation of the temporal dynamics of a stage-structured population. The growth dynamics is determined only by the main biological processes： development of an individual, mortality, reproduction. Different approaches in modeling the development process of an individual are implemented： stochastic advection-diffusion models （backward-forward dispersion models）, and stochastic development models where regression effects, defined as negative development on the status of an individual, are forbidden （forward dispersion models）. Some properties of the residence times of an individual in a stage are investigated： in particular, their role in the calibration of the development models and in the estimation of some parameters introduced in the model equation. As a study case a multi-stage pelagic copepod population is considered. Trying to separate the effects of the main biological processes on the temporal dynamics, numerical simulations have been carried out in some idealized situations： first only the development of the individuals, neglecting mortality and reproduction, is considered; then the mortality process is introduced, and finally both the mortality and reproduction processes. The results of the numerical simulations, are compared and discussed.展开更多
基金Project(BE2010043) supported by the Technology Support Program of Jiangsu Province,ChinaProject(CXZZ13_0928) supported by the Graduate Education Innovation Project of Jiangsu Province,China
文摘The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.
基金Supported by the National Natural Science Foundation of China(Nos.40906004,40890153,41176008,and 91028008)the National High Technology Research and Development Program of China(863 Program)(No.2008AA09A402)+2 种基金the Polar Science Strategic Foundation of China(No.20080206)the Key Lab Open Research Foundation of China(No.KP201006)the National Key Technology Research and Development Program of China(No.2006BAB18B02)
文摘In this paper, we present measurements of velocity, temperature, salinity, and turbulence collected in Prydz Bay, Antarctica, during February, 2005. The dissipation rates of turbulent kinetic energy （e） and diapycnal diffusivities （Ks） were estimated along a section in front of the Amery Ice Shelf. The dissipation rates and diapycnal diffusivities were spatially non-uniform, with higher values found in the western half of the section where E reached 10.7 W/kg and Kz reached 10.2 mVs, about two and three orders of magnitude higher than those in the open ocean, respectively. In the western half of the section both the dissipation rates and diffusivities showed a high-low-high vertical structure. This vertical structure may have been determined by internal waves in the upper layer, where the ice shelf draft acts as a possible energy source, and by bottom-generated internal waves in the lower layer, where both tides and geostrophic currents are possible energy sources. The intense diapycnal mixing revealed in our observations could contribute to the production of Antarctic Bottom Water in Prydz Bay.
基金support from the 973 Program of China (Grant No. 2008CB425803)the West Light Foundation of the CAS (Grant No. 09R2200200)
文摘In China,gravity retaining walls are widely used as protection structures against rockfalls,debris flows and debris avalanches along the roads in mountainous areas.In this paper,the Discrete Element Method(DEM) has been used to investigate the impact of granular avalanches and debris flows on retaining walls.The debris is modeled as two dimensional circular disks that interact through frictional sliding contacts.The basic equations that control the deformation and motion of the particles are introduced.A series of numerical experiments were conducted on an idealized debris slide impacting a retaining wall.The parametric study has been performed to examine the influences of slope geometry,travel distance of the sliding mass,wall position,and surface friction on the impact force exerted on the wall.Results show that:1) the force achieves its maximum value when slope angle is equal to 60°,as it varies from 30° to 75°;2) an approximate linear relationship between the impact force and the storage area length is determined.
文摘The article deals with the experimental studies of atmosphere indistinct radiation structure. The information extraction background of dot size thermal object presence in atmosphere is reasonable. Indistinct generalization of experimental study regularities technique of space-time irregularity radiation structure in infrared wave range is offered. The approach to dot size thermal object detection in atmosphere is proved with a help of threshold method in the thermodynamic and turbulent process conditions, based on the indistinct statement return task solution.
基金supported by the National Natural Science Foundation of China (Grant Nos. 91116001,91016028 and 91216303)Fok Ying Tung Education Foundation (Grant No. 131055)a fund for owner of outstanding doctorial dissertation from the Education Ministry of China
文摘The paper evaluates the evolvement of coherent structures and penetration height of gaseous transverse jet penetration into a supersonic turbulent flow.The high spatiotemporal resolution coherent structures of the jet plume are obtained by utilizing the nanoparticle-based planar laser scattering technique(NPLS).The evolving pattern of the coherent structures generated on the upwind surface of the transverse jet is analyzed based on the NPLS images.The shedding eddies from the jet near-field have lower convection velocity along freestream direction,while vortex growth rate is apparently higher than the far-field.Farther downstream,the large-scale eddies have less deformation and translate at velocities near the freestream velocity.Thus the near-field determines the scale of eddies in the far-field and affects the whole mixing process.The effect of injection stagnation pressure on the coherent structures is discussed and a modified penetration correlation is proposed based on an edge approximation definition and least square method with various injection pressures.
基金supported by the National Natural Science Foundation of China(Nos.91541203 and 51676204)the Fenglei Youth Innovation Fund of China Aerodynamics Research and Development Center(No.PJD20170186)。
文摘This paper aims at probing the flow characteristics of a jet in supersonic crossflow(JISC)by installing a vortex generator(VG)upstream of the jet orifice.Nanoparticle planar laser scattering(NPLS)and stereo-particle image velocimetry(SPIV)technologies were employed to observe the flowfield,and three cases were designed for comparison.CASE0 stands for JISC without passive VG.In CASE1 and CASE2,VG is installed at 20 mm and 80 mm upstream away from the jet orifice,respectively.Transient flow structures show that two flow modes exist when the VG wake interacts with the JISC.In CASE1,vortices are induced from both sides of the jet plume because of the VG wake.This leads to a complex streamwise vortex system.Penetration and lateral diffusion are enhanced.In CASE2,intermittent large-scale eddies in the VG wake cause large streamwise vortices at the windward side of the jet.The penetration depth is also enhanced while the lateral diffusion is restrained.In addition,experimental results show that the penetration depth is approximately 8.5%higher in CASE1 than that in CASE0,and the lateral diffusion is larger by about 17.0%.In CASE2,the penetration is increased by about 26.2%,while the lateral diffusion is enhanced by just 0.5%.
文摘A Lagrangian modeling approach is applied to the numerical simulation of the temporal dynamics of a stage-structured population. The growth dynamics is determined only by the main biological processes： development of an individual, mortality, reproduction. Different approaches in modeling the development process of an individual are implemented： stochastic advection-diffusion models （backward-forward dispersion models）, and stochastic development models where regression effects, defined as negative development on the status of an individual, are forbidden （forward dispersion models）. Some properties of the residence times of an individual in a stage are investigated： in particular, their role in the calibration of the development models and in the estimation of some parameters introduced in the model equation. As a study case a multi-stage pelagic copepod population is considered. Trying to separate the effects of the main biological processes on the temporal dynamics, numerical simulations have been carried out in some idealized situations： first only the development of the individuals, neglecting mortality and reproduction, is considered; then the mortality process is introduced, and finally both the mortality and reproduction processes. The results of the numerical simulations, are compared and discussed.
