A new stochastic optimal control strategy for randomly excited quasi-integrable Hamiltonian systems using magneto-rheological (MR) dampers is proposed. The dynamic be- havior of an MR damper is characterized by the Bo...A new stochastic optimal control strategy for randomly excited quasi-integrable Hamiltonian systems using magneto-rheological (MR) dampers is proposed. The dynamic be- havior of an MR damper is characterized by the Bouc-Wen hysteretic model. The control force produced by the MR damper is separated into a passive part incorporated in the uncontrolled system and a semi-active part to be determined. The system combining the Bouc-Wen hysteretic force is converted into an equivalent non-hysteretic nonlinear stochastic control system. Then It?o stochastic di?erential equations are derived from the equivalent system by using the stochastic averaging method. A dynamical programming equation for the controlled di?usion processes is established based on the stochastic dynamical programming principle. The non-clipping nonlin- ear optimal control law is obtained for a certain performance index by minimizing the dynamical programming equation. Finally, an example is given to illustrate the application and e?ectiveness of the proposed control strategy.展开更多
An innovative photoelectrode, TiO2/Ti mesh electrode, was prepared by anodisation. In anodisation, 0.5 mol/L H2SO4 was used as electrolytic solution, the current had been constantly 1A from the beginning of the oxidat...An innovative photoelectrode, TiO2/Ti mesh electrode, was prepared by anodisation. In anodisation, 0.5 mol/L H2SO4 was used as electrolytic solution, the current had been constantly 1A from the beginning of the oxidation until reaching a designed voltage. Results showed that the photocatalytic activity of electrode was better when the designed voltage was 160 V. The morphology and the crystalline texture of the TiO2 film on mesh electrode were examined by scanning electronic microscopy and Raman spectroscopy respectively. The examination results indicated that the structure and properties of the film depended on anodisation rate, and the anatase was the dominant component under the controlled experimental conditions. Degradation of Rhodamine B in photocatalytic （PC） and photoelectrocatalytic （PEC） reaction was investigated.展开更多
An innovative photoelectrode, TiO 2/Ti mesh electrode, was prepared by galvanostaticanodisation. The morphology and the crystalline texture of the TiO 2 film on mesh electrode were examined by scanning electronic micr...An innovative photoelectrode, TiO 2/Ti mesh electrode, was prepared by galvanostaticanodisation. The morphology and the crystalline texture of the TiO 2 film on mesh electrode were examined by scanning electronic microscopy and Raman spectroscopy respectively. The examination results indicated that the structure and properties of the film depended on anodisation rate, and the anatase was the dominant component under the controlled experimental conditions. Degradation of Rose Bengal(RB) in photocatalytic(PC) and photoelectrocatalytic(PEC) reaction was investigated, the results demonstrated that electric biasing could improve the efficiency of photocatalytic reaction. The measurement results of TOC in photoelectrocatalytic degradation showed that the mineralisation of RB was complete relatively. The comparison between the degradation efficiency of RB in PEC process and that in aqueous TiO 2 dispersion was conducted. The results showed that the apparent first order rate constant of RB degradation in PEC process was larger than that in aqueous dispersion with 0 1%—0 3% TiO 2 powder, but was smaller than that in aqueous dispersion with 1 0% TiO展开更多
The thick plate is commonly used for the pile cap and the transfer plate, and a proper analysis of it can greatly affect the cost of the thick plate. In actual practice, soft support condition is sometimes adopted by ...The thick plate is commonly used for the pile cap and the transfer plate, and a proper analysis of it can greatly affect the cost of the thick plate. In actual practice, soft support condition is sometimes adopted by engineers for modeling of thick plates. In this paper, the limitations of soft support in the determination of deflection and bending moment with very thick plates are studied. The distribution of superstructure ioadings to pile caps and piles is also carefully investigated.展开更多
In this paper,incompressible,double-diffusive convection is simulated using finite-difference schemes,The navier-Stokes equations are expressed in terms of stream function and vorticity.Because of the existence of lar...In this paper,incompressible,double-diffusive convection is simulated using finite-difference schemes,The navier-Stokes equations are expressed in terms of stream function and vorticity.Because of the existence of large velocity,temperature and salinity gradients in boundary layers,a boundary-fitted coordinate system is used to concentrate the grid points near the wall and fit complex boundaries.The fiite-difference methods used include the high-order accurate upwind difference scheme,It is shown that the scheme is a good candidate for direct simulations of double-diffusive convection flows.The proposed method is first applied to symmetry breaking and overturning states in thermohalinedriven flows in trapezoid basins,The basic phenomena agree well with those by Dijkstra and Molemaker(1997,J.Fluid Mech.331 169) and Quon and Ghil(1992,J.Fluid Mech.245 449),but symmetry breaking and overturning states can occur in an asymmetric geometrical region without perturbations.Then the method is applied to double-diffusive convections in a cavity with opposing horizontal temperature and concentration gradients at large thermal(Rt).solutal (Rs) Rayleigh numbers and Lewis number,There are three straight sides and a sine curve side in the cavity,Basically numerical results are in agreement with those of Lee and Hyun(1990 Int.J.Heat Mass Transfer 33 1619) qualitatively,but eddies mixing in the top left-hand coner near the curved wall affects the layered structure.展开更多
Concentrations and spatial distributions of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were measured at 8 sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of Pearl River Del...Concentrations and spatial distributions of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were measured at 8 sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of Pearl River Delta Region (PRDR), China during 2001 winter period and 2002 summer period. PM2.5 (particle diameter smaller than 2.5μm)and PM10 (particle diameter smaller than 10 μm) samples were collected on pre-fired quartz filters with mini-volume samplers and analyzed using thermal optical reflectance (TOR) method. The average PM2.5 and PM10 level were 60.1naceous aerosol accounted for 37.8% of the PM2.5 and 32.8% of the PM10. The highest concentrations of OC and EC were observed at Guangzhou city in both winter and summer seasons. The average OC/EC ratios were 2.4 for PM2.5and 2.5 for PM10, indicating the presence of secondary organic aerosols. The OC and EC in PRDR were found to be strongly correlated (correlation coefficients ＞0.6), which implied that similar emission source contribute to the ambient carbon particles.展开更多
A three-dimensional Large Eddy Simulation (LES) has been performed of hydrodynamic behavior of turbulent flow in open channel that the lower part of the domain is occupied by a drag force layer to represent vegetation...A three-dimensional Large Eddy Simulation (LES) has been performed of hydrodynamic behavior of turbulent flow in open channel that the lower part of the domain is occupied by a drag force layer to represent vegetation. One equation model is used to closing the resolvable scale equations. The turbulent characteristic length is parameterized by a k-l model. A phenomenal model is employed to express the performance of vegetation in the open channel. The result reveals that the present model has the capacity of describing three-dimensional structure of large eddy appearing in turbulent flow in open channel with vegetation region and has the capacity of tracing the development of large eddies.展开更多
A new method based on mass fluxes and observed ozone profiles was developed to estimate crosstropopause ozone flux. Using this method, we estimated the cross-tropopause ozone flux in a stratospheric-tropospheric excha...A new method based on mass fluxes and observed ozone profiles was developed to estimate crosstropopause ozone flux. Using this method, we estimated the cross-tropopause ozone flux in a stratospheric-tropospheric exchange event that occurred over East Asia in March 2001.The result revealed that the ozone flux across the tropopause in this event was an order of magnitude higher than the global and hemispheric average. Compared to the traditional method using a linear relationship between ozone mixing ratio and potential vorticity near the tropopause, the cross-tropopause ozone flux evaluated with ozonesonde data was somewhat higher, although the orders of the two values were the same.展开更多
Methods were developed to determine the mass ratios of carbon isotopes in trace amounts of aerosol carbon- ate. A Finnigan MAT 252 mass spectrometer fitted with an on-line Kiel device was to determine the C/12C ratio ...Methods were developed to determine the mass ratios of carbon isotopes in trace amounts of aerosol carbon- ate. A Finnigan MAT 252 mass spectrometer fitted with an on-line Kiel device was to determine the C/12C ratio in CO2 13 produced from the carbonate. A study using these methods was conducted to characterize the carbonate carbon isotopes in aerosol samples collected in Xi’an on dusty and normal days during March and April 2002. Results of the study demonstrate that insights into the origin of the dust can be deduced from its isotopic composition. That is, the δ C of 13 carbonate for dust storm samples ranged from ?1.4‰ to ?4.2‰, and this is consistent with sandy materials in dust source regions upwind. In contrast, for non-dusty days δ13C ranged from ?7.5% to ?9.3‰, which is more similar to fine particles emitted from local surface soils. Comparisons of dust storm aerosols with surface soils from source regions and with aerosol samples collected downwind indicate that the δ C values did not change appreciably during long- 13 range transport. Therefore, carbon isotopes have the poten- tial for distinguishing among source materials, and this ap- proach provides a powerful new tool for identifying dust provenance.展开更多
Since 70’s, the economy and society in the Pearl River Delta region have been undergoing a great development. Pollution control and environment protection have received much public attention. As heavy metals are an i...Since 70’s, the economy and society in the Pearl River Delta region have been undergoing a great development. Pollution control and environment protection have received much public attention. As heavy metals are an important toxic pollutant source in this area and are not biodegradable in general, a lot of scientists in China, especially in Southern China, devote their focus on studying the pollution caused by heavy metals in the Pearl River Estuary (PRE). This paper presents a comprehensive review on the heavy metal pollution research and its related research in this area. It is suggested that the study of heavy metal pollution in PRE should be coupled with water movement, sediment motion and tidal characteristics in this region. Studying core sediments in various locations is recommended to reveal the history of heavy metal pollution in PRE and improve the understanding of the fate and transport of metals.展开更多
A two-layer model, with the upper layer being the perfect fluid and the lower layer being the pseudo-plastic fluid describing water wave attenuation over mud bed, was established. A simplified method based on the prin...A two-layer model, with the upper layer being the perfect fluid and the lower layer being the pseudo-plastic fluid describing water wave attenuation over mud bed, was established. A simplified method based on the principle of equivalent work was applied to solve the boundary value problems. The computational results of the model show that the two-layer perfect fluid model and the perfect-viscous fluid model are all special cases of the present model. The complex nonlinear properties of wave attenuation over mud bed, can be explained by the present model, e.g., the wave dissipation rate decreases with the wave height in certain cases, while the small wave propagates over mud bed with less energy dissipation and large wave attenuates rapidly in other cases. Other factors influencing the wave attenuation were also discussed.展开更多
基金The Project Advanced Buildings technology in a Dense Urban Environment of Hong Kong Polytechnic University the Application Lab of Digital Seismic Wave Data in Center for Analysis and Prediction+1 种基金 China Seismological Bureau and the Earthquake Prediction
基金Project supported by the Zhejiang Provincial Natural Sciences Foundation (No. 101046) and the foundation fromHong Kong RGC (No. PolyU 5051/02E).
文摘A new stochastic optimal control strategy for randomly excited quasi-integrable Hamiltonian systems using magneto-rheological (MR) dampers is proposed. The dynamic be- havior of an MR damper is characterized by the Bouc-Wen hysteretic model. The control force produced by the MR damper is separated into a passive part incorporated in the uncontrolled system and a semi-active part to be determined. The system combining the Bouc-Wen hysteretic force is converted into an equivalent non-hysteretic nonlinear stochastic control system. Then It?o stochastic di?erential equations are derived from the equivalent system by using the stochastic averaging method. A dynamical programming equation for the controlled di?usion processes is established based on the stochastic dynamical programming principle. The non-clipping nonlin- ear optimal control law is obtained for a certain performance index by minimizing the dynamical programming equation. Finally, an example is given to illustrate the application and e?ectiveness of the proposed control strategy.
基金TheScientificResearchFoundationofHarbinInstituteofTechnology (No .HIT .2 0 0 1.5 6)
文摘An innovative photoelectrode, TiO2/Ti mesh electrode, was prepared by anodisation. In anodisation, 0.5 mol/L H2SO4 was used as electrolytic solution, the current had been constantly 1A from the beginning of the oxidation until reaching a designed voltage. Results showed that the photocatalytic activity of electrode was better when the designed voltage was 160 V. The morphology and the crystalline texture of the TiO2 film on mesh electrode were examined by scanning electronic microscopy and Raman spectroscopy respectively. The examination results indicated that the structure and properties of the film depended on anodisation rate, and the anatase was the dominant component under the controlled experimental conditions. Degradation of Rhodamine B in photocatalytic （PC） and photoelectrocatalytic （PEC） reaction was investigated.
文摘An innovative photoelectrode, TiO 2/Ti mesh electrode, was prepared by galvanostaticanodisation. The morphology and the crystalline texture of the TiO 2 film on mesh electrode were examined by scanning electronic microscopy and Raman spectroscopy respectively. The examination results indicated that the structure and properties of the film depended on anodisation rate, and the anatase was the dominant component under the controlled experimental conditions. Degradation of Rose Bengal(RB) in photocatalytic(PC) and photoelectrocatalytic(PEC) reaction was investigated, the results demonstrated that electric biasing could improve the efficiency of photocatalytic reaction. The measurement results of TOC in photoelectrocatalytic degradation showed that the mineralisation of RB was complete relatively. The comparison between the degradation efficiency of RB in PEC process and that in aqueous TiO 2 dispersion was conducted. The results showed that the apparent first order rate constant of RB degradation in PEC process was larger than that in aqueous dispersion with 0 1%—0 3% TiO 2 powder, but was smaller than that in aqueous dispersion with 1 0% TiO
文摘The thick plate is commonly used for the pile cap and the transfer plate, and a proper analysis of it can greatly affect the cost of the thick plate. In actual practice, soft support condition is sometimes adopted by engineers for modeling of thick plates. In this paper, the limitations of soft support in the determination of deflection and bending moment with very thick plates are studied. The distribution of superstructure ioadings to pile caps and piles is also carefully investigated.
文摘In this paper,incompressible,double-diffusive convection is simulated using finite-difference schemes,The navier-Stokes equations are expressed in terms of stream function and vorticity.Because of the existence of large velocity,temperature and salinity gradients in boundary layers,a boundary-fitted coordinate system is used to concentrate the grid points near the wall and fit complex boundaries.The fiite-difference methods used include the high-order accurate upwind difference scheme,It is shown that the scheme is a good candidate for direct simulations of double-diffusive convection flows.The proposed method is first applied to symmetry breaking and overturning states in thermohalinedriven flows in trapezoid basins,The basic phenomena agree well with those by Dijkstra and Molemaker(1997,J.Fluid Mech.331 169) and Quon and Ghil(1992,J.Fluid Mech.245 449),but symmetry breaking and overturning states can occur in an asymmetric geometrical region without perturbations.Then the method is applied to double-diffusive convections in a cavity with opposing horizontal temperature and concentration gradients at large thermal(Rt).solutal (Rs) Rayleigh numbers and Lewis number,There are three straight sides and a sine curve side in the cavity,Basically numerical results are in agreement with those of Lee and Hyun(1990 Int.J.Heat Mass Transfer 33 1619) qualitatively,but eddies mixing in the top left-hand coner near the curved wall affects the layered structure.
基金This study is supported by China NSFC project(40205018)Research Grants Council of Hong Kong(BQ-500)G-V951 of the Hong Kong Polytechnic University.
文摘Concentrations and spatial distributions of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were measured at 8 sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of Pearl River Delta Region (PRDR), China during 2001 winter period and 2002 summer period. PM2.5 (particle diameter smaller than 2.5μm)and PM10 (particle diameter smaller than 10 μm) samples were collected on pre-fired quartz filters with mini-volume samplers and analyzed using thermal optical reflectance (TOR) method. The average PM2.5 and PM10 level were 60.1naceous aerosol accounted for 37.8% of the PM2.5 and 32.8% of the PM10. The highest concentrations of OC and EC were observed at Guangzhou city in both winter and summer seasons. The average OC/EC ratios were 2.4 for PM2.5and 2.5 for PM10, indicating the presence of secondary organic aerosols. The OC and EC in PRDR were found to be strongly correlated (correlation coefficients ＞0.6), which implied that similar emission source contribute to the ambient carbon particles.
文摘A three-dimensional Large Eddy Simulation (LES) has been performed of hydrodynamic behavior of turbulent flow in open channel that the lower part of the domain is occupied by a drag force layer to represent vegetation. One equation model is used to closing the resolvable scale equations. The turbulent characteristic length is parameterized by a k-l model. A phenomenal model is employed to express the performance of vegetation in the open channel. The result reveals that the present model has the capacity of describing three-dimensional structure of large eddy appearing in turbulent flow in open channel with vegetation region and has the capacity of tracing the development of large eddies.
文摘A new method based on mass fluxes and observed ozone profiles was developed to estimate crosstropopause ozone flux. Using this method, we estimated the cross-tropopause ozone flux in a stratospheric-tropospheric exchange event that occurred over East Asia in March 2001.The result revealed that the ozone flux across the tropopause in this event was an order of magnitude higher than the global and hemispheric average. Compared to the traditional method using a linear relationship between ozone mixing ratio and potential vorticity near the tropopause, the cross-tropopause ozone flux evaluated with ozonesonde data was somewhat higher, although the orders of the two values were the same.
文摘Methods were developed to determine the mass ratios of carbon isotopes in trace amounts of aerosol carbon- ate. A Finnigan MAT 252 mass spectrometer fitted with an on-line Kiel device was to determine the C/12C ratio in CO2 13 produced from the carbonate. A study using these methods was conducted to characterize the carbonate carbon isotopes in aerosol samples collected in Xi’an on dusty and normal days during March and April 2002. Results of the study demonstrate that insights into the origin of the dust can be deduced from its isotopic composition. That is, the δ C of 13 carbonate for dust storm samples ranged from ?1.4‰ to ?4.2‰, and this is consistent with sandy materials in dust source regions upwind. In contrast, for non-dusty days δ13C ranged from ?7.5% to ?9.3‰, which is more similar to fine particles emitted from local surface soils. Comparisons of dust storm aerosols with surface soils from source regions and with aerosol samples collected downwind indicate that the δ C values did not change appreciably during long- 13 range transport. Therefore, carbon isotopes have the poten- tial for distinguishing among source materials, and this ap- proach provides a powerful new tool for identifying dust provenance.
文摘Since 70’s, the economy and society in the Pearl River Delta region have been undergoing a great development. Pollution control and environment protection have received much public attention. As heavy metals are an important toxic pollutant source in this area and are not biodegradable in general, a lot of scientists in China, especially in Southern China, devote their focus on studying the pollution caused by heavy metals in the Pearl River Estuary (PRE). This paper presents a comprehensive review on the heavy metal pollution research and its related research in this area. It is suggested that the study of heavy metal pollution in PRE should be coupled with water movement, sediment motion and tidal characteristics in this region. Studying core sediments in various locations is recommended to reveal the history of heavy metal pollution in PRE and improve the understanding of the fate and transport of metals.
基金This work was supported by the National Natural Science Foundation of China (Grant No: 50279029)the Central Funding of Hong Kong Polytechnic University (Grant No: GT219)Hong Kong RGC/NSFC Funding. (Grant No: NSFC/HKU 26)
文摘A two-layer model, with the upper layer being the perfect fluid and the lower layer being the pseudo-plastic fluid describing water wave attenuation over mud bed, was established. A simplified method based on the principle of equivalent work was applied to solve the boundary value problems. The computational results of the model show that the two-layer perfect fluid model and the perfect-viscous fluid model are all special cases of the present model. The complex nonlinear properties of wave attenuation over mud bed, can be explained by the present model, e.g., the wave dissipation rate decreases with the wave height in certain cases, while the small wave propagates over mud bed with less energy dissipation and large wave attenuates rapidly in other cases. Other factors influencing the wave attenuation were also discussed.
