A multi-parameter nonlinear elasto-plastic constitutive model which can fully capture the three typical features of stress-strain response, linearity, plasticity-like stress plateau and densification phases was develo...A multi-parameter nonlinear elasto-plastic constitutive model which can fully capture the three typical features of stress-strain response, linearity, plasticity-like stress plateau and densification phases was developed. The functional expression of each parameter was determined using uniaxial compression tests for aluminum alloy foams. The parameters of the model can be systematically varied to describe the effect of relative density which may be responsible for the changes in yield stress and hardening-like or softening-like behavior at various strain rates. A comparison between model predictions and experimental results of the aluminum alloy foams was provided to validate the model. It was proved to be useful in the selection of the optimal-density and energy absorption foam for a specific application at impact events.展开更多
We investigate the binding energies of excitons in a strained （111）-oriented zinc-blende GaN/Al0.3 Ga0.7 N quantum well screened by the electron-hole （e-h） gas under hydrostatic pressure by combining a variational...We investigate the binding energies of excitons in a strained （111）-oriented zinc-blende GaN/Al0.3 Ga0.7 N quantum well screened by the electron-hole （e-h） gas under hydrostatic pressure by combining a variational method and a selfconsistent procedure. A built-in electric field produced by the strain-induced piezoelectric polarization is considered in our calculations. The result indicates that the binding energies of excitons increase nearly linearly with pressure,even though the modification of strain with hydrostatic pressure is considered, and the influence of pressure is more apparent under higher e-h densities. It is also found that as the density of an e-h gas increases,the binding energies first increase slowly to a maximum and then decrease rapidly when the e-h density is larger than about 1 ×10^11 cm^-2. The excitonic binding energies increase obviously as the barrier thickness decreases due to the decrease of the built-in electric field.展开更多
The binding of pefloxacin mesylate （PFLX） to bovine lactoferrin （BLf） and human serum albumin （HSA） in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant ...The binding of pefloxacin mesylate （PFLX） to bovine lactoferrin （BLf） and human serum albumin （HSA） in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant K and the binding sites n were obtained by fluorescence quenching method. The binding distance r and energy-transfer efficiency E between pefloxacin mesylate and bovine lactoferrin as well as human serum albumin were also obtained according to the mechanism of Forster-type dipole-dipole nonradiative energy-transfer. The effects of pefloxacin mesylate on the conformations of bovine lactoferrin and human serum albumin were also analyzed using synchronous fluorescence spectroscopy.展开更多
In order to obtain magnetorheological （MR） elastomers with high magnetorheological effect, a family of anisotropic rubber-based MR elastomers was developed using a new form of chemical modification. Three different ...In order to obtain magnetorheological （MR） elastomers with high magnetorheological effect, a family of anisotropic rubber-based MR elastomers was developed using a new form of chemical modification. Three different kinds of surfactants, i.e. anionic, nonionic and compound surfactants, were employed separately to modify iron particles. The MR effect was evaluated by measuring the dynamic shear modulus of MR elastomer with a magneto-combined dynamic mechanical analyzer. Results show that the relative MR effect can be up to 188% when the iron particles are modified with 15% Span 80. Besides the surface activity of Span 80, however, such high modifying effect is partly due to the plasticizing effect of Span 80. Compared with the single surfactant, the superior surface activity of compound surfactant makes the relative MR effect reach 77% at a low content of 0.4%. Scanning electron microscope observation shows that the modification of compound surfactant results in perfect compatibility between particles and rubber matrix and special self-assembled structure of particles. Such special structure has been proved beneficial to the improvement of the relative MR effect.展开更多
By using in situ daily observations in East China during 1961-2007 and NCEP reanalysis data, the methods of statistical analyses, urban minus rural and observation minus reanalysis, it is revealed that the observed cl...By using in situ daily observations in East China during 1961-2007 and NCEP reanalysis data, the methods of statistical analyses, urban minus rural and observation minus reanalysis, it is revealed that the observed climate change and surface warming in East China were mainly induced by urbanization. The results show that East China has experienced two warmer periods of 1930s and 1980s in the past century; from 1951 to 2007, the regional mean temperature increased at a rate of 0.14℃ per decade; heat waves happened in urban center more frequently, and local climate showed a warming and dry trend; there was no significant linear trend in regional mean precipitation in the past 50 years. Urbanization was a crucial element for the regional warming; about 44% of the warming was due to heat island effect in the mega city.展开更多
The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In ord...The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In order to describe the energy dissipation by the motion of the structure under dynamic loading,a damping model which only includes stiffness damp stress was proposed and incorporated into the proposed rate dependent model to consider the energy dissipation at the material scale.The proposed model was developed in ABAQUS via UMAT and was verified by the simulations of concrete specimens under both tension and compression uniaxial loading at different strain rates.The nonlinear analysis of Koyna concrete dam under earthquake motions indicates that adding stiffness damp into the constitutive model can significantly enhance the calculation efficiency of the dynamic implicit analysis for greatly improving the numerical stability of the model.Considering strain rate effect in the model can affect the displacement reflection of this structure for slightly enhancing the displacement of the top,and can improve the calculation efficiency for greatly reducing the cost time.展开更多
Paper deals about testing of device with gravity assisted heat pipes and about researching of wick heat pipes used to effective heat transfers from power switches of energy converter. At first, to simulate ambient con...Paper deals about testing of device with gravity assisted heat pipes and about researching of wick heat pipes used to effective heat transfers from power switches of energy converter. At first, to simulate ambient condition was designed thermostatic chamber where was monitoring temperature course on main parts of cooling device （energy converter, air cooler and heat pipes） at various position of cooling device. It was found, if the cooling device is in tilt position the cooling performance is better. But if the tilt angel of gravity assisted heat pipe is higher the heat transfer is lower. From reason improve heat transfer cooling device at tilt angle are manufactured heat pipes with the sintered, mesh screen and grooved capillary structures and tested their thermal performance at vertical and tilt angel 45~ position by calorimetric method. Article describes manufacturing process and thermal performance measuring method of wick heat pipes. This experiment testify that the wick heat pipe is able operate at tilt angle position than gravity assisted heat pipe and application of wick heat pipes into cooling device will improve his cooling performance.展开更多
基金Projects (90716005, 10802055, 10972153) supported by the National Natural Science Foundation of ChinaProject (2007021005) supported by the Natural Science Foundation of Shanxi Province, China+2 种基金Project supported by the Postdoctoral Science Foundation of ChinaProject supported by the Homecomings Foundation, ChinaProject supported by the Top Young Academic Leaders of Higher Learning Institutions of Shanxi, China
文摘A multi-parameter nonlinear elasto-plastic constitutive model which can fully capture the three typical features of stress-strain response, linearity, plasticity-like stress plateau and densification phases was developed. The functional expression of each parameter was determined using uniaxial compression tests for aluminum alloy foams. The parameters of the model can be systematically varied to describe the effect of relative density which may be responsible for the changes in yield stress and hardening-like or softening-like behavior at various strain rates. A comparison between model predictions and experimental results of the aluminum alloy foams was provided to validate the model. It was proved to be useful in the selection of the optimal-density and energy absorption foam for a specific application at impact events.
文摘We investigate the binding energies of excitons in a strained （111）-oriented zinc-blende GaN/Al0.3 Ga0.7 N quantum well screened by the electron-hole （e-h） gas under hydrostatic pressure by combining a variational method and a selfconsistent procedure. A built-in electric field produced by the strain-induced piezoelectric polarization is considered in our calculations. The result indicates that the binding energies of excitons increase nearly linearly with pressure,even though the modification of strain with hydrostatic pressure is considered, and the influence of pressure is more apparent under higher e-h densities. It is also found that as the density of an e-h gas increases,the binding energies first increase slowly to a maximum and then decrease rapidly when the e-h density is larger than about 1 ×10^11 cm^-2. The excitonic binding energies increase obviously as the barrier thickness decreases due to the decrease of the built-in electric field.
基金Project (No. 20173050) supported by the National Natural ScienceFoundation of China
文摘The binding of pefloxacin mesylate （PFLX） to bovine lactoferrin （BLf） and human serum albumin （HSA） in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant K and the binding sites n were obtained by fluorescence quenching method. The binding distance r and energy-transfer efficiency E between pefloxacin mesylate and bovine lactoferrin as well as human serum albumin were also obtained according to the mechanism of Forster-type dipole-dipole nonradiative energy-transfer. The effects of pefloxacin mesylate on the conformations of bovine lactoferrin and human serum albumin were also analyzed using synchronous fluorescence spectroscopy.
基金ACKNOWLEDGMENTS This work was supported by the Natioal Natural Science Foundation of China （No.10672154） and the Specialized Research Fund for the Doctoral Program of Higher Education （No.20050358010）. The Scholarship BRJH funding of Chinese Academy of Sciences is also appreciated.
文摘In order to obtain magnetorheological （MR） elastomers with high magnetorheological effect, a family of anisotropic rubber-based MR elastomers was developed using a new form of chemical modification. Three different kinds of surfactants, i.e. anionic, nonionic and compound surfactants, were employed separately to modify iron particles. The MR effect was evaluated by measuring the dynamic shear modulus of MR elastomer with a magneto-combined dynamic mechanical analyzer. Results show that the relative MR effect can be up to 188% when the iron particles are modified with 15% Span 80. Besides the surface activity of Span 80, however, such high modifying effect is partly due to the plasticizing effect of Span 80. Compared with the single surfactant, the superior surface activity of compound surfactant makes the relative MR effect reach 77% at a low content of 0.4%. Scanning electron microscope observation shows that the modification of compound surfactant results in perfect compatibility between particles and rubber matrix and special self-assembled structure of particles. Such special structure has been proved beneficial to the improvement of the relative MR effect.
基金supported by the Climate Change Special Foundation of China Meteorological Administration(No.CCSF-09-10 and CCSF201202)National Natural Science Foundation of China (No.41001023)+1 种基金CAS Pilot Special Project (No.XDA05090204)Jiangsu Research and Innovation Program for Graduate Student (No.CXZZ12-0497)
文摘By using in situ daily observations in East China during 1961-2007 and NCEP reanalysis data, the methods of statistical analyses, urban minus rural and observation minus reanalysis, it is revealed that the observed climate change and surface warming in East China were mainly induced by urbanization. The results show that East China has experienced two warmer periods of 1930s and 1980s in the past century; from 1951 to 2007, the regional mean temperature increased at a rate of 0.14℃ per decade; heat waves happened in urban center more frequently, and local climate showed a warming and dry trend; there was no significant linear trend in regional mean precipitation in the past 50 years. Urbanization was a crucial element for the regional warming; about 44% of the warming was due to heat island effect in the mega city.
基金Project(2006BAJ03A03)supported by the National Key Technology R&D Program during the 11th Five-Year Plan Period of China
文摘The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In order to describe the energy dissipation by the motion of the structure under dynamic loading,a damping model which only includes stiffness damp stress was proposed and incorporated into the proposed rate dependent model to consider the energy dissipation at the material scale.The proposed model was developed in ABAQUS via UMAT and was verified by the simulations of concrete specimens under both tension and compression uniaxial loading at different strain rates.The nonlinear analysis of Koyna concrete dam under earthquake motions indicates that adding stiffness damp into the constitutive model can significantly enhance the calculation efficiency of the dynamic implicit analysis for greatly improving the numerical stability of the model.Considering strain rate effect in the model can affect the displacement reflection of this structure for slightly enhancing the displacement of the top,and can improve the calculation efficiency for greatly reducing the cost time.
文摘Paper deals about testing of device with gravity assisted heat pipes and about researching of wick heat pipes used to effective heat transfers from power switches of energy converter. At first, to simulate ambient condition was designed thermostatic chamber where was monitoring temperature course on main parts of cooling device （energy converter, air cooler and heat pipes） at various position of cooling device. It was found, if the cooling device is in tilt position the cooling performance is better. But if the tilt angel of gravity assisted heat pipe is higher the heat transfer is lower. From reason improve heat transfer cooling device at tilt angle are manufactured heat pipes with the sintered, mesh screen and grooved capillary structures and tested their thermal performance at vertical and tilt angel 45~ position by calorimetric method. Article describes manufacturing process and thermal performance measuring method of wick heat pipes. This experiment testify that the wick heat pipe is able operate at tilt angle position than gravity assisted heat pipe and application of wick heat pipes into cooling device will improve his cooling performance.
