In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti 49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1?...In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti 49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1?100 ℃ with strain rates of 10 -3 10 -1 s -1 . Within this range, the deformation behavior obeys the power law relationship, which can be described using the kinetic rate equation. The stress exponent, n , has a value of about 5.0, and the apparent activation energy is about 320 J/mol, which fits well with the value estimated in previous investigations. The results show that, the dependence of flow stress on the recrystallized grain size can be expressed by the equation: σ=K 1d rex -0 56 . The relationship between the deformed microstructure and the process control parameter can be expressed by the formula: lg d rex =-0 281?1gZ +3 908?1.展开更多
Based on the transport phenomena theory, the passive mixing of water and ethanol in different threedimensional microchannels is simulated numerically. The average variance of water volume fraction is used to index the...Based on the transport phenomena theory, the passive mixing of water and ethanol in different threedimensional microchannels is simulated numerically. The average variance of water volume fraction is used to index the mixing efficiency in the cases with different Reynolds number and different fabricated mixers. The results show that the efficiency of liquid mixing is progressively dependent on the convective transport as the Reynolds number increases. The efficiency of serpentine microchannel decreases with the increasing Reynolds number in the laminar regime. Altering the aspect ratio of channel inlet section has no significant effect on the mixing efficiency. Increasing the area of channel inlet section will cause the decrease of the mixing efficiency. The mixing in serpentine channels is the most efficient among three different mixers because of the existence of second flow introduced by its special structure.展开更多
In order to apply physical simulation results to natural gas hydrate reservoir parameters to provide a theoretical framework for the design of a development plan,an analytical equation method was used to obtain the si...In order to apply physical simulation results to natural gas hydrate reservoir parameters to provide a theoretical framework for the design of a development plan,an analytical equation method was used to obtain the similarity criteria of natural gas hydrate reservoir development by physical simulation,based on a mathematical model of natural gas hydrate development.Given the approach of numerical simulation,a sensitivity analysis for all parameters was carried out,which specifically demonstrated that initial temperature is the most important parameter.Parameters of thermal conductivity coefficients are not necessary for conducting the NGH dissociation process,which will fundamentally simplify the design and establishment of the model.The analysis provides a sound theoretical basis and design principles for particular similarity.展开更多
Based on 18 global climate models' simulations of the 20th century climate, a set of experiments within phase five of the Coupled Model Inter-comparison Project (CMIP5), the performances of simulating the present ...Based on 18 global climate models' simulations of the 20th century climate, a set of experiments within phase five of the Coupled Model Inter-comparison Project (CMIP5), the performances of simulating the present climate over China are assessed. Compared with observations, models can capture the dominant features of the geographic distributions of temperature and precipitation during 1961-2005. For the temporal changes of temperature, models appear to have a good performance on reproducing the warming tendency but show limited skills for precipitation. For the regional mean temperature and precipitation over the whole of China, most models underestimate the actual temperature and overestimate precipitation. Concerning the standard deviations of simulations by the 18 models, they are larger for temperature in the western part of China, while the standard deviations are larger for precipitation in the South.展开更多
A new serve plastic deformation(SPD) including initial forward extrusion and subsequent shearing process(ES) was proposed.The influence of the ES forming on the grain refinement of the microstructure was researched.Th...A new serve plastic deformation(SPD) including initial forward extrusion and subsequent shearing process(ES) was proposed.The influence of the ES forming on the grain refinement of the microstructure was researched.The components of ES forming die were manufactured and installed to Gleeble1500D thermo-mechanical simulator.The microstructure observations were carried out on the as-extruded rods(as-received) and ES formed rods.From the simulation results,ES forming can increase the cumulative strain enormously and the volume fraction of dynamic recrystallization.From the physical modeling results,the microstructures can be refined.展开更多
An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal a...An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid （coal） are modeled with the discrete element method, and the flow of fluid （gas and water） such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid-fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.展开更多
To evaluate the downscaling ability with respect to tropical cyclones(TCs)near China and its sensitivity to the model physics representation,the authors performed a multi-physics ensemble simulation with the regional ...To evaluate the downscaling ability with respect to tropical cyclones(TCs)near China and its sensitivity to the model physics representation,the authors performed a multi-physics ensemble simulation with the regional Climate-Weather Research and Forecasting(CWRF)model at a 30 km resolution driven by ERA-Interim reanalysis data.The ensemble consisted of 28 integrations during 1979-2016 with varying CWRF physics configurations.Both CWRF and ERA-Interim can generally capture the seasonal cycle and interannual variation of the TC number near China,but evidently underestimate them.The CWRF downscaling and its multi-physics ensemble can notably reduce the underestimation and significantly improve the simulation of the TC occurrences.The skill enhancement is especially large in terms of the interannual variation,which is most sensitive to the cumulus scheme,followed by the boundary layer,surface and radiation schemes,but weakly sensitive to the cloud and microphysics schemes.Generally,the Noah surface scheme,CAML(CAM radiation scheme as implemented by Liang together with the diagnostic cloud cover scheme of Xu and Randall(1996))radiation scheme,prognostic cloud scheme,and Thompson microphysics scheme stand out for their better performance in simulating the interannual variation of TC number.However,the Emanuel cumulus and MYNN boundary layer schemes produce severe interannual biases.Our study provides a valuable reference for CWRF application to improve the understanding and prediction of TC activity.展开更多
The northern Batinah occupies approximately 12,150 km2 in the north of Oman Quaternary deposits and Neogene＇s upper Fats form the aquifer units. MODFLOW compatible MT3D was used for simulation development of the area...The northern Batinah occupies approximately 12,150 km2 in the north of Oman Quaternary deposits and Neogene＇s upper Fats form the aquifer units. MODFLOW compatible MT3D was used for simulation development of the area. It can be concluded that： （1） The groundwater in the Batinah area generally flows from the south-west to the gulf of Oman in the north-east; （2） Recharge takes place through direct recharge from rainfall and wadi flow by about 902 ×10^3 ma/day; （3） The hydraulic conductivity attains a relatively wide range between 0.02 m/day and 78 m/day and 0.02 m/day and 60 m/day for the Quaternary and Fars respectively; （4） There is probably less potential for groundwater abstraction in the northern part of the area; （5） The water level decreased by about 6 m over 24 years and （6） The increase of salinity most likely due to a contribution of sea water intrusion from the gulf along the coast. It is recommended that： （1） automatic well control system should be installed to accurate measurements of abstraction; （2） further analysis under different future scenarios should be made and （3） formulate an integrated management plan for the basin.展开更多
A dynamic material model of Mg-4.51Al-1.19Zn-0.5Mn-0.5Ca(AZ41,mass fraction,%)magnesium alloy was put forward.The results show that the dynamic material model can characterize the deformation behavior and microstructu...A dynamic material model of Mg-4.51Al-1.19Zn-0.5Mn-0.5Ca(AZ41,mass fraction,%)magnesium alloy was put forward.The results show that the dynamic material model can characterize the deformation behavior and microstructure evolution and describe the relations among flow stress,strain,strain rates and deformation temperatures.Statistical analysis shows the validity of the proposed model.The model predicts that lower deformation temperature and higher strain rate cause the sharp strain hardening. Meanwhile,the flow stress curve turns into a steady state at high temperature and lower strain rate.The moderate temperature of 350 ℃and strain rate of 0.01 s-1 are appropriate to this alloy.展开更多
Ti0.5Al0.25Ni0.25 alloy prepared by vacuum induction melting was studied.The phase composition was analyzed with X-ray technique and EDS analysis,and its electrochemical properties were investigated at various tempera...Ti0.5Al0.25Ni0.25 alloy prepared by vacuum induction melting was studied.The phase composition was analyzed with X-ray technique and EDS analysis,and its electrochemical properties were investigated at various temperatures.Electrochemical reaction kinetic parameters were also studied with proper electrochemical techniques.The influence of the secondary corrosion reaction on the anodic linear polarization measurement was also analyzed by theoretical simulation.The results show that,proper ball-milling with nickel powders is beneficial to electrochemical performance.The theoretical simulation proves that,the existence of the side reaction can disturb the measurement of electrochemical reaction kinetic parameters.展开更多
Coal and gas outburst is one of the most serious natural calamities in collieries. And protective layer mining is an effective regional method for preventing and controlling coal outburst. However, how to rationally d...Coal and gas outburst is one of the most serious natural calamities in collieries. And protective layer mining is an effective regional method for preventing and controlling coal outburst. However, how to rationally determine the mining safety range in coal mining of protective layer with quantitative analysis is a difficult problem in rock mechanics and mining engineering so far. Then in this paper applied solid gas interaction mechanics for gas leakage flow, the solid gas interaction analysis for the safety range of up protective layer mining has been achieved with the results of experimental research and in situ measurements so that the result of numerical simulation for the difficult problem is closer to reality. Furthermore, the safety range of up protective layer mining can be determined with time dependent based on the result of numerical simulation.展开更多
We explore recurrence properties arising from dynamical approach to the van der Waerden theorem and similar combinatorial problems. We describe relations between these properties and study their consequences for dynam...We explore recurrence properties arising from dynamical approach to the van der Waerden theorem and similar combinatorial problems. We describe relations between these properties and study their consequences for dynamics. In particular, we present a measure-theoretical analog of a result of Glasner on multi-transitivity of topologically weakly mixing minimal maps. We also obtain a dynamical proof of the existence of a C-set with zero Banach density.展开更多
This paper presents a reality-virtual fusional campus environment.It is an online 3D platform with some aspects of real information merged together.The whole platform is based on OpenSimulator with detailed geo-models...This paper presents a reality-virtual fusional campus environment.It is an online 3D platform with some aspects of real information merged together.The whole platform is based on OpenSimulator with detailed geo-models to represent the university campus.Some preliminary experiments were done to integrate the realistic information with the virtual campus for making the geo-environment not only with detailed indoor and outdoor models,but also with the real representations of the physical world.The overall motivation is to provide a framework with strong support for reality-virtuality fusional modeling in a collaborative 3D online platform for research purposes.展开更多
Surface eigenstress and eigendisplacement models were used to investigate the surface stress, surface relaxation and surface elasticity of thin films with different surface orientations. Molecular dynamics simulations...Surface eigenstress and eigendisplacement models were used to investigate the surface stress, surface relaxation and surface elasticity of thin films with different surface orientations. Molecular dynamics simulations and first-principles calculations were conducted on face-centered cubic Au films with the focus on relaxation induced nonlinear initial deformation. The simu- lation results verify the theoretical predictions of the size dependency of surface energy density and surface stress, and the non- linear scaling law of the size-dependent Young＇s modulus of thin films. The mechanism of the size-dependent behaviors was further explored at the atomic bonding level with the charge density field. The Au atomic bonding at surfaces is enhanced compared to its interior counterpart and therefore the nominal Young＇s modulus of the Au thin films is larger when the film thickness is smaller.surface elasticity,展开更多
Saframycin A(SFM-A),a tetrahydroisoquinoline antibiotic isolated from Streptomyces lavendulae,shows potent anti-proliferation activities against a variety of tumor cell lines,and shares the core structure with ecteina...Saframycin A(SFM-A),a tetrahydroisoquinoline antibiotic isolated from Streptomyces lavendulae,shows potent anti-proliferation activities against a variety of tumor cell lines,and shares the core structure with ecteinascidin 743(ET-743),the anticancer drug for soft-tissue sarcoma.Characterization of the SFM-A biosynthetic gene cluster revealed three nonribosomal peptide synthetase genes and a series of genes encoding oxygenases.To investigate the function of sfmO2 gene,encoding a FAD-dependent monooxygenase/hydroxylase,we constructed the gene replacement mutant(△sfmO2) strain S.lavendulae TL2007 and the corresponding gene complementation mutant strain S.lavendulae TL2008.A novel compound,SFM-O,was isolated from the △sfmO2 replacement mutant strain and its structure was characterized by comparison to the HRMS and NMR spectra of SFM-A.These findings indicated that SfmO2 is responsible for the oxidation of ring A in the biosynthetic pathway of SFM-A,and the new compound SFM-O could be considered as an advanced intermediate in the semisynthesis of ET-743.展开更多
The quasi-steady methods based on mixing models have been widely applied to flow computations of turbomachinery multi- stages in aerospace engineering. Meanwhile, the unsteady numerical simulation has also been used d...The quasi-steady methods based on mixing models have been widely applied to flow computations of turbomachinery multi- stages in aerospace engineering. Meanwhile, the unsteady numerical simulation has also been used due to its ability in obtaining time-dependent flow solutions. In the paper, two different mixing treatments and the corresponding flux balanced ones are presented to exchange the flow solutions on the interfaces between adjacent blade rows. The four mixing treatments are then used for flow computations of a subsonic 1.5-stage axial turbine and a quasi-l.5-stage transonic compressor rotor. The results are compared with those by unsteady numerical method, which is implemented by using the sliding mesh technique. The effects of the quasi-steady and unsteady computation methods on the conservation of flow solutions across the interfaces are presented and addressed. Furthermore, the influence of mixing treatments on shock wave and flow separation of the transonic compressor rotor is presented in detail. All the results demonstrate that the flux balanced mixing treatments can be used for multi-stage flow computations with improved performance on interface conservation, even in the complex flows.展开更多
文摘In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti 49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1?100 ℃ with strain rates of 10 -3 10 -1 s -1 . Within this range, the deformation behavior obeys the power law relationship, which can be described using the kinetic rate equation. The stress exponent, n , has a value of about 5.0, and the apparent activation energy is about 320 J/mol, which fits well with the value estimated in previous investigations. The results show that, the dependence of flow stress on the recrystallized grain size can be expressed by the equation: σ=K 1d rex -0 56 . The relationship between the deformed microstructure and the process control parameter can be expressed by the formula: lg d rex =-0 281?1gZ +3 908?1.
基金Supported by the National Natural Science Foundation of China (No. 20299030).
文摘Based on the transport phenomena theory, the passive mixing of water and ethanol in different threedimensional microchannels is simulated numerically. The average variance of water volume fraction is used to index the mixing efficiency in the cases with different Reynolds number and different fabricated mixers. The results show that the efficiency of liquid mixing is progressively dependent on the convective transport as the Reynolds number increases. The efficiency of serpentine microchannel decreases with the increasing Reynolds number in the laminar regime. Altering the aspect ratio of channel inlet section has no significant effect on the mixing efficiency. Increasing the area of channel inlet section will cause the decrease of the mixing efficiency. The mixing in serpentine channels is the most efficient among three different mixers because of the existence of second flow introduced by its special structure.
基金supported by the China Petroleum and Chemical Corporation (No.P06070)the National Natural Science Foundation of China (No.50404003)
文摘In order to apply physical simulation results to natural gas hydrate reservoir parameters to provide a theoretical framework for the design of a development plan,an analytical equation method was used to obtain the similarity criteria of natural gas hydrate reservoir development by physical simulation,based on a mathematical model of natural gas hydrate development.Given the approach of numerical simulation,a sensitivity analysis for all parameters was carried out,which specifically demonstrated that initial temperature is the most important parameter.Parameters of thermal conductivity coefficients are not necessary for conducting the NGH dissociation process,which will fundamentally simplify the design and establishment of the model.The analysis provides a sound theoretical basis and design principles for particular similarity.
基金supported by the National Natural Science Foundation of China(2009CB421407 and 2010CB950501)
文摘Based on 18 global climate models' simulations of the 20th century climate, a set of experiments within phase five of the Coupled Model Inter-comparison Project (CMIP5), the performances of simulating the present climate over China are assessed. Compared with observations, models can capture the dominant features of the geographic distributions of temperature and precipitation during 1961-2005. For the temporal changes of temperature, models appear to have a good performance on reproducing the warming tendency but show limited skills for precipitation. For the regional mean temperature and precipitation over the whole of China, most models underestimate the actual temperature and overestimate precipitation. Concerning the standard deviations of simulations by the 18 models, they are larger for temperature in the western part of China, while the standard deviations are larger for precipitation in the South.
基金Project(2007CB613700) supported by the National Basic Research Program of ChinaProject(2007BAG06B04) supported by the National Science and Technology Pillar Program during the 11th Five-Year Plan Period+1 种基金Project(50725413) supported by the National Natural Science Foundation of ChinaProject(CSTC2009AB4008) supported by Chongqing Science and Technology Development Program,China
文摘A new serve plastic deformation(SPD) including initial forward extrusion and subsequent shearing process(ES) was proposed.The influence of the ES forming on the grain refinement of the microstructure was researched.The components of ES forming die were manufactured and installed to Gleeble1500D thermo-mechanical simulator.The microstructure observations were carried out on the as-extruded rods(as-received) and ES formed rods.From the simulation results,ES forming can increase the cumulative strain enormously and the volume fraction of dynamic recrystallization.From the physical modeling results,the microstructures can be refined.
文摘An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid （coal） are modeled with the discrete element method, and the flow of fluid （gas and water） such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid-fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.
基金supported by the National Climate Center of China under Grants 2211011816501。
文摘To evaluate the downscaling ability with respect to tropical cyclones(TCs)near China and its sensitivity to the model physics representation,the authors performed a multi-physics ensemble simulation with the regional Climate-Weather Research and Forecasting(CWRF)model at a 30 km resolution driven by ERA-Interim reanalysis data.The ensemble consisted of 28 integrations during 1979-2016 with varying CWRF physics configurations.Both CWRF and ERA-Interim can generally capture the seasonal cycle and interannual variation of the TC number near China,but evidently underestimate them.The CWRF downscaling and its multi-physics ensemble can notably reduce the underestimation and significantly improve the simulation of the TC occurrences.The skill enhancement is especially large in terms of the interannual variation,which is most sensitive to the cumulus scheme,followed by the boundary layer,surface and radiation schemes,but weakly sensitive to the cloud and microphysics schemes.Generally,the Noah surface scheme,CAML(CAM radiation scheme as implemented by Liang together with the diagnostic cloud cover scheme of Xu and Randall(1996))radiation scheme,prognostic cloud scheme,and Thompson microphysics scheme stand out for their better performance in simulating the interannual variation of TC number.However,the Emanuel cumulus and MYNN boundary layer schemes produce severe interannual biases.Our study provides a valuable reference for CWRF application to improve the understanding and prediction of TC activity.
文摘The northern Batinah occupies approximately 12,150 km2 in the north of Oman Quaternary deposits and Neogene＇s upper Fats form the aquifer units. MODFLOW compatible MT3D was used for simulation development of the area. It can be concluded that： （1） The groundwater in the Batinah area generally flows from the south-west to the gulf of Oman in the north-east; （2） Recharge takes place through direct recharge from rainfall and wadi flow by about 902 ×10^3 ma/day; （3） The hydraulic conductivity attains a relatively wide range between 0.02 m/day and 78 m/day and 0.02 m/day and 60 m/day for the Quaternary and Fars respectively; （4） There is probably less potential for groundwater abstraction in the northern part of the area; （5） The water level decreased by about 6 m over 24 years and （6） The increase of salinity most likely due to a contribution of sea water intrusion from the gulf along the coast. It is recommended that： （1） automatic well control system should be installed to accurate measurements of abstraction; （2） further analysis under different future scenarios should be made and （3） formulate an integrated management plan for the basin.
基金Project(Y2008F27)supported by the Natural Science Foundation of Shandong Province,China
文摘A dynamic material model of Mg-4.51Al-1.19Zn-0.5Mn-0.5Ca(AZ41,mass fraction,%)magnesium alloy was put forward.The results show that the dynamic material model can characterize the deformation behavior and microstructure evolution and describe the relations among flow stress,strain,strain rates and deformation temperatures.Statistical analysis shows the validity of the proposed model.The model predicts that lower deformation temperature and higher strain rate cause the sharp strain hardening. Meanwhile,the flow stress curve turns into a steady state at high temperature and lower strain rate.The moderate temperature of 350 ℃and strain rate of 0.01 s-1 are appropriate to this alloy.
文摘Ti0.5Al0.25Ni0.25 alloy prepared by vacuum induction melting was studied.The phase composition was analyzed with X-ray technique and EDS analysis,and its electrochemical properties were investigated at various temperatures.Electrochemical reaction kinetic parameters were also studied with proper electrochemical techniques.The influence of the secondary corrosion reaction on the anodic linear polarization measurement was also analyzed by theoretical simulation.The results show that,proper ball-milling with nickel powders is beneficial to electrochemical performance.The theoretical simulation proves that,the existence of the side reaction can disturb the measurement of electrochemical reaction kinetic parameters.
文摘Coal and gas outburst is one of the most serious natural calamities in collieries. And protective layer mining is an effective regional method for preventing and controlling coal outburst. However, how to rationally determine the mining safety range in coal mining of protective layer with quantitative analysis is a difficult problem in rock mechanics and mining engineering so far. Then in this paper applied solid gas interaction mechanics for gas leakage flow, the solid gas interaction analysis for the safety range of up protective layer mining has been achieved with the results of experimental research and in situ measurements so that the result of numerical simulation for the difficult problem is closer to reality. Furthermore, the safety range of up protective layer mining can be determined with time dependent based on the result of numerical simulation.
基金supported by the National Science Centre (Grant No. DEC-2012/07/E/ ST1/00185)National Natural Science Foundation of China (Grant Nos. 11401362, 11471125, 11326135, 11371339 and 11431012)+1 种基金Shantou University Scientific Research Foundation for Talents (Grant No. NTF12021)the Project of LQ1602 IT4Innovations Excellence in Science
文摘We explore recurrence properties arising from dynamical approach to the van der Waerden theorem and similar combinatorial problems. We describe relations between these properties and study their consequences for dynamics. In particular, we present a measure-theoretical analog of a result of Glasner on multi-transitivity of topologically weakly mixing minimal maps. We also obtain a dynamical proof of the existence of a C-set with zero Banach density.
基金the Direct Grant of the Chinese University of Hong Kong (No.2021064)the National High Technology Research and Development Program of China (No.2010AA122202)
文摘This paper presents a reality-virtual fusional campus environment.It is an online 3D platform with some aspects of real information merged together.The whole platform is based on OpenSimulator with detailed geo-models to represent the university campus.Some preliminary experiments were done to integrate the realistic information with the virtual campus for making the geo-environment not only with detailed indoor and outdoor models,but also with the real representations of the physical world.The overall motivation is to provide a framework with strong support for reality-virtuality fusional modeling in a collaborative 3D online platform for research purposes.
基金supported by the Hong Kong Research Grants Council(Grant No.622312)
文摘Surface eigenstress and eigendisplacement models were used to investigate the surface stress, surface relaxation and surface elasticity of thin films with different surface orientations. Molecular dynamics simulations and first-principles calculations were conducted on face-centered cubic Au films with the focus on relaxation induced nonlinear initial deformation. The simu- lation results verify the theoretical predictions of the size dependency of surface energy density and surface stress, and the non- linear scaling law of the size-dependent Young＇s modulus of thin films. The mechanism of the size-dependent behaviors was further explored at the atomic bonding level with the charge density field. The Au atomic bonding at surfaces is enhanced compared to its interior counterpart and therefore the nominal Young＇s modulus of the Au thin films is larger when the film thickness is smaller.surface elasticity,
基金supported in part by grants from the National Natural Science Foundation of China(20832009,and 20921091)the Chinese Academy of Sciences and Open Funding Project of the State Key Laboratory of Bioreactor Engineering
文摘Saframycin A(SFM-A),a tetrahydroisoquinoline antibiotic isolated from Streptomyces lavendulae,shows potent anti-proliferation activities against a variety of tumor cell lines,and shares the core structure with ecteinascidin 743(ET-743),the anticancer drug for soft-tissue sarcoma.Characterization of the SFM-A biosynthetic gene cluster revealed three nonribosomal peptide synthetase genes and a series of genes encoding oxygenases.To investigate the function of sfmO2 gene,encoding a FAD-dependent monooxygenase/hydroxylase,we constructed the gene replacement mutant(△sfmO2) strain S.lavendulae TL2007 and the corresponding gene complementation mutant strain S.lavendulae TL2008.A novel compound,SFM-O,was isolated from the △sfmO2 replacement mutant strain and its structure was characterized by comparison to the HRMS and NMR spectra of SFM-A.These findings indicated that SfmO2 is responsible for the oxidation of ring A in the biosynthetic pathway of SFM-A,and the new compound SFM-O could be considered as an advanced intermediate in the semisynthesis of ET-743.
基金supported by the National Natural Science Foundation of China(Grant Nos.51376009&51676003)
文摘The quasi-steady methods based on mixing models have been widely applied to flow computations of turbomachinery multi- stages in aerospace engineering. Meanwhile, the unsteady numerical simulation has also been used due to its ability in obtaining time-dependent flow solutions. In the paper, two different mixing treatments and the corresponding flux balanced ones are presented to exchange the flow solutions on the interfaces between adjacent blade rows. The four mixing treatments are then used for flow computations of a subsonic 1.5-stage axial turbine and a quasi-l.5-stage transonic compressor rotor. The results are compared with those by unsteady numerical method, which is implemented by using the sliding mesh technique. The effects of the quasi-steady and unsteady computation methods on the conservation of flow solutions across the interfaces are presented and addressed. Furthermore, the influence of mixing treatments on shock wave and flow separation of the transonic compressor rotor is presented in detail. All the results demonstrate that the flux balanced mixing treatments can be used for multi-stage flow computations with improved performance on interface conservation, even in the complex flows.
