The internal structures of metallic products are important in realizing functional applications.Considering the manufacturing of inner structures,laser-based powder bed fusion(L-PBF)is an attractive approach because i...The internal structures of metallic products are important in realizing functional applications.Considering the manufacturing of inner structures,laser-based powder bed fusion(L-PBF)is an attractive approach because its layering principle enables the fabrication of parts with customized interior structures.However,the inferior surface quality of L-PBF components hinders its productization progress seriously.In this article,process,basic forms,and applications relevant to L-PBF internal structures are reviewed comprehensively.The causes of poor surface quality and differences in the microstructure and property of the surface features of L-PBF inner structures are presented to provide a perspective of their surface characteristics.Various polishing technologies for L-PBF components with inner structures are presented,whereas their strengths and weaknesses are summarized along with a discussion on the challenges and prospects for improving the interior surface quality of L-PBF parts.展开更多
The axial flux permanent magnet(AFPM)generator with double-sided internal stator structure is highly suitable for vertical axis wind turbines due to its high power density.The performance of the AFPM generator with do...The axial flux permanent magnet(AFPM)generator with double-sided internal stator structure is highly suitable for vertical axis wind turbines due to its high power density.The performance of the AFPM generator with double-sided internal stator structure can be improved by the reasonable design of electromagnetic parameters.To further improve the overall performance of the AFPM generator with double-sided internal stator structure,multivariable(coil widthω_(c),permanent magnet thickness h,pole arc coefficient α_(p) and working air gap l_(g))and multi-objective(generator efficiencyη,total harmonic distortion of the voltage THD and induced electromotive force amplitude EMF)functional relationships are innovatively established.Orthogonal analysis,mean analysis and variance analysis are performed on the influence parameters by combining the Taguchi method and response surface methodology to study the influence degrees of each influence parameter on the optimization objectives to determine the most appropriate electromagnetic parameters.The optimization results are verified by 3D finite element analysis.The optimized APFM generator with double-sided internal stator structure exhibits superior economy,stronger magnetic density,higher efficiency and improved power quality.展开更多
There is an urgent need for small-diameter artificial blood vessels in clinic.Physical,chemical and biological factors should be integrated to avoid thrombosis and intimal hyperplasia after implantation and to promote...There is an urgent need for small-diameter artificial blood vessels in clinic.Physical,chemical and biological factors should be integrated to avoid thrombosis and intimal hyperplasia after implantation and to promote successful fabrication of small-diameter artificial blood vessels.From a physical perspective,the internal oriented structures of natural blood vessels plays an important role in guiding the directional growth of cells,improving the blood flow environment,and promoting the regeneration of vascular tissue.In this review,the effects of the oriented structures on cells,including endothelial cells(ECs),smooth muscle cells(SMCs)and stem cells,as well as the effect of the oriented structures on hemodynamics and vascular tissue remodeling and regeneration are introduced.Various forms of oriented structures(fibers,grooves,channels,etc.)and their construction methods are also reviewed.Conclusions and future perspectives are given.It is expected to give some references to relevant researches.展开更多
Every year on 22 April, we have celebrated Earth Day and the beautiful planet we call home. Earth Day, established in 1970, has been used to highlight our planet’s environmental challenges and raise awareness of the ...Every year on 22 April, we have celebrated Earth Day and the beautiful planet we call home. Earth Day, established in 1970, has been used to highlight our planet’s environmental challenges and raise awareness of the importance of protecting our world for future generations [1]. To provide the protection of our planet, we should explain Earth’s environmental challenges to the best of our knowledge in frames of contemporary Geophysics. This paper gives a short overview of the developed Hypersphere World-Universe Model (WUM) and pay particular attention to the principal role of Dark Matter (DM) in the Earth’s life. In this manuscript, we discuss different aspects of the Earth: a condition of Young Earth before the Beginning of life on It;Internal Structure;“The 660-km Boundary” that we named Geomagma;Random Variations of Earth’s Rotational Speed on a daily basis;Origin of Moon;Expanding Earth;Internal Heating;Faint Young Sun paradox;Geocorona and Planetary Coronas;High-Energy Atmospheric Physics. WUM proposed principally different ways to solve the problems of Internal Heating, Origin of the Moon, and Faint Young Sun paradox based on DM core of the Earth. The Model revealed the fact that the Sun Activity causes the Geomagma Activity and, as a consequence, Random Variations of Earth’s Rotational Speed by the varying Sun’s magnetic field.展开更多
Following developments in artificial intelligence and big data technology,the level of intelligence in intelligent vessels has been improved.Intelligent vessels are being developed into unmanned surface vehicles(USVs)...Following developments in artificial intelligence and big data technology,the level of intelligence in intelligent vessels has been improved.Intelligent vessels are being developed into unmanned surface vehicles(USVs),which have widely interested scholars in the shipping industry due to their safety,high efficiency,and energy-saving qualities.Considering the current development of USVs,the types of USVs and applications domestically and internationally are being investigated.USVs emerged with technological developments and their characteristics show some differences from traditional vessels,which brings some problems and advantages for their application.Certain maritime regulations are not applicable to USVs and must be changed.The key technologies in the current development of USVs are being investigated.While the level of intelligence is improving,the protection of cargo cannot be neglected.An innovative approach to the internal structure of USVs is proposed,where the inner hull can automatically recover its original state in case of outer hull tilting.Finally,we summarize the development status of USVs,which are an inevitable direction of development in the marine field.展开更多
The tidal Love numbers of the Moon are a set of nondimensional parameters that describe the deformation responses of the Moon to the tidal forces of external celestial bodies.They play an important role in the theoret...The tidal Love numbers of the Moon are a set of nondimensional parameters that describe the deformation responses of the Moon to the tidal forces of external celestial bodies.They play an important role in the theoretical calculation of the Moon’s tidal deformation and the inversion of its internal structure.In this study,we introduce the basic theory for the theoretical calculation of the tidal Love numbers and propose a new method of solving the tidal Love numbers:the spectral element method.Moreover,we explain the mathematical theory and advantages of this method.On the basis of this new method,using 10 published lunar internal structure reference models,the lunar surface and lunar internal tidal Love numbers were calculated,and the influence of different lunar models on the calculated Love numbers was analyzed.Results of the calculation showed that the difference in the second-degree lunar surface Love numbers among different lunar models was within 8.5%,the influence on the maximum vertical displacement on the lunar surface could reach±8.5 mm,and the influence on the maximum gravity change could reach±6μGal.Regarding the influence on the Love numbers inside the Moon,different lunar models had a greater impact on the Love numbers h_(2) and l_(2) than on k_(2) in the lower lunar mantle and core.展开更多
Jupiter’s magnetic field is thought to be generated in its deep metallic hydrogen region through dynamo action,yet the detailed dynamic process remains poorly understood.Numerical simulations have produced Jupiter-li...Jupiter’s magnetic field is thought to be generated in its deep metallic hydrogen region through dynamo action,yet the detailed dynamic process remains poorly understood.Numerical simulations have produced Jupiter-like magnetic fields,albeit using different control parameters and reference state models.In this study,we investigate the influence of different reference state models,based on ab initio calculations and based on the polytropic equation of state.In doing so,we perform five anelastic convection dynamo simulations that can be divided into two groups.In each group,different reference states are used while other control parameters and conditions are set to be identical.We find the reference state model can be very influential for the simulations in which buoyancy force is dominant over the Lorentz force.In this regime,different dynamical outcomes can be attributed to the effective buoyancy force resulting from different reference states.For simulations in which the Lorentz force is dominant over the buoyancy force,however,dynamo actions tend to be insensitive to different reference state models.If Jupiter’s dynamo is in a strong field regime,i.e.,the Lorentz force plays a dominant role,our numerical results suggest that Jupiter’s internal reference state,which remains poorly constrained,may play a minor role in the dynamo process of the planet.展开更多
To improve the electrocatalytic conversion of carbon dioxide(CO_(2))into C_(2+)products(such as ethylene(C_(2)H_(4))and ethanol(CH_(3)CH_(2)OH),etc.)is of great importance,but remains challenging.Herein,we proposed a ...To improve the electrocatalytic conversion of carbon dioxide(CO_(2))into C_(2+)products(such as ethylene(C_(2)H_(4))and ethanol(CH_(3)CH_(2)OH),etc.)is of great importance,but remains challenging.Herein,we proposed a strategy that directs the C–C coupling pathway through enriching and confining the carbon monoxide(CO)intermediate to internal pores of Cu nanocubes,for electrocatalytic reduction of CO_(2)into C_(2+)chemicals.In H-type cell,the Faraday efficiency(FE)for ethylene and ethanol reaches 70.3%at−1.28 V versus the reversible hydrogen electrode(vs.RHE),with a current density of 47.9 mA·cm^(−2).In flow cell,the total current density is up to 340.3 mA·cm^(−2)at^(−2).38 V(vs.RHE)and the FE for C_(2+)products is 67.4%.Experimental and theoretical studies reveal that both the CO intermediate adsorption and C–C coupling reaction on such an internal porous catalyst are facilitated,thus improving CO_(2)-to-C_(2+)conversion efficiency.展开更多
Small bodies are among the best tracers of our Solar System’s history.A large number of space missions to small bodies(past and future)offer a unique opportunity to use these bodies as a natural laboratory to study t...Small bodies are among the best tracers of our Solar System’s history.A large number of space missions to small bodies(past and future)offer a unique opportunity to use these bodies as a natural laboratory to study the different processes,mechanical structures,and responses that drive the origin and evolution of small bodies,which are connected to the origin,evolution,and current architecture of the Solar System.Images of small bodies sent by spacecraft have revealed unexpectedly rich and complex geological worlds.In addition to very diverse compositions,small bodies in the Solar System have highly diverse shapes and structures,which reflect both different evolutionary paths and material properties.Furthermore,each individual body has diverse geological features on its surface,which include craters of various sizes and depths,boulders of different sizes and morphologies,lineaments,fractures,pits,signatures of landslides,terraces,and ridges.Such a geological richness could not be detected via ground-based observations,and we are still at the beginning of understanding their significance on the low-gravity surfaces on which they manifest.The combination of space mission data and numerical modeling allows us to enrich our understanding of the origin,evolution,and physical properties of these fascinating bodies.For instance,starting from the shape models,bulk densities,and spin rates determined from space mission data,we can investigate the formation mechanisms that lead to the observed properties of small bodies.We can also infer the interior and mechanical properties(e.g.,friction and cohesion)that allow a small body to be structurally stable,as well as its further potential evolution under processes such as a spin rate increase or an impact.Then,considering the various processes that these bodies experience during their evolution,we can investigate how these processes modify their properties and,in turn,how those properties influence the outcome of these processes.This paper reviews our current knowledge of small-body shapes and structures and discusses the various processes that are responsible for their formation and evolution,which can modify the characteristics of the bodies.We separately consider each population of small bodies,although in some cases,such as active asteroids and comets,the distinction between two populations solely in terms of physical properties is not clear.We then summarize the main findings regarding the physical properties of small bodies that have been the target of rendezvous or sample return missions.展开更多
Changes in structure of oral solid dosage forms(OSDF) elementally determine the drug release and its therapeutic effects.In this research,synchrotron radiation X-ray micro-computed tomography was utilized to visualize...Changes in structure of oral solid dosage forms(OSDF) elementally determine the drug release and its therapeutic effects.In this research,synchrotron radiation X-ray micro-computed tomography was utilized to visualize the 3 D structure of enteric coated pellets recovered from the gastrointestinal tract of rats.The structures of pellets in solid state and in vitro compendium media were measured.Pellets in vivo underwent morphological and structural changes which differed significantly from those in vitro compendium media.Thus,optimizations of the dissolution media were performed to mimic the appropriate in vivo conditions by introducing pepsin and glass microspheres in media.The sphericity,pellet volume,pore volume and porosity of the in vivo esomeprazole magnesium pellets in stomach for2 h were recorded 0.47,1.55 × 10^(8)μm^(3),0.44 × 10^(8)μm^(3)and 27.6%,respectively.After adding pepsin and glass microspheres,the above parameters in vitro reached to 0.44,1.64 × 10^(8)μm^(3)0.38 × 10^(8)μm^(3)and 23.0%,respectively.Omeprazole magnesium pellets behaved similarly.The structural features of pellets between in vitro media and in vivo condition were bridged successfully in terms of 3 D structures to ensure better design,characterization and quality control of advanced OSDF.展开更多
Fuel spray characteristics directly determine the formation pattern and quality of the fuel/air mixture in an engine,and thus affect the combustion process.For this reason,the improvement and optimization of fuel inje...Fuel spray characteristics directly determine the formation pattern and quality of the fuel/air mixture in an engine,and thus affect the combustion process.For this reason,the improvement and optimization of fuel injection systems is crucial to the development of engine technologies.The fuel jet breakup and atomization process is a complex liquid-gas two-phase turbulent flow system that has not yet been fully elucidated.Owing to the limitations of standard optical measurement techniques,the spray breakup mechanism and its interaction with the nozzle internal flow are still unclear.However,in recent years synchrotron radiation(SR)X-ray imaging technologies have been widely applied in engine fuel injection studies because of the higher energy and brilliance of third-generation SR light sources.This review provides a brief introduction to the development of SR technology and compares the critical parameters of the primary third-generation SR light sources available worldwide.The basic principles and applications of various X-ray imaging technologies with regard to nozzle internal structure measurements,visualization of in-nozzle flow characteristics and quantitative analyses of near-field spray transient dynamics are examined in detail.展开更多
A comparative computational fluid dynamics(CFD)study was conducted on the three different types of pressurized water reactor(PWR)upper plenum,named TYPE 1(support columns(SCs)and control rod guide tubes(CRGTs)with two...A comparative computational fluid dynamics(CFD)study was conducted on the three different types of pressurized water reactor(PWR)upper plenum,named TYPE 1(support columns(SCs)and control rod guide tubes(CRGTs)with two large windows),TYPE 2(SCs and CRGTs without windows),and TYPE 3(two parallel perforated barrel shells and CRGTs).First,three types of upper plenum geometry information were collected,simplified,and adopted into the BORA facility,which is a 1/5 scale system of the four-loop PWR reactor.Then,the geometry,including the upper half core,upper plenum region,and hot legs,was built using the Salome platform.After that,an unsteady calculation to simulate the reactor balance operation at hot full power scenario was performed.Finally,the differences of flowrate distribution at the core outlet and temperature distribution and transverse velocity inside the hot legs with different upper plenum internals were compared.The results suggest that TYPE 1 upper plenum internals cause the largest flowrate difference at the core outlet while TYPE 3 leads to the most even distributed flowrate.The distribution and evolution pattern of the tangential velocity inside hot legs is highly dependent on the upper plenum internals.Two counter-rotating swirls exist inside the TYPE 1 hot leg and only one swirl revolving around the hog leg axis exist inside the TYPE 2 hot leg.For TYPE 3,two swirls like that of TYPE 1 rotating around the hot leg axis significantly increase the temperature homogenization speed.This research provides meaningful guidelines for the future optimization and design of advanced PWR upper plenum internal structures.展开更多
文摘The internal structures of metallic products are important in realizing functional applications.Considering the manufacturing of inner structures,laser-based powder bed fusion(L-PBF)is an attractive approach because its layering principle enables the fabrication of parts with customized interior structures.However,the inferior surface quality of L-PBF components hinders its productization progress seriously.In this article,process,basic forms,and applications relevant to L-PBF internal structures are reviewed comprehensively.The causes of poor surface quality and differences in the microstructure and property of the surface features of L-PBF inner structures are presented to provide a perspective of their surface characteristics.Various polishing technologies for L-PBF components with inner structures are presented,whereas their strengths and weaknesses are summarized along with a discussion on the challenges and prospects for improving the interior surface quality of L-PBF parts.
基金funded by Project Supported by Postdoctoral Science Foundation of Jiangsu Province,Grant No.2019k237.
文摘The axial flux permanent magnet(AFPM)generator with double-sided internal stator structure is highly suitable for vertical axis wind turbines due to its high power density.The performance of the AFPM generator with double-sided internal stator structure can be improved by the reasonable design of electromagnetic parameters.To further improve the overall performance of the AFPM generator with double-sided internal stator structure,multivariable(coil widthω_(c),permanent magnet thickness h,pole arc coefficient α_(p) and working air gap l_(g))and multi-objective(generator efficiencyη,total harmonic distortion of the voltage THD and induced electromotive force amplitude EMF)functional relationships are innovatively established.Orthogonal analysis,mean analysis and variance analysis are performed on the influence parameters by combining the Taguchi method and response surface methodology to study the influence degrees of each influence parameter on the optimization objectives to determine the most appropriate electromagnetic parameters.The optimization results are verified by 3D finite element analysis.The optimized APFM generator with double-sided internal stator structure exhibits superior economy,stronger magnetic density,higher efficiency and improved power quality.
文摘There is an urgent need for small-diameter artificial blood vessels in clinic.Physical,chemical and biological factors should be integrated to avoid thrombosis and intimal hyperplasia after implantation and to promote successful fabrication of small-diameter artificial blood vessels.From a physical perspective,the internal oriented structures of natural blood vessels plays an important role in guiding the directional growth of cells,improving the blood flow environment,and promoting the regeneration of vascular tissue.In this review,the effects of the oriented structures on cells,including endothelial cells(ECs),smooth muscle cells(SMCs)and stem cells,as well as the effect of the oriented structures on hemodynamics and vascular tissue remodeling and regeneration are introduced.Various forms of oriented structures(fibers,grooves,channels,etc.)and their construction methods are also reviewed.Conclusions and future perspectives are given.It is expected to give some references to relevant researches.
文摘Every year on 22 April, we have celebrated Earth Day and the beautiful planet we call home. Earth Day, established in 1970, has been used to highlight our planet’s environmental challenges and raise awareness of the importance of protecting our world for future generations [1]. To provide the protection of our planet, we should explain Earth’s environmental challenges to the best of our knowledge in frames of contemporary Geophysics. This paper gives a short overview of the developed Hypersphere World-Universe Model (WUM) and pay particular attention to the principal role of Dark Matter (DM) in the Earth’s life. In this manuscript, we discuss different aspects of the Earth: a condition of Young Earth before the Beginning of life on It;Internal Structure;“The 660-km Boundary” that we named Geomagma;Random Variations of Earth’s Rotational Speed on a daily basis;Origin of Moon;Expanding Earth;Internal Heating;Faint Young Sun paradox;Geocorona and Planetary Coronas;High-Energy Atmospheric Physics. WUM proposed principally different ways to solve the problems of Internal Heating, Origin of the Moon, and Faint Young Sun paradox based on DM core of the Earth. The Model revealed the fact that the Sun Activity causes the Geomagma Activity and, as a consequence, Random Variations of Earth’s Rotational Speed by the varying Sun’s magnetic field.
基金Shanghai High-level Local University Innovation Team(Maritime Safety&Technical Support)the National Natural Science Foundation of China (Grant No. 42176217)
文摘Following developments in artificial intelligence and big data technology,the level of intelligence in intelligent vessels has been improved.Intelligent vessels are being developed into unmanned surface vehicles(USVs),which have widely interested scholars in the shipping industry due to their safety,high efficiency,and energy-saving qualities.Considering the current development of USVs,the types of USVs and applications domestically and internationally are being investigated.USVs emerged with technological developments and their characteristics show some differences from traditional vessels,which brings some problems and advantages for their application.Certain maritime regulations are not applicable to USVs and must be changed.The key technologies in the current development of USVs are being investigated.While the level of intelligence is improving,the protection of cargo cannot be neglected.An innovative approach to the internal structure of USVs is proposed,where the inner hull can automatically recover its original state in case of outer hull tilting.Finally,we summarize the development status of USVs,which are an inevitable direction of development in the marine field.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB4 1000000)the National Natural Science Foundation of China (Grant Nos. 42104006, 41974023, 42174101, 41874094, 41874026)the self-deployed foundation of the State Key Laboratory of Geodesy and Earth’s Dynamics (Grant No. S21L6404)
文摘The tidal Love numbers of the Moon are a set of nondimensional parameters that describe the deformation responses of the Moon to the tidal forces of external celestial bodies.They play an important role in the theoretical calculation of the Moon’s tidal deformation and the inversion of its internal structure.In this study,we introduce the basic theory for the theoretical calculation of the tidal Love numbers and propose a new method of solving the tidal Love numbers:the spectral element method.Moreover,we explain the mathematical theory and advantages of this method.On the basis of this new method,using 10 published lunar internal structure reference models,the lunar surface and lunar internal tidal Love numbers were calculated,and the influence of different lunar models on the calculated Love numbers was analyzed.Results of the calculation showed that the difference in the second-degree lunar surface Love numbers among different lunar models was within 8.5%,the influence on the maximum vertical displacement on the lunar surface could reach±8.5 mm,and the influence on the maximum gravity change could reach±6μGal.Regarding the influence on the Love numbers inside the Moon,different lunar models had a greater impact on the Love numbers h_(2) and l_(2) than on k_(2) in the lower lunar mantle and core.
基金supported by the B-type Strategic Priority Program of the CAS (XDB41000000)the preresearch project on Civil Aerospace Technologies of CNSA (D020308)the Macao Foundationsupport from STFC, grant number ST/S00047X/1 held at the University of Leeds.
文摘Jupiter’s magnetic field is thought to be generated in its deep metallic hydrogen region through dynamo action,yet the detailed dynamic process remains poorly understood.Numerical simulations have produced Jupiter-like magnetic fields,albeit using different control parameters and reference state models.In this study,we investigate the influence of different reference state models,based on ab initio calculations and based on the polytropic equation of state.In doing so,we perform five anelastic convection dynamo simulations that can be divided into two groups.In each group,different reference states are used while other control parameters and conditions are set to be identical.We find the reference state model can be very influential for the simulations in which buoyancy force is dominant over the Lorentz force.In this regime,different dynamical outcomes can be attributed to the effective buoyancy force resulting from different reference states.For simulations in which the Lorentz force is dominant over the buoyancy force,however,dynamo actions tend to be insensitive to different reference state models.If Jupiter’s dynamo is in a strong field regime,i.e.,the Lorentz force plays a dominant role,our numerical results suggest that Jupiter’s internal reference state,which remains poorly constrained,may play a minor role in the dynamo process of the planet.
基金supported by the National Natural Science Foundation of China(Nos.22033009 and 22121002).
文摘To improve the electrocatalytic conversion of carbon dioxide(CO_(2))into C_(2+)products(such as ethylene(C_(2)H_(4))and ethanol(CH_(3)CH_(2)OH),etc.)is of great importance,but remains challenging.Herein,we proposed a strategy that directs the C–C coupling pathway through enriching and confining the carbon monoxide(CO)intermediate to internal pores of Cu nanocubes,for electrocatalytic reduction of CO_(2)into C_(2+)chemicals.In H-type cell,the Faraday efficiency(FE)for ethylene and ethanol reaches 70.3%at−1.28 V versus the reversible hydrogen electrode(vs.RHE),with a current density of 47.9 mA·cm^(−2).In flow cell,the total current density is up to 340.3 mA·cm^(−2)at^(−2).38 V(vs.RHE)and the FE for C_(2+)products is 67.4%.Experimental and theoretical studies reveal that both the CO intermediate adsorption and C–C coupling reaction on such an internal porous catalyst are facilitated,thus improving CO_(2)-to-C_(2+)conversion efficiency.
基金We thank W.F.Bottke for his helpful and constructive comments.We acknowledge the support of the French Space Agency CNES for their participation in the various space missions devoted to asteroids,as well as the ESA.This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No.870377(project NEO-MAPP).Yun Zhang acknowledges funding support from the Doeblin Federation and from the program Bonus,Qualit´e,Recherche(BQR)of the Observatoire de la Cˆote d’Azur.
文摘Small bodies are among the best tracers of our Solar System’s history.A large number of space missions to small bodies(past and future)offer a unique opportunity to use these bodies as a natural laboratory to study the different processes,mechanical structures,and responses that drive the origin and evolution of small bodies,which are connected to the origin,evolution,and current architecture of the Solar System.Images of small bodies sent by spacecraft have revealed unexpectedly rich and complex geological worlds.In addition to very diverse compositions,small bodies in the Solar System have highly diverse shapes and structures,which reflect both different evolutionary paths and material properties.Furthermore,each individual body has diverse geological features on its surface,which include craters of various sizes and depths,boulders of different sizes and morphologies,lineaments,fractures,pits,signatures of landslides,terraces,and ridges.Such a geological richness could not be detected via ground-based observations,and we are still at the beginning of understanding their significance on the low-gravity surfaces on which they manifest.The combination of space mission data and numerical modeling allows us to enrich our understanding of the origin,evolution,and physical properties of these fascinating bodies.For instance,starting from the shape models,bulk densities,and spin rates determined from space mission data,we can investigate the formation mechanisms that lead to the observed properties of small bodies.We can also infer the interior and mechanical properties(e.g.,friction and cohesion)that allow a small body to be structurally stable,as well as its further potential evolution under processes such as a spin rate increase or an impact.Then,considering the various processes that these bodies experience during their evolution,we can investigate how these processes modify their properties and,in turn,how those properties influence the outcome of these processes.This paper reviews our current knowledge of small-body shapes and structures and discusses the various processes that are responsible for their formation and evolution,which can modify the characteristics of the bodies.We separately consider each population of small bodies,although in some cases,such as active asteroids and comets,the distinction between two populations solely in terms of physical properties is not clear.We then summarize the main findings regarding the physical properties of small bodies that have been the target of rendezvous or sample return missions.
基金financial support from National Key R&D Program of China(2020YFE0201700)Major New Drugs Innovation and Development(2017ZX09101001-005,China)+1 种基金the National Natural Science Foundation of China(81803441,81803446 and 81773645)Youth Innovation Promotion Association CAS(2018323,China)。
文摘Changes in structure of oral solid dosage forms(OSDF) elementally determine the drug release and its therapeutic effects.In this research,synchrotron radiation X-ray micro-computed tomography was utilized to visualize the 3 D structure of enteric coated pellets recovered from the gastrointestinal tract of rats.The structures of pellets in solid state and in vitro compendium media were measured.Pellets in vivo underwent morphological and structural changes which differed significantly from those in vitro compendium media.Thus,optimizations of the dissolution media were performed to mimic the appropriate in vivo conditions by introducing pepsin and glass microspheres in media.The sphericity,pellet volume,pore volume and porosity of the in vivo esomeprazole magnesium pellets in stomach for2 h were recorded 0.47,1.55 × 10^(8)μm^(3),0.44 × 10^(8)μm^(3)and 27.6%,respectively.After adding pepsin and glass microspheres,the above parameters in vitro reached to 0.44,1.64 × 10^(8)μm^(3)0.38 × 10^(8)μm^(3)and 23.0%,respectively.Omeprazole magnesium pellets behaved similarly.The structural features of pellets between in vitro media and in vivo condition were bridged successfully in terms of 3 D structures to ensure better design,characterization and quality control of advanced OSDF.
基金This study was supported by the National Natural Science Foundation(U1832179)as a Key Project of the SSRF(2016-SSRF-ZD-004512).
文摘Fuel spray characteristics directly determine the formation pattern and quality of the fuel/air mixture in an engine,and thus affect the combustion process.For this reason,the improvement and optimization of fuel injection systems is crucial to the development of engine technologies.The fuel jet breakup and atomization process is a complex liquid-gas two-phase turbulent flow system that has not yet been fully elucidated.Owing to the limitations of standard optical measurement techniques,the spray breakup mechanism and its interaction with the nozzle internal flow are still unclear.However,in recent years synchrotron radiation(SR)X-ray imaging technologies have been widely applied in engine fuel injection studies because of the higher energy and brilliance of third-generation SR light sources.This review provides a brief introduction to the development of SR technology and compares the critical parameters of the primary third-generation SR light sources available worldwide.The basic principles and applications of various X-ray imaging technologies with regard to nozzle internal structure measurements,visualization of in-nozzle flow characteristics and quantitative analyses of near-field spray transient dynamics are examined in detail.
基金the National Natural Science Foundation of China(Grant No.12075185).
文摘A comparative computational fluid dynamics(CFD)study was conducted on the three different types of pressurized water reactor(PWR)upper plenum,named TYPE 1(support columns(SCs)and control rod guide tubes(CRGTs)with two large windows),TYPE 2(SCs and CRGTs without windows),and TYPE 3(two parallel perforated barrel shells and CRGTs).First,three types of upper plenum geometry information were collected,simplified,and adopted into the BORA facility,which is a 1/5 scale system of the four-loop PWR reactor.Then,the geometry,including the upper half core,upper plenum region,and hot legs,was built using the Salome platform.After that,an unsteady calculation to simulate the reactor balance operation at hot full power scenario was performed.Finally,the differences of flowrate distribution at the core outlet and temperature distribution and transverse velocity inside the hot legs with different upper plenum internals were compared.The results suggest that TYPE 1 upper plenum internals cause the largest flowrate difference at the core outlet while TYPE 3 leads to the most even distributed flowrate.The distribution and evolution pattern of the tangential velocity inside hot legs is highly dependent on the upper plenum internals.Two counter-rotating swirls exist inside the TYPE 1 hot leg and only one swirl revolving around the hog leg axis exist inside the TYPE 2 hot leg.For TYPE 3,two swirls like that of TYPE 1 rotating around the hot leg axis significantly increase the temperature homogenization speed.This research provides meaningful guidelines for the future optimization and design of advanced PWR upper plenum internal structures.
