This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooli...This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooling systems.Through a combination of numerical simulation and experimental validation,the technical advantages and mechanisms of immersion cooling are systematically explored.Simulation results indicate that under a 3C fast-charging condition(inlet temperature 20℃,flow rate 36 L/min),the immersion cooling structure 3demonstrates a triple enhancement in thermal performance compared to the cold plate structure 1:a 13.06%reduction in peak temperature,a 31.67%decrease in overall maximum temperature difference,and a 47.62%decrease in single-cell temperature deviation,while also reducing flow resistance by 33.61%.Furthermore,based on the immersion cooling model,a small battery module comprising seven cylindrical cells was designed for thermal runaway testing via nail penetration.The results show that the peak temperature of the triggered cell was limited to 437.6℃,with a controllable temperature rise gradient of only 3.35℃/s and a rapid cooling rate of 0.6℃/s.The maximum temperature rise of adjacent cells was just 64.8℃,effectively inhibiting thermal propagation.Post-test disassembly revealed that the non-triggered cells retained>99.2%of their original voltage and>99%structural integrity,confirming the module’s ability to achieve“localized failure with global stability.”展开更多
The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for e...The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for efficient extraction.This study systematically investigates the impact of liquid nitrogen immersion(LNI)on the coal’s pore structure and its mechanism of enhancing permeability with a combination of quantitative nuclear magnetic resonance(NMR)analysis,nitrogen adsorption experiments,and fractal dimension calculations.The results demonstrate that LNI can damage the coal’s pore structure and promote fracture expansion through thermal stress induction and moisture phase transformation,thereby enhancing the permeability of coal seams.The T_(2)peak area in the NMR experiments on coal samples subjected to LNI treatment shows a significant increase,the Brunauer-Emmett-Teller(BET)specific surface area decreases to 6.02 m^(2)/g,and the Barrett-Joyner-Halenda(BJH)total pore volume increases to 14.99 mm^(3)/g.Furthermore,changes in fractal dimensions(D_(1)rising from 2.804 to 2.837,and D_(2)falling from 2.757 to 2.594)indicate a notable enhancement in the complexity of the pore structure.With increasing LNI cycles,the adsorption capacity of the coal samples diminishes,suggesting a significant optimization of the pore structure.This optimization is particularly evident in the reconstruction of the micropore structure,which in turn greatly enhances the complexity and connectivity of the sample’s pore network.In summary,the study concludes that LNI technology can effectively improve the permeability of coal seams and the extraction efficiency of coalbed methane by optimizing the micropore structure and enhancing pore connectivity,which offers a potential method for enhancing the permeability of gas-bearing coal seams and facilitating the development and utilization of coalbed methane.展开更多
Nanocomposite multilayer TiBN coatings were prepared on Si(100) and 9Cr18Mo substrates using TiBN composite cathode plasma immersion ion implantation and deposition technique(PIIID). Synthesis of TiBN composite cathod...Nanocomposite multilayer TiBN coatings were prepared on Si(100) and 9Cr18Mo substrates using TiBN composite cathode plasma immersion ion implantation and deposition technique(PIIID). Synthesis of TiBN composite cathodes was conducted by powder metallurgy technology and the content of hexagonal boron nitride(h-BN) was changed from 8% to 40%(mass fraction). The as-deposited coatings were characterized by energy dispersive spectrometer(EDS), grazing incidence X-ray diffraction(GIXRD), Fourier Transform Infrared Spectroscopy(FTIR) and high resolution transmission electron microcopy(HRTEM). EDS results show that the B content of the coatings was varied from 3.71% to 13.84%(molar fraction) when the composition of the h-BN in the composited cathodes was changed from 8 % to 40%(mass fraction). GIXRD results reveal that the TiBN coatings with a B content of 8% has the main diffraction peak of TiN(200),(220) and(311), and these peaks disappear when the B content is increased. FTIR analysis of the multilayer coatings showed the presence of h-BN in all coatings. TEM images reveal that all coatings have the characteristics of self-forming nanocomposite multilayers, where the nanocomposites are composed of face-centered cubic Ti N or h-BN nanocrystalline embedded in amorphous matrix. The tribological tests reveal that the Ti BN coatings exhibit a marked decrease of coefficient at room temperature(~0.25). The improved properties were found to be derived from the comprehensiveness of the self-forming multilayers structure and the h-BN solid lubrication effects in the coatings.展开更多
Approaches to efficiency in manufacturing and assem bl y over the past 100 years have concentrated frequently on the twin themes of div iding jobs done by people into defined segments and to automating as many of tho ...Approaches to efficiency in manufacturing and assem bl y over the past 100 years have concentrated frequently on the twin themes of div iding jobs done by people into defined segments and to automating as many of tho se segments as possible. This approach to manufacturing engineering may be char acterised as one of deconstruction and replacement so far as the role of the hum an being is concerned. More recently design engineering has been approached in a similar light with research into ’intelligent’ methods involving, for example, expert systems or genetic algorithms to handle an increasing proportion of desi gn tasks. Expert systems are predicated on the idea that it is possible to capture and systemise significant amounts of professional knowledge: a task that has proved with experience to be much more difficult than when such systems wer e first proposed. Genetic algorithms, notwithstanding considerable research eff ort, have yet to make significant inroads into the practise of design and manufa cture. This paper will draw on new and previous experimental work carried out with supp ort from industry to propose an alternative approach that is enabled by the prod ucts of modern information technology. In this paradigm it is recognised that t he involvement of the human design expert is, for the time being at least, inevi table. Rather than seeking to reduce or even eliminate the " expert" with his or her tacit knowledge, the aim is to provide the expert with interactive to ols including immersive virtual reality so that implicit, human expertise can be applied effectively in the design cycle. The proposed approach is considered in the context of a particularly costly and difficult task, namely the design and planning for manufacture and assembly of c able harnesses for use in electro-mechanical artefacts. The efficient and reli able manufacture of cabling systems for many such products in the aerospace, aut omotive and IT sectors provides diverse challenges to designers, manufacturers a nd cable installers. Cable harness layouts are often so complex that design tend s to be carried out as an end activity, which may lead to higher costs, or even a product redesign. Current practice usually requires scaled or full-sized phys ical prototypes onto which the cable layout is constructed as the last productio n process. This is the case even when advanced CAD systems are used for this an d other parts of the design. Problems encountered at the cable harness design st age have a marked impact on the time needed for new product introductions. A prototype immersive system for cable harness design, developed by the research team has been used tested in experiments carried out in collaboration with indu stry. This work has shown that the task completion times obtained by the partici pants were between two and five times faster in than current CAD systems; even t hough the experiments were heavily biased towards CAD. The Virtual Reality inter face, with fewer mouse clicks and keyboard inputs, appears to have a significant impact on completion times. Cable harness design requires in-depth three-dimensional spatial reasoning whi ch CAD systems tend to lack due to their conventional flat screen display. Resul ts so far show evidence that the two or three degrees of freedom of movement on a flat screen provided by current CAD cable harness systems inhibits the user’s ability to route cable layouts especially in complex 3D assemblies. Immersive V R, on the other hand gives users the ability to change their viewpoint quickly a nd provides six degrees of freedom of movement thus showing great promise as a s uitable environment for routing cable. Initial results and feedback from the industrial partners are encouraging and su pport the theme of the research paradigm. Rather than seeking to reduce or even eliminate the ’expert’ with his or her tacit knowledge, the aim is to provide t he expert with interactive tools including immersive virtual reality so that implicit, human expertise can be applied most展开更多
The corrosion properties of aluminum-lithium(Al-Li) alloys, which are potential materials used to construct for tanks of liquid rockets or missiles, are essential for safe propellant storage and transport. In order to...The corrosion properties of aluminum-lithium(Al-Li) alloys, which are potential materials used to construct for tanks of liquid rockets or missiles, are essential for safe propellant storage and transport. In order to manifest the corrosion resistance of the 2195 Al-Li alloy in practical propellant tanks filled with N2O4, the alloy was soaked in 30% nitric acid solution, an accelerating corrosion environment, to test its corrosion behavior. Scanning electron microscopy(SEM) and transmission electron microscopy(TEM)were used to characterize microstructure and corrosion morphology of the alloy. Focused ion beam(FIB),combined with SEM, was used to demonstrate localized corrosion features and the propagation of corrosion pathways beneath the alloy surface. It was found that the corrosion network was formed with most intergranular corrosion and sparse intragranular corrosion. Additionally, the distribution and number of intermetallic particles influenced the localized corrosion degree and the direction of corrosion pathways. Aggregated particles made corrosion pathways continuously and caused more severe corrosion. The results from this work were valid and useful to corrosion prevention and protection for storage safety on propellant tanks in N_(2)O_(4).展开更多
As a new kind of air-hardening soil reinforcement material,polymer is being widely applied in river-bank slope reinforcement and ecological slope protection area.Thus,more attention should be paid to study the charact...As a new kind of air-hardening soil reinforcement material,polymer is being widely applied in river-bank slope reinforcement and ecological slope protection area.Thus,more attention should be paid to study the characteristics of reinforced soil after immersion.In this study,water-induced changes in strength characteristics of sand reinforced with polymer and fibers were reported.Several factors,including polymer content(1%,2%,3%and 4%by weight of dry sand),immersion time(6,12,24 and 48 h),dry density(1.40,1.45,1.50,1.55 and 1.60 g/cm^(3),)and fiber content(0.2%,0.4%,0.6%and 0.8%by weight of dry sand)which may influence the strength characteristics of reinforced sand after immersion were analyzed.The microstructure of reinforced sand was analyzed with nuclear magnetic resonance(NMR)and scanning electron microscope(SEM).Experimental results indicate that the compressive strength increases with the increase of polymer content and decreases with the increase of immersion time;the softening coefficients decrease with the increase of the polymer content and immersion time and increase with an increment in density and fiber content.Fiber plays an active role in reducing water-induced loss of strength at 0.6%content.展开更多
A small spring fed stream precipitates calcite by outgassing of CO<sub>2</sub> due to chemically controlled inorganic processes. The chemical composition of the water was measured along 9 stations downstre...A small spring fed stream precipitates calcite by outgassing of CO<sub>2</sub> due to chemically controlled inorganic processes. The chemical composition of the water was measured along 9 stations downstream with respect to Ca<sup>2+</sup>, Mg<sup>2+</sup>, Na<sup>+</sup>,K<sup>+</sup>, Cl<sup>-</sup>, carbonate alkalinlty, and SO<sub>4</sub><sup>2-</sup>. Temperature and pH were measured in situ. Small rectangular shaped tablets of limestone from the area were immersed into the stream for short periods and water analyses were carried out at the same time. From weight increase of the tablets, precipitation rates展开更多
Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale m...Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale model test of sand-flow method. The real-time data of sand-deposit height and radius were obtained by the self-developed sand-deposit detectors. The test results show that the detecting method is simple and has high precision. In the use of sand-flow method, the sand-carrying capability of fluid is limited, and sand particles are all transported to the sand-deposit periphery through crater, gap and chutes after the sand deposit formed. The diffusion range of the particles outside the sand-deposit does not exceed 2.0 m. Severe sorting of sand particles is not observed because of the unique oblique-layered depositing process. The temporal and spatial distributions of gap and chutes directly affect the sand-deposit expansion, and the expansion trend of the average sand-deposit radius accords with quadratic time-history curve.展开更多
Bone marrow derived mesenchymal stem cells(MSCs)have been widely used to promote the repair or regeneration of damaged tissues.In previous studies,we have developed several stem cells based strategies to promote the b...Bone marrow derived mesenchymal stem cells(MSCs)have been widely used to promote the repair or regeneration of damaged tissues.In previous studies,we have developed several stem cells based strategies to promote the bone repair,which includes the BMP-2 gene medicine,construction of tissue engineering bone in bioreactor and clinical trial of enriched stem cell therapy.Among these studies,one challenge is to construct the tissue engineered bone at the large scale which face the problem of poor survivor of seeding cells in the scaffold interior.In our studies,the porousβ-TCP cylindrical scaffolds loading with MSCs were continuously perfused by a customized bioreactor(dynamic culture)at different flow rate or were immersed展开更多
Immersive virtual product development is a new desi gn , developing and evaluation method of integrated product and processing tragedie s, which using VR, multi-discipline simulation and scientific visualization tec h...Immersive virtual product development is a new desi gn , developing and evaluation method of integrated product and processing tragedie s, which using VR, multi-discipline simulation and scientific visualization tec hnologies. Users may have the experiences of being part of a cyberspace environm ent with the ability to navigate and manipulate objects which have properties an d behaviors that correspond to those of the real world objects. We present a fra mework and prototype system of an immerse VPD (IVPD) which enables users to navi gate and interact with 3D peripherals with the display system. The framework of IVPD which we have defined can meet these requirements. In the immersive virtual environment, design will include four main parts: 3D CAD/modeler, multidiscipli ne simulations, CAM and discrete system simulation. 3D CAD/modeler can create 3D geometric objects and import models from other commercial softwares such as UG, CATIA etc. It can also store all kinds of models into databases with hierarchy which will provide geometric models with simulations and evaluations in later pr ocedures. Multidiscipline simulations can integrate many simulations such as FEA , CFD, Noisy and etc. Each kind of these simulation softwares will reflect a cer tain aspect of product or component’s performances. CAM, as a successor of prod uct development, mainly simulates the manufacturing procedures in the computer. Discrete system simulation will able to see the layout problems for a factory. I t is very useful for production management. Participants may actively view the v irtual world revolving around them while others control navigation and simul ations, and may interact with other members such as pass an object from one embo died manikin to another.展开更多
An iterative direct-forcing immersed boundary method is extended and used to solve convection heat transfer problems.The pressure,momentum source,and heat source at immersed boundary points are calculated simultaneous...An iterative direct-forcing immersed boundary method is extended and used to solve convection heat transfer problems.The pressure,momentum source,and heat source at immersed boundary points are calculated simultaneously to achieve the best coupling.Solutions of convection heat transfer problems with both Dirichlet and Neumann boundary conditions are presented.Two approaches for the implementation of Neumann boundary condition,i.e.direct and indirect methods,are introduced and compared in terms of accuracy and computational efficiency.Validation test cases include forced convection on a heated cylinder in an unbounded flow field and mixed convection around a circular body in a lid-driven cavity.Furthermore,the proposed method is applied to study the mixed convection around a heated rotating cylinder in a square enclosure with both iso-heat flux and iso-thermal boundary conditions.Computational results show that the order of accuracy of the indirect method is less than the direct method.However,the indirect method takes less computational time both in terms of the implementation of the boundary condition and the post processing time required to compute the heat transfer variables such as the Nusselt number.It is concluded that the iterative direct-forcing immersed boundary method is a powerful technique for the solution of convection heat transfer problems with stationary/moving boundaries and various boundary conditions.展开更多
文摘This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooling systems.Through a combination of numerical simulation and experimental validation,the technical advantages and mechanisms of immersion cooling are systematically explored.Simulation results indicate that under a 3C fast-charging condition(inlet temperature 20℃,flow rate 36 L/min),the immersion cooling structure 3demonstrates a triple enhancement in thermal performance compared to the cold plate structure 1:a 13.06%reduction in peak temperature,a 31.67%decrease in overall maximum temperature difference,and a 47.62%decrease in single-cell temperature deviation,while also reducing flow resistance by 33.61%.Furthermore,based on the immersion cooling model,a small battery module comprising seven cylindrical cells was designed for thermal runaway testing via nail penetration.The results show that the peak temperature of the triggered cell was limited to 437.6℃,with a controllable temperature rise gradient of only 3.35℃/s and a rapid cooling rate of 0.6℃/s.The maximum temperature rise of adjacent cells was just 64.8℃,effectively inhibiting thermal propagation.Post-test disassembly revealed that the non-triggered cells retained>99.2%of their original voltage and>99%structural integrity,confirming the module’s ability to achieve“localized failure with global stability.”
基金Projects(52204226,52104204,52474276)supported by the National Natural Science Foundation of ChinaProject(tsqnz20221140)supported by the Taishan Scholars Project of China+1 种基金Projects(ZR2022QE243,ZR2024ME097)supported by the Natural Science Foundation of Shandong Province of ChinaProject(252300421010)supported by the Excellent Youth Foundation of Henan Scientific Committee,China。
文摘The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for efficient extraction.This study systematically investigates the impact of liquid nitrogen immersion(LNI)on the coal’s pore structure and its mechanism of enhancing permeability with a combination of quantitative nuclear magnetic resonance(NMR)analysis,nitrogen adsorption experiments,and fractal dimension calculations.The results demonstrate that LNI can damage the coal’s pore structure and promote fracture expansion through thermal stress induction and moisture phase transformation,thereby enhancing the permeability of coal seams.The T_(2)peak area in the NMR experiments on coal samples subjected to LNI treatment shows a significant increase,the Brunauer-Emmett-Teller(BET)specific surface area decreases to 6.02 m^(2)/g,and the Barrett-Joyner-Halenda(BJH)total pore volume increases to 14.99 mm^(3)/g.Furthermore,changes in fractal dimensions(D_(1)rising from 2.804 to 2.837,and D_(2)falling from 2.757 to 2.594)indicate a notable enhancement in the complexity of the pore structure.With increasing LNI cycles,the adsorption capacity of the coal samples diminishes,suggesting a significant optimization of the pore structure.This optimization is particularly evident in the reconstruction of the micropore structure,which in turn greatly enhances the complexity and connectivity of the sample’s pore network.In summary,the study concludes that LNI technology can effectively improve the permeability of coal seams and the extraction efficiency of coalbed methane by optimizing the micropore structure and enhancing pore connectivity,which offers a potential method for enhancing the permeability of gas-bearing coal seams and facilitating the development and utilization of coalbed methane.
基金Projects(21573054,21327002,51401201)supported by the National Natural Science Foundation of ChinaProject(U1537214)supported by the Joint Funds Key Project of the National Natural Science Foundation of ChinaProject(51535003)supported by the State Key Program of National Natural Science of China
文摘Nanocomposite multilayer TiBN coatings were prepared on Si(100) and 9Cr18Mo substrates using TiBN composite cathode plasma immersion ion implantation and deposition technique(PIIID). Synthesis of TiBN composite cathodes was conducted by powder metallurgy technology and the content of hexagonal boron nitride(h-BN) was changed from 8% to 40%(mass fraction). The as-deposited coatings were characterized by energy dispersive spectrometer(EDS), grazing incidence X-ray diffraction(GIXRD), Fourier Transform Infrared Spectroscopy(FTIR) and high resolution transmission electron microcopy(HRTEM). EDS results show that the B content of the coatings was varied from 3.71% to 13.84%(molar fraction) when the composition of the h-BN in the composited cathodes was changed from 8 % to 40%(mass fraction). GIXRD results reveal that the TiBN coatings with a B content of 8% has the main diffraction peak of TiN(200),(220) and(311), and these peaks disappear when the B content is increased. FTIR analysis of the multilayer coatings showed the presence of h-BN in all coatings. TEM images reveal that all coatings have the characteristics of self-forming nanocomposite multilayers, where the nanocomposites are composed of face-centered cubic Ti N or h-BN nanocrystalline embedded in amorphous matrix. The tribological tests reveal that the Ti BN coatings exhibit a marked decrease of coefficient at room temperature(~0.25). The improved properties were found to be derived from the comprehensiveness of the self-forming multilayers structure and the h-BN solid lubrication effects in the coatings.
文摘Approaches to efficiency in manufacturing and assem bl y over the past 100 years have concentrated frequently on the twin themes of div iding jobs done by people into defined segments and to automating as many of tho se segments as possible. This approach to manufacturing engineering may be char acterised as one of deconstruction and replacement so far as the role of the hum an being is concerned. More recently design engineering has been approached in a similar light with research into ’intelligent’ methods involving, for example, expert systems or genetic algorithms to handle an increasing proportion of desi gn tasks. Expert systems are predicated on the idea that it is possible to capture and systemise significant amounts of professional knowledge: a task that has proved with experience to be much more difficult than when such systems wer e first proposed. Genetic algorithms, notwithstanding considerable research eff ort, have yet to make significant inroads into the practise of design and manufa cture. This paper will draw on new and previous experimental work carried out with supp ort from industry to propose an alternative approach that is enabled by the prod ucts of modern information technology. In this paradigm it is recognised that t he involvement of the human design expert is, for the time being at least, inevi table. Rather than seeking to reduce or even eliminate the " expert" with his or her tacit knowledge, the aim is to provide the expert with interactive to ols including immersive virtual reality so that implicit, human expertise can be applied effectively in the design cycle. The proposed approach is considered in the context of a particularly costly and difficult task, namely the design and planning for manufacture and assembly of c able harnesses for use in electro-mechanical artefacts. The efficient and reli able manufacture of cabling systems for many such products in the aerospace, aut omotive and IT sectors provides diverse challenges to designers, manufacturers a nd cable installers. Cable harness layouts are often so complex that design tend s to be carried out as an end activity, which may lead to higher costs, or even a product redesign. Current practice usually requires scaled or full-sized phys ical prototypes onto which the cable layout is constructed as the last productio n process. This is the case even when advanced CAD systems are used for this an d other parts of the design. Problems encountered at the cable harness design st age have a marked impact on the time needed for new product introductions. A prototype immersive system for cable harness design, developed by the research team has been used tested in experiments carried out in collaboration with indu stry. This work has shown that the task completion times obtained by the partici pants were between two and five times faster in than current CAD systems; even t hough the experiments were heavily biased towards CAD. The Virtual Reality inter face, with fewer mouse clicks and keyboard inputs, appears to have a significant impact on completion times. Cable harness design requires in-depth three-dimensional spatial reasoning whi ch CAD systems tend to lack due to their conventional flat screen display. Resul ts so far show evidence that the two or three degrees of freedom of movement on a flat screen provided by current CAD cable harness systems inhibits the user’s ability to route cable layouts especially in complex 3D assemblies. Immersive V R, on the other hand gives users the ability to change their viewpoint quickly a nd provides six degrees of freedom of movement thus showing great promise as a s uitable environment for routing cable. Initial results and feedback from the industrial partners are encouraging and su pport the theme of the research paradigm. Rather than seeking to reduce or even eliminate the ’expert’ with his or her tacit knowledge, the aim is to provide t he expert with interactive tools including immersive virtual reality so that implicit, human expertise can be applied most
基金National Natural Science Foundation of China (Grant No.52075541)Shaanxi Province Natural Science Foundation (Grant No. 2022JM-243) to provide fund for conducting experiments。
文摘The corrosion properties of aluminum-lithium(Al-Li) alloys, which are potential materials used to construct for tanks of liquid rockets or missiles, are essential for safe propellant storage and transport. In order to manifest the corrosion resistance of the 2195 Al-Li alloy in practical propellant tanks filled with N2O4, the alloy was soaked in 30% nitric acid solution, an accelerating corrosion environment, to test its corrosion behavior. Scanning electron microscopy(SEM) and transmission electron microscopy(TEM)were used to characterize microstructure and corrosion morphology of the alloy. Focused ion beam(FIB),combined with SEM, was used to demonstrate localized corrosion features and the propagation of corrosion pathways beneath the alloy surface. It was found that the corrosion network was formed with most intergranular corrosion and sparse intragranular corrosion. Additionally, the distribution and number of intermetallic particles influenced the localized corrosion degree and the direction of corrosion pathways. Aggregated particles made corrosion pathways continuously and caused more severe corrosion. The results from this work were valid and useful to corrosion prevention and protection for storage safety on propellant tanks in N_(2)O_(4).
基金Project(41472241)supported by the National Natural Science Foundation of ChinaProject(KJXM2019028)supported by the Natural Resources Science and Technology Project of Jiangsu Province,ChinaProject(2019B17314)supported by the Fundamental Research Funds for the Central Universities,China。
文摘As a new kind of air-hardening soil reinforcement material,polymer is being widely applied in river-bank slope reinforcement and ecological slope protection area.Thus,more attention should be paid to study the characteristics of reinforced soil after immersion.In this study,water-induced changes in strength characteristics of sand reinforced with polymer and fibers were reported.Several factors,including polymer content(1%,2%,3%and 4%by weight of dry sand),immersion time(6,12,24 and 48 h),dry density(1.40,1.45,1.50,1.55 and 1.60 g/cm^(3),)and fiber content(0.2%,0.4%,0.6%and 0.8%by weight of dry sand)which may influence the strength characteristics of reinforced sand after immersion were analyzed.The microstructure of reinforced sand was analyzed with nuclear magnetic resonance(NMR)and scanning electron microscope(SEM).Experimental results indicate that the compressive strength increases with the increase of polymer content and decreases with the increase of immersion time;the softening coefficients decrease with the increase of the polymer content and immersion time and increase with an increment in density and fiber content.Fiber plays an active role in reducing water-induced loss of strength at 0.6%content.
文摘A small spring fed stream precipitates calcite by outgassing of CO<sub>2</sub> due to chemically controlled inorganic processes. The chemical composition of the water was measured along 9 stations downstream with respect to Ca<sup>2+</sup>, Mg<sup>2+</sup>, Na<sup>+</sup>,K<sup>+</sup>, Cl<sup>-</sup>, carbonate alkalinlty, and SO<sub>4</sub><sup>2-</sup>. Temperature and pH were measured in situ. Small rectangular shaped tablets of limestone from the area were immersed into the stream for short periods and water analyses were carried out at the same time. From weight increase of the tablets, precipitation rates
基金Project(51108190) supported by the National Natural Science Foundation of ChinaProject(2012ZC27) supported by the Independence Research Subject from State Key Laboratory of Subtropical Building Science,ChinaProject(GTCC 2008-253) supported by the Research Subject from Guangzhou City,China
文摘Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale model test of sand-flow method. The real-time data of sand-deposit height and radius were obtained by the self-developed sand-deposit detectors. The test results show that the detecting method is simple and has high precision. In the use of sand-flow method, the sand-carrying capability of fluid is limited, and sand particles are all transported to the sand-deposit periphery through crater, gap and chutes after the sand deposit formed. The diffusion range of the particles outside the sand-deposit does not exceed 2.0 m. Severe sorting of sand particles is not observed because of the unique oblique-layered depositing process. The temporal and spatial distributions of gap and chutes directly affect the sand-deposit expansion, and the expansion trend of the average sand-deposit radius accords with quadratic time-history curve.
基金supported by grants from the National Natural Science Foundation of China (10872131,81172549,31271015)a grant from the Shanghai Science and Technology Development Fund (11XD1403300)the key disciplines program of the Shanghai Municipal Education Commission(J50206)
文摘Bone marrow derived mesenchymal stem cells(MSCs)have been widely used to promote the repair or regeneration of damaged tissues.In previous studies,we have developed several stem cells based strategies to promote the bone repair,which includes the BMP-2 gene medicine,construction of tissue engineering bone in bioreactor and clinical trial of enriched stem cell therapy.Among these studies,one challenge is to construct the tissue engineered bone at the large scale which face the problem of poor survivor of seeding cells in the scaffold interior.In our studies,the porousβ-TCP cylindrical scaffolds loading with MSCs were continuously perfused by a customized bioreactor(dynamic culture)at different flow rate or were immersed
文摘Immersive virtual product development is a new desi gn , developing and evaluation method of integrated product and processing tragedie s, which using VR, multi-discipline simulation and scientific visualization tec hnologies. Users may have the experiences of being part of a cyberspace environm ent with the ability to navigate and manipulate objects which have properties an d behaviors that correspond to those of the real world objects. We present a fra mework and prototype system of an immerse VPD (IVPD) which enables users to navi gate and interact with 3D peripherals with the display system. The framework of IVPD which we have defined can meet these requirements. In the immersive virtual environment, design will include four main parts: 3D CAD/modeler, multidiscipli ne simulations, CAM and discrete system simulation. 3D CAD/modeler can create 3D geometric objects and import models from other commercial softwares such as UG, CATIA etc. It can also store all kinds of models into databases with hierarchy which will provide geometric models with simulations and evaluations in later pr ocedures. Multidiscipline simulations can integrate many simulations such as FEA , CFD, Noisy and etc. Each kind of these simulation softwares will reflect a cer tain aspect of product or component’s performances. CAM, as a successor of prod uct development, mainly simulates the manufacturing procedures in the computer. Discrete system simulation will able to see the layout problems for a factory. I t is very useful for production management. Participants may actively view the v irtual world revolving around them while others control navigation and simul ations, and may interact with other members such as pass an object from one embo died manikin to another.
文摘An iterative direct-forcing immersed boundary method is extended and used to solve convection heat transfer problems.The pressure,momentum source,and heat source at immersed boundary points are calculated simultaneously to achieve the best coupling.Solutions of convection heat transfer problems with both Dirichlet and Neumann boundary conditions are presented.Two approaches for the implementation of Neumann boundary condition,i.e.direct and indirect methods,are introduced and compared in terms of accuracy and computational efficiency.Validation test cases include forced convection on a heated cylinder in an unbounded flow field and mixed convection around a circular body in a lid-driven cavity.Furthermore,the proposed method is applied to study the mixed convection around a heated rotating cylinder in a square enclosure with both iso-heat flux and iso-thermal boundary conditions.Computational results show that the order of accuracy of the indirect method is less than the direct method.However,the indirect method takes less computational time both in terms of the implementation of the boundary condition and the post processing time required to compute the heat transfer variables such as the Nusselt number.It is concluded that the iterative direct-forcing immersed boundary method is a powerful technique for the solution of convection heat transfer problems with stationary/moving boundaries and various boundary conditions.
