冻土的水热耦合问题一直是冻胀融沉的主要原因之一,涉及到土壤中水分的迁移、热量的传递以及相变过程。在多年冻土和季节冻土区,由于环境因素的影响,冻土路基容易发生不均匀沉降、冻胀融沉等灾害,这些灾害都与水分迁移、相变以及温度变...冻土的水热耦合问题一直是冻胀融沉的主要原因之一,涉及到土壤中水分的迁移、热量的传递以及相变过程。在多年冻土和季节冻土区,由于环境因素的影响,冻土路基容易发生不均匀沉降、冻胀融沉等灾害,这些灾害都与水分迁移、相变以及温度变化息息相关。为了解决冻土水热耦合问题,本文通过COMSOL Multiphysic软件建立水热耦合的二维模型,研究不同水头压力作用下同一时间段温度和压力的影响、对流出边界总热通量的影响、对总液态水体积的影响,以及对最低温度的影响进行分析,模拟了3种不同水头压力的工况。结果表明:同一时间段的温度和压力随着水头压力的增加而变化;流出边界离开系统的总热通量也随着水头压力的增大而增大;不同工况下水头梯度越大,冰块融化速度越快,达到总液态水体积最大值的时间越短。The hydrothermal coupling problem of frozen soil has always been one of the main reasons for frost heave and thaw settlement, involving the migration of water in the soil, heat transfer, and phase change process. In permafrost and seasonal permafrost areas, due to environmental factors, permafrost roadbeds are prone to disasters such as uneven settlement, frost heave and thaw settlement, which are closely related to water migration, phase change, and temperature changes. In order to solve the problem of hydrothermal coupling in permafrost, this paper establishes a two-dimensional model of hydrothermal coupling using COMSOL Multiphysic software. The influence of temperature and pressure at the same time period under different head pressures, the influence on the total heat flux at the outflow boundary, the influence on the total liquid water volume, and the influence on the minimum temperature are studied. Three different head pressure working conditions are simulated. The results show that the temperature and pressure during the same time period change with the increase of head pressure;The total heat flux leaving the system at the outflow boundary also increases with the increase of head pressure;The larger the head gradient under different working conditions, the faster the melting rate of ice, and the shorter the time to reach the maximum total liquid water volume.展开更多
Thermal-electric bilayer invisibility cloak can prevent the heat flux and electric current from touching the object without distorting the external temperature and electric potential fields simultaneously.In this pape...Thermal-electric bilayer invisibility cloak can prevent the heat flux and electric current from touching the object without distorting the external temperature and electric potential fields simultaneously.In this paper,we design an omnidirectional thermal-electric invisibility cloak with anisotropic geometry.Based on the theory of neutral inclusion,the anisotropic effective thermal and electric conductivities of confocal elliptical bilayer core-shell structure are derived,thus obtaining the anisotropic matrix material to eliminate the external disturbances omnidirectionally.The inner shell of the cloak is selected as an insulating material to shield the heat flux and electric current.Then,the omnidirectional thermal-electric cloaking effect is verified numerically and experimentally based on the theoretical anisotropic matrix and manufactured composite structure,respectively.Furthermore,we achieve the thermal-electric cloaking effect under a specific direction of heat flux and electric current using the isotropic natural materials to broaden the selection range of materials.The method proposed to eliminate anisotropy and achieve the omnidirectional effect could also be expanded to other different physical fields for the metadevices with different functions.展开更多
Silicon monoxide(SiO)(silicon[Si]mixed with silicon dioxide[SiO_(2)])/graphite(Gr)composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion...Silicon monoxide(SiO)(silicon[Si]mixed with silicon dioxide[SiO_(2)])/graphite(Gr)composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion batteries.The major bottleneck for SiO/Gr composite anode is the poor cyclability arising from the stress/strain behaviors due to the mismatch between two heterogenous materials during the lithiation/delithiation process.To date,a meticulous and quantitative understanding of the highly nonlinear coupling behaviors of such materials is still lacking.Herein,an electro–chemo–mechanics-coupled detailed model containing particle geometries is established.The underlying mechanism of the regulation between SiO and Gr components during electrochemical cycling is quantitatively revealed.We discover that increasing the SiO weight percentage(wt%)reduces the utilization efficiency of the active materials at the same 1C rate charging and enhances the hindering effects of stress-driven flux on diffusion.In addition,the mechanical constraint demonstrates a balanced effect on the overall performance of cells and the local behaviors of particles.This study provides new insights into the fundamental interactions between SiO and Gr materials and advances the investigation methodology for the design and evaluation of next-generation high-energydensity batteries.展开更多
文摘冻土的水热耦合问题一直是冻胀融沉的主要原因之一,涉及到土壤中水分的迁移、热量的传递以及相变过程。在多年冻土和季节冻土区,由于环境因素的影响,冻土路基容易发生不均匀沉降、冻胀融沉等灾害,这些灾害都与水分迁移、相变以及温度变化息息相关。为了解决冻土水热耦合问题,本文通过COMSOL Multiphysic软件建立水热耦合的二维模型,研究不同水头压力作用下同一时间段温度和压力的影响、对流出边界总热通量的影响、对总液态水体积的影响,以及对最低温度的影响进行分析,模拟了3种不同水头压力的工况。结果表明:同一时间段的温度和压力随着水头压力的增加而变化;流出边界离开系统的总热通量也随着水头压力的增大而增大;不同工况下水头梯度越大,冰块融化速度越快,达到总液态水体积最大值的时间越短。The hydrothermal coupling problem of frozen soil has always been one of the main reasons for frost heave and thaw settlement, involving the migration of water in the soil, heat transfer, and phase change process. In permafrost and seasonal permafrost areas, due to environmental factors, permafrost roadbeds are prone to disasters such as uneven settlement, frost heave and thaw settlement, which are closely related to water migration, phase change, and temperature changes. In order to solve the problem of hydrothermal coupling in permafrost, this paper establishes a two-dimensional model of hydrothermal coupling using COMSOL Multiphysic software. The influence of temperature and pressure at the same time period under different head pressures, the influence on the total heat flux at the outflow boundary, the influence on the total liquid water volume, and the influence on the minimum temperature are studied. Three different head pressure working conditions are simulated. The results show that the temperature and pressure during the same time period change with the increase of head pressure;The total heat flux leaving the system at the outflow boundary also increases with the increase of head pressure;The larger the head gradient under different working conditions, the faster the melting rate of ice, and the shorter the time to reach the maximum total liquid water volume.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.11572090)the Fundamental Research Funds for the Central Universities(Grant No.3072022GIP0202).
文摘Thermal-electric bilayer invisibility cloak can prevent the heat flux and electric current from touching the object without distorting the external temperature and electric potential fields simultaneously.In this paper,we design an omnidirectional thermal-electric invisibility cloak with anisotropic geometry.Based on the theory of neutral inclusion,the anisotropic effective thermal and electric conductivities of confocal elliptical bilayer core-shell structure are derived,thus obtaining the anisotropic matrix material to eliminate the external disturbances omnidirectionally.The inner shell of the cloak is selected as an insulating material to shield the heat flux and electric current.Then,the omnidirectional thermal-electric cloaking effect is verified numerically and experimentally based on the theoretical anisotropic matrix and manufactured composite structure,respectively.Furthermore,we achieve the thermal-electric cloaking effect under a specific direction of heat flux and electric current using the isotropic natural materials to broaden the selection range of materials.The method proposed to eliminate anisotropy and achieve the omnidirectional effect could also be expanded to other different physical fields for the metadevices with different functions.
文摘Silicon monoxide(SiO)(silicon[Si]mixed with silicon dioxide[SiO_(2)])/graphite(Gr)composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion batteries.The major bottleneck for SiO/Gr composite anode is the poor cyclability arising from the stress/strain behaviors due to the mismatch between two heterogenous materials during the lithiation/delithiation process.To date,a meticulous and quantitative understanding of the highly nonlinear coupling behaviors of such materials is still lacking.Herein,an electro–chemo–mechanics-coupled detailed model containing particle geometries is established.The underlying mechanism of the regulation between SiO and Gr components during electrochemical cycling is quantitatively revealed.We discover that increasing the SiO weight percentage(wt%)reduces the utilization efficiency of the active materials at the same 1C rate charging and enhances the hindering effects of stress-driven flux on diffusion.In addition,the mechanical constraint demonstrates a balanced effect on the overall performance of cells and the local behaviors of particles.This study provides new insights into the fundamental interactions between SiO and Gr materials and advances the investigation methodology for the design and evaluation of next-generation high-energydensity batteries.
