Background:Cotton(Gossypium hirsutum L.)is often grown in locations characterized by high atmospheric evaporative demand.It has been hypothesized that plants which resist hydraulic flow under this condition will limit...Background:Cotton(Gossypium hirsutum L.)is often grown in locations characterized by high atmospheric evaporative demand.It has been hypothesized that plants which resist hydraulic flow under this condition will limit water use and conserve soil water.Therefore,in a series of controlled environment experiments ten cotton cultivars were exposed to two different temperature and vapor pressure deficit(VPD)conditions(i.e.,38℃,>3 kPa and 32℃,1∼1.5 kPa)as well as a progressive soil drying.Then,individual differences in shoot hydraulic conductance(K_(shoot))was measured using a hydraulic conductance flow meter(HCFM).Physiological parameters were reported included leaf area,dry leaf weight,stomatal conductance(g_(s)),and water use efficiency coefficient(WUE_(k)).Results:Differences were observed in K_(shoot) among cultivars under the 38℃,>3 kPa but not the 32℃,1∼1.5 kPa environment.Under the 38℃,>3 kPa environment,correlations were found between K_(shoot),stomatal conductance(gs),VPD breakpoint,WUEk,total leaf area,dry leaf weight,fraction transpirable soil water(FTSW)threshold,and slope of TR decline after FTSW threshold.Conclusion:Results show that the ability of some cotton cultivars to restrict water loss under high evaporative demand through early stomatal closure is associated with the cultivars’K_(shoot).The K_(shoot) is influential in the limitation of TR trait under high temperature and VPD.展开更多
The effects of surface roughness, strain rate, friction coefficient and pressure on real contact area were analyzed based on the research of Stupkiewicz. The real contact area model taking account of the effect of fri...The effects of surface roughness, strain rate, friction coefficient and pressure on real contact area were analyzed based on the research of Stupkiewicz. The real contact area model taking account of the effect of friction and deformation of material was obtained. The model of contact conductance at the rolling interface was obtained by integrating the specific feature of heat transfer through the interface of continuous roll-casting. The results indicate that the real contact area increases obviously when the material is under yield, and the real contact area varies inversely with surface roughness, whereas it varies exponentially with friction coefficient, strain rate and pressure, and the power factor depends on strain rate.展开更多
The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper （Capsicum annuum Linn.） and two C4 plants, sorghum （Sorghum bicolor L.Moench） and maize （Zea mays Linn.）. Three spec...The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper （Capsicum annuum Linn.） and two C4 plants, sorghum （Sorghum bicolor L.Moench） and maize （Zea mays Linn.）. Three species were irrigated with three different water treatment levels of 100%, 66% and 33% which gave a comparison of tolerance and adaptation to irrigation and two different levels of water stress. The measurements of transpiration rate and stomatal conductance were done between 8.00 a.m. and 16.00 p.m. with measurements about each 1.5 h with an infrared gas analyzer. The results showed that Z. mays probably due to a higher leaf area had very low values and was significantly different （LSD pairwise comparison） from C. annuum and S. bicolor. The hypotheses that C4 plants and C3 plants have different transpiration rates and stomatal conductance could not be shown with the results. However, the hypotheses that for the same species, the highest values in transpiration rate and stomatal conductance were with the 100% irrigation treatment and the lowest values were with the 33% irrigation treatment could be accepted due to the results of this trial.展开更多
In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to...In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.展开更多
To develop proton-conducting materials with high hydrothermal and acid-base stability and to elucidate the proton-transport mechanism through visualized structural analysis,two new lanthanum phosphite-oxalates with 3D...To develop proton-conducting materials with high hydrothermal and acid-base stability and to elucidate the proton-transport mechanism through visualized structural analysis,two new lanthanum phosphite-oxalates with 3D frameworks,designated as[La(HPO_(3))(C_(2)O_(4))0.5(H_(2)O)_(2)](La‑1)and(C_(6)H_(16)N_(2))(H_(3)O)[La_(2)(H_(2)PO_(3))_(3)(C_(2)O_(4))_(3)(H_(2)O)](La‑2)(C_(6)H_(14)N_(2)=cis-2,6-dimethylpiperazine),were prepared by hydrothermal and solvothermal conduction,respectively.La‑1 was constructed with lanthanum phosphite 2D layers and C_(2)O_(4)^(2-)groups,whereas La‑2 was constructed with lanthanum oxalate 2D layers and H_(2)PO^(3-)groups.Alternating current(AC)impedance spectra indicate that the pro-ton conductivities of both compounds could reach 10^(-4)S·cm^(-1)and remain highly durable at 75℃and 98%of rela-tive humidity(RH).Due to the abundance of H-bonds in La‑2,theσof La‑2 was higher than that of La‑1.La‑1 exhibited excellent water and pH stability.CCDC:2439965,La‑1;443776,La‑2.展开更多
Energy storage is a key factor in the drive for carbon neutrality and carbon nanotubes(CNTs)may have an important role in this.Their intrinsic sp2 covalent structure gives them excellent electrical conductivity,mechan...Energy storage is a key factor in the drive for carbon neutrality and carbon nanotubes(CNTs)may have an important role in this.Their intrinsic sp2 covalent structure gives them excellent electrical conductivity,mechanical strength,and chemical stability,making them suitable for many uses in energy storage,such as lithium-ion batteries(LIBs).Currently,their use in LIBs mainly focuses on conductive networks,current collectors,and dry electrodes.The review outlines advances in the use of CNTs in the cathodes and anodes of LIBs,especially in the electrode fabrication and mechanical sensors,as well as providing insights into their future development.展开更多
The rapid development of the information era has led to in-creased power consumption,which generates more heat.This requires more efficient thermal management systems,with the most direct ap-proach being the developme...The rapid development of the information era has led to in-creased power consumption,which generates more heat.This requires more efficient thermal management systems,with the most direct ap-proach being the development of su-perior thermal interface materials(TIMs).Mesocarbon microbeads(MCMBs)have several desirable properties for this purpose,includ-ing high thermal conductivity and excellent thermal stability.Although their thermal conductivity(K)may not be exceptional among all carbon materials,their ease of production and low cost make them ideal filler materials for developing a new generation of carbon-based TIMs.We report the fabrication of high-performance TIMs by incorporating MCMBs in a polyimide(PI)framework,producing highly graphitized PI/MCMB(PM)foams and anisotropic polydimethylsiloxane/PM(PDMS/PM)composites with a high thermal conductivity using directional freezing and high-temperature thermal annealing.The resulting materials had a high through-plane(TP)K of 15.926 W·m^(−1)·K^(−1),4.83 times that of conventional thermally conductive silicone pads and 88.5 times higher than that of pure PDMS.The composites had excellent mechanical properties and thermal stability,meeting the de-mands of modern electronic products for integration,multi-functionality,and miniaturization.展开更多
Realizing effective enhancement in the thermally conductive performance of polymer bonded explosives(PBXs) is vital for improving the resultant environmental adaptabilities of the PBXs composites. Herein, a kind of pr...Realizing effective enhancement in the thermally conductive performance of polymer bonded explosives(PBXs) is vital for improving the resultant environmental adaptabilities of the PBXs composites. Herein, a kind of primary-secondary thermally conductive network was designed by water-suspension granulation, surface coating, and hot-pressing procedures in the graphene-based PBXs composites to greatly increase the thermal conductive performance of the composites. The primary network with a threedimensional structure provided the heat-conducting skeleton, while the secondary network in the polymer matrix bridged the primary network to increase the network density. The enhancement efficiency in the thermally conductive performance of the composites reached the highest value of 59.70% at a primary-secondary network ratio of 3:1. Finite element analysis confirmed the synergistic enhancement effect of the primary and secondary thermally conductive networks. This study introduces an innovative approach to designing network structures for PBX composites, significantly enhancing their thermal conductivity.展开更多
This paper examined how microstructure influences the homogenized thermal conductivity of cellular structures and revealed a surface-induced size-dependent effect.This effect is linked to the porous microstructural fe...This paper examined how microstructure influences the homogenized thermal conductivity of cellular structures and revealed a surface-induced size-dependent effect.This effect is linked to the porous microstructural features of cellular structures,which stems from the degree of porosity and the distri-bution of the pores.Unlike the phonon-driven surface effect at the nanoscale,the macro-scale surface mechanism in thermal cellular structures is found to be the microstructure-induced changes in the heat conduction path based on fully resolved 3D numerical simulations.The surface region is determined by the microstructure,characterized by the intrinsic length.With the coupling between extrinsic and intrinsic length scales under the surface mechanism,a surface-enriched multiscale method was devel-oped to accurately capture the complex size-dependent thermal conductivity.The principle of scale separation required by classical multiscale methods is not necessary to be satisfied by the proposed multiscale method.The significant potential of the surface-enriched multiscale method was demon-strated through simulations of the effective thermal conductivity of a thin-walled metamaterial struc-ture.The surface-enriched multiscale method offers higher accuracy compared with the classical multiscale method and superior efficiency over high-fidelity finite element methods.展开更多
During the storage of composite propellants, the migration of plasticizers and other unbonded additives at the interfaces of liner adhesives has garnered significant attention in understanding liner failure mechanisms...During the storage of composite propellants, the migration of plasticizers and other unbonded additives at the interfaces of liner adhesives has garnered significant attention in understanding liner failure mechanisms, aging processes, and safety performance. However, there is currently no non-destructive and quantitative detection method for migration of plasticizers in propellant liner. In this study, we developed a HTPB sensing liner by incorporating conductive fillers-namely carbon black(CB), carbon nanotubes(CNTs), and graphene nanoplatelets(GNP)-into the HTPB matrix. The synergistic interaction between CNTs and GNP facilitates the formation of a tunneling conductive network that imparts electrical conductivity to the HTPB liner. To elucidate the functional relationship between conductivity and nitroglycerin(NG) migration, we applied the HTPB sensing liner onto double base propellant surfaces and measured both the conductivity of the sensing layer and NG migration during a 71°C accelerated aging experiment. The results shows that when CNTs/GNP content reaches 3wt%, there is an exponential correlation between conductivity and NG migration with a fitting degree of 0.9652;the average response sensitivity of ΔR/R0 relative to NG migration is calculated as 41.69, with an average deviation of merely5.67% between NG migrations derived from conductivity fittings compared to those obtained via TGA testing results. Overall, this sensing liner exhibits excellent capabilities for detecting NG migration nondestructively and quantitatively while offering a novel approach for assessing interfacial component migrations as well as debonding defects in propellants-a promising avenue for future self-monitoring strategies regarding propellant integrity.展开更多
This study prepared a class of RDX-based composite microspheres(RAF)containing ADN and FKM2602.The reaction kinetics of RAF composite microspheres were effectively improved by maintaining the system's high energy ...This study prepared a class of RDX-based composite microspheres(RAF)containing ADN and FKM2602.The reaction kinetics of RAF composite microspheres were effectively improved by maintaining the system's high energy and safety performance.In the close packing state,when the heating rate is rapid,the thermal stability of RAF composite microspheres is better than that of RDX;the close packing state will reduce the degree of freedom of RDX and ADN reaction but will increase the degree of freedom of RAF composite microsphere reaction.The thermal conductivity of RAF composite microspheres is close to that of RDX.In the ignition experiment,the flame of RAF composite microspheres can be maintained without the external heat source.Regarding safety,the H50of RAF composite microspheres was 274.04%higher than that of RDX.The detonation velocity of RAF composite microspheres is slightly higher than that of raw material RDX.Overall,these findings highlight the effectiveness of ADN in enhancing the reaction kinetics of RDX-based composites.展开更多
This study examines the intricate occurrences of thermal and solutal Marangoni convection in three-layered flows of viscous fluids,with a particular emphasis on their relevance to renewable energy systems.This researc...This study examines the intricate occurrences of thermal and solutal Marangoni convection in three-layered flows of viscous fluids,with a particular emphasis on their relevance to renewable energy systems.This research examines the flow of a three-layered viscous fluid,considering the combined influence of heat and solutal buoyancy driven Rayleigh-Bénard convection,as well as thermal and solutal Marangoni convection.The homotopy perturbation method is used to examine and simulate complex fluid flow and transport phenomena,providing important understanding of the fundamental physics and assisting in the optimization of various battery configurations.The inquiry examines the primary elements that influence Marangoni convection and its impact on battery performance,providing insights on possible enhancements in energy storage devices.The findings indicate that the velocity profiles shown graphically exhibit a prominent core zone characterized by the maximum speed,which progressively decreases as it approaches the walls of the channel.This study enhances our comprehension of fluid dynamics and the transmission of heat and mass in intricate systems,which has substantial ramifications for the advancement of sustainable energy solutions.展开更多
走航式海洋多参数剖面测量系统(moving vessel profiler,MVP)是一种集成程度和自动化程度都较高的海洋调查设备,能对海洋多要素进行同时观测,获得水平方向的高分辨率数据资料。由于温度和电导率传感器响应时间的不匹配,MVP下放速度过快...走航式海洋多参数剖面测量系统(moving vessel profiler,MVP)是一种集成程度和自动化程度都较高的海洋调查设备,能对海洋多要素进行同时观测,获得水平方向的高分辨率数据资料。由于温度和电导率传感器响应时间的不匹配,MVP下放速度过快(峰值速度4 m/s)而造成非常明显的盐度尖峰现象。本研究结合Fofonoff(F)法、时间常数指数递归数字滤波(Giles and McDougall,GM)法和Grose提出的盐度尖峰订正方案,提出了一种新的方法,即MCT(match conductivity and temperature response time)法,通过对压力、温度和电导率传感器进行响应时间的匹配来减弱盐度尖峰。将SBE-9型CTD资料作为标准,发现订正后的资料与CTD盐度曲线的互相关系数为0.917,误差比订正前减小80%。对比35°N断面修正前后的盐度资料,订正后温盐跃层处出现的低盐区域消失。MVP的应用比常规海洋调查仪器CTD对于海洋现象的观测更有优势。展开更多
Drought stress is one of the major constraints on turf growth and performance in northern China. Based on previous assessments of drought tolerance levels, four varieties of Kentucky bluegrass （Poa pratensis L.） rep...Drought stress is one of the major constraints on turf growth and performance in northern China. Based on previous assessments of drought tolerance levels, four varieties of Kentucky bluegrass （Poa pratensis L.） representing different types （＇Baron＇, BVMG type; ＇Blackstone＇, Cheri type; ＇Kenblue＇, Midwest type; and ＇Bluemoon＇, Midnight type） were chosen for this study. Grass materials were established in a glasshouse, and the changes in their photosynthetic and metabolic characteristics were analyzed during a period of imposed drought stress. Drought stress led to decrease in chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate in all four cultivars, but the relative changes in each characteristic varied among varieties. The results also showed that changes in the photosynthetic and metabolic characteristics of different varieties under drought stress were related to the morphological characteristics of the plants. Varieties with longer narrow leaves, longer roots, higher root-to-shoot ratios, and higher chlorophyll contents showed greater rates of photosynthesis and stomatal conductance, and lower transpiration rates.展开更多
Nanopipette based scanning probe technique is a versatile tool in non-contact imaging in biology.In addition to the topographic imaging,its capability of localized delivery of bio-active molecules is emerging.In this ...Nanopipette based scanning probe technique is a versatile tool in non-contact imaging in biology.In addition to the topographic imaging,its capability of localized delivery of bio-active molecules is emerging.In this mini review,we introduce the applications of nanopipette in single-cell researches with a focus on localized delivery.The working principles of three delivery modes including resistive pulse,pressure-driven flow,and electroosmotic flow-driven delivery are summarized and compared.Their applications in single-cell researches are reviewed.The current technical challenges in scanning ion conductance microscopy-based delivery,and their growing influence in medicine and pharmacologic researches are also discussed.展开更多
文摘Background:Cotton(Gossypium hirsutum L.)is often grown in locations characterized by high atmospheric evaporative demand.It has been hypothesized that plants which resist hydraulic flow under this condition will limit water use and conserve soil water.Therefore,in a series of controlled environment experiments ten cotton cultivars were exposed to two different temperature and vapor pressure deficit(VPD)conditions(i.e.,38℃,>3 kPa and 32℃,1∼1.5 kPa)as well as a progressive soil drying.Then,individual differences in shoot hydraulic conductance(K_(shoot))was measured using a hydraulic conductance flow meter(HCFM).Physiological parameters were reported included leaf area,dry leaf weight,stomatal conductance(g_(s)),and water use efficiency coefficient(WUE_(k)).Results:Differences were observed in K_(shoot) among cultivars under the 38℃,>3 kPa but not the 32℃,1∼1.5 kPa environment.Under the 38℃,>3 kPa environment,correlations were found between K_(shoot),stomatal conductance(gs),VPD breakpoint,WUEk,total leaf area,dry leaf weight,fraction transpirable soil water(FTSW)threshold,and slope of TR decline after FTSW threshold.Conclusion:Results show that the ability of some cotton cultivars to restrict water loss under high evaporative demand through early stomatal closure is associated with the cultivars’K_(shoot).The K_(shoot) is influential in the limitation of TR trait under high temperature and VPD.
基金Project(1999064906) supported by the National Key Fundamental Research and Development of China
文摘The effects of surface roughness, strain rate, friction coefficient and pressure on real contact area were analyzed based on the research of Stupkiewicz. The real contact area model taking account of the effect of friction and deformation of material was obtained. The model of contact conductance at the rolling interface was obtained by integrating the specific feature of heat transfer through the interface of continuous roll-casting. The results indicate that the real contact area increases obviously when the material is under yield, and the real contact area varies inversely with surface roughness, whereas it varies exponentially with friction coefficient, strain rate and pressure, and the power factor depends on strain rate.
基金Supported by the Major Program of the National Natural Science Foundation of China (30671679)National Key Technology R&D Program in the 11th Five Year Plan of China (2006BAD03A04-03)
文摘The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper （Capsicum annuum Linn.） and two C4 plants, sorghum （Sorghum bicolor L.Moench） and maize （Zea mays Linn.）. Three species were irrigated with three different water treatment levels of 100%, 66% and 33% which gave a comparison of tolerance and adaptation to irrigation and two different levels of water stress. The measurements of transpiration rate and stomatal conductance were done between 8.00 a.m. and 16.00 p.m. with measurements about each 1.5 h with an infrared gas analyzer. The results showed that Z. mays probably due to a higher leaf area had very low values and was significantly different （LSD pairwise comparison） from C. annuum and S. bicolor. The hypotheses that C4 plants and C3 plants have different transpiration rates and stomatal conductance could not be shown with the results. However, the hypotheses that for the same species, the highest values in transpiration rate and stomatal conductance were with the 100% irrigation treatment and the lowest values were with the 33% irrigation treatment could be accepted due to the results of this trial.
文摘In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.
文摘To develop proton-conducting materials with high hydrothermal and acid-base stability and to elucidate the proton-transport mechanism through visualized structural analysis,two new lanthanum phosphite-oxalates with 3D frameworks,designated as[La(HPO_(3))(C_(2)O_(4))0.5(H_(2)O)_(2)](La‑1)and(C_(6)H_(16)N_(2))(H_(3)O)[La_(2)(H_(2)PO_(3))_(3)(C_(2)O_(4))_(3)(H_(2)O)](La‑2)(C_(6)H_(14)N_(2)=cis-2,6-dimethylpiperazine),were prepared by hydrothermal and solvothermal conduction,respectively.La‑1 was constructed with lanthanum phosphite 2D layers and C_(2)O_(4)^(2-)groups,whereas La‑2 was constructed with lanthanum oxalate 2D layers and H_(2)PO^(3-)groups.Alternating current(AC)impedance spectra indicate that the pro-ton conductivities of both compounds could reach 10^(-4)S·cm^(-1)and remain highly durable at 75℃and 98%of rela-tive humidity(RH).Due to the abundance of H-bonds in La‑2,theσof La‑2 was higher than that of La‑1.La‑1 exhibited excellent water and pH stability.CCDC:2439965,La‑1;443776,La‑2.
文摘Energy storage is a key factor in the drive for carbon neutrality and carbon nanotubes(CNTs)may have an important role in this.Their intrinsic sp2 covalent structure gives them excellent electrical conductivity,mechanical strength,and chemical stability,making them suitable for many uses in energy storage,such as lithium-ion batteries(LIBs).Currently,their use in LIBs mainly focuses on conductive networks,current collectors,and dry electrodes.The review outlines advances in the use of CNTs in the cathodes and anodes of LIBs,especially in the electrode fabrication and mechanical sensors,as well as providing insights into their future development.
文摘The rapid development of the information era has led to in-creased power consumption,which generates more heat.This requires more efficient thermal management systems,with the most direct ap-proach being the development of su-perior thermal interface materials(TIMs).Mesocarbon microbeads(MCMBs)have several desirable properties for this purpose,includ-ing high thermal conductivity and excellent thermal stability.Although their thermal conductivity(K)may not be exceptional among all carbon materials,their ease of production and low cost make them ideal filler materials for developing a new generation of carbon-based TIMs.We report the fabrication of high-performance TIMs by incorporating MCMBs in a polyimide(PI)framework,producing highly graphitized PI/MCMB(PM)foams and anisotropic polydimethylsiloxane/PM(PDMS/PM)composites with a high thermal conductivity using directional freezing and high-temperature thermal annealing.The resulting materials had a high through-plane(TP)K of 15.926 W·m^(−1)·K^(−1),4.83 times that of conventional thermally conductive silicone pads and 88.5 times higher than that of pure PDMS.The composites had excellent mechanical properties and thermal stability,meeting the de-mands of modern electronic products for integration,multi-functionality,and miniaturization.
基金supported by the National Natural Science Foundation of China (Grant Nos. 22475179 and 22275173)。
文摘Realizing effective enhancement in the thermally conductive performance of polymer bonded explosives(PBXs) is vital for improving the resultant environmental adaptabilities of the PBXs composites. Herein, a kind of primary-secondary thermally conductive network was designed by water-suspension granulation, surface coating, and hot-pressing procedures in the graphene-based PBXs composites to greatly increase the thermal conductive performance of the composites. The primary network with a threedimensional structure provided the heat-conducting skeleton, while the secondary network in the polymer matrix bridged the primary network to increase the network density. The enhancement efficiency in the thermally conductive performance of the composites reached the highest value of 59.70% at a primary-secondary network ratio of 3:1. Finite element analysis confirmed the synergistic enhancement effect of the primary and secondary thermally conductive networks. This study introduces an innovative approach to designing network structures for PBX composites, significantly enhancing their thermal conductivity.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB1714600)the National Natural Science Foundation of China(Grant No.52175095)the Young Top-Notch Talent Cultivation Program of Hubei Province of China.
文摘This paper examined how microstructure influences the homogenized thermal conductivity of cellular structures and revealed a surface-induced size-dependent effect.This effect is linked to the porous microstructural features of cellular structures,which stems from the degree of porosity and the distri-bution of the pores.Unlike the phonon-driven surface effect at the nanoscale,the macro-scale surface mechanism in thermal cellular structures is found to be the microstructure-induced changes in the heat conduction path based on fully resolved 3D numerical simulations.The surface region is determined by the microstructure,characterized by the intrinsic length.With the coupling between extrinsic and intrinsic length scales under the surface mechanism,a surface-enriched multiscale method was devel-oped to accurately capture the complex size-dependent thermal conductivity.The principle of scale separation required by classical multiscale methods is not necessary to be satisfied by the proposed multiscale method.The significant potential of the surface-enriched multiscale method was demon-strated through simulations of the effective thermal conductivity of a thin-walled metamaterial struc-ture.The surface-enriched multiscale method offers higher accuracy compared with the classical multiscale method and superior efficiency over high-fidelity finite element methods.
基金funded by Zhijian Laboratory Open Fund,Rocket Force University of Engineering(Grant No.2023-ZJSYS-KF01-03).
文摘During the storage of composite propellants, the migration of plasticizers and other unbonded additives at the interfaces of liner adhesives has garnered significant attention in understanding liner failure mechanisms, aging processes, and safety performance. However, there is currently no non-destructive and quantitative detection method for migration of plasticizers in propellant liner. In this study, we developed a HTPB sensing liner by incorporating conductive fillers-namely carbon black(CB), carbon nanotubes(CNTs), and graphene nanoplatelets(GNP)-into the HTPB matrix. The synergistic interaction between CNTs and GNP facilitates the formation of a tunneling conductive network that imparts electrical conductivity to the HTPB liner. To elucidate the functional relationship between conductivity and nitroglycerin(NG) migration, we applied the HTPB sensing liner onto double base propellant surfaces and measured both the conductivity of the sensing layer and NG migration during a 71°C accelerated aging experiment. The results shows that when CNTs/GNP content reaches 3wt%, there is an exponential correlation between conductivity and NG migration with a fitting degree of 0.9652;the average response sensitivity of ΔR/R0 relative to NG migration is calculated as 41.69, with an average deviation of merely5.67% between NG migrations derived from conductivity fittings compared to those obtained via TGA testing results. Overall, this sensing liner exhibits excellent capabilities for detecting NG migration nondestructively and quantitatively while offering a novel approach for assessing interfacial component migrations as well as debonding defects in propellants-a promising avenue for future self-monitoring strategies regarding propellant integrity.
基金supported by the Natural Science Foundation of Shanxi Province(Grant No.202203021221120)The Open Fund of MCRI-Shannxi Laboratory of Energetic Materials(Grant No.204-J-2024-2622)。
文摘This study prepared a class of RDX-based composite microspheres(RAF)containing ADN and FKM2602.The reaction kinetics of RAF composite microspheres were effectively improved by maintaining the system's high energy and safety performance.In the close packing state,when the heating rate is rapid,the thermal stability of RAF composite microspheres is better than that of RDX;the close packing state will reduce the degree of freedom of RDX and ADN reaction but will increase the degree of freedom of RAF composite microsphere reaction.The thermal conductivity of RAF composite microspheres is close to that of RDX.In the ignition experiment,the flame of RAF composite microspheres can be maintained without the external heat source.Regarding safety,the H50of RAF composite microspheres was 274.04%higher than that of RDX.The detonation velocity of RAF composite microspheres is slightly higher than that of raw material RDX.Overall,these findings highlight the effectiveness of ADN in enhancing the reaction kinetics of RDX-based composites.
基金Project(52276068)supported by the National Natural Science Foundation of China。
文摘This study examines the intricate occurrences of thermal and solutal Marangoni convection in three-layered flows of viscous fluids,with a particular emphasis on their relevance to renewable energy systems.This research examines the flow of a three-layered viscous fluid,considering the combined influence of heat and solutal buoyancy driven Rayleigh-Bénard convection,as well as thermal and solutal Marangoni convection.The homotopy perturbation method is used to examine and simulate complex fluid flow and transport phenomena,providing important understanding of the fundamental physics and assisting in the optimization of various battery configurations.The inquiry examines the primary elements that influence Marangoni convection and its impact on battery performance,providing insights on possible enhancements in energy storage devices.The findings indicate that the velocity profiles shown graphically exhibit a prominent core zone characterized by the maximum speed,which progressively decreases as it approaches the walls of the channel.This study enhances our comprehension of fluid dynamics and the transmission of heat and mass in intricate systems,which has substantial ramifications for the advancement of sustainable energy solutions.
文摘走航式海洋多参数剖面测量系统(moving vessel profiler,MVP)是一种集成程度和自动化程度都较高的海洋调查设备,能对海洋多要素进行同时观测,获得水平方向的高分辨率数据资料。由于温度和电导率传感器响应时间的不匹配,MVP下放速度过快(峰值速度4 m/s)而造成非常明显的盐度尖峰现象。本研究结合Fofonoff(F)法、时间常数指数递归数字滤波(Giles and McDougall,GM)法和Grose提出的盐度尖峰订正方案,提出了一种新的方法,即MCT(match conductivity and temperature response time)法,通过对压力、温度和电导率传感器进行响应时间的匹配来减弱盐度尖峰。将SBE-9型CTD资料作为标准,发现订正后的资料与CTD盐度曲线的互相关系数为0.917,误差比订正前减小80%。对比35°N断面修正前后的盐度资料,订正后温盐跃层处出现的低盐区域消失。MVP的应用比常规海洋调查仪器CTD对于海洋现象的观测更有优势。
基金Supported by the National Natural Science Foundation of China (30871735 31272191)+1 种基金the Natural Science Foundation of Heilongjiang Province(C0207 C200619)
文摘Drought stress is one of the major constraints on turf growth and performance in northern China. Based on previous assessments of drought tolerance levels, four varieties of Kentucky bluegrass （Poa pratensis L.） representing different types （＇Baron＇, BVMG type; ＇Blackstone＇, Cheri type; ＇Kenblue＇, Midwest type; and ＇Bluemoon＇, Midnight type） were chosen for this study. Grass materials were established in a glasshouse, and the changes in their photosynthetic and metabolic characteristics were analyzed during a period of imposed drought stress. Drought stress led to decrease in chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate in all four cultivars, but the relative changes in each characteristic varied among varieties. The results also showed that changes in the photosynthetic and metabolic characteristics of different varieties under drought stress were related to the morphological characteristics of the plants. Varieties with longer narrow leaves, longer roots, higher root-to-shoot ratios, and higher chlorophyll contents showed greater rates of photosynthesis and stomatal conductance, and lower transpiration rates.
基金support from the National Institute of General Medical Sciences(1R35G M147172-01).
文摘Nanopipette based scanning probe technique is a versatile tool in non-contact imaging in biology.In addition to the topographic imaging,its capability of localized delivery of bio-active molecules is emerging.In this mini review,we introduce the applications of nanopipette in single-cell researches with a focus on localized delivery.The working principles of three delivery modes including resistive pulse,pressure-driven flow,and electroosmotic flow-driven delivery are summarized and compared.Their applications in single-cell researches are reviewed.The current technical challenges in scanning ion conductance microscopy-based delivery,and their growing influence in medicine and pharmacologic researches are also discussed.
