Acoustic fatigue life evaluation is essential for thermal protection struc- tures due to the severe thermo-acoustic load in service. A study on temperature- dependence of acoustic fatigue life for a C/SiC panel is pre...Acoustic fatigue life evaluation is essential for thermal protection struc- tures due to the severe thermo-acoustic load in service. A study on temperature- dependence of acoustic fatigue life for a C/SiC panel is presented in this paper. Effects of temperature on both the structural responses and the S-N curves are investigated. The Dirlik method is adopted to predict the fatigue life of a C/SiC panel at three different temperatures respectively. Significant differences are ob- served from the results of numerical simulations between the fatigue lives of the panel in the three cases. The temperature-dependence of acoustic fatigue life of a C/SiC panel is verified, and fatigue test of the material needs to be more atten- tively performed.展开更多
In this paper,we consider an initial boundary value problem for the nonhomo-geneous heat-conducting magnetohydrodynamic fuids when the viscosityμ,magnetic dif-fusivity v and heat conductivity k depend on the temperat...In this paper,we consider an initial boundary value problem for the nonhomo-geneous heat-conducting magnetohydrodynamic fuids when the viscosityμ,magnetic dif-fusivity v and heat conductivity k depend on the temperature according to μ(0)=°,k(0)=08,v(0)=07,withα,>0,β≥0.We prove the global existence of a unique strong solution provided that ■ is suitably small.In addition,we also get some results of the large-time behavior and exponential decay estimates.展开更多
Silicone gel is a prevailing material for encapsulation in insulated gate bipolar transistor(IGBT)power modules.The space charge transport behavior in silicone gel is significant to evaluate the electrical insulation ...Silicone gel is a prevailing material for encapsulation in insulated gate bipolar transistor(IGBT)power modules.The space charge transport behavior in silicone gel is significant to evaluate the electrical insulation characteristics.This paper focuses on the trap characteristics and electrical properties of the silicone gel,which were rarely studied before.The experiments are performed on the surface potential decay of silicone gel after the charge injection.Then,the energy distributions of electron or hole traps are determined by a double-trap energy level model,which can be fitted by the Gaussian distribution.In addition,the mobilities of positive and negative charges are determined,which are 1.38×10^(-12) m^(2)·V^(-1)·s^(-1) and 1.74×10^(12) m^(2)·V^(-1)·s^(-1),respectively.Furthermore,considering the heat as a byproduct resulting in thermal issues,the temperature-dependence of surface potential decay characteristics are also studied in this paper.When temperature rises,the decay rate of surface potential increases,especially when the temperature is higher than 80℃.Finally,the contrastive analysis illustrates that the trap characteristics of silicone gel are between the trap characteristics in liquid-state material and solid-state material,which supports the phenomenon that silicone gel is more resistive to the sharp edges in power modules.This work can provide a useful reference for the design of encapsulation in high-voltage IGBT power modules.展开更多
Temperature plays a crucial role in regulating polymorphism in supramolecular polymers.Understanding the mechanism behind temperature-dependent supramolecular polymorphism is crucial as it provides an opportunity to t...Temperature plays a crucial role in regulating polymorphism in supramolecular polymers.Understanding the mechanism behind temperature-dependent supramolecular polymorphism is crucial as it provides an opportunity to tailor polymorphs for specific properties and applications.In this study,we present our findings on a naphthalimide-substituted benzene-1,3,5-tricarboxamide derivative,R-Nap-1,which exhibits two distinct polymerization pathways at varying temperatures.At 313 K,polymerization results in the formation of an M-chiral polymorph,whereas at 253 K,a P-chiral polymorph is formed.Both polymorphs are notably stable,remaining unchanged for over six months under ambient conditions.Theoretical calculations and experimental investigations allowed us to elucidate the mechanisms underlying these polymorphic transformations.The formation of the M-chiral polymorph at 313 K is attributed to the nucleation and growth of R-Nap-1 monomers once their concentration surpasses a critical threshold.Conversely,at lower temperatures(e.g.,253 K),the monomers undergo facile transformation into dimers due to a lower energy barrier and reduced Gibbs energy compared to the monomeric state.Subsequently,these dimers undergo nucleation-elongation to form the P-chiral polymorph when their concentration exceeds the critical polymerization concentration.The stability and lack of interconversion between the two polymorphs can be attributed to their close thermodynamic stabilities,as evidenced by variable-temperature CD spectra and DFT calculations.These findings highlight the importance of accurate temperature control in supramolecular polymerization processes,making a significant contribution to the understanding of supramolecular polymorphism,thus advancing the field of supramolecular chemistry.展开更多
With the increasingly widespread application of rubber in many fields,there is a growing demand for quantitative characterization of temperature-dependent mechanical properties in high-temperature service environments...With the increasingly widespread application of rubber in many fields,there is a growing demand for quantitative characterization of temperature-dependent mechanical properties in high-temperature service environments.The critical tearing energy is an important criterion for determining whether rubber materials will experience tearing instability,while tear strength is a key parameter for rubber materials to resist tearing.It is necessary to quantitatively characterize their evolution with temperature.Current theoretical research mainly relies on fitting a large amount of experimental data,which is not convenient for engineering applications.Therefore,in this work,a temperature-dependent critical tearing energy model is firstly developed based on the force-heat equivalence energy density principle.This model considers the equivalent relationship between the critical tearing energy required for crack instability propagation and the thermal energy stored in the rubber material.It is demonstrated that our model has higher prediction accuracy when compared to other models.Furthermore,combining with the Griffith fracture theory,temperature-dependent tear strength models applicable to three different crack modes are separately established.These models are validated using experimental data for Mode I opening cracks and ModeⅢtearing cracks,and good consistency is achieved.Additionally,a quantitative analysis of the influence of elastic modulus on tear strength at different temperatures is conducted.This work provides a reliable way for predicting temperature-dependent tearing instability behavior and offers beneficial suggestions for improving the tear strength of rubber materials at different temperatures.展开更多
In reptiles,such as the red-eared slider turtle(Trachemys scripta elegans),gonadal sex determination is highly dependent on the environmental temperature during embryonic stages.This complex process,which leads to dif...In reptiles,such as the red-eared slider turtle(Trachemys scripta elegans),gonadal sex determination is highly dependent on the environmental temperature during embryonic stages.This complex process,which leads to differentiation into either testes or ovaries,is governed by the finely tuned expression of upstream genes,notably the testis-promoting gene Dmrt1 and the ovary-promoting gene Foxl2.Recent studies have identified epigenetic regulation as a crucial factor in testis development,with the H3K27me3 demethylase KDM6B being essential for Dmrt1 expression in T.s.elegans.However,whether KDM6B alone can induce testicular differentiation remains unclear.In this study,we found that overexpression of Kdm6b in T.s.elegans embryos induced the male development pathway,accompanied by a rapid increase in the gonadal expression of Dmrt1 at 31°C,a temperature typically resulting in female development.Notably,this sex reversal could be entirely rescued by Dmrt1 knockdown.These findings demonstrate that Kdm6b is sufficient for commitment to the male pathway,underscoring its role as a critical epigenetic regulator in the sex determination of the red-eared slider turtle.展开更多
Dimethyl sulfoxide(DMSO)plays an important role in chemistry,biology and industry.The S=O stretching vibration serves as a sensitive probe of its structure under different chemical environments.However,spectral assign...Dimethyl sulfoxide(DMSO)plays an important role in chemistry,biology and industry.The S=O stretching vibration serves as a sensitive probe of its structure under different chemical environments.However,spectral assignment for the S=O stretching vibration of liquid DMSO remains unclear due to the interference of CH_(3)antisymmetric rocking and different aggregates,leading to the confusion in explaining the microstructures of liquid DMSO.Here,the S=O stretching spectra in pure DMSO and in extremely diluted CCl_(4)solution were investigated with temperaturedependent Raman spectroscopy.It is shown that CH_(3)antisymmetric rocking does not significantly interfere with the S=O band profile due to its low Raman intensity.Three decomposed peaks at 1027,1042 and 1055 cm^(-1)in liquid DMSO show obviously different intensity variety upon the temperature increasing.Combined with quantum chemistry calculation on(DMSO)_(n)(n=1-4)clusters,Raman spectra in the S=O stretching region were assigned and the simultaneous presence of the monomer,dimer and trimmer in liquid DMSO were concluded.These results contribute to a more detailed molecular understanding of the structure of DMSO in the liquid state.展开更多
Comparing to the conventional polyoxometalate(POM)-templated silver(Ag)clusters,asymmetrically covered POM-templated Ag clusters have been rarely reported.In this work,a new Ag cluster,H[Co(SiW_(11)O_(39))Co_(4)(OH)_(...Comparing to the conventional polyoxometalate(POM)-templated silver(Ag)clusters,asymmetrically covered POM-templated Ag clusters have been rarely reported.In this work,a new Ag cluster,H[Co(SiW_(11)O_(39))Co_(4)(OH)_(3)(NO_(3))_(2)(SiW_(9)O_(34))@Ag_(37)(^(t)BuC≡C)_(23)(NO_(3))_(2)(DMF)_(3)](Ag_(37)Co_(5)),has been successfully prepared using a facile solvothermal approach.Such a unique asymmetrical architecture is ascribed to the uneven charge distribution of the in situ generated[Co(SiW_(11)O_(39))]^(6-)and[Co_(4)(OH)_(3)(NO_(3))_(2)(SiW_(9)O_(34))]^(7-)moieties,leading to the asymmetrical coverage of alkynyl-protected Ag shell.Various physicochemical and catalytic studies revealed that the resulting solid-state Ag_(37)Co_(5) crystals exhibited interesting temperature-dependent photoluminescence property,efficient and recyclable photothermal conversion ability,and good catalytic activity towards the detoxication of 4-nitrophenol.展开更多
In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical prop...In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical properties of FCC_CoNiV MPEAs were comparatively predicted,where the alloys were modeled as the ordered configurations based on our previously predicted site occupying fractions(SOFs),as well as disordered configuration based on traditional special quasi-random structure(SQS).The ordering behavior not only improves the thermodynamic stability of the structure,but also increases the elastic properties and Vickers hardness.For example,at 973 K,the predicted bulk modulus(B),shear modulus(G),Young’s modulus(E),and Vickers hardness(HV)of FCC_CoNiV MPEA based on SOFs configuration are 187.82,79.03,207.93,and 7.58 GPa,respectively,while the corresponded data are 172.58,57.45,155.14,and 4.64 GPa for the SQS configuration,respectively.The Vickers hardness predicted based on SOFs agrees considerably well with the available experimental data,while it is underestimated obviously based on SQS.展开更多
In the early stages of oil exploration,oil is produced through processes such as well drilling.Later,hot water may be injected into the well to improve production.A key challenge is understanding how the temperature a...In the early stages of oil exploration,oil is produced through processes such as well drilling.Later,hot water may be injected into the well to improve production.A key challenge is understanding how the temperature and velocity of the injected hot water affect the production rate.This is the focus of the current study.It proposes variableviscosity mathematical models for heat and water saturation in a reservoir containing Bonny-light crude oil,with the aim of investigating the effects of water temperature and velocity on the recovery rate.First,two sets of experimental data are used to construct explicit temperature-dependent viscosity models for Bonny-light crude oil and water.These viscosity models are incorporated into the Buckley-Leverette equation for the dynamics of water saturation.A convex combination of the thermal conductivities of oil and water is used to formulate a heat propagation model.A finite volume scheme with temperature-dependent HLL numerical flux is proposed for saturation,while a finite difference approximation is derived for the heat model,both on a staggered grid.The convergence of the method is verified numerically.Simulations are conducted with different parameter values.The results show that at a wall temperature of 10℃,an increase in the injection velocity from 0.1 to 0.25 increases the production rate from 8.33%to 20.8%.Meanwhile,with an injection velocity of v=1,an increase in the temperature of the injected water from 25℃ to 55℃ increases production rate from 59.48%to 61.95%.Therefore,it is concluded that an increase in either or both the temperature and velocity of the injected water leads to increased oil production,which is physically realistic.This indicates that the developed model is able to give useful insights into hot water flooding.展开更多
Objective To investigate the role of environmental factor—temperature in the regulation of aging process by unc-13 and sbt-1 in Caenorhabditis elegans. Methods The lifespan, the speed of pharynx pumping, and the inte...Objective To investigate the role of environmental factor—temperature in the regulation of aging process by unc-13 and sbt-1 in Caenorhabditis elegans. Methods The lifespan, the speed of pharynx pumping, and the intestinal autofluorescence of unc-13 and sbt-1 mutants were examined at different temperature conditions. In addition, to exclude the possible influences from other factors in unc-13 and sbt-1 mutants, the dauer formation, the thermotaxis, the brood size and the population percentage of the mutants expressing hsp16.2-gfp were further investigated. Results Mutations of unc-13 and sbt-1 significantly increased the mean and the maximum lifespans of nematodes cultured at 20 oC and 25 oC, while no noticeable increase was found at 15 oC in either the mean or the maximum lifespan. Investigations on the speed of pharynx pumping and the intestinal autofluorescence suggested that at 20 oC and 25 oC, mutations of unc-13 and sbt-1 could slow the aging process and delay the accumulation of aging-related cellular damage. Meanwhile, mutations of unc-13 or sbt-1 did not affect the dauer formation or the thermotaxis to different temperatures in nematodes. In contrast, at 20 oC and 25 oC conditions, mutations of unc-13 and sbt-1 significantly decreased the brood size and the percentage of nematodes expressing hsp16.2-gfp, while no such differences were detected at 15 oC. Moreover, the thermotolerance of unc-13 and sbt-1 mutants could be greatly strengthened after the 16-h heat shock at 35 oC. Conclusion The regulation of aging by unc-13 and sbt-1 is temperature-dependent. And the alterations in reproduction capability and stress response may be associated with the formation of this temperature-dependent property.展开更多
The shot-range interaction and the atomic anharmonic vibration are both considered, and then the analytic functions of the Debye temperature, the specific capacity and the thermal conductivity of graphene with the tem...The shot-range interaction and the atomic anharmonic vibration are both considered, and then the analytic functions of the Debye temperature, the specific capacity and the thermal conductivity of graphene with the temperature are obtained. The influence of anharmonic vibration on these thermal physical properties is also investigated. Some theoretical results are given. If only the harmonic approximation is considered, the Debye temperature of the graphene is unrelated to the temperature. If the anharmonic terms are considered, it increases slowly with the increasing temperature. The molar heat capacity of the graphene increases nonlinearly with the increasing temperature. The mean free path of phonons and the thermal conductivity of the graphene decrease nonlinearly with the increasing temperature. The relative changes of the Debye temperature, the specific heat capacity and the thermal conductivity caused by the anharmonic terms increase with the increasing temperature. The anharmonic effect of atomic vibration becomes more significant under higher temperature.展开更多
Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and ab...Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films＇ exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I（3-x）Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.展开更多
Based on the generalized thermoelasticity proposed by Green and Lindsay, the dynamic response of generalized thermoelastic problems with temperature-dependent material properties is investigated. The governing equatio...Based on the generalized thermoelasticity proposed by Green and Lindsay, the dynamic response of generalized thermoelastic problems with temperature-dependent material properties is investigated. The governing equations are formulated and found to be nonlinear because of the temperature-dependence of properties. Owing to the nonlinearity of the governing equations, the finite element method is resorted to for solution. The results obtained show that the temperature-dependent properties influence the variables considered by reducing their magnitudes. This indicates that taking the temperature-dependence of properties into consideration in the investigation of generalized thermoelastic problems is necessary and practical for accurately predicting the thermoelastic behavior.展开更多
This work focuses on transient thermal behavior of radial fins of rectangular,triangular and hyperbolic profiles with temperature-dependent properties.A hybrid numerical algorithm which combines differential transform...This work focuses on transient thermal behavior of radial fins of rectangular,triangular and hyperbolic profiles with temperature-dependent properties.A hybrid numerical algorithm which combines differential transformation(DTM) and finite difference(FDM) methods is utilized to theoretically study the present problem.DTM and FDM are applied to the time and space domains of the problem,respectively.The accuracy of this method solution is checked against the numerical solution.Then,the effects of some applicable parameters were studied comparatively.Since a broad range of governing parameters are investigated,the results could be useful in a number of industrial and engineering applications.展开更多
The temperature-dependent structural changes in 1-butyl-3-methylimidazolium tetrafluoride([Bmim]FeCl4)magnetic ionic liquid(MIL)were investigated by using in-situ X-ray absorption fine structure(XAFS)combined with Ram...The temperature-dependent structural changes in 1-butyl-3-methylimidazolium tetrafluoride([Bmim]FeCl4)magnetic ionic liquid(MIL)were investigated by using in-situ X-ray absorption fine structure(XAFS)combined with Raman spectroscopy and DFT calculations.XAFS re sults revealed that the coordination number and bond length of Fe-Cl in the anion of[Bmim]FeCl4 MIL decreased with increments in temperature.These results directly reflected the dissociation of tetrahedral structure[FeCl4]^-,and the formation of bridge-chain[Fe2 Cl5]^+,and[FeCl2]^+species in the anion of[Bmim]FeCl4 MIL.These behaviors indicated that[FeCl4]^-dissociation was endothermic,and was promoted by increased temperature.The results obtained through XAFS were in agreement with those obtained through Raman spectroscopy and DFT calculations.展开更多
An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2...An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2-D)thermo-elasticity theory.Firstly,the beam was divided into a series of layers with uniform material properties along the interfaces of the beam.The uniform thermo-load acted on each layer was transformed into a combination of the normal surface forces acted at the two ends and the transverse thermo-load.Secondly,the state space method was employed to obtain the general solutions of displacements and stresses in an arbitrary layer.Thirdly,based on the interfacial continuity conditions between adjacent layers,the relations of displacement and stress components between the top and bottom layers of the beam were recursively derived by use of the transfer-matrix method.The unknowns in the solutions can be solved by the mechanical loads acted on the top and bottom surfaces.The convergence of the present solutions was checked.The comparative study of the present solutions with the Timoshenko’s solutions and the finite element(FE)solutions was carried out.The effects of material properties variable with temperature on the thermo-elastic behavior of laminated beams were discussed in detail.展开更多
Highly luminescent water-soluble CdTe quantum dots （QDs） have been synthesized with an electrogenerated precursor. The obtained CdTe QDs can possess good crystallizability, high quantum yield （QY） and favorable st...Highly luminescent water-soluble CdTe quantum dots （QDs） have been synthesized with an electrogenerated precursor. The obtained CdTe QDs can possess good crystallizability, high quantum yield （QY） and favorable stability. Furthermore, a detection system is designed firstly for the investigation of the temperature-dependent PL of the QDs. ？2009 Yu Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
We demonstrate transitions of hopping behaviors for delocalized electrons through the discrete dopant-induced quantum dots in n-doped silicon junctionless nanowire transistors by the temperature-dependent conductance ...We demonstrate transitions of hopping behaviors for delocalized electrons through the discrete dopant-induced quantum dots in n-doped silicon junctionless nanowire transistors by the temperature-dependent conductance characteristics.There are two obvious transition platforms within the critical temperature regimes for the experimental conductance data,which are extracted from the unified transfer characteristics for different temperatures at the gate voltage positions of the initial transconductance gm peak in Vg1 and valley in Vg2. The crossover temperatures of the electron hopping behaviors are analytically determined by the temperature-dependent conductance at the gate voltages Vg1 and Vg2. This finding provides essential evidence for the hopping electron behaviors under the influence of thermal activation and long-range Coulomb interaction.展开更多
A series of linear stability analysis is carried out on the onset of thermal convection in the presence of spatial variations of viscosity, thermal conductivity and expansivity. We consider the temporal evolution of a...A series of linear stability analysis is carried out on the onset of thermal convection in the presence of spatial variations of viscosity, thermal conductivity and expansivity. We consider the temporal evolution of an infinitesimal perturbation superimposed to a static （motionless） and con- ductive state in a basally-heated planar layer. From the changes in flow patterns with increasing the amplitudes of temperature dependence of viscosity, we identified the transition into the ＂stagnant-lid＂ （ST） regime, where the convection occurs only beneath a thick and stagnant-lid of cold fluid at the top surface. Detailed analysis showed a significant increase of the aspect ratio of convection cells in ST regime induced by the spatial variations in thermal conductivity and/or expansivity： the horizon- tal length scale of ST convection can be enlarged by up to 50% with 10 times increase of thermal conductivity with depth. We further developed an analytical model of ST convection which success- fully reproduced the mechanism of increasing horizontal length scale of ST regime convection cells for given spatial variations in physical properties. Our findings may highlight the essential roles of the spatial variation of thermal conductivity on the convection patterns in the mantle.展开更多
基金supported by the National Natural Science Foundation of China(10902024)the National Aerospace Science Foundation of China(20090869009)+1 种基金the New Century Excellent Talent in University(NCET-11-0086)the Research Fund for the Doctoral Program of Higher Education of China(20130092120039)
文摘Acoustic fatigue life evaluation is essential for thermal protection struc- tures due to the severe thermo-acoustic load in service. A study on temperature- dependence of acoustic fatigue life for a C/SiC panel is presented in this paper. Effects of temperature on both the structural responses and the S-N curves are investigated. The Dirlik method is adopted to predict the fatigue life of a C/SiC panel at three different temperatures respectively. Significant differences are ob- served from the results of numerical simulations between the fatigue lives of the panel in the three cases. The temperature-dependence of acoustic fatigue life of a C/SiC panel is verified, and fatigue test of the material needs to be more atten- tively performed.
基金supported by the National Natural Science Foundation of China(No.11931013)the Natural Science Foundation of Guangxi Province(No.2022GXNSFDA035078)the Foundamental Research Funds for the Central Universities,CHD(No.300102122115).
文摘In this paper,we consider an initial boundary value problem for the nonhomo-geneous heat-conducting magnetohydrodynamic fuids when the viscosityμ,magnetic dif-fusivity v and heat conductivity k depend on the temperature according to μ(0)=°,k(0)=08,v(0)=07,withα,>0,β≥0.We prove the global existence of a unique strong solution provided that ■ is suitably small.In addition,we also get some results of the large-time behavior and exponential decay estimates.
基金This work was supported by the National Natural Science Foundation of China-the State Grid Corporation Joint Fund for Smart Grid(U1766219)the Fundamental Research Funds for the Central Universities(2019QN120).
文摘Silicone gel is a prevailing material for encapsulation in insulated gate bipolar transistor(IGBT)power modules.The space charge transport behavior in silicone gel is significant to evaluate the electrical insulation characteristics.This paper focuses on the trap characteristics and electrical properties of the silicone gel,which were rarely studied before.The experiments are performed on the surface potential decay of silicone gel after the charge injection.Then,the energy distributions of electron or hole traps are determined by a double-trap energy level model,which can be fitted by the Gaussian distribution.In addition,the mobilities of positive and negative charges are determined,which are 1.38×10^(-12) m^(2)·V^(-1)·s^(-1) and 1.74×10^(12) m^(2)·V^(-1)·s^(-1),respectively.Furthermore,considering the heat as a byproduct resulting in thermal issues,the temperature-dependence of surface potential decay characteristics are also studied in this paper.When temperature rises,the decay rate of surface potential increases,especially when the temperature is higher than 80℃.Finally,the contrastive analysis illustrates that the trap characteristics of silicone gel are between the trap characteristics in liquid-state material and solid-state material,which supports the phenomenon that silicone gel is more resistive to the sharp edges in power modules.This work can provide a useful reference for the design of encapsulation in high-voltage IGBT power modules.
基金supported by the Chinese Academy of Sciences CAS Project for Young Scientists in Basic Research(No.YSBR-027)。
文摘Temperature plays a crucial role in regulating polymorphism in supramolecular polymers.Understanding the mechanism behind temperature-dependent supramolecular polymorphism is crucial as it provides an opportunity to tailor polymorphs for specific properties and applications.In this study,we present our findings on a naphthalimide-substituted benzene-1,3,5-tricarboxamide derivative,R-Nap-1,which exhibits two distinct polymerization pathways at varying temperatures.At 313 K,polymerization results in the formation of an M-chiral polymorph,whereas at 253 K,a P-chiral polymorph is formed.Both polymorphs are notably stable,remaining unchanged for over six months under ambient conditions.Theoretical calculations and experimental investigations allowed us to elucidate the mechanisms underlying these polymorphic transformations.The formation of the M-chiral polymorph at 313 K is attributed to the nucleation and growth of R-Nap-1 monomers once their concentration surpasses a critical threshold.Conversely,at lower temperatures(e.g.,253 K),the monomers undergo facile transformation into dimers due to a lower energy barrier and reduced Gibbs energy compared to the monomeric state.Subsequently,these dimers undergo nucleation-elongation to form the P-chiral polymorph when their concentration exceeds the critical polymerization concentration.The stability and lack of interconversion between the two polymorphs can be attributed to their close thermodynamic stabilities,as evidenced by variable-temperature CD spectra and DFT calculations.These findings highlight the importance of accurate temperature control in supramolecular polymerization processes,making a significant contribution to the understanding of supramolecular polymorphism,thus advancing the field of supramolecular chemistry.
基金the National Natural Science Foundation of China(12172069)the Graduate Scientific Research and Innovation Foundation of Chongqing(CYS23078)for their support in this research.
文摘With the increasingly widespread application of rubber in many fields,there is a growing demand for quantitative characterization of temperature-dependent mechanical properties in high-temperature service environments.The critical tearing energy is an important criterion for determining whether rubber materials will experience tearing instability,while tear strength is a key parameter for rubber materials to resist tearing.It is necessary to quantitatively characterize their evolution with temperature.Current theoretical research mainly relies on fitting a large amount of experimental data,which is not convenient for engineering applications.Therefore,in this work,a temperature-dependent critical tearing energy model is firstly developed based on the force-heat equivalence energy density principle.This model considers the equivalent relationship between the critical tearing energy required for crack instability propagation and the thermal energy stored in the rubber material.It is demonstrated that our model has higher prediction accuracy when compared to other models.Furthermore,combining with the Griffith fracture theory,temperature-dependent tear strength models applicable to three different crack modes are separately established.These models are validated using experimental data for Mode I opening cracks and ModeⅢtearing cracks,and good consistency is achieved.Additionally,a quantitative analysis of the influence of elastic modulus on tear strength at different temperatures is conducted.This work provides a reliable way for predicting temperature-dependent tearing instability behavior and offers beneficial suggestions for improving the tear strength of rubber materials at different temperatures.
基金supported by the National Natural Science Foundation of China(32325049,U22A20529,32303000)Zhejiang Provincial Natural Science Foundation(LQ24C190009)+1 种基金Ningbo Natural Science Foundation(2022J192)Zhejiang Provincial Top Key Discipline of Biological Engineering(1741000592)。
文摘In reptiles,such as the red-eared slider turtle(Trachemys scripta elegans),gonadal sex determination is highly dependent on the environmental temperature during embryonic stages.This complex process,which leads to differentiation into either testes or ovaries,is governed by the finely tuned expression of upstream genes,notably the testis-promoting gene Dmrt1 and the ovary-promoting gene Foxl2.Recent studies have identified epigenetic regulation as a crucial factor in testis development,with the H3K27me3 demethylase KDM6B being essential for Dmrt1 expression in T.s.elegans.However,whether KDM6B alone can induce testicular differentiation remains unclear.In this study,we found that overexpression of Kdm6b in T.s.elegans embryos induced the male development pathway,accompanied by a rapid increase in the gonadal expression of Dmrt1 at 31°C,a temperature typically resulting in female development.Notably,this sex reversal could be entirely rescued by Dmrt1 knockdown.These findings demonstrate that Kdm6b is sufficient for commitment to the male pathway,underscoring its role as a critical epigenetic regulator in the sex determination of the red-eared slider turtle.
基金supported by the National Natural Science Foundation of China(Nos.21873002,22073088,12374001).
文摘Dimethyl sulfoxide(DMSO)plays an important role in chemistry,biology and industry.The S=O stretching vibration serves as a sensitive probe of its structure under different chemical environments.However,spectral assignment for the S=O stretching vibration of liquid DMSO remains unclear due to the interference of CH_(3)antisymmetric rocking and different aggregates,leading to the confusion in explaining the microstructures of liquid DMSO.Here,the S=O stretching spectra in pure DMSO and in extremely diluted CCl_(4)solution were investigated with temperaturedependent Raman spectroscopy.It is shown that CH_(3)antisymmetric rocking does not significantly interfere with the S=O band profile due to its low Raman intensity.Three decomposed peaks at 1027,1042 and 1055 cm^(-1)in liquid DMSO show obviously different intensity variety upon the temperature increasing.Combined with quantum chemistry calculation on(DMSO)_(n)(n=1-4)clusters,Raman spectra in the S=O stretching region were assigned and the simultaneous presence of the monomer,dimer and trimmer in liquid DMSO were concluded.These results contribute to a more detailed molecular understanding of the structure of DMSO in the liquid state.
基金financially supported by the National Natural Science Foundation of China(Nos.21871025,21831001)the Recruitment Program of Global Experts(Young Talents)Beijing Institute of Technology(BIT)Excellent Young Scholars Research Fund.
文摘Comparing to the conventional polyoxometalate(POM)-templated silver(Ag)clusters,asymmetrically covered POM-templated Ag clusters have been rarely reported.In this work,a new Ag cluster,H[Co(SiW_(11)O_(39))Co_(4)(OH)_(3)(NO_(3))_(2)(SiW_(9)O_(34))@Ag_(37)(^(t)BuC≡C)_(23)(NO_(3))_(2)(DMF)_(3)](Ag_(37)Co_(5)),has been successfully prepared using a facile solvothermal approach.Such a unique asymmetrical architecture is ascribed to the uneven charge distribution of the in situ generated[Co(SiW_(11)O_(39))]^(6-)and[Co_(4)(OH)_(3)(NO_(3))_(2)(SiW_(9)O_(34))]^(7-)moieties,leading to the asymmetrical coverage of alkynyl-protected Ag shell.Various physicochemical and catalytic studies revealed that the resulting solid-state Ag_(37)Co_(5) crystals exhibited interesting temperature-dependent photoluminescence property,efficient and recyclable photothermal conversion ability,and good catalytic activity towards the detoxication of 4-nitrophenol.
基金financially supported by the State Administration for Market Regulation,China(No.2021MK050)the National Natural Science Foundation of China(Nos.50971043,51171046,21973012)+3 种基金the Key Research and Development Program of China(Nos.2022YFB3807200,CISRI-21T62450ZD)the Natural Science Foundation of Fujian Province,China(Nos.2021J01590,2020J01351,2018J01754,2020J01474)the Student Research and Training Program(SRTP) of Fuzhou University,China(No.29320)Fujian Provincial Department of Science & Technology,China(No.2021H6011)。
文摘In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical properties of FCC_CoNiV MPEAs were comparatively predicted,where the alloys were modeled as the ordered configurations based on our previously predicted site occupying fractions(SOFs),as well as disordered configuration based on traditional special quasi-random structure(SQS).The ordering behavior not only improves the thermodynamic stability of the structure,but also increases the elastic properties and Vickers hardness.For example,at 973 K,the predicted bulk modulus(B),shear modulus(G),Young’s modulus(E),and Vickers hardness(HV)of FCC_CoNiV MPEA based on SOFs configuration are 187.82,79.03,207.93,and 7.58 GPa,respectively,while the corresponded data are 172.58,57.45,155.14,and 4.64 GPa for the SQS configuration,respectively.The Vickers hardness predicted based on SOFs agrees considerably well with the available experimental data,while it is underestimated obviously based on SQS.
文摘In the early stages of oil exploration,oil is produced through processes such as well drilling.Later,hot water may be injected into the well to improve production.A key challenge is understanding how the temperature and velocity of the injected hot water affect the production rate.This is the focus of the current study.It proposes variableviscosity mathematical models for heat and water saturation in a reservoir containing Bonny-light crude oil,with the aim of investigating the effects of water temperature and velocity on the recovery rate.First,two sets of experimental data are used to construct explicit temperature-dependent viscosity models for Bonny-light crude oil and water.These viscosity models are incorporated into the Buckley-Leverette equation for the dynamics of water saturation.A convex combination of the thermal conductivities of oil and water is used to formulate a heat propagation model.A finite volume scheme with temperature-dependent HLL numerical flux is proposed for saturation,while a finite difference approximation is derived for the heat model,both on a staggered grid.The convergence of the method is verified numerically.Simulations are conducted with different parameter values.The results show that at a wall temperature of 10℃,an increase in the injection velocity from 0.1 to 0.25 increases the production rate from 8.33%to 20.8%.Meanwhile,with an injection velocity of v=1,an increase in the temperature of the injected water from 25℃ to 55℃ increases production rate from 59.48%to 61.95%.Therefore,it is concluded that an increase in either or both the temperature and velocity of the injected water leads to increased oil production,which is physically realistic.This indicates that the developed model is able to give useful insights into hot water flooding.
基金supported by grants from the National Natural Science Foundation of China (No.30771113, 30870810)the Program for New Century Excellent Talents in Universitythe Innovative Research Program for Undergraduates in China (No. C2007052)
文摘Objective To investigate the role of environmental factor—temperature in the regulation of aging process by unc-13 and sbt-1 in Caenorhabditis elegans. Methods The lifespan, the speed of pharynx pumping, and the intestinal autofluorescence of unc-13 and sbt-1 mutants were examined at different temperature conditions. In addition, to exclude the possible influences from other factors in unc-13 and sbt-1 mutants, the dauer formation, the thermotaxis, the brood size and the population percentage of the mutants expressing hsp16.2-gfp were further investigated. Results Mutations of unc-13 and sbt-1 significantly increased the mean and the maximum lifespans of nematodes cultured at 20 oC and 25 oC, while no noticeable increase was found at 15 oC in either the mean or the maximum lifespan. Investigations on the speed of pharynx pumping and the intestinal autofluorescence suggested that at 20 oC and 25 oC, mutations of unc-13 and sbt-1 could slow the aging process and delay the accumulation of aging-related cellular damage. Meanwhile, mutations of unc-13 or sbt-1 did not affect the dauer formation or the thermotaxis to different temperatures in nematodes. In contrast, at 20 oC and 25 oC conditions, mutations of unc-13 and sbt-1 significantly decreased the brood size and the percentage of nematodes expressing hsp16.2-gfp, while no such differences were detected at 15 oC. Moreover, the thermotolerance of unc-13 and sbt-1 mutants could be greatly strengthened after the 16-h heat shock at 35 oC. Conclusion The regulation of aging by unc-13 and sbt-1 is temperature-dependent. And the alterations in reproduction capability and stress response may be associated with the formation of this temperature-dependent property.
基金Supported by the National Natural Science Foundation of China under Grant No 11574253the Scientific and Technological Research Program of Chongqing Municipal Education Commission under Grant Nos KJ1601111 and KJ1601118the Basic and Frontier Research Projects of Chongqing under Grant No cstc2015jcyjA40054
文摘The shot-range interaction and the atomic anharmonic vibration are both considered, and then the analytic functions of the Debye temperature, the specific capacity and the thermal conductivity of graphene with the temperature are obtained. The influence of anharmonic vibration on these thermal physical properties is also investigated. Some theoretical results are given. If only the harmonic approximation is considered, the Debye temperature of the graphene is unrelated to the temperature. If the anharmonic terms are considered, it increases slowly with the increasing temperature. The molar heat capacity of the graphene increases nonlinearly with the increasing temperature. The mean free path of phonons and the thermal conductivity of the graphene decrease nonlinearly with the increasing temperature. The relative changes of the Debye temperature, the specific heat capacity and the thermal conductivity caused by the anharmonic terms increase with the increasing temperature. The anharmonic effect of atomic vibration becomes more significant under higher temperature.
基金supported by the International Science and Technology Cooperation Program of Science and Technology Bureau of Changchun City,China(Grant No.12ZX68)
文摘Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films＇ exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I（3-x）Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.
基金supported by the National Natural Science Foundation of China(Nos.11372123 and 11072101)the Natural Science Foundation of Gansu Province(No.1107RJZA151)+1 种基金the Fundamental Research Funds for the Universities of GansuHong-Liu Excellent Talents Program of Lanzhou University of Technology
文摘Based on the generalized thermoelasticity proposed by Green and Lindsay, the dynamic response of generalized thermoelastic problems with temperature-dependent material properties is investigated. The governing equations are formulated and found to be nonlinear because of the temperature-dependence of properties. Owing to the nonlinearity of the governing equations, the finite element method is resorted to for solution. The results obtained show that the temperature-dependent properties influence the variables considered by reducing their magnitudes. This indicates that taking the temperature-dependence of properties into consideration in the investigation of generalized thermoelastic problems is necessary and practical for accurately predicting the thermoelastic behavior.
文摘This work focuses on transient thermal behavior of radial fins of rectangular,triangular and hyperbolic profiles with temperature-dependent properties.A hybrid numerical algorithm which combines differential transformation(DTM) and finite difference(FDM) methods is utilized to theoretically study the present problem.DTM and FDM are applied to the time and space domains of the problem,respectively.The accuracy of this method solution is checked against the numerical solution.Then,the effects of some applicable parameters were studied comparatively.Since a broad range of governing parameters are investigated,the results could be useful in a number of industrial and engineering applications.
基金sponsored by the National Natural Science Foundation of China(Nos.21802095,11805261)Shanghai Sailing Program(No.19YF1458200)+1 种基金the China Postdoctoral Science Foundation(No.2017M621468)the Joint Funds of the National Natural Science Foundation of China(No.U1832152)。
文摘The temperature-dependent structural changes in 1-butyl-3-methylimidazolium tetrafluoride([Bmim]FeCl4)magnetic ionic liquid(MIL)were investigated by using in-situ X-ray absorption fine structure(XAFS)combined with Raman spectroscopy and DFT calculations.XAFS re sults revealed that the coordination number and bond length of Fe-Cl in the anion of[Bmim]FeCl4 MIL decreased with increments in temperature.These results directly reflected the dissociation of tetrahedral structure[FeCl4]^-,and the formation of bridge-chain[Fe2 Cl5]^+,and[FeCl2]^+species in the anion of[Bmim]FeCl4 MIL.These behaviors indicated that[FeCl4]^-dissociation was endothermic,and was promoted by increased temperature.The results obtained through XAFS were in agreement with those obtained through Raman spectroscopy and DFT calculations.
基金Project(2012CB026205)supported by the National Basic Research Program of ChinaProjects(51608264,51778289)supported by the National Natural Science Foundation of ChinaProject(2014Y01)supported by the Transportation Science and Technology Project of Jiangsu Province,China
文摘An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2-D)thermo-elasticity theory.Firstly,the beam was divided into a series of layers with uniform material properties along the interfaces of the beam.The uniform thermo-load acted on each layer was transformed into a combination of the normal surface forces acted at the two ends and the transverse thermo-load.Secondly,the state space method was employed to obtain the general solutions of displacements and stresses in an arbitrary layer.Thirdly,based on the interfacial continuity conditions between adjacent layers,the relations of displacement and stress components between the top and bottom layers of the beam were recursively derived by use of the transfer-matrix method.The unknowns in the solutions can be solved by the mechanical loads acted on the top and bottom surfaces.The convergence of the present solutions was checked.The comparative study of the present solutions with the Timoshenko’s solutions and the finite element(FE)solutions was carried out.The effects of material properties variable with temperature on the thermo-elastic behavior of laminated beams were discussed in detail.
基金supported by National Natural Science Foundation of China(Nos.60571031,60501009 and 90406023)National Basic Research Program of China(Nos.2006CB933206 and 2006CB705602).
文摘Highly luminescent water-soluble CdTe quantum dots （QDs） have been synthesized with an electrogenerated precursor. The obtained CdTe QDs can possess good crystallizability, high quantum yield （QY） and favorable stability. Furthermore, a detection system is designed firstly for the investigation of the temperature-dependent PL of the QDs. ？2009 Yu Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
基金Project supported by the National Key R&D Program of China(Grant No.2016YFA0200503)the National Natural Science Foundation of China(Grant No.61327813)
文摘We demonstrate transitions of hopping behaviors for delocalized electrons through the discrete dopant-induced quantum dots in n-doped silicon junctionless nanowire transistors by the temperature-dependent conductance characteristics.There are two obvious transition platforms within the critical temperature regimes for the experimental conductance data,which are extracted from the unified transfer characteristics for different temperatures at the gate voltage positions of the initial transconductance gm peak in Vg1 and valley in Vg2. The crossover temperatures of the electron hopping behaviors are analytically determined by the temperature-dependent conductance at the gate voltages Vg1 and Vg2. This finding provides essential evidence for the hopping electron behaviors under the influence of thermal activation and long-range Coulomb interaction.
基金acknowledge thorough support from the Global COE program from the Ministry of Education, Culture, Sports and Technology (MEXT) of Japan
文摘A series of linear stability analysis is carried out on the onset of thermal convection in the presence of spatial variations of viscosity, thermal conductivity and expansivity. We consider the temporal evolution of an infinitesimal perturbation superimposed to a static （motionless） and con- ductive state in a basally-heated planar layer. From the changes in flow patterns with increasing the amplitudes of temperature dependence of viscosity, we identified the transition into the ＂stagnant-lid＂ （ST） regime, where the convection occurs only beneath a thick and stagnant-lid of cold fluid at the top surface. Detailed analysis showed a significant increase of the aspect ratio of convection cells in ST regime induced by the spatial variations in thermal conductivity and/or expansivity： the horizon- tal length scale of ST convection can be enlarged by up to 50% with 10 times increase of thermal conductivity with depth. We further developed an analytical model of ST convection which success- fully reproduced the mechanism of increasing horizontal length scale of ST regime convection cells for given spatial variations in physical properties. Our findings may highlight the essential roles of the spatial variation of thermal conductivity on the convection patterns in the mantle.
