The reduced-activation ferritic/martensitic(RAFM)steel CLF-1 has been designed as a candidate structural material for nuclear fusion energy reactors.For engineering mechanical design,the effects of temperature on the ...The reduced-activation ferritic/martensitic(RAFM)steel CLF-1 has been designed as a candidate structural material for nuclear fusion energy reactors.For engineering mechanical design,the effects of temperature on the strain distribution of CLF-1 steel during uniaxial tensile tests were explored within the temperature range from room temperature to 650°C using uniaxial tensile tests combined with in situ digital image correlation analysis.Strain-concentrated regions alternately distributed±45°along the tensile direction could be attributed to the shear stress having the maximum value at±45°along the tensile direction and the coordinated deformation of the microstructure.The total strain distribution changed from a normal distribution to a lognormal distribution with increasing deformation owing to the competition between the elastic and plastic strains at all test temperatures.Strain localization has a strong relationship with temperature at the same engineering strain because of the temperature effects on dynamic strain aging(DSA).The stronger the DSA effect,the stronger the strain localization.With increasing temperature,the stronger the strain localization at the same strain,the weaker the plasticity,that is,DSA-induced embrittlement,and the slower the strength decline,that is,DSA-induced hardening.展开更多
Employing variational method of Pekar type(VMPT), this paper investigates the first-excited state energy(FESE), excitation energy and transition frequency of the strongly-coupled polaron in the Cs I quantum pseudodot(...Employing variational method of Pekar type(VMPT), this paper investigates the first-excited state energy(FESE), excitation energy and transition frequency of the strongly-coupled polaron in the Cs I quantum pseudodot(QPD)with electric field. The temperature effects on the strong-coupling polaron in electric field are calculated by using the quantum statistical theory(QST). The results from the present investigation show that the FESE, excitation energy and transition frequency increase(decrease) firstly and then at lower(higher) temperature regions. They are decreasing functions of the electric field strength.展开更多
The temperature and the size dependences of the self-trapping energy of a polaron in a GaAs parabolic quantum dot are investigated by the second order Rayleigh-Schrodinger perturbation method using the framework of th...The temperature and the size dependences of the self-trapping energy of a polaron in a GaAs parabolic quantum dot are investigated by the second order Rayleigh-Schrodinger perturbation method using the framework of the effective mass approximation. The numerical results show that the self-trapping energies of polaron in GaAs parabolic quantum dots shrink with the enhancement of temperature and the size of the quantum dot. The results also indicate that the temperature effect becomes obvious in small quantum dots展开更多
The influence of high temperature effects on the protrusion of Mach stem in strong shock reflection over a wedge was numerically investigated. A two-dimensional inviscid solver applies finite volume method and unstruc...The influence of high temperature effects on the protrusion of Mach stem in strong shock reflection over a wedge was numerically investigated. A two-dimensional inviscid solver applies finite volume method and unstructured quadrilateral grids were employed to simulate the flow. Theoretical analysis was also conducted to understand the phenomenon. Both numerical and theoretical results indicate a wall-jet penetrating forward is responsible for the occurrence of Mach stem protrusion. The protrusion degree seems to depend on the thermal energy buffer capacity of the testing gas. Approaches to increase the energy buffer capacity, such as vibrational relaxation, molecular dissociation, and increase of frozen heat caoacitv, all tend to escalate the orotrusion effect.展开更多
The temperature effects on the photoluminescence(PL) properties of porous silicon(PS) have been observed in the early stage. However, the obtained results are different. Through repeated experiments, some different an...The temperature effects on the photoluminescence(PL) properties of porous silicon(PS) have been observed in the early stage. However, the obtained results are different. Through repeated experiments, some different and useful information are got, which benefits us in that PL properties of porous silicon can be fully made use of. Firstly, samples with porosity of 76% and 49% were chosen to study the exciting temperature effects on the PL spectrum. For the samples with low porosity, the decreasing temperature causes the peak wavelength to be red-shifting and that of the samples with high porosity to present the blue-shifting trend. The light intensity of both reaches the maximum at -10℃. These experimental results can be well explained with the synthesized center PL model based on the quantum confinement model, other than the PL efficiency function σ(λ). Thereafter, PL properties of PS samples fabricated separately under the temperature of -10℃, 0℃, 10℃, 20℃ and 30℃ were studied. The results indicate that with the decrease of the etching temperature, the PL intensity increases from 406.7 to 716.6 and the peak wavelength blue-shifts from 698.9nm to 671.8nm. The WHFM of the PL spectrum dramatically narrows. At the same time, the images observed by AFM show that with the decreasing temperature, the holes are becoming deeper and the porosity is higher, which suggests that the decreasing temperature accelerates the etching rate.展开更多
Recent experimental and theoretical studies show that energy efficiency, which measures the amount of infor- mation processed by a neuron with per unit of energy consumption, plays an important role in the evolution o...Recent experimental and theoretical studies show that energy efficiency, which measures the amount of infor- mation processed by a neuron with per unit of energy consumption, plays an important role in the evolution of neural systems. Here we calculate the information rates and energy efficieneies of the Hodgkin-Huxley （HH） neuron model at different temperatures in a noisy environment. It is found that both the information rate and energy efficiency are maximized by certain temperatures. Though the information rate and energy efficiency cannot be maximized simultaneously, the neuron holds a high information processing capacity at the tempera- ture corresponding to the maximal energy efficiency. Our results support the idea that the energy efficiency is a selective pressure that influences the evolution of nervous systems.展开更多
Finite element simulations were conducted to explore the effects of high temperatures on the loading capacity of slab-column connection for the concrete flat-plate structures by the finite element analysis software AB...Finite element simulations were conducted to explore the effects of high temperatures on the loading capacity of slab-column connection for the concrete flat-plate structures by the finite element analysis software ABAQUS.The structure used for the simulation is a slab which thickness is 150 mm with a 300 mm square column in the middle of slab,the column height is 450mm.The size of this slab is the same as experiments conducted by previous paper[1].Based on the results of simulation,the punching capacity of this structure not experienced high temperature can be predicted with very good accuracy.But the result from simulations underestimated the loading capacity of the structure after it has been cooled by around 10%.This phenomenon is a little bit conflicts with the known experimental results,however,it can be adjusted by modify the material parameters built-in the software.This article is focus on how to best simulate the concrete behavior for both linear and nonlinear part under the room temperature and cooling after experience a very high temperature.展开更多
Seasonal variation of stable isotopes in precipitation of Kathmandu Valley on the southem slope of Himalaya was carried out to understand the controlling mechanism of amount and temperature effect on the basis of one ...Seasonal variation of stable isotopes in precipitation of Kathmandu Valley on the southem slope of Himalaya was carried out to understand the controlling mechanism of amount and temperature effect on the basis of one year stable isotope data from 2010 to 2011. Highly depleted isotope values in major rainy period are obtained just after the onset of precipitation in summer, which ac- counts for ＂amount effect＂ due to saturation isotopic compositions in high moisture condition, whereas, the higher values in winter are indicative to regional vapors （temperature effect） recycling of various sources. An abrupt depletion of isotope values in mid- June, indicates the onset date of monsoon precipitation, by the replacement of winter air mass with southem monsoon. Thus, pre- cipitation isotopes are a tool revealing the onset date of summer monsoon and temporal features of variability, in local and regional monsoons precipitations. A comparison of long term monthly values of 5180, temperature, and precipitation with GNIP 6180 data shows the temporal variations of stable isotopes are mostly controlled by amount and temperature effects. During summer mon- soon, the amount effects are stronger for high values of precipitation （R=0.7） and altitude effect appears for low moisture in late rainy season, thus from December to June （winter to pre-monsoon） the controlling features of isotopes remains under the temper- ature effect. A temporal rate of temperature effect is derived as 0.04%0 per year which indicates a dry signal of atmospheric condition and a temperature relation 5180=（0.371±0.08）T＋（0.156±0.05） is obtained from this analysis. The meteoric water lines of Kathmandu before and after monsoon onset of 2011, are found as 5D=（4.36±0.3）5180＋（15.66±1.2） and 5D=（6.91±0.2）S180-（7.92±2.26） from lab samples result, and 5D=9.25180＋11.725 and 5D=8.535180＋16.65 from GNIP data, which lacks the consistency both for slopes and intercepts values for the study period. The mean lapse rate values of δ18O and δD from GNIP data are obtained as -0.002‰/m and -0.015 ‰/m, which indicate the altitudinal effects in regional precipitation of the southern slope of Himalayas. This study estimates new stable isotopes data in recent precipitation using simple methodology which can be important for regional precipitation monitoring systems, environmental change and paleo-climatic studies.展开更多
On the condition of electric-LO phonon strong coupling in a parabolic quantum dot,we obtain theeigenenergy and the eigenfunctions of the ground state and the first-excited state using the variational method ofPekar ty...On the condition of electric-LO phonon strong coupling in a parabolic quantum dot,we obtain theeigenenergy and the eigenfunctions of the ground state and the first-excited state using the variational method ofPekar type.This system in a quantum dot may be employed as a two-level quantum system-qubit.When the electronis in the superposition state of the ground state and the first-excited state,we obtain the time evolution of the electrondensity.The relations of the probability density of electron on the temperature and the electron-LO-phonon couplingconstant and the relations of the period of oscillation on the temperature,the electron-LO-phonon coupling constant,the Coulomb binding parameter and the confinement length are derived.The results show that the probability densityof electron oscillates with a period when the electron is in the superposition state of the ground and the first-excitedstate,and show that there are different laws that the probability density of electron and the period of oscillation changewith the temperature and the electron-LO-phonon coupling constant when the temperature is lower or higher.Andit is obtained that the period of oscillation decreases with increasing the Coulomb bound potential and increases withincreasing the confinement length not only at lower temperatures but also at higher temperatures.展开更多
High geothermal temperatures appear to be unfavorable for the construction of tunnels in slate rocks with high overburden. To investigate the mechanical characteristics of slates at various levels of geothermal temper...High geothermal temperatures appear to be unfavorable for the construction of tunnels in slate rocks with high overburden. To investigate the mechanical characteristics of slates at various levels of geothermal temperature, conventional triaxial compression tests at different levels of confining stress were carried out at 4 different temperatures from 20℃ to 120℃. The obtained results show high confining pressures weaken the thermal effects on rock mechanical characteristics while higher temperatures enhance the effect of confining pressure.At higher levels of confining stress the thermal effects on the rock strength characteristics decrease. The higher the temperature, the larger is the effect of confining pressure on the mechanical characteristics of the slate. Increase of temperature leads to a decrease of the peak strength but increases the deformability and ductility of the slate, the thermo effect on the peak strength and Poisson's ratio is larger than on the elastic modulus. Higher temperatures reduce the shear strength of slate, the decrease is mainly caused by a decrease of the cohesion. In general, the slate samples fail in shear failure.展开更多
Based on the test results obtained from the single-step test and the incremental-step test at room temperature and 240℃, a probabilistic assessment of temperature effects on the cyclic stress-strum response and the f...Based on the test results obtained from the single-step test and the incremental-step test at room temperature and 240℃, a probabilistic assessment of temperature effects on the cyclic stress-strum response and the fatigue life of 1Cr18Ni9Ti steel weld metal is performed. In orber to assess the temperature effect on cyclic stress amplitude where there is a scatter of the material cyclic constitution, a probabilistic assessment approach on the basis of probabilistic modified Ramberg-Osgood relations is introduced.The investigation shows that the cyclic stress amplitude and the scatter of cyclic stress amplitude data are decreased at 240℃. Similarly, from the consideration of the fatigue life scatter a probabilistic assessment of temperature effect on the fatigue life is suggested on the basis of probabilistic Langer S-N relations. The investigation shows that the crack initiation life is increased and the scatter of crack initiation life data is decreased at 240℃.展开更多
In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to character...In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to characterize the strength of the backfill. However, the actual working temperature of slopes varies, and natural phenomena such as rainfall and groundwater infiltration commonly result in unsaturated soil conditions, with cracks typically present in cohesive slopes. This study introduces a novel approach for assessing the stability of unsaturated soil stepped slopes under varying temperatures, incorporating the effects of open and vertical cracks. Utilizing the kinematic approach and gravity increase method, we developed a three-dimensional (3D) rotational wedge failure mechanism to simulate slope collapse, enhancing the traditional two-dimensional analyses. We integrated temperature-dependent functions and nonlinear shear strength equations to evaluate the impact of temperature on four typical unsaturated soil types. A particle swarm optimization algorithm was employed to calculate the safety factor, ensuring our method’s accuracy by comparing it with existing studies. The results indicate that considering 3D effects yields a higher safety factor, while cracks reduce slope stability. Each unsaturated soil exhibits a distinctive temperature response curve, highlighting the importance of understanding soil types in the design phase.展开更多
The temperature effect of rock failure has primarily focused on high temperature and large temperature gradients.However,the temperature range of engineered rocks in high ground temperature tunnel is generally within ...The temperature effect of rock failure has primarily focused on high temperature and large temperature gradients.However,the temperature range of engineered rocks in high ground temperature tunnel is generally within 100℃.For this,this study conducts real-time thermomechanical coupling tests with small temperature gradient within the engineering temperature.We analyzed rock mechanical parameter,rock failure characteristics,and acoustic emission(AE)and energy characteristics.The results indicate that the strength,peak strain,elastic modulus,and peak energy storage of sandstone decrease with increasing temperature.The peak AE count of sandstone in triaxial test at high temperature decreases with increasing temperature.The RA(Rising time/Amplitude)and AF(Average frequency)parameters associated with the AE signals indicate that the shear and tensile cracks are produced almost simultaneously throughout the rock failure process with increasing temperature.The PFC(particle flow code)simulation results show that the crack number of PBM(parallel bond model)specimen at high σ_(3) is significantly higher than that at low σ_(3) and the cracks number difference under high and low σ_(3) also rises as the temperature increases.Finally,the strength attenuation characteristics are explained by the competition and coupling action of temperature and σ_(3).This paper provides theoretical insights into rock failure mechanisms under thermomechanical coupling related to underground engineering.展开更多
Diamond is a promising semiconductor material for future space exploration,owing to its unique atomic and electronic structures.However,diamond materials and related devices still suffer from irradiation damage under ...Diamond is a promising semiconductor material for future space exploration,owing to its unique atomic and electronic structures.However,diamond materials and related devices still suffer from irradiation damage under space irradiation involving high-energy irradiating particles.The study of the generation and evolution of point defects can help understand the irradiation damage mechanisms in diamond.This study systematically investigated the defect dynamics of diamond in 162 crystallographic directions uniformly selected on a spherical surface using molecular dynamics simulations,with primary knock-on atom(PKA)energies up to 20 keV,and temperatures ranging from 300 K to 1800 K.The results reveal that the displacement threshold energy of diamond changes periodically with crystallographic directions,which is related to the shape of potential energy surface along that direction.Additionally,the number of residual defects correlates positively with PKA energy.However,temperature has dual competing effects:while it enhances the probability of atomic displacement,it simultaneously suppresses the probability of defect formation by accelerating defect recombination.The calculation of sparse radial distribution function indicates that the defect distribution shows a certain degree of similarity in the short-range region across different PKA energies.As the PKA energy increases,defect clusters tend to become larger in size and more numerous in quantity.This study systematically investigates the anisotropy of displacement threshold energy and elucidates the relationship between various irradiation conditions and the final states of irradiation-induced defects.展开更多
The design scheme of a sandwich-structure betavoltaic microbattery based on silicon using63Ni is presented in this paper.This structure differs from a monolayer energy conversion unit.The optimization of various physi...The design scheme of a sandwich-structure betavoltaic microbattery based on silicon using63Ni is presented in this paper.This structure differs from a monolayer energy conversion unit.The optimization of various physical parameters and the effects of temperature on the microbattery were studied through MCNP.For the proposed optimization design,P-type silicon was used as the substrate for the betavoltaic microbattery.Based on the proposed theory,a sandwich microbattery with a shallow junction was fabricated.The temperature dependence of the device was also measured.The open-circuit voltaic(Voc)temperature dependence of the optimized sandwich betavoltaic microbattery was linear.However,the Voc of the betavoltaic microbattery with a high-resistance substrate exponentially decreased over the range of room temperature in the experiment and simulation.In addition,the sandwich betavoltaic microbattery offered higher power than the monolayer betavoltaic one.The results of this paper provide a significant technical reference for optimizing the design and studying temperature effects on betavoltaics of the same type.展开更多
The temperature-induced variation in operating force of flow control valves may result in performance degradation or even jam faults of fuel metering unit(FMU), which significantly affects the safety of aircrafts. In ...The temperature-induced variation in operating force of flow control valves may result in performance degradation or even jam faults of fuel metering unit(FMU), which significantly affects the safety of aircrafts. In this work, an analytical modeling approach of temperature-sensitive operating-force of servo valve is proposed to investigate the temperature characteristics in varying temperature conditions. Considering the temperature effects, a new extended model of flow force is built and an analytical model of valve friction is also derived theoretically based on the dynamic clearance induced by thermal effects. The extremum condition of friction is obtained to analyze the characteristic-temperature points where jam faults occur easily. The numerical results show that flow force increases firstly and then decreases as temperature increases under a constant valve opening. The maximum friction of flow servo valve can be uniquely determined when the structural parameters and ambient temperature are given. The worst situation just happens at the characteristic-temperature points, which are linearly related to the axial temperature gradients of valve spool. Such evaluations may give an explanation for the temperature-induced jam faults of vulnerable valves and provide a reference for designers to determine a suitable workingtemperature range of valves in practice.展开更多
At present, the most researches on the protected effect of shelterbelt are on the basis of the two scales of forest belts and networks. However, with the further research on the global environmental change, more atten...At present, the most researches on the protected effect of shelterbelt are on the basis of the two scales of forest belts and networks. However, with the further research on the global environmental change, more attention was paid to the regional climate effect of shelterbelt. In present study, we analyzed the temperature effect of the shelterbelt at regional scale by using the land surface temperature （LST） data from the moderate resolution imaging spectroradiometer （MODIS） at Yushu, Nong＇an, Dehui, and Fuyu in Jilin Province of China from March to October in 2008. Results show that the shelterbelt can increase the soil temperature of the protected farmland as compared with no shelterbelt zone, with the increment of 0.57oC per day in fine shelterbelt and 0.38oC per day in the normal shelterbelt. Moreover, the correlation analysis of the air temperature, precipitation and the soil type and the shelterbelt effect shows that the air temperature and precipitation are negatively correlated with the shelterbelt effects, that is, the more the temperature and precipitation are, the less the effect produced. While the impact of the soil types on the shelterbelt＇s effect is not very obvious as a whole. This paper draws significance in terms of analyzing the effects of the shelterbelt on the soil temperature at regional scale utilizing the remotely sensed data and GIS technique.展开更多
Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introdu...Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical tests.Under a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 MPa.and the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 MPa.The temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test results.We point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part permeability.Furthermore,we discuss the effect of temperature on the two parts in the rock.The results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective stress.Considering that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.展开更多
The armyworm Mythimna roseilinea（Walker） is a major pest of grain crops in South China. So far little is known about its basic biology and ecology, making prediction of population dynamics difficult. This study exam...The armyworm Mythimna roseilinea（Walker） is a major pest of grain crops in South China. So far little is known about its basic biology and ecology, making prediction of population dynamics difficult. This study examined the relationships of individual development and population growth with temperature based on an age-stage, two-sex life table of M. roseilinea reared on maize in the laboratory at 18, 21, 24, 27 and 30℃. The highest values of net reproductive rate（R_0） and fecundity were observed at 21 and 24℃, respectively. Both the intrinsic rate of increase（r） and finite rate of increase（λ） increased significantly and mean generation time（T） decreased significantly with increasing temperature. M. roseilinea was able to develop, survive and lay eggs at all temperature regimes tested. Development rates of the egg, larval, pupal, as well as the whole pre-oviposition stages had a positive linear relationship with temperature. The calculated development threshold temperatures of egg, larval, pupal, pre-oviposition and total pre-oviposition stages were 13.29, 8.39, 14.35, 7.42, and 12.24℃, respectively, and their effective accumulated temperatures were 63.59, 445.00, 211.11, 89.02, and 698.95 degree-days, respectively. These results provide insight into temperature-based phenology and population ecology of this insect pest and will allow population prediction and management available in the field.展开更多
To study the dynamic properties of the concrete subjected to impulsive loading, stress-time curves of concrete in different velocities were measured using split Hopkinson pressure bar (SHPB).Effects of temperature and...To study the dynamic properties of the concrete subjected to impulsive loading, stress-time curves of concrete in different velocities were measured using split Hopkinson pressure bar (SHPB).Effects of temperature and strain rate on the dynamic yield strength and constitutive relation of the con-crete were analyzed. The dynamic mechanical properties of the reinforced concrete are subjected to high strain rates when it is at a relatively low temperature. But with temperature increasing, the temperature softening effect makes the strength of the concrete weaken and the impact toughness of the concrete is saliently relative to strain rate effect. So, strain rate effect, strain hardening and temperature softening work together on the dynamic mechanical capability of concrete and the relation between them is relatively complex.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12175231 and 11805131)Anhui Natural Science Foundation of China(No.2108085J05)the Collaborative Innovation Program of Hefei Science Center,CAS(No.2022HSC-CIP009)。
文摘The reduced-activation ferritic/martensitic(RAFM)steel CLF-1 has been designed as a candidate structural material for nuclear fusion energy reactors.For engineering mechanical design,the effects of temperature on the strain distribution of CLF-1 steel during uniaxial tensile tests were explored within the temperature range from room temperature to 650°C using uniaxial tensile tests combined with in situ digital image correlation analysis.Strain-concentrated regions alternately distributed±45°along the tensile direction could be attributed to the shear stress having the maximum value at±45°along the tensile direction and the coordinated deformation of the microstructure.The total strain distribution changed from a normal distribution to a lognormal distribution with increasing deformation owing to the competition between the elastic and plastic strains at all test temperatures.Strain localization has a strong relationship with temperature at the same engineering strain because of the temperature effects on dynamic strain aging(DSA).The stronger the DSA effect,the stronger the strain localization.With increasing temperature,the stronger the strain localization at the same strain,the weaker the plasticity,that is,DSA-induced embrittlement,and the slower the strength decline,that is,DSA-induced hardening.
基金Supported by the National Natural Science Foundation of China under Grant No.11464033
文摘Employing variational method of Pekar type(VMPT), this paper investigates the first-excited state energy(FESE), excitation energy and transition frequency of the strongly-coupled polaron in the Cs I quantum pseudodot(QPD)with electric field. The temperature effects on the strong-coupling polaron in electric field are calculated by using the quantum statistical theory(QST). The results from the present investigation show that the FESE, excitation energy and transition frequency increase(decrease) firstly and then at lower(higher) temperature regions. They are decreasing functions of the electric field strength.
文摘The temperature and the size dependences of the self-trapping energy of a polaron in a GaAs parabolic quantum dot are investigated by the second order Rayleigh-Schrodinger perturbation method using the framework of the effective mass approximation. The numerical results show that the self-trapping energies of polaron in GaAs parabolic quantum dots shrink with the enhancement of temperature and the size of the quantum dot. The results also indicate that the temperature effect becomes obvious in small quantum dots
文摘The influence of high temperature effects on the protrusion of Mach stem in strong shock reflection over a wedge was numerically investigated. A two-dimensional inviscid solver applies finite volume method and unstructured quadrilateral grids were employed to simulate the flow. Theoretical analysis was also conducted to understand the phenomenon. Both numerical and theoretical results indicate a wall-jet penetrating forward is responsible for the occurrence of Mach stem protrusion. The protrusion degree seems to depend on the thermal energy buffer capacity of the testing gas. Approaches to increase the energy buffer capacity, such as vibrational relaxation, molecular dissociation, and increase of frozen heat caoacitv, all tend to escalate the orotrusion effect.
文摘The temperature effects on the photoluminescence(PL) properties of porous silicon(PS) have been observed in the early stage. However, the obtained results are different. Through repeated experiments, some different and useful information are got, which benefits us in that PL properties of porous silicon can be fully made use of. Firstly, samples with porosity of 76% and 49% were chosen to study the exciting temperature effects on the PL spectrum. For the samples with low porosity, the decreasing temperature causes the peak wavelength to be red-shifting and that of the samples with high porosity to present the blue-shifting trend. The light intensity of both reaches the maximum at -10℃. These experimental results can be well explained with the synthesized center PL model based on the quantum confinement model, other than the PL efficiency function σ(λ). Thereafter, PL properties of PS samples fabricated separately under the temperature of -10℃, 0℃, 10℃, 20℃ and 30℃ were studied. The results indicate that with the decrease of the etching temperature, the PL intensity increases from 406.7 to 716.6 and the peak wavelength blue-shifts from 698.9nm to 671.8nm. The WHFM of the PL spectrum dramatically narrows. At the same time, the images observed by AFM show that with the decreasing temperature, the holes are becoming deeper and the porosity is higher, which suggests that the decreasing temperature accelerates the etching rate.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11105062,11275003,11265014 and 11275084the Fundamental Research Funds for the Central Universities under Grant No LZUJBKY-2015-119
文摘Recent experimental and theoretical studies show that energy efficiency, which measures the amount of infor- mation processed by a neuron with per unit of energy consumption, plays an important role in the evolution of neural systems. Here we calculate the information rates and energy efficieneies of the Hodgkin-Huxley （HH） neuron model at different temperatures in a noisy environment. It is found that both the information rate and energy efficiency are maximized by certain temperatures. Though the information rate and energy efficiency cannot be maximized simultaneously, the neuron holds a high information processing capacity at the tempera- ture corresponding to the maximal energy efficiency. Our results support the idea that the energy efficiency is a selective pressure that influences the evolution of nervous systems.
文摘Finite element simulations were conducted to explore the effects of high temperatures on the loading capacity of slab-column connection for the concrete flat-plate structures by the finite element analysis software ABAQUS.The structure used for the simulation is a slab which thickness is 150 mm with a 300 mm square column in the middle of slab,the column height is 450mm.The size of this slab is the same as experiments conducted by previous paper[1].Based on the results of simulation,the punching capacity of this structure not experienced high temperature can be predicted with very good accuracy.But the result from simulations underestimated the loading capacity of the structure after it has been cooled by around 10%.This phenomenon is a little bit conflicts with the known experimental results,however,it can be adjusted by modify the material parameters built-in the software.This article is focus on how to best simulate the concrete behavior for both linear and nonlinear part under the room temperature and cooling after experience a very high temperature.
基金supported by the Ph.D.program of Institute of Tibetan Plateau Research,ITPCAS
文摘Seasonal variation of stable isotopes in precipitation of Kathmandu Valley on the southem slope of Himalaya was carried out to understand the controlling mechanism of amount and temperature effect on the basis of one year stable isotope data from 2010 to 2011. Highly depleted isotope values in major rainy period are obtained just after the onset of precipitation in summer, which ac- counts for ＂amount effect＂ due to saturation isotopic compositions in high moisture condition, whereas, the higher values in winter are indicative to regional vapors （temperature effect） recycling of various sources. An abrupt depletion of isotope values in mid- June, indicates the onset date of monsoon precipitation, by the replacement of winter air mass with southem monsoon. Thus, pre- cipitation isotopes are a tool revealing the onset date of summer monsoon and temporal features of variability, in local and regional monsoons precipitations. A comparison of long term monthly values of 5180, temperature, and precipitation with GNIP 6180 data shows the temporal variations of stable isotopes are mostly controlled by amount and temperature effects. During summer mon- soon, the amount effects are stronger for high values of precipitation （R=0.7） and altitude effect appears for low moisture in late rainy season, thus from December to June （winter to pre-monsoon） the controlling features of isotopes remains under the temper- ature effect. A temporal rate of temperature effect is derived as 0.04%0 per year which indicates a dry signal of atmospheric condition and a temperature relation 5180=（0.371±0.08）T＋（0.156±0.05） is obtained from this analysis. The meteoric water lines of Kathmandu before and after monsoon onset of 2011, are found as 5D=（4.36±0.3）5180＋（15.66±1.2） and 5D=（6.91±0.2）S180-（7.92±2.26） from lab samples result, and 5D=9.25180＋11.725 and 5D=8.535180＋16.65 from GNIP data, which lacks the consistency both for slopes and intercepts values for the study period. The mean lapse rate values of δ18O and δD from GNIP data are obtained as -0.002‰/m and -0.015 ‰/m, which indicate the altitudinal effects in regional precipitation of the southern slope of Himalayas. This study estimates new stable isotopes data in recent precipitation using simple methodology which can be important for regional precipitation monitoring systems, environmental change and paleo-climatic studies.
基金Supported by National Natural Science Foundation of China under Grant No.10747002Research Funds from Qufu Normal University under Grant No.XJZ200839
文摘On the condition of electric-LO phonon strong coupling in a parabolic quantum dot,we obtain theeigenenergy and the eigenfunctions of the ground state and the first-excited state using the variational method ofPekar type.This system in a quantum dot may be employed as a two-level quantum system-qubit.When the electronis in the superposition state of the ground state and the first-excited state,we obtain the time evolution of the electrondensity.The relations of the probability density of electron on the temperature and the electron-LO-phonon couplingconstant and the relations of the period of oscillation on the temperature,the electron-LO-phonon coupling constant,the Coulomb binding parameter and the confinement length are derived.The results show that the probability densityof electron oscillates with a period when the electron is in the superposition state of the ground and the first-excitedstate,and show that there are different laws that the probability density of electron and the period of oscillation changewith the temperature and the electron-LO-phonon coupling constant when the temperature is lower or higher.Andit is obtained that the period of oscillation decreases with increasing the Coulomb bound potential and increases withincreasing the confinement length not only at lower temperatures but also at higher temperatures.
基金supported by National Natural Science Foundation of China(Grant No.41230635)Projects of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Grant No.SKLGP2013Z004)+1 种基金The Cultivating programme of middle-aged backbone teachers of Chengdu University of Technology(Grant No.JXGG201703)Key Projects of Education Department of Sichuan Province(Grant No.16ZA0095)
文摘High geothermal temperatures appear to be unfavorable for the construction of tunnels in slate rocks with high overburden. To investigate the mechanical characteristics of slates at various levels of geothermal temperature, conventional triaxial compression tests at different levels of confining stress were carried out at 4 different temperatures from 20℃ to 120℃. The obtained results show high confining pressures weaken the thermal effects on rock mechanical characteristics while higher temperatures enhance the effect of confining pressure.At higher levels of confining stress the thermal effects on the rock strength characteristics decrease. The higher the temperature, the larger is the effect of confining pressure on the mechanical characteristics of the slate. Increase of temperature leads to a decrease of the peak strength but increases the deformability and ductility of the slate, the thermo effect on the peak strength and Poisson's ratio is larger than on the elastic modulus. Higher temperatures reduce the shear strength of slate, the decrease is mainly caused by a decrease of the cohesion. In general, the slate samples fail in shear failure.
文摘Based on the test results obtained from the single-step test and the incremental-step test at room temperature and 240℃, a probabilistic assessment of temperature effects on the cyclic stress-strum response and the fatigue life of 1Cr18Ni9Ti steel weld metal is performed. In orber to assess the temperature effect on cyclic stress amplitude where there is a scatter of the material cyclic constitution, a probabilistic assessment approach on the basis of probabilistic modified Ramberg-Osgood relations is introduced.The investigation shows that the cyclic stress amplitude and the scatter of cyclic stress amplitude data are decreased at 240℃. Similarly, from the consideration of the fatigue life scatter a probabilistic assessment of temperature effect on the fatigue life is suggested on the basis of probabilistic Langer S-N relations. The investigation shows that the crack initiation life is increased and the scatter of crack initiation life data is decreased at 240℃.
基金Project(51378510) supported by the National Natural Science Foundation of China。
文摘In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to characterize the strength of the backfill. However, the actual working temperature of slopes varies, and natural phenomena such as rainfall and groundwater infiltration commonly result in unsaturated soil conditions, with cracks typically present in cohesive slopes. This study introduces a novel approach for assessing the stability of unsaturated soil stepped slopes under varying temperatures, incorporating the effects of open and vertical cracks. Utilizing the kinematic approach and gravity increase method, we developed a three-dimensional (3D) rotational wedge failure mechanism to simulate slope collapse, enhancing the traditional two-dimensional analyses. We integrated temperature-dependent functions and nonlinear shear strength equations to evaluate the impact of temperature on four typical unsaturated soil types. A particle swarm optimization algorithm was employed to calculate the safety factor, ensuring our method’s accuracy by comparing it with existing studies. The results indicate that considering 3D effects yields a higher safety factor, while cracks reduce slope stability. Each unsaturated soil exhibits a distinctive temperature response curve, highlighting the importance of understanding soil types in the design phase.
基金supported by the National Natural Science Foundation of China(Grant Nos.42107211 and 42130719)the Natural Science Foundation of Sichuan Province(Grant No.2025ZNSFSC0097).
文摘The temperature effect of rock failure has primarily focused on high temperature and large temperature gradients.However,the temperature range of engineered rocks in high ground temperature tunnel is generally within 100℃.For this,this study conducts real-time thermomechanical coupling tests with small temperature gradient within the engineering temperature.We analyzed rock mechanical parameter,rock failure characteristics,and acoustic emission(AE)and energy characteristics.The results indicate that the strength,peak strain,elastic modulus,and peak energy storage of sandstone decrease with increasing temperature.The peak AE count of sandstone in triaxial test at high temperature decreases with increasing temperature.The RA(Rising time/Amplitude)and AF(Average frequency)parameters associated with the AE signals indicate that the shear and tensile cracks are produced almost simultaneously throughout the rock failure process with increasing temperature.The PFC(particle flow code)simulation results show that the crack number of PBM(parallel bond model)specimen at high σ_(3) is significantly higher than that at low σ_(3) and the cracks number difference under high and low σ_(3) also rises as the temperature increases.Finally,the strength attenuation characteristics are explained by the competition and coupling action of temperature and σ_(3).This paper provides theoretical insights into rock failure mechanisms under thermomechanical coupling related to underground engineering.
基金supported by the Science and Technology Innovation Program of Hunan Province,China(Grant No.2021RC4026)the National Natural Science Foundation of China(Grant Nos.12204538,12104507,and 92365203)Hunan Provincial Science Fund for Distinguished Young Scholars(Grant No.2022JJ10060).
文摘Diamond is a promising semiconductor material for future space exploration,owing to its unique atomic and electronic structures.However,diamond materials and related devices still suffer from irradiation damage under space irradiation involving high-energy irradiating particles.The study of the generation and evolution of point defects can help understand the irradiation damage mechanisms in diamond.This study systematically investigated the defect dynamics of diamond in 162 crystallographic directions uniformly selected on a spherical surface using molecular dynamics simulations,with primary knock-on atom(PKA)energies up to 20 keV,and temperatures ranging from 300 K to 1800 K.The results reveal that the displacement threshold energy of diamond changes periodically with crystallographic directions,which is related to the shape of potential energy surface along that direction.Additionally,the number of residual defects correlates positively with PKA energy.However,temperature has dual competing effects:while it enhances the probability of atomic displacement,it simultaneously suppresses the probability of defect formation by accelerating defect recombination.The calculation of sparse radial distribution function indicates that the defect distribution shows a certain degree of similarity in the short-range region across different PKA energies.As the PKA energy increases,defect clusters tend to become larger in size and more numerous in quantity.This study systematically investigates the anisotropy of displacement threshold energy and elucidates the relationship between various irradiation conditions and the final states of irradiation-induced defects.
基金supported by the National Natural Science Foundation of China(Grant No.11205088)the Aeronautical Science Foundation of China(Grant No.2012ZB52021)+1 种基金the Funding of Jiangsu Innovation Program for Graduate Education(Grant No.CXZZ12_0146)Fundamental Research Funds for the Central Universities
文摘The design scheme of a sandwich-structure betavoltaic microbattery based on silicon using63Ni is presented in this paper.This structure differs from a monolayer energy conversion unit.The optimization of various physical parameters and the effects of temperature on the microbattery were studied through MCNP.For the proposed optimization design,P-type silicon was used as the substrate for the betavoltaic microbattery.Based on the proposed theory,a sandwich microbattery with a shallow junction was fabricated.The temperature dependence of the device was also measured.The open-circuit voltaic(Voc)temperature dependence of the optimized sandwich betavoltaic microbattery was linear.However,the Voc of the betavoltaic microbattery with a high-resistance substrate exponentially decreased over the range of room temperature in the experiment and simulation.In addition,the sandwich betavoltaic microbattery offered higher power than the monolayer betavoltaic one.The results of this paper provide a significant technical reference for optimizing the design and studying temperature effects on betavoltaics of the same type.
基金co-supported by the National Science and Technology Major Project of China (Nos. 2017-V-0011-0062,2017-V-0010-0060)National Natural Science Foundation of China (Nos. 51620105010,51875014 and 51575019)+1 种基金Natural Science Foundation of Beijing Municipality of China (No.L171003)Program 111 of China。
文摘The temperature-induced variation in operating force of flow control valves may result in performance degradation or even jam faults of fuel metering unit(FMU), which significantly affects the safety of aircrafts. In this work, an analytical modeling approach of temperature-sensitive operating-force of servo valve is proposed to investigate the temperature characteristics in varying temperature conditions. Considering the temperature effects, a new extended model of flow force is built and an analytical model of valve friction is also derived theoretically based on the dynamic clearance induced by thermal effects. The extremum condition of friction is obtained to analyze the characteristic-temperature points where jam faults occur easily. The numerical results show that flow force increases firstly and then decreases as temperature increases under a constant valve opening. The maximum friction of flow servo valve can be uniquely determined when the structural parameters and ambient temperature are given. The worst situation just happens at the characteristic-temperature points, which are linearly related to the axial temperature gradients of valve spool. Such evaluations may give an explanation for the temperature-induced jam faults of vulnerable valves and provide a reference for designers to determine a suitable workingtemperature range of valves in practice.
基金supported by the Knowledge Innovation Program of the Chinese Academy Sciences (No. KZCX1-YW-08-02-01)National High-tech Research and development Program of China(No. 2006AA10Z227)
文摘At present, the most researches on the protected effect of shelterbelt are on the basis of the two scales of forest belts and networks. However, with the further research on the global environmental change, more attention was paid to the regional climate effect of shelterbelt. In present study, we analyzed the temperature effect of the shelterbelt at regional scale by using the land surface temperature （LST） data from the moderate resolution imaging spectroradiometer （MODIS） at Yushu, Nong＇an, Dehui, and Fuyu in Jilin Province of China from March to October in 2008. Results show that the shelterbelt can increase the soil temperature of the protected farmland as compared with no shelterbelt zone, with the increment of 0.57oC per day in fine shelterbelt and 0.38oC per day in the normal shelterbelt. Moreover, the correlation analysis of the air temperature, precipitation and the soil type and the shelterbelt effect shows that the air temperature and precipitation are negatively correlated with the shelterbelt effects, that is, the more the temperature and precipitation are, the less the effect produced. While the impact of the soil types on the shelterbelt＇s effect is not very obvious as a whole. This paper draws significance in terms of analyzing the effects of the shelterbelt on the soil temperature at regional scale utilizing the remotely sensed data and GIS technique.
基金financially supported by the International Science&Technology Cooperation Program of China(Grant No.2012DFA60760)
文摘Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical tests.Under a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 MPa.and the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 MPa.The temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test results.We point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part permeability.Furthermore,we discuss the effect of temperature on the two parts in the rock.The results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective stress.Considering that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.
基金funded by the Special Fund for Agro-scientific Research in the Public Interest of China (201403031)the China Agriculture Research System (CARS-22)+2 种基金the National Key Research and Development Program of China (2017YFD0201802, 2017YFD0201701)he National Natural Science Foundation of China (31672019, 31371947)the Beijing Natural Science Foundation, China (6172030)
文摘The armyworm Mythimna roseilinea（Walker） is a major pest of grain crops in South China. So far little is known about its basic biology and ecology, making prediction of population dynamics difficult. This study examined the relationships of individual development and population growth with temperature based on an age-stage, two-sex life table of M. roseilinea reared on maize in the laboratory at 18, 21, 24, 27 and 30℃. The highest values of net reproductive rate（R_0） and fecundity were observed at 21 and 24℃, respectively. Both the intrinsic rate of increase（r） and finite rate of increase（λ） increased significantly and mean generation time（T） decreased significantly with increasing temperature. M. roseilinea was able to develop, survive and lay eggs at all temperature regimes tested. Development rates of the egg, larval, pupal, as well as the whole pre-oviposition stages had a positive linear relationship with temperature. The calculated development threshold temperatures of egg, larval, pupal, pre-oviposition and total pre-oviposition stages were 13.29, 8.39, 14.35, 7.42, and 12.24℃, respectively, and their effective accumulated temperatures were 63.59, 445.00, 211.11, 89.02, and 698.95 degree-days, respectively. These results provide insight into temperature-based phenology and population ecology of this insect pest and will allow population prediction and management available in the field.
基金Supported by National Natural Science Foundation of China(No.10602048)
文摘To study the dynamic properties of the concrete subjected to impulsive loading, stress-time curves of concrete in different velocities were measured using split Hopkinson pressure bar (SHPB).Effects of temperature and strain rate on the dynamic yield strength and constitutive relation of the con-crete were analyzed. The dynamic mechanical properties of the reinforced concrete are subjected to high strain rates when it is at a relatively low temperature. But with temperature increasing, the temperature softening effect makes the strength of the concrete weaken and the impact toughness of the concrete is saliently relative to strain rate effect. So, strain rate effect, strain hardening and temperature softening work together on the dynamic mechanical capability of concrete and the relation between them is relatively complex.
