An isothermal section of the Mg-Nd-Gd ternary system at 723 K was established by diffusion triple technique and electron probe microanalysis (EPMA). Mg3Gd and Mg3Nd form a continuous solid solution (Gd,Nd)3Mg, and...An isothermal section of the Mg-Nd-Gd ternary system at 723 K was established by diffusion triple technique and electron probe microanalysis (EPMA). Mg3Gd and Mg3Nd form a continuous solid solution (Gd,Nd)3Mg, and a continuous solid solution (Gd,Nd)Mg is also formed between MgGd and MgNd. Mg7Gd, Mg5Gd, Mg2Gd, Mg41Nd5, (Gd,Nd)3Mg and (Gd,Nd)Mg are found in the ternary system. In these intermetallic phases, Mg7Gd has been reported to be a metastable phase in previous literatures. The solubilities of Mg, Gd and Nd in all the phases were detected. Furthermore, four three-phase equilibria, α(Mg)+Mg7Gd+Mg41Nd5, Mg7Gd+Mg5Gd+Mg41Nd5, Mg5Gd+Mg41Nd5+(Gd,Nd)3Mg and (Gd,Nd)3Mg+(Gd,Nd)Mg+Mg2Gd, were identified in the isothermal section.展开更多
A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numeri...A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numerical results show that the frozen depth mainly depends on the soil′s moisture content and ambient temperature. The heat transfer loss of horizontal GHE tends to grow with the increase of the soil′s moisture content and the decrease of ambient temperature. Backfilled materials with optimal thermal conductivity can reduce the thermal loss effectively in the frozen soil. The applicability of the Chinese national standard “Technical Code for Ground Source Heat Pump (GB 50366-2005)” is verified. For a ground source heat pump project, the feasible layout of horizontal GHE should be determined based on the integration of the soil′s structure, backfilled materials, weather data, and economic analysis.展开更多
Numerical simulation and experiments were introduced to develop AA4045/AA3003 cladding billets with different clad-ratios. The temperature fields, microstructures and mechanical properties near interface were investig...Numerical simulation and experiments were introduced to develop AA4045/AA3003 cladding billets with different clad-ratios. The temperature fields, microstructures and mechanical properties near interface were investigated in detail. The results show that cladding billets with different clad-ratios were fabricated successfully. Si and Mn elements diffused across the bonding interface and formed diffusion layer. With the increase of clad-layer thickness, the interfacial region transforms from semisolid-solid state to liquid-solid state and the diffusion layer increased from 10 to 25 μm. The hardness at interface is higher than that of AA3003 side but lower than that of the other side. The bonding strength increased with the clad-layer thickness, attributing to solution strengthening due to elements diffusion. The cladding billets were extruded into clad pipe by indirect extrusion process after homogenization. The clad pipe remained the interfacial characteristics of as-cast cladding billet and the heredity of clad-ratio during deformation was testified.展开更多
The phonon and thermodynamics properties of face-centered cubic CaF2 at high pressure and high temperature are investigated by using the shell model interatomic pair potential within General Utility Lattice Program (...The phonon and thermodynamics properties of face-centered cubic CaF2 at high pressure and high temperature are investigated by using the shell model interatomic pair potential within General Utility Lattice Program (GULP). The phonon dispersion curves and the corresponding density of state (PDOS) in this work are consistent with the experimental data and other theoretical results. The transverse optical (TO) and longitudinal optical (LO) mode splitting as well as heat capacity at constant volume Cv and entropy S versus pressure and temperature are also obtained.展开更多
A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can ch...A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can change in the radial direction. The carbon dioxide is used as the gasification agent that reacts with the char and form carbon monoxide. The presence of both solid and gaseous phase species makes the reaction heterogeneous. The char particle is considered with varying porosity that also allows the change in the surface area of the particle. A time invariant temperature and pressure profile is used at which the Arrhenius rate constant and diffusion is calculated. The mass conservation of model results in the form of two coupled partial differential and one ordinary differential equation. The equations are solved with a set of initial and boundary conditions using the bulk species concentration at the particle surface. A second order accurate central differencing scheme is used to discretize space while backward differencing is used to discretize time. Finally, the results are presented for the concentration distribution of CO and CO2 in radial direction with respect to time. It shows that, maximum concentration of CO is present at the center of the particle while the concentration gradient becomes higher near the particle surface. The nonlinear concentration trend due to the diffusion is effectively captured. The results show that, completed conversion of char depend upon the time provided for the reaction which can be reduced by decreasing the size of particle or increasing the reaction temperature. The sensitivity study of temperature and initial porosity also performed and showed that temperature has high impact on char conversion as compare to initial porosity.展开更多
The temperature characteristics of VCSEL using proton implantation are described,compared with its edge-emitting counterpart.Implant-confined VCSEL operation has been realized up to 120 ℃.These records of high operat...The temperature characteristics of VCSEL using proton implantation are described,compared with its edge-emitting counterpart.Implant-confined VCSEL operation has been realized up to 120 ℃.These records of high operating temperature are caused by high characteristic temperature. The relevant physical mechanisms including their dependence on temperature and carrier density are considered. The temperature sensitivity of the threshold current is not strongly increasing with higher temperature.展开更多
The photos, which are done by electron microscope, of the condensed disperse phase, surrounding high-temperature metal particles are presented. The dependence of concentration of condensed dispersive phase which surro...The photos, which are done by electron microscope, of the condensed disperse phase, surrounding high-temperature metal particles are presented. The dependence of concentration of condensed dispersive phase which surrounds a high-temperature metal particle upon the temperature of the particle was obtained. The dependence of concentration of electrons in condensed dispersive phase upon the temperature of the particle was studied. The dependence of an equilibrium charge of a metal particle surrounded with condensed disperse phase on the temperature of a particle in a positive and negative region is presented. The dependence of a charge of a metal particle on time at the fixed temperature is obtained.展开更多
Objective To observe clinical effect of warm needing plus cupping at back on facial paralysis. Methods Forty cases of peripheral facial paralysis were firstly treated with warm needling. Cuánzhú (攒竹 BL 2...Objective To observe clinical effect of warm needing plus cupping at back on facial paralysis. Methods Forty cases of peripheral facial paralysis were firstly treated with warm needling. Cuánzhú (攒竹 BL 2), Yángbái (阳白 GB 14), Sīzhúkōng (丝竹空 TE 23), Sìbái (四白 ST 2), Tīnghuì (听会 GB 2), Yìfēng (翳 风 TE 17), Dìcāng (地仓 ST 4), Jiáchē (颊车 ST 6), Yíngxiāng (迎香 LI 20) and Hég (合谷 LI 4) were selected and warm needling was applied at Tīnghuì (听 会 GB 2). Needles were retained for 30 min, once a day. Cupping at back was then applied at bilateral Fèishū (肺俞 BL 13), Píshū (脾俞 BL 20), Shènshū (肾 俞 BL 23) in the Bladder Meridian of Foot-Taiyang for 10 min, once a day for first five days and then once every other day. Ten days of treatment were taken as a treatment course with one day interval between courses. The efficacy was observed after two treatment courses. Results Twenty-six cases were cured, ten cases were markedly effective, three cases were effective and one case was failed. The total effective rate was 97.5% (39/40). Conclusion From theory of coldness to treat facial paralysis, efficacy is significant with warm needling and cupping at the Bladder Meridian of Foot-Taiyang.展开更多
OBJECTIVE:To study the effects of temperature on different facial areas by suspended moxibustion at two points,Zusanli(ST 36) and Hegu(LI 4),and probe the phenomena underlying self-regulation in the human body after t...OBJECTIVE:To study the effects of temperature on different facial areas by suspended moxibustion at two points,Zusanli(ST 36) and Hegu(LI 4),and probe the phenomena underlying self-regulation in the human body after thermal stimulation.METHODS:Thirty healthy volunteers accepted moxibustion over Zusanli(ST 36) and Hegu(LI 4),and the order of moxibustion points was randomly determined.Moxibustion method:suspension of moxibustion over Zusanli(ST 36) and Hegu(LI 4) on both sides was performed using an ignited moxa stick stuck in a support for 20 min.Observation method:An infrared thermal image of the face was taken before and after suspended moxibustion using a CK350 medical infrared thermal imaging instrument.Data analysis:A thermal microscopic section view system(TMTSys) was used to analyze the change in temperature in special facial areas.Statistical analysis was carried out using SPSS 14.0 software.RESULTS:Before moxibustion was suspended,the facial thermal image showed a T-shaped thermal area related to the vascular distribution with even temperature and good symmetry on both sides.Suspended moxibustion over Zusanli(ST 36) have a very significant increase in temperature at the forehead,around the nose,at the corners of the mouth,and at the cheeks and lips(P<0.01).Suspended moxibustion over Hegu(LI 4) also have a significant(P<0.05) increase in temperature around the nose,the corners of the mouth,the cheeks,and lips,where has a new high temperature area was formed(P<0.01).Suspended moxibustion over Hegu(LI 4) raised the temperature at the middle point of the lips more obviously than did Zusanli(ST 36) in the same person,(P<0.05).After 10 min of moxibustion over Zusanli(ST 36) and Hegu(LI 4),the change in temperature in the facial area reached its peak value.CONCLUSIONS:Facial infrared thermography of healthy people revealed a T-shaped thermal area reflecting a physiological thermal area.Moxibustion over Zusanli(ST 36) or Hegu(LI 4) raised the temperature in this facial T-shaped thermal area.Hegu(LI 4) led to the formation of a new thermal area in the lips.The time required for moxibustion to regulate human body temperature was 10 min.展开更多
The spectral radiative entransy flux and the total radiative entransy flux are defined for the steady radiative heat transfer processes in enclosures composed of non-isothermal or non-grey, opaque, diffuse surfaces. B...The spectral radiative entransy flux and the total radiative entransy flux are defined for the steady radiative heat transfer processes in enclosures composed of non-isothermal or non-grey, opaque, diffuse surfaces. Based on the definitions, the radiative entransy flux balance equation and the radiative entransy dissipation functions are introduced under spectral and total wavelength condition. Furthermore, the minimum principle of radiative entransy loss, the extreme principle of radiative entransy dissipation and the minimum principle of radiative thermal resistance are developed. The minimum prirlciple of radiative en- transy loss shows that the potential and the net radiative heat flux distribution which meet the control equations and the boundary conditions would make the radiative entransy loss minimum if the net radiative heat flux or the potential distribution of the radiative heat transfer system is given. The extreme principle of radiative entransy dissipation indicates that the minimum radiative entransy dissipation leads to the minimum average potential difference for the prescribed total radiative heat exchange and the maximum radiative entransy dissipation leads to the maximum radiative heat exchange for the prescribed average potential difference. Moreover, the minimum principle of radiative thermal resistance tells us that the aforementioned extreme values of radiative entransy dissipation both correspond to the minimum value of radiative thermal resistance. Application examples are given for the extreme principle of spectral radiative entransy dissipation and the minimum principle of spectral radiative thermal resistance, and the principles are proved to be applicable.展开更多
The Weather Research and Forecasting (WRF) model, the Princeton Ocean Model (POM), and the wave model (WAVEWATCH III) are used to develop a coupled atmosphere-wave-ocean model, which involves different physical ...The Weather Research and Forecasting (WRF) model, the Princeton Ocean Model (POM), and the wave model (WAVEWATCH III) are used to develop a coupled atmosphere-wave-ocean model, which involves different physical pro- cesses including air-forcing, ocean feedback, wave-induced mixing and wave-current interaction. In this paper, typhoon KAEMI (2006) has been examined to investigate the effect of wind-current interaction on ocean response based on the coupled atmosphere-ocean-wave model, i.e., considering the sea surface currents in the calculation of wind stress. The results show that the wind-current interaction has a noticeable impact on the simulation of 10 m-winds. The model involving the effect of the wind-current interaction can dramatically improve the typhoon prediction. The wind-current interaction prevents excessive momentum fluxes from being transferred into the upper ocean, which contributes to a much smaller turbulence kinetic energy (TKE), vertical diffusivity, and horizontal advection and diffusion. The Sea Surface Temperature (SST) cooling induced by the wind-current interaction during the initial stage of typhoon development is so minor that the typhoon intensity is not very sen- sitive to it. When the typhoon reaches its peak, its winds can disturb thermocline, and the cold water under the thermocline is pumped up. However, this cooling process is weakened by the wind-current interaction, as ocean feedback delays the decay of the typhoon. Meanwhile, the temperature below the depth of 30 m shows an inertial oscillation with a period about 40 hours (-17°N) when sudden strong winds beat on the ocean. Due to faster currents, the significant wave height decreases as ignoring the wind-current interaction, while this process has a very small effect on the dominant wave length.展开更多
With significantly enhanced irradiation resistance,high-temperature strength,and creep resistance,oxide-dispersion-strengthened tungsten(ODS-W)alloys present tremendous potential for high-temperature applications.Howe...With significantly enhanced irradiation resistance,high-temperature strength,and creep resistance,oxide-dispersion-strengthened tungsten(ODS-W)alloys present tremendous potential for high-temperature applications.However,the oxide particles tend to segregate at W grain boundary and grow up(even to micron),greatly suppressing their strengthening effect.It is always a great challenge to effectively refine and disperse the oxide particles at W grain boundary.Here,we successfully developed a new type of cation-doped W-Y2O3 alloy via a wet chemical method and subsequent low-temperature sintering.It was found that proper cation doping could not only significantly refine the intergranular Y2O3 second phase particles but also dramatically improve the sinterability of W matrix.These doping effects,as a result,simultaneously enhance the strength and ductility of the W-Y2O3 alloy.It was confirmed that the segregation of cation dopants at the W/Y2O3 interface is the origin of these doping effects.Furthermore,X-ray photoemission spectra(XPS)analyses confirmed that cation dopant segregation also obviously affects the chemical bonding(i.e.,W–O bond)along the W/Y2O3 interface.As a result,the ratelimiting mechanism for W grain growth is influenced remarkably,explaining well the difference of W grain size in various cation-doped W-Y2O3 alloys.For the refinement of intergranular Y2O3 particles,it can be understood well from both thermodynamic and kinetic views.Detailedly,W/Y2O3 interfacial energy and atom mobility for Y2O3 coarsening are all limited by cation dopant segregation.More importantly,this cation-doping approach can also be applicable to other ODS alloys for enhancing their comprehensive mechanical properties.展开更多
We report on the fabrication of a class of surface-enhanced Raman scattering(SERS)active thermometers,which consists of60 nm gold nanoparticles,encoded with Raman-active dyes,and a layer of thermoresponsive poly(N-iso...We report on the fabrication of a class of surface-enhanced Raman scattering(SERS)active thermometers,which consists of60 nm gold nanoparticles,encoded with Raman-active dyes,and a layer of thermoresponsive poly(N-isopropylacrylamide)(PNIPAM)brush with different chain lengths.These SERS-active nanoparticles can be optimized to maintain spectrally silent when staying as single particles in dispersion.Increasing temperature in a wide range from 25 to 55°C can reversibly induce the interparticle self-aggregation and turn on the SERS fingerprint signals with up to 58-fold of enhancement by taking advantage of the interparticle plasmonic coupling generated in the process of thermo-induced nanoparticles self-aggregation.Moreover,the most significative point is that these SERS probes could maintain their response to temperature and present all fingerprint signals in the presence of a colored complex.However,the UV-Vis spectra can distinguish the differences faintly and the solution color shows little change in such complex mixture.This proof-of-concept and Raman technique applied here allow for dynamic SERS platform for onsite temperature detection in a wide temperature range and offer unique advantages over other detection schemes.展开更多
基金Projects(50731002,50971136)supported by the National Natural Science Foundation of China
文摘An isothermal section of the Mg-Nd-Gd ternary system at 723 K was established by diffusion triple technique and electron probe microanalysis (EPMA). Mg3Gd and Mg3Nd form a continuous solid solution (Gd,Nd)3Mg, and a continuous solid solution (Gd,Nd)Mg is also formed between MgGd and MgNd. Mg7Gd, Mg5Gd, Mg2Gd, Mg41Nd5, (Gd,Nd)3Mg and (Gd,Nd)Mg are found in the ternary system. In these intermetallic phases, Mg7Gd has been reported to be a metastable phase in previous literatures. The solubilities of Mg, Gd and Nd in all the phases were detected. Furthermore, four three-phase equilibria, α(Mg)+Mg7Gd+Mg41Nd5, Mg7Gd+Mg5Gd+Mg41Nd5, Mg5Gd+Mg41Nd5+(Gd,Nd)3Mg and (Gd,Nd)3Mg+(Gd,Nd)Mg+Mg2Gd, were identified in the isothermal section.
基金Supported by Tianjin Scientific Development Foundation (No.013112811-1) .
文摘A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numerical results show that the frozen depth mainly depends on the soil′s moisture content and ambient temperature. The heat transfer loss of horizontal GHE tends to grow with the increase of the soil′s moisture content and the decrease of ambient temperature. Backfilled materials with optimal thermal conductivity can reduce the thermal loss effectively in the frozen soil. The applicability of the Chinese national standard “Technical Code for Ground Source Heat Pump (GB 50366-2005)” is verified. For a ground source heat pump project, the feasible layout of horizontal GHE should be determined based on the integration of the soil′s structure, backfilled materials, weather data, and economic analysis.
基金Project(2015B090926013)supported by the Science and Technology Program of Guangdong Province,ChinaProject(20170540307)supported by the Natural Science Foundation of Liaoning Province,China
文摘Numerical simulation and experiments were introduced to develop AA4045/AA3003 cladding billets with different clad-ratios. The temperature fields, microstructures and mechanical properties near interface were investigated in detail. The results show that cladding billets with different clad-ratios were fabricated successfully. Si and Mn elements diffused across the bonding interface and formed diffusion layer. With the increase of clad-layer thickness, the interfacial region transforms from semisolid-solid state to liquid-solid state and the diffusion layer increased from 10 to 25 μm. The hardness at interface is higher than that of AA3003 side but lower than that of the other side. The bonding strength increased with the clad-layer thickness, attributing to solution strengthening due to elements diffusion. The cladding billets were extruded into clad pipe by indirect extrusion process after homogenization. The clad pipe remained the interfacial characteristics of as-cast cladding billet and the heredity of clad-ratio during deformation was testified.
基金supported by the National Natural Science Foundation of China under Grant No.10576020
文摘The phonon and thermodynamics properties of face-centered cubic CaF2 at high pressure and high temperature are investigated by using the shell model interatomic pair potential within General Utility Lattice Program (GULP). The phonon dispersion curves and the corresponding density of state (PDOS) in this work are consistent with the experimental data and other theoretical results. The transverse optical (TO) and longitudinal optical (LO) mode splitting as well as heat capacity at constant volume Cv and entropy S versus pressure and temperature are also obtained.
文摘A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can change in the radial direction. The carbon dioxide is used as the gasification agent that reacts with the char and form carbon monoxide. The presence of both solid and gaseous phase species makes the reaction heterogeneous. The char particle is considered with varying porosity that also allows the change in the surface area of the particle. A time invariant temperature and pressure profile is used at which the Arrhenius rate constant and diffusion is calculated. The mass conservation of model results in the form of two coupled partial differential and one ordinary differential equation. The equations are solved with a set of initial and boundary conditions using the bulk species concentration at the particle surface. A second order accurate central differencing scheme is used to discretize space while backward differencing is used to discretize time. Finally, the results are presented for the concentration distribution of CO and CO2 in radial direction with respect to time. It shows that, maximum concentration of CO is present at the center of the particle while the concentration gradient becomes higher near the particle surface. The nonlinear concentration trend due to the diffusion is effectively captured. The results show that, completed conversion of char depend upon the time provided for the reaction which can be reduced by decreasing the size of particle or increasing the reaction temperature. The sensitivity study of temperature and initial porosity also performed and showed that temperature has high impact on char conversion as compare to initial porosity.
文摘The temperature characteristics of VCSEL using proton implantation are described,compared with its edge-emitting counterpart.Implant-confined VCSEL operation has been realized up to 120 ℃.These records of high operating temperature are caused by high characteristic temperature. The relevant physical mechanisms including their dependence on temperature and carrier density are considered. The temperature sensitivity of the threshold current is not strongly increasing with higher temperature.
文摘The photos, which are done by electron microscope, of the condensed disperse phase, surrounding high-temperature metal particles are presented. The dependence of concentration of condensed dispersive phase which surrounds a high-temperature metal particle upon the temperature of the particle was obtained. The dependence of concentration of electrons in condensed dispersive phase upon the temperature of the particle was studied. The dependence of an equilibrium charge of a metal particle surrounded with condensed disperse phase on the temperature of a particle in a positive and negative region is presented. The dependence of a charge of a metal particle on time at the fixed temperature is obtained.
文摘Objective To observe clinical effect of warm needing plus cupping at back on facial paralysis. Methods Forty cases of peripheral facial paralysis were firstly treated with warm needling. Cuánzhú (攒竹 BL 2), Yángbái (阳白 GB 14), Sīzhúkōng (丝竹空 TE 23), Sìbái (四白 ST 2), Tīnghuì (听会 GB 2), Yìfēng (翳 风 TE 17), Dìcāng (地仓 ST 4), Jiáchē (颊车 ST 6), Yíngxiāng (迎香 LI 20) and Hég (合谷 LI 4) were selected and warm needling was applied at Tīnghuì (听 会 GB 2). Needles were retained for 30 min, once a day. Cupping at back was then applied at bilateral Fèishū (肺俞 BL 13), Píshū (脾俞 BL 20), Shènshū (肾 俞 BL 23) in the Bladder Meridian of Foot-Taiyang for 10 min, once a day for first five days and then once every other day. Ten days of treatment were taken as a treatment course with one day interval between courses. The efficacy was observed after two treatment courses. Results Twenty-six cases were cured, ten cases were markedly effective, three cases were effective and one case was failed. The total effective rate was 97.5% (39/40). Conclusion From theory of coldness to treat facial paralysis, efficacy is significant with warm needling and cupping at the Bladder Meridian of Foot-Taiyang.
基金Supported by the National Natural Science Foundation (No.30973795)
文摘OBJECTIVE:To study the effects of temperature on different facial areas by suspended moxibustion at two points,Zusanli(ST 36) and Hegu(LI 4),and probe the phenomena underlying self-regulation in the human body after thermal stimulation.METHODS:Thirty healthy volunteers accepted moxibustion over Zusanli(ST 36) and Hegu(LI 4),and the order of moxibustion points was randomly determined.Moxibustion method:suspension of moxibustion over Zusanli(ST 36) and Hegu(LI 4) on both sides was performed using an ignited moxa stick stuck in a support for 20 min.Observation method:An infrared thermal image of the face was taken before and after suspended moxibustion using a CK350 medical infrared thermal imaging instrument.Data analysis:A thermal microscopic section view system(TMTSys) was used to analyze the change in temperature in special facial areas.Statistical analysis was carried out using SPSS 14.0 software.RESULTS:Before moxibustion was suspended,the facial thermal image showed a T-shaped thermal area related to the vascular distribution with even temperature and good symmetry on both sides.Suspended moxibustion over Zusanli(ST 36) have a very significant increase in temperature at the forehead,around the nose,at the corners of the mouth,and at the cheeks and lips(P<0.01).Suspended moxibustion over Hegu(LI 4) also have a significant(P<0.05) increase in temperature around the nose,the corners of the mouth,the cheeks,and lips,where has a new high temperature area was formed(P<0.01).Suspended moxibustion over Hegu(LI 4) raised the temperature at the middle point of the lips more obviously than did Zusanli(ST 36) in the same person,(P<0.05).After 10 min of moxibustion over Zusanli(ST 36) and Hegu(LI 4),the change in temperature in the facial area reached its peak value.CONCLUSIONS:Facial infrared thermography of healthy people revealed a T-shaped thermal area reflecting a physiological thermal area.Moxibustion over Zusanli(ST 36) or Hegu(LI 4) raised the temperature in this facial T-shaped thermal area.Hegu(LI 4) led to the formation of a new thermal area in the lips.The time required for moxibustion to regulate human body temperature was 10 min.
基金supported by Tsinghua University Initiative Scientific Research Program
文摘The spectral radiative entransy flux and the total radiative entransy flux are defined for the steady radiative heat transfer processes in enclosures composed of non-isothermal or non-grey, opaque, diffuse surfaces. Based on the definitions, the radiative entransy flux balance equation and the radiative entransy dissipation functions are introduced under spectral and total wavelength condition. Furthermore, the minimum principle of radiative entransy loss, the extreme principle of radiative entransy dissipation and the minimum principle of radiative thermal resistance are developed. The minimum prirlciple of radiative en- transy loss shows that the potential and the net radiative heat flux distribution which meet the control equations and the boundary conditions would make the radiative entransy loss minimum if the net radiative heat flux or the potential distribution of the radiative heat transfer system is given. The extreme principle of radiative entransy dissipation indicates that the minimum radiative entransy dissipation leads to the minimum average potential difference for the prescribed total radiative heat exchange and the maximum radiative entransy dissipation leads to the maximum radiative heat exchange for the prescribed average potential difference. Moreover, the minimum principle of radiative thermal resistance tells us that the aforementioned extreme values of radiative entransy dissipation both correspond to the minimum value of radiative thermal resistance. Application examples are given for the extreme principle of spectral radiative entransy dissipation and the minimum principle of spectral radiative thermal resistance, and the principles are proved to be applicable.
基金supported by the National Public Benefit(Meteorology)Research Foundation of China(Grant No.GYHY201106004)the National Natural Science Foundation of China(Grant No.41005029)
文摘The Weather Research and Forecasting (WRF) model, the Princeton Ocean Model (POM), and the wave model (WAVEWATCH III) are used to develop a coupled atmosphere-wave-ocean model, which involves different physical pro- cesses including air-forcing, ocean feedback, wave-induced mixing and wave-current interaction. In this paper, typhoon KAEMI (2006) has been examined to investigate the effect of wind-current interaction on ocean response based on the coupled atmosphere-ocean-wave model, i.e., considering the sea surface currents in the calculation of wind stress. The results show that the wind-current interaction has a noticeable impact on the simulation of 10 m-winds. The model involving the effect of the wind-current interaction can dramatically improve the typhoon prediction. The wind-current interaction prevents excessive momentum fluxes from being transferred into the upper ocean, which contributes to a much smaller turbulence kinetic energy (TKE), vertical diffusivity, and horizontal advection and diffusion. The Sea Surface Temperature (SST) cooling induced by the wind-current interaction during the initial stage of typhoon development is so minor that the typhoon intensity is not very sen- sitive to it. When the typhoon reaches its peak, its winds can disturb thermocline, and the cold water under the thermocline is pumped up. However, this cooling process is weakened by the wind-current interaction, as ocean feedback delays the decay of the typhoon. Meanwhile, the temperature below the depth of 30 m shows an inertial oscillation with a period about 40 hours (-17°N) when sudden strong winds beat on the ocean. Due to faster currents, the significant wave height decreases as ignoring the wind-current interaction, while this process has a very small effect on the dominant wave length.
基金the National Natural Science Foundation of China(51822404)the Science and Technology Program of Tianjin(19YFZCGX00790 and 18YFZCGX00070)+1 种基金the Natural Science Foundation of Tianjin(18JCYBJC17900)the Seed Foundation of Tianjin University(2018XRX-0005)。
文摘With significantly enhanced irradiation resistance,high-temperature strength,and creep resistance,oxide-dispersion-strengthened tungsten(ODS-W)alloys present tremendous potential for high-temperature applications.However,the oxide particles tend to segregate at W grain boundary and grow up(even to micron),greatly suppressing their strengthening effect.It is always a great challenge to effectively refine and disperse the oxide particles at W grain boundary.Here,we successfully developed a new type of cation-doped W-Y2O3 alloy via a wet chemical method and subsequent low-temperature sintering.It was found that proper cation doping could not only significantly refine the intergranular Y2O3 second phase particles but also dramatically improve the sinterability of W matrix.These doping effects,as a result,simultaneously enhance the strength and ductility of the W-Y2O3 alloy.It was confirmed that the segregation of cation dopants at the W/Y2O3 interface is the origin of these doping effects.Furthermore,X-ray photoemission spectra(XPS)analyses confirmed that cation dopant segregation also obviously affects the chemical bonding(i.e.,W–O bond)along the W/Y2O3 interface.As a result,the ratelimiting mechanism for W grain growth is influenced remarkably,explaining well the difference of W grain size in various cation-doped W-Y2O3 alloys.For the refinement of intergranular Y2O3 particles,it can be understood well from both thermodynamic and kinetic views.Detailedly,W/Y2O3 interfacial energy and atom mobility for Y2O3 coarsening are all limited by cation dopant segregation.More importantly,this cation-doping approach can also be applicable to other ODS alloys for enhancing their comprehensive mechanical properties.
基金supported by the Fundamental Research Funds for the Central Universities
文摘We report on the fabrication of a class of surface-enhanced Raman scattering(SERS)active thermometers,which consists of60 nm gold nanoparticles,encoded with Raman-active dyes,and a layer of thermoresponsive poly(N-isopropylacrylamide)(PNIPAM)brush with different chain lengths.These SERS-active nanoparticles can be optimized to maintain spectrally silent when staying as single particles in dispersion.Increasing temperature in a wide range from 25 to 55°C can reversibly induce the interparticle self-aggregation and turn on the SERS fingerprint signals with up to 58-fold of enhancement by taking advantage of the interparticle plasmonic coupling generated in the process of thermo-induced nanoparticles self-aggregation.Moreover,the most significative point is that these SERS probes could maintain their response to temperature and present all fingerprint signals in the presence of a colored complex.However,the UV-Vis spectra can distinguish the differences faintly and the solution color shows little change in such complex mixture.This proof-of-concept and Raman technique applied here allow for dynamic SERS platform for onsite temperature detection in a wide temperature range and offer unique advantages over other detection schemes.