Phase structure of sputtered Ta coating in the negative glow space and LPH effect were explored.The whole coating/substrate system is substrate→physically gas-absorbed Fe surface→oxygen-enriched TaOx layer→amorphou...Phase structure of sputtered Ta coating in the negative glow space and LPH effect were explored.The whole coating/substrate system is substrate→physically gas-absorbed Fe surface→oxygen-enriched TaOx layer→amorphous Ta→αandβdual phase→singleαphase.After LPH course,micro structure of Ta coating shows intact,only a few cracks emerge after 100 laser pulses,exhibiting thin HAZ but thick Fe/Ta ICZ,without martensitic transformation.For the electrodeposited Cr coating,continuous thermal stresses produce many extra micro-crack,substrate oxidation and martensitic transformation,leading to crack propagations and final bulk delamination,without any ICZ.展开更多
Producing high-brightness and high-charge(〉100 pC) electron bunches at blowout regime requires ultrashort laser pulses with high fluence. The effects of laser pulse heating of the copper photocathode are analyzed i...Producing high-brightness and high-charge(〉100 pC) electron bunches at blowout regime requires ultrashort laser pulses with high fluence. The effects of laser pulse heating of the copper photocathode are analyzed in this paper. The electron and lattice temperature is calculated using an improved two-temperature model, and an extended Dowell-Schmerge model is employed to calculate the thermal emittance and quantum efficiency. A timedependent growth of the thermal emittance and the quantum efficiency is observed. For a fixed amount of charge,the projected thermal emittance increases with decreasing laser radius, and this effect should be taken into account in laser optimization at blowout regime. Moreover, laser damage threshold fluence is simulated, showing that the maximum local fluence should be less than 40 mJ/cm^2 to prevent damage to the cathode.展开更多
Boom clay formation is a potential natural host rock for geological disposal of high-level nuclear waste in Belgium.Heating pulse tests with controlled power supply(maximum temperature was limited to 85℃) and contr...Boom clay formation is a potential natural host rock for geological disposal of high-level nuclear waste in Belgium.Heating pulse tests with controlled power supply(maximum temperature was limited to 85℃) and controlled hydraulic boundary conditions were performed under nearly constant volume conditions to study the impact of thermal loading on the clay formation.Selected test results of intact borehole samples retrieved in horizontal direction are presented and discussed.The study focuses on the time evolution of temperature and pore water pressure changes along heating and cooling paths,i.e.pore pressure build-up during quasi-undrained heating and later dissipation at constant temperature.展开更多
Non-equilibrium molecular dynamics simulations of liquid water in picosecond high-power terahertz pulses are performed by using a non-polarizable potential model. Numerical results show that the energy absorption of w...Non-equilibrium molecular dynamics simulations of liquid water in picosecond high-power terahertz pulses are performed by using a non-polarizable potential model. Numerical results show that the energy absorption of water molecules exhibits a pronounced resonance with THz pulses in the frequency range of 14-17 THz. With the THz pulse at resonant frequencies, the maximum temperature is about 562 K by heating the water at room temperature. Further investigation indicates that the results are independent of the size of the nanoscale water box. The efficiency of energy transfer by resonant absorption is more than seven times of microwave heating. These studies show promising applications of ultrashort THz pulses.展开更多
Enhancements of edge zonal flows,radial electric fields,and turbulence are observed in electron cyclotron resonance heating-heated plasmas(Zhao et al 2013 Nucl.Fusion 53083011).In this paper,the effects of sawtooth he...Enhancements of edge zonal flows,radial electric fields,and turbulence are observed in electron cyclotron resonance heating-heated plasmas(Zhao et al 2013 Nucl.Fusion 53083011).In this paper,the effects of sawtooth heat pulses on flows and turbulence are presented.These experiments are performed using multiple Langmuir probe arrays in the edge plasmas of the HL-2A tokamak.The edge zonal flows,radial electric fields,and turbulence are all enhanced by sawteeth.Propagation of the zonal flow and turbulence intensities is also observed.The delay time of the maximal intensity of the electric fields,zonal flows,and turbulence with respect to the sawtooth crashes is estimated as~1 ms and comparable to that of the sawtooth-triggered intermediate phases.Not only the zonal flows but also the radial electric fields lag behind the turbulence.Furthermore,the intensities of both the zonal flows and electric fields nearly linearly increase/decrease with the increase/decrease of the turbulence intensity.A double-source predator-prey model analysis suggests that a relatively strong turbulence source may contribute to the dominant zonal flow formation during sawtooth cycles.展开更多
The nonlinear thermoelastic responses of an elastic medium exposed to laser generated shortpulse heating are investigated in this article. The thermal wave propagation of generalized thermoelastic medium under the imp...The nonlinear thermoelastic responses of an elastic medium exposed to laser generated shortpulse heating are investigated in this article. The thermal wave propagation of generalized thermoelastic medium under the impact of thermal loading with energy dissipation is the focus of this research. To model the thermal boundary condition(in the form of thermal conduction),generalized Cattaneo model(GCM) is employed. In the reference configuration, a nonlinear coupled Lord-Shulman-type generalized thermoelasticity formulation using finite strain theory(FST) is developed and the temperature dependency of the thermal conductivity is considered to derive the equations. In order to solve the time-dependent and nonlinear equations, Newmark’s numerical time integration technique and an updated finite element algorithm is applied and to ensure achieving accurate continuity of the results, the Hermitian elements are used instead of Lagrangian’s. The numerical responses for different factors such as input heat flux and nonlinear terms are expressed graphically and their impacts on the system’s reaction are discussed in detail.The results of the study are presented for Green–Lindsay model and the findings are compared with Lord-Shulman model especially with regards to heat wave propagation. It is shown that the nature of the laser’s thermal shock and its geometry are particularly determinative in the final stage of deformation. The research also concluded that employing FST leads to achieving more accuracy in terms of elastic deformations;however, the thermally nonlinear analysis does not change the results markedly. For this reason, the nonlinear theory of deformation is required in laser related reviews, while it is reasonable to ignore the temperature changes compared to the reference temperature in deriving governing equations.展开更多
A pulsed-wire wall probe measurement system was developed in this paper,which can be used for measuring wall Parameters in separated flow- The operating princi-ple was described and the way of probe calibration was gi...A pulsed-wire wall probe measurement system was developed in this paper,which can be used for measuring wall Parameters in separated flow- The operating princi-ple was described and the way of probe calibration was given. Wall parameters of back-ward-facing and forward-facing step flow were measured,and the wall nows structure andcharacters were revealed.展开更多
This paper numerically investigates the effect of the location of a horizontal fin on the melting of a phase change material(PCM)inside a rectangular enclosure heated by multiple discrete pulsed protruding heat source...This paper numerically investigates the effect of the location of a horizontal fin on the melting of a phase change material(PCM)inside a rectangular enclosure heated by multiple discrete pulsed protruding heat sources.The fin and the phase change material filling the enclosure store the thermal energy extracted from the heat sources,in sensible and latent forms.The heat sources are assumed to simulate electronic components undergoing a superheating technical issue.By extracting heat from the electronics,the PCM plays the role of a heat sink.To analyze the thermal behavior and predict the cooling performance of the proposed cooling system,we derive a nonlinear mathematical model based on mass,momentum and energy conservation laws.Several numerical investigations are conducted to quantify the influence of the fin position on the thermal behavior and the cooling performance of the heat sink.Predictions include the transient maximum temperature occurring inside the heat sources and the liquid volume.A comparison between our numerical results and experimental data selected from the literature shows a good agreement.The main conclusion is that the presence of the fin leads to a slight increase in the melting time.展开更多
A mathematical model is presented to describe transient behavior of heat transfer and fluid flow in stationary pulsed current tungsten inert gas (PC-TIG) weld pool, which considers three kinds of driving, forces for w...A mathematical model is presented to describe transient behavior of heat transfer and fluid flow in stationary pulsed current tungsten inert gas (PC-TIG) weld pool, which considers three kinds of driving, forces for weld pool convection, i,e. buoyancyforce, electromagnetic force and surface tension force. furthermore. the effect of vaporization heat flux at the free surface of weld pool and the temperature coefficient of surface tenston which is a function of temperatuer and composition are considered in the model In order to accelerate the convergence of iteration the AST(additive source term)method which concerns with the thermal energv boundary conditions is extended successfully to deal with the momentum boundary conditions by which the transient momentum equation and energy equation are mutually coupled. At the same time. ADI (Alternating direction implicit) method and DBC (double blocks correction) technque are employed to solve the finite difference equations. The results of numerical simulation demonstrate the transient behavior of PC-TIG weld pool, as well as the periodic variation of fluid flow and heat transfer with the periodic variation of welding current in stationary PC-TIG weld pool. The theoretical predictions based on this model are, shown to be in good accordance with the experimental measurements.展开更多
The electrocaloric effect in thin films of an electrocaloric material has the potential to be used for efficient cooling systems for high power electronic devices. We numerically calculated the effect of parameters in...The electrocaloric effect in thin films of an electrocaloric material has the potential to be used for efficient cooling systems for high power electronic devices. We numerically calculated the effect of parameters in electrocaloric refrigeration with a thermal switch of fluid motion on the thermal performance. The system of changing air and water flow with the pulse generation of cold energy increased the heat transfer efficiency to 67% at a frequency of 5 Hz. The optimum time delay of water flow to increase the heat transfer efficiency was zero at low frequency and became half of the time period to change heat for a high frequency of 100 Hz. When the heat transfer efficiency was high, the final temperature change in water flow was not the maximum temperature change.展开更多
Conventional charging methods for lithium-ion battery(LIB)are challenged with vital problems at low temperatures:risk of lithium(Li)plating and low charging speed.This study proposes a fast-charging strategy without L...Conventional charging methods for lithium-ion battery(LIB)are challenged with vital problems at low temperatures:risk of lithium(Li)plating and low charging speed.This study proposes a fast-charging strategy without Li plating to achieve high-rate charging at low temperatures with bidirectional chargers.The strategy combines the pulsed-heating method and the optimal charging method via precise control of the battery states.A thermo-electric coupled model is developed based on the pseudo-twodimensional(P2D)electrochemical model to derive charging performances.Two current maps of pulsed heating and charging are generated to realize real-time control.Therefore,our proposed strategy achieves a 3 C equivalent rate at 0℃ and 1.5 C at-10℃ without Li plating,which is 10–30 times faster than the traditional methods.The entropy method is employed to balance the charging speed and the energy efficiency,and the charging performance is further enhanced.For practical application,the power limitation of the charger is considered,and a 2.4 C equivalent rate is achieved at 0℃ with a 250 kW maximum power output.This novel strategy significantly expands LIB usage boundary,and increases charging speed and battery safety.展开更多
The tropical arboreal species Brazilian mahogany(Swietenia macrophylla) is very important economically and ecologically,for which understanding ecophysiological variables such as sap flow will improve understanding of...The tropical arboreal species Brazilian mahogany(Swietenia macrophylla) is very important economically and ecologically,for which understanding ecophysiological variables such as sap flow will improve understanding of the species and its cultivation.This paper aims to measure uncertainties(U) involved in the application of the heat ratio method for determining sap flow in Brazilian mahogany using sets of heating probes and thermometers installed on plants of 18 months of age,cultivated in Yellow Latosol,under a weighing lysimeter and located in a protected environment.The uncertainty in sap flow was calculated as the combination of uncertainty in the thermal diffusivity(U_(k)),conductive section(U_(Sc)) and corrected sap velocity(U_(Vc)).U_(k) had greater weight in determining the flow of sap in Brazilian mahogany,when compared to U_(Sc) and U_(Vc).The thermal diffusivity during the cycle,or period evaluated,must be adjusted to improve the accuracy of the heat ratio method because the sap flow overestimated transpiration by 15.0%.When soil water was optimal In addition,the vapor pressure deficit linearly and indirectly influenced the SF with a difference of 14.6%.展开更多
An electron cyclotron resonance heating (ECRH) system with a maximum output power of 1 MW, a frequency of 68 GHz and a duration of ls was operated on HL-2A tokamak. The temperature profile control and the sawtooth b...An electron cyclotron resonance heating (ECRH) system with a maximum output power of 1 MW, a frequency of 68 GHz and a duration of ls was operated on HL-2A tokamak. The temperature profile control and the sawtooth behaviour during ECRH experiments are investigated. ‘Density pumpout' during on-axis ECRH is analysed. Features of confinement and electron heat transport during ECRH are studied.展开更多
It is found that in HT-7 ohmic plasma, main energy loss comes from electron heat conduction, hence quantitative data of electron heat diffusivity is a very important issue for investigation of electron heat transporta...It is found that in HT-7 ohmic plasma, main energy loss comes from electron heat conduction, hence quantitative data of electron heat diffusivity is a very important issue for investigation of electron heat transportation behavior in different target plasmas so as to get high performance plasma. A time-to-peak method of the heat pulse propagation originating from the sawtooth activity on the soft x-ray intensity signal has been adopted to experimentally determine electron heat diffusivity XeHP on the HT-7 tokamak. Aiming to improve the signal-to-noise (S/N) ratio of the original signal to get a stable and reasonable electron heat diffusivity XeHD value, some data processing methods, including average of tens of sawteeth, is discussed. The electron heat diffusivity XeHP is larger than XePB which is determined from the balance of background plasma power. Based on variation of the measured electron heat diffusivity XeHP, performances of different high confinement plasmas are analyzed.展开更多
Temperature measurement by IR (infrared) camera was performed oll HT-T tokamak. particularly during long pulse discharges, during which the temperature of the hot spots on the belt limiter exceeded 1000℃. The heat ...Temperature measurement by IR (infrared) camera was performed oll HT-T tokamak. particularly during long pulse discharges, during which the temperature of the hot spots on the belt limiter exceeded 1000℃. The heat load on the surface of the movable limiter could be obtained through ANSYS with the temperature measured by IR-camera. This work could be important for the temperature measurement and heat load study on the first wall of EAST device.展开更多
The plasma synthetic jet is a novel flow control approach which is currently being studied. In this paper its characteristic and control effect on supersonic flow is investigated both experimentally and numerically. I...The plasma synthetic jet is a novel flow control approach which is currently being studied. In this paper its characteristic and control effect on supersonic flow is investigated both experimentally and numerically. In the experiment, the formation of plasma synthetic jet and its propagation velocity in quiescent air are recorded and calculated with time resolved schlieren method. The jet velocity is up to 100 m/s and no remarkable difference has been found after changing discharge parameters. When applied in Mach 2 supersonic flow, an obvious shockwave can be observed. In the modeling of electrical heating, the arc domain is not defined as an initial condition with fixed temperature or pressure, but a source term with time-varying input power density, which is expected to better describe the influence of heating process. Velocity variation with different heating efficiencies is presented and discussed and a peak velocity of 850 m/s is achieved in still air with heating power density of 5.0 · 1012W/m3. For more details on the interaction between plasma synthetic jet and supersonic flow, the plasma synthetic jet induced shockwave and the disturbances in the boundary layer are numerically researched. All the results have demonstrated the control authority of plasma synthetic jet onto supersonic flow.展开更多
基金financial support of the project from the National Natural Science Foundation of China(No.51701223)。
文摘Phase structure of sputtered Ta coating in the negative glow space and LPH effect were explored.The whole coating/substrate system is substrate→physically gas-absorbed Fe surface→oxygen-enriched TaOx layer→amorphous Ta→αandβdual phase→singleαphase.After LPH course,micro structure of Ta coating shows intact,only a few cracks emerge after 100 laser pulses,exhibiting thin HAZ but thick Fe/Ta ICZ,without martensitic transformation.For the electrodeposited Cr coating,continuous thermal stresses produce many extra micro-crack,substrate oxidation and martensitic transformation,leading to crack propagations and final bulk delamination,without any ICZ.
基金Supported by National Natural Science Foundation of China(11375097)
文摘Producing high-brightness and high-charge(〉100 pC) electron bunches at blowout regime requires ultrashort laser pulses with high fluence. The effects of laser pulse heating of the copper photocathode are analyzed in this paper. The electron and lattice temperature is calculated using an improved two-temperature model, and an extended Dowell-Schmerge model is employed to calculate the thermal emittance and quantum efficiency. A timedependent growth of the thermal emittance and the quantum efficiency is observed. For a fixed amount of charge,the projected thermal emittance increases with decreasing laser radius, and this effect should be taken into account in laser optimization at blowout regime. Moreover, laser damage threshold fluence is simulated, showing that the maximum local fluence should be less than 40 mJ/cm^2 to prevent damage to the cathode.
基金support provided by EIG EURIDICE/SCK.CEN(Belgium)through a PhD collaboration project with International Centre for Numerical Methods in Engineering(CIMNE,Spain)
文摘Boom clay formation is a potential natural host rock for geological disposal of high-level nuclear waste in Belgium.Heating pulse tests with controlled power supply(maximum temperature was limited to 85℃) and controlled hydraulic boundary conditions were performed under nearly constant volume conditions to study the impact of thermal loading on the clay formation.Selected test results of intact borehole samples retrieved in horizontal direction are presented and discussed.The study focuses on the time evolution of temperature and pore water pressure changes along heating and cooling paths,i.e.pore pressure build-up during quasi-undrained heating and later dissipation at constant temperature.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10975033,11404070 and 11275048the Science Foundation for Youths of Guangxi Province under Grant No 2014GXNSFBA118022the Scientific Research Foundation of Guangxi Education Department under Grant No 2013ZD039
文摘Non-equilibrium molecular dynamics simulations of liquid water in picosecond high-power terahertz pulses are performed by using a non-polarizable potential model. Numerical results show that the energy absorption of water molecules exhibits a pronounced resonance with THz pulses in the frequency range of 14-17 THz. With the THz pulse at resonant frequencies, the maximum temperature is about 562 K by heating the water at room temperature. Further investigation indicates that the results are independent of the size of the nanoscale water box. The efficiency of energy transfer by resonant absorption is more than seven times of microwave heating. These studies show promising applications of ultrashort THz pulses.
基金National Natural Science Foundation of China(Nos.12075057,11775069,11320101005,and 11875020)National Magnetic Confinement Fusion Science Program of China(No.2017YFE0301201)+3 种基金East China University of Technology,Doctoral Foundation(Nos.DHBK 2017134 and DHBK 2018059)Grant-in-Aid for Scientific Research of the Japan Society for the Promotion of Science(Nos.15H02155,15H02335,21K03513)Landmark Achievements in Nuclear Science and Technology(No.xxkjs2018011)Natural Science Foundation of Jiangxi Province(Nos.20202ACBL201002 and 0192ACB80006)。
文摘Enhancements of edge zonal flows,radial electric fields,and turbulence are observed in electron cyclotron resonance heating-heated plasmas(Zhao et al 2013 Nucl.Fusion 53083011).In this paper,the effects of sawtooth heat pulses on flows and turbulence are presented.These experiments are performed using multiple Langmuir probe arrays in the edge plasmas of the HL-2A tokamak.The edge zonal flows,radial electric fields,and turbulence are all enhanced by sawteeth.Propagation of the zonal flow and turbulence intensities is also observed.The delay time of the maximal intensity of the electric fields,zonal flows,and turbulence with respect to the sawtooth crashes is estimated as~1 ms and comparable to that of the sawtooth-triggered intermediate phases.Not only the zonal flows but also the radial electric fields lag behind the turbulence.Furthermore,the intensities of both the zonal flows and electric fields nearly linearly increase/decrease with the increase/decrease of the turbulence intensity.A double-source predator-prey model analysis suggests that a relatively strong turbulence source may contribute to the dominant zonal flow formation during sawtooth cycles.
文摘The nonlinear thermoelastic responses of an elastic medium exposed to laser generated shortpulse heating are investigated in this article. The thermal wave propagation of generalized thermoelastic medium under the impact of thermal loading with energy dissipation is the focus of this research. To model the thermal boundary condition(in the form of thermal conduction),generalized Cattaneo model(GCM) is employed. In the reference configuration, a nonlinear coupled Lord-Shulman-type generalized thermoelasticity formulation using finite strain theory(FST) is developed and the temperature dependency of the thermal conductivity is considered to derive the equations. In order to solve the time-dependent and nonlinear equations, Newmark’s numerical time integration technique and an updated finite element algorithm is applied and to ensure achieving accurate continuity of the results, the Hermitian elements are used instead of Lagrangian’s. The numerical responses for different factors such as input heat flux and nonlinear terms are expressed graphically and their impacts on the system’s reaction are discussed in detail.The results of the study are presented for Green–Lindsay model and the findings are compared with Lord-Shulman model especially with regards to heat wave propagation. It is shown that the nature of the laser’s thermal shock and its geometry are particularly determinative in the final stage of deformation. The research also concluded that employing FST leads to achieving more accuracy in terms of elastic deformations;however, the thermally nonlinear analysis does not change the results markedly. For this reason, the nonlinear theory of deformation is required in laser related reviews, while it is reasonable to ignore the temperature changes compared to the reference temperature in deriving governing equations.
文摘A pulsed-wire wall probe measurement system was developed in this paper,which can be used for measuring wall Parameters in separated flow- The operating princi-ple was described and the way of probe calibration was given. Wall parameters of back-ward-facing and forward-facing step flow were measured,and the wall nows structure andcharacters were revealed.
文摘This paper numerically investigates the effect of the location of a horizontal fin on the melting of a phase change material(PCM)inside a rectangular enclosure heated by multiple discrete pulsed protruding heat sources.The fin and the phase change material filling the enclosure store the thermal energy extracted from the heat sources,in sensible and latent forms.The heat sources are assumed to simulate electronic components undergoing a superheating technical issue.By extracting heat from the electronics,the PCM plays the role of a heat sink.To analyze the thermal behavior and predict the cooling performance of the proposed cooling system,we derive a nonlinear mathematical model based on mass,momentum and energy conservation laws.Several numerical investigations are conducted to quantify the influence of the fin position on the thermal behavior and the cooling performance of the heat sink.Predictions include the transient maximum temperature occurring inside the heat sources and the liquid volume.A comparison between our numerical results and experimental data selected from the literature shows a good agreement.The main conclusion is that the presence of the fin leads to a slight increase in the melting time.
文摘A mathematical model is presented to describe transient behavior of heat transfer and fluid flow in stationary pulsed current tungsten inert gas (PC-TIG) weld pool, which considers three kinds of driving, forces for weld pool convection, i,e. buoyancyforce, electromagnetic force and surface tension force. furthermore. the effect of vaporization heat flux at the free surface of weld pool and the temperature coefficient of surface tenston which is a function of temperatuer and composition are considered in the model In order to accelerate the convergence of iteration the AST(additive source term)method which concerns with the thermal energv boundary conditions is extended successfully to deal with the momentum boundary conditions by which the transient momentum equation and energy equation are mutually coupled. At the same time. ADI (Alternating direction implicit) method and DBC (double blocks correction) technque are employed to solve the finite difference equations. The results of numerical simulation demonstrate the transient behavior of PC-TIG weld pool, as well as the periodic variation of fluid flow and heat transfer with the periodic variation of welding current in stationary PC-TIG weld pool. The theoretical predictions based on this model are, shown to be in good accordance with the experimental measurements.
文摘The electrocaloric effect in thin films of an electrocaloric material has the potential to be used for efficient cooling systems for high power electronic devices. We numerically calculated the effect of parameters in electrocaloric refrigeration with a thermal switch of fluid motion on the thermal performance. The system of changing air and water flow with the pulse generation of cold energy increased the heat transfer efficiency to 67% at a frequency of 5 Hz. The optimum time delay of water flow to increase the heat transfer efficiency was zero at low frequency and became half of the time period to change heat for a high frequency of 100 Hz. When the heat transfer efficiency was high, the final temperature change in water flow was not the maximum temperature change.
基金supported by the National Natural Science Foundation of China(52177217 and 52037006)the Beijing Natural Science Foundation(3212031)。
文摘Conventional charging methods for lithium-ion battery(LIB)are challenged with vital problems at low temperatures:risk of lithium(Li)plating and low charging speed.This study proposes a fast-charging strategy without Li plating to achieve high-rate charging at low temperatures with bidirectional chargers.The strategy combines the pulsed-heating method and the optimal charging method via precise control of the battery states.A thermo-electric coupled model is developed based on the pseudo-twodimensional(P2D)electrochemical model to derive charging performances.Two current maps of pulsed heating and charging are generated to realize real-time control.Therefore,our proposed strategy achieves a 3 C equivalent rate at 0℃ and 1.5 C at-10℃ without Li plating,which is 10–30 times faster than the traditional methods.The entropy method is employed to balance the charging speed and the energy efficiency,and the charging performance is further enhanced.For practical application,the power limitation of the charger is considered,and a 2.4 C equivalent rate is achieved at 0℃ with a 250 kW maximum power output.This novel strategy significantly expands LIB usage boundary,and increases charging speed and battery safety.
基金supported by the Ministry of Science,Technology,Innovation,Communication(MCTIC)the Foundation for Research Support of Goias State(FAPEG)+2 种基金the National Council for Scientific and Technological Development (CNPq)the Federal Institute Goiano (IF Goiano)the Federal University of B ahia Reconcavo (UFRB)。
文摘The tropical arboreal species Brazilian mahogany(Swietenia macrophylla) is very important economically and ecologically,for which understanding ecophysiological variables such as sap flow will improve understanding of the species and its cultivation.This paper aims to measure uncertainties(U) involved in the application of the heat ratio method for determining sap flow in Brazilian mahogany using sets of heating probes and thermometers installed on plants of 18 months of age,cultivated in Yellow Latosol,under a weighing lysimeter and located in a protected environment.The uncertainty in sap flow was calculated as the combination of uncertainty in the thermal diffusivity(U_(k)),conductive section(U_(Sc)) and corrected sap velocity(U_(Vc)).U_(k) had greater weight in determining the flow of sap in Brazilian mahogany,when compared to U_(Sc) and U_(Vc).The thermal diffusivity during the cycle,or period evaluated,must be adjusted to improve the accuracy of the heat ratio method because the sap flow overestimated transpiration by 15.0%.When soil water was optimal In addition,the vapor pressure deficit linearly and indirectly influenced the SF with a difference of 14.6%.
基金supported by National Natural Science Foundation of China (No.10235010)
文摘An electron cyclotron resonance heating (ECRH) system with a maximum output power of 1 MW, a frequency of 68 GHz and a duration of ls was operated on HL-2A tokamak. The temperature profile control and the sawtooth behaviour during ECRH experiments are investigated. ‘Density pumpout' during on-axis ECRH is analysed. Features of confinement and electron heat transport during ECRH are studied.
基金The project supported by National Natural Science Foundation (Nos. 10375070, 10305012)and also supported partially by the core university program between China and Japan
文摘It is found that in HT-7 ohmic plasma, main energy loss comes from electron heat conduction, hence quantitative data of electron heat diffusivity is a very important issue for investigation of electron heat transportation behavior in different target plasmas so as to get high performance plasma. A time-to-peak method of the heat pulse propagation originating from the sawtooth activity on the soft x-ray intensity signal has been adopted to experimentally determine electron heat diffusivity XeHP on the HT-7 tokamak. Aiming to improve the signal-to-noise (S/N) ratio of the original signal to get a stable and reasonable electron heat diffusivity XeHD value, some data processing methods, including average of tens of sawteeth, is discussed. The electron heat diffusivity XeHP is larger than XePB which is determined from the balance of background plasma power. Based on variation of the measured electron heat diffusivity XeHP, performances of different high confinement plasmas are analyzed.
基金National Natural Science Foundation of China(No.10305011)
文摘Temperature measurement by IR (infrared) camera was performed oll HT-T tokamak. particularly during long pulse discharges, during which the temperature of the hot spots on the belt limiter exceeded 1000℃. The heat load on the surface of the movable limiter could be obtained through ANSYS with the temperature measured by IR-camera. This work could be important for the temperature measurement and heat load study on the first wall of EAST device.
基金supported by the National Natural Science Foundation of China(Nos.51407197,11472306,11372352)
文摘The plasma synthetic jet is a novel flow control approach which is currently being studied. In this paper its characteristic and control effect on supersonic flow is investigated both experimentally and numerically. In the experiment, the formation of plasma synthetic jet and its propagation velocity in quiescent air are recorded and calculated with time resolved schlieren method. The jet velocity is up to 100 m/s and no remarkable difference has been found after changing discharge parameters. When applied in Mach 2 supersonic flow, an obvious shockwave can be observed. In the modeling of electrical heating, the arc domain is not defined as an initial condition with fixed temperature or pressure, but a source term with time-varying input power density, which is expected to better describe the influence of heating process. Velocity variation with different heating efficiencies is presented and discussed and a peak velocity of 850 m/s is achieved in still air with heating power density of 5.0 · 1012W/m3. For more details on the interaction between plasma synthetic jet and supersonic flow, the plasma synthetic jet induced shockwave and the disturbances in the boundary layer are numerically researched. All the results have demonstrated the control authority of plasma synthetic jet onto supersonic flow.