We conduct an experimental study supported by theoretical analysis of single laser ablating copper to investigate the interactions between laser and material at different sample temperatures,and predict the changes of...We conduct an experimental study supported by theoretical analysis of single laser ablating copper to investigate the interactions between laser and material at different sample temperatures,and predict the changes of ablation morphology and lattice temperature.For investigating the effect of sample temperature on femtosecond laser processing,we conduct experiments on and simulate the thermal behavior of femtosecond laser irradiating copper by using a two-temperature model.The simulation results show that both electron peak temperature and the relaxation time needed to reach equilibrium increase as initial sample temperature rises.When the sample temperature rises from 300 K to 600 K,the maximum lattice temperature of the copper surface increases by about 6500 K under femtosecond laser irradiation,and the ablation depth increases by 20%.The simulated ablation depths follow the same general trend as the experimental values.This work provides some theoretical basis and technical support for developing femtosecond laser processing in the field of metal materials.展开更多
A three-dimensional, two-temperature(2T) model of a lamellar cathode arc is constructed,drawing upon the conservation equations for mass, momentum, electron energy, and heavy particle energy, in addition to Maxwell...A three-dimensional, two-temperature(2T) model of a lamellar cathode arc is constructed,drawing upon the conservation equations for mass, momentum, electron energy, and heavy particle energy, in addition to Maxwell's equations. The model aims to elucidate how the physical properties of electrons and heavy particles affect heat transfer and fluid flow in a lamellar cathode arc. This is achieved by solving and comparing the fields of electron temperature,heavy particle temperature, fluid flow, current density, and Lorentz force distribution under varying welding currents. The results show that the guiding effect of the lamellar cathode on current density, the inertial drag effect of moving arc, and the attraction effect of Lorentz force at the lamellar cathode tip primarily govern the distribution of the arc's physical fields. The guiding effect localizes the current density to the front end of the lamellar cathode, particularly where the discharge gap is minimal. Both the inertial drag effect and the attraction effect of Lorentz force direct arc flow toward its periphery. Under the influence of the aforementioned factors, the physical fields of the lamellar cathode arc undergo expansion and shift counter to the arc's direction of motion. A reduction in welding current substantially weakens the guiding effect,causing the arc's physical fields to deviate further in the direction opposite to the arc motion. In comparison with a cylindrical cathode arc, the physical fields of the lamellar cathode arc are markedly expanded, leading to a reduction in current density, electron temperature, heavy particle temperature, cathode jet flow velocity, and Lorentz force.展开更多
A two temperature CO_(2) refrigeration system with economizer is proposed and compared with the traditional dual-temperature CO_(2) refrigeration system based on energy consumption,exergy and economic analysis.Using g...A two temperature CO_(2) refrigeration system with economizer is proposed and compared with the traditional dual-temperature CO_(2) refrigeration system based on energy consumption,exergy and economic analysis.Using genetic algorithm multi-objective optimization method,taking the COP,exergy loss and total economic cost as the objective functions to find the best design conditions of the two systems.The Pareto fronts are obtained at different ambient temperatures.Technique for order preference by similarity to an ideal solution decision-making method is adopted to determine the optimum state points.The simulation results show that when operating at different ambient temperatures,the introduction of economizer can improve COP,reduce exergy loss and the overall economic cost rate of the two-temperature CO_(2) refrigeration system.In addition,economic analyses take the impact of carbon dioxide emission cost and electricity price into consideration.The results indicate that with the increase of CO_(2) emission cost and electricity price,the hourly economic cost of both systems increases,but the hourly economic cost of the two-temperature CO_(2) refrigeration system with economizer system is always lower than that of conventional two-temperature CO_(2) refrigeration system.展开更多
The present paper is concerned with the wave propagation in a micropolar thermoelastic solid with distinct two temperatures under the effect of the magnetic field in the presence of the gravity field and an internal h...The present paper is concerned with the wave propagation in a micropolar thermoelastic solid with distinct two temperatures under the effect of the magnetic field in the presence of the gravity field and an internal heat source.The formulation of the problem is applied in the context of the three-phase-lag model and Green-Naghdi theory without dissipation.The medium is a homogeneous isotropic thermoelastic in the half-space.The exact expressions of the considered variables are obtained by using normal mode analysis.Comparisons are made with the results in the two theories in the absence and presence of the magnetic field as well as the two-temperature parameter.A comparison is also made in the two theories for different values of an internal heat source.展开更多
The transverse mass spectra of protons, pions, kaons, Lambda and Antilambda produced in central nucleus-nucleus collisions at high energies are described by using one-temperature and two-temperature emission pictures....The transverse mass spectra of protons, pions, kaons, Lambda and Antilambda produced in central nucleus-nucleus collisions at high energies are described by using one-temperature and two-temperature emission pictures. The calculated results are compared and found to be in good agreement with the experimental data of the E895, E866 and E917 Collaborations measured in central Au-Au collisions at the Alternating Gradient Synchrotron （AGS） energies and the NA49 Collaboration measured in central Pb-Pb collisions at the Super Proton Synchrotron （SPS） energies. It is demonstrated that the transverse mass distributions of protons, kaons, Lambda and Antilambda, except for Lambda hyperons produced in central Pb-Pb collisions at 158 A GeV, can be described by using the one-temperature emission picture, and for pions, we need to use the two-temperature emission picture.展开更多
In this paper, non-equilibrium ignition conditions for magnetized cylindrical deuterium–tritium plasma in the presence of an axial magnetic field have been investigated. It is expected that temperature imbalance betw...In this paper, non-equilibrium ignition conditions for magnetized cylindrical deuterium–tritium plasma in the presence of an axial magnetic field have been investigated. It is expected that temperature imbalance between ions and electrons as well as the axial magnetic field will relax the threshold of ignition conditions.Therefore, ignition conditions for this model are derived numerically involving the energy balance equation at the stagnation point. It has been derived using parametric space including electron and ion temperature(T_e, T_i), areal density(q R), and seed magnetic field-dependent free parameters of B/q, mB, and BR. For B/ρ < 10~6 G cm^3 g^(-1),mB < 4 × 10~4 G cm g^(-1), and BR <3 × 10~5 G cm, the minimum fuel areal density exceeds between ρR >0.002 g cm^(-2), ρR> 0.25 g cm^(-2), and ρR > 0.02 g cm^(-2),respectively. The practical equilibrium conditions also addressed which is in good agreement with the corresponding one-temperature magnetized mode proposed in previous studies. Moreover, it has been shown that the typical criterion of BR ≥(6.13–4.64) × 10~5 G cm would be expectable. It is also confirmed that the minimum product of areal density times fuel temperature in equilibrium model is located in the range of T = 6–8 keV for all these free parameters, depending on the magnitude of the magnetic field. This is the entry point for the non-equilibrium model consistent with equilibrium model.展开更多
A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and...A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.展开更多
Extreme ultraviolet(EUV)light plays an important role in various fields such as material characterization and semiconductor manufacturing.It is also a potential approach in material fabrication at atomic and close-to-...Extreme ultraviolet(EUV)light plays an important role in various fields such as material characterization and semiconductor manufacturing.It is also a potential approach in material fabrication at atomic and close-to-atomic scales.However,the material removal mechanism has not yet been fully understood.This paper studies the interaction of a femtosecond EUV pulse with monocrystalline silicon using molecular dynamics(MD)coupled with a two-temperature model(TTM).The photoionization mechanism,an important process occurring at a short wavelength,is introduced to the simulation and the results are compared with those of the traditional model.Dynamical processes including photoionization,atom desorption,and laser-induced shockwave are discussed under various fluencies,and the possibility of single atomic layer removal is explored.Results show that photoionization and the corresponding bond breakage are the main reasons of atom desorption.The method developed can be further employed to investigate the interaction between high-energy photons and the material at moderate fluence.展开更多
In order to investigate the relationship between the flow-field parameters outside the vehicle and the altitude,this paper takes the Atmospheric Reentry Demonstrator(ARD)with an angle of attack of-20°as the resea...In order to investigate the relationship between the flow-field parameters outside the vehicle and the altitude,this paper takes the Atmospheric Reentry Demonstrator(ARD)with an angle of attack of-20°as the research object and adopts a two-temperature model coupled with the shear-stress transport k-ωturbulence model to focus on the variation of flow-field parameters including flow-field pressure,Mach number and temperature with the reentry altitude.It is found that the flow-field high-pressure region and low-Mach region both appear in the shock layer near the head of the ARD,while the maximum pressure of the surface appears on the windward side of the ARD's head with a toroidal distribution,and the numerical magnitude is inversely proportional to the radius of the torus.With fluid through the shoulder of the ARD flow expansion plays a dominant role,the airflow velocity increases,the Mach number of the windward side of the rear cone increases and the flow-field pressure and surface pressure rapidly decrease.When the fluid passes through the shock layer,the translational-rotation temperature will increase before the vibration-electron temperature,there is a thermal non-equilibrium effect and the two temperatures will rapidly decrease again when approaching the surface of the ARD due to the existence of temperature gradient.At the same time,both the windward side of the shoulder and the back cover of the ARD suffer from a large thermal load and require thermal protection.展开更多
The study considers a homogeneous isotropic thermo-visco-elastic solid with hyperbolic two-temperature to cope up with its two-dimensional(2 D)deformations.The heat conduction equation is influenced by the Thomson coe...The study considers a homogeneous isotropic thermo-visco-elastic solid with hyperbolic two-temperature to cope up with its two-dimensional(2 D)deformations.The heat conduction equation is influenced by the Thomson coefficient.Lord-Shulman’s theory is used to modify the basic governing equations.A method called"normal mode analysis"is utilized to attain the magnetic field,stress,conductive and thermodynamic temperature,and displacement components.Also,a number of numerical calculations are performed and discussed to understand the impact of hyperbolic two-temperatures,Thomson parameter,and viscosity on the material mentioned above.展开更多
Femtosecond pulsed lasers have been widely used over the past decades due to their capability to fabricate precise patterns at the micro-and nano-lengths scales. A key issue for efficient material processing is the de...Femtosecond pulsed lasers have been widely used over the past decades due to their capability to fabricate precise patterns at the micro-and nano-lengths scales. A key issue for efficient material processing is the determination of the laser parameters used in the experimental set ups. Despite a systematic investigation that has been performed to highlight the impact of every parameter independently, little attention has been drawn on the role of the substrate material on which the irradiated solid is placed. In this work, the influence of the substrate is emphasised for films of various thicknesses, which demonstrates that both the optical and thermophysical properties of the substrate affect the thermal fingerprint on the irradiated film while the impact is manifested to be higher at smaller film sizes. Two representative materials, silicon and fused silica, have been selected as typical substrates for thin films(gold and nickel) of different optical and thermophysical behaviour and the thermal response and damage thresholds are evaluated for the irradiated solids. The pronounced influence of the substrate is aimed to pave the way for new and more optimised designs of laserbased fabrication set ups and processing schemes.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2019YFA0307701)the National Natural Science Foundation of China(Grant Nos.11674128,11674124,and 11974138).
文摘We conduct an experimental study supported by theoretical analysis of single laser ablating copper to investigate the interactions between laser and material at different sample temperatures,and predict the changes of ablation morphology and lattice temperature.For investigating the effect of sample temperature on femtosecond laser processing,we conduct experiments on and simulate the thermal behavior of femtosecond laser irradiating copper by using a two-temperature model.The simulation results show that both electron peak temperature and the relaxation time needed to reach equilibrium increase as initial sample temperature rises.When the sample temperature rises from 300 K to 600 K,the maximum lattice temperature of the copper surface increases by about 6500 K under femtosecond laser irradiation,and the ablation depth increases by 20%.The simulated ablation depths follow the same general trend as the experimental values.This work provides some theoretical basis and technical support for developing femtosecond laser processing in the field of metal materials.
基金National Natural Science Foundation of China (No. 51605384)the Natural Science Foundation of Gansu Province,China (No. 21JR7RA308)。
文摘A three-dimensional, two-temperature(2T) model of a lamellar cathode arc is constructed,drawing upon the conservation equations for mass, momentum, electron energy, and heavy particle energy, in addition to Maxwell's equations. The model aims to elucidate how the physical properties of electrons and heavy particles affect heat transfer and fluid flow in a lamellar cathode arc. This is achieved by solving and comparing the fields of electron temperature,heavy particle temperature, fluid flow, current density, and Lorentz force distribution under varying welding currents. The results show that the guiding effect of the lamellar cathode on current density, the inertial drag effect of moving arc, and the attraction effect of Lorentz force at the lamellar cathode tip primarily govern the distribution of the arc's physical fields. The guiding effect localizes the current density to the front end of the lamellar cathode, particularly where the discharge gap is minimal. Both the inertial drag effect and the attraction effect of Lorentz force direct arc flow toward its periphery. Under the influence of the aforementioned factors, the physical fields of the lamellar cathode arc undergo expansion and shift counter to the arc's direction of motion. A reduction in welding current substantially weakens the guiding effect,causing the arc's physical fields to deviate further in the direction opposite to the arc motion. In comparison with a cylindrical cathode arc, the physical fields of the lamellar cathode arc are markedly expanded, leading to a reduction in current density, electron temperature, heavy particle temperature, cathode jet flow velocity, and Lorentz force.
基金supported by the National Key Research and Development Program of China (Grant No.2019YFB1704204)the National Natural Science Foundation of China (Grant No.12002348).
基金supported by the National Natural Science Foundation of China (Grant No. 51776110)。
文摘A two temperature CO_(2) refrigeration system with economizer is proposed and compared with the traditional dual-temperature CO_(2) refrigeration system based on energy consumption,exergy and economic analysis.Using genetic algorithm multi-objective optimization method,taking the COP,exergy loss and total economic cost as the objective functions to find the best design conditions of the two systems.The Pareto fronts are obtained at different ambient temperatures.Technique for order preference by similarity to an ideal solution decision-making method is adopted to determine the optimum state points.The simulation results show that when operating at different ambient temperatures,the introduction of economizer can improve COP,reduce exergy loss and the overall economic cost rate of the two-temperature CO_(2) refrigeration system.In addition,economic analyses take the impact of carbon dioxide emission cost and electricity price into consideration.The results indicate that with the increase of CO_(2) emission cost and electricity price,the hourly economic cost of both systems increases,but the hourly economic cost of the two-temperature CO_(2) refrigeration system with economizer system is always lower than that of conventional two-temperature CO_(2) refrigeration system.
文摘The present paper is concerned with the wave propagation in a micropolar thermoelastic solid with distinct two temperatures under the effect of the magnetic field in the presence of the gravity field and an internal heat source.The formulation of the problem is applied in the context of the three-phase-lag model and Green-Naghdi theory without dissipation.The medium is a homogeneous isotropic thermoelastic in the half-space.The exact expressions of the considered variables are obtained by using normal mode analysis.Comparisons are made with the results in the two theories in the absence and presence of the magnetic field as well as the two-temperature parameter.A comparison is also made in the two theories for different values of an internal heat source.
基金Supported by National Natural Science Foundation of China (10975095)Natural Science Foundation of Shanxi Province(2007011005)
文摘The transverse mass spectra of protons, pions, kaons, Lambda and Antilambda produced in central nucleus-nucleus collisions at high energies are described by using one-temperature and two-temperature emission pictures. The calculated results are compared and found to be in good agreement with the experimental data of the E895, E866 and E917 Collaborations measured in central Au-Au collisions at the Alternating Gradient Synchrotron （AGS） energies and the NA49 Collaboration measured in central Pb-Pb collisions at the Super Proton Synchrotron （SPS） energies. It is demonstrated that the transverse mass distributions of protons, kaons, Lambda and Antilambda, except for Lambda hyperons produced in central Pb-Pb collisions at 158 A GeV, can be described by using the one-temperature emission picture, and for pions, we need to use the two-temperature emission picture.
文摘In this paper, non-equilibrium ignition conditions for magnetized cylindrical deuterium–tritium plasma in the presence of an axial magnetic field have been investigated. It is expected that temperature imbalance between ions and electrons as well as the axial magnetic field will relax the threshold of ignition conditions.Therefore, ignition conditions for this model are derived numerically involving the energy balance equation at the stagnation point. It has been derived using parametric space including electron and ion temperature(T_e, T_i), areal density(q R), and seed magnetic field-dependent free parameters of B/q, mB, and BR. For B/ρ < 10~6 G cm^3 g^(-1),mB < 4 × 10~4 G cm g^(-1), and BR <3 × 10~5 G cm, the minimum fuel areal density exceeds between ρR >0.002 g cm^(-2), ρR> 0.25 g cm^(-2), and ρR > 0.02 g cm^(-2),respectively. The practical equilibrium conditions also addressed which is in good agreement with the corresponding one-temperature magnetized mode proposed in previous studies. Moreover, it has been shown that the typical criterion of BR ≥(6.13–4.64) × 10~5 G cm would be expectable. It is also confirmed that the minimum product of areal density times fuel temperature in equilibrium model is located in the range of T = 6–8 keV for all these free parameters, depending on the magnitude of the magnetic field. This is the entry point for the non-equilibrium model consistent with equilibrium model.
文摘A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.
基金supported financially by the National Natural Science Foundation(Grant No.52035009)the‘111’project of the State Administration of Foreign Experts Affairs and the Ministry of Education of China(Grant No.B07014).
文摘Extreme ultraviolet(EUV)light plays an important role in various fields such as material characterization and semiconductor manufacturing.It is also a potential approach in material fabrication at atomic and close-to-atomic scales.However,the material removal mechanism has not yet been fully understood.This paper studies the interaction of a femtosecond EUV pulse with monocrystalline silicon using molecular dynamics(MD)coupled with a two-temperature model(TTM).The photoionization mechanism,an important process occurring at a short wavelength,is introduced to the simulation and the results are compared with those of the traditional model.Dynamical processes including photoionization,atom desorption,and laser-induced shockwave are discussed under various fluencies,and the possibility of single atomic layer removal is explored.Results show that photoionization and the corresponding bond breakage are the main reasons of atom desorption.The method developed can be further employed to investigate the interaction between high-energy photons and the material at moderate fluence.
基金Project supported by the National Natural Science Foundation of China(Grant No.12175177)the China Postdoctoral Science Foundation(Grant No.2021M693889)。
文摘In order to investigate the relationship between the flow-field parameters outside the vehicle and the altitude,this paper takes the Atmospheric Reentry Demonstrator(ARD)with an angle of attack of-20°as the research object and adopts a two-temperature model coupled with the shear-stress transport k-ωturbulence model to focus on the variation of flow-field parameters including flow-field pressure,Mach number and temperature with the reentry altitude.It is found that the flow-field high-pressure region and low-Mach region both appear in the shock layer near the head of the ARD,while the maximum pressure of the surface appears on the windward side of the ARD's head with a toroidal distribution,and the numerical magnitude is inversely proportional to the radius of the torus.With fluid through the shoulder of the ARD flow expansion plays a dominant role,the airflow velocity increases,the Mach number of the windward side of the rear cone increases and the flow-field pressure and surface pressure rapidly decrease.When the fluid passes through the shock layer,the translational-rotation temperature will increase before the vibration-electron temperature,there is a thermal non-equilibrium effect and the two temperatures will rapidly decrease again when approaching the surface of the ARD due to the existence of temperature gradient.At the same time,both the windward side of the shoulder and the back cover of the ARD suffer from a large thermal load and require thermal protection.
基金the Taif University Researchers Supporting Project in Taif University of Saudi Arabia(No.TURSP-2020/230)。
文摘The study considers a homogeneous isotropic thermo-visco-elastic solid with hyperbolic two-temperature to cope up with its two-dimensional(2 D)deformations.The heat conduction equation is influenced by the Thomson coefficient.Lord-Shulman’s theory is used to modify the basic governing equations.A method called"normal mode analysis"is utilized to attain the magnetic field,stress,conductive and thermodynamic temperature,and displacement components.Also,a number of numerical calculations are performed and discussed to understand the impact of hyperbolic two-temperatures,Thomson parameter,and viscosity on the material mentioned above.
基金Projects(862016(Bio Combs4Nanofibres)HELLAS-CH+1 种基金MIS 5002735) funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” and co-financed by Greece and the EU (European Regional Development Fund)Project (COST Action TUMIEE) supported by COST-European Cooperation in Science and Technology。
文摘Femtosecond pulsed lasers have been widely used over the past decades due to their capability to fabricate precise patterns at the micro-and nano-lengths scales. A key issue for efficient material processing is the determination of the laser parameters used in the experimental set ups. Despite a systematic investigation that has been performed to highlight the impact of every parameter independently, little attention has been drawn on the role of the substrate material on which the irradiated solid is placed. In this work, the influence of the substrate is emphasised for films of various thicknesses, which demonstrates that both the optical and thermophysical properties of the substrate affect the thermal fingerprint on the irradiated film while the impact is manifested to be higher at smaller film sizes. Two representative materials, silicon and fused silica, have been selected as typical substrates for thin films(gold and nickel) of different optical and thermophysical behaviour and the thermal response and damage thresholds are evaluated for the irradiated solids. The pronounced influence of the substrate is aimed to pave the way for new and more optimised designs of laserbased fabrication set ups and processing schemes.
