Large diamond crystals were successfully synthesized by a FeNi C system using the temperature gradient method under high-pressure high-temperature conditions. The assembly of the growth cell was improved and the growt...Large diamond crystals were successfully synthesized by a FeNi C system using the temperature gradient method under high-pressure high-temperature conditions. The assembly of the growth cell was improved and the growth process of diamond was investigated. Effects of the symmetry of the carbon convection field around the growing diamond crystal were investigated systematically by adjusting the position of the seed crystal in the melted catalyst/solvent. The results indicate that the morphologies and metal inclusion distributions of the synthetic diamond crystals vary obviously in both symmetric and non-symmetric carbon convection fields with temperature. Moreover, the finite element method was applied to analyze the carbon convection mode of the melted catalyst/solvent around the diamond crystal. This work is helpful for understanding the growth mechanism of diamond.展开更多
In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and the boundary conditions developed...In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and the boundary conditions developed in the previous paper are applied to the calculation of photoionization rate. Based on the modified model, the characteristics of low temperature subatmospheric air discharge under 13 kV direct current voltage are discussed, including needle-plate and needle-needle electrode structures. Firstly, in order to verify the reliability of the model, a numerical example and an experimental verification were carried out for the modified model respectively. Both verification results show that the model can ensure the accuracy and repeatability of the calculation. Secondly, according to the calculation results of the modified model, under the same voltage and spacing, the reduced electric field under low temperature subatmosphere pressure is larger than that under normal temperature and atmospheric pressure. The high electric field leads to the air discharge at low temperature and sub atmospheric pressure entering the streamer initiation stage earlier, and has a faster propagation speed in the streamer development stage, which shortens the overall discharge time. Finally, the discharge characteristics of the two electrode structures are compared, and it is found that the biggest difference between them is that there is a pre-ionization region near the cathode in the needle-needle electrode structure. When the pre-ionization level reaches 1013 cm-3, the propagation speed of the positive streamer remains unchanged throughout the discharge process, and is no longer affected by the negative streamer. The peak value of electric field decreases with the increase of pre-ionization level, and tends to be constant during streamer propagation. Based on the previous paper, this paper constructs the air discharge model under non-uniform electric field, complements with the previous paper, and forms a relatively complete set of air discharge simulation system under low temperature and sub atmospheric pressure, which provides a certain reference for future research.展开更多
We briefly introduce a new high-pressure transport measurement system integrated with low temperature and magnetic field that is being established as one of the user experimental stations of the Synergetic Extreme Con...We briefly introduce a new high-pressure transport measurement system integrated with low temperature and magnetic field that is being established as one of the user experimental stations of the Synergetic Extreme Condition User Facilities in the Huairou District of Beijing, China. To demonstrate the capabilities of the system for condensed matter research, the emergence of some pressure-induced phenomena and physics related to superconductivity found previously is also introduced, and then a perspective for such an advanced high-pressure system is presented.展开更多
Theoretical analysis is made on the temperature field at the time of pulse current discharge in a metal structure with an elliptical embedding crack. In finding the temperature field, analogy between the current flow ...Theoretical analysis is made on the temperature field at the time of pulse current discharge in a metal structure with an elliptical embedding crack. In finding the temperature field, analogy between the current flow through an elliptical embedding crack and the fluid flow through a barrier is made based on the similarity principle. Boundary conditions derived from this theory are introduced so that the distribution of current density and the temperature field expressions can be obtained. The study provides a theoretic basis to the applications of stopping spatial crack with electromagnetic heating.展开更多
In this paper,an efficient boundary condition is applied to solve the photoionization rate,and a two-dimensional numerical simulation is carried out for the development and propagation of an air streamer at low temper...In this paper,an efficient boundary condition is applied to solve the photoionization rate,and a two-dimensional numerical simulation is carried out for the development and propagation of an air streamer at low temperature and sub-atmospheric pressure.The results show that the new boundary condition improves the calculation accuracy,but the influence of photoionization on the streamer discharge process is not obvious.The discharge current in the development of streamer discharge is defined,and the corresponding expression of the positive and negative streamer discharge current is given.The influence of the electric field exceeding the threshold value on the discharge process is preliminarily introduced.In the process of discharge,only the propagation velocity of the streamer is obviously higher than that of normal temperature and pressure,and the trend of the other parameters is basically the same as that described in the previous paper.The above results give us a deeper understanding of the discharge characteristics under low temperature and sub-atmospheric pressure,which has certain significance for the development of aviation and high voltage engineering.展开更多
As a common practice,a large hydro-generator will operate in leading phase conditions to absorb the reactive power of the power grid.However,the accurate and precise prediction of the leading phase operation capacity ...As a common practice,a large hydro-generator will operate in leading phase conditions to absorb the reactive power of the power grid.However,the accurate and precise prediction of the leading phase operation capacity of a large hydro-generator has always been a formidable challenge to engineers and academicians because it is extremely hard to compute the eddy currents and losses as well as the local overheating in the pressure plate and finger.To address this problem,a full three dimensional(3D)finite element model and method of the coupled eddy current and temperature fields in the end region of a large hydro-generator are developed.The equivalent medium parameters used in the computations are comprehensively discussed.Moreover,some numerically based solution methodologies for accurate computation of the field and armature currents under different leading phase conditions are proposed.Numerical results on the coupled eddy current and temperature fields in the end regions of a 250 MW hydro-generator confirm positively the feasibility of the present work.展开更多
A combined action of plasma convection and pitch-angle diffusion of electrons and protons leads to the formation of plasma pressure distribution in the magnetosphere on the night side, and, as it is known, steady elec...A combined action of plasma convection and pitch-angle diffusion of electrons and protons leads to the formation of plasma pressure distribution in the magnetosphere on the night side, and, as it is known, steady electric bulk currents are connected to distribution of gas pressure. The divergence of these bulk currents brings about a spatial distribution of field-aligned currents, i.e. magnetospheric sources of ionospheric current. The projection (mapping) of the plasma pressure relief onto the ionosphere corresponds to the form and position of the auroral oval. This projection, like the real oval, executes a motion with a change of the convection electric field, and expands with an enhancement of the field. Knowing the distribution (3D) of the plasma pressure we can determine the places of MHD-compressor and MHD-generators location in the magnetosphere. Unfortunately, direct observations of plasma distribution in the magnetosphere are faced with large difficulties, because pressure must be known everywhere in the plasma sheet at high resolution, which in situ satellites have been unable to provide. Modeling of distribution of plasma pressure (on ~ 3-12 Re) is very important, because the data from multisatellite magnetospheric missions for these purposes would be a very expensive project.展开更多
Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was estab...Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was established.The differential method was used to do the coupled numerical calculation,and the calculation results were compared with experimental and field data to verify the accuracy of the model.When the interactions between temperature,pressure and hydration reaction are considered,the calculation accuracy of the model proposed is within 5.6%,which can meet the engineering requirements.A series of numerical simulation was conducted to find out the variation pattern of temperature,pressure and hydration degree during the cement curing.The research results show that cement temperature increases dramatically as a result of the heat of cement hydration.With the development of cement gel strength,the pore pressure of cement slurry decreases gradually to even lower than the formation pressure,causing gas channeling;the transient temperature and pressure have an impact on the rate of cement hydration reaction,so cement slurry in the deeper part of wellbore has a higher rate of hydration rate as a result of the high temperature and pressure.For well cementing in deep water regions,the low temperature around seabed would slow the rate of cement hydration and thus prolong the cementing cycle.展开更多
It is well known that the critical current density of a superconductor depends on its size, shape, nature of doping and the manner of preparation. It is suggested here that the collective effect of such differences fo...It is well known that the critical current density of a superconductor depends on its size, shape, nature of doping and the manner of preparation. It is suggested here that the collective effect of such differences for different samples of the same superconductor is to endow them with different values of the Fermi energy—a single property to which may be attributed the observed variation in their critical current densities. The study reported here extends our earlier work concerned with the generalized BCS equations [Malik, G.P. (2010) Physica B, 405, 3475-3481;Malik, G.P. (2013) WJCMP, 3,103-110]. We develop here for the first time a framework of microscopic equations that incorporates all of the following parameters of a superconductor: temperature, momentum of Cooper pairs, Fermi energy, applied magnetic field and critical current density. As an application of this framework, we address the different values of critical current densities of Bi-2212 for non-zero values of temperature and applied magnetic field that have been reported in the literature.展开更多
Cable-in-conduit conductor (CICC) conductor sample of the PF2 coil for ITER was tested in the SULTAN facility. According to the test results, the CICC conductor sample exhibited a stable performance regarding the cu...Cable-in-conduit conductor (CICC) conductor sample of the PF2 coil for ITER was tested in the SULTAN facility. According to the test results, the CICC conductor sample exhibited a stable performance regarding the current sharing temperature. Under the typical operational conditions of a current of 45 kA, a magnetic field of 4 T and a temperature of 5 K for PF2, the test result for the conductor current sharing temperature is 6.71 K, with a temperature margin of 1.71 K. For a comparison thermal-hydraulic analysis of the PF2 conductor was carried out using GANDALF code in a 1-D model, and the result is consistent with the test one.展开更多
A transient temperature field model in a thrust magnetic bearing is built in which the heat resources come mainly from the eddy-current loss of solid cores and the copper loss of coils. The transient temperature field...A transient temperature field model in a thrust magnetic bearing is built in which the heat resources come mainly from the eddy-current loss of solid cores and the copper loss of coils. The transient temperature field, system temperature rise and the thermo-equilibrium state during the rotor starting-up are calculated considering only the copper loss and the eddy-current loss. The numerical results indicate that the temperatures in coils and in magnets rise rapidly, their thermo-equilibrium states are formed within a short time. The temperatures in a thrust-disk and in a rotor rise slowly, their thermo-equilibrium states are formed aller a long period time. The temperatures of the thrust-disk and the rotor are far higher than the temperatures of coils and/or magnets aller the thermo-equilibrium state has come into being.展开更多
GaSb p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with an atomic layer deposited Al2O3 gate dielectric and a self-aligned Si-implanted source/drain are experimentally demonstrated. Temperat...GaSb p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with an atomic layer deposited Al2O3 gate dielectric and a self-aligned Si-implanted source/drain are experimentally demonstrated. Temperature dependent electrical characteristics are investigated. Different electrical behaviors are observed in two temperature regions, and the un- derlying mechanisms are discussed. It is found that the reverse-bias pn junction leakage of the drain/substrate is the main component of the off-state drain leakage current, which is generation-current dominated in the low temperature regions and is diffusion-current dominated in the high temperature regions. Methods to further reduce the off-state drain leakage current are given.展开更多
The negative DC corona discharge in air at atmospheric pressure was investigated in a needle-to-water system to obtain the pressure distribution of corona ionic wind.The deformation of water surface was measured and t...The negative DC corona discharge in air at atmospheric pressure was investigated in a needle-to-water system to obtain the pressure distribution of corona ionic wind.The deformation of water surface was measured and the distribution of wind pressure over the water surface was calculated.The effects of varying discharge parameters,such as applied voltage,gap spacing,tip radius of needle,and the shape of grounded electrode,on the wind pressure were studied.The measured wind pressure ranges from several Pa to several tens of Pa and up to 33 Pa over a small area;the pressure is comparatively large in the center and decreases quickly outwards.In the experiment system,a higher voltage on a 3 mm gap resulted in a stronger pressure of the ionic wind;around the onset voltage,using a needle with tip radius of 50μm obtained a larger wind pressure than using a needle with 100μm tip radius,but the latter one can produce larger pressure at higher voltages.Plus,the shape of the grounded electrode only influences the wind pressure a little.展开更多
After discovering high temperature superconducting materials 20 years ago, the preparation of applicable HTS materials has been pursued along with HTS mechanism and characteristic study. At present, the focus on the a...After discovering high temperature superconducting materials 20 years ago, the preparation of applicable HTS materials has been pursued along with HTS mechanism and characteristic study. At present, the focus on the applied HTS technology has been moving to the industrial preparations from the laboratory research stage, and the technology has been well verified for practical applications from small to large scales. The fabrication techniques of engineering HTS materials are being industrialized; and various HTS devices are also on the way towards practical applications. This paper provides a comprehensive summary on the applied high temperature superconductivity with regard to various applicable HTS materials, their preparation techniques and charac- terization, and applications in a wide range.展开更多
For the pressure enthalpy of high pressure pneumatics, the computational fluid dynamics(CFD)simulation based on ideal gas assumption fails to obtain the real temperature information. Therefore, we propose a method to ...For the pressure enthalpy of high pressure pneumatics, the computational fluid dynamics(CFD)simulation based on ideal gas assumption fails to obtain the real temperature information. Therefore, we propose a method to compensate the pressure enthalpy of throttling for CFD simulation based on ideal gas assumption.Firstly, the pressure enthalpy is calculated for the pressure range of 0.101 to 30 MPa and the temperature range of 190 to 298 K based on Soave-Redlich-Kwong(S-R-K) equation. Then, a polynomial fitting equation is applied to practical application in the above mentioned range. The basic idea of the compensation method is to convert the pressure enthalpy difference between inlet air and nodes into the compensation temperature. In the above temperature and pressure range, the compensated temperature is close to the real one, and the relative temperature drop error is below 10%. This error is mainly caused by the velocity difference of the orifice between the real and ideal gas models. Finally, this compensation method performs an icing analysis for practical high pressure slide pilot valve.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50572032, 50731006, and 50801030)the Young Scientists Fund of the National Natural Science Foundation of China (Grant Nos. 51001042 and 51002045)
文摘Large diamond crystals were successfully synthesized by a FeNi C system using the temperature gradient method under high-pressure high-temperature conditions. The assembly of the growth cell was improved and the growth process of diamond was investigated. Effects of the symmetry of the carbon convection field around the growing diamond crystal were investigated systematically by adjusting the position of the seed crystal in the melted catalyst/solvent. The results indicate that the morphologies and metal inclusion distributions of the synthetic diamond crystals vary obviously in both symmetric and non-symmetric carbon convection fields with temperature. Moreover, the finite element method was applied to analyze the carbon convection mode of the melted catalyst/solvent around the diamond crystal. This work is helpful for understanding the growth mechanism of diamond.
基金the National Key RESEARCH and Development Program of the Ministry of Science and Technology‘Life Prediction and Operation Risk Assessment of UHV Equipment under long-term Service conditions(No.2017YFB0902705)’for supporting this workthe No.703 Research Institute of CSIC(China Shipbuilding Industry Corporation)Yunnan Electric Test&Research Institute Group CO.,Ltd for assistance in this paper.
文摘In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and the boundary conditions developed in the previous paper are applied to the calculation of photoionization rate. Based on the modified model, the characteristics of low temperature subatmospheric air discharge under 13 kV direct current voltage are discussed, including needle-plate and needle-needle electrode structures. Firstly, in order to verify the reliability of the model, a numerical example and an experimental verification were carried out for the modified model respectively. Both verification results show that the model can ensure the accuracy and repeatability of the calculation. Secondly, according to the calculation results of the modified model, under the same voltage and spacing, the reduced electric field under low temperature subatmosphere pressure is larger than that under normal temperature and atmospheric pressure. The high electric field leads to the air discharge at low temperature and sub atmospheric pressure entering the streamer initiation stage earlier, and has a faster propagation speed in the streamer development stage, which shortens the overall discharge time. Finally, the discharge characteristics of the two electrode structures are compared, and it is found that the biggest difference between them is that there is a pre-ionization region near the cathode in the needle-needle electrode structure. When the pre-ionization level reaches 1013 cm-3, the propagation speed of the positive streamer remains unchanged throughout the discharge process, and is no longer affected by the negative streamer. The peak value of electric field decreases with the increase of pre-ionization level, and tends to be constant during streamer propagation. Based on the previous paper, this paper constructs the air discharge model under non-uniform electric field, complements with the previous paper, and forms a relatively complete set of air discharge simulation system under low temperature and sub atmospheric pressure, which provides a certain reference for future research.
文摘We briefly introduce a new high-pressure transport measurement system integrated with low temperature and magnetic field that is being established as one of the user experimental stations of the Synergetic Extreme Condition User Facilities in the Huairou District of Beijing, China. To demonstrate the capabilities of the system for condensed matter research, the emergence of some pressure-induced phenomena and physics related to superconductivity found previously is also introduced, and then a perspective for such an advanced high-pressure system is presented.
基金Project supported by the National Natural Science Foundation of China (No.50675190)
文摘Theoretical analysis is made on the temperature field at the time of pulse current discharge in a metal structure with an elliptical embedding crack. In finding the temperature field, analogy between the current flow through an elliptical embedding crack and the fluid flow through a barrier is made based on the similarity principle. Boundary conditions derived from this theory are introduced so that the distribution of current density and the temperature field expressions can be obtained. The study provides a theoretic basis to the applications of stopping spatial crack with electromagnetic heating.
基金supported by the No.703 Research Institute of CSIC(China Shipbuilding Industry Corporation)and Yunnan Electric Test&Research Institute Group CO.,Ltd.
文摘In this paper,an efficient boundary condition is applied to solve the photoionization rate,and a two-dimensional numerical simulation is carried out for the development and propagation of an air streamer at low temperature and sub-atmospheric pressure.The results show that the new boundary condition improves the calculation accuracy,but the influence of photoionization on the streamer discharge process is not obvious.The discharge current in the development of streamer discharge is defined,and the corresponding expression of the positive and negative streamer discharge current is given.The influence of the electric field exceeding the threshold value on the discharge process is preliminarily introduced.In the process of discharge,only the propagation velocity of the streamer is obviously higher than that of normal temperature and pressure,and the trend of the other parameters is basically the same as that described in the previous paper.The above results give us a deeper understanding of the discharge characteristics under low temperature and sub-atmospheric pressure,which has certain significance for the development of aviation and high voltage engineering.
文摘As a common practice,a large hydro-generator will operate in leading phase conditions to absorb the reactive power of the power grid.However,the accurate and precise prediction of the leading phase operation capacity of a large hydro-generator has always been a formidable challenge to engineers and academicians because it is extremely hard to compute the eddy currents and losses as well as the local overheating in the pressure plate and finger.To address this problem,a full three dimensional(3D)finite element model and method of the coupled eddy current and temperature fields in the end region of a large hydro-generator are developed.The equivalent medium parameters used in the computations are comprehensively discussed.Moreover,some numerically based solution methodologies for accurate computation of the field and armature currents under different leading phase conditions are proposed.Numerical results on the coupled eddy current and temperature fields in the end regions of a 250 MW hydro-generator confirm positively the feasibility of the present work.
文摘A combined action of plasma convection and pitch-angle diffusion of electrons and protons leads to the formation of plasma pressure distribution in the magnetosphere on the night side, and, as it is known, steady electric bulk currents are connected to distribution of gas pressure. The divergence of these bulk currents brings about a spatial distribution of field-aligned currents, i.e. magnetospheric sources of ionospheric current. The projection (mapping) of the plasma pressure relief onto the ionosphere corresponds to the form and position of the auroral oval. This projection, like the real oval, executes a motion with a change of the convection electric field, and expands with an enhancement of the field. Knowing the distribution (3D) of the plasma pressure we can determine the places of MHD-compressor and MHD-generators location in the magnetosphere. Unfortunately, direct observations of plasma distribution in the magnetosphere are faced with large difficulties, because pressure must be known everywhere in the plasma sheet at high resolution, which in situ satellites have been unable to provide. Modeling of distribution of plasma pressure (on ~ 3-12 Re) is very important, because the data from multisatellite magnetospheric missions for these purposes would be a very expensive project.
基金Supported by the National Natural Science Foundation of China(U1762216)China National Science and Technology Major Project(2016ZX05028-001-03)
文摘Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was established.The differential method was used to do the coupled numerical calculation,and the calculation results were compared with experimental and field data to verify the accuracy of the model.When the interactions between temperature,pressure and hydration reaction are considered,the calculation accuracy of the model proposed is within 5.6%,which can meet the engineering requirements.A series of numerical simulation was conducted to find out the variation pattern of temperature,pressure and hydration degree during the cement curing.The research results show that cement temperature increases dramatically as a result of the heat of cement hydration.With the development of cement gel strength,the pore pressure of cement slurry decreases gradually to even lower than the formation pressure,causing gas channeling;the transient temperature and pressure have an impact on the rate of cement hydration reaction,so cement slurry in the deeper part of wellbore has a higher rate of hydration rate as a result of the high temperature and pressure.For well cementing in deep water regions,the low temperature around seabed would slow the rate of cement hydration and thus prolong the cementing cycle.
文摘It is well known that the critical current density of a superconductor depends on its size, shape, nature of doping and the manner of preparation. It is suggested here that the collective effect of such differences for different samples of the same superconductor is to endow them with different values of the Fermi energy—a single property to which may be attributed the observed variation in their critical current densities. The study reported here extends our earlier work concerned with the generalized BCS equations [Malik, G.P. (2010) Physica B, 405, 3475-3481;Malik, G.P. (2013) WJCMP, 3,103-110]. We develop here for the first time a framework of microscopic equations that incorporates all of the following parameters of a superconductor: temperature, momentum of Cooper pairs, Fermi energy, applied magnetic field and critical current density. As an application of this framework, we address the different values of critical current densities of Bi-2212 for non-zero values of temperature and applied magnetic field that have been reported in the literature.
基金supported by the Priority Base Research Development Project of China (No. 0559730532)
文摘Cable-in-conduit conductor (CICC) conductor sample of the PF2 coil for ITER was tested in the SULTAN facility. According to the test results, the CICC conductor sample exhibited a stable performance regarding the current sharing temperature. Under the typical operational conditions of a current of 45 kA, a magnetic field of 4 T and a temperature of 5 K for PF2, the test result for the conductor current sharing temperature is 6.71 K, with a temperature margin of 1.71 K. For a comparison thermal-hydraulic analysis of the PF2 conductor was carried out using GANDALF code in a 1-D model, and the result is consistent with the test one.
基金This project is supported by National Natural Science Foundation of China (No.50505030)Key Technology R&D Program of Shanghai Municipal (No.031111001).
文摘A transient temperature field model in a thrust magnetic bearing is built in which the heat resources come mainly from the eddy-current loss of solid cores and the copper loss of coils. The transient temperature field, system temperature rise and the thermo-equilibrium state during the rotor starting-up are calculated considering only the copper loss and the eddy-current loss. The numerical results indicate that the temperatures in coils and in magnets rise rapidly, their thermo-equilibrium states are formed within a short time. The temperatures in a thrust-disk and in a rotor rise slowly, their thermo-equilibrium states are formed aller a long period time. The temperatures of the thrust-disk and the rotor are far higher than the temperatures of coils and/or magnets aller the thermo-equilibrium state has come into being.
基金Project supported by the National Basic Research Program of China(Grant No.2011CBA00602)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011ZX02708-002)
文摘GaSb p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with an atomic layer deposited Al2O3 gate dielectric and a self-aligned Si-implanted source/drain are experimentally demonstrated. Temperature dependent electrical characteristics are investigated. Different electrical behaviors are observed in two temperature regions, and the un- derlying mechanisms are discussed. It is found that the reverse-bias pn junction leakage of the drain/substrate is the main component of the off-state drain leakage current, which is generation-current dominated in the low temperature regions and is diffusion-current dominated in the high temperature regions. Methods to further reduce the off-state drain leakage current are given.
基金Project supported by National Key Laboratory of Science and Technology on Electro-mechanical Dynamic Control of China(2011C3606)
文摘The negative DC corona discharge in air at atmospheric pressure was investigated in a needle-to-water system to obtain the pressure distribution of corona ionic wind.The deformation of water surface was measured and the distribution of wind pressure over the water surface was calculated.The effects of varying discharge parameters,such as applied voltage,gap spacing,tip radius of needle,and the shape of grounded electrode,on the wind pressure were studied.The measured wind pressure ranges from several Pa to several tens of Pa and up to 33 Pa over a small area;the pressure is comparatively large in the center and decreases quickly outwards.In the experiment system,a higher voltage on a 3 mm gap resulted in a stronger pressure of the ionic wind;around the onset voltage,using a needle with tip radius of 50μm obtained a larger wind pressure than using a needle with 100μm tip radius,but the latter one can produce larger pressure at higher voltages.Plus,the shape of the grounded electrode only influences the wind pressure a little.
文摘After discovering high temperature superconducting materials 20 years ago, the preparation of applicable HTS materials has been pursued along with HTS mechanism and characteristic study. At present, the focus on the applied HTS technology has been moving to the industrial preparations from the laboratory research stage, and the technology has been well verified for practical applications from small to large scales. The fabrication techniques of engineering HTS materials are being industrialized; and various HTS devices are also on the way towards practical applications. This paper provides a comprehensive summary on the applied high temperature superconductivity with regard to various applicable HTS materials, their preparation techniques and charac- terization, and applications in a wide range.
基金the National Natural Science Foundation of China(No.51205421)the Fund of the Key Laboratory of Sensing Technology and Biomedical Instruments of Guangdong Province(No.2011A060901013)
文摘For the pressure enthalpy of high pressure pneumatics, the computational fluid dynamics(CFD)simulation based on ideal gas assumption fails to obtain the real temperature information. Therefore, we propose a method to compensate the pressure enthalpy of throttling for CFD simulation based on ideal gas assumption.Firstly, the pressure enthalpy is calculated for the pressure range of 0.101 to 30 MPa and the temperature range of 190 to 298 K based on Soave-Redlich-Kwong(S-R-K) equation. Then, a polynomial fitting equation is applied to practical application in the above mentioned range. The basic idea of the compensation method is to convert the pressure enthalpy difference between inlet air and nodes into the compensation temperature. In the above temperature and pressure range, the compensated temperature is close to the real one, and the relative temperature drop error is below 10%. This error is mainly caused by the velocity difference of the orifice between the real and ideal gas models. Finally, this compensation method performs an icing analysis for practical high pressure slide pilot valve.