Anodic bonding between silicon and glass with dou bl e electric fields is presented.By this means,the damage caused by the electric f ield to the movable part during bonding can be avoided and the experiment result s ...Anodic bonding between silicon and glass with dou bl e electric fields is presented.By this means,the damage caused by the electric f ield to the movable part during bonding can be avoided and the experiment result s show that.展开更多
We conduct a theoretical study on the properties of a bound polaron in a quantum well under an electric field using linear combination operator and unitary transformation methods, which are valid in the whole range of...We conduct a theoretical study on the properties of a bound polaron in a quantum well under an electric field using linear combination operator and unitary transformation methods, which are valid in the whole range of electron-LO phonon coupling. The changing relations between the ground-state energy of the bound polaron in the quantum well and the Coulomb bound potential, the electric field strength, and the well width are derived. The numerical results show that the ground-state energy increases with the increase of the electric field strength and the Coulomb bound potential and decreases as the well width increases.展开更多
A comprehensive mathematical model of annulus-electromagnetic direct chill (A-EMDC) casting of A357 aluminum alloy was established with corresponding experimental verification. The model was based on a combination o...A comprehensive mathematical model of annulus-electromagnetic direct chill (A-EMDC) casting of A357 aluminum alloy was established with corresponding experimental verification. The model was based on a combination of the commercial finite element package ANSYS and the commercial finite volume package FLUENT. The effects of structural parameters on fluid flow, temperature field and solidification during A-EMDC process were investigated numerically. The results show that structural parameters such as annulus gap width, annulus gap position, and centre pipe length influence the flow and temperature fields. The smaller the annulus gap width is, the more uniform the temperature is, and the smaller the temperature gradient is. With increasing the centre pipe length, the circular flow would decrease due to the dislocation of centre pipe. Specially, when the annulus gap is located at periphery of the billet, the temperature gradient of the longitudinal direction in the solidification region falls evidently.展开更多
In order to improve the quality of clad ingots, diverse physical fields including electromagnetic stirring, power ultrasonic and compound field of ultrasonic and electromagnetic stirring were attempted to prepare clad...In order to improve the quality of clad ingots, diverse physical fields including electromagnetic stirring, power ultrasonic and compound field of ultrasonic and electromagnetic stirring were attempted to prepare clad ingots of 3003/4004 alloys. The solidification structures near the interface in clad ingots were investigated. The experiment results indicate that the solidification structure of 4004 alloy changes from dendritic crystals to petal-like grains when the clad ingot is treated by electromagnetic stirring. With the effect of power ultrasonic, the solidified microstructure of 4004 alloy exhibits the refinement of both primary a(A1) and eutectic silicon. Under the compound field, the primary a(A1) is refined, the morphology of eutectic silicon has a transition from a coarse plate-like form without treatment or thin acicular-like form with power ultrasonic to fine coral-like form.展开更多
In order to suppress the airwave noise in marine controlled-source electromagnetic (CSEM) data, we propose a 3D deconvolution (3DD) interferometry method with a synthetic aperture source and obtain the relative an...In order to suppress the airwave noise in marine controlled-source electromagnetic (CSEM) data, we propose a 3D deconvolution (3DD) interferometry method with a synthetic aperture source and obtain the relative anomaly coefficient (RAC) of the EM field reflection responses to show the degree for suppressing the airwave. We analyze the potential of the proposed method for suppressing the airwave, and compare the proposed method with traditional methods in their effectiveness. A method to select synthetic source length is derived and the effect of the water depth on RAC is examined via numerical simulations. The results suggest that 3DD interferometry method with a synthetic source can effectively suppress the airwave and enhance the potential of marine CSEM to hydrocarbon exploration.展开更多
The electroplastic effect in AZ31B magnesium alloy sheet was investigated through uniaxial tensile tests. In order to show the athermal effect of the electrical pulses, two types of uniaxial tensile tests at the same ...The electroplastic effect in AZ31B magnesium alloy sheet was investigated through uniaxial tensile tests. In order to show the athermal effect of the electrical pulses, two types of uniaxial tensile tests at the same testing temperature were carried out: uniaxial tension in environmental cabinet and uniaxial tension with electrical pulses. In addition, the distribution of temperature field in the cross-section area during uniaxial tension with electrical pulses was simulated. The results show that the distribution of temperature field along the cross-section area is homogeneous. By comparing the true stress?true strain curves of AZ31B alloy under uniaxial tensile tests, the athermal effect with electrical pulses was confirmed. The microstructure evolution after the uniaxial tension was studied by optical microscopy. The results indicate that the electrical pulses induced dynamic recrystallization plays an important role in the decrease of flow stress. Finally, a flow stress model of AZ31B sheet taking the influence of electroplastic effect into account was proposed and validated. The results demonstrate that the calculated data fit the experimental data well.展开更多
The experimental study of natural convection in allglass evacuated tube solar collectors is performed through the experimental platform of the solar-assisted fuel cell system.The experimental facility includes solar c...The experimental study of natural convection in allglass evacuated tube solar collectors is performed through the experimental platform of the solar-assisted fuel cell system.The experimental facility includes solar collectors with different length and diameter tubes, different coating materials, and with / without guide plates, respectively. Threedimensional mathematical models on natural and forced convections in the solar collectors are established and the experimental data is validated by field synergy and entransy principles. The results of natural convection show that the water temperature increases and thermal efficiency decreases gradually with the evacuated tube length. The thermal efficiency increases when absorption rates increase from 0. 95 to 1. 0 and emission rates decrease from 0. 16 to 0. 06. The thermal efficiency of solar collectors is increased after being equipped with the guide plate, which is attributed to the disappearance of the mixed flowand the enhancement of the heat transfer at the bottom of the evacuated tube. The results of forced convertion indicate that the Reynolds, Nusselt and entransy increments of the horizontal double collectors are higher than those of the vertical single collector while the entransy dissipation is lower than that of the vertical single collector. It is concluded that the solar collectors with guide plates are suitable for natural convection while the double horizontal collectors are suitable for forced convection in the thermal field of solar-assisted fuel cell systems with lowand medium temperatures.展开更多
A novel dual output phase-shift distribution transformer ( DOPSDT ) is proposed based on the electromagnetic filtering theory. First, its structural characteristics, winding connection mode and turn number ratio for...A novel dual output phase-shift distribution transformer ( DOPSDT ) is proposed based on the electromagnetic filtering theory. First, its structural characteristics, winding connection mode and turn number ratio for special phase shifting are investigated. Secondly, the balance formulation of harmonic magneto-motive forces is derived and the electromagnetic filtering principle of the DOPSDT is introduced. The harmonic mitigating performance under different nonlinear load conditions are also analyzed using the field-circuit coupled method, The analysis results show that the DOPSDT can mitigate the primary current distortion even under severe nonlinear load conditions. By applying the zero sequence flux cancellation and phase-shift techniques at their secondary windings, the DOPSDT can significantly reduce the 3rd, 5th, 7th, 9th, 15th, 17th and 19th harmonics within its secondary windings.展开更多
Interactions of three heavy metal ions, Cu^2+, Cd^2+, and Pb^2+, and, for comparison, Na^+ with electrodialytic clay fractions (less than 2μm in diameter) of four paddy soils as well as a yellow-brown soil as a...Interactions of three heavy metal ions, Cu^2+, Cd^2+, and Pb^2+, and, for comparison, Na^+ with electrodialytic clay fractions (less than 2μm in diameter) of four paddy soils as well as a yellow-brown soil as a control soil were evaluated based on measurements of the Wien effect in dilute suspensions with a clay concentration of 10 g kg^-1 in four nitrate solutions of 2 × 10^-4/z mol L^-1, where z is the cation valence, and a nitric acid solution of 3 × 10^-5 mol L^-1, Field strengths ranging from 15 to 230 kV cm^-1 were applied for measuring the electrical conductivities (ECs) of the suspensions. The mean free binding energies between the various cations and all of the soils determined from exchange equilibrium increased in the order: Na^+ 〈 Cd^2+ 〈 Cu^2+ 〈 Pb^2+. In general, the ECs of the suspensions in the sodium nitrate solution were smaller than those of the suspensions in the heavy metal solutions because of the lower electrophoretic mobility of sodium compared to the divalent cations. In terms of relative electrical conductivity-field strength relationships, relative electrical conductivity (REC) of suspensions containing various cations at field strengths larger than about 50 kV cm^-1 were in the descending order: Na^+ 〉 Cu^2+ 〉 Cd^2+ 〉 Pb^2+ for all tested soils. A characteristic parameter of the REC-field strength curves, AREC200, REC at a field strength of 200 kV cm^-1 minus that at the local minimum of the concave segment of the REC-field strength curves, characterized the strength of adsorption of the cations stripped off by the applied strong electrical field, and for all soils the values of AREC200 were generally in the order: Na^+ 〈 Cu^2+ ≤ Cd^2+ 〈 Pb^2+.展开更多
Under the external AC and DC electric field, the effective response of nonlinear spherical coated composites, which obey the constitutive relation of electric displaeement and electric field, is investigated in the di...Under the external AC and DC electric field, the effective response of nonlinear spherical coated composites, which obey the constitutive relation of electric displaeement and electric field, is investigated in the dilute limit by using the perturbation method. The local potentials in inclusion and host regions are derived at all harmonics. Moreover, the formulae of the effective linear and nonlinear responses are given in the dilute limit.展开更多
An improved Monte Carlo method was used to simulate the motion of electrons in c-C4F8 and SF6 gas mixtures for pulsed townsend discharge. The electron swarm parameters such as effective ionization coefficient, -↑α a...An improved Monte Carlo method was used to simulate the motion of electrons in c-C4F8 and SF6 gas mixtures for pulsed townsend discharge. The electron swarm parameters such as effective ionization coefficient, -↑α and drift velocity over the E/N range from 280~700 Td(1Td=10^-21 V·m^2) were calculated by employing a set of cross sections available in literature. From the variation cure of -↑α with SF6 partial pressure p, the limiting field (E/N)lim of gas mixture at different gas content was determined. It is found that the limiting field of c-C4F8 and SF6 gas mixture is higher than that of pure SF6 at any SF6 mixture ratio. Simulation results show excellent agreement with experiment data available in previous literature.展开更多
In this work,the chromium aluminum nitride(CrAlN)coatings were prepared on TC11 titanium alloy by composite magnetic field cathodic arc ion plating with controllable pulse electromagnetic combined with permanent magne...In this work,the chromium aluminum nitride(CrAlN)coatings were prepared on TC11 titanium alloy by composite magnetic field cathodic arc ion plating with controllable pulse electromagnetic combined with permanent magnet.The effects of electromagnetic frequency on the morphology,microstructure,nano-hardness and elastic modulus of the coatings were investigated by scanning electron microscope(SEM),X-ray diffraction(XRD)and nano-indenter.This paper has mainly studied the influence of CrAlN coatings which are prepared at various electromagnetic frequencies on the wear and erosion resistance through a series of wear and solid particle erosion experiments.It was found that the deposition rate of CrAlN coatings increases with the increase of electromagnetic frequency.And CrAlN coatings all preferentially grew along the(111)crystal plane.At 16.7 Hz,with the increase of pulsed electromagnetic frequency,the hardness is the highest(23.6 GPa)and the adhesion is the highest(41.5 N).In addition,the coating deposition exhibited the best wear and solid erosion resistance at 16.7 Hz and 33.3 Hz,the friction coefficient is about 0.35,and the erosion rate is about 0.2μm/g at 30°and less than 1μm/g at 90°,respectively.These results indicate that the CrAlN coating formed at an appropriate pulsed electromagnetic frequency can achieve excellent mechanical properties,wear and solid erosion resistance.展开更多
For converter transformer, AC-DC combined electric field can trigger space charge accumulation on oil-impregnated pressboard interface. The accumulation of space charge on oil-pressboard interface can result in electr...For converter transformer, AC-DC combined electric field can trigger space charge accumulation on oil-impregnated pressboard interface. The accumulation of space charge on oil-pressboard interface can result in electric field distortion, trend to trigger surface discharge of barriers. This paper studied the influence of surface charge on flashover voltage of oil-impregnated pressboard under AC-DC combined electric field. The study finds that the flashover voltage of oil-pressboard interface under negative polarity DC superimposed AC electric field is higher than that.of positive DC superimposed AC voltage to form composite electric field. It was found that homopolar surface charge has been accumulated on the interface of oil-pressboard with positive or negative DC voltage through measuring surface potential by the electrostatic capacitive probe. The surface charge produced electric field in the opposite direction, which weakening the synthetic electric field strength. What's more, under the same conditions, the negative surface charge density oil-pressboard is much larger than the positive.展开更多
Langevin dynamics simulations were conducted to study the collapse of grafted partially charged 4-arm star chains onto the oppositely charged grafting electrode in the presence of trivalent salt coions.Simulation resu...Langevin dynamics simulations were conducted to study the collapse of grafted partially charged 4-arm star chains onto the oppositely charged grafting electrode in the presence of trivalent salt coions.Simulation results reveal that the average charge fraction of the grafted star chains and the salt concentration play critical roles in the competitive adsorption of charged monomers and trivalent salt coions onto the oppositely charged electrode.For grafted star chains with relatively high charge fraction,charged monomers are the dominant species collapsing on the oppositely charged electrode with the emergence of charge reversal on the grafting electrode.At a low charge fraction such that the total amount of charges on a grafted star molecule is comparable to that of a trivalent salt coion,trivalent salt coions absorb more strongly onto the electrode than grafted stars even at very low salt concentration.It is found that at relatively low charge fraction of star chains,the addition of trivalent salt coions does not lead to charge overcompensation of the surface charges on the grafting electrode.The stretching of star brushes under an electric field in the presence of trivalent salt coions was also briefly investigated.展开更多
The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D<SUP>-</SUP> center, which consists of a positive ion located on the z-axis at a distance from the two-dimens...The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D<SUP>-</SUP> center, which consists of a positive ion located on the z-axis at a distance from the two-dimensional quantum dot plane and two electrons in the dot plane bound by the ion, is investigated at arbitrary strength of magnetic field by making use of the method of few-body physics. Discontinuous ground-state energy transitions induced by the magnetic field are reported. The dependence of the binding energy of the D<SUP>-</SUP> ground state on the quantum dot radius is obtained. A considerable enhancement of the binding is found for the D<SUP>-</SUP> ground state, which results from the confinement of electrons and electron-phonon coupling.展开更多
We here explore black holes in the third order Lovelock gravity coupling with nonlinear Born-Infeld electro- magnetic field. Considering special second and third order coefficients (&g = 363 = a2), we analyze the t...We here explore black holes in the third order Lovelock gravity coupling with nonlinear Born-Infeld electro- magnetic field. Considering special second and third order coefficients (&g = 363 = a2), we analyze the thermodynamics of third order Lovelock-Born-Infeld black holes and, in 7-dimensional AdS space-time, discuss the stability of black holes in different event horizon structures. We find that the cosmological constant A plays an important role in the distribution of black hole stable regions.展开更多
文摘Anodic bonding between silicon and glass with dou bl e electric fields is presented.By this means,the damage caused by the electric f ield to the movable part during bonding can be avoided and the experiment result s show that.
文摘We conduct a theoretical study on the properties of a bound polaron in a quantum well under an electric field using linear combination operator and unitary transformation methods, which are valid in the whole range of electron-LO phonon coupling. The changing relations between the ground-state energy of the bound polaron in the quantum well and the Coulomb bound potential, the electric field strength, and the well width are derived. The numerical results show that the ground-state energy increases with the increase of the electric field strength and the Coulomb bound potential and decreases as the well width increases.
基金Project (2009AA03Z534) supported by the Hi-tech Research and Development Program of China Project (2006CB605203) supported by National Basic Research Program of China
文摘A comprehensive mathematical model of annulus-electromagnetic direct chill (A-EMDC) casting of A357 aluminum alloy was established with corresponding experimental verification. The model was based on a combination of the commercial finite element package ANSYS and the commercial finite volume package FLUENT. The effects of structural parameters on fluid flow, temperature field and solidification during A-EMDC process were investigated numerically. The results show that structural parameters such as annulus gap width, annulus gap position, and centre pipe length influence the flow and temperature fields. The smaller the annulus gap width is, the more uniform the temperature is, and the smaller the temperature gradient is. With increasing the centre pipe length, the circular flow would decrease due to the dislocation of centre pipe. Specially, when the annulus gap is located at periphery of the billet, the temperature gradient of the longitudinal direction in the solidification region falls evidently.
基金Project(51074031)supported by the National Natural Science Foundation of ChinaProject supported by the Korea National Project
文摘In order to improve the quality of clad ingots, diverse physical fields including electromagnetic stirring, power ultrasonic and compound field of ultrasonic and electromagnetic stirring were attempted to prepare clad ingots of 3003/4004 alloys. The solidification structures near the interface in clad ingots were investigated. The experiment results indicate that the solidification structure of 4004 alloy changes from dendritic crystals to petal-like grains when the clad ingot is treated by electromagnetic stirring. With the effect of power ultrasonic, the solidified microstructure of 4004 alloy exhibits the refinement of both primary a(A1) and eutectic silicon. Under the compound field, the primary a(A1) is refined, the morphology of eutectic silicon has a transition from a coarse plate-like form without treatment or thin acicular-like form with power ultrasonic to fine coral-like form.
基金supported by the national project"Deep Exploration Technology and Experimentation"(SinoProbe-09-02)
文摘In order to suppress the airwave noise in marine controlled-source electromagnetic (CSEM) data, we propose a 3D deconvolution (3DD) interferometry method with a synthetic aperture source and obtain the relative anomaly coefficient (RAC) of the EM field reflection responses to show the degree for suppressing the airwave. We analyze the potential of the proposed method for suppressing the airwave, and compare the proposed method with traditional methods in their effectiveness. A method to select synthetic source length is derived and the effect of the water depth on RAC is examined via numerical simulations. The results suggest that 3DD interferometry method with a synthetic source can effectively suppress the airwave and enhance the potential of marine CSEM to hydrocarbon exploration.
基金Projects(50975174,51275297)supported by the National Natural Science Foundation of ChinaProject(20100073110044)supported by the Education Ministry of China
文摘The electroplastic effect in AZ31B magnesium alloy sheet was investigated through uniaxial tensile tests. In order to show the athermal effect of the electrical pulses, two types of uniaxial tensile tests at the same testing temperature were carried out: uniaxial tension in environmental cabinet and uniaxial tension with electrical pulses. In addition, the distribution of temperature field in the cross-section area during uniaxial tension with electrical pulses was simulated. The results show that the distribution of temperature field along the cross-section area is homogeneous. By comparing the true stress?true strain curves of AZ31B alloy under uniaxial tensile tests, the athermal effect with electrical pulses was confirmed. The microstructure evolution after the uniaxial tension was studied by optical microscopy. The results indicate that the electrical pulses induced dynamic recrystallization plays an important role in the decrease of flow stress. Finally, a flow stress model of AZ31B sheet taking the influence of electroplastic effect into account was proposed and validated. The results demonstrate that the calculated data fit the experimental data well.
基金The National Natural Science Foundation of China(No.51376110,51541604)the Major International(Regional) Joint Research Project of the National Natural Science Foundation of China(No.61320106011)
文摘The experimental study of natural convection in allglass evacuated tube solar collectors is performed through the experimental platform of the solar-assisted fuel cell system.The experimental facility includes solar collectors with different length and diameter tubes, different coating materials, and with / without guide plates, respectively. Threedimensional mathematical models on natural and forced convections in the solar collectors are established and the experimental data is validated by field synergy and entransy principles. The results of natural convection show that the water temperature increases and thermal efficiency decreases gradually with the evacuated tube length. The thermal efficiency increases when absorption rates increase from 0. 95 to 1. 0 and emission rates decrease from 0. 16 to 0. 06. The thermal efficiency of solar collectors is increased after being equipped with the guide plate, which is attributed to the disappearance of the mixed flowand the enhancement of the heat transfer at the bottom of the evacuated tube. The results of forced convertion indicate that the Reynolds, Nusselt and entransy increments of the horizontal double collectors are higher than those of the vertical single collector while the entransy dissipation is lower than that of the vertical single collector. It is concluded that the solar collectors with guide plates are suitable for natural convection while the double horizontal collectors are suitable for forced convection in the thermal field of solar-assisted fuel cell systems with lowand medium temperatures.
基金The Program for Special Talent in Six Fields of Jiangsu Province (2011-ZBZZ-016)the Postdoctoral Science Foundation of Jiangsu Province (No. 0902038C)
文摘A novel dual output phase-shift distribution transformer ( DOPSDT ) is proposed based on the electromagnetic filtering theory. First, its structural characteristics, winding connection mode and turn number ratio for special phase shifting are investigated. Secondly, the balance formulation of harmonic magneto-motive forces is derived and the electromagnetic filtering principle of the DOPSDT is introduced. The harmonic mitigating performance under different nonlinear load conditions are also analyzed using the field-circuit coupled method, The analysis results show that the DOPSDT can mitigate the primary current distortion even under severe nonlinear load conditions. By applying the zero sequence flux cancellation and phase-shift techniques at their secondary windings, the DOPSDT can significantly reduce the 3rd, 5th, 7th, 9th, 15th, 17th and 19th harmonics within its secondary windings.
基金Project supported by the National Key Basic Research Support Foundation of China (No. 2002CB410808)the National Natural Science Foundation of China (No. 40401030)
文摘Interactions of three heavy metal ions, Cu^2+, Cd^2+, and Pb^2+, and, for comparison, Na^+ with electrodialytic clay fractions (less than 2μm in diameter) of four paddy soils as well as a yellow-brown soil as a control soil were evaluated based on measurements of the Wien effect in dilute suspensions with a clay concentration of 10 g kg^-1 in four nitrate solutions of 2 × 10^-4/z mol L^-1, where z is the cation valence, and a nitric acid solution of 3 × 10^-5 mol L^-1, Field strengths ranging from 15 to 230 kV cm^-1 were applied for measuring the electrical conductivities (ECs) of the suspensions. The mean free binding energies between the various cations and all of the soils determined from exchange equilibrium increased in the order: Na^+ 〈 Cd^2+ 〈 Cu^2+ 〈 Pb^2+. In general, the ECs of the suspensions in the sodium nitrate solution were smaller than those of the suspensions in the heavy metal solutions because of the lower electrophoretic mobility of sodium compared to the divalent cations. In terms of relative electrical conductivity-field strength relationships, relative electrical conductivity (REC) of suspensions containing various cations at field strengths larger than about 50 kV cm^-1 were in the descending order: Na^+ 〉 Cu^2+ 〉 Cd^2+ 〉 Pb^2+ for all tested soils. A characteristic parameter of the REC-field strength curves, AREC200, REC at a field strength of 200 kV cm^-1 minus that at the local minimum of the concave segment of the REC-field strength curves, characterized the strength of adsorption of the cations stripped off by the applied strong electrical field, and for all soils the values of AREC200 were generally in the order: Na^+ 〈 Cu^2+ ≤ Cd^2+ 〈 Pb^2+.
文摘Under the external AC and DC electric field, the effective response of nonlinear spherical coated composites, which obey the constitutive relation of electric displaeement and electric field, is investigated in the dilute limit by using the perturbation method. The local potentials in inclusion and host regions are derived at all harmonics. Moreover, the formulae of the effective linear and nonlinear responses are given in the dilute limit.
文摘An improved Monte Carlo method was used to simulate the motion of electrons in c-C4F8 and SF6 gas mixtures for pulsed townsend discharge. The electron swarm parameters such as effective ionization coefficient, -↑α and drift velocity over the E/N range from 280~700 Td(1Td=10^-21 V·m^2) were calculated by employing a set of cross sections available in literature. From the variation cure of -↑α with SF6 partial pressure p, the limiting field (E/N)lim of gas mixture at different gas content was determined. It is found that the limiting field of c-C4F8 and SF6 gas mixture is higher than that of pure SF6 at any SF6 mixture ratio. Simulation results show excellent agreement with experiment data available in previous literature.
基金Projects(2017GDAS CX-0202,2017GDAS CX-0111,2018 GDAS CX-0402) supported by Guangdong Academy of Science’ Special Project of Science and Technology Development,ChinaProject(2014B070705007) supported by Guangdong Science and Technology Plan Project,China+1 种基金Project(2016A030312015) supported by Scientific Research Fund of Guangdong Province,ChinaProject(2017A070701027) supported by Guangdong Science and Technology Program,China。
文摘In this work,the chromium aluminum nitride(CrAlN)coatings were prepared on TC11 titanium alloy by composite magnetic field cathodic arc ion plating with controllable pulse electromagnetic combined with permanent magnet.The effects of electromagnetic frequency on the morphology,microstructure,nano-hardness and elastic modulus of the coatings were investigated by scanning electron microscope(SEM),X-ray diffraction(XRD)and nano-indenter.This paper has mainly studied the influence of CrAlN coatings which are prepared at various electromagnetic frequencies on the wear and erosion resistance through a series of wear and solid particle erosion experiments.It was found that the deposition rate of CrAlN coatings increases with the increase of electromagnetic frequency.And CrAlN coatings all preferentially grew along the(111)crystal plane.At 16.7 Hz,with the increase of pulsed electromagnetic frequency,the hardness is the highest(23.6 GPa)and the adhesion is the highest(41.5 N).In addition,the coating deposition exhibited the best wear and solid erosion resistance at 16.7 Hz and 33.3 Hz,the friction coefficient is about 0.35,and the erosion rate is about 0.2μm/g at 30°and less than 1μm/g at 90°,respectively.These results indicate that the CrAlN coating formed at an appropriate pulsed electromagnetic frequency can achieve excellent mechanical properties,wear and solid erosion resistance.
文摘For converter transformer, AC-DC combined electric field can trigger space charge accumulation on oil-impregnated pressboard interface. The accumulation of space charge on oil-pressboard interface can result in electric field distortion, trend to trigger surface discharge of barriers. This paper studied the influence of surface charge on flashover voltage of oil-impregnated pressboard under AC-DC combined electric field. The study finds that the flashover voltage of oil-pressboard interface under negative polarity DC superimposed AC electric field is higher than that.of positive DC superimposed AC voltage to form composite electric field. It was found that homopolar surface charge has been accumulated on the interface of oil-pressboard with positive or negative DC voltage through measuring surface potential by the electrostatic capacitive probe. The surface charge produced electric field in the opposite direction, which weakening the synthetic electric field strength. What's more, under the same conditions, the negative surface charge density oil-pressboard is much larger than the positive.
基金supported by the National Natural Science Foundation of China (No.21774067)the support from K. C. Wong Magna Fund in Ningbo University。
文摘Langevin dynamics simulations were conducted to study the collapse of grafted partially charged 4-arm star chains onto the oppositely charged grafting electrode in the presence of trivalent salt coions.Simulation results reveal that the average charge fraction of the grafted star chains and the salt concentration play critical roles in the competitive adsorption of charged monomers and trivalent salt coions onto the oppositely charged electrode.For grafted star chains with relatively high charge fraction,charged monomers are the dominant species collapsing on the oppositely charged electrode with the emergence of charge reversal on the grafting electrode.At a low charge fraction such that the total amount of charges on a grafted star molecule is comparable to that of a trivalent salt coion,trivalent salt coions absorb more strongly onto the electrode than grafted stars even at very low salt concentration.It is found that at relatively low charge fraction of star chains,the addition of trivalent salt coions does not lead to charge overcompensation of the surface charges on the grafting electrode.The stretching of star brushes under an electric field in the presence of trivalent salt coions was also briefly investigated.
文摘The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D<SUP>-</SUP> center, which consists of a positive ion located on the z-axis at a distance from the two-dimensional quantum dot plane and two electrons in the dot plane bound by the ion, is investigated at arbitrary strength of magnetic field by making use of the method of few-body physics. Discontinuous ground-state energy transitions induced by the magnetic field are reported. The dependence of the binding energy of the D<SUP>-</SUP> ground state on the quantum dot radius is obtained. A considerable enhancement of the binding is found for the D<SUP>-</SUP> ground state, which results from the confinement of electrons and electron-phonon coupling.
基金Supported by National Natural Science Foundation of China under Grant No. 10875060
文摘We here explore black holes in the third order Lovelock gravity coupling with nonlinear Born-Infeld electro- magnetic field. Considering special second and third order coefficients (&g = 363 = a2), we analyze the thermodynamics of third order Lovelock-Born-Infeld black holes and, in 7-dimensional AdS space-time, discuss the stability of black holes in different event horizon structures. We find that the cosmological constant A plays an important role in the distribution of black hole stable regions.