Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet d...Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet deposited in a conical tube or on a conical fibre. We perform an experiment to investigate the directional motion of a droplet in an open conical tube. Our theoretical analysis and experimental observations both demonstrate that surface tension can drive the droplet to move in the conical tube. The critical condition of the liquid moving in the conical tube is presented. We also analyse a droplet on a conical hydrophilic fibre, which can move from the thinner to the thicker end.展开更多
A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me...A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me） almost has no impact on the reconnection rate, however it can significantly affect electron behaviour in the diffusion region. For the case with larger mass ratio, the width of electron current sheet becomes smaller and the outflow region along the separatrix is smaller, hence the peak of the electron outflow speed is essentially larger. Density cavities and the parallel electric field E// along the separatrix can be found in the case with larger mass ratio, which may have significant influences on the acceleration and heating of the electrons near the X point.展开更多
We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measur...We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measured. Experimental results have shown that the graded dispersion with ZnO nanowhiskers contributes to broadband microwave absorption. In other words, the absorption band depends on the graded dispersion configuration of ZnO nanowhiskers in polyester matrix.展开更多
We report a femtosecond optical parametric oscillator based on MgO-doped PPLN synchronously pumped by a mode-locked Ti：sapphire laser. The wavelengths of the signal and idler are continuously tuned from 1100 to 1300h...We report a femtosecond optical parametric oscillator based on MgO-doped PPLN synchronously pumped by a mode-locked Ti：sapphire laser. The wavelengths of the signal and idler are continuously tuned from 1100 to 1300hm and from 2080 to 2930nm, respectively, by changing the pump wavelength and the OPO cavity length. The maximum signal output power of 130mW at the wavelength of 1225nm is obtained, pumped by 900roW of 800hm laser radiation. This corresponds to a total conversion efficiency of 22.1%. The signal pulse duration is measured to be 167fs by intensity autocorrelation with chirped mirrors for intracavity dispersion compensation.展开更多
We theoretically analyse the temperature effects on a surface plasmon resonance （SPR） sensor in Kretschmann configuration. The temperature effects include the thermo-optic effect and the dispersion of thermal-optic ...We theoretically analyse the temperature effects on a surface plasmon resonance （SPR） sensor in Kretschmann configuration. The temperature effects include the thermo-optic effect and the dispersion of thermal-optic coefficient in the dielectric along with the thermal expansion effect, phonon-electron scattering and electron-electron scattering in the metal layer. We simulate the temperature dependence of the resonance position and the sensitivity of the SPR sensor under wavelength-interrogation and angular-interrogation mode of operation and the differences are pointed out in the two modes.展开更多
The ground-state energy and effective mass of an acoustic polaron in one dimension are calculated by using an electron-longitudinal-acoustic-phonon interaction Hamiltonian derived here. The self-trapping of the acoust...The ground-state energy and effective mass of an acoustic polaron in one dimension are calculated by using an electron-longitudinal-acoustic-phonon interaction Hamiltonian derived here. The self-trapping of the acoustic polaron is discussed. It is found that the critical coupling constant shifts toward weaker electron-phonon interaction with the increasing cutoff wave vector and the products of the critical coupling constant by the cutoff wave vector tend to a certain value. The self-trapping of acoustic polarons in one dimension is easier to be realized than that in three- and two-dimensional systems. The self-trapping transition of acoustic polarons is expected to be observed in the one dimensional systems of alkali halides and wide-band-gap semiconductors.展开更多
For a nonholonomic mechanics system with the action of small disturbance, the Lie symmetrical perturbation and adiabatic invariants of generalized Hojman type are studied under general infinitesimal transformations of...For a nonholonomic mechanics system with the action of small disturbance, the Lie symmetrical perturbation and adiabatic invariants of generalized Hojman type are studied under general infinitesimal transformations of groups in which the generalized coordinates and time are variable. On the basis of the invariance of disturbed nonholonomic dynamical equations under general infinitesimal transformations, the determining equations, the constrained restriction equations and the additional restriction equations of Lie symmetries of the system are constructed, which only depend on the variables t, qs and q^.s. Based on the definition of higher-order adiabatic invariants of a mechanical system, the perturbation of Lie symmetries for a nonholonomic system with the action of small disturbance is investigated, and the Lie symmetrical adiabatic invariants, the weakly Lie symmetrical adiabatic invariants and the strongly Lie symmetrical adiabatic invariants of generalized Hojman type of disturbed nonholonomic systems are obtained. An example is given to illustrate applications of the results.展开更多
We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion be...We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion beam sputtering method. The LIDTs of AR coatings are measured in vacuum and in atmosphere, respectively. It is exhibited that contaminations in vacuum are easily to be absorbed onto optical surface because of lower pressure, and they become origins of damage, resulting in the decrease of LIDT from 24.5J/cm^2 in air to 15.TJ/cm^2 in vacuum. The LIDT of coatings in vacuum has is slightly changed compared with the value in atmosphere after the organic contaminations are wiped off. These results indicate that organic contaminations are the main reason of the LIDT decrease in vacuum. Additionally, damage morphologies have distinct changes from vacuum to atmosphere because of the differences between the residual stress and thermal decomposability of filmy materials.展开更多
We perform a theoretical study on a low dark current InGaAs/GaAs very-long-wavelength （〉 12 μm） quantum well infrared photodetector （VLW-QWIP）, based on a double barrier resonant tunnelling structure （DBRTS）. ...We perform a theoretical study on a low dark current InGaAs/GaAs very-long-wavelength （〉 12 μm） quantum well infrared photodetector （VLW-QWIP）, based on a double barrier resonant tunnelling structure （DBRTS）. The ground tunnelling state of the central quantum well （QW） of the DBRTS can resonate with the first excited bound state of the doped InGaAs QW by adjusting the structure parameters of the DBRTS. Investigation of the carrier transport performance of this device is carried out based on quantum wave transport theory. It has been shown that the dark current in this device can be significantly reduced by two orders compared to conventional InGaAs/GaAs VLW-QWIPs, while the photocurrent is almost the same as those in conventional VLW-QWIPs. This DBRTS integrated VLW-QWIP structure may stimulate the experimental investigation for VLW-QWIPs at high operation temperatures.展开更多
Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3 （001） substrate by metal organic deposition method. All YBCO films were fired at 820 ℃ in humidity range of 2.6%-19.7% atmosphere. Mi...Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3 （001） substrate by metal organic deposition method. All YBCO films were fired at 820 ℃ in humidity range of 2.6%-19.7% atmosphere. Microstructure of YBCO thin films was analyzed by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Superconducting properties of YBCO films were measured by four-probe method. XRD results showed that the second phase （such as BaF2）and a-axis-oriented grains existed in the films prepared at 2.6% humidity condition; a-axis-oriented grains increased in the film prepared at higher than 4.2% humidity condition; almost pure c-axias-oriented grains existed in the films fired at 4.2% humidity condition. Morphologies of the YBCO films showed that all films had a smooth and crack-free surface. YBCO film prepared at 4.2% humidity condition showed Jc value of 3.3 MA/cm^2 at 77 K in self-field.展开更多
We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2＋] on particle size and photoluminescence （PL） of ZnS：Mn^2＋ nanocrystMs. By changing the [S^2-]/[Zn^2＋] ratio from 0.6 （Zn-rich） to 2.0 （S-...We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2＋] on particle size and photoluminescence （PL） of ZnS：Mn^2＋ nanocrystMs. By changing the [S^2-]/[Zn^2＋] ratio from 0.6 （Zn-rich） to 2.0 （S-rich）, the particle size increases from nearly 2. 7nm to about 4.Ohm. The increase in the ratio of [S^2-]/[Zn^2＋] cadses a decrease of PL emission intensity of ZnS host while a distinct increase of Mn^2＋ emission. The maximum intensity for the luminescence of Mn^2＋ emission is observed at the ratio of [S^2-]/[Zn^2＋] ≈ 1.5. The possible mechanism for the results is discussed by filling of S^2- vacancies and the increase of Mn^2＋ ions incorporated into ZnS lattices.展开更多
Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices a...Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.展开更多
REBa_(2)Cu_(3)O_(7−x)(REBCO)coated conductors,owing to its high tensile strength and current‐carrying ability in a background field,are widely regarded a promising candidate in high‐field applications.Despite the gr...REBa_(2)Cu_(3)O_(7−x)(REBCO)coated conductors,owing to its high tensile strength and current‐carrying ability in a background field,are widely regarded a promising candidate in high‐field applications.Despite the great potentials,recent studies have highlighted the challenges posed by screening currents,which are featured by a highly nonuniform current distribution in the superconducting layer.In this paper,we report a comprehensive study on the behaviors of screening currents in a compact REBCO coil,specifically the screeningcurrent‐induced magnetic fields and strains.Experiments were carried out in the self‐generated magnetic field and a background field,respectively.In the self‐field condition,the full hysteresis of the magnetic field was obtained by applying current sweeps with repeatedly reversed polarity,as the nominal center field reached 9.17 T with a maximum peak current of 350 A.In a background field of 23.15 T,the insert coil generated a center field of 4.17 T with an applied current of 170 A.Ultimately,a total center field of 32.58 T was achieved before quench.Both the sequential model and the coupled model considering the perpendicular field modification due to conductor deformation are applied.The comparative study shows that,for this coil,the electromagnetic–mechanical coupling plays a trivial role in self‐field conditions up to 9 T.In contrast,with a high axial field dominated by the background field,the coupling effect has a stronger influence on the predicted current and strain distributions.Further discussions regarding the role of background field on the strains in the insert suggest potential design strategies to maximize the total center field.展开更多
The elastoplastic mechanical behaviour of an epoxy-impregnated REBCO pancake winding under cryogenics and high magnetic field is investigated in the frame of finite element(FE)modelling.A two-dimensional axisymmetric ...The elastoplastic mechanical behaviour of an epoxy-impregnated REBCO pancake winding under cryogenics and high magnetic field is investigated in the frame of finite element(FE)modelling.A two-dimensional axisymmetric electromagnetic-thermal-structure multi-physics multi-layer FE model with main layers of the coated conductor and insulation materials is developed.The radial stress and hoop stress on each constituent layer induced by thermal mismatch stress during cooling are investigated.The mechanical behaviour of each constituent material is also analysed by considering the thermal mismatch stress and electromagnetic force under 20 T background field.The results show that discrete stresses appear in all the constituent materials indicating that the multi-layer winding model containing the main constituent materials is necessary for the accurate stress analysis in an epoxy-impregnated REBCO winding.The stress of each constituent material induced by thermal mismatch during cooling process are too high to be ignored in the subsequent electromagnetic structure analysis.The mechanical-magnetic coupling analyses show that the stresses of all the constituent materials increase with the transport current.The plastic failure mainly induced by hoop stress successively occurs on copper stabilizer and Hastelloy substrate of the innermost turn,and the plastic region propagates from the inner turns to the outer turns with the increase of transport current.The failure of the superconducting layer occurs before the yield in Hastelloy due to the direct action of Lorentz force on the superconducting layers.The transverse tensile stress increases with the increasing transport current,indicating that the risk of transverse delamination failure increases with the increase of transport current.The mechanical failure modes including delamination within the conductor,plastic deformation in substrate and crack in superconducting layer should be seriously considered.展开更多
In order to obtain the sharp cube texture,a new process,the intermediate annealing rolling technique,has been introduced to prepare the Ni7W substrate.In this paper,a cubic texture content up to 98.5%within 10°of...In order to obtain the sharp cube texture,a new process,the intermediate annealing rolling technique,has been introduced to prepare the Ni7W substrate.In this paper,a cubic texture content up to 98.5%within 10°of the standard cubic orientation is obtained in the final substrate and the influence of this improved rolling technique on the cube texture formation has been discussed.The results show that the increased cube texture in the Ni7W substrate is caused by the optimized deformation texture and the increased nucleated fraction of the cube grains.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10732050, 10525210 and 10121202
文摘Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet deposited in a conical tube or on a conical fibre. We perform an experiment to investigate the directional motion of a droplet in an open conical tube. Our theoretical analysis and experimental observations both demonstrate that surface tension can drive the droplet to move in the conical tube. The critical condition of the liquid moving in the conical tube is presented. We also analyse a droplet on a conical hydrophilic fibre, which can move from the thinner to the thicker end.
基金Supported by the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KZCX3-SW-144, the National Science Foundation of China under Grant Nos 60608015, and the Doctoral Fund of Qingdao University of Science and Technology.
文摘A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me） almost has no impact on the reconnection rate, however it can significantly affect electron behaviour in the diffusion region. For the case with larger mass ratio, the width of electron current sheet becomes smaller and the outflow region along the separatrix is smaller, hence the peak of the electron outflow speed is essentially larger. Density cavities and the parallel electric field E// along the separatrix can be found in the case with larger mass ratio, which may have significant influences on the acceleration and heating of the electrons near the X point.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50572010, 50742007 and 10672020, the National Defense Founds of China under Grant Nos A2220061080, and the National Key Basic Research Programme of China under Grant No 5131803.
文摘We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measured. Experimental results have shown that the graded dispersion with ZnO nanowhiskers contributes to broadband microwave absorption. In other words, the absorption band depends on the graded dispersion configuration of ZnO nanowhiskers in polyester matrix.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60490280, 60621063 and 60308001. We gratefully acknowledge HC Photonics Co. for providing excellent PPLN crystal. We thank NIE Yu- Xin and HAN Hai-Nian for helpful discussions.
文摘We report a femtosecond optical parametric oscillator based on MgO-doped PPLN synchronously pumped by a mode-locked Ti：sapphire laser. The wavelengths of the signal and idler are continuously tuned from 1100 to 1300hm and from 2080 to 2930nm, respectively, by changing the pump wavelength and the OPO cavity length. The maximum signal output power of 130mW at the wavelength of 1225nm is obtained, pumped by 900roW of 800hm laser radiation. This corresponds to a total conversion efficiency of 22.1%. The signal pulse duration is measured to be 167fs by intensity autocorrelation with chirped mirrors for intracavity dispersion compensation.
基金Supported by the National Basic Research Programme of China under Grant No 2006cb302905, the National Science Foundation of China under Grant No 10474093, the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCX3.Syw.H02, and the National High-Technology Research and Development Programme of China under Grant No 2007AA06Z420.
文摘We theoretically analyse the temperature effects on a surface plasmon resonance （SPR） sensor in Kretschmann configuration. The temperature effects include the thermo-optic effect and the dispersion of thermal-optic coefficient in the dielectric along with the thermal expansion effect, phonon-electron scattering and electron-electron scattering in the metal layer. We simulate the temperature dependence of the resonance position and the sensitivity of the SPR sensor under wavelength-interrogation and angular-interrogation mode of operation and the differences are pointed out in the two modes.
基金Supported by the PhD Progress Foundation of Higher Education of China under Grant No 20040126003, and the Natural Science Foundation of Inner Mongol of China under Grant No 200408020101.
文摘The ground-state energy and effective mass of an acoustic polaron in one dimension are calculated by using an electron-longitudinal-acoustic-phonon interaction Hamiltonian derived here. The self-trapping of the acoustic polaron is discussed. It is found that the critical coupling constant shifts toward weaker electron-phonon interaction with the increasing cutoff wave vector and the products of the critical coupling constant by the cutoff wave vector tend to a certain value. The self-trapping of acoustic polarons in one dimension is easier to be realized than that in three- and two-dimensional systems. The self-trapping transition of acoustic polarons is expected to be observed in the one dimensional systems of alkali halides and wide-band-gap semiconductors.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10372053 and 10472040.
文摘For a nonholonomic mechanics system with the action of small disturbance, the Lie symmetrical perturbation and adiabatic invariants of generalized Hojman type are studied under general infinitesimal transformations of groups in which the generalized coordinates and time are variable. On the basis of the invariance of disturbed nonholonomic dynamical equations under general infinitesimal transformations, the determining equations, the constrained restriction equations and the additional restriction equations of Lie symmetries of the system are constructed, which only depend on the variables t, qs and q^.s. Based on the definition of higher-order adiabatic invariants of a mechanical system, the perturbation of Lie symmetries for a nonholonomic system with the action of small disturbance is investigated, and the Lie symmetrical adiabatic invariants, the weakly Lie symmetrical adiabatic invariants and the strongly Lie symmetrical adiabatic invariants of generalized Hojman type of disturbed nonholonomic systems are obtained. An example is given to illustrate applications of the results.
文摘We investigate the influence of vacuum organic contaminations on laser-induced damage threshold （LIDT） of optical coatings. Anti-reflective （AIR） coatings at 1064 nm made by Ta2 O5/SiO2 are deposited by the ion beam sputtering method. The LIDTs of AR coatings are measured in vacuum and in atmosphere, respectively. It is exhibited that contaminations in vacuum are easily to be absorbed onto optical surface because of lower pressure, and they become origins of damage, resulting in the decrease of LIDT from 24.5J/cm^2 in air to 15.TJ/cm^2 in vacuum. The LIDT of coatings in vacuum has is slightly changed compared with the value in atmosphere after the organic contaminations are wiped off. These results indicate that organic contaminations are the main reason of the LIDT decrease in vacuum. Additionally, damage morphologies have distinct changes from vacuum to atmosphere because of the differences between the residual stress and thermal decomposability of filmy materials.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60476031 and 10474020
文摘We perform a theoretical study on a low dark current InGaAs/GaAs very-long-wavelength （〉 12 μm） quantum well infrared photodetector （VLW-QWIP）, based on a double barrier resonant tunnelling structure （DBRTS）. The ground tunnelling state of the central quantum well （QW） of the DBRTS can resonate with the first excited bound state of the doped InGaAs QW by adjusting the structure parameters of the DBRTS. Investigation of the carrier transport performance of this device is carried out based on quantum wave transport theory. It has been shown that the dark current in this device can be significantly reduced by two orders compared to conventional InGaAs/GaAs VLW-QWIPs, while the photocurrent is almost the same as those in conventional VLW-QWIPs. This DBRTS integrated VLW-QWIP structure may stimulate the experimental investigation for VLW-QWIPs at high operation temperatures.
基金supported by the National 863 Program of Ministry of Science and Technology of China (2007AA03Z216)
文摘Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3 （001） substrate by metal organic deposition method. All YBCO films were fired at 820 ℃ in humidity range of 2.6%-19.7% atmosphere. Microstructure of YBCO thin films was analyzed by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Superconducting properties of YBCO films were measured by four-probe method. XRD results showed that the second phase （such as BaF2）and a-axis-oriented grains existed in the films prepared at 2.6% humidity condition; a-axis-oriented grains increased in the film prepared at higher than 4.2% humidity condition; almost pure c-axias-oriented grains existed in the films fired at 4.2% humidity condition. Morphologies of the YBCO films showed that all films had a smooth and crack-free surface. YBCO film prepared at 4.2% humidity condition showed Jc value of 3.3 MA/cm^2 at 77 K in self-field.
基金Supported by the National Natural Science Foundation of China under Grant No 10674074, and the Tianjin Natural Science Foundation under Grant Nos 06TXTJJC14601 and 07JCYBJC06400.
文摘We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2＋] on particle size and photoluminescence （PL） of ZnS：Mn^2＋ nanocrystMs. By changing the [S^2-]/[Zn^2＋] ratio from 0.6 （Zn-rich） to 2.0 （S-rich）, the particle size increases from nearly 2. 7nm to about 4.Ohm. The increase in the ratio of [S^2-]/[Zn^2＋] cadses a decrease of PL emission intensity of ZnS host while a distinct increase of Mn^2＋ emission. The maximum intensity for the luminescence of Mn^2＋ emission is observed at the ratio of [S^2-]/[Zn^2＋] ≈ 1.5. The possible mechanism for the results is discussed by filling of S^2- vacancies and the increase of Mn^2＋ ions incorporated into ZnS lattices.
文摘Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.
基金supported by the National MCF Energy R&D Program under Grant No.2022YFE03150103the National Natural Science Foundation of China(NSFC)under Grant No.52277026the BK21 FOUR program of the Education and Research Program for Future ICT Pioneers,Seoul National University in 2023.
文摘REBa_(2)Cu_(3)O_(7−x)(REBCO)coated conductors,owing to its high tensile strength and current‐carrying ability in a background field,are widely regarded a promising candidate in high‐field applications.Despite the great potentials,recent studies have highlighted the challenges posed by screening currents,which are featured by a highly nonuniform current distribution in the superconducting layer.In this paper,we report a comprehensive study on the behaviors of screening currents in a compact REBCO coil,specifically the screeningcurrent‐induced magnetic fields and strains.Experiments were carried out in the self‐generated magnetic field and a background field,respectively.In the self‐field condition,the full hysteresis of the magnetic field was obtained by applying current sweeps with repeatedly reversed polarity,as the nominal center field reached 9.17 T with a maximum peak current of 350 A.In a background field of 23.15 T,the insert coil generated a center field of 4.17 T with an applied current of 170 A.Ultimately,a total center field of 32.58 T was achieved before quench.Both the sequential model and the coupled model considering the perpendicular field modification due to conductor deformation are applied.The comparative study shows that,for this coil,the electromagnetic–mechanical coupling plays a trivial role in self‐field conditions up to 9 T.In contrast,with a high axial field dominated by the background field,the coupling effect has a stronger influence on the predicted current and strain distributions.Further discussions regarding the role of background field on the strains in the insert suggest potential design strategies to maximize the total center field.
基金the National Natural Science Foundation of China(11902129,11932008)the China Postdoctoral Science Foundation(2019T120963)the Fundamental Research Funds for the Central Universities(lzujbky-2020-pd03,lzujbky-2021-kb06).
文摘The elastoplastic mechanical behaviour of an epoxy-impregnated REBCO pancake winding under cryogenics and high magnetic field is investigated in the frame of finite element(FE)modelling.A two-dimensional axisymmetric electromagnetic-thermal-structure multi-physics multi-layer FE model with main layers of the coated conductor and insulation materials is developed.The radial stress and hoop stress on each constituent layer induced by thermal mismatch stress during cooling are investigated.The mechanical behaviour of each constituent material is also analysed by considering the thermal mismatch stress and electromagnetic force under 20 T background field.The results show that discrete stresses appear in all the constituent materials indicating that the multi-layer winding model containing the main constituent materials is necessary for the accurate stress analysis in an epoxy-impregnated REBCO winding.The stress of each constituent material induced by thermal mismatch during cooling process are too high to be ignored in the subsequent electromagnetic structure analysis.The mechanical-magnetic coupling analyses show that the stresses of all the constituent materials increase with the transport current.The plastic failure mainly induced by hoop stress successively occurs on copper stabilizer and Hastelloy substrate of the innermost turn,and the plastic region propagates from the inner turns to the outer turns with the increase of transport current.The failure of the superconducting layer occurs before the yield in Hastelloy due to the direct action of Lorentz force on the superconducting layers.The transverse tensile stress increases with the increasing transport current,indicating that the risk of transverse delamination failure increases with the increase of transport current.The mechanical failure modes including delamination within the conductor,plastic deformation in substrate and crack in superconducting layer should be seriously considered.
基金Funded by the Beijing Municipal Natural Science Foundation(No.2212025)National Natural Science Foundation of China(No.12042506)+1 种基金Magnetic Resonance Union of Chinese Academy of Sciences(No.2020GZL001)the General Program of Science and Technology Development Project of Beijing Municipal Education Commission(No.KM202010005007)。
文摘In order to obtain the sharp cube texture,a new process,the intermediate annealing rolling technique,has been introduced to prepare the Ni7W substrate.In this paper,a cubic texture content up to 98.5%within 10°of the standard cubic orientation is obtained in the final substrate and the influence of this improved rolling technique on the cube texture formation has been discussed.The results show that the increased cube texture in the Ni7W substrate is caused by the optimized deformation texture and the increased nucleated fraction of the cube grains.
