We investigate the dc Josephson effect in one-dimensional junctions where a ring conductor is sandwiched between two semiconductor nanowires with proximity-induced superconductivity. Peculiar features of the Josephson...We investigate the dc Josephson effect in one-dimensional junctions where a ring conductor is sandwiched between two semiconductor nanowires with proximity-induced superconductivity. Peculiar features of the Josephson effect arise due to the interplay of spin-orbit interaction and external Zeenmn field. By tuning the Zeeman field orientation, the device can vary from 0 to π junction. Afore importantly, nonzero ,losephson current is possible at zero phase difference across the junction. Although this anomalous Josephson current is not relevant to the topological phase transition, its magnitude can be significantly enhanced whe, n the nanowire, s become topological superconductors where Majorana bound states emerge. Distinct modulation patterns are obtained for the semiconductor nanowires in the topologically trivial and non-trivial phases. These results are useful to probe the topological phase transition in semiconductor nanowire junctions via the dc Josephson effect.展开更多
A self-consistent model was adopted to study the time evolution of low-voltage pulsed DC glow discharge. The distributions of electric field, ion density and electron density in nitrogen were investigated in our simul...A self-consistent model was adopted to study the time evolution of low-voltage pulsed DC glow discharge. The distributions of electric field, ion density and electron density in nitrogen were investigated in our simulation, and the temporal shape of the discharge current was also obtained. Our results show that the dynamic behaviors of the discharge depends strongly on the applied pulse voltage, and the use of higher pulse voltages results in a significantly increase of discharge current and a decrease of discharge delay time. The current-voltage characteristic cMculated by adjusting secondary electron emission coefficient for different applied pulse voltage under the gas pressure of 1 Torr is found in a reasonable agreement with the experimental results.展开更多
Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic device...Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic devices.However,owing to the working mechanisms of conventional DC TENGs,generating a stable DC output from reciprocating motion remains a challenge.Accordingly,we propose a bidirectional rotating DC TENG(BiR-TENG),which can generate DC outputs,regardless of the direction of rotation,from reciprocating motions.The distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC output.Furthermore,it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational direction.Owing to these tailored design strategies and subsequent optimizations,the BiR-TENG could generate an effective unidirectional DC output.Applications of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this output.This study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions,highlighting the suitability of DC outputs as an energy source for electronic devices.展开更多
This paper reports that a series of silver oxide （AgzO） films are deposited on glass substrates by direct-current reactive magnetron sputtering at a substrate temperature of 250 ℃ and an oxygen flux ratio of 15：18...This paper reports that a series of silver oxide （AgzO） films are deposited on glass substrates by direct-current reactive magnetron sputtering at a substrate temperature of 250 ℃ and an oxygen flux ratio of 15：18 by modifying the sputtering power （SP）. The AgxO films deposited apparently show a structural evolution from cubic biphased （AgO ＋ Ag20） to cubic single-phased （Ag20）, and to biphased （Ag20 ＋ AgO） structure. Notably, the cubic single-phased Ag20 fihn is deposited at the SP = 105 W and an AgO phase with （220） orientation discerned in the Ag^O films deposited using the SP 〉 105 W. The transmissivity and refiectivity of the AgxO films in transparent region decrease with the increase the SP, whereas the absorptivity inversely increases with the increase of the SP. These results may be due to the structural evolution and the increasing film thickness. A redshift of the films＇ absorption edges determined in terms of Tauc formula clearly occurs from 3.1 eV to 2.73 eV with the increase of the SP.展开更多
The key plasma parameters under different discharge modes, such as heavy-particle and electron temperatures, electron number density, and nonequilibrium volume of plasmas, play important roles in various applications ...The key plasma parameters under different discharge modes, such as heavy-particle and electron temperatures, electron number density, and nonequilibrium volume of plasmas, play important roles in various applications of gas discharge plasmas. In this study, a self-consistent two-dimensional nonequilibrium fluid model coupled with an external circuit model is established to reveal the mechanisms related to the discharge modes, including the normal glow, abnormal glow,arc, and glow-to-arc transition modes, with an atmospheric-pressure direct-current(DC) argon discharge as a model plasma system. The modeling results show that, under different discharge modes, the most significant difference between the preceding four discharge modes lies in the current and energy transfer processes on the cathode side. On one hand, the current to the cathode surface is mainly delivered by the ions coming from the plasma column under the glow discharge mode due to the low temperature of the solid cathode, whereas the thermionic and secondary electrons emitted from the hot cathode surface play a very important role under the arc mode with a higher cathode surface temperature and higher ion flux toward the cathode. On the other hand, the energy transfer channel on the cathode side changes from mainly heating the solid cathode under the glow mode to simultaneously heating both the solid cathode and plasma column under the arc mode with an increase in the discharge current. Consequently, the power density in the cathode sheath(P_c) was used as a key parameter for judging different discharge modes, and the range of(0.28–1.2) × 10^(12) W m^(-3) was determined as a critical window of P_c corresponding to the glow-to-arc-mode transition for the atmospheric-pressure DC argon discharge, which was also verified by comparison with the experimental results in this study and the data in the previous literature.展开更多
Corona discharge suppression for high-voltage direct-current(HVDC)transmission lines at line terminals such as converter stations is a subject that requires attention.In this paper,a method based on a conductor covere...Corona discharge suppression for high-voltage direct-current(HVDC)transmission lines at line terminals such as converter stations is a subject that requires attention.In this paper,a method based on a conductor covered with dielectric film is proposed and implemented through a bench-scale setup.Compared with the bare conductor,the corona discharge suppression effect of the dielectric-film-covered conductor under positive polarity is studied from the composite field strength and ion current density using a line-plate experimental device.The influences of film thickness and film material on the corona discharge suppression effect are investigated.The charge accumulation and dissipation characteristics of different film materials are also studied.The results show that the conductor covered with dielectric film has excellent ability to inhibit corona discharge.The ground-level composite field strength of the conductor covered with dielectric film is lower than its nominal field strength,and its ion current density is at the nA m^(−2) level.The corona threshold voltage can be promoted by increasing the film thickness,but the ability to inhibit corona discharge becomes weak.The larger the surface electric field strength,the more charge accumulated,but the faster the charge dissipation rate.Compared with polyvinyl chloride film,cross-linked polyethylene film has stronger charge accumulation ability and slower charge dissipation rate,which can better restrain the corona discharge of HVDC transmission lines.展开更多
Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and ...Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.展开更多
Recently H_(2)^(+)ion beam finds widespread use in many fields,and the demand of high-current H_(2)^(+)ion sources is urgent for numerous applications.However,there are currently almost no reported ion sources capable...Recently H_(2)^(+)ion beam finds widespread use in many fields,and the demand of high-current H_(2)^(+)ion sources is urgent for numerous applications.However,there are currently almost no reported ion sources capable of generating a directcurrent(DC)H_(2)^(+)beam with tens of mA current.In previous work at Peking University(PKU),H_(2)^(+)ion beams with a current of over 40 mA have been obtained in pulse mode,and a current of 16 mA was achieved in DC mode.In this paper,we report the generation of a DC H_(2)^(+)ion beam with a current of 22 mA extracted from an improved miniaturized microwave driven ion source(MMDIS).Beam analysis shows that the H_(2)^(+)fraction in the extracted beam is about 70%.The emittance of the mixed hydrogen beam is about 0.12π·mm·mrad.These results provide references for the applications of H_(2)^(+)beam and the design of H_(2)^(+)ion source.展开更多
The negative ion based neutral beam injector(NNBI)with a beam energy of 400 keV is one of the subsystems at the Comprehensive Research fAcility for Fusion Technology(CRAFT)in China.The distributed capacitance of the h...The negative ion based neutral beam injector(NNBI)with a beam energy of 400 keV is one of the subsystems at the Comprehensive Research fAcility for Fusion Technology(CRAFT)in China.The distributed capacitance of the high-voltage components is an important basis for the design of surge suppression devices at CRAFT NNBI.This study conducted calculations of distributed capacitance for the key components,including the high-voltage deck,transmission line and isolation transformer in the power supply system using the finite element method.The relationship between the high-voltage deck(HVD)distributed capacitance and the distance from the wall is discussed.The differences in distributed capacitance and energy storage between noncoaxial and coaxial transmission lines are also debated.Finally,the capacitance between the primary and secondary windings of the-400 kV isolation transformer,as well as between the secondary winding and the oil tank casing,was calculated.展开更多
基金Supported by the Fundamental Research Funds for the Central Universities under Grant No 15D210901the National Natural Science Foundation of China under Grant Nos 11174049 and 61290301the National University Student Innovation Program under Grant No 14T10902
文摘We investigate the dc Josephson effect in one-dimensional junctions where a ring conductor is sandwiched between two semiconductor nanowires with proximity-induced superconductivity. Peculiar features of the Josephson effect arise due to the interplay of spin-orbit interaction and external Zeenmn field. By tuning the Zeeman field orientation, the device can vary from 0 to π junction. Afore importantly, nonzero ,losephson current is possible at zero phase difference across the junction. Although this anomalous Josephson current is not relevant to the topological phase transition, its magnitude can be significantly enhanced whe, n the nanowire, s become topological superconductors where Majorana bound states emerge. Distinct modulation patterns are obtained for the semiconductor nanowires in the topologically trivial and non-trivial phases. These results are useful to probe the topological phase transition in semiconductor nanowire junctions via the dc Josephson effect.
基金supported by the Program for Innovative Research Team of High Education in Liaoning province of China (No.2009T055)
文摘A self-consistent model was adopted to study the time evolution of low-voltage pulsed DC glow discharge. The distributions of electric field, ion density and electron density in nitrogen were investigated in our simulation, and the temporal shape of the discharge current was also obtained. Our results show that the dynamic behaviors of the discharge depends strongly on the applied pulse voltage, and the use of higher pulse voltages results in a significantly increase of discharge current and a decrease of discharge delay time. The current-voltage characteristic cMculated by adjusting secondary electron emission coefficient for different applied pulse voltage under the gas pressure of 1 Torr is found in a reasonable agreement with the experimental results.
基金This work was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2022R1C1C1008831).This work was also supported by the Human Resources Development of the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant funded by the Ministry of Trade,Industry and Energy of Korea(No.RS-2023-00244330).S J P was supported by Basic Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2018R1A6A1A03025526).
文摘Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic devices.However,owing to the working mechanisms of conventional DC TENGs,generating a stable DC output from reciprocating motion remains a challenge.Accordingly,we propose a bidirectional rotating DC TENG(BiR-TENG),which can generate DC outputs,regardless of the direction of rotation,from reciprocating motions.The distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC output.Furthermore,it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational direction.Owing to these tailored design strategies and subsequent optimizations,the BiR-TENG could generate an effective unidirectional DC output.Applications of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this output.This study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions,highlighting the suitability of DC outputs as an energy source for electronic devices.
基金supported by the National Natural Science Foundation of China (Grant No. 60807001)the National Basic Research Program of China (Grant No. 2011CB201605)the Foundation of Henan Educational Committee (Grant No. 2010A140017)
文摘This paper reports that a series of silver oxide （AgzO） films are deposited on glass substrates by direct-current reactive magnetron sputtering at a substrate temperature of 250 ℃ and an oxygen flux ratio of 15：18 by modifying the sputtering power （SP）. The AgxO films deposited apparently show a structural evolution from cubic biphased （AgO ＋ Ag20） to cubic single-phased （Ag20）, and to biphased （Ag20 ＋ AgO） structure. Notably, the cubic single-phased Ag20 fihn is deposited at the SP = 105 W and an AgO phase with （220） orientation discerned in the Ag^O films deposited using the SP 〉 105 W. The transmissivity and refiectivity of the AgxO films in transparent region decrease with the increase the SP, whereas the absorptivity inversely increases with the increase of the SP. These results may be due to the structural evolution and the increasing film thickness. A redshift of the films＇ absorption edges determined in terms of Tauc formula clearly occurs from 3.1 eV to 2.73 eV with the increase of the SP.
基金supported by National Natural Science Foundation of China (No. 12075132)。
文摘The key plasma parameters under different discharge modes, such as heavy-particle and electron temperatures, electron number density, and nonequilibrium volume of plasmas, play important roles in various applications of gas discharge plasmas. In this study, a self-consistent two-dimensional nonequilibrium fluid model coupled with an external circuit model is established to reveal the mechanisms related to the discharge modes, including the normal glow, abnormal glow,arc, and glow-to-arc transition modes, with an atmospheric-pressure direct-current(DC) argon discharge as a model plasma system. The modeling results show that, under different discharge modes, the most significant difference between the preceding four discharge modes lies in the current and energy transfer processes on the cathode side. On one hand, the current to the cathode surface is mainly delivered by the ions coming from the plasma column under the glow discharge mode due to the low temperature of the solid cathode, whereas the thermionic and secondary electrons emitted from the hot cathode surface play a very important role under the arc mode with a higher cathode surface temperature and higher ion flux toward the cathode. On the other hand, the energy transfer channel on the cathode side changes from mainly heating the solid cathode under the glow mode to simultaneously heating both the solid cathode and plasma column under the arc mode with an increase in the discharge current. Consequently, the power density in the cathode sheath(P_c) was used as a key parameter for judging different discharge modes, and the range of(0.28–1.2) × 10^(12) W m^(-3) was determined as a critical window of P_c corresponding to the glow-to-arc-mode transition for the atmospheric-pressure DC argon discharge, which was also verified by comparison with the experimental results in this study and the data in the previous literature.
基金by State Grid Shandong Electric Power Company(52062618001M)。
文摘Corona discharge suppression for high-voltage direct-current(HVDC)transmission lines at line terminals such as converter stations is a subject that requires attention.In this paper,a method based on a conductor covered with dielectric film is proposed and implemented through a bench-scale setup.Compared with the bare conductor,the corona discharge suppression effect of the dielectric-film-covered conductor under positive polarity is studied from the composite field strength and ion current density using a line-plate experimental device.The influences of film thickness and film material on the corona discharge suppression effect are investigated.The charge accumulation and dissipation characteristics of different film materials are also studied.The results show that the conductor covered with dielectric film has excellent ability to inhibit corona discharge.The ground-level composite field strength of the conductor covered with dielectric film is lower than its nominal field strength,and its ion current density is at the nA m^(−2) level.The corona threshold voltage can be promoted by increasing the film thickness,but the ability to inhibit corona discharge becomes weak.The larger the surface electric field strength,the more charge accumulated,but the faster the charge dissipation rate.Compared with polyvinyl chloride film,cross-linked polyethylene film has stronger charge accumulation ability and slower charge dissipation rate,which can better restrain the corona discharge of HVDC transmission lines.
基金Supported by the RU Top-Down under Grant No 1001/CSS/870019
文摘Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.
基金supported by the National Natural Science Foundation of China(Grant No.11975036)support from the State Key Laboratory of Nuclear Physics and Technology at PKU.
文摘Recently H_(2)^(+)ion beam finds widespread use in many fields,and the demand of high-current H_(2)^(+)ion sources is urgent for numerous applications.However,there are currently almost no reported ion sources capable of generating a directcurrent(DC)H_(2)^(+)beam with tens of mA current.In previous work at Peking University(PKU),H_(2)^(+)ion beams with a current of over 40 mA have been obtained in pulse mode,and a current of 16 mA was achieved in DC mode.In this paper,we report the generation of a DC H_(2)^(+)ion beam with a current of 22 mA extracted from an improved miniaturized microwave driven ion source(MMDIS).Beam analysis shows that the H_(2)^(+)fraction in the extracted beam is about 70%.The emittance of the mixed hydrogen beam is about 0.12π·mm·mrad.These results provide references for the applications of H_(2)^(+)beam and the design of H_(2)^(+)ion source.
基金supported by the Comprehensive Research Facility for Fusion Technology Program of China(No.2018000052-73-01-001228)National Natural Science Foundation of China(No.11975263)Postgraduate Research and Practice Innovation Program of NUAA(No.xcxjh20231501)。
文摘The negative ion based neutral beam injector(NNBI)with a beam energy of 400 keV is one of the subsystems at the Comprehensive Research fAcility for Fusion Technology(CRAFT)in China.The distributed capacitance of the high-voltage components is an important basis for the design of surge suppression devices at CRAFT NNBI.This study conducted calculations of distributed capacitance for the key components,including the high-voltage deck,transmission line and isolation transformer in the power supply system using the finite element method.The relationship between the high-voltage deck(HVD)distributed capacitance and the distance from the wall is discussed.The differences in distributed capacitance and energy storage between noncoaxial and coaxial transmission lines are also debated.Finally,the capacitance between the primary and secondary windings of the-400 kV isolation transformer,as well as between the secondary winding and the oil tank casing,was calculated.
