Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular...Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. ~urthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.展开更多
This paper describes the principles of operation and the physical model of an advanced AC-DC converter generator （with the electronic converter acting as an AC-DC rectifier with reverse-conducting MOSFETs （metal-oxi...This paper describes the principles of operation and the physical model of an advanced AC-DC converter generator （with the electronic converter acting as an AC-DC rectifier with reverse-conducting MOSFETs （metal-oxide semiconductor field-effect transistors） as fast-electronic switches with a relatively low ON-state voltage drop） for HSVs. An AC-DC converter, when seen as an AC-DC rectifier, can be used in many fields, e.g., for multi-functional AC-DC/DC-AC convener generator^starter and conventional DC-AC convener motors and AC-DC converter generators or generator sets, welding machines, etc. The paper also describes a novel AC-DC convener, with reverse-conducting transistors and without the use of optoelectronic separation （which does not require a separate power supply）, which may be easily realized in IC （integrated-circuit） technology. Computer simulation allows for waveform evaluation for timing analysis of all components of the AC-DC-converter＇s physical model, both during normal operation as well as in some states of emergency. The paper also presents the results of bench experimental studies where the MOSFETs were used as fast-electronic switches with a relatively low ON-state voltage drop. For experimental studies, a novel AC-DC converter has been put together on the Mitsubishi FM600TU-3A module. The AC-DC converter with reverse-conducting transistors in a double-way connection has a lot of advantages compared to the conventional AC-DC convener acting as a diode rectifier, such as higher energy efficiency and greater reliability resulting from the lower temperature of electronic switches.展开更多
We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is ...We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is deter- mined to be a Si 170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300meV, which is a result of the large capacitance of a small silicon quantum dot （-1.8 nm）. This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time.展开更多
Co-crystallization of dithiocarbamate complexes[M^(Ⅱ)(S_(2)CNEt_(2))_(2)](M=Cu 1,Ni 2,Pd 3,Pt 4)and 1,3,5-triiodotrifluorobenzene(FIB)gives an isomorphic series of(1-4)·2FIB co-crystals exhibiting quadruple Cu/N...Co-crystallization of dithiocarbamate complexes[M^(Ⅱ)(S_(2)CNEt_(2))_(2)](M=Cu 1,Ni 2,Pd 3,Pt 4)and 1,3,5-triiodotrifluorobenzene(FIB)gives an isomorphic series of(1-4)·2FIB co-crystals exhibiting quadruple Cu/Ni/Pd/Pt isostructural exchange.In the structures of(1-4)·2FIB,the halogen-bonded C-I…M(Ni,Pd,Pt)and semicoordination M…I-C(Cu)metal-involving contacts were identified by X-ray diffractometry and their nature was verified theoretically.The directionality of the I_(σ-hole)…d_(z)^(2)M^(Ⅱ) and M^(Ⅱ)…I_(electron belt)interactions depends on the identity of a metal center:on going from a rather electrophilic Cu^(Ⅱ) to substantially more nucleophilic Ni^(Ⅱ),Pd^(Ⅱ),and Pt^(Ⅱ) centers,we observed the electron belt-to-σ-hole switch of a noncovalently bound iodine(I)of FIB and,correspondingly,its shift from semicoordination to halogen bonding.The negative values of the electrostatic potentials(given in parentheses)were estimated for all metal centers and they decrease in the order Cu^(Ⅱ)(-8.8)>Ni^(Ⅱ)(-24.5)>Pd^(Ⅱ)(-28.6)>Pt^(Ⅱ)(-33.3 kcal mol^(-1)).Despite the negative potentials at all M^(Ⅱ)s,the semicoordinative contact Cu…I was established by the recognition of the LP(I)→LP*(Cu)charge transfer using natural bond orbital(NBO)analysis and the comparison of electron density(ED)and electrostatic potential(ESP)minima positions along the I…Cu bond paths.In the case of the rather nucleophilic(although positively charged)Pd^(Ⅱ) and Pt^(Ⅱ) centers,the contacts C-I…d_(z)^(2)[Pd]and C-I…d_(z)^(2)[Pt]can be attributed to the unconventional metal-involving halogen bonding;these contacts are among the strongest(4.30 and 5.42 kcal mol^(-1),correspondingly)between any metal center and iodine(Ⅰ)-based σ-hole donors.展开更多
High Te superconductor （HTS） technology has been used to develop a unique high Q resonant circuit. Such circuit or device has some special characteristics such as very high voltage generation. Theoretical study and ...High Te superconductor （HTS） technology has been used to develop a unique high Q resonant circuit. Such circuit or device has some special characteristics such as very high voltage generation. Theoretical study and experimental approaches have proceeded for the concept verification. This paper presents the theory about this high Q resonant circuit. The operation principle of the circuit is described. A practical prototype for HTS high voltage generation is also demonstrated. The experiment result shows that very high voltages can be achieved by the developed method using HTS technology.展开更多
High temperature superconducting （HTS） power inductor and its control technology have been studied and analyzed in the paper. Based on the results of simulations and practical experiments, a controlled release schem...High temperature superconducting （HTS） power inductor and its control technology have been studied and analyzed in the paper. Based on the results of simulations and practical experiments, a controlled release scheme has been proposed and verified for developing a practical HTS SMES prototype.展开更多
To achieve wide-range, high-integration, and real-time performance on the neutron flux measurement on the HL-2A tokamak, a digital neutron flux measuring（DNFM） system based on the peripheral component interconnectio...To achieve wide-range, high-integration, and real-time performance on the neutron flux measurement on the HL-2A tokamak, a digital neutron flux measuring（DNFM） system based on the peripheral component interconnection（PCI） e Xtension for Instrumentation express（PXIe） bus was designed.This system comprises a charge-sensitive preamplifier and a field programmable gate array（FPGA）-based main electronics plug-in. The DNFM totally covers source-range and intermediate-range neutron flux measurements, and increases system integration by a large margin through joining the pulse-counting mode and Campbell mode. Meanwhile, the neutron flux estimation method based on pulse piling proportions is able to choose and switch measuring modes in accordance with current flux, and this ensures the accuracy of measurements when the neutron flux changes suddenly. It has been demonstrated by simulated signals that the DNFM enhances the full-scale measuring range up to 1.9×10^8cm^-2s^-1, with relative error below 6.1%. The DNFM has been verified to provide a high temporal sensitivity at 10 ms time intervals on a single fission chamber on HL-2A.展开更多
By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of the dihydroazulene optical molecular switch. Th...By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of the dihydroazulene optical molecular switch. Three kinds of adsorption sites including the hollow, bridge and top sites are studied. The two forms of this molecule, namely the open form and the closed form, can reversibly switch from each other upon photoexcitation. Their transmission spectra are remarkably distinctive. Theoretical results show that the current of the closed form is always significantly larger than that of the open form for all three adsorption sites, which promises this system as possibly one of the good candidates for optical switches due to its unique advantage, and which may have some potential applications in the future molecular circuit.展开更多
Bistable mixed valence compounds have thermodynamically accessible phases at certain temperatures,and the electron transfer switches the electronic configurations by applying external stimuli like heat and light.Therm...Bistable mixed valence compounds have thermodynamically accessible phases at certain temperatures,and the electron transfer switches the electronic configurations by applying external stimuli like heat and light.Thermally induced phase transition temperatures range widely,while the photo-induced state conversions need irradiation at very low temperatures,such as below 30 K,and the photo-induced metastable state relaxes rapidly at low temperatures.We prepared new mixed-valence compounds of[Fe(bipy)(CN)_(4)]_(2)[CoL_(2)](L=4-[(1E)-2-phenyldiazenyl]pyridine for 1-papy and 4-(2-phenylethynyl)pyridine for 1-pepy)in which cyanide-bridged squared cores form corner-shared chains with substantial interchain π-π contacts.Mössbauser spectra revealed that 1-papy and 1-pepy are in the high-spin(HS)state[(Fe_(LS)^(Ⅲ))_(2)Co_(HS)^(Ⅱ)]at 300 K and the low-spin(LS)state[Fe_(LS)^(Ⅱ)Fe_(LS)^(Ⅲ)Co_(LS)^(Ⅲ)]at 78 K,confirming the occurrence of the electron transfer coupled spin transition(ETCST).Magnetic susceptibility measurements suggested their Tc values of 231 and 260 K,respectively.Photoirradiation(808 nm)for 1-papy and 1-pepy at 10 K induced the state conversion from the[LS]to the[HS^(*)]state,and the metastable[HS]^(*)state relaxed to the thermodynamically stable[LS]states at temperatures(Trelax)of 130 and 90 K,respectively.Furthermore,the[LS]states in 1-papy and 1-pepy were fully converted to the[HS^(*)]states by light irradiation at 78 and 50 K,respectively.The X-ray structural analyses showed characteristic coordination bond lengths for the metal ions in each electronic state before and after light irradiation,but shortened intrachain π_(L)⋯π_(L) contact distances,from 3.726(4)to 3.688(4)Å,were observed for 1-papy upon the state conversion from the[LS]to the[HS^(*)]state,despite the swollen cell volumes from 2479 to 2566Å^(3),respectively.Photomagneto and structural studies suggest that the intermolecular interactions increase the light-induced state conversion and relaxation temperatures.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11004156the Natural Science Foundation of Shaanxi Province under Grant No 2014JM1025+2 种基金the Science and Technology Star Project of Shaanxi Province under Grant No2016KJXX-38the Special Foundation of Key Academic Subjects Development of Shaanxi Province under Grant No 2008-169the Xi'an Polytechnic University Young Scholar Supporting Plan under Grant No 2013-06
文摘Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. ~urthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.
文摘This paper describes the principles of operation and the physical model of an advanced AC-DC converter generator （with the electronic converter acting as an AC-DC rectifier with reverse-conducting MOSFETs （metal-oxide semiconductor field-effect transistors） as fast-electronic switches with a relatively low ON-state voltage drop） for HSVs. An AC-DC converter, when seen as an AC-DC rectifier, can be used in many fields, e.g., for multi-functional AC-DC/DC-AC convener generator^starter and conventional DC-AC convener motors and AC-DC converter generators or generator sets, welding machines, etc. The paper also describes a novel AC-DC convener, with reverse-conducting transistors and without the use of optoelectronic separation （which does not require a separate power supply）, which may be easily realized in IC （integrated-circuit） technology. Computer simulation allows for waveform evaluation for timing analysis of all components of the AC-DC-converter＇s physical model, both during normal operation as well as in some states of emergency. The paper also presents the results of bench experimental studies where the MOSFETs were used as fast-electronic switches with a relatively low ON-state voltage drop. For experimental studies, a novel AC-DC converter has been put together on the Mitsubishi FM600TU-3A module. The AC-DC converter with reverse-conducting transistors in a double-way connection has a lot of advantages compared to the conventional AC-DC convener acting as a diode rectifier, such as higher energy efficiency and greater reliability resulting from the lower temperature of electronic switches.
基金Supported by the National Key Research and Development Program of China under Grant No 2017YFA0303200the National Natural Science Foundation of China under Grant Nos U1732273,U1732159,91421109,91622115,11522432,11574217 and 61774133the Natural Science Foundation of Jiangsu Province under Grant No BK20160659
文摘We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is deter- mined to be a Si 170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300meV, which is a result of the large capacitance of a small silicon quantum dot （-1.8 nm）. This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time.
基金supported by the Russian Foundation for Basic Research(20-03-00073)Saint Petersburg State University for a postdoctoral fellowship.
文摘Co-crystallization of dithiocarbamate complexes[M^(Ⅱ)(S_(2)CNEt_(2))_(2)](M=Cu 1,Ni 2,Pd 3,Pt 4)and 1,3,5-triiodotrifluorobenzene(FIB)gives an isomorphic series of(1-4)·2FIB co-crystals exhibiting quadruple Cu/Ni/Pd/Pt isostructural exchange.In the structures of(1-4)·2FIB,the halogen-bonded C-I…M(Ni,Pd,Pt)and semicoordination M…I-C(Cu)metal-involving contacts were identified by X-ray diffractometry and their nature was verified theoretically.The directionality of the I_(σ-hole)…d_(z)^(2)M^(Ⅱ) and M^(Ⅱ)…I_(electron belt)interactions depends on the identity of a metal center:on going from a rather electrophilic Cu^(Ⅱ) to substantially more nucleophilic Ni^(Ⅱ),Pd^(Ⅱ),and Pt^(Ⅱ) centers,we observed the electron belt-to-σ-hole switch of a noncovalently bound iodine(I)of FIB and,correspondingly,its shift from semicoordination to halogen bonding.The negative values of the electrostatic potentials(given in parentheses)were estimated for all metal centers and they decrease in the order Cu^(Ⅱ)(-8.8)>Ni^(Ⅱ)(-24.5)>Pd^(Ⅱ)(-28.6)>Pt^(Ⅱ)(-33.3 kcal mol^(-1)).Despite the negative potentials at all M^(Ⅱ)s,the semicoordinative contact Cu…I was established by the recognition of the LP(I)→LP*(Cu)charge transfer using natural bond orbital(NBO)analysis and the comparison of electron density(ED)and electrostatic potential(ESP)minima positions along the I…Cu bond paths.In the case of the rather nucleophilic(although positively charged)Pd^(Ⅱ) and Pt^(Ⅱ) centers,the contacts C-I…d_(z)^(2)[Pd]and C-I…d_(z)^(2)[Pt]can be attributed to the unconventional metal-involving halogen bonding;these contacts are among the strongest(4.30 and 5.42 kcal mol^(-1),correspondingly)between any metal center and iodine(Ⅰ)-based σ-hole donors.
文摘High Te superconductor （HTS） technology has been used to develop a unique high Q resonant circuit. Such circuit or device has some special characteristics such as very high voltage generation. Theoretical study and experimental approaches have proceeded for the concept verification. This paper presents the theory about this high Q resonant circuit. The operation principle of the circuit is described. A practical prototype for HTS high voltage generation is also demonstrated. The experiment result shows that very high voltages can be achieved by the developed method using HTS technology.
文摘High temperature superconducting （HTS） power inductor and its control technology have been studied and analyzed in the paper. Based on the results of simulations and practical experiments, a controlled release scheme has been proposed and verified for developing a practical HTS SMES prototype.
基金support by the HL-2A experimental teamsupported by National Natural Science Foundation of China(Nos.11375195,11575184)National Magnetic Confinement Fusion Energy Development Research(No.2013GB104003)
文摘To achieve wide-range, high-integration, and real-time performance on the neutron flux measurement on the HL-2A tokamak, a digital neutron flux measuring（DNFM） system based on the peripheral component interconnection（PCI） e Xtension for Instrumentation express（PXIe） bus was designed.This system comprises a charge-sensitive preamplifier and a field programmable gate array（FPGA）-based main electronics plug-in. The DNFM totally covers source-range and intermediate-range neutron flux measurements, and increases system integration by a large margin through joining the pulse-counting mode and Campbell mode. Meanwhile, the neutron flux estimation method based on pulse piling proportions is able to choose and switch measuring modes in accordance with current flux, and this ensures the accuracy of measurements when the neutron flux changes suddenly. It has been demonstrated by simulated signals that the DNFM enhances the full-scale measuring range up to 1.9×10^8cm^-2s^-1, with relative error below 6.1%. The DNFM has been verified to provide a high temporal sensitivity at 10 ms time intervals on a single fission chamber on HL-2A.
基金supported by the National Natural Science Foundation of China (Grant No. 11004156)the National Basic Research Program of China (Grant No. 2009CB929204)+1 种基金the Education Department Foundation of Shaanxi Province, China (Grant No. 09JK461)the Fundament Research of Xi’an Polytechnic University (Grant No. 09XG09)
文摘By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of the dihydroazulene optical molecular switch. Three kinds of adsorption sites including the hollow, bridge and top sites are studied. The two forms of this molecule, namely the open form and the closed form, can reversibly switch from each other upon photoexcitation. Their transmission spectra are remarkably distinctive. Theoretical results show that the current of the closed form is always significantly larger than that of the open form for all three adsorption sites, which promises this system as possibly one of the good candidates for optical switches due to its unique advantage, and which may have some potential applications in the future molecular circuit.
基金supported by the National Natural Science Foundation of China(Grants,22025101,22222103,22173015,21871039,91961114,22071017,22103009 and 22203013)the Fundamental Research Funds for the Central Universities,China(DUT22LAB606).
文摘Bistable mixed valence compounds have thermodynamically accessible phases at certain temperatures,and the electron transfer switches the electronic configurations by applying external stimuli like heat and light.Thermally induced phase transition temperatures range widely,while the photo-induced state conversions need irradiation at very low temperatures,such as below 30 K,and the photo-induced metastable state relaxes rapidly at low temperatures.We prepared new mixed-valence compounds of[Fe(bipy)(CN)_(4)]_(2)[CoL_(2)](L=4-[(1E)-2-phenyldiazenyl]pyridine for 1-papy and 4-(2-phenylethynyl)pyridine for 1-pepy)in which cyanide-bridged squared cores form corner-shared chains with substantial interchain π-π contacts.Mössbauser spectra revealed that 1-papy and 1-pepy are in the high-spin(HS)state[(Fe_(LS)^(Ⅲ))_(2)Co_(HS)^(Ⅱ)]at 300 K and the low-spin(LS)state[Fe_(LS)^(Ⅱ)Fe_(LS)^(Ⅲ)Co_(LS)^(Ⅲ)]at 78 K,confirming the occurrence of the electron transfer coupled spin transition(ETCST).Magnetic susceptibility measurements suggested their Tc values of 231 and 260 K,respectively.Photoirradiation(808 nm)for 1-papy and 1-pepy at 10 K induced the state conversion from the[LS]to the[HS^(*)]state,and the metastable[HS]^(*)state relaxed to the thermodynamically stable[LS]states at temperatures(Trelax)of 130 and 90 K,respectively.Furthermore,the[LS]states in 1-papy and 1-pepy were fully converted to the[HS^(*)]states by light irradiation at 78 and 50 K,respectively.The X-ray structural analyses showed characteristic coordination bond lengths for the metal ions in each electronic state before and after light irradiation,but shortened intrachain π_(L)⋯π_(L) contact distances,from 3.726(4)to 3.688(4)Å,were observed for 1-papy upon the state conversion from the[LS]to the[HS^(*)]state,despite the swollen cell volumes from 2479 to 2566Å^(3),respectively.Photomagneto and structural studies suggest that the intermolecular interactions increase the light-induced state conversion and relaxation temperatures.
