Heterojunction has been widely used in vibration-driven piezocatalysis for enhanced charges separation,while the weak interfaces seriously affect the efficiency during mechanical deformations due to prepared by tradit...Heterojunction has been widely used in vibration-driven piezocatalysis for enhanced charges separation,while the weak interfaces seriously affect the efficiency during mechanical deformations due to prepared by traditional step-by-step methods.Herein,the intimate contact interfaces with shared S atoms are ingeniously constructed in SnS_(2)/SnS anchored on porous carbon by effective interface engineering,which is in-situ derived from temperature-dependent self-transformation of SnS_(2).Benefiting from intimate contact interfaces,the piezoelectricity is remarkably improved due to the larger interfacial dipole moment caused by uneven distribution of charges.Importantly,vibration-induced piezoelectric polarization field strengthens the interfacial electric field to further promote the separation and migration of charges.The dynamic charges then transfer in porous carbon with high conductivity and adsorption for significantly improved piezocatalytic activity.The degradation efficiency of bisphenol A(BPA)is 6.3 times higher than SnS_(2) and H_(2) evolution rate is increased by 3.8 times.Compared with SnS_(2)/SnS prepared by two-step solvothermal method,the degradation efficiency of BPA and H2 evolution activity are increased by 3 and 2 times,respectively.It provides a theoretical guidance for developing various multiphase structural piezocatalyst with strong interface interactions to improve the piezocatalytic efficiency.展开更多
To improve the data quality of converted waves, and better identify and suppress the strong ground-roll interference in three-component （3C） seismic recordings on land, we present an adaptive polarization filtering ...To improve the data quality of converted waves, and better identify and suppress the strong ground-roll interference in three-component （3C） seismic recordings on land, we present an adaptive polarization filtering method, which can effectively separate the ground- roll interference by combining complex polarization and instantaneous polarization analysis. The ground roll noise is characterized by elliptical plane polarization, strong energy, low apparent velocity, and low frequency. After low-pass filtering of the 3C data input within a given time-window of the ground roll, the complex covariance matrix is decomposed using the sliding time window with overlapping data and length that depends on the dominant ground-roll frequency. The ground-roll model is established using the main eigenvectors, and the ground roll is detected and identified using the instantaneous polarization area attributes and average energy constraints of the ground-roll zone. Finally, the ground roll is subtracted. The threshold of the method is stable and easy to select, and offers good ground- roll detection. The method is a robust polarization filtering method. Model calculations and actual data indicate that the method can effectively identify and attenuate ground roll while preserving the effective signals.展开更多
Density functional method （B3p86） was used to optimize the structure of the molecule Fe2. The result showed that the ground electronic state for the molecule Fe2 is nonet state instead of septet state, which indicat...Density functional method （B3p86） was used to optimize the structure of the molecule Fe2. The result showed that the ground electronic state for the molecule Fe2 is nonet state instead of septet state, which indicates that there is a spin polarization effect in the molecule Fe2, i.e., in which there are 8 parallel spin electrons.In this case, the number of the unpaired d-orbit electrons is the largest, and these electrons occupy different spatial orbitals so that the energy of the molecule Fe2 is minimized. Meanwhile, the spin pollution was not found because the wave functions of the ground state do not mix with those of the higher energy states. In addition, the Murrell-Sorbie potential functions with the parameters for the ground electronic state and other exited electronic states of the molecule Fe2 were derived. The dissociation energy, equilibrium bond length and the vibration frequency for the ground electronic state of the molecule Fe2 are 3.5522 eV, 0.2137 nm and 292.914 cm^-1, respectively. Its force constants f2, f3 and f4 are 1.4115×1^02 a J/nm^2, -37.1751×103^aJ/nm^3 and 98.7596× 10^4 a J/nm^4, respectively. The other spectroscopic parameters ωexe, Be and αe for the ground electronic state of Fe2 are 0.3522, 0.0345 and 0.4963× 10^-4 cm^-1, respectively.展开更多
A new method of nanocontact fabrication for Adreev reflection measurement based on the nanopore method using a SiN membrane with focused ion beam technique is presented. With this method, controllable, clean,tensionle...A new method of nanocontact fabrication for Adreev reflection measurement based on the nanopore method using a SiN membrane with focused ion beam technique is presented. With this method, controllable, clean,tensionless nano-contacts for spin polarization probing can be obtained. Measurements of the fabricated samples show complicated spectral structures with a zero bias anomaly and dip structures from quasipartical interactions. A control sample of Co40Fe40B20 is measured with Nb tip method. None of the measured spectra can be explained satisfactorily by present theory. Further analysis of the contact interface and a more complete theory are needed to extract a reliable spin polarization message with the point contact Andreev reflection method.展开更多
At 105 K, strontium titanate is known to undergo an antiferrodistortive transition transform-ing from cubic to tetragonal structure as a result of the rotation of the oxygen octahedral around a cubic axe. Based on the...At 105 K, strontium titanate is known to undergo an antiferrodistortive transition transform-ing from cubic to tetragonal structure as a result of the rotation of the oxygen octahedral around a cubic axe. Based on the Curie principle, the order parameter is determined to be a third-order complete symmetry polarization tensor. To take into account of quantum effects,the dielectric permittivity is measured from Landau free energy, and the Curie Weiss-type behavior is analyzed. From crystallization chemistry viewpoint, the dielectric behavior at low temperature is connected to small radius of Sr^2＋, which is much easier to move around the oxygen octahedral than Ba^2＋ in BaTiO3 or Pb^2＋ in PbTiO3.展开更多
Based on density functional theory （DFT） calculations, we investigate the spin-related properties of spinless-hole injected organic molecule pentacene （Pc）. DFT calculations reveal that there is spontaneous spin p...Based on density functional theory （DFT） calculations, we investigate the spin-related properties of spinless-hole injected organic molecule pentacene （Pc）. DFT calculations reveal that there is spontaneous spin polarization in Pc when spinless-hole is injected. The chargeinduced magnetic moment of Pc increases linearly with the increasing of the extra hole charge amount and its maximum can be up to 1 μB per injected spinless-hole per Pc molecule. The magnetic moment is expected due to the injected unpaired charge. The injected hole will preferably ll the spin-splitted carbon pz orbitals, which makes the Pc molecule spin polarize.展开更多
Based on ab initio theory, the interracial spin polarization of a benzene-dithiolate molecule vertically adsorbed on a nickel surface is investigated by adopting different microscopic con- tact configurations. The res...Based on ab initio theory, the interracial spin polarization of a benzene-dithiolate molecule vertically adsorbed on a nickel surface is investigated by adopting different microscopic con- tact configurations. The results demonstrate a strong dependence of the interfacial spin polarization on the contact configuration, where the sign of spin polarization may vary from positive to negative with the change of contact configuration. By analyzing the projected density of states, an interracial orbital hybridization between the 3d orbital of the nickel atom and the sp3 hybridized orbital of the sulfur atom is observed. We also simulated the interracial adsorption in mechanically controllable break junction experiments. The magne- toresistance obtained from Julliere model is about 27% based on the calculated interracial spin polarization, which is consistent with experimental measurement.展开更多
We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combin...We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combined with non-equilibrium Green＇s function technique. We observe robust negative di erential resistance （NDR） effect in all examined molecular junctions. Through analyzing the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of electrodes and the bias-dependent effective coupling between the central molecular orbitals and the electrode subbands are responsible for the observed NDR phenomenon. In addition, the obvious di erence of the transmission spectra of two spin channels is observed in some bias ranges, which leads to the near perfect spin-filtering effect. These theoretical findings imply that GNRs with nitrogenvacancy defects hold great potential for building molecular devices.展开更多
We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the de...We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the degreeof spin-polarization strongly depends on the transverse wave-vector and the temperature.These interesting propertiesmay be helpful to spin-polarize electrons into semiconductors,and this device may be used as a spin filter.展开更多
Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd a...Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.展开更多
Control design is important for proton exchange membrane fuel cell (PEMFC) generator. This work researched the anode system of a 60-kW PEMFC generator. Both anode pressure and humidity must be maintained at ideal leve...Control design is important for proton exchange membrane fuel cell (PEMFC) generator. This work researched the anode system of a 60-kW PEMFC generator. Both anode pressure and humidity must be maintained at ideal levels during steady operation. In view of characteristics and requirements of the system, a hybrid intelligent PID controller is designed specifically based on dynamic simulation. A single neuron PI controller is used for anode humidity by adjusting the water injection to the hydrogen cell. Another incremental PID controller, based on the diagonal recurrent neural network (DRNN) dynamic identification, is used to control anode pressure to be more stable and exact by adjusting the hydrogen flow rate. This control strategy can avoid the coupling problem of the PEMFC and achieve a more adaptive ability. Simulation results showed that the control strategy can maintain both anode humidity and pressure at ideal levels regardless of variable load, nonlinear dynamic and coupling characteristics of the system. This work will give some guides for further control design and applications of the total PEMFC generator.展开更多
基金National Natural Science Foundation of China(52102133)Natural Science Foundation of Jiangsu Province,China(BK20210354)+1 种基金Fundamental Research Funds for the Central Universities(30921011217)Young Elite Scientists Sponsorship Program by CAST(2021-2023QNRC001)。
文摘Heterojunction has been widely used in vibration-driven piezocatalysis for enhanced charges separation,while the weak interfaces seriously affect the efficiency during mechanical deformations due to prepared by traditional step-by-step methods.Herein,the intimate contact interfaces with shared S atoms are ingeniously constructed in SnS_(2)/SnS anchored on porous carbon by effective interface engineering,which is in-situ derived from temperature-dependent self-transformation of SnS_(2).Benefiting from intimate contact interfaces,the piezoelectricity is remarkably improved due to the larger interfacial dipole moment caused by uneven distribution of charges.Importantly,vibration-induced piezoelectric polarization field strengthens the interfacial electric field to further promote the separation and migration of charges.The dynamic charges then transfer in porous carbon with high conductivity and adsorption for significantly improved piezocatalytic activity.The degradation efficiency of bisphenol A(BPA)is 6.3 times higher than SnS_(2) and H_(2) evolution rate is increased by 3.8 times.Compared with SnS_(2)/SnS prepared by two-step solvothermal method,the degradation efficiency of BPA and H2 evolution activity are increased by 3 and 2 times,respectively.It provides a theoretical guidance for developing various multiphase structural piezocatalyst with strong interface interactions to improve the piezocatalytic efficiency.
基金supported by the National Natural Science Foundation of China(No.41074080)the Important National Science&Technology Specific Projects(No.2011ZX05019-008)
文摘To improve the data quality of converted waves, and better identify and suppress the strong ground-roll interference in three-component （3C） seismic recordings on land, we present an adaptive polarization filtering method, which can effectively separate the ground- roll interference by combining complex polarization and instantaneous polarization analysis. The ground roll noise is characterized by elliptical plane polarization, strong energy, low apparent velocity, and low frequency. After low-pass filtering of the 3C data input within a given time-window of the ground roll, the complex covariance matrix is decomposed using the sliding time window with overlapping data and length that depends on the dominant ground-roll frequency. The ground-roll model is established using the main eigenvectors, and the ground roll is detected and identified using the instantaneous polarization area attributes and average energy constraints of the ground-roll zone. Finally, the ground roll is subtracted. The threshold of the method is stable and easy to select, and offers good ground- roll detection. The method is a robust polarization filtering method. Model calculations and actual data indicate that the method can effectively identify and attenuate ground roll while preserving the effective signals.
基金This work was supported by the National Natural Science Foundation of China （No. 10574096） the Research Fund for the Doctoral Program of High Education （No. 20050610010）.
文摘Density functional method （B3p86） was used to optimize the structure of the molecule Fe2. The result showed that the ground electronic state for the molecule Fe2 is nonet state instead of septet state, which indicates that there is a spin polarization effect in the molecule Fe2, i.e., in which there are 8 parallel spin electrons.In this case, the number of the unpaired d-orbit electrons is the largest, and these electrons occupy different spatial orbitals so that the energy of the molecule Fe2 is minimized. Meanwhile, the spin pollution was not found because the wave functions of the ground state do not mix with those of the higher energy states. In addition, the Murrell-Sorbie potential functions with the parameters for the ground electronic state and other exited electronic states of the molecule Fe2 were derived. The dissociation energy, equilibrium bond length and the vibration frequency for the ground electronic state of the molecule Fe2 are 3.5522 eV, 0.2137 nm and 292.914 cm^-1, respectively. Its force constants f2, f3 and f4 are 1.4115×1^02 a J/nm^2, -37.1751×103^aJ/nm^3 and 98.7596× 10^4 a J/nm^4, respectively. The other spectroscopic parameters ωexe, Be and αe for the ground electronic state of Fe2 are 0.3522, 0.0345 and 0.4963× 10^-4 cm^-1, respectively.
文摘A new method of nanocontact fabrication for Adreev reflection measurement based on the nanopore method using a SiN membrane with focused ion beam technique is presented. With this method, controllable, clean,tensionless nano-contacts for spin polarization probing can be obtained. Measurements of the fabricated samples show complicated spectral structures with a zero bias anomaly and dip structures from quasipartical interactions. A control sample of Co40Fe40B20 is measured with Nb tip method. None of the measured spectra can be explained satisfactorily by present theory. Further analysis of the contact interface and a more complete theory are needed to extract a reliable spin polarization message with the point contact Andreev reflection method.
文摘At 105 K, strontium titanate is known to undergo an antiferrodistortive transition transform-ing from cubic to tetragonal structure as a result of the rotation of the oxygen octahedral around a cubic axe. Based on the Curie principle, the order parameter is determined to be a third-order complete symmetry polarization tensor. To take into account of quantum effects,the dielectric permittivity is measured from Landau free energy, and the Curie Weiss-type behavior is analyzed. From crystallization chemistry viewpoint, the dielectric behavior at low temperature is connected to small radius of Sr^2＋, which is much easier to move around the oxygen octahedral than Ba^2＋ in BaTiO3 or Pb^2＋ in PbTiO3.
文摘Based on density functional theory （DFT） calculations, we investigate the spin-related properties of spinless-hole injected organic molecule pentacene （Pc）. DFT calculations reveal that there is spontaneous spin polarization in Pc when spinless-hole is injected. The chargeinduced magnetic moment of Pc increases linearly with the increasing of the extra hole charge amount and its maximum can be up to 1 μB per injected spinless-hole per Pc molecule. The magnetic moment is expected due to the injected unpaired charge. The injected hole will preferably ll the spin-splitted carbon pz orbitals, which makes the Pc molecule spin polarize.
文摘Based on ab initio theory, the interracial spin polarization of a benzene-dithiolate molecule vertically adsorbed on a nickel surface is investigated by adopting different microscopic con- tact configurations. The results demonstrate a strong dependence of the interfacial spin polarization on the contact configuration, where the sign of spin polarization may vary from positive to negative with the change of contact configuration. By analyzing the projected density of states, an interracial orbital hybridization between the 3d orbital of the nickel atom and the sp3 hybridized orbital of the sulfur atom is observed. We also simulated the interracial adsorption in mechanically controllable break junction experiments. The magne- toresistance obtained from Julliere model is about 27% based on the calculated interracial spin polarization, which is consistent with experimental measurement.
基金This work was partially supported by the National Natural Science Foundation of China （No.20903003 and No.21273208）, the Anhui Provincial Natural Science Foundation （No.1408085QB26）, the China Postdoctoral Science Foundation （No.2012M511409）, the Supercomputer Center of Chinese Academy of Sciences, and University of Science and Technology of China and Shanghai Supercomputer Centers.
文摘We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combined with non-equilibrium Green＇s function technique. We observe robust negative di erential resistance （NDR） effect in all examined molecular junctions. Through analyzing the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of electrodes and the bias-dependent effective coupling between the central molecular orbitals and the electrode subbands are responsible for the observed NDR phenomenon. In addition, the obvious di erence of the transmission spectra of two spin channels is observed in some bias ranges, which leads to the near perfect spin-filtering effect. These theoretical findings imply that GNRs with nitrogenvacancy defects hold great potential for building molecular devices.
基金Supported by Hubei Province Key Laboratory of Systems Science in Metallurgical Process (Wuhan University of Science and Technology) under Grant No.C201018 the National Natural Science Foundation of China under Grant No.10805035
文摘We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the degreeof spin-polarization strongly depends on the transverse wave-vector and the temperature.These interesting propertiesmay be helpful to spin-polarize electrons into semiconductors,and this device may be used as a spin filter.
文摘Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.
基金Project (No. 2002AA517020) supported by the Hi-Tech Research and Development Program (863) of China
文摘Control design is important for proton exchange membrane fuel cell (PEMFC) generator. This work researched the anode system of a 60-kW PEMFC generator. Both anode pressure and humidity must be maintained at ideal levels during steady operation. In view of characteristics and requirements of the system, a hybrid intelligent PID controller is designed specifically based on dynamic simulation. A single neuron PI controller is used for anode humidity by adjusting the water injection to the hydrogen cell. Another incremental PID controller, based on the diagonal recurrent neural network (DRNN) dynamic identification, is used to control anode pressure to be more stable and exact by adjusting the hydrogen flow rate. This control strategy can avoid the coupling problem of the PEMFC and achieve a more adaptive ability. Simulation results showed that the control strategy can maintain both anode humidity and pressure at ideal levels regardless of variable load, nonlinear dynamic and coupling characteristics of the system. This work will give some guides for further control design and applications of the total PEMFC generator.
