Closed-orbit theory is a semiclassical technique for explaining the spectra of Rydberg atoms in external fields. Using the closed-orbit theory and classical perturbation theory, we calculate the scaled recurrence spec...Closed-orbit theory is a semiclassical technique for explaining the spectra of Rydberg atoms in external fields. Using the closed-orbit theory and classical perturbation theory, we calculate the scaled recurrence spectra of Lithium atom in magnetic field plus a weak perpendicular electric field. The results show when the crossed electric field is added, the recurrence spectra are weakened greatly. As the scaled electric field f increases, the peaks of the recurrence spectra lose strength. Some recurrences are very sensitive and fall off rapidly as f increases; others persist till much higher f . As the electric field is stronger, some of the peaks revive. This phenomenon, caused by the interference among the electron waves that return to the nucleus, can be computed from the azimuthal dependence of the classical closed orbits.展开更多
Taking nanocrystalline Nd_2Fe_(14)B as a typical sample, based on Herzer′s random anisotropy theory and the cubic grain model, the partial exchange-coupling interaction model was established and the dependence of eff...Taking nanocrystalline Nd_2Fe_(14)B as a typical sample, based on Herzer′s random anisotropy theory and the cubic grain model, the partial exchange-coupling interaction model was established and the dependence of effective anisotropy constant K_(eff) on grain size was investigated. Calculation results reveal that the exchange-coupling interaction enhances and the effective anisotropy of material K_(eff) decreases with the reduction of grain size. The variation of K_(eff) is basically the same as that of coercivity. The decrease of effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline Nd_2Fe_(14)B permanent magnetic material.展开更多
The influences of quenching speed and current annealing on the magnetic properties of Nd9Fe86B5 ribbons were investigated. There is an optimum quenching speed (v ≈ 15 m/s) for preparing hard magnetic ribbons, where t...The influences of quenching speed and current annealing on the magnetic properties of Nd9Fe86B5 ribbons were investigated. There is an optimum quenching speed (v ≈ 15 m/s) for preparing hard magnetic ribbons, where the remanence of 1.22 T, the intrinsic coercivity of 521 kA?m?1 and the energy products of 150 kJ?m?3 are obtained. After annealing ribbons prepared with v = 20 m/s at a dc current of 0.85 A, the remanence reaches a quite large value of 1.47 T, which attributes to the strong exchange coupling interactions between the fine grains of Nd2Fe14B and α-Fe.展开更多
The influence of solidification rate on the microstructure of (Nd,Dy)(12.8)(Fe,Co)(80.7)B-6.5 cast strips was reported in this paper. The strips prepared at different wheel speeds were analyzed by X-ray diffraction (X...The influence of solidification rate on the microstructure of (Nd,Dy)(12.8)(Fe,Co)(80.7)B-6.5 cast strips was reported in this paper. The strips prepared at different wheel speeds were analyzed by X-ray diffraction (XRD). The microstructure of the strips was investigated by backscattered scanning microscope (BSM). The XRD results show that the strips are mainly composed of the main phase (T-1) existing apparent alignment along [00L]. The thickness of T-1 columnar grains is larger when the solidification rate is lower and the over-small isotropic microcrystalline appear on the cooling surface of the strips when the solidification rate is too high. The adequate wheel speed for obtaining the optimum microstructure of the strips is about V = 2.0 m/s. The strip prepared at V = 2.0 m/s possesses suitable thickness and the highest alignment degree of T-1 columnar grains, uniformly distributed Nd-rich phase, and no existence of alpha-Fe phase. This kind of cast strip is an ideal starting material for preparing sintered magnets with high magnetic properties.展开更多
The giant magnetoimpedance effect of the nanocrystalline ribbonFe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) (atom fraction in %) was investigated. There is an optimumannealing temperature (T_A≈ 998 K) for obtaining the larges...The giant magnetoimpedance effect of the nanocrystalline ribbonFe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) (atom fraction in %) was investigated. There is an optimumannealing temperature (T_A≈ 998 K) for obtaining the largest GMI (giant magneto-impedance) effectin the ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11). The ribbon with longer ribbon length has strongerGMI effect, which may be connected with the demagnetization effect of samples. The frequencyf_(max), where the maximum magnetoimpedance GMI(Z)_(max) = [(Z(H) - Z(0))/Z(0)]_(max) occurs, isnear the intersecting frequency f_i of the curves of GMI(R), GMI(X), and GMI(Z) versus frequency.The magnetoreactance GMI(X) decreases monotonically with increasing frequency, which may be due tothe decrease of permeability. In contrast, with the AC (alternating current) frequency increasing,the inagnetore-sistance GMI(R) increases at first, undergoes a peak, and under then drops. Theincrease of the magnetoresistance may result from the enhancement of the skin effect with frequency.The maximum magnetoimpedance value GMI(Z)_(max) under H = 7.2 kA/m is about -56.18% at f= 0.3 MHzfor the nanocrystalline ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) with the annealing temperatureT_A= 998 K and the ribbon length L = 6 cm.展开更多
Using core-scattered closed-orbit theory and region-splitting iterative method, we calculated the scaled recurrence spectra of helium atom in parallel electric and magnetic fields. Closed orbits in the corresponding c...Using core-scattered closed-orbit theory and region-splitting iterative method, we calculated the scaled recurrence spectra of helium atom in parallel electric and magnetic fields. Closed orbits in the corresponding classical system have also been obtained. When we search the closed orbits, in order to remove the Coulomb singularity of the classical Hamiltonian motion equations, we implement the Kustaanheimo-Stiefel transformation, which transforms the system from a three-dimensional to a four-dimensional one. The Fourier transformed spectrum of helium atom has allowed direct comparison between peaks in such plot and the scaled action values of closed orbits. The results are compared with those of the hydrogen case, which shows that the core-scattered effects play an important role in the recurrence spectra of the multi-electron Rydberg atom.展开更多
The influences of silica volume fraction, electrolyte concentration and pH value upon the stress dependence of elastic modulus G′and viscous modulus G″ were investigated. The results show that the suspension transfo...The influences of silica volume fraction, electrolyte concentration and pH value upon the stress dependence of elastic modulus G′and viscous modulus G″ were investigated. The results show that the suspension transforms from a liquid-like state to a solid-like state with increasing the volume fraction of silica. Such a solid-like state can be transformed back into a liquid-like state under the application of a larger stress. At the higher volume fraction, the larger critical stress is required to induce the transition from solid-like to liquid-like state. As the electrolyte concentration decreases or pH value increases, the inter-particle force increases, which causes the state transition to occur at a higher stress.展开更多
Organic electrooptical （EO） chromophores are now gaining more attention because the property of organic photorefrative （PR） materials could be controlled by doped EO chromophores. In this paper, nonlinear optical ...Organic electrooptical （EO） chromophores are now gaining more attention because the property of organic photorefrative （PR） materials could be controlled by doped EO chromophores. In this paper, nonlinear optical （NLO） properties of a new group of organic electrooptical chromophores, synthesized recently in our laboratory, were elucidated theoretically with the quantum chemical density functional theory （DFT） and the intermediate neglect of differential overlap Hamilton and the configuration interaction （INDO/CI）, as well as semiemperical Austin Model 1 （AM1） methods. The electronic transition intensity, dipole moment and the second-order polarizability were obtained. The results show this group of chromophores possess appropriate optical absorption property and good electrooptical property and optical activity. The second-order polarizabilities β are as large as the order of 10-29 to 10-28 ESU, indicating the promising applications in the future. The physical mechanism of NLO is discussed by means of molecular orbital and electronic charge distribution.展开更多
Transparent conducting Al-doped zinc oxide (ZnO:AI) films with good adhesion have been deposited on polyimide thin film substrates by r.f. magnetron sputtering technique at low substrate temperature (25-180℃). The st...Transparent conducting Al-doped zinc oxide (ZnO:AI) films with good adhesion have been deposited on polyimide thin film substrates by r.f. magnetron sputtering technique at low substrate temperature (25-180℃). The structural, optical and electrical properties of the deposited films were investigated. High quality films with electrical resistivity as low as 8.5×10-4 Ω·cm and the average transmittance over 74% in the wavelength range of the visible spectrum have been obtained. The electron carrier concentrations are in the range from 2.9×1020 to 7.1×1020 cm-3 with mobilities from 4 to 8.8 cm2 V-1s-1. The densities of the films are in the range from 4.58 to 5.16 g/cm-3.展开更多
文摘Closed-orbit theory is a semiclassical technique for explaining the spectra of Rydberg atoms in external fields. Using the closed-orbit theory and classical perturbation theory, we calculate the scaled recurrence spectra of Lithium atom in magnetic field plus a weak perpendicular electric field. The results show when the crossed electric field is added, the recurrence spectra are weakened greatly. As the scaled electric field f increases, the peaks of the recurrence spectra lose strength. Some recurrences are very sensitive and fall off rapidly as f increases; others persist till much higher f . As the electric field is stronger, some of the peaks revive. This phenomenon, caused by the interference among the electron waves that return to the nucleus, can be computed from the azimuthal dependence of the classical closed orbits.
基金Project supported by National‘863’Project (2002AA324050 2002AA302602) and Natural Science Foundation of China(50371046) and Doctoral Foundation of China (20040422014)
文摘Taking nanocrystalline Nd_2Fe_(14)B as a typical sample, based on Herzer′s random anisotropy theory and the cubic grain model, the partial exchange-coupling interaction model was established and the dependence of effective anisotropy constant K_(eff) on grain size was investigated. Calculation results reveal that the exchange-coupling interaction enhances and the effective anisotropy of material K_(eff) decreases with the reduction of grain size. The variation of K_(eff) is basically the same as that of coercivity. The decrease of effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline Nd_2Fe_(14)B permanent magnetic material.
基金This work was financially supported by the Hi-Tech Research and Development Program (863 Program) of China (No. 2002AA302602 and No. 2001AA324010).
文摘The influences of quenching speed and current annealing on the magnetic properties of Nd9Fe86B5 ribbons were investigated. There is an optimum quenching speed (v ≈ 15 m/s) for preparing hard magnetic ribbons, where the remanence of 1.22 T, the intrinsic coercivity of 521 kA?m?1 and the energy products of 150 kJ?m?3 are obtained. After annealing ribbons prepared with v = 20 m/s at a dc current of 0.85 A, the remanence reaches a quite large value of 1.47 T, which attributes to the strong exchange coupling interactions between the fine grains of Nd2Fe14B and α-Fe.
基金This work was financially supported by the High Technology Research and Development Program of China ("863"program) (No. 2002AA324050 and 2002AA302602) and the National Natural Science Foundation of China (No. 50371046).
文摘The influence of solidification rate on the microstructure of (Nd,Dy)(12.8)(Fe,Co)(80.7)B-6.5 cast strips was reported in this paper. The strips prepared at different wheel speeds were analyzed by X-ray diffraction (XRD). The microstructure of the strips was investigated by backscattered scanning microscope (BSM). The XRD results show that the strips are mainly composed of the main phase (T-1) existing apparent alignment along [00L]. The thickness of T-1 columnar grains is larger when the solidification rate is lower and the over-small isotropic microcrystalline appear on the cooling surface of the strips when the solidification rate is too high. The adequate wheel speed for obtaining the optimum microstructure of the strips is about V = 2.0 m/s. The strip prepared at V = 2.0 m/s possesses suitable thickness and the highest alignment degree of T-1 columnar grains, uniformly distributed Nd-rich phase, and no existence of alpha-Fe phase. This kind of cast strip is an ideal starting material for preparing sintered magnets with high magnetic properties.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50271036)
文摘The giant magnetoimpedance effect of the nanocrystalline ribbonFe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) (atom fraction in %) was investigated. There is an optimumannealing temperature (T_A≈ 998 K) for obtaining the largest GMI (giant magneto-impedance) effectin the ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11). The ribbon with longer ribbon length has strongerGMI effect, which may be connected with the demagnetization effect of samples. The frequencyf_(max), where the maximum magnetoimpedance GMI(Z)_(max) = [(Z(H) - Z(0))/Z(0)]_(max) occurs, isnear the intersecting frequency f_i of the curves of GMI(R), GMI(X), and GMI(Z) versus frequency.The magnetoreactance GMI(X) decreases monotonically with increasing frequency, which may be due tothe decrease of permeability. In contrast, with the AC (alternating current) frequency increasing,the inagnetore-sistance GMI(R) increases at first, undergoes a peak, and under then drops. Theincrease of the magnetoresistance may result from the enhancement of the skin effect with frequency.The maximum magnetoimpedance value GMI(Z)_(max) under H = 7.2 kA/m is about -56.18% at f= 0.3 MHzfor the nanocrystalline ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) with the annealing temperatureT_A= 998 K and the ribbon length L = 6 cm.
文摘Using core-scattered closed-orbit theory and region-splitting iterative method, we calculated the scaled recurrence spectra of helium atom in parallel electric and magnetic fields. Closed orbits in the corresponding classical system have also been obtained. When we search the closed orbits, in order to remove the Coulomb singularity of the classical Hamiltonian motion equations, we implement the Kustaanheimo-Stiefel transformation, which transforms the system from a three-dimensional to a four-dimensional one. The Fourier transformed spectrum of helium atom has allowed direct comparison between peaks in such plot and the scaled action values of closed orbits. The results are compared with those of the hydrogen case, which shows that the core-scattered effects play an important role in the recurrence spectra of the multi-electron Rydberg atom.
基金the National Natural Science Foundation of China(No.2 0 2 4 30 0 2 )
文摘The influences of silica volume fraction, electrolyte concentration and pH value upon the stress dependence of elastic modulus G′and viscous modulus G″ were investigated. The results show that the suspension transforms from a liquid-like state to a solid-like state with increasing the volume fraction of silica. Such a solid-like state can be transformed back into a liquid-like state under the application of a larger stress. At the higher volume fraction, the larger critical stress is required to induce the transition from solid-like to liquid-like state. As the electrolyte concentration decreases or pH value increases, the inter-particle force increases, which causes the state transition to occur at a higher stress.
文摘Organic electrooptical （EO） chromophores are now gaining more attention because the property of organic photorefrative （PR） materials could be controlled by doped EO chromophores. In this paper, nonlinear optical （NLO） properties of a new group of organic electrooptical chromophores, synthesized recently in our laboratory, were elucidated theoretically with the quantum chemical density functional theory （DFT） and the intermediate neglect of differential overlap Hamilton and the configuration interaction （INDO/CI）, as well as semiemperical Austin Model 1 （AM1） methods. The electronic transition intensity, dipole moment and the second-order polarizability were obtained. The results show this group of chromophores possess appropriate optical absorption property and good electrooptical property and optical activity. The second-order polarizabilities β are as large as the order of 10-29 to 10-28 ESU, indicating the promising applications in the future. The physical mechanism of NLO is discussed by means of molecular orbital and electronic charge distribution.
基金This work was supported by the National Natural Science Foundation of China(No.60276044)the Ministry of Education of China Science and Technology Study Accented Term.
文摘Transparent conducting Al-doped zinc oxide (ZnO:AI) films with good adhesion have been deposited on polyimide thin film substrates by r.f. magnetron sputtering technique at low substrate temperature (25-180℃). The structural, optical and electrical properties of the deposited films were investigated. High quality films with electrical resistivity as low as 8.5×10-4 Ω·cm and the average transmittance over 74% in the wavelength range of the visible spectrum have been obtained. The electron carrier concentrations are in the range from 2.9×1020 to 7.1×1020 cm-3 with mobilities from 4 to 8.8 cm2 V-1s-1. The densities of the films are in the range from 4.58 to 5.16 g/cm-3.
