In this paper, five types of similarity reductions of Whitham-Broer-kaup equations in shallow water are given by both the classical Lie approach and the direct method. The Painlevé Ⅱ type reduction equation obtained by the classical Lie approach is only the special case of that obtained by the direct method. In the similarity reduction results of the direct method, three types of singularity points, i.e., poles, algebraic branch points and logarithmic branch points. are included.
In this paper, five types of similarity reductions of Whitham-Broer-kaup equations in shallow water are given by both the classical Lie approach and the direct method. The Painlevé Ⅱ type reduction equation obtained by the classical Lie approach is only the special case of that obtained by the direct method. In the similarity reduction results of the direct method, three types of singularity points, i.e., poles, algebraic branch points and logarithmic branch points. are included.
Taking the optical system as a prototype, this paper demonstrates that a quasi-thermodynamic model for dissipative systems, satisfying the principle of detailed balance, may be developed, which is parallel to the traditional thermodynamics. The present systems are described by the generalized dynamical equation of nonlinear optical cavities, introduced in previous work of Ou Fa et al. In view of the quasi-thermodynamic model, the critical phenomena and phase transitions in optical bistability are discussed systematically and generally. By taking the advantage of Ginzburg-Landau's model, the fluctuations and correlations near the (second kind of) critical point of optical bistability are studied also. So the Landau's theory of phase transitions in equilibrium thermodynamics is generalized to the bistable dissipative systems far from equilibrium.
Taking the optical system as a prototype, this paper demonstrates that a quasi-thermodynamic model for dissipative systems, satisfying the principle of detailed balance, may be developed, which is parallel to the traditional thermodynamics. The present systems are described by the generalized dynamical equation of nonlinear optical cavities, introduced in previous work of Ou Fa et al. In view of the quasi-thermodynamic model, the critical phenomena and phase transitions in optical bistability are discussed systematically and generally. By taking the advantage of Ginzburg-Landau's model, the fluctuations and correlations near the (second kind of) critical point of optical bistability are studied also. So the Landau's theory of phase transitions in equilibrium thermodynamics is generalized to the bistable dissipative systems far from equilibrium.
In this paper, the electronic structures and energy levels of the complex ion (CrO4) as Cr-O distance changes are analyzed with the spin-polarized MS-Xα method, Under the symmetry Td the one-electron energy levels and eignfunctions, electronic configuration of ground state, optical transitions of lower excited state,and schematic diagram of the energy levels of the three complex ions,(CrO4)6-,(CrO4)5- and (CrO4)4-, are given, When the distance of ligands from the central ion is sma. ller than 2?(R≤2?), the results given by crystal field theory is not satisfactory. In this case, the influence of the distance of ligands from the central ion and the influence of the 4s or 4p atomic orbits in the central ion(transition metal ions to be considered must be taken into aceount.
In this paper, the electronic structures and energy levels of the complex ion (CrO4) as Cr-O distance changes are analyzed with the spin-polarized MS-Xα method, Under the symmetry Td the one-electron energy levels and eignfunctions, electronic configuration of ground state, optical transitions of lower excited state,and schematic diagram of the energy levels of the three complex ions,(CrO4)6-,(CrO4)5- and (CrO4)4-, are given, When the distance of ligands from the central ion is sma. ller than 2?(R≤2?), the results given by crystal field theory is not satisfactory. In this case, the influence of the distance of ligands from the central ion and the influence of the 4s or 4p atomic orbits in the central ion(transition metal ions to be considered must be taken into aceount.
A perturbation method is used to evaluate the energy levels and oscillator strengths of sodium atoms (m=-2,π2=+)in a strong magnetic field. The main features of the calculated spectra which lie in the strong-field-mixing regime agree well with the corresponding experimental results. Besides the conventional quasi-Landau resonance with spacing equal to 1.5?ωc (ωc is the electron cyclotron frequency) near the zero field ionization limit, a series of resonance spacings are found and analysed using the zero order energy formula and the Fourier transform technique. The values of these spacings are in consistent with other theoretical results. Based on the perturbation method, a quantum mechanical explanation for the spacings is given. These resonance spacings are independent of the applied exernal magnetic field.
A perturbation method is used to evaluate the energy levels and oscillator strengths of sodium atoms (m=-2,π2=+)in a strong magnetic field. The main features of the calculated spectra which lie in the strong-field-mixing regime agree well with the corresponding experimental results. Besides the conventional quasi-Landau resonance with spacing equal to 1.5?ωc (ωc is the electron cyclotron frequency) near the zero field ionization limit, a series of resonance spacings are found and analysed using the zero order energy formula and the Fourier transform technique. The values of these spacings are in consistent with other theoretical results. Based on the perturbation method, a quantum mechanical explanation for the spacings is given. These resonance spacings are independent of the applied exernal magnetic field.
Schaber and Martin have investigated exp rimentally the properties of the yield of (Na14Cl13)+ clusters in detail. They obtained the yield of (Na14Cl13)+ clusters as a function of oven-nozzle distance with the quadrupole mass spectrometer. In the present paper, by using the fractal theory, the distribution function is numericalls simulated and analyzed theoretically.
Schaber and Martin have investigated exp rimentally the properties of the yield of (Na14Cl13)+ clusters in detail. They obtained the yield of (Na14Cl13)+ clusters as a function of oven-nozzle distance with the quadrupole mass spectrometer. In the present paper, by using the fractal theory, the distribution function is numericalls simulated and analyzed theoretically.
The field squeezing effect for off-resonant two-photon laser with an injected signal in good-cavity limit is studied by means of Fokker-Planck equation of the peneralized Wigner distribution. Under certain off-resonance condition, the field squeezing effect of two-photon laser may be observed.
The field squeezing effect for off-resonant two-photon laser with an injected signal in good-cavity limit is studied by means of Fokker-Planck equation of the peneralized Wigner distribution. Under certain off-resonance condition, the field squeezing effect of two-photon laser may be observed.
Two level atoms are injected into ideal cavity one by one to interact with the light field therein which intially is in coherent state. In one-photon transition case, the quadrature variance could be reduced by this means for suitably chosen interaction time t. But there exists some limitation, the squeezing will become worse if the number of times K is too large. In twophoton transition case, for large mean photon tumber N and optimum interaction time t = π/ g2, analytical formula for dependence of quadrature variance on N and K can be obtained. This formula shows that deep squeezing can be achieved by suitably chosen K. And the larger the N is, the stronger the achievable squeezing will be.
Two level atoms are injected into ideal cavity one by one to interact with the light field therein which intially is in coherent state. In one-photon transition case, the quadrature variance could be reduced by this means for suitably chosen interaction time t. But there exists some limitation, the squeezing will become worse if the number of times K is too large. In twophoton transition case, for large mean photon tumber N and optimum interaction time t = π/ g2, analytical formula for dependence of quadrature variance on N and K can be obtained. This formula shows that deep squeezing can be achieved by suitably chosen K. And the larger the N is, the stronger the achievable squeezing will be.
In this paper, the squeezing properties of orthonormal eigenstates of high order power of photon annihilation operator αk (k≥3) are studied. It is shown that the amplitude Nth-power squeezing (k=2N) can exist in the eigenstates when k is even.
In this paper, the squeezing properties of orthonormal eigenstates of high order power of photon annihilation operator αk (k≥3) are studied. It is shown that the amplitude Nth-power squeezing (k=2N) can exist in the eigenstates when k is even.
In this paper, a detailed analysis of the relationship between various criterion factors and result errors of a lot of simultaneous equations for X-ray quantitative phase analysis is carried out and the factor g for quantitative criticizing the stability of the equations is found. According to the g factor of the different equations composed by the different samples combination, one can select the normal equation to get the precise results. Practical quantitative analysis, have proved that the new method is quite explicit and applicable.
In this paper, a detailed analysis of the relationship between various criterion factors and result errors of a lot of simultaneous equations for X-ray quantitative phase analysis is carried out and the factor g for quantitative criticizing the stability of the equations is found. According to the g factor of the different equations composed by the different samples combination, one can select the normal equation to get the precise results. Practical quantitative analysis, have proved that the new method is quite explicit and applicable.
The behavior of internal friction during strain ageing and amplitude-dependent effect behaved in high purity aluminium were studied. After specimen is twisted to a certain degree, internal friction exhibits anomalously amplitude dependent effect. This can be observed in a large temperature region but does not appear in completely annealed or elongated specimens. The way of twisting deformation of specimen can affect amplitude-dependent effect. As the purity is lower, the anomalously amplitude-dependent effect is not so easy to be observed. It is considered that the appearance of anomalously amplitude-dependent effect is attributed to the reason that deformation leads to high enough dislocation density and much smaller region allowed for the movement of dislocations. The increase of nternal friction during strain ageing at room temperature is suggested to be due to the dislocation slip aided by vacancy produced through deformation.
The behavior of internal friction during strain ageing and amplitude-dependent effect behaved in high purity aluminium were studied. After specimen is twisted to a certain degree, internal friction exhibits anomalously amplitude dependent effect. This can be observed in a large temperature region but does not appear in completely annealed or elongated specimens. The way of twisting deformation of specimen can affect amplitude-dependent effect. As the purity is lower, the anomalously amplitude-dependent effect is not so easy to be observed. It is considered that the appearance of anomalously amplitude-dependent effect is attributed to the reason that deformation leads to high enough dislocation density and much smaller region allowed for the movement of dislocations. The increase of nternal friction during strain ageing at room temperature is suggested to be due to the dislocation slip aided by vacancy produced through deformation.
Tre vapor-solid phase transition of the motybdenum oxide was investigated in the stochastic nonlinear system which was in far from equilibrium state. Some thin molybdena crystals and various two-dimensional fractal structures consisted of the molybdena whiskers were ob-served. The possible mechanism of the fractal structures is discussed in terms of nonequilibrium thermodynamics of irreversible processes and a nucleation aggregation model is proposed.
Tre vapor-solid phase transition of the motybdenum oxide was investigated in the stochastic nonlinear system which was in far from equilibrium state. Some thin molybdena crystals and various two-dimensional fractal structures consisted of the molybdena whiskers were ob-served. The possible mechanism of the fractal structures is discussed in terms of nonequilibrium thermodynamics of irreversible processes and a nucleation aggregation model is proposed.
In this paper, we report the results of the growth of a series of ZnSe films on (100) GaAs at different substrate temperatures by hot wall epitaxy. The quality of ZnSe films has been studied by X-ray diffraction, Raman scattering and photoluminescence. The results show that: 1) We have got (100)-oriented single crystal fillms, but the quality becomes worse when lowering the substrate temperature. When the substrate temperature is below 300℃ there appears the (111)-oriented twins in the (100ZnSe. 2) When the substrate temperature is 350℃, Ga atom diffusion from the substrate to the ZnSe epitaxial layer is serious.
In this paper, we report the results of the growth of a series of ZnSe films on (100) GaAs at different substrate temperatures by hot wall epitaxy. The quality of ZnSe films has been studied by X-ray diffraction, Raman scattering and photoluminescence. The results show that: 1) We have got (100)-oriented single crystal fillms, but the quality becomes worse when lowering the substrate temperature. When the substrate temperature is below 300℃ there appears the (111)-oriented twins in the (100ZnSe. 2) When the substrate temperature is 350℃, Ga atom diffusion from the substrate to the ZnSe epitaxial layer is serious.
Various reconstructions (c(2×6), (1×3) and (2×3)) of the GaSb (100) surface have been studied by LEED, XPS and UPS. All the three reconstructed surfaces are terminated by Sb atoms with some rows missing. Annealing in an Sb environment of both MBE-prepared, Sbdimerized c(2×6) reconstruction and IBA-prepared, Gaislands-existing (2×3) reconstruction leads to the same (1×3) reconstruction.
Various reconstructions (c(2×6), (1×3) and (2×3)) of the GaSb (100) surface have been studied by LEED, XPS and UPS. All the three reconstructed surfaces are terminated by Sb atoms with some rows missing. Annealing in an Sb environment of both MBE-prepared, Sbdimerized c(2×6) reconstruction and IBA-prepared, Gaislands-existing (2×3) reconstruction leads to the same (1×3) reconstruction.
We report a detailed photoreflectance study at 300 and 77K of a set of GaAs/ Al0.23Ga0.77As double quantum well samples with different barrier widths Lb0.23Ga0.77As valence band to the first electron confined state and from the first light hole confined state to the bottom of the Al0.23Ga0.77As conduction band. By using these transitions the conduction band-edge discontinuity has been determined to be Qcb
Acta Physica Sinica. 1992 41(8): 1322-1329. Published 1992-04-05
]]>
We report a detailed photoreflectance study at 300 and 77K of a set of GaAs/ Al0.23Ga0.77As double quantum well samples with different barrier widths Lb0.23Ga0.77As valence band to the first electron confined state and from the first light hole confined state to the bottom of the Al0.23Ga0.77As conduction band. By using these transitions the conduction band-edge discontinuity has been determined to be Qcb
Acta Physica Sinica. 1992 41(8): 1322-1329. Published 1992-04-05
]]>
This paper is devoted to the study of electronic and phonon spectra of a kind of generalized Fibonacci quasiperiodic chain (Twins model). Renormalization group results show that the electronic spectrum has a trifurcating selfs milar structure but the middle subbends in every hierarchy are similar to spetral structure of the periodic systems. The analysis is confirmed by numerical results. While the phoson spectrum shows the same spectral structure as that of the Fibonacci chain.
This paper is devoted to the study of electronic and phonon spectra of a kind of generalized Fibonacci quasiperiodic chain (Twins model). Renormalization group results show that the electronic spectrum has a trifurcating selfs milar structure but the middle subbends in every hierarchy are similar to spetral structure of the periodic systems. The analysis is confirmed by numerical results. While the phoson spectrum shows the same spectral structure as that of the Fibonacci chain.
A reasonable model is proposed to calculatee the temperature dependence of photoconductivity (PC) in a-Si:H and a-Si:H/a-SiNx:H super lattices. Simmons-Taylor theory and the occupation statistics of correlated defects are used to describe band tail states and dangling bonds states. As in a-Si:H/a-SiNx:H superlattices, the electronic potential and charge distributions resulting from space-charge doping are calculated at various amounts of transferred charge and different asymmetry boundary conditions. The DC and PC are calculated with corresponding space potential and charge distributions. It is found that the enhancements of DC and PC in superlattices are mainly determined by the amouns of injected charge, and the influence of interface asymmetry is slight.
A reasonable model is proposed to calculatee the temperature dependence of photoconductivity (PC) in a-Si:H and a-Si:H/a-SiNx:H super lattices. Simmons-Taylor theory and the occupation statistics of correlated defects are used to describe band tail states and dangling bonds states. As in a-Si:H/a-SiNx:H superlattices, the electronic potential and charge distributions resulting from space-charge doping are calculated at various amounts of transferred charge and different asymmetry boundary conditions. The DC and PC are calculated with corresponding space potential and charge distributions. It is found that the enhancements of DC and PC in superlattices are mainly determined by the amouns of injected charge, and the influence of interface asymmetry is slight.
The infrared refleotion spectra of Y1-xPrxBa2Cu3O7+δ(x = 0,0.1,0.2,0.4,0.5, 0.6, 1.0) are measured in the temprature range of 4.2 to 300K. The measurements show that Ba mode has double mode behavior, the strength of which inverses with increasing x, and that the position of the reflection peak at 194cm-1, which has been identified as Y mode of YBa2Cu3O7+δ, is indenpendent of the density of Pr, i. e, the position of the peak does not change whether the Y is partially or totally substitued by Pr. This indicates that in Y1-xPrxBa2Cu3O7+δ the valence of Pr is tetra-valent. The substitution of Pr make the mobile holes localize around Pr, thereby lead to the suppression of superconductivity.
The infrared refleotion spectra of Y1-xPrxBa2Cu3O7+δ(x = 0,0.1,0.2,0.4,0.5, 0.6, 1.0) are measured in the temprature range of 4.2 to 300K. The measurements show that Ba mode has double mode behavior, the strength of which inverses with increasing x, and that the position of the reflection peak at 194cm-1, which has been identified as Y mode of YBa2Cu3O7+δ, is indenpendent of the density of Pr, i. e, the position of the peak does not change whether the Y is partially or totally substitued by Pr. This indicates that in Y1-xPrxBa2Cu3O7+δ the valence of Pr is tetra-valent. The substitution of Pr make the mobile holes localize around Pr, thereby lead to the suppression of superconductivity.
In this work, 119Sn is used as probe-atom, nd room temperature Mossbauer measurement of Bi1.68Pb0.32Sr1.75Ca1.75Cu2.65-xSnxOy(x=0.2-0.8) sample is performed. Combined with the results of X-ray diffraction and electric characteristic measurement, the relation between the occupancy of Sn in the sample and its electric characteristics is analysed, and an conclusion that squarecoordinated Cu performs a chief influence on the electric characteristic of high-transition-temperature (Tc) phase superconductor is reached.
In this work, 119Sn is used as probe-atom, nd room temperature Mossbauer measurement of Bi1.68Pb0.32Sr1.75Ca1.75Cu2.65-xSnxOy(x=0.2-0.8) sample is performed. Combined with the results of X-ray diffraction and electric characteristic measurement, the relation between the occupancy of Sn in the sample and its electric characteristics is analysed, and an conclusion that squarecoordinated Cu performs a chief influence on the electric characteristic of high-transition-temperature (Tc) phase superconductor is reached.
Properties of a series of superconducting compounds of nominal composition (Bi2-x,Nbx)Sr2Ca2(Cu3-yNby)Ox(x=0-1.0, y=0-1.0) have been investigated using electrical resistivity, a.c magnetic susceptibility and X-ray powder diffraction measurements. When x =0.2-0.3 or y=0.2, 2223 phase (Tc～110K) in samples is significantly enhanced. The added Nb in the sample with Bi1.7Nb0.3Sr2Ca2Cu3Oy has obvious effect of promoting 2223 phase. When furthermore doping Ba as replacing Sr in BiNbSrCaCuO, it is observed that double-doped Nb-Ba has more evident enhancing the high-Tc phase formation than single-doping Nb. The doped Nb-Ba in sample with nominal composition Bi1.7Nb0.3Sr1.8Ba0.2Ca2Cu3Oy is distinctly favour to formation of 2223 phase. From TGA experiment, the weight of sample doping Nb(Ba) at ～600℃ begin to increase by absorbing oxygen. By XPS of O1s in sample doped with Nb(Ba), the shoulder peak at ～529eV is more evident except for ～531eV as main peak.
Properties of a series of superconducting compounds of nominal composition (Bi2-x,Nbx)Sr2Ca2(Cu3-yNby)Ox(x=0-1.0, y=0-1.0) have been investigated using electrical resistivity, a.c magnetic susceptibility and X-ray powder diffraction measurements. When x =0.2-0.3 or y=0.2, 2223 phase (Tc～110K) in samples is significantly enhanced. The added Nb in the sample with Bi1.7Nb0.3Sr2Ca2Cu3Oy has obvious effect of promoting 2223 phase. When furthermore doping Ba as replacing Sr in BiNbSrCaCuO, it is observed that double-doped Nb-Ba has more evident enhancing the high-Tc phase formation than single-doping Nb. The doped Nb-Ba in sample with nominal composition Bi1.7Nb0.3Sr1.8Ba0.2Ca2Cu3Oy is distinctly favour to formation of 2223 phase. From TGA experiment, the weight of sample doping Nb(Ba) at ～600℃ begin to increase by absorbing oxygen. By XPS of O1s in sample doped with Nb(Ba), the shoulder peak at ～529eV is more evident except for ～531eV as main peak.
The structural and magnetic properties of the two sources deposited Fe/Pd superlattices were studied. The samples were prepared by keeping the thickness of Pd layers dpd at 30? and varying dFe from 56 to 5.7?. The reduced saturation magnetization of Fe/Pd superlatti-ces, σt increased with the decrease of dFe this was due to the polarization effect of Pd. The effective thickness of polarization effect dpd was found as about 10? at 0K. The temperature dependence of magnetization followed Bloch T3/2 law in the range of 7-300K. and the spin-wave stiffness constant B increased with the decrease of dFe The Curie temperature, Tc decreased with dFe The 57Fe conversion electron M?ssbauer spectrum illustrated that the polarization effect existed among the layers, and there were no magnetic enhancing effect and 'dead layer effect' on the Fe atoms at the interfaces.
The structural and magnetic properties of the two sources deposited Fe/Pd superlattices were studied. The samples were prepared by keeping the thickness of Pd layers dpd at 30? and varying dFe from 56 to 5.7?. The reduced saturation magnetization of Fe/Pd superlatti-ces, σt increased with the decrease of dFe this was due to the polarization effect of Pd. The effective thickness of polarization effect dpd was found as about 10? at 0K. The temperature dependence of magnetization followed Bloch T3/2 law in the range of 7-300K. and the spin-wave stiffness constant B increased with the decrease of dFe The Curie temperature, Tc decreased with dFe The 57Fe conversion electron M?ssbauer spectrum illustrated that the polarization effect existed among the layers, and there were no magnetic enhancing effect and 'dead layer effect' on the Fe atoms at the interfaces.
The normal ground state stability of infinite polyacenacene is investigated by means of the method of quantum field theory in statistical physics. The condensed phases such as charge density wave (CDW), spin density wave (SDV) and superconducting phases are predicted within the random phase approximation (RPA). In particular, we show that there is a possibility that polyacenacene could be a high temperature superconductor.
The normal ground state stability of infinite polyacenacene is investigated by means of the method of quantum field theory in statistical physics. The condensed phases such as charge density wave (CDW), spin density wave (SDV) and superconducting phases are predicted within the random phase approximation (RPA). In particular, we show that there is a possibility that polyacenacene could be a high temperature superconductor.
The transfer-matrix method is employed to investigate the spin waves in a magnetic super-lattice with a single-ion uniaxial anisotropy. The dispersion equation of the spin waves is obtained. The effect of anisotropy strength on the spin waves spectrum is also discussed.
The transfer-matrix method is employed to investigate the spin waves in a magnetic super-lattice with a single-ion uniaxial anisotropy. The dispersion equation of the spin waves is obtained. The effect of anisotropy strength on the spin waves spectrum is also discussed.
The variation of surface enhanced Raman scattering was observed as a small amount of KCl was added in SERS system and the intensity ratio of characteristic Raman peaks was detected for two kinds of molecules. In addition the change of orientation of adsorbed molecule on the silver surface was also analysed.
The variation of surface enhanced Raman scattering was observed as a small amount of KCl was added in SERS system and the intensity ratio of characteristic Raman peaks was detected for two kinds of molecules. In addition the change of orientation of adsorbed molecule on the silver surface was also analysed.
CO, O and K coadsorption on Cu(lll) at oom temperature was investigated using high resolution electron energy loss spectroscopy (HREELS). The experimental results show that CO can adsorb on Cu(lll) surface precovered with K at room temperature and coadsorption of CO and K produce the K-O complexes. The K-O complexes can form only from the depolarized K at higher K coverage (θk>0.04).
CO, O and K coadsorption on Cu(lll) at oom temperature was investigated using high resolution electron energy loss spectroscopy (HREELS). The experimental results show that CO can adsorb on Cu(lll) surface precovered with K at room temperature and coadsorption of CO and K produce the K-O complexes. The K-O complexes can form only from the depolarized K at higher K coverage (θk>0.04).