The singular perturbation solution of Boltzmann equation for the plane geometry is generalized to the spherical case. Based on a specific model, some characteristics in the initial stage of relaxation process are discussed.
The singular perturbation solution of Boltzmann equation for the plane geometry is generalized to the spherical case. Based on a specific model, some characteristics in the initial stage of relaxation process are discussed.
The paper presents a nonlinear MHD equation describing 2-D inhomogeneous magnetized plasma. Then a 2-D solitary vortex solution was given. Its structure is similar to the solution obtained in papers [2, 3], but it differs from the latter in several aspects. There is no restriction on the values of vortex speeds and the solitary waves can propagate in any direction in the plane with magnetic field B as its normal. The plasma is adhered to the vortex and moving along with it across B. This implies that the existence of solitary vortices is connected with anomalous transport of plasma.
The paper presents a nonlinear MHD equation describing 2-D inhomogeneous magnetized plasma. Then a 2-D solitary vortex solution was given. Its structure is similar to the solution obtained in papers [2, 3], but it differs from the latter in several aspects. There is no restriction on the values of vortex speeds and the solitary waves can propagate in any direction in the plane with magnetic field B as its normal. The plasma is adhered to the vortex and moving along with it across B. This implies that the existence of solitary vortices is connected with anomalous transport of plasma.
Combining the MHD equilibrium equation of axisymmetric plasma with a flux sur-face-averaged description of the plasma, the evolutional configurations of adiabatic com-pressional plasma equilibria are computed. The results are consistent well with the analytic scaling laws given by Furth and Yoshikawa. Some results of the configuration evolu-tion for two types of compressional plasma are presented.
Combining the MHD equilibrium equation of axisymmetric plasma with a flux sur-face-averaged description of the plasma, the evolutional configurations of adiabatic com-pressional plasma equilibria are computed. The results are consistent well with the analytic scaling laws given by Furth and Yoshikawa. Some results of the configuration evolu-tion for two types of compressional plasma are presented.
Electron conduction losses due to magnetic flutter produced by resistive interchange instabilities and the resulted confinement deterioration mechanism are investigated analytically. Using approximate solutions of MHD equations for even and odd potential parities, the potential and magnetic perturbation levels at saturation are estimated. These results are used to calculate the stochastic magnetic field diffusion coefficients. An expression for the anomalous electron thermal conductivity is then derived for collision-less and collisional regimes. Scaling laws for energy confinement are infered therefrom.
Electron conduction losses due to magnetic flutter produced by resistive interchange instabilities and the resulted confinement deterioration mechanism are investigated analytically. Using approximate solutions of MHD equations for even and odd potential parities, the potential and magnetic perturbation levels at saturation are estimated. These results are used to calculate the stochastic magnetic field diffusion coefficients. An expression for the anomalous electron thermal conductivity is then derived for collision-less and collisional regimes. Scaling laws for energy confinement are infered therefrom.
When the amplitude of waves exceeds a certain threshold, the stochasticity occurs both in the velocity space and configuration space. It is found that spatial diffusion and directional flow, which are much stronger than the classical processes, may be driven by waves in the k×B0 direction. In toroidal plasma, the spatial diffusion and bootstrap current, which are much stronger than the neoclassical processes, may be produced by the wave-driven velocity diffusion effect. The wave-enhanced bootstrap current is available for current drive.
When the amplitude of waves exceeds a certain threshold, the stochasticity occurs both in the velocity space and configuration space. It is found that spatial diffusion and directional flow, which are much stronger than the classical processes, may be driven by waves in the k×B0 direction. In toroidal plasma, the spatial diffusion and bootstrap current, which are much stronger than the neoclassical processes, may be produced by the wave-driven velocity diffusion effect. The wave-enhanced bootstrap current is available for current drive.
An inverse proportionality between the specific contact resistance ρc of n-type GaAs and its carrier concentration ND has been shown by a lot of experimental facts. In this paper, a comment is made on the various viewpoints about this phenomenon in the literatures and their shortages are pointed out as well. According to the band structure of ohmic contact, a new model, assuming that ρc consists of two parts (ρ(c1) and ρ(c2)), is put forward. ρ(c1) occurs between the contact metal and its underlying highly doped semiconductor layer (NDc) after alloying. ρc2 is brought about by a barrier appeared due to the concentration difference between the NDc and the active layer ND. If the alloying process is optimized and thus the NDc is very high, then ρ(c1) is very small and ρ(c2) gives the main contribution to ρc. In this case an inverse proportionality between ρc and NDcan be found, if NDc (Nc is the effective state density). When ND> Nc, ρ(c2) can be neglected due to the disappearance of the barrier. In this case, ρc is determined by ρc1, which should depend only on NDc. Based on the above description, a theoretical deduction was carried out and the result not only can explain the experimental data of n-type GaAs ohmic contact very well, but also the experimental facts of p-type Si ohmic contact presented in the literatures. We believe that this model can also be extended to the case of other III-V compound semiconductors, such as p-type GaAs and P-type InP etc.
An inverse proportionality between the specific contact resistance ρc of n-type GaAs and its carrier concentration ND has been shown by a lot of experimental facts. In this paper, a comment is made on the various viewpoints about this phenomenon in the literatures and their shortages are pointed out as well. According to the band structure of ohmic contact, a new model, assuming that ρc consists of two parts (ρ(c1) and ρ(c2)), is put forward. ρ(c1) occurs between the contact metal and its underlying highly doped semiconductor layer (NDc) after alloying. ρc2 is brought about by a barrier appeared due to the concentration difference between the NDc and the active layer ND. If the alloying process is optimized and thus the NDc is very high, then ρ(c1) is very small and ρ(c2) gives the main contribution to ρc. In this case an inverse proportionality between ρc and NDcan be found, if NDc (Nc is the effective state density). When ND> Nc, ρ(c2) can be neglected due to the disappearance of the barrier. In this case, ρc is determined by ρc1, which should depend only on NDc. Based on the above description, a theoretical deduction was carried out and the result not only can explain the experimental data of n-type GaAs ohmic contact very well, but also the experimental facts of p-type Si ohmic contact presented in the literatures. We believe that this model can also be extended to the case of other III-V compound semiconductors, such as p-type GaAs and P-type InP etc.
The thermal desorption spectra of propene and oxygen adsorbed on blue tungsten oxide WO2.90 have been measured by means of flash heating the sample in ultra high vacuum. It has been discovered that at room temperature only one adsorption state of propene on blue tungsten oxide surface exists, which corresponds to a desorption peak at the temperature around 100℃ appeared in the thermal desorption spectra. The desor- ption parameters determined by the experiment are: n=l (first order desorption) and the activation energy of desorption Ed=10.1 kcal/mol. The probability of forming stable adsorption state of propene on blue tungsten oxide decreases as the sample temperature increases. At room temperature, the blue tungsten oxide doesn't interact with oxygen significantly. But after raising the temperature to above 300℃, WO2.90 is oxidized into WO3 accompanying with a strong adsorption of oxygen. This implies that the blue tungsten oxide could be used as a promising oxygen getter in the vacuum valves.
The thermal desorption spectra of propene and oxygen adsorbed on blue tungsten oxide WO2.90 have been measured by means of flash heating the sample in ultra high vacuum. It has been discovered that at room temperature only one adsorption state of propene on blue tungsten oxide surface exists, which corresponds to a desorption peak at the temperature around 100℃ appeared in the thermal desorption spectra. The desor- ption parameters determined by the experiment are: n=l (first order desorption) and the activation energy of desorption Ed=10.1 kcal/mol. The probability of forming stable adsorption state of propene on blue tungsten oxide decreases as the sample temperature increases. At room temperature, the blue tungsten oxide doesn't interact with oxygen significantly. But after raising the temperature to above 300℃, WO2.90 is oxidized into WO3 accompanying with a strong adsorption of oxygen. This implies that the blue tungsten oxide could be used as a promising oxygen getter in the vacuum valves.
It is well known from electron optics that spherical aberration and defocus modify the diffraction plane wave function by a phase shifty and the coherent amplitude and phase-contrast transfer functions are cosy and siny. Consequently, the inverse Fourier transforms of cosy and siny are the real and imaginary parts of impulse response. The locations of the zeros and extrema of the amplitude- and phase-contrast transfer functions are presented. These zeros and extrema devide the diffraction plane into a series of annular regions. When the value of the dimensionless defocus is selected as △=N1/2 (N is a positive integer), the integrals of transfer function over corresponding annular regions are equal. Equivalently, their contributions to the central value of the impulse response are of the same value. The conditions for maximizing or minimizing the integrals of cosy on siny (i.e. maximizing or minimizing the central value or intensity of impulse response) has been suggested. In the present paper, the condition for the mean-square optimum approximation of impulse response with the ideal Airy distribution has also been discussed.
It is well known from electron optics that spherical aberration and defocus modify the diffraction plane wave function by a phase shifty and the coherent amplitude and phase-contrast transfer functions are cosy and siny. Consequently, the inverse Fourier transforms of cosy and siny are the real and imaginary parts of impulse response. The locations of the zeros and extrema of the amplitude- and phase-contrast transfer functions are presented. These zeros and extrema devide the diffraction plane into a series of annular regions. When the value of the dimensionless defocus is selected as △=N1/2 (N is a positive integer), the integrals of transfer function over corresponding annular regions are equal. Equivalently, their contributions to the central value of the impulse response are of the same value. The conditions for maximizing or minimizing the integrals of cosy on siny (i.e. maximizing or minimizing the central value or intensity of impulse response) has been suggested. In the present paper, the condition for the mean-square optimum approximation of impulse response with the ideal Airy distribution has also been discussed.
The observation of optical rotary echos by Stark switching in infra-red region is reported. Optical rotary echo is a nutation echo and has a long relaxation time which makes it particularly useful in the study of relaxation process. An improvment of experimental condition has been made and a theoretical calculation of rotary echo is presented.
The observation of optical rotary echos by Stark switching in infra-red region is reported. Optical rotary echo is a nutation echo and has a long relaxation time which makes it particularly useful in the study of relaxation process. An improvment of experimental condition has been made and a theoretical calculation of rotary echo is presented.
This paper discusses the relationship between operator methods and matrix methods in optics. Based on the definition of optical variable operators and the hypothesis that optical operators of linear optical systems are unitary, the relation equation dealing with the relationship between operator methods and matrix methods in optics has been obtained from the general property of linear systems. For a given optical system, its optical operator can be derived from its optical matrix by solving the relation equation. And if the optical operator of a system is given, its optical matrix can also be derived from that equation. Thus the equivalency between operator methods and matrix methods in optics is demonstrated. Finally, the physical significance of the optical operator h has been pointed out.
This paper discusses the relationship between operator methods and matrix methods in optics. Based on the definition of optical variable operators and the hypothesis that optical operators of linear optical systems are unitary, the relation equation dealing with the relationship between operator methods and matrix methods in optics has been obtained from the general property of linear systems. For a given optical system, its optical operator can be derived from its optical matrix by solving the relation equation. And if the optical operator of a system is given, its optical matrix can also be derived from that equation. Thus the equivalency between operator methods and matrix methods in optics is demonstrated. Finally, the physical significance of the optical operator h has been pointed out.
Etch pits on (100) and (001) surface of KDP crystals have been revealed by chemical etchant and optical observations. Based on the distribution and morphology as well as the type of dislocations and other defects on KDP crystals of different qualities, a brief discussion on the formation of the dislocations is given.
Etch pits on (100) and (001) surface of KDP crystals have been revealed by chemical etchant and optical observations. Based on the distribution and morphology as well as the type of dislocations and other defects on KDP crystals of different qualities, a brief discussion on the formation of the dislocations is given.
The phase diagram of the ternary Gd-Co-Cu system with Gd content 34.8 wt% at room temperature has been determined by X-ray diffraction.The isothermal section was found to consist of five singlephase regions (i. e. α, σ,δ,γ and θ),seven two-phase regions (i. e. α+β, β+δ,δ+θ,θ+γ,γ+α,θ+α and σ+θ) and three three-phase regions (i.e.α+β+θ,α+θ+γ and β+θ+δ). No new phase has been observed. X-ray analysis showed that maximum solubility of Cu in Co is about 4wt% and maximum solubility of Gd in β-phase is about 3wt%.
The phase diagram of the ternary Gd-Co-Cu system with Gd content 34.8 wt% at room temperature has been determined by X-ray diffraction.The isothermal section was found to consist of five singlephase regions (i. e. α, σ,δ,γ and θ),seven two-phase regions (i. e. α+β, β+δ,δ+θ,θ+γ,γ+α,θ+α and σ+θ) and three three-phase regions (i.e.α+β+θ,α+θ+γ and β+θ+δ). No new phase has been observed. X-ray analysis showed that maximum solubility of Cu in Co is about 4wt% and maximum solubility of Gd in β-phase is about 3wt%.
The neodymium-nickel binary system has been studied by X-ray diffraction method and differential thermal analysis and the phase diagram determined.In this system, the following eight intermetallic compounds were observed: Nd3 Ni (M. P. 590℃), Nd7Ni3(M. P. 616℃), NdNi (M.P.780℃), NdNi2(decomposes at 940℃),NdNi3 (decomposes at 1030℃), Nd2Ni7 (decomposes at 1234℃), NdNi5(M.P. 1420℃)and Nd2Ni17. Intermetallic compound Nd2Ni17 forms peritectically 1300℃ and decomposes through a eutectoid reaction into Ni and NdNi5 at 1250℃. Five eutectics occur: Nd-Nd3Ni (570℃,～19at%Ni), Nd3Ni-Nd7Ni3 (565℃,～27at%Ni),Nd7Ni3-NdNi (540℃,～35at%Ni),NdNi-NdNi2(720℃,56at%Ni) and Nd2Ni17-Ni (1290℃,91at%Ni). Neither Nd in Ni nor Ni in Nd shows any detectable solid solubility.
The neodymium-nickel binary system has been studied by X-ray diffraction method and differential thermal analysis and the phase diagram determined.In this system, the following eight intermetallic compounds were observed: Nd3 Ni (M. P. 590℃), Nd7Ni3(M. P. 616℃), NdNi (M.P.780℃), NdNi2(decomposes at 940℃),NdNi3 (decomposes at 1030℃), Nd2Ni7 (decomposes at 1234℃), NdNi5(M.P. 1420℃)and Nd2Ni17. Intermetallic compound Nd2Ni17 forms peritectically 1300℃ and decomposes through a eutectoid reaction into Ni and NdNi5 at 1250℃. Five eutectics occur: Nd-Nd3Ni (570℃,～19at%Ni), Nd3Ni-Nd7Ni3 (565℃,～27at%Ni),Nd7Ni3-NdNi (540℃,～35at%Ni),NdNi-NdNi2(720℃,56at%Ni) and Nd2Ni17-Ni (1290℃,91at%Ni). Neither Nd in Ni nor Ni in Nd shows any detectable solid solubility.
It is found that the diffraction, obtained by using X-ray divergent beam technique-back reflection Kossel method, of pure and Ti-diffused LiNbO3 crystals become abnormal in the vicinity of 75℃.The Pseudo-Kossel lines of such crystal planes as (11010), (01110), (0118), (1108), (03312), (33012), are found to be severely distorted but still continuous. The pattern's distortion shows approximately two-fold symmetry about x-plane and therefore the crystal's triad axis of symmetry along x-direction is destroyed.It is also found that the distortions of pseudo-Kossel lines arising from high Bragg angle diffraction planes are smaller than those arising from lower angle diffraction planes.
It is found that the diffraction, obtained by using X-ray divergent beam technique-back reflection Kossel method, of pure and Ti-diffused LiNbO3 crystals become abnormal in the vicinity of 75℃.The Pseudo-Kossel lines of such crystal planes as (11010), (01110), (0118), (1108), (03312), (33012), are found to be severely distorted but still continuous. The pattern's distortion shows approximately two-fold symmetry about x-plane and therefore the crystal's triad axis of symmetry along x-direction is destroyed.It is also found that the distortions of pseudo-Kossel lines arising from high Bragg angle diffraction planes are smaller than those arising from lower angle diffraction planes.
The EXAFS measurement needs to disperse the incident X-ray beam with monochro-mating crystal. Beside the. continuous and some characteristic spectrum from nonsynch-rotron radiation, 'negative peak' sometimes occur. It will distort the signal desired. This paper reports the detailed investigation of the 'negative peak' and the interpretation with X-ray multiple diffraction. Fially, the method to avoid it is discussed.
The EXAFS measurement needs to disperse the incident X-ray beam with monochro-mating crystal. Beside the. continuous and some characteristic spectrum from nonsynch-rotron radiation, 'negative peak' sometimes occur. It will distort the signal desired. This paper reports the detailed investigation of the 'negative peak' and the interpretation with X-ray multiple diffraction. Fially, the method to avoid it is discussed.
We studied the carrier profile tail formed in GaAs materials of 28Si+ implanting into Cr-doped semi-insulating substrate, including the effects of annealing temperature and time. The effects of carrier profile tail on GaAs MESFET output characteristics simulated by computer were in accord with measured results, indicating that the profile tail does make the abnormal output characteristics in MESFET. The origin of profile tail in connection with Si background in GaAs substrate and Cr redistribution during high temperature annealing was discussed.
We studied the carrier profile tail formed in GaAs materials of 28Si+ implanting into Cr-doped semi-insulating substrate, including the effects of annealing temperature and time. The effects of carrier profile tail on GaAs MESFET output characteristics simulated by computer were in accord with measured results, indicating that the profile tail does make the abnormal output characteristics in MESFET. The origin of profile tail in connection with Si background in GaAs substrate and Cr redistribution during high temperature annealing was discussed.
A three-level atom interacting with a strong and a weak monochromatic laser is investigated by means of the dress unitary transformation technique. The two-photon process characteritics is analysed and the fluorescence spectrum of atom is presented, it is shown that they depend on both the intensity of driving field and the detuning.
A three-level atom interacting with a strong and a weak monochromatic laser is investigated by means of the dress unitary transformation technique. The two-photon process characteritics is analysed and the fluorescence spectrum of atom is presented, it is shown that they depend on both the intensity of driving field and the detuning.
In ZnS waveguide thin film, using the possitively mode-looked ps (aser beam and light wave coupler, phase matching between foundamental mode TE3(ω) and second harmonic mode TE3(2ω) has been obtained and third harmonic spectra was also observed. The width of the spectral curve were 1.3 and 1.4? respectively. The conversion efficiency of second harmonic is 1.8×10-3 while the incident foundamental power is 20 MW.
In ZnS waveguide thin film, using the possitively mode-looked ps (aser beam and light wave coupler, phase matching between foundamental mode TE3(ω) and second harmonic mode TE3(2ω) has been obtained and third harmonic spectra was also observed. The width of the spectral curve were 1.3 and 1.4? respectively. The conversion efficiency of second harmonic is 1.8×10-3 while the incident foundamental power is 20 MW.
Degenerate four-wave mixing effect was studied in dye-dissolving liquid crystal iu its nematic phase. Thermal grating was generated after resonant absorption of light by the dye. The anisotropy of signal and thermal grating relaxation time were also studied.
Degenerate four-wave mixing effect was studied in dye-dissolving liquid crystal iu its nematic phase. Thermal grating was generated after resonant absorption of light by the dye. The anisotropy of signal and thermal grating relaxation time were also studied.
We investigate how the pulse number of the set of fluctuations effects the mode-locking. The effects of the length of laser cavity on the mode-locking 'window' and mode-locking threshold are als studies for Nd-glass and Nd: YAG lasers.
We investigate how the pulse number of the set of fluctuations effects the mode-locking. The effects of the length of laser cavity on the mode-locking 'window' and mode-locking threshold are als studies for Nd-glass and Nd: YAG lasers.