The fast expansion processes in a spherically symmetrical laser-plasma are investigated. The analytic expressions for the density, velocity and energy scaling law of fast ions under ambipolar acceleration are found. Explanations are given on various possible mechanisms which are responsible for the formation of the multipeaked distribution of ion kinetic energies.
The electron cyclotron maser instability is analyzed for the following case, in which a relativistic monoenergetic electron beam is injected into a background plasma, but the beam direction is initially oblique to the ambient magnetic field. We consider that the electron plasma frequency is comparable to the electron cyclotron frequency associated with the external magnetic field and study the situation: (1) the background plasma density n0 is much larger than that of the suprathermal electron ns and (2) n0s. The relativistic effects destablized the o and x mode with frequencies respectively in the vicinity of the fundamental and the second harmonic of the electron cyclotron frequencies. The growth rates of both modes are computed and discussed.
The low-temperature magnetizations of liquid-quenched Au-Ni alloys containing 42 to 55 at% Ni have been measured in an uniform magnetic field (2 to 70kOe) using a motor-driven vibrating sample magnetometer. The spontaneous magnetic moments at 1.5 K were obtained. And the Curie temperatures were determined from Arrott-Noa-kes plots. The measured magnetic moments are first compared with the average moments calculated from Perrier nearestneighbor model. Furthermore, we not only consider the Ni nearest neighbors but also the Ni second-nearest neighbors. The simple model of an environment-dependent moment is presented. It is assumed that one Ni atom has a moment μNi=0.606 μs if surrounded by at least 11 Ni atoms as nearest and second-nearest neighbors (the numbers of the nearest and the second-nearest neighbor are 18 for fee structure), and no moment if not. The calculated values from this model fit the measured values well. The existence of spin clusters and their interactions are discussed. The averagevalues of the internal field μBH/kB, which present the ferromagnetic interaction betweenspin clusters, are estimated.
The M?ssbauer spectra of the ferrite system, Li(0.5(1-x))ZnxFe(2.5-0.5x)O4, were studied at 77 K, 195 K and room temperature in an external magnetic field parallel to the gamma-ray direction. With increasing x and decreasing temperature, the second and the fifth lines of the six magnetic splittings were observed to become clearer, which proves convincingly the existence of canting of the moment of Fe3+ populated in the (B)-sublattice of the LiZn-ferrites. The agreement between magnetizations calculated on the basis of M?ssbauer parameters and measured by the magnetic experiment is satis-factory.
A lot of numerical investigation of equations of rf-biased Josephson junctions is carried out, in which the interference term is included in current-phase relation. Chaotic behavior, sequence of period-doubling bifurcations, inverse sequence of chaotic band and intermittent chaos are found seperately in various parameter regions. The convergent factor δ n of 2n Psequence and the ratio Φ(k)/Φ(k+1) are calculated, where Φ(k) is the average height of the peaks corresponding to 2kP in the power spectrum. We also study the symmetry possessed by period solutions and its relation to the nature of approach to chaos
Numerical investigations of a differential equation describing a rf-biased Josephson junction, in which the interference term current is included, are carried out in some parameter region. The existanee of the intermittant transition to chaos is obtained and the critical exponent of the scaling law is determined in agreement with theoretical predictions. Furthermore, the Lyapunov exponent is calculated for several parameters, then the fractal dimension of strange attraetor dL is obtained, its dependence on the Lyapunov exponent is defined by Kaplan and Yorke. In addition, the Kolmogorov capacity of strange attractor dc is also calculated by box-counting algorithm. Such calculated values of dL and dc are close to each other as expected.
In this paper, a new method for determining the crystallite size from line profile analysis is presented. The diffraction line profiles are fitted by weighted Gauss-Cau-chy combination functions. By using Fourier transform method, the integral width of pure physical brodening function f(x) can be obtained directly without assumption about the profile f(x). The method is more accurate, simple and convenient than the usually used methods of approximate functions, and the artificial and arbitrary nature of the assumption about function f(x) are avoided.
In studying the kinetics of crystal growth from the melt, it is extremely important to measure the crystallization front temperature. In order to carry out in situ observations of growth around room-temperature, a thermally regulating stage on polarized-light microscope was constructed. The temperature at the crystallization front of salol was measured by a c.c, thermocouple with diameter 25 μm. The results of measurement showed that using present apparatus, the rate of latent heat removal was constant in a supercooling stationary melt in the range of △T<3.0℃. The increament of temperature at the front was about 1% of the supercooling in the melt bulk.The thermally regulating stage we designed can be useful in the study of the kina-tics of crystal growth.
In the Li2O-B2O3-SiO2 glasses with Li2O≥30 mol%, substitution of Li2O for B2O3 or SiO2 leads to increase the amount of borate and silicate groups with non-bridging oxygen in glass network; while substitution of B2O3 for SiO2 leads to increase the amount of borate groups with or without non-bridging oxygen and silicate groups with non-bridging oxygen.
In this paper, on the basis of providing wave front solutions to Schl?gl model of chemical reaction concerning first order phase transition, the wave profiles describing the concentration distributions in critical nuclei and bubbles are studied by means of a perturbation-matching method and the approximate values of the radii of nuclei and bubbles are found.
The γ-Fe2O3 magnetic powder samples with Co-doping prepared by different technological process and some other magnetic powder products were studied by means of M?ssbauer effect of 57Fe, magnetism measurements and chemical analysis. The experimental results indicate that the changes of coercivity are related to microstructure, this is shown in the M?ssbauer spectra.
Through the examination of L12 type superconductors, we obtained the expression for the superconducting critical temperature Tc of L12 type superconductors: Tc=(15.9TBV(B)GA)/(M1/2 V(L12)GB) where TB is the superconducting critical temperature of pure B, V(B) is the atomie volume of pure B, V (L12) is the average atomic volume of the L12 type compound, M is the average atomic wight of the compound, and GA ,GB are Gordy electronegative values.
Measurements of the variation of ultrasonic second harmonic wave amplitudes with the specimen temperatures and the fundamental wave amplitudes are made in molecular crystal naphthalene by using a modified pulse echo technique. Explanation of the experimental results is given and problems for further investigation are suggested.
Based upon the geometrical and topological method, the conformal anomaly for pure gravity in a curved space-time is discussed, and a new expression αεabcdΩabΛΩcd+βεabcdHabΛHcd of the conformal anomaly for pure gravity is obtained, where α, βare two arbitrary constants,Ωab and Hab are Riemann curvature 2-form and eonformal invariant curvature 2-form respectively introduced by Thomas. In the expression the first term is proportional to Euler class, the second term contains not only the ordinary Weyl tensor square but also the other conformal invariants.
In this work, we solved the decoupling problem of the Dirac equation with non-zero rest mass in a Kerr-Newman-De Sitter background. The physical solutions of the Dirac equation with non-zero rest mass are found outside the event horizon of Kerr-Newman-De Sitter space-time by a proper transformation. The Hawking thermal spectra formula is also dirived. The problem of the Hawking evaporation of Dirac particles in Kerr-Newman-De Sitter black hole background is thus solved.
UV coherent radiation at 327 nm, 328 nm, 330 nm and 333 nm is generated by four-wave parametric process in sodium vapour. The spectral characteristics is examined. The signal at 333 mn has narrower line width and wider tunable range. So it is possible to use it as a coherent UV source.
Raman spectrum of pyridine has been investigated at high hydrostatic pressure, the pressure behavior of the vibration modes below and above phase transitions has been studied. A kind of crystalline-plastic phase transition was observed near 60 kbar. A satellite peak at the high frequency side of the ring breathing mode 992cm-1 was detected, which shifted more rapidly to ward high frequency with pressure. It is supposed to be the ring breathing mode of adsorbed (interface) molecules on the surface of ruby particles which was used for pressure calibration. The satellite is extremely enhanced, possibly by a mechanism of Mie structure resonance scattering.
The ethanol media is pumped by a 5321? single laser pulse of 200 ps duration. The backward Stokes pulse of 14 ps duration and the forward Stokes pulse of 26 ps duration are obtained simultaneously. Theoretieal discussion is also given in this paper.
The conduction charateristics of Na-β(β″)-Al2O3 containing (1-10wt%) fine carbon particles have been investigated. The study shows that the samples containing less than 6 wt% of carbon are still fast ionic conductors and their conductivity is one to two orders of magnitude higher than that of pure Na-β(β″)-Al2O3. The electrical parameters of the samples, such as the bulk resistance, grain boundary resistance, double layer capacitance and leakage current resistance vary with content of carbon. These influences of carbon have been discussed here in some detail. The measurement of conductivity in temperature range from -40℃ to 80℃ shows that Na-β(β″)-Al2O3 containing less than 6 wt% of carbon are good materials for making double layer capacitor.
The microscopic defects in AlPO4 crystals have been studied by means of X-Ray diffraction topography. It was found that the major defects in these crystals are growth layers, precipitaties and dislocations. The density of dislocations is maximum near the crystal surface, and is less in the center of the crystal. The dislocation originates in thermal stress and the latticdistortion induced by the precipitaties or growth layers. The Burgers vector of most of dislocations is of the type b=(a+c) 〈1123〉, and that of the others is b=a. The relationship between growth conditions and crystal defects are analysed. We think that for improving the perfection of crystals, it is important to control temperature fluctuation during crystal growth, and especially the cooling rate after the growth process.