By using the reductive perturbation method, the carrier wave modulation propagating in a weakly viscous fluid-filled elastic tube is investigated. It is shown that such a process can be described by equation A_{τ}+iBA_{ξξ}+iC|A|^{2}A+DA=0 and the amplitude of envelope soliton will decrease as it propagates away.

Using Feynman's method of disentangling operators, an exact expression of evolution operator of harmonic oscillator with time-varying frequency is obtained. The parameters in this expression are related to the time-varying frequency directly. Some implications are further investigated, including general form of linear and quadratic invariants and evolution of Wigner function.

The percolation clusters with varying occupy probability were constructed in this paper. Viscous fingering (VF) in percolation cluster, based on the assumption that bond radii are Rayleigh distribution, is investigated by means of successive over-relaxation technique. The fractal dimension for VF in percolation cluster is calculated. The result shows that it can increase fractal dimension of VF as increase of percolation probability of reduce of viscous ratio. VF's fractal dimension of porous media in the limit viscous ratio →∞ is found to be identical with that in diffusion limited-aggregation. We have found that the topology and the geometry of the porous medium have strong effects on the displacement processes and the structure of the VF. We find that the sweep efficiency of the displacement processes mainly depends upon the length of the network system and also on the viscosity ratio. Moreover, the fractional flow of injected fluid as a function of mean saturation is obtained.

Effects of spatial inhomogeneity with symmetric potentials in one-dimensional quantum sine-Gordon model are treated by use of the variational Gaussian wave functional method. The properties of the ground state and the critical point of the system are investigated.

A new model of vertical vibration isolation system is presented in the paper. It is principally constructed by mounting an additional mass on the simplest passive vertical isolator, which can give rise to gravitational positive feedback. By theoretical analyzing and numerical calculating, we come to a conclusion that the resonant frequency is decreased in the new system, which agrees with the result of the experiment.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

We have studied the interface electronic structures and the chemical reaction of the Fe overlayer deposited on S-passivated GaAs(100). The chemical bond and electronic structure are different from Fe/GaAs, and the reaction between As and Fe is weakened by S atoms. This is beneficial to the magnetism in the interface. In the first stage of deposition, Fe clusters is form near S atoms due to the large electronegativity of S. The S atoms remain at the interface with Fe coverage. Magnetic ordering feature is found at a coverage higher than 0.6 nm. According to the large exchange splitting in valence band spectra, we suggest that Fe phase transition from bcc to fcc occurs with increasing coverage.

La_{0.82}Sr_{0.18}MnO_{3} have been investigated. With grain growth, both an evident decrease of magnetization and the lattice distortions have been simultaneously observed. The phenomenon suggests a structure-coupled change of magnetism in the hole-doped manganese perovskite.

Low-frequency internal friction (IF) of SrBi_{2}Ta_{2}O_{9}(SBT) ceramics has been measured at temperatures ranging from 293 to 623 K. Two IF peaks, with their locations around 393 K (P1) and 569 K (P2) (f≈1.58 Hz), respectively, are observed. P1 is found to be associated with a relaxation process with activation energy of 0.97 eV and pre-exponential factor of 3.58×10^{-14} s. Peak shape analyses reveal that P1 can be well described by a broadened Debye peak with the width parameter β from 2.70 to 2.92. The mechanism responsible for P1 is proposed to be relaxation of oxygen vacancies near domain walls(DWs). P2 is considered to arise from viscous motion of DWs since it shows characteristics of static hysteresis type. Comparisons for the IF behavior between SBT and Pb(Zr, Ti)O_{3}(PZT) suggest that in SBT oxygen vacancies are much less localized near DWs than that in PZT. This result provides a possible explanation for the weak DW pinning due to oxygen vacancies in SBT.

According to Judd-Ofelt parameter calculation and energy transfer theory, the cross-relaxation process of the Tm^{3+} ions is investigated. A four-level system of coupled rate equations is established to study the fluorescence dynamics of Tm^{3+} in LiYF_{4} crystal. Attentions are focused on the upconversion luminescence ^{1}G_{4}→^{3}H_{6} (483.0 nm) in Tm^{3+}:LiYF_{4}. The relationship between the avalanche properties (critical pump rate, fluorescence intensity and buildup time) originated by resonant excited state absorption and the doped Tm^{3+} concentration is discussed, and some useful conclusions are drawn.

The thermally cycled samples of Cu-23at%Zn-10at%Al have been studied by means of positron annihilation. It is shown that vacancies and their movement seem to be the leading factors resulting in thermoelastic martensite stabilization based on the fact that stabilization was no longer present and the great decrease of positron parameters after the samples in martensite were thermally cycled.

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