Research on the Correlation of the Fluctuating Density Gradient of the Compressible Flows

This work is to study a role of the fluctuating density gradient in the compressible flows tbr the computational fluid dynamics （CFD）. A new anisotropy tensor with the fluctuating density gradient is introduced, and is used for an invariant modeling technique to model the turbulent density gradient correlation equation derived from the continuity equation. The modeling equation is decomposed into three groups proportional to the mean velocity, proportional to the mean strain rate, and proportional to the mean density. The characteristics of the correlation in a wake are extracted from the results by the two dimensional direct simulation, and shows the strong correlation with the vortices in the wake near the body. Thus, it can be concluded that the correlation of the density gradient is a significant parameter to describe the quick generation of the turbulent property in the compressible flows.

Competition of Quantum Anomalous Hall States and Charge Density Wave in a Correlated Topological Model

We investigate the topological phase transition driven by non-local electronic correlations in a realistic quantum anomalous Hall model consisting of d_(xy)–d_(x^(2)-y^(2)) orbitals. Three topologically distinct phases defined in the noninteracting limit evolve to different charge density wave phases under correlations. Two conspicuous conclusions were obtained: The topological phase transition does not involve gap-closing and the dynamical fluctuations significantly suppress the charge order favored by the next nearest neighbor interaction. Our study sheds light on the stability of topological phase under electronic correlations, and we demonstrate a positive role played by dynamical fluctuations that is distinct to all previous studies on correlated topological states.

Plasma Model of Generation and Slip of Linear Defects in Crystalline Materials

In dielectrics and semiconductors, a plasma model of the generation and slip of dislocations is considered, where under shock loads in a generalized space of rectangular pulses an alternating field forms a distribution of pairs of photoelectrons and cations;these electrons with velocities Ve create δ-collisions with cold plasma from free electrons and holes with masses me and mh (mh ≫ me), they emit and absorb longitudinal electron plasma waves whose phase velocities wpw / kpw are close to or are equal to the velocities Ve, while the frequencies wpw and wave numbers kpw of the wave packet of plasma waves are complex, the short-wave components of this wave packet at kpw ⋅ ae ≫ 1 (ae -Debye screening radius) decay in the core linear defect, and its long-wavelength components propagate in the region of the medium surrounding the core of the defect at kpw ⋅ ae <≅ 1. When a defect is generated, the distribution of cations under the influence of the internal Coulomb field shifts to the region of the first peak (protrusion) of the electron plasma wave, thereby forming a vacancy valley. When sliding under the influence of an external electric field, a cationic plasma wave consisting of a vacancy valley and two cationic protrusions moves against the background of an additional potential relief created by an electron plasma wave near the core of the defect. It has been shown that δ-collisions create flows of dynamic large-scale correlations of plasma fluctuations in the form of asymptotics of different-time correlators of density and potential fluctuations as t → +∞.

The effect of a layer of varying density on spatial correlation of sea-bottom backscattering signal

The research is about the effect of a layer of varying density of sea-bottom sediments on spatial correlation of sea-bottom backscattering. The relationship between scattering cross section and spatial correlation is that backscattering cross section decreases quickly and the spatial correlation becomes stronger as the incident angle increases. Therefore, the density- depth profile is introduced into sea-bottom high-frequency backscattering echo model, which is used to simulate sea-bottom backscattering and calculate the function of spatial correlation. The influence of the density gradient on spatial correlation of sea-bottom backscattering is investigated by analyzing the relations between vertical gradient of density and the scattering cross section. As can be seen from the simulation results, the impact of the density gradient on the spatial correlation is found more significant. While the density gradient increases, the scattering cross-section and the radius of the spatial correlation broaden, the spatial correlation becomes stronger. At the same time, the scattering cross-section decreases more quickly as the incident angle increases.

Deuterium NMR Studies on the Orientational Order Generated in Strained Rubbers

The present paper deals with the induced orientational order of the probe molecules dissolved in the uniaxially strained rubbers measured by using deuterium NMR. The distinctive dependence of the quadrupolar splitting on the swelling, elongation and crosslinking density was observed. The orientational order arising from the correlation between chain segments decreases with the increase of the numbers of both links between junctions and solvent molecules around segments.

Cyclostationary Modeling of Surface Electromyography Signal During Gait Cycles and Its Application for Cerebral Palsy Diagnosis

Cerebral palsy(CP) is a group of permanent movement disorders that appear in early childhood.The electromyography(EMG) signal analysis and the gait analysis are two most commonly used methods in the clinic. In this paper, a cyclostationary model of the EMG signal is proposed. The model can combine the aforementioned two methods. The EMG signal acquired during the gait cycles is assumed to be cyclostationary due to the physiological characteristics of the EMG signal production. Then, the spectral correlation density is used to analyze the cyclic frequency(corresponding to the gait cycles) and spectral frequency(the frequency of EMG signal) in a waterfall representation of the two kinds of frequencies. The experiments show that the asymptomatic(normal) subjects and symptomatic subjects(with CP) can be distinguished from the spectral correlation density in a range of cyclic frequencies.