Numerical simulation of supersonic reacting mixing layer

In this paper, the supersonic chemically reacting mixing layer is simulated with the third order ENN scheme, based on the Navier-Stokes equations, containing transport equations of all species. The numerical results show that the thickness of mixing layer increases gradually along the flow direction, and that the Kelvin-Helmholtz instabilities may not exist in mixing layer flows. The project supported by the National Natural Science Foundation of China     

The problems of nonlinear bending for orthotropic rectangular plate with four clamped edges

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Coherent fine scale eddies in turbulence transition of spatially-developing mixing layer

To investigate the relationship between characteristics of the coherent fine scale eddy and a laminar–turbulent transition, a direct numerical simulation (DNS) of a spatially-developing turbulent mixing layer with Re_ω,0 = 700 was conducted. On the onset of the transition, strong coherent fine scale eddies appears in the mixing layer. The most expected value of maximum azimuthal velocity of the eddy is 2.0 times Kolmogorov velocity (u_k), and decreases to 1.2u_k, which is an asymptotic value in the fully-developed state, through the transition. The energy dissipation rate around the eddy is twice as high compared with that in the fully-developed state. However, the most expected diameter and eigenvalues ratio of strain rate acting on the coherent fine scale eddy are maintained to be 8 times Kolmogorov length (η) and :β:γ = −5:1:4 in the transition process. In addition to Kelvin–Helmholtz rollers, rib structures do not disappear in the transition process and are composed of lots of coherent fine scale eddies in the fully-developed state instead of a single eddy observed in early stage of the transition or in laminar flow.     

Understanding the effect of inhomogeneous fuel–air mixing on knocking characteristics of various ethanol reference fuels with RON 100 using rapid compression machine

We investigated the effect of inhomogeneous mixing of a fuel–air mixture in a spark-ignition engine on knocking characteristics and the dependency of the effect on the fuel, especially for various ethanol reference fuels with a fixed RON of 100. We assumed that a locally lean spot and rich spots exist in the end gas owing to inhomogeneous mixing and calculated their thermodynamic states with a multizone spark-ignition engine simulation. Subsequently, the ignition delay around the state was measured using a rapid compression machine at varying temperatures and equivalence ratios. The obtained results were processed to calculate ξ, which is the ratio of sound speed to auto-ignition propagation speed, and $?$, defined as the time required for acoustic front to exit the hot spot divided by the excitation time. Then, we analyzed the knocking occurrence and intensity from the locally lean spot and rich spots based on Zel'dovich and Bradley's ξ–$?$ theory. Our results show that the lean spot has a shorter ignition delay than the stoichiometric mixture (ξ?>?0) regardless of the ethanol content, whereas the rich spot does not (ξ?<?0), implying that only the lean spot can initiate knocking. This is because the temperature of the lean spot is higher than the surrounding mixture owing to its higher specific heat ratio and less charge cooling effect. In addition, the knocking intensity from the lean spot is found to be maximized with ERF0, showing the largest ${\xi }^{?2}$ value. Further analysis was conducted by dividing ξ into the effect of the temperature gradient, ξ_T, and that of the equivalence ratio gradient, ξ_?. Consequently, we found that the magnitude of ξ_T is related to the activation energy of the fuel, while that of ξ_? is determined by the dependency of the pre-heat release characteristics of the fuel on the equivalence ratio.     

基于四波混频过程和线性分束器产生四组份纠缠

多组份纠缠是量子信息处理的重要资源,它的产生通常涉及到许多复杂的线性和非线性过程.本文从理论上提出了一种利用两个独立的四波混频过程和线性分束器产生真正的四组份纠缠的方案,其中,线性分束器的作用是将两个独立的四波混频过程联系起来.首先应用部分转置正定判据研究了强度增益对四组份纠缠的影响,结果表明,在整个增益区域内都存在真正的四组份纠缠,并且随着强度增益的增加,纠缠也在增强.然后研究了线性分束器的透射率对四组份纠缠的影响,发现只要线性分束器的透射率不为0或1,该系统也可以产生真正的四组份纠缠.最后,通过研究该系统可能存在的三组份纠缠和两组份纠缠来揭示该系统的纠缠结构.本文理论结果为实验上利用原子系综四波混频过程产生真正的四组份纠缠提供了可靠的方案.     

Structural and optical properties of CuSe2 nanocrystals formed in thin solid Cu–Se film

This paper describes the structural and optical properties of Cu–Se thin films. The surface morphology of thin films was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Formation of Cu–Se thin films is concluded to proceed unevenly, in the form of islands which later grew into agglomerates. The structural characterization of Cu–Se thin film was investigated using X-ray diffraction pattern (XRD). The presence of two-phase system is observed. One is the solid solution of Cu in Se and the other is low-pressure modification of CuSe₂. The Raman spectroscopy was used to identify and quantify the individual phases present in the Cu–Se films. Red shift and asymmetry of Raman mode characteristic for CuSe₂ enable us to estimate nanocrystal dimension. In the analysis of the far-infrared reflection spectra, numerical model for calculating the reflectivity coefficient of layered system, which includes film with nanocrystalite inclusions (modeled by Maxwell-Garnett approximation) and substrate, has been applied.     

Numerical analysis of enhanced mixing in a Gallay tote blender

The mixing performance of a multi-bladed baffle inserted into a traditional Gallay tote blender is explored by graphic processing unit-based discrete element method software. The mixing patterns and rates are investigated for a binary mixture, represented by two different colors, under several loading profiles. The baffle effectively enhances the convective mixing both in the axial and radial directions, because of the disturbance it causes to the initial flowing layer and solid-body zone, compared with a blender without a baffle. The axial mixing rate is affected by the gap between the baffle and the wall on the left and right sides, and an optimal blade length corresponds to the maximum mixing rate. However, the radial mixing rate increases with the blade length almost monotonically.     

Strong approximation for ρ-mixing sequences

We establish strong invariance principles for sums of stationary ρ-mixing random variables with finite and infinite second moments under weaker mixing rates.Some earlier results are improved.As applications,some results of the law of the iterated logarithm with finite and infinite variance are obtained,also a conjecture raised by Shao in 1993 is solved.     

Nuclear Structure and Electromagnetic Transitions Investigation in Er Isotopes within Framework of Interacting Boson Model

Interacting Boson Model-2(IBM-2)is used to determine the Hamiltonian for Er nuclei.Fit values of parameters are used to construct the Hamiltonian,energy levels and electromagnetic transitions(B(E2),B(M1))multipole mixing ratios(δ(E2/M1))for some even-even Er nuclei and monopole transition probability are estimated.New ideas are used for counting bosons number at N=64 and results are compared with previous works.     

Optical switching and alignment of antiferroelectric liquid crystals containing an azo group

The optical properties of two kinds of photochromic antiferroelectric liquid crystal (AFLC) containing an azo group have been examined. Depending on the substituting group at the chiral centre, these AFLCs showed different photoinduced phase transitions by Ar⁺ laser light irradiation. This phase transition has led to a new form of optical switching controlled by a bias voltage. In addition, it was found that these AFLCs caused an azimuthal photoalignment effect regulated by linearly polarized Ar⁺ laser light irradiation. These phenomena were applied to image storage.