The investigation of coherent structures in the wall region of a supersonic turbulent boundary layer based on DNS database

Through temporal mode direct numerical simulation, flow field database of a fully developed turbulent boundary layer on a flat plate with Mach number 4.5 and Reynolds number Reθ =1094 has been obtained. Commonly used detection meth- ods in experiments are applied to detecting coherent structures in the flow field, and it is found that coherent structures do exist in the wall region of a supersonic turbulent boundary layer. The detected results show that a low-speed streak is de- tected by using the Mu-level method, the rising parts of this streak are detected by using the second quadrant method, and the crossing regions from a low-speed streak to the high-speed one are detected by using the VITA method respectively. Notwithstanding that different regions are detected by different methods, they are all accompanied by quasi-stream-wise vortex structures.     

Phase-averaged waveforms of Reynolds stress in wall turbulence during the burst events of coherent structures

The time sequence signals of instantaneous longitudinal and normal velocity components at different vertical locations in the turbulent boundary layer over a smooth flat plate have been finely measured by constant temperature anemometry of model IFA-300 and X-shaped hot-wire sensor probe in a wind tunnel. The longitudinal and normal velocity components have been decomposed into multi-scales by wavelet transform. The upward eject and downward sweep motions in a burst process of coherent structure have been detected by the maximum energy criterion of identifying burst event in wall turbulence through wavelet analysis. The relationships of phase-averaged waveforms among longitudinal velocity component, normal velocity component and Reynolds stress component have been studied through a correlation function method. The dynamics course of coherent structures and their effects on statistical characteristics of turbulent flows are analyzed. Supported by the National Natural Science Foundation of China (Grant No. 10472081), the Program for New Century Excellent Talents in Universities of Ministry of Education of China, and Tianjin Science and Technology Development Plan (Grant No. 06TXTJJC13800)     

Inflow conditions for spatial direct numerical simulation of turbulent boundary layers

The inflow conditions for spatial direct numerical simulation (SDNS) of turbulent boundary layers should reflect the characteristics of upstream turbulence, which is a puzzle. In this paper a new method is suggested, in which the flow field obtained by using temporal direct numerical simulation (TDNS) for fully developed turbulent flow (only flow field for a single moment is sufficient) can be used as the inflow of SDNS with a proper transformation. The calculation results confirm that this method is feasible and effective. It is also found that, under a proper time-space transformation, all statistics of the fully developed turbulence obtained by both temporal mode and spatial mode DNS are in excellent agreement with each other, not only qualitatively, but also quantitatively. The normal-wise distributions of mean flow profile, turbulent Mach number and the root mean square (RMS) of the fluctuations of various variables, as well as the Reynolds stresses of the fully developed turbulence obtained by using SDNS, bear similarity in nature. Supported by the National Natural Science Foundation of China (Grant No. 90205021), the China Postdoctoral Science Foundation (Grant No. 20060400707), and the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 200328), and partially supported by Liu-Hui Center of Applied Mathematics, Nankai University and Tianjin University     

Quantum secure direct communication over the collective amplitude damping channel

An efficient quantum secure direct communication protocol is presented over the amplitude damping channel. The protocol encodes logical bits in two-qubit noiseless states, and so it can function over a quantum channel subjected to collective amplitude damping. The feature of this protocol is that the sender encodes the secret directly on the quantum states, the receiver decodes the secret by performing determinate measurements, and there is no basis mismatch. The transmission’s safety is ensured by the nonorthogonality of the noiseless states traveling forward and backward on the quantum channel. Moreover, we construct the efficient quantum circuits to implement channel encoding and information encoding by means of primitive operations in quantum computation. Supported by the National Natural Science Foundation of China (Grant Nos. 60873191 and 60821001), the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 200800131016), the Natural Science Foundation of Beijing (Grant No. 4072020), the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601), and the ISN Open Foundation     

Optical bistability and multistability via atomic coherence in the quasi-Λ-type atomic system

The steady-state optical bistability (OB) and optical multistability (OM) behavior in the quasi-Λ-type atomic system driven by a probe field and a coherent coupling field inside a unidirectional ring cavity are shown, and the effects of coupling-field detuning and coupling-field intensity on the OB and OM behavior are investigated. The transition from OB to OM or vice versa is found by varying the detuning of the coherent coupling field or by adjusting the intensity of the coupling field. The influence of the atomic cooperation parameter on the OM behavior is also discussed. Supported by the Natural Science Foundation of Jiangxi of China (Grant No. 2007GZW0819), the National Basic Research Program of China (Grant No. 2005CB724508), and the Foundation of Talent of Jinggang of Jiangxi Province (Grant No. 2008DQ00400)     

Comparison between the 3D numerical simulation and experiment of the bubble near different boundaries

Based on the potential flow theory, the vortex ring is introduced to simulate the toroidal bubble, and the boundary element method is applied to simulate the evolution of the bubble. Elastic-plasticity of structure being taken into account, the interaction between the bubble and the elastic-plastic structure is computed by combining the boundary element method (BEM) and the finite element method (FEM), and a corresponding 3D computing program is developed. This program is used to simulate the three-dimensional bubble dynamics in free field, near wall and near the elastic-plastic structure, and the numerical results are compared with the existing experimental results. The error is within 10%. The effects of different boundaries upon the bubble dynamics are presented by studying the bubble dynamics near different boundaries. Supported by the National Natural Science Foundation of China (Grant No. 50779007), the National Science Foundation for Young Scientists of China (Grant No. 50809018), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070217074), the Defense Advanced Research Program of Science and Technology of Ship Industry (Grant No. 07J1.1.6), and Harbin Engineering University Foundation (Grant No. HEUFT07069)     

Large eddy simulation of city micro-atmospheric environment

Air quality is one of the important conditions for a better residence life in the populated urban area and it is closed related to the micro-atmospheric environment. Atmospheric environment is controlled by air motion with multi-scales in the city, while air flows in the residence area are of micro-scale atmospheric motion. This paper introduces a modern numerical simulation method, i.e. large eddy simulation (LES), for studying micro-atmospheric flows in the city residence area. For the complex flow features in the residence area, the proper application of LES is studied and various numerical methods are compared in order to investigate their effects on the prediction accuracy of micro-atmospheric flows, for instance, roughness elements and immersed boundary method for complex terrain, different subgrid models and so on. The wind field (including turbulence properties) and contaminant dispersion are computed by the proposed method for a model and a realistic residence area, and the numerical results are in good agreement with the experimental measurements. Supported by the National Natural Science Foundation of China (Grant No. 10572073) and Foundation for Development of Science and Technology in Macao (Grant No. 022/2006/A)     

Analysis of the forces acting on the saltating particles in the coupled wind-sand-electricity fields

Based on the theoretical model describing the saltation of sand particles in the coupled wind-sand-electricity fields, the numerical simulations of the forces acting on saltating particles, such as the aerodynamic drag force, Magnus effect, Saffman force and electrostatic force, are analyzed in comparison to the gravity force of the particles in the steady windblown sand movement. Furthermore, the laws of the above forces vary with the friction velocity, the diameter of the sand particle, the initial angular velocity and the lift-off velocity are discussed. Supported by the National Natural Science Foundation of China (Grant Nos. 10772075 and 10772074), the Key Project of the National Natural Science Foundation of China (Grant No.10532040), and the Program for New Century Excellent Talents in University (Grant No. NCET-04-0979)     

Structures and electronic properties of SimN8-m（0 〈 m 〈 8） clusters： a density functional theory study

The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si N-Si-N... alternative chains. The bond lengths of single Si-N bonds are very close to the corresponding values of the bulk and other SiN clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.     

Self-organization effect in poly（3-hexylthiophene）： methanofullerenes solar cells

This paper studies the self-organization of the polymer in solar cells based on poly（3-hexylthiophene）： [6, 6]-phenyl C61-butyric acid methyl ester by controlling the growth rate of active layer. These blend films are characterized by UV-vis absorption spectroscopy, charge-transport dark J - V curve, x-ray diffraction pattern curve, and atomic force microscopy. The results indicate that slowing down the drying process of the wet films leads to an enhanced selforganization, which causes an increased hole transport. Increased incident light absorption, higher carrier mobility, and balanced carrier transport in the active layer explain the enhancement in the device performance, the power conversion efficiency of 3.43% and fill factor up to 64.6% are achieved under Air Mass 1.5, 100 mW/cm^2.     

Strong optical transmission through the ellipsoid metal-film nanohole arrays

The transmission characteristics of a metallic film with subwavelength ellipsoid nanohole arrays are investigated by using the three-dimensional finite-difference time-domain (3D-FDTD) method. The extraordinary transmission is attributed to the collaboration of localized waveguide resonance and surface plasmon resonance. The influences of the lattice constant and the hole shape on the transmission are studied. By analyzing the picture of electric field and electromagnetic energy distribution, we show the mechanisms of the two different resonances: Localized waveguide resonance mode can be confined inside the ellipsoid holes region, while electric field and electromagnetic energy are localized separately at the two ends of ellipsoid holes for the surface plasma resonance mode. Supported by the National Natural Science Foundation of China (Grant No. 60708014), the Distinguished Youth Foundation of Hunan Province (Grant No. 03JJY1008), the Science Foundation for Post-doctorate of China (Grant No. 2004035083), and the Natural Science Foundation of Hunan Province (Grant No. 06JJ20034)     

The fractal measurement of experimental images of supersonic turbulent mixing layer

Flow visualization of supersonic mixing layer has been studied based on the high spatiotemporal resolution Nano-based Planar Laser Scattering(NPLS) method in SML-1 wind tunnel. The corresponding images distinctly reproduced the flow structure of laminar,transitional and turbulent region,with which the fractal measurement can be implemented. Two methods of measuring fractal dimension were introduced and compared. The fractal dimension of the transitional region and the fully developing turbulence region of supersonic mixing layer were measured based on the box-counting method. In the transitional region,the fractal dimension will increase with turbulent intensity. In the fully developing turbulent region,the fractal dimension will not vary apparently for different flow structures,which em-bodies the self-similarity of supersonic turbulence.     

Comparing the efficiencies of different detect strategies in the ping-pong protocol

The way to compare the efficiencies of different detect strategies (DSs) in the “ping-pong” protocol is studied. The trade-off between information gain and disturbance is calculated and compared for different DSs. The comparison result primely tallies with our intuitional analysis. It is shown that the analysis of this trade-off is a feasible way to compare the performances of different DSs in theory. Supported by the National High Technology Research and Development Program of China (Grant No. 2006AA01Z419), the National Natural Science Foundation of China (Grant Nos. 90604023 and 6087319), the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601), the Natural Science Foundation of Beijing (Grant No. 4072020), and the ISN Open Foundation.     

Generation of two-mode SU(2) and SU(1,1) cat states in a two-dimensional anisotropic ion trap

A scheme is proposed for generating two-mode SU(2) and SU(1,1) cat states for an ion trapped in a two-dimensional (2D) anisotropic harmonic potential trap. In the scheme the ion is excited by two laser beams in the trap plane. After an interaction time, a measurement on the internal state collapses the ion motion onto a superposition of two SU(2) or SU(1,1) coherent states depending on the laser frequencies. This work was supported by the National Natural Science Foundation of China under Grant No. 60008003, Fujian Provincial Natural Science Foundation of China under Grant Nos. K20004 and F0110027, and Funds from Fuzhou University.     

Revisiting the security of quantum dialogue and bidirectional quantum secure direct communication

From the perspective of information theory and cryptography, the security of two quantum dialogue protocols and a bidirectional quantum secure direct communication (QSDC) protocol was analyzed, and it was pointed out that the transmitted information would be partly leaked out in them. That is, any eavesdropper can elicit some information about the secrets from the public annunciations of the legal users. This phenomenon should have been strictly forbidden in a quantum secure communication. In fact, this problem exists in quite a few recent proposals and, therefore, it deserves more research attention in the following related study. Supported by the National High Technology Research and Development Program of China (Grant No. 2006AA01Z419), the National Natural Science Foundation of China (Grant Nos. 90604023 and 60373059), the National Research Foundation for the Doctoral Program of Higher Education of China (Grant No. 20040013007), the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601), the Natural Science Foundation of Beijing (Grant No. 4072020) and the ISN Open Foundation     

First-principles study of interphase Ni3Sn in Sn--Ni alloy for anode of lithium ion battery

This paper investigates the mechanism of Li insertion into interphase Ni3Sn in Ni-Sn alloy for the anode of lithium ion battery by means of the first-principles plane-wave pseudopotential. Compared with other phases, it is found that the Ni3Sn has larger relative expansion ratio and lower electrochemical potential, with its specific plateaus voltage around 0.3 eV when lithium atoms are filled in all octahedral interstitial sites, and the relative expansion ratio increasing dramatically when the lithiated phase transits from octahedral interstitial sites to tetrahedral interstitial sites. So this phase is a devastating phase for whole alloy electrode materials.     

Recent progress in medical photonics

The field of medical photonics is rapidly expanding, and a wide variety of optical technologies and instruments have recently been developed for diagnostic, therapeutic and basic science applications in medicine. This review presents the recent advances and application of medical photonics, and the obtained results from our laboratory are highlighted. Finally, the challenges and future prospects for the transition from technological exploration to clinical studies are discussed. Supported by the National Natural Science Foundation of China (Grant No. 60678054), the PhD Program Foundation of Ministry of Education (Grant No. 200803940001), the Key Grants from Ministry of Education (Grant No. 209063), and the Fujian Provincial Natural Science Foundation (Grant No. 2008J0001)     

Generalized two-mode coherent-entangled state with real parameters

The coherent-entangled state |α, x; λ> with real parameters λ is proposed in the two-mode Fock space, which exhibits the properties of both the coherent and entangled states. The completeness relation of |α, x; λ> is proved by virtue of the technique of integral within an ordered product of operators. The corresponding squeezing operator is derived, with its own squeezing properties. Furthermore, generalized P-representation in the coherent-entangled state is constructed. Finally, it is revealed that superp...     

Optimal controlled teleportation via several kinds of three-qubit states

The probability of successful controlled teleportation of an unknown qubit using a general three-particle state is investigated. The analytic expressions of maximal probabilities via several kinds of tripartite states are given, including a tripartite Greenberger-Horne-Zeilinger state and a tripartite W-state. Supported by the National Natural Science Foundation of China (Grant No. 10671054), the Key Project of Science and Technology Research of Ministry of Education of China (Grant No. 207011), and the Natural Science Foundation of Hebei Province, China (Grant No. 07M006)     

Study on cerebral microcirculation by Optical Doppler Tomography

Optical Doppler Tomography (ODT) provides a novel method to measure the blood flow velocity in vessels with the diameter at micrometer scale. Rats with cranial window are used as a model, and the changes in the blood flow velocity of cerebral arterioles in sensory cortex are measured in real time with an established ODT system, under electrical stimulation and drug administration. The results show significant differences in the blood flow velocity between experimental groups and control groups, demonstrating the feasibility of ODT in the cerebral microcirculation study. Compared with the conventional Doppler ultrasound, ODT provides much higher spatial resolution, and thus holds a promising future in the application of the cerebral microcirculation study, especially in the observation of the blood flow velocity in micrometer scale vessels. Supported by the National Hi-Tech Research and Development Program of China (863 Program)(Grant No. 2006AA02Z4E0), the National Natural Science Foundation of China (Grant Nos. 60378041, 60478040, 60878057 and 30770685), the Program for New Century Excellent Talents in University (Grant No. NCET-04-0528), and the Opening Project of MOE Key Laboratory of Laser Life Science, South China Normal University