Research of the rapid pressure-strain correlation model in the rapid distortion limit

Even though a number of rapid pressure-strain models have been suggested and successfully tested for different flow situations by various authors,the model proposals still exhibit some apparent deficiencies when subjected to the flows with rapid distortion. From Mansour's relatively straightforward rapid distortion analysis,if an initially anisotropic flow undergoes a purely rapid rotation,the anisotropy measures will exhibit the behavior of the damped oscillations. Within the current framework of modeling the rapid pressure-strain correlation,i.e.,the models based on the assumption that the M-tensor for the rapid pressure-strain term is expand-able in the Reynolds-stress anisotropy tensor alone,all the model predictions fail to give the damped oscillations in the turbulence anisotropy. In the case of initially isotropic turbulence subjected to rapid distortion,Sj?gren and Johansson showed that all the existing rapid pressure-strain models would deliver the identical path in the anisotropy-invariant map for both homogeneous plane strain and shear flows. The rapid distortion analysis shows two distinct curves reflecting different flow physics. In this work,we try to present a possible way to create a system that can overcome these deficiencies with the aid of the rapid distortion theory (RDT).     

An Improved Car-Following Model for Multiphase Vehicular Traffic Flow and Numerical Tests

This paper attempts to introduce an improved difference model that modifies a car-following model, which takes the next-nearest-neighbor interaction into account. The hnprovement of this model over the previous one lies in that it performs more realistically in the dynamical motion for small delay time. The traffic behavior of the improved model is investigated with analytic and numerical methods with the finding that the new consideration could further stabilize traffic flow. And some simulation tests verify that the proposed model can demonstrate some complex physical features observed recently in real traffic such as the existence of three phases： free flow, coexisting flow, and jam flow; spontaneous formation of density waves; sudden flow drop in flow-density plane; traffic hysteresis in transition between the free and the coexisting flow. Furthermore, th.e improved model also predicts that the stable state to relative density in the coexisting flow is insusceptible to noise.     

Yield estimation of metallic layers in integrated circuits

In the existing models of estimating the yield and critical area, the defect outline is usually assumed to be circular, but the observed real defect outlines are irregular in shape. In this paper, estimation of the yield and critical area is made using the Monte Carlo technique and the relationship between the errors of yield estimated by circular defect and the rectangle degree of the defect is analysed. The rectangular model of a real defect is presented, and the yield model is provided correspondingly. The models take into account an outline similar to that of an original defect, the characteristics of two-dimensional distribution of defects, the feature of a layout routing, and the character of yield estimation. In order to make the models practicable, the critical area computations related to rectangular defect and regular (vertical or horizontal) routing are discussed. The critical areas associated with rectangular defect and non-regular routing are developed also, based on the mathematical morphology. The experimental results show that the new yield model may predict the yield caused by real defects more accurately than the circular model. It is significant that the yield is accurately estimated using the proposed model for IC metals.     

A velocity-difference-separation model for car-following theory

We introduce a velocity-difference-separation model that modifies the previous models in the literature. The improvement of this new model over the previous ones lies in that it not only theoretically retains many strong points of the previous ones, but also performs more realistically than others in the dynamical evolution of congestion. Furthermore, the proposed model is investigated with analytic and numerical methods, with the finding that it can demonstrate some complex physical features observed in real traffic such as the existence of three phases: free flow, synchronized flow, and wide moving jam; sudden flow drop in flow-density plane; and traffic hysteresis in transition between the free and the synchronized flow.     

The effect of ACC vehicles to mixed traffic flow consisting of manual and ACC vehicles

This paper studies the effect of adaptive cruise control （ACC） system on traffic flow by using simulations. The multiple headway and velocity difference （MHVD） model is used to depict the motion of ACC vehicles, and the simulation results are compared with the optimal velocity （OV） model which is used to depict the motion of manual vehicles. Compared the cases between the manual and the ACC vehicle flow, the fundamental diagram can be classified into four regions： I, II, III, IV. In low and high density the flux of the two models is the same; in region II the free flow region of the MHVD model is enlarged, and the flux of the MHVD model is larger than that of the OV model; in region III serious jams occur in the OV model while the ACC system suppresses the jams in the MHVD model and the traffic flow is in order, but the flux of the OV model is larger than that of the MHVD model. Similar phenomena also appeared in mixed traffic flow which consists of manual and ACC vehicles. The results indicate that ACC vehicles have significant effect on traffic flow. The improvement induced by ACC vehicles decreases with the increasing proportion of ACC vehicles.     

Investigation of the fluid flow in an isolated rotor-stator system with a peripheral opening

This paper deals with an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotor and a stator. The system is not subjected to any superimposed radial flow. The periphery of the cavity is opened to the atmosphere so that the solid body rotation for infinite discs is not always observed. Emphasis was placed on develop- ment of an asymptotic approach and a step-by-step method to compute the radial distribution of the core swirl ratio and the static pressure on the stator side. The theory also includes the radial and axial velocities in the core region. The numerical simulation has been conducted with the commercial CFD code Fluent 6.1. The k- SST turbulence model is used, with the assumption of 2D-axisymmetric and steady flow. CFD validations have been performed by comparison of the numerical results with the corresponding theoretical results. Numerical and experimental results are in good agreement with analytical solutions.     

Numerical investigation of non-local electron transport in laser-produced plasmas

Non-local electron transport in laser-produced plasmas under inertial confinement fusion (ICF) conditions is studied based on Fokker-Planck (FP) and hydrodynamic simulations. A comparison between the classical Spitzer--H\"arm (SH) transport model and non-local transport models has been made. The result shows that among those non-local models the Epperlein and Short (ES) model of heat flux is in reasonable agreement with the FP simulation in overdense region. However, the non-local models are invalid in the hot underdense plasmas. Hydrodynamic simulation is performed with the flux limiting model and the non-local model, separately. The simulation results show that in the underdense region of the laser-produced plasmas the temperature given by the flux limiting model is significantly higher than that given with the non-local model.     

Quintessence models with an oscillating equation of state and their potentials

In this paper, we investigate the quintessence models with an oscillating equation of state (EOS) and its potentials. From the constructed potentials, which have an EOS of $\omega_{\phi}=\omega_0+\omega_1\sin z$, we find that they are all the oscillating functions of the field $\phi$, and the oscillating amplitudes decrease (or increase) with $\phi$. From the evolutive equation of the field $\phi$, we find that this is caused by the expansion of the universe. This also makes it very difficult to build a model whose EOS oscillates forever. However one can build a model with EOS oscillating for a certain period of time. Then we discuss three quintessence models, which are the combinations of the invert power law functions and the oscillating functions of the field $\phi$. We find that they all follow the oscillating EOS.     

Dark count in single-photon avalanche diodes:A novel statistical behavioral model

Dark count is one of the inherent noise types in single-photon diodes,which may restrict the performances of detectors based on these diodes.To formulate better designs for peripheral circuits of such diodes,an accurate statistical behavioral model of dark current must be established.Research has shown that there are four main mechanisms that contribute to the dark count in single-photon avalanche diodes.However,in the existing dark count models only three models have been considered,thus leading to inaccuracies in these models.To resolve these shortcomings,the dark current caused by carrier diffusion in the neutral region is deduced by multiplying the carrier detection probability with the carrier particle current at the boundary of the depletion layer.Thus,a comprehensive dark current model is constructed by adding the dark current caused by carrier diffusion to the dark current caused by the other three mechanisms.To the best of our knowledge,this is the first dark count simulation model into which incorporated simultaneously are the thermal generation,trap-assisted tunneling,band-to-band tunneling mechanisms,and carrier diffusion in neutral regions to evaluate dark count behavior.The comparison between the measured data and the simulation results from the models shows that the proposed model is more accurate than other existing models,and the maximum of accuracy increases up to 31.48%when excess bias voltage equals 3.5 V and temperature is 50℃.     

Turbulence modulation model for gas–particle flow based on probability density function approach

The paper focuses on the turbulence modulation problem in gas–particle flow with the use of probability density function(PDF) approach. By means of the PDF method, a general statistical moment turbulence modulation model without considering the trajectory difference between two phases is derived from the Navier–Stokes equations. A new turbulence production term induced by the dispersed-phase is analyzed and considered. Furthermore, the trajectory difference between two media is taken into account. Subsequently, a new k–ε turbulence modulation model in dilute particle-laden flow is successfully set up. Then, the changes to several terms, including the turbulence production, dissipation, and diffusion terms, are well described consequently. The promoted model provides a more probable explanation for the modification of particles on the turbulence. Finally, we applied the model to simulate a gas–particle turbulence flow case in a wall jet, and found that the simulation results agree well with the experimental data.     

Elastic collisions of sulfur and hydrogen in their ground states at low temperatures and spectroscopic parameters of SH（X^2∏） radical

This paper constructs the interaction potential of the SH（X^2∏） radical by using the coupled-cluster singlesdoubles-approximate-triples theory combining the correlation-consistent quintuple basis set augmented with the diffuse functions, aug-cc-pV5Z, in the valence range. Employing the potential, it accurately determines the spectroscopic parameters. The present De, Re, ωe, ωeχe, ae and Be values are of 3.7767eV, 0.13424nm, 2699.846 cm^-1, 47.7055 cm^-1, 0.2639cm^-1 and 9.4414 cm^-1, respectively, which are in excellent agreement with those obtained from the measure- ments. A total of 19 vibrational states has been found when J = 0 by solving the radial SchrSdinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which are in good accord with the experimental results. The total and various partial-wave cross sections are computed for the elastic collisions of sulfur and hydrogen in their ground states at low temperatures when two atoms approach each other along the SH（X^2∏） potential energy curve. Over the impact energy range from 1.0×10^-11 to 1.0×10^-4 a.u., eight shape resonances have been found in the total elastic cross sections. For each shape resonance, the resonant energy is accurately calculated. Careful investigations have pointed out that these resonances result from the 1 = 0, 1, 2, 3, 4, 6, 7, 8 partial-wave contributions.     

Spontaneous magnetostriction of Y2Fe16Al compound

The structure and magnetic properties of Y₂Fe₁₆Al compound have been investigated by means of x-ray diffraction and magnetization measurements. The Y₂Fe Fe₁₆Al compound has a hexagonal Th$_{2}$Ni$_{17}$-type structure. Negative thermal expansion was found in Y₂Fe₁₆Al compound in the temperature range from 332 to 438K by x-ray dilatometry. The coefficient of the average thermal expansion is \alpha =-3.4\times 10^-5K^-1. The spontaneous magnetostrictive deformations from 293 to 427K have been calculated based on the differences between the experimental values of the lattice parameters and the corresponding values extrapolated from the paramagnetic range. The result shows that the spontaneous volume magnetostrictive deformation \textit{$\omega $}$_{\rm S}$ decreases from 5.4$\times $10^-3to near zero with temperature increasing from 293 to 427K, the spontaneous linear magnetostrictive deformation \textit{$\lambda $}$_{\rm c}$ along the $c$ axis is much larger than the spontaneous linear magnetostrictive deformation \textit{$\lambda $}$_{\rm a}$ in basal-plane in the same temperature range except near 427K.     

Enhanced optical nonlinear absorption of graded Au--TiO2 composite films

This paper reports that single-layer and graded Au-TiO2 granular composite films with Au atom content 15%- 66% were prepared by using reactive co-sputtering technique. The third-order optical nonlinearity of single-layer and graded composite films was investigated by using s- and p-polarized Z-scans in femtosecond time scale. The nonlinear absorption coefficient βeff of single-layer Au-TiO2 films is measured to be -2.3×10^3-0.76×10^3 cm/GW with Au atom content 15%-66%. The βeff value of the 10-layer Au-TiO2 graded film is enhanced to be -2.1×10^4cm/GW calculated from p-polarized Z-scans, which is about ten times the maximum βeff of single-layer films. Broadened response in the wavelength region 730-860 nm of the enhanced optical nonlinearity of graded Au-TiO2 composite films was also investigated.     

Elastic collisions between Si and D atoms at low temperatures and accurate analytic potential energy function and molecular constants of the SiD（χ^2П） radical

Interaction potential of the SiD(X2Π) radical is constructed by using the CCSD(T) theory in combination with the largest correlation-consistent quintuple basis set augmented with the diffuse functions in the valence range. Using the interaction potential, the spectroscopic parameters are accurately determined. The present D0, De, Re, ωe, αe and Be values are of 3.0956 eV, 3.1863 eV, 0.15223 nm, 1472.894 cm-1, 0.07799 cm-1 and 3.8717 cm-1, respectively, which are in excellent agreement with the measurements. A total of 26 vibrational states is predicted when J=0 by solving the radial Schro¨dinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J=0 are reported for the first time, which are in good accord with the available experiments. The total and various partial-wave cross sections are calculated for the elastic collisions between Si and D atoms in their ground states at 1.0×10-11–1.0×10-3 a.u. when the two atoms approach each other along the SiD(X2Π) potential energy curve. Four shape resonances are found in the total elastic cross sections, and their resonant energies are of 1.73×10-5, 4.0×10-5, 6.45×10-5 and 5.5×10-4 a.u., respectively. Each shape resonance in the total elastic cross sections is carefully investigated. The results show that the shape of the total elastic cross sections is mainly dominated by the s partial wave at very low temperatures. Because of the weakness of the shape resonances coming from the higher partial waves, most of them are passed into oblivion by the strong s partial-wave elastic cross sections.     

Surface critical behavior of fluids: Lennard-Jones fluid near a weakly attractive substrate

The phase behavior of fluids near weakly attractive substrates is studied by computer simulations of the coexistence curve of a Lennard-Jones (LJ) fluid confined in a slitlike pore. The temperature dependence of the density profiles of the LJ fluid was used to study the surface critical behavior. A universal critical behavior of the local order parameter, defined as the difference between the local densities of the coexisting liquid and vapor phases at some distance from the pore walls, , is observed in a wide temperature range and found to be consistent with the surface critical behavior of the Ising model. Near the surface the dependence of the order parameter on the reduced temperature obeys a scaling law ~1 with a critical exponent 1 of about 0.8, corresponding to the surface transition. A crossover from bulk-like to surface-like critical behavior occurs, when the distance to the surface is about twice the correlation length at the given temperature. Relations between the and transitions in Ising systems and the surface critical behavior of fluids are discussed.     

Electronic and optical properties of the zinc-blende structured LiZnN under pressure

The electronic and optical properties of the cubic zinc-blende (ZB) structured filled tetrahedral semiconductor α-LiZnN under pressure are investigated by using \textit{ab initio} plane wave pseudopotential density functional theory method within the generalized gradient approximation (GGA). The electronic band structure and the density of state under pressure are systematically described. The basic optical constants, including the reflection and absorption spectra, the energy-loss function, the complex refractive index and the dielectric function, are calculated and analysed at different external pressures. Our results suggested that the ZB α-LiZnN is transparent in the partially ultra-violet to the visible light region, and it seems that the transparency is hardly affected by the pressure.     

Dy2 AlFe13 Mn3 化合物的本征磁致伸缩

通过X-射线衍射及磁测量手段研究了Dy2AlFe13Mn3化合物的结构及磁性质。研究结果表明Dy2AlFe13Mn3化合物具有六角相的Th2Ni17型结构。通过X-射线热膨胀测定法发现Dy2AlFe13Mn3化合物在245到344K的温度范围内存在负热膨胀现象，其平均热膨胀系数为α＝-1.1×10-4K-1K-1。在105到360K的温度范围内，通过比较磁性状态下的晶胞参数和由高温顺磁状态外延得到的低温顺磁状态下的晶胞参数间的差别计算了Dy2AlFe13Mn3化合物的本征磁致伸缩。结果表明Dy2AlFe13Mn3化合物的本征体磁致伸缩ωS在105到245K的温度范围内随着温度的升高而增大，由105K时的7.0×10-3 增加到245K时的9.1×10-3。随着温度的进一步升高，ωS反而减小。沿c轴方向的本征线磁致伸缩λc随着温度的升高而减小。基面内的本征线磁致伸缩λa在105到270K的温度范围内随着温度的升高而增大，从105K时的0.8×10-3增大到270K时的3.4×10-3，然后随着温度的进一步升高而减小。     

Effective action for phase fluctuations in <Emphasis Type="Italic">d</Emphasis>-wave superconductors near a Mott transition

Phase fluctuations of a d-wave superconducting order parameter are theoretically studied in the context of high-T_c cuprates. We consider an extended t-J model describing electrons in a layer which also contains long-range Coulomb interactions. The constraint of having at most singly occupied sites is enforced by an additional Hubbard term. The Heisenberg interaction is decoupled by a d-wave order parameter in the particle-particle channel. Assuming first that the equilibrium state has long-range phase order, the effective action is derived perturbatively for small fluctuations within a path integral formalism, in the presence of the Coulomb and Hubbard interaction terms. In a second step, a more general derivation of is performed in terms of a gradient expansion which only assumes that the gradients of the order parameter are small whereas the value of the phase may be large. We show that in the phase-only approximation the resulting reduces in leading order in the field gradients to the perturbative one which thus allows to treat also the case without long-range phase order or vortices. Our result generalizes previous expressions for to the case of interacting electrons, is explicitly gauge invariant, and avoids problematic singular gauge transformations.     

An experimental test of the scaling prediction for the spatial distribution of water during the drying of colloidal films

A Peclet number, Pe, for the drying of colloidal films can be used as a predictor of the uniformity of water concentration in the direction normal to the film. Uniform drying is predicted to occur when Pe < 1, whereas with , a layer of packed particles is expected to develop above a more dilute layer. Routh and Zimmerman have more recently proposed that the particle concentration gradient between the packed and dilute layers, , will scale as . Here, this scaling relation is tested experimentally with magnetic resonance profiling data obtained from waterborne colloidal films dried under conditions to yield a range of Pe. It is found that increases with Pe but scales as . This disagreement with the prediction can be attributed to an underestimate of Pe when there are greater non-uniformities of drying, because of an unquantified slowing down of the evaporation rate.     

Correspondence between classical dynamics and recurrence spectra of Rydberg hydrogen atom near a metal surface

The chaotic behaviours of the Rydberg hydrogen atom near a metal surface are presented. A numerical comparison of Poincare surfaces of section with recurrence spectra for a few selected scaled energies indicates the correspondence between classical motion and quantum properties of an excited electron. Both results demonstrate that the scaled energy dominates sensitively the dynamical properties of system. There exists a critical scaled energy εc, for ε 〈 εc, the system is near-integrable, and as the decrease of ε the spectrum is gradually rendered regular and finally turns into a pure Coulomb field situation. On the contrary, if ε 〉 εc, with the increase of ε, the system tends to be non-integrable, the ergodic motion in phase space presages that chaotic motion appears, and more and more electrons are adsorbed on the metal surface, thus the spectrum becomes gradually simple.