Dependence of multiplicity and transverse energy distributions on nuclear geometry at RHIC

We study the dependence of multiplicity and transverse energy on nuclear geometry at RHIC at SNN^1/2 =19.6,130,and 200 GeV basing on ellipsoidal decay model.It is found that the ellipsoidal decay model can describe the data well.     

Large eddy simulation of orientation and rotation of ellipsoidal particles in isotropic turbulent flows

The rotational motion and orientational distribution of ellipsoidal particles in turbulent flows are of significance in environmental and engineering applications. Whereas the translational motion of an ellipsoidal particle is controlled by the turbulent motions at large scales, its rotational motion is determined by the fluid velocity gradient tensor at small scales, which raises a challenge when predicting the rotational dispersion of ellipsoidal particles using large eddy simulation (LES) method due to the lack of subgrid scale (SGS) fluid motions. We report the effects of the SGS fluid motions on the orientational and rotational statistics, such as the alignment between the long axis of ellipsoidal particles and the vorticity, the mean rotational energy at various aspect ratios against those obtained with direct numerical simulation (DNS) and filtered DNS. The performances of a stochastic differential equation (SDE) model for the SGS velocity gradient seen by the particles and the approximate deconvolution method (ADM) for LES are investigated. It is found that the missing SGS fluid motions in LES flow fields have significant effects on the rotational statistics of ellipsoidal particles. Alignment between the particles and the vorticity is weakened; and the rotational energy of the particles is reduced in LES. The SGS-SDE model leads to a large error in predicting the alignment between the particles and the vorticity and over-predicts the rotational energy of rod-like particles. The ADM significantly improves the rotational energy prediction of particles in LES.     

Distribution characteristic of scattering field for an ellipsoidal target irradiated by an electromagnetic wave from an arbitrary direction

It is of great importance for engineering applications to obtain the expression of scattering field for an ellipsoidal target irradiated by an electromagnetic wave from an arbitrary direction. Literature relevant to this problem is seldom found. In this paper, the scattering field for an ellipsoidal target is presented by utilizing the scale transformation of electromagnetic field and the rotation of coordinate system, with an electromagnetic wave projecting on the target from an arbitrary direction. The obtained result is in good agreement with the solution available from the literature if we consider the scale factors to be unity. Taking a conducting ellipsoidal target for sample, we perform the partial simulations of the ellipsoidal model and a plant leaf model by choosing different scale factors. The obtained results show that the distribution characteristic of scattering field is sensitively affected by the polarization of the incident wave and varies not much with the incident wave angle but changes with the observation point. At some points the scattering energy arrives at its maximum.     

Simulation of x-ray transmission through an ellipsoidal capillary

This paper develops a simulation program for x-ray transmission in an ellipsoidal capillary based on a ray-tracing method.The influence of the parameters of ellipsoidal capillary and x-ray energy on transmission efficiency,full width at half maximum and power density gain of x-ray beams through an ellipsoidal capillary was analysed by this program.It shows that the particular rules of the ellipsoidal capillary x-ray lens are different from the polycapillary lens.Furthermore,this analysis method can be applied to the optimized design of ellipsoidal capillary.     

Electronic heat capacity of bismuth

The observed electronic heat capacity of bismuth is found to be in better agreement with the values calculated on the ellipsoidal nonparabolic (ENP) model than on the ellipsoidal parabolic (EP) model. Values of γ obtained experimentally and from the ENP model are 8.5 ± 1.5 and 8.28 respectively while the EP model gives 6.8 (from Kao's parameters) and 5.0 (from Williams, and Smith et al. parameters).     

Breakdown of a gas in superimposed d.c. and h.f. electric fields

By means of a time resolution it was found that the electric breakdown of air at atmospheric pressure between a charged plate and a spike, on which a torch discharge is burning, gaves rise to comparatively stable ellipsoidal plasma formations — plasmoids. Their dimensions stay within 2÷10 mm, velocity 0÷4 ms, acceleration –210÷1500 ms^–2. Their life time is 10^–2 s in magnitude. They decay either at the spike electrode, or when the actual breakdown takes place, or they desintegrate in the inter-electrode space.     

Trianionic gold clusters

Using Penning-trap experiments and a shell-correction method incorporating ellipsoidal shape deformations, we investigate the formation and stability patterns of trianionic gold clusters. Theory and experiment are in remarkable agreement concerning appearance sizes and electronic shell effects. In contrast to multiply cationic clusters, decay of the trianionic gold clusters occurs primarily via electron autodetachment and tunneling through a Coulomb barrier, rather than via fission. Received 9 January 2001     

超疏水聚合物表面的水滴蒸发模拟

基于质量守恒和Fick第一定律，模拟了水滴在超疏水聚合物表面的蒸发全过程．研究从以往的接触角<90±扩展到>150±，液滴形貌扩展为椭球球帽模型进行疏水表面蒸发模拟．水滴在超疏水PC和FPU/PMMA表面蒸发的实验结果显示，计算的椭球球帽模型可以更好的反映出液滴接触角和高度的变化情况，并且不同聚合物表面接触角的相同变化趋势也揭示出微-纳二级结构表面结构不仅影响液滴接触角，也影响液滴蒸发模式．     

数字电影反光镜3D扫描面形检测与评价

通过3D扫描的方法,对椭球反光镜的面形进行了检测,并与标准椭球面形进行最佳拟合对比,以E210反光镜为例。结果表明:3D扫描能够完成椭球反光镜的检测,E210反光镜在底孔部位存在加工过量,在端口部位存在近似十字形对称的加工不足的现象,加工误差范围为-0.06 mm ~+0.08 mm,符合轮廓度误差0.1 mm的要求。3D扫描点云能够进行逆向反求并建立实际反射面模型,进一步模拟反光镜的反射光斑形状、大小等参数,模拟结果与检测结果一致。     

Theory of FID NMR signal dephasing induced by mesoscopic magnetic field inhomogeneities in biological systems.

A theory of the NMR signal dephasing due to the presence of tissue-specific magnetic field inhomogeneities is developed for a two-compartment model. Randomly distributed magnetized objects of finite size embedded in a given media are modeled by ellipsoids of revolution (prolate and oblate spheroids). The model can be applied for describing blood vessels in a tissue, red blood cells in the blood, marrow within trabecular bones, etc. The time dependence of the dephasing function connected with the spins inside of the objects, s(i), is shown to be expressed by Fresnel functions and creates a powder-type signal in the frequency domain. The short-time regime of the dephasing function for spins outside the objects, s(e), is always characterized by Gaussian time dependence, s(e) approximately exp[-zeta(k)(t/tc)2], with zeta being a volume fraction occupied by the objects, t(c) being a characteristic dephasing time, and the coefficient k depending on the ellipsoid's shape through the aspect ratio of its axes (a/c). The long-time asymptotic behavior of s(e) is always "quasispherical"-linear exponential in time, s(e) approximately exp(-zetaCt/tc), with the same "spherical" decay rate for any ellipsoidal shape. For long prolate spheroids (a/c)<1, there exists an intermediate characteristic regime with a linear exponential time behavior and an aspect-ratio-dependent decay rate smaller than (zetaC/tc).     

Ultrasonic backscattering in polycrystals with elongated single phase and duplex microstructures

An analytical solution for a three dimensional integral representation of the backscattering (BS) coefficient in polycrystals with elongated (generally ellipsoidal) grains is obtained; it is a natural generalization of the known explicit result for the BS coefficient in polycrystals with spherical grains. New insights into the dependence of the BS signal on frequency and averaged ellipsoidal grain radii are obtained. In particular it has been shown that the dominant factor for the backscattering is the averaged interaction length of the ellipsoidal grain in the direction of wave propagation, instead of the ellipsoidal cross-section. The theory was applied to a simplified model of Ti alloy duplex microstructure and was compared with experiment. For the experimental data analysis directional backscattering ratios are introduced and shown to be advantageous for characterization of duplex elongated microstructures/microtextures. In addition to the geometrical parameters of the elongated microtextures, the BS directional ratios depend on the newly introduced nondimensional material parameter q. The parameter q exhibits the relative contribution of the second phase (crystallites) to the backscattering signal, the effect of which is measurable and important. Comparison of the model with experiment shows there is a significant advantage in using the directional ratios of backscattering coefficients for data analysis.     

回转椭球反射镜的检验与检测仪器的设计

本文介绍了根据椭球光学性质研制的FJG-1型椭球反射镜检测仪。它为检验回转椭球反射镜建立了面积有效率、光轴偏移量、f_1值允差与反射率四项技术指标,并给出了检测仪的设计原理与操作方法。最后对仪器的误差及运行效果进行了分析。     

Study of liquid crystal phases with a model soft ellipsoid contact potential

We propose a soft ellipsoid contact potential model (SECP) for a pair of identical uniaxial ellipsoidal molecules, considering the configuration dependent energy anisotropy explicitly along with their geometrical aspects. The present model is an extension of the ellipsoid contact potential (ECP), main contribution of which was to determine the correct contact function of the ellipsoidal core. Expressions for intermolecular forces and torques derived analytically from this new model pair interaction potential are presented hereto to make it useful for molecular dynamics simulation study. We also report on some observations of molecular dynamics simulation study to demonstrate the ability of this realistic coarse-grained potential in generating some important liquid crystal phases.     

Control of spontaneous emission by complex nanostructures

Spontaneous emission in the presence of complex nanostructures is discussed by use of a calculational scheme that permits us to deal with interfaces of arbitrary shape. Control over the field associated with the emission is shown to be attainable. In particular, decay rates are offered for geometries that lead to focusing and collimation of near- and far-field distributions. Emission from axially symmetric gratings is shown to lead to narrow angular distributions of emission, and focusing at the foci of dielectric ellipsoids is achieved for dimensions comparable with the wavelength. In the latter case the total emission rate for two atoms in an ellipsoidal cavity is shown to be enhanced in a way that deviates from the predictions of the Dicke effect by means of intermediate- and far-field contributions.     

一种基于离轴椭球面的小光程差波面整形系统

为了实现空间中一定距离的近似等光程光束传输,设计了一种包含离轴椭球面反射镜的波面整形系统。基于几何光学与初级像差理论,结合Zemax光学设计软件,分析了椭球面反射镜圆锥系数、离轴量对像面处光程差的影响;设计了平面-椭球面反射镜和双椭球面反射镜2种光学结构的波面整形系统,并比较了2种结构的公差。分析结果表明:平面-椭球面反射系统和双椭球面反射系统均实现了空间中1 m距离的光束传输,且2种结构系统在3 mm物高视场和孔径角为6°条件下,各视场光瞳之间的光程差分别为0.14 mm和0.04 mm,因此,双椭球面反射结构整形效果优于平面-椭球面反射系统,但双椭球面反射结构对公差的敏感度更高。     

Accurate monoenergetic electron parameters of laser wakefield in a bubble model

A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived. The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal model and it explains the mono-energetic electron trajectory more accurately, especially at the relativistic region. As a result, the quasi-mono-energetic electrons output beam interacting with the laser plasma can be more appropriately described with this model.     

Shape-based ultrasound tomography using a Born model with application to high intensity focused ultrasound therapy

A shaped-based ultrasound tomography method is proposed to reconstruct ellipsoidal objects using a linearized scattering model. The method is motivated by the desire to detect the presence of lesions created by high intensity focused ultrasound (HIFU) in applications of cancer therapy. The computational size and limited view nature of the relevant three-dimensional inverse problem renders impractical the use of traditional pixel-based reconstruction methods. However, by employing a shape-based parametrization it is only necessary to estimate a small number of unknowns describing the geometry of the lesion, in this paper assumed to be ellipsoidal. The details of the shape-based nonlinear inversion method are provided. Results obtained from a commercial ultrasound scanner and a tissue phantom containing a HIFU-like lesion demonstrate the feasibility of the approach where a 20 mm x 5 mm x 6 mm ellipsoidal inclusion was detected with an accuracy of around 5%.     

The Ostwald ripening at nanoengineering of InAsSbP spherical and ellipsoidal quantum dots on InAs (100) surface

We present the results of growth of quasi-ternary InAsSbP spherical and ellipsoidal quantum dots (QDs) on InAs (100) surface by the method of liquid-phase epitaxy. Coarsening of QDs due to coalescence and Ostwald ripening was investigated by atomic-force and scanning electron microscopy. Ellipsoidal QDs prolated in [010] and oblated in [001] directions have been grown. Elongation ratios for the ellipsoidal QDs were measured in all three directions. It is shown that elongation of spherical QDs to ellipsoidal is started at QDs diameter of ～50 nm. Shape transformation of the QDs’ size distribution function from the Gram-Charlier-like to the Gaussian and then to the Lifshits-Slezov-like distribution was revealed at increasing the nucleation time.     

Acoustic characteristics of pulse detonation engine with ellipsoidal reflector

Acoustic characteristics of a pulse detonation engine(PDE) with and without an ellipsoidal reflector are numerically and experimentally investigated. A two-dimensional(2 D) non-splitting unstructured triangular mesh Euler solver based on the space-time conservation element and solution element(CE/SE) method is employed to simulate the flow field of a PDE.The numerical results clearly demonstrate the external flow field of the PDE. The effect of an ellipsoidal reflector on the flow field characteristic near the PDE exit is investigated. The formation process of reflected shock wave and reflected jet shock are reported in detail. An acoustic measurement system is established for the PDE acoustic testing. The experimental results show that the ellipsoidal reflector changes the sound waveform and directivity of PDE sound. The reflected shock wave and reflected jet shock result in two more positive pressure peaks in the sound waveform. The ellipsoidal reflector changes the directivity of PDE sound from 20 to 0. It is found that the peak sound pressure level(PSPL) and overall sound pressure level(OASPL) each obtain an increment when the PDE is installed with a reflector. The maximum relative increase ratio of PSPL and OASPL are obtained at the focus point F2, whose values are 6.1% and 6.84% respectively. The results of the duration of the PDE sound indicate that the reflecting and focusing wave generated by the reflector result in the increment of A duration and B duration before and near focus point F2. Results show that the ellipsoidal reflector has a great influence on the acoustic characteristic of PDE sound. The research is helpful for understanding the influence of an ellipsoidal reflector on the formation and propagation process of PDE sound.