左手介质椭圆光波导基模传播特性

在椭圆柱坐标系中,采用分离变量方法,得出了左手介质椭圆光波导本征方程的近似解,通过数值计算,分析了椭圆波导偏心率、左手介质的电容率、磁导率对椭圆光波导基模传播特性的影响,并将左介质光波导与右手介质光波导基模特性进行对比,得出左手介质光波导的基模特性与右手介质光波导基模特性差别不大的结论.     

由波模频移确定矩形管道沉积层的厚度

提出了用波模的频率偏移求矩形管道中沉积层厚度的方法。在已知无沉积层矩形管道内横截面的情形下,将测量的波模频率与用有限元计算得到的波模频率进行比对,确定沉积层的厚度。给出了有限元计算结果以及实验结果(长15m,截面为449mm×425mm的矩形管道,沉积层厚度分别为40mm和60mm)及其相对误差。实验和有限元计算的结果有很好的一致性,验证了本方法的正确性。     

脊加载椭圆波导的多项式表示分析方法

采用Rayleigh-Ritz方法和多项式表示对脊加载椭圆波导的传输特性进行了分析.数值计算与电磁仿真软件结果能很好地符合.研究了不同尺寸对脊波导带宽的影响，对这类结构的优化具有指导意义.     

理想流体的法拉第波模态

研究了理想流体的法拉第波模态.由法拉第波的振幅方程给出了稳定条件下的色散关系,利用参量共振方程得到了在亚简谐条件下本征波矢的取值范围.引入几何模型,在一定实验条件下,可以简单而直观地预测模态及其花纹图案.解释了不同模态的竞争情况,对比分析了相图关系的理论预测结果,几何模型的预测与实验及理论计算结果相符合.     

钇铁石榴石自旋波导管中磁钉扎对自旋波模的影响（英文）

利用微磁模拟,研究钇铁石榴石自旋波导管边界的磁钉扎对其中自旋波动力学的影响。模拟结果表明：磁钉扎引起的双磁子散射将自旋波散射到多个方向,使得自旋波在k空间的分布更加分散。自旋波模的演化表明：不同自旋波模的共振场不同,而双磁子散射使得自旋波模的共振场更为接近。另外,双磁子散射通过改变自旋波模的弛豫速率,改变了自旋波模的共振强度,幅度可达40%。增大自旋波导能够降低磁钉扎的影响,可以用来提升自旋波导的性能。     

周向超声导波对管道纵向缺陷检测的研究

在弹性动力学理论的基础上,研究了管道中周向超声导波的传播及其频散特性,并数值计算了周向导波的频散曲线。通过所建立的超声导波实验系统,在理论上与实验上研究了斜探头的入射角、频率及周向导波模态的关系,并在外径为88.8 mm、内径为80.8 mm的管道中激励出特定的单一模态周向导波;同时,利用单一模态周向导波对该管道表面上长25 mm、宽1 mm、深0.7 mm的人工缺陷进行了检测。结果表明,同在板中激励单一Lamb波模态类似,选用特定角度的斜探头与特定频率可在管道中激励出单一周向导波模态并有望应用于管道缺陷的检测。     

螺旋扭曲椭圆管层流换热与流阻特性模拟分析

对螺旋扭曲椭圆管内的层流换热与流阻特性进行了理论分析和数值计算,给出了努谢尔数和阻力系数的准则关系式。表明螺旋扭曲椭圆管可较大程度地强化层流换热,其流阻增加较小,同功耗下的强化传热评判指标可达2～4。将螺旋扭曲椭圆管换热器应用于炼油装置中,节能效益显著。     

双离子成份等离子体的离子声色散关系

 以离子温度与电子温度之比为参数,将等离子体介电函数作展开,由此解析地求解了双离子成分等离子体的离子声快、慢波模的色散关系。与现有的其它解析理论相比较,所得到的解析公式更加准确。     

轻微非共面腔的输出片应力作用研究

 建立了计算轻微非共面腔输出光椭圆度的数学模型,分析了R. H. Moore专利中的理论计算错误,计算分析了输出片的应力作用对输出光椭圆度的影响,发现：输出镜片的应力作用对环形激光器顺时针方向和逆时针方向输出光椭圆度的非对称有影响。通过实验验证了理论计算的正确性。得出R. H. Moore, S. W. Hammons等人在专利中提出的调腔方法存在错误,它不能有效地消除环形激光器中由腔体轻微异面所引起的磁效应。     

液体中光击穿所激发声场的理论研究

以液体中光击穿所激发声场为研究对象,在等离子体椭球模型的基础上,为方便理论计算,简化等离子体椭球模型,提出了等离子体椭圆盘模型,对光击穿所激发声场进行了理论研究.得到了等离子体椭圆盘辐射声场的声压规律,并利用椭圆坐标变换,依据马修函数特性和模态的正交性,求得了等离子体椭圆盘振动位移的解析表达式.     

Eccentricity fluctuations are not the only source of elliptic flow fluctuations in a multiphase transport model

Sources of event-by-event elliptic flow fluctuations in relativistic heavy-ion collisions are investigated in a multiphase parton transport model(AMPT).Besides the well-known initial eccentricity fluctuations,several other sources of elliptic flow dynamical fluctuations are identified.One is fluctuations in initial parton configurations at a given eccentricity.Configuration fluctuations are found to be as important as eccentricity fluctuations in elliptic flow development.A second is quantum fluctuations in parton-parton interactions during system evolution.A third is fluctuations caused by hadronization and final-state hadronic scatterings.The magnitudes of these fluctuations are investigated relative to the eccentricity fluctuations and the average elliptic flow magnitude.The fluctuations from the latter two sources are found to be negative.The results may have important implications for the interpretation of elliptic flow data.     

System size, energy, pseudorapidity, and centrality dependence of elliptic flow

This Letter presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system.     

Pumping Power Minimization in Staggered Finned Circular and Elliptic-Tube Heat Exchangers in Turbulent Flow

An experimental study aimed at minimizing pumping power required to supply air through a finned tube bundle configuration is presented in this article. Results were obtained for the Reynolds number based on the smaller ellipse axis (RE_2b) ranging from 2,650 to 10,600, i.e., in turbulent flow. In the turbulent regime, pressure drops are expected to vary with eccentricity. Experimental optimization results for finned circular and elliptic tubes show that pumping power can be minimized with respect to tube spacing and eccentricity. In comparison with values obtained for circular tubes, the optimal elliptical arrangements show pumping power reductions from 5% to 10%.     

Stability of elliptic vortex solitons in anisotropic nonlocal media

Elliptic vortex solitons are investigated in anisotropic nonlocal media with more general formulations. We address the existence and dynamics of such solitons analytically and numerically. The solution of elliptic vortex solitons depends on the eccentricity of both the input beam and nonlocal response function. With different degrees of nonlocality, we numerically investigate the evolution of the elliptic vortex solitons, and find that, typically, the elliptic vortex solitons with single and double charges collapse into spiraling dipole- and tripolelike soliton clusters, respectively.     

Scattering by a homogeneous anisotropic-coated conducting elliptic cylinder

A solution to the two-dimensional scattering properties of a conducting elliptic cylinder coated with a homogeneous anisotropic elliptical shell is obtained. The conducting elliptic cylinder and the shell have the same eccentricity. The transmitted and scattered fields of the anisotropic shell are expressed as Mathieu functions in elliptic coordinates. The unknown coefficients of the scattered and transmitted fields are solved with the aid of the boundary conditions and the Galerkin's method. Only the transverse magnetic (TM) polarization is presented and the transverse electric (TE) polarization can be obtained in the same way. Some numerical results are presented and discussed. As expected the result is in agreement with that available when the coated elliptic cylinder degenerates to a coated circular one.     

NeXSPheRIO results on elliptic flow and directed flow for Au+Au and Cu+Cu collisions at RHIC

Hydrodynamics has been rather successful at describing results obtained in relativistic nuclear collisions at RHIC. Here we show results obtained with NeXSPheRIO on Au+Au collisions and the less studied Cu+Cu collisions. We study elliptic flow and its connection with eccentricity suggested by PHOBOS, as well as present elliptic flow fluctuations. We also show results for directed flow and compare with PHOBOS and STAR data.     

Two-body nucleon-nucleon correlations in Glauber-like models

We investigate the role of the central two-body nucleon-nucleon correlations on typical quantities observed in relativistic heavy-ion collisions. Basic correlation measures, such as the fluctuations of the participant eccentricity, initial size fluctuations, or the fluctuations of the number of sources producing particles, are sensitive at the level 10–20% to the inclusion of the two-body correlations. However, the realistic correlation function gives virtually indistinguishable results from the hard-core repulsion with the expulsion distance set to ∼0.9 fm. In the second part of the talk we compare the spherical and Gaussian wounding profiles and find that the latter, which is more realistic, leads to reduced eccentricity and fluctuations. This has significance for precision studies of the elliptic flow.     

Flow measurements via two-particle azimuthal correlations in Au + Au collisions at sqrt [s(NN)]=130 GeV

Two-particle azimuthal correlation functions are presented for charged hadrons produced in Au+Au collisions at the Relativistic Heavy Ion Collider (sqrt [s(NN)]=130 GeV). The measurements permit determination of elliptic flow without event-by-event estimation of the reaction plane. The extracted elliptic flow values (v2) show significant sensitivity to both the collision centrality and the transverse momenta of emitted hadrons, suggesting rapid thermalization and relatively strong velocity fields. When scaled by the eccentricity of the collision zone epsilon, the scaled elliptic flow shows little or no dependence on centrality for charged hadrons with relatively low p(T). A breakdown of this epsilon scaling is observed for charged hadrons with pT >1.0 GeV/c.     

激波作用不同椭圆氦气柱过程中流动混合研究

在激波与气柱相互作用问题中,压力与密度间断不平行产生的斜压涡量会引起流动的不稳定性,从而促进物质间的混合.本文基于双通量模型,结合五阶加权基本无振荡(WENO)格式,求解多组分二维Navier-Stokes方程,分析激波作用面积相同结构不同的椭圆气柱所致的流动和混合.数值结果清晰地显示了激波诱导Richtmyer-Meshkov不稳定性引起的气柱界面变形和波系演化.同时定量地从界面运动、界面结构参数变化(长度和高度)、气柱体积压缩率、环量及混合率等角度分析激波诱导的流动混合机制,研究椭圆几何构型对氦气混合过程的影响.结果表明,界面及相关参数的演化与气柱初始形状密切相关.当激波沿椭圆长轴作用于气柱时,气柱前端出现空气射流结构,且射流不断增长并渗透到下游界面,致使气柱分离成两个独立涡团,离心率越大,射流发展越快;同时激波作用气柱后在界面处产生不规则反射现象.圆形气柱界面演化与这种作用情形类似.当激波沿椭圆短轴作用于气柱时,界面上游出现类平面结构,随后平面上下缘处产生涡旋,主导流动发展,激波在界面作用产生规则反射,离心率越大,这些现象越明显.界面高度、长度、体积压缩率也因此有所差异.对界面演化、环量和混合率的综合分析表明,激波沿长轴作用于气柱且离心率较大时,流动发展较快,不稳定性导致的流动越复杂,越有利于氦气与环境介质的混合.     

Eccentricity and elliptic flow in proton-proton collisions from parton evolution

It has been argued that high-multiplicity proton-proton collisions at the LHC may exhibit collective phenomena usually studied in the context of heavy-ion collisions, such as elliptic flow. We study this issue using DIPSY—a Monte Carlo event generator based on the QCD dipole model. We calculate the eccentricity of the transverse area defined by the spatial distribution of produced gluons. The resulting elliptic flow is estimated to be about 6%, comparable to the value in nucleus-nucleus collisions at RHIC and the LHC. Experimentally, elliptic flow is inferred from the azimuthal correlation between hadrons, which receives contributions from collective flow, and from various other effects referred to as “nonflow”. We discuss how to identify in experiments the signal of flow in the presence of large nonflow effects.