Density profiles and solvation force for a liquid in a slit

Computer simulations and density functional theory results are reported for a Lennard-Jones liquid in a slit or pore formed by two parallel hard walls. Both density profiles and solvation forces are computed. Two classes of calculation are performed. In the first class, a high bulk density is selected and, starting from a high temperature, the temperature is reduced until the temperature corresponding to bulk liquid—vapour coexistence is reached. For small slit widths or exceedingly large widths, the density in the slit decreases continuously until the slit is virtually empty or ‘dry’. When the slit width is somewhat larger than a molecular diameter, but still finite, the density in the slit decreases continuously as the temperature is decreased until there is an abrupt change in the density in the slit. Below this temperature, the density is smaller. Further decreases in the temperature, result in a continuous decrease in the slit density until the slit is virtually empty. In the second class, the density and temperature for bulk coexistence are chosen and the bulk density is increased. At the temperature and bulk density for bulk coexistence, the slit is virtually empty and remains so for all widths that we consider. As the bulk density is increased at constant temperature, the slit remains empty as the width is increased until some specific width is reached and then starts to fill abruptly. The agreement of the density functional and simulation results is qualitative but good.     

Finite Temperature Semiclassical Approach for Local Potentials

The nucleon distribution, kinetic energy density, free energy density and entropy density up to the second order in h are derived in a finite temperature semiclassical approach for two local potentials, harmonic oscillator and Woods-Saxon potentiale. The preaent results are compared with the exact quantum reaults for both potentials. The comparison justifies the extension of semiclassical approximation from zero temperature to finite temperature.     

Mikrowellendiagnostik von Instabilitäten des Säulenplasmas Elektronendichte, -temperatur und Helligkeitsverlauf in selbsterregten laufenden Schichten einer Wasserstoffentladung

Microwave methods are used to obtain the periodic variations in time and space of some plasma parameters. The electron density is obtained using a time-display of the reflection coefficient due to a plasma-perturbed cavity, and the electron temperature from the noise signal of a Dicke radiometer gated periodically. Assuming simple one-dimensional sinusoidal variations of temperature and density, the fundamental convolution integrals relating the appropriate cavity parameters to the plasma properties are solved and formulas are obtained to calculate the real fluctuating quantities. Also in that case where the lenghth of the cavity field region equals the dimension of the variations the correct phase relation between electron temperature and density is obtained. The method is used for diagnostics of self exited moving striations in hydrogen. The striations (frequency 24 kHz, striation lenghts ～1 cm) move from cathode to anode and the sequence of the different maxima for an observer in rest is electron density, temperature and light-emission. The phase shift between density and temperature is about 90 degrees, the appropriate density variation is 10:1 and the temperature variation >2:1.     

Nonlocal gravity-induced density profiles in gases near the critical point

The gravitational field induces density gradients in gases near the critical point. These density gradients are usually evaluated with the assumption that the relationship between the local density and local chemical potential is the same as for a macroscopic system in thermodynamic equilibrium. Very close to the critical point the assumption of local equilibrium ceases to be valid. In this paper we obtain the actual density profiles including nonlocal effects. For this purpose we extend the theory of van der Waals and of Fisk and Widom for the interfacial density profile below the critical temperature to the one-phase region above the critical temperature. The nonlocal effects in the density profiles are found to be significant in temperature intervals that are accessible with currently available experimental techniques for temperature control.     

CHIRAL PHASE TRANSITION IN A MODEL WITH DYNAMICAL SPONTANEOUS-SYMMETRY-BREAKING AT FINITE TEMPERATURE AND DENSITY

The chiral-symmetry-restoring phase transition in a model with dynamical spontaneous-symmetry-breaking is discussed qualitatively,making use of an approximation method.The selfconsistency equation of the model is established.The condensation and mass of fermions as well as the temperature or density dependence of energy density and specific heat are obtained.It turns out that,in this approximation,the chiral-phase-transition is second order at zero chemical potential and finite temperature; and the transition is first order for both cases at finite temperature and density and at zero temperature and finite density,this moment.the transition temperature or density from broken phase to normal phase differs from that from normal phase to broken phase.     

溴化亚铜激光气体温度的径向分布与时间变化

应用脉冲期间等离子体电子温度和电子密度实验值,通过一自洽模型,得到了CuBr激光气体温度、原子密度的径向分布与时间变化。中心气体温度1400—1800K。中心温度随时间的波动达300-500K。气体原子密度的径向分布呈一凹形。 关键词：     

Density correlations induced by temperature fluctuations in a photon gas

The impact of angular temperature variations on the thermodynamic variables and real-space correlation functions of black-body radiation are analyzed. In particular, the effect of temperature fluctuations on the number density and energy density correlations of the cosmic microwave background (CMB) is studied. The angular temperature fluctuations are modeled by an isotropic and homogeneous Gaussian random field, whose autocorrelation function is defined on the unit sphere in momentum space. This temperature correlation function admits an angular Fourier transform which determines the density correlations in real space induced by temperature fluctuations. In the case of the CMB radiation, the multipole coefficients of the angular power spectrum defining the temperature correlation function have been measured by the Planck satellite. The fluctuation-induced perturbation of the equilibrium variables (internal energy, entropy, heat capacity and compressibility) can be quantified in terms of the measured multipole coefficients by expanding the partition function around the equilibrium state in powers of the temperature random field. The real-space density correlations can also be extracted from the measured temperature power spectrum. Both the number density and energy density correlations of the electromagnetic field are long-range, admitting power-law decay; in the case of the energy density correlation, the fluctuation-induced correlation overpowers the isotropic equilibrium correlation in the long-distance limit.     

Effect of Parallel-Plate Geometry on Mode Transition Behavior in Argon Microplasmas: Two-Dimensional Simulation

A two-dimensional self-consistent fluid model is employed to investigate radio-frequency process parameters on the plasma properties in Ar microdischarges. The neutral gas density and temperature balance equations are taken into account. We mainly investigate the effect of the electrode gap on the spatial distribution of the electron density and electron temperature profiles, due to a mode transition from the regime(secondary electrons emission is responsible for the significant ionization) to the regime(sheath oscillations and bulk electrons are responsible for sustaining discharge) induced by a sudden decrease of electron density and electron temperature.The pressure, radio-frequency sources frequency and voltage effects on the electron density are also elaborately investigated.     

PICPMCC 数值模拟四阳极直流辉光放电

利用OOPIC 代码并结合MCC 方法考察四阳极低气压直流辉光放电中粒子间的碰撞, 并对其进行了数值模拟。首先分析OOPIC 代码的计算流程, 给出模拟的边界条件和时间、空间步进; 然后对所得到的等离子体密度、温度的分布情况进行了分析。结果表明, 放电气压、电流以及环电极的有效宽度均影响等离子体密度和温度的径向分布。当气压为300Pa 时, 电子密度在径向较大范围内是均匀分布的, 而当气压升高到800Pa 时, 其径向不均匀增大, 且总的密度和电子的平均温度下降。放电电流的增大使得等离子体密度和温度均相应升高。但环电极有效宽度的减小使得等离子体密度的分布更不均匀, 并使总的密度和平均温度均下降。     

键合界面阻抗对VCSEL的电、热学特性的影响

采用一电阻层来表征键合界面处的阻抗.通过求泊松方程、电流密度方程、载流子扩散方程以及有源层结压降方程自洽解的方法，计算了VCSEL的电势分布，进而求解热传导方程，得到VCSEL的温度分布.详细分析了键合界面阻抗对晶片键合结构垂直腔面发射激光器内部的电势分布、温度分布以及有源层中的注入电流密度、载流子浓度、结压降和温度沿径向分布的影响.     

激光烧蚀硬铝产生等离子体温度和力学效应测量

 为了研究激光推进技术中激光与材料相互作用的机制，获取等离子体状态参数及力学参数，采用Nd:YAG被动调Q固体激光器烧蚀硬铝，通过激光诱导等离子体光谱技术测得等离子体光谱和温度，由冲量摆测得力学参数。实验结果显示：在激光功率密度0.534×10⁸ W/cm²时，靶材表面的等离子体温度在等离子体辐射过程中呈二次曲线衰减；改变靶材等离子体点燃阈值附近的激光功率密度时，随着功率密度的增加，等离子体温度、冲量耦合系数也随着增大，当功率密度达到靶材的等离子体点燃阈值时，各参数达到最大，此后随着功率密度增加，由于等离子体对能量的屏蔽作用，导致靶材表面的等离子体温度降低，等离子体获得的动能减少，靶材耦合的冲量降低。     

正则系综条件下空化空泡形成的分子动力学模拟

液体中空化现象的研究对减少空蚀破坏, 提高空化空泡的有效利用具有重要意义.本文采用分子动力学模拟的方法, 对正则系综条件下系统中空化的发生特性进行研究, 分析空化发生的机理, 讨论温度、数密度等因素对空化发生的影响, 并与格子Boltzmann方法进行了比较.模拟结果表明: 温度和数密度的变化, 都对系统中的空化产生显著影响.其中, 温度升高, 使系统中空化空泡的形成由稳定变得不稳定, 最终难以形成.数密度降低, 则会促进空化空泡的形成.随着数密度的减小, 温度对空化空泡形成的影响程度下降.     

Temperature dependence of Hall electron density of GaN-based heterostructures

The theoretic calculation and analysis of the temperature dependence of Hall electron density of a sample AlGaN/GaN heterostructure has been carried out in the temperature range from 77 to 300K. The densities of the two-dimensional electron gas and the bulk electrons are solved by self-consistent calculation of one-dimensional Schr?dinger and Poisson equations at different temperatures, which allow for the variation of energy gap and structure strain, and are used for evaluation of the temperature dependence of Hall electron density. The calculated Hall electron density agrees with the measured one quite well with the appropriate bulk mobility data. Analysis revealed that for the temperature range considered, even in the heterostructures with a small bulk conductance the factors that determine the Hall mobility and electron density could be of different sources, and not just the two-dimensional electron gas as generally supposed.     

HL-2A装置偏滤器物理分析及其实验的初步证实

采用偏滤器物理分析的“两点”模型,分别计算了HL-2A装置线性状态和高再循环状态的边缘等离子体参数,包括偏滤器靶板的等离子体温度、密度和入射功率,以及上游等离子体温度、密度和平行功率密度的衰减长度。用该模型对线性状态预计的靶板温度和密度与实验结果进行了比较,结果符合较好。     

���ö�Ŀ������Ż��ƶ�ICF�Ȱ�״̬�ľ���ֲ�

提出了一种以多目标参数优化确定热斑的温度和密度径向分布的方法。用热斑中心位置和燃料界面位置对应的电子温度、靶剩余烧蚀层峰值密度、剩余烧蚀层质量与初始烧蚀层质量的比值以及燃料与烧蚀层分界面位置构成五维变量空间参数空间的每个点描述一组温度和密度分布。将实验测量的X射线图像的归一化强度分布与理论模型计算的强度分布的方差作为两个目标函数;另一个目标函数是实验测量的热斑的平均温度与理论模型计算的平均温度的方差。通过多目标遗传算法搜索五维参数空间获得最优参数,从而获得最优的温度和密度分布。对KB显微镜配合X射线胶片测量的实验结果进行了计算,给出了热斑的最佳温度和密度的径向分布。由测试算例发现,温度分布对目标函数的依赖较强。     

感应耦合等离子体的1维流体力学模拟

 采用双极扩散近似的流体力学模型，通过数值模拟方法研究了射频感应耦合等离子体(ICP)中等离子体密度和电子温度等物理量的空间分布，其中射频源的功率沉积由动力学理论给出。分析了不同的射频线圈的驱动电流和放电气压对等离子体密度和电子温度空间分布的影响。在低气压下，等离子体密度基本上保持空间均匀分布。随着放电压强的增加，等离子体密度的分布呈现出明显的空间不均匀性。当线圈电流增大时，等离子体密度和电子温度都随着增大。     

与核密度及温度相关的核子相对论微观光学势

在Walecka模型、热场动力学和相对论Dirac-Bruckner-Hartree-Fock计算结果基础上,研究了在不同核密度和各种温度情况下的核子相对论微观光学势及其相应的薛定谔等效势和平均自由程,计算结果表明,对于不同的温度,核子的薛定谔等效势与平均自由程随核密度变化较为敏感,而核温度对核子的薛定谔等效势和平均自由程的影响随着核密度的增加变大.     

含单缺陷层的一维可调谐磁化等离子体光子晶体滤波特性研究

采用在等温近似的条件下,以等离子体的上升时间、温度和密度为可调谐参量,用磁化等离子体的分段线形电流密度卷积时域有限差分算法研究了含单一缺陷层的一维磁化等离子体光子晶体的滤波特性.以高斯脉冲为激励源,用算法公式得到的电磁波透射系数来讨论了等离子体上升时间、温度、等离子体层密度对其滤波特性的影响.结果表明,改变等离子体上升时间和等离子体层密度可以实现对滤波通道的调整.谐振频率不能通过改变温度进行调整.     

Density profiles in tokamaks from electron cyclotron radiation spectra

Measurement of the line shape of optically thick and optically thin lines in the electron cyclotron radiation spectrum emitted by a tokamak plasma may yield both electron temperature and density profiles. Currently temperature profiles are routinely extracted from optically thick lines. Consequently, this paper is addressed to the density profile problem. Algorithms for extracting density profiles are outlined in the case of uncontrolled reflection and controlled reflection of the cyclotron radiation within the tokamak vacuum chamber.