利用图形计算器和ＣＢＬ实验室系统测量空气的绝热指数

介绍图形计算器、ＣＢＬ及硅压力传感器系统特性,并用于精确测量空气绝热指数。     

Complex scale-free networks with tunable power-law exponent and clustering

We introduce a network evolution process motivated by the network of citations in the scientific literature. In each iteration of the process a node is born and directed links are created from the new node to a set of target nodes already in the network. This set includes m$m$ “ambassador” nodes and l$l$ of each ambassador’s descendants where m$m$ and l$l$ are random variables selected from any choice of distributions _pl$p_l$ and _qm$q_m$. The process mimics the tendency of authors to cite varying numbers of papers included in the bibliographies of the other papers they cite. We show that the degree distributions of the networks generated after a large number of iterations are scale-free and derive an expression for the power-law exponent. In a particular case of the model where the number of ambassadors is always the constant m$m$ and the number of selected descendants from each ambassador is the constant l$l$, the power-law exponent is (2l+1)/l$(2l+1)/l$. For this example we derive expressions for the degree distribution and clustering coefficient in terms of l$l$ and m$m$. We conclude that the proposed model can be tuned to have the same power law exponent and clustering coefficient of a broad range of the scale-free distributions that have been studied empirically.     

钛团簇的结构及电子亲和势的理论研究

基于密度泛函理论详细地研究了金属钛的小尺寸团簇的稳定结构及电子性质。具体采用的计算方法是B3LYP/CEP-121G。在这项工作中,我们发现计算的电子亲和势的值与实验值符合的很好,但与原先的理论研究有些不同。     

Particle dynamics during adiabatic expansion of a plasma bunch

The renormalization-group approach is used to obtain an exact solution to the self-consistent Vlasov kinetic equations for plasma particles in the quasi-neutral approximation. This solution describes the one-dimensional adiabatic expansion of a plasma bunch into a vacuum for arbitrary initial particle velocity distributions. Ion acceleration is studied for two-temperature Maxwellian and super-Gaussian initial electron distributions, which predetermine distinctly different ion spectra. The solution found is used to describe the acceleration of ions of two types. The relative acceleration efficiency of light and heavy ions as a function of atomic weights and number densities is analyzed. The solutions obtained are of practical importance in describing ion acceleration during the interaction of an ultrashort laser pulse with nanoplasma, for example, cluster plasma or plasma produced when thin foils are irradiated by a laser.     

Equilibrium formation and growth of droplets on soluble nuclei by adiabatic expansion

Summary A thermodynamic approach is used to describe the formation and the growth upon soluble nuclei due to an adiabatic expansion. Using the conservation laws, several parameters may be expressed as functions of pressure, which is here the only independent variable. In particular, the variation of the droplet radius with pressure is presented.

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Riassunto Si propone un modello termodinamico di formazione e crescita di gocce su nuclei solubili per effetto di un’espansione adiabatica. Sfruttando le leggi di conservazione è posibile esprimere vari parametri in funzione della pressione, che è qui l’unica variabile indipendente. Il modello mostra, in particolare, la variazione del raggio della goccia con la pressione.

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New effective adiabatic approach to the muonic three-body scattering problem

The effective adiabatic approach to analysis of the three-particle interaction is presented. It gives a possibility to represent even in a simple two-level approximation all qualitative peculiarities of mesic atomic resonance reactions and to obtain a good quantitative agreement with different cumbersome calculations.     

Cyclotron-resonance maser with adiabatic magnetic pumping in a low-density plasma

The conditions under which the magnetic adiabatic compression of a plasma in a direct magnetic trap is accompanied by the accumulation of high energy in the hot anisotropic electron component are found. The basic instabilities resulting in the emission of the accumulated energy in the form of a pulse of stimulated electromagnetic radiation are analyzed. The possibility of creating terahertz radiation sources with the use of the magnetic compression of the plasma is discussed.     

The effective dielectric constant of a dispersion of clustering spheres

If one measures the dielectric constant of a water in oil microemulsion the large increase of this dielectric constant both as function of the temperature as well as a function of the volume fraction of water suggests that the water droplets will bind together in clusters. In order to analyse this suggestion in more detail we derive a systematic expansion of the Clausius-Mossotti function in terms of integrals over products of excess cluster polarizabilities and correlation functions. It is found that the excess polarizability of a cluster of spherical droplets is zero except when the spheres almost touch each other. Crucial for this property is the fact that the water spheres are conducting or if they are not conducting have a dielectric constant much larger than the dielectric constant of oil. The large increase of the dielectric constant is a consequence of the increase of the number of bound clusters. An explicit formula is given for the resulting temperature and volume fraction dependence of the dielectric constant.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Filamentation of lower-hybrid turbulence by adiabatic perturbations in a magnetized plasma

It is shown that stationary turbulence consisting of an ensemble of small amplitude lower hybrid wave packets becomes unstable against adiabatic perturbations along the external magnetic field. The growth rate and the threshold of the instability are calculated.     

Alpha clustering and the stellar nucleosynthesis of carbon

The astrophysical S-factor and reaction rates for the triple-alpha process are calculated in the direct-capture model. It is shown that the stellar carbon production is extremely sensitive to small variations in the N-N interaction.     

Influence of oxygen plasma treatment on boron carbon nitride film composition

Variations in the composition and bonds of boron carbon nitride (BCN) film caused due to an oxygen (O₂) plasma ashing process are investigated for a low dielectric constant (low-k) insulating film for next generation LSI devices. The O₂ plasma treatment is preformed for BCN samples with various C compositions. The etching rate of BCN films with an O₂ plasma decreases with increasing C composition. The reaction of O atoms is suppressed in the BCN film with a high C composition. B-N and B-C bonds with lower bond energies are easily broken by the O₂ plasma and replaced by the generation of B-O, N-O, and C-O bonds. The B-atom concentration for all samples is decreased significantly by the O₂ plasma treatment. Ion bombardment may play a more dominant role than the O-atom reaction in the etching of the BCN film. The existence of C-N bonds with a high bonding energy may suppress etching and incorporation of O atoms.     

Equilibrium of a gravitating plasma in a dipolar magnetic field

The equilibria of plasma in a dipolar magnetic field under the gravitational influence of a massive body (a star or black hole) and a self gravitating plasma are considered. Analytical solutions are found that can be useful for understanding the physics of plasma flows in accretion disks and star formation.     

Dust ion-acoustic solitary waves in a hot adiabatic magnetized dusty plasma

The basic features of obliquely propagating dust ion-acoustic (DIA) solitary waves in a hot adiabatic magnetized dusty plasma (containing adiabatic inertia-less electrons, adiabatic inertial ions, and negatively charged static dust) have been investigated. The reductive perturbation method has been employed to derive the Korteweg-de Vries (KdV) equation which admits a small amplitude solitary wave solution. The combined effects of plasma particle (electron and ion) adiabaticity, ion-dust collision, and external magnetic field (obliqueness), which are found to significantly modify the basic features of the small but finite-amplitude DIA solitary waves are explicitly examined. The implications of our results in space and laboratory dusty plasmas are briefly discussed.     

Particle composition and clustering in hadron-hadron collisions

Particle composition in hadron-hadron collisions is discussed in connection with clustering production of hadrons. The effective Lagrangians for the decay processes of theC -andC -type clusters are introduced. The particle composition is calculated by using the flavorSU(3) symmetry. The calculated results for particle composition as well as averaged transverse momenta are in agreement with ISR, SPS and Tevatron data.     

Stochastic clustering of the surface at the interaction of a plasma with materials

The inhomogeneous stochastic clustering of the surface with the self-similarity of the granularity structure from nano- to macroscales is observed in various materials after the action of intense high-temperature plasma flows in nuclear fusion facilities. The spectral and statistical characteristics of hierarchical granularity and scale invariance are estimated. They qualitatively differ from the properties of the simplest Brownian surface roughness and clustering under other conditions possibly because of universal mechanisms of the formation of stochastic clustering of materials under the action of a high-temperature plasma.     

Equilibrium characteristics of strong ion sheaths in a partiallyionized plasma

Experiments have been carried out to study the equilibrium characteristics of strong ion sheaths (eΦ/T_e≫1) in a partially ionized argon plasma. An improved method of potential measurement in the sheath is described. The potential profile shows deviations from Child's law and the reduction of sheath size with pressure. Energy analysis of ions reaching the negative biased electrode show that the ions are not monoenergetic but have a spread in energies which depends on neutral pressure     

Nonlinear adiabatic models of ion-acoustic waves in dust plasma

Nonlinear adiabatic models of ion-acoustic waves in a dust plasma are developed. The problem of the structure of subsonic periodic and supersonic solitary ion-acoustic waves is exactly solved analytically under the assumption of a constant charge of dust particles; the critical Mach numbers for the solitary wave are determined. The problem of the wave structure is solved numerically for the case when the charge of dust particles was assumed to be variable.     

Equilibrium lengths of railgun plasma armatures

Recent data have shown that the length of railgun plasma armatures increases with bore size. The mechanisms for plasma growth and mass loss are treated analytically through a simple thermodynamic model in which mass is added through ablation of bore materials and lost through friction. It is assumed that at the bore wall, a thin boundary layer is formed in the plasma in which the velocity is sufficiently slow that the boundary layer is left behind the bulk of the plasma. Using the scaling relations of J.D. Powell and J. Batteh (1983), a functional relationship between the plasma length l_p and bore height h of the form l_p=kh^α, where α≃0.68. Using the model developed in the present work, a linear relationship between l_p and h is derived, but the proportionality factor depends on temperature, plasma conductivity, velocity, and boundary-layer thickness. Predictions of the model are interpreted in the light of available data. The model is shown to predict lengths which are in reasonable agreement with the observed data