Analysis of the low—lying spectrum of the He—tetramer

There is a type of nodal surface imposed by symmetry on wavefunctions.These surfaces are crucial to the ordering of low-lying states.Based on an analysis of this type of surface and based on existing theoretical results,the feature of the low-lying spectrum of the He-tetramer is studied,and the candidates of bound states and narrow resonances are suggested.     

Telecommunications—the state of the art

This article is a survey of the technological foundations of telecommunications, including both point-to-point electrical communication wing wires, cables and other guiding media. and radio wave broadcasting to many receivers via terrestrial transmitters or Earth-orbiting space satellites. The characteristics of analogue and digital telecommunication signals, the means available for their transmission and switching me described, together with the organization of local distribution, national and global networks. The various services that can be provided over such networks, including in addition to telephonic communication, audio and video conferencing, data and facsimile transmission and new vied-display data/information access services (Teletext) are outlined. Finally, the sociological implications of these technological and service developments me considered, for example in terms of their impact on urban and rural planning, where people live and work, and on energy economy by reducing the need to travel.     

Study of the electronic structure of the quasicrystalline Ti—Zr—Ni system

Photoelectron spectra and optical absorption spectra for clean surfaces of quasicrystalline samples of the Ti—Zr—Ni system are measured. The resonant photoelectron spectra are also measured in the range of photon energies corresponding to Ni 2p and Zr 3d absorption thresholds. The change in the intensities of the spectrum of the valence band near the Zr 3d threshold is insignificant. The emission of Auger electrons increases near the Ni 2p threshold in a resonance way. Our studies make it possible to reveal certain specific features of the electronic structure of quasicrystals, which can be used to construct models of actual electronic structures of quasi-crystalline materials.     

Effect of the Coadsorption of CO and O2 on the Phase Diagram of the Ziff—Gulari—Barshad Model

The effect of the coadsorption of CO and O2 on the Ziff-Gulari-Barshad surface catalytic reaction system in studied by Monte Carlo simulation.The coadsorption of both species adds an extra reaction step to the classical Ziff-Gulari-Barshad model.It is shown that the second-order phase transition from the reactive state to the O-passivated state in the Ziff-Gulari-Barshad model is eliminated,and the production rate of CO2 increases linearly along the fraction yco of CO in gas phase when it is low,in agreement with experimental results.We also find that the increase of the probability of the coadsorption leads to the decrease of the critical value of yco of the discontinuous phase transition to the CO-passivated state.     

Renormalization of the contribution of the electron—electron interaction to the conductivity of two-dimensional electron systems

The contribution of the electron—electron interaction to the conductivity of the two-dimensional electron gas in an In_x Ga_1-x As single quantum well with different disorder strengths was experimentally studied. It is shown that the data are described well within the framework of the one-loop approximation of the renormalization group theory so long as the conductivity of the system remains higher than around 15e ²/μh.     

Scaling of the shear viscosity of the system nitrobenzene—n-hexane in the critical region

The shear viscosity of the system nitrobenzene—n-hexane was measured along the isochores near the critical concentration. By applying the empirical formula η = η_idε^-Φ _sp, the critical exponent of the shear viscosity Φ was determined.     

Scaling of the shear viscosity of the system nitrobenzene —n-heptane in the critical region

The temperature dependence of shear viscosity of the system nitrobenzene-n-heptane has been studied near the critical concentration. The critical exponent of the shear viscosity Φ was calculated from the empirical formula and compared with the theoretical and experimental results obtained for other critical systems. The shear viscosity satisfies scaling law relations similar to those previously established for equilibrium properties.     

P2—a new measurement of the weak charge of the proton

After ten years of experience with parity-violating electron-proton-scattering, the preparatory work on a new high precision parity-violation experiment in Mainz has begun. Project P2 is bound to measure the weak charge of the proton to a relative uncertainty of 1.9 %, which corresponds to a relative uncertainty of 0.15 % for $\sin^2{\theta_{W}}$ . This can be achieved by measuring the parity-violating asymmetry in elastic electron-proton-scattering to a relative precision of 1.7 % at E _beam~200 MeV and Q ²~0.005 GeV². In this proceeding, we will discuss the achievable precision within project P2 as well as the experimental concept and present first results of studies involving Monte Carlo methods.     

Study of the Bc—Meson Lifetime

We in terms of optical theorem estimate the lifetime of Bc meson with the parameters which are determined by fitting the data for the lifetimes and inclusive semileptonic decays of various B and D mesons.In the estimation,we find that the bound-state effects are important,and take them into account carefully in the framework which attributes the effects to the effective masses of the decay heavy quarks in the inclusive processes.We also find that to c liftime the peguin contribution is enhanced due to possible interference between peguin and the tree part c1O1 c2O2,.     

Cost of power—the user's perspective

Abstract

With the advent of fiber in the loop, transmission of power ceases to be through the traditional communications medium, and the objective of powering voice lines over fiber with the same reliability goals as plain old telephone service (POTS) raises several technological, regulatory, and business issues. In order to power the optical network unit (ONU) and provide backup power for it during commercial power outages, three strategies are identified: 1) providing loop powering from a ?48 volt CO/CEV power plant; 2) providing power and backup power locally, from or near the end of the loop in proximity to the OW; and 3) providing power from the curb or a power node. This paper constructs economic models to determine the worth of a watt at the 5-volt logic level at an ONU for each of the powering strategies. By normalizing all costs to the worth of a watt, comparisons can be made and appropriate architectures can be selected for various applications.     

Effects of Magnetic Field on the Valence Bond Property of the Double—Quantum—Dot Molecule

The effects of the magnetic field on the valence bond property of the double-quantum-dot molecule are numerically studied by the finite element method and perturbation approach because of the absence of cylindrical symmetry in the horizontally coupled dots.The calculation results show that the energy value of the ground state changes differently from that of the first excited state with increasing magnetic field strength,and they cross under a certain magnetic field.The increasing magnetic field makes the covalent bond state change into an ionic bond state,which agrees qualitatively with experimental results and and makes ionic bond states remain.The oscillator strength of transition between covalent bond states decreases distinctly with the increasing magnetic field strength,when the molecule is irradiated by polarized light.Such a phenomenon is possibly useful for actual applications.     

Fractal Solutions of the Nizhnik—Novikov—Veselov Equation

Considering that some types of fractal solutions may appear in many (2 1)-dimensional soliton equations because some arbitrary functions can be included in the exact solutions,we use some special types of lower dimensional fractal functions to construct higher dimensional fractal solutions of the Nizhnik-Novikov-Veselov equation.The static eagle-shape fractal solutions,fractal dromion solutions and the fractal lump solutions are given in detail.     

Beyond the method of images—the interaction of charged particles with real surfaces

A knowledge of the potential energy of a point charge outside a planar surface is important for understanding many charge transfer processes and surface spectroscopies. Whilst the ‘theory of images’ of classical electrostatics can be used to derive this potential, the result is valid only for static charges far from the surface. In this paper we describe recent attempts to consider moving charges near real surfaces, with particular reference to surfaces with dielectric overlayers, and we review experimental studies of the effects of the image force.     

Experimental study of the Plasma Fluorination of Y—Ba—Cu—O Thin Films

We have experimentally studied the surface mjodifications of Y-Ba-Cu-O (YBCO) thin films using CF4 plasma.The intensity of the plasma fluorination was controlled by controlled by changing the biasing voltage and the time of the plasma treatment.Microstructural analyses reveal that the oxygen content of the YBCO thin films was changed.Transport measurements of sufficient fluorinated YBCO films imply that the films changed totally into an oxygen-deficient semi-conducting state.From these experimental results,we believe that plasma fluorination is quite a useful method to form controllable a thin barrier layer in fabricating interface engineered junctions and to form a stable narrow weak-link region in fabricating planar superconductor-normal-superconductor junctions.     

Calculating the dielectric anisotropy of nematic liquid crystals: a reinvestigation of the Maier——Meier theory

This paper investigates the average dielectric permittivity (\overline ε ) in the Maier--Meier theory for calculating the dielectric anisotropy (Δε) of nematic liquid crystals. For the reason that \overline ε of nematics has the same expression as the dielectric permittivity of the isotropic state, the Onsager equation for isotropic dielectric was used to calculate it. The computed \overline ε shows reasonable agreement with the results of the numerical methods used in the literature. Molecular parameters, such as the polarizability and its anisotropy, the dipole moment and its angle with the molecular long axis, were taken from semi-empirical quantum chemistry (MOCPAC/AM1) modeling. The calculated values of Δε according to the Maier--Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.     

Study of the influence of higher—order Laue zones on the exit wavefunction

Based on an analytical expression of electron dynamical diffraction derived recently,the exit wavefunctions of nonperiodic samples have been calculated.The results have shown that the amplitude and phase obtained by the analytical expression were in good agreement with those obtained using the multi-slice method.Besides,the influence of the higher-order Laue zone on the wavefunction for different sample thickness was studied in detail and the results showed that the exit wavefunction is dominated by the zero-order Laue zone.When the sample is very thin,the influence of the higher-order Laue zone should be considered.     

Numerical Simulation of the Two—State Decoherence Model of Nano—Spin Systems

We have studied the two-state random decoherence model of the V15 system (Phys.Rev.Lett.84(2000)3458) with the k‘partial tracing of the environment’ method.The linearity relation between the averaged decoherence time and the random dipolar interaction amplitude is verified.The distribution function of decoherence time spreads more widely as the amplitude of the random field is decreased,hence it is difficult to define a decoherence time for the system.     

Study of the mechanism of the particle—substrate interaction in the case of the impact of a supersonic heterogeneous flow on a flat solid wall

The mechanism of the interaction between a particle and a flat substrate in the case of the inleakage of a supersonic heterogeneous flow to a solid wall is studied. The equation of energy balance in the area of particle impact on the substrate is considered. This makes it possible to calculate the weight-averaged temperatures of the heated particle segment and also the average temperature of the heated substrate segment in the contact area during the impact. This equation is an adequate mathematical model of the physical process of special-coating deposition on different metal surfaces, including the structural components of air- and spacecraft, by the gas-dynamic method at low temperatures.