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.     

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.     

Six—Parameter Exponential—Type Potential and the Identity for the Exponential—Type Potentials

We propose a six-parameter exponential-type potential (SPEP),which has been shown to be a shapeinvariant potential with a translation of parameters.For this reducible potential,the exact energy levels are obtained by using the supersymmetric shape invariance technique.Choosing appropriate parameters,four classes of exponential-type potentials and their exact energy spectra are reduced from the SPEP and a general energy level formula,respectively.Each class shows the identity except for the different definitions of parameters.     

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.     

Remarks on the Schur—Howe—Sergeev Duality

We establish a new Howe duality between a pair of two queer Lie superalgebras (q(m),q(n)). This gives a representation theoretic interpretation of a well-known combinatorial identity for Schur Q-functions. We further establish the equivalence between this new Howe duality and the Schur–Sergeev duality between q(n) and a central extension of the hyperoctahedral group H _k. We show that the zero-weight space of a q(n)-module with highest weight given by a strict partition of n is an irreducible module over the finite group parameterized by . We also discuss some consequences of this Howe duality.     

Exact Solution of the Milburn Equation for the Two—Mode Two—Photon Jaynes—Cummings Model

We adopt an algebraic method to study the two-mode two-photon Jaynes-Cummings model governed by the Milburn equation and find an exact solution of Milburn equation of the system.The influence of the intrinsic decoherence on the nonclassical effects of the system is also discussed.     

Abundant Symmetries and Exact Compacton—Like Structures in the Two—Parameter Family of the Estevez—Mansfield—Clarkson Equations

The two-parameter family of Estevez-Mansfield-Clarkson equations with fully nonlinear dispersion (called E(m,n) equations),(uz^m)zzτ γ(uz^nuτ)z uττ=0 which is a generalized model of the integrable Estevez-Mansfield-Clarkson equation uzzzτ γ(uzuzτ uzzuτ) uττ=0,is presented.Five types of symmetries of the E9m,n) equation are obtained by making use of the direct reduction method.Using these obtained reductions and some simple transformations,we obtain the solitary-like wave solutions of E(1,n) equation.In addition,we also find the compacton solutions (which are solitary waves with the property that after colliding with other compacton solutions,they reemerge with the same coherent shape) of E(3,2) equation and E(m,m-1) for its potentials,say,uz,and compacton-like solutions of E(m,m-1) equations,respectively.Whether there exist compacton-like solutions of the other E(m,n) equation with m≠n 1 is still an open problem.     

Probabilistic Teleportation of the Three—Particle Entangled State by the Partial Three—Particle Entangled State and the Three—Particle Entangled W State

We present a scheme to teleport an unknown three-particle entangled state from a sender to either one of two receivers. The partial three-particle entangled state and the three-particle entangled W state are considered as the quantum channels. An unknown three-particle entangled state can be perfectly teleported probabilistically by performing two generalized Bell measurements and the Hadamard operation at the sender‘s side and introducing an appropriate unitary transformation in each receiver‘s laboratory conditioned on the simple measurement outcome of the other. All kinds of unitary transformations are given in details. This scheme can be directly generalized to teleport an unknown three-particle entangled state from a sender to any one of N receivers by the partial three-particle entangled state and the (N 1)-particle entangled W state.     

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.     

Einstein—Podolsky—Rosen Correlations and the Preferred Frame

The correlation function of spin measurements of two spin- particles in two moving inertial frames is derived within the framework of the Lorentz covariant quantum mechanics with the preferred frame. The localization of the particles during the detection and proper transformation properties under the action of the Lorentz group of the spin operator are taken into account. Some special cases and approximations of the calculated correlation function are discussed.     

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.     

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,.     

Extending the First—Order Post—Newtonian Scheme in Multiple Systems to the Second—Order Contributions to Light Propagation

We extend the first-order post-Newtonian scheme in multiple systems presented by Damour-Soffel-Xu to the second-order contribution to light propagation without changing the virtue of the scheme on the linear partial differential equations of the potential and vector potential.The spatial components of the metric are extended to the second-order level both in a global coordinates(qij/c^4) and a local coordinates(Qab/c^4).The equations of qij(or Qab)are obtained from the field the field equations.The relationship between qji and Qab are also presented.In the special case of the solar system(isotropic condition is applied(qij=δijq)),we obtain the solution of q.Finally,a further extension of the second-order contributoions in the parametrized post-Newtonian formalism is discussed.     

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.     

Spectroscopic Investigation on the Charge—Transfer Complex of 2,4,6—Trinitrophenol with the Polycyclicamine 1,4,8,11-Tetraazacyclotetradecane

Abstract

The reaction between 2,4,6-trinitrophenol(TNP) and the polycyclicamine 1,4,8,11-tetraazacyclotetradecane (TACTD) in solvents such as chloroform and carbontetrachloride have been studied spectrophotometrically using UV—VIS, and IR methods. The results indicate the formation of a 1:2 charge—transfer complex with formula((TACTD)(TNP)₂). The charge-transfer absorption in this complex appears arounds 410 nm. The values of both the equilibrium constant, K, and the molar extinction coefficient, ?, for the reaction in different solvents are calculated for the CT-complex. These values were used to understand the solvent effects on the course of the reaction. All observed infrared bands for the formed solid complex are assigned.     

Mean—Field Calculations for the Three—Dimensional Holstein Model

The electron-phonon Holstein model is studied in three spatial dimensions.It is argued that this model can be used to account for major features of the high-Tc BaPb1-xBixO3 and BaxK1-xBiO3 systems.Mean-field calculations are performed via a path integral representation of the model.Charge-density-wave order parameters and transition temperatures are obtained.     

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.     

Influence of the Boundary Condition on the Short—Time Dynamic Behaviour of the Ising—Like Phase Transition in Square—LOattice Fully Frustrated XY Models

We investigate the influence of the boundary condition on the short-time dynamic behaviour of the Ising-like phase transition in square-lattice fully frustrated (FF) XY models with periodic and fluctuating twist boundary conditions.The transition temperature Tc and the dynamic and static critical exponents z,2β/υ and υ are estimated for both cases using short-time dynamic scaling analysis.The results show that both models have the same critical exponents,indicating that the boundary condition has nearly no effect on the short-time dynamic behaviour of the FFXY model.     

Entropy in the NUT—Kerr—Newman Black Holes in the Background of de Sitter Spacetime

We calculate the entropy of the fermion field in the NUT-Kerr-Newman black holes in the background of the de Sitter spacetime by using the improved brick-wall method and the membrane model.Here the Euler characteristic of the black holes is over two.The results show that,as the cut-off is properly chosen,the entropy in the black hole satisfies the Bekenstein-Hawking area law.