Natural convection from a vertical cone in a porous medium due to the combined effects of heat and mass diffusion with non-uniform wall temperature/concentration or heat/mass flux and suction/injection

An analysis has been carried out to study the non-Darcy natural convention flow of Newtonian fluids on a vertical cone embedded in a saturated porous medium with power-law variation of the wall temperature/concentration or heat/mass flux and suction/injection with the streamwise distance x. Both non-similar and self-similar solutions have been obtained. The effects of non-Darcy parameter, ratio of the buoyancy forces due to mass and heat diffusion, variation of wall temperature/concentration or heat/mass flux and suction/injection on the Nusselt and Sherwood numbers have been studied.

Theory For The Anomalous Hall Constant Of Mixed-Valence Systems

We show that the large anomalous Hall constants of mixed-valence and Kondo-lattice systems can be understood in terms of a simple resonant-level Fermi-liquid model. Splitting of a narrow, orbitally unquenched, spin-orbit split, f resonance in a magnetic field leads to strong skew scattering of band electrons. We interpret both the anomalous signs and the strong temperature dependence of Hall mobilities in CeCu2Si2, SmB6, and CePd3 in terms of this theory.

Gauge theory of a group of diffeomorphisms. I. General principles

Any (N+M)-parameter Lie group G with an N-parameter subgroup H can be realized as a global group of diffeomorphisms on an M-dimensional base space B, with representations in terms of transformation laws of fields on B belonging to linear representations of H. The gauged generalization of the global diffeomorphisms consists of general diffeomorphisms (or coordinate transformations) on a base space together with a local action of H on the fields. The particular applications of the scheme to space-time symmetries is discussed in terms of Lagrangians, field equations, currents, and source identities. Journal of Mathematical Physics is copyrighted by The American Institute of Physics.

Resonances, scattering theory, and rigged Hilbert spaces

The problem of decaying states and resonances is examined within the framework of scattering theory in a rigged Hilbert space formalism. The stationary free,''in,'' and ''out'' eigenvectors of formal scattering theory, which have a rigorous setting in rigged Hilbert space, are considered to be analytic functions of the energy eigenvalue. The value of these analytic functions at any point of regularity, real or complex, is an eigenvector with eigenvalue equal to the position of the point. The poles of the eigenvector families give origin to other eigenvectors of the Hamiltonian: the singularities of the ''out'' eigenvector family are the same as those of the continued S matrix, so that resonances are seen as eigenvectors of the Hamiltonian with eigenvalue equal to their location in the complex energy plane. Cauchy theorem then provides for expansions in terms of ''complete'' sets of eigenvectors with complex eigenvalues of the Hamiltonian. Applying such expansions to the survival amplitude of a decaying state, one finds that resonances give discrete contributions with purely exponential time behavior; the background is of course present, but explicitly separated. The resolvent of the Hamiltonian, restricted to the nuclear space appearing in the rigged Hilbert space, can be continued across the absolutely continuous spectrum; the singularities of the continuation are the same as those of the ''out'' eigenvectors. The free, ''in'' and ''out'' eigenvectors with complex eigenvalues and those corresponding to resonances can be approximated by physical vectors in the Hilbert space, as plane waves can. The need for having some further physical information in addition to the specification of the total Hamiltonian is apparent in the proposed framework. The formalism is applied to the Lee–Friedrichs model and to the scattering of a spinless particle by a local central potential. Journal of Mathematical Physics is copyrighted by The American Institute of Physics.

Salan: A microprocessor-based medium speed experimental local area network

In this paper the implementation and application of a microprocessor-based medium speed experimental local area network using a coaxial cable transmission medium are dealt with. A separate unidirectional control wire has been used in order to provide a collision-free and fair medium access arbitration. As an application of the network, the design of a packet voice communication system is discussed.

Analysis of drop formation at conical tips : 1. Theory

The phenomenon of drop formation at conical tips under near zero flow conditions has been investigated using a theoretical approach. The analysis permits the prediction of drop profile and drop volume, until the onset of instability. A semiempirical approach based on the similarity of drop shapes has been adopted to predict the detaching drop volumes at conical tips. The effects of base diameter of the cone, cone angle, interfacial tension, and the densities of the drop and the surrounding fluid on the maximum and detached drop volumes are predicted.

Theory of the mixed valent state

After briefly discussing the question of a distinct mixed valent state and theoretical models for it, the area of greatest theoretical success, namely the mixed valent impurity, is reviewed. Applications to spectroscopy, energetics and Hall effect are then putlined. The independent impurity approximation is inadequate for many properties of the bulk system, which depend on lattice coherence. A recent auxiliary or slave boson approach with a simple mean field limit and fluctuation corrections is summarized. Finally the mixed valent semiconductor is discussed as an outstanding problem.

On anomalous U(1) gauge theory in four dimensions

We discuss the consistency, unitarity and Lorentz invariance of an anomalous U(1) gauge theory in four dimensions. Our analysis is based on an effective low-energy action valid in the chiral symmetry broken phase. The allegedly bad properties of anomalous theories (except non-renormalizability) are examined. It is shown that, in the low-energy context, the theory can be consistently and unitarily quantised, and is formally Lorentz covariant.

Note on the one-parameter scaling theory of localisation

The necessary and sufficient condition for the existence of the one-parameter scale function, the /Munction, is obtained exactly. The analysis reveals certain inconsistency inherent in the scaling theory, and tends to support Motts’ idea of minimum metallic conductivity.

Synthesis and Characterization of Carbon-Coated LiNi1/3Co1/3Mn1/3O2 in a Single Step by an Inverse Microemulsion Route

Layered LiNi1/3Co1/3Mn1/3O2, which is isostructural to LiCoO2, is considered as a potential cathode material. A layer of carbon coated on the particles improves the electrode performance, Which is attributed to an increase of the grain connectivity and also to protection of metal oxide from chemical reaction. The present work involves in situ synthesis of carbon-coated submicrometer-sized particles of LiNi1/3Co1/3Mn1/3O2 in an inverse microemulsion medium in the presence of glucose. The precursor obtained from the reaction is heated in air at 900 degrees C for 6 h to get crystalline LiNi1/3Co1/3Mn1/3O2. The carbon coating is found to impart porosity as well as higher surface area in relation to bare samples of the compound. The electrochemical characterization studies provide that carbon-coated LiNi1/3Co1/3Mn1/3O2 samples exhibit improved rate capability and cycling performance. The carbon coatings are shown to suppress the capacity fade, which is normally observed for the bare compound. Impedance spectroscopy data provide additional evidence for the beneficial effect of a carbon coating on LiNi1/3Co1/3Mn1/3O2 particles.

AILaNb2O7:A new series of layered perovskites exhibiting ion exchange and intercalation behaviour

A new series of layered perovskite oxides, AILaNb2O7 (A = Li, Na, K, Rb, Cs, NH4) constituting n = 2 members of the family A A′n−1BnO3n+1, has been prepared. Their structure consists of double perovskite slabs interleaved by A atoms. Hydrated HLaNb2O7 is formed by topotactic proton exchange of the A atoms in ALaNb2O7 (A = K, Rb, Cs). The hydrate readily loses water to give anhydrous HLaNb2O7 which is isostructural with RbLaNb2O7. HLaNb2O7 exhibits Bronsted acidity forming intercalation compounds with bases such as n-octylamine and pyridine.

Thermodynamic scaling theory for impurities in metals

A perturbative scaling theory for calculating static thermodynamic properties of arbitrary local impurity degrees of freedom interacting with the conduction electrons of a metal is presented. The basic features are developments of the ideas of Anderson and Wilson, but the precise formulation is new and is capable of taking into account band-edge effects which cannot be neglected in certain problems. Recursion relations are derived for arbitrary interaction Hamiltonians up to third order in perturbation theory. A generalized impurity Hamiltonian is defined and its scaling equations are derived up to third order. The strategy of using such perturbative scaling equations is delineated and the renormalization-group aspects are discussed. The method is illustrated by applying it to the single-impurity Kondo problem whose static properties are well understood.

Hole Pairing In Antiferromagnetically Correlated Layered Oxides

We have considered a two-band Hubbard model having interlaced Cu-3d(x2−y2) and O-2p(x, y) orbitals representing the CuO2 square planes. Simple CuO2 -cluster calculation suggests that the additional holes created by doping stay mainly on oxygen. Motion of an oxygen hole interlacing with the antiferromagnetically correlated background of copper spins, creates a string of high energy spin configuration of finite length giving mass renormalization. Another hole of opposite spin can now anneal this string tension providing a triangular pairing potential for large pair momentum. The latter implies unusual Bose condensation of the wake-bound compact Bose-like pairs on a non-zero momentum shell. Effect of disorder favouring condensation at the mobility edge is pointed out.