Perturbation Approach to Lattice Instabilities in Quasi-One-Dimensional Conductors

1979 ◽  
pp. 227-245 ◽  
Author(s):  
L. J. Sham
Keyword(s):  
Perturbation Approach ◽  
One Dimensional

Näherungslösung einer verallgemeinerten Nernst-Planck-Gleichung für ein eindimensionales Membranmodell / Approximative Solution of a Generalized Nernst-Planck-equation for a one Dimensional Membran-model

1976 ◽  
Vol 31 (7) ◽  
pp. 815-822
Author(s):  
J. Schröter ◽  
H.-P. Stormberg
Keyword(s):  
External Field ◽  
Planck Equation ◽  
Zeroth Approximation ◽  
Perturbation Approach ◽  
One Dimensional ◽  
Low Concentration ◽  
Fixed Charges ◽  
First Approximation ◽  
Starting Point ◽  
Approximative Solution

AbstractThe starting-point of this paper are generalized Nernst Planck equations, which are deduced microscopically. Using a perturbation approach a result of this equation is given for a constant external field and a membran, which has a low concentration of fixed charges. The used conditions give a zeroth approximation which describes the homogeneous electrolyte. The first approximation shows the influence of the fixed charges, the friction between ions and membran and the influence of the correlations. The flows and the concentrations are then calculated for a system with equal concentrations on both sides of the membran.

Quarter-Filled Extended Hubbard Model at Strong Coupling

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3339-3342 ◽  
Author(s):  
W. F. Lee ◽  
H. Q. Lin
Keyword(s):  
Hubbard Model ◽  
Strong Coupling ◽  
Coulomb Interaction ◽  
State Energy ◽  
Nearest Neighbor ◽  
Spin Correlation ◽  
Perturbation Approach ◽  
Effective Hamiltonian ◽  
Extended Hubbard Model ◽  
One Dimensional

We apply a perturbation approach to study the quarter-filled extended Hubbard model at strong coupling limit. An effective Hamiltonian up to sixth order in t/U and t/V (t defines electron hopping, U defines on-site Coulomb interaction, and V defines nearest-neighbor Coulomb interaction) for one-dimensional chains was obtained. The spin-spin correlation functions were involved, which can be obtained after comparing to the ground state energy numerically obtained from the phase diagram.

A simple model of wave–current interaction

2015 ◽  
Vol 775 ◽  
pp. 328-348 ◽  
Author(s):  
Nicoletta Tambroni ◽  
Paolo Blondeaux ◽  
Giovanna Vittori
Keyword(s):  
Wave Propagation ◽  
Perturbation Approach ◽  
Wave Steepness ◽  
One Dimensional ◽  
Steady Current ◽  
Order Of Magnitude ◽  
Current Interaction ◽  
Viscous Boundary ◽  
The Waves ◽  
Theoretical Results

The interaction between a steady current and propagating surface waves is investigated by means of a perturbation approach, which assumes small values of the wave steepness and considers current velocities of the same order of magnitude as the amplitude of the velocity oscillations induced by wave propagation. The problems, which are obtained at the different orders of approximation, are characterized by a further parameter which is the ratio between the thickness of the bottom boundary layer and the length of the waves and turns out to be even smaller than the wave steepness. However, the solution is determined from the bottom up to the free surface, without the need to split the fluid domain into a core region and viscous boundary layers. Moreover, the procedure, which is employed to solve the problems at the different orders of approximation, reduces them to one-dimensional problems. Therefore, the solution for arbitrary angles between the direction of the steady current and that of wave propagation can be easily obtained. The theoretical results are compared with experimental measurements; the fair agreement found between the model results and the laboratory measurements supports the model findings.

A Perturbation Approach for Predicting Wave Propagation in One-Dimensional Nonlinear Periodic Structures

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Raj K. Narisetti ◽  
Michael J. Leamy ◽  
Massimo Ruzzene
Keyword(s):  
Wave Propagation ◽  
Numerical Simulations ◽  
Perturbation Analysis ◽  
Periodic Structures ◽  
Harmonic Wave ◽  
Dispersion Relations ◽  
Perturbation Approach ◽  
One Dimensional ◽  
Chain Unit ◽  
Unit Cells

Wave propagation in one-dimensional nonlinear periodic structures is investigated through a novel perturbation analysis and accompanying numerical simulations. Several chain unit cells are considered featuring a sequence of masses connected by linear and cubic springs. Approximate closed-form, first-order dispersion relations capture the effect of nonlinearities on harmonic wave propagation. These relationships document amplitude-dependent behavior to include tunable dispersion curves and cutoff frequencies, which shift with wave amplitude. Numerical simulations verify the dispersion relations obtained from the perturbation analysis. The simulation of an infinite domain is accomplished by employing viscous-based perfectly matched layers appended to the chain ends. Numerically estimated wavenumbers show good agreement with the perturbation predictions. Several example chain unit cells demonstrate the manner in which nonlinearities in periodic systems may be exploited to achieve amplitude-dependent dispersion properties for the design of tunable acoustic devices.

Recent Developments in the Analysis and Design of Extended Surface

1983 ◽  
Vol 105 (2) ◽  
pp. 302-306 ◽  
Author(s):  
A. D. Snider ◽  
A. D. Kraus
Keyword(s):  
Perturbation Approach ◽  
Heat Sources ◽  
Approximate Computation ◽  
One Dimensional ◽  
Analysis And Design ◽  
Recent Developments ◽  
Extended Surface ◽  
Flow Configurations ◽  
Transfer Properties

Earlier papers by the authors developed a new set of parameters for characterizing heat transfer properties of single fins and fins in arrays of extended surface. The use of these parameters has facilitated the solutions to several interesting fin problems, namely: a more careful characterization of one-dimensional flow configurations, a method for accommodating continuously distributed heat sources along the fin, a perturbation approach for the approximate computation of the parameters, and new insights into the precepts of the optimal fin shape. These developments are reported in this paper.

A one-dimensional self-gravitating stellar gas

1966 ◽  
Vol 25 ◽  
pp. 46-48 ◽  
Author(s):  
M. Lecar
Keyword(s):  
Gravitational Field ◽  
Phase Space ◽  
Motion Picture ◽  
Space Distribution ◽  
Two Dimensional ◽  
One Dimensional ◽  
Phase Space Distribution ◽  
Dimensional Phase Space ◽  
The Mean

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.

Electron-Mirror Microscopic Aspects of Ferroelectric Domains of BaTiO3 And Ca2Sr (C2H5CO2)6

1970 ◽  
Vol 28 ◽  
pp. 478-479
Author(s):  
Teruo Someya ◽  
Jinzo Kobayashi
Keyword(s):  
Surface Layer ◽  
Electric Fields ◽  
Quantitative Study ◽  
Recent Progress ◽  
Ferroelectric Domain ◽  
Resolving Power ◽  
Surface Pattern ◽  
Crystal Surfaces ◽  
One Dimensional ◽  
Ferroelectric Domains

Recent progress in the electron-mirror microscopy (EMM), e.g., an improvement of its resolving power together with an increase of the magnification makes it useful for investigating the ferroelectric domain physics. English has recently observed the domain texture in the surface layer of BaTiO3. The present authors ) have developed a theory by which one can evaluate small one-dimensional electric fields and/or topographic step heights in the crystal surfaces from their EMM pictures. This theory was applied to a quantitative study of the surface pattern of BaTiO3).

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

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