Search results for "model [interaction]"
showing 10 items of 1495 documents
Radiative zone solar magnetic fields and g modes
2005
We consider a generalized model of seismic-wave propagation that takes into account the effect of a central magnetic field in the Sun. We determine the g-mode spectrum in the perturbative magnetic field limit using a one-dimensional Magneto-Hydrodynamics (MHD) picture. We show that central magnetic fields of about 600-800 kG can displace the pure g-mode frequencies by about 1%, as hinted by the helioseismic interpretation of GOLF observations.
Ultrasonic cavity solitons
2007
We report on a new type of localized structure, an ultrasonic cavity soliton, supported by large aspect-ratio acoustic resonators containing viscous media. These states of the acoustic and thermal fields are robust structures, existing whenever a spatially uniform solution and a periodic pattern coexist. Direct proof of their existence is given both through the numerical integration of the model and through the analysis and numerical integration of a generalized Swift-Hohenberg equation, derived from the microscopic equations under conditions close to nascent bistability. An analytical solution for the ultrasonic cavity soliton is given.
Topology of multiplex heterogeneous networks of Hodgkin-Huxley-type of models with bistability leading to stabilization stable equilibrium
2021
The dynamics of a multiplex heterogeneous networks of oscillators is studied. Two types of very similar models based on the Hodgkin-Huxley formalism are used as the basic elements of the network: the first one demonstrates bursting oscillations; the second one manifests bistability between bursting oscillations and stable equilibrium. Multiplex networks were developed and investigated, assuming more active communication between models with bistability. Different topologies of the networks are studied. It is shown that in this case it is enough to have one element with bistability in the subnetworks in order to stabilize the equilibrium state in the entire network.
Lusternik-Schnirelmann Critical Values and Bifurcation Problems
1987
We present a method to calculate bifurcation branches for nonlinear two point boundary value problems of the following type $$ \{ _{u(a) = u(b) = 0,}^{ - u'' = \lambda G'(u)} $$ (1.1) where G : R → R is a smooth mapping. This problem can be formulated equivalently as $$ g' \left(u \right)= \mu u, $$ (1.2) where $$ g \left(u \right)= \overset{b} {\underset{a} {\int}} G \left(u \left(t \right) \right) dt $$ (1.3) and μ = 1/λ. Solutions of this problem can be found by locating the critical points of the functional g : H → R on the spheres \(S_r= \lbrace x \in H \mid \;\parallel x \parallel =r \rbrace, r >0.\) (The Lagrange multiplier theorem.)
The Zero-Check for Eliminating Non-Significant Elements
1970
During continued matrix operations like the simplex method a lot of small non-significant elements, the actual value of which is zero,usually augment the working coefficient matrix. These elements are caused by round-off errors. They arise in the following manner in a computation of the type: $${\rm{d}}\, = \,{\rm{a}}\,{\rm{ - }}\,{\rm{b}}{\rm{.c}}$$ with e.g. the data (in FORTRAN notation) $${\rm{a}}\, = \,{\rm{2}}\,{\rm{ = }}\,{\rm{.20000000}}\,{\rm{E}}\,{\rm{01}}$$ $${\rm{b}}\, = \,{\rm{6}}\,{\rm{ = }}\,{\rm{.60000000}}\,{\rm{E}}\,{\rm{01}}$$ $${\rm{c}}\, = \,{\rm{1/3}}\,{\rm{ = }}\,{\rm{.33333333}}\,{\rm{E}}\,{\rm{00}}$$
Electronic structure of Gold, Aluminum and Gallium Superatom Complexes
2011
Using ab initio computational techniques on crystal determined clusters, we report on the similarities and differences of Al${}_{50}$(C${}_{5}$(CH${}_{3}{{)}_{5})}_{12}$, Ga${}_{23}$(N(Si(CH${}_{3}{)}_{3}$)${}_{2}$)${}_{11}$, and Au${}_{102}$(SC${}_{7}$O${}_{2}$H${}_{5}$)${}_{44}$ ligand-protected clusters. Each of the ligand-protected clusters in this study shows a similar stable character which can be described via an electronic shell model. We show here that the same type of analysis leads consistently to derivation of a superatomic electronic counting rule, independently of the metal and ligand compositions. One can define the cluster core as the set of atoms where delocalized single-an…
Effects of nonlinear sweep in the Landau-Zener-Stueckelberg effect
2002
We study the Landau-Zener-Stueckelberg (LZS) effect for a two-level system with a time-dependent nonlinear bias field (the sweep function) W(t). Our main concern is to investigate the influence of the nonlinearity of W(t) on the probability P to remain in the initial state. The dimensionless quantity epsilon = pi Delta ^2/(2 hbar v) depends on the coupling Delta of both levels and on the sweep rate v. For fast sweep rates, i.e., epsilon << l and monotonic, analytic sweep functions linearizable in the vicinity of the resonance we find the transition probability 1-P ~= epsilon (1+a), where a>0 is the correction to the LSZ result due to the nonlinearity of the sweep. Further increase …
Controlled type-I–type-II transition in GaAs/AlAs/AlxGa1−xAs double-barrier quantum wells
1997
We show that the insertion of extremely narrow AlAs layers in double-barrier GaAs/AlAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quantum wells results in a variety of electronic configurations, thus providing a powerful tool for tailoring the electronic transitions in GaAs heterostructures. In particular, the transition from type-I to type-II recombination is shown to occur in correspondence with variations by a single monolayer in the thickness of the AlAs and/or GaAs layers. Drastic changes in the recombination lifetimes are correspondingly observed; at the same time, the photoluminescence efficiency is found to be almost independent of the type-I-…
Structure-property relations in the distorted ordered double perovskite Sr2InReO6
2011
The rock-salt ordered type double perovskite Sr${}_{2}$InReO${}_{6}$ is systematically investigated by means of powder x-ray diffraction, neutron powder diffraction, temperature-dependent electrical transport, heat capacity and magnetic susceptibility measurements, and electronic band structure calculations. The crystal structure of Sr${}_{2}$InReO${}_{6}$ is revised to be monoclinic (cryolite structure type, space group $P$2${}_{1}$/$n$) with all structural distortions according to the high-symmetry aristotype due to tilting of the InO${}_{6}$ and ReO${}_{6}$ octahedra, respectively. Sr${}_{2}$InReO${}_{6}$ is a Mott insulator with variable-range hopping. Two 5$d$ electrons are unpaired an…
Observation of a charge delocalization from Se vacancies inBi2Se3: A positron annihilation study of native defects
2016
By means of positron annihilation lifetime spectroscopy, we have investigated the native defects present in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, which belongs to the family of topological insulators. We experimentally demonstrate that selenium vacancy defects $({\text{V}}_{\text{Se1}})$ are present in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ as-grown samples, and that their charge is delocalized as temperature increases. At least from 100 K up to room temperature both ${\text{V}}_{\text{Se1}}^{0}$ and ${\text{V}}_{\text{Se1}}^{+}$ charge states coexist. The observed charge delocalization determines the contribution of ${\text{V}}_{\text{Se1}}$ defects to the $n$-type conductivity of ${\mathrm{…