Sintering dynamics and thermal stability of novel configurations of Ag clusters

Monte Carlo simulations with second-moment approximation of tight-binding potential were applied to study the sintering dynamics and thermal stability for novel configurations of Ag clusters. Simulations under elevated temperatures utilizing various configurations indicated that sintering processes were strongly affected by temperature and initial design configurations. Ag clusters re-aligned themselves at the onset of sintering, forming clear necks of varying stabilities and different matter diffusion routes between clusters due to differences in initial design configurations. Notably, different Ag cluster design configurations displayed variable melting temperatures. The methodical simulation of design configurations can elucidate strategies to maintain desirable nanocluster structure during sintering processes.     

Temperature independent length optimization of L-band EDFAs providing flat gain

In this study, single stage (SS), double-stage (DS), and gain flattened (GF) DS L-band erbium-doped fiber amplifier (EDFA) configurations are designed in order to obtain a flat gain amplifier. Temperature dependence of the mentioned configurations is also analyzed. Maximum spectral dependence of EDFA gain with respect to temperature is obtained for SS EDFA design while smaller spectral dependence of gains is obtained for both DS and GF DS L-EDFA configurations. It is observed that the maximum temperature dependence is in the range of 1570-1580 nm band for all configurations. It has also been found that for all configurations, reducing the temperature has greater effect than raising the temperature on EDFA gain. The overall results show that a temperature independent L-band configuration has not been possible. However, for some signal wavelengths, the erbium-doped fiber (EDF) lengths at which the gain is temperature independent are observed.     

Chaotic Behavior of a Pseudoinverse Layered Neural Network

Evolution of configurations in a pseudoinverse layered neural network is studied, and exact expressions for the evolution of the distance between two configurations are obtained in the thermodynamic limit. Exact results are presented and comparisons to computer simulations are made. Our results show that the distance between t,wo arbitrarily close configurations may increase, implying chaotic behavior.     

Elastic stability of DNA configurations. II. Supercoiled plasmids with self-contact

Configurations of protein-free DNA miniplasmids are calculated with the effects of impenetrability and self-contact forces taken into account by using exact solutions of Kirchhoff's equations of equilibrium for elastic rods of circular cross section. Bifurcation diagrams are presented as graphs of excess link, DeltaL, versus writhe, W, and the stability criteria derived in paper I of this series are employed in a search for regions of such diagrams that correspond to configurations that are stable, in the sense that they give local minima to elastic energy. Primary bifurcation branches that originate at circular configurations are composed of configurations with D(m) symmetry (m=2,3,...). Among the results obtained are the following. (i) There are configurations with C2 symmetry forming secondary bifurcation branches which emerge from the primary branch with m=3, and bifurcation of such secondary branches gives rise to tertiary branches of configurations without symmetry. (ii) Whether or not self-contact occurs, a noncircular configuration in the primary branch with m=2, called branch alpha, is stable when for it the derivative dDeltaL/dW, computed along that branch, is strictly positive. (iii) For configurations not in alpha, the condition dDeltaL/dW>0 is not sufficient for stability; in fact, each nonplanar contact-free configuration that is in a branch other than alpha is unstable. A rule relating the number of points of self-contact and the occurrence of intervals of such contact to the magnitude of DeltaL, which in paper I was found to hold for segments of DNA subject to strong anchoring end conditions, is here observed to hold for computed configurations of protein-free miniplasmids.     

Development of an analytical potential to include excited configurations

Excited configurations are very important in dense plasma physics. In this work we propose a new analytical potential for excited configurations obtained from another one for ground configuration. With this potential several atomic magnitudes have been calculated for ions in excited configurations analyzing what kind of excited configurations introduce more influences in those magnitudes. Using this potential, atomic data generated are satisfactorily compared with those obtained using other analytical potential using sophisticated self-consistent codes, and with others available in the bibliography.     

First-principles combinatorial design of transition temperatures in multicomponent systems: the case of Mn in GaAs

The transition temperature TC of multicomponent systems--ferromagnetic, superconducting, or ferroelectric--depends strongly on the atomic arrangement, but an exhaustive search of all configurations for those that optimize TC is difficult, due to the astronomically large number of possibilities. Here we address this problem by parametrizing the TC of a set of approximately 50 input configurations, calculated from first principles, in terms of configuration variables ("cluster expansion"). Once established, this expansion allows us to search almost effortlessly the transition temperature of arbitrary configurations. We apply this approach to search for the configuration of Mn dopants in GaAs having the highest ferromagnetic Curie temperature. Our general approach of cluster expanding physical properties opens the way to design based on exploring a large space of configurations.     

Minimal Sandpiles on Hexagonal Lattice

We study the minimal recurrent configurations of the Abelian sandpile model on the hexagonal lattice referred to the dynamics of a nonconservative sandpile model. The one-to-one correspondence between these configurations and the set of maximally oriented spanning trees on the triangular sublattice is constructed. We derive the correlation functions in minimal recurrent configurations on a quasi-one-dimensional 2 × N lattice, compare them with correlations for ordinary recurrent configurations, and argue for asymptotic equivalence between them.     

Fluctuating solutions for the evolution of domain walls

A class of oscillating Lorentz-covariant configurations for the evolution of the domain walls in diverse dimensions are analytically obtained. It is shown that the oscillating solutions in the case of domain walls are responsible for structures which are larger than the usual kink-like configurations and, in the Lorentz-covariant evolution case, lead to long-standing configurations.     

Reduction of surface transport noise by ground roughness

Measured insertion losses due to the ground effects associated with low configurations of loosely stacked household bricks on a car park are reported. A particularly successful design has the form of a two brick high square lattice which is found to offer a similar insertion loss to regularly-spaced parallel wall arrays of the same height but twice the total width. Part of the insertion loss due to the roughness configurations is the result of transfer of incident sound energy to surface waves which can be reduced by introducing wall absorption or material absorption in the form, for example, of shallow gravel layer. Predicted finite length effects have been explored using a Pseudo-Spectral Time Domain Method, which models the complete 3D roughness profile. It is concluded from measurements and predictions that the lattice design has less dependence on azimuthal source-receiver angle than parallel wall configurations. These predictions are supported by measurements of level difference spectra as a function of azimuthal angle. A 2D Boundary Element Method gives predictions that agree well with data for parallel wall arrays up to 16 m long and it is used to investigate the potential insertion loss of longer configurations up to 0.3 m high. It has been found possible also to make predictions of the insertion loss due to infinitely long 3D lattices using the 2D BEM with the lattice represented by the surface impedance derived from fitting short range data with a slit-pore impedance model. The insertion losses of recessed configurations are predicted to be approximately 3 dB less than those of embossed configurations of the same size. Outdoor experiments also show that pathways can be made through such roughness configurations without significantly affecting their insertion loss. It is concluded that artificial roughness configurations could achieve substantial noise reduction along surface transport corridors without breaking line of sight between source and receiver, thereby proving useful alternatives to noise barriers.     

High-beta equilibria of drift-optimized compact stellarators

Compact stellarator configurations have been obtained with good neoclassical confinement that are stable to both pressure- and current-driven modes for high values of beta. These configurations are drift-optimized tokamak-stellarator hybrids with a high-shear tokamak-like rotational transform profile and /B/ that is approximately poloidally symmetric. The bootstrap current is consistent with the required equilibrium current and, while larger than that in existing stellarators, is typically only a small fraction (1/3-1/5) of that in an equivalent tokamak. These configurations have strong magnetic wells and consequently high interchange stability beta limits up to beta=23%. Because of the reduced bootstrap current, these configurations are stable to low-n ideal MHD kink modes with no wall stabilization for values of beta ( approximately 7%-11%) significantly larger than in an equivalent advanced tokamak.     

The classical mechanics of one-dimensional systems of infinitely many particles

We apply the existence theorem for solutions of the equations of motion for infinite systems to study the time evolution of measures on the set of locally finite configurations of particles. The set of allowed initial configurations and the time evolution mappings are shown to be measurable. It is shown that infinite volume limit states of thermodynamic ensembles at low activity or for positive potentials are concentrated on the set of allowed initial configurations and are invariant under the time evolution. The total entropy per unit volume is shown to be constant in time for a large class of states, if the potential satisfies a stability condition.On leave from: Department of Mathematics, University of California, Berkeley, California.     

Microscopic study of configuration mixing in the interacting boson model

The microscopic foundation of the configuration-mixing interacting boson model, as proposed by Duval and Barrett, is explored. In this model, the normal shell-model configurations are supplemented by intruder configurations that arise by exciting a proton pair from one major shell to the next. A computationally-efficient generalized-seniority formalism for treating the mixing of these two configurations is described. Boson mixing parameters are obtained using the Otsuka-Arima-Iachello mapping procedure. Specific application to configuration mixing in the Cd isotopes is reported. The successes and failures of the calculations are assessed and suggestions for future work are made.     

Group-theoretic method for determining the number of superlattices in alloys of a given composition

The influence of the crystallographic symmetry of the lattice of an alloy on the various configurations of occupation of the sublattices by different species of atoms is investigated with regard for the concentrations of the latter. Two occupation configurations are considered to be equivalent if one can be reduced to the other by a transformation from the Fedorov lattice group. The equivalence classes of occupation configurations correspond to superlattices in the alloy. The machinery of the theory of group representations and the theory of invariants is used to determine the number of superlattices and their geometry.     

Traveling patterns in cellular automata

A method to identify the invariant subsets of bi-infinite configurations of cellular automata that propagate rigidly with a constant velocity nu is described. Causal traveling configurations, propagating at speeds not greater than the automaton range, mid R:numid R:相似文献   

Current induced exchange switching of magnetic junctions with cubic anisotropy of a free layer

The stability of equilibrium configurations of magnetic junctions with a free layer of cubic anisotropy with two axes in the layer plane has been analyzed. Variants of switching between different configurations have been considered. It has been demonstrated that the possibility exists of considerably decreasing the threshold current density necessary for switching. Numerical simulation of the dynamics of switching between different configurations has been performed.     

Wetting in Multiphase Systems with Complex Geometries

We address the shape and distribution of two-phase systems embedded within a third phase. To motivate this work, we begin by describing transmission electron microscopy observations of the configurations adopted by the solid and vapor phases of lead when these are confined together within a silicon cavity. We then perform analytical calculations of the stability of various possible configurations of two-phase systems confined in a cubic-shaped cavity. The most stable configurations are a function of the volume ratio of the two phases in the cavity, and of a parameter describing the wetting behavior in the three-phase system. The wealth of configurations obtained for embedded solid/fluid or condensed/fluid phases within a solid cavity is presented. Wetting anisotropy on the walls of the cavity, and the faceted or isotropic character of the interface between the two embedded phases, are shown to be physical parameters that determine the number of possible stable configurations.     

Effects of electrode configuration on cochlear implant modulation detection thresholds

Cochlear implant function, as assessed by psychophysical measures, varies from one stimulation site to another within a patient's cochlea. This suggests that patient performance might be improved by selection of the best-functioning sites for the processor map. In evaluating stimulation sites for such a strategy, electrode configuration is an important variable. Variation across stimulation sites in loudness-related measures (detection thresholds and maximum comfortable loudness levels), is much larger for stimulation with bipolar electrode configurations than with monopolar configurations. The current study found that, in contrast to the loudness-related measures, magnitudes of across-site means and the across-site variances of modulation detection thresholds were not dependent on electrode configuration, suggesting that the mechanisms underlying variation in these various psychophysical measures are not all the same. The data presented here suggest that bipolar and monopolar electrode configurations are equally effective in identifying good and poor stimulation sites for modulation detection but that the across-site patterns of modulation detection thresholds are not the same for the two configurations. Therefore, it is recommended to test all stimulation sites using the patient's clinically assigned electrode configuration when performing psychophysical evaluation of a patient's modulation detection acuity to select sites for the processor map.     

Self-Similar Transformation and Vertex Configurations of the Octagonal Ammann-Beenker Tiling

Based on the matching rules for squares and rhombuses,we study the self-similar transformation and the vertex configurations of the Ammann-Beenker tiling.The structural properties of the configurations and their relations during the self-similar transformation are obtained.Our results reveal the distribution correlations of the configurations,which provide an intuitive understanding of the octagonal quasi-periodic structure and also give implications for growing perfect quasi-periodic tiling according to the local rules.     

Avoidance of pomeron-f identity through systematic treatment of overlap contributions to the cylinder

We formulate a unitary equation for the cylinder term in the topoligical expansion which includes a systematic treatment of the overlap configurations to phase space as well as the periphal configurations. If the overlap contributions has Regge pole behavior, then the singlet cylinder plus planar exchange has two output poles which, for suitable values of the parameters, can be identified with a distinct pomeron and shifted f-trajectories.     

On the contribution of triply-excited and quadruply-excited configurations to electron correlation energies in closed-shell systems

The contribution made by triply-excited and quadruply-excited configurations to electron correlation energies in closed-shell systems is examined in detail. Many-body perturbation theory is used to calculate the contribution of these configurations to the correlation energies in 25 atoms and molecules. Calculations are performed for the nitrogen, carbon monoxide and carbon monosulphide molecules for a range of nuclear geometries.