Search results for "PERTURBATION"
showing 10 items of 811 documents
Line broadening coefficient calculations for methane perturbed by nitrogen
2010
Abstract We report semiclassical line broadening calculations for methane perturbed by nitrogen at room temperature. For this, we have developed a symmetrized version of the Robert and Bonamy theory. The interaction potential was built from electrostatic (octopole and hexadecapole for methane, quadrupole for nitrogen) and atom–atom contributions. The relative (classical) trajectories of the molecules were computed in the frame of the usual parabolic model, through analytical formula. High orders of developments had to be used for the short range molecular interactions. As a consequence, a combination of symbolic computation and source code generation was employed to implement practical calc…
Advanced Analysis of Propagation Losses in Rectangular Waveguide Structures Using Perturbation of Boundary Conditions
2011
In this paper, propagation losses effects present in rectangular waveguide structures are rigorously considered. For this purpose, a new formulation based on the perturbation of the boundary conditions on the metallic walls of the waveguides combined with an Integral-Equation (IE) analysis technique is proposed. Following this advanced technique, the drawbacks of the classical power-loss method are overcome and a complex modal propagation constant is computed. To validate this theory, we have successfully compared our results with numerical data of lossy hollow waveguides. Next, a Computed-Aided-Design (CAD) software package based on such a novel modal analysis tool has been used to predict…
Perturbation of the Lyapunov spectra of periodic orbits
2012
We describe all Lyapunov spectra that can be obtained by perturbing the derivatives along periodic orbits of a diffeomorphism. The description is expressed in terms of the finest dominated splitting and Lyapunov exponents that appear in the limit of a sequence of periodic orbits, and involves the majorization partial order. Among the applications, we give a simple criterion for the occurrence of universal dynamics.
Gut microbiota disturbance during antibiotic therapy: a multi-omic approach
2014
It is known that the gastrointestinal tract (GIT) microbiota responds to different antibiotics in different ways and that while some antibiotics do not induce disturbances of the community, others drastically influence the richness, diversity, and prevalence of bacterial taxa. However, the metabolic consequences thereof, independent of the degree of the community shifts, are not clearly understood. In a recent article, we used an integrative OMICS approach to provide new insights into the metabolic shifts caused by antibiotic disturbance. The study presented here further suggests that specific bacterial lineage blooms occurring at defined stages of antibiotic intervention are mostly associa…
''Active Collisions in Altered Gravity Reveal Eye-Hand Coordination Strategies''
2012
White, Olivier | Lefevre, Philippe | Wing, Alan M. | Bracewell, R. Martyn | Thonnard, Jean-Louis; International audience; ''Most object manipulation tasks involve a series of actions demarcated by mechanical contact events, and gaze is usually directed to the locations of these events as the task unfolds. Typically, gaze foveates the target 200 ms in advance of the contact. This strategy improves manual accuracy through visual feedback and the use of gaze-related signals to guide the hand/ object. Many studies have investigated eye-hand coordination in experimental and natural tasks; most of them highlighted a strong link between eye movements and hand or object kinematics. In this experime…
Excited-state non-radiative decay in stilbenoid compounds: An: Ab initio quantum-chemistry study on size and substituent effects
2019
In the framework of optoelectronic luminescent materials, non-radiative decay mechanisms are relevant to interpret efficiency losses. These radiationless processes are herein studied theoretically for a series of stilbenoid derivatives, including distyrylbenzene (DSB) and cyano-substituted distyrylbenzene (DCS) molecules in vacuo. Given the difficulties of excited-state reaction path determinations, a simplified computational strategy is defined based on the exploration of the potential energy surfaces (PES) along the elongation, twisting, and pyramidalization of the vinyl bonds. For such exploration, density functional theory (DFT), time-dependent (TD)DFT, and complete-active-space self-co…
Electronic Shell Structure and the Crystal Field Splitting in Simple Metals Clusters
1991
An upper limit for the number of atoms in metal clusters capable of exhibiting electronic shell structure has been estimated by comparing the energy difference between the highest occupied and the lowest unoccupied state with the crystal field splitting. The former is obtained by solving the Schrodinger equation for a spherical potential well with hard walls while the latter is obtained from the band structure of the solid. The results indicate that shell structures may persist in clusters containing as many as a million atoms.
Photophysical properties of the triangular [Au(HNCOH)]3 complex and its dimer
2020
Rate constants for radiative and non-radiative transitions of the [Au(HNCOH)]3 complex and its dimer were calculated within the Herzberg–Teller approximation based on quantum mechanical principles. A high triplet quantum yield was estimated for the monomer. Internal conversion (IC) was found to be the major competing process to the intersystem crossing (ISC) from the lowest excited singlet state (S1) to the lowest triplet state (T1). ISC and IC from the spin-mixed 1 state also dominate the triplet relaxation process resulting in a negligible phosphorescence quantum yield for the monomer. The IC and ISC rate constants of the dimer are considerably smaller due to much lower Franck–Condon fact…
Shaping communities of local optima by perturbation strength
2017
Recent work discovered that fitness landscapes induced by Iterated Local Search (ILS) may consist of multiple clusters, denoted as funnels or communities of local optima. Such studies exist only for perturbation operators (kicks) with low strength. We examine how different strengths of the ILS perturbation operator affect the number and size of clusters. We present an empirical study based on local optima networks from NK fitness landscapes. Our results show that a properly selected perturbation strength can help overcome the effect of ILS getting trapped in clusters of local optima. This has implications for designing effective ILS approaches in practice, where traditionally only small per…
Discrete-timeH − ∕ H ∞ sensor fault detection observer design for nonlinear systems with parameter uncertainty
2013
SUMMARY This work concerns robust sensor fault detection observer (SFDO) design for uncertain and disturbed discrete-time Takagi–Sugeno (T–S) systems using H − ∕ H ∞ criterion. The principle of the proposed approach is based on simultaneously minimizing the perturbation effect and maximizing the fault effect on the residual vector. Furthermore, by introducing slack decision matrices and taking advantage of the descriptor formulation, less conservative sufficient conditions are proposed leading to easier linear matrix inequalities (LMIs). Moreover, the proposed (SFDO) design conditions allow dealing with unmeasurable premise variables. Finally, a numerical example and a truck–trailer system…