Search results for " Local"
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Electron correlation in metal clusters, quantum dots and quantum rings
2009
This short review presents a few case studies of finite electron systems for which strong correlations play a dominant role. In simple metal clusters, the valence electrons determine stability and shape of the clusters. The ionic skeleton of alkali metals is soft, and cluster geometries are often solely determined by electron correlations. In quantum dots and rings, the electrons may be confined by an external electrostatic potential, formed by a gated heterostructure. In the low density limit, the electrons may form so-called Wigner molecules, for which the many-body quantum spectra reveal the classical vibration modes. High rotational states increase the tendency for the electrons to loca…
A tabu search algorithm for assigning teachers to courses
2002
In this paper we deal with the problem of assigning teachers to courses in a secondary school. The problem appears when a timetable is to be built and the teaching assignments are not fixed. We have developed a tabu search algorithm to solve the problem. The parameters involved in the algorithm have been estimated by using multiple regression techniques. The computational results, obtained on a set of Spanish secondary schools, show that the solutions obtained by this automatic procedure can be favourably compared with the solutions proposed by the experts.
Understanding the molecular mechanism of the [3 + 2] cycloaddition reaction of benzonitrile oxide toward electron-richN-vinylpyrrole: a DFT study
2016
The [3 + 2] cycloaddition (32CA) reaction of benzonitrile oxide, BNO 2, with an electron-rich N-vinylpyrrole derivative, NVP 3a, in the presence of dichloromethane, has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-31G(d) level. This 32CA reaction presents a relatively high activation Gibbs free energy as a result of the low polar character of this zwitterionic-type (zw-type) reaction. Analyses of the calculated relative Gibbs free energies and transition state geometries indicate that the studied 32CA reaction, in excellent agreement with experimental outcomes, takes place in a complete regioselective manner as a consequence of the steric repulsion…
Unveiling the Ionic Diels-Alder Reactions within the Molecular Electron Density Theory
2021
The ionic Diels–Alder (I-DA) reactions of a series of six iminium cations with cyclopentadiene have been studied within the Molecular Electron Density Theory (MEDT). The superelectrophilic character of iminium cations, ω >
Gold(I) Complexes of Ferrocenyl Polyphosphines: Aurophilic Gold Chloride Formation and Phosphine-Concerted Shuttling of a Dinuclear [ClAu···AuCl] Fra…
2016
International audience; A smart steric control of the metallocene backbone in bis- and poly(phosphino)ferrocene ligands favors intramolecular aurophilic interactions between [AuCl] fragments in polynuclear gold(I) complexes. We synthesized and characterized by multinuclear NMR and X-ray diffraction analysis mono-, di-, and polynuclear gold complexes of constrained ferrocenyl diphosphines, which bear either bulky tert-butyl groups or more flexible siloxane substituents at the cyclopentadienyl rings. The complexes meso-1,1'-bis-(diphenylphosphino)-3,3'-di-tert-butylferrocene (4-m), rac-1,1'-bis[bis-(5-methy1-2-furyl)phosphino]-3,3'-di-tert-butyfferrocene (5-r), and rac-1,1'-bis ( diphenylphos…
MULTIPLE CRACKS LOCALIZATION FOR THIN COATING FILM LAYERS IN PURE BENDING
2018
Recently, accurate small scale four-point bending flexural tests, for superalloy specimens with multiple ceramic type external coating film layers, have shown that under high loading, the failure mechanism is characterized by the development of complex multiple surface cracks, followed by interior interlayers debonding mechanisms. The final stage is then the complete debonding of the fragmented thermal coating, which leave the interior superalloy completely uncoated. The mechanical problem has an high technological relevance, since failure, or just severe damage, of the ceramic coating, can jeopardize the functionality of structural elements working at high temperature and under severe load…
Strain localization and crack propagation in finite elements augmented with embedded interphases
2022
Many engineering problems present the need to model discontinuities that arise when materials are outside their elastic limit. In quasi-brittle materials strains progressively localize in narrow bands, usually leaving elastic the surrounding bulk material. In the framework of FE models, considerable progresses have been done in order to correctly model strain localization and damage propagation; they could be mainly divided into two groups: discrete crack models and smeared crack models. In the ambit of discrete crack models, we propose a computational methodology which is based on the Augmented-Finite Element Method (A-FEM) [1]. Our formulation consists in the implementation of an intra-el…
Pianificazione strategica tra sviluppo locale e policentrismo: alcune evidenze empiriche sul caso siciliano
2009
Strategic planning, local development and policentrism: empirical evidence for Sicily The aim of this paper is the analysis of metropolitan strategic planning in Sicily. Urban areas are becoming important units for territorial cohesion policy and strategic planning represents more and more an important policy instrument. Evidence of a policentric pattern is tested across 30 strategic plans carried out by Sicilian cities in order to derive useful insights for policy implications. Methods and Results This study uses multidimensional scaling and rank-size regressions across Sicilian Functional Urban Areas (FUA) as well as descriptive information drawn from strategic plans in order to identify …
Forme del fritto: alcune esperienze di consumo
2020
Questo capitolo propone uno studio sul campo di una pratica alimentare che caratterizza la Sicilia e, in particolare, la città di Palermo: lo street food. Lo street food palermitano si caratterizza per essere indissolubilmente legato alla frittura, una modalità di cottura pervasiva tanto nei mercati storici della città, quanto in quei luoghi chiusi che, in forme diverse, tentano di replicarne l'esperienza. Il fritto è, ancor prima che una modalità di cottura dei cibi, un particolare dispositivo ambientale e sensoriale, che pregiudica olfattivamente gli spazi di vendita e consumo e che spinge, alcuni format di distribuzione, a limitarne la pervasività. Vedremo, in questo senso, come la diffe…
Locally convex quasi $C^*$-normed algebras
2012
Abstract If A 0 [ ‖ ⋅ ‖ 0 ] is a C ∗ -normed algebra and τ a locally convex topology on A 0 making its multiplication separately continuous, then A 0 ˜ [ τ ] (completion of A 0 [ τ ] ) is a locally convex quasi ∗-algebra over A 0 , but it is not necessarily a locally convex quasi ∗-algebra over the C ∗ -algebra A 0 ˜ [ ‖ ⋅ ‖ 0 ] (completion of A 0 [ ‖ ⋅ ‖ 0 ] ). In this article, stimulated by physical examples, we introduce the notion of a locally convex quasi C ∗ -normed algebra, aiming at the investigation of A 0 ˜ [ τ ] ; in particular, we study its structure, ∗-representation theory and functional calculus.