Search results for " Cluster"
showing 10 items of 2162 documents
Kohn-Sham Decomposition in Real-Time Time-Dependent Density-Functional Theory An Efficient Tool for Analyzing Plasmonic Excitations
2017
The real-time-propagation formulation of time-dependent density-functional theory (RT-TDDFT) is an efficient method for modeling the optical response of molecules and nanoparticles. Compared to the widely adopted linear-response TDDFT approaches based on, e.g., the Casida equations, RT-TDDFT appears, however, lacking efficient analysis methods. This applies in particular to a decomposition of the response in the basis of the underlying single-electron states. In this work, we overcome this limitation by developing an analysis method for obtaining the Kohn-Sham electron-hole decomposition in RT-TDDFT. We demonstrate the equivalence between the developed method and the Casida approach by a be…
Self-Consistent Charge Density-Functional Tight-Binding Parametrization for Pt–Ru Alloys
2017
We present a self-consistent charge density-functional tight-binding (SCC-DFTB) parametrization for PtRu alloys, which is developed by employing a training set of alloy cluster energies and forces obtained from Kohn-Sham density-functional theory (DFT) calculations. Extensive simulations of a testing set of PtRu alloy nanoclusters show that this SCC-DFTB scheme is capable of capturing cluster formation energies with high accuracy relative to DFT calculations. The new SCC-DFTB parametrization is employed within a genetic algorithm to search for global minima of PtRu clusters in the range of 13-81 atoms and the emergence of Ru-core/Pt-shell structures at intermediate alloy compositions, consi…
A Self-Consistent Charge Density-Functional Tight-Binding Parameterization for Pt-Ru Alloys
2017
We present a self-consistent charge density-functional tight-binding (SCC-DFTB) parametrization for PtRu alloys, which is developed by employing a training set of alloy cluster energies and forces obtained from Kohn–Sham density-functional theory (DFT) calculations. Extensive simulations of a testing set of PtRu alloy nanoclusters show that this SCC-DFTB scheme is capable of capturing cluster formation energies with high accuracy relative to DFT calculations. The new SCC-DFTB parametrization is employed within a genetic algorithm to search for global minima of PtRu clusters in the range of 13–81 atoms and the emergence of Ru-core/Pt-shell structures at intermediate alloy compositions, consi…
A Statistical Approach for A-Posteriori Deployment of Microclimate Sensors in Museums: A Case Study
2022
[EN] The deployment of sensors is the first issue encountered when microclimate monitoring is planned in spaces devoted to the conservation of artworks. Sometimes, the first decision regarding the position of sensors may not be suitable for characterising the microclimate close to climate sensitive artworks or should be revised in light of new circumstances. This paper fits into this context by proposing a rational approach for a posteriori deployment of microclimate sensors in museums where long-term temperature and relative humidity observations were available (here, the Rosenborg Castle, Copenhagen, Denmark). Different statistical tools such as box-and-whisker plots, principal component …
El profesorado de la Universidad de La Rioja: ¿resistente al burnout?
2019
El cansancio emocional, la despersonalización y la falta de realización personal son los tres rasgos característicos del burnout o Síndrome de Quemarse por el Trabajo (SQT), un síndrome conceptualizado como una respuesta emocional ante el estrés laboral crónico. El objetivo principal de esta investigación fue conocer la prevalencia del SQT en la Universidad de La Rioja. Se realizó un muestreo estratificado con afijación proporcional a los departamentos de esta universidad y 138 docentes respondieron al Maslach Burnout Inventory. Los resultados indicaron que un 9,4% de los docentes presenta niveles medios o altos de SQT, una cifra que indica, en congruencia con estudios de la misma naturalez…
Regional Disparities and Spatial Dependence of Bankruptcy in Spain
2021
Firm survival, bankruptcy, and turnaround are of great interest nowadays. Bankruptcy is the ultimate resource for a company to survive when it is affected by a severe decline. Thus, determinants of firm turnaround and survival in the context of bankruptcy are of interest to researchers, managers, and policy-makers. Prior turnaround literature has broadly studied firm-specific factors for turnaround success. However, location-specific factors remain relatively unstudied despite their increasing relevance. Thus, this paper aims to evaluate the existence of spatial dependence on the outcome of the bankruptcy procedure. Economic geography and business literature suggest that location matters an…
Buone pratiche e strumenti di analisi per l’apprendimento, l’insegnamento e l’inclusione
2022
Il presente lavoro, nato in seno al progetto di ricerca “Best practices and tools of analysis in schools and community contexts: learning, teaching & inclusion”, avviato su fondi del Dipartimento SPPEFF dell’Università di Palermo, nel marzo 2019 e giunto alla sua seconda fase. La metodologia di ricerca utilizzata – perché ritenuta adeguata a perseguire le finalità fissate e a fornire una visione complessa ed articolata del fenomeno investigato – è stata quella del Mixed Method, con particolare riferimento all’Explanatory Design: Participant Selection Model di Creswell, Plano Clark, et al. (2003). L’«Explanatory Design is a two-phase mixed methods design. The overall purpose of this desi…
Exploring a large dataset : typical behavior of UHF signal propagation
2020
Radioverkon suunnittelua ja käyttöä varten täytyy radio aaltojen eteneminen ymmärtää hyvin. Tässä tutkimuksessa tutustutaan laajaan mittausaineistoon hetkellisiä tehoja maanlaajuisesta UHF verkosta. Spektrianalyysillä todettiin mitatussa tehossa olevan jaksollista vaihtelua taajuuksilla kerran ja kahdesti päivässä. Myös nopeampaa vaihtelua välillä 0:1 mHz ja 1:4 mHz todettiin 34% yhteyksistä. Hierarkisella ryhmittelyllä etsittiin tyypilliset mittausten arvojakaumat. Saaduissa arvojakaumien ryhmissä oli eri levyisiä vasemmalle tai oikealle vinoja tai symmetrisiä jakaumia. The design and operation of radio networks requires good understanding of radio propagation. This study explores a datase…
Improvements and applications of the elements of prototype-based clustering
2018
Clustering or cluster analysis is an essential part of data mining, machine learning, and pattern recognition. The most popularly applied clustering methods are partitioning-based or prototype-based methods. Prototype-based clustering methods usually have easy implementability and good scalability. These methods, such as K-means clustering, have been used for different applications in various fields. On the other hand, prototype-based clustering methods are typically sensitive to initialization, and the selection of the number of clusters for knowledge discovery purposes is not straightforward. In the era of big data, in high-velocity, ever-growing datasets, which can also be erroneous, outl…
The SO2F2 quasi-spherical top: Correspondence between tensorial and Watson's formalisms
2006
Abstract The SO2F2 quasi-spherical top molecule with C2v symmetry is considered as a distorted spherical top deriving from the SO 4 2 − tetrahedral ion. We present here a detailed correspondence between the tensorial formalism using the Td⊃C2v reorientation and the usual Hamiltonian of Watson. We have also performed ab initio calculations in order to determine the centrifugal distorsion constants in the vibrational ground state.