1,721,620 research outputs found
Mathematical models and methods for Electromagnetism on fractal geometries
Full text linkThis work summarizes the research path done by Walter Arrighetti during his three years of Doctorate of Research in Electromagnetism at Università degli Studi di Roma “La Sapienza,” Rome, under the guidance of Professor Giorgio Gerosa. This work was mainly motivated by the struggle to find simpler and simpler models to introduce complex geometries (like fractal ones, for example, which are complicated but far from being ‘irregular’) in physical field theories like the Classical Electrodynamics, and which stand at the base of most contemporary applied research activities: from antennas (of any sizes, bandwidths and operational distances) to waveguides & resonators (for devices ranging from IC motherboards , to high-speed fibre channel links), to magnetic resonance (RMI) devices (for both diagnostic and research purposes), all the way up to particle accelerators. All of these models need not only a solid physical base, but also a specifically crafted ensemble of mathematical methods, in order to tackle with problems which “standard-geometry” models (both in the continuum and the discrete cases) are not best-suited for. During his previous years of study towards the Laurea degree in Electronic Engineering, the author used different approaches toward Fractal Electrodynamics, form purely-analytical, to computer-assisted numerical simulations of applied electromagnetic structures (both radiating and wave-guiding), down to algebraic-topological ones. The latter approaches, more often than not, proved to be the best way to start with, because the author found out that self-similarity (a property which many complicated geometries —even non-fractal ones— seem to, at least, tend to possess) can be easily interpreted as a topological symmetry, wonderfully described using “ad hoc” nontrivial algebraic languages. Whatever can be successfully described in the language of Algebra (either via numbers, symmetry groups, graphs, polynomials, etc.) is then always simplified (or “quotiented” — so to speak in a more strict mathematical language) and, when numerical computation takes the way towards the solution of a specific applied problem, those simplifications turn in handy to reduce the complexity of it. For example, the strict self-similarity possessed by some fractals (like those generated via an Iterated Function System — or IFS) allows to numerically store the geometrical data for a fractal object in a sequence of simpler and simpler data which are, for example, instantly recovered by a computer starting from the simplest data (like simplices, squares/cubes, circles/spheres and regular polygons/polytopes). For the same reason, all the physical properties that depend on the geometry (or the topology — i.e. basically the number of “holes” or inner connections) of the domain can be reduced, estimated or be even completely known a priori, even before a numerical simulation is performed. In this work, several of these methods (coming from apparently different branches of pure and applied Mathematics) are presented and finally joined with Electromagnetism equations to solve some more or less applied problems. Since many of the mathematical tools used to build the studied models and methods are advanced and generally not sufficiently known to experts in either such different fields, the first two Chapters are devoted to a brief introduction of some purely mathematical topics. In that context, the author found that the best way to accomplish this was to re-write all those different results from different branches of both pure and applied Mathematics in a formalism as more solid and unified as possible, with continuous links back and forth to different topics (and to the next more applied Chapters). That approach is seldom found in most graduate-level texts. For example, very similar mathematical objects may be even called or classified in different ways, according to the different mathematical contexts they are introduced in, which is exactly the opposite philosophy which has guided underneath in writing these first Chapters. On the other end, simpler and more trivial mathematical definitions, formalisms or electromagnetic problems, when not elsewhere referenced to, can be found in [9], Arrighetti W., Analisi di Strutture Elettromagnetiche Frattali, the author’s Laurea degree dissertation (currently only in Italian language). The most original part of the work is in the last three Chapters where —always using the same “language” and helping with cross-links, as well as to the Bibliography— methods are introduced and then applied to model some electromagnetic problems (previously either unsolved — or already-known, but here solved with a different, usually simpler, or at least more elegant approach)
LA GESTIONE STRATEGICA DELLE RISORSE UMANE: UN NUOVO PATTO TRA DIREZIONE DEL PERSONALE E MANAGEMENT
No full textPRIMO PREMIO BEST PAPER 2005La capacità di attrarre e trattenere persone competenti e motivate è da tempo considerata una leva fondamentale per il successo delle imprese, e il valore del capitale umano rappresenta uno degli ingredienti chiave per la realizzazione di una strategia aziendale vincente.Al di là di mode e retorica è opinione diffusa quella di attribuire un’accresciuta importanza strategica alla combinazione delle pratiche di gestione delle risorse umane.A tali convinzioni è opportuno che seguano tanto pragmatiche e precise decisioni, scelte e azioni manageriali per la creazione di una personnel idea, quanto lo sviluppo delle competenze necessarie a supportare i conseguenti investimenti.In questo articolo, dopo aver chiarito il concetto di vantaggio competitivo basato sulle persone e la sua espressione in pratiche e sistemi di Strategic Human Resource Management (SHRM), si presentano i risultati di una ricerca che, a partire da alcune evidenze sulla relazione tra pratiche di gestione delle risorse umane, ambiente competitivo e performance economico-finanziarie dell’impresa, indaga condizioni e opzioni per lo sviluppo di un approccio strategico alla gestione delle persone sia nella prospettiva del top management sia in quella delle direzioni del personal
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Turbid-water coral assemblages: a case study from the Oligocene Tertiary Piedmont Basin (N Italy)
No full textIn the geological record, but also at the present time, coral assemblages thriving in
permanently or episodically turbid waters as a result of terrigenous input are much
more common than what is expected, thinking to the conventional optimal conditions
for coral reef growth (i.e. warm, well-illuminated, oligothrophic shallow waters of the
tropics and subtropics). Despite, in fact, relatively high turbidity conditions, restricted
light penetration, and the presence of often mobile terrigenous sediment substrates,
active coral growth is well developed and many coral bioconstructions in the past are
actually associated with marly and mixed carbonate-siliciclastic sediments.
In the Tertiary Piedmont Basin (northern Italy) coral assemblages and associated bioconstructions
developed under terrigenous sedimentation during the Oligocene. They
occur in siliciclastic conglomerates and sandstone of fan delta and clay-rich prodelta
settings.
Collected data provide information basically about the composition of the coral assemblages,
facies and depositional products of coral growth together with taphonomic
aspects.
The succession is characterized by the episodic production of abundant coral rubble of
the branching corals Acropora and Stylophora. These rudstone and floatstone facies
are distinguished on the base of their sedimentological and paleontological aspects,
and taphonomic features such as bioerosion and encrustation provide useful information
about the different effetcts of turbidity and sediment accumulation. Coral rubble
deposits are often buried or occasionaly represent a hard substrate for successive coral
growth.
Corals in growth position also occur and consist of a suite of phaceloid and massive
colonies (Caulastrea, Goniopora, Astreopora, Diploria, Favia, Antiguastrea) with
growth habits and morphological characters typical of sediment-resistant corals. These
corals form monospecific clusters or, especially towards the top of the succession, can
co-exist together to form a small “framework”. Diversity and thickness of these coral
bioconstructions, however, are quite reduced compared to many other Oligocene coral
assemblages, suggesting that sediment imput, restricted light penetration, and maybe
episodic high concentration of nutrients, were major controls on coral growth and
carbonate production
Coral bioherms and biostromes in the muddy bottomset of a fandelta system (Oligocene, Tertiary Piedmont Basin, Italy)
No full textTransaction Costs and Service aggregation structures: eFirm strategic charters
No full textItalian Organization and Information Systems Researchers Annual Meeting, Rome, Ital
- …
