Bessel beam propagation: Energy localization and velocity

The propagation of a Bessel beam (or Bessel-X wave) is analyzed on the basis of a vectorial treatment. The electric and magnetic fields are obtained by considering a realistic situation able to generate that kind of scalar field. Specifically, we analyze the field due to a ring-shaped aperture over a metallic screen on which a linearly polarized plane wave impinges. On this basis, and in the far field approximation, we can obtain information about the propagation of energy flux and the velocity of the energy.Comment: 6 pages, 4 figure

New Tools for the Optimized Follow-Up of Imminent Impactors

The solar system is populated with, other than planets, a wide variety of minor bodies, the majority of which are represented by asteroids. Most of their orbits are comprised of those between Mars and Jupiter, thus forming a population named Main Belt. However, some asteroids can run on trajectories that come close to, or even intersect, the orbit of the Earth. These objects are known as Near Earth Asteroids (NEAs) or Near Earth Objects (NEOs) and may entail a risk of collision with our planet. Predicting the occurrence of such collisions as early as possible is the task of Impact Monitoring (IM). Dedicated algorithms are in charge of orbit determination and risk assessment for any detected NEO, but their efficiency is limited in cases in which the object has been observed for a short period of time, as is the case with newly discovered asteroids and, more worryingly, imminent impactors: objects due to hit the Earth, detected only a few days or hours in advance of impacts. This timespan might be too short to take any effective safety countermeasure. For this reason, a necessary improvement of current observation capabilities is underway through the construction of dedicated telescopes, e.g., the NEO Survey Telescope (NEOSTEL), also known as “Fly-Eye”. Thanks to these developments, the number of discovered NEOs and, consequently, imminent impactors detected per year, is expected to increase, thus requiring an improvement of the methods and algorithms used to handle such cases. In this paper we present two new tools, based on the Admissible Region (AR) concept, dedicated to the observers, aiming to facilitate the planning of follow-up observations of NEOs by rapidly assessing the possibility of them being imminent impactors and the remaining visibility time from any given station

Estrategias que favorecen u obstaculizan el desarrollo local en el marco de la globalización

En este artículo se analizan las estrategias emprendidas desde los ámbitos locales en el marco de la globalización y se destaca cómo, si bien algunas de ellas favorecen su posicionamiento, otras lo obstaculizan. Se presentan tres casos de estudio en el Estado de México: San Mateo Atenco, Valle de Bravo y Villa Guerrero. Se logró identificar ciertas capacidades de los actores sociales que permiten recurrir a estrategias de concertación que favorecen el desarrollo local; sin embargo, ahí donde se carece de ellas el desarrollo se obstaculiza. El análisis de estas capacidades se hace a partir de tres variables independientes: capacidad organizacional, capacidad instrumental y capacidad sistémica. Se pretende demostrar cómo el desarrollo local depende de estas variables en los ámbitos internacional, nacional y local, en un contexto globalizado

Seismic risk of Open Spaces in Historic Built Environments: A matrix-based approach for emergency management and disaster response

Abstract Earthquakes affect the safety of the users hosted in both indoor and outdoor urban built environments, especially in Historic Built Environments (HBEs). Many full HBE-scale risk-assessment methods are defined, while methodologies oriented to local analysis of meso-scale elements, such as Open Spaces (OSs), are still limited. Nevertheless, OSs play a crucial role in the first emergency phases, like in the evacuation process, since they host emergency paths and gathering areas. The seismic risk of an OS mainly depends on the combination of the damage suffered from facing buildings and the exposure, which mainly refers to the quantification of human lives. Damage levels result from the combination of vulnerability and hazard-related issues, while exposure is essentially affected by the number of OS users, whose spatial distribution is strongly time-dependent. Methods to quickly combine these issues are needed, especially in view of the deeper insights for the implementation of risk-reduction strategies (i.e. according to simulation-based approaches). This work offers a novel methodology to quickly perform Seismic Risk Assessment and Management of an OS by correlating damage levels to exposure-related issues. The method is composed of two specific matrices, which are developed according to quick literature-based approaches prone to rapid meso-scale applications in HBEs, also by non-expert technicians. The "damage matrix" links the site hazard to the building vulnerability. The assessed damage levels are combined with the users' exposure into the "consequences matrix", to estimate the risk in emergency conditions for the OS users, thus supporting decision-makers in promoting robustness/preparedness strategies

Retablo del amor y de la muerte

Mochi, V. (1999). Retablo del amor y de la muerte. La madriguera. (17):63-64. http://hdl.handle.net/10251/41764.Importación Masiva63641

The Acquisition of Functional Categories in English as an L2 in Classroom Setting: A Minimalist Approach

Discuto l’acquisizione delle categorie funzionali(vP,TP,CP,etc.)in Inglese come L2 in una situazione formale di apprendimento. In classi, cioè, di apprendenti italiani: universitari(cap.6)e scuola media di primo grado(cap.7 e 8). In particolare studio l’acquisizione delle Yes/No Questions e degli Imperativi. La tesi è divisa in due parti: Parte I(teorica), Parte II(sperimentale, basata cioè su raccolta, analisi e discussione di dati originali). Parte I Theoretical Preliminaries E’la parte teorica.Attraverso un percorso che va dal generale allo specifico, nel capitolo 1illustro il contesto in cui l’acquisizione delle categorie funzionali è stato osservato: è cioè, all’interno della L2 in un ambiente non-naturale di apprendimento(e.g. a scuola). Nel capitolo 2 spieg operché ho scelto un approccio generativo per studiarlo; ne introduco i principi generali e ne riassumo l’importanza in relazione dell’acquisizione della lingua straniera. Nel capitolo 3 esploro gli ultimi sviluppi della teoria con il Programma Minimalista e l’impatto che esso ha avuto sullo specifico settore di indagine. Nel capitolo 4 esamino in modo dettagliato la rappresentazione e l’architettura interna delle categorie funzionali nella grammatica dell’apprendente L2. Infine,nel capitolo 5, che conclude la parte teorica, offro un’analisi critica della varie ipotesi che sono state formulate riguardo il loro apprendimento in L2 dalla Full Transfer/FullAccess Hypothesis di Schwartz e Sprouse alla Local Impairment Hypothesis di Beck. Di seguito riassumo in modo più dettagliato il contenuto di ogni capitolo. Parte II Data Analysis E’ la parte sperimentale, quella cioè in cui presento dati originali in modo sistematico,raccolti sia attraverso produzioni scritte svolte dastudenti di scuola media(capitoli 7 e 8),sia attraverso composizione di studentiu niversitari(capitolo 6). Nei tre capitoli che la compongono, quindi, analizzo i dati; eseguo calcoli statistici per confermare e rifiutare l’ipotesi di partenza(ipotesi nulla)e, infine propongo ipotesi alternative. In particolare formulo un principio, quello della SLA-Relativized Merge and Check in cui propongo che nella seconda lingua per combinare due oggetti sintattici e controllarne i tratti interni onde produrre frasi, e' sufficiente che i due oggetti abbiano in comune un solo tratto. Oltre a ciò, tale tratto può essere inter-linguistico; cioè un tratto di una delle parole combinate può avere il valore assegnatoli dalla L2 mentrel ’altro tratto(quello della parola con cui la prima parola viene associata), può conservare quello assegnatoli dalla L1 senza che ciò impedisca allo studente di combinarle con successo nella sua interlingu

retrofitting and adaptability in urban areas

Abstract It is becoming more and more fundamental to develop a new approach to the dwelling in the contemporary world of architecture. If the Candilis revolution was based on humanism and regionalism, the current reaction should focus its attention on technology and a multicultural perspective. Technology has already occupied a main role in the design process, however it is not in the case of a multicultural approach. What the modernists started to call 'Habitat' was intrinsic to the society they were working for. The project was designed in regards to one singular habitat, with one use for society. We developed that approach and have continued to use this mono perspective. It is now necessary not to carry the analysis and the research from one singular point of view but to expand on this analysis and research to incorporate the voices of many [1]