1,721,127 research outputs found
CARTOGRAFIA DELLE TRACCE DI VALANGA SUL VERSANTE MERIDIONALE DELLE MALACOSTE (CATENA DEL GRAN SASSO, ABRUZZO) AVALANCHE TRAILS DETECTION ON THE SOUTHERN HILLSIDE OF THE MALACOSTE RIDGE (GRAN SASSO RANGE, ABRUZZO)
No full textLe valanghe consistono in masse di neve in rapida discesa su pendii ripidi e costituiscono un grave pericolo naturale nella maggior parte delle aree montane innevate del mondo. Esse rappresentano uno dei processi più significativi negli ambienti montani in quanto contribuiscono dinamicamente all’evoluzione del paesaggio alpino incrementando la velocità dei processi geomorfologici, impattando sulla foresta e mettendo a rischio popolazione ed infrastrutture. La popolarità degli sport invernali e l’incremento del turismo di montagna registrata nel periodo COVID hanno portato ad una maggiore esposizione sociale alle valanghe e ad un numero crescente di vittime a causa dell'azione diretta di questo fenomeno. Utilizzando gli ormai famosi software dedicati all’osservazione della Terra basati su immagini telerilevate, è stato eseguito un rilevamento speditivo delle tracce, delle forme e dei depositi caratteristici di movimenti nevosi in massa (valanghe, colate detritiche nivali e fluvio-nivali) avvenuti nel passato geologicamente recente sul fronte meridionale della catena del Gran Sasso. Come area campione, è stata scelta la fascia compresa tra il Valico delle Capannelle e Valle Fredda, a est di Fonte Cerreto: zona diffusamente frequentata per tutto il periodo invernale e primaverile, sia per attività sportiva che per semplice transito verso le zone turistiche. Sono state rilevate e cartografate 85 tracce di valanghe (avvenute nel periodo compreso tra il 2007 ed il 2017) e riconosciuti i principali corpi sedimentari fluvio-nivali caratteristici di depositi tipo mass-flow a matrice nevosa densa, i quali testimoniano la massima estensione raggiunta dai corpi di valanga più antichi. Sono stati distinti due casi limite di eventi: a) valanghe dense (wet snow avalanches), dove la dinamica di flusso è dominata dal moto delle particelle di ghiaccio; e b) valanghe polverose (powder snow avalanches), con velocità maggiori, fronte valanghivo più ampio e dinamica dominata dalle turbolenze dell'aria che sostiene le particelle di neve. I dati raccolti indicano come anche versanti con pendenze modeste (30-40%), siano potenzialmente in grado di produrre valanghe di grandi dimensioni quando l’accumulo di neve abbia lo spessore e le caratteristiche opportune. Le tracce lasciate sulla vegetazione indicano che questi fenomeni, possono propagarsi su fronti molto larghi e a considerevoli distanze. L’analisi geomorfologica, aerofotogrammetrica e cartografica delle tracce degli eventi di valanga sulla copertura vegetale e sul terreno, permette di definire le aree percorse dalle valanghe, contribuendo così a valutarne la pericolosità, anche quando l’informazione storica non sia disponibile
Non-linear photoemission from polycrystalline molybdenum irradiated by 790 nm-150 fs laser pulses
No full textThe total yield photoemission of a polycrystalline molybdenum sample irradiated by 790 nm-150 fs laser pulses is measured in the absence of space charge saturation. The extracted charge versus the laser intensity, measured over three decades of the extracted charge, which represents a significant extension of the previous experiments, gives us the opportunity to test the so-called thermally assisted non-linear photoemission model. The present results show non-linear photoemission behavior that can be explained, as expected, by a thermally assisted 3-photon emission. However a pure 4-photon emission could not be discarded. To take aim at clarifying this question the related non-linear coefficients are calculated and a scaling law for the probability of different multiphoton orders is proposed
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
Effective mass and momentum-resolved intrinsic linewidth of image-potential states on Ag(100)
No full textNon-linear photoemission from W and Cu investigated by total-yield correlation measurements
No full textNonlinear photoelectric emission from Cu and W is investigated by subpicosecond laser pulses. Using a pump and probe technique, total-yield correlation measurements are obtained without space-charge saturation. The effects of the heating of the conduction electrons induced by the laser pulses are shown, considering the peak to background contrast ratio of the experimental correlation trace. The present analysis clarifies the consequences of a transient nonequilibrium temperature difference between electrons and the lattice on the correlation trace, confirming for W the presence of a thermally assisted photoemission mechanism
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