1,720,959 research outputs found
Mechanical and hydraulic properties of unsaturated layered pyroclastic ashes in landslide-prone areas of Campania (Italy)
No full textAir-fall pyroclastic soil deposits usually display a loose fabric composed of alternating layers of ashes and pumices. Such deposits, when lying on steep slopes, represent a major geohazard due to the occurrence of landslides. This is the case of the carbonate massifs in Campania (southern Italy), a wide landslide-prone area of approximately 400 km2 covered with pyroclastic soils. In such cohesionless deposits, the additional shear strength provided by soil suction in unsaturated conditions is important for ensuring slope stability and can be jeopardized by soil wetting during rainwater infiltration. This paper provides a comprehensive view of the hydraulic and shear strength characteristics of different layers of pyroclastic deposits at different sites in Campania, revealing a broad view of their similarities and differences. To that end, some datasets from previous studies and novel data are gathered, linking the index properties, the hydraulic behavior of the soils and the contribution of suction to the shear strength of the studied materials. Two types of ashes at different positions within the stratigraphic sequence are identified: ashes interbedded between pumice layers, where landslide failure surfaces usually occur, and altered ashes in contact with the bedrock, which affects water leakage from the overlying soil profile. The former show quite uniform characteristics, and this allowed testing some predictive models for the assessment of the unsaturated shear strength of pyroclastic ashes in the absence of direct measurements. In contrast, the latter may exhibit significantly different behaviors, with great variability in hydraulic and mechanical properties
Simulation of the dynamic behavior of the phenomenon of mass removal for fast flows using the discrete element method *
No full textLos deslizamientos de tierra han sido siempre un problema que afecta a la sociedad, ocasionando pérdidas tanto materiales como humanas, por lo que se hace necesario encontrar mejores estrategias para predecir y medir su poder destructivo. Esta investigación se centra en medir el alcance y velocidad de una masa deslizante de material desagregado a través de simulaciones numéricas, con el fin de dejar las bases para futuras investigaciones que puedan ayudar a mitigar las pérdidas producidas a corto y mediano plazo por el fenómeno de remoción de masas. En este documento se muestra la implementación del Método de Elementos Discretos (Discrete Element Method, DEM), un método numérico usado en el estudio de medios discontinuos, para investigar el comportamiento dinámico de las partículas de tierra de un deslizamiento. El propósito principal es simular, a través de un software libre, un deslizamiento de partículas, calibrándolo con los datos obtenidos de una campaña experimental de un canal de flujo denominado Collaptes V1.0, desarrollado por el grupo de investigación de la UIS: INME. Se logró a través del software ESyS-Particle una simulación del comportamiento dinámico del fenómeno de remoción de masas, obteniendo las variables de desplazamiento y velocidad a lo largo de todo su recorrido, calibrando la simulación de forma cualitativa, modificando los parámetros de repulsión elástica y resistencia del medio. Además se logró estimar la fuerza promedio que tiene cada una de las partículas a lo largo de su trayectoria.PregradoIngeniero Civillook after better strategies to predict and measure its destructive power. This investigation will center in measure the reach and velocity of a landslide through numerical simulations and settle down bases for future investigations that can help to minimize the losses produced in short or medium term. It was investigated through different literary sources programming language and numerical methods, as well as some basic programming tutorials for the free software. This work implements the Discrete Element Method, DEM, used in the research of discontinuum mechanics, to investigate the particle dynamic behavior of a landslide. The principal end is simulating, through the free software, a model of a particles landslide, calibrating it with the data obtained in an experimental campaign of a flow canal named Collaptes V1.0, developed by the INME group. It has achieved through ESyS-Particle software a simulation of the dynamic behavior of a landslide, getting the variables of displacement and velocity in all its way, calibrating the simulation in a qualitative form, modifying the parameters of elastic repulsion and medium resistance. Besides, it has estimated the average force that every particle has through its trajectory
Mass removal flow modelling through an analytical bidimensional model*
No full textEl presente estudio propone la solución numérica de un modelo de flujo de escombros en dos dimensiones mediante el Método de Volúmenes Finitos. Se usan esquemas de discretización cuadráticos y de Diferencias Centrales para discretizar los términos de la ecuación de conservación del momentum lineal, así como también los términos de la ecuación de conservación de la masa. También se lleva a cabo una campaña experimental en un canal que permite el análisis del flujo de un material granular, empleando técnicas de adquisición y procesamiento de imágenes. Con los datos obtenidos de la campaña experimental, se hace una comparación mediante la simulación numérica del flujo y se lleva a cabo un proceso de calibración del modelo numérico. Adicionalmente se muestra un caso de estudio de un evento de flujo de escombros ocurrido en el municipio de Girón, Santander. En el estudio se realizaron levantamientos topográficos con Vehículo Aéreo No Tripulado y con Escáner Láser Terrestre, cuyos datos se procesaron para simular la superficie de flujo del material. Finalmente se compara la respuesta numérica tras simular el caso de estudio con dos modelos; mediante un modelo 1D y mediante el modelo 2D aquí mencionado. *MaestríaMagíster en Ingeniería CivilThis study aims to show the numerical solution of a bidimensional Debris Flow model throughout the Finite Volume Method. The terms in the continuity and linear momentum conservation equations (i.e. Convection and Diffusion) are approached by Central Differencing and quadratic schemes. It is also carried out an experimental campaign in a channel that allows the analysis of the flow of a granular material, using image acquisition and image processing techniques. With the data of the experimental campaign a comparison is made by means of the numerical simulation of the flow and a process of calibration of the numerical model is carried out. Additionally, it is shown a case study of a debris flow event occurred in the municipality of Girón, Santander. In the study, topographic surveys were carried out with an Unmanned Aerial Vehicle and with a Terrestrial Laser Scanner, which data has been processed to simulate the surface bed of the material flow. Finally, the numerical simulation in the case study is compared with two models, using a 1D model and using the 2D model mentioned here.
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Monitoring of hydrological variables for improvement of shallow landslides prediction in pyroclastic slopes of Campania
No full textVariations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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