The use of airborne LiDAR data for the analysis of debris flow events in Switzerland

A methodology of magnitude estimates for debris flow events is described using airborne LiDAR data. Light Detection And Ranging (LiDAR) is a widely used technology to generate digital elevation information. LiDAR data in alpine regions can be obtained by several commercial companies where the automated filtering process is proprietary and varies from companies to companies. This study describes the analysis of geomorphologic changes using digital terrain models derived from commercial LiDAR data. The estimation of the deposition volumes is based on two digital terrain models covering the same area but differing in their time of survey. In this study two surveyed deposition areas of debris flows, located in the canton of Berne, Switzerland, were chosen as test cases. We discuss different grid interpolating techniques, other preliminary work and the accuracy of the used LiDAR data and volume estimates

Comparison of 2D debris-flow simulation models with field events

Three two-dimensional (2D) debris-flow simulation models are applied to two large well-documented debris-flow events which caused major deposition of solid material on the fan. The models are based on a Voellmy fluid rheology reflecting turbulent-like and basal frictional stresses, a quadratic rheologic formulation including Bingham, collisional and turbulent stresses, and a Herschel-Bulkley rheology representing a viscoplastic fluid. The rheologic or friction parameters of the models are either assumed a priori or adjusted to best match field observations. All three models are capable of reasonably reproducing the depositional pattern on the alluvial fan after the models have been calibrated using historical data from the torrent. Accurate representation of the channel and fan topography is especially important to achieve a good replication of the observed deposition patter

Bedload transport fluctuations, flow conditions, and disequilibrium ratio at the Swiss Erlenbach stream: results from 27 years of high-resolution temporal measurements

Based on measurements with the Swiss plate geophone system with a 1 min temporal resolution, bedload transport fluctuations were analysed as a function of the flow and transport conditions in the Swiss Erlenbach stream. The study confirms a finding from an earlier event-based analysis of the same bedload transport data, which showed that the disequilibrium ratio of measured to calculated transport rate (disequilibrium condition) influences the sediment transport behaviour. To analyse the transport conditions, the following elements were examined to characterise bedload transport fluctuations: (i) the autocorrelation coefficient of bedload transport rates as a function of lag time (memory effect), (ii) the critical discharge at the start and end of a transport event, (iii) the variability in the bedload transport rates, and (iv) a hysteresis index as a measure of the strength of bedload transport during the rising and falling limb of the hydrograph. This study underlines that above-average disequilibrium conditions, which are associated with a larger sediment availability on the streambed, generally have a stronger effect on subsequent transport conditions than below-average disequilibrium conditions, which are associated with comparatively less sediment availability on the streambed. The findings highlight the important roles of the sediment availability on the streambed, the disequilibrium ratio, and the hydraulic forcing in view of a better understanding of the bedload transport fluctuations in a steep mountain stream.</p

Comparison of flow resistance relations for debris flows using a one-dimensional finite element simulation model

International audienceThis paper describes a one-dimensional finite element code for debris flows developed to model the flow within a steep channel and the stopping conditions on the fan. The code allows the systematic comparison of a wide variety of previously proposed one-phase flow resistance laws using the same finite element solution method. The one-dimensional depth-averaged equations of motion and the numerical model are explained. The model and implementation of the flow resistance relations was validated using published analytical results for the dam break case. Reasonable agreement for the front velocities and stopping location for a debris-flow event in the Kamikamihori torrent in Japan can be achieved with turbulent flow resistance relations including "stop" terms which allow the flow to come to rest on a gently sloping surface. While it is possible to match the overall bulk flow behavior using relatively simple flow resistance relations, they must be calibrated. A sensitivity analysis showed that the shape of the upstream input hydrograph does not much affect the flow conditions in the lower part of the flow path, whereas the event volume is much more important

A construção social das emoções estéticas: análise dos processos de formação de instrumentistas

The literature on the issues of relationships between music and emotions shows that much of the work is based on an inner and subjective perspective, thus deriving in a working scheme in which emotions are generally regarded as an effect or a response to music as a stimulus. The historical-cultural model of emotional development (Vygotsky, 2004) allows us to address this problem from a more contextual perspective, as it takes into account the culturally constructed dimension of human reality (§ 1). On the one hand, it takes into account the processes of double mediation of art works, both as cultural products and as specialized social practices, and hence as a development vector (§ 2). Through a clinical analysis of didactic training situations (§ 3), we intend to approach aesthetic relationships with art works as one of the main fields for emotional development, examining their transformative mediations (§ 4). The analysis of a particular case, the training of performers for "a home-grown musical interpretation of traditional music of the Andes" allows us to address the issue of cultural transmission in emotional development (§ 5), opening research paths on the relationships between music and emotion (§ 6).La literatura sobre la problemática de las relaciones entre música y emociones muestra que gran parte de los trabajos se basan en una perspectiva “internalista y subjetiva”, de la cual se desprende un modelo de funcionamiento en el que la emociones son generalmente un efecto o una respuesta de la música como estímulo. El modelo histórico-cultural de desarrollo de las emociones (Vygostki, 2004) nos permite abordar esta problemática desde una perspectiva más contextual y teniendo en cuenta la dimensión culturalmente construida de la realidad humana (§1). Por un lado, esta concepción tiene en cuenta los procesos de doble mediación de las obras, en tanto que productos culturales y en tanto que prácticas sociales especializadas, como vector de desarrollo (§2). Desde un análisis clínico de las situaciones didácticas de formación (§3), abordamos una definición de las relaciones estéticas a las obras como uno de los principales campos para el desarrollo emocional, y analizamos las mediaciones de formación que las transforman (§4). El análisis de un tipo de caso particular, el de la formación de los músicos intérpretes a “una interpretación musical autóctona de la música tradicional de los Andes”, nos permite abordar la problemática de la transmisión cultural en el desarrollo de las emociones (§5) y abrir pistas sobre investigación de la relación música-emociones (§6).Palabras clave:  Educación estética, teoría de las emociones, clínica didáctica, etnomusicología.A literatura sobre a problemática das relações entre música e emoções mostra, que grande parte dos trabalhos baseiam-se numa perspectiva “internalista e subjetiva”, da qual desprende-se um modelo de funcionamento no que as emoções são geralmente um efeito o uma resposta da música como estimulo. O modelo histórico-cultural de desenvolvimento das emoções (Vygostki, 2004) deixa-nós abordar esta problemática desde uma perspectiva mais contextual e tendo em conta a dimensão culturalmente construída da realidade humana (§1). Por um lado, esta concepção tem em conta os processos de dupla mediação das obras, em tanto que produtos culturais e em tanto que práticas sociais especializadas, como vector de desenvolvimento (§2). Desde uma análise clinica das situações didáticas de formação (§3) abordamos uma definição das relações estéticas às obras como um dos principais campos para o desenvolvimento emocional, e analisamos as mediações de formação que as transformam (§4). A análise de um tipo de caso particular, o da formação dos músicos interpretes a “uma interpretação musical própria da música tradicional dos Andes” permite para nós, abordar a problemática da transmissão cultural no desenvolvimento das emoções (§5) e abrir dicas sobre pesquisa da relação música-emoções (§6)

La escucha-descubrimiento y el aprendizaje de la postura de espectador. Contribuciones a una didáctica de la recepción cultural en el medio escolar

Resumen: En el marco de las reflexiones actuales en educación artística, la investigación sobre las prácticas docentes constituye un campo central para entender qué, cómo y por qué se enseñan ciertos contenidos artísticos. La observación y análisis de las prácticas muestra que el aprendizaje es el resultado de una actividad conjunta, docente- alumnos, en la construcción de contenidos. A partir del análisis de una secuencia sobre la escucha musical, mostramos cómo el contenido de enseñanza se construye a partir de las prácticas sociales, colectivas y privadas, pero igualmente a partir de objetivos escolares. Estos últimos necesitan ser concientizados por el docente afín de que no se constituyan en obstáculos a la comprensión y vivencia de los aprendizajes ligados a la escucha musical.Resumo: No marco das reflexões atuais em educação artística, a pesquisa nas práticas educacionais constitui um campo central para compreender o quê, como e por que determinados conteúdos artísticos são ensinados. A observação e análise das práticas mostra que a aprendizagem é o resultado de uma actividade conjunta docentes-estudantes na construção de conteúdos. Da análise de uma seqüência sobre a escuta musical, nós mostramos como o conteúdo do ensino é construído a partir das práticas sociais coletivas e privadas, assím como das metas escolares. Estas últimas precisam ser concientizadas pelo docente para que não representem um obstáculo na compreensão e a experiência dos aprendizados relacionados com a escuta musical

Inertial drag and lift forces for coarse grains on rough alluvial beds measured using in-grain accelerometers

Quantifying the force regime that controls the movement of a single grain during fluvial transport has historically proven to be difficult. Inertial micro-electromechanical system (MEMS) sensors (sensor assemblies that mainly comprise micro-accelerometers and gyroscopes) can used to address this problem using a “smart pebble”: a mobile inertial measurement unit (IMU) enclosed in a stone-like assembly that can measure directly the forces on a particle during sediment transport. Previous research has demonstrated that measurements using MEMS sensors can be used to calculate the dynamics of single grains over short time periods, despite limitations in the accuracy of the MEMS sensors that have been used to date. This paper develops a theoretical framework for calculating drag and lift forces on grains based on IMU measurements. IMUs were embedded a spherical and an ellipsoidal grain and used in flume experiments in which flow was increased until the grain moved. Acceleration measurements along three orthogonal directions were then processed to calculate the threshold force for entrainment, resulting in a statistical approximation of inertial impulse thresholds for both the lift and drag components of grain inertial dynamics. The ellipsoid IMU was also deployed in a series of experiments in a steep stream (Erlenbach, Switzerland). The inertial dynamics from both sets of experiments provide direct measurement of the resultant forces on sediment particles during transport, which quantifies (a) the effect of grain shape and (b) the effect of varied-intensity hydraulic forcing on the motion of coarse sediment grains during bedload transport. Lift impulses exert a significant control on the motion of the ellipsoid across hydraulic regimes, despite the occurrence of higher-magnitude and longer-duration drag impulses. The first-order statistical generalisation of the results suggests that the kinetics of the ellipsoid are characterised by low- or no-mobility states and that the majority of mobility states are controlled by lift impulses

Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

Substantial uncertainties in bedload transport predictions in steep streams have encouraged intensive efforts towards the development of surrogate monitoring technologies. One such system, the Swiss plate geophone (SPG), has been deployed and calibrated in numerous steep channels, mainly in the Alps. Calibration relationships linking the signal recorded by the SPG system to the intensity and characteristics of transported bedload can vary substantially between different monitoring stations, likely due to site-specific factors such as flow velocity and bed roughness. Furthermore, recent flume experiments on the SPG system have shown that site-specific calibration relationships can be biased by elastic waves resulting from impacts occurring outside the plate boundaries. Motivated by these findings, we present a hybrid calibration procedure derived from flume experiments and an extensive dataset of 308 direct field measurements at four different SPG monitoring stations. Our main goal is to investigate the feasibility of a general, site-independent calibration procedure for inferring fractional bedload transport from the SPG signal. First, we use flume experiments to show that sediment size classes can be distinguished more accurately using a combination of vibrational frequency and amplitude information than by using amplitude information alone. Second, we apply this amplitude-frequency method to field measurements to derive general calibration coefficients for 10 different grain-size fractions. The amplitude-frequency method results in more homogeneous signal responses across all sites and significantly improves the accuracy of fractional sediment flux and grain-size estimates. We attribute the remaining site-to-site discrepancies to large differences in flow velocity and discuss further factors that may influence the accuracy of these bedload estimates.ISSN:2196-632XISSN:2196-631

Formación docente: retos y dificultades para poner al alumno en interacción con el objeto artístico

El estudio que se presenta parte de la necesidad de aproximarse a la praxis artística tal y como toma forma a través de las prácticas escolares que se realizan en el aula, y encuentra un campo de estudio en las prácticas profesionales de los estudiantes durante su formación como docentes. El objetivo fundamental se centra en incrementar la comprensión sobre como desarrollan su trabajo, y hacer emerger posibles problemas y necesidades de la formación inicial del profesorado. Metodológicamente, este estudio está basado en el análisis contrastado de dos situaciones de enseñanza a partir de las categorías de la Teoría de la Acción Didáctica Conjunta (TADC), desarrolladas en el campo de la didáctica comparada (Sensevy & Mercier, 2007). Estas categorías sirven para describir y comprender, respectivamente: a) la evolución del medio didáctico y de los contenidos de enseñanza, b) el rol del docente y de los alumnos en la transformación de este medio y la manera en que trabajan sus posturas de experticia respecto a los retos de la tarea; c) finalmente, la organización temporal de las tareas y de los momentos de avance en los saberes a enseñar. El estudio también se interesa en otras dos categorías de análisis, el binomio devolución-regulación, en tanto que gestos profesionales de manejo de los tres tipos de procesos mencionados, que indagaremos a partir de las evidencias identificadas en las interacciones verbales, gestuales y proxémicas