Interplay of entrainment and rheology in snow avalanches: a numerical study

A one-dimensional evolution equation for the slope-normal velocity profile of a streamwise uniform avalanche over an entrainable bed is derived. The boundary conditions are no slip at the bed, a stress-free surface and constant bed shear stress equal to the shear strength of the snow cover. The resulting equation is solved numerically by means of finite differences on a regular grid with a superposed fine grid near the erosion front that is adjusted at each time-step. The first exploratory simulations yield realistic entrainment rates and show that the entrainment rate tends towards a constant value while the flow depth and the velocity increase linearly with time for all investigated rheologies. It is shown that there indeed exists a rheology-independent asymptotic solution to the equation of motion of an entraining slab if the bottom friction is equal to the bed shear strength; the asymptotic acceleration is found to be half the downslope gravitational acceleration. The model can easily be extended to general path profiles, non-uniform flows and variable snow properties

Modelling of short runout propagation landslides and debris flows

This paper proposes an extension of methods used to predict the propagation of landslides having a long runout to smaller landslides with much shorter propagation distances. The method is based on: (1) a depth-integrated mathematical model including the coupling between the soil skeleton and the pore fluids, (2) suitable rheological models describing the relation between the stress and the rate of deformation tensors for fluidised soils and (3) a meshless numerical method, Smooth Particle Hydrodynamics, which separates the computational mesh (or set of computational nodes) from the mesh describing the terrain topography, which is of structured type – thus accelerating search operations. The proposed model is validated using two examples for which there are analytical solutions, and then it is applied to two short runout landslides which happened in Hong Kong in 1995, for which there is available information

Involving Students in Teacher Education Assessment?: A Case Study of a Peer Evaluation Experience

Este estudio, sobre la calificación de exámenes parciales como estrategia de aprendizaje estrechamente relacionada con algunas competencias profesionales y con el desarrollo de mejores procesos de aprendizaje, se realizó en tres centros de Formación Inicial del Profesorado. Tras la realización de exámenes parciales, éstos fueron corregidos in-situ por iguales (mediante una plantilla diseñada “ad hoc”) y posteriormente por el profesor. Además, el alumnado cumplimentó un cuestionario en el que valoró esa experiencia de coevaluación. Los objetivos del estudio fueron: (a) comparar la calificación otorgada por los iguales con la otorgada por el profesorado; y (b) obtener las valoraciones del alumnado sobre la experiencia. Los resultados indican que (a) las correlaciones de las notas entre alumnado y profesorado oscilaron entre .66 y .90, si bien la media de notas del alumnado fue más baja que la del profesorado; y (b) el alumnado valoró positivamente la experiencia de coevaluación como actividad de aprendizaje.This study covered the grading of partial exams as a learning strategy closely linked to a range of professional competencies and the development of better learning processes. It took place in three teacher education programs. After students undertook partial exams, these were marked in-situ by peers (using an ad-hoc marking scheme) and, later on, by the tutor. Furthermore, students responded to a questionnaire in which they gave their opinions regarding that peer-grading assessment experience. The purposes of the study were: (a) to compare the grades given by the students with those given by the tutors; and (b) to gather the students’ opinions on the experience. The results indicate that (a) the correlations between the grades given by the students and tutors ranged from .66 to .90, although the average grades of the student group were lower than those of the tutors; and (b) the students valued positively the experience of peer-grading as a learning activity

Mathematical and Numerical Modeling in Maritime Geomechanics

A theoretical and numerical framework to model the foundation of marine offshore structures is presented. The theoretical model is composed by a system of partial differential equations describing coupling between seabed solid skeleton and pore fluids (water, air, oil,…) combined with a system of ordinary differential equations describing the specific constitutive relation of the seabed soil skeleton. Once the theoretical model is described, the finite element numerical procedure to achieve an approximate solution of the governing equations is outlined. In order to validate the proposed theoretical and numerical framework the seaward tilt mechanism induced by the action of breaking waves over a vertical breakwater is numerically reproduced. The results numerically attained are in agreement with the main conclusions drawn from the literature associated with this failure mechanis

Implicación y regulación del trabajo del alumnado en los sistemas de evaluación formativa en educación superior

El objetivo de este estudio es analizar cuál es la relación entre la utilización de sistemas de evaluación formativa en educación superior y la implicación y la organización y distribución del trabajo del alumnado a lo largo del cuatrimestre. La muestra utilizada es de3.304 alumnos, correspondientes a 50 asignaturas de 16 universidades españolas. Se utiliza la Escala de Sistemas de Evaluación perteneciente al cuestionario sobre metodología y evaluación en la formación inicial del profesorado, en el que se plantean diferentes cuestiones relacionadas con la vía de evaluación formativa. Se ha empleado un análisis cuantitativo descriptivo (medias, DT y varianzas) e inferencial (tablas de contingencia y χ2, correlaciones y ANOVA). El alumnado valora positivamente este sistema de evaluación recibido, asumiendo la necesidad de implicarse desde el comienzo en la asignatura y de buscar estrategias para regular su trabajo. También se demuestra que el alumnado que más veces ha participado en estas vías de evaluación presenta un nivel de implicación mayor, algo que también sucede con el alumnado de cuarto curso. Sin embargo, el hecho de haberse matriculado una o más veces en la misma asignatura no muestra relación significativa con una mayor o menor implicación.The aim of this study is to analyze what is the relationship between involvement and the organization and distribution of work that have university students in connection with formative assessment received. The sample is 3.304 students for 50 subjects in 16 Spanish universities. Scale Assessment Systems belonging to the questionnaire on the evaluation methodology and initial teacher is used, in which there are different issues about formative assessment. It has used a quantitative descriptive analysis (means, variances and DT) and inferential (contingency tables and χ2, correlation and ANOVA). Students welcome this evaluation system received, assuming the need to be involved from the beginning in the subject and find strategies to regulate their work. It also demonstrates that students who participated more often in these assessment processes present a higher level of involvement, which also happens to fourth grade students. However, the fact that he enrolled one or more times in the same subject does not show significance with greater or lesser involvement

FTCS finite difference scheme GPGPU parallel computing for the heat conduction equation = Programación en paralelo GPGPU del método en diferencias finitas FTCS para la ecuación del calor

En el presente artículo se muestran las ventajas de la programación en paralelo resolviendo numéricamente la ecuación del calor en dos dimensiones a través del método de diferencias finitas explícito centrado en el espacio FTCS. De las conclusiones de este trabajo se pone de manifiesto la importancia de la programación en paralelo para tratar problemas grandes, en los que se requiere un elevado número de cálculos, para los cuales la programación secuencial resulta impracticable por el elevado tiempo de ejecución. En la primera sección se describe brevemente los conceptos básicos de programación en paralelo. Seguidamente se resume el método de diferencias finitas explícito centrado en el espacio FTCS aplicado a la ecuación parabólica del calor. Seguidamente se describe el problema de condiciones de contorno y valores iniciales específico al que se va a aplicar el método de diferencias finitas FTCS, proporcionando pseudocódigos de una implementación secuencial y dos implementaciones en paralelo. Finalmente tras la discusión de los resultados se presentan algunas conclusiones. In this paper the advantages of parallel computing are shown by solving the heat conduction equation in two dimensions with the forward in time central in space (FTCS) finite difference method. Two different levels of parallelization are consider and compared with traditional serial procedures. We show in this work the importance of parallel computing when dealing with large problems that are impractical or impossible to solve them with a serial computing procedure. In the first section a summary of parallel computing approach is presented. Subsequently, the forward in time central in space (FTCS) finite difference method for the heat conduction equation is outline, describing how the heat flow equation is derived in two dimensions and the particularities of the finite difference numerical technique considered. Then, a specific initial boundary value problem is solved by the FTCS finite difference method and serial and parallel pseudo codes are provided. Finally after results are discussed some conclusions are presented