Search results for "FEA"
showing 10 items of 4862 documents
Hydro-mechanical analysis of volcanic ash slopes during rainfall
2016
Rainfall-induced landslides in volcanic ashes represent a major natural hazard in many regions around the world. Owing to their loose structure, volcanic ash slopes are prone to rainfall-induced landslides. The paper presents a continuum modelling approach for the analysis of wetting-induced instability phenomena at the onset of failure in loose volcanic ash slopes. A numerical simulation of a landslide-prone volcanic slope in Costa Rica is carried out with a two-dimensional hydro-mechanical finite-element slope model. A constitutive model based on the effective stress concept extended to partially saturated conditions is used to reproduce the volcanic ash hydro-mechanical behaviour. The m…
Landslides and gully slope erosion on the banks of the Gauja River between the towns of Sigulda and Līgatne
2013
This study examines contemporary and past slope erosion processes in the Gauja River valley and adjoining area between the towns of Sigulda and Līgatne. In the field survey landslides and gullies were mapped. Spatial landslide and gully data were correlated with the landslide- and gully-related features (local relief, slope lithology, slope form, slope angle and density of gullies). A novel approach was applied to establish the relationships between slope processes and factors influencing them. This approach uses correlation between raster values of landslide-related factors in specific slope sections and the number of slope processes in these sections to determine the areas prone to slope …
ESTIMATION OF OCEANIC PARTICULATE ORGANIC CARBON WITH MACHINE LEARNING
2020
Understanding and quantifying ocean carbon sinks of the planet is of paramount relevance in the current scenario of global change. Particulate organic carbon (POC) is a key biogeochemical parameter that helps us characterize export processes of the ocean. Ocean color observations enable the estimation of bio-optical proxies of POC (i.e. particulate backscattering coefficient, bbp) in the surface layer of the ocean quasi-synoptically. In parallel, the Argo program distributes vertical profiles of the physical properties with a global coverage and a high spatio-temporal resolution. Merging satellite ocean color and Argo data using a neural networkbased method has already shown strong potentia…
HIGH-RESOLUTION SURFACE AND BED TOPOGRAPHY MAPPING OF RUSSELL GLACIER (SW GREENLAND) USING UAV AND GPR
2020
Abstract. This study presents the detailed survey of the northern marginal part of Russell Glacier, SW Greenland using the combination of unmanned aerial vehicle (UAV) photogrammetry and low-frequency ground penetrating radar (GPR) measurements. Obtained digital elevation model (DEM) and ice thickness data from GPR data allowed the generation of high precision subglacial topography model. We report uncertainties arising from GPR, GPS, and DEM suggesting sufficient accuracy for the reconstruction of glacier bed topography. GPR data and generated subglacial topography model does not reveal any possible Nye channel that could be incised into the bedrock, however, we were able to detect englaci…
IMAGE-BASED MODELING TECHNIQUES FOR ARCHITECTURAL HERITAGE 3D DIGITALIZATION: LIMITS AND POTENTIALITIES
2013
Abstract. 3D reconstruction from images has undergone a revolution in the last few years. Computer vision techniques use photographs from data set collection to rapidly build detailed 3D models. The simultaneous applications of different algorithms (MVS), the different techniques of image matching, feature extracting and mesh optimization are inside an active field of research in computer vision. The results are promising: the obtained models are beginning to challenge the precision of laser-based reconstructions. Among all the possibilities we can mainly distinguish desktop and web-based packages. Those last ones offer the opportunity to exploit the power of cloud computing in order to car…
Documenting the light sensitivity of Spanish Levantine rock art paintings
2015
[EN] A case study to evaluate the use of microfading spectrometry (MFS) for the study of colored systems found in prehistoric rock art paintings was conducted in the Cova Remígia rock-shelter, Castellón (Spain). This rock shelter is part of the rock art sites of the Mediterranean basin on the Iberian Peninsula included in UNESCO s World Heritage List. Some of the paintings belonging to this group are exposed to environmental factors including natural daylight, wind and rain, depending on the time of the day and the season of the year. Therefore, their preservation is a major concern to stakeholders and researchers responsible for protecting and studying these prehistoric paintings. The expe…
Influences of rhythm- and timbre-related musical features on characteristics of music-induced movement
2013
Music makes us move. Several factors can affect the characteristics of such movements, including individual factors or musical features. For this study, we investigated the effect of rhythm- and timbre-related musical features as well as tempo on movement characteristics. Sixty participants were presented with 30 musical stimuli representing different styles of popular music, and instructed to move along with the music. Optical motion capture was used to record participants’ movements. Subsequently, eight movement features and four rhythm- and timbre-related musical features were computationally extracted from the data, while the tempo was assessed in a perceptual experiment. A subsequent c…
Analysis and Performance Evaluation of the IEEE 802.16 ARQ Mechanism
2008
The IEEE 802.16 standard defines the ARQ mechanismas a part of the MAC layer. The functioning of the ARQmechanism depends on a number of parameters. The IEEE802.16 specification defines them but it does not provide concrete values and solutions. This paper studies the key features and parameters of the 802.16 ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, an algorithm to build block sequences, the ARQ feedback intensity, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and the ARQ block size. We ran simulation scenarios to study these parameters and how they impact the performance of application protoc…
The magnesium isotope record of cave carbonate archives
2012
Here we explore the potential of magnesium (&delta;<sup>26</sup>Mg) isotope time-series data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco), the warm-temperate (Germany), the equatorial-humid (Peru) and the cold-humid (Austria) climate zones. Changes in the calcite magnesium isotope signature with time are compared against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a …
Temperature variability in the Iberian Range since 1602 inferred from tree-ring records
2017
Abstract. Tree rings are an important proxy to understand the natural drivers of climate variability in the Mediterranean Basin and hence to improve future climate scenarios in a vulnerable region. Here, we compile 316 tree-ring width series from 11 conifer sites in the western Iberian Range. We apply a new standardization method based on the trunk basal area instead of the tree cambial age to develop a regional chronology which preserves high- to low-frequency variability. A new reconstruction for the 1602–2012 period correlates at −0.78 with observational September temperatures with a cumulative mean of the 21 previous months over the 1945–2012 calibration period. The new IR2Tmax reconstr…