Search results for "VOLUME"
showing 10 items of 1932 documents
Influence of geometric variations on LV activation times: A study on an atlas-based virtual population
2010
We present the fully automated pipeline we have developed to obtain electrophysiological simulations of the heart on a large atlas-based virtual population. This virtual population was generated from a statistical model of left ventricular geometry, represented by a surface model. Correspondence between tetrahedralized volumetric meshes was obtained using Thin Plate Spline warps. Simulations are based on the fast solving of Eikonal equations, and stimulation sites correspond to physiological activation. We report variations of total activation time introduced by geometry, as well as variations in the location of last activation. The obtained results suggest that the total activation time ha…
Sensitivity analysis of mesh warping and subsampling strategies for generating large scale electrophysiological simulation data
2011
The analysis of large-scale simulation data from virtual populations can be effective to gain computational insight into disease mechanisms and treatment strategies, which can serve for generating hypotheses for and focusing subsequent clinical trials. This can be instrumental in shortening the critical path in medical product development and more cost-effective clinical trials. A previously published pipeline established point correspondence among volumetric meshes to enable meaningful statistics on cardiac electrophysiological simulations on the anatomical distribution of a large-scale virtual population. Thin Plate Splines (TPS), derived from surface deformations, were used to warp a tem…
Fibre break failure processes in unidirectional composites: evaluation of critical damage states
2016
Earlier work which successfully modelled the kinetics of fibre breakage in unidirectional composites under monotonic tensile loading has been extended to quantify the kinetics of fibre failure during both monotonic and sustained tensile loading. In both cases, failure was seen to occur when a critical density of large clusters (more than 16 fibres are broken within the representative volume element) of fibre breaks developed. However, in monotonic loading failure occurred very quickly after the first development of these large clusters, whereas under sustained loading the composite could accommodate greater levels of large clusters because of the lower applied load. This article is part of …
Benchmark study of undrained triaxial testing of Opalinus Clay shale: Results and implications for robust testing
2021
Triaxial testing of argillaceous rocks and shales is significantly more challenging than conventional rock mechanical testing. The challenges are mainly related to the very low permeability of these geomaterials, and their sensitivity to exposure of atmosphere and brines, which induces variations of water content, suction and effective stress. There are currently no international standards to guide service laboratories for robust testing procedures for shales. A benchmark study of undrained triaxial testing was therefore initiated with three leading service laboratories in shale testing, performing 13 tests and using two different methods of establishing sample saturation prior to deformati…
Steering of a Sub-GeV electron beam through planar channeling enhanced by rechanneling
2014
We report the observation of efficient steering of a 855 MeV electron beam at MAMI (MAinzer MIkrotron) facilities by means of planar channeling and volume reflection in a bent silicon crystal. A $30.5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ thick plate of (211) oriented Si was bent to cause quasimosaic deformation of the (111) crystallographic planes, which were used for coherent interaction with the electron beam. The experimental results are analogous to those recorded some years ago at energy higher than 100 GeV, which is the only comparable study to date. Monte Carlo simulations demonstrated that rechanneling plays a considerable role in a particle's dynamics and hinders the spoiling…
Respiratory Parameters after Systemic Corticotropin-Releasing Hormone Administration
1991
Neuroanatomical studies on the distribution of corticotropin-releasing hormone (CRH) and its receptors (7) as well as physiological data suggest a regulatory function of endogenous CRH in hypothalamic and extrahypothalamic brain areas [1, 4]. Endogenous CRH acts within the endocrine hypothalamo-pituitary-adrenal axis and affects cardiovascular regulation and respiration through extrahypothalamic pathways. CRH also stimulates gluconeogenesis and release of plasma-catecholamines. Our experiments in humans also demonstrate an influence on respiration and on heart rate activity after systemic application of CRH. Respiratory parameters and heart rate were analyzed during steady-state conditions …
Effects of Individual Changes in Training Distribution on Maximal Aerobic Capacity in Well-Trained Cross-Country Skiers: A Follow-Up Study
2021
The purpose of this study was to evaluate individual changes in training distribution and the subsequent effects on maximal oxygen uptake (VO2max). The participants were well-trained cross-country skiers who had performed a year with no substantial changes in training prior to this study. Six cross-country skiers, who were participants in a larger previous study, volunteered for a follow-up study. All skiers performed self-motivated changes in training distribution for a new preparation period in this follow-up, generally by more high-intensity training (HIT). All training characteristics were registered from training diaries. During the follow-up period, all skiers performed an incremental…
The application of a reduced volume method for the simulation of the characterisation of a carbon fibre pressure vessel
2018
International audience; The characteristics of advanced composite materials make them ideally suited for use in pressure vessels for storing gas as fuel for ground transport vehicles. It has been found that the failure process starts with randomly distributed fibre breaks and as the loading continues, they coalesce into clusters of fibre breaks which lead to failure [4]. However, improvements are needed to reduce computational times when performing full-scale simulations. The reduced volume method is therefore applied to the stochastic fibre break model related to the concept of an integral range. This method allows the calculation for a certain volume of a laminate that statistically repre…
Comparison between the MHFEM formulation and a 2nd spatial order FV formulation of the linear groundwater flow problem
2008
Mixed and Mixed Hybrid Finite Elements (MHFE) methods have been widely used in the last decade for simulation of groundwater flow problem, petroleum reservoir problems, potential flow problems, etc. The main advantage of these methods is that, unlike the classical Galerkin approach, they guarantee local and global mass balance, as well the flux continuity between inter-element sides. The simple shape of the control volume, where the mass conservation is satisfied, makes also easier to couple this technique with a Finite Volume technique in the time splitting approach for the solution of advection-dispersion problems. In the present paper a new second spatial approximation order Finite Volum…
Reproduction of Baltic cod, Gadus morhua (Actinopterygii: Gadiformes: Gadidae), in the Gotland Basin: Causes of annual variability
2015
Background. The Gotland Basin spawning ground is one of three main spawning areas of Baltic cod, Gadus morhua Linnaeus, 1758. The threshold water parameters for cod development are the salinity exceeding 11‰ and the oxygen level above 2 mL· L–1. Such conditions are only present when the 11‰ isohaline is above the 2 mL· L–1 isooxygen. In such situation the water volume between the isolines is called the “suitable reproduction volume”. When the position of the isolines is reversed, the salinity and the oxygen level of the water layer demarcated by them are below the required thresholds and as such the water is unsuitable for the cod development. We refer to it as the “unsuitable reproduction …