Search results for "VOLUMES"

Nonlocal Second Order Vehicular Traffic Flow Models And Lagrange-Remap Finite Volumes

2011

In this paper a second order vehicular macroscopic model is derived from a microscopic car–following type model and it is analyzed. The source term includes nonlocal anticipation terms. A Finite Volume Lagrange–remap scheme is proposed.

Etude numérique de la convection forcée turbulente dans un dissipateur thermique composé de plusieurs rangées d'ailettes de différentes formes

2016

In this thesis, we present an numerical study of turbulent forced convection in a heat sink provided with a transverse baffle in the bypass. The first model is composed of plates fins and the second consists of adding pin fins between the plates fins. The governing equations, based on the k- SSt turbulence model, are disscredized and solved by the finite volume method and the SIMPLE algorithm. Dynamic results are presented in terms of velocity fields, profiles of the axial velocities in selected sections and pressure drop. The thermal study is presented in terms of temperature fields and the distribution of Nusselt number. A ratio between the thermal and dynamic performances is presented to…

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…

Comparison between the MHFEM formulation and a 2nd spatial order FV formulation of the linear ground problem

2008

Comparison of different 2nd order formulations for the solution of the 2D groundwater flow problem over irregular triangular meshes

2009

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 MHFE formulation is proposed for the solution …

F75Determining fetal lung volume using three-dimensional-ultrasonography

2000

Background The aim of the study was to establish fetal lung, thoracic and heart volume nomograms using 3D-ultrasonography. Method For this purpose 115 fetuses were examined (between 18 and 33 weeks of gestation) using Voluson 530D (Kretztechnik, Austria) ultrasound device and 5 MHZ three-dimensional annular volume transducer. Lung volumes of 15 fetuses suffering from skeletal dysplasia, renal agenesis or hydrothorax and secondary pulmonary hypoplasia were compared with previously established nomograms. Results Lung volumes in the pathologic group of fetuses compared to the nomograms were below the 5% for gestational age. Conclusion The encouraging first results suggest that this method coul…

Repräsentiert der HRCT-Emphysemindex die gesamte Lunge?

2005

Purpose: Comparison of emphysema index derived of thin section MD-CT of the entire lung volume and HRCT, simulated by calculation of every twentieth image of the whole data-set. Materials and Methods: Pulmonary emphysema was quantified by semiautomatic, segmentation of lung borders and assessment of lung volume and emphysema volume within these borders. The emphysema index (pixel index) was calculated. Statistical analysis was done by the sign-test and Bland-Altman-analysis. Results: Median lung volume, emphysema volume and emphysema index are significantly higher in simulated HRCT. Median lung volume (emphysema volume) calculated by HRCT is 5118 ml (407 ml) and 5040 ml (367 ml) calculated …

Compromised Lung Volume and Hemostatic Abnormalities in COVID-19 Pneumonia: Results from an Observational Study on 510 Consecutive Patients

2021

Background: Hemostatic abnormalities have been described in COVID-19, and pulmonary microthrombosis was consistently found at autopsy with concomitant severe lung damage. Methods: This is a retrospective observational cross-sectional study including consecutive patients with COVID-19 pneumonia who underwent unenhanced chest CT upon admittance at the emergency room (ER) in one large academic hospital. QCT was used for the calculation of compromised lung volume (%CL). Clinical data were retrieved from patients’ files. Laboratory data were obtained upon presentation at the ER. Aim: The aim of this study was to evaluate the correlation between hemostatic abnormalities and lung involvement in pa…

What we learn about bipolar disorder from large-scale neuroimaging

2020

Abstract MRI‐derived brain measures offer a link between genes, the environment and behavior and have been widely studied in bipolar disorder (BD). However, many neuroimaging studies of BD have been underpowered, leading to varied results and uncertainty regarding effects. The Enhancing Neuro Imaging Genetics through Meta‐Analysis (ENIGMA) Bipolar Disorder Working Group was formed in 2012 to empower discoveries, generate consensus findings and inform future hypothesis‐driven studies of BD. Through this effort, over 150 researchers from 20 countries and 55 institutions pool data and resources to produce the largest neuroimaging studies of BD ever conducted. The ENIGMA Bipolar Disorder Workin…

Microchimerism in multiple sclerosis: The association between sex of offspring and MRI features in women with multiple sclerosis

2023

AimsDuring pregnancy, fetal cells can migrate to the mother via blood circulation. A percentage of these cells survive in maternal tissues for decades generating a population of fetal microchimeric cells (fMCs), whose biological role is unclear. The aim of this study was to investigate the association between the sex of offspring, an indirect marker of fMCs, and magnetic resonance imaging (MRI) features in women with multiple sclerosis (MS).MethodsWe recruited 26 nulliparous MS patients (NPp), 20 patients with at least one male son (XYp), and 8 patients with only daughters (XXp). Each patient underwent brain MR scan to acquire 3D-T2w FLAIR FatSat and 3D-T1w FSPGR/TFE. Lesion Segmentation To…