Space-Time Transfinite Interpolation of Volumetric Material Properties

The paper presents a novel technique based on extension of a general mathematical method of transfinite interpolation to solve an actual problem in the context of a heterogeneous volume modelling area. It deals with time-dependent changes to the volumetric material properties (material density, colour and others) as a transformation of the volumetric material distributions in space-time accompanying geometric shape transformations such as metamorphosis. The main idea is to represent the geometry of both objects by scalar fields with distance properties, to establish in a higher-dimensional space a time gap during which the geometric transformation takes place, and to use these scalar fields to apply the new space-time transfinite interpolation to volumetric material attributes within this time gap. The proposed solution is analytical in its nature, does not require heavy numerical computations and can be used in real-time applications. Applications of this technique also include texturing and displacement mapping of time-variant surfaces, and parametric design of volumetric microstructures

Distance based heterogeneous volume modelling.

Natural objects, such as bones and watermelons, often have a heterogeneous composition and complex internal structures. Material properties inside the object can change abruptly or gradually, and representing such changes digitally can be problematic. Attribute functions represent physical properties distribution in the volumetric object. Modelling complex attributes within a volume is a complex task. There are several approaches to modelling attributes, but distance functions have gained popularity for heterogeneous object modelling because, in addition to their usefulness, they lead to predictability and intuitiveness. In this thesis, we consider a unified framework for heterogeneous volume modelling, specifically using distance fields. In particular, we tackle various issues associated with them such as the interpolation of volumetric attributes through time for shape transformation and intuitive and predictable interpolation of attributes inside a shape. To achieve these results, we rely on smooth approximate distance fields and interior distances. This thesis deals with outstanding issues in heterogeneous object modelling, and more specifically in modelling functionally graded materials and structures using different types of distances and approximation thereof. We demonstrate the benefits of heterogeneous volume modelling using smooth approximate distance fields with various applications, such as adaptive microstructures, morphological shape generation, shape driven interpolation of material properties through time and shape conforming interpolation of properties. Distance based modelling of attributes allows us to have a better parametrization of the object volume and design gradient properties across an object. This becomes more important nowadays with the growing interest in rapid prototyping and digital fabrication of heterogeneous objects and can find practical applications in different industries

Mécanismes d'oxydation de l'acier liquide lors de l'Interaction Corium-Béton à haute température en cas d'accident grave de réacteur nucléaire

In case of severe nuclear accident, the loss of coolant leads to the formation of a high temperature liquid mixture (T>2500K) of nuclear fuel and structural materials inside the vessel. After the vessel failure, the corium could interact with the concrete of the reactor pit. The metallic phase inside the corium during corium-concrete interaction, changes the ablation processes and release H2 and CO. The aim of the PhD thesis was to study the kinetics and mechanisms of the liquid steel oxidation during corium-concrete interaction. In this way, the study was divided in three parts: with calculations at the thermodynamic equilibrium, with analytical experiments and with prototypical experiments. The results of oxidation analyses during prototypical experiments show that gases inside the concrete are not the only one source of oxidation and that another source outside the concrete have to participate to the oxidation mechanism. The analytical experiments and the thermodynamic approach show that the corium can oxidize the metallic phase whereas the concrete oxides cannot. The oxidation mechanism of liquid steel is based on high chromium and iron oxidation leading to their depletion. Oxidation of nickel does not occur, it would be mainly evaporated according to the thermodynamic calculations. Thanks to the kinetic study, the rates of the liquid steel oxidation by O2 et CO2 have been found and a phenomenological model have been proposed to estimate the steel oxidation during the prototypical experiments.En cas d' accident grave de réacteur nucléaire, la perte de réfrigérant peut conduire à la formation d'un mélange liquide à haute température (T>2500K) constitué majoritairement du combustible nucléaire et des matériaux de structure (corium). En cas de rupture de la cuve, le corium est susceptible d'interagir avec le béton de l'enceinte de confinement. Au contact du béton, la présence d'acier liquide modifie les processus d'ablation du béton et entraine une production de H2 et CO. Les objectifs de cette thèse étaient de déterminer la cinétique d'oxydation de l'acier liquide dans ces conditions, et d'identifier les mécanismes prépondérants. Pour répondre à ces objectifs, trois volets ont été développés: une approche à l'équilibre thermodynamique, des expériences analytiques à effets séparés et des expériences intégrales avec du corium prototypique. L'analyse des expériences intégrales montre que les gaz relâchés par le béton ne sont pas les seules sources d'oxydation, mais qu'une source d'oxydation extérieure au béton participe aux mécanismes d'oxydation. Les expériences analytiques ainsi que les calculs à l'équilibre thermodynamique ont montré que le corium, par sa capacité à devenir sur-stoechiométrique, est une source d'oxydation supplémentaire. Au contraire, les oxydes du béton ne participent pas au mécanisme d'oxydation. Le mécanisme d'oxydation de l'acier liquide est basé sur une oxydation relativement forte du chrome et du fer. Le nickel n'est pas oxydé, et serait consommé préférentiellement par Évaporation d'après les calculs thermodynamiques. L'étude cinétique de l'oxydation a permis d'une part d'établir deux lois cinétiques d'oxydation par O2 et CO2 et d'autre part de proposer une modélisation de la cinétique d'oxydation de l'acier lors des essais intégraux

Development of CMOS pixel sensors for tracking and vertexing in high energy physics experiments

CMOS pixel sensors (CPS) represent a novel technological approach to building charged particle detectors. CMOS processes allow to integrate a sensing volume and readout electronics in a single silicon die allowing to build sensors with a small pixel pitch ($\sim 20 \mu m$) and low material budget ($\sim 0.2-0.3\% X_0$) per layer. These characteristics make CPS an attractive option for vertexing and tracking systems of high energy physics experiments. Moreover, thanks to the mass production industrial CMOS processes used for the manufacturing of CPS the fabrication construction cost can be significantly reduced in comparison to more standard semiconductor technologies. However, the attainable performance level of the CPS in terms of radiation hardness and readout speed is mostly determined by the fabrication parameters of the CMOS processes available on the market rather than by the CPS intrinsic potential. The permanent evolution of commercial CMOS processes towards smaller feature sizes and high resistivity epitaxial layers leads to the better radiation hardness and allows the implementation of accelerated readout circuits. The TowerJazz $0.18 \mu m$ CMOS process being one of the most relevant examples recently became of interest for several future detector projects. The most imminent of these project is an upgrade of the Inner Tracking System (ITS) of the ALICE detector at LHC. It will be followed by the Micro-Vertex Detector (MVD) of the CBM experiment at FAIR. Other experiments like ILD consider CPS as one of the viable options for flavour tagging and tracking sub-systems

Drug-Induced Inhibition of Mitochondrial Fatty Acid Oxidation and Steatosis

Mitochondrial Dysfunction and Diseases (H Jaeschke, Section Editor)International audienceDrug-induced inhibition of mitochondrial fatty acid β-oxidation (mtFAO) is a key mechanism whereby drugs can induce steatosis. The type and severity of this liver lesion is dependent on the residual mtFAO flux. Indeed, a severe inhibition of mtFAO leads to microvesicular steatosis, hypoglycemia and liver failure, which can be favored by genetic predispositions. In contrast, moderate impairment of mtFAO can cause macrovacuolar steatosis, which is by itself a benign lesion. In the long-term, however, macrovacuolar steatosis can progress with some drugs to steatohepatitis. Interestingly, drugs that are more likely to cause steatohepatitis are those impairing the mitochondrial respiratory chain (MRC) activity. Indeed, MRC impairment favors not only hepatic fat accretion but also oxidative stress and lipid peroxidation. Drugs inhibiting mtFAO could be more toxic in obese patients with preexisting nonalcoholic fatty liver disease (NAFLD) since higher mtFAO is a key metabolic adaptation to curb fat accretion during NAFLD

Sequential supplementary firing in natural gas combined cycle with carbon capture: A technology option for Mexico for low-carbon electricity generation and CO<inf>2</inf> enhanced oil recovery

Combined cycle gas turbine power plants with sequential supplementary firing in the heat recovery steam generator could be an attractive alternative for markets with access to competitive natural gas prices, with an emphasis on capital cost reduction, and where supply of carbon dioxide for Enhanced Oil Recovery (EOR) is important. Sequential combustion makes use of the excess oxygen in gas turbine exhaust gas to generate additional CO2, but, unlike in conventional supplementary firing, allows keeping gas temperatures in the heat recovery steam generator below 820 °C, avoiding a step change in capital costs. It marginally decreases relative energy requirements for solvent regeneration and amine degradation. Power plant models integrated with capture and compression process models of Sequential Supplementary Firing Combined Cycle (SSFCC) gas-fired units show that the efficiency penalty is 8.2% points LHV compared to a conventional natural gas combined cycle power plant with the same capture technology. The marginal thermal efficiency of natural gas firing in the heat recovery steam generator can increase with supercritical steam generation to reduce the efficiency penalty to 5.7% points LHV. Although the efficiency is lower than the conventional configuration, the increment in the power output of the combined steam cycle leads a reduction of the number of gas turbines, at a similar power output to that of a conventional natural gas combined cycle. This has a positive impact on the number of absorbers and the capital costs of the post combustion capture plant by reducing the total volume of flue gas by half on a normalised basis. The relative reduction of overall capital costs is, respectively, 15.3% and 9.1% for the subcritical and the supercritical combined cycle configurations with capture compared to a conventional configuration. For a gas price of $2/MMBTU, the Total Revenue Requirement (TRR) - a metric combining levelised cost of electricity and revenue from EOR - of subcritical and supercritical sequential supplementary firing is consistently lower than that of a conventional NGCC by, respectively, 2.2 and 5.7$/MWh at 0 $/t CO2 and by 4.9 and 6.7$/MWh at $50/t CO2. At a gas price of$4/MMBTU and $6/MMBTU, the TRR of a subcritical configuration is consistently lower for any carbon selling price higher than 2.5$/t CO2 and 37 $/t CO2 respectively

Virtual sculpting and 3D printing for young people with disabilities

In this paper, we present the SHIVA project which was designed to provide virtual sculpting tools for young people with complex disabilities, to allow them to engage with artistic and creative activities that they might otherwise never be able to access. Modern 3D printing then allows us to physically build their creations. To achieve this, we combined our expertise in education, accessible technology, user interfaces and geometric modelling. We built a generic accessible graphical user interface (GUI) and a suitable geometric modelling system and used these to produce two prototype modelling exercises. These tools were deployed in a school for students with complex disabilities and are now being used for a variety of educational and developmental purposes. In this paper, we present the project's motivations, approach and implementation details together with initial results, including 3D printed objects designed by young people who have disabilties