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Multi-Objective Optimization Methodology for Net Zero Energy Buildings
No full textInternational audienceThe challenge in Net Zero Energy Building (NZEB) design is to find the best combination of design strategies that will face the energy performance problems of a particular building. This paper presents a methodology for the simulation-based multi-criteria optimization of NZEBs. Its main features include four steps: building simulation, optimization process, multi-criteria decision making (MCDM) and testing solution's robustness. The methodology is applied to investigate the cost-effectiveness potential for optimizing the design of NZEBs in different case studies taken as diverse climatic zones in Lebanon and France. The investigated design parameters include: external walls and roof insulation thickness, windows glazing type, cooling and heating set points, and window to wall ratio. Furthermore, the inspected RE systems include: solar domestic hot water (SDHW) and photovoltaic (PV) array. The proposed methodology is a useful tool to enhance NZEBs design and to facilitate decision making in early phases of building design. Specifically, the non-dominated sorting genetic algorithm (NSGA-II) is chosen in order to minimize thermal, electrical demands and life cycle cost (LCC) while reaching the net zero energy balance; thus getting the Pareto-front. A ranking decision making technique Elimination and Choice Expressing the Reality (ELECTRE III) is applied to the Pareto-front so as to obtain one optimal solution
Surendettement des particuliers - Traitement du surendettement (Chapitre)
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Thioautotrophic ectosymbiosis in Pseudovorticella sp., a peritrich ciliate species colonizing wood falls in marine mangrove
No full textInternational audienceCiliates represent a diversified group of protists known to establish symbioses with prokaryotic microorganisms. They are mainly phagotrophs and symbiotic relationships with bacteria can give them an important advantage in chemosynthetic environments. The aim of this study is to describe the thiotrophic association that occurs between the peritrich ciliate Pseudovorticella sp. and potential sulfur-oxidizing bacteria. Investigations at microscopic scale (LM, SEM, TEM) showed ectosymbiotic bacteria covering the surface of the body of Pseudovorticella sp. According to 16S rDNA phylogenetic analysis, these ectosymbiotic bacteria belong to-proteobacteria and are phylogenetically close to the symbiont of the recently described Zoothamnium ignavum, which inhabits shallow-water wood falls. FISH experiments, using symbiont specific probes, clearly indicate that these ectosymbiotic bacteria are also ingested into food vacuoles. Electron lucent granules observed in TEM in the cytoplasm of the ectosymbiotic bacteria have been identified as sulfur granules by Raman microspectrometry analyses. Raman microspec-trometry analyses confirmed the thiotrophic nature of this relationship already suggested by the results obtained by TEM and phylogeny. A complete sulfur map was then performed to investigate the sulfur distribution in the zooid. Results show that the relationship between this protist and its bacterial partner is a thiotrophic ectosymbiosis
The axial skeleton of the Siberian sturgeon: development, organization, structure and new insights on ossification and mineralization of vertebral elements
No full textInternational audienceThis two-volume book set focuses on the Siberian sturgeon. Acipenser baerii Brandt 1869, one of the 27 “existing” sturgeon species, is a native species of the Siberian catchments, where – as in many other parts of the world – the sturgeon populations are now threatened. Sturgeon farming practices targeting caviar and meat production have been expanding worldwide since the 1990s, and have seen a further increase since the turn of the century. Among the handful of sturgeon species used for significant production, the most dominant is the Siberian sturgeon. Given its peculiar phylogenetic position as a chondrostei and its use as a biological model in e.g. France, the species has also attracted the attention of biologists
A Reduced-Order Discontinuous Galerkin Method Based on POD for Electromagnetic Simulation
No full textInternational audienceThis paper is concerned with the design of a reduced-order discontinuous Galerkin (DG) method based on the proper orthogonal decomposition (POD) method for electromagnetic simulation. A centered flux approximation for surface integral and a second-order leap-frog scheme for advancing in time are applied in the classical DG method. The POD basis is created by the eigensystem of the correlation matrix, which is generated by the snapshot matrix whose columns are the snapshot vectors extracted from the high-fidelity DG simulation. The POD discontinuous Galerkin time-domain formulation with lower dimension and sufficiently high accuracy is established by applying a Galerkin projection for the semidiscrete DG scheme. The overall goal is to reduce the computational cost while maintaining an acceptable level of accuracy. Numerical experiments for electromagnetic problems illustrate the performance of the proposed reduction method
What sets the central structure of dark matter haloes?
No full textInternational audienceDark matter (DM) haloes forming near the thermal cut-off scale of the density perturbations are unique, since they are the smallest objects and form through monolithic gravitational collapse, while larger haloes contrastingly have experienced mergers. While standard cold dark matter (CDM) simulations readily produce haloes that follow the universal Navarro-Frenk-White (NFW) density profile with an inner slope, , with , recent simulations have found that when the free-streaming cut-off expected for the CDM model is resolved, the resulting haloes follow nearly power-law density profiles of . In this paper, we study the formation of density cusps in haloes using idealized -body simulations of the collapse of proto-haloes. When the proto-halo profile is initially cored due to particle free-streaming at high redshift, we universally find profiles irrespective of the proto-halo profile slope outside the core and large-scale non-spherical perturbations. Quite in contrast, when the proto-halo has a power-law profile, then we obtain profiles compatible with the NFW shape when the density slope of the proto-halo patch is shallower than a critical value, , while the final slope can be steeper for \alpha_{\rm ini}\ga 0.3. We further demonstrate that the profiles are sensitive to small scale noise, which gradually drives them towards an inner slope of , where they become resilient to such perturbations. We demonstrate that the solutions are in hydrostatic equilibrium, largely consistent with a simple analytic model, and provide arguments that angular momentum appears to determine the inner slope
Long wave asymptotics for the Euler–Korteweg system
Full text linkInternational audienceThe Euler–Korteweg system (EK) is a fairly general nonlinear waves model in mathematical physics that includes in particular the fluid formulation of the NonLinear Schrödinger equation (NLS). Several asymptotic regimes can be considered, regarding the length and the amplitude of waves. The first one is the free wave regime, which yields long acoustic waves of small amplitude. The other regimes describe a single wave or two counter propagating waves emerging from the wave regime. It is shown that in one space dimension those waves are governed either by inviscid Burgers or by Korteweg-de Vries equations, depending on the spatio-temporal and amplitude scalings. In higher dimensions, those waves are found to solve Kadomtsev-Petviashvili equations. Error bounds are provided in all cases. These results extend earlier work on defocussing (NLS) (and more specifically the Gross–Pitaevskii equation), and sheds light on the qualitative behavior of solutions to (EK), which is a highly nonlinear system of PDEs that is much less understood in general than (NLS)
Melting of a phase change material in presence of natural convection and radiation: A simplified model
No full textInternational audienceIn this article, a simplified model for melting of a phase change material (PCM) in presence of natural convection and radiation is presented. A modified enthalpy method is adopted to solve the phase change problem, the natural convection occurring in the liquid PCM is accounted for using the enhanced thermal conductivity approach coupled with the scaling theory, and the absorbed shortwave radiation flux is added into the energy equation as a source term using a simplified solution algorithm. Two dimensional implicit finite volume method is used to solve the energy equation. First, the simplified model for melting with natural convection is validated using a CFD model, in addition to experimental and numerical benchmark solutions for a test case. Then, the simplified model for melting with combined natural convection and radiation is applied to the melting of a fatty acid eutectic filled in glass bricks, which will be used later to model the annual thermal behavior of a special translucent façade. This complete model is validated against the lattice Boltzmann-discrete ordinate method LBM-DOM. It was shown that (1) the proposed simplified model is simple to implement and its simulations run significantly faster than those of CFD models and LBM-DOM model. Consequently, it can be easily integrated into an energy simulation tool for yearly performance evaluation, (2) during PCM melting process, natural convection has a noteworthy role as it enhances the average fraction of liquid and the position of the melting front, (3) shortwave radiation enhances the average liquid fraction