Modélisation stochastique de la solidification eutectique équiaxe

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Liquid cooling in thermal management systems has been implemented mostly through the use of thermal interface materials, which introduce in in-series parasitic thermal resistances and reduced thermal performance. To achieve the full potential of liquid cooling, cooling structures should be fabricated directly in-chip, enabling effective heat transfer near the junction. In this work, we investigate an integrated cooling module encompassing enhanced fin structures (diamond-shaped and square pin fins) with an

Many physical, chemical, financial, and ecological processes show the presence of a threshold, which may affect their dynamics. For instance, chemical reactions occur when the energy reaches the activation value; for insurance companies and banks, ruin may happen when the balance drops down a minimum amount; in fluvial hydraulics, sediment transport, and morphodynamic processes start when bed shear stresses (i.e., flow discharge) overcome a critical threshold. Other processes may show the presence of additi

Composite materials are often produced by pressure-infiltration of a liquid matrix into a preform of packed solid fibers or particles. Capillary forces that intervene in this process are quantified by measuring saturation curves, which are plots of the fraction pore space filled with the matrix versus the pressure difference between the matrix and the atmosphere initially present in the porous preform to be infiltrated. We have constructed an apparatus capable of measuring saturation curves at high temperat

We study the single-phase flow in a saturated, bounded heterogeneous porous medium. We model the permeability as a log-normal random field. We perform a perturbation analysis, expanding the solution in Taylor series. The series is directly computable in the case of a random field parametrized by a finite number of random variables. On the other hand, in the case of an infinite dimensional random field, suitable equations satisfied by the derivatives of the stochastic solution can be derived. We give a theor

As the performances of Solid Oxide Fuel Cells (SOFC) get attractive, long term degradation becomes the main issue for this technology. Therefore it is essential to localise the origin of degradation and to understand its mechanisms in order to find solutions and to improve SOFC durability. Microstructural evolution of anode supported solid oxide fuel cells (SOFC) during medium-term stack testing has been characterized by scanning electron microscopy (SEM). A new technique is presented using low acceleration

This paper describes a new method to determine the equivalent heat transfer coefficients, i.e., radial and azimuthal, in CICC's with parallel cooling channels. The method is based on the measurement of the steady state temperature response to a step heating. The experiment is modelled by a set of transport equations for the temperature distribution that contain explicitly the parametric dependence on the transverse heat transfer coefficients. The equations are solved analytically and the values of the equiv

This work focuses on the stochastic properties of boresight determination between a strapdown IMU and a frame-based imaging sensor. The core of the stochastic model is a rigorous error propagation of the estimated input accuracies and their correlations.

Calorimetry has shown real potential at bench-scale for chem. and biochem. processes. The aim of this work was therefore to scale-up the system by adaptation of a std. com. available 300-L pilot-scale bioreactor. To achieve this, all heat flows entering or leaving the bioreactor were identified and the necessary instrumentation implemented to enable online monitoring and dynamic heat balance estn. Providing that the signals are sufficiently precise, such a heat balance would enable calcn. of the heat releas

Computer simulations of granular materials are often based on the Distinct Element Method (DEM) where each grain is considered individually. Since large quantities of grains are required to perform realistic experiments, high performance computing is mandatory. This paper presents the basis of the DEM, a sequential algorithm for spherical grains in 3D and the adaptations to obtain a parallel version of that algorithm. Visualization is also discussed, as the drawing and animation of large sets of grains requ

The tolerances of semi-continuously cast products of aluminium alloys are very critical if the scalping of the ingot faces is to be minimised before rolling. In the steady state regime of casting, the dimensions of the section of the solidified ingot are lower than those of the mould in the Direct Chill Casting (DCC) or of the inductor in the Electromagnetic Casting (EMC). The contraction of the section, several percents, is larger than the value associated with the thermal contraction of the solid and is a

The densification rate and microstructural evolution of powder compacts densifying by solution-reprecipitation in the presence of a liquid phase are predicted with the assumption that solid particles are equisized spheres randomly packed and pulled together by a liquid that wets perfectly both the solid and its grain boundaries. The influences of applied pressure, initial packing density and of the ''sphering force'' due to changes in solid particle shape are accounted for. The resulting sintering rate reta

Rhombohedral Pb(Zr0.70Ti0.30)O-3 thin films of four different well-defined textures, namely, (100), (111), bimodal (110)/(111), and (100)/(111), were prepared by a sol-gel method. The films were characterized in terms of grain size, presence of second phases, surface roughness, columnarity of grains, and other microstructural features. The dielectric, ferroelectric, and fatigue properties were investigated, with emphasis on the hysteresis switching characteristics. Results are discussed from the reference p

The motivation to this research is the study of the optimal stopping problem for multiparameter processes : given a random process depending on finitely many parameters t = (t1,…,tn), which if stopped at point t in the parameter set produces a reward Xt, what random stopping point T = (T1,…,Tn) maximizes the expected reward ? This is a natural model for a gambler who has the choice of playing several different games and of stopping at the most advantageous time. Of course, the decision to stop at a given po

Modélisation stochastique de la solidification eutectique équiaxe

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Integration of Jet Impingement with Enhanced Pin Fin Structures for In-Chip Cooling of Power Electronics

The selective boundary crossing in stochastic processes driven by white shot noise

Capillarity in pressure infiltration: influence of percolation and wetting angle

MATHICSE Technical Report : Perturbation analysis for the Darcy problem with log-normal permeability

Quantitative study of Ni-zirconia anode micro- and nanostructure related to SOFC stack degradation

Analysis of the transverse heat transfer coefficients in a dual channel ITER-type cable-in-conduit conductor

Towards A More Rigorous Boresight Determination: Theory, Technology and Realities of Inertial/GPS Sensor Orientation

Development of a large-scale biocalorimeter to monitor and control bioprocesses

Parallel DEM Simulations of Granular Materials

Direct chill and electromagnetic casting of aluminium alloys: Thermomechanical effects and solidification aspects

Kinetics of densification by solution-reprecipitation

Influence of texture on the switching behavior of Pb(Zr0.70Ti0.30)O3 sol-gel derived thin films

Randomization in the two-parameter optimal stopping problem : combinatorial, probabilistic and infinitesimal methods