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Level-crossing distributions of kinematic variables in multidirectional second-order ocean waves
No full textThe conditional value of a stationary random process, given the level-upcrossing of another dependent stationary random process, is considered. Assuming that both processes are weakly non-Gaussian, an analytical approximation for the related conditional distribution is derived. It is based on a trivariate Edgeworth expansion truncated to non-Gaussian terms of lowest order, to which Rice's formula is then applied. As an application, the effect of level-upcrossing conditioning in second-order ocean waves is investigated. Upcrossing events are monitored for the sea surface elevation. The conditional distributions of different kinematic variables, given upcrossing, are considered for different sea-state configurations. Predictions from the analytical model are compared with numerical data obtained from Monte Carlo experiments. It is found that the analytical approximation provides conditional mean and variance in good agreement with numerical data, although moderate discrepancies appear for the sea states with the most severe wave steepnesses. Regarding the conditional skewness, given upcrossing, results are mixed, with significant discrepancies between the analytical approximation and numerical estimates, in a number of cases. An Edgeworth-type approximation is also provided for the upcrossing frequency and compared with Monte Carlo estimates; this analytical estimate is found to be accurate over a wide range of crossing levels
Multistage Optimization of a Petroleum Production System with Material Balance Model
No full textInternational audienceIn this paper, we propose a mathematical formulation for the management of an oil production network as a multistage optimization problem. The reservoir is modeled as a controlled dynamical system by using material balance equations. We use a dynamic programming algorithm to solve the optimization problem. Two numerical applications illustrate our work: the first one consists in optimizing the production of a gas reservoir, whereas the second one tackles an oil reservoir with water injection
Global Solution of Quadratic Problems by Interval Methods and Convex Reformulation
No full textInternational audienc
Direction-of-Arrival Based Technique for Estimation of Primary User Beam Width
No full textInternational audienceWe consider a single transmitter and multiple receivers equipped with multiple antennas to exploit the spatial characteristics for transmission. To allow the receiver to transmit simultaneously with the transmitter but in a different direction, the receivers use two methods to estimate the half-power beamwidth of the transmitting signal. The first method uses the received power of the transmitter using the Energy Detector (ED). The second method relies on the Direction-of-Arrivals (DoA) at the receivers that are collected using conventional beamforming (BF) method. The performance analysis of the beamwidth estimation is investigated by calculating two metrics. The first is an angular interval that is missed and not detected as a part of the beam. The second is a false detection interval. The simulation results show that the DoA-based technique provides lower false detections compared to the ED-based method, with a tax of a slight increase in the angular missed detection. In addition, our DoA-based approach handles a Rayleigh channel whereas the ED-based technique fails to recover the BW in such a scenario
Time-Varying Optimization of Networked Systems With Human Preferences
No full textInternational audienc
An Empirical Study of the Influence of Seafloor Morphology on the Uncertainty of Bathymetric Data
No full textInternational audienc
Les métiers à responsabilité confrontés aux différences culturelles de valeurs personnelles : le cas de l'océanisation des cadres dans le secteur du tourisme en Polynésie française
No full textInternational audienc
Modélisation électrique de la cellule par une méthode volumes finis
No full textInternational audienceLa modélisation électrique de la cellule, et en particulier l'obtention de la tension transmembranaire, est un problème important en bio-électromagnétisme (électroporation). Dans ce cadre, une modélisation électro-quasi statique est utilisée pour décrire le problème sous forme d'équation de Poisson. Dans cet article, nous proposons une méthode basée sur les volumes finis pour résoudre numériquement le problème. Elle permet de prendre en compte les discontinuités de façon rigoureuse sur des maillages très déformés. La méthode est testée numériquement sur un modèle 2D d'une cellule circulaire (membrane et cytoplasme) soumise à un champ uniforme, puis à un champ électrique pulsé
Effect of impact velocity on the mechanical behavior of a composite plate under slamming impact
No full textInternational audienc
Influence of Moisture Diffusion on the Dynamic Compressive Behavior of Glass/Polyester Composite Joints for Marine Engineering Applications
No full textInternational audienceThermoset polymers offer great opportunities for mass production of fiber-reinforced composites and are being adopted across a large range of applications within the automotive, aerospace, construction and renewable energy sectors. They are usually chosen for marine engineering applications for their excellent mechanical behavior, including low density and low-cost compared to conventional materials. In the marine environment, these materials are confronted by severe conditions, thus there is the necessity to understand their mechanical behavior under critical loads. The high strain rate performance of bonded joints composite under hygrothermal aging has been studied in this paper. Initially, the bonded composite specimens were hygrothermal aged with the conditions of 50 °C and 80% in temperature and relative humidity, respectively. After that, gravimetric testing is used to describe the moisture diffusion properties for the adhesively bonded composite samples and exhibit lower weight gain for this material. Then, the in-plane dynamic compression experiments were carried out at different impact pressures ranging from 445 to 1240 s−1 using the SHPB (Split Hopkinson Pressure Bar) technique. The experimental results demonstrated that the dynamic behavior varies with the variation of strain rate. Buckling and delamination of fiber are the dominant damage criteria observed in the sample during in-plane compression tests