The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform

Xin Feng - One of the best experts on this subject based on the ideXlab platform.

  • a fuzzy Stop Criterion for genetic algorithms using performance estimation
    World Congress on Computational Intelligence, 1994
    Co-Authors: L Meyer, Xin Feng
    Abstract:

    This article presents a new approach for analyzing the solution performance of genetic algorithms (GAs). An adaptive filtering algorithm is combined with a predicting algorithm and memory data from previous GA iterations to estimate the value of the GA's "optimal" solution. If the current GA iteration value is above a certain user-defined acceptance level, the iteration process is Stopped and the GA calculates a belief and uncertainty estimations of the found solution. Results indicate this new approach is preferable to the traditional GA iteration approach, in terms of cost/performance and in decreasing the amount of time the GA searches for acceptable solutions. >

Pierre Pestiaux - One of the best experts on this subject based on the ideXlab platform.

  • time representations and mathematical models for process scheduling problems
    Computers & Chemical Engineering, 2011
    Co-Authors: Sylvain Mouret, Ignacio E Grossmann, Pierre Pestiaux
    Abstract:

    During the last 15 years, many mathematical models have been developed in order to solve process operation scheduling problems, using discrete or continuous time representations. In this paper, we present a unied representation and modeling approach for process scheduling problems. Four dierent time representations are presented, compared, and applied to single-stage and multi-stage batch scheduling problems, as well as crude-oil operations scheduling problems. We introduce three solution methods that can be used to achieve global optimality or obtain near-optimal solutions depending on the Stop Criterion used. Computational results show that the Multi-Operation Sequencing time representation is superior to the others as it allows ecient symmetry-breaking and requires fewer priority-slots, thus leading to smaller model sizes.

Helcio R B Orlande - One of the best experts on this subject based on the ideXlab platform.

  • parameter estimation and model selection for water sorption in a wood fibre material
    Wood Science and Technology, 2020
    Co-Authors: Julien Berger, Thibaut Colinart, Bruna R Loiola, Helcio R B Orlande
    Abstract:

    The sorption curve is an essential feature for the modelling of heat and mass transfer in porous building materials. Several models have been proposed in the literature to represent the amount of moisture content in the material according to the water activity (or capillary pressure) level. These models are based on analytical expressions and few parameters that need to be estimated by inverse analysis. This article investigates the reliability of eight models through the accuracy of the estimated parameters. For this, experimental data for a wood fibre material are generated with special attention to the Stop Criterion to capture long time kinetic constants. Among five sets of measurements, the best estimate is computed. The reliability of the models is then discussed. After proving the theoretical identifiability of the unknown parameters for each model, the primary identifiability is analysed. It evaluates whether the parameters influence on the model output is sufficient to proceed the parameter estimation with accuracy. For this, a continuous derivative-based approach is adopted. Seven models have a low primary identifiability for at least one parameter. Indeed, when estimating the unknown parameters using the experimental observations, the parameters with low primary identifiability exhibit large uncertainties. Finally, an Approximation Bayesian Computation algorithm is used to simultaneously select the best model and estimate the parameters that best represent the experimental data. The GAB and Fredlund-Xing models, together with a proposed model in this work, were the best ones selected by this algorithm.

L Sonneland - One of the best experts on this subject based on the ideXlab platform.

  • automated salt body extraction from seismic data using the level set method
    First Break, 2013
    Co-Authors: Jarle Haukas, Roaldsdotter O Ravndal, B H Fotland, A Bounaim, L Sonneland
    Abstract:

    A solution for automated salt body extraction from seismic data has been developed. The solution is based on a level set algorithm, used in combination with seismic attributes that discriminate between salt and sediments and highlight top and base salt reflections and terminations of sediments against salt. In an automated process, steps to obtain the gross volume of salt are combined with local adjustments to place the salt boundary at the appropriate attribute extrema. The process also includes a local Stop Criterion based on a salt boundary confidence measure. The ability to separate completed salt boundary parts from uncertain regions where the salt boundary has not been identified enables the interpreter to focus on the parts where manual interpretation is required. User constraints, including manual interpretations, are honoured by the algorithm. The methodology is demonstrated on a multi-client seismic data set from the Gulf of Mexico.

Ionescu Livia - One of the best experts on this subject based on the ideXlab platform.

  • Analytical Solution for Low-Thrust Transfer Orbits using Bang-Bang Control without Gravity Losses
    2019
    Co-Authors: Ionescu Livia
    Abstract:

    This thesis research has focused on developing an analytical solution for low-thrust transfer orbits. Low-thrust propulsion is an attractive option for space manoeuvres and transfers, since it provides a large specific impulse and hence efficient use of propellant. Thus, the propellant mass can be decreased, which brings advantages such as higher payload mass and extended mission life.Two constraints have been posed on the thrust acceleration, which often appear as a result of optimal solutions. Firstly, only bang-bang control is allowed, thus the rocket engine can only be turned on or off. Secondly, no radial thrust is allowed, such that no gravity losses occur. The modified equinoctial elements have been chosen to describe the trajectory. If it is assumed that the eccentricity is equal to zero, analytical solutions have been derived. While this seems as a substantial restriction on the developed method, it is shown that the analytical solution provides very reasonable results for eccentricities smaller than 0.2. Furthermore, separate analytical expressions have been developed when no in-plane thrust acts on the spacecraft. For the implementation of the bang-bang control, each individual revolution around the central body is allowed to have two thrust arcs and two coasts arcs, where the analytical solutions have been used to describe the motion of the spacecraft during the thrust arcs. By cleverly choosing the switching points where the rocket engine is turned on and off, the transfer orbit is achieved in an efficient way. The performance of the developed algorithm has been assessed for different input parameters. More specifically, different magnitudes of thrust accelerations have been analyzed. Furthermore, the lengths of the thrust and coast arcs, together with the direction of the thrust force, have been varied to evaluate the applicability of the algorithm. Lastly, the algorithm has been tested with the introduction of a Stop Criterion, which determines the required propellant and time of flight to arrive at a set target element. The algorithm has proved to give results with relatively good accuracy for orbits with an eccentricity smaller than 0.2. However, if the time of flight or the thrust acceleration become too high, less feasible solutions are perceived.Aerospace Engineerin