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See detailExplicit Control Force and Torque Determination for Satellite Formation-Keeping with Attitude Requirements
Cho, Hancheol ULg; Udwadia, Firdaus

in Journal of Guidance Control and Dynamics (2013), 36(2), 589-605

A simple analytical approach for formation-keeping of satellites in the presence of both orbital and attitude requirements is developed. A leader satellite is assumed to be in a J2-perturbed circular ... [more ▼]

A simple analytical approach for formation-keeping of satellites in the presence of both orbital and attitude requirements is developed. A leader satellite is assumed to be in a J2-perturbed circular reference orbit and each follower satellite is required to stay in its prescribed, desired orbit with respect to the leader satellite, and at the same time, to point to an arbitrarily chosen specific spot in space that may be time-varying. Nonlinear relative dynamics is considered in its entirety without any approximations, and nonlinear controllers are designed to exactly satisfy the desired orbital and attitude mission requirements for the formation. The analytical approach leads to a separation principle that points out when orbital control is completely unaffected by attitude control. In the presence of sensor measurement noise that leads to incorrect initial conditions at the start of the control maneuver the approach asymptotically satisfies both the orbital and attitude control requirements, at any desired rate of convergence depending on mission requirements. The effect of small unmodelled dynamics is also considered. A numerical example demonstrates the simplicity of the approach, its ease of implementation, accuracy of results, and its robustness to both sensor measurement errors and unmodelled dynamics. [less ▲]

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See detailAn explicit discontinuous Galerkin method for non-linear solid dynamics. Formulation, parallel implementation and scalability properties.
Noels, Ludovic ULg; Radovitzky, Raúl

in International Journal for Numerical Methods in Engineering (2008), 74

An explicit-dynamics spatially-discontinuous Galerkin (DG) formulation for non-linear solid dynamics is proposed and implemented for parallel computation. Discontinuous Galerkin methods have particular ... [more ▼]

An explicit-dynamics spatially-discontinuous Galerkin (DG) formulation for non-linear solid dynamics is proposed and implemented for parallel computation. Discontinuous Galerkin methods have particular appeal in problems involving complex material response, e.g. non-local behavior and failure, as, even in the presence of discontinuities, they provide a rigorous means of ensuring both consistency and stability. In the proposed method, these are guaranteed: the former by the use of average numerical fluxes, and the latter by the introduction of appropriate quadratic terms in the weak formulation. The semi-discrete system of ordinary differential equations is integrated in time using a conventional second-order central-difference explicit scheme. A stability criterion for the time integration algorithm, accounting for the influence of the DG discretization stability, is derived for the equivalent linearized system. This approach naturally lends itself to efficient parallel implementation. The resulting DG computational framework is implemented in three dimensions via specialized interface elements. The versatility, robustness and scalability of the overall computational approach are all demonstrated in problems involving stress-wave propagation and large plastic deformations. [less ▲]

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See detailExplicit dynamic with X-FEM to handle complex geometries
Rosycki, P.; Béchet, Eric ULg; Moës, Nicolas

Scientific conference (2006)

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See detailExplicit dynamics with X-FEM to handle complex geometries
Moes, Nicolas; Rozycki, P.; Béchet, Eric ULg

Scientific conference (2006)

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See detail«Explicit e cornice nel Sistema periodico di Primo Levi»
Moreno, Paola ULg

in Maeder, Costantino; Vannicelli, Andrea (Eds.) Cerchio e spirale approdo e avvio. L’explicit nella narrativa breve dalla fine dell’Ottocento a oggi, Actes du Colloque L’explicit nella narrativa breve post-unitaria. (2001)

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See detailAn Explicit Formula for the Natural and Conformally Invariant Quantization
Radoux, Fabian ULg

in Letters in Mathematical Physics (2009), 89

Lecomte (Prog Theor Phys Suppl 144:125–132, 2001) conjectured the existence of a natural and conformally invariant quantization. In Mathonet and Radoux (Existence of natural and conformally invariant ... [more ▼]

Lecomte (Prog Theor Phys Suppl 144:125–132, 2001) conjectured the existence of a natural and conformally invariant quantization. In Mathonet and Radoux (Existence of natural and conformally invariant quantizations of arbitrary symbols, math.DG 0811.3710), we gave a proof of this theorem thanks to the theory of Cartan connections. In this paper, we give an explicit formula for the natural and conformally invariant quantization of trace-free symbols thanks to the method used in Mathonet and Radoux and to tools already used in Radoux [Lett Math Phys 78(2):173–188, 2006] in the projective setting. This formula is extremely similar to the one giving the natural and projectively invariant quantization in Radoux. [less ▲]

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See detailExplicit formula for the natural and projectively equivariant quantization
Radoux, Fabian ULg

in Letters in Mathematical Physics (2006), 78

In [Prog Theor Phys Suppl 49(3):173–196, 1999], Lecomte conjectured the existence of a natural and projectively equivariant quantization. In [math.DG/0208171, Submitted], Bordemann proved this existence ... [more ▼]

In [Prog Theor Phys Suppl 49(3):173–196, 1999], Lecomte conjectured the existence of a natural and projectively equivariant quantization. In [math.DG/0208171, Submitted], Bordemann proved this existence using the framework of Thomas–Whitehead connections. In [Lett Math Phys 72(3):183–196, 2005], we gave a new proof of the same theorem thanks to the Cartan connections. After these works, there was no explicit formula for the quantization. In this paper, we give this formula using the formula in terms of Cartan connections given in [Lett Math Phys 72(3):183–196, 2005]. This explicit formula constitutes the generalization to any order of the formulae at second and third orders soon published by Bouarroudj in [Lett Math Phys 51(4):265–274, 2000] and [C R Acad Sci Paris Sér I Math 333(4):343–346, 2001]. [less ▲]

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See detailExplicit Multi Model Predictive Control of a Waste Heat Rankine Based System for Heavy Duty Trucks
Grelet, Vincent; Dufour, Pascal; Nadri, Madiha et al

in Proceedings of the 54th IEEE Conference on Decision and Control (2015)

This paper presents an explicit multi-model predictive controller (MMPC) for a waste heat recovery system (WHRS) mounted on a heavy duty truck engine. WHRS based on the Rankine cycle principle attracts a ... [more ▼]

This paper presents an explicit multi-model predictive controller (MMPC) for a waste heat recovery system (WHRS) mounted on a heavy duty truck engine. WHRS based on the Rankine cycle principle attracts a lot of interest in the heavy duty industry, over the past few years, to decrease the fuel consumption and reach the future pollutant emissions standards. Control issues have still to be faced before the integration of such a system into a vehicle. Model predictive controllers suits really well for our control purpose due to their ability to handle online optimal control problem. This paper focuses on the development of an explicit control law based on MMPC with aim to control the fluid temperature at the inlet of the expansion machine in order to increase the system performance and the reliability. [less ▲]

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See detailAn explicit projection method for solving incompressible Navier-Stokes equations
Detrembleur, Sylvain ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Proceedings of the 2nd International Junior Researcher and Engineer Workshop on Hydraulic Structures (2008)

Detailed reference viewed: 64 (16 ULg)
See detailAn explicit projection method for solving incompressible Navier-Stokes equations
Detrembleur, Sylvain ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Pagliara, Stefano (Ed.) Hydraulic Structures (2008)

Detailed reference viewed: 11 (1 ULg)
See detailAn explicit projection method for solving incompressible Navier-Stokes equations
Detrembleur, Sylvain ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Pagliara, Stephano (Ed.) Hydraulic Structures (2008)

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See detailExplicit similarities and expected variabilities: the Initial Upper Paleolithic in Northeast Asia
Zwyns, N.; Teyssandier, N.; Izuho, M. et al

Conference (2014, September 19)

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See detailExplicit Solution to the Full Nonlinear Problem for Satellite Formation-keeping
Cho, Hancheol ULg; Udwadia, Firdaus

in Acta Astronautica (2010), 67(3-4), 369-387

This paper presents simple and exact formation-keeping guidance schemes that use a new method that is rooted in some recent advances in analytical dynamics. As a result of this new approach, explicit ... [more ▼]

This paper presents simple and exact formation-keeping guidance schemes that use a new method that is rooted in some recent advances in analytical dynamics. As a result of this new approach, explicit control inputs to exactly maintain a given formation configuration are easily determined using continuous thrust propulsion systems. The complete nonlinear problem is addressed, and no linearizations and/or approximations are made. The approach provides a marked improvement over existing results in that the control forces, which cause geometric formation-keeping constraints to be exactly satisfied for arbitrary reference orbits, are found in closed form. For Keplerian reference orbits, a much simpler and explicit expression for the control needed to exactly satisfy formation-keeping constraints than hereto available is obtained. The paper also includes explicit control results when the follower is inserted into orbit with incorrect initial conditions, as usually happens in practice. The Hill reference frame, which is often more intuitive for formation-keeping, is used in the analysis. While this paper takes an example of a projected circular formation, the methodology that is developed can be applied to any desired configuration or orbital requirements. Extensive computational simulations are performed to demonstrate the ease of implementation, and the numerical accuracy provided by the approach developed herein. [less ▲]

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See detailAn explicit test for the contribution of environmental maternal effects to rapid clinal differentiation in an invasive plant
Monty, Arnaud ULg; Lebeau, Julie; Meerts, Pierre et al

in Journal of Evolutionary Biology (2009), 22(5), 917-926

Population differentiation of alien invasive plants within their non-native range has received increasingly more attention. Common gardens are typically used to assess the levels of genotypic ... [more ▼]

Population differentiation of alien invasive plants within their non-native range has received increasingly more attention. Common gardens are typically used to assess the levels of genotypic differentiation among populations. However, in such experiments, environmental maternal effects can influence phenotypic variation among individuals if seed sources are collected from field populations under variable environmental regimes. In the present study, we investigated the causes of an altitudinal cline in an invasive plant. Seeds were collected from Senecio inaequidens (Asteraceae) populations along an altitudinal gradient in southern France. In addition, seeds from the same populations were generated by intra-population crossings in a climatic chamber. The two seed lots were grown in a common garden in Central Belgium to identify any evidence of environmentally induced maternal effects and/or an altitudinal cline in a suite of life-history traits. Results failed to detect any environmental maternal effects. However, an altitudinal cline in plant height and above-ground biomass was found to be independent of the maternal environment. [less ▲]

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See detailExplicit Thermodynamic Properties Using Radial Basis Functions Neural Networks
Adam, Olivier; Léonard, Olivier ULg

in Proceedings of the second SIAM international Conference on Data Mining (2002)

Gas turbine design, development, monitoring and maintenance are widely based on numerical simulations of the steady and transient engine performance. Most of the equations that are solved in the ... [more ▼]

Gas turbine design, development, monitoring and maintenance are widely based on numerical simulations of the steady and transient engine performance. Most of the equations that are solved in the simulation programs involve the thermodynamic properties of the fluid flowing through the engine. These properties depend on temperature, pressure, humidity and fuel dosage. As the solution of chemical equilibrium is not compatible with real-time computations, a chemical solver is used off-line to generate a large database which neural networks are trained on. These networks are built on radial basis functions such as multiquadrics. A forward selection approach is used to select data points from the training set as the centers of the transfer functions. The selection stops when the prediction error starts growing. The resulting networks for specific heat and enthalpy of the gas mixture are 3 orders of magnitude faster than the chemical solver. In order to further increase the efficiency and the generalization capabilities of the model, an external optimization solver has been used to tune the shape of the transfer functions. Several solutions are proposed and preliminary results are presented. [less ▲]

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See detailExpliquer la conscience
Rosenthal, David; Dewalque, Arnaud ULg

in Dewalque, Arnaud; Gauvry, Charlotte (Eds.) Conscience et Représentation. Introduction aux théories représentationnelles de l'esprit (2016)

French translation of D. Rosenthal, "Explaining Consciousness", in D. Chalmers (ed.), Philosophy of Mind. Classical and Contemporary Readings, New York, Oxford University Press, 2002, p. 406-421.

Detailed reference viewed: 39 (0 ULg)
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See detail‘De exploitatie van intellectuele eigendom via licentieverlening – Capita selecta’
Vanbrabant, Bernard ULg; Van Couter, Yves

in La propriété intellectuelle omniprésente dans l'entreprise (2008)

Detailed reference viewed: 50 (2 ULg)