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See detailLazy planning under uncertainty by optimizing decisions on an ensemble of incomplete disturbance trees
Defourny, Boris ULiege; Ernst, Damien ULiege; Wehenkel, Louis ULiege

in Defourny, Boris; Ernst, Damien; Wehenkel, Louis (Eds.) Recent Advances in Reinforcement Learning (2008)

This paper addresses the problem of solving discrete-time optimal sequential decision making problems having a disturbance space W composed of a finite number of elements. In this context, the problem of ... [more ▼]

This paper addresses the problem of solving discrete-time optimal sequential decision making problems having a disturbance space W composed of a finite number of elements. In this context, the problem of finding from an initial state x0 an optimal decision strategy can be stated as an optimization problem which aims at finding an optimal combination of decisions attached to the nodes of a disturbance tree modeling all possible sequences of disturbances w0, w1, . . ., w(T−1) in W^T over the optimization horizon T. A significant drawback of this approach is that the resulting optimization problem has a search space which is the Cartesian product of O(|W|^(T−1)) decision spaces U, which makes the approach computationally impractical as soon as the optimization horizon grows, even if W has just a handful of elements. To circumvent this difficulty, we propose to exploit an ensemble of randomly generated incomplete disturbance trees of controlled complexity, to solve their induced optimization problems in parallel, and to combine their predictions at time t = 0 to obtain a (near-)optimal first-stage decision. Because this approach postpones the determination of the decisions for subsequent stages until additional information about the realization of the uncertain process becomes available, we call it lazy. Simulations carried out on a robot corridor navigation problem show that even for small incomplete trees, this approach can lead to near-optimal decisions. [less ▲]

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See detailLazy sensors for the scheduling of measurement samples transmission in linear closed loops over networks
Forni, Fulvio ULiege; Galeani, Sergio; Nesic, Dragan et al

in 49th IEEE Conference on Decision and Control (cdc 2010) (2010)

We consider an exponentially stable close-loop interconnection of a continuous linear plant and a continuous linear controller, and we study the problem of interconnecting the plant output to the ... [more ▼]

We consider an exponentially stable close-loop interconnection of a continuous linear plant and a continuous linear controller, and we study the problem of interconnecting the plant output to the controller input through a network. We propose a family of "lazy sensors" whose goal is to transmit the measured plant output information as little as possible while preserving closed-loop stability. In particular, we propose three transmission policies, providing conditions on the transmission parameters. These guarantee global asymptotic stability when the plant state is available, and global practical stability when the plant state is not available. Simulation results confirm the effectiveness of the proposed strategies. [less ▲]

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See detailLBG-SQUARE - Fault Tolerant, Locality-Aware Co-allocation in P2P Grids
Dethier, Gérard ULiege; Briquet, Cyril ULiege; Marchot, Pierre ULiege et al

in Huang, Zhiyi; Xu, Zhiwei; Rountree, Nathan (Eds.) et al Ninth International Conference On Parallel And Distributed Computing, Applications And Technologies : PDCAT 2008 (2008, December)

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily ... [more ▼]

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily-communicating, long-running Tasks. They thus require co-allocation of multiple reliable resources for extended periods of time. P2P Grids are totally decentralized and provide on-demand, transparent access to edge resources, e.g. Internet-connected, non-dedicated desktop computers. A P2P Grid has the potential to provide access to a large number of resources at the fraction of the cost of a dedicated cluster. However, edge resources are heterogeneous in performance and intrinsically unreliable: Task execution failures are common due to resource preemption or resource failure. Furthermore, P2P Grid schedulers usually target sets of independent computational Tasks, i.e. so-called Bags of Tasks applications. It is therefore not trivial to deploy and run an Iterative Stencil application on a P2P Grid. Checkpointing is a common fault-tolerance mechanism in High Performance Distributed Computing, often based on a centralized architecture. Locality-aware co-allocation in P2P Grids has been recently investigated. Checkpointing and locality-aware co-allocation yet have to be integrated in P2P Grids. We propose to provide co-allocation through an existing middleware-level Bag of Tasks scheduling mechanism. We also introduce a layer of fault-tolerance for the Iterative Stencils that relies on a scalable, application-level, P2P checkpointing mechanism. Finally, LBG-SQUARE is described. This software results from the combination of a specific Iterative Stencil application (a Computational Fluid Dynamics simulation software called LaBoGrid) with a P2P Grid middleware (Lightweight Bartering Grid). [less ▲]

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See detailLBR-5, a Ship Hull Optimization Tool
Rigo, Philippe ULiege; Hage, André ULiege

in SIMOUEST’2000, European Conference, Marine Technology (2000, November)

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See detailThe LBTI Fizeau imager - I. Fundamental gain in high-contrast imaging
Patru, F.; Esposito, S.; Puglisi, A. et al

in Monthly Notices of the Royal Astronomical Society (2017), 472

We show by numerical simulations a fundamental gain in contrast when combining coherently monochromatic light from two adaptive optics (AO) telescopes instead of using a single stand-alone AO telescope ... [more ▼]

We show by numerical simulations a fundamental gain in contrast when combining coherently monochromatic light from two adaptive optics (AO) telescopes instead of using a single stand-alone AO telescope, assuming efficient control and acquisition systems at high speed. A contrast gain map is defined as the normalized point spread functions (PSFs) ratio of a single Large Binocular Telescope (LBT) aperture over the dual Large Binocular Telescope Interferometer (LBTI) aperture in Fizeau mode. The global gain averaged across the AO-corrected field of view is improved by a factor of 2 in contrast in long exposures and by a factor of 10 in contrast in short exposures (i.e. in exposures, respectively, longer or shorter than the coherence time). The fringed speckle halo in short exposures contains not only high-angular resolution information, as stated by speckle imaging and speckle interferometry, but also high-contrast imaging information. A high-gain zone is further produced in the valleys of the PSF formed by the dark Airy rings and/or the dark fringes. Earth rotation allows us to exploit various areas in the contrast gain map. A huge-contrast gain in narrow zones can be achieved when both a dark fringe and a dark ring overlap on to an exoplanet. Compared to a single 8-m LBT aperture, the 23-m LBTI Fizeau imager can provide a gain in sensitivity (by a factor of 4), a gain in angular resolution (by a factor of 3) and, as well, a gain in raw contrast (by a factor of 2-1000 varying over the AO-corrected field of view). [less ▲]

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See detailThe LBTI Fizeau imager – II. Sensitivity of the PSF and the MTF to adaptive optics errors and to piston errors
Patru, F.; Esposito, S.; Puglisi, A. et al

in Monthly Notices of the Royal Astronomical Society (2017), 472

We show numerical simulations with monochromatic light in the visible for the LBTI Fizeau imager, including opto-dynamical aberrations due here to adaptive optics (AO) errors and to differential piston ... [more ▼]

We show numerical simulations with monochromatic light in the visible for the LBTI Fizeau imager, including opto-dynamical aberrations due here to adaptive optics (AO) errors and to differential piston fluctuations, while other errors have been neglected. The achievable Strehl by the LBTI using two AO is close to the Strehl provided by a single standalone AO system, as long as other differential wavefront errors are mitigated. The LBTI Fizeau imager is primarily limited by the AO performance and by the differential piston/tip–tilt errors. Snapshots retain high-angular resolution and high-contrast imaging information by freezing the fringes against piston errors. Several merit functions have been critically evaluated in order to characterize point spread functions and the modulation transfer functions for high-contrast imaging applications. The LBTI Fizeau mode can provide an image quality suitable for standard science cases (i.e. a Strehl above 70 per cent) by performing both at a time: an AO correction better than ≈λ/18 RMS for both short and long exposures, and a piston correction better than ≈λ/8 RMS for long exposures or simply below the coherence length for short exposures. Such results, which can be applied to any observing wavelength, suggest that AO and piston control at the LBTI would already improve the contrast at near- and mid-infrared wavelengths. Therefore, the LBTI Fizeau imager can be used for high-contrast imaging, providing a high-Strehl regime (by both AO systems), a cophasing mode (by a fringe tracker) and a burst mode (by a fast camera) to record fringed speckles in short exposures. [less ▲]

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See detailThe LBTI hunt for observable signatures of terrestrial systems (HOSTS) survey: a key NASA science program on the road to exoplanet imaging missions
Danchi, W.; Bailey, V.; Bryden, G. et al

in Optical and Infrared Interferometry IV (2014, July 01)

The Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS) program on the Large Binocular Telescope Interferometer (LBTI) will survey nearby stars for faint exozodiacal dust (exozodi ... [more ▼]

The Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS) program on the Large Binocular Telescope Interferometer (LBTI) will survey nearby stars for faint exozodiacal dust (exozodi). This warm circumstellar dust, analogous to the interplanetary dust found in the vicinity of the Earth in our own system, is produced in comet breakups and asteroid collisions. Emission and/or scattered light from the exozodi will be the major source of astrophysical noise for a future space telescope aimed at direct imaging and spectroscopy of terrestrial planets (exo- Earths) around nearby stars. About 20% of nearby field stars have cold dust coming from planetesimals at large distances from the stars (Eiroa et al. 2013, A&A, 555, A11; Siercho et al. 2014, ApJ, 785, 33). Much less is known about exozodi; current detection limits for individual stars are at best ~ 500 times our solar system's level (aka. 500 zodi). LBTI-HOSTS will be the first survey capable of measuring exozodi at the 10 zodi level (3σ). Detections of warm dust will also reveal new information about planetary system architectures and evolution. We will describe the motivation for the survey and progress on target selection, not only the actual stars likely to be observed by such a mission but also those whose observation will enable sensible extrapolations for stars that will not be observed with LBTI. We briefly describe the detection of the debris disk around η Crv, which is the first scientific result from the LBTI coming from the commissioning of the instrument in December 2013, shortly after the first time the fringes were stabilized. [less ▲]

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See detailLC determination of oxprenolol enantiomers in human plasma using dialysis as on-line sample preparation technique
Ceccato, Attilio ULiege; Toussaint, B.; Chiap, Patrice ULiege et al

in Journal de Pharmacie de Belgique (1996), 51

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See detailLC method for the determination of R-timolol in S-timolol maleate: Validation of its ability to quantify and uncertainty assessment.
Marini Djang'Eing'A, Roland ULiege; Chiap, Patrice ULiege; Boulanger, Bruno ULiege et al

in Talanta (2006), 68(4), 1166-1175

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel ... [more ▼]

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel validation strategy based on the accuracy profiles was used to select the most appropriate regression model, to assess the method accuracy within well defined acceptance limits and to determine the limits of quantitation as well as the concentration range. The validation phase was completed by the investigation of the risk profiles of various acceptable regression models in order to ensure the risk of obtaining the future measurements outside the acceptance limits fixed a priori. On the other hand, the present paper also shows how data used in this validation approach can be used to estimate the measurement uncertainty. The uncertainty derived from beta-expectation tolerance interval (sigma(Tol)(2)), which is equal to the uncertainty of measurements as well as the expanded uncertainty (U(x)) using a coverage factor k=2 was estimated. The uncertainty estimates obtained from validation data were finally compared with those obtained from interlaboratory and robustness studies. [less ▲]

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See detailLC method for the simultaneous determination of R-timolol and other closely related impurities in S-timolol maleate: Optimization by use of an experimental design
Marini Djang'Eing'A, Roland ULiege; Chiap, Patrice ULiege; Boulanger, Bruno ULiege et al

in Journal of Separation Science (2003), 26(9-10), 809-817

A liquid chromatography (LC) method using cellulose tris(3,5-dimethylphenylcarbamate) (5 mum) as chiral stationary phase (CSP) and a mixture of hexane, 2-propanol, and diethylamine as mobile phase was ... [more ▼]

A liquid chromatography (LC) method using cellulose tris(3,5-dimethylphenylcarbamate) (5 mum) as chiral stationary phase (CSP) and a mixture of hexane, 2-propanol, and diethylamine as mobile phase was developed for the simultaneous determination of R-timolol and other potential related substances in S-timolol maleate samples. An experimental design was elaborated in order to test the effects of the different selected factors. Three factors were studied simultaneously, namely the concentrations of 2-propanol and diethylamine as well as the column temperature. The effects of these factors were evaluated statistically. Optimal LC conditions were then deduced by applying a multicriteria decision making approach, namely Derringer's desirability function, for the responses of interest. The developed LC method was compared to the European Pharmacopoeia method and was applied to the determination of R-timolol and other related substances in several samples of S-timolol maleate from different sources. [less ▲]

Detailed reference viewed: 43 (5 ULiège)
See detailLc-chip versus UHPLC-tandem mass spectrometry for the quantitation of estetrol and estradiol without derivatization after whole blood microsampling
Nys, Gwenaël ULiege; Servais, Anne-Catherine ULiege; Pequeux, Christel ULiege et al

Conference (2017, March 29)

the aim of this work was to conduct a PK study on mice to select the most appropriate administration route for E2 and E4 formulations. To achieve this goal, a reference method for the quantitation of both ... [more ▼]

the aim of this work was to conduct a PK study on mice to select the most appropriate administration route for E2 and E4 formulations. To achieve this goal, a reference method for the quantitation of both estrogens after whole blood microsampling was developed and validated on a UHPLC-MS/MS system. This reference method was later transferred on LC-chip device and both methods were compared in terms of analytical parameters such as response function, accuracy, precision, trueness and limit of quantification. [less ▲]

Detailed reference viewed: 20 (0 ULiège)
See detailLC-MS for metabolomics
Fillet, Marianne ULiege

Conference (2011)

Detailed reference viewed: 16 (0 ULiège)