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See detailOptimal design of a CO2 capture unit with assessment of solvent degradation
Léonard, Grégoire ULg

Doctoral thesis (2013)

CO2 capture in power plants by absorption in amine solvents is a technology aiming at the reduction of CO2 emissions while simultaneously addressing the growth of the global energy demand. However, the ... [more ▼]

CO2 capture in power plants by absorption in amine solvents is a technology aiming at the reduction of CO2 emissions while simultaneously addressing the growth of the global energy demand. However, the energy impact of this technology on the power plant efficiency is high and amine solvent degradation induces a non-negligible environmental impact. The main innovation of this thesis is to combine both aspects within a process model based on experimental data of solvent degradation. This model leads to the identification of optimal operating conditions for the CO2 capture process, from an energetic as well as environmental point of view. [less ▲]

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See detailOptimal design of fixtures for vibration testing of structures on electro-dynamic shaker
Poncelet, Fabien ULg; Marin, Frédéric; Fleury, Claude ULg et al

Conference given outside the academic context (2005)

The structural design of fixtures for vibration testing of structures on electro-dynamic shakers correspond to a constrained optimization problem. The design methodology proposed in this paper is based on ... [more ▼]

The structural design of fixtures for vibration testing of structures on electro-dynamic shakers correspond to a constrained optimization problem. The design methodology proposed in this paper is based on topological optimization tools. It is illustrated on industrial application examples such as the vibration testing of a space mirror and a street lighting device. [less ▲]

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See detailOptimal design of multi-subject blocked fMRI experiments.
Maus, Bärbel ULg; van Breukelen, Gerard J P; Goebel, Rainer et al

in NeuroImage (2011), 56(3), 1338-1352

The design of a multi-subject fMRI experiment needs specification of the number of subjects and scanning time per subject. For example, for a blocked design with conditions A or B, fixed block length and ... [more ▼]

The design of a multi-subject fMRI experiment needs specification of the number of subjects and scanning time per subject. For example, for a blocked design with conditions A or B, fixed block length and block order ABN, where N denotes a null block, the optimal number of cycles of ABN and the optimal number of subjects have to be determined. This paper presents a method to determine the optimal number of subjects and optimal number of cycles for a blocked design based on the A-optimality criterion and a linear cost function by which the number of cycles and the number of subjects are restricted. Estimation of individual stimulus effects and estimation of contrasts between stimulus effects are both considered. The mixed-effects model is applied and analytical results for the A-optimal number of subjects and A-optimal number of cycles are obtained under the assumption of uncorrelated errors. For correlated errors with a first-order autoregressive (AR1) error structure, numerical results are presented. Our results show how the optimal number of cycles and subjects depend on the within- to between-subject variance ratio. Our method is a new approach to determine the optimal scanning time and optimal number of subjects for a multi-subject fMRI experiment. In contrast to previous results based on power analyses, the optimal number of cycles and subjects can be described analytically and costs are considered. [less ▲]

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See detailOptimal design of outdoor lighting systems by genetic algorithms - Discussion
Embrechts, Jean-Jacques ULg

in Lighting Research & Technology (2003), 35(3), 278-280

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See detailThe Optimal Design of the VSI T2 Control Chart
Faraz, Alireza ULg; Kazemzadeh, R. B.; Heuchenne, Cédric ULg et al

in Journal of Iranian Statistical Society (2010), 9(1), 1-19

Recent studies have shown that the variable sampling interval (VSI) scheme helps practitioners detect process shifts more quickly than the classical scheme (FRS). In this paper, the economically and ... [more ▼]

Recent studies have shown that the variable sampling interval (VSI) scheme helps practitioners detect process shifts more quickly than the classical scheme (FRS). In this paper, the economically and statistically optimal design of the VSI T2 control chart for monitoring the process mean vector is investigated. The cost model proposed by Lorenzen and Vance (1986) is minimized through a genetic algorithm (GA) approach. Then the effects of the costs and operating parameters on the optimal design (OD) of the chart parameters and resulting operating loss through a fractional factorial design is systematically studied and finally, based on the ANOVA results, a Meta model to facilitate implementation in industry is proposed to determine the OD of the VSI T2 control chart parameters from the process and cost parameters [less ▲]

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See detailOptimal dimensioning of pipe networks: the new situation when the distribution and the transportation functions are disconnected
Bakhouya, Bouchra; de Wolf, Daniel ULg

Conference (2008, January)

In [9], De Wolf and Smeers consider the problem of the optimal dimensioning of a gas transmission network when the topology of the network is known. The pipe diameters must been chosen to minimize the sum ... [more ▼]

In [9], De Wolf and Smeers consider the problem of the optimal dimensioning of a gas transmission network when the topology of the network is known. The pipe diameters must been chosen to minimize the sum of the investment and operating costs. This two stage prob- lem was solved by application of the bundle method for nonsmooth optimization. This model does not re ect any more the current situation on the gas industry. Today, the transportation function and gas buying func- tion are separated. This work considers the new situation for the trans- portation company. The objective for the transportation company is to determine the ows in the network that minimize the energy used for the gas transport. This corresponds to the minimization of the power used in the compressors. We introduce in the investment problem new decision variables, namely the maximal power of the compressor. We present here rst results obtained on the belgian gas network and on a realistic network corresponding to a part of the french network. [less ▲]

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See detailOptimal discovery with probabilistic expert advice
Bubeck, Sébastien; Ernst, Damien ULg; Garivier, Aurélien

in Proceedings of the 51st IEEE Conference on Decision and Control (CDC 2012) (2012, December)

Motivated by issues of security analysis for power systems, we analyze a new problem, called optimal discovery with probabilistic expert advice. We address it with an algorithm based on the optimistic ... [more ▼]

Motivated by issues of security analysis for power systems, we analyze a new problem, called optimal discovery with probabilistic expert advice. We address it with an algorithm based on the optimistic paradigm and the Good-Turingmissing mass estimator. We show that this strategy attains the optimal discovery rate in a macroscopic limit sense, under some assumptions on the probabilistic experts. We also provide numerical experiments suggesting that this optimal behavior may still hold under weaker assumptions. [less ▲]

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See detailOptimal discovery with probabilistic expert advice: finite time analysis and macroscopic optimality
Bubeck, Sébastien; Ernst, Damien ULg; Garivier, Aurélien

in Journal of Machine Learning Research (2013), 14

We consider an original problem that arises from the issue of security analysis of a power system and that we name optimal discovery with probabilistic expert advice. We address it with an algorithm based ... [more ▼]

We consider an original problem that arises from the issue of security analysis of a power system and that we name optimal discovery with probabilistic expert advice. We address it with an algorithm based on the optimistic paradigm and on the Good-Turing missing mass estimator. We prove two different regret bounds on the performance of this algorithm under weak assumptions on the probabilistic experts. Under more restrictive hypotheses, we also prove a macroscopic optimality result, comparing the algorithm both with an oracle strategy and with uniform sampling. Finally, we provide numerical experiments illustrating these theoretical findings. [less ▲]

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See detailThe optimal distance of TGV which operate on the classic railway
Marchal, Jean ULg; Han, B.

in Proceedings of the 1998 International Conference on Traffic and Transportation Studies (ICTTS’98 (1998)

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See detailOPTIMAL ELECTRODES SETTING FOR TRANSCUTANEOUS ELECTRICAL STIMULATION OF THE QUADRICEPS
Vanderthommen, Marc ULg; Troka, Sylvie; Demoulin, Christophe ULg

in Loland, S.; Fasting, K.; Ommundsen, Y. (Eds.) et al Book of Abstracts of 14th annual Congress of the European College of Sport Science (2009, June)

Introduction Treatment or training sessions with neuromuscular electrical stimulations (NMES) are generally performed in a transcutaneous manner with the aid of surface electrodes. Several investigators ... [more ▼]

Introduction Treatment or training sessions with neuromuscular electrical stimulations (NMES) are generally performed in a transcutaneous manner with the aid of surface electrodes. Several investigators have highlighted the benefits of quadriceps stimulation during rehabilitation following traumatic injury or surgery of the knee and during physical preparation of athletes (Kramer and Mendryyk, 1982). However, the practical modalities of quadriceps stimulation (number, size and localization of electrodes) remain controversial (Vanderthommen and Duchateau, 2007). The present work aimed to determine the optimal electrodes setting for NMES applied to the quadriceps. Methods Twenty physically active men (23 ± 2 years, 180 ± 8 cm, 75 ± 12 Kg) underwent first an evaluation of left quadriceps maximal isometric voluntary torque (QMIVT). The exact localization of the motor points of vastus medialis (MPVM) and vastus lateralis (MPVL) was also determined. Then, we tested unilaterally, isometrically and consecutively five electrodes settings (ES) including rectangular (10 x 5 cm) (RE) or square (5 x 5 cm) (SE) electrodes, with identical stimulation parameters (biphasic symmetric rectangular pulses, 80 Hz, pulse duration 0.35 ms, constant current intensity (42 ± 11 mA)): ES1= 1 channel, 2 RE transversally on the thigh (with the distal electrode placed on MPVM and MPVL); ES2= 1 channel, 2 RE longitudinally on MPVM and MPVL; ES3= 1 channel, 2 SE on MPVM and MPVL; ES4= 2 channels, 4 SE (with 2 SE placed on MPVM and MPVL); ES5= 2 channels, channel 1= 1 SE on MPVM and 1 RE transversally on the proximal part of the thigh, channel 2= 1 SE on MPVL and 1 RE transversally on the proximal part of the thigh. For each ES we measured the electrostimulated torque. Results The mean QMIVT reached 200 ± 51 Nm. The MPVM and MPVL were situated 10 ± 2 cm and 14 ± 3 from the patellar base, respectively. The stimulated contractions reached 9.2 ± 7.4 Nm (4.6% of QMIVT) for ES1, 8 ± 4.8 Nm (4% of QMIVT) for ES2, 15 ± 8.3 Nm (7.5% of QMIVT) for ES3, 16.3 ± 7.7 Nm (8.2% of QMIVT) for ES4 and 40.4 ± 11.3 Nm (20.2% of QMIVT) for ES5 (p<0.05). Discussion During NMES programs it appears crucial to use a proper electrode setting ensuring efficient muscle recruitment and therefore optimized training effects. However, physiotherapists and trainers often place electrodes empirically especially for NMES applied to the quadriceps. This study demonstrated the relevance of using two channels for quadriceps NMES and of setting, for each channel, one small “excitative” electrode exactly on the motor point of vastus medialis or lateralis and one bigger “dispersive” electrode transversally on the proximal part of the thigh (in order to close the circuit). References Kramer JF, Mendryyk SW. (1982). Phys Ther, 4, 1657-1667. Vanderthommen M, Duchateau J. (2007). Exerc Sport Sci Rev, 35, 180-185. [less ▲]

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See detailOptimal Enforcement of Competition Policy: The Commitments Procedure under Uncertainty
Gautier, Axel ULg; Petit, Nicolas ULg

E-print/Working paper (2015)

Since the introduction of a commitments procedure in EU antitrust policy (Article 9 of Council Regulation 1/2003), the European Commission has extensively settled cases of alleged anticompetitive ... [more ▼]

Since the introduction of a commitments procedure in EU antitrust policy (Article 9 of Council Regulation 1/2003), the European Commission has extensively settled cases of alleged anticompetitive practices. In this paper, we use a formal model of law enforcement (Bebchuk, 1984; Shavell, 1988) to identify the optimal procedure to resolve cases in a context of uncertainty related to the law (L-uncertainty) and to the facts (F-uncertainty). We show that commitments are suboptimal when L-uncertainty is high. Furthermore, the generalized use of commitments creates an additional risk of under-enforcement when F-uncertainty is significant. [less ▲]

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See detailOptimal Enforcement of Competition Policy: The Commitments Procedure under Uncertainty
Gautier, Axel ULg

Scientific conference (2015, April 09)

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See detailOptimal Enforcement of Competition Policy: The Commitments Procedure under Uncertainty
Gautier, Axel ULg

Scientific conference (2015, January 08)

Detailed reference viewed: 4 (0 ULg)
See detailOptimal Enforcement of Competition Policy: The Commitments Procedure under Uncertainty
Gautier, Axel ULg

Scientific conference (2014, May 22)

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See detailOptimal experimental designs for funtional magnetic resonance imaging
Maus, Bärbel ULg

Doctoral thesis (2011)

Detailed reference viewed: 12 (1 ULg)
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See detailOptimal extraction of multiple overlapping spectra using a maximum entropy algorithm
Khmil, S. V.; Surdej, Jean ULg

in Astronomy and Astrophysics (2002), 387(1), 347-355

A general algorithm of slit spectra extraction for a system of point-like sources (e.g. multiple lensed images of a quasar) has been developed, assuming that the point-spread function (PSF) induced by the ... [more ▼]

A general algorithm of slit spectra extraction for a system of point-like sources (e.g. multiple lensed images of a quasar) has been developed, assuming that the point-spread function (PSF) induced by the measuring instrument and/or atmosphere and the positions of the spectra relative to the CCD frame are unknown. The main idea of the algorithm is to successively apply the maximum entropy method to each set of parameters, such as the spectra, the PSF, and the spectra positions, in order to iteratively improve their values. The algorithm uses all the a priori knowledge about the spectra (e.g. flux positivity, flux ratios between the components, astrometry, etc.) to compute the initial parameter sets. The main features of the algorithm, its implementation, as well as some important aspects of its practical use, are discussed in detail. Two sets of simulated spectroscopic data have been built in order to show the most characteristic properties of the algorithm and to justify its aplication to the spectra extraction of the gravitational lens system Q1009-0252 A [less ▲]

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