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See detailOn-line stability and dynamic security assessment of electric power systems
Ribbens-Pavella, Mania; Van Cutsem, Thierry ULg; Rousseaux, Patricia ULg

in Proceedings of the IFAC Symposium on Planning and Operation of Electric Energy Systems (1985)

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See detailOn-Line Transient Engine Diagnostics in a Kalman Filtering Framework
Borguet, Sébastien ULg; Dewallef, Pierre ULg; Léonard, Olivier ULg

in Proceedings of the ASME Turbo Expo 2005 (2005, June)

A common assumption made in the performance assessment of a turbine engine for aircraft propulsion consists in restricting the data processing to steady-state data. This especially holds for on-board ... [more ▼]

A common assumption made in the performance assessment of a turbine engine for aircraft propulsion consists in restricting the data processing to steady-state data. This especially holds for on-board performance monitoring of a commercial aircraft which spends up to 90% of the time in cruise flight where such conditions are satisfied. The present contribution is intended to investigate the ability of a diagnosis method to process unsteady data rather than steady-state data. The aim of this unsteady approach is to strongly reduce the time and the efforts spent to obtain a reliable diagnosis. In order to assess the improvements in terms of diagnosis efficiency and engine operability, the resulting diagnostic method is tested for different degradations that can be expected on commercial turbofans. The results are also compared to those obtained from cruise flight steady-state data in order to balance the two approaches. [less ▲]

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See detailOn-line transient stability constrained ATC calculations
Avilas-Rosales, R.; Ruiz-Vega, Daniel; Ernst, Damien ULg et al

in Proceedings of the IEEE Power Engineering Society Summer Meeting 2000 - Volume 2 (2000)

Transient Stability Assessment, preventive control measures and dynamic A X calculations are addressed for the new deregulated EMS system. The combination of time domain analysis, SIME and Optimal Power ... [more ▼]

Transient Stability Assessment, preventive control measures and dynamic A X calculations are addressed for the new deregulated EMS system. The combination of time domain analysis, SIME and Optimal Power Flow provide a reliable solution for future transaction requirements and the current operating point. [less ▲]

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See detailOn-Line Validation of Measurements on Jet Engines Using Automatic Learning Methods
Dewallef, Pierre ULg; Léonard, Olivier ULg

in Proceedings od the 15th ISABE Conference (2001)

Nowadays, turbine engine tests are processed using an open loop, i.e. the measurements are verified and treated a posteriori, sometimes weeks or months after the end of the test. The purpose of the ... [more ▼]

Nowadays, turbine engine tests are processed using an open loop, i.e. the measurements are verified and treated a posteriori, sometimes weeks or months after the end of the test. The purpose of the present project is to develop a new methodology which enables real time detection of faulty measurements and the suppression of the source of these faults during the test. The validation of the measurements is achieved by a “robust” parameter identification [1]. Such a method is called robust in the sense that it can cope with 20 to 30% of faulty measurements. The robustness is insured by a distribution of the measurement noise, as introduced by Huber [7, 8], that takes into account the possibility of faults. The purpose of a parameter identification is to find the set of parameters which has most likely generated the measurements observed on the process. This leads to an optimisation problem that has to be solved for the parameters. The measurements are linked to the parameters through a non-linear model, leading to a large system of equations for modern jet engines. If no physical model of the process can be made available or if this model is too complex to allow real time validation, automatic learning methods may provide a solution: • either a mathematical representation is generated, directly based on the measurements (online learning), • or a database is first generated, based on the existing (but expensive) physical model, the database being subsequently used to build a statistical model (off-line learning). Neural networks seem to be very suitable for modeling the behavior of turbojets, avoiding the resolution of a time-consuming non-linear system. In this paper neural networks are tested to generate a mathematical representation of a single flow, single spool and variable geometry nozzle turbojet, from a data base of “measurements” generated by a physical model of the engine. Only the off-line learning approach is considered. [less ▲]

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See detailOn-line voltage security assessment
Vournas, Costas; Van Cutsem, Thierry ULg

in Savulescu, Savu (Ed.) Real-time stability in power systems: Techniques for the early detection of the risk of blackout (2006)

This chapter deals with voltage security assessment and its on-line application. Methods for contingency analysis are briefly reviewed. The associated con-cepts of transfer capability, loadability limit ... [more ▼]

This chapter deals with voltage security assessment and its on-line application. Methods for contingency analysis are briefly reviewed. The associated con-cepts of transfer capability, loadability limit, and secure operation margin are explored in some detail. Methods for preventive security control are outlined. An application of on-line VSA in the control center of a real system is then de-scribed and typical results available to operators are presented. [less ▲]

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See detailOn-Line Voltage Security Assessment of the Hellenic Interconnected System
Vournas, Costas; Manos, George; Kabouris, John et al

(2003, June 26)

This paper describes the on-line Voltage Security Assessment environment developed within the framework of the EU-sponsored OMASES project, as well as its application to the Greek Interconnected Power ... [more ▼]

This paper describes the on-line Voltage Security Assessment environment developed within the framework of the EU-sponsored OMASES project, as well as its application to the Greek Interconnected Power System. The heart of all computations is a fast time-domain method. Security is analyzed with respect to power transfers in critical corridors or power consumption in load areas. Results take on the form of either precontingency secure operation limits, or post-contingency loadability limits, together with various diagnosis tips. Typical results obtained during the test phase of the project are reported. [less ▲]

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See detailOn-site follow up of the characterisitics of controlled backfill, using the Time Domain Reflectometry moisture-measurement method.
Gille, A.; Geerts, G.; Mella, J.-P. et al

Conference (2003, June)

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See detailOn-the-fly domain adaptation of binary classifiers
Pierard, Sébastien ULg; Marcos Alvarez, Alejandro ULg; Lejeune, Antoine ULg et al

in 23rd Belgian-Dutch Conference on Machine Learning (BENELEARN) (2014, June 06)

This work considers the on-the-fly domain adaptation of supervised binary classifiers, learned off-line, in order to adapt them to a target context. The probability density functions associated to ... [more ▼]

This work considers the on-the-fly domain adaptation of supervised binary classifiers, learned off-line, in order to adapt them to a target context. The probability density functions associated to negative and positive classes are supposed to be mixtures of the source distributions. Moreover, the mixture weights and the priors are only available at runtime. We present a theoretical solution to this problem, and demonstrate the effectiveness of the proposed approach on a real computer vision application. Our theoretical solution is applicable to any classifier approximating Bayes' classifier. [less ▲]

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See detailOn-the-go georeferenced measurements of soil mechanical strength and differenciation of soil structure.
Destain, Marie-France ULg; Sirjacobs, Damien ULg; Hanquet, Bernard et al

in Geophysical Research Abstracts (2008)

Soil strength is defined as the resistance which as to be overcome to obtain a given soil deformation. Amongst the numerous methods developed to measure soil strength, two are classically used. On one ... [more ▼]

Soil strength is defined as the resistance which as to be overcome to obtain a given soil deformation. Amongst the numerous methods developed to measure soil strength, two are classically used. On one hand, a laboratory method based on triaxial tests of undisturbed soil samples allows the estimation of cohesion and internal friction angle by the Mohr-Coulomb equation. On the other hand, measuring soil penetration resistance by pushing a cone into a soil is a widely used technique. Both techniques deliver discontinuous field information and are not suited to produce digital soil mapping. The objectives of this paper are to present a sensor able to continuously measure soil strength variations. The sensor was constituted of a thin blade pulled in the soil at a constant depth and speed and a beam which transferred the soil-blade forces to a transducer fixed on a vehicle. The transducer measures the draft force Fx, the vertical force Fz and the moment My thanks to an octagonal ring dynamometer. A measurement chain was developed to acquire simultaneously the signals provides by the soil strength sensor and those of a DGPS. Signal processing was notably based on geostatistics and allows soil mapping [1]. Four fields representative of the soils used in silty areas for arable production in Belgium were selected. The measurements were repeated several times during 1999-2003. Targeted test plots were chosen in each field to perform reference measurements, namely granulometry, cohesion, friction angle, pF, water content, dry bulk density, and cone index. The within-field studies revealed high variability caused by texture, history, traffic, etc., and showed a correlation between the sensor signals and physical parameters, such as cone index and soil moisture, as long as no over-consolidation of the soil occurred [2]. To assess the similarity of soil strength between the fields, the data Fx, Fz and My were classified by using canonical variates (CV). The two first CV represented 95.9 % of the variability, which means that two main variables contain the essential part of the information. In a plane (Fz, Fx), three clusters could be distinguished. The first one (trials 1 and 5), characterized by a low draft and a high Fz, corresponded to trials performed in March on soils ploughed during the winter, naked or covered with small vegetation, and characterized by small values of cone index. The second one (trials 2, 3, 4, 7) with high values of Fx and Fz grouped measurements done just after wheat harvest in August. The third cluster (trials 6) corresponded to measurements performed during wheat growth. It may be concluded that the signals from the sensor treated by suited statistical analysis have the potential to differentiate soil structures at a field scale. REFERENCES [1] Sirjacobs D., Hanquet B., Lebeau F., Destain M.-F. (2002). On-line mechanical resistance mapping and correlation with soil physical properties for precision agriculture. Soil and Tillage Research 64, 231-242. [2] Hanquet B., Sirjacobs D., Destain M.-F., Frankinet M., Verbrugge J.-C. (2004). Analysis of soil variability measured with a soil strength sensor. Precision Agriculture, 5, 227-246. [less ▲]

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See detailOnboard implementation of the GHER model for the Black Sea, with SST and CTD data assimilation
Vandenbulcke, Luc ULg; Capet, Arthur ULg; Beckers, Jean-Marie ULg et al

in Journal of Operational Oceanography (2010), 3(2), 47-54

The first operational implementation of the GHER hydrodynamic model is described. It took place onboard the research vessel Alliance with all computation and sharing of forecasts being realised from the ... [more ▼]

The first operational implementation of the GHER hydrodynamic model is described. It took place onboard the research vessel Alliance with all computation and sharing of forecasts being realised from the vessel in near-real time. The forecasts were realised in the context of the Turkish Straits System 2008 campaign, which aimed at the real-time characterisation of the Marmara Sea and (south-western) Black Sea. The model performed badly at first, mainly because of poor initial conditions. Hence, as the model includes a reduced-rank extended Kalman filter assimilation scheme, after a hindcast where sea surface temperature and temperature and salinity profiles were assimilated, the model yielded realistic forecasts. Furthermore, the time required to run a one-day simulation (about 300 seconds of simulation, or 500 with pre-processing and data transfers included) was very limited and thus operational use of the model is possible. [less ▲]

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See detailonce a day administration of amikacine in neonates: assessment of nephrotoxicity and ototoxicity
Battisti, Oreste ULg; Langhendries, J. P.; Bertrand, J. M. et al

in Developmental Pharmacology and Therapeutics (1993), 20

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See detailOnce daily administration of amikacin. Adaptation to neonatology for infants less than 3 days of postnatal age
Battisti, Oreste ULg

in Médecine et Maladies Infectieuses (1993), 23

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See detailOnce weekly alendronate produces a greater decrease in bone resorption than daily risedronate
Hosking, D.; Adami, S.; Felsenberg, D. et al

in Osteoporosis International (2002), 13(S1), 18

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See detailOnce weekly alendronate produces a greater decrease in bone resorption than daily risedronate
Hosking, D.; Adami, Silvio; Felsenberg, D. et al

in Annals of the Rheumatic Diseases (2002, June), 61(Suppl.1),

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See detailOnce weekly alendronate produces a greater decrease in bone resorption than does daily risedronate
Hosking, D.; Adami, S.; Felsenberg, D. et al

in Journal of Bone and Mineral Research (2002, September), 17(S1), 370

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See detailOnce weekly alendronate produces a greater increase in bone mineral density than daily risedronate
Hosking, D; Adami, S; Felsenberg, D et al

in Calcified Tissue International (2003), 72

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See detailOnce weekly alendronate produces a greater increase in bone mineral density than daily risedronate
Hosking, D.; Adami, S.; Felsenberg, D. et al

in BONE (2003), 32(S7), 207

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See detailOnce-a-day administration of amikacin in neonates: assessment of nephrotoxicity and ototoxicity
Battisti, Oreste ULg; Langhendries, J. P.; Bertrand, J. M. et al

in Developmental Pharmacology and Therapeutics (1992), 20

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See detailOnce-a-day administration of amikacin in neonates: clinical evidence of the validity of a pharmacokinetic according to the gestational age
Battisti, Oreste ULg; Wallemacq P; Langhendries JP

in Early Human Development (1994), 38

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