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See detailComparison of contrast enhanced three dimensional echocardiography with MIBI gated SPECT for the evaluation of left ventricular function
Cosyns, Bernard; Haberman, David; Droogmans, Steven et al

in Cardiovascular Ultrasound (2009), 7

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See detaila comparison of control strategies applied to an existing ice-storage system
Lemort, Vincent ULg

(2005, April)

While ice storage systems are designed according to a defined strategy for warm day loads, it is interesting to consider other conventional control strategies for mid-season day loads. These different ... [more ▼]

While ice storage systems are designed according to a defined strategy for warm day loads, it is interesting to consider other conventional control strategies for mid-season day loads. These different control strategies, applied to an existing cooling plant, are compared in terms of operating costs and energy consumption. A simplified cooling plant model is built. The chillers, cooling towers, and the ice storage system are modeled as different systems connected together. A time stage equal to 15 minutes is considered to simulate the different control strategies. Existing technical constraints and set points are met. The operating costs of the cooling plant are evaluated by taking into account both the energy and the demand cost rate. In off-design conditions, savings of operating costs are made only if the storage tanks are fully discharged after being fully charged. In this case, ice storage systems reduce the operating costs of the cooling plant by shifting a significant fraction of on-peak energy consumption to off-peak periods and by reducing the on-peak demand. But at the same time, the introduction of an ice storage system in a cooling plant causes the electrical energy consumption to rise because the thermal efficiency of the chillers is reduced when working in ice formation mode. [less ▲]

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See detailComparison of control strategies for waste heat recovery Organic Rankine Cycle systems
Lemort, Vincent ULg; Zoughaib, Assaad; Quoilin, Sylvain ULg

(2011, October)

This paper investigates the control of waste heat recovery Organic Rankine Cycle systems. A dynamic simulation model of the system was developed under Modelica language. This model associates the sub ... [more ▼]

This paper investigates the control of waste heat recovery Organic Rankine Cycle systems. A dynamic simulation model of the system was developed under Modelica language. This model associates the sub-models of the different components of the system: the evaporator, a scroll expander, the condenser, the liquid receiver and the pump. Both the speeds of the expander and of the pump are controlled in order to adjust the evaporating pressure and maintain the superheat at the outlet of the evaporator. Two types of controllers were implemented: Proportional Integral (PI) and Model Predictive Control (MPC) controllers. The PI controller on the expander speed is able to adjust the evaporating pressure with a high accuracy. It is also shown that the MPC controller on the pump speed maintains the superheat close to the set point value with a much better performance than the PI controller. Hence, the use of a MPC controller allows decreasing the set point value on the superheat without any risk of feeding the expansion machine with liquid droplets. [less ▲]

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See detailComparison of copy-methods of computer-generated holograms in dichromated gelatin
Habraken, Serge ULg; Roose, Stéphane ULg

in Proceedings of HOLO 3 (1991, November 20)

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See detailComparison of corticosterone, cortisol, triglycerides, aspartateaminotransferase and uric acid plasma concentrations during a foie gras production period in male mule ducks (Anas platyrhynchos X Cairina moschata)
Flament, Aline; Delleur, Valéry ULg; Poulipoulis, Anastassios ULg et al

in British Poultry Science (2012), 53(4), 408-414

1 Corticosterone, cortisol, triglycerides, aspartate aminotransferase (AST) and uric acid (UA) plasma concentration were measured at 8 and 12 weeks of age, at slaughtering and 45 min after an ... [more ▼]

1 Corticosterone, cortisol, triglycerides, aspartate aminotransferase (AST) and uric acid (UA) plasma concentration were measured at 8 and 12 weeks of age, at slaughtering and 45 min after an adrenocorticotrophic hormone (ACTH) stimulation test (8 weeks of age) in twelve male mule ducks. 2 No significant increase of corticosterone was found during the force feeding period. 3 Comparison of corticosterone and cortisol levels indicates that cortisol can be considered as a reliable acute stress indicator in future routine examinations. 4 Triglycerides and AST plasma concentrations progressively increased from pre-force feeding period to slaughtering. 5 UA plasma concentrations also increased from the start at 8 weeks of age to mid-force feeding time but no difference was noticed between mid-force feeding period and slaughtering. [less ▲]

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See detailComparison of cross-field pitting in fresh, dried and charcoalified softwoods
Gerards, Thomas ULg; Damblon, Freddy ULg; Wauthoz, B. et al

in Iawa Journal (2007), 28(1), 49-60

Cross-field pitting is one of the most reliable characters for softwood identifi cation. During charcoalification, a range of severe qualitative and quantitative modifications may occur in cross-field ... [more ▼]

Cross-field pitting is one of the most reliable characters for softwood identifi cation. During charcoalification, a range of severe qualitative and quantitative modifications may occur in cross-field pitting. As most fossil or archaeological wood remains are preserved as charcoal (fusain), the question arises whether these modifications hamper the accurate identification of some taxa. This work is a systematic biometric study of a wide range of gymnosperm cross-field pitting after experimental charcoalification. We focused on the window-like, piceoid, taxodioid, cupressoid, araucarioid and podocarpoid cross-field pitting types. Our main results are the following: 1) Cross-field pits of wood specimens dried out before charcoalification are hidden by a thin closing wall; in this case, it is often impossible to discriminate between the various types of cross-field pitting. 2) Piceoid cross-field pitting becomes taxodioid-like after charcoalification. 3) Biometric study of charred softwood cross-field pitting dimensions shows that the ratios between height and width of pit aperture and border allow us to distinguish and characterise four types of pitting (window-like, piceoid, taxodioid, cupressoid + araucarioid + podocarpoid [= CAP]). The discrimination within the CAP type requires further investigation. [less ▲]

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See detailComparison of damage models in the virtual testing of composites
Bruyneel, Michaël ULg; Delsemme, Jean-Pierre; Jetteur, Philippe

in proceedings of the SAMPE Technical Conference 2013 (2013, October)

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See detailComparison of Data Transfer Methods between Meshes in the Frame of the Arbitrary Lagrangian Eulerien Formalism
Bussetta, Philippe ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Proceedings of "Fifth International Conference on Advanced COmputationalMethods in ENgineering" (2011, November)

In nonlinear solid Mechanics, the Arbitrary Lagrangian Eulerian (ALE) formalism is a common way to avoid mesh distortion when very large deformations occur in the modelled process. Usually, the ALE ... [more ▼]

In nonlinear solid Mechanics, the Arbitrary Lagrangian Eulerian (ALE) formalism is a common way to avoid mesh distortion when very large deformations occur in the modelled process. Usually, the ALE resolution procedure is based on an “operator split”, the second part of which is a Data Transfer between two meshes sharing the same topology (same number of nodes and same number of element neighbours for each of them). Thanks to this interesting property, classical ALE transfer algorithms can bemuchmore optimised in terms of CPU time than the ones that are used in the frame of a complete remeshing. However, the resulting CPU-efficient transfer schemes suffer from two main drawbacks. The first one is a spurious crosswind diffusion coming from the corner fluxes that have been neglected. The second issue is the number of explicit transfer steps which may become very large when the element size decreases. In this paper, these classical ALE Data Transfer methods are compared to more general algorithms which do not make any assumption on the topology of both meshes. [less ▲]

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See detailComparison of Data Transfer Methods between two different meshes
Bussetta, Philippe ULg; Ponthot, Jean-Philippe ULg

in Proceedings of "IV International Conference on Computational Methods for Coupled Problems in Science and Engineering" (2011, June)

Many problems solved with the finite element method require more than one mesh (i.e. one specific mesh for each Physic or a remeshing is needed). The Data Transfer Method used, has a great importance in ... [more ▼]

Many problems solved with the finite element method require more than one mesh (i.e. one specific mesh for each Physic or a remeshing is needed). The Data Transfer Method used, has a great importance in the capacity to solve the problem and in the reliability of the solution. In general, the data is composed of two kinds of fields (defined thanks to the nodal values or at the integration points). In this paper, the more used Data Transfer Method is compared with the Data Transfer Methods based on a Weak Form (using Mortar Element or Finite Volume). [less ▲]

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See detailA Comparison of Departure Time of Day Formulations
Lurkin, Virginie ULg; Garrow, Laurie; Higgins, Matthew et al

E-print/Working paper (2016)

Airline passengers’ itinerary choices are influenced by many factors including carriers, prices, the number of connections, and departure times. This paper compares three different methods that have been ... [more ▼]

Airline passengers’ itinerary choices are influenced by many factors including carriers, prices, the number of connections, and departure times. This paper compares three different methods that have been used to model departure time of day preferences. The first is a discrete formulation that uses indicator variables to represent the hour of departure. The next two methods are based on a continuous formulation that uses a series of sine and cosine functions. One assumes departure time preferences over a 24-hour cycle and the other uses shorter cycle lengths that account for fewer departures during certain hours of the day. We compare models using itineraries in the Continental U.S. that are separated by two time zones. Although the discrete formulation fits the data better, the two continuous time of day formulations are preferred as they provide more intuitive predictions and require fewer parameters. Results between the two continuous time of day formulations are similar but differ in how strongly they weight itineraries that depart very early or very late in the day. Based on empirical results, we recommend testing both 24-hour and less than 24-hour cycle lengths for a particular dataset. [less ▲]

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See detailComparison of deposition images obtained by use of an ultrafine 99m-technetium-labeled carbon dry aerosol with ventilation images obtained by use of 81m-krypton gas for evaluation of pulmonary dysfunction in calves.
Votion, Dominique ULg; Coghe, J. D.; Lekeux, Pierre ULg

in American Journal of Veterinary Research (2001), 62(12), 1881-6

OBJECTIVE: To characterize the accuracy of an ultrafine 99m-technetium-labeled carbon dry aerosol for use in assessment of regional ventilation in calves with pulmonary dysfunction. ANIMALS: 7 Belgian ... [more ▼]

OBJECTIVE: To characterize the accuracy of an ultrafine 99m-technetium-labeled carbon dry aerosol for use in assessment of regional ventilation in calves with pulmonary dysfunction. ANIMALS: 7 Belgian White and Blue calves. PROCEDURE: The ultrafine aerosol was assessed by comparing deposition (D) images with ventilation (V) images obtained by use of 81 m-krypton (81mKr) gas via D-to-V ratio (D:V) image analysis in calves during spontaneous breathing (SB) and during experimentally induced pulmonary dysfunction (ePD). RESULTS: Mismatching index (LrTot) calculated on the D:V images revealed a good match (LrTot, 0.96 +/- 0.01) between D and V distribution patterns in calves during SB. Calculation of the ultrafine aerosol penetration index relative to 81mKr (PIRel) revealed preferential distribution of the ultrafine aerosol in lung parenchyma (PIRel, 1.13 +/- 0.11). In ePD, heterogeneity in the D:V distribution was observed (LrTot, 0.78 +/- 0.10) as a result of ultrafine aerosol particles impaction in airways as indicated by PIRel (0.66 +/- 0.16) and a proportion of pixels more radioactive in D images, compared with V images, that was located in the central part of the lung (475 +/- 77% in ePD vs 32.8 +/- 5.7% in SB). However, this central deposition did not prevent visual examination of the entire ventilated lung. CONCLUSIONS AND CLINICAL RELEVANCE: The ultrafine aerosol appears suitable for use in examination of ventilated parts of lungs of cattle, even those with impaired pulmonary function. However, airway impaction of ultrafine aerosol particles impedes the quantification of regional ventilation in cattle with abnormal lung function. [less ▲]

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See detailComparison of Destructive Methods to Appraise the Mechanical Integrity of a Concrete Surface
Courard, Luc ULg; Bissonnette, Benoît; Vaysburd, Alex et al

in Concrete Repair Bulletin (2012), 25(4), 22-30

Depending on the technique being used, the concrete removal operation prior to repair can be harmful to the residual concrete skin left on the structure. Whenever a tight bond between the repair and the ... [more ▼]

Depending on the technique being used, the concrete removal operation prior to repair can be harmful to the residual concrete skin left on the structure. Whenever a tight bond between the repair and the old concrete is required, the soundness of the prepared surface should thus be assessed. Although this is widely recognized, there is no standard method intended to characterize the integrity of a concrete substrate after concrete removal. This paper presents the results of an investigation intended to assess and compare quantitatively different test methods, namely the Schmidt rebound hammer, the pull-out test and the pull-off test, to evaluate superficial mechanical integrity of a substrate after concrete removal operations. Although it does not yield a precise evaluation of compressive strength, the Schmidt rebound hammer test is recognized as a useful tool for performing quick surveys to assess concrete uniformity. The pull-off test is very well correlated with the splitting-tensile test, but it is not suited for vertical and overhead surfaces. The Capo pull-out test has limited interest for surface preparation, as it is applicable to flat surfaces only. Conversely, the accelerated pull-out test showed interesting potential as a simple and relatively rapid means for assessing the mechanical integrity of a concrete surface prior to repair for any type of concrete surface. More work is definitely required to refine the procedures and develop performance criteria. Nevertheless, it appears from the results generated in this study that the combination Schmidt hammer / pull-off test could fill the needs for the evaluation of horizontal surfaces after concrete removal, while the combination Schmidt hammer / accelerated pull-out test could be used effectively on vertical and overhead surfaces. [less ▲]

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See detailCOMPARISON OF DIABETES CONTROL ONE YEAR AFTER GASTRIC BYPASS AND MAGENSTRASSE AND MILL PROCEDURES
SCHLECK, Michael ULg; KOHNEN, Laurent ULg; DE FLINES, Jenny ULg et al

Poster (2015, May)

Bariatric surgery has become a main therapy of type 2 diabetes in the obese population. The best surgical procedure to achieve diabetes control remains debated. Gastric bypass would be the preferred ... [more ▼]

Bariatric surgery has become a main therapy of type 2 diabetes in the obese population. The best surgical procedure to achieve diabetes control remains debated. Gastric bypass would be the preferred option according to its incretin stimulating potential. We compared in this study gastric bypass surgery to a pure restrictive procedure in terms of diabetes control at 1 year. [less ▲]

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See detailA comparison of diagnosis of pregnancy in the goat via transrectal ultrasound scanning, progesterone, and pregnancy-associated glycoprotein assays
Gonzalez, Fernando; Cabrera, F.; Batista, M. et al

in Theriogenology (2004), 62(6), 1108-1115

Real-time ultrasound scanning (US) via the transrectal route, progesterone (P4) assay, and pregnancy-associated glycoprotein (PAG) detection can be used to diagnose pregnancy at around 3 weeks after ... [more ▼]

Real-time ultrasound scanning (US) via the transrectal route, progesterone (P4) assay, and pregnancy-associated glycoprotein (PAG) detection can be used to diagnose pregnancy at around 3 weeks after breeding. Although several studies have been carried out to evaluate each of these different methods individually, it is difficult to establish adequate comparisons due to differences, such as the breed of goat, age, and farming conditions, among others. The aim of the present paper is to compare the accuracy of diagnosis of pregnancy using transrectal US, P4 assay and PAG detection at the same time and on the same animals. Canary dairy goats (n = 143) were synchronized with an 11-day fluorogestone acetate (FGA) intravaginal sponge followed by PGF(2 alpha), and eCG 2 days before the FGA withdrawal. Blood samples were collected on Days 20, 22, 24, and 26 after mating to determine P4 and PAG concentrations. Transrectal US examinations were performed at the same time. There were 79 pregnant goats and another 64 non-pregnant. The US via the transrectal method and the determination of PAG concentrations provide very accurate pregnancy diagnosis at 24-26 days after breeding; on the contrary, P4 assay on plasma samples performed on Day 22 after breeding was accurate, in this case, in detecting pregnant animals but did not always detect the non-pregnant does. [less ▲]

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See detailComparison of different approaches to evaluate External Quality Assessment Data.
Coucke, Wim; China, Bernard; Delattre, Isabelle et al

in Clinica Chimica Acta (2012), 413(5-6), 582-6

In EQA programs, Z-scores are used to evaluate laboratory performance. They should indicate poorly performing laboratories, regardless of the presence of outliers. For this, two different types of ... [more ▼]

In EQA programs, Z-scores are used to evaluate laboratory performance. They should indicate poorly performing laboratories, regardless of the presence of outliers. For this, two different types of approaches exist. The first type are "outlier-based" approaches, which first exclude outlying values, calculate the average and standard deviation on the remaining data and obtain Z-scores for all values (e.g., Grubbs and Dixon). The second type includes the "robust" approaches (e.g., Tukey and Qn or the algorithm recommended by ISO). The different approaches were assessed by randomly generated samples from the Normal and Student t distributions. Part of the sample data were contaminated with outliers. The number of false and true outliers was recorded and subsequently, Positive and Negative Predictive Values were derived. Also, the sampling mean and variability were calculated for location and scale estimators. The various approaches performed similarly for sample sizes above 10 and when outliers were at good distance from the centre. For smaller sample sizes and closer outliers, however, the approaches performed quite differently. Tukey's method was characterised by a high true and a high false outlier rate, while the ISO and Qn approaches demonstrated weak performance. Grubbs test yielded overall the best results. [less ▲]

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See detailComparison of different assimilation schemes in an operational assimilation system with Ensemble Kalman Filter
Yan, Yajing; Barth, Alexander ULg; Beckers, Jean-Marie ULg et al

Poster (2016)

In this paper, four assimilation schemes, including an intermittent assimilation scheme (INT) and three incremental assimilation schemes (IAU 0, IAU 50 and IAU 100), are compared in the same assimilation ... [more ▼]

In this paper, four assimilation schemes, including an intermittent assimilation scheme (INT) and three incremental assimilation schemes (IAU 0, IAU 50 and IAU 100), are compared in the same assimilation experiments with a realistic eddy permitting primitive equation model of the North Atlantic Ocean using the Ensemble Kalman Filter. The three IAU schemes differ from each other in the position of the increment update window that has the same size as the assimilation window. 0, 50 and 100 correspond to the degree of superposition of the increment update window on the current assimilation window. Sea surface height, sea surface temperature, and temperature profiles at depth collected between January and December 2005 are assimilated. Sixty ensemble members are generated by adding realistic noise to the forcing parameters related to the temperature. The ensemble is diagnosed and validated by comparison between the ensemble spread and the model/observation difference, as well as by rank histogram before the assimilation experiments The relevance of each assimilation scheme is evaluated through analyses on thermohaline variables and the current velocities. The results of the assimilation are assessed according to both deterministic and probabilistic metrics with independent/semi-independent observations. For deterministic validation, the ensemble means, together with the ensemble spreads are compared to the observations, in order to diagnose the ensemble distribution properties in a deterministic way. For probabilistic validation, the continuous ranked probability score (CRPS) is used to evaluate the ensemble forecast system according to reliability and resolution. The reliability is further decomposed into bias and dispersion by the reduced centered random variable (RCRV) score in order to investigate the reliability properties of the ensemble forecast system. [less ▲]

Detailed reference viewed: 13 (1 ULg)