Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailComparison of ozone-induced effects on lung mechanics and hemodynamics in the rabbit.
Delaunois, Annie ULg; Segura, P.; Montano, L. M. et al

in Toxicology and Applied Pharmacology (1998), 150(1), 58-67

The effects of rabbit exposure to ozone (O3)(0.4 ppm for 4 h) on pulmonary mechanical properties and hemodynamics have been investigated on the isolated perfused lung model. Tracheal pressure, airflow ... [more ▼]

The effects of rabbit exposure to ozone (O3)(0.4 ppm for 4 h) on pulmonary mechanical properties and hemodynamics have been investigated on the isolated perfused lung model. Tracheal pressure, airflow, and tidal volume were measured in order to calculate lung resistance (RL) and dynamic compliance (Cdyn). Using the arterial/venous/double occlusion method, the total pressure gradient (deltaPT) was partitioned into four components (arterial, pre-, postcapillary and venous). Dose-response curves to acetylcholine (ACh), substance P (SP), and histamine were constructed in lungs isolated from rabbits immediately or 48 h after air or O3 exposure O3 induced a significant increase in the baseline value of deltaPt, more markedly 48 h after the exposure. Immediately after the exposure, O3 partly inhibited the ACh-, SP-, and histamine-induced decreases in Cdyn and increases in RL. This inhibitory effect was still in part present 48 h after O3 treatment. In the groups studied immediately after exposure, O3 did not significantly modify the ACh-, SP-, and histamine-induced vasoconstriction. Forty-eight hours after exposure, O3 induced a contractile response to ACh and SP in the arterial segment but decreased the response to histamine. We conclude that O3 can induce direct vascular constriction. Directly, but also 48 h after exposure, O3 can inhibit the ACh-, SP-, and histamine-induced changes in lung mechanical properties. Ozone can also induce some changes in the intensity and in the location of the vascular responses to ACh, SP, and histamine. [less ▲]

Detailed reference viewed: 16 (0 ULg)
Full Text
See detailComparison of parameterization schemes for solving the discrete material optimization problem of composite structures
Duysinx, Pierre ULg; Guillermo Alonso, Maria ULg; Gao, Tong et al

Conference (2013, September)

In the context of weight reduction challenges in aerospace, automotive, and energy engineering problems, composite materials are gaining a revived interested. Because of the problem complexity and the ... [more ▼]

In the context of weight reduction challenges in aerospace, automotive, and energy engineering problems, composite materials are gaining a revived interested. Because of the problem complexity and the large number of design variables, their design of composite structures is greatly facilitated by using optimization techniques. While several formulations have been proposed for composite structure design, Stegmann and Lund [1] have showed that composite optimization can take advantage of the topology optimization approach. The fundamental idea of the Discrete Material Optimization (DMO) approach is 1/ to formulate the composite optimization problem as an optimal material selection problem in which the different laminates and ply orientations are considered as different materials and 2/ to solve the optimization problem using continuous existence variables. To transform the discrete problem into a continuous one, one introduces a suitable parametrization identifying each material by a unique set of design variables while the material properties are expressed as a weighted sum of all candidate materials. Using DMO approach, one can solve within a common approach, different design problems such as laminate distribution problem, stacking sequence optimization... The inherent difficulties of the discrete material selection using topology optimization are 1/ to find efficiency interpolation and penalization schemes of the material properties and 2/ to be able to tailor an efficient solution algorithm to handle very large scale optimization problems. Besides the reference DMO scheme by Lund and his co-authors, other interpolation schemes have been proposed: In this paper, work we are considering and comparing DMO with two other schemes namely the Shape Function with Penalization Parameterization (SFP) by Bruyneel [2] and it recent extension, the Bi-value Coding Parametrization (BCP) by Gao et al. [3]. In particular, the work considers the different schemes in the perspective of solving large-scale industrial applications. The work considers several aspects of the different schemes: • Nature of the different interpolation schemes, • Penalization strategies (power law (SIMP), RAMP, Tsai-Halpin or polynomial), • Number of design variables, the size and complexity of the optimization problem, • Sensitivity to local optima, to the initial design variable, and the development of continuous penalization techniques, • Ability to be extended to various formulations from compliance problems to local restrictions and buckling. As a major drawback, DMO, SFP and BCP approaches increase dramatically the number of design variables. Because of the computational burden to solve the optimization problems, in most of DMO implementations, the considered structural responses are generally limited to compliance-like objective functions. In order to extend the DMO formulation, the work investigates the selection of the most appropriate and efficient optimization algorithms to handle the problems. Different schemes of the sequential convex programming are compared. At first the classic schemes MMA and CONLIN are tested. Then more advanced schemes of the MMA family (Bruyneel et al. [4]) are experimented. The work and the comparisons are carried out on several numerical applications related to the selection of optimal local fibre orientations (with up to 36 candidate material orientations) in membrane and shell aerospace or automotive structures. The various numerical test problems include academic examples and benchmarks inspired by industrial applications. [less ▲]

Detailed reference viewed: 21 (0 ULg)
Full Text
See detailComparison of parameterization schemes for solving the discrete material optimization problem of composite structures
Duysinx, Pierre ULg; Guillermo Alonso, Maria ULg; Tong, Gao et al

in Halftka, Raphael; KIM, Nam Ho (Eds.) Proceeding of the 10th World Congress on Structural And Multidisciplinary Optimization (2013, May 19)

Optimal design of composite structures can be formulated as an optimal selection of material in a list of different laminates. Based on the seminal work by Stegmann and Lund, the optimal problem can be ... [more ▼]

Optimal design of composite structures can be formulated as an optimal selection of material in a list of different laminates. Based on the seminal work by Stegmann and Lund, the optimal problem can be stated as a topology optimization problem with multiple materials. The research work carries out a large investigation of different interpolation and penalization schemes for the optimal material selection problem. Besides the classical Design Material Optimization (DMO) scheme and the recent Shape Function with Penalization (SFP) scheme by Bruyneel, the research introduces a generalization of the SFP approach using a bi-value coding parameterization (BCP) by Gao, Zhang and Duysinx. The paper provides a comparison of the different parameterization approaches. It also proposes alternative penalization schemes and it investigates the effect of the power penalization. Finally, we discuss the solution aspects in the perspective of solving large-scale industrial applications. The conclusions are illustrated by a numerical application for the compliance maximization of an in-plane composite ply. [less ▲]

Detailed reference viewed: 14 (0 ULg)
Peer Reviewed
See detailA comparison of parametric and non-parametric distance functions: with application to European Railways
Coelli, Tim; Perelman, Sergio ULg

in European Journal of Operational Research (1999), (117), 326-339

In this paper we use multi-output distance functions to investigate technical inefficiency in European railways. The principle aim of the paper is to compare the results obtained from the three ... [more ▼]

In this paper we use multi-output distance functions to investigate technical inefficiency in European railways. The principle aim of the paper is to compare the results obtained from the three alternative methods of estimating multioutput distance functions. Namely, the construction of a parametric frontier using linear programming; data envelopment analysis (DEA) and corrected ordinary least squares (COLS). Input-orientated, output-orientated and constant returns to scale (CRS) distance functions are estimated and compared. The results indicate a strong degree of correlation between the input- and output-orientated results for each of the three methods. There are also significant correlations observed between the results obtained using the alternative estimation methods. The strongest correlations being between the parametric linear programming and the COLS methods. Finally, the paper concludes with the suggestion that a combination of the technical efficiency scores, obtained from the three different methods, be used as the preferred set of scores. This idea is borrowed from the time-series forecasting literature. [less ▲]

Detailed reference viewed: 104 (1 ULg)
Full Text
Peer Reviewed
See detailComparison of parametric excitation and excitation of an elastic stay cable
Denoël, Vincent ULg; Degée, Hervé ULg

in Proceedings of the 7th European Conference on Structural Dynamics (2008)

In cable-stayed bridge applications, the vertical vibrations of a bridge deck induce vertical motions of the cable anchors that may cause large amplitudes oscillations of the cables. This vertical motion ... [more ▼]

In cable-stayed bridge applications, the vertical vibrations of a bridge deck induce vertical motions of the cable anchors that may cause large amplitudes oscillations of the cables. This vertical motion is not collinear with the cable chord and can be split into a transverse and an axial component. The latter one is responsible for a parametric excitation. Since this phenomenon leads to serious dynamic instability, whereas the transverse component provides simple resonances only, the transverse anchor motion is often disregarded or considered in a separate analysis. However, because of the cable’s non linear behaviour, the response of the cable under both components cannot simply be added. It is thus important to consider at once this actual “cable excitation”, rather than approaching it by an axial excitation, as often reported in the study of parametric excitations. In this paper, the difference between the two modes of excitation is illustrated with a finite element model. The simplicity of the model allows an efficient parametric study of the vibrations of a cable under both excitations, for various cable inclinations and anchor frequencies. [less ▲]

Detailed reference viewed: 80 (12 ULg)
Full Text
Peer Reviewed
See detailComparison of participants and non-participants to the ORISCAV-LUX population-based study on cardiovascular risk factors in Luxembourg
Alkerwi, A; Sauvageot, N; Couffignal, S et al

in Atherosclerosis. Supplements (2009), 204(2), 624-635

Detailed reference viewed: 17 (2 ULg)
Full Text
Peer Reviewed
See detailComparison of participants and non-participants to the ORISCAV-LUX population-based study on cardiovascular risk factors in Luxembourg.
Alkerwi, Ala'a; Sauvageot, Nicolas; Couffignal, Sophie et al

in BMC Medical Research Methodology (2010), 10

BACKGROUND: Poor response is a major concern in public health surveys. In a population-based ORISCAV-LUX study carried out in Grand-Duchy of Luxembourg to assess the cardiovascular risk factors, the non ... [more ▼]

BACKGROUND: Poor response is a major concern in public health surveys. In a population-based ORISCAV-LUX study carried out in Grand-Duchy of Luxembourg to assess the cardiovascular risk factors, the non-response rate was not negligible. The aims of the present work were: 1) to investigate the representativeness of study sample to the general population, and 2) to compare the known demographic and cardiovascular health-related profiles of participants and non-participants. METHODS: For sample representativeness, the participants were compared to the source population according to stratification criteria (age, sex and district of residence). Based on complementary information from the "medical administrative database", further analysis was carried out to assess whether the health status affected the response rate. Several demographic and morbidity indicators were used in the univariate comparison between participants and non-participants. RESULTS: Among the 4452 potentially eligible subjects contacted for the study, there were finally 1432 (32.2%) participants. Compared to the source population, no differences were found for gender and district distribution. By contrast, the youngest age group was under-represented while adults and elderly were over-represented in the sample, for both genders. Globally, the investigated clinical profile of the non-participants was similar to that of participants. Hospital admission and cardiovascular health-related medical measures were comparable in both groups even after controlling for age. The participation rate was lower in Portuguese residents as compared to Luxembourgish (OR = 0.58, 95% CI: 0.48-0.69). It was also significantly associated with the professional status (P < 0.0001). Subjects from the working class were less receptive to the study than those from other professional categories. CONCLUSION: The 32.2% participation rate obtained in the ORISCAV-LUX survey represents the realistic achievable rate for this type of multiple-stage, nationwide, population-based surveys. It corresponds to the expected rate upon which the sample size was calculated. Given the absence of discriminating health profiles between participants and non-participants, it can be concluded that the response rate does not invalidate the results and allows generalizing the findings for the population. [less ▲]

Detailed reference viewed: 32 (10 ULg)
Peer Reviewed
See detailComparison of patient's voice quality for T1A glottis carcinoma after endoscopic laser surgery or radiotherapy
Poncelet, Mélanie; DEMEZ, Pierre ULg; Moreau, Pierre ULg et al

Conference (2014, July 30)

Detailed reference viewed: 18 (0 ULg)
Full Text
Peer Reviewed
See detailComparison of PCDD/Fs and cPCBs levels in commercial pasteurized cow's milk in Wallonia (Belgium)
Focant, Jean-François ULg; Pirard, C.; Andre, J.-E. et al

in Organohalogen Compounds (2001), 51

Detailed reference viewed: 9 (0 ULg)
Peer Reviewed
See detailComparison of performance, water intake and feeding behaviour of weaned pigs fed either pellets or meal
Laitat, Martine ULg; Vandenheede, Marc ULg; Desiron, Alain et al

in Animal Science (1999), 69

Performance, water intake and feeding behaviour of two groups of 30 (trial 1), 40 (trial 2) or 50 (trial 3) weaned pigs offered either pellets ol meal of the same formulation were compared. Average daily ... [more ▼]

Performance, water intake and feeding behaviour of two groups of 30 (trial 1), 40 (trial 2) or 50 (trial 3) weaned pigs offered either pellets ol meal of the same formulation were compared. Average daily weight gains (ADG) were higher for pigs given pellets rather than meal in trials 2 (413 v. 363 g/day P < 0.001) and 3 (356 v. 324 g/day, P < 0.05). Mean daily water intake (DWI) was higher with meal than with pellets but only during trial 1 (2.31 y. 1.65 l/day, P < 0.01). The occupation time (OT) and the number of animals using the feeder simultaneously (N) were higher when pigs were given meal rather than pellets, whatever the animal density: trial 1: 82.6 v. 69.9% (P = 0.05) and 3.8 v. 2.3 (P < 0.01); trial 2: 90.9 v. 77.9% (P > 0.05) and 5.2 v. 3.1 (P < 0.01); trial 3: 96.2 v. 83.6% (P < 0.05) and 5.9 v. 3.8 (P < 0.01). When using pellets, OT and N were always significantly lower during the night than during the day but when using meal in groups of 40 and 50, OT during the night was almost as high as during the day. The greater the group size, the lower were ADG (both diets) and DWI (only with meal) and the higher were OT and N (both diets). Furthermore, significant linens and curvilinear regressions of DWI, OT and N according to time were calculated. In conclusion, pigs need more time to eat meal than to eat pellets. Thus the number of pigs per feeder has to be adapted to the food presentation. Too high number of pigs per feeder impairs feeding behaviour and eventually welfare, by preventing preferential diurnal feeding activity and this may affect productivity [less ▲]

Detailed reference viewed: 69 (0 ULg)
Full Text
See detailComparison of phenotypic and genotypic tropism determination in triple-class-experienced HIV patients eligible for maraviroc treatment.
Vandekerckhove, Linos; Verhofstede, Chris; Demecheleer, Els et al

in Journal of Antimicrobial Chemotherapy (2011), 66(2), 265-72

BACKGROUND: Determination of HIV-1 tropism is a pre-requisite to the use of CCR5 antagonists. This study evaluated the potential of population genotypic tropism tests (GTTs) in clinical practice, and the ... [more ▼]

BACKGROUND: Determination of HIV-1 tropism is a pre-requisite to the use of CCR5 antagonists. This study evaluated the potential of population genotypic tropism tests (GTTs) in clinical practice, and the correlation with phenotypic tropism tests (PTTs) in patients accessing routine HIV care. METHODS: Forty-nine consecutive plasma samples for which an original Trofile(TM) assay was performed were obtained from triple-class-experienced patients in need of a therapy change. Viral tropism was defined as the consensus of three or more tropism calls obtained from the combination of two independent population PTT assays (Trofile Biosciences, San Francisco, CA, USA, and Virco, Beerse, Belgium), population GTTs and GTTs based on ultra-deep sequencing. If no consensus was reached, a clonal PTT was performed in order to finalize the tropism call. This two-step approach allowed the definition of a reference tropism call. RESULTS: According to the reference tropism result, 35/49 samples were CCR5 tropic (R5) (patients eligible for maraviroc treatment) and 14/49 were assigned as non-R5 tropic. The non-R5 samples [patients not eligible for maraviroc treatment according to the FDA/European Medicines Agency (EMEA) label] group included both the CXCR4 (X4) samples and the dual and mixed CCR5/CXCR4 (R5/X4) samples. Compared with Trofile(TM) population PTTs, population GTTs showed a higher sensitivity (97%) and a higher negative predictive value (91%), but almost equal specificity and an equal positive predictive value. CONCLUSIONS: In line with recent reports from clinical trial data, our data support the use of population genotypic tropism testing as a tool for tropism determination before the start of maraviroc. [less ▲]

Detailed reference viewed: 37 (6 ULg)
Full Text
Peer Reviewed
See detailComparison of photon with electron boost in treatment of early stage breast cancer
Kovacs, A.; Hadjiev Janaki; LAKOSI, Ferenc ULg et al

in Pathology Oncology Research (2008), 14(2), 193-7

In the treatment of early stage breast cancer breast conserving surgery (BCS) followed by whole breast irradiation (WBI) is a standard method. The impact of the tumor bed boost following WBI is well ... [more ▼]

In the treatment of early stage breast cancer breast conserving surgery (BCS) followed by whole breast irradiation (WBI) is a standard method. The impact of the tumor bed boost following WBI is well-defined, but there are various delivery methods. In this study the electron and the photon boost techniques were compared. For 78 early stage breast cancer patients both CT based 3D conformal photon boost and electron boost plans were created. For dosimetric comparison coverage index (CI), external volume index (EI) and conformality index (COIN) were studied. Lung volume receiving a dose of 2 Gy was also reviewed. Seventy-eight patients with 156 plans were compared. The mean tumor bed volume was measured as 61.39 cm3 the mean tumor bed-skin distance was 3.13 cm. In the case of CI and COIN significant differences were found in favor of the photon boost. In the comparison of EI no significant difference was detected between the two techniques. The mean lung volume receiving 2 Gy were 42.3 and 168.35 cm3, for photons and electrons respectively. In the adjuvant treatment of early stage breast cancer WBI followed by conformal photon boost showed to be superior to electron boost in focus of the COIN and CI. [less ▲]

Detailed reference viewed: 4 (0 ULg)
Full Text
Peer Reviewed
See detailA comparison of physical activation of carbon xerogels with carbon dioxide with chemical activation using hydroxides
Contreras, María S; Páez, Carlos A; Zubizarreta, Leire et al

in Carbon (2010), 48(11), 3157-3168

Carbon xerogels synthesized with a fixed resorcinol/sodium carbonate molar ratio (R/C) were physically activated using CO2. The effect of activation temperature and activation time on the final properties ... [more ▼]

Carbon xerogels synthesized with a fixed resorcinol/sodium carbonate molar ratio (R/C) were physically activated using CO2. The effect of activation temperature and activation time on the final properties of the activated carbon xerogels was evaluated. The specific surface area increases from ~600 m2 g-1 to 2000 m2 g-1 and more by increasing the temperature and duration of the activation step. A comparison between physical activation with CO2 and chemical activation with hydroxides was also performed: it was found that both processes produce an increase of the micropore volume and specific surface area without altering the meso-macroporosity developed during the synthesis. However, chemical activation can lead to the development of the narrow microporosity mainly whereas, in physical activation, the widening of the narrow micropores takes place whatever the process conditions. [less ▲]

Detailed reference viewed: 75 (15 ULg)
Full Text
Peer Reviewed
See detailComparison of physical education teaching events' perception by beginning and experienced teachers
Cloes, Marc ULg; Vandersmissen, Axel; Piéron, Maurice

in Carreiro da Costa, F.; Diniz, J.; Carvalho, L. (Eds.) et al Proceedings of the AIESEP International Seminar "Research on Teaching. Research on Teacher Education" (2000)

Detailed reference viewed: 23 (2 ULg)
Full Text
See detailCOMPARISON OF PIEZOELECTRIC AND CRUSHER MEASUREMENTS OF CHAMBER PRESSURE WITH FINITE ELEMENT MODELING RESULTS
Coghe, Frédéric; Elkarous, Lamine ULg

in International Symposium on Ballistics (2013, April 23)

Detailed reference viewed: 46 (22 ULg)
Full Text
Peer Reviewed
See detailA comparison of piston, screw and scroll expanders for small scale Rankine cycle systems
Lemort, Vincent ULg; Guillaume, Ludovic ULg; Legros, Arnaud ULg et al

in Proceedings of the 3rd International Conference on Microgeneration and Related Technologies (2013, April)

This paper aims at helping the designer of micro-scale Rankine Cycle heat engines to best select the expander among piston, screw and scroll machines. The first part of the paper presents a state of the ... [more ▼]

This paper aims at helping the designer of micro-scale Rankine Cycle heat engines to best select the expander among piston, screw and scroll machines. The first part of the paper presents a state of the art of these three technologies of positive displacement machines. The technical constraints inherent to each machine (rotational speed, pressure ratios, maximum temperatures, volumetric expansion ratios, etc.) are listed and the performance mentioned in the open technical and scientific literature is presented. The second part of the paper deals with the modeling of such expanders. Different simulation models are proposed: black-box, grey-box and white-box models. These three categories of modeling are specifically adapted to different purposes: design of the expander, design of the micro-CHP system, and dynamic simulation/control of the CHP unit. The last part of the paper presents a graphical methodology of selection of expansion machines and working fluids based on operating maps. It is stressed that the selections of both the expansion machine and working fluid should be conducted simultaneously. [less ▲]

Detailed reference viewed: 288 (14 ULg)
Full Text
Peer Reviewed
See detailComparison of plant defense elicitor properties of amphiphilic compounds from plant-associated bacteria
Mariutto, M.; Fernandez, O.; Thonart, Philippe ULg et al

in Bulletin OILB/SROP = IOBC/WPRS Bulletin (2013), 89

Detailed reference viewed: 36 (9 ULg)
Full Text
Peer Reviewed
See detailComparison of plasma cardiac troponins T and I in chronically hemodialyzed patients in relation to cardiac status and age
Chapelle, Jean-Paul ULg; Dubois, Bernard ULg; Bovy, Christophe ULg et al

in Clinical Chemistry & Laboratory Medicine (2002), 40(3), 240-245

Detailed reference viewed: 8 (0 ULg)
Peer Reviewed
See detailComparison of plyometric training combined with electrical stimulation versus plyometric training alone on vertical jump and sprint performance
Lehance, Cédric ULg; Vanderthommen, Marc ULg; Croisier, Jean-Louis ULg et al

in Abstract Book of the 4th International Conference on Strength Training (Serres, Greece) (2004, November)

Detailed reference viewed: 43 (3 ULg)