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See detailEstimation of rubber sliding friction from asperity interaction modeling
Bui, Q. V.; Ponthot, Jean-Philippe ULg

in Wear (2002), 252(1-2), 150-160

Interaction between a soft rubber asperity and its hard counterpart is traced with the help of a finite element computation. The analysis is aimed to estimate the influence of adhesion between rubber and ... [more ▼]

Interaction between a soft rubber asperity and its hard counterpart is traced with the help of a finite element computation. The analysis is aimed to estimate the influence of adhesion between rubber and rigid surfaces and the energy losses arising from the deformation of rubber bulk to the sliding resistance. At the contact zone, interfacial bonds are formed due to adhesion and their resistance to sliding is represented by the shear strength of the contact interface. In the rubber bulk, the hysteresis loss is calculated using an appropriate model of the viscoelastic mechanical behavior of rubber for large strains. Dependence of friction on sliding speeds and temperature is hence detected. Influence of surface roughness and contact pressure on friction is also examined. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailEstimation of sediment storage in Ardenne's floodplains (Belgium) during the last centuries
Houbrechts, Geoffrey ULg; Mols, Julien; Petit, François ULg

Conference (2007)

Estimation of the sediment storage in floodplains is the focus of several researchers. One of the main difficulties is to date alluvial deposits which do not contain organic matters or which are more ... [more ▼]

Estimation of the sediment storage in floodplains is the focus of several researchers. One of the main difficulties is to date alluvial deposits which do not contain organic matters or which are more recent than 200 BP. Consequently, we developed a relative dating method, based on the presence of iron slag. These residues have been produced since the end of the 14th century by the former metal works located near rivers of the Ardenne region. In order to use slag as a stratigraphical tracer, we dated the periods of furnace activity from historical studies and we analysed vertical slag concentration in alluvial silty deposits. These data allowed us to reconstruct the topography of several floodplains at the inception of the metal works, to evaluate sedimentation rates and to estimate lateral channel mobility. Given important deforestations due to the production of charcoal for the iron metallurgy, we observed an increase of the sedimentation rates during the last centuries. [less ▲]

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See detailEstimation of shortening rate since late Pleistocene in the Aksu area on the southern flank of the Tianshan
Wang, X.; Jia, C. Z.; Hubert, Aurelia ULg et al

in Science in China. Series D : Earth Sciences (2001), 44

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See detailEstimation of surface soil organic matter by means of hyperspectral data analysis.
Touré, Souleymane; Tychon, Bernard ULg

Conference (2003, September 04)

This presentation shows results from two different hyperspectral instruments for the assessment of soil organic content of agricultural soils in southern Belgium.

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See detailEstimation of surface soil organic matter by means of hyperspectral data analysis.
Touré, Souleymane; Tychon, Bernard ULg

Conference (2003, November 19)

Data acquired from field campaign and hyperspectral airborne sensors were processed to determine the surface soil organic matter of an agricultural area located in Southern Belgium. The method adopted was ... [more ▼]

Data acquired from field campaign and hyperspectral airborne sensors were processed to determine the surface soil organic matter of an agricultural area located in Southern Belgium. The method adopted was based on a forward stepwise multiple regression analysis linking soil organic matter and hyperspectral data from two airborne sensors working in the visible and infrared domain. The results were validated successfully from an independent set of sampling points. It is concluded that the hyperspectral remote sensing approach is promising for soil organic matter prediction. Furthermore, this approach could even be improved if disturbance factors are removed. [less ▲]

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See detailEstimation of temporal lags for the inference of gene regulatory networks from time series (inproceedings) Author
Lopes, Miguel; Meyer, Patrick ULg; Bontempi, Gianluca

in In proceedings of BENELEARN'12 (2012)

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See detailEstimation of test-day model (co)variance components across breeds using New Zealand dairy cattle data
Vanderick, Sylvie ULg; Harris, Bevin; Pryce, Jenny et al

in Journal of Dairy Science (2009), 92(3), 1240-1252

In New Zealand, a large proportion of cows are currently crossbreds, mostly Holstein-Friesians (HF) x Jersey (JE). The genetic evaluation system for milk yields is considering the same additive genetic ... [more ▼]

In New Zealand, a large proportion of cows are currently crossbreds, mostly Holstein-Friesians (HF) x Jersey (JE). The genetic evaluation system for milk yields is considering the same additive genetic effects for all breeds. The objective was to model different additive effects according to parental breeds to obtain first estimates of correlations among breed-specific effects and to study the usefulness of this type of random regression test-day model. Estimates of (co) variance components for purebred HF and JE cattle in purebred herds were computed by using a single-breed model. This analysis showed differences between the 2 breeds, with a greater variability in the HF breed. (Co) variance components for purebred HF and JE and crossbred HF x JE cattle were then estimated by using a complete multibreed model in which computations of complete across-breed (co)variances were simplified by correlating only eigenvectors for HF and JE random regressions of the same order as obtained from the single-breed analysis. Parameter estimates differed more strongly than expected between the single-breed and multibreed analyses, especially for JE. This could be due to differences between animals and management in purebred and nonpurebred herds. In addition, the model used only partially accounted for heterosis. The multibreed analysis showed additive genetic differences between the HF and JE breeds, expressed as genetic correlations of additive effects in both breeds, especially in linear and quadratic Legendre polynomials (respectively, 0.807 and 0.604). The differences were small for overall milk production (0.926). Results showed that permanent environmental lactation curves were highly correlated across breeds; however, intraherd lactation curves were also affected by the breed-environment interaction. This result may indicate the existence of breed-specific competition effects that vary through the different lactation stages. In conclusion, a multibreed model similar to the one presented could optimally use the environmental and genetic parameters and provide breed-dependent additive breeding values. This model could also be a useful tool to evaluate crossbred dairy cattle populations like those in New Zealand. However, a routine evaluation would still require the development of an improved methodology. It would also be computationally very challenging because of the simultaneous presence of a large number of breeds. [less ▲]

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See detailEstimation of the 1900-2100 Greenland ice sheet surface mass balance
Fettweis, Xavier ULg

Conference (2008, April 15)

Results from a 37-year simulation (1970-2006) over the Greenland ice sheet (GrIS) with the regional climate model MAR reveals that more than 97% of the interannual variability of the modelled Surface Mass ... [more ▼]

Results from a 37-year simulation (1970-2006) over the Greenland ice sheet (GrIS) with the regional climate model MAR reveals that more than 97% of the interannual variability of the modelled Surface Mass Balance (SMB) is explained by the GrIS summer temperature anomaly and the GrIS annual precipitation anomaly. This dependence is also fully confirmed by another model using the ECMWF (re)analysis. This multiple regression is then used to empirically estimate the GrIS SMB since 1900 from climatological time series and reanalysises. The projected SMB changes in the 21st century are investigated with the set of simulations performed with AOGCM's for the IPCC Fourth Assessment Report. These estimations show that the high surface mass loss rates of these last years (1998, 2003, 2006) are not unprecedented in the GrIS history of the last hundred years. The minimum SMB rate seems to be occurred in the 1930's due to a combination of dryer and warmer years than now although the effect of the man-induced global warming was not perceptible at that time. The AOGCM's project that the SMB rate of the 1930s would be common at the end of this century. The temperature would be higher than in the 1930s but the increase of accumulation would partly offset the acceleration of surface melt due to the temperature increase. If no change will occur in the iceberg discharge rate, such negative SMB rates would be not large enough to significantly increase in the future the fresh meltwater flux from the GrIS into the ocean. However, these assumptions are based on an empirical multiple regression only currently validated and the accuracy and time homogeneity of the data sets and AOGCM results used in these estimations constitute a large uncertainty. [less ▲]

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See detailEstimation of the 1900-2100 Greenland ice sheet surface mass balance
Fettweis, Xavier ULg; Hanna, E.; Gallée, H. et al

Conference (2008, April)

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See detailEstimation of the charge carrier localization length from Gaussian fluctuations in the magneto-thermopower of La0.6Y0.1Ca0.3MnO3
Sergeenkov, S.; Bougrine, Hassan ULg; Ausloos, Marcel ULg et al

in Physical Review. B : Condensed Matter (1999), 60(17), 12322-12328

The magneto-thermoelectric power (TEP) Delta S(T,H) of perovskite-type manganese oxide La0.6Y0.1Ca0.3MnO3 is found to exhibit a sharp peak at some temperature T*=170 K. By approximating the true shape of ... [more ▼]

The magneto-thermoelectric power (TEP) Delta S(T,H) of perovskite-type manganese oxide La0.6Y0.1Ca0.3MnO3 is found to exhibit a sharp peak at some temperature T*=170 K. By approximating the true shape of the measured magneto-TEP in the vicinity of T* by a linear triangle of the form Delta S(T,H) similar or equal to S-p(H)+/-B+/-(H)(T* - T), we observe that B-(H)similar or equal to 2B(+)(H). We adopt the electron localization scenario and introduce a Ginzburg-Landau (GL)-type theory which incorporates the two concurrent phase transitions, viz., the paramagnetic-ferromagnetic transition at the Curie point T-C and the "metal-insulator'' (M-I) transition at T-MI. The latter is characterized by the divergence of the field-dependent charge carrier localization length xi(T,H) at some characteristic field H-o. Calculating the average and fluctuation contributions to the total magnetization and the transport entropy related magneto-TEP Delta S(T,H) within the GL theory, we obtain a simple relationship between T* and the above two critical temperatures (T-C and T-MI). The observed slope ratio B-(H)/B+(H) is found to be governed by the competition between the electron-spin exchange JS and the induced magnetic energy MsHo. The comparison of our data with the model predictions produce T-C = 195 K, JS = 40 meV, M-o = 0.4M(s), and xi(o) = 5 Angstrom for the estimates of the Curie temperature, the exchange coupling constant, the critical magnetization, and the localization length, respectively. The magneto-TEP data obtained by other authors are discussed and Found to be consistent with the model predictions as well. [[S0163-1829(99)00734-1]. [less ▲]

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See detailEstimation of the comparative therapeutic superiority of QD and BID dosing regimens, based on integrated analysis of dosing history data and pharmacokinetics
Comté, Laetitia ULg; Vrijens, Bernard ULg; Tousset, Eric et al

in Journal of Pharmacokinetics and Pharmacodynamics (2007), 34(4), 549-558

Once-daily dosing almost invariably shows a slightly higher percentage of prescribed doses taken than does twice-daily dosing. Many pharmaceutical scientists, regulators, and prescribers have considered ... [more ▼]

Once-daily dosing almost invariably shows a slightly higher percentage of prescribed doses taken than does twice-daily dosing. Many pharmaceutical scientists, regulators, and prescribers have considered this finding to signify the therapeutic superiority of once-daily dosing. The therapeutically more relevant question, however, is not the percentage of prescribed doses taken but the comparative impact of missed doses on the pharmacologic effects of a drug under the two dosing regimens. A key point in this regard is that the pharmacokinetic equivalent of a single missed once-daily dose is 2-3 sequentially omitted twice-daily doses. Thus, an important parameter in comparing the two regimens is the probability of two or three twice-daily doses being sequentially omitted, versus the probability of missing a single once-daily dose. Our data indicate that the probability of sequential omission of 2-3 twice daily doses is half the probability of omission of a single once-daily dose. For that reason, a twice-daily regimen could prove to be superior to a once-daily regimen in maintaining drug concentrations within a therapeutically desirable range. A more important consideration, however, is to maintain not just the concentration of drug in plasma, but the drug's therapeutic action. The duration of therapeutic drug action following a last-taken dose is not only drug-specific, but also, for some drug, dependent on the pharmacodynamic properties. Judging the comparative superiority of one dosing regimen over another requires knowledge of the drug's duration action after a last-taken dose, plus knowledge of the comparative probabilities of the various patterns of dose omission. When applied to HIV protease inhibitors, a twice-daily regimen appears to be better than an once-daily regimen in maintaining therapeutically effective drug actions. [less ▲]

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See detailEstimation of the dominance variance for postweaning gain in the US Limousin population
Gengler, Nicolas ULg; Misztal, I.; Bertrand, J. K. et al

in Journal of Animal Science (1998), 76(10), 2515-2520

The objective of this study was to estimate the dominance variance for postweaning gain in Limousin cattle. Data included 215,326 records of postweaning gain from 205 to 365 d, provided by the North ... [more ▼]

The objective of this study was to estimate the dominance variance for postweaning gain in Limousin cattle. Data included 215,326 records of postweaning gain from 205 to 365 d, provided by the North American Limousin Foundation. Parental dominance subclasses were formed and related using the method of Hoeschele and VanRaden. Variance components were estimated using Method R based on six samples of 50%. Fixed effects in the model included contemporary group apd covariates for inbreeding and breed composition (percentage Limousin). Heterozygosity was negatively correlated with breed composition (< -.99) and was therefore not included in the model. Two types of contemporary groups used as original groups from the National Cattle Evaluation were partially based on breed composition. Original contemporary groups that were too homogeneous for breed composition were replaced by herd-year-sex classes. Two models were used with the two data sets. Model 1 contained the fixed effects described above and an additive genetic effect. Model 2 Included a dominance effect in addition to the effects contained in Model 1. In total, four combinations of contemporary group x model were used. Dominance variance was computed as being four times the estimated parental subclass variance. Estimates for inbreeding depression and breed composition (percentage Limousin) were all small and not greatly affected by inclusion of dominance effects or changes in contemporary groups. Estimates of the additive variance (expressed as percentage of the phenotypic variance) were only slightly affected, with values between 20 and 21%. Dominance estimates were highly affected when passing from original (10%) and to alternative contemporary groups (18%). Such large values may indicate that dominance is important for postweaning gain. Results showed the advantage of an individual dominance approach based on sire-dam combinations; therefore, expected gains through the use of specific combination ability as a part of the mating selection criteria for growth might be high. [less ▲]

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See detailAn estimation of the endogenous secretion of calcitonin in normal and pre and postmenopausal osteoporotic women
Reginster, Jean-Yves ULg; DEROISY, Rita ULg; Franchimont, P

in Journal of Bone and Mineral Research (1988), 3(S1), 159

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See detailAn estimation of the endogenous secretion of calcitonin in normal and pre and postmenopausal osteoporotic women
Reginster, Jean-Yves ULg; DEROISY, Rita ULg; Denis, D et al

in Gynecological Endocrinology : The Official Journal of the International Society of Gynecological Endocrinology (1988), 2

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See detailEstimation of the error density in a semi-parametric transformation model.
Samb, Rawane; Heuchenne, Cédric ULg; Van Keilegom, Ingrid

E-print/Working paper (2011)

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See detailEstimation of the error density in a semiparametric transformation model
Colling, Benjamin; Heuchenne, Cédric ULg; Samb, Rawane et al

in Annals of the Institute of Statistical Mathematics (2014)

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See detailEstimation of the Error Distribution in a Semiparametric Transformation Model
Heuchenne, Cédric ULg; Samb, Rawane; Van Keilegom, Ingrid

Scientific conference (2011, November 15)

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See detailEstimation of the error distribution in nonparametric regression with cross-sectional data
Heuchenne, Cédric ULg; Laurent, Géraldine ULg

E-print/Working paper (2014)

In this article, we study the nonparametric regression model Y=m(X)+varepsilon where m(x)=E[Y|X=x] and sigma²(x)=Var[varepsilon|X=x] are unknown smooth functions, and the error varepsilon has zero mean ... [more ▼]

In this article, we study the nonparametric regression model Y=m(X)+varepsilon where m(x)=E[Y|X=x] and sigma²(x)=Var[varepsilon|X=x] are unknown smooth functions, and the error varepsilon has zero mean and finite variance conditionally on X=x. The problem consists in estimating the cumulative distribution function of the error in a nonparametric way when the couple (X,Y) is obtained by cross-sectional sampling while the positive response Y can be right-censored. We propose a new estimator for the error distribution function based on the estimators of m(.) and sigma²(.) described in Heuchenne and Laurent 2014. A bootstrap procedure is developed to solve the critical problem of the smoothing parameter choice. We assess the performance of the proposed estimator through simulations. Finally, a data set based on the mortality of diabetics is analyzed. (Heuchenne Cédric and Laurent Géraldine, Nonparametric regression with cross-sectional data: an alternative to conditional product-limit estimators, 2014) [less ▲]

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