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See detailEstimating survival rates in ecological studies with small unbalanced sample sizes: an alternative Bayesian point estimator
Damgaard, Christian; Fayolle, Adeline ULg

in Computational Ecology and Software (2011), 1(4), 243-248

Increasingly, the survival rates in experimental ecology are presented using odds ratios or log response ratios, but the use of ratio metrics has a problem when all the individuals have either died or ... [more ▼]

Increasingly, the survival rates in experimental ecology are presented using odds ratios or log response ratios, but the use of ratio metrics has a problem when all the individuals have either died or survived in only one replicate. In the empirical ecological literature, the problem often has been ignored or circumvented by different, more or less ad hoc approaches. Here, it is argued that the best summary statistic for communicating ecological results of frequency data in studies with small unbalanced samples may be the mean of the posterior distribution of the survival rate. The developed approach may be particularly useful when effect size indexes, such as odds ratios, are needed to compare frequency data between treatments, sites or studies. [less ▲]

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See detailEstimating Systematic Risk in the Presence of Thin Trading and Conditional Heteroscedasticity
Corhay, Albert ULg; Tourani Rad, Alireza; Urbain, Jean-Pierre

in In The Money (1997), 2

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See detailEstimating The Cost of Improving Quality in Electricity Distribution: A Parametric Distance Function Approach
Coelli, Tim; Gautier, Axel ULg; Perelman, Sergio ULg et al

in Energy Policy (2013), 53

The quality of electricity distribution is being more and more scrutinized by regulatory authorities, with explicit reward and penalty schemes based on quality targets having been introduced in many ... [more ▼]

The quality of electricity distribution is being more and more scrutinized by regulatory authorities, with explicit reward and penalty schemes based on quality targets having been introduced in many countries (France, Germany, Italy, UK,...). It is then of prime importance to know the cost of improving the quality for a distribution system operator. In this paper, we focus on one dimension of quality, the continuity of supply, and we estimated the cost of preventing power outages. For that, we make use of the parametric distance function approach, assuming that outages enter in the firm production set as an input, an imperfect substitute for maintenance activities and capital investment. This allows us to identify the sources of technical inefficiency and the underlying trade-­‐off faced by operators between quality and other inputs and costs. For this purpose, we use panel data on 92 electricity distribution units operated by ERDF (Electricité de France - Réseau Distribution) in the 2003–2005 financial years. Assuming a multi-output multi-input translog technology, we estimate that the cost of preventing one interruption varies substantily among the distribution units from 2.7 € to 15.7 €. Furthermore, as one would expect, marginal quality improvements tend to be more expensive as quality itself improves. [less ▲]

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See detailEstimating the costs of collective treatment of wastewater : the case of Walloon Region (Belgium)
Dogot, Thomas ULg; Xanthoulis, Y.; Fonder, N. et al

Conference (2009)

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See detailEstimating the costs of collective treatment of wastewater: the case of Walloon Region (Belgium)
Dogot, Thomas ULg; Xanthoulis, Yanni; Fonder, Nathalie et al

in Water Science & Technology (2010), 62(3), 640-648

This paper contributes to a better understanding of costs for collective wastewater treatment in the Walloon Region (Belgium). Based on a large set of data, unit costs to population equivalents are ... [more ▼]

This paper contributes to a better understanding of costs for collective wastewater treatment in the Walloon Region (Belgium). Based on a large set of data, unit costs to population equivalents are modelled. Considering investment as well as exploitation costs, the model includes not only wastewater treatment plants but also collector and sewage networks in an integrated approach at the technical basin level. Beyond this modelling, each type of process is analyzed independently in order to explore the structure of investment costs and their variation factors. Then, the model was used to forecast the upcoming expenses for 36 areas which are not yet equipped with collective wastewater treatment facilities. In light of these results, strategic choices for decision makers are discussed. [less ▲]

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See detailEstimating the driver function of a cardiovascular system model
Stevenson, D; Hann, CE; Chase, JG et al

in Proceedings of CONTROL 2010 (2010)

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See detailEstimating the economic impact of a possible equine and human epidemic of West Nile virus infection in Belgium
Humblet, Marie-France ULg; Vandeputte, Sébastien; Fecher-Bourgeois, Fabienne ULg et al

in Eurosurveillance (2016), 21(31),

This study aimed at estimating, in a prospective scenario, the potential economic impact of a possible epidemic of WNV infection in Belgium, based on 2012 values for the equine and human health sectors ... [more ▼]

This study aimed at estimating, in a prospective scenario, the potential economic impact of a possible epidemic of WNV infection in Belgium, based on 2012 values for the equine and human health sectors, in order to increase preparedness and help decision-makers. Modelling of risk areas, based on the habitat suitable for Culex pipiens, the main vector of the virus, allowed us to determine equine and human populations at risk. Characteristics of the different clinical forms of the disease based on past epidemics in Europe allowed morbidity among horses and humans to be estimated. The main costs for the equine sector were vaccination and replacement value of dead or euthanised horses. The choice of the vaccination strategy would have important consequences in terms of cost. Vaccination of the country’s whole population of horses, based on a worst-case scenario, would cost more than EUR 30 million; for areas at risk, the cost would be around EUR 16–17 million. Regarding the impact on human health, short-term costs and socio-economic losses were estimated for patients who developed the neuroinvasive form of the disease, as no vaccine is available yet for humans. Hospital charges of around EUR 3,600 for a case of West Nile neuroinvasive disease and EUR 4,500 for a case of acute flaccid paralysis would be the major financial consequence of an epidemic of West Nile virus infection in humans in Belgium. [less ▲]

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See detailEstimating the error distribution function of a heteroskedastic nonparametric regression of cure model data
Chown, Justin; Heuchenne, Cédric ULg; Van Keilegom, Ingrid

Conference (2015)

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See detailEstimating the Greenland ice sheet surface mass balance contribution to future sea level rise using the regional atmospheric climate model MAR
Fettweis, Xavier ULg; Franco, Bruno ULg; Tedesco, M. et al

in Cryosphere (The) (2013), 7

To estimate the sea level rise (SLR) originating from changes in surface mass balance (SMB) of the Greenland ice sheet (GrIS), we present 21st century climate projections obtained with the regional ... [more ▼]

To estimate the sea level rise (SLR) originating from changes in surface mass balance (SMB) of the Greenland ice sheet (GrIS), we present 21st century climate projections obtained with the regional climate model MAR (Modèle Atmosphérique Régional), forced by output of three CMIP5 (Coupled Model Intercomparison Project Phase 5) general circulation models (GCMs). Our results indicate that in a warmer climate, mass gain from increased winter snowfall over the GrIS does not compensate mass loss through increased meltwater run-off in summer. Despite the large spread in the projected near-surface warming, all the MAR projections show similar non-linear increase of GrIS surface melt volume because no change is projected in the general atmospheric circulation over Greenland. By coarsely estimating the GrIS SMB changes from GCM output, we show that the uncertainty from the GCM-based forcing represents about half of the projected SMB changes. In 2100, the CMIP5 ensemble mean projects a GrIS SMB decrease equivalent to a mean SLR of +4 ± 2 cm and +9 ± 4 cm for the RCP (Representative Concentration Pathways) 4.5 and RCP 8.5 scenarios respectively. These estimates do not consider the positive melt–elevation feedback, although sensitivity experiments using perturbed ice sheet topographies consistent with the projected SMB changes demonstrate that this is a significant feedback, and highlight the importance of coupling regional climate models to an ice sheet model. Such a coupling will allow the assessment of future response of both surface processes and ice-dynamic changes to rising temperatures, as well as their mutual feedbacks. [less ▲]

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See detailEstimating the out-of-sample predictive ability of trading rules: a robust bootstrap approach
Hambuckers, julien ULg; Heuchenne, Cédric ULg

in Journal of Forecasting (2016), 35(4), 347-372

In this paper, we provide a novel way to estimate the out-of-sample predictive ability of a trading rule. Usually, this ability is estimated using a sample splitting scheme, true out-of-sample data being ... [more ▼]

In this paper, we provide a novel way to estimate the out-of-sample predictive ability of a trading rule. Usually, this ability is estimated using a sample splitting scheme, true out-of-sample data being rarely available. We argue that this method makes a poor use of the available data and creates data mining possibilities. Instead, we introduce an alternative .632 bootstrap approach. This method enables to build in- sample and out-of-sample bootstrap datasets that do not overlap but exhibit the same time dependencies. We show in a simulation study that this technique drastically reduces the mean squared error of the estimated predictive ability. We illustrate our methodology on IBM, MSFT and DJIA stock prices, where we compare 11 trading rules speci cations. For the considered datasets, two different filter rule specifications have the highest out-of-sample mean excess returns. However, all tested rules cannot beat a simple buy-and-hold strategy when trading at a daily frequency. [less ▲]

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See detailEstimating the out-of-sample predictive ability of trading rules: a robust bootstrap approach
Hambuckers, julien ULg; Heuchenne, Cédric ULg

E-print/Working paper (2014)

In this paper, we estimate the out-of-sample predictive ability of a set of trading rules. Usually, this ability is estimated using a rolling-window sample-splitting scheme, true out-of-sample data being ... [more ▼]

In this paper, we estimate the out-of-sample predictive ability of a set of trading rules. Usually, this ability is estimated using a rolling-window sample-splitting scheme, true out-of-sample data being rarely available. We argue that this method makes a poor use of the available information and creates data mining possibilities. Instead, we introduce an alternative bootstrap approach, based on the .632 bootstrap principle. This method enables to build in-sample and out-of-sample bootstrap data sets that do not overlap and exhibit the same time dependencies. We illustrate our methodology on IBM and Microsoft daily stock prices, where we compare 11 trading rules specifications. For the data sets considered, two different filter rule specifications have the highest out-of-sample mean excess returns. However, all tested rules cannot beat a simple buy-and-hold strategy when trading at a daily frequency. [less ▲]

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See detailEstimating the p-mode frequencies of the solar twin 18 Scorpii
Bazot, M.; Campante, T.L.; Chaplin, W.J. et al

in Astronomy and Astrophysics (2012), 544

Solar twins have been a focus of attention for more than a decade, because their structure is extremely close to that of the Sun. Today, thanks to high-precision spectrometers, it is possible to use ... [more ▼]

Solar twins have been a focus of attention for more than a decade, because their structure is extremely close to that of the Sun. Today, thanks to high-precision spectrometers, it is possible to use asteroseismology to probe their interiors. Our goal is to use time series obtained from the HARPS spectrometer to extract the oscillation frequencies of 18 Sco, the brightest solar twin. We used the tools of spectral analysis to estimate these quantities. We estimate 52 frequencies using an MCMC algorithm. After examination of their probability densities and comparison with results from direct MAP optimization, we obtain a minimal set of 21 reliable modes. The identification of each pulsation mode is straightforwardly accomplished by comparing to the well-established solar pulsation modes. We also derived some basic seismic indicators using these values. These results offer a good basis to start a detailed seismic analysis of 18 Sco using stellar models. [less ▲]

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See detailEstimating the parameters of a 3-D root distribution function from root observations with the trench profile method: case study with simulated and field-observed root data
Vansteenkiste, Joachim; Van Loon, Jelle; Garré, Sarah ULg et al

in Plant and Soil (2013)

Background and Aims Root length density (RLD) is a parameter that is difficult to measure, but crucial to estimate water and nutrient uptake by plants. In this study a novel approach is presented to ... [more ▼]

Background and Aims Root length density (RLD) is a parameter that is difficult to measure, but crucial to estimate water and nutrient uptake by plants. In this study a novel approach is presented to characterize the 3-D root length distribution by supplementing data of the 3-D distribution of root intersections with data of root length density from a limited number of soil cores. Methods The method was evaluated in a virtual experiment using the RootTyp model and a field experiment with cauliflower (Brassica oleracea L. botrytis) and leek (Allium porrum, L.). Results The virtual experiment shows that total root length and root length distribution can be accurately estimated using the novel approach. Implementation of the method in a field experiment was successful for characterizing the growth of the root distribution with time both for cauliflower and leek. In contrast with the virtual experiment, total root length could not be estimated based upon root intersection measurements in the field. Conclusions The novel method of combining root intersection data with root length density data from core samples is a powerful tool to supply root water uptake models with root system information. [less ▲]

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See detailEstimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry
Kains, N.; Bramich, D. M.; Arellano Ferro, A. et al

in Astronomy and Astrophysics (2013), 555

<BR /> Aims: We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this ... [more ▼]

<BR /> Aims: We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this cluster and refine the periods of known variables; we then used our variable star light curves to derive values for the cluster's parameters. <BR /> Methods: We used difference image analysis to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible. We also derived an estimate for the age of the cluster by fitting theoretical isochrones to our colour-magnitude diagram (CMD). <BR /> Results: Out of 13 stars previously catalogued as variables, we find that only 4 are bona fide variables. We detect two new RR Lyrae variables, and confirm two additional RR Lyrae candidates from the literature. We also detect four other new variables, including an eclipsing blue straggler system, and an SX Phoenicis star. This amounts to a total number of confirmed variable stars in M 30 of 12. We perform Fourier decomposition of the light curves of the RR Lyrae stars to derive cluster parameters using empirical relations. We find a cluster metallicity [Fe/H][SUB]ZW[/SUB] = -2.01 ± 0.04, or [Fe/H][SUB]UVES[/SUB] = -2.11 ± 0.06, and a distance of 8.32 ± 0.20 kpc (using RR0 variables), 8.10 kpc (using one RR1 variable), and 8.35 ± 0.42 kpc (using our SX Phoenicis star detection in M 30). Fitting isochrones to the CMD, we estimate an age of 13.0 ± 1.0 Gyr for M 30. This work is based on data collected by MiNDSTEp with the Danish 1.54 m telescope at the ESO La Silla Observatory.The full light curves, an extract of which is shown in Table 2 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A36">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A36</A>Tables 8-10, and Figs. 6 and 9 are available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailEstimating the residual distribution in a semiparametric transformation model.
Heuchenne, Cédric ULg; Samb, Rawane; Van Keilegom, Ingrid

E-print/Working paper (2011)

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See detailEstimating the revenues of a hydrogen-based high-capacity storage device: methodology and results
François-Lavet, Vincent ULg; Fonteneau, Raphaël ULg; Ernst, Damien ULg

in Proceedings des 9èmes Journée Francophones de Planification, Décision et Apprentissage (2014, May)

This paper proposes a methodology to estimate the maximum revenue that can be generated by a company that operates a high-capacity storage device to buy or sell electricity on the day-ahead electricity ... [more ▼]

This paper proposes a methodology to estimate the maximum revenue that can be generated by a company that operates a high-capacity storage device to buy or sell electricity on the day-ahead electricity market. The methodology exploits the Dynamic Programming (DP) principle and is specified for hydrogen-based storage devices that use electrolysis to produce hydrogen and fuel cells to generate electricity from hydrogen. Experimental results are generated using historical data of energy prices on the Belgian market. They show how the storage capacity and other parameters of the storage device influence the optimal revenue. The main conclusion drawn from the experiments is that it may be interesting to invest in large storage tanks to exploit the inter-seasonal price fluctuations of electricity. [less ▲]

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See detailEstimating Ventricular Stroke Work from Aortic Pressure Waveform
Kamoi, Shun; Pretty, Christopher; Chiew, Yeong Shiong et al

Poster (2014, November 28)

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See detailEstimating Ventricular Stroke Work from Aortic Pressure Waveform
Kamoi, Shun; Pretty, Christopher; Chiew, Yeong Shiong et al

in 13th Belgian Day on Biomedical Engineering (2014, November 28)

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See detailEstimation and approximation in multidimensional dynamics
Frasso, Gianluca ULg; Jaeger, Jonathan ULg; Lambert, Philippe ULg

E-print/Working paper (2013)

Differential equations (DEs) are commonly used to describe dynamic systems evolving in one (ordinary differential equations or ODEs) or in more than one dimensions (partial differential equations or PDEs ... [more ▼]

Differential equations (DEs) are commonly used to describe dynamic systems evolving in one (ordinary differential equations or ODEs) or in more than one dimensions (partial differential equations or PDEs). In real data applications the parameters involved in the DE models are usually unknown and need to be estimated from the available measurements together with the state function. In this paper, we present frequentist and Bayesian approaches for the joint estimation of the parameters and of the state functions involved in PDEs. We also propose two strategies to include differential (initial and/or boundary) conditions in the estimation procedure. We evaluate the performances of the proposed strategy on simulated and real data applications. [less ▲]

Detailed reference viewed: 59 (13 ULg)