On particle filters applied to electricity load forecasting

We are interested in the online prediction of the electricity load, within the Bayesian framework of dynamic models. We offer a review of sequential Monte Carlo methods, and provide the calculations needed for the derivation of so-called particles filters. We also discuss the practical issues arising from their use, and some of the variants proposed in the literature to deal with them, giving detailed algorithms whenever possible for an easy implementation. We propose an additional step to help make basic particle filters more robust with regard to outlying observations. Finally we use such a particle filter to estimate a state-space model that includes exogenous variables in order to forecast the electricity load for the customers of the French electricity company \'Electricit\'e de France and discuss the various results obtained

Consistency of the posterior distribution and MLE for piecewise linear regression

We prove the weak consistency of the posterior distribution and that of the Bayes estimator for a two-phase piecewise linear regression mdoel where the break-point is unknown. The non-differentiability of the likelihood of the model with regard to the break- point parameter induces technical difficulties that we overcome by creating a regularised version of the problem at hand. We first recover the strong consistency of the quantities of interest for the regularised version, using results about the MLE, and we then prove that the regularised version and the original version of the problem share the same asymptotic properties

Construction of an informative hierarchical prior for a small sample with the help of historical data and application to electricity load forecasting

We are interested in the estimation and prediction of a parametric model on a short dataset upon which it is expected to overfit and perform badly. To overcome the lack of data (relatively to the dimension of the model) we propose the construction of an informative hierarchical Bayesian prior based upon another longer dataset which is assumed to share some similarities with the original, short dataset. We illustrate the performance of our prior on simulated dataset from three standard models. Then we apply the methodology to a working model for the electricity load forecasting on real datasets, where it leads to a substantial improvement of the quality of the predictions

Les aspects de l'organisation du travail et la détresse psychologique : une explication de l'intention des travailleurs de donner leur démission

Les employeurs sont à la recherche constante de nouvelles approches et méthodes en vue d'assurer la rétention de leurs employés. En raison de leur fréquence, des coûts qu'ils entraînent et des conséquences néfastes sur le climat de travail, les départs volontaires s'avèrent un sérieux problème pour les organisations. Il est donc important de se pencher sur le mécanisme à travers lequel les travailleurs décident de démissionner. Les écrits sur le sujet montrent que l'intention de quitter constitue le principal prédicteur des départs volontaires. Notre étude concerne donc spécifiquement l'intention de quitter. Parmi les facteurs à l'origine de l'intention de quitter figurent notamment les caractéristiques de l'emploi. En effet, il a été largement démontré qu'une lourde demande psychologique, une faible latitude décisionnelle, les conflits et l'ambiguïté de rôle contribuent à intensifier l'intention de quitter l'organisation. Pour expliquer l'effet que produisent les caractéristiques de l'emploi sur l'intention de quitter, les études ont également mis en évidence le rôle médiateur d'un certain nombre d'attitudes, notamment la satisfaction au travail et l'engagement organisationnel. Récemment, quelques recherches ont porté sur le rôle médiateur d'un problème particulier de santé mentale, à savoir le burnout. Or, jusqu'à maintenant la question de la détresse psychologique est restée inexplorée. L'objectif de notre recherche consiste donc à déterminer le rôle médiateur de la détresse psychologique dans la relation entre les caractéristiques de l'emploi et l'intention de quitter l'organisation. La détresse psychologique fait référence à un état psychologique pénible caractérisé par l'irritabilité, l'anxiété, la tristesse, le découragement et l'autodépréciation. Afin de réaliser notre objectif de recherche, nous avons mobilisé le modèle des exigences et du contrôle (job demands – Control Model ; Karasek, 1979), ainsi que la théorie de la conservation des ressources (Hobfoll, 1989). Ce cadre théorique a permis de formuler neuf hypothèses concernant les liens directs et indirects entre les caractéristiques de l'emploi, la détresse psychologique et l'intention de quitter. Notre objectif de recherche a été réalisé dans le cadre d'une étude corrélationnelle à coupe transversale, laquelle s'inscrit dans une démarche hypothético-déductive. Pour les besoins de notre étude, les 2 630 préposés de trois centres d'appels au Québec ont été invités à répondre à un questionnaire électronique (Harrisson, Cloutier et Béland-Ouellette, 2012). Au total, 659 préposés ont répondu à notre enquête, ce qui représente un taux de réponse de 24.59 %. Afin de vérifier nos hypothèses de recherche, nous avons utilisé la technique de la régression linéaire multiple. Pour réaliser les tests de médiation, nous avons suivi les étapes que proposent Baron et Kenny (1986). Nos résultats soutiennent sept des neuf hypothèses de recherche. Conformément avec nos hypothèses, nos résultats ont montré que les caractéristiques du travail (demande psychologique, latitude décisionnelle, conflit de rôle), à l'exception de l'ambiguïté de rôle, sont des prédicteurs de la détresse psychologique et de l'intention de quitter. De plus, l'effet de la demande psychologique et du conflit de rôle sur l'intention de quitter passe entièrement par la détresse psychologique (médiation totale). La détresse psychologique joue un rôle médiateur partiel dans la relation entre la latitude décisionnelle et l'intention de quitter. Par ces résultats, ce mémoire procure une contribution additionnelle à la compréhension de l'intention de quitter et ouvre la porte à plusieurs autres études sur le sujet. Afin de conclure, ces résultats aideront aussi les entreprises à mieux comprendre l'intention de quitter chez leurs employés et permettront d'agir de façon préventive.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : Caractéristiques de l'emploi, stresseur, risques psychosociaux, demande psychologique, santé mentale, détresse psychologique, intention de quitter, départ volontair

Effect of an isoenergetic traditional Mediterranean diet on apolipoprotein A-I kinetic in men with metabolic syndrome

BACKGROUND: The impact of the Mediterranean diet (MedDiet) on high-density lipoprotein (HDL) kinetics has not been studied to date. The objective of this study was therefore to investigate the effect of the MedDiet in the absence of changes in body weight on apolipoprotein (apo) A-I kinetic in men with metabolic syndrome (MetS). METHODS: Twenty-six men with MetS (NCEP-ATP III) were recruited from the general community. In this fixed sequence study, participants’ diet was first standardized to a control diet reflecting current averages in macronutrient intake in North American men, with all foods and beverages provided under isoenergetic conditions for 5 weeks. Participants were then fed an isoenergetic MedDiet over a subsequent period of 5 weeks to maintain their weight constant. During the last week of each diet, participants received a single bolus dose of [5,5,5-(2)H(3)] (L)-leucine and fasting blood samples were collected at predetermined time points. ApoA-I kinetic was determined by multicompartmental modeling using isotopic enrichment data over time. Data were analyses using MIXED models. RESULTS: The response of HDL-cholesterol (C) to MedDiet was heterogeneous, such that there was no mean change compared with the control diet. Plasma apoA-I concentration (−3.9%) and pool size (−5.3%, both P < 0.05) were significantly lower after MedDiet and apoA-I production rate tended to be reduced (−5.7%, P = 0.07) with no change in apoA-I fractional catabolic rate (FCR, -1.6%, P = 0.64). Participants among whom HDL-C concentrations were increased with MedDiet (responders: mean ∆HDL-C: +9.9 ± 3.2%, N = 11) showed significantly greater reductions in apoA-I FCR and in apoB and very-low-density lipoprotein-triglycerides (VLDL-TG) concentrations (all P < 0.04) than those among whom HDL-C levels were reduced after the MedDiet (non-responders: mean ∆HDL-C: -12.0 ± 3.9%, N = 8). Correlation analysis revealed that only variations in apoA-I FCR (r = -0.48, P = 0.01) and in plasma VLDL-TG (r = −0.45, P = 0.03) concentrations were correlated with the individual HDL-C response to the MedDiet. CONCLUSIONS: Data from this controlled feeding study suggest that the heterogeneous response of HDL-C to MedDiet, in the absence of important weight loss, is primarily related to individual variations in apoA-I FCR and in plasma VLDL-TG concentrations. TRIAL REGISTRATION: ClinicalTrial.gov registration number: NCT0098865

Are French Canadians able to accurately self-rate the quality of their diet? Insights from the PREDISE study

Cette étude se propose principalement de comparer l’autoévaluation de la qualité du régime alimentaire à un score de qualité nutritionnelle globale et à évaluer la prédictibilité de l’autoévaluation concernant l’adhésion aux recommandations de saine alimentation. Cette étude examine aussi la possible influence des caractéristiques individuelles sur l’association entre l’autoévaluation du régime alimentaire et le score de qualité nutritionnelle globale. Dans le cadre du projet PRédicteurs Individuels, Sociaux et Environnementaux (PREDISE), 1045 participants (51 % femmes) du Québec (Canada) ont autoévalué la qualité de leur régime alimentaire (« En général, diriez-vous que vos habitudes alimentaires sont : excellentes, très bonnes, bonnes, passables ou mauvaises? »). Les données de trois rappels alimentaires de 24 h via Internet ont permis le calcul du Healthy Eating Index (C-HEI), un indicateur de qualité nutritionnelle globale. Les participants percevaient leurs habitudes alimentaires comme étant excellentes (2,4 %), très bonnes (22,7 %), bonnes (49,5 %), passables (20,3 %) ou mauvaises (5,1 %). Le C-HEI variait significativement entre les catégories d’autoévaluation dans la direction attendue (p 68) de saine alimentation en présentant une sensibilité de 44,5 % et une spécificité de 81,5 % (statistique C = 0,63). L’association entre l’autoévaluation et le C-HEI était modifiée significativement par le sexe (p interaction = 0,0131); les femmes avaient un C-HEI plus élevé que les hommes dans les catégories « bonnes » et « passables ». L’autoévaluation du régime alimentaire permet de donner un aperçu de la qualité du régime alimentaire d’une population. Cependant, les résultats de cette étude suggèrent d’utiliser ces données avec prudence compte tenu de leur faible prédictibilité concernant l’adhésion aux recommandations de saine alimentation. Des caractéristiques individuelles sont susceptibles d’influencer l’aptitude à autoévaluer adéquatement la qualité du régime alimentaire.The main objective of this study was to compare self-rated diet quality to a more comprehensive score of diet quality and to assess the ability of self-rated diet quality to predict adherence to healthy eating guidelines. This study also aimed at evaluating the influence of individual characteristics on the association between self-rated diet quality and the overall diet quality score. As part of the PREDISE study, 1045 participants (51% women) from the Province of Québec, Canada, self-rated their diet quality (“In general, would you say that your dietary habits are: excellent, very good, good, fair, or poor?”). Three web-based 24-hour food recalls were completed, generating data for the calculation of the Canadian Healthy Eating Index (C-HEI), an overall diet quality indicator. Participants rated their diet quality as excellent (2.4%), very good (22.7%), good (49.5%), fair (20.3%) or poor (5.1%). The C-HEI significantly differed between diet ratings, in the expected direction (p<0.0001). Self-rated diet quality predicted adherence to healthy eating guidelines (i.e. C-HEI>68) with a sensitivity of 44.5% and a specificity of 81.5% (c-statistic=0.63). Sex significantly modified the association between self-rated diet quality and C-HEI (p interaction=0.0131); women had higher C-HEI than men in the “good” and “fair” ratings. Self-rated diet quality can be useful to obtain an overview of the diet quality of a population. Results of this study suggest that such data should be used with caution given its poor ability to predict adherence to healthy eating guidelines. Individual characteristics may influence one’s ability to appropriately self-evaluate diet quality

Transitioning to sustainable dietary patterns: learnings from animal-based and plant-based dietary patterns in French Canadian adults

IntroductionMany dietary guidelines promote the substitution of animal proteins with plant-based proteins for health benefits but also to help transitioning toward more sustainable dietary patterns. The aim of this study was to examine the food and nutrient characteristics as well as the overall quality and costs of dietary patterns consistent with lower intakes of animal-based protein foods and with higher intakes of plant-based protein foods among French Canadian adults.MethodsDietary intake data, evaluated with 24 h recalls, from 1,147 French-speaking adults of the PRÉDicteurs Individuels, Sociaux et Environnementaux (PREDISE) study conducted between 2015 and 2017 in Québec were used. Usual dietary intakes and diet costs were estimated with the National Cancer Institute’s multivariate method. Consumption of animal- and plant-based protein foods was classified into quarters (Q) and differences in food and nutrient intakes, Healthy Eating Food Index (HEFI)-2019 scores and diet costs across quarters were assessed using linear regression models adjusted for age and sex.ResultsParticipants with lower intakes of animal-based protein foods (Q1 vs. Q4) had a higher HEFI-2019 total score (+4.0 pts, 95% CI, 0.9 to 7.1) and lower daily diet costs (-1.9 $CAD, 95$CAD, 95% CI, -0.7 to 0.7).DiscussionIn a perspective of diet sustainability, results from this study among French-speaking Canadian adults suggest that a shift toward a dietary pattern focused primarily on lower amounts of animal-based protein foods may be associated with a better diet quality at lower costs. On the other hand, transitioning to a dietary pattern focused primarily on higher amounts of plant-based protein foods may further improve the diet quality at no additional cost

Development and validation of the food liking questionnaire in a french-canadian population

The purpose of this study was to develop and validate a questionnaire assessing food liking in a French-Canadian population. A questionnaire was developed, in which participants were asked to rate their degree of liking of 50 food items. An expert panel evaluated the content validity. For the validation study, 150 men and women completed the questionnaire twice. An Exploratory Factor Analysis (EFA) was performed to assess the number of subscales of the questionnaire. Internal consistency and test-retest reliability of the subscales were evaluated. Concurrent validity was assessed through correlations between liking scores and self-reported frequencies of consumption. Comments from the experts led to changes in the list of foods included in the questionnaire. The EFA revealed a two-factor structure for the questionnaire (i.e., savory and sweet foods) and led to the removal of nine items, resulting in a 32-item questionnaire. The two subscales revealed good internal consistency (Cronbach alphas: 0.85 and 0.89) and test-retest reliability (p = 0.84 and 0.86). The questionnaire demonstrated adequate concurrent validity, with moderate correlations between food liking and self-reported frequency of consumption (r = 0.19–0.39, ps < 0.05). This new Food Liking Questionnaire assessing liking of a variety of savory and sweet foods demonstrated good psychometric properties in every validation step. This questionnaire will be useful to explore the role of food liking and its interactions with other factors in predicting eating behaviors and energy intake

Intakes of total, free, and naturally occurring sugars in the french-speaking adult population of the province of Québec, Canada : the PREDISE study

The objective of this study was to characterize the intakes of different types of sugars in an age- and sex-representative sample of French-speaking adults from five regions of the Province of Québec, Canada, enrolled in the cross-sectional PREDISE (PRÉDicteurs Individuels, Sociaux et Environnementaux) study (n = 1147, 18–65 years old; 50.2% women). Because only total sugar content of foods and beverages is available in the Canadian Nutrient File (CNF) 2015, the initial step of this study was thus to build a database of free and naturally occurring sugars content of each food item and recipe included in the R24W, which is an automated, self-administered, web-based, 24-h dietary recall validated to estimate nutrient intakes in French-speaking adults of the Province of Québec. Total sugars were manually differentiated into free and naturally occurring sugars using a systematic algorithm based on previously published systematic algorithms. The World Health Organization (WHO)’s free sugar definition was used to differentiate total sugars into free and naturally occurring sugars. Dietary intake estimates were assessed using three 24-h dietary recalls completed with the R24W. Mean total, free, and naturally occurring sugar intakes were 116.4 g (19.3% of daily energy intake (%E)), 72.5 g (11.7%E), and 44.0 g (7.5%E), respectively. Over half (57.3%) of the overall sample did not meet the WHO’s recommendation to consume less than 10%E from free sugars. Women had a higher %E from naturally occurring sugars than men and being younger was associated with a greater %E from free sugars. Sugar intakes among French-speaking adults from the Province of Québec were mainly in the form of free sugars, with the majority of the population exceeding the WHO recommendation regarding free sugar intake. This suggests that public health efforts towards reducing free sugar intake in this population are relevant and necessary, considering that overconsumption of free sugars negatively influences health outcomes