1,341 research outputs found
Robust stepwise regression.
No full textThe selection of an appropriate sub-set of explanatory variables to use in a linear regression model is an important aspect of a statistical analysis. Classical stepwise regression could be invalidated by a few outling observations. We introduce a robust F-test in order to perform a stepwise regression that is robust against the presence of outliers. The introduced methodology is asymptotically equivalent to the classical one when no contamination is present. Some examples and simulation are presented
Robust stepwise regression
No full textThe selection of an appropriate subset of explanatory variables to use in a linear regression model is an important aspect of a statistical analysis. Classical stepwise regression is often used with this aim but it could be invalidated by a few outlying observations. In this paper, we introduce a robust F-test and a robust stepwise regression procedure based on weighted likelihood in order to achieve robustness against the presence of outliers. The introduced methodology is asymptotically equivalent to the classical one when no contamination is present. Some examples and simulation are presented.
Un amour de Proust, Alfred Agostinelli (1888-1914)
No full textInternational audienceThis first biography of Alfred Agostinelli, Proust's chauffeur, presented by Proust as his secretary, sheds light on the primordial role he played in the life of the author of La Recherche and the genesis of his work.Alfred Agostinelli was this handsome young man, with a sulphurous reputation, whom Proust met in Cabourg in 1907, and of whom he said that, along with his father and mother, he was one of the people he had loved the most. On the front page of the Figaro, he evoked her "young beardless face", compared her to Saint Cecilia, to "a nun of speed" and prophesied her death in an accident. He sheltered him with his girlfriend in his home, noted his actions in his notebooks, and pursued him to Monaco to obtain his return after their separation.Unpublished documents from public and private archives, testimonies, drafts of the writer have allowed Jean-Marc Quaranta to go beyond the clichés and to draw for the first time a precise portrait of Agostinelli, to deliver the account of his life and especially to restore the true relationship, of a rare intensity, that he maintained with Marcel Proust until their rupture and his tragic disappearance in May 1914.Unexpected and well-founded information on the writer's biography decisively renews the knowledge we had about the years 1913-1914, which were essential in the development of his work. Thanks to these new elements, it is possible to better identify and understand the beginnings of La Prisonnière and Albertine disparue, of which Agostinelli was the main inspiration.Cette première biographie d’Alfred Agostinelli, le chauffeur de Proust présenté par ce dernier comme son secrétaire, éclaire le rôle primordial qu’il eut dans l’existence de l’auteur de la Recherche et la genèse de son oeuvre.Alfred Agostinelli fut ce beau jeune homme, à la réputation sulfureuse, rencontré à Cabourg en 1907, dont Proust disait qu’il était avec son père et sa mère l’une des personnes qu’il avait le plus aimée. En première page du Figaro, il évoque son « jeune visage imberbe », le compare à sainte Cécile, à « une nonne de la vitesse » et prophétise sa mort dans un accident. Il l’abrite sous son toit avec sa compagne, note ses faits et gestes dans ses carnets, le poursuit jusqu’à Monaco pour obtenir son retour après leur séparation.Documents inédits issus d’archives publiques et privées, témoignages, brouillons de l’écrivain ont permis à Jean-Marc Quaranta de dépasser les clichés et de dresser pour lapremière fois un portrait précis d’Agostinelli, de livrer le récit de sa vie et surtout de restituer la véritable relation, d’une rare intensité, qu’il entretint avec Marcel Proust jusqu’à leur rupture et à sa disparition tragique en mai 1914.Des informations inattendues et solidement étayées sur la biographie de l’écrivain renouvellent de manière décisive les connaissances que l’on pouvait avoir sur les années 1913-1914, essentielles dans l’élaboration de son oeuvre. Grâce à ces éléments nouveaux, il est possible de mieux cerner et comprendre les prémices de La Prisonnière et d’Albertine disparue dont Agostinelli fut le principal inspirateur
5d bim: Tools and methods for digital project construction management
No full textThe traditional workflows used to define construction costs are characterized by a series of common criticalities due to physiological inefficiencies of analogical or not-completely-digital processes. These include the waste of man-hours due to continuous requests for clarification by the computer scientist, or the transmission of partial or unverified information by the design team, or even inaccurate and approximate measurements based on 2D drawings. This can lead to lower levels of reliability of cost estimations with consequent design risks and the need for variants in progress, exceeding the project budget or the expected timeframe. The BIM approach can mitigate these risks, but it is necessary to define a planned and robust method that supports the consistency between the items of calculation and the elements of the model. This method needs to be based on a structured breakdown of the building and the activities necessary to the project, according to a clearly planned methodology. Therefore, it is necessary to define an approach capable of generating digital workflows and automatically updating quantities (especially in the event of changes to the project), as well as to ensure the correspondence between modelled elements and computation items, in order to have a consistent workflow and make immediate and clear the updating of information on each project document. The paper is oriented to the definition of a structure for cost planning process, which uses the experimentation of computer tools aimed at extracting the quantities directly from the model, allowing the automatic update in case of changes, through the use of a PBS (project breakdown structure), shared with the entire design team, and using a code system associated with the elements of the model, the calculation, but also to specialist reports, detailed graphics and schedules
Renewable sources urban cells microgrid. A case study
No full textNowadays, microgrid technologies play a relevant role in the research field as well as in the commercial market. The opportunity to provide electricity in wide areas without using centralized electrical infrastructure networks is a reliable key for achieving the European Union sustainability goals. In this regard, the proposed research aims at describing an electric microgrid configuration powered by a photovoltaic system, supplying three school buildings located in the center of Italy. Additionally, the resilience theme is deeply investigated, analyzing the use of an emergency generator system (EGS) in case of electric grid blackouts. MATLAB/Simulink was chosen to simulate the users’ energy demand as well as to calculate the microgrid performance. Results show that almost the total consumption of the microgrid is covered by the photovoltaic system, and the use of an EGS allows energy resilience and moderate economic savings for the communit
A novel comprehensive paradigm for the etiopathogenesis of multiple sclerosis: therapeutic approaches and future perspectives on its treatment
No full textIt is well recognized that variation in the geographical distribution of prevalence of multiple sclerosis (MS) exists: increasing the latitude its prevalence increases as well, but the underlying causes of such dissimilarity still remained elusive as of today. Currently, the most accredited hypothesis is that the closer to the equator the more pronounced is the amount of sunlight which, in turn, increases the production of vitamin D. Cholecalciferol is indeed deficient in MS patients, but this factor does not explain by itself the etiopathogenesis of the disease. In the present study, to search for a pattern and provide a model of the disease’s etiology consistent with this regional factor, as well with its changing ethnic, sex-ratio, lifestyle variations and the other unexplained aspects of MS, an extensive analysis of peer-reviewed literature and data was conducted. The arisen hypothesis was that, increasing the latitude, the factor that varies and can have the stronger effect on the human organism, is the continuous and ever-increasing diversity of the natural light–dark cycle. The consequent effort of the suprachiasmatic nucleus to entrain the organism’s circadian rhythm affects the hypothalamic–pituitary–adrenal axis resulting in desynchronizing the central and peripheral circadian clocks and pathologizing the immunitary system. To verify such hypothesis, a theoretical framework of the etiopathogenesis, coherent with the gathered literature, was conceived and a demonstration to corroborate it was eventually devised and performed. The results underscored that people living in countries subjected to a further circadian disruptive factor, as daylight saving time, have a 6.35 times higher prevalence of MS than States placed on their same latitude that do not observe it, thus strongly supporting the hypothesis. As further reinforcement of the conclusions, it is worth mentioning that the levels of polyamines rise abruptly in autoimmune diseases. Moreover, among their numerous roles, these polycations participate to the regulation of the circadian clock so their sudden variation might disrupt it. Following these interesting findings, new perspectives in therapies are, therefore, proposed
Follicular lymphoma: still six characters in search of an author?
No full textFollicular lymphoma (FL) is regarded as a distinct entity in the literature as well as in the 2008 edition of the WHO classification of tumours of haematopoietic and lymphoid tissues.Nevertheless, there are still several issues that are matters of controversy such as the grading system or the exact biological location of grade 3B FL. This makes FL somewhat like the Six characters in search of an author of Pirandello's comedy. Here, we revise the morphology and pathobiology of FL by highlighting both the areas remaining critical and future perspectives. This review was inspired by the reappraisal of Professor Lennert's personal archive that represents a unique legacy for the entire scientific community
Comment on: Linguistic and cognitive abnormalities in children with benign partial epilepsy with centro-temporal spikes (BCECTS).
No full textA robust seemingly unrelated regressions for row-wise and cell-wise contamination
No full textThe Seemingly Unrelated Regressions (SUR) model is a wide used estimation procedure in econometrics, insurance and finance, where very often, the regression model contains more than one equation. Unknown parameters, regression coefficients and covariances among the errors terms, are estimated using algorithms based on Generalized Least Squares or Maximum Likelihood, and the method, as a whole, is very sensitive to outliers. To overcome this problem M-estimators and S-estimators are proposed in the literature together with fast algorithms. However, these procedures are only able to cope with row-wise outliers in the error terms, while their performance becomes very poor in the presence of cell-wise outliers and as the number of equations increases. A new robust approach is proposed which is able to perform well under both contamination types as well as it is fast to compute. Illustrations based on Monte Carlo simulations and a real data example are provided
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