Reformulation semi-lisse appliquée au problème de complémentarité

Ce mémoire fait une revue des notions élémentaires concernant le problème de complé- mentarité. On y fait aussi un survol des principales méthodes connues pour le résoudre. Plus précisément, on s’intéresse à la méthode de Newton semi-lisse. Un article proposant une légère modification à cette méthode est présenté. Cette nouvelle méthode compétitive est démontrée convergente. Un second article traitant de la complexité itérative de la méthode de Harker et Pang est aussi introduit

Itérations d’un processus avec mémoire défini par l’application tente

Dans cet article, on étudie le processus avec mémoire défini par : [chi]n+1 = [florin]([alpha]xn + (1 − [alpha])[chi]n−1) où [florin] est l’application tente, 0 < [alpha] < 1 et [chi]i ∈ [0,1]. On voit que dans le cas [alpha] = 1/2, tous les points sont de période trois ou le seront éventuellement sauf pour deux points fixes. On termine en présentant des conjectures énoncées par P. Góra dont certaines qui ne sont pas prouvées actuellement pour [alpha (n'est) pas égal à] 1/2. [Symboles non conformes

Algorithmes de Newton-min polyédriques pour les problèmes de complémentarité

The semismooth Newton method is a very efficient approach for computing a zero of a large class of nonsmooth equations. When the initial iterate is sufficiently close to a regular zero and the function is strongly semismooth, the generated sequence converges quadratically to that zero, while the iteration only requires to solve a linear system.If the first iterate is far away from a zero, however, it is difficult to force its convergence using linesearch or trust regions because a semismooth Newton direction may not be a descent direction of the associated least-square merit function, unlike when the function is differentiable. We explore this question in the particular case of a nonsmooth equation reformulation of the nonlinear complementarity problem, using the minimum function. We propose a globally convergent algorithm using a modification of a semismooth Newton direction that makes it a descent direction of the least-square function. Instead of requiring that the direction satisfies a linear system, it must be a feasible point of a convex polyhedron; hence, it can be computed in polynomial time. This polyhedron is defined by the often very few inequalities, obtained by linearizing pairs of functions that have close negative values at the current iterate; hence, somehow, the algorithm feels the proximity of a "bad kink" of the minimum function and acts accordingly.In order to avoid as often as possible the extra cost of having to find a feasible point of a polyhedron, a hybrid algorithm is also proposed, in which the Newton-min direction is accepted if a sufficient-descent-like criterion is satisfied, which is often the case in practice. Global convergence to regular points is proved; the notion of regularity is associated with the algorithm and is analysed with care.L'algorithme de Newton semi-lisse est très efficace pour calculer un zéro d'une large classe d'équations non lisses. Lorsque le premier itéré est suffisamment proche d'un zéro régulier et si la fonction est fortement semi-lisse, la suite générée converge quadratiquement vers ce zéro, alors que l'itération ne requière que la résolution d'un système linéaire.Cependant, si le premier itéré est éloigné d'un zéro, il est difficile de forcer sa convergence par recherche linéaire ou régions de confiance, parce que la direction de Newton semi-lisse n'est pas nécessairement une direction de descente de la fonction de moindres-carrés associée, contrairement au cas où la fonction à annuler est différentiable. Nous explorons cette question dans le cas particulier d'une reformulation par équation non lisse du problème de complémentarité non linéaire, en utilisant la fonction minimum. Nous proposons un algorithme globalement convergent, utilisant une direction de Newton semi-lisse modifiée, qui est de descente pour la fonction de moindres-carrés. Au lieu de requérir la satisfaction d'un système linéaire, cette direction doit être intérieur à un polyèdre convexe, ce qui peut se calculer en temps polynomial. Ce polyèdre est défini par souvent très peu d'inégalités, obtenus en linéarisant des couples de fonctions qui ont des valeurs négatives proches à l'itéré courant; donc, d'une certaine manière, l'algorithme est capable d'estimer la proximité des "mauvais plis" de la fonction minimum et d'agir en conséquence.De manière à éviter au si souvent que possible le coût supplémentaire lié au calcul d'un point admissible de polyèdre, un algorithme hybride est également proposé, dans lequel la direction de Newton-min est acceptée si un critère de décroissance suffisante est vérifié, ce qui est souvent le cas en pratique. La convergence globale vers des points régulier est démontrée; la notion de régularité est associée à l'algorithme et est analysée avec soin

AXES at TRECVid 2011

The AXES project participated in the interactive known-item search task (KIS) and the interactive instance search task (INS) for TRECVid 2011. We used the same system architecture and a nearly identical user interface for both the KIS and INS tasks. Both systems made use of text search on ASR, visual concept detectors, and visual similarity search. The user experiments were carried out with media professionals and media students at the Netherlands Institute for Sound and Vision, with media professionals performing the KIS task and media students participating in the INS task. This paper describes the results and findings of our experiments

AXES at TRECVid 2011

Abstract The AXES project participated in the interactive known-item search task (KIS) and the interactive instance search task (INS) for TRECVid 2011. We used the same system architecture and a nearly identical user interface for both the KIS and INS tasks. Both systems made use of text search on ASR, visual concept detectors, and visual similarity search. The user experiments were carried out with media professionals and media students at the Netherlands Institute for Sound and Vision, with media professionals performing the KIS task and media students participating in the INS task. This paper describes the results and findings of our experiments

Amyloid and tau pathology associations with personality traits, neuropsychiatric symptoms, and cognitive lifestyle in the preclinical phases of sporadic and autosomal dominant Alzheimer’s disease

Background Major prevention trials for Alzheimer’s disease (AD) are now focusing on multidomain lifestyle interventions. However, the exact combination of behavioral factors related to AD pathology remains unclear. In 2 cohorts of cognitively unimpaired individuals at risk of AD, we examined which combinations of personality traits, neuropsychiatric symptoms, and cognitive lifestyle (years of education or lifetime cognitive activity) related to the pathological hallmarks of AD, amyloid-β, and tau deposits. Methods A total of 115 older adults with a parental or multiple-sibling family history of sporadic AD (PREVENT-AD [PRe-symptomatic EValuation of Experimental or Novel Treatments for AD] cohort) underwent amyloid and tau positron emission tomography and answered several questionnaires related to behavioral attributes. Separately, we studied 117 mutation carriers from the DIAN (Dominant Inherited Alzheimer Network) study group cohort with amyloid positron emission tomography and behavioral data. Using partial least squares analysis, we identified latent variables relating amyloid or tau pathology with combinations of personality traits, neuropsychiatric symptoms, and cognitive lifestyle. Results In PREVENT-AD, lower neuroticism, neuropsychiatric burden, and higher education were associated with less amyloid deposition (p = .014). Lower neuroticism and neuropsychiatric features, along with higher measures of openness and extraversion, were related to less tau deposition (p = .006). In DIAN, lower neuropsychiatric burden and higher education were also associated with less amyloid (p = .005). The combination of these factors accounted for up to 14% of AD pathology. Conclusions In the preclinical phase of both sporadic and autosomal dominant AD, multiple behavioral features were associated with AD pathology. These results may suggest potential pathways by which multidomain interventions might help delay AD onset or progression

Simple scoring system to predict in-hospital mortality after surgery for infective endocarditis

BACKGROUND: Aspecific scoring systems are used to predict the risk of death postsurgery in patients with infective endocarditis (IE). The purpose of the present study was both to analyze the risk factors for in-hospital death, which complicates surgery for IE, and to create a mortality risk score based on the results of this analysis. METHODS AND RESULTS: Outcomes of 361 consecutive patients (mean age, 59.1\ub115.4 years) who had undergone surgery for IE in 8 European centers of cardiac surgery were recorded prospectively, and a risk factor analysis (multivariable logistic regression) for in-hospital death was performed. The discriminatory power of a new predictive scoring system was assessed with the receiver operating characteristic curve analysis. Score validation procedures were carried out. Fifty-six (15.5%) patients died postsurgery. BMI >27 kg/m2 (odds ratio [OR], 1.79; P=0.049), estimated glomerular filtration rate 55 mm Hg (OR, 1.78; P=0.032), and critical state (OR, 2.37; P=0.017) were independent predictors of in-hospital death. A scoring system was devised to predict in-hospital death postsurgery for IE (area under the receiver operating characteristic curve, 0.780; 95% CI, 0.734-0.822). The score performed better than 5 of 6 scoring systems for in-hospital death after cardiac surgery that were considered. CONCLUSIONS: A simple scoring system based on risk factors for in-hospital death was specifically created to predict mortality risk postsurgery in patients with IE

Reformulation semi-lisse appliquée au problème de complémentarité

Ce mémoire fait une revue des notions élémentaires concernant le problème de complé- mentarité. On y fait aussi un survol des principales méthodes connues pour le résoudre. Plus précisément, on s’intéresse à la méthode de Newton semi-lisse. Un article proposant une légère modification à cette méthode est présenté. Cette nouvelle méthode compétitive est démontrée convergente. Un second article traitant de la complexité itérative de la méthode de Harker et Pang est aussi introduit