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Simon, Thomas. "Produit Beta-Gamma et régularité du signe." Studia Scientiarum Mathematicarum Hungarica 51, no. 4 (2014): 429–53. http://dx.doi.org/10.1556/sscmath.51.2014.4.1280.
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On étudie la positivité complète du noyau de convolution multiplicatif T associé au produit de deux variables aléatoires indépendantes B(a, b) et Γ(c). Ce noyau T est complétement positif d’ordre infini si b ∈ ℕ* ou si d = a + b − c ∈ ℕ. Dans les autres cas la régularité du signe de T a toujours un ordre fini, qui est ici calculé. Plus précisément, pour tout n ≧ 1 on montre que T est complètement positif d’ordre n + 1 si et seulement si (d, b) est situé au dessus d’un certain escalier \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{bbm} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\mathcal{E}_n$$ \end{document} dessiné dans le demi-plan supérieur. Cet escalier caractérise aussi la constance du signe de plusieurs déterminants associés á la fonction hypergéométrique confluente de seconde espèce.
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Vincent, Stephanie, Richard Planells, Catherine Defoort, et al. "Genetic polymorphisms and lipoprotein responses to diets." Proceedings of the Nutrition Society 61, no. 4 (2002): 427–34. http://dx.doi.org/10.1079/pns2002177.
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RésuméAlors que l'alimentation de l'homme a beaucoup évoluée depuis ses origines, le génome humain est resté très stable. Pourtant, de très nombreux gènes ont des polymorphismes connus. En fait, on considère maintenant que les principales pathologies humaines (maladies cardiovasculaires, diabète, obésité et cancers) résultent d'une interaction entre des facteurs de succeptibilité génétique et des facteurs de l'environement, dont l'alimentation. Dans le domaine du métabolisme des lipoprotéines et des maladies cardiovasculaires, des polymorphimes de plusieurs gènes ont été identifiés et associés aux niveaux des paramètres lipidiques ou aà des réponses variables aux régimes, comme pour les apoprotéines (apo) E, B, A-IV et C-III, le LDL récepteur, la protéine microsomiale de transport (MTP), la protéine de liason des acides gras (FABP), la protéine de transport des esters de cholésterol (CETP), la lipoprotéine lipase ou la lipase hepatique. Nous réalisons une étude d'intervention à Marseille dans le but d'étudier l'interaction
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Wright, John, Anne Lecours, Claude Duchesne, and Stéphane Sabourin. "Le profil psychosocial de couples consultant à une clinique de fertilité." Santé mentale au Québec 15, no. 2 (2006): 89–106. http://dx.doi.org/10.7202/031564ar.
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Résumé L'objectif de la présente étude est de tracer le profil psychosocial de couples consultant à une clinique de fertilité. Plus spécifiquement, il s'agit (a) de comparer le statut psychosocial de sujets consultant à une clinique de fertilité à celui de sujets normaux ou d'individus souffrant de problèmes psychologiques, (b) de déterminer s'il existe des différences de profil entre les hommes et les femmes consultant pour un problème de fertilité" et (c) d'évaluer s'il est possible de prédire la nature du profil psychosocial des sujets à partir de diverses caractéristiques sociodémographiques et médicales. L'échantillon se compose de 30 couples qui consultent un spécialiste de la clinique de fertilité d'un hôpital de la région de Montréal. L'analyse des résultats démontre que le profil psychosocial des sujets consultant à une clinique de fertilité se situe à mi-chemin entre celui de sujets normaux et celui d'individus souffrant de problèmes psychologiques. Le statut psychologique des hommes et des femmes consultant à une clinique de fertilité diffère sur trois variables: dépression, estime de soi et stress. Enfin, les analyses de régression multiple ont permis d'identifier plusieurs caractéristiques médicales reliées à l'ampleur des difficultés psychosociales rapportées par les sujets infertiles. Le profil psychosocial de couples consultant à une clinique de fertilité
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Sana, Madiha, and Muhammad Mustahsan. "Finite Element Approximation of Optimal Control Problem with Weighted Extended B-Splines." Mathematics 7, no. 5 (2019): 452. http://dx.doi.org/10.3390/math7050452.
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In this research article, an optimal control problem (OCP) with boundary observations is approximated using finite element method (FEM) with weighted extended B-splines (WEB-splines) as basis functions. This type of OCP has a distinct aspect that the boundary observations are outward normal derivatives of state variables, which decrease the regularity of solution. A meshless FEM is proposed using WEB-splines, defined on the usual grid over the domain, R 2 . The weighted extended B-spline method (WEB method) absorbs the regularity problem as the degree of the B-splines is increased. Convergence analysis is also performed by some numerical examples.
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YEN, JOHN, REZA LANGARI, and LIANG WANG. "PRINCIPAL COMPONENTS, B-SPLINES, AND FUZZY SYSTEM REDUCTION." International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 04, no. 06 (1996): 561–72. http://dx.doi.org/10.1142/s0218488596000317.
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This paper proposes to use the method of principal components to reduce the dimensionality of input space and the B-splines to represent the membership functions of input variables. A model reduction strategy, which is based on Johansen’s optimality theorem, also suggested. The utility of this approach is illustrated using a fuzzy system modeling example.
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Rahayu, Putri Indi, and Pardomuan Robinson Sihombing. "PENERAPAN REGRESI NONPARAMETRIK KERNEL DAN SPLINE DALAM MEMODELKAN RETURN ON ASSET (ROA) BANK SYARIAH DI INDONESIA." JURNAL MATEMATIKA MURNI DAN TERAPAN EPSILON 14, no. 2 (2021): 115. http://dx.doi.org/10.20527/epsilon.v14i2.2968.
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Sharia Bank Return On Assets (ROA) modeling in Indonesia in 2018 aims to analyze the relationship pattern of Retturn On Assets (ROA) with interest rates. The analysis that is often used for modeling is regression analysis. Regression analysis is divided into two, namely parametric and nonparametric. The most commonly used nonparametric regression methods are kernel and spline regression. In this study, the nonparametric regression used was kernel regression with the Nadaraya-Watson (NWE) estimator and Local Polynomial (LPE) estimator, while the spline regression was smoothing spline and B-splines. The fitting curve results show that the best model is the B-splines regression model with a degree of 3 and the number of knots 5. This is because the B-splines regression model has a smooth curve and more closely follows the distribution of data compared to other regression curves. The B-splines regression model has a determination coefficient of R ^ 2 of 74.92%,%, meaning that the amount of variation in the ROA variable described by the B-splines regression model is 74.92%, while the remaining 25.8% is explained by other variables not included in the model.
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Gu, Sheng Li, and Fu Ming Wang. "Evolutionary Structural Shape Optimization Based on Adaptive FEM and Boundary Representation of B-Spline." Advanced Materials Research 562-564 (August 2012): 1575–82. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.1575.
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This paper presents a structural shape optimization algorithm based on the evolutionary structural optimization (ESO) method in conjunction with element error estimate and adaptive FEM. B-splines are used to describe the boundary of the design domain; the shape of these B-splines is governed by a set of master nodes which can be taken as the design variables. The optimal shape of the design boundary with constant stress is achieved iteratively by the movement and update of the position of the master nodes based on nodal stress leveling. The result quality, in terms of accuracy and efficiency, is tested and discussed with an analytical solution.
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Zhang, Dai Yuan. "An Improved Algorithm Using B-Spline Weight Functions for Training Feedforward Neural Networks." Applied Mechanics and Materials 278-280 (January 2013): 1301–4. http://dx.doi.org/10.4028/www.scientific.net/amm.278-280.1301.
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An improved algorithm using B-splines as weight functions for training neural networks is proposed. There is no need for training neural networks or solving linear equations. The most important advantage is that we can get the forms of weight functions by the given patterns directly. Each of weight function is a one-variable function and takes one associated input point (input neuron) as its argument. The form of each weight function is a linear combination of some B-splines defined on the sets of given input variables (input knots or input patterns), whose coefficients are associated with the given output patterns. Some examples are presented to illustrate good performance of the new algorithm.
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Faezian, Ghassem, Ahmad Darabi, and Nader Sargolzaei. "Customized shape optimization of switched reluctance motor using B-Splines." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 40, no. 3 (2021): 402–13. http://dx.doi.org/10.1108/compel-07-2020-0250.
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Purpose This study aims to design the rotor geometry of switched reluctance motor (SRM) in a completely flexible way. In the proposed method, there is no default geometry for the rotor. The initial geometry of the rotor can start from a circle or any other shape and depending on the required performance takes the final shape during the optimal design. In this way, the best performance, possible with geometric design, can be achieved. Design/methodology/approach The rotor boundary of a 4/2 SRM is defined by a few B-splines. Some control points are located around the rotor and changing their locations causes customized changes in the rotor boundary. Locations of these points are defined as design variables. A 2-D finite element analysis using MATLAB/PDE is applied to the SRM model and sensitivity analysis is used to optimization design by means of minimizing of objective function. Findings The proposed method has many more capabilities for matching different objective functions. For the suggested objective function, while the conventional rotor torque profile difference with the desired torque profile reaches 40%, this difference for B-spline rotor is about 17%. Experimental results from a prototype motor have a close agreement with analysis results. Originality/value The B-splines have been used to design machines and electromagnetic devices. However, this method is used for the first time in design of the whole rotor of a SRM.
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Lara-Ramirez, Jose Edgar, Carlos Hugo Garcia-Capulin, Maria de Jesus Estudillo-Ayala, Juan Gabriel Avina-Cervantes, Raul Enrique Sanchez-Yanez, and Horacio Rostro-Gonzalez. "Parallel Hierarchical Genetic Algorithm for Scattered Data Fitting through B-Splines." Applied Sciences 9, no. 11 (2019): 2336. http://dx.doi.org/10.3390/app9112336.
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Curve fitting to unorganized data points is a very challenging problem that arises in a wide variety of scientific and engineering applications. Given a set of scattered and noisy data points, the goal is to construct a curve that corresponds to the best estimate of the unknown underlying relationship between two variables. Although many papers have addressed the problem, this remains very challenging. In this paper we propose to solve the curve fitting problem to noisy scattered data using a parallel hierarchical genetic algorithm and B-splines. We use a novel hierarchical structure to represent both the model structure and the model parameters. The best B-spline model is searched using bi-objective fitness function. As a result, our method determines the number and locations of the knots, and the B-spline coefficients simultaneously and automatically. In addition, to accelerate the estimation of B-spline parameters the algorithm is implemented with two levels of parallelism, taking advantages of the new hardware platforms. Finally, to validate our approach, we fitted curves from scattered noisy points and results were compared through numerical simulations with several methods, which are widely used in fitting tasks. Results show a better performance on the reference methods.
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Gomes, Lorrayne, Milena Vieira Lima, Jeferson Corrêa Ribeiro, et al. "FUNÇÕES SPLINES APLICADAS EM DADOS DE CRESCIMENTO." COLLOQUIUM AGRARIAE 13, Especial 2 (2017): 222–34. http://dx.doi.org/10.5747/ca.2017.v13.nesp2.000229.
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In animal breeding, new methodologies can be applied in statistical analysis to improve the genetic evaluation and, for this reason, they have been the subject in several studies. In the last years, several research works have intended the model development with more adjustable functions to the distinct variables. A set of functions known as Spline functions has called the attention of researches. Then, the purpose of this review is to discuss the use of Spline functions that are applied to growth data in animal breeding. Splines are segmented regression functions that are united by points known as joint points and have the ability to improve the curvature of models and, therefore, the function adjustment. These functions have interesting properties such as the interpolatory nature, less multicolinearity problems, parameter linearity and the ability of increasing the approximation domain, all of which provide estimates in a wide range of possible values. There are three types of Spline functions: natural spline functions, smoothing spline 223 Colloquium Agrariae, vol. 13, n. Especial 2, Jan–Jun, 2017, p. 222-234. ISSN: 1809-8215. DOI: 10.5747/ca.2017.v13.nesp2.000229 functions or nonparametric regression and B-splines functions. These latter functions are more applied to animal breeding, mainly as alternatives to random regression models (RRM) that use the Legendre polynomials. The matrices formed by RRMs with the use of B-spline functions or Legendre polynomials are more scarce and easier to be inverted. Then, the use of Spline functions has been more intensified in the last years because studies have had the purpose of improving the adjustment with less model parameters in functions. New studies will allow improving the methodology and finding out new applications to the Spline functions.
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Baltanás, Angel, Wolfgang Brauneis, Dan L. Danielopol, and Johann Linhart. "Morphometric Methods for Applied Ostracodology: Tools for Outline Analysis of Nonmarine Ostracodes." Paleontological Society Papers 9 (November 2003): 101–18. http://dx.doi.org/10.1017/s1089332600002175.
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Morphometric techniques for the analysis of shape change in organisms have experienced a noteworthy development in the last decade. But despite the significant contributions that ostracodologists made to the field, their use in standard ostracode research is far from common. This contribution stresses the usefulness of morphometric methods to describe ostracode valve outlines and to summarize shape changes cued by environmental factors. Focus is on nonmarine ostracodes which are generally poorly ornamented so that their carapaces offer few landmarks for characterization of morphological change. Out of several alternatives three techniques for shape analysis are applied here: the B-splines method for approximative description of ostracode contours, Elliptic Fourier Analysis (EFA) and a Generalized (Resistant Fit) Procrustes Analysis. B-splines method is presented here for the first time within a biological framework and both its mathematical basis and practical usage are discussed. Additionally a computer program, Morphomatica, developed for performing B-splines analyses of ostracod outlines is briefly documented.Three case studies exemplify here how morphometric analysis might help either to detect environmental influences in ostracode shape or to show how morphological diversity of ostracode valve reflects environmental change. First, morphological variability within a clonal lineage of Heterocypris barbara (Gauthier and Brehm) is shown to be related to environmental variables (mainly temperature) when raised under controlled conditions in the lab. Second, carapace variability at the population level is explored in a widely distributed species (Limnocythere inopinata Baird) sampled from distant localities. Morphometric analyses illustrate how such variability is not related to geographic distance but to environmental conditions. Finally, patterns of temporal change in morphological diversity of a widely distributed ostracode group, the Candoninae, are elucidated by using the B-splines method combined with multivariate statistical analysis.It is concluded that morphometric methods deserve to be included in the methodological toolbox of practicing ostracodologists as they can provide useful information in ecological and paleoecological research.
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LEE, H. W. J., K. L. TEO, W. R. LEE, and S. WANG. "CONSTRUCTION OF SUBOPTIMAL FEEDBACK CONTROL FOR CHAOTIC SYSTEMS USING B-SPLINES WITH OPTIMALLY CHOSEN KNOT POINTS." International Journal of Bifurcation and Chaos 11, no. 09 (2001): 2375–87. http://dx.doi.org/10.1142/s0218127401003498.
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In this paper we consider a class of optimal control problem involving a chaotic system, where all admissible controls are required to satisfy small boundedness constraints. A numerical approach is developed to seek for an optimal feedback control for the optimal control problem. In this approach, the state space is partitioned into subregions, and the controller is approximated by a linear combination of a modified third order B-spline basis functions. The partition points are also taken as decision variables in this formulation. An algorithm based on this approach is proposed. To show the effectiveness of the proposed method, a control problem involving the Lorenz system is solved by the proposed approach. The numerical results demonstrate that the method is efficient in the construction of a robust, near-optimal control.
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Su, Liyun, Tianshun Yan, Yanyong Zhao, and Fenglan Li. "Local Polynomial Regression Solution for Partial Differential Equations with Initial and Boundary Values." Discrete Dynamics in Nature and Society 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/201678.
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Local polynomial regression (LPR) is applied to solve the partial differential equations (PDEs). Usually, the solutions of the problems are separation of variables and eigenfunction expansion methods, so we are rarely able to find analytical solutions. Consequently, we must try to find numerical solutions. In this paper, two test problems are considered for the numerical illustration of the method. Comparisons are made between the exact solutions and the results of the LPR. The results of applying this theory to the PDEs reveal that LPR method possesses very high accuracy, adaptability, and efficiency; more importantly, numerical illustrations indicate that the new method is much more efficient than B-splines and AGE methods derived for the same purpose.
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Tran, Han Duc, and Binh Huy Nguyen. "An isogeometric SGBEM for crack problems of magneto-electro-elastic materials." Vietnam Journal of Mechanics 39, no. 2 (2017): 135–47. http://dx.doi.org/10.15625/0866-7136/8691.
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The isogeometric symmetric Galerkin boundary element method is applied for the analysis of crack problems in two-dimensional magneto-electro-elastic domains. In this method, the field variables of the governing integral equations as well as the geometry of the problems are approximated using non-uniform rational B-splines (NURBS) basis functions. The key advantage of this method is that the isogeometric analysis and boundary element method deal only with the boundary of the domain. To verify the accuracy of the proposed method, numerical examples for crack problems in infinite and finite domains are examined. It is observed that the computed generalized stress intensity factors obtained by the proposed method agree well with the exact solutions and other references.
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Bélanger, Marc. "Les Chambres de commerce." Recherches sociographiques 9, no. 1-2 (2005): 85–103. http://dx.doi.org/10.7202/055394ar.
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L'étude qui suit découle d'une recherche entreprise en 1965 sur les chambres de commerce. Elle fait suite à l'intérêt que suscita chez l'auteur la communication de Jean-Charles Falardeau sur L'origine et L'ascension des hommes d'affaires dans la société canadienne-française au Ve Colloque de l'Association internationale des sociologues de langue française tenu, au lac Beauport, en 1964. Analysant l'accès des hommes d'affaires au statut de catégorie dirigeante, Jean-Charles Falardeau soulignait l'importance des chambres de commerce en tant que laboratoires de leurs attitudes et de leurs idéologies et en tant que cadres professionnels d'organisation. Bien que l'auteur partage l'opinion exprimée par Jean-Charles Falardeau quant à l'intérêt que présenterait une histoire de ce mouvement dans le Québec, cet exposé n'a rien d'un essai historique. Son propos est tout autre; on sait que traditionnellement les chambres se sont donné comme objectif de «favoriser et d'améliorer le commerce et le bien-être économique, civique et social» de leur district. À un moment où le gouvernement cherche à mettre sur pied des conseils économiques régionaux et où se poursuivent des expériences comme celle du B. A. E. Q., il n'est certes pas sans intérêt d'étudier les réactions des chambres de commerce. Celles-ci sont généralement reconnues comme des organismes représentant les hommes d'affaires. Par ailleurs, il est vrai que, dans plusieurs régions, elles ont présidé à la formation de conseils économiques. Il y a néanmoins lieu de se demander si l'hypothèse de Jean-Charles Falardeau est valable pour l'ensemble des chambres de commerce; nous serions portés, quant à nous, à faire l'hypothèse que certaines chambres, épousant les tensions socio-économiques du milieu, s'apparentent à des coopératives de développement plus qu'à des groupes de pression. Au reste, Jean-Charles Falardeau n'écarte pas cette possibilité. Il reconnaît, à la suite de Fernand Ouellet, que la Chambre de Québec, au gré d'une participation accrue des francophones québécois, en vint à se préoccuper essentiellement d'intérêts proprement locaux et régionaux. En effet, devant contrer les difficultés que posait l'évolution économique du milieu, elle entreprit de grossir ses effectifs en élargissant ses critères d'admission. D'organisme de défense et de promotion économique, elle se transforma de la sorte en organisme de promotion communautaire. Nos recherches nous ont conduits à poser le problème de la cohérence dans la diversité au sein d'une organisation regroupant environ 270 chambres de commerce constituant 32 régionales. Toutefois, dans le cadre de cet exposé, nous nous appliquerons plutôt a faire ressortir une certaine correspondance entre la diversité de l'action des chambres et l'axe de développement rural-urbain. À cette fin, nous procéderons en trois étapes. Dans une première, appliquant au Québec un modèle regroupant les facteurs de différenciation de l'action, nous tenterons de formuler quelques hypothèses relatives à l'interrelation entre le niveau de développement de divers milieux et le type d'action caractéristique des chambres dans ces milieux. L'élaboration d'une double typologie et les opinions recueillies auprès de militants permettront de contrôler la validité de ces hypothèses. Dans une seconde étape, nous limitant à quelques variables, nous montrerons en quoi se différencient les chambres des milieux hautement urbanisés et celles des autres milieux. Enfin, une troisième étape permettra de formuler quelques hypothèses quant aux problèmes que pose la participation des organismes appartenant à une même Fédération mais œuvrant dans des milieux dont le niveau d'urbanisation est très inégal.
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Gacono, Carl B., and J. Reid Meloy. "Rorschach Research and the Psychodiagnosis of Antisocial and Psychopathic Personalities." Rorschachiana 22, no. 1 (1997): 130–48. http://dx.doi.org/10.1027/1192-5604.22.1.130.
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Depuis des décennies, les cliniciens se sont intéressés à l’utilisation du Rorschach dans le diagnostic de la psychopathie. Pourtant, c’est seulement depuis une quinzaine d’années que ce type d’investigation est devenue vraiment pertinente à travers des recherches valides et fiables, grâce aux progrès réalisés dans l’évaluation de la psychopathie et la technologie du Rorschach. En 1984, armés de cette “nouvelle” technologie, nous avons entamé nos recherches sur les personnalités antisociales et psychopathiques. Utilisant le Trouble de la Personnalité Antisociale (TPA) et la Psychopathie comme mesures indépendantes, et les variables Rorschach comme mesures dépendantes, nous avons tenté de comprendre le continuum antisocial d’un point de vue psychodynamique et développemental, tout en tenant compte des aspects psychobiologiques, psychodynamiques et de style cognitif. Nous avons posé plusieurs questions: le Rorschach peut-il “établir la carte” du fonctionnement de la personnalité et de la structure intrapsychique des individus présentant des Troubles de la Conduite (TC) et des TPA, et est-ce que cette “carte” Rorschach validerait de manière empirique les modèles théoriques tels que la pathologie de l’attachement, l’absence d’anxiété, l’agressivité, et l’aspect grandiose qui sont associés à la psychopathie? Compte tenu des différences parmi les délinquants, le Rorschach saurait-il discriminer entre groupes TC et TPA d’après leurs niveaux de pathologie? Et encore, le Rorschach pouvait-il discriminer entre les TPA et les autres troubles de personnalité de Type B? Nous avons obtenu un haut degré de concordance entre les données empiriques et la théorie. Nous avons trouvé des déficits de l’attachement (T = 0) chez 88% des troubles de comportement chez les enfants, 86% des adolescents TC, 71% des femmes TCA, 79% des hommes TCA, 91% des hommes psychopathes et 70% des hommes TCA schizophrènes. Les résultats du Y sont congruents avec le passage à l’acte considéré comme une défense contre l’angoisse dans les groupes d’enfants et adolescents TC. Contrairement aux enfants non consultants et aux adultes psychopathes, les enfants TC s’évaluent de manière négative lorsqu’ils se comparent aux autres (EGO < 0,33 = 72%). Les adolescents TC diffèrent aussi des adolescents dysthymiques et non consultants: ils montrent moins de capacité d’attachement, sont moins anxieux, et manifestent moins d’intérêt pour les autres en tant que des objets entiers et humains réels. Les adolescents TC psychopathes présentent les même déficits. Les psychopathes TCA adultes de sexe masculin montrent moins de capacité d’attachement, éprouve moins d’anxiété et sont plus grandioses que les TCA non psychopathes. Les psychopathes se montrent tout aussi grandiose que les hommes aux Troubles de Personnalité Narcissique non hospitalisés, tout aussi “limites” que les hommes aux Troubles de la Personnalité Limite, cependant qu’ils sont moins anxieux et moins attachés. Les femmes adultes antisociales, bien qu’elles manifestent plus d’affects dysphoriques que les hommes TCA psychopathes, montrent moins de capacité d’attachement et d’affect que les femmes aux Troubles de la Personnalité Limite. L’expression de l’aspect grandiose diffère entre hommes psychopathes, enfants TC et femmes TCA, ce qui suggère des différences dans les niveaux de développement et selon le sexe. Bien que le Rorschach ne doive pas être utilisé de manière isolée à des fins de diagnostic psychologique, nos premiers résultats montrent tout l’intérêt qu’il présente pour comprendre la psychologie des personnalités antisociales et psychopathiques. Nos travaux sur le Rorschach constituent aussi un modèle pour l’étude d’autres troubles de personnalité.
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Abdessalem, Jarraya, Dammak Fakhreddine, Abid Said, and Haddar Mohamed. "Shape optimization for a hyperelastic axisymmetric structure." Journal of Engineering, Design and Technology 12, no. 2 (2014): 177–94. http://dx.doi.org/10.1108/jedt-10-2011-0072.
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Purpose – This paper aims to describe a shape optimization for hyperelastic axisymmetric structure with an exact sensitivity method. Design/methodology/approach – The whole shape optimization process is carried out by integrating a closed geometric shape in the real space R2 with boundaries defined by B-splines curves. An exact sensitivity analysis and a mathematical programming method (SQP: Sequential Quadratic Programming) are implemented. The design variables are the control points' coordinates which minimize the Von-Mises criteria, with a constraint that the total material volume of the structure remains constant. The feasibility of the proposed methods is carried out by two numerical examples. Results show that the exact Jacobian has an important computing time reduction. Findings – Numerical examples are presented to illustrate its performance. Originality/value – In this work, the sensitivity performance is computed using two numerical methods: the efficient finite difference scheme and the exact Jacobian.
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Heinrich, Martin, and Rüdiger Schwarze. "Genetic Algorithm Optimization of the Volute Shape of a Centrifugal Compressor." International Journal of Rotating Machinery 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/4849025.
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A numerical model for the genetic optimization of the volute of a centrifugal compressor for light commercial vehicles is presented. The volute cross-sectional shape is represented by cubic B-splines and its control points are used as design variables. The goal of the global optimization is to maximize the average compressor isentropic efficiency and total pressure ratio at design speed and four operating points. The numerical model consists of a density-based solver in combination with the SSTk-ωturbulence model with rotation/curvature correction and the multiple reference frame approach. The initial validation shows a good agreement between the numerical model and test bench measurements. As a result of the optimization, the average total pressure rise and efficiency are increased by over1.0%compared to the initial designs of the optimization, while the maximum efficiency rise is nearly 2.5% atm˙corr=0.19 kg/s.
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Erfort, Gareth, Theodor Willem Von Backström, and Gerhard Venter. "Numerical optimisation of a small-scale wind turbine through the use of surrogate modelling." Journal of Energy in Southern Africa 28, no. 3 (2017): 79. http://dx.doi.org/10.17159/2413-3051/2017/v28i3a2368.
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Wind conditions in South Africa are suitable for small-scale wind turbines, with wind speeds below 7 m.s−1. This investigation is about a methodology to optimise a full wind turbine using a surrogate model. A previously optimised turbine was further optimised over a range of wind speeds in terms of a new parameterisation methodology for the aerodynamic profile of the turbine blades, using non-uniform rational B-splines to encompass a wide range of possible shapes. The optimisation process used a genetic algorithm to evaluate an input vector of 61 variables, which fully described the geometry, wind conditions and rotational speed of the turbine. The optimal performance was assessed according to a weighted coefficient of power, which rated the turbine blade’s ability to extract power from the available wind stream. This methodology was validated using XFOIL to assess the final solution. The results showed that the surrogate model was successful in providing an optimised solution and, with further refinement, could increase the coefficient of power obtained.
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Shah, D. A., E. D. De Wolf, P. A. Paul, and L. V. Madden. "Functional Data Analysis of Weather Variables Linked to Fusarium Head Blight Epidemics in the United States." Phytopathology® 109, no. 1 (2019): 96–110. http://dx.doi.org/10.1094/phyto-11-17-0386-r.
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In past efforts, input weather variables for Fusarium head blight (FHB) prediction models in the United States were identified after following some version of the window-pane algorithm, which discretizes a continuous weather time series into fixed-length windows before searching for summary variables associated with FHB risk. Functional data analysis, on the other hand, reconstructs the assumed continuous process (represented by a series of recorded weather data) by using smoothing functions, and is an alternative way of working with time series data with respect to FHB risk. Our objective was to functionally model weather-based time series data linked to 865 observations of FHB (covering 16 states and 31 years in total), classified as epidemics (FHB disease index ≥ 10%) and nonepidemics (FHB disease index < 10%). Altogether, 94 different time series variables were modeled by penalized cubic B-splines for the smoothing function, from 120 days pre-anthesis to 20 days post-anthesis. Functional mean curves, standard deviations, and first derivatives were plotted for FHB epidemics relative to nonepidemics. Function-on-scalar regressions assessed the temporal trends of the magnitude and significance of the mean difference between functionally represented weather time series associated with FHB epidemics and nonepidemics. The mean functional weather-variable curve for epidemics started to deviate, in general, from that for nonepidemics as early as 40 days pre-anthesis for several weather variables. The greatest deviations were often near anthesis, the period of maximum susceptibility of wheat to FHB-causing fungi. The most consistent separations between the mean functional curves were seen with the daily averages of moisture-related variables (such as average relative humidity) and with variables summarizing the daily variation in temperature (as opposed to the daily mean). Functional data analysis was useful for extending our knowledge of relationships between weather variables and FHB epidemics.
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Weaver, Paul M., Zhang Ming Wu, and Gangadharan Raju. "Optimisation of Variable Stiffness Plates." Applied Mechanics and Materials 828 (March 2016): 27–48. http://dx.doi.org/10.4028/www.scientific.net/amm.828.27.
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Variable angle tow (VAT) describes fibres in a composite lamina that have been steered curvilinearly. In so doing, substantially enlarged freedom for stiffness tailoring of composite laminates is enabled. VAT composite structures have been shown to have improved buckling and postbuckling load carrying capability when compared to straight fibre composites. However, their structural analysis and optimal design is more computationally expensive due to the exponential increase in number of variables associated with spatially varying planar fibre orientations in addition to stacking sequence considerations. In this work, an efficient two-level optim isation framework using lamination parameters as design variables has been enhanced and general ised to the design of VAT plates. Explicit stiffness matrices are found in terms of component material invariants and lamination parameters. The convex hull property of B-splines is exploited to ensure point-wise feasibility of lamination parameters. In addition, a small set of explicit closed-form expressions is used to define the feasible region of two in-plane and two out-of-plane lamination parameters, which are used for the design of orthotropic laminates. Finally, numerical examples of plates under compression loading with different boundary conditions and aspect ratios are investigated. Reliable optimal solutions demonstrate the robustness and computational efficiency of the proposed optimisation methodology.
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Krzyścin, J. W. "Nonlinear (MARS) modeling of long-term variations of surface UV-B radiation as revealed from the analysis of Belsk, Poland data for the period 1976–2000." Annales Geophysicae 21, no. 8 (2003): 1887–96. http://dx.doi.org/10.5194/angeo-21-1887-2003.
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Abstract. A new, powerful statistical technique, multivariate adaptive regression splines (MARS), is applied to reproduce monthly fractional deviations of UV-B doses over Belsk, Poland, during the snowless (May–October) part of the year in the period 1976–2000. Two kinds of regressors were used: local ones (total ozone, percentage of sky covered by low-, mid-, high-level clouds or total solar radiation over Belsk) and non-local ones, i.e. those describing the long-distance forcings on the surface UV-B due to changes in the global atmospheric circulation. Standard indices of the Quasi-Biennial, North Atlantic, El Niño-Southern Oscillations, and the 11-year solar activity were used as non-local regressors. The results there indicate that the MARS procedure is able to reproduce the observed year-to-year and decadal oscillations in the UV data. The MARS model yields better model-observation agreement than an ordinary least-squares fit based on the same set of regressors. It is found that MARS is capable of handling interactions between the local and non-local regressors, suggesting a possible nonlinear nature of connections between variables characterizing the atmospheric transparency over Belsk and the long-distance forcings. MARS enables a reconstruction of the surface UV-B variations over any site based on the cloud and ozone data presently stored on web pages.Key words. Atmospheric composition and structure (aerosols and particles; biosphere-atmosphere interactions)
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Silva Junior, Julio Cesar Araujo da. "An S-Shaped Crude Oil Price Return-Implied Volatility Relation: Parametric and Nonparametric Estimations." International Journal of Economics and Finance 9, no. 12 (2017): 54. http://dx.doi.org/10.5539/ijef.v9n12p54.
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Oil market movements have important implications for portfolio management and hedge strategies for investors who negotiate this commodity. Studies involving the relation of the CBO Crude Oil ETF Volatility Index (OVX) and the United States Oil Fund (USO) return are small in number and do not explore some aspects related to the asymmetry and nonlinearity of this relation. Therefore, this article proposes an analysis about the relation between return and volatility, using parametric and nonparametric methods. To do so, a daily data series from 2007 to 2016, ordinary least squares, quantile regressions and the nonparametric B-splines methods were used. The results indicated a negative, asymmetric and nonlinear contemporary relation between the variables. The effects of negative returns were more pronounced than the positive ones in volatility. In addition, it was found that the relation is not the same for different quantiles. Nonparametric estimates suggested that the positive returns have a convex profile and the negative returns have a concave profile. It indicated the downward-sloping reclined S-curve for the 0.05, 0.90 and 0.95 quantiles of volatility.
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CHRISTENSEN, OLE, BRIGITTE FORSTER, and PETER MASSOPUST. "DIRECTIONAL TIME–FREQUENCY ANALYSIS VIA CONTINUOUS FRAMES." Bulletin of the Australian Mathematical Society 92, no. 2 (2015): 268–81. http://dx.doi.org/10.1017/s0004972715000337.
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Grafakos and Sansing [‘Gabor frames and directional time–frequency analysis’, Appl. Comput. Harmon. Anal.25 (2008), 47–67] have shown how to obtain directionally sensitive time–frequency decompositions in $L^{2}(\mathbb{R}^{n})$ based on Gabor systems in $L^{2}(\mathbb{R})$. The key tool is the ‘ridge idea’, which lifts a function of one variable to a function of several variables. We generalise their result in two steps: first by showing that similar results hold starting with general frames for $L^{2}(\mathbb{R}),$ in the settings of both discrete frames and continuous frames, and second by extending the representations to Sobolev spaces. The first step allows us to apply the theory to several other classes of frames, for example wavelet frames and shift-invariant systems, and the second one significantly extends the class of examples and applications. We consider applications to the Meyer wavelet and complex B-splines. In the special case of wavelet systems we show how to discretise the representations using ${\it\epsilon}$-nets.
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Villordon, Arthur, Christopher Clark, Don Ferrin, and Don LaBonte. "Using Growing Degree Days, Agrometeorological Variables, Linear Regression, and Data Mining Methods to Help Improve Prediction of Sweetpotato Harvest Date in Louisiana." HortTechnology 19, no. 1 (2009): 133–44. http://dx.doi.org/10.21273/hortsci.19.1.133.
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Predictive models of optimum sweetpotato (Ipomoea batatas) harvest in relation to growing degree days (GDD) will benefit producers and researchers by ensuring maximum yields and high quality. A GDD system has not been previously characterized for sweetpotato grown in Louisiana. We used a data set of 116 planting dates and used a combination of minimum cv, linear regression (LR), and several algorithms in a data mining (DM) mode to identify candidate methods of estimating relationships between GDD and harvest dates. These DM algorithms included neural networks, support vector machine, multivariate adaptive regression splines, regression trees, and generalized linear models. We then used candidate GDD methods along with agrometeorological variables to model US#1 yield using LR and DM methodology. A multivariable LR model with the best adjusted r2 was based on GDD calculated using this method: maximum daily temperature (Tmax) – base temperature (B), where if Tmax > ceiling temperature [C (90 °F)], then Tmax = C, and where GDD = 0 if minimum daily temperature <60 °F. The following climate-related variables contributed to the improvement of adjusted r2 of the LR model: mean relative humidity 20 days after transplanting (DAT), maximum air temperature 20 DAT, and maximum soil temperature 10 DAT (log 10 transformed). In the DM mode, this GDD method and the LR model also demonstrated high predictive accuracy as quantified using mean square error. Using this model, we propose to schedule test harvests at GDD = 2600. The harvest date can further be optimized by predicting US#1 yield using GDD in combination with climate-based predictor variables measured within 20 DAT.
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Azizi, Mahmood Reza, and Rahmatolah Khani. "An algorithm for smooth trajectory planning optimization of isotropic translational parallel manipulators." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, no. 12 (2015): 1987–2002. http://dx.doi.org/10.1177/0954406215588988.
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This paper presents a new algorithm for smooth trajectory planning optimization of isotropic translational parallel manipulators (ITPM) that their Jacobian matrices are constant and diagonal over the whole robot workspace. The basic motivation of this work is to formulate the robot kinematic and geometric constraints in terms of optimization variables to reduce the mathematical complexity and running time of the resulting algorithm which are important issues in trajectory planning optimization. To achieve this aim, the end-effector trajectory of ITPMs in Cartesian space is defined using fifth-order B-Splines, and as a main contribution, all of the actuators limitations and robot constraints are formulated in terms of B-Spline parameters with no need of any information about the workspace geometry. Then the total required energy, total time of motion, and maximum absolute value of actuators’ jerk are defined as objective functions and non-dominated sorting genetic algorithm-II (NSGA-II) is used to solve the resulting nonlinear constrained multi-objective optimization problem. Finally, the proposed algorithm is implemented in MATLAB software for Cartesian parallel manipulator (CPM) as a case study, and the results are demonstrated and discussed. The obtained results show the significant performance of the proposed algorithm with no need to evaluate the robot’s constraints and boundaries of its workspace in each point of the end-effector trajectory.
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Anevlavi, Dimitra, and Kostas Belibassakis. "An Adjoint Optimization Prediction Method for Partially Cavitating Hydrofoils." Journal of Marine Science and Engineering 9, no. 9 (2021): 976. http://dx.doi.org/10.3390/jmse9090976.
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Much work has been done over the past years to obtain a better understanding, predict and alleviate the effects of cavitation on the performance of lifting surfaces for hydrokinetic turbines and marine propellers. Lifting-surface sheet cavitation, when addressed as a free-streamline problem, can be predicted up to a desirable degree of accuracy using numerical methods under the assumptions of ideal flow. Typically, a potential solver is used in conjunction with geometric criteria to determine the cavity shape, while an iterative scheme ensures that all boundary conditions are satisfied. In this work, we propose a new prediction model for the case of partially cavitating hydrofoils in a steady flow that treats the free-streamline problem as an inverse problem. The objective function is based on the assumption that on the cavity boundary, the pressure remains constant and is evaluated at each optimization cycle using a source-vorticity BEM solver. The attached cavity is parametrized using B-splines, and the control points are included in the design variables along with the cavitation number. The sensitivities required for the gradient-based optimization are derived using the continuous adjoint method. The proposed numerical scheme is compared against other methods for the NACA 16-series hydrofoils and is found to predict well both the cavity shape and cavitation number for a given cavity length.
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Arfè, Andrea, Piero Quatto, Antonella Zambon, Hugh J. MacIsaac, and Marina Manca. "Long-Term Changes in the Zooplankton Community of Lake Maggiore in Response to Multiple Stressors: A Functional Principal Components Analysis." Water 11, no. 5 (2019): 962. http://dx.doi.org/10.3390/w11050962.
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We describe the long-term (1981–2008) dynamics of several physico-chemical and biological variables and how their changes may have influenced zooplankton structure in Lake Maggiore (Italy). Data was available for the 1981–1992 and 1995–2008 periods. Standardized time-series for temperature and total phosphorus (TP), chlorophyll-a, phytoplankton density (cel m−3), and cell size (µm3), as well as zooplankton structure (Copepoda, Cladocera, and Rotifera density, ind m−3) were smoothed using penalized B-splines and analyzed using Functional Principal Components (FPCs) to assess their dominant modes of variation. The first four FPCs explained 55% of 1981–1992 and 65% of 1995–2008 overall variation. Results showed that temperature fluctuated during the study period, particularly during 1988–1992 with a general tendency to increase. TP showed a declining trend with some reversions in the pattern observed in the years 1992, 1999, and 2000. Phytoplankton estimators and chlorophyll-a concentration showed a variable trend along the study period. Zooplankton groups also had a variable trend along the study period with a general increase in density of large carnivorous (mainly Bythotrephes longimanus) and a decrease of large herbivorous (mainly Daphnia), and a similar increase in the ratio of raptorial to microphagous rotifers. Our results suggest that the lake experienced a strong trophic change associated with oligotrophication, followed by pronounced climate-induced changes during the latter period. TP concentration was strongly associated with changes in abundance of some zooplankton taxa.
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Zhang, Shuyi, Bo Yang, Hong Xie, and Moru Song. "Applications of an Improved Aerodynamic Optimization Method on a Low Reynolds Number Cascade." Processes 8, no. 9 (2020): 1150. http://dx.doi.org/10.3390/pr8091150.
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The effect of cascade aerodynamic optimization on turbomachinery design is very significant. However, for most traditional cascade optimization methods, aerodynamic parameters are considered as boundary conditions and rarely directly used as the optimization variables to realize optimization. Given this problem, this paper proposes an improved cascade aerodynamic optimization method in which an incidence angle and nine geometric parameters are used to parameterize the cascade and one modified optimization algorithm is adopted to find the cascade with the optimal aerodynamic performance. The improved parameterization approach is based on the Non-Uniform Rational B-Splines (NURBS) method, the camber line superposing thickness distribution molding (CLSTDM) method, and the plane cascade design method. To rapidly and effectively find the cascade with the largest average lift-drag ratio within a certain range of incidence angles, modified particle swarm optimization combined with the modified very fast simulated annealing algorithm (PSO-MVFSA) is adopted. To verify the feasibility of the method, a cascade with NACA4412 and a practical cascade are optimized. It is found that the average lift-drag ratios of two optimal performance cascades are respectively increased by 13.38% and 15.21% in comparison to those of two original cascades. Meanwhile, through optimizing the practical cascade of the Blade D500, under different volume flow rates, the pressure coefficient of the optimized cascade is increased by an average of more than 6.12% compared to that of the prototype, and the average efficiency is increased by 11.15%. Therefore, this improved aerodynamic optimization method is reliable and feasible for the performance improvement of cascades with a low Reynolds number.
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Zou, Zhihong, Jin Chen, and Xiaoping Pang. "Task space-based dynamic trajectory planning for digging process of a hydraulic excavator with the integration of soil–bucket interaction." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 233, no. 3 (2018): 598–616. http://dx.doi.org/10.1177/1464419318812589.
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In this paper, a task space-based methodology for dynamic trajectory planning for digging process of a hydraulic excavator is presented, with the integration of soil–bucket interaction. An extended soil–bucket interaction model, which adds the resistive moment compared to the previous models, is provided in this research. This improved model is validated by comparing with the measurement data taken from field experiments before integrating it into a dynamic model of an excavator. Further, Newton–Euler method is used for the derivation of the dynamics of each link of the excavator to determine the joint forces, which can cause the machine damage. The position and orientation trajectories of the bucket in the task space are parameterized by using the B-splines, so as to achieve the task-oriented operations and ensure the operation flexibility. The joint space motion characteristics are obtained by solving the inverse kinematics of the working mechanism of an excavator. Moreover, to avoid the operation uncertainty for a given bucket tip position trajectory and reduce the computational effort, the self-motion parameters are introduced when solving the inverse kinematics of the redundant working mechanism. All these self-motion parameters are taken as a set of design variables in the trajectory optimization problem. Also, the limits on the hydraulic driving forces, joint angles, angular velocities and accelerations, as well as bucket capacity are considered as the optimization constraints for the digging process. Finally, optimization examples of two typical digging categories (i.e. level digging work and slope digging work) are given to demonstrate and verify the capabilities of the new methodology proposed in this research. The results show that the proposed method can effectively generate the optimal trajectories satisfying the following criteria: time efficiency, energy efficiency, and least machine damage. This work lays a solid foundation for motion planning and autonomous control of an excavator.
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Dang Manh, Nguyen, Anton Evgrafov, Jens Gravesen, and Domenico Lahaye. "Iso-geometric shape optimization of magnetic density separators." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 33, no. 4 (2014): 1416–33. http://dx.doi.org/10.1108/compel-07-2013-0234.
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Purpose – The waste recycling industry increasingly relies on magnetic density separators. These devices generate an upward magnetic force in ferro-fluids allowing to separate the immersed particles according to their mass density. Recently, a new separator design has been proposed that significantly reduces the required amount of permanent magnet material. The purpose of this paper is to alleviate the undesired end-effects in this design by altering the shape of the ferromagnetic covers of the individual poles. Design/methodology/approach – The paper represents the shape of the ferromagnetic pole covers with B-splines and defines a cost functional that measures the non-uniformity of the magnetic field in an area above the poles. The authors apply an iso-geometric shape optimization procedure, which allows us to accurately represent, analyze and optimize the geometry using only a few design variables. The design problem is regularized by imposing constraints that enforce the convexity of the pole cover shapes and is solved by a non-linear optimization procedure. The paper validates the implementation of the algorithm using a simplified variant of the design problem with a known analytical solution. The algorithm is subsequently applied to the problem posed. Findings – The shape optimization attains its target and yields pole cover shapes that give rise to a magnetic field that is uniform over a larger domain. Research limitations/implications – This increased magnetic field uniformity is obtained at the cost of a pole cover shape that differs per pole. This limitation has negligible impact on the manufacturing of the separator. The new pole cover shapes therefore lead to improved performance of the density separation. Practical implications – Due to the larger uniformity the generated field, these shapes should enable larger amounts of waste to be processed than the previous design. Originality/value – This paper treats the shapes optimization of magnetic density separators systematically and presents new shapes for the ferromagnetic poles covers.
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DOREAU, M., R. BAUMONT, and J. M. PEREZ. "Avant-propos." INRAE Productions Animales 24, no. 5 (2011): 411–14. http://dx.doi.org/10.20870/productions-animales.2011.24.5.3274.
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Les impacts environnementaux liés aux productions animales sont pris en considération depuisau moins deux décennies. Mais jusqu’à une date récente, ils étaient considérés comme des «dommagescollatéraux» résultant de la nécessité de nourrir la planète. Depuis le rapport de la FAO«Livestock’s long shadow» (Steinfeld et al 2006), les préoccupations environnementales liées enparticulier aux gaz à effet de serre (GES) ont pris une importance croissante auprès des acteursdes filières animales et des décideurs politiques. Elles sont désormais au centre de la réflexion surle développement de l’élevage. En témoignent des documents dépassant le cadre de l’agriculturecomme la publication des propositions du «Grenelle 2» par le gouvernement français, ou la feuillede route de l’Union Européenne pour une baisse drastique des émissions de gaz carbonique àl’échéance de 2050. En fait, le problème est planétaire, car la consommation mondiale de produitsanimaux augmente, tendance appelée à se poursuivre en raison de l’évolution démographiqueet de l’accroissement de la part des produits animaux dans l’alimentation dans les pays endéveloppement et émergents (Gerber et al 2011).
 La revue INRA Productions animales a publié depuis plusieurs années de nombreux articlesrelatifs aux relations entre élevage et environnement, analysées sous divers angles. Récemmentdes articles relatifs aux polluants ou aux aspects environnementaux plus globaux ont été publiésdans le cadre de trois numéros thématiques : «Porcherie verte» avec notamment des articles surles éléments à risque et les émissions gazeuses lors de la gestion des effluents (Bonneau et al2008a, b), «Les nouveaux enjeux de la nutrition et de l’alimentation du porc» avec un article surles relations entre nutrition et excrétion de polluants (Dourmad et al 2009), et «Elevage en régionschaudes» avec un article consacré aux impacts et services environnementaux (Blanfort et al2011). Des articles ont également été publiés sur la quantification des émissions de méthane parles animaux d’élevage en France (Vermorel et al 2008) et sur la modélisation des émissions deméthane chez les ruminants (Sauvant et al 2009). Enfin, les moyens de réduire les rejets porcinset avicoles par la génétique ont été analysés (Mignon-Grasteau et al 2010). A signaler aussi lenuméro spécial «Elevage bio» en 2009, qui analysait les systèmes d’élevage biologique sans toutefoisdiscuter leurs avantages au plan environnemental.
 La réduction des émissions de GES par l’élevage est devenue un enjeu majeur des recherchessur les systèmes d’élevage et en nutrition animale. Ce dossier composé de quatre articles estconsacré aux GES en élevage bovin en mettant l’accent sur le méthane. En effet dans la plupartdes systèmes laitiers et à viande, le méthane est le gaz à effet de serre qui contribue le plus auxémissions, exprimées en équivalent gaz carbonique, comme le montre le premier article (Dollé etal 2011) qui replace les émissions de méthane dans l’ensemble des émissions de gaz à effet deserre. Un travail considérable a été réalisé pour évaluer et comparer les systèmes français, et lesINRA Productions Animales, 2011, numéro 5situer dans un contexte plus global : depuis quelques années les émissions induites par des systèmesd’élevage très divers sont étudiées dans le monde, principalement en Europe. Le deuxièmearticle (Sauvant et al 2011) analyse les relations étroites entre la production de méthane et les fermentationsdans le rumen selon la nature du régime alimentaire, puis discute la précision des principaleséquations empiriques de prévision de la production de méthane, ainsi que des modèlesmécanistes qui ont été développés. Des voies d’amélioration sont proposées. Dans un troisièmearticle (Popova et al 2011), les mécanismes de production de méthane dans le rumen sont analysés.Un intérêt particulier est porté au rôle des Archaea méthanogènes, microorganismes qui constituentun domaine spécifique du règne vivant et qui sont les seuls à produire du méthane à partirde l’hydrogène. La compréhension des mécanismes est un élément majeur pour prévoir les effetspossibles d’une ration, d’un additif, d’une biotechnologie sur la production de méthane. Laconnaissance actuelle de ces effets est présentée dans un quatrième article (Doreau et al 2011),centré sur les résultats obtenus in vivo. Il est en effet important de confronter les annonces faitesà partir d’essais in vitro, ou d’un seul essai in vivo mené sur le court terme, aux résultats d’étudesapprofondies reposant sur une base expérimentale solide.
 Ce dossier dresse un bilan des recherches et de l’état des connaissances sur le méthane entérique,et mentionne les principaux leviers d’action pour réduire les émissions des trois principauxgaz à effet de serre. Une vision plus large nécessiterait le développement d’aspects complémentaires.En premier lieu, celui des émissions de méthane et de protoxyde d’azote liées aux effluents.Elles sont toutefois très mal connues et éminemment variables, comme l’ont souligné Hassounaet al (2010) qui ont développé une méthode permettant de les évaluer en bâtiments. En deuxièmelieu, l'impact des nombreuses voies permettant de réduire les émissions de protoxyde d'azote auchamp doit être évalué. Ainsi, serait nécessaire une analyse portant sur les différents moyens permettantde limiter la fertilisation azotée minérale (fertilisation «de précision», recours aux légumineuses,inhibition des réactions de nitrification/dénitrification dans les sols, meilleure gestiondu pâturage…) qui sont seulement évoqués dans le texte de Dollé et al (2011). Enfin, la séquestrationde carbone par les prairies doit être prise en compte dans l’analyse de la contribution desélevages de ruminants au réchauffement climatique. Les valeurs actuellement retenues sont probablementsous-estimées (Soussana et al 2010), mais les résultats récents mettent en évidence unetrès grande variabilité de ce stockage de carbone, liée non seulement au type de végétation et auxconditions pédologiques, mais aussi, entre autres, au type d’exploitation par les animaux et auxaléas climatiques (Klumpp et al 2011).
 Le réchauffement climatique est actuellement considéré par les médias et les décideurs politiquescomme l’urgence en termes de protection de notre environnement. Cela ne doit pas faireoublier qu’il est nécessaire de prendre en compte simultanément l’épuisement de certaines ressourcescomme l’énergie fossile et les phosphates, la raréfaction des réserves en eau, la compétitionpour les surfaces agricoles, et la pollution de l’air, des sols et de l’eau par différentes moléculesminérales et organiques. L’analyse des impacts environnementaux, en tant que composantede la durabilité des systèmes d’élevage, doit donc être multifactorielle et prendre également encompte les services environnementaux et sociétaux de l’élevage, une activité qui fait vivre plusd’un milliard d’habitants de notre planète.
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Ollberding, Nicholas J., Andrew M. Evens, Briseis Aschebrook-Kilfoy, et al. "The Impact of Cigarette Smoking On Overall Survival in Non-Hodgkin Lymphoma." Blood 120, no. 21 (2012): 5100. http://dx.doi.org/10.1182/blood.v120.21.5100.5100.
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Abstract Abstract 5100 Introduction: Smoking has been suggested as a potential risk factor for the development of non-Hodgkin lymphoma (NHL). However, the prognostic impact of smoking in patients with NHL has not been well studied and may have important implications regarding outcome. Methods: In a population-based cohort of 308 NHL patients diagnosed between 1999 and 2002, we examined the association between cigarette smoking habits prior to NHL diagnosis and overall survival (OS). Multivariable Cox proportional hazards models adjusted for age, gender, and education were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for all NHL, and for follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). Measurements of smoking included categories for smoking status, pack-years of smoking, years of smoking, daily number of cigarettes smoked, and years since quitting smoking. Continuous exposures for cigarette smoking were also examined with potential non-linear relations tested using restricted cubic splines. We conducted subgroup analyses adjusting for established clinical and prognostic variables. Results: In the patient cohort, a total of 96 deaths occurred over a median follow-up period of 8. 2 years. For all NHL cases, current smokers had worse survival (HR=1. 8 [1. 0–3. 1], ptrend=0. 07, for risk of all-cause mortality) when compared to never smokers. The inferior survival was also associated with pack-years of smoking (HR=1. 5 [0. 9–2. 4], ptrend=0. 12, for >30 pack-years) and smoking duration (HR=1. 5 [0. 9–2. 3], ptrend=0. 13, for >30 years). Smoking remained an independent predictor of OS after adjustment for initial treatment, stage at diagnosis and the presence of B symptoms: HR=2. 6 [1. 1–6. 3], ptrend=0. 03, for current smokers; HR=2. 4 [1. 1–5. 6], ptrend=0. 03, for patients with >30 pack-years of cigarette smoking; and HR=2. 5 [1. 2–5. 5], ptrend=0. 02, for patients smoking longer than 30 years. Among former smokers, a shorter interval from quitting to diagnosis was associated with worse survival (per 5 years of quitting cigarette smoking, HR=0. 9 [0. 8–1. 0], ptrend=0. 06). The associations with cigarette smoking and OS were stronger for FL than for DLBCL. In analyses stratified by age at diagnosis, the associations for current smokers (HR=3. 7 [1. 5–9. 2], ptrend=0. 01), daily number of cigarettes smoked (HR=2. 8 [1. 0–7. 5], ptrend=0. 04), and years of cigarette smoking (HR=3. 0 [1. 1–8. 3], ptrend=0. 04) were stronger for patients diagnosed at <60 years of age. The risk estimates for smoking with OS did not depart from unity among those diagnosed at ≥ 60 years of age. The associations between cigarette smoking and OS were similar for men and women. Conclusion: Our data suggest that cigarette smoking prior to diagnosis is associated with inferior OS in NHL patients. The reduction in survival is most prominent for patients diagnosed at <60 years of age and for those with FL. Among former smokers, greater time from cessation of smoking to diagnosis may improve OS. Further research examining the impact of smoking cession on OS among NHL patients is warranted. Disclosures: No relevant conflicts of interest to declare.
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Rawat, Angel, Raghu Piska, A. Rajagopal, and Mokarram Hossain. "Nonlocal plasticity-based damage modeling in quasi-brittle materials using an isogeometric approach." Engineering Computations 38, no. 6 (2021): 2604–30. http://dx.doi.org/10.1108/ec-12-2019-0562.
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Purpose This paper aims to present a nonlocal gradient plasticity damage model to demonstrate the crack pattern of a body, in an elastic and plastic state, in terms of damage law. The main objective of this paper is to reconsider the nonlocal theory by including the material in-homogeneity caused by damage and plasticity. The nonlocal nature of the strain field provides a regularization to overcome the analytical and computational problems induced by softening constitutive laws. Such an approach requires C1 continuous approximation. This is achieved by using an isogeometric approximation (IGA). Numerical examples in one and two dimensions are presented. Design/methodology/approach In this work, the authors propose a nonlocal elastic plastic damage model. The nonlocal nature of the strain field provides a regularization to overcome the analytical and computational problems induced by softening constitutive laws. An additive decomposition of strains in to elastic and inelastic or plastic part is considered. To obtain stable damage, a higher gradient order is considered for an integral equation, which is obtained by the Taylor series expansion of the local inelastic strain around the point under consideration. The higher-order continuity of nonuniform rational B-splines (NURBS) functions used in isogeometric analysis are adopted here to implement in a numerical scheme. To demonstrate the validity of the proposed model, numerical examples in one and two dimensions are presented. Findings The proposed nonlocal elastic plastic damage model is able to predict the damage in an accurate manner. The numerical results are mesh independent. The nonlocal terms add a regularization to the model especially for strain softening type of materials. The consideration of nonlocality in inelastic strains is more meaningful to the physics of damage. The use of IGA framework and NURBS basis functions add to the nonlocal nature in approximations of the field variables. Research limitations/implications The method can be extended to 3D. The model does not consider the effect of temperature and the dissipation of energy due to temperature. The method needs to be implemented for more real practical problems and compare with experimental work. This is an ongoing work. Practical implications The nonlocal models are suitable for predicting damage in quasi brittle materials. The use of elastic plastic theories allows to capture the inelastic deformations more accurately. Social implications The nonlocal models are suitable for predicting damage in quasi brittle materials. The use of elastic plastic theories allows to capture the inelastic deformations more accurately. Originality/value The present work includes the formulation and implementation of a nonlocal damage plasticity model using an isogeometric discretization, which is the novel contribution of this paper. An implicit gradient enhancement is considered to the inelastic strain. During inelastic deformations, the proposed strain tensor partitioning allows the use of a distinct potential surface and distinct failure criterion for both damage and plasticity models. The use of NURBS basis functions adds to more nonlocality in the approximation.
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Heimfeld, Shelly, Ted Gooley, Mary Flowers, et al. "Effect of Peripheral Blood Stem Cell (PBSC) Graft Composition on Graft Versus Host Disease (GVHD) and Mortality After Allogeneic Transplantation." Blood 116, no. 21 (2010): 676. http://dx.doi.org/10.1182/blood.v116.21.676.676.
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Abstract Abstract 676 We investigated the relationship of PBSC graft composition on GVHD and survival in 2,350 allogeneic transplant recipients from a single institution. Characteristics of the cohort included: median age: 50 (0.5-79); disease risk: low 12%, intermediate 41%, high 35%; HLA-matched sibling donor 53% and reduced-intensity conditioning 36%. Graft composition cell subsets included stem/progenitors (CD34+), monocytes (CD14+), B (CD20+), NK (CD3-CD56+), NK/T (CD3+CD56+), dendritic cell subsets (DC1 and DC2), and T-cell subsets (CD3+CD4+, CD3+CD8+, Memory, Naïve, Regulatory), measured by multicolor FACS analyses and expressed as infused cell subset/kg of actual recipient weight. Cell doses were modeled as continuous linear variables, by quartiles, or by cubic splines (allowing for non-linear models). Results: In contrast with previous findings, increasing CD34+ cell dose was not statistically associated with acute GVHD (p=0.49), chronic GVHD (p=0.91) or survival (p=0.74). However, several other cell subsets showed important associations. Shown in Figure 1 is a cubic spline graph of the hazard ratio (HR) of chronic GVHD as a function of CD3+CD4+ T-cell dose relative to a relatively low dose of 0.5 × 107/kg. A highly significant correlation was found between larger doses of CD14+ monocytes and less chronic GVHD (p<0.001). Figure 2 displays the HR results compared to a dose of 0.5 × 108 CD14 cells/kg, indicating a strong association in the alternative donor setting (p<0.001: by quartile analysis HR=0.59 for Q4 vs. Q1; p=.0004), and remained a suggestive trend in the matched sibling group. For the overall mortality analysis, several cell subsets showed significant associations. Patients receiving higher doses of NK cells had lower survival (p=0.007). Higher doses of memory CD4 was also found to be associated with lower survival, but the effect appeared to be restricted to the matched-sibling donor group (p=0.007). Increasing doses of DC1 were also associated with worse survival (p=0.02) for both reduced intensity and ablative conditioning groups, although the dose response was stronger in the ablative group (HR=1.17 Q4 vs. Q1). In contrast, higher doses of with NK/T cells correlated with lower mortality (p=0.01) but only in the matched-sibling group (Q4 vs. Q1, HR=0.78, p=0.05). Conclusions: In this large, single center study, no associations of CD34 cell dose with GVHD or overall mortality were found. Further, our results suggest that previously reported associations between T cell dose and chronic GVHD are primarily driven by CD4 content in PBSC, and restricted to the matched-sibling donor (Figure 1). The lack of correlation with alternative donors may reflect differences in T-cell responses to the greater minor histocompatibility divergence with alternative donors, or changes in donor T-cell functionality associated with the higher dose of G-CSF (16 μg/kg/day) used for sibling donor mobilization at our center. To our knowledge, the correlation of higher CD14 dose with a reduced incidence of chronic GVHD is a novel finding, perhaps reflecting the known shift to a more immunosuppressive function of monocytes after G-CSF exposure. Similarly, reduced survival associated with higher doses of NK, memory CD4, and DC1 cells, and improved survival with greater numbers of NK/T cells represent new findings that will require additional analyses. Altogether, these correlations of GVHD and mortality with PBSC cell subsets support the concept that engineering of grafts could result in improved outcomes with allogeneic transplantation. Disclosures: No relevant conflicts of interest to declare.
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Maurer, Matthew J., Lasse H. Jakobsen, Norbert Schmitz, et al. "Age and Time to Progression Predict Overall Survival (OS) in Patients with Diffuse Large B-Cell Lymphoma (DLBCL) Who Progress Following Frontline Immunochemotherapy (IC)." Blood 134, Supplement_1 (2019): 400. http://dx.doi.org/10.1182/blood-2019-124017.
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Background: Disease progression (PD) after frontline IC therapy for DLBCL is a clinically significant event and only 20-40% of patients achieve durable remissions with salvage chemotherapy. Patients who experience early PD or have disease refractory to IC have especially poor outcomes. Chimeric antigen receptor T-cell therapy has emerged as a novel effective therapy for selected cases of relapsed or refractory (r/r) DLBCL, although its availability is limited by cost and logistic challenges. Simple, clinically applicable prognostic tools would be useful for selecting patients for consideration for novel therapies vs those who are more likely to be successfully managed by conventional therapies, but few have been developed for r/r DLBCL. Methods: Model building was performed in patients with PD after IC from 13 frontline, multicenter, randomized DLBCL clinical trials from the SEAL Consortium. All patients received rituximab and an anthracycline-based combination IC and were followed systematically; however therapy received, clinical, and laboratory data at progression were not available. OS was defined as time from first progression until death from any cause. Associations between variables and OS were evaluated using Cox models; splines were used to model functional forms. Validation was performed in the University of Iowa/Mayo Clinic SPORE Molecular Epidemiology Resource (MER) and Danish LYFO cohorts. Model performance was assessed using time-dependent concordance indices (c-stat), Brier scores, and calibration with metrics evaluated at two years from progression. Results: Model Development (SEAL): 1125 of 5112 patients had PD after IC. Median time to PD (TTP) was 11.8 months (IQR 6.6-23.5); median age at PD was 68 years (IQR 60-73). At a median follow-up of 21 months from PD (IQR 7-43), 732 patients (65%) had died and 24 month overall survival after PD (OS24) was 35% (95% CI: 32-38). TTP was strongly associated with post PD OS (spline p-value&lt;0.0001) with OS24 ranging from 18% in patients with TTP &lt;6 months compared to 69% in patients with TTP &gt; 36 months (Figure A). Additionally, age at PD (spline p-value&lt;0.0001) was associated with post PD OS. A model consisting of age at PD including patients 40-80 years and TTP ranging 0-60 months was created (n=1011, Figure B) due to sparse data outside these intervals. C-stat was 0.67, and the model was well calibrated (predicted OS24 = 34% vs. actual OS24 = 34%). External Validation (MER): The model was validated in 290 patients with DLBCL who initiated 2nd line therapy after PD to IC. Median age at PD was younger than the SEAL cohort at 62 years (IQR 57-70). Patients with biopsy proven indolent histology at relapse were excluded. Median TTP was 8.2 months (IQR 5.1-17.0). At a median follow-up of 87 months from PD, 201 patients (69%) had died. OS24 was 47% (95% CI: 41-53). The model showed similar concordance (c-stat=0.65), but underestimated OS24 (predicted =33% vs. 47% actual, Figure C). External Validation (LYFO): The model was validated in 599 patients with DLBCL and PD after frontline IC. Median age at PD was 67 years (IQR 60-73). Median TTP was 10.1 months (IQR 6.0-19.4). At a median follow-up of 82 months from PD, 435 patients (73%) had died. OS24 was 38% (95% CI: 34-42). The model showed similar concordance (c-stat=0.67) when applied to the LYFO cohort, but again underestimated OS24 (predicted =32% vs. 38% actual, Figure D). Case vignettes: A 74 year old patient who progressed 9 months after diagnosis would have a predicted OS24 of 20%. A 58 year old patient who progressed 32 months after diagnosis would have a predicted OS24 of 65% Conclusions: TTP to following IC is strongly associated with post-progression survival in DLBCL. We developed a model from the largest frontline clinical trial dataset in DLBCL and validated a simple to apply clinical prognostic tool in the r/r setting. The model allows better understanding of expected outcomes in r/r DLBCL and can aid design and interpretation of trial results in this setting. The model underestimated the actual survival probability when applied to non-trial validation cohorts. Recalibration of the model for transplant eligible patients and development of smartphone based point-of-care application of the model is ongoing. Figure Disclosures Maurer: Celgene: Research Funding; Nanostring: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees. Schmitz:Riemser: Consultancy, Honoraria; Celgene: Equity Ownership; Gilead: Honoraria; Novartis: Honoraria. Farooq:Kite Pharma: Research Funding; Celgene: Honoraria. Flowers:Optimum Rx: Consultancy; Burroughs Wellcome Fund: Research Funding; BeiGene: Consultancy, Research Funding; Karyopharm: Consultancy; AstraZeneca: Consultancy; Gilead: Consultancy, Research Funding; Eastern Cooperative Oncology Group: Research Funding; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy, Research Funding; Bayer: Consultancy; TG Therapeutics: Research Funding; Acerta: Research Funding; Celgene: Consultancy, Research Funding; National Cancer Institute: Research Funding; Denovo Biopharma: Consultancy; Pharmacyclics/Janssen: Consultancy, Research Funding; Spectrum: Consultancy; Millenium/Takeda: Research Funding; AbbVie: Consultancy, Research Funding; V Foundation: Research Funding. Frederiksen:Alexion: Research Funding; Gilead: Research Funding; Abbvie: Research Funding; Janssen Pharmaceuticals: Research Funding; Novartis: Research Funding. Cunningham:Eli Lilly: Research Funding; 4SC: Research Funding; Bayer: Research Funding; MedImmune: Research Funding; Celgene: Research Funding; AstraZeneca: Research Funding; Merrimack: Research Funding; Sanofi: Research Funding; Amgen: Research Funding; Janssen: Research Funding; Merck: Research Funding; Clovis: Research Funding. Jørgensen:Gilead: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Poeschel:Amgen: Other: Travel, accommodations, expenses; Abbvie: Other: Travel, accomodations, expenses; Hexal: Speakers Bureau; Roche: Other: Travel, accomodations, expenses. Nowakowski:F. Hoffmann-La Roche Ltd: Research Funding; Curis: Research Funding; Selvita: Membership on an entity's Board of Directors or advisory committees; NanoString: Research Funding; MorphoSys: Consultancy, Research Funding; Genentech, Inc.: Research Funding; Bayer: Consultancy, Research Funding; Celgene: Consultancy, Research Funding. Seymour:Takeda: Consultancy; Celgene: Consultancy, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Research Funding, Speakers Bureau; Acerta: Consultancy; Janssen: Consultancy, Research Funding; Roche: Consultancy, Research Funding, Speakers Bureau. Merli:Takeda: Honoraria, Other: Travel Expenses; Gilead: Honoraria; Mundipharma: Honoraria; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses, Research Funding; Sandoz: Membership on an entity's Board of Directors or advisory committees; Teva: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: Travel Expenses; Janssen: Honoraria. Haioun:novartis: Honoraria; celgene: Honoraria; roche: Consultancy; celgene: Consultancy; gilead: Consultancy; takeda: Consultancy; janssen cilag: Consultancy; amgen: Honoraria; servier: Honoraria. Tilly:roche: Membership on an entity's Board of Directors or advisory committees; servier: Honoraria; merck: Honoraria; Gilead: Honoraria; Janssen: Honoraria; BMS: Honoraria; Karyopharm: Consultancy; Astra-Zeneca: Consultancy; Celgene: Consultancy, Research Funding; Roche: Consultancy. Salles:Amgen: Honoraria, Other: Educational events; BMS: Honoraria; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis, Servier, AbbVie, Karyopharm, Kite, MorphoSys: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Epizyme: Consultancy, Honoraria; Roche, Janssen, Gilead, Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events. El-Galaly:Roche: Employment, Other: Travel support; Takeda: Other: Travel support.
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Visontai, Mirkó, and Nathan Williams. "Les polynômes eul\IeC èriens stables de type B." Discrete Mathematics & Theoretical Computer Science DMTCS Proceedings vol. AR,..., Proceedings (2012). http://dx.doi.org/10.46298/dmtcs.3040.
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International audience We give a multivariate analog of the type B Eulerian polynomial introduced by Brenti. We prove that this multivariate polynomial is stable generalizing Brenti's result that every root of the type B Eulerian polynomial is real. Our proof combines a refinement of the descent statistic for signed permutations with the notion of real stability—a generalization of real-rootedness to polynomials in multiple variables. The key is that our refined multivariate Eulerian polynomials satisfy a recurrence given by a stability-preserving linear operator. Nous prèsentons un raffinement multivariè d'un polynôme eulèrien de type B dèfini par Brenti. En prouvant que ce polynôme est stable nous gènèralisons un rèsultat de Brenti selon laquel chaque racine du polynôme eulèrien de type B est rèelle. Notre preuve combine un raffinement de la statistique des descentes pour les permutations signèes avec la stabilitè—une gènèralisation de la propriètè d'avoir uniquement des racines rèelles aux polynômes en plusieurs variables. La connexion est que nos polynômes eulèriens raffinès satisfont une rècurrence donnèe par un opèrateur linèaire qui prèserve la stabilitè.
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Turner, Cameron J., and Richard H. Crawford. "N -Dimensional Nonuniform Rational B-Splines for Metamodeling." Journal of Computing and Information Science in Engineering 9, no. 3 (2009). http://dx.doi.org/10.1115/1.3184599.
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Nonuniform rational B-splines (NURBs) have unique properties that make them attractive for engineering metamodeling applications. NURBs are known to accurately model many different continuous curve and surface topologies in one- and two-variate spaces. However, engineering metamodels of the design space often require hypervariate representations of multidimensional outputs. In essence, design space metamodels are hyperdimensional constructs with a dimensionality determined by their input and output variables. To use NURBs as the basis for a metamodel in a hyperdimensional space, traditional geometric fitting techniques must be adapted to hypervariate and hyperdimensional spaces composed of both continuous and discontinuous variable types. In this paper, we describe the necessary adaptations for the development of a NURBs-based metamodel called a hyperdimensional performance model or HyPerModel. HyPerModels are capable of accurately and reliably modeling nonlinear hyperdimensional objects defined by both continuous and discontinuous variables of a wide variety of topologies, such as those that define typical engineering design spaces. We demonstrate this ability by successfully generating accurate HyPerModels of ten trial functions laying the foundation for future work with N-dimensional NURBs in design space applications.
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Wang, Mingming, and Xiaoping Qian. "Efficient Filtering in Topology Optimization via B-Splines1." Journal of Mechanical Design 137, no. 3 (2015). http://dx.doi.org/10.1115/1.4029373.
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This paper presents a B-spline based approach for topology optimization of three-dimensional (3D) problems where the density representation is based on B-splines. Compared with the usual density filter in topology optimization, the new B-spline based density representation approach is advantageous in both memory usage and central processing unit (CPU) time. This is achieved through the use of tensor-product form of B-splines. As such, the storage of the filtered density variables is linear with respect to the effective filter size instead of the cubic order as in the usual density filter. Numerical examples of 3D topology optimization of minimal compliance and heat conduction problems are demonstrated. We further reveal that our B-spline based density representation resolves the bottleneck challenge in multiple density per element optimization scheme where the storage of filtering weights had been prohibitively expensive.
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Natarajan, S., A. J. M. Ferreira, and Hung Nguyen-Xuan. "Analysis of cross-ply laminated plates using isogeometric analysis and unified formulation." Curved and Layered Structures 1, no. 1 (2014). http://dx.doi.org/10.2478/cls-2014-0001.
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AbstractIn this paper, we study the static bending and free vibration of cross-ply laminated composite plates using sinusoidal deformation theory. The plate kinematics is based on the recently proposed Carrera Unified Formulation (CUF), and the field variables are discretized with the non-uniform rational B-splines within the framework of isogeometric analysis (IGA). The proposed approach allows the construction of higher-order smooth functions with less computational effort.Moreover, within the framework of IGA, the geometry is represented exactly by the Non-Uniform Rational B-Splines (NURBS) and the isoparametric concept is used to define the field variables. On the other hand, the CUF allows for a systematic study of two dimensional plate formulations. The combination of the IGA with the CUF allows for a very accurate prediction of the field variables. The static bending and free vibration of thin and moderately thick laminated plates are studied. The present approach also suffers fromshear locking when lower order functions are employed and shear locking is suppressed by introducing a modification factor. The effectiveness of the formulation is demonstrated through numerical examples.
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Schober, Peter, Julian Valentin, and Dirk Pflüger. "Solving High-Dimensional Dynamic Portfolio Choice Models with Hierarchical B-Splines on Sparse Grids." Computational Economics, January 4, 2021. http://dx.doi.org/10.1007/s10614-020-10061-x.
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AbstractDiscrete time dynamic programming to solve dynamic portfolio choice models has three immanent issues: firstly, the curse of dimensionality prohibits more than a handful of continuous states. Secondly, in higher dimensions, even regular sparse grid discretizations need too many grid points for sufficiently accurate approximations of the value function. Thirdly, the models usually require continuous control variables, and hence gradient-based optimization with smooth approximations of the value function is necessary to obtain accurate solutions to the optimization problem. For the first time, we enable accurate and fast numerical solutions with gradient-based optimization while still allowing for spatial adaptivity using hierarchical B-splines on sparse grids. When compared to the standard linear bases on sparse grids or finite difference approximations of the gradient, our approach saves an order of magnitude in total computational complexity for a representative dynamic portfolio choice model with varying state space dimensionality, stochastic sample space, and choice variables.
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Tamsir, Mohammad, Neeraj Dhiman, F. S. Gill, and Robin. "Approximation of 3D convection diffusion equation using DQM based on modified cubic trigonometric B-splines." Journal of Computational Methods in Sciences and Engineering, September 10, 2020, 1–10. http://dx.doi.org/10.3233/jcm-200034.
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This paper presents an approximate solution of 3D convection diffusion equation (CDE) using DQM based on modified cubic trigonometric B-spline (CTB) basis functions. The DQM based on CTB basis functions are used to integrate the derivatives of space variables which transformed the CDE into the system of first order ODEs. The resultant system of ODEs is solved using SSPRK (5,4) method. The solutions are approximated numerically and also presented graphically. The accuracy and efficiency of the method is validated by comparing the solutions with existing numerical solutions. The stability analysis of the method is also carried out.
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Prystavka, Р. О. "The density distribution function renewal process of three variables by means of the polynomial spline based on the b-splines." Proceedings of the National Aviation University 17, no. 2 (2003). http://dx.doi.org/10.18372/2306-1472.2.11904.
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Al Bedah, Abdulmohsen, and John J. Uicker. "Contact Prediction Between Moving Objects Bounded by Curved Surfaces." Journal of Computing and Information Science in Engineering 12, no. 1 (2011). http://dx.doi.org/10.1115/1.4005453.
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This paper presents an algorithm for exact contact prediction between moving objects bounded by curved surfaces. The algorithm uses hierarchies of oriented bounding boxes (HOBBs) and local numerical methods for finding contact. Objects need not be convex and are described using the B-rep scheme. The bounding faces are represented by nonuniform rational B-splines (NURBS). The collision time is sought in short time intervals during the motion, during which time is one of the problem variables. HOBBs are based on curvature regions of the surfaces. This criterion ensures that local numerical methods will converge to the contact points if they exist. The patches enclosed in overlapping leaf nodes are tested for contact by solving a system of nonlinear equations, based on the type of collision expected. The types of collision studied are cusp–cusp, cusp–ridge, cusp–face, ridge–ridge, ridge–face, and face–face collisions. The current algorithm is implemented and compared to an efficient polyhedral collision package, and results appear promising.
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Xiang, Yujiang. "An Inverse Dynamics Optimization Formulation With Recursive B-Spline Derivatives and Partition of Unity Contacts: Demonstration Using Two-Dimensional Musculoskeletal Arm and Gait." Journal of Biomechanical Engineering 141, no. 3 (2019). http://dx.doi.org/10.1115/1.4042436.
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In this study, an inverse dynamics optimization formulation and solution procedure is developed for musculoskeletal simulations. The proposed method has three main features: high order recursive B-spline interpolation, partition of unity, and inverse dynamics formulation. First, joint angle and muscle force profiles are represented by recursive B-splines. The formula for high order recursive B-spline derivatives is derived for state variables calculation. Second, partition of unity is used to handle the multicontact indeterminacy between human and environment during the motion. The global forces and moments are distributed to each contacting point through the corresponding partition ratio. Third, joint torques are inversely calculated from equations of motion (EOM) based on state variables and contacts to avoid numerical integration of EOM. Therefore, the design variables for the optimization problem are joint angle control points, muscle force control points, knot vector, and partition ratios for contacting points. The sum of muscle stress/activity squared is minimized as the cost function. The constraints are imposed for human physical constraints and task-based constraints. The proposed formulation is demonstrated by simulating a trajectory planning problem of a planar musculoskeletal arm with six muscles. In addition, the gait motion of a two-dimensional musculoskeletal model with sixteen muscles is also optimized by using the approach developed in this paper. The gait optimal solution is obtained in about 1 min central processing unit (CPU) time. The predicted kinematics, kinetics, and muscle forces have general trends that are similar to those reported in the literature.
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Lia Rahmati, Hadiana Qanita, and Miftahuddin. "Identifikasi Faktor-Faktor Yang Mempengaruhi Produk Domestik Regional Bruto (Pdrb) Di Provinsi Aceh Menggunakan Generalized Additive Models Dengan Basis B-Spline." Talenta Conference Series: Science and Technology (ST) 2, no. 2 (2019). http://dx.doi.org/10.32734/st.v2i2.462.
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Laju pertumbuhan ekonomi merupakan indikator penting dalam mengukur perkembangan suatu daerah. Tingkat pertumbuhan ekonomi dapat diukur dengan Produk Domestik Regional Bruto (PDRB). Tingkat pertumbuhan ekonomi dapat dipengaruhi oleh beberapa faktor. Tingkat pengangguran terbuka, rasio ketergantungan, tingkat pertumbuhan penduduk, dan tingkat pendidikan terakhir di DI-DIII yang dapat menjadi penentu pertumbuhan ekonomi di Provinsi Aceh. Penelitian ini bertujuan untuk mendapatkan model terbaik dalam memeriksa faktor-faktor yang mempengaruhi PDRB di Provinsi Aceh. Pemodelan dilakukan menggunakan Generalized Additive Model (GAM) dengan basis B-Splines. Penelitian ini menggunakan data PDRB tahun 2013-2015 di Provinsi Aceh. Hasil menunjukkan bahwa variabel keempat yang diuji memiliki efek signifikan terhadap PDRB di Provinsi Aceh. Pengaruh kuantitas yang diperoleh ialah sebesar 50,1%. Ini berarti bahwa tingkat pengangguran terbuka, rasio ketergantungan, tingkat pertumbuhan penduduk, dan tingkat pendidikan terakhir di DI-DIII yang menjadi faktor penentu PDRB di Aceh sebesar 50,1%. 
 
 The rate of economy growth is an important indicator in measuring of the development of an area. The economic growth rate can be measured by GRDP CP (Gross Regional Domestic Product on Constant Prices). Economic growth rates can be influenced by some factors. The open unemployment rate, dependency ratio, the rate of population growth, and the last level of education in DI-DIII that can be determinants of economic growth in Aceh Province. This research aims to get the best model in examining the factors that affect the GRDP in Aceh Province. Modeling is done using Generalized Additive Models (GAM) with base B-Splines. This research uses data GRDP CP 2013-2015 year in Aceh Province. The result is the fourth variables being tested has significant effects to the GRDP in Aceh Province. Influence of the quantity obtained is amounting to 50.1%. It means that the open unemployment rate, dependency ratio, the rate of population growth, and the last level of education in DI-DIII tobe deciding factors GRDP in Aceh is 50.1%.
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Nguyen, Nam V., H. Nguyen-Xuan, and Jaehong Lee. "A quasi-three-dimensional isogeometric model for porous sandwich functionally graded plates reinforced with graphene nanoplatelets." Journal of Sandwich Structures & Materials, July 4, 2021, 109963622110204. http://dx.doi.org/10.1177/10996362211020451.
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The purpose of this study is to present a quasi-three-dimensional (quasi-3D) shear deformation theory for static bending and free vibration analyses of porous sandwich functionally graded (FG) plates with graphene nanoplatelets (GPLs) reinforcement. In addition, we propose a novel sandwich plate model with various outstanding features in terms of structural performance. The quasi-3D theory-based isogeometric analysis (IGA) in conjunction with refined plate theory (RPT) is first exploited to capture adequately the thickness stretching effect for porous sandwich FG plate structures reinforced with GPLs. The Non-Uniform Rational B-Splines (NURBS)-based IGA is employed in order to describe exactly the geometry models as well as approximate the unknown field with higher-order derivatives and continuity requirements while the RPT model includes only four essential variables. The sandwich FG plates consist of a core layer containing internal pores reinforced by GPLs and two functionally graded materials (FGMs) skin layers. Effective mechanical properties can be evaluated by employing the Halpin-Tsai model along with the rule of mixture. Various combinations of two porosity distributions and three GPL dispersions in the core layer are thoroughly investigated. Several numerical investigations are conducted to examine the effects of several key parameters on the static bending and free vibration behaviors of sandwich FG plate structures.
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Zang, Quansheng, Jun Liu, Yang Zhou, and Gao Lin. "On Investigation of Liquid Sloshing in Cylindrical Tanks With Single and Multiply Connected Domains Using Isogeometric Boundary Element Method." Journal of Pressure Vessel Technology 143, no. 2 (2020). http://dx.doi.org/10.1115/1.4048321.
Full textAbstract:
Abstract This paper explores an isogeometric boundary element method (IGA-BEM) for sloshing problems in cylindrical tanks with single and multiply connected domains. Instead of the Lagrange basis functions used in the standard BEM, the nonuniform rational B-splines (NURBS) basis functions are introduced to approximate the geometries of the problem boundaries and the unknown variables. Compared with the Lagrange basis functions, NURBS basis functions can accurately reconstruct the geometric boundary of analysis domain with almost no error, and all the data information for NURBS basis functions can be directly obtained from the computer-aided design (cad) or computer-aided engineering (cae) commercial software, which implies the modeling process of IGA-BEM is more simple than that of the standard BEM. NURBS makes it possible for the IGA-BEM to realize the seamless connection between cad and cae software with relative higher calculation accuracy than the standard BEM. Based on the weighted residual method as well as the divergence theorem, the IGA-BEM is developed for the single and multiply connected domains, whose boundaries are separately defined in the parameter space by different knot vectors. The natural sloshing frequencies of the liquid sloshing in a circular cylindrical tank with a coaxial or an off-center circular pipe, an elliptical cylindrical tank with an elliptical pipe, a circular cylindrical tank with multiple pipes are estimated with the introduced method by assuming an ideal (inviscid and incompressible) liquid, irrotational small-amplitude sloshing, and the linear free-surface condition. The comparison between the results obtained by the proposed method and those in the existing literatures shows very good agreements, which verifies the proposed model well. Meanwhile, the effects of radius ratio, liquid depth, number, and location of internal pipe (pipes) on the natural sloshing frequency and sloshing mode are analyzed carefully, and some conclusions are outlined finally.
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Yeung, Stanley Ming Hol, António W. Gomes-Neto, Maryse C.J. Osté, et al. "P1625HIGHER DIETARY ACID LOAD IS ASSOCIATED WITH INCREASED RISK FOR KIDNEY FUNCTION DECLINE AND GRAFT FAILURE IN KIDNEY TRANSPLANT RECIPIENTS." Nephrology Dialysis Transplantation 35, Supplement_3 (2020). http://dx.doi.org/10.1093/ndt/gfaa142.p1625.
Full textAbstract:
Abstract Background and Aims Dietary acid load is associated with low grade metabolic acidosis and might accelerate kidney function decline in patients with chronic kidney disease (CKD). We investigated whether dietary acid load, estimated as net endogenous acid production (NEAP), is associated with kidney function decline in kidney transplant recipients (KTR) and to what extent this association is mediated by variation in venous bicarbonate (HCO3-). Method We used data from 642 KTR with a functioning graft ≥1 year after transplantation who were enrolled in the Transplantlines Food & Nutrition Cohort Study between 2008-2011. We applied the Frassetto equation (NEAP = (54.5 X protein (g/d) / potassium (mEq/d) - 10.2)) to calculate NEAPFFQ using intake reported in food frequency questionnaires and NEAPUrine from assessments of 24 hours urinary urea and potassium excretion. Patients were divided into tertiles of NEAP and differences across tertiles were analyzed by ANOVA, Kruskall-Wallis and Chi-Square tests, as appropriate. Cox regression models were used to study the associations between NEAPFFQ and NEAPUrine (both continuous variables and categories) with the composite endpoint kidney function decline, defined as doubling of serum creatinine or graft failure. Mediation analyses were performed to evaluate whether these associations were explained by venous bicarbonate. Results Mean age was 53±13 years, 56.1% were men, and mean eGFR was 52±20 ml/min/1.73m2. Patients within the highest tertile of NEAPFFQ were younger (P=0.04), more recently transplanted (P=0.002), consumed less fruit and vegetables (P&lt;0.001), more fish (P=0.001), less alcohol (P=0.01), more meat (P&lt;0.001) and had lower serum HCO3- concentration (P=0.02). During a median follow-up time of 5.3 (4.1-6.0) years, 121 (18.8%) patients developed kidney function decline. In multivariable Cox regression analysis, higher NEAPFFQ (per SD increase) was associated with increased risk of kidney function decline, independent of potential confounders, including age, sex, BMI, time after transplantation, primary kidney disease, eGFR and proteinuria (adjusted HR 1.30; 95%CI 1.10-1.53, P=0.002). Compared to patients in the lowest NEAPFFQ tertile, those in the highest tertile had a &gt;1.5 higher risk of kidney function decline (adjusted HR 1.67; 95%CI 1.07-2.62, P=0.03). We observed similar results using NEAPUrine as the study exposure (adjusted HR 1.46 per SD increase; 95%CI 1.24-1.73, P&lt;0.001; adjusted HR 1.99; 95%CI 1.24-3.18, P=0.004 for patients in the highest versus lowest tertile of NEAPUrine). These associations between NEAPFFQ (Figure A) and NEAPUrine (Figure B) with kidney function decline were visualized by fitting multivariable Cox regression models based on restricted cubic splines. Mediation analyses estimated that venous HCO3- at baseline mediated 19.3% (P=0.008) of the association between NEAPFFQ and kidney function decline and 26.5% (P=0.002) of the association between NEAPUrine with kidney function decline. Conclusion Higher NEAP is associated with a higher risk for kidney function decline in KTR, and this association was in part mediated by venous HCO3-. We speculate that reducing dietary acid load might mitigate the risk of kidney function decline in KTR.