37 research outputs found
Ricardo Rojas: a Journey to the Interior, the Popular Culture and the Unconscious
No full textEste artículo indaga en torno a las figuraciones del intelectual presentes en algunos ensayos y conferencias de Rojas. En estos trabajos, el autor se auto-define como un intérprete del mestizaje, dispuesto a viajar, en términos simbólicos, hacia el pasado histórico y hacia el inconsciente colectivo, para recuperar las significaciones profundas presentes en el folclore. Además, analiza el modo en que la correspondencia intercambiada con los peruanos Luis Valcárcel y Uriel García, entre otros, deja ver la presencia de fuertes lazos de solidaridad intelectual, la circulación fluida de ideas y la formación conjunta de archivos arqueológicos y fotográficos del mundo indígena. El diálogo de Rojas con estos intelectuales peruanos redunda en una mutua legitimación regionalista, incluyendo una positiva americanización e indigenización simbólica de la Argentina.This article analyzes representations of the intellectual that appeared in essays and conferences of Ricardo Rojas. In these works, the author defines himself as an interpreter of miscegenation, willing to travel, in symbolic terms, to the historical past and toward a collective unconscious to recover the deep meanings that exist in folklore. It also analyzes the way that interchanges with Peruvians Luis Varcárcel and Uriel García, among others, allows one to see the existence of strong ties of intellectual solidarity, the free flow of ideas, and the joint formation of archeological and photographical archives of the indigenous world. Rojas’ dialogue with these Peruvian intellectuals results in a mutual regionalist legitimation, including a positive Americanization –and a symbolic indigenization– of Argentina.
and toward a collective unconscious to recover the deep meanings that exist in folklore.
It also analyzes the way that interchanges with Peruvians Luis Varcárcel and Uriel García, among others, allows one to see the existence of strong ties of intellectual solidarity, the free flow of ideas, and the joint formation of archeological and photographical archives of the indigenous world. Rojas’ dialogue with these Peruvian intellectuals results in a mutual regionalist legitimation, including a positive Americanization –and a symbolic indigenization– of Argentina.Fil: Mailhe, Alejandra Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Humanidades y Ciencias Sociales. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales; Argentin
Approximate message passing for compressed sensing magnetic resonance imaging
No full textMagnetic Resonance Imaging (MRI) is a non-invasive, non-ionising imaging modality with unrivalled soft tissue contrast. A key consideration for MRI is data acquisition time, which is limited by inherent technological and physiological constraints. Compressed sensing is a relatively recent framework that can reduce the MRI acquisition time by undersampling randomly and exploiting presumed redundancies in the data.
The Approximate Message Passing (AMP) algorithm is an iterative compressed sensing method that efficiently reconstructs signals that have been sampled with i.i.d. sub-Gaussian sensing matrices. However, when Fourier coefficients of a signal with non-uniform spectral density are sampled, such as in MRI, AMP performs poorly in practice.
In response, this thesis proposes the Variable Density Approximate Message Passing (VDAMP) algorithm for undersampled MRI data. We present three versions of VDAMP: single-coil VDAMP, where receiver coil sensitivities are ignored, Parallel-VDAMP (P-VDAMP), which includes coil sensitivities, and Denoising-P-VDAMP (D-P-VDAMP), which incorporates the statistical modelling capabilities of neural networks. Central to VDAMP is a property that we term "coloured state evolution", where the difference between the intermediate image estimate at a given iteration and the ground truth is distributed according to a zero-mean Gaussian with known covariance. We demonstrate that coloured state evolution can be leveraged to yield an algorithm that converges rapidly, and to a competitive reconstruction quality, without the need to hand-tune model parameters
Updating of a possibilistic knowledge base by crisp or fuzzy transition rules
No full textInternational audienceIn this paper, partial knowledge about the possible transitions which can take place in a dynamical environment is represented by a set of pairs of propositional formulae, with the following intended meaning: If the first one is true then the second will be true at the next step. More generally, a certainty level representing the lower bound of a necessity measure can be associated with the second formula for modelling uncertain transitions. A possibilistic transition graph relating possible states can be deduced from these pairs and used for updating an uncertain knowledge base encoded in possibilistic logic and semantically associated to a possibility distribution. The updating of the base can be directly performed at the syntactic level from the transition pairs and the possibilistic logic formulas, in agreement with the semantics of the base and of the transitions. As there are many sets of pairs that represent the same transition graph, it is convenient to find a representative in this class that gives the easiest syntactic computations. Besides, a second type of weighted pairs of formulas is introduced for refining the representation of the available information about transitions. While the first type of pairs encodes the transitions that are not non-impossible (using necessity measures), the second type of pairs provides the transitions whose possibility is guaranteed. This constitutes a bipolar description of the possible transitions
Raw juice extraction from sugar cane and sugar beet
No full textDocument uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
Modèles et algorithmes pour la modélisation parcimonieuse de signaux de grande dimension
No full textCette thèse propose des algorithmes rapides pour les représentations parcimonieuses. Les représentations parcimonieuses consistent à approcher le signal par une combinaison linéaire de peu d'atomes choisis dans un dictionnaire redondant (plus d'atomes que la dimension du signal). Comment décomposer un signal donné sur un dictionnaire donné ? C'est un problème NP-complet. Les algorithmes approchés existants sont trop coûteux pour être employés sur de grands signaux ou bien calculent une approximation grossière. Nous proposons un nouvel algorithme, LocOMP, qui passe à l'échelle sans sacrifier la qualité d'approximation. LocOMP nécessite des dictionnaires locaux : la longueur du support d'un atome est petite devant celle du signal. Comment apprendre un dictionnaire qui permet la représentation parcimonieuse d'une famille de signaux donnée ? C'est un problème encore plus complexe : on le résout habituellement en itérant plusieurs décompositions parcimonieuses. Nous proposons une amélioration de l'algorithme d'Olshausen-Field qui optimise le dictionnaire par descente de gradient à pas fixe. Nous exprimons le pas optimal la descente. L'algorithme converge ainsi plus vite vers un meilleur dictionnaire. Enfin, nous avons appliqué ces outils pour isoler les signaux de fibrillation atriale dans l'électrocardiogramme du patient. La fibrillation atriale est une arythmie cardiaque : les atria tremblent au lieu de battre. On souhaite observer la fibrillation dans l'ECG, mais elle est mélangée à l'activité ventriculaire. Notre méthode de séparation est basée sur l'apprentissage d'un dictionnaire pour la fibrillation et un pour l'activité ventriculaire, tous deux appris sur le même ECG.This thesis provides fast algorithms for sparse representations. Sparse representations consist in modelling the signal as a linear combination of a few atoms chosen among a redundant (more atoms than the signal dimension) dictionary. How to decompose a given signal over a given dictionary? This problem is NP-Complete. Existing suboptimal algorithms are either to slow to be applied on large signals or compute coarse approximations. We propose a new algorithm, LocOMP, that is both scalable and achieves good approximation quality. LocOMP only works with local dictionaries: the support of an atom is much shorter than the signal length. How to learn a dictionary on which a given class of signals can be decomposed? This problem is even more difficult: its resolution usually involves several sparse decompositions. We propose to improve the Olshausen-Field algorithm. It optimizes the dictionary via fixed step gradient descent. We show how to compute the optimal step. This makes the algorithm converge faster towards a better dictionary. These algorithms were applied to the study of atrial fibrillation. Atrial fibrillation is a common heart arrhythmia: the atria start vibrating instead of beating. One would like to observe I in the patient's ECG but the ECG is a mixture of fibrillation and ventricular activity. Our separation method is based on the learning of one dictionary for the fibrillation and one for the ventricular activity, both of them learnt on the patient's ECG.RENNES1-BU Sciences Philo (352382102) / SudocRENNES-INRIA Rennes Irisa (352382340) / SudocSudocFranceF
Dictionary learning via projected maximal exploration
No full textThis work presents a geometrical analysis of the
Large Step Gradient Descent (LGD) dictionary learning algorithm.
LGD updates the atoms of the dictionary using a gradient
step with a step size equal to twice the optimal step size.
We show that the large step gradient descent can be understood
as a maximal exploration step where one goes as far away as
possible without increasing the the error. We also show that the
LGD iteration is monotonic when the algorithm used for the
sparse approximation step is close enough to orthogonal
Ricardo Rojas: viaje al interior, la cultura popular y el inconsciente
No full textThis article analyzes representations of the intellectual that appeared in essays and conferences of Ricardo Rojas. In these works, the author defines himself as an interpreter of miscegenation, willing to travel, in symbolic terms, to the historical past and toward a collective unconscious to recover the deep meanings that exist in folklore. It also analyzes the way that interchanges with Peruvians Luis Varcárcel and Uriel García, among others, allows one to see the existence of strong ties of intellectual solidarity, the free flow of ideas, and the joint formation of archeological and photographical archives of the indigenous world. Rojas’ dialogue with these Peruvian intellectuals results in a mutual regionalist legitimation, including a positive Americanization –and a symbolic indigenization– of Argentina.Este artículo indaga en torno a las figuraciones del intelectual presentes en algunos ensayos y conferencias de Ricardo Rojas. En estos trabajos, el autor se auto-define como un intérprete del mestizaje, dispuesto a viajar, en términos simbólicos, hacia el pasado histórico y hacia el inconsciente colectivo, para recuperar las significaciones “profundas” presentes en el folclore. Además, el texto analiza el modo en que la correspondencia intercambiada con los peruanos Luis Valcárcel y Uriel García, entre otros, deja ver la presencia de fuertes lazos de solidaridad intelectual, la circulación fluida de ideas y la formación conjunta de archivos arqueológicos y fotográficos del mundo indígena. El diálogo de Rojas con estos intelectuales peruanos redunda en una mutua legitimación regionalista, incluyendo una positiva americanización –e indigenización simbólica– de la Argentina
Fast orthogonal sparse approximation algorithms over local dictionaries
No full textIn this work we present a new greedy algorithm for sparse approximation called LocOMP. LocOMP is meant to be run on local dictionaries made of atoms with much shorter supports than the signal length. This notably encompasses shift-invariant dictionaries and time–frequency dictionaries, be they monoscale or multiscale. In this case, very fast implementations of Matching Pursuit are already available. LocOMP is almost as fast as Matching Pursuit while approaching the signal almost as well as the much slower Orthogonal Matching Pursuit.LTS
Ricardo Rojas: a journey to the interior, the popular culture and the unconscious
No full textEste artículo indaga en torno a las figuraciones del intelectual presentes en algunos ensayos y conferencias de Ricardo Rojas. En estos trabajos, el autor se autodefine como un intérprete del mestizaje, dispuesto a viajar, en términos simbólicos, hacia el pasado histórico y hacia el inconsciente colectivo, para recuperar las significaciones “profundas” presentes en el folclore. Además, el texto analiza el modo en que la correspondencia intercambiada con los peruanos Luis Valcárcel y Uriel García, entre otros, deja ver la presencia de fuertes lazos de solidaridad intelectual, la circulación fluida de ideas y la formación conjunta de archivos arqueológicos y fotográficos del mundo indígena. El diálogo de Rojas con estos intelectuales peruanos redunda en una mutua legitimación regionalista, incluyendo una positiva americanización –e indigenización simbólica– de la Argentina.This article analyzes representations of the intellectual that appeared in essays and conferences of Ricardo Rojas. In these works, the author defines himself as an interpreter of miscegenation, willing to travel, in symbolic terms, to the historical past and toward a collective unconscious to recover the deep meanings that exist in folklore. It also analyzes the way that interchanges with Peruvians Luis Varcárcel and Uriel García, among others, allows one to see the existence of strong ties of intellectual solidarity, the free flow of ideas, and the joint formation of archeological and photographical archives of the indigenous world. Rojas' dialogue with these Peruvian intellectuals results in a mutual regionalist legitimation, including a positive Americanization -and a symbolic indigenization- of Argentina.Facultad de Humanidades y Ciencias de la Educació
Pseudoarchéologie et politique chez Jacques de Mahieu
No full textThe French intellectual Jacques de Mahieu (who was linked to the collaborationist extreme right in France, and close to Peronism when he migrated to Argentina after the liberation of France from the Nazis) introduced a particularly reactionary inflection within the interdiscursive debate on the role of archaeology in the definition of continental identity, by deploying the hypothesis of a pre-Hispanic conquest of the continent by the Vikings and the Knights Templar, who would have reached even the Argentine northwest, thus being responsible for all indigenous civilizational achievements. This paper focuses on the essay El imperiovikingo de Tiahuanacu (The Viking Empire of Tiahuanacu, 1985 [1982]), considering some points of contact between de Mahieu’s thesis and the previous esoteric speculations concerning the American romantic Indianism and its derivations linked to Nazism. At the same time, this paper establishes a dialogue between the ideas implicit therein on social, cultural and political dynamics with the reflections of this same author on biopolitics and the “organized community”, elaborated in previous decades.El intelectual francés Jacques de Mahieu (vinculado a la extrema derecha colaboracionista en Francia, y próximo al peronismo al migrar al país, tras la liberación de Francia de los nazis) introduce una inflexión especialmente reaccionaria al interior del debate interdiscursivo en torno al papel de la arqueología en la definición de la identidad continental, al desplegar la hipótesis de una conquista prehispánica del continente, por parte de los vikingos y los caballeros templarios, quienes habrían alcanzado incluso el noroeste argentino, siendo los responsables de todos los logros civilizatorios indígenas. Este artículo se centra en el ensayo El imperio vikingo de Tiahuanacu (1985 [1982]), considerando algunos puntos de contacto entre las tesis de de Mahieu y las especulaciones esotéricas previas del indianismo romántico americano y sus derivas vinculadas con el nazismo. Al mismo tiempo, este trabajo pone en diálogo las ideas allí implícitas sobre la dinámica social, cultural y política, con las reflexiones del mismo autor sobre la biopolítica y la “comunidad organizada”, elaboradas en décadas previas.L’intellectuel français Jacques de Mahieu (lié à l’extrême droite collaborationniste en France, et proche du péronisme lors de son immigration dans le pays, après la libération de la France du nazisme) introduit une inflexion particulièrement réactionnaire dans le débat interdiscursif autour du rôle de l’archéologie dans la définition de l’identité continentale, en déployant l’hypothèse d’une conquête préhispanique du continent, par les Vikings et les Templiers, qui auraient même atteint le nord-ouest de l’Argentine, étant ceux qui sont responsables de toutes les réalisations civilisationnelles autochtones. Cet article se concentre sur l’essai El imperiovikingo de Tiahuanacu (L’empire viking de Tiahuanacu, 1985 [1982]), considérant quelques points de contact entre les thèses de Mahieu et les spéculations ésotériques antérieures sur l’indianisme romantique américain et ses dérives liées au nazisme. En même temps, cet ouvrage fait dialoguer les idées qui y sont implicites sur les dynamiques sociales, culturelles et politiques, avec les réflexions du même auteur sur la biopolitique et la “communauté organisée”, développées au cours des décennies précédentes
