Flat systems, equivalence and trajectory generation

Flat systems, an important subclass of nonlinear control systems introduced via differential-algebraic methods, are defined in a differential geometric framework. We utilize the infinite dimensional geometry developed by Vinogradov and coworkers: a control system is a diffiety, or more precisely, an ordinary diffiety, i.e. a smooth infinite-dimensional manifold equipped with a privileged vector field. After recalling the definition of a Lie-Backlund mapping, we say that two systems are equivalent if they are related by a Lie-Backlund isomorphism. Flat systems are those systems which are equivalent to a controllable linear one. The interest of such an abstract setting relies mainly on the fact that the above system equivalence is interpreted in terms of endogenous dynamic feedback. The presentation is as elementary as possible and illustrated by the VTOL aircraft

Continuum approach to wide shear zones in quasi-static granular matter

Slow and dense granular flows often exhibit narrow shear bands, making them ill-suited for a continuum description. However, smooth granular flows have been shown to occur in specific geometries such as linear shear in the absence of gravity, slow inclined plane flows and, recently, flows in split-bottom Couette geometries. The wide shear regions in these systems should be amenable to a continuum description, and the theoretical challenge lies in finding constitutive relations between the internal stresses and the flow field. We propose a set of testable constitutive assumptions, including rate-independence, and investigate the additional restrictions on the constitutive relations imposed by the flow geometries. The wide shear layers in the highly symmetric linear shear and inclined plane flows are consistent with the simple constitutive assumption that, in analogy with solid friction, the effective-friction coefficient (ratio between shear and normal stresses) is a constant. However, this standard picture of granular flows is shown to be inconsistent with flows in the less symmetric split-bottom geometry - here the effective friction coefficient must vary throughout the shear zone, or else the shear zone localizes. We suggest that a subtle dependence of the effective-friction coefficient on the orientation of the sliding layers with respect to the bulk force is crucial for the understanding of slow granular flows.Comment: 11 pages, 7 figure

Converging roads: the latest science from the 2017 IAS HIV Cure and Cancer Forum

Conference presented in the 2017 IAS HIV Cure and Cancer Forum took place in Paris on 22–23 July.S

Memory-unit design for real-time-digital-signal-processing applications

The increase in the complexity of signal processing and image algorithms, under the execution time constraint, and taking into consideration the new constraints (area, speed, consumption etc .), makes exploration space a manually unachievable concept . The framework development for design became a necessity at that time, so as to offer estimation tools and semi-automatic synthesis to the designer, allowing the design of different parts of the application . In the last decade, scheduling and resources allocation algorithms (operators, registers etc .) have given rise to a number of synthesis tools of a high level for the designing of operative and control parts . However, if these tools allow the designing of these two units in a more or less automatic way, then it is not the same for the memorisation unit which should, most of the time, be explicitly designed . The evolution of applications, notably in signal processing, applies itself, not only to the operative system part, but also and above all, to the memorisation ; this last point can rapidly become the critical point in the implementation .L'augmentation de complexité des algorithmes de traitement du signal et de l'image, sous contrainte de temps d'exécution, et la prise en compte de nouvelles contraintes (surface, vitesse, consommation, etc) rend l'exploration de l'espace de conception irréalisable de manière manuelle. Le développement de plates-formes de conception est alors devenu une nécessité afin d'offrir aux concepteurs des outils d'estimation et de synthèse semi-automatique permettant de concevoir les différentes parties d'une application. Dans la dernière décennie, les méthodes d'ordonnancement et d'assignation des ressources (opérateurs, registres, ...etc) ont donné naissance à de nombreux outils de synthèse de haut niveau pour la conception des parties opérative et de contrôle. Toutefois, si ces outils permettent de concevoir de manière plus ou moins automatique ces deux unités, il n'en est pas de même pour l'unité de mémorisation qui doit, la plupart du temps, être conçue explicitement. L'évolution des applications, notamment dans le domaine du traitement du signal, s'applique non seulement à la partie opérative du système, mais aussi et surtout à la mémorisation; cette dernière pouvant rapidement devenir le point critique de la mise en œuvre. Ce papier présente une méthodologie de conception de ces unités. Partant d'une description des besoins en terme de mémorisation, nous décomposons la synthèse des mémoires en quatre étapes. Cette synthèse vient alors compléter le flot de conception d'un outil de synthèse d'architectures (par exemple de l'outil Gaut)

Nouvelles interconnexions globales à haut débit pour la réalisation de microsystèmes communicants de type SIP.

4 pagesNational audienceLes microsystèmes intégrés sur puces (SoC) ou en boîtier (SiP) sont actuellement en plein essor et nécessitent le développement de nouvelles structures d'interconnexions reliant les différents blocs fonctionnels entre eux. Nous proposons dans ce papier l'étude du concept d'interconnexion RF par couplage capacitif qui est une solution intéressante pour remplacer les interconnexions classiques. Dans un premier temps nous décrivons le principe de cette technique et montrons à l'aide de simulations circuits de type ADS, la faisabilité de ce concept. Nous présentons ensuite la caractérisation d'un canal de type microruban, réalisée sous HFSS ainsi que son comportement dans le domaine temporel. I. Introductio

Análisis biomecánico del pie protésico Bioc-dm2

La marcha humana es uno de los aspectos que comprometen directamente el nivel de bienestar del ser humano, además deimpactar de manera emocional y física, también en el cotidiano vivir. Para este estudio nos encontramos inmersos en el reto de poder mejoraralgunas condiciones de la marcha en un paciente que haya sufrido pérdida de miembros inferiores, específicamente a nivel transtibial o transfemoral.Dado que nuestro propósito fue el análisis, diseño y manufactura de un componente protésico de miembro inferior que supla las necesidades propiasy de funcionalidad, es necesario construir un pie con todos los estándares de calidad que constituya todos y cada uno de los movimientos requeridospara formar el complejo patrón fundamental de la marcha; además que pueda soportar el peso fácilmente y el uso cotidiano además de lascaracterísticas físicas de nuestro paciente objeto de estudio. Al realizar la validación física y en la marcha humana, se observa una respuestaadecuada en términos mecánicos, de material de construcción y el dinamismo del componente, evidenciando la adecuada construcción y ensambledel componente. Por otro lado, podemos evidenciar que el diseño y la verificación del componente nos muestra un elemento competitivo, comparadocon los elementos existentes en el mercado; Haciendo necesario la verificación ante Instituto Nacional de Vigilancia de Medicamentos y AlimentosINVIMA, y la puesta en marcha del dispositivo replicador de uso, para la verificación del componente frente a la norma ISO 10328.Walking is one of the aspects directly compromising human wellbeing, as it has a physical and emotional impact in daily life.For this study, we delve into the challenge of improving some walking conditions in a patient suffering lower limb loss, specifically at transtibialor transfemoral levels. Given that our purpose was the analysis, design and manufacture of a lower-limb prosthetic component, which fills the needsfor functionality, it became necessary to build a foot with all the quality standards associated to each and all movements required to form thecomplex fundamental pattern of walking. Besides, this foot should also easily endure weight, daily use and physical characteristics of the patientobject of this study. When performing physical validation and during human walk, a proper response is observed in terms of mechanics, materialsand dynamics of the component, thus making evident proper construction and assembly. On the other hand, it is feasible that design and verificationof the component provided a competitive element, as compared to existing elements currently in the market. The previous situation generated theneed for verification from the National Institute for Medications and Food (INVIMA), as well as the revision of the use replying device, forcomponent verification, in accordance with ISO 10328

Economic and psychological burden of scheduled surgery cancellation in a sub-Saharan country (Burkina Faso)

Background: Cancellation of scheduled surgery creates a financial burden for hospitals, caregivers and patients. Cancellation causes emotional stress, which impacts on outcomes. In poor countries where the adequacy of healthcare is limited, the ethical dilemma created by scheduled surgery cancellation is particularly important.Objective: To identify the incidence, cost and emotional impact of elective surgical cancellation in a teaching hospital in BurkinoFaso.Methods: A four month, prospective, observational study was undertaken in a teaching hospital (Yalgado Ouedraogo). All surgical patients were eligible. The causes of cancellation, financial cost and patients’ emotional response were assessed. The cost was estimated using a tool adapted for the economic cost of African job types.Results: During the study period, 1 088 cases were scheduled to undergo inpatient surgery. Of these, 239 cases (21.9%) were cancelled. Among the cancelled cases, 237 were cancelled during preparation in the surgical ward and two cases were cancelled in the operation room. A large number of the patients were housewives (n = 87). The highest cancellation rate (35.9%) was found in general surgery. Cancellation was judged avoidable in 214 cases (89.5%). The total cost of surgery cancellation to the hospital was US$19 147 (mean value US$ 80 per patient). Patients lost a mean of US$62.70, which represented 117.6$ 4 989 ). Cancellation caused a negative emotional reaction in 205 patients (85.7%) and ‘sadness’ was the most frequent (54.8%; n = 131). Cancellation resulted in 163 days of work lost.Conclusion: Based on income, the cost of day of surgery cancellation was high in Burkina Faso.Keywords: cost, emotional reaction, psychology, surgery cancellatio