Jurnal Edukasi
Not a member yet
4879 research outputs found
Sort by
Wireless nanosensors for embedded measurement in concrete structures
No full textNICOM 5 - Fifth International Symposium on Nanotechnology in Construction, CHICAGO, ETATS-UNIS, 24-/05/2015 - 26/05/2015In this work we propose a wireless architecture for embedded monitoring in concrete. The modular structure of the system allows it to be adapted to different types of sensors. We present the application of such architecture for the detection of microcracks in concrete. A carbon nanotube strain sensor recently developed by the group is used to track mechanical deformations. Full temperature compensation is achieved by a specific conditioning circuit
Improved numerical integration for locking treatment in isogeometric structural elements. Part II: Plates and shells
No full textInternational audienceHighlights • We model Reissner–Mindlin isogeometric plates and shells. • We examine membrane and shear locking in bending dominated problems. • Higher continuity elements exhibit superior accuracy when no locking occurs. • We extend one-dimensional reduced quadrature rules to two-dimensional rules. • We assess the performance of the schemes using the shell obstacle course problems. Abstrac
Axisymmetric eddy current inspection of highly conducting thin layers via asymptotic models
No full textInternational audienceThin copper deposits covering the steam generator tubes can blind eddy current probes in non-destructive testings of problematic faults and are therefore important to be identified. Existing methods based on shape reconstruction using eddy current signals encounter difficulties of high numerical costs due to the layer's small thickness and high conductivity. In this article, we approximate the axisymmetric eddy current problem with some appropriate asymptotic models using effective transmission conditions representing the thin deposits. In these models, the geometrical information related to the deposit is transformed into parameter coefficients on a fictitious interface. Standard iterative inversion algorithm is then applied to the asymptotic models in order to reconstruct the thickness of the thin copper layers. Numerical tests both validating the asymptotic model and benefit of the inversion procedure are provided
A quasi-backscattering problem for inverse acoustic scattering in the Born regime
No full textInternational audienceWe consider the problem of detecting three-dimensional inclusions from quasi-backscattering far field data generated by an incident field of time-harmonic fixed frequency plane waves modeled with the Born approximation. We assume only partial far field data is known and use a sampling-type method to reconstruct small obstacles and extended spherical obstacles. In particular, at the location of a device transmitting an incident wave, we assume far field data is collected only along a line extending a short distance from the transmitting device. Several numerical examples are provided to demonstrate the effectiveness of the approach
Assimilation de Données et Mesures Primaires REP
No full textA Pressurized Water Reactor (PWR) Reactor Coolant System (RCS) is a highly complex physical process: heterogeneous power, flow and temperature distributions are difficult to be accurately measured, since instrumentations are limited in number, thus leading to the relevant safety and protection margins.EDF R&D is seeking to assess the potential benefits of applying Data Assimilation to a PWR's RCS (Reactor Coolant System) measurements, in order to improve the estimators for parameters of a reactor's operating setpoint, i.e. improving accuracy and reducing uncertainties and biases of measured RCS parameters.In this thesis, we define a 0D semi-empirical model for RCS, satisfying the description level usually chosen by plant operators, and construct a Monte-Carlo Method (inspired from Ensemble Methods) in order to use this model with Data Assimilation tools. We apply this method on simulated data in order to assess the reduction of uncertainties on key parameters: results are beyond expectations, however strong hypotheses are required, implying a careful preprocessing of input data.Le circuit primaire d'un réacteur à eau pressurisée (REP) est un système thermohydraulique complexe, présentant des champs hétérogènes de puissances, températures et débits dans des conditions extrêmes : l'instrumentation in situ est limitée en nombre, localisation et précision. De ce fait, la connaissance de ces paramètres de fonctionnement est impactée par des incertitudes de représentativité notamment, prises en compte dans la conception et intégrées dans les protections d'exploitation.Dans ce contexte, EDF R&D cherche à évaluer les apports potentiels de l'Assimilation de Données, un ensemble d'outils mathématiques très utilisé en géosciences qui permettent de corriger des estimations issus de modèles à l'aide de mesures provenant du système réel modélisé, pour une meilleure caractérisation (justesse, incertitudes) des paramètres du point de fonctionnement primaire nominal.Dans cette thèse, nous définissons un modèle semi-empirique 0D adapté au niveau de description usuellement choisi par les exploitants, et développons une méthodologie (de type Monte-Carlo et inspirée des Méthodes d'Ensemble) pour utiliser ce modèle dans un cadre d'Assimilation de Données. L'application de cette méthodologie à des données simulées permet d'évaluer la réduction des incertitudes pesant sur les paramètres-clés : les résultats sont au-delà des espérances initiales mais nécessitent des hypothèses fortes impliquant un prétraitement soigneux des données d'entrée
Geographic distribution of zonal wind and UV albedo at cloud top level from VMC camera on Venus Express: Influence of Venus topography through stationary gravity waves vertical propagation
No full textInternational audienceBased on the analysis of UV images (at 365 nm) of Venus cloud top collected with VMC camera on board Venus Express [4,5], it is found that the zonal wind speed south of the equator (from 5°S to 15°s) shows a conspicuous variation with geographic longitude of Venus, correlated with underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the up lift of air when the horizontal wind encounters a mountain slope. The cloud albedo map at 365 nm varies also in longitude and latitude, perhaps the result of increased vertical mixing associated to wave breaking, and decreased abundance of the UV absorber which makes the contrast in images
Secular Stagnation: Theory and Remedies
No full textThis paper relies on a Ramsey model with money to o¤er a simple theory of secular stagnation. The permanent failure of the economy to produce at full capacity results from three features: (i) The combination of the zero lower bound on the nominal interest rate and of an in ‡ation ceiling imposes a lower bound on the real interest rate; (ii) Some dynastic households have a high propensity to save, due to a preference for wealth; (iii) A downward wage rigidity breaks the de ‡ationary spiral resulting from the lack of demand. In this framework, I derive the paradox of ‡exibility, of thrift, and of toil. If the in ‡ation ceiling cannot be raised, then the government needs to rely on …scal policy to escape secular stagnation. However, a conventional …scal stimulus is not an e¢ cient response to a permanent liquidity trap, and can even be welfare reducing. The solution is instead to tax household wealth and to subsidize income from physical capital, through an investment subsidy or a reduction in the taxation of corporate income. This optimal policy is revenue neutral and implements the …rst-best allocation of resources. However, to avoid a jump in the price level upon implementation of the optimal policy, the government needs to redeem the money that had previously been supplied to …nance public de…cits
An adequate compositional encoding of bigraph structure in linear logic with subexponentials
No full textInternational audienceIn linear logic, formulas can be split into two sets: classical (those that can be used as many times as necessary) or linear (those that are consumed and no longer available after being used). Subexponentials generalize this notion by allowing the formulas to be split into many sets, each of which can then be specified to be classical or linear. This flexibility increases its expressiveness: we already have adequate encodings of a number of other proof systems, and for computational models such as concurrent constraint programming, in linear logic with subexponentials (SEL). Bigraphs were proposed by Milner in 2001 as a model for ubiquitous computing, subsuming models of computation such as CCS and the π-calculus and capable of modeling connectivity and locality at the same time. In this work we present an encoding of the bigraph structure in SEL, thus giving an indication of the expressive power of this logic, and at the same time providing a framework for reasoning and operating on bigraphs. Our encoding is adequate and therefore the operations of composition and juxtaposition can be performed on the logical level. Moreover, all the proof-theoretical tools of SEL become available for querying and proving properties of bigraph structures
Sons as Widowhood Insurance: Evidence from Senegal
No full textExploiting original data from a Senegalese household survey, we provide evidence that fertility choices are partly driven by women's needs for widowhood insurance. We use a duration model of birth intervals to show that women most at risk in case of widowhood intensify their fertility, shortening birth spacing, until they get a son. Insurance through sons might entail substantial health costs since short birth spacing raises maternal and infant mortality rates
Elastocapillary Instability in Mitochondrial Fission
No full textInternational audienceMitochondria are dynamic cell organelles that constantly undergo fission and fusion events. These dynamical processes, which tightly regulate mitochondrial morphology, are essential for cell physiology. Here we propose an elastocapillary mechanical instability as a mechanism for mitochondrial fission. We experimentally induce mitochondrial fission by rupturing the cell's plasma membrane. We present a stability analysis that successfully explains the observed fission wavelength and the role of mitochondrial morphology in the occurrence of fission events. Our results show that the laws of fluid mechanics can describe mitochondrial morphology and dynamics