Littérature scientifique sur le sujet « Extensions confinées »
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Articles de revues sur le sujet "Extensions confinées"
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De Sarkar, Tanmay. « The prevalence of web browser extensions use in library services : an exploratory study ». Electronic Library 33, no 3 (1 juin 2015) : 334–54. http://dx.doi.org/10.1108/el-04-2013-0063.
Texte intégralRésumé :
Purpose – The paper aims to present an outline how libraries are harnessing browser extensions to provide an easy and convenient access to library resources and services. Investigating the features, purposes of use and types of browser extensions prevalent among libraries in different regions, the paper seeks to measure the degree of implementation of browser extensions. Design/methodology/approach – Stratified sampling method was followed to select academic libraries, and convenient sampling method was applied to select public libraries from four continents – Asia, Oceania, Europe and North America. Two-step web content analysis was applied to gather data along the select dimensions. Findings – The study contributes to the recent advances in application of browser extension with numerous examples focussing on the relevance of different approaches adopted by the libraries. Providing a framework of proportionate implementation along checkpoints, the study also highlights degree of acceptance of browser extension among libraries in different regions. Research limitations/implications – The investigation was restricted to libraries having English websites and confined to four continents only. This study aims at improving understanding among the librarians about the intended use and application of browser extension and helping them benchmark their effort in support of education, research and training. The current investigation expands the scope of future research on remaining regions and website whose contents are in non-English language to attain a broader perspective of its implementation. Originality/value – The article may guide library professionals to use, develop and promote the implementation of browser extension in libraries. The checkpoints used here may serve as bedrock for framing questionnaire and interview schedule for conducting future research examining users’ perception of browser extension in the context of library resources and usage pattern, to fully comprehend its practicability and usefulness.
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Wilson, Elizabeth Parker, Pablo Granado, Pablo Santolaria, Oriol Ferrer et Josep Anton Muñoz. « Inversion of accommodation zones in salt-bearing extensional systems : insights from analog modeling ». Solid Earth 14, no 7 (12 juillet 2023) : 709–39. http://dx.doi.org/10.5194/se-14-709-2023.
Texte intégralRésumé :
Abstract. This work uses sandbox analog models to analyze the formation and subsequent inversion of a decoupled extensional system comprised of two segmented half-grabens separated by a diffuse accommodation zone with thick early syn-rift salt. The segmented half-grabens strike perpendicular to the direction of extension and subsequent shortening. Rifting first created a basement topography that was infilled by model salt, followed by a second phase of extension and sedimentation, followed afterwards by inversion. During the second phase of extension, syn-rift syncline minibasins developed above the basement extensional system and extended beyond the confines of the fault blocks. Sedimentary downbuilding and extension initiated the migration of model salt to the basement highs, forming salt anticlines, reactive diapirs, and salt walls perpendicular to the direction of extension, except for along the intervening accommodation zone where a slightly oblique salt anticline developed. Inversion resulted in decoupled cover and basement thrust systems. Thrusts in the cover system nucleated along squeezed salt structures and along primary welds. New primary welds developed where the cover sequence touched down on basement thrust tips due to uplift, salt extrusion, and syn-contractional downbuilding caused by the loading of syn-contractional sedimentation. Model geometries reveal the control imposed by the basement configuration and distribution of salt in the development of a thrust front from the inversion of a salt-bearing extensional system. In 3D, the interaction of salt migrating from adjacent syn-rift basins can modify the expected salt structure geometry, which may in turn influence the location and style of thrust in the cover sequence upon inversion. Results are compared to the Northern Lusitanian Basin, offshore Portugal, and the Isábena area of the South-Central Pyrenees, Spain.
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Lee, Doojin, et Amy Q. Shen. « Interfacial Tension Measurements in Microfluidic Quasi-Static Extensional Flows ». Micromachines 12, no 3 (6 mars 2021) : 272. http://dx.doi.org/10.3390/mi12030272.
Texte intégralRésumé :
Droplet microfluidics provides a versatile tool for measuring interfacial tensions between two immiscible fluids owing to its abilities of fast response, enhanced throughput, portability and easy manipulations of fluid compositions, comparing to conventional techniques. Purely homogeneous extension in the microfluidic device is desirable to measure the interfacial tension because the flow field enables symmetric droplet deformation along the outflow direction. To do so, we designed a microfluidic device consisting of a droplet production region to first generate emulsion droplets at a flow-focusing area. The droplets are then trapped at a stagnation point in the cross junction area, subsequently being stretched along the outflow direction under the extensional flow. These droplets in the device are either confined or unconfined in the channel walls depending on the channel height, which yields different droplet deformations. To calculate the interfacial tension for confined and unconfined droplet cases, quasi-static 2D Darcy approximation model and quasi-static 3D small deformation model are used. For the confined droplet case under the extensional flow, an effective viscosity of the two immiscible fluids, accounting for the viscosity ratio of continuous and dispersed phases, captures the droplet deformation well. However, the 2D model is limited to the case where the droplet is confined in the channel walls and deforms two-dimensionally. For the unconfined droplet case, the 3D model provides more robust estimates than the 2D model. We demonstrate that both 2D and 3D models provide good interfacial tension measurements under quasi-static extensional flows in comparison with the conventional pendant drop method.
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Watters, Thomas R., Francis Nimmo et Mark S. Robinson. « Extensional troughs in the Caloris Basin of Mercury : Evidence of lateral crustal flow ». Geology 33, no 8 (1 août 2005) : 669–72. http://dx.doi.org/10.1130/g21678ar.1.
Texte intégralRésumé :
Abstract Thirty years ago Mariner 10 revealed extensional troughs that form giant polygons in the floor material of the Caloris impact basin, Mercury. The polygonal troughs occur in the interior of the basin and overprint wrinkle ridges formed in an earlier stage of compression. In contrast, lunar and martian basins exhibit extensional troughs that are circumferential and confined to basin margins. Loading by basin-filling material can explain the extensional and compressional features seen in deformed lunar and martian basins, but not the existence of the Caloris polygonal troughs. Here we suggest that the Caloris troughs formed from late-stage basin uplift and extension due to lateral flow of a relatively thick crust toward the basin center. If such lateral flow occurs, the resulting timing, location, and magnitude of the extensional stresses predicted by our model are consistent with those inferred from the polygonal troughs. These results are not strongly dependent on the degree of lateral flow or the assumed crustal rigidity. For a dry plagioclase rheology and likely radiogenic heat fluxes, the crustal thickness around Caloris is 90–140 km. Similar late-stage uplift and extension probably do not occur in basins on the Moon and Mars because their crusts are too thin to allow analogous lateral flow.
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Cifra, Peter, Zuzana Benková et Tomáš Bleha. « Chain Extension of DNA Confined in Channels ». Journal of Physical Chemistry B 113, no 7 (19 février 2009) : 1843–51. http://dx.doi.org/10.1021/jp806126r.
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Pegler, Samuel S. « The dynamics of confined extensional flows ». Journal of Fluid Mechanics 804 (31 août 2016) : 24–57. http://dx.doi.org/10.1017/jfm.2016.516.
Texte intégralRésumé :
I present a theoretical and experimental study of floating viscous fluid films introduced into a channel of finite length, motivated by the flow of glacial ice shelves. The dynamics are characterized by a mixture of viscous extensional stresses, transverse shear stresses and a driving buoyancy force. A theory based on a width-integrated model is developed and investigated using analytical, asymptotic and numerical methods. With fluid introduced at a constant rate, the flow is found to approach a steady state with two possible asymptotic forms depending on the length of the channel. For channel lengths less than half the width, the flow is similar to a purely extensional one-dimensional flow, characterized by concave surface profiles and being insensitive to the position of the channel exit (or calving front). Greater lengths result in a more complex asymptotic structure in which the flow adjusts over a short distance towards a prevailing flow of universal dimensionless form. In complete contrast to the extensional regime, the prevailing flow is controlled by the position of the channel exit. Data from a new laboratory experiment involving particle velocimetry of a floating fluid film compares well with the predicted along-channel velocity. Motivated by glaciological application, the analysis is generalized to power-law rheologies and the results used to classify the flow regimes of a selection of ice shelves. The prediction for the frontal speed is in good agreement with geophysical data, indicating that the universal profile predicted by the theory is common in nature.
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MEZGER, JOCHEN E., et CEES W. PASSCHIER. « Polymetamorphism and ductile deformation of staurolite–cordierite schist of the Bossòst dome : indication for Variscan extension in the Axial Zone of the central Pyrenees ». Geological Magazine 140, no 5 (septembre 2003) : 595–612. http://dx.doi.org/10.1017/s0016756803008112.
Texte intégralRésumé :
The Bossòst dome is an E–W-trending elongated structural and metamorphic dome developed in Cambro-Ordovician metasedimentary rocks in the Variscan Axial Zone of the central Pyrenees. A steep fault separates a northern half-dome, cored by massif granite, from an E–W-trending doubly plunging antiform with granitic sills and dykes in the core to the south. The main foliation is a flat-lying S1/2 schistosity that grades into a steeper-dipping slaty cleavage at the dome margins. Three major deformational and two metamorphic phases can be differentiated. S1/2 schistosity is an axial planar cleavage to W-vergent recumbent folding that probably occurred in mid-Westphalian time. Peak regional metamorphism M1 is characterized by static growth of staurolite and garnet following thermal relaxation of the previously thickened crust. Strong non-coaxial deformation recording uniform top-to-the-SE extension during D2a is preserved in staurolite–garnet schists in a 1.5 km thick, shallowly SE-dipping zone in the southeastern dome. A 500 m thick contact aureole (M2) was imprinted on the regionally metamorphosed rocks following the intrusion the Bossòst granite during D2b. More coaxial deformation prevailed during synkinematic growth of M2 phases in the inner part of the contact aureole around the northern part of the dome, where it obliterated D2a fabrics. Progressive non-coaxial deformation continued in the southeastern antiform and is recorded by late-synkinematic growth of cordierite. Successive overprinting of the M1 staurolite–garnet assemblage by andalusite and cordierite of M2 is preserved in the southern part. The assemblage muscovite+cordierite+staurolite+biotite is considered metastable, given the low Mn and Zn contents of staurolite and cordierite, and interpreted as the result of prograde metamorphism during decompression. P–T conditions during M2 were approximately 3 kbar and 600 °C. Pervasive crenulations and mesoscopic to regional southerly verging folds are the result of D3 NNE–SSW compression post-dating ductile deformation and contact metamorphism. Polymetamorphic assemblages of the Bossòst dome preserve a regionally confined zone of ESE-directed extensional shearing within an overall N–S compressional setting. Exact timing of extensional shearing is not known, but can be constrained by recumbent folding during the mid-Westphalian and granitic intrusions, which confine it to Late Carboniferous time (c. 305 Ma). Crustal-scale flat-lying extensional shear zones with similar orientation and time frame are observed in the Hospitalêt massif of the eastern Axial Zone. This suggests that crustal extension, though probably restricted by regional strain partitioning over orthogneiss or intruding granitic bodies within an overall compressive setting, was not uncommon in Late Carboniferous time in the Axial Zone of the Pyrenees.
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Morapedi, Setumile. « Passive constructions in Setswana ». JULACE : Journal of the University of Namibia Language Centre 3, no 1 (30 juin 2018) : 38–52. http://dx.doi.org/10.32642/julace.v3i1.1374.
Texte intégralRésumé :
The paper analyses passive constructions in Setswana from morpho-syntactic view point, showing that the suffixation of a passive morpheme to the verb reduces the argument structure of the verb. Previous studies carried out in Setswana verbal suffixes have confined their investigations to these morphemes as elements of morphology but have failed to observe that these affixes overlap into syntax. Chebanne (1996) observes that in Setswana, verbal extensions can combine with a single verbal base but fail to observe the overlap into syntax. Further, the studies do not give any insight in the features that Setswana shares with other Bantu languages. The passive construction in Setswana, like in other Bantu languages, is a bit complex in the sense that the verbal extension –iw brings into effect the dropping of the subject, and the object becomes the grammatical subject, thus rendering the transitive verb, such as, apaya ‘cook’ intransitive. Conversely, other derivational suffixes, such as applicative and causative, increase the verb’s arguments by two. For instance, the suffixation of the verbal suffix –el suggests an entity carrying out the action and somebody benefiting. The paper also compares passive with other verbal extensions such as neuter, applicative, causatives and reciprocals. It shows that while the passive occurs with most verbs and other verbal extensions, such as, applicative or causative suffixes, the neuter is rigid in occurring with other verbal extensions. The paper also appeals to Lexical Mapping Theory, whose role is to constrain mapping relations between thematic roles, such as an agent or patient and the corresponding grammatical functions, such as the subject, patient and oblique that have been subcategorized for by predicates
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Scholz, Christopher A., Donna J. Shillington, Lachlan J. M. Wright, Natalie Accardo, James B. Gaherty et Patrick Chindandali. « Intrarift fault fabric, segmentation, and basin evolution of the Lake Malawi (Nyasa) Rift, East Africa ». Geosphere 16, no 5 (10 juillet 2020) : 1293–311. http://dx.doi.org/10.1130/ges02228.1.
Texte intégralRésumé :
Abstract The Lake Malawi (Nyasa) Rift, in the East African Rift System (EARS), is an ideal modern analogue for the study of extensional tectonic systems in low strain rate settings. The seismically active rift contains the 700-m-deep Lake Malawi, one of the world’s oldest and largest freshwater lakes with one of the most diverse endemic faunal assemblages on Earth. Modern and reprocessed legacy multichannel seismic-reflection data are constrained by velocity information from a wide-angle seismic experiment to evaluate variability in extension, segmentation, and timing of fault development along the 550-km-long rift zone. Fault geometries and patterns of synrift sediment fills show that the Lake Malawi Rift is composed of three asymmetric rift segments, with intervening accommodation zone morphologies controlled by the degree of overlap between segment border faults. Most extension occurs on the basin border faults, and broadly distributed extension is only observed at one accommodation zone, where no border fault overlap is observed. Structural restorations indicate a weakly extended rift system (∼7 km), with diminishing values of extension and thinner rift fill from north to south, suggesting a progressively younger rift to the south. There is no evidence of diking, sill injection, or extrusives within the synrift fill of the Lake Malawi Rift, although the volcanic load of the Rungwe magmatic system north of the lake and related subsidence may explain the presence of anomalously thick synrift fill in the northernmost part of the lake. The thickest synrift depocenters (∼5.5 km) are confined to narrow 10- to 20-km-wide zones adjacent to each rift segment border fault, indicating concentration of strain on border faults rather than intrarift faults. Intrarift structures control axial sediment delivery in the North and Central rift segments, focusing sediment into confined areas resulting in localized overpressure and shale diapirs. The asymmetric, basement-controlled relief was established early in rift development. When overprinted with frequent high-amplitude hydroclimate fluctuations, which are well documented for this basin, the resulting highly variable landscape and lake morphometry through time likely impacted the diverse endemic faunas that evolved within the basin. New seismic-reflection data, augmented by wide-angle seismic data and age constraints from drill core, offer the most highly resolved 3D view to date of latest Cenozoic extensional deformation in East Africa and provide a foundation for hazards analysis, resource assessments, and constraining deformation in a low strain rate, magma-poor active rift.
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Tu, Michael Q., Hung V. Nguyen, Elliel Foley, Michael I. Jacobs et Charles M. Schroeder. « 3D manipulation and dynamics of soft materials in 3D flows ». Journal of Rheology 67, no 4 (15 juin 2023) : 877. http://dx.doi.org/10.1122/8.0000600.
Texte intégralRésumé :
Flow-based manipulation of particles is an essential tool for studying soft materials, but prior work has nearly exclusively relied on using two-dimensional (2D) flows generated in planar microfluidic geometries. In this work, we demonstrate 3D trapping and manipulation of freely suspended particles, droplets, and giant unilamellar vesicles in 3D flow fields using automated flow control. Three-dimensional flow fields including uniaxial extension and biaxial extension are generated in 3D-printed fluidic devices combined with active feedback control for particle manipulation in 3D. Flow fields are characterized using particle tracking velocimetry complemented by finite-element simulations for all flow geometries. Single colloidal particles (3.4 μm diameter) are confined in low viscosity solvent (1.0 mPa s) near the stagnation points of uniaxial and biaxial extensional flow for long times (≥10 min) using active feedback control. Trap stiffness is experimentally determined by analyzing the power spectral density of particle position fluctuations. We further demonstrate precise manipulation of colloidal particles along user-defined trajectories in three dimensions using automated flow control. Newtonian liquid droplets and GUVs are trapped and deformed in precisely controlled uniaxial and biaxial extensional flows, which is a new demonstration for 3D flow fields. Overall, this work extends flow-based manipulation of particles and droplets to three dimensions, thereby enabling quantitative analysis of colloids and soft materials in complex nonequilibrium flows.
Thèses sur le sujet "Extensions confinées"
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Benzoni, Séverin. « Classification des filtrations dynamiques et étude des systèmes d'entropie positive ». Electronic Thesis or Diss., Normandie, 2024. https://theses.hal.science/tel-04835404.
Texte intégralRésumé :
Dans cette thèse, nous explorons les structures possibles des systèmes dynamiques de la forme $\bfX :=(X, \A, \mu, T)$ et leurs tribus facteur $\B \subset \A$. Les deux premiers chapitres étudient les différentes façons dont une tribu facteur $\B$ peut s'inclure dans un système dynamique $\bfX :=(X, \A, \mu, T)$, c'est-à-dire que nous étudions certaines structures possibles de l'\emph{extension} $\A \arr \B$. Dans le premier chapitre, nous considérons les concepts de \emph{super-innovations} et de \emph{standardité} des extensions, inspirés de la théorie des filtrations. Un point important est l'introduction de la notion d'\emph{extensions confinées}, qui nous intéressent parce qu'elles n'ont pas de super-innovation. Nous donnons plusieurs exemples et étudions des propriétés supplémentaires de ces extensions, y compris des résultats de relèvement. Ensuite, nous montrons notre résultat principal : l'existence d'extensions non-standard. Enfin, ce résultat trouve une application dans l'étude des filtrations dynamiques, qui sont les filtrations de la forme $(\F_n)_{n \leq 0}$ telles que chaque $\F_n$ est une tribu facteur. Nous montrons qu'il existe des \emph{filtrations dynamiques I-confortables non standard}.Le deuxième chapitre approfondit l'étude des extensions confinées en trouvant un nouveau type de telles extensions, dans le cadre des suspensions de Poisson : nous prenons un système dynamique $(X, \mu, T)$ en mesure $\s$-finie infinie et une extension compacte $(X \times G, \mu \otimes m_G, T_\phi)$, puis nous considérons l'extension de Poisson correspondante $((X \times G)^*, (\mu \otimes m_G)^*, (T_\phi)_*) \to (X^*, \mu^*, T_*)$. Nous donnons des conditions sous lesquelles cette extension est confinée et construisons un exemple qui correspond à ces conditions.Enfin, le troisième chapitre se concentre sur une famille de filtrations dynamiques : les \emph{filtrations de Pinsker faible}. L'existence de ces filtrations sur tout système ergodique provient d'un résultat récent d'Austin \cite{austin}, et elles se présentent comme un outil potentiel pour décrire les systèmes à entropie positive. Nous explorons les liens entre la structure asymptotique des filtrations de Pinsker faible et les propriétés du système dynamique sous-jacent. Naturellement, nous demandons aussi si, sur un système donné, la structure des filtrations de Pinsker faible est unique à isomorphisme près. Nous donnons une réponse partielle, dans le cas où le système sous-jacent est un schéma de Bernoulli. Nous concluons notre travail en donnant deux exemples explicites de filtrations de Pinsker faibleIn this thesis, we explore the possible structures of measure preserving dynamical systems of the form $\bfX :=(X, \A, \mu, T)$ and their factor $\s$-algebras $\B \subset \A$. The first two chapters investigate various ways in which a factor $\s$-algebra $\B$ can sit in a dynamical system $\bfX :=(X, \A, \mu, T)$, i.e. we study some possible structures of the \emph{extension} $\A \arr \B$. In the first chapter, we consider the concepts of \emph{super-innovations} and \emph{standardness} of extensions, which are inspired from the theory of filtrations. An important focus of our work is the introduction of the notion of \emph{confined extensions}, which first interested us because they have no super-innovation. We give several examples and study additional properties of confined extensions, including several lifting results. Then, we show our main result: the existence of non-standard extensions. Finally, this result finds an application to the study of dynamical filtrations, i.e. filtrations of the form $(\F_n)_{n \leq 0}$ such that each $\F_n$ is a factor $\s$-algebra. We show that there exist \emph{non-standard I-cosy dynamical filtrations}.The second chapter furthers the study of confined extensions by finding a new kind of such extensions, in the setup of Poisson suspensions: we take an infinite $\s$-finite measure-preserving dynamical system $(X, \mu, T)$ and a compact extension $(X \times G, \mu \otimes m_G, T_\phi)$, then we consider the corresponding Poisson extension $((X \times G)^*, (\mu \otimes m_G)^*, (T_\phi)_*) \to (X^*, \mu^*, T_*)$. We give conditions under which that extension is confined and build an example which fits those conditions.Lastly, the third chapter focuses on a family of dynamical filtrations: \emph{weak Pinsker filtrations}. The existence of those filtrations on any ergodic system comes from a recent result by Austin \cite{austin}, and they present themselves as a potential tool to describe positive entropy systems. We explore the links between the asymptotic structure of weak Pinsker filtrations and the properties of the underlying dynamical system. Naturally, we also ask whether, on a given system, the structure of weak Pinsker filtrations is unique up to isomorphism. We give a partial answer, in the case where the underlying system is Bernoulli. We conclude our work by giving two explicit examples of weak Pinsker filtrations
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Wang, Aijuan. « Experimental and numerical investigation of the confinement effect on the impinging flame in a compartment ». Electronic Thesis or Diss., Bourges, INSA Centre Val de Loire, 2021. http://www.theses.fr/2021ISAB0002.
Texte intégralRésumé :
Le phénomène de flamme de diffusion impactant une paroi est fréquent dans les scénarios d’incendie en milieu clos. Celui-ci peut entraîner à avoir des conséquences désastreuses en termes de vie humaine et de biens matériels. En effet, lorsqu'une flamme incidente se produit dans un compartiment, elle peut augmenter le risque de propagation du feu de celui-ci vers une autre pièce à travers une explosion de fumée représentant une menace pour les personnes pié-gées. Afin d’apporter des éléments de compréhension sur le comportement de ce type de flamme, de nombreuses études ont réalisé. Celles-ci se sont intéressées sur des flammes impac-tant un plafond en milieu ouvert ou semi-confiné. Cependant il y a peu, voire aucuns travaux qui se sont penchés sur l’étude du comportement d’une flamme incidente dans un compartiment confiné sous ventilé. Dans l’objectif d’apporter des éléments de compréhension en lien avec l’effet du confinement sur la dynamique d’une flamme impactant un plafond, une étude expé-rimentale et numérique est réalisée dans le cadre de cette thèse.L’ensemble des données a été obtenu à l’aide d’un dispositif expérimental représentant un appartement d’étudiant à échelle réduite.Le banc d'essai est un compartiment représentant une maquette d’appartement à petite échelle (1 :10). La conception et dimensionnement a été réalisée sur la base des lois de simili-tudes. Les niveaux de confinement ont été définis en fonction des ouvertures de l’enceinte et du débit calorifique potentielle. A partir de ces deux paramètres, le niveau de confinement peut être associé à la richesse de l’enceinte. Pour cela, huit débits caloriques différents ainsi que cinq possibilités d’ouvertures ont été proposés. À partir des expériences réalisées avec les huit débits calorifiques et les cinq configurations d’ouvertures, l'effet de confinement sur la dynamique d’une flamme impactant un plafond a été effectué en se basant sur les paramètres physico-chimiques, tels que l'extension de la flamme, l'oscillation de la flamme, la distribution de la température et l'analyse des gaz.De plus, grâce à la modélisation numérique de la flamme impactant le plafond à l’aide du code CFD : Fire Dynamics Simulator (FDS), il a été possible d’apporter des éléments supplé-mentaires dans l’analyse des écoulements réactifs associée à l’interaction flamme paroi en fonc-tion du niveau de confinement. Le choix des modèles numériques a été effectué à partir d’une étude préliminaire visant à justifier la fiabilité et la précision du modèle numérique à reproduire les données expérimentales ainsi que des évolutions obtenues à partir de corrélations empiriques obtenues dans les littératures.A partir des analyses réalisées dans cette étude, il est possible de fournir des éléments de décisions lors de la conception et la mise en place de détecteurs d'incendie au plafond dans un compartiment et également d’aider à une meilleure estimation de la probabilité de propagation du feu lors d'un incendie de compartiment par le biais d’une explosion de fumée riche en gaz imbrûlésThe phenomenon of diffusion impinging flame is common in industrials, leading to disas-trous consequences in terms of life and property. When impinging flame occurs in a compart-ment, it may enhance the risk of fire propagation and pose a greater threat to trapped people. Lots of studies dealt with flame impinging an unconfined or confined ceiling while little work focused on the impinging flame in a confined compartment. With the objective of providing understanding related to the confinement effect on the impinging flame in a compartment, both experimental and numerical studies carried out to build up the framework of this thesis. A compartment model representing a reduced scale (1:10) student compartment was uti-lized based on the scaling law such that a test bench with suitable instrumentations for carrying out measurements was developed. Configurations of five confinement levels were constructed by the condition of windows and door in the compartment and heat release rate (HRR) was var-ied between 0.5 kW and 18.6 kW. Through series of experiments, the confinement effect on the dynamics of flame impinging a ceiling was addressed with physicochemical parameters, such as flame extension, flame oscillation, temperature distribution and gas analysis. In addition, on account of the numerical modeling of flame impinging a ceiling using the CFD code: Fire Dynamics Simulator (FDS), it was possible to provide additional elements in the analysis of reactive flows associated with the flame-wall interaction as a function of the confinement level. The choice of numerical models was made on the basis of a preliminary study aimed at justifying the reliability and precision of the numerical modelling in reproducing the experimental data as well as the empirical correlations obtained in the literatures. From the analyzes in this study, it is possible to provide guidance for fire safety engineering in the field of fire risk assessment and fire protection design of buildings
Livres sur le sujet "Extensions confinées"
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Victor, Elias, Turner-Fairbank Highway Research Center et Earth Engineering & Sciences, Inc., dir. Development of protocols for confined extension/creep testing of geosynthetics for highway applications. McLean, VA : U.S. Dept. of Transportation, Federal Highway Administration, Research and Development, Turner-Fairbank Highway Research Center, 1998.
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Development of protocols for confined extension/creep testing of geosynthetics for highway applications : Publication no. FHWA-RD-97-143. McLean, VA (6300 Georgetown Pike, McLean 22101-2296) : U.S. Dept. of Transportation, Federal Highway Administration, Research and Development, Turner-Fairbank Highway Research Center, 1998.
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Keshav, Satish, et Alexandra Kent. Inflammatory bowel disease. Sous la direction de Patrick Davey et David Sprigings. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199568741.003.0203.
Texte intégralRésumé :
Inflammatory bowel disease (IBD) encompasses ulcerative colitis (UC) and Crohn’s disease (CD). Both conditions cause chronic relapsing inflammation in the gastrointestinal (GI) tract, but have different characteristics. UC causes diffuse mucosal inflammation limited to the colon, extending proximally from the anal verge, with the rectum involved in 95% of patients. UC is described in terms of the disease extent: proctitis (confined to the rectum), proctosigmoiditis (disease confined to the recto-sigmoid colon), distal disease (distal to the splenic flexure), and pan-colitis (the entire large intestine). The extent of disease can change, with proximal extension seen in approximately a third of patients with proctitis, although there is great variation between studies. CD causes inflammation that can affect the entire thickness of the wall of the intestine, and is not confined to the mucosa. CD can affect any part of the GI tract. The terminal ileum is affected in approximately 80% of cases, the colon in approximately 60% of cases, and the rectum and perianal region in approximately 40% of cases. CD is classified by location (ileal, colonic, ileocolonic, upper GI tract), by the presence of stricturing or penetrating disease, and by the age of onset (before or after the age of 40). Penetrating disease refers to the development of fistulae, which can lead to complications such as abscesses or perforations. An earlier age at onset is associated with more complicated disease. The diagnosis of UC or CD is established through a combination of clinical, endoscopic, radiological, and histological criteria rather than by any single modality. Occasionally, it is not possible to establish an unequivocal diagnosis of CD or UC in IBD, and a third category, accounting for nearly 10% of cases, is used, termed IBD unclassified.
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Field, Clive D. Counting Religion in Britain, 1970-2020. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192849328.001.0001.
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Counting Religion in Britain, 1970–2020, the fourth volume in the author’s chronological history of British secularization, sheds significant new light on the nature, scale, and timing of religious change in Britain during the past half-century, with particular reference to quantitative sources. Adopting a key performance indicators approach, twenty-one facets of personal religious belonging, behaving, and believing are examined, offering a much wider range of lenses through which the health of religion can be viewed and appraised than most contemporary scholarship (which is typically confined to one or two measures). Summative analysis of these indicators, by means of a secularization dashboard, leads to a reaffirmation of the validity of secularization (in its descriptive sense) as the dominant narrative and direction of travel since 1970, while acknowledging that it is an incomplete process and without endorsing all aspects of the paradigmatic expression of secularization as a by-product of modernization. The appendix of 173 tables, a discrete statistical reference work in its own right, besides supporting (and being cross-referenced in) the main text, is designed as an extension to 2020 of the appendix of tables to 1970 in the acclaimed 1977 Clarendon Press volume Churches and Churchgoers: Patterns of Church Growth in the British Isles since 1700, by Robert Currie, Alan Gilbert, and Lee Horsley. As well as covering statistics generated by faith communities and the state, as did the 1977 book, the appendix to Counting Religion in Britain, 1970–2020 includes a wide variety of time series from national sample surveys.
Chapitres de livres sur le sujet "Extensions confinées"
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Fontaine, G., S. Poncet et E. Serre. « Multidomain Extension of a Pseudospectral Algorithm for the Direct Simulation of Wall-Confined Rotating Flows ». Dans Lecture Notes in Computational Science and Engineering, 261–71. Cham : Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-01601-6_21.
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Marques, José Carlos, et Pedro Góis. « Diaspora Policies, Consular Services and Social Protection for Portuguese Citizens Abroad ». Dans IMISCOE Research Series, 387–407. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-51245-3_23.
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Abstract Portugal is a traditional country of emigration with a multigenerational diaspora spread across a large number of countries. In the last 50 years, especially after the 1974 revolution, it developed a welfare state that responds to the needs of residents (including immigrants). Traditionally, this welfare state has been described as fragile in comparison with other welfare regimes in Europe. Nevertheless, it was built as a universal welfare system based on jus solis and deterritorialized jus sanguinis regime. The study of the extension of social protection to Portuguese citizens living abroad had not yet received sufficient attention, albeit recurrent news on measures and strategies that the state put in practice to assist Portuguese emigrants in need. This chapter will survey some of the recent policies to reach citizens abroad by showing the limits of the Portuguese welfare state in action. Through these policies and actions, Portugal projects an image of an always-present state that extents its national powers beyond the limits of its territorially confined borders.
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Lutz, Alexander, et Axel Lachmeyer. « SciPPPer : Automatic Lock-Passage for Inland Vessels – Practical Results Focusing on Control Performance ». Dans Lecture Notes in Civil Engineering, 959–68. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-6138-0_85.
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AbstractNavigating through locks is one of the most challenging tasks that skippers have to perform in inland navigation. Typical dimensions of a ship (width = 11.45 m) and a lock (width = 12 m) result in an error margin of less than 30 cm to the left and to the right of the ship when navigating within a lock chamber. Typical inland vessels on European waters have a length of 82 to 186 m. The wheel house on cargo vessels is located close to the stern of the vessel. This leads to low visibility of the bow in the lock chamber. In order to cope with this issue, a deck hand monitors the bow and announces distances to the skipper via radio. The quality of this information depends on the deck hand’s ability to judge distances correctly and is prone to error. This highly demanding maneuver needs to be performed up to 15 times per day. Each lock passage can take up to 30 minutes. The research project SciPPPer aims at automating this complex navigational task.The German acronym SciPPPer stands for Schleusenassistenzsystem basierend auf PPP und VDES für die Binnenschifffahrt – lock assistant system based on PPP and VDES for inland navigation. The idea is to fully automate the navigation into and out of a lock using high-precision GNSS (Global Navigation Satellite System) with PPP (precise point positioning) correction data which is transmitted from shore to ship using VDES (VHF Data Exchange System), an extension to AIS (Automatic Identification System). This absolute measurement data is complemented by relative measurement data using LiDAR and automotive RADAR and fused with inertial measurement data delivered by a mechanical gyro system. Apart from the challenge of precisely measuring the position and orientation of the vessel within the lock chamber, the control task poses an interesting problem as well. This contribution introduces both, the measuring and the control problem. However, the focus lies on the results of the control performance that was achieved on a full-bridge simulator as well as during real-world trials. A full-bridge simulator was used in order to test the control strategy and its algorithms safely. A number of different actuator configurations were investigated. Typical inland cargo vessels use one or two propellers with Kort nozzle and a twin rudder behind each propeller and a 360° turnable bow thruster. Typical inland passenger vessels use several (2–4) 360° turnable rudder propellers as main propulsion as well as a 360° turnable bow thruster or a classical tunnel thruster which can only apply forces to starboard or portside. These typical configurations were examined by simulation. The real-world trials were performed on a passenger vessel with three rudder propellers as main propulsion as well as a classical tunnel bow thruster acting left and right.This contribution presents the results of the simulator study as well as the real-world trials in terms of control performance. It explains specific challenges due to the navigation within an extremely confined space. The contribution concludes with lessons learned as well as an outlook focusing on the potential of the introduction of such a system to the inland navigation market.
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Schacher, Tom, et Tim Hart. « 13. House extensions ». Dans Constructing low-rise confined masonry buildings, 117–20. Practical Action Publishing, 2018. http://dx.doi.org/10.3362/9781780449906.013.
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« Deformation characteristics under confined triaxial extension stress ». Dans Rock Mechanics in Civil and Environmental Engineering, 95–98. CRC Press, 2010. http://dx.doi.org/10.1201/b10550-14.
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Reid, J. Nicholas. « Confine and Control ». Dans Prisons in Ancient Mesopotamia, 37–64. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780192849618.003.0003.
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In Chapter 2 I discuss key terms denoting some form of detention in ancient Mesopotamia in relation to the socio-economic status of the various types of prisoners housed in these centers of detention. What will be demonstrated is that the overwhelming evidence suggests that most prisoners were not held because of “crimes.” This is not to suggest that imprisonment did not relate to disputes and “criminal” activity. Rather, imprisonment was utilized throughout the judicial process. But this intersection between “crime” and detention seems to be a practical extension of existing mechanisms (administrative bodies, guards, etc.), rather than a prison in the strict sense.
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Takahashi, M., H. Park, Y. Fujii et M. Sato. « Deformation behavior and shear wave velocity under confined triaxial extension stress ». Dans Rock Engineering and Rock Mechanics : Structures in and on Rock Masses, 179–82. CRC Press, 2014. http://dx.doi.org/10.1201/b16955-27.
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Wakatani, Masahiro. « A Description Of Magnetically Confined Plasmas ». Dans Stellarator and Heliotron Devices, 55–100. Oxford University PressNew York, NY, 1998. http://dx.doi.org/10.1093/oso/9780195078312.003.0003.
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Abstract In this chapter we introduce fundamental equations for applications in the rest of this book. First, we describe the properties of high-temperature plasmas in section 3.2. For the study of collective phenomena, the Vlasov equation is introduced by using a phase space description for a many-particle system in section 3.3. Then magnetohydrodynamic (MHD) approximation is described. For the investigation of plasma dynamics in an inhomogeneous magnetic field, or particularly in a three-dimensional magnetic field such as the stellarator and the heliotron, one-fluid magnetohydrodynamic equations are the most appropriate and reasonable theoretical tool, and are explained in section 3.4. An extension to include the anisotropic pressure in MHD approximation is also given. The anisotropy appears between the parallel and perpendicular pressures, where the direction of the magnetic field vector is the reference for these pressures. When the MHD equations are linearized for the study of the dynamics of small-amplitude perturbations, three types of MHD waves appear, as shown in section 3.5 these are also important ingredients in the study of MHD instabilities in chapter 5. As an approximation to the Vlasov equation, the drift-kinetic equation is shown in section 3.6, which is useful in the study of collisional transport of magnetically confined toroidal plasmas. In order to study the transport phenomena of toroidal plasmas, the collision term in the phase space description is important. In the transport equations based on the moments of the Boltzmann equation (or the Vlasov equation with the collision term) collisional effects are included through resistivity, viscosity, and transport coefficients for density and temperature (see section 3.7). Finally, for an approximate description of heliotron plasma, we introduce averaged MHD equations in section 3.8: these are widely used to discuss the macroscopic behavior of heliotron plasma in this book.
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Quarteroni, Alfio, et Alberto Valli. « Discretised Equations and Domain Decomposition Methods ». Dans Domain Decomposition Methods for Partial Differential Equations, 41–70. Oxford University PressOxford, 1999. http://dx.doi.org/10.1093/oso/9780198501787.003.0002.
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Abstract In this chapter the general principles previously introduced will be accommodated to treat the finite dimensional approximation of differential problems. We confine our analysis to the Poisson problem. However, its extension to the case of the more general symmetric elliptic boundary value problem (1.4.1) is straightforward and will be left to the interested reader. On the other hand, other kind of equations, either stationary or time-dependent, will be addressed from Chapter 5 onwards.
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Macdonald, Francis A., W. Adolph Yonkee, Rebecca M. Flowers et Nicholas L. Swanson-Hysell. « Neoproterozoic of Laurentia ». Dans Laurentia : Turning Points in the Evolution of a Continent. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.1220(19).
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ABSTRACT Neoproterozoic to Cambrian isolation of Laurentia during the breakup of Rodinia was associated with multiple large igneous provinces, protracted multiphase rifting, and variable subsidence histories along different margin segments. In this contribution, we develop a paleogeographic model for the Neoproterozoic tectonic evolution of Laurentia based on available stratigraphic, paleomagnetic, petrologic, geochronologic, and thermochronologic data. Early Tonian strata are confined to intracontinental basins in northern Laurentia. Breakup of Rodinia around Laurentia began in earnest with emplacement of the ca. 778 Ma Gunbarrel large igneous province, interpreted to have accompanied separation of the North China block along the Yukon promontory, and onset of localized, intracratonic extension southward along the western margin. Eruption of the ca. 760–740 Ma Mount Rogers volcanic complex along the Southern Appalachian segment of the eastern margin may record extension associated with separation of the Kalahari or South American terranes. At about the same time, the Australia-Mawson blocks began separating from the Sonoran segment of the southern margin and Mojave promontory. Emplacement of the ca. 720 Ma Franklin large igneous province along the northern margin was likely associated with separation of Siberia and was followed by widespread bimodal volcanism and extension along the western margin spanning ca. 720–670 Ma, leading to partial separation of continental fragments, possibly including Tasmania, Zealandia, and Tarim. Emplacement of the ca. 615 Ma Central Iapetus magmatic province along the eastern margin marked rifting that led to separation of Baltica and Amazonia, and partial separation of the Arequipa-Pampia-Antofalla fragments. During the late Ediacaran to Cambrian, the western, northern, eastern, and southern margins all experienced a second episode of local extension and mafic magmatism, including emplacement of the ca. 585 Ma Grenville dikes and ca. 540–532 Ma Wichita large igneous province, leading to final separation of continental fragments and Cambrian rift-drift transitions on each margin. Cryogenian rifting on the western and northern margins and segments of the eastern margin was contemporaneous with low-latitude glaciation. Sturtian and Marinoan glacial deposits and their distinctive ca. 660 Ma and 635 Ma cap carbonates provide important event horizons that are correlated around the western and northern margins. Evidence for Ediacaran glaciation is absent on Laurentia, with the exception of glacial deposits in Scotland, and putative glacial deposits in Virginia, which both formed on the poleward edge of Laurentia. Patterns of exhumation and deposition on the craton display spatial variability, likely controlled by the impingement of mantle plumes associated with mantle upwelling and extensional basin formation during the piecemeal breakup of Rodinia. Glaciation and eustasy were secondary drivers for the distribution of erosion and Neoproterozoic sedimentation on North America.
Actes de conférences sur le sujet "Extensions confinées"
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Lhuillier, Emmanuel, Tung Hu Dang, Adrien Khalili, David Darson, Pierre Potet et Angela Vasanelli. « Nanophotonics applied to the design of nanocrystal based infrared sensor ». Dans CLEO : Applications and Technology, JM4D.3. Washington, D.C. : Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_at.2024.jm4d.3.
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It's fascinating to witness the significant progress achieved in leveraging colloidal nanocrystals as a viable platform for infrared optoelectronics. Their adaptability as a spin-coatable resist with infrared photoactive properties has spurred developments that transcend mere material advancements and delve deeply into advanced device design. A standout accomplishment in the infrared domain is the development of infrared cameras utilizing nanocrystal thin films as their active layers. This marks a paradigm shift in infrared imaging, challenging the long-held focus on high-quality monocrystalline thin films. The emergence of nanocrystal films, despite being highly polycrystalline, enables the fabrication of cost-effective sensors that are beginning to rival established technologies like InGaAs, especially in the short-wave infrared.Among potential materials, HgTe1 stands out as the most versatile platform, capable of spanning the entire infrared spectrum from visible wavelengths for the most confined forms to THz2 frequencies for bulk-like particles. In this presentation, I will begin by reviewing recent advancements in transitioning HgTe nanocrystal films from single-pixel sensors to high-quality imagers34.However, achieving such imagers marks just the beginning of the journey. One key challenge revolves around the interaction between light and matter. The polycrystalline nature, while enabling cost-effective sensors, does come with a trade-off – reduced mobility compared to bulk films, limiting the efficiency of charge collection. Therefore, introducing processes to focus light on a film thickness within which transport remains efficient becomes critical. In the latter part of the presentation, I will demonstrate how the incorporation of nanophotonic structures can introduce new functionalities such as actively reconfigurable spectral responses5 and the extension of the device's spectral response into the mid-infrared range.The broad spectral tunability of HgTe nanocrystals also positions them favorably for thermal imaging. However, in this spectral range, the entire device architecture needs a reevaluation compared to visible wavelengths. Notably, the transparent conductive oxide layers typically used as electrodes exhibit weak transmission characteristics, necessitating alternative designs for transparent and conductive electrodes. Here, I will illustrate how the utilization of exalted transmission effects can enhance the design of high-performance mid-infrared sensors.6Schematic illustrating transformation of nanocrystal solution into an infrared focal plane array and finally exemple of image obtained with the imager
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Brown, John Paul, et Rajarajan Narayanasamy Naidu. « Lateral Extension in Response to Late Stage Transpression, An Example from the Zhdanov Field, Caspian Sea - An Alternative to Flower Structures. » Dans Gas & Oil Technology Showcase and Conference. SPE, 2023. http://dx.doi.org/10.2118/214213-ms.
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Abstract The Zhdanov Field is located on the eastern margin of the Caspian Sea and is geologically a part of the Apsheron-PreBalkan Fault Zone which crosses the Caspian Sea from Azerbaijan to Turkmenistan. Structurally, the field is part of an east-west orientated plunging anticline (hereafter referred to as the Cheleken Nose) that plunges westwards from the Cheleken Dome for over 25 km into the Caspian Sea. The structure of the Zhdanov Field formed in response to Pleistocene to Recent (post Apsheron) transpressive reactivation of a pre-existing fault at the Miocene and deeper levels (hereafter referred to as the Zhdanov Fault). Transpressive reactivation of the deep-seated fault created a southward verging reverse offset at the Miocene level with up to 600m of vertical displacement, with an unknown amount of lateral or strike slip offset. Data from the orientations of associated fault structures and borehole breakout data indicate that the stress field associated with the reactivation was a north-south compression with the maximum horizontal stress orientated 007 degrees N which is consistent with regional Caspian Sea tectonics. The overlying Pliocene to Recent, Red Series stratigraphy accommodated the reactivation and vertical displacement on the Zhdanov Fault on a series of extensional faults which strike NNE-SSW, orthogonal to the strike of the underlying fault. Because the extensional faults are dominantly post sedimentary, the faults have a planar geometry which form a set of domino style faults that show rigid rotation of the Red Series stratigraphy between faults. The extension direction of the planar faults is sub-parallel to the major east-west fold axis and orthogonal to the southward maximum dip direction of the fold structure which is to the south. The extension direction is therefore orthogonal to the extension direction that would be expected to occur due to gravity driven extension. Instead, the extensional faults represent lateral extension, or expulsion along the strike of the fold that was driven by the ongoing north-south compression which effectively prevented gravity driven extensional movement to the south. The extensional fault set all downthrow to the west aligning with the down plunge direction of the Cheleken Nose. The extensional fault set is likely to have been formed as a response to vertical offset in a structurally confined compressional / transpressional setting. The orientation and movement direction of the resulting extensional fault set is in direct contrast to that which would be expected in either gravity driven extension, or a positive Flower Structure that is commonly associated with transpressive strike slip faults. Lateral expulsion on extensional faults associated with transpression is valid from a kinematic and stress orientation stand point and is therefore a valid alternative to Flower Structures. At the Zhdanov Field, the series of tilted fault blocks created by the lateral extension may lead to new exploration opportunities with potential fault traps throughout the Red Series stratigraphy.
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Jain, Abhinandan. « Recursive Algorithms Using Local Constraint Embedding for Multibody System Dynamics ». Dans ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-87663.
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This paper describes a constraint embedding approach for handling of local closure constraints in multibody system dynamics. The approach uses spatial operator techniques to eliminate local-loop constraints from a system to effectively convert it into a tree-topology system. This conversion to a tree-topology allows the direct application of the host of available techniques including mass matrix factorization and inversion to be applied to the system dynamics. One application is the extension of the well-known recursive O(N) forward dynamics for solving the system dynamics of these systems. The algorithms are especially applicable to systems where the constraints are confined to small-subgraphs within the system topology. The paper provides background on the spatial operator approach, the extensions for handling embedded constraints, and concludes with examples of such constraints.
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Keller, James M., Mihail Popescu et Dustin Gibeson. « An extension of a confined space evacuation model to human geography ». Dans IGARSS 2012 - 2012 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2012. http://dx.doi.org/10.1109/igarss.2012.6350861.
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Otto, Kevin N., et Erik K. Antonsson. « Extensions to the Taguchi Method of Product Design ». Dans ASME 1991 Design Technical Conferences. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/detc1991-0026.
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Abstract The Taguchi method of product design is an experimental approximation to minimizing the expected value of target variance for certain classes of problems. Taguchi’s method is extended to designs which involve variables each of which has a range of values all of which must be satisfied (necessity), and designs which involve variables each of which has a range of values any of which might be used (possibility). Tuning parameters, as a part of the design process, are also introduced into Taguchi’s method. The method is also extended to solve design problems with constraints, invoking the methods of constrained optimization. Finally, the Taguchi method uses a factorial method to search the design space, with a confined definition of an optimal solution. This is compared with other methods of searching the design space and their definition of an optimal solution.
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Souza Mendes, P. R., R. L. Thompson et A. O. Nieckele. « Analysis of the Convergent Channel as an Extensional Rheometer ». Dans ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1170.
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Abstract An important aspect while designing an “R2 z = constant” convergent channel as an extensional rheometer is the appropriate choice of the geometrical parameters and of the Reynolds number range of operation. The higher is the Reynolds number value, the thinner will be the boundary layer where the undesirable no-slip effect is confined, as discussed in the literature. However, if the Reynolds number, Re, is too large, then shear-related pressure losses become important, which is also undesirable in rheometry. Therefore, one design task is to find a range of Re within which the boundary layer is thin enough, and the velocity field in most of the domain is reasonably close to the desired kinematics. In this work we obtained numerical solutions for the flow of Newtonian and viscoelastic fluids through a convergent channel, for representative ranges of Re, dimensionless channel length, L, and dimensionless axial coordinate of inlet section, z0. For all cases, we determined fields of flow type, where regions of shear and of extension can be visualized. Among other findings, it is shown that, depending on the geometrical and flow characteristics, most of the mechanical energy dissipated can be due to shear effects, so that the extensional viscosity cannot be determined via pressure drop measurements.
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Mayne, R. W. « Position and Motion Planning in a Confined Region via Nonlinear Programming ». Dans ASME 1987 Design Technology Conferences. American Society of Mechanical Engineers, 1987. http://dx.doi.org/10.1115/detc1987-0015.
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Abstract This paper describes the formulation of a position and motion planning problem in an optimization setting. Emphasis is placed on planning movements in a confined workspace where contacts must be avoided. The formulation includes the possibility of extra degrees of freedom and is demonstrated in detail on a simple robot problem. Robot positioning and trajectory planning are considered within a two dimensional workspace and a recursive quadratic programming procedure is used for the optimization. The results presented herein show satisfactory performance and considerable promise for extension to more complex configurations and three dimensions.
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Moser, Patrick, Silvestro Barbarino et Farhan Gandhi. « Helicopter Rotor Blade Chord Extension Morphing Using a Centrifugally Actuated von-Mises Truss ». Dans ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8053.
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Previous studies have shown that chord extension morphing over a spanwise section of helicopter rotor blades can reduce main rotor power requirement in stall-dominant flight conditions while at the same time being able to increase the maximum gross weight, altitude, and flight speed capability of the aircraft. This study examines a centrifugally driven, fully passive chord morphing mechanism for helicopter rotor blades. It is based on a von-Mises truss situated aft of the leading-edge spar, connected to a rigid extension plate which deploys through a slit in the trailing-edge. When the rotor RPM increases beyond a critical value the chordwise component of centrifugal (CF) force on the von-Mises truss and plate assembly results in the deployment of the plate beyond the slit in the trailing edge, effectively increasing chord length. On reducing the RPM, a retraction spring pulls the plate back within the confines of the blade. This study presents the design process, iterations and the final design solution for a configuration that undergoes 20% chord extension. A prototype was fabricated and tested on the bench-top as well as on a rotor test stand at rotational speeds simulating 70% full-scale CF loads. The test results demonstrate that the concept works. However, effects such as friction lead to higher force (or RPM) requirements for deployment than predicted by simulation, and are present during retraction as well. The effects are more pronounced in the high CF field in the rotor test.
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Terrapon, Vincent E., Yves Dubief, Parviz Moin et Eric S. G. Shaqfeh. « Brownian Dynamics Simulation in a Turbulent Channel Flow ». Dans ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45680.
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The dynamics of different bead-spring models is investigated in a turbulent channel flow. In particular, the FENE, the FENE-P and the FENE multichain models are compared. In the case of the FENE-P model, both the Brownian Dynamics and the constitutive equations are used. It is shown that the different models produce qualitatively similar results for the mean extension and the mean stresses. This qualitative behaviour is also reproduced for different extensibility parameters. It is also found that the action of polymers is confined in the near wall region where the polymers are mainly oriented in the streamwise direction.
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Dukhan, Nihad. « Analysis of Darcy Flow in Confined Porous Media Including Wall Effect ». Dans ASME 2011 Small Modular Reactors Symposium. ASMEDC, 2011. http://dx.doi.org/10.1115/smr2011-6637.
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Effective cooling lies at the heart of reactor design and safe operation. Materials for cooling systems include solid porous media (e.g. metal foam). This is due to the large surface area per unit volume and the random internal structure of such porous medium. The former promotes heat exchange rates by providing large surface area, while the latter enhances it by providing vigorous mixing of the working fluid, which gives rise to what is called dispersion (an added mechanism of heat transfer). Hence, momentum transport in porous media is critical for heat transfer analysis, computation and design. Porous media are also used as storage of nuclear waste. In such applications, the porous medium is confined by solid boundaries. These impermeable boundaries give rise to shear stress and boundary layers, which strongly influence the velocity field and the pressure drop inside the porous medium. The velocity field directly influence the heat transfer rate, while the pressure drop determines the required pumping power. The Brinkman-extended Darcy equation describes the momentum transport due to fully developed Newtonian fluid flow in confined porous media. This equation is an extension of the famous Darcy equation, and it contains the viscous shear at the boundaries as well as the viscous shear on the internal surface of the porous medium. The equation is solved analytically inside and outside the boundary layer in a cylindrical porous-media system. As, expected, the volume-averaged velocity decays as the distance from the boundary increases. The mean and maximum velocities are obtained and their behavior is investigated in terms of the Darcy number and the ratio of the effective to the actual fluid viscosity. The friction factor is defined based on the mean velocity and is found to be inversely proportional to the Reynolds number, the Darcy number and the mean velocity. The analytical velocity can be directly substituted in the governing convection heat transfer equation to assess the heat transfer performance of confined cylindrical heat exchange systems.