Spelling suggestions: "subject:"4points"" "subject:"5points""
431 |
Etude expérimentale et numérique des modes de déformation d'un explosif compriméVial, Jérôme 24 October 2013 (has links) (PDF)
L'utilisation industrielle ou militaire des explosifs est largement répandue. La sécurité est devenue un axe majeur avec notamment l'ignition involontaire des explosifs composés de HMX lors des impacts à basse vitesse. L'objectif de cette thèse est de contribuer à la compréhension des mécanismes dissipatifs à l'origine des échauffements locaux dans le matériau. Le développement d'un essai aux barres d'Hopkinson a permis de coupler de grandes vitesses de déformations à des pressions élevées pour compléter les données expérimentales. Cet essai a montré un angle de frottement quasiment identique à celui obtenu en quasistatique mais une contrainte de cohésion supérieure d'environ 25 MPa. Ensuite, pour observer les mécanismes pouvant être sources d'échauffement, un essai de compression dans la tranche a été développé avec des observations en temps réel. Celles-ci ont permis de conclure qu'il y a très peu de frottements entre les gros grains et la matrice (l'ensemble des petits grains, du liant et de la porosité). De la plasticité des grains de HMX a pu être observée mais surtout beaucoup d'endommagement dans certaines zones y compris dans la matrice. Une microfissuration très intense de certains grains a été observée. Parallèlement, une représentation numérique biphasique (gros grains de HMX et matrice) de toute la microstructure du matériau a été considérée. Une confrontation entre les observations expérimentales et les simulations a permis de déterminer le seuil de plasticité du HMX. Le comportement de la matrice a été identifié pour prendre en compte l'effet de vitesse et l'endommagement observé. Enfin, les confrontations entre les essais et les simulations de ceux-ci ont montré que les échauffements devraient plutôt se localiser dans la matrice que dans les gros grains de HMX et que le mécanisme le plus probable est le frottement de lèvres de microfissures.
|
432 |
Points de déclenchement myofascial : les effets de la compression ischémique manuelle sur le seuil de la douleur et le contrôle du mouvement du membre supérieurEsparza Yanez, Wilmer 09 December 2010 (has links) (PDF)
Les PTM sont une source de douleur régionale et de dysfonctionnements neuromusculaires. Ils sont couramment associés à une hyperalgésie, à des troubles comportementaux et des restrictionsfonctionnelles. La douleur est bien documentée dans la littérature scientifique mais les études de ses conséquences sur le mouvement reposent exclusivement sur l'analyse de gestes simples. L'objectif dece travail est d'étudier la douleur myofasciale du membre supérieur et de vérifier si une technique de thérapie manuelle influençant cette douleur permet de rétablir la performance motrice d'un mouvement fonctionnel. Quatre études ont été réalisées afin d'analyser : 1) la performance motrice d'un mouvement elliptique dans le plan horizontal ; 2) dans le plan frontal et d'une tâche de tapement ; 3) la douleur sur le membre supérieur non atteint chez des sujets ayant subi un AVC ; 4) l'incidence de la douleur chez le personnel soignant d'un centre hospitalier. Les résultats indiquent que la présence de PTM produit la douleur myofasciale et : 1) n'influence pas significativement la performance motrice d'un mouvement elliptique horizontal ; 2) altère la performance motrice d'un mouvement elliptique frontal et d'une tâche de tapement chez les sujets présentant des PTM ; 3) modifie aussi la fonction motrice de l'extrémité supérieure ipsilatérale à la lésion ; 4) touche 8,43% du personnel soignant, étant bilatérale et pouvant conduire à des arrêts maladie dans 14,28 % des cas. L'application d'une technique de compression ischémique locale permet de retrouver la quasi-totalité de la fonction motrice. Il semblerait qu'une reprogrammation du mouvement s'avère nécessaire pour récupérer totalement la fonction motrice.
|
433 |
Qualification et amélioration de la précision de systèmes de balayage laser mobiles par extraction d'arêtesPoreba, Martyna 18 June 2014 (has links) (PDF)
Au cours de ces dernières décennies, le développement de Systèmes Mobiles de Cartographie, soutenu par un progrès technologique important, est devenu plus apparent. Il a été stimulé par le besoin grandissant de collecte d'informations géographiques précises sur l'environnement. Nous considérons, au sein de cette thèse, des solutions pour l'acquisition des nuages de points mobiles de qualité topographique (précision centimétrique). Il s'agit, dans cette tâche, de mettre au point des méthodes de qualification des données, et d'en améliorer sur les erreurs systématiques par des techniques d'étalonnage et de recalage adéquates.Nous décrivons une démarche innovante d'évaluation de l'exactitude et/ou de la précision des relevés laser mobiles. Celle-ci repose sur l'extraction et la comparaison des entités linéaires de la scène urbaine. La distance moyenne calculée entre les segments appariés, étant la distance modifiée de Hausdorff, sert à noter les nuages par rapport à des références existantes. Pour l'extraction des arêtes, nous proposons une méthode de détection d'intersections entre segments plans retrouvés via un algorithme de RANSAC enrichi d'une analyse de composantes connexes. Nous envisageons également une démarche de correction de relevés laser mobiles à travers un recalage rigide fondé, lui aussi, sur les éléments linéaires. Enfin, nous étudions la pertinence des segments pour en déduire les paramètres de l'étalonnage extrinsèque du système mobile. Nous testons nos méthodes sur des données simulées et des données réelles acquises dans le cadre du projet TerraMobilita.
|
434 |
Konsten att bryta upp utan att bryta ihop : Om individers behov av studie- och yrkesvägledning i vändpunkterJansson, Nathalie, Söderlund, Sofia January 2014 (has links)
Uppsatsen undersöker behovet av och tillgången till studie- och yrkesvägledning i vändpunkter och utgår från karriärvalsteorin Careerships definition av dessa. Alla individer ställs inför flera vändpunkter under sitt liv och vissa är mer tydliga än andra. Tidigare forskning visar att individer med fler valmöjligheter inom sin vändpunkt upplever ett större behov av studie- och yrkesvägledning än individer med få valmöjligheter. Ofta upplever exempelvis arbetssökande ett litet handlingsutrymme och lågt förtroende för myndighetsutövare. Undersökningens resultat visar att behovet men också tillfredsställelsen av studie- och yrkesvägledning är störst inom grundskolan och lägst för gruppen arbetssökande. I uppsatsen diskuteras om intresset för studie- och yrkesvägledning skulle öka i vuxengrupper om fler gavs möjlighet att ingå i en kontinuerlig studie- och yrkesvägledningsprocess. / This essay examines the need for career counselling when reaching a turning point based on the career selection theory, Careership. All individuals are recurrently faced with turning points during their career, some clearer than others. Previous research indicates that individuals with more options in their turning point feel a greater need for career counselling than individuals with fewer choices. For example jobseekers often experience that they have little room for manoeuvres and a low confidence in authorities. The result from this study shows that the need for and also the satisfaction with career counselling are biggest in elementary school and the lowest for jobseekers. In the essay we discuss whether the interest in seeking for career counselling would increase if grown ups were given the opportunity to be a part of a continuous career counsellingprocess.
|
435 |
On Some Problems in Transcendental Number Theory and Diophantine ApproximationNguyen, Ngoc Ai Van 19 December 2013 (has links)
In the first part of this thesis, we present the first non-trivial small value estimate that applies to an algebraic group of dimension 2 and which involves large sets of points. The algebraic group that we consider is the product ℂ× ℂ*, of the additive group ℂ by the multiplicative group ℂ*. Our main result assumes the existence of a sequence (PD)D ≥1 of non-zero polynomials in ℤ [X1, X2] taking small absolute values at many translates of a fixed point (ξ, η) in ℂ × ℂ* by consecutive multiples of a rational point (r, s) ∈ (ℚ*)2 with s = ±1. Under precise conditions on the size of the coefficients of the polynomials PD, the number of translates of (ξ, η) and the absolute values of the polynomials PD at these points, we conclude that both ξ and η are algebraic over ℚ. We also show that the conditions that we impose are close from being best possible upon comparing them with what can be achieved through an application of Dirichlet’s box principle.
In the second part of the thesis, we consider points of the form θ = (1,θ1 , . . . ,θd-1 ,ξ) where {1,θ1 , . . . ,θd-1 } is a basis of a real number field K of degree d ≥ 2 over ℚ and where ξ is a real number not in K. Our main results provide sharp upper bounds for the uniform exponent of approximation to θ by rational points, denoted λ ̂(θ), and for its dual uniform exponent of approximation, denoted τ ̂(θ). For d = 2, these estimates are best possible thanks to recent work of Roy. We do not know if they are best possible for other values of d. However, in Chapter 2, we provide additional information about rational approximations to such a point θ assuming that its exponent λ ̂(θ) achieves our upper bound. In the course of the proofs, we introduce new constructions which are interesting by themselves and should be useful for future research.
|
436 |
Seawater intrusion risks and controls for safe use of coastal groundwater under multiple change pressuresMazi, Aikaterini January 2014 (has links)
In the era of intense pressures on water resources, the loss of groundwater by increased seawater intrusion (SWI), driven by climate, sea level and landscape changes, may be critical for many people living in commonly populous coastal regions. Analytical solutions have been derived here for interface flow in coastal aquifers, which allow for simple quantification of SWI under extended conditions from previously available such solutions and are suitable for first-order regional vulnerability assessment and mapping of the implications of climate- and landscape-driven change scenarios and related comparisons across various coastal world regions. Specifically, the derived solutions can account for the hydraulically significant aquifer bed slope in quantifying the toe location of a fresh-seawater sharp interface in the present assessments of vulnerability and safe exploitation of regional coastal groundwater. Results show high nonlinearity of SWI responses to hydro-climatic and groundwater pumping changes on the landside and sea level rise on the marine side, implying thresholds, or tipping points, which, if crossed, may lead abruptly to major SWI of the aquifer. Critical limits of coastal groundwater change and exploitation have been identified and quantified in direct relation to prevailing local-regional conditions and stresses, defining a safe operating space for the human use of coastal groundwater. Generally, to control SWI, coastal aquifer management should focus on adequate fresh groundwater discharge to the sea, rather than on maintaining a certain hydraulic head at some aquifer location. First-order vulnerability assessments for regional Mediterranean aquifers of the Nile Delta Aquifer, the Israel Coastal Aquifer and the Cyprus Akrotiri Aquifer show that in particular the first is seriously threatened by advancing seawater. Safe operating spaces determined for the latter two show that the current pumping schemes are not sustainable under declining recharge. / <p>The thesis was founded by two research programmes: NEO private-academic sector partnership and Ekoklim, a strategic governmental funding through Stockholm University</p><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p><p> </p>
|
437 |
Pit veiklos kryptys, ugdant mokinius karjerai / Activity areas of professional information points when educating pupils for their careerVisockytė, Kristina 27 February 2014 (has links)
Tyrimo aktualumas: Moksleiviui besimokančiam bendrojo lavinimo mokykloje profesijos pasirinkimas yra labai svarbus ir sudėtingas uždavinys. Dažnai jaunuoliai nežino kokią profesiją pasirinkti. Tikslingam pasirinkimui reikalinga profesinio informavimo pagalba. Šiai pagalbai suteikti mokyklose yra įkurti profesinio informavimo taškai (PIT). Labai svarbu, kad profesinio informavimo taškai veiktų efektyviai, nes nuo to priklauso ar jaunuoliai gebės priimti racionalų profesijos pasirinkimo sprendimą.
Siekiant gerinti profesinio informavimo kokybę, vykdomi projektai. Strateginiai dokumentai numato karjeros projektavimo, tarp jų ir ugdymo karjerai paslaugas kreipti taip, kad jos prisidėtų prie visą gyvenimą trunkančių mokymosi ir karjeros kompetencijų ugdymo, integruoto į mokymo ir studijų programas. Šiuo metu vykdomas projektas ,,Ugdymo karjerai ir stebėsenos modelių sukūrimas ir plėtra bendrajame lavinime ir profesiniame mokyme“, kuriuo siekiama modernizuoti ir pagerinti profesinio informavimo kokybę. Tad aktualu išsiaiškinti apie šiuo metu profesinio informavimo taškų vykdomą praktinę veiklą, ar vykdomi projektai siekant gerinti profesinio informavimo kokybę duoda naudos.
Tyrimo objektas: Profesinio informavimo taškų veikla ugdant mokinius karjerai
Tyrimo tikslas: Remiantis mokslinės literatūros, dokumentų analize bei profesijos patarėjų atsakymų duomenimis išanalizuoti profesinio informavimo taškų veiklos kryptis, ugdant mokinius karjerai.
Tyrimo metodai: pedagoginės... [toliau žr. visą tekstą] / Relevance of the research: Selection of a profession for a pupil studying in a general education school is a very important and complex task. Very often young people do not know what profession to choose. Professional information assistance is required for the expedient choice. In order to provide this assistance, professional information points (PIP) were established in schools. It is very important that professional information points operate efficiently since from them depends whether young people will be able to take a rational professional choice decision.
In order to improve the quality of professional information, projects have been implemented. It is provided for by strategic documents that career projecting, including services related to career development, are directed in such a way that they contribute to development of life-learning and career competences integrated to teaching and study programs. Currently, project “Elaboration and development of education for career and observation in general education and professional training” has been carried out with which it is striven to modernize and improve the quality of professional information. Therefore, it is relevant to ascertain any practical activities carried out by professional information points, whether the projects being implemented give any benefit when improving the quality of professional information.
Object of the research: Activities of professional information points when educating pupils for their... [to full text]
|
438 |
Urban Balconies As Public Open Areas A Case Study: BursaOzaslan, Aslihan 01 December 2005 (has links) (PDF)
The need for the public areas within urban environments is increasing day by day. This thesis focuses on urban balconies as one of the important element of public open areas. Their historical backgrounds, contribution to the cities, categorization and exemplification form important topics for explaining the concept.
The study also searches the important natural features that effect the urban development of Bursa and questions the place of urban balconies between them. While explaining the past and the present situations, types and the usages of urban balconies& / #8217 / of Bursa / this thesis emphasizes their existing but neglected qualitative and quantitative values, that have the potential to play an important role for the physical shaping of the city so as the formation of urban image. Related to this, also the importance of the revitalization of the urban balconies as public open areas takes part in this study.
Key Words: Urban Balconies, Vista Points, Topographical Features, Public Open Areas, Bursa.
|
439 |
Efficient Calibration and Predictive Error Analysis for Highly-Parameterized Models Combining Tikhonov and Subspace Regularization TechniquesMatthew James Tonkin Unknown Date (has links)
The development and application of environmental models to help understand natural systems, and support decision making, is commonplace. A difficulty encountered in the development of such models is determining which physical and chemical processes to simulate, and on what temporal and spatial scale(s). Modern computing capabilities enable the incorporation of more processes, at increasingly refined scales, than at any time previously. However, the simulation of a large number of fine scale processes has undesirable consequences: first, the execution time of many environmental models has not declined despite advances in processor speed and solution techniques; and second, such complex models incorporate a large number of parameters, for which values must be assigned. Compounding these problems is the recognition that since the inverse problem in groundwater modeling is non-unique the calibration of a single parameter set does not assure the reliability of model predictions. Practicing modelers are, then, faced with complex models that incorporate a large number of parameters whose values are uncertain, and that make predictions that are prone to an unspecified amount of error. In recognition of this, there has been considerable research into methods for evaluating the potential for error in model predictions arising from errors in the values assigned to model parameters. Unfortunately, some common methods employed in the estimation of model parameters, and the evaluation of the potential error associated with model parameters and predictions, suffer from limitations in their application that stem from an emphasis on obtaining an over-determined, parsimonious, inverse problem. That is, common methods of model analysis exhibit artifacts from the propagation of subjective a-priori parameter parsimony throughout the calibration and predictive error analyses. This thesis describes theoretical and practical developments that enable the estimation of a large number of parameters, and the evaluation of the potential for error in predictions made by highly parameterized models. Since the focus of this research is on the use of models in support of decision making, the new methods are demonstrated by application to synthetic applications, where the performance of the method can be evaluated under controlled conditions; and to real-world applications, where the performance of the method can be evaluated in terms of trade-offs in computational effort versus calibration results and the ability to rigorously yet expediently investigate predictive error. The applications suggest that the new techniques are applicable to a range of environmental modeling disciplines. Mathematical innovations described in this thesis focus on combining complementary regularized inversion (calibration) techniques with novel methods for analyzing model predictive error. Several of the innovations are founded on explicit recognition of the existence of the calibration solution and null spaces – that is, that with the available observations there are some (combinations of) parameters that can be estimated; and there are some (combinations of) parameters that cannot. The existence of a non-trivial calibration null space is at the heart of the non-uniqueness problem in model calibration: this research expands upon this concept by recognizing that there are combinations of parameters that lie within the calibration null space yet possess non-trivial projections onto the predictive solution space, and these combinations of parameters are at the heart of predictive error analysis. The most significant contribution of this research is the attempt to develop a framework for model analysis that promotes computational efficiency in both the calibration and the subsequent analysis of the potential for error in model predictions. Fundamental to this framework is the use of a large number of parameters, the use of Tikhonov regularization, and the use of subspace techniques. Use of a large number of parameters enables parameter detail to be represented in the model at a scale approaching true variability; the use of Tikhonov constraints enables the modeler to incorporate preferred conditions on parameter values and/or their variation throughout the calibration and the predictive analysis; and, the use of subspace techniques enables model calibration and predictive analysis to be undertaken expediently, even when undertaken using a large number of parameters. This research focuses on the inability of the calibration process to accurately identify parameter values: it is assumed that the models in question accurately represent the relevant processes at the relevant scales so that parameter and predictive error depend only on parameter detail not represented in the model and/or accurately inferred through the calibration process. Contributions to parameter and predictive error arising from incorrect model identification are outside the scope of this research.
|
440 |
Strategic management of artificial watering points for biodiversity conservationMontague-Drake, Rebecca, School of Biological, Earth & Environmental Sciences, UNSW January 2004 (has links)
Since pastoralism began in Australia???s rangelands, the number of artificial watering points (AWPs) has increased dramatically, such that today, few areas of rangeland are further than 10 km from water. This increased availability of water has caused many ecological impacts. Unfortunately, such impacts are poorly understood in the context of an Australian conservation reserve, thus hindering strategic management. This study examined the spatial distribution of vertebrate (kangaroos, small mammals, lizards and avifauna) and vegetative variables around open AWPs as well as AWPs that have been closed since pastoralism (sheep-grazing) ceased nearly thirty years ago in Sturt National Park, arid New South Wales. The study also examined vertebrate use of AWPs, with a particular emphasis on kangaroos and avifauna. The study revealed that most variables showed few differences in spatial distribution with distance from open and closed AWPs, thus suggesting that the observed piospheric impacts were primarily attributable to historical sheep-grazing. Indeed, piospheric patterns were weak suggesting some recovery over the last thirty years. That kangaroos did not exhibit water-focused grazing is no surprise, since despite their regular use of AWPs, particularly during hot, dry times, the current spatial arrangement of AWPs facilitates regular travel to, and from, such resources allowing kangaroos, like much other fauna, to distribute themselves in relation to food and shelter preferences rather than in relation to water supply. In contrast, the majority of avifaunal groups (excluding ground-dwelling species) were clustered around open AWPs, often irrespective of season, because of food and water requirements. Such spatial concentrations of avifauna are thought to cause a range of interspecific effects. Experimental AWP closure and GIS modelling showed that whilst closure of AWPs will increase the average distance to water, which will have key benefits, the majority of areas in Sturt National Park would still be accessible to most water-dependent species even if all unused AWPs were closed. Strategic retention of AWPs to replace water sources lost since European settlement, aid threatened and migratory species??? conservation and enhance nature-based tourism opportunities is thus recommended and an example of a strategic management and monitoring plan outlined.
|
Page generated in 0.0432 seconds