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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Modelling, control and supervision for a class of hybrid systems

Esteva Payet, Santiago 13 March 2003 (has links)
The aim of this thesis is to narrow the gap between two different control techniques: the continuous control and the discrete event control techniques DES. This gap can be reduced by the study of Hybrid systems, and by interpreting as Hybrid systems the majority of large-scale systems. In particular, when looking deeply into a process, it is often possible to identify interaction between discrete and continuous signals. Hybrid systems are systems that have both continuous, and discrete signals. Continuous signals are generally supposed continuous and differentiable in time, since discrete signals are neither continuous nor differentiable in time due to their abrupt changes in time. Continuous signals often represent the measure of natural physical magnitudes such as temperature, pressure etc. The discrete signals are normally artificial signals, operated by human artefacts as current, voltage, light etc.Typical processes modelled as Hybrid systems are production systems, chemical process, or continuos production when time and continuous measures interacts with the transport, and stock inventory system. Complex systems as manufacturing lines are hybrid in a global sense. They can be decomposed into several subsystems, and their links. Another motivation for the study of Hybrid systems is the tools developed by other research domains. These tools benefit from the use of temporal logic for the analysis of several properties of Hybrid systems model, and use it to design systems and controllers, which satisfies physical or imposed restrictions.This thesis is focused in particular types of systems with discrete and continuous signals in interaction. That can be modelled hard non-linealities, such as hysteresis, jumps in the state, limit cycles, etc. and their possible non-deterministic future behaviour expressed by an interpretable model description. The Hybrid systems treated in this work are systems with several discrete states, always less than thirty states (it can arrive to NP hard problem), and continuous dynamics evolving with expression: with Ki ¡ Rn constant vectors or matrices for X components vector. In several states the continuous evolution can be several of them Ki = 0.In this formulation, the mathematics can express Time invariant linear system. By the use of this expression for a local part, the combination of several local linear models is possible to represent non-linear systems. And with the interaction with discrete events of the system the model can compose non-linear Hybrid systems.Especially multistage processes with high continuous dynamics are well represented by the proposed methodology. Sate vectors with more than two components, as third order models or higher is well approximated by the proposed approximation. Flexible belt transmission, chemical reactions with initial start-up and mobile robots with important friction are several physical systems, which profits from the benefits of proposed methodology (accuracy).The motivation of this thesis is to obtain a solution that can control and drive the Hybrid systems from the origin or starting point to the goal. How to obtain this solution, and which is the best solution in terms of one cost function subject to the physical restrictions and control actions is analysed. Hybrid systems that have several possible states, different ways to drive the system to the goal and different continuous control signals are problems that motivate this research.The requirements of the system on which we work is: a model that can represent the behaviour of the non-linear systems, and that possibilities the prediction of possible future behaviour for the model, in order to apply an supervisor which decides the optimal and secure action to drive the system toward the goal.Specific problems can be determined by the use of this kind of hybrid models are: - The unity of order.- Control the system along a reachable path.- Control the system in a safe path.- Optimise the cost function.- Modularity of controlThe proposed model solves the specified problems in the switching models problem, the initial condition calculus and the unity of the order models. Continuous and discrete phenomena are represented in Linear hybrid models, defined with defined eighth-tuple parameters to model different types of hybrid phenomena. Applying a transformation over the state vector : for LTI system we obtain from a two-dimensional SS a single parameter, alpha, which still maintains the dynamical information. Combining this parameter with the system output, a complete description of the system is obtained in a form of a graph in polar representation.Using Tagaki-Sugeno type III is a fuzzy model which include linear time invariant LTI models for each local model, the fuzzyfication of different LTI local model gives as a result a non-linear time invariant model. In our case the output and the alpha measure govern the membership function.Hybrid systems control is a huge task, the processes need to be guided from the Starting point to the desired End point, passing a through of different specific states and points in the trajectory. The system can be structured in different levels of abstraction and the control in three layers for the Hybrid systems from planning the process to produce the actions, these are the planning, the process and control layer.In this case the algorithms will be applied to robotics ¡V a domain where improvements are well accepted ¡V it is expected to find a simple repetitive processes for which the extra effort in complexity can be compensated by some cost reductions. It may be also interesting to implement some control optimisation to processes such as fuel injection, DC-DC converters etc.In order to apply the RW theory of discrete event systems on a Hybrid system, we must abstract the continuous signals and to project the events generated for these signals, to obtain new sets of observable and controllable events. Ramadge & Wonham¡¦s theory along with the TCT software give a Controllable Sublanguage of the legal language generated for a Discrete Event System (DES). Continuous abstraction transforms predicates over continuous variables into controllable or uncontrollable events, and modifies the set of uncontrollable, controllable observable and unobservable events. Continuous signals produce into the system virtual events, when this crosses the bound limits. If this event is deterministic, they can be projected. It is necessary to determine the controllability of this event, in order to assign this to the corresponding set, , controllable, uncontrollable, observable and unobservable set of events.Find optimal trajectories in order to minimise some cost function is the goal of the modelling procedure. Mathematical model for the system allows the user to apply mathematical techniques over this expression. These possibilities are, to minimise a specific cost function, to obtain optimal controllers and to approximate a specific trajectory.The combination of the Dynamic Programming with Bellman Principle of optimality, give us the procedure to solve the minimum time trajectory for Hybrid systems. The problem is greater when there exists interaction between adjacent states.In Hybrid systems the problem is to determine the partial set points to be applied at the local models. Optimal controller can be implemented in each local model in order to assure the minimisation of the local costs. The solution of this problem needs to give us the trajectory to follow the system. Trajectory marked by a set of set points to force the system to passing over them.Several ways are possible to drive the system from the Starting point Xi to the End point Xf. Different ways are interesting in: dynamic sense, minimum states, approximation at set points, etc. These ways need to be safe and viable and RchW. And only one of them must to be applied, normally the best, which minimises the proposed cost function. A Reachable Way, this means the controllable way and safe, will be evaluated in order to obtain which one minimises the cost function.Contribution of this work is a complete framework to work with the majority Hybrid systems, the procedures to model, control and supervise are defined and explained and its use is demonstrated. Also explained is the procedure to model the systems to be analysed for automatic verification.Great improvements were obtained by using this methodology in comparison to using other piecewise linear approximations. It is demonstrated in particular cases this methodology can provide best approximation.The most important contribution of this work, is the Alpha approximation for non-linear systems with high dynamics While this kind of process is not typical, but in this case the Alpha approximation is the best linear approximation to use, and give a compact representation.
12

Att arbeta under högsäsong i Åre som lokalbefolkning och säsongsarbetare : En kvalitativ studie om hur olika livsstilar skapar grupperingar inom hotell- och restaurangbranschen

Archer, Amanda, Krokstedt, Alma January 2016 (has links)
The purpose of this essay is to gain a deeper understanding of the social relations that take place at work between locals and seasonal workers in Åre, and to find out whether there exists a division between those who work and live seasonal in Åre and those who permanently live and work in Åre. The method used is a qualitative method with semi-structured interviews consisting of four seasonal workers and three locals in Åre from a storytelling perspective. The general results show that there is a strong division between these two groups because of their completely separate lifestyles, but still it does not exist any overall conflict between them. Their working relationship overall was decent but they were not socialized beyond work or even had a thought for that either. The strong division between these groups created a feeling of exclusion, the one group felt that it did not belong to the other and vice versa. Opinions about seasonal workers different habits and behavior in Åre compared to their habits at home arose, which both groups were aware of solidified the grouping. / Syftet med denna uppsats är att få en djupare förståelse över de sociala relationer som sker på arbetet mellan lokalbefolkningen och säsongsarbetarna i Åre, samt ta reda på om det existerar en uppdelning mellan de som arbetar samt bor säsong i Åre och de som permanent arbetar och bor i Åre. Metoden som vi använt är kvalitativ metod med semistrukturerade intervjuer med fyra säsongsarbetare och tre lokala från Åre utifrån ett berättande perspektiv. Det generella resultatet visar på att det existerar en stark uppdelning mellan dessa två grupper då de lever helt åtskilda liv men att trots detta inte existerar någon övergripande konflikt mellan dem. Deras arbetsrelation fungerade bra men de umgicks ej utöver arbetet eller hade en önskan om det heller. Utanförskapen var utgjord av de två grupperingarna, att den ena gruppen kände att den inte tillhörde den andra och vice versa. Det uppstod åsikter om säsongsarbetarnas annorlunda vanor och beteende i Åre jämfört med deras vanor hemma, vilket båda var väl medvetna om förstärkte grupperingen.
13

Někoho zachránit a někoho ignorovat: Etnografie humanitární odpovědi na uprchlickou krizi v Řecku / Saving some, ignoring others: An ethnography of the humanitarian response to the refugee crisis in Greece

Gut, Petr January 2018 (has links)
In this auto-ethnography, I use my experience of volunteering during the 'European refugee crisis' to pose a critique of how humanitarian aid is negotiated in its everyday practice. I identify four main groups of actors involved in the negotiation, namely the aid-workers, the volunteers, the locals and the refugees themselves. The goal of this work is to explore the mechanisms and causes of the marginalisation of the locals, and most importantly, of the refugees in this negotiation. Following De Genova's theory of migrant "illegalisation" I argue that the marginalisation of refugees is a result of the way the European border regime operates and I explore both the complicity of humanitarians in this regime and also how they challenged it. Following Agier's theory of the "humanitarian government", I argue that there is very little space for agency of people designated as refugees in humanitarian aid, and I analyse the power of aid-workers over the refugees. Last but not least, I use Pandolfi's concept of the humanitarian apparatus as a form of "migrant sovereignty" to show how humanitarians partly took over the local political practices in a setting of a humanitarian crisis on one of the Greek islands, and I describe the effects of this take-over on the local population.
14

Lokalbefolkning och turister - tillsammans eller separerade? : En studie om turismens sociokulturella effekter.

Afkari, Pegah, Gregerson, Jenny January 2009 (has links)
<p>This study investigates how the host community of Tenerife perceives the socio-cultural effects of tourism on the island. The method chosen for the study was qualitative interviews which were performed with six respondents, each born in Spain, living permanently in Tenerife and employed within service-related occupations. The interview material was interpreted and handled according to a hermeneutic approach. The results of the study showed that the respondents had an over-all positive perception of tourism. Perceived positive socio-cultural effects were related to cultural and linguistic influences. Problems related to alcohol and community disorder were believed to be negative effects although they were not present to the same extent according to the respondents. The sociological theory “us and them” could be applied to this study since the locals chose to live and spend their free-time outside the tourist areas.</p><p> </p>
15

Lokalbefolkning och turister - tillsammans eller separerade? : En studie om turismens sociokulturella effekter.

Afkari, Pegah, Gregerson, Jenny January 2009 (has links)
This study investigates how the host community of Tenerife perceives the socio-cultural effects of tourism on the island. The method chosen for the study was qualitative interviews which were performed with six respondents, each born in Spain, living permanently in Tenerife and employed within service-related occupations. The interview material was interpreted and handled according to a hermeneutic approach. The results of the study showed that the respondents had an over-all positive perception of tourism. Perceived positive socio-cultural effects were related to cultural and linguistic influences. Problems related to alcohol and community disorder were believed to be negative effects although they were not present to the same extent according to the respondents. The sociological theory “us and them” could be applied to this study since the locals chose to live and spend their free-time outside the tourist areas.
16

On Sandwiched Surface Singularities and Complete Ideals

Fernández Sánchez, Jesús 01 November 2004 (has links)
The original interest in sandwiched singularities comes from a natural question posed by J. Nash in the early sixties to H. Hironaka: “Does a finite succession of Nash transformations or normalized Nash transformations resolve the singularities of a reduced algebraic variety?” In 1975, A. Nobile proved that, in characteristic zero, a Nash transformation is an isomorphism only in case the original variety is already non-singular. It turns out, in particular, that curve singularities are resolved by a succession of Nash transformations. Rebasoo proved in his Ph. D. thesis that Nash transformations also resolve certain kinds of quasi-homogeneous hypersurface singularities in (C)3. In 1982, G. Gonzalez-Sprinberg proved that normalized Nash transformations resolve rational double points and cyclic quotients singularities of surfaces. Then, H. Hironaka proved that after a finite succession of normalized Nash transformations one obtains a surface “X” which birationally dominates a non-singular surface. By definition, the singularities of “X” are sandwiched singularities. Some years later, M. Spivakovsky proves that sandwiched singularities are resolved by normalized Nash transformations, thus giving a positive answer to the original question posed by Nash for the case of surfaces over C. Since then, a constant interest in sandwiched singularities has been shown, and they have been deeply studied from the point of view of deformation theory by de Jong and van Straten, and also by Stolen and Mohring. Sandwiched singularities have been also studied as a nice testing ground for the Nash and the wedge Problem by Lejeune-Jalabert and Reguera, where the main idea is to extend combinatorial arguments for toric surface singularities to sandwiched ones. Sandwiched singularities are the singularities obtained by blowing-up a complete ideal in the local ring of a regular point on a surface. They are rational surface singularities (roughly speaking, isolated singularities whose resolution has no effect on the arithmetic genus of the surface) and among them are included all cyclic quotients and minimal surface singularities. Sandwiched singularities are Cohen-Macaulay, but are not complete intersections and in general, there are no simple equations for them. The purpose of this memoir is to study sandwiched singularities through their relationship to the infinitely near base points of the complete ideals blownup to obtain them. Now, we briefly summarize the main contents of each one of the chapters. Chapter I is of preliminary nature and gives references to the literature for proofs. Concepts and well-known facts about infinitely near points, weighted clusters, complete ideals and rational and sandwiched surface singularities are reviewed and some consequences that are needed in the memoir are derived. In Chapter II we establish the main link between the study of sandwiched singularities and the theory of Enriques diagrams of weighted clusters and we derive some results on sandwiched singularities by using the unloading procedure. Chapter III deals essentially with the principality of divisors going through a sandwiched singularity. It is well known that Wei divisors going through a singularity (X, Q) are not Cartier divisors in general. In Chapter IV we use the results of Chapter III to explore the connection between the ideal sheaves on “X” with finite cosupport contained in the exceptional locus and the complete m(o)-primary ideals in R. Chapter V is devoted to derive consequences related to the Nash conjecture of arcs for sandwiched singularities. In Appendix A, we provide the listings of three programs in language C implementing some of the algorithms proposed. These programs have been used to compute some of the examples presented throughout the memoir. Part of the results of this thesis has been published or will be published in: • J. Fernandez-Sanchez, On sandwiched singularities and complete ideals, J. Pure Appl. Algebra 185 (2003), no. 1-3, 165-175. [19] • J. Fernandez-Sanchez, Nash families of smooth arcs on a sandwiched singularity, To appear in Math. Proc. Cambridge. Philos. Soc. [18] • J. Fernandez-Sanchez, Equivalence of the Nash conjecture for primitive and sandwiched singularities, To appear in Proc. Amer. Math. Soc. [17]
17

L'art urbain des graffitis : expérimentation des frontières esthétiques / Urban art of graffitis : experimentation of aesthetic boundaries

Burgi, Gary 14 November 2016 (has links)
Un graffiti est exposé à la vue de tous dans la rue : lieu du passage, de l’échange, de l’intenseproximité. Un regard doit-il/peut-il se constituer, se conformer à un lieu d’approximation, dedistance, de rencontre, de conflit ?Or, exposer ce type d’oeuvre ailleurs, semble, a priori, une hérésie ; sa décontextualisation, unpléonasme. En quoi l’acte d’exposer contredit-il cette pratique urbaine, si, littéralement, un graffitiest directement accessible à nos sens, exposé ? Le mur est-il une frontière qui fait écran, entre lemonde du réel et de l’irréel ?Une représentation persiste inconsciemment : l’art urbain peut aussi faireconsensus. Comment autrui intervient-il dans ce type de représentation ?Avec des hypothèses élaborées à partir d’oeuvres urbaines, un corpus d’image constituera uneméthode de recherche pour engager un dialogue avec le corps du passant, suivant les modalités deproduction ou de création de cette vision de graffiti.Une expérimentation des frontières esthétiques, peut-elle rendre compte, a posteriori, dudevenir de l’anonymat d’une oeuvre d’art réalisée sur les surfaces anonymes et phénoménales de laville ?La comparaison du corps d’un être humain à celui d’une ville, est-elle fortuite ? Cetteréduction de l’homme au mur, dit métaphoriquement, est-elle constitutive de rapportshumains ? Réels, fictifs ? Relatifs ?Comment l’art peut-il former dans l’urgence un regard historique, voire collectif, sans ladistance ? / A graffiti is exposed for every body in the street : place of passage, exchange, of the intenseproximity. Should or could a glance be able to constitute itself or to observe itself, a place ofapproximation, of distance, of meeting, of conflict ?But, to expose this type of work elsewhere, seems, a priori, a heresy ; its decontextualization,a pleonasm. How does the act of exposing contradict this urban practice, if, literally, a graffiti isdirectly accessible to our senses, exposed ? Is the wall a boundary between the real and the unreal ?A representation persists unconsciously : urban art can also make a consensus. How doesanother person intervene in this type of representation ?With hypotheses developed from urban works, a corpus of images will constitute a researchmethod for engaging a dialogue with the body of the passer-by, according to the modalities ofproduction or creation of this vision of graffiti.Can an experiment on aesthetic borders explain, a posteriori, the future of the anonymity of apiece of art produced on the anonymous and phenomenal surfaces of the city ?Is the comparison between the body of a human being and the corpse of a city, fortuitous ? Isthis reduction of the man to the wall, metaphorically speaking, constitutive of human relationships ?Real, fictional ? Relative ?How can art form in the emergency a historical view and collective, without distance ?
18

Överturism som ett fenomen: Fallet Gamla Stan : En kvalitativ undersökning av fenomenet överturism

Deibl, Hind, Papadogiannakis, Minos, Wilkon, Sandra January 2020 (has links)
Syftet och målet med denna studie var dels att undersöka fenomenet överturism genom att titta närmare på större europeiska städer såsom Barcelona och Venedig. Men även gå på djupet med hur detta fenomen har uppstått och ifall det kan appliceras på vår egen hemstad Stockholm, och specifikt Gamla Stan. Genom att genomföra kvalitativa intervjuer med både näringsidkare och lokalbefolkning hoppas vi få en bättre förståelse för hur avtrycket av turister manifesterar sig i överturism och ifall det finns en generell attityd gentemot detta. Vi bör ha i åtanke att, generellt sett så kommer turister till Gamla stan (som är en huvudattraktion för de miljoner besökare Sverige årligen tar emot) med all säkerhet att spendera tid på ön, på grund av dess centrala läge och möjligheten att gå igenom stan på så pass kort tid. Utöver det ekonomiska avtryck som detta medför har det också en påverkan på lokalbefolkningen, som möts av ett ökande antal besökare för varje år, särskilt under de tre sommarmånaderna. Medan fler ur lokalbefolkningen ser turisterna som orörliga objekt och i vissa fall störningsmoment så erkänner näringsidkare turisternas betydelse för deras verksamhet, och att affärsrörelser på något sätt är beroende av turister då de säkrar deras överlevnad. / The purpose and aim of this study is to through carefully examining the phenomenon of overtourism by looking closely at other major European destinations such as Barcelona, Venice, Dubrovnik and Santorini, go in depth with how this phenomenonhas appeared and perhaps if it can be applied to our home city of Stockholm, and specifically the Old Town, “Gamla Stan”. By conducting qualitative interviews with both business owners and residents we hope to get a better understanding of how the impact of tourists applies itself and if there is a certain attitude towards this. Not only is it clear that this phenomenonhas brought changes to many destinations over the last few years. In Barcelona the attitude towards tourist has reached almost violent levels, with some cases of locals attacking tourists and targeting traveling group with slogans etc, We have to consider that in general, people that visit Gamla Stan, which is a major attraction for the millions of tourists that travel to Stockholm every year, almost certainly will spend at least some time on this island because of its central location and convenient walk-through possibilities. Besides the economic imprint this also affects the local residents, who are faced with a growing number of visitors, especiallyin the three summer months.
19

Apprentissage pour la reconnaissance d'actions humaines en vidéo

Klaser, Alexander 31 July 2010 (has links) (PDF)
<p>Cette thèse s'intéresse à la reconnaissance des actions humaines dans des données vidéo réalistes, tels que les films. À cette fin, nous développons des algorithmes d'extraction de caractéristiques visuelles pour la classification et la localisation d'actions.</p> <p>Dans une première partie, nous étudions des approches basées sur les sacs-de-mots pour la classification d'action. Dans le cas de vidéo réalistes, certains travaux récents qui utilisent le modèle sac-de-mots pour la représentation d'actions ont montré des résultats prometteurs. Par conséquent, nous effectuons une comparaison approfondie des méthodes existantes pour la détection et la description des caractéristiques locales. Ensuite, nous proposons deux nouvelles approches pour la descriptions des caractéristiques locales en vidéo. La première méthode étend le concept d'histogrammes sur les orientations de gradient dans le domaine spatio-temporel. La seconde méthode est basée sur des trajectoires de points d'intérêt détectés spatialement. Les deux descripteurs sont évalués avec une représentation par sac-de-mots et montrent une amélioration par rapport à l'état de l'art pour la classification d'actions.</p> <p>Dans une seconde partie, nous examinons comment la détection de personnes peut contribuer à la reconnaissance d'actions. Tout d'abord, nous développons une approche qui combine la détection de personnes avec une représentation sac-de-mots. La performance est évaluée pour la classification d'actions à plusieurs niveaux d'échelle spatiale. Ensuite, nous explorons la localisation spatio-temporelle des actions humaines dans les films. Nous étendons une approche de suivi de personnes pour des vidéos réalistes. En outre, nous développons une représentation d'actions qui est adaptée aux détections de personnes. Nos expériences suggèrent que la détection de personnes améliore significativement la localisation d'actions. De plus, notre système montre une grande amélioration par rapport à l'état de l'art actuel.</p>
20

Local Cooperation in Water Management : A Minor Field Study from South India

Ståhlberg, Camilla January 2006 (has links)
<p>Decentralized development approaches have in recent years gained wide acceptance in policy circles. In India the national and the state</p><p>governments have for a long time undertaken the primary responsibility for water management. In recent years however, there has been a clear shift of policy towards increased reliance on the local communities. This thesis deals with the capacity of rural communities in India to manage their water resources in a sustainable way.</p><p>Through a case study of water management in a South Indian village opportunities and barriers for rural communities in India to manage their water resources in a sustainable way is analysed. The thesis deals with both formal and informal institutions involved in the water management.Factors that can promote and obstruct locals’ contribution in water management are discussed. Also the role of external actors such as NGOs, the Panchayats and the government is dealt with, and how they may facilitate a development towards sustainability and increased locals’ contribution in order to achieve a sustainable community bases water management.</p><p>Theories on collective action and the commons have been used in the analysis. These theories deal with how to get people to cooperate regarding the management of common resources such as water in order to achieve higher collective benefits. The study is primarily based on 66 semistructured qualitative interviews with local water users in a village in Andhra Pradesh.</p> / <p>Decentralized development approaches have in recent years gained wide acceptance in policy circles. In India the national and the state</p><p>governments have for a long time undertaken the primary responsibility for water management. In recent years however, there has been a clear shift of policy towards increased reliance on the local communities. This thesis deals with the capacity of rural communities in India to manage their water resources in a sustainable way.</p><p>Through a case study of water management in a South Indian village opportunities and barriers for rural communities in India to manage their water resources in a sustainable way is analysed. The thesis deals with both formal and informal institutions involved in the water management.Factors that can promote and obstruct locals’ contribution in water management are discussed. Also the role of external actors such as NGOs, the Panchayats and the government is dealt with, and how they may facilitate a development towards sustainability and increased locals’ contribution in order to achieve a sustainable community bases water management.</p><p>Theories on collective action and the commons have been used in the analysis. These theories deal with how to get people to cooperate regarding the management of common resources such as water in order to achieve higher collective benefits. The study is primarily based on 66 semistructured qualitative interviews with local water users in a village in Andhra Pradesh.</p> / The ISRN in the pdf-file is incorrect. The correct ISRN is shown below.

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