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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.
441

Métastabilité du modèle de Blume-Capel / Metastability of the Blume-Capel model

Lemire, Paul 29 June 2018 (has links)
Les travaux de cette thèse portent sur l’étude de la métastabilité du modèle de Blume-Capel. Il s’agit d’un modèle introduit en 1966 dans lequel évoluent au cours du temps des spins à trois états +1, -1, 0, représentant respectivement une particulechargée positivement, négativement, et l’absence de particule, sur un réseau. La thèse est structurée en deux parties. La première partie contient un travail en collaboration avec C. Landim qui est paru dans la revue Journal of Statistical Physics. L’article traite du comportement métastable du modèle de Blume-Capel lorsque la température tend vers 0, dans le cas où la taille du domaine dans lequel vit le processus est fixée durant l’évolution. La seconde partie est consacrée à l’extension des résultats du premier papier au cas où la taille de la boite croît exponentiellement vite vers +1 lorsque la température décroît vers 0. Pour ce modèle, sur une très grande échelle de temps, trois états métastables subsistent, à savoir les états où le tore est respectivement remplis par des spins négatifs, positifs, ou "nuls". Il est démontré qu’avec probabilité 1, partant de la configuration n’ayant que des spins négatifs, le processus visite la configuration n’ayant que des spins "nuls" avant de visiter la configuration n’ayant que des spins positifs.Les résultats de la thèse consistent notamment à caractériser les configurations critiques et à fournir des estimations précises des temps d’atteinte des états stables. / This thesis is about the study of the metastability of the Blume-Capel model. This model, introduced in 1966, is a nearest-neighbor spin system where the single spin variable takes three possible values +1, -1, 0. One can interpret it as a system ofparticles with spins. The value 0 of the spin corresponds to the absence of particle, whereas the values ± correspond to the presence of a particle with the respective spin. The thesis is divided in two parts. The first part is an article published in Journal of Statistical Physics with C. Landim. We prove the metastable behavior of the Blume-Capel model when the temperature decreases to 0 on a fixed size torus.The second part is dedicated to the generalization of these results to the case of a torus which size increases to +1 as the temperature decreases to 0. For this model, three metastable states -1, 0,+1 remain on a very large time scale, where -1, 0,+1 stand for the configuration where the torus is respectively filled with -1’s, 0’s and +1’s. We prove that starting from -1, the process visits 0 before reaching +1 with very high probability. We also caracterize the critical configurations and provide sharp estimates of the transition times.
442

The influence of glide path preparation on the failure rate of nickel-titanium reciprocating instruments

Jonker, Casper Hendrik January 2013 (has links)
Introduction: The aim of this in vitro study was to determine the influence of two glide path preparation methods on the fracture rate of the Primary 25/08 WaveOne reciprocating instrument. The number of simulator Endo-Training-Blocks in each group were calculated at the time of instrument fracture and compared to determine the influence of glide path preparation on the failure rate of the Primary 25/08 WaveOne reciprocating instrument. Preparation times for different glide path methods and total time for root canal preparation, with or without glide path, was also calculated. Materials and Methods: Simulator Endo-Training-Blocks (n = 300) were selected and randomly divided into 3 groups (n = 100). The 3 groups were then sub-divided into 5 smaller groups (n = 20). Root canal preparation was done with new primary 25/08 WaveOne instruments allocated to each group (5 in total for each group, 1 for each sub-group) following different methods for glide path preparation. Group 1: no glide path (control); Group 2: glide path preparation with stainless-steel hand files (size 10 K-File followed by size 15 K-File and finally size 20 K-File until loose fitting); and Group 3: glide path preparation with rotary PathFiles (size 10 K-File until loose fitting followed by PathFile no.1 (ISO 13 tip), PathFile no.2 (ISO 16 tip) and finally PathFile no. 3 (ISO 19 tip)). The Primary 25/08 WaveOne reciprocating instrument was used with the WaveOne endodontic motor in “WaveOne All “mode with a brushing motion on the outstroke. Simulated root canals were irrigated with sterile water and Glyde was used as lubricating agent. The outcome was measured by recording how many simulators could be prepared with one instrument before instrument breakage occurred. The preparation protocol was repeated 5 times. The time it took to prepare the glide path and the total preparation time was also calculated. The data of the different parts of the project were collected and statistically analysed using the ANOVA / Bonferroni test. Results: Glide path preparation with PathFiles was significantly faster (13.3 s ± 2.60 s) than with hand files (25.1 s ± 1.70 s) (P < 0.001). The highest number of simulators could be prepared after glide path preparation was performed with PathFiles (19.2 ± 0.84) (P < 0.001). Pairwise comparisons at the Bonferroni adjusted significance level of 0.017 demonstrated that there were statistical significant differences (P < 0.001) when PathFiles (19.2 ± 0.84) and hand files (17.6 ±1.14) were compared to the no glide path group (7.4 ± 0.89). There was no statistical significant difference between PathFiles and hand files groups. Total Preparation time was significantly shorter (P < 0.001) when an initial glide path was prepared with PathFiles (12.7 ± 0.22 s). The longest preparation time (P < 0.001) was calculated in group 1 where no glide path (21.2 ± 0.20 s) was present and the Endo-Training-Blocks were left undisturbed. Conclusion: Initial glide path preparation with PathFiles resulted in shorter preparation time (glide path and total preparation) and allowed a higher number of simulators prepared before failure of the WaveOne instrument. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Odontology / unrestricted
443

Problem specific heuristics for group scheduling problems in cellular manufacturing

Neufeld, Janis Sebastian 21 April 2016 (has links)
The group scheduling problem commonly arises in cellular manufacturing systems, where parts are grouped into part families. It is characterized by a sequencing task on two levels: on the one hand, a sequence of jobs within each part family has to be identified while, on the other hand, a family sequence has to be determined. In order to solve this NP-hard problem usually heuristic solution approaches are used. In this thesis different aspects of group scheduling are discussed and problem specific heuristics are developed to solve group scheduling problems efficiently. Thereby, particularly characteristic properties of flowshop group scheduling problems, such as the structure of a group schedule or missing operations, are identified and exploited. In a simulation study for job shop manufacturing cells several novel dispatching rules are analyzed. Furthermore, a comprehensive review of the existing group scheduling literature is presented, identifying fruitful directions for future research.
444

Virtuelle und experimentelle Methoden bei der Produktentwicklung einer Handhabungseinheit zur automatisierten Ablage technischer Textilien

Richrath, Marvin, Thoben, Klaus-Dieter, Franke, Jan, Ohlendorf, Jan-Hendrik January 2016 (has links)
Inhalt In diesem Beitrag wird die Kombination von virtuellen und experimentellen Methoden im Produktentwicklungsprozess am Beispiel einer Handhabungseinheit zur automatisierten Ablage technischer Textilien thematisiert. Um das Automatisierungspotenzial in den Fertigungsprozessen zum Aufbau von Faserverbundstrukturen zu erschließen, entwickelt das Institut für integrierte Produktentwicklung (BIK) seit längerem Handhabungseinheiten für technische Textilien. Eine automatisierte Fertigung soll die Reproduzierbarkeit und die Qualität von Bauteilen erhöhen, um z.B. den Beanspruchungen bei größer werdenden Rotorblättern von Windenergieanlagen gerecht zu werden. Ein weiteres Ziel der Automatisierung besteht in der Reduzierung von Prozesszeiten und Fertigungskosten, um den Fertigungsstandort Deutschland in Zukunft attraktiv zu gestalten. Die erfolgreiche Umsetzung der Produktentwicklung erfolgt am BIK unter kombinierter Anwendung von virtuellen und experimentellen Methoden. Insbesondere bei der Handhabung von technischen Textilien, deren biege- und schubweichen Materialeigenschaften nur mit hohem Aufwand in einer virtuellen Umgebung abgebildet werden können, ist das Durchführen von experimentellen Methoden bei komplex ablaufenden dynamischen Prozessen notwendig, um nicht vorhersehbares Materialverhalten zu identifizieren.
445

Das Rückkehrzeitentheorem von Bourgain

Fritzsch, Simon 20 February 2019 (has links)
Eine Verallgemeinerung der klassischen Resultate von Von Neumann und Birkhoff ist die Frage nach gewichteten Versionen ihrer Theoreme. Eine zentrale Antwort auf diese Fragestellung lieferte Jean Bourgain 1988 mit seinem Rückkehrzeitentheorem. Aufbauend auf dem Beweis von Bourgain, Furstenberg, Katznelson und Ornstein aus dem Jahr 1989 sowie dem Buch von Assani präsentieren wir einen ausführlichen und vollständigen Beweis und besprechen insbesondere den Fall von dynamischen Systemen mit rein atomarer invarianter sigma-Algebra. / In this diploma thesis we present a detailed proof of Bourgain's Return Times Theorem due to Bourgain, Furstenberg, Katznelson and Ornstein following their paper as well as the book by Assani. In particular, we discuss the case of systems with a purely atomic invariant sigma-algebra in all details.
446

Optimization of Production Scheduling at IKEA Industry Hultsfred

Anemyr, Mattias January 2020 (has links)
IKEA Industry has factories in several locations where one location is in Hultsfred, Småland. IKEA Industry Hultsfred produces IKEA:s wardrobe collection PAX. In 2018, 2.8 million wardrobes were manufactured in Hultsfred. This thesis covers the subject of constructing and developing an optimization model which has the same characteristics as the plinth production at IKEA Industry Hultsfred. This means that the optimization model must consider production sequence; the setup time is different depending on which products that have been produced in the machine earlier. The thesis also covers to investigate how much time that is necessary to produce the plinths to Hultsfred, Portugal, and Germany under different circumstances. This thesis also balances inventory levels and setup time. I.e., how the inventory levels are changed if more emphasis is put into minimizing setup time, and the other way around. The results show that lower inventory levels and setup times are achievable over seven days if the production planning technique is changed.
447

Jak orientovat sociální vztahy v době krize? / How to orient social relations in times of crisis?

Littmann, Petr January 2020 (has links)
This work that called How to orientate social relationships in the crisis period? is concerned with works of three chosen authors of European philosophical phenomenological tradition in the twentieth and twenty-first centuries. They are Zygmunt Bauman (Pole), Byung-Chul Han (Korean living in Europe for longer time) and Anna Hogenová (Czech). This work has built according to uniform scheme for all three authors. It presents their life and work shortly then presents their ideas and conceptions in a longer face. It also presents response of their works by chosen authors from The Czech Republic and foreigners. Important ideas and conceptions have to serve as a possible way in a help for social work and also for description, analysis, possible development and solution of problems that arise in the crisis period or - as well as told with Bauman - in liquid times. This work has written i terms of Christian Crisis and Pastoral Work - Diaconia so it contents also reference to this subject of study. This work derives from works of three main authors and from works of next ones, too. An important part is a work with Holy Scripture.
448

Fältstudier av produktionstidplan på Kv. Solägget / Field studies of the production schedule at the block Solägget

Lindgren, Linnea January 2010 (has links)
Under drygt två månader har produktionen vid JM Entreprenads projekt Kv. Solägget följts för att med utgångspunkt i projektets produktionstidplan, aktuell verklig position, diverse dokument samt i intervjuer avgöra varför fortskridandet eventuellt avviker från det planerade, där främst förseningar var intressanta. Kv. Solägget genomförs på generalentreprenad åt JM AB och följer således de arbetsmetoder som används inom JM AB. En väsentlig skillnad mellan JM AB och JM Entreprenad är att JM Entreprenad inte är lika väl inkörda på gällande enhetstider och rutiner som JM AB:s hantverkare är. Genom att i tidigt skede sätta in ytterligare resurser än vad som var planerat i kalkylen undvek man att under tiden för min fältstudie uppnå en avvikelse som motsvarar en försening och snarare lyckades arbeta in ett försprång på upp till två veckor. För att möjliggöra en produktion utan förseningar behandlar rapporten hårda, mjuka och yttre faktorer med en betydelsefull utgångspunkt i vikten av att åstadkomma en väl utarbetad planering inför produktionsstart och på så sätt i ett tidigt skede ta ställning till möjliga faktorer som kan komma att påverka avstämningarna mot produktionstidplanen på ett negativt sätt. / During around two months the production of the project of JM Entreprenad named the block Solägget has been followed contraining to the basis of the production schedule, the current actual position, documents of the project and also interviews to determine why the progression may be different from the planned, why the mainly interesting were to analyze the delays. The block Solägget is implemented on a general contractor for JM AB and therefore the project follows the practices of JM AB. One significant difference between JM AB and JM Entreprenad is that JM Entreprenad isn´t as used to the current unit times and routines as JM AB are. By the early deployment of additional resources than what were planned in advance the delays were avoided during the period of my field study and instead JM Entreprenad managed to work up a lead of up to two weeks. To enable a production without any delays this report treats hard, soft and external factors with an important basis of the importance of achieving a well-established planning before starting any production and in that way consider possible factors that may affect the reconciliation of the production schedule in a negative way. / 2010:12
449

Passenger waiting strategies on railway platforms - Effects of information and platform facilities - : Case study Sweden and Japan

Pettersson, Pierre January 2011 (has links)
Abstract The Swedish railway has during many years received low customer satisfaction scores. Reasons for this are reliability, service and information concerns. The focus of this master thesis lies on the railway platform. The platform is an important part to the factors above as its information and facilities, which constitute a part of the service before the trip, could contribute in causing delays and reliability issues. This study investigates the behaviour of passengers on railway platforms and the effect that information, seats and entrances along the platform has on that behaviour. The goal is to find advantages and disadvantages and propose improvements in a Swedish setting. Platforms and trains that have been studied are in Stockholm, Sweden and Tokyo, Japan. Platform distributions and individual behaviour on the platforms are recorded with three different and relatively easy methods. Results of the Swedish study show aggregate trends where passengers tend to cluster around entrances and seats. Many Swedish passengers do not believe themselves to have enough information to know where their car will stop. These passengers do mostly not know that information exist and on average stand much further away from their closest door, when the train arrives, compared to passengers that believe themselves to know where their car will stop along the platform. The results of the Japanese study show that almost all passengers stand close to their door. From the findings in not only this, but also other studies, four aggregate properties in order to get better railway platforms are finally presented. These properties are reliability, clarity and availability of information and good location of seats and other facilities. Suggestions for tangible improvements for the Swedish railway platforms are finally given. Among these improvements are new information screens and standardized information and stopping position of trains.
450

Asymptotische Resultate über Lokalzeiten von Irrfahrten im Zd

Becker, Mathias 13 November 2013 (has links)
Gegenstand der vorliegenden Dissertation ist das Verhalten sogenannter Selbstüberschneidungslokalzeiten $\\|\\ell_t\\|_p^p$ einer zeitstetigen Irrfahrt $(S_r)_r$ auf dem $d$-dimensionalen Gitter $\\Z^d$. Dabei ist für $p>1$ die Funktion $\\ell_t$ definiert durch $$ \\ell_t(z):=\\int_{0}^{t}\\1_{\\{S_r=z\\}}\\,\\d r\\nonumber $$ und bezeichnet die Aufenthaltsdauer der Irrfahrt bis zum Zeitpunkt $t\\in(0,\\infty)$ im Punkt $z\\in\\Z^d$. Ziel ist es, ein Prinzip großer Abweichungen zu entwickeln, d.h. das Hauptaugenmerk liegt auf dem asymptotischen Verhalten der Wahrscheinlichkeit, dass die Selbstüberschneidungslokalzeiten von ihrem Erwartungswert in erheblichem Maße nach oben abweichen. Mit anderen Worten; es soll das asymptotische Verhalten von $$ \\log\\P(\\|\\ell_t\\|_p^p\\geq r^p_t) $$ genau bestimmt werden, wobei $r_t^p\\in(0,\\infty)$ schneller als der Erwartungswert $\\E[\\|\\ell_t\\|_p^p]$ gegen unendlich streben soll. Dieses Verhalten kann dabei durch $t$, $r_t$ und eine gewisse Variationsformel beschrieben werden. Es wird sich herausstellen, dass es zwei Fälle zu betrachten gilt, in denen sich das probabilistisch beste Verhalten stark unterscheidet; die genaue Position des Phasenübergangs hängt dabei von den Parametern $p$ und $d$ ab. Im Vorgriff auf die Resultate kann man festhalten, dass die nötigen Selbstüberschneidungen in kleinen Dimensionen (im sogenannten subkritischen Fall) über einen großen Bereich erfolgen, aufgrund dessen bei der mathematischen Modellierung eine Reskalierung erforderlich ist. In hohen Dimensionen (dem sogenannten superkritischen Fall) ist dies nicht nötig, da die erforderlichen Selbstüberschneidungen innerhalb eines begrenzten Intervalles erfolgen. Das Interesse an der Untersuchung entstand unter anderem aus der Verbindung zu Modellen der statistischen Mechanik (parabolisches Anderson Modell) und zur Variationsanalysis. In der Vergangenheit wurde eine Vielzahl an Methoden benutzt, um dieses Problem zu lösen. In der vorliegenden Dissertation soll die sogenannte Momentenmethode bestmöglich ausgereizt werden und es wird gezeigt, welche Ergebnisse damit möglich sind.

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