• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1567
  • 677
  • 417
  • 265
  • 170
  • 144
  • 120
  • 79
  • 71
  • 34
  • 32
  • 32
  • 16
  • 15
  • 13
  • Tagged with
  • 4194
  • 1153
  • 835
  • 769
  • 496
  • 410
  • 391
  • 375
  • 350
  • 329
  • 310
  • 309
  • 299
  • 280
  • 267
  • 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.
501

Antibacterial agent formulation and delivery with external triggered release

Luo, Dong January 2017 (has links)
Antibacterial agent delivery is of great importance in medicine and dentistry since the bacterial infections are still one of the major reasons for hospitalization and mortality. Despite of the development of technique and pharmacy, more antimicrobial agents are optimized and utilized to treat infections, and their action of principal is better understood which lay a foundation for developing strategies for infection treatment. Over the last decades, many delivery systems have been established to deliver bacterial agents and maintain a sustained activity against them. However, the bacteria are always developing and finding a way to defend themselves. A more responsive antibacterial agent delivery system, which can release the active substances on demand to match the stages of diseases, is highly desirable. Therefore, it motivates us to carry out the work to develop a multifunctional delivery system for antibacterial particle formulation and encapsulation based on the layer-by-layer self-assembly technique and electrospinning, to manipulate the release with external triggers, such as near-infrared (NIR) light and alternating magnetic field (AMF). Strategically, two different kinds of antibacterial agents, chlorhexidine and doxycycline, were studied. Chlorhexidine was fabricated into spherical particles and functionalized with both gold and magnetite nanoparticles, and doxycycline was encapsulated within microcapsules which were also functionalized with magnetite nanoparticles. Their release kinetics and possibilities to trigger the release with either a NIR light or AMF was explored. The first two chapters of the thesis give a general introduction and literature review on the current use of antibacterial agents and the problems concerned, strategies already developed for antibacterial agent delivery, and the potential triggers to induce a smart release. In chapter 3, a brief description of materials and methods, and instruments is presented. Chapter 4 is about chlorhexidine particle formulation. Firstly, particulation of chlorhexidine and mechanism of 4 spherical interconnected structure formation was explored, and then the chlorhexidine particles are encapsulated either by LbL assembly or spray-drying. The chlorhexidine spheres were also functionalized with gold nanorods and Fe3O4 nanoparticles to achieve NIR light and magnetic field manipulated release, and the effect of nanoparticles on the formation of chlorhexidine spheres was also studied. When the chlorhexidine particles were incorporated into electrospun fibers, a sustained antibacterial activity was demonstrated. Chapter 5 is about the delivery of doxycycline to cells with microcapsules and the sustained intracellular doxycycline activity was demonstrated via EGFP expression when the cells were engineered with a tetracycline regulated gene expression system. Intracellular triggered release and upregulation of EGFP expression was achieved by an AMF. The results successfully demonstrated the possibility of chlorhexidine and doxycycline delivery and NIR light/AMF triggered release, which is promising for a future application in medicine and dentistry.
502

Estrutura e agência nas relações internacionais : análise da relação entre processos de construção do estado e a evolução dos sistemas políticos internacionais

Brancher, Pedro Txai Leal January 2017 (has links)
Este trabalho trata da relação entre competição, estrutura e agência nas Relações Internacionais. Ele se estrutura em três partes. A primeira parte contextualiza o estudo na agenda de pesquisa dos Estudos Estratégicos Internacionais. Para tanto, discute-se a pertinência do debate agente–estrutura, bem como delimitam-se os pressupostos ontológicos que nortearão o restante do trabalho. A segunda parte é o artigo. Analisam-se os efeitos da competição no processo de evolução dos sistemas políticos internacionais, sistemas políticos nacionais e estados. Por conta disso, discute-se a ontologia de cada objeto de análise e, em seguida, busca-se os mecanismos causais que conectam suas respectivas trajetórias evolutivas. De acordo com os atores e meios envolvidos, três dimensões de competição social são identificadas: competição internacional; construção do estado; e concorrência regulada. A hipótese de trabalho é que os resultados das interações entre as estratégias escolhidas pelos agentes para enfrentar o tipo de competição com que se deparam causam mudanças na estrutura dos sistemas políticos internacionais, nacionais e nas características das organizações políticas estatais. Na terceira parte, discute-se as implicações teóricas e práticas decorrentes do trabalho, bem como são assinaladas perspectivas para a continuação da agenda de pesquisa. Sugere-se que a incorporação de conceitos e categorias desenvolvidas pela literatura de Teoria de Sistemas e da Complexidade é fundamental para a superação de dicotomias ontológicas e epistemológicas nas ciências sociais. Ademais, argumenta-se que o aperfeiçoamento das organizações políticas é indissociável da compreensão de que a busca por defesa e segurança pelos estados não é apenas uma força destruidora, mas também pode produzir efeitos que potencializam a coesão social e expandem direitos fundamentais. Logo, propõe-se que a agenda de pesquisa decorrente desse trabalho deverá se debruçar sobre a questão de quais são as condições em que interações competitivas contribuem para o surgimento de organizações políticas capazes de sobreviverem e atuarem no sistema político internacional contemporâneo, bem como proverem segurança, bem-estar e direitos políticos para seus cidadãos. / This paper deals with the relationship among competition, structure and agency in International Relations. The study is structured in three parts. The first part contextualizes the work in the research agenda of the International Strategic Studies. Therefore, we discuss the relevance of the agent-structure debate, and delimit the ontological assumptions and that will guide the rest of the study. The second part is the article. It analyzes the effects of competition in the process of evolution of international political systems, national political systems and states. On that account, discusses the ontology of each object of analysis, and then seeks the causal mechanisms that connect their evolutionary trajectories. According to the actors and means involved three dimensions of social competition are identified: international competition; construction of state; and regulated competition. The working hypothesis is that the results of the interactions among the strategies chosen by agents to cope with the kind of competition they encounter cause changes in the structure of international political systems, national political systems and in the characteristics of the state political organizations. In the third part, it is discussed theoretical and practical implications resulting from study, and also prospects for the continuation of the research agenda. It is suggested that the incorporation of concepts and categories developed by Systems and Complexity Theory is fundamental to overcoming ontological and epistemological dichotomies in the social sciences. Moreover, it is argued that the improvement of our political organizations is inseparable from the understanding that the search for security and defense by states is not only a destructive force, but can also produce effects that enhance social cohesion and expansion of fundamental rights. Therefore, it is proposed that the research agenda derived from the study should lean over the question of what are the conditions under which competitive interactions contribute to the emergence of political organizations able not only to survive and act in the contemporary international political system, but also provide security, welfare, and political rights to its citizens.
503

Conception et Optimisation Distribuée d’un Système d’Information des Services d’Aide à la Mobilité Urbaine Basé sur une Ontologie Flexible dans le Domaine de Transport / Design and Optimization of Distributed Information Systems of Services to Aid Urban Mobility Based on a Flexible Ontology in the Transport Domain

Saad, Sawsan 10 December 2010 (has links)
De nos jours, les informations liées au déplacement et à la mobilité dans un réseau de transport représentent sans aucun doute un potentiel important.Ces travaux visent à mettre en œuvre un Système d’Information de Service d’Aide à la Mobilité Urbaine (SISAMU).Le SISAMU doit pouvoir procéder par des processus de décomposition des requêtes simultanées en un ensemble de tâches indépendantes. Chaque tâche correspond à un service qui peut être proposé par plusieurs fournisseurs d’information en concurrence, avec différents coûts, temps de réponse et formats. Le SISAMU est lié à un Réseau informatique Etendu et distribué de Transport Multimodal (RETM) qui comporte plusieurs sources d’information hétérogènes des différents services proposés aux utilisateurs de transport. L’aspect dynamique, distribué et ouvert du problème, nous a conduits à adopter une modélisation multi-agent pour assurer au système une évolution continue et une flexibilité pragmatique. Pour ce faire, nous avons proposé d’automatiser la modélisation des services en utilisant la notion d’ontologie. Notre SISAMU prend en considération les éventuelles perturbations sur le RETM.Ansi, nous avons créé un protocole de négociation entre les agents. Le protocole de négociation proposé qui utilise l’ontologie de la cartographie se base sur un système de gestion des connaissances pour soutenir l'hétérogénéité sémantique. Nous avons détaillé l’Algorithme de Reconstruction Dynamique des Chemins des Agents (ARDyCA) qui est basé sur l’approche de l’ontologie cartographique. Finalement, les résultats présentés dans cette thèse justifient l’utilisation de l’ontologie flexible et son rôle dans le processus de négociation / Nowadays, information related on displacement and mobility in a transport network represents certainly a significant potential. So, this work aims to modeling, to optimize and to implement an Information System of Services to Aid the Urban Mobility (ISSAUM).The ISSAUM has firstly to decompose each set of simultaneous requests into a set of sub-requests called tasks. Each task corresponds to a service which can be proposed different by several information providers with different. An information provider which aims to propose some services through our ISSAUM has to register its ontology. Indeed, ISSAUM is related to an Extended and distributed Transport Multimodal Network (ETMN) which contains several heterogeneous data sources. The dynamic and distributed aspects of the problem incite us to adopt a multi-agent approach to ensure a continual evolution and a pragmatic flexibility of the system. So, we proposed to automate the modeling of services by using ontology idea. Our ISSAUM takes into account possible disturbance through the ETMN. In order to satisfy user requests, we developed a negotiation protocol between our system agents. The proposed ontology mapping negotiation model based on the knowledge management system for supporting the semantic heterogeneity and it organized as follow: Negotiation Layer (NL), the Semantic Layer (SEL), and the Knowledge Management Systems Layer(KMSL).We detailed also the reassignment process by using Dynamic Reassigned Tasks (DRT) algorithm supporting by ontology mapping approach. Finally, the experimental results presented in this thesis, justify the using of the ontology solution in our system and its role in the negotiation process
504

Structure, morphology and performance relationships of organic photovoltaic devices : the block copolymer approach

Deribew, Dargie Hailu 14 July 2013 (has links)
Ce travail se focalise sur l’étude de cellules solaires organiques modèles basées sur le mélange de poly(3-hexylthiophène) (P3HT) et de l'ester méthylique de l'acide [6,6]-phényl C61 butyrique (PCBM). La corrélation entre la morphologie de la couche active, les paramètres de mises en œuvre et le rendement photovoltaïque a été soigneusement étudiée afin d’obtenir l’optimisation de l’efficacité de tels dispositifs. Une méthode originale pour contrôler la séparation de phases dans ces mélanges a été proposée et consiste à l'intégration de copolymères blocs comme additifs. Trois copolymères séquencés ont été utilisés en tant qu’agents de nanostructuration et/ou d'agents de nucléation. Il a notamment été montré que l'incorporation de P3HT-b-PI permet l'augmentation du nombre de cristallites de P3HT tout en limitant l’agglomération du PCBM. D'autre part, l'incorporation de P3HT-b-P4VP dans les mélanges de P3HT:PCBM a permis de contrôler l'orientation des cristallites de P3HT, améliorant par ce fait le transport de charge dans les dispositifs. / This work investigates organic solar cells made of a blend of polymeric materials based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as model system. The correlation between the photovoltaic active layer morphology and the performance of the organic solar cell is thoroughly investigated. The chosen method for controlling phase separation in the polymeric blends is to incorporate block copolymers as additives. Three systematically selected block copolymers were used as nanostructuring and/or nucleating agents. Indeed, the incorporation of P3HT-b-PI induces the increase in the number of P3HT crystallites as well as suppresses the growth of PCBM aggregates. On the other hand, the incorporation of P3HT-b-P4VP into P3HT:PCBM decreases the crystallization of P3HT but increases its face-on orientation, a requirement for an enhanced charge transport in organic PV devices.
505

Development of Agent-based Models for Economic Simulation / Vývoj agentních modelů pro ekonomickou simulaci

Šalamon, Tomáš January 2005 (has links)
This thesis is about the development of agent-based models that are a method of simulation of economic processes and environments using multi-agent systems. Agent-based modeling seems to be an unappreciated approach that is expected and has a potential for a much wider application than it actually has. The purpose of thiswork is to evaluate the reasons for such situation and to offer solutions. The following were identified among the reasons for a low utilization of the method: a wide gap between theory and practice in the field, doubtful reliability of the method, lowconfidence in its results, complexity, missing methodologies, problems with suitable development frameworks, limitations of computational performance, a lack of awareness among the public and certain other problems. Agentology; (i.e. a methodology for the development of agent-based models) was proposed in this thesis in order to address issues regarding the development of agent-based models. There are six defined roles of project participants in the methodology: expert, analyst, modeler, platform specialist, programmer and tester. The design and development process consists of four phases and nine steps beginning with task formulation, conceptual modeling, and platformspecific modeling to the development of the system. For the design phases, agent modeling language for agent-based models was derived.
506

Élaboration de particules de latex composites à base d'oxyde de cérium par polymérisation radicalaire en milieu aqueux dispersé / Synthesis of cerium oxide nanocomposite latexes through radical polymerization in aqueous dispersed media

Zgheib, Nancy 21 October 2011 (has links)
Nous décrivons dans ce travail l’élaboration de latex nanocomposites à base d’oxyde de cérium en vue d’applications dans le domaine des revêtements. Deux procédés originaux ont été développés afin de contrôler la morphologie des particules. Dans un premier temps, nous avons tiré parti de la forte densité de charges des nanoparticules d’oxyde de cérium pour stabiliser des particules de latex obtenues par polymérisation en émulsion ou en miniémulsion « de Pickering ». Dans les deux cas, la réaction est conduite en présence des particules inorganiques et d’un agent complexant à caractère acide, l’acide méthacrylique, en l’absence de tout tensioactif. Des particules de latex, décorées en surface par les nanoparticules d’oxyde de cérium ont été ainsi synthétisées. Par la suite, une stratégie qui consiste à utiliser des chaînes de polymères hydrophiles, réactivables (macro-agent RAFT) et préalablement adsorbées à la surface des nanoparticules d’oxyde de cérium a été envisagée. Ces chaînes polymères comportant à la fois des fonctions carboxyliques et un groupe trithiocarbonate terminal sont capables de stabiliser la suspension colloïdale des nanoparticules et de réamorcer la polymérisation en mode semi-continu permettant ainsi l’encapsulation de l’oxyde de cérium. Une optimisation visant à utiliser un procédé batch a également été évaluée. Quelle que soit la stratégie employée, une attention toute particulière a été portée à la stabilité colloïdale du milieu ainsi qu’à la cinétique de la réaction. La morphologie des particules composites a été caractérisée par MET et cryo-MET et reliée aux conditions de modification de surface et de polymérisation / This work describes the elaboration of nanocomposite latexes containing cerium dioxide nanoparticles for coating applications. Two original approaches have been developed to control the particle morphology. First, we took advantage of the high charge density of cerium dioxide nanoparticles to stabilize latex particles obtained via emulsion or “Pickering” miniemulsion polymerization. In both cases the reaction was conducted in the presence of the inorganic particles and methacrylic acid as a complexing agent, in the absence of any added surfactant. Armored latex particles covered with cerium dioxide nanoparticules were obtained by this method. Subsequently, another approach based on the use of living hydrophilic polymer chains (macroRAFT agents) previously adsorbed on the surface of the cerium dioxide nanoparticles was considered. These copolymers both containing carboxylic acid groups and carrying a thiocarbonylthio end group led to stable aqueous dispersion of the nanoparticles and could chain extend to form an encapsulating polymer shell under starved feed emulsion polymerization conditions. An optimization using a batch process was also evaluated. For both approaches, particular attention was paid to the colloidal stability of the medium and to the kinetics of the reaction. The morphology of the nanocomposite latex particles was characterized by TEM and cryo-TEM and correlated with the surface modification and the experimental conditions
507

Multi-Agent systems and organizations / Multi-Agent systems and organizations

Kúdela, Lukáš January 2012 (has links)
Multi-agent systems (MAS) are emerging as a promising paradigm for conceptualizing, designing and implementing large-scale heterogeneous software systems. The key advantage of looking at components in such systems as autonomous agents is that as agents they are capable of flexible self-organization, instead of being rigidly organized by the system's architect. However, self-organization is like evolution-it takes a lot of time and the results are not guaranteed. More often than not, the system's architect has an idea about how the agents should organize themselves-what types of organizations they should form. In our work, we tried to solve the problem of modelling organizations and their roles in a MAS, independent of the particular agent platform on which the MAS will eventually run. First and foremost, we have proposed a metamodel for expressing platform-independent organization models. Furthermore, we have implemented the proposed metamodel for the Jade agent platform as a module extending this framework. Finally, we have demonstrated the use of our module by modelling three specific organizations: remote function invocation, arithmetic expression evaluation and sealed-bid auction. Our work shows how to separate the behaviour acquired through a role from the behaviour intrinsic to an agent. This...
508

Multi-agent-based DDoS detection on big data systems

Osei, Solomon January 2018 (has links)
The Hadoop framework has become the most deployed platform for processing Big Data. Despite its advantages, Hadoop s infrastructure is still deployed within the secured network perimeter because the framework lacks adequate inherent security mechanisms against various security threats. However, this approach is not sufficient for providing adequate security layer against attacks such as Distributed Denial of Service. Furthermore, current work to secure Hadoop s infrastructure against DDoS attacks is unable to provide a distributed node-level detection mechanism. This thesis presents a software agent-based framework that allows distributed, real-time intelligent monitoring and detection of DDoS attack at Hadoop s node-level. The agent s cognitive system is ingrained with cumulative sum statistical technique to analyse network utilisation and average server load and detect attacks from these measurements. The framework is a multi-agent architecture with transducer agents that interface with each Hadoop node to provide real-time detection mechanism. Moreover, the agents contextualise their beliefs by training themselves with the contextual information of each node and monitor the activities of the node to differentiate between normal and anomalous behaviours. In the experiments, the framework was exposed to TCP SYN and UDP flooding attacks during a legitimate MapReduce job on the Hadoop testbed. The experimental results were evaluated regarding performance metrics such as false-positive ratio, false-negative ratio and response time to attack. The results show that UDP and TCP SYN flooding attacks can be detected and confirmed on multiple nodes in nineteen seconds with 5.56% false-positive ration, 7.70% false-negative ratio and 91.5% success rate of detection. The results represent an improvement compared to the state-of the-art.
509

A Coverage Metric to Aid in Testing Multi-Agent Systems

Linn, Jane Ostergar 01 December 2017 (has links)
Models are frequently used to represent complex systems in order to test the systems before they are deployed. Some of the most complicated models are those that represent multi-agent systems (MAS), where there are multiple decision makers. Brahms is an agent-oriented language that models MAS. Three major qualities affect the behavior of these MAS models: workframes that change the state of the system, communication activities that coordinate information between agents, and the schedule of workframes. The primary method to test these models that exists is repeated simulation. Simulation is useful insofar as interesting test cases are used that enable the simulation to explore different behaviors of the model, but simulation alone cannot be fully relied upon to adequately cover the test space, especially in the case of non-deterministic concurrent systems. It takes an exponential number of simulation trials to uncover schedules that reveal unexpected behaviors. This thesis defines a coverage metric to make simulation more meaningful before verification of the model. The coverage metric is divided into three different metrics: workframe coverage, communication coverage, and schedule coverage. Each coverage metric is defined through static analysis of the system, resulting in the coverage requirements of that system. These coverage requirements are compared to the logged output of the simulation run to calculate the coverage of the system. The use of the coverage metric is illustrated in several empirical studies and explored in a detailed case study of the SATS concept (Small Aircraft Transportation System). SATS outlines the procedures aircraft follow around runways that do not have communication towers. The coverage metric quantifies the test effort, and can be used as a basis for future automated test generation and active test.
510

Volontärsrekryteringen hos svenska idrottsevenemang : En studie kring hur svenska idrottsevenemang rekryterar volontärer

Antonsson, Lucas, Popperyd, Dennis January 2019 (has links)
Det här arbetet syftar till att ta reda på hur svenska idrottsevenemang går tillväga när de rekryterar sina volontärer. Volontärers betydelse på det svenska samhället är otroligt stor då de skapar oerhört viktiga ekonomiska förutsättningar för flera svenska idrottsföreningar. Att rekrytera volontärer är inte enkelt då volontärerna idag förväntar sig någon sorts belöning av sin insats. Spelar storleken hos ett evenemang någon roll gällande hur man rekryterar? För att komma fram till ett resultat i studien så har det använts kvalitativa metoder i form utav intervjuer med volontärsansvariga hos varje idrottsevenemang, för att djupare kunna förstå deras tankesätt och den rekryteringsprocess de använt sig utav. Det har använts en teori framställd av Bourdieu (1991) som handlar om hur volontärer reagerar gentemot sina roller i olika evenemang och vad de förväntar sig i utbyte mot sin arbetskraft. Resultatet på vår studie visade att det finns en skillnad gällande hur stora och små evenemang rekryterar. Generellt rekryterar de stora evenemangen volontärer ifrån idrottsföreningar medan de mindre evenemangen inte har samma förutsättningar så de behöver nå ut till olika volontärssegment i form utav pensionärer, studenter etc. Hur evenemangen rekryterar genom att motivera olika sorters människor är en viktig del av resultatet.

Page generated in 0.252 seconds