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1
Smiley, W. J. "Collision detection scheme for unmanned aircraft using passive Panospheric§T§M Imaging sensor". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0002/MQ44858.pdf.
2
Kubrak, Boris. "Direct numerical simulation of gas transfer at the air-water interface in a buoyant-convective flow environment". Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10196.
Abstract (sommario):
The gas transfer process across the air-water interface in a buoyant-convective environment has been investigated by Direct Numerical Simulation (DNS) to gain improved understanding of the mechanisms that control the process. The process is controlled by a combination of molecular diffusion and turbulent transport by natural convection. The convection when a water surface is cooled is combination of the Rayleigh-B´enard convection and the Rayleigh-Taylor instability. It is therefore necessary to accurately resolve the flow field as well as the molecular diffusion and the turbulent transport which contribute to the total flux. One of the challenges from a numerical point of view is to handle the very different levels of diffusion when solving the convection-diffusion equation. The temperature diffusion in water is relatively high whereas the molecular diffusion for most environmentally important gases is very low. This low molecular diffusion leads to steep gradients in the gas concentration, especially near the interface. Resolving the steep gradients is the limiting factor for an accurate resolution of the gas concentration field. Therefore a detailed study has been carried out to find the limits of an accurate resolution of the transport for a low diffusivity scalar. This problem of diffusive scalar transport was studied in numerous 1D, 2D and 3D numerical simulations. A fifth-order weighted non-oscillatory scheme (WENO) was deployed to solve the convection of the scalars, in this case gas concentration and temperature. The WENO-scheme was modified and tested in 1D scalar transport to work on non-uniform meshes. To solve the 2D and 3D velocity field the incompressible Navier-Stokes equations were solved on a staggered mesh. The convective terms were solved using a fourth-order accurate kinetic energy conserving discretization while the diffusive terms were solved using a fourth-order central method. The diffusive terms were discretized using a fourth-order central finite difference method for the second derivative. For the time-integration of the velocity field a second-order Adams-Bashworth method was employed. The Boussinesq approximation was employed to model the buoyancy due to temperature differences in the water. A linear relationship between temperature and density was assumed. A mesh sensitivity study found that the velocity field is fully resolved on a relatively coarse mesh as the level of turbulence is relatively low. However a finer mesh for the gas concentration field is required to fully capture the steep gradients that occur because of its low diffusivity. A combined dual meshing approach was used where the velocity field was solved on a coarser mesh and the scalar field (gas concentration and temperature) was solved on an overlaying finer submesh. The velocities were interpolated by a second-order method onto the finer sub-mesh. A mesh sensitivity study identified a minimum mesh size required for an accurate solution of the scalar field for a range of Schmidt numbers from Sc = 20 to Sc = 500. Initially the Rayleigh-B´enard convection leads to very fine plumes of cold liquid of high gas concentration that penetrate the deeper regions. High concentration areas remain in fine tubes that are fed from the surface. The temperature however diffuses much stronger and faster over time and the results show that temperature alone is not a good identifier for detailed high concentration areas when the gas transfer is investigated experimentally. For large timescales the temperature field becomes much more homogeneous whereas the concentration field stays more heterogeneous. However, the temperature can be used to estimate the overall transfer velocity KL. If the temperature behaves like a passive scalar a relation between Schmidt or Prandtl number and KL is evident. A qualitative comparison of the numerical results from this work to existing experiments was also carried out. Laser Induced Fluorescence (LIF) images of the oxygen concentration field and Schlieren photography has been compared to the results from the 3D simulations, which were found to be in good agreement. A detailed quantitative analysis of the process was carried out. A study of the horizontally averaged convective and diffusive mass flux enabled the calculation of transfer velocity KL at the interface. With KL known the renewal rate r for the so called surface renewal model could be determined. It was found that the renewal rates are higher than in experiments in a grid stirred tank. The horizontally averaged mean and fluctuating concentration profiles were analysed and from that the boundary layer thickness could be accurately monitored over time. A lot of this new DNS data obtained in this research might be inaccessible in experiments and reveal previously unknown details of the gas transfer at the air water interface.
3
Mojsejenko, Dimitri. "ESTIMATING PASSIVE MATERIAL PROPERTIES AND FIBER ORIENTATION IN A MYOCARDIAL INFARCTION THROUGH AN OPTIMIZATION SCHEME USING MRI AND FE SIMULATION". UKnowledge, 2014. http://uknowledge.uky.edu/me_etds/41.
Abstract (sommario):
Myocardial infarctions induce a maladaptive ventricular remodeling process that independently contributes to heart failure. In order to develop effective treatments, it is necessary to understand the way and extent to which the heart undergoes remodeling over the course of healing. There have been few studies to produce any data on the in-vivo material properties of infarcts, and much less on the properties over the time course of healing. In this paper, the in-vivo passive material properties of an infarcted porcine model were estimated through a combined use of magnetic resonance imaging, catheterization, finite element modeling, and a genetic algorithm optimization scheme. The collagen fiber orientation at the epicardial and endocardial surfaces of the infarct were included in the optimization. Data from porcine hearts (N=6) were taken at various time points after infarction, specifically 1 week, 4 weeks, and 8 weeks post-MI. The optimized results shared similarities with previous studies. In particular, the infarcted region was shown to dramatically increase in stiffness at 1 week post-MI. There was also evidence of a subsequent softening of the infarcted region at later time points post infarction. Fiber orientation results varied greatly but showed a shift toward a more circumferential orientation.
4
Mohamed, Jessica Rose. "The development of a kernel to detect Ziphius cavirostris vocalizations and a performance assessment of an automated passive acoustic detection scheme". Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Sept/08Sep%5FMohamed.pdf.
Abstract (sommario):
Thesis (M.S. in Meterology and Physical Oceanography)--Naval Postgraduate School, September 2008.Thesis Advisor(s): Chiu, Ching-Sang ; Miller, Christopher W. "September 2008." Description based on title screen as viewed on .November 4, 2008. Includes bibliographical references (p. 35-36). Also available in print.
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Akhavanfoomani, Aria. "Derivative-free stochastic optimization, online learning and fairness". Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAG001.
Abstract (sommario):
Dans cette thèse, nous étudions d'abord le problème de l'optimisation d'ordre zéro dans le cadre actif pour des fonctions lisses et trois classes différentes de fonctions : i) les fonctions qui satisfont la condition de Polyak-Łojasiewicz, ii) les fonctions fortement convexes, et iii) la classe plus large des fonctions non convexes fortement lisses.De plus, nous proposons un nouvel algorithme basé sur la randomisation de type l1, et nous étudions ses propriétés pour les fonctions convexes Lipschitz dans un cadre d'optimisation en ligne. Notre analyse est due à la dérivation d'une nouvelle inégalité de type Poincar'e pour la mesure uniforme sur la sphère l1 avec des constantes explicites.Ensuite, nous étudions le problème d'optimisation d'ordre zéro dans les schémas passifs. Nous proposons une nouvelle méthode pour estimer le minimiseur et la valeur minimale d'une fonction de régression lisse et fortement convexe f. Nous dérivons des limites supérieures pour cet algorithme et prouvons des limites inférieures minimax pour un tel cadre.Enfin, nous étudions le problème du bandit contextuel linéaire sous contraintes d'équité où un agent doit sélectionner un candidat dans un pool, et où chaque candidat appartient à un groupe sensible. Nous proposons une nouvelle notion d'équité qui est pratique dans l'exemple susmentionné. Nous concevons une politique avide qui calcule une estimation du rang relatif de chaque candidat en utilisant la fonction de distribution cumulative empirique, et nous prouvons sa propriété optimaleIn this thesis, we first study the problem of zero-order optimization in the active setting for smooth and three different classes of functions: i) the functions that satisfy the Polyak-Łojasiewicz condition, ii) strongly convex functions, and iii) the larger class of highly smooth non-convex functions.Furthermore, we propose a novel algorithm that is based on l1-type randomization, and we study its properties for Lipschitz convex functions in an online optimization setting. Our analysis is due to deriving a new Poincar'e type inequality for the uniform measure on the l1-sphere with explicit constants.Then, we study the zero-order optimization problem in the passive schemes. We propose a new method for estimating the minimizer and the minimum value of a smooth and strongly convex regression function f. We derive upper bounds for this algorithm and prove minimax lower bounds for such a setting.In the end, we study the linear contextual bandit problem under fairness constraints where an agent has to select one candidate from a pool, and each candidate belongs to a sensitive group. We propose a novel notion of fairness which is practical in the aforementioned example. We design a greedy policy that computes an estimate of the relative rank of each candidate using the empirical cumulative distribution function, and we proved its optimal property
6
Élise, Simon. "Développement d’indices écoacoustiques pour caractériser et suivre l’état et le fonctionnement des écosystèmes coralliens". Thesis, La Réunion, 2019. http://www.theses.fr/2019LARE0041.
Abstract (sommario):
Les récifs coralliens sont l’écosystème marin le plus complexe, mais aussi le plus menacé par les perturbations croissantes liées aux activités anthropiques. Leur conservation représente un véritable défi. Alors que le maintien des récifs au plus proche de leurs configurations et dynamiques actuelles doit être privilégié, nous devons également nous préparer à une évolution rapide de leur fonctionnement et adapter réseaux et outils de suivis à cette nouvelle situation. Des avancées technologiques récentes ont permis l’émergence d’outils innovants qui pourraient permettre à court terme d’augmenter considérablement la résolution spatio-temporelle des suivis. Parmi eux, l’acoustique passive est en plein essor. L’objet de cette thèse a été d’affiner son cadre d’utilisation pour évaluer et suivre l’état écologique et le fonctionnement des écosystèmes coralliens. Des enregistrements des paysages sonores et des relevés écologiques (assemblages de poissons et habitat) ont été réalisés sur 31 récifs de pente externe autour de trois îles de l’Indo-pacifique avec des caractéristiques environnementales variables, incluant des pressions anthropiques contrastées. L’analyse des résultats obtenus avec différentes combinaisons de paramètres d’échantillonnage (bande de fréquences, moment du cycle journalier choisi pour réaliser l’enregistrement, durée des échantillons de son) a permis de sélectionner un protocole d’échantillonnage basé sur les deux types d’indices écoacoustiques les plus utilisés pour l’étude des récifs coralliens. Ce protocole permet la caractérisation rapide et fiable de l’état écologique des récifs. En se basant sur ces lignes directrices, la capacité de six indices écoacoustiques à évaluer des fonctions clé de l’écosystème corallien a ensuite été démontrée. En comparant les apports de l’acoustique passive et de données environnementales pouvant être collectées par télédétection, la plus-value de l’utilisation d’indices écoacoustiques pour prédire la structure des assemblages de poissons récifaux a été identifiée et quantifiée. Une application de l’approche écoacoustique au suivi continu d’un site isolé a mis en évidence le potentiel particulièrement important de l’acoustique passive comme outil d’appui à la gestion dans ce type de contexte. Face à l’ampleur et à la vitesse des changements climatiques annoncés, les méthodes de suivi employées aujourd’hui, basées sur la présence d’observateur in situ, seront vraisemblablement insuffisantes. Combinée à d’autres outils de suivi, l’acoustique passive pourrait contribuer à détecter rapidement les perturbations des écosystèmes, condition indispensable pour en comprendre les causes et mettre en œuvre des réponses rapides et adaptéesCoral reefs are the most complex of marine ecosystems, but also the most threatened by ecological disruption resulting directly or indirectly from human activities. Their conservation represents a huge challenge. While maintaining coral reefs as close as possible to their current configurations and dynamics is among the highest priorities, we must also prepare for rapid changes in their functioning and adapt monitoring tools and networks to this new situation. Recent technological advances enabled the emergence of innovative tools with the potential to drastically increase the spatio-temporal resolution of coral reef monitoring. Among these, Passive Acoustic Monitoring (PAM) is on the rise. The aim of this thesis was to improve and facilitate the use of PAM as a tool for the assessment and monitoring of coral reefs’ ecological states and functioning. Soundscape recordings and ecological surveys (reef fish assemblages and habitat) were performed at 31 outer reef slope sites around three Indo-Pacific islands with variable environmental characteristics, including contrasted anthropogenic pressures. Analysing the results obtained with multiple combinations of sampling settings (frequency bandwidth, time of sampling (day/night), and sample duration) allowed the selection of a sampling scheme based on the two types of indices mostly used in coral reef studies. This scheme enables a rapid and reliable categorisation of reef’s ecological states. Based on these sampling guidelines, the capacity of six ecoacoustic indices to evaluate coral reef key functions was demonstrated. By comparing the contributions of PAM and coarse environmental data that could be sampled remotely, the added value of using ecoacoustic indices to predict reef fish assemblage structure was identified and quantified. An application of ecoacoustics to the continuous monitoring of a remote site highlighted the strong potential of PAM as a supporting tool for managers in such context. In view of the amplitude and velocity of expected climatic changes, current observer-based monitoring methods are likely to be exceeded. Combined to other monitoring tools, PAM could contribute to promptly detect ecosystem disturbances, which is essential to understand their causes and put in place rapid and adapted responses
7
Bousset, Marc. "Orientation d'un schema par passage d'un flot dans les angles". Paris, EHESS, 1993. http://www.theses.fr/1993EHES0028.
Abstract (sommario):
L'orientation bipolaire d'un graphe biconnexe est une orientation acyclique de ses aretes qui n'admet qu'une seule source et un seul puits. Nous etudions deux algorithmes d'orientation bipolaire d'un graphe plan biconnexe, avec prise en compte dans ces algorithmes de contraintes de laterialite. Notre approche de l'orientation bipolaire d'un graphe plan repose sur la theorie du marquage en deux couleurs des angles introduite par p. Rosenstiehl. Nous proposons une nouvelle propriete geometrique des angles d'un graphe plan et une methode graphique pour la torsion d'une partie de la figure par le moyen d'une courbe fremee du plan traversant les angles de couleurs alternees. Les invariants locaux sur les couleurs permettent la recherche d'une orientation bipolaire par la programmation lineaire. Nous mettons en oeuvre un algorithme de flots en 0(n sqrt(n)) a travers les angles, generant une orientation bipolaire sous contraintes si elle existe et, dans le cas contraire, permettant de determiner les incompatibilites et de modifier dynamiquement le graphe pour les resoudre. Il s'ensuit une solution topologique au probleme de la representation graphique de certains circuits electriques. Les algorithme de faible complexite mis en oeuvre autorisent le traitement de grands reseaux industriels dans des temps negligeables par rapport au temps d'affichage a l'ecranThe bipolar orientation of a 2-connected graph is an acyclic orientation of its edges, with only one source and only one sink. We studytwo algorithms for the bipolar orientation of a plane 2-connected graph, which take laterality constraints into account. Our approach of the bipolar orientation of a plane graph is based on the theory of the 2-colour marking of the angles introduced by p. Rosenstiehl. We give a new geometric property of the angles of a plane graph and a graphic method for twisting a part of a diagram by means of a closed curve of the plane traversing angles coloured alternately. The local invariants on the colours allow us to compute a bipolar orientation by linear programming. We use an 0(n sqrt(n)) flow algorithm through the angles, which generates a bipolar orientation under contraints if one exists and, otherwise, enables us to determine incompatibilities and to dynamically modify the graph to solve them. There follows a topological solution to the problem of the graphic representation of some electrical circuits. The low-comolexity algorithms allow the processing of large industrial networks within short times
8
Liette, Jared V. "New paradigms to control coupled powertrain and frame motions using concurrent passive and active mounting schemes". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1401134376.
9
Dourado, Diego Marques. "Estratégias para aumento da eficiência espectral e energética em redes TWDM-PON". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18155/tde-11092017-113611/.
Abstract (sommario):
O problema estudado relaciona-se ao planejamento de redes ópticas de acesso TWDM (Time and Wavelength Division Multiplexing), tendo como meta prover meios para atender ao consumo crescente de banda e, ao mesmo tempo, associar o mesmo ao menor consumo de energia possível e disponibilizar serviços de qualidade aos usuários da rede. Neste contexto, após a apresentação de uma revisão bibliográfica, alguns trabalhos foram selecionados como referências base para o estudo. Neste, foram analisadas técnicas de gerenciamento do comprimento de onda numa possível migração tecnológica dos equipamentos de acesso à rede pelo lado do usuário, as unidades de rede óptica (ONUs), considerando ser possível aproveitar de forma eficiente a distribuição de ONUs em cada par de comprimentos de onda, e como resultado, desligar interfaces de gerenciamento para economia de energia. Em paralelo a este objetivo, foram agregados métodos de \"registro adaptativo\" para melhorar o desempenho das ONUs que estão migrando e/ou entrando na rede, evitando colisões entre seus sinais e aumentando as chances de registro no terminal de linha óptico (OLT). Além do mais, o trabalho aborda o cumprimento do contrato de serviços (SLA) por parte das operadoras de telecomunicações, bem como oferece meios de estruturar uma rede óptica passiva (PON) para oferecer serviços com garantia de métricas de qualidade (QoS). Diferentes cenários foram tratados ao variar a porcentagem de usuários ativos na rede, e percebeu-se que, quando a PON opera com baixo índice de atividade (média 10% de ONUs ativas), foi possível economizar mais de 80% de energia em interfaces de gerenciamento. Por outro lado, ao envolver cenários mais realistas em redes ópticas (média de 50% de ONUs ativas), o TWDM-PON economizou quase 50% de energia nestas interfaces ao ser configurado com baixo período de migração (5 minutos). Além disso, alcançou um SLA de aproximadamente 100%, um valor considerado acima do usual quando se trata de cumprimento de serviços. Como uma tecnologia emergente, o TWDM-PON destaca-se num cenário que deve ser planejado para ser compatível com tecnologias implantadas, e além de disso, superar o legado de redes PON na economia de energia e qualidade de serviços oferecidos.The problem studied is related to the planning of optical access networks TWDM (Time and Wavelength Division Multiplexing), aiming to provide means to meet the increasing bandwidth consumption and, at the same time, associating it to the lowest possible power consumption and providing quality services to the network users. In this context, following the presentation of a literature review, some studies were selected as a reference basis for the study. In this, some wavelength management techniques were analyzed aiming a possible technological migration of the network access equipment at the user side, the optical network units (ONU), whereas it is possible to use efficiently the ONUs distribution in each pair of wavelength. As a result, it becomes possible to switch off some management interfaces thus assuring a degree of power consumption save. In parallel, methods for providing an \"adaptive record\" of ONUs have been aggregated to improve the performance of those ONUs that are migrating and/or entering the network, avoiding collisions between their signals and increasing the chance of their registration in the optical line terminal (OLT). Furthermore, this work deals with the fulfillment of the service agreement (SLA) signed by telecommunications operators and proposes ways to design a passive optical network (PON) in order to offer services with quality metrics assurance (QoS). Different scenarios were treated to vary the percentage of active users on the network, and it was noticed that when the PON operates with low rate of activity (average 10% of active ONUs), it was possible to save over 80% energy in the management interfaces. Moreover, by involving more realistic scenarios in optical networks (50%, in average, of active ONUs), the TWDM-PON saved almost 50% of energy at the interfaces to be configured with low migration period (5 minutes). Additionally, it reached an SLA of approximately 100%, a value considered above the usual when it comes to compliance services. As an emerging technology, TWDM-PON stands out in a scenario that should be designed to be compatible with deployed technologies, and beyond that, to overcome the legacy of PON networks in energy saving and quality of services offered.
10
Ngo, Long. "Computationally sound automated proofs of cryptographic schemes". Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/54668/1/Long_Ngo__Thesis.pdf.
Abstract (sommario):
Proving security of cryptographic schemes, which normally are short algorithms, has been known to be time-consuming and easy to get wrong. Using computers to analyse their security can help to solve the problem. This thesis focuses on methods of using computers to verify security of such schemes in cryptographic models.
The contributions of this thesis to automated security proofs of cryptographic schemes can be divided into two groups: indirect and direct techniques. Regarding indirect ones, we propose a technique to verify the security of public-key-based key exchange protocols. Security of such protocols has been able to be proved automatically using an existing tool, but in a noncryptographic model. We show that under some conditions, security in that non-cryptographic model implies security in a common cryptographic one, the Bellare-Rogaway model [11]. The implication enables one to use that existing tool, which was designed to work with a different type of model, in order to achieve security proofs of public-key-based key exchange protocols in a cryptographic model.
For direct techniques, we have two contributions. The first is a tool to verify Diffie-Hellmanbased key exchange protocols. In that work, we design a simple programming language for specifying Diffie-Hellman-based key exchange algorithms. The language has a semantics based on a cryptographic model, the Bellare-Rogaway model [11]. From the semantics, we build a Hoare-style logic which allows us to reason about the security of a key exchange algorithm, specified as a pair of initiator and responder programs.
The other contribution to the direct technique line is on automated proofs for computational indistinguishability. Unlike the two other contributions, this one does not treat a fixed class of protocols. We construct a generic formalism which allows one to model the security problem of a variety of classes of cryptographic schemes as the indistinguishability between two pieces of information. We also design and implement an algorithm for solving indistinguishability problems. Compared to the two other works, this one covers significantly more types of schemes, but consequently, it can verify only weaker forms of security.
11
Bielefeld, Kris [Verfasser], e Rolf [Akademischer Betreuer] Mülhaupt. "Thermoresponsive Kern-Schale-Hydrogelpartikel für den Einsatz in der passiven Gebäudekühlung und der atmosphärischen Wassergewinnung". Freiburg : Universität, 2020. http://d-nb.info/1222436310/34.
12
Serlenga, Lorenzo. "Effects of transfers on liabilities of pension schemes". Master's thesis, Instituto Superior de Economia e Gestão, 2020. http://hdl.handle.net/10400.5/20994.
Abstract (sommario):
Mestrado em Actuarial ScienceNos últimos anos, as regras de adesão aos planos de pensões no Reino Unido tornaram-se mais flexíveis e a maioria dos membros passou a ter a possibilidade de mudar de um plano para outro, de acordo com as suas necessidades pessoais e financeiras. Isto significa que um dado membro, se assim o desejar, pode transferir o valor acumulado das contribuições feitas em seu favor para um outro fundo. A opção de transferir é justificada sobretudo pelo facto de os planos CD serem mais flexíveis na forma como os benefícios são recebidos e, às vezes, permitirem um maior controlo do membro sobre a forma como o dinheiro é investido - As transferências são um procedimento complexo do ponto de vista atuarial: os administradores precisam de calcular o montante que deve ser entregue ao membro que sai, uma tarefa realizada com a assistência do atuário do plano, que tem que definir os pressupostos económicos e demográficos necessários para o cálculo. Este trabalho resulta de um estágio no Lisbon Service Centre da Willis Tower Watson, onde estive envolvido no processo de avaliação de fundos de pensões do Reino Unido, com o objetivo de projetar as responsabilidades futuras dos planos. A legislação impõe que as empresas do Reino Unido realizem avaliações, pelo menos, a cada três anos, dada a importância, tanto para os membros como para as empresas, de conhecer o respetivo nível de financiamento e a situação financeira, em geral.
In the last years the regulations for pension plans membership became more flexible and most members have now the possibility to move from a scheme to another, according to their personal and financial needs. This means members are able to move their accumulated pots through a transfer, and this usually happens from a Defined Benefit (DB) to a Defined Contribution (DC) scheme. The option to transfer is justified because DC schemes are characterized by more freedom regarding the way benefits are collected and sometimes more control on the way the money is invested - although the member will take on the investment risk, the longevity risk and the income management risk. Transfers are a complex procedure from the actuarial point of view: trustees need to calculate the lump sum to be provided to the member leaving the scheme, a task performed with the assistance of actuaries, who are asked to set the economic and demographic assumptions required for the calculation. This work is a result of an internship at the Lisbon Service Center of Willis Tower Watson, where I have been involved in the UK pension fund valuation process, with the objective of projecting the future liability of schemes. Legislation imposes that UK firms must perform valuations of the schemes at least every three years, given the importance, both for members and clients, of knowing their funding position and financial situation.
info:eu-repo/semantics/publishedVersion
13
Dressel, Kai Ingo [Verfasser], Magdalena [Akademischer Betreuer] Scheck-Wenderoth e Peter A. [Akademischer Betreuer] Kukla. "Subsidence evolution of the conjugate passive continental margins of southwestern Africa and eastern Argentina / Kai Ingo Dressel ; Magdalena Scheck-Wenderoth, Peter A. Kukla". Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/113307894X/34.
14
Raabe, Armin, e Nicole Mölders. "Evaluation of cloudiness and snowfall simulated by a semi-spectral and a bulk-parameterization scheme of cloud microphysics for the passage of a Baltic heat cyclone". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213950.
Abstract (sommario):
The differences in the concepts of two different parameterizations of cloud microphysics are analyzed. Simulations alternatively applying these parameterizations are performed for a Baltic heat cyclone event. The results of the simulations are compared to each other as well as to observed distributions of cloudiness and snowfall. The main differences between the simulated distributions result from the assumptions on ice, the ice classes, and size distributions of the cloud and precipitating particles. Both schemes succeeded in predicting the position and the main structure of the main cloud and snowfall fields. Nevertheless, the more convective type parameterization overestimates, while the other one underestimates snowfallDie Unterschiede in den Konzepten zweier unterschiedlicher Parametrisierungen der Wolkenmikrophysik werden analysiert. Die Ergebnisse der Simulationen werden miteinander und mit den beobachteten Wolken- und Schneeverteilungen für eine Baltische Wärmezyklone verglichen. Die wesentlichen Unterschiede in den berechneten Verteilungen resultieren aus den verschiedenen Annahmen über Wolkeneis, die Eisklassen und die Größenverteilungen der Wolken- und Niederschlagspartikel. Beide Schemata sagen die Position und die wesentlichen Strukturen der Wolken- und Schneeverteilungen erfolgreich vorher. Dennoch überschätzt das eher konvektive Schema den Schneefall, während das andere ihn unterschätzt
15
Raabe, Armin, e Nicole Mölders. "Evaluation of cloudiness and snowfall simulated by a semi-spectral and a bulk-parameterization scheme of cloud microphysics for the passage of a Baltic heat cyclone". Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 12 = Meteorologische Arbeiten aus Leipzig ; 4 (1999), S. 59-70, 1999. https://ul.qucosa.de/id/qucosa%3A15107.
Abstract (sommario):
The differences in the concepts of two different parameterizations of cloud microphysics are analyzed. Simulations alternatively applying these parameterizations are performed for a Baltic heat cyclone event. The results of the simulations are compared to each other as well as to observed distributions of cloudiness and snowfall. The main differences between the simulated distributions result from the assumptions on ice, the ice classes, and size distributions of the cloud and precipitating particles. Both schemes succeeded in predicting the position and the main structure of the main cloud and snowfall fields. Nevertheless, the more convective type parameterization overestimates, while the other one underestimates snowfall.Die Unterschiede in den Konzepten zweier unterschiedlicher Parametrisierungen der Wolkenmikrophysik werden analysiert. Die Ergebnisse der Simulationen werden miteinander und mit den beobachteten Wolken- und Schneeverteilungen für eine Baltische Wärmezyklone verglichen. Die wesentlichen Unterschiede in den berechneten Verteilungen resultieren aus den verschiedenen Annahmen über Wolkeneis, die Eisklassen und die Größenverteilungen der Wolken- und Niederschlagspartikel. Beide Schemata sagen die Position und die wesentlichen Strukturen der Wolken- und Schneeverteilungen erfolgreich vorher. Dennoch überschätzt das eher konvektive Schema den Schneefall, während das andere ihn unterschätzt.
16
Faleh, Alaeddine. "Allocation stratégique d’actifs et ALM pour les régimes de retraites". Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10084.
Abstract (sommario):
La présente thèse s’intéresse aux modèles d’allocation stratégiques d’actifs et à leurs applications pour la gestion des réserves financières des régimes de retraite par répartition, en particulier ceux partiellement provisionnés. L’étude de l’utilité des réserves pour un système par répartition et a fortiori de leur gestion reste un sujet peu exploré. Les hypothèses classiques sont parfois jugées trop restrictives pour décrire l'évolution complexe des réserves. De nouveaux modèles et de nouveaux résultats sont développés à trois niveaux : la génération de scénarios économiques (GSE), les techniques d’optimisation numérique et le choix de l’allocation stratégique optimale dans un contexte de gestion actif-passif (ALM). Dans le cadre de la génération de scénarios économiques et financiers, certains indicateurs de mesure de performance du GSE ont été étudiés. Par ailleurs, des améliorations par rapport à ce qui se pratique usuellement lors de la construction du GSE ont été apportées, notamment au niveau du choix de la matrice de corrélation entre les variables modélisées. Concernant le calibrage du GSE, un ensemble d’outils permettant l’estimation de ses différents paramètres a été présenté. Cette thèse a également accordé une attention particulière aux techniques numériques de recherche de l'optimum, qui demeurent des questions essentielles pour la mise en place d'un modèle d'allocation. Une réflexion sur un algorithme d’optimisation globale d’une fonction non convexe et bruitée a été développée. L’algorithme permet de moduler facilement, au moyen de deux paramètres, la réitération de tirages dans un voisinage des points solutions découverts, ou à l’inverse l’exploration de la fonction dans des zones encore peu explorées. Nous présentons ensuite des techniques novatrices d'ALM basées sur la programmation stochastique. Leur application a été développée pour le choix de l’allocation stratégique d’actifs des régimes de retraite par répartition partiellement provisionnés. Une nouvelle méthodologie pour la génération de l’arbre des scénarios a été adoptée à ce niveau. Enfin, une étude comparative du modèle d’ALM développé avec celui basé sur la stratégie Fixed-Mix a été effectuée. Différents tests de sensibilité ont été par ailleurs mis en place pour mesurer l’impact du changement de certaines variables clés d’entrée sur les résultats produits par notre modèle d’ALMThis thesis focuses on the strategic asset allocation models and on their application for the financial reserve management of a pay-as-you-go (PAYG) retirement schemes, especially those with partial provision. The study of the reserve utility for a PAYG system and of their management still leaves a lot to be explored. Classical hypothesis are usually considered too restrictive for the description of the complex reserve evolution. New models and new results have been developed over three levels : economic scenario generation (ESG), numerical optimization techniques and the choice of optimal strategic asset allocation in the case of an Asset-Liability Management (ALM). For the generation of financial and economic scenarios, some ESG performance indicators have been studied. Also, we detailed and proposed to improve ESG construction, notably the choice of the correlation matrix between modelled variables. Then, a set of tools were presented so that we could estimate ESG parameters variety. This thesis has also paid particular attention to numerical techniques of optimum research, which is an important step for the asset allocation implementation. We developed a reflexion about a global optimisation algorithm of a non convex and a noisy function. The algorithm allows for simple modulating, through two parameters, the reiteration of evaluations at an observed point or the exploration of the noisy function at a new unobserved point. Then, we presented new ALM techniques based on stochastic programming. An application to the strategic asset allocation of a retirement scheme with partial provision is developed. A specific methodology for the scenario tree generation was proposed at this level. Finally, a comparative study between proposed ALM model and Fixed-Mix strategy based model was achieved. We also made a variety of a sensitivity tests to detect the impact of the input values changes on the output results, provided by our ALM model
17
Carvalho, Tiago Lima de. "Asset-liability management in pension funds". Master's thesis, Instituto Superior de Economia e Gestão, 2020. http://hdl.handle.net/10400.5/21054.
Abstract (sommario):
Mestrado em Mathematical FinanceOs fundos de pensão têm uma participação representativa nos mercados financeiros, seja considerando o capital investido ou o perfil de escolha de ativos. Nos planos de pensão de benefício definido, o foco é assegurar cobrir os passivos com os ativos existentes. A gestão de ativos e passivos (em inglês ALM) é o conjunto de métodos e ferramentas projetadas com a finalidade de orientar como os fundos devem investir seus ativos a fim de que, em determinada data, seja possível pagar seus passivos. Este conceito é amplamente utilizado em empresas seguradoras e fundos de pensão. O portfolio de investimentos é construído de acordo com análises de mercado, definição dos riscos em que o fundo deseja se expor e os objetivos de retorno. O propósito deste projeto é, aplicando a teoria de investimentos orientados a passivos, recuperar o nível de financiamento de um fundo de pensões, a fim de cumprir com as metas do esquema e se expondo ao menor risco possível. Este projeto terá como informação base a estimativa dos passivos, da taxa de juros e da inflação. A partir deles, contruiremos o portfolio de investimentos, projetaremos o fluxo de caixa e monitoraremos o risco de não cumprimento dos objetivos. Para validar a consistência do modelo, iremos comparar contra uma estratégia mais arriscada. As conclusões, após contextualização (prática e teórica), demonstram que é possível recuperar o nível de financiamento, de acordo com prazos estabelecidos e com um nível moderado de risco.
Pension funds have a very representative role in the financial markets, considering investments made and the asset allocations profile. In defined benefit pension schemes, the major focus is to secure the participants future payments with the accumulated contributions. Or, in other words, to cover the liabilities with the assets. Asset Liability Management (ALM) is a collection of methodologies and tools structured to guide the assets investments in order to protect the liabilities. This concept has been used largely in insurance companies and pension funds. It analyzes market expectations, scheme risks and objectives, in order to create the best asset investment option. The purpose of this project is, using a Liability Driven Investment (LDI) technique, recover the Funding Ratio of a pension fund, achieve the scheme goals and minimize the risk. Project liabilities, interest rate and inflation are the bases of this work. Build the asset portfolio, project the fund cashflow and track the risk are the principal steps to achieve the goal. To check the results adherence, the output will be compared with a bold recovery strategy. To conclude, after setting the context (theoretical and practical perspectives), the work will show how to recover a Funding Ratio using a developed model and keeping the risk inside pension plan limits.
info:eu-repo/semantics/publishedVersion
18
Jobic, Yann. "Numerical approach by kinetic methods of transport phenomena in heterogeneous media". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4723/document.
Abstract (sommario):
Les phénomènes de transport en milieux poreux sont étudiés depuis près de deux siècles, cependant les travaux concernant les milieux fortement poreux sont encore relativement peu nombreux. Les modèles couramment utilisés pour les poreux classiques (lits de grains par exemple) sont peu applicables pour les milieux fortement poreux (les mousses par exemple), un certain nombre d’études ont été entreprises pour combler ce manque. Néanmoins, les résultats expérimentaux et numériques caractérisant les pertes de charge dans les mousses sont fortement dispersés. Du fait des progrès de l’imagerie 3D, une tendance émergente est la détermination des paramètres des lois d’écoulement à partir de simulations directes sur des géométries reconstruites. Nous présentons ici l’utilisation d’une nouvelle approche cinétique pour résoudre localement les équations de Navier-Stokes et déterminer les propriétés d’écoulement (perméabilité, dispersion, ...)A novel kinetic scheme satisfying an entropy condition is developed, tested and implemented for the simulation of practical problems. The construction of this new entropic scheme is presented. A classical hyperbolic system is approximated by a discrete velocity vector kinetic scheme (with the simplified BGK collisional operator), but applied to an inviscid compressible gas dynamics system with a small Mach number parameter, according to the approach of Carfora and Natalini (2008). The numerical viscosity is controlled, and tends to the physical viscosity of the Navier-Stokes system. The proposed numerical scheme is analyzed and formulated as an explicit finite volume flux vector splitting (FVS) scheme that is very easy to implement. It is close in spirit to Lattice Boltzmann schemes, but it has the advantage to satisfy a discrete entropy inequality under a CFL condition and a subcharacteristic stability condition involving a cell Reynolds number. The new scheme is proved to be second-order accurate in space. We show the efficiency of the method in terms of accuracy and robustness on a variety of classical benchmark tests. Some physical problems have been studied in order to show the usefulness of both schemes. The LB code was successfully used to determine the longitudinal dispersion of metallic foams, with the use of a novel indicator. The entropic code was used to determine the permeability tensor of various porous media, from the Fontainebleau sandstone (low porosity) to a redwood tree sample (high porosity). These results are pretty accurate. Finally, the entropic framework is applied to the advection-diffusion equation as a passive scalar
19
N'guessan, Marc-Arthur. "Space adaptive methods with error control based on adaptive multiresolution for the simulation of low-Mach reactive flows". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASC017.
Abstract (sommario):
Ce travail vise au développement de nouvelles méthodes numériques adaptatives pour la simulation numérique de phénomènes physiques multi-échelles en temps et en espace. Nous nous concentrons sur les écoulements réactifs à faible nombre de Mach, caractéristiques d'un grand nombre de configurations industrielles telles que la convection naturelle, la dynamique de fronts de flamme ou encore les décharges plasmas. La raideur associée à ce type de problèmes, que ce soit via le terme source chimique qui présente un large spectre d'échelles de temps caractéristiques ou encore via la présence de forts gradients très localisés associés aux fronts de réaction, génère des difficultés numériques considérables. Il est donc nécessaire de concevoir des méthodes sur mesure pour traiter la raideur de telles applications, afin d'obtenir des résultats d'une grande précision avec un coût calcul raisonnable. Dans ce cadre général, nous introduisons de nouvelles méthodes numériques pour la résolution des équations de Navier-Stokes incompressibles, une étape importante dans la réalisation d'un solveur hydrodynamique pour les écoulements à faible nombre de Mach. Nous construisons un solveur volumes finis avec adaptation de maillage par l'analyse de multirésolution, qui permet un contrôle a priori des erreurs générées par l'adaptation de maillage. Pour ce faire, nous développons un nouveau schéma de volumes finis collocalisé, avec un traitement original des modes de pression et de vitesse parasites qui n'affecte pas la précision de la discrétisation spatiale. Cette dernière est couplée à un nouveau schéma de Runge-Kutta additif d'ordre 3 pour les écoulements incompressibles, qui présente des propriétés de stabilité adaptées à la raideur des équations différentielles algébriques semi-explicites d'index 2. L'ensemble de cette stratégie est implémentée dans le code de calcul scientifique mrpy. Ce dernier est écrit en Python, et repose sur la librairie PETSc, écrite en C, pour le traitement des opérations d'algèbre linéaire. Nous évaluons l'efficacité algorithmique de cette stratégie par la simulation numérique d'un transport de scalaire passif dans un écoulement incompressible sur maillage adaptatif. Ce travail présente donc un nouveau solveur hydrodynamique d'ordre élevé pour les écoulements incompressibles, avec adaptation de maillage par multirésolution et contrôle d'erreur, qui peut être étendu aux écoulements à faible nombre de MachWe address the development of new numerical methods for the efficient resolution of stiff Partial Differential Equations modelling multi-scale time/space physical phenomena. We are more specifically interested in low Mach reacting flow processes, that cover various real-world applications such as flame dynamics at low gas velocity, buoyant jet flows or plasma/flow interactions. It is well-known that the numerical simulation of these problems is a highly difficult task, due to the large spectrum of spatial and time scales caused by the presence of nonlinear The adaptive spatial discretization is coupled to a new 3rd-order additive Runge-Kutta method for the incompressible Navier-Stokes equations, combining a 3rd-order, A-stable, stiffly accurate, 4-stage ESDIRK method for the algebraic linear part of these equations, and a 4th-order explicit Runge-Kutta scheme for the nonlinear convective part. This numerical strategy is implemented from scratch in the in-house numerical code mrpy. This software is written in Python, and relies on the PETSc library, written in C, for linear algebra operations. We assess the capabilities of this mechanisms taking place into dynamic fronts. In this general context, this work introduces dedicated numerical tools for the resolution of the incompressible Navier-Stokes equations, an important first step when designing an hydrodynamic solver for low Mach flows. We build a space adaptive numerical scheme to solve incompressible flows in a finite-volume context, that relies on multiresolution analysis with error control. To this end, we introduce a new collocated finite-volume method on adaptive rectangular grids, with an original treatment of the spurious pressure and velocity modes that does not alter the precision of the discretization technique. new hydrodynamic solver in terms of speed and efficiency, in the context of scalar transport on adaptive grids. Hence, this study presents a new high-order hydrodynamics solver for incompressible flows, with grid adaptation by multiresolution, that can be extended to the more general low-Mach flow configuration
20
Chen, Shih-Yu, e 陳世又. "Low Power Driving Scheme for Passive Matrix-OLED". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/70083969293937549953.
Abstract (sommario):
碩士國立臺灣大學
電子工程學研究所
91
Abstract Small size passive matrix organic light emitting display (PM-OLED) has the advantages of simple manufacture process and low total cost. Base on the PMOLED characteristics, a low power consumption column driver and row driver was developed for color PMOLED. We provide two methods for reducing the power consumption of driving system: low total current 16-gray scale pulse width modulation (PWM) output driving current control circuit, and a energy recovery design for precharge circuit.
21
"A multicast overlay scheme for wavelength division multiplexed passive optical networks". 2009. http://library.cuhk.edu.hk/record=b5893893.
Abstract (sommario):
Zhang, Yin.Thesis submitted in: December 2008.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (leaves 56-60).
Abstracts in English and Chinese.
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Telecommunications network hierarchy --- p.2
Chapter 1.2 --- PON architectures for access networks --- p.4
Chapter 1.2.1 --- TDM-PON --- p.5
Chapter 1.2.2 --- WDM-PON --- p.7
Chapter 1.3 --- Data delivery mode in WDM-PON --- p.8
Chapter 1.3.1 --- Point-to-point --- p.8
Chapter 1.3.2 --- Broadcast --- p.9
Chapter 1.3.3 --- Multicast --- p.10
Chapter 1.4 --- Motivation of this thesis --- p.10
Chapter 1.5 --- Outline of this thesis --- p.13
Chapter Chapter 2 --- Previous Multicast Architectures in WDM-PON --- p.14
Chapter 2.1 --- Introduction --- p.15
Chapter 2.2 --- Previous WDM-PON architectures with multicast capability --- p.15
Chapter 2.2.1 --- Subcarrier multiplexing --- p.16
Chapter 2.2.2 --- All-optical based multicast enabled architecture --- p.18
Chapter 2.3 --- Summary --- p.21
Chapter Chapter 3 --- A Multicast enabled WDM-PON Architecture Using ASK-DPSK Orthogonal Modulation --- p.23
Chapter 3.1 --- Introduction --- p.24
Chapter 3.2 --- System architecture --- p.25
Chapter 3.3 --- Experimental Demonstration --- p.27
Chapter 3.4 --- Discussion --- p.31
Chapter 3.5 --- Summary --- p.36
Chapter Chapter 4 --- A WG filtering and its suppression in quaternary ASK-DPSK based multicast enabled WDM-PON --- p.37
Chapter 4.1 --- Introduction --- p.38
Chapter 4.2 --- Principle of narrowband filtering --- p.38
Chapter 4.3 --- Simulation model --- p.40
Chapter 4.4 --- Simulation results and discussion --- p.42
Chapter 4.4.1 --- Different extinction ratios --- p.43
Chapter 4.4.2 --- Different AWG filter shape and bandwidth --- p.47
Chapter 4.5 --- Summary --- p.50
Chapter Chapter 5 --- Summary and Future Works --- p.51
Chapter 5.1 --- Summary of the thesis --- p.52
Chapter 5.2 --- Future works --- p.53
List of Publications --- p.55
BIBLIOGRAPHY --- p.56
22
Shieh, Bing-shun, e 謝炳順. "Dynamic Wavelength Allocation Scheme for Applications of Ethernet Passive Optical Networks". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/x8sewd.
Abstract (sommario):
碩士國立中央大學
光電科學研究所碩士在職專班
96
This work proposes the dynamic wavelength allocation mechanism to solve the problem of sudden traffic loading for the Ethernet passive optical networks(PON). Ethernet PON has recently been considered as the most prospective application technology in access network. It is adopted the point-to-multi-point(P2MP) topology construction,Which can greatly reduce the amount of optical fiber and the disbursement. Moreover the DWA mechanism provides the bandwidth sharing across multiple physical PONs. A flexible new optical access solution is reached by combing the tunable lasers, the arrayed waveguide gratings, and the coarse/fine filters. The excellent stability of the network can bridge the gap between conventional TDM PONs and WDM PONs, and the powerful architecture is a promising candidate of the optical access networks for the next generation. This structure is composed of the single mode laser, the tunable laser, the array waveguide, and the buffer storage device. The probability model distribution is calculated by the MATLAB, and the mechanism of optimal separation is determined by the computer simulation. This system is tested through the measured reaction time or the flow capacity of network on campus network when the traffic load increases up to a loading level. It is shown that the DWA system, can effectively solve the problems when the load increases, Which is the most economical and simplest local network infrastructure for the PONs.
23
Chuen-Yi, Lin. "A New Credit-Based Dynamic Bandwidth Allocation Scheme for Ethernet Passive Optical Networks". 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0005-2906200613082300.
24
Lin, Chuen-Yi, e 林純儀. "A New Credit-Based Dynamic Bandwidth Allocation Scheme for Ethernet Passive Optical Networks". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/39581720346483782506.
Abstract (sommario):
碩士中興大學
資訊科學系所
94
Ethernet Passive Optical Network (EPON) has been considered as a promising solution for next-generation broadband access networks due to its low cost, simplicity, and scalability. A critical issue of EPONs is bandwidth allocation of the shared upstream channel between end users. Some bandwidth allocation schemes based on interleaved polling have been proposed. However, none of them outperforms the others under all traffic loads. The credit-based scheme has an edge over the others in the case of light load, while the limited scheme prevails in the case of heavy load. We propose a new credit-based bandwidth allocation scheme that performs well under all traffic loads. In the proposed scheme, the size of the credit is dynamically determined by the OLT (Optical Line Terminal) according to each ONU''s (Optical Network Unit''s) traffic situation and the entire system load. Besides, the OLT has a maximum transmission window size limit for each ONU. Every ONU can transmit data up to the maximum window size per cycle. Simulation results verify that our proposed scheme has impressive performance under all traffic loads.
25
Lee, Li-an, e 李禮安. "Protecting User Privacy with Dynamic Identity-Based Scheme for Low-cost Passive RFID Tags". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/64576290045410787799.
Abstract (sommario):
碩士國立交通大學
資訊科學與工程研究所
94
Radio Frequency Identification (RFID) is said to be the next generation bar code, which features contactless identification without visibility. We benefit greatly by adopting RFID in a variety of daily applications such as warehouse management, toll collection, library management, etc. However, RFID transmits data through radio frequency signals; therefore, attackers could analyze the radio frequency signals to acquire private data from users. If user privacy is not protected, users will be susceptible to personal identification and tracking by an adversary. User privacy may include data privacy and location privacy. To protect both of them, the output of tags must be encrypted and unpredictable. Furthermore, the acceptable cost of a passive RFID tag, which is no more than five cents, severely restricts the resources available for security. Schemes that protect user privacy in RFID applications are classified into three main categories: authentication, encryption, and dynamic identity. However, authentication-based schemes are easily broken. Because low-cost RFID tags do not contain tamper-resistant mechanisms, an adversary can steal the key for the authentication protocol. Encryption-based schemes can protect data privacy, but location privacy is still vulnerable since the ciphertext remains the same. Dynamic identity schemes are limited by exhaustive search problem, and the tag is still traceable in the period between identity updates. In this thesis, we proposed a feasible scheme based on one-way hash function for low-cost passive RFID tags. Each tag has a dynamic identity. Therefore the output of tag changes each time. We also proved that the scheme can protect both data privacy and location privacy against threats of replay attacks, eavesdropping, spoofing, man-in-the-middle attack, and message loss.
26
"A remodulation scheme for wavelength-division multiplexing passive optical network using time-interleaved differential phase shift keying modulation format". 2011. http://library.cuhk.edu.hk/record=b5894827.
Abstract (sommario):
Li, Pulan.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references (p. 60-66).
Abstracts in English and Chinese.
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Overview of wavelength division multiplexed passive optical network (WDM-PON) and colorless optical network unit (ONU) --- p.1
Chapter 1.2 --- Implementation of colorless ONU --- p.4
Chapter 1.3 --- Rayleigh backscattering in WDM-PON --- p.6
Chapter 1.4 --- Motivation of this thesis --- p.9
Chapter 1.5 --- Outline of this thesis --- p.11
Chapter Chapter 2 --- Previous works of remodulation for WDM-PON --- p.12
Chapter 2.1 --- Introduction --- p.12
Chapter 2.2 --- Devices utilized by colorless ONU in remodulation schemes --- p.13
Chapter 2.2.1 --- Injection-locked Fabry-Perot laser diode at ONU --- p.13
Chapter 2.2.2 --- Reflective semiconductor optical amplifier --- p.15
Chapter 2.2.3 --- Reflective electro-absorption modulator and semiconductor optical amplifier (REAM-SOA) --- p.17
Chapter 2.3 --- Modulation methods in remodulation schemes --- p.18
Chapter 2.4 --- Summary --- p.23
Chapter Chapter 3 --- A remodulation scheme based on time-interleaved DPSK modulation format --- p.25
Chapter 3.1 --- Introduction --- p.25
Chapter 3.2 --- Operation principle: time-interleaving technology for phase-modulated signal --- p.27
Chapter 3.3 --- System architecture --- p.28
Chapter 3.4 --- Experimental results and discussion --- p.31
Chapter 3.5 --- Effect of timing misalignment on proposed remodulation scheme --- p.33
Chapter 3.6 --- Summary --- p.35
Chapter Chapter 4 --- Enhanced Tolerance to Rayleigh Backscattering in Remodulation Scheme Using Time-Interleaved DPSK Format --- p.37
Chapter 4.1 --- Introduction --- p.37
Chapter 4.2 --- Studies on Rayleigh backscattering suppression in optical domain --- p.39
Chapter 4.2.1 --- RB suppression in carrier-distributed schemes --- p.39
Chapter 4.2.2 --- RB suppression in remodulation schemes --- p.40
Chapter 4.2 --- Experimental setup and results --- p.42
Chapter 4.3 --- Discussion on RB suppression effect of the proposed scheme --- p.46
Chapter 4.3.1 --- Theoretical study and simulation results --- p.46
Chapter 4.3.2 --- Experimental demonstration of spectral relationship between signals and RB crosstalk --- p.49
Chapter 4.4 --- Summary --- p.53
Chapter Chapter 5 --- Conclusion and Future Works --- p.55
Chapter 5.1 --- Conclusion of this thesis --- p.55
Chapter 5.2 --- Future works --- p.57
List of Publications --- p.59
Bibliography --- p.60
27
Chen, Wei-Han, e 陳韋翰. "A Hybrid Checkpointing Scheme in Message Passing Systems". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/95930666895997913830.
Abstract (sommario):
碩士國立成功大學
會計學系碩博士班
95
If we apply checkpoint-based protocols to achieve fault-tolerance, besides taking checkpoints, it is a significant issue to ensure that consistent global states can be recovered when failures occur. Additional failure-free coordination overheads are ineluctable so that reduce the performance. Recently, many intensive researches have been studied to eliminate such overheads including by analyzing distributed programs and statically inserting checkpoint statements at the proper places in the source code. In this thesis, we propose a hybrid checkpoint scheme to leverage the advantages of both static analysis and online checkpointing. An algorithm to find orphan-free coupling nodes in extended control flow graph is shown and we apply it to several commonly used inter-process interacting paradigms. Tightly coupling strategy is to avoid any trouble path that checkpoint X happened before checkpoint Y from different processes in the CFG. However,if the application being analyzed may have trouble paths while executing operations in loops, it is unnecessary for tightly coupling strategy to move the checkpoint statement outside the loop to avoid trouble paths. Under our hybrid checkpoint scheme, the extent of recovery from failures can be bounded to at most one checkpoint interval such that domino effect will never appear.
28
Mu, Pei Wen, e 穆佩雯. "A Study on Link Load Balance Mechanism Performance with Passive Measurement Schemes". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/30363410322958544816.
Abstract (sommario):
碩士國防管理學院
國防資訊研究所
95
As E-commerce era coming, it is important for an enterprise to implement a reliable network environment with lower costs; the link load balance (LLB) mechanism is one possible solution. With the LLB, a multihoming enterprise network environment can be support for enterprises to avoid congesting and disconnecting over the links which an enterprise network connects to the Internet. However, LLB operations involve algorithms, measurement cost, measurement frequency, traffic dispatching mode; LLB would support different traffic transmission performance with combinations of algorithms, measurement cost, measurement frequency, traffic dispatching mode. Therefore, operation costs and traffic transmission performance of LLB is an important issue. This study discusses traffic transmission performance of three passive measurement algorithms, weighted round robin (WRR), least connection first (LCF), and weighted least connection first (WLCF), with different measurement costs, measurement frequencies, dispatching modes, and amounts of user connections. An emulation environment is implemented with the Q-balancer devices in this study. Several emulation scenarios are executed and many emulation data are collected. Examining the emulation data, several interested results are found and they can help enterprises with multihoming network environment to improve traffic transmission performance over the links connect to the Internet.
29
Falcone, Paolo. "Passive radar based on WiFi transmissions: signal processing schemes and experimental results". Doctoral thesis, 2013. http://hdl.handle.net/11573/917544.
Abstract (sommario):
Aim of this work is to study innovative techniques and processing strategies for a new passive sensor for short range surveillance. The principle of work of the sensor will be based on the passive radar principle, and WiFi transmissions - which usually provide Internet access within local areas - will be exploited by the passive
sensor to detect, localize and classify targets.
30
Shing-Shiu, Ko. "Fiber Raman Amplifiers: Novel Pumping Schemes and Their Applications in Passive Optical Ring Networks". 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1307200602401100.
31
Ko, Shing-Shiu, e 柯星旭. "Fiber Raman Amplifiers: Novel Pumping Schemes and Their Applications in Passive Optical Ring Networks". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/53510622159390539410.
Abstract (sommario):
碩士國立臺灣大學
光電工程學研究所
94
The importance of optical fiber communication is increasing in modern world. In optical fiber communication system networks, the application of optical amplifiers can avoid the signal distortion from transformation between electrical and optical signals and then provide even longer transmission span and permit even more components regardless of the loss increment. At present, the dominant optical amplifiers are erbium-doped fiber amplifiers (EDFAs), which have a characteristic of fixed amplification bandwidth. With the rising of internet popularization, wider bandwidth is required to satisfy the increasing requirement of the data quantity. This demand is limited by EDFAs’ characteristic. Another optical amplifier, fiber Raman amplifier (FRA), which has the characteristic of flexible amplification bandwidth, is a candidate to fulfill this demand. The lack of high power Raman pump light in the past, is solved with the development of high-power semiconductor and fiber lasers. Now the application of FRAs attracts people’s attention again. The demand of high-power Raman pump light in FRAs is due to the low gain coefficient of the existing optical fibers. To achieve a suitable gain level, this demand of high-power pump is unavoidable. However, the higher the pump power is, the more severe the nonlinearity problem will be introduced. The performance of Raman pump light will greatly affect the performance of FRAs. In this thesis, we first focus on the relationship between Raman pumping schemes and the noise performance of FRAs. We further propose a combined pumping scheme to achieve better performance. Although FRAs are often used in long-haul systems, we believe they can also benefit metropolitan networks with its better noise performance. In this thesis, we also investigate the appropriate application of FRAs in passive optical ring networks. We find that the performance of FRAs is very sensitive to the component loss. Because in metropolitan networks, many passive components should be included in addition to optical fibers, they introduced additional losses. In practice, the components have different losses. We investigate the impact of component losses and provide a way to optimize the performance of the Raman amplifier through proper arrangement of these components with different losses.
32
Chang, Ruey-Rong, e 張瑞榮. "The implementation of message passing Scheme and developing environment of Macro C". Thesis, 1990. http://ndltd.ncl.edu.tw/handle/68726057670432028234.
33
Hassan, Wan Hafiza Binti Wan. "Effects of enhancing performance in fiber-wireless networks". Thesis, 2015. https://vuir.vu.edu.au/30148/.
Abstract (sommario):
The convergence of optical and wireless technologies has given rise to the fiber-wireless
(Fi-Wi) network. This network combines the huge capacity of optical fiber with the
ubiquity and mobility of wireless networks. Fiber to the premises (FTTP) combined
with wireless local area network (WLAN) in home distribution is now becoming a
reality. However, network congestion in the wireless access link still limits end user
performance, especially in dense residential areas. Therefore, this thesis focuses on
the enhancement of the wireless media in Fi-Wi networks.
The thesis considers the realisation of Fi-Wi networks using the gigabit passive
optical network (GPON) and the infrastructure based WLAN. The study shows the
binary exponential backoff (BEB) adopted in the medium access control (MAC) pro-
tocol for the IEEE 802.11 WLAN standard is the key factor inhibiting WLAN perfor-
mance. The standard distributed coordination function (DCF) access method used
by WLAN today provides equal chance of transmissions to all stations. This equal-
ity can lead to unfairness between uplink (UL) and downlink (DL) transmissions
because the number of active wireless users normally exceeds the number of access
points. Generally the Fi-Wis access point (AP) requires greater media access than
any of its associate wireless users (WUs) because of the predominance of downlink
traffic. Thus, techniques to maximize the network throughput and provide fairness
between UL and DL transmissions are proposed. Traffic information obtained from
monitoring both GPON and WLAN networks is utilized in the proposed schemes.
34
Lindseth, Adelaide Virginia. "Determining temporal recording schemes for underwater acoustic monitoring studies". Thesis, 2019. https://hdl.handle.net/2144/34796.
Abstract (sommario):
Soundscape Ecology, the physical combination of sounds at a particular time and place, is a rapidly growing field. As acoustic technology advances, several possible future uses of passive acoustic monitoring (PAM), such as biodiversity counts and monitoring of habitat health, are being explored. This thesis is divided into two chapters; each is a stand-alone paper. The first chapter provides a review of soundscape ecology, ambient sound, current recording methods and data analysis used in PAM studies, and identifies several major future recommendations for the field. One of these recommendations is to standardize recording methods and indices used during analysis in long-term studies. The second chapter analyzes a 55-minute continuous recording on a coral reef in Tunicate Cove, Belize in 1996 by Professor P. Lobel. This recording was then subsampled with several intermittent recording schedules to explore the amount of acoustic information lost as periods of active and inactive recording vary. The continuous recording consisted of a high frequency band (3-4 kHz), which may correspond to abiotic sounds, and a low frequency band (0.1-0.5 kHz), which generally corresponds to biotic sounds. Two recording schedules, 30 seconds every 4 minutes and 2 minutes every 10 minutes, were significantly correlated with the continuous recording. The statistical significance of the other five recording schedules varied among the three parameters tested in this study (average power (dB), average entropy, and aggregate entropy).
35
Coutinho, João de Alcantâra Sá de Sousa. "Comparison of Discretization Schemes for Simulation of Transport of a Passive Scalar in an Open-Channel Confluence". Master's thesis, 2021. https://hdl.handle.net/10216/134151.
36
Coutinho, João de Alcantâra Sá de Sousa. "Comparison of Discretization Schemes for Simulation of Transport of a Passive Scalar in an Open-Channel Confluence". Dissertação, 2021. https://hdl.handle.net/10216/134151.
37
Chuang, Yo-Hsuan, e 莊祐軒. "A V2V-Based Fast Handoff Scheme Using IP Address Passing for Vehicular Ad-Hoc Networks". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/47731195931156909439.
Abstract (sommario):
碩士國立高雄應用科技大學
資訊管理系
99
In VANETs, each vehicle should obtain an IP address for its identification before connecting to the Internet or getting some information from the Internet. Due to the rapid movement of vehicles, each vehicle must perform a handoff procedure between different access points. To ensure that the transmission of packets is not interrupted, the handoff scheme for VANETs is a key design issue. In view of this, we design a V2V-based fast handoff scheme using IP address passing for VANETs in this thesis. The proposed scheme allows a leaving vehicle in the exit area to pass an IP address which has been identified by the duplicate address detection (DAD) procedure to the vehicles in the entry area directly. In addition, the leaving vehicle in the exit area can also pass an IP address to the vehicles in the middle area if there is no vehicles in the entry area. Therefore, our scheme can reduce the use of Dynamic Host Configuration Protocol (DHCP) to obtain an IP address. Because DAD results in the largest delay of the whole DHCP procedure, our scheme can thus improve the utilization of IP address, reduce the time of acquiring an IP address, and reduce the whole handoff time.
38
Lasalle-Ratelle, Jérémie. "Implantation des futures sur un système distribué par passage de messages". Thèse, 2010. http://hdl.handle.net/1866/4900.
Abstract (sommario):
Ce mémoire présente une implantation de la création paresseuse de tâches desti-
née à des systèmes multiprocesseurs à mémoire distribuée. Elle offre un sous-ensemble des fonctionnalités du Message-Passing Interface et permet de paralléliser certains problèmes qui se partitionnent difficilement de manière statique grâce à un système de
partitionnement dynamique et de balancement de charge. Pour ce faire, il se base sur le
langage Multilisp, un dialecte de Scheme orienté vers le traitement parallèle, et implante
sur ce dernier une interface semblable à MPI permettant le calcul distribué multipro-
cessus. Ce système offre un langage beaucoup plus riche et expressif que le C et réduit
considérablement le travail nécessaire au programmeur pour pouvoir développer des
programmes équivalents à ceux en MPI. Enfin, le partitionnement dynamique permet
de concevoir des programmes qui seraient très complexes à réaliser sur MPI. Des tests
ont été effectués sur un système local à 16 processeurs et une grappe à 16 processeurs
et il offre de bonnes accélérations en comparaison à des programmes séquentiels équiva-
lents ainsi que des performances acceptables par rapport à MPI. Ce mémoire démontre
que l’usage des futures comme technique de partitionnement dynamique est faisable sur
des multiprocesseurs à mémoire distribuée.This master’s thesis presents an implementation of lazy task creation for distributed memory multiprocessors. It offers a subset of Message-Passing Interface’s functionality and allows parallelization of some problems that are hard to statically partition thanks to its dynamic partitionning and load balancing system. It is based on Multilisp, a Scheme dialect for parallel computing, and implements an MPI like interface on top of it. It offers a richer and more expressive language than C and simplify the work needed to developp programs similar to those in MPI. Finally, dynamic partitioning allows some programs that would be very hard to develop in MPI. Tests were made on a 16 cpus computer and on a 16 cpus cluster. The system gets good accelerations when compared to equivalent sequential programs and acceptable performances when compared to MPI. It shows that it is possible to use futures as a dynamic partitioning method on distributed memory multiprocessors.
39
Tseng, Chao-Ching, e 曾昭清. "Research on Supplier Assessment, Quality Improvement and Credibility of Subjective and Objective Scoring Schemes – Taking Taiwan\'s Passive Components as an Example". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/qxrq8f.
Abstract (sommario):
碩士國立彰化師範大學
企業管理學系
107
ABSTRACT This research, using evaluation and assessment provided by appropriate suppliers, ensures the data to become more transparent and closer to reality through the assessment and evaluation process management. Even under the circumstances of having more subjective than objective observations, more information still can be distilled from original data. This study will use a passive component company as a case. In regards to the supplier evaluation method, there are nine sub-evaluation indicators. All of aforementioned indicators add up to 100% and will be assessed and explored both subjectively and objectively. In order to effectively establish a monitoring mechanism for a supplier evaluation and find possible anomalies (i.e. over- or under-estimations), we will use K-Means method to target the evaluations of A and B factories from the first quarter of 2017 to the first quarter of 2018 by comparing the original evaluation result with that of the K-Means method categorized into three probable outcomes (i.e. A, B, and C). Grades A, B, and C that belong to qualified suppliers represent a score of 95 points and more, a score of 90 but below 95 points, and a score of 85 but below 90 points, respectively. We hope to find and address the problem through this study, as well as establish a set of objective evaluations to increase quality and ensure consistent supply in the long run.
40
"Study of architectures and protection schemes for high-speed WDM-based passive optical access networks utilizing centralized light sources for colorless optical network units". 2006. http://library.cuhk.edu.hk/record=b5893002.
Abstract (sommario):
Zhang Bo.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (leaves 55-59).
Abstracts in English and Chinese.
Chapter Chapter 1 --- Introduction to Passive Optical Networks --- p.1
Chapter 1.1 --- Passive Optical Network (PON) --- p.2
Chapter 1.1.1 --- PON architecture --- p.3
Chapter 1.1.2 --- PON benefits --- p.4
Chapter 1.2 --- The History of PON --- p.4
Chapter 1.3 --- WDM-PON --- p.5
Chapter 1.4 --- Outline of This Thesis --- p.8
Chapter Chapter 2 --- Previous Schemes for Colorless ONU Operation in WDM-PON --- p.9
Chapter 2.1 --- Introduction --- p.10
Chapter 2.2 --- Previous WDM-PON Architectures for Colorless ONU Operation --- p.10
Chapter 2.2.1 --- Spectrum slicing BLS employed at the ONU --- p.11
Chapter 2.2.2 --- Centralized broadband light source (BLS) for upstream optical carrier supply --- p.12
Chapter 2.2.3 --- Reuse of the downstream carrier at the ONU --- p.17
Chapter 2.3 --- Summary --- p.21
Chapter Chapter 3 --- WDM-PON with a Centralized Supercontinuum Broadband Light Source for Colorless ONUs --- p.23
Chapter 3.1 --- Introduction --- p.24
Chapter 3.1.1 --- Introduction to Supercontinuum Generation --- p.24
Chapter 3.1.2 --- Introduction to Photonic Crystal Fibers --- p.25
Chapter 3.1.3 --- Supercontinuum Generation in a Photonic Crystal Fiber --- p.27
Chapter 3.2 --- WDM-PON with Centralized Supercontinuum Broadband Light Source --- p.27
Chapter 3.2.1 --- Motivation --- p.27
Chapter 3.2.2 --- Proposed access network --- p.28
Chapter 3.2.3 --- Experimental demonstration and results --- p.30
Chapter 3.2.4 --- Discussions --- p.32
Chapter 3.2.5 --- Conclusion --- p.34
Chapter 3.3 --- Broadcast Signal Delivery over a WDM-PON based on Supercontinuum Generation --- p.34
Chapter 3.3.1 --- Motivation --- p.34
Chapter 3.3.2 --- Proposed network architecture --- p.35
Chapter 3.3.3 --- Experiment results and discussions --- p.36
Chapter 3.3.4 --- Conclusion --- p.38
Chapter 3.4 --- Summary --- p.38
Chapter Chapter 4 --- A Survivable WDM-PON with Colorless Optical Network Units --- p.39
Chapter 4.1 --- Introduction --- p.40
Chapter 4.2 --- Previous Protection Schemes --- p.40
Chapter 4.3 --- A Survivable WDM-PON with Centralized BLS --- p.44
Chapter 4.3.1 --- Network topology and wavelength assignment --- p.45
Chapter 4.3.2 --- Protection operation principles --- p.46
Chapter 4.3.3 --- Experimental results --- p.47
Chapter 4.4 --- Summary --- p.48
Chapter Chapter 5 --- Summary and Future Work --- p.50
Chapter 5.1 --- Summary of the Thesis --- p.51
Chapter 5.2 --- Future Work --- p.52
LIST OF PUBLICATIONS --- p.54
REFERENCES --- p.55