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The Global ETD Search service is a free service for researchers
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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.
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Showing 1 to 7 of 7 (0.1 seconds)| 1 |
Selective Cooperation for Dual-Hop Cooperative Communication NetworksTsai, Tsung-hao 25 August 2010 (has links)
In cooperative communications systems, multiple relays selection scheme and adaptive relay selection scheme are usually adopted. In both schemes, the system makes selections based on instantaneous channel status. However, such schemes have an extremely high computational complexity. In particular, when the channels experience fast fading, the systems do not have sufficient to make a correct decision.
In this thesis, statistical channel properties are utilized in deciding whether cooperative transmission should be adopted or not. In our investigations, the cooperative mechanism includes direct transmission (DT), decode-and-forward (DF) relaying and amplify-and-forward (AF) relaying. The Ergodic capacity is adopted throughout the theoretical analyses. In addition, a number of approximated thresholds are derived to assist the decision process.
Simulation experiments are conducted to verify the derived results. It is shown that the proposed transmission scheme using the cooperative thresholds is effective in deciding when the cooperative communication is necessary.
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Modélisation et optimisation du contrôle de l’encéphalite japonaise au Cambodge / Modelling and optimization of japanese encephalitis control in CambodiaDiallo, Alpha Oumar II 27 November 2018 (has links)
L’encéphalite Japonaise (EJ) est une maladie zoonotique virale et c’est la principale cause d'encéphalite humaine en Asie et le Pacifique. Elle est due à un Flavivirus, transmis de l’animal à l'Homme par des moustiques, elle peut se transmettre entre porcs par contact direct. Malgré une baisse significative des cas d’EJ dans de nombreux pays suite à la mise en place de programmes de vaccination, l’EJ continue à sévir d’une manière importante en Asie. Notre objectif dans cette thèse est de (i) construire un modèle mathématique de la dynamique de transmission du virus de l’EJ (VEJ), (ii) paramétrer ce modèle pour déterminer l’importance de la transmission directe entre porcs en milieu naturel (iii) et déterminer des stratégies de contrôle. Nous avons développé un modèle de propagation du VEJ. Ensuite, nous avons adapté ce modèle pour avoir deux modèles intégrant la transmission vectorielle seulement ou une combinaison de la transmission vectorielle et directe. Nos résultats montrent que la transmission directe entre porcs pourrait contribuer à la dynamique de transmission du VEJ dans le contexte Cambodgien, toutefois elle ne pourrait pas permettre toute seule une épidémie. Enfin, nous avons considéré la lutte anti-vectorielle, la vaccination des truies et la gestion d’élevages en bandes pour déterminer des stratégies de contrôle pour éradiquer le VEJ au sein des troupeaux de porcs, baisser les avortements des truies, évaluer les risques pour les humains vivant à proximité des fermes et des abattoirs ainsi que le coût-efficacité de la vaccination. Nos résultats confirment que la lutte anti-vectorielle est le meilleur moyen pour contrôler le VEJ. La vaccination des truies gestantes fait diminuer les avortements comme attendu. Paradoxalement, si le contrôle vectoriel est moyen l’efficacité de la vaccination pourrait être compromise. La gestion d’élevages en bandes a un faible impact sur l'incidence et les avortements, par conséquent sur le contrôle de l’EJ. Combiner la vaccination des truies et la lutte anti-vectorielle pourrait être une alternative et/ou une mesure supplémentaire à la vaccination humaine pour réduire à la fois l'incidence de l'EJ chez l'Homme et l'impact économique de l'infection du au VEJ dans les élevages des porcs. / Japanese encephalitis (JE) is a viral zoonotic disease and it is the leading cause of human encephalitis in Asia and the Pacific. Japanese encephalitis virus (JEV) is a Flavivirus of the family of Flaviviridae transmitted from animals to human by mosquitoes, direct transmission between pigs can occur via direct contact. Despite a significant decline in JE cases in many countries as a result of vaccination programs, JE continues to have a significant impact in Asia. Our objective in this thesis is to (i) built a mathematical model of the transmission dynamics of JEV, (ii) parameterize this model to determine the importance of direct transmission between pigs under field conditions (iii) and determine control strategies. We developed a propagation model of JEV. Next, we adapted this model to have two models incorporating vector-borne transmission alone or a combination of vector-borne and direct transmission. Our findings suggest that direct transmission between pigs does contribute to transmission dynamics of JEV in Cambodia; although, alone direct transmission cannot sustain an outbreak. Finally, we considered vector control, sow vaccination, and herd management to determine control strategies to eradicate JEV in pig herds, reduce sow abortions, assess the risk for human beings living in the vicinity of pig herds and near pig slaughterhouse, and the cost-effectiveness of vaccination. Our results confirm that vector control is the best way to control JEV. Vaccination of pregnant sows reduces abortions as expected. Paradoxically, if the vector control is medium the effectiveness of the vaccination could be compromised. Herd management has a low impact on incidence and abortions, therefore on JE control. Combining sow vaccination and vector control could be an alternative and/or an additional measure to human vaccination to reduce both JE incidence in humans and the economic impact of JE infection on pig breeding.
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Multi-Scale Modelling of Vector-Borne DiseasesMathebula, Dephney 21 September 2018 (has links)
PhD (Mathematics) / Department of Mathematics and Applied Mathematics / In this study, we developed multiscale models of vector-borne diseases. In general, the transmission
of vector-borne diseases can be considered as falling into two categories, i.e. direct transmission
and environmental transmission. Two representative vector-borne diseases, namely; malaria
which represents all directly transmitted vector-borne diseases and schistosomiasis which represents
all environmentally transmitted vector-borne diseases were studied. Based on existing
mathematical modelling science base, we established a new multiscale modelling framework
that can be used to evaluate the effectiveness of vector-borne diseases treatment and preventive
interventions. The multiscale models consisted of systems of nonlinear ordinary differential
equations which were studied for the provision of solutions to the underlying problem of the
disease transmission dynamics. Relying on the fact that there is still serious lack of knowledge
pertaining to mathematical techniques for the representation and construction of multiscale
models of vector-bone diseases, we have developed some grand ideas to placate this gap. The
central idea in multiscale modelling is to divide a modelling problem such as a vector-bone disease
system into a family of sub-models that exist at different scales and then attempt to study
the problem at these scales while simultaneously linking the sub-models across these scales.
For malaria, we formulated the multiscale models by integrating four submodels which are: (i)
a sub-model for the mosquito-to-human transmission of malaria parasite, (ii) a sub-model for
the human-to-mosquito transmission of malaria parasite, (iii) a within-mosquito malaria parasite
population dynamics sub-model and (iv) a within-human malaria parasite population dynamics
sub-model. For schistosomiasis, we integrated the two subsystems (within-host and between-host
sub-models) by identifying the within-host and between-host variables and parameters associated
with the environmental dynamics of the pathogen and then designed a feedback of the variables
and parameters across the within-host and between-host sub-models. Using a combination of analytical
and computational tools we adequately accounted for the influence of the sub-models in
the different multiscale models. The multiscale models were then used to evaluate the effectiveness
of the control and prevention interventions that operate at different scales of a vector-bone
disease system. Although the results obtained in this study are specific to malaria and schistosomiasis,
the multiscale modelling frameworks developed are robust enough to be applicable to
other vector-borne diseases. / NRF
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Cinema ao vivo e experiências audiovisuais em tempo real / -Molina Júnior, Jair Sanches 15 September 2017 (has links)
Refletir sobre as experiências com imagens e sons em tempo real é pensar em uma ampla gama de possibilidades e experiências pela humanidade, desde os tempos mais remotos. Pelo fato dessas experiências audiovisuais em tempo real serem numerosas no tempo e no espaço, e já amplamente citada em diferentes estudos, esta apresentação tem por objetivo realizar um recorte mais restrito às experiências audiovisuais em tempo real no campo cinematográfico contemporâneo: uma arte, meio e processo em expansão que culmina na existência de um fenômeno semiótico, realizado principalmente através de modos experimentais com a presença do(s) autor(es) concebendo a experiência audiovisual, conjuntamente ao aparato tecnológico e ao público, todos participantes da criação e exibição da obra audiovisual no mesmo tempo em que ela ocorre, em transmissão direta para a tela de cinema, monitores, telas digitais ou espaços arquitetônicos. Com base em obras audiovisuais realizadas entre 2007 a 2017 desenvolveremos uma reflexão e análise das poéticas e técnicas das experiências audiovisuais em tempo real, de maneira a compreender com um olhar mais atento as possibilidades criativas e contribuir com a reflexão sobre estes formatos do audiovisual contemporâneo, cujos meios e processos estão em contínua expansão de suas fronteiras. Em estética do cinema, esta pesquisa segue em continuidade aos estudos e práticas do cinema experimental e em sua vértice ao cinema expandido. / Reflecting about real-time imagery and sounds experiences is thinking about a wide range of possibilities and experiences for humanity, from the earliest times. Because the real-time audiovisual experiences are numerous in time and space, and already widely quoted in different studies, this presentation aims to make a more restricted cut-off to real-time audiovisual experiences in the contemporary cinematographic field: an art, medium and an expanding process that culminates in the existence of a semiotic phenomenon, performed mainly through experimental modes with the presence of the author(s) directing the audiovisual experience in real-time, together with the technological apparatus, the cast, and the public, all participants in the creation and exhibition of the audiovisual work at the same time as it occurs, in direct transmission to the cinema screen, monitors, digital screens or architectural spaces. Based on audiovisual works carried out between 2007 and 2017 we will develop a reflection and analysis of the poetics and techniques of audiovisual experiences in real-time, in order to understand with a closer look the creatives possibilities in live cinema and contribute with reflection on these forms of the contemporary audiovisual, whose means and processes are in continuous expansion of its borders. In aesthetics of the cinema, this research follows in continuity to the studies and practices of the experimental cinema, and in its vertex to the expanded cinema.
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Performance evaluation and protocol design of fixed-rate and rateless coded relaying networksNikjah, Reza 06 1900 (has links)
The importance of cooperative relaying communication in substituting for, or complementing,
multiantenna systems is described, and a brief literature review is presented.
Amplify-and-forward (AF) and decode-and-forward (DF) relaying are investigated and
compared for a dual-hop relay channel. The optimal strategy, source and relay optimal
power allocation, and maximum cooperative gain are determined for the relay channel. It
is shown that while DF relaying is preferable to AF relaying for strong source-relay links,
AF relaying leads to more gain for strong source-destination or relay-destination links.
Superimposed and selection AF relaying are investigated for multirelay, dual-hop relaying.
Selection AF relaying is shown to be globally strictly outage suboptimal. A necessary
condition for the selection AF outage optimality, and an upper bound on the probability of
this optimality are obtained. A near-optimal power allocation scheme is derived for superimposed
AF relaying.
The maximum instantaneous rates, outage probabilities, and average capacities of multirelay,
dual-hop relaying schemes are obtained for superimposed, selection, and orthogonal
DF relaying, each with parallel channel cooperation (PCC) or repetition-based cooperation
(RC). It is observed that the PCC over RC gain can be as much as 4 dB for the outage
probabilities and 8.5 dB for the average capacities. Increasing the number of relays deteriorates
the capacity performance of orthogonal relaying, but improves the performances of
the other schemes.
The application of rateless codes to DF relaying networks is studied by investigating
three single-relay protocols, one of which is new, and three novel, low complexity multirelay
protocols for dual-hop networks. The maximum rate and minimum energy per bit and
per symbol are derived for the single-relay protocols under a peak power and an average
power constraint. The long-term average rate and energy per bit, and relay-to-source usage
ratio (RSUR), a new performance measure, are evaluated for the single-relay and multirelay
protocols. The new single-relay protocol is the most energy efficient single-relay scheme
in most cases. All the multirelay protocols exhibit near-optimal rate performances, but are
vastly different in the RSUR.
Several future research directions for fixed-rate and rateless coded cooperative systems,
and frameworks for comparing these systems, are suggested. / Communications
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Performance evaluation and protocol design of fixed-rate and rateless coded relaying networksNikjah, Reza Unknown Date
No description available.
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Cinema ao vivo e experiências audiovisuais em tempo real / -Jair Sanches Molina Júnior 15 September 2017 (has links)
Refletir sobre as experiências com imagens e sons em tempo real é pensar em uma ampla gama de possibilidades e experiências pela humanidade, desde os tempos mais remotos. Pelo fato dessas experiências audiovisuais em tempo real serem numerosas no tempo e no espaço, e já amplamente citada em diferentes estudos, esta apresentação tem por objetivo realizar um recorte mais restrito às experiências audiovisuais em tempo real no campo cinematográfico contemporâneo: uma arte, meio e processo em expansão que culmina na existência de um fenômeno semiótico, realizado principalmente através de modos experimentais com a presença do(s) autor(es) concebendo a experiência audiovisual, conjuntamente ao aparato tecnológico e ao público, todos participantes da criação e exibição da obra audiovisual no mesmo tempo em que ela ocorre, em transmissão direta para a tela de cinema, monitores, telas digitais ou espaços arquitetônicos. Com base em obras audiovisuais realizadas entre 2007 a 2017 desenvolveremos uma reflexão e análise das poéticas e técnicas das experiências audiovisuais em tempo real, de maneira a compreender com um olhar mais atento as possibilidades criativas e contribuir com a reflexão sobre estes formatos do audiovisual contemporâneo, cujos meios e processos estão em contínua expansão de suas fronteiras. Em estética do cinema, esta pesquisa segue em continuidade aos estudos e práticas do cinema experimental e em sua vértice ao cinema expandido. / Reflecting about real-time imagery and sounds experiences is thinking about a wide range of possibilities and experiences for humanity, from the earliest times. Because the real-time audiovisual experiences are numerous in time and space, and already widely quoted in different studies, this presentation aims to make a more restricted cut-off to real-time audiovisual experiences in the contemporary cinematographic field: an art, medium and an expanding process that culminates in the existence of a semiotic phenomenon, performed mainly through experimental modes with the presence of the author(s) directing the audiovisual experience in real-time, together with the technological apparatus, the cast, and the public, all participants in the creation and exhibition of the audiovisual work at the same time as it occurs, in direct transmission to the cinema screen, monitors, digital screens or architectural spaces. Based on audiovisual works carried out between 2007 and 2017 we will develop a reflection and analysis of the poetics and techniques of audiovisual experiences in real-time, in order to understand with a closer look the creatives possibilities in live cinema and contribute with reflection on these forms of the contemporary audiovisual, whose means and processes are in continuous expansion of its borders. In aesthetics of the cinema, this research follows in continuity to the studies and practices of the experimental cinema, and in its vertex to the expanded cinema.
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