Die Dissertation erforscht die Unsicherheit, Sensitivität und Grenzen großskaliger Erosionsmodelle. Die Modellierung basiert auf der allgemeinen Bodenabtragsgleichung (ABAG), Sedimenteintragsverhältnissen (SDR) und europäischen Daten. Für mehrere Regionen Europas wird die Bedeutung der Unsicherheit topographischer Modellparameter, ABAG-Faktoren und kritischer Schwebstofffrachten für die Anwendbarkeit empirischer Modelle zur Beschreibung von Sedimentfrachten und SDR von Flusseinzugsgebieten untersucht. Der Vergleich alternativer Modellparameter sowie Kalibrierungs- und Validierungsdaten zeigt, dass schon grundlegende Modellentscheidungen mit großen Unsicherheiten behaftet sind. Zur Vermeidung falscher Modellvorhersagen sind kalibrierte Modelle genau zu dokumentieren. Auch wenn die geschickte Wahl nicht-topographischer Algorithmen die Modellgüte regionaler Anwendungen verbessern kann, so gibt es nicht die generell beste Lösung. Die Ergebnisse zeigen auch, dass SDR-Modelle stets mit Sedimentfrachten und SDR kalibriert und evaluiert werden sollten. Mit diesem Ansatz werden eine neue europäische Bodenabtragskarte und ein verbessertes SDR-Modell für Einzugsgebiete nördlich der Alpen und in Südosteuropa abgeleitet. In anderen Regionen Europas ist das SDR-Modell bedingt nutzbar. Die Studien zur jährlichen Variabilität der Bodenerosion zeigen, dass jahreszeitlich gewichtete Niederschlagsdaten geeigneter als ungewichtete sind. Trotz zufriedenstellender Modellergebnisse überwinden weder sorgfältige Algorithmenwahl noch Modellverbesserungen die Grenzen europaweiter SDR-Modelle. Diese bestehen aus der Diskrepanz zwischen modellierten Bodenabtrags- und maßgeblich zur beobachteten bzw. kritischen Sedimentfracht beitragenden Prozessen sowie der außergewöhnlich hohen Sedimentmobilisierung durch Hochwässer. Die Integration von nicht von der ABAG beschriebenen Prozessen und von Starkregentagen sowie die Disaggregation kritischer Frachten sollte daher weiter erforscht werden. / This dissertation thesis addresses the uncertainty, sensitivity and limitations of large-scale erosion models. The modelling framework consists of the universal soil loss equation (USLE), sediment delivery ratios (SDR) and European data. For several European regions, the relevance of the uncertainty in topographic model parameters, USLE factors and critical yields of suspended solids for the applicability of empirical models to predict sediment yields and SDR of river catchments is systematically evaluated. The comparison of alternative model parameters as well as calibration and validation data shows that even basic modelling decisions are associated with great uncertainties. Consequently, calibrated models have to be well-documented to avoid misapplication. Although careful choices of non-topographic algorithms can also be helpful to improve the model quality in regional applications, there is no definitive universal solution. The results also show that SDR models should always be calibrated and evaluated against sediment yields and SDR. With this approach, a new European soil loss map and an improved SDR model for river catchments north of the Alps and in Southeast Europe are derived. For other parts of Europe, the SDR model is of limited use. The studies on the annual variability of soil erosion reveal that seasonally weighted rainfall data is more appropriate than unweighted data. Despite satisfactory model results, neither the careful algorithm choice nor model improvements overcome the limitations of pan-European SDR models. These limitations are related to the mismatch of modelled soil loss processes and the relevant processes contributing to the observed or critical sediment load as well as the extraordinary sediment mobilisation during floods. Therefore, further research on integrating non-USLE processes and heavy-rainfall data as well as on disaggregating critical yields is needed.

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Made available in DSpace on 2011-05-04T12:36:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2009 / O Instituto Oswaldo Cruz, unidade de pesquisa biomédica da Fundação Oswaldo Cruz, quer chegar em 2015 como um Instituto de Pesquisa e Tecnologia internacional de excelência, formador de cientistas e técnicos, reconhecido pela qualidade de sua ação de referência de diagnóstico, assistência e vigilância epidemiológica e capaz de responder às demandas na área de saúde com rapidez e confiabilidade. Este trabalho apresenta uma proposta de estudo prospectivo como ferramenta indispensável de planejamento estratégico para subsidiar a tomada de decisões e a formulação das políticas institucionais que façam o Instituto Oswaldo Cruz alcançar suavisão de futuro. A metodologia utilizada envolveu a realização de revisão da literatura para a construção do referencial teórico, a análise comparativa de três estudos prospectivos realizados no país e um realizado por instituição estrangeira e a identificação dos instrumentos e ferramentas utilizados nesses estudos. O resultado foi a apresentação de uma proposta de estudo prospectivo dividido em três fases: Inicial, de coleta, tratamento e sistematização da informação; Principal, de análise e interpretação da informação e produção do conhecimento; e de Comprometimento, de disseminação dos resultados, que propiciará ao IOC alcançar a excelência descrita em sua visão de futuro. / The Oswaldo Cruz Institute, the Oswaldo Cruz Foundation's biomedical research unit, is aiming to reach 2015 as "a international Institute of Research and Technology of excelence, former of scientists and technicians, acknowledged by the quality of its actions of reference to diagnosis, assistance and epidemiologic surveillance, and able to respond to the demands in the health area with agility and reliability." This paper represents a proposal of prospective study as an indispensable strategic planning tool to subsidize the decision making and the formulation of institutional policies to make the Oswaldo Cruz Institute reach its vision of the future. The methodology used involved the realisation of a literature review in order to build the theoretical referential, the comparative analysis of three prospective studies made in the country and one made by a foreign institution and the identification of the instruments and tools used in these studies. The result was the presentation of a prospective study proposal divided in three phases: the Inicial one, of collection, treatment and sistematization of the information; the Principal one, of analysis and interpretation of this information and the knowledgement production; and the Commitment one, of dissemination of the results, wich will propiciate the Institute Oswaldo Cruz to reach the excelence described in its vision of the future.

A wireless sensor network (WSN) is a collection of sensor nodes distributed over a geographical region to obtain the environmental data. It can have different types of applications ranging from low data rate event driven and monitoring applications to high data rate real time industry and military applications. Energy efficiency and reliability are the two major design issues which should be handled efficiently at all the layers of communication protocol stack, due to resource constraint sensor nodes and erroneous nature of wireless channel respectively. Media access control (MAC) is the protocol which deals with the problem of packet collision due to simultaneous transmissions by more than one neighboring sensor nodes. Time Division Multiple Access based (TDMA-based) and contention-based are the two major types of MAC protocols used in WSNs. In general, the TDMA-based channel access mechanisms perform better than the contention-based channel access mechanisms, in terms of channel utilization, reliability and power consumption, specially for high data rate applications in wireless sensor networks (WSNs). TDMA-based channel access employs a predefined schedule so that the nodes can transmit at their allotted time slots. Based on the frequency of scheduling requirement, the existing distributed TDMA-scheduling techniques can be classified as either static or dynamic. The primary purpose of static TDMA-scheduling algorithms is to improve the channel utilization by generating a schedule of smaller length. But, they usually take longer time to generate such a schedule, and hence, are not suitable for WSNs, in which the network topology changes dynamically. On the other hand, dynamic TDMA-scheduling algorithms generate a schedule quickly, but they are not efficient in terms of generated schedule length. We suggest a new approach to TDMA-scheduling for WSNs, that can bridge the gap between these two extreme types of TDMA-scheduling techniques, by providing the flexibility to trade-off between the schedule length and the time required to generate the schedule, as per the requirements of the underlying applications and channel conditions. The suggested TDMA-scheduling works in two phases. In the first phase, we generate a valid TDMA schedule quickly, which need not have to be very efficient in terms of schedule length. In the second phase, we iteratively reduce the schedule length in a manner, such that the process of schedule length reduction can be terminated after the execution of an arbitrary number of iterations, and still be left with a valid schedule. This step provides the flexibility to trade-off the schedule length with the time required to generate the schedule. In the first phase of above TDMA-scheduling approach, we propose two randomized, distributed and parallel TDMA-scheduling algorithms viz., Distributed TDMA Slot Scheduling (DTSS) and Randomized and Distributed TDMA (RD-TDMA) scheduling algorithm. Both the algorithms are based on graph coloring approach, which generate a TDMA schedule quickly with a fixed schedule length ( Colouring), where is the maximum degree of any node in the graph to be colored. The two algorithms differ in the channel access mechanism used by them to transmit control messages, and in the generated schedule for different modes of communication, i.e., unicast, multicast and broadcast. The novelty of the proposed algorithms lies in the methods, by which an uncolored node detects that the slot picked by it is different from the slots picked by all the neighboring nodes, and the selection of probabilities with which the available slots can be picked up. Furthermore, to achieve faster convergence we introduce the idea of dynamic slot-probability update as per which the nodes update their slot-probability by considering the current slot-probability of their neighboring nodes. Under the second phase of the proposed TDMA-scheduling approach, we provide two randomized and distributed schedule compaction algorithms, viz., Distributed Schedule Compaction (DSC) and Distributed Schedule Length Reduction (DSLR) algorithm, as the mechanism to trade-off the scheduling time with the generated schedule length. These algorithms start with a valid TDMA schedule and progressively compress it in each round of execution. Additionally, Furthermore, the execution of these algorithms can be stopped after an arbitrary number of rounds as per the requirements of underlying applications. Even though TDMA-based MAC protocols avoid packet loss due to collision, due to erroneous nature of wireless medium, they alone are not sufficient to ensure the reliable transmission in WSNs. Automatic Repeat reQuest (ARQ) is the technique commonly used to provide error control for unicast data transmission. Unfortunately, ARQ mechanisms cannot be used for reliable multicast/broadcast transmission in WSNs. To solve this issue, we propose a virtual token-based channel access and feedback protocol (VTCAF) for link level reliable multicasting in single-hop wireless networks. The VTCAF protocol introduces a virtual (implicit) token passing mechanism based on carrier sensing to avoid the collision between feedback messages. The delay performance is improved in VTCAF protocol by reducing the number of feedback messages. Besides, the VTCAF protocol is parametric in nature and can easily trade-off reliability with the delay as per the requirements of the underlying applications. Finally, by integrating all the works, viz., TDMA-scheduling algorithms (DTSS/RD-TDMA), schedule compaction algorithms and link layer feedback mechanism for reliable multicast/ broadcast, we propose a TDMA-based energy aware and reliable MAC protocol, named TEA-MAC for multi-hop WSNs. Similar to VTCAF, TEA-MAC protocol uses the combination of ACK-based and NACK-based approaches to ensure reliable communication. But, instead of using virtual token-based channel access, it uses contention-based channel access for NACK transmission. All the algorithms and protocols proposed in this thesis are distributed, parallel and fault tolerant against packet losses to support scalability, faster execution and robustness respectively. The simulations have been performed using Castalia network simulator to evaluate the performance of proposed algorithms/protocols and also to compare their performance with the existing algorithms/protocols. We have also performed theoretical analysis of these algorithms/protocols to evaluate their performance. Additionally, we have shown the correctness of proposed algorithms/protocols by providing the necessary proofs, whenever it was required. The simulation results together with theoretical analysis show that, in addition to the advantage of trading the runtime with schedule length, the proposed TDMA scheduling approach achieves better runtime and schedule length performance than existing algorithms. Additionally, the TEA-MAC protocol is able to considerably improve the reliability and delay performance of multicast communication in WSNs.

Ce travail s’attache à répondre à deux préoccupations majeures :<p>-déterminer le statut sociolinguistique du kindubile, parler des enfants de la rue de Lubumbashi appelés « shege ».<p>-préciser les contextes de mobilisation du kindubile par les shege ainsi que les différentes significations qu’il revêt à leurs yeux.<p>Il est basé sur un corpus très hétérogène: les données verbales (entretiens semi-directifs, libres, récits de vie, chansons et surnoms) et les matériaux picturaux (graffitis, tags et dessins) produits par les enfants eux-mêmes. Les analyses sont inspirées en linguistique par la pragmatique et en sociologie par l’interactionnisme symbolique, la théorie de l’acteur et du système ainsi que la théorie dispositionnaliste de Bernard Lahire. <p>Cette dissertation a conduit aux résultats suivants :<p>-le kindubile est un argot swahili. Sa grammaire est globalement identique à celle du kiswahili de Lubumbashi. La seule différence s’observe au niveau du lexique. Celui-ci, outre les procédés de création cryptique (adjonctions, suppressions, permutations et leur combinaison reste prolixe et focalisé sur certains registres seulement :la nourriture, l’argent, la débrouille, la violence et la sexualité. Ces domaines demeurent hautement significatifs à leur yeux d’autant plus qu’ils sont corrélés et indispensables à la vie de rue.<p>-Les enfants de la rue recourent à l’argot pour communiquer entre eux, pour un repli identitaire (ils veulent s’affirmer comme un groupe particulier et en même temps être reconnus autant que respectés comme des personnes humaines à part entière). Ils recourent également au kindubile pour crypter leur message en parlant des stupéfiants, de la sexualité ou en voulant subtiliser un bien à quelqu’un). Ils emploient aussi le kindubile comme un espace de défoulement. En effet, ils expriment leur mécontentement de la société qui les a produits mais craignant les représailles, ils préfèrent s’exprimer en argot. Ils parlent aussi kindubile pour provoquer la peur chez leur interlocuteur lorsqu’ils le jugent nécessaire.<p> / Doctorat en Langues et lettres / info:eu-repo/semantics/nonPublished