Recently, there has been an increasing interest in robotics related to multi-robot applications. Such systems can be involved in several tasks such as collaborative search and rescue, aerial transportation, surveillance, and monitoring, to name a few. There are two possible architectures for the autonomous control of multi-robot systems. In the centralized architecture, a master controller communicates with all the robots to collect information. It uses this information to make decisions for the entire system and then sends commands to each robot. In contrast, in the distributed architecture, each robot makes its own decision independent from a central authority. While distributed architecture is a more portable solution, it comes at the expense of extensive information exchange (communication). The extensive communication between robots can result in decision delays because of which distributed architecture is often impractical for systems with strict real-time constraints, e.g. when decisions have to be taken in the order of milliseconds. In this thesis, we propose a distributed framework that strikes a balance between limited communicated information and reasonable system-wide performance while running in real-time. We implement the proposed approach in a game setting of two competing teams of drones, defenders and attackers. Defending drones execute a proposed linear program algorithm (using only onboard computing modules) to obstruct attackers from infiltrating a defense zone while having minimal local message passing. Another main contribution is that we developed a realistic simulation environment as well as lab and outdoor hardware setups of customized drones for testing the system in realistic scenarios. Our software is completely open-source and fully integrated with the well-known Robot Operating System (ROS) in hopes to make our work easily reproducible and for rapid future improvements.

Thesis. 1976. Sc.D.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / Microfiche copy available in Archives and Barker. / Vita. / Bibliography: p. 175-181. / by Jaynarayan H. Lala. / Sc.D.

Cette étude porte sur l’allocation de ressources radio dans les réseaux LTE à forte mobilité. En particulier, il s’agit de concevoir des stratégies d’allocation de ressources capables d’améliorer la qualité de service des flux multimédia dans un contexte de forte mobilité des terminaux. Pour atteindre ces objectifs, l’étude a été menée en deux étapes. Dans un premier temps les travaux se sont déroulés dans un contexte où l’aspect forte mobilité n’a pas été pris en compte. Cela a permis de bien maitriser tous les aspects liés à l’allocation de ressources dans le LTE tout en proposant de nouvelles méthodes meilleures que celles existantes. Une fois cette tâche accomplie, l’aspect forte mobilité a été ajouté au problème et des stratégies adaptées à ce contexte ont été proposées. Néanmoins, dû aux différences entre les liens montants et descendants, l’étude a été menée dans les deux directions. Comme première contribution, nous avons conçu deux stratégies pour améliorer l’allocation de ressources sur la liaison descendante dans un contexte où la forte mobilité n’a pas été prise en compte. La première méthode est un mécanisme qui améliore cette allocation en particulier dans les scénarios d’overbooking en faisant un compromis entre l’équité, le débit global du système et les exigences de qualité de service des applications. La seconde stratégie permet non seulement de satisfaire aux contraintes de délais mais également de garantir un très faible taux de perte de paquets aux services de type multimédias. Les performances des systèmes proposés ont été évaluées par des simulations en les comparant à d’autres mécanismes dans la littérature. Les analyses ont démontré leur efficacité et révélé qu’elles obtenaient les meilleures performances. Notre deuxième contribution a permis d’améliorer l’allocation de ressources toujours dans un contexte de non prise en compte de la forte mobilité, mais cette fois ci sur le lien montant et pour des flux de type vidéo téléphonie. Nous avons conçu un nouveau protocole qui réduit de façon considérable les retards causés par l’allocation dynamique des ressources. L’idée consiste à allouer des ressources à ces trafics en utilisant une stratégie semi-persistante associée à un processus de pré-allocation. Les performances de notre méthode ont été évaluées par simulations et les résultats ont montré qu’elle fournissait le meilleur support en qualité de service. La dernière partie de nos travaux s’est intéressée au problème d’allocation de ressources dans les scénarios de fortes mobilités des terminaux. Dans cette partie, nous avons élaboré deux stratégies efficaces convenant aux scénarios véhiculaires. La première méthode est une technique permettant de maintenir le niveau de qualité de service nécessaire pour le bon fonctionnement des applications vidéo des utilisateurs ayant les vitesses les plus élevées. Elle consiste à déterminer en fonction des différentes vitesses des utilisateurs, le taux minimum de rapports CQI à envoyer à la station de base. Quant à la seconde stratégie, c’est un procédé d’ordonnancement opportuniste qui améliore la qualité de service des applications vidéo des utilisateurs ayant les vitesses les plus élevées. Avec cette stratégie, ces utilisateurs obtiennent une plus grande priorité et acquièrent ainsi beaucoup plus de ressources. / Abstract Our thesis focuses on issues related to resources allocation in LTE Networks. In particular the purpose of this study is to design efficient scheduling algorithms to improve the QoS of real time flows in a context of high mobility of the users. To reach this goal, the study has been carried out in two steps. At first, in order to have an expert knowledge of the key facets of LTE scheduling, we conducted the study in a context where the high mobility aspect of the node was not taken into account. This helped not only to critically analyze the literature but also to propose new schemes to improve QoS of real time applications. After that, the high mobility parameter has been added and innovative methods dealing with this context have been designed. Nevertheless due to the existing differences between the downlink and the uplink, the issue was tackled in each of the aforementioned directions. We firstly addressed the problem of improving the scheduling of downlink communications in a context where the high mobility was not taken into account. Two major methods have been designed for this purpose. The first one is an innovative scheme which improves resources assignment in overbooking scenarios by doing a trade-off between fairness, overall system through put and QoS requirements. The second one is an enhanced scheduling scheme which provides strict delay bounds and guarantees very low packet loss rate to multimedia flows. The performance of the proposed schemes have been evaluated by simulations and compared to other schemes in the literature. The analyses demonstrated their effectiveness and showed that they outperformed the existing ones. The second contribution concerned the problem of improving the scheduling of uplink communications in a context where the high mobility was not taken into account. We designed a novel scheduling protocol which improves resources allocation for videotelephony flows and reduces the delay caused by dynamic scheduling. It consists in scheduling such traffics using a semi-persistent strategy associated with a provisioning process. The performance of our proposed method have been evaluated by simulations and results demonstrated its effectiveness by showing that it improved videotelephony flows performance and provided the best QoS support compared to the dynamic scheduling.The last contribution addressed the problem of resources allocation in high mobility scenarios. In this part, the high mobility aspect was taken into account for designing suitable schemes for vehicular scenarios. We proposed in this way two efficient strategies. The first one is a technique which maintains the required level of QoS for supporting video users at high velocities. It consists in identifying depending on the UEs velocity, the minimum CQI reports rate in order to maintain the required QoS. The second proposed strategy is an opportunistic method which improves the performance of high speed video users. With this strategy, more priority are given to the UEs having the highest velocity. Simulations results demonstrated its effectiveness and showed that it improved the QoS support of video users having the highest velocity.

by Ching-Ting, Ng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 79-82). / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.5 / Chapter 2.1 --- Protocols tackling site failure --- p.5 / Chapter 2.2 --- Protocols tackling Partition Failure --- p.6 / Chapter 2.2.1 --- Primary site --- p.6 / Chapter 2.2.2 --- Quorum Consensus Protocol --- p.7 / Chapter 2.2.3 --- Missing Writes --- p.10 / Chapter 2.2.4 --- Virtual Partition Protocol --- p.11 / Chapter 2.3 --- Protocols to enhance the Performance of Updating --- p.11 / Chapter 2.3.1 --- Independent Updates and Incremental Agreement in Replicated Databases --- p.12 / Chapter 2.3.2 --- A Transaction Replication Scheme for a Replicated Database with Node Autonomy --- p.13 / Chapter 3 --- Transaction Replication Scheme --- p.17 / Chapter 3.1 --- A TRS for a Replicated Database with Node Autonomy --- p.17 / Chapter 3.1.1 --- Example --- p.17 / Chapter 3.1.2 --- Problem --- p.18 / Chapter 3.1.3 --- Network Model --- p.18 / Chapter 3.1.4 --- Transaction and Data Model --- p.19 / Chapter 3.1.5 --- Histories and One-Copy Serializability --- p.20 / Chapter 3.1.6 --- Transaction Broadcasting Scheme --- p.21 / Chapter 3.1.7 --- Local Transactions --- p.22 / Chapter 3.1.8 --- Public Transactions --- p.23 / Chapter 3.1.9 --- A Conservative Timestamping Algorithm --- p.24 / Chapter 3.1.10 --- Decentralized Two-Phase Commit --- p.25 / Chapter 3.1.11 --- Partition Failures --- p.27 / Chapter 4 --- Simulation Model --- p.29 / Chapter 4.1 --- Simulation Model --- p.29 / Chapter 4.1.1 --- Model Design --- p.29 / Chapter 4.2 --- Implement at ion --- p.37 / Chapter 4.2.1 --- Simulation --- p.37 / Chapter 4.2.2 --- Simulation Language --- p.37 / Chapter 5 --- Performance Results and Analysis --- p.39 / Chapter 5.1 --- Simulation Results and Data Analysis --- p.39 / Chapter 5.1.1 --- Experiment 1 : Variation of TRS Period --- p.44 / Chapter 5.1.2 --- Experiment 2 : Variation of Clock Synchronization --- p.47 / Chapter 5.1.3 --- Experiment 3 : Variation of Ratio of Local to Public Transaction --- p.49 / Chapter 5.1.4 --- Experiment 4 : Variation of Number of Operations --- p.51 / Chapter 5.1.5 --- Experiment 5 : Variation of Message Transmit Delay --- p.55 / Chapter 5.1.6 --- Experiment 6 : Variation of the Interarrival Time of Transactions --- p.58 / Chapter 5.1.7 --- Experiment 7 : Variation of Operation CPU cost --- p.61 / Chapter 5.1.8 --- Experiment 8 : Variation of Disk I/O time --- p.64 / Chapter 5.1.9 --- Experiment 9 : Variation of Cache Hit Ratio --- p.66 / Chapter 5.1.10 --- Experiment 10 : Variation of Number of Data Access --- p.68 / Chapter 5.1.11 --- Experiment 11 : Variation of Read Operation Ratio --- p.70 / Chapter 5.1.12 --- Experiment 12 : Variation of One Site Failed --- p.72 / Chapter 5.1.13 --- Experiment 13 : Variation of Sites Available --- p.74 / Chapter 6 --- Conclusion --- p.77 / Bibliography --- p.79 / Chapter A --- Implementation --- p.83 / Chapter A.1 --- Assumptions of System Model --- p.83 / Chapter A.1.1 --- Program Description --- p.83 / Chapter A.1.2 --- TRS System --- p.85 / Chapter A. 1.3 --- Common Functional Modules for Majority Quorum and Tree Quo- rum Protocol --- p.88 / Chapter A.1.4 --- Majority Quorum Consensus Protocol --- p.90 / Chapter A. 1.5 --- Tree Quorum Protocol --- p.91

No description available.

Este trabalho de pesquisa apresenta a fundamentação teórica da simulação de sistemas, a motivação e os objetivos para o estudo e o desenvolvimento de técnicas para efetuar a simulação em tempo real. Este trabalho apresenta o desenvolvimento da Arquitetura de Software da ferramenta de Engenharia denominada FASTR (Ferramenta de engenharia para Aplicação de Simulação em Tempo Real), que possui o objetivo de alimentar o sistema de simulação com dados da planta industrial em tempo real. Este trabalho também apresenta a arquitetura de Hardware empregada para testar e validar a FASTR. Os testes, resultados e análises obtidos com a FASTR são apresentados neste trabalho para comprovar e convalidar a aplicabilidade da mesma como ferramenta de engenharia para análise de projetos e de análise de desempenhos de plantas industriais automatizadas. / This research work presents the theoretical basis of systems simulation, the motivation and the objectives of study and development of techniques to execute real time simulation. This research work presents the development of Software Arquitecture of the engineering tool named FASTR (engineering tool for application of real time simulation in automated industrial plants), that has the objective of feeding the simulation system with data of the industrial plant in real time. This work also presents the used Hardware Architecture to test and to validate the FASTR. The tests, results and analyses obtained with the FASTR are presented in this work to prove and to validate the applicability of the same one as an engineering tool for analysis of projects and analysis of performances of automated industrial plants.

Sistemas de controle precisam trabalhar com restrições temporais rigorosas para garantir seu correto funcionamento, sendo por isso considerados sistemas de tempo-real. Quando tais sistemas são distribuídos, as redes de sensores, atuadores e controladores estão interligados em geral, por redes de campo. Nesse contexto, as redes de campo desempenham um papel extremamente importante no comportamento global do sistema. O presente trabalho de pesquisa apresenta a descrição do processo de desenvolvimento de um system on-chip (SoC) para um sistema de controle. Diferentemente das abordagens clássicas, o trabalho está focado em implementar o sistema baseado em um paradigma diferenciado, baseado em lógica reprogramável. Apresenta-se o projeto e construção dos IP cores necessários para controlar um motor DC, utilizando o barramento control area network (CAN) para obter uma plataforma distribuída. A arquitetura on chip utilizada está baseada na especificação CoreConnect da IBM. São expostos, ainda, trabalhos de simulação tanto dos componentes isolados, como do sistema integrado, de forma a realizar uma comparação qualitativa do processo de desenvolvimento / Control systems require strict time constraints to work properly, being therefore considered real-time systems. When such systems are distributed, controllers, sensors, and actuators are generally interconnected by fieldbuses. In this context the fieldbuses play an important role in the system global behavior. This research presents the description of the development process of a system-on-chip SoC. Differentiated from the classical approaches, this work focus the implementation of a reprogrammable logic based system. This work explain the necessary IP cores implementation, allowing a DC motor control, using a control area network (CAN) bus to reach a distributed platform. The on-chip architecture used is based on the IBM CoreConnect specification. Moreover it shows isolated components and integral system simulations, in such a way to obtain a qualitative comparison of development processes

Hydrometeorology researchers use data-products like rainfall maps, quarter-hourly, hourly & daily rainfall accumulation maps, and reflectivity maps to drive their hydrological models. There are many sources available from which to generate such products e.g. (1) Weather-radar scan data, (2) Rain-gauge data and (3) Satellite maps, to name a few. Researchers, however, prefer to deal directly with the data-product, rather than deal with the details of sensor data-collection, data-management, storage, quality-control, processing and format conversion. Many researchers would additionally like a real-time continuous 'feed' of customized hydrometeorology data-products to drive their hydrological models in a real-time continuous fashion. Hydro-NEXRAD II is a new system that is currently being developed at IIHR-Hydroscience and Engineering (at The University of Iowa) to address this need. The system provides rapid and user-friendly access to the aforementioned user-customized hydrometeorology data-products in file formats convenient to researchers. Products are generated using near real-time Weather Surveillance Doppler Radar (WSR-88D) data from the National Weather Service's NEXRAD (NEXt generation RADar) radar-network. The architecture, design and engineering details of Hydro-NEXRAD II are the subject of this thesis.

For any speech category there are multiple sources of information (both acoustic and contextual) that are relevant to categorization. Complicating matters further, these sources of information are not always available simultaneously, but present themselves over the course of several hundred milliseconds. These features of spoken language complicate an already difficult task, and raise three important questions: 1) how do listeners weight different cues to the same speech category, 2) how do listeners integrate asynchronous information during speech perception and 3) how do listeners cope with contextual variability. While these questions have been explored, to varying degrees, with adults, there have been very few attempts to explore these questions from a developmental perspective. Furthermore, some of the more complex interactions between these factors remain uncharted territory even in the adult literature. For example, while adult listeners compensate for context when categorizing speech, and utilize acoustic cues as soon as they become available, we still do not know how this process is affected by context. This dissertation addresses these lingering issues by assessing 7-year-olds', 12-year-olds' and adults' perception of the /s-ʃ/ contrast (one that is influenced by multiple acoustic cues and context) using eye-tracking and the visual world paradigm. This work demonstrates that there is considerable development between 7 and 12 years of age for the /s-ʃ/ contrast in terms of real-time cue integration, cue-weighting and context compensation, and that development likely continues beyond these ages. In addition, the adult work demonstrates, for the first time, a pattern of real-time cue integration in which listeners' (both adult and child) buffer acoustic cues. Finally, several hypotheses are considered that may account for these findings, including the possibility that the unique developmental pattern of fricative perception may play an important role in understanding why adults buffer this contrast, and the implications of buffered speech perception are discussed.

The extensive use of tetrachloroethene (PCE) and trichloroethene (TCE) as cleaning solvents has resulted in widespread contamination of groundwater systems with vinyl chloride (VC). VC, a known human carcinogen, is primarily formed in groundwater via incomplete anaerobic reductive dechlorination of PCE and TCE. Aerobic, methane-degrading bacteria (methanotrophs), which are capable of VC cometabolism while growing on methane, could be important in natural attenuation of VC plumes that escape anaerobic treatment. Real-time PCR (qPCR) represents an innovative approach for detecting and quantifying the presence and activity of these VC-degrading microbes. Immediate applications of this technique include use in a laboratory setting to help elucidate the potential bacterial-substrate interactions occurring in the subsurface environments at these contaminated sites; interactions that could ultimately affect the role of methanotrophs in VC degradation. This technique could also provide lines of evidence for natural attenuation of VC, thus support existing anaerobic bioremediation technologies that generate VC as a metabolic intermediate. In this work, we evaluated several PCR primer sets from the literature for use in methanotroph qPCR assays of groundwater samples. PCR primers targeting two functional genes involved in VC cometabolism, pmoA (sub-unit of particulate methane monooxygenase (pMMO)) and mmoX (sub-unit of soluble MMO (sMMO)), as well as 16S rRNA gene primers that targeted Bacteria, and Type I and Type II methanotrophs were tested. These assays were made quantitative by constructing standard curves with DNA from Methylococcus capsulatus (Type I) and Methylocystis sp. strain Rockwell (Type II). Primer sets were evaluated by comparing gene abundance estimated against known amounts of Type I and Type II methanotroph DNA. After primer validation, an effort to substantiate this methanotroph qPCR method was made by attempting to investigate methanotroph populations in groundwater samples from VC-contaminated sites. Some samples studied were also subjected to 16S rRNA gene pyrosequencing, allowing for relative abundance comparisons with qPCR analyses. Following our primer assessment experiments, effective primer sets were used to estimate the presence of methanotrophs at environmental sites in Soldotna, Alaska; Naval Air Station Oceana, Virginia Beach, Virginia; and Carver, Massachusetts. Results showed that methanotrophs were present in nearly all wells sampled from all environmental sites. Estimations of methanotroph relative abundance in environmental samples were determined by comparing the Type I and Type II primer estimates to those of the 16S universal primers. Methanotrophs in these groundwater samples ranged from 0.2% to 6.6% of the total bacterial population. Pyrosequencing analysis of the same samples showed methanotroph relative abundances that ranged from 1.7% to 54%. In groundwater samples where both DNA and RNA was extracted, the quantities of functional gene transcripts per gene copy was compared, revealing that the transcripts/gene ratio for both pmoA and mmoX was less than one, implying relatively low methanotroph activity. Analysis of mmoX environmental sample dissociation curves revealed a double peak, indicating possible non-specific PCR products. Our data suggests that most of the qPCR primer sets used in the environmental samples adequately detect methanotrophs, though the mmoX primers need to be further validated. These primer sets will be useful for supporting VC bioremediation strategies by providing a rapid, convincing, and cost effective alternative the enrichment culture technique currently employed. Comparison of qPCR and pyrosequencing analysis revealed biases in either one, or both techniques. Finally, our preliminary transcripts/gene data suggests that the methanotrophs at the Carver site are not actively expressing pMMO and sMMO genes above basal levels.