The X-Ray imaging technology opened a new branch of science in which the internal porous structure can be captured and the reconstructed volume can be used for fluid flow simulations and structural measurements. However, there is still the question of how the internal structure of the pore space impacts in the observed simulations. A way to characterize this internal structure is by simplifying it into well-defined elements and the interaction between them, describing it as a network. The interaction between elements are the edges of the network and elements are the nodes. This opens the possibility of applying complex network theory on the characterization of porous media which has proven to give powerful insights into how the structure of porous materials influences on the dynamics of the permeating fluid. The problem with this description is in definition of the basic elements that will compose the network, since there isnt a consensus on this definition. The purpose of this work is to provide a method to analyze μCT data through networks in which the separation of the space is done in a semi-continuous method. The recovering of the pores local geometry is captured through a network analysis method of centrality, instead of a geometrical definition. This way the intrinsic morphology of the samples is what governs the pore-space separation into different entities. The method developed is based on the network extraction method Max Spheres Algorithm (MSA). The volumetric data is recovered through a network composed by sphere cells. The output of this process are two distinct networks: the complete volume network and a network which represents the variation of the channels diameter. These networks give unbiased real information on pore connectivity and can provide important data to better understand the morphology and topology of the samples. This method was successfully applied to samples of Berea sandstone, Estaillades carbonate, and to characterize the morphology of wormholes. Wormhole is the denomination of the channel formed after the application of an acid treatment as a stimulation procedure of an oil reservoir, a method of EOR (Enhanced oil recovery). This treatment consists of a reactive fluid flow injected in the inner rock of the reservoir, which creates a preferential path (wormhole) that optimizes the extraction of the hydrocarbon fluids. / A microtomografia de raios-X permitiu a evolução de uma nova área da ciência aplicada a meios porosos: a Rocha Digital. Através desta técnica, todo o espaço poroso é recuperado, e é possível entender a dinâmica do fluido que o permeia através de simulações computacionais. No entanto, ainda há a questão de como a estrutura do meio influencia nos resultados observados. Entender questões como connectividade e clusterização de regiões podem dar informações valiosas sobre como a origem do meio poroso influencia na dinâmica do fluido que o permeia. Esta avaliação do meio é possível através da simplificação do mesmo em uma rede de conexão de elementos básicos e as interações entre estes. O problema com a descrição do meio poroso em uma rede de conexão é que não existe um consenso na definição destes elementos básicos. O propósito deste trabalho foi encontrar uma maneira de descrever o meio que fosse aplicável a qualquer litologia, e que se aproximasse ao máximo dos dados extraídos pela micro tomografia para a análise das topologias de diferentes rochas através de teoria de redes complexas.Para isso, utilizamos o algoritmo robusto de extração de redes de poros, esferas máximas, como base para dividir o espaço-poroso em células esféricas. Desta forma, todo o volume do espaço poroso observado através da micro tomografia é recuperado e descrito em uma rede de conexão. O resultado final do método aplicado é uma rede que descreve o meio completo e uma rede que descreve o eixo medial das interconexões entre poros. A geometria local dos poros é recuperada através de um critério de centralidade de rede, assim a separação é governada pela morfologia intrínseca das amostras, ao invés de fatores geométricos.Desta forma podemos analisar o efeito da tortuosidade real do meio, assim como a interconexão entre poros, com relação a permeabilidade do meio.O método se mostrou eficaz na análise de rochas com diferentes litologias: arenito (Berea) e carbonato (Estaillades). O método também foi aplicado na avaliação da estrutura de canais formados pelo processo de acidificação de rochas (wormholes).

<p>There is a seemingly endless miniaturization of electronic components, which has enabled designers to build sophisticated computing structureson silicon chips. Consequently, electronic systems are continuously improving with new and more advanced functionalities. Design complexity ofthese Systems on Chip (SoC) is reduced by the use of pre-designed cores. However, several problems related to the interconnection of coresremain. Network on Chip (NoC) is a new SoC design paradigm, which targets the interconnect problems using classical network concepts. Still,SoC cores show large variance in size and functionality, whereas several NoC benefits relate to regularity and homogeneity.</p><p>This thesis studies some network aspects which are characteristic to NoC systems. One is the issue of area wastage in NoC due to cores of varioussizes. We elaborate on using oversized regions in regular mesh NoC and identify several new design possibilities. Adverse effects of regions oncommunication are outlined and evaluated by simulation.</p><p>Deadlock freedom is an important region issue, since it affects both the usability and performance of routing algorithms. The concept of faultyblocks, used in deadlock free fault-tolerant routing algorithms has similarities with rectangular regions. We have improved and adopted one suchalgorithm to provide deadlock free routing in NoC with regions. This work also offers a methodology for designing topology agnostic, deadlockfree, highly adaptive application specific routing algorithms. The methodology exploits information about communication among tasks of anapplication. This is used in the analysis of deadlock freedom, such that fewer deadlock preventing routing restrictions are required.</p><p>A comparative study of the two proposed routing algorithms shows that the application specific algorithm gives significantly higher performance.But, the fault-tolerant algorithm may be preferred for systems requiring support for general communication. Several extensions to our work areproposed, for example in areas such as core mapping and efficient routing algorithms. The region concept can be extended for supporting reuse ofa pre-designed NoC as a component in a larger hierarchical NoC.</p>

Growing complexity of Systems on Chip (SoC) introduces interconnection problems. As a solution for communication bottleneck the new paradigm, Networks on Chip (NoC), has been proposed. Along with high performance and reliability, NoC brings in area and energy constraints. In this thesis we mainly concentrate on keeping communication-centric design environment fault-tolerant while considering area overhead. The previous researches suggest the adoption solution for fault-tolerance from multiprocessor architectures. However, multiprocessor architectures have excessive reliance on buffering leading to costly solutions. We propose to reconsider general router model by introducing central buffers which reduces buffer size. Besides, we offer a new fault-tolerant routing algorithm which effectively utilizes buffers at hand without additional buffers out of detriment to performance.

M. Tech. Electrical Engineering. / Aims to develope a detection procedure whose objective function is to try as much as possible not to impact heavily on the resource constrained sensor nodes.

An open queueing network model (QNM) is proposed for wormhole-routed hypercubes with finite buffers and deterministic routing subject to a compound Poisson arrival process (CPP) with geometrically distributed batches or, equivalently, a generalised exponential (GE) interarrival time distribution. The GE/G/1/K queue and appropriate GE-type flow formulae are adopted, as cost-effective building blocks, in a queue-by-queue decomposition of the entire network. Consequently, analytic expressions for the channel holding time, buffering delay, contention blocking and mean message latency are determined. The validity of the analytic approximations is demonstrated against results obtained through simulation experiments. Moreover, it is shown that the wormholerouted hypercubes suffer progressive performance degradation with increasing traffic variability (burstiness).

The X-Ray imaging technology opened a new branch of science in which the internal porous structure can be captured and the reconstructed volume can be used for fluid flow simulations and structural measurements. However, there is still the question of how the internal structure of the pore space impacts in the observed simulations. A way to characterize this internal structure is by simplifying it into well-defined elements and the interaction between them, describing it as a network. The interaction between elements are the edges of the network and elements are the nodes. This opens the possibility of applying complex network theory on the characterization of porous media which has proven to give powerful insights into how the structure of porous materials influences on the dynamics of the permeating fluid. The problem with this description is in definition of the basic elements that will compose the network, since there isnt a consensus on this definition. The purpose of this work is to provide a method to analyze &mu;CT data through networks in which the separation of the space is done in a semi-continuous method. The recovering of the pores local geometry is captured through a network analysis method of centrality, instead of a geometrical definition. This way the intrinsic morphology of the samples is what governs the pore-space separation into different entities. The method developed is based on the network extraction method Max Spheres Algorithm (MSA). The volumetric data is recovered through a network composed by sphere cells. The output of this process are two distinct networks: the complete volume network and a network which represents the variation of the channels diameter. These networks give unbiased real information on pore connectivity and can provide important data to better understand the morphology and topology of the samples. This method was successfully applied to samples of Berea sandstone, Estaillades carbonate, and to characterize the morphology of wormholes. Wormhole is the denomination of the channel formed after the application of an acid treatment as a stimulation procedure of an oil reservoir, a method of EOR (Enhanced oil recovery). This treatment consists of a reactive fluid flow injected in the inner rock of the reservoir, which creates a preferential path (wormhole) that optimizes the extraction of the hydrocarbon fluids. / A microtomografia de raios-X permitiu a evolução de uma nova área da ciência aplicada a meios porosos: a Rocha Digital. Através desta técnica, todo o espaço poroso é recuperado, e é possível entender a dinâmica do fluido que o permeia através de simulações computacionais. No entanto, ainda há a questão de como a estrutura do meio influencia nos resultados observados. Entender questões como connectividade e clusterização de regiões podem dar informações valiosas sobre como a origem do meio poroso influencia na dinâmica do fluido que o permeia. Esta avaliação do meio é possível através da simplificação do mesmo em uma rede de conexão de elementos básicos e as interações entre estes. O problema com a descrição do meio poroso em uma rede de conexão é que não existe um consenso na definição destes elementos básicos. O propósito deste trabalho foi encontrar uma maneira de descrever o meio que fosse aplicável a qualquer litologia, e que se aproximasse ao máximo dos dados extraídos pela micro tomografia para a análise das topologias de diferentes rochas através de teoria de redes complexas.Para isso, utilizamos o algoritmo robusto de extração de redes de poros, esferas máximas, como base para dividir o espaço-poroso em células esféricas. Desta forma, todo o volume do espaço poroso observado através da micro tomografia é recuperado e descrito em uma rede de conexão. O resultado final do método aplicado é uma rede que descreve o meio completo e uma rede que descreve o eixo medial das interconexões entre poros. A geometria local dos poros é recuperada através de um critério de centralidade de rede, assim a separação é governada pela morfologia intrínseca das amostras, ao invés de fatores geométricos.Desta forma podemos analisar o efeito da tortuosidade real do meio, assim como a interconexão entre poros, com relação a permeabilidade do meio.O método se mostrou eficaz na análise de rochas com diferentes litologias: arenito (Berea) e carbonato (Estaillades). O método também foi aplicado na avaliação da estrutura de canais formados pelo processo de acidificação de rochas (wormholes).

Mobile Ad Hoc Network (MANET) is a collection of communication devices or nodes that wish to communicate without any fixed infrastructure and pre-determined organization of available links. The nodes in MANET themselves are responsible for dynamically discovering other nodes to communicate. Although the ongoing trend is to adopt ad hoc networks for commercial uses due to their certain unique properties, the main challenge is the vulnerability to security attacks. A number of challenges like open peer-to-peer network architecture, stringent resource constraints, shared wireless medium, dynamic network topology etc. are posed in MANET. As MANET is quickly spreading for the property of its capability in forming temporary network without the aid of any established infrastructure or centralized administration, security challenges has become a primary concern to provide secure communication. In this thesis, we identify the existent security threats an ad hoc network faces, the security services required to be achieved and the countermeasures for attacks in each layer. To accomplish our goal, we have done literature survey in gathering information related to various types of attacks and solutions, as well as we have made comparative study to address the threats in different layers. Finally, we have identified the challenges and proposed solutions to overcome them. In our study, we have found that necessity of secure routing protocol is still a burning question. There is no general algorithm that suits well against the most commonly known attacks such as wormhole, rushing attack etc. In conclusion, we focus on the findings and future works which may be interesting for the researchers like robust key management, trust based systems, data security in different layer etc. However, in short, we can say that the complete security solution requires the prevention, detection and reaction mechanisms applied in MANET.

With the increasing demand of computation capabilities, many-core processors are gain-ing more and more attention. As a communication subsystem many-core processors, Network-on-Chip (NoC) draws a lot of attention in the related research fields. A NoC is used to deliver messages among different cores. For many applications, timeliness is of great importance, especially when the application has hard real-time requirements. Thus, the worst-case end-to-end delays of all the messages passing through a NoC should be concerned. Unfortunately, there is no existing analysis tool that can support multiple NoC architectures as well as provide a user-friendly interface.This thesis focuses on a wormhole switched NoC using different arbitration policies which are Fixed Priority (FP) and Round Robin (RR) respectively. FP based arbitration policy includes distinct and shared priority based arbitration policies. We have developed a timing analysis tool targeting the above NoC designs. The Graphical User Interface (GUI) in the tool can simplify the operation of users. The tool takes characteristics of flow sets as input, and returns results regarding the worst-case end-to-end delay of each flow. These results can be used to assist the design of real-time applications on the corre-sponding platform.A number of experiments have been generated to compare different arbitration mecha-nisms using the developed tool. The evaluation focuses on the effect of different param-eters including the number of flows and the number of virtual-channels in a NoC, and the number of hops of each flow. In the first set of experiment, we focus on the schedulabil-ity ratio achieved by different arbitration policies regarding the number of flows. The sec-ond set of experiments focus on the comparison between NoCs with different number of virtual-channels. In the last set of experiments, we compare different arbitration mecha-nisms with respect to the worst-case end-to-end latencies.

There is a seemingly endless miniaturization of electronic components, which has enabled designers to build sophisticated computing structureson silicon chips. Consequently, electronic systems are continuously improving with new and more advanced functionalities. Design complexity ofthese Systems on Chip (SoC) is reduced by the use of pre-designed cores. However, several problems related to the interconnection of coresremain. Network on Chip (NoC) is a new SoC design paradigm, which targets the interconnect problems using classical network concepts. Still,SoC cores show large variance in size and functionality, whereas several NoC benefits relate to regularity and homogeneity. This thesis studies some network aspects which are characteristic to NoC systems. One is the issue of area wastage in NoC due to cores of varioussizes. We elaborate on using oversized regions in regular mesh NoC and identify several new design possibilities. Adverse effects of regions oncommunication are outlined and evaluated by simulation. Deadlock freedom is an important region issue, since it affects both the usability and performance of routing algorithms. The concept of faultyblocks, used in deadlock free fault-tolerant routing algorithms has similarities with rectangular regions. We have improved and adopted one suchalgorithm to provide deadlock free routing in NoC with regions. This work also offers a methodology for designing topology agnostic, deadlockfree, highly adaptive application specific routing algorithms. The methodology exploits information about communication among tasks of anapplication. This is used in the analysis of deadlock freedom, such that fewer deadlock preventing routing restrictions are required. A comparative study of the two proposed routing algorithms shows that the application specific algorithm gives significantly higher performance.But, the fault-tolerant algorithm may be preferred for systems requiring support for general communication. Several extensions to our work areproposed, for example in areas such as core mapping and efficient routing algorithms. The region concept can be extended for supporting reuse ofa pre-designed NoC as a component in a larger hierarchical NoC.

In the past, various approaches to the high performance numerical computing problem have been explored. Recently, researchers have begun to explore the possibilities of using Field Programmable Gate Arrays (FPGAs) to solve numerically intensive problems. FPGAs offer the possibility of customization to any given application, while not sacrificing applicability to a wide problem domain. Further, the implementation of data flow graphs directly in silicon makes FPGAs very attractive for these types of problems. Unfortunately, current FPGAs suffer from a number of inadequacies with respect to the task. They have lower transistor densities than ASIC solutions, and hence less potential computational power per unit area. Routing overhead generally makes an FPGA solution slower than an ASIC design. Bit-oriented computational units make them unnecessarily inefficient for implementing tasks that are generally word-oriented. And finally, in large volumes, FPGAs tend to be more expensive per unit due to their lower transistor density. To combat these problems, researchers are now exploiting the unique advantage that FPGAs exhibit over ASICs: reconfigurability. By customizing the FPGA to the task at hand, as the application executes, it is hoped that the cost-performance product of an FPGA system can be shown to be a better solution than a system implemented by a collection of custom ASICs. Such a system is called a Configurable Computing Machine (CCM). Many aspects of the design of the FPGAs available today hinder the exploration of this field. This thesis addresses many of these problems and presents the embodiment of those solutions in the Colt CCM. By offering word grain reconfiguration and the ability to partially reconfigure at computational element resolution, the Colt can offer higher effective utilization over traditional FPGAs. Further, the majority of the pins of the Colt can be used for both normal I/O and for chip reconfiguration. This provides higher reconfiguration bandwidth contrasted with the low percentage of pins used for reconfiguration of FPGAs. Finally, Colt uses a distributed reconfiguration mechanism called Wormhole Run-Time Reconfiguration (RTR) that allows multiple data ports to simultaneously program different sections of the chip independently. Used as the primary example of Wormhole RTR in the patent application, Colt is the first system to employ this computing paradigm. / Ph. D.