No description available.

No description available.

In this work, two topics of reservoir simulations are discussed. The first topic is the two-phase compositional flow simulation in hydrocarbon reservoir. The major obstacle that impedes the applicability of the simulation code is the long run time of the simulation procedure, and thus speeding up the simulation code is necessary. Two means are demonstrated to address the problem: parallelism in physical space and the application of sparse grids in parameter space. The parallel code can gain satisfactory scalability, and the sparse grids can remove the bottleneck of flash calculations. Instead of carrying out the flash calculation in each time step of the simulation, a sparse grid approximation of all possible results of the flash calculation is generated before the simulation. Then the constructed surrogate model is evaluated to approximate the flash calculation results during the simulation. The second topic is the wormhole propagation simulation in carbonate reservoir. In this work, different from the traditional simulation technique relying on the Darcy framework, we propose a new framework called Darcy-Brinkman-Forchheimer framework to simulate wormhole propagation. Furthermore, to process the large quantity of cells in the simulation grid and shorten the long simulation time of the traditional serial code, standard domain-based parallelism is employed, using the Hypre multigrid library. In addition to that, a new technique called “experimenting field approach” to set coefficients in the model equations is introduced. In the 2D dissolution experiments, different configurations of wormholes and a series of properties simulated by both frameworks are compared. We conclude that the numerical results of the DBF framework are more like wormholes and more stable than the Darcy framework, which is a demonstration of the advantages of the DBF framework. The scalability of the parallel code is also evaluated, and good scalability can be achieved. Finally, a mixed finite element scheme is proposed for the wormhole simulation.

This thesis proposes an innovative wormhole detection scheme to detect wormhole attacks using computational intelligence and an artificial neural network (ANN). The aim of the proposed research is to develop a detection scheme that can detect wormhole attacks (In-band, out of band, hidden wormhole attack, active wormhole attack) in both uniformly and non-uniformly distributed sensor networks. Furthermore, the proposed research does not require any special hardware and causes no significant network overhead throughout the network. Most importantly, the probable location of the wormhole nodes can be tracked down by the proposed ANN-based detection scheme. We evaluate the efficacy of the proposed detection scheme in terms of detection accuracy, false positive rate, and false negative rate. The performance of the proposed model is also compared with other machine learning techniques (i.e. SVM and regularized nonlinear logistic regression (LR) based detection models) based detection schemes. The simulation results show that proposed ANN-based detection model outperforms the SVM and LR based detection schemes in terms of detection accuracy, false positive rate, and false negative rates. / February 2017

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Wormholes sÃo estruturas exÃticas que podem ligar regiÃes longÃnquas do espaÃo e por isso sÃo bastante visados como objeto de pesquisa. Pode-se mostrar que buracos negros possuem modos de vibraÃÃo amortecidos, os chamados de modos quase-normais. Esses modos sÃo responsÃveis por irradiar as ondas gravitacionais para espaÃo. Isso se deve ao fato de pequenas perturbaÃÃes na mÃtrica poderem ser descritas pelas equaÃÃes de Einstein, em forma de equaÃÃes de onda. Esse comportamento à semelhante para wormholes, onde devemos encontrar um potencial de Regge-Wheeler associado a equaÃÃo de onda. Nosso objetivo nesse trabalho serà tentar ver se à possÃvel encontrarmos um potencial do tipo Regge-Wheeler para um wormhole, que se supÃem ser sustentado pela matÃria escura na regiÃo dos halos galÃcticos. E por consequÃncia, verificarmos se à possÃvel determinar modos quase-normais usando o mÃtodo WKB, para esse wormhole em particular. / Wormholes are exotic structures that can connect distant regions of space and therefore are highly targeted as a research object. It can be shown that black holes have damped vibration modes, The so-called quasi-normal modes. These modes are responsible for radiating gravitational waves to space. This is due to the fact that small disturbances in the metric can be described by Einsteinâs equations, in the form of wave equations. This behavior is similar for wormholes, where we must find a Regge-Wheeler potential associated with the wave equation. Our goal in this work will be to see if it is possible to find Regge-Wheeler potential for a wormhole, Which are supposed to be sustained by dark matter in the region of galactic halos. And consequently, Verify if it is possible to determine quasi-normal modes using the WKB method, for that particular wormhole.

State-of-the-art onboard spacecraft avionics use SpaceWire networks to interconnect payload data-handling sub-systems. This includes high data-rate sensors and instruments, processing units, and memory devices. SpaceWire is an interconnection network composed of nodes and routers connected by bi-directional, point-to-point, high-speed, serial-data communication links. SpaceWire is established as one of the main data-handling protocols and is being used on many ESA, NASA and JAXA spacecraft. SpaceWire is very successful for being fast, flexible and simple to use and implement. However it does not implement Quality of Service mechanisms, which aim to provide guarantees in terms of reliability and timely delivery to data generated by network clients. Quality of Service is increasingly being deployed in commercial ground technologies and its availability for space applications, which requires high reliability and performance, is of high interest for the space community. This thesis researches how Quality of Service can be provided to existing SpaceWire networks. Existing solutions for ground-based technologies cannot be directly used because of the constraints imposed by the limitations of space-qualified electronics. Due to these limitations SpaceWire uses wormhole routing which has many benefits but makes it more challenging to obtain timing guarantees and to achieve a deterministic behaviour. These challenges are addressed in this work with a careful analysis of existing Quality of Service techniques and the implementation of a novel set of protocols specifically designed for SpaceWire networks. These new protocols target specific use cases and utilise different mechanisms to achieve the required reliability, timely delivery and determinism. Traditional and novel techniques are deployed for first time in SpaceWire networks. In particular, segmentation, acknowledgements, retry, time-division multiplexing an cross-layer techniques are considered, analysed, implemented and evaluated with extensive prototyping efforts. SpaceWire provides high-rate data transfers but the next generation of payload instruments are going to require multi-gigabit capabilities. SpaceFibre is a new onboard networking technology under development which aims to satisfy these new requirements, keeping compatibility with SpaceWire user-applications. As a new standard, SpaceFibre offers the opportunity to implement Quality of Service techniques without the limitations imposed by the SpaceWire standard. The last part of this thesis focuses on the specification of the SpaceFibre standard in order to provide the Quality of Service required by next generation of space applications. This work includes analytical studies, software simulations, and hardware prototyping of new concepts which are the basis of the Quality of Service mechanisms defined in the new SpaceFibre standard. Therefore, a critical contribution is made to the definition and evaluation of a novel Quality of Service solution which provides high reliability, bandwidth reservation, priority and deterministic delivery to SpaceFibre links.

OLIVEIRA, R. dos. Wormhole do halo central da galáxia e modos quase-normais. 2017. 79 f. Dissertação (Mestrado em Física) – Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Giordana Silva (giordana.nascimento@gmail.com) on 2017-04-12T22:32:15Z No. of bitstreams: 1 2017_dis_roliveira.pdf: 2016508 bytes, checksum: b13e51c1946445379ebd0aa6da75f18b (MD5) / Approved for entry into archive by Giordana Silva (giordana.nascimento@gmail.com) on 2017-04-12T22:32:44Z (GMT) No. of bitstreams: 1 2017_dis_roliveira.pdf: 2016508 bytes, checksum: b13e51c1946445379ebd0aa6da75f18b (MD5) / Made available in DSpace on 2017-04-12T22:32:44Z (GMT). No. of bitstreams: 1 2017_dis_roliveira.pdf: 2016508 bytes, checksum: b13e51c1946445379ebd0aa6da75f18b (MD5) Previous issue date: 2017 / Wormholes are exotic structures that can connect distant regions of space and therefore are highly targeted as a research object. It can be shown that black holes have damped vibration modes, The so-called quasi-normal modes. These modes are responsible for radiating gravitational waves to space. This is due to the fact that small disturbances in the metric can be described by Einstein’s equations, in the form of wave equations. This behavior is similar for wormholes, where we must find a Regge-Wheeler potential associated with the wave equation. Our goal in this work will be to see if it is possible to find Regge-Wheeler potential for a wormhole, Which are supposed to be sustained by dark matter in the region of galactic halos. And consequently, Verify if it is possible to determine quasi-normal modes using the WKB method, for that particular wormhole. / Wormholes são estruturas exóticas que podem ligar regiões longínquas do espaço e por isso são bastante visados como objeto de pesquisa. Pode-se mostrar que buracos negros possuem modos de vibração amortecidos, os chamados de modos quase-normais. Esses modos são responsáveis por irradiar as ondas gravitacionais para espaço. Isso se deve ao fato de pequenas perturbações na métrica poderem ser descritas pelas equações de Einstein, em forma de equações de onda. Esse comportamento é semelhante para wormholes, onde devemos encontrar um potencial de Regge-Wheeler associado a equação de onda. Nosso objetivo nesse trabalho será tentar ver se é possível encontrarmos um potencial do tipo Regge-Wheeler para um wormhole, que se supõem ser sustentado pela matéria escura na região dos halos galácticos. E por consequência, verificarmos se é possível determinar modos quase-normais usando o método WKB, para esse wormhole em particular.

No description available.

Configurable Computing is a technology which attempts to increase computational power by customizing the computational platform to the specific problem at hand. An experimental computing model known as wormhole run-time reconfiguration allows for partial reconfiguration and is highly scalable. In this approach, configuration information and data are grouped together in a computing unit called a stream, which can tunnel through the chip creating a series of interconnected pipelines. The Colt/Stallion project at Virginia Tech implements this computing model into integrated circuits. In order to create applications for this platform, a compiler is needed which can convert a human readable description of an algorithm into the sequences of configuration information understood by the chip itself. This thesis covers two compilers which perform this task. The first compiler, Tier1, requires a programmer to explicitly describe placement and routing inside of the chip. This could be considered equivalent to an assembler for a traditional microprocessor. The second compiler, Tier2, allows the user to express a problem as a dataflow graph. Actual placing and routing of this graph onto the physical hardware is taken care of through the use of a genetic algorithm. A description of the two languages is presented, followed by example applications. In addition, experimental results are included which examine the behavior of the genetic algorithm and how alterations to various genetic operator probabilities affects performance. / Master of Science

SpaceWire est un standard de réseau embarqué promu par l'Agence Spatiale Européenne qui envisage de l'utiliser comme réseau bord unique dans ses futures satellites. SpaceWire utilise un mécanisme de routage Wormhole pour réduire la consommation mémoire des routeurs et les coûts associés. Cependant,le routage Wormhole peut engendrer des blocages en cascade dans les routeurs et, par conséquent,d'importantes variations des délais de livraison des paquets.Comme le réseau doit être partagé par des flux critiques et non-critiques, les concepteurs réseau ont besoin d'un outil leur permettant de vérifier le respect des contraintes temporelles des messages critiques. Pour réaliser cet outil, nous avons choisi comme métrique une borne supérieure sur le délai pire-cas de bout en bout d'un paquet traversant un réseau SpaceWire. Au cours de la thèse, nous avons proposé trois méthodes permettant de calculer cette borne. Les trois méthodes utilisent des hypothèses différentes et ont chacune des avantages et des inconvénients. D'une part, les deux premières méthodes sont très générales et ne nécessitent pas d'hypothèses restrictives sur le trafic en entrée du réseau. D'autre part, la troisième méthode nécessite des hypothèses plus précises sur le trafic en entrée. Elle est donc moins générale mais donne la plupart du temps des bornes plus serrées que les deux autres méthodes. Dans cette thèse, nous avons appliqué ces différentes méthodes à une architecture de référence fournie par Thales Alenia Space afin d'en comparer les résultats. Nous avons également appliqué ces méthodes à des exemples plus simples afin de déterminer l'influence de différents paramètres sur les bornes fournies par nos méthodes. / The SpaceWire network standard is promoted by the ESA and is scheduled to be used as the sole onboard network for future satellites. SpaceWire uses a wormhole routing mechanism to reduce memoryconsumption and the associated costs. However, wormhole routing can lead to packet blocking in routerswhich creates large variations in end-to-end delays. As the network will be shared by real-time and nonreal-time traffic, network designers require a tool to check that temporal constraints are verified for allthe critical messages. The metric we chose for this tool is an upper-bound on the worst-case end-to-enddelay of a packet traversing a SpaceWire network. This metric is simpler to compute than the exact delayof each packet and provide enough guarantee to the network designers. During the thesis, we designed three methods to compute this upper-bound. The three methods use different assumptions and have different advantages and drawbacks. On the one hand, the first two methods are very general and do not require strong assumptions on the input traffic. On the other hand, the third method requires more specific assumptions on the input traffic. Thus, it is less general but usually gives tighter bounds than the two other methods. In the thesis, we apply those methods to a case study provided by Thales Alenia Space and compare the results. We also compare the three methods on several smaller networks to study the impact of various parameters on their results.