Papers by Jamilson Ramalho Dantas
Case Studies on Transport Policy, 2021
Abstract Mobility issues may create various inconveniences in urban areas due to traffic light de... more Abstract Mobility issues may create various inconveniences in urban areas due to traffic light delays, traffic jams and acidents. Alternatives have been created to improve public transportation. One of them is the Bus rapid transit system (BRT), delivering convincing results from a cost-effective perspective; i.e., lower deployment costs and a greater number of passengers. This paper proposes a Stochastic Petri Net (SPN) model for performance evaluation of the BRT system, focusing on the mean system size, mean queue size, mean queue time and the probability that the user will miss the bus (discard probability). Scenarios based on the BRT system were created, improving a set of solutions being with a variation in headways and in the number of vehicles on the route. The results show that, from a management perspective, it is up to the decision maker to define which is the most important metric at a given moment and, thus, to define the start intervals, as well as the number of vehicles to have on the route. Under the perspective in study, the best scenario is presented with headways of 300s and 5 vehicles in the route, operating as the one that leads to lower waiting times for passengers.
Resumo. Tradicionalmente, pesquisadores utilizam simulações para testar redes ad hoc. No entanto,... more Resumo. Tradicionalmente, pesquisadores utilizam simulações para testar redes ad hoc. No entanto, a simulação de grandes redes ainda é uma tarefa muito tediosa que consome uma grande quantidade do poder computacional da ferramenta. A ferramenta de simulação a ser comparada é o JiST/SWANTS, que é relativamente nova e tem a promessa de fornecer importantes vantagens de desempenho em comparação a ferramenta mais utilizada, o NS-2. Este trabalho tem como objetivo principal, apresentar uma comparação entre os simuladores de redes ad hoc, utilizando o protocolo e o modelo de mobilidade implementados nos mesmo. Usando parâmetros idênticos de entrada, foram comparadas e analisadas as reais diferenças entre os simuladores.
Conference Proceedings - IEEE International Conference on Systems, Man and Cybernetics, 2012
ABSTRACT High availability in cloud computing services is essential for maintaining customer conf... more ABSTRACT High availability in cloud computing services is essential for maintaining customer confidence and avoiding revenue losses due to SLA violation penalties. Since the software and hardware components of cloud infrastructures may have limited reliability, fault tolerance mechanisms are a means of achieving the necessary dependability requirements. This paper investigates the benefits of a warm-standy replication mechanism in a Eucalyptus cloud computing environment. A hierarchical heterogeneous modeling approach is used to represent a redundant architecture and compare its availability to that of a non-redundant architecture. Both hardware and software failures are considered in the proposed analytical models. The results show an enhanced dependability for the proposed redundant system, as well as a decrease in the annual downtime. The results also demonstrate that the simple replacement of hardware by more reliable machines would not produce improvements in system availability to the same extent as would the fault tolerant approach.
Mathematical Problems in Engineering, 2014
For several years cloud computing has been generating considerable debate and interest within IT ... more For several years cloud computing has been generating considerable debate and interest within IT corporations. Since cloud computing environments provide storage and processing systems that are adaptable, efficient, and straightforward, thereby enabling rapid infrastructure modifications to be made according to constantly varying workloads, organizations of every size and type are migrating to web-based cloud supported solutions. Due to the advantages of the pay-per-use model and scalability factors, current video on demand (VoD) streaming services rely heavily on cloud infrastructures to offer a large variety of multimedia content. Recent well documented failure events in commercial VoD services have demonstrated the fundamental importance of maintaining high availability in cloud computing infrastructures, and hierarchical modeling has proved to be a useful tool for evaluating the availability of complex systems and services. This paper presents an availability model for a video s...
10th International Conference on Network and Service Management (CNSM) and Workshop, 2014
Due to advantages such as the pay-per-use model and a highly scalable environment, cloud infrastr... more Due to advantages such as the pay-per-use model and a highly scalable environment, cloud infrastructures are commonly employed by Video on Demand (VoD) streaming services to supply an extensive range of multimedia content to users. However, recent events have demonstrated to commercial VoD service providers the fundamental importance of ensuring highly available cloud computing infrastructures. This paper examines the effectiveness of applying availability modeling to a VoD cloud environment which has no redundancy mechanisms included in its architecture. The analysis employs a combinatorial modeling strategy consisting of RDB models and Markov chains. Sensitivity analysis is also applied to identify the critical points in the system with respect to availability. The outcome of the research clearly shows that the modeling strategy, together with the sensitivity analysis, has a key role to play in the identification of those components on which resources should be focused in order to achieve increased system availability
2013 IEEE International Conference on Systems, Man, and Cybernetics, 2013
ABSTRACT Cloud computing has expanded in recent years due to many effects, such as accessibility,... more ABSTRACT Cloud computing has expanded in recent years due to many effects, such as accessibility, reliability, and collaboration. To provide those functionalities high availability is in demand, which implies a higher electric energy consumption by the computers that support the cloud infrastructure. Studies that pay attention to this electric energy consumption are important due to its impact on sustainability and operational costs. This paper proposes a power load distribution algorithm (PLDA) to optimize electrical flows of power infrastructures. The PLDA adopts the Energy Flow Model (EFM) as its basis. The EFM is a model that computes sustainability impacts and cost issues, while it respects the energy providing restrictions of each component. In addition, a case study illustrates the applicability of the proposed PLDA through the analysis of six private cloud power architectures. Considerable results were observed, including a reduction on energy consumption of 10.7%, and an improvement (reduction) on the environmental impact of over 140% was obtained.
O presente trabalho tem por finalidade auxiliar e complementar o ensino-aprendizagem de disciplin... more O presente trabalho tem por finalidade auxiliar e complementar o ensino-aprendizagem de disciplinas nas areas de computacao, eletronica e mecânica com a utilizacao de um robo denominado RecArd. Na tentativa de contribuir para uma mudanca por meio da viabilizacao de aulas praticas, utilizou-se a plataforma de prototipagem Arduino e atraves desta montou-se o robo controlado com um smartphone e com capacidade de desviar de obstaculos. A ferramenta apresentou potencialidades que sao consideradas relevantes no processo de ensino-aprendizagem, principalmente, em areas multidisciplinares. Com base nos experimentos e resultados, pode-se indicar que o uso da robotica na educacao deve ser considerado como modelo reformulador de metodos de ensino.
As aplicações de Serious Games com foco na educação estão se tornando recorrentes e abrem caminho... more As aplicações de Serious Games com foco na educação estão se tornando recorrentes e abrem caminho para diversas vantagens dentro da sociedade e do mundo contemporâneo. Uma preocupação evidente é com a disciplina de física, em que a eletricidade é uma das áreas que possuem mais estudos referentes à dificuldade de aprendizagem devido à abstração do conteúdo. Portanto, o objetivo do presente artigo é descrever o desenvolvimento de uma metodologia que auxilie no ensino-aprendizagem de conteúdos de eletricidade básica de modo lúdico e educativo para os discentes. Para isso, foi desenvolvido o jogo da memória conhecido por Jogo Genius utilizando a Plataforma Arduíno. Com o jogo, os discentes foram incentivados a aprender de dois modos: o primeiro consistiu no interesse dos próprios estudantes instigados pela curiosidade provida por parte da Plataforma Arduíno e, posteriormente, pelo interesse oriundo do jogo. Além disso, foi possível auxiliar na didática do docente. As aulas tornaram-se mais práticas e mais voltadas à realidade. Os discentes puderam conhecer componentes eletrônicos e entender como esses funcionam.
Computing, 2015
High availability in cloud computing services is essential for maintaining customer confidence an... more High availability in cloud computing services is essential for maintaining customer confidence and avoiding revenue losses due to SLA violation penalties. Since the software and hardware components of cloud infrastructures may have limited reliability, the use of redundant components and multiple clusters may be required to achieve the expected level of dependability while also increasing the computational capacity. A drawback of such improvements is the respective impact on the capital and increase in acquisition and operational costs. This paper presents availability models for private cloud architectures based on Eucalyptus platform, and presents a comparison of costs between these architectures and similar infrastructure rented from a public cloud provider. Metrics for capacity-oriented availability and system steady-state availability are used to compare architectures with distinct numbers of clusters. A heterogeneous hierarchical modeling approach is employed to represent the systems considering both hardware and software failures. The results highlight that improvements on the availability are not significant when increasing the system to more than two clusters. The analysis also shows that the average available capacity is close to the maximum possible capacity in all architectures, and that it takes 18 months, in average, for these private cloud architectures to pay off the cost equivalent to the computational capacity rented from a public cloud.
Energies, 2020
The Internet has been going through significant transformations and changing the world around us.... more The Internet has been going through significant transformations and changing the world around us. We can also see the Internet to be used in many areas, for innumerable purposes, and, currently, it is even used by objects. This evolution leads to the Internet of Things (IoT) paradigm. This new concept can be defined as a system composed of storage resources, sensor devices, controllers, applications, and network infrastructure, in order to provide specific services to its users. Since IoT comprises heterogeneous components, the creation of these systems, the communication, and maintenance of their components became a complex task. In this paper, we present a dependability model to evaluate an IoT system. Amid different systems, we chose to assess availability in a smart building. The proposed models allow us to calculate estimations of other measures besides steady-state availability, such as reliability. Thus, it was possible to notice that there was no considerable gain of availab...
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Papers by Jamilson Ramalho Dantas