Navegando por Assunto "Confiabilidade"

Agora exibindo 1 - 5 de 5

Acesso aberto (Open Access)
Confiabilidade aplicada à análise da estabilidade de taludes: um estudo de caso de uma encosta fluvial no norte amazônico
(Universidade Federal do Pará, 2021-04-02) NASCIMENTO, Rafael Silva do; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
Among the geotechnical structures, the river slopes stand out for the uncertainties in their properties. In addition, the use of coupled reliability methods in the analysis of slopes has grown, in contrast to deterministic methods that do not consider uncertainties. In this context, the present work presents the study of the reliability of a fluvial slope in the Amazon region that suffered a rupture. For this, three reliability methodologies were used (Monte Carlo, FOSM and PEM), using the limit equilibrium method and finite elements. The properties of the hillside soft clays were treated as random variables and the reliability indicators for each methodology were obtained. In addition, sensitivity analyzes of these parameters were carried out. The results of the slice models were compared to the numerical results. Finally, it was concluded that the uncertainties in the properties of soft soils were not sufficient to cause the rupture of the slope, therefore, another factor(s) must have triggered the rupture.
Acesso aberto (Open Access)
Cross-layer optimizations for multimedia distribution over Wireless Multimedia Sensor Networks and Flying Ad-Hoc Networks with quality of experience support
(Universidade Federal do Pará, 2014-07-16) ROSÁRIO, Denis Lima do; BRAUN, Torsten Ingo; http://lattes.cnpq.br/5439824326239585; CERQUEIRA, Eduardo Coelho; http://lattes.cnpq.br/1028151705135221
The proliferation of multimedia content and the demand for new audio or video services have fostered the development of a new era based on multimedia information, which allowed the evolution of Wireless Multimedia Sensor Networks (WMSNs) and also Flying Ad-Hoc Networks (FANETs). In this way, live multimedia services require realtime video transmissions with a low frame loss rate, tolerable end-to-end delay, and jitter to support video dissemination with Quality of Experience (QoE) support. Hence, a key principle in a QoE-aware approach is the transmission of high priority frames (protect them) with a minimum packet loss ratio, as well as network overhead. Moreover, multimedia content must be transmitted from a given source to the destination via intermediate nodes with high reliability in a large scale scenario. The routing service must cope with dynamic topologies caused by node failure or mobility, as well as wireless channel changes, in order to continue to operate despite dynamic topologies during multimedia transmission. Finally, understanding user satisfaction on watching a video sequence is becoming a key requirement for delivery of multimedia content with QoE support. With this goal in mind, solutions involving multimedia transmissions must take into account the video characteristics to improve video quality delivery. The main research contributions of this thesis are driven by the research question how to provide multimedia distribution with high energy-efficiency, reliability, robustness, scalability, and QoE support over wireless ad hoc networks. The thesis addresses several problem domains with contributions on different layers of the communication stack. At the application layer, we introduce a QoE-aware packet redundancy mechanism to reduce the impact of the unreliable and lossy nature of wireless environment to disseminate live multimedia content. At the network layer, we introduce two routing protocols, namely video-aware Multi-hop and multi-path hierarchical routing protocol for Efficient VIdeo transmission for static WMSN scenarios (MEVI), and cross-layer link quality and geographical-aware beaconless OR protocol for multimedia FANET scenarios (XLinGO). Both protocols enable multimedia dissemination with energy-efficiency, reliability and QoE support. This is achieved by combining multiple cross-layer metrics for routing decision in order to establish reliable routes.
Acesso aberto (Open Access)
Manutenção autônoma em uma lavadora de garrafas: estudo de caso
(Universidade Federal do Pará, 2021-08-26) SERRA NETO, Mário Reis; OLIVEIRA, Kleber Bittencourt; http://lattes.cnpq.br/3202890124751363
Due to the competitive drive and the search for continuous improvements at low cost, industrial maintenance has become a strategic factor in companies. Thus, the objective of this study is to analyze the performance of a piece of equipment and the applicability of autonomous maintenance and its gains. The methodology was based on the identification of efficiency gaps in a production line, correlated with the proper yield of each equipment in the production line, consequently with the equipment's failure modes. Through the collected data, several fronts were analyzed and failure analysis tools were used to take effective actions. It was concluded that it is possible to act preventively using autonomous maintenance, so that the machine operator can identify the problem in its initial phase and develop actions to definitively solve the problem.
Acesso aberto (Open Access)
Modelagem da disponibilidade de uma unidade geradora da UHE-Tucuruí
(Universidade Federal do Pará, 2013-07-04) MOREIRA, Pedro Igor Carvalho; NEVES, Renato Martins das; http://lattes.cnpq.br/6538317425557058
Since 2004, the regulatory rules in the Brazilian Electricity Sector has changed. The agents who act in this market have experienced a rise in new business disputes, showing an increase in competitiveness. The availability of physical assets and maintenance costs are presented as key points of these agents competitiveness. This work aims to present a methodology of Availability Analysis of Repairable Systems during the design or operational phases, covering the measurement of maintenance costs versus the acquisition costs to an expected performance level. The suggested methodology takes the System Block Diagram and exports to the Successful Tree Analysis format, composed by logic gates "AND" and "OR" where each represents a subsystem in the main system. The analyst may re-evaluate the system's topology, adding or removing redundancies in order to adjust the performance to the requirements of availability, acquisition and maintenance costs. As results of this work were identified gaps in the standards rules which defines how to control the assets performance, was established a systematic integration of modeling techniques for reliability and availability, performance indicators of Scheduled Maintenance were incorporated, different scenarios were modeled for an Oil Circulation System and was applied to an entire Hydraulic Generating Unit by modeling the critical components in the main systems.
Acesso aberto (Open Access)
Otimização da confiabilidade e usabilidade de testes funcionais de processo produtivo na empresa “tucumã sem casca” de cable modems do pólo industrial de Manaus
(Universidade Federal do Pará, 2022-03-21) BARBOSA FILHO, Geraldo Freitas; LEITE, Jandecy Cabral; http://lattes.cnpq.br/7279183940171317
The jig equipment responsible for the function tests are complex and highly capable machines used in the electronics industry to validate the functionality of analogic and digital devices or any other product of electronic factories of the industry pole of Manaus. In the studied process, those machines are operated in a series configuration, and the effect of a failure in this type of configuration is very critical, as the simplest failure can impact the production process and generate losses for the company. This work aims to assess the behavior of test equipment in a cable modem and set top box production processes, to make analysis of the failures happened during this production process, to guide a reliability study that enable the maintenance manager to make decisions about how to deal with equipment aiming to reduce failure rates and use proper maintenance practices to allow reliability to be maximized