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Scheduling Operations and SMED: Complementary Ways to Improve Productivity
Publication . Santos, Fernando Charrua; Santos, Beatrice Paiva; Calderón-Arce, Cindy; Figueroa-Mata, Geovanni; Lima, Tânia M.
In most real cases the problem of scheduling operations are sequence de-pendent, that is, the setup time depends on the sequencing of tasks/batches in the ma-chine. Given the current industrial manufacturing trends and requirements such as high variability, customization and reduction of product life cycles, organizations seek to implement new methodologies to adapt and respond with more flexibly to new demands of the global markets. Thus, this work sought to analyse, inspired by a real case of the textile industry, how production scheduling can be understood as a complement to SMED in order to achieve productivity improvement. In the case under analysis we presented the problem of scheduling tasks in uniform parallel machines with sequence-dependent setup times. The main objective of this work was to minimize the total pro-duction time. To this goal, optimization heuristics were used, in this case, simulated annealing algorithm, that demonstrated how the use of heuristics can be an advantage to reduce setup times when associated with other methodologies such as SMED.
Parametric study by means of 3D CFD to improve the airflow pattern and temperature distribution in data center rooms
Publication . Macedo, Diogo Gonçalves Costa e Silva de; Godina, Radu; Gaspar, Pedro Dinis; Silva, Pedro Dinho da; Covas, Miguel Trigueiros
The processing efficacy and energy efficiency of data centers (DC) is directly related with the cooling
performance of the air-conditioning systems. The cooling effectiveness depends on airflow pattern
and temperature distribution. This paper presents the parametric study of three-dimensional (3D)
computational fluid dynamics (CFD) models to improve these technical characteristics. In this case
study the most suitable thermal load, as deemed by the organization, of the heat flow boundary
condition is simulated and studied for maximum and minimum airflow. The analysis of the numerical
results provides a prediction of the thermal performance, i.e., the lower values and spatial gradients
(hot spots) of air temperature and velocity while maintaining the computational processing
requirements. These results allow the development of an optimized CFD model for setting up the
operational parameters of CRAC systems for DC rooms.
Comparison of DBD plasma actuators flow control authority in different modes of actuation
Publication . Abdollahzadehsangroudi, M.; Páscoa, J.C.; Oliveira, P.J.
The principal mechanisms by which DBD plasma actuators influence flow characteristics, and are thus able to control that flow, depend strongly on their modes of actuation. Here two different modes based on steady and unsteady actuation are compared and investigated. A simple sinusoidal voltage distribution and a duty cycled sinusoidal voltage were considered for these purposes. Leading edge separation around a stalled NACA 0012 airfoil at Re=3 ×10^16 is considered as test case. A simplified phenomenological model which uses the correct scale of the plasma body force is considered for the modeling of the plasma actuator effects. The steady actuation results show that flow control can be effectively achieved by this mode of operation with continuous injection of momentum in the boundary layer. Unsteady actuation with an imposed frequency equal to the calculated natural frequencies of the flow gives rise to a resonance actuation effect.
Optimization of FPSO Glen Lyon Mooring Lines
Publication . Figueiredo, Paulo Alexandre Rodrigues de Vasconcelos; Brojo, Francisco Miguel Ribeiro Proença
During oil and gas inspection and extraction operations both in deep and ultra-deep water, vessel
mooring is a very important factor for the development of oil fields. For these depths, standard
stand-alone surface facilities e.g. jack up rigs or offshore fixed platforms are not suitable
due to the harsh collinear and non-collinear environment in-situ (location, waves, surface and
underwater current, sea tides, ice, etc.). For deep sea wells clusters, it is usual to use floating
production storage offloading (FPSO) as surface platforms for long time exploitation periods.
Subsea expenditure, refers the cost of the subsea project and generally includes the capital
expenditures (capex) and operational expenditures (opex). In the production of hydrocarbons
capex and opex exponentially increases with increasing depth, resulting in a need for precise detailed
design phase for analysis of systems to verify components strength, ductility and fatigue,
stiffness, instabilities, corrosion etc.
The design of oilfields is most of the times overrated (in a very conservative way) due to several
requirements and complex models of costs evaluation. After detailed phase and installation
of all facilities and components, as well as due to the expected life design for hydrocarbons
exploitation all anchoring system shall withstand the environmental loads in order to not compromise
the operation.
Each oilfield has a unique development, since environmental phenomena are unique in each
earth location. This work refers to the optimization process of an anchoring system for deep
waters in the Schiehallion Field, or in other words, the complete development of the mooring
system for a FPSO, from the positioning in-situ with environmental conditions and vessel
characteristics (Orcaflex), further optimization of the mooring system for an equivalent system
(Matlab), mechanical design of the mooring system (CATIA), structural detailed analysis (Altair
and Nastran) as fatigue life analysis.
In order to reproduce all the mooring process, it is performed and initial comparison of the
former FPSO (Schiehallion FPSO) that has been working in-situ since 1993 till its replacement for
the new vessel (Glen Lyon FPSO). Due to the latest discoveries in the oilfield, the project has to
be redesigned alongside with former wells and having in consideration recent discovered wells.
Further optimization of the complete fixation system was verified as well as finally detailed
structural analysis of specific components in key locations with higher margin of failure.
Within this work, all the methodology which led to the optimization of Glen Lyon mooring lines
was fully detailed from vessel analysis to detailed mooring mechanical design, constraints and
requirements were applied, trade-offs and assumptions made during this critical development
phase are presented and discussed.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
5876
Funding Award Number
UID/EMS/00151/2013