6,277 research outputs found
Uma metaheurÃstica para a programação de projectos com multi-modos e recursos limitados
Este artigo apresenta uma nova abordagem (MM-GAV-FBI), aplicável ao
problema da programação de projectos com restrições de recursos e vários modos de execução
por actividade, problema conhecido na literatura anglo-saxónica por MRCPSP. Cada projecto
tem um conjunto de actividades com precedências tecnológicas definidas e um conjunto de
recursos limitados, sendo que cada actividade pode ter mais do que um modo de realização. A
programação dos projectos é realizada com recurso a um esquema de geração de planos
(do inglês Schedule Generation Scheme - SGS) integrado com uma metaheurÃstica. A
metaheurÃstica é baseada no paradigma dos algoritmos genéticos. As prioridades das
actividades são obtidas a partir de um algoritmo genético. A representação cromossómica
utilizada baseia-se em chaves aleatórias. O SGS gera planos não-atrasados. Após a
obtenção de uma solução é aplicada uma melhoria local. O objectivo da abordagem é
encontrar o melhor plano (planning), ou seja, o plano que tenha a menor duração
temporal possÃvel, satisfazendo as precedências das actividades e as restrições de
recursos. A abordagem proposta é testada num conjunto de problemas retirados da
literatura da especialidade e os resultados computacionais são comparados com outras
abordagens. Os resultados computacionais validam o bom desempenho da abordagem,
não apenas em termos de qualidade da solução, mas também em termos de tempo útil.As the complexity of projects increases, the requirement of an organized
planning and scheduling process is enhanced. The need for organized planning and scheduling
of a construction project is influenced by a variety of factors (e.g., project size and number of
project activities). To plan and schedule a construction project, activities must be defined
sufficiently. The level of detail determines the number of activities contained within the
project plan and schedule. So, finding feasible schedules which efficiently use scarce resources is a challenging task within project management. In this context, the well-known
Resource Constrained Project Scheduling Problem (RCPSP) has been studied during the last
decades. In the RCPSP the activities of a project have to be scheduled such that the makespan
of the project is minimized. So, the technological precedence constraints have to be observed
as well as limitations of the renewable resources required to accomplish the activities. Once
started, an activity may not be interrupted. This problem has been extended to a more realistic
model, the multi-mode resource constrained project scheduling problem (MRCPSP), where
each activity can be performed in one out of several modes. Each mode of an activity
represents an alternative way of combining different levels of resource requirements with a
related duration. Each renewable resource has a limited availability such as manpower and
machines for the entire project. The objective of the MRCPSP problem is minimizing the
makespan. While the exact methods are available for providing optimal solution for small
problems, its computation time is not feasible for large-scale problems. This paper presents a
genetic algorithm-based approach (MM-GAV-FBI) for the multi-mode resource constrained
project scheduling problem. The idea of this new approach is integrating a genetic algorithm
with a schedule generation scheme. This study also proposes applying a local search
procedure trying to improve the initial solution. The chromosome representation of the
problem is based on random keys. The schedule is constructed using a schedule generation
scheme (SGS) in which the priorities of the activities are defined by the genetic algorithm.
The experimental results of MM-GAV-FBI on project instances show that this approach is an
effective method for solving the MRCPSP
Project scheduling under multiple resources constraints using a genetic algorithm
The resource constrained project scheduling problem (RCPSP) is a difficult problem in combinatorial
optimization for which extensive investigation has been devoted to the development of efficient algorithms.
During the last couple of years many heuristic procedures have been developed for this problem, but still these
procedures often fail in finding near-optimal solutions. This paper proposes a genetic algorithm for the resource
constrained project scheduling problem. The chromosome representation of the problem is based on random
keys. The schedule is constructed using a heuristic priority rule in which the priorities and delay times of the
activities are defined by the genetic algorithm. The approach was tested on a set of standard problems taken from
the literature and compared with other approaches. The computational results validate the effectiveness of the
proposed algorithm
A two-level genetic algorithm for the multi-mode resource-constrained project scheduling problem
This paper presents a genetic algorithm for the multimode
resource-constrained project scheduling problem (MRCPSP),
in which multiple execution modes are available for each of the
activities of the project. The objective function is the minimization of
the construction project completion time. To solve the problem, is
applied a two-level genetic algorithm, which makes use of two
separate levels and extend the parameterized schedule generation
scheme by introducing an improvement procedure. It is evaluated the
quality of the schedule and present detailed comparative
computational results for the MRCPSP, which reveal that this
approach is a competitive algorithm
Analysis of the velocity field of granular hopper flow
We report the analysis of radial characteristics of the flow of granular
material through a conical hopper. The discharge is simulated for various
orifice sizes and hopper opening angles. Velocity profiles are measured along
two radial lines from the hopper cone vertex: along the main axis of the cone
and along its wall. An approximate power law dependence on the distance from
the orifice is observed for both profiles, although differences between them
can be noted. In order to quantify these differences, we propose a Local Mass
Flow index that is a promising tool in the direction of a more reliable
classification of the flow regimes in hoppers
Applying semantic web technologies to knowledge sharing in aerospace engineering
This paper details an integrated methodology to optimise Knowledge reuse and sharing, illustrated with a use case in the aeronautics domain. It uses Ontologies as a central modelling strategy for the Capture of Knowledge from legacy docu-ments via automated means, or directly in systems interfacing with Knowledge workers, via user-defined, web-based forms. The domain ontologies used for Knowledge Capture also guide the retrieval of the Knowledge extracted from the data using a Semantic Search System that provides support for multiple modalities during search. This approach has been applied and evaluated successfully within the aerospace domain, and is currently being extended for use in other domains on an increasingly large scale
The alignment of the polarization of HAe/Be stars with the interstellar magnetic field
We present a study of the correlation between the direction of the symmetry
axis of the circumstellar material around intermediate mass young stellar
objects and that of the interstellar magnetic field. We use CCD polarimetric
data on 100 Herbig Ae/Be stars. A large number of them shows intrinsic
polarization, which indicates that their circumstellar envelopes are not
spherical. The interstellar magnetic field direction is estimated from the
polarization of field stars. There is an alignment between the position angle
of the Herbig Ae/Be star polarization and that of the field stars for the most
polarized objects. This may be an evidence that the ambient interstellar
magnetic field plays a role in shaping the circumstellar material around young
stars of intermediate mass and/or in defining their angular momentum axis.Comment: ApJ accepte
Enhancing elderly mobility through IoT using textiles: a review
The aging of population worldwide and the increasing of average life expectancy of the world population become a social and economic problem for society. It's necessary to provide solutions which can maintain the independency of elderly and their mobility, along more time, avoiding the unnecessary perma-nence in hospitals and institutions for the elderly. The use of IoT using textiles is a very interesting approach because of the proximity of people to these materials. This work reviews the development on IoT using textiles to increase the mobility of elderly people and concludes that this is a field of growing interest. Although, there is few investigation, especially in what concerns studies focusing on the im-portance of improving the mobility of the elderly. There are studies that lead to the possibility of promoting this physical capability but have not been designed for that purpose, but we believe that approach of the problem of mobility of elderly people using the IoT based on clothes should be treated with specificity, because the consequences of this not happening, will affect not only the elderly but the whole society.info:eu-repo/semantics/publishedVersio
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