Biography:

One of their most recent publications is A multi-stage non-deterministic model for project scheduling under resources constraints. Which was published in journal European Journal of Operational Research.

More information about L. Valadares Tavares research including statistics on their citations can be found on their Copernicus Academic profile page.

L. Valadares Tavares's Articles: (5)

A multi-stage non-deterministic model for project scheduling under resources constraints

AbstractNowadays the general purpose of project scheduling is the development of decision-aids to help managers improving the planning, the programming and the control of their projects. This target is hard to be achieved because projects have complex descriptions and because such decisions include multiple choices about the allocation of resources and the project calendar, which have to be improved in terms of several criteria such as total duration, net present value, risk of failing to meet the planned durations for important fractions of the project, etc.A review of the major approaches adopted to describe projects in terms of time and resources is presented in this paper showing that, unfortunately, too large deterministic models are usually obtained for projects with a realistic size.A new formulation of the general problem of project scheduling under resources constraints is proposed in this paper considering the project as a sequence of stages. According to this approach, the project can be studied as a sequence of decisions on resources allocation where each time interval between successive decisions (stage duration) is explicitly formulated as a decision variable.This formulation is very powerful and flexible as it avoids large amounts of binary variables and it allows progressive levels of detail concerning the discretization of the project schedule.Also, non-deterministic attributes can be introduced and the optimization problem can be easily solved for most common objective functions.Analytical solutions can also be deduced using the proposed model if specific hypotheses about the restrictions on durations and resources are assumed.

The strategic development of human resources: The challenge of OR

AbstractThe relevance and utility of OR methodology and techniques to support the design and implementation of strategies to qualify and upgrade human resources are scrutinized in this ppaper identifying priority areas to receive support from OR.

A comparative morphologic analysis of benchmark sets of project networks

AbstractThe performance of methods to manage projects depends heavily on the features of their project networks. This is particularly true for methods devoted to project scheduling, risk analysis and resources allocation. Therefore, a long line of research has been developed to generate benchmark sets of project networks and several sets have been proposed in the literature. Unfortunately, no comparative analyses of their features were published and hence serious doubts about the comparability of results using different benchmark sets can be raised. In this paper, a multi-dimensional taxonomy for the morphology of project networks is used and four benchmark sets are evaluated: Patterson collection of problems (Patterson JH. A comparison of exact approaches for solving the multiple constrained resource, project scheduling problem. Management Science 1984;30:854–867) and the sets produced by the generators due to Agrawal et al. Agrawal MK, Elmaghraby SE, Herroelen WS. DAGEN a generator of testsets for project activity nets. European Journal of Operational Research 1996;90:376–382, Kolisch et al. Kolisch R, Sprecher A, Drexl A. Characterization and generation of a general class of resource — constrained project scheduling problems. Management Science 1995;41:1693–1703, Tavares Tavares LV. Advanced models in project management. Kluwer, 1999 and Tavares et al. Tavares LV, Antunes Ferreira JA, Coelho JS. The risk of delay of a project in terms of the morphology of its network. European Journal of Operational Research 1999;119:510–537. Original results about the lack of representativeness of these sets are obtained showing that misleading conclusions can be deduced. The last set is, by far, that one covering most extensively the morphologic space of instances which could be foreseen because the generation of networks is carried out in terms of an wider range of parameters. This conclusion is quite useful for project managers willing to assess alternative methods to solve their problems based on project networks.

An acyclic outranking model to support group decision making within organizations

AbstractA model to support group decision making within the board of any organization to select an alternative from a short list is proposed using a pairwise relation: consensus relation.This relation avoids elementary cyclicity which is a general shortcoming of previous models and satisfies transitivity under special conditions (weak transitivity). This relation is represented by a triangle-free graph and has important implications for Public Choice Theory such as the special relevance of the 2/3 majority rule and for Multicriteria Decision Making (MCDM) to improve outranking models.The proposed model can be easily applied as shown by the example presented.The contributions obtained from this model do not only include the selection of the recommended alternative(s) but also very useful representations and measures of the level of cultural consensus and dissent of the board members which can be used to improve their composition and behavior.

Invited ReviewA review of major paradigms and models for the design of civil engineering systems

AbstractIn this paper, the author presents the five classical paradigms of the process of design in civil engineering and identifies a new emerging paradigm: the interactive multi-attribute learning paradigm. This paradigm is studied in terms of actors, structures and OR instruments which can help to fulfil its application to modern design of civil engineering systems.

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