9,496 research outputs found
A modied branch and cut procedure for resource portfolio problem under relaxed resource dedication policy
Multi-project scheduling problems are characterized by the way resources are
managed in the problem environment. The general approach in multi-project
scheduling literature is to consider resource capacities as a common pool that
can be shared among all projects without any restrictions or costs. The way
the resources are used in a multi-project environment is called resource management policy and the aforementioned assumption is called Resource Sharing
Policy in this study. The resource sharing policy is not a generalization
for multi-project scheduling environments and different resource management
policies maybe defined to identify characteristics of different problem environments.
In this study, we present a resource management policy which prevents sharing of resources among projects but allows resource transfers when a project starts after the completion of another one. This policy is called the Relaxed Resource Dedication (RRD) Policy in this study. The general resource capacities might or might not be decision variables. We will treat here the case where the general available amounts of resources are decision variables to be determined subject to a limited budget. We call this problem as the Resource Portfolio Problem (RPP). In this study, RPP is investigated under RRD policy and a modified Branch and Cut (B&C)procedure based on CPLEX is proposed. The B&C procedure of CPLEX is modified with different branching strategies, heuristic solution approaches and valid inequalities. The computational studies presented demonstrate the effectiveness of the proposed solution approaches
Multi-mode resource constrained multi-project scheduling and resource portfolio problem
This paper introduces a multi-project problem environment which involves
multiple projects with assigned due dates; with activities that have alternative
resource usage modes; a resource dedication policy that does not allow
sharing of resources among projects throughout the planning horizon; and a
total budget. There are three issues to face when investigating this multiproject environment. First, the total budget should be distributed among
different resource types to determine the general resource capacities which
correspond to the total amount for each renewable resource to be dedicated
to the projects. With the general resource capacities at hand, the next issue
is to determine the amounts of resources to be dedicated to the individual
projects. With the dedication of resources accomplished, the scheduling
of the projects' activities reduces to the multi-mode resource constrained
project scheduling problem (MRCPSP) for each individual project. Finally
the last issue is the effcient solution of the resulting MRCPSPs. In this paper,
this multi-project environment is modeled in an integrated fashion and designated as the Resource Portfolio Problem. A two-phase and a monolithic
genetic algorithm are proposed as two solution approaches each of which
employs a new improvement move designated as the combinatorial auction
for resource portfolio and the combinatorial auction for resource dedication.
Computational study using test problems demonstrated the effectiveness of
the solution approach proposed
A hierarchical approach to multi-project planning under uncertainty
We survey several viewpoints on the management of the planning complexity of multi-project organisations under uncertainty. A positioning framework is proposed to distinguish between different types of project-driven organisations, which is meant to aid project management in the choice between the various existing planning approaches. We discuss the current state of the art of hierarchical planning approaches both for traditional manufacturing and for project environments. We introduce a generic hierarchical project planning and control framework that serves to position planning methods for multi-project planning under uncertainty. We discuss multiple techniques for dealing with the uncertainty inherent to the different hierarchical stages in a multi-project organisation. In the last part of this paper we discuss two cases from practice and we relate these practical cases to the positioning framework that is put forward in the paper
A hierarchical approach to multi-project planning under uncertainty.
We survey several viewpoints on the management of the planning complexity of multi-project organisations under uncertainty. A positioning framework is proposed to distinguish between different types of project-driven organisations, which is meant to aid project management in the choice between the various existing planning approaches. We discuss the current state of the art of hierarchical planning approaches both for traditional manufacturing and for project environments. We introduce a generic hierarchical project planning and control framework that serves to position planning methods for multi-project planning under uncertainty. We discuss multiple techniques for dealing with the uncertainty inherent to the different hierarchical stages in a multi-project organisation. In the last part of this paper we discuss two cases from practice and we relate these practical cases to the positioning framework that is put forward in the paper.Choice; Complexity; Framework; Hierarchical models; Management; Manufacturing; Methods; Multi-project organisations; Planning; Project management; Project planning; Uncertainty;
Automatisierte Generierung und Simulation von Hyper-Heuristiken für stochastische Multi-Modus-Multi-Projekt-ressourcenbeschränkte Projekt- und Systemplanungsprobleme mit Umrüstzeiten
A simulation framework is presented which covers both generation and simulation of production planning and control problems which include transfer times and stochastic influences and therefore extend classical multi-mode multi-project RCPSPs. This allows for systematic and in-depth investigations of the quality and the behaviour of heuristics. In addition, the automated design of heuristics based on Boolean operators applied to relations of problem specific quantities leads on average to better results than a manual selection and adjustment of heuristic strategies
Multi-mode resource constrained multi-project scheduling and resource portfolio problem
This paper introduces a multi-project problem environment which involves
multiple projects with assigned due dates; activities that have alternative resource usage modes; a resource dedication policy that does not allow sharing
of resources among projects throughout the planning horizon; and a total
budget. Three issues arise when investigating this multi-project environment.
First, the total budget should be distributed among different resource
types to determine the general resource capacities, which correspond to the
total amount for each renewable resource to be dedicated to the projects.
With the general resource capacities at hand, the next issue is to determine
the amounts of resources to be dedicated to the individual projects. The
dedication of resources reduces the scheduling of the projects' activities to
a multi-mode resource constrained project scheduling problem (MRCPSP)for each individual project. Finally, the last issue is the ecient solution
of the resulting MRCPSPs. In this paper, this multi-project environment is
modeled in an integrated fashion and designated as the Resource Portfolio
Problem. A two-phase and a monolithic genetic algorithm are proposed as
two solution approaches, each of which employs a new improvement move
designated as the combinatorial auction for resource portfolio and the combinatorial auction for resource dedication. A computational study using test
problems demonstrated the effectiveness of the solution approach proposed.
Keywords: Project scheduling, resource portfolio problem, multi-project
scheduling, resource dedication, resource preference
Unified Concept of Bottleneck
The term `bottleneck` has been extensively used in operations management literature. Management paradigms like the Theory of Constraints focus on the identification and exploitation of bottlenecks. Yet, we show that the term has not been rigorously defined. We provide a classification of bottleneck definitions available in literature and discuss several myths associated with the concept of bottleneck. The apparent diversity of definitions raises the question whether it is possible to have a single bottleneck definition which has as much applicability in high variety job shops as in mass production environments. The key to the formulation of an unified concept of bottleneck lies in relating the concept of bottleneck to the concept of shadow price of resources. We propose an universally applicable bottleneck definition based on the concept of average shadow price. We discuss the procedure for determination of bottleneck values for diverse production environments. The Law of Diminishing Returns is shown to be a sufficient but not necessary condition for the equivalence of the average and the marginal shadow price. The equivalence of these two prices is proved for several environments. Bottleneck identification is the first step in resource acquisition decisions faced by managers. The definition of bottleneck presented in the paper has the potential to not only reduce ambiguity regarding the meaning of the term but also open a new window to the formulation and analysis of a rich set of problems faced by managers.
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