A.F. Carazo

Solving a comprehensive model for multiobjective project portfolio selection

Any organization is routinely faced with the need to make decisions regarding the selection and scheduling of project portfolios from a set of candidate projects. We propose a multiobjective binary programming model that facilitates both obtaining efficient portfolios in line with the set of objectives pursued by the organization, as well as their scheduling regarding the optimum time to launch each project within the portfolio without the need for a priori information on the decision-makers preferences. Resource constraints, the possibility of transferring resources not consumed in a given a period to the following one, and project interdependence have also been taken into account. Given that the complexity of this problem increases as the number of projects and the number of objectives increase, we solve it using a metaheuristic procedure based on Scatter Search that we call SS-PPS (Scatter Search for Project Portfolio Selection). The characteristics and effectiveness of this method are compared with other heuristic approaches (SPEA and a fully random procedure) using computational experiments on randomly generated instances. Statement of scope and purpose: This paper describes a model to aid in the selection and scheduling of project portfolios within an organization. The model was designed assuming strong interdependence between projects, which therefore have to be assessed in groups, while allowing individual projects to start at different times depending on resource availability or any other strategic or political requirements, which involves timing issues. The simultaneous combination of project portfolio selection and scheduling under general conditions involves known drawbacks that we attempt to remedy. Finally, the model takes into account multiple objectives without requiring a priori specifications regarding the decision-makers preferences. The resolution of the problem was approached using a metaheuristic procedure, which showed by computational experiments good performance compared with other heuristics.

Multi-Criteria Project Portfolio Selection

A very common problem in businesses consists in the planning and allocation of a limited set of resources among a set of candidate projects in order to fund them and carry them out within a given time horizon. Several issues must be taken into account during this decision process: multiple and conflicting objectives, different types of constraints, the planning horizon, and the interdependences between some projects (synergies, precedence, complementarity, incompatibility, etc.).This chapter provides an in-depth analysis of the main contributions that different authors have made in this field under a multi-criteria approach. The study describes the evolution in the treatment of the key aspects that define the problem of project portfolio selection and shows the advantages and disadvantages of the different approaches. Finally, taking into account all the previously mentioned aspects, a global and very flexible mathematical model is presented that will help decision makers to decide how to invest their scarce resources among a set of candidate projects, that is, how to choose a project portfolio.

Effectiveness of virtual reality training for balance and gait rehabilitation in people with multiple sclerosis: a systematic review and meta-analysis:

Objective: To evaluate the evidence for the use of virtual reality to treat balance and gait impairments in multiple sclerosis rehabilitation. Design: Systematic review and meta-analysis of randomized controlled trials and quasi-randomized clinical trials. Methods: An electronic search was conducted using the following databases: MEDLINE (PubMed), Physiotherapy Evidence Database (PEDro), Cochrane Database of Systematic Reviews (CDSR) and (CINHAL). A quality assessment was performed using the PEDro scale. The data were pooled and a meta-analysis was completed. This systematic review was conducted in accordance with the (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) PRISMA guideline statement. It was registered in the PROSPERO database (CRD42016049360). Results: A total of 11 studies were included. The data were pooled, allowing meta-analysis of seven outcomes of interest. A total of 466 participants clinically diagnosed with multiple sclerosis were analysed. Results showed that virtual reality balance training is more effective than no intervention for postural control improvement (standard mean difference (SMD) = −0.64; 95% confidence interval (CI) = −1.05, −0.24; P = 0.002). However, significant overall effect was not showed when compared with conventional training (SMD = −0.04; 95% CI = −0.70, 0.62; P = 0.90). Inconclusive results were also observed for gait rehabilitation. Conclusion: Virtual reality training could be considered at least as effective as conventional training and more effective than no intervention to treat balance and gait impairments in multiple sclerosis rehabilitation.