Browsing by Author "Flores, Diego"

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    A binary monkey search algorithm variation for solving the set covering problem
    (2020) Crawford, Broderick; Soto, Ricardo; Olivares, Rodrigo; Embry, Gabriel; Flores, Diego; Palma, Wenceslao; Castro, Carlos; Paredes, Fernando; Rubio, Jose-Miguel
    In complexity theory, there is a widely studied grouping of optimization problems that belongs to the non-deterministic polynomial-time hard set. One of them is the set covering problem, known as one of Karp's 21-complete problems, and it consists of finding a subset of decision variables for satisfying a set of constraints at the minimum feasible cost. However, due to the nature of the problem, this cannot be solved using traditional complete algorithms for hard instances. In this work, we present an improved binary version of the monkey search algorithm for solving the set covering problem. Originally, this approximate method was naturally inspired by the cognitive behavior of monkeys for climbing mountains.We propose a new climbing process with a better exploratory capability and a newcooperation procedure to reduce the number of unfeasible solutions. For testing this approach, we present a detailed computational results section, where we illustrate how this variation of the monkey search algorithm is capable of reaching various global optimums for a well-known instance set from the easley's OR-Library and how it outperforms many other heuristics and meta-heuristics addressed in the literature. Moreover, we add a complete statistical analysis to show the effectiveness of the proposed approach with respect to the original version.
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    Risk Allocation in Unsolicited and Solicited Road Public-Private Partnerships: Sustainability and Management Implications
    (2020) Castelblanco, Gabriel; Guevara, Jose; Mesa, Harrison; Flores, Diego
    Risk allocation plays a crucial role in the successful development of public-private partnership (PPP) projects. However, despite being an important topic for scholars and practitioners, the existing literature does not provide sufficient evidence on how managing risks in solicited (SP) and unsolicited (USP) road PPP projects, and subsequently, on what the sustainability implications are for such managerial processes. This study aims to extend risk allocation studies by analyzing contracts in Chilean highway PPPs over the last decade based on a systematic content analysis framework and case study data. The framework was developed through line-by-line coding of contract provisions associated with risk-related issues, and data were collected from semi-structured interviews with Chilean PPP practitioners. Results show that, although the majority of risks are either shared or transferred to the private party in most contracts, there are important variations in the way allocation procedures are implemented for SPs and USPs. Contracts analyzed revealed that risk arrangement mechanisms have usually focused on the economic dimension of sustainability without fully incorporating social and environmental considerations, increasing protests in the long-term. Conclusions indicate that risk allocation procedures and sustainability considerations are highly dependent on project-specific features and contextual factors. Overall, the analysis uncovers that the level of autonomy given to the private sector in both SPs and USPs has contributed to properly manage technical and economic risks, but has failed to successfully allocate social and environmental concerns.