Robust flight-to-gate assignment using flight presence probabilities

In this paper we present a novel method to improve the robustness of solutions to the Flight-to-Gate Assignment Problem (FGAP), with the aim to reduce the need for gate re-planning due to unpredicted flight schedule disturbances in the daily operations at an airport. We propose an approach in which the deterministic gate constraints are replaced by stochastic gate constraints that incorporate the inherent stochastic flight delays in such a way so as to ensure that the expected gate conflict probability of two flights assigned to the same gate at the same time does not exceed a user-specified value. The novel approach is integrated into an existing multiple time slot FGAP model that relies on a binary integer programming formulation and is tested using real-life data pertaining to Amsterdam Airport Schiphol. The results confirm that the proposed approach holds out great promise to improve the robustness of the FGAP solutions.     

Port competition in Latin America and the Caribbean: the role of concessions and competition policy

Appropriate port regulation and competitive forces tend to be related to higher levels of operational and economic performance of ports. From a policy-making perspective, pursuing efficiency and securing competition in ports to reach a level playing field is a two-step process requiring (1) ex-ante regulations to set the rules that maximize the competition for the market, especially when the policy objective is to attract private operations to ports on competitive concession processes and (2) ex-post competition policy to monitor and preserve competition in the market. This paper studies port regulation in Latin America and the Caribbean (LAC) from a competition perspective, analyzing both ex-ante and ex-post policies implemented in the region. The analysis reveals that the competitive environment in LAC is low, giving room for possible anticompetitive practices in the LAC port sector. Since the end of the 1990s, approximately 80% of container terminals in the region were granted to only five companies. Chile and Mexico have been found to be the best practices in the region, with better conditions assuring robust competition in the market. The main policy implication from this analysis is the need for a stronger involvement of antitrust agencies throughout the port concession processes.     

Comparison of sediment profile image data with profiles of oxygen and Eh from sediment cores

A study of oil and gas development in the Gulf of Mexico provided a unique opportunity to compare data from sediment profile images (SPI) with that of sediment cores collected at locations in the central Gulf of Mexico from 1034 to 1175 m. Variables measured from SPI included sediment grain-size, sediment texture, apparent depth of oxygen penetration (aDOP) into the sediments, and parameters related to biogenic activity (tubes, burrows, feeding pits or mounds, and subsurface feeding voids). Variables measured from the sediment cores included sedimentation rate, dissolved oxygen profiles, and redox potential (Eh). There was a high degree of concordance between the two data sets based on correlation analysis. For example, the correlation between aDOP and maximum penetration of oxygen into the sediment was 0.69. For deep-sea sediment, SPI provides a means by which general geochemical conditions of near surface sediment can be remotely assessed providing a quick method for mapping surficial geochemistry over large areas.