On the Performance of the Subtour Elimination Constraints Approach for the p‐Regions Problem: A Computational Study

The p‐regions is a mixed integer programming (MIP) model for the exhaustive clustering of a set of n geographic areas into p spatially contiguous regions while minimizing measures of intraregional heterogeneity. This is an NP‐hard problem that requires a constant research of strategies to increase the size of instances that can be solved using exact optimization techniques. In this article, we explore the benefits of an iterative process that begins by solving the relaxed version of the p‐regions that removes the constraints that guarantee the spatial contiguity of the regions. Then, additional constraints are incorporated iteratively to solve spatial discontinuities in the regions. In particular we explore the relationship between the level of spatial autocorrelation of the aggregation variable and the benefits obtained from this iterative process. The results show that high levels of spatial autocorrelation reduce computational times because the spatial patterns tend to create spatially contiguous regions. However, we found that the greatest benefits are obtained in two situations: (1) when ; and (2) when the parameter p is close to the number of clusters in the spatial pattern of the aggregation variable.     

Moving pictures: Memory and photography among the Arhuaco of the Sierra Nevada de Santa Marta,Colombia

This article traces the changing uses and meanings of a set of ethnographic photographs that represent a contentious period in the history of the Arhuaco, an indigenous group that inhabits the Sierra Nevada de Santa Marta, in Northern Colombia. Based on archival sources and fieldwork, I explore their role in the 1910s when they were created by Swedish anthropologist Gustaf Bolinder, and also analyse indigenous re-significations and contests over the meaning of the photographs in 2010s as a process that is intertwined with their present struggles. I study their use by an Arhuaco media-maker who incorporated them into a historical documentary film and debates among community members around possible interpretations of the pictures. Through this case study I seek to contribute to the expanding scholarship on the history of anthropological photography, and in particular to recent efforts to move beyond vertical colonial readings and emphasize indigenous agency. I argue for the need of a more nuanced understanding of indigenous and non-indigenous uses of photography that takes into account a shared history and does not naturalize differences. Furthermore, I trace the changing meanings of photographs in order to illuminate the historicity implied in the process of attributing meaning to the past.     

Historical Mortars from the Fortified Upper Town of Eivissa (Balearic Islands,Spain)

Samples of mortars and stone of Portal de ses Taules from the Renaissance city walls of Eivissa (16th century) were characterized using thermal analysis— thermogravimetry and derivative thermogravimetry (DTG)—x-ray diffractometry, and scanning electron microscopy. The granulometric fraction of particle size <63 μm was selected as representative of the binder, while the fraction 0.5–1 mm was taken as representative of the aggregate in order to characterize mortar samples. The results show that local materials were used. Lime was the main component of most of the samples tested. Thermal analysis revealed the hydraulic nature of the lime mortars. High amounts of sodium chloride were found in the samples analysed.