Abstract

Abstract

Abstract
The stacking problem is a hard combinatorial optimization problem with high practical interest in, for example, steel storage or container port operations. In this problem, a set of items is stored in a warehouse for a period of time, and a crane is used to place them in a limited number of stacks. Since the entrance and exit of items occurs in an arbitrary order, items may have to be relocated in order to reach and deliver other items below them. The objective of the problem is to find a feasible sequence of movements that delivers all items, while minimizing the total number of movements. We study the scalability of an exact approach to this problem, and propose two heuristic methods to solve it approximately. The two heuristic approaches are a multiple simulation algorithm using semi-greedy construction heuristics, and a stochastic best-first tree search algorithm. The two methods are compared in a set of challenging instances, revealing a superior performance of the tree search approach in most cases.

Abstract

Abstract
In the literature, the most widely referred approaches regarding forest harvesting scheduling problems involving environmental concerns have typically addressed constraints on the maximum clear-cut area. Nevertheless, the solutions arising from those approaches in general display a loss of habitat availability. Such loss endangers the survival of many wild species. This study presents a branch-and-bound procedure designed to find good feasible solutions, in a reasonable time, to forest harvest scheduling problems with constraints on the clear-cut area and habitat availability. Two measures are applied for the habitat availability constraints: the area of all habitats and the connectivity between them. In each branch of the branch-and-bound tree, a partial solution leads to two children nodes, corresponding to the cases of harvesting or not harvesting a given stand in a given period. Pruning is based on constraint violations or unreachable objective values. Computational results are reported.

Abstract
Health information systems are becoming ubiquitous throughout healthcare delivery processes. Governments, enticed by the potential for improved patient care and cost reduction, are pushing for more integrated IT systems in healthcare. However, the successful adoption of these systems depends on the value they create as a service for healthcare professionals and how they support their activities. Following a call for more multidisciplinary research in health information systems and increased end-user participation in HIS development, this study presents a service perspective that considers users of health information systems (HIS) as active partners and co-creators of value, instead of passive recipients of the functionalities brought by these IT systems. From a service perspective we frame healthcare professionals as customers of HIS, and analyze how they can better support healthcare provision. We present an in-depth study of primary care professionals experience with the HIS of the Portuguese National Health Service. Experience was systematized using Customer Experience Modeling, a method that takes into account the holistic nature of experience. Results portray and evaluate HIS according to professionals' experience requirements. They also show a fragmented reality where HIS usefulness is being hampered by integration and performance issues. HIS design guidelines are also posited. © 2013 IEEE.