Abstract
In recent years several countries have set up policies that allow exchange of kidneys between two or more incompatible patient-donor pairs. These policies lead to what is commonly known as kidney exchange programs. The underlying optimization problems can be formulated as integer programming models. Previously proposed models for kidney exchange programs have exponential numbers of constraints or variables, which makes them fairly difficult to solve when the problem size is large. In this work we propose two compact formulations for the problem, explain how these formulations can be adapted to address some problem variants, and provide results on the dominance of some models over others. Finally we present a systematic comparison between our models and two previously proposed ones via thorough computational analysis. Results show that compact formulations have advantages over non-compact ones when the problem size is large.

Abstract

Abstract
According to [1], in order to share knowledge and information it is necessary to share a set of conceptual structures within a collaborative network. Therefore, to develop an organizational information system it is required to engage in a negotiation process so that it is possible to obtain a common vocabulary. To support and improve such process, this paper presents an approach that takes advantage of some of the features of recommendation systems (RS), which will be extremely useful to help collaborative networks construct a high- level conceptualization about a specific domain.

Abstract

Abstract

Abstract
Throughout an academic year, in every Educational Institution, a considerable number of days and human resources are spent trying to manually perform a task that can be automated and optimized - the creation of timetables. In a time where the need to reduce costs has become part of the day to day reality of all Educational Institutions, it is unthinkable to continue working with this kind of approach. The automatic creation of timetables for Education is one of the most studied problems by the scientific community. However, almost all studies have been based on very simplified models of reality, not having thus a practical application. This paper presents an automated and optimized generator of timetables and the results obtained with its use under real conditions.