Monitoring and Assessment of Desertification and Land Degradation: Knowledge Management, Institutions and Economics: White Paper of the DSD Working Group 3

The White Paper is a review of leading scientific knowledge on the role of knowledge management, institutions and economics in monitoring and assessment of land degradation and desertification. It provides key recommendations for more effective policies and actions for combating desertification both withn the UNCCD and beyond. This White Paper is the result of an international collaboration and consultation led jointly by the Association of DesertNet International and the United Nations University - Institute for Water, Environment and Health (UNU-INWEH), of the Dryland Science for Development Consortium (DSD). The findings were presented at the First UNCCD Scientific Conference held during the COP-9 in Buenos Aires, 2009.

A mixed-integer linear programming approach to the optimization of event-bus schedules: a scheduling application in the tourism sector

This paper deals with “The Enchanted Journey,” which is a daily event tour booked by Bollywood-film fans. During the tour, the participants visit original sites of famous Bollywood films at various locations in Switzerland; moreover, the tour includes stops for lunch and shopping. Each day, up to five buses operate the tour. For operational reasons, however, two or more buses cannot stay at the same location simultaneously. Further operative constraints include time windows for all activities and precedence constraints between some activities. The planning problem is how to compute a feasible schedule for each bus. We implement a two-step hierarchical approach. In the first step, we minimize the total waiting time; in the second step, we minimize the total travel time of all buses. We present a basic formulation of this problem as a mixed-integer linear program. We enhance this basic formulation by symmetry-breaking constraints, which reduces the search space without loss of generality. We report on computational results obtained with the Gurobi Solver. Our numerical results show that all relevant problem instances can be solved using the basic formulation within reasonable CPU time, and that the symmetry-breaking constraints reduce that CPU time considerably.