Abstract
The unit commitment (UC) problem is a well-known combinatorial optimization problem arising in operations planning of power systems. It involves deciding both the scheduling of power units, when each unit should be turned on or off, and the economic dispatch problem, how much power each of the on units should produce, in order to meet power demand at minimum cost while satisfying a set of operational and technological constraints. This problem is typically formulated as nonlinear mixed-integer programming problem and has been solved in the literature by a huge variety of optimization methods, ranging from exact methods (such as dynamic programming and branch-and-bound) to heuristic methods (genetic algorithms, simulated annealing, and particle swarm). Here, we discuss how the UC problem can be formulated with an optimal control model, describe previous discrete-time optimal control models, and propose a continuous-time optimal control model. The continuous-time optimal control formulation proposed has the advantage of involving only real-valued decision variables (controls) and enables extra degrees of freedom as well as more accuracy, since it allows to consider sets of demand data that are not sampled hourly.

Abstract
This research aims to help in establishing new legislative directives by testing their impact both on the company profits and on the life of city residents. A case study is developed and conducted in collaboration with the city hall and with eight companies (four freight transport companies and four retailer companies). The impacts are computed by simulating the companies operation under the new legislation and the new routes are used to analyze the impacts on the city traffic, noise, and congestion.

Abstract
Hop constraints are used to limit the number of links between two given points in a network, this way improving the quality of service by increasing the availability and reliability of the network. They have been applied to a limited number of problems, although their application can be of the greatest importance both from the academical and practical points-of-view. In this work, we survey relevant and recent works on hop-constrained problems focusing on problems with free shaped solutions.

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Abstract
Performance evaluation increasingly assumes a more important role in any organizational environment. In the transport area, the drivers are the company’s image and for this reason it is important to develop and increase their performance and commitment to the company goals. This evaluation can be used to motivate driver to improve their performance and to discover training needs. This work aims to create a performance appraisal evaluation model of the drivers based on the multi-criteria decision aid methodology. The MMASSI (Multicriteria Methodology to Support Selection of Information Systems) methodology was adapted by using a template supporting the evaluation according to the freight transportation company in study. The evaluation process involved all drivers (collaborators being evaluated), their supervisors and the company management. The final output is a ranking of the drivers, based on their performance, for each one of the scenarios used.

Abstract