5,258 research outputs found

    Stochastic Programming for Engineering Design

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    Stochastické programování a optimalizace jsou velmi užitečné nástroje pro řešení široké škály inženýrských úloh zahrnujících neurčitost. Diplomová práce se zabývá stochastickým programováním a jeho aplikací při řešení logistických úloh. Teoretická část práce je věnována jak základním pojmům z teorie grafů, tak pojmům souvisejících s matematickým, lineárním, celočíselným a stochastickým programováním. Pozornost je věnována také návaznosti zmíněných pojmů na logistiku. Druhá část se zabývá tvorbou vlastních úloh prezentujících stochastické logistické modely, jejich implementací a výsledky.Stochastic programming and optimization are both useful tools to solve a wide variety of engineering problems - including uncertainty. This thesis deals with stochastic programming applied to logistic problems. The theoretical part aims to introduce basic terms of graph theory and terms related to mathematical, linear, integer and stochastic programming. It will also put these terms into the specific context of logistics. The second part aims to apply such concepts to the development of suitable stochastic logistic models and to present their implementations and results.

    The new Dutch timetable: The OR revolution

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    In December 2006, Netherlands Railways introduced a completely new timetable. Its objective was to facilitate the growth of passenger and freight transport on a highly utilized railway network, and improve the robustness of the timetable resulting in less train delays in the operation. Further adjusting the existing timetable constructed in 1970 was not option anymore, because further growth would then require significant investments in the rail infrastructure. Constructing a railway timetable from scratch for about 5,500 daily trains was a complex problem. To support this process, we generated several timetables using sophisticated operations research techniques, and finally selected and implemented one of these timetables. Furthermore, because rolling-stock and crew costs are principal components of the cost of a passenger railway operator, we used innovative operations research tools to devise efficient schedules for these two resources. The new resource schedules and the increased number of passengers resulted in an additional annual profit of 40 million euros (60million)ofwhichabout10millioneuroswerecreatedbyadditionalrevenues.Weexpectthistoincreaseto70millioneuros(60 million) of which about 10 million euros were created by additional revenues. We expect this to increase to 70 million euros (105 million) annually in the coming years. However, the benefits of the new timetable for the Dutch society as a whole are much greater: more trains are transporting more passengers on the same railway infrastructure, and these trains are arriving and departing on schedule more than they ever have in the past. In addition, the rail transport system will be able to handle future transportation demand growth and thus allow cities to remain accessible. Therefore, people can switch from car transport to rail transport, which will reduce the emission of greenhouse gases.

    System balance for extended logistic systems

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    Bibliography: p. 29.S.C. Graves and J. Keilson

    Designing a Recycling Network for the Circular Economy of Plastics with Different Multi-Criteria Optimization Approaches

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    A growing plastic production increases the pressure on waste management systems, which have to cope with greater volumes of plastic waste. Increased plastics recycling can reduce environmental impacts by lowering the need for primary plastics production and thus fossil resources demand. Current research is mainly focused on identifying environmentally friendly recycling technologies for different waste streams. However, recycling capacities must also be expanded to handle the waste generated. Therefore, this paper develops multiple exemplary multi-criteria optimization models to design an optimal recycling network. The models are deployed in a case study for plastic packaging waste in Europe for an advanced mechanical recycling process. We compare the different multi-criteria optimization approaches, how they balance environmental and economic aspects differently, and how this affects the recycling network design. Finally, we compare the optimization approaches and find goal programming the most promising approach for recycling network design that ensures a balance between economic and environmental objectives
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