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You searched for subject:(Soft time windows). Showing records 1 – 2 of 2 total matches.

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Delft University of Technology

1. Slotboom, Cynthia (author). The impact of soft time windows with penalties on the objective values of large real-world Vehicle Routing Problems.

Degree: 2019, Delft University of Technology

In a Vehicle Routing Problem with Time Windows (VRPTW), orders have to be picked up and delivered within certain time windows. In practice, planners often allow violations of these time windows, when the solutions with violations have better objective values. This is done by changing the problem into a Vehicle Routing Problem with Soft Time Windows (VRPSTW). In this thesis, the effect of soft time windows on the objective values of a real-world VRP is analysed for multiple single-day cases of a distribution company. The used algorithm is a heuristic, based on local search methods. At first, a sensitivity analysis is performed on the sensitivity of the number of planned tasks to the time window tolerance. The addition of time window tolerance increases the number of planned tasks in most of the cases. Furthermore, when the tolerance increases, the number of planned tasks generally increases as well, until the number of planned tasks is equal to the number of tasks that is planned when the time windows are completely removed. In the second part of the experiments, trade-offs between the cost function and the amount of violation are investigated, by varying the slope of the linear penalty function (for a fixed tolerance). In general, a higher penalty leads to a lower amount of violation and a higher cost (without penalties), but this is not a monotone correlation. For the smaller cases, the costs can be lowered by 4.8% to 9.0%. To reach this minimum cost, an average violation of 1 to 7 minutes per task has to be accepted. For the bigger cases, only the lowest penalty values lead to a cost improvement. Here, the lowest cost value is achieved by choosing the zero function as the penalty function, which means that the corresponding solution contains a large amount of violation.

Applied Mathematics

Advisors/Committee Members: van Essen, Theresia (mentor), Gijswijt, Dion (graduation committee), Keijzer, Marleen (graduation committee), Delft University of Technology (degree granting institution).

Subjects/Keywords: VRP; Soft time windows; Real-world problems; Local search

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Slotboom, C. (. (2019). The impact of soft time windows with penalties on the objective values of large real-world Vehicle Routing Problems. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:4ddd6740-2f74-4fcd-aa9f-c0477015f5ba

Chicago Manual of Style (16th Edition):

Slotboom, Cynthia (author). “The impact of soft time windows with penalties on the objective values of large real-world Vehicle Routing Problems.” 2019. Masters Thesis, Delft University of Technology. Accessed October 25, 2020. http://resolver.tudelft.nl/uuid:4ddd6740-2f74-4fcd-aa9f-c0477015f5ba.

MLA Handbook (7th Edition):

Slotboom, Cynthia (author). “The impact of soft time windows with penalties on the objective values of large real-world Vehicle Routing Problems.” 2019. Web. 25 Oct 2020.

Vancouver:

Slotboom C(. The impact of soft time windows with penalties on the objective values of large real-world Vehicle Routing Problems. [Internet] [Masters thesis]. Delft University of Technology; 2019. [cited 2020 Oct 25]. Available from: http://resolver.tudelft.nl/uuid:4ddd6740-2f74-4fcd-aa9f-c0477015f5ba.

Council of Science Editors:

Slotboom C(. The impact of soft time windows with penalties on the objective values of large real-world Vehicle Routing Problems. [Masters Thesis]. Delft University of Technology; 2019. Available from: http://resolver.tudelft.nl/uuid:4ddd6740-2f74-4fcd-aa9f-c0477015f5ba


Georgia Tech

2. Daniel, Aang. Routing and Scheduling with Time Windows: Models and Algorithms for Tramp Sea Cargos and Rail Car-Blocks.

Degree: PhD, Industrial and Systems Engineering, 2006, Georgia Tech

This thesis introduces a new model formulation to solve routing and scheduling problems, with the main applications in answering routing and scheduling problems faced by a sea-cargo shipping company and a railroad company. For the work in sea-cargo routing and scheduling, we focus on the tramp shipping operation. Tramp shipping is a demand-driven type of shipping operation which does not have fixed schedules. The schedules are based on the pickup and download locations of profitable service requests. Given set of products distributed among a set of ports, with each product having pickup and download time windows and a destination port, the problem is to find the schedule for a fleet of ships that maximizes profit over a specified time horizon. The problem is modeled as a Mixed Integer Non-Linear Program and reformulated as an equivalent Mixed Integer Linear Program. Three heuristic methods, along with computational results, are presented. We also exploit the special structure enjoyed by our model and introduce an upper-bounding problem to the model. With a little modification, the model is readily extendable to reflect soft time windows and inter-ship cargo-transfers. The other part of our work deals with train routing and scheduling. A typical train shipment consists of a set of cars having a common origin and destination. To reduce the handling of individual shipments as they travel, shipments are grouped into blocks. The problem is that given sets of blocks to be carried from origins to destinations, construct the most cost effective train routes and schedules and determine block-to-train assignments, such that the number of block transfers (block swaps) between trains, the number of trains used, and some other cost measures are minimized. Incorporating additional precedence requirements, the modeling techniques from the shipping research are employed to formulate a mixed integer nonlinear program for this train routing and scheduling problem. Computational results are presented. Advisors/Committee Members: Al-Khayyal, Faiz (Committee Chair), Barnes, Earl (Committee Member), Johnson, Ellis (Committee Member), Karimi, IA (Committee Member), Sokol, Joel (Committee Member).

Subjects/Keywords: Scheduling; Optimal schedule; Cargo transfer model; Routing and scheduling with time windows; Bilinear constraints; Vehicle routing; Pickup and delivery problem; Train routing and scheduling; Sea cargo routing and scheduling; Sea cargo routing; VRP; Train scheduling; Soft time windows; Set packing; Optimal train schedule; Cargo ships; Optimum ship routing; Scheduling; Mathematical models

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Daniel, A. (2006). Routing and Scheduling with Time Windows: Models and Algorithms for Tramp Sea Cargos and Rail Car-Blocks. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/19698

Chicago Manual of Style (16th Edition):

Daniel, Aang. “Routing and Scheduling with Time Windows: Models and Algorithms for Tramp Sea Cargos and Rail Car-Blocks.” 2006. Doctoral Dissertation, Georgia Tech. Accessed October 25, 2020. http://hdl.handle.net/1853/19698.

MLA Handbook (7th Edition):

Daniel, Aang. “Routing and Scheduling with Time Windows: Models and Algorithms for Tramp Sea Cargos and Rail Car-Blocks.” 2006. Web. 25 Oct 2020.

Vancouver:

Daniel A. Routing and Scheduling with Time Windows: Models and Algorithms for Tramp Sea Cargos and Rail Car-Blocks. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2020 Oct 25]. Available from: http://hdl.handle.net/1853/19698.

Council of Science Editors:

Daniel A. Routing and Scheduling with Time Windows: Models and Algorithms for Tramp Sea Cargos and Rail Car-Blocks. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/19698

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