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Documents authored by Schmidt, Christiane

Document
DOI: 10.4230/OASIcs.ATMOS.2024.6
Two-Stage Weekly Shift Scheduling for Train Dispatchers

Authors: Tomas Lidén, Christiane Schmidt, and Rabii Zahir

Published in: OASIcs, Volume 123, 24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024)

Abstract
We consider the problem of creating weekly shift schedules for train dispatchers, which conform to a variety of operational constraints, in particular, several work and rest time restrictions. We create the schedules in a two-stage process. First, using a previously presented IP model, we create a set of feasible daily shifts, which takes care of minimum-rest and shift-length requirements, taskload bounds, and combinability of dispatching areas. We then formulate an IP model to combine these daily shifts into weekly schedules, enforcing that each daily shift is covered by some dispatcher every day of the week, while ensuring that the weekly schedules comply with various restrictions on working hours from a union agreement. With this approach, we aim to identify "good" sets of daily shifts for the longer schedules. We run experiments for real-world sized input and consider different distributions of the daily shifts w.r.t. shift length and ratio of night shifts. Daily shifts with shift-length variability, relatively few long shifts, and a low ratio of night shifts generally yield better weekly schedules. The runtime for the second stage with the best daily-shift pattern is below three hours, which - together with the runtime for stage 1 of ca. 2 hours per run - can be feasible for real-world use.
Cite as

Tomas Lidén, Christiane Schmidt, and Rabii Zahir. Two-Stage Weekly Shift Scheduling for Train Dispatchers. In 24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024). Open Access Series in Informatics (OASIcs), Volume 123, pp. 6:1-6:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{liden_et_al:OASIcs.ATMOS.2024.6,
  author =	{Lid\'{e}n, Tomas and Schmidt, Christiane and Zahir, Rabii},
  title =	{{Two-Stage Weekly Shift Scheduling for Train Dispatchers}},
  booktitle =	{24th Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2024)},
  pages =	{6:1--6:16},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-350-8},
  ISSN =	{2190-6807},
  year =	{2024},
  volume =	{123},
  editor =	{Bouman, Paul C. and Kontogiannis, Spyros C.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2024.6},
  URN =		{urn:nbn:de:0030-drops-211944},
  doi =		{10.4230/OASIcs.ATMOS.2024.6},
  annote =	{Keywords: shift scheduling, IP, train dispatcher shift scheduling}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2016.9
Automatic Design of Aircraft Arrival Routes with Limited Turning Angle

Authors: Tobias Andersson Granberg, Tatiana Polishchuk, Valentin Polishchuk, and Christiane Schmidt

Published in: OASIcs, Volume 54, 16th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2016)

Abstract
We present an application of Integer Programming to the design of arrival routes for aircraft in a Terminal Maneuvering Area (TMA). We generate operationally feasible merge trees of curvature-constrained routes, using two optimization criteria: (1) total length of the tree, and (2) distance flown along the tree paths. The output routes guarantee that the overall traffic pattern in the TMA can be monitored by air traffic controllers; in particular, we keep merge points for arriving aircraft well separated, and we exclude conflicts between arriving and departing aircraft. We demonstrate the feasibility of our method by experimenting with arrival routes for a runway at Arlanda airport in the Stockholm TMA. Our approach can easily be extended in several ways, e.g., to ensure that the routes avoid no-fly zones.
Cite as

Tobias Andersson Granberg, Tatiana Polishchuk, Valentin Polishchuk, and Christiane Schmidt. Automatic Design of Aircraft Arrival Routes with Limited Turning Angle. In 16th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2016). Open Access Series in Informatics (OASIcs), Volume 54, pp. 9:1-9:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{granberg_et_al:OASIcs.ATMOS.2016.9,
  author =	{Granberg, Tobias Andersson and Polishchuk, Tatiana and Polishchuk, Valentin and Schmidt, Christiane},
  title =	{{Automatic Design of Aircraft Arrival Routes with Limited Turning Angle}},
  booktitle =	{16th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2016)},
  pages =	{9:1--9:13},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-021-7},
  ISSN =	{2190-6807},
  year =	{2016},
  volume =	{54},
  editor =	{Goerigk, Marc and Werneck, Renato F.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2016.9},
  URN =		{urn:nbn:de:0030-drops-65336},
  doi =		{10.4230/OASIcs.ATMOS.2016.9},
  annote =	{Keywords: Air Traffic Management, Standard Terminal Arrival Routes, Standard Instrument Departures, Integer programming, Turn constraints}
}
Document
DOI: 10.4230/DagSemProc.06421.8
Polygon Exploration with Discrete Vision

Authors: Sándor Fekete and Christiane Schmidt

Published in: Dagstuhl Seminar Proceedings, Volume 6421, Robot Navigation (2007)

Abstract
With the advent of autonomous robots with two- and three-dimensional scanning capabilities, classical visibility-based exploration methods from computational geometry have gained in practical importance. However, real-life laser scanning of useful accuracy does not allow the robot to scan continuously while in motion; instead, it has to stop each time it surveys its environment. This requirement was studied by Fekete, Klein and N"uchter for the subproblem of looking around a corner, but until now has not been considered for whole polygonal regions. We give the first comprehensive algorithmic study for this important algorithmic problem that combines stationary art gallery-type aspects with watchman-type issues in an online scenario. We show that there is a lower bound of $Omega(sqrt{n})$ on the competitive ratio in an orthogonal polygon with holes; we also demonstrate that even for orthoconvex polygons, a competitive strategy can only be achieved for limited aspect ratio $A$, i.e., for a given lower bound on the size of an edge. Our main result is an $O(log A)$-competitive strategy for simple rectilinear polygons, which is best possible up to constants.
Cite as

Sándor Fekete and Christiane Schmidt. Polygon Exploration with Discrete Vision. In Robot Navigation. Dagstuhl Seminar Proceedings, Volume 6421, pp. 1-23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2007)

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@InProceedings{fekete_et_al:DagSemProc.06421.8,
  author =	{Fekete, S\'{a}ndor and Schmidt, Christiane},
  title =	{{Polygon Exploration with Discrete Vision}},
  booktitle =	{Robot Navigation},
  pages =	{1--23},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2007},
  volume =	{6421},
  editor =	{S\'{a}ndor Fekete and Rudolf Fleischer and Rolf Klein and Alejandro Lopez-Ortiz},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.06421.8},
  URN =		{urn:nbn:de:0030-drops-8714},
  doi =		{10.4230/DagSemProc.06421.8},
  annote =	{Keywords: Searching, scan cost, visibility problems, watchman problems, online searching, competitive strategies, autonomous mobile robots.}
}
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