Publications

Journal Articles

[1] C. Bazgan, A. Herzel, S. Ruzika, C. Thielen, D. Vanderpooten, Approximating multiobjective optimization problems: How exact can you be?, Mathematical Methods of Operations Research (online first), https://doi.org/10.1007/s00186-023-00836-x.

[2] J. Boeckmann, C. Thielen, New ways in municipal flood mitigation: A mixed-integer programming approach and its practical application, Operations Research Forum (online first), https://doi.org/10.1007/s43069-023-00246-z.

[3] S. Helfrich, A. Herzel, S. Ruzika, C. Thielen, Using scalarizations for the approximation of multiobjective optimization problems: Towards a general theory, Mathematical Methods of Operations Research (online first), https://doi.org/10.1007/s00186-023-00823-2.

[4] J. Boeckmann, U. Pferschy, C. Thielen, Approximating single- and multi-objective nonlinear sum and product knapsack problems, Discrete Optimization 48 (2023) 100771.

[5] A. Herzel, S. Helfrich, S. Ruzika, C. Thielen, Approximating biobjective minimization problems using general ordering cones, Journal of Global Optimization 86 (2023) 393–415.

[6] S. Helfrich, A. Herzel, S. Ruzika, C. Thielen, An approximation algorithm for a general class of multi-parametric optimization problems, Journal of Combinatorial Optimization 44 (2022) 1459-1494.

[7] C. Bazgan, A. Herzel, S. Ruzika, C. Thielen, D. Vanderpooten, An approximation algorithm for a general class of parametric optimization problems, Journal of Combinatorial Optimization 43 (2022) 1328-1358.

[8] C. Bazgan, S. Ruzika, C. Thielen, D. Vanderpooten, The power of the weighted sum secularization for approximating multiobjective optimization problems, Theory of Computing Systems 66 (2022) 395-415.

[9] S. Boesen, A. Raith, C. Thielen, J. Tidswell, Enforcing fuel-optimal traffic patterns, EURO Journal on Transportation and Logistics 10 (2021) 100060.

[10] J. Tidswell, A. Downward, C. Thielen, A. Raith, Minimising emissions in traffic assignment with non-monotonic arc costs, Transportation Research Part B: Methodological 153 (2021) 70-90.

[11] J. Boeckmann, C. Thielen, A (B+1)-approximation for network flow interdiction with unit costs, Discrete Applied Mathematics (online first), doi.org/10.1016/j.dam.2021.07.008.

[12] A. Giudici, T. Lu, C. Thielen, R. Zuidwijk, An analysis of the stability of hinterland container transport cooperation, Transportation Science 55 (2021) 1170-1186.

[13] U. Pferschy, J. Schauer, C. Thielen, Approximating the product knapsack problem, Optimization Letters 15 (2021) 2529-2540.

[14] C. Bazgan, A. Herzel, S. Ruzika, C. Thielen, D. Vanderpooten, One-exact approximate Pareto sets, Journal of Global Optimization 80 (2021) 87-115.

[15] A. Herzel, S. Ruzika, C. Thielen, Approximation methods for multiobjective optimization problems: A survey, INFORMS Journal on Computing 33 (2021) 1284-1299.

[16] Z. Abel, J. Bosboom, M. Coulombe, E. D. Demaine, L. Hamilton, A. Hesterberg, J. Kopinsky, J. Lynch, M. Rudoy, C. Thielen, Who witnesses The Witness? Finding witnesses in The Witness is hard and sometimes impossible, Theoretical Computer Science 839 (2020) 41–102.

[17] K. Riga, K. Jahr, C. Thielen, A. Borrmann, Mixed integer programming for dynamic tower crane and storage area optimization on construction sites, Automation in Construction 120 (2020) Article 103384.

[18] S. O. Krumke, C. Thielen, P. Weinschenk, S. Westphal, Full implementation of social choice functions in dominant strategies, International Journal of Game Theory 48 (1) (2019) 337–361.

[19] A. Herzel, M. Hopf, C. Thielen, Multistage interval scheduling games, Journal of Scheduling 22 (3) (2019) 359–377.

[20] C. Thielen, Duty rostering for physicians at a department of orthopedics and trauma surgery, Operations Research for Health Care 19 (2018) 80–91.

[21] H. Corsten, M. Hopf, B. Kasper, C. Thielen, Assortment planning for multiple chain stores, OR Spectrum 40 (4) (2017) 875–912.

[22] P. Halffmann, S. Ruzika, C. Thielen, D. Willems, A general approximation method for bicriteria minimization problems, Theoretical Computer Science 695 (2017) 1–15.

[23] M. Holzhauser, S. O. Krumke, C. Thielen, On the complexity and approximability of budget-constrained minimum cost flows, Information Processing Letters 126 (2017) 24–29.

[24] M. Bender, C. Thielen, S. Westphal, Online interval scheduling with a bounded number of failures, Journal of Scheduling 20 (2017) 443–457.

[25] M. Hopf, C. Thielen, O. Wendt, Competitive algorithms for multistage online scheduling, European Journal of Operational Research 260 (2) (2017) 468–481.

[26] A. Giudici, P. Halffmann, S. Ruzika, C. Thielen, Approximation schemes for the parametric knapsack problem, Information Processing Letters 120 (2017) 11–15.

[27] M. Holzhauser, S. O. Krumke, C. Thielen, A network simplex method for the budget-constrained minimum cost flow problem, European Journal of Operational Research 259 (3) (2017) 864–872.

[28] M. Holzhauser, S. O. Krumke, C. Thielen, Maximum flows in generalized processing networks, Journal of Combinatorial Optimization 33 (4) (2017) 1226–1256.

[29] A. Chassein, S. O. Krumke, C. Thielen, Capacitated network design games with weighted players, Networks 68 (2) (2016) 141–158.

[30] C. Thielen, M. Tiedemann, S. Westphal, The online knapsack problem with incremental capacity, Mathematical Methods of Operations Research 83 (2) (2016) 207–242.

[31] M. Holzhauser, S. O. Krumke, C. Thielen, Budget-constrained minimum cost flows, Journal of Combinatorial Optimization 31 (4) (2016) 1720–1745.

[32] M. Holzhauser, S. O. Krumke, C. Thielen, Convex generalized flows, Discrete Applied Mathematics 190-191 (2015) 86–99.

[33] M. Bender, C. Thielen, S. Westphal, Packing items into several bins facilitates approximating the separable assignment problem, Information Processing Letters 115 (6–8) (2015) 570–575.

[34] S. O. Krumke, C. Thielen, The generalized assignment problem with minimum quantities, European Journal of Operational Research 228 (1) (2013) 46–55.

[35] C. Thielen, S. Westphal, Complexity and approximability of the maximum flow problem with minimum quantities, Networks 62 (2) (2013) 125–131.

[36] C. Thielen, S. Westphal, Approximation algorithms for TTP(2), Mathematical Methods of Operations Research 76 (1) (2012) 1–20.

[37] S. O. Krumke, C. Thielen, C. Zeck, Extensions to online delay management on a single train line: New bounds for delay minimization and profit maximization, Mathematical Methods of Operations Research 74 (1) (2011) 53–75.

[38] S. O. Krumke, C. Thielen, S. Westphal, Interval scheduling on related machines, Computers and Operations Research 38 (12) (2011) 1836–1844.

[39] S. O. Krumke, C. Thielen, Minimum cost flows with minimum quantities, Information Processing Letters 111 (11) (2011) 533–537.

[40] C. Thielen, S. Westphal, Complexity of the traveling tournament problem, Theoretical Computer Science 412 (4-5) (2011) 345–351.

[41] C. Thielen, S. O. Krumke, Truthful mechanisms for selfish routing and two-parameter agents, Theory of Computing Systems 49 (1) (2011) 196–223.

 

Articles in Refereed Conference Proceedings

[42] J. Boeckmann, C. Thielen, A. Wittmann, Complexity of the Temporal Shortest Path Interdiction Problem, in: Proceeding of the 2nd Symposium on Algorithmic Foundations of Dynamic Networks (SAND), Vol. 257 of LIPIcs, 2023, pp. 9:1-9:20.

[43] J. Boeckmann, C. Thielen, An approximation algorithm for network flow interdiction with unit costs and two capacities, in: Proceeding of the 18th Cologne-Twente Workshop on Graphs and Combinatorial Optimization (CTW), Vol. 5 of AIRO, 2020, pp. 157-169.

[44] C. Bazgan, A. Herzel, S. Ruzika, C. Thielen, D. Vanderpooten, An FPTAS for a general class of parametric optimization problems, in: Proceedings of the 25th International Computing and Combinatorics Conference (COCOON), Vol. 11653 of LNCS, 2019, pp. 25–37.

[45] A. Giudici, T. Lu, C. Thielen, R. Zuidwijk, Sending a reliable cost-efficient flow through a stochastic timevarying network, in: Proceedings of the 10th Triennial Symposium on Transportation Analysis (TRISTAN), 2019, pp. 1–4.

[46] F. D. Schwahn, C. Thielen, The complexity of escaping labyrinths and enchanted forests, in: Proceedings of the 9th International Conference on Fun with Algorithms (FUN), Vol. 100 of LIPIcs, 2018, pp. 30:1–13.

[47] H. Corsten, M. Hopf, B. Kasper, C. Thielen, Regionalized assortment planning for multiple chain stores, in: A. Fink, A. Fügenschuh, M. Geiger (Eds.), Operations Research Proceedings 2016 – Selected Papers of the Annual International Conference of the German Operations Research Society (GOR), Springer, 2018, pp. 451–457.

[48] A. Raith, C. Thielen, J. Tidswell, Modelling and optimising fuel consumption in traffic assignment problems, in: Proceedings of the 38th Australasian Transport Research Forum (ATRF), 2016, pp. 1–13.

[49] K. Kölker, C. Mannweiler, C. Thielen, K. Lütjens, Time relaxed itinerary-based route development for airline networks, in: Proceedings of the 9th Triennial Symposium on Transportation Analysis (TRISTAN), 2016, pp. 1–4.

[50] I. Hamling, M. O’Sullivan, C. Thielen, C. Walker, Improving resource efficiency in Internet cafés by virtualization and optimal user allocation, in: Proceedings of the 8th IEEE/ACM International Conference on Utility and Cloud Computing (UCC), 2015, pp. 1–9.

[51] S. Worreschk, I. Kaufmann Alves, T. G. Schmitt, C. Thielen, Optimization of transformation processes of drainage systems in rural areas, in: Proceedings of the 13th International Conference on Urban Drainage (ICUD), 2014, pp. 1–8.

[52] T. G. Schmitt, S. Worreschk, I. Kaufmann Alves, F. Herold, C. Thielen, An optimization and decision support tool for long-term strategies in the transformation of urban water infrastructure, in: Proceedings of the 11th International Conference on Hydroinformatics (HIC), 2014, pp. 1–8.

[53] S. O. Krumke, F. D. Schwahn, C. Thielen, Being negative makes life NP-hard (for product sellers), in: Proceedings of the 7th International Conference on Fun with Algorithms (FUN), Vol. 8496 of LNCS, 2014, pp. 277–288.

[54] M. Bender, C. Thielen, S. Westphal, A constant factor approximation for the generalized assignment problem with minimum quantities and unit size items, in: Proceedings of the 38th International Symposium on Mathematical Foundations of Computer Science (MFCS), Vol. 8087 of LNCS, 2013, pp. 135–145.

[55] S. O. Krumke, C. Thielen, S. Westphal, Interval scheduling on related machines: Complexity and online algorithms, in: Proceedings of the 10th Workshop on Models and Algorithms for Planning and Scheduling Problems (MAPSP), 2011, pp. 236–238.

[56] C. Thielen, S. Westphal, Approximating the traveling tournament problem with maximum tour length 2, in: Proceedings of the 21st International Symposium on Algorithms and Computation (ISAAC), Vol. 6507 of LNCS, 2010, pp. 303–314.

[57] C. Thielen, S. Westphal, A combinatorial algorithm for strong implementation of social choice functions, in: Proceedings of the 3rd International Workshop on Computational Social Choice (COMSOC), 2010, pp. 331–341.

[58] C. Thielen, S. O. Krumke, Strong implementation of social choice function in dominant strategies, in: Proceedings of the 3rd International Workshop on Computational Social Choice (COMSOC), 2010, pp. 319–330.

[59] C. Thielen, S. O. Krumke, Truthful mechanisms for selfish routing and two-parameter agents, in: Proceedings of the 2nd International Symposium on Algorithmic Game Theory (SAGT), Vol. 5814 of LNCS, 2009, pp. 36–47.

[60] C. Thielen, S. O. Krumke, Complexity of strong implementability, in: Proceedings of the 4th Athens Colloquium on Algorithms and Complexity (ACAC), Vol. 4 of EPTCS, 2009, pp. 1–12.

[61] C. Thielen, Generalized truthful mechanisms for scheduling verifiable related machines, in: Proceedings of the 9th Workshop on Models and Algorithms for Planning and Scheduling Problems (MAPSP), 2009, pp. 198–200.

[62] C. Thielen, S. O. Krumke, A general scheme for designing monotone algorithms for scheduling problems with precedence constraints, in: Proceedings of the 6th Workshop on Approximation and Online Algorithms (WAOA), Vol. 5426 of LNCS, 2008, pp. 105–118.