120 citations · 186 across the 14 of their papers we have counts for
15 papers
Integrated patient-to-room and nurse-to-patient assignment in hospital wards
Tabea Brandt, Tom Lorenz Klein, Melanie Reuter-Oppermann +4
Assigning patients to rooms and nurses to patients are critical tasks within hospitals that directly affect patient and staff satisfaction, quality of care, and hospital efficiency…
Integrated Planning in Hospitals: A Review
Sebastian Rachuba, Melanie Reuter-Oppermann, Clemens Thielen
Efficient planning of scarce resources in hospitals is a challenging task for which a large variety of Operations Research and Management Science approaches have been developed sin…
Efficiently Constructing Convex Approximation Sets in Multiobjective Optimization Problems
Stephan Helfrich, Stefan Ruzika, Clemens Thielen
Convex approximation sets for multiobjective optimization problems are a well-studied relaxation of the common notion of approximation sets. Instead of approximating each image of…
Using Scalarizations for the Approximation of Multiobjective Optimization Problems: Towards a General Theory
Stephan Helfrich, Arne Herzel, Stefan Ruzika +1
We study the approximation of general multiobjective optimization problems with the help of scalarizations. Existing results state that multiobjective minimization problems can be…
Approximating Multiobjective Optimization Problems: How exact can you be?
Cristina Bazgan, Arne Herzel, Stefan Ruzika +2
It is well known that, under very weak assumptions, multiobjective optimization problems admit -approximation sets (also called -P…
Operational Research: Methods and Applications
Fotios Petropoulos, Gilbert Laporte, Emel Aktas +79
Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This…
Approximating Biobjective Minimization Problems Using General Ordering Cones
Arne Herzel, Stephan Helfrich, Stefan Ruzika +1
This article investigates the approximation quality achievable for biobjective minimization problems with respect to the Pareto cone by solutions that are (approximately) optimal w…
An Approximation Algorithm for a General Class of Multi-Parametric Optimization Problems
Stephan Helfrich, Arne Herzel, Stefan Ruzika +1
In a widely-studied class of multi-parametric optimization problems, the objective value of each solution is an affine function of real-valued parameters. Then, the goal is to prov…
One-Exact Approximate Pareto Sets
Arne Herzel, Cristina Bazgan, Stefan Ruzika +2
Papadimitriou and Yannakakis show that the polynomial-time solvability of a certain singleobjective problem determines the class of multiobjective optimization problems that admit…
The Power of the Weighted Sum Scalarization for Approximating Multiobjective Optimization Problems
Cristina Bazgan, Stefan Ruzika, Clemens Thielen +1
We determine the power of the weighted sum scalarization with respect to the computation of approximations for general multiobjective minimization and maximization problems. Additi…
The Product Knapsack Problem: Approximation and Complexity
Ulrich Pferschy, Joachim Schauer, Clemens Thielen
We consider the product knapsack problem, which is the variant of the classical 0-1 knapsack problem where the objective consists of maximizing the product of the profits of the se…
A General Approximation Method for Bicriteria Minimization Problems
Pascal Halffmann, Stefan Ruzika, Clemens Thielen +1
We present a general technique for approximating bicriteria minimization problems with positive-valued, polynomially computable objective functions. Given and a polynomi…
On the Complexity and Approximability of Budget-Constrained Minimum Cost Flows
Michael Holzhauser, Sven O. Krumke, Clemens Thielen
We investigate the complexity and approximability of the budget-constrained minimum cost flow problem, which is an extension of the traditional minimum cost flow problem by a secon…
A Network Simplex Method for the Budget-Constrained Minimum Cost Flow Problem
Michael Holzhauser, Sven O. Krumke, Clemens Thielen
We present a specialized network simplex algorithm for the budget-constrained minimum cost flow problem, which is an extension of the traditional minimum cost flow problem by a sec…
Complexity of Strong Implementability
Clemens Thielen, Sven O. Krumke
We consider the question of implementability of a social choice function in a classical setting where the preferences of finitely many selfish individuals with private information…