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153
Citations
Citations since 2017
Publications
Publications (29)
Zusammenfassung
Die Europäische Union strebt mit den Maßnahmen des Fit-for-55-Pakets eine Verringerung der CO 2 -Emissionen bis 2030 um 55% an, verglichen mit dem Stand von 1990. Diese Reduktion soll durch verschiedene Maßnahmen erreicht werden, die auch die kommerzielle Luftfahrt betreffen. Dies sind unter anderem eine Verschärfung des Emissionsha...
View Video Presentation: https://doi.org/10.2514/6.2022-3546.vid Long range drones (either fixed wing or VTOL) represent a novel approach for monitoring and inspection of extensive longitudinal infrastructures such as power lines, pipelines and railway tracks including overhead lines. This paper proposes a method to find efficient system of systems...
In this paper, we present a globally applicable approach for estimating the potential passenger demand for On- Demand Inter-City Air Mobility based on three different use cases. All of these cases are concerned with pas- sengers who nowadays travel with conventional airlines, and might choose On-Demand Air Mobility (ODAM) as an alternative mode of...
How do changing jet fuel prices impact airline revenues? As expenses for jet fuel are one of the most relevant cost factors for airlines, their economic success largely depends on the ability to match changes on the cost side with an adaption on the revenue side. While previous studies primarily focused on the impact of fuel price changes to consum...
Commercial airlines pay navigation charges for each flight in the European airspace. These charges differ between countries. Thus, flying detours may lead to reduced costs if the longer route uses the airspace of countries with cheaper charges. In this paper, we analyze this incentive for flying routes longer than the shortest ones. While previous...
We present Woorpje, a string solver for bounded word equations (i.e., equations where the length of each variable is upper bounded by a given integer). Our algorithm works by reformulating the satisfiability of bounded word equations as a reachability problem for nondeterministic finite automata, and then carefully encoding this as a propositional...
We present Woorpje, a string solver for bounded word equations (i.e., equations where the length of each variable is upper bounded by a given integer). Our algorithm works by reformulating the satisfiability of bounded word equations as a reachability problem for nondeterministic finite automata, and then carefully encoding this as a propositional...
Solving avoidability problems in the area of string combinatorics often requires, in an initial step, the construction, via a computer program, of a very long word that does not contain any word that matches a given pattern. It is well known that this is a computationally hard task. Despite being rather straightforward that, ultimately, all such ta...
We suggest some benchmarks based on a propositional
encoding of tree decompositions of graphs.
The computation of a cyber-physical system's reaction to a stimulus typically involves the execution of several tasks. The delay between stimulus and reaction thus depends on the interaction of these tasks and is subject to timing constraints. Such constraints exist for a number of reasons and range from possible impacts on customer experiences to...
While the theoretical aspects concerning the computation of tree
width - one of the most important graph parameters - are well
understood, it is not clear how it can be computed
practically.We present the open source Java library
Jdrasil that implements several different state of the art
algorithms for this task. By experimentally comparing these
a...
The Directed Layering Problem (DLP) solves a step of the widely used layer-based approach to automatically draw directed acyclic graphs. To cater for cyclic graphs, usually a preprocessing step is used that solves the Feedback Arc Set Problem (FASP) to make the graph acyclic before a layering is determined. Here we present the Generalized Layering...
The Directed Layering Problem (DLP) solves a step of the widely used layer-based approach to automatically draw directed acyclic graphs. To cater for cyclic graphs, usually a preprocessing step is used that solves the Feedback Arc Set Problem (FASP) to make the graph acyclic before a layering is determined.
Here we present the Generalized Layering...
We present a new sorting network on 24 channels, which uses only 12 layers, improving the previously best known bound by one layer. By monotonicity, this also implies improved sorting networks for 23 channels. This result was obtained by combining techniques for generating prefixes of sorting networks with propositional encodings.
The Directed Layering Problem (DLP) solves a step of the widely used layer-based approach to automatically draw directed acyclic graphs. To cater for cyclic graphs, usually a preprocessing step is used that solves the Feedback Arc Set Problem (FASP) to make the graph acyclic before a layering is determined. Here we present the Generalized Layering...
Parallel Constraint Programming (CP) solvers typically split the search space in disjoint subspaces, and run solvers independently on these. This may induce significant overhead when solving optimization problems. Parallel Boolean Satisfiability (SAT) solvers typically run a portfolio of solvers, all solving the same problem but sharing some limite...
This paper studies new properties of the front and back ends of a sorting
network, and illustrates the utility of these in the search for new bounds on
optimal sorting networks. Search focuses first on the "outsides" of the network
and then on the inner part. All previous works focus only on properties of the
front end of networks and on how to app...
Two words are called k-abelian equivalent, if they share the same multiplicities for all factors of length at most k. We present an optimal linear time algorithm for identifying all occurrences of factors in a text that are k-abelian equivalent to some pattern P. Moreover, an optimal algorithm for finding the largest k for which two words are k-abe...
We present new parallel sorting networks for $17$ to $20$ inputs. For $17,
19,$ and $20$ inputs these new networks are faster (i.e., they require less
computation steps) than the previously known best networks. Therefore, we
improve upon the known upper bounds for minimal depth sorting networks on $17,
19,$ and $20$ channels. Furthermore, we show t...
The exchange of learnt clauses is a key feature in parallel SAT solving. We present an approach based on a communication graph. Each solver thread corresponds to a node in this graph. Communication between two solvers is allowed if the respective nodes are connected by an edge. This yields another dimension in controlling the amount of communicatio...
We present new parallel sorting networks for $17$ to $20$ inputs. For $17,
19,$ and $20$ inputs these new networks are faster (i.e., they require less
computation steps) than the previously known best networks. Therefore, we
improve upon the known upper bounds for minimal depth sorting networks on $17,
19,$ and $20$ channels. The networks were obta...
The introduction of multicore hardware to the field of embedded and safety-critical systems implies great safety challenges. An important issue in this context is the migration of legacy code to multicore systems. In this paper, we present approaches to support the migration process in the domain of safety-critical, embedded systems. Given a progra...
The introduction of multicore hardware to the field of embedded and safety-critical systems implies great challenges. An important issue in this context is the migration of legacy code to multicore systems. Starting from the field of formal verification, we aim to improve the usability of our methods for software engineers. In this paper, we presen...
We present a robust EPTAS for scheduling on identical machines. The running time for adding one job is bounded by 2O((1/ε2) log3(1/ε)). The migration factor required to gain a (1+ ε)-approximate schedule in each iteration is bounded by 2O((1/ε) log2(1/ε)).
Projects
Project (1)
While the theoretical aspects concerning the computation of tree width - one
of the most important graph parameters - are well understood, it is not clear
how it can be computed practically. As tree width has a wide range of
applications, \eg in bioinformatics or artificial intelligence, this lack of
understanding hinders the applicability of many important algorithms in the
real world.
