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  • 101
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    The maximum diversity assortment selection problem (2021)
    Details
    Publication Date: 2024-03-06
    Description: In this article, we introduce the Maximum Diversity Assortment Selection Problem (MDASP), which is a generalization of the two-dimensional Knapsack Problem (2D-KP). Given a set of rectangles and a rectangular container, the goal of 2D-KP is to determine a subset of rectangles that can be placed in the container without overlapping, i.e., a feasible assortment, such that a maximum area is covered. MDASP is to determine a set of feasible assortments, each of them covering a certain minimum threshold of the container, such that the diversity among them is maximized. Thereby, diversity is defined as the minimum or average normalized Hamming distance of all assortment pairs. MDASP was the topic of the 11th AIMMS-MOPTA Competition in 2019. The methods described in this article and the resulting computational results won the contest. In the following, we give a definition of the problem, introduce a mathematical model and solution approaches, determine upper bounds on the diversity, and conclude with computational experiments conducted on test instances derived from the 2D-KP literature.
    Language: English
    Type: article , doc-type:article
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  • 102
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    Simulation data: Data-driven model reduction of agent-based systems using the Koopman generator (2021)
    Details
    Publication Date: 2024-03-18
    Language: English
    Type: researchdata , doc-type:ResearchData
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  • 103
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    cmdtools (2021)
    Details
    Publication Date: 2024-03-18
    Description: Python implementation of severals tools (PCCA, AJC, SQRA, P/Q estimation) for the analysis of dynamical systems from the transfer operator perspective.
    Language: English
    Type: software , doc-type:Other
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  • 104
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    Data-driven model reduction of agent-based systems using the Koopman generator (2021)
    Details
    Publication Date: 2024-03-18
    Description: The dynamical behavior of social systems can be described by agent-based models. Although single agents follow easily explainable rules, complex time-evolving patterns emerge due to their interaction. The simulation and analysis of such agent-based models, however, is often prohibitively time-consuming if the number of agents is large. In this paper, we show how Koopman operator theory can be used to derive reduced models of agent-based systems using only simulation or real-world data. Our goal is to learn coarse-grained models and to represent the reduced dynamics by ordinary or stochastic differential equations. The new variables are, for instance, aggregated state variables of the agent-based model, modeling the collective behavior of larger groups or the entire population. Using benchmark problems with known coarse-grained models, we demonstrate that the obtained reduced systems are in good agreement with the analytical results, provided that the numbers of agents is sufficiently large.
    Language: English
    Type: article , doc-type:article
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  • 105
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    Agent-based modeling: Population limits and large timescales (2021)
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    Publication Date: 2024-03-18
    Description: Modeling, simulation and analysis of interacting agent systems is a broad field of research, with existing approaches reaching from informal descriptions of interaction dynamics to more formal, mathematical models. In this paper, we study agent-based models (ABMs) given as continuous-time stochastic processes and their pathwise approximation by ordinary and stochastic differential equations (ODEs and SDEs, respectively) for medium to large populations. By means of an appropriately adapted transfer operator approach we study the behavior of the ABM process on long time scales. We show that, under certain conditions, the transfer operator approach allows to bridge the gap between the pathwise results for large populations on finite timescales, i.e., the SDE limit model, and approaches built to study dynamical behavior on long time scales like large deviation theory. The latter provides a rigorous analysis of rare events including the associated asymptotic rates on timescales that scale exponentially with the population size. We demonstrate that it is possible to reveal metastable structures and timescales of rare events of the ABM process by finite-length trajectories of the SDE process for large enough populations. This approach has the potential to drastically reduce computational effort for the analysis of ABMs.
    Language: English
    Type: article , doc-type:article
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  • 106
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    Combining XOR and Partner Checkpointing for Resilient Multilevel Checkpoint/Restart (2021)
    Details
    Publication Date: 2024-04-05
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 107
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    Registration-based Tracking of Regions Defined by Level Sets of Time-dependent Scalar Fields (2021)
    Details
    Publication Date: 2024-04-05
    Description: This thesis is concerned with the wide field of feature tracking in time-dependent data. Many solutions already exist for the tracking of various features in scalar fields that are given as discrete time steps. In the field of meteorology, recently published precipitation data of the COSMO-REA2 reanalysis system gave rise to the analysis of precipitation at a convective scale for which a tracking of precipitation cells over time is desired. A previous study indicated that a tracking based on the widely used overlap criterion does not perform well for the reanalysis data. Based on a novel set of requirements, a new approach to the tracking of regions in time-dependent scalar fields is developed in the course of this thesis and applied in a prototypical study to example datasets of the COSMO-REA2 system. Despite the concrete motivation of using the developed method for subsequent studies of precipitation, the tracking approach is designed to be applicable for arbitrary scalar quantities that can conceptually be given on uniform grids of arbitrary dimensions. Based on a detailed description of the utilized methods, this thesis presents a novel tracking solution whose correspondence identification is based on image registration of successive time steps in combination with a hierarchical watershed segmentation by means of which features are extracted. The proposed implementation allows for an efficient generation of tracking results under the premise that the registration-based correspondence information has been precomputed.
    Language: English
    Type: masterthesis , doc-type:masterThesis
    Format: application/pdf
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  • 108
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    On the Regression Model for Generalized Normal Distributions (2021)
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    Publication Date: 2024-04-26
    Description: The traditional linear regression model that assumes normal residuals is applied extensively in engineering and science. However, the normality assumption of the model residuals is often ineffective. This drawback can be overcome by using a generalized normal regression model that assumes a non-normal response. In this paper, we propose regression models based on generalizations of the normal distribution. The proposed regression models can be used effectively in modeling data with a highly skewed response. Furthermore, we study in some details the structural properties of the proposed generalizations of the normal distribution. The maximum likelihood method is used for estimating the parameters of the proposed method. The performance of the maximum likelihood estimators in estimating the distributional parameters is assessed through a small simulation study. Applications to two real datasets are given to illustrate the flexibility and the usefulness of the proposed distributions and their regression models.
    Language: English
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  • 109
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    Controlling transient gas flow in real-world pipeline intersection areas (2021)
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    Publication Date: 2024-04-26
    Description: Compressor stations are the heart of every high-pressure gas transport network. Located at intersection areas of the network they are contained in huge complex plants, where they are in combination with valves and regulators responsible for routing and pushing the gas through the network. Due to their complexity and lack of data compressor stations are usually dealt with in the scientific literature in a highly simplified and idealized manner. As part of an ongoing project with one of Germany's largest Transmission System Operators to develop a decision support system for their dispatching center, we investigated how to automatize control of compressor stations. Each station has to be in a particular configuration, leading in combination with the other nearby elements to a discrete set of up to 2000 possible feasible operation modes in the intersection area. Since the desired performance of the station changes over time, the configuration of the station has to adapt. Our goal is to minimize the necessary changes in the overall operation modes and related elements over time, while fulfilling a preset performance envelope or demand scenario. This article describes the chosen model and the implemented mixed integer programming based algorithms to tackle this challenge. By presenting extensive computational results on real world data we demonstrate the performance of our approach.
    Language: English
    Type: article , doc-type:article
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  • 110
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    Distribution System Planning with Battery Storage using Multiperiod Optimal Power Flow (2021)
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    Publication Date: 2024-04-26
    Description: The ongoing energy transition introduces new challenges for distribution networks and brings about the need to expand existing power grid capacities. In order to contain network expansion and with it economic costs, utilization of various flexibility options to reduce expansion needs is discussed. This paper proposes a multiperiod optimal power flow (MPOPF) approach with a new continuous network expansion formulation to optimize the deployment of flexibility options under the objective of minimizing network expansion costs. In a comparison of the newly proposed continuous network expansion formulation with an existing mixed integer formulation and a continuous interpretation of the latter the here proposed formulation is shown to be useful in order to obtain a solvable problem and contain computational efforts. The presented MPOPF including the flexibility options storage units and curtailment is then assessed on synthetic medium voltage grids and applied to evaluate the benefit of a combined vs. a stepwise optimization of these flexibility options. It is demonstrated that using a local solver the proposed approach is applicable and yields a solution in reasonable time. Furthermore, it is shown that the combined optimization generally leads to a more efficient utilization of the considered flexibility options and therefore lower grid expansion costs than the stepwise consideration.
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 111
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    Modeling and forecasting gas network flows with multivariate time series and mathematical programming approach (2021)
    Details
    Publication Date: 2024-04-26
    Description: With annual consumption of approx. 95 billion cubic me-ters and similar amounts of gas just transshipped through Germany toother EU states, Germany’s gas transport system plays a vital role inEuropean energy supply. The complex, more than 40,000 km long high-pressure transmission network is controlled by several transmission sys-tem operators (TSOs) whose main task is to provide security of supplyin a cost-efficient way. Given the slow speed of gas flows through the gastransmission network pipelines, it has been an essential task for the gasnetwork operators to enhance the forecast tools to build an accurate andeffective gas flow prediction model for the whole network. By incorpo-rating the recent progress in mathematical programming and time seriesmodeling, we aim to model natural gas network and predict gas in- andout-flows at multiple supply and demand nodes for different forecastinghorizons. Our model is able to describe the dynamics in the network bydetecting the key nodes, which may help to build an optimal manage-ment strategy for transmission system operators.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 112
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    Deep learning for spatio-temporal supply anddemand forecasting in natural gas transmission networks (2021)
    Details
    Publication Date: 2024-04-26
    Description: Germany is the largest market for natural gas in the European Union, with an annual consumption of approx. 95 billion cubic meters. Germany's high-pressure gas pipeline network is roughly 40,000 km long, which enables highly fluctuating quantities of gas to be transported safely over long distances. Considering that similar amounts of gas are also transshipped through Germany to other EU states, it is clear that Germany's gas transport system is essential to the European energy supply. Since the average velocity of gas in a pipeline is only 25km/h, an adequate high-precision, high-frequency forecasting of supply and demand is crucial for efficient control and operation of such a transmission network. We propose a deep learning model based on spatio-temporal convolutional neural networks (DLST) to tackle the problem of gas flow forecasting in a complex high-pressure transmission network. Experiments show that our model effectively captures comprehensive spatio-temporal correlations through modeling gas networks and consistently outperforms state-of-the-art benchmarks on real-world data sets by at least 21%. The results demonstrate that the proposed model can deal with complex nonlinear gas network flow forecasting with high accuracy and effectiveness.
    Language: English
    Type: article , doc-type:article
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  • 113
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    Deep learning for spatio-temporal supply and demand forecasting in natural gas transmission networks (2021)
    Details
    Publication Date: 2024-04-26
    Description: Germany is the largest market for natural gas in the European Union, with an annual consumption of approx. 95 billion cubic meters. Germany's high-pressure gas pipeline network is roughly 40,000 km long, which enables highly fluctuating quantities of gas to be transported safely over long distances. Considering that similar amounts of gas are also transshipped through Germany to other EU states, it is clear that Germany's gas transport system is essential to the European energy supply. Since the average velocity of gas in a pipeline is only 25km/h, an adequate high-precision, high-frequency forecasting of supply and demand is crucial for efficient control and operation of such a transmission network. We propose a deep learning model based on spatio-temporal convolutional neural networks (DLST) to tackle the problem of gas flow forecasting in a complex high-pressure transmission network. Experiments show that our model effectively captures comprehensive spatio-temporal correlations through modeling gas networks and consistently outperforms state-of-the-art benchmarks on real-world data sets by at least 21$\%$. The results demonstrate that the proposed model can deal with complex nonlinear gas network flow forecasting with high accuracy and effectiveness.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 114
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    A hierarchical optimization approach to robust design of energy supply systems based on a mixed-integer linear model (2021)
    Details
    Publication Date: 2024-04-26
    Description: In designing energy supply systems, designers should heighten the robustness in performance criteria against the uncertainty in energy demands. In this paper, a robust optimal design method using a hierarchical mixed-integer linear programming (MILP) method is proposed to maximize the robustness of energy supply systems under uncertain energy demands based on a mixed-integer linear model. A robust optimal design problem is formulated as a three-level min-max-min MILP one by expressing uncertain energy demands by intervals, evaluating the robustness in a performance criterion based on the minimax regret criterion, and considering relationships among integer design variables, uncertain energy demands, and integer and continuous operation variables. This problem is solved by evaluating upper and lower bounds for the minimum of the maximum regret of the performance criterion repeatedly outside, and evaluating lower and upper bounds for the maximum regret repeatedly inside. Different types of optimization problems are solved by applying a hierarchical MILP method developed for ordinary optimal design problems without and with its modifications. In a case study, the proposed approach is applied to the robust optimal design of a cogeneration system. Through the study, its validity and effectiveness are ascertained, and some features of the obtained robust designs are clarified.
    Language: English
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  • 115
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    Robust Approximation of Chance Constrained DC Optimal Power Flow under Decision-Dependent Uncertainty (2021)
    Details
    Publication Date: 2024-04-26
    Description: We propose a mathematical optimization model and its solution for joint chance constrained DC Optimal Power Flow. In this application, it is particularly important that there is a high probability of transmission limits being satisfied, even in the case of uncertain or fluctuating feed-in from renewable energy sources. In critical network situations where the network risks overload, renewable energy feed-in has to be curtailed by the transmission system operator (TSO). The TSO can reduce the feed-in in discrete steps at each network node. The proposed optimization model minimizes curtailment while ensuring that there is a high probability of transmission limits being maintained. The latter is modeled via (joint) chance constraints that are computationally challenging. Thus, we propose a solution approach based on the robust safe approximation of these constraints. Hereby, probabilistic constraints are replaced by robust constraints with suitably defined uncertainty sets constructed from historical data. The ability to discretely control the power feed-in then leads to a robust optimization problem with decision-dependent uncertainties, i.e. the uncertainty sets depend on decision variables. We propose an equivalent mixed-integer linear reformulation for box uncertainties with the exact linearization of bilinear terms. Finally, we present numerical results for different test cases from the Nesta archive, as well as for a real network. We consider the discrete curtailment of solar feed-in, for which we use real-world weather and network data. The experimental tests demonstrate the effectiveness of this method and run times are very fast. Moreover, on average the calculated robust solutions only lead to a small increase in curtailment, when compared to nominal solutions.
    Language: English
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  • 116
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    Effect of model reduction by time aggregation in multiobjective optimal design of energy supply systems by a hierarchical MILP method (2021)
    Details
    Publication Date: 2024-04-26
    Description: The mixed-integer linear programming (MILP) method has been applied widely to optimal design of energy supply systems. A hierarchical MILP method has been proposed to solve such optimal design problems efficiently. In addition, a method of reducing model by time aggregation has been proposed to search design candidates accurately and efficiently at the upper level. In this paper, the hierarchical MILP method and model reduction by time aggregation are applied to the multiobjective optimal design. The methods of clustering periods by the order of time series, by the k-medoids method, and based on an operational strategy are applied for the model reduction. As a case study, the multiobjective optimal design of a gas turbine cogeneration system is investigated by adopting the annual total cost and primary energy consumption as the objective functions, and the clustering methods are compared with one another in terms of the computation efficiency. It turns out that the model reduction by any clustering method is effective to enhance the computation efficiency when importance is given to minimizing the first objective function, but that the model reduction only by the k-medoids method is effective very limitedly when importance is given to minimizing the second objective function.
    Language: English
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  • 117
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    Modeling functional time series and mixed-type predictors with partially functional autoregressions* (2021)
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    Publication Date: 2024-04-26
    Description: In many business and economics studies, researchers have sought to measure the dynamic dependence of curves with high-dimensional mixed-type predictors. We propose a partially functional autoregressive model (pFAR) where the serial dependence of curves is controlled by coefficient operators that are defined on a two-dimensional surface, and the individual and group effects of mixed-type predictors are estimated with a two-layer regularization. We develop an efficient estimation with the proven asymptotic properties of consistency and sparsity. We show how to choose the sieve and tuning parameters in regularization based on a forward-looking criterion. In addition to the asymptotic properties, numerical validation suggests that the dependence structure is accurately detected. The implementation of the pFAR within a real-world analysis of dependence in German daily natural gas flow curves, with seven lagged curves and 85 scalar predictors, produces superior forecast accuracy and an insightful understanding of the dynamics of natural gas supply and demand for the municipal, industry, and border nodes, respectively.
    Language: English
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  • 118
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    Optimization of Stationary Expansion Planning and Transient Network Control by Mixed-Integer Nonlinear Programming (2021)
    Details
    Publication Date: 2024-04-26
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 119
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    Statistical analysis and modeling for detecting regime changes in gas nomination time series (2021)
    Details
    Publication Date: 2024-04-26
    Description: As a result of the legislation for gas markets introduced by the European Union in 2005, separate independent companies have to conduct the transport and trading of natural gas. The current gas market of Germany, which has a market value of more than 54 billion USD, consists of Transmission System Operators (TSO), network users, and traders. Traders can nominate a certain amount of gas anytime and anywhere in the network. Such unrestricted access for the traders, on the other hand, increase the uncertainty in the gas supply management. Some customers’ behaviors may cause abrupt structural changes in gas flow time series. In particular, it is a challenging task for the TSO operators to predict gas nominations 6 to 10 hours ahead. In our study, we aim to investigate the regime changes in the time series of nominations to predict the 6 to 10 hours ahead of gas nominations.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 120
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    CMAP-LAP: Configurable Massively Parallel Solver for Lattice Problems (2021)
    Details
    Publication Date: 2024-04-26
    Description: Lattice problems are a class of optimization problems that are notably hard. There are no classical or quantum algorithms known to solve these problems efficiently. Their hardness has made lattices a major cryptographic primitive for post-quantum cryptography. Several different approaches have been used for lattice problems with different computational profiles; some suffer from super-exponential time, and others require exponential space. This motivated us to develop a novel lattice problem solver, CMAP-LAP, based on the clever coordination of different algorithms that run massively in parallel. With our flexible framework, heterogeneous modules run asynchronously in parallel on a large-scale distributed system while exchanging information, which drastically boosts the overall performance. We also implement full checkpoint-and-restart functionality, which is vital to high-dimensional lattice problems. Through numerical experiments with up to 103,680 cores, we evaluated the performance and stability of our system and demonstrated its high capability for future massive-scale experiments.
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 121
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    CMAP-LAP: Configurable Massively Parallel Solver for Lattice Problems (2021)
    Details
    Publication Date: 2024-04-26
    Description: Lattice problems are a class of optimization problems that are notably hard. There are no classical or quantum algorithms known to solve these problems efficiently. Their hardness has made lattices a major cryptographic primitive for post-quantum cryptography. Several different approaches have been used for lattice problems with different computational profiles; some suffer from super-exponential time, and others require exponential space. This motivated us to develop a novel lattice problem solver, CMAP-LAP, based on the clever coordination of different algorithms that run massively in parallel. With our flexible framework, heterogeneous modules run asynchronously in parallel on a large-scale distributed system while exchanging information, which drastically boosts the overall performance. We also implement full checkpoint-and-restart functionality, which is vital to high-dimensional lattice problems. Through numerical experiments with up to 103,680 cores, we evaluated the performance and stability of our system and demonstrated its high capability for future massive-scale experiments.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 122
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    Blending hydrogen into natural gas: An assessment of the capacity of the German gas grid; Technical Report (2021)
    Details
    Publication Date: 2024-04-26
    Description: In the transition towards a pure hydrogen infrastructure, utilizing the existing natural gas infrastructure is a necessity. In this study, the maximal technically feasible injection of hydrogen into the existing German natural gas transmission network is analysed with respect to regulatory limits regarding the gas quality. We propose a transient tracking model based on the general pooling problem including linepack. The analysis is conducted using real-world hourly gas flow data on a network of about 10,000 km length.
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  • 123
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    Massively parallel sharing lattice basis reduction (2021)
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    Publication Date: 2024-04-26
    Description: For cryptanalysis in lattice-based schemes, the performance evaluation of lattice basis reduction using high-performance computers is becoming increasingly important for the determination of the security level. We propose a distributed and asynchronous parallel reduction algorithm based on randomization and DeepBKZ, which is an improved variant of the block Korkine-Zolotarev (BKZ) reduction algorithm. Randomized copies of a lattice basis are distributed to up to 103,680 cores and independently reduced in parallel, while some basis vectors are shared asynchronously among all processes via MPI. There is a trade-off between randomization and information sharing; if a substantial amount of information is shared, all processes will work on the same problem, thereby diminishing the benefit of parallelization. To monitor this balance between randomness and sharing, we propose a metric to quantify the variety of lattice bases. We empirically find an optimal parameter of sharing for high-dimensional lattices. We demonstrate the efficacy of our proposed parallel algorithm and implementation with respect to both performance and scalability through our experiments.
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  • 124
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    Interface stability of compressible fluids in porous media (2021)
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    Publication Date: 2024-04-26
    Description: The stability of flows in porous media plays a vital role in transiting energy supply from natural gas to hydrogen, especially for estimating the usability of existing underground gas storage infrastructures. Thus, this research aims to analyze the interface stability of the tangential-velocity discontinuity between two compressible gases by using Darcy's model to include the porosity effect. The results shown in this research will be a basis for considering whether underground gas storages in porous material can be used to store hydrogen. We show the relation between the Mach number M, the viscosity \mu, and the porosity \epsilon on the stability of the interface. This interface stability affects gases' withdrawal and injection processes, thus will help us to determine the velocity which with gas can be extracted and injected into the storage effectively. By imposing solid walls along the flow direction, the critical values of these parameters regarding the stability of the interface are smaller than when considering no walls. The consideration of bounded flows approaches the problem more realistically. In particular, this analysis plays a vital role when considering two-dimensional gas flows in storages and pipes.
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  • 125
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    Effect of water depth on Kelvin - Helmholtz instability in a shallow-water flow (2021)
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    Publication Date: 2024-04-26
    Description: It is well known that the interface between two regions of an incompressible ideal fluid flow moving in a relative motion is necessarily destabilized, regardless of the velocity difference's strength. This phenomenon is the so-called Kelvin-Helmholtz instability (KHI). However, a large number of works demonstrated a surprising result that the instability is suppressed for shallow water flows; the interface is stabilized if the Froude number, defined by the velocity difference's ratio to the gravity wave's speed, is sufficiently large. In a limited way, these authors have been used the shallow-water equations without the higher-order effect of the dispersive terms. Thus, this investigation aims to examine these higher-order dispersive effects to analyze the interface stability problem of tangential-velocity discontinuity in shallow-water flows. In particular, we use the Green-Naghdi equations to introduce the dispersive terms related to the depth and the depth-averaged horizontal velocities of the fluid. We show that the interface stability depends on the Froude number (i.e., the velocity difference's strength) and the water depth. A critical value of the Froude number to stabilize the interface is smaller than the case of no dispersive terms, and the flow in a deeper region is more stable than in a shallower one. We also consider the distribution of kinetic and potential energy to clarify a feature characteristic of a large class of instabilities in shallow water flow. The instability of flows is caused by the decrease in the kinetic energy during the perturbation of waves. This phenomenon is known as negative energy modes and plays a vital role in applying the model to industrial equipment. A conclusion is that the equipartition of energies occurs if and only if the velocity difference is zero and the water depth is shallow enough to ignore the dispersive terms.
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  • 126
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    Instability of a tangential discontinuity surface in a three-dimensional compressible medium (2021)
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    Publication Date: 2024-04-26
    Description: Compressible flows appear in many natural and technological processes, for instance, the flow of natural gases in a pipe system. Thus, a detailed study of the stability of tangential velocity discontinuity in compressible media is relevant and necessary. The first early investigation in two-dimensional (2D) media was given more than 70 years ago. In this article, we continue investigating the stability in three-dimensional (3D) media. The idealized statement of this problem in an infinite spatial space was studied by Syrovatskii in 1954. However, the omission of the absolute sign of cos θ with θ being the angle between vectors of velocity and wave number in a certain inequality produced the inaccurate conclusion that the flow is always unstable for entire values of the Mach number M. First, we revisit this case to arrive at the correct conclusion, namely that the discontinuity surface is stabilized for a large Mach number with a given value of the angle θ. Next, we introduce a real finite spatial system such that it is bounded by solid walls along the flow direction. We show that the discontinuity surface is stable if and only if the dispersion relation equation has only real roots, with a large value of the Mach number; otherwise, the surface is always unstable. In particular, we show that a smaller critical value of the Mach number is required to make the flow in a narrow channel stable.
    Language: English
    Type: article , doc-type:article
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    Faster algorithms for Steiner tree and related problems: From theory to practice (2021)
    Details
    Publication Date: 2024-04-26
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
    Format: application/pdf
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  • 128
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    Inference of historical influence networks (2021)
    Details
    Publication Date: 2024-05-16
    Description: We study the romanization process of northern Africa from 50 BC till 300 AD. Our goal is to infer the communication strength between different subregions, based on the evolution of the status of cities. Herefore, we use the general inverse infection model, that infers the weights of a known underlying network, given observations of the spreading on this network. As infection process we choose the SI metapopulation model, where I stands for a city with a Roman status. To solve the minimization problem we use the particle swarm optimization algorithm with a specific choice of parameters.
    Language: German
    Type: conferenceobject , doc-type:conferenceObject
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  • 129
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    Prediction of Covid-19 spreading and optimal coordination of counter-measures: From microscopic to macroscopic models to Pareto fronts (2021)
    Details
    Publication Date: 2024-06-13
    Language: English
    Type: article , doc-type:article
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  • 130
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    Liberating structures : Entscheidungsfindung revolutionieren (2021)
    München :Verlag Franz Vahlen GmbH,
    Details
    Title: Liberating structures : Entscheidungsfindung revolutionieren
    Author: Steinhöfer, Daniel
    Publisher: München :Verlag Franz Vahlen GmbH,
    Year of publication: 2021
    Pages: 120 Seiten
    ISBN: 978-3-8006-5929-6
    Type of Medium: Book
    Language: German
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  • 131
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    Crashkurs BWA : betriebswirtschaftliche Auswertungen erstellen, lesen und verstehen (2021)
    Details
    Title: Crashkurs BWA : betriebswirtschaftliche Auswertungen erstellen, lesen und verstehen
    Author: Träger, Elisabeth
    Edition: 1. Auflage
    Year of publication: 2021
    Pages: 180 Seiten
    ISBN: 978-3-648-13768-0
    Type of Medium: Book
    Language: German
    URL: Inhaltstext
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  • 132
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    Book
    Introduction to Quantum Computing / (2021)
    Basel :Springer International Publishing,
    Details
    Title: Introduction to Quantum Computing /
    Author: LaPierre, Ray
    Publisher: Basel :Springer International Publishing,
    Year of publication: 2021
    Pages: 368 Seiten
    ISBN: 978-3-030-69317-6
    Type of Medium: Book
    Language: English
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  • 133
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    Book
    Forschungsdatenmanagement und Recht : Datenschutz-, Urheber- und Vertragsrecht (2021)
    Feldkirch/Düns :Neugebauer,
    Details
    Title: Forschungsdatenmanagement und Recht : Datenschutz-, Urheber- und Vertragsrecht
    Author: Baumann, Paul
    Contributer: Krahn, Philipp , Lauber-Rönsberg, Anne
    Publisher: Feldkirch/Düns :Neugebauer,
    Year of publication: 2021
    Pages: 304 Seiten
    ISBN: 978-3-85376-328-5
    Type of Medium: Book
    Language: German
    URL: Inhaltsverzeichnis
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  • 134
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    Book
    Git Handbuch für Einsteiger : Der leichte Weg zum Git-Experten (2021)
    Landshut :BMU Media Verlag,
    Details
    Title: Git Handbuch für Einsteiger : Der leichte Weg zum Git-Experten
    Author: Fuchs, Paul
    Publisher: Landshut :BMU Media Verlag,
    Year of publication: 2021
    Pages: 307 Seiten
    ISBN: 978-3-96645-119-2
    Type of Medium: Book
    Language: German
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  • 135
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    Book
    Git für Dummies / (2021)
    Weinheim :Wiley-VCH,
    Details
    Title: Git für Dummies /
    Author: Kaufmann, Michael
    Contributer: Binkle, Harald
    Publisher: Weinheim :Wiley-VCH,
    Year of publication: 2021
    Pages: 417 Seiten
    ISBN: 978-3-527-71697-5
    Type of Medium: Book
    Language: German
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  • 136
    Book
    Book
    Linear Algebra : Theory, Intuition, Code (2021)
    Sincxpress Bv,
    Details
    Title: Linear Algebra : Theory, Intuition, Code
    Author: Cohen, Mike X
    Publisher: Sincxpress Bv,
    Year of publication: 2021
    Pages: 548 S.
    ISBN: 978-90-831366-0-8
    Type of Medium: Book
    Language: German
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  • 137
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    Handbuch Prüfung ortsveränderlicher elektrischer Geräte : Prüfabläufe, Grenz- und Richtwerte gem. DIN VDE 0701-0702 für die Prüfung vor Ort (2021)
    Forum Verlag Herkert,
    Details
    Title: Handbuch Prüfung ortsveränderlicher elektrischer Geräte : Prüfabläufe, Grenz- und Richtwerte gem. DIN VDE 0701-0702 für die Prüfung vor Ort
    Contributer: Donath, Karl [Verfasser] , Rottmann, Rainer [Verfasser] , Gavrancic, Milan [Verfasser] , Orgel, Christian [Verfasser]
    Edition: 4. überarbeitete Auflage
    Publisher: Forum Verlag Herkert,
    Year of publication: 2021
    Pages: 311 Seiten
    ISBN: 978-3-96314-615-2
    Type of Medium: Book
    Language: German
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  • 138
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    Book
    Handbuch Prüfung ortsfester elektrischer Anlagen und Betriebsmittel : Prüfabläufe, Grenz- und Richtwerte gem. DIN VDE 0100-600 und 0105-100 für die Prüfung vor Ort (2021)
    Forum Verlag Herkert,
    Details
    Title: Handbuch Prüfung ortsfester elektrischer Anlagen und Betriebsmittel : Prüfabläufe, Grenz- und Richtwerte gem. DIN VDE 0100-600 und 0105-100 für die Prüfung vor Ort
    Author: Donath, Karl [Verfasser]
    Contributer: Rottmann, Rainer [Verfasser] , Orgel, Christian [Verfasser]
    Edition: 4. überarbeitete Auflage
    Publisher: Forum Verlag Herkert,
    Year of publication: 2021
    Pages: 374 Seiten
    Type of Medium: Book
    Language: German
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  • 139
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    Book
    HTML und CSS : das umfassende Handbuch (2021)
    Bonn :Rheinwerk Verlag,
    Details
    Title: HTML und CSS : das umfassende Handbuch
    Author: Wolf, Jürgen
    Edition: 4., aktualisierte und überarbeitete Auflage
    Publisher: Bonn :Rheinwerk Verlag,
    Year of publication: 2021
    Pages: 1158 Seiten
    ISBN: 978-3-8362-8117-1
    Type of Medium: Book
    Language: German
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  • 140
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    Book
    Docker : das Praxisbuch für Entwickler und DevOps-Teams (2021)
    Details
    Title: Docker : das Praxisbuch für Entwickler und DevOps-Teams
    Author: Öggl, Bernd
    Contributer: Kofler, Michael
    Edition: 3. Aufl.
    Year of publication: 2021
    Pages: 496 S. : , Illustrationen, Diagramme
    ISBN: 978-3-8362-8634-3
    Type of Medium: Book
    Language: German
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  • 141
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    Muster : Theorie der digitalen Gesellschaft (2021)
    München :C.H. Beck,
    Details
    Title: Muster : Theorie der digitalen Gesellschaft
    Author: Nassehi, Armin
    Edition: 1. Auflage
    Publisher: München :C.H. Beck,
    Year of publication: 2021
    Pages: 352 Seiten
    ISBN: 978-3-406-76786-9
    Type of Medium: Book
    Language: German
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  • 142
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    ¬The¬ science of science / (2021)
    Cambridge :Cambridge University Press,
    Details
    Title: ¬The¬ science of science /
    Author: Wang, Dashun
    Contributer: Barabási, Albert-László
    Publisher: Cambridge :Cambridge University Press,
    Year of publication: 2021
    Pages: x, 303 Seiten
    ISBN: 978-1-108-71695-6
    Type of Medium: Book
    Language: English
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  • 143
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    Book
    Grundlagen der Eingruppierung TVöD und TV-L : das aktuelle Eingruppierungsrecht im öffentlichen Dienst (2021)
    Berlin :Walhalla und Praetoria Verlag,
    Details
    Title: Grundlagen der Eingruppierung TVöD und TV-L : das aktuelle Eingruppierungsrecht im öffentlichen Dienst
    Author: Richter, Achim
    Contributer: Gamisch, Annett , Mohr, Thomas
    Edition: 7., aktualisierte Auflage, Bearbeitungsstand: Juni 2017
    Publisher: Berlin :Walhalla und Praetoria Verlag,
    Year of publication: 2021
    Pages: 112 Seiten
    ISBN: 978-3-8029-1599-4
    Type of Medium: Book
    Language: German
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  • 144
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    Book
    Crashkurs Internes Kontrollsystem für Buchhaltung und Steuern / (2021)
    Details
    Title: Crashkurs Internes Kontrollsystem für Buchhaltung und Steuern /
    Author: Alves, Winfried
    Edition: 2. völlig überarbeitete und erweiterte Auflage
    Year of publication: 2021
    Pages: 167 Seiten
    ISBN: 978-3-648-14049-9
    Type of Medium: Book
    Language: German
    URL: Inhaltstext
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  • 145
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    Book
    Schwierige Geschäftsvorfälle richtig buchen / (2021)
    Freiburg im Breisgau :Haufe-Lexware,
    Details
    Title: Schwierige Geschäftsvorfälle richtig buchen /
    Author: Thomsen, Iris
    Contributer: Zöllner, Nikolaus
    Edition: 15. Auflage
    Publisher: Freiburg im Breisgau :Haufe-Lexware,
    Year of publication: 2021
    Pages: 413 Seiten
    ISBN: 978-3-648-14840-2
    Type of Medium: Book
    Language: German
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  • 146
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    Book
    Programming Rust : fast, safe systems development (2021)
    Beijing ; Boston ; Farnham ; Sebastopol :O'Reilly,
    Details
    Title: Programming Rust : fast, safe systems development
    Author: Blandy, Jim
    Contributer: Orendorff, Jason , Tindall, Leonora
    Edition: Second edition
    Publisher: Beijing ; Boston ; Farnham ; Sebastopol :O'Reilly,
    Year of publication: 2021
    Pages: xix, 711 Seiten
    ISBN: 9781492052562
    Type of Medium: Book
    Language: English
    Parallel Title: Erscheint auch als Druck-Ausgabe 978-1-492-05259-3
    URL: https://search.ebscohost.com/login.aspx?direct=true&db=nlebk&AN=2949563&site=ehost-live
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  • 147
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    Book
    Erfurter Kommentar zum Arbeitsrecht (2021)
    München :C.H. Beck,
    Details
    Title: Erfurter Kommentar zum Arbeitsrecht
    Contributer: Müller-Glöge, Rudi , Preis, Ulrich , Gallner, Inken
    Edition: 22. Auflage
    Publisher: München :C.H. Beck,
    Year of publication: 2021
    Pages: 3100 Seiten
    ISBN: 978-3-406-77038-8
    Type of Medium: Book
    Language: German
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  • 148
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    Book
    Götzendämmerung : Kunst und Künstliche Intelligenz (2021)
    Bielefeld :transcript,
    Details
    Title: Götzendämmerung : Kunst und Künstliche Intelligenz
    Contributer: Dotzler, Bernhard J. , Karpat, Berkan
    Publisher: Bielefeld :transcript,
    Year of publication: 2021
    Pages: 154 Seiten
    ISBN: 978-3-8376-5976-4
    Type of Medium: Book
    Language: German
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  • 149
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    Exploration of different wave patterns in a model of the bovine estrous cycle by Fourier analysis (2016)
    Details
    Publication Date: 2022-03-11
    Description: Cows typically have different numbers of follicular waves during their hormonal cycle. Understanding the underlying regulations leads to insights into the reasons for declined fertility, a phenomenon that has been observed during the last decades. We present a systematic approach based on Fourier analysis to examine how parameter changes in a model of the bovine estrous cycle lead to different wave patterns. Even without any biological considerations, this allows to detect the responsible model parameters that control the type of periodicity of the solution, thus supporting experimental planning of animal scientists.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 150
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    Integrated Optimization of Rolling Stock Rotations for Intercity Railways (2016)
    Details
    Publication Date: 2020-08-05
    Description: This paper proposes a highly integrated solution approach for rolling stock planning problems in the context of long distance passenger traffic between cities. The main contributions are a generic hypergraph-based mixed-integer programming model for the considered rolling stock rotation problem and an integrated algorithm for its solution. The newly developed algorithm is able to handle a large spectrum of industrial railway requirements, such as vehicle composition, maintenance constraints, infrastructure capacities, and regularity aspects. We show that our approach has the power to produce rolling stock rotations that can be implemented in practice. In this way, the rolling stock rotations at the largest German long distance operator Deutsche Bahn Fernverkehr AG could be optimized by an automated system utilizing advanced mathematical programming techniques.
    Language: English
    Type: article , doc-type:article
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  • 151
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    The Optical Chirality Flux as a Useful Far-Field Probe of Chiral Near Fields (2016)
    Details
    Publication Date: 2022-01-07
    Language: English
    Type: article , doc-type:article
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  • 152
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    Exploiting Solving Phases for Mixed-Integer Programs (2016)
    Details
    Publication Date: 2020-08-05
    Description: Modern MIP solving software incorporates dozens of auxiliary algorithmic components for supporting the branch-and-bound search in finding and improving solutions and in strengthening the relaxation. Intuitively, a dynamic solving strategy with an appropriate emphasis on different solving components and strategies is desirable during the search process. We propose an adaptive solver behavior that dynamically reacts on transitions between the three typical phases of a MIP solving process: The first phase objective is to find a feasible solution. During the second phase, a sequence of incumbent solutions gets constructed until the incumbent is eventually optimal. Proving optimality is the central objective of the remaining third phase. Based on the MIP-solver SCIP, we demonstrate the usefulness of the phase concept both with an exact recognition of the optimality of a solution, and provide heuristic alternatives to make use of the concept in practice.
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 153
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    FFMK: A Fast and Fault-tolerant Microkernel-based System for Exascale Computing (2016)
    Details
    Publication Date: 2021-01-22
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 154
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    Methoden zur Reduktion der Rechenzeit linearer Optimierungsmodelle in der Energiewirtschaft - Eine Performance-Analyse (2016)
    Details
    Publication Date: 2020-08-05
    Description: Dieser Beitrag stellt mögliche Ansätze zur Reduktion der Rechenzeit von linearen Optimierungsproblemen mit energiewirtschaftlichem Anwendungshintergrund vor. Diese Ansätze bilden im Allgemeinen die Grundlage für konzeptionelle Strategien zur Beschleunigung von Energiesystemmodellen. Zu den einfachsten Beschleunigungsstrategien zählt die Verkleinerung der Modelldimensionen, was beispielsweise durch Ändern der zeitlichen, räumlichen oder technologischen Auflösung eines Energiesystemmodells erreicht werden kann. Diese Strategien sind zwar häufig ein Teil der Methodik in der Energiesystemanalyse, systematische Benchmarks zur Bewertung ihrer Effektivität werden jedoch meist nicht durchgeführt. Die vorliegende Arbeit adressiert genau diesen Sachverhalt. Hierzu werden Modellinstanzen des Modells REMix in verschiedenen Größenordnungen mittels einer Performance-Benchmark-Analyse untersucht. Die Ergebnisse legen zum einen den Schluss nahe, dass verkürzte Betrachtungszeiträume das größte Potential unter den hier analysierten Strategien zur Reduktion von Rechenzeit bieten. Zum anderen empfiehlt sich die Verwendung des Barrier-Lösungsverfahrens mit multiplen Threads unter Vernachlässigung des Cross-Over.
    Language: German
    Type: conferenceobject , doc-type:conferenceObject
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  • 155
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    Fast In-Memory Checkpointing with POSIX API for Legacy Exascale-Applications (2016)
    Details
    Publication Date: 2021-01-22
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 156
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    Effects of carbamazepine and two of its metabolites on the non-biting midge Chironomus riparius in a sediment full life cycle toxicity test (2016)
    Details
    Publication Date: 2021-02-05
    Description: The antiepileptic drug carbamazepine (CBZ) and its main metabolites carbamazepine-10,11-epoxide (EP-CBZ) and 10,11-dihydro-10,11-dihydroxy-carbamazepine (DiOH-CBZ) were chosen as test substances to assess chronic toxicity on the non-biting midge Chironomus riparius. All three substances were tested in a 40-day sediment full life cycle test (according to OECD 233) in which mortality, emergence, fertility, and clutch size were evaluated. In addition, these parameters were integrated into the population growth rate to reveal population relevant effects. With an LC50 of 0.203 mg/kg (time-weighted mean), the metabolite EP-CBZ was significantly more toxic than the parent substance CBZ (LC50: 1.11 mg/kg). Especially mortality, emergence, and fertility showed to be sensitive parameters under the exposure to CBZ and EP-CBZ. By using classical molecular dynamics (MD) simulations, the binding of CBZ to the ecdysone receptor was investigated as one possible mode of action but showed to be unlikely. The second metabolite DiOH-CBZ did not show any effects within the tested concentration rage (0.171 – 1.22 mg/kg). Even though CBZ was less toxic compared to EP-CBZ, CBZ is found in the environment at much higher concentrations and causes therefore a higher potential risk for sediment dwelling organisms compared to its metabolites. Nevertheless, the current study illustrates the importance of including commonly found metabolites into the risk assessment of parent substances.
    Language: English
    Type: article , doc-type:article
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  • 157
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    The Freight Train Routing Problem for Congested Railway Networks with Mixed Traffic (2016)
    Details
    Publication Date: 2020-08-05
    Description: We consider the following freight train routing problem (FTRP). Given is a transportation network with fixed routes for passenger trains and a set of freight trains (requests), each defined by an origin and destination station pair. The objective is to calculate a feasible route for each freight train such that the sum of all expected delays and all running times is minimal. Previous research concentrated on microscopic train routings for junctions or inside major stations. Only recently approaches were developed to tackle larger corridors or even networks. We investigate the routing problem from a strategic perspective, calculating the routes in a macroscopic transportation network of Deutsche Bahn AG. In this context, macroscopic refers to an aggregation of complex and large real-world structures into fewer network elements. Moreover, the departure and arrival times of freight trains are approximated. The problem has a strategic character since it asks only for a coarse routing through the network without the precise timings. We provide a mixed-integer nonlinear programming (MINLP) formulation for the FTRP, which is a multicommodity flow model on a time-expanded graph with additional routing constraints. The model’s nonlinearities originate from an algebraic approximation of the delays of the trains on the arcs of the network by capacity restraint functions. The MINLP is reduced to a mixed-integer linear model (MILP) by piecewise linear approximation. The latter is solved by a state-of-the art MILP solver for various real-world test instances.
    Language: English
    Type: article , doc-type:article
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  • 158
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    A novel method for undisturbed long-term observation of the honey bee (Apis mellifera) behaviour – illustrated by the hygienic behaviour towards Varroa infestation (2016)
    Details
    Publication Date: 2017-04-03
    Language: English
    Type: article , doc-type:article
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  • 159
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    Genome-wide association study of a Varroa-specific defense behavior in honeybees (Apis mellifera) (2016)
    Details
    Publication Date: 2016-06-09
    Language: English
    Type: article , doc-type:article
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  • 160
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    Integrated Line Planning and Passenger Routing: Connectivity and Transfers (2016)
    Details
    Publication Date: 2020-08-05
    Description: The integrated line planning and passenger routing problem is an important planning problem in service design of public transport. A major challenge is the treatment of transfers. A main property of a line system is its connectivity. In this paper we show that analysing the connecvitiy aspect of a line plan gives a new idea to handle the transfer aspect of the line planning problem.
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 161
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    Konzipierung und Implementierung eines Quota-Protokolls in objektbasierten Dateisystemen (2016)
    Details
    Publication Date: 2020-11-16
    Description: Verteilte Dateisysteme, wie sie unter anderem in Cloud-Umgebungen eingesetzt werden, werden häufig von verschiedenen Anwendern und Anwendungen zeitgleich verwendet. Da diese Ressourcen in Cloud-Umgebungen gemietet sind, muss sichergestellt werden, dass ein Kunde nur die Ressourcen verwenden kann, für die er bezahlt hat. Andernfalls könnten andere Kunden beeinträchtigt werden. Solch eine Obergrenze wird auch als Quota bezeichnet. Speziell für objektbasierte Dateisysteme, bei denen die Metadaten einer Datei von den Dateiinhalten getrennt gespeichert und verwaltet werden, erfordert die Forcierung einer Quota ein verteiltes Protokoll. Im Rahmen der vorliegenden Arbeit wurde ein Quota-Protokoll für objektbasierte Dateisysteme entwickelt und implementiert. Bei einer aktiven Quota wird zunächst ein Teil des Speicherplatzes für eine bestimmte Datei blockiert, der als Voucher bezeichnet wird. Anschließend wird dem Client die maximale Dateigröße in signierter Form zugewiesen. Sie ergibt sich aus der Summe der bisherigen Dateigröße und allen erstellten Vouchers. Durch diesen Ansatz können die Speicherserver bei jedem Zugriff lokal prüfen, ob der Schreibzugriff die maximale Dateigröße überschreiten würde. Reicht diese nicht aus, muss ein zusätzlicher Voucher erstellt werden, sofern noch Speicherplatz verfügbar ist. Nicht verbrauchter Speicherplatz wird am Ende wieder freigegeben. Zusätzlich unterstützt das Protokoll die Verteilung der Inhalte einer Datei auf mehrere Server (Striping) sowie Sparse-Dateien, bei denen beliebige Bereiche der Datei leer bleiben. Die Implementierung erfolgte im objektbasierten Dateisystem XtreemFS. Dabei wurden spezielle Funktionen von XtreemFS, wie die Dateireplikation, mit einbezogen. In einer abschließenden Evaluation wurde der Einfluss des implementierten Quota- Protokolls bezüglich der Performanz von XtreemFS untersucht. Dabei zeigte sich zunächst, dass bei einer aktiven Quota die Performanz beim Schreiben großer Daten- mengen abhängig von der eingestellten Voucher-Größe ist. Ist diese zu niedrig gewählt, so muss der Client seine maximale Dateigröße durch zusätzliche Anfragen beim Metada- tenserver erhöhen, was die Performanz negativ beeinträchtigt. Bei einer Voucher-Größe von 100 MiB wurde beim Schreiben einer 10 GiB-Datei ein Performanzverlust von unter 2% gemessen, verglichen mit dem Entwicklungsstand ohne implementiertes Quota- Protokoll. Bei der Erstellung mehrerer 64 KiB-Dateien wurde aufgrund zusätzlicher Nachrichten ein Verlust von rund 8% gemessen.
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 162
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    Ray Tracing Boundary Value Problems: Simulation and SAFT Reconstruction for Ultrasonic Testing (2016)
    Details
    Publication Date: 2022-01-07
    Description: The application of advanced imaging techniques for the ultrasonic inspection of inhomogeneous anisotropic materials like austenitic and dissimilar welds requires information about acoustic wave propagation through the material, in particular travel times between two points in the material. Forward ray tracing is a popular approach to determine traveling paths and arrival times but is ill suited for inverse problems since a large number of rays have to be computed in order to arrive at prescribed end points. In this contribution we discuss boundary value problems for acoustic rays, where the ray path between two given points is determined by solving the eikonal equation. The implementation of such a two point boundary value ray tracer for sound field simulations through an austenitic weld is described and its efficiency as well as the obtained results are compared to those of a forward ray tracer. The results are validated by comparison with experimental results and commercially available UT simulation tools. As an application, we discuss an implementation of the method for SAFT (Synthetic Aperture Focusing Technique) reconstruction. The ray tracer calculates the required travel time through the anisotropic columnar grain structure of the austenitic weld. There, the formulation of ray tracing as a boundary value problem allows a straightforward derivation of the ray path from a given transducer position to any pixel in the reconstruction area and reduces the computational cost considerably.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 163
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    ILP heuristics and a new exact method for bi-objective 0/1 ILPs: Application to FTTx-network design (2016)
    Details
    Publication Date: 2020-08-05
    Language: English
    Type: article , doc-type:article
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  • 164
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    Digitale Langzeitarchivierung: Mustervorlage für Übernahmevereinbarungen (2016)
    Details
    Publication Date: 2020-12-11
    Description: Digitale Langzeitarchivierung erfolgt auf Grundlage verbindlicher Regelungen zwischen Langzeitarchiv und Datengeber. Detaillierte organisatorische und technische Bedingungen für Datenübernahmen werden dabei in Absprache zwischen den Kooperationspartnern in einer Übernahmevereinbarung festgehalten. Im Rahmen der Entwicklung des Langzeitarchivs EWIG am Zuse Institute Berlin ist die hier dokumentierte Mustervorlage für Übernahmevereinbarungen entstanden.
    Language: German
    Type: reportzib , doc-type:preprint
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  • 165
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    Robust Allocation of Operating Rooms with Lognormal case Durations (2016)
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    Publication Date: 2020-08-05
    Description: The problem of allocating operating rooms (OR) to surgical cases is a challenging task, involving both combinatorial aspects and uncertainty handling. In this article, we formulate this problem as a job shop scheduling problem, in which the job durations follow a lognormal distribution. We propose to use a cutting-plane approach to solve a robust version of this optimization problem. To this end, we develop an algorithm based on fixed-point iterations to solve the subproblems that identify worst-case scenarios and generate cut inequalities. The procedure is illustrated with numerical experiments based on real data from a major hospital in Berlin.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 166
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    Portfoliooptimierung mittels mathematischer Optimierung (2016)
    Details
    Publication Date: 2020-08-05
    Language: German
    Type: bachelorthesis , doc-type:bachelorThesis
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  • 167
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    Multiband Robust Optimization for optimal energy offering under price uncertainty (2016)
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    Publication Date: 2020-08-05
    Description: We consider the problem of a price-taker generating company that wants to select energy offering strategies for its generation units, to maximize the profit while considering the uncertainty of market price. First, we review central references available in literature about the use of Robust Optimization (RO) for price-uncertain energy offering, pointing out how they can expose to the risk of suboptimal and even infeasible offering. We then propose a new RO method for energy offering that overcomes all the limits of other RO methods. We show the effectiveness of the new method on realistic instances provided by our industrial partners, getting very high increases in profit. Our method is based on Multiband Robustness (MR - Büsing, D'Andreagiovanni, 2012), an RO model that refines the classical RO model by Bertsimas and Sim, while maintaining its computational tractability and accessibility. MR is essentially based on the use of histogram-like uncertainty sets, which result particularly suitable to represent empirical distributions commonly available in uncertain real-world optimization problems.
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 168
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    Solving Open MIP Instances with ParaSCIP on Supercomputers using up to 80,000 Cores (2016)
    Details
    Publication Date: 2022-03-14
    Description: This paper describes how we solved 12 previously unsolved mixed-integer program- ming (MIP) instances from the MIPLIB benchmark sets. To achieve these results we used an enhanced version of ParaSCIP, setting a new record for the largest scale MIP computation: up to 80,000 cores in parallel on the Titan supercomputer. In this paper we describe the basic parallelization mechanism of ParaSCIP, improvements of the dynamic load balancing and novel techniques to exploit the power of parallelization for MIP solving. We give a detailed overview of computing times and statistics for solving open MIPLIB instances.
    Language: English
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  • 169
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    Towards an accurate solution of wireless network design problems (2016)
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    Publication Date: 2020-08-05
    Description: The optimal design of wireless networks has been widely studied in the literature and many optimization models have been proposed over the years. However, most models directly include the signal-to-interference ratios representing service coverage conditions. This leads to mixed-integer linear programs with constraint matrices containing tiny coefficients that vary widely in their order of magnitude. These formulations are known to be challenging even for state-of-the-art solvers: the standard numerical precision supported by these solvers is usually not sufficient to reliably guarantee feasible solutions. Service coverage errors are thus commonly present. Though these numerical issues are known and become evident even for small-sized instances, just a very limited number of papers has tried to tackle them, by mainly investigating alternative non-compact formulations in which the sources of numerical instabilities are eliminated. In this work, we explore a new approach by investigating how recent advances in exact solution algorithms for linear and mixed-integer programs over the rational numbers can be applied to analyze and tackle the numerical difficulties arising in wireless network design models.
    Language: English
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  • 170
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    Thermal energy and charge currents in multi-terminal nanorings (2016)
    Details
    Publication Date: 2020-03-10
    Description: We study in experiment and theory thermal energy and charge transfer close to the quantum limit in a ballistic nanodevice, consisting of multiply connected one-dimensional electron waveguides. The fabricated device is based on an AlGaAs/GaAs heterostructure and is covered by a global top-gate to steer the thermal energy and charge transfer in the presence of a temperature gradient, which is established by a heating current. The estimate of the heat transfer by means of thermal noise measurements shows the device acting as a switch for charge and thermal energy transfer. The wave-packet simulations are based on the multi-terminal Landauer-Büttiker approach and confirm the experimental finding of a mode-dependent redistribution of the thermal energy current, if a scatterer breaks the device symmetry.
    Language: English
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  • 171
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    Three Enhancements for Optimization-Based Bound Tightening (2016)
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    Publication Date: 2022-03-14
    Description: Optimization-based bound tightening (OBBT) is one of the most effective procedures to reduce variable domains of nonconvex mixed-integer nonlinear programs (MINLPs). At the same time it is one of the most expensive bound tightening procedures, since it solves auxiliary linear programs (LPs)—up to twice the number of variables many. The main goal of this paper is to discuss algorithmic techniques for an efficient implementation of OBBT. Most state-of-the-art MINLP solvers apply some restricted version of OBBT and it seems to be common belief that OBBT is beneficial if only one is able to keep its computational cost under control. To this end, we introduce three techniques to increase the efficiency of OBBT: filtering strategies to reduce the number of solved LPs, ordering heuristics to exploit simplex warm starts, and the generation of Lagrangian variable bounds (LVBs). The propagation of LVBs during tree search is a fast approximation to OBBT without the need to solve auxiliary LPs. We conduct extensive computational experiments on MINLPLib2. Our results indicate that OBBT is most beneficial on hard instances, for which we observe a speedup of 17% to 19% on average. Most importantly, more instances can be solved when using OBBT.
    Language: English
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  • 172
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    Challenges facing an understanding of the nature of low-energy excited states in photosynthesis (2016)
    Details
    Publication Date: 2020-05-06
    Description: While the majority of the photochemical states and pathways related to the biological capture of solar energy are now well understood and provide paradigms for artificial device design, additional low-energy states have been discovered in many systems with obscure origins and significance. However, as low-energy states are naively expected to be critical to function, these observations pose important challenges. A review of known properties of low energy states covering eight photochemical systems, and options for their interpretation, are presented. A concerted experimental and theoretical research strategy is suggested and outlined, this being aimed at providing a fully comprehensive understanding.
    Language: English
    Type: article , doc-type:article
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  • 173
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    Mathematical Modelling of Follicular Maturation in Cows and Women (2016)
    Details
    Publication Date: 2022-03-11
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 174
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    SCIP: Global Optimization of Mixed-Integer Nonlinear Programs in a Branch-and-Cut Framework (2016)
    Details
    Publication Date: 2020-08-05
    Description: This paper describes the extensions that were added to the constraint integer programming framework SCIP in order to enable it to solve convex and nonconvex mixed-integer nonlinear programs (MINLPs) to global optimality. SCIP implements a spatial branch-and-bound algorithm based on a linear outer-approximation, which is computed by convex over- and underestimation of nonconvex functions. An expression graph representation of nonlinear constraints allows for bound tightening, structure analysis, and reformulation. Primal heuristics are employed throughout the solving process to find feasible solutions early. We provide insights into the performance impact of individual MINLP solver components via a detailed computational study over a large and heterogeneous test set.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 175
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    Ende-zu-Ende Verschlüsselung in XtreemFS (2016)
    Details
    Publication Date: 2021-01-21
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 176
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    The Monte Carlo Computation Error of Transition Probabilities (2016)
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    Publication Date: 2016-07-22
    Description: In many applications one is interested to compute transition probabilities of a Markov chain. This can be achieved by using Monte Carlo methods with local or global sampling points. In this article, we analyze the error by the difference in the $L^2$ norm between the true transition probabilities and the approximation achieved through a Monte Carlo method. We give a formula for the error for Markov chains with locally computed sampling points. Further, in the case of reversible Markov chains, we will deduce a formula for the error when sampling points are computed globally. We will see that in both cases the error itself can be approximated with Monte Carlo methods. As a consequence of the result, we will derive surprising properties of reversible Markov chains.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 177
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    A Two Dimensional Fiber Grating Coupler on SOI for Mode Division Multiplexing (2016)
    Details
    Publication Date: 2020-03-09
    Language: English
    Type: article , doc-type:article
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  • 178
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    An Extended Formulation for the Line Planning Problem (2016)
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    Publication Date: 2020-08-05
    Description: In this paper we present a novel extended formulation for the line planning problem that is based on what we call “configurations” of lines and frequencies. Configurations account for all possible options to provide a required transportation capacity on an infrastructure edge. The proposed configuration model is strong in the sense that it implies several facet-defining inequalities for the standard model: set cover, symmetric band, MIR, and multicover inequalities. These theoretical findings can be confirmed in computational results. Further, we show how this concept can be generalized to define configurations for subsets of edges; the generalized model implies additional inequalities from the line planning literature.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 179
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    Prior estimation and Bayesian inference from large cohort data sets (2016)
    Details
    Publication Date: 2021-07-06
    Description: One of the main goals of mathematical modelling in systems biology related to medical applications is to obtain patient-specific parameterisations and model predictions. In clinical practice, however, the number of available measurements for single patients is usually limited due to time and cost restrictions. This hampers the process of making patient-specific predictions about the outcome of a treatment. On the other hand, data are often available for many patients, in particular if extensive clinical studies have been performed. Using these population data, we propose an iterative algorithm for contructing an informative prior distribution, which then serves as the basis for computing patient-specific posteriors and obtaining individual predictions. We demonsrate the performance of our method by applying it to a low-dimensional parameter estimation problem in a toy model as well as to a high-dimensional ODE model of the human menstrual cycle, which represents a typical example from systems biology modelling.
    Language: English
    Type: reportzib , doc-type:preprint
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  • 180
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    Computation Schemes for Transfer Operators (2016)
    Details
    Publication Date: 2016-06-09
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 181
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    Inside Finite Elements (2016)
    Details
    Publication Date: 2019-01-29
    Description: All relevant implementation aspects of finite element methods are discussed in this book. The focus is on algorithms and data structures as well as on their concrete implementation. Theory is covered as far as it gives insight into the construction of algorithms.Throughout the exercises a complete FE-solver for scalar 2D problems will be implemented in Matlab/Octave.
    Language: English
    Type: book , doc-type:book
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  • 182
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    Allosteric and Chelate Cooperativity in Divalent Crown Ether–Ammonium Complexes with Strong Binding Enhancements (2016)
    Details
    Publication Date: 2020-04-29
    Language: English
    Type: article , doc-type:article
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  • 183
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    Iterative Refinement for Linear Programming (2016)
    Details
    Publication Date: 2021-02-01
    Description: We describe an iterative refinement procedure for computing extended precision or exact solutions to linear programming problems (LPs). Arbitrarily precise solutions can be computed by solving a sequence of closely related LPs with limited precision arithmetic. The LPs solved share the same constraint matrix as the original problem instance and are transformed only by modification of the objective function, right-hand side, and variable bounds. Exact computation is used to compute and store the exact representation of the transformed problems, while numeric computation is used for solving LPs. At all steps of the algorithm the LP bases encountered in the transformed problems correspond directly to LP bases in the original problem description. We show that this algorithm is effective in practice for computing extended precision solutions and that it leads to a direct improvement of the best known methods for solving LPs exactly over the rational numbers. Our implementation is publically available as an extension of the academic LP solver SoPlex.
    Language: English
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  • 184
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    An (MI)LP-based Primal Heuristic for 3-Architecture Connected Facility Location in Urban Access Network Design (2016)
    Details
    Publication Date: 2020-08-05
    Description: We investigate the 3-architecture Connected Facility Location Problem arising in the design of urban telecommunication access networks integrating wired and wireless technologies. We propose an original optimization model for the problem that includes additional variables and constraints to take into account wireless signal coverage represented through signal-to-interference ratios. Since the problem can prove very challenging even for modern state-of-the art optimization solvers, we propose to solve it by an original primal heuristic that combines a probabilistic fixing procedure, guided by peculiar Linear Programming relaxations, with an exact MIP heuristic, based on a very large neighborhood search. Computational experiments on a set of realistic instances show that our heuristic can find solutions associated with much lower optimality gaps than a state-of-the-art solver.
    Language: English
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  • 185
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    Quantitative Defect Reconstruction in Active Thermography for Fiber-Reinforced Composites (2016)
    Details
    Publication Date: 2022-01-07
    Description: Carbon-fiber reinforced composites are becoming more and more important in the production of light-weight structures, e.g., in the automotive and aerospace industry. Thermography is often used for non-destructive testing of these products, especially to detect delaminations between different layers of the composite. In this presentation, we aim at methods for defect reconstruction from thermographic measurements of such carbon-fiber reinforced composites. The reconstruction results shall not only allow to locate defects, but also give a quantitative characterization of the defect properties. We discuss the simulation of the measurement process using finite element methods, as well as the experimental validation on flat bottom holes. Especially in pulse thermography, thin boundary layers with steep temperature gradients occurring at the heated surface need to be resolved. Here we use the combination of a 1D analytical solution combined with numerical solution of the remaining defect equation. We use the simulations to identify material parameters from the measurements. Finally, fast heuristics for reconstructing defect geometries are applied to the acquired data, and compared for their accuracy and utility in detecting different defects like back surface defects or delaminations.
    Language: English
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  • 186
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    Perfect f-Matchings and f-Factors in Hypergraphs - A Combinatorial Approach (2016)
    Details
    Publication Date: 2022-03-11
    Description: We prove characterizations of the existence of perfect f-matchings in uniform mengerian and perfect hypergraphs. Moreover, we investigate the f-factor problem in balanced hypergraphs. For uniform balanced hypergraphs we prove two existence theorems with purely combinatorial arguments, whereas for non-uniform balanced hypergraphs we show that the f-factor problem is NP-hard.
    Language: English
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  • 187
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    Makespan and Tardiness in Activity Networks with Lognormal Activity Durations (2016)
    Details
    Publication Date: 2020-08-05
    Description: We propose an algorithm to approximate the distribution of the completion time (makespan) and the tardiness costs of a project, when durations are lognormally distributed. This problem arises naturally for the optimization of surgery scheduling, where it is very common to assume lognormal procedure times. We present an analogous of Clark's formulas to compute the moments of the maximum of a set of lognormal variables. Then, we use moment matching formulas to approximate the earliest starting time of each activity of the project by a shifted lognormal variable. This approach can be seen as a lognormal variant of a state-of-the-art method used for the statistical static timing analysis (SSTA) of digital circuits. We carried out numerical experiments with instances based on real data from the application to surgery scheduling. We obtained very promising results, especially for the approximation of the mean overtime in operating rooms, for which our algorithm yields results of a similar quality to Monte-Carlo simulations requiring an amount of computing time several orders of magnitude larger.
    Language: English
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  • 188
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    On the origin of inner coma structures observed by Rosetta during a diurnal rotation of comet 67P/Churyumov-Gerasimenko (2016)
    Details
    Publication Date: 2020-03-19
    Description: The Rosetta probe around comet 67P/Churyumov–Gerasimenko (67P) reveals an anisotropic dust distribution of the inner coma with jet-like structures. The physical processes leading to jet formation are under debate, with most models for cometary activity focusing on localized emission sources, such as cliffs or terraced regions. Here we suggest, by correlating high-resolution simulations of the dust environment around 67P with observations, that the anisotropy and the background dust density of 67P originate from dust released across the entire sunlit surface of the nucleus rather than from few isolated sources. We trace back trajectories from coma regions with high local dust density in space to the non-spherical nucleus and identify two mechanisms of jet formation: areas with local concavity in either two dimensions or only one. Pits and craters are examples of the first case; the neck region of the bi-lobed nucleus of 67P is an example of the latter case. The conjunction of multiple sources, in addition to dust released from all other sunlit areas, results in a high correlation coefficient (~0.8) of the predictions with observations during a complete diurnal rotation period of 67P.
    Language: English
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  • 189
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    Big Data Analytics on Cray XC Series DataWarp using Hadoop, Spark and Flink (2016)
    Details
    Publication Date: 2021-01-21
    Language: English
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  • 190
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    An Extended Network Interdiction Problem for Optimal Toll Control (2016)
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    Publication Date: 2021-01-22
    Description: We study an extension of the shortest path network interdiction problem and present a novel real-world application in this area. We consider the problem of determining optimal locations for toll control stations on the arcs of a transportation network. We handle the fact that drivers can avoid control stations on parallel secondary roads. The problem is formulated as a mixed integer program and solved using Benders decomposition. We present experimental results for the application of our models to German motorways.
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  • 191
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    Numerical characterization of symmetry properties for photonic crystals with hexagonal lattice (2016)
    Details
    Publication Date: 2018-08-02
    Description: We present a numerical method to characterize the symmetry properties of photonic crystal (PhC) modes based on field distributions, which themselves can be obtained numerically. These properties can be used to forecast specific features of the optical response of such systems, e.g. which modes are allowed to couple to external radiation fields. We use 2D PhCs with a hexagonal lattice of holes in dielectric as an example and apply our technique to reproduce results from analytical considerations. Further, the method is extended to fully vectorial problems in view of 3D PhCs and PhC slabs, its functionality is demonstrated using test cases and, finally, we provide an efficient implementation. The technique can thus readily be applied to output data of all band structure computation methods or even be embedded – gaining additional information about the mode symmetry.
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  • 192
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    A Nearly Exact Propagation Algorithm for Energetic Reasoning in O(n^2 log n) (2016)
    Details
    Publication Date: 2020-08-05
    Description: In constraint programming, energetic reasoning constitutes a powerful start time propagation rule for cumulative scheduling problems (CuSP). In this paper, we first present an improved time interval checking algorithm that is derived from a polyhedral model. In a second step, we extend this algorithm to an energetic reasoning propagation algorithm with complexity O(n^2 log n) where n denotes the number of jobs. The key idea is based on a new sweep line subroutine that efficiently evaluates the relevant time intervals for all jobs. In particular, our algorithm yields at least one possible energetic reasoning propagation for each job. Finally, we show that on the vast number of relevant time intervals our approach yields the maximum possible propagation according to the energetic reasoning rule.
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    On the In-Flight Rest Assignment Problem (2016)
    Details
    Publication Date: 2020-08-05
    Description: The airplane has changed the world in a tremendous way. Efficient scheduling of airmen and aircrafts is of considerable importance for cost-effectiveness of compa- nies. Attentiveness of flight crew members is vital as fatigue can lead to severe accidents. Therefore, duty times of flight crews are strictly limited. Long distance flights may be difficult to schedule with only one set of crew members. Furthermore, pertu- bations of the schedules may entail exchanging the entire crew, which confounds multiday schedules. A new EU regulation introduced in-flight rest: a schedule may extend pilots’ duty times if they rest for a certain time in designated crew compart- ments provided aboard airplanes. Of course they have to be replaced in that period of time. This thesis examines the in-flight rest assignment problem, which is the decision problem whether a given schedule allows for all crew members to take their compul- sory rest. The problem can be seen as multimachine scheduling problem. Efficient algorithms for special cases were developed and an alternative approach for entire hard cases is discussed.
    Language: English
    Type: masterthesis , doc-type:masterThesis
    Format: application/pdf
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  • 194
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    PolySCIP (2016)
    Details
    Publication Date: 2020-08-05
    Description: PolySCIP is a new solver for multi-criteria integer and multi-criteria linear programs handling an arbitrary number of objectives. It is available as an official part of the non-commercial constraint integer programming framework SCIP. It utilizes a lifted weight space approach to compute the set of supported extreme non-dominated points and unbounded non-dominated rays, respectively. The algorithmic approach can be summarized as follows: At the beginning an arbitrary non-dominated point is computed (or it is determined that there is none) and a weight space polyhedron created. In every next iteration a vertex of the weight space polyhedron is selected whose entries give rise to a single-objective optimization problem via a combination of the original objectives. If the ptimization of this single-objective problem yields a new non-dominated point, the weight space polyhedron is updated. Otherwise another vertex of the weight space polyhedron is investigated. The algorithm finishes when all vertices of the weight space polyhedron have been investigated. The file format of PolySCIP is based on the widely used MPS format and allows a simple generation of multi-criteria models via an algebraic modelling language.
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 195
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    Well-posed Bayesian inverse problems and heavy-tailed stable Banach space priors (2016)
    Details
    Publication Date: 2021-10-28
    Description: This article extends the framework of Bayesian inverse problems in infinite-dimensional parameter spaces, as advocated by Stuart (Acta Numer. 19:451–559, 2010) and others, to the case of a heavy-tailed prior measure in the family of stable distributions, such as an infinite-dimensional Cauchy distribution, for which polynomial moments are infinite or undefined. It is shown that analogues of the Karhunen–Loève expansion for square-integrable random variables can be used to sample such measures. Furthermore, under weaker regularity assumptions than those used to date, the Bayesian posterior measure is shown to depend Lipschitz continuously in the Hellinger metric upon perturbations of the misfit function and observed data.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 196
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    Optical simulation of complex nanostructured solar cells with a reduced basis method (2016)
    Details
    Publication Date: 2017-04-07
    Description: Simulations of optical processes and complex nanostructured devices have become omnipresent in recent years in several fields of current research and industrial applications, not limited to the field of photovoltaics. Devices or processes are optimized with respect to a certain objective where the underlying physical processes are described by partial differential equations. In photovoltaics and photonics electromagnetic fields are investigated which are governed by Maxwell’s equations. In this thesis a reduced basis method for the solution of the parameter dependent electromagnetic scattering problem with arbitrary parameters is developed. The method is developed with the specific challenges arising in optical simulations of thin-film silicon solar cells in mind. These are large in domain size and have a complex three-dimensional structure, making optimization tasks infeasible if high-accuracy of the electromagnetic field solution is required. The application of the empirical interpolation methods allows to expand an arbitrary parameter dependence affinely. Thus not only geometries, but also material tensors and source fields can be parameterized. Additionally, the required non-linear post-processing steps of the electromagnetic field to derive energy fluxes or volume absorption are addressed. The reduced basis method allows to reduce the computational costs by orders of magnitude compared to efficient finite element solvers. In addition, an efficient tailored domain decomposition algorithm is presented to model incoherent layers or illuminations in optical systems efficiently. This is of particular interest for solar cells in superstrate configuration where the absorber is illuminated through a glass substrate. The developed methods are employed in application examples taken from collaborations with experimentalists active in the joint lab “BerOSE” (Berlin Joint Lab for Optical Simulations for Energy Research). The optical model of a thin-film silicon multi-junction with incoherent light-trapping is characterized in great detail. The computational gains through hybrid, hp adaptive finite elements are studied and the incoherent domain decomposition algorithm is applied to model a more realistic light-trapping by the glass substrate. The numerical examples of a hexagonal nano-hole array and multi-junction silicon solar cell with a tunable intermediate reflector layer show that the reduced basis method is well suited as a forward solver for modeling and optimization tasks arising in photovoltaics and photonics. Reduced models for illumination and geometric parameters are built providing up to five orders of magnitude savings in computational costs. Resonance phenomena present in the nano-hole array example are detected and the model adapts itself automatically.
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 197
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    Cameron--Martin theorems for sequences of Cauchy-distributed random variables (2016)
    Details
    Publication Date: 2021-10-28
    Description: Given a sequence of Cauchy-distributed random variables defined by a sequence of location parameters and a sequence of scale parameters, we consider another sequence of random variables that is obtained by perturbing the location or scale parameter sequences. Using a result of Kakutani on equivalence of infinite product measures, we provide sufficient conditions for the equivalence of laws of the two sequences.
    Language: English
    Type: article , doc-type:article
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  • 198
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    The Monte Carlo Computation Error of Transition Probabilities (2016)
    Details
    Publication Date: 2016-07-22
    Description: In many applications one is interested to compute transition probabilities of a Markov chain. This can be achieved by using Monte Carlo methods with local or global sampling points. In this article, we analyze the error by the difference in the $L^2$ norm between the true transition probabilities and the approximation achieved through a Monte Carlo method. We give a formula for the error for Markov chains with locally computed sampling points. Further, in the case of reversible Markov chains, we will deduce a formula for the error when sampling points are computed globally. We will see that in both cases the error itself can be approximated with Monte Carlo methods. As a consequence of the result, we will derive surprising properties of reversible Markov chains.
    Language: English
    Type: article , doc-type:article
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  • 199
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    Passenger routing for periodic timetable optimization (2016)
    Details
    Publication Date: 2020-08-05
    Description: The task of periodic timetabling is to determine trip arrival and departure times in a public transport system such that travel and transfer times are minimized. This paper investigates periodic timetabling models with integrated passenger routing. We show that different routing models can have a huge influence on the quality of the entire system: Whatever metric is applied, the performance ratios of timetables w.r.t. different routing models can be arbitrarily large. Computations on a real-world instance for the city of Wuppertal substantiate the theoretical findings. These results indicate the existence of untapped optimization potentials that can be used to improve the efficiency of public transport systems by integrating passenger routing.
    Language: English
    Type: article , doc-type:article
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  • 200
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    Cameron--Martin theorems for sequences of Cauchy-distributed random variables (2016)
    Details
    Publication Date: 2021-10-28
    Description: Given a sequence of Cauchy-distributed random variables defined by a sequence of location parameters and a sequence of scale parameters, we consider another sequence of random variables that is obtained by perturbing the location or scale parameter sequences. Using a result of Kakutani on equivalence of infinite product measures, we provide sufficient conditions for the equivalence of laws of the two sequences.
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
    Library Location Call Number Volume/Issue/Year Availability
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    OPUS
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