541 Works

Entwicklung einer Simulationsmethodik zur schnellen Dimensionierung komplexer Materialflusssysteme

Svenja Bahnsen, Harald Köck, Johannes Hinckeldeyn & Jochen Kreutzfeldt
Simulation models play an important role in the planning and development in intralogistics. Especially the layout and dimensioning of order picking processes, warehouses and handling engineering is often based on static estimations and rules of thumb. This leads to inferior planning results, because dynamic effects, such as peaks of orders, and sequential process steps are often neglected. The most common solution at the moment are event discrete simulation models, which create a significant workload for...

Deep-Learning-Verfahren zur 3D-Objekterkennung in der Logistik

Marko Thiel, Johannes Hinckeldeyn & Jochen Kreutzfeldt
The reliable detection of objects in sensor data is a fundamental requirement for the autono-mization of logistic processes. Especially the recognition of objects in 3D sensor data is important for flexible autonomous applications. Deep learning represents the state of the art for object recognition in 2D image data. This article presents various current approaches to use deep learning for 3D object recognition. An essential feature of these approaches is the use of point clouds as...

Nanoporous-gold-polypyrrole hybrid materials for millimeter-sized free standing actuators

Benedikt Roschning & Jörg Weissmüller
Advanced Materials Interfaces published by Wiley-VCH GmbH This work studies the actuation of hybrid materials made from nanoporous gold, polypyrrole, and aqueous electrolyte. The deposition protocol affords a conformal polypyrrole coating on the entire internal interface of millimeter-sized nanoporous metal specimens made by dealloying. The hybrid material emerges when the remaining pore space is filled with perchloric acid. The metal serves as load-bearing and electronically conductive substrate, the polypyrrole as functional active component for actuation,...

Deciding Whether a Grid is a Topological Subgraph of a Planar Graph is NP-Complete

Andrea Jiménez & Tina Janne Schmidt
The Topological Subgraph Containment (TSC) Problem is to decide, for two given graphs G and H, whether H is a topological subgraph of G. It is known that the TSC Problem is NP-complete when H is part of the input, that it can be solved in polynomial time when H is fixed, and that it is fixed-parameter tractable by the order of H. Motivated by the great significance of grids in graph theory and algorithms...

The impact of modular product architectures in PSS design: a systematic literature review

Christoph Rennpferdt, Erik Greve & Dieter Krause

Time-variant rule-based reliability of corroded structures by Monte Carlo simulation

Karoline M. Neumann, Bernt J. Leira, Ole Tom Vårdal & Sören Ehlers
General widespread corrosion is of increasing concern for structural reliability of ageing marine structures, particularly for semi-submersible pontoons. Conditional failure rate, also termed hazard function is sought to describe the increasing maintenance required with age. Literature is reviewed connecting corrosion degradation to hazard rate, either through a time degrading limit state function, or statistical data for time to failure. Here, a rule based failure definition is applied based on corrosion tolerance levels, together with a...

Linear kernels and linear-time algorithms for finding large cuts

Michael Etscheid & Matthias Mnich
The maximum cut problem in graphs and its generalizations are fundamental combinatorial problems. Several of these cut problems were recently shown to be fixed-parameter tractable and admit polynomial kernels when parameterized above the tight lower bound measured by the size and order of the graph. In this paper we continue this line of research and considerably improve several of those results: We show that an algorithm by Crowston et al. [ICALP 2012] for (Signed) Max-Cut...

Polynomial kernels for deletion to classes of acyclic digraphs

Matthias Mnich & Erik Jan van Leeuwen
We consider the problem to find a set X of vertices (or arcs) with |X| <= k in a given digraph G such that D = G-X is an acyclic digraph. In its generality, this is DIRECTED FEEDBACK VERTEX SET or DIRECTED FEEDBACK ARC SET respectively. The existence of a polynomial kernel for these problems is a notorious open problem in the field of kernelization, and little progress has been made. In this paper, we...

Joint learning of geometric and probabilistic constellation shaping

Maximilian Stark, Fayçal Ait Aoudia & Jakob Hoydis

Investigation of the pressure drop in refrigerant pipes of an R744 automotive air conditioning system

Christoph Subei & Gerhard Schmitz
This paper presents a test rig to measure the pressure drop of the refrigerant R744 (CO2) in refrigerant pipes of an automotive air conditioning system. The experimental layout is basically a cooling cycle. In a measurement section, arbitrary shaped pipes of an automotive air conditioning system can be installed. As boundary conditions mass flow, pressure and enthalpy of the refrigerant at the inlet are independently adjustable to values that cover the whole operating range of...

Automated selection and assembly of sets of blades for jet engine compressors and turbines

Maik Dammann & Thorsten Schüppstuhl

Bewertung von Power-to-Gas-Anlagen mittels dynamischer Systemsimulation

Lisa Andresen & Gerhard Schmitz
Mittels dynamischer Systemsimulation wird die Kopplung des Hochdruckgasnetzes der Stadt Hamburg mit dem Stromnetz untersucht. Dabei wird das technische Potential der regenerativen Erzeugung, der Speicherung und der Einspeisung von Wasserstoff in das Gasnetz analysiert. Der Modellierungsansatz wird beschrieben. Den Szenariorahmen bildet der geplante Ausbau der fluktuierenden Erneuerbaren Energien im Jahr 2050 und der Strom- und Gasbedarf in 2012. Die Elektrolyseure werden nur dann betrieben, wenn die Residuallast negativ ist. In einer Jahressimulation wird, unter Berücksichtigung...

Optimizing the start-up process of post-combustion capture plants by varying the solvent flow rate

Thomas Marx-Schubach & Gerhard Schmitz

Spline- and hp-basis functions of higher differentiability in the finite cell method

Stefan Kollmannsberger, Davide D'Angella, Ernst Rank, Wadhah Garhuom, Simeon Hubrich, Alexander Düster, Paolo Di Stolfo & Andreas Schröder
In this paper, the use of hp-basis functions with higher differentiability properties is discussed in the context of the finite cell method and numerical simulations on complex geometries. For this purpose, Ck hp-basis functions based on classical B-splines and a new approach for the construction of C1 hp-basis functions with minimal local support are introduced. Both approaches allow for hanging nodes, whereas the new C1 approach also includes varying polynomial degrees. The properties of the...

A review of life cycle assessment studies of electric vehicles with a focus on resource use

Iulia Dolganova, Anne Rödl, Vanessa Bach, Martin Kaltschmitt & Matthias Finkbeiner
Changes in the mobility patterns have evoked concerns about the future availability of certain raw materials necessary to produce alternative drivetrains and related batteries. The goal of this article is to determine if resource use aspects are adequately reflected within life cycle assessment (LCA) case studies of electric vehicles (EV). Overall, 103 LCA studies on electric vehicles from 2009 to 2018 are evaluated regarding their objective, scope, considered impact categories, and assessment methods—with a focus...

Parallel-in-time integration of kinematic dynamos

Andrew T. Clarke, Christopher J. Davies, Daniel Ruprecht & Steven M. Tobias

Temperature field due to a moving heat source in machining orthotropic composites with arbitrary fiber orientation

Jan Philipp Mehnen, Wolfgang Hintze, Lars Köttner & Robert von Wenserski
Milling of fiber reinforced plastics (FRP) is challenging with respect to surface integrity and tool wear due to high process temperatures. The maximum temperatures occurring in the workpiece determine the extent of the matrix decomposition area. Improving the workpiece quality therefore requires an understanding of its internal temperature distribution during milling. However, steep temperature gradients and high mechanical stress make measurements of temperature fields in the cutting zone difficult. In addition, thermal properties change depending...

Skin lesion classification using ensembles of multi-resolution EfficientNets with meta data

Nils Thorben Gessert, Maximilian Nielsen, Mohsin Shaikh, René Werner & Alexander Schlaefer

Fabrication of highly filled composites with an innovative miniaturized spouted bed

Hannah Sophia Rothberg, Swantje Pietsch, Gerold A. Schneider & Stefan Heinrich
In nature bio-composites such as nacre show remarkable mechanical properties due to their complex hierarchical structure and high-volume fraction of its hard component. These composites are highly interesting for structural applications in different branches of industries for mechanical engineering and process technology. The aim of this work was to provide a scalable method for the production of highly filled composites by mimicking the structure of bio-composites. Therefore, composites from iron oxide (Fe2O3) and SBC-polymer (styrene-butadiene...

A Collaborative approach for an integrated modeling of urban air transportation systems

Malte Niklaß, Niclas Dzikus, Majed Swaid, Jan Berling, Benjamin Lührs, Alexander Lau, Ivan Terekhov & Volker Gollnick
The current push in automation, communication, and electrical energy storage technologies has the potential to lift urban mobility into the sky. As several urban air mobility (UAM) concepts are conceivable, all relevant physical effects as well as mutual interrelations of the UAM system have to be addressed and evaluated at a sufficient level of fidelity before implementation. Therefore, a collaborative system of systems modeling approach for UAM is presented. To quickly identify physical effects and...

Influence of oil, dispersant, and pressure on microbial communities from the Gulf of Mexico

Nuttapol Noirungsee, Steffen Hackbusch, Juan Viamonte Dominguez, Paul Bubenheim, Andreas Liese & Rudolf Müller

Platform of design method for developing mobility-preserving products

Kristin Paetzold, Sandro Wartzack & Dieter Krause

Concept for Markerless 6D Tracking Employing Volumetric Optical Coherence Tomography

Matthias Schlüter, Lukas Glandorf, Martin Gromniak, Thore Saathoff & Alexander Schlaefer
Optical tracking systems are widely used, for example, to navigate medical interventions. Typically, they require the presence of known geometrical structures, the placement of artificial markers, or a prominent texture on the target’s surface. In this work, we propose a 6D tracking approach employing volumetric optical coherence tomography (OCT) images. OCT has a micrometer-scale resolution and employs near-infrared light to penetrate few millimeters into, for example, tissue. Thereby, it provides sub-surface information which we use...

Implementing computer-assisted exams in a course on numericalanalysis for engineering students

Karsten Kruse & Christian Seifert

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