@incollection{Ulke2024, author = {Ulke, Bernd}, title = {Boden, Baugrube, Verbau}, series = {Zahlentafeln f{\"u}r den Baubetrieb}, booktitle = {Zahlentafeln f{\"u}r den Baubetrieb}, editor = {Krause, Thomas and Ulke, Bernd and Ferger, Martin}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-41329-3 (Print)}, doi = {10.1007/978-3-658-41330-9_9}, pages = {499 -- 658}, year = {2024}, abstract = {Die L{\"o}sung den Baugrund betreffender Fragestellungen beginnen i. d. R. mit der Durchf{\"u}hrung von Baugrunderkundungen, um alle notwendigen Parameter zu erhalten, die f{\"u}r die Planung und Durchf{\"u}hrung von Bauvorhaben notwendig sind. Im Folgenden werden die wichtigsten Erkundungen in Abh{\"a}ngigkeit der erforderlichen G{\"u}teklasse der Proben beschrieben und vorgestellt.}, language = {de} } @techreport{Drescher2021, type = {Working Paper}, author = {Drescher, Hans Paul}, title = {Turbulence - minimum dissipation and maximum macroscopic momentum exchange}, pages = {44 Seiten}, year = {2021}, abstract = {The minimum dissipation requirement of the thermodynamics of irreversible processes is applied to characterize the existence of laminar and non-laminar, and the co-existence of laminar and turbulent flow zones. Local limitations of the different zones and three different forms of transition are defined. For the Couette flow a non-local "corpuscular" flow mechanism explains the logarithmic law-of-the-wall, maximum turbulent dimensions and a value x=0,415 for the v. K{\´a}rm{\´a}n constant. Limitations of the logarithmic law near the wall and in the centre of the experiment are interpreted.}, language = {en} } @techreport{Drescher2018, type = {Working Paper}, author = {Drescher, Hans Paul}, title = {The irreversible thermodynamic's theorem of minimum entropy production applied to the laminar and the turbulent Couette flow}, pages = {48 Seiten}, year = {2018}, abstract = {Analyzing thermodynamic non-equilibrium processes, like the laminar and turbulent fluid flow, the dissipation is a key parameter with a characteristic minimum condition. That is applied to characterize laminar and turbulent behaviour of the Couette flow, including its transition in both directions. The Couette flow is chosen as the only flow form with constant shear stress over the flow profile, being laminar, turbulent or both. The local dissipation defines quantitative and stable criteria for the transition and the existence of turbulence. There are basic results: The Navier Stokes equations cannot describe the experimental flow profiles of the turbulent Couette flow. But they are used to quantify the dissipation of turbulent fluctuation. The dissipation minimum requires turbulent structures reaching maximum macroscopic dimensions, describing turbulence as a "non-local" phenomenon. At the transition the Couette flow profiles and the shear stress change by a factor ≅ 5 due to a change of the "apparent" turbulent viscosity by a calculated factor ≅ 27. The resulting difference of the laminar and the turbulent profiles results in two different Reynolds numbers and different loci of transition, which are identified by calculation.}, language = {en} } @article{PieronekKleefeld2024, author = {Pieronek, Lukas and Kleefeld, Andreas}, title = {On trajectories of complex-valued interior transmission eigenvalues}, series = {Inverse problems and imaging : IPI}, volume = {18}, journal = {Inverse problems and imaging : IPI}, number = {2}, publisher = {AIMS}, address = {Springfield, Mo}, issn = {1930-8337 (Print)}, doi = {10.3934/ipi.2023041}, pages = {480 -- 516}, year = {2024}, abstract = {This paper investigates the interior transmission problem for homogeneous media via eigenvalue trajectories parameterized by the magnitude of the refractive index. In the case that the scatterer is the unit disk, we prove that there is a one-to-one correspondence between complex-valued interior transmission eigenvalue trajectories and Dirichlet eigenvalues of the Laplacian which turn out to be exactly the trajectorial limit points as the refractive index tends to infinity. For general simply-connected scatterers in two or three dimensions, a corresponding relation is still open, but further theoretical results and numerical studies indicate a similar connection.}, language = {en} } @article{SchoppRohrbachLangeretal.2024, author = {Schopp, Christoph and Rohrbach, Felix and Langer, Luc and Heuermann, Holger}, title = {Detection of welding wire length by active S11 measurement}, series = {IEEE Transactions on Plasma Science}, journal = {IEEE Transactions on Plasma Science}, number = {Early Access}, publisher = {IEEE}, issn = {0093-3813 (Print)}, doi = {10.1109/TPS.2024.3356659}, pages = {1 -- 6}, year = {2024}, abstract = {A novel method to determine the extruded length of a metallic wire for a directed energy deposition (DED) process using a microwave (MW) plasma jet with a straight-through wire feed is presented. The method is based on the relative comparison of the measured frequency response obtained by the large-signal scattering parameter (Hot-S) technique. In the practical working range, repeatability of less than 6\% for a nonactive plasma and 9\% for the active plasma state is found. Measurements are conducted with a focus on a simple solution to decrease the processing time and reduce the integration time of the process into the existing hardware. It is shown that monitoring a single frequency for magnitude and phase changes is sufficient to achieve good accuracy. A combination of different measurement values to determine the length is possible. The applicability to different diameter of the same material is shown as well as a contact detection of the wire and metallic substrate.}, language = {en} } @article{BoehnischBraunMuscarelloetal.2024, author = {B{\"o}hnisch, Nils and Braun, Carsten and Muscarello, Vincenzo and Marzocca, Pier}, title = {About the wing and whirl flutter of a slender wing-propeller system}, series = {Journal of Aircraft}, journal = {Journal of Aircraft}, publisher = {AIAA}, address = {Reston, Va.}, issn = {1533-3868}, doi = {10.2514/1.C037542}, pages = {1 -- 14}, year = {2024}, abstract = {Next-generation aircraft designs often incorporate multiple large propellers attached along the wingspan (distributed electric propulsion), leading to highly flexible dynamic systems that can exhibit aeroelastic instabilities. This paper introduces a validated methodology to investigate the aeroelastic instabilities of wing-propeller systems and to understand the dynamic mechanism leading to wing and whirl flutter and transition from one to the other. Factors such as nacelle positions along the wing span and chord and its propulsion system mounting stiffness are considered. Additionally, preliminary design guidelines are proposed for flutter-free wing-propeller systems applicable to novel aircraft designs. The study demonstrates how the critical speed of the wing-propeller systems is influenced by the mounting stiffness and propeller position. Weak mounting stiffnesses result in whirl flutter, while hard mounting stiffnesses lead to wing flutter. For the latter, the position of the propeller along the wing span may change the wing mode shapes and thus the flutter mechanism. Propeller positions closer to the wing tip enhance stability, but pusher configurations are more critical due to the mass distribution behind the elastic axis.}, language = {en} } @article{TurdumamatovBeldaHeuermann2024, author = {Turdumamatov, Samat and Belda, Aljoscha and Heuermann, Holger}, title = {Shaping a decoupled atmospheric pressure microwave plasma with antenna structures, Maxwell's equations, and boundary conditions}, series = {IEEE Transactions on Plasma Science}, journal = {IEEE Transactions on Plasma Science}, number = {Early Access}, publisher = {IEEE}, issn = {0093-3813 (Print)}, doi = {10.1109/TPS.2024.3383589}, pages = {1 -- 9}, year = {2024}, abstract = {This article addresses the need for an innovative technique in plasma shaping, utilizing antenna structures, Maxwell's laws, and boundary conditions within a shielded environment. The motivation lies in exploring a novel approach to efficiently generate high-energy density plasma with potential applications across various fields. Implemented in an E01 circular cavity resonator, the proposed method involves the use of an impedance and field matching device with a coaxial connector and a specially optimized monopole antenna. This setup feeds a low-loss cavity resonator, resulting in a high-energy density air plasma with a surface temperature exceeding 3500 o C, achieved with a minimal power input of 80 W. The argon plasma, resembling the shape of a simple monopole antenna with modeled complex dielectric values, offers a more energy-efficient alternative compared to traditional, power-intensive plasma shaping methods. Simulations using a commercial electromagnetic (EM) solver validate the design's effectiveness, while experimental validation underscores the method's feasibility and practical implementation. Analyzing various parameters in an argon atmosphere, including hot S -parameters and plasma beam images, the results demonstrate the successful application of this technique, suggesting its potential in coating, furnace technology, fusion, and spectroscopy applications.}, language = {en} } @article{StiemerThomaBraun2023, author = {Stiemer, Luc Nicolas and Thoma, Andreas and Braun, Carsten}, title = {MBT3D: Deep learning based multi-object tracker for bumblebee 3D flight path estimation}, series = {PLoS ONE}, volume = {18}, journal = {PLoS ONE}, number = {9}, publisher = {PLOS}, address = {San Fancisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0291415}, pages = {e0291415}, year = {2023}, abstract = {This work presents the Multi-Bees-Tracker (MBT3D) algorithm, a Python framework implementing a deep association tracker for Tracking-By-Detection, to address the challenging task of tracking flight paths of bumblebees in a social group. While tracking algorithms for bumblebees exist, they often come with intensive restrictions, such as the need for sufficient lighting, high contrast between the animal and background, absence of occlusion, significant user input, etc. Tracking flight paths of bumblebees in a social group is challenging. They suddenly adjust movements and change their appearance during different wing beat states while exhibiting significant similarities in their individual appearance. The MBT3D tracker, developed in this research, is an adaptation of an existing ant tracking algorithm for bumblebee tracking. It incorporates an offline trained appearance descriptor along with a Kalman Filter for appearance and motion matching. Different detector architectures for upstream detections (You Only Look Once (YOLOv5), Faster Region Proposal Convolutional Neural Network (Faster R-CNN), and RetinaNet) are investigated in a comparative study to optimize performance. The detection models were trained on a dataset containing 11359 labeled bumblebee images. YOLOv5 reaches an Average Precision of AP = 53, 8\%, Faster R-CNN achieves AP = 45, 3\% and RetinaNet AP = 38, 4\% on the bumblebee validation dataset, which consists of 1323 labeled bumblebee images. The tracker's appearance model is trained on 144 samples. The tracker (with Faster R-CNN detections) reaches a Multiple Object Tracking Accuracy MOTA = 93, 5\% and a Multiple Object Tracking Precision MOTP = 75, 6\% on a validation dataset containing 2000 images, competing with state-of-the-art computer vision methods. The framework allows reliable tracking of different bumblebees in the same video stream with rarely occurring identity switches (IDS). MBT3D has much lower IDS than other commonly used algorithms, with one of the lowest false positive rates, competing with state-of-the-art animal tracking algorithms. The developed framework reconstructs the 3-dimensional (3D) flight paths of the bumblebees by triangulation. It also handles and compares two alternative stereo camera pairs if desired.}, language = {en} } @masterthesis{Pauls2024, type = {Bachelor Thesis}, author = {Pauls, Benjamin}, title = {Energiewende im Stromsektor: Nachhaltigkeit {\"u}ber Umweltschutz hinaus}, school = {Fachhochschule Aachen}, pages = {IV, 88 Seiten}, year = {2024}, abstract = {Die Energiewende wird h{\"a}ufig als „nachhaltig" bezeichnet, das genaue Begriffsverst{\"a}ndnis bleibt jedoch vage. Diese Transformation von fossilen und nuklearen hin zu erneuerbaren Energiequellen steht im Fokus der Treibhausgasneutralit{\"a}t. So soll dem fortschreitenden Klimawandel entgegengetreten werden. Das Thema der vorliegenden Arbeit ist die Definition eines m{\"o}glichen Verst{\"a}ndnisses von „Nachhaltigkeit" in der Energiewende des deutschen Stromsektors. Die leitenden Forschungsfragen lauten: Was kann im Zusammenhang mit der Energiewende im Stromsektor Deutschlands unter Nachhaltigkeit verstanden werden? Inwieweit unterscheidet sich dieses Verst{\"a}ndnis von der bisherigen Herangehensweise? Die Datenbasis zur Beantwortung dieser liefern sechs leitfadengest{\"u}tzte Expert:inneninterviews. Als Analysemethode dient die inhaltliche Strukturierung nach Mayring (2015). Die qualitative Studie hat gezeigt, dass eine nachhaltige Energiewende den Menschen und die Natur zentralisiert. Weiter aufgeschl{\"u}sselt stehen die drei Nachhaltigkeitsdimensionen und die Generationengerechtigkeit. Dabei dient die {\"o}konomische Dimension der sozialen und {\"o}kologischen. Wichtig sind die Inklusion und Beteiligung von Bev{\"o}lkerung, Unternehmen und Politik. Gleichzeitig ist sie Herausforderung und Chance f{\"u}r einen positiven gesellschaftlichen Wandel. Technisch dienen Windenergie- und Photovoltaikanlagen als Energielieferanten und Wasserstoffsysteme als Zwischenspeicher, Stabilit{\"a}tssicherung und zur Kopplung der Sektoren. Damit ist Nachhaltigkeit die Chance, die Energiewende richtig zu gestalten und damit {\"u}ber Klimaneutralit{\"a}t hinauszugehen}, language = {de} } @article{BiewendtBlaschkeBoehnert2021, author = {Biewendt, Marcel and Blaschke, Florian and B{\"o}hnert, Arno}, title = {A review of contemporary challenges in business culture}, series = {International Journal of Applied Research in Business and Management}, volume = {2}, journal = {International Journal of Applied Research in Business and Management}, number = {1}, publisher = {Wohllebe \& Ross Publishing}, address = {Hamburg}, issn = {2700-8983}, doi = {10.51137/ijarbm.2021.2.1.1}, pages = {1 -- 12}, year = {2021}, abstract = {The following article deals with the basic principles of intercultural management and possible improvements in terms of cultural, ethnic and gender diversification. The results are exemplarily applied to a bank located in Germany. The aim of this paper is to find out to what extent intercultural management could improve the productivity of Relatos-Bank in dealing with foreign employees or employees with a different cultural background. To achieve this goal, the authors con-duct a literature research. The main sources of information are books, journal articles and internet sources. It becomes clear that especially the different perceptions of different generations have a potential for conflict, which can be counteracted by applying presented scientific models. Equalizing the salaries of female and male employees and equalizing the rights and distribution of power could also be the key to becoming an open-minded, dynamic and fair organization that is pre-pared for the rapidly changing environment in which it operates.}, language = {en} }