534 Works

Softcomputing : introduction to machine learning

Karl-Heinz Zimmermann
Einführung in das maschinelle Lernen

Fuel planning strategies considering operational uncertainties of aerodynamic formation flight

Majed Swaid, Tobias Marks, Florian Linke & Volker Gollnick
The operational concept of aerodynamic formation flight, also referred to as aircraft wake-surfing for efficiency (AWSE), has high potential in terms of fuel savings and climate impact mitigation. In order to implement this concept, many technological and operational challenges have to be coped with. As the fuel consumption during a mission strongly depends on a successful execution of AWSE, the existing uncertainties regarding flight planning increase. While a conservative fuel planning ensures a follower to...

Influence of freezing parameters on the formation of internal porous structure and its impact on freeze-drying kinetics

Patrick Levin, Vincent Meunier, Ulrich Kessler & Stefan Heinrich
The main objective of this study was firstly to investigate the influence of freezing process parameters on the formation of the internal structure of frozen coffee granules. It was investigated how these frozen internal structures affect the drying kinetics during freeze-drying. A design of experiment study was carried out using the response surface method to quantify the influence of the freezing step that occurs in a scraped surface heat exchanger (SSHE). Therefore, the coffee extract...

Addition of riboflavin-coupled magnetic beads increases current production in bioelectrochemical systems via the increased formation of anode-biofilms

Tutut Arinda, Laura-Alina Philipp, David Rehnlund, Miriam Edel, Jonas Chodorski, Markus Stöckl, Dirk Holtmann, Roland Ulber, Johannes Gescher & Katrin Sturm-Richter
Shewanella oneidensis is one of the best-understood model organisms for extracellular electron transfer. Endogenously produced and exported flavin molecules seem to play an important role in this process and mediate the connection between respiratory enzymes on the cell surface and the insoluble substrate by acting as electron shuttle and cytochrome-bound cofactor. Consequently, the addition of riboflavin to a bioelectrochemical system (BES) containing S. oneidensis cells as biocatalyst leads to a strong current increase. Still, an...

Efficient biochemical production of acetoin from carbon dioxide using Cupriavidus necator H16

Carina Windhorst & Johannes Gescher
Background: Cupriavidus necator is the best-studied knallgas (also termed hydrogen oxidizing) bacterium and provides a model organism for studying the production of the storage polymer polyhydroxybutyrate (PHB). Genetically engineered strains could be applied for the autotrophic production of valuable chemicals. Nevertheless, the efficiency of the catalyzed processes is generally believed to be lower than with acetogenic bacteria. Experimental data on the potential efficiency of autotrophic production with C. necator are sparse. Hence, this study aimed...

Helixfräsen und Bohren von laseradditiv gefertigten Bauteilen aus Titan für Luftfahrtanwendungen

Robert von Wenserski
Bionisch optimierte Bauteile, die mittels selektivem Laserschmelzen (SLS) hergestellt werden, etablieren sich als Luftfahrtkomponenten. Bei diesen Bauteilen sind beim SLS Stützstrukturen in waagerechten Bohrungen unerlässliche. Für die Entfernung dieser Stützstrukturen werden in dieser Arbeit die Verfahren Helixfräsen und Bohren untersucht. Mittels der aufgestellten Modelle lassen sich Abhängigkeiten zwischen den Eingriffsbedingungen, dem Verlauf der Bearbeitungskräfte, der Spanbildung und der Qualität an der Bohrungsinnenwand ableiten.

Development of a production chain from vegetable biowaste to platform chemicals

Annemarie Schmidt, Gunnar Sturm, Christian Jonas Lapp, Daniel Siebert, Florencia Saravia, Harald Horn, Padma Priya Ravi, Andreas Lemmer & Johannes Gescher
Background: A future bioeconomy relies on the development of technologies to convert waste into valuable compounds. We present here an attempt to design a biotechnological cascade for the conversion of vegetable waste into acetoin and electrical energy. Results: A vegetable waste dark fermentation effluent containing mainly acetate, butyrate and propionate was oxidized in a bioelectrochemical system. The achieved average current at a constant anode potential of 0 mV against standard hydrogen electrode was 177.5 ±...

Soluble versions of outer membrane cytochromes function as exporters for heterologously produced cargo proteins

Helge M. Dietrich, Miriam Edel, Thea Viola Bursać, Manfred Meier, Katrin Sturm-Richter & Johannes Gescher
This study reveals that it is possible to secrete truncated versions of outer membrane cytochromes into the culture supernatant and that these proteins can provide a basis for the export of heterologously produced proteins. Different soluble and truncated versions of the outer membrane cytochrome MtrF were analyzed for their suitability to be secreted. A protein version with a very short truncation of the N-terminus to remove the recognition sequence for the addition of a lipid...

Initial integral product and assembly structuring: a case study

Jan Küchenhof & Dieter Krause
Modular product structuring has been proven an effective way to satisfy a high sales variety with low internal product and process complexity but is usually carried out on existing structures. To support the modular new product development, this contribution shows the initial structuring of integrated product and assembly structures based on a variance-oriented product structure. With help of a perspective-based modularization approach, consolidating the product life phases of procurement, assembly and sales, modular product and...

Bayesian physics-based modeling of tau propagation in Alzheimer's disease

Amelie Schäfer, Mathias Peirlinck, Kevin Linka & Ellen Kuhl
Amyloid-β and hyperphosphorylated tau protein are known drivers of neuropathology in Alzheimer's disease. Tau in particular spreads in the brains of patients following a spatiotemporal pattern that is highly sterotypical and correlated with subsequent neurodegeneration. Novel medical imaging techniques can now visualize the distribution of tau in the brain in vivo, allowing for new insights to the dynamics of this biomarker. Here we personalize a network diffusion model with global spreading and local production terms...

„Ein Blick zurück, ein Blick nach vorn - Ihr Sommersemester 2020“ – Ergebnisse der zweiten Lehrendenbefragung an der Technischen Universität Hamburg

Sara Bornhöft, Christiane Arndt, Tina Jessica Ladwig & Sönke Knutzen
Im Sommersemester 2020 wurden zwei Befragungen an der Technischen Universität Hamburg (TUHH) durch das Institut für Technische Bildung und Hochschuldidaktik (ITBH), die Hamburg Open Online University HOOU@TUHH und das Zentrum für Lehre und Lernen (ZLL) durchgeführt. Befragt wurden Lehrende und Studierende an der TUHH. Die Ergebnisse finden sich unter https://doi.org/10.15480/336.2833. Basierend auf den Ergebnissen der Lehrendenbefragung wurde eine weitere Befragung unter Lehrenden (18.08. - 06.09.2020) durchgeführt. Die Befragung wurde erneut mit LimeSurvey umgesetzt. Der Aufruf...

Deep learning for automatic lung disease analysis in chest x-rays

Ivo-Matteo Baltruschat
Diese Arbeit befasst sich mit der automatischen Analyse von Thorax-Röntgenbildern mithilfe von Deep Learning, einer sich schnell entwickelnden Methode des maschinellen Lernens. Nach einer detaillierten Evaluierung von CNN-Architekturen auf dem ChestX-ray14 -Datensatz wird gezeigt, wie Modelle angepasst werden können, um Nicht-Bild-Merkmale einzubeziehen und ihre Leistung zu verbessern. Um das Erscheinungsbild von CXRs zu vereinfachen und CNNs dabei zu helfen, mit hochdimensionalen und begrenzten Daten umzugehen, sowie um ihre Leistung zu verbessern, wurde eine Reihe von...

Assessing the effectiveness of research-based active learning materials for introductory engineering mechanics

Julie Direnga
Ingenieure, die an deutschen Hochschulen ausgebildet werden, sollen dazu in der Lage sein, ihr erworbenes Wissen in unbekannten Situationen sinnvoll anzuwenden. Dazu ist ein solides Verständnis der Kernkonzepte einer Disziplin notwendig. Diese Dissertation widmet sich der Wirksamkeitsmessung von forschungsbasierten Lernmaterialien zur Förderung von konzeptionellem Verständnis in den Grundlagen der Technischen Mechanik in drei Teilen: Sie untersucht Concept Inventories als Messinstrumente im deutschen Hochschulkontext, diskutiert etablierte und alternative Analysemethoden der damit gewonnenen Daten und demonstriert die...

Numerische Untersuchung des Manövrierverhaltens von Schiffen während des Stoppmanövers

Jan Clemens Neitzel-Petersen
Im Rahmen dieser Arbeit wird das Manövrierverhalten von Schiffen während des Stoppvorgangs untersucht und ein Verfahren entwickelt, mit welchem das Aufstoppen eines Schiffs mit einem Koeffizientenmodell unter Berücksichtigung der sich während des Manövers reduzierenden Schiffsgeschwindigkeit numerisch berechnet werden kann. Die Manövrierkoeffizienten werden mithilfe einer RANS-Methode bestimmt, mit der auch die Propeller-Rumpf-Interaktion analysiert und durch geeignete Koeffizienten abgebildet wird. Anhand geführter Stoppversuche im Schlepptank wird die Methode validiert.

Investigation of student thinking about the voltage across open switches

Denise Duday
Student understanding in the field of electrical engineering has been researched for some time. Especially the research of student ideas regarding DC circuits has been given special focus in previous studies. It has been observed that the majority of the students assume the voltage across an open switch to be zero. Further, the studies proposed several student misconceptions that caused this incorrect assumption. In this work, two sets of student interviews were conducted and analyzed....

Digitale Assistenzsysteme in der Industrie : Visualisierungskonzept

Robert Rost
Digitale Assistenzsysteme haben das Potential die papierbasierte Informations- und Kommunikationsbasis in der Industrie zu ersetzen. Hierbei ist die Digitalisierung keineswegs ein Selbstzweck, denn die Systeme bieten die Flexibilität die bereitgestellten Informationen und Funktionen präzise am Nutzer und dem jeweiligen Anwendungsfall auszurichten. Der dadurch entstehende Mehrwert für industrielle Prozesse wie die Montage [Frie16] oder die Instandhaltung [Melu19] komplexer Produkte konnten bereits hinlänglich nachgewiesen werden. Bei der Gestaltung der primär informatorischen Assistenzsysteme stellt sich je-doch stets die...

Dissimilar titanium and titanium aluminide joints manufactured by laser beam welding and laser additive manufacturing

Irmela Burkhardt
Durch die zunehmenden Anforderungen an Leichtbaukonstruktionen motiviert, ist das Ziel ungleichartige Ti- und γ-TiAl-Ti-Legierungs-Verbindungen aus Blechen rissfrei mittels Laserstrahlschweißen herzustellen. Dies wurde durch Vorheizen erreicht. Die Rissentstehung konnte der Mikrostruktur-Phasen-Entwicklung zugeordnet werden. Der Einfluss der Grenzfläche auf den Versagensort und die Zugeigenschaften wurde durch Zugversuche ermittelt. Zudem wurde das gewonnene Wissen bezüglich der Mikrostruktur-Phasen-Entwicklung an der Grenzfläche erfolgreich auf laserauftragsgeschweißte Strukturen übertragen und die Grenzen der Übertragbarkeit bezüglich der Rissbildung aufgezeigt. Folglich wurden die Grundlagen...

Resilience through aroecology and ecological restoration : the system of rice intensification with intercropping

Tavseef Mairaj Shah & Ralf Otterpohl

Sensitivity analysis for ship squat predictions using Sobol’ indices

Li Xia, Zaojian Zou, Zi-Hao Wang & Lu Zou
Ship’s sinkage, trim and resistance will increase when entering shallow waters. It is of great significance to investigate the squat of ship in shallow and confined navigation areas. However, there are many factors affecting the ship’s squat, such as speed of the ship, block coefficient, water depth and draught of the ship et al. In this paper, the contribution of these factors to the squat is measured in empirical formula models using Sobol’s indices which...

Investigation of training data selection in the black-box modeling of ship maneuvering motion

Zihao Wang, Carlos Guedes Soares & Zaojian Zou
For the identification modeling of ship maneuvering motion, comparisons between various training data are conducted to select appropriate excitation signal with maximum dynamic information, thereby ensuring the generalization ability of the identified model. The identification framework is black-box modeling based on the (“nu”)-support vector machine algorithm with radial basis function kernel, which automatically controls the number of support vectors and keeps sparsity. A Mariner class ship is taken as the study object, and the training...

Numerical and Test Analysis for Resistance and Self-Propulsion Performance of a Trailing Suction Hopper Dredger

Zhigao Luo & Long Yu
Resistance and self-propulsion performances of trailing suction hopper dredger (TSHD) remains a hot issue in predicting and improving performances of TSHD. In this paper, the CFD simulation technology and overset technology are used to calculate the resistance performance of TSHD at different velocities, and the results are accord with the model test results. Then overset technology is used to calculate the self-propelled performances of THSD equipped with different propellers under different working conditions. The results...

Damping of non-linear and irregular long-crested free-surface waves using forcing zones

Robinson Peric & Moustafa Abdel-Maksoud
Forcing-zone-type approaches (such as absorbing layers, damping zones, sponge layers, relaxation zones, etc.) can be used to reduce undesired wave reflections at the domain boundaries in flow simulations with free-surface waves. They introduce source terms in one or several of the governing equations in a zone adjacent to the corresponding domain boundaries, with the intention of gradually forcing the solution within the zone towards some reference solution. These source terms contain case-dependent parameters that require...

Numerical study of sloshing motion on unstructured mesh using UMTHINC

Mohamed M. Kamra & Changhong Hu
The numerical simulations of sloshing motions are performed for different test cases with various filling levels and oscillation frequencies. The numerical results are analyzed and compared with experimental data. The numerical computations are performed with a Volume Of Fluid (VOF) based Reynolds-Averaged Navier-Stokes (RANS) solver. Our in-house numerical solver employs the unstructured multi-dimensional tangent hyperbolic interface capturing method (UMTHINC) for free-surface capturing combined with various turbulence models. The sloshing motion is numerically modeled using the...

Software-In-the-Loop Method to Predict the Global Dynamic Responses of Full-scale Floating Wind Turbines by Artificial Neural Network

Peng Chen, Zhiqiang Hu & Changhong Hu
The design of floating offshore wind turbines (FOWTs) need accurate predictions of full-scale global dynamic responses. Conventional basin experimental method can hardly be used directly to predict the full-scale global dynamic responses of FOWTs, due to the dissimilarity of aerodynamic load and hydrodynamic load. Besides, numerical simulation methods are not reliable enough at this moment due to the lack of full-scale data validation. Therefore, it is necessary to find an accurate, economic and efficient approach...

Diffraction of wavefront around cylinders

R. P. Li, X. B. Chen & W. Y. Duan
The diffraction of transient waves around an infinite cylinder vertically fixed in deepwater is considered. The velocity potential and corresponding normal derivatives on the cylinder surface are expanded by the Laguerre function in vertical direction and Fourier series along the circumference. Green’s Theorem is applied in the domain external to the cylinder, to obtain the so-called Dirichlet-to-Neumann (DtN) operator, which represents the relationship between series expansion coefficients related to the velocity potential and its normal...

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