457 Works

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...

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...

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...

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....

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.

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...

Wireless geophone networks for land seismic data acquisition: a survey, tutorial and performance evaluation

Aliyu Makama, Koojana Kuladinithi & Andreas Timm-Giel
Seismic data acquisition in oil and gas exploration employs a large-scale network of geophone sensors deployed in thousands across a survey field. A central control unit acquires and processes measured data from geophones to come up with an image of the earth’s subterranean structure to locate oil and gas traps. Conventional seismic acquisition systems rely on cables to connect each sensor. Although cable-based systems are reliable, the sheer amount of cable required is tremendous, causing...

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...

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.

Toward a better understanding of team decision processes : combining laboratory experiments with agent-based modeling

Iris Lorscheid & Matthias Meyer
Despite advances in the field, we still know little about the socio-cognitive processes of team decisions, particularly their emergence from an individual level and transition to a team level. This study investigates team decision processes by using an agent-based model to conceptualize team decisions as an emergent property. It uses a mixed-method research design with a laboratory experiment providing qualitative and quantitative input for the model’s construction, as well as data for an output validation...

Digitalisierung messbar machen : ein soziotechnisches KPI-Modell für die digitale Transformation

Felix Krol, Birgit von See & Wolfgang Kersten
Eine erfolgreiche digitale Transformation hin zum Zielbild der Industrie 4.0 ist heute bereits für viele Unternehmen ein entscheidendes Wettbewerbskriterium. Die anhaltende globale COVID-19-Pandemie hat die Notwendigkeit der Digitalisierung in den Unternehmen deutlich gemacht und diese zusätzlich beschleunigt. Insbesondere in dieser Zeit sind die Unternehmen jedoch mit einer ungewissen Auftrags- und Ertragslage konfrontiert und müssen ihre Investitionsbudgets zielgerichtet einsetzen. Als Entscheidungsgrundlage bietet sich die Bestimmung der digitalen Reife mithilfe eines fundierten Kennzahlensystems an. Dieser Beitrag entwickelt...

Stakeholder participation in the planning and design of nature-based solutions : insights from CLEVER Cities Project in Hamburg

Alessandro Arlati, Anne Rödl, Sopho Kanjaria-Christian & Jörg Knieling
Cities are essential players in responding to the present complex environmental and social challenges, such as climate change. The nature-based solution (NbS) concept is identified in the scientific discourse and further recognized by the European Commission as a part of the solution to address such challenges. Deploying NbS in urban contexts requires the cooperation of different public and private stakeholders to manage those processes. In this paper, the experiences of establishing and managing NbS-related processes...

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...

Toward ATM resiliency : a deep CNN to predict number of delayed flights and ATFM delay

Rasoul Sanaei, Brian Alphonse Pinto & Volker Gollnick
The European Air Traffic Management Network (EATMN) is comprised of various stakeholders and actors. Accordingly, the operations within EATMN are planned up to six months ahead of target date (tactical phase). However, stochastic events and the built-in operational flexibility (robustness), along with other factors, result in demand and capacity imbalances that lead to delayed flights. The size of the EATMN and its complexity challenge the prediction of the total network delay using analytical methods or...

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...

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...

An energy-efficient adaptive course control system for ocean surface ships

Changyuan Chen, Manases Tello Ruiz, Guillaume Delefortrie, Marc Vantorre & Evert Lataire
In order to improve the performance and the energy efficiency (rudder actions) of the ship control system in presence of changing environmental conditions and system uncertainty, this paper develops a novel adaptive fuzzy-PID course controller with a dynamic compensator and a nonlinear feedback for the autonomous surface ship. Firstly, an adaptive PID control strategy, whose control parameters are real-time adjusted by the fuzzy system, is designed to achieve the optimal control effect and the robust...

Numerical investigation of cavitation and hydrodynamic characteristics of damaged propeller

Minsheng Zhao & Decheng Wan
In the present study, a numerical simulation of cavitation flows around a damaged and a complete four –bladed E779A propeller has been carried out. The numerical results can be used as a reference to evaluate the working ability of a propeller in case of damage. In numerical simulation, the damaged propeller is simplified as the INSEAN E779A propeller missing one blade, hence, it’s a three-bladed. The typical unsteady dynamics are predicted by the RANS method...

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