TY - JOUR A1 - Böhnisch, Nils A1 - Braun, Carsten A1 - Muscarello, Vincenzo A1 - Marzocca, Pier T1 - About the wing and whirl flutter of a slender wing–propeller system JF - Journal of Aircraft N2 - 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. Y1 - 2024 U6 - https://doi.org/10.2514/1.C037542 SN - 1533-3868 SP - 1 EP - 14 PB - AIAA CY - Reston, Va. ER - TY - JOUR A1 - Stiemer, Luc Nicolas A1 - Thoma, Andreas A1 - Braun, Carsten T1 - MBT3D: Deep learning based multi-object tracker for bumblebee 3D flight path estimation JF - PLoS ONE N2 - 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. Y1 - 2023 U6 - https://doi.org/10.1371/journal.pone.0291415 SN - 1932-6203 N1 - Corresponding author: Luc Nicolas Stiemer VL - 18 IS - 9 PB - PLOS CY - San Fancisco ER - TY - JOUR A1 - Wild, Dominik A1 - Schrezenmeier, Johannes A1 - Czupalla, Markus A1 - Förstner, Roger T1 - Thermal Characterization of additive manufactured Integral Structures for Phase Change Applications JF - 2020 International Conference on Environmental Systems N2 - “Infused Thermal Solutions” (ITS) introduces a method for passive thermal control to stabilize structural components thermally without active heating and cooling systems, by using phase change material (PCM) in combination with lattice – both embedded into an additive manufactured integral structure. The technology is currently under development. This paper presents the results of the thermal property measurements performed on additive manufactured ITS breadboards. Within the breadboard campaigns key characteristics of the additive manufactured specimens were derived: Mechanical parameters: specimen impermeability, minimum wall thickness, lattice structure, subsequent heat treatment. Thermal properties: thermo-optical surface properties of the additive manufactured raw material, thermal conductivity and specific heat capacity measurements. As a conclusion the paper introduces an overview of potential ITS hardware applications, expected to increase the thermal performance. Y1 - 2020 PB - Texas Tech University ER - TY - JOUR A1 - Schopen, Oliver A1 - Narayan, Sriram A1 - Beckmann, Marvin A1 - Najmi, Aezid-Ul-Hassan A1 - Esch, Thomas A1 - Shabani, Bahman T1 - An EIS approach to quantify the effects of inlet air relative humidity on the performance of proton exchange membrane fuel cells: a pathway to developing a novel fault diagnostic method JF - International Journal of Hydrogen Energy N2 - In this work, the effect of low air relative humidity on the operation of a polymer electrolyte membrane fuel cell is investigated. An innovative method through performing in situ electrochemical impedance spectroscopy is utilised to quantify the effect of inlet air relative humidity at the cathode side on internal ionic resistances and output voltage of the fuel cell. In addition, algorithms are developed to analyse the electrochemical characteristics of the fuel cell. For the specific fuel cell stack used in this study, the membrane resistance drops by over 39 % and the cathode side charge transfer resistance decreases by 23 % after increasing the humidity from 30 % to 85 %, while the results of static operation also show an increase of ∼2.2 % in the voltage output after increasing the relative humidity from 30 % to 85 %. In dynamic operation, visible drying effects occur at < 50 % relative humidity, whereby the increase of the air side stoichiometry increases the drying effects. Furthermore, other parameters, such as hydrogen humidification, internal stack structure, and operating parameters like stoichiometry, pressure, and temperature affect the overall water balance. Therefore, the optimal humidification range must be determined by considering all these parameters to maximise the fuel cell performance and durability. The results of this study are used to develop a health management system to ensure sufficient humidification by continuously monitoring the fuel cell polarisation data and electrochemical impedance spectroscopy indicators. KW - PEM fuel cell KW - Electrochemical impedance spectroscopy KW - Relative air humidity KW - Active humidity control KW - Impedance analysis Y1 - 2024 SN - 0360-3199 (print) U6 - https://doi.org/10.1016/j.ijhydene.2024.01.218 SN - 1879-3487 (online) VL - 58 IS - 8 SP - 1302 EP - 1315 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schopen, Oliver A1 - Shah, Neel A1 - Esch, Thomas A1 - Shabani, Bahman T1 - Critical quantitative evaluation of integrated health management methods for fuel cell applications JF - International Journal of Hydrogen Energy N2 - Online fault diagnostics is a crucial consideration for fuel cell systems, particularly in mobile applications, to limit downtime and degradation, and to increase lifetime. Guided by a critical literature review, in this paper an overview of Health management systems classified in a scheme is presented, introducing commonly utilised methods to diagnose FCs in various applications. In this novel scheme, various Health management system methods are summarised and structured to provide an overview of existing systems including their associated tools. These systems are classified into four categories mainly focused on model-based and non-model-based systems. The individual methods are critically discussed when used individually or combined aimed at further understanding their functionality and suitability in different applications. Additionally, a tool is introduced to evaluate methods from each category based on the scheme presented. This tool applies the technique of matrix evaluation utilising several key parameters to identify the most appropriate methods for a given application. Based on this evaluation, the most suitable methods for each specific application are combined to build an integrated Health management system. KW - Fuel cell KW - Health management system KW - Online diagnostic KW - Fault detection KW - Non-model-based Evaluation Y1 - 2024 U6 - https://doi.org/10.1016/j.ijhydene.2024.05.156 SN - 0360-3199 VL - 70 SP - 370 EP - 388 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Saretzki, Charlotte A1 - Bergmann, Ole A1 - Dahmann, Peter A1 - Janser, Frank A1 - Keimer, Jona A1 - Machado, Patricia A1 - Morrison, Audry A1 - Page, Henry A1 - Pluta, Emil A1 - Stübing, Felix A1 - Küpper, Thomas T1 - Are small airplanes safe with regards to COVID-19 transmission? JF - Journal of Travel Medicine Y1 - 2021 U6 - https://doi.org/10.1093/jtm/taab105 SN - 1708-8305 VL - 28 IS - 7 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Ulmer, Jessica A1 - Braun, Sebastian A1 - Cheng, Chi-Tsun A1 - Dowey, Steve A1 - Wollert, Jörg T1 - A human factors-aware assistance system in manufacturing based on gamification and hardware modularisation JF - International Journal of Production Research N2 - Assistance systems have been widely adopted in the manufacturing sector to facilitate various processes and tasks in production environments. However, existing systems are mostly equipped with rigid functional logic and do not provide individual user experiences or adapt to their capabilities. This work integrates human factors in assistance systems by adjusting the hardware and instruction presented to the workers’ cognitive and physical demands. A modular system architecture is designed accordingly, which allows a flexible component exchange according to the user and the work task. Gamification, the use of game elements in non-gaming contexts, has been further adopted in this work to provide level-based instructions and personalised feedback. The developed framework is validated by applying it to a manual workstation for industrial assembly routines. KW - Human factors KW - assistance system KW - gamification KW - adaptive systems KW - manufacturing Y1 - 2023 U6 - https://doi.org/10.1080/00207543.2023.2166140 SN - 0020-7543 (Print) SN - 1366-588X (Online) PB - Taylor & Francis ER -