TY - JOUR A1 - Möhren, Felix A1 - Bergmann, Ole A1 - Janser, Frank A1 - Braun, Carsten T1 - Assessment of structural mechanical effects related to torsional deformations of propellers JF - CEAS Aeronautical Journal N2 - Lifting propellers are of increasing interest for Advanced Air Mobility. All propellers and rotors are initially twisted beams, showing significant extension–twist coupling and centrifugal twisting. Torsional deformations severely impact aerodynamic performance. This paper presents a novel approach to assess different reasons for torsional deformations. A reduced-order model runs large parameter sweeps with algebraic formulations and numerical solution procedures. Generic beams represent three different propeller types for General Aviation, Commercial Aviation, and Advanced Air Mobility. Simulations include solid and hollow cross-sections made of aluminum, steel, and carbon fiber-reinforced polymer. The investigation shows that centrifugal twisting moments depend on both the elastic and initial twist. The determination of the centrifugal twisting moment solely based on the initial twist suffers from errors exceeding 5% in some cases. The nonlinear parts of the torsional rigidity do not significantly impact the overall torsional rigidity for the investigated propeller types. The extension–twist coupling related to the initial and elastic twist in combination with tension forces significantly impacts the net cross-sectional torsional loads. While the increase in torsional stiffness due to initial twist contributes to the overall stiffness for General and Commercial Aviation propellers, its contribution to the lift propeller’s stiffness is limited. The paper closes with the presentation of approximations for each effect identified as significant. Numerical evaluations are necessary to determine each effect for inhomogeneous cross-sections made of anisotropic material. KW - Lifting propeller KW - Extension–twist coupling KW - Trapeze effect KW - Centrifugal twisting moment Y1 - 2024 U6 - https://doi.org/10.1007/s13272-024-00737-7 SN - 1869-5590 (eISSN) SN - 1869-5582 N1 - Corresponding author: Felix Möhren PB - Springer CY - Wien ER - TY - JOUR A1 - Clausnitzer, Julian A1 - Kleefeld, Andreas T1 - A spectral Galerkin exponential Euler time-stepping scheme for parabolic SPDEs on two-dimensional domains with a C² boundary JF - Discrete and Continuous Dynamical Systems - Series B N2 - We consider the numerical approximation of second-order semi-linear parabolic stochastic partial differential equations interpreted in the mild sense which we solve on general two-dimensional domains with a C² boundary with homogeneous Dirichlet boundary conditions. The equations are driven by Gaussian additive noise, and several Lipschitz-like conditions are imposed on the nonlinear function. We discretize in space with a spectral Galerkin method and in time using an explicit Euler-like scheme. For irregular shapes, the necessary Dirichlet eigenvalues and eigenfunctions are obtained from a boundary integral equation method. This yields a nonlinear eigenvalue problem, which is discretized using a boundary element collocation method and is solved with the Beyn contour integral algorithm. We present an error analysis as well as numerical results on an exemplary asymmetric shape, and point out limitations of the approach. KW - Nonlinear eigenvalue problems KW - Boundary integral equations, KW - Exponential Euler scheme, KW - Parabolic SPDEs Y1 - 2024 U6 - https://doi.org/10.3934/dcdsb.2023148 SN - 1531-3492 SN - 1553-524X (eISSN) VL - 29 IS - 4 SP - 1624 EP - 1651 PB - AIMS CY - Springfield ER - TY - JOUR A1 - Ayala, Rafael Ceja A1 - Harris, Isaac A1 - Kleefeld, Andreas T1 - Direct sampling method via Landweber iteration for an absorbing scatterer with a conductive boundary JF - Inverse Problems and Imaging N2 - In this paper, we consider the inverse shape problem of recovering isotropic scatterers with a conductive boundary condition. Here, we assume that the measured far-field data is known at a fixed wave number. Motivated by recent work, we study a new direct sampling indicator based on the Landweber iteration and the factorization method. Therefore, we prove the connection between these reconstruction methods. The method studied here falls under the category of qualitative reconstruction methods where an imaging function is used to recover the absorbing scatterer. We prove stability of our new imaging function as well as derive a discrepancy principle for recovering the regularization parameter. The theoretical results are verified with numerical examples to show how the reconstruction performs by the new Landweber direct sampling method. Y1 - 2024 U6 - https://doi.org/10.3934/ipi.2023051 SN - 1930-8337 SN - 1930-8345 (eISSN) VL - 18 IS - 3 SP - 708 EP - 729 PB - AIMS CY - Springfield ER - TY - JOUR A1 - Golland, Alexander T1 - Datenschutz beim Einsatz künstlicher Intelligenz im Unternehmen JF - NWB N2 - Seit Ende 2022 prägt das Schlagwort „Künstliche Intelligenz“ (KI) nicht nur den rechtswissenschaftlichen Diskurs. Die allgemeine Verfügbarkeit von generativen KI-Modellen, allen voran die großen Sprachmodelle (Large Language Models, kurz: LLM) wie ChatGPT von OpenAI oder Bing AI von Microsoft, erfreuen sich größter Beliebtheit: LLM sind in der Lage, auf Grundlage statistischer Methoden – eine entsprechende Schnittstelle (Interface) vorausgesetzt – auch technisch wenig versierten Nutzern verständliche Antworten auf ihre Fragen zu liefern. Dabei werden nicht nur umfassend Nutzerdaten verarbeitet, sondern auch auf weitere personenbezogene Daten zugegriffen sowie neue Daten erzeugt. Der Beitrag geht der Frage nach, welche spezifischen datenschutzrechtlichen Herausforderungen sich für Unternehmen beim Einsatz solcher LLM stellen. Y1 - 2024 SN - 0028-3460 IS - 6 SP - 425 EP - 432 PB - NWB CY - Herne ER - TY - JOUR A1 - Timme, Michael T1 - Kaufvertrag: Das Zusammentreffen von Beschaffenheitsvereinbarung und Gewährleistungsausschluss – ein Spannungsverhältnis JF - Monatsschrift für Deutsches Recht N2 - Wer A sagt, muss zumindest im Kaufrecht nicht immer B sagen: Es kommt nicht selten vor, dass sich in einem Kaufvertrag einerseits ein wirksamer Ausschluss der Gewährleistung des Verkäufers für Sachmängel findet, die Parteien aber andererseits gleichwohl eine Beschaffenheitsvereinbarung für bestimmte Eigenschaften vertraglich festlegen. In diesem Problemfeld führt eine aktuelle Entscheidung des BGH zu weiteren Klärungen für die Praxis (BGH, Urt. v. 10.4.2024 – VIII ZR 161/23, MDR 2024, 706). Der folgende Beitrag setzt sich mit den vielfältigen Aspekten der Entscheidung auseinander und erläutert, aus welchen Gründen der BGH dem Käufer einige goldene Brücken für einen Schadensersatzanspruch gebaut hat. Y1 - 2024 U6 - https://doi.org/10.9785/mdtr-2024-781203 SN - 2194-4202 (online) SN - 0340-1812 (print) VL - 78 IS - 12 SP - 745 EP - 748 PB - Verlag Dr. Otto Schmidt CY - Köln ER - TY - JOUR A1 - Tix, Julian A1 - Moll, Fabian A1 - Krafft, Simone A1 - Betsch, Matthias A1 - Tippkötter, Nils T1 - Hydrogen production from enzymatic pretreated organic waste with thermotoga neapolitana JF - Energies N2 - Biomass from various types of organic waste was tested for possible use in hydrogen production. The composition consisted of lignified samples, green waste, and kitchen scraps such as fruit and vegetable peels and leftover food. For this purpose, the enzymatic pretreatment of organic waste with a combination of five different hydrolytic enzymes (cellulase, amylase, glucoamylase, pectinase and xylase) was investigated to determine its ability to produce hydrogen (H2) with the hydrolyzate produced here. In course, the anaerobic rod-shaped bacterium T. neapolitana was used for H2 production. First, the enzymes were investigated using different substrates in preliminary experiments. Subsequently, hydrolyses were carried out using different types of organic waste. In the hydrolysis carried out here for 48 h, an increase in glucose concentration of 481% was measured for waste loads containing starch, corresponding to a glucose concentration at the end of hydrolysis of 7.5 g·L−1. In the subsequent set fermentation in serum bottles, a H2 yield of 1.26 mmol H2 was obtained in the overhead space when Terrific Broth Medium with glucose and yeast extract (TBGY medium) was used. When hydrolyzed organic waste was used, even a H2 yield of 1.37 mmol could be achieved in the overhead space. In addition, a dedicated reactor system for the anaerobic fermentation of T. neapolitana to produce H2 was developed. The bioreactor developed here can ferment anaerobically with a very low loss of produced gas. Here, after 24 h, a hydrogen concentration of 83% could be measured in the overhead space. KW - biological hydrogen KW - organic waste KW - dark fermentation KW - hydrolysis KW - pretreatment Y1 - 2024 U6 - https://doi.org/10.3390/en17122938 SN - 1996-1073 N1 - Corresponding author: Nils Tippkötter VL - 17 IS - 12 PB - MDPI CY - Basel ER - TY - JOUR A1 - Varriale, Ludovica A1 - Hengsbach, Jan-Niklas A1 - Guo, Tianyi A1 - Kuka, Katrin A1 - Tippkötter, Nils A1 - Ulber, Roland T1 - Sustainable production of lactic acid using a perennial ryegrass as feedstock—a comparative study of fermentation at the bench- and reactor-scale, and ensiling JF - Sustainability N2 - Perennial ryegrass (Lolium perenne) is an underutilized lignocellulosic biomass that has several benefits such as high availability, renewability, and biomass yield. The grass press-juice obtained from the mechanical pretreatment can be used for the bio-based production of chemicals. Lactic acid is a platform chemical that has attracted consideration due to its broad area of applications. For this reason, the more sustainable production of lactic acid is expected to increase. In this work, lactic acid was produced using complex medium at the bench- and reactor scale, and the results were compared to those obtained using an optimized press-juice medium. Bench-scale fermentations were carried out in a pH-control system and lactic acid production reached approximately 21.84 ± 0.95 g/L in complex medium, and 26.61 ± 1.2 g/L in press-juice medium. In the bioreactor, the production yield was 0.91 ± 0.07 g/g, corresponding to a 1.4-fold increase with respect to the complex medium with fructose. As a comparison to the traditional ensiling process, the ensiling of whole grass fractions of different varieties harvested in summer and autumn was performed. Ensiling showed variations in lactic acid yields, with a yield up to 15.2% dry mass for the late-harvested samples, surpassing typical silage yields of 6–10% dry mass. KW - lactobacillus KW - lactic acid KW - ensiling KW - fermentation KW - perennial ryegrass KW - renewable resources KW - bio-based economy Y1 - 2024 U6 - https://doi.org/10.3390/su16188054 SN - 2071-1050 N1 - This article belongs to the Section "Environmental Sustainability and Applications" VL - 16 IS - 18 PB - MDPI CY - Basel ER - TY - JOUR A1 - Golland, Alexander A1 - Schröer, Jan-Erik T1 - Error 404 im Vergabeverfahren: Datenschutz nicht gefunden? JF - VergabeR N2 - Das Thema Datenschutz wurde bei der öffentlichen Auftragsvergabe bislang vor allem in Bezug auf Drittlandtransfers personenbezogener Daten in die USA diskutiert. Jedoch spielt der Datenschutz für das Vergabeverfahren und für die Ausführung datenschutzrelevanter Leistungen generell eine wesentliche Rolle. Gleichwohl herrschen bislang unter öffentlichen Auftraggebern Schwierigkeiten, datenschutzrechtlich relevante Fallkonstellationen zu erkennen, die möglichen Risiken daraus abzuleiten und, sofern dies gelingt, diesen Risiken angemessen zu begegnen. Der vorliegende Beitrag befasst sich mit der datenschutzrechtlichen Verantwortlichkeit, ihren Folgen und den daraus resultierenden Konsequenzen für die Gestaltung von Vergabeverfahren und Vergabeunterlagen. Y1 - 2024 SN - 2366-2247 IS - 2 SP - 75 EP - 92 PB - Wolters Kluwer CY - Köln ER - TY - JOUR A1 - Adels, Klaudia A1 - Thönnessen, Vera A1 - Monakhova, Yulia T1 - Complementary instrumental techniques applied to pain relieving tablets in an undergraduate laboratory experiment JF - Journal of Chemical Education N2 - Several unconnected laboratory experiments are usually offered for students in instrumental analysis lab. To give the students a more rational overview of the most common instrumental techniques, a new laboratory experiment was developed. Marketed pain relief drugs, familiar consumer products with one to three active components, namely, acetaminophen (paracetamol), acetylsalicylic acid (ASA), and caffeine, were selected. Common analytical methods were compared regarding the performance of qualitative and quantitative analysis of unknown tablets: UV–visible (UV–vis), infrared (IR), and nuclear magnetic resonance (NMR) spectroscopies, as well as high-performance liquid chromatography (HPLC). The students successfully uncovered the composition of formulations, which were divided into three difficulty categories. Students were shown that in addition to simple mixtures handled in theoretical classes, the composition of complex drug products can also be uncovered. By comparing the performance of different techniques, students deepen their understanding and compare the efficiency of analytical methods in the context of complex mixtures. The laboratory experiment can be adjusted for graduate level by including extra tasks such as method optimization, validation, and 2D spectroscopic techniques. KW - Instrumental analysis KW - Spectroscopy KW - Liquid chromatography KW - Qualitative and quantitative determination KW - Drugs Y1 - 2024 U6 - https://doi.org/10.1021/acs.jchemed.4c00681 SN - 0021-9584 (Print) SN - 1938-1328 (Online) PB - ACS ER - TY - JOUR A1 - Akimbekov, Nuraly A1 - Digel, Ilya A1 - Zhubanova, Azhar A1 - Tastambek, Kuanysh T. A1 - Tepecik, Atakan A1 - Sherelkhan, Dinara T1 - Biotechnological potentials of surfactants in coal utilization: a review JF - Environmental Science and Pollution Research N2 - The quest for scientifically advanced and sustainable solutions is driven by growing environmental and economic issues associated with coal mining, processing, and utilization. Consequently, within the coal industry, there is a growing recognition of the potential of microbial applications in fostering innovative technologies. Microbial-based coal solubilization, coal beneficiation, and coal dust suppression are green alternatives to traditional thermochemical and leaching technologies and better meet the need for ecologically sound and economically viable choices. Surfactant-mediated approaches have emerged as powerful tools for modeling, simulation, and optimization of coal-microbial systems and continue to gain prominence in clean coal fuel production, particularly in microbiological co-processing, conversion, and beneficiation. Surfactants (surface-active agents) are amphiphilic compounds that can reduce surface tension and enhance the solubility of hydrophobic molecules. A wide range of surfactant properties can be achieved by either directly influencing microbial growth factors, stimulants, and substrates or indirectly serving as frothers, collectors, and modifiers in the processing and utilization of coal. This review highlights the significant biotechnological potential of surfactants by providing a thorough overview of their involvement in coal biodegradation, bioprocessing, and biobeneficiation, acknowledging their importance as crucial steps in coal consumption. KW - Coal KW - Surfactants KW - Microorganisms KW - Biosolubilization KW - Biobeneficiation Y1 - 2024 U6 - https://doi.org/10.1007/s11356-024-34892-5 SN - 1614-7499 VL - 31 SP - 55099 EP - 55118 PB - Springer CY - Berlin ER -