TY - RPRT A1 - Drescher, Hans Paul T1 - Critical review of the 1. Stokes’ problem and consequences for mixed turbulent/laminar flow N2 - The “1. Stokes’ problem”, the “suddenly accelerated flat wall”, is the oldest application of the Navier-Stokes equations. Stokes’ solution of the “problem” does not comply with the mathematical theorem of Cauchy and Kowalewskaya on the “Uniqueness and Existence” of solutions of partial differential equations and violates the physical theorem of minimum entropy production/dissipation of the Thermodynamics of Irreversible Processes. The result includes very high local shear stresses and dissipation rates. That is of special interest for the theory of turbulent and mixed turbulent/laminar flow. A textbook solution of the “1. Stokes Problem” is the Couette flow, which has a constant sheer stress along a linear profile. A consequence is that the Navier-Stokes equations do not describe any S-shaped part of a turbulent profile found in any turbulent Couette experiment. The paper surveys arguments referring to that statement, concerning the history of >150 years. Contrary to this there is always a Navier-Stokes solution near the wall, observed by a linear part of the Couette profile. There a turbulent description (e.g. by the logarithmic law-of-the-wall) fails completely. That is explained by the minimum dissipation requirement together with the Couette feature τ = const. The local co-existence of a turbulent zone and a laminar zone near the wall is stable and observed also at high Reynolds-Numbers. Y1 - 2024 ER - TY - JOUR A1 - Yoshinobu, Tatsuo A1 - Miyamoto, Ko-ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef T1 - Field-effect sensors combined with the scanned light pulse technique: from artificial olfactory images to chemical imaging technologies JF - Chemosensors N2 - The artificial olfactory image was proposed by Lundström et al. in 1991 as a new strategy for an electronic nose system which generated a two-dimensional mapping to be interpreted as a fingerprint of the detected gas species. The potential distribution generated by the catalytic metals integrated into a semiconductor field-effect structure was read as a photocurrent signal generated by scanning light pulses. The impact of the proposed technology spread beyond gas sensing, inspiring the development of various imaging modalities based on the light addressing of field-effect structures to obtain spatial maps of pH distribution, ions, molecules, and impedance, and these modalities have been applied in both biological and non-biological systems. These light-addressing technologies have been further developed to realize the position control of a faradaic current on the electrode surface for localized electrochemical reactions and amperometric measurements, as well as the actuation of liquids in microfluidic devices. KW - visualization KW - light-addressing technologies KW - scanned light pulse technique KW - field-effect structure KW - MOS KW - metal-oxide-semiconductor structure KW - catalytic metal KW - electronic nose KW - gas sensor KW - artificial olfactory image Y1 - 2024 U6 - https://doi.org/10.3390/chemosensors12020020 SN - 2227-9040 N1 - This article belongs to the Special Issue "An Exciting Journey of Chemical Sensors and Biosensors: A Theme Issue in Honor of Professor Ingemar Lundström" Corresponding author: Tatsuo Yoshinobu, Michael J. Schöning VL - 12 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bertz, Morten A1 - Schöning, Michael Josef A1 - Molinnus, Denise A1 - Homma, Takayuki T1 - Influence of temperature, light, and H₂O₂ concentration on microbial spore inactivation: in-situ Raman spectroscopy combined with optical trapping JF - Physica status solidi (a) applications and materials science N2 - To gain insight on chemical sterilization processes, the influence of temperature (up to 70 °C), intense green light, and hydrogen peroxide (H₂O₂) concentration (up to 30% in aqueous solution) on microbial spore inactivation is evaluated by in-situ Raman spectroscopy with an optical trap. Bacillus atrophaeus is utilized as a model organism. Individual spores are isolated and their chemical makeup is monitored under dynamically changing conditions (temperature, light, and H₂O₂ concentration) to mimic industrially relevant process parameters for sterilization in the field of aseptic food processing. While isolated spores in water are highly stable, even at elevated temperatures of 70 °C, exposure to H₂O₂ leads to a loss of spore integrity characterized by the release of the key spore biomarker dipicolinic acid (DPA) in a concentration-dependent manner, which indicates damage to the inner membrane of the spore. Intensive light or heat, both of which accelerate the decomposition of H₂O₂ into reactive oxygen species (ROS), drastically shorten the spore lifetime, suggesting the formation of ROS as a rate-limiting step during sterilization. It is concluded that Raman spectroscopy can deliver mechanistic insight into the mode of action of H₂O₂-based sterilization and reveal the individual contributions of different sterilization methods acting in tandem. KW - hydrogen peroxide KW - optical spore trapping KW - Raman spectroscopy KW - sterilization conditions KW - temperature Y1 - 2024 U6 - https://doi.org/10.1002/pssa.202300866 SN - 1862-6319 (Online) SN - 1862-6300 (Print) N1 - Corresponding author: Michael J. Schöning IS - Early View PB - Wiley-VCH CY - Berlin ER - TY - JOUR A1 - Schoenrock, Britt A1 - Muckelt, Paul E. A1 - Hastermann, Maria A1 - Albracht, Kirsten A1 - MacGregor, Robert A1 - Martin, David A1 - Gunga, Hans-Christian A1 - Salanova, Michele A1 - Stokes, Maria J. A1 - Warner, Martin B. A1 - Blottner, Dieter T1 - Muscle stiffness indicating mission crew health in space JF - Scientific Reports N2 - Muscle function is compromised by gravitational unloading in space affecting overall musculoskeletal health. Astronauts perform daily exercise programmes to mitigate these effects but knowing which muscles to target would optimise effectiveness. Accurate inflight assessment to inform exercise programmes is critical due to lack of technologies suitable for spaceflight. Changes in mechanical properties indicate muscle health status and can be measured rapidly and non-invasively using novel technology. A hand-held MyotonPRO device enabled monitoring of muscle health for the first time in spaceflight (> 180 days). Greater/maintained stiffness indicated countermeasures were effective. Tissue stiffness was preserved in the majority of muscles (neck, shoulder, back, thigh) but Tibialis Anterior (foot lever muscle) stiffness decreased inflight vs. preflight (p < 0.0001; mean difference 149 N/m) in all 12 crewmembers. The calf muscles showed opposing effects, Gastrocnemius increasing in stiffness Soleus decreasing. Selective stiffness decrements indicate lack of preservation despite daily inflight countermeasures. This calls for more targeted exercises for lower leg muscles with vital roles as ankle joint stabilizers and in gait. Muscle stiffness is a digital biomarker for risk monitoring during future planetary explorations (Moon, Mars), for healthcare management in challenging environments or clinical disorders in people on Earth, to enable effective tailored exercise programmes. KW - Ageing KW - Anatomy KW - Muscle KW - Musculoskeletal system KW - Physiology Y1 - 2024 U6 - https://doi.org/10.1038/s41598-024-54759-6 SN - 2045-2322 N1 - Corresponding author: Dieter Blottner VL - 14 IS - Article number: 4196 PB - Springer Nature CY - London ER - TY - CHAP A1 - Wittig, M. A1 - Rütters, René A1 - Bragard, Michael ED - Reiff-Stephan, Jörg ED - Jäkel, Jens ED - Schwarz, André T1 - Application of RL in control systems using the example of a rotatory inverted pendulum T2 - Tagungsband AALE 2024 : Fit für die Zukunft: praktische Lösungen für die industrielle Automation N2 - In this paper, the use of reinforcement learning (RL) in control systems is investigated using a rotatory inverted pendulum as an example. The control behavior of an RL controller is compared to that of traditional LQR and MPC controllers. This is done by evaluating their behavior under optimal conditions, their disturbance behavior, their robustness and their development process. All the investigated controllers are developed using MATLAB and the Simulink simulation environment and later deployed to a real pendulum model powered by a Raspberry Pi. The RL algorithm used is Proximal Policy Optimization (PPO). The LQR controller exhibits an easy development process, an average to good control behavior and average to good robustness. A linear MPC controller could show excellent results under optimal operating conditions. However, when subjected to disturbances or deviations from the equilibrium point, it showed poor performance and sometimes instable behavior. Employing a nonlinear MPC Controller in real time was not possible due to the high computational effort involved. The RL controller exhibits by far the most versatile and robust control behavior. When operated in the simulation environment, it achieved a high control accuracy. When employed in the real system, however, it only shows average accuracy and a significantly greater performance loss compared to the simulation than the traditional controllers. With MATLAB, it is not yet possible to directly post-train the RL controller on the Raspberry Pi, which is an obstacle to the practical application of RL in a prototyping or teaching setting. Nevertheless, RL in general proves to be a flexible and powerful control method, which is well suited for complex or nonlinear systems where traditional controllers struggle. KW - Rotatory Inverted Pendulum KW - MPC KW - LQR KW - PPO KW - Reinforcement Learning Y1 - 2024 SN - 978-3-910103-02-3 U6 - https://doi.org/10.33968/2024.53 N1 - 20. AALE-Konferenz. Bielefeld, 06.03.-08.03.2024. (Tagungsband unter https://doi.org/10.33968/2024.29) SP - 241 EP - 248 PB - le-tex publishing services GmbH CY - Leipzig ER - TY - JOUR A1 - Adels, Klaudia A1 - Monakhova, Yulia T1 - Low-field NMR spectroscopic study of e-cigarettes: Is determination of only nicotine and organic carrier solvents possible? JF - Microchemical Journal N2 - Electronic cigarettes (e-cigarettes) have become popular worldwide with the market growing exponentially in some countries. The absence of product standards and safety regulations requires urgent development of analytical methodologies for the holistic control of the growing diversity of such products. An approach based on low-field nuclear magnetic resonance (LF-NMR) at 80 MHz is presented for the simultaneous determination of key parameters: carrier solvents (vegetable glycerine (VG), propylene glycol (PG) and water), total nicotine as well as free-base nicotine fraction. Moreover, qualitative and quantitative determination of fourteen weak organic acids deliberately added to enhance sensory characteristics of e-cigarettes was possible. In most cases these parameters can be rapidly and conveniently determined without using any sample manipulation such as dilution, extraction or derivatization steps. The method was applied for 37 authentic e-cigarettes samples. In particular, eight different organic acids with the content up to 56 mg/mL were detected. Due to its simplicity, the method can be used in routine regulatory control as well as to study release behaviour of nicotine and other e-cigarettes constituents in different products. KW - Electronic cigarettes KW - Low field NMR KW - Carrier solvents KW - Free-base nicotine KW - Weak organic acids Y1 - 2024 U6 - https://doi.org/10.1016/j.microc.2024.110859 SN - 1095-9149 N1 - Corresponding author: Yulia Monakhova VL - 203 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Block, Simon A1 - Viebahn, Peter A1 - Jungbluth, Christian T1 - Analysing direct air capture for enabling negative emissions in Germany: an assessment of the resource requirements and costs of a potential rollout in 2045 JF - Frontiers in Climate N2 - Direct air capture (DAC) combined with subsequent storage (DACCS) is discussed as one promising carbon dioxide removal option. The aim of this paper is to analyse and comparatively classify the resource consumption (land use, renewable energy and water) and costs of possible DAC implementation pathways for Germany. The paths are based on a selected, existing climate neutrality scenario that requires the removal of 20 Mt of carbon dioxide (CO2) per year by DACCS from 2045. The analysis focuses on the so-called “low-temperature” DAC process, which might be more advantageous for Germany than the “high-temperature” one. In four case studies, we examine potential sites in northern, central and southern Germany, thereby using the most suitable renewable energies for electricity and heat generation. We show that the deployment of DAC results in large-scale land use and high energy needs. The land use in the range of 167–353 km2 results mainly from the area required for renewable energy generation. The total electrical energy demand of 14.4 TWh per year, of which 46% is needed to operate heat pumps to supply the heat demand of the DAC process, corresponds to around 1.4% of Germany's envisaged electricity demand in 2045. 20 Mt of water are provided yearly, corresponding to 40% of the city of Cologne‘s water demand (1.1 million inhabitants). The capture of CO2 (DAC) incurs levelised costs of 125–138 EUR per tonne of CO2, whereby the provision of the required energy via photovoltaics in southern Germany represents the lowest value of the four case studies. This does not include the costs associated with balancing its volatility. Taking into account transporting the CO2 via pipeline to the port of Wilhelmshaven, followed by transporting and sequestering the CO2 in geological storage sites in the Norwegian North Sea (DACCS), the levelised costs increase to 161–176 EUR/tCO2. Due to the longer transport distances from southern and central Germany, a northern German site using wind turbines would be the most favourable. KW - rollout KW - economics KW - Germany KW - negative emissions KW - carbon dioxide removal KW - climate neutrality KW - DAC KW - direct air capture Y1 - 2024 U6 - https://doi.org/10.3389/fclim.2024.1353939 SN - 2624-9553 VL - 6 PB - Frontiers CY - Lausanne ER - TY - CHAP A1 - Schneider, Dominik A1 - Wisselink, Frank A1 - Czarnecki, Christian A1 - Nölle, Nikolai T1 - Benefits and framework conditions for information-driven business models concerning the Internet of Things T2 - Digitalization in companies N2 - In the context of the increasing digitalization, the Internet of Things (IoT) is seen as a technological driver through which completely new business models can emerge in the interaction of different players. Identified key players include traditional industrial companies, municipalities and telecommunications companies. The latter, by providing connectivity, ensure that small devices with tiny batteries can be connected almost anywhere and directly to the Internet. There are already many IoT use cases on the market that provide simplification for end users, such as Philips Hue Tap. In addition to business models based on connectivity, there is great potential for information-driven business models that can support or enhance existing business models. One example is the IoT use case Park and Joy, which uses sensors to connect parking spaces and inform drivers about available parking spaces in real time. Information-driven business models can be based on data generated in IoT use cases. For example, a telecommunications company can add value by deriving more decision-relevant information – called insights – from data that is used to increase decision agility. In addition, insights can be monetized. The monetization of insights can only be sustainable, if careful attention is taken and frameworks are considered. In this chapter, the concept of information-driven business models is explained and illustrated with the concrete use case Park and Joy. In addition, the benefits, risks and framework conditions are discussed. Y1 - 2024 SN - 978-3-658-39093-8 (Print) SN - 978-3-658-39094-5 (eBook) U6 - https://doi.org/10.1007/978-3-658-39094-5_5 SP - 59 EP - 75 PB - Springer CY - Wiesbaden ER - 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 - Koch, Christopher A1 - Böhnisch, Nils A1 - Verdonck, Hendrik A1 - Hach, Oliver A1 - Braun, Carsten T1 - Comparison of unsteady low- and mid-fidelity propeller aerodynamic methods for whirl flutter applications JF - Applied Sciences N2 - Aircraft configurations with propellers have been drawing more attention in recent times, partly due to new propulsion concepts based on hydrogen fuel cells and electric motors. These configurations are prone to whirl flutter, which is an aeroelastic instability affecting airframes with elastically supported propellers. It commonly needs to be mitigated already during the design phase of such configurations, requiring, among other things, unsteady aerodynamic transfer functions for the propeller. However, no comprehensive assessment of unsteady propeller aerodynamics for aeroelastic analysis is available in the literature. This paper provides a detailed comparison of nine different low- to mid-fidelity aerodynamic methods, demonstrating their impact on linear, unsteady aerodynamics, as well as whirl flutter stability prediction. Quasi-steady and unsteady methods for blade lift with or without coupling to blade element momentum theory are evaluated and compared to mid-fidelity potential flow solvers (UPM and DUST) and classical, derivative-based methods. Time-domain identification of frequency-domain transfer functions for the unsteady propeller hub loads is used to compare the different methods. Predictions of the minimum required pylon stiffness for stability show good agreement among the mid-fidelity methods. The differences in the stability predictions for the low-fidelity methods are higher. Most methods studied yield a more unstable system than classical, derivative-based whirl flutter analysis, indicating that the use of more sophisticated aerodynamic modeling techniques might be required for accurate whirl flutter prediction. KW - Aeroelasticity KW - Flutter KW - Propeller whirl flutter KW - Unsteady aerodynamics KW - 1P hub loads Y1 - 2024 U6 - https://doi.org/10.3390/app14020850 SN - 2076-3417 VL - 14 IS - 2 SP - 1 EP - 28 PB - MDPI CY - Basel ER -