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On-Demand Transport Services as a Supplement to Public Transport in Suburban Areas: A Comparison of Traditional and Modern Demand Responsive Transport Services in a Household Survey in the Suburban Area of Hamburg
No full textApp-based ridepooling offers the chance to provide a high-quality public transportation service in areas that have been inadequately served so far. One of the main strengths of ridepooling services is their ability to offer direct access to the public transport system and thus provide an attractive service on the first and last mile. While traditional on-demand services have so far been quite inflexible, due to having a fixed timetable, needing to be ordered in advance of the trip via a call centre, app-based ridepooling promises a true on-demand service for the user. This study is based on a household survey carried out in June/July 2022 in suburban areas of Hamburg, Germany's second-largest city. We investigated one area with a modern app-based on-demand service, as well as one area with traditional dial-a-ride transport with telephone booking options. Similarities as well as differences in the perception of these different services were investigated. The results show that the modern on-demand services are significantly better known and more frequently used than the traditional dial-a-ride transport services. At the same time, the same features of demand responsive transport (DRT) service are shown to be important to people, regardless of the type of DRT service offered. In particular, flexible booking options should be highlighted, which modern demand responsive transport is better able to fulfil
Conversion of natural tissues and food waste into aerogels and their application in oleogelation
No full textIn this work, various natural tissues were for the first time directly converted into nanostructured aerogels by utilizing their intrinsic (meso-)porosity. In contrast to common aerogel production, no use of pure biopolymers, their extraction, dissolution, gelation or use of additives (e.g. crosslinkers, acids and bases) was necessary. The production process required washing of the wet starting material with water, a solvent exchange with ethanol and drying with supercritical CO2. The resulting materials exhibited low bulk densities (0.01–0.12 g cm−3), significant specific surface areas (108–446 m2 g−1) and mesopore volumes (0.3–2.6 cm3 g−1). Assessment of 20 different tissues including fruit pulp and peel, vegetable pulp, and mushrooms showed the generality of the approach. A broad spectrum of different microstructures was identified, whereas especially textural properties of samples derived from water rich pulp were highly similar to those found in classical biopolymer aerogels, for instance based on pectin or cellulose. Furthermore, the capability of the materials to structure liquid sunflower oil was shown: the produced oleogels exhibited exceptionally high oil uptake (max. 99%) and rheological properties similar to those of solid fats. Results suggest that supercritical drying of tissues (e.g. based on food waste) is a suitable approach for their upcycling into value added materials by a complete green and sustainable process. This research also contributes to sustainable development by transforming food waste into valuable aerogels and promoting science education through accessible, open-source STEM resources
Measuring transport poverty with a mixed-methods approach. A comparative case study of the German cities Berlin and Hamburg
No full textThis mixed-methods study examines transport poverty in Berlin and Hamburg, combining GIS-based spatial analysis of public transport (PT) service levels with qualitative interviews of 40 welfare recipients about their transport experiences. The research reveals that low-income residents do not have worse absolute access to PT, but per-capita service is poorer due to high population density. This highlights inequities where crowded transport systems diminish service quality. The interviews also show that high PT fares, before the introduction of the €58 “Deutschlandticket,” had been a major barrier, forcing individuals to choose between transport and other essential needs like food and housing. This financial constraint limits mobility, employment, and social interaction. The study’s integration of GIS analysis and personal interviews provides a comprehensive view of transport poverty, capturing both systemic issues and individual coping strategies. The findings suggest a typology of seven mobility types among low-income residents, offering policymakers a framework for targeted interventions. Recommendations include fare reductions, improved per-capita services in dense areas, and enhanced support for vulnerable groups to address both systemic inequalities and financial barriers, advancing a transport equity agenda that promotes social inclusion.In unserer Mixed-Methods-Studie untersuchen wir Mobilitätsarmut in Berlin und Hamburg. Dafür kombinieren wir eine GIS-basierte räumliche Analyse des öffentlichen Nahverkehrsangebots (ÖPNV) mit qualitativen Interviews über den Mobilitätsalltag mit 40 Personen, die "Hartz IV" beziehen. Die Untersuchung zeigt, dass einkommensarme Menschen in den beiden Metropolen nicht per se einen schlechteren Zugang zum ÖPNV haben, allerdings ist das Pro-Kopf-Angebot aufgrund der hohen Bevölkerungsdichte in Quartieren mit niedriger Kaufkraft strukturell weniger ausgeprägt. Dies verdeutlicht die wahrgenommene Ungleichheit, die in Form überfüllter Verkehrsmittel geäußert wird. Aus den Interviews geht auch hervor, dass die hohen Fahrpreise vor der Einführung des 58€-Deutschlandtickets ein großes Hindernis darstellten, das die Menschen dazu zwang, ihr Mobilitätsbedürfnis gegenüber anderen Grundbedürfnissen wie Nahrung und Wohnen abzuwägen. Dieser finanzielle Zwang schränkt(e) Mobilität, Beschäftigung und soziale Interaktion ein. Die in der Studie vorgenommene Integration von GIS-Analysen und Interviews bietet einen umfassenden Überblick über Mobilitätsarmut und erfasst sowohl systemische Probleme als auch individuelle Bewältigungsstrategien. Die Ergebnisse legen eine Typologie von sieben Mobilitätstypen unter einkommensschwachen Bevölkerungsgruppen nahe und eröffnen einen Rahmen für zielgruppenspezifische Maßnahmen. Dazu zählen unter anderem Fahrpreisermäßigungen, ein verbessertes Pro-Kopf-Angebot in dicht besiedelten Gebieten und eine verstärkte Unterstützung für vulnerable Gruppen, um strukturelle Ungleichheiten und finanzielle Hindernisse abzubauen und somit Teilhabe und Verkehrsgerechtigkeit zu fördern.Deutsche Forschungsgemeinschaft (DFG
Theory and modeling of transport for simple fluids in nanoporous materials: from microscopic to coarse-grained descriptions
No full textWe present the state-of-the-art of theoretical modeling, molecular simulation, and coarse-graining strategies for the transport of gases and liquids in nanoporous materials (pore size 1-100 nm). Special emphasis is placed on the transport of small molecules in zeolites, active carbons, metal-organic frameworks, but also in nanoporous materials with larger pores such as ordered and disordered mesoporous oxides. We present different atomistic and mesoscopic methods as well as available theoretical formalisms to describe such a complex problem. Attention is given to the investigation of different molecular transport coefficients─including the self, collective and transport diffusivities─but also to the determination of free energy barriers and their role in overall adsorption/separation process rates. We further introduce other available approaches such as hierarchical simulations and upscaling strategies. This review focuses on simple fluids in prototypical nanoporous materials. While the phenomena covered here capture the main physical mechanisms in such systems, complex molecules will exhibit additional specific features. For the sake of clarity and brevity, we also omit multicomponent systems (e.g., fluid mixtures, electrolytes, etc.) and electrokinetic effects arising when charged systems are considered (ionic species, charged surfaces, etc.), both of which add to the complexity
Enabling oxygen-dependent biocatalysis under fine bubble aeration in a rotating bed reactor
No full textThe scope of the thesis is the detailed investigation and demonstration of different approaches to overcome mass transfer limitations for the oxidative biocatalytic application in a modified reaction vessel of a rotating bed reactor. The benefits of the fine bubble aeration method over macrobubble aeration in application with a rotating packed bed reactor are demonstrated. Improved reaction rate and gas utilization are shown, resulting in increased catalytic productivity. Biocatalyst reuse, leading to efficient utilization of oxidases, was successfully applied. Considering the process limitations, the findings extend the potential use of fine bubble aeration for sustainable biotransformation processes using a rotating packed bed reactor.Das Ziel dieser Arbeit ist die detaillierte Untersuchung und Demonstration verschiedener experimenteller Ansätze zur Überwindung der Stofftransportlimitierung für oxidative biokatalytische Anwendungen in einem modifizierten Reaktionsgefäß mit rotierendem begasten Festbettreaktor. Die Vorteile der neuen feinblasigen Begasungsmethode gegenüber der makroblasigen Begasung werden demonstriert. Verbesserte Reaktionsgeschwindigkeit und Gasausnutzung wurden nachgewiesen, was die katalytische Produktivität erhöht. Die Wiederverwendung von Biokatalysatoren als Beitrag zur effizienten Nutzung von Oxidasen wird im Detail dargelegt. Unter Berücksichtigung der Prozessgrenzen erweitern die Ergebnisse die potenzielle Anwendung der Feinblasenbegasung für nachhaltige Biotransformationen in einem rotierenden begasten Festbettreaktor
A quantitative comparison of electrode positions for respiratory surface EMG
No full textObjective: Respiratory surface electromyography (sEMG) is a promising physiological signal for analyzing respiratory effort, patient-ventilator asynchrony, and respiratory training. In clinical research, a wide variety of different setups are used and no consensus has yet been reached on the positioning of electrodes. Therefore, this work aims to quantitatively compare both unilateral and bilateral bipolar electrode leads. Methods: Recordings of diaphragmatic and intercostal muscle activity were performed in 20 young and healthy adults using a setup with 64 electrodes placed in relation to prominent anatomical lines. Subjects completed three breathing maneuvers: 300 s quiet breathing, 5 maximum inspiratory pressure (MIP) trials, and 15 breaths of resistance breathing at 20 % of the MIP. To quantify the performance of differential electrode leads, three metrics were determined: the ratio between inspiratory muscle activity and (1) baseline noise (SNRbase), (2) expiratory muscle activity (SNRexp), and (3) ECG interference (SNREMG-ECG). Results: The study revealed considerable differences between bipolar electrode positions. Our results support the use of bilateral positions on the midclavicular line and parasternal line for measuring diaphragm and intercostal activity. For intercostal muscles, there is a high flexibility in positioning electrodes more lateral or medial, if necessary. Unilateral leads do not appear to outperform the bilateral configuration as SNR metrics were consistently smaller. Conclusion: This study provides recommendations for electrode placements and is a first step towards standardization of respiratory sEMG measurements. Significance: This electrode lead standardization will be essential to increase clinical acceptance in the future
Additive manufacturing of ceramics via the laser powderbed fusion process
No full textAdditive manufacturing (AM) of ceramics presents both exciting opportunities and significant challenges, particularly with the laser-based AM processes. Ceramics are known for their special properties, such as high strength, corrosion resistance, and temperature stability, but their inherent brittleness and high processing demands make AM more complex. This review provides an updated overview of the most common AM techniques for ceramics, including direct energy deposition, binder jetting, laminated object manufacturing, and material extrusion-based techniques. However, the focus is placed on the laser powder bed fusion (LPBF) of ceramics, a technique that has gained increasing attention for its ability to fabricate complex ceramic parts with enhanced quality. The review delves into the key causes of critical defects commonly observed in LPBF, such as porosity, cracking, spattering, and surface roughness. Recent advancements in addressing these issues are discussed, along with the limitations of current defect prevention strategies. Furthermore, the review provides an updated analysis of the mechanical properties of LPBF-fabricated ceramics, giving insights into how processing parameters influence the performance of ceramic LPBF-printed parts. Modeling and simulation techniques are also reviewed, highlighting their role in enhancing understanding of ceramic behavior during LPBF. Overall, this review highlights recent progress and current challenges in ceramic AM techniques, while exploring future research opportunities, such as process optimization and defect prevention strategies
Buckling tests of cylindrical composite shells in multiaxial loading
No full textThin-walled cylindrical composite shells are prone to buckling failure in a variety of load cases. The number of influencing factors and comparably small amount of test data on combined load cases, which regularly occur in application, pose a major design challenge. Two experimental campaigns on the buckling of thin-walled cylindrical composite shells in multiaxial loading are carried out with two nominally identical specimens with a radius-to-thickness-ratio of 375. The results of buckling tests with combined axial compression and torsion, compression and bending, as well as all three buckling critical load types are presented. The influence of the loading direction of bending and torsion is shown, and the effects of repeated mounting of the specimens in the test rig as well as the scatter of buckling loads are discussed. Comparison of test results with the established NASA SP-8007 guideline and perfect buckling loads shows major qualitative and quantitative differences in the load interaction curves
Illuminating bioprocess responses to metal-based nanoparticles addition along hydrogen and methane production pathways : a review
No full textRecent research has discussed the positive impacts of metal-based nanoparticles (NPs) on bioprocesses producing either hydrogen (H2) or methane (CH4). The enhancement has been explained by mechanisms such as direct interspecies electron transfer (DIET), metal corrosion, and dissimilatory reduction. Such interactions could induce further benefits, such as controlling oxidation–reduction potential (ORP), mitigating toxicants, promoting enzymatic activity, and altering the microbiome, which have not yet been comprehensively discussed. Factors like metal type, oxidation state, and size of NPs are crucial for their reactivity and corresponding responses. This review discusses how different redox potentials of metals can regulate metabolic pathways and how NPs and their reactive ions can eliminate toxicants (e.g., sulfate) and enhance the activity of intra- and extracellular enzymes. The enrichment of responsive microorganisms in correlation with NPs is further discussed. A better understanding of the multifaceted role of metal-based NPs can guide potential new incorporation strategies to improve bioprocesses
Predicting solvation free energies for neutral molecules in any solvent with openCOSMO-RS
No full textIn this study, we introduce openCOSMO-RS 24a, an improved version of the open-source COSMO-RS model parameterized using quantum chemical calculations from ORCA 6.0, leveraging a comprehensive dataset that includes solvation free energies, partition coefficients, and infinite dilution activity coefficients for various solutes and solvents mainly at 25 °C. This is the first version of the model also capable of predicting solvation free energies based on ORCA calculations. Additionally, we develop a Quantitative Structure-Property Relationships model to predict molar volumes of the solvents, an essential requirement for predicting solvation free energies and partition coefficients from structure alone. Our results show that openCOSMO-RS 24a achieves an average absolute deviation of 0.45 kcal mol1 for solvation free energies, 0.76 for the logarithm of the partition coefficients, and 0.51 for the logarithm of infinite dilution activity coefficients, demonstrating improvements over the previous openCOSMO-RS 22 parameterization and comparable results to COSMOtherm 24 BP-TZVP. The user interface was extended to be able to use it as solvation model directly from within ORCA 6.0 or from the command line to provide researchers with a robust tool for applications in chemical and materials science