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Methane is a valuable energy source helping to mitigate the growing energy demand worldwide. However, as a potent greenhouse gas, it has also gained additional attention due to its environmental impacts. The biological production of methane is performed primarily hydrogenotrophically from H2 and CO2 by methanogenic archaea. Hydrogenotrophic methanogenesis also represents a great interest with respect to carbon re-cycling and H2 storage. The most significant carbon source, extremely rich in complex organic matter for microbial degradation and biogenic methane production, is coal. Although interest in enhanced microbial coalbed methane production is continuously increasing globally, limited knowledge exists regarding the exact origins of the coalbed methane and the associated microbial communities, including hydrogenotrophic methanogens. Here, we give an overview of hydrogenotrophic methanogens in coal beds and related environments in terms of their energy production mechanisms, unique metabolic pathways, and associated ecological functions.
Ga-doped Li7La3Zr2O12 garnet solid electrolytes exhibit the highest Li-ion conductivities among the oxide-type garnet-structured solid electrolytes, but instabilities toward Li metal hamper their practical application. The instabilities have been assigned to direct chemical reactions between LiGaO2 coexisting phases and Li metal by several groups previously. Yet, the understanding of the role of LiGaO2 in the electrochemical cell and its electrochemical properties is still lacking. Here, we are investigating the electrochemical properties of LiGaO2 through electrochemical tests in galvanostatic cells versus Li metal and complementary ex situ studies via confocal Raman microscopy, quantitative phase analysis based on powder X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. The results demonstrate considerable and surprising electrochemical activity, with high reversibility. A three-stage reaction mechanism is derived, including reversible electrochemical reactions that lead to the formation of highly electronically conducting products. The results have considerable implications for the use of Ga-doped Li7La3Zr2O12 electrolytes in all-solid-state Li-metal battery applications and raise the need for advanced materials engineering to realize Ga-doped Li7La3Zr2O12for practical use.
The thermal conductivity of components manufactured using Laser Powder Bed Fusion (LPBF), also called Selective Laser Melting (SLM), plays an important role in their processing. Not only does a reduced thermal conductivity cause residual stresses during the process, but it also makes subsequent processes such as the welding of LPBF components more difficult. This article uses 316L stainless steel samples to investigate whether and to what extent the thermal conductivity of specimens can be influenced by different LPBF parameters. To this end, samples are set up using different parameters, orientations, and powder conditions and measured by a heat flow meter using stationary analysis. The heat flow meter set-up used in this study achieves good reproducibility and high measurement accuracy, so that comparative measurements between the various LPBF influencing factors to be tested are possible. In summary, the series of measurements show that the residual porosity of the components has the greatest influence on conductivity. The degradation of the powder due to increased recycling also appears to be detectable. The build-up direction shows no detectable effect in the measurement series.
Within ESA's Cosmic Vision 2015-2025 plan, a mission to explore the Saturnian System, with special emphasis on its two moons Titan and Enceladus, was selected for study, termed TANDEM (Titan and Enceladus Mission). In this paper, we describe an optimized mission design for a TANDEM-derived solar electric propulsion (SEP) mission. We have chosen the SEP mission scenario for the interplanetary transfer of the TANDEM spacecraft because all feasible gravity assist sequences for a chemical transfer between 2015 and 2025 result in long flight times of about nine years. Our SEP system is based on the German RIT ion engine. For our optimized mission design, we have extensively explored the SEP parameter space (specific impulse, thrust level, power level) and have calculated an optimal interplanetary trajectory for each setting. In contrast to the original TANDEM mission concept, which intends to use two launch vehicles and an all-chemical transfer, our SEP mission design requires only a single Ariane 5 ECA launch for the same payload mass. Without gravity assist, it yields a faster and more flexible transfer with a fight time of less than seven years, and an increased payload ratio. Our mission design proves thereby the capability of SEP even for missions into the outer solar system.
Producing fresh water from saline water has become one of the most difficult challenges to overcome especially with the high demand and shortage of fresh water. In this context, as part of a collaboration with Germany, the authors propose a design and implementation of a pilot multi-stage solar desalination system (MSD), remotely controlled, at Douar Al Hamri in the rural town of Boughriba in the province of Berkane, Morocco. More specifically, they present their contribution on the remote control and supervision system, which makes the functioning of the MSD system reliable and guarantees the production of drinking water for the population of Douar. The results obtained show that the electronic cards and computer communication software implemented allow the acquisition of all electrical (currents, voltages, powers, yields), thermal (temperatures of each stage), and meteorological (irradiance and ambient temperature), remote control and maintenance (switching on, off, data transfer). By comparing with the literature carried out in the field of solar energy, the authors conclude that the MSD and electronic desalination systems realized during this work represent a contribution in terms of the reliability and durability of providing drinking water in rural and urban areas.
Tracking healthy habits : Digitale Anwendung zur Förderung von gesunder
Ernährung und Verhalten
(2024)
"Tracking healthy habits" ist eine App, die darauf abzielt, gesündere Essgewohnheiten und mehr Bewegung zu fördern, indem sie verschiedene messbare Metriken erfasst. Die Anwendung legt einen besonderen Schwerpunkt auf das Verfolgen von Kalorien, um Nutzer:innen dabei zu helfen, ihre tägliche Kalorienaufnahme zu kontrollieren und ein besseres Verständnis für Lebensmittel zu entwickeln. Ein übermäßiger Konsum ungesunder Lebensmittel und Bewegungsmangel können sich negativ auf den geistigen und körperlichen Zustand auswirken. Daher unterstützt diese App Nutzer:innen dabei, gesündere Gewohnheiten zu entwickeln und Disziplin zu fördern. Die Hauptziele von "Tracking Healthy Habits" sind die Förderung gesünderer Essgewohnheiten, die Unterstützung langfristiger Verhaltensänderungen durch kontinuierliches Monitoring und die Verbesserung der körperlichen sowie geistigen Gesundheit.
Harte Arbeit, Hunger, Unterkühlung und Ungewissheit – dies war der normale Alltag der Trudarmee im 2. Weltkrieg. Ekatharina, eine deutsche Sowjetbürgerin, wurde wie viele andere gegen ihren Willen in diese Armee eingezogen. Die Bachelorarbeit „Ekatharina – Leben in der Trudarmee“ behandelt den Lebensabschnitt einer Überlebenden, der Urgroßmutter der Autorin, in Form eines Graphic Novels. In der Trudarmee, auch Arbeitsarmee genannt, musste sie unter schweren Bedingungen Zwangsarbeit verrichten, wie arbeiten in der Schmiede, Bäume fällen oder Stämme schleppen. Das Projekt soll nicht nur die Erinnerungen und das kulturelle Gut bewahren, es soll auch die Familiengeschichte erforschen, die Vergangenheit verständlich gestalten und die beteiligten Personen in Ehren halten.
Drink me
(2024)
„Drink me“ ist ein Kurzfilm über drei Freunde auf einer Party, auf der ein mysteriöses Getränk verteilt wird, das die Partygäste in einen besonderen Rausch versetzt. Die Farben fangen an zu leuchten, die Musik wird klarer, alles fühlt sich intensiver an. Bis sich die Wahrnehmung der Protagonistin Ally plötzlich verändert: Vom bunt leuchtenden Rauschzustand zur scheinbaren Realität: Einem grauen, kalten Bunker voller abgewrackter Gestalten. Ally versucht die Party zu verlassen, doch während ihre Wahrnehmungen immer weiter verschwimmen, verliert sie gleichzeitig allmählich ihr Bewusstsein. Der Film bietet durch die Darstellung der verschiedenen Wahrnehmungszustände und das Verschwimmen derer ein visuell besonders spannendes Erlebnis.
Die Menschheit lebt über ihre Verhältnisse: Permanent übersteigt unser Verbrauch die uns jährlich zur Verfügung stehenden Ressourcen. Der Energiebedarf digitaler Anwendungen wird dabei meist unterschätzt. Wie Interaction-Designer:innen einen Beitrag zur Entwicklung nachhaltiger Websites leisten können, ist aktuell nur durch aufwendige Recherche zu beantworten. Die Bachelorarbeit »Seeds« stellt einen Schritt im Prozess zu mehr Nachhaltigkeit dar. Sie umfasst ein Toolkit, bestehend aus einer Website und einem Plugin für gängige Designtools. Dieses bündelt alle Informationen, um das Internet barriereärmer, sozialer, ethischer und eben auch ökologisch verträglicher zu gestalten. Während die Website eine Anlaufstelle für den Wissensaufbau darstellt, unterstützt das Plugin bei der Entwicklung eigener Designs, ohne dass Gestalter:innen den Designprozess verlassen müssen.
In der heutigen Welt sind Kinder in zunehmendem Maße Stress aus verschiedenen Quellen wie schulischen Anforderungen, familiärem Druck und ungewohnten Situationen ausgesetzt. Dieser Aspekt wird von vielen Erwachsenen oft vernachlässigt. Das kann dazu führen, dass sich bei Kindern Frustration und Ärger aufstauen. Insbesondere das schulische Umfeld stellt ein erhebliches Stresspotenzial dar, da von den Kindern hohe Leistungen erwartet werden. Leistungsdruck, soziale Erwartungen und Frustration tragen zu diesem Eindruck bei. Auch der Unterricht bildet da keine Ausnahme und ist aufgrund seiner zentralen Bedeutung eine potenzielle Stressquelle. Als spezialisierter Begleiter bietet HypnoStress den Kindern die Möglichkeit, mit hypnosebasierten Techniken die Stressoren des Alltags zu bewältigen und sich auf neue Herausforderungen vorzubereiten.
Ecosystems : Neuinterpretation von Elementen der Savanne zu Objekten zwischen Kunst und Design.
(2024)
Das Projekt „Ecosystems“ (deutsch Ökosysteme) beschreibt die zusammenhängende Entwicklung eines Produktsystems, inspiriert von einzelnen Elementen der afrikanischen Savanne. Das Ökosystem und alle damit verbundenen Strukturen werden als Grundlage für die Konzeption der Objekte genutzt und fortlaufend weitgehend abstrahiert. Die Produktkollektion, bestehend aus sechs verschiedenen Möbeln und Objekten, stellt zusammen das Ökosystem der afrikanischen Savanne dar. Elemente der Savanne können ganz unterschiedlicher Natur sein. Sowohl die bekannten Tiere, wie die sogenannten Big Five, kleine Savannenbewohner:innen oder unterschiedliche Pflanzen bilden zusammen die Grundlage für das Ökosystem. Jedes Objekt bezieht die Inspiration dabei aus einem anderen Element der Savanne. Die Grundlage der Objekte bildet dabei nicht allein das optische Erscheinungsbild der Tiere und Pflanzen, sondern vielmehr die damit verbundenen Emotionen und Reaktionen.
This dissertation uses in first stage a macroeconomic investigation to examine the dependence, influence and corruption of socio-economic development through effects of sustainability and resource management. The conducted research found that the state's dependence on its citizens decreases when the state's sources of revenue are largely detached and independent of the citizens' financial resources. In this case, financial resources are taxes and duties provided by the citizens. One possible consequence is the restriction of state investment in its citizens. Both the qualitative literature review and the quantitative data analysis revealed a negative correlation between socio-economic development and the resource economy's share of GDP for the period under study. The microeconomic investigation was primarily conducted through an intensive literature review. It was shown that the rebound effect as such is already very well researched. However, it also became clear that avoidance strategies for the rebound effect and links to sustainability initiatives are scarce or non-existent. The need for a redesign of the impact analysis with regard to technological innovations and their influence on resource consumption and resource management has become clear on the basis of the present study. Further, emerging and developing countries in particular, which will be confronted in the foreseeable future not only with the fundamental problems of resource abundance in the overall economic context, but also with the issues of their sustainable use, should be confronted with these problems as early as possible in order to find solutions in a timely manner.
Rocket engine test facilities and launch pads are typically equipped with a guide tube. Its purpose is to ensure the controlled and safe routing of the hot exhaust gases. In addition, the guide tube induces a suction that effects the nozzle flow, namely the flow separation during transient start-up and shut-down of the engine. A cold flow subscale nozzle in combination with a set of guide tubes was studied experimentally
to determine the main influencing parameters.
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.
The replacement of existing spillway crests or gates with labyrinth weirs is a proven techno-economical means to increase the discharge capacity when rehabilitating existing structures. However, additional information is needed regarding energy dissipation of such weirs, since due to the folded weir crest, a three-dimensional flow field is generated, yielding more complex overflow and energy dissipation processes. In this study, CFD simulations of labyrinth weirs were conducted 1) to analyze the discharge coefficients for different discharges to compare the Cd values to literature data and 2) to analyze and improve energy dissipation downstream of the structure. All tests were performed for a structure at laboratory scale with a height of approx. P = 30.5 cm, a ratio of the total crest length to the total width of 4.7, a sidewall angle of 10° and a quarter-round weir crest shape. Tested headwater ratios were 0.089 ≤ HT/P ≤ 0.817. For numerical simulations, FLOW-3D Hydro was employed, solving the RANS equations with use of finite-volume method and RNG k-ε turbulence closure. In terms of discharge capacity, results were compared to data from physical model tests performed at the Utah Water Research Laboratory (Utah State University), emphasizing higher discharge coefficients from CFD than from the physical model. For upstream heads, some discrepancy in the range of ± 1 cm between literature, CFD and physical model tests was identified with a discussion regarding differences included in the manuscript. For downstream energy dissipation, variable tailwater depths were considered to analyze the formation and sweep-out of a hydraulic jump. It was found that even for high discharges, relatively low downstream Froude numbers were obtained due to high energy dissipation involved by the three-dimensional flow between the sidewalls. The effects of some additional energy dissipation devices, e.g. baffle blocks or end sills, were also analyzed. End sills were found to be non-effective. However, baffle blocks with different locations may improve energy dissipation downstream of labyrinth weirs.