500 Naturwissenschaften und Mathematik
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Electroplating generates high volumes of rinse water that is contaminated with heavy metals. This study presents an approach for direct metal recovery and recycling from simulated rinse water, made up of an electroplating electrolyte used in industry, using reverse osmosis (RO). To simulate the real industrial application, the process was examined at various permeate fluxes, ranging from 3.75 to 30 L·m−2·h−1 and hydraulic pressures up to 80 bar. Although permeance decreased significantly with increasing water recovery, rejections of up to 93.8% for boric acid, >99.9% for chromium and 99.6% for sulfate were observed. The final RO retentate contained 8.40 g/L chromium and was directly used in Hull cell electroplating tests. It was possible to deposit cold-hued chromium layers under a wide range of relevant current densities, demonstrating the reusability of the concentrate of the rinsing water obtained by RO.
Water scarcity drives governments in arid and semi-arid regions to promote strategies for improving water use efficiency. Water-related research generally also plays an important role in the same countries and for the same reason. However, it remains unclear how to link the implementation of new government strategies and water-related research. This article’s principal objective is to present a novel approach that defines water-related research gaps from the point of view of a government strategy. The proposed methodology is based on an extensive literature review, followed by a systematic evaluation of the topics covered both in grey and peer-reviewed literature. Finally, we assess if and how the different literature sources contribute to the goals of the water strategy. The methodology was tested by investigating the impact of the water strategy of Jordan’s government (2008–2022) on the research conducted in the Azraq Basin, considering 99 grey and peer-reviewed documents. The results showed an increase in the number of water-related research documents from 37 published between 1985 and 2007 to 62 published between 2008 and 2018. This increase should not, however, be seen as a positive impact of increased research activity from the development of Jordan’s water strategy. In fact, the increase in water-related research activity matches the increasing trend in research production in Jordan generally. Moreover, the results showed that only about 80% of the documents align with the goals identified in the water strategy. In addition, the distribution of the documents among the different goals of the strategy is heterogeneous; hence, research gaps can be identified, i.e., goals of the water-strategy that are not addressed by any of the documents sourced. To foster innovative and demand-based research in the future, a matrix was developed that linked basin-specific research focus areas (RFAs) with the MWI strategy topics. In doing so, the goals that are not covered by a particular RFA are highlighted. This analysis can inspire researchers to develop and apply new topics in the Azraq Basin to address the research gaps and strengthen the connection between the RFAs and the strategy topics and goals. Moreover, the application of the proposed methodology can motivate future research to become demand-driven, innovative, and contribute to solving societal challenges.
A novel approach to manufacture components with integrated conductor paths involves embedding and sintering an isotropic conductive adhesive (ICA) during fused filament fabrication (FFF). However, the molten plastic is deposited directly onto the adhesive path which causes an inhomogeneous displacement of the uncured ICA. This paper presents a 3D printing strategy to achieve a homogeneous cross-section of the conductor path. The approach involves embedding the ICA into a printed groove and sealing it with a wide extruded plastic strand. Three parameter studies are conducted to obtain a consistent cavity for uniform formation of the ICA path. Specimens made of polylactic acid (PLA) with embedded ICA paths are printed and evaluated. The optimal parameters include a groove printed with a layer height of 0.1 mm, depth of 0.4 mm, and sealed with a PLA strand of 700 µm diameter. This resulted in a conductor path with a homogeneous cross-section, measuring 660 µm ± 22 µm in width (relative standard deviation: 3.3%) and a cross-sectional area of 0.108 mm2 ± 0.008 mm2 (relative standard deviation 7.2%). This is the first study to demonstrate the successful implementation of a printing strategy for embedding conductive traces with a homogeneous cross-sectional area in FFF 3D printing.
Polyimides rank among the most heat-resistant polymers and find application in a variety of fields, including transportation, electronics, and membrane technology. The aim of this work is to study the structural, thermal, mechanical, and gas permeation properties of polyimide based nanocomposite membranes in flat sheet configuration. For this purpose, numerous advanced techniques such as atomic force microscopy (AFM), SEM, TEM, TGA, FT-IR, tensile strength, elongation test, and gas permeability measurements were carried out. In particular, BTDA–TDI/MDI (P84) co-polyimide was used as the matrix of the studied membranes, whereas multi-wall carbon nanotubes were employed as filler material at concentrations of up to 5 wt.% All studied films were prepared by the dry-cast process resulting in non-porous films of about 30–50 μm of thickness. An optimum filler concentration of 2 wt.% was estimated. At this concentration, both thermal and mechanical properties of the prepared membranes were improved, and the highest gas permeability values were also obtained. Finally, gas permeability experiments were carried out at 25, 50, and 100 ◦C with seven different pure gases. The results revealed that the uniform carbon nanotubes dispersion lead to enhanced gas permeation properties.
In the Mesoamerican forest Selva Maya, multiple driving forces create an imbalance in the sensitive human-nature relation and demand for innovative management strategies for its re-establishment. Within the Guatemalan Maya Biosphere Reserve (MBR), core areas are under strict protective legislation and agricultural activity is permitted only within a bordering buffer zone (BZ), which covers great part of the Guatemalan department Petén. Here, the implementation of agroecological practices by multiple stakeholders aims at tackling the principle driving forces of environmental degradation and thus at reducing the pressure on Central America’s largest tropical forest area. Since 2011, the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) has assisted local stakeholders by carrying out the project “Conservation and sustainable use of the Selva Maya”. This project has offered technical support, cooperated with national institutions, and assisted multiple target groups to nudge agroecological transitions at the household and community level. As the establishment of agroecological systems face main obstacles stemming from the socio-ecological setting of the respective area, the following work presents a context specific analysis for the adaption of established strategies in the MBR BZ. Therefore, it raises the following research questions: What are the current properties of the socio-ecological system that describes the BZ? How has the GIZ’s project nudged and guided agroecological transitions? Which factors have favored or limited the turn to agroecological farming? And finally: Which recommendations derive for the navigation of agroecological transitions? The overall research approach is orientated on the framework of ecosystem stewardship1 and incorporates elements of system theory and resilience science. The framework has been adapted by combining two approaches on different management levels. The social-ecological system approach2 is used to describe the socio-ecological system of the BZ, while the evaluation of the pilot groups‘ AESs follows the Mexican MESMIS3 approach for sustainability assessments. By the integration of both approaches, it is revealed that the socio-economic context impedes or hinders the implementation of agroecological strategies for the majority of farmers. The application of the MESMIS framework has revealed that the installed monitoring mechanism is dysfunctional. Findings further indicate that there is potential for transitions of individual AESs, but they demand investments and support with the current circumstances of reducing farmers’ vulnerability. The rapidly decreasing social and environmental conditions for family farmers in the BZ are most likely not addressed by solutions that the agroecological approach tackles. Recommendations for the immediate improvement of the strategy include adjustments of the project’s proceedings as well as fundamental changes in conservation paradigm and governance to maintain the necessary functionality of the socio-ecological system.
Die vorliegende Masterarbeit behandelt die Bewertung der eingegangenen Unternehmensrisiken im Rahmen der Lebensversicherung und die hiervon abgeleiteten Auswirkungen zur Unternehmenssteuerung.
Dabei wird einerseits die Angemessenheit der sog. „Standardformel“ nach Solvency II überprüft, die in den europäischen Mitgliedsstaaten einen weitestgehend einheitlichen Ansatz bei der Bewertung der Risiken von Versicherungsunternehmen verwendet. Andererseits werden unter ökonomischen Überlegungen versicherungsmathematische Methoden vorgestellt, wie ein Lebensversicherer seine Risiken unternehmensindividueller ermitteln und damit seinen tatsächlichen Risikokapitalbedarf bestimmen kann.
Zur Quantifizierung der Ergebnisse werden die Berechnungsvorgaben der Standardformel für ausgewählte Risikomodule nachgebildet und mit den in dieser Arbeit vorgestellten unternehmensindividuellen Berechnungen verglichen und analysiert. Es zeigt sich, dass trotz der Komplexität des Solvency II-Modells eine noch differenziertere Herangehensweise notwendig ist, damit ein einzelnes Unternehmen seine Risiken adäquat und möglichst individuell bestimmen kann. Zur Gewährleistung einer nicht bestandsgefährdenden Unternehmensfortführung müssen die Versicherungsunternehmen bei Betrachtung ihrer Risiken mithilfe des EU-weiten Aufsichtssystems Solvency II in der Lage sein, die korrekten Rückschlüsse zur Unternehmenssteuerung zu ziehen. Die in dieser Arbeit vorgestellten versicherungsmathematischen Ansätze können dabei den Prozess zur unternehmenseigenen Risiko- und Solvabilitätsbeurteilung (ORSA) unterstützen.
An Analytical Investigation of Natural Convection of a Van Der Waals Gas over a Vertical Plate
(2021)
The study focused on a theoretical study of natural convection in a van der Waals gasnear a vertical plate. A novel simplified form of the van der Waals equation derived in the studyenabled analytical modeling of fluid flow and heat transfer. Analytical solutions were obtained forthe velocity and temperature profiles, as well as the Nusselt numbers. It was revealed that nonlineareffects considered by the van der Waals equation of state contribute to acceleration or decelerationof the flow. This caused respective enhancement or deterioration of heat transfer. Results for a vander Waals gas were compared with respective computations using an ideal gas model. Limits of theapplicability of the simplified van der Waals equations were pinpointed.
Die Dokumentation und Untersuchung von Massenbewegungen ist der entscheidende Schritt, um die Gefahr, die von ihnen ausgeht, zu identifizieren und im nächsten Schritt zu minimieren. Vor allem in Bergregionen kann dies im Extremfall Menschenleben retten.
Folglich untersucht diese Arbeit auf Grund bestehender Gefahr die räumliche Verteilung von Massenbewegungen in den drei iranischen Provinzen Alborz, Qazvin und Teheran.
In Anbetracht der immer weiter wachsenden Städte im erdbeben- und somit massenbewegungsgefährdeten Elbursgebirge wird mittels zweier quantitativer Analysen der isolierte Einfluss von straßen- und schienengebundener Verkehrsinfrastruktur auf Massenbewegungen (in den drei Provinzen) untersucht.
Beide Analysen vergleichen ausschließlich die lokale Häufung von Massenbewegungen mit dem vorhandenen Straßen- und Schienennetz: in der ersten Analyse durch das Vergleichen stattgefundener Massenbewegungen innerhalb von Teilgebieten des untersuchten Gebiets, in der zweiten Analyse werden die Häufungen in verschiedenen Abständen zu Straßen erfasst.
Anknüpfend an die zweite Analyse wird eine Bewertung der Häufigkeiten getätigt.
Es ergeben sich folgende wesentliche Erkenntnisse aus dieser Bachelorarbeit:
• Die Aussagekraft der Analysen kann höchstens so groß sein wie die Richtigkeit, Vollständigkeit und Detailliertheit der zur Verfügung gestellten Datenbanken
• Die verhältnismäßig große Fläche des Untersuchungsgebietes stellt eine hohe Fehlerquelle dar (z.B. durch das große Datenvolumen)
• Eine Anfälligkeitsanalyse auf Grund eines isoliert betrachteten Auslösefaktors ist mit vielen Fehlern und Annahmen behaftet (z.B. muss zunächst einmal angenommen werden, dass Massenbewegungen nicht durch andere Faktoren ausgelöst werden)
• Eine erhöhte Anfälligkeit des Untersuchungsgebietes gegenüber Massenbewegungen innerhalb von 50 m Abstand zu Straßen konnte durch die in dieser Arbeit beschriebenen „Straßenpufferanalyse“ nachgewiesen werden.
Die Analysen sind mit dem Programm ArcGIS durchgeführt. Ihre detaillierte Beschreibung ermöglicht es dem Leser, die Analysen weiterzuführen oder mit anderen Parametern zu wiederholen. Weiterführende Analysen beispielsweise in Form einer Risikokarte verhelfen den Menschen, Sachgüter und die Umwelt z.B. durch nachhaltige Bebauungspläne zu schützen.
Due to the global phenomenon of climate change the region of Mara Siana is projected to increasingly face extreme weather events that particularly comprise prolonged droughts and
heavier rainfalls. To be able to adequately adapt to these changing circumstances and maintain their livelihoods communities need to build respective capacities. As the main objective, this research aims at determining landowners’ climate change adaptative capacity (CCAC) across different villages in Mara Siana. Accordingly, a semi-quantitative approach was carried out including qualitative interviews and the subsequent quantitative calculation of CCAC based on a multidimensional indicator set and a respective coding
system. In addition to predominantly positive results of socio-cultural characteristics and the quality of natural resources, this work reveals clear weaknesses and potential for improvement in the areas of income security and financial stability, the expansion and resilience of infrastructure, and the relationship between communities and local authorities. Moreover, differences in capacity results are not only identified between the investigated villages as well as between individual households but also systemic disadvantage in capacity building affecting female landowners and community members can be indicated from the obtained interview data. Therefore, this research gives concrete recommendations for the implementation and verification of suitable adaptive measures that are particularly tailored for the improvement of low-performance indicators while following a gendertransformative approach and thus hold the potential to increase CCAC in the long-term.
Climate change includes the change of the long-term average values and the change of the tails of probability density functions, where the extreme events are located. However, obtaining average values are more straightforward than the high temporal resolution information necessary to catch the extreme events on those tails. Such information is difficult to get in areas lacking sufficient rain stations. Thanks to the development of Satellite Precipitation Estimates with a daily resolution, this problem has been overcome, so Extreme Precipitation Indices (EPI) can be calculated for the entire Colombian territory. However, Colombia is strongly affected by the ENSO (El Niño—Southern Oscillation) phenomenon. Therefore, it is pertinent to ask if the EPI’s long-term change due to climate change is more critical than the anomalies due to climate variability induced by the warm and cold phases of ENSO (El Niño and La Niña, respectively). In this work, we built EPI annual time series at each grid-point of the selected Satellite Precipitation Estimate (CHIRPSv2) over Colombia to answer the previous question. Then, the Mann-Whitney-Wilcoxon test was used to compare the samples drawn in each case (i.e., change tests due to both long-term and climatic variability). After performing the analyses, we realized that the importance of the change depends on the region analyzed and the considered EPI. However, some general conclusions became evident: during El Niño years (La Niña), EPI’s anomaly follows the general trend of reduction -drier conditions- (increase; -wetter conditions-) observed in Colombian annual precipitation amount, but only on the Pacific, the Caribbean, and the Andean region. In the Eastern plains of Colombia (Orinoquía and Amazonian region), EPI show a certain insensitivity to change due to climatic variability. On the other hand, EPI’s long-term changes in the Pacific, the Caribbean, and the Andean region are spatially scattered. Still, long-term changes in the eastern plains have a moderate spatial consistency with statistical significance.