- Einführung in die Thematik des Hebelflechtens - Ermittlung der mechanisch-/tribologischen Kennwerte von Fadenmaterialien - FE-Modellbildung der Fadenmaterialien im Flechtprozess - FE-Simulation eines Zugversuches mit implementierten Werkstoffdaten und Definition eines einfachen Schädigungskriteriums - Prozesssimulation des Flechtvorganges

In striving to produce high quality cast components from recycled aluminium alloys,imperfections have to be considered, because recycled aluminium usually containsmore of it. However, there are great energy savings to be made by using recycledaluminium; as little as 5% of the energy needed for primary aluminium productionmay be required. High quality castings are dependent on, besides alloy chemistry, bothmelt quality and the casting process; the focus of this work is related to the meltquality.This thesis aims to increase knowledge about imperfections, foremost about Fe-richparticles, oxides/bifilms, and porosity. Experiments were performed at industrialfoundry facilities and in a laboratory environment. Melt quality was evaluated byproducing samples with the reduced pressure test (RPT), from which both densityindex (DI) and bifilm index (BI) could be measured, results that were related to tensiletest properties. Data from tensile test samples were analysed, and fracture surfacesand cross sections were studied in both light microscope and in scanning electronmicroscope (SEM). For the purpose of investigating nucleation of primary Fe-richparticles (sludge) differential scanning calorimetry (DSC) was used.In the analysis of results, a correlation between the morphology of particles and tensileproperties were found. And elongated Fe-rich β-particles were seen to fracturethrough cleavage towards the centre. However, DI and BI have not been possible torelate to tensile properties.The nucleation temperature of primary Fe-rich particles were found to increase withincreased Fe, Mn, and Cr contents, i.e. the sludge factor (SF), regardless of cooling rate.For a set SF, an increase of cooling rate will decrease the nucleation temperature.

Midlatitudinal hydrated sulfates on Mars may influence brine pH, atmospheric humidity, and collectively water activity. These factors affect the habitability of the planetary subsurface and the preservation of relict biomolecules. Regolith at grain sizes smaller than gravel, constituting the bulk of the Martian subsurface at regional scales, may be a primary repository of chemical alteration, mechanical alteration, and biosignatures. The Mars Odyssey Gamma Ray Spectrometer with hundreds of kilometers of lateral resolution and compositional sensitivity to decimeter depth provides unique insight into this component of the regolith, which we call soil. Advancing the globally compelling association between H2O and S established by our previous work, we characterize latitudinal variations in the association between H and S, as well as in the hydration state of soil. Represented by H2O:S molar ratios, the hydration state of candidate sulfates increases with latitude in the northern hemisphere. In contrast, hydration states generally decrease with latitude in the south. Furthermore, we observe that H2O concentration may affect the degree of sulfate hydration more than S concentration. Limited H2O availability in soil-atmosphere exchange and in subsurface recharge could explain such control exerted by H2O on salt hydration. Differences in soil thickness, ground ice table depths, atmospheric circulation, and insolation may contribute to hemispheric differences in the progression of hydration with latitude. Our observations support chemical association of H2O with S in the southern hemisphere as suggested by Karunatillake et al. (2014), including the possibility of Fe sulfates as a key mineral group.

Ubicado en el asentamiento Humano denominado El mirador II, en Pamplona Alta, distrito de San Juan de Miraflores, se construyo el colegio # 65 de la asociación Fe y Alegría del Perú. El presente trabajo tiene como finalidad dar a conocer, la topografía de lugar, los procedimientos constructivos, controles de productividad, acceso, logística, clima y el trabajo social que se realizó para la construcción del colegio. El colegio comprende la construcción de seis pabellones de tres niveles cada uno, distribuidos en dos plataformas a diferentes niveles, el cual se conectarán por dos puentes metálicos. Contará con aulas de estudio, salas de computó, biblioteca, talleres de corte y confección, Secretariado, electricidad, costura y carpintería. Se impartirá, educación desde la etapa de educación inicial hasta secundaria, con capacitaciones técnicas. Albergará a 1500 niños de la zona, desde la etapa de educación inicial hasta secundaria.

Memoria (licenciado en ciencias jurídicas y sociales) / Esta investigación consta de una memoria, la cual pretende examinar los fundamentos, expresión normativa y aspectos críticos del principio de la buena fe en los procedimientos laborales chilenos. En el primer capítulo nos aproximaremos al origen histórico del concepto de la Buena Fe, para esto será necesario hacer una mirada más amplia a la disputa argumentativa entre las corrientes publicistas y garantistas del proceso, viendo como la hegemonía una sobre otra es el fenómeno que propicia la inclusión en los distintos ordenamientos del concepto de la buena fe; en el segundo capítulo, veremos el sentido moralizante e ideológico del proceso que conlleva la existencia del concepto en comento, el carácter de concepto jurídicamente indeterminado, su lugar dentro de las distintas teorías del proceso, los deberes en los cuales se expresa y, especialmente el mecanismo de análisis propuesto por Damaska. En el tercer capítulo, identificaremos las manifestaciones normativas de este principio en el procedimiento laboral chileno actual, desde las más generales a normas particulares que lo consagren, desentrañando, a partir de los elementos avanzados en este trabajo, las ideas detrás de las normas y sus consecuencias prácticas. Se finalizará el presente trabajo con las naturales y lógicas conclusiones que correspondan.

Background Running is a popular form of exercise that more than 55 million Americans actively participate. Endurance running like marathon and half- marathon is getting increasingly popular among active runners. Although the effect of running is considered beneficial to bone health, the direct relationship between strains and strain gradients occurred during long distance running and bone changes is still not clear. Especially, given a high rate of injury associated with the first-time marathon, understanding the direct effect of strain stimuli on bone health is an important issue. Based on the previous studies, we hypothesized that the higher values of strain will induce bone adaptation more effectively and will lead to higher bone osteogenic changes. Since osteocytes sense shear stress caused by the interstitial fluid flow, which is created by the deformations, and regulate activities of osteoblasts and osteoclast that govern bone adaptation, we also hypothesized that the local strain gradient will create pressure differences within the interstitial fluid network and will increase fluid flow. Furthermore, due to that increased fluid flow, the regions with the higher strain gradient will experience a higher amount of bone adaptation. Thus, in this study, our purpose was to define the effect of the strains and strain gradients on bone changes within distal tibia, which is the most prone anatomical site to low risk stress fracture, during training for first-time marathon. Methods High-resolution and low-resolution computed tomographic (CT) images of the distal tibia were obtained before and after a self-selected training from runners who were actively training to participate in their first-time marathon in the next calendar year. The low resolution scan covered a 69.864 mm length of the distal end of the tibia while the high resolution CT scan covered a 9.02 mm region of the distal tibia. Using low resolution CT image based subject specific finite element (FE) models, the strains and strain gradients of the distal tibia at the instance of the peak ground reaction force (GRF) were calculated. The baseline and follow-up high resolution CT scans were used in high resolution peripheral quantitative CT (HRpQCT) analysis and the estimation of bone changes over the training period. Finally, the effect of strains and strain gradients on the distal tibia bone changes was estimated based on the FE model driven strain values and HRpQCT analysis driven bone changes. We used a linear mixed model to define the relationship between strain values and bone changes in the distal tibia. Results The strain values that occurred during marathon training had significant effects on bone changes in the distal tibia. Particularly, the strain gradients showed a higher effect than the strains. In the cortical compartment, the strain gradients, which were calculated as a strain difference of a node from the surrounding nodes (Strain Gradient-1), affected the bone mineral density (BMD) negatively, and per 1000 µε increase resulted in 2.123% decrease in the cortical BMD. The strain gradients, which were calculated as a strain difference of a node from the surrounding nodes normalized to distance to surrounding nodes (Strain Gradient-2), presented a positive effect on the cortical bone volume with a slope of 4.335% / 1000 µε. In the trabecular compartment, the strain gradient-1 showed negative effects on the percent change in BMD and bone mineral density (BMC), whereas the strain gradient-2 showed positive effects on the percent change in BMD and BMC. Conclusion The linear mixed model analysis revealed a statistically significant (p < 0.05) relationship between strain gradients that occurred during running and distal tibia bone changes. The strains, biometrics, and initial parameters of bone did not show any significant effect on the bone changes. The connection between local strain environment and bone changes in the distal tibia investigated in this study is an important step to understand the mechanism of mechanically induced bone adaptation.

Scour is a phenomenon of soil erosion around foundations under currents and waves. It is a major cause for the disruption to water-borne structures such as bridges and marine structures. Pile foundations supporting these structures are required to be designed against the scour damage. However, at present, there is no accepted method for the design of piles in scoured conditions probably due to an inadequate understanding of scour effects on foundations. Although numerous efforts have been made to evaluate the scour effects on single piles using numerical simulations and centrifuges tests, the scour susceptibility of piles in different soil properties is still not well understood. Furthermore, there is no study concerning scour effects on the lateral responses of pile groups. Therefore, a series of three-dimensional finite element (FE) parametric analyses were conducted to investigate scour effects on lateral behavior of both single piles and free-head pile groups by varying scour-hole dimensions, soil properties, pile properties, and pile group configurations. Moreover, to facilitate the routine design, a modified p-y method that was modified based on the widely used p-y method was proposed for both scoured single piles and pile groups, and was validated against the results from the FE analyses. The results show that scour induced lateral capacity loss to both single piles and pile groups, which was approximately 10% more in dense sands than that in loose sands. Simplification of local scour as a general scour that has been commonly used in general design practice resulted in a maximum of 17% underestimate of lateral capacity of pile foundations. Pile groups were more susceptible to scour than single piles under equivalent scour conditions. A pile group with smaller pile spacing or larger pile numbers tended to experience less lateral capacity loss due to scour. / Graduate / 2020-08-19

Le coefficient de couplage électromécanique (CCEM) est un paramètre essentiel pour la description des matériaux piézoélectriques, il traduit la conversion d’énergie électrique en énergie mécanique et vice versa. Ce coefficient de couplage est étudié et déterminé dans le cadre de cette thèse pour des céramiques piézoélectriques. Ces dernières sont utilisées pour trois structures différentes ; la première structure étudiée est constituée d’une poutre longue et mince avec des petits patchs collés symétriquement sur les deux faces de la poutre en Aluminium, la seconde structure se compose d’une poutre courte et épaisse avec deux grands patchs. La dernière structure étudiée est une plaque composite multicouche du type aéronautique avec un seul grand patch. Ces trois structures ont été étudiées afin de déterminer le coefficient de couplage électromécanique effectif qui est considéré comme un indicateur de performance de l’amortissement passif shunté. Ce coefficient de couplage a été évalué de différentes manières en utilisant différents paramètres dont les conditions limites électriques, les propriétés élastiques des patchs, les propriétés modales de la poutre seule ainsi que les facteurs de couplages piézoélectriques. Une première étude expérimentale a été menée sur la poutre longue pour deux types de configurations en court circuit et circuit ouvert pour identifier ses propriétés modales. La poutre longue a été simulée pour deux types de polarisations, identiques et opposées, et simulée dans les deux codes Ansys® et Abaqus®. L’influence de la condition d’équipotentielle sur le coefficient de couplage a été étudiée. Une seconde campagne expérimentale et numérique sur une autre structure a été nécessaire pour valider les résultats obtenus. Pour pouvoir atteindre cet objectif, il était nécessaire de travailler sur une structure plus courte et plus rigide. Ainsi, la poutre courte a été simulée dans Ansys® et les résultats obtenus ont confirmé la nécessité de prendre en compte l’équipotentialité sur les faces des patchs. Cette condition a pour effet de réduire le couplage électromécanique et parfois de découpler certains modes. L’écart résultant de la corrélation expérimentale / numérique des deux poutres instrumentées a incité à recaler les modèles numériques. Ce recalage peut se présenter sous trois formes : mécanique en remplaçant l’encastrement par des ressorts linéaires, électrique en remplaçant les capacités fournies par le fabricant par les valeurs mesurées expérimentalement et électromécanique en utilisant les deux recalages précédents simultanément. Les deux poutres ont ensuite été simulées en déformations planes et contraintes planes et recalées afin d’approcher les résultats expérimentaux. L’étude de ces deux structures a permis de confronter les différentes méthodes d’évaluation du CCEM effectif, d’évaluer l’influence de l’équipotentialité sur les faces des électrodes et de comparer les simulations bidimensionnelles aux tridimensionnelles. Une plaque composite multicouche du type aéronautique a été ensuite étudiée pour généraliser la méthode d’évaluation du CCEM effectif pour les structures minces composites. La plaque seule a d’abord été simulée dans Ansys® pour valider le modèle numérique. Des tests sur la structure adaptative ont ensuite été menés pour l’évaluation du CCEM expérimental. La position choisie du patch a été déterminée par une analyse de l’énergie de déformation de la plaque seule pour les modes d’intérêt. Cette méthode de placement du patch s’est avérée efficace dans le sens où elle a conduit à des CCEM effectifs élevés pour certains modes de la bande de fréquence retenue. / The electromechanical coupling coefficient (EMCC) is an important parameter for the description of piezoelectric materials; it measures the conversion of electrical energy into mechanical one and vice versa. The coupling coefficient is studied and determined in this dissertation for piezoelectric ceramics. The latter are used for different structures: the first studied one is a long and thin Aluminium beam with small patches bonded symmetrically on its faces, the second one is a short and thick Aluminium beam with symmetrically bonded two large patches, and the third structure is considered more complex because it is an aeronautic-type multilayer composite plate with a single large patch. These three structures were studied to determine the electromechanical coupling coefficient which is considered as a performance indicator for passive shunted damping. The coupling coefficient was evaluated in different ways using different parameters, including the electrical boundary conditions, the elastic properties of the patches, the modal properties of the base beam and the piezoelectric coupling factor. A first experimental study was conducted on the long beam for two configurations, short circuit and open circuit, to identify its modal properties. The long beam was simulated for two configurations of polarization, same and opposite, in Ansys® and Abaqus® commercial codes. The equipotential condition influence on the coupling coefficient has been studied. A second experimental and numerical campaign for a different structure was necessary to validate the obtained results. For this purpose, it was necessary to work on a shorter and more stiff structure. Thus, the short beam was simulated in Ansys® which results have confirmed the necessity to consider the equipotentiality of the patches faces. This condition was found to reduce the electromechanical coupling and to uncouple some modes. The difference between experimental and numerical results of both adaptive structures was reduced by updating the numerical models. This updating is made in three ways: mechanically, by replacing the theoretical clamp conditions by linear springs, electrically, by replacing the capacities provided by the supplier by the experimental measured values, and electromechanically by considering previous updatings simultaneously. Both beams were simulated in 2D plane-strain and plane-stress and updated in order to approximate the experimental results. The study of these two structures allowed to assess different methods for the evaluation of the EMCC, to evaluate the influence of the equipotentiality constraints on the electroded faces, and to compare two-dimensional simulations to three-dimensional ones. Finally, an aeronautic-type multilayer plate composite has been studied in order to generalize the evaluation method of the EMCC for thin composite structures. The base plate was first simulated in Ansys® in order to validate the numerical model, then tests of the adaptive plate were conducted in order to evaluate the experimental EMCC. The selected position of the patch results from a strain energy analysis of the base plate for the mode of interest. The patch placement method was efficient in the sense that it provided high EMCC for some modes in the retained frequency range.

Strikt anaerobe Bakterien wie Clostridium difficile und C. scatologenes verwenden GRE, um die chemisch ungünstige Decarboxylierung von 4-Hydroxyphenylacetat zu p-Cresol zu katalysieren. Das Enzymsystem besteht aus einer Decarboxylase und dem zugehörigen Aktivierungsenzym. Die 4-Hydroxyphenylacetat-Decarboxylase (4Hpad) besitzt zusätzlich zum Protein-basierten Glycinradikal eine weitere Untereinheit mit bis zu zwei [4Fe-4S] Clustern und repräsentiert hierdurch eine neue Klasse von Fe/S-Cluster-haltigen GREs, die aromatische Verbindungen umsetzen. Das Aktivierungsenzym (4Hpad-AE) weicht vom Standardtypus ab, indem es zusätzlich zum S-Adenosylmethionin(SAM)-bindenden [4Fe-4S]-Cluster (RS-Cluster) mindestens einen weiteren [4Fe-4S]-Cluster bindet. In dieser Studie wurden heterologe Expressions- und Reinigungsprotokolle für 4Hpad und 4Hpad-AE entwickelt. Kristallstrukturen von 4Hpad cokristallisiert mit den Substraten (4-Hydroxyphenylacetat, 3,4-Dihydroxyphenylacetat) und dem Inhibitor (4-Hydroxyphenylacetamid) zeigten geringe strukturelle Änderungen im aktiven Zentrum des Proteins. Die Radikalbildung am 4Hpad-AE wurde durch die Überprüfung einer klassischen reduktiven Spaltung von SAM zu den Reaktionsprodukten 5’-Deoxyadenosin und Methionin bestätigt. EPR- und Mössbauer-Spektroskopische Analysen zeigten, dass 4Hpad-AE mindestens einen zusätzlichen [4Fe-4S] Cluster neben dem einzelnen RS-Cluster enthält. Die katalytische Notwendigkeit eines zusätzlichen Clusters wurde durch eine Mutationsanalyse untersucht, wobei eine verkürzte Version des Enzyms ohne die zusätzliche Cystein-reiche Insertion konstruiert wurde. Das verkürzte Mutante ohne die Bindungsmotive für die zusätzlichen Cluster gekennzeichnet, die Konfiguration, Stöchiometrie und die Funktion der zusätzlichen Cluster diagnostizieren. / 4-hydroxyphenylacetate decarboxylase (4Hpad) is a two [4Fe-4S] cluster containing glycyl radical enzyme proposed to use a glycyl/thiyl radical dyad to catalyze the last step of tyrosine fermentation in Clostridium difficile and C. scatologenes by a Kolbe-type decarboxylation. The decarboxylation product p-cresol is a virulence factor of the human pathogen C. difficile. The small subunit of 4Hpad may have a regulatory function with the Fe/S clusters involved in complex formation and radical dissipation in the absence of substrate. The respective activating enzyme (4Hpad-AE) has one or two [4Fe-4S] cluster(s) in addition to the SAM-binding [4Fe-4S] cluster (RS cluster). The role of these auxiliary clusters is still under debate with proposed functions including structural integrity and conduit for electron transfer to the RS cluster. This study shows the optimized expression and purification protocols for the decarboxylase and the co-crystallization experiments and binding studies with 4-hydroxy-phenylacetate and 3,4-dihydroxyphenylacetate and with the inhibitor 4-hydroxy-phenylacetamide. The purification and characterization of active site mutants of decarboxylase are also done. Concerning 4-HPAD-AE, we report on the purification of code-optimized variants, and on spectroscopic and kinetic studies to characterize the respective i) SAM binding enthalpies, ii) rates for reductive cleavage of SAM and iii) putative functions of the additional Fe/S clusters. The truncated mutant lacking the binding motifs for the auxiliary clusters is characterized to diagnose the configuration, stoichiometry and function of the auxiliary clusters.

Gegenstand der Untersuchungen war die Reduktion von Stickoxiden (NOx und N2O) an verschiedenartig präparierten Eisenkatalysatoren (Fe-MF, Fe-beta, Fe-SBA-15). Die Katalysatoren wurden nach Synthese, Kalzinierung und Katalyse mittels EPR und UV/VIS-DRS charakterisiert, und darüber hinaus auch in-situ während des Kalzinierens. Isolierte Eisenspezies aggregieren im Verlauf der Kalzinierung bei 873 K. Sowohl höhere Heizraten beim Kalziniervorgang, als auch ein höheres Si/Al-Verhältnis des Trägermaterials verstärken die Neigung zur Aggregatbildung leicht. Die Verwendung des Katalysators für die SCR von NO führt zu weiterem Wachstum und zur Restrukturierung der FexOy-Cluster. Die Eisenkatalysatoren wurden weiterhin mittels in-situ Methoden (EPR, UV/VIS-DRS, FTIR) untersucht während der SCR von NO durch NH3 und Isobutan, der SCR von N2O mit CO, und im Strom der entsprechenden reinen Eduktgase. Die Ergebnisse korrelieren mit dem katalytischen Verhalten der Materialien. Verschiedene Fe3+-Spezies, welche sich durch ein unterschiedliches Redoxverhalten auszeichnen, wurden identifiziert. UV/VIS-Messungen erlauben die Schlußfolgerung, daß isolierte, oktaedrisch koordinierte Fe3+?Spezies leichter zu reduzieren sind als tetradrisch koordinierte. Im Gegensatz zu isoliertem Fe3+ lassen sich FexOx-Cluster leichter oxidieren als reduzieren, und verbleiben daher unter Reaktionsbedingungen trivalent. Durch ihr hohes Oxidationspotential kommt es, vor allem für die Reaktion mit Isobutan, zur unerwünschten Totaloxidation des Reduktanden. Der Anteil isolierter Fe3+ Spezies korreliert mit der Aktivität der Katalysatoren für die SCR von NO und N2O. Weiterhin hängt zumindest für die Reaktion zwischen N2O und CO der Reaktionsmechanismus von der Art der vorliegenden Eisenspezies ab: an isolierten Plätzen erfolgt die Reduktion des N2O an dem an Fe3+ gebundenen CO. An FexOy-Clustern hingegen läuft die Reaktion als Redoxprozeß (Fe3+ / Fe2+) unter Bildung eines radikalischen Intermediates O-. Der Einfluß der Porengeometrie des Trägermaterials auf die katalytische Aktivität wurde an Katalysatoren mit ähnlichem Eisengehalt und ähnlicher Art und Verteilung der Eisenspezies studiert (Fe-MFI, Fe-SBA-15). Die drastisch höhere Aktivität von Fe-MFI belegt, daß die Lokalisierung der aktiven Komponente in einer Pore mit passender Geometrie (Größe und Struktur) essentiell für die katalytischen Eigenschaften ist. Als weitere, die Aktivität stark beeinflussen Größe, wurde für die Reaktion von NO mit Ammoniak und auch mit Isobutan die Azidität identifiziert, die jedoch für die katalytische Zersetzung oder Reduktion mit N2O keine Rolle spielt. / The reduction of nitrogen oxides (NOx and N2O) was investigated over Fe-catalysts (Fe-MFI, Fe-beta and Fe-SBA-15) which were prepared by different methods have been analyzed by EPR and UV/VIS-DRS ex situ after synthesis, calcination and use in catalysis as well as in situ during calcination. It was found that aggregated species are formed at the expense of isolated Fe species upon calcination at 873 K, and that aggregate formation is slightly favored by calcination with higher heating rates as well as by high Si/Al ratio of the support. Use in SCR of NO leads to further growth and restructuring of FexOy clusters. These Fe-catalysts were studied by in situ EPR, in situ UV/VIS-DRS and in situ FT-IR spectroscopy during SCR of NO with NH3 or isobutane and during SCR of N2O with CO as well as during interaction with single feed components. The results were related to the catalytic behaviour. Different types of isolated Fe3+ sites with different reducibility were identified. Based on FT-IR results which revealed that NO reacts preferably with trivalent Fe, it is concluded that Fe3+ ions reduced under reaction conditions to Fe2+ do probably not contribute to catalytic activity. In general, the degree of steady-state Fe site reduction during NH3-SCR is markedly lower than during isobutane-SCR. This might be the reason for the lower activity of Fe-catalysts in the latter reaction. UV/VIS-DRS results suggest that isolated Fe3+ in octahedral coordination is easier reduced than tetrahedral Fe3+. In contrast to isolated Fe3+ species, FexOy clusters are much faster reoxidized than reduced and, thus, remain essentially trivalent under reaction conditions. Due to their higher oxidation potential, they cause undesired total oxidation of the reductant being much more severe in the case of isobutane. A correlation was found between the fraction of isolated Fe+3 sites in the catalysts and their activity for SCR of NO and N2O. The reaction mechanism of SCR of N2O with CO is Fe site dependent. Over isolated Fe sites, the reduction of N2O occurs via coordinated CO species on Fe3+ sites. The reaction over FexOy sites proceeds via a redox Fe3+/Fe2+ process with intermediate formation of O- radicals. The effect of pore geometry of the support on the catalytic activity was studied by comparing catalytic performance of Fe-MFI and Fe-SBA-15 which contain similar iron content and show similar nature and distribution of Fe species as evidenced by UV/VIS-DRS and EPR. Fe-MFI revealed to be much more active than Fe-SBA-15 in all reactions studied. This clearly illustrates that the confinement of the iron species in pores of suitable geometry (structure and size) is essential to originate their remarkable catalytic properties. Acidity is essential for SCR of NO with NH3 or isobutane but it is not mandatory for direct decomposition or SCR of N2O.