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The Bengal Fan on different temporal and spatial scales : Integrating seismoacoustic and IODP Expedition 354 data to examine internal and external controls on depositional processes
Get PDFSubmarine fans are regarded as excellent archives for long- and short-term climate variations and the continental uplift/erosion history. The Bengal Fan has attracted particular scientific attention as is it the primary sink of Himalayan material and, thus, recorder of one of the key areas in the global climate system. A comprehensive understanding of the fana s complex depositional dynamics is an essential prerequisite to ultimately connect changes in the sedimentary sink with changes in the source. The here presented thesis examines the depositional dynamics of the Bengal Fan. A unique, integrated dataset of echosounder and multichannel seismic data, results from IODP Expedition 354 drilling, and a novel, system-specific age-depth model enables an overarching study of the architecture, stratigraphy, and depositional processes of the Bengal Fan and channel-levee systems at various scales. The outcome of this thesis provides new insights into the architectural and stratigraphic evolution of the lower Bengal Fan and marks a significant advancement towards an extensive understanding of the sedimentary archive in is full complexity
The Force that Keeps you Going : Enthusiasm in Vocational Education and Training (VET) Teachers' Work
Get PDFContext: Enthusiasm has been noted to increase productivity and quality at work. In teachers' work, this has a connection to student learning and motivation, as well as teaching quality. In the context of Finnish vocational education and training (VET), research on enthusiasm appears especially topical and relevant because of the ongoing wide reform with emphasis on productivity and efficiency. Approach: In this study, Finnish VET teachers' enthusiasm at work was studied qualitatively. Three research questions were set for this study: (1) How do VET teachers describe their enthusiasm?; (2) What factors strengthen their enthusiasm, according to their descriptions?; and (3) What factors weaken their enthusiasm, according to their descriptions? Altogether, 103 teachers who voluntarily participated in the study completed an online questionnaire on enthusiasm. The data were analyzed through qualitative content analysis. Findings: According to the results, the teachers who participated in the study were very interested in their work. They wanted to share how they experienced enthusiasm in their work. Their enthusiasm manifested as their willingness to develop their skills and expertise. It also showed in their dedication, good job performance, and positive feelings about their work. Student encounters, a positive atmosphere, and work interactions were the main sources of enthusiasm. Lack of resources, changes, cuts in the VET budget, and a lousy work atmosphere weakened enthusiasm. Conclusion: The study found that enthusiasm manifested itself in ways that correspond well with the current VET productivity and efficiency goals. Because enthusiasm was strengthened especially when teachers were working with students, it seems important to ensure a supportive work environment for students also after the VET reform. Positive interactions, collegial support, and working together can help teachers to succeed and to maintain enthusiasm in their everyday work. According to the results of this study, supervisors may play a central role in facilitating teacher enthusiasm
Faktoren beruflicher Kompetenzenwicklung südafrikanischer Auszubildender in ausgewählten technischen Berufen
Get PDFMeasuring professional competence on the basis of a large-scale assessment is still a comparatively young discipline, especially in an international context. Only since 2005 with the so-called Feasibility Study for a VET-PISA as an initiative of the German BMBF and - almost simultaneously - in 2006, with the development of a competence model within the frame of the first KOMET project funded by the Hessian Ministry of Culture, and a subsequent Chinese comparison project in 2009, one can speak of relevant preliminary work and first experiences in this area. So far, it is only the experience of the COMET network, which can be referred to for the area of actually conducted international surveys. This dissertation is based on data collected within the South African COMET project, which was carried out between 2013 and 2016 as an integral part of the research project VET Research and Development in South Africa on behalf of and in close cooperation with South African Sector Education and Training Authority merSETA. In an international context, the South African COMET project is the third largest project after those in Germany and China: more than 1400 persons took part in the competence tests, including some TVET college teachers and trainers involved in the project. The research method used within the course of this project is described in chapter 1 that sets out the categorical framework of this study and further in chapter 4, which explains the COMET methodology in more depth before presenting the actual analysis. The extensive data collected as part of this project relates to competence tests and surveys on the vocational identity and commitment of South African apprentices in the occupations of electrician, mechatronics, motor mechanic and welder. At the same time, data on test motivation and the general context of vocational learning were collected at a total of 23 test sites that participated in the tests. This made it possible to examine and to compare competence development under the various conditions of learning, with regard to the various types of training providers and, in principle, to review preliminary findings from a pilot project in 2011-2012 (which only offered some limited insights into competence development in one occupation). At the same time the data allows for an in-depth analysis of the connection between test motivation and competence development, an investigation for which, to date, corresponding knowledge has only been available in the German-speaking context. Vocational (and organisational) identity, occupational (and organisational) commitment which are regarded as a dimension of the professional competence development have as well been measured and analysed in view of the different occupations and training providers. Where possible, correlations have been calculated that helped to recognize the factors that determine training quality. The South African COMET project also provided an opportunity to review and to contribute so some general findings of the preceding international COMET studies, among others on the stagnation of vocational competence development in the course of training and to show how such stagnation can be overcome, also in the South African case. Finally, due to the voluntary participation of company trainers and subject teachers from participating TVET colleges it was possible to draw preliminary, albeit limited conclusions about the interesting question to which extent teachers and trainers transfer their own problem-solving horizon onto their students
Methode zur adaptiven thermischen Prozessführung beim Laser-Strahlschmelzverfahren
No full textIn the laser beam melting process, one key aspect to achieve parts of high quality and dimensional accuracy is to ensure thermal stability throughout the build-up process. Compared to the consolidated material, the powder has thermally insulating properties. Thus, the desired quality can only be reached if the heat input takes into account the amount of powder in the vicinity of each point to be melted. This requirement is not properly considered by most of the available systems. They usually keep the laser power and scan rate constant or perform only basic adaptations. In overhanging regions, heat accumulates from track to track causing sintering effects, enlarged weld pools, and other overheating effects, making them particularly prone to defects. This leads to low dimensional accuracy, porosity, and also process abortion. Motivated by these problems, this work presents a method for an automatized and localized thermal management of the process with the aim to improve the dimensional accuracy of powder-sided surfaces. For this purpose, the local thermodynamics have been analyzed, and an adaptation theory developed regarding where, when, and how to deal with overheating through adjustment of the process parameters. These measures have been successfully demonstrated in finite element simulations. On the basis of these theoretical findings, a convergent and efficient algorithm has been developed that analyzes the local geometry and topology of the part. It identifies critical structures to create a enhanced pre-processing method with adapted exposure information. After having established an interface to the machines, the methods have been evaluated and validated experimentally. The experiments conducted with stainless steel 1.4404 as the powder material have shown significant improvement of the dimensional accuracy: the deviations from the desired shape have been reduced by up to 61% down to Standard melt pool depth without affecting the part density. The experimental studies in this work were focused on the adaptation of the energy input, but the pre-processing can be extended by further adaptation methods such as, for example, introduction of delay times between the scan tracks or adjustment of the scanning order. These are necessary to build up larger overhanging areas. However, a challenge that then arises is the susceptibility due to lower stiffness of the initial layers over the powder to thermally induced deformations. This needs to be overcome in parallel in order to extend the process limits
Zooplankton performance in a changing ocean : adaptive capacities to a shifting food regime in the North Sea
Get PDFZooplanktonic organisms are often vulnerable to fluctuations in food supply. Their population dynamics is directly influenced by changes in phytoplankton availability and nutritional quality, which in turn is affected by changes in parameters such as nutrient loading. The aim of this study was to investigate how nitrogen (N) limitation in prey (i.e., food quality) affects the performance of zooplankton. Females of the copepod Temora longicornis and larvae of the polychaete Lanice conchilega were sampled in May and June 2016 off the German island of Helgoland, in the southern North Sea, for five-day laboratory feeding experiments. They were fed with diets of different quality - diatoms and dinoflagellates cultured in nutrient-replete (Diat and Dino , respectively) and in N-depleted (Diata and Dinoa , respectively) conditions. Sodium bicarbonate enriched with the 13C isotope (NaH13CO3) was added to prey cultures in order to label dietary fatty acids (FA) and to follow carbon (C) transfer into copepods and polychaetes. Zooplankton performance was assessed by analysis of the elemental and biochemical compositions and of the assimilation and turnover of C in copepods and polychaetes, and by measuring copepod physiological rates. Copepods feeding on Dino had the highest investment in somatic and reproductive growth. Copepods feeding on Diata had the highest N excretion rates. Egestion was a major pathway for eliminating excess C, and low food quality affected respiration rates and the intensity and speed with which dissolved organic carbon leaked from faecal pellets. Copepod physiological rates indicated that dinoflagellates are a food source of superior or similar quality to diatoms under nutrient-replete or N-depleted conditions, respectively. In addition, copepods feeding on Diata showed the highest lipid C assimilation and turnover rates. These results suggest a shift in copepod resource allocation (reproductive output or lipid accumulation) depending on food quality. Experiments with the polychaete revealed that larvae are able to regulate their lipid C content (homeostasis) regardless of the availability of dietary FA via selective accumulation and biosynthesis of FA. Lipid C assimilation results from both species, together with literature data, were used to formulate a hypothesis on different patterns of lipid homeostasis in zooplankton. These results present a robust contribution towards a better understanding of how zooplanktonic organisms might be affected by changes in the quality of their prey in the near future
The 'Dangers of Decentralization' and Their Relevance to Local Public Services
Get PDFThis dissertation empirically evaluates the relevance of the three prominent dangers of fiscal decentralization, namely inefficiencies, regional inequalities and deficient accountability for the provision of local public goods related to health, education and public security. The major argument holds that the promise of fiscal decentralization theory does not always materialize. In fact, decentralization reforms should assess the risks related to increased inefficiencies, regional inequalities and deficient accountability in the context of public service provision. Also, the dissertation adds further insights to a debate which is characterized by a strong focus on the relationship between decentralization and economic growth, by a misconception of the notion of a efficiency and by a lacking understanding of the micro-level mechanisms that underlie macro-level effects
Theoretical Aspects of Relativistic Geodesy
Get PDFIn this thesis, I show how fundamental geodetic notions can be defined within a general relativistic framework. Among the concepts that are analyzed there are the relativistic gravity potential, the geoid, the normal gravity field and its potential, as well as the genuinely relativistic definition of chronometric height. Moreover, a simple procedure for the operational preservation of a chosen level surface of the relativistic gravity potential is investigated. For all these concepts, the respective Newtonian notions are recovered in the weak-field limit. In the first-order (parametrized) post-Newtonian expansion the results previously published in the literature are obtained and it is shown how they are embedded into the present framework. Magnitudes of leading-order relativistic corrections to the geoid as well as redshift and acceleration measurements are calculated in a simple gravity field model. After the most important geodetic notions are introduced, the theory of General Relativity and the mathematical formalism are briefly discussed. Emphasis lies on some exact solutions to Einstein's vacuum field equation. These spacetimes are used in the following to either estimate relativistic effects or generalize geodetic concepts. Proceeding to a relativistic theory of gravity changes the underlying stage on which all physics takes place. The involved mathematical structure, related to the description of a curved spacetime, causes conventional geodetic notions to become ill-defined in the framework of General Relativity. Here, it is shown how relativistic generalizations of these notions can be constructed, working without any kind of weak-field approximation. The approach is mainly based on a so-called redshift potential of which the level sets foliate a stationary spacetime into isochronometric surfaces. It gives rise to the definition of a relativistic gravity potential which is used intensively. In particular, using a parametrized post-Newtonian spacetime for the Earth, the magnitude of relativistic corrections to the geoid is investigated in a simple Earth model. In the last part, the relation between proper time on the geoid and the defining constant L g in the IAU resolutions is discussed and a consistent relativistic definition for chronometric heights is proposed. Finally, relativistic orbital effects are compared to non-gravitational perturbations of satellite orbits and relativistic gravity gradiometry is investigated to link geodesic deviation to the curvature of spacetime, which is determinable by geodetic measurements
Laser Drilling of Tool Steel under Plasma Atmosphere
Get PDFLaser drilling of microholes into tool steel (1.2379) with a diameter of about 100 microm and 3 mm depth still constitutes a challenge. Expulsion of the molten metal and its accumulation around the drill hole necessitates a post processing of the surface. Melting processes within the drill hole causes a hole geometry diverging cylindrical shape and the energy input results in microstructure defects and fissures. Concerning this matter, the influence of gas pressure within the scale of vacuum pressure and the use of various process gases (active gas: O2, air; passive gas: Ar, He, N2) to the drilling process was analyzed within this thesis. Furthermore, the impact of an additional cold low-pressure plasma, which was generated above the opening of the drill hole, on the drilling process was examined. The aim was to achieve a reduced accumulation of molten metal on the surface, an improved cylindricity of the drill hole as well as a lowered thermal stress on the component through these procedures. For this purpose, microholes were drilled in a vacuum chamber into tool steel by percussion drilling method at different pressure levels and process gases. The expulsion of molten metal as well as the annealing colors on the sample surface was measured with an optical microscope and laser scanning microscope. By cross-section preparation the drill hole was visualized and measured
The impact of biogeochemical processes on the composition of dissolved organic matter in marine subsurface sediments
Get PDFOrganic matter in marine sediments is one of the largest pools of reduced carbon on Earth. It had been known as recalcitrant carbon pool with scarce living biomasses. The findings of microbes at several kilometers below seafloor suggest there is a substantial amount of living biomasses in the subsurface sediments under extreme conditions, for example, decreasing labile biomolecules as carbon sources, electron acceptors, and thermal conditions at deeper layers. Those microbes might drive a slow but extensive carbon flow and play an important role in the carbon cycle in deep Earth. It is not known how the microbes could survive on the recalcitrant organic matter (ROM) leftover . The gap of knowledge is especially in the initial step of degradation process: how the ROM is degraded to assimilable substrates. Dissolved organic matter (DOM) encompasses the analytical window for the initial degradation of ROM. However, the DOM pool is complex and comprises tens of thousands of formulae. Therefore, this study focused on firstly the method of DOM characterization, secondly the DOM cycling and degradation process in subseafloor sediment. In further, this study aims to answer the questions: how the degradation patterns of organic matter change with environmental condition in the subsurface sediments, which are highly stratified by redox conditions and thermal gradients. In summary, this dissertation addressed the interactions between microbes and DOM in stratified anaerobic sediments by combinations of EEMs and FT-ICR MS. It is indicated that the metabolism of microbes is sensitive and adaptive to environmental conditions, which ultimately influence the carbon and nitrogen flow in subsurface sediments due to the change of microbial metabolisms and abiotic processes