656 research outputs found
Hollow cathode sputtering system - installation, operation and theoretical background
The objective of this work was to assemble, install and operate a hollow cathode sputtering system (HCSS). Therefore a complex vacuum system was built to create the right sputtering environment. The purpose of the HCSS is to develop advanced thin conducting oxides (TCOs) as well as high resistivity transparent (HRT) layers which are used for thin film photovoltaic technology, particularly cadmium telluride based and copper indium gallium selenide based solar cells.
A theoretical background of the thin film technology and a comparison of different deposition methods in regards to the sputtering process is provided. Thereby, an in-depth investigation of zinc oxide (ZnO), tin oxide (SnO2), and cadmium stannate (Cd2SnO4) is presented. Furthermore, the operating characteristics of a hollow cathode are described. A detailed analysis of the different system components, as well as their functions, is thoroughly elucidated. Moreover, important system parameters required for the correct operation of the HCSS are identified
Anderson localization through Polyakov loops: lattice evidence and Random matrix model
We investigate low-lying fermion modes in SU(2) gauge theory at temperatures
above the phase transition. Both staggered and overlap spectra reveal
transitions from chaotic (random matrix) to integrable (Poissonian) behavior
accompanied by an increasing localization of the eigenmodes. We show that the
latter are trapped by local Polyakov loop fluctuations. Islands of such "wrong"
Polyakov loops can therefore be viewed as defects leading to Anderson
localization in gauge theories. We find strong similarities in the spatial
profile of these localized staggered and overlap eigenmodes. We discuss
possible interpretations of this finding and present a sparse random matrix
model that reproduces these features.Comment: 11 pages, 23 plots in 11 figures; some comments and references added,
some axis labels corrected; journal versio
A concept for quantitative characterization of the air balance in Bavarian forest soils
Site-specific descriptions of soil water balance and soil air balance are important for tree species selection in forestry. We present a concept for describing the soil air balance for Bavaria. It is an enhancement of an empirical multiple linear regression model that explains soil oxygen deficiency in terms of topographic, climate and soil parameters. We modelled numerous combinations of site conditions with the hydrologic model LWF-Brook 90 to determine an estimator for soil oxygen deficiency. This estimator reflects water logging that persists for a certain length of time. In a second step we will develop a new regression model and combine this information with topographical information about additional water fluxes in a GIS. We aim to combine both steps in order to describe the air balance of forest soils for the entirety of Bavaria.Da neben der Beschreibung des Wasserhaushaltes auch die Kenntnis ĂŒber Luftmangel fĂŒr die standortgerechte Baumartenwahl wichtig ist, wird ein Konzept fĂŒr die bayernweite Beschreibung des Lufthaushaltes vorgestellt. Es ist eine Weiterentwicklung eines empirischen Regressionsmodells, das die StaunĂ€sse mittels GelĂ€ndeparametern, Klima und Bodendaten abschĂ€tzt. Dazu wurden mit dem Wasserhaushaltsprogramm LWF-Brook 90 zahlreiche Kombinationen von Standortsfaktoren simuliert und eine SchĂ€tzgröĂe fĂŒr Luftmangel ausgegeben. Diese GröĂe beschreibt die EinschrĂ€nkung des Lufthaushaltes ĂŒber einen lĂ€ngeren Zeitraum. In einem weiteren Schritt wird dieser deterministische Luftmangelparameter ĂŒber ein neues Regressionsmodell abgeleitet und mit zusĂ€tzlichen topographischen Informationen ĂŒber Zu- und AbflĂŒsse in einem GIS kombiniert. Ziel ist es, fĂŒr ganz Bayern den Lufthaushalt von Waldböden zu beschreiben
Variant configuration for IT-services and its impact on the service request fulfillment process
IT organizations are currently facing a trade-off between standardization and customer individuality. Standardization is onemeans to realize scale economies, is prerequisite to automate the delivery of IT-services and hence a possibility to cut costs.Best-practice frameworks like ITIL also drive the standardization efforts by defining IT-service catalogues and standardprocesses. Upcoming or rather ongoing trends like on-demand computing require standardization to assure efficientallocation of resources. But on the other hand customers of IT-services are confronted with increasing competition in theirbusiness that provokes individuality of their processes. Consequently IT-services must also be adjustable or customizable tomeet the customersâ needs. The resulting variety must be handled efficiently by the IT organization to stay or becomecompetitive. One means to cope with variety in the service request fulfillment process is variant configuration. In ourcontribution we discuss how variant configuration mechanisms can be applied on IT-services and what impact variantconfiguration has for the service request fulfillment process
Electricity powering combustion: hydrogen engines
Hydrogen is ameans to chemically store energy. It can be used to buffer energy in a society increasingly relying on renewable but intermittent energy or as an energy vector for sustainable transportation. It is also attractive for its potential to power vehicles with (near-) zero tailpipe emissions. The use of hydrogen as an energy carrier for transport applications is mostly associated with fuel cells. However, hydrogen can also be used in an internal combustion engine (ICE). When converted to or designed for hydrogen operation, an ICE can attain high power output, high efficiency and ultra low emissions. Also, because of the possibility of bi-fuel operation, the hydrogen engine can act as an accelerator for building up a hydrogen infrastructure. The properties of hydrogen are quite different from the presently used hydrocarbon fuels, which is reflected in the design and operation of a hydrogen fueled ICE (H2ICE). These characteristics also result in more flexibility in engine control strategies and thus more routes for engine optimization. This article describes the most characteristic features of H2ICEs, the current state of H2ICE research and demonstration, and the future prospects
Cost-effectiveness of caries excavations in different risk groups â a micro- simulation study
Background Whilst being the most prevalent disease worldwide, dental caries is
increasingly concentrated in high-risk populations. New caries treatments
should therefore be evaluated not only in terms of their cost-effectiveness in
individuals, but also their effects on the distribution of costs and benefits
across different populations. To treat deep caries, there are currently three
strategies: selective (one-step incomplete), stepwise (two-step incomplete)
and complete excavation. Building on prior research that found selective
excavation generally cost-effective, we compared the costs-effectiveness of
different excavations in low- and high-risk patients, hypothesizing that
selective excavation had greater cost-effectiveness-advantages in patients
with high compared with low risk. Methods An average tooth-level Markov-model
was constructed following the posterior teeth in an initially 18-year old male
individual, either with low or high risk, over his lifetime. Risk was assumed
to be predicted by several parameters (oral hygiene, social position, dental
service utilization), with evidence-based transition probabilities or hazard
functions being adjusted for different risk status where applicable. Total
lifetime treatment costs were estimated for German healthcare, with both mixed
public-private and only private out-of-pocket costs being calculated. For
cost-effectiveness-analysis, micro-simulations were performed and joint
parameter uncertainty introduced by random sampling of probabilities. Cohort
analyses were used for assessing the underlying reasons for potential
differences between strategies and populations. Results Selective excavation
was more effective and less costly than both alternatives regardless of an
individualâs risk. All three strategies were less effective and more costly in
patients with high compared with low risk, whilst the differences between risk
groups were smallest for selective excavation. Thus, the cost-effectiveness-
advantages of selective excavation were more pronounced in high-risk groups,
who also benefitted the most from reduced private out-of-pocket treatment
costs. Conclusions Whilst caries excavation does not tackle the underlying
sources for both the development of caries lesions and the potential
differences of individualsâ risk status, selective excavation seems most
suitable to treat deep lesions, especially in patients with high risk, who
over-proportionally benefit from the resulting health-gains and cost-savings
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