A Ni(II) porphyrin functionalized with an alkyl carboxylic acid (3) has been synthesized to model the chemical behavior of the heaviest portion of petroleum, the asphaltenes. Specifically, porphyrin ...3 is used in spectroscopic studies to probe aggregation with a second asphaltene model compound containing basic nitrogen (4), designed to mimic asphaltene behavior. NMR spectroscopy documents self-association of the porphyrin and aggregation with the second model compound in solution, and a Job's plot suggests a 1 : 2 stoichiometry for compounds 3 and 4.
We consider additive Schwarz domain decomposition preconditioners for piecewise linear finite element approximations of elliptic PDEs with highly variable coefficients. In contrast to standard ...analyses, we do not assume that the coefficients can be resolved by a coarse mesh. This situation arises often in practice, for example in the computation of flows in heterogeneous porous media, in both the deterministic and (Monte–Carlo simulated) stochastic cases. We consider preconditioners which combine local solves on general overlapping subdomains together with a global solve on a general coarse space of functions on a coarse grid. We perform a new analysis of the preconditioned matrix, which shows rather explicitly how its condition number depends on the variable coefficient in the PDE as well as on the coarse mesh and overlap parameters. The classical estimates for this preconditioner with linear coarsening guarantee good conditioning only when the coefficient varies mildly inside the coarse grid elements. By contrast, our new results show that, with a good choice of subdomains and coarse space basis functions, the preconditioner can still be robust even for large coefficient variation inside domains, when the classical method fails to be robust. In particular our estimates prove very precisely the previously made empirical observation that the use of low-energy coarse spaces can lead to robust preconditioners. We go on to consider coarse spaces constructed from multiscale finite elements and prove that preconditioners using this type of coarsening lead to robust preconditioners for a variety of binary (i.e., two-scale) media model problems. Moreover numerical experiments show that the new preconditioner has greatly improved performance over standard preconditioners even in the random coefficient case. We show also how the analysis extends in a straightforward way to multiplicative versions of the Schwarz method.
Methane emissions from active or closed landfills can be reduced by means of methane oxidation enhanced in properly designed landfill covers, known as “biocovers”. Biocovers usually consist of a ...coarse gas distribution layer to balance gas fluxes placed beneath an appropriate substrate layer. The application of such covers implies use of measurement methods and evaluation approaches, both during the planning stage and throughout the operation of biocovers in order to demonstrate their efficiency. Principally, various techniques, commonly used to monitor landfill surface emissions, can be applied to control biocovers. However, particularly when using engineered materials such as compost substrates, biocovers often feature several altered, specific properties when compared to conventional covers, e.g., respect to gas permeability, physical parameters including water retention capacity and texture, and methane oxidation activity. Therefore, existing measuring methods should be carefully evaluated or even modified prior to application on biocovers. This paper discusses possible strategies to be applied in monitoring biocover functionality. On the basis of experiences derived from investigations and large-scale field trials with compost biocovers in Austria, an assessment approach has been developed. A conceptual draft for monitoring biocover performance and recommendations for practical application are presented.
Abstract
The TRISTAN project is the upgrade of the KATRIN experiment designed for the search of sterile neutrinos by replacing the current KATRIN detector with a multipixel SDD (Silicon Drift ...Detector) matrix. We have characterized SDDs response to electrons using a SEM (Scanning Electron Microscope) as an electron source and a Geant4-based simulation whose output is processed with an empirical function to reproduce data. We have crosschecked this model by reconstructing backscattering measurements obtained using a radioactive electron source.
During the biological treatment of waste organic matter undergoes considerable changes. Degradation and transformation, mineralization and humification take place. These processes correspond to ...different energy contents, which are reflected by the characteristic thermal behavior of the samples. Waste materials such as compost, municipal solid waste and waste from abandoned landfills have been investigated in this study to demonstrate the applicability of thermal methods in waste management. The use of the total sample, thus avoiding chemical extraction, has proved to be advantageous in the management of complex materials. Nevertheless, waste compounds were also characterized. TG/DTG and the curves of the CO
2 ion current have been recorded in order to shed light on changes occurring in humic acids during composting.
Thermal characteristics were attributed to different stages of decomposition of landfill materials. Further to the assessment of unknown landfills process control was carried out to evaluate the efficiency of aeration.
A simple procedure that it not based on the comparison of a series of data but rather enables assessment of an individual sample is described for use in the evaluation of organic matter present in municipal solid waste.
Sterile neutrinos are a minimal extension of the standard model of particle physics. A promising model-independent way to search for sterile neutrinos is via high-precision β-spectroscopy. The ...Karlsruhe tritium neutrino (KATRIN) experiment, equipped with a novel multi-pixel silicon drift detector focal plane array and read-out system, named the TRISTAN detector, has the potential to supersede the sensitivity of previous laboratory-based searches. In this work we present the characterization of the first silicon drift detector prototypes with electrons and we investigate the impact of uncertainties of the detector's response to electrons on the final sterile neutrino sensitivity.
Expanding the detection efficiency of silicon drift detectors Schlosser, D.M.; Lechner, P.; Lutz, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2010, Letnik:
624, Številka:
2
Journal Article
Recenzirano
Odprti dostop
To expand the detection efficiency Silicon Drift Detectors (SDDs) with various customized radiation entrance windows, optimized detector areas and geometries have been developed. Optimum values for ...energy resolution, peak to background ratio (P/B) and high count rate capability support the development. Detailed results on sensors optimized for light element detection down to Boron or even lower will be reported. New developments for detecting medium and high X-ray energies by increasing the effective detector thickness will be presented. Gamma-ray detectors consisting of a SDD coupled to scintillators like CsI(Tl) and LaBr
3(Ce) have been examined. Results of the energy resolution for the
137Cs 662
keV line and the light yield (LY) of such detector systems will be reported.
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