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  • 1
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 72-73 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The rapid degradation observed in InP/InGaAsP mushroom stripe lasers covered with phosphosilicate glass (PSG) was investigated by comparing the light-current characteristics as a function of the preparation technique. We were able to show that the PSG-covering layer is not the reason for the rapid degradation. By inspecting the light-current characteristics before and after degradation and by additional underetching the laser structure after degradation we were able to localize the degraded regions on the open side walls of the InGaAsP active layer.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 548-552 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The Zn diffusion into InP and In0.57Ga0.43As was studied. A comparison of three diffusion methods is presented, i.e., boat diffusion, diffusion from As- or P-doped spin-on films, and diffusion from In-doped spin-on films. The diffusion into samples made by different growth methods was investigated, i.e., bulk grown wafers, liquid-phase epitaxial films (LPE), and metalorganic vapor-phase epitaxial films (MOVPE). The in-depth profiles found are from the double diffusion front type, p+ -p−-n. The p+ -p− junction position depends on the diffusion method but not significantly on the growth method of the sample, while the p−-n junction depends on both. For example, with As or P in the spin-on film, a shallow p+ -p− junction and a deep p−-n junction appear. With In in the spin-on film, a deep p+ -p− junction with a negligibly small p− region is found. Diffusion into bulk and MOVPE samples usually yields deeper p−-n junctions than into LPE samples. Owing to the fact that in the presented experiments the amount of P, As, In, Ga, or the respective vacancies VP, VAs, VIn, VGa differ, we are able to check which of the existing diffusion models are applicable here. We propose an independent trapping of the mobile interstitially diffusing Zni by two immobile vacancy centers, i.e., Zn on VIn or VGa in the p+ region and Zn on VAsZnVAs or VPZnVP in the p− region.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] A key challenge of functional genomics today is to generate well-annotated data sets that can be interpreted across different platforms and technologies. Large-scale functional genomics data often fail to connect to standard experimental approaches of gene characterization in individual ...
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2016-06-26
    Beschreibung: The excavation damaged zone (EDZ) around the backfilled tunnels of a geological repository represents a possible release path for radionuclides, corrosion and degradation gases that needs to be adequately addressed by safety assessment (SA) modelling tools. The hydromechanical phenomena associated with the creation and temporal evolution of the EDZ are of high complexity, precluding detailed representations of the EDZ in conventional SA. Thus, simplified EDZ models mimicking the safety-relevant features of the EDZ are required. In this context, a heuristic modelling approach has been developed to represent the creation and evolution of the EDZ in an abstracted and simplified manner. The key features addressed are the stochastic character of the excavation-induced fracture network and the self-sealing processes associated with the re-saturation after backfilling of the tunnels. The approach has been applied to a range of generic repository settings to investigate the impact of repository depth and in situ conditions on the hydraulic significance of the EDZ after repository closure. The model has been benchmarked with a dataset from a self-sealing experiment at the Mont Terri underground rock laboratory (URL), demonstrating the ability of the approach to mimic the evolution of the hydraulic significance of the EDZ during the re-saturation phase.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 1987-07-13
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
  • 7
    Publikationsdatum: 2014-04-11
    Beschreibung: For the characterization of gas migration through a low-permeability clay host rock for deep underground repositories, a comprehensive understanding of the relevant phenomena of gas and fluid flow through low-permeability clay is required. The National Cooperative for the Disposal of Radioactive Waste (Nagra) in Switzerland has developed a comprehensive programme to characterize gas flow in low-permeability Opalinus Clay through laboratory tests and detailed numerical analyses for developing appropriate constitutive models. Laboratory tests were performed on cores by two different laboratories, the Laboratory for Soil Mechanics at EPFL and the Department of Geotechnical Engineering and Geosciences at UPC. Loading tests were performed by both laboratories to study rock compressibility at different stress levels and water permeability dependence on void ratio. The water retention behaviour demonstrated by EPFL and UPC produced comparable results. Water permeability tests and fast controlled-volume air injection experiments were performed in a triaxial cell under isotropic stress conditions on two samples with flow parallel and normal to the bedding planes. A confining stress of 15 MPa was applied during gas testing, corresponding to a lithostatic pressure at a depth of c. 600 m below ground. For detailed analyses, the two-phase flow code TOUGH2 (Pruess et al. 1999) was used. This considers fluid flow in both liquid and gas phases under the influence of pressure, viscous and gravity forces, according to Darcy's law. The standard analyses could not reproduce the measured pressure responses well, and the calibrated hydraulic and two-phase parameters were not consistent with the preceding water test and laboratory analyses. Implementing the non-linear behaviour in terms of the observed relationship between changes in void ratio and associated changes in permeability under different stress conditions significantly improved the simulated results, resulting in a conceptual model that well reproduced the observed injection pressure and outflow responses for both tests, parallel and normal to bedding, using a consistent parameter set.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 2018
    Beschreibung: 〈p〉Stratigraphic sequences in boreholes are commonly estimated by interpreting combinations of well logs. The interpretation is generally tedious and is made some time after log completion, which often leads to a loss of valuable first-hand information gathered on-site. This may lead to delayed or potentially poor on-site decisions. To make things worse, the standard interpretation of well logs is, at least to a certain degree, subjective and based on the manipulation of data, which may be difficult to trace in the long term. Small changes in lithology are often disregarded and alternating thin layers presenting different lithologies are often combined in one single (notably thicker) stratigraphic unit. Therefore an automatic parameter-based and thus traceable and objective quick look at the lithology immediately after log completion represents both a valuable tool to help with on-site decisions and a solid, mathematically based starting point for further physically based interpretations carried out by log analysts. We present a workflow for the interpretation of well logs defined as an optimization problem. The workflow is applied to the characterization of metre- to decametre-scale stratigraphic units along 13 boreholes in northern Switzerland (one-dimensional resolution) and to millimetre-scale features over a wall at the Mont Terri underground rock laboratory in Switzerland (two-dimensional resolution). The results show that: (1) the workflow accurately maps lithological changes; (2) the interaction with the analyst is minimized, which reduces the subjectivity of the interpretation; and (3) outputs are available for on-site decisions.〈/p〉
    Print ISSN: 0375-6440
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2018
    Beschreibung: 〈p〉A prediction–evaluation approach is developed to assess the propagation of parameter, conceptual and scenario uncertainties in the estimated near-field temperatures of the full-scale emplacement experiment at the Mont Terri rock laboratory. The uncertainty assessment is performed using a three-dimensional thermo-hydraulic numerical model of the full-scale emplacement experiment that represents the emplaced materials and surrounding Opalinus Clay and accounts for heat generation at the heaters. The propagation of parametric uncertainties is assessed using a first-order second-moment method supplemented by Monte Carlo simulations sampling the uncertain parameter space. The risk of uncertain parameters resulting in the failure of the maximum temperature criteria is evaluated with a first-order reliability method. Conceptual and scenario uncertainties are evaluated with deterministic simulation variants. After the conclusion of predictive modelling, a mid-term evaluation of the temperature predictions is performed through a comparison with measurements after 2.5 years of heating. The comparison indicates that the best estimates of temperature agree well with the measurements and that the 95% error bands assessed with parametric uncertainty envelope the measured values in almost all locations. Additional comparison with the measured degree of water saturation and the relative humidity is performed to assess the hydraulic behaviour and set the ground for the long-term evaluation, which will include predictions of the near-field pore pressures.〈/p〉
    Print ISSN: 0375-6440
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 2018
    Beschreibung: 〈p〉A key component of the site comparison planned for the deep geological disposal of spent fuel and high-level waste (SF/HLW) in Switzerland is the assessment of the evolution of repository-induced perturbations in the repository nearfield associated with thermal effects from heat production due to radioactive decay of radionuclides, as well as gas pressures developing in the backfilled underground structures from the anaerobic corrosion of the steel waste canisters and tunnel support materials. The assessment of such effects is integrated in the site comparison through safety indicators used to evaluate repository performance. In this context, probabilistic assessments need to integrate the uncertainty of the entire ensemble of input parameters, and estimate the propagation to these indicators in a reliable and computationally efficient manner. This paper presents the development of a methodology for an indicator-based assessment of heat- and gas-induced effects in a SF/HLW repository in Opalinus Clay integrating a probabilistic treatment of parametric uncertainty. The workflow is demonstrated using preliminary data, repository configurations and indicators. Complementary simulations are presented to demonstrate the feedback to the optimization of repository design in order to mitigate repository-induced effects that can potentially compromise the safety function of the engineered and natural barriers.〈/p〉
    Print ISSN: 0375-6440
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
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