Measurements of armour layer roughness geometry function and porosity     

Jochen Aberle 《Acta Geophysica》2007,55(1):23-32

The roughness geometry function of the interfacial sublayer of a gravel-bed armour layer was measured directly by filling water stepwise into a laboratory flume and indirectly from a digital elevation model (DEM) of the surface. The results of both methods are compared and show that the DEM can be used to reliably estimate the roughness density function for a wide range of the interfacial sublayer. The direct measurements revealed an absolute minimum of porosity at the level of the roughness trough which is significantly smaller than porosity in the undisturbed subsurface and porosity estimates obtained from relationships found in the literature. The significance of the results for hydraulic engineering and ecological applications is highlighted.  相似文献   

Macrophytes and phytobenthos as indicators of ecological status in German lakes — a contribution to the implementation of the water framework directive     

Jochen Schaumburg  Christine Schranz  Gabriele Hofmann  Doris Stelzer  Susanne Schneider  Ursula Schmedtje 《Limnologica》2004,34(4):302-314

A new assessment system for macrophytes and phytobenthos in German lakes according to the Water Framework Directive of the European Community is described. Based on biological, chemical and hydromorphological data from about 100 lake sites covering the main ecoregions, hydromorphological lake types and degradation forms, biocoenotic types could be defined. For developing a classification system the quality element macrophytes and phytobenthos was divided into two components: macrophytes and benthic diatoms. For macrophytes 4 and for benthic diatoms 4 lake types were identified. The benthic vegetation at reference conditions is described and degradation is characterised as deviation in benthic vegetation species composition and abundance from the reference biocoenosis. For classification in five ecological status classes, several metrics were developed and used in combination with existing indices. For a few of the described lake types further investigations are necessary before a classification can be developed.  相似文献   

Automatic regional moment tensor inversion in the European-Mediterranean region   总被引：4，自引：0，他引：4  

Fabrizio Bernardi  Jochen Braunmiller  Urs Kradolfer  Domenico Giardini 《Geophysical Journal International》2004,157(2):703-716

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Integrated Framework for the Simulation of Biological Invasions in a Heterogeneous Landscape     

Peng Ming  Jochen Albrecht 《Transactions in GIS》2004,8(3):309-334

In the integrated framework presented in this article, a geographical information system serves as a shell to integrate spatial, dynamic and stochastic perspectives of biological invasions in a coherent workflow. A decision tree model stratifies the landscape with respect to spatial susceptibility and builds the spatial biophysical structure for the simulation of species invasion. A dynamic diffusion model evaluates the temporal changes of species to provide the dynamic parameters for the simulation. A simulation model derived from percolation theory simulates species invasion by combining spatial and dynamic information, and explicitly representing spatio‐temporal patterns of invasions within the GIS‐percolation environment. The simulation illustrates the great influence of spatial structure and connectivity of landscape on the diffusion of the species.  相似文献   

Certification of ERM‐EB400, the First Matrix Reference Material for Lead Isotope Amount Ratios,and ERM‐AE142, a Lead Solution Providing a Lead Isotopic Composition at the Edge of Natural Variation     

Jochen Vogl  Yong‐Hyeon Yim  Kyoung‐Seok Lee  Heidi Goenaga‐Infante  Dmitriy Malinovskiy  Sarah Hill  Tongxiang Ren  Jun Wang  Robert D. Vocke  Karen E. Murphy  Naoko Nonose  Olaf Rienitz  Janine Noordmann 《Geostandards and Geoanalytical Research》2019,43(1):23-37

Lead isotope amount ratios are commonly used in diverse fields such as archaeometry, geochemistry and forensic science. Currently, five reference materials with certified lead isotope amount ratios are available, namely NIST SRM 981, 982 and 983, GBW‐04442 and NMIJ 3681‐a. Only NIST SRM 981 and NMIJ 3681‐a have approximately natural isotopic compositions, and NIST SRM 981 is predominantly used for correcting mass discrimination/mass fractionation in the applied mass spectrometric procedures. Consequently, there is no other certified reference material available to be used for validation and/or quality control of the analytical procedures applied to lead isotope amount ratio measurements. To fill this gap, two new reference materials have been produced and certified for their lead isotope amount ratios. For both certified reference materials, complete uncertainty budgets have been calculated and SI traceability has been established. This provides the users with independent means for validating and verifying their analytical procedures and for conducting quality control measures. ERM‐EB400 is a bronze material with a nominal lead mass fraction of 45 mg kg^?1 and certified lead isotope amount ratios of n(²⁰⁶Pb)/n(²⁰⁴Pb) = 18.072(17) mol mol^?1, n(²⁰⁷Pb)/n(²⁰⁴Pb) = 15.578(18) mol mol^?1 and n(²⁰⁸Pb)/n(²⁰⁴Pb) = 38.075(46) mol mol^?1 with the associated expanded uncertainties (k = 2) given in brackets. ERM‐AE142 is a high‐purity solution of lead in 2% nitric acid with a nominal mass fraction of 100 mg kg^?1 and certified Pb isotope amount ratios of n(²⁰⁶Pb)/n(²⁰⁴Pb) = 21.114(17) mol mol^?1, n(²⁰⁷Pb)/n(²⁰⁴Pb) = 15.944(17) mol mol^?1 and n(²⁰⁸Pb)/n(²⁰⁴Pb) = 39.850(44) mol mol^?1 with the associated expanded uncertainties (k = 2) given in brackets. Both materials are specifically designed to fall within the natural lead isotopic variation and to assist users with the validation and verification of their analytical procedures. Note that while one of these reference materials requires the chemical separation of Pb from its matrix (ERM‐EB400), the other does not (ERM‐AE142). As additional information, δ^208/206Pb_{NIST SRM981} values are provided for both materials. For ERM‐AE142, a delta value of δ^208/206Pb_{NIST SRM981} = ?28.21(30)‰ was obtained, and for ERM‐EB400, a delta value of δ^208/206Pb_NIST SRM981= ?129.47(38)‰ was obtained, with the associated expanded uncertainties (k = 2) given in brackets.  相似文献   

Spatio-temporal assessment of perfluorinated compounds in the Brisbane River system,Australia: Impact of a major flood event     

Christie Gallen  Christine Baduel  Foon Yin Lai  Kristie Thompson  Jack Thompson  Michael Warne  Jochen F. Mueller 《Marine pollution bulletin》2014

Perfluorinated chemicals including PFOA and PFOS have been widely used in consumer products and have become ubiquitous pollutants widely distributed in the aqueous environment. Following a major flood event in 2011, water samples were collected along a spatial gradient of the Brisbane River system to provide an initial estimate of the release of PFASs from flooded urban areas. PFOA (mean concentrations 0.13–6.1 ng L⁻¹) and PFOS (mean concentrations 0.18–15 ng L⁻¹) were the most frequently detected and abundant PFASs. Mean total PFASs concentrations increased from 0.83 ng L⁻¹ at the upstream Wivenhoe Dam to 40 ng L⁻¹ at Oxley Creek, representing an urban catchment. Total masses of PFOA and PFOS delivered into Moreton Bay from January to March were estimated to be 5.6 kg and 12 kg respectively. From this study, urban floodwaters appear to be a previously overlooked source of PFASs into the surrounding environment.  相似文献   

Bed load transport by bed form migration   总被引：1，自引：1，他引：0  

Jochen Aberle  Stephen E. Coleman  Vladimir I. Nikora 《Acta Geophysica》2012,60(6):1720-1743

A theoretically-based methodology is presented for the determination of bed load transport from high-resolution measurements of bed surface elevations for steady-state or developing dunes. The methodology is based on the general form of the Exner equation for sediment continuity and requires information on the distribution of sediment volume concentration as well as the migration velocity of bed layers. In order to determine layer speeds, a new method based on cross-correlation analysis of elevation slices is proposed. The methodology is tested using artificially-created data as well as data from a physical model and from a flume study of developing bed forms. The analyses show the applicability of the method to determine bed load transport without the need to introduce assumptions about the form of the migrating surface. It is shown that predicted transport rates match measured or theoretical transport rates for steadily moving bed forms of an arbitrary shape. The method can also be used to predict transport rates over deforming bed forms, with the reasons for potential deviations between predicted and measured or theoretical transport rates for deforming bed forms identified and discussed. It is further shown that a simplified bulk-surface approach, that is relatively straightforward to apply and in which it is assumed that bed-layer velocity is constant with depth, gives results that are comparable to analyses based on determined bed-layer velocity variation with depth.  相似文献   

The 2013 European Seismic Hazard Model: key components and results   总被引：11，自引：5，他引：6  

Jochen Woessner  Danciu Laurentiu  Domenico Giardini  Helen Crowley  Fabrice Cotton  Gottfried Grünthal  Gianluca Valensise  Ronald Arvidsson  Roberto Basili  Mine Betül Demircioglu  Stefan Hiemer  Carlo Meletti  Roger W. Musson  Andrea N. Rovida  Karin Sesetyan  Massimiliano Stucchi  The SHARE Consortium 《Bulletin of Earthquake Engineering》2015,13(12):3553-3596

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Impacts of blending on dilution of negatively buoyant brine discharge in a shallow tidal sea     

Jochen Kämpf 《Marine pollution bulletin》2009,58(7):1032-1038

A fine-resolution three-dimensional hydrodynamic model is applied to study the dilution of desalination brine discharged into a tidal sea. Based on given inflow rate and salinity excess of discharge brine, this study explores variations in mid-field dilutions when other low-salinity wastewater is added to the discharge. Findings reveal that this blending leads to a decrease in dilution in the mixing zone and therefore to higher levels of pollutants in this zone, while, on the other hand, the mixing zone occupies a smaller area. The reason is that the discharge of brine creates a density-driven flow that operates to partially remove effluent from the discharge location. This removal is less efficient for the decrease in density excess of the discharge. Hence, in an ambient sea of moderate mixing, blending can be expected to increase the risk of marine pollution in the mixing zone.  相似文献   

Spatio-temporal Slip, and Stress Level on the Faults within the Western Foothills of Taiwan: Implications for Fault Frictional Properties     

Ya-Ju Hsu  Jean-Philippe Avouac  Shui-Beih Yu  Chien-Hsin Chang  Yih-Min Wu  Jochen Woessner 《Pure and Applied Geophysics》2009,166(10-11):1853-1884

We use preseismic, coseismic, and postseismic GPS data of the 1999 Chi-Chi earthquake to infer spatio-temporal variation of fault slip and frictional behavior on the Chelungpu fault. The geodetic data shows that coseismic slip during the Chi-Chi earthquake occurred within a patch that was locked in the period preceding the earthquake, and that afterslip occurred dominantly downdip from the ruptured area. To first-order, the observed pattern and the temporal evolution of afterslip is consistent with models of the seismic cycle based on rate-and-state friction. Comparison with the distribution of temperature on the fault derived from thermo-kinematic modeling shows that aseismic slip becomes dominant where temperature is estimated to exceed 200° at depth. This inference is consistent with the temperature induced transition from velocity-weakening to velocity-strengthening friction that is observed in laboratory experiments on quartzo-feldspathic rocks. The time evolution of afterslip is consistent with afterslip being governed by velocity-strengthening frictional sliding. The dependency of friction, μ, on the sliding velocity, V, is estimated to be ${{\partial \mu }/{\partial \, {\rm ln}\, V}} = 8 \times 10^{ - 3}$ . We report an azimuthal difference of about 10–20° between preseismic and postseismic GPS velocities, which we interpret to reflect the very low shear stress on the creeping portion of the décollement beneath the Central Range, of the order of 1–3 MPa, implying a very low friction of about 0.01. This study highlights the importance of temperature and pore pressure in determining fault frictional sliding.  相似文献