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  • 1
    Book
    Book
    Universitäts- und Landesbibliothek Sachsen-Anhalt
    Language: English
    Description: Transportprozesse in der ungesättigten Zone sind aufgrund ihrer Komplexität und Nichtlinearität schwer zu untersuchen. Diese Arbeit untersucht ungesättigten Fluss angetrieben durch einen Einheitsgradienten mit Fokus auf: (i) Dispersion des inerten gelösten Stoffes als Funktion des Wassergehalts, λ(θ), und (ii) Transport von Citrat-beschichteten und bodengebundenen Silbernanopartikeln (Ag-NP) als Funktion von hydrologischen und chemischen Faktoren. Ergebnisse sind: (i) Der Transport von Tracer und Ag NP ist empfindlich gegenüber der Geometrie des Strömungsfeldes und dies hängt von der Porenstruktur, der Strömungsgeschwindigkeit (jw) und θ ab. (ii) λ (θ) ist nichtlinear und eine dritte Materialeigenschaft zusätzlich zu den hydraulischen Funktionen θ (hm) und K (hm) von porösen Medien. (iii) Ag-NP Durchbruchskurven (BTCs) sind im Vergleich zu Tracer-BTCs aufgrund von physikalischen und chemischen Wechselwirkungen wesentlich modifiziert und haben eine reduzierte Beweglichkeit bei pH = 5 als bei pH = 9. (iv) Chemische Kräfte dominieren bodengebundenen Ag-NP-Transport, während Scherkräfte den Citrat-beschichteten NP-Transport aufgrund einer komplexen Lösungs-Chemie für die n-förmigen Ag-NPs dominieren. Die Mobilität von konstruierten Ag NP, die der Umwelt ausgesetzt sind, kann durch die ubiquitäre Anwesenheit von biogeochemischen Grenzflächen begrenzt werden.... ; Transport processes in the unsaturated zone are difficult to examine due to their complexity and non-linearity. This thesis investigates for unit gradient unsaturated flow: (i) solute (inert) dispersivity as a function of water content, λ(θ) and (ii) transport of citrate-coated and soil-aged Ag nanoparticles (NP) as a function of hydrologic and chemical factors. The findings include: (i) Transport of tracer and Ag NP is sensitive to the geometry of flow field and this depends on pore structure, flow rate (jw) and θ. (ii) λ(θ) is non-linear and a third material property in addition to the hydraulic functions, θ(hm) and K(hm), of porous media. (iii) Ag NP breakthrough curves (BTCs) are substantially modified relative to tracer BTCs due to both physical and chemical interactions and there was reduced Ag NP mobility at pH = 5 than at pH = 9. (iv) Chemical forces dominate soil-aged Ag NP transport whereas shear forces dominate citrate-coated NP transport due to a complex solution chemistry for the soil-aged Ag NPs. The mobility of engineered Ag NP exposed to the environment may be limited by the ubiquitous presence of biogeochemical interfaces....
    Keywords: Transportprozesse; Ungesättigte Zone; Einheitsgradienten; Dispersion; Durchbruchskurven; Inerter Gelöster Stoff; Silbernanopartikeln ; Transport Processes; Unsaturated Zone; Unit Gradient; Dispersivity; Breakthrough Curves; Inert Solute; Ag Nanoparticles ; Ddc::500 Naturwissenschaften Und Mathematik::550 Geowissenschaften, Geologie::550 Geowissenschaften
    Source: DataCite
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  • 2
    In: Water Resources Research, June 2017, Vol.53(6), pp.4709-4724
    Description: The relaxation dynamics toward a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron‐based X‐ray tomography (X‐ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces, and relaxes the contact angle toward the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X‐ray CT, and (ii) a slow relaxation with characteristic time scales of 1–4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardly ever attained in practice when conducting two‐phase experiments in which a flux boundary condition is changed from flow to no‐flow. Implications for experiments with pressure boundary conditions are discussed. What happens to fluids in a porous medium after pumping is stopped? Fast X‐ray tomography shows that even in a sample smaller than a sugar cube fluid interfaces continue to move for hours until an optimal fluid configuration is reached. The pace is limited by slow relaxation of dynamic contact angles. Therefore hydrostatic equilibrium, which is the state at which all fluid interfaces come to rest, is hardly ever attained in practice when conducting two‐phase flow experiments where the flow is stopped in much larger soil or rock samples. Relaxation dynamics through internal redistribution of fluids after fast drainage occurs in two stages A quick dissipation within seconds is followed by slow relaxation within several hours due to relaxation of dynamic contact angles Fluid configurations during relaxation are very different from those during quasi‐static drainage and imbibition
    Keywords: Two‐Phase Flow ; Dynamic Effects ; Hydraulic Nonequilibrium ; Dynamic Contact Angle ; Fluid Configuration ; Fluid Topology
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 3
  • 4
    Language: English
    In: SOIL Discussions, 10/04/2017, pp.1-15
    ISSN: SOIL Discussions
    E-ISSN: 2199-3998
    Source: CrossRef
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  • 5
    Language: English
    In: Environmental Earth Sciences, 2017, Vol.76(1), pp.1-25
    Description: This article provides an overview about the Bode River catchment that was selected as the hydrological observatory and main region for hydro-ecological research within the TERrestrial ENvironmental Observatories Harz/Central German Lowland Observatory. It first provides information about the general characteristics of the catchment including climate, geology, soils, land use, water quality and aquatic ecology, followed by the description of the interdisciplinary research framework and the monitoring concept with the main components of the multi-scale and multi-temporal monitoring infrastructure. It also shows examples of interdisciplinary research projects aiming to advance the understanding of complex hydrological processes under natural and anthropogenic forcings and their interactions in a catchment context. The overview is complemented with research work conducted at a number of intensive research sites, each focusing on a particular functional zone or specific components and processes of the hydro-ecological system.
    Keywords: Monitoring ; Catchment ; Water quality ; Observatory ; Water fluxes
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 6
    Language: English
    Description: During the last decades, the functional power and complexity of automotive E/E architectures grew radically and is going to grow further. We identified two key factors namely autonomy and intelligence. Both pose research challenges for the next generation E/E architecture. We aim to tackle the design challenges with methods and technologies. We propose in this project statement to use a service-oriented architecture on top of an in-vehicle communication network based on time-sensitive networking. Moreover, a rigor risk analysis and mitigation approach enables synthesis of a safety controller. A learning architecture facilitates a shift towards user centralization by proactively adapting functions according to user profiles. In addition, further functions might need to be learned at run-time....
    Keywords: Automotive ; Safety Assurance ; Service-Oriented Architectures ; Communication ; Timesensitive Network ; Deep Learning ; Machine Learning ; Artificial Intelligence
    ISBN: 978-3-88579-669-5
    ISSN: 1617-5468
    Source: DataCite
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