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  • 1
    UID:
    b3kat_BV047199846
    Format: 606 Seiten
    ISBN: 9783739830506 , 3739830506
    Note: Dissertation Universität Hildesheim 2019
    Additional Edition: Erscheint auch als Online-Ausgabe, PDF ISBN 978-3-7398-8050-1
    Language: German
    Subjects: General works , Sociology
    RVK:
    RVK:
    Keywords: Instagram ; Computerunterstützte Kommunikation ; Online-Community ; Autoshaping ; Instagram ; Online-Community ; Subjekt ; Medienkonsum ; Kommunikation ; Hochschulschrift ; Hochschulschrift
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  • 2
    UID:
    b3kat_BV047663906
    Format: 1 Online-Ressource (606 Seiten) , Illustrationen
    ISBN: 9783739880501
    Content: Wie wirkt sich die Nutzung der bildbasierten sozialen Netzwerkseite Instagram auf die Nutzenden aus? Basierend auf empirischen Daten geht die Studie davon aus, dass das Verhältnis zwischen Plattform und Nutzenden keine Einbahnstraße ist: Instagram als ,digitales Ökosystem' setzt bestimmte Nutzungsrahmen. Wie und wie sehr die Plattformarchitektur die Nutzenden beeinflusst, hängt jedoch von deren Aneignungsweisen ab. Je stärker Instagram in den Alltag integriert wird und je mehr Bedeutung das soziale Netzwerk für das Selbst gewinnt, desto spezifischer sind die Effekte der Plattform. Likes begünstigen dabei u.a. die Ausbildung einer instagramtypischen Subjektform, die Bildkommunikation wiederum fördert spezifische Gemeinschaftsformen und Affektkulturen. Die Studie leistet einen Beitrag zum Verständnis der Dynamiken sozialer Netzwerke und von Mensch-Technik-Interaktion
    Additional Edition: Erscheint auch als Druck-Ausgabe ISBN 978-3-7398-3050-6
    Language: German
    Subjects: General works , Sociology
    RVK:
    RVK:
    Keywords: Instagram ; Computerunterstützte Kommunikation ; Online-Community ; Autoshaping ; Instagram ; Online-Community ; Subjekt ; Medienkonsum ; Kommunikation ; Hochschulschrift ; Hochschulschrift
    URL: Volltext  (URL des Erstveröffentlichers)
    URL: Volltext  (URL des Erstveröffentlichers)
    URL: Cover
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  • 3
    UID:
    gbv_845986651
    Format: xv, 103 Seiten , Illustrationen
    Content: Stream water and groundwater are important fresh water resources but their water quality is deteriorated by harmful solutes introduced by human activities. The interface between stream water and the subsurface water is an important zone for retention, transformation and attenuation of these solutes. Streambed structures enhance these processes by increased water and solute exchange across this interface, denoted as hyporheic exchange. This thesis investigates the influence of hydrological and morphological factors on hyporheic water and solute exchange as well as redox-reactions in fluvial streambed structures on the intermediate scale (10–30m). For this purpose, a three-dimensional numerical modeling approach for coupling stream water flow with porous media flow is used. Multiple steady state stream water flow scenarios over different generic pool-riffle morphologies and a natural in-stream gravel bar are simulated by a computational fluid dynamics code that provides the hydraulic head distribution at the streambed. These heads are subsequently used as the top boundary condition of a reactive transport groundwater model of the subsurface beneath the streambed. Ambient groundwater that naturally interacts with the stream water is considered in scenarios of different magnitudes of downwelling stream water (losing case) and upwelling groundwater (gaining case). Also, the neutral case, where stream stage and groundwater levels are balanced is considered. Transport of oxygen, nitrate and dissolved organic carbon and their reaction by aerobic respiration and denitrification are modeled. The results show that stream stage and discharge primarily induce hyporheic exchange flux and solute transport with implications for specific residence times and reactions at both the fully and partially submerged structures. Gaining and losing conditions significantly diminish the extent of the hyporheic zone, the water exchange flux, and shorten residence times for both the fully and partially submerged structures. With increasing magnitude of gaining or losing conditions, these metrics exponentially decrease. Stream water solutes are transported mainly advectively into the hyporheic zone and hence their influx corresponds directly to the infiltrating water flux. Aerobic respiration takes place in the shallow streambed sediments, coinciding to large parts with the extent of the hyporheic exchange flow. Denitrification occurs mainly as a “reactive fringe” surrounding the aerobic zone, where oxygen concentration is low and still a sufficient amount of stream water carbon source is available. The solute consumption rates and the efficiency of the aerobic and anaerobic reactions depend primarily on the available reactive areas and the residence times, which are both controlled by the interplay between hydraulic head distribution at the streambed and the gradients between stream stage and ambient groundwater. Highest solute consumption rates can be expected under neutral conditions, where highest solute flux, longest residence times and largest extent of the hyporheic exchange occur. The results of this thesis show that streambed structures on the intermediate scale have a significant potential to contribute to a net solute turnover that can support a healthy status of the aquatic ecosystem.
    Note: kumulative Dissertation , Dissertation Mathematisch-Naturwissenschaftliche Fakultät der Universität Potsdam 2015
    Additional Edition: Erscheint auch als Online-Ausgabe Trauth, Nico Flow and reactive transport modeling at the stream-groundwater interface
    Language: English
    Keywords: Flussbett ; Flusswasser ; Grundwasser ; Grundwasserstrom ; Stoffübertragung ; Modellierung ; Oberflächengewässer ; Grundwasserleiter ; Hydraulik ; Hydrogeologie ; Flussinsel ; Numerisches Modell ; Hochschulschrift
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  • 4
    UID:
    gbv_1733686606
    Format: XXVI, 175 Blätter , Illustrationen, Diagramme, Karten
    Content: Studies on the unsustainable use of groundwater resources are still considered incipient since it is frequently a poorly understood and managed, devalued and inadequately protected natural resource. Groundwater Recharge (GWR) is one of the most challenging elements to estimate since it can rarely be measured directly and cannot easily be derived from existing data. To overcome these limitations, many hydro(geo)logists have combined different approaches to estimate large-scale GWR, namely: remote sensing products, such as IMERG product; Water Budget Equation, also in combination with hydrological models, and; Geographic Information System (GIS), using estimation formulas. For intermediary-scale GWR estimation, there exist: Non-invasive Cosmic-Ray Neutron Sensing (CRNS); wireless networks from local soil probes; and soil hydrological models, such as HYDRUS. Accordingly, this PhD thesis aims, on the one hand, to demonstrate a GIS-based model coupling for estimating the GWR distribution on a large scale in tropical wet basins. On the ...
    Note: Dissertation Universität Potsdam 2020 , Dissertation Federal University of Paraíba (UFPB, Brazil) 2020
    Additional Edition: Erscheint auch als Online-Ausgabe Romero Barbosa, Luís Groundwater recharge in tropical wet regions via GIS-based methods and cosmic-ray neutron sensing Potsdam, 2020
    Language: English
    Keywords: Paraíba ; Fernerkundung ; Grundwasserbildung ; Bodenwasserhaushalt ; Kosmische Strahlung ; Neutronenstrahlung ; Brasilien ; Tropen ; Grundwasserhaushalt ; Hochschulschrift
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  • 5
    UID:
    gbv_1014324343
    Format: XIII, 123 Seiten , Illustrationen, Diagramme
    Content: The functioning of the surface water-groundwater interface as buffer, filter and reactive zone is important for water quality, ecological health and resilience of streams and riparian ecosystems. Solute and heat exchange across this interface is driven by the advection of water. Characterizing the flow conditions in the streambed is challenging as flow patterns are often complex and multidimensional, driven by surface hydraulic gradients and groundwater discharge. This thesis presents the results of an integrated approach of studies, ranging from the acquisition of field data, the development of analytical and numerical approaches to analyse vertical temperature profiles to the detailed, fully-integrated 3D numerical modelling of water and heat flux at the reach scale. All techniques were applied in order to characterize exchange flux between stream and groundwater, hyporheic flow paths and temperature patterns. The study was conducted at a reach-scale section of the lowland Selke River, characterized by distinctive pool riffle…
    Note: Enthält 3 Publikationen , kumulative Dissertation , Dissertation Universität Potsdam 2017
    Additional Edition: Erscheint auch als Online-Ausgabe Munz, Matthias Water flow and heat transport modelling at the interface between river and aquifer Potsdam, 2018
    Language: English
    Keywords: Oberflächenwasser ; Grundwasser ; Hochschulschrift
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  • 6
    UID:
    gbv_832334456
    Format: XVIII, 164 Seiten , Illustrationen
    Content: This cumulative dissertation explored the use of the detection of natural background of fast neutrons, the so-called cosmic-ray neutron sensing (CRS) approach to measure field-scale soil moisture in cropped fields. Primary cosmic rays penetrate the top atmosphere and interact with atmospheric particles. Such interaction results on a cascade of high-energy neutrons, which continue traveling through the atmospheric column. Finally, neutrons penetrate the soil surface and a second cascade is produced with the so-called secondary cosmic-ray neutrons (fast neutrons). Partly, fast neutrons are absorbed by hydrogen (soil moisture). Remaining neutrons scatter back to the atmosphere, where its flux is inversely correlated to the soil moisture content, therefore allowing a non-invasive indirect measurement of soil moisture. The CRS methodology is mainly evaluated based on a field study carried out on a farmland in Potsdam (Brandenburg, Germany) along three crop seasons with corn, sunflower and winter rye; a bare soil period; and two winter periods. Also, field monitoring was carried out in the Schaefertal catchment (Harz, Germany) for long-term testing of CRS against ancillary data. In the first experimental site, the CRS method was calibrated and validated using different approaches of soil moisture measurements. In a period with corn, soil moisture measurement at the local scale was performed at near-surface only, and in subsequent periods (sunflower and winter rye) sensors were placed in three depths (5 cm, 20 cm and 40 cm). The direct transfer of CRS calibration parameters between two vegetation periods led to a large overestimation of soil moisture by the CRS. Part of this soil moisture overestimation was attributed to an underestimation of the CRS observation depth during the corn period ( 5-10 cm), which was later recalculated to values between 20-40 cm in other crop periods (sunflower and winter rye). According to results from these monitoring periods with different crops, vegetation played an important role on the CRS measurements. Water contained also in crop biomass, above and below ground, produces important neutron moderation. This effect was accounted for by a simple model for neutron corrections due to vegetation. It followed crop development and reduced overall CRS soil moisture error for periods of sunflower and winter rye. In Potsdam farmland also inversely-estimated soil hydraulic parameters were determined at the field scale, using CRS soil moisture from the sunflower period. A modelling framework coupling HYDRUS-1D and PEST was applied. Subsequently, field-scale soil hydraulic properties were compared against local scale soil properties (modelling and measurements). Successful results were obtained here, despite large difference in support volume. Simple modelling framework emphasizes future research directions with CRS soil moisture to parameterize field scale models. In Schaefertal catchment, CRS measurements were verified using precipitation and evapotranspiration data. At the monthly resolution, CRS soil water storage was well correlated to these two weather variables. Also clearly, water balance could not be closed due to missing information from other compartments such as groundwater, catchment discharge, etc. In the catchment, the snow influence to natural neutrons was also evaluated. As also observed in Potsdam farmland, CRS signal was strongly influenced by snow fall and snow accumulation. A simple strategy to measure snow was presented for Schaefertal case. Concluding remarks of this dissertation showed that (a) the cosmic-ray neutron sensing (CRS) has a strong potential to provide feasible measurement of mean soil moisture at the field scale in cropped fields; (b) CRS soil moisture is strongly influenced by other environmental water pools such as vegetation and snow, therefore these should be considered in analysis; (c) CRS water storage can be used for soil hydrology modelling for determination of soil hydraulic parameters; and (d) CRS approach has strong potential for long term monitoring of soil moisture and for addressing studies of water balance.
    Note: Enthält 3 Publikationen , Abweichendes Erscheinungsjahr auf der Titelseite: 2013 , Dissertation Universität Potsdam 2014
    Additional Edition: Erscheint auch als Online-Ausgabe Rivera Villarreyes, Carlos Andres Cosmic-ray neutron sensing for soil moisture measurements in cropped fields 2014
    Language: English
    Keywords: Neutronenstrahlung ; Kosmische Strahlung ; Streuung ; Bodenfeuchte ; Messung ; Feldversuch ; Hochschulschrift
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  • 7
    UID:
    gbv_1757505466
    Format: VII, 120 Blätter , Illustrationen, Diagramme, Karten
    Content: Bank filtration is an effective water treatment technique and is widely adopted in Europe along major rivers. It is the process where surface water penetrates the riverbed, flows through the aquifer, and then is extracted by near-bank production wells. By flowing in the subsurface flow passage, the water quality can be improved by a series of beneficial processes. Long-term riverbank filtration also produces colmation layers on the riverbed. The colmation layer may act as a bioactive zone that is governed by biochemical and physical processes owing to its enrichment of microbes and organic matter. Low permeability may strongly limit the surface water infiltration and further lead to a decreasing recoverable ratio of production wells.The removal of the colmation layer is therefore a trade-off between the treatment capacity and treatment efficiency. The goal of this Ph.D. thesis is to focus on the temporal and spatial change of the water quality and quantity along the flow path of a hydrogeological heterogeneous riverbank filtration ...
    Note: Dissertation Universität Potsdam 2020
    Additional Edition: Erscheint auch als Online-Ausgabe Wang, Weishi Influence of river reconstruction at a bank filtration site Potsdam, 2021
    Language: English
    Keywords: Uferfiltration ; Hochschulschrift
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  • 8
    UID:
    kobvindex_ZLB34715292
    Format: 606 S.
    ISBN: 9783739880501
    Content: Wie wirkt sich die Nutzung der bildbasierten sozialen Netzwerkseite Instagram auf die Nutzenden aus? Basierend auf empirischen Daten geht die Studie davon aus, dass das Verhältnis zwischen Plattform und Nutzenden keine Einbahnstraße ist: Instagram als 'digitales Ökosystem' setzt bestimmte Nutzungsrahmen. Wie und wie sehr die Plattformarchitektur die Nutzenden beeinflusst, hängt jedoch von deren Aneignungsweisen ab. Je stärker Instagram in den Alltag integriert wird und je mehr Bedeutung das soziale Netzwerk für das Selbst gewinnt, desto spezifischer sind die Effekte der Plattform. Likes begünstigen dabei u.a. die Ausbildung einer instagramtypischen Subjektform, die Bildkommunikation wiederum fördert spezifische Gemeinschaftsformen und Affektkulturen. Die Studie leistet einen Beitrag zum Verständnis der Dynamiken sozialer Netzwerke und von Mensch-Technik-Interaktion.
    Note: Sascha Oswald ist wissenschaftlicher Mitarbeiter am Institut für Sozialwissenschaften der Stiftung Universität Hildesheim. Er studierte Soziologie und Sprachwissenschaften an der Universität Konstanz. Seine Forschungsschwerpunkte sind Qualitative Medien- und Kommunikationsforschung, Körper- und Emotionssoziologie sowie Subjekt- und Praxistheorien. Mit vorliegender Untersuchung wurde er 2019 an der Universität Hildesheim promoviert.
    Language: German
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  • 9
    UID:
    gbv_1014323061
    Format: 1 Online-Ressource (XIII, 123 Seiten, 7980 KB) , Illustrationen, Diagramme
    Content: The functioning of the surface water-groundwater interface as buffer, filter and reactive zone is important for water quality, ecological health and resilience of streams and riparian ecosystems. Solute and heat exchange across this interface is driven by the advection of water. Characterizing the flow conditions in the streambed is challenging as flow patterns are often complex and multidimensional, driven by surface hydraulic gradients and groundwater discharge. This thesis presents the results of an integrated approach of studies, ranging from the acquisition of field data, the development of analytical and numerical approaches to analyse vertical temperature profiles to the detailed, fully-integrated 3D numerical modelling of water and heat flux at the reach scale. All techniques were applied in order to characterize exchange flux between stream and groundwater, hyporheic flow paths and temperature patterns. The study was conducted at a reach-scale section of the lowland Selke River, characterized by distinctive pool riffle…
    Note: kumulative Dissertation , Dissertation Universität Potsdam 2017
    Additional Edition: Erscheint auch als Druck-Ausgabe Munz, Matthias Water flow and heat transport modelling at the interface between river and aquifer Potsdam, 2017
    Language: English
    Keywords: Oberflächenwasser ; Grundwasser ; Hochschulschrift
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  • 10
    UID:
    gbv_1010087622
    Format: 1 Online-Ressource (223 S., 11357 KB) , Diagramme, Illustrationen
    Note: Dissertation Universität Potsdam 2017
    Additional Edition: Erscheint auch als Druck-Ausgabe Schrön, Martin Cosmic-ray neutron sensing and its applications to soil and land surface hydrology München : Verlag Dr. Hut, 2017 ISBN 3843931399
    Additional Edition: ISBN 9783843931397
    Language: English
    Subjects: Engineering
    RVK:
    Keywords: Neutronenstrahlung ; Kosmische Strahlung ; Streuung ; Bodenfeuchte ; Messung ; Hochschulschrift
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