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Results 1-6 of 6 (Search time: 0.11 seconds).
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  • The Effects of Timing of Inundation on Soil Physical Quality in the Water‐Level Fluctuation Zone of the Three Gorges Reservoir Region, China

    • Authors: Cui, J.;  Advisor: -;  Participants: Tang, X.; Zhang, W.; Liu, C. (2018)

  • oil samples were taken from depths of 0 to 10, 10 to 20, 20 to 30, and 30 to 40 cm. Soil structural quality was assessed by the visual evaluation of soil structure (VESS) method in situ; mean weight diameter (MWD) and mass fractal dimension (Dm) were measured to represent soil aggregate stability; and the soil water retention curve and computed microtomography (micro‐CT) images were used to show soil pore networks. Our findings show a deterioration of soil structure indicated by a high structural quality (Sq) score in VESS (the higher the Sq score, the worse the soil structural quality) and a decline in soil aggregate stability indicated by low MWD and low Dm in the WLF zone. The data from both the soil water retention curve and micro‐CT images demonstrate a deterioration of soil ph...
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  • X‐ray Micro‐CT: How Soil Pore Space Description Can Be Altered by Image Processing

    • Authors: Smet, S.;  Advisor: -;  Participants: Plougonven, E.; Leonard, A.; Degré, A.; Beckers, E. (2018)

  • The analyses were based on five performance indicators: misclassification error, non‐region uniformity, and relative errors in porosity, conductance, and pore shape. Three levels of pre‐segmentation noise reduction were tested, as well as two levels of post‐segmentation noise reduction. Three segmentation methods were tested (two global and one local). For the local method, the threshold intervals were selected from two concepts: one based on the histogram shape and the other on the image visible‐porosity value. The results indicate that pre‐segmentation noise reduction significantly (p < 0.05) improves segmentation quality, but post‐segmentation noise reduction is detrimental. The results also suggest that global and local methods perform in a similar way when noise reduction is ap...
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  • Noninvasive Imaging of Processes in Natural Porous Media: From Pore to Field Scale

    • Authors: Pohlmeier, A.;  Advisor: -;  Participants: Garré, S.; Roose, T. (2018)

  • Noninvasive, high‐resolution imaging techniques are important for visualizing water flow and transport processes in soils, which are natural porous media. They are a key to understanding effects such as crop production, water resource restoration, CO2 sequestration, or the transport and fate of pollutants. During the last two decades, the development of three‐dimensional imaging techniques such as nuclear magnetic resonance imaging (NMR and MRI), X‐ray computed tomography (CT), and neutron CT has made significant progress possible in the study of soil processes. This special section presents examples of X‐ray CT and NMR from the small‐column scale to the application of portable NMR equipment in the field, along with some important advances in image processing that make it possible t...
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  • Combining X‐ray Computed Tomography and Visible Near‐Infrared Spectroscopy for Prediction of Soil Structural Properties

    • Authors: Katuwal, S.;  Advisor: -;  Participants: Hermansen, C.; Knadel, M.; Moldrup, P.; Greve, M.H.; de Jonge, L.W. (2018)

  • In this study, the potential of using vis‐NIR spectroscopy to predict X‐ray CT derived soil structural properties was investigated. In this study, 127 soil samples from six agricultural fields within Denmark with a wide range of textural properties and organic C (OC) contents were studied. Macroporosity (>1.2 mm in diameter) and CTmatrix (the density of the field‐moist soil matrix devoid of large macropores and stones) were determined from X‐ray CT scans of undisturbed soil cores (19 by 20 cm). Both macroporosity and CTmatix are soil structural properties that affect the degree of preferential transport. Bulk soils from the 127 sampling locations were scanned with a vis‐NIR spectrometer (400–2500 nm). Macroporosity and CTmatrix were statistically predicted with partial least squares...
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  • TopCap: A Tool to Quantify Soil Surface Topology and Subsurface Structure

    • Authors: Garbout, A.;  Advisor: -;  Participants: Sturrock, C.J.; Armenise, E.; Ahn, S.; Simmons, R.W.; Doerr, S.; Ritz, K.; Mooney, S.J. (2018)

  • This provides important information such as how a connected structure might permit solute infiltration or gaseous diffusion through the surface and beyond into the subsurface matrix. A previous limitation to this approach had been the inability to segment and quantify the actual three‐dimensional structural complexity at the surface, rather than a predefined geometrically simplistic volume immediately below it. To overcome this, we formulated TopCap, a novel algorithm that operates with ImageJ as a plugin and automatically captures the actual three‐dimensional surface morphology, segments the pore structure within the acquired volume, and provides a series of incisive morphological measurements of the associated porous architecture. TopCap provides rapid, automated analysis of the i...
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  • Quantitative Analysis of Water Infiltration in Soil Cores Using X‐Ray

    • Authors: Weller, U.;  Advisor: -;  Participants: Leuther, F.; Schlüter, S.; Vogel, H. (2018)

  • X‐ray radiography is a suitable approach to study water dynamics in undisturbed soil. However, beam hardening impairs the deduction of soil moisture changes from X‐ray attenuation, especially when studying infiltration of water into cylindrical soil columns. We developed a calibration protocol to correct for beam hardening effects that enables the quantitative determination of changing average water content in two‐dimensional projections. The method works for a broad range of materials and is easy to implement. Moreover, we studied the drift of X‐ray attenuation values due to the detector latency and eliminated its contribution to the quantitative analysis. Finally we could visualize the dynamics of infiltrating water into undisturbed cylindrical soil samples.
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