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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of Impact Hammer Rebound to Estimate Rock Drillability (2000)
    Springer
    Rock mechanics and rock engineering 33 (2000), S. 1-13 
    Details
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Summary ¶In this paper, the piston rebound common to both the Schmidt Impact Hammer and down-hole hammer drills has been analyzed and calculated by means of stress wave theory and the energy conservation law. A quantitative relationship between the amount of rebound of the piston and the impact resistance index, or hardness of the rock, has been established. Those analytical results will not only be of benefit in acquiring a deep understanding of the usable range and condition of the Schmidt Impact Hammer, but also provide a definite answer to the feasibility of using the hammer rebound in drills with down-hole hammer tool to carry out a real time measurement of the nature of the formation under the bit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s006030050001
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    Paper (German National Licenses)
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  • 2
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    Suspended sediment and total dissolved solid yield patterns at the headwaters of Urumqi River, northwestern China: a comparison between glacial and non-glacial catchments (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2013-08-03
    Description: In order to understand the differences in the suspended sediment and total dissolved solid (TDS) yield patterns between the glacial and non-glacial catchments at the headwaters of Urumqi River, Northwestern China, water samples were collected from a glacier catchment and an empty cirque catchment within the region, during three melting seasons from 2006 to 2008. These samples were analyzed to estimate suspended sediment and TDS concentrations, fluxes and erosion rates in the two adjoining catchments. There were remarked differences in suspended sediment and TDS yield patterns between the two catchments. Suspended sediment concentrations were controlled mainly by the sediment source, whereas TDS concentrations were primarily related to the hydrologic interaction with soil minerals. Generally, the glacial catchment had much higher suspended sediment and TDS yields, together with higher denudation rates, than the non-glacial catchment. Overall, glacial catchment was mainly dominated by physical denudation process, whereas the non-glacial catchment was jointly influenced by physical and chemical denudation processes. The observed differences in material delivery patterns were mainly controlled by the runoff source and the glacial processes. The melting periods of glacier and snow were typically the most important time for the suspended sediment and TDS yields. Meanwhile, episodic precipitation events could generate disproportionately large yields. Subglacial hydrology dynamics, glaciers pluck and grind processes could affect erodibility, and the large quantities of dust stored on the glacier surface provided additional sources for suspended sediment transport in the glacial catchment. These mechanisms imply that, in response to climate change, the catchment behavior will be modified significantly in this region, in terms of material flux. This article is protected by copyright. All rights reserved.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell
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  • 3
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    Calibrating the Spatiotemporal Root Density Distribution for Macroscopic Water Uptake Models Using Tikhonov Regularization (2018)
    Wiley-Blackwell
    Details
    Publication Date: 2018-02-27
    Description: Macroscopic root water uptake models proportional to a root density distribution function (RDDF) are most commonly used to model water uptake by plants. As the water uptake is difficult and labor-intensive to measure, these models are often calibrated by inverse modeling. Most previous inversion studies assume RDDF to be constant with depth and time or dependent on only depth for simplification. However, under field conditions this function varies with type of soil and root growth and thus changes with both depth and time. This study proposes an inverse method to calibrate both spatially and temporally varying RDDF in unsaturated water flow modeling. To overcome the difficulty imposed by the ill-posedness, the calibration is formulated as an optimization problem in the framework of the Tikhonov regularization theory, adding additional constraint to the objective function. Then the formulated nonlinear optimization problem is numerically solved with an efficient algorithm on the basis of the finite element method. The advantage of our method is that the inverse problem is translated into a Tiknonov regularization functional minimization problem and then solved based on the variational construction, which circumvents the computational complexity in calculating the sensitivity matrix involved in many derivative-based parameter estimation approaches (e.g., Levenberg-Marquardt optimization). Moreover, the proposed method features optimization of RDDF without any prior form, which is applicable to a more general root water uptake model. Numerical examples are performed to illustrate the applicability and effectiveness of the proposed method. Finally, discussions on the stability and extension of this method are presented.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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