Littérature scientifique sur le sujet « Soil surface parameter »
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Articles de revues sur le sujet "Soil surface parameter"
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Schreiner, Simon, Dubravko Culibrk, Michele Bandecchi, Wolfgang Gross et Wolfgang Middelmann. « Soil monitoring for precision farming using hyperspectral remote sensing and soil sensors ». at - Automatisierungstechnik 69, no 4 (1 avril 2021) : 325–35. http://dx.doi.org/10.1515/auto-2020-0042.
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Abstract This work describes an approach to calculate pedological parameter maps using hyperspectral remote sensing and soil sensors. These maps serve as information basis for automated and precise agricultural treatments by tractors and field robots. Soil samples are recorded by a handheld hyperspectral sensor and analyzed in the laboratory for pedological parameters. The transfer of the correlation between these two data sets to aerial hyperspectral images leads to 2D-parameter maps of the soil surface. Additionally, rod-like soil sensors provide local 3D-information of pedological parameters under the soil surface. The goal is to combine the area-covering 2D-parameter maps with the local 3D-information to extrapolate large-scale 3D-parameter maps using AI approaches.
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Dumbrovský, Miroslav, Ivana Kameníčková, Jana Podhrázská, František Pavlík et Veronika Sobotková. « Evaluation of soil conservation technologies from the perspective of selected physical soil properties and infiltration capacity of the soil ». Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 59, no 1 (2011) : 37–48. http://dx.doi.org/10.11118/actaun201159010037.
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This paper evaluates different technologies of soil cultivation (conventional and minimization) in terms of physical properties and water regime of soils, where infiltration of surface water is a major component of subsurface water. Soil physical properties (the current humidity, reduced bulk density, porosity, water retention capacity of soil, pore distribution and soil aeration) is determined from soil samples taken from the organic horizon according to standard methodology. To observe the infiltration characteristics of surface layers of topsoil, the drench method (double ring infiltrometers) was used. For the evaluation of field measurements of infiltration, empirical and physically derived equations by Kostiakov and Philip and the three-parameter Philip-type equation were used. The Philip three-parameter equation provides physical based parameters near the theoretical values, a good estimation of saturated hydraulic conductivity Ks and sorptivity C1. The parameter S of Philip’s equation describes the real value of the sorptivity of the soil. Experimental research work on the experimental plots H. Meziříčko proceeded in the years 2005–2008.
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Marthews, T. R., C. A. Quesada, D. R. Galbraith, Y. Malhi, C. E. Mullins, M. G. Hodnett et I. Dharssi. « High-resolution hydraulic parameter maps for surface soils in tropical South America ». Geoscientific Model Development 7, no 3 (6 mai 2014) : 711–23. http://dx.doi.org/10.5194/gmd-7-711-2014.
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Abstract. Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded data sets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soil profile water movement across the region to 30 cm depth. Optimal hydraulic parameter values are given for the Brooks and Corey, Campbell, van Genuchten–Mualem and van Genuchten–Burdine soil hydraulic models, which are widely used hydraulic sub-models in land surface models. This has been possible through interpolating soil measurements from several sources through the SOTERLAC soil and terrain data base and using the most recent pedotransfer functions (PTFs) derived for South American soils. All soil parameter data layers are provided at 15 arcsec resolution and available for download, this being 20x higher resolution than the best comparable parameter maps available to date. Specific examples are given of the use of PTFs and the importance highlighted of using PTFs that have been locally parameterised and that are not just based on soil texture. We discuss current developments in soil hydraulic modelling and how high-resolution parameter maps such as these can improve the simulation of vegetation development and productivity in land surface models.
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Marthews, T. R., C. A. Quesada, D. R. Galbraith, Y. Malhi, C. E. Mullins, M. G. Hodnett et I. Dharssi. « High-resolution hydraulic parameter maps for surface soils in tropical South America ». Geoscientific Model Development Discussions 6, no 4 (17 décembre 2013) : 6741–74. http://dx.doi.org/10.5194/gmdd-6-6741-2013.
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Abstract. Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded datasets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soil profile water movement across the region to 30 cm depth. Optimal hydraulic parameter values are given for the Brooks and Corey, Campbell, van Genuchten–Mualem and van Genuchten–Burdine soil hydraulic models, which are widely-used hydraulic sub-models in Land Surface Models. This has been possible through interpolating soil measurements from several sources through the SOTERLAC soil and terrain database and using the most recent pedotransfer functions (PTFs) derived for South American soils. All soil parameter data layers are provided at 15 arcsec resolution and available for download, this being 20 × higher resolution than the best comparable parameter maps available to date. Specific examples are given of the use of PTFs and the importance highlighted of using PTFs that have been locally-parameterised and that are not just based on soil texture. Details are provided specifically on how to assemble the ancillary data files required for grid-based vegetation simulation using the Joint UK Land Environment Simulator (JULES). We discuss current developments in soil hydraulic modelling and how high-resolution parameter maps such as these can improve the simulation of vegetation development and productivity in land surface models.
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Mohanty, Binayak P., et Jianting Zhu. « Effective Hydraulic Parameters in Horizontally and Vertically Heterogeneous Soils for Steady-State Land–Atmosphere Interaction ». Journal of Hydrometeorology 8, no 4 (1 août 2007) : 715–29. http://dx.doi.org/10.1175/jhm606.1.
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Abstract In this study, the authors investigate effective soil hydraulic parameter averaging schemes for steady-state flow in heterogeneous shallow subsurfaces useful to land–atmosphere interaction modeling. “Effective” soil hydraulic parameters of the heterogeneous shallow subsurface are obtained by conceptualizing the soil as an equivalent homogeneous medium. It requires that the effective homogeneous soil discharges the same mean surface moisture flux (evaporation or infiltration) as the heterogeneous media. Using the simple Gardner unsaturated hydraulic conductivity function, the authors derive the effective value for the saturated hydraulic conductivity Ks or the shape factor α under various hydrologic scenarios and input hydraulic parameter statistics. Assuming one-dimensional vertical moisture movement in the shallow unsaturated soils, both scenarios of horizontal (across the surface landscape) and vertical (across the soil profile) heterogeneities are investigated. The effects of hydraulic parameter statistics, surface boundary conditions, domain scales, and fractal dimensions in case of nested soil hydraulic property structure are addressed. Results show that the effective parameters are dictated more by the α heterogeneity for the evaporation scenario and mainly by Ks variability for the infiltration scenario. Also, heterogeneity orientation (horizontal or vertical) of soil hydraulic parameters impacts the effective parameters. In general, an increase in both the fractal dimension and the domain scale enhances the heterogeneous effects of the parameter fields on the effective parameters. The impact of the domain scale on the effective hydraulic parameters is more significant as the fractal dimension increases.
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Fang, Xu, Anna Muntwyler, Pascal Schneider, Iso Christl, Peng Wang, Fang-Jie Zhao et Ruben Kretzschmar. « Exploring Key Soil Parameters Relevant to Arsenic and Cadmium Accumulation in Rice Grain in Southern China ». Soil Systems 6, no 2 (14 avril 2022) : 36. http://dx.doi.org/10.3390/soilsystems6020036.
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Paddy soils in some areas of southern China are contaminated by arsenic (As) and cadmium (Cd), threatening human health via the consumption of As- and/or Cd-tainted rice. To date, a quantitative understanding of how soil characteristics control As and Cd accumulation in rice grains under field conditions is still deficient. Based on 31 paired soil-grain samples collected in southern China, we statistically explored which soil parameter or parameter combination from various soil analyses best estimates As and Cd in rice. We found that CaCl2 extraction of field-moist soil collected at rice harvest provided the best estimation (R2adj = 0.47–0.60) for grain Cd followed by dry soil CaCl2 extraction (R2adj = 0.38–0.49), where CaCl2 extractable Cd from moist or dry soil was the dominant soil parameter. Compared to soil totals, parameters from neither dry soil ascorbate-citrate extraction nor anoxic soil incubation improved model performance for grain As (R2adj ≤ 0.44), despite their closer relevance to soil redox conditions during plant As uptake. A key role of soil-available sulfur in controlling grain As was suggested by our models. Our approach and results may help develop potential soil amendment strategies for decreasing As and/or Cd accumulation in soils.
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Nie, S., J. Zhu et Y. Luo. « Simultaneous estimation of land surface scheme states and parameters using the ensemble Kalman filter : idealized twin experiments ». Hydrology and Earth System Sciences Discussions 8, no 1 (28 janvier 2011) : 1433–68. http://dx.doi.org/10.5194/hessd-8-1433-2011.
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Abstract. The performance of the ensemble Kalman filter (EnKF) in soil moisture assimilation applications is investigated in the context of simultaneous state-parameter estimation in the presence of uncertainties from model parameters, initial soil moisture condition and atmospheric forcing. A physically-based land surface model is used for this purpose. Using a series of idealized twin experiments, model generated near-surface soil moisture observations are assimilated to estimate soil moisture state and three hydraulic parameters (the saturated hydraulic conductivity, the saturated soil moisture suction and a soil texture empirical parameter) in the model. The single imperfect parameter can be successfully estimated using the EnKF. Results show that all the three estimated parameters converge toward their respective true values, while the root mean squared errors (RMSE) of soil moisture associated with these parameters is on average reduced by 54% and 53% comparing with the non-parameter-estimation benchmark RMSE for near-surface layer and root zone layer, respectively. The performance of simultaneous multi-parameter estimation is significant degraded, mainly because the inherent balance relationship of these parameters is broken and the degree of freedom increases in assimilation processes. By introducing constraints between estimated parameters, the performance of the constraint-based simultaneous multi-parameter estimations are as good as that of single-parameter cases even assimilating temporal-sparse observations. In terms of the relative root mean squared error (RRE), the constraint-based estimation cases can achieve 36% to 53% in near-surface layer and 25% to 50% in root zone layer for different assimilation intervals ranging from 1-day to 40-days. This result suggests that the greatest advantage of this method can be displayed with a proper temporal-sparse assimilation interval of 10-days as actual measurement interval of conventional in situ soil moisture observations. As these obtained constraints are mostly in statistical sense, this constraint-based simultaneous state-parameter estimation scheme is supposed to be suitable for other land surface models in soil moisture assimilation applications.
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ZHENG, Xingming, Kai ZHAO et Xiaojie LI. « Accuracy Analysis of Agriculture Soil Surface Roughness Parameter ». Journal of Geo-information Science 15, no 5 (2013) : 752. http://dx.doi.org/10.3724/sp.j.1047.2013.00752.
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Lehrsch, G. A., F. D. Whisler et M. J. M. Römkens. « Selection of a Parameter Describing Soil Surface Roughness ». Soil Science Society of America Journal 52, no 5 (septembre 1988) : 1439–45. http://dx.doi.org/10.2136/sssaj1988.03615995005200050044x.
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Nie, S., J. Zhu et Y. Luo. « Simultaneous estimation of land surface scheme states and parameters using the ensemble Kalman filter : identical twin experiments ». Hydrology and Earth System Sciences 15, no 8 (3 août 2011) : 2437–57. http://dx.doi.org/10.5194/hess-15-2437-2011.
Texte intégralRésumé :
Abstract. The performance of the ensemble Kalman filter (EnKF) in soil moisture assimilation applications is investigated in the context of simultaneous state-parameter estimation in the presence of uncertainties from model parameters, soil moisture initial condition and atmospheric forcing. A physically based land surface model is used for this purpose. Using a series of identical twin experiments in two kinds of initial parameter distribution (IPD) scenarios, the narrow IPD (NIPD) scenario and the wide IPD (WIPD) scenario, model-generated near surface soil moisture observations are assimilated to estimate soil moisture state and three hydraulic parameters (the saturated hydraulic conductivity, the saturated soil moisture suction and a soil texture empirical parameter) in the model. The estimation of single imperfect parameter is successful with the ensemble mean value of all three estimated parameters converging to their true values respectively in both NIPD and WIPD scenarios. Increasing the number of imperfect parameters leads to a decline in the estimation performance. A wide initial distribution of estimated parameters can produce improved simultaneous multi-parameter estimation performances compared to that of the NIPD scenario. However, when the number of estimated parameters increased to three, not all parameters were estimated successfully for both NIPD and WIPD scenarios. By introducing constraints between estimated hydraulic parameters, the performance of the constrained three-parameter estimation was successful, even if temporally sparse observations were available for assimilation. The constrained estimation method can reduce RMSE much more in soil moisture forecasting compared to the non-constrained estimation method and traditional non-parameter-estimation assimilation method. The benefit of this method in estimating all imperfect parameters simultaneously can be fully demonstrated when the corresponding non-constrained estimation method displays a relatively poor parameter estimation performance. Because all these constraints between parameters were obtained in a statistical sense, this constrained state-parameter estimation scheme is likely suitable for other land surface models even with more imperfect parameters estimated in soil moisture assimilation applications.
Thèses sur le sujet "Soil surface parameter"
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Ben, Khadhra Kais. « Surface Parameter Estimation using Bistatic Polarimetric X-band Measurements ». Doctoral thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200801439.
Texte intégralRésumé :
To date only very few bistatic measurements (airborne or in controlled laboratories) have been reported. Therefore most of the current remote sensing methods are still focused on monostatic (backscatter) measurements. These methods, based on theoretical, empirical or semi-empirical models, enable the estimation of soil roughness and the soil humidity (dielectric constant). For the bistatic case only theoretical methods have been developed and tested with monostatic data. Hence, there still remains a vital need to gain of experience and knowledge about bistatic methods and data. The main purpose of this thesis is to estimate the soil moisture and the soil roughness by using full polarimetric bistatic measurements. In the experimental part, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different statistical roughness and different moistures controlled by a TDR (Time Domain Reflectivity) system. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, bistatic surface scattering analyses of the calibrated data set were discussed. Then, the specular algorithm was used to estimate the soil moisture of two surface roughnesses (rough and smooth) has been reported. A new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness was presented. Also, the sensitivity of phase and reflectivity with regard to moisture variation in the specular direction was evaluated. Finally, the first results and validations of bistatic radar polarimetry for the specular case of surface scattering have been introducedAktuell sind nur sehr wenige Messungen mit bistatischem Radar durchgeführt worden, sei es von Flugzeuggetragenen Systemen oder durch spezielle Aufbauten im Labor. Deshalb basieren die meisten der bekannten Methoden zur Fernerkundung mit Radar auf monostatis-chen Messungen der Rückstreuung des Radarsignals. Diese Methoden, die auf theoretischen, empirischen oder halb-empirischen Modellen basieren, ermöglichen die Schätzung der Oberfächenrauhigkeit und die Bodenfeuchtigkeit (Dielektrizitätskonstante). Im bistatischen Fall wurden bisher nur theoretische Modelle entworfen, die mittels monostatischer Messungen getestet wurden. Aus diesem Grund ist es von großer Bedeutung, Erfahrung und Wissen über die physikalischen Effekte in bistatischen Konfigurationen zu sammeln. Das Hauptziel der vorliegenden Dissertation ist es, anhand vollpolarimetrischer, bistatischer Radarmessungen die Oberfächenrauhigkeit und Bodenfeuchtigkeit zu bestimmen. Im experimentellen Teil der Arbeit werden die Ergebnisse bistatischer Messungen präsentiert, die in der Bistatic Measurement Facility (BMF) des DLR Oberpfaffenhofen aufgenommen wurden. Die Datensätze umfassen Messungen von Böden unterschiedlicher statistischer Rauhigkeit und Feuchtigkeit, die mittels eines Time Domain Reflectivity (TDR) Systems bestimmt werden. Zur Kalibration des BMF wurde die Isolated Antenna Calibration Technique (IACT) verwendet und anhand der Messung der Reflektivität von Wasser überprüft. Im zweiten Teil der vorliegenden Arbeit wird anhand der kalibrierten Daten eine Analyse der Oberflächenstreuung in bistatischen Konfigurationen vorgenommen. Im Anschluss daran wird mittels des Specular Algorithm eine Schätzung der Bodenfeuchte zweier Proben unter- schiedlicher Rauhigkeit (rau und fein) durchgeführt. Ein neues Verfahren zur Schätzung der Oberfächenrauhigkeit, das auf dem kohärenten Term der Integral Equation Method (IEM) basiert, wurde eingeführt. Daneben wird die Empfindlichkeit der Phase sowie der Reflektivität des vorwärtsgestreuten Signals gegenüber Veränderungen der Bodenfeuchtigkeit analysiert. Schließlich werden erste Ergebnisse und Validierungen bistatischer Radarpolarimetrie für den Fall der Vorwärtsstreuung präsentiert
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Ben, Khadhra Kais. « Surface Parameter Estimation using Bistatic Polarimetric X-band Measurements ». Doctoral thesis, Deutsches Zentrum für Luft- und Raumfahrt e.V. in der Helmholtz-Gemeinschaft, 2007. https://monarch.qucosa.de/id/qucosa%3A18987.
Texte intégralRésumé :
To date only very few bistatic measurements (airborne or in controlled laboratories) have been reported. Therefore most of the current remote sensing methods are still focused on monostatic (backscatter) measurements. These methods, based on theoretical, empirical or semi-empirical models, enable the estimation of soil roughness and the soil humidity (dielectric constant). For the bistatic case only theoretical methods have been developed and tested with monostatic data. Hence, there still remains a vital need to gain of experience and knowledge about bistatic methods and data. The main purpose of this thesis is to estimate the soil moisture and the soil roughness by using full polarimetric bistatic measurements. In the experimental part, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different statistical roughness and different moistures controlled by a TDR (Time Domain Reflectivity) system. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, bistatic surface scattering analyses of the calibrated data set were discussed. Then, the specular algorithm was used to estimate the soil moisture of two surface roughnesses (rough and smooth) has been reported. A new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness was presented. Also, the sensitivity of phase and reflectivity with regard to moisture variation in the specular direction was evaluated. Finally, the first results and validations of bistatic radar polarimetry for the specular case of surface scattering have been introduced.Aktuell sind nur sehr wenige Messungen mit bistatischem Radar durchgeführt worden, sei es von Flugzeuggetragenen Systemen oder durch spezielle Aufbauten im Labor. Deshalb basieren die meisten der bekannten Methoden zur Fernerkundung mit Radar auf monostatis-chen Messungen der Rückstreuung des Radarsignals. Diese Methoden, die auf theoretischen, empirischen oder halb-empirischen Modellen basieren, ermöglichen die Schätzung der Oberfächenrauhigkeit und die Bodenfeuchtigkeit (Dielektrizitätskonstante). Im bistatischen Fall wurden bisher nur theoretische Modelle entworfen, die mittels monostatischer Messungen getestet wurden. Aus diesem Grund ist es von großer Bedeutung, Erfahrung und Wissen über die physikalischen Effekte in bistatischen Konfigurationen zu sammeln. Das Hauptziel der vorliegenden Dissertation ist es, anhand vollpolarimetrischer, bistatischer Radarmessungen die Oberfächenrauhigkeit und Bodenfeuchtigkeit zu bestimmen. Im experimentellen Teil der Arbeit werden die Ergebnisse bistatischer Messungen präsentiert, die in der Bistatic Measurement Facility (BMF) des DLR Oberpfaffenhofen aufgenommen wurden. Die Datensätze umfassen Messungen von Böden unterschiedlicher statistischer Rauhigkeit und Feuchtigkeit, die mittels eines Time Domain Reflectivity (TDR) Systems bestimmt werden. Zur Kalibration des BMF wurde die Isolated Antenna Calibration Technique (IACT) verwendet und anhand der Messung der Reflektivität von Wasser überprüft. Im zweiten Teil der vorliegenden Arbeit wird anhand der kalibrierten Daten eine Analyse der Oberflächenstreuung in bistatischen Konfigurationen vorgenommen. Im Anschluss daran wird mittels des Specular Algorithm eine Schätzung der Bodenfeuchte zweier Proben unter- schiedlicher Rauhigkeit (rau und fein) durchgeführt. Ein neues Verfahren zur Schätzung der Oberfächenrauhigkeit, das auf dem kohärenten Term der Integral Equation Method (IEM) basiert, wurde eingeführt. Daneben wird die Empfindlichkeit der Phase sowie der Reflektivität des vorwärtsgestreuten Signals gegenüber Veränderungen der Bodenfeuchtigkeit analysiert. Schließlich werden erste Ergebnisse und Validierungen bistatischer Radarpolarimetrie für den Fall der Vorwärtsstreuung präsentiert.
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Gómez, Jesús Emilio. « Development of an extended hyperbolic model for concrete-to-soil interfaces ». Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28375.
Texte intégralRésumé :
Placement and compaction of the backfill behind an earth retaining wall may induce a vertical shear force at the soil-to-wall interface. This vertical shear force, or downdrag, is beneficial for the stability of the structure. A significant reduction in construction costs may result if the downdrag is accounted for during design. This potential reduction in costs is particularly interesting in the case of U.S. Army Corps of Engineers lock walls.
A simplified procedure is available in the literature for estimating the downdrag force developed at the wall-backfill interface during backfilling of a retaining wall. However, finite element analyses of typical U.S. Army Corps of Engineers lock walls have shown that the magnitude of the downdrag force may decrease during operation of the lock with a rise in the water table in the backfill. They have also shown that pre- and post-construction stress paths followed by interface elements often involve simultaneous changes in shear and normal stresses and unloading-reloading. The hyperbolic formulation for interfaces (Clough and Duncan 1971) is accurate for modeling the interface response in the primary loading stage under constant normal stress. However, it has not been extended to model simultaneous changes in shear and normal stresses or unloading-reloading of the interface.
The purpose of this research was to develop an interface model capable of giving accurate predictions of the interface response under field loading conditions, and to implement this model in a finite element program. In order to develop the necessary experimental data, a series of tests were performed on interfaces between concrete and two different types of sand. The tests included initial loading, staged shear, unloading-reloading, and shearing along complex stress paths.
An extended hyperbolic model for interfaces was developed based on the results of the tests. The model is based on Clough and Duncan (1971) hyperbolic formulation, which has been extended to model the interface response to a variety of stress paths. Comparisons between model calculations and tests results showed that the model provides accurate estimates of the response of interfaces along complex stress paths. The extended hyperbolic model was implemented in the finite element program SOILSTRUCT-ALPHA, used by the U.S. Army Corps of Engineers for analyses of lock walls.
A pilot-scale test was performed in the Instrumented Retaining Wall (IRW) at Virginia Tech that simulated construction and operation of a lock wall. SOILSTRUCT-ALPHA analyses of the IRW provided accurate estimates of the downdrag magnitude throughout inundation of the backfill. It is concluded that the extended hyperbolic model as implemented in SOILSTRUCT-ALPHA is adequate for routine analyses of lock walls.Ph. D.
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Aubert, Maëlle. « Caractérisation de l’état de surface des sols nus agricoles par imagerie radar TerraSAR-X ». Electronic Thesis or Diss., Paris, AgroParisTech, 2012. http://www.theses.fr/2012AGPT0047.
Texte intégralRésumé :
Dans un contexte de développement durable, la gestion des sols et des ressources en eau est un enjeu primordial non seulement d’un point de vue environnemental mais aussi socio-économique. L’humidité, la rugosité, la composition et la structure du sol sont des variables clés pour la compréhension et la modélisation des catastrophes naturelles telles que l’érosion, la sécheresse ou les inondations. Pour des sols nus agricoles (très propices au ruissellement), de nombreuses études ont déjà montré le potentiel des données RADAR acquises en bande C pour la cartographie de l'humidité et la rugosité du sol. Cependant l’application de ces méthodes dans un cadre opérationnel était limitée.Dans ce contexte, les travaux de cette thèse présentent un premier volet sur l’analyse de la sensibilité aux états de surface (EDS) du sol du signal en bande X du capteur TerraSAR-X à très haute résolution spatiale et temporelle. Différentes configurations TerraSAR-X ont été analysées et les résultats ont permis de définir les configurations instrumentales optimales pour caractériser chaque paramètre d’EDS du sol. La comparaison de la sensibilité du capteur TerraSAR-X à celle des capteurs en bande C montre que le capteur TerraSAR-X est sans conteste le plus adapté pour estimer et cartographier l’humidité du sol à des échelles fines (50 m²).Le second volet était de développer une méthode permettant d’estimer et de cartographier l’humidité des sols nus agricoles. Dans ce but, les méthodes d'inversion généralement utilisées en bande C ont été testées sur les données en bande X. La précision sur les estimations d’humidité issues de l'algorithme d’inversion du signal TerraSAR-X a été déterminée et l’applicabilité de la méthode sur de nombreux sites d'étude a été testée avec succès. Une chaine de traitements cartographiques allant de la détection des sols nus à l’estimation de l’humidité et ne nécessitant qu’une seule image TerraSAR-X a été développée. Cette chaine innovante de traitements cartographiques « automatique et autonome » devrait permettre d’utiliser les données TerraSAR-X pour cartographier l’humidité du sol en mode opérationnelIn the context of sustainable development, soil and water resources management is a key issue from not only the environmental point of view, but also from a socioeconomic perspective. Soil moisture, roughness, composition, and slaking crusts are some key variables used to understand and model natural hazards, such as erosion, drought and floods. For agricultural bare soils (most subject to runoff), numerous studies have already shown the potential of C-band RADAR data for the mapping of soil moisture and roughness. However, the application of these methods in operational settings remained limited.In this context, the first objective of this thesis was to analyse the sensitivity of X-band TerraSAR-X sensors to soil surface characteristics (SSC) at high spatial and temporal resolutions. Different TerraSAR-X configurations were evaluated and results were used to define the optimal instrumental configuration for the characterization of each SSC parameter. The comparison of TerraSAR-X sensor sensitivity with equivalent levels recorded with the C-band sensor showed that the TerraSAR-X sensor is undoubtedly the most suitable of the two when estimating and mapping soil moisture at a fine scale (50 m²).The second objective of this work was to develop a method to estimate and map soil moisture levels of agricultural bare soil. To achieve this goal, methods that are commonly used to retrieve soil moisture from C-band, have been tested on X-band data. The accuracy of soil moisture estimations using an empirical algorithm was determined, and validated successfully over numerous study sites. A mapping process based uniquely on TerraSAR-X data, both for bare soil detection and for the estimation of soil moisture content, was developed. This innovative chain of « automatic and autonomous» mapping processing steps should enable the utilization of TerraSAR-X data for the mapping of soil moisture levels in operational conditions
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AUTRET, MARYLINE. « Etude theorique de la sensibilite du signal retrodiffuse en hyperfrequence aux parametres caracteristiques d'un sol agricole : humidite et rugosite ». Paris 7, 1987. http://www.theses.fr/1987PA077269.
Texte intégralRésumé :
Une etude theorique utilisant un modele de simulation, base sur l'approximation scalaire des champs, a permis d'estimer la sensibilite du coefficient de diffusion a une variation relative des parametres de surface, en fonction des caracteristiques radar. Les resultats ont montre que la configuration, jugee optimale, pour une mesure de l'humidite de surface necessite l'utilisation simultanee de deux polarisations (hh et vv), un angle d'incidence eleve (35**(o)) et une frequence de la bande x
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Weber, Rodrigo Carreira. « Comportamiento de un suelo compactado bajo un estado generalizado de tensiones ». Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/669679.
Texte intégralRésumé :
This thesis analyzes the hydro-mechanical behavior under a generalized stress state of a compacted mixture of sand (30%) and clayey (70%) at a low density. The experimental study focuses on the analysis of shear strength at different stress paths and at different initial suction values (as-compacted), and the response to collapse due to saturation. For the investigation a conventional triaxial equipment and a hollow cylinder apparatus with automatic control of internal and external chamber pressures, back pressure and axial stress and torque were used. The equipment was not adapted for the measurement of deformations of unsaturated soils, being necessary a calibration of the volumes of the chambers and the relation with the change of volume of the sample. Preliminary tests were performed to better understand the studied of the mixture, like compaction tests, retention curve, oedometer compressibility tests and direct shear and obtain strength, suction and permeability parameters. The shear strength was analyzed through tests carried out in conventional triaxial equipment and in hollow cylinder apparatus, with different stress paths, changing the stress state, valued by parameter b (or Lode angle) and different compaction water content. Low deformation cyclic tests were performed to obtain the shear module in hollow cylinder, using two types of soil, the sand / clayey mixture and a MX-80 bentonite, seeking to analyze the possibilities of testing with the equipment and compare it to the results obtained in other. The results showed that the module obtained in other equipment is greater than those found in hollow cylinder, approaching with increasing deformations, behavior observed for both materials. The collapse tests were performed with constant mean stress (p= 200kPa), different values of deviator stress (q= 10, 75, 185kPa) and different intermediate stress values (b= 0, 0,5, 0,8). The results of the shear strength allowed to define the variation of the critical state line with the Lode angle and the matric suction. Different yield surface models were used for isotropic and anisotropic surface, to verify the rotation of the surface and observe the presence of anisotropic behavior. In all models the change in the critical state line due to the Lode angle was considered. The yield surfaces adjusted well to the experimental results, considering the inclination of the surface and the dependence of the Lode angle. It was observed that the size of the yield surface depends on the suction and the state of tension applied and, a relationship of the parameters was proposed, in order to normalize the yield surface. It was noted that the surface has an inclination due to static compaction, which can be obtained by compaction stresses. It was also observed that this inclination may change depending on the value of b applied to the stress path. Saturation tests under generalized load were analyzed using the BBM model (Barcelona Basic Model) and showed a greater dependence on the magnitude of the deviator stress applied than on the variation of parameter b, and presented a good relationship with the total deformation values. An empirical equation was proposed to estimate the potential for collapse for the different values of b in hollow cylinder, triaxial and oedometer tests.Esta tesis analiza el comportamiento hidro-mecánico bajo un estado generalizado de tensiones de una mezcla de arena (30%) y arcilla (70%) compactada a una baja densidad. El estudio experimental se centra en el análisis de la resistencia al corte a diferentes trayectorias tensionales a diferentes valores de succión inicial (post compactación) y, a la respuesta al colapso debido la saturación. Para la investigación, se utilizó un equipo triaxial convencional y un equipo de cilindro hueco con control automático de las presiones de cámara interna y externa, de cola y de tensión axial y torque. El equipo no estaba adaptado para la medición de deformaciones de suelos no saturados, siendo necesario una calibración de los volúmenes de las cámaras y la relación con el cambio de volumen de la muestra. Se realizaron ensayos preliminares de compactación, curva de retención, ensayos de compresibilidad edométrica y corte directo, para conocer mejor la mezcla estudiada y obtener parámetros de resistencia, succión y permeabilidad. La resistencia al corte fue analizada a través de ensayos ejecutados en equipo triaxial convencional y en un equipo de cilindro hueco, con diferentes trayectorias tensionales y variando el estado de tensiones, valorado por el parámetro b (o ángulo de Lode) y a diferentes humedades de compactación. Se realizaron ensayos de deformación cíclica a baja deformación para la obtención del módulo de corte en cilindro hueco, utilizando dos tipos de suelo, la mezcla arena/arcilla y una bentonita MX-80, buscando analizar las diferentes posibilidades de ensayos con el equipo y compararlo a los resultados obtenidos en otros equipos. Los resultados mostraron que el módulo obtenido en otros equipos es mayor inicialmente que los encontrados en cilindro hueco, acercándose con el aumento de las deformaciones, comportamiento observado para ambos materiales. Los ensayos de saturación fueron realizados con tensión media constante (p=200kPa), diferentes valores de tensión desviadora (10, 75, 185kPa) y diferentes valores de b (0, 0.5, 0.8). Los resultados de los ensayos de resistencia al corte permitieron definir la variación de la línea de estado crítico con el ángulo de Lode y la succión matricial. Se utilizaron diferentes modelos para la superficie de fluencia, isótropa y anisótropa, para analizar el comportamiento del material y observar la presencia de un comportamiento anisótropo. En todos los modelos se consideró el cambio en la línea de estado crítico debido al ángulo de Lode. Las superficies de fluencia se ajustaron bien a los resultados experimentales, considerando la inclinación de la superficie y la dependencia del ángulo de Lode. Se observó que el tamaño de la superficie de fluencia depende de la succión y del estado de tensión aplicado y, se propuso una relación de los parámetros, a fin de normalizar las superficies de fluencia. Se notó que la superficie presenta una inclinación debido la compactación estática, la cual puede ser obtenida por las tensiones de compactación. También se observó que esta inclinación puede sufrir cambios dependiendo del valor de b aplicado a la trayectoria de tensión. Los ensayos de saturación bajo carga generalizada fueron analizados utilizando el modelo BBM (Barcelona Basic Model) y mostraron una dependencia mayor de la magnitud de la tensión desviadora aplicada que de la variación del parámetro b, y presentó buena relación con los valores totales de deformación. Se propuso una ecuación empírica para estimar el potencial de colapso para los diferentes valores de b en ensayos en cilindro hueco, triaxial y edómetro.
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Luke, Catherine M. « Modelling aspects of land-atmosphere interaction : thermal instability in peatland soils and land parameter estimation through data assimilation ». Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3229.
Texte intégralRésumé :
The land (or ‘terrestrial’) biosphere strongly influences the exchange of carbon, energy and water between the land surface and the atmosphere. The size of the land carbon store and the magnitude of the interannual variability of the carbon exchange make models of the land surface a vital component in climate models. This thesis addresses two aspects of land surface modelling: soil respiration and phenology modelling, using different techniques with the goal of improving model representation of land-atmosphere interaction. The release of heat associated with soil respiration is neglected in the vast majority of large-scale models but may be critically important under certain circumstances. In this thesis, the effect of this heat release is considered in two ways. Firstly, a deliberately simple model for soil temperature and soil carbon, including biological heating, is constructed to investigate the effect of thermal energy generated by microbial respiration on soil temperature and soil carbon stocks, specifically in organic soils. Secondly, the mechanism for biological self-heating is implemented in the Joint UK Land Environment Simulator (JULES), in order to investigate the impacts of the extra feedback in a complex model. With the intention of improving estimates of the parameters governing modelled land surface processes, a data assimilation system based on the JULES land surface model is presented. The ADJULES data assimilation system uses information from the derivative of JULES (or adjoint) to search for a locally optimum parameter set by calibrating against observations. In this thesis, ADJULES is used with satellite-derived vegetation indices to improve the modelling of phenology in JULES.
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Sahebi, Mahmod Reza. « Understanding microwave backscattering of bare soils by using the inversion of surface parameters, neural networks and genetic algorithm ». Thèse, Université de Sherbrooke, 2003. http://savoirs.usherbrooke.ca/handle/11143/2736.
Texte intégralRésumé :
Estimates of the physical parameters of the soil surface, namely moisture content and surface roughness, are important for hydrological and agricultural studies, as they appear to be the two major parameters for runoff forecasting in an agricultural watershed. Radar has high potentiality for the remote measurement of soil surface parameters. In particular, the investigation of the radar backscattering response of bare soil surfaces is an important issue in remote sensing because of its capacity for retrieving the desired physical parameters of the surface. The objective of this study is to formulate and to constrain a methodology for solving the inverse problem for the operational retrieval of soil surface roughness and moisture. To separate the effects of the different parameters on the measured signal over complex areas, multi-technique concepts (multi-polarization, multi-angular, multi-sensor, multi-frequency, and multi-temporal) are the main solution. In this work, based on a simulation study, three different configurations, multi-polarization, multi-frequency and multi-angular, are compared to obtain the best configuration for estimating surface parameters and the multi-angular configuration gives the best results. Based on these results, this study was continued according to five different phases: (1) A new index, the NBRI (Normalized radar Backscatter soil Roughness Index), using the multi-angular approach was presented. This index can estimate and classify surface roughness in agricultural fields using two radar images with different incidence angles. (2) A new linear empirical model to estimate soil surface moisture using RADARSAT-1 data was proposed. This model can provide soil moisture with reduced errors of estimation compared to other linear models. (3) Inversion of the surface parameters using nonlinear classical methods. In this case, the Newton-Raphson method, an iterative numerical method, was used in the retrieval algorithm to solve the inverse problem. (4) In this phase, the neural network technique, with a dynamic learning method, was applied to invert the soil surface parameters from the radar data. The results were obtained through performance testing on two different input schemes (one and two data series) and two different databases (theoretical and empirical). The advantage of the multi-angular set with measured data is apparent. These results are the best in this study. (5) Finally, a novel genetic algorithm (GA) was developed to retrieve soil surface parameters. In this study, it is shown that the genetic algorithms, as an optimization technique, can estimate simultaneously soil moisture and surface roughness from only one radar image.
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Costa, Roner Ferreira da. « Estudo de sensibilidade do modelo Brams variáveis dos parâmetros de superfície do Nordeste do Brasil ». reponame:Repositório Institucional da UFC, 2007. http://www.repositorio.ufc.br/handle/riufc/12542.
Texte intégralRésumé :
COSTA, Roner Ferreira da. Estudo de sensibilidade do modelo Brams variáveis dos parâmetros de superfície do Nordeste do Brasil. 2007. 76 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2007.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-05-29T22:10:07Z No. of bitstreams: 1 2007_dis_rfcosta.pdf: 970792 bytes, checksum: cb8cda8b3f31847a5d98d052c2c5ac87 (MD5)
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In this work a numeric experiment was accomplished with the model BRAMS (Brazilian Regional Atmospheric Modeling System) with the purpose of studying the changes in the surface variables due to the variations of the surface parameters as soil moisture and the vegetation class in the Northeast of Brazil which are input in BRAMS. They were made three simulations, the first (simulation control) it was initialized with the standard files of the own model, the second simulation was maintained the class of vegetation pattern (Deciduous shrub) and just altering the soil moisture and the third simulation alters the vegetation for semi-desert besides reducing the humidity of the soil. Also a validation of the model was accomplished with a soil humidity made calculations starting from observed data of precipitation. It is verified that the humidity of the soil and the vegetation have a strong influences on the climate of the Northeast area of Brazil; however it is not very significant in the weather forecast.
Neste trabalho foi realizado um experimento numérico com o modelo BRAMS (Brazilian Regional Atmospheric Modeling System) com a finalidade de estudar as mudanças verificadas nas variáveis de superfície devido às variações dos parâmetros de superfície tais como, umidade do solo e a classe de vegetação no Nordeste do Brasil que alimentam o BRAMS. Foram feitas três simulações, a primeira (simulação controle) foi inicializadas com os arquivos padrões do próprio modelo, a segunda simulação foi mantido a classe de vegetação padrão (Deciduous shrub) alterando apenas a umidade do solo e a terceira simulação altera a vegetação para semi-deserto além de reduzir a umidade do solo. Também foi realizada uma validação do modelo com uma umidade de solo calculada a partir de dados observados de precipitação. Verifica-se que a umidade do solo e a vegetação têm uma forte influência sobre o clima da região Nordeste do Brasil, porém não é muito significativa na previsão do tempo.
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Park, So Jeong. « Propriétés électriques et modélisation des dispositifs MOS avanvés : dispositif FD-SOI, transistors sans jonctions (JLT) et transistor à couche mince à semi-conducteur d'oxyde amorphe ». Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00954637.
Texte intégralRésumé :
Selon la feuille de route des industriels de la microélectronique (ITRS), la dimension critiqueminimum des MOSFET en 2026 ne devrait être que de 6 nm [1]. La miniaturisation du CMOS reposeessentiellement sur deux approches, à savoir la réduction des dimensions géométriques physiques etdes dimensions équivalentes. La réduction géométrique des dimensions conduit à la diminution desdimensions critiques selon la " loi " de Moore, qui définit les tendances de l'industrie dessemiconducteurs. Comme la taille des dispositifs est réduite de façon importante, davantage d'effortssont consentis pour maintenir les performances des composants en dépit des effets de canaux courts,des fluctuations induites par le nombre de dopants.... [2-4]. D'autre part, la réduction des dimensionséquivalentes devient de plus en plus importante de nos jours et de nouvelles solutions pour laminiaturisation reposant sur la conception et les procédés technologiques sont nécessaires. Pour cela,des solutions nouvelles sont nécessaires, en termes de matériaux, d'architectures de composants et detechnologies, afin d'atteindre les critères requis pour la faible consommation et les nouvellesfonctionnalités pour les composants futurs ("More than Moore" et "Beyond CMOS"). A titred'exemple, les transistors à film mince (TFT) sont des dispositifs prometteurs pour les circuitsélectroniques flexibles et transparents.
Livres sur le sujet "Soil surface parameter"
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Zydroń, Tymoteusz. Wpływ systemów korzeniowych wybranych gatunków drzew na przyrost wytrzymałości gruntu na ścinanie. Publishing House of the University of Agriculture in Krakow, 2019. http://dx.doi.org/10.15576/978-83-66602-46-5.
Texte intégralRésumé :
The aim of the paper was to determine the influence of root systems of chosen tree species found in the Polish Flysch Carpathians on the increase of soil shear strength (root cohesion) in terms of slope stability. The paper's goal was achieved through comprehensive tests on root systems of eight relatively common in the Polish Flysch Carpathians tree species. The tests that were carried out included field work, laboratory work and analytical calculations. As part of the field work, the root area ratio (A IA) of the roots was determined using the method of profiling the walls of the trench at a distance of about 1.0 m from the tree trunk. The width of the. trenches was about 1.0 m, and their depth depended on the ground conditions and ranged from 0.6 to 1.0 m below the ground level. After preparing the walls of the trench, the profile was divided into vertical layers with a height of 0.1 m, within which root diameters were measured. Roots with diameters from 1 to 10 mm were taken into consideration in root area ratio calculations in accordance with the generally accepted methodology for this type of tests. These measurements were made in Biegnik (silver fir), Ropica Polska (silver birch, black locust) and Szymbark (silver birch, European beech, European hornbeam, silver fir, sycamore maple, Scots pine, European spruce) located near Gorlice (The Low Beskids) in areas with unplanned forest management. In case of each tested tree species the samples of roots were taken, transported to the laboratory and then saturated with water for at least one day. Before testing the samples were obtained from the water and stretched in a. tensile testing machine in order to determine their tensile strength and flexibility. In general, over 2200 root samples were tested. The results of tests on root area ratio of root systems and their tensile strength were used to determine the value of increase in shear strength of the soils, called root cohesion. To this purpose a classic Wu-Waldron calculation model was used as well as two types of bundle models, the so called static model (Fiber Bundle Model — FIRM, FBM2, FBM3) and the deformation model (Root Bundle Model— RBM1, RBM2, mRBM1) that differ in terms of the assumptions concerning the way the tensile force is distributed to the roots as well as the range of parameters taken into account during calculations. The stability analysis of 8 landslides in forest areas of Cicikowicleie and Wignickie Foothills was a form of verification of relevance of the obtained calculation results. The results of tests on root area ratio in the profile showed that, as expected, the number of roots in the soil profile and their ApIA values are very variable. It was shown that the values of the root area ratio of the tested tree species with a diameter 1-10 ram are a maximum of 0.8% close to the surface of the ground and they decrease along with the depth reaching the values at least one order of magnitude lower than close to the surface at the depth 0.5-1.0 m below the ground level. Average values of the root area ratio within the soil profile were from 0.05 to 0.13% adequately for Scots pine and European beech. The measured values of the root area ratio are relatively low in relation to the values of this parameter given in literature, which is probably connected with great cohesiveness of the soils and the fact that there were a lot of rock fragments in the soil, where the tests were carried out. Calculation results of the Gale-Grigal function indicate that a distribution of roots in the soil profile is similar for the tested species, apart from the silver fir from Bie§nik and European hornbeam. Considering the number of roots, their distribution in the soil profile and the root area ratio it appears that — considering slope stability — the root systems of European beech and black locust are the most optimal, which coincides with tests results given in literature. The results of tensile strength tests showed that the roots of the tested tree species have different tensile strength. The roots of European beech and European hornbeam had high tensile strength, whereas the roots of conifers and silver birch in deciduous trees — low. The analysis of test results also showed that the roots of the studied tree species are characterized by high variability of mechanical properties. The values Of shear strength increase are mainly related to the number and size (diameter) of the roots in the soil profile as well as their tensile strength and pullout resistance, although they can also result from the used calculation method (calculation model). The tests showed that the distribution of roots in the soil and their tensile strength are characterized by large variability, which allows the conclusion that using typical geotechnical calculations, which take into consideration the role of root systems is exposed to a high risk of overestimating their influence on the soil reinforcement. hence, while determining or assuming the increase in shear strength of soil reinforced with roots (root cohesion) for design calculations, a conservative (careful) approach that includes the most unfavourable values of this parameter should be used. Tests showed that the values of shear strength increase of the soil reinforced with roots calculated using Wu-Waldron model in extreme cases are three times higher than the values calculated using bundle models. In general, the most conservative calculation results of the shear strength increase were obtained using deformation bundle models: RBM2 (RBMw) or mRBM1. RBM2 model considers the variability of strength characteristics of soils described by Weibull survival function and in most cases gives the lowest values of the shear strength increase, which usually constitute 50% of the values of shear strength increase determined using classic Wu-Waldron model. Whereas the second model (mRBM1.) considers averaged values of roots strength parameters as well as the possibility that two main mechanism of destruction of a root bundle - rupture and pulling out - can occur at the same. time. The values of shear strength increase calculated using this model were the lowest in case of beech and hornbeam roots, which had high tensile strength. It indicates that in the surface part of the profile (down to 0.2 m below the ground level), primarily in case of deciduous trees, the main mechanism of failure of the root bundle will be pulling out. However, this model requires the knowledge of a much greater number of geometrical parameters of roots and geotechnical parameters of soil, and additionally it is very sensitive to input data. Therefore, it seems practical to use the RBM2 model to assess the influence of roots on the soil shear strength increase, and in order to obtain safe results of calculations in the surface part of the profile, the Weibull shape coefficient equal to 1.0 can be assumed. On the other hand, the Wu-Waldron model can be used for the initial assessment of the shear strength increase of soil reinforced with roots in the situation, where the deformation properties of the root system and its interaction with the soil are not considered, although the values of the shear strength increase calculated using this model should be corrected and reduced by half. Test results indicate that in terms of slope stability the root systems of beech and hornbeam have the most favourable properties - their maximum effect of soil reinforcement in the profile to the depth of 0.5 m does not usually exceed 30 kPa, and to the depth of 1 m - 20 kPa. The root systems of conifers have the least impact on the slope reinforcement, usually increasing the soil shear strength by less than 5 kPa. These values coincide to a large extent with the range of shear strength increase obtained from the direct shear test as well as results of stability analysis given in literature and carried out as part of this work. The analysis of the literature indicates that the methods of measuring tree's root systems as well as their interpretation are very different, which often limits the possibilities of comparing test results. This indicates the need to systematize this type of tests and for this purpose a root distribution model (RDM) can be used, which can be integrated with any deformation bundle model (RBM). A combination of these two calculation models allows the range of soil reinforcement around trees to be determined and this information might be used in practice, while planning bioengineering procedures in areas exposed to surface mass movements. The functionality of this solution can be increased by considering the dynamics of plant develop¬ment in the calculations. This, however, requires conducting this type of research in order to obtain more data.
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Rathgeber-Lawrence, Rhonda Ann. The effects of soil moisture content and the dynamic properties of the track surface on the kinematic parameters of horses galloping on the straightaway. 1992.
Trouver le texte intégralChapitres de livres sur le sujet "Soil surface parameter"
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Yadav, Ajit, Momin Raisoddin, B. Sayyad Shafiyoddin et R. Mohammed Zeeshan. « Evaluation of Oh Model for Estimating Surface Parameter of Soil Using L-Band and C-Band SAR Data ». Dans Communications in Computer and Information Science, 268–77. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0493-5_24.
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Brackmann, Lukas, Arne Röttger, Hoang-Giang Bui, Sahir Butt, Golnaz Hoormazdi, Abdiel Ramon Leon Bal, Sebastian Priebe et al. « Excavation Simulations and Cutting Tool Wear ». Dans Interaction Modeling in Mechanized Tunneling, 93–164. Cham : Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-24066-9_3.
Texte intégralRésumé :
AbstractThe mechanized tunnel construction is carried out by tunnel boring machines, in which the soil in front of the working face is removed, and the tunnel lining is carried out with shotcrete or the setting of segments and their back injection. Advancements in this field aim towards increase of the excavation efficiency and increase of the tool lifetime, especially in rock-dominated grounds. The latter is achieved by understanding the wear mechanisms abrasion and surface-fatigue, and by knowledge of the microstructure-property relation of the utilized materials. Improvements for tool concepts are derived, based on experiments and simulations. A key parameter towards efficient rock excavation is the shape of the cutting edge of the utilized disc cutters. Sharp cutting edges have proven to generate higher rock excavation rates compared to blunt ones. The compressive strength of the utilized steel has to be high, to inhibit plastic deformation and thereby to maintain sharp cutting edges. This requirement competes with the demand for toughness, which is necessary to avoid crack-growth in the case of cyclic loading. Solutions for this contradiction lie in specially designed multiphase microstructures, containing both hard particles and ductile microstructural constituents. Besides adapting the alloying concept, these required microstructures and the associated properties can be adjusted by specific heat-treatments.
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Manzi, Hilda, et Joseph P. Gweyi-Onyango. « Agro-ecological Lower Midland Zones IV and V in Kenya Using GIS and Remote Sensing for Climate-Smart Crop Management ». Dans African Handbook of Climate Change Adaptation, 965–91. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_35.
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AbstractFood production in Kenya and Africa in recent past has experienced vagaries of weather fluctuations which ultimately have affected crop yield. Farming in Kenya is localized in specific Agro-ecological zones, hence understanding crop growth responses in particular regions is crucial in planning and management for purposes of accelerating adoption. A number of strategies for adoption and adaptation to changing weather patterns have been deployed yet only limited challenges have been partially addressed or managed. This chapter examines previous methods used in classifying agro-ecological zones and further provides additional insightful parameters that can be adopted to enable farmers understand and adapt better to the current variable and unpredictable cropping seasons. The chapter scrutinizes past and current documented information on agro-ecological zonal valuations coupled with the use of earth observation components such as air temperature at surface, land surface temperature, evapotranspiration, soil, temperature, and soil and moisture content in order to better understand and effectively respond to new phenomena occurring as a result of climate change in the marginal agricultural areas. Significant variations in precipitation, ambient temperature, soil moisture content, and soil temperature become evident when earth observation data are used in evaluation of agro-ecological lower midland zones IV and V. The said variations cut across areas within the agro-ecological zones that have been allocated similar characteristics when assigning cropping seasons. The chapter summarizes the outcomes of various streams of contributions that have reported significant shifts or changes in rainfall and temperature patterns across Kenya and wider Eastern Africa region. The chapter highlights the need for re-evaluation of the agro-ecological zones based on the recent earth observation datasets in their diversity. The research emphasizes the use of multiple climate and soil-related parameters in understanding climate change in the other marginal areas of Kenya.
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Manzi, Hilda, et Joseph P. Gweyi-Onyango. « Agro-ecological Lower Midland Zones IV and V in Kenya Using GIS and Remote Sensing for Climate-Smart Crop Management ». Dans African Handbook of Climate Change Adaptation, 1–27. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-42091-8_35-1.
Texte intégralRésumé :
AbstractFood production in Kenya and Africa in recent past has experienced vagaries of weather fluctuations which ultimately have affected crop yield. Farming in Kenya is localized in specific Agro-ecological zones, hence understanding crop growth responses in particular regions is crucial in planning and management for purposes of accelerating adoption. A number of strategies for adoption and adaptation to changing weather patterns have been deployed yet only limited challenges have been partially addressed or managed. This chapter examines previous methods used in classifying agro-ecological zones and further provides additional insightful parameters that can be adopted to enable farmers understand and adapt better to the current variable and unpredictable cropping seasons. The chapter scrutinizes past and current documented information on agro-ecological zonal valuations coupled with the use of earth observation components such as air temperature at surface, land surface temperature, evapotranspiration, soil, temperature, and soil and moisture content in order to better understand and effectively respond to new phenomena occurring as a result of climate change in the marginal agricultural areas. Significant variations in precipitation, ambient temperature, soil moisture content, and soil temperature become evident when earth observation data are used in evaluation of agro-ecological lower midland zones IV and V. The said variations cut across areas within the agro-ecological zones that have been allocated similar characteristics when assigning cropping seasons. The chapter summarizes the outcomes of various streams of contributions that have reported significant shifts or changes in rainfall and temperature patterns across Kenya and wider Eastern Africa region. The chapter highlights the need for re-evaluation of the agro-ecological zones based on the recent earth observation datasets in their diversity. The research emphasizes the use of multiple climate and soil-related parameters in understanding climate change in the other marginal areas of Kenya.
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Tügel, Franziska, Ahmed Hadidi, Ilhan Özgen-Xian, Jingming Hou et Reinhard Hinkelmann. « Validation of Flash Flood Simulations Using Satellite Images and Community-Based Observations—Impact of Infiltration and Small-Scale Topographical Features ». Dans Natural Disaster Science and Mitigation Engineering : DPRI reports, 183–207. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-2904-4_6.
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AbstractThis work is aimed at investigating flash floods in the region of El Gouna, Egypt, by using a 2D robust shallow-water model that incorporates the Green-Ampt model to find the most realistic infiltration setting for this desert area. The results of different infiltration settings are compared to inundation areas observed from LANDSAT 8 images as well as to community-based information and photographs to validate the results despite scarce data availability. The model tends to overestimate infiltration in the study area if tabulated Green-Ampt parameters for the dominant soil texture class are considered. Specifically, bare soils with no vegetation tend to develop a surface crust, leading to significantly decreased infiltration rates during heavy rainfalls. Comparing the results of different infiltration settings with the observed data showed that the crust approach or the consideration of sandy clay loam instead of sand led to more plausible results for the considered study area than those obtained using the values for sand from two different sources in the literature. Furthermore, small-scale structures, which are not appropriately captured in the original digital surface model, but significantly affect the resulting flow field, have been included based on the available information leading to much more plausible results.
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Shutko, A. M. « Remote Sensing of Soil Moisture and Moisture Related Parameters by Means of Microwave Radiometry : Instruments, Data, and Examples of Application in Hydrology ». Dans Land Surface Processes in Hydrology, 263–73. Berlin, Heidelberg : Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-60567-3_15.
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Jjagwe, Aisha, Vincent Kakembo et Barasa Bernard. « Land Use Cover Types and Forest Management Options for Carbon in Mabira Central Forest Reserve ». Dans African Handbook of Climate Change Adaptation, 2733–54. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_145.
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AbstractMabira Central Forest Reserve (CFR), one of the biggest forest reserves in Uganda, has increasingly undergone encroachments and deforestation. This chapter presents the implications of a range of forest management options for carbon stocks in the Mabira CFR. The effects of forest management options were reviewed by comparing above-ground biomass (AGB), carbon, and soil organic carbon (SOC) in three management zones. The chapter attempts to provide estimates of AGB and carbon stocks (t/ha) of forest (trees) and SOC using sampling techniques and allometric equations. AGB and carbon were obtained from a count of 143 trees, measuring parameters of diameter at breast height (DBH), crown diameter (CW), and height (H) with tree coordinates. It also makes use of the Velle (Estimation of standing stock of woody biomass in areas where little or no baseline data are available. A study based on field measurements in Uganda. Norges Landbrukshoegskole, Ås, 1995) allometric equations developed for Uganda to estimate AGB.The strict nature reserve management zone was noted to sink the highest volume of carbon of approximately 6,771,092.34 tonnes, as compared to the recreation zone (2,196,467.59 tonnes) and production zone (458,903.57 tonnes). A statistically significant relationship was identified between AGB and carbon. SOC varied with soil depth, with the soil surface of 0–10 cm depth registering the highest mean of 2.78% across all the management zones. Soil depth and land use/cover types also had a statistically significant effect on the percentage of SOC (P = 0.05). A statistically significant difference at the 95% significance level was also identified between the mean carbon stocks from one level of management zones to another. Recommendations include: demarcating forest boundaries to minimize encroachment, enforcement of forestry policy for sustainable development, promote reforestation, and increase human resources for efficient monitoring of the forest compartments.
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Matsuoka, H., S. H. Liu et T. Ohashi. « Model test on granular soil slope and determination of strength parameters under low confining stresses near slope surface ». Dans Slope Stability Engineering, 681–86. London : Routledge, 2021. http://dx.doi.org/10.1201/9780203739600-3.
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Vinoth, B. « Determination of Geometric Attenuation Parameters of Surface Amplitude in Soil Medium Due to Installation of Impact Pile Casing ». Dans Lecture Notes in Civil Engineering, 327–38. Singapore : Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-6456-4_35.
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Mahmoudi, Elham, Jan Düllmann, Lukas Heußner, Raoul Hölter, Andre Lamert, Shorash Miro, Thomas Möller et al. « Advance Reconnaissance and Optimal Monitoring ». Dans Interaction Modeling in Mechanized Tunneling, 9–91. Cham : Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-24066-9_2.
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AbstractEffective exploration techniques during mechanized tunneling are of high importance in order to prevent severe surface settlements as well as a damage of the tunnel boring machine, which in turn would lead to additional costs and a standstill in the construction process. A seismic methodology called full waveform inversion can bring a considerable improvement compared to state-of-the-art seismic methods in terms of precision. Another method of exploration during mechanized tunneling is to continuously monitor subsurface behavior and then use this data to identify disturbances through pattern recognition and machine learning techniques. Various probabilistic methods for conducting system identification and proposing an appropriate monitoring plan are developed in this regard. Furthermore, ground conditions can be determined by studying boring machine data collected during the excavation. The active and passive obtained data during performance of a shield driven machine were used to estimate soil parameters. The monitoring campaign can be extended to include above-ground structural surveillance as well as terrestrial and satellite data to track displacements of existing infrastructure caused by tunneling. The available radar data for the Wehrhahn-line project are displayed and were utilized to precisely monitor the process of anticipated uplift by injections and any subsequent ground building settlements.
Actes de conférences sur le sujet "Soil surface parameter"
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« Towards soil hydraulic parameter retrieval from land surface models using near-surface soil moisture data ». Dans 19th International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand (MSSANZ), Inc., 2011. http://dx.doi.org/10.36334/modsim.2011.i2.bandara.
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Munoz-Martin, J. F., R. Onrubia, D. Pascual, H. Park, A. Camps, C. Rudiger, J. P. Walker et A. Monerris. « Parameter Considerations for the Retrieval of Surface Soil Moisture from Spaceborne GNSS-R ». Dans IGARSS 2021 - 2021 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2021. http://dx.doi.org/10.1109/igarss47720.2021.9554196.
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Leng, Pei, Xiaoning Song, Jianwei Ma et Xinhui Li. « Sensitivity analysis on surface soil moisture to the time parameter of land surface variables : Application with remote sensing data ». Dans 2011 19th International Conference on Geoinformatics. IEEE, 2011. http://dx.doi.org/10.1109/geoinformatics.2011.5980725.
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Iagnemma, Karl, Carmine Senatore, Brian Trease, Raymond Arvidson, Keith Bennett, Amy Shaw, Feng Zhou, Lauren Van Dyke et Randel Lindemann. « Terramechanics Modeling of Mars Surface Exploration Rovers for Simulation and Parameter Estimation ». Dans ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-48770.
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In 1997 and 2004, small wheeled robots (“rovers”) landed on the surface of Mars to conduct scientific experiments focused on understanding the planet’s climate history, surface geology, and potential for past or present life. Recently, the Mars Exploration Rover (MER) “Spirit” became deeply embedded in regolith at a site called Troy, ending its mission as a mobile science platform. The difficulty faced in navigating mobile robots over sloped, rocky, and deformable terrain has highlighted the importance of developing accurate simulation tools for use in a predictive mobility modeling capacity. These simulation tools require accurate knowledge of terrain model parameters. This paper describes a terramechanics-based tool for simulation of rover mobility. It also describes ongoing work toward estimation of terrain parameters of Mars soil.
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Lucau-Danila, Cozmin, Moira Callens, Pierre Defourny, Niko E. C. Verhoest et Valentijn R. N. Pauwels. « Vegetation parameter retrieval from SAR data using near-surface soil moisture estimates derived from a hydrological model ». Dans Remote Sensing, sous la direction de Manfred Owe et Guido D'Urso. SPIE, 2005. http://dx.doi.org/10.1117/12.627574.
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Verma, Nidhi, Pooja Mishra et Neetesh Purohit. « Effect of Surface Roughness Parameter on Soil Moisture of Wheat Field in Growing Stage : an Application of Sentinel-1 SAR Data ». Dans IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2019. http://dx.doi.org/10.1109/igarss.2019.8898651.
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Wang, Hongchang, Zhen Jiang, Kaiquan Ding, Guozhong Zhang, Abouelnadar Salem et Yuan Gao. « Research on Drag Reduction Performance of Sliding Plate of Rice Direct Seeding Machine Based on Non Smooth Structure of Loach Surface ». Dans 11th Asia-Pacific Regional Conference of the ISTVS. International Society for Terrain-Vehicle Systems, 2022. http://dx.doi.org/10.56884/kual5071.
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Sliding plate was the key soil-engaging component of rice direct seeding and planting machinery. It has the problems of large sliding resistance and serious soil adhesion. which has a serious negative impact on the operation efficiency and quality of rice planting machinery. Reducing the soil adhesion and resistance between sliding plate and soil can significantly improve the operation effect of the whole machine and reduce power consumption. Loach moves freely and flexibly in the mud and has highly efficient lubrication and drag reduction effects. The movement state of sliding plate was similar to that of loach, as well as the working environment and conditions. Therefore, the sliding plate of rice direct seeding machine was selected as the research object and the loach as the bionic prototype. The macroscopic and microscopic structure characteristics of the scales were observed, the results showed that the body surface of the loach was covered by scales, and the scales had a ridged non-smooth structure. The simulation analysis of the drag reduction performance of the non-smooth structure based on Fluent was carried out, the results show that the maximum drag reduction rate was 2.55% at the speed of 1m/s. The bionic sliding plate of rice direct-seeding machine was constructed based on the non-smooth structure of loach body surface, and its working performance was simulated and analyzed. The single factor test results show that at the speed of 1m/s, the drag reduction rate of ribbed height in the range of 3.5mm to 4.5mm was relatively high, the drag reduction rate of ribbed width in the range of 4mm-5mm was relatively high; the drag reduction rate was relatively high when the distance between ribs was in the range of 4mm5mm. The results of orthogonal test show that the order of primary and secondary factors of bionic structure parameters affecting drag reduction rate was ribbed spacing > ribbed width > ribbed height. The optimal parameter combination was ribbing height 4mm, ribbing width 4.5mm, ribbing spacing, and the optimal drag reduction rate was 4.21%. The results of this study can provide theoretical support for bionic design of soil engaging components of rice planting machinery in wet and soft paddy field.
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Sivasithamparam, Nallathamby, et Jorge Castro. « A Framework for Versatile Shape of Yield Surfaces for Structured Aniso-tropic Soft Soils ». Dans The 13th Baltic Sea Region Geotechnical Conference. Vilnius Gediminas Technical University, 2016. http://dx.doi.org/10.3846/13bsgc.2016.022.
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A framework based on logarithmic contractancy is proposed to produce versatile shapes of yield surfaces for structured anisotropic clays. The recently proposed constitutive model (E-SCLAY1S) is an extension of existing model called S-CLAY1S, which is a Cam Clay type model that accounts for anisotropy and structure. A new parameter called contractancy parameter is introduced to control the shape of the yield surface as well as the plastic potential (as an associated flow rule is applied). This new parameter can be used to fit the coefficient of earth pressure at rest, the undrained shear strength or the stiffness under shearing stress paths predicted by the model. The model predicts the uniqueness of the critical state line and its slope is independent of the contractancy parameter. The effect of the shape of the yield surface was investigated on computed results of a benchmark embankment constructed on Bothkennar (Scotland) clay by employing the E-SCLAY1S model as a user-defined soil model into the PLAXIS finite element code. The results demonstrate that the contribution of the shape of yield surface (logarithmic contractancy parameter) have a relatively large effect on lateral movement of subsoil beneath the toe of the embankment compared to the settlement of subsoil at the centre of the embankment.
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Yang, Le, Qinghui Lai, Liangliang Zhao, Peihang Li, Zhihong Zhang et Zhaoyang Chen. « Parameters Calibration of Red Clay Soil in Hilly Area of Southwest China for Discrete Element Simulation Based on Repose Angle Test ». Dans 11th Asia-Pacific Regional Conference of the ISTVS. International Society for Terrain-Vehicle Systems, 2022. http://dx.doi.org/10.56884/bocw9283.
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Its southwest's rugged and mountainous terrain has thick soil, which causes high resistance, poor efficiency, and sometimes even the impossibility to operate agricultural equipment. Using discrete element simulation, a cutting-edge technical technique, it is possible to optimize the agricultural machinery elements that come into contact with the soil in order to reduce drag and increase efficiency. Although there are presently no precise and trustworthy discrete element modeling parameters for red clay, the physical characteristics of red clay in the hilly and mountainous regions of the southwest are unique. As a result, in this study, the soil moisture content was 12.5%1% and 18.3%1%, respectively, for the actual working environment of the soil moisture content of 10%–20% in the hilly and mountainous areas of southwest China, and the experiment's measurement of the accumulation angle was 38.54°. This subject of the study was clay. To calibrate the appropriate model's physical characteristics, use the Hertz-Mindlin with JKR contact model in the EDEM simulation software. Prior to simulating the accumulation angle of soil particles, the intrinsic physical parameter values of the red loam soil are first obtained through actual experiments. The range of soil contact mechanical parameters in the GEMM database is then used to determine the optimal value interval of the contact parameters determined by the steepest slope test. In order to determine the regression model of the soil accumulation angle, the quadratic regression rotation orthogonal combination test is used to obtain the second-order regression model of the accumulation angle and the significant parameters. The significant parameters are then optimized using the actual accumulation angle as the target. In the end, it was found that the following contact mechanics characteristics worked well together in the EDEM simulation test: JKR surface energy 8 J/m2, restitution coefficient 0,35, dynamic friction coefficient 0,13, and static friction coefficient 0,56. The relative inaccuracy determined by the actual physical test is 1.80%, and the stacking angle is 39.24°. The study's findings demonstrate that the method has a high degree of calibration accuracy and is both reasonable and useful for calibrating soil discrete element simulation parameters. The pertinent calibration parameters can serve as a technological foundation for investigating machine-soil interaction and machine-tool optimization research in southwest China's hilly and mountainous regions.
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Ahmed, Khaled I., Abobakr Almashhor et Mohamed H. Ahmed. « Simulation-Based Correlation for Saved Energy in Ground Source Heat Exchangers for Middle East Region ». Dans ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-66381.
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Abstract Shallow geothermal energy is a renewable energy source used to reduce electric demand to produce cooling and heating of buildings. The temperature at a specific ground level is constant year-round depends on the geographic region. It can be utilized by exchanging heat in the hot weather (cooling) or cold weather (heating) using Ground Source Heat Exchangers GSHE. Many attempts have been proposed to investigate the GSHE controlling factors with a lack of interconnection effects of mutual inclusive parameters. The current work investigates the interconnection relation of seven factors; three geometrical factors, two thermophysical factors, and two operational and environmental factors. The studied geometrical factors are the wellbore diameter and length and the tube diameter. The thermal conductivities of the wellbore grout and soil are the studied two thermophysical properties. The two studied operational and environmental factors are the circulating fluid flow rate, circulating fluid input temperature difference with the soil temperature. A 2D axisymmetric CFD model is built to investigate the effect of the controlling parameters on the targeted output saved energy per tube length. Third-order surface response of the main output is achieved using a hybrid Box-Behnken Central-Composite design of experiments methods DOE. The Box-Behnken method concerns the mid of extremes, and the Central-Composite method concerns the rotatable variable interconnections. Although both methods are designed for second-order response surfaces, the proposed hybrid method can accurately predict third-order correlation using the Stepwise regression method on 136 design points. The nonlinear correlation is verified using another 100 random verification points, showing a root mean squared error of less than 1.5 [W/m]. The significance of each parameter on the target normalized saved energy is presented and discussed. The pipe diameter, grout conductivity, soil conductivity, and temperature difference are the most significant parameters controlling the GSHE performance. The water mass flow rate is lesser significant, while the grout diameter is insignificant. The response surface study has shown high normalized saved energy of 100 [W/m] of the pipe length for the investigated domains.
Rapports d'organisations sur le sujet "Soil surface parameter"
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Workman, Austin, et Jay Clausen. Meteorological property and temporal variable effect on spatial semivariance of infrared thermography of soil surfaces for detection of foreign objects. Engineer Research and Development Center (U.S.), juin 2021. http://dx.doi.org/10.21079/11681/41024.
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The environmental phenomenological properties responsible for the thermal variability evident in the use of thermal infrared (IR) sensor systems is not well understood. The research objective of this work is to understand the environmental and climatological properties contributing to the temporal and spatial thermal variance of soils. We recorded thermal images of surface temperature of soil as well as several meteorological properties such as weather condition and solar irradiance of loamy soil located at the Cold Regions Research and Engineering Lab (CRREL) facility. We assessed sensor performance by analyzing how recorded meteorological properties affected the spatial structure by observing statistical differences in spatial autocorrelation and dependence parameter estimates.
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Yermiyahu, Uri, Thomas Kinraide et Uri Mingelgrin. Role of Binding to the Root Surface and Electrostatic Attraction in the Uptake of Heavy Metal by Plants. United States Department of Agriculture, 2000. http://dx.doi.org/10.32747/2000.7586482.bard.
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The principal accomplishment of the research supported by BARD was progress toward a comprehensive view of cell-surface electrical effects (both in cell walls [CWs] and at plasma membrane [PM] surfaces) upon ion uptake, intoxication, and amelioration. The research confirmed that electrostatic models (e.g., Gouy-Chapman-Stern [G-C-S]), with parameter values contributed by us, successfully predict ion behavior at cell surfaces. Specific research objectives 1. To characterize the sorption of selected heavy metals (Cu, Zn, Pb, Cd) to the root PM in the presence of other cations and organic ligands (citric and humic acids). 2. To compute the parameters of a G-C-S model for heavy-metal sorption to the root PM. 3. To characterize the accumulation of selected heavy metals in various plant parts. 4. To determine whether model-computed ion binding or ion activities at root PM surfaces predict heavy-metal accumulation in whole roots, root tips, or plant shoots. 5. To determine whether measured ion binding by protoplast-free roots (i.e., root CWs) predicts heavy-metal accumulation in whole roots, root tips, or plant shoots. 6. To correlate growth inhibition, and other toxic responses, with the measured and computed factors mentioned above. 7. To determine whether genotypic differences in heavy-metal accumulation and toxic responses correlate with genotypic differences in parameters of the G-C-S model. Of the original objectives, all except for objective 7 were met. Work performed to meet the other objectives, and necessitated on the basis of experimental findings, took the time that would have been required to meet objective 7. In addition, work with Pb was unsuccessful due to experimental complications and work on Cd is still in progress. On the other hand, the uptake and toxicity of the anion, selenate was characterized with respect to electrostatic effects and the influences of metal cations. In addition, the project included more theoretical work, supported by experimentation, than was originally planned. This included transmembrane ion fluxes considered in terms of PM-surface electrical potentials and the influence of CWs upon ion concentrations at PM surfaces. A important feature of the biogeochemistry of trace elements in the rhizosphere is the interaction between plant-root surfaces and the ions present in the soil solution. The ions, especially the cations, of the soil solution may be accumulated in the aqueous phases of cell surfaces external to the PMs, sometimes referred to as the "water free space" and the "Donnan free space". In addition, ions may bind to the CW components or to the PM surface with variable binding strength. Accumulation at the cell surface often leads to accumulation in other plant parts with implications for the safety and quality of foods. A G-C-S model for PMs and a Donnan-plus-binding model for CWs were used successfully to compute electrical potentials, ion binding, and ion concentration at root-cell surfaces. With these electrical potentials, corresponding values for ion activities may be computed that are at least proportional to actual values also. The computed cell-surface ion activities predict and explain ion uptake, intoxication, and amelioration of intoxication much more accurately than ion activities in the bulk-phase rooting medium.
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Clausen, Jay, Michael Musty, Anna Wagner, Susan Frankenstein et Jason Dorvee. Modeling of a multi-month thermal IR study. Engineer Research and Development Center (U.S.), juillet 2021. http://dx.doi.org/10.21079/11681/41060.
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Inconsistent and unacceptable probability of detection (PD) and false alarm rates (FAR) due to varying environmental conditions hamper buried object detection. A 4-month study evaluated the environmental parameters impacting standoff thermal infra-red(IR) detection of buried objects. Field observations were integrated into a model depicting the temporal and spatial thermal changes through a 1-week period utilizing a 15-minute time-step interval. The model illustrates the surface thermal observations obtained with a thermal IR camera contemporaneously with a 3-d presentation of subsurface soil temperatures obtained with 156 buried thermocouples. Precipitation events and subsequent soil moisture responses synchronized to the temperature data are also included in the model simulation. The simulation shows the temperature response of buried objects due to changes in incoming solar radiation, air/surface soil temperature changes, latent heat exchange between the objects and surrounding soil, and impacts due to precipitation/changes in soil moisture. Differences are noted between the thermal response of plastic and metal objects as well as depth of burial below the ground surface. Nearly identical environmental conditions on different days did not always elicit the same spatial thermal response.
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Snyder, Victor A., Dani Or, Amos Hadas et S. Assouline. Characterization of Post-Tillage Soil Fragmentation and Rejoining Affecting Soil Pore Space Evolution and Transport Properties. United States Department of Agriculture, avril 2002. http://dx.doi.org/10.32747/2002.7580670.bard.
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Tillage modifies soil structure, altering conditions for plant growth and transport processes through the soil. However, the resulting loose structure is unstable and susceptible to collapse due to aggregate fragmentation during wetting and drying cycles, and coalescense of moist aggregates by internal capillary forces and external compactive stresses. Presently, limited understanding of these complex processes often leads to consideration of the soil plow layer as a static porous medium. With the purpose of filling some of this knowledge gap, the objectives of this Project were to: 1) Identify and quantify the major factors causing breakdown of primary soil fragments produced by tillage into smaller secondary fragments; 2) Identify and quantify the. physical processes involved in the coalescence of primary and secondary fragments and surfaces of weakness; 3) Measure temporal changes in pore-size distributions and hydraulic properties of reconstructed aggregate beds as a function of specified initial conditions and wetting/drying events; and 4) Construct a process-based model of post-tillage changes in soil structural and hydraulic properties of the plow layer and validate it against field experiments. A dynamic theory of capillary-driven plastic deformation of adjoining aggregates was developed, where instantaneous rate of change in geometry of aggregates and inter-aggregate pores was related to current geometry of the solid-gas-liquid system and measured soil rheological functions. The theory and supporting data showed that consolidation of aggregate beds is largely an event-driven process, restricted to a fairly narrow range of soil water contents where capillary suction is great enough to generate coalescence but where soil mechanical strength is still low enough to allow plastic deforn1ation of aggregates. The theory was also used to explain effects of transient external loading on compaction of aggregate beds. A stochastic forInalism was developed for modeling soil pore space evolution, based on the Fokker Planck equation (FPE). Analytical solutions for the FPE were developed, with parameters which can be measured empirically or related to the mechanistic aggregate deformation model. Pre-existing results from field experiments were used to illustrate how the FPE formalism can be applied to field data. Fragmentation of soil clods after tillage was observed to be an event-driven (as opposed to continuous) process that occurred only during wetting, and only as clods approached the saturation point. The major mechanism of fragmentation of large aggregates seemed to be differential soil swelling behind the wetting front. Aggregate "explosion" due to air entrapment seemed limited to small aggregates wetted simultaneously over their entire surface. Breakdown of large aggregates from 11 clay soils during successive wetting and drying cycles produced fragment size distributions which differed primarily by a scale factor l (essentially equivalent to the Van Bavel mean weight diameter), so that evolution of fragment size distributions could be modeled in terms of changes in l. For a given number of wetting and drying cycles, l decreased systematically with increasing plasticity index. When air-dry soil clods were slightly weakened by a single wetting event, and then allowed to "age" for six weeks at constant high water content, drop-shatter resistance in aged relative to non-aged clods was found to increase in proportion to plasticity index. This seemed consistent with the rheological model, which predicts faster plastic coalescence around small voids and sharp cracks (with resulting soil strengthening) in soils with low resistance to plastic yield and flow. A new theory of crack growth in "idealized" elastoplastic materials was formulated, with potential application to soil fracture phenomena. The theory was preliminarily (and successfully) tested using carbon steel, a ductile material which closely approximates ideal elastoplastic behavior, and for which the necessary fracture data existed in the literature.
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Matus, Sean, et Daniel Gambill. Automation of gridded HEC-HMS model development using Python : initial condition testing and calibration applications. Engineer Research and Development Center (U.S.), novembre 2022. http://dx.doi.org/10.21079/11681/46126.
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The US Army Corps of Engineers’s (USACE) Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) rainfall-runoff model is widely used within the research community to develop both event-based and continuous rainfall-runoff models. The soil moisture accounting (SMA) algorithm is commonly used for long-term simulations. Depending on the final model setup, 12 to 18 parameters are needed to characterize the modeled watershed’s canopy, surface, soil, and routing processes, all of which are potential calibration parameters. HEC-HMS includes optimization tools to facilitate model calibration, but only initial conditions (ICs) can be calibrated when using the gridded SMA algorithm. Calibrating a continuous SMA HEC-HMS model is an iterative process that can require hundreds of simulations, a time intensive process requiring automation. HEC-HMS is written in Java and is predominantly run through a graphical user interface (GUI). As such, conducting a long-term gridded SMA calibration is infeasible using the GUI. USACE Construction Engineering Research Laboratory (CERL) has written a workflow that utilizes the existing Jython application programming interface (API) to batch run HEC-HMS simulations with Python. The workflow allows for gridded SMA HEC-HMS model sensitivity and calibration analyses to be conducted in a timely manner.
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Warrick, Arthur W., Gideon Oron, Mary M. Poulton, Rony Wallach et Alex Furman. Multi-Dimensional Infiltration and Distribution of Water of Different Qualities and Solutes Related Through Artificial Neural Networks. United States Department of Agriculture, janvier 2009. http://dx.doi.org/10.32747/2009.7695865.bard.
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The project exploits the use of Artificial Neural Networks (ANN) to describe infiltration, water, and solute distribution in the soil during irrigation. It provides a method of simulating water and solute movement in the subsurface which, in principle, is different and has some advantages over the more common approach of numerical modeling of flow and transport equations. The five objectives were (i) Numerically develop a database for the prediction of water and solute distribution for irrigation; (ii) Develop predictive models using ANN; (iii) Develop an experimental (laboratory) database of water distribution with time; within a transparent flow cell by high resolution CCD video camera; (iv) Conduct field studies to provide basic data for developing and testing the ANN; and (v) Investigate the inclusion of water quality [salinity and organic matter (OM)] in an ANN model used for predicting infiltration and subsurface water distribution. A major accomplishment was the successful use of Moment Analysis (MA) to characterize “plumes of water” applied by various types of irrigation (including drip and gravity sources). The general idea is to describe the subsurface water patterns statistically in terms of only a few (often 3) parameters which can then be predicted by the ANN. It was shown that ellipses (in two dimensions) or ellipsoids (in three dimensions) can be depicted about the center of the plume. Any fraction of water added can be related to a ‘‘probability’’ curve relating the size of the ellipse (or ellipsoid) that contains that amount of water. The initial test of an ANN to predict the moments (and hence the water plume) was with numerically generated data for infiltration from surface and subsurface drip line and point sources in three contrasting soils. The underlying dataset consisted of 1,684,500 vectors (5 soils×5 discharge rates×3 initial conditions×1,123 nodes×20 print times) where each vector had eleven elements consisting of initial water content, hydraulic properties of the soil, flow rate, time and space coordinates. The output is an estimate of subsurface water distribution for essentially any soil property, initial condition or flow rate from a drip source. Following the formal development of the ANN, we have prepared a “user-friendly” version in a spreadsheet environment (in “Excel”). The input data are selected from appropriate values and the output is instantaneous resulting in a picture of the resulting water plume. The MA has also proven valuable, on its own merit, in the description of the flow in soil under laboratory conditions for both wettable and repellant soils. This includes non-Darcian flow examples and redistribution and well as infiltration. Field experiments were conducted in different agricultural fields and various water qualities in Israel. The obtained results will be the basis for the further ANN models development. Regions of high repellence were identified primarily under the canopy of various orchard crops, including citrus and persimmons. Also, increasing OM in the applied water lead to greater repellency. Major scientific implications are that the ANN offers an alternative to conventional flow and transport modeling and that MA is a powerful technique for describing the subsurface water distributions for normal (wettable) and repellant soil. Implications of the field measurements point to the special role of OM in affecting wettability, both from the irrigation water and from soil accumulation below canopies. Implications for agriculture are that a modified approach for drip system design should be adopted for open area crops and orchards, and taking into account the OM components both in the soil and in the applied waters.
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Gouveia, F. Protocol for computation of surface boundary layer parameters used to determine soil moisture flux from meteorological data collected at LLNL, 1992--93. Office of Scientific and Technical Information (OSTI), mars 1993. http://dx.doi.org/10.2172/10177264.
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Vecherin, Sergey, Stephen Ketcham, Aaron Meyer, Kyle Dunn, Jacob Desmond et Michael Parker. Short-range near-surface seismic ensemble predictions and uncertainty quantification for layered medium. Engineer Research and Development Center (U.S.), septembre 2022. http://dx.doi.org/10.21079/11681/45300.
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To make a prediction for seismic signal propagation, one needs to specify physical properties and subsurface ground structure of the site. This information is frequently unknown or estimated with significant uncertainty. This paper describes a methodology for probabilistic seismic ensemble prediction for vertically stratified soils and short ranges with no in situ site characterization. Instead of specifying viscoelastic site properties, the methodology operates with probability distribution functions of these properties taking into account analytical and empirical relationships among viscoelastic variables. This yields ensemble realizations of signal arrivals at specified locations where statistical properties of the signals can be estimated. Such ensemble predictions can be useful for preliminary site characterization, for military applications, and risk analysis for remote or inaccessible locations for which no data can be acquired. Comparison with experiments revealed that measured signals are not always within the predicted ranges of variability. Variance-based global sensitivity analysis has shown that the most significant parameters for signal amplitude predictions in the developed stochastic model are the uncertainty in the shear quality factor and the Poisson ratio above the water table depth.
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Crowley, David E., Dror Minz et Yitzhak Hadar. Shaping Plant Beneficial Rhizosphere Communities. United States Department of Agriculture, juillet 2013. http://dx.doi.org/10.32747/2013.7594387.bard.
Texte intégralRésumé :
PGPR bacteria include taxonomically diverse bacterial species that function for improving plant mineral nutrition, stress tolerance, and disease suppression. A number of PGPR are being developed and commercialized as soil and seed inoculants, but to date, their interactions with resident bacterial populations are still poorly understood, and-almost nothing is known about the effects of soil management practices on their population size and activities. To this end, the original objectives of this research project were: 1) To examine microbial community interactions with plant-growth-promoting rhizobacteria (PGPR) and their plant hosts. 2) To explore the factors that affect PGPR population size and activity on plant root surfaces. In our original proposal, we initially prqposed the use oflow-resolution methods mainly involving the use of PCR-DGGE and PLFA profiles of community structure. However, early in the project we recognized that the methods for studying soil microbial communities were undergoing an exponential leap forward to much more high resolution methods using high-throughput sequencing. The application of these methods for studies on rhizosphere ecology thus became a central theme in these research project. Other related research by the US team focused on identifying PGPR bacterial strains and examining their effective population si~es that are required to enhance plant growth and on developing a simulation model that examines the process of root colonization. As summarized in the following report, we characterized the rhizosphere microbiome of four host plant species to determine the impact of the host (host signature effect) on resident versus active communities. Results of our studies showed a distinct plant host specific signature among wheat, maize, tomato and cucumber, based on the following three parameters: (I) each plant promoted the activity of a unique suite of soil bacterial populations; (2) significant variations were observed in the number and the degree of dominance of active populations; and (3)the level of contribution of active (rRNA-based) populations to the resident (DNA-based) community profiles. In the rhizoplane of all four plants a significant reduction of diversity was observed, relative to the bulk soil. Moreover, an increase in DNA-RNA correspondence indicated higher representation of active bacterial populations in the residing rhizoplane community. This research demonstrates that the host plant determines the bacterial community composition in its immediate vicinity, especially with respect to the active populations. Based on the studies from the US team, we suggest that the effective population size PGPR should be maintained at approximately 105 cells per gram of rhizosphere soil in the zone of elongation to obtain plant growth promotion effects, but emphasize that it is critical to also consider differences in the activity based on DNA-RNA correspondence. The results ofthis research provide fundamental new insight into the composition ofthe bacterial communities associated with plant roots, and the factors that affect their abundance and activity on root surfaces. Virtually all PGPR are multifunctional and may be expected to have diverse levels of activity with respect to production of plant growth hormones (regulation of root growth and architecture), suppression of stress ethylene (increased tolerance to drought and salinity), production of siderophores and antibiotics (disease suppression), and solubilization of phosphorus. The application of transcriptome methods pioneered in our research will ultimately lead to better understanding of how management practices such as use of compost and soil inoculants can be used to improve plant yields, stress tolerance, and disease resistance. As we look to the future, the use of metagenomic techniques combined with quantitative methods including microarrays, and quantitative peR methods that target specific genes should allow us to better classify, monitor, and manage the plant rhizosphere to improve crop yields in agricultural ecosystems. In addition, expression of several genes in rhizospheres of both cucumber and whet roots were identified, including mostly housekeeping genes. Denitrification, chemotaxis and motility genes were preferentially expressed in wheat while in cucumber roots bacterial genes involved in catalase, a large set of polysaccharide degradation and assimilatory sulfate reduction genes were preferentially expressed.
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Schlossnagle, Trevor H., Janae Wallace, et Nathan Payne. Analysis of Septic-Tank Density for Four Communities in Iron County, Utah - Newcastle, Kanarraville, Summit, and Paragonah. Utah Geological Survey, décembre 2022. http://dx.doi.org/10.34191/ri-284.
Texte intégralRésumé :
Iron County is a semi-rural area in southwestern Utah that is experiencing an increase in residential development. Although much of the development is on community sewer systems, many subdivisions use septic tank soil-absorption systems for wastewater disposal. Many of these septic-tank systems overlie the basin-fill deposits that compose the principal aquifer for the area. The purpose of our study is to provide tools for waterresource management and land-use planning. In this study we (1) characterize the water quality of four areas in Iron County (Newcastle, Kanarraville, Summit, and Paragonah) with emphasis on nutrients, and (2) provide a mass-balance analysis based on numbers of septic-tank systems, groundwater flow available for mixing, and baseline nitrate concentrations, and thereby recommend appropriate septic-system density requirements to limit water-quality degradation. We collected 57 groundwater samples and three surface water samples across the four study areas to establish baseline nitrate concentrations. The baseline nitrate concentrations for Newcastle, Kanarraville, Summit, and Paragonah are 1.51 mg/L, 1.42 mg/L, 2.2 mg/L, and 1.76 mg/L, respectively. We employed a mass-balance approach to determine septic-tank densities using existing septic systems and baseline nitrate concentrations for each region. Nitrogen in the form of nitrate is one of the principal indicators of pollution from septic tank soil-absorption systems. To provide recommended septic-system densities, we used a mass-balance approach in which the nitrogen mass from projected additional septic tanks is added to the current nitrogen mass and then diluted with groundwater flow available for mixing plus the water added by the septic-tank systems themselves. We used an allowable degradation of 1 mg/L with respect to nitrate. Groundwater flow volume available for mixing was calculated from existing hydrogeologic data. We used data from aquifer tests compiled from drinking water source protection documents to derive hydraulic conductivity from reported transmissivities. Potentiometric surface maps from existing publications and datasets were used to determine groundwater flow directions and hydraulic gradients. Our results using the mass balance approach indicate that the most appropriate recommended maximum septic-tank densities in Newcastle, Kanarraville, Summit, and Paragonah are 23 acres per system, 7 acres per system, 5 acres per system, and 11 acres per system, respectively. These recommendations are based on hydrogeologic parameters used to estimate groundwater flow volume. Public valley-wide sewer systems may be a better alternative to septic-tank systems where feasible.