Dissertations / Theses on the topic 'Soil temperature – Mathematical models'
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1
Jean, Karm-Ervin. "Models Describing the Sea Level Rise in Key West, Florida." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2274.
Full textAbstract:
Lately, we have been noticing an unusual rise in the sea level near many Floridian cities. By 2060, scientists believe that the sea level in the city of Key West will reach between 22.86 to 60.96 centimeters (Strauss et al. 2012). The consequences of sea level rise are unpleasant by gradually tearing away our beaches and natural resources, destroying our homes and businesses, etc. Definitively, a continual increase of the sea level will affect everyone either directly or indirectly.
In this study, the sea level measurements of four Floridian coastal cities (including Key West) are collected in order to describe their trend toward sea level rise over the past 100 years. After the comparisons, some models describing the sea level rise in the city of Key West, Florida, are developed. Any inferences for these above cities may well be extended to similar ones.
2
Barrett, Gary Edward. "Infiltration in water repellent soil." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28618.
Full textAbstract:
Observations made at Goat Meadows - a small sub-alpine basin located near Pemberton, British Columbia -demonstrated that a layer which is either water repellent or has only a limited affinity for water is present at most vegetated sites. The layer is typically a few centimetres in thickness, and is usually located at or near the top of the profile: it was present only in the zone of accumulation of organic matter. The spatial distribution of the layer did not appear to be related to the distribution of any particular species of plant. Sampling of sub-alpine sites in the Cascade, Selkirk, and Purcell Mountains indicated that such layers are common in the alpine - sub-alpine ecotone of southern British Columbia.
The relationship between ponding depth and infiltration rate was explored through experiments conducted on samples collected near Ash Lake, in Goat Meadows. These samples were chosen for analysis because the repellent layer was in excess of thirty centimetres thick at this site. Infiltration rates remained below 2x10⁻⁹ m/s for all samples, even given ponding depths of up to forty centimetres. Breakthrough of liquid water was not observed, even after one month, which implies that most of the infiltration occurred as vapour transfer.
In order to observe the movement of liquid water through water repellent media, a plexiglas cell was constructed. A synthetic water repellent sand with uniform surface properties was used as the medium. It was found that up to some critical depth, there was no entry of water into the medium. As the ponding depth was increased in steps, the front would advance in steps: it remained stationary between these step-increases in ponding depth. As the front advanced, protuberances or "fingers" began to develop. At some critical ponding depth, a finger would grow without bound. These observations pose a challenge to existing models of infiltration, since it appears that heterogeneity at the scale of individual pores must be invoked to explain them, but it is usually assumed that the properties of a porous medium are continuous at this scale.
The thermodynamics of filling and emptying of pores is considered with emphasis on the effects of pore shape and of variations in the physicochemical properties at the scale of the pore. This thermodynamic analysis provides the conceptual basis for development of a model of infiltration in which pore-scale heterogeneity is preserved. Although it was not developed as such, the model follows the approach of cellular automata, in which local relations between pores or "cells" govern the behaviour of the system. The model replicated the observations of infiltration into synthetic water repellent porous media well: both the halting advance of the front as the ponding depth was increased and the development of fingers were simulated. The fact that such complex behaviour was predicted using only a simple set of physically based rules confirms the power of the approach.Arts, Faculty of
Geography, Department of
Graduate
3
Sorooshian, Soroosh, and Vijai Kumar Gupta. "Improving the Reliability of Compartmental Models: Case of Conceptual Hydrologic Rainfall-Runoff Models." Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/614011.
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Romanel, Celso 1952. "DYNAMIC SOIL-STRUCTURE INTERACTION IN A LAYERED MEDIUM." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276511.
Full textAbstract:
The most popular method in dynamic soil-structure interaction analysis is the finite element method. The versatility in problems involving different materials and complex geometries is its main advantage, yet FEM can not simulate unbounded domains completely. A hybrid method is proposed in this research, which models the near field (structure and surrounding soil) by finite elements and the far field by a continuum approach. The system is excited by monochromatic body waves (P and SV) propagating with oblique incidence and harmonic time dependence. The far field problem is solved using Thomson-Haskell formulation associated with the delta matrix technique. The soil profile does not contain any soft layer and the layers are assumed to be linearly elastic, isotropic, homogeneous and perfectly bonded at the interfaces. Two-dimensional (in-plane) formulation is considered and the analysis is performed on both k- and o-planes through time and spatial Fourier transforms of the field equations and boundary conditions. (Abstract shortened with permission of author.)
5
Park, Soojin. "Modelling soil-landform continuum on a three-dimensional hillslope." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670238.
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6
Washburne, James Clarke. "A distributed surface temperature and energy balance model of a semi-arid watershed." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186800.
Full textAbstract:
A simple model of surface and sub-surface soil temperature was developed at the watershed scale (-100 km²) in a semi-arid rangeland environment. The model consisted of a linear combination of air temperature and net radiation and assumed: (1) topography controls the spatial distribution of net radiation, (2) near-surface air temperature and incoming solar radiation are relatively homogeneous at the watershed scale and are available from ground stations and (3) soil moisture dominates transient soil thermal property variability. Multiplicative constants were defined to account for clear sky diffuse radiation, soil thermal inertia, an initially fixed ratio between soil heat flux and net radiation and exponential attenuation of solar radiation through a partial canopy. The surface temperature can optionally be adjusted for temperature and emissivity differences between mixed bare soil and vegetation canopies. Model development stressed physical simplicity and commonly available spatial and temporal data sets. Slowly varying surface characteristics, such as albedo, vegetation density and topography were derived from a series of Landsat TM images and a 7.5" USGS digital elevation model at a spatial resolution of 30 m. Diurnally variable atmospheric parameters were derived from a pair of ground meteorological stations using 30-60 min averages. One site was used to drive the model, the other served as a control to estimate model error. Data collected as part of the Monsoon '90 and WG '92 field experiments over the ARS Walnut Gulch Experimental Watershed in SE Arizona were used to validate and test the model. Point, transect and spatially distributed values of modeled surface temperature were compared with synchronous ground, aircraft and satellite thermal measurements. There was little difference between ground and aircraft measurements of surface reflectance and temperature which makes aircraft transects the preferred method to "ground truth" satellite observations. Mid-morning modeled surface temperatures were within 2° C of observed values at all but satellite scales, where atmospheric water vapor corrections complicate the determination of accurate temperatures. The utility of satellite thermal measurements and models to study various ground phenomena (e.g. soil thermal inertia and surface energy balance) were investigated. Soil moisture anomalies were detectable, but were more likely associated with average near-surface soil moisture levels than individual storm footprints.
7
Mtundu, Nangantani Davies Godfrey. "The Stochastic Behavior of Soil Moisture and Its Role in Catchment Response Models." PDXScholar, 1987. https://pdxscholar.library.pdx.edu/open_access_etds/527.
Full textAbstract:
The object of current efforts at investigating catchment response is to derive a physically based stochastic model of the watershed. Recent studies have, however, indicated that a limiting factor in deriving such models is the dependence of hydrologic response on initial soil moisture. The dependence affects the distributions and moments of the hydrological processes being investigated. A stochastic model of soil moisture dynamics is developed in the form of a pair of stochastic differential equations (SDE's) of the Ito type. The sources of stochasticity are linked to the random inputs of rainfall and evapotranspiration (ET). One of the SDE's describes the "surplus" case, in which sufficient infiltration always occurs to allow for moisture depletion by the processes of drainage through and ET out of the root zone. The other SDE represents the "deficit" case, in which lack of adequate moisture leads only to an ET-controlled depletion process. Sample functions and moments of moisture evolution are obtained from the SDE's. From the general model of soil moisture, a specific model of initial soil moisture (the moisture at the beginning of a rainstorm event) is developed and its moments are derived. Furthermore, the probability distribution of initial moisture is postulated to permit the assessment of how initial moisture affects the estimation of hydrologic response. The moisture dynamics model reveals that the stochastic properties of moisture ae sensitive to initial conditions in the watershed only for less permeable soils under the "surplus" state but are practically insensitive to such conditions for more permeable soils. The stochastic properties are also less sensitive to initial conditions for all soil types whenever under the "deficit" state. These results suggest that hydrologic processes, such as precipitation excess and infiltration, depend on initial moisture only in regions where the soils are generally less permeable and where the climate tends to sustain a "wet" environment, whereas in arid or semi-arid regions, such processes would not depend on initial moisture. These conclusions imply that, in arid regions, an effective value of initial moisture such as the mean can be used to estimate the properties of the hydrologic processes, whereas in "wet" environments, more accurate values of the properties must be "weighted" based on the probability distribution of initial soil moisture.
8
Musa, Zulkarnain 1964. "An accelerated conjugate direction procedure for slope stability analysis." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276912.
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CSLIP2 (De Natale, 1987) is the only slope stability program that utilizes a "direction set" optimization routine in its search for the minimum safety factor. However, CSLIP2 which employs Powell's Conjugate Direction Method permits only the horizontal and vertical directions (x and y) to be used as the initial direction set. The efficiency of the existing search routine is improved by replacing the x-y coordinate directions with initial directions that are parallel to and perpendicular to the principal axis of the safety factor contours.
9
Romanel, Celso. "A global-local approach for dynamic soil-structure interaction analysis of deeply embedded structures in a layered medium." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184762.
Full textAbstract:
The most popular method for dynamic soil-structure interaction analysis is the finite element method. The versatility in problems involving different materials and complex geometries is its main advantage, yet the FEM can not simulate unbounded domains completely. Several schemes have been proposed to overcome this shortcoming, such as the use of either imperfect or perfect transmitting boundaries, infinite elements and hybrid techniques. However, most of them were derived on the assumption that the soil mass can be represented as a homogeneous material despite the fact that stratified soil deposits are a common occurrence in nature. A hybrid method is proposed in this research for soil-structure interaction analysis in the frequency domain involving a multilayered linear elastic half-space. The near field region (structure and a portion of soil surrounding it) is modeled by finite elements while the far field formulation is obtained through the classical wave propagation theory based on the assumption that the actual scattered wave fields can be represented by a set of line sources. Traction reciprocity between the two regions is satisfied exactly, while the displacement continuity across the common interface is enforced in a least-squares sense. The two-dimensional system is excited by harmonic body waves (P and SV) propagating with oblique incidence. The structure can be considered either on the surface or deeply embedded in the multilayered half-space. Analytic solutions for the far field domain is obtained through the combined response of four simple problems that take into account the overall effects of the incident, reflected and scattered wave fields. The delta matrix technique is employed in order to eliminate the loss of precision problem associated with the Thomson-Haskell matrix method in its original form. Special numerical schemes are used to transform the solution from the κ- into the ω-plane due to the presence of poles on the path of integration. The few numerical examples studied in this research validate the proposed hybrid technique, but the relatively high computational cost required for evaluation of the Green's functions is still a serious drawback. Some suggestions are made to minimize the problem as well as to extend this technique to cases involving material attenuation and forced vibrations.
10
Sande, Leif Andrew. "Experimental Studies on Infiltration/Soil-Water Movement Processes and Green-AMPT Modeling." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/29329.
Full textAbstract:
Experimental studies on infiltration/soil-water movement processes are vital to
better understanding movement of soil-water in the vadose zone. The objective of this
experimental research was to investigate infiltration/soil-water movement processes
utilizing laboratory experiments and computer modeling. Small scale laboratory soil box
infiltration experiments were conducted and utilized for the improved parameterization of
the Green-Ampt (GA) saturated moisture content parameter to produce an effective
moisture content parameter (Be) for utilization in a modified GA model. By incorporating ?e
values into GA modeling, modeling results showed greatly improved wetting front
prediction across different soil conditions. A new soil packing method was proposed for
replicating complex microtopographical surfaces with uniform bulk densities in laboratory
soil box experiments which proved efficient and effective at accomplishing both objectives.
A rainfall simulator and an instantaneous-profile laser scanner were used to simulate
rainfall and quantify surface microtopography for experiments. The results clearly show the
effect of microtopography on infiltration and soil-water movement characteristics. This
offers valuable insight into infiltration/soil-water movement processes as affected by
different soil and surface microtopographic conditions.National Science Foundation (Grant No. EAR-0907588)
11
Hendrickson, Jene Diane, and Soroosh Sorooshian. "CALIBRATION OF RAINFALL-RUNOFF MODELS USING GRADIENT-BASED ALGORITHMS AND ANALYTIC DERIVATIVES." Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/614186.
Full textAbstract:
In the past, derivative-based optimization algorithms have not
frequently been used to calibrate conceptual rainfall -riff (CRR)
models, partially due to difficulties associated with obtaining the
required derivatives. This research applies a recently- developed
technique of analytically computing derivatives of a CRR model to a
complex, widely -used CRR model. The resulting least squares response
surface was found to contain numerous discontinuities in the surface
and derivatives. However, the surface and its derivatives were found
to be everywhere finite, permitting the use of derivative -based
optimization algorithms. Finite difference numeric derivatives were
computed and found to be virtually identical to analytic derivatives.
A comparison was made between gradient (Newton- Raphsoz) and
direct (pattern search) optimization algorithms. The pattern search
algorithm was found to be more robust. The lower robustness of the
Newton-Raphsoi algorithm was thought to be due to discontinuities and a
rough texture of the response surface.
12
Alvenäs, Gunnel. "Evaporation, soil moisture and soil temperature of bare and cropped soils /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5714-9.pdf.
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Huang, Xin, and 黃昕. "Exploring critical-state behaviour using DEM." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206742.
Full textAbstract:
The critical state soil mechanics (CSSM) framework originally proposed by Schofield & Wroth (1968) has been shown to capture the mechanical behaviour of soils effectively. The particulate implementation of the discrete element method (DEM) can replicate many of the complex mechanical characteristics associated with sand. This research firstly shows that the CSSM framework is useful to assess whether a DEM simulation gives a response that is representative of a real soil. The research then explores the capacity of DEM to extend understanding of soil behaviour within the CSSM framework.
The influence of sample size on the critical-state response observed in DEM simulations that use rigid-wall boundaries was examined. The observed sensitivity was shown to be caused by higher void ratios and lower contact densities adjacent to the boundaries. When the void ratio (e) and mean stress (p’) of the homogeneous interior regions were considered, the influence of sample size on the position of the critical state line (CSL) in e-log(p’) space diminished.
A parametric study on the influence of the interparticle friction (μ) on the load-deformation response was carried out. The macro-scale stress-deformation characteristics were nonlinearly related to μ and the particle-scale measures (fabric, contact force distribution, etc.) varied systematically with μ. The limited effect of increases in μ on the overall strength at high μ values (μ>0.5) is attributable to transition from sliding-dominant to rolling-dominant contact behaviour. A μ value higher than 0.5 leads to a CSL in e-log(p’) space that does not capture real soil response.
True-triaxial simulations with different intermediate stress ratios (b) were performed. The dependency of strength on b agreed with empirical failure criteria for sands and was related to a change of buckling modes of the strong force chains as b increased. DEM simulations showed that the position of the CSL in e-log(p’) space depends on the intermediate stress ratio b. This sensitivity seems to be related to the dependency of the directional fabric anisotropy on b. The link between the state parameter and both soil strength and dilatancy proposed by Jefferies & Been (2006) was reproduced in DEM simulations.
A new rotational resistance model was proposed and it was shown that the new model can qualitatively capture the influence of particle shape on the mechanical behaviour of sand. However, it was shown that the effect of rotational resistance is limited and to quantitatively compare the DEM simulation results with laboratory testing data, e.g., the critical-state loci, it is necessary to use non-spherical particles.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
14
Galadima, A., and J. C. Silvertooth. "Mathematical Models of Potassium Release Kinetics for Sonoran Desert Soils of Arizona." College of Agriculture, University of Arizona (Tucson, AZ), 1998. http://hdl.handle.net/10150/210381.
Full textAbstract:
The objective of this study was to determine the potassium (K) release kinetics of clay samples from 10 agricultural representative soils of Arizona by successive extraction using Ca-saturated cation resin. A 1993 physical and chemical characterization of the soils revealed that all soils contain smectite-mica K bearing minerals. Four mathematical models (power function, Elovich, parabolic diffusion and first-order) were used to describe the nonexchangeable K release reaction involving 700-hr cumulative reaction time. Comparison of the models using the coefficient of determination (r²) and the standard error of the estimate (SE) indicated that the Elovich and the power function equations overall displayed the best fit. The first-order rate and for the most part, the parabolic diffusion equation did not describe the K release very well. The constants a and b for the Elovich and the power function equations, which represent the intercept and the release rate of the nonexchangeable K respectively, are at least in the order of magnitude as those found by others in several previous studies.
15
Zhao, Qian, and 赵倩. "A thermomechanical approach to constitutive modeling of geomaterials." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47166836.
Full textAbstract:
Modeling of the mechanical behavior of geomaterials is a fundamental yet very
difficult problem in geotechnical engineering. The difficulty lies in that the
engineering behavior of geomaterials is strongly nonlinear and anisotropic,
depending on confining pressure, void ratio, stress history, and drainage conditions.
A traditional approach to the modeling of geomaterials is to formulate empirical
equations to fit experimental data. Generally, this approach is not able to provide
physical insights into the diverse responses observed in the soil mechanics
laboratories. Another conventional approach is to make use of the classical
plasticity theory, established mainly for metals, to develop constitutive models for
geomaterials. While this approach is capable of shedding light on the mechanisms
involved, it has been recognized that such models may violate the basic laws of
physics.
The objective of this thesis is to apply a new approach to constructing constitutive
models for geomaterials, by making use of thermomechanical principles. The
essence of the new approach is that the constitutive behavior of geomaterials can be
completely determined once two thermomechanical potentials, i.e. the free energy
and dissipation rate functions, are specified. The yield function and flow rule in the
classical plasticity theory can be established from the two potentials, and the
models so derived satisfy the basic laws of physics automatically. In this thesis, the
theoretical framework for constructing thermomechanical models is introduced.
Several concepts in relation to plastic work, dissipated and stored energy are
discussed. Both the isotropic and anisotropic models are formulated and realized in
this framework and the generated predictions are compared with the test data of a
series of triaxial compression tests on sand. To address the important density- and
pressure-dependent behaviors of sand in the framework, a state-dependent
thermomechanical model is developed, by introducing the state parameter into the
dissipation rate function such that a unique set of model parameters is able to
predict the behaviors of sand for a wide variation of densities and pressures. Finally,
a thermomechanical model for predicting the complex unloading and reloading
behaviors of sand is developed by modifying the hardening laws, and the
performance of this model is investigated.published_or_final_version
Civil Engineering
Master
Master of Philosophy
16
Ma, Zhiwen. "A combined differential and integral model for high temperature fuel cells." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15831.
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He, Shu Yu. "Field study on influence of atmospheric parameters and vegetation on variation of soil suction around tree vicinity." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3868734.
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Richard, Paul François. "A computer analysis of the flow of water and nutrients in agricultural soils as affected by subsurface drainage." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29171.
Full textAbstract:
A computer model was developed in order to determine the effects of drainage practices on nutrient losses from level agricultural soils.
The model performs a daily simulation of the vertical flow of water, nitrogen, phosphorus, and heat, and of the growth of crops. A water flow submodel calculates the depth of the water table based on daily predictions of evaporation, transpiration, flow to drains and ditches, and deep percolation. An original saturated-unsaturated flow algorithm is used to determine moisture infiltration, redistribution, and upward flow in the soil matrix, as well as bypassing flow in the soil macropores and horizontal flux between the soil matrix and the macropores, and surface runoff. Nutrient movement occurs by mass flow. Heat flow, nutrient biochemical transformations, and crop growth are determined by using well established relations.
Field tests were carried out for a period of two years on an experimental site in the Lower Fraser Valley of British Columbia. The water table depth was measured on a continuous basis. Grab samples of drainwater and observation wells were obtained periodically and analyzed for nitrogen (N0₃-N, NH₄-N, and TKN) and phosphorus (P0₄-P and TP). The field results show a decrease in the concentration of all nutrients over the sampling period, and provide evidence that denitrification and bypassing flow are important mechanisms affecting the nutrient balance of this soil.
These results were used to calibrate the model. An excellent fit of the observed water table profile and an adequate fit of the observed drain concentration of nitrate were obtained. The simulation revealed that bypassing flow is a very important transfer mechanism in this soil and must be included in order to obtain a satisfactory fit of the experimental data.
A sensitivity analysis of the model showed that the patterns of moisture flow have a predominant influence on the rate of nutrient leaching. In particular, it was found that the nutrient concentration in drain water is a strong function of the hydraulic conductivity of the soil matrix and of the horizontal distance between the soil macropores, which control the ratio of moisture flow in the soil matrix to the macropore flow and the lateral diffusion of nutrients between the soil matrix and the macropores.
The effects of four different drainage designs on nutrient losses were simulated over a period of two years for three different soils and two different nutrient distributions in the soil. It was found that there is a large difference between the amount of nutrients leached from drainage systems using different drainage coefficients. There was also a large difference in the response of two drainage designs based on the same drainage coefficient but using different depth and spacing of drains. Transient effects, as determined by the initial vertical distribution of the nutrients, were seen to remain dominant over the two year duration of the simulation.
The model was found to be useful in explaining the apparent contradictions found in the literature assessing the effects of subsurface drainage on nutrient losses. The results from the model show these effects to be strongly site and condition specific. Furthermore, the model shows that soils and drainage designs that produce similar volumes of drain flow may exhibit very different leaching responses, and that drainage designs equivalent from a hydraulic standpoint can be very dissimilar in their potential for leaching nutrients. The model provides a tool which can be used to determine the appropriateness of different drainage designs in soils where minimizing nutrient losses is critical.Science, Faculty of
Resources, Environment and Sustainability (IRES), Institute for
Graduate
19
Xu, Wenwei. "Development of a Steady-State River Hydrodynamic and Temperature Model Based on CE-QUAL-W2." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1619.
Full textAbstract:
CE-QUAL-W2 is a 2-D hydrodynamic and water quality model that has been applied to reservoirs, lakes, river systems, and estuaries throughout the world. However, when this model is applied for shallow systems, this model requires a long calculation time to maintain numerical stability, compared to applications of reservoirs or deeper river systems.
To solve this problem, a new hydrodynamic and temperature model was built based on the framework of CE-QUAL-W2 but that allows for steady-state hydrodynamic computations. By calculating the hydrodynamics at steady-state, the time step for stability is relaxed and simulations can proceed at much higher time steps. The rest of the model framework is still used for water quality state variables, in this case, temperature. The algorithm used for computing the water surface elevation is Manning's equation.
This thesis study is one part of the Willamette Water 2100 project (Santelmann et al., 2012), which examines hydrological, ecological, and human factors affecting water scarcity in the Willamette River Basin. This study included three stages: (1) Convert six existing CE-QUAL-W2 V3.1 models into a newer version: CE-QUAL-W2 V3.7. (2) Develop the steady-state model code in FORTRAN. (3) Test the steady-state model on three river systems in the Willamette River Basin at Year 2001 and 2002.
The result proved that the steady-state model could reduce the computing time by 90% for river applications, while predicting dynamic river temperature with high accuracy at a two-minute time scale. This new model will be employed to simulate the future of the Willamette River System at a decadal or centennial timescales, addressing river temperature concerns and fish habitat issues.
20
Kjellander, Kalle. "Two Simple Soil Temperature Models: Applied and Tested on Sites in Sweden." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-255003.
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Al-Khateeb, Ashraf Kamal. "Modelling of low-temperature laser produced plasmas." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322766.
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Weaver, Anthony T. "On assimilating sea surface temperature data into an ocean general circulation model." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29204.
Full textAbstract:
The feasibility of sea surface temperature (SST) data improving the performance of an ocean general circulation model (OGCM) is investigated through a series of idealized numerical experiments. The GFDL Bryan-Cox-Semtner primitive equation model is set-up as an eddy resolving, unforced, flat bottomed channel of uniform depth. 'Observed'
SST data taken from a reference ocean established in a control run are continuously
assimilated into an 'imperfect' model using a simple 'nudging' scheme based on a surface relaxation condition of the form Q = C(SST — T₁) where Q is the heat flux and T₁ is the temperature at the top level of the model. The rate of assimilation is controlled by adjusting the constant inverse relaxation time parameter C.
Numerical experiments indicate that the greatest improvement in the model fields is achieved in the extreme case of infinite assimilation (i.e., C = ᅇ) in which the 'observed' SST is directly inserted into the model. This improvement is quantified by monitoring the reduction in the root mean square (RMS) errors relative to the simulated
reference ocean. Assimilation with longer relaxation time-scales (i.e., smaller C's) proves quite ineffective in reducing the RMS errors. The improvement in the direct insertion numerical experiment stems from the model's ability to transfer assimilated SST into subsurface information through strong advective processes. The assimilation of cool surface data induces convective overturning which transfers the 'cool' information
downward rapidly but adversely affects the vertical thermal structure by an unrealistic deepening of the mixed layer. By contrast, warm surface data do not penetrate
downward readily. Thus, the systematically biased downward flux of coolness gradually produces unrealistically cool subsurface waters.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
23
Ahmad, Faheem. "Numerical modelling of transport of pollutant through soils." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08182009-040239/.
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Liu, Ying, and 劉影. "Limit equilibrium methods for slope stability analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B42576684.
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Liou, Chorng-Lii. "An improved formulation of the temperature dependence of the Gummel-Poon bipolar transistor model equations." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4361.
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A number of shortcomings were found after complete derivation of the temperature dependence of equations, and the expressions related to the Early effect in the present Gummel-Poon 2 model, as implemented in the TEKSPICE program. The formulation and application of improved model equations is presented, followed by a detailed comparison of the existing model with the one developed in this work.
26
Sun, Tek-kei, and 孫廸麒. "Numerical modeling of skin friction and penetration problems in geotechnical engineering." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/195991.
Full textAbstract:
Numerical modeling using finite element method (FEM) is well-recognized as a powerful method for both engineers and researchers to solve boundary value problems. In the modeling of geotechnical problems, the analyses are often limited to simple static problems with either steady-state effective or total stress approach while the transient response (development and dissipation of excess pore water pressure, uex) is seldom considered. Besides, infinitesimal small soil deformation is usually assumed. The simulation is further complicated when the soil-structure interaction problems involve significant soil displacements; like a pile subject to negative skin friction (NSF) and a cone/pile penetration. However, conventional FEM analysis prematurely terminates due primarily to excessive mesh distortion. One could see that simulating a transient problem with large deformation and distortion remains a great challenge. In this study, advanced FE simulations are performed to give new insights into the problems of (1) a pile subject to NSF; and (2) a cone penetration. The transient response of the NSF problem is modeled with the fluid-coupled consolidation technique and geometric nonlinearity. The fluid-coupled cone penetration problem is modeled with a newly developed adaptive approach.
The NSF and cone penetration simulations involve complex soil-structure interface modeling. Two types of modified interface responses are developed and verified which consider fluid coupling. The developed algorithm is applied to back analyze a case history of a pile subject to NSF induced by surcharge loading. Promising results were shown. Development of dragload and neutral plane (NP) with time is studied. NP locates at 75% of the pile embedded length (D) in long-term. Next, a parametric study is performed to investigate the influences of pile geometries, ground compressibility and loading conditions towards the pile responses. The long-term NP locates at around 0.55D to 0.65D in the studied engineering scenarios. The maximum downdrag can be up to 10% of the pile diameter. NP shifts upward when the head load increases. A simple design chart is proposed which helps engineers to estimate the long-term axial load distribution. An illustrative example is given to demonstrate the application and performance of the chart.
The study is extended to investigate the cone penetration problem. An advanced adaptive method is developed and implemented into the FE package ABAQUS to resolve the problems of numerical instability, excessive mesh distortion and premature termination. The proposed method is verified by modeling a ground consolidation problem. Next, total stress back analysis of cone penetration is conducted with the proposed method. The development of cone factor predicted by the proposed method gives a better match with the laboratory result when comparing with the built-in ALE method. Next, the development and dissipation of uex during cone advancing with the proposed method and fluid-coupled technique is investigated. uex develops dramatically around the cone tip. The soil permeability is back calculated from the dissipation test and agrees well with the input value. It is believed that the construction effects of a press-in pile and the subsequence NSF on that pile can be modeled by utilizing the finding of this study.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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SOMASUNDARAM, SUJITHAN. "CONSTITUTIVE MODELLING FOR ANISOTROPIC HARDENING BEHAVIOR WITH APPLICATIONS TO COHESIONLESS SOILS (INDUCED, KINEMATIC, NON-ASSOCIATIVENESS)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/188165.
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A constitutive model based on rate-independent elastoplasticity concepts is developed to simulate the behavior of geologic materials under arbitrary three-dimensional stress paths, stress reversals and cyclic loading. The model accounts for the various factors such as friction, stress path, stress history, induced anisotropy and initial anisotropy that influence the behavior of geologic materials. A hierarchical approach is adapted whereby models of progressively increasing sophistication are developed from a basic isotropic-hardening associative model. The influence of the above factors is captured by modifying the basic model for anisotropic (kinematic) hardening and deviation from normality (nonassociativeness). Both anisotropic hardening and deviation from normality are incorporated by introducing into the formulation a second order tensor whose evolution is governed by the level of induced anisotropy in the material. In the stress-space this formulation may be interpreted as a translating potential surface Q that moves in a fixed field of isotropic yield surfaces. The location of the translating surface in the stress-space, at any stage of the deformation, is given by the 'induced anisotropy' tensor. A measure to represent the level of induced anisotropy in the material is defined. The validity of this representation is investigated based on a series of special stress path tests in the cubical triaxial device on samples of Leighton Buzzard sand. The significant parameters of the models are defined and determined for three sands based on results of conventional laboratory test results. The model is verified with respect to laboratory multiaxial test data under various paths of loading, unloading, reloading and cyclic loading.
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Davary, Kamran. "Soil moisture redistribution modeling with artificial neural networks." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36905.
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This study sought to investigate the application of artificial neural networks (ANN) and fuzzy inference systems (FIS) to variably saturated soil moisture (VSSM) redistribution modelling. An enhanced approach to such modelling, that lessens computation costs, facilitates input preparation, handles data uncertainty, and realistically simulates soil moisture redistribution, was our main objective.An initial review of existing soil hydrology models provided greater insight into current modelling challenges and a general classification of the models. The application of AI techniques as alternative tools for soil hydrology modelling was explored.
A one-dimensional (1D) model based on ANN and FIS was developed. To estimate fluxes more accurately, multiple ANNs were trained and combined by way of an FIS. The main body of the model employed the ANN-FIS module to model soil moisture redistribution throughout the profile. When tested against the SWAP93 model, the ANN-FIS model gave a good match and maximum error of <8%; however, it did not show a notable computation cost shift.
The investigation proceeded with development of another ANN-based 1D modelling approach. This time, the soil profile or flow region, regardless of its depth, was divided into ten equal parts (compartments). The ANN was trained to estimate moisture patterns for a whole soil profile, from the previous day's soil moisture pattern and boundary conditions, and the current day's boundary conditions. The model was tested against SWAP93 where an average SCORE of 90.4 indicated a good match. The computation cost of the ANN-based model was about one-third that of SWAP93.
At this point the study sought to develop a 3D modelling approach. The ANN was trained to estimate the nodal soil moisture changes through time under the influence of six neighbouring nodes (in a 3D space, two on each axis). The model's accuracy was tested against the SWMS-3D model. An average SCORE of 91 and a 15-fold decrease in computation costs showed a quite acceptable performance. Results suggest that this approach is potentially capable of realistically modelling 3D VSSM redistribution with less computation time.
Finally, pros and cons of these ANN-based modelling approaches are compared and contrasted, and some recommendations on future work are given.
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Al-Zubaidi, Hussein Ali Mahdi. "3D Hydrodynamic, Temperature, and Water Quality Numerical Model for Surface Waterbodies: Development, Verification, and Field Case Studies." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4500.
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Numerical modeling has become a major tool for managing water quality in surface waterbodies such as rivers, lakes, reservoirs, and estuaries. Since the two-dimensional longitudinal/vertical model CE-QUAL-W2 is a well-known model and it has been applied to thousands of waterbodies around the world successfully, its numerical scheme was adapted to develop a new three-dimensional numerical model for simulating hydrodynamics, temperature, and water quality in surface waterbodies. Finite difference approximations were used to solve the fluid dynamic governing equations of continuity, free water surface, momentums, and mass transport. No coordinate transformations were performed and the z-coordinate system has been used. Higher-order schemes (QUICK, QUICKEST, and ULTIMATE QUICKEST) in addition to the UPWIND scheme were used for the advective temperature and mass transport. A novel numerical approach was used for the numerical formulation of the three-dimensional scheme. This approach forced the numerical solution of the free surface equation to be a tri-diagonal matrix form rather than a more computationally intensive penta-diagonal matrix solution. This new approach was done by linking a method called line-by-line with the free water surface numerical solution. Another new approach was that the three-dimensional numerical scheme involved a simultaneous solution of hydrodynamics, temperature, and water quality at every model time level instead of saving the hydrodynamic results to be used later for water quality simulation. Hence, this scheme allowed feedback between the hydrodynamics and water quality every time step. In addition, various unique numerical algorithms were employed from CE-QUAL-W2 such as the W2 turbulence model, selective withdrawal theory, surface heat fluxes, and water quality sources and sinks, making the three-dimensional model built on well-tested algorithms.
To test the model structure and assumptions, an analytical verification was performed by comparing model predictions to known analytical exact solutions test cases. Good agreement was showed by the model for all of these tests. A computation of the volume balance over the simulation period was also incorporated within the model to assess how well the code performed. Sensitivity tests were also made varying bed and wind shear.
The model was also applied to three reservoirs in the USA as field case studies: Lake Chaplain in WA, Laurance Lake in OR, and Cooper Creek Reservoir in OR. The model was validated by comparing the model predictions of water levels, velocities, vertical temperature profiles, and dissolved oxygen with field data. Through these real applications, the numerical predictions of the 3D model showed good agreement with field data based on error statistics. The model results of each field case study were discussed separately. In the Lake Chaplain model application, the study was focused on the importance of the higher-order schemes compared to the first-order UPWIND scheme. The model predictions of temperature were determined by using the UPWIND, QUICK, and QUICKEST scheme and compared with field data. The Error statistics of the model predictions compared to field data were an absolute mean error (AME) of 0.065 m for the water level predictions and an overall AME of 1.62 °C, 1.09 °C, and 1.23 °C for the temperature predictions by using the UPWIND, QUICK, and QUICKEST scheme, respectively. In the Laurance Lake model application, a comparison was performed between the present 3D model and the 2D CE-QUAL-W2. Since the 3D model was build based on CE-QUAL-W2, differences between the two models were evaluated. Error statistics between the model predictions of water level and temperature compared to field data showed that both models were in good agreement with field data. However, the 3D model AME (0.30 m for the water level predictions and 0.48 °C for the temperature predictions) was higher than the 2D model (0.03 m for the water level predictions and 0.42 °C for the temperature predictions). Finally, the Cooper Creek Reservoir case study was done to show the model predictions of temperature and dissolved oxygen. In this application, vertical temperature profiles were covered the entire simulation period in order to show how the model transfer heat between stratification and non- stratification conditions. The model showed good agreement with field data (0.12 m AME for the water level predictions, 1.00 °C overall AME for the temperature predictions, and 1.32 g/m3 overall AME for the dissolved oxygen predictions).
Finally, comparisons were made between CE-QUAL-W2 and the 3D model. The 2D model generally performed better in the tests cases if the model user is unconcerned about lateral impacts. The 3D model is important to use when lateral currents and variation in the lateral dimension are important.
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Chen, Chen, and 陈晨. "Numerical studies of phase fluctuations in cuprate superconductors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46482623.
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Liu, Pengyu. "Maximum likelihood estimation of an unknown change-point in the parameters of a multivariate Gaussian series with applications to environmental monitoring." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Dissertations/Spring2010/p_liu_041610.pdf.
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Chin, Victor B. L. "The dynamic response of pile-soil interfaces during pile driving and dynamic testing events." Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9421.
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Odeh, Inakwu Ominyi Akots. "Soil pattern recognition in a South Australian subcatchment /." Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09pho23.pdf.
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Deknatel, William Brockway. "USE OF THE SOLUTION MODELS TO CALCULATE THE ACTIVITY COMPOSITION RELATIONS OF MAGNESIAN CALCITES (SOLID, CARBONATES)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/291512.
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Abou, Nahra Joumana. "Modeling phosphorus transport in soil and water." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102946.
Full textAbstract:
The main objective of this project was to investigate and model phosphorus (P) transport in soil column studies. A model named HYDRUS-NICA was developed, by coupling a hydrological and transport model (HYDRUS-1D model) with an aqueous chemical model (non-ideal competitive adsorption - NICA), to improve the predictions of P transport in soil and water. The HYDRUS-NICA model was developed by replacing the non-linear empirical (Freundlich and Langmuir) equations of the HYDRUS-1D model with the NICA model equations. The numerical accuracy of the HYDRUS-NICA model was then evaluated by comparing the relative errors produced by the HYDRUS-NICA and HYDRUS-1D models. The results showed that the numerical schemes of the HYDRUS-NICA code are stable.The ability of the NICA model to describe phosphate (PO4) adsorption to soil particles was tested using soils collected from agricultural fields in southern Quebec. The surface charge and PO4 adsorption capacity of these soils were measured. Results were used to estimate the NICA model parameters using a non-linear fitting function. The NICA model accurately described the surface charge of these soils and the PO4 adsorption processes.
The HYDRUS-1D model was applied to simulate water flow and PO4 transport in re-constructed soil column experiments. The HYDRUS-1D model was calibrated based on physical and chemical parameters that were estimated from different experiments. Overall, the HYDRUS-1D model successfully simulated the water flow in the columns; however, it overestimated the final adsorbed PO4 concentrations in the soil. The discrepancies in the results suggested that the HYDRUS-1D model could not account for the differences in the soil structure found in the columns, or that the Freundlich isotherm could not adequately describe PO4 adsorption.
The HYDRUS-NICA model was calibrated and validated with results from re-packed column experiments. The simulated results were then compared with results obtained by the HYDRUS-1D model. The overall goodness-of-fit for the HYDRUS-1D model simulations was classified as poor. The HYDRUS-NICA model improved significantly the prediction of PO4 transport, with the coefficient of modeling efficiency values being close to unity, and the coefficient of residual mass values being close to zero. The HYDRUS-NICA model can be used as a tool to improve the prediction of PO4 transport at the field scale.
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Yamamoto, Nobutaka. "Numerical analysis of shallow circular foundations on sands." University of Western Australia. School of Civil and Resource Engineering, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0038.
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This thesis describes a numerical investigation of shallow circular foundations resting on various types of soil, mainly siliceous and calcareous sands. An elasto-plastic constitutive model, namely the MIT-S1 model (Pestana, 1994), which can predict the rate independent behaviour of different types of soils ranging through uncemented sands, silts and clays, is used to simulating the compression, drained triaxial shear and shallow circular foundation responses. It is found that this model provides a reasonable fit to measured behaviour, particularly for highly compressible calcareous sands, because of the superior modelling of the volumetric compression. The features of the MIT-S1 model have been used to investigate the effects of density, stress level (or foundation size), inherent anisotropy and material type on the response of shallow foundations. It was found that the MIT-S1 model is able to distinguish responses on dilatant siliceous and compressible calcareous sands by relatively minor adjustment of the model parameters. Kinematic mechanisms extracted from finite element calculations show different deformation patterns typical for these sands, with a bulb of compressed material and punching shear for calcareous sand, and a classical rupture failure pattern accompanied by surface heave for siliceous sand. Moreover, it was observed that the classical failure pattern transforms gradually to a punching shear failure pattern as the foundation size increases. From this evidence, a dimensional transition between these failure mechanisms can be defined, referred to as the critical size. The critical size is also the limiting foundation size to apply conventional bearing capacity analyses. Alternative approaches are needed, focusing mainly on the soil compressibility, for shallow foundations greater than the critical size. Two approaches, 1-D compression and bearing modulus analyses, have been proposed for those foundation conditions. From the validations, the former is applicable for extremely large foundations, very loose soil conditions and highly compressible calcareous materials, while the latter is suitable for moderate levels of compressibility or foundation size. It is suggested that appropriate assessment of compression features is of great importance for shallow foundation analysis on sand.
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Gutmann, Ethan D. "The determination of soil hydraulic properties in land surface models from remotely sensed surface temperature." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303868.
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Faria, Rogério Teixeira de. "Simulation of irrigation requirements for Parana State, Brazil." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41290.
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A risk analysis of drought and an assessment of irrigation requirements were ascertained for a wheat (Triticum aestivum L.) crop in Parana, Brazil, using 28 years of historical weather data. Two soil moisture models, The Versatile Soil Moisture Budget (VB4) and SWACROP models, were compared using data from six wheat cropping periods. The models showed good performance in predicting soil moisture contents, but SWACROP underpredicted soil evaporation and runoff, and VB4 did not separate evapotranspiration into its components. Therefore, a new soil moisture model was proposed. In the new model, a Darcy type equation was used to calculate fluxes in the soil profile, and inputs of daily rainfall and potential evapotranspiration were partitioned during the day using simple disaggregation methods. Crop growth input parameters, interacting with weather and soil inputs, were used to calculate a detailed output of the water balance components. The validation of the model showed predictions of soil water contents and evapotranspiration in close agreement with field data.A crop yield model based on the stress day index approach was selected from an evaluation of seven crop-water production functions using wheat field data. This model was combined with the soil moisture model to assess risks of drought during the establishment and development of non-irrigated wheat crops with different planting dates. Irrigation management strategies were simulated to identify net system delivery capacities and application frequencies that promote maximum yield with minimum requirements of water. Yield reductions in non-irrigated wheat due to water stress varied between 16%, for early plantings, to 50%, for late plantings. Maximum yields with minimum applied water was obtained by the use of low intensity (5 to 10 mm) and frequent (3 to 5 days) irrigations. System delivery capacity requirements varied from 1.5 to 3.0 mm/day, according to planting dates.
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Uchaipichat, Anuchit Civil & Environmental Engineering Faculty of Engineering UNSW. "Experimental investigation and constitutive modelling of thermo-hydro-mechanical coupling in unsaturated soils." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/22068.
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A thermo-elastic-plastic model for unsaturated soils has been presented based on the effective stress principle considering the thermo-mechanical and suction coupling effects. The thermo-elastic-plastic constitutive equations for stress-strain relations of the solid skeleton and changes in fluid content and entropy for unsaturated soils have been established. A plasticity model is derived from energy considerations. The model derived covers both associative and non-associative flow behaviours and the modified Cam-Clay is considered as a special case. All model coefficients are identified in terms of measurable parameters. To verify the proposed model, an experimental program has been developed. A series of controlled laboratory tests were carried out on a compacted silt sample using a triaxial equipment modified for testing unsaturated soils at elevated temperatures. Imageprocessing technique was used for measuring the volume change of the samples subjected to mechanical, thermal and hydric loading. It is shown that the effective critical state parameters M, ???? and ???? are independent of temperature and matric suction. Nevertheless, the shape of loading collapse (LC) curve was affected by temperature and suction. Furthermore, the temperature change affected the soil water characteristic curve and an increase in temperature caused a decrease in the air entry suction. The simulations from the proposed model are compared with the experimental results. The model calibration was performed to extract the model parameters from the experimental results. Good agreement between the results predicted using the proposed model and the experimental results was obtained in all cases.
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Liauh, Chihng-Tsung 1960. "Estimating three-dimensional temperature fields during hyperthermia: Studies of the optimal regularization parameter and time sampling." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276907.
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During hyperthermia therapy it is desirable to know the entire temperature field in the treatment region. Tikhonov regularization of order zero has been implemented. The accuracy of the estimates depends upon the value of regularization parameter, which has an optimal value that is dependent on the perfusion pattern and magnitude. The transient power-off time sampling length (i.e. the amount of transient data used) influences the accuracy of the estimates, and an optimal sampling length exists. The effects of additive noise are investigated, as are the effects of the initial guess of the perfusion values, and the effect of both symmetric and asymmetric blood perfusion patterns. The asymmetric patterns with noisy data are the most difficult cases to evaluate. The cases studied are not a comprehensive set, but a representative set whose results continue to show the feasibility of using state and parameter estimation methods to reconstruct the entire temperature field. (Abstract shortened with permission of author.)
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Barrows, Richard James. "Two Dimensional Finite Element Modeling of Swift Delta Soil Nail Wall by "ABAQUS"." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4741.
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Soil nail walls are a form of mechanical earth stabilization for cut situations. They consist of the introduction of passive inclusions (nails) into soil cut lifts. These nailed lifts are then tied together with a structural facing (usually shotcrete) . The wall lifts are constructed incrementally from the top of cut down. Soil nail walls are being recognized as having potential for large cost savings over other alternatives. The increasing need to provide high capacity roadways in restricted rights of way under structures such as bridges will require increasing use of techniques such as combined soil nail and piling walls. The Swift Delta Soil Nail wall required installing nails between some of the existing pipe piling on the Oregon Slough Bridge. This raised questions of whether the piling would undergo internal stress changes due to the nail wall construction. Thus, it was considered necessary to understand the soil nail wall structure interaction in relation to the existing pile supported abutment. The purpose of this study was to investigate the Swift Delta Wall using finite element (FE) modeling techniques. Valuable data were available from the instrumentation of the swift Delta Wall. These data were compared with the results of the FE modeling. This study attempts to answer the following two questions: 1. Is there potential for the introduction of new bending stresses to the existing piling? 2. Is the soil nail wall system influenced by the presence of the piling? A general purpose FE code called ABAQUS was used to perform both linear and non-linear analyses. The analyses showed that the piling definitely underwent some stress changes. In addition they also indicated that piling influence resulted in lower nail stresses. Comparison of measured data to predicted behavior showed good agreement in wall face deflection but inconsistent agreement in nail stresses. This demonstrated the difficulty of modeling a soil nail due to the many variables resulting from nail installation.
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Barchyn, Thomas Edward, and University of Lethbridge Faculty of Arts and Science. "Field-based aeolian sediment transport threshold measurement : sensors, calculation methods, and standards as a strategy for improving inter-study comparison." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Geography, 2010, 2010. http://hdl.handle.net/10133/2616.
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Aeolian sediment transport threshold is commonly defined as the minimum wind speed (or shear stress) necessary for wind-driven sediment transport. Threshold is a core parameter in most models of aeolian transport. Recent advances in methodology for field-based measurement of threshold show promise for improving parameterizations; however, investigators have varied in choice of method and sensor. The impacts of modifying measurement system configuration are unknown. To address this, two field tests were performed: (i) comparison of four piezoelectric sediment transport sensors, and (ii) comparison of four calculation methods. Data from both comparisons suggest that threshold measurements are non-negligibly modified by measurement system configuration and are incomparable. A poor understanding of natural sediment transport dynamics suggests that development of calibration methods could be difficult. Development of technical standards was explored to improve commensurability of measurements. Standards could assist future researchers with data syntheses and integration.xi, 108 leaves : ill. ; 29 cm
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王偉洪 and Wai-hung Wong. "A study of constitutive models on engineering properties of Hong Kong marine clay." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31214745.
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Cooke, Richard. "Development of phenomenologically-based distribution fitting procedures and spatial processes for mixed population soil properties." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07122007-103941/.
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Zhou, Maichun, and 周買春. "Modified Xinanjiang model and its incorporation with GIS and topmodel." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31241402.
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Brown, Rollins Patrick. "Predicting the ultimate axial resistance of single driven piles." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3025000.
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Awad, Barre Mohamed 1955. "APPLICATION OF THE SIMPLEX METHOD TO SLOPE STABILITY ANALYSIS." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276340.
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Huang, Fang. "Modeling patterns of small scale spatial variation in soil." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-011106-155345/.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: spatial variations; nested random effects models; semivariogram models; kriging methods; multiple logistic regression models; missing; multiple imputation. Includes bibliographical references (p. 35-36).
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Nelson, Edward L. "Temperature, pressure, and infrared image survey of an axisymmetric heated exhaust plume." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-171052/.
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Bosch, David Dean 1958. "Derivation and application of effective parameters for modeling moisture flow in heterogeneous unsaturated porous media." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/191158.
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Spatial variability of porous media often prevents precise physical characterization of the system. In order to model moisture and solute transport through this media, certain sacrifices in precision must be made. Physical characteristics of the system must be averaged over large scales, lumping the small scale variability into the large scale characterization. Although this precludes a precise definition of the small scale flow characteristics, parameterization is much more attainable. This study addresses methods for determining effective hydraulic conductivity of unsaturated porous media. Effective conductivity is used to describe the large scale behavior of the system. Different methods for calculating the effective conductivity are presented and compared. Results indicate that the unit mean gradient method produces good estimates of the effective conductivity and can be applied using limited field data. The zone of correlation of the hydraulic parameters can be used in experimental design to minimize the errors associated with estimation of the mean pressure. An inverse method for evaluating the optimum effective hydraulic parameters is presented. Results indicate the optimization procedure is more sensitive to wetting than to drying conditions. Because of interaction between the hydraulic parameters, concurrent optimization of more than two of the parameters based on soil pressure data alone is not advised. Anisotropy in an unsaturated soil was found to be a function of the profile mean soil pressure. Results indicate the effective conductivity for flow parallel to soil layering can be estimated from the arithmetic mean of the unsaturated conductivity values for each of the layers and is between the harmonic and geometric means of these data for flow perpendicular to the layering. Estimates of the effective unsaturated hydraulic conductivity obtained through stochastic analysis agreed well with simulation results. Deviations between the stochastic predictions and simulation results are larger when the variability of the soil profile is greater and begin to deviate significantly when the variance of ln K(ψ₀) exceeds 5.0 and the variance of a exceeds 0.02 1/cm².