An open, object-based modeling approach for simulating subsurface heterogeneity
Bennett, J.; Ross, M.; Haslauer, C. P.; Cirpka, O. A.
2017-12-01
Characterization of subsurface heterogeneity with respect to hydraulic and geochemical properties is critical in hydrogeology as their spatial distribution controls groundwater flow and solute transport. Many approaches of characterizing subsurface heterogeneity do not account for well-established geological concepts about the deposition of the aquifer materials; those that do (i.e. process-based methods) often require forcing parameters that are difficult to derive from site observations. We have developed a new method for simulating subsurface heterogeneity that honors concepts of sequence stratigraphy, resolves fine-scale heterogeneity and anisotropy of distributed parameters, and resembles observed sedimentary deposits. The method implements a multi-scale hierarchical facies modeling framework based on architectural element analysis, with larger features composed of smaller sub-units. The Hydrogeological Virtual Reality simulator (HYVR) simulates distributed parameter models using an object-based approach. Input parameters are derived from observations of stratigraphic morphology in sequence type-sections. Simulation outputs can be used for generic simulations of groundwater flow and solute transport, and for the generation of three-dimensional training images needed in applications of multiple-point geostatistics. The HYVR algorithm is flexible and easy to customize. The algorithm was written in the open-source programming language Python, and is intended to form a code base for hydrogeological researchers, as well as a platform that can be further developed to suit investigators' individual needs. This presentation will encompass the conceptual background and computational methods of the HYVR algorithm, the derivation of input parameters from site characterization, and the results of groundwater flow and solute transport simulations in different depositional settings.
Rouholahnejad, E.; Fan, Y.; Kirchner, J. W.; Miralles, D. G.
2017-12-01
Most Earth system models (ESM) average over considerable sub-grid heterogeneity in land surface properties, and overlook subsurface lateral flow. This could potentially bias evapotranspiration (ET) estimates and has implications for future temperature predictions, since overestimations in ET imply greater latent heat fluxes and potential underestimation of dry and warm conditions in the context of climate change. Here we quantify the bias in evaporation estimates that may arise from the fact that ESMs average over considerable heterogeneity in surface properties, and also neglect lateral transfer of water across the heterogeneous landscapes at global scale. We use a Budyko framework to express ET as a function of P and PET to derive simple sub-grid closure relations that quantify how spatial heterogeneity and lateral transfer could affect average ET as seen from the atmosphere. We show that averaging over sub-grid heterogeneity in P and PET, as typical Earth system models do, leads to overestimation of average ET. Our analysis at global scale shows that the effects of sub-grid heterogeneity will be most pronounced in steep mountainous areas where the topographic gradient is high and where P is inversely correlated with PET across the landscape. In addition, we use the Total Water Storage (TWS) anomaly estimates from the Gravity Recovery and Climate Experiment (GRACE) remote sensing product and assimilate it into the Global Land Evaporation Amsterdam Model (GLEAM) to correct for existing free drainage lower boundary condition in GLEAM and quantify whether, and how much, accounting for changes in terrestrial storage can improve the simulation of soil moisture and regional ET fluxes at global scale.
Bianchi, Marco; Kearsey, Timothy; Kingdon, Andrew
2015-12-01
Realistic representations of geological complexity are important to address several engineering and environmental challenges. The spatial distribution of properties controlling physical and geochemical processes can be effectively described by the geological structure of the subsurface. In this work, we present an approach to account for geological structure in geostatistical simulations of categorical variables. The approach is based on the extraction of information from a deterministic conceptualization of the subsurface, which is then used in the geostatistical analysis for the development of models of spatial correlation and as soft conditioning data. The approach was tested to simulate the distribution of four lithofacies in highly heterolithic Quaternary deposits. A transition probability-based stochastic model was implemented using hard borehole data and soft data extracted from a 3-D deterministic lithostratigraphic model. Simulated lithofacies distributions were also used as input in a flow model for numerical simulation of hydraulic head and groundwater flux. The outputs from these models were compared to corresponding values from models based exclusively on borehole data. Results show that soft lithostratigraphic information increases the accuracy and reduces the uncertainty of these predictions. The representation of the geological structure also allows a more precise definition of the spatial distribution of prediction uncertainty, here quantified with a metric based on Shannon information entropy. Correlations between prediction uncertainties for lithofacies, hydraulic heads and groundwater fluxes were also investigated. The results from this analysis provide useful insights about the incorporation of soft geological data into stochastic realizations of subsurface heterogeneity, and emphasize the critical importance of this type of information for reducing the uncertainty of simulations considering flux-dependent processes.
The potential of imaging subsurface heterogeneities by local, natural earthquakes
Nishitsuji, Y.; Doi, I.; Draganov, D.S.
2014-01-01
We have developed a new imaging technique of subsurface heterogeneities that uses Sp-waves from natural earthquakes. This technique can be used as a first screening tool in frontier exploration areas before conventional active exploration. Analyzing Sp-waves from 28 earthquakes (Mj 2.0 to 4.2)
Identifying Heterogeneities in Subsurface Environment using the Level Set Method
Energy Technology Data Exchange (ETDEWEB)
Lei, Hongzhuan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lu, Zhiming [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vesselinov, Velimir Valentinov [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-08-25
These are slides from a presentation on identifying heterogeneities in subsurface environment using the level set method. The slides start with the motivation, then explain Level Set Method (LSM), the algorithms, some examples are given, and finally future work is explained.
Modeling the subsurface structure of sunspots
Moradi, H.; Baldner, C.; Birch, A.C.; Braun, D.C.; Cameron, R.H.; Duvall Jr., T.L.; Gizon, L.; Haber, D.; Hanasoge, S.M.; Hindman, B.W.; Jackiewicz, J.; Khomenko, E.; Komm, R.; Rajaguru, P.; Rempel, M.; Roth, M.; Schlichenmaier, R.; Schunker, H.; Spruit, H.C.; Strassmeier, K.G.; Thompson, M.J.; Zharkov, S.
2010-01-01
While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate
Modeling subsurface contamination at Fernald
International Nuclear Information System (INIS)
Jones, B.W.; Flinn, J.C.; Ruwe, P.R.
1994-01-01
The Department of Energy's Fernald site is located about 20 miles northwest of Cincinnati. Fernald produced refined uranium metal products from ores between 1953 and 1989. The pure uranium was sent to other DOE sites in South Carolina, Tennessee, Colorado,and Washington in support of the nation's strategic defense programs. Over the years of large-scale uranium production, contamination of the site's soil and groundwater occurred.The contamination is of particular concern because the Fernald site is located over the Great Miami Aquifer, a designated sole-source drinking water aquifer. Contamination of the aquifer with uranium was found beneath the site, and migration of the contamination had occurred well beyond the site's southern boundary. As a result, Fernald was placed on the National Priorities (CERCLA/Superfund) List in 1989. Uranium production at the site ended in 1989,and Fernald's mission has been changed to one of environmental restoration. This paper presents information about computerized modeling of subsurface contamination used for the environmental restoration project at Fernald
A fully subordinated linear flow model for hillslope subsurface stormflow
Zhang, Yong; Baeumer, Boris; Chen, Li; Reeves, Donald M.; Sun, HongGuang
2017-04-01
Hillslope subsurface stormflow exhibits complex patterns when natural soils with multiscale heterogeneity impart a spatiotemporally nonlocal memory on flow dynamics. To efficiently quantify such nonlocal flow responses, this technical note proposes a fully subordinated flow (FSF) equation where the time- and flow-subordination capture the temporal and spatial memory, respectively. Results show that the time-subordination component of the FSF model captures a wide range of delayed flow response due to various degrees of soil heterogeneity (especially for low-conductivity zones), while the model's flow-subordination term accounts for the rapid flow responses along preferential flow paths. In the FSF model, parameters defining spatiotemporal memory functions may be related to soil properties, while other parameters such as scalar factors controlling the overall advection and diffusion are difficult to predict and can be estimated from subsurface stormflow hydrographs. These parameters can be constants at the hillslope scale because the spatiotemporal subordination, an upscaling technique, can capture the impact of system heterogeneity on flow dynamics, leading to a linear FSF model that might be applicable for various slopes. Valid scale, limitation and extension of the FSF model, and modification of the model for other complex hydrological dynamics are also discussed.
Directional Dipole Model for Subsurface Scattering
DEFF Research Database (Denmark)
Frisvad, Jeppe Revall; Hachisuka, Toshiya; Kjeldsen, Thomas Kim
2014-01-01
Rendering translucent materials using Monte Carlo ray tracing is computationally expensive due to a large number of subsurface scattering events. Faster approaches are based on analytical models derived from diffusion theory. While such analytical models are efficient, they miss out on some...... translucency effects in the rendered result. We present an improved analytical model for subsurface scattering that captures translucency effects present in the reference solutions but remaining absent with existing models. The key difference is that our model is based on ray source diffusion, rather than...... similar to that of the standard dipole model, but we now have positive and negative ray sources with a mirrored pair of directions. Our model is as computationally efficient as existing models while it includes single scattering without relying on a separate Monte Carlo simulation, and the rendered images...
Modelling Nitrogen Transformation in Horizontal Subsurface Flow ...
African Journals Online (AJOL)
A mathematical model was developed to permit dynamic simulation of nitrogen interaction in a pilot horizontal subsurface flow constructed wetland receiving effluents from primary facultative pond. The system was planted with Phragmites mauritianus, which was provided with root zone depth of 75 cm. The root zone was ...
A New Kind of Single-Well Tracer Test for Assessing Subsurface Heterogeneity
Hansen, S. K.; Vesselinov, V. V.; Lu, Z.; Reimus, P. W.; Katzman, D.
2017-12-01
Single-well injection-withdrawal (SWIW) tracer tests have historically been interpreted using the idealized assumption of tracer path reversibility (i.e., negligible background flow), with background flow due to natural hydraulic gradient being an un-modeled confounding factor. However, we have recently discovered that it is possible to use background flow to our advantage to extract additional information about the subsurface. To wit: we have developed a new kind of single-well tracer test that exploits flow due to natural gradient to estimate the variance of the log hydraulic conductivity field of a heterogeneous aquifer. The test methodology involves injection under forced gradient and withdrawal under natural gradient, and makes use of a relationship, discovered using a large-scale Monte Carlo study and machine learning techniques, between power law breakthrough curve tail exponent and log-hydraulic conductivity variance. We will discuss how we performed the computational study and derived this relationship and then show an application example in which our new single-well tracer test interpretation scheme was applied to estimation of heterogeneity of a formation at the chromium contamination site at Los Alamos National Laboratory. Detailed core hole records exist at the same site, from which it was possible to estimate the log hydraulic conductivity variance using a Kozeny-Carman relation. The variances estimated using our new tracer test methodology and estimated by direct inspection of core were nearly identical, corroborating the new methodology. Assessment of aquifer heterogeneity is of critical importance to deployment of amendments associated with in-situ remediation strategies, since permeability contrasts potentially reduce the interaction between amendment and contaminant. Our new tracer test provides an easy way to obtain this information.
Umezawa, Osamu; Morita, Motoaki; Yuasa, Takayuki; Morooka, Satoshi; Ono, Yoshinori; Yuri, Tetsumi; Ogata, Toshio
2014-01-01
Subsurface crack initiation in high-cycle fatigue has been detected as {0001} transgranular facet in titanium alloys at low temperature. The discussion on the subsurface crack generation was reviewed. Analyses by neutron diffraction and full constraints model under tension mode as well as crystallographic identification of the facet were focused. The accumulated tensile stress along may be responsible to initial microcracking on {0001} and the crack opening.
Ezzedine, S. M.; McNab, W. W.
2007-12-01
Long-term monitoring (LTM) is particularly important for contaminants which are mitigated by natural processes of dilution, dispersion, and degradation. At many sites, LTM can require decades of expensive sampling at tens or even hundreds of existing monitoring wells, resulting in hundreds of thousands, or millions of dollars per year for sampling and data management. Therefore, contaminant sampling tools, methods and frequencies are chosen to minimize waste and data management costs while ensuring a reliable and informative time-history of contaminant measurement for regulatory compliance. The interplay play between cause (i.e. subsurface heterogeneities, sampling techniques, measurement frequencies) and effect (unreliable data and measurements gap) has been overlooked in many field applications which can lead to inconsistencies in time- histories of contaminant samples. In this study we address the relationship between cause and effect for different hydrogeological sampling settings: porous and fractured media. A numerical model has been developed using AMR-FEM to solve the physicochemical processes that take place in the aquifer and the monitoring well. In the latter, the flow is governed by the Navier-Stokes equations while in the former the flow is governed by the diffusivity equation; both are fully coupled to mimic stressed conditions and to assess the effect of dynamic sampling tool on the formation surrounding the monitoring well. First of all, different sampling tools (i.e., Easy Pump, Snapper Grab Sampler) were simulated in a monitoring well screened in different homogeneous layered aquifers to assess their effect on the sampling measurements. Secondly, in order to make the computer runs more CPU efficient the flow in the monitoring well was replaced by its counterpart flow in porous media with infinite permeability and the new model was used to simulate the effect of heterogeneities, sampling depth, sampling tool and sampling frequencies on the
Integrated geomechanical modelling for deep subsurface damage
Wees, J.D. van; Orlic, B.; Zijl, W.; Jongerius, P.; Schreppers, G.J.; Hendriks, M.
2001-01-01
Government, E&P and mining industry increasingly demand fundamental insight and accurate predictions on subsurface and surface deformation and damage due to exploitation of subsurface natural resources, and subsurface storage of energy residues (e.g. CO2). At this moment deformation is difficult to
Discriminative Random Field Models for Subsurface Contamination Uncertainty Quantification
Arshadi, M.; Abriola, L. M.; Miller, E. L.; De Paolis Kaluza, C.
2017-12-01
Application of flow and transport simulators for prediction of the release, entrapment, and persistence of dense non-aqueous phase liquids (DNAPLs) and associated contaminant plumes is a computationally intensive process that requires specification of a large number of material properties and hydrologic/chemical parameters. Given its computational burden, this direct simulation approach is particularly ill-suited for quantifying both the expected performance and uncertainty associated with candidate remediation strategies under real field conditions. Prediction uncertainties primarily arise from limited information about contaminant mass distributions, as well as the spatial distribution of subsurface hydrologic properties. Application of direct simulation to quantify uncertainty would, thus, typically require simulating multiphase flow and transport for a large number of permeability and release scenarios to collect statistics associated with remedial effectiveness, a computationally prohibitive process. The primary objective of this work is to develop and demonstrate a methodology that employs measured field data to produce equi-probable stochastic representations of a subsurface source zone that capture the spatial distribution and uncertainty associated with key features that control remediation performance (i.e., permeability and contamination mass). Here we employ probabilistic models known as discriminative random fields (DRFs) to synthesize stochastic realizations of initial mass distributions consistent with known, and typically limited, site characterization data. Using a limited number of full scale simulations as training data, a statistical model is developed for predicting the distribution of contaminant mass (e.g., DNAPL saturation and aqueous concentration) across a heterogeneous domain. Monte-Carlo sampling methods are then employed, in conjunction with the trained statistical model, to generate realizations conditioned on measured borehole data
Gottschalk, Ian P.; Hermans, Thomas; Knight, Rosemary; Caers, Jef; Cameron, David A.; Regnery, Julia; McCray, John E.
2017-12-01
Geophysical data have proven to be very useful for lithological characterization. However, quantitatively integrating the information gained from acquiring geophysical data generally requires colocated lithological and geophysical data for constructing a rock-physics relationship. In this contribution, the issue of integrating noncolocated geophysical and lithological data is addressed, and the results are applied to simulate groundwater flow in a heterogeneous aquifer in the Prairie Waters Project North Campus aquifer recharge site, Colorado. Two methods of constructing a rock-physics transform between electrical resistivity tomography (ERT) data and lithology measurements are assessed. In the first approach, a maximum likelihood estimation (MLE) is used to fit a bimodal lognormal distribution to horizontal crosssections of the ERT resistivity histogram. In the second approach, a spatial bootstrap is applied to approximate the rock-physics relationship. The rock-physics transforms provide soft data for multiple point statistics (MPS) simulations. Subsurface models are used to run groundwater flow and tracer test simulations. Each model's uncalibrated, predicted breakthrough time is evaluated based on its agreement with measured subsurface travel time values from infiltration basins to selected groundwater recovery wells. We find that incorporating geophysical information into uncalibrated flow models reduces the difference with observed values, as compared to flow models without geophysical information incorporated. The integration of geophysical data also narrows the variance of predicted tracer breakthrough times substantially. Accuracy is highest and variance is lowest in breakthrough predictions generated by the MLE-based rock-physics transform. Calibrating the ensemble of geophysically constrained models would help produce a suite of realistic flow models for predictive purposes at the site. We find that the success of breakthrough predictions is highly
A one-dimensional model of subsurface hillslope flow
Jason C. Fisher
1997-01-01
Abstract - A one-dimensional, finite difference model of saturated subsurface flow within a hillslope was developed. The model uses rainfall, elevation data, a hydraulic conductivity, and a storage coefficient to predict the saturated thickness in time and space. The model was tested against piezometric data collected in a swale located in the headwaters of the North...
A Theoretical Study of Subsurface Drainage Model Simulation of ...
African Journals Online (AJOL)
A three-dimensional variable-density groundwater flow model, the SEAWAT model, was used to assess the influence of subsurface drain spacing, evapotranspiration and irrigation water quality on salt concentration at the base of the root zone, leaching and drainage in salt affected irrigated land. The study was carried out ...
Forward modeling of gravity data using geostatistically generated subsurface density variations
Phelps, Geoffrey
2016-01-01
Using geostatistical models of density variations in the subsurface, constrained by geologic data, forward models of gravity anomalies can be generated by discretizing the subsurface and calculating the cumulative effect of each cell (pixel). The results of such stochastically generated forward gravity anomalies can be compared with the observed gravity anomalies to find density models that match the observed data. These models have an advantage over forward gravity anomalies generated using polygonal bodies of homogeneous density because generating numerous realizations explores a larger region of the solution space. The stochastic modeling can be thought of as dividing the forward model into two components: that due to the shape of each geologic unit and that due to the heterogeneous distribution of density within each geologic unit. The modeling demonstrates that the internally heterogeneous distribution of density within each geologic unit can contribute significantly to the resulting calculated forward gravity anomaly. Furthermore, the stochastic models match observed statistical properties of geologic units, the solution space is more broadly explored by producing a suite of successful models, and the likelihood of a particular conceptual geologic model can be compared. The Vaca Fault near Travis Air Force Base, California, can be successfully modeled as a normal or strike-slip fault, with the normal fault model being slightly more probable. It can also be modeled as a reverse fault, although this structural geologic configuration is highly unlikely given the realizations we explored.
Integrated Surface/subsurface flow modeling in PFLOTRAN
Energy Technology Data Exchange (ETDEWEB)
Painter, Scott L [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-10-01
Understanding soil water, groundwater, and shallow surface water dynamics as an integrated hydrological system is critical for understanding the Earth’s critical zone, the thin outer layer at our planet’s surface where vegetation, soil, rock, and gases interact to regulate the environment. Computational tools that take this view of soil moisture and shallow surface flows as a single integrated system are typically referred to as integrated surface/subsurface hydrology models. We extend the open-source, highly parallel, subsurface flow and reactive transport simulator PFLOTRAN to accommodate surface flows. In contrast to most previous implementations, we do not represent a distinct surface system. Instead, the vertical gradient in hydraulic head at the land surface is neglected, which allows the surface flow system to be eliminated and incorporated directly into the subsurface system. This tight coupling approach leads to a robust capability and also greatly simplifies implementation in existing subsurface simulators such as PFLOTRAN. Successful comparisons to independent numerical solutions build confidence in the approximation and implementation. Example simulations of the Walker Branch and East Fork Poplar Creek watersheds near Oak Ridge, Tennessee demonstrate the robustness of the approach in geometrically complex applications. The lack of a robust integrated surface/subsurface hydrology capability had been a barrier to PFLOTRAN’s use in critical zone studies. This work addresses that capability gap, thus enabling PFLOTRAN as a community platform for building integrated models of the critical zone.
A subsurface model of the beaver meadow complex
Nash, C.; Grant, G.; Flinchum, B. A.; Lancaster, J.; Holbrook, W. S.; Davis, L. G.; Lewis, S.
2015-12-01
Wet meadows are a vital component of arid and semi-arid environments. These valley spanning, seasonally inundated wetlands provide critical habitat and refugia for wildlife, and may potentially mediate catchment-scale hydrology in otherwise "water challenged" landscapes. In the last 150 years, these meadows have begun incising rapidly, causing the wetlands to drain and much of the ecological benefit to be lost. The mechanisms driving this incision are poorly understood, with proposed means ranging from cattle grazing to climate change, to the removal of beaver. There is considerable interest in identifying cost-effective strategies to restore the hydrologic and ecological conditions of these meadows at a meaningful scale, but effective process based restoration first requires a thorough understanding of the constructional history of these ubiquitous features. There is emerging evidence to suggest that the North American beaver may have had a considerable role in shaping this landscape through the building of dams. This "beaver meadow complex hypothesis" posits that as beaver dams filled with fine-grained sediments, they became large wet meadows on which new dams, and new complexes, were formed, thereby aggrading valley bottoms. A pioneering study done in Yellowstone indicated that 32-50% of the alluvial sediment was deposited in ponded environments. The observed aggradation rates were highly heterogeneous, suggesting spatial variability in the depositional process - all consistent with the beaver meadow complex hypothesis (Polvi and Wohl, 2012). To expand on this initial work, we have probed deeper into these meadow complexes using a combination of geophysical techniques, coring methods and numerical modeling to create a 3-dimensional representation of the subsurface environments. This imaging has given us a unique view into the patterns and processes responsible for the landforms, and may shed further light on the role of beaver in shaping these landscapes.
Prediction of Geological Subsurfaces Based on Gaussian Random Field Models
Energy Technology Data Exchange (ETDEWEB)
Abrahamsen, Petter
1997-12-31
During the sixties, random functions became practical tools for predicting ore reserves with associated precision measures in the mining industry. This was the start of the geostatistical methods called kriging. These methods are used, for example, in petroleum exploration. This thesis reviews the possibilities for using Gaussian random functions in modelling of geological subsurfaces. It develops methods for including many sources of information and observations for precise prediction of the depth of geological subsurfaces. The simple properties of Gaussian distributions make it possible to calculate optimal predictors in the mean square sense. This is done in a discussion of kriging predictors. These predictors are then extended to deal with several subsurfaces simultaneously. It is shown how additional velocity observations can be used to improve predictions. The use of gradient data and even higher order derivatives are also considered and gradient data are used in an example. 130 refs., 44 figs., 12 tabs.
Two dimentional modeling of subsurface structure over upper Benue ...
African Journals Online (AJOL)
The subsurface lithology obtained from 2D modelling of the residual field showed the presence of two lithological units. The sedimentary rock unit underlined by the basement rock consists of shales, sandstones, limestones, siltstones, clay and non-marine facies. The Basement rock units were composed of pegmatite, ...
Modelling near subsurface temperature with mixed type boundary ...
Indian Academy of Sciences (India)
available. We have developed such a thermal model of near subsurface region which includes both heat .... Such a boundary condition has been used in hydrother- mal studies (Heasler et al. 1990). In case, the heat transfer coefficient H tends to infinity, soil temper- ..... Davis M G, Harris R N and Chapman D H 2010 Repeat.
A spatial and temporal continuous surface-subsurface hydrologic model
Xiao, Qing-Fu; Ustin, Susan L.; Wallender, Wesley W.
1996-12-01
A hydrologic model integrating surface-subsurface processes was developed based on spatial and temporal continuity theory. The raster-based mass balance hydrologic model consists of several submodels which determine spatial and temporal patterns in precipitation, surface flow, infiltration, subsurface flow, and the linkages between these submodels. Model parameters and variables are derived directly or indirectly from satellite remote sensing data, topographic maps, soil maps, literature, and weather station data and are stored in a Geographic Information System (GIS) database used for visualization. Surface resolution of cells in the model is 20 m by 20 m (pixel resolution of the Systeme Probatoire d'Observation de la Terre (SPOT) satellite image) over a 2511 km2 study area around the Crazy Mountains, Alaska, a watershed on the Arctic Circle draining into the Yukon River. The outputs from this model illustrate the interaction of physical and biologic factors on the partitioning of hydrologic components in a complex landscape.
Subsurface stormflow modeling with sensitivity analysis using a Latin-hypercube sampling technique
International Nuclear Information System (INIS)
Gwo, J.P.; Toran, L.E.; Morris, M.D.; Wilson, G.V.
1994-09-01
Subsurface stormflow, because of its dynamic and nonlinear features, has been a very challenging process in both field experiments and modeling studies. The disposal of wastes in subsurface stormflow and vadose zones at Oak Ridge National Laboratory, however, demands more effort to characterize these flow zones and to study their dynamic flow processes. Field data and modeling studies for these flow zones are relatively scarce, and the effect of engineering designs on the flow processes is poorly understood. On the basis of a risk assessment framework and a conceptual model for the Oak Ridge Reservation area, numerical models of a proposed waste disposal site were built, and a Latin-hypercube simulation technique was used to study the uncertainty of model parameters. Four scenarios, with three engineering designs, were simulated, and the effectiveness of the engineering designs was evaluated. Sensitivity analysis of model parameters suggested that hydraulic conductivity was the most influential parameter. However, local heterogeneities may alter flow patterns and result in complex recharge and discharge patterns. Hydraulic conductivity, therefore, may not be used as the only reference for subsurface flow monitoring and engineering operations. Neither of the two engineering designs, capping and French drains, was found to be effective in hydrologically isolating downslope waste trenches. However, pressure head contours indicated that combinations of both designs may prove more effective than either one alone
Multiple Scenario Generation of Subsurface Models
DEFF Research Database (Denmark)
Cordua, Knud Skou
In geosciences, as well as in astrophysics, direct observations of a studied physical system and objects are not always accessible. Instead, indirect observations have to be used in order to obtain information about the unknown system, which leads to an inverse problem. Such geoscientific inverse....... Finally, the probabilistic formulation provides a means of analyzing uncertainties and potential multiple-scenario solutions to be used for risk assessments in relation to, e.g., reservoir characterization and forecasting. Prior models rely on information from old data sets or expert knowledge in form of......, e.g., training images that expresses structural, lithological, or textural features. Statistics obtained from these types of observations will be referred to as sample models. Geostatistical sampling algorithms use a sample model as input and produce multiple realizations of the model parameters...
Inverse Modeling of Geological Heterogeneity for Goal-Oriented Aquifer Characterization
Savoy, Heather Marie
2017-01-01
Characterizing the spatial heterogeneity of aquifer properties, particularly hydraulic conductivity, is paramount in groundwater modeling when the transport and fate of contaminants need to be predicted. The field of geostatistics has focused on describing this heterogeneity with spatial random functions. The field of stochastic hydrogeology uses these functions to incorporate uncertainty about the subsurface in groundwater modeling predictions. Bayesian inference can update prior knowledge a...
Linear Regression Models for Estimating True Subsurface ...
Indian Academy of Sciences (India)
47
The objective is to minimize the processing time and computer memory required .... Survey. 65 time to acquire extra GPR or seismic data for large sites and picking the first arrival time. 66 to provide the needed datasets for the joint inversion are also .... The data utilized for the regression modelling was acquired from ground.
Linear Regression Models for Estimating True Subsurface ...
Indian Academy of Sciences (India)
47
of the processing time and memory space required to carry out the inversion with the. 29. SCLS algorithm. ... consumption of time and memory space for the iterative computations to converge at. 54 minimum data ..... colour scale and blanking as the observed true resistivity models, for visual assessment. 163. The accuracy ...
Characterisation of the Groningen subsurface for seismic hazard and risk modelling
Kruiver, P.P.; Wiersma, A.; Kloosterman, F.H.; Lange, G. de; Korff, M.; Stafleu, J.; Harting, R.; Gunnink, J.L.; Green, R.A.; Elk, J. van; Doornhof, D.
2017-01-01
The shallow subsurface of Groningen, the Netherlands, is heterogeneous due to its formation in a Holocene tidal coastal setting on a periglacially and glacially inherited landscape with strong lateral variation in subsurface architecture. Soft sediments with low, small-strain shear wave velocities
Energy Technology Data Exchange (ETDEWEB)
Maxwell, R M; Kollet, S J
2007-08-23
The impact of three-dimensional subsurface heterogeneity on hillslope runoff generated by excess infiltration (so called Hortonian runoff) is examined. A fully-coupled, parallel subsurface overland flow model is used to simulate runoff from an idealized hillslope. Ensembles of correlated, Gaussian random fields of saturated hydraulic conductivity are used to create uncertainty and variability (i.e. structure) due to subsurface heterogeneity. A large number of cases are simulated in a parametric manner with variance of the hydraulic conductivity varied over two orders of magnitude. These cases include rainfall rates above, equal and below the geometric mean of the hydraulic conductivity distribution. These cases are also compared to theoretical considerations of runoff production based on simple assumptions regarding (1) the rainfall rate and the value of hydraulic conductivity in the surface cell using a spatially-indiscriminant approach; and (2) a percolation-theory type approach to incorporate so-called runon. Simulations to test the ergodicity of hydraulic conductivity on hillslope runoff are also performed. Results show three-dimensional features (particularly in the vertical dimension) in the hydraulic conductivity distributions that create shallow perching, which has an important effect on runoff behavior that is fundamentally different in character than previous two dimensional analyses. The simple theories are shown to be very poor predictors of the saturated area that might runoff due to excess infiltration. It is also shown that ergodicity is reached only for a large number of integral scales ({approx}30) and not for cases where the rainfall rate is less than the geometric mean of the saturated hydraulic conductivity.
Fiber Bundle Model Under Heterogeneous Loading
Roy, Subhadeep; Goswami, Sanchari
2018-03-01
The present work deals with the behavior of fiber bundle model under heterogeneous loading condition. The model is explored both in the mean-field limit as well as with local stress concentration. In the mean field limit, the failure abruptness decreases with increasing order k of heterogeneous loading. In this limit, a brittle to quasi-brittle transition is observed at a particular strength of disorder which changes with k. On the other hand, the model is hardly affected by such heterogeneity in the limit where local stress concentration plays a crucial role. The continuous limit of the heterogeneous loading is also studied and discussed in this paper. Some of the important results related to fiber bundle model are reviewed and their responses to our new scheme of heterogeneous loading are studied in details. Our findings are universal with respect to the nature of the threshold distribution adopted to assign strength to an individual fiber.
SeiVis: An Interactive Visual Subsurface Modeling Application.
Hollt, T; Freiler, W; Gschwantner, F; Doleisch, H; Heinemann, G; Hadwiger, M
2012-12-01
The most important resources to fulfill today's energy demands are fossil fuels, such as oil and natural gas. When exploiting hydrocarbon reservoirs, a detailed and credible model of the subsurface structures is crucial in order to minimize economic and ecological risks. Creating such a model is an inverse problem: reconstructing structures from measured reflection seismics. The major challenge here is twofold: First, the structures in highly ambiguous seismic data are interpreted in the time domain. Second, a velocity model has to be built from this interpretation to match the model to depth measurements from wells. If it is not possible to obtain a match at all positions, the interpretation has to be updated, going back to the first step. This results in a lengthy back and forth between the different steps, or in an unphysical velocity model in many cases. This paper presents a novel, integrated approach to interactively creating subsurface models from reflection seismics. It integrates the interpretation of the seismic data using an interactive horizon extraction technique based on piecewise global optimization with velocity modeling. Computing and visualizing the effects of changes to the interpretation and velocity model on the depth-converted model on the fly enables an integrated feedback loop that enables a completely new connection of the seismic data in time domain and well data in depth domain. Using a novel joint time/depth visualization, depicting side-by-side views of the original and the resulting depth-converted data, domain experts can directly fit their interpretation in time domain to spatial ground truth data. We have conducted a domain expert evaluation, which illustrates that the presented workflow enables the creation of exact subsurface models much more rapidly than previous approaches.
SeiVis: An interactive visual subsurface modeling application
Hollt, Thomas
2012-12-01
The most important resources to fulfill today’s energy demands are fossil fuels, such as oil and natural gas. When exploiting hydrocarbon reservoirs, a detailed and credible model of the subsurface structures is crucial in order to minimize economic and ecological risks. Creating such a model is an inverse problem: reconstructing structures from measured reflection seismics. The major challenge here is twofold: First, the structures in highly ambiguous seismic data are interpreted in the time domain. Second, a velocity model has to be built from this interpretation to match the model to depth measurements from wells. If it is not possible to obtain a match at all positions, the interpretation has to be updated, going back to the first step. This results in a lengthy back and forth between the different steps, or in an unphysical velocity model in many cases. This paper presents a novel, integrated approach to interactively creating subsurface models from reflection seismics. It integrates the interpretation of the seismic data using an interactive horizon extraction technique based on piecewise global optimization with velocity modeling. Computing and visualizing the effects of changes to the interpretation and velocity model on the depth-converted model on the fly enables an integrated feedback loop that enables a completely new connection of the seismic data in time domain and well data in depth domain. Using a novel joint time/depth visualization, depicting side-by-side views of the original and the resulting depth-converted data, domain experts can directly fit their interpretation in time domain to spatial ground truth data. We have conducted a domain expert evaluation, which illustrates that the presented workflow enables the creation of exact subsurface models much more rapidly than previous approaches. © 2012 IEEE.
Theoretical analysis of non-Gaussian heterogeneity effects on subsurface flow and transport
Riva, Monica; Guadagnini, Alberto; Neuman, Shlomo P.
2017-04-01
Much of the stochastic groundwater literature is devoted to the analysis of flow and transport in Gaussian or multi-Gaussian log hydraulic conductivity (or transmissivity) fields, Y(x)=ln\\func K(x) (x being a position vector), characterized by one or (less frequently) a multiplicity of spatial correlation scales. Yet Y and many other variables and their (spatial or temporal) increments, ΔY, are known to be generally non-Gaussian. One common manifestation of non-Gaussianity is that whereas frequency distributions of Y often exhibit mild peaks and light tails, those of increments ΔY are generally symmetric with peaks that grow sharper, and tails that become heavier, as separation scale or lag between pairs of Y values decreases. A statistical model that captures these disparate, scale-dependent distributions of Y and ΔY in a unified and consistent manner has been recently proposed by us. This new "generalized sub-Gaussian (GSG)" model has the form Y(x)=U(x)G(x) where G(x) is (generally, but not necessarily) a multiscale Gaussian random field and U(x) is a nonnegative subordinator independent of G. The purpose of this paper is to explore analytically, in an elementary manner, lead-order effects that non-Gaussian heterogeneity described by the GSG model have on the stochastic description of flow and transport. Recognizing that perturbation expansion of hydraulic conductivity K=eY diverges when Y is sub-Gaussian, we render the expansion convergent by truncating Y's domain of definition. We then demonstrate theoretically and illustrate by way of numerical examples that, as the domain of truncation expands, (a) the variance of truncated Y (denoted by Yt) approaches that of Y and (b) the pdf (and thereby moments) of Yt increments approach those of Y increments and, as a consequence, the variogram of Yt approaches that of Y. This in turn guarantees that perturbing Kt=etY to second order in σYt (the standard deviation of Yt) yields results which approach those we obtain
DEFF Research Database (Denmark)
Kristensen, Andreas Houlberg; Poulsen, Tjalfe; Mortensen, Lars
2010-01-01
Quantifying the spatial variability of factors affecting natural attenuation of hydrocarbons in the unsaturated zone is important to (i) performing a reliable risk assessment and (ii) evaluating the possibility for bioremediation of petroleum-polluted sites. Most studies to date have focused...... on the shallow unsaturated zone. Based on a data set comprising analysis of about 100 soil samples taken in a 16-m-deep unsaturated zone polluted with volatile petroleum compounds, we statistically and geostatistically analyzed values of essential soil properties. The subsurface of the site was highly layered...
Data inversion in coupled subsurface flow and geomechanics models
International Nuclear Information System (INIS)
Iglesias, Marco A; McLaughlin, Dennis
2012-01-01
We present an inverse modeling approach to estimate petrophysical and elastic properties of the subsurface. The aim is to use the fully coupled geomechanics-flow model of Girault et al (2011 Math. Models Methods Appl. Sci. 21 169–213) to jointly invert surface deformation and pressure data from wells. We use a functional-analytic framework to construct a forward operator (parameter-to-output map) that arises from the geomechanics-flow model of Girault et al. Then, we follow a deterministic approach to pose the inverse problem of finding parameter estimates from measurements of the output of the forward operator. We prove that this inverse problem is ill-posed in the sense of stability. The inverse problem is then regularized with the implementation of the Newton-conjugate gradient (CG) algorithm of Hanke (1997 Numer. Funct. Anal. Optim. 18 18–971). For a consistent application of the Newton-CG scheme, we establish the differentiability of the forward map and characterize the adjoint of its linearization. We provide assumptions under which the theory of Hanke ensures convergence and regularizing properties of the Newton-CG scheme. These properties are verified in our numerical experiments. In addition, our synthetic experiments display the capabilities of the proposed inverse approach to estimate parameters of the subsurface by means of data inversion. In particular, the added value of measurements of surface deformation in the estimation of absolute permeability is quantified with respect to the standard history matching approach of inverting production data with flow models. The proposed methodology can be potentially used to invert satellite geodetic data (e.g. InSAR and GPS) in combination with production data for optimal monitoring and characterization of the subsurface. (paper)
Energy Technology Data Exchange (ETDEWEB)
Ali, Melkamu; Ye, Sheng; Li, Hongyi; Huang, Maoyi; Leung, Lai-Yung R.; Fiori, Aldo; Sivapalan, Murugesu
2014-07-19
Subsurface stormflow is an important component of the rainfall-runoff response, especially in steep forested regions. However; its contribution is poorly represented in current generation of land surface hydrological models (LSMs) and catchment-scale rainfall-runoff models. The lack of physical basis of common parameterizations precludes a priori estimation (i.e. without calibration), which is a major drawback for prediction in ungauged basins, or for use in global models. This paper is aimed at deriving physically based parameterizations of the storage-discharge relationship relating to subsurface flow. These parameterizations are derived through a two-step up-scaling procedure: firstly, through simulations with a physically based (Darcian) subsurface flow model for idealized three dimensional rectangular hillslopes, accounting for within-hillslope random heterogeneity of soil hydraulic properties, and secondly, through subsequent up-scaling to the catchment scale by accounting for between-hillslope and within-catchment heterogeneity of topographic features (e.g., slope). These theoretical simulation results produced parameterizations of the storage-discharge relationship in terms of soil hydraulic properties, topographic slope and their heterogeneities, which were consistent with results of previous studies. Yet, regionalization of the resulting storage-discharge relations across 50 actual catchments in eastern United States, and a comparison of the regionalized results with equivalent empirical results obtained on the basis of analysis of observed streamflow recession curves, revealed a systematic inconsistency. It was found that the difference between the theoretical and empirically derived results could be explained, to first order, by climate in the form of climatic aridity index. This suggests a possible codependence of climate, soils, vegetation and topographic properties, and suggests that subsurface flow parameterization needed for ungauged locations must
Energy Technology Data Exchange (ETDEWEB)
Hamilton, D.S.; Raeuchle, S.K.; Holtz, M.H. [Bureau of Economic Geology, Austin, TX (United States)] [and others
1997-08-01
We applied an integrated geologic, geophysical, and engineering approach devised to identify heterogeneities in the subsurface that might lead to reserve growth opportunities in our analysis of the Oficina Formation at Budare field, Venezuela. The approach involves 4 key steps: (1) Determine geologic reservoir architecture; (2) Investigate trends in reservoir fluid flow; (3) Integrate fluid flow trends with reservoir architecture; and (4) Estimate original oil-in-place, residual oil saturation, and remaining mobile oil, to identify opportunities for reserve growth. There are three main oil-producing reservoirs in the Oficina Formation that were deposited in a bed-load fluvial system, an incised valley-fill, and a barrier-strandplain system. Reservoir continuity is complex because, in addition to lateral facies variability, the major Oficina depositional systems were internally subdivided by high-frequency stratigraphic surfaces. These surfaces define times of intermittent lacustrine and marine flooding events that punctuated the fluvial and marginal marine sedimentation, respectively. Syn and post depositional faulting further disrupted reservoir continuity. Trends in fluid flow established from initial fluid levels, response to recompletion workovers, and pressure depletion data demonstrated barriers to lateral and vertical fluid flow caused by a combination of reservoir facies pinchout, flooding shale markers, and the faults. Considerable reserve growth potential exists at Budare field because the reservoir units are highly compartment by the depositional heterogeneity and structural complexity. Numerous reserve growth opportunities were identified in attics updip of existing production, in untapped or incompletely drained compartments, and in field extensions.
Nonparametric estimation in models for unobservable heterogeneity
Hohmann, Daniel
2014-01-01
Nonparametric models which allow for data with unobservable heterogeneity are studied. The first publication introduces new estimators and their asymptotic properties for conditional mixture models. The second publication considers estimation of a function from noisy observations of its Radon transform in a Gaussian white noise model.
Modelling income processes with lots of heterogeneity
DEFF Research Database (Denmark)
Browning, Martin; Ejrnæs, Mette; Alvarez, Javier
2010-01-01
We model earnings processes allowing for lots of heterogeneity across agents. We also introduce an extension to the linear ARMA model which allows the initial convergence in the long run to be different from that implied by the conventional ARMA model. This is particularly important for unit root...
Development of anomaly detection models for deep subsurface monitoring
Sun, A. Y.
2017-12-01
Deep subsurface repositories are used for waste disposal and carbon sequestration. Monitoring deep subsurface repositories for potential anomalies is challenging, not only because the number of sensor networks and the quality of data are often limited, but also because of the lack of labeled data needed to train and validate machine learning (ML) algorithms. Although physical simulation models may be applied to predict anomalies (or the system's nominal state for that sake), the accuracy of such predictions may be limited by inherent conceptual and parameter uncertainties. The main objective of this study was to demonstrate the potential of data-driven models for leakage detection in carbon sequestration repositories. Monitoring data collected during an artificial CO2 release test at a carbon sequestration repository were used, which include both scalar time series (pressure) and vector time series (distributed temperature sensing). For each type of data, separate online anomaly detection algorithms were developed using the baseline experiment data (no leak) and then tested on the leak experiment data. Performance of a number of different online algorithms was compared. Results show the importance of including contextual information in the dataset to mitigate the impact of reservoir noise and reduce false positive rate. The developed algorithms were integrated into a generic Web-based platform for real-time anomaly detection.
Abdoulhalik, Antoifi; Ahmed, Ashraf A.
2017-10-01
The main purpose of this work was to examine how aquifer layering impacts the ability of subsurface dams to retain seawater intrusion (SWI) and to clean up contaminated coastal aquifers using both experimental and numerical techniques. Four different layering configurations were investigated, including a homogeneous case (case H), and three different layered cases where a low permeability layer was set at the top of the aquifer (case LH), at the middle part of the aquifer as interlayer (case HLH), and at the lower part of the aquifer (case HL). The subsurface dam was able to retain the saltwater wedge associated with a drop of the hydraulic gradient from 0.0158 down to 0.0095 in all the cases, thereby achieving up to 78% reduction in the saltwater toe length. In cases LH and HLH, the start of the saltwater spillage was delayed compared to the homogeneous case, and the time taken for the freshwater zone to be fully contaminated (post-spillage) was twice and three times longer, respectively. By contrast, the existence of a low K layer at the bottom of the aquifer (case HL) considerably weakened the ability of dams to retain the intrusion, allowing for quicker saltwater spillage past the wall. The natural cleanup of SWI-contaminated coastal aquifers was, for the first time, evidenced in heterogeneous settings. Depending on the stratification pattern, the presence of stratified layers however prolonged the cleanup time to various degrees, compared to the homogeneous scenario, particularly in case HL, where the cleanup time was nearly 50% longer.
Model of monopolistic competition with heterogeneous labor
Directory of Open Access Journals (Sweden)
Filatov Alexander
2017-01-01
Full Text Available The paper presents a tool for modelling monopolistic competition markets, based on Dixit-Stiglitz ideology but taking into account heterogeneity at labor market. We analyse several modifications of a two-sector general equilibrium model. In the basic one with two levels of workers qualification their shares are determined endogenously on the base of comparison between the higher wage of the skilled worker and heterogeneous education costs, also taking into account the labor mobility between the manufacture and agriculture sector. The model is generalized for the case of continuous distribution of labor qualification. The impact of the model parameters (ratio of fixed and variable costs, market size, heterogeneity in productivity, elasticity of substitution, etc. on the obtained equilibrium prices, quantities, wages, number and size of firms, social welfare is investigated.
Elements of complexity in subsurface modeling, exemplified with three case studies
Energy Technology Data Exchange (ETDEWEB)
Freedman, Vicky L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rockhold, Mark [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bacon, Diana H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Freshley, Mark D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wellman, Dawn M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2017-04-03
There are complexity elements to consider when applying subsurface flow and transport models to support environmental analyses. Modelers balance the benefits and costs of modeling along the spectrum of complexity, taking into account the attributes of more simple models (e.g., lower cost, faster execution, easier to explain, less mechanistic) and the attributes of more complex models (higher cost, slower execution, harder to explain, more mechanistic and technically defensible). In this paper, modeling complexity is examined with respect to considering this balance. The discussion of modeling complexity is organized into three primary elements: 1) modeling approach, 2) description of process, and 3) description of heterogeneity. Three examples are used to examine these complexity elements. Two of the examples use simulations generated from a complex model to develop simpler models for efficient use in model applications. The first example is designed to support performance evaluation of soil vapor extraction remediation in terms of groundwater protection. The second example investigates the importance of simulating different categories of geochemical reactions for carbon sequestration and selecting appropriate simplifications for use in evaluating sequestration scenarios. In the third example, the modeling history for a uranium-contaminated site demonstrates that conservative parameter estimates were inadequate surrogates for complex, critical processes and there is discussion on the selection of more appropriate model complexity for this application. All three examples highlight how complexity considerations are essential to create scientifically defensible models that achieve a balance between model simplification and complexity.
Computational model of heterogeneous heating in melanin
Kellicker, Jason; DiMarzio, Charles A.; Kowalski, Gregory J.
2015-03-01
Melanin particles often present as an aggregate of smaller melanin pigment granules and have a heterogeneous surface morphology. When irradiated with light within the absorption spectrum of melanin, these heterogeneities produce measurable concentrations of the electric field that result in temperature gradients from thermal effects that are not seen with spherical or ellipsoidal modeling of melanin. Modeling melanin without taking into consideration the heterogeneous surface morphology yields results that underestimate the strongest signals or over{estimate their spatial extent. We present a new technique to image phase changes induced by heating using a computational model of melanin that exhibits these surface heterogeneities. From this analysis, we demonstrate the heterogeneous energy absorption and resulting heating that occurs at the surface of the melanin granule that is consistent with three{photon absorption. Using the three{photon dluorescence as a beacon, we propose a method for detecting the extents of the melanin granule using photothermal microscopy to measure the phase changes resulting from the heating of the melanin.
Emerge - A Python environment for the modeling of subsurface transfers
Lopez, S.; Smai, F.; Sochala, P.
2014-12-01
The simulation of subsurface mass and energy transfers often relies on specific codes that were mainly developed using compiled languages which usually ensure computational efficiency at the expense of relatively long development times and relatively rigid software. Even if a very detailed, possibly graphical, user-interface is developed the core numerical aspects are rarely accessible and the smallest modification will always need a compilation step. Thus, user-defined physical laws or alternative numerical schemes may be relatively difficult to use. Over the last decade, Python has emerged as a popular and widely used language in the scientific community. There already exist several libraries for the pre and post-treatment of input and output files for reservoir simulators (e.g. pytough). Development times in Python are considerably reduced compared to compiled languages, and programs can be easily interfaced with libraries written in compiled languages with several comprehensive numerical libraries that provide sequential and parallel solvers (e.g. PETSc, Trilinos…). The core objective of the Emerge project is to explore the possibility to develop a modeling environment in full Python. Consequently, we are developing an open python package with the classes/objects necessary to express, discretize and solve the physical problems encountered in the modeling of subsurface transfers. We heavily relied on Python to have a convenient and concise way of manipulating potentially complex concepts with a few lines of code and a high level of abstraction. Our result aims to be a friendly numerical environment targeting both numerical engineers and physicist or geoscientists with the possibility to quickly specify and handle geometries, arbitrary meshes, spatially or temporally varying properties, PDE formulations, boundary conditions…
Low-Rank Kalman Filtering in Subsurface Contaminant Transport Models
El Gharamti, Mohamad
2010-12-01
Understanding the geology and the hydrology of the subsurface is important to model the fluid flow and the behavior of the contaminant. It is essential to have an accurate knowledge of the movement of the contaminants in the porous media in order to track them and later extract them from the aquifer. A two-dimensional flow model is studied and then applied on a linear contaminant transport model in the same porous medium. Because of possible different sources of uncertainties, the deterministic model by itself cannot give exact estimations for the future contaminant state. Incorporating observations in the model can guide it to the true state. This is usually done using the Kalman filter (KF) when the system is linear and the extended Kalman filter (EKF) when the system is nonlinear. To overcome the high computational cost required by the KF, we use the singular evolutive Kalman filter (SEKF) and the singular evolutive extended Kalman filter (SEEKF) approximations of the KF operating with low-rank covariance matrices. The SEKF can be implemented on large dimensional contaminant problems while the usage of the KF is not possible. Experimental results show that with perfect and imperfect models, the low rank filters can provide as much accurate estimates as the full KF but at much less computational cost. Localization can help the filter analysis as long as there are enough neighborhood data to the point being analyzed. Estimating the permeabilities of the aquifer is successfully tackled using both the EKF and the SEEKF.
Modelling Interconnectedness of Subsurface Flow Processes from a ...
African Journals Online (AJOL)
The study determined subsurface flow processes of 92.3 ha catchment area in order to examine functional relationship among the surface and subsurface flow variables from the water balance components data. Days without rainfall had zero infiltration while peak values of infiltrated water corresponded with peak rainfall.
Heterogeneous expectations in monetary DSGE models
Massaro, D.
2013-01-01
This paper derives a general New Keynesian framework with heterogeneous expectations by explicitly solving the micro-foundations underpinning the model. The resulting reduced form is analytically tractable and encompasses the representative rational agent benchmark as a special case. We specify a
Prospect Theory in the Heterogeneous Agent Model
Czech Academy of Sciences Publication Activity Database
Polach, J.; Kukačka, Jiří
(2018) ISSN 1860-711X R&D Projects: GA ČR(CZ) GBP402/12/G097 Institutional support: RVO:67985556 Keywords : Heterogeneous Agent Model * Prospect Theory * Behavioral finance * Stylized facts Subject RIV: AH - Economics OBOR OECD: Finance Impact factor: 0.931, year: 2016 http://library.utia.cas.cz/separaty/2018/E/kukacka-0488438. pdf
Testing spatial heterogeneity with stock assessment models
DEFF Research Database (Denmark)
Jardim, Ernesto; Eero, Margit; Silva, Alexandra
2018-01-01
This paper describes a methodology that combines meta-population theory and stock assessment models to gain insights about spatial heterogeneity of the meta-population in an operational time frame. The methodology was tested with stochastic simulations for different degrees of connectivity betwee...
Molecular Simulation towards Efficient and Representative Subsurface Reservoirs Modeling
Kadoura, Ahmad
2016-09-01
This dissertation focuses on the application of Monte Carlo (MC) molecular simulation and Molecular Dynamics (MD) in modeling thermodynamics and flow of subsurface reservoir fluids. At first, MC molecular simulation is proposed as a promising method to replace correlations and equations of state in subsurface flow simulators. In order to accelerate MC simulations, a set of early rejection schemes (conservative, hybrid, and non-conservative) in addition to extrapolation methods through reweighting and reconstruction of pre-generated MC Markov chains were developed. Furthermore, an extensive study was conducted to investigate sorption and transport processes of methane, carbon dioxide, water, and their mixtures in the inorganic part of shale using both MC and MD simulations. These simulations covered a wide range of thermodynamic conditions, pore sizes, and fluid compositions shedding light on several interesting findings. For example, the possibility to have more carbon dioxide adsorbed with more preadsorbed water concentrations at relatively large basal spaces. The dissertation is divided into four chapters. The first chapter corresponds to the introductory part where a brief background about molecular simulation and motivations are given. The second chapter is devoted to discuss the theoretical aspects and methodology of the proposed MC speeding up techniques in addition to the corresponding results leading to the successful multi-scale simulation of the compressible single-phase flow scenario. In chapter 3, the results regarding our extensive study on shale gas at laboratory conditions are reported. At the fourth and last chapter, we end the dissertation with few concluding remarks highlighting the key findings and summarizing the future directions.
Sculpting Mountains: Interactive Terrain Modeling Based on Subsurface Geology.
Cordonnier, Guillaume; Cani, Marie-Paule; Benes, Bedrich; Braun, Jean; Galin, Eric
2018-05-01
Most mountain ranges are formed by the compression and folding of colliding tectonic plates. Subduction of one plate causes large-scale asymmetry while their layered composition (or stratigraphy) explains the multi-scale folded strata observed on real terrains. We introduce a novel interactive modeling technique to generate visually plausible, large scale terrains that capture these phenomena. Our method draws on both geological knowledge for consistency and on sculpting systems for user interaction. The user is provided hands-on control on the shape and motion of tectonic plates, represented using a new geologically-inspired model for the Earth crust. The model captures their volume preserving and complex folding behaviors under collision, causing mountains to grow. It generates a volumetric uplift map representing the growth rate of subsurface layers. Erosion and uplift movement are jointly simulated to generate the terrain. The stratigraphy allows us to render folded strata on eroded cliffs. We validated the usability of our sculpting interface through a user study, and compare the visual consistency of the earth crust model with geological simulation results and real terrains.
Canales, I.; Fucugauchi, J. U.; Perez-Cruz, L. L.; Camargo, A. Z.; Perez-Cruz, G.
2011-12-01
Asymmetries in the geophysical signature of Chicxulub crater are being evaluated to investigate on effects of impact angle and trajectory and pre-existing target structural controls for final crater form. Early studies interpreted asymmetries in the gravity anomaly in the offshore sector to propose oblique either northwest- and northeast-directed trajectories. An oblique impact was correlated to the global ejecta distribution and enhanced environmental disturbance. In contrast, recent studies using marine seismic data and computer modeling have shown that crater asymmetries correlate with pre-existing undulations of the Cretaceous continental shelf, suggesting a structural control of target heterogeneities. Documentation of Yucatan subsurface stratigraphy has been limited by lack of outcrops of pre-Paleogene rocks. The extensive cover of platform carbonate rocks has not been affected by faulting or deformation and with no rivers cutting the carbonates, information comes mainly from the drilling programs and geophysical surveys. Here we revisit the subsurface stratigraphy in the crater area from the well log data and cores retrieved in the drilling projects and marine seismic reflection profiles. Other source of information being exploited comes from the impact breccias, which contain a sampling of disrupted target sequences, including crystalline basement and Mesozoic sediments. We analyze gravity and seismic data from the various exploration surveys, including multiple Pemex profiles in the platform and the Chicxulub experiments. Analyses of well log data and seismic profiles identify contacts for Lower Cretaceous, Cretaceous/Jurassic and K/Pg boundaries. Results show that the Cretaceous continental shelf was shallower on the south and southwest than on the east, with emerged areas in Quintana Roo and Belize. Mesozoic and upper Paleozoic sediments show variable thickness, possibly reflecting the crystalline basement regional structure. Paleozoic and Precambrian
Modeling vaccination in a heterogeneous metapopulation system
Lachiany, Menachem
2016-09-01
We present here a multicity SIS epidemic model with vaccination. The model describes the dynamics of heterogeneous metapopulations that contain imperfectly vaccinated individuals. The effect of vaccination on heterogeneous multicity models has not been previously studied. We show that under very generic conditions, the epidemic threshold does not depend on the diffusion coefficient of the vaccinated individuals, but it does depend on the diffusion coefficient of the infected population. We then show, using a novel methodology, that the reproduction number is determined by the homogeneous model parameters and by the maximal number of neighbors a city can have, when the diffusion coefficient of the infected population is low. Finally, we present numerical simulations to support the analytical results.
A Unified 3D Spatial Data Model for Surface and Subsurface Spatial ...
African Journals Online (AJOL)
user
surface. LoD maps for surface and subsurface integration exist for most city centres but the 3D component is lacking and this ... the integration of surface and subsurface models are discussed and a geometric, topological 3D object oriented model is sug- gested. .... dimensional (3D) continuous geological stratigraphy,.
Plampin, M. R.; Lassen, R. N.; Sakaki, T.; Pawar, R.; Jensen, K.; Illangasekare, T. H.
2013-12-01
A concern for geologic carbon sequestration is the potential for CO2 stored in deep geologic formations to leak upward into shallow freshwater aquifers where it can have potentially detrimental impacts to the environment and human health. Understanding the mechanisms of CO2 exsolution, migration and accumulation (collectively referred to as 'gas evolution') in the shallow subsurface is critical to predict and mitigate the environmental impacts. During leakage, CO2 can move either as free-phase or as a dissolved component of formation brine. CO2 dissolved in brine may travel upward into shallow freshwater systems, and the gas may be released from solution. In the shallow aquifer, the exsolved gas may accumulate near interfaces between soil types, and/or create flow paths that allow the gas to escape through the vadose zone to the atmosphere. The process of gas evolution in the shallow subsurface is controlled by various factors, including temperature, dissolved CO2 concentration, water pressure, background water flow rate, and geologic heterogeneity. However, the conditions under which heterogeneity controls gas phase evolution have not yet been precisely defined and can therefore not yet be incorporated into models used for environmental risk assessment. The primary goal of this study is to conduct controlled laboratory experiments to help fill this knowledge gap. With this as a goal, a series of intermediate-scale laboratory experiments were conducted to observe CO2 gas evolution in porous media at multiple scales. Deionized water was saturated with dissolved CO2 gas under a specified pressure (the saturation pressure) before being injected at a constant volumetric flow rate into the bottom of a 1.7 meter-tall by 5.7 centimeter-diameter column or a 2.4 meter-tall by 40 centimeter-wide column that were both filled with sand in various heterogeneous packing configurations. Both test systems were initially saturated with fresh water and instrumented with soil
Modelling Configuration Knowledge in Heterogeneous Product Families
DEFF Research Database (Denmark)
Queva, Matthieu Stéphane Benoit; Männistö, Tomi; Ricci, Laurent
2011-01-01
the variability in such heterogeneous product families. Our approach is based on a framework that aims to cater for the different stakeholders involved in the modelling and management of the product family. The modelling approach is centred around the concepts of views, types and constraints and is illustrated...... by a motivation example. Furthermore, as a proof of concept, a prototype has been implemented for configuring a non-trivial heterogeneous product family.......Product configuration systems play an important role in the development of Mass Customisation. The configuration of complex product families may nowadays involve multiple design disciplines, e.g. hardware, software and services. In this paper, we present a conceptual approach for modelling...
Modeling CO2 Gas Migration of Shallow Subsurface CO2 Leakage Experiments
Porter, M. L.; Plampin, M. R.; Pawar, R.; Illangasekare, T. H.
2013-12-01
Leakage of injected CO2 into shallow subsurface aquifers or back into the atmosphere at geologic carbon sequestration sites is a risk that must be minimized. One potential CO2 leakage pathway involves the transport of dissolved CO2 into a shallow aquifer where the CO2 exsolves, forming a free CO2 gas phase that subsequently migrates through the aquifer. In order to reduce the negative effects of CO2 exsolution, it is important to fully understand each of the processes controlling the movement CO2, as well as the effects of aquifer heterogeneity on the overall fate and transport of CO2. In this work, we present multiphase flow simulations of intermediate scale CO2 exsolution experiments. The multiphase flow simulations were carried out using the Finite Element Heat and Mass Transfer code (FEHM) developed at Los Alamos National Laboratory. Simulations were first designed to model experiments conducted in two different homogeneous packed sands. PEST (Parameter Estimation and Uncertainty Analysis) was used to optimize multiphase flow parameters (i.e., porosity, permeability, relative permeability, and capillary pressure) within FEHM. The optimized parameters were subsequently used to model heterogeneous experiments consisting of various packing configurations using the same sands. Comparisons of CO2 saturation between experiments and simulations will be presented and analyzed.
Nousiainen, Riikka; Warsta, Lassi; Turunen, Mika; Huitu, Hanna; Koivusalo, Harri; Pesonen, Liisa
2015-10-01
Effectiveness of a subsurface drainage system decreases with time, leading to a need to restore the drainage efficiency by installing new drain pipes in problem areas. The drainage performance of the resulting system varies spatially and complicates runoff and nutrient load generation within the fields. We presented a method to estimate the drainage performance of a heterogeneous subsurface drainage system by simulating the area with the three-dimensional hydrological FLUSH model. A GIS analysis was used to delineate the surface runoff contributing area in the field. We applied the method to reproduce the water balance and to investigate the effectiveness of a subsurface drainage network of a clayey field located in southern Finland. The subsurface drainage system was originally installed in the area in 1971 and the drainage efficiency was improved in 1995 and 2005 by installing new drains. FLUSH was calibrated against total runoff and drain discharge data from 2010 to 2011 and validated against total runoff in 2012. The model supported quantification of runoff fractions via the three installed drainage networks. Model realisations were produced to investigate the extent of the runoff contributing areas and the effect of the drainage parameters on subsurface drain discharge. The analysis showed that better model performance was achieved when the efficiency of the oldest drainage network (installed in 1971) was decreased. Our analysis method can reveal the drainage system performance but not the reason for the deterioration of the drainage performance. Tillage layer runoff from the field was originally computed by subtracting drain discharge from the total runoff. The drains installed in 1995 bypass the measurement system, which renders the tillage layer runoff calculation procedure invalid after 1995. Therefore, this article suggests use of a local correction coefficient based on the simulations for further research utilizing data from the study area.
Mathematical analysis of epidemiological models with heterogeneity
Energy Technology Data Exchange (ETDEWEB)
Van Ark, J.W.
1992-01-01
For many diseases in human populations the disease shows dissimilar characteristics in separate subgroups of the population; for example, the probability of disease transmission for gonorrhea or AIDS is much higher from male to female than from female to male. There is reason to construct and analyze epidemiological models which allow this heterogeneity of population, and to use these models to run computer simulations of the disease to predict the incidence and prevalence of the disease. In the models considered here the heterogeneous population is separated into subpopulations whose internal and external interactions are homogeneous in the sense that each person in the population can be assumed to have all average actions for the people of that subpopulation. The first model considered is an SIRS models; i.e., the Susceptible can become Infected, and if so he eventually Recovers with temporary immunity, and after a period of time becomes Susceptible again. Special cases allow for permanent immunity or other variations. This model is analyzed and threshold conditions are given which determine whether the disease dies out or persists. A deterministic model is presented; this model is constructed using difference equations, and it has been used in computer simulations for the AIDS epidemic in the homosexual population in San Francisco. The homogeneous version and the heterogeneous version of the differential-equations and difference-equations versions of the deterministic model are analyzed mathematically. In the analysis, equilibria are identified and threshold conditions are set forth for the disease to die out if the disease is below the threshold so that the disease-free equilibrium is globally asymptotically stable. Above the threshold the disease persists so that the disease-free equilibrium is unstable and there is a unique endemic equilibrium.
Smart predictors in the heterogeneous agent model
Czech Academy of Sciences Publication Activity Database
Baruník, Jozef; Vácha, Lukáš; Vošvrda, Miloslav
2009-01-01
Roč. 4, č. 2 (2009), s. 163-172 ISSN 1860-711X R&D Projects: GA ČR GP402/08/P207; GA ČR GA402/09/0965 Grant - others:GAUK(CZ) 46108 Institutional research plan: CEZ:AV0Z10750506 Keywords : Heterogeneous agent model * Market structure * Smart traders * Hurst exponent Subject RIV: AH - Economics
3D modelling of the shallow subsurface of Zeeland, the Netherlands
Stafleu, J.; Busschers, F.S.; Maljers, D.; Menkovic, A.
2011-01-01
The Geological Survey of the Netherlands aims at building a 3D geological voxel model of the upper 30 m of the subsurface of the Netherlands in order to provide a sound basis for subsurface related questions on, amongst others, groundwater extraction and management, land subsidence studies,
International Nuclear Information System (INIS)
Majer, Ernest L.; Brockman, Fred J.
1999-01-01
This research is an integrated project which uses physical (geophysical and hydrologic) and innovative geophysical imaging and microbial characterization methods to identify key scales of physical heterogeneities that affect bioremediation. In the this effort data from controlled laboratory and in situ experiments at the Idaho National Engineering and Environmental (INEEL) Test Area North (TAN) site were used to determine the dominant physical characteristics (lithologic, structural, and hydrologic) that can be imaged in situ and correlated with flow and transport properties. Emphasis was placed on identifying fundamental scales of variation of physical parameters that control transport behavior relative to subsurface microbial dynamics that could be used to develop a predictive model. A key hypothesis of the work was that nutrient flux and transport properties are key factors in controlling microbial dynamics, and that geophysical techniques could be used to identify the critical physical properties and scales controlling transport. This hypothesis was essentially validated. The goal was not only to develop and apply methods to monitor the spatial and temporal distribution of the bioremediation in fractured sites such as TAN, but also to develop methods applicable to a wider range of DOE sites. The outcome has been an improved understanding of the relationship between physical, chemical and microbial processes in heterogeneous environments, thus applicable to the design and monitoring of bioremediation strategies for a variety of environments. In this EMSP work we demonstrated that high resolution geophysical methods have considerable resolving power, especially when linked with modern advanced processing and interpretation. In terms of basic science, in addition to providing innovative methods for monitoring bioremediation, the work also provided a strong motivation for developing and extending high resolution geophysical methods
Two-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals (2DFATMIC) Model
This model simulates subsurface flow, fate, and transport of contaminants that are undergoing chemical or biological transformations. This model is applicable to transient conditions in both saturated and unsaturated zones.
Three-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals (3DFATMIC) Model
This model simulates subsurface flow, fate and transport of contaminants that are undergoing chemical or biological transformations. The model is applicable to transient conditions in both saturated and unsaturated zones.
International Nuclear Information System (INIS)
Becker, B.H.
2002-01-01
A source release model was developed to determine the release of contaminants into the shallow subsurface, as part of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) evaluation at the Idaho National Engineering and Environmental Laboratory's (INEEL) Subsurface Disposal Area (SDA). The output of the source release model is used as input to the subsurface transport and biotic uptake models. The model allowed separating the waste into areas that match the actual disposal units. This allows quantitative evaluation of the relative contribution to the total risk and allows evaluation of selective remediation of the disposal units within the SDA
Modeling the Dutch subsurface: From paper product towards dissemination of a 3D-digital model
Dulk, M. den; Doornenbal, J.C.; Veen, J.H. ten
2015-01-01
The Geological Survey of the Netherlands carried out several major mapping projects to construct a consistent, regional-scale petroleum geological framework for the deep subsurface of the Netherlands, both on- and offshore. In the last decade the modeling approach has developed into a fully digital
Modeling subsurface fluxes of dissolved organic carbon at the hillslope scale
Dusek, Jaromir; Vogel, Tomas; Dohnal, Michal; Barth, Johannes A. C.; Sanda, Martin; Marx, Anne; Jankovec, Jakub
2017-04-01
Reliable quantitative prediction of water movement and fluxes of dissolved organic carbon (DOC) at both hillslope and catchment scales remains a challenge due to complex boundary conditions and soil spatial heterogeneity. In this study, a one-dimensional dual-continuum vertical flow and transport model was used to analyze subsurface transport processes in a forest hillslope soil over a period of 2.5 years. Among the processes determining the DOC distribution in the soil profile the microbially mediated transformations of DOC, dependent on soil moisture and soil temperature conditions, were considered. To quantify uncertainty associated with the model parameterization, Monte Carlo analysis was performed. The model was applied to describe the transformation of DOC source into output signal observed in the hillslope stormflow. Despite the complex nature of microbial transformations that caused uncertainty in model parameters and subsequent prediction of DOC transport, the simulated temporal patterns of DOC concentration in stormflow showed similar behavior to that reflected in the observed DOC fluxes. Due to preferential flow, the hillslope DOC export was higher than the amounts that are usually found in the available literature.
Phenotypic heterogeneity in modeling cancer evolution.
Directory of Open Access Journals (Sweden)
Ali Mahdipour-Shirayeh
Full Text Available The unwelcome evolution of malignancy during cancer progression emerges through a selection process in a complex heterogeneous population structure. In the present work, we investigate evolutionary dynamics in a phenotypically heterogeneous population of stem cells (SCs and their associated progenitors. The fate of a malignant mutation is determined not only by overall stem cell and non-stem cell growth rates but also differentiation and dedifferentiation rates. We investigate the effect of such a complex population structure on the evolution of malignant mutations. We derive exactly calculated results for the fixation probability of a mutant arising in each of the subpopulations. The exactly calculated results are in almost perfect agreement with the numerical simulations. Moreover, a condition for evolutionary advantage of a mutant cell versus the wild type population is given in the present study. We also show that microenvironment-induced plasticity in invading mutants leads to more aggressive mutants with higher fixation probability. Our model predicts that decreasing polarity between stem and non-stem cells' turnover would raise the survivability of non-plastic mutants; while it would suppress the development of malignancy for plastic mutants. The derived results are novel and general with potential applications in nature; we discuss our model in the context of colorectal/intestinal cancer (at the epithelium. However, the model clearly needs to be validated through appropriate experimental data. This novel mathematical framework can be applied more generally to a variety of problems concerning selection in heterogeneous populations, in other contexts such as population genetics, and ecology.
Modelling near subsurface temperature with mixed type boundary ...
Indian Academy of Sciences (India)
geothermal data to extract both climate and groundwater flow signals. 1. Introduction. There is great interest to know past climate, especially to infer any anthropogenic signals in present climate by inter-comparison. The obser- vations of subsurface thermal regime in boreholes have been used to infer earth's thermal history.
A neural network model for non invasive subsurface stratigraphic identification
International Nuclear Information System (INIS)
Sullivan, John M. Jr.; Ludwig, Reinhold; Lai Qiang
2000-01-01
Ground-Penetrating Radar (GRP) is a powerful tool to examine the stratigraphy below ground surface for remote sensing. Increasingly GPR has also found applications in microwave NDE as an interrogation tool to assess dielectric layers. Unfortunately, GPR data is characterized by a high degree of uncertainty and natural physical ambiguity. Robust decomposition routines are sparse for this application. We have developed a hierarchical set of neural network modules which split the task of layer profiling into consecutive stages. Successful GPR profiling of the subsurface stratigraphy is of key importance for many remote sensing applications including microwave NDE. Neural network modules were designed to accomplish the two main processing goals of recognizing the 'subsurface pattern' followed by the identification of the depths of the subsurface layers like permafrost, groundwater table, and bedrock. We used an adaptive transform technique to transform raw GPR data into a small feature vector containing the most representative and discriminative features of the signal. This information formed the input for the neural network processing units. This strategy reduced the number of required training samples for the neural network by orders of magnitude. The entire processing system was trained using the adaptive transformed feature vector inputs and tested with real measured GPR data. The successful results of this system establishes the feasibility the feasibility of delineating subsurface layering nondestructively
A multi-region approach to modeling subsurface flow
International Nuclear Information System (INIS)
Gwo, J.P.; Yeh, G.T.; Wilson, G.V.
1990-01-01
In this approach the media are assumed to contain n pore-regions at any physical point. Each region has different pore size and hydrologic parameters. Inter-region exchange is approximated by a linear transfer process. Based on the mass balance principle, a system of equations governing the flow and mass exchange in structured or aggregated soils is derived. This system of equations is coupled through linear transfer terms representing the interchange among different pore regions. A numerical MUlti-Region Flow (MURF) model, using the Galerkin finite element method to facilitate the treatment of local and field-scale heterogeneities, is developed to solve the system of equations. A sparse matrix solver is used to solve the resulting matrix equation, which makes the application of MURF to large field problems feasible in terms of CPU time and storage limitations. MURF is first verified by applying it to a ponding infiltration problem over a hill slope, which is a single-region problem and has been previously simulated by a single-region model. Very good agreement is obtained between the results from the two different models. The MURF code is thus partially verified. It is then applied to a two-region fractured medium to investigate the effects of multi-region approach on the flow field. The results are comparable to that obtained by other investigators. (Author) (15 refs., 6 figs., tab.)
Vázquez-Suñé, Enric; Ángel Marazuela, Miguel; Velasco, Violeta; Diviu, Marc; Pérez-Estaún, Andrés; Álvarez-Marrón, Joaquina
2016-09-01
The overdevelopment of cities since the industrial revolution has shown the need to incorporate a sound geological knowledge in the management of required subsurface infrastructures and in the assessment of increasingly needed groundwater resources. Additionally, the scarcity of outcrops and the technical difficulty to conduct underground exploration in urban areas highlights the importance of implementing efficient management plans that deal with the legacy of heterogeneous subsurface information. To deal with these difficulties, a methodology has been proposed to integrate all the available spatio-temporal data into a comprehensive spatial database and a set of tools that facilitates the analysis and processing of the existing and newly added data for the city of Barcelona (NE Spain). Here we present the resulting actual subsurface 3-D geological model that incorporates and articulates all the information stored in the database. The methodology applied to Barcelona benefited from a good collaboration between administrative bodies and researchers that enabled the realization of a comprehensive geological database despite logistic difficulties. Currently, the public administration and also private sectors both benefit from the geological understanding acquired in the city of Barcelona, for example, when preparing the hydrogeological models used in groundwater assessment plans. The methodology further facilitates the continuous incorporation of new data in the implementation and sustainable management of urban groundwater, and also contributes to significantly reducing the costs of new infrastructures.
Modelling Preference Heterogeneity for Theatre Tickets
DEFF Research Database (Denmark)
Baldin, Andrea; Bille, Trine
2018-01-01
This article analyses the behavioural choice for theatre tickets using a rich data set for 2010–2013 from the sale system of the Royal Danish National Theatre. A consumer who decides to attend a theatre production faces multiple sources of price variation that involves a choice by the consumer...... among different ticket alternatives. Three modelling approaches are proposed in order to model ticket purchases: conditional logit with socio-demographic characteristics, nested logit and latent class. These models allow us explicitly to take into account consumers’ preference heterogeneity with respect...... to the attributes associated with each ticket alternative (quality of the seat and day of the performance). In addition, the willingness to pay of choice attributes is estimated. Final results suggest that customers’ characteristics in terms of age and frequency of theatre attendance characterize different patterns...
Final Report: A Model Management System for Numerical Simulations of Subsurface Processes
Energy Technology Data Exchange (ETDEWEB)
Zachmann, David
2013-10-07
The DOE and several other Federal agencies have committed significant resources to support the development of a large number of mathematical models for studying subsurface science problems such as groundwater flow, fate of contaminants and carbon sequestration, to mention only a few. This project provides new tools to help decision makers and stakeholders in subsurface science related problems to select an appropriate set of simulation models for a given field application.
Modelling Preference Heterogeneity for Theatre Tickets
DEFF Research Database (Denmark)
Baldin, Andrea; Bille, Trine
This paper analyzes the behavioural choice for theatre tickets using a rich dataset for 2010-2013 from the sale system of the Royal Danish National Theatre. A consumer who decides to attend a theater production faces multiple sources of price variation that depends on: socio-economic characterist......This paper analyzes the behavioural choice for theatre tickets using a rich dataset for 2010-2013 from the sale system of the Royal Danish National Theatre. A consumer who decides to attend a theater production faces multiple sources of price variation that depends on: socio......-economic characteristics, quality of the seat, day of the performance and timing of purchase. Except for the first case, factors of price differentiation involves a choice by the consumer among different ticket alternatives. Two modelling approaches, namely multinomial logit (with socio-demographic characteristics......) and latent class are proposed in order to model ticket purchase behaviour. These models allow us explicitly to take into account consumers' preference heterogeneity with respect to the attributes associated to each ticket alternative In addition, the distribution of the willingness-to-pay (WTP) of choice...
3D subsurface modelling reveals the shallow geology of Amsterdam
Schokker, J.; Bakker, M.A.W.; Dubelaar, C.W.; Dambrink, R.M.; Harting, R.
2015-01-01
Amsterdam is situated on the coastal-deltaic plain of the western Netherlands. Its geographical position brought the city prosperity, but also created huge challenges associated with heterogeneous and often adverse ground conditions. This paper explores the geology of Amsterdam to a depth of c. 100
Srinivas, G.; Chowdary, Jasti S.; Gnanaseelan, C.; Prasad, K. V. S. R.; Karmakar, Ananya; Parekh, Anant
2018-03-01
In the present study the association between mean and interannual subsurface temperature bias over the equatorial Indian Ocean (EIO) is investigated during boreal summer (June through September; JJAS) in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. Anomalously high subsurface warm bias (greater than 3 °C) over the eastern EIO (EEIO) region is noted in CFSv2 during summer, which is higher compared to other parts of the tropical Indian Ocean. Prominent eastward current bias in the upper 100 m over the EIO region induced by anomalous westerly winds is primarily responsible for subsurface temperature bias. The eastward currents transport warm water to the EEIO and is pushed down to subsurface due to downwelling. Thus biases in both horizontal and vertical currents over the EIO region support subsurface warm bias. The evolution of systematic subsurface warm bias in the model shows strong interannual variability. These maximum subsurface warming episodes over the EEIO are mainly associated with La Niña like forcing. Strong convergence of low level winds over the EEIO and Maritime continent enhanced the westerly wind bias over the EIO during maximum warming years. This low level convergence of wind is induced by the bias in the gradient in the mean sea level pressure with positive bias over western EIO and negative bias over EEIO and parts of western Pacific. Consequently, changes in the atmospheric circulation associated with La Niña like conditions affected the ocean dynamics by modulating the current bias thereby enhancing the subsurface warm bias over the EEIO. It is identified that EEIO subsurface warming is stronger when La Niña co-occurred with negative Indian Ocean Dipole events as compared to La Niña only years in the model. Ocean general circulation model (OGCM) experiments forced with CFSv2 winds clearly support our hypothesis that ocean dynamics influenced by westerly winds bias is primarily
Towards inverse modeling of intratumor heterogeneity
Brutovsky Branislav; Horvath Denis
2015-01-01
Development of resistance limits efficiency of present anticancer therapies and preventing it remains a big challenge in cancer research. It is accepted, at the intuitive level, that resistance emerges as a consequence of the heterogeneity of cancer cells at the molecular, genetic and cellular levels. Produced by many sources, tumor heterogeneity is extremely complex time dependent statistical characteristics which may be quantified by measures defined in many differen...
Towards Inverse Modeling of Intratumoral Heterogeneity
Brutovsky, Branislav; Horvath, Denis
2014-01-01
Development of resistance limits efficiency of present anticancer therapies and preventing it remains big challenge in cancer research. It is accepted, at intuitive level, that the resistance emerges as a consequence of cancer cells heterogeneity at molecular, genetic and cellular levels. Produced by many sources, tumor heterogeneity is extremely complex time dependent statistical characteristics which may be quantified by the measures defined in many different ways, most of them coming from ...
Hokanson, Kelly; Carrera-Hernández, Jaime; Devito, Kevin; Mendoza, Carl
2016-04-01
The Boreal Plains (BP) region of Canada is experiencing high levels of anthropogenic activity and may be susceptible to climate change to various degrees. The BP is characterized by heterogeneous glacial landforms, with large contrasts in storage and transmissivity, which when coupled with wet-dry climate cycles, results in complex groundwater-surface water interactions. Predicting the impacts of land use change, climate change, and the future performance of constructed and reclaimed landscapes is currently not possible due to our limited knowledge regarding the natural variability of water table fluctuations, geochemistry, and salinity across the various glacial landforms in the BP. We compare isotopes, EC, chemistry (DOC, Ca, Mg, SO4) and water table position between a drought (2003) and a wet (2013) year to examine the interactions between climate, landform, and geology on the variation in landscape connectivity and overall salinity distribution. Data were collected from surface waters to a depth of 40 m, along a 50 km transect encompassing pond-wetland-forestland sequences across the major glacial depositional types typical of the BP (coarse textured glaciofluvial outwash, fine textured stagnant ice moraine, and lacustrine clay plain). Within each landform, sites range from isolated local flow systems to large intermediate scale flow systems. High spatial variability of water table fluctuations and salinity illustrate the strong regional controls that climate and geology exerts over scales of groundwater flow between landforms and surface water bodies across the BP, reinforcing the need to link surface water and groundwater processes when developing conceptual models. Additionally, when coupled with a strong, physical hydrogeologic conceptual model, synoptic chemical and isotopic surveys can be used to confirm scales and directions of flow; however, without an understanding of the climatic and geologic influence of the region, such data cannot be used as a
Los Alamos Radiation Hydrocode Models of Asteroid Mitigation by a Subsurface Explosion
Weaver, R.; Plesko, C. S.; Dearholt, W.
2010-12-01
Mitigation of a potentially hazardous object (PHO) by a nuclear subsurface explosion is considered. In this new work we examine non-central subsurface emplacements and seek an optimal depth-of-burial for various explosion energies. This intervention methodology has been popularized in media presentations and is considered as one possible method of impact-hazard mitigation. We present new RAGE radiation hydrocode models of the shock-generated disruption of PHOs by subsurface nuclear bursts and deflection from shallow buried bursts using scenario-specific models from authentic RADAR shape models. We will show 2D and 3D models for the disruption by a large energy source at the center and near the edge (mitigation) of such PHO models (1-10 Mton TNT equivalent), specifically for asteroid 25143 Itokawa. Parametric studies will be done on: the value of the source energy (from 100 Kton to 10 Mton), the parameters in the Steinberg-Guinan strength model used and the internal composition of the object from uniform composition to a “rubble pile” distribution. Specifically we are interested in assessing the optimum depth of burial and energy required to essentially disrupt and/or move the PHO and therefore mitigate the hazard. Recollection will be considered. (LA-UR-10-05860) A subsurface 1 Mt explosion near the long-axis surface of an Itokawa shape model with a non-uniform internal composition. The resulting velocity imparted to the bulk remainder of the object is ~50 m/s.
Fully Integrated Atmospheric, Surface, and Subsurface Model of the California Basin
Davison, J. H.; Hwang, H. T.; Sudicky, E. A.; Mallia, D. V.; Lin, J. C.
2016-12-01
The recent drought in the Western United States has crippled agriculture in California's Central Valley. Farmers, facing reduced surface water flow, have turned to groundwater as their primary solution to the water crisis. However, the unsustainable pumping rates seen throughout California have drastically decreased the surface and subsurface water levels. For this reason, we developed a coupled subsurface, surface, and atmospheric model for the entire California Basin that captures the feedbacks between the three domains at an extremely high spatial and temporal resolution. Our coupled model framework integrates HydroGeoSphere (HGS), a fully implicit three-dimensional control-volume finite element surface and variably saturated subsurface model with evapotranspiration process, to Weather Research and Forecasting (WRF), a three-dimensional mesoscale nonhydrostatic atmospheric model. HGS replaces the land surface component within WRF, and provides WRF with the actual evapotranspiration (AET) and soil saturation. In return, WRF provides HGS with the potential evapotranspiration (PET) and precipitation fluxes. The flexible coupling technique allows HGS and WRF to have unique meshing and projection characteristics and links the domains based on their geographic coordinates (i.e., latitude and longitude). The California Basin model successfully simulated similar drawdown rates to the Gravity Recovery and Climate Experiment (GRACE) and replicated the Klamath and Sacramento River hydrographs. Furthermore, our simulation results reproduced field measured precipitation and evapotranspiration. Currently, our coupled California Basin model is the most complete water resource simulator because we combine the surface, subsurface, and atmosphere into a single domain.
Towards inverse modeling of intratumor heterogeneity
Brutovsky, Branislav; Horvath, Denis
2015-08-01
Development of resistance limits efficiency of present anticancer therapies and preventing it remains a big challenge in cancer research. It is accepted, at the intuitive level, that resistance emerges as a consequence of the heterogeneity of cancer cells at the molecular, genetic and cellular levels. Produced by many sources, tumor heterogeneity is extremely complex time dependent statistical characteristics which may be quantified by measures defined in many different ways, most of them coming from statistical mechanics. In this paper, we apply the Markovian framework to relate population heterogeneity to the statistics of the environment. As, from an evolutionary viewpoint, therapy corresponds to a purposeful modi- fication of the cells' fitness landscape, we assume that understanding general relationship between the spatiotemporal statistics of a tumor microenvironment and intratumor heterogeneity will allow to conceive the therapy as an inverse problem and to solve it by optimization techniques. To account for the inherent stochasticity of biological processes at cellular scale, the generalized distancebased concept was applied to express distances between probabilistically described cell states and environmental conditions, respectively.
Brogi, Cosimo; Huisman, Johan Alexander; Kaufmann, Manuela Sarah; von Hebel, Christian; van der Kruk, Jan; Vereecken, Harry
2017-04-01
Soil subsurface structures can play a key role in crop performance, especially during water stress periods. Geophysical techniques like electromagnetic induction EMI have been shown to be able of providing information about dominant shallow subsurface features. However, previous work with EMI has typically not reached beyond the field scale. The objective of this study is to use large-scale multi-configuration EMI to characterize patterns of soil structural organization (layering and texture) and the associated impact on crop vegetation at the km2 scale. For this, we carried out an intensive measurement campaign and collected high spatial resolution multi-configuration EMI data on an agricultural area of approx. 1 km2 (102 ha) near Selhausen (North Rhine-Westphalia, Germany) with a maximum depth of investigation of around 2.5 m. We measured using two EMI instruments simultaneously with a total of nine coil configurations. The instruments were placed inside polyethylene sleds that were pulled by an all-terrain-vehicle along parallel lines with a spacing of 2 to 2.5 m. The driving speed was between 5 and 7 km h-1 and we used a 0.2 Hz sampling frequency to obtain an in-line resolution of approximately 0.3 m. The survey area consists of almost 50 different fields managed in different way. The EMI measurements were collected between April and December 2016 within a few days after the harvest of each field. After data acquisition, EMI data were automatically filtered, temperature corrected, and interpolated onto a common grid. The resulting EMI maps allowed us to identify three main areas with different subsurface heterogeneities. The differences between these areas are likely related to the late quaternary geological history (Pleistocene and Holocene) of the area that resulted in spatially variable soil texture and layering, which has a strong impact on spatio-temporal soil water content variability. The high resolution surveys also allowed us to identify small scale
Model for the prediction of subsurface strata movement due to underground mining
Cheng, Jianwei; Liu, Fangyuan; Li, Siyuan
2017-12-01
The problem of ground control stability due to large underground mining operations is often associated with large movements and deformations of strata. It is a complicated problem, and can induce severe safety or environmental hazards either at the surface or in strata. Hence, knowing the subsurface strata movement characteristics, and making any subsidence predictions in advance, are desirable for mining engineers to estimate any damage likely to affect the ground surface or subsurface strata. Based on previous research findings, this paper broadly applies a surface subsidence prediction model based on the influence function method to subsurface strata, in order to predict subsurface stratum movement. A step-wise prediction model is proposed, to investigate the movement of underground strata. The model involves a dynamic iteration calculation process to derive the movements and deformations for each stratum layer; modifications to the influence method function are also made for more precise calculations. The critical subsidence parameters, incorporating stratum mechanical properties and the spatial relationship of interest at the mining level, are thoroughly considered, with the purpose of improving the reliability of input parameters. Such research efforts can be very helpful to mining engineers’ understanding of the moving behavior of all strata over underground excavations, and assist in making any damage mitigation plan. In order to check the reliability of the model, two methods are carried out and cross-validation applied. One is to use a borehole TV monitor recording to identify the progress of subsurface stratum bedding and caving in a coal mine, the other is to conduct physical modelling of the subsidence in underground strata. The results of these two methods are used to compare with theoretical results calculated by the proposed mathematical model. The testing results agree well with each other, and the acceptable accuracy and reliability of the
Emergence of heterogeneity in an agent-based model
Abdullah, Wan Ahmad Tajuddin Wan
2002-01-01
We study an interacting agent model of a game-theoretical economy. The agents play a minority-subsequently-majority game and they learn, using backpropagation networks, to obtain higher payoffs. We study the relevance of heterogeneity to performance, and how heterogeneity emerges.
IDENTIFIABILITY VERSUS HETEROGENEITY IN GROUNDWATER MODELING SYSTEMS
Directory of Open Access Journals (Sweden)
A M BENALI
2003-06-01
Full Text Available Review of history matching of reservoirs parameters in groundwater flow raises the problem of identifiability of aquifer systems. Lack of identifiability means that there exists parameters to which the heads are insensitive. From the guidelines of the study of the homogeneous case, we inspect the identifiability of the distributed transmissivity field of heterogeneous groundwater aquifers. These are derived from multiple realizations of a random function Y = log T whose probability distribution function is normal. We follow the identifiability of the autocorrelated block transmissivities through the measure of the sensitivity of the local derivatives DTh = (∂hi ∕ ∂Tj computed for each sample of a population N (0; σY, αY. Results obtained from an analysis of Monte Carlo type suggest that the more a system is heterogeneous, the less it is identifiable.
Elsheikh, A. H.
2013-12-01
Calibration of subsurface flow models is an essential step for managing ground water aquifers, designing of contaminant remediation plans, and maximizing recovery from hydrocarbon reservoirs. We investigate an efficient sampling algorithm known as nested sampling (NS), which can simultaneously sample the posterior distribution for uncertainty quantification, and estimate the Bayesian evidence for model selection. Model selection statistics, such as the Bayesian evidence, are needed to choose or assign different weights to different models of different levels of complexities. In this work, we report the first successful application of nested sampling for calibration of several nonlinear subsurface flow problems. The estimated Bayesian evidence by the NS algorithm is used to weight different parameterizations of the subsurface flow models (prior model selection). The results of the numerical evaluation implicitly enforced Occam\\'s razor where simpler models with fewer number of parameters are favored over complex models. The proper level of model complexity was automatically determined based on the information content of the calibration data and the data mismatch of the calibrated model.
Directory of Open Access Journals (Sweden)
Kul Khand
2017-11-01
Full Text Available Agricultural subsurface drainage changes the field hydrology and potentially the amount of water available to the crop by altering the flow path and the rate and timing of water removal. Evapotranspiration (ET is normally among the largest components of the field water budget, and the changes in ET from the introduction of subsurface drainage are likely to have a greater influence on the overall water yield (surface runoff plus subsurface drainage from subsurface drained (TD fields compared to fields without subsurface drainage (UD. To test this hypothesis, we examined the impact of subsurface drainage on ET at two sites located in the Upper Midwest (North Dakota-Site 1 and South Dakota-Site 2 using the Landsat imagery-based METRIC (Mapping Evapotranspiration at high Resolution with Internalized Calibration model. Site 1 was planted with corn (Zea mays L. and soybean (Glycine max L. during the 2009 and 2010 growing seasons, respectively. Site 2 was planted with corn for the 2013 growing season. During the corn growing seasons (2009 and 2013, differences between the total ET from TD and UD fields were less than 5 mm. For the soybean year (2010, ET from the UD field was 10% (53 mm greater than that from the TD field. During the peak ET period from June to September for all study years, ET differences from TD and UD fields were within 15 mm (<3%. Overall, differences between daily ET from TD and UD fields were not statistically significant (p > 0.05 and showed no consistent relationship.
3D subsurface temperature model of Europe for geothermal exploration
Limberger, J.; Wees, J.D. van
2014-01-01
For the assessment of geothermal resources in Europe we constructed a digital 3D temperature model of the European crust and sedimentary basins, incorporating publicly available temperature data. Using European crustal thickness models and indirect parameters such as surface heat flow measurements,
From intuition to statistics in building subsurface structural models
Brandenburg, J.P.; Alpak, F.O.; Naruk, S.; Solum, J.
2011-01-01
Experts associated with the oil and gas exploration industry suggest that combining forward trishear models with stochastic global optimization algorithms allows a quantitative assessment of the uncertainty associated with a given structural model. The methodology is applied to incompletely imaged structures related to deepwater hydrocarbon reservoirs and results are compared to prior manual palinspastic restorations and borehole data. This methodology is also useful for extending structural interpretations into other areas of limited resolution, such as subsalt in addition to extrapolating existing data into seismic data gaps. This technique can be used for rapid reservoir appraisal and potentially have other applications for seismic processing, well planning, and borehole stability analysis.
Modelling near subsurface temperature with mixed type boundary ...
Indian Academy of Sciences (India)
... of transfer coefficient and groundwater flux. There are significant changes in temperature and depth profiles due to changes in the transfer coefficient and groundwater flux. The analytical model will find applications in the interpretation of the borehole geothermal data to extract both climate and groundwater flow signals.
Coupled modelling of subsurface water flux for an integrated flood risk management
Directory of Open Access Journals (Sweden)
T. Sommer
2009-07-01
Full Text Available Flood events cause significant damage not only on the surface but also underground. Infiltration of surface water into soil, flooding through the urban sewer system and, in consequence, rising groundwater are the main causes of subsurface damage. The modelling of flooding events is an important part of flood risk assessment. The processes of subsurface discharge of infiltrated water necessitate coupled modelling tools of both, surface and subsurface water fluxes. Therefore, codes for surface flooding, for discharge in the sewerage system and for groundwater flow were coupled with each other. A coupling software was used to amalgamate the individual programs in terms of mapping between the different model geometries, time synchronization and data exchange. The coupling of the models was realized on two scales in the Saxon capital of Dresden (Germany. As a result of the coupled modelling it could be shown that surface flooding dominates processes of any flood event. Compared to flood simulations without coupled modelling no substantial changes of the surface inundation area could be determined. Regarding sewerage, the comparison between the influx of groundwater into sewerage and the loading due to infiltration by flood water showed infiltration of surface flood water to be the main reason for sewerage overloading. Concurrent rainfalls can intensify the problem. The infiltration of the sewerage system by rising groundwater contributes only marginally to the loading of the sewerage and the distribution of water by sewerage has only local impacts on groundwater rise. However, the localization of risk areas due to rising groundwater requires the consideration of all components of the subsurface water fluxes. The coupled modelling has shown that high groundwater levels are the result of a multi-causal process that occurs before and during the flood event.
Lin, Youzuo; Huang, Lianjie
2017-11-01
Reverse-time migration has the potential to image complex subsurface structures, including steeply-dipping fault zones, but the method requires an accurate velocity model. Acoustic- and elastic-waveform inversion is a promising tool for high-resolution velocity model building. Because of the ill-posedness of acoustic- and elastic-waveform inversion, it is a great challenge to obtain accurate velocity models containing sharp interfaces. To improve velocity model building, we develop an acoustic- and elastic-waveform inversion method with an interface-guided modified total-variation regularization scheme to improve the inversion accuracy and robustness, particularly for models with sharp interfaces and steeply-dipping fault zones with widths much smaller than the seismic wavelength. The new regularization scheme incorporates interface information into seismic full-waveform inversion. The interface information of subsurface interfaces is obtained iteratively using migration imaging during waveform inversion. Seismic migration is robust for subsurface imaging. Our new acoustic- and elastic-waveform inversion takes advantage of the robustness of migration imaging to improve velocity estimation. We use synthetic seismic data for a complex model containing sharp interfaces and several steeply-dipping fault zones to validate the improved capability of our new acoustic- and elastic-waveform inversion method. Our inversion results are much better than those produced without using interface-guided regularization. Acoustic- and elastic-waveform inversion with an interface-guided modified total-variation regularization scheme has the potential to accurately build subsurface velocity models with sharp interfaces and/or steep fault zones.
Combining Deterministic structures and stochastic heterogeneity for transport modeling
Zech, Alraune; Attinger, Sabine; Dietrich, Peter; Teutsch, Georg
2017-04-01
Contaminant transport in highly heterogeneous aquifers is extremely challenging and subject of current scientific debate. Tracer plumes often show non-symmetric but highly skewed plume shapes. Predicting such transport behavior using the classical advection-dispersion-equation (ADE) in combination with a stochastic description of aquifer properties requires a dense measurement network. This is in contrast to the available information for most aquifers. A new conceptual aquifer structure model is presented which combines large-scale deterministic information and the stochastic approach for incorporating sub-scale heterogeneity. The conceptual model is designed to allow for a goal-oriented, site specific transport analysis making use of as few data as possible. Thereby the basic idea is to reproduce highly skewed tracer plumes in heterogeneous media by incorporating deterministic contrasts and effects of connectivity instead of using unimodal heterogeneous models with high variances. The conceptual model consists of deterministic blocks of mean hydraulic conductivity which might be measured by pumping tests indicating values differing in orders of magnitudes. A sub-scale heterogeneity is introduced within every block. This heterogeneity can be modeled as bimodal or log-normal distributed. The impact of input parameters, structure and conductivity contrasts is investigated in a systematic manor. Furthermore, some first successful implementation of the model was achieved for the well known MADE site.
Modeling heterogeneous unsaturated porous media flow at Yucca Mountain
Energy Technology Data Exchange (ETDEWEB)
Robey, T.H. [Spectra Research Inst., Albuquerque, NM (United States)
1994-03-01
Geologic systems are inherently heterogeneous and this heterogeneity can have a significant impact on unsaturated flow through porous media. Most previous efforts to model groundwater flow through Yucca Mountain have used stratigraphic units with homogeneous properties. However, modeling heterogeneous porous and fractured tuff in a more realistic manner requires numerical methods for generating heterogeneous simulations of the media, scaling of material properties from core scale to computational scale, and flow modeling that allows channeling. The Yucca Mountain test case of the INTRAVAL project is used to test the numerical approaches. Geostatistics is used to generate more realistic representations of the stratigraphic units and heterogeneity within units is generated using sampling from property distributions. Scaling problems are reduced using an adaptive grid that minimizes heterogeneity within each flow element. A flow code based on the dual mixed-finite-element method that allows for heterogeneity and channeling is employed. In the Yucca Mountain test case, the simulated volumetric water contents matched the measured values at drill hole USW UZ-16 except in the nonwelded portion of Prow Pass.
Modeling heterogeneous unsaturated porous media flow at Yucca Mountain
International Nuclear Information System (INIS)
Robey, T.H.
1994-01-01
Geologic systems are inherently heterogeneous and this heterogeneity can have a significant impact on unsaturated flow through porous media. Most previous efforts to model groundwater flow through Yucca Mountain have used stratigraphic units with homogeneous properties. However, modeling heterogeneous porous and fractured tuff in a more realistic manner requires numerical methods for generating heterogeneous simulations of the media, scaling of material properties from core scale to computational scale, and flow modeling that allows channeling. The Yucca Mountain test case of the INTRAVAL project is used to test the numerical approaches. Geostatistical methods are used to generate more realistic representations of the stratigraphic units and heterogeneity within units is generated using sampling from property distributions. Scaling problems are reduced using an adaptive grid that minimizes heterogeneity within each flow element. A flow code based on the dual mixed-finite-element method that allows for heterogeneity and channeling is employed. In the Yucca Mountain test case, the simulated volumetric water contents matched the measured values at drill hole USW UZ-16 except in the nonwelded portion of Prow Pass
Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site
Energy Technology Data Exchange (ETDEWEB)
Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Brady D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Christian D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Last, George V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Michelle H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kaplan, Daniel I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2015-09-01
The fate and transport of 129I in the environment and potential remediation technologies are currently being studied as part of environmental remediation activities at the Hanford Site. A conceptual model describing the nature and extent of subsurface contamination, factors that control plume behavior, and factors relevant to potential remediation processes is needed to support environmental remedy decisions. Because 129I is an uncommon contaminant, relevant remediation experience and scientific literature are limited. Thus, the conceptual model also needs to both describe known contaminant and biogeochemical process information and to identify aspects about which additional information needed to effectively support remedy decisions. this document summarizes the conceptual model of iodine behavior relevant to iodine in the subsurface environment at the Hanford site.
Underwater Signal Modeling for Subsurface Classification Using Computational Intelligence.
Setayeshi, Saeed
In the thesis a method for underwater layered media (UWLM) modeling is proposed, and a simple nonlinear structure for implementation of this model based on the behaviour of its characteristics and the propagation of the acoustic signal in the media accounting for attenuation effects is designed. The model that responds to the acoustic input is employed to test the artificial intelligence classifiers ability. Neural network models, the basic principles of the back-propagation algorithm, and the Hopfield model of associative memories are reviewed, and they are employed to use min-max amplitude ranges of a reflected signal of UWLM based on attenuation effects, to define the classes of the synthetic data, detect its peak features and estimate parameters of the media. It has been found that there is a correlation between the number of layers in the media and the optimum number of nodes in the hidden layer of the neural networks. The integration of the result of the neural networks that classify and detect underwater layered media acoustic signals based on attenuation effects to prove the correspondence between the peak points and decay values has introduced a powerful tool for UWLM identification. The methods appear to have applications in replacing original system, for parameter estimation and output prediction in system identification by the proposed networks. The results of computerized simulation of the UWLM modeling in conjunction with the proposed neural networks training process are given. Fuzzy sets is an idea that allows representing and manipulating inexact concepts, fuzzy min-max pattern classification method, and the learning and recalling algorithms for fuzzy neural networks implementation is explained in this thesis. A fuzzy neural network that uses peak amplitude ranges to define classes is proposed and evaluated for UWLM pattern recognition. It is demonstrated to be able to classify the layered media data sets, and can distinguish between the peak points
Heterogeneous information network model for equipment-standard system
Yin, Liang; Shi, Li-Chen; Zhao, Jun-Yan; Du, Song-Yang; Xie, Wen-Bo; Yuan, Fei; Chen, Duan-Bing
2018-01-01
Entity information network is used to describe structural relationships between entities. Taking advantage of its extension and heterogeneity, entity information network is more and more widely applied to relationship modeling. Recent years, lots of researches about entity information network modeling have been proposed, while seldom of them concentrate on equipment-standard system with properties of multi-layer, multi-dimension and multi-scale. In order to efficiently deal with some complex issues in equipment-standard system such as standard revising, standard controlling, and production designing, a heterogeneous information network model for equipment-standard system is proposed in this paper. Three types of entities and six types of relationships are considered in the proposed model. Correspondingly, several different similarity-measuring methods are used in the modeling process. The experiments show that the heterogeneous information network model established in this paper can reflect relationships between entities accurately. Meanwhile, the modeling process has a good performance on time consumption.
Jackisch, Conrad; Demand, Dominic; Allroggen, Niklas; Loritz, Ralf; Zehe, Erwin
2017-04-01
In order to discuss hypothesis testing in hydrology, the question of the solid foundation of such tests has to be answered. But how certain are we about our measurements of the components of the water balance and the states and dynamics of the complex systems? What implicit assumptions or bias are already embedded in our perception of the processes? How can we find light in the darkness of heterogeneity? We will contribute examples from experimental findings, modelling approaches and landscape analysis to the discussion. Example soil moisture and the soil continuum: The definition of soil moisture as fraction of water in the porous medium assumes locally well-mixed conditions. Moreover, a unique relation of soil water retention presumes instant local thermodynamic equilibrium in the pore water arrangement. We will show findings from soil moisture responses to precipitation events, from irrigation experiments, and from a model study of initial infiltration velocities. The results highlight, that the implicit assumption relating soil moisture state dynamics with actual soil water flow is biased towards the slow end of the actual velocity distribution and rather blind for preferential flow acting in a very small proportion of the pore space. Moreover, we highlight the assumption of a well-defined continuum during the extrapolation of point-scale measurements and why spatially and temporally continuous observation techniques of soil water states are essential for advancing our understanding and development of subsurface process theories. Example hydraulic conductivity: Hydraulic conductivity lies at the heart of hydrological research and modelling. Its values can range across several orders of magnitude at a single site alone. Yet, we often consider it a crisp, effective parameter. We have conducted measurements of soil hydraulic conductivity in the lab and in the field. Moreover, we assessed infiltration capacity and conducted plot-scale irrigation experiments to
Zehe, Erwin; Jackisch, Conrad; Rodriguez, Nicolas; Klaus, Julian
2017-04-01
Only a minute amount of global fresh water is stored in the unsaturated zone. Yet this tiny compartment controls soil microbial activity and associated trace gas emissions, transport and transformations of contaminants, plant productivity, runoff generation and groundwater recharge. To date, the processes controlling renewal and age of different fractions of the soil water stock are far from being understood. Current theories and process concepts were largely inferred either from over-simplified laboratory experiments, or non-exhaustive point observations and tracer data in the field. Tracer data provide key but yet integrated information about the distribution of travel times of the tracer molecules to a certain depth or on their travel depth distribution within a given time. We hence are able to observe the "effect" of soil structure i.e. partitioning of infiltrating water between fast preferential and slow flow paths and imperfect subsequent mixing between these flow paths in the subsurface and the related plant water uptake. However, we are not able to study the "cause" - because technologies for in-situ observations of flow, flow path topology and exchange processes at relevant interfaces have up to now not been at hand. In the present study we will make use of a Lagrangian model for subsurface water dynamics to explore how subsurface heterogeneity and mixing among different storage fractions affects residence time distribution in the unsaturated zone in a forward approach. Soil water is represented by particles of constant mass, which travel according to the Itô form of the Fokker Planck equation. The model concept builds on established soil physics by estimating the drift velocity and the diffusion term based on the soil water characteristics. The model has been shown to simulate capillary driven soil moisture dynamics in good accordance with a) the Richards equation and b) observed soil moisture data in different soil. The particle model may furthermore
Stochastic description of heterogeneities of permeability within groundwater flow models
International Nuclear Information System (INIS)
Cacas, M.C.; Lachassagne, P.; Ledoux, E.; Marsily, G. de
1991-01-01
In order to model radionuclide migration in the geosphere realistically at the field scale, the hydrogeologist needs to be able to simulate groundwater flow in heterogeneous media. Heterogeneity of the medium can be described using a stochastic approach, that affects the way in which a flow model is formulated. In this paper, we discuss the problems that we have encountered in modelling both continuous and fractured media. The stochastic approach leads to a methodology that enables local measurements of permeability to be integrated into a model which gives a good prediction of groundwater flow on a regional scale. 5 Figs.; 8 Refs
Wijewardana, Y N S; Shilpadi, A T; Mowjood, M I M; Kawamoto, K; Galagedara, L W
2017-02-01
The assessment of polluted areas and municipal solid waste (MSW) sites using non-destructive geophysical methods is timely and much needed in the field of environmental monitoring and management. The objectives of this study are (i) to evaluate the ground-penetrating radar (GPR) wave responses as a result of different electrical conductivity (EC) in groundwater and (ii) to conduct MSW stratification using a controlled lysimeter and modeling approach. A GPR wave simulation was carried out using GprMax2D software, and the field test was done on two lysimeters that were filled with sand (Lysimeter-1) and MSW (Lysimeter-2). A Pulse EKKO-Pro GPR system with 200- and 500-MHz center frequency antennae was used to collect GPR field data. Amplitudes of GPR-reflected waves (sub-surface reflectors and water table) were studied under different EC levels injected to the water table. Modeling results revealed that the signal strength of the reflected wave decreases with increasing EC levels and the disappearance of the subsurface reflection and wave amplitude reaching zero at higher EC levels (when EC >0.28 S/m). Further, when the EC level was high, the plume thickness did not have a significant effect on the amplitude of the reflected wave. However, it was also found that reflected signal strength decreases with increasing plume thickness at a given EC level. 2D GPR profile images under wet conditions showed stratification of the waste layers and relative thickness, but it was difficult to resolve the waste layers under dry conditions. These results show that the GPR as a non-destructive method with a relatively larger sample volume can be used to identify highly polluted areas with inorganic contaminants in groundwater and waste stratification. The current methods of MSW dumpsite investigation are tedious, destructive, time consuming, costly, and provide only point-scale measurements. However, further research is needed to verify the results under heterogeneous aquifer
Modeling Approaches for Describing Microbial Population Heterogeneity
DEFF Research Database (Denmark)
Lencastre Fernandes, Rita
in a computational (CFD) fluid dynamic model. The anaerobic Growth of a budding yeast population in a continuously run microbioreactor was used as example. The proposed integrated model describes the fluid flow, the local cell size and cell cycle position distributions, as well as the local concentrations of glucose...
Lee, S. K.; Lee, Y.; Lee, C.
2016-12-01
Estimation of deep temperature is significant procedure for exploration, development and sustainable use of geothermal resources in the geothermal area. For estimating subsurface temperature, there have been suggested many techniques for indirect geothermometers, such as mineral geothermometer, hydrochemical geothermometer, isotropic geothermometer, electromagnetic (EM) geothermometer and so forth. In this study, we have tested the feasibility of EM geothermometer using integrated frameworks of geothermal and geo-electromagnetic models. For this purpose, we have developed geothermal temperature model together with EM model based on common earth model, which satisfies all observed geoscientific data set including surface geology, structural geology, well log data, and geophysical data. We develop a series of plugin modules for integration of geo-electromagnetic modeling and inversion algorithms on a common geological modeling platform. The subsurface temperature with time are modeled by solving heat transfer equations using finite element method (FEM). The temperature dependent conductivity model are obtained by the temperature-conductivity relations to perform geo-electromagnetic modeling, such as magnetotelluric to analyze temperature model from EM data.
Energy Technology Data Exchange (ETDEWEB)
Ganusov, Vitaly V [Los Alamos National Laboratory
2008-01-01
Estimation of division and death rates of lymphocytes in different conditions is vital for quantitative understanding of the immune system. Deuterium, in the form of deuterated glucose or heavy water, can be used to measure rates of proliferation and death of lymphocytes in vivo. Inferring these rates from labeling and delabeling curves has been subject to considerable debate with different groups suggesting different mathematical models for that purpose. We show that the three models that are most commonly used are in fact mathematically identical and differ only in their interpretation of the estimated parameters. By extending these previous models, we here propose a more mechanistic approach for the analysis of data from deuterium labeling experiments. We construct a model of 'kinetic heterogeneity' in which the total cell population consists of many sub-populations with different rates of cell turnover. In this model, for a given distribution of the rates of turnover, the predicted fraction of labeled DNA accumulated and lost can be calculated. Our model reproduces several previously made experimental observations, such as a negative correlation between the length of the labeling period and the rate at which labeled DNA is lost after label cessation. We demonstrate the reliability of the new explicit kinetic heterogeneity model by applying it to artificially generated datasets, and illustrate its usefulness by fitting experimental data. In contrast to previous models, the explicit kinetic heterogeneity model (1) provides a mechanistic way of interpreting labeling data; (2) allows for a non-exponential loss of labeled cells during delabeling, and (3) can be used to describe data with variable labeling length.
International Nuclear Information System (INIS)
Sato, Hiroaki
2014-01-01
In the Niigata area, which suffered from several large earthquakes such as the 2007 Chuetsu-oki earthquake, geographical observation that elucidates the S-wave structure of the underground is advancing. Modeling of S-wave velocity structure in the subsurface is underway to enable simulation of long-period ground motion. The one-dimensional velocity model by inverse analysis of micro-tremors is sufficiently appropriate for long-period site response but not for short-period, which is important for ground motion evaluation at NPP sites. The high-frequency site responses may be controlled by the strength of heterogeneity of underground structure because the heterogeneity of the 1D model plays an important role in estimating high-frequency site responses and is strongly related to the damping factor of the 1D layered velocity model. (author)
Test of theoretical models for ultrafast heterogeneous electron ...
Indian Academy of Sciences (India)
Administrator
with the predictions of different theoretical models for light-induced ultrafast heterogeneous electron transfer (HET). ... theory model based on molecular dynamics simulations for the vibrational modes were also considered. Based on the known vibrational .... Pseudo 3D map of a 2PPE measurement with. Pe' achored via the ...
INTEGRATION OF HETEROGENOUS DIGITAL SURFACE MODELS
Directory of Open Access Journals (Sweden)
R. Boesch
2012-08-01
Full Text Available The application of extended digital surface models often reveals, that despite an acceptable global accuracy for a given dataset, the local accuracy of the model can vary in a wide range. For high resolution applications which cover the spatial extent of a whole country, this can be a major drawback. Within the Swiss National Forest Inventory (NFI, two digital surface models are available, one derived from LiDAR point data and the other from aerial images. Automatic photogrammetric image matching with ADS80 aerial infrared images with 25cm and 50cm resolution is used to generate a surface model (ADS-DSM with 1m resolution covering whole switzerland (approx. 41000 km2. The spatially corresponding LiDAR dataset has a global point density of 0.5 points per m2 and is mainly used in applications as interpolated grid with 2m resolution (LiDAR-DSM. Although both surface models seem to offer a comparable accuracy from a global view, local analysis shows significant differences. Both datasets have been acquired over several years. Concerning LiDAR-DSM, different flight patterns and inconsistent quality control result in a significantly varying point density. The image acquisition of the ADS-DSM is also stretched over several years and the model generation is hampered by clouds, varying illumination and shadow effects. Nevertheless many classification and feature extraction applications requiring high resolution data depend on the local accuracy of the used surface model, therefore precise knowledge of the local data quality is essential. The commercial photogrammetric software NGATE (part of SOCET SET generates the image based surface model (ADS-DSM and delivers also a map with figures of merit (FOM of the matching process for each calculated height pixel. The FOM-map contains matching codes like high slope, excessive shift or low correlation. For the generation of the LiDAR-DSM only first- and last-pulse data was available. Therefore only the point
Equatorial Indian Ocean subsurface current variability in an Ocean General Circulation Model
Gnanaseelan, C.; Deshpande, Aditi
2018-03-01
The variability of subsurface currents in the equatorial Indian Ocean is studied using high resolution Ocean General Circulation Model (OGCM) simulations during 1958-2009. February-March eastward equatorial subsurface current (ESC) shows weak variability whereas strong variability is observed in northern summer and fall ESC. An eastward subsurface current with maximum amplitude in the pycnocline is prominent right from summer to winter during strong Indian Ocean Dipole (IOD) years when air-sea coupling is significant. On the other hand during weak IOD years, both the air-sea coupling and the ESC are weak. This strongly suggests the role of ESC on the strength of IOD. The extension of the ESC to the summer months during the strong IOD years strengthens the oceanic response and supports intensification and maintenance of IODs through modulation of air sea coupling. Although the ESC is triggered by equatorial winds, the coupled air-sea interaction associated with IODs strengthens the ESC to persist for several seasons thereby establishing a positive feedback cycle with the surface. This suggests that the ESC plays a significant role in the coupled processes associated with the evolution and intensification of IOD events by cooling the eastern basin and strengthening thermocline-SST (sea surface temperature) interaction. As the impact of IOD events on Indian summer monsoon is significant only during strong IOD years, understanding and monitoring the evolution of ESC during these years is important for summer monsoon forecasting purposes. There is a westward phase propagation of anomalous subsurface currents which persists for a year during strong IOD years, whereas such persistence or phase propagation is not seen during weak IOD years, supporting the close association between ESC and strength of air sea coupling during strong IOD years. In this study we report the processes which strengthen the IOD events and the air sea coupling associated with IOD. It also unravels
Habitat heterogeneity hypothesis and edge effects in model metacommunities.
Hamm, Michaela; Drossel, Barbara
2017-08-07
Spatial heterogeneity is an inherent property of any living environment and is expected to favour biodiversity due to a broader niche space. Furthermore, edges between different habitats can provide additional possibilities for species coexistence. Using computer simulations, this study examines metacommunities consisting of several trophic levels in heterogeneous environments in order to explore the above hypotheses on a community level. We model heterogeneous landscapes by using two different sized resource pools and evaluate the combined effect of dispersal and heterogeneity on local and regional species diversity. This diversity is obtained by running population dynamics and evaluating the robustness (i.e., the fraction of surviving species). The main results for regional robustness are in agreement with the habitat heterogeneity hypothesis, as the largest robustness is found in heterogeneous systems with intermediate dispersal rates. This robustness is larger than in homogeneous systems with the same total amount of resources. We study the edge effect by arranging the two types of resources in two homogeneous blocks. Different edge responses in diversity are observed, depending on dispersal strength. Local robustness is highest for edge habitats that contain the smaller amount of resource in combination with intermediate dispersal. The results show that dispersal is relevant to correctly identify edge responses on community level. Copyright © 2017 Elsevier Ltd. All rights reserved.
Smart Agents and Sentiment in the Heterogeneous Agent Model
Czech Academy of Sciences Publication Activity Database
Vácha, Lukáš; Baruník, Jozef; Vošvrda, Miloslav
2009-01-01
Roč. 18, č. 3 (2009), s. 209-219 ISSN 1210-0455 R&D Projects: GA MŠk(CZ) LC06075; GA ČR GP402/08/P207; GA ČR(CZ) GA402/09/0965 Institutional research plan: CEZ:AV0Z10750506 Keywords : heterogeneous agent model * market structure * smart traders * Hurst exponent Subject RIV: AH - Economics http://library.utia.cas.cz/separaty/2009/E/vacha- smart agents and sentiment in the heterogeneous agent model.pdf
Viscosity of Heterogeneous Silicate Melts: A Non-Newtonian Model
Liu, Zhuangzhuang; Blanpain, Bart; Guo, Muxing
2017-12-01
The recently published viscosity data of heterogeneous silicate melts with well-documented structure and experimental conditions are critically re-analyzed and tabulated. By using these data, a non-Newtonian viscosity model incorporating solid fraction, solid shape, and shear rate is proposed on the basis of the power-law equation. This model allows calculating the viscosity of the heterogeneous silicate melts with solid fraction up to 34 vol pct. The error between the calculated and measured data is evaluated to be 32 pct, which is acceptable considering the large error in viscosity measurement of the completely liquid silicate melt.
Wavelets and Sentiment in the Heterogeneous Agents Model
Czech Academy of Sciences Publication Activity Database
Vácha, Lukáš; Vošvrda, Miloslav
2008-01-01
Roč. 15, č. 25 (2008), s. 41-56 ISSN 1212-074X R&D Projects: GA ČR GP402/08/P207; GA ČR GA402/07/1113; GA ČR(CZ) GA402/06/0990 Institutional research plan: CEZ:AV0Z10750506 Keywords : heterogeneous agents model * market sentiment * Hurst exponent * wavelets Subject RIV: AH - Economics http://library.utia.cas.cz/separaty/2008/E/vacha-wavelets and sentiment in the heterogeneous agents model.pdf
Directory of Open Access Journals (Sweden)
T. J. Bohn
2013-10-01
Full Text Available We used a process-based model to examine the role of spatial heterogeneity of surface and sub-surface water on the carbon budget of the wetlands of the West Siberian Lowland over the period 1948–2010. We found that, while surface heterogeneity (fractional saturated area had little overall effect on estimates of the region's carbon fluxes, sub-surface heterogeneity (spatial variations in water table depth played an important role in both the overall magnitude and spatial distribution of estimates of the region's carbon fluxes. In particular, to reproduce the spatial pattern of CH4 emissions recorded by intensive in situ observations across the domain, in which very little CH4 is emitted north of 60° N, it was necessary to (a account for CH4 emissions from unsaturated wetlands and (b use spatially varying methane model parameters that reduced estimated CH4 emissions in the northern (permafrost half of the domain (and/or account for lower CH4 emissions under inundated conditions. Our results suggest that previous estimates of the response of these wetlands to thawing permafrost may have overestimated future increases in methane emissions in the permafrost zone.
Hwang, H.-T.; Park, Y.-J.; Frey, S. K.; Berg, S. J.; Sudicky, E. A.
2015-12-01
This work presents an iterative, water balance based approach to estimate actual evapotranspiration (ET) with integrated surface/subsurface flow models. Traditionally, groundwater level fluctuation methods have been widely accepted and used for estimating ET and net groundwater recharge; however, in watersheds where interactions between surface and subsurface flow regimes are highly dynamic, the traditional method may be overly simplistic. Here, an innovative methodology is derived and demonstrated for using the water balance equation in conjunction with a fully-integrated surface and subsurface hydrologic model (HydroGeoSphere) in order to estimate ET at watershed and sub-watershed scales. The method invokes a simple and robust iterative numerical solution. For the proof of concept demonstrations, the method is used to estimate ET for a simple synthetic watershed and then for a real, highly-characterized 7000 km2 watershed in Southern Ontario, Canada (Grand River Watershed). The results for the Grand River Watershed show that with three to five iterations, the solution converges to a result where there is less than 1% relative error in stream flow calibration at 16 stream gauging stations. The spatially-averaged ET estimated using the iterative method shows a high level of agreement (R2 = 0.99) with that from a benchmark case simulated with an ET model embedded directly in HydroGeoSphere. The new approach presented here is applicable to any watershed that is suited for integrated surface water/groundwater flow modelling and where spatially-averaged ET estimates are useful for calibrating modelled stream discharge.
3D modeling of carbonates petro-acoustic heterogeneities
Baden, Dawin; Guglielmi, Yves; Saracco, Ginette; Marié, Lionel; Viseur, Sophie
2015-04-01
Characterizing carbonate reservoirs heterogeneity is a challenging issue for Oil & Gas Industry, CO2 sequestration and all kinds of fluid manipulations in natural reservoirs, due to the significant impact of heterogeneities on fluid flow and storage within the reservoir. Although large scale (> meter) heterogeneities such as layers petrophysical contrasts are well addressed by computing facies-based models, low scale (geo-modeler. This method successfully allowed detecting and imaging in three dimensions differential diagenesis effects characterized by the occurrence of decimeter-scale diagenetic horizons in samples assumed to be homogeneous and/or different diagenetic sequences between shells filling and the packing matrix. We then discuss how small interfaces such as cracks, stylolithes and laminations which are also imaged may have guided these differential effects, considering that understanding the processes may be taken as an analogue to actual fluid drainage complexity in deep carbonate reservoir.
Iqbal, Mohammad Z.
2000-06-01
In the Cedar River watershed of northeastern Iowa, USA, water quality in 17 out of 20 private wells indicates that groundwater is contaminated with nitrate from agricultural leachates. In nine of the wells, nitrate concentration exceeds the US Environmental Protection Agency recommended maximum contaminant level (MCL) of 45 mg/L (as NO3 -) for drinking purposes. Solute-transport investigations determined that the surficial loam sediments, the Quaternary sand and gravel deposits, and the glacial till deposits form layered heterogeneity in the subsurface. The resulting conductivity contrast causes a capillary barrier, thereby altering the mechanisms of vertical tracer movement. Storm-water tracing with potassium bromide, corn fertilizer, and fluorescein dye indicates that macropore flow occurs only within the upper 0.9 m of loamy sediments. An average breakthrough concentration of 204 mg/L bromide at 0.3 m depth on day 3 after the storm event supports the hypothesis of macropore flow in the surficial soils. Fluorescein dye was recovered at a depth of 0.3 m with a peak concentration of 650 μg/L at approximately 5 days after the storm event. The loamy sediment layer is underlain by the Iowan Pebble Band, a pebbly layer admixed with sand, developed in post-glacial time. In the field experiments, preferential flow of the tracers was predominantly vertical within the loamy sediments but rapidly changed to a horizontal matrix flow upon entering the materials of higher saturated hydraulic conductivity in the Pebble Band. The Pebble Band is underlain by low-conductivity deposits of pre-Illinoian till. Even though the upper oxidized portion of the glacial till is reported to have macropores, the Pebble Band prevented deeper infiltration of storm water by maintaining a strong component of horizontal hydraulic gradient. Chemical data indicate that the Pebble Band is a hydraulic-conductivity boundary that abruptly changes the unsaturated-flow mechanism from macropore flow to
Modeling the effects of vegetation heterogeneity on wildland fire behavior
Atchley, A. L.; Linn, R.; Sieg, C.; Middleton, R. S.
2017-12-01
Vegetation structure and densities are known to drive fire-spread rate and burn severity. Many fire-spread models incorporate an average, homogenous fuel density in the model domain to drive fire behavior. However, vegetation communities are rarely homogenous and instead present significant heterogeneous structure and fuel densities in the fires path. This results in observed patches of varied burn severities and mosaics of disturbed conditions that affect ecological recovery and hydrologic response. Consequently, to understand the interactions of fire and ecosystem functions, representations of spatially heterogeneous conditions need to be incorporated into fire models. Mechanistic models of fire disturbance offer insight into how fuel load characterization and distribution result in varied fire behavior. Here we use a physically-based 3D combustion model—FIRETEC—that solves conservation of mass, momentum, energy, and chemical species to compare fire behavior on homogenous representations to a heterogeneous vegetation distribution. Results demonstrate the impact vegetation heterogeneity has on the spread rate, intensity, and extent of simulated wildfires thus providing valuable insight in predicted wildland fire evolution and enhanced ability to estimate wildland fire inputs into regional and global climate models.
Connectivity ranking of heterogeneous random conductivity models
Rizzo, C. B.; de Barros, F.
2017-12-01
To overcome the challenges associated with hydrogeological data scarcity, the hydraulic conductivity (K) field is often represented by a spatial random process. The state-of-the-art provides several methods to generate 2D or 3D random K-fields, such as the classic multi-Gaussian fields or non-Gaussian fields, training image-based fields and object-based fields. We provide a systematic comparison of these models based on their connectivity. We use the minimum hydraulic resistance as a connectivity measure, which it has been found to be strictly correlated with early time arrival of dissolved contaminants. A computationally efficient graph-based algorithm is employed, allowing a stochastic treatment of the minimum hydraulic resistance through a Monte-Carlo approach and therefore enabling the computation of its uncertainty. The results show the impact of geostatistical parameters on the connectivity for each group of random fields, being able to rank the fields according to their minimum hydraulic resistance.
Modeling of Bandwidth Aggregation over Heterogeneous Wireless Access Networks
DEFF Research Database (Denmark)
Popovska Avramova, Andrijana; Dittmann, Lars
2012-01-01
Motivated by the multihomming capability of the mobile devices and the fact that the heterogeneous wireless access networks overlap in coverage, mobile operators are looking for solutions that will benefit by simultaneous use of the available multiple access interfaces. Multipath or multilink...... applications. The analysis is performed on a multipath model developed with OPNET Modeler, which is an advanced research tool that supports modeling and integration of various kinds of built-in networks....
Risk Prediction Models for Oral Clefts Allowing for Phenotypic Heterogeneity
Directory of Open Access Journals (Sweden)
Yalu eWen
2015-08-01
Full Text Available Oral clefts are common birth defects that have a major impact on the affected individual, their family and society. World-wide, the incidence of oral clefts is 1/700 live births, making them the most common craniofacial birth defects. The successful prediction of oral clefts may help identify sub-population at high risk, and promote new diagnostic and therapeutic strategies. Nevertheless, developing a clinically useful oral clefts risk prediction model remains a great challenge. Compelling evidences suggest the etiologies of oral clefts are highly heterogeneous, and the development of a risk prediction model with consideration of phenotypic heterogeneity may potentially improve the accuracy of a risk prediction model. In this study, we applied a previously developed statistical method to investigate the risk prediction on sub-phenotypes of oral clefts. Our results suggested subtypes of cleft lip and palate have similar genetic etiologies (AUC=0.572 with subtypes of cleft lip only (AUC=0.589, while the subtypes of cleft palate only (CPO have heterogeneous underlying mechanisms (AUCs for soft CPO and hard CPO are 0.617 and 0.623, respectively. This highlighted the potential that the hard and soft forms of CPO have their own mechanisms despite sharing some of the genetic risk factors. Comparing with conventional methods for risk prediction modeling, our method considers phenotypic heterogeneity of a disease, which potentially improves the accuracy for predicting each sub-phenotype of oral clefts.
Heterogeneous Agent Model with Memory and Asset Price Behaviour
Czech Academy of Sciences Publication Activity Database
Vošvrda, Miloslav; Vácha, Lukáš
2003-01-01
Roč. 12, č. 2 (2003), s. 155-168 ISSN 1210-0455 R&D Projects: GA ČR GA402/00/0439; GA ČR GA402/01/0034 Institutional research plan: CEZ:AV0Z1075907 Keywords : efficient markets hypothesis * technical trading rules * heterogeneous agent model with memory and learning Subject RIV: AH - Economics
Performance Modeling for Heterogeneous Wireless Networks with Multiservice Overflow Traffic
DEFF Research Database (Denmark)
Huang, Qian; Ko, King-Tim; Iversen, Villy Bæk
2009-01-01
. Multiservice loss analysis based on multi-dimensional Markov chain becomes intractable in these networks due to intensive computations required. This paper focuses on performance modeling for heterogeneous wireless networks based on a hierarchical overlay infrastructure. A method based on decomposition...
Heterogenous Agents Model with the Worst Out Algorithm
Czech Academy of Sciences Publication Activity Database
Vácha, Lukáš; Vošvrda, Miloslav
-, č. 8 (2006), s. 3-19 ISSN 1801-5999 Institutional research plan: CEZ:AV0Z10750506 Keywords : efficient market hypothesis * fractal market hypothesis * agents' investment horizons * agents' trading strategies * technical trading rules * heterogeneous agent model with stochastic memory * Worst out algorithm Subject RIV: AH - Economics
Formal heterogeneous system modeling with SystemC
DEFF Research Database (Denmark)
Niaki, Seyed Hosein Attarzadeh; Jakobsen, Mikkel Koefoed; Sulonen, Tero
2012-01-01
Electronic System Level (ESL) design of embedded systems proposes raising the abstraction level of the design entry to cope with the increasing complexity of such systems. To exploit the benefits of ESL, design languages should allow specification of models which are a) heterogeneous, to describe...
Energy Technology Data Exchange (ETDEWEB)
Jack Istok; Melora Park; James McKinley; Chongxuan Liu; Lee Krumholz; Anne Spain; Aaron Peacock; Brett Baldwin
2007-04-19
The overall goal of this project is to develop and test a thermodynamic network model for predicting the effects of substrate additions and environmental perturbations on microbial growth, community composition and system geochemistry. The hypothesis is that a thermodynamic analysis of the energy-yielding growth reactions performed by defined groups of microorganisms can be used to make quantitative and testable predictions of the change in microbial community composition that will occur when a substrate is added to the subsurface or when environmental conditions change.
Mathematical models of tumor heterogeneity and drug resistance
Greene, James
In this dissertation we develop mathematical models of tumor heterogeneity and drug resistance in cancer chemotherapy. Resistance to chemotherapy is one of the major causes of the failure of cancer treatment. Furthermore, recent experimental evidence suggests that drug resistance is a complex biological phenomena, with many influences that interact nonlinearly. Here we study the influence of such heterogeneity on treatment outcomes, both in general frameworks and under specific mechanisms. We begin by developing a mathematical framework for describing multi-drug resistance to cancer. Heterogeneity is reflected by a continuous parameter, which can either describe a single resistance mechanism (such as the expression of P-gp in the cellular membrane) or can account for the cumulative effect of several mechanisms and factors. The model is written as a system of integro-differential equations, structured by the continuous "trait," and includes density effects as well as mutations. We study the limiting behavior of the model, both analytically and numerically, and apply it to study treatment protocols. We next study a specific mechanism of tumor heterogeneity and its influence on cell growth: the cell-cycle. We derive two novel mathematical models, a stochastic agent-based model and an integro-differential equation model, each of which describes the growth of cancer cells as a dynamic transition between proliferative and quiescent states. By examining the role all parameters play in the evolution of intrinsic tumor heterogeneity, and the sensitivity of the population growth to parameter values, we show that the cell-cycle length has the most significant effect on the growth dynamics. In addition, we demonstrate that the agent-based model can be approximated well by the more computationally efficient integro-differential equations, when the number of cells is large. The model is closely tied to experimental data of cell growth, and includes a novel implementation of
Energy Technology Data Exchange (ETDEWEB)
Boerresen, Knut Arne
1996-12-31
Hydrocarbon recovery from subsurface reservoirs has become increasingly dependent on advanced recovery techniques that require improved understanding of the physics of fluid flow within and across geological units including small-scale heterogeneities and fractures. In this thesis, impacts from heterogeneities on local fluid flow are studied experimentally by means of imaging techniques to visualize fluid flow in two dimensions during flooding of larger reservoir models. Part 1 reflects the multi-disciplinary collaboration, by briefly introducing the relevant geology, the literature on experiments on fluid flow in bedded structures, and outlining the applied numerical simulator and imaging techniques applied to visualize fluid flow. The second part contains a synopsis of displacement experiments in naturally laminated sandstones and in crossbed laboratory models, and of the impact from incipient shear fractures on oil recovery. The detailed results obtained from the experiments and simulations are described in six papers, all included. 215 refs., 108 figs., 16 tabs.
International Nuclear Information System (INIS)
Elsheikh, Ahmed H.; Wheeler, Mary F.; Hoteit, Ibrahim
2014-01-01
A Hybrid Nested Sampling (HNS) algorithm is proposed for efficient Bayesian model calibration and prior model selection. The proposed algorithm combines, Nested Sampling (NS) algorithm, Hybrid Monte Carlo (HMC) sampling and gradient estimation using Stochastic Ensemble Method (SEM). NS is an efficient sampling algorithm that can be used for Bayesian calibration and estimating the Bayesian evidence for prior model selection. Nested sampling has the advantage of computational feasibility. Within the nested sampling algorithm, a constrained sampling step is performed. For this step, we utilize HMC to reduce the correlation between successive sampled states. HMC relies on the gradient of the logarithm of the posterior distribution, which we estimate using a stochastic ensemble method based on an ensemble of directional derivatives. SEM only requires forward model runs and the simulator is then used as a black box and no adjoint code is needed. The developed HNS algorithm is successfully applied for Bayesian calibration and prior model selection of several nonlinear subsurface flow problems
Modeling hourly subsurface drainage using steady-state and transient methods
Xian, Changchi; Qi, Zhiming; Tan, Chin S.; Zhang, Tie-Quan
2017-07-01
Computer models have been frequently used to simulate the hydrologic and environmental processes in subsurface-drained cropland. The widely-tested steady-state Hooghoudt (ssH) equation, implemented in the Root Zone Water Quality Model (RZWQM2, version 2.94.00), serves in simulating subsurface drainage. However, transient methods such as the integrated Hooghoudt (inH) and van Schilfgaarde (vanS) equations have seldom been implemented in models. In the present study, RZWQM2's hydrologic component was modified to initiate the soil water redistribution process when rainfall occurred. The three drainage equations (ssH, inH and vanS) were tested in each of two versions of RZWQM2 (original and modified). Field data from Iowa (2007-2008) and Ontario (2009-2010) were used to evaluate different model version × equation combinations' simulation accuracy at both daily and hourly scales, evaluated using the percent of bias (PBIAS), Nash-Sutcliffe efficiency coefficient (NSE), and the Index of Agreement (IoA). On a daily scale and across equations, for the Iowa data the original model (PBIAS ⩽ 14.96, NSE ⩾ 0.40, ⩾ 0.69) was outperformed by the modified model (PBIAS ⩽ 6.48, NSE ⩾ 0.70, IoA ⩾ 0.76). Similarly, for the Ontario data, the original model (PBIAS ⩽ 8.87, NSE ⩾ 0.19, IoA ⩾ 0.65) was outperformed by the modified model (PBIAS ⩽ 3.59, NSE ⩾ 0.31, IoA ⩾ 0.67). However, based on a parity of PBIAS, NSE and IoA values, hourly scale tile drainage computed using the modified model equipped with transient equations did not improve model performance compared with the original ssH equation.
Modeling connected and autonomous vehicles in heterogeneous traffic flow
Ye, Lanhang; Yamamoto, Toshiyuki
2018-01-01
The objective of this study was to develop a heterogeneous traffic-flow model to study the possible impact of connected and autonomous vehicles (CAVs) on the traffic flow. Based on a recently proposed two-state safe-speed model (TSM), a two-lane cellular automaton (CA) model was developed, wherein both the CAVs and conventional vehicles were incorporated in the heterogeneous traffic flow. In particular, operation rules for CAVs are established considering the new characteristics of this emerging technology, including autonomous driving through the adaptive cruise control and inter-vehicle connection via short-range communication. Simulations were conducted under various CAV-penetration rates in the heterogeneous flow. The impact of CAVs on the road capacity was numerically investigated. The simulation results indicate that the road capacity increases with an increase in the CAV-penetration rate within the heterogeneous flow. Up to a CAV-penetration rate of 30%, the road capacity increases gradually; the effect of the difference in the CAV capability on the growth rate is insignificant. When the CAV-penetration rate exceeds 30%, the growth rate is largely decided by the capability of the CAV. The greater the capability, the higher the road-capacity growth rate. The relationship between the CAV-penetration rate and the road capacity is numerically analyzed, providing some insights into the possible impact of the CAVs on traffic systems.
Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site
Energy Technology Data Exchange (ETDEWEB)
Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Brady D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Christian D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kyle, Jennifer E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tfaily, Malak M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Snyder, Michelle MV [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cantrell, Kirk J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Saunders, Danielle L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawter, Amanda R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Oostrom, Martijn L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tartakovsky, Guzel D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Leavy, Ian I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McElroy, Erin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Appriou, Delphine [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sahajpal, Rahul [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Carroll, Matthew M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chu, Rosalie K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cordova, Elsa [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Last, George V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Hope [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kaplan, Daniel I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Garcia, Whitney L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kerisit, Sebastien N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Odeta [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bowden, Mark E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Frances N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Toyoda, Jason G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Plymale, Andrew E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2017-09-01
Isotopes of iodine were generated during plutonium production within the nine production reactors at the U.S. Department of Energy Hanford Site. The short half-life 131I that was released from the fuel into the atmosphere during the dissolution process (when the fuel was dissolved) in the Hanford Site 200 Area is no longer present at concentrations of concern in the environment. The long half-life 129I generated at the Hanford Site during reactor operations was (1) stored in single-shell and double-shell tanks, (2) discharged to liquid disposal sites (e.g., cribs and trenches), (3) released to the atmosphere during fuel reprocessing operations, or (4) captured by off-gas absorbent devices (silver reactors) at chemical separations plants (PUREX, B-Plant, T-Plant, and REDOX). Releases of 129I to the subsurface have resulted in several large, though dilute, plumes in the groundwater. There is also 129I remaining in the vadose zone beneath disposal or leak locations. The fate and transport of 129I in the environment and potential remediation technologies are currently being studied as part of environmental remediation activities at the Hanford Site. A conceptual model describing the nature and extent of subsurface contamination, factors that control plume behavior, and factors relevant to potential remediation processes is needed to support environmental remedy decisions. Because 129I is an uncommon contaminant, relevant remediation experience and scientific literature are limited. In addition, its behavior in subsurface is different from that of other more common and important contaminants (e.g., U, Cr and Tc) in terms of sorption (adsorption and precipitation), and aqueous phase species transformation via redox reactions. Thus, the conceptual model also needs to both describe known contaminant and biogeochemical process information and identify aspects about which additional information is needed to effectively support remedy decisions.
Overview of research and development in subsurface fate and transport modeling
International Nuclear Information System (INIS)
Sullivan, T.M.; Chehata, M.
1995-05-01
The US Department of Energy is responsible for the remediation of over 450 different subsurface-contaminated sites. Contaminant plumes at these sites range in volume from several to millions of cubic yards. The concentration of contaminants also ranges over several orders of magnitude. Contaminants include hazardous wastes such as heavy metals and organic chemicals, radioactive waste including tritium, uranium, and thorium, and mixed waste, which is a combination of hazardous and radioactive wastes. The physical form of the contaminants includes solutes, nonaqueous phase liquids (NAPLs), and vapor phase contaminants such as volatilized organic chemicals and radon. The subject of contaminant fate and transport modeling is multi-disciplinary, involving hydrology, geology, microbiology, chemistry, applied mathematics, computer science, and other areas of expertise. It is an issue of great significance in the United States and around the world. As such, many organizations have substantial programs in this area. In gathering data to prepare this report, a survey was performed of research and development work that is funded by US government agencies to improve the understanding and mechanistic modeling of processes that control contaminant movement through subsurface systems. Government agencies which fund programs that contain fate and transport modeling components include the Environmental Protection Agency, Nuclear Regulatory Commission, Department of Agriculture, Department of Energy, National Science Foundation, Department of Defense, United States Geological Survey, and National Institutes of Health
Analytical modeling of the subsurface volatile organic vapor concentration in vapor intrusion.
Shen, Rui; Pennell, Kelly G; Suuberg, Eric M
2014-01-01
The inhalation of volatile and semi-volatile organic compounds that intrude from a subsurface contaminant source into indoor air has become the subject of health and safety concerns over the last twenty years. Building subslab and soil gas contaminant vapor concentration sampling have become integral parts of vapor intrusion field investigations. While numerical models can be of use in analyzing field data and in helping understand the subslab and soil gas vapor concentrations, they are not widely used due to the perceived effort in setting them up. In this manuscript, we present a new closed-form analytical expression describing subsurface contaminant vapor concentrations, including subslab vapor concentrations. The expression was derived using Schwarz-Christoffel mapping. Results from this analytical model match well the numerical modeling results. This manuscript also explores the relationship between subslab and exterior soil gas vapor concentrations, and offers insights on what parameters need to receive greater focus in field studies. Copyright © 2013 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Ana Vazquez Alejos
2013-01-01
Full Text Available The frequency-dependent behavior in subsurface and through-the-wall media is analyzed in this paper as well as the formation of the Brillouin precursor waveforms inherently related to this feature. The emergence of these forerunners is presented as a plausible form to explain classical impairments observed in imaging technologies. The evolution of mono- and multicycle rectangular and first derivative Gaussian pulses through two dispersive media—concrete blocks and soil—is analyzed using a frequency-domain technique and the Debye dielectric model to characterize the media, at operating frequencies below 3 GHz. The frequency-domain approach facilitated to check the influence of some parameters considered critical for the precursor emergence—operating frequency, input pulse configuration, and internal structure of the underlying medium—results in a versatile tool suitable for any kind of modulated input signal propagated through any dispersive medium. The internal multireflection model has been considered as the most suitable model to describe the transmission process underlying both subsurface and through-wall imaging technologies. Two different moisture contents have been considered for concrete as a parameter to determine the performance of through-wall imaging radar from the precursor formation perspective. The results reveal that precursor is a phenomenon to take into account for application demanding larger signal-to-noise ratios.
Integrated geomechanical modelling at TNO for assessement of deep subsurface risks
Orlic, B.; Fokker, P.; Zijl, W.; Scheffers, B.
2001-01-01
Public authorities, E & P and the mining industry increasingly demand fundamental insight and accurate predictions on subsurface and surface deformation and damage due to exploitation of subsurface natural resources, and subsurface storage of energy residues (e.g. CO2). At this moment deformation is
Bayesian interference in heterogeneous dynamic panel data models: three essays.
Ciccarelli, Matteo
2001-01-01
The task of this work is to discuss issues conceming the specification, estimation, inference and forecasting in multivariate dynamic heterogeneous panel data models from a Bayesian perspective. Three essays linked by a few conraion ideas compose the work. Multivariate dynamic models (mainly VARs) based on micro or macro panel data sets have become increasingly popular in macroeconomics, especially to study the transmission of real and monetary shocks across economies. This great use...
Formal heterogeneous system modeling with SystemC
DEFF Research Database (Denmark)
Niaki, Seyed Hosein Attarzadeh; Jakobsen, Mikkel Koefoed; Sulonen, Tero
2012-01-01
Electronic System Level (ESL) design of embedded systems proposes raising the abstraction level of the design entry to cope with the increasing complexity of such systems. To exploit the benefits of ESL, design languages should allow specification of models which are a) heterogeneous, to describe...... to focus on specifying the pure functional aspects. A key advantage is that the formalism is used to export the structure and behavior of the models via introspection as an abstract representation for further analysis and synthesis....
Three-dimensional Subsurface Geological Modeling of the Western Osaka Plane based on Borehole Data
Nonogaki, S.; Masumoto, S.; Nemoto, T.
2012-12-01
Three-dimensional (3D) geological model of subsurface structure plays an important role in developing infrastructures. In particular, the 3D geological model in urban area is quite helpful to solve social problems such as underground utilization, environmental preservation, and disaster assessment. Over the past few years, many studies have been made on algorithms for 3D geological modeling. However, most of them have given little attention to objectivity of the model and traceability of modeling procedures. The purpose of this study is to develop an algorithm for constructing a 3D geological model objectively and for maintaining high-traceability of modeling procedures. For the purpose of our work, we proposed a new algorithm for 3D geological modeling using gridded geological boundary surfaces and the "logical model of geologic structure". The geological boundary surface is given by a form of Digital Elevation Model (DEM). The DEM is generated based on geological information such as elevation, strike and dip by using a unique spline-fitting method. The logical model of geological structure is a mathematical model that defines a positional relation between geological boundary surfaces and geological units. The model is objectively given by recurrence formula derived from a sequence of geological events arranged in chronological order. We applied the proposed algorithm into constructing a 3D subsurface geological model of the western Osaka Plane, southwest Japan. The data used for 3D geological modeling is a set of borehole data provided by Osaka City and Kansai Geoinformatics Agency. As a result, we constructed a 3D model consistent with the subjective model reported in other studies. In addition, all information necessary for modeling, such as the used geological information, the parameters of surface fitting, and the logical model, was stored in text files. In conclusion, we can not only construct 3D geological model objectively but also maintain high
A two-dimensional analytical model of vapor intrusion involving vertical heterogeneity
Yao, Yijun; Verginelli, Iason; Suuberg, Eric M.
2017-05-01
In this work, we present an analytical chlorinated vapor intrusion (CVI) model that can estimate source-to-indoor air concentration attenuation by simulating two-dimensional (2-D) vapor concentration profile in vertically heterogeneous soils overlying a homogenous vapor source. The analytical solution describing the 2-D soil gas transport was obtained by applying a modified Schwarz-Christoffel mapping method. A partial field validation showed that the developed model provides results (especially in terms of indoor emission rates) in line with the measured data from a case involving a building overlying a layered soil. In further testing, it was found that the new analytical model can very closely replicate the results of three-dimensional (3-D) numerical models at steady state in scenarios involving layered soils overlying homogenous groundwater sources. By contrast, by adopting a two-layer approach (capillary fringe and vadose zone) as employed in the EPA implementation of the Johnson and Ettinger model, the spatially and temporally averaged indoor concentrations in the case of groundwater sources can be higher than the ones estimated by the numerical model up to two orders of magnitude. In short, the model proposed in this work can represent an easy-to-use tool that can simulate the subsurface soil gas concentration in layered soils overlying a homogenous vapor source while keeping the simplicity of an analytical approach that requires much less computational effort.
A two-dimensional analytical model of vapor intrusion involving vertical heterogeneity.
Yao, Yijun; Verginelli, Iason; Suuberg, Eric M
2017-05-01
In this work, we present an analytical chlorinated vapor intrusion (CVI) model that can estimate source-to-indoor air concentration attenuation by simulating two-dimensional (2-D) vapor concentration profile in vertically heterogeneous soils overlying a homogenous vapor source. The analytical solution describing the 2-D soil gas transport was obtained by applying a modified Schwarz-Christoffel mapping method. A partial field validation showed that the developed model provides results (especially in terms of indoor emission rates) in line with the measured data from a case involving a building overlying a layered soil. In further testing, it was found that the new analytical model can very closely replicate the results of three-dimensional (3-D) numerical models at steady state in scenarios involving layered soils overlying homogenous groundwater sources. By contrast, by adopting a two-layer approach (capillary fringe and vadose zone) as employed in the EPA implementation of the Johnson and Ettinger model, the spatially and temporally averaged indoor concentrations in the case of groundwater sources can be higher than the ones estimated by the numerical model up to two orders of magnitude. In short, the model proposed in this work can represent an easy-to-use tool that can simulate the subsurface soil gas concentration in layered soils overlying a homogenous vapor source while keeping the simplicity of an analytical approach that requires much less computational effort.
Averaging principle for second-order approximation of heterogeneous models with homogeneous models.
Fibich, Gadi; Gavious, Arieh; Solan, Eilon
2012-11-27
Typically, models with a heterogeneous property are considerably harder to analyze than the corresponding homogeneous models, in which the heterogeneous property is replaced by its average value. In this study we show that any outcome of a heterogeneous model that satisfies the two properties of differentiability and symmetry is O(ε(2)) equivalent to the outcome of the corresponding homogeneous model, where ε is the level of heterogeneity. We then use this averaging principle to obtain new results in queuing theory, game theory (auctions), and social networks (marketing).
An iterative stochastic ensemble method for parameter estimation of subsurface flow models
International Nuclear Information System (INIS)
Elsheikh, Ahmed H.; Wheeler, Mary F.; Hoteit, Ibrahim
2013-01-01
Parameter estimation for subsurface flow models is an essential step for maximizing the value of numerical simulations for future prediction and the development of effective control strategies. We propose the iterative stochastic ensemble method (ISEM) as a general method for parameter estimation based on stochastic estimation of gradients using an ensemble of directional derivatives. ISEM eliminates the need for adjoint coding and deals with the numerical simulator as a blackbox. The proposed method employs directional derivatives within a Gauss–Newton iteration. The update equation in ISEM resembles the update step in ensemble Kalman filter, however the inverse of the output covariance matrix in ISEM is regularized using standard truncated singular value decomposition or Tikhonov regularization. We also investigate the performance of a set of shrinkage based covariance estimators within ISEM. The proposed method is successfully applied on several nonlinear parameter estimation problems for subsurface flow models. The efficiency of the proposed algorithm is demonstrated by the small size of utilized ensembles and in terms of error convergence rates
Energy Technology Data Exchange (ETDEWEB)
Ye, Sheng; Li, Hongyi; Huang, Maoyi; Ali, Melkamu; Leng, Guoyong; Leung, Lai-Yung R.; Wang, Shaowen; Sivapalan, Murugesu
2014-07-21
Subsurface stormflow is an important component of the rainfall–runoff response, especially in steep terrain. Its contribution to total runoff is, however, poorly represented in the current generation of land surface models. The lack of physical basis of these common parameterizations precludes a priori estimation of the stormflow (i.e. without calibration), which is a major drawback for prediction in ungauged basins, or for use in global land surface models. This paper is aimed at deriving regionalized parameterizations of the storage–discharge relationship relating to subsurface stormflow from a top–down empirical data analysis of streamflow recession curves extracted from 50 eastern United States catchments. Detailed regression analyses were performed between parameters of the empirical storage–discharge relationships and the controlling climate, soil and topographic characteristics. The regression analyses performed on empirical recession curves at catchment scale indicated that the coefficient of the power-law form storage–discharge relationship is closely related to the catchment hydrologic characteristics, which is consistent with the hydraulic theory derived mainly at the hillslope scale. As for the exponent, besides the role of field scale soil hydraulic properties as suggested by hydraulic theory, it is found to be more strongly affected by climate (aridity) at the catchment scale. At a fundamental level these results point to the need for more detailed exploration of the co-dependence of soil, vegetation and topography with climate.
An iterative stochastic ensemble method for parameter estimation of subsurface flow models
Elsheikh, Ahmed H.
2013-06-01
Parameter estimation for subsurface flow models is an essential step for maximizing the value of numerical simulations for future prediction and the development of effective control strategies. We propose the iterative stochastic ensemble method (ISEM) as a general method for parameter estimation based on stochastic estimation of gradients using an ensemble of directional derivatives. ISEM eliminates the need for adjoint coding and deals with the numerical simulator as a blackbox. The proposed method employs directional derivatives within a Gauss-Newton iteration. The update equation in ISEM resembles the update step in ensemble Kalman filter, however the inverse of the output covariance matrix in ISEM is regularized using standard truncated singular value decomposition or Tikhonov regularization. We also investigate the performance of a set of shrinkage based covariance estimators within ISEM. The proposed method is successfully applied on several nonlinear parameter estimation problems for subsurface flow models. The efficiency of the proposed algorithm is demonstrated by the small size of utilized ensembles and in terms of error convergence rates. © 2013 Elsevier Inc.
A "mental models" approach to the communication of subsurface hydrology and hazards
Gibson, Hazel; Stewart, Iain S.; Pahl, Sabine; Stokes, Alison
2016-05-01
Communicating information about geological and hydrological hazards relies on appropriately worded communications targeted at the needs of the audience. But what are these needs, and how does the geoscientist discern them? This paper adopts a psychological "mental models" approach to assess the public perception of the geological subsurface, presenting the results of attitudinal studies and surveys in three communities in the south-west of England. The findings reveal important preconceptions and misconceptions regarding the impact of hydrological systems and hazards on the geological subsurface, notably in terms of the persistent conceptualisation of underground rivers and the inferred relations between flooding and human activity. The study demonstrates how such mental models can provide geoscientists with empirical, detailed and generalised data of perceptions surrounding an issue, as well reveal unexpected outliers in perception that they may not have considered relevant, but which nevertheless may locally influence communication. Using this approach, geoscientists can develop information messages that more directly engage local concerns and create open engagement pathways based on dialogue, which in turn allow both geoscience "experts" and local "non-experts" to come together and understand each other more effectively.
De Lucia, Marco; Kempka, Thomas; Jatnieks, Janis; Kühn, Michael
2017-04-01
Reactive transport simulations - where geochemical reactions are coupled with hydrodynamic transport of reactants - are extremely time consuming and suffer from significant numerical issues. Given the high uncertainties inherently associated with the geochemical models, which also constitute the major computational bottleneck, such requirements may seem inappropriate and probably constitute the main limitation for their wide application. A promising way to ease and speed-up such coupled simulations is achievable employing statistical surrogates instead of "full-physics" geochemical models [1]. Data-driven surrogates are reduced models obtained on a set of pre-calculated "full physics" simulations, capturing their principal features while being extremely fast to compute. Model reduction of course comes at price of a precision loss; however, this appears justified in presence of large uncertainties regarding the parametrization of geochemical processes. This contribution illustrates the integration of surrogates into the flexible simulation framework currently being developed by the authors' research group [2]. The high level language of choice for obtaining and dealing with surrogate models is R, which profits from state-of-the-art methods for statistical analysis of large simulations ensembles. A stand-alone advective mass transport module was furthermore developed in order to add such capability to any multiphase finite volume hydrodynamic simulator within the simulation framework. We present 2D and 3D case studies benchmarking the performance of surrogates and "full physics" chemistry in scenarios pertaining the assessment of geological subsurface utilization. [1] Jatnieks, J., De Lucia, M., Dransch, D., Sips, M.: "Data-driven surrogate model approach for improving the performance of reactive transport simulations.", Energy Procedia 97, 2016, p. 447-453. [2] Kempka, T., Nakaten, B., De Lucia, M., Nakaten, N., Otto, C., Pohl, M., Chabab [Tillner], E., Kühn, M
Drilling Load Model of an Inchworm Boring Robot for Lunar Subsurface Exploration
Directory of Open Access Journals (Sweden)
Weiwei Zhang
2017-01-01
Full Text Available In the past decade, the wireline robot has received increasing attention due to the advantages of light weight, low cost, and flexibility compared to the traditional drilling instruments in space missions. For the lunar subsurface in situ exploration mission, we proposed a type of wireline robot named IBR (Inchworm Boring Robot drawing inspiration from the inchworm. Two auger tools are utilized to remove chips for IBR, which directly interacted with the lunar regolith in the drilling process. Therefore, for obtaining the tools drilling characteristics, the chips removal principle of IBR is analyzed and its drilling load model is further established based on the soil mechanical theory in this paper. And then the proposed theoretical drilling load model is experimentally validated. In addition, according to the theoretical drilling load model, this paper discusses the effect of the drilling parameters on the tools drilling moments and power consumption. These results imply a possible energy-efficient control strategy for IBR.
Developing and applying heterogeneous phylogenetic models with XRate.
Directory of Open Access Journals (Sweden)
Oscar Westesson
Full Text Available Modeling sequence evolution on phylogenetic trees is a useful technique in computational biology. Especially powerful are models which take account of the heterogeneous nature of sequence evolution according to the "grammar" of the encoded gene features. However, beyond a modest level of model complexity, manual coding of models becomes prohibitively labor-intensive. We demonstrate, via a set of case studies, the new built-in model-prototyping capabilities of XRate (macros and Scheme extensions. These features allow rapid implementation of phylogenetic models which would have previously been far more labor-intensive. XRate 's new capabilities for lineage-specific models, ancestral sequence reconstruction, and improved annotation output are also discussed. XRate 's flexible model-specification capabilities and computational efficiency make it well-suited to developing and prototyping phylogenetic grammar models. XRate is available as part of the DART software package: http://biowiki.org/DART.
A heterogeneous lattice gas model for simulating pedestrian evacuation
Guo, Xiwei; Chen, Jianqiao; Zheng, Yaochen; Wei, Junhong
2012-02-01
Based on the cellular automata method (CA model) and the mobile lattice gas model (MLG model), we have developed a heterogeneous lattice gas model for simulating pedestrian evacuation processes in an emergency. A local population density concept is introduced first. The update rule in the new model depends on the local population density and the exit crowded degree factor. The drift D, which is one of the key parameters influencing the evacuation process, is allowed to change according to the local population density of the pedestrians. Interactions including attraction, repulsion, and friction between every two pedestrians and those between a pedestrian and the building wall are described by a nonlinear function of the corresponding distance, and the repulsion forces increase sharply as the distances get small. A critical force of injury is introduced into the model, and its effects on the evacuation process are investigated. The model proposed has heterogeneous features as compared to the MLG model or the basic CA model. Numerical examples show that the model proposed can capture the basic features of pedestrian evacuation, such as clogging and arching phenomena.
Accounting for small scale heterogeneity in ecohydrologic watershed models
Burke, W.; Tague, C.
2017-12-01
Spatially distributed ecohydrologic models are inherently constrained by the spatial resolution of their smallest units, below which land and processes are assumed to be homogenous. At coarse scales, heterogeneity is often accounted for by computing store and fluxes of interest over a distribution of land cover types (or other sources of heterogeneity) within spatially explicit modeling units. However this approach ignores spatial organization and the lateral transfer of water and materials downslope. The challenge is to account both for the role of flow network topology and fine-scale heterogeneity. We present a new approach that defines two levels of spatial aggregation and that integrates spatially explicit network approach with a flexible representation of finer-scale aspatial heterogeneity. Critically, this solution does not simply increase the resolution of the smallest spatial unit, and so by comparison, results in improved computational efficiency. The approach is demonstrated by adapting Regional Hydro-Ecologic Simulation System (RHESSys), an ecohydrologic model widely used to simulate climate, land use, and land management impacts. We illustrate the utility of our approach by showing how the model can be used to better characterize forest thinning impacts on ecohydrology. Forest thinning is typically done at the scale of individual trees, and yet management responses of interest include impacts on watershed scale hydrology and on downslope riparian vegetation. Our approach allow us to characterize the variability in tree size/carbon reduction and water transfers between neighboring trees while still capturing hillslope to watershed scale effects, Our illustrative example demonstrates that accounting for these fine scale effects can substantially alter model estimates, in some cases shifting the impacts of thinning on downslope water availability from increases to decreases. We conclude by describing other use cases that may benefit from this approach
Heterogeneous modelling and finite element analysis of the femur
Directory of Open Access Journals (Sweden)
Zhang Binkai
2017-01-01
Full Text Available As the largest and longest bone in the human body, the femur has important research value and application prospects. This paper introduces a fast reconstruction method with Mimics and ANSYS software to realize the heterogeneous modelling of the femur according to Hu distribution of the CT series, and simulates it in various situations by finite element analysis to study the mechanical characteristics of the femur. The femoral heterogeneous model shows the distribution of bone mineral density and material properties, which can be used to assess the diagnosis and treatment of bone diseases. The stress concentration position of the femur under different conditions can be calculated by the simulation, which can provide reference for the design and material selection of prosthesis.
Marchenko, Sergey; van Pelt, Ward J. J.; Claremar, Björn; Pohjola, Veijo; Pettersson, Rickard; Machguth, Horst; Reijmer, Carleen
2017-03-01
Deep preferential percolation of melt water in snow and firn brings water lower along the vertical profile than a laterally homogeneous wetting front. This widely recognized process is an important source of uncertainty in simulations of subsurface temperature, density and water content in seasonal snow and in firn packs on glaciers and ice sheets. However, observation and quantification of preferential flow is challenging and therefore it is not accounted for by most of the contemporary snow/firn models. Here we use temperature measurements in the accumulation zone of Lomonosovfonna, Svalbard, done in April 2012 - 2015 using multiple thermistor strings to describe the process of water percolation in snow and firn. Effects of water flow through the snow and firn profile are further explored using a coupled surface energy balance - firn model forced by the output of the regional climate model WRF. In situ air temperature, radiation and surface height change measurements are used to constrain the surface energy and mass fluxes. To account for the effects of preferential water flow in snow and firn we test a set of depth-dependent functions allocating a certain fraction of the melt water available at the surface to each snow/firn layer. Experiments are performed for a range of characteristic percolation depths and results indicate a reduction in root mean square difference between the modeled and measured temperature by up to a factor of two compared to the results from the default water infiltration scheme. This illustrates the significance of accounting for preferential water percolation to simulate subsurface conditions. The suggested approach to parameterization of the preferential water flow requires low additional computational cost and can be implemented in layered snow/firn models applied both at local and regional scales, for distributed domains with multiple mesh points.
Kerschke, Dorit; Schilling, Maik; Simon, Andreas; Wächter, Joachim
2014-05-01
application enables an intuitive navigation through all available information and allows the visualization of geological maps (2D), seismic transects (2D/3D), wells (2D/3D), and the 3D-model. These achievements will alleviate spatial and geological data management within the German State Geological Offices and foster the interoperability of heterogeneous systems. It will provide guidance to a systematic subsurface management across system, domain and administrative boundaries on the basis of a federated spatial data infrastructure, and include the public in the decision processes (e-Governance). Yet, the interoperability of the systems has to be strongly propelled forward through agreements on standards that need to be decided upon in responsible committees. The project B3D is funded with resources from the European Fund for Regional Development (EFRE).
Clustered iterative stochastic ensemble method for multi-modal calibration of subsurface flow models
Elsheikh, Ahmed H.
2013-05-01
A novel multi-modal parameter estimation algorithm is introduced. Parameter estimation is an ill-posed inverse problem that might admit many different solutions. This is attributed to the limited amount of measured data used to constrain the inverse problem. The proposed multi-modal model calibration algorithm uses an iterative stochastic ensemble method (ISEM) for parameter estimation. ISEM employs an ensemble of directional derivatives within a Gauss-Newton iteration for nonlinear parameter estimation. ISEM is augmented with a clustering step based on k-means algorithm to form sub-ensembles. These sub-ensembles are used to explore different parts of the search space. Clusters are updated at regular intervals of the algorithm to allow merging of close clusters approaching the same local minima. Numerical testing demonstrates the potential of the proposed algorithm in dealing with multi-modal nonlinear parameter estimation for subsurface flow models. © 2013 Elsevier B.V.
Energy Technology Data Exchange (ETDEWEB)
Kantar, C.; Dodge, C.; Demiray, H.; Dogan, N.M.
2011-01-26
Chromium (III) binding by exopolymeric substances (EPS) isolated from Pseudomonas putida P18, Pseudomonas aeruginosa P16 and Pseudomonas stutzeri P40 strains were investigated by the determination of conditional stability constants and the concentration of functional groups using the ion-exchange experiments and potentiometric titrations. Spectroscopic (EXAFS) analysis was also used to obtain information on the nature of Cr(III) binding with EPS functional groups. The data from ion-exchange experiments and potentiometric titrations were evaluated using a non-electrostatic discrete ligand approach. The modeling results show that the acid/base properties of EPSs can be best characterized by invoking four different types of acid functional groups with arbitrarily assigned pK{sub a} values of 4, 6, 8 and 10. The analysis of ion-exchange data using the discrete ligand approach suggests that while the Cr binding by EPS from P. aeruginosa can be successfully described based on a reaction stoichiometry of 1:2 between Cr(III) and HL{sub 2} monoprotic ligands, the accurate description of Cr binding by EPSs extracted from P. putida and P. stutzeri requires postulation of 1:1 Cr(III)-ligand complexes with HL{sub 2} and HL{sub 3} monoprotic ligands, respectively. These results indicate that the carboxyl and/or phosphoric acid sites contribute to Cr(III) binding by microbial EPS, as also confirmed by EXAFS analysis performed in the current study. Overall, this study highlights the need for incorporation of Cr-EPS interactions into transport and speciation models to more accurately assess microbial Cr(VI) reduction and chromium transport in subsurface systems, including microbial reactive treatment barriers.
Energy Technology Data Exchange (ETDEWEB)
C Kantar; H Demiray; N Dogan; C Dodge
2011-12-31
Chromium (III) binding by exopolymeric substances (EPS) isolated from Pseudomonas putida P18, Pseudomonas aeruginosa P16 and Pseudomonas stutzeri P40 strains were investigated by the determination of conditional stability constants and the concentration of functional groups using the ion-exchange experiments and potentiometric titrations. Spectroscopic (EXAFS) analysis was also used to obtain information on the nature of Cr(III) binding with EPS functional groups. The data from ion-exchange experiments and potentiometric titrations were evaluated using a non-electrostatic discrete ligand approach. The modeling results show that the acid/base properties of EPSs can be best characterized by invoking four different types of acid functional groups with arbitrarily assigned pK{sub a} values of 4, 6, 8 and 10. The analysis of ion-exchange data using the discrete ligand approach suggests that while the Cr binding by EPS from P. aeruginosa can be successfully described based on a reaction stoichiometry of 1:2 between Cr(III) and HL{sub 2} monoprotic ligands, the accurate description of Cr binding by EPSs extracted from P. putida and P. stutzeri requires postulation of 1:1 Cr(III)-ligand complexes with HL{sub 2} and HL{sub 3} monoprotic ligands, respectively. These results indicate that the carboxyl and/or phosphoric acid sites contribute to Cr(III) binding by microbial EPS, as also confirmed by EXAFS analysis performed in the current study. Overall, this study highlights the need for incorporation of Cr-EPS interactions into transport and speciation models to more accurately assess microbial Cr(VI) reduction and chromium transport in subsurface systems, including microbial reactive treatment barriers.
Jago-on, Karen Ann Bianet; Kaneko, Shinji; Fujikura, Ryo; Fujiwara, Akimasa; Imai, Tsuyoshi; Matsumoto, Toru; Zhang, Junyi; Tanikawa, Hiroki; Tanaka, Katsuya; Lee, Backjin; Taniguchi, Makoto
2009-04-15
This paper synthesizes existing information and knowledge on subsurface environments to understand the major cause and effect relationships of subsurface environmental issues by using the DPSIR (Driving force-Pressure-Status-Impact-Response) approach as the framework of analysis. Description is given to the major subsurface environmental issues common among the selected Asian cities (Bangkok, Jakarta, Manila, Osaka, Seoul, Taipei and Tokyo), such as excessive groundwater abstraction, land subsidence and groundwater contamination. The DPSIR framework is used to analyze the issues and problems of subsurface in key stages and suggestions are made for additional indicators to improve our description of the stages of urban development for the future.
Dual states estimation of a subsurface flow-transport coupled model using ensemble Kalman filtering
El Gharamti, Mohamad
2013-10-01
Modeling the spread of subsurface contaminants requires coupling a groundwater flow model with a contaminant transport model. Such coupling may provide accurate estimates of future subsurface hydrologic states if essential flow and contaminant data are assimilated in the model. Assuming perfect flow, an ensemble Kalman filter (EnKF) can be used for direct data assimilation into the transport model. This is, however, a crude assumption as flow models can be subject to many sources of uncertainty. If the flow is not accurately simulated, contaminant predictions will likely be inaccurate even after successive Kalman updates of the contaminant model with the data. The problem is better handled when both flow and contaminant states are concurrently estimated using the traditional joint state augmentation approach. In this paper, we introduce a dual estimation strategy for data assimilation into a one-way coupled system by treating the flow and the contaminant models separately while intertwining a pair of distinct EnKFs, one for each model. The presented strategy only deals with the estimation of state variables but it can also be used for state and parameter estimation problems. This EnKF-based dual state-state estimation procedure presents a number of novel features: (i) it allows for simultaneous estimation of both flow and contaminant states in parallel; (ii) it provides a time consistent sequential updating scheme between the two models (first flow, then transport); (iii) it simplifies the implementation of the filtering system; and (iv) it yields more stable and accurate solutions than does the standard joint approach. We conducted synthetic numerical experiments based on various time stepping and observation strategies to evaluate the dual EnKF approach and compare its performance with the joint state augmentation approach. Experimental results show that on average, the dual strategy could reduce the estimation error of the coupled states by 15% compared with the
Macheras, Panos
2016-01-01
The state of the art in Biopharmaceutics, Pharmacokinetics, and Pharmacodynamics Modeling is presented in this new second edition book. It shows how advanced physical and mathematical methods can expand classical models in order to cover heterogeneous drug-biological processes and therapeutic effects in the body. The book is divided into four parts; the first deals with the fundamental principles of fractals, diffusion and nonlinear dynamics; the second with drug dissolution, release, and absorption; the third with epirical, compartmental, and stochastic pharmacokinetic models, with two new chapters, one on fractional pharmacokinetics and one on bioequivalence; and the fourth mainly with classical and nonclassical aspects of pharmacodynamics. The classical models that have relevance and application to these sciences are also considered throughout. This second edition has new information on reaction limited models of dissolution, non binary biopharmaceutic classification system, time varying models, and interf...
Heterogeneous Community-based mobility model for human opportunistic network
DEFF Research Database (Denmark)
Hu, Liang; Dittmann, Lars
2009-01-01
Human opportunistic networks can facilitate wireless content dissemination while humans are on the move. In such a network, content is disseminated via nodes relaying and nodes mobility (human mobility). Thus it is essential to understand and model the real human mobility. We present...... a heterogeneous community-based random way-point (HC-RWP) mobility model that captures the four important properties of real human mobility. These properties are based on both intuitive observations of daily human mobility and analysis of empirical mobility traces. By discrete event simulation, we show HC......-RWP captures essential statistic features of wide range of real human mobility traces reported in previous studies....
Subsurface Bio-Immobilization of Plutonium: Experiment and Model Validation Study
Energy Technology Data Exchange (ETDEWEB)
Reed, Donald; Rittmann, Bruce
2006-06-01
The goal of this project is to conduct a concurrent experimental and modeling study centered on the interactions of Shewanella algae BrY with plutonium and uranium species and phases. The most important objective of this research is to investigate the long-term stability of bioprecipitated immobilized actinide phases under changing redox conditions in biologically active systems. The long-term stability of bio-immobilized actinides (e.g. by bio-reduction) is a key criteria that defines the utility and effectiveness of a remediation/containment strategy for subsurface actinide contaminants. Plutonium, which is the focus of this project, is the key contaminant of concern at several DOE sites.
DEFF Research Database (Denmark)
Balling, N.; Poulsen, Søren Erbs; Bording, Thue Sylvester
2015-01-01
Most of the Danish area is characterized by deep sedimentary basins with a great potential for exploitation of geothermal energy. Geothermal reservoirs are present at various depths and temperatures. Currently, three geothermal plants are operating producing warm water for district heating purposes...... of different conductivity. Mean geothermal gradients from surface to depths of 1000 to 3000 m are generally between 20 and 35 °C/km. The subsurface thermal structure is clearly dominated by conduction. Advection by groundwater migration is generally insignificant. Heat flow increases significantly with depth...... due to perturbation from long-term palaeoclimatic surface temperature variations. Examples of modelled temperature distribution for selected geothermal reservoir are shown. In the Gassum Formation, which is present in most of the Danish area, temperatures are largely between 35 and 90 °C for depths...
A coupled surface/subsurface flow model accounting for air entrapment and air pressure counterflow
DEFF Research Database (Denmark)
Delfs, Jens Olaf; Wang, Wenqing; Kalbacher, Thomas
2013-01-01
the mass exchange between compartments. A benchmark test, which is based on a classic experimental data set on infiltration excess (Horton) overland flow, identified a feedback mechanism between surface runoff and soil air pressures. Our study suggests that air compression in soils amplifies surface runoff......This work introduces the soil air system into integrated hydrology by simulating the flow processes and interactions of surface runoff, soil moisture and air in the shallow subsurface. The numerical model is formulated as a coupled system of partial differential equations for hydrostatic (diffusive...... wave) shallow flow and two-phase flow in a porous medium. The simultaneous mass transfer between the soil, overland, and atmosphere compartments is achieved by upgrading a fully established leakance concept for overland-soil liquid exchange to an air exchange flux between soil and atmosphere. In a new...
Fagerlund, F.; Niemi, A.
2007-01-01
The subsurface spreading behaviour of gasoline, as well as several other common soil- and groundwater pollutants (e.g. diesel, creosote), is complicated by the fact that it is a mixture of hundreds of different constituents, behaving differently with respect to e.g. dissolution, volatilisation, adsorption and biodegradation. Especially for scenarios where the non-aqueous phase liquid (NAPL) phase is highly mobile, such as for sudden spills in connection with accidents, it is necessary to simultaneously analyse the migration of the NAPL and its individual components in order to assess risks and environmental impacts. Although a few fully coupled, multi-phase, multi-constituent models exist, such models are highly complex and may be time consuming to use. A new, somewhat simplified methodology for modelling the subsurface migration of gasoline while taking its multi-constituent nature into account is therefore introduced here. Constituents with similar properties are grouped together into eight fractions. The migration of each fraction in the aqueous and gaseous phases as well as adsorption is modelled separately using a single-constituent multi-phase flow model, while the movement of the free-phase gasoline is essentially the same for all fractions. The modelling is done stepwise to allow updating of the free-phase gasoline composition at certain time intervals. The output is the concentration of the eight different fractions in the aqueous, gaseous, free gasoline and solid phases with time. The approach is evaluated by comparing it to a fully coupled multi-phase, multi-constituent numerical simulator in the modelling of a typical accident-type spill scenario, based on a tanker accident in northern Sweden. Here the PCFF method produces results similar to those of the more sophisticated, fully coupled model. The benefit of the method is that it is easy to use and can be applied to any single-constituent multi-phase numerical simulator, which in turn may have
Yoo, Jin Woo
In my 1st essay, the study explores Pennsylvania residents. willingness to pay for development of renewable energy technologies such as solar power, wind power, biomass electricity, and other renewable energy using a choice experiment method. Principle component analysis identified 3 independent attitude components that affect the variation of preference, a desire for renewable energy and environmental quality and concern over cost. The results show that urban residents have a higher desire for environmental quality and concern less about cost than rural residents and consequently have a higher willingness to pay to increase renewable energy production. The results of sub-sample analysis show that a representative respondent in rural (urban) Pennsylvania is willing to pay 3.8(5.9) and 4.1(5.7)/month for increasing the share of Pennsylvania electricity generated from wind power and other renewable energy by 1 percent point, respectively. Mean WTP for solar and biomass electricity was not significantly different from zero. In my second essay, heterogeneity of individual WTP for various renewable energy technologies is investigated using several different variants of the multinomial logit model: a simple MNL with interaction terms, a latent class choice model, a random parameter mixed logit choice model, and a random parameter-latent class choice model. The results of all models consistently show that respondents. preference for individual renewable technology is heterogeneous, but the degree of heterogeneity differs for different renewable technologies. In general, the random parameter logit model with interactions and a hybrid random parameter logit-latent class model fit better than other models and better capture respondents. heterogeneity of preference for renewable energy. The impact of the land under agricultural conservation easement (ACE) contract on the values of nearby residential properties is investigated using housing sales data in two Pennsylvania
A Direct Method of Hydraulic Conductivity Structure Identification for Subsurface Transport Modeling
Zhang, Y.; Jiao, J.
2016-12-01
Solute transport in aquifers is strongly influenced by the spatial distribution of subsurface hydraulic conductivity (K), while limited drilling in data-sparse environments typically results in lack of data characterizing both the K and the in-situ fluid flow boundary conditions (BC). To characterize such environments, we present an efficient direct inverse method to simultaneously identify aquifer K pattern, its values, and the flow field. The method ensures fluid flow continuity using local approximate solutions of the governing equation conditioned to limited hydraulic measurements, while physics of the flow is enforced making the inverse problem well-posed. A single system of equations is assembled and solved, from which parameters and BC can be simultaneously estimated. For problems with irregular and regular K distributions, inversion is demonstrated for different measurement types, quality, and quantity. When measurement error is increased, the estimated K pattern is largely insensitive to the error, although the inverted flow field suffers greater inaccuracy. Local conductivity and Darcy flux measurements are found to have similar information content, although subtle differences exist in the inverted flow fields when long-term contaminant release is simulated. Local conductivity measurements lead to better identification of conductivity pattern, values, and the hydraulic head field; Darcy flux measurements lead to more accurate estimation of the velocity field and thus improved transport predictions. Overall, the velocity fields estimated based on the hydraulic data can lead to reasonable predictions of contaminant migration and breakthrough under unknown aquifer BC. We further argue that the goal of pattern inversion is to recover a sufficient level of detail to make transport prediction approximately accurate. Depending on the desired accuracy, fine-scale heterogeneity can be recovered only at increased characterization cost. Future work will (1) evaluate
International Nuclear Information System (INIS)
Wang, Yifeng; Papenguth, Hans W.
2000-01-01
Microbial degradation of organic matter is a driving force in many subsurface geochemical systems, and therefore may have significant impacts on the fate of radionuclides released into subsurface environments. In this paper, the authors present a general reaction-transport model for microbial metabolism, redox chemistry, and radionuclide migration in subsurface systems. The model explicitly accounts for biomass accumulation and the coupling of radionuclide redox reactions with major biogeochemical processes. Based on the consideration that the biomass accumulation in subsurface environments is likely to achieve a quasi-steady state, they have accordingly modified the traditional microbial growth kinetic equation. They justified the use of the biogeochemical models without the explicit representation of biomass accumulation, if the interest of modeling is in the net impact of microbial reactions on geochemical processes. They then applied their model to a scenario in which an oxic water flow containing both uranium and completing organic ligands is recharged into an oxic aquifer in a carbonate formation. The model simulation shows that uranium can be reduced and therefore immobilized in the anoxic zone created by microbial degradation
Macheras, Panos
2006-01-01
The state of the art in Biopharmaceutics, Pharmacokinetics, and Pharmacodynamics Modeling is presented in this book. It shows how advanced physical and mathematical methods can expand classical models in order to cover heterogeneous drug-biological processes and therapeutic effects in the body. The book is divided into four parts; the first deals with the fundamental principles of fractals, diffusion and nonlinear dynamics; the second with drug dissolution, release, and absorption; the third with empirical, compartmental, and stochastic pharmacokinetic models, and the fourth mainly with nonclassical aspects of pharmacodynamics. The classical models that have relevance and application to these sciences are also considered throughout. Many examples are used to illustrate the intrinsic complexity of drug administration related phenomena in the human, justifying the use of advanced modeling methods. This timely and useful book will appeal to graduate students and researchers in pharmacology, pharmaceutical scienc...
Radiative transfer model for heterogeneous 3-D scenes
Kimes, D. S.; Kirchner, J. A.
1982-01-01
A general mathematical framework for simulating processes in heterogeneous 3-D scenes is presented. Specifically, a model was designed and coded for application to radiative transfers in vegetative scenes. The model is unique in that it predicts (1) the directional spectral reflectance factors as a function of the sensor's azimuth and zenith angles and the sensor's position above the canopy, (2) the spectral absorption as a function of location within the scene, and (3) the directional spectral radiance as a function of the sensor's location within the scene. The model was shown to follow known physical principles of radiative transfer. Initial verification of the model as applied to a soybean row crop showed that the simulated directional reflectance data corresponded relatively well in gross trends to the measured data. However, the model can be greatly improved by incorporating more sophisticated and realistic anisotropic scattering algorithms
Need to improve SWMM's subsurface flow routing algorithm for green infrastructure modeling
SWMM can simulate various subsurface flows, including groundwater (GW) release from a subcatchment to a node, percolation out of storage units and low impact development (LID) controls, and rainfall derived inflow and infiltration (RDII) at a node. Originally, the subsurface flow...
Elsheikh, Ahmed H.
2014-02-01
A Hybrid Nested Sampling (HNS) algorithm is proposed for efficient Bayesian model calibration and prior model selection. The proposed algorithm combines, Nested Sampling (NS) algorithm, Hybrid Monte Carlo (HMC) sampling and gradient estimation using Stochastic Ensemble Method (SEM). NS is an efficient sampling algorithm that can be used for Bayesian calibration and estimating the Bayesian evidence for prior model selection. Nested sampling has the advantage of computational feasibility. Within the nested sampling algorithm, a constrained sampling step is performed. For this step, we utilize HMC to reduce the correlation between successive sampled states. HMC relies on the gradient of the logarithm of the posterior distribution, which we estimate using a stochastic ensemble method based on an ensemble of directional derivatives. SEM only requires forward model runs and the simulator is then used as a black box and no adjoint code is needed. The developed HNS algorithm is successfully applied for Bayesian calibration and prior model selection of several nonlinear subsurface flow problems. © 2013 Elsevier Inc.
Sarjan, Achmad Fajar Narotama; Niasari, Sintia Windhi
2017-07-01
There are some of geothermal prospects around Java Island. One of them are located in Telomoyo Volcano area, Magelang, Central Java. The existence of hot spring manifestations in Telomoyo Volcano area shows the presence of geothermal system. The upflow zone of this geothermal system was formed in the caldera of Telomoyo Volcano area, while the outflow zone was formed around Candi Umbul. In addition, from the geological map shows a geological structure assumed as a normal fault with southwest-northeast orientation that was caused by the volcanic activity. The aim of this research is to give a brief introduction about subsurface resistivity beneath Telomoyo Volcano area using 1-D magnetotelluric forward model. Thus, we can determine the possibility of data that will obtained during the acquisition process based on the geological model that was made. The apparent resistivity, phase, and period values were obtained from the forward modeling process. The result from this study is a 1-D resistivity section with synthetics curves of each geothermal model. In each model the presence of clay cap characterized by a low resistivity layer. A layer below the clay cap with a medium resistivity value interpreted as the reservoir of this geothermal system. The heat source of this geothermal area is characterized by a low resistivity that is located at depth 4000-5500m. This study is still in progress to acquire the exact values of resistivity from each layer from the field data acquisition in Telomoyo Volcano area, Magelang.
Kempka, Thomas; Nakaten, Benjamin; De Lucia, Marco; Nakaten, Natalie; Otto, Christopher; Pohl, Maik; Tillner, Elena; Kühn, Michael
2016-04-01
Utilization of the geological subsurface for production and storage of hydrocarbons, chemical energy and heat as well as for waste disposal requires the quantification and mitigation of environmental impacts as well as the improvement of georesources utilization in terms of efficiency and sustainability. The development of tools for coupled process simulations is essential to tackle these challenges, since reliable assessments are only feasible by integrative numerical computations. Coupled processes at reservoir to regional scale determine the behaviour of reservoirs, faults and caprocks, generally demanding for complex 3D geological models to be considered besides available monitoring and experimenting data in coupled numerical simulations. We have been developing a flexible numerical simulation framework that provides efficient workflows for integrating the required data and software packages to carry out coupled process simulations considering, e.g., multiphase fluid flow, geomechanics, geochemistry and heat. Simulation results are stored in structured data formats to allow for an integrated 3D visualization and result interpretation as well as data archiving and its provision to collaborators. The main benefits in using the flexible simulation framework are the integration of data geological and grid data from any third party software package as well as data export to generic 3D visualization tools and archiving formats. The coupling of the required process simulators in time and space is feasible, while different spatial dimensions in the coupled simulations can be integrated, e.g., 0D batch with 3D dynamic simulations. User interaction is established via high-level programming languages, while computational efficiency is achieved by using low-level programming languages. We present three case studies on the assessment of geological subsurface utilization based on different process coupling approaches and numerical simulations.
El-Amin, Mohamed
2011-05-15
Injection of CO2 in hydrocarbon reservoir has double benefit. On the one hand, it is a profitable method due to issues related to global warming, and on the other hand it is an effective mechanism to enhance hydrocarbon recovery. Such injection associates complex processes involving, e.g., solute transport of dissolved materials, in addition to local changes in density of the phases. Also, increasing carbon dioxide injection may cause a structural deformation of the medium, so it is important to include such effect into the model. The structural deformation modelling in carbon sequestration is important to evaluate the medium stability to avoid CO2 leakage to the atmosphere. On the other hand, geologic formation of the medium is usually heterogeneous and consists of several layers of different permeability. In this work we conduct numerical simulation of two-phase flow in a heterogeneous porous medium domain with dissolved solute transport as well as structural deformation effects. The solute transport of the dissolved component is described by concentration equation. The structural deformation for geomechanics is derived from a general local differential balance equation with neglecting the local mass balance of solid phase and the inertial force term. The flux continuity condition is used at interfaces between different permeability layers of the heterogeneous medium. We analyze the vertical migration of a CO2 plume injected into a 2D layered reservoir. Analysis of distribution of flow field components such as saturation, pressures, velocities, and CO2 concentration are presented.
Modeling Breast Cancer Intertumor and Intratumor Heterogeneity Using Xenografts.
Bruna, Alejandra; Rueda, Oscar M; Caldas, Carlos
2016-01-01
Breast cancer is a heterogeneous disease that can be stratified in at least 10 different subtypes. We present here a platform for derivation of preclinical models based on patient-derived tumor xenografts (PDTXs) that represent these subgroups. These models preserve the transcriptome, methylome, copy-number, and mutational landscape features of the tumor of origin through different passaging. Furthermore, the intratumoral composition of these models is formed by communities of clones very similar to the ones present in the originating tumor. Finally, we show that short-term cultures of cells from these models (PDTX-derived tumor cells, PDTCs) also preserve the molecular features of the tumor and can be used for high-throughput drug testing of single compounds or combinations, with high reproducibility and clinical predictive power. © 2016 Bruna et al; Published by Cold Spring Harbor Laboratory Press.
Accounting for household heterogeneity in general equilibrium economic growth models
International Nuclear Information System (INIS)
Melnikov, N.B.; O'Neill, B.C.; Dalton, M.G.
2012-01-01
We describe and evaluate a new method of aggregating heterogeneous households that allows for the representation of changing demographic composition in a multi-sector economic growth model. The method is based on a utility and labor supply calibration that takes into account time variations in demographic characteristics of the population. We test the method using the Population-Environment-Technology (PET) model by comparing energy and emissions projections employing the aggregate representation of households to projections representing different household types explicitly. Results show that the difference between the two approaches in terms of total demand for energy and consumption goods is negligible for a wide range of model parameters. Our approach allows the effects of population aging, urbanization, and other forms of compositional change on energy demand and CO 2 emissions to be estimated and compared in a computationally manageable manner using a representative household under assumptions and functional forms that are standard in economic growth models.
Heterogeneous Agents Model with the Worst Out Algorithm
Czech Academy of Sciences Publication Activity Database
Vošvrda, Miloslav; Vácha, Lukáš
I, č. 1 (2007), s. 54-66 ISSN 1802-4696 R&D Projects: GA MŠk(CZ) LC06075; GA ČR(CZ) GA402/06/0990 Grant - others:GA UK(CZ) 454/2004/A-EK/FSV Institutional research plan: CEZ:AV0Z10750506 Keywords : Efficient Markets Hypothesis * Fractal Market Hypothesis * agents' investment horizons * agents' trading strategies * technical trading rules * heterogeneous agent model with stochastic memory * Worst out Algorithm Subject RIV: AH - Economics
Subsurface Science Program Bibliography, 1985--1992
International Nuclear Information System (INIS)
1992-08-01
The Subsurface Science Program sponsors long-term basic research on (1) the fundamental physical, chemical, and biological mechanisms that control the reactivity, mobilization, stability, and transport of chemical mixtures in subsoils and ground water; (2) hydrogeology, including the hydraulic, microbiological, and geochemical properties of the vadose and saturated zones that control contaminant mobility and stability, including predictive modeling of coupled hydraulic-geochemical-microbial processes; and (3) the microbiology of deep sediments and ground water. TWs research, focused as it is on the natural subsurface environments that are most significantly affected by the more than 40 years of waste generation and disposal at DOE sites, is making important contributions to cleanup of DOE sites. Past DOE waste-disposal practices have resulted in subsurface contamination at DOE sites by unique combinations of radioactive materials and organic and inorganic chemicals (including heavy metals), which make site cleanup particularly difficult. The long- term (10- to 30-year) goal of the Subsurface Science Program is to provide a foundation of fundamental knowledge that can be used to reduce environmental risks and to provide a sound scientific basis for cost-effective cleanup strategies. The Subsurface Science Program is organized into nine interdisciplinary subprograms, or areas of basic research emphasis. The subprograms currently cover the areas of Co-Contaminant Chemistry, Colloids/Biocolloids, Multiphase Fluid Flow, Biodegradation/ Microbial Physiology, Deep Microbiology, Coupled Processes, Field-Scale (Natural Heterogeneity and Scale), and Environmental Science Research Center
Yang, C.; Romanak, K.; Hovorka, S.
2009-12-01
Soil gas monitoring is one cost-effective approach to detect CO2 leak at geological sequestration sites. Therefore understanding CO2 gas transport in soil zones is important for detection of CO2 leaks. A field experiment of a small CO2 release was conducted at the Brackenridge Field Laboratory, the University of Texas at Austin. The field site consists of one injection well, two sensor wells and one gas station well (Figure 1). The injection well was completed with a PVC pipe to a depth of 1.1 m below surface. CO2 sensors were deployed in sensor wells about 42 cm from the injection well at depths of 1.1 m having no subsurface PVC pipes but only a PVC protector cap at the surface. The gas monitoring station about 72 cm away from the injection well contains 3 copper tubes each set at different depths in sand pack isolated with bentonite clay. The CO2 release experiment started on March 4, 2009. A total 36.76 liters of CO2 were injected at 1 m depth at a rate of 100 ml/minute for 6 hours. Subsurface CO2 gas concentrations (before, during, and after the injection) were continuously monitored in sensor wells. Real-time CO2 concentrations were monitored at the gas station using an SRI 8610 gas chromatograph (GC) fitted with flame ionization detector (FID) and a thermal conductivity detector (TCD). A numerical model was constructed to simulate CO2 release experiments. The model takes into account CO2 diffusion and dissolution in pore water. Air in the pore space is assumed stagnant. Model domain consists of four soil layers and one atmospheric layer. The groundwater table is about 2.4 meters below ground surface. The model was calibrated with respect to diffusion coefficient (transport parameter) and the injection rate (mass parameter). Model results fit well with CO2 measurements at the sensor wells and the gas station. However, the calibrated injection rate underestimates measured injection rate.
Re-evaluation of a subsurface injection experiment for testing flow and transport models
Energy Technology Data Exchange (ETDEWEB)
Fayer, M.J.; Lewis, R.E.; Engelman, R.E.; Pearson, A.L.; Murray, C.J.; Smoot, J.L. Lu, A.H. [Pacific Northwest Lab., Richland, WA (United States); Randall, P.R. [Three Rivers Scientific, Richland, WA (United States); Wegener, W.H. [Hoquiam High School, Hoquiam, WA (United States)
1995-12-01
The current preferred method for disposal of low-level radioactive waste (LLW) at the Hanford Site is to vitrify the wastes so they can be stored in a near-surface, shallow-land burial facility (Shord 1995). Pacific Northwest Laboratory (PNL) managed the PNL Vitrification Technology Development (PVTD) Project to assist Westinghouse Hanford Company (WHC) in designing and assessing the performance of a disposal facility for the vitrified LLW. Vadose zone flow and transport models are recognized as necessary tools for baseline risk assessments of stored waste forms. The objective of the Controlled Field Testing task of the PVTD Project is to perform and analyze field experiments to demonstrate the appropriateness of conceptual models for the performance assessment. The most convincing way to demonstrate appropriateness is to show that the model can reproduce the movement of water and contaminants in the field. Before expensive new experiments are initiated, an injection experiment conducted at the Hanford Site in 1980 (designated the ``Sisson and the Lu experiment``) should be completely analyzed and understood. Briefly, in that test, a solution containing multiple tracers was injected at a single point into the subsurface sediments. The resulting spread of the water and tracers was monitored in wells surrounding the injection point. Given the advances in knowledge, computational capabilities, and models over the last 15 years, it is important to re-analyze the data before proceeding to other experiments and history-matching exercises.
Audebert, M; Oxarango, L; Duquennoi, C; Touze-Foltz, N; Forquet, N; Clément, R
2016-09-01
Leachate recirculation is a key process in the operation of municipal solid waste landfills as bioreactors. To ensure optimal water content distribution, bioreactor operators need tools to design leachate injection systems. Prediction of leachate flow by subsurface flow modelling could provide useful information for the design of such systems. However, hydrodynamic models require additional data to constrain them and to assess hydrodynamic parameters. Electrical resistivity tomography (ERT) is a suitable method to study leachate infiltration at the landfill scale. It can provide spatially distributed information which is useful for constraining hydrodynamic models. However, this geophysical method does not allow ERT users to directly measure water content in waste. The MICS (multiple inversions and clustering strategy) methodology was proposed to delineate the infiltration area precisely during time-lapse ERT survey in order to avoid the use of empirical petrophysical relationships, which are not adapted to a heterogeneous medium such as waste. The infiltration shapes and hydrodynamic information extracted with MICS were used to constrain hydrodynamic models in assessing parameters. The constraint methodology developed in this paper was tested on two hydrodynamic models: an equilibrium model where, flow within the waste medium is estimated using a single continuum approach and a non-equilibrium model where flow is estimated using a dual continuum approach. The latter represents leachate flows into fractures. Finally, this methodology provides insight to identify the advantages and limitations of hydrodynamic models. Furthermore, we suggest an explanation for the large volume detected by MICS when a small volume of leachate is injected. Copyright © 2016 Elsevier Ltd. All rights reserved.
Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts
Energy Technology Data Exchange (ETDEWEB)
Grass, Michael Edward [Univ. of California, Berkeley, CA (United States)
2008-09-01
Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H_{2} and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.
Energy Technology Data Exchange (ETDEWEB)
Lovley, Derek R.
2012-10-31
This project successfully accomplished its goal of coupling genome-scale metabolic models with hydrological and geochemical models to predict the activity of subsurface microorganisms during uranium bioremediation. Furthermore, it was demonstrated how this modeling approach can be used to develop new strategies to optimize bioremediation. The approach of coupling genome-scale metabolic models with reactive transport modeling is now well enough established that it has been adopted by other DOE investigators studying uranium bioremediation. Furthermore, the basic principles developed during our studies will be applicable to much broader investigations of microbial activities, not only for other types of bioremediation, but microbial metabolism in diversity of environments. This approach has the potential to make an important contribution to predicting the impact of environmental perturbations on the cycling of carbon and other biogeochemical cycles.
Modelling long-distance seed dispersal in heterogeneous landscapes.
Energy Technology Data Exchange (ETDEWEB)
Levey, Douglas, J.; Tewlsbury, Joshua, J.; Bolker, Benjamin, M.
2008-01-01
1. Long-distance seed dispersal is difficult to measure, yet key to understanding plant population dynamics and community composition. 2. We used a spatially explicit model to predict the distribution of seeds dispersed long distances by birds into habitat patches of different shapes. All patches were the same type of habitat and size, but varied in shape. They occurred in eight experimental landscapes, each with five patches of four different shapes, 150 m apart in a matrix of mature forest. The model was parameterized with smallscale movement data collected from field observations of birds. In a previous study we validated the model by testing its predictions against observed patterns of seed dispersal in real landscapes with the same types and spatial configuration of patches as in the model. 3. Here we apply the model more broadly, examining how patch shape influences the probability of seed deposition by birds into patches, how dispersal kernels (distributions of dispersal distances) vary with patch shape and starting location, and how movement of seeds between patches is affected by patch shape. 4. The model predicts that patches with corridors or other narrow extensions receive higher numbers of seeds than patches without corridors or extensions. This pattern is explained by edgefollowing behaviour of birds. Dispersal distances are generally shorter in heterogeneous landscapes (containing patchy habitat) than in homogeneous landscapes, suggesting that patches divert the movement of seed dispersers, ‘holding’ them long enough to increase the probability of seed defecation in the patches. Dispersal kernels for seeds in homogeneous landscapes were smooth, whereas those in heterogenous landscapes were irregular. In both cases, long-distance (> 150 m) dispersal was surprisingly common, usually comprising approximately 50% of all dispersal events. 5. Synthesis . Landscape heterogeneity has a large influence on patterns of long-distance seed dispersal. Our
Wakai, A.; Senna, S.; Jin, K.; Cho, I.; Matsuyama, H.; Fujiwara, H.
2017-12-01
To estimate damage caused by strong ground motions from a large earthquake, it is important to accurately evaluate broadband ground-motion characteristics in wide area. For realizing that, it is one of the important issues to model detailed subsurface structure from top surface of seismic bedrock to ground surface.Here, we focus on Kanto area, including Tokyo, where there are thicker sedimentary layers. We, first, have ever collected deep bore-hole data, soil physical properties obtained by some geophysical explorations, geological information and existing models for deep ground from top surface of seismic bedrock to that of engineering bedrock, and have collected a great number of bore-hole data and surficial geological ones for shallow ground from top surface of engineering bedrock to ground surface. Using them, we modeled initial geological subsurface structure for each of deep ground and shallow one. By connecting them appropriately, we constructed initial geological subsurface structure models from top surface of seismic bedrock to ground surface.In this study, we first collected a lot of records obtained by dense microtremor observations and earthquake ones in the whole Kanto area. About microtremor observations, we conducted measurements from large array with the size of hundreds of meters to miniature array with the size of 60 centimeters to cover both of deep ground and shallow one. And then, using ground motion characteristics such as disperse curves and H/V(R/V) spectral ratios obtained from these records, the initial geological subsurface structure models were improved in terms of velocity structure from top surface of seismic bedrock to ground surface in the area.We will report outlines on microtremor array observations, analysis methods and improved subsurface structure models.
A mobile-mobile transport model for simulating reactive transport in connected heterogeneous fields
Lu, Chunhui; Wang, Zhiyuan; Zhao, Yue; Rathore, Saubhagya Singh; Huo, Jinge; Tang, Yuening; Liu, Ming; Gong, Rulan; Cirpka, Olaf A.; Luo, Jian
2018-05-01
Mobile-immobile transport models can be effective in reproducing heavily tailed breakthrough curves of concentration. However, such models may not adequately describe transport along multiple flow paths with intermediate velocity contrasts in connected fields. We propose using the mobile-mobile model for simulating subsurface flow and associated mixing-controlled reactive transport in connected fields. This model includes two local concentrations, one in the fast- and the other in the slow-flow domain, which predict both the concentration mean and variance. The normalized total concentration variance within the flux is found to be a non-monotonic function of the discharge ratio with a maximum concentration variance at intermediate values of the discharge ratio. We test the mobile-mobile model for mixing-controlled reactive transport with an instantaneous, irreversible bimolecular reaction in structured and connected random heterogeneous domains, and compare the performance of the mobile-mobile to the mobile-immobile model. The results indicate that the mobile-mobile model generally predicts the concentration breakthrough curves (BTCs) of the reactive compound better. Particularly, for cases of an elliptical inclusion with intermediate hydraulic-conductivity contrasts, where the travel-time distribution shows bimodal behavior, the prediction of both the BTCs and maximum product concentration is significantly improved. Our results exemplify that the conceptual model of two mobile domains with diffusive mass transfer in between is in general good for predicting mixing-controlled reactive transport, and particularly so in cases where the transfer in the low-conductivity zones is by slow advection rather than diffusion.
Recovery Act: Web-based CO{sub 2} Subsurface Modeling
Energy Technology Data Exchange (ETDEWEB)
Paolini, Christopher; Castillo, Jose
2012-11-30
The Web-based CO{sub 2} Subsurface Modeling project focused primarily on extending an existing text-only, command-line driven, isothermal and isobaric, geochemical reaction-transport simulation code, developed and donated by Sienna Geodynamics, into an easier-to-use Web-based application for simulating long-term storage of CO{sub 2} in geologic reservoirs. The Web-based interface developed through this project, publically accessible via URL http://symc.sdsu.edu/, enables rapid prototyping of CO{sub 2} injection scenarios and allows students without advanced knowledge of geochemistry to setup a typical sequestration scenario, invoke a simulation, analyze results, and then vary one or more problem parameters and quickly re-run a simulation to answer what-if questions. symc.sdsu.edu has 2x12 core AMD Opteron™ 6174 2.20GHz processors and 16GB RAM. The Web-based application was used to develop a new computational science course at San Diego State University, COMP 670: Numerical Simulation of CO{sub 2} Sequestration, which was taught during the fall semester of 2012. The purpose of the class was to introduce graduate students to Carbon Capture, Use and Storage (CCUS) through numerical modeling and simulation, and to teach students how to interpret simulation results to make predictions about long-term CO{sub 2} storage capacity in deep brine reservoirs. In addition to the training and education component of the project, significant software development efforts took place. Two computational science doctoral and one geological science masters student, under the direction of the PIs, extended the original code developed by Sienna Geodynamics, named Sym.8. New capabilities were added to Sym.8 to simulate non-isothermal and non-isobaric flows of charged aqueous solutes in porous media, in addition to incorporating HPC support into the code for execution on many-core XSEDE clusters. A successful outcome of this project was the funding and training of three new computational
Heterogeneity in Pure Microbial Systems: Experimental Measurements and Modeling.
González-Cabaleiro, Rebeca; Mitchell, Anca M; Smith, Wendy; Wipat, Anil; Ofiţeru, Irina D
2017-01-01
Cellular heterogeneity influences bioprocess performance in ways that until date are not completely elucidated. In order to account for this phenomenon in the design and operation of bioprocesses, reliable analytical and mathematical descriptions are required. We present an overview of the single cell analysis, and the mathematical modeling frameworks that have potential to be used in bioprocess control and optimization, in particular for microbial processes. In order to be suitable for bioprocess monitoring, experimental methods need to be high throughput and to require relatively short processing time. One such method used successfully under dynamic conditions is flow cytometry. Population balance and individual based models are suitable modeling options, the latter one having in particular a good potential to integrate the various data collected through experimentation. This will be highly beneficial for appropriate process design and scale up as a more rigorous approach may prevent a priori unwanted performance losses. It will also help progressing synthetic biology applications to industrial scale.
Rosolem, R.; Rahman, M.; Kollet, S. J.; Wagener, T.
2017-12-01
Understanding the impacts of land cover and climate changes on terrestrial hydrometeorology is important across a range of spatial and temporal scales. Earth System Models (ESMs) provide a robust platform for evaluating these impacts. However, current ESMs lack the representation of key hydrological processes (e.g., preferential water flow, and direct interactions with aquifers) in general. The typical "free drainage" conceptualization of land models can misrepresent the magnitude of those interactions, consequently affecting the exchange of energy and water at the surface as well as estimates of groundwater recharge. Recent studies show the benefits of explicitly simulating the interactions between subsurface and surface processes in similar models. However, such parameterizations are often computationally demanding resulting in limited application for large/global-scale studies. Here, we take a different approach in developing a novel parameterization for groundwater dynamics. Instead of directly adding another complex process to an established land model, we examine a set of comprehensive experimental scenarios using a very robust and establish three-dimensional hydrological model to develop a simpler parameterization that represents the aquifer to land surface interactions. The main goal of our developed parameterization is to simultaneously maximize the computational gain (i.e., "efficiency") while minimizing simulation errors in comparison to the full 3D model (i.e., "robustness") to allow for easy implementation in ESMs globally. Our study focuses primarily on understanding both the dynamics for groundwater recharge and discharge, respectively. Preliminary results show that our proposed approach significantly reduced the computational demand while model deviations from the full 3D model are considered to be small for these processes.
Heterogeneous traffic flow modelling using second-order macroscopic continuum model
Mohan, Ranju; Ramadurai, Gitakrishnan
2017-01-01
Modelling heterogeneous traffic flow lacking in lane discipline is one of the emerging research areas in the past few years. The two main challenges in modelling are: capturing the effect of varying size of vehicles, and the lack in lane discipline, both of which together lead to the 'gap filling' behaviour of vehicles. The same section length of the road can be occupied by different types of vehicles at the same time, and the conventional measure of traffic concentration, density (vehicles per lane per unit length), is not a good measure for heterogeneous traffic modelling. First aim of this paper is to have a parsimonious model of heterogeneous traffic that can capture the unique phenomena of gap filling. Second aim is to emphasize the suitability of higher-order models for modelling heterogeneous traffic. Third, the paper aims to suggest area occupancy as concentration measure of heterogeneous traffic lacking in lane discipline. The above mentioned two main challenges of heterogeneous traffic flow are addressed by extending an existing second-order continuum model of traffic flow, using area occupancy for traffic concentration instead of density. The extended model is calibrated and validated with field data from an arterial road in Chennai city, and the results are compared with those from few existing generalized multi-class models.
Alslaibi, Tamer M; Abunada, Ziyad; Abu Amr, Salem S; Abustan, Ismail
2017-09-22
Landfills are one of the main point sources of groundwater pollution. This research mainly aims to assess the risk of nitrate [Formula: see text] transport from the unlined landfill to subsurface layers and groundwater using experimental results and the SESOIL model. Samples from 12 groundwater wells downstream of the landfill were collected and analyzed in 2008, 21 years after the landfill construction. The average [Formula: see text] concentration in the wells was 54 mg/L, slightly higher than the World Health Organization ([Formula: see text] 50 mg/L) standards. SESOIL model was used to predict the [Formula: see text] concentration at the bottom of the unsaturated zone. Results indicated that the current mean [Formula: see text] concentration at the bottom of the unsaturated zone is 75 mg/L. the model predicted that the level of NO 3 will increased up to 325 mg/L within 30 years. Accordingly, the [Formula: see text] concentration in groundwater wells near the landfill area is expected to gradually increase with time. Although the current risk associated with the [Formula: see text] level might not be harm to adults, however, it might pose severe risks to both adults and infants in the near future due to [Formula: see text] leaching. Urgent mitigation measures such as ﬁnal cell cover (cap), lining system and vertical expansion should be considered at the landfill to protect the public health in the area.
Senthilkumar, M.; Elango, L.
2011-06-01
Groundwater modelling is widely used as a management tool to understand the behaviour of aquifer systems under different hydrological stresses, whether induced naturally or by humans. The objective of this study was to assess the effect of a subsurface barrier on groundwater flow in the Palar River basin, Tamil Nadu, southern India. Groundwater is supplied to a nearby nuclear power plant and groundwater also supplies irrigation, industrial and domestic needs. In order to meet the increasing demand for groundwater for the nuclear power station, a subsurface barrier/dam was proposed across Palar River to increase the groundwater heads and to minimise the subsurface discharge of groundwater into the sea. The groundwater model used in this study predicted that groundwater levels would increase by about 0.1-0.3 m extending out a distance of about 1.5-2 km from the upstream side of the barrier, while on the downstream side, the groundwater head would lower by about 0.1-0.2 m. The model also predicted that with the subsurface barrier in place the additional groundwater requirement of approximately 13,600 m3/day (3 million gallons (UK)/day) can be met with minimum decline in regional groundwater head.
Pore-scale modelling of the combined effect of physical and chemical heterogeneity on reactive flows
Oliveira, T. D. S.; Bijeljic, B.; Blunt, M. J.
2016-12-01
We perform direct numerical simulations to study the combined impact of physical and chemical heterogeneity in subsurface rock to provide insights into the source of the discrepancy observed between mineral dissolution rates observed in laboratory experiments and in field-scale natural systems. The ultimate goal of this work is to use pore-scale simulation to compute upscaled properties - such as effective reaction rate - for use in larger-scale models.We present a methodology to simulate multispecies reactive flow through pore-space images obtained from micro-tomography. Using the sequential non-iterative approach, we couple the simulation of the transport equations with an advanced geochemical solver designed specifically for applications that require sequential equilibrium calculations. This geochemical solver uses novel numerical methods for the solution of multiphase chemical equilibrium and kinetics problems in a well-stirred batch model. Our model assumes that reactions can be classified into fast reactions, which are considered to be in equilibrium, and slow reactions, considered to be controlled by kinetics. This assumption of partial equilibrium simplifies the problem by replacing differential equations with algebraic ones. We allow for chemical heterogeneity of the solid phase by associating each voxel to a different mineral and reaction rate. A steady-state flow problem is solved in the pore space using a finite volume method to calculate the velocity field. Then we solve an advection-diffusion equation for the concentration and, modelling each liquid voxel as a well-mixed batch with a solid wall where applicable, we calculate reaction using the aforementioned geochemical solver. Both fluid-fluid and fluid-solid reactions are considered, geometry changes due to dissolution and precipitation are taken into account, and the velocity field is updated. We present the validation tests for acidic brine injected into rock for a range of transport (P
Specifying initial stress for dynamic heterogeneous earthquake source models
Andrews, D.J.; Barall, M.
2011-01-01
Dynamic rupture calculations using heterogeneous stress drop that is random and self-similar with a power-law spatial spectrum have great promise of producing realistic ground-motion predictions. We present procedures to specify initial stress for random events with a target rupture length and target magnitude. The stress function is modified in the depth dimension to account for the brittle-ductile transition at the base of the seismogenic zone. Self-similar fluctuations in stress drop are tied in this work to the long-wavelength stress variation that determines rupture length. Heterogeneous stress is related to friction levels in order to relate the model to physical concepts. In a variant of the model, there are high-stress asperities with low background stress. This procedure has a number of advantages: (1) rupture stops naturally, not at artificial barriers; (2) the amplitude of short-wavelength fluctuations of stress drop is not arbitrary: the spectrum is fixed to the long-wavelength fluctuation that determines rupture length; and (3) large stress drop can be confined to asperities occupying a small fraction of the total rupture area, producing slip distributions with enhanced peaks.
Modeling of GPR Clutter Caused by Soil Heterogeneity
Directory of Open Access Journals (Sweden)
Kazunori Takahashi
2012-01-01
Full Text Available In small-scale measurements, ground-penetrating radar (GPR often uses a higher frequency to detect a small object or structural changes in the ground. GPR becomes more sensitive to the natural heterogeneity of the soil when a higher frequency is used. Soil heterogeneity scatters electromagnetic waves, and the scattered waves are in part observed as unwanted reflections that are often referred to as clutter. Data containing a great amount of clutter are difficult to analyze and interpret because clutter disturbs reflections from objects of interest. Therefore, modeling GPR clutter is useful to assess the effectiveness of GPR measurements. In this paper, the development of such a technique is discussed. This modeling technique requires the permittivity distribution of soil (or its geostatistical properties and gives a nominal value of clutter power. The paper demonstrates the technique with the comparison to the data from a GPR time-lapse measurement. The proposed technique is discussed in regard to its applicability and limitations based on the results.
Reactive transport modeling of subsurface arsenic removal systems in rural Bangladesh.
Rahman, M M; Bakker, M; Patty, C H L; Hassan, Z; Röling, W F M; Ahmed, K M; van Breukelen, B M
2015-12-15
Subsurface Arsenic Removal (SAR) is a technique for in-situ removal of arsenic from groundwater. Extracted groundwater is aerated and re-injected into an anoxic aquifer, where the oxygen in the injected water reacts with ferrous iron in the aquifer to form hydrous ferric oxide (HFO). Subsequent extraction of groundwater contains temporarily lower As concentrations, because As sorbs onto the HFO. Injection, storage, and extraction together is called a cycle. A reactive transport model (RTM) was developed in PHREEQC to determine the hydrogeochemical processes responsible for As (im)mobilization during experimental SAR operation performed in Bangladesh. Oxidation of Fe(II) and As(III) were modeled using kinetic-rate expressions. Cation exchange, precipitation of HFO, and surface complexation, were modeled as equilibrium processes. A best set of surface complexation reactions and corresponding equilibrium constants was adopted from previous studies to simulate all 20 cycles of a SAR experiment. The model gives a reasonable match with observed concentrations of different elements in the extracted water (e.g., the r(2) value of As was 0.59 or higher). As concentrations in the extracted water are governed by four major processes. First, As concentration decreases in response to the elevated pH of injection water and likewise increases when native neutral pH groundwater flows in. Second, the sorption capacity for As increases due to the gradual buildup of HFO. Third, As sorption is enhanced by preferential removal of As(V). Fourth, competitive sorption of Si limits the capacity of freshly precipitated HFO for As sorption. Transferability of the developed reactive transport model was demonstrated through successful application of the model, without further calibration, to two additional SAR sites in Bangladesh. This gives confidence that the model could be useful to assess potential SAR performance at locations in Bangladesh based on local hydrogeochemical conditions
Simulation of Subsurface Multiphase Contaminant Extraction Using a Bioslurping Well Model
Energy Technology Data Exchange (ETDEWEB)
Matos de Souza, Michelle; Oostrom, Mart; White, Mark D.; Cardoso da Silva, Gerson; Barbosa, Maria Claudia
2016-07-12
Subsurface simulation of multiphase extraction from wells is notoriously difficult. Explicit representation of well geometry requires small grid resolution, potentially leading to large computational demands. To reduce the problem dimensionality, multiphase extraction is mostly modeled using vertically-averaged approaches. In this paper, a multiphase well model approach is presented as an alternative to simplify the application. The well model, a multiphase extension of the classic Peaceman model, has been implemented in the STOMP simulator. The numerical solution approach accounts for local conditions and gradients in the exchange of fluids between the well and the aquifer. Advantages of this well model implementation include the option to simulate the effects of well characteristics and operation. Simulations were conducted investigating the effects of extraction location, applied vacuum pressure, and a number of hydraulic properties. The obtained results were all consistent and logical. A major outcome of the test simulations is that, in contrast with common recommendations to extract from either the gas-NAPL or the NAPL-aqueous phase interface, the optimum extraction location should be in between these two levels. The new model implementation was also used to simulate extraction at a field site in Brazil. The simulation shows a good match with the field data, suggesting that the new STOMP well module may correctly represent oil removal. The field simulations depend on the quality of the site conceptual model, including the porous media and contaminant properties and the boundary and extraction conditions adopted. The new module may potentially be used to design field applications and analyze extraction data.
Bernardes, Paulo; Pereira, Bruno; Alves, Mafalda; Fontes, Luís; Sousa, Andreia; Martins, Manuela; Magalhães, Fernanda; Pimenta, Mário
2017-04-01
Braga is one of the oldest cities of the Iberian NW and as of so, the research team's studying the city's historical core for the past 40 years is often confronted with the unpredictability factor laying beneath an urban site with such a long construction history. In fact, Braga keeps redesigning its urban structure over itself on for the past 2000 years, leaving us with a research object filled with an impressive set of construction footprints from the various planning decisions that were taken in the city along its historical path. Aiming for a predicting understanding of the subsoil, we have used near surface geophysics as an effort of minimizing the areas of intervention for traditional archaeological survey techniques. The Seminário de Santiago integrated geophysical survey is an example of the difficulties of interpreting geophysical models in very complex subsurface scenarios. This geophysical survey was planned in order to aid the requalification project being designed for this set of historical buildings, that are estimated to date back to the 16h century, and that were built over one of the main urban arteries of both roman and medieval layers of Braga. We have used both GPR as well as ERT methods for the geophysical survey, but for the purpose of this article, we will focus in the use of the ERT alone. For the interpretation of the geophysical models we've cross-referenced the dense knowledge existing over the building's construction phases with the complex geophysical data collected, using mathematical processing and volume-based visualization techniques, resorting to the use of Res2Inv©, Paraview© and Voxler® software's. At the same time we tried to pinpoint the noise caused by the past 30 year's infrastructural interventions regarding the replacement of the building's water and sanitation systems and for which we had no design plants, regardless of its recent occurring. The deep impact of this replacement actions revealed by the archaeological
Huang, M.; Bisht, G.; Zhou, T.; Chen, X.; Dai, H.; Hammond, G. E.; Riley, W. J.; Downs, J.; Liu, Y.; Zachara, J. M.
2016-12-01
A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively-parallel multi-physics reactive tranport model (PFLOTRAN). The coupled model (CLM-PFLOTRAN) is applied to a 400m×400m study domain instrumented with groundwater monitoring wells in the Hanford 300 Area along the Columbia River. CLM-PFLOTRAN simulations are performed at three different spatial resolutions over the period 2011-2015 to evaluate the impact of spatial resolution on simulated variables. To demonstrate the difference in model simulations with and without lateral subsurface flow, a vertical-only CLM-PFLOTRAN simulation is also conducted for comparison. Results show that the coupled model is skillful in simulating stream-aquifer interactions, and the land-surface energy partitioning can be strongly modulated by groundwater-river water interactions in high water years due to increased soil moisture availability caused by elevated groundwater table. In addition, spatial resolution does not seem to impact the land surface energy flux simulations, although it is a key factor for accurately estimating the mass exchange rates at the boundaries and associated biogeochemical reactions in the aquifer. The coupled model developed in this study establishes a solid foundation for understanding co-evolution of hydrology and biogeochemistry along the river corridors under historical and future hydro-climate changes.
Elsheikh, Ahmed H.
2014-02-01
An efficient Bayesian calibration method based on the nested sampling (NS) algorithm and non-intrusive polynomial chaos method is presented. Nested sampling is a Bayesian sampling algorithm that builds a discrete representation of the posterior distributions by iteratively re-focusing a set of samples to high likelihood regions. NS allows representing the posterior probability density function (PDF) with a smaller number of samples and reduces the curse of dimensionality effects. The main difficulty of the NS algorithm is in the constrained sampling step which is commonly performed using a random walk Markov Chain Monte-Carlo (MCMC) algorithm. In this work, we perform a two-stage sampling using a polynomial chaos response surface to filter out rejected samples in the Markov Chain Monte-Carlo method. The combined use of nested sampling and the two-stage MCMC based on approximate response surfaces provides significant computational gains in terms of the number of simulation runs. The proposed algorithm is applied for calibration and model selection of subsurface flow models. © 2013.
Surface complexation models for uranium adsorption in the sub-surface environment
International Nuclear Information System (INIS)
Payne, T.E.
2007-01-01
Adsorption experiments with soil component minerals under a range of conditions are being used to develop models of uranium(VI) uptake in the sub-surface environment. The results show that adsorption of U on iron oxides and clay minerals is influenced by chemical factors including the pH, partial pressure of CO 2 , and the presence of ligands such as phosphate. Surface complexation models (SCMs) can be used to simulate U adsorption on these minerals. The SCMs are based on plausible mechanistic assumptions and describe the experimental data more adequately than Kd values or sorption isotherms. It is conceptually possible to simulate U sorption data on complex natural samples by combining SCMs for individual component minerals. This approach was used to develop a SCM for U adsorption to mineral assemblages from Koongarra (Australia), and produced a reasonable description of U uptake. In order to assess the applicability of experimental data to the field situation, in-situ measurements of U distributions between solid and liquid phases were undertaken at the Koongarra U deposit. This field partitioning data showed a satisfactory agreement with laboratory sorption data obtained under comparable conditions. (author)
Modeling and Analysis of New Products Diffusion on Heterogeneous Networks
Directory of Open Access Journals (Sweden)
Shuping Li
2014-01-01
Full Text Available We present a heterogeneous networks model with the awareness stage and the decision-making stage to explain the process of new products diffusion. If mass media is neglected in the decision-making stage, there is a threshold whether the innovation diffusion is successful or not, or else it is proved that the network model has at least one positive equilibrium. For networks with the power-law degree distribution, numerical simulations confirm analytical results, and also at the same time, by numerical analysis of the influence of the network structure and persuasive advertisements on the density of adopters, we give two different products propagation strategies for two classes of nodes in scale-free networks.
Stylized facts from a threshold-based heterogeneous agent model
Cross, R.; Grinfeld, M.; Lamba, H.; Seaman, T.
2007-05-01
A class of heterogeneous agent models is investigated where investors switch trading position whenever their motivation to do so exceeds some critical threshold. These motivations can be psychological in nature or reflect behaviour suggested by the efficient market hypothesis (EMH). By introducing different propensities into a baseline model that displays EMH behaviour, one can attempt to isolate their effects upon the market dynamics. The simulation results indicate that the introduction of a herding propensity results in excess kurtosis and power-law decay consistent with those observed in actual return distributions, but not in significant long-term volatility correlations. Possible alternatives for introducing such long-term volatility correlations are then identified and discussed.
2006-06-01
The New Hampshire Department of Transportation initiated this research to develop a geographical information system (GIS) that : visualizes subsurface conditions three dimensionally by pulling together geotechnical data containing spatial references....
Deep Ground Penetrating Radar (GPR) WIPL-D Models of Buried Sub-Surface Radiators
National Research Council Canada - National Science Library
Norgard, John D; Wicks, Michael C; Musselman, Randy L
2005-01-01
.... A new Ground Penetrating Radar (GPR) concept is proposed in this paper to use subsurface radiators, delivered as earth penetrating non-explosive, electronic e-bombs, as the source of strong radiated transmissions for GPR experiments...
CSIR Research Space (South Africa)
Van Der Merwe, CJ
1993-09-01
Full Text Available The report describes the findings of the research project on subsurface drainage. The need for drainage was quantified by evaluating HVS tests on wet pavements. Geotextiles were investigated and various tests performed. Soil/geotextile compatibility...
Directory of Open Access Journals (Sweden)
A. Stanley Raj
2015-01-01
Full Text Available Soft computing based geoelectrical data inversion differs from conventional computing in fixing the uncertainty problems. It is tractable, robust, efficient, and inexpensive. In this paper, fuzzy logic clustering methods are used in the inversion of geoelectrical resistivity data. In order to characterize the subsurface features of the earth one should rely on the true field oriented data validation. This paper supports the field data obtained from the published results and also plays a crucial role in making an interdisciplinary approach to solve complex problems. Three clustering algorithms of fuzzy logic, namely, fuzzy C-means clustering, fuzzy K-means clustering, and fuzzy subtractive clustering, were analyzed with the help of fuzzy inference system (FIS training on synthetic data. Here in this approach, graphical user interface (GUI was developed with the integration of three algorithms and the input data (AB/2 and apparent resistivity, while importing will process each algorithm and interpret the layer model parameters (true resistivity and depth. A complete overview on the three above said algorithms is presented in the text. It is understood from the results that fuzzy logic subtractive clustering algorithm gives more reliable results and shows efficacy of soft computing tools in the inversion of geoelectrical resistivity data.
An optimization model to design and manage subsurface drip irrigation system for alfalfa
Kandelous, M.; Kamai, T.; Vrugt, J. A.; Simunek, J.; Hanson, B.; Hopmans, J. W.
2010-12-01
Subsurface drip irrigation (SDI) is one of the most efficient and cost-effective methods for watering alfalfa plants. Lateral installation depth and distance, emitter discharge, and irrigation time and frequency of SDI, in addition to soil and climatic conditions affect alfalfa’s root water uptake and yield. Here we use a multi-objective optimization approach to find optimal SDI strategies. Our approach uses the AMALGAM evolutionary search method, in combination with the HYDRUS-2D unsaturated flow model to maximize water uptake by alfalfa’s plant roots, and minimize loss of irrigation and drainage water to the atmosphere or groundwater. We use a variety of different objective functions to analyze SDI. These criteria include the lateral installation depth and distance, the lateral discharge, irrigation duration, and irrigation frequency. Our framework includes explicit recognition of the soil moisture status during the simulation period to make sure that the top soil is dry for harvesting during the growing season. Initial results show a wide spectrum of optimized SDI strategies for different root distributions, soil textures and climate conditions. The developed tool should be useful in helping farmers optimize their irrigation strategy and design.
Modeling antimicrobial tolerance and treatment of heterogeneous biofilms.
Zhao, Jia; Seeluangsawat, Paisa; Wang, Qi
2016-12-01
A multiphasic, hydrodynamic model for spatially heterogeneous biofilms based on the phase field formulation is developed and applied to analyze antimicrobial tolerance of biofilms by acknowledging the existence of persistent and susceptible cells in the total population of bacteria. The model implements a new conversion rate between persistent and susceptible cells and its homogeneous dynamics is bench-marked against a known experiment quantitatively. It is then discretized and solved on graphic processing units (GPUs) in 3-D space and time. With the model, biofilm development and antimicrobial treatment of biofilms in a flow cell are investigated numerically. Model predictions agree qualitatively well with available experimental observations. Specifically, numerical results demonstrate that: (i) in a flow cell, nutrient, diffused in solvent and transported by hydrodynamics, has an apparent impact on persister formation, thereby antimicrobial persistence of biofilms; (ii) dosing antimicrobial agents inside biofilms is more effective than dosing through diffusion in solvent; (iii) periodic dosing is less effective in antimicrobial treatment of biofilms in a nutrient deficient environment than in a nutrient sufficient environment. This model provides us with a simulation tool to analyze mechanisms of biofilm tolerance to antimicrobial agents and to derive potentially optimal dosing strategies for biofilm control and treatment. Copyright © 2016 Elsevier Inc. All rights reserved.
Modeling saltwater intrusion in highly heterogeneous coastal aquifers
Safi, Amir; El-Fadel, Mutasem; Doummar, Joanna; Abou Najm, Majdi; Alameddine, Ibrahim
2016-04-01
In this study, a 3D variable-density flow and solute transport model SEAWAT was used to examine the impact of macroscopic variation in a soil matrix on widening or narrowing the thickness of the saltwater-freshwater mixing zone. Located along the Eastern Mediterranean (Beirut), the pilot aquifer consists of karstified limestone of Cretaceous age overlain by Upper Tertiary and Quaternary unconsolidated deposits. The model used the advanced pilot-points parameterization coupled with PEST to characterize spatial heterogeneity. Historically simulated water levels were relied upon to reduce potential numerical instabilities induced by insensitive parameters in transient calibration. The latter demonstrated a high degree of heterogeneity in the middle parts of the aquifer and along western coastlines with specification of a high hydraulic conductivity and low storativity in fault networks. The response of the aquifer to seasonal stresses such as climate cycles, pumping rates and recharge rates was manifested as high fluctuations in potentiometric surface due to potential fast flow pathways along faults. The final distribution of saltwater intrusion supports two mechanisms 1) lateral encroachment of recent seawater into the western zone of the aquifer which is of most concern due to high horizontal hydraulic conductivity in the wave direction and 2) upconing in the northwest and southwest of the aquifer due to large vertical hydraulic conductivities that tend to exacerbate the vertical movement of salinity. Acknowledgments This study is part of a program on climate change and seawater intrusion along the Eastern Mediterranean funded by the International Development Research Center (IDRC) of Canada at the American University of Beirut (AUB). Special thanks are extended to Dr. Charlotte Macalister at IDRC for her support and feedback in implementing this program.
National Research Council Canada - National Science Library
Downer, Charles
2003-01-01
This document is a primer for use of the Watershed Modeling System (WMS) interface with the physically based, distributed-parameter hydrologic model Gridded Surface Subsurface Hydrologic Analysis (GSSHA...
DEFF Research Database (Denmark)
Fuchs, Sven; Balling, Niels
2016-01-01
The subsurface temperature field and the geothermal conditions in sedimentary basins are frequently examined by using numerical thermal models. For those models, detailed knowledge of rock thermal properties are paramount for a reliable parameterization of layer properties and boundary conditions...
Development of a Cloud Resolving Model for Heterogeneous Supercomputers
Sreepathi, S.; Norman, M. R.; Pal, A.; Hannah, W.; Ponder, C.
2017-12-01
A cloud resolving climate model is needed to reduce major systematic errors in climate simulations due to structural uncertainty in numerical treatments of convection - such as convective storm systems. This research describes the porting effort to enable SAM (System for Atmosphere Modeling) cloud resolving model on heterogeneous supercomputers using GPUs (Graphical Processing Units). We have isolated a standalone configuration of SAM that is targeted to be integrated into the DOE ACME (Accelerated Climate Modeling for Energy) Earth System model. We have identified key computational kernels from the model and offloaded them to a GPU using the OpenACC programming model. Furthermore, we are investigating various optimization strategies intended to enhance GPU utilization including loop fusion/fission, coalesced data access and loop refactoring to a higher abstraction level. We will present early performance results, lessons learned as well as optimization strategies. The computational platform used in this study is the Summitdev system, an early testbed that is one generation removed from Summit, the next leadership class supercomputer at Oak Ridge National Laboratory. The system contains 54 nodes wherein each node has 2 IBM POWER8 CPUs and 4 NVIDIA Tesla P100 GPUs. This work is part of a larger project, ACME-MMF component of the U.S. Department of Energy(DOE) Exascale Computing Project. The ACME-MMF approach addresses structural uncertainty in cloud processes by replacing traditional parameterizations with cloud resolving "superparameterization" within each grid cell of global climate model. Super-parameterization dramatically increases arithmetic intensity, making the MMF approach an ideal strategy to achieve good performance on emerging exascale computing architectures. The goal of the project is to integrate superparameterization into ACME, and explore its full potential to scientifically and computationally advance climate simulation and prediction.
Hoon, Stephen R.; Felde, Vincent J. M. N. L.; Drahorad, Sylvie L.; Felix-Henningsen, Peter
2015-04-01
Soil penetrometers are used routinely to determine the shear strength of soils and deformable sediments both at the surface and throughout a depth profile in disciplines as diverse as soil science, agriculture, geoengineering and alpine avalanche-safety (e.g. Grunwald et al. 2001, Van Herwijnen et al. 2009). Generically, penetrometers comprise two principal components: An advancing probe, and a transducer; the latter to measure the pressure or force required to cause the probe to penetrate or advance through the soil or sediment. The force transducer employed to determine the pressure can range, for example, from a simple mechanical spring gauge to an automatically data-logged electronic transducer. Automated computer control of the penetrometer step size and probe advance rate enables precise measurements to be made down to a resolution of 10's of microns, (e.g. the automated electronic micropenetrometer (EMP) described by Drahorad 2012). Here we discuss the determination, modelling and interpretation of biologically crusted dryland soil sub-surface structures using automated micropenetrometry. We outline a model enabling the interpretation of depth dependent penetration resistance (PR) profiles and their spatial differentials using the model equations, σ {}(z) ={}σ c0{}+Σ 1n[σ n{}(z){}+anz + bnz2] and dσ /dz = Σ 1n[dσ n(z) /dz{} {}+{}Frn(z)] where σ c0 and σ n are the plastic deformation stresses for the surface and nth soil structure (e.g. soil crust, layer, horizon or void) respectively, and Frn(z)dz is the frictional work done per unit volume by sliding the penetrometer rod an incremental distance, dz, through the nth layer. Both σ n(z) and Frn(z) are related to soil structure. They determine the form of σ {}(z){} measured by the EMP transducer. The model enables pores (regions of zero deformation stress) to be distinguished from changes in layer structure or probe friction. We have applied this method to both artificial calibration soils in the
Dynamic model of the formation of collective heterogeneous boiling nuclei
International Nuclear Information System (INIS)
Class, G.
1977-01-01
Following a discussion of the wettability of solids by liquids and the associated wetting angles, details are given on the wetting angle hysteresis. Moreover the phenomenon of boundary line creep is demonstrated; the anticipated boundary line creep rates in the order of 10 -5 mm/sec are made responsible for the dynamic behaviour of boiling nuclei (waiting time effect and related phenomena). Probable shapes of boiling nuclei and their physico-chemical conditions are discussed. Finally, a statistical dynamical model is outlined. It describes the formation of heterogeneous boiling nuclei in a collective of latent boiling nuclei. On the basis of simple models, a quantitatively usable formulation is presented for the expected distribution functions for the boiling probability as a function of superheat, time, and system parameters. This simplified model of computation is evaluated numerically and the results are discussed with respect to the applicability to experimental data. Based on this computational model it should be possible to obtain preliminary insights into the physico-chemical phenomena which take place at the interface and which are relevant to boiling nuclei. (Auth.)
Intercomparison of Multiscale Modeling Approaches in Simulating Subsurface Flow and Transport
Yang, X.; Mehmani, Y.; Barajas-Solano, D. A.; Song, H. S.; Balhoff, M.; Tartakovsky, A. M.; Scheibe, T. D.
2016-12-01
Hybrid multiscale simulations that couple models across scales are critical to advance predictions of the larger system behavior using understanding of fundamental processes. In the current study, three hybrid multiscale methods are intercompared: multiscale loose-coupling method, multiscale finite volume (MsFV) method and multiscale mortar method. The loose-coupling method enables a parallel workflow structure based on the Swift scripting environment that manages the complex process of executing coupled micro- and macro-scale models without being intrusive to the at-scale simulators. The MsFV method applies microscale and macroscale models over overlapping subdomains of the modeling domain and enforces continuity of concentration and transport fluxes between models via restriction and prolongation operators. The mortar method is a non-overlapping domain decomposition approach capable of coupling all permutations of pore- and continuum-scale models with each other. In doing so, Lagrange multipliers are used at interfaces shared between the subdomains so as to establish continuity of species/fluid mass flux. Subdomain computations can be performed either concurrently or non-concurrently depending on the algorithm used. All the above methods have been proven to be accurate and efficient in studying flow and transport in porous media. However, there has not been any field-scale applications and benchmarking among various hybrid multiscale approaches. To address this challenge, we apply all three hybrid multiscale methods to simulate water flow and transport in a conceptualized 2D modeling domain of the hyporheic zone, where strong interactions between groundwater and surface water exist across multiple scales. In all three multiscale methods, fine-scale simulations are applied to a thin layer of riverbed alluvial sediments while the macroscopic simulations are used for the larger subsurface aquifer domain. Different numerical coupling methods are then applied between
Heterogeneous Epidemic Model for Assessing Data Dissemination in Opportunistic Networks
DEFF Research Database (Denmark)
Rozanova, Liudmila; Alekseev, Vadim; Temerev, Alexander
2014-01-01
that amount of data transferred between network nodes possesses a Pareto distribution, implying scale-free properties. In this context, more heterogeneity in susceptibility means the less severe epidemic progression, and, on the contrary, more heterogeneity in infectivity leads to more severe epidemics...... — assuming that the other parameter (either heterogeneity or susceptibility) stays fixed. The results are general enough to be useful for estimating the epidemic progression with no significant acquired immunity — in the cases where Pareto distribution holds....
Heterogeneous nucleation of ice on model carbon surfaces
Molinero, V.; Lupi, L.; Hudait, A.
2014-12-01
Carbonaceous particles account for 10% of the particulate matter in the atmosphere. The experimental investigation of heterogeneous freezing of water droplets by carbonaceous particles reveals widespread ice freezing temperatures. The origin of the soot and its oxidation and aging modulate its ice nucleation ability, however, it is not known which structural and chemical characteristics of soot account for the variability in ice nucleation efficiency. We find that atomically flat carbon surfaces promote heterogeneous nucleation of ice, while molecularly rough surfaces with the same hydrophobicity do not. We investigate a large set of graphitic surfaces of various dimensions and radii of curvature consistent with those of soot in experiments, and find that variations in nanostructures alone could account for the spread in the freezing temperatures of ice on soot in experiments. A characterization of the nanostructure of soot is needed to predict its ice nucleation efficiency. Atmospheric oxidation and aging of soot modulates its ice nucleation ability. It has been suggested that an increase in the ice nucleation ability of aged soot results from an increase in the hydrophilicity of the surfaces upon oxidation. Oxidation, however, also impacts the nanostructure of soot, making it difficult to assess the separate effects of soot nanostructure and hydrophilicity in experiments. We investigate the effect of changes in hydrophilicity of model graphitic surfaces on the freezing temperature of ice. Our results indicate that the hydrophilicity of the surface is not in general a good predictor of ice nucleation ability. We find a correlation between the ability of a surface to promote nucleation of ice and the layering of liquid water at the surface. The results of this work suggest that ordering of liquid water in contact with the surface plays an important role in the heterogeneous ice nucleation mechanism. References: L. Lupi, A. Hudait and V. Molinero, J. Am. Chem. Soc
Nixon, Zachary; Michel, Jacqueline
2015-04-07
To better understand the distribution of remaining lingering subsurface oil residues from the Exxon Valdez oil spill (EVOS) along the shorelines of Prince William Sound (PWS), AK, we revised previous modeling efforts to allow spatially explicit predictions of the distribution of subsurface oil. We used a set of pooled field data and predictor variables stored as Geographic Information Systems (GIS) data to generate calibrated boosted tree models predicting the encounter probability of different categories of subsurface oil. The models demonstrated excellent predictive performance as evaluated by cross-validated performance statistics. While the average encounter probabilities at most shoreline locations are low across western PWS, clusters of shoreline locations with elevated encounter probabilities remain in the northern parts of the PWS, as well as more isolated locations. These results can be applied to estimate the location and amount of remaining oil, evaluate potential ongoing impacts, and guide remediation. This is the first application of quantitative machine-learning based modeling techniques in estimating the likelihood of ongoing, long-term shoreline oil persistence after a major oil spill.
Carranza, Coleen; van der Ploeg, Martine
2017-04-01
Accurate estimates of water content in the soil profile are essential for environmental and climate modeling studies. Current trends for estimating profile soil moisture incorporate remote sensing methods for mapping soil moisture at greater spatial coverage but is limited to the upper soil layers (e.g. 5cm for radar satellites). Data assimilation methods offer promising computational techniques to translate mapped surface soil moisture to estimates of profile soil moisture, in conjunction with physical models. However, a variety of factors, such as differences in the drying rates, can lead to "decoupling" (Capehart and Carlson, 1997) of surface and subsurface soil moisture. In other words, surface soil moisture conditions no longer reflect or represent subsurface conditions. In this study, we investigated the relation and observed decoupling between surface and subsurface soil moisture from 15-minute interval time series datasets in four selected Dutch agricultural fields (SM_05, SM_09, SM_13, SM_20) from the soil moisture network in Twente region. The idea is that surface soil moisture conditions will be reflected in the subsurface after a certain time lag because of its movement or flow from the surface. These lagged associations were analysed using distributed lag non-linear model (DLNM). This statistical technique provides a framework to simultaneously represent non-linear exposure-response dependencies and delayed effects. DNLM was applied to elucidate which surface soil moisture conditions resulted in a high association to subsurface values, indicating good correlation between the two zones. For example, initial results for this ongoing study from SM_13 show an overall low but increasing association from dry to intermediate soil moisture values (0 to 25%). At this range of values, we say that the two zones are decoupled. Above these values towards near saturated conditions ( 40%), associations between the two zones remain high. For predictor
Main, C E; Yool, A; Holliday, N P; Popova, E E; Jones, D O B; Ruhl, H A
2017-01-15
Little is known about the fate of subsurface hydrocarbon plumes from deep-sea oil well blowouts and their effects on processes and communities. As deepwater drilling expands in the Faroe-Shetland Channel (FSC), oil well blowouts are a possibility, and the unusual ocean circulation of this region presents challenges to understanding possible subsurface oil pathways in the event of a spill. Here, an ocean general circulation model was used with a particle tracking algorithm to assess temporal variability of the oil-plume distribution from a deep-sea oil well blowout in the FSC. The drift of particles was first tracked for one year following release. Then, ambient model temperatures were used to simulate temperature-mediated biodegradation, truncating the trajectories of particles accordingly. Release depth of the modeled subsurface plumes affected both their direction of transport and distance travelled from their release location, and there was considerable interannual variability in transport. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.
Thin inclusion approach for modelling of heterogeneous conducting materials
Lavrov, Nikolay; Smirnova, Alevtina; Gorgun, Haluk; Sammes, Nigel
Experimental data show that heterogeneous nanostructure of solid oxide and polymer electrolyte fuel cells could be approximated as an infinite set of fiber-like or penny-shaped inclusions in a continuous medium. Inclusions can be arranged in a cluster mode and regular or random order. In the newly proposed theoretical model of nanostructured material, the most attention is paid to the small aspect ratio of structural elements as well as to some model problems of electrostatics. The proposed integral equation for electric potential caused by the charge distributed over the single circular or elliptic cylindrical conductor of finite length, as a single unit of a nanostructured material, has been asymptotically simplified for the small aspect ratio and solved numerically. The result demonstrates that surface density changes slightly in the middle part of the thin domain and has boundary layers localized near the edges. It is anticipated, that contribution of boundary layer solution to the surface density is significant and cannot be governed by classic equation for smooth linear charge. The role of the cross-section shape is also investigated. Proposed approach is sufficiently simple, robust and allows extension to either regular or irregular system of various inclusions. This approach can be used for the development of the system of conducting inclusions, which are commonly present in nanostructured materials used for solid oxide and polymer electrolyte fuel cell (PEMFC) materials.
Oxide-supported metal clusters: models for heterogeneous catalysts
International Nuclear Information System (INIS)
Santra, A K; Goodman, D W
2003-01-01
Understanding the size-dependent electronic, structural and chemical properties of metal clusters on oxide supports is an important aspect of heterogeneous catalysis. Recently model oxide-supported metal catalysts have been prepared by vapour deposition of catalytically relevant metals onto ultra-thin oxide films grown on a refractory metal substrate. Reactivity and spectroscopic/microscopic studies have shown that these ultra-thin oxide films are excellent models for the corresponding bulk oxides, yet are sufficiently electrically conductive for use with various modern surface probes including scanning tunnelling microscopy (STM). Measurements on metal clusters have revealed a metal to nonmetal transition as well as changes in the crystal and electronic structures (including lattice parameters, band width, band splitting and core-level binding energy shifts) as a function of cluster size. Size-dependent catalytic reactivity studies have been carried out for several important reactions, and time-dependent catalytic deactivation has been shown to arise from sintering of metal particles under elevated gas pressures and/or reactor temperatures. In situ STM methodologies have been developed to follow the growth and sintering kinetics on a cluster-by-cluster basis. Although several critical issues have been addressed by several groups worldwide, much more remains to be done. This article highlights some of these accomplishments and summarizes the challenges that lie ahead. (topical review)
Sun, N; Elimelech, M; Sun, N Z; Ryan, J N
2001-06-01
A two-dimensional model for colloid transport in geochemically and physically heterogeneous porous media is presented. The model considers patchwise geochemical heterogeneity, which is suitable to describe the chemical variability of many surficial aquifers with ferric oxyhydroxide-coated porous matrix, as well as spatial variability of hydraulic conductivity, which results in heterogeneous flow field. The model is comprised of a transient fluid flow equation, a transient colloid transport equation, and an equation for the dynamics of colloid deposition and release. Numerical simulations were carried out with the model to investigate the colloid transport behavior in layered and randomly heterogeneous porous media. Results demonstrate that physical and geochemical heterogeneities markedly affect the colloid transport behavior. Layered physical or geochemical heterogeneity can result in distinct preferential flow paths of colloidal particles. Furthermore, the combined effect of layered physical and geochemical heterogeneity may result in enhanced or reduced preferential flow of colloids. Random distribution of physical heterogeneity (hydraulic conductivity) results in a random flow field and an irregularly distributed colloid concentration profile in the porous medium. Contrary to random physical heterogeneity, the effect of random patchwise geochemical heterogeneity on colloid transport behavior is not significant. It is mostly the mean value of geochemical heterogeneity rather than its distribution that governs the colloid transport behavior.
International Nuclear Information System (INIS)
Olatunbosun, O. O.
1998-01-01
The subject pertains to the implementation of the full range of subsurface uncertainties in life cycle probabilistic forecasting and its extension to project cash flows using the methodology of probabilities. A new tool has been developed in the probabilistic application of Crystal-Ball which can model reservoir volumetrics, life cycle production forecasts and project cash flows in a single environment. The tool is modular such that the volumetrics and cash flow modules are optional. Production forecasts are often generated by applying a decline equation to single best estimate values of input parameters such as initial potential, decline rate, abandonment rate etc -or sometimes by results of reservoir simulation. This new tool provides a means of implementing the full range of uncertainties and interdependencies of the input parameters into the production forecasts by defining the input parameters as probability density functions, PDFs and performing several iterations to generate an expectation curve forecast. Abandonment rate is implemented in each iteration via a link to an OPEX model. The expectation curve forecast is input into a cash flow model to generate a probabilistic NPV. Base case and sensitivity runs from reservoir simulation can likewise form the basis for a probabilistic production forecast from which a probabilistic cash flow can be generated. A good illustration of the application of this tool is in the modelling of the production forecast for a well that encounters its target reservoirs in OUT/ODT situation and thus has significant uncertainties. The uncertainty in presence and size (if present) of gas cap and dependency between ultimate recovery and initial potential amongst other uncertainties can be easily implemented in the production forecast with this tool. From the expectation curve forecast, a probabilistic NPV can be easily generated. Possible applications of this tool include: i. estimation of range of actual recoverable volumes based
Interpretation and modeling of a subsurface injection test, 200 East Area, Hanford, Washington
International Nuclear Information System (INIS)
Smoot, J.L.; Lu, A.H.
1994-11-01
A tracer experiment was conducted in 1980 and 1981 in the unsaturated zone in the southeast portion of the Hanford 200 East Area near the Plutonium-Uranium Extraction (PUREX) facility. The field design consisted of a central injection well with 32 monitoring wells within an 8-m radius. Water containing radioactive and other tracers was injected weekly during the experiment. The unique features of the experiment were the documented control of the inputs, the experiment's three-dimensional nature, the in-situ measurement of radioactive tracers, and the use of multiple injections. The spacing of the test wells provided reasonable lag distribution for spatial correlation analysis. Preliminary analyses indicated spatial correlation on the order of 400 to 500 cm in the vertical direction. Previous researchers found that two-dimensional axisymmetric modeling of moisture content generally underpredicts lateral spreading and overpredicts vertical movement of the injected water. Incorporation of anisotropic hydraulic properties resulted in the best model predictions. Three-dimensional modeling incorporated the geologic heterogeneity of discontinuous layers and lenses of sediment apparent in the site geology. Model results were compared statistically with measured experimental data and indicate reasonably good agreement with vertical and lateral field moisture distributions
Bayesian Uncertainty Quantification for Subsurface Inversion Using a Multiscale Hierarchical Model
Mondal, Anirban
2014-07-03
We consider a Bayesian approach to nonlinear inverse problems in which the unknown quantity is a random field (spatial or temporal). The Bayesian approach contains a natural mechanism for regularization in the form of prior information, can incorporate information from heterogeneous sources and provide a quantitative assessment of uncertainty in the inverse solution. The Bayesian setting casts the inverse solution as a posterior probability distribution over the model parameters. The Karhunen-Loeve expansion is used for dimension reduction of the random field. Furthermore, we use a hierarchical Bayes model to inject multiscale data in the modeling framework. In this Bayesian framework, we show that this inverse problem is well-posed by proving that the posterior measure is Lipschitz continuous with respect to the data in total variation norm. Computational challenges in this construction arise from the need for repeated evaluations of the forward model (e.g., in the context of MCMC) and are compounded by high dimensionality of the posterior. We develop two-stage reversible jump MCMC that has the ability to screen the bad proposals in the first inexpensive stage. Numerical results are presented by analyzing simulated as well as real data from hydrocarbon reservoir. This article has supplementary material available online. © 2014 American Statistical Association and the American Society for Quality.
Modeling energy fluxes in heterogeneous landscapes employing a mosaic approach
Klein, Christian; Thieme, Christoph; Priesack, Eckart
2015-04-01
Recent studies show that uncertainties in regional and global climate and weather simulations are partly due to inadequate descriptions of the energy flux exchanges between the land surface and the atmosphere. One major shortcoming is the limitation of the grid-cell resolution, which is recommended to be about at least 3x3 km² in most models due to limitations in the model physics. To represent each individual grid cell most models select one dominant soil type and one dominant land use type. This resolution, however, is often too coarse in regions where the spatial diversity of soil and land use types are high, e.g. in Central Europe. An elegant method to avoid the shortcoming of grid cell resolution is the so called mosaic approach. This approach is part of the recently developed ecosystem model framework Expert-N 5.0. The aim of this study was to analyze the impact of the characteristics of two managed fields, planted with winter wheat and potato, on the near surface soil moistures and on the near surface energy flux exchanges of the soil-plant-atmosphere interface. The simulated energy fluxes were compared with eddy flux tower measurements between the respective fields at the research farm Scheyern, North-West of Munich, Germany. To perform these simulations, we coupled the ecosystem model Expert-N 5.0 to an analytical footprint model. The coupled model system has the ability to calculate the mixing ratio of the surface energy fluxes at a given point within one grid cell (in this case at the flux tower between the two fields). This approach accounts for the differences of the two soil types, of land use managements, and of canopy properties due to footprint size dynamics. Our preliminary simulation results show that a mosaic approach can improve modeling and analyzing energy fluxes when the land surface is heterogeneous. In this case our applied method is a promising approach to extend weather and climate models on the regional and on the global scale.
Salim, Juma K.; Dillon, Carl R.; Saghaian, Sayed H.; Kanakasabai, Murali
2005-01-01
A comparison of decision rules has been made for case studies of corn production using subsurface drip irrigation under three agricultural management practices (no irrigation, uniform irrigation, and variable rate irrigation). The uniform irrigation strategy appeared to perform the best than the other two management practices under different risk scenarios.
Reactive transport modeling of subsurface arsenic removal systems in rural Bangladesh.
Rahmann, M.M.; Bakker, M.; Patty, C.H.L.; Hassan, Z.; Roling, W.F.M.; Ahmed, K.M.; van Breukelen, B.M.
2015-01-01
Subsurface Arsenic Removal (SAR) is a technique for in-situ removal of arsenic from groundwater. Extracted groundwater is aerated and re-injected into an anoxic aquifer, where the oxygen in the injected water reacts with ferrous iron in the aquifer to form hydrous ferric oxide (HFO). Subsequent
Wasch, L.J.; Koenen, M.; Wollenweber, J.; Tambach, T.J.
2015-01-01
To ensure the safety of a CO 2 storage site and containment of CO 2 in the subsurface, the integrity of wellbore materials must be maintained. Field and laboratory studies have shown CO 2 -induced reactivity of wellbore cement, but these results have to be extrapolated to the extended time span of
Iterative approach to modeling subsurface stormflow based on nonlinear, hillslope-scale physics
Spaaks, J.H.; Bouten, W.; McDonnell, J.J.
2009-01-01
Soil water transport in small, humid, upland catchments is often dominated by subsurface stormflow. Recent studies of this process suggest that at the plot scale, generation of transient saturation may be governed by threshold behavior, and that transient saturation is a prerequisite for lateral
Yustin Kamah, Muhammad; Armando, Adilla; Larasati Rahmani, Dinda; Paramitha, Shabrina
2017-12-01
Geophysical methods such as gravity and magnetotelluric methods commonly used in conventional and unconventional energy exploration, notably for exploring geothermal prospect. They used to identify the subsurface geology structures which is estimated as a path of fluid flow. This study was conducted in Kamojang Geothermal Field with the aim of highlighting the volcanic lineament in West Java, precisely in Guntur-Papandayan chain where there are three geothermal systems. Kendang Fault has predominant direction NE-SW, identified by magnetotelluric techniques and gravity data processing techniques. Gravity techniques such as spectral analysis, derivative solutions, and Euler deconvolution indicate the type and geometry of anomaly. Magnetotelluric techniques such as inverse modeling and polar diagram are required to know subsurface resistivity charactersitics and major orientation. Furthermore, the result from those methods will be compared to geology information and some section of well data, which is sufficiently suitable. This research is very useful to trace out another potential development area.
Deep subsurface microbial processes
Lovley, D.R.; Chapelle, F.H.
1995-01-01
Information on the microbiology of the deep subsurface is necessary in order to understand the factors controlling the rate and extent of the microbially catalyzed redox reactions that influence the geophysical properties of these environments. Furthermore, there is an increasing threat that deep aquifers, an important drinking water resource, may be contaminated by man's activities, and there is a need to predict the extent to which microbial activity may remediate such contamination. Metabolically active microorganisms can be recovered from a diversity of deep subsurface environments. The available evidence suggests that these microorganisms are responsible for catalyzing the oxidation of organic matter coupled to a variety of electron acceptors just as microorganisms do in surface sediments, but at much slower rates. The technical difficulties in aseptically sampling deep subsurface sediments and the fact that microbial processes in laboratory incubations of deep subsurface material often do not mimic in situ processes frequently necessitate that microbial activity in the deep subsurface be inferred through nonmicrobiological analyses of ground water. These approaches include measurements of dissolved H2, which can predict the predominant microbially catalyzed redox reactions in aquifers, as well as geochemical and groundwater flow modeling, which can be used to estimate the rates of microbial processes. Microorganisms recovered from the deep subsurface have the potential to affect the fate of toxic organics and inorganic contaminants in groundwater. Microbial activity also greatly influences 1 the chemistry of many pristine groundwaters and contributes to such phenomena as porosity development in carbonate aquifers, accumulation of undesirably high concentrations of dissolved iron, and production of methane and hydrogen sulfide. Although the last decade has seen a dramatic increase in interest in deep subsurface microbiology, in comparison with the study of
Assessing clustering strategies for Gaussian mixture filtering a subsurface contaminant model
Liu, Bo
2016-02-03
An ensemble-based Gaussian mixture (GM) filtering framework is studied in this paper in term of its dependence on the choice of the clustering method to construct the GM. In this approach, a number of particles sampled from the posterior distribution are first integrated forward with the dynamical model for forecasting. A GM representation of the forecast distribution is then constructed from the forecast particles. Once an observation becomes available, the forecast GM is updated according to Bayes’ rule. This leads to (i) a Kalman filter-like update of the particles, and (ii) a Particle filter-like update of their weights, generalizing the ensemble Kalman filter update to non-Gaussian distributions. We focus on investigating the impact of the clustering strategy on the behavior of the filter. Three different clustering methods for constructing the prior GM are considered: (i) a standard kernel density estimation, (ii) clustering with a specified mixture component size, and (iii) adaptive clustering (with a variable GM size). Numerical experiments are performed using a two-dimensional reactive contaminant transport model in which the contaminant concentration and the heterogenous hydraulic conductivity fields are estimated within a confined aquifer using solute concentration data. The experimental results suggest that the performance of the GM filter is sensitive to the choice of the GM model. In particular, increasing the size of the GM does not necessarily result in improved performances. In this respect, the best results are obtained with the proposed adaptive clustering scheme.
Birkigt, Jan; Stumpp, Christine; Małoszewski, Piotr; Nijenhuis, Ivonne
2018-04-15
In recent years, constructed wetland systems have become into focus as means of cost-efficient organic contaminant management. Wetland systems provide a highly reactive environment in which several removal pathways of organic chemicals may be present at the same time; however, specific elimination processes and hydraulic conditions are usually separately investigated and thus not fully understood. The flow system in a three dimensional pilot-scale horizontal subsurface constructed wetland was investigated applying a multi-tracer test combined with a mathematical model to evaluate the flow and transport processes. The results indicate the existence of a multiple flow system with two distinct flow paths through the gravel bed and a preferential flow at the bottom transporting 68% of tracer mass resulting from the inflow design of the model wetland system. There the removal of main contaminant chlorobenzene was up to 52% based on different calculation approaches. Determined retention times in the range of 22d to 32.5d the wetland has a heterogeneous flow pattern. Differences between simulated and measured tracer concentrations in the upper sediment indicate diffusion dominated processes due to stagnant water zones. The tracer study combining experimental evaluation with mathematical modeling demonstrated the complexity of flow and transport processes in the constructed wetlands which need to be taken into account during interpretation of the determining attenuation processes. Copyright © 2017 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Gwo, J.P.; Jardine, P.M.; Yeh, G.T.; Wilson, G.V.
1995-04-01
Matrix diffusion, a diffusive mass transfer process,in the structured soils and geologic units at ORNL, is believe to be an important subsurface mass transfer mechanism; it may affect off-site movement of radioactive wastes and remediation of waste disposal sites by locally exchanging wastes between soil/rock matrix and macropores/fractures. Advective mass transfer also contributes to waste movement but is largely neglected by researchers. This report presents the first documented 2-D multiregion solute transport code (MURT) that incorporates not only diffusive but also advective mass transfer and can be applied to heterogeneous porous media under transient flow conditions. In this report, theoretical background is reviewed and the derivation of multiregion solute transport equations is presented. Similar to MURF (Gwo et al. 1994), a multiregion subsurface flow code, multiplepore domains as suggested by previous investigators (eg, Wilson and Luxmoore 1988) can be implemented in MURT. Transient or steady-state flow fields of the pore domains can be either calculated by MURF or by modelers. The mass transfer process is briefly discussed through a three-pore-region multiregion solute transport mechanism. Mass transfer equations that describe mass flux across pore region interfaces are also presented and parameters needed to calculate mass transfer coefficients detailed. Three applications of MURT (tracer injection problem, sensitivity analysis of advective and diffusive mass transfer, hillslope ponding infiltration and secondary source problem) were simulated and results discussed. Program structure of MURT and functions of MURT subroutiness are discussed so that users can adapt the code; guides for input data preparation are provided in appendices
Hailegeorgis, Teklu T.; Alfredsen, Knut
2018-02-01
Reliable runoff estimation is important for design of water infrastructure and flood risk management in urban catchments. We developed a spatially distributed Precipitation-Runoff (P-R) model that explicitly represents the land cover information, performs integrated modelling of surface and subsurface components of the urban precipitation water cycle and flow routing. We conducted parameter calibration and validation for a small (21.255 ha) stormwater catchment in Trondheim City during Summer-Autumn events and season, and snow-influenced Winter-Spring seasons at high spatial and temporal resolutions of respectively 5 m × 5 m grid size and 2 min. The calibration resulted in good performance measures (Nash-Sutcliffe efficiency, NSE = 0.65-0.94) and acceptable validation NSE for the seasonal and snow-influenced periods. The infiltration excess surface runoff dominates the peak flows while the contribution of subsurface flow to the sewer pipes also augments the peak flows. Based on the total volumes of simulated flow in sewer pipes (Qsim) and precipitation (P) during the calibration periods, the Qsim/P ranges from 21.44% for an event to 56.50% for the Winter-Spring season, which are in close agreement with the observed volumes (Qobs/P). The lowest percentage of precipitation volume that is transformed to the total simulated runoff in the catchment (QT) is 79.77%. Computation of evapotranspiration (ET) indicated that the ET/P is less than 3% for the events and snow-influenced seasons while it is about 18% for the Summer-Autumn season. The subsurface flow contribution to the sewer pipes are markedly higher than the total surface runoff volume for some events and the Summer-Autumn season. The peakiest flow rates correspond to the Winter-Spring season. Therefore, urban runoff simulation for design and management purposes should include two-way interactions between the subsurface runoff and flow in sewer pipes, and snow-influenced seasons. The developed urban P-R model is
International Nuclear Information System (INIS)
Lytle, R.J.
1978-01-01
Imaging techniques that can be used to translate seismic and electromagnetic wave signals into visual representation are briefly discussed. The application of these techniques is illustrated on the example of determining the subsurface structure of a proposed power plant. Imaging makes the wave signals intelligible to the non-geologists. R and D work needed in this area are tabulated
Digital Geological Model (DGM): a 3D raster model of the subsurface of the Netherlands
Gunnink, J.L.; Maljers, D.; Gessel, S.F. van; Menkovic, A.; Hummelman, H.J.
2013-01-01
A 3D geological raster model has been constructed of the onshore of the Netherlands. The model displays geological units for the upper 500 m in 3D in an internally consistent way. The units are based on the lithostratigraphical classification of the Netherlands. This classification is used to
Ermolieva, T.Y.; Fischer, G.; Obersteiner, M.
2003-01-01
This paper discusses an integrated model capable of dealing with spatial and temporal heterogeneities induced by extreme events, in particular weather related catastrophes. The model can be used for quite different problems which take explicitly into account the specifics of catastrophic risks: highly mutually dependent losses, inherent capacity of information, the need for long-term perspectives (temporal heterogeneity) and geographically explicit analyses (spatial heterogeneity) with respec...
Heterogeneity in Returns to Work Experience: A Dynamic Model of Female Labor Force Participation
Ken Yamada
2009-01-01
This paper provides structural estimates of heterogeneous returns to work experience for Japanese married women. A dynamic model of labor force participation is used to account for dynamic self-selection into employment. Heterogeneity is incorporated into the model in a way that allows for the multidimensional skill heterogeneity in employment and home production and for the individual-specific slope and curvature of experience effect on earnings. The structural estimates and their comparison...
Energy Technology Data Exchange (ETDEWEB)
Sokrut, Nikolay; Werner, Kent; Holmen, Johan [Golder Associates AB, Uppsala (Sweden)
2007-01-15
Since 2002, the Swedish Nuclear Fuel and Waste Management Co (SKB) performs site investigations in the Simpevarp area, for the siting of a deep geological repository for spent nuclear fuel. The site descriptive modelling includes conceptual and quantitative modelling of surface-subsurface water interactions, which are key inputs to safety assessment and environmental impact assessment. Such modelling is important also for planning of continued site investigations. In this report, the distributed hydrological model ECOFLOW is applied to the Laxemar subarea to test the ability of the model to simulate surface water and near-surface groundwater flow, and to illustrate ECOFLOW's advantages and drawbacks. The ECOFLOW model area is generally characterised by large areas of exposed or shallow bedrock. The ECOFLOW modelling results are compared to previous results produced by MIKE SHE-MIKE 11 and PCRaster-POLFLOW, in order to check whether non-calibrated surface and subsurface water flows computed by ECOFLOW are consistent with these previous results. The analyses include quantification and comparison of inflow and outflow terms of the water balance, as well as analyses of groundwater recharge-discharge patterns. ECOFLOW is used to simulate a one-year non calibrated period, considering seven catchments (including three areas with direct runoff to the sea) within the Laxemar subarea. The modelling results show the ability of the model to produce reasonable results for a model domain including both porous media (Quaternary deposits) and discontinuous media (bedrock). The results demonstrate notable differences in the specific discharge between the considered catchments, with specific discharge values in the range 157-212 mm/year; the lowest value (the Lake Frisksjoen catchment) may however be erroneous due to numerical instability in the model. Overall, these results agree with specific discharge values computed by MIKE SHE-MIKE 11 and PCRaster-POLFLOW (190 and 128
Uncertainty in Model parameter Estimates and Impacts on Risk and Decision Making in the Subsurface
Enzenhöfer, R.; Helmig, R.; Nowak, W.; Binning, P. J.
2010-12-01
Advection-based well-head protection zones are commonly used to manage the risk of contamination to drinking water wells. Current Water Safety Plans recommend that catchment managers and stakeholders control and monitor all possible hazards within catchments. In order to do this it is important to not only map the protection zones, but also to characterize their uncertainty. Here the four intrinsic well vulnerability criteria of Frind et al. (2006) are cast in a probabilistic framework. The criteria employ advective-dispersive transport models to determine the: (1) Peak arrival time at the well, (2) peak concentration level, (3) arrival time of threshold concentrations and (4) time of exposure. Our probabilistic framework yields catchment-wide maps of the probability of exceeding each of these criteria. We separate the uncertainty of plume location and actual dilution by resolving heterogeneity with high-resolution Monte-Carlo simulations. To keep computational costs low, we adopt a reverse transport formulation, and combine it with the temporal moment approach for model reduction. We recover the time-dependent breakthrough curves and well vulnerability criteria from the temporal moments by Maximum Entropy reconstruction in log-time. Our method is independent of dimensionality, boundary conditions and other sources of uncertainty. It can be coupled with any method for conditioning on available data. For simplicity, we demonstrate the concept on a 2D example that involves synthetic data. Our approach delivers indispensable information on exposure risk and improves the basis for risk-informed well head management.
A modelling approach for the heterogeneous oxidation of elastomers
Herzig, A.; Sekerakova, L.; Johlitz, M.; Lion, A.
2017-09-01
The influence of oxygen on elastomers, known as oxidation, is one of the most important ageing processes and becomes more and more important for nowadays applications. The interaction with thermal effects as well as antioxidants makes oxidation of polymers a complex process. Based on the polymer chosen and environmental conditions, the ageing processes may behave completely different. In a lot of cases the influence of oxygen is limited to the surface layer of the samples, commonly referred to as diffusion-limited oxidation. For the lifetime prediction of elastomer components, it is essential to have detailed knowledge about the absorption and diffusion behaviour of oxygen molecules during thermo-oxidative ageing and how they react with the elastomer. Experimental investigations on industrially used elastomeric materials are executed in order to develop and fit models, which shall be capable of predicting the permeation and consumption of oxygen as well as changes in the mechanical properties. The latter are of prime importance for technical applications of rubber components. Oxidation does not occur homogeneously over the entire elastomeric component. Hence, material models which include ageing effects have to be amplified in order to consider heterogeneous ageing, which highly depends on the ageing temperature. The influence of elevated temperatures upon accelerated ageing has to be critically analysed, and influences on the permeation and diffusion coefficient have to be taken into account. This work presents phenomenological models which describe the oxygen uptake and the diffusion into elastomers based on an improved understanding of ongoing chemical processes and diffusion limiting modifications. On the one side, oxygen uptake is modelled by means of Henry's law in which solubility is a function of the temperature as well as the ageing progress. The latter is an irreversible process and described by an inner differential evolution equation. On the other side
Berlin, M.; Vasudevan, M.; Kumar, G. Suresh; Nambi, Indumathi M.
2015-04-01
The vertical transport of petroleum hydrocarbons from a surface spill through an unsaturated subsurface system is of major concern in assessing the vulnerability of groundwater contamination. A realistic representation on fate and transport of volatile organic compounds at different periods after spill is quite challenging due to the variation in the source behaviour at the surface of spill as well as the variation in the hydrodynamic parameters and the associated inter-phase partitioning coefficients within the subsurface. In the present study, a one dimensional numerical model is developed to simulate the transport of benzene in an unsaturated subsurface system considering the effect of volatilization, dissolution, adsorption and microbial degradation of benzene for (i) constant continuous source, (ii) continuous decaying source, and (iii) residual source. The numerical results suggest that volatilization is the important sink for contaminant removal considering the soil air migration within the unsaturated zone. It is also observed that the coupled effect of dissolution and volatilization is important for the decaying source at the surface immediately after the spill, whereas rate-limited dissolution from residually entrapped source is responsible for the extended contamination towards later period.
Kömle, Norbert I.; Poganski, Joshua; Kargl, Günter; Grygorczuk, Jerzy
2015-05-01
Several planetary lander missions conducted in the past and planned for the near future have instruments on board, which are dedicated to the determination of various material properties, among them mechanical properties of the surface like material strength and penetration resistance. In this paper two instruments are considered in more detail: (i) the MUPUS penetrator, a device aboard the Lander Philae of ESA's Rosetta mission, and (ii) the Mole HP3, which is part of the payload of NASA's next Discovery mission InSight, due for landing on Mars in 2016. Both devices are driven by hammering mechanisms designed to work under low or micro-gravity conditions and blaze themselves a trail into the subsurface of their respective target bodies. Naturally the speed with which this process takes place and if penetration is possible at all depends on the mechanical properties of the soil. However, a quantitative evaluation of soil mechanical parameters from measured depth-versus-time data is not a straightforward task. In this paper we apply an old technique, originally developed for modelling the driving of a pile into the ground, to describe the performance of penetrators and Moles developed for planetary applications. The numerical pile driving model of Smith (1962) is scaled and adapted for this purpose and used to predict the penetration behaviour of these instruments in dependence of their internal construction and the properties of the soil they are driven in. The model computes the permanent set of the surrounding soil in response to one hammer blow cycle as well as the oscillations and waves excited inside the devices and in the surrounding soil. Both the penetration resistance of the tip and the resistance caused by friction of the penetrator along the cylindrical side wall are calculated. By comparing the modelling results with previous laboratory measurements it is demonstrated that the models produce realistic results and can be used both as tools for proper
International Nuclear Information System (INIS)
1997-01-01
The first detailed comprehensive simulation study to evaluate fate and transport of wastes disposed in the Subsurface Disposal Area (SDA), at the Radioactive Waste Management Complex (RWMC), Idaho National Engineering and Environmental Laboratory (INEEL) has recently been conducted. One of the most crucial parts of this modeling was the source term or release model. The current study used information collected over the last five years defining contaminant specific information including: the amount disposed, the waste form (physical and chemical properties) and the type of container used for each contaminant disposed. This information was used to simulate the release of contaminants disposed in the shallow subsurface at the SDA. The DUST-MS model was used to simulate the release. Modifications were made to allow the yearly disposal information to be incorporated. The modeling includes unique container and release rate information for each of the 42 years of disposal. The results from this simulation effort are used for both a groundwater and a biotic uptake evaluation. As part of this modeling exercise, inadequacies in the available data relating to the release of contaminants have been identified. The results from this modeling study have been used to guide additional data collection activities at the SDA for purposes of increasing confidence in the appropriateness of model predictions
Church, Jonathan R.
New condensed matter metrologies are being used to probe ever smaller length scales. In support of the diverse field of materials research synchrotron based spectroscopies provide sub-micron spatial resolutions and a breadth of photon wavelengths for scientific studies. For electronic materials the thinnest layers in a complementary metal-oxide-semiconductor (CMOS) device have been reduced to just a few nanometers. This raises concerns for layer uniformity, complete surface coverage, and interfacial quality. Deposition processes like chemical vapor deposition (CVD) and atomic layer deposition (ALD) have been shown to deposit the needed high-quality films for the requisite thicknesses. However, new materials beget new chemistries and, unfortunately, unwanted side-reactions and by-products. CVD/ALD tools and chemical precursors provided by our collaborators at Air Liquide utilized these new chemistries and films were deposited for which novel spectroscopic characterization methods were used. The second portion of the thesis focuses on fading and decomposing paint pigments in iconic artworks. Efforts have been directed towards understanding the micro-environments causing degradation. Hard X-ray photoelectron spectroscopy (HAXPES) and variable kinetic energy X-ray photoelectron spectroscopy (VKE-XPS) are advanced XPS techniques capable of elucidating both chemical environments and electronic band structures in sub-surface regions of electronic materials. HAXPES has been used to study the electronic band structure in a typical CMOS structure; it will be shown that unexpected band alignments are associated with the presence of electronic charges near a buried interface. Additionally, a computational modeling algorithm, Bayes-Sim, was developed to reconstruct compositional depth profiles (CDP) using VKE-XPS data sets; a subset algorithm also reconstructs CDP from angle-resolved XPS data. Reconstructed CDP produced by Bayes-Sim were most strongly correlated to the real
Saebi, Tina; Foss, Nicolai Juul
2015-01-01
-This is the author's version of the article:"Business models for open innovation: Matching heterogeneous open innovation strategies with business model dimensions", European Management Journal, Volume 33, Issue 3, June 2015, Pages 201–213 Research on open innovation suggests that companies benefit differentially from adopting open innovation strategies; however, it is unclear why this is so. One possible explanation is that companies' business models are not attuned to open strategies. Ac...
El Gharamti, Mohamad
2014-02-01
The accuracy of groundwater flow and transport model predictions highly depends on our knowledge of subsurface physical parameters. Assimilation of contaminant concentration data from shallow dug wells could help improving model behavior, eventually resulting in better forecasts. In this paper, we propose a joint state-parameter estimation scheme which efficiently integrates a low-rank extended Kalman filtering technique, namely the Singular Evolutive Extended Kalman (SEEK) filter, with the prominent complex-step method (CSM). The SEEK filter avoids the prohibitive computational burden of the Extended Kalman filter by updating the forecast along the directions of error growth only, called filter correction directions. CSM is used within the SEEK filter to efficiently compute model derivatives with respect to the state and parameters along the filter correction directions. CSM is derived using complex Taylor expansion and is second order accurate. It is proven to guarantee accurate gradient computations with zero numerical round-off errors, but requires complexifying the numerical code. We perform twin-experiments to test the performance of the CSM-based SEEK for estimating the state and parameters of a subsurface contaminant transport model. We compare the efficiency and the accuracy of the proposed scheme with two standard finite difference-based SEEK filters as well as with the ensemble Kalman filter (EnKF). Assimilation results suggest that the use of the CSM in the context of the SEEK filter may provide up to 80% more accurate solutions when compared to standard finite difference schemes and is competitive with the EnKF, even providing more accurate results in certain situations. We analyze the results based on two different observation strategies. We also discuss the complexification of the numerical code and show that this could be efficiently implemented in the context of subsurface flow models. © 2013 Elsevier B.V.
A LATENT CLASS POISSON REGRESSION-MODEL FOR HETEROGENEOUS COUNT DATA
WEDEL, M; DESARBO, WS; BULT, [No Value; RAMASWAMY, [No Value
1993-01-01
In this paper an approach is developed that accommodates heterogeneity in Poisson regression models for count data. The model developed assumes that heterogeneity arises from a distribution of both the intercept and the coefficients of the explanatory variables. We assume that the mixing
Tran, A. P.; Dafflon, B.; Hubbard, S. S.; Bisht, G.; Peterson, J.; Ulrich, C.; Romanovsky, V. E.; Kneafsey, T. J.; Wu, Y.
2015-12-01
Quantitative characterization of the soil surface-subsurface hydrological and thermal processes is essential as they are primary factors that control the biogeochemical processes, ecological landscapes and greenhouse gas fluxes. In the Artic region, the surface-subsurface hydrological and thermal regimes co-interact and are both largely influenced by soil texture and soil organic content. In this study, we present a coupled inversion scheme that jointly inverts hydrological, thermal and geophysical data to estimate the vertical profiles of clay, sand and organic contents. Within this inversion scheme, the Community Land Model (CLM4.5) serves as a forward model to simulate the land-surface energy balance and subsurface hydrological-thermal processes. Soil electrical conductivity (from electrical resistivity tomography), temperature and water content are linked together via petrophysical and geophysical models. Particularly, the inversion scheme accounts for the influences of the soil organic and mineral content on both of the hydrological-thermal dynamics and the petrophysical relationship. We applied the inversion scheme to the Next Generation Ecosystem Experiments (NGEE) intensive site in Barrow, AK, which is characterized by polygonal-shaped arctic tundra. The monitoring system autonomously provides a suite of above-ground measurements (e.g., precipitation, air temperature, wind speed, short-long wave radiation, canopy greenness and eddy covariance) as well as below-ground measurements (soil moisture, soil temperature, thaw layer thickness, snow thickness and soil electrical conductivity), which complement other periodic, manually collected measurements. The preliminary results indicate that the model can well reproduce the spatiotemporal dynamics of the soil temperature, and therefore, accurately predict the active layer thickness. The hydrological and thermal dynamics are closely linked to the polygon types and polygon features. The results also enable the
Cross-layer Modelling for Heterogeneous MPSoCs
DEFF Research Database (Denmark)
Madsen, Jan
2005-01-01
One of the challenges of designing a heterogeneous multiprocessor SoC is to find the right partitioning of the application onto the platform architecture. The right partitioning is dependent on the characteristics of the processors and the network connecting them, as well as the application. We p...
Accounting for heterogeneity of public lands in hedonic property models
Charlotte Ham; Patricia A. Champ; John B. Loomis; Robin M. Reich
2012-01-01
Open space lands, national forests in particular, are usually treated as homogeneous entities in hedonic price studies. Failure to account for the heterogeneous nature of public open spaces may result in inappropriate inferences about the benefits of proximate location to such lands. In this study the hedonic price method is used to estimate the marginal values for...
New Keynesian model dynamics under heterogeneous expectations and adaptive learning
Czech Academy of Sciences Publication Activity Database
Fukač, Martin
-, č. 5 (2006), s. 1-41 R&D Projects: GA MŠk LC542 Institutional research plan: CEZ:AV0Z70850503 Keywords : imperfect and heterogeneous knowledge * adaptive learning * monetary policy Subject RIV: AH - Economics http://www.cnb.cz/www.cnb.cz/en/research/research_publications/cnb_wp/index.html
Yang, Lurong; Wang, Xinyu; Mendoza-Sanchez, Itza; Abriola, Linda M
2018-04-01
Sequestered mass in low permeability zones has been increasingly recognized as an important source of organic chemical contamination that acts to sustain downgradient plume concentrations above regulated levels. However, few modeling studies have investigated the influence of this sequestered mass and associated (coupled) mass transfer processes on plume persistence in complex dense nonaqueous phase liquid (DNAPL) source zones. This paper employs a multiphase flow and transport simulator (a modified version of the modular transport simulator MT3DMS) to explore the two- and three-dimensional evolution of source zone mass distribution and near-source plume persistence for two ensembles of highly heterogeneous DNAPL source zone realizations. Simulations reveal the strong influence of subsurface heterogeneity on the complexity of DNAPL and sequestered (immobile/sorbed) mass distribution. Small zones of entrapped DNAPL are shown to serve as a persistent source of low concentration plumes, difficult to distinguish from other (sorbed and immobile dissolved) sequestered mass sources. Results suggest that the presence of DNAPL tends to control plume longevity in the near-source area; for the examined scenarios, a substantial fraction (43.3-99.2%) of plume life was sustained by DNAPL dissolution processes. The presence of sorptive media and the extent of sorption non-ideality are shown to greatly affect predictions of near-source plume persistence following DNAPL depletion, with plume persistence varying one to two orders of magnitude with the selected sorption model. Results demonstrate the importance of sorption-controlled back diffusion from low permeability zones and reveal the importance of selecting the appropriate sorption model for accurate prediction of plume longevity. Large discrepancies for both DNAPL depletion time and plume longevity were observed between 2-D and 3-D model simulations. Differences between 2- and 3-D predictions increased in the presence of
Comment on Hoffman and Rovine (2007): SPSS MIXED can estimate models with heterogeneous variances.
Weaver, Bruce; Black, Ryan A
2015-06-01
Hoffman and Rovine (Behavior Research Methods, 39:101-117, 2007) have provided a very nice overview of how multilevel models can be useful to experimental psychologists. They included two illustrative examples and provided both SAS and SPSS commands for estimating the models they reported. However, upon examining the SPSS syntax for the models reported in their Table 3, we found no syntax for models 2B and 3B, both of which have heterogeneous error variances. Instead, there is syntax that estimates similar models with homogeneous error variances and a comment stating that SPSS does not allow heterogeneous errors. But that is not correct. We provide SPSS MIXED commands to estimate models 2B and 3B with heterogeneous error variances and obtain results nearly identical to those reported by Hoffman and Rovine in their Table 3. Therefore, contrary to the comment in Hoffman and Rovine's syntax file, SPSS MIXED can estimate models with heterogeneous error variances.
Energy Technology Data Exchange (ETDEWEB)
Wohleber, X
1997-11-17
The TIBERE Model is a neutron leakage method based on B{sub 1} heterogeneous transport equation resolution. In this work, we have studied the influence of the reflection mode at the boundary of the assembly. In particular the White boundary condition has been implemented in the APOLLO2 neutron transport code. We have compared the two TIBERE kinds of boundary conditions (specular and white) with the classical B{sub 1} homogeneous leakage method in the modelling of some reactors. We have remarked the better capability of the TIBERE Model to compute voided assemblies. The white boundary condition is also able to compute a completely voided assembly and, besides, wins a factor 10 in CPU time in comparison with the specular boundary condition. These two heterogenous leakage formalisms have been tested on a partially voided experiment and have shown that the TIBERE Model can compute this kind of situation with a greater precision than the classical B{sub 1} homogeneous leakage method, and with a shorter computational time. (author)
The effect of soil heterogeneity on ATES performance
Sommer, W.; Rijnaarts, H.; Grotenhuis, T.; van Gaans, P.
2012-04-01
Due to an increasing demand for sustainable energy, application of Aquifer Thermal Energy Storage (ATES) is growing rapidly. Large-scale application of ATES is limited by the space that is available in the subsurface. Especially in urban areas, suboptimal performance is expected due to thermal interference between individual wells of a single system, or interference with other ATES systems or groundwater abstractions. To avoid thermal interference there are guidelines on well spacing. However, these guidelines, and also design calculations, are based on the assumption of a homogeneous subsurface, while studies report a standard deviation in logpermeability of 1 to 2 for unconsolidated aquifers (Gelhar, 1993). Such heterogeneity may create preferential pathways, reducing ATES performance due to increased advective heat loss or interference between ATES wells. The role of hydraulic heterogeneity of the subsurface related to ATES performance has received little attention in literature. Previous research shows that even small amounts of heterogeneity can result in considerable uncertainty in the distribution of thermal energy in the subsurface and an increased radius of influence (Ferguson, 2007). This is supported by subsurface temperature measurements around ATES wells, which suggest heterogeneity gives rise to preferential pathways and short-circuiting between ATES wells (Bridger and Allen, 2010). Using 3-dimensional stochastic heat transport modeling, we quantified the influence of heterogeneity on the performance of a doublet well energy storage system. The following key parameters are varied to study their influence on thermal recovery and thermal balance: 1) regional flow velocity, 2) distance between wells and 3) characteristics of the heterogeneity. Results show that heterogeneity at the scale of a doublet ATES system introduces an uncertainty up to 18% in expected thermal recovery. The uncertainty increases with decreasing distance between ATES wells. The
Simultaneous HPAM/SDS Injection in Heterogeneous/Layered Models
M. H. Sedaghat; A. Zamani; S. Morshedi; R. Janamiri; M. Safdari; I. Mahdavi; A. Hosseini; A. Hatampour
2013-01-01
Although lots of experiments have been done in enhanced oil recovery, the number of experiments which consider the effects of local and global heterogeneity on efficiency of enhanced oil recovery based on the polymer-surfactant flooding is low and rarely done. In this research, we have done numerous experiments of water flooding and polymer-surfactant flooding on a five spot glass micromodel in different conditions such as different positions of layers. In these experiments, five different mi...
Negara, Ardiansyah
2015-05-01
Anisotropy of hydraulic properties of the subsurface geologic formations is an essential feature that has been established as a consequence of the different geologic processes that undergo during the longer geologic time scale. With respect to subsurface reservoirs, in many cases, anisotropy plays significant role in dictating the direction of flow that becomes no longer dependent only on driving forces like the pressure gradient and gravity but also on the principal directions of anisotropy. Therefore, there has been a great deal of motivation to consider anisotropy into the subsurface flow and transport models. In this dissertation, we present subsurface flow modeling in single and dual continuum anisotropic porous media, which include the single-phase groundwater flow coupled with the solute transport in anisotropic porous media, the two-phase flow with gravity effect in anisotropic porous media, and the natural gas flow in anisotropic shale reservoirs. We have employed the multipoint flux approximation (MPFA) method to handle anisotropy in the flow model. The MPFA method is designed to provide correct discretization of the flow equations for general orientation of the principal directions of the permeability tensor. The implementation of MPFA method is combined with the experimenting pressure field approach, a newly developed technique that enables the solution of the global problem breaks down into the solution of multitude of local problems. The numerical results of the study demonstrate the significant effects of anisotropy of the subsurface formations. For the single-phase groundwater flow coupled with the solute transport modeling in anisotropic porous media, the results shows the strong impact of anisotropy on the pressure field and the migration of the solute concentration. For the two-phase flow modeling with gravity effect in anisotropic porous media, it is observed that the buoyancy-driven flow, which emerges due to the density differences between the
Bridger, David W.
2006-01-01
A modelling study was carried out to evaluate the influence of aquifer heterogeneity, as represented by geologic layering, on heat transport and storage in aquifer thermal energy storage (ATES) systems. An existing ATES system installed within a heterogeneous aquifer system in Agassiz, British Columbia, Canada was used as a case study. Two 3D heat transport models of the study site were developed and calibrated using the heat transport code FEFLOW, including: a "simple" model domain with unif...
Randomly-fluctuating heterogeneous continuum model of a ballasted railway track
de Abreu Corrêa, Lucio; Quezada, Juan Carlos; Cottereau, Régis; d'Aguiar, Sofia Costa; Voivret, Charles
2017-11-01
This paper proposes a description of a granular medium as a stochastic heterogeneous continuum medium. The heterogeneity of the material properties field recreates the heterogeneous stress field in a granular medium. The stochastic approach means that only statistical information, easily available, is required to construct the model. The heterogeneous continuum model is Calibrated with respect to discrete simulations of a set of railway ballast samples. As they are continuum-based, the equilibrium equations can be solved on a large scale using a parallel implementation of an explicit time discretization scheme for the Finite Element Method. Simulations representative of the influence on the environment of the passage of a train on a ballasted railway track clearly show the influence of the heterogeneity. These simulations seem to correlate well with previously unexplained overly damped measurements in the free field.
International Nuclear Information System (INIS)
Unesaki, Hironobu; Takeda, Toshikazu
1988-01-01
Neutron streaming in a fast breeder reactor fuel assembly caused by the double heterogeneity structure is estimated by double heterogeneous modelling. The conventional pin cell model, a two-region subassembly model and the exact pin cluster model are used to take into account the streaming effect caused by the pin cell structure and the surrounding wrapper tube structure. The heterogeneity of wrapper tube and its surrounding sodium is explicitly considered. The streaming effect is evaluated based on Benoist's diffusion coefficient. The total streaming effect caused by the double heterogeneity structure of a fuel subassembly is found to be -0.2 % dk/kk' for k eff , which is almost twice that obtained from the conventional pin cell model of -0.1 % dk/kk'. (author)
Programming strategy for efficient modeling of dynamics in a population of heterogeneous cells.
Hald, Bjørn Olav; Garkier Hendriksen, Morten; Sørensen, Preben Graae
2013-05-15
Heterogeneity is a ubiquitous property of biological systems. Even in a genetically identical population of a single cell type, cell-to-cell differences are observed. Although the functional behavior of a given population is generally robust, the consequences of heterogeneity are fairly unpredictable. In heterogeneous populations, synchronization of events becomes a cardinal problem-particularly for phase coherence in oscillating systems. The present article presents a novel strategy for construction of large-scale simulation programs of heterogeneous biological entities. The strategy is designed to be tractable, to handle heterogeneity and to handle computational cost issues simultaneously, primarily by writing a generator of the 'model to be simulated'. We apply the strategy to model glycolytic oscillations among thousands of yeast cells coupled through the extracellular medium. The usefulness is illustrated through (i) benchmarking, showing an almost linear relationship between model size and run time, and (ii) analysis of the resulting simulations, showing that contrary to the experimental situation, synchronous oscillations are surprisingly hard to achieve, underpinning the need for tools to study heterogeneity. Thus, we present an efficient strategy to model the biological heterogeneity, neglected by ordinary mean-field models. This tool is well posed to facilitate the elucidation of the physiologically vital problem of synchronization. The complete python code is available as Supplementary Information. bjornhald@gmail.com or pgs@kiku.dk Supplementary data are available at Bioinformatics online.
Kang, P. K.; Le Borgne, T.; Dentz, M.; Bour, O.; Juanes, R.
2014-12-01
Quantitative modeling of flow and transport through fractured geological media is challenging due to the inaccessibility of the underlying medium properties and the complex interplay between heterogeneity and small scale transport processes such as heterogeneous advection, matrix diffusion, hydrodynamic dispersion and adsorption. This complex interplay leads to anomalous (non-Fickian) transport behavior, the origin of which remains a matter of debate: whether it arises from variability in fracture permeability (velocity heterogeneity), connectedness in the fracture network (velocity correlation), or interaction between fractures and matrix. Here we show that this uncertainty of heterogeneity- vs. correlation-controlled transport can be resolved by combining convergent and push-pull tracer tests because flow reversibility is strongly dependent on correlation, whereas late-time scaling of breakthrough curves is mainly controlled by heterogeneity. We build on this insight, and propose a Lagrangian statistical model that takes the form of a continuous time random walk (CTRW) with correlated particle velocities. In this framework, flow heterogeneity and flow correlation are quantified by a Markov process of particle transition times that is characterized by a distribution function and a transition probability. Our transport model captures the anomalous behavior in the breakthrough curves for both push-pull and convergent flow geometries, with the same set of parameters. We validate our model in the Ploemeur observatory in France. Thus, the proposed correlated CTRW modeling approach provides a simple yet powerful framework for characterizing the impact of flow correlation and heterogeneity on transport in fractured media.
Stochastic modeling for reliability shocks, burn-in and heterogeneous populations
Finkelstein, Maxim
2013-01-01
Focusing on shocks modeling, burn-in and heterogeneous populations, Stochastic Modeling for Reliability naturally combines these three topics in the unified stochastic framework and presents numerous practical examples that illustrate recent theoretical findings of the authors. The populations of manufactured items in industry are usually heterogeneous. However, the conventional reliability analysis is performed under the implicit assumption of homogeneity, which can result in distortion of the corresponding reliability indices and various misconceptions. Stochastic Modeling for Reliability fills this gap and presents the basics and further developments of reliability theory for heterogeneous populations. Specifically, the authors consider burn-in as a method of elimination of ‘weak’ items from heterogeneous populations. The real life objects are operating in a changing environment. One of the ways to model an impact of this environment is via the external shocks occurring in accordance with some stocha...
A Multianalyzer Machine Learning Model for Marine Heterogeneous Data Schema Mapping
Directory of Open Access Journals (Sweden)
Wang Yan
2014-01-01
Full Text Available The main challenges that marine heterogeneous data integration faces are the problem of accurate schema mapping between heterogeneous data sources. In order to improve the schema mapping efficiency and get more accurate learning results, this paper proposes a heterogeneous data schema mapping method basing on multianalyzer machine learning model. The multianalyzer analysis the learning results comprehensively, and a fuzzy comprehensive evaluation system is introduced for output results’ evaluation and multi factor quantitative judging. Finally, the data mapping comparison experiment on the East China Sea observing data confirms the effectiveness of the model and shows multianalyzer’s obvious improvement of mapping error rate.
Energy Technology Data Exchange (ETDEWEB)
Bisht, Gautam; Huang, Maoyi; Zhou, Tian; Chen, Xingyuan; Dai, Heng; Hammond, Glenn E.; Riley, William J.; Downs, Janelle L.; Liu, Ying; Zachara, John M.
2017-01-01
A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion
Directory of Open Access Journals (Sweden)
G. Bisht
2017-12-01
Full Text Available A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5 and a massively parallel multiphysics reactive transport model (PFLOTRAN. The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater–river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater–river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater–river-water exchange at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result
Bisht, Gautam; Huang, Maoyi; Zhou, Tian; Chen, Xingyuan; Dai, Heng; Hammond, Glenn E.; Riley, William J.; Downs, Janelle L.; Liu, Ying; Zachara, John M.
2017-12-01
A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater-river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater-river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater-river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion into the
Bezbaruah, Achintya N; Zhang, Tian C
2009-01-01
It has been long established that plants play major roles in a treatment wetland. However, the role of plants has not been incorporated into wetland models. This study tries to incorporate wetland plants into a biochemical oxygen demand (BOD) model so that the relative contributions of the aerobic and anaerobic processes to meeting BOD can be quantitatively determined. The classical dissolved oxygen (DO) deficit model has been modified to simulate the DO curve for a field subsurface flow constructed wetland (SFCW) treating municipal wastewater. Sensitivities of model parameters have been analyzed. Based on the model it is predicted that in the SFCW under study about 64% BOD are degraded through aerobic routes and 36% is degraded anaerobically. While not exhaustive, this preliminary work should serve as a pointer for further research in wetland model development and to determine the values of some of the parameters used in the modified DO deficit and associated BOD model. It should be noted that nitrogen cycle and effects of temperature have not been addressed in these models for simplicity of model formulation. This paper should be read with this caveat in mind.
Boosting iterative stochastic ensemble method for nonlinear calibration of subsurface flow models
Elsheikh, Ahmed H.
2013-06-01
A novel parameter estimation algorithm is proposed. The inverse problem is formulated as a sequential data integration problem in which Gaussian process regression (GPR) is used to integrate the prior knowledge (static data). The search space is further parameterized using Karhunen-Loève expansion to build a set of basis functions that spans the search space. Optimal weights of the reduced basis functions are estimated by an iterative stochastic ensemble method (ISEM). ISEM employs directional derivatives within a Gauss-Newton iteration for efficient gradient estimation. The resulting update equation relies on the inverse of the output covariance matrix which is rank deficient.In the proposed algorithm we use an iterative regularization based on the ℓ2 Boosting algorithm. ℓ2 Boosting iteratively fits the residual and the amount of regularization is controlled by the number of iterations. A termination criteria based on Akaike information criterion (AIC) is utilized. This regularization method is very attractive in terms of performance and simplicity of implementation. The proposed algorithm combining ISEM and ℓ2 Boosting is evaluated on several nonlinear subsurface flow parameter estimation problems. The efficiency of the proposed algorithm is demonstrated by the small size of utilized ensembles and in terms of error convergence rates. © 2013 Elsevier B.V.
Unobserved Heterogeneity in the Binary Logit Model with Cross-Sectional Data and Short Panels
DEFF Research Database (Denmark)
Holm, Anders; Jæger, Mads Meier; Pedersen, Morten
This paper proposes a new approach to dealing with unobserved heterogeneity in applied research using the binary logit model with cross-sectional data and short panels. Unobserved heterogeneity is particularly important in non-linear regression models such as the binary logit model because, unlike...... in linear regression models, estimates of the effects of observed independent variables are biased even when omitted independent variables are uncorrelated with the observed independent variables. We propose an extension of the binary logit model based on a finite mixture approach in which we conceptualize...
Lifetime of dynamic heterogeneity in strong and fragile kinetically constrained spin models
International Nuclear Information System (INIS)
Leonard, Sebastien; Berthier, Ludovic
2005-01-01
Kinetically constrained spin models are schematic coarse-grained models for the glass transition which represent an efficient theoretical tool to study detailed spatio-temporal aspects of dynamic heterogeneity in supercooled liquids. Here, we study how spatially correlated dynamic domains evolve with time and compare our results to various experimental and numerical investigations. We find that strong and fragile models yield different results. In particular, the lifetime of dynamic heterogeneity remains constant and roughly equal to the alpha relaxation time in strong models, while it increases more rapidly in fragile models when the glass transition is approached
International Nuclear Information System (INIS)
Lü, Xiaoshu; Lu, Tao; Kibert, Charles J.; Viljanen, Martti
2015-01-01
Highlights: • This paper presents a new modeling method to forecast energy demands. • The model is based on physical–statistical approach to improving forecast accuracy. • A new method is proposed to address the heterogeneity challenge. • Comparison with measurements shows accurate forecasts of the model. • The first physical–statistical/heterogeneous building energy modeling approach is proposed and validated. - Abstract: Energy consumption forecasting is a critical and necessary input to planning and controlling energy usage in the building sector which accounts for 40% of the world’s energy use and the world’s greatest fraction of greenhouse gas emissions. However, due to the diversity and complexity of buildings as well as the random nature of weather conditions, energy consumption and loads are stochastic and difficult to predict. This paper presents a new methodology for energy demand forecasting that addresses the heterogeneity challenges in energy modeling of buildings. The new method is based on a physical–statistical approach designed to account for building heterogeneity to improve forecast accuracy. The physical model provides a theoretical input to characterize the underlying physical mechanism of energy flows. Then stochastic parameters are introduced into the physical model and the statistical time series model is formulated to reflect model uncertainties and individual heterogeneity in buildings. A new method of model generalization based on a convex hull technique is further derived to parameterize the individual-level model parameters for consistent model coefficients while maintaining satisfactory modeling accuracy for heterogeneous buildings. The proposed method and its validation are presented in detail for four different sports buildings with field measurements. The results show that the proposed methodology and model can provide a considerable improvement in forecasting accuracy
Directory of Open Access Journals (Sweden)
Stephen T. THRELKELD
2000-08-01
Full Text Available We compared the use of ternary and bivariate diagrams to distinguish the effects of atmospheric precipitation, rock weathering, and evaporation on inland surface and subsurface water chemistry. The three processes could not be statistically differentiated using bivariate models even if large water bodies were evaluated separate from small water bodies. Atmospheric precipitation effects were identified using ternary diagrams in water with total dissolved salts (TDS 1000 mg l-1. A principal components analysis showed that the variability in the relative proportions of the major ions was related to atmospheric precipitation, weathering, and evaporation. About half of the variation in the distribution of inorganic ions was related to rock weathering. By considering most of the important inorganic ions, ternary diagrams are able to distinguish the contributions of atmospheric precipitation, rock weathering, and evaporation to inland water chemistry.
Elsheikh, Ahmed H.
2013-06-01
We introduce a nonlinear orthogonal matching pursuit (NOMP) for sparse calibration of subsurface flow models. Sparse calibration is a challenging problem as the unknowns are both the non-zero components of the solution and their associated weights. NOMP is a greedy algorithm that discovers at each iteration the most correlated basis function with the residual from a large pool of basis functions. The discovered basis (aka support) is augmented across the nonlinear iterations. Once a set of basis functions are selected, the solution is obtained by applying Tikhonov regularization. The proposed algorithm relies on stochastically approximated gradient using an iterative stochastic ensemble method (ISEM). In the current study, the search space is parameterized using an overcomplete dictionary of basis functions built using the K-SVD algorithm. The proposed algorithm is the first ensemble based algorithm that tackels the sparse nonlinear parameter estimation problem. © 2013 Elsevier Ltd.
Simulation study of axial ultrasound transmission in heterogeneous cortical bone model
Takano, Koki; Nagatani, Yoshiki; Matsukawa, Mami
2017-07-01
Ultrasound propagation in a heterogeneous cortical bone was studied. Using a bovine radius, the longitudinal wave velocity distribution in the axial direction was experimentally measured in the MHz range. The bilinear interpolation and piecewise cubic Hermite interpolation methods were applied to create a three-dimensional (3D) precise velocity model of the bone using experimental data. By assuming the uniaxial anisotropy of the bone, the distributions of all elastic moduli of a 3D heterogeneous model were estimated. The elastic finite-difference time-domain method was used to simulate axial ultrasonic wave propagation. The wave propagation in the initial model was compared with that in the thinner model, where the inner part of the cortical bone model was removed. The wave front of the first arriving signal (FAS) slightly depended on the heterogeneity in each model. Owing to the decrease in bone thickness, the propagation behavior also changed and the FAS velocity clearly decreased.
Petrov, P.; Newman, G. A.
2011-12-01
Recent developments in high resolution imaging technology of subsurface objects involves a combination of different geophysical measurements (gravity, EM and seismic). A joint image of the subsurface geophysical attributes (velocity, electrical conductivity and density) requires the consistent treatment of the different geophysical data due to their differing physical nature. For example, in conducting media, which is typical of the Earth's interior, EM energy propagation is defined by a diffusive mechanism and may be characterized by two specific length scales: wavelength and skin depth. However, the propagation of seismic signals is a multiwave process and is characterized by a set of wavelengths. Thus, to consistently treat seismic and electromagnetic data an additional length scale is needed for seismic data that does not directly depend on a wavelength and describes a diffusive process, similar to EM wave propagation in the subsurface. Works by Brown et al.(2005), Shin and Cha(2008), and Shin and Ha(2008) suggest that an artificial damping of seismic wave fields via Laplace-Fourier transformation can be an effective approach to obtain a seismic data that have similar spatial resolution to EM data. The key benefit of such transformation is that diffusive wave-field inversion works well for both data sets: seismic (Brown et al.,2005; Shin and Cha,2008) and electromagnetic (Commer and Newman,2008; Newman et al.,2010). With the recent interest in the Laplace-Fourier domain full waveform inversion, 3D fourth and second-order finite-difference schemes for modeling of seismic wave propagation have been developed (Petrov and Newman, 2010). Incorporation of attenuation and anisotropy into a velocity model is a necessary step for a more realistic description of subsurface media. Here we consider the extension of our method which includes attenuation and VTI anisotropy. Our approach is based on the integro-interpolation technique for velocity-stress formulation. Seven
Experimental methods and modeling techniques for description of cell population heterogeneity
DEFF Research Database (Denmark)
Lencastre Fernandes, Rita; Nierychlo, M.; Lundin, L.
2011-01-01
With the continuous development, in the last decades, of analytical techniques providing complex information at single cell level, the study of cell heterogeneity has been the focus of several research projects within analytical biotechnology. Nonetheless, the complex interplay between...... environmental changes and cellular responses is yet not fully understood, and the integration of this new knowledge into the strategies for design, operation and control of bioprocesses is far from being an established reality. Indeed, the impact of cell heterogeneity on productivity of large scale cultivations...... methods for monitoring cell population heterogeneity as well as model frameworks suitable for describing dynamic heterogeneous cell populations. We will furthermore underline the highly important coordination between experimental and modeling efforts necessary to attain a reliable quantitative description...
Directory of Open Access Journals (Sweden)
Akanda Md. Abdus Salam
2017-03-01
Full Text Available Individual heterogeneity in capture probabilities and time dependence are fundamentally important for estimating the closed animal population parameters in capture-recapture studies. A generalized estimating equations (GEE approach accounts for linear correlation among capture-recapture occasions, and individual heterogeneity in capture probabilities in a closed population capture-recapture individual heterogeneity and time variation model. The estimated capture probabilities are used to estimate animal population parameters. Two real data sets are used for illustrative purposes. A simulation study is carried out to assess the performance of the GEE estimator. A Quasi-Likelihood Information Criterion (QIC is applied for the selection of the best fitting model. This approach performs well when the estimated population parameters depend on the individual heterogeneity and the nature of linear correlation among capture-recapture occasions.
Program overview: Subsurface science program
International Nuclear Information System (INIS)
1994-03-01
The OHER Subsurface Science Program is DOE's core basic research program concerned with subsoils and groundwater. These practices have resulted in contamination by mixtures of organic chemicals, inorganic chemicals, and radionuclides. A primary long-term goal is to provide a foundation of knowledge that will lead to the reduction of environmental risks and to cost-effective cleanup strategies. Since the Program was initiated in 1985, a substantial amount of research in hydrogeology, subsurface microbiology, and the geochemistry of organically complexed radionuclides has been completed, leading to a better understanding of contaminant transport in groundwater and to new insights into microbial distribution and function in the subsurface environments. The Subsurface Science Program focuses on achieving long-term scientific advances that will assist DOE in the following key areas: providing the scientific basis for innovative in situ remediation technologies that are based on a concept of decontamination through benign manipulation of natural systems; understanding the complex mechanisms and process interactions that occur in the subsurface; determining the influence of chemical and geochemical-microbial processes on co-contaminant mobility to reduce environmental risks; improving predictions of contaminant transport that draw on fundamental knowledge of contaminant behavior in the presence of physical and chemical heterogeneities to improve cleanup effectiveness and to predict environmental risks
Nitrate reduction in geologically heterogeneous catchments
DEFF Research Database (Denmark)
Refsgaard, Jens Christian; Auken, Esben; Bamberg, Charlotte A.
2014-01-01
In order to fulfil the requirements of the EU Water Framework Directive nitrate load from agricultural areas to surface water in Denmark needs to be reduced by about 40%. The regulations imposed until now have been uniform, i.e. the same restrictions for all areas independent of the subsurface...... conditions. Studies have shown that on a national basis about 2/3 of the nitrate leaching from the root zone is reduced naturally, through denitrification, in the subsurface before reaching the streams. Therefore, it is more cost-effective to identify robust areas, where nitrate leaching through the root...... the entire catchment. However, as distributed models often do not include local scale hydrogeological heterogeneities, they are typically not able to make accurate predictions at scales smaller than they are calibrated. We present a framework for assessing nitrate reduction in the subsurface...
Ciliary heterogeneity within a single cell: the Paramecium model.
Aubusson-Fleury, Anne; Cohen, Jean; Lemullois, Michel
2015-01-01
Paramecium is a single cell able to divide in its morphologically differentiated stage that has many cilia anchored at its cell surface. Many thousands of cilia are thus assembled in a short period of time during division to duplicate the cell pattern while the cell continues swimming. Most, but not all, of these sensory cilia are motile and involved in two main functions: prey capture and cell locomotion. These cilia display heterogeneity, both in their length and their biochemical properties. Thanks to these properties, as well as to the availability of many postgenomic tools and the possibility to follow the regrowth of cilia after deciliation, Paramecium offers a nice opportunity to study the assembly of the cilia, as well as the genesis of their diversity within a single cell. In this paper, after a brief survey of Paramecium morphology and cilia properties, we describe the tools and the protocols currently used for immunofluorescence, transmission electron microscopy, and ultrastructural immunocytochemistry to analyze cilia, with special recommendations to overcome the problem raised by cilium diversity. Copyright © 2015. Published by Elsevier Inc.
Revealing spatially heterogeneous relaxation in a model nanocomposite
Energy Technology Data Exchange (ETDEWEB)
Cheng, Shiwang; Bocharova, Vera [Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Mirigian, Stephen; Schweizer, Kenneth S. [Department of Materials Science and Chemistry, Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States); Carrillo, Jan-Michael Y.; Sumpter, Bobby G. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Sokolov, Alexei P., E-mail: sokolov@utk.edu [Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Department of Chemistry, Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States)
2015-11-21
The detailed nature of spatially heterogeneous dynamics of glycerol-silica nanocomposites is unraveled by combining dielectric spectroscopy with atomistic simulation and statistical mechanical theory. Analysis of the spatial mobility gradient shows no “glassy” layer, but the α-relaxation time near the nanoparticle grows with cooling faster than the α-relaxation time in the bulk and is ∼20 times longer at low temperatures. The interfacial layer thickness increases from ∼1.8 nm at higher temperatures to ∼3.5 nm upon cooling to near bulk T{sub g}. A real space microscopic description of the mobility gradient is constructed by synergistically combining high temperature atomistic simulation with theory. Our analysis suggests that the interfacial slowing down arises mainly due to an increase of the local cage scale barrier for activated hopping induced by enhanced packing and densification near the nanoparticle surface. The theory is employed to predict how local surface densification can be manipulated to control layer dynamics and shear rigidity over a wide temperature range.
Evaluating 3-D and 1-D mathematical models for mass transport in heterogeneous biofilms
DEFF Research Database (Denmark)
Morgenroth, Eberhard Friedrich; Eberl, H.; van Loosdrecht, M. C. M.
2000-01-01
Results from a three dimensional model for heterogeneous biofilms including the numerical solution of hydrodynamics were compared to simplified one dimensional models. A one dimensional model with a variable diffusion coefficient over the thickness of the biofilm was well suited to approximate av...... in a growing biofilm and in a mushroom type biofilm assuming different modes of detachment....
Surface-complexation models for sorption onto heterogeneous surfaces
International Nuclear Information System (INIS)
Harvey, K.B.
1997-10-01
This report provides a description of the discrete-logK spectrum model, together with a description of its derivation, and of its place in the larger context of surface-complexation modelling. The tools necessary to apply the discrete-logK spectrum model are discussed, and background information appropriate to this discussion is supplied as appendices. (author)
Modelling heterogeneity of concrete using 2D lattice network for ...
Indian Academy of Sciences (India)
In this paper, numerical modelling of fracture in concrete using two-dimensional lattice model is presented and also a few issues related to lattice modelling technique applicable to concrete fracture are reviewed. A comparison is made with acoustic emission (AE) events with the number of fractured elements. To implement ...
Gosses, M. J.; Wöhling, Th.; Moore, C. R.; Dann, R.; Scott, D. M.; Close, M.
2012-04-01
-specific prediction target under consideration. Therefore, the worth of individual observation locations may differ for different prediction targets. Our evaluation is based on predictions of lowland stream discharge resulting from changes in land use and irrigation in the upper Central Plains catchment. In our analysis, we adopt the model predictive uncertainty analysis method by Moore and Doherty (2005) which accounts for contributions from both measurement errors and uncertain structural heterogeneity. The method is robust and efficient due to a linearity assumption in the governing equations and readily implemented for application in the model-independent parameter estimation and uncertainty analysis toolkit PEST (Doherty, 2010). The proposed methods can be applied not only for the evaluation of monitoring networks, but also for the optimization of networks, to compare alternative monitoring strategies, as well as to identify best cost-benefit monitoring design even prior to any data acquisition.
Holloway, Jean E.; Rudy, Ashley C. A.; Lamoureux, Scott F.; Treitz, Paul M.
2017-06-01
Warming of the Arctic in recent years has led to changes in the active layer and uppermost permafrost. In particular, thick active layer formation results in more frequent thaw of the ice-rich transient layer. This addition of moisture, as well as infiltration from late season precipitation, results in high pore-water pressures (PWPs) at the base of the active layer and can potentially result in landscape degradation. To predict areas that have the potential for subsurface pressurization, we use susceptibility maps generated using a generalized additive model (GAM). As model response variables, we used active layer detachments (ALDs) and mud ejections (MEs), both formed by high PWP conditions at the Cape Bounty Arctic Watershed Observatory, Melville Island, Canada. As explanatory variables, we used the terrain characteristics elevation, slope, distance to water, topographic position index (TPI), potential incoming solar radiation (PISR), distance to water, normalized difference vegetation index (NDVI; ME model only), geology, and topographic wetness index (TWI). ALDs and MEs were accurately modelled in terms of susceptibility to disturbance across the study area. The susceptibility models demonstrate that ALDs are most probable on hill slopes with gradual to steep slopes and relatively low PISR, whereas MEs are associated with higher elevation areas, lower slope angles, and areas relatively far from water. Based on these results, this method identifies areas that may be sensitive to high PWPs and helps improve our understanding of geomorphic sensitivity to permafrost degradation.
Directory of Open Access Journals (Sweden)
J. E. Holloway
2017-06-01
Full Text Available Warming of the Arctic in recent years has led to changes in the active layer and uppermost permafrost. In particular, thick active layer formation results in more frequent thaw of the ice-rich transient layer. This addition of moisture, as well as infiltration from late season precipitation, results in high pore-water pressures (PWPs at the base of the active layer and can potentially result in landscape degradation. To predict areas that have the potential for subsurface pressurization, we use susceptibility maps generated using a generalized additive model (GAM. As model response variables, we used active layer detachments (ALDs and mud ejections (MEs, both formed by high PWP conditions at the Cape Bounty Arctic Watershed Observatory, Melville Island, Canada. As explanatory variables, we used the terrain characteristics elevation, slope, distance to water, topographic position index (TPI, potential incoming solar radiation (PISR, distance to water, normalized difference vegetation index (NDVI; ME model only, geology, and topographic wetness index (TWI. ALDs and MEs were accurately modelled in terms of susceptibility to disturbance across the study area. The susceptibility models demonstrate that ALDs are most probable on hill slopes with gradual to steep slopes and relatively low PISR, whereas MEs are associated with higher elevation areas, lower slope angles, and areas relatively far from water. Based on these results, this method identifies areas that may be sensitive to high PWPs and helps improve our understanding of geomorphic sensitivity to permafrost degradation.
Energy Technology Data Exchange (ETDEWEB)
Oostrom, Mart; Thorne, Paul D.; Zhang, Z. F.; Last, George V.; Truex, Michael J.
2008-12-17
Three-dimensional simulations considered migration of dense, nonaqueous phase liquid (DNAPL) consisting of CT and co disposed organics in the subsurface as a function of the properties and distribution of subsurface sediments and of the properties and disposal history of the waste. Simulations of CT migration were conducted using the Water-Oil-Air mode of Subsurface Transport Over Multiple Phases (STOMP) simulator. A large-scale model was configured to model CT and waste water discharge from the major CT and waste-water disposal sites.
Lowry, B. W.; Zhou, W.; Smartgeo
2010-12-01
The Muddy Creek landslide complex is a large area of active and reactivating landslides that impact the operation of both a state highway and Paonia Reservoir in Gunnison County, Colorado, United States. Historically, the monitoring of this slide has been investigated using disparate techniques leading to protracted analysis and project knowledge attrition. We present an integrated, data-driven investigation framework that supports continued kinematic monitoring, document cataloging, and subsurface modeling of the landslide complex. A geospatial information system (GIS) was integrated with a visual programming based subsurface model to facilitate modular integration of monitoring data with borehole information. Subsurface modeling was organized by material type and activity state based on multiple sources of kinematic measurement. The framework is constructed to modularly integrate remotely sensed imagery and other spatial datasets such as ASTER, InSAR, and LiDAR derived elevation products as more precise datasets become available. The framework allows for terrestrial LiDAR survey error estimation, borehole siting, and placement of wireless sensor (GPS, accelerometers, geophysical ) networks for optimized spatial relevance and utility. Coordinated spatial referencing within the GIS facilitates geotechnical and hydrogeological modeling input generation and common display of modeling outputs. Kinematic data fusion techniques are accomplished with integration of instrumentation, surficial feature tracking, subsurface classification, and 3D interpolation. The framework includes dynamic decision support including landslide dam failure estimates, back-flooding scenario planning that can be accessed by multiple agencies and stakeholders.
Discrete time duration models with group-level heterogeneity
DEFF Research Database (Denmark)
Frederiksen, Anders; Honoré, Bo; Hu, Loujia
2007-01-01
Dynamic discrete choice panel data models have received a great deal of attention. In those models, the dynamics is usually handled by including the lagged outcome as an explanatory variable. In this paper we consider an alternative model in which the dynamics is handled by using the duration...... in the current state as a covariate. We propose estimators that allow for group-specific effect in parametric and semiparametric versions of the model. The proposed method is illustrated by an empirical analysis of job durations allowing for firm-level effects....
Directory of Open Access Journals (Sweden)
C. Lanni
2012-11-01
Full Text Available Topographic index-based hydrological models have gained wide use to describe the hydrological control on the triggering of rainfall-induced shallow landslides at the catchment scale. A common assumption in these models is that a spatially continuous water table occurs simultaneously across the catchment. However, during a rainfall event isolated patches of subsurface saturation form above an impeding layer and their hydrological connectivity is a necessary condition for lateral flow initiation at a point on the hillslope.
Here, a new hydrological model is presented, which allows us to account for the concept of hydrological connectivity while keeping the simplicity of the topographic index approach. A dynamic topographic index is used to describe the transient lateral flow that is established at a hillslope element when the rainfall amount exceeds a threshold value allowing for (a development of a perched water table above an impeding layer, and (b hydrological connectivity between the hillslope element and its own upslope contributing area. A spatially variable soil depth is the main control of hydrological connectivity in the model. The hydrological model is coupled with the infinite slope stability model and with a scaling model for the rainfall frequency–duration relationship to determine the return period of the critical rainfall needed to cause instability on three catchments located in the Italian Alps, where a survey of soil depth spatial distribution is available. The model is compared with a quasi-dynamic model in which the dynamic nature of the hydrological connectivity is neglected. The results show a better performance of the new model in predicting observed shallow landslides, implying that soil depth spatial variability and connectivity bear a significant control on shallow landsliding.
Using Dirichlet Processes for Modeling Heterogeneous Treatment Effects across Sites
Miratrix, Luke; Feller, Avi; Pillai, Natesh; Pati, Debdeep
2016-01-01
Modeling the distribution of site level effects is an important problem, but it is also an incredibly difficult one. Current methods rely on distributional assumptions in multilevel models for estimation. There it is hoped that the partial pooling of site level estimates with overall estimates, designed to take into account individual variation as…
Moghadas, D.; André, F.; Vereecken, H.; Lambot, S.
2009-04-01
Water is a vital resource for human needs, agriculture, sanitation and industrial supply. The knowledge of soil water dynamics and solute transport is essential in agricultural and environmental engineering as it controls plant growth, hydrological processes, and the contamination of surface and subsurface water. Increased irrigation efficiency has also an important role for water conservation, reducing drainage and mitigating some of the water pollution and soil salinity. Geophysical methods are effective techniques for monitoring the vadose zone. In particular, electromagnetic induction (EMI) can provide in a non-invasive way important information about the soil electrical properties at the field scale, which are mainly correlated to important variables such as soil water content, salinity, and texture. EMI is based on the radiation of a VLF EM wave into the soil. Depending on its electrical conductivity, Foucault currents are generated and produce a secondary EM field which is then recorded by the EMI system. Advanced techniques for EMI data interpretation resort to inverse modeling. Yet, a major gap in current knowledge is the limited accuracy of the forward model used for describing the EMI-subsurface system, usually relying on strongly simplifying assumptions. We present a new low frequency EMI method based on Vector Network Analyzer (VNA) technology and advanced forward modeling using a linear system of complex transfer functions for describing the EMI loop antenna and a three-dimensional solution of Maxwell's equations for wave propagation in multilayered media. VNA permits simple, international standard calibration of the EMI system. We derived a Green's function for the zero-offset, off-ground horizontal loop antenna and also proposed an optimal integration path for faster evaluation of the spatial-domain Green's function from its spectral counterpart. This new integration path shows fewer oscillations compared with the real path and permits to avoid the
Cook, Wesley G; Arechiga, Adam; Dobson, Leslie Ann V; Boyd, Kenny
2014-04-01
In the United States, there is currently an increase in admissions to psychiatric hospitals, diagnostic heterogeneity, briefer stays, and a lack of inpatient research. Most traditional group therapy models are constructed for longer-term homogeneous patients. Diagnostically homogeneous groups even outperform heterogeneous groups. However, changes in health care have created a clinical dilemma in psychiatric hospitals where groups have become characterized by brief duration, rapid turnover, and diagnostic heterogeneity. A literature review offered little in the way of treatment recommendations, let alone a model or empirical basis, for facilitating these types of groups. Common factors from group therapy studies were extracted. Based on an integration of these studies, a process-oriented psychoeducational (POP) treatment model is recommended. This model is theoretically constructed and outlined for future study.
Li, Wei; Zhang, Yan; Cui, Lijuan; Zhang, Manyin; Wang, Yifei
2015-08-01
A horizontal subsurface flow constructed wetland (HSSF-CW) was designed to improve the water quality of an artificial lake in Beijing Wildlife Rescue and Rehabilitation Center, Beijing, China. Artificial neural networks (ANNs), including multilayer perceptron (MLP) and radial basis function (RBF), were used to model the removal of total phosphorus (TP). Four variables were selected as the input parameters based on the principal component analysis: the influent TP concentration, water temperature, flow rate, and porosity. In order to improve model accuracy, alternative ANNs were developed by incorporating meteorological variables, including precipitation, air humidity, evapotranspiration, solar heat flux, and barometric pressure. A genetic algorithm and cross-validation were used to find the optimal network architectures for the ANNs. Comparison of the observed data and the model predictions indicated that, with careful variable selection, ANNs appeared to be an efficient and robust tool for predicting TP removal in the HSSF-CW. Comparison of the accuracy and efficiency of MLP and RBF for predicting TP removal showed that the RBF with additional meteorological variables produced the most accurate results, indicating a high potentiality for modeling TP removal in the HSSF-CW.
Ellis, Jonathan S; Bazylak, Aimy
2012-06-21
Trapping of carbon in deep underground brine-filled reservoirs is a promising approach for the reduction of atmospheric greenhouse gas emissions. However, estimation of the amount of carbon dioxide (CO(2)) that can be captured in a given reservoir and the long-term storage stability remain a challenge. One difficulty lies in the estimation of local capillary pressure effects that arise from mineral surface heterogeneity inherent in underground geological formations. As a preliminary step to address this issue, we have performed dynamic pore network modelling (PNM) simulations of two-phase immiscible flow in two-dimensional structured porous media with contact angle heterogeneity under typical reservoir conditions. We begin by characterizing the network with a single, uniform contact angle. We then present saturation patterns for networks with homogeneous and heterogeneous contact angles distributions, based on two common reservoir minerals: quartz and mica, both of which have been well-characterized experimentally for their brine-CO(2) contact angles. At lower flow rates, we found moderately higher saturations for the heterogeneous networks than for the homogeneous ones. To characterize the fingering patterns, we have introduced R as the ratio of filled throats to the total network saturation. Based on this measure, the heterogeneous networks demonstrated thicker fingering patterns than the homogeneous networks. The computed saturation patterns demonstrate the importance of considering surface heterogeneity in pore-scale modelling of deep saline aquifers.
Advective transport in heterogeneous aquifers: Are proxy models predictive?
Fiori, A.; Zarlenga, A.; Gotovac, H.; Jankovic, I.; Volpi, E.; Cvetkovic, V.; Dagan, G.
2015-12-01
We examine the prediction capability of two approximate models (Multi-Rate Mass Transfer (MRMT) and Continuous Time Random Walk (CTRW)) of non-Fickian transport, by comparison with accurate 2-D and 3-D numerical simulations. Both nonlocal in time approaches circumvent the need to solve the flow and transport equations by using proxy models to advection, providing the breakthrough curves (BTC) at control planes at any x, depending on a vector of five unknown parameters. Although underlain by different mechanisms, the two models have an identical structure in the Laplace Transform domain and have the Markovian property of independent transitions. We show that also the numerical BTCs enjoy the Markovian property. Following the procedure recommended in the literature, along a practitioner perspective, we first calibrate the parameters values by a best fit with the numerical BTC at a control plane at x1, close to the injection plane, and subsequently use it for prediction at further control planes for a few values of σY2≤8. Due to a similar structure and Markovian property, the two methods perform equally well in matching the numerical BTC. The identified parameters are generally not unique, making their identification somewhat arbitrary. The inverse Gaussian model and the recently developed Multi-Indicator Model (MIM), which does not require any fitting as it relates the BTC to the permeability structure, are also discussed. The application of the proxy models for prediction requires carrying out transport field tests of large plumes for a long duration.
A mixture model for expression deconvolution from RNA-seq in heterogeneous tissues.
Li, Yi; Xie, Xiaohui
2013-01-01
RNA-seq, a next-generation sequencing based method for transcriptome analysis, is rapidly emerging as the method of choice for comprehensive transcript abundance estimation. The accuracy of RNA-seq can be highly impacted by the purity of samples. A prominent, outstanding problem in RNA-seq is how to estimate transcript abundances in heterogeneous tissues, where a sample is composed of more than one cell type and the inhomogeneity can substantially confound the transcript abundance estimation of each individual cell type. Although experimental methods have been proposed to dissect multiple distinct cell types, computationally "deconvoluting" heterogeneous tissues provides an attractive alternative, since it keeps the tissue sample as well as the subsequent molecular content yield intact. Here we propose a probabilistic model-based approach, Transcript Estimation from Mixed Tissue samples (TEMT), to estimate the transcript abundances of each cell type of interest from RNA-seq data of heterogeneous tissue samples. TEMT incorporates positional and sequence-specific biases, and its online EM algorithm only requires a runtime proportional to the data size and a small constant memory. We test the proposed method on both simulation data and recently released ENCODE data, and show that TEMT significantly outperforms current state-of-the-art methods that do not take tissue heterogeneity into account. Currently, TEMT only resolves the tissue heterogeneity resulting from two cell types, but it can be extended to handle tissue heterogeneity resulting from multi cell types. TEMT is written in python, and is freely available at https://github.com/uci-cbcl/TEMT. The probabilistic model-based approach proposed here provides a new method for analyzing RNA-seq data from heterogeneous tissue samples. By applying the method to both simulation data and ENCODE data, we show that explicitly accounting for tissue heterogeneity can significantly improve the accuracy of transcript abundance
Tran, A. P.; Dafflon, B.; Hubbard, S.
2017-12-01
Soil organic carbon (SOC) is crucial for predicting carbon climate feedbacks in the vulnerable organic-rich Arctic region. However, it is challenging to achieve this property due to the general limitations of conventional core sampling and analysis methods. In this study, we develop an inversion scheme that uses single or multiple datasets, including soil liquid water content, temperature and ERT data, to estimate the vertical profile of SOC content. Our approach relies on the fact that SOC content strongly influences soil hydrological-thermal parameters, and therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. The scheme includes several advantages. First, this is the first time SOC content is estimated by using a coupled hydrogeophysical inversion. Second, by using the Community Land Model, we can account for the land surface dynamics (evapotranspiration, snow accumulation and melting) and ice/liquid phase transition. Third, we combine a deterministic and an adaptive Markov chain Monte Carlo optimization algorithm to better estimate the posterior distributions of desired model parameters. Finally, the simulated subsurface variables are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using synthetic experiments. The results show that compared to inversion of single dataset, joint inversion of these datasets significantly reduces parameter uncertainty. The joint inversion approach is able to estimate SOC content within the shallow active layer with high reliability. Next, we apply the scheme to estimate OC content along an intensive ERT transect in Barrow, Alaska using multiple datasets acquired in the 2013-2015 period. The preliminary results show a good agreement between modeled and measured soil temperature, thaw layer thickness and electrical resistivity. The accuracy of estimated SOC content
Subsurface characterization of 67P/Churyumov-Gerasimenko's Abydos Site
Brugger, B.; Mousis, O.; Morse, A.; Marboeuf, U.; Jorda, L.; Guilbert-Lepoutre, A.; Andrews, D.; Barber, S.; Lamy, P.; Luspay-Kuti, A.; Mandt, K.; Morgan, G.; Sheridan, S.; Vernazza, P.; Wright, I. P.
2015-12-01
We investigate the subsurface structure of comet 67P/Churyumov-Gerasimenko at the landing site of Rosetta's descent module Philae. We use a cometary nucleus model with an optimized parametrization and assume an initial composition derived from Rosetta/ROSINA measurements. We compare the CO and CO_2 outgassing rates derived from our model with those measured in situ by the Ptolemy experiment aboard the Philae module on November 12, 2014. We find results that allow us to place two main constraints on the subsurface structure of this region: a low CO/CO_2 molar ratio is needed in the nucleus, and the dust/ice mass ratio is higher at Abydos than in the rest of the nucleus. These specific constraints on Abydos support the statement of an important heterogeneity in 67P/Churyumov-Gerasimenko's nucleus.
Heterogeneous meshing and biomechanical modeling of human spine.
Teo, J C M; Chui, C K; Wang, Z L; Ong, S H; Yan, C H; Wang, S C; Wong, H K; Teoh, S H
2007-03-01
We aim to develop a patient-specific biomechanical model of human spine for the purpose of surgical training and planning. In this paper, we describe the development of a finite-element model of the spine from the VHD Male Data. The finite-element spine model comprises volumetric elements suitable for deformation and other finite-element analysis using ABAQUS. The mesh generation solution accepts segmented radiological slices as input, and outputs three-dimensional (3D) volumetric finite element meshes that are ABAQUS compliant. The proposed mesh generation method first uses a grid plane to divide the contours of the anatomical boundaries and its inclusions into discrete meshes. A grid frame is then built to connect the grid planes between any two adjacent planes using a novel scheme. The meshes produced consist of brick elements in the interior of the contours and with tetrahedral and wedge elements at the boundaries. The nodal points are classified according to their materials and hence, elements can be assigned different properties. The resultant spine model comprises a detailed model of the 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, and S1. Each of the vertebrae and intervertebral disc has between 1200 and 6000 elements, and approximately 1200 elements, respectively. The accuracy of the resultant VHD finite element spine model was good based on visual comparison of volume-rendered images of the original CT data, and has been used in a computational analysis involving needle insertion and static deformation. We also compared the mesh generated using our method against two automatically generated models; one consists of purely tetrahedral elements and the other hexahedral elements.
Assessing and accounting for time heterogeneity in stochastic actor oriented models
Lospinoso, Joshua A.; Schweinberger, Michael; Snijders, Tom A. B.; Ripley, Ruth M.
This paper explores time heterogeneity in stochastic actor oriented models (SAOM) proposed by Snijders (Sociological methodology. Blackwell, Boston, pp 361-395, 2001) which are meant to study the evolution of networks. SAOMs model social networks as directed graphs with nodes representing people,
E. Korkmaz (Evsen)
2014-01-01
markdownabstract__Abstract__ Recent years have seen many advances in quantitative models in the marketing literature. Even though these advances enable model building for a better understanding of customer purchase behavior and customer heterogeneity such that firms develop optimal targeting and
Heterogeneity in Wage Setting Behavior in a New-Keynesian Model
Eijffinger, S.C.W.; Grajales Olarte, A.; Uras, R.B.
2015-01-01
In this paper we estimate a New-Keynesian DSGE model with heterogeneity in price and wage setting behavior. In a recent study, Coibion and Gorodnichenko (2011) develop a DSGE model, in which firms follow four different types of price setting schemes: sticky prices, sticky information, rule of thumb,
Geng, Xiaolong; Boufadel, Michel C.; Cui, Fangda
2017-08-01
A numerical study was undertaken to investigate subsurface release and fate of benzene and toluene in a tidally influenced beach. The simulations were conducted by using a numerical model BIOMARUN, which coupled a multi-Monod kinetic model BIOB to a density-dependent variably saturated groundwater flow model MARUN. The fate and transport of the contaminant plume were characterized by computing its centroid trajectory, spreading area and percentage of biodegradation in beach saturated and unsaturated zone, respectively. Key factors likely affecting this process were investigated, including tide amplitude, capillarity and hydraulic conductivity. It was found that aerobic biodegradation was the major fate of the contaminant plume in the beach. Tidal action twisted the centroid of the contaminant plume during its migration in the beach, which increased the residence time of the plume in the beach. High tidal range significantly altered the spatial distribution of the contaminant biodegradation in the beach. In contrast, the capillary fringe had impacts on the percentage of benzene biodegraded in the saturated and unsaturated zone of the beach. The increase in capillary fringe enhanced the percentage of the contaminant biodegraded in the unsaturated zone, up to 40%, which is comparable to that in the saturated zone. Hydraulic conductivity seemed to have large impacts on the biodegradation rate of the contaminant in the beach. Higher hydraulic conductivity induced faster contaminant biodegradation in the beach.
DEFF Research Database (Denmark)
Huang, Qian; Huang, Yue-Cai; Ko, King-Tim
2011-01-01
A hierarchical overlay structure is an alternative solution that integrates existing and future heterogeneous wireless networks to provide subscribers with better mobile broadband services. Traffic loss performance in such integrated heterogeneous networks is necessary for an operator's network...... dimensioning and planning. This paper investigates the computationally efficient loss performance modeling for multiservice in hierarchical heterogeneous wireless networks. A speed-sensitive call admission control (CAC) scheme is considered in our model to assign overflowed calls to appropriate tiers....... This approach avoids unnecessary and frequent handoff between cells and reduces signaling overheads. An approximation model with guaranteed accuracy and low computational complexity is presented for the loss performance of multiservice traffic. The accuracy of numerical results is validated by comparing...
Stochastic models of solute transport in highly heterogeneous geologic media
Energy Technology Data Exchange (ETDEWEB)
Semenov, V.N.; Korotkin, I.A.; Pruess, K.; Goloviznin, V.M.; Sorokovikova, O.S.
2009-09-15
A stochastic model of anomalous diffusion was developed in which transport occurs by random motion of Brownian particles, described by distribution functions of random displacements with heavy (power-law) tails. One variant of an effective algorithm for random function generation with a power-law asymptotic and arbitrary factor of asymmetry is proposed that is based on the Gnedenko-Levy limit theorem and makes it possible to reproduce all known Levy {alpha}-stable fractal processes. A two-dimensional stochastic random walk algorithm has been developed that approximates anomalous diffusion with streamline-dependent and space-dependent parameters. The motivation for introducing such a type of dispersion model is the observed fact that tracers in natural aquifers spread at different super-Fickian rates in different directions. For this and other important cases, stochastic random walk models are the only known way to solve the so-called multiscaling fractional order diffusion equation with space-dependent parameters. Some comparisons of model results and field experiments are presented.
Modelling heterogeneity of concrete using 2D lattice network for ...
Indian Academy of Sciences (India)
present work brings out certain finer details which are not available explicitly in the earlier works. Keywords. Concrete fracture; lattice model; Fuller distribution; ... examples are cement mortar and concrete in civil engineering. ..... Although acoustic emission technique is a well established non destructive testing (NDT).
A duopoly model with heterogeneous congestion-sensitive customers
Mandjes, M.R.H.; Timmer, Judith B.
2003-01-01
This paper analyzes a model with multiple firms (providers), and two classes of customers. These customers classes are characterized by their attitude towards `congestion' (caused by other customers using the same resources); a firm is selected on the basis of both the prices charged by the firms,
A duopoly model with heterogeneous congestion-sensitive customers.
Mandjes, M.R.H.; Timmer, J.
2007-01-01
Abstract This paper analyzes a model with two firms (providers), and two classes of customers. These customers classes are characterized by their attitude towards ‘congestion’ (caused by other customers using the same resources); a firm is selected on the basis of both the prices charged by the
A duopoly model with heterogeneous congestion-sensitive customers
Mandjes, M.R.H.; Timmer, Judith B.
This paper analyzes a model with two firms (providers), and two classes of customers. These customers classes are characterized by their attitude towards ‘congestion’ (caused by other customers using the same resources); a firm is selected on the basis of both the prices charged by the firms, and
Confidence Intervals for Assessing Heterogeneity in Generalized Linear Mixed Models
Wagler, Amy E.
2014-01-01
Generalized linear mixed models are frequently applied to data with clustered categorical outcomes. The effect of clustering on the response is often difficult to practically assess partly because it is reported on a scale on which comparisons with regression parameters are difficult to make. This article proposes confidence intervals for…
Directory of Open Access Journals (Sweden)
Spyridon Liakas
2017-08-01
Full Text Available The particulate discrete element method (DEM can be employed to capture the response of rock, provided that appropriate bonding models are used to cement the particles to each other. Simulations of laboratory tests are important to establish the extent to which those models can capture realistic rock behaviors. Hitherto the focus in such comparison studies has either been on homogeneous specimens or use of two-dimensional (2D models. In situ rock formations are often heterogeneous, thus exploring the ability of this type of models to capture heterogeneous material behavior is important to facilitate their use in design analysis. In situ stress states are basically three-dimensional (3D, and therefore it is important to develop 3D models for this purpose. This paper revisits an earlier experimental study on heterogeneous specimens, of which the relative proportions of weaker material (siltstone and stronger, harder material (sandstone were varied in a controlled manner. Using a 3D DEM model with the parallel bond model, virtual heterogeneous specimens were created. The overall responses in terms of variations in strength and stiffness with different percentages of weaker material (siltstone were shown to agree with the experimental observations. There was also a good qualitative agreement in the failure patterns observed in the experiments and the simulations, suggesting that the DEM data enabled analysis of the initiation of localizations and micro fractures in the specimens.
A Unified Model Explaining Heterogeneous Ziegler-Natta Catalysis
Credendino, Raffaele
2015-08-12
We propose a model for MgCl2 supported Ziegler-Natta catalysts capable to reconcile the discrepancies emerged in the last 20 years, when experimental data were tried to be rationalized by molecular models. We show that step defects on the neglected but thermodynamically more stable (104) facet of MgCl2 can lead to sites for strong TiCl4 adsorption. The corresponding Ti-active site is stereoeselective, and its stereoselectivity can be enhanced by coordination of Al-alkyls or Lewis bases in the close proximity. The surface energy of the step defected (104) MgCl2 facet is clearly lower than that of the well accepted (110) facet.
Heterogeneity effects in power-grid network models
Ódor, Géza; Hartmann, Bálint
2018-01-01
We have compared the phase synchronization transition of the second order Kuramoto model on 2D lattices and on large, synthetic power-grid networks, generated from real data. The latter are weighted, hierarchical modular networks. Due to the inertia the synchronization transitions are of first order type, characterized by fast relaxation and hysteresis by varying the global coupling parameter $K$. Finite size scaling analysis shows that there is no real phase transition in the thermodynamic l...
Prakash, Kumar Ravi; Nigam, Tanuja; Pant, Vimlesh
2018-04-01
A coupled atmosphere-ocean-wave model was used to examine mixing in the upper-oceanic layers under the influence of a very severe cyclonic storm Phailin over the Bay of Bengal (BoB) during 10-14 October 2013. The coupled model was found to improve the sea surface temperature over the uncoupled model. Model simulations highlight the prominent role of cyclone-induced near-inertial oscillations in subsurface mixing up to the thermocline depth. The inertial mixing introduced by the cyclone played a central role in the deepening of the thermocline and mixed layer depth by 40 and 15 m, respectively. For the first time over the BoB, a detailed analysis of inertial oscillation kinetic energy generation, propagation, and dissipation was carried out using an atmosphere-ocean-wave coupled model during a cyclone. A quantitative estimate of kinetic energy in the oceanic water column, its propagation, and its dissipation mechanisms were explained using the coupled atmosphere-ocean-wave model. The large shear generated by the inertial oscillations was found to overcome the stratification and initiate mixing at the base of the mixed layer. Greater mixing was found at the depths where the eddy kinetic diffusivity was large. The baroclinic current, holding a larger fraction of kinetic energy than the barotropic current, weakened rapidly after the passage of the cyclone. The shear induced by inertial oscillations was found to decrease rapidly with increasing depth below the thermocline. The dampening of the mixing process below the thermocline was explained through the enhanced dissipation rate of turbulent kinetic energy upon approaching the thermocline layer. The wave-current interaction and nonlinear wave-wave interaction were found to affect the process of downward mixing and cause the dissipation of inertial oscillations.
Directory of Open Access Journals (Sweden)
K. R. Prakash
2018-04-01
Full Text Available A coupled atmosphere–ocean–wave model was used to examine mixing in the upper-oceanic layers under the influence of a very severe cyclonic storm Phailin over the Bay of Bengal (BoB during 10–14 October 2013. The coupled model was found to improve the sea surface temperature over the uncoupled model. Model simulations highlight the prominent role of cyclone-induced near-inertial oscillations in subsurface mixing up to the thermocline depth. The inertial mixing introduced by the cyclone played a central role in the deepening of the thermocline and mixed layer depth by 40 and 15 m, respectively. For the first time over the BoB, a detailed analysis of inertial oscillation kinetic energy generation, propagation, and dissipation was carried out using an atmosphere–ocean–wave coupled model during a cyclone. A quantitative estimate of kinetic energy in the oceanic water column, its propagation, and its dissipation mechanisms were explained using the coupled atmosphere–ocean–wave model. The large shear generated by the inertial oscillations was found to overcome the stratification and initiate mixing at the base of the mixed layer. Greater mixing was found at the depths where the eddy kinetic diffusivity was large. The baroclinic current, holding a larger fraction of kinetic energy than the barotropic current, weakened rapidly after the passage of the cyclone. The shear induced by inertial oscillations was found to decrease rapidly with increasing depth below the thermocline. The dampening of the mixing process below the thermocline was explained through the enhanced dissipation rate of turbulent kinetic energy upon approaching the thermocline layer. The wave–current interaction and nonlinear wave–wave interaction were found to affect the process of downward mixing and cause the dissipation of inertial oscillations.
Marcel, Jean; Abate Essi, Jean Marcel; Nouck, Philippe Njandjock; Sanda, Oumarou; Manguelle-Dicoum, Eliézer
2018-03-01
Belonging to the Cameroon Volcanic Line (CVL), the western part of Cameroon is an active volcanic zone with volcanic eruptions and deadly gas emissions. The volcanic flows generally cover areas and bury structural features like faults. Terrestrial gravity surveys can hardly cover entirely this mountainous area due to difficult accessibility. The present work aims to evaluate gravity data derived from the geopotential field model, EGM2008 to investigate the subsurface of the CVL. The methodology involves upward continuation, horizontal gradient, maxima of horizontal gradient-upward continuation combination and Euler deconvolution techniques. The lineaments map inferred from this geopotential field model confirms several known lineaments and reveals new ones covered by lava flows. The known lineaments are interpreted as faults or geological contacts such as the Foumban fault and the Pan-African Belt-Congo craton contact. The lineaments highlighted coupled with the numerous maar lakes identified in this volcanic sector attest of the vulnerability of the CVL where special attention should be given for geohazard prevention.
Micromechanical modeling of dynamic fracture in heterogeneous materials
Zhai, Jun
Fracture is the principal mode of failure for a variety of materials under dynamic conditions. The mathematical complexity precludes analytical solution to be obtained. The difficulty is especially pronounced when material inhomogeneities and anisotropy need to be considered. Recently, alumina/titanium diboride (Al2O3/TiB 2) composites with a wide range of micro and nano phase sizes and phase morphologies have been developed in the School of Materials Science and Engineering at Georgia Tech. In order to understand failure mechanisms in this material system and the influence of phase morphologies and phase size on fracture resistance, a numerical framework is needed to explicitly account for arbitrary microstructures and fracture patterns. Micromechanical modeling and simulation provide an important approach for analyzing the effects of material inhomogeneity and anisotropy over a range of microscopic length scales. A framework is proposed in this research for explicit modeling and simulation of microscopic damage/fracture/failure processes. The model and approach account for the real arbitrary microstructural morphologies. A cohesive finite element method (CFEM) based on cohesive surface theory is used. A fully dynamic kinetic framework and finite deformation kinematic formulation are used. Mesh independence of solution is studied and verified. Idealized microstructures containing circular and elliptical particles and real microstructures with arbitrary morphologies are used to investigate the effects of phase morphologies, phase size and phase anisotropy on fracture of this ceramic composite system. Numerical results show that rnicrostructural variations give rise to a range of fracture resistance. Higher fracture resistance is obtained from microstructures with fine evenly distributed microstructural reinforcement entities. The failure mode is found to be significantly influenced by the interfacial bonding strength between the phases. Two distinct failure modes
To Model Chemical Reactivity in Heterogeneous Emulsions, Think Homogeneous Microemulsions.
Bravo-Díaz, Carlos; Romsted, Laurence Stuart; Liu, Changyao; Losada-Barreiro, Sonia; Pastoriza-Gallego, Maria José; Gao, Xiang; Gu, Qing; Krishnan, Gunaseelan; Sánchez-Paz, Verónica; Zhang, Yongliang; Dar, Aijaz Ahmad
2015-08-25
Two important and unsolved problems in the food industry and also fundamental questions in colloid chemistry are how to measure molecular distributions, especially antioxidants (AOs), and how to model chemical reactivity, including AO efficiency in opaque emulsions. The key to understanding reactivity in organized surfactant media is that reaction mechanisms are consistent with a discrete structures-separate continuous regions duality. Aggregate structures in emulsions are determined by highly cooperative but weak organizing forces that allow reactants to diffuse at rates approaching their diffusion-controlled limit. Reactant distributions for slow thermal bimolecular reactions are in dynamic equilibrium, and their distributions are proportional to their relative solubilities in the oil, interfacial, and aqueous regions. Our chemical kinetic method is grounded in thermodynamics and combines a pseudophase model with methods for monitoring the reactions of AOs with a hydrophobic arenediazonium ion probe in opaque emulsions. We introduce (a) the logic and basic assumptions of the pseudophase model used to define the distributions of AOs among the oil, interfacial, and aqueous regions in microemulsions and emulsions and (b) the dye derivatization and linear sweep voltammetry methods for monitoring the rates of reaction in opaque emulsions. Our results show that this approach provides a unique, versatile, and robust method for obtaining quantitative estimates of AO partition coefficients or partition constants and distributions and interfacial rate constants in emulsions. The examples provided illustrate the effects of various emulsion properties on AO distributions such as oil hydrophobicity, emulsifier structure and HLB, temperature, droplet size, surfactant charge, and acidity on reactant distributions. Finally, we show that the chemical kinetic method provides a natural explanation for the cut-off effect, a maximum followed by a sharp reduction in AO efficiency with
Mouse genetic model for clinical and immunological heterogeneity of leishmaniasis
Czech Academy of Sciences Publication Activity Database
Lipoldová, Marie; Svobodová, M.; Havelková, Helena; Krulová, Magdalena; Badalová, Jana; Nohýnková, E.; Hart, A. A. M.; Schlegel, David; Volf, P.; Demant, P.
2002-01-01
Roč. 54, č. 3 (2002), s. 174-183 ISSN 0093-7711 R&D Projects: GA MZd NM28; GA ČR GA310/00/0760; GA MŠk OK 394 Grant - others:Howard Hughes Medical Institute(US) HHMI55000323; WHO(XX) TDR I.D. 970772; EC(XE) ERBI-C15-CT98-0317; EC(XE) BIO-4-CT98-0445 Institutional research plan: CEZ:AV0Z5052915 Keywords : Leishmaniasis * mouse model * complex disease Subject RIV: EC - Immunology Impact factor: 2.475, year: 2002
Bridging the Semantic Gap Between Heterogeneous Modeling Formalisms and FMI
2014-04-25
the timed semantics of FMI. While in the case of encoding a discrete-event (DE) actor such as those used in Ptolemy [7, 12] as an FMU, we need to...in a number of languages and tools such as ns-3, VHDL, SimEvents, and Ptolemy [7]. The semantics of DE have been formalized in various papers, e.g...sense, since there are specialized tools (e.g., Ptolemy ) for SDF modeling and simulation. What is interesting about the above mapping, however, is that
Molenaar, Dylan; de Boeck, Paul
2018-02-01
In item response theory modeling of responses and response times, it is commonly assumed that the item responses have the same characteristics across the response times. However, heterogeneity might arise in the data if subjects resort to different response processes when solving the test items. These differences may be within-subject effects, that is, a subject might use a certain process on some of the items and a different process with different item characteristics on the other items. If the probability of using one process over the other process depends on the subject's response time, within-subject heterogeneity of the item characteristics across the response times arises. In this paper, the method of response mixture modeling is presented to account for such heterogeneity. Contrary to traditional mixture modeling where the full response vectors are classified, response mixture modeling involves classification of the individual elements in the response vector. In a simulation study, the response mixture model is shown to be viable in terms of parameter recovery. In addition, the response mixture model is applied to a real dataset to illustrate its use in investigating within-subject heterogeneity in the item characteristics across response times.
Energy Technology Data Exchange (ETDEWEB)
Das, Sumanta; Maroli, Amit; Singh, Sudhanshu S.; Stannard, Tyler; Xiao, Xianghui; Chawla, Nikhilesh; Neithalath, Narayanan
2016-06-01
This paper presents a microstructure-guided modeling approach to predict the effective elastic response of heterogeneous materials, and demonstrates its application toward two highly heterogeneous, uncon- ventional structural binders, i.e., iron carbonate and fly ash geopolymer. Microstructural information from synchrotron X-ray tomography (XRT) and intrinsic elastic properties of component solid phases from statistical nanoindentation are used as the primary inputs. The virtual periodic 3D microstructure reconstructed using XRT, along with periodic boundary conditions is used as a basis for strain- controlled numerical simulation scheme in the linear elastic range to predict the elastic modulus as well as the stresses in the microstructural phases. The elastic modulus of the composite material predicted from the microstructure-based constitutive modeling approach correlates very well with experimental measurements for both the materials considered. This technique efficiently links the microstructure to mechanical properties of interest and helps develop material design guidelines for novel heterogeneous composites
A model of non-Gaussian diffusion in heterogeneous media
Lanoiselée, Yann; Grebenkov, Denis S.
2018-04-01
Recent progress in single-particle tracking has shown evidence of the non-Gaussian distribution of displacements in living cells, both near the cellular membrane and inside the cytoskeleton. Similar behavior has also been observed in granular materials, turbulent flows, gels and colloidal suspensions, suggesting that this is a general feature of diffusion in complex media. A possible interpretation of this phenomenon is that a tracer explores a medium with spatio-temporal fluctuations which result in local changes of diffusivity. We propose and investigate an ergodic, easily interpretable model, which implements the concept of diffusing diffusivity. Depending on the parameters, the distribution of displacements can be either flat or peaked at small displacements with an exponential tail at large displacements. We show that the distribution converges slowly to a Gaussian one. We calculate statistical properties, derive the asymptotic behavior and discuss some implications and extensions.
A Unified 3D Spatial Data Model for Surface and Subsurface Spatial ...
African Journals Online (AJOL)
A simulation of the above, on and below 3D spatial models for man-made constructions at differ-ent LoDs is presented. A simulation of this with regards to mining and cadastre is also presented. The model presented can be adopted in realising 3D GIS for mining and 3D cadastre can be realised in Ghana. Further work is ...
Modeling reproductive trajectories of roe deer females: fixed or dynamic heterogeneity?
Plard, F; Bonenfant, C; Delormeb, D; Gaillard, J M
2012-12-01
The relative role of dynamic and fixed heterogeneity in shaping the individual heterogeneity observed in most life-history traits remains difficult to quantify. In a recent work, Tuljapurkar et al. (2009) suggested modeling individual heterogeneity in lifetime reproductive success by a null model building reproductive trajectories from a first-order Markov chain. According to this model, among-individual differences in reproductive trajectories would be generated by the stochastic transitions among reproductive states (such as breeder and non-breeder) due to dynamic heterogeneity. In this work, we analyze the individual variation in three reproductive metrics (reproductive status, fecundity, and reproductive success) in two populations of roe deer intensively monitored using Tuljapurkar et al. (2009)’s dynamic model. Moreover, we challenge the Tuljapurkar model previously used as a biological null model to test whether the observed distribution of reproductive success over the lifetime was generated by a stochastic process by modifying two steps of the previous model to build a full stochastic model. We show that a distribution generated by the full dynamic model proposed by Tuljapurkar et al. (2009) can be consistently interpreted as only generated from a stochastic biological process provided that the probabilities of transition among reproductive states used are independent of the current reproductive state and that the positive covariation that usually occurs between survival and reproduction among individuals is removed. Only the reproductive status of roe deer females could be restricted to a stochastic process described by the full stochastic model, probably because most females (>90%) were breeders in a given year. The fecundity of roe deer females could not be adequately described by the full dynamic and full stochastic model, and the observed distribution of female reproductive success differed from the one generated by a full dynamic model in which
Aji Hapsoro, Cahyo; Purqon, Acep; Srigutomo, Wahyu
2017-07-01
2-D Time Domain Electromagnetic (TDEM) has been successfully conducted to illustrate the value of Electric field distribution under the Earth surface. Electric field compared by magnetic field is used to analyze resistivity and resistivity is one of physical properties which very important to determine the reservoir potential area of geothermal systems as one of renewable energy. In this modeling we used Time Domain Electromagnetic method because it can solve EM field interaction problem with complex geometry and to analyze transient problems. TDEM methods used to model the value of electric and magnetic fields as a function of the time combined with the function of distance and depth. The result of this modeling is Electric field intensity value which is capable to describe the structure of the Earth’s subsurface. The result of this modeling can be applied to describe the Earths subsurface resistivity values to determine the reservoir potential of geothermal systems.
Mitchell, Drew; Fahrenholtz, Samuel; MacLellan, Christopher; Bastos, Dhiego; Rao, Ganesh; Prabhu, Sujit; Weinberg, Jeffrey; Hazle, John; Stafford, Jason; Fuentes, David
2018-02-05
We evaluated a physics-based model for planning for magnetic resonance-guided laser interstitial thermal therapy for focal brain lesions. Linear superposition of analytical point source solutions to the steady-state Pennes bioheat transfer equation simulates laser-induced heating in brain tissue. The line integral of the photon attenuation from the laser source enables computation of the laser interaction with heterogeneous tissue. Magnetic resonance thermometry data sets (n = 31) were used to calibrate and retrospectively validate the model's thermal ablation prediction accuracy, which was quantified by the Dice similarity coefficient (DSC) between model-predicted and measured ablation regions (T > 57 °C). A Gaussian mixture model was used to identify independent tissue labels on pre-treatment anatomical magnetic resonance images. The tissue-dependent optical attenuation coefficients within these labels were calibrated using an interior point method that maximises DSC agreement with thermometry. The distribution of calibrated tissue properties formed a population model for our patient cohort. Model prediction accuracy was cross-validated using the population mean of the calibrated tissue properties. A homogeneous tissue model was used as a reference control. The median DSC values in cross-validation were 0.829 for the homogeneous model and 0.840 for the heterogeneous model. In cross-validation, the heterogeneous model produced a DSC higher than that produced by the homogeneous model in 23 of the 31 brain lesion ablations. Results of a paired, two-tailed Wilcoxon signed-rank test indicated that the performance improvement of the heterogeneous model over that of the homogeneous model was statistically significant (p < 0.01).
Stochastic modelling of landfill processes incorporating waste heterogeneity and data uncertainty
International Nuclear Information System (INIS)
Zacharof, A.I.; Butler, A.P.
2004-01-01
A landfill is a very complex heterogeneous environment and as such it presents many modelling challenges. Attempts to develop models that reproduce these complexities generally involve the use of large numbers of spatially dependent parameters that cannot be properly characterised in the face of data uncertainty. An alternative method is presented, which couples a simplified microbial degradation model with a stochastic hydrological and contaminant transport model. This provides a framework for incorporating the complex effects of spatial heterogeneity within the landfill in a simplified manner, along with other key variables. A methodology for handling data uncertainty is also integrated into the model structure. Illustrative examples of the model's output are presented to demonstrate effects of data uncertainty on leachate composition and gas volume prediction
Niedermeier, Dennis; Ervens, Barbara; Clauss, Tina; Voigtländer, Jens; Wex, Heike; Hartmann, Susan; Stratmann, Frank
2014-01-01
In a recent study, the Soccer ball model (SBM) was introduced for modeling and/or parameterizing heterogeneous ice nucleation processes. The model applies classical nucleation theory. It allows for a consistent description of both apparently singular and stochastic ice nucleation behavior, by distributing contact angles over the nucleation sites of a particle population assuming a Gaussian probability density function. The original SBM utilizes the Monte Carlo technique, which hampers its usage in atmospheric models, as fairly time-consuming calculations must be performed to obtain statistically significant results. Thus, we have developed a simplified and computationally more efficient version of the SBM. We successfully used the new SBM to parameterize experimental nucleation data of, e.g., bacterial ice nucleation. Both SBMs give identical results; however, the new model is computationally less expensive as confirmed by cloud parcel simulations. Therefore, it is a suitable tool for describing heterogeneous ice nucleation processes in atmospheric models.
Dynamic modeling of porous heterogeneous micro/nanobeams
Ebrahimi, Farzad; Jafari, Ali; Reza Barati, Mohammad
2017-12-01
In the present paper, the thermo-mechanical vibration characteristics of a functionally graded (FG) porous microbeam subjected to various types of thermal loadings are investigated based on modified couple stress theory and exact position of neutral axis. The FG micro/nanobeam is modeled via a refined hyperbolic beam theory in which the shear deformation effect is verified without the shear correction factor. A modified power-law distribution which contains porosity volume fraction is used to describe the graded material properties of the FG micro/nanobeam. The temperature field has uniform, linear and nonlinear distributions across the thickness. The governing equations and the related boundary conditions are derived by Hamilton's principle and they are solved applying an analytical solution which satisfies various boundary conditions. A comparison study is performed to verify the present formulation with the known data in the literature and a good agreement is observed. The parametric study covered in this paper includes several parameters, such as thermal loadings, porosity volume fraction, power-law exponents, slenderness ratio, scale parameter and various boundary conditions on natural frequencies of porous FG micro/nanobeams in detail.
El Gharamti, Mohamad
2012-04-01
Accurate knowledge of the movement of contaminants in porous media is essential to track their trajectory and later extract them from the aquifer. A two-dimensional flow model is implemented and then applied on a linear contaminant transport model in the same porous medium. Because of different sources of uncertainties, this coupled model might not be able to accurately track the contaminant state. Incorporating observations through the process of data assimilation can guide the model toward the true trajectory of the system. The Kalman filter (KF), or its nonlinear invariants, can be used to tackle this problem. To overcome the prohibitive computational cost of the KF, the singular evolutive Kalman filter (SEKF) and the singular fixed Kalman filter (SFKF) are used, which are variants of the KF operating with low-rank covariance matrices. Experimental results suggest that under perfect and imperfect model setups, the low-rank filters can provide estimates as accurate as the full KF but at much lower computational effort. Low-rank filters are demonstrated to significantly reduce the computational effort of the KF to almost 3%. © 2012 American Society of Civil Engineers.
Maladen, Ryan D; Ding, Yang; Umbanhowar, Paul B; Kamor, Adam; Goldman, Daniel I
2011-09-07
We integrate biological experiment, empirical theory, numerical simulation and a physical model to reveal principles of undulatory locomotion in granular media. High-speed X-ray imaging of the sandfish lizard, Scincus scincus, in 3 mm glass particles shows that it swims within the medium without using its limbs by propagating a single-period travelling sinusoidal wave down its body, resulting in a wave efficiency, η, the ratio of its average forward speed to the wave speed, of approximately 0.5. A resistive force theory (RFT) that balances granular thrust and drag forces along the body predicts η close to the observed value. We test this prediction against two other more detailed modelling approaches: a numerical model of the sandfish coupled to a discrete particle simulation of the granular medium, and an undulatory robot that swims within granular media. Using these models and analytical solutions of the RFT, we vary the ratio of undulation amplitude to wavelength (A/λ) and demonstrate an optimal condition for sand-swimming, which for a given A results from the competition between η and λ. The RFT, in agreement with the simulated and physical models, predicts that for a single-period sinusoidal wave, maximal speed occurs for A/λ ≈ 0.2, the same kinematics used by the sandfish.
Satterlee, Andrew B; Attayek, Peter; Midkiff, Bentley; Huang, Leaf
2017-03-17
ᅟ: Accurate and quantitative dosimetry for internal radiation therapy can be especially challenging, given the heterogeneity of patient anatomy, tumor anatomy, and source deposition. Internal radiotherapy sources such as nanoparticles and monoclonal antibodies require high resolution imaging to accurately model the heterogeneous distribution of these sources in the tumor. The resolution of nuclear imaging modalities is not high enough to measure the heterogeneity of intratumoral nanoparticle deposition or intratumoral regions, and mathematical models do not represent the actual heterogeneous dose or dose response. To help answer questions at the interface of tumor dosimetry and tumor biology, we have modeled the actual 3-dimensional dose distribution of heterogeneously delivered radioactive nanoparticles in a tumor after systemic injection. 24 h after systemic injection of dually fluorescent and radioactive nanoparticles into a tumor-bearing mouse, the tumor was cut into 342 adjacent sections and imaged to quantify the source distribution in each section. The images were stacked to generate a 3D model of source distribution, and a novel MATLAB code was employed to calculate the dose to cells on a middle section in the tumor using a low step size dose kernel. The average dose calculated by this novel 3D model compared closely with standard ways of calculating average dose, and showed a positive correlation with experimentally determined cytotoxicity in vivo. The high resolution images allowed us to determine that the dose required to initiate radiation-induced H2AX phosphorylation was approximately one Gray. The nanoparticle distribution was further used to model the dose distribution of two other radionuclides. The ability of this model to quantify the absorbed dose and dose response in different intratumoral regions allows one to investigate how source deposition in different tumor areas can affect dose and cytotoxicity, as well as how characteristics of the
Sainath, Kamalesh; Teixeira, Fernando L.
2016-05-01
We propose a full-wave pseudo-analytical numerical electromagnetic (EM) algorithm to model subsurface induction sensors, traversing planar-layered geological formations of arbitrary EM material anisotropy and loss, which are used, for example, in the exploration of hydrocarbon reserves. Unlike past pseudo-analytical planar-layered modeling algorithms that impose parallelism between the formation's bed junctions, our method involves judicious employment of Transformation Optics techniques to address challenges related to modeling relative slope (i.e., tilting) between said junctions (including arbitrary azimuth orientation of each junction). The algorithm exhibits this flexibility, both with respect to loss and anisotropy in the formation layers as well as junction tilting, via employing special planar slabs that coat each ;flattened; (i.e., originally tilted) planar interface, locally redirecting the incident wave within the coating slabs to cause wave fronts to interact with the flattened interfaces as if they were still tilted with a specific, user-defined orientation. Moreover, since the coating layers are homogeneous rather than exhibiting continuous material variation, a minimal number of these layers must be inserted and hence reduces added simulation time and computational expense. As said coating layers are not reflectionless however, they do induce artificial field scattering that corrupts legitimate field signatures due to the (effective) interface tilting. Numerical results, for two half-spaces separated by a tilted interface, quantify error trends versus effective interface tilting, material properties, transmitter/receiver spacing, sensor position, coating slab thickness, and transmitter and receiver orientation, helping understand the spurious scattering's effect on reliable (effective) tilting this algorithm can model. Under the effective tilting constraints suggested by the results of said error study, we finally exhibit responses of sensors
Comolli, Alessandro; Hakoun, Vivien; Dentz, Marco
2017-04-01
Achieving the understanding of the process of solute transport in heterogeneous porous media is of crucial importance for several environmental and social purposes, ranging from aquifers contamination and remediation, to risk assessment in nuclear waste repositories. The complexity of this aim is mainly ascribable to the heterogeneity of natural media, which can be observed at all the scales of interest, from pore scale to catchment scale. In fact, the intrinsic heterogeneity of porous media is responsible for the arising of the well-known non-Fickian footprints of transport, including heavy-tailed breakthrough curves, non-Gaussian spatial density profiles and the non-linear growth of the mean squared displacement. Several studies investigated the processes through which heterogeneity impacts the transport properties, which include local modifications to the advective-dispersive motion of solutes, mass exchanges between some mobile and immobile phases (e.g. sorption/desorption reactions or diffusion into solid matrix) and spatial correlation of the flow field. In the last decades, the continuous time random walk (CTRW) model has often been used to describe solute transport in heterogenous conditions and to quantify the impact of point heterogeneity, spatial correlation and mass transfer on the average transport properties [1]. Open issues regarding this approach are the possibility to relate measurable properties of the medium to the parameters of the model, as well as its capability to provide predictive information. In a recent work [2] the authors have shed new light on understanding the relationship between Lagrangian and Eulerian dynamics as well as on their evolution from arbitrary initial conditions. On the basis of these results, we derive a CTRW model for the description of Darcy-scale transport in d-dimensional media characterized by spatially random permeability fields. The CTRW approach models particle velocities as a spatial Markov process, which is
Advanced core-analyses for subsurface characterization
Pini, R.
2017-12-01
The heterogeneity of geological formations varies over a wide range of length scales and represents a major challenge for predicting the movement of fluids in the subsurface. Although they are inherently limited in the accessible length-scale, laboratory measurements on reservoir core samples still represent the only way to make direct observations on key transport properties. Yet, properties derived on these samples are of limited use and should be regarded as sample-specific (or `pseudos'), if the presence of sub-core scale heterogeneities is not accounted for in data processing and interpretation. The advent of imaging technology has significantly reshaped the landscape of so-called Special Core Analysis (SCAL) by providing unprecedented insight on rock structure and processes down to the scale of a single pore throat (i.e. the scale at which all reservoir processes operate). Accordingly, improved laboratory workflows are needed that make use of such wealth of information by e.g., referring to the internal structure of the sample and in-situ observations, to obtain accurate parameterisation of both rock- and flow-properties that can be used to populate numerical models. We report here on the development of such workflow for the study of solute mixing and dispersion during single- and multi-phase flows in heterogeneous porous systems through a unique combination of two complementary imaging techniques, namely X-ray Computed Tomography (CT) and Positron Emission Tomography (PET). The experimental protocol is applied to both synthetic and natural porous media, and it integrates (i) macroscopic observations (tracer effluent curves), (ii) sub-core scale parameterisation of rock heterogeneities (e.g., porosity, permeability and capillary pressure), and direct 3D observation of (iii) fluid saturation distribution and (iv) the dynamic spreading of the solute plumes. Suitable mathematical models are applied to reproduce experimental observations, including both 1D and 3D
Samkoe, Kimberley S.; Bates, Brent D.; Tselepidakis, Niki N.; DSouza, Alisha V.; Gunn, Jason R.; Ramkumar, Dipak B.; Paulsen, Keith D.; Pogue, Brian W.; Henderson, Eric R.
2017-12-01
Wide local excision (WLE) of tumors with negative margins remains a challenge because surgeons cannot directly visualize the mass. Fluorescence-guided surgery (FGS) may improve surgical accuracy; however, conventional methods with direct surface tumor visualization are not immediately applicable, and properties of tissues surrounding the cancer must be considered. We developed a phantom model for sarcoma resection with the near-infrared fluorophore IRDye 800CW and used it to iteratively define the properties of connective tissues that typically surround sarcoma tumors. We then tested the ability of a blinded surgeon to resect fluorescent tumor-simulating inclusions with ˜1-cm margins using predetermined target fluorescence intensities and a Solaris open-air fluorescence imaging system. In connective tissue-simulating phantoms, fluorescence intensity decreased with increasing blood concentration and increased with increasing intralipid concentrations. Fluorescent inclusions could be resolved at ≥1-cm depth in all inclusion concentrations and sizes tested. When inclusion depth was held constant, fluorescence intensity decreased with decreasing volume. Using targeted fluorescence intensities, a blinded surgeon was able to successfully excise inclusions with ˜1-cm margins from fat- and muscle-simulating phantoms with inclusion-to-background contrast ratios as low as 2∶1. Indirect, subsurface FGS is a promising tool for surgical resection of cancers requiring WLE.
Atomic structure of graphene supported heterogeneous model catalysts
International Nuclear Information System (INIS)
Franz, Dirk
2017-04-01
Graphene on Ir(111) forms a moire structure with well defined nucleation centres. Therefore it can be utilized to create hexagonal metal cluster lattices with outstanding structural quality. At diffraction experiments these 2D surface lattices cause a coherent superposition of the moire cell structure factor, so that the measured signal intensity scales with the square of coherently scattering unit cells. This artificial signal enhancement enables the opportunity for X-ray diffraction to determine the atomic structure of small nano-objects, which are hardly accessible with any experimental technique. The uniform environment of every metal cluster makes the described metal cluster lattices on graphene/Ir(111) an attractive model system for the investigation of catalytic, magnetic and quantum size properties of ultra-small nano-objects. In this context the use of x-rays provides a maximum of flexibility concerning the possible sample environments (vacuum, selected gases, liquids, sample temperature) and allows in-situ/operando measurements. In the framework of the present thesis the structure of different metal clusters grown by physical vapor deposition in an UHV environment and after gas exposure have been investigated. On the one hand the obtained results will explore many aspects of the atomic structure of these small metal clusters and on the other hand the presented results will proof the capabilities of the described technique (SXRD on cluster lattices). For iridium, platinum, iridium/palladium and platinum/rhodium the growth on graphene/Ir(111) of epitaxial, crystalline clusters with an ordered hexagonal lattice arrangement has been confirmed using SXRD. The clusters nucleate at the hcp sites of the moire cell and bind via rehybridization of the carbon atoms (sp 2 → sp 3 ) to the Ir(111) substrate. This causes small displacements of the substrate atoms, which is revealed by the diffraction experiments. All metal clusters exhibit a fcc structure, whereupon
Boundedly rational learning and heterogeneous trading strategies with hybrid neuro-fuzzy models
Bekiros, S.D.
2009-01-01
The present study deals with heterogeneous learning rules in speculative markets where heuristic strategies reflect the rules-of-thumb of boundedly rational investors. The major challenge for "chartists" is the development of new models that would enhance forecasting ability particularly for time
Sommer, W.T.
2015-01-01
Modelling and monitoring of Aquifer Thermal Energy Storage
Impacts of heterogeneity, thermal interference and bioremediation
Wijbrand Sommer
PhD thesis, Wageningen University, Wageningen, NL (2015)
ISBN 978-94-6257-294-2
Abstract
Aquifer
Field scale heterogeneity of redox conditions in till-upscaling to a catchment nitrate model
DEFF Research Database (Denmark)
Hansen, J.R.; Erntsen, V.; Refsgaard, J.C.
2008-01-01
Point scale studies in different settings of glacial geology show a large local variation of redox conditions. There is a need to develop an upscaling methodology for catchment scale models. This paper describes a study of field-scale heterogeneity of redox-interfaces in a till aquitard within an...
Demchenko, Y.; Ngo, C.; de Laat, C.; Lee, C.
2014-01-01
This paper presents on-going research to define the basic models and architecture patterns for federated access control in heterogeneous (multi-provider) multi-cloud and inter-cloud environment. The proposed research contributes to the further definition of Intercloud Federation Framework (ICFF)
Sommer, W.T.
2015-01-01
Modelling and monitoring of Aquifer Thermal Energy Storage Impacts of heterogeneity, thermal interference and bioremediation Wijbrand Sommer
PhD thesis, Wageningen University, Wageningen, NL (2015)
ISBN 978-94-6257-294-2 Abstract Aquifer thermal energy storage (ATES) is
Atomic structure of graphene supported heterogeneous model catalysts
Energy Technology Data Exchange (ETDEWEB)
Franz, Dirk
2017-04-15
Graphene on Ir(111) forms a moire structure with well defined nucleation centres. Therefore it can be utilized to create hexagonal metal cluster lattices with outstanding structural quality. At diffraction experiments these 2D surface lattices cause a coherent superposition of the moire cell structure factor, so that the measured signal intensity scales with the square of coherently scattering unit cells. This artificial signal enhancement enables the opportunity for X-ray diffraction to determine the atomic structure of small nano-objects, which are hardly accessible with any experimental technique. The uniform environment of every metal cluster makes the described metal cluster lattices on graphene/Ir(111) an attractive model system for the investigation of catalytic, magnetic and quantum size properties of ultra-small nano-objects. In this context the use of x-rays provides a maximum of flexibility concerning the possible sample environments (vacuum, selected gases, liquids, sample temperature) and allows in-situ/operando measurements. In the framework of the present thesis the structure of different metal clusters grown by physical vapor deposition in an UHV environment and after gas exposure have been investigated. On the one hand the obtained results will explore many aspects of the atomic structure of these small metal clusters and on the other hand the presented results will proof the capabilities of the described technique (SXRD on cluster lattices). For iridium, platinum, iridium/palladium and platinum/rhodium the growth on graphene/Ir(111) of epitaxial, crystalline clusters with an ordered hexagonal lattice arrangement has been confirmed using SXRD. The clusters nucleate at the hcp sites of the moire cell and bind via rehybridization of the carbon atoms (sp{sup 2} → sp{sup 3}) to the Ir(111) substrate. This causes small displacements of the substrate atoms, which is revealed by the diffraction experiments. All metal clusters exhibit a fcc structure
Recommended Parameter Values for INEEL Subsurface Disposal Area Source Release Modeling
Energy Technology Data Exchange (ETDEWEB)
Riley, Robert G.; Lopresti, Charles A.
2004-06-23
The purpose of this report is to summarize 1) associated information and values for key release model parameters (i.e., best estimate, minimum and maximum) obtained where possible from published experimental data, 2) a structure for selection of sensitivity tests cases that can be used to identify test cases, and 3) recommended test cases for selected contaminants of potential concern to assess remedy effectiveness against a no-treatment base case.
Maladen, Ryan D.; Ding, Yang; Umbanhowar, Paul B.; Kamor, Adam; Goldman, Daniel I.
2011-01-01
We integrate biological experiment, empirical theory, numerical simulation and a physical model to reveal principles of undulatory locomotion in granular media. High-speed X-ray imaging of the sandfish lizard, Scincus scincus, in 3 mm glass particles shows that it swims within the medium without using its limbs by propagating a single-period travelling sinusoidal wave down its body, resulting in a wave efficiency, η, the ratio of its average forward speed to the wave speed, of approximately 0...
Energy Technology Data Exchange (ETDEWEB)
Streile, G.P.; Simmons, C.S.
1986-09-01
Theoretical and computer modeling capability for assessing the subsurface movement and fate of organic contaminants in groundwater was examined. Hence, this study is particularly concerned with energy-related, organic compounds that could enter a subsurface environment and move as components of a liquid phase separate from groundwater. The migration of organic chemicals that exist in an aqueous dissolved state is certainly a part of this more general scenario. However, modeling of the transport of chemicals in aqueous solution has already been the subject of several reviews. Hence, this study emphasizes the multiphase scenario. This study was initiated to focus on the important physicochemical processes that control the behavior of organic substances in groundwater systems, to evaluate the theory describing these processes, and to search for and evaluate computer codes that implement models that correctly conceptualize the problem situation. This study is not a code inventory, and no effort was made to identify every available code capable of representing a particular process.
Models for assessment of public-private partnership projects in subsurface management
Directory of Open Access Journals (Sweden)
И. С. Калгина
2017-04-01
Full Text Available Aims and goals of this paper. The article is devoted to analysis of issues related to development of public-private partnership (PPP projects in mineral resources sector of Russia. The special emphasis is given to the most common PPP model in the field of industrial infrastructure construction using the Investment Fund of RF. We offer specific tools to be used with Russian models for assessment of PPP projects and forecasting of its efficiency for its participants. This model allows evaluating the results of the whole deposit development process, constructing graphs of all types of expenditures and revenues (by years, and having rent assessment of deposit NPV (net present value and internal rent rate (IRR.Methods and results. The iteration process at each step enables assessment of budget revenue forecast, living standards indexes, ecological parameters and performance indicators, as well as a certain variant of PPP project implementation for investors (direct government expenses on implementation of infrastructure objects and environmental activities, tax benefits. We have a set of tools for supporting the management decision making process in developing efficient PPP mechanism, balancing long-term government interests, private sector and local people interests arising during socio-economic development of mineral resources area. This method using the suggested tools for analyzing efficiency of a specific partnership mechanism is shown on the examples of projects of developing different deposits in Transbaikal region.
Normal linear models with genetically structured residual variance heterogeneity: a case study
DEFF Research Database (Denmark)
Sorensen, Daniel; Waagepetersen, Rasmus Plenge
2003-01-01
Normal mixed models with different levels of heterogeneity in the residual variance are fitted to pig litter size data. Exploratory analysis and model assessment is based on examination of various posterior predictive distributions. Comparisons based on Bayes factors and related criteria favour...... models with a genetically structured residual variance heterogeneity. There is, moreover, strong evidence of a negative correlation between the additive genetic values affecting litter size and those affecting residual variance. The models are also compared according to the purposes for which they might...... be used, such as prediction of 'future' data, inference about response to selection and ranking candidates for selection. A brief discussion is given of some implications for selection of the genetically structured residual variance model....
Long-Run Effects in Large Heterogeneous Panel Data Models with Cross-Sectionally Correlated Errors
Chudik, Alexander; Mohaddes, Kamiar; Pesaran, M Hashem; Raissi, Mehdi
2016-01-01
This paper develops a cross-sectionally augmented distributed lag (CS-DL) approach to the estimation of long-run effects in large dynamic heterogeneous panel data models with cross-sectionally dependent errors. The asymptotic distribution of the CS-DL estimator is derived under coefficient heterogeneity in the case where the time dimension (T) and the cross-section dimension (N) are both large. The CS-DL approach is compared with more standard panel data estimators that are based on autoregre...
Long-run effects in large heterogenous panel data models with cross-sectionally correlated errors
Chudik, Alexander; Mohaddes, Kamiar; Pesaran, M. Hashem; Raissi, Mehdi
2015-01-01
This paper develops a cross-sectionally augmented distributed lag (CS-DL) approach to the estimation of long-run effects in large dynamic heterogeneous panel data models with cross-sectionally dependent errors. The asymptotic distribution of the CS-DL estimator is derived under coefficient heterogeneity in the case where the time dimension (T) and the cross-section dimension (N) are both large. The CS-DL approach is compared with more standard panel data estimators that are based on autoregre...
Chow, L.; Fai, S.
2017-08-01
The digitization and abstraction of existing buildings into building information models requires the translation of heterogeneous datasets that may include CAD, technical reports, historic texts, archival drawings, terrestrial laser scanning, and photogrammetry into model elements. In this paper, we discuss a project undertaken by the Carleton Immersive Media Studio (CIMS) that explored the synthesis of heterogeneous datasets for the development of a building information model (BIM) for one of Canada's most significant heritage assets - the Centre Block of the Parliament Hill National Historic Site. The scope of the project included the development of an as-found model of the century-old, six-story building in anticipation of specific model uses for an extensive rehabilitation program. The as-found Centre Block model was developed in Revit using primarily point cloud data from terrestrial laser scanning. The data was captured by CIMS in partnership with Heritage Conservation Services (HCS), Public Services and Procurement Canada (PSPC), using a Leica C10 and P40 (exterior and large interior spaces) and a Faro Focus (small to mid-sized interior spaces). Secondary sources such as archival drawings, photographs, and technical reports were referenced in cases where point cloud data was not available. As a result of working with heterogeneous data sets, a verification system was introduced in order to communicate to model users/viewers the source of information for each building element within the model.
Directory of Open Access Journals (Sweden)
L. Chow
2017-08-01
Full Text Available The digitization and abstraction of existing buildings into building information models requires the translation of heterogeneous datasets that may include CAD, technical reports, historic texts, archival drawings, terrestrial laser scanning, and photogrammetry into model elements. In this paper, we discuss a project undertaken by the Carleton Immersive Media Studio (CIMS that explored the synthesis of heterogeneous datasets for the development of a building information model (BIM for one of Canada’s most significant heritage assets – the Centre Block of the Parliament Hill National Historic Site. The scope of the project included the development of an as-found model of the century-old, six-story building in anticipation of specific model uses for an extensive rehabilitation program. The as-found Centre Block model was developed in Revit using primarily point cloud data from terrestrial laser scanning. The data was captured by CIMS in partnership with Heritage Conservation Services (HCS, Public Services and Procurement Canada (PSPC, using a Leica C10 and P40 (exterior and large interior spaces and a Faro Focus (small to mid-sized interior spaces. Secondary sources such as archival drawings, photographs, and technical reports were referenced in cases where point cloud data was not available. As a result of working with heterogeneous data sets, a verification system was introduced in order to communicate to model users/viewers the source of information for each building element within the model.
van den Hove, J. C.; Ailleres, L.; Betts, P. G.; Cas, R. A. F.
2014-12-01
Lake Purrumbete Maar of the Newer Volcanics Province, south-eastern Australia is one of the largest maar volcanoes in the world with a near circular crater up to 2800 m in diameter and hosting a 45 m deep crater lake. Surrounding tephra ring deposits are comprised of cross-bedded fine ash and lapilli-ash deposits typical of efficient subsurface phreatomagmatic eruptive activity. Erupted accessory lithics suggest subsurface phreatomagmatic activity occurred to a depth no greater than 250 m, whilst irregular clast shapes and peperitic textures observed in marl lithics suggest the host rock was poorly consolidated during eruptive activity. To further understand factors controlling Lake Purrumbete Maars immense size, high resolution lake and land-based gravity and magnetic data were collected for use in forward modelling of the subsurface architecture associated with the maar. Collection of gravity data presented a unique challenge due to the nature of measuring small changes in gravitational forces (structure, consistent with maars hosted within poorly consolidated sediments. 2.5-D forward models were used to produce a 3-D reference model for property and geometry inversions, to test and optimise the modelled features. Inversions suggest the major vents likely occur to a greater depth than 240 m as suggested in the initial reference model.
Directory of Open Access Journals (Sweden)
C. Lu
2015-05-01
Full Text Available The paper aims to evaluate the impacts of the average hydraulic conductivity of the heterogeneous aquifer on the estimated hydraulic conductivity using the observations from pumping tests. The results of aquifer tests conducted at a karst aquifer are first introduced. A MODFLOW groundwater flow model was developed to perform numerical pumping tests, and the heterogeneous hydraulic conductivity (K field was generated using the Monte Carlo method. The K was estimated by the Theis solution for an unconfined aquifer. The effective hydraulic conductivity (Ke was calculated to represent the hydraulic conductivity of a heterogeneous aquifer. The results of numerical simulations demonstrate that Ke increase with the mean of hydraulic conductivity (EK, and decrease with the coefficient of variation of the hydraulic conductivity (Cv. The impact of spatial variability of K on the estimated Ke at two observation wells with smaller EK is less significant compared to the cases with larger EK.
Geologically based model of heterogeneous hydraulic conductivity in an alluvial setting
Fogg, Graham E.; Noyes, Charles D.; Carle, Steven F.
Information on sediment texture and spatial continuity are inherent to sedimentary depositional facies descriptions, which are therefore potentially good predictors of spatially varying hydraulic conductivity (K). Analysis of complex alluvial heterogeneity in Livermore Valley, California, USA, using relatively abundant core descriptions and field pumping-test data, demonstrates a depositional-facies approach to characterization of subsurface heterogeneity. Conventional textural classifications of the core show a poor correlation with K; however, further refinement of the textural classifications into channel, levee, debris-flow, and flood-plain depositional facies reveals a systematic framework for spatial modeling of K. This geologic framework shows that most of the system is composed of very low-K flood-plain materials, and that the K measurements predominantly represent the other, higher-K facies. Joint interpretation of both the K and geologic data shows that spatial distribution of K in this system could not be adequately modeled without geologic data and analysis. Furthermore, it appears that K should not be assumed to be log-normally distributed, except perhaps within each facies. Markov chain modeling of transition probability, representing spatial correlation within and among the facies, captures the relevant geologic features while highlighting a new approach for statistical characterization of hydrofacies spatial variability. The presence of fining-upward facies sequences, cross correlation between facies, as well as other geologic attributes captured by the Markov chains provoke questions about the suitability of conventional geostatistical approaches based on variograms or covariances for modeling geologic heterogeneity. Résumé Les informations sur la texture des sédiments et leur continuité spatiale font partie des descriptions de faciès sédimentaires de dépôt. Par conséquent, ces descriptions sont d'excellents prédicteurs potentiels des
Lehermeier, Christina; Schön, Chris-Carolin; de Los Campos, Gustavo
2015-09-01
Plant breeding populations exhibit varying levels of structure and admixture; these features are likely to induce heterogeneity of marker effects across subpopulations. Traditionally, structure has been dealt with as a potential confounder, and various methods exist to "correct" for population stratification. However, these methods induce a mean correction that does not account for heterogeneity of marker effects. The animal breeding literature offers a few recent studies that consider modeling genetic heterogeneity in multibreed data, using multivariate models. However, these methods have received little attention in plant breeding where population structure can have different forms. In this article we address the problem of analyzing data from heterogeneous plant breeding populations, using three approaches: (a) a model that ignores population structure [A-genome-based best linear unbiased prediction (A-GBLUP)], (b) a stratified (i.e., within-group) analysis (W-GBLUP), and (c) a multivariate approach that uses multigroup data and accounts for heterogeneity (MG-GBLUP). The performance of the three models was assessed on three different data sets: a diversity panel of rice (Oryza sativa), a maize (Zea mays L.) half-sib panel, and a wheat (Triticum aestivum L.) data set that originated from plant breeding programs. The estimated genomic correlations between subpopulations varied from null to moderate, depending on the genetic distance between subpopulations and traits. Our assessment of prediction accuracy features cases where ignoring population structure leads to a parsimonious more powerful model as well as others where the multivariate and stratified approaches have higher predictive power. In general, the multivariate approach appeared slightly more robust than either the A- or the W-GBLUP. Copyright © 2015 by the Genetics Society of America.
Sun, Fengxin; Wang, Jufeng; Cheng, Rongjun; Ge, Hongxia
2018-02-01
The optimal driving speeds of the different vehicles may be different for the same headway. In the optimal velocity function of the optimal velocity (OV) model, the maximum speed vmax is an important parameter determining the optimal driving speed. A vehicle with higher maximum speed is more willing to drive faster than that with lower maximum speed in similar situation. By incorporating the anticipation driving behavior of relative velocity and mixed maximum speeds of different percentages into optimal velocity function, an extended heterogeneous car-following model is presented in this paper. The analytical linear stable condition for this extended heterogeneous traffic model is obtained by using linear stability theory. Numerical simulations are carried out to explore the complex phenomenon resulted from the cooperation between anticipation driving behavior and heterogeneous maximum speeds in the optimal velocity function. The analytical and numerical results all demonstrate that strengthening driver's anticipation effect can improve the stability of heterogeneous traffic flow, and increasing the lowest value in the mixed maximum speeds will result in more instability, but increasing the value or proportion of the part already having higher maximum speed will cause different stabilities at high or low traffic densities.
Jang, Myoseon; Czoschke, Nadine M; Northcross, Amanda L; Cao, Gang; Shaof, David
2006-05-01
A predictive model for secondary organic aerosol (SOA) formation by both partitioning and heterogeneous reactions was developed for SOA created from ozonolysis of alpha-pinene in the presence of preexisting inorganic seed aerosols. SOA was created in a 2 m3 polytetrafluoroethylene film indoor chamber under darkness. Extensive sets of SOA experiments were conducted varying humidity, inorganic seed compositions comprising of ammonium sulfate and sulfuric acid, and amounts of inorganic seed mass. SOA mass was decoupled into partitioning (OM(P)) and heterogeneous aerosol production (OM(H)). The reaction rate constant for OM(H) production was subdivided into three categories (fast, medium, and slow) to consider different reactivity of organic products for the particle phase heterogeneous reactions. The influence of particle acidity on reaction rates was treated in a previous semiempirical model. Model OM(H) was developed with medium and strong acidic seed aerosols, and then extrapolated to OM(H) in weak acidic conditions, which are more relevant to atmospheric aerosols. To demonstrate the effects of preexisting glyoxal derivatives (e.g., glyoxal hydrate and dimer) on OM(H), SOA was created with a seed mixture comprising of aqueous glyoxal and inorganic species. Our results show that heterogeneous SOA formation was also influenced by preexisting reactive glyoxal derivatives.
International Nuclear Information System (INIS)
Verbist, K.; Cronelis, W. M.; McLaren, R.; Gabriels, D.; Soto, G.
2009-01-01
In arid and semi-arid zones runoff harvesting techniques are often applied to increase the water retention and infiltration on steep slopes. Additionally, they act as an erosion control measure to reduce land degradation hazards. Both in literature and in the field, a large variety of runoff collecting systems are found, as well as large variations in design and dimensions. Therefore, detailed measurements were performed on a semi-arid slope in central Chile to allow identification of the effect of a simple water harvesting technique on soil water availability. For this purpose, twenty two TDR-probes were installed and were monitored continuously during and after a simulated rainfall event. These data were used to calibrate the 3D distributed flow model HydroGeoSphere, to assess the runoff components and soil water retention as influenced by the water harvesting technique, both under simulated and natural rainfall conditions. (Author) 6 refs.
Topcuoglu, B. D.; Stewart, L. C.; Butterfield, D. A.; Huber, J. A.; Holden, J. F.
2016-12-01
Approximately 1 giga ton (Gt, 1015 g) of CH4 is formed globally per year from H2, CO2 and acetate through methanogenesis, largely by methanogens growing in syntrophic association with anaerobic microbes that hydrolyze and ferment biopolymers. However, our understanding of methanogenesis in hydrothermal regions of the subseafloor and potential syntrophic methanogenesis at thermophilic temperatures (i.e., >50°C) is nascent. In this study, the growth of natural assemblages of thermophilic methanogens from Axial Seamount was primarily limited by H2 availability. Heterotrophs supported thermophilic methanogenesis by H2 syntrophy in microcosm incubations of hydrothermal fluids at 55°C and 80°C supplemented with tryptone only. Based on 16S rRNA gene sequencing, only heterotrophic archaea that produce H2, H2-consuming methanogens, and sulfate reducing archaea were found in 80°C tryptone microcosms from Marker 113 vent. No bacteria were found. In 55°C tryptone microcosms, sequences were found from H2-producing bacteria and H2-consuming methanogens and sulfate-reducing bacteria. In order to model the impact of H2 syntrophy at hyperthemophilic temperatures, a co-culture was established consisting of the H2-producing hyperthermophilic heterotroph Thermococcus paralvinellae and a H2-consuming hyperthermophilic methanogen Methanocaldococcus bathoardescens. When grown alone in a chemostat, the growth rates and steady-state cell concentrations of T. paralvinellae decreased significantly when a high H2 (70 µM) background was present. H2 inhibition was ameliorated by the production of formate, but in silico modeling suggests less energetic yield for the cells. H2 syntrophy relieved H2 inhibition for both the heterotroph and the methanogenic partners. The results demonstrate that thermophilic H2 syntrophy can support methanogenesis within natural microbial assemblages and may be an important alternative energy source for thermophilic autotrophs in marine geothermal environments.
Drzewiecki, Wojciech
2016-12-01
In this work nine non-linear regression models were compared for sub-pixel impervious surface area mapping from Landsat images. The comparison was done in three study areas both for accuracy of imperviousness coverage evaluation in individual points in time and accuracy of imperviousness change assessment. The performance of individual machine learning algorithms (Cubist, Random Forest, stochastic gradient boosting of regression trees, k-nearest neighbors regression, random k-nearest neighbors regression, Multivariate Adaptive Regression Splines, averaged neural networks, and support vector machines with polynomial and radial kernels) was also compared with the performance of heterogeneous model ensembles constructed from the best models trained using particular techniques. The results proved that in case of sub-pixel evaluation the most accurate prediction of change may not necessarily be based on the most accurate individual assessments. When single methods are considered, based on obtained results Cubist algorithm may be advised for Landsat based mapping of imperviousness for single dates. However, Random Forest may be endorsed when the most reliable evaluation of imperviousness change is the primary goal. It gave lower accuracies for individual assessments, but better prediction of change due to more correlated errors of individual predictions. Heterogeneous model ensembles performed for individual time points assessments at least as well as the best individual models. In case of imperviousness change assessment the ensembles always outperformed single model approaches. It means that it is possible to improve the accuracy of sub-pixel imperviousness change assessment using ensembles of heterogeneous non-linear regression models.
Yue, S. S.; Wen, Y. N.; Lv, G. N.; Hu, D.
2013-10-01
In recent years, the increasing development of cloud computing technologies laid critical foundation for efficiently solving complicated geographic issues. However, it is still difficult to realize the cooperative operation of massive heterogeneous geographical models. Traditional cloud architecture is apt to provide centralized solution to end users, while all the required resources are often offered by large enterprises or special agencies. Thus, it's a closed framework from the perspective of resource utilization. Solving comprehensive geographic issues requires integrating multifarious heterogeneous geographical models and data. In this case, an open computing platform is in need, with which the model owners can package and deploy their models into cloud conveniently, while model users can search, access and utilize those models with cloud facility. Based on this concept, the open cloud service strategies for the sharing of heterogeneous geographic analysis models is studied in this article. The key technology: unified cloud interface strategy, sharing platform based on cloud service, and computing platform based on cloud service are discussed in detail, and related experiments are conducted for further verification.
Hoogendoorn, Martine; Feenstra, Talitha L; Asukai, Yumi; Briggs, Andrew H; Borg, Sixten; Dal Negro, Roberto W; Hansen, Ryan N; Jansson, Sven-Arne; Leidl, Reiner; Risebrough, Nancy; Samyshkin, Yevgeniy; Wacker, Margarethe E; Rutten-van Mölken, Maureen P M H
2016-01-01
OBJECTIVES: To assess how suitable current chronic obstructive pulmonary disease (COPD) cost-effectiveness models are to evaluate personalized treatment options for COPD by exploring the type of heterogeneity included in current models and by validating outcomes for subgroups of patients. METHODS: A
Multi-Robot Systems for Subsurface Planetary Exploration Project
National Aeronautics and Space Administration — The proposed innovation is a heterogeneous multi-robot team developed as a platform for effective subsurface planetary exploration. State-of-art robotic exploration...
Reactive transport modeling in the subsurface environment with OGS-IPhreeqc
He, Wenkui; Beyer, Christof; Fleckenstein, Jan; Jang, Eunseon; Kalbacher, Thomas; Naumov, Dimitri; Shao, Haibing; Wang, Wenqing; Kolditz, Olaf
2015-04-01
Worldwide, sustainable water resource management becomes an increasingly challenging task due to the growth of population and extensive applications of fertilizer in agriculture. Moreover, climate change causes further stresses to both water quantity and quality. Reactive transport modeling in the coupled soil-aquifer system is a viable approach to assess the impacts of different land use and groundwater exploitation scenarios on the water resources. However, the application of this approach is usually limited in spatial scale and to simplified geochemical systems due to the huge computational expense involved. Such computational expense is not only caused by solving the high non-linearity of the initial boundary value problems of water flow in the unsaturated zone numerically with rather fine spatial and temporal discretization for the correct mass balance and numerical stability, but also by the intensive computational task of quantifying geochemical reactions. In the present study, a flexible and efficient tool for large scale reactive transport modeling in variably saturated porous media and its applications are presented. The open source scientific software OpenGeoSys (OGS) is coupled with the IPhreeqc module of the geochemical solver PHREEQC. The new coupling approach makes full use of advantages from both codes: OGS provides a flexible choice of different numerical approaches for simulation of water flow in the vadose zone such as the pressure-based or mixed forms of Richards equation; whereas the IPhreeqc module leads to a simplification of data storage and its communication with OGS, which greatly facilitates the coupling and code updating. Moreover, a parallelization scheme with MPI (Message Passing Interface) is applied, in which the computational task of water flow and mass transport is partitioned through domain decomposition, whereas the efficient parallelization of geochemical reactions is achieved by smart allocation of computational workload over
Power in the heterogeneous connections model: The emergence of core-periphery networks
Persitz, Dotan
2009-01-01
The heterogeneous connections model is a generalization of the homogeneous connections model of Jackson and Wolinsky (1996) in which the intrinsic value of each connection is set by a discrete, positive and symmetric function that depends solely on the types of the two end agents. Core periphery networks are defined as networks in which the agents' set can be partitioned into two subsets, one in which the members are completely connected among themselves and the other where there are no inter...
The analysis of an SEIR rumor propagation model on heterogeneous network
Liu, Qiming; Li, Tao; Sun, Meici
2017-03-01
Considering that the exposed nodes may become the removed nodes at a rate, we present a novel rumor propagation SEIR model on heterogeneous network. We give formula of the rumor spreading threshold for the model and analyze the globally dynamical behaviors of the rumor free equilibrium set. Meanwhile, we discuss two immunization strategies for the rumor spreading. Numerical simulations are given to demonstrate the main results.
Modelling the time-dependent rheological behaviour of heterogeneous brittle rocks
Xu, Tao; Tang, Chun-an; Zhao, Jian; Li, Lianchong; Heap, M. J.
2012-06-01
A 2-D numerical model for brittle creep and stress relaxation is proposed for the time-dependent brittle deformation of heterogeneous brittle rock under uniaxial loading conditions. The model accounts for material heterogeneity through a stochastic local failure stress field, and local material degradation using an exponential material softening law. Importantly, the model introduces the concept of a mesoscopic renormalization to capture the co-operative interaction between microcracks in the transition from distributed to localized damage. The model also describes the temporal and spatial evolution of acoustic emissions, including their size (energy released), in the medium during the progressive damage process. The model is first validated using previously published experimental data and is then used to simulate brittle creep and stress relaxation experiments. The model accurately reproduces the classic trimodal behaviour (primary, secondary and tertiary creep) seen in laboratory brittle creep (constant stress) experiments and the decelerating stress during laboratory stress relaxation (constant strain) experiments. Brittle creep simulations also show evidence of a 'critical level of damage' before the onset of tertiary creep and the initial stages of localization can be seen as early as the start of the secondary creep phase, both of which have been previously observed in experiments. Stress relaxation simulations demonstrate that the total amount of stress relaxation increases when the level of constant axial strain increases, also corroborating with previously published experimental data. Our approach differs from previously adopted macroscopic approaches, based on constitutive laws, and microscopic approaches that focus on fracture propagation. The model shows that complex macroscopic time-dependent behaviour can be explained by the small-scale interaction of elements and material degradation. The fact that the simulations are able to capture a similar time
International Nuclear Information System (INIS)
Montazer, P.; Hammermeister, D.; Ginanni, J.
1994-01-01
The long-term effect of changes in atmospheric climatological conditions on subsurface hydrological conditions in the unsaturated zone in and environments is an important factor in defining the performance of a high-level and low-level radioactive waste repositories in geological environment. Computer simulation coupled with paleohydrological studies can be used to understand and quantify the potential impact of future climatological conditions on repository performance. A-TOUGH efficiently simulates (given current state-of-the-art technology) the physical processes involved in the near-surface atmosphere and its effect on subsurface conditions. This efficiency is due to the numerical techniques used in TOUGH and the efficient computational techniques used in V-TOUGH to solve non-linear thermodynamic equations that govern the flux of vapor and energy within subsurface porous and fractured media and between these media and the atmosphere
A matrix approach to the statistics of longevity in heterogeneous frailty models
Directory of Open Access Journals (Sweden)
Hal Caswell
2014-09-01
Full Text Available Background: The gamma-Gompertz model is a fixed frailty model in which baseline mortality increasesexponentially with age, frailty has a proportional effect on mortality, and frailty at birth follows a gamma distribution. Mortality selects against the more frail, so the marginal mortality rate decelerates, eventually reaching an asymptote. The gamma-Gompertz is one of a wider class of frailty models, characterized by the choice of baseline mortality, effects of frailty, distributions of frailty, and assumptions about the dynamics of frailty. Objective: To develop a matrix model to compute all the statistical properties of longevity from thegamma-Gompertz and related models. Methods: I use the vec-permutation matrix formulation to develop a model in which individuals are jointly classified by age and frailty. The matrix is used to project the age and frailty dynamicsof a cohort and the fundamental matrix is used to obtain the statistics of longevity. Results: The model permits calculation of the mean, variance, coefficient of variation, skewness and all moments of longevity, the marginal mortality and survivorship functions, the dynamics of the frailty distribution, and other quantities. The matrix formulation extends naturally to other frailty models. I apply the analysis to the gamma-Gompertz model (for humans and laboratory animals, the gamma-Makeham model, and the gamma-Siler model, and to a hypothetical dynamic frailty model characterized by diffusion of frailty with reflecting boundaries.The matrix model permits partitioning the variance in longevity into components due to heterogeneity and to individual stochasticity. In several published human data sets, heterogeneity accounts for less than 10Š of the variance in longevity. In laboratory populations of five invertebrate animal species, heterogeneity accounts for 46Š to 83Š ofthe total variance in longevity.
Force Sensor Based Tool Condition Monitoring Using a Heterogeneous Ensemble Learning Model
Directory of Open Access Journals (Sweden)
Guofeng Wang
2014-11-01
Full Text Available Tool condition monitoring (TCM plays an important role in improving machining efficiency and guaranteeing workpiece quality. In order to realize reliable recognition of the tool condition, a robust classifier needs to be constructed to depict the relationship between tool wear states and sensory information. However, because of the complexity of the machining process and the uncertainty of the tool wear evolution, it is hard for a single classifier to fit all the collected samples without sacrificing generalization ability. In this paper, heterogeneous ensemble learning is proposed to realize tool condition monitoring in which the support vector machine (SVM, hidden Markov model (HMM and radius basis function (RBF are selected as base classifiers and a stacking ensemble strategy is further used to reflect the relationship between the outputs of these base classifiers and tool wear states. Based on the heterogeneous ensemble learning classifier, an online monitoring system is constructed in which the harmonic features are extracted from force signals and a minimal redundancy and maximal relevance (mRMR algorithm is utilized to select the most prominent features. To verify the effectiveness of the proposed method, a titanium alloy milling experiment was carried out and samples with different tool wear states were collected to build the proposed heterogeneous ensemble learning classifier. Moreover, the homogeneous ensemble learning model and majority voting strategy are also adopted to make a comparison. The analysis and comparison results show that the proposed heterogeneous ensemble learning classifier performs better in both classification accuracy and stability.
Stochastic modeling of macrodispersion in unsaturated heterogeneous porous media. Final report
Energy Technology Data Exchange (ETDEWEB)
Yeh, T.C.J.
1995-02-01
Spatial heterogeneity of geologic media leads to uncertainty in predicting both flow and transport in the vadose zone. In this work an efficient and flexible, combined analytical-numerical Monte Carlo approach is developed for the analysis of steady-state flow and transient transport processes in highly heterogeneous, variably saturated porous media. The approach is also used for the investigation of the validity of linear, first order analytical stochastic models. With the Monte Carlo analysis accurate estimates of the ensemble conductivity, head, velocity, and concentration mean and covariance are obtained; the statistical moments describing displacement of solute plumes, solute breakthrough at a compliance surface, and time of first exceedance of a given solute flux level are analyzed; and the cumulative probability density functions for solute flux across a compliance surface are investigated. The results of the Monte Carlo analysis show that for very heterogeneous flow fields, and particularly in anisotropic soils, the linearized, analytical predictions of soil water tension and soil moisture flux become erroneous. Analytical, linearized Lagrangian transport models also overestimate both the longitudinal and the transverse spreading of the mean solute plume in very heterogeneous soils and in dry soils. A combined analytical-numerical conditional simulation algorithm is also developed to estimate the impact of in-situ soil hydraulic measurements on reducing the uncertainty of concentration and solute flux predictions.
Directory of Open Access Journals (Sweden)
Milcah C. Scott
2016-12-01
Full Text Available Osteosarcoma (OS is a heterogeneous and rare disease with a disproportionate impact because it mainly affects children and adolescents. Lamentably, more than half of patients with OS succumb to metastatic disease. Clarification of the etiology of the disease, development of better strategies to manage progression, and methods to guide personalized treatments are among the unmet health needs for OS patients. Progress in managing the disease has been hindered by the extreme heterogeneity of OS; thus, better models that accurately recapitulate the natural heterogeneity of the disease are needed. For this study, we used cell lines derived from two spontaneous canine OS tumors with distinctly different biological behavior (OS-1 and OS-2 for heterotypic in vivo modeling that recapitulates the heterogeneous biology and behavior of this disease. Both cell lines demonstrated stability of the transcriptome when grown as orthotopic xenografts in athymic nude mice. Consistent with the behavior of the original tumors, OS-2 xenografts grew more rapidly at the primary site and had greater propensity to disseminate to lung and establish microscopic metastasis. Moreover, OS-2 promoted formation of a different tumor-associated stromal environment than OS-1 xenografts. OS-2-derived tumors comprised a larger percentage of the xenograft tumors than OS-1-derived tumors. In addition, a robust pro-inflammatory population dominated the stromal cell infiltrates in OS-2 xenografts, whereas a mesenchymal population with a gene signature reflecting myogenic signaling dominated those in the OS-1 xenografts. Our studies show that canine OS cell lines maintain intrinsic features of the tumors from which they were derived and recapitulate the heterogeneous biology and behavior of bone cancer in mouse models. This system provides a resource to understand essential interactions between tumor cells and the stromal environment that drive the progression and metastatic propensity of
van Neerven, Sanne M.; Tieken, Mathijs; Vermeulen, Louis; Bijlsma, Maarten F.
2016-01-01
Resolving the origin of intratumor heterogeneity has proven to be one of the central challenges in cancer research during recent years. Two theoretical models explaining the emergence of intratumor heterogeneity have come to dominate cancer biology literature: the clonal evolution model and the
Roy, Mousumi; Lewis, Megan; Johnson, Alex; George, Nicolas; Rowe, Charlotte; Guardincerri, Elena
2018-03-01
Imaging shallow subsurface density structure is an important goal in a variety of applications, from hydrogeology to seismic and volcanic hazard assessment. We assess the effectiveness of surface and subsurface gravity measurements in estimating the density structure of a well-characterized rock volume: the mesa (a small, flat-topped plateau) upon which the town of Los Alamos, New Mexico, USA is located. Our gravity measurements were made on the mesa surface above a horizontal tunnel and underground, within the tunnel. We demonstrate that, in the absence of other geophysical data such as seismic data or muon attenuation, subsurface (tunnel) gravity measurements are critical to accurately recovering geologic structure. Without the tunnel data, our resolution is limited to roughly the surface gravity station spacing, but by including the tunnel data we can resolve structure to a depth of 10 times the surface gravity station spacing. Densities were obtained using both forward modeling and a Bayesian inverse modeling approach, incorporating relevant constraints from geologic observations. We find that Bayesian inversion, with geologically relevant prior, is a superior approach to the forward models in terms of both robustness and efficiency and correctly predicts the orientation and elevation of important geologic features.
Modeling of high-frequency wave propagation in the heterogenous Earth using screen method
Ding, Y.; Zheng, Y.
2017-12-01
High-frequency (1Hz) wave propagation modeling in the heterogenous Earth is difficult due to computation cost. We have developed one alternative method to do high-frequency wave propagation locally in the Earth. First, we divide the heterogeneous Earth model into two parts: the background gradient velocity model, and the velocity perturbation. Then we trace rays from the source to the Earth surface and make screens perpendicular to the rays. We propagate the wavefield in each screen by Kirchhoff surface integral and account for the velocity perturbations with a phase shift. Recursively, the algorithm will propagate the wavefield locally from the source to the surface. The result is compared with that from the finite difference method.
A MODEL OF HETEROGENEOUS DISTRIBUTED SYSTEM FOR FOREIGN EXCHANGE PORTFOLIO ANALYSIS
Directory of Open Access Journals (Sweden)
Dragutin Kermek
2006-06-01
Full Text Available The paper investigates the design of heterogeneous distributed system for foreign exchange portfolio analysis. The proposed model includes few separated and dislocated but connected parts through distributed mechanisms. Making system distributed brings new perspectives to performance busting where software based load balancer gets very important role. Desired system should spread over multiple, heterogeneous platforms in order to fulfil open platform goal. Building such a model incorporates different patterns from GOF design patterns, business patterns, J2EE patterns, integration patterns, enterprise patterns, distributed design patterns to Web services patterns. The authors try to find as much as possible appropriate patterns for planned tasks in order to capture best modelling and programming practices.
Yang, Jie; Graf, Thomas; Herold, Maria; Ptak, Thomas
2013-06-01
Coastal aquifers are complex hydrologic systems because many physical processes interact: (i) variably saturated flow, (ii) spatial-temporal fluid density variations, (iii) tidal fluctuations, (iv) storm surges overtopping dykes, and (v) surface runoff of storm water. The HydroGeoSphere model is used to numerically simulate coastal flow dynamics, assuming a fully coupled surface-subsurface approach, accounting for all processes listed above. The diffusive wave approximation of the St. Venant equation is used to describe surface flow. Surface flow and salt transport are fully coupled with subsurficial variably saturated, variable-density flow and salt transport through mathematical terms that represent exchange of fluid mass and solute mass, respectively. Tides and storm surges induce a time-variant head that is applied to nodes of the surface domain. The approach is applied to real cases of tide and storm surge events. Tide simulation results confirm the existence of a recirculating zone, forming beneath the upper part of the intertidal zone. By monitoring the exchange fluid flux rates through the beach, it was found that the major inflow to the aquifer takes place at the upper part of the intertidal zone, which explains the formation of the recirculating zone. The recirculating zone is forming particularly during rising tide. Results from a storm surge simulation show that plume fingers develop below the flooded land surface. Natural remediation by seaward flowing freshwater is relatively slow, such that reducing the salt concentration in the aquifer down to drinking water standards takes up to 10 years. Copyright © 2013 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Lijuan Cui
2016-11-01
Full Text Available We monitored the water quality and hydrological conditions of a horizontal subsurface constructed wetland (HSSF-CW in Beijing, China, for two years. We simulated the area-based constant and the temperature coefficient with the first-order kinetic model. We examined the relationships between the nitrogen (N removal rate, N load, seasonal variations in the N removal rate, and environmental factors—such as the area-based constant, temperature, and dissolved oxygen (DO. The effluent ammonia (NH4+-N and nitrate (NO3−-N concentrations were significantly lower than the influent concentrations (p < 0.01, n = 38. The NO3−-N load was significantly correlated with the removal rate (R2 = 0.96, p < 0.01, but the NH4+-N load was not correlated with the removal rate (R2 = 0.02, p > 0.01. The area-based constants of NO3−-N and NH4+-N at 20 °C were 27 ± 26 (mean ± SD and 14 ± 10 m∙year−1, respectively. The temperature coefficients for NO3−-N and NH4+-N were estimated at 1.004 and 0.960, respectively. The area-based constants for NO3−-N and NH4+-N were not correlated with temperature (p > 0.01. The NO3−-N area-based constant was correlated with the corresponding load (R2 = 0.96, p < 0.01. The NH4+-N area rate was correlated with DO (R2 = 0.69, p < 0.01, suggesting that the factors that influenced the N removal rate in this wetland met Liebig’s law of the minimum.
A heterogeneous model for burnup calculation in high temperature gas-cooled reactors
International Nuclear Information System (INIS)
Perfetti, C. M.; Angahie, S.; Baxter, A.; Ellis, C.
2008-01-01
A high resolution MCNPX model is developed to simulate nuclear design characteristics and fuel cycle features of High Temperature Gas-Cooled Reactors. Contrary to the conventional approach in the MCNPX model, fuel regions containing TRISO particles are not homogenized. A cube corner distribution approximation is used to directly model randomly dispersed TRISO fuel particles in a graphite matrix. The universe filling technique is used cover the entire range of fuel particles in the core. The heterogeneous MCNPX model is applied to simulate and analyze the complete fuel cycle of the General Atomics Plutonium-Consumption Modular Helium Reactor (PC-MHR). The PC-MHR reactor design is a variation of the General Atomic MHR design and is designed for the consumption or burning of excess Russian weapons plutonium. The MCNPX burnup calculation of the PC-MHR includes the simulation of a 260 effective full-power day fuel cycle at 600 MWt. Results of the MCNPX calculations suggest that during 260 effective full-power day cycle, 40% reduction in the whole core Pu-239 inventory could be achieved. Results of heterogeneous MCNPX burnup calculations in PC-MHR are compared with results of deterministically calculated values obtained from DIF3D codes. For the 260 effective full-power day cycle, the difference in mass Pu-239 mass reduction calculation using heterogeneous MCNPX and homogeneous DIF3D models is 6%. The difference in MCNPX and DIF3D calculated results for higher actinides are mostly higher than 6%. (authors)
Investigating melting induced mantle heterogeneities in plate driven mantle convection models
Price, M.; Davies, H.; Panton, J.
2017-12-01
Observations from geochemistry and seismology continue to suggest a range of complex heterogeneity in Earth's mantle. In the deep mantle, two large low velocity provinces (LLVPs) have been regularly observed in seismic studies, with their longevity, composition and density compared to the surrounding mantle debated. The cause of these observed LLVPs is equally uncertain, with previous studies advocating either thermal or thermo-chemical causes. There is also evidence that these structures could provide chemically distinct reservoirs within the mantle, with recent studies also suggesting there may be additional reservoirs in the mantle, such as bridgmanite-enriched ancient mantle structures (BEAMS). One way to test these hypotheses is using computational models of the mantle, with models that capture the full 3D system being both complex and computationally expensive. Here we present results from our global mantle model TERRA. Using our model, we can track compositional variations in the convecting mantle that are generated by self-consistent, evolving melting zones. Alongside the melting, we track trace elements and other volatiles which can be partitioned during melting events, and expelled and recycled at the surface. Utilising plate reconstruction models as a boundary condition, the models generate the tectonic features observed at Earth's surface, while also organising the lower mantle into recognisable degree-two structures. This results in our models generating basaltic `oceanic' crusts which are then brought into the mantle at tectonic boundaries, providing additional chemical heterogeneity in the mantle volume. Finally, by utilising thermodynamic lookup tables to convert the final outputs from the model to seismic structures, together with resolution filters for global tomography models, we are able to make direct comparisons between our results and observations. By varying the parameters of the model, we investigate a range of current hypotheses for
Fractal density modeling of crustal heterogeneity from the KTB deep hole
Chen, Guoxiong; Cheng, Qiuming
2017-03-01
Fractal or multifractal concepts have significantly enlightened our understanding of crustal heterogeneity. Much attention has focused on 1/f scaling natures of physicochemical heterogeneity of Earth crust from fractal increment perspective. In this study, fractal density model from fractal clustering point of view is used to characterize the scaling behaviors of heterogeneous sources recorded at German Continental Deep Drilling Program (KTB) main hole, and of special contribution is the local and global multifractal analysis revisited by using Haar wavelet transform (HWT). Fractal density modeling of mass accumulation generalizes the unit of rock density from integer (e.g., g/cm3) to real numbers (e.g., g/cmα), so that crustal heterogeneities with respect to source accumulation are quantified by singularity strength of fractal density in α-dimensional space. From that perspective, we found that the bulk densities of metamorphic rocks exhibit fractal properties but have a weak multifractality, decreasing with the depth. The multiscaling natures of chemical logs also have been evidenced, and the observed distinct fractal laws for mineral contents are related to their different geochemical behaviors within complex lithological context. Accordingly, scaling distributions of mineral contents have been recognized as a main contributor to the multifractal natures of heterogeneous density for low-porosity crystalline rocks. This finally allows us to use de Wijs cascade process to explain the mechanism of fractal density. In practice, the proposed local singularity analysis based on HWT is suggested as an attractive high-pass filtering to amplify weak signatures of well logs as well as to delineate microlithological changes.
Optimization and universality of Brownian search in a basic model of quenched heterogeneous media
Godec, Aljaž; Metzler, Ralf
2015-05-01
The kinetics of a variety of transport-controlled processes can be reduced to the problem of determining the mean time needed to arrive at a given location for the first time, the so-called mean first-passage time (MFPT) problem. The occurrence of occasional large jumps or intermittent patterns combining various types of motion are known to outperform the standard random walk with respect to the MFPT, by reducing oversampling of space. Here we show that a regular but spatially heterogeneous random walk can significantly and universally enhance the search in any spatial dimension. In a generic minimal model we consider a spherically symmetric system comprising two concentric regions with piecewise constant diffusivity. The MFPT is analyzed under the constraint of conserved average dynamics, that is, the spatially averaged diffusivity is kept constant. Our analytical calculations and extensive numerical simulations demonstrate the existence of an optimal heterogeneity minimizing the MFPT to the target. We prove that the MFPT for a random walk is completely dominated by what we term direct trajectories towards the target and reveal a remarkable universality of the spatially heterogeneous search with respect to target size and system dimensionality. In contrast to intermittent strategies, which are most profitable in low spatial dimensions, the spatially inhomogeneous search performs best in higher dimensions. Discussing our results alongside recent experiments on single-particle tracking in living cells, we argue that the observed spatial heterogeneity may be beneficial for cellular signaling processes.
Directory of Open Access Journals (Sweden)
Hadi Parvizi
2018-01-01
Full Text Available Hydraulic fracturing technologies play a major role in the global energy supply and affect oil pricing. The current oil price fluctuations within 40 to 55 USD per barrel have caused diminished economical margins for hydraulic fracturing projects. Hence, successful decision making the for execution of hydraulic fracturing projects requires a higher level of integration of technical, commercial, and uncertainty analyses. However, the complexity of hydraulic fracturing modeling, and the sensitivity and the effects of uncertainty of reservoir heterogeneity on well performance renders the integration of such studies rather impractical. The impact of reservoir heterogeneity on hydraulic fracturing performance has been quantified by the introduction of Heterogeneity Impact Factor (HIF and formulas have been developed to forecast well performance using HIF. These advances provide a platform for introducing a practical approach for introducing the Risk of Commercial Failure (RCF due to reservoir heterogeneity in hydraulic fracturing projects. This paper defines such a parameter and the methodology to calculate it in a time-efficient manner. The proposed approach has been exercised on a real project in which a RCF of 20% is computed. The analysis also covers the sensitivity on Capital Expenditure (CAPEX, Operational Expenditure (OPEX, gas price, HIF and discount rate.
Morohashi, Mineo; Ohashi, Yoshiaki; Tani, Saeka; Ishii, Kotaro; Itaya, Mitsuhiro; Nanamiya, Hideaki; Kawamura, Fujio; Tomita, Masaru; Soga, Tomoyoshi
2007-08-01
The soil bacterium Bacillus subtilis forms dormant, robust spores as a tactic to ensure survival under conditions of starvation. However, the sporulating culture includes sporulating and non-sporulating cells, because a portion of the cell population initiates sporulation in wild-type strain. We anticipated that the population effect must be considered carefully to analyse samples yielding population heterogeneity. We first built a mathematical model and simulated for signal transduction of the sporulation cue to see what mechanisms are responsible for generating the heterogeneity. The simulated results were confirmed experimentally, where heterogeneity is primarily modulated by negative feedback circuits, resulting in generation of a bistable response within the sporulating culture. We also confirmed that mutants relevant to negative feedback yield either sporulating or non-sporulating subpopulations. To see the effect of molecular mechanism between sporulating and non-sporulating cells in distinct manner, metabolome analysis was conducted using the above mutants. The metabolic profiles exhibited distinct characteristics with time regardless of whether sporulation was initiated or not. In addition, several distinct characteristics of metabolites were observed between strains, which was inconsistent with previously reported data. The results imply that careful consideration must be made in the interpretation of data obtained from cells yielding population heterogeneity.
Duclaux, Guillaume; Huismans, Ritske S.; May, Dave
2015-04-01
How and why do continents break? More than two decades of analogue and 2D plane-strain numerical experiments have shown that despite the origin of the forces driving extension, the geometry of continental rifts falls into three categories - or modes: narrow rift, wide rift, or core complex. The mode of extension itself is strongly influenced by the rheology (and rheological behaviour) of the modelled layered system. In every model, an initial thermal or mechanical heterogeneity, such as a weak seed or a notch, is imposed to help localise the deformation and avoid uniform stretching of the lithosphere by pure shear. While it is widely accepted that structural inheritance is a key parameter for controlling rift localisation - as implied by the Wilson Cycle - modelling the effect of lithospheric heterogeneities on the long-term tectonic evolution of an extending plate in full 3D remains challenging. Recent progress in finite-element methods applied to computational tectonics along with the improved accessibility to high performance computers, now enable to switch from plane strain thermo-mechanical experiments to full 3D high-resolution experiments. Here we investigate the role of mechanical heterogeneities on rift opening, linkage and propagation during extension of a layered lithospheric systems with pTatin3d, a geodynamics modeling package utilising the material-point-method for tracking material composition, combined with a multigrid finite-element method to solve heterogeneous, incompressible visco-plastic Stokes problems. The initial model setup consists in a box of 1200 km horizontally by 250 km deep. It includes a 35 km layer of continental crust, underlaid by 85 km of sub-continental lithospheric mantle, and an asthenospheric mantle. Crust and mantle have visco-plastic rheologies with a pressure dependent yielding, which includes strain weakening, and a temperature, stress, strain-rate-dependent viscosity based on wet quartzite rheology for the crust, and wet
LDRD final report : mesoscale modeling of dynamic loading of heterogeneous materials
Energy Technology Data Exchange (ETDEWEB)
Robbins, Joshua [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Dingreville, Remi Philippe Michel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Voth, Thomas Eugene [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Furnish, Michael David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2013-12-01
Material response to dynamic loading is often dominated by microstructure (grain structure, porosity, inclusions, defects). An example critically important to Sandia's mission is dynamic strength of polycrystalline metals where heterogeneities lead to localization of deformation and loss of shear strength. Microstructural effects are of broad importance to the scientific community and several institutions within DoD and DOE; however, current models rely on inaccurate assumptions about mechanisms at the sub-continuum or mesoscale. Consequently, there is a critical need for accurate and robust methods for modeling heterogeneous material response at this lower length scale. This report summarizes work performed as part of an LDRD effort (FY11 to FY13; project number 151364) to meet these needs.
Wang, Huai-Chun; Minh, Bui Quang; Susko, Edward; Roger, Andrew J
2018-03-01
Proteins have distinct structural and functional constraints at different sites that lead to site-specific preferences for particular amino acid residues as the sequences evolve. Heterogeneity in the amino acid substitution process between sites is not modeled by commonly used empirical amino acid exchange matrices. Such model misspecification can lead to artefacts in phylogenetic estimation such as long-branch attraction. Although sophisticated site-heterogeneous mixture models have been developed to address this problem in both Bayesian and maximum likelihood (ML) frameworks, their formidable computational time and memory usage severely limits their use in large phylogenomic analyses. Here we propose a posterior mean site frequency (PMSF) method as a rapid and efficient approximation to full empirical profile mixture models for ML analysis. The PMSF approach assigns a conditional mean amino acid frequency profile to each site calculated based on a mixture model fitted to the data using a preliminary guide tree. These PMSF profiles can then be used for in-depth tree-searching in place of the full mixture model. Compared with widely used empirical mixture models with $k$ classes, our implementation of PMSF in IQ-TREE (http://www.iqtree.org) speeds up the computation by approximately $k$/1.5-fold and requires a small fraction of the RAM. Furthermore, this speedup allows, for the first time, full nonparametric bootstrap analyses to be conducted under complex site-heterogeneous models on large concatenated data matrices. Our simulations and empirical data analyses demonstrate that PMSF can effectively ameliorate long-branch attraction artefacts. In some empirical and simulation settings PMSF provided more accurate estimates of phylogenies than the mixture models from which they derive.
A bootstrap test for instrument validity in heterogeneous treatment effect models
Kitagawa, Toru
2013-01-01
This paper develops a specification test for the instrument validity conditions in the heterogeneous treatment effect model with a binary treatment and a discrete instrument. A necessary testable implication for the joint restriction of instrument exogeneity and instrument monotonicity is given by nonnegativity of point-identifiable complier's outcome densities. Our specification test infers this testable implication using a Kolmogorov-Smirnov type test statistic. We provide a bootstrap algor...
Czech Academy of Sciences Publication Activity Database
Kukačka, Jiří; Baruník, Jozef
2013-01-01
Roč. 392, č. 23 (2013), s. 5920-5938 ISSN 0378-4371 R&D Projects: GA ČR GA402/09/0965 Institutional support: RVO:67985556 Keywords : Heterogeneous agent model * Behavioural finance * Herding * Overconfidence * Market sentiment * Stock market crash Subject RIV: AH - Economics Impact factor: 1.722, year: 2013 http://library.utia.cas.cz/separaty/2013/E/barunik-0395344.pdf
Modeling Integration and Reuse of Heterogeneous Terminologies in Faceted Browsing Systems
Harris, Daniel R.
2016-01-01
We integrate heterogeneous terminologies into our category-theoretic model of faceted browsing and show that existing terminologies and vocabularies can be reused as facets in a cohesive, interactive system. Commonly found in online search engines and digital libraries, faceted browsing systems depend upon one or more taxonomies which outline the structure and content of the facets available for user interaction. Controlled vocabularies or terminologies are often externally curated and are av...
Supervised learning methods in modeling of CD4+ T cell heterogeneity
Lu, Pinyi; Abedi, Vida; Mei, Yongguo; Hontecillas, Raquel; Hoops, Stefan; Carbo, Adria; Bassaganya-Riera, Josep
2015-01-01
Background Modeling of the immune system – a highly non-linear and complex system – requires practical and efficient data analytic approaches. The immune system is composed of heterogeneous cell populations and hundreds of cell types, such as neutrophils, eosinophils, macrophages, dendritic cells, T cells, and B cells. Each cell type is highly diverse and can be further differentiated into subsets with unique and overlapping functions. For example, CD4+ T cells can be differentiated into T...
2016-06-01
MODELING OF IMPACT RESPONSE OF HETEROGENEOUS ENERGETIC COMPOSITES submitted to Dr. Douglas Allen Dalton Defense Threat Reduction Agency J9-BAS...materials from density functional theory with van der Waals, thermal, and zero-point energy corrections," Applied Physics Letters, vol. 97, Dec 20 2010...REDUCTION AGENCY 8725 JOHN J. KINGMAN ROAD STOP 6201 FORT BELVOIR, VA 22060 ATTN: A. DALTON DEFENSE TECHNICAL INFORMATION CENTER
Modeling and Analysis of Non-Orthogonal MBMS Transmission in Heterogeneous Networks
Zhang, Zhengquan; Ma, Zheng; Xiao, Ming; Fan, Pingzhi
2017-01-01
Broadcasting/multicasting is an efficient mechanism for multimedia communications due to its high spectrum efficiency, which achieves point-to-multipoint transmission on the same radio resources. To satisfy the increasing demands for multimedia broadcast multicast service (MBMS), we present a power domain non-orthogonal MBMS transmission scheme in a K-tier heterogeneous network (HetNet). Firstly, the system model, usage scenarios, and fundamentals of the presented scheme are discussed. Next, ...
Why are Housing Prices so Volatile? Income Shocks in a Stochastic Heterogeneous-Agents Model
Fracois Ortalo-Magne; Sven Rady
2000-01-01
Building on a stochastic life-cycle model with credit constraints and heterogeneous agents and dwellings, this paper clarifies the contribution of income fluctuations to housing price volatility. First, housing prices are shown to depend on the current income of young households. Empirical evidence from the UK and the US shows that this income variable is more volatile than aggregate income. Data also suggest that the income of young households affects housing prices independently of aggregat...
Heterogeneity and Scaling in Geologic Media
Energy Technology Data Exchange (ETDEWEB)
Gregory N. Boitnott; Gilles Y. Bussod; Paul N. Hagin; Stephen R. Brown
2005-04-18
The accurate characterization and remediation of contaminated subsurface environments requires the detailed knowledge of subsurface structures and flow paths. Enormous resources are invested in scoping and characterizing sites using core sampling, 3-D geophysical surveys, well tests, etc.... Unfortunately, much of the information acquired is lost to compromises and simplifications made in constructing numerical grids for the simulators used to predict flow and transport from the contaminated area to the accessible environment. In rocks and soils, the bulk geophysical and transport properties of the matrix and of fracture systems are determined by the juxtaposition of geometric features at many length scales. In the interest of computational efficiency, recognized heterogeneities are simplified, averaged out, or entirely ignored in spite of recent studies that recognize that: (1) Structural and lithologic heterogeneities exist on all scales in rocks. (2) Small heterogeneities influence, and can control the physical and chemical properties of rocks. In this work we propose a physically based approach for the description and treatment of heterogeneities, that highlights the use of laboratory equipment designed to measure the effect on physical properties of fine scale heterogeneities observed in rocks and soils. We then discuss the development of an integration methodology that uses these measurements to develop and upscale flow and transport models. Predictive simulations are 'calibrated' to the measured heterogeneity data, and subsequently upscaled in a way that is consistent with the transport physics and the efficient use of environmental geophysics. This methodology provides a more accurate interpretation and representation of the subsurface for both environmental engineering and remediation. We show through examples, (i) the important influence of even subtle heterogeneity in the interpreting of geophysical data, and (ii) how physically based upscaling
Mellor, Andrew; Mobilia, Mauro; Zia, R. K. P.
2016-02-01
We introduce a heterogeneous nonlinear q-voter model with zealots and two types of susceptible voters, and study its non-equilibrium properties when the population is finite and well mixed. In this two-opinion model, each individual supports one of two parties and is either a zealot or a susceptible voter of type q 1 or q 2. While here zealots never change their opinion, a q i -susceptible voter (i=1,2) consults a group of q i neighbors at each time step, and adopts their opinion if all group members agree. We show that this model violates the detailed balance whenever q1 \
Directory of Open Access Journals (Sweden)
Drzewiecki Wojciech
2016-12-01
Full Text Available In this work nine non-linear regression models were compared for sub-pixel impervious surface area mapping from Landsat images. The comparison was done in three study areas both for accuracy of imperviousness coverage evaluation in individual points in time and accuracy of imperviousness change assessment. The performance of individual machine learning algorithms (Cubist, Random Forest, stochastic gradient boosting of regression trees, k-nearest neighbors regression, random k-nearest neighbors regression, Multivariate Adaptive Regression Splines, averaged neural networks, and support vector machines with polynomial and radial kernels was also compared with the performance of heterogeneous model ensembles constructed from the best models trained using particular techniques.
Controlling Subsurface Fractures and Fluid Flow: A Basic Research Agenda
Energy Technology Data Exchange (ETDEWEB)
Pyrak-Nolte, Laura J [Purdue Univ., West Lafayette, IN (United States); DePaolo, Donald J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Pietraß, Tanja [USDOE Office of Science, Washington, DC (United States)
2015-05-22
. In response, the Office of Science, through its Office of Basic Energy Science (BES), convened a roundtable consisting of 15 national lab, university and industry geoscience experts to brainstorm basic research areas that underpin the SubTER goals but are currently underrepresented in the BES research portfolio. Held in Germantown, Maryland on May 22, 2015, the round-table participants developed a basic research agenda that is detailed in this report. Highlights include the following: -A grand challenge calling for advanced imaging of stress and geological processes to help understand how stresses and chemical substances are distributed in the subsurface—knowledge that is critical to all aspects of subsurface engineering; -A priority research direction aimed at achieving control of fluid flow through fractured media; -A priority research direction aimed at better understanding how mechanical and geochemical perturbations to subsurface rock systems are coupled through fluid and mineral interactions; -A priority research direction aimed at studying the structure, permeability, reactivity and other properties of nanoporous rocks, like shale, which have become critical energy materials and exhibit important hallmarks of mesoscale materials; -A cross-cutting theme that would accelerate development of advanced computational methods to describe heterogeneous time-dependent geologic systems that could, among other potential benefits, provide new and vastly improved models of hydraulic fracturing and its environmental impacts; -A cross-cutting theme that would lead to the creation of “geo-architected materials” with controlled repeatable heterogeneity and structure that can be tested under a variety of thermal, hydraulic, chemical and mechanical conditions relevant to subsurface systems; -A cross-cutting theme calling for new laboratory studies on both natural and geo-architected subsurface materials that deploy advanced high-resolution 3D imaging and chemical analysis
Large-scale model of flow in heterogeneous and hierarchical porous media
Chabanon, Morgan; Valdés-Parada, Francisco J.; Ochoa-Tapia, J. Alberto; Goyeau, Benoît
2017-11-01
Heterogeneous porous structures are very often encountered in natural environments, bioremediation processes among many others. Reliable models for momentum transport are crucial whenever mass transport or convective heat occurs in these systems. In this work, we derive a large-scale average model for incompressible single-phase flow in heterogeneous and hierarchical soil porous media composed of two distinct porous regions embedding a solid impermeable structure. The model, based on the local mechanical equilibrium assumption between the porous regions, results in a unique momentum transport equation where the global effective permeability naturally depends on the permeabilities at the intermediate mesoscopic scales and therefore includes the complex hierarchical structure of the soil. The associated closure problem is numerically solved for various configurations and properties of the heterogeneous medium. The results clearly show that the effective permeability increases with the volume fraction of the most permeable porous region. It is also shown that the effective permeability is sensitive to the dimensionality spatial arrangement of the porous regions and in particular depends on the contact between the impermeable solid and the two porous regions.
Ng, Kim Choon
2017-08-31
The adsorbate-adsorbent thermodynamics are complex as it is influenced by the pore size distributions, surface heterogeneity and site energy distribution, as well as the adsorbate properties. Together, these parameters defined the adsorbate uptake forming the state diagrams, known as the adsorption isotherms, when the sorption site energy on the pore surfaces are favorable. The available adsorption models for describing the vapor uptake or isotherms, hitherto, are individually defined to correlate to a certain type of isotherm patterns. There is yet a universal approach in developing these isotherm models. In this paper, we demonstrate that the characteristics of all sorption isotherm types can be succinctly unified by a revised Langmuir model when merged with the concepts of Homotattic Patch Approximation (HPA) and the availability of multiple sets of site energy accompanied by their respective fractional probability factors. The total uptake (q/q*) at assorted pressure ratios (P/P s ) are inextricably traced to the manner the site energies are spread, either naturally or engineered by scientists, over and across the heterogeneous surfaces. An insight to the porous heterogeneous surface characteristics, in terms of adsorption site availability has been presented, describing the unique behavior of each isotherm type.
Directory of Open Access Journals (Sweden)
Martin Gregory T
2004-11-01
Full Text Available Abstract Background Investigation of bioheat transfer problems requires the evaluation of temporal and spatial distributions of temperature. This class of problems has been traditionally addressed using the Pennes bioheat equation. Transport of heat by conduction, and by temperature-dependent, spatially heterogeneous blood perfusion is modeled here using a transport lattice approach. Methods We represent heat transport processes by using a lattice that represents the Pennes bioheat equation in perfused tissues, and diffusion in nonperfused regions. The three layer skin model has a nonperfused viable epidermis, and deeper regions of dermis and subcutaneous tissue with perfusion that is constant or temperature-dependent. Two cases are considered: (1 surface contact heating and (2 spatially distributed heating. The model is relevant to the prediction of the transient and steady state temperature rise for different methods of power deposition within the skin. Accumulated thermal damage is estimated by using an Arrhenius type rate equation at locations where viable tissue temperature exceeds 42°C. Prediction of spatial temperature distributions is also illustrated with a two-dimensional model of skin created from a histological image. Results The transport lattice approach was validated by comparison with an analytical solution for a slab with homogeneous thermal properties and spatially distributed uniform sink held at constant temperatures at the ends. For typical transcutaneous blood gas sensing conditions the estimated damage is small, even with prolonged skin contact to a 45°C surface. Spatial heterogeneity in skin thermal properties leads to a non-uniform temperature distribution during a 10 GHz electromagnetic field exposure. A realistic two-dimensional model of the skin shows that tissue heterogeneity does not lead to a significant local temperature increase when heated by a hot wire tip. Conclusions The heat transport system model of the
DEFF Research Database (Denmark)
Kessler, Timo Christian; Klint, K.E.S.; Renard, P.
2010-01-01
In low-permeability clay tills subsurface transport is governed by preferential flow in sand lenses and fractures. A proper geological model requires the integration of these features, i.e. the spatial distribution of the geological heterogeneities. Detailed mapping of sand lenses has been done a...
Safety analysis in subsurface repositories
International Nuclear Information System (INIS)
1985-06-01
The development of mathematical models to represent the repository-geosphere-biosphere system, and the development of a structure for data acquisition, processing, and use to analyse the safety of subsurface repositories, are presented. To study the behavior of radionuclides in geosphere a laboratory to determine the hydrodynamic dispersion coefficient was constructed. (M.C.K.) [pt
Optimization of large-scale heterogeneous system-of-systems models.
Energy Technology Data Exchange (ETDEWEB)
Parekh, Ojas; Watson, Jean-Paul; Phillips, Cynthia Ann; Siirola, John; Swiler, Laura Painton; Hough, Patricia Diane (Sandia National Laboratories, Livermore, CA); Lee, Herbert K. H. (University of California, Santa Cruz, Santa Cruz, CA); Hart, William Eugene; Gray, Genetha Anne (Sandia National Laboratories, Livermore, CA); Woodruff, David L. (University of California, Davis, Davis, CA)
2012-01-01
Decision makers increasingly rely on large-scale computational models to simulate and analyze complex man-made systems. For example, computational models of national infrastructures are being used to inform government policy, assess economic and national security risks, evaluate infrastructure interdependencies, and plan for the growth and evolution of infrastructure capabilities. A major challenge for decision makers is the analysis of national-scale models that are composed of interacting systems: effective integration of system models is difficult, there are many parameters to analyze in these systems, and fundamental modeling uncertainties complicate analysis. This project is developing optimization methods to effectively represent and analyze large-scale heterogeneous system of systems (HSoS) models, which have emerged as a promising approach for describing such complex man-made systems. These optimization methods enable decision makers to predict future system behavior, manage system risk, assess tradeoffs between system criteria, and identify critical modeling uncertainties.
Thinning of heterogeneous lithosphere: insights from field observations and numerical modelling
Petri, B.; Duretz, T.; Mohn, G.; Schmalholz, S. M.
2017-12-01
The nature and mechanisms of formation of extremely thinned continental crust (continental passive margins document the heterogeneous nature of the lithosphere characterized, among others, by lithological variations and structural inheritance. This contribution aims at investigating the mechanisms of extreme lithospheric thinning by exploring in particular the role of initial heterogeneities by coupling field observations from fossil passive margins and numerical models of lithospheric extension. Two field examples from the Alpine Tethys margins outcropping in the Eastern Alps (E Switzerland and N Italy) and in the Southern Alps (N Italy) were selected for their exceptional level of preservation of rift-related structures. This situation enables us to characterize (1) the pre-rift architecture of the continental lithosphere, (2) the localization of rift-related deformation in distinct portion of the lithosphere and (3) the interaction between initial heterogeneities of the lithosphere and rift-related structures. In a second stage, these observations are integrated in high-resolution, two-dimensional thermo-mechanical models taking into account various patterns of initial mechanical heterogeneities. Our results show the importance of initial pre-rift architecture of the continental lithosphere during rifting. Key roles are given to high-angle and low-angle normal faults, anastomosing shear-zones and decoupling horizons. We propose that during the first stages of thinning, deformation is strongly controlled by the complex pre-rift architecture of the lithosphere, localized along major structures responsible for the lateral extrusion of mid to lower crustal levels. This extrusion juxtaposes mechanically stronger levels in the hyper-thinned continental crust, being exhumed by subsequent low-angle normal faults. Altogether, these results highlight the critical role of the extraction of mechanically strong layers of the lithosphere during the extreme thinning of the
Fuzzy Logic-Based Model That Incorporates Personality Traits for Heterogeneous Pedestrians
Directory of Open Access Journals (Sweden)
Zhuxin Xue
2017-10-01
Full Text Available Most models designed to simulate pedestrian dynamical behavior are based on the assumption that human decision-making can be described using precise values. This study proposes a new pedestrian model that incorporates fuzzy logic theory into a multi-agent system to address cognitive behavior that introduces uncertainty and imprecision during decision-making. We present a concept of decision preferences to represent the intrinsic control factors of decision-making. To realize the different decision preferences of heterogeneous pedestrians, the Five-Factor (OCEAN personality model is introduced to model the psychological characteristics of individuals. Then, a fuzzy logic-based approach is adopted for mapping the relationships between the personality traits and the decision preferences. Finally, we have developed an application using our model to simulate pedestrian dynamical behavior in several normal or non-panic scenarios, including a single-exit room, a hallway with obstacles, and a narrowing passage. The effectiveness of the proposed model is validated with a user study. The results show that the proposed model can generate more reasonable and heterogeneous behavior in the simulation and indicate that individual personality has a noticeable effect on pedestrian dynamical behavior.
Computational Model of Antidepressant Response Heterogeneity as Multi-pathway Neuroadaptation
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Mariam B. Camacho
2017-12-01
Full Text Available Current hypotheses cannot fully explain the clinically observed heterogeneity in antidepressant response. The therapeutic latency of antidepressants suggests that therapeutic outcomes are achieved not by the acute effects of the drugs, but rather by the homeostatic changes that occur as the brain adapts to their chronic administration. We present a computational model that represents the known interactions between the monoaminergic neurotransmitter-producing brain regions and associated non-monoaminergic neurotransmitter systems, and use the model to explore the possible ways in which the brain can homeostatically adjust to chronic antidepressant administration. The model also represents the neuron-specific neurotransmitter receptors that are known to adjust their strengths (expressions or sensitivities in response to chronic antidepressant administration, and neuroadaptation in the model occurs through sequential adjustments in these receptor strengths. The main result is that the model can reach similar levels of adaptation to chronic administration of the same antidepressant drug or combination along many different pathways, arriving correspondingly at many different receptor strength configurations, but not all of those adapted configurations are also associated with therapeutic elevations in monoamine levels. When expressed as the percentage of adapted configurations that are also associated with elevations in one or more of the monoamines, our modeling results largely agree with the percentage efficacy rates of antidepressants and antidepressant combinations observed in clinical trials. Our neuroadaptation model provides an explanation for the clinical reports of heterogeneous outcomes among patients chronically administered the same antidepressant drug regimen.
An improved multi-value cellular automata model for heterogeneous bicycle traffic flow
Energy Technology Data Exchange (ETDEWEB)
Jin, Sheng [College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, 310058 China (China); Qu, Xiaobo [Griffith School of Engineering, Griffith University, Gold Coast, 4222 Australia (Australia); Xu, Cheng [Department of Transportation Management Engineering, Zhejiang Police College, Hangzhou, 310053 China (China); College of Transportation, Jilin University, Changchun, 130022 China (China); Ma, Dongfang, E-mail: mdf2004@zju.edu.cn [Ocean College, Zhejiang University, Hangzhou, 310058 China (China); Wang, Dianhai [College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, 310058 China (China)
2015-10-16
This letter develops an improved multi-value cellular automata model for heterogeneous bicycle traffic flow taking the higher maximum speed of electric bicycles into consideration. The update rules of both regular and electric bicycles are improved, with maximum speeds of two and three cells per second respectively. Numerical simulation results for deterministic and stochastic cases are obtained. The fundamental diagrams and multiple states effects under different model parameters are analyzed and discussed. Field observations were made to calibrate the slowdown probabilities. The results imply that the improved extended Burgers cellular automata (IEBCA) model is more consistent with the field observations than previous models and greatly enhances the realism of the bicycle traffic model. - Highlights: • We proposed an improved multi-value CA model with higher maximum speed. • Update rules are introduced for heterogeneous bicycle traffic with maximum speed 2 and 3 cells/s. • Simulation results of the proposed model are consistent with field bicycle data. • Slowdown probabilities of both regular and electric bicycles are calibrated.
An improved multi-value cellular automata model for heterogeneous bicycle traffic flow
International Nuclear Information System (INIS)
Jin, Sheng; Qu, Xiaobo; Xu, Cheng; Ma, Dongfang; Wang, Dianhai
2015-01-01
This letter develops an improved multi-value cellular automata model for heterogeneous bicycle traffic flow taking the higher maximum speed of electric bicycles into consideration. The update rules of both regular and electric bicycles are improved, with maximum speeds of two and three cells per second respectively. Numerical simulation results for deterministic and stochastic cases are obtained. The fundamental diagrams and multiple states effects under different model parameters are analyzed and discussed. Field observations were made to calibrate the slowdown probabilities. The results imply that the improved extended Burgers cellular automata (IEBCA) model is more consistent with the field observations than previous models and greatly enhances the realism of the bicycle traffic model. - Highlights: • We proposed an improved multi-value CA model with higher maximum speed. • Update rules are introduced for heterogeneous bicycle traffic with maximum speed 2 and 3 cells/s. • Simulation results of the proposed model are consistent with field bicycle data. • Slowdown probabilities of both regular and electric bicycles are calibrated
Analysis of Two-Worm Interaction Model in Heterogeneous M2M Network
Directory of Open Access Journals (Sweden)
Jinhua Ma
2015-10-01
Full Text Available With the rapid development of M2M (Machine-to-Machine networks, the damages caused by malicious worms are getting more and more serious. By considering the influences of the network heterogeneity on worm spreading, we are the first to study the complex interaction dynamics between benign worms and malicious worms in heterogeneous M2M network. We analyze and compare three worm propagation models based on different immunization schemes. By investigating the local stability of the worm-free equilibrium, we obtain the basic reproduction number R0 . Besides, by using suitable Lyapunov functions, we prove that the worm-free equilibrium is globally asymptotically stable if R0 ≤ 1 , otherwise unstable. The dynamics of worm models is completely determined by R0 . In the absence of birth, death and users’ treatment, we obtain the final size formula of worms. This study shows that the nodes with higher node degree are more susceptible to be infected than those with lower node degree. In addition, the effects of various immunization schemes are studied. Numerical simulations verify our theoretical results. The research results are meaningful for us to further understand the spread of worms in heterogeneous M2M network, and enact effectual control tactics.
Pineda, M.; Eftimie, R.
2017-12-01
The directed motion of cell aggregates toward a chemical source occurs in many relevant biological processes. Understanding the mechanisms that control this complex behavior is of great relevance for our understanding of developmental biological processes and many diseases. In this paper, we consider a self-propelled particle model for the movement of heterogeneous subpopulations of chemically interacting cells towards an imposed stable chemical gradient. Our simulations show explicitly how self-organisation of cell populations (which could lead to engulfment or complete cell segregation) can arise from the heterogeneity of chemotactic responses alone. This new result complements current theoretical and experimental studies that emphasise the role of differential cell-cell adhesion on self-organisation and spatial structure of cellular aggregates. We also investigate how the speed of individual cell aggregations increases with the chemotactic sensitivity of the cells, and decreases with the number of cells inside the aggregates
Soler-Sagarra, Joaquim; Carrera, Jesús; Bonet Gil, Enrique; Becker, Pablo; Rossi, Riccardo
2017-04-01
Modeling solute transport in porous media with high heterogeneity faces two challenges. First, the dispersion dependency with scale has to be reproduced. This is important because real application may have kilometric dimensions although some processes occur at pore scale. Second, a good representation of the mix process is of paramount importance because it leads to chemical reactions. Finding an equation that satisfies these conditions is needed. Although some methods (Correlated Continuous Time Random Walk, hybrid methods…) provide a partial response to these problems, no any proposed solution to date characterizes efficiently all parameters involved in reactive transport. In this contribution a new formulation to reproduce the solute evolution in heterogeneous media is proposed. The formulation is based on the Water Mixing Approach method and the velocity distribution is discretized as well as space and time. Therefore concentration is a variable in space, time and velocity. Promising results have been obtained from this assumption.
Modeling of heterogeneous elastic materials by the multiscale hp-adaptive finite element method
Klimczak, Marek; Cecot, Witold
2018-01-01
We present an enhancement of the multiscale finite element method (MsFEM) by combining it with the hp-adaptive FEM. Such a discretization-based homogenization technique is a versatile tool for modeling heterogeneous materials with fast oscillating elasticity coefficients. No assumption on periodicity of the domain is required. In order to avoid direct, so-called overkill mesh computations, a coarse mesh with effective stiffness matrices is used and special shape functions are constructed to account for the local heterogeneities at the micro resolution. The automatic adaptivity (hp-type at the macro resolution and h-type at the micro resolution) increases efficiency of computation. In this paper details of the modified MsFEM are presented and a numerical test performed on a Fichera corner domain is presented in order to validate the proposed approach.
Coexistence of equilibria in a New Keynesian model with heterogeneous beliefs
International Nuclear Information System (INIS)
Agliari, Anna; Pecora, Nicolò; Spelta, Alessandro
2015-01-01
The recent macroeconomic literature has been stressing the importance of considering heterogeneous expectations while addressing monetary policy. In this paper we consider a standard New Keynesian model, described by a two-dimensional nonlinear map, to analyze the bifurcation structure when agents have heterogeneous expectations and update their beliefs based on past performance. Depending on the degree of reactivity of the monetary policy to inflation and output deviations from the target equilibrium, different kind of dynamics may occur. We find that multiple equilibria and complicated dynamics, associated to codimension-2 bifurcations, may arise even if the monetary policy is set to respond more than point for point to inflation, as the Taylor principle prescribes. We show that if the monetary policy accommodates for a sufficient degree of output stabilization, complicated dynamics can be avoided and the number of coexisting equilibria reduces.
Schalge, Bernd; Rihani, Jehan; Haese, Barbara; Baroni, Gabriele; Erdal, Daniel; Haefliger, Vincent; Lange, Natascha; Neuweiler, Insa; Hendricks-Franssen, Harrie-Jan; Geppert, Gernot; Ament, Felix; Kollet, Stefan; Cirpka, Olaf; Saavedra, Pablo; Han, Xujun; Attinger, Sabine; Kunstmann, Harald; Vereecken, Harry; Simmer, Clemens
2017-04-01
Currently, an integrated approach to simulating the earth system is evolving where several compartment models are coupled to achieve the best possible physically consistent representation. We used the model TerrSysMP, which fully couples subsurface, land surface and atmosphere, in a synthetic study that mimicked the Neckar catchment in Southern Germany. A virtual reality run at a high resolution of 400m for the land surface and subsurface and 1.1km for the atmosphere was made. Ensemble runs at a lower resolution (800m for the land surface and subsurface) were also made. The ensemble was generated by varying soil and vegetation parameters and lateral atmospheric forcing among the different ensemble members in a systematic way. It was found that the ensemble runs deviated for some variables and some time periods largely from the virtual reality reference run (the reference run was not covered by the ensemble), which could be related to the different model resolutions. This was for example the case for river discharge in the summer. We also analyzed the spread of model states as function of time and found clear relations between the spread and the time of the year and weather conditions. For example, the ensemble spread of latent heat flux related to uncertain soil parameters was larger under dry soil conditions than under wet soil conditions. Another example is that the ensemble spread of atmospheric states was more influenced by uncertain soil and vegetation parameters under conditions of low air pressure gradients (in summer) than under conditions with larger air pressure gradients in winter. The analysis of the ensemble of fully coupled model simulations provided valuable insights in the dynamics of land-atmosphere feedbacks which we will further highlight in the presentation.
Jasinski, Michael; Eastman, Joseph; Borak, Jordan
2010-01-01
The sensitivity of mesoscale weather prediction model to a vegetation roughness initialization is investigated for the south central United States. Three different roughness databases are employed: i) a control or standard lookup table roughness that is a function only of land cover type, ii) a spatially heterogeneous roughness database previously derived using a physically based procedure and MODIS imagery, and iii) a MODIS climatologic roughness database that possesses the same spatial heterogeneity as (i) but with mean land class values from (ii). The model used is the Weather Research and Forecast Model (WRF) coupled to the Community Land Model within the Land Information System (LIS). For each simulation, a statistical comparison is made between modeled results and ground observations from meteorological stations within the Oklahoma mesonet and surrounding region during IHOP20O2. A sensitivity analysis on the impact the MODIS-based roughness fields is also made through a time-series intercomparison of temperature bias, probability of detection (POD), average wind speed, boundary layer height, and turbulent kinetic energy (TKE) the results that, for the current replacement of the standard land-cover type based roughness values with the satellite-derived fields statistically improves model performance for most of the observed variables. Further, the satellite-based roughness enhances the surface wind speed, PBL height and TKE production on the order of 3 to l0 percent, with a lesser effect over grassland and cropland domains, and the greater effect over mixed land cover domains
A Bio-Inspired QoS-Oriented Handover Model in Heterogeneous Wireless Networks
Directory of Open Access Journals (Sweden)
Daxin Tian
2014-01-01
Full Text Available We propose a bio-inspired model for making handover decision in heterogeneous wireless networks. It is based on an extended attractor selection model, which is biologically inspired by the self-adaptability and robustness of cellular response to the changes in dynamic environments. The goal of the proposed model is to guarantee multiple terminals’ satisfaction by meeting the QoS requirements of those terminals’ applications, and this model also attempts to ensure the fairness of network resources allocation, in the meanwhile, to enable the QoS-oriented handover decision adaptive to dynamic wireless environments. Some numerical simulations are preformed to validate our proposed bio-inspired model in terms of adaptive attractor selection in different noisy environments. And the results of some other simulations prove that the proposed handover scheme can adapt terminals’ network selection to the varying wireless environment and benefits the QoS of multiple terminal applications simultaneously and automatically. Furthermore, the comparative analysis also shows that the bio-inspired model outperforms the utility function based handover decision scheme in terms of ensuring a better QoS satisfaction and a better fairness of network resources allocation in dynamic heterogeneous wireless networks.
Role of Soft-Tissue Heterogeneity in Computational Models of Deep Brain Stimulation.
Howell, Bryan; McIntyre, Cameron C
Bioelectric field models of deep brain stimulation (DBS) are commonly utilized in research and industrial applications. However, the wide range of different representations used for the human head in these models may be responsible for substantial variance in the stimulation predictions. Determine the relative error of ignoring cerebral vasculature and soft-tissue heterogeneity outside of the brain in computational models of DBS. We used a detailed atlas of the human head, coupled to magnetic resonance imaging data, to construct a range of subthalamic DBS volume conductor models. We incrementally simplified the most detailed base model and quantified changes in the stimulation thresholds for direct activation of corticofugal axons. Ignoring cerebral vasculature altered predictions of stimulation thresholds by brain altered predictions between -44 % and 174%. Heterogeneity in the soft tissues of the head, if unaccounted for, introduces a degree of uncertainty in predicting electrical stimulation of neural elements that is not negligible and thereby warrants consideration in future modeling studies. Copyright © 2016 Elsevier Inc. All rights reserved.
Underground Habitats in the Río Tinto Basin: A Model for Subsurface Life Habitats on Mars
Fernández-Remolar, David C.; Prieto-Ballesteros, Olga; Rodríguez, Nuria; Gómez, Felipe; Amils, Ricardo; Gómez-Elvira, Javier; Stoker, Carol R.
2008-10-01
A search for evidence of cryptic life in the subsurface region of a fractured Paleozoic volcanosedimentary deposit near the source waters of the Río Tinto River (Iberian pyrite belt, southwest Spain) was carried out by Mars Astrobiology Research and Technology Experiment (MARTE) project investigators in 2003 and 2004. This conventional deep-drilling experiment is referred to as the MARTE ground truth drilling project. Boreholes were drilled at three sites, and samples from extracted cores were analyzed with light microscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. Core leachates were analyzed with ion chromatography, and borehole fluids were analyzed with ion and gas chromatography. Key variables of the groundwater system (e.g. , pO2, pH, and salinity) exhibit huge ranges probably due to surficial oxygenation of overall reducing waters, physical mixing of waters, and biologically mediated water-rock interactions. Mineral distribution is mainly driven by the pH of subsurface solutions, which range from highly acidic to neutral. Borehole fluids contain dissolved gases such as CO2, CH4, and H2. SEM-EDS analyses of core samples revealed evidence of microbes attacking pyrite. The Río Tinto alteration mechanisms may be similar to subsurface weathering of the martian crust and provide insights into the possible (bio)geochemical cycles that may have accompanied underground habitats in extensive early Mars volcanic regions and associated sulfide ores.
An X-FEM model of crack propagation in the matrix of randomly reinforced heterogeneous media
Shalimov, A. S.; Tashkinov, M. A.
2017-12-01
The paper deals with the development of fracture models for polydisperse inhomogeneous media with random arrangement of inclusions. An extended finite element method (X-FEM) is used, according to which crack growth is described by special enriched functions in combination with additional degrees of freedom. Modeling of crack development is performed in the Abaqus software. The influence of stress concentrators in the form of peculiarities of a heterogeneous structure on the process of crack propagation is investigated, particular cases of representative volume elements are considered.
Energy Technology Data Exchange (ETDEWEB)
Contreras, Anthony Marshall [Univ. of California, Berkeley, CA (United States)
2006-05-20
In order to better understand the fundamental components that govern catalytic activity, two-dimensional model platinum nanocatalyst arrays have been designed and fabricated. These catalysts arrays are meant to model the interplay of the metal and support important to industrial heterogeneous catalytic reactions. Photolithography and sub-lithographic techniques such as electron beam lithography, size reduction lithography and nanoimprint lithography have been employed to create these platinum nanoarrays. Both in-situ and ex-situ surface science techniques and catalytic reaction measurements were used to correlate the structural parameters of the system to catalytic activity.
Towards a Complete Model for Software Component Deployment on Heterogeneous Platform
Directory of Open Access Journals (Sweden)
Švogor Ivan
2014-12-01
Full Text Available This report briefly describes an ongoing research related to optimization of allocating software components to heterogeneous computing platform (which includes CPU, GPU and FPGA. Research goal is also presented, along with current hot topics of the research area, related research teams, and finally results and contribution of my research. It involves mathematical modelling which results in goal function, optimization method which finds a suboptimal solution to the goal function and a software modeling tool which enables graphical representation of the problem at hand and help developers determine component placement in the system design phase.
A hierarchy of models for simulating experimental results from a 3D heterogeneous porous medium
Vogler, Daniel; Ostvar, Sassan; Paustian, Rebecca; Wood, Brian D.
2018-04-01
In this work we examine the dispersion of conservative tracers (bromide and fluorescein) in an experimentally-constructed three-dimensional dual-porosity porous medium. The medium is highly heterogeneous (σY2 = 5.7), and consists of spherical, low-hydraulic-conductivity inclusions embedded in a high-hydraulic-conductivity matrix. The bimodal medium was saturated with tracers, and then flushed with tracer-free fluid while the effluent breakthrough curves were measured. The focus for this work is to examine a hierarchy of four models (in the absence of adjustable parameters) with decreasing complexity to assess their ability to accurately represent the measured breakthrough curves. The most information-rich model was (1) a direct numerical simulation of the system in which the geometry, boundary and initial conditions, and medium properties were fully independently characterized experimentally with high fidelity. The reduced-information models included; (2) a simplified numerical model identical to the fully-resolved direct numerical simulation (DNS) model, but using a domain that was one-tenth the size; (3) an upscaled mobile-immobile model that allowed for a time-dependent mass-transfer coefficient; and, (4) an upscaled mobile-immobile model that assumed a space-time constant mass-transfer coefficient. The results illustrated that all four models provided accurate representations of the experimental breakthrough curves as measured by global RMS error. The primary component of error induced in the upscaled models appeared to arise from the neglect of convection within the inclusions. We discuss the necessity to assign value (via a utility function or other similar method) to outcomes if one is to further select from among model options. Interestingly, these results suggested that the conventional convection-dispersion equation, when applied in a way that resolves the heterogeneities, yields models with high fidelity without requiring the imposition of a more
Gory, Jeffrey J; Sweeney, Holly C; Reif, David M; Motsinger-Reif, Alison A
2012-11-05
Determining the genes responsible for certain human traits can be challenging when the underlying genetic model takes a complicated form such as heterogeneity (in which different genetic models can result in the same trait) or epistasis (in which genes interact with other genes and the environment). Multifactor Dimensionality Reduction (MDR) is a widely used method that effectively detects epistasis; however, it does not perform well in the presence of heterogeneity partly due to its reliance on cross-validation for internal model validation. Cross-validation allows for only one "best" model and is therefore inadequate when more than one model could cause the same trait. We hypothesize that another internal model validation method known as a three-way split will be better at detecting heterogeneity models. In this study, we test this hypothesis by performing a simulation study to compare the performance of MDR to detect models of heterogeneity with the two different internal model validation techniques. We simulated a range of disease models with both main effects and gene-gene interactions with a range of effect sizes. We assessed the performance of each method using a range of definitions of power. Overall, the power of MDR to detect heterogeneity models was relatively poor, especially under more conservative (strict) definitions of power. While the overall power was low, our results show that the cross-validation approach greatly outperformed the three-way split approach in detecting heterogeneity. This would motivate using cross-validation with MDR in studies where heterogeneity might be present. These results also emphasize the challenge of detecting heterogeneity models and the need for further methods development.
Yucel, G.; Van Daalen, C.
2008-01-01
This study constitutes a methodological inquiry in a larger research context on transition dynamics, and it focuses on the issue of actor heterogeneity in modeling such processes. On the one hand heterogeneity at the actor level (i.e. heterogeneity among actor groups, heterogeneity among actors in a
Energy Technology Data Exchange (ETDEWEB)
Dalgaard, T., E-mail: tommy.dalgaard@agrsci.dk [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Hutchings, N. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Dragosits, U. [CEH Edinburgh, Bush Estate, Penicuik, Midlothian EH26 0QB, Scotland (United Kingdom); Olesen, J.E.; Kjeldsen, C. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Drouet, J.L.; Cellier, P. [INRA, UMR Environnement et Grandes Cultures, BP 01, 78850 Thiverval-Grignon (France)
2011-11-15
The aim of this study is to illustrate the importance of farm scale heterogeneity on nitrogen (N) losses in agricultural landscapes. Results are exemplified with a chain of N models calculating farm-N balances and distributing the N-surplus to N-losses (volatilisation, denitrification, leaching) and soil-N accumulation/release in a Danish landscape. Possible non-linearities in upscaling are assessed by comparing average model results based on (i) individual farm level calculations and (ii) averaged inputs at landscape level. Effects of the non-linearities that appear when scaling up from farm to landscape are demonstrated. Especially in relation to ammonia losses the non-linearity between livestock density and N-loss is significant (p > 0.999), with around 20-30% difference compared to a scaling procedure not taking this non-linearity into account. A significant effect of farm type on soil N accumulation (p > 0.95) was also identified and needs to be included when modelling landscape level N-fluxes and greenhouse gas emissions. - Highlights: > Farm-N balances and the distribution on types of N-losses are modelled for 56 farms. > Farm type significantly affects N-losses and soil-N accumulation. > A non-linear relation between livestock density and ammonia loss is identified. > Approaches for upscaling from farm to landscape level are discussed. > Accounting farm heterogeneity is important when upscaling N-losses. - This study illustrates the importance of including non-linear effects of farm and landscape heterogeneity on the modelling and upscaling of farm nitrogen losses and greenhouse gas emissions in agricultural landscapes.
International Nuclear Information System (INIS)
Dalgaard, T.; Hutchings, N.; Dragosits, U.; Olesen, J.E.; Kjeldsen, C.; Drouet, J.L.; Cellier, P.
2011-01-01
The aim of this study is to illustrate the importance of farm scale heterogeneity on nitrogen (N) losses in agricultural landscapes. Results are exemplified with a chain of N models calculating farm-N balances and distributing the N-surplus to N-losses (volatilisation, denitrification, leaching) and soil-N accumulation/release in a Danish landscape. Possible non-linearities in upscaling are assessed by comparing average model results based on (i) individual farm level calculations and (ii) averaged inputs at landscape level. Effects of the non-linearities that appear when scaling up from farm to landscape are demonstrated. Especially in relation to ammonia losses the non-linearity between livestock density and N-loss is significant (p > 0.999), with around 20-30% difference compared to a scaling procedure not taking this non-linearity into account. A significant effect of farm type on soil N accumulation (p > 0.95) was also identified and needs to be included when modelling landscape level N-fluxes and greenhouse gas emissions. - Highlights: → Farm-N balances and the distribution on types of N-losses are modelled for 56 farms. → Farm type significantly affects N-losses and soil-N accumulation. → A non-linear relation between livestock density and ammonia loss is identified. → Approaches for upscaling from farm to landscape level are discussed. → Accounting farm heterogeneity is important when upscaling N-losses. - This study illustrates the importance of including non-linear effects of farm and landscape heterogeneity on the modelling and upscaling of farm nitrogen losses and greenhouse gas emissions in agricultural landscapes.
Loveland, Jonathan P; Bhattacharjee, Subir; Ryan, Joseph N; Elimelech, Menachem
2003-09-01
To examine colloid transport in geochemically heterogeneous porous media at a scale comparable to field experiments, we monitored the migration of silica-coated zirconia colloids in a two-dimensional layered porous media containing sand coated to three different extents by ferric oxyhydroxides. Transport of the colloids was measured over 1.65 m and 95 days. Colloid transport was modeled by an advection-dispersion-deposition equation incorporating geochemical heterogeneity and colloid deposition dynamics (blocking). Geochemical heterogeneity was represented as favorable (ferric oxyhydroxide-coated) and unfavorable (uncoated sand) deposition surface areas. Blocking was modeled as random sequential adsorption (RSA). Release of deposited colloids was negligible. The time to colloid breakthrough after the onset of blocking increased with increasing ferric oxyhydroxide-coated surface area. As the ferric oxyhydroxide surface area increased, the concentration of colloids in the breakthrough decreased. Model-fits to the experimental data were made by inverse solutions to determine the fraction of surface area favorable for deposition and the deposition rate coefficients for the favorable (ferric oxyhydroxide-coated) and unfavorable sites. The favorable deposition rate coefficient was also calculated by colloid filtration theory. The model described the time to colloid breakthrough and the blocking effect reasonably well and estimated the favorable surface area fraction very well for the two layers with more than 1% ferric oxyhydroxide coating. If mica edges in the uncoated sand were considered as favorable surface area in addition to the ferric oxyhydroxide coatings, the model predicted the favorable surface area fraction accurately for the layer with less than 1% ferric oxyhydroxide coating.
Bias and uncertainty in regression-calibrated models of groundwater flow in heterogeneous media
Cooley, R.L.; Christensen, S.
2006-01-01
Groundwater models need to account for detailed but generally unknown spatial variability (heterogeneity) of the hydrogeologic model inputs. To address this problem we replace the large, m-dimensional stochastic vector ?? that reflects both small and large scales of heterogeneity in the inputs by a lumped or smoothed m-dimensional approximation ????*, where ?? is an interpolation matrix and ??* is a stochastic vector of parameters. Vector ??* has small enough dimension to allow its estimation with the available data. The consequence of the replacement is that model function f(????*) written in terms of the approximate inputs is in error with respect to the same model function written in terms of ??, ??,f(??), which is assumed to be nearly exact. The difference f(??) - f(????*), termed model error, is spatially correlated, generates prediction biases, and causes standard confidence and prediction intervals to be too small. Model error is accounted for in the weighted nonlinear regression methodology developed to estimate ??* and assess model uncertainties by incorporating the second-moment matrix of the model errors into the weight matrix. Techniques developed by statisticians to analyze classical nonlinear regression methods are extended to analyze the revised method. The analysis develops analytical expressions for bias terms reflecting the interaction of model nonlinearity and model error, for correction factors needed to adjust the sizes of confidence and prediction intervals for this interaction, and for correction factors needed to adjust the sizes of confidence and prediction intervals for possible use of a diagonal weight matrix in place of the correct one. If terms expressing the degree of intrinsic nonlinearity for f(??) and f(????*) are small, then most of the biases are small and the correction factors are reduced in magnitude. Biases, correction factors, and confidence and prediction intervals were obtained for a test problem for which model error is
3D bioprinting: improving in vitro models of metastasis with heterogeneous tumor microenvironments
Albritton, Jacob L.
2017-01-01
ABSTRACT Even with many advances in treatment over the past decades, cancer still remains a leading cause of death worldwide. Despite the recognized relationship between metastasis and increased mortality rate, surprisingly little is known about the exact mechanism of metastatic progression. Currently available in vitro models cannot replicate the three-dimensionality and heterogeneity of the tumor microenvironment sufficiently to recapitulate many of the known characteristics of tumors in vivo. Our understanding of metastatic progression would thus be boosted by the development of in vitro models that could more completely capture the salient features of cancer biology. Bioengineering groups have been working for over two decades to create in vitro microenvironments for application in regenerative medicine and tissue engineering. Over this time, advances in 3D printing technology and biomaterials research have jointly led to the creation of 3D bioprinting, which has improved our ability to develop in vitro models with complexity approaching that of the in vivo tumor microenvironment. In this Review, we give an overview of 3D bioprinting methods developed for tissue engineering, which can be directly applied to constructing in vitro models of heterogeneous tumor microenvironments. We discuss considerations and limitations associated with 3D printing and highlight how these advances could be harnessed to better model metastasis and potentially guide the development of anti-cancer strategies. PMID:28067628
Hot News Recommendation System from Heterogeneous Websites Based on Bayesian Model
Directory of Open Access Journals (Sweden)
Zhengyou Xia
2014-01-01
Full Text Available The most current news recommendations are suitable for news which comes from a single news website, not for news from different heterogeneous news websites. Previous researches about news recommender systems based on different strategies have been proposed to provide news personalization services for online news readers. However, little research work has been reported on utilizing hundreds of heterogeneous news websites to provide top hot news services for group customers (e.g., government staffs. In this paper, we propose a hot news recommendation model based on Bayesian model, which is from hundreds of different news websites. In the model, we determine whether the news is hot news by calculating the joint probability of the news. We evaluate and compare our proposed recommendation model with the results of human experts on the real data sets. Experimental results demonstrate the reliability and effectiveness of our method. We also implement this model in hot news recommendation system of Hangzhou city government in year 2013, which achieves very good results.
Hot news recommendation system from heterogeneous websites based on bayesian model.
Xia, Zhengyou; Xu, Shengwu; Liu, Ningzhong; Zhao, Zhengkang
2014-01-01
The most current news recommendations are suitable for news which comes from a single news website, not for news from different heterogeneous news websites. Previous researches about news recommender systems based on different strategies have been proposed to provide news personalization services for online news readers. However, little research work has been reported on utilizing hundreds of heterogeneous news websites to provide top hot news services for group customers (e.g., government staffs). In this paper, we propose a hot news recommendation model based on Bayesian model, which is from hundreds of different news websites. In the model, we determine whether the news is hot news by calculating the joint probability of the news. We evaluate and compare our proposed recommendation model with the results of human experts on the real data sets. Experimental results demonstrate the reliability and effectiveness of our method. We also implement this model in hot news recommendation system of Hangzhou city government in year 2013, which achieves very good results.
Hot News Recommendation System from Heterogeneous Websites Based on Bayesian Model
Xia, Zhengyou; Xu, Shengwu; Liu, Ningzhong; Zhao, Zhengkang
2014-01-01
The most current news recommendations are suitable for news which comes from a single news website, not for news from different heterogeneous news websites. Previous researches about news recommender systems based on different strategies have been proposed to provide news personalization services for online news readers. However, little research work has been reported on utilizing hundreds of heterogeneous news websites to provide top hot news services for group customers (e.g., government staffs). In this paper, we propose a hot news recommendation model based on Bayesian model, which is from hundreds of different news websites. In the model, we determine whether the news is hot news by calculating the joint probability of the news. We evaluate and compare our proposed recommendation model with the results of human experts on the real data sets. Experimental results demonstrate the reliability and effectiveness of our method. We also implement this model in hot news recommendation system of Hangzhou city government in year 2013, which achieves very good results. PMID:25093207
3D bioprinting: improving in vitro models of metastasis with heterogeneous tumor microenvironments
Directory of Open Access Journals (Sweden)
Jacob L. Albritton
2017-01-01
Full Text Available Even with many advances in treatment over the past decades, cancer still remains a leading cause of death worldwide. Despite the recognized relationship between metastasis and increased mortality rate, surprisingly little is known about the exact mechanism of metastatic progression. Currently available in vitro models cannot replicate the three-dimensionality and heterogeneity of the tumor microenvironment sufficiently to recapitulate many of the known characteristics of tumors in vivo. Our understanding of metastatic progression would thus be boosted by the development of in vitro models that could more completely capture the salient features of cancer biology. Bioengineering groups have been working for over two decades to create in vitro microenvironments for application in regenerative medicine and tissue engineering. Over this time, advances in 3D printing technology and biomaterials research have jointly led to the creation of 3D bioprinting, which has improved our ability to develop in vitro models with complexity approaching that of the in vivo tumor microenvironment. In this Review, we give an overview of 3D bioprinting methods developed for tissue engineering, which can be directly applied to constructing in vitro models of heterogeneous tumor microenvironments. We discuss considerations and limitations associated with 3D printing and highlight how these advances could be harnessed to better model metastasis and potentially guide the development of anti-cancer strategies.
DEFF Research Database (Denmark)
Fenger, Mogens; Linneberg, A.; Werge, Thomas Mears
2008-01-01
syndrome", which is known to be a heterogeneous and polygenic condition with a clinical endpoint (type 2 diabetes mellitus). In the model presented here, genetic factors were not included and no genetic model is assumed except that genes operate in networks. The impact of stratification of the study......BACKGROUND: Biological systems are interacting, molecular networks in which genetic variation contributes to phenotypic heterogeneity. This heterogeneity is traditionally modelled as a dichotomous trait (e.g. affected vs. non-affected). This is far too simplistic considering the complexity...... and genetic variations of such networks. METHODS: In this study on type 2 diabetes mellitus, heterogeneity was resolved in a latent class framework combined with structural equation modelling using phenotypic indicators of distinct physiological processes. We modelled the clinical condition "the metabolic...
Energy Technology Data Exchange (ETDEWEB)
Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kwicklis, Edward Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Birdsell, Kay Hanson [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrod, Jeremy Ashcraft [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-10-18
This progress report for fiscal year 2015 (FY15) describes the development of discrete fracture network (DFN) models for Pahute Mesa. DFN models will be used to upscale parameters for simulations of subsurface flow and transport in fractured media in Pahute Mesa. The research focuses on modeling of groundwater flow and contaminant transport using DFNs generated according to fracture characteristics observed in the Topopah Spring Aquifer (TSA) and the Lava Flow Aquifer (LFA). This work will improve the representation of radionuclide transport processes in large-scale, regulatory-focused models with a view to reduce pessimistic bounding approximations and provide more realistic contaminant boundary calculations that can be used to describe the future extent of contaminated groundwater. Our goal is to refine a modeling approach that can translate parameters to larger-scale models that account for local-scale flow and transport processes, which tend to attenuate migration.
Boccia, E.; Luther, S.; Parlitz, U.
2017-05-01
In cardiac tissue, electrical spiral waves pinned to a heterogeneity can be unpinned (and eventually terminated) using electric far field pulses and recruiting the heterogeneity as a virtual electrode. While for isotropic media the process of unpinning is much better understood, the case of an anisotropic substrate with different conductivities in different directions still needs intensive investigation. To study the impact of anisotropy on the unpinning process, we present numerical simulations based on the bidomain formulation of the phase I of the Luo and Rudy action potential model modified due to the occurrence of acute myocardial ischaemia. Simulating a rotating spiral wave pinned to an ischaemic heterogeneity, we compare the success of sequences of far field pulses in the isotropic and the anisotropic case for spirals still in transient or in steady rotation states. Our results clearly indicate that the range of pacing parameters resulting in successful termination of pinned spiral waves is larger in anisotropic tissue than in an isotropic medium. This article is part of the themed issue `Mathematical methods in medicine: neuroscience, cardiology and pathology'.
Morales-Casique, E.; Lezama-Campos, J. L.; Guadagnini, A.; Neuman, S. P.
2013-05-01
Modeling tracer transport in geologic porous media suffers from the corrupt characterization of the spatial distribution of hydrogeologic properties of the system and the incomplete knowledge of processes governing transport at multiple scales. Representations of transport dynamics based on a Fickian model of the kind considered in the advection-dispersion equation (ADE) fail to capture (a) the temporal variation associated with the rate of spreading of a tracer, and (b) the distribution of early and late arrival times which are often observed in field and/or laboratory scenarios and are considered as the signature of anomalous transport. Elsewhere we have presented exact stochastic moment equations to model tracer transport in randomly heterogeneous aquifers. We have also developed a closure scheme which enables one to provide numerical solutions of such moment equations at different orders of approximations. The resulting (ensemble) average and variance of concentration fields were found to display a good agreement against Monte Carlo - based simulation results for mildly heterogeneous (or well-conditioned strongly heterogeneous) media. Here we explore the ability of the moment equations approach to describe the distribution of early arrival times and late time tailing effects which can be observed in Monte-Carlo based breakthrough curves (BTCs) of the (ensemble) mean concentration. We show that BTCs of mean resident concentration calculated at a fixed space location through higher-order approximations of moment equations display long tailing features of the kind which is typically associated with anomalous transport behavior and are not represented by an ADE model with constant dispersive parameter, such as the zero-order approximation.
Directory of Open Access Journals (Sweden)
M. Cocco
2005-06-01
Full Text Available We investigate the effects of non-uniform distribution of constitutive parameters on the dynamic propagation of an earthquake rupture. We use a 2D finite difference numerical method and we assume that the dynamic rupture propagation is governed by a rate- and state-dependent constitutive law. We first discuss the results of several numerical experiments performed with different values of the constitutive parameters a (to account for the direct effect of friction, b (controlling the friction evolution and L (the characteristic length-scale parameter to simulate the dynamic rupture propagation on homogeneous faults. Spontaneous dynamic ruptures can be simulated on velocity weakening (a < b fault patches: our results point out the dependence of the traction and slip velocity evolution on the adopted constitutive parameters. We therefore model the dynamic rupture propagation on heterogeneous faults. We use in this study the characterization of different frictional regimes proposed by Boatwright and Cocco (1996 based on different values of the constitutive parameters a, b and L. Our numerical simulations show that the heterogeneities of the L parameter affect the dynamic rupture propagation, control the peak slip velocity and weakly modify the dynamic stress drop and the rupture velocity. Moreover, a barrier can be simulated through a large contrast of L parameter. The heterogeneity of a and b parameters affects the dynamic rupture propagation in a more complex way. A velocity strengthening area (a > b can arrest a dynamic rupture, but can be driven to an instability if suddenly loaded by the dynamic rupture front. Our simulations provide a picture of the complex interactions between fault patches having different frictional properties and illustrate how the traction and slip velocity evolutions are modified during the propagation on heterogeneous faults. These results involve interesting implications for slip duration and fracture
A review of predictive nonlinear theories for multiscale modeling of heterogeneous materials
Matouš, Karel; Geers, Marc G. D.; Kouznetsova, Varvara G.; Gillman, Andrew
2017-02-01
Since the beginning of the industrial age, material performance and design have been in the midst of innovation of many disruptive technologies. Today's electronics, space, medical, transportation, and other industries are enriched by development, design and deployment of composite, heterogeneous and multifunctional materials. As a result, materials innovation is now considerably outpaced by other aspects from component design to product cycle. In this article, we review predictive nonlinear theories for multiscale modeling of heterogeneous materials. Deeper attention is given to multiscale modeling in space and to computational homogenization in addressing challenging materials science questions. Moreover, we discuss a state-of-the-art platform in predictive image-based, multiscale modeling with co-designed simulations and experiments that executes on the world's largest supercomputers. Such a modeling framework consists of experimental tools, computational methods, and digital data strategies. Once fully completed, this collaborative and interdisciplinary framework can be the basis of Virtual Materials Testing standards and aids in the development of new material formulations. Moreover, it will decrease the time to market of innovative products.
A review of predictive nonlinear theories for multiscale modeling of heterogeneous materials
International Nuclear Information System (INIS)
Matouš, Karel; Geers, Marc G.D.; Kouznetsova, Varvara G.; Gillman, Andrew
2017-01-01
Since the beginning of the industrial age, material performance and design have been in the midst of innovation of many disruptive technologies. Today's electronics, space, medical, transportation, and other industries are enriched by development, design and deployment of composite, heterogeneous and multifunctional materials. As a result, materials innovation is now considerably outpaced by other aspects from component design to product cycle. In this article, we review predictive nonlinear theories for multiscale modeling of heterogeneous materials. Deeper attention is given to multiscale modeling in space and to computational homogenization in addressing challenging materials science questions. Moreover, we discuss a state-of-the-art platform in predictive image-based, multiscale modeling with co-designed simulations and experiments that executes on the world's largest supercomputers. Such a modeling framework consists of experimental tools, computational methods, and digital data strategies. Once fully completed, this collaborative and interdisciplinary framework can be the basis of Virtual Materials Testing standards and aids in the development of new material formulations. Moreover, it will decrease the time to market of innovative products.
A review of predictive nonlinear theories for multiscale modeling of heterogeneous materials
Energy Technology Data Exchange (ETDEWEB)
Matouš, Karel, E-mail: kmatous@nd.edu [Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556 (United States); Geers, Marc G.D.; Kouznetsova, Varvara G. [Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven (Netherlands); Gillman, Andrew [Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556 (United States)
2017-02-01
Since the beginning of the industrial age, material performance and design have been in the midst of innovation of many disruptive technologies. Today's electronics, space, medical, transportation, and other industries are enriched by development, design and deployment of composite, heterogeneous and multifunctional materials. As a result, materials innovation is now considerably outpaced by other aspects from component design to product cycle. In this article, we review predictive nonlinear theories for multiscale modeling of heterogeneous materials. Deeper attention is given to multiscale modeling in space and to computational homogenization in addressing challenging materials science questions. Moreover, we discuss a state-of-the-art platform in predictive image-based, multiscale modeling with co-designed simulations and experiments that executes on the world's largest supercomputers. Such a modeling framework consists of experimental tools, computational methods, and digital data strategies. Once fully completed, this collaborative and interdisciplinary framework can be the basis of Virtual Materials Testing standards and aids in the development of new material formulations. Moreover, it will decrease the time to market of innovative products.
Model determination in a case of heterogeneity of variance using sampling techniques.
Varona, L; Moreno, C; Garcia-Cortes, L A; Altarriba, J
1997-01-12
A sampling determination procedure has been described in a case of heterogeneity of variance. The procedure makes use of the predictive distributions of each data given the rest of the data and the structure of the assumed model. The computation of these predictive distributions is carried out using a Gibbs Sampling procedure. The final criterion to compare between models is the Mean Square Error between the expectation of predictive distributions and real data. The procedure has been applied to a data set of weight at 210 days in the Spanish Pirenaica beef cattle breed. Three proposed models have been compared: (a) Single Trait Animal Model; (b) Heterogeneous Variance Animal Model; and (c) Multiple Trait Animal Model. After applying the procedure, the most adjusted model was the Heterogeneous Variance Animal Model. This result is probably due to a compromise between the complexity of the model and the amount of available information. The estimated heritabilities under the preferred model have been 0.489 ± 0.076 for males and 0.331 ± 0.082 for females. RESUMEN: Contraste de modelos en un caso de heterogeneidad de varianzas usando métodos de muestreo Se ha descrito un método de contraste de modelos mediante técnicas de muestreo en un caso de heterogeneidad de varianza entre sexos. El procedimiento utiliza las distribucviones predictivas de cada dato, dado el resto de datos y la estructura del modelo. El criterio para coparar modelos es el error cuadrático medio entre la esperanza de las distribuciones predictivas y los datos reales. El procedimiento se ha aplicado en datos de peso a los 210 días en la raza bovina Pirenaica. Se han propuesto tres posibles modelos: (a) Modelo Animal Unicaracter; (b) Modelo Animal con Varianzas Heterogéneas; (c) Modelo Animal Multicaracter. El modelo mejor ajustado fue el Modelo Animal con Varianzas Heterogéneas. Este resultado es probablemente debido a un compromiso entre la complejidad del modelo y la cantidad de datos
International Nuclear Information System (INIS)
Ganapathysubramanian, Baskar; Zabaras, Nicholas
2007-01-01
In recent years, there has been intense interest in understanding various physical phenomena in random heterogeneous media. Any accurate description/simulation of a process in such media has to satisfactorily account for the twin issues of randomness as well as the multilength scale variations in the material properties. An accurate model of the material property variation in the system is an important prerequisite towards complete characterization of the system response. We propose a general methodology to construct a data-driven, reduced-order model to describe property variations in realistic heterogeneous media. This reduced-order model then serves as the input to the stochastic partial differential equation describing thermal diffusion through random heterogeneous media. A decoupled scheme is used to tackle the problems of stochasticity and multilength scale variations in properties. A sparse-grid collocation strategy is utilized to reduce the solution of the stochastic partial differential equation to a set of deterministic problems. A variational multiscale method with explicit subgrid modeling is used to solve these deterministic problems. An illustrative example using experimental data is provided to showcase the effectiveness of the proposed methodology
Monden, Rei; Stegeman, Alwin; Conradi, Henk Jan; de Jonge, Peter; Wardenaar, Klaas J
2016-01-01
Background: Depression heterogeneity has hampered development of adequate prognostic models. Therefore, more homogeneous clinical entities (e.g. dimensions, subtypes) have been developed, but their differentiating potential is limited because neither captures all relevant variation across persons,
Agha Mohammad Ali Kermani, Mehrdad; Fatemi Ardestani, Seyed Farshad; Aliahmadi, Alireza; Barzinpour, Farnaz
2017-01-01
Influence maximization deals with identification of the most influential nodes in a social network given an influence model. In this paper, a game theoretic framework is developed that models a competitive influence maximization problem. A novel competitive influence model is additionally proposed that incorporates user heterogeneity, message content, and network structure. The proposed game-theoretic model is solved using Nash Equilibrium in a real-world dataset. It is shown that none of the well-known strategies are stable and at least one player has the incentive to deviate from the proposed strategy. Moreover, violation of Nash equilibrium strategy by each player leads to their reduced payoff. Contrary to previous works, our results demonstrate that graph topology, as well as the nodes' sociability and initial tendency measures have an effect on the determination of the influential node in the network.
DEFF Research Database (Denmark)
Stjernholm, M.; Poslad, S.; Zuo, L.
2004-01-01
The Environmental Data Exchange Network for Inland Water (EDEN-IW) project's main aim is to develop a system for making disparate and heterogeneous databases of Inland Water quality more accessible to users. The core technology is based upon a combination of: ontological model to represent...... a Semantic Web based data model for IW; software agents as an infrastructure to share and reason about the IW se-mantic data model and XML to make the information accessible to Web portals and mainstream Web services. This presentation focuses on the Semantic Web or Onto-logical model. Currently, we have...... successfully demonstrated the use of our systems to semantically integrate two main database resources from IOW and NERI - these are available on-line. We are in the process of adding further databases and sup-porting a wider variety of user queries such as Decision Support System queries....
Hodgkinson, Jonathan; Cox, Malcolm E.; McLoughlin, Stephen; Huftile, Gary J.
2008-01-01
Sediment mineralogy, quartz-grain surface-textures, grain-size analysis, bore-hole logging and ground penetrating radar are combined to develop a three dimensional stratigraphic model of a back-barrier sand island in southeast Queensland, Australia. The island consists of an unconsolidated sedimentary pile above an erosional bounding surface at the top of the underlying bedrock. The stratigraphy is complex, recording the shift in depositional environments from fluvio-deltaic to strandplain, via estuarine stages of evolution. The back-barrier island deposits are correlated with the stratigraphy of the adjacent coastal plain to the west and the barrier island to the east. Extrapolation of optically stimulated luminescence dates obtained from the barrier island combined with direct dating of the back-barrier island sediments is used to constrain the depositional age and chronology of the back-barrier island stratigraphy. The modern depositional environment evolved from a chenier plain into a barrier island system by the flooding of an interdune swale and development of a shore-parallel back-barrier tidal lagoon. The lithological heterogeneity of the back-barrier island succession was controlled by the presence of a bedrock incised palaeovalley and changes in relative sea-level. Sedimentary facies associations constrain the spatial distribution of hydraulic properties controlled by lithological heterogeneity. Post-depositional alteration horizons are integrated with the facies model to account for the effects of weathering and diagenesis on hydraulic behaviour. The derived hydrostratigraphy describes a vertically stacked, dual aquifer, island groundwater system consisting of a semi-confined palaeovalley aquifer overlain by an unconfined strand-plain aquifer. Hydrostratigraphic analysis based on sedimentary facies associations, integrated with post-depositional alteration characteristics reveals great complexity of groundwater systems within small island settings. The
Moody, M.; Bailey, B.; Stoll, R., II
2017-12-01
Understanding how changes in the microclimate near individual plants affects the surface energy budget is integral to modeling land-atmosphere interactions and a wide range of near surface atmospheric boundary layer phenomena. In urban areas, the complex geometry of the urban canopy layer results in large spatial deviations of turbulent fluxes further complicating the development of models. Accurately accounting for this heterogeneity in order to model urban energy and water use requires a sub-plant level understanding of microclimate variables. We present analysis of new experimental field data taken in and around two Blue Spruce (Picea pungens) trees at the University of Utah in 2015. The test sites were chosen in order study the effects of heterogeneity in an urban environment. An array of sensors were placed in and around the conifers to quantify transport in the soil-plant-atmosphere continuum: radiative fluxes, temperature, sap fluxes, etc. A spatial array of LEMS (Local Energy Measurement Systems) were deployed to obtain pressure, surrounding air temperature and relative humidity. These quantities are used to calculate the radiative and turbulent fluxes. Relying on measurements alone is insufficient to capture the complexity of microclimate distribution as one reaches sub-plant scales. A spatially-explicit radiation and energy balance model previously developed for deciduous trees was extended to include conifers. The model discretizes the tree into isothermal sub-volumes on which energy balances are performed and utilizes incoming radiation as the primary forcing input. The radiative transfer component of the model yields good agreement between measured and modeled upward longwave and shortwave radiative fluxes. Ultimately, the model was validated through an examination of the full energy budget including radiative and turbulent fluxes through isolated Picea pungens in an urban environment.
A statistical model for the wettability of surfaces with heterogeneous pore geometries
Brockway, Lance; Taylor, Hayden
2016-10-01
We describe a new approach to modeling the wetting behavior of micro- and nano-textured surfaces with varying degrees of geometrical heterogeneity. Surfaces are modeled as pore arrays with a Gaussian distribution of sidewall reentrant angles and a characteristic wall roughness. Unlike conventional wettability models, our model considers the fraction of a surface’s pores that are filled at any time, allowing us to capture more subtle dependences of a liquid’s apparent contact angle on its surface tension. The model has four fitting parameters and is calibrated for a particular surface by measuring the apparent contact angles between the surface and at least four probe liquids. We have calibrated the model for three heterogeneous nanoporous surfaces that we have fabricated: a hydrothermally grown zinc oxide, a film of polyvinylidene fluoride (PVDF) microspheres formed by spinodal decomposition, and a polytetrafluoroethylene (PTFE) film with pores defined by sacrificial polystyrene microspheres. These three surfaces show markedly different dependences of a liquid’s apparent contact angle on the liquid’s surface tension, and the results can be explained by considering geometric variability. The highly variable PTFE pores yield the most gradual variation of apparent contact angle with probe liquid surface tension. The PVDF microspheres are more regular in diameter and, although connected in an irregular manner, result in a much sharper transition from non-wetting to wetting behavior as surface tension reduces. We also demonstrate, by terminating porous zinc oxide with three alternative hydrophobic molecules, that a single geometrical model can capture a structure’s wetting behavior for multiple surface chemistries and liquids. Finally, we contrast our results with those from a highly regular, lithographically-produced structure which shows an extremely sharp dependence of wettability on surface tension. This new model could be valuable in designing and
A comparison of methods for representing random taste heterogeneity in discrete choice models
DEFF Research Database (Denmark)
Fosgerau, Mogens; Hess, Stephane
2009-01-01
This paper reports the findings of a systematic study using Monte Carlo experiments and a real dataset aimed at comparing the performance of various ways of specifying random taste heterogeneity in a discrete choice model. Specifically, the analysis compares the performance of two recent advanced...... distributions. Both approaches allow the researcher to increase the number of parameters as desired. The paper provides a range of evidence on the ability of the various approaches to recover various distributions from data. The two advanced approaches are comparable in terms of the likelihoods achieved...
Houben, Georg J.; Stoeckl, Leonard; Mariner, Katrina E.; Choudhury, Anis S.
2018-03-01
Geological heterogeneity of the subsurface, caused by both discrete features and spatially distributed hydraulic conductivity fields, affects the flow of coastal groundwater. It influences the shape and the position of the interface between saltwater and freshwater, as well as the location and flux rate of freshwater discharge to the ocean. Fringing reefs lead to a bimodal regime of freshwater discharge, with discharge at the beach face and through deeper, submarine springs. Impermeable vertical flow barriers (dykes) lead to an impoundment of fresh groundwater and a compartmentalization of the aquifer but also to a delayed expulsion of saline water. Spatially distributed conductivity fields affect the shape of the interface and the geometry of the saltwater wedge. Higher effective conductivities lead to a further landward intrusion of the wedge toe. These flow characteristics can be important for groundwater extraction, the delineation of protection zones and the assessment of contaminant transport to coastal ecosystems.
Gan, Yanjun; Liang, Xin-Zhong; Duan, Qingyun; Choi, Hyun Il; Dai, Yongjiu; Wu, Huan
2015-06-01
An uncertainty quantification framework was employed to examine the sensitivities of 24 model parameters from a newly developed Conjunctive Surface-Subsurface Process (CSSP) land surface model (LSM). The sensitivity analysis (SA) was performed over 18 representative watersheds in the contiguous United States to examine the influence of model parameters in the simulation of terrestrial hydrological processes. Two normalized metrics, relative bias (RB) and Nash-Sutcliffe efficiency (NSE), were adopted to assess the fit between simulated and observed streamflow discharge (SD) and evapotranspiration (ET) for a 14 year period. SA was conducted using a multiobjective two-stage approach, in which the first stage was a qualitative SA using the Latin Hypercube-based One-At-a-Time (LH-OAT) screening, and the second stage was a quantitative SA using the Multivariate Adaptive Regression Splines (MARS)-based Sobol' sensitivity indices. This approach combines the merits of qualitative and quantitative global SA methods, and is effective and efficient for understanding and simplifying large, complex system models. Ten of the 24 parameters were identified as important across different watersheds. The contribution of each parameter to the total response variance was then quantified by Sobol' sensitivity indices. Generally, parameter interactions contribute the most to the response variance of the CSSP, and only 5 out of 24 parameters dominate model behavior. Four photosynthetic and respiratory parameters are shown to be influential to ET, whereas reference depth for saturated hydraulic conductivity is the most influential parameter for SD in most watersheds. Parameter sensitivity patterns mainly depend on hydroclimatic regime, as well as vegetation type and soil texture. This article was corrected on 26 JUN 2015. See the end of the full text for details.
Directory of Open Access Journals (Sweden)
Eric P. Baumer
2012-05-01
Full Text Available BACKGROUND The present research evaluates the possibility of spatial heterogeneity in the effects on neighborhood crime rates of both traditional demographic indicators - immigrant concentration, racial composition, socioeconomic disadvantage, and residential instability - and a contemporary aspect of housing transition - foreclosure - that has garnered significant attention in recent scholarship. OBJECTIVE This research advances previous research by explicitly assessing the merits of the typical "global" or "one size fits all" approach that has been applied in most neighborhood studies of demographic context and neighborhood crime rates by juxtaposing it against an alternative strategy - geographically weighted regression (GWR - that highlights the potentially significant "local" variability in model parameters. We assess the local variation of these relationships for census tracts within the city of Chicago. METHODS This paper utilizes GWR to test for spatial heterogeneity in the effects of demographic context and other predictors on neighborhood crime rates. We map local parameter estimates and t-values generated from the GWR models to highlight some of the patterns of demographic context observed in our analysis. CONCLUSIONS GWR results indicate significant variation across Chicago census tracts in the estimates of logged percent black, immigrant concentration, and foreclosure for both robbery and burglary rates. The observed effects of socioeconomic disadvantage on robbery rates and residential stability on burglary rates also are found to vary across local neighborhood clusters in Chicago. Visual inspection of these effects illuminates the importance of supplementing current approaches by "thinking locally" when developing theoretical explanations and empirical models of how demographic context shapes crime rates.
Moghaddasi, L; Bezak, E; Harriss-Phillips, W
2016-05-07
Clinical target volume (CTV) determination may be complex and subjective. In this work a microscopic-scale tumour model was developed to evaluate current CTV practices in glioblastoma multiforme (GBM) external radiotherapy. Previously, a Geant4 cell-based dosimetry model was developed to calculate the dose deposited in individual GBM cells. Microscopic extension probability (MEP) models were then developed using Matlab-2012a. The results of the cell-based dosimetry model and MEP models were combined to calculate survival fractions (SF) for CTV margins of 2.0 and 2.5 cm. In the current work, oxygenation and heterogeneous radiosensitivity profiles were incorporated into the GBM model. The genetic heterogeneity was modelled using a range of α/β values (linear-quadratic model parameters) associated with different GBM cell lines. These values were distributed among the cells randomly, taken from a Gaussian-weighted sample of α/β values. Cellular oxygen pressure was distributed randomly taken from a sample weighted to profiles obtained from literature. Three types of GBM models were analysed: homogeneous-normoxic, heterogeneous-normoxic, and heterogeneous-hypoxic. The SF in different regions of the tumour model and the effect of the CTV margin extension from 2.0-2.5 cm on SFs were investigated for three MEP models. The SF within the beam was increased by up to three and two orders of magnitude following incorporation of heterogeneous radiosensitivities and hypoxia, respectively, in the GBM model. However, the total SF was shown to be overdominated by the presence of tumour cells in the penumbra region and to a lesser extent by genetic heterogeneity and hypoxia. CTV extension by 0.5 cm reduced the SF by a maximum of 78.6 ± 3.3%, 78.5 ± 3.3%, and 77.7 ± 3.1% for homogeneous and heterogeneous-normoxic, and heterogeneous hypoxic GBMs, respectively. Monte-Carlo model was developed to quantitatively evaluate SF for genetically
Montesinos, F. G.; Arnoso, J.; Luque, T.; Benavent, T.; Vieira, R.
2009-04-01
It is firmly established that, of all the geodetic or geophysical techniques available, gravity modelling plays an important role in helping us to understand volcanic structures. We present here a study of the structural setting of the volcanic island of La Gomera by the analysis and interpretation of high-resolution gravity data obtained over the island. The gravity data allow us to model the main subsurface anomaly sources of the island, which are related with its volcanic evolution. Our outcome is consistent with the results of previous geophysical and volcanological studies. La Gomera island occupies a central position in the Canarian archipelago. This archipelago is the result of construction and destruction of successive large edifices covering a time span of several million years. Intrusion of magma has caused the development of an enormous amount of dikes that constituted step by step the main framework of the hypabyssal roots of these edifices. La Gomera has a surface about 372 km2 with a roughly circular contour and it is characterised by its central massif of 1487 meters height, dropping steeply to the sea. This island is the only one on the archipelago with no signs of Pleistocene volcanic activity. Its distinctive morphological feature is the intense degree of erosion in all formations, with deep, vertical-walled valleys that cut the island radially and in which the tabular successions of basalts can be seen. The most complex and interesting unit of La Gomera is its Basal Complex, which crops out in a restricted area located at the North and it is formed of plutonic volcanic and sedimentary rocks cut by an extremely dense dyke network. According to several authors, the characteristics of this complex seem to support the hypothesis that these rocks were formed by processes of magmatic sedimentation in a fairly turbulent medium. These conditions could correspond, for instance, to the ones in a reservoir beneath a volcano. Another possibility is that this
Understanding Heterogeneity in Clinical Cohorts Using Normative Models: Beyond Case-Control Studies.
Marquand, Andre F; Rezek, Iead; Buitelaar, Jan; Beckmann, Christian F
2016-10-01
Despite many successes, the case-control approach is problematic in biomedical science. It introduces an artificial symmetry whereby all clinical groups (e.g., patients and control subjects) are assumed to be well defined, when biologically they are often highly heterogeneous. By definition, it also precludes inference over the validity of the diagnostic labels. In response, the National Institute of Mental Health Research Domain Criteria proposes to map relationships between symptom dimensions and broad behavioral and biological domains, cutting across diagnostic categories. However, to date, Research Domain Criteria have prompted few methods to meaningfully stratify clinical cohorts. We introduce normative modeling for parsing heterogeneity in clinical cohorts, while allowing predictions at an individual subject level. This approach aims to map variation within the cohort and is distinct from, and complementary to, existing approaches that address heterogeneity by employing clustering techniques to fractionate cohorts. To demonstrate this approach, we mapped the relationship between trait impulsivity and reward-related brain activity in a large healthy cohort (N = 491). We identify participants who are outliers within this distribution and show that the degree of deviation (outlier magnitude) relates to specific attention-deficit/hyperactivity disorder symptoms (hyperactivity, but not inattention) on the basis of individualized patterns of abnormality. Normative modeling provides a natural framework to study disorders at the individual participant level without dichotomizing the cohort. Instead, disease can be considered as an extreme of the normal range or as-possibly idiosyncratic-deviation from normal functioning. It also enables inferences over the degree to which behavioral variables, including diagnostic labels, map onto biology. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
Li, Qi-Lang; Wong, S. C.; Min, Jie; Tian, Shuo; Wang, Bing-Hong
2016-08-01
This study examines the cellular automata traffic flow model, which considers the heterogeneity of vehicle acceleration and the delay probability of vehicles. Computer simulations are used to identify three typical phases in the model: free-flow, synchronized flow, and wide moving traffic jam. In the synchronized flow region of the fundamental diagram, the low and high velocity vehicles compete with each other and play an important role in the evolution of the system. The analysis shows that there are two types of bistable phases. However, in the original Nagel and Schreckenberg cellular automata traffic model, there are only two kinds of traffic conditions, namely, free-flow and traffic jams. The synchronized flow phase and bistable phase have not been found.
Social dynamics with peer support on heterogeneous networks . The "mafia model"
Balbás Gambra, M.; Frey, E.
2011-10-01
Human behavior often exhibits a scheme in which individuals adopt indifferent, neutral, or radical positions on a given topic. The mechanisms leading to community formation are strongly related with social pressure and the topology of the contact network. Here, we discuss an approach to model social behavior which accounts for the protection by alike peers proportional to their relative abundance in the closest neighborhood. We explore the ensuing non-linear dynamics emphasizing the role of the specific structure of the social network, modeled by scale-free graphs. We find that both coexistence of opinions and consensus on the default position are possible stationary states of the model. In particular, we show how these states critically depend on the heterogeneity of the social network and the specific distribution of external control elements.
Directory of Open Access Journals (Sweden)
Mahmoud O. Elish
2013-01-01
Full Text Available Accurate estimation of software development effort is essential for effective management and control of software development projects. Many software effort estimation methods have been proposed in the literature including computational intelligence models. However, none of the existing models proved to be suitable under all circumstances; that is, their performance varies from one dataset to another. The goal of an ensemble model is to manage each of its individual models’ strengths and weaknesses automatically, leading to the best possible decision being taken overall. In this paper, we have developed different homogeneous and heterogeneous ensembles of optimized hybrid computational intelligence models for software development effort estimation. Different linear and nonlinear combiners have been used to combine the base hybrid learners. We have conducted an empirical study to evaluate and compare the performance of these ensembles using five popular datasets. The results confirm that individual models are not reliable as their performance is inconsistent and unstable across different datasets. Although none of the ensemble models was consistently the best, many of them were frequently among the best models for each dataset. The homogeneous ensemble of support vector regression (SVR, with the nonlinear combiner adaptive neurofuzzy inference systems-subtractive clustering (ANFIS-SC, was the best model when considering the average rank of each model across the five datasets.
Energy Technology Data Exchange (ETDEWEB)
Doligez, B.; Eschard, R. [Institut Francais du Petrole, Rueil Malmaison (France); Geffroy, F. [Centre de Geostatistique, Fontainebleau (France)] [and others
1997-08-01
The classical approach to construct reservoir models is to start with a fine scale geological model which is informed with petrophysical properties. Then scaling-up techniques allow to obtain a reservoir model which is compatible with the fluid flow simulators. Geostatistical modelling techniques are widely used to build the geological models before scaling-up. These methods provide equiprobable images of the area under investigation, which honor the well data, and which variability is the same than the variability computed from the data. At an appraisal phase, when few data are available, or when the wells are insufficient to describe all the heterogeneities and the behavior of the field, additional constraints are needed to obtain a more realistic geological model. For example, seismic data or stratigraphic models can provide average reservoir information with an excellent areal coverage, but with a poor vertical resolution. New advances in modelisation techniques allow now to integrate this type of additional external information in order to constrain the simulations. In particular, 2D or 3D seismic derived information grids, or sand-shale ratios maps coming from stratigraphic models can be used as external drifts to compute the geological image of the reservoir at the fine scale. Examples are presented to illustrate the use of these new tools, their impact on the final reservoir model, and their sensitivity to some key parameters.
Baumberg, V.; Helmschrot, J.; Steudel, T.; Göhmann, H.; Fischer, C.; Flügel, W.-A.
2014-09-01
The neighbouring river systems Cubango and Cuito drain the southeastern part of the Angolan Highlands and form the Okavango River after their confluence, thus providing 95% of the Okavango River discharge. Although they are characterised by similar environmental conditions, runoff records indicate remarkable differences regarding the hydrological dynamics. The Cubango River is known for rapid discharges with high peaks and low baseflow whereas the Cuito runoff appears more balanced. These differences are mainly caused by heterogeneous geological conditions or terrain features. The Cubango headwaters are dominated by crystalline bedrock and steeper, v-shaped valleys while the Cuito system is characterised by wide, swampy valleys and thick sand layers, thus attenuating runoff. This study presents model exercises which have been performed to assess and quantify these effects by applying the distributive model J2000g for each sub-basin. The models provide reasonable results representing the spatio-temporal runoff pattern, although some peaks are over- or underestimated, particularly in the Cuito catchment. This is explained by the scarce information on extent and structure of storages, such as aquifers or swamps, in the Cuito system. However, the model results aid understanding of the differences of both tributaries in runoff generation and underpin the importance of floodplains regarding the control of runoff peaks and low flows in the Cuito system. Model exercises reveal that basin heterogeneity needs to be taken into account and must be parameterised appropriately for reliable modelling and assessment of the entire Okavango River basin for managing the water resources of the transboundary Okavango River in a harmonious way.
Mao, Zhun; Saint-André, Laurent; Bourrier, Franck; Stokes, Alexia; Cordonnier, Thomas
2015-08-01
In mountain ecosystems, predicting root density in three dimensions (3-D) is highly challenging due to the spatial heterogeneity of forest communities. This study presents a simple and semi-mechanistic model, named ChaMRoots, that predicts root interception density (RID, number of roots m(-2)). ChaMRoots hypothesizes that RID at a given point is affected by the presence of roots from surrounding trees forming a polygon shape. The model comprises three sub-models for predicting: (1) the spatial heterogeneity - RID of the finest roots in the top soil layer as a function of tree basal area at breast height, and the distance between the tree and a given point; (2) the diameter spectrum - the distribution of RID as a function of root diameter up to 50 mm thick; and (3) the vertical profile - the distribution of RID as a function of soil depth. The RID data used for fitting in the model were measured in two uneven-aged mountain forest ecosystems in the French Alps. These sites differ in tree density and species composition. In general, the validation of each sub-model indicated that all sub-models of ChaMRoots had good fits. The model achieved a highly satisfactory compromise between the number of aerial input parameters and the fit to the observed data. The semi-mechanistic ChaMRoots model focuses on the spatial distribution of root density at the tree cluster scale, in contrast to the majority of published root models, which function at the level of the individual. Based on easy-to-measure characteristics, simple forest inventory protocols and three sub-models, it achieves a good compromise between the complexity of the case study area and that of the global model structure. ChaMRoots can be easily coupled with spatially explicit individual-based forest dynamics models and thus provides a highly transferable approach for modelling 3-D root spatial distribution in complex forest ecosystems. © The Author 2015. Published by Oxford University Press on behalf of the