Solute transport in aggregated and layered porous media

International Nuclear Information System (INIS)

Koch, S.

1993-01-01

This work is a contribution to research in soil physics dealing with solute transport in porous media. The influence of structural inhomogeneities on solute transport is investigated. Detailed experiments at the laboratory scale are used to enlighten distinct processes which cannot be studied separately at field scale. Two main aspects are followed up: (i) to show the influence of aggregation of a porous medium on breakthrough time and spreading of an inert tracer and consequences on the estimation of parameter values of models describing solute transport in aggregated systems, (ii) to investigate the influences on the dispersion process when stratification is perpendicular to the direction of flow. Several concepts of modelling solute transport in soil are discussed. Models based on the convection-dispersion equation (CDE) are emphasized because they are used here to model solute transport experiments conducted with aggregated porous media. Stochastic concepts are introduced to show the limitations of the deterministic CDE approaches. Experiments are done in columns containing two kinds of solid phases and were saturated with water. The solid phases are porous and solid glass beads exhibiting a distinctly unimodal or bimodal pore size distribution. Experimental breakthrough curves (BTCs) are modelled with the CDE, a bicontinuum model with a phenomenological mass transfer rate and a bicontinuum spherical diffusion model. Experiments are also done in columns that are unsaturated containing porous materials that are layered. Flow is made at a steady rate. It is shown that layer boundaries have a severe influence on lateral mixing. They may force streamlines to converge or cause a lateral redistribution of solutes. (author) figs., tabs., 122 refs

Exact and Numerical Solutions of a Spatially-Distributed Mathematical Model for Fluid and Solute Transport in Peritoneal Dialysis

Directory of Open Access Journals (Sweden)

Roman Cherniha

2016-06-01

Full Text Available The nonlinear mathematical model for solute and fluid transport induced by the osmotic pressure of glucose and albumin with the dependence of several parameters on the hydrostatic pressure is described. In particular, the fractional space available for macromolecules (albumin was used as a typical example and fractional fluid void volume were assumed to be different functions of hydrostatic pressure. In order to find non-uniform steady-state solutions analytically, some mathematical restrictions on the model parameters were applied. Exact formulae (involving hypergeometric functions for the density of fluid flux from blood to tissue and the fluid flux across tissues were constructed. In order to justify the applicability of the analytical results obtained, a wide range of numerical simulations were performed. It was found that the analytical formulae can describe with good approximation the fluid and solute transport (especially the rate of ultrafiltration for a wide range of values of the model parameters.

Temporal moment analysis of solute transport in a coupled fracture ...

Indian Academy of Sciences (India)

by considering an inlet boundary condition of constant continuous source in a single fracture. The effect of various fracture-skin parameters like porosity, thickness and ... Study on fluid flow and transport of solute through fractures has been an .... of solutes is happening normal to the direction of flow due to the free molecular.

Semianalytical solutions of radioactive or reactive tracer transport in layered fractured media

International Nuclear Information System (INIS)

Moridis, G.J.; Bodvarsson, G.S.

2001-01-01

In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive tracers (solutes or colloids) through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the matrix account for (a) diffusion, (b) surface diffusion (for solutes only), (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first order chemical reactions. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Additionally, the colloid transport equations account for straining and velocity adjustments related to the colloidal size. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of 3 H, 237 Np and 239 Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity. 239 Pu colloid transport problems in multilayered systems indicate significant colloid accumulations at straining interfaces but much faster transport of the colloid than the corresponding strongly sorbing solute species

Field-scale water flow and solute transport : SWAP model concepts, parameter estimation and case studies = [Waterstroming en transport van opgeloste stoffen op veldschaal

NARCIS (Netherlands)

Dam, van J.C.

2000-01-01

Water flow and solute transport in top soils are important elements in many environmental studies. The agro- and ecohydrological model SWAP (Soil-Water-Plant-Atmosphere) has been developed to simulate simultaneously water flow, solute transport, heat flow and crop growth at field scale

Soil transport parameters of potassium under a tropical saline soil condition using STANMOD

Science.gov (United States)

Suzanye da Silva Santos, Rafaelly; Honorio de Miranda, Jarbas; Previatello da Silva, Livia

2015-04-01

Environmental responsibility and concerning about the final destination of solutes in soil, so more studies allow a better understanding about the solutes behaviour in soil. Potassium is a macronutrient that is required in high concentrations, been an extremely important nutrient for all agricultural crops. It plays essential roles in physiological processes vital for plant growth, from protein synthesis to maintenance of plant water balance, and is available to plants dissolved in soil water while exchangeable K is loosely held on the exchange sites on the surface of clay particles. K will tend to be adsorbed onto the surface of negatively charged soil particles. Potassium uptake is vital for plant growth but in saline soils sodium competes with potassium for uptake across the plasma membrane of plant cells. This can result in high Na+:K+ ratios that reduce plant growth and eventually become toxic. This study aimed to obtain soil transport parameters of potassium in saline soil, such as: pore water velocity in soil (v), retardation factor (R), dispersivity (λ) and dispersion coefficient (D), in a disturbed sandy soil with different concentrations of potassium chlorate solution (KCl), which is one of the most common form of potassium fertilizer. The experiment was carried out using soil samples collected in a depth of 0 to 20 cm, applying potassium chlorate solution containing 28.6, 100, 200 and 500 mg L-1 of K. To obtain transport parameters, the data were adjusted with the software STANMOD. At low concentrations, interaction between potassium and soil occur more efficiently. It was observed that only the breakthrough curve prepared with solution of 500 mg L-1 reached the applied concentration, and the solution of 28.6 mg L-1 overestimated the parameters values. The STANMOD proved to be efficient in obtaining potassium transport parameters; KCl solution to be applied should be greater than 500 mg L-1; solutions with low concentrations tend to overestimate

The use of non-dimensional representation of the solute transport equations

International Nuclear Information System (INIS)

Laurens, J.-M.

1988-07-01

This report presents the results obtained in a pilot investigation into the use of non-dimensional representations of the solute transport equations, so as to improve the efficiency of the PRA codes used by the DoE and its contractors. A reduced set of parameters was obtained for a single layer transport model. As expected, the response was shown to be highly sensitive on the new parameters. A faster convergence of the system was observed when the sampling technique used was changed to take into account the properties of the new parameters, such that uniform coverage of the reduced parameter hyperspace was achieved. (author)

Bayesian estimation of the hydraulic and solute transport properties of a small-scale unsaturated soil column

Directory of Open Access Journals (Sweden)

Moreira Paulo H. S.

2016-03-01

Full Text Available In this study the hydraulic and solute transport properties of an unsaturated soil were estimated simultaneously from a relatively simple small-scale laboratory column infiltration/outflow experiment. As governing equations we used the Richards equation for variably saturated flow and a physical non-equilibrium dual-porosity type formulation for solute transport. A Bayesian parameter estimation approach was used in which the unknown parameters were estimated with the Markov Chain Monte Carlo (MCMC method through implementation of the Metropolis-Hastings algorithm. Sensitivity coefficients were examined in order to determine the most meaningful measurements for identifying the unknown hydraulic and transport parameters. Results obtained using the measured pressure head and solute concentration data collected during the unsaturated soil column experiment revealed the robustness of the proposed approach.

Modeling water flow and solute transport in unsaturated zone inside NSRAWD project

International Nuclear Information System (INIS)

Constantin, A.; Diaconu, D.; Bucur, C.; Genty, A.

2015-01-01

The NSRAWD project (2010-2013) - Numerical Simulations for Radioactive Waste Disposal was initiated under a collaboration agreement between the Institute for Nuclear Research and the French Alternative Energies and Atomic Energy Commission (CEA). The context of the project was favorable to combine the modeling activities with an experimental part in order to improve and validate the numerical models used so far to simulate water flow and solute transport at Saligny site, Romania. The numerical models developed in the project were refined and validated on new hydrological data gathered between 2010-2012 by a monitoring station existent on site which performs automatic determination of soil water content and matrix potential, as well as several climate parameters (wind, temperature and precipitations). Water flow and solute transport was modeled in transient conditions, by taking into consideration, as well as neglecting the evapotranspiration phenomenon, on the basis of a tracer test launched on site. The determination of dispersivities for solute transport was targeted from the solute plume. The paper presents the main results achieved in the NSRAWD project related to water flow and solute transport in the unsaturated area of the Saligny site. The results indicated satisfactory predictions for the simulation of water flow in the unsaturated area, in steady state and transient conditions. In the case of tracer transport modeling, dispersivity coefficients could not be finally well fitted for the data measured on site and in order to obtain a realistic preview over the values of these parameters, further investigations are recommended. The article is followed by the slides of the presentation

Effect of fractional parameter on neutron transport in finite disturbed reactors with quadratic scattering

International Nuclear Information System (INIS)

Sallah, M.; Margeanu, C. A.

2016-01-01

The space-fractional neutron transport equation is used to describe the neutrons transport in finite disturbed reactors. It is approximated using the Pomraning-Eddington technique to yield two space-fractional differential equations, in terms of neutron density and net neutron flux. These resultant equations are coupled into a fractional diffusion-like equation for the neutron density whose solution is obtained by using Laplace transformation method. The solution is represented in terms of the Mittag-Leffler function and its different orders. The scattering is considered as quadratic scattering to offer a more realistic, compact representation of the system, and to increase the accuracy of the estimated neutronic parameters. The results are presented graphically to illustrate the fractional parameter effect in addition to the effect of radiative-transfer properties on the physical parameters of interest (reflection coefficient, transmission coefficient, neutron energy, and net neutron flux). The neutron transport problem in finite disturbed reactor with quadratic scattering is considered in investigating the shielding effectiveness, by using MAVRIC shielding module from SCALE6 programs package. The fractional parameter can be used to adjust the analysed data on neutron energy and flux, both for the theoretical model and the neutron transport application. (authors)

Optimal solution of full fuzzy transportation problems using total integral ranking

Science.gov (United States)

Sam’an, M.; Farikhin; Hariyanto, S.; Surarso, B.

2018-03-01

Full fuzzy transportation problem (FFTP) is a transportation problem where transport costs, demand, supply and decision variables are expressed in form of fuzzy numbers. To solve fuzzy transportation problem, fuzzy number parameter must be converted to a crisp number called defuzzyfication method. In this new total integral ranking method with fuzzy numbers from conversion of trapezoidal fuzzy numbers to hexagonal fuzzy numbers obtained result of consistency defuzzyfication on symmetrical fuzzy hexagonal and non symmetrical type 2 numbers with fuzzy triangular numbers. To calculate of optimum solution FTP used fuzzy transportation algorithm with least cost method. From this optimum solution, it is found that use of fuzzy number form total integral ranking with index of optimism gives different optimum value. In addition, total integral ranking value using hexagonal fuzzy numbers has an optimal value better than the total integral ranking value using trapezoidal fuzzy numbers.

Numerical solution of the radionuclide transport equation

International Nuclear Information System (INIS)

Hadermann, J.; Roesel, F.

1983-11-01

A numerical solution of the one-dimensional geospheric radionuclide chain transport equation based on the pseudospectral method is developed. The advantages of this approach are flexibility in incorporating space and time dependent migration parameters, arbitrary boundary conditions and solute rock interactions as well as efficiency and reliability. As an application the authors investigate the impact of non-linear sorption isotherms on migration in crystalline rock. It is shown that non-linear sorption, in the present case a Freundlich isotherm, may reduce concentration at the geosphere outlet by orders of magnitude provided the migration time is comparable or larger than the half-life of the nuclide in question. The importance of fixing dispersivity within the continuum approach is stressed. (Auth.)

Ajuste de parâmetros de transporte de solutos no solo utilizando Matlab 6.5 Adjustment of soil solute transport parameters with Matlab 6.5

Directory of Open Access Journals (Sweden)

Anderson L. de Souza

2011-12-01

Full Text Available O sucesso na utilização de modelos matemáticos no estudo do transporte de íons no solo está intimamente ligado à precisão com que os parâmetros de transporte envolvidos neste processo são estabelecidos. De maneira geral, tais parâmetros são determinados mediante a resolução de um problema de otimização não linear em que os dados experimentais, obtidos em ensaios de deslocamento miscível, são ajustados a um modelo teórico. Neste sentido, a utilização de softwares de alta performance no ajuste destes parâmetros mostra-se vantajosa, uma vez que, além da consistência e da disponibilidade de ferramentas numéricas preexistentes, possibilita a incorporação de novas rotinas de acordo com o fenômeno que se queira simular. Sendo assim, este trabalho teve como objetivo desenvolver, em ambiente MATLAB 6.5, uma rotina computacional para a otimização dos seguintes parâmetros de transporte: fator de retardamento (R e coeficiente de dispersão (D. A rotina desenvolvida foi aplicada a dados experimentais de três ensaios de deslocamento miscível do íon potássio em colunas preenchidas com um Latossolo Vermelho- -Amarelo, fase arenosa. A qualidade dos ajustes obtidos foi avaliada utilizando-se do coeficiente de exatidão. Concluiu-se que a rotina proposta apresentou ótimo desempenho, o que, além de reforçar a consistência do método numérico utilizado, indica que a rotina proposta neste trabalho pode contribuir com o avanço dos estudos teóricos da dinâmica da água e de solutos em meios porosos não saturados.The successful use of mathematical models in studies of solute transport in soil is dependent on the accuracy to which the transport parameters involved in this process can be specified. In general, these parameters are determined by using nonlinear optimization techniques to fit theoretical models to experimental data obtained in miscible displacement experiments. The use, therefore, of high-performance software to

Analytical solutions of a fractional diffusion-advection equation for solar cosmic-ray transport

International Nuclear Information System (INIS)

Litvinenko, Yuri E.; Effenberger, Frederic

2014-01-01

Motivated by recent applications of superdiffusive transport models to shock-accelerated particle distributions in the heliosphere, we analytically solve a one-dimensional fractional diffusion-advection equation for the particle density. We derive an exact Fourier transform solution, simplify it in a weak diffusion approximation, and compare the new solution with previously available analytical results and with a semi-numerical solution based on a Fourier series expansion. We apply the results to the problem of describing the transport of energetic particles, accelerated at a traveling heliospheric shock. Our analysis shows that significant errors may result from assuming an infinite initial distance between the shock and the observer. We argue that the shock travel time should be a parameter of a realistic superdiffusive transport model.

A Mathematical Model of Solute Coupled Water Transport in Toad Intestine Incorporating Recirculation of the Actively Transported Solute

DEFF Research Database (Denmark)

Larsen, Erik Hviid; Sørensen, Jakob Balslev; Sørensen, Jens Nørkær

2000-01-01

those of tight junction and interspace basement membrane by convection-diffusion. With solute permeability of paracellular pathway large relative to paracellular water flow, the paracellular flux ratio of the solute (influx/outflux) is small (2-4) in agreement with experiments. The virtual solute......A mathematical model of an absorbing leaky epithelium is developed for analysis of solute coupled water transport. The non-charged driving solute diffuses into cells and is pumped from cells into the lateral intercellular space (lis). All membranes contain water channels with the solute passing...... increases with hydraulic conductance of the pathway carrying water from mucosal solution into lis. Uphill water transport is accomplished, but with high hydraulic conductance of cell membranes strength of transport is obscured by water flow through cells. Anomalous solvent drag occurs when back flux...

Predictability of solute transport in diffusion-controlled hydrogeologic regimes

International Nuclear Information System (INIS)

Gillham, R.W.; Cherry, J.A.

1983-01-01

Hydrogeologic regimes that are favourable for the subsurface management of low-level radioactive wastes must have transport properties that will limit the migration velocity of contaminants to some acceptably low value. Of equal importance, for the purpose of impact assessment and licensing, is the need to be able to predict, with a reasonable degree of certainty and over long time periods, what the migration velocity of the various contaminants of interest will be. This paper presents arguments to show that in addition to having favourable velocity characteristics, transport in saturated, diffusion-controlled hydrogeologic regimes is considerably more predictable than in the most common alternatives. The classical transport models for unsaturated, saturated-advection-controlled and saturated-diffusion-controlled environments are compared, with particular consideration being given to the difficulties associated with the characterization of the respective transport parameters. Results are presented which show that the diffusion of non-reactive solutes and solutes that react according to a constant partitioning ratio (K/sub d/) are highly predictable under laboratory conditions and that the diffusion coefficients for the reactive solutes can be determined with a reasonable degree of accuracy from independent measurements of bulk density, porosity, distribution coefficient and tortuosity. Field evidence is presented which shows that the distribution of environmental isotopes and chloride in thick clayey deposits is consistent with a diffusion-type transport process in these media. These results are particularly important in that they not only demonstrate the occurrence of diffusion-controlled hydrogeologic regimes, but they also demonstrate the predictability of the migration characteristics over very long time periods

Coupled Spatio-Temporal Patterns of Solute Transport, Metabolism and Nutrient Uptake in Streams

Science.gov (United States)

Kurz, M. J.; Schmidt, C.

2017-12-01

Slower flow velocities and longer residence times within stream transient storage (TS) zones facilitate interaction between solutes and microbial communities, potentially increasing local rates of metabolic activity. Multiple factors, including channel morphology and substrate, variable hydrology, and seasonal changes in biological and physical parameters, result in changes in the solute transport dynamics and reactivity of TS zones over time and space. These changes would be expected to, in turn, influence rates of whole-stream ecosystem functions such as metabolism and nutrient uptake. However, the linkages between solute transport and ecosystem functioning within TS zones, and the contribution of TS zones to whole-stream functioning, are not always so straight forward. This may be due, in part, to methodological challenges. In this study we investigated the influence of stream channel hydro-morphology and substrate type on reach (103 m) and sub-reach (102 m) scale TS and ecosystem functioning. Patterns in solute transport, metabolism and nitrate uptake were tracked from April through October in two contrasting upland streams using several methods. The two streams, located in the Harz Mountains, Germany, are characterized by differing size (0.02 vs. 0.3 m3/s), dominant stream channel substrate (bedrock vs. alluvium) and sub-reach morphology (predominance of pools, riffles and glides). Solute transport parameters and respiration rates at the reach and sub-reach scale were estimated monthly from coupled pulse injections of the reactive tracer resazurin (Raz) and conservative tracers uranine and salt. Raz, a weakly fluorescent dye, irreversibly transforms to resorufin (Rru) under mildly reducing conditions, providing a proxy for aerobic respiration. Daily rates of primary productivity, respiration and nitrate retention at the reach scale were estimated using the diel cycles in dissolved oxygen and nitrate concentrations measured by in-situ sensors. Preliminary

Explicit finite-difference solution of two-dimensional solute transport with periodic flow in homogenous porous media

Directory of Open Access Journals (Sweden)

Djordjevich Alexandar

2017-12-01

Full Text Available The two-dimensional advection-diffusion equation with variable coefficients is solved by the explicit finitedifference method for the transport of solutes through a homogenous two-dimensional domain that is finite and porous. Retardation by adsorption, periodic seepage velocity, and a dispersion coefficient proportional to this velocity are permitted. The transport is from a pulse-type point source (that ceases after a period of activity. Included are the firstorder decay and zero-order production parameters proportional to the seepage velocity, and periodic boundary conditions at the origin and at the end of the domain. Results agree well with analytical solutions that were reported in the literature for special cases. It is shown that the solute concentration profile is influenced strongly by periodic velocity fluctuations. Solutions for a variety of combinations of unsteadiness of the coefficients in the advection-diffusion equation are obtainable as particular cases of the one demonstrated here. This further attests to the effectiveness of the explicit finite difference method for solving two-dimensional advection-diffusion equation with variable coefficients in finite media, which is especially important when arbitrary initial and boundary conditions are required.

Solute carrier transporters: Pharmacogenomics research ...

African Journals Online (AJOL)

Aghogho

2010-12-27

Dec 27, 2010 ... This paper reviews the solute carrier transporters and highlights the fact that there is much to be learnt from .... transporters, drug targets, effect or proteins and meta- ... basolateral or apical plasma membrane of polarized cells,.

Application of multiphysics models to efficient design of experiments of solute transport across articular cartilage.

Science.gov (United States)

Pouran, Behdad; Arbabi, Vahid; Weinans, Harrie; Zadpoor, Amir A

2016-11-01

Transport of solutes helps to regulate normal physiology and proper function of cartilage in diarthrodial joints. Multiple studies have shown the effects of characteristic parameters such as concentration of proteoglycans and collagens and the orientation of collagen fibrils on the diffusion process. However, not much quantitative information and accurate models are available to help understand how the characteristics of the fluid surrounding articular cartilage influence the diffusion process. In this study, we used a combination of micro-computed tomography experiments and biphasic-solute finite element models to study the effects of three parameters of the overlying bath on the diffusion of neutral solutes across cartilage zones. Those parameters include bath size, degree of stirring of the bath, and the size and concentration of the stagnant layer that forms at the interface of cartilage and bath. Parametric studies determined the minimum of the finite bath size for which the diffusion behavior reduces to that of an infinite bath. Stirring of the bath proved to remarkably influence neutral solute transport across cartilage zones. The well-stirred condition was achieved only when the ratio of the diffusivity of bath to that of cartilage was greater than ≈1000. While the thickness of the stagnant layer at the cartilage-bath interface did not significantly influence the diffusion behavior, increase in its concentration substantially elevated solute concentration in cartilage. Sufficient stirring attenuated the effects of the stagnant layer. Our findings could be used for efficient design of experimental protocols aimed at understanding the transport of molecules across articular cartilage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Study of reactive solutes transport and PAH migration in unsaturated soils

International Nuclear Information System (INIS)

Gujisaite, V.; Simonnot, M.O.; Gujisaite, V.; Morel, J.L.; Ouvrard, S.; Simonnot, M.O.; Gaudet, J.P.

2005-01-01

-silty uncontaminated soil or a sand and a model porous medium constituted of sand in which coal tar particles are dispersed. In a second time, column experiments will be carried out with a PAH contaminated soil from a former coking plant and with a multi-polluted industrial soil (PAH, heavy metals) to study PAH migration. For each studied soil, we will also determine the water retention curve in order to find the best operating conditions for our experiments with unsaturated flow. Modelling of solutes transfer in soils is also needed to improve understanding of the fate of contaminants and for risk assessment. However, it is difficult to take into account at the same time flow and interactions in models. Different models and numerical codes have been developed for solute transport. We have chosen to use the CXTFIT code, in order to model our results. This code allows indeed modelling of reactive solute transport in unsaturated porous media as well as under saturated conditions. It is usually used to estimate solute transport parameters using a nonlinear least-squares parameter optimization method. It may be used to solve the inverse problem by fitting a variety of mathematical solutions of theoretical transport models, based upon the one-dimensional convection-dispersion equation (CDE), to experimental results. The program may also be used to solve the direct or forward problem to determine concentrations as a function of time and/or position. This study at a bench scale will enable us at first to develop a methodology under unsaturated conditions and also to better understand the dominating mechanisms which control PAH transfer and availability in natural soils, especially by quantifying the impact of parameters like soil water content, water flow or the presence of plants. This is a first step before the change of scale (lysimeter). Modelling of the observed processes will also enable us to predict long term fate of PAH in soils

A quasilinear model for solute transport under unsaturated flow

International Nuclear Information System (INIS)

Houseworth, J.E.; Leem, J.

2009-01-01

We developed an analytical solution for solute transport under steady-state, two-dimensional, unsaturated flow and transport conditions for the investigation of high-level radioactive waste disposal. The two-dimensional, unsaturated flow problem is treated using the quasilinear flow method for a system with homogeneous material properties. Dispersion is modeled as isotropic and is proportional to the effective hydraulic conductivity. This leads to a quasilinear form for the transport problem in terms of a scalar potential that is analogous to the Kirchhoff potential for quasilinear flow. The solutions for both flow and transport scalar potentials take the form of Fourier series. The particular solution given here is for two sources of flow, with one source containing a dissolved solute. The solution method may easily be extended, however, for any combination of flow and solute sources under steady-state conditions. The analytical results for multidimensional solute transport problems, which previously could only be solved numerically, also offer an additional way to benchmark numerical solutions. An analytical solution for two-dimensional, steady-state solute transport under unsaturated flow conditions is presented. A specific case with two sources is solved but may be generalized to any combination of sources. The analytical results complement numerical solutions, which were previously required to solve this class of problems.

Mathematical modeling of solute transport in the subsurface

International Nuclear Information System (INIS)

Naymik, T.G.

1987-01-01

A review of key works on solute transport models indicates that solute transport processes with the exception of advection are still poorly understood. Solute transport models generally do a good job when they are used to test scientific concepts and hypotheses, investigate natural processes, systematically store and manage data, and simulate mass balance of solutes under certain natural conditions. Solute transport models generally are not good for predicting future conditions with a high degree of certainty, or for determining concentrations precisely. The mathematical treatment of solute transport far surpasses their understanding of the process. Investigations of the extent of groundwater contamination and methods to remedy existing problems show the along-term nature of the hazard. Industrial organic compounds may be immiscible in water, highly volatile, or complexed with inorganic as well as other organic compounds; many remain stable in nature almost indefinitely. In the worst case, future disposal of hazardous waste may be restricted to deep burial, as is proposed for radioactive wastes. For investigations pertinent to transport of radionuclides from a geologic repository, the process cannot be fully understood without adequate thermodynamic and kinetic data bases

Reactive silica transport in fractured porous media: Analytical solutions for a system of parallel fractures

Science.gov (United States)

Yang, Jianwen

2012-04-01

A general analytical solution is derived by using the Laplace transformation to describe transient reactive silica transport in a conceptualized 2-D system involving a set of parallel fractures embedded in an impermeable host rock matrix, taking into account of hydrodynamic dispersion and advection of silica transport along the fractures, molecular diffusion from each fracture to the intervening rock matrix, and dissolution of quartz. A special analytical solution is also developed by ignoring the longitudinal hydrodynamic dispersion term but remaining other conditions the same. The general and special solutions are in the form of a double infinite integral and a single infinite integral, respectively, and can be evaluated using Gauss-Legendre quadrature technique. A simple criterion is developed to determine under what conditions the general analytical solution can be approximated by the special analytical solution. It is proved analytically that the general solution always lags behind the special solution, unless a dimensionless parameter is less than a critical value. Several illustrative calculations are undertaken to demonstrate the effect of fracture spacing, fracture aperture and fluid flow rate on silica transport. The analytical solutions developed here can serve as a benchmark to validate numerical models that simulate reactive mass transport in fractured porous media.

Continuous time random walk analysis of solute transport in fractured porous media

Energy Technology Data Exchange (ETDEWEB)

Cortis, Andrea; Cortis, Andrea; Birkholzer, Jens

2008-06-01

The objective of this work is to discuss solute transport phenomena in fractured porous media, where the macroscopic transport of contaminants in the highly permeable interconnected fractures can be strongly affected by solute exchange with the porous rock matrix. We are interested in a wide range of rock types, with matrix hydraulic conductivities varying from almost impermeable (e.g., granites) to somewhat permeable (e.g., porous sandstones). In the first case, molecular diffusion is the only transport process causing the transfer of contaminants between the fractures and the matrix blocks. In the second case, additional solute transfer occurs as a result of a combination of advective and dispersive transport mechanisms, with considerable impact on the macroscopic transport behavior. We start our study by conducting numerical tracer experiments employing a discrete (microscopic) representation of fractures and matrix. Using the discrete simulations as a surrogate for the 'correct' transport behavior, we then evaluate the accuracy of macroscopic (continuum) approaches in comparison with the discrete results. However, instead of using dual-continuum models, which are quite often used to account for this type of heterogeneity, we develop a macroscopic model based on the Continuous Time Random Walk (CTRW) framework, which characterizes the interaction between the fractured and porous rock domains by using a probability distribution function of residence times. A parametric study of how CTRW parameters evolve is presented, describing transport as a function of the hydraulic conductivity ratio between fractured and porous domains.

Demographic and transportation parameters in RADTRAN

International Nuclear Information System (INIS)

Brogan, J.D.; Cashwell, J.W.; Neuhauser, K.S.

1989-01-01

Recent efforts at Sandia National Laboratories have focused not only on modification of the RADTRAN transportation risk analysis code but also on updating the default parameters for population, land use, and roadway characteristics used by the code. Changes to the code have been discussed earlier in this Conference. This paper summarizes the results of a review of transportation and demographic parameters, performed to complement recent model modifications

Influence of pore structure on solute transport in degraded and undegraded fen peat soils

Directory of Open Access Journals (Sweden)

C. Kleimeier

2017-10-01

Full Text Available In peat soils, decomposition and degradation reduce the proportion of large pores by breaking down plant debris into smaller fragments and infilling inter-particle pore spaces. This affects water flow and solute migration which, in turn, influence reactive transport processes and biogeochemical functions. In this study we conducted flow-through reactor experiments to investigate the interplay between pore structure and solute transport in samples of undegraded and degraded peat collected in Canada and Germany, respectively. The pore size distributions and transport parameters were characterised using the breakthrough curve and two-region non-equilibrium transport model analyses for a non-reactive solute. The results of transport characterisation showed a higher fraction of immobile pores in the degraded peat with higher diffusive exchanges of solutes between the mobile and immobile pores associated with the dual-porosity structure. The rates of steady-state potential nitrate reduction were compared with pore fractions and exchange coefficients to investigate the influence of pore structure on the rates of nitrate reduction. The results indicated that the degraded peat has potential to provide the necessary boundary conditions to support nitrate removal and serves as a favourable substrate for denitrification, due to the nature of its pore structure and its lower organic carbon content compared to undegraded peat.

An Experimental Study on Solute Transport in One-Dimensional Clay Soil Columns

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Muhammad Zaheer

2017-01-01

Full Text Available Solute transport in low-permeability media such as clay has not been studied carefully up to present, and we are often unclear what the proper governing law is for describing the transport process in such media. In this study, we composed and analyzed the breakthrough curve (BTC data and the development of leaching in one-dimensional solute transport experiments in low-permeability homogeneous and saturated media at small scale, to identify key parameters controlling the transport process. Sodium chloride (NaCl was chosen to be the tracer. A number of tracer tests were conducted to inspect the transport process under different conditions. The observed velocity-time behavior for different columns indicated the decline of soil permeability when switching from tracer introducing to tracer flushing. The modeling approaches considered were the Advection-Dispersion Equation (ADE, Two-Region Model (TRM, Continuous Time Random Walk (CTRW, and Fractional Advection-Dispersion Equation (FADE. It was found that all the models can fit the transport process very well; however, ADE and TRM were somewhat unable to characterize the transport behavior in leaching. The CTRW and FADE models were better in capturing the full evaluation of tracer-breakthrough curve and late-time tailing in leaching.

A stochastic solution of the advective transport equation with uncertainty

International Nuclear Information System (INIS)

Williams, M.M.R.

1991-01-01

A model has been developed for calculating the transport of water-borne radionuclides through layers of porous materials, such as rock or clay. The model is based upon a purely advective transport equation, in which the fluid velocity is a random variable, thereby simulating dispersion in a more realistic manner than the ad hoc introduction of a dispersivity. In addition to a random velocity field, which is an observable physical phenomenon, allowance is made for uncertainty in our knowledge of the parameters which enter the equation, e.g. the retardation coefficient. This too, is assumed to be a random variable and contributes to the stochasticity of the resulting partial differential equation of transport. The stochastic differential equation can be solved analytically and then ensemble averages taken over the associated probability distribution of velocity and retardation coefficient. A method based upon a novel form of the central limit theorem of statistics is employed to obtain tractable solutions of a system consisting of many serial legs of varying properties. One interesting conclusion is that the total flux out of a medium is significantly underestimated by using the deterministic solution with an average transit time compared with that from the stochastically averaged solution. The theory is illustrated numerically for a number of physically relevant cases. (author) 8 figs., 4 tabs., 7 refs

Modeling variably saturated subsurface solute transport with MODFLOW-UZF and MT3DMS

Science.gov (United States)

Morway, Eric D.; Niswonger, Richard G.; Langevin, Christian D.; Bailey, Ryan T.; Healy, Richard W.

2013-01-01

The MT3DMS groundwater solute transport model was modified to simulate solute transport in the unsaturated zone by incorporating the unsaturated-zone flow (UZF1) package developed for MODFLOW. The modified MT3DMS code uses a volume-averaged approach in which Lagrangian-based UZF1 fluid fluxes and storage changes are mapped onto a fixed grid. Referred to as UZF-MT3DMS, the linked model was tested against published benchmarks solved analytically as well as against other published codes, most frequently the U.S. Geological Survey's Variably-Saturated Two-Dimensional Flow and Transport Model. Results from a suite of test cases demonstrate that the modified code accurately simulates solute advection, dispersion, and reaction in the unsaturated zone. Two- and three-dimensional simulations also were investigated to ensure unsaturated-saturated zone interaction was simulated correctly. Because the UZF1 solution is analytical, large-scale flow and transport investigations can be performed free from the computational and data burdens required by numerical solutions to Richards' equation. Results demonstrate that significant simulation runtime savings can be achieved with UZF-MT3DMS, an important development when hundreds or thousands of model runs are required during parameter estimation and uncertainty analysis. Three-dimensional variably saturated flow and transport simulations revealed UZF-MT3DMS to have runtimes that are less than one tenth of the time required by models that rely on Richards' equation. Given its accuracy and efficiency, and the wide-spread use of both MODFLOW and MT3DMS, the added capability of unsaturated-zone transport in this familiar modeling framework stands to benefit a broad user-ship.

Composite Transport Model and Water and Solute Transport across Plant Roots: An Update.

Science.gov (United States)

Kim, Yangmin X; Ranathunge, Kosala; Lee, Seulbi; Lee, Yejin; Lee, Deogbae; Sung, Jwakyung

2018-01-01

The present review examines recent experimental findings in root transport phenomena in terms of the composite transport model (CTM). It has been a well-accepted conceptual model to explain the complex water and solute flows across the root that has been related to the composite anatomical structure. There are three parallel pathways involved in the transport of water and solutes in roots - apoplast, symplast, and transcellular paths. The role of aquaporins (AQPs), which facilitate water flows through the transcellular path, and root apoplast is examined in terms of the CTM. The contribution of the plasma membrane bound AQPs for the overall water transport in the whole plant level was varying depending on the plant species, age of roots with varying developmental stages of apoplastic barriers, and driving forces (hydrostatic vs. osmotic). Many studies have demonstrated that the apoplastic barriers, such as Casparian bands in the primary anticlinal walls and suberin lamellae in the secondary cell walls, in the endo- and exodermis are not perfect barriers and unable to completely block the transport of water and some solute transport into the stele. Recent research on water and solute transport of roots with and without exodermis triggered the importance of the extension of conventional CTM adding resistances that arrange in series (epidermis, exodermis, mid-cortex, endodermis, and pericycle). The extension of the model may answer current questions about the applicability of CTM for composite water and solute transport of roots that contain complex anatomical structures with heterogeneous cell layers.

Hyporheic less-mobile porosity and solute transport in porous media

Science.gov (United States)

MahmoodPoorDehkordy, F.; Briggs, M. A.; Day-Lewis, F. D.; Scruggs, C.; Singha, K.; Zarnetske, J. P.; Lane, J. W., Jr.; Bagtzoglou, A. C.

2017-12-01

Solute transport and reactive processes are strongly influenced by hydrodynamic exchange with the hyporheic zone. Contaminant transport and redox zonation in the hyporheic zone and near-stream aquifer can be impacted by the exchange between mobile and less-mobile porosity zones in heterogeneous porous media. Less-mobile porosity zones can be created by fine materials with tight pore throats (e.g. clay, organics) and in larger, well-connected pores down gradient of flow obstructions (e.g. sand behind cobbles). Whereas fluid sampling is primarily responsive to the more-mobile domain, tracking solute tracer dynamics by geoelectrical methods provides direct information about both more- and less-mobile zones. During tracer injection through porous media of varied pore connectivity, a lag between fluid and bulk electrical conductivity is observed, creating a hysteresis loop when plotted in conductivity space. Thus, the combination of simultaneous fluid and bulk electrical conductivity measurements enables a much improved quantification of less-mobile solute dynamics compared to traditional fluid-only sampling approaches. We have demonstrated the less-mobile porosity exchange in laboratory-scale column experiments verified by simulation models. The experimental approach has also been applied to streambed sediments in column and reach-scale field experiments and verified using numerical simulation. Properties of the resultant hysteresis loops can be used to estimate exchange parameters of less-mobile porosity. Our integrated approach combining field experiments, laboratory experiments, and numerical modeling provides new insights into the effect of less-mobile porosity on solute transport in the hyporheic zone.

Composite Transport Model and Water and Solute Transport across Plant Roots: An Update

Directory of Open Access Journals (Sweden)

Yangmin X. Kim

2018-02-01

Full Text Available The present review examines recent experimental findings in root transport phenomena in terms of the composite transport model (CTM. It has been a well-accepted conceptual model to explain the complex water and solute flows across the root that has been related to the composite anatomical structure. There are three parallel pathways involved in the transport of water and solutes in roots – apoplast, symplast, and transcellular paths. The role of aquaporins (AQPs, which facilitate water flows through the transcellular path, and root apoplast is examined in terms of the CTM. The contribution of the plasma membrane bound AQPs for the overall water transport in the whole plant level was varying depending on the plant species, age of roots with varying developmental stages of apoplastic barriers, and driving forces (hydrostatic vs. osmotic. Many studies have demonstrated that the apoplastic barriers, such as Casparian bands in the primary anticlinal walls and suberin lamellae in the secondary cell walls, in the endo- and exodermis are not perfect barriers and unable to completely block the transport of water and some solute transport into the stele. Recent research on water and solute transport of roots with and without exodermis triggered the importance of the extension of conventional CTM adding resistances that arrange in series (epidermis, exodermis, mid-cortex, endodermis, and pericycle. The extension of the model may answer current questions about the applicability of CTM for composite water and solute transport of roots that contain complex anatomical structures with heterogeneous cell layers.

Ion Transport in Organic Electrolyte Solution through the Pore Channels of Anodic Nanoporous Alumina Membranes

International Nuclear Information System (INIS)

Fukutsuka, Tomokazu; Koyamada, Kohei; Maruyama, Shohei; Miyazaki, Kohei; Abe, Takeshi

2016-01-01

Highlights: • Ion transport in organic electrolyte solution in macro- and meso-pores was focused. • Anodic nanoporous alumina membrane was used as a porous material. • The specific ion conductivities drastically decreased in macro- and meso-pores. - Abstract: For the development of high energy density lithium-ion batteries with the high rate performance, the enhancement of the ion transport in the electrolyte solutions impregnated in the porous electrodes is a key. To study the ion transport in porous electrodes, anodic nanoporous alumina (APA) self-standing membranes with macro- or meso-pores were used as model porous materials. These membranes had nearly spherical pore channels of discrete 20–68 nm in diameters. By using the geometric shape of the pores, we attempted to evaluate the specific ion conductivities of the organic electrolyte solution dissolving lithium salt simply. AC impedance spectroscopy measurement of a four-electrode cell with membranes showed one depressed semi-circle in the Nyquist plots and this semi-circle can be assigned as the ion transport resistance in the pores. The specific ion conductivities evaluated from the ion transport resistances and the geometric parameters showed very small values, even in the macro-pores, as compared with that of the bulk electrolyte solution.

New two- and three-parameter solutions of the MPST equation

International Nuclear Information System (INIS)

Krori, K.D.; Chaudhury, T.; Bhattacharjee, R.

1981-01-01

Some new two- and three-parameter solutions of the MPST (Misra et al. Phys. Rev.; D7:1587 (1973)) equation are presented. All the three-parameter solutions are physical in the sense of asymptotic flatness. The simplest member of the three-parameter series of solutions is identical with a three-parameter solution of the static Einstein-Maxwell equations recently discovered by Bonnor (J. Phys. A.; 12:853 (1979)). (author)

Exact solution of the neutron transport equation in spherical geometry

Energy Technology Data Exchange (ETDEWEB)

Anli, Fikret; Akkurt, Abdullah; Yildirim, Hueseyin; Ates, Kemal [Kahramanmaras Suetcue Imam Univ. (Turkey). Faculty of Sciences and Letters

2017-03-15

Solution of the neutron transport equation in one dimensional slab geometry construct a basis for the solution of neutron transport equation in a curvilinear geometry. Therefore, in this work, we attempt to derive an exact analytical benchmark solution for both neutron transport equations in slab and spherical medium by using P{sub N} approximation which is widely used in neutron transport theory.

Riccati-parameter solutions of nonlinear second-order ODEs

International Nuclear Information System (INIS)

Reyes, M A; Rosu, H C

2008-01-01

It has been proven by Rosu and Cornejo-Perez (Rosu and Cornejo-Perez 2005 Phys. Rev. E 71 046607, Cornejo-Perez and Rosu 2005 Prog. Theor. Phys. 114 533) that for some nonlinear second-order ODEs it is a very simple task to find one particular solution once the nonlinear equation is factorized with the use of two first-order differential operators. Here, it is shown that an interesting class of parametric solutions is easy to obtain if the proposed factorization has a particular form, which happily turns out to be the case in many problems of physical interest. The method that we exemplify with a few explicitly solved cases consists in using the general solution of the Riccati equation, which contributes with one parameter to this class of parametric solutions. For these nonlinear cases, the Riccati parameter serves as a 'growth' parameter from the trivial null solution up to the particular solution found through the factorization procedure

Spatial model of convective solute transport in brain extracellular space does not support a "glymphatic" mechanism.

Science.gov (United States)

Jin, Byung-Ju; Smith, Alex J; Verkman, Alan S

2016-12-01

A "glymphatic system," which involves convective fluid transport from para-arterial to paravenous cerebrospinal fluid through brain extracellular space (ECS), has been proposed to account for solute clearance in brain, and aquaporin-4 water channels in astrocyte endfeet may have a role in this process. Here, we investigate the major predictions of the glymphatic mechanism by modeling diffusive and convective transport in brain ECS and by solving the Navier-Stokes and convection-diffusion equations, using realistic ECS geometry for short-range transport between para-arterial and paravenous spaces. Major model parameters include para-arterial and paravenous pressures, ECS volume fraction, solute diffusion coefficient, and astrocyte foot-process water permeability. The model predicts solute accumulation and clearance from the ECS after a step change in solute concentration in para-arterial fluid. The principal and robust conclusions of the model are as follows: (a) significant convective transport requires a sustained pressure difference of several mmHg between the para-arterial and paravenous fluid and is not affected by pulsatile pressure fluctuations; (b) astrocyte endfoot water permeability does not substantially alter the rate of convective transport in ECS as the resistance to flow across endfeet is far greater than in the gaps surrounding them; and (c) diffusion (without convection) in the ECS is adequate to account for experimental transport studies in brain parenchyma. Therefore, our modeling results do not support a physiologically important role for local parenchymal convective flow in solute transport through brain ECS. © 2016 Jin et al.

Approximations for transport parameters and self-averaging properties for point-like injections in heterogeneous media

International Nuclear Information System (INIS)

Eberhard, Jens

2004-01-01

We focus on transport parameters in heterogeneous media with a flow modelled by an ensemble of periodic and Gaussian random fields. The parameters are determined by ensemble averages. We study to what extent these averages represent the behaviour in a single realization. We calculate the centre-of-mass velocity and the dispersion coefficient using approximations based on a perturbative expansion for the transport equation, and on the iterative solution of the Langevin equation. Compared with simulations, the perturbation theory reproduces the numerical results only poorly, whereas the iterative solution yields good results. Using these approximations, we investigate the self-averaging properties. The ensemble average of the velocity characterizes the behaviour of a realization for large times in both ensembles. The dispersion coefficient is not self-averaging in the ensemble of periodic fields. For the Gaussian ensemble the asymptotic dispersion coefficient is self-averaging. For finite times, however, the fluctuations are so large that the average does not represent the behaviour in a single realization

Nonrelativistic grey Sn-transport radiative-shock solutions

International Nuclear Information System (INIS)

Ferguson, J. M.; Morel, J. E.; Lowrie, R. B.

2017-01-01

We present semi-analytic radiative-shock solutions in which grey Sn-transport is used to model the radiation, and we include both constant cross sections and cross sections that depend on temperature and density. These new solutions solve for a variable Eddington factor (VEF) across the shock domain, which allows for interesting physics not seen before in radiative-shock solutions. Comparisons are made with the grey nonequilibrium-diffusion radiative-shock solutions of Lowrie and Edwards [1], which assumed that the Eddington factor is constant across the shock domain. It is our experience that the local Mach number is monotonic when producing nonequilibrium-diffusion solutions, but that this monotonicity may disappear while integrating the precursor region to produce Sn-transport solutions. For temperature- and density-dependent cross sections we show evidence of a spike in the VEF in the far upstream portion of the radiative-shock precursor. We show evidence of an adaptation zone in the precursor region, adjacent to the embedded hydrodynamic shock, as conjectured by Drake [2, 3], and also confirm his expectation that the precursor temperatures adjacent to the Zel’dovich spike take values that are greater than the downstream post-shock equilibrium temperature. We also show evidence that the radiation energy density can be nonmonotonic under the Zel’dovich spike, which is indicative of anti-diffusive radiation flow as predicted by McClarren and Drake [4]. We compare the angle dependence of the radiation flow for the Sn-transport and nonequilibriumdiffusion radiation solutions, and show that there are considerable differences in the radiation flow between these models across the shock structure. Lastly, we analyze the radiation flow to understand the cause of the adaptation zone, as well as the structure of the Sn-transport radiation-intensity solutions across the shock structure.

Transport Visualization for Studying Mass Transfer and Solute Transport in Permeable Media

International Nuclear Information System (INIS)

Roy Haggerty

2004-01-01

Understanding and predicting mass transfer coupled with solute transport in permeable media is central to several energy-related programs at the US Department of Energy (e.g., CO 2 sequestration, nuclear waste disposal, hydrocarbon extraction, and groundwater remediation). Mass transfer is the set of processes that control movement of a chemical between mobile (advection-dominated) domains and immobile (diffusion- or sorption-dominated) domains within a permeable medium. Consequences of mass transfer on solute transport are numerous and may include (1) increased sequestration time within geologic formations; (2) reduction in average solute transport velocity by as much as several orders of magnitude; (3) long ''tails'' in concentration histories during removal of a solute from a permeable medium; (4) poor predictions of solute behavior over long time scales; and (5) changes in reaction rates due to mass transfer influences on pore-scale mixing of solutes. Our work produced four principle contributions: (1) the first comprehensive visualization of solute transport and mass transfer in heterogeneous porous media; (2) the beginnings of a theoretical framework that encompasses both macrodispersion and mass transfer within a single set of equations; (3) experimental and analytical tools necessary for understanding mixing and aqueous reaction in heterogeneous, granular porous media; (4) a clear experimental demonstration that reactive transport is often not accurately described by a simple coupling of the convection-dispersion equation with chemical reaction equations. The work shows that solute transport in heterogeneous media can be divided into 3 regimes--macrodispersion, advective mass transfer, and diffusive mass transfer--and that these regimes can be predicted quantitatively in binary media. We successfully predicted mass transfer in each of these regimes and verified the prediction by completing quantitative visualization experiments in each of the regimes, the

Regional flow and solute transport modeling for site suitability. Part I

International Nuclear Information System (INIS)

Rowe, J.; Miller, I.

1979-12-01

The nature of regional flow systems in large sedimentary basins will largely determine the effectiveness of regional flow as a barrier to radionuclide escape from deep geologic repositories. The purpose of the work reported herein and the proposed future work is to develop a methodology for evaluating regional flow barriers by using numerical models. The Williston Basin was chosen as an archetype case for the regional modeling study. However, due to the simplified nature of the study, the results are not meant to represent the behavior of a repository actually placed within the Williston Basin. The major components of this Phase I study are: (1) assembly and reduction of available data; (2) formulation of a simplified geohydrologic model; (3) computer simulation of fluid flow; and (4) computer simulation of solute transport. As of this report, the first two items are essentially completed. Computer simulation of fluid flow will require some revision and further study, which will be done in the second phase of this study. Computer simulation of solute transport has been considered only on a very preliminary basis. Important conclusions of this Phase I study are as follows. Assembly and reduction of data require an extensive work effort. Generally, the parameters describing fluid flow are poorly known on a regional basis and those describing solute transport are unknown

Regional flow and solute transport modeling for site suitability. Part I

Energy Technology Data Exchange (ETDEWEB)

Rowe, J.; Miller, I.

1979-12-01

The nature of regional flow systems in large sedimentary basins will largely determine the effectiveness of regional flow as a barrier to radionuclide escape from deep geologic repositories. The purpose of the work reported herein and the proposed future work is to develop a methodology for evaluating regional flow barriers by using numerical models. The Williston Basin was chosen as an archetype case for the regional modeling study. However, due to the simplified nature of the study, the results are not meant to represent the behavior of a repository actually placed within the Williston Basin. The major components of this Phase I study are: (1) assembly and reduction of available data; (2) formulation of a simplified geohydrologic model; (3) computer simulation of fluid flow; and (4) computer simulation of solute transport. As of this report, the first two items are essentially completed. Computer simulation of fluid flow will require some revision and further study, which will be done in the second phase of this study. Computer simulation of solute transport has been considered only on a very preliminary basis. Important conclusions of this Phase I study are as follows. Assembly and reduction of data require an extensive work effort. Generally, the parameters describing fluid flow are poorly known on a regional basis and those describing solute transport are unknown.

Solute transport across the articular surface of injured cartilage.

Science.gov (United States)

Chin, Hooi Chuan; Moeini, Mohammad; Quinn, Thomas M

2013-07-15

Solute transport through extracellular matrix (ECM) is important to physiology and contrast agent-based clinical imaging of articular cartilage. Mechanical injury is likely to have important effects on solute transport since it involves alteration of ECM structure. Therefore it is of interest to characterize effects of mechanical injury on solute transport in cartilage. Using cartilage explants injured by an established mechanical compression protocol, effective partition coefficients and diffusivities of solutes for transport across the articular surface were measured. A range of fluorescent solutes (fluorescein isothiocyanate, 4 and 40kDa dextrans, insulin, and chondroitin sulfate) and an X-ray contrast agent (sodium iodide) were used. Mechanical injury was associated with a significant increase in effective diffusivity versus uninjured explants for all solutes studied. On the other hand, mechanical injury had no effects on effective partition coefficients for most solutes tested, except for 40kDa dextran and chondroitin sulfate where small but significant changes in effective partition coefficient were observed in injured explants. Findings highlight enhanced diffusive transport across the articular surface of injured cartilage, which may have important implications for injury and repair situations. Results also support development of non-equilibrium methods for identification of focal cartilage lesions by contrast agent-based clinical imaging. Copyright © 2013 Elsevier Inc. All rights reserved.

Parameter optimization for surface flux transport models

Science.gov (United States)

Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.; Petrie, G. J. D.

2017-11-01

Accurate prediction of solar activity calls for precise calibration of solar cycle models. Consequently we aim to find optimal parameters for models which describe the physical processes on the solar surface, which in turn act as proxies for what occurs in the interior and provide source terms for coronal models. We use a genetic algorithm to optimize surface flux transport models using National Solar Observatory (NSO) magnetogram data for Solar Cycle 23. This is applied to both a 1D model that inserts new magnetic flux in the form of idealized bipolar magnetic regions, and also to a 2D model that assimilates specific shapes of real active regions. The genetic algorithm searches for parameter sets (meridional flow speed and profile, supergranular diffusivity, initial magnetic field, and radial decay time) that produce the best fit between observed and simulated butterfly diagrams, weighted by a latitude-dependent error structure which reflects uncertainty in observations. Due to the easily adaptable nature of the 2D model, the optimization process is repeated for Cycles 21, 22, and 24 in order to analyse cycle-to-cycle variation of the optimal solution. We find that the ranges and optimal solutions for the various regimes are in reasonable agreement with results from the literature, both theoretical and observational. The optimal meridional flow profiles for each regime are almost entirely within observational bounds determined by magnetic feature tracking, with the 2D model being able to accommodate the mean observed profile more successfully. Differences between models appear to be important in deciding values for the diffusive and decay terms. In like fashion, differences in the behaviours of different solar cycles lead to contrasts in parameters defining the meridional flow and initial field strength.

Transport parameters of thin, supported cathode layers in solid oxide fuel cells (SOFCs); Transportparameter duenner, getraegerter Kathodenschichten der oxidkeramischen Brennstoffzelle

Energy Technology Data Exchange (ETDEWEB)

Wedershoven, Christian

2010-12-22

The aim of this work was to determine the transport properties of thin cathode layers, which are part of the composite layer of a fabricated anode-supported solid oxide fuel cell (SOFC). The transport properties of the anode and cathode have a significant influence on the electrochemical performance of a fuel cell stack and therefore represent an important parameter when designing fuel cell stacks. In order to determine the transport parameters of the cathode layers in a fabricated SOFC, it is necessary to permeate the thin cathode layer deposited on the gas-tight electrolyte with a defined gas transport. These thin cathode layers cannot be fabricated as mechanically stable single layers and cannot therefore be investigated in the diffusion and permeation experiments usually used to determine transport parameters. The setup of these experiments - particularly the sample holder - was therefore altered in this work. The result of this altered setup was a three-dimensional flow configuration. Compared to the conventional setup, it was no longer possible to describe the gas transport in the experiments with an analytical one-dimensional solution. A numerical solution process had to be used to evaluate the measurements. The new setup permitted a sufficiently symmetrical gas distribution and thus allowed the description of the transport to be reduced to a two-dimensional description, which significantly reduced the computational effort required to evaluate the measurements. For pressure-induced transport, a parametrized coherent expression of transport could be derived. This expression is equivalent to the analytical description of the transport in conventional measurement setups, with the exception of parameters that describe the geometry of the gas diffusion. In this case, a numerical process is not necessary for the evaluation. Using the transport parameters of mechanically stable anode substrates, which can be measured both in the old and the new setups, the old and

Solute transport in soil

NARCIS (Netherlands)

Zee, van der S.E.A.T.M.; Leijnse, A.

2013-01-01

Solute transport is of importance in view of the movement of nutrient elements, e.g. towards the plant root system, and because of a broad range of pollutants. Pollution is not necessarily man induced, but may be due to geological or geohydrological causes, e.g. in the cases of pollution with

Effects of turbulent hyporheic mixing on reach-scale solute transport

Science.gov (United States)

Roche, K. R.; Li, A.; Packman, A. I.

2017-12-01

Turbulence rapidly mixes solutes and fine particles into coarse-grained streambeds. Both hyporheic exchange rates and spatial variability of hyporheic mixing are known to be controlled by turbulence, but it is unclear how turbulent mixing influences mass transport at the scale of stream reaches. We used a process-based particle-tracking model to simulate local- and reach-scale solute transport for a coarse-bed stream. Two vertical mixing profiles, one with a smooth transition from in-stream to hyporheic transport conditions and a second with enhanced turbulent transport at the sediment-water interface, were fit to steady-state subsurface concentration profiles observed in laboratory experiments. The mixing profile with enhanced interfacial transport better matched the observed concentration profiles and overall mass retention in the streambed. The best-fit mixing profiles were then used to simulate upscaled solute transport in a stream. Enhanced mixing coupled in-stream and hyporheic solute transport, causing solutes exchanged into the shallow subsurface to have travel times similar to the water column. This extended the exponential region of the in-stream solute breakthrough curve, and delayed the onset of the heavy power-law tailing induced by deeper and slower hyporheic porewater velocities. Slopes of observed power-law tails were greater than those predicted from stochastic transport theory, and also changed in time. In addition, rapid hyporheic transport velocities truncated the hyporheic residence time distribution by causing mass to exit the stream reach via subsurface advection, yielding strong exponential tempering in the in-stream breakthrough curves at the timescale of advective hyporheic transport through the reach. These results show that strong turbulent mixing across the sediment-water interface violates the conventional separation of surface and subsurface flows used in current models for solute transport in rivers. Instead, the full distribution of

The secret to successful solute-transport modeling

Science.gov (United States)

Konikow, Leonard F.

2011-01-01

Modeling subsurface solute transport is difficult—more so than modeling heads and flows. The classical governing equation does not always adequately represent what we see at the field scale. In such cases, commonly used numerical models are solving the wrong equation. Also, the transport equation is hyperbolic where advection is dominant, and parabolic where hydrodynamic dispersion is dominant. No single numerical method works well for all conditions, and for any given complex field problem, where seepage velocity is highly variable, no one method will be optimal everywhere. Although we normally expect a numerically accurate solution to the governing groundwater-flow equation, errors in concentrations from numerical dispersion and/or oscillations may be large in some cases. The accuracy and efficiency of the numerical solution to the solute-transport equation are more sensitive to the numerical method chosen than for typical groundwater-flow problems. However, numerical errors can be kept within acceptable limits if sufficient computational effort is expended. But impractically long

Fluid transport with time on peritoneal dialysis: the contribution of free water transport and solute coupled water transport

NARCIS (Netherlands)

Coester, Annemieke M.; Smit, Watske; Struijk, Dirk G.; Krediet, Raymond T.

2009-01-01

Ultrafiltration in peritoneal dialysis occurs through endothelial water channels (free water transport) and together with solutes across small pores: solute coupled water transport. A review is given of cross-sectional studies and on the results of longitudinal follow-up

Solute transport and storage mechanisms in wetlands of the Everglades, south Florida

Science.gov (United States)

Harvey, Judson W.; Saiers, James E.; Newlin, Jessica T.

2005-01-01

Solute transport and storage processes in wetlands play an important role in biogeochemical cycling and in wetland water quality functions. In the wetlands of the Everglades, there are few data or guidelines to characterize transport through the heterogeneous flow environment. Our goal was to conduct a tracer study to help quantify solute exchange between the relatively fast flowing water in the open part of the water column and much more slowly moving water in thick floating vegetation and in the pore water of the underlying peat. We performed a tracer experiment that consisted of a constant‐rate injection of a sodium bromide (NaBr) solution for 22 hours into a 3 m wide, open‐ended flume channel in Everglades National Park. Arrival of the bromide tracer was monitored at an array of surface water and subsurface samplers for 48 hours at a distance of 6.8 m downstream of the injection. A one‐dimensional transport model was used in combination with an optimization code to identify the values of transport parameters that best explained the tracer observations. Parameters included dimensions and mass transfer coefficients describing exchange with both short (hours) and longer (tens of hours) storage zones as well as the average rates of advection and longitudinal dispersion in the open part of the water column (referred to as the “main flow zone”). Comparison with a more detailed set of tracer measurements tested how well the model's storage zones approximated the average characteristics of tracer movement into and out of the layer of thick floating vegetation and the pore water in the underlying peat. The rate at which the relatively fast moving water in the open water column was exchanged with slowly moving water in the layer of floating vegetation and in sediment pore water amounted to 50 and 3% h−1, respectively. Storage processes decreased the depth‐averaged velocity of surface water by 50% relative to the water velocity in the open part of the water

Spatial model of convective solute transport in brain extracellular space does not support a “glymphatic” mechanism

Science.gov (United States)

Jin, Byung-Ju; Smith, Alex J.

2016-01-01

A “glymphatic system,” which involves convective fluid transport from para-arterial to paravenous cerebrospinal fluid through brain extracellular space (ECS), has been proposed to account for solute clearance in brain, and aquaporin-4 water channels in astrocyte endfeet may have a role in this process. Here, we investigate the major predictions of the glymphatic mechanism by modeling diffusive and convective transport in brain ECS and by solving the Navier–Stokes and convection–diffusion equations, using realistic ECS geometry for short-range transport between para-arterial and paravenous spaces. Major model parameters include para-arterial and paravenous pressures, ECS volume fraction, solute diffusion coefficient, and astrocyte foot-process water permeability. The model predicts solute accumulation and clearance from the ECS after a step change in solute concentration in para-arterial fluid. The principal and robust conclusions of the model are as follows: (a) significant convective transport requires a sustained pressure difference of several mmHg between the para-arterial and paravenous fluid and is not affected by pulsatile pressure fluctuations; (b) astrocyte endfoot water permeability does not substantially alter the rate of convective transport in ECS as the resistance to flow across endfeet is far greater than in the gaps surrounding them; and (c) diffusion (without convection) in the ECS is adequate to account for experimental transport studies in brain parenchyma. Therefore, our modeling results do not support a physiologically important role for local parenchymal convective flow in solute transport through brain ECS. PMID:27836940

Simulation of unsaturated flow and nonreactive solute transport in a heterogeneous soil at the field scale

International Nuclear Information System (INIS)

Rockhold, M.L.

1993-02-01

A field-scale, unsaturated flow and solute transport experiment at the Las Cruces trench site in New Mexico was simulated as part of a ''blind'' modeling exercise to demonstrate the ability or inability of uncalibrated models to predict unsaturated flow and solute transport in spatially variable porous media. Simulations were conducted using a recently developed multiphase flow and transport simulator. Uniform and heterogeneous soil models were tested, and data from a previous experiment at the site were used with an inverse procedure to estimate water retention parameters. A spatial moment analysis was used to provide a quantitative basis for comparing the mean observed and simulated flow and transport behavior. The results of this study suggest that defensible predictions of waste migration and fate at low-level waste sites will ultimately require site-specific data for model calibration

Estimation of light transport parameters in biological media using ...

Indian Academy of Sciences (India)

Estimation of light transport parameters in biological media using coherent backscattering ... backscattered light for estimating the light transport parameters of biological media has been investigated. ... Pramana – Journal of Physics | News.

Charge transport parameters of HBC at different temperatures

Energy Technology Data Exchange (ETDEWEB)

Kirkpatrick, J. [Max Planck Institut fuer Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); Department of Physics, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Marcon, V.; Kremer, K.; Andrienko, D. [Max Planck Institut fuer Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); Nelson, J. [Department of Physics, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom)

2008-05-15

We study the dependence on temperature of the charge transport parameters for hexabenzocoronene (HBC). Following from Marcus theory, two charge transport parameters will be calculated: the transfer integral and the difference in site energies. These parameters are strongly dependent on the orientation and position of molecules. Position and orientation of molecules are determined using molecular dynamics. Transfer integrals are calculated from a simplified INDO method. A technique to compute energetic disorder, that is the spread in site energies for the charge carriers, is developed. In the herringbone phase transfer integrals are higher, but so is energetic disorder. We consider three derivatives of HBC with different side chains, which lead to different phase behaviour and distributions of charge transport parameters. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Analyzing the effects of instillation volume on intravesical delivery using biphasic solute transport in a deformable geometry.

Science.gov (United States)

Smith, Sean G; Griffith, Boyce E; Zaharoff, David A

2018-04-05

Ailments of the bladder are often treated via intravesical delivery-direct application of therapeutic into the bladder through a catheter. This technique is employed hundreds of thousands of times every year, but protocol development has largely been limited to empirical determination. Furthermore, the numerical analyses of intravesical delivery performed to date have been restricted to static geometries and have not accounted for bladder deformation. This study uses a finite element analysis approach with biphasic solute transport to investigate several parameters pertinent to intravesical delivery including solute concentration, solute transport properties and instillation volume. The volume of instillation was found to have a substantial impact on the exposure of solute to the deeper muscle layers of the bladder, which are typically more difficult to reach. Indeed, increasing the instillation volume from 50-100 ml raised the muscle solute exposure as a percentage of overall bladder exposure from 60-70% with higher levels achieved for larger instillation volumes. Similar increases were not seen for changes in solute concentration or solute transport properties. These results indicate the role that instillation volume may play in targeting particular layers of the bladder during an intravesical delivery.

A study on the adsorption and subsurface transport of radioactive solutes in the presence of chelating agents

International Nuclear Information System (INIS)

Baik, Min Hoon

1994-02-01

In this study, adsorption and transport models were developed to analyze the effect of chelating agents on the adsorption and subsurface transport of radioactive solutes. The effect of chelating agents on the adsorption of radioactive solutes was analyzed by developing an adsorption model based upon the extended concept of distribution coefficient reflecting the presence of chelating agents. Also, a batch adsorption experiment was conducted in order to validate the developed adsorption model and to investigate the effect of chelating agent on the adsorption of radioactive metal solutes. In this experiment, a Cobalt(II)/EDTA/Bentonite system was considered as a representative chelation/adsorption system. It was found from the results that the presence of chelating agents significantly reduced the adsorbing capacity of geologic media such as clay minerals and soils. Thus it was concluded that the presence of chelating agents even in a small amount could contribute to the mobilization of radioactive solutes from radioactive waste burial sites by reducing the adsorbing capacity of geologic media. The effect of chelating agents on the transport of radioactive solutes in subsurface porous media was analyzed by formulating an advective-dispersive transport model which incorporated chelate formation, adsorption, decay, and degradations and by introducing the concept of a tenad. Particularly the governing equation for the tenad of radioactive solutes, M, was presented as a linear partial differential form by introducing the extended distribution coefficient, K D . The calculated results from the model showed that the transport rate of the chelated radionuclides was much greater than that of the free ionic radionuclides. This much faster transport of the chelated radionuclides was found to be due to the lower retardation factor of the chelated radionuclides than the free ionic radionuclides. The effect of parameters on the transport of radioactive solutes was also analyzed

A three-dimensional neutron transport benchmark solution

International Nuclear Information System (INIS)

Ganapol, B.D.; Kornreich, D.E.

1993-01-01

For one-group neutron transport theory in one dimension, several powerful analytical techniques have been developed to solve the neutron transport equation, including Caseology, Wiener-Hopf factorization, and Fourier and Laplace transform methods. In addition, after a Fourier transform in the transverse plane and formulation of a pseudo problem, two-dimensional (2-D) and three-dimensional (3-D) problems can be solved using the techniques specifically developed for the one-dimensional (1-D) case. Numerical evaluation of the resulting expressions requiring an inversion in the transverse plane have been successful for 2-D problems but becomes exceedingly difficult in the 3-D case. In this paper, we show that by using the symmetry along the beam direction, a 2-D problem can be transformed into a 3-D problem in an infinite medium. The numerical solution to the 3-D problem is then demonstrated. Thus, a true 3-D transport benchmark solution can be obtained from a well-established numerical solution to a 2-D problem

CFEST Coupled Flow, Energy & Solute Transport Version CFEST005 User’s Guide

Energy Technology Data Exchange (ETDEWEB)

Freedman, Vicky L.; Chen, Yousu; Gilca, Alex; Cole, Charles R.; Gupta, Sumant K.

2006-07-20

The CFEST (Coupled Flow, Energy, and Solute Transport) simulator described in this User’s Guide is a three-dimensional finite-element model used to evaluate groundwater flow and solute mass transport. Confined and unconfined aquifer systems, as well as constant and variable density fluid flows can be represented with CFEST. For unconfined aquifers, the model uses a moving boundary for the water table, deforming the numerical mesh so that the uppermost nodes are always at the water table. For solute transport, changes in concentra¬tion of a single dissolved chemical constituent are computed for advective and hydrodynamic transport, linear sorption represented by a retardation factor, and radioactive decay. Although several thermal parameters described in this User’s Guide are required inputs, thermal transport has not yet been fully implemented in the simulator. Once fully implemented, transport of thermal energy in the groundwater and solid matrix of the aquifer can also be used to model aquifer thermal regimes. The CFEST simulator is written in the FORTRAN 77 language, following American National Standards Institute (ANSI) standards. Execution of the CFEST simulator is controlled through three required text input files. These input file use a structured format of associated groups of input data. Example input data lines are presented for each file type, as well as a description of the structured FORTRAN data format. Detailed descriptions of all input requirements, output options, and program structure and execution are provided in this User’s Guide. Required inputs for auxillary CFEST utilities that aide in post-processing data are also described. Global variables are defined for those with access to the source code. Although CFEST is a proprietary code (CFEST, Inc., Irvine, CA), the Pacific Northwest National Laboratory retains permission to maintain its own source, and to distribute executables to Hanford subcontractors.

Coupling between solute transport and chemical reactions models

International Nuclear Information System (INIS)

Samper, J.; Ajora, C.

1993-01-01

During subsurface transport, reactive solutes are subject to a variety of hydrodynamic and chemical processes. The major hydrodynamic processes include advection and convection, dispersion and diffusion. The key chemical processes are complexation including hydrolysis and acid-base reactions, dissolution-precipitation, reduction-oxidation, adsorption and ion exchange. The combined effects of all these processes on solute transport must satisfy the principle of conservation of mass. The statement of conservation of mass for N mobile species leads to N partial differential equations. Traditional solute transport models often incorporate the effects of hydrodynamic processes rigorously but oversimplify chemical interactions among aqueous species. Sophisticated chemical equilibrium models, on the other hand, incorporate a variety of chemical processes but generally assume no-flow systems. In the past decade, coupled models accounting for complex hydrological and chemical processes, with varying degrees of sophistication, have been developed. The existing models of reactive transport employ two basic sets of equations. The transport of solutes is described by a set of partial differential equations, and the chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. An important consideration in any approach is the choice of primary dependent variables. Most existing models cannot account for the complete set of chemical processes, cannot be easily extended to include mixed chemical equilibria and kinetics, and cannot handle practical two and three dimensional problems. The difficulties arise mainly from improper selection of the primary variables in the transport equations. (Author) 38 refs

Pathogen transport in groundwater systems: contrasts with traditional solute transport

Science.gov (United States)

Hunt, Randall J.; Johnson, William P.

2017-06-01

Water quality affects many aspects of water availability, from precluding use to societal perceptions of fit-for-purpose. Pathogen source and transport processes are drivers of water quality because they have been responsible for numerous outbreaks resulting in large economic losses due to illness and, in some cases, loss of life. Outbreaks result from very small exposure (e.g., less than 20 viruses) from very strong sources (e.g., trillions of viruses shed by a single infected individual). Thus, unlike solute contaminants, an acute exposure to a very small amount of contaminated water can cause immediate adverse health effects. Similarly, pathogens are larger than solutes. Thus, interactions with surfaces and settling become important even as processes important for solutes such as diffusion become less important. These differences are articulated in "Colloid Filtration Theory", a separate branch of pore-scale transport. Consequently, understanding pathogen processes requires changes in how groundwater systems are typically characterized, where the focus is on the leading edges of plumes and preferential flow paths, even if such features move only a very small fraction of the aquifer flow. Moreover, the relatively short survival times of pathogens in the subsurface require greater attention to very fast (solute transport mechanisms discussed here, a more encompassing view of water quality and source water protection is attained. With this more holistic view and theoretical understanding, better evaluations can be made regarding drinking water vulnerability and the relation between groundwater and human health.

Nonpoint source solute transport normal to aquifer bedding in heterogeneous, Markov chain random fields

Science.gov (United States)

Zhang, Hua; Harter, Thomas; Sivakumar, Bellie

2006-06-01

Facies-based geostatistical models have become important tools for analyzing flow and mass transport processes in heterogeneous aquifers. Yet little is known about the relationship between these latter processes and the parameters of facies-based geostatistical models. In this study, we examine the transport of a nonpoint source solute normal (perpendicular) to the major bedding plane of an alluvial aquifer medium that contains multiple geologic facies, including interconnected, high-conductivity (coarse textured) facies. We also evaluate the dependence of the transport behavior on the parameters of the constitutive facies model. A facies-based Markov chain geostatistical model is used to quantify the spatial variability of the aquifer system's hydrostratigraphy. It is integrated with a groundwater flow model and a random walk particle transport model to estimate the solute traveltime probability density function (pdf) for solute flux from the water table to the bottom boundary (the production horizon) of the aquifer. The cases examined include two-, three-, and four-facies models, with mean length anisotropy ratios for horizontal to vertical facies, ek, from 25:1 to 300:1 and with a wide range of facies volume proportions (e.g., from 5 to 95% coarse-textured facies). Predictions of traveltime pdfs are found to be significantly affected by the number of hydrostratigraphic facies identified in the aquifer. Those predictions of traveltime pdfs also are affected by the proportions of coarse-textured sediments, the mean length of the facies (particularly the ratio of length to thickness of coarse materials), and, to a lesser degree, the juxtapositional preference among the hydrostratigraphic facies. In transport normal to the sedimentary bedding plane, traveltime is not lognormally distributed as is often assumed. Also, macrodispersive behavior (variance of the traveltime) is found not to be a unique function of the conductivity variance. For the parameter range

A mixture theory model of fluid and solute transport in the microvasculature of normal and malignant tissues. I. Theory.

Science.gov (United States)

Schuff, M M; Gore, J P; Nauman, E A

2013-05-01

In order to better understand the mechanisms governing transport of drugs, nanoparticle-based treatments, and therapeutic biomolecules, and the role of the various physiological parameters, a number of mathematical models have previously been proposed. The limitations of the existing transport models indicate the need for a comprehensive model that includes transport in the vessel lumen, the vessel wall, and the interstitial space and considers the effects of the solute concentration on fluid flow. In this study, a general model to describe the transient distribution of fluid and multiple solutes at the microvascular level was developed using mixture theory. The model captures the experimentally observed dependence of the hydraulic permeability coefficient of the capillary wall on the concentration of solutes present in the capillary wall and the surrounding tissue. Additionally, the model demonstrates that transport phenomena across the capillary wall and in the interstitium are related to the solute concentration as well as the hydrostatic pressure. The model is used in a companion paper to examine fluid and solute transport for the simplified case of an axisymmetric geometry with no solid deformation or interconversion of mass.

Data acquisition of mass transport parameters

International Nuclear Information System (INIS)

Iwasaki, Riyo; Hama, Katsuhiro; Morikawa, Keita; Hosoya, Shinichi

2017-02-01

Tono Geoscience Center of Japan Atomic Energy Agency (JAEA) has been carrying out the Mizunami Underground Research Laboratory (MIU) Project, which is a scientific study understanding the deep geological environment as a basis of research and development for geological disposal of high level radioactive wastes. The aim of the MIU project is to establish comprehensive techniques for the investigation, analysis and assessment of the deep geological environment in fractured crystalline rock, and to develop a range of engineering techniques for deep underground application. This project has three overlapping phases: Surface-based investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III). Currently, the project is being carried out under the Phase III. Mass transport study is mainly performed as part of Phase III project. In Phase III, the goal of mass transport study is to obtain a better understanding of mass transport phenomena in the geological environment as well as to develop technologies for measurement of the mass transport parameters, model construction, numerical analysis and validation of those technologies. This study was planned to understand the influence of the geological characteristics of fracture on the mass transport parameters. This report presents the results of diffusion experiment, observation of polished thin section, sorption experiment and porophysicality measurement. (author)

Estimation and upscaling of dual-permeability model parameters for the transport of E.coli D21g in soils with preferential flow

Science.gov (United States)

Dual-permeability models are increasingly used to quantify the transport of solutes and microorganisms in soils with preferential flow. An ability to accurately determine the model parameters and their variation with preferential pathway characteristics is crucial for predicting the transport of mi...

Assessment of applications of transport models on regional scale solute transport

Science.gov (United States)

Guo, Z.; Fogg, G. E.; Henri, C.; Pauloo, R.

2017-12-01

Regional scale transport models are needed to support the long-term evaluation of groundwater quality and to develop management strategies aiming to prevent serious groundwater degradation. The purpose of this study is to evaluate the capacity of previously-developed upscaling approaches to accurately describe main solute transport processes including the capture of late-time tails under changing boundary conditions. Advective-dispersive contaminant transport in a 3D heterogeneous domain was simulated and used as a reference solution. Equivalent transport under homogeneous flow conditions were then evaluated applying the Multi-Rate Mass Transfer (MRMT) model. The random walk particle tracking method was used for both heterogeneous and homogeneous-MRMT scenarios under steady state and transient conditions. The results indicate that the MRMT model can capture the tails satisfactorily for plume transported with ambient steady-state flow field. However, when boundary conditions change, the mass transfer model calibrated for transport under steady-state conditions cannot accurately reproduce the tailing effect observed for the heterogeneous scenario. The deteriorating impact of transient boundary conditions on the upscaled model is more significant for regions where flow fields are dramatically affected, highlighting the poor applicability of the MRMT approach for complex field settings. Accurately simulating mass in both mobile and immobile zones is critical to represent the transport process under transient flow conditions and will be the future focus of our study.

Effect of Porosity and Concentration Polarization on Electrolyte Diffusive Transport Parameters through Ceramic Membranes with Similar Nanopore Size

Directory of Open Access Journals (Sweden)

Virginia Romero

2014-08-01

Full Text Available Diffusive transport through nanoporous alumina membranes (NPAMs produced by the two-step anodization method, with similar pore size but different porosity, is studied by analyzing membrane potential measured with NaCl solutions at different concentrations. Donnan exclusion of co-ions at the solution/membrane interface seem to exert a certain control on the diffusive transport of ions through NPAMs with low porosity, which might be reduced by coating the membrane surface with appropriated materials, as it is the case of SiO2. Our results also show the effect of concentration polarization at the membrane surface on ionic transport numbers (or diffusion coefficients for low-porosity and high electrolyte affinity membranes, which could mask values of those characteristic electrochemical parameters.

How Sensitive Are Transdermal Transport Predictions by Microscopic Stratum Corneum Models to Geometric and Transport Parameter Input?

Science.gov (United States)

Wen, Jessica; Koo, Soh Myoung; Lape, Nancy

2018-02-01

While predictive models of transdermal transport have the potential to reduce human and animal testing, microscopic stratum corneum (SC) model output is highly dependent on idealized SC geometry, transport pathway (transcellular vs. intercellular), and penetrant transport parameters (e.g., compound diffusivity in lipids). Most microscopic models are limited to a simple rectangular brick-and-mortar SC geometry and do not account for variability across delivery sites, hydration levels, and populations. In addition, these models rely on transport parameters obtained from pure theory, parameter fitting to match in vivo experiments, and time-intensive diffusion experiments for each compound. In this work, we develop a microscopic finite element model that allows us to probe model sensitivity to variations in geometry, transport pathway, and hydration level. Given the dearth of experimentally-validated transport data and the wide range in theoretically-predicted transport parameters, we examine the model's response to a variety of transport parameters reported in the literature. Results show that model predictions are strongly dependent on all aforementioned variations, resulting in order-of-magnitude differences in lag times and permeabilities for distinct structure, hydration, and parameter combinations. This work demonstrates that universally predictive models cannot fully succeed without employing experimentally verified transport parameters and individualized SC structures. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Fluid flow and convective transport of solutes within the intervertebral disc.

Science.gov (United States)

Ferguson, Stephen J; Ito, Keita; Nolte, Lutz P

2004-02-01

Previous experimental and analytical studies of solute transport in the intervertebral disc have demonstrated that for small molecules diffusive transport alone fulfils the nutritional needs of disc cells. It has been often suggested that fluid flow into and within the disc may enhance the transport of larger molecules. The goal of the study was to predict the influence of load-induced interstitial fluid flow on mass transport in the intervertebral disc. An iterative procedure was used to predict the convective transport of physiologically relevant molecules within the disc. An axisymmetric, poroelastic finite-element structural model of the disc was developed. The diurnal loading was divided into discrete time steps. At each time step, the fluid flow within the disc due to compression or swelling was calculated. A sequentially coupled diffusion/convection model was then employed to calculate solute transport, with a constant concentration of solute being provided at the vascularised endplates and outer annulus. Loading was simulated for a complete diurnal cycle, and the relative convective and diffusive transport was compared for solutes with molecular weights ranging from 400 Da to 40 kDa. Consistent with previous studies, fluid flow did not enhance the transport of low-weight solutes. During swelling, interstitial fluid flow increased the unidirectional penetration of large solutes by approximately 100%. Due to the bi-directional temporal nature of disc loading, however, the net effect of convective transport over a full diurnal cycle was more limited (30% increase). Further study is required to determine the significance of large solutes and the timing of their delivery for disc physiology.

Assessment of assembly homogenized two-steps core dynamic calculations using direct whole core transport solutions

International Nuclear Information System (INIS)

Hursin, Mathieu; Downar, Thomas J.; Yoon, Joo Il; Joo, Han Gyu

2016-01-01

Highlights: • Reactivity initiated accident analysis with direct whole core transient transport code. • Comparison with usual “two steps” procedure. • Effect of effective delayed neutron fraction definition on energy deposition in the fuel. • Effect of homogenized few-group cross sections generation at the assembly level on energy deposition in the fuel. • Effect of effective fuel temperature definition on energy deposition in the fuel. - Abstract: The impact of the approximations in the “two-steps” procedure used in the current generation of nodal simulators for core transient calculations is assessed by using a higher order solution obtained from a direct, whole core, transient transport calculation. A control rod ejection accident in an idealized minicore is analyzed with PARCS, which uses the two-steps procedure and DeCART which provides the higher order solution. DeCART is used as lattice code to provide the homogenized cross sections and kinetics parameters to PARCS. The approximations made by using (1) the homogenized few-group cross sections and kinetic parameters generated at the assembly level, (2) an effective delayed neutrons fraction, (3) an effective fuel temperature and (4) the few-group formulation are investigated in terms of global and local core power behavior. The results presented in the paper show that the current two-steps procedure produces sufficiently accurate transient results with respect to the direct whole core calculation solution, provided that its parameters are carefully generated using the prescriptions described in the present article.

Multiscale modelling of dual-porosity porous media; a computational pore-scale study for flow and solute transport

Science.gov (United States)

de Vries, Enno T.; Raoof, Amir; van Genuchten, Martinus Th.

2017-07-01

Many environmental and agricultural applications involve the transport of water and dissolved constituents through aggregated soil profiles, or porous media that are structured, fractured or macroporous in other ways. During the past several decades, various process-based macroscopic models have been used to simulate contaminant transport in such media. Many of these models consider advective-dispersive transport through relatively large inter-aggregate pore domains, while exchange with the smaller intra-aggregate pores is assumed to be controlled by diffusion. Exchange of solute between the two domains is often represented using a first-order mass transfer coefficient, which is commonly obtained by fitting to observed data. This study aims to understand and quantify the solute exchange term by applying a dual-porosity pore-scale network model to relatively large domains, and analysing the pore-scale results in terms of the classical dual-porosity (mobile-immobile) transport formulation. We examined the effects of key parameters (notably aggregate porosity and aggregate permeability) on the main dual-porosity model parameters, i.e., the mobile water fraction (ϕm) and the mass transfer coefficient (α). Results were obtained for a wide range of aggregate porosities (between 0.082 and 0.700). The effect of aggregate permeability was explored by varying pore throat sizes within the aggregates. Solute breakthrough curves (BTCs) obtained with the pore-scale network model at several locations along the domain were analysed using analytical solutions of the dual-porosity model to obtain estimates of ϕm and α. An increase in aggregate porosity was found to decrease ϕm and increase α, leading to considerable tailing in the BTCs. Changes in the aggregate pore throat size affected the relative flow velocity between the intra- and inter-aggregate domains. Higher flow velocities within the aggregates caused a change in the transport regime from diffusion dominated to more

Sustainable freight transport in South Africa:Domestic intermodal solutions

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Jan H. Havenga

2011-11-01

Full Text Available Due to the rapid deregulation of freight transport in South Africa two decades ago, and low historical investment in rail (with resultant poor service delivery, an integrated alternative to road and rail competition was never developed. High national freight logistics costs, significant road infrastructure challenges and environmental impact concerns of a road-dominated freight transport market have, however, fuelled renewed interest in intermodal transport solutions. In this article, a high-level business case for domestic intermodal solutions in South Africa is presented. The results demonstrate that building three intermodal terminals to connect the three major industrial hubs (i.e. Gauteng, Durban and Cape Town through an intermodal solution could reduce transport costs (including externalities for the identified 11.5 million tons of intermodalfriendly freight flows on the Cape and Natal corridors by 42% (including externalities.

The solute carrier 6 family of transporters

DEFF Research Database (Denmark)

Bröer, Stefan; Gether, Ulrik

2012-01-01

of these transporters is associated with a variety of diseases. Pharmacological inhibition of the neurotransmitter transporters in this family is an important strategy in the management of neurological and psychiatric disorders. This review provides an overview of the biochemical and pharmacological properties......The solute carrier 6 (SLC6) family of the human genome comprises transporters for neurotransmitters, amino acids, osmolytes and energy metabolites. Members of this family play critical roles in neurotransmission, cellular and whole body homeostasis. Malfunction or altered expression...... of the SLC6 family transporters....

From analytical solutions of solute transport equations to multidimensional time-domain random walk (TDRW) algorithms

Science.gov (United States)

Bodin, Jacques

2015-03-01

In this study, new multi-dimensional time-domain random walk (TDRW) algorithms are derived from approximate one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) analytical solutions of the advection-dispersion equation and from exact 1-D, 2-D, and 3-D analytical solutions of the pure-diffusion equation. These algorithms enable the calculation of both the time required for a particle to travel a specified distance in a homogeneous medium and the mass recovery at the observation point, which may be incomplete due to 2-D or 3-D transverse dispersion or diffusion. The method is extended to heterogeneous media, represented as a piecewise collection of homogeneous media. The particle motion is then decomposed along a series of intermediate checkpoints located on the medium interface boundaries. The accuracy of the multi-dimensional TDRW method is verified against (i) exact analytical solutions of solute transport in homogeneous media and (ii) finite-difference simulations in a synthetic 2-D heterogeneous medium of simple geometry. The results demonstrate that the method is ideally suited to purely diffusive transport and to advection-dispersion transport problems dominated by advection. Conversely, the method is not recommended for highly dispersive transport problems because the accuracy of the advection-dispersion TDRW algorithms degrades rapidly for a low Péclet number, consistent with the accuracy limit of the approximate analytical solutions. The proposed approach provides a unified methodology for deriving multi-dimensional time-domain particle equations and may be applicable to other mathematical transport models, provided that appropriate analytical solutions are available.

Optical photon transport in powdered-phosphor scintillators. Part II. Calculation of single-scattering transport parameters

Energy Technology Data Exchange (ETDEWEB)

Poludniowski, Gavin G. [Joint Department of Physics, Division of Radiotherapy and Imaging, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT, United Kingdom and Centre for Vision Speech and Signal Processing (CVSSP), Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Evans, Philip M. [Centre for Vision Speech and Signal Processing (CVSSP), Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2013-04-15

Purpose: Monte Carlo methods based on the Boltzmann transport equation (BTE) have previously been used to model light transport in powdered-phosphor scintillator screens. Physically motivated guesses or, alternatively, the complexities of Mie theory have been used by some authors to provide the necessary inputs of transport parameters. The purpose of Part II of this work is to: (i) validate predictions of modulation transform function (MTF) using the BTE and calculated values of transport parameters, against experimental data published for two Gd{sub 2}O{sub 2}S:Tb screens; (ii) investigate the impact of size-distribution and emission spectrum on Mie predictions of transport parameters; (iii) suggest simpler and novel geometrical optics-based models for these parameters and compare to the predictions of Mie theory. A computer code package called phsphr is made available that allows the MTF predictions for the screens modeled to be reproduced and novel screens to be simulated. Methods: The transport parameters of interest are the scattering efficiency (Q{sub sct}), absorption efficiency (Q{sub abs}), and the scatter anisotropy (g). Calculations of these parameters are made using the analytic method of Mie theory, for spherical grains of radii 0.1-5.0 {mu}m. The sensitivity of the transport parameters to emission wavelength is investigated using an emission spectrum representative of that of Gd{sub 2}O{sub 2}S:Tb. The impact of a grain-size distribution in the screen on the parameters is investigated using a Gaussian size-distribution ({sigma}= 1%, 5%, or 10% of mean radius). Two simple and novel alternative models to Mie theory are suggested: a geometrical optics and diffraction model (GODM) and an extension of this (GODM+). Comparisons to measured MTF are made for two commercial screens: Lanex Fast Back and Lanex Fast Front (Eastman Kodak Company, Inc.). Results: The Mie theory predictions of transport parameters were shown to be highly sensitive to both grain size

The future of public transport in light of solutions for sustainable transport development

Directory of Open Access Journals (Sweden)

Kazimierz LEJDA

2017-06-01

Full Text Available The paper highlights possible directions in the development of sustainable public transport solutions. When appropriately identified and implemented, such solutions can contribute to improved quality of urban life by reducing the adverse effects of transport on human health and the natural environment. The paper also raises questions about implementing pedestrian traffic zones, expanding the level of cycling, and introducing a workable parking policy, congestion charges, electromobility and intelligent systems for road traffic management in conurbations.

Reactive solute transport in an asymmetrical fracture-rock matrix system

Science.gov (United States)

Zhou, Renjie; Zhan, Hongbin

2018-02-01

The understanding of reactive solute transport in a single fracture-rock matrix system is the foundation of studying transport behavior in the complex fractured porous media. When transport properties are asymmetrically distributed in the adjacent rock matrixes, reactive solute transport has to be considered as a coupled three-domain problem, which is more complex than the symmetric case with identical transport properties in the adjacent rock matrixes. This study deals with the transport problem in a single fracture-rock matrix system with asymmetrical distribution of transport properties in the rock matrixes. Mathematical models are developed for such a problem under the first-type and the third-type boundary conditions to analyze the spatio-temporal concentration and mass distribution in the fracture and rock matrix with the help of Laplace transform technique and de Hoog numerical inverse Laplace algorithm. The newly acquired solutions are then tested extensively against previous analytical and numerical solutions and are proven to be robust and accurate. Furthermore, a water flushing phase is imposed on the left boundary of system after a certain time. The diffusive mass exchange along the fracture/rock matrixes interfaces and the relative masses stored in each of three domains (fracture, upper rock matrix, and lower rock matrix) after the water flushing provide great insights of transport with asymmetric distribution of transport properties. This study has the following findings: 1) Asymmetric distribution of transport properties imposes greater controls on solute transport in the rock matrixes. However, transport in the fracture is mildly influenced. 2) The mass stored in the fracture responses quickly to water flushing, while the mass stored in the rock matrix is much less sensitive to the water flushing. 3) The diffusive mass exchange during the water flushing phase has similar patterns under symmetric and asymmetric cases. 4) The characteristic distance

Mass transfer processes and field-scale transport of organic solutes

International Nuclear Information System (INIS)

Brusseau, M.L.

1990-01-01

The influence of mass transfer processes, such as sorption/desorption and mass transfer between immiscible liquids and water, on the transport of organic solutes is discussed. Rate-limited sorption of organic solutes caused by a diffusion-constrained mechanism is shown to be significant under laboratory conditions. The significance of the impact of nonequilibrium sorption on field-scale transport is scale dependent. The impact of organic liquids on mass transfer and transport of organic solutes depends upon the nature of the solute and the nature and form of the organic liquid. For example, while retardation of nonionic solutes is decreased in mixed-solvent systems, (i.e. systems comprised of water and a miscible organic liquid or an immiscible liquid present in concentrations below phase separation), the retardation of organic acids may, in some cases, increase with addition of a cosolvent. While the presence of an immiscible liquid existing as a mobile phase will reduce retention of organic solutes, the presence of residual saturation of an immiscible liquid can significantly increase retention. A model is presented that incorporates the effects of retention resulting from residual saturation, as well as nonequilibrium sorption, on the transport of organic solutes. (Author) (70 refs., 3 figs.)

End-Member Formulation of Solid Solutions and Reactive Transport

Energy Technology Data Exchange (ETDEWEB)

Lichtner, Peter C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-09-01

A model for incorporating solid solutions into reactive transport equations is presented based on an end-member representation. Reactive transport equations are solved directly for the composition and bulk concentration of the solid solution. Reactions of a solid solution with an aqueous solution are formulated in terms of an overall stoichiometric reaction corresponding to a time-varying composition and exchange reactions, equivalent to reaction end-members. Reaction rates are treated kinetically using a transition state rate law for the overall reaction and a pseudo-kinetic rate law for exchange reactions. The composition of the solid solution at the onset of precipitation is assumed to correspond to the least soluble composition, equivalent to the composition at equilibrium. The stoichiometric saturation determines if the solid solution is super-saturated with respect to the aqueous solution. The method is implemented for a simple prototype batch reactor using Mathematica for a binary solid solution. Finally, the sensitivity of the results on the kinetic rate constant for a binary solid solution is investigated for reaction of an initially stoichiometric solid phase with an undersaturated aqueous solution.

Reexamining ultrafiltration and solute transport in groundwater

Science.gov (United States)

Neuzil, C. E.; Person, Mark

2017-06-01

Geologic ultrafiltration—slowing of solutes with respect to flowing groundwater—poses a conundrum: it is consistently observed experimentally in clay-rich lithologies, but has been difficult to identify in subsurface data. Resolving this could be important for clarifying clay and shale transport properties at large scales as well as interpreting solute and isotope patterns for applications ranging from nuclear waste repository siting to understanding fluid transport in tectonically active environments. Simulations of one-dimensional NaCl transport across ultrafiltering clay membrane strata constrained by emerging data on geologic membrane properties showed different ultrafiltration effects than have often been envisioned. In relatively high-permeability advection-dominated regimes, salinity increases occurred mostly within membrane units while their effluent salinity initially fell and then rose to match solute delivery. In relatively low-permeability diffusion-dominated regimes, salinity peaked at the membrane upstream boundary and effluent salinity remained low. In both scenarios, however, only modest salinity changes (up to ˜3 g L-1) occurred because of self-limiting tendencies; membrane efficiency declines as salinity rises, and although sediment compaction increases efficiency, it is also decreases permeability and allows diffusive transport to dominate. It appears difficult for ultrafiltration to generate brines as speculated, but widespread and less extreme ultrafiltration effects in the subsurface could be unrecognized. Conditions needed for ultrafiltration are present in settings that include topographically-driven flow systems, confined aquifer systems subjected to injection or withdrawal, compacting basins, and accretionary complexes.

Mathematical model formulation and validation of water and solute transport in whole hamster pancreatic islets.

Science.gov (United States)

Benson, James D; Benson, Charles T; Critser, John K

2014-08-01

Optimization of cryopreservation protocols for cells and tissues requires accurate models of heat and mass transport. Model selection often depends on the configuration of the tissue. Here, a mathematical and conceptual model of water and solute transport for whole hamster pancreatic islets has been developed and experimentally validated incorporating fundamental biophysical data from previous studies on individual hamster islet cells while retaining whole-islet structural information. It describes coupled transport of water and solutes through the islet by three methods: intracellularly, intercellularly, and in combination. In particular we use domain decomposition techniques to couple a transmembrane flux model with an interstitial mass transfer model. The only significant undetermined variable is the cellular surface area which is in contact with the intercellularly transported solutes, Ais. The model was validated and Ais determined using a 3×3 factorial experimental design blocked for experimental day. Whole islet physical experiments were compared with model predictions at three temperatures, three perfusing solutions, and three islet size groups. A mean of 4.4 islets were compared at each of the 27 experimental conditions and found to correlate with a coefficient of determination of 0.87±0.06 (mean ± SD). Only the treatment variable of perfusing solution was found to be significant (p<0.05). We have devised a model that retains much of the intrinsic geometric configuration of the system, and thus fewer laboratory experiments are needed to determine model parameters and thus to develop new optimized cryopreservation protocols. Additionally, extensions to ovarian follicles and other concentric tissue structures may be made. Copyright © 2014 Elsevier Inc. All rights reserved.

Estimation of geochemical parameters for assessing subsurface transport at the Savannah River Plant: Environmental information document

International Nuclear Information System (INIS)

Looney, B.B.; Grant, M.W.; King, C.M.

1987-03-01

Geochemical parameter estimates to be used in assessing the subsurface transport of chemicals from Savannah River Plant (SRP) waste sites are presented. Specifically, reference values for soil-solution distribution coefficients, solubility, leach rates, and retardation coefficients are estimated for 31 inorganic chemicals (assuming speciation is governed by reasonable assumptions about controlling variables such as Eh and pH) and 36 organic compounds. Additionally, facilitated transport (the association of chemicals with inorganic and organic ligands or colloids resulting in relatively high mobility) was estimated using field data to derive a fraction of the disposal mass which was assumed to be mobile. Hydrologic parameters such as dispersion coefficient, average moisture content in vadose zone, bulk density, and effective porosity are also presented. The estimates are based on site-specific studies when available, combined with technical literature

Identification of biomolecule mass transport and binding rate parameters in living cells by inverse modeling

Directory of Open Access Journals (Sweden)

Shirmohammadi Adel

2006-10-01

Full Text Available Abstract Background Quantification of in-vivo biomolecule mass transport and reaction rate parameters from experimental data obtained by Fluorescence Recovery after Photobleaching (FRAP is becoming more important. Methods and results The Osborne-Moré extended version of the Levenberg-Marquardt optimization algorithm was coupled with the experimental data obtained by the Fluorescence Recovery after Photobleaching (FRAP protocol, and the numerical solution of a set of two partial differential equations governing macromolecule mass transport and reaction in living cells, to inversely estimate optimized values of the molecular diffusion coefficient and binding rate parameters of GFP-tagged glucocorticoid receptor. The results indicate that the FRAP protocol provides enough information to estimate one parameter uniquely using a nonlinear optimization technique. Coupling FRAP experimental data with the inverse modeling strategy, one can also uniquely estimate the individual values of the binding rate coefficients if the molecular diffusion coefficient is known. One can also simultaneously estimate the dissociation rate parameter and molecular diffusion coefficient given the pseudo-association rate parameter is known. However, the protocol provides insufficient information for unique simultaneous estimation of three parameters (diffusion coefficient and binding rate parameters owing to the high intercorrelation between the molecular diffusion coefficient and pseudo-association rate parameter. Attempts to estimate macromolecule mass transport and binding rate parameters simultaneously from FRAP data result in misleading conclusions regarding concentrations of free macromolecule and bound complex inside the cell, average binding time per vacant site, average time for diffusion of macromolecules from one site to the next, and slow or rapid mobility of biomolecules in cells. Conclusion To obtain unique values for molecular diffusion coefficient and

Solutions to Improve Person Transport System in the Pitesti City by Analyzing Public Transport vs. Private Transport

Science.gov (United States)

Mihaela, Istrate; Alexandru, Boroiu; Viorel, Nicolae; Ionel, Vieru

2017-10-01

One of the major problems facing the Pitesti city is the road congestion that occurs in the central area of the city during the peak hours. With all the measures taken in recent years - the widening of road arteries, increasing the number of parking spaces, the creation of overground road passages - it is obvious that the problem can only be solved by a new philosophy regarding urban mobility: it is no longer possible to continue through solutions to increase the accessibility of the central area of the city, but it is necessary, on the contrary, to promote a policy of discouraging the penetration of vehicles in the city center, coupled with a policy of improving the connection between urban public transport and county public transport. This new approach is also proposed in the new Urban Mobility Plan of Pitesti city, under development. The most convincing argument for the necessity of this new orientation in the Pitesti city mobility plan is based on the analysis of the current situation of passenger transport on the territory of Pitesti city: the analysis of “public transport versus private transport” reveals a very low occupancy rate for cars and the fact that the road surface required for a passenger (the dynamic area) is much higher in the case of private transport than in the case of public transport. Measurements of passenger flows and vehicle flows on the 6 penetration ways in the city have been made and the calculations clearly demonstrate the benefits of an urban public transport system connected by “transshipment buses” to be made at the edge of the city, to the county public transport system. In terms of inter-county transport, it will continue to be connected to the urban public transport system by existing bus Station, within the city: South Bus Station and North Bus Station. The usefulness of the paper is that it identifies the solutions for sustainable mobility in Pitesti city and proposes concrete solutions for the development of the

Modelling transport of water and solutes in future wetlands in Forsmark

Energy Technology Data Exchange (ETDEWEB)

Vikstroem, Maria; Gustafsson, Lars-Goeran [DHI Water and Environment AB, Vaexjoe (Sweden)

2006-03-15

The Forsmark area consists of a number of natural wetlands. As a part of the evaluation of wetlands in the safety assessment for the area, possible future wetlands are being studied with respect to hydrology and transport mechanisms. A sensitivity analyses is performed to point out the governing parameters for the wetland hydraulics. The analysis of future wetlands is carried out using the hydrological model system Mike SHE. Mike SHE has been used to describe the near-surface hydrology for a regional model area in Forsmark. Three types of areas have been chosen. Today's lake Bolundfjaerden is because of its shallow depth likely to develop into a mire in the future. As it is situated in the downstream part of the regional model area, the runoff to the lake from upstream surface water system is significant. Lake Eckarfjaerden is situated in the upstream part of the catchment at a higher altitude and with a smaller inflow. Lake Puttan is situated above a planned layout of the repository and has a potential to receive discharges from a repository. It also lies in the downstream part of a large discharge area. The topography of the future mires is assumed to be flat, up to today's mean water level in each lake. To transport the surface runoff through the wetland, streams or water courses are assumed to form within the peat. The analyses of future wetlands in the Forsmark area show that the hydraulic conditions that exists today will somewhat alter as the peat is formed. For Bolundsfjaerden, where there during present conditions are weak discharge areas, a recharge area has formed during the summer. This can be explained by the amount of surface water that forms on the surface which increases the head elevation in the upper soil layers. The same holds for Eckarfjaerden, while Puttan after the peat has developed still is a discharge area due to its naturally strong discharge position close to the sea. Different vegetation and development stages for the peat have

Modelling transport of water and solutes in future wetlands in Forsmark

International Nuclear Information System (INIS)

Vikstroem, Maria; Gustafsson, Lars-Goeran

2006-03-01

The Forsmark area consists of a number of natural wetlands. As a part of the evaluation of wetlands in the safety assessment for the area, possible future wetlands are being studied with respect to hydrology and transport mechanisms. A sensitivity analyses is performed to point out the governing parameters for the wetland hydraulics. The analysis of future wetlands is carried out using the hydrological model system Mike SHE. Mike SHE has been used to describe the near-surface hydrology for a regional model area in Forsmark. Three types of areas have been chosen. Today's lake Bolundfjaerden is because of its shallow depth likely to develop into a mire in the future. As it is situated in the downstream part of the regional model area, the runoff to the lake from upstream surface water system is significant. Lake Eckarfjaerden is situated in the upstream part of the catchment at a higher altitude and with a smaller inflow. Lake Puttan is situated above a planned layout of the repository and has a potential to receive discharges from a repository. It also lies in the downstream part of a large discharge area. The topography of the future mires is assumed to be flat, up to today's mean water level in each lake. To transport the surface runoff through the wetland, streams or water courses are assumed to form within the peat. The analyses of future wetlands in the Forsmark area show that the hydraulic conditions that exists today will somewhat alter as the peat is formed. For Bolundsfjaerden, where there during present conditions are weak discharge areas, a recharge area has formed during the summer. This can be explained by the amount of surface water that forms on the surface which increases the head elevation in the upper soil layers. The same holds for Eckarfjaerden, while Puttan after the peat has developed still is a discharge area due to its naturally strong discharge position close to the sea. Different vegetation and development stages for the peat have been

Numerical solution of the transport equation describing the radon transport from subsurface soil to buildings

International Nuclear Information System (INIS)

Savovic, S.; Djordjevich, A.; Ristic, G.

2012-01-01

A theoretical evaluation of the properties and processes affecting the radon transport from subsurface soil into buildings is presented in this work. The solution of the relevant transport equation is obtained using the explicit finite difference method (EFDM). Results are compared with analytical steady-state solution reported in the literature. Good agreement is found. It is shown that EFDM is effective and accurate for solving the equation that describes radon diffusion, advection and decay during its transport from subsurface to buildings, which is especially important when arbitrary initial and boundary conditions are required. (authors)

Carrier mediated transport through supported liquid membranes; determination of transport parameters from a single transport experiment

NARCIS (Netherlands)

Chrisstoffels, L.A.J.; Struijk, Wilhelmina; de Jong, Feike; Reinhoudt, David

1996-01-01

This paper describes a time-dependent transport model for carrier assisted cation transport through supported liquid membranes. The model describes the flux of salt as a function of time and two parameters viz. the diffusion coefficient of the cation complex (D), and the extraction constant (Kex).

How ISCO Can Interfere in Soil Pore Distribution and Solute Transport

Science.gov (United States)

Favero, M.; Freitas, J. G.; Furquim, S. A. C.; Thomson, N. R.; Cooper, M.

2016-12-01

Recently in situ chemical oxidation (ISCO) has been a remedy of choice for sites contaminated with organic compounds. However, the impact of the chemical oxidant on soil properties and, therefore, on solute transport and remediation efficiency still lacks understanding. This research effort sought to evaluate the changes in soil physical properties and solute transport behavior in a typical tropical soil (Oxisol) resulting from exposure to persulfate. The Oxisol used had a microaggregate structure, resulting in a relatively high hydraulic conductivity despite the high clay content (67%). One-dimensional laboratory experiments were performed using a saturated undisturbed column. The injection of an ideal tracer (bromide), a reactive tracer (phenol) and persulfate (12 ± 1 gL-1 for 30 d) were performed consecutively. The tracer tests were repeated following persulfate injection. Transport parameters (longitudinal dispersivity: αL and retardation factor: R) and the effective porosity (ne) were obtained by fitting the breakthrough curves with an analytical solution for one-dimensional transport. Micromorphological analyses of porosity were conducted on impregnated soil blocks from control and oxidized systems. The bromide and phenol tracer test data yielded αL of 2.431 ± 0.002 cm, ne of 41.99 ± 1.52 %, R of 1.10, and a first-order decay rate coefficient of 6.5x10-5 min-1 prior to persulfate exposure. The effluent persulfate concentration stabilized at C/Co of 0.8 after 4 d of injection and the breakthrough was delayed relative to bromide. Concurrent with the breakthrough of persulfate, the pH decreased and a progressive release of Al (III) over the first 4 d with subsequent stabilization were observed. Following persulfate exposures the hydraulic conductivity increased about one-order of magnitude. Micromorphological analysis showed that persulfate produced alterations in poroids types, with an increase of complex packing voids. It was verified that persulfate

New methods For Modeling Transport Of Water And Solutes In Soils

DEFF Research Database (Denmark)

Møldrup, Per

Recent models for water and solute transport in unsaturated soils have been mechanistically based but numerically very involved. This dissertation concerns the development of mechanistically-based but numerically simple models for calculating and analyzing transport of water and solutes in soil...

A singular one-parameter family of solutions in cubic superstring field theory

Energy Technology Data Exchange (ETDEWEB)

Arroyo, E. Aldo [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, 09210-170 São Paulo, SP (Brazil)

2016-05-03

Performing a gauge transformation of a simple identity-like solution of superstring field theory, we construct a one-parameter family of solutions, and by evaluating the energy associated to this family, we show that for most of the values of the parameter the solution represents the tachyon vacuum, except for two isolated singular points where the solution becomes the perturbative vacuum and the half brane solution.

Transport-constrained extensions of collision and track length estimators for solutions of radiative transport problems

International Nuclear Information System (INIS)

Kong, Rong; Spanier, Jerome

2013-01-01

In this paper we develop novel extensions of collision and track length estimators for the complete space-angle solutions of radiative transport problems. We derive the relevant equations, prove that our new estimators are unbiased, and compare their performance with that of more conventional estimators. Such comparisons based on numerical solutions of simple one dimensional slab problems indicate the the potential superiority of the new estimators for a wide variety of more general transport problems

Diffusion Dominant Solute Transport Modelling in Fractured Media Under Deep Geological Environment - 12211

Energy Technology Data Exchange (ETDEWEB)

Kwong, S. [National Nuclear Laboratory (United Kingdom); Jivkov, A.P. [Research Centre for Radwaste and Decommissioning and Modelling and Simulation Centre, University of Manchester (United Kingdom)

2012-07-01

Deep geologic disposal of high activity and long-lived radioactive waste is gaining increasing support in many countries, where suitable low permeability geological formation in combination with engineered barriers are used to provide long term waste contaminant and minimise the impacts to the environment and risk to the biosphere. This modelling study examines the solute transport in fractured media under low flow velocities that are relevant to a deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes. The effects of water velocity in the fracture, matrix porosity and diffusion on solute transport are investigated and discussed. Some illustrative modelled results are presented to demonstrate the use of the model to examine the effects of media degradation on solute transport, under the influences of hydrogeological (diffusion dominant) and microbially mediated chemical processes. The challenges facing the prediction of long term degradation such as cracks evolution, interaction and coalescence are highlighted. The potential of a novel microstructure informed modelling approach to account for these effects is discussed, particularly with respect to investigating multiple phenomena impact on material performance. The GRM code is used to examine the effects of media degradation for a geological waste disposal package, under the combined hydrogeological (diffusion dominant) and chemical effects in low groundwater flow conditions that are typical of deep geological disposal systems. An illustrative reactive transport modelling application demonstrates the use of the code to examine the interplay of kinetic controlled biogeochemical reactive processes with advective and diffusive transport, under the influence of media degradation. The initial model results are encouraging which show the

Mathematical modeling of fluid and solute transport in peritoneal dialysis

OpenAIRE

Waniewski, Jacek

2001-01-01

Optimization of peritoneal dialysis schedule and dialysis fluid composition needs, among others, methods for quantitative assessment of fluid and solute transport. Furthermore, an integrative quantitative description of physiological processes within the tissue, which contribute to the net transfer of fluid and solutes, is necessary for interpretation of the data and for predictions of the outcome of possible intervention into the peritoneal transport system. The current pro...

Multiscale Roughness Influencing on Transport Behavior of Passive Solute through a Single Self-affine Fracture

Science.gov (United States)

Dou, Z.

2017-12-01

In this study, the influence of multi-scale roughness on transport behavior of the passive solute through the self-affine fracture was investigated. The single self-affine fracture was constructed by the successive random additions (SRA) and the fracture roughness was decomposed into two different scales (i.e. large-scale primary roughness and small-scale secondary roughness) by the Wavelet analysis technique. The fluid flow in fractures, which was characterized by the Forchheimer's law, showed the non-linear flow behaviors such as eddies and tortuous streamlines. The results indicated that the small-scale secondary roughness was primarily responsible for the non-linear flow behaviors. The direct simulations of asymptotic passive solute transport represented the Non-Fickian transport characteristics (i.e. early arrivals and long tails) in breakthrough curves (BTCs) and residence time distributions (RTDs) with and without consideration of the secondary roughness. Analysis of multiscale BTCs and RTDs showed that the small-scale secondary roughness played a significant role in enhancing the Non-Fickian transport characteristics. We found that removing small-scale secondary roughness led to the lengthening arrival and shortening tail. The peak concentration in BTCs decreased as the secondary roughness was removed, implying that the secondary could also enhance the solute dilution. The estimated BTCs by the Fickian advection-dispersion equation (ADE) yielded errors which decreased with the small-scale secondary roughness being removed. The mobile-immobile model (MIM) was alternatively implemented to characterize the Non-Fickian transport. We found that the MIM was more capable of estimating Non-Fickian BTCs. The small-scale secondary roughness resulted in the decreasing mobile domain fraction and the increasing mass exchange rate between immobile and mobile domains. The estimated parameters from the MIM could provide insight into the inherent mechanism of roughness

Parameters of Solidifying Mixtures Transporting at Underground Ore Mining

Directory of Open Access Journals (Sweden)

Golik Vladimir

2017-01-01

Full Text Available The article is devoted to the problem of providing mining enterprises with solidifying filling mixtures at underground mining. The results of analytical studies using the data of foreign and domestic practice of solidifying mixtures delivery to stopes are given. On the basis of experimental practice the parameters of transportation of solidifying filling mixtures are given with an increase in their quality due to the effect of vibration in the pipeline. The mechanism of the delivery process and the procedure for determining the parameters of the forced oscillations of the pipeline, the characteristics of the transporting processes, the rigidity of the elastic elements of pipeline section supports and the magnitude of vibrator’ driving force are detailed. It is determined that the quality of solidifying filling mixtures can be increased due to the rational use of technical resources during the transportation of mixtures, and as a result the mixtures are characterized by a more even distribution of the aggregate. The algorithm for calculating the parameters of the pipe vibro-transport of solidifying filling mixtures can be in demand in the design of mineral deposits underground mining technology.

Parameters of Solidifying Mixtures Transporting at Underground Ore Mining

Science.gov (United States)

Golik, Vladimir; Dmitrak, Yury

2017-11-01

The article is devoted to the problem of providing mining enterprises with solidifying filling mixtures at underground mining. The results of analytical studies using the data of foreign and domestic practice of solidifying mixtures delivery to stopes are given. On the basis of experimental practice the parameters of transportation of solidifying filling mixtures are given with an increase in their quality due to the effect of vibration in the pipeline. The mechanism of the delivery process and the procedure for determining the parameters of the forced oscillations of the pipeline, the characteristics of the transporting processes, the rigidity of the elastic elements of pipeline section supports and the magnitude of vibrator' driving force are detailed. It is determined that the quality of solidifying filling mixtures can be increased due to the rational use of technical resources during the transportation of mixtures, and as a result the mixtures are characterized by a more even distribution of the aggregate. The algorithm for calculating the parameters of the pipe vibro-transport of solidifying filling mixtures can be in demand in the design of mineral deposits underground mining technology.

MODIFIED N.R.C. VERSION OF THE U.S.G.S. SOLUTE TRANSPORT MODEL. VOLUME 2. INTERACTIVE PREPROCESSOR PROGRAM

Science.gov (United States)

The methods described in the report can be used with the modified N.R.C. version of the U.S.G.S. Solute Transport Model to predict the concentration of chemical parameters in a contaminant plume. The two volume report contains program documentation and user's manual. The program ...

Solute transport model for radioisotopes in layered soil

International Nuclear Information System (INIS)

Essel, P.

2010-01-01

The study considered the transport of a radioactive solute in solution from the surface of the earth down through the soil to the ground water when there is an accidental or intentional spillage of a radioactive material on the surface. The finite difference method was used to model the spatial and temporal profile of moisture content in a soil column using the θ-based Richard's equation leading to solution of the convective-dispersive equation for non-adsorbing solutes numerically. A matlab code has been generated to predict the transport of the radioactive contaminant, spilled on the surface of a vertically heterogeneous soil made up of two layers to determine the residence time of the solute in the unsaturated zone, the time it takes the contaminant to reach the groundwater and the amount of the solute entering the groundwater in various times and the levels of pollution in those times. The model predicted that, then there is a spillage of 7.2g of tritium, on the surface of the ground at the study area, it will take two years for the radionuclide to enter the groundwater and fifteen years to totally leave the unsaturated zone. There is therefore the need to try as much as possible to avoid intentional or accidental spillage of the radionuclide since it has long term effect. (au)

Numerical investigations of solute transport in bimodal porous media under dynamic boundary conditions

Science.gov (United States)

Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel; Vanderborght, Jan

2016-04-01

behavior depends on the magnitude of the flow rates and hydraulic conductivity curves of the materials. Based on the unsaturated hydraulic conductivity at the intersection point of conductivity curves, we are able to define an estimate of flow rates at which the dynamic of the upper boundary condition significantly alters preferential flow paths through the system. If flow rates are low, with regard to the materials hydraulic conductivity at the intersection point, the influence of dynamic boundary conditions is small. If flow rates are in the range of the unsaturated hydraulic conductivity at intersection, solute is trapped in the fine material during upwards transport, which results in a more pronounced tailing. For flow rates exceeding the intersection conductivity, a redistribution at the soil surface can occur. References: Bechtold, M., S. Haber-Pohlmeier, J. Vanderborght, A. Pohlmeier, T.P.A. Ferré and H. Veerecken. 2011a. Near-surface solute redistribution during evaporation. Geophys. Res. Lett., 38, L17404, doi:10.1029/2011GL048147. Bechtold, M., J. Vanderborght, O. Ippisch and H. Vereecken. 2011b. Efficient random walk particle tracking algorithm for advective dispersive transport in media with discontinuous dispersion coefficients and water contents. Water Resour. Res., 47, W10526, doi: 10.1029/2010WR010267. Ippisch O., H.-J. Vogel and P. Bastian. 2006. Validity limits fort he van Genuchten-Mualem model and implications for parameter estimation and numerical simulation. Adv. Water Resour., 29, 1780-1789, doi: 10.1016/j.advwateres.2005.12.011. Lehmann, P. and D. Or. 2009. Evaporation and capillary coupling across vertical textural contrasts in porous media. Phys. Rev. E, 80, 046318, doi:10.1103/PhysRevE.80.046318.

Reactive solute transport in streams: A surface complexation approach for trace metal sorption

Science.gov (United States)

Runkel, Robert L.; Kimball, Briant A.; McKnight, Diane M.; Bencala, Kenneth E.

1999-01-01

A model for trace metals that considers in-stream transport, metal oxide precipitation-dissolution, and pH-dependent sorption is presented. Linkage between a surface complexation submodel and the stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron- oxide-coated streambed) is defined as a surface with a temporally constant solid concentration. Limited contact between solutes in the water column and the static surface is considered using a pseudokinetic approach. A dynamic surface (e.g., freshly precipitated metal oxides) has a temporally variable solid concentration and is in equilibrium with the water column. Transport and deposition of solute mass sorbed to the dynamic surface is represented in the stream transport equations that include precipitate settling. The model is applied to a pH-modification experiment in an acid mine drainage stream. Dissolved copper concentrations were depressed for a 3 hour period in response to the experimentally elevated pH. After passage of the pH front, copper was desorbed, and dissolved concentrations returned to ambient levels. Copper sorption is modeled by considering sorption to aged hydrous ferric oxide (HFO) on the streambed (static surface) and freshly precipitated HFO in the water column (dynamic surface). Comparison of parameter estimates with reported values suggests that naturally formed iron oxides may be more effective in removing trace metals than synthetic oxides used in laboratory studies. The model's ability to simulate pH, metal oxide precipitation-dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between trace metal chemistry and hydrologic transport at the field scale.

Positive solution of a time and energy dependent neutron transport problem

International Nuclear Information System (INIS)

Pao, C.V.

1975-01-01

A constructive method is given for the determination of a solution and an existence--uniqueness theorem for some nonlinear time and energy dependent neutron transport problems, including the linear transport system. The geometry of the medium under consideration is allowed to be either bounded or unbounded which includes the geometry of a finite or infinite cylinder, a half-space and the whole space R/subm/ (m=1,2,center-dotcenter-dotcenter-dot). Our approach to the problem is by successive approximation which leads to various recursion formulas for the approximations in terms of explicit integrations. It is shown under some Lipschitz conditions on the nonlinear functions, which describe the process of neutrons absorption, fission, and scattering, that the sequence of approximations converges to a unique positive solution. Since these conditions are satisfied by the linear transport equation, all the results for the nonlinear system are valid for the linear transport problem. In the general nonlinear problem, the existence of both local and global solutions are discussed, and an iterative process for the construction of the solution is given

Numerical modelling of solute transport at Forsmark with MIKE SHE. Site descriptive modelling SDM-Site Forsmark

Energy Technology Data Exchange (ETDEWEB)

Gustafsson, Lars-Goeran; Sassner, Mona (DHI Sverige AB, Stockholm (Sweden)); Bosson, Emma (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

2008-12-15

The Swedish Nuclear Fuel and Waste Management Company (SKB) is performing site investigations at two different locations in Sweden, referred to as the Forsmark and Laxemar areas, with the objective of siting a final repository for high-level radioactive waste. Data from the site investigations are used in a variety of modelling activities. This report presents model development and results of numerical transport modelling based on the numerical flow modelling of surface water and near-surface groundwater at the Forsmark site. The numerical modelling was performed using the modelling tool MIKE SHE and is based on the site data and conceptual model of the Forsmark areas. This report presents solute transport applications based on both particle tracking simulations and advection-dispersion calculations. The MIKE SHE model is the basis for the transport modelling presented in this report. Simulation cases relevant for the transport from a deep geological repository have been studied, but also the pattern of near surface recharge and discharge areas. When the main part of the modelling work presented in this report was carried out, the flow modelling of the Forsmark site was not finalised. Thus, the focus of this work is to describe the sensitivity to different transport parameters, and not to point out specific areas as discharge areas from a future repository (this is to be done later, within the framework of the safety assessment). In the last chapter, however, results based on simulations with the re-calibrated MIKE SHE flow model are presented. The results from the MIKE SHE water movement calculations were used by cycling the calculated transient flow field for a selected one-year period as many times as needed to achieve the desired simulation period. The solute source was located either in the bedrock or on top of the model. In total, 15 different transport simulation cases were studied. Five of the simulations were particle tracking simulations, whereas the rest

Transport of organic solutes through amorphous teflon AF films.

Science.gov (United States)

Zhao, Hong; Zhang, Jie; Wu, Nianqiang; Zhang, Xu; Crowley, Katie; Weber, Stephen G

2005-11-02

Fluorous media have great potential for selective extraction (e.g., as applied to organic synthesis). Fluorous polymer films would have significant advantages in fluorous separations. Stable films of Teflon AF 2400 were cast from solution. Films appear defect-free (SEM; AFM). Rigid aromatic solutes are transported (from chloroform solution to chloroform receiving phase) in a size-dependent manner (log permeability is proportional to -0.0067 times critical volume). Benzene's permeability is about 2 orders of magnitude higher than in comparable gas-phase experiments. The films show selectivity for fluorinated solutes in comparison to the hydrogen-containing control. Transport rates are dependent on the solvent making up the source and receiving phases. The effect of solvent is, interestingly, not due to changes in partition ratio, but rather it is due to changes in the solute diffusion coefficient in the film. Solvents plasticize the films. A less volatile compound, -COOH-terminated poly(hexafluoropropylene oxide) (4), plasticizes the films (T(g) = -40 degrees C). Permeabilities are decreased in comparison to 4-free films apparently because of decreased diffusivity of solutes. The slope of dependence of log permeability on critical volume is not changed, however.

Analytical solution to the hybrid diffusion-transport equation

International Nuclear Information System (INIS)

Nanneh, M.M.; Williams, M.M.R.

1986-01-01

A special integral equation was derived in previous work using a hybrid diffusion-transport theory method for calculating the flux distribution in slab lattices. In this paper an analytical solution of this equation has been carried out on a finite reactor lattice. The analytical results of disadvantage factors are shown to be accurate in comparison with the numerical results and accurate transport theory calculations. (author)

Increasing parameter certainty and data utility through multi-objective calibration of a spatially distributed temperature and solute model

Directory of Open Access Journals (Sweden)

C. Bandaragoda

2011-05-01

Full Text Available To support the goal of distributed hydrologic and instream model predictions based on physical processes, we explore multi-dimensional parameterization determined by a broad set of observations. We present a systematic approach to using various data types at spatially distributed locations to decrease parameter bounds sampled within calibration algorithms that ultimately provide information regarding the extent of individual processes represented within the model structure. Through the use of a simulation matrix, parameter sets are first locally optimized by fitting the respective data at one or two locations and then the best results are selected to resolve which parameter sets perform best at all locations, or globally. This approach is illustrated using the Two-Zone Temperature and Solute (TZTS model for a case study in the Virgin River, Utah, USA, where temperature and solute tracer data were collected at multiple locations and zones within the river that represent the fate and transport of both heat and solute through the study reach. The result was a narrowed parameter space and increased parameter certainty which, based on our results, would not have been as successful if only single objective algorithms were used. We also found that the global optimum is best defined by multiple spatially distributed local optima, which supports the hypothesis that there is a discrete and narrowly bounded parameter range that represents the processes controlling the dominant hydrologic responses. Further, we illustrate that the optimization process itself can be used to determine which observed responses and locations are most useful for estimating the parameters that result in a global fit to guide future data collection efforts.

Numerical modelling of solute transport at Forsmark with MIKE SHE. Site descriptive modelling SDM-Site Forsmark

International Nuclear Information System (INIS)

Gustafsson, Lars-Goeran; Sassner, Mona; Bosson, Emma

2008-12-01

The Swedish Nuclear Fuel and Waste Management Company (SKB) is performing site investigations at two different locations in Sweden, referred to as the Forsmark and Laxemar areas, with the objective of siting a final repository for high-level radioactive waste. Data from the site investigations are used in a variety of modelling activities. This report presents model development and results of numerical transport modelling based on the numerical flow modelling of surface water and near-surface groundwater at the Forsmark site. The numerical modelling was performed using the modelling tool MIKE SHE and is based on the site data and conceptual model of the Forsmark areas. This report presents solute transport applications based on both particle tracking simulations and advection-dispersion calculations. The MIKE SHE model is the basis for the transport modelling presented in this report. Simulation cases relevant for the transport from a deep geological repository have been studied, but also the pattern of near surface recharge and discharge areas. When the main part of the modelling work presented in this report was carried out, the flow modelling of the Forsmark site was not finalised. Thus, the focus of this work is to describe the sensitivity to different transport parameters, and not to point out specific areas as discharge areas from a future repository (this is to be done later, within the framework of the safety assessment). In the last chapter, however, results based on simulations with the re-calibrated MIKE SHE flow model are presented. The results from the MIKE SHE water movement calculations were used by cycling the calculated transient flow field for a selected one-year period as many times as needed to achieve the desired simulation period. The solute source was located either in the bedrock or on top of the model. In total, 15 different transport simulation cases were studied. Five of the simulations were particle tracking simulations, whereas the rest

Effects of coal gangue content on water movement and solute transport in a China loess plateau soil

Energy Technology Data Exchange (ETDEWEB)

Beibei, Zhou; Quanjiu, Wang [Institute of Water Resources and Hydro-electric Engineering, Xi' an University of Technology, Xi' an (China); State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A and F University, Yangling, Shaanxi (China); Ming' an, Shao; Mingxia, Wen [State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A and F University, Yangling, Shaanxi (China); College of Resources and Environment, Northwest A and F University, Yangling, Shaanxi (China); Horton, Robert [Department of Agronomy, Iowa State University, Ames, Iowa (United States)

2010-11-15

The mining industry has grown strongly in China in recent decades, resulting in large amounts of coal gangues, which cause water and soil pollution, soil erosion, and various other environmental problems. They are often used in reclamation projects in attempts to restore land damaged by mining, hence they are frequently present (in widely varying proportions) in the topsoil in areas around mines. Their presence can strongly affect key soil variables, including its bulk density, structure, water retention, water movement, and solute transport rates. In the study presented here, the effects of gangue contents on infiltration, saturated hydraulic conductivity, and solute transport parameters of a Chinese Loess plateau soil were examined. The results show that infiltration rates and saturated hydraulic conductivity decreased with increasing gangue content. The Peck-Watson equation modeled these relationships well, but Bouwer-Rice equations provided poorer matches with the acquired data. Cumulative infiltration over time was described well by both the Philip equation and Kostiakov equation. Both the simplified convection-dispersion equation and a two-region model described the solute transport processes well. In addition, the dispersion increased, while both the Peclet number and mobile water fraction decreased, with increases in gangue contents. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Radionuclide transport in fractured porous media -- Analytical solutions for a system of parallel fractures with a constant inlet flux

International Nuclear Information System (INIS)

Chen, C.T.; Li, S.H.

1997-01-01

Analytical solutions are developed for the problem of radionuclide transport in a system of parallel fractures situated in a porous rock matrix. A constant flux is used as the inlet boundary condition. The solutions consider the following processes: (a) advective transport along the fractures; (b) mechanical dispersion and molecular diffusion along the fractures; (c) molecular diffusion from a fracture to the porous matrix; (d) molecular diffusion within the porous matrix in the direction perpendicular to the fracture axis; (e) adsorption onto the fracture wall; (f) adsorption within the porous matrix, and (g) radioactive decay. The solutions are based on the Laplace transform method. The general transient solution is in the form of a double integral that is evaluated using composite Gauss-Legendre quadrature. A simpler transient solution that is in the form of a single integral is also presented for the case that assumes negligible longitudinal dispersion along the fractures. The steady-state solutions are also provided. A number of examples are given to illustrate the effects of various important parameters, including: (a) fracture spacing; (b) fracture dispersion coefficient; (c) matrix diffusion coefficient; (d) fracture width; (e) groundwater velocity; (f) matrix retardation factor; and (g) matrix porosity

A Finite-Difference Solution of Solute Transport through a Membrane Bioreactor

Directory of Open Access Journals (Sweden)

B. Godongwana

2015-01-01

Full Text Available The current paper presents a theoretical analysis of the transport of solutes through a fixed-film membrane bioreactor (MBR, immobilised with an active biocatalyst. The dimensionless convection-diffusion equation with variable coefficients was solved analytically and numerically for concentration profiles of the solutes through the MBR. The analytical solution makes use of regular perturbation and accounts for radial convective flow as well as axial diffusion of the substrate species. The Michaelis-Menten (or Monod rate equation was assumed for the sink term, and the perturbation was extended up to second-order. In the analytical solution only the first-order limit of the Michaelis-Menten equation was considered; hence the linearized equation was solved. In the numerical solution, however, this restriction was lifted. The solution of the nonlinear, elliptic, partial differential equation was based on an implicit finite-difference method (FDM. An upwind scheme was employed for numerical stability. The resulting algebraic equations were solved simultaneously using the multivariate Newton-Raphson iteration method. The solution allows for the evaluation of the effect on the concentration profiles of (i the radial and axial convective velocity, (ii the convective mass transfer rates, (iii the reaction rates, (iv the fraction retentate, and (v the aspect ratio.

Ground-water solute transport modeling using a three-dimensional scaled model

International Nuclear Information System (INIS)

Crider, S.S.

1987-01-01

Scaled models are used extensively in current hydraulic research on sediment transport and solute dispersion in free surface flows (rivers, estuaries), but are neglected in current ground-water model research. Thus, an investigation was conducted to test the efficacy of a three-dimensional scaled model of solute transport in ground water. No previous results from such a model have been reported. Experiments performed on uniform scaled models indicated that some historical problems (e.g., construction and scaling difficulties; disproportionate capillary rise in model) were partly overcome by using simple model materials (sand, cement and water), by restricting model application to selective classes of problems, and by physically controlling the effect of the model capillary zone. Results from these tests were compared with mathematical models. Model scaling laws were derived for ground-water solute transport and used to build a three-dimensional scaled model of a ground-water tritium plume in a prototype aquifer on the Savannah River Plant near Aiken, South Carolina. Model results compared favorably with field data and with a numerical model. Scaled models are recommended as a useful additional tool for prediction of ground-water solute transport

Optimization of process and solution parameters in electrospinning polyethylene oxide

CSIR Research Space (South Africa)

Jacobs, V

2011-11-01

Full Text Available This paper reports the optimization of electrospinning process and solution parameters using factorial design approach to obtain uniform polyethylene oxide (PEO) nanofibers. The parameters studied were distance between nozzle and collector screen...

Transport of Liquid Phase Organic Solutes in Liquid Crystalline Membranes

OpenAIRE

Han, Sangil

2010-01-01

Porous cellulose nitrate membranes were impregnated with 8CB and PCH5 LCs (liquid crystals) and separations of solutes dissolved in aqueous phases were performed while monitoring solute concentration via UV-VIS spectrometry. The diffusing organic solutes, which consist of one aromatic ring and various functional groups, were selected to exclude molecular size effects on the diffusion and sorption. We studied the effects on solute transport of solute intra-molecular hydrogen bonding and so...

System for sampling active solutions in transport container; Systeme de prelevements de solutions actives sur les recipients de transport

Energy Technology Data Exchange (ETDEWEB)

Fradin, J.

1958-12-03

This report presents a system aimed at sampling active solution from a specific transport container (SCRGR model) while transferring this solution with a maximum safety. The sampling principle is described (a flexible tube connected to the receiving container, with a needle at the other end which goes through a rubber membrane and enters a plunger tube). Its benefits are outlined (operator protection, reduction of contamination risk; only the rubber membrane is removed and replaced). Some manufacturing details are described concerning the membrane and the cover.

Chlorovirus-mediated membrane depolarization of Chlorella alters secondary active transport of solutes.

Science.gov (United States)

Agarkova, Irina; Dunigan, David; Gurnon, James; Greiner, Timo; Barres, Julia; Thiel, Gerhard; Van Etten, James L

2008-12-01

Paramecium bursaria chlorella virus 1 (PBCV-1) is the prototype of a family of large, double-stranded DNA, plaque-forming viruses that infect certain eukaryotic chlorella-like green algae from the genus Chlorovirus. PBCV-1 infection results in rapid host membrane depolarization and potassium ion release. One interesting feature of certain chloroviruses is that they code for functional potassium ion-selective channel proteins (Kcv) that are considered responsible for the host membrane depolarization and, as a consequence, the efflux of potassium ions. This report examines the relationship between cellular depolarization and solute uptake. Annotation of the virus host Chlorella strain NC64A genome revealed 482 putative transporter-encoding genes; 224 are secondary active transporters. Solute uptake experiments using seven radioactive compounds revealed that virus infection alters the transport of all the solutes. However, the degree of inhibition varied depending on the solute. Experiments with nystatin, a drug known to depolarize cell membranes, produced changes in solute uptake that are similar but not identical to those that occurred during virus infection. Therefore, these studies indicate that chlorovirus infection causes a rapid and sustained depolarization of the host plasma membrane and that this depolarization leads to the inhibition of secondary active transporters that changes solute uptake.

Solute transport with periodic input point source in one-dimensional ...

African Journals Online (AJOL)

JOY

groundwater flow velocity is considered proportional to multiple of temporal function and ζ th ... One-dimensional solute transport through porous media with or without .... solute free. ... the periodic concentration at source of the boundary i.e.,. 0.

An analytical model for solute transport through a GCL-based two-layered liner considering biodegradation

Energy Technology Data Exchange (ETDEWEB)

Guan, C. [Institute of Hydrology and Water Resources Engineering, Zhejiang University, Hangzhou 310058 (China); Xie, H.J., E-mail: xiehaijian@zju.edu.cn [Institute of Hydrology and Water Resources Engineering, Zhejiang University, Hangzhou 310058 (China); MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou 310058 (China); Wang, Y.Z.; Chen, Y.M.; Jiang, Y.S.; Tang, X.W. [MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou 310058 (China)

2014-01-01

An analytical model for solute advection and dispersion in a two-layered liner consisting of a geosynthetic clay liner (GCL) and a soil liner (SL) considering the effect of biodegradation was proposed. The analytical solution was derived by Laplace transformation and was validated over a range of parameters using the finite-layer method based software Pollute v7.0. Results show that if the half-life of the solute in GCL is larger than 1 year, the degradation in GCL can be neglected for solute transport in GCL/SL. When the half-life of GCL is less than 1 year, neglecting the effect of degradation in GCL on solute migration will result in a large difference of relative base concentration of GCL/SL (e.g., 32% for the case with half-life of 0.01 year). The 100-year solute base concentration can be reduced by a factor of 2.2 when the hydraulic conductivity of the SL was reduced by an order of magnitude. The 100-year base concentration was reduced by a factor of 155 when the half life of the contaminant in the SL was reduced by an order of magnitude. The effect of degradation is more important in approving the groundwater protection level than the hydraulic conductivity. The analytical solution can be used for experimental data fitting, verification of complicated numerical models and preliminary design of landfill liner systems. - Highlights: •Degradation of contaminants was considered in modeling solute transport in GCL/SL. •Analytical solutions were derived for assessment of GCL/SL with degradation. •Degradation in GCL can be ignored as half-life is larger than 1 year. •Base concentration is more sensitive to half-life of SL than to permeability of SL.

An analytical model for solute transport through a GCL-based two-layered liner considering biodegradation

International Nuclear Information System (INIS)

Guan, C.; Xie, H.J.; Wang, Y.Z.; Chen, Y.M.; Jiang, Y.S.; Tang, X.W.

2014-01-01

An analytical model for solute advection and dispersion in a two-layered liner consisting of a geosynthetic clay liner (GCL) and a soil liner (SL) considering the effect of biodegradation was proposed. The analytical solution was derived by Laplace transformation and was validated over a range of parameters using the finite-layer method based software Pollute v7.0. Results show that if the half-life of the solute in GCL is larger than 1 year, the degradation in GCL can be neglected for solute transport in GCL/SL. When the half-life of GCL is less than 1 year, neglecting the effect of degradation in GCL on solute migration will result in a large difference of relative base concentration of GCL/SL (e.g., 32% for the case with half-life of 0.01 year). The 100-year solute base concentration can be reduced by a factor of 2.2 when the hydraulic conductivity of the SL was reduced by an order of magnitude. The 100-year base concentration was reduced by a factor of 155 when the half life of the contaminant in the SL was reduced by an order of magnitude. The effect of degradation is more important in approving the groundwater protection level than the hydraulic conductivity. The analytical solution can be used for experimental data fitting, verification of complicated numerical models and preliminary design of landfill liner systems. - Highlights: •Degradation of contaminants was considered in modeling solute transport in GCL/SL. •Analytical solutions were derived for assessment of GCL/SL with degradation. •Degradation in GCL can be ignored as half-life is larger than 1 year. •Base concentration is more sensitive to half-life of SL than to permeability of SL

Development of solute transport models in YMPYRÄ framework to simulate solute migration in military shooting and training areas

Science.gov (United States)

Warsta, L.; Karvonen, T.

2017-12-01

There are currently 25 shooting and training areas in Finland managed by The Finnish Defence Forces (FDF), where military activities can cause contamination of open waters and groundwater reservoirs. In the YMPYRÄ project, a computer software framework is being developed that combines existing open environmental data and proprietary information collected by FDF with computational models to investigate current and prevent future environmental problems. A data centric philosophy is followed in the development of the system, i.e. the models are updated and extended to handle available data from different areas. The results generated by the models are summarized as easily understandable flow and risk maps that can be opened in GIS programs and used in environmental assessments by experts. Substances investigated with the system include explosives and metals such as lead, and both surface and groundwater dominated areas can be simulated. The YMPYRÄ framework is composed of a three dimensional soil and groundwater flow model, several solute transport models and an uncertainty assessment system. Solute transport models in the framework include particle based, stream tube and finite volume based approaches. The models can be used to simulate solute dissolution from source area, transport in the unsaturated layers to groundwater and finally migration in groundwater to water extraction wells and springs. The models can be used to simulate advection, dispersion, equilibrium adsorption on soil particles, solubility and dissolution from solute phase and dendritic solute decay chains. Correct numerical solutions were confirmed by comparing results to analytical 1D and 2D solutions and by comparing the numerical solutions to each other. The particle based and stream tube type solute transport models were useful as they could complement the traditional finite volume based approach which in certain circumstances produced numerical dispersion due to piecewise solution of the

Controlling the transport of an ion: classical and quantum mechanical solutions

International Nuclear Information System (INIS)

Fürst, H A; Poschinger, U G; Schmidt-Kaler, F; Singer, K; Goerz, M H; Koch, C P; Murphy, M; Montangero, S; Calarco, T

2014-01-01

The accurate transport of an ion over macroscopic distances represents a challenging control problem due to the different length and time scales that enter and the experimental limitations on the controls that need to be accounted for. Here, we investigate the performance of different control techniques for ion transport in state-of-the-art segmented miniaturized ion traps. We employ numerical optimization of classical trajectories and quantum wavepacket propagation as well as analytical solutions derived from invariant based inverse engineering and geometric optimal control. The applicability of each of the control methods depends on the length and time scales of the transport. Our comprehensive set of tools allows us make a number of observations. We find that accurate shuttling can be performed with operation times below the trap oscillation period. The maximum speed is limited by the maximum acceleration that can be exerted on the ion. When using controls obtained from classical dynamics for wavepacket propagation, wavepacket squeezing is the only quantum effect that comes into play for a large range of trapping parameters. We show that this can be corrected by a compensating force derived from invariant based inverse engineering, without a significant increase in the operation time. (paper)

Stochastic dynamics modeling solute transport in porous media modeling solute transport in porous media

CERN Document Server

Kulasiri, Don

2002-01-01

Most of the natural and biological phenomena such as solute transport in porous media exhibit variability which can not be modeled by using deterministic approaches. There is evidence in natural phenomena to suggest that some of the observations can not be explained by using the models which give deterministic solutions. Stochastic processes have a rich repository of objects which can be used to express the randomness inherent in the system and the evolution of the system over time. The attractiveness of the stochastic differential equations (SDE) and stochastic partial differential equations (SPDE) come from the fact that we can integrate the variability of the system along with the scientific knowledge pertaining to the system. One of the aims of this book is to explaim some useufl concepts in stochastic dynamics so that the scientists and engineers with a background in undergraduate differential calculus could appreciate the applicability and appropriateness of these developments in mathematics. The ideas ...

New diffusion-like solutions of one-speed transport equations in spherical geometry

International Nuclear Information System (INIS)

Sahni, D.C.

1988-01-01

Stationary, one-speed, spherically symmetric transport equations are considered in a conservative medium. Closed-form expressions are obtained for the angular flux ψ(r, μ) that yield a total flux varying as 1/r by using Sonine transforms. Properties of this solution are studied and it is shown that the solution can not be identified as a diffusion mode solution of the transport equation. Limitations of the Sonine transform technique are noted. (author)

The linkage among ambulance transports, death and climate parameters in Asahikawa City, Japan.

Science.gov (United States)

Kataoka, Hiroaki; Mochimasu, Kazumi Dokai; Katayama, Akihiko; Kanda, Kanae Oda; Sakano, Noriko; Tanaka, Keiko; Miyatake, Nobuyuki

2015-01-01

The aim of this study was to investigate the linkage among climate parameters, total ambulance transports and the number of deaths in Asahikawa City in northern Japan. Monthly data on total ambulance transports and the number of deaths from January 2004 to December 2011 were obtained from Asahikawa City Fire Department and the Asahikawa City official website. Climate parameters for the required period were also obtained from the Japan Meteorological Agency, Japan. To adjust for the population, we also used monthly population data on Asahikawa City. The linkage among climate parameters, total ambulance transports and the number of deaths was evaluated by ecological analysis. The mean air temperature in the Asahikawa area was 7.3 ± 10.1 °C. Total ambulance transports (/a hundred thousand people/day) and the number of deaths (/a hundred thousand people/day) were 10.0 ± 0.6 and 2.6 ± 0.3, respectively. Using quadratic curves, total ambulance transports and the number of deaths were weakly correlated with some climate parameters. The number of deaths was weakly and positively correlated with total ambulance transports. A weak linkage among climate parameters, total ambulance transports and the number of deaths was noted in Asahikawa City, Japan. However, these associations were not as high as expected.

Fluid flow and convective transport of solutes within the intervertebral disc

NARCIS (Netherlands)

Ferguson, S.J.; Ito, K.; Nolte, L.P.

2004-01-01

Previous experimental and analytical studies of solute transport in the intervertebral disc have demonstrated that for small molecules diffusive transport alone fulfils the nutritional needs of disc cells. It has been often suggested that fluid flow into and within the disc may enhance the transport

X-ray CT-Derived Soil Characteristics Explain Varying Air, Water, and Solute Transport Properties across a Loamy Field

DEFF Research Database (Denmark)

Paradelo Pérez, Marcos; Katuwal, Sheela; Møldrup, Per

2016-01-01

-derived parameters by using a best subsets regression analysis. The regression coefficients improved using CTmatrix, limiting macroporosity, and genus density, while the best model for t0.05 used CTmatrix only. The scanning resolution and the time for soil structure development after mechanical activities could......The characterization of soil pore space geometry is important for explaining fluxes of air, water, and solutes through soil and understanding soil hydrogeochemical functions. X-ray computed tomography (CT) can be applied for this characterization, and in this study CT-derived parameters were used...... to explain water, air, and solute transport through soil. Forty-five soil columns (20 by 20 cm) were collected from an agricultural field in Estrup, Denmark, and subsequently scanned using a medical CT scanner. Nonreactive tracer leaching experiments were performed in the laboratory along with measurements...

Stable solutions of nonlocal electron heat transport equations

International Nuclear Information System (INIS)

Prasad, M.K.; Kershaw, D.S.

1991-01-01

Electron heat transport equations with a nonlocal heat flux are in general ill-posed and intrinsically unstable, as proved by the present authors [Phys. Fluids B 1, 2430 (1989)]. A straightforward numerical solution of these equations will therefore lead to absurd results. It is shown here that by imposing a minimal set of constraints on the problem it is possible to arrive at a globally stable, consistent, and energy conserving numerical solution

Demonstrations in Solute Transport Using Dyes: Part II. Modeling.

Science.gov (United States)

Butters, Greg; Bandaranayake, Wije

1993-01-01

A solution of the convection-dispersion equation is used to describe the solute breakthrough curves generated in the demonstrations in the companion paper. Estimation of the best fit model parameters (solute velocity, dispersion, and retardation) is illustrated using the method of moments for an example data set. (Author/MDH)

Analysis of solute transport in plants using positron emission tomography

International Nuclear Information System (INIS)

Partelova, D.

2016-01-01

In the first part of the work, geometrically and radiochemically characterized standards (phantoms) imitating the plant tissues and allowing the exact quantification of visualised radioindicator in plant tissues were designed and prepared within the study of visual and analytical characteristics of used positron emission tomograph (microPET system) commercially developed for animal objects at visualization of thin objects. Individual experiments carried out by exposure of excised leaves of tobacco (Nicotiana tabacum L.) or radish (Raphanus sativus L.) in solutions of 2-deoxy-2-fluoro-D-glucose labelled with positron emitter 18 F (2-[ 18 F]FDG) containing 10-, 100-, or 1000-times higher concentrations of D-glucose (c glu ) in comparison with the original 2-[ 18 F]FDG solution showed that the significant changes in visualisation of 2-[ 18 F]FDG distribution as well as in chemical portion of 2-[ 18 F]FDG within the leaf blade were observed as result of increased c glu . In the experiments with the whole plants of tobacco or radish exposed in 2-[ 18 F]FDG solution through the root system, only minimal translocation of 18 F radioactivity into the above-ground parts of plants, also in the case of increased c glu , was observed, which suggest the role of root system as a selective barrier of 2-[ 18 F]FDG transport from roots to the above-ground parts. On the basis of mentioned knowledge and analytical approaches (application of prepared phantoms), the dynamic study of 2-[ 18 F]FDG uptake and transport within the excised leaf of tobacco or whole radish plant was carried out. The description of these processes was realized through the 3D PET images and through the quantification of 2-[ 18 F]FDG distribution within the chosen regions of interest from the point of view of accumulated 18 F radioactivity (in Bq) or amount of D-glucose (in μg) as well. Application of methods of multivariate analysis allows to found the similarities between studied objects mainly from the point

Coupled Fluid, Energy, and Solute Transport (CFEST) model: Formulation and user's manual

International Nuclear Information System (INIS)

Gupta, S.K.; Cole, C.R.; Kincaid, C.T.; Monti, A.M.

1987-10-01

The CFEST (Coupled Fluid, Energy, and Solute Transport) code has been developed to analyze coupled hydrologic, thermal, and solute transport processes. It treats single-pahse Darcy ground-water flow in a horizontal or vertical plane, or in fully three-dimensional space under nonisothermal conditions. The code has the capability to model discontinuous and continuous layering, time-dependent and constant sources/sinks, and transient as well as steady-stae ground-water flow. The code offers a wide choice of boundary conditions such as precsribed heads, nodal injection or withdrawal, constant or spatially varying infiltration rates, and welemental source/sink. Initial conditions for the flow analysis can be prescribed pressure or hydraulic head. The heterogeneity in aquifer permeability and porosity can be described by geologic unit or explicity for given elements. Three-dimensional elelments are generated from user-defined well logs at each surface node. To facilitate interaction between disciplines, support programs are provided to plot the finite element grid, well logs, contour maps of input and output parameters, and vertical cross sections. Ground-water travel paths and times and volumetric rates from a specified point can be determined from support programs. This report includes governing partial differential equations, finite element formulation, a use's manual, verification test examples, sample problems, and source listings. 36 refs., 121 figs., 36 tabs

New constructive solutions for building of transport construction facilities

Directory of Open Access Journals (Sweden)

Babayev Vladimir

2017-01-01

Full Text Available New structural systems for civil and transport engineering were examined. The basis for the formation of the proposed reinforced concrete structures is the ideology of reducing its dead weight, with a given bearing capacity, the realization of which is accomplished by burial during concreting large-sized liners of a given shape and manufactured from lightweight, inexpensive composite materials. The process of erecting these systems is presented in two forms: for flat structures - using self-tightening concrete, and for curvilinear ones - by using shotcrete technologies. The second direction is presented by steel-reinforced concrete structures. These structural systems were created on the basis of innovative component and methods of rationalization of parameters. The basis of the above methods is a compiler which includes the finite element method, adaptive evolution method and special iterative procedures. Experimental verification of structural solutions and formation procedures for suggested systems was performed. Comparison between theoretical and experimental data is given. Suggested systems were implemented in a number of building companies.

Measuruement of transport parameters on multiphase flows

International Nuclear Information System (INIS)

Kipphan, H.

1976-01-01

A method working on the basis of the correlation measuring technique is developed and tested on gas-solid flows in pipelines to measure transport parameters of the solid phase. Firstly, flows with stationary and site-independent average values are considered; finally, a few data on the measurement of instationary flows follow. (orig.) [de

Approximate solutions for the two-dimensional integral transport equation. Solution of complex two-dimensional transport problems

International Nuclear Information System (INIS)

Sanchez, Richard.

1980-11-01

This work is divided into two parts: the first part deals with the solution of complex two-dimensional transport problems, the second one (note CEA-N-2166) treats the critically mixed methods of resolution. A set of approximate solutions for the isotropic two-dimensional neutron transport problem has been developed using the interface current formalism. The method has been applied to regular lattices of rectangular cells containing a fuel pin, cladding, and water, or homogenized structural material. The cells are divided into zones that are homogeneous. A zone-wise flux expansion is used to formulate a direct collision probability problem within a cell. The coupling of the cells is effected by making extra assumptions on the currents entering and leaving the interfaces. Two codes have been written: CALLIOPE uses a cylindrical cell model and one or three terms for the flux expansion, and NAUSICAA uses a two-dimensional flux representation and does a truly two-dimensional calculation inside each cell. In both codes, one or three terms can be used to make a space-independent expansion of the angular fluxes entering and leaving each side of the cell. The accuracies and computing times achieved with the different approximations are illustrated by numerical studies on two benchmark problems and by calculations performed in the APOLLO multigroup code [fr

Stochastic analysis of transport of conservative solutes in caisson experiments

International Nuclear Information System (INIS)

Dagan, G.

1995-01-01

The Los Alamos National Laboratory has conducted in the past a series of experiments of transport of conservative and reactive solutes. The experimental setup and the experimental results are presented in a series of reports. The main aim of the experiments was to validate models of transport of solutes in unsaturated flow at the caisson intermediate scale, which is much larger than the one pertaining to laboratory columns. First attempts to analyze the experimental results were by one-dimensional convective-dispersion models. These models could not explain the observed solute breakthrough curves and particularly the large solute dispersion in the caisson effluent Since there were some question marks about the uniformity of water distribution at the caisson top, the transport experiments were repeated under conditions of saturated flow. In these experiments constant heads were applied at the top and the bottom of the caisson and the number of concentration monitoring stations was quadrupled. The analysis of the measurements by the same one-dimensional model indicated clearly that the fitted dispersivity is much larger than the pore-sole dispersivity and that it grows with the distance in an approximately linear fashion. This led to the conclusion, raised before, that transport in the caisson is dominated by heterogeneity effects, i.e. by spatial variability of the material Such effects cannot be captured by traditional one-dimensional models. In order to account for the effect of heterogeneity, the saturated flow experiments have been analyzed by using stochastic transport modeling. The apparent linear growth of dispersivity with distance suggested that the system behaves like a stratified one. Consequently, the model of Dagan and Bresier has been adopted in order to interpret concentration measurements. In this simple model the caisson is viewed as a bundle of columns of different permeabilities, which are characterized by a p.d.f. (probability denasity function)

Colloid transport in porous media: impact of hyper-saline solutions.

Science.gov (United States)

Magal, Einat; Weisbrod, Noam; Yechieli, Yoseph; Walker, Sharon L; Yakirevich, Alexander

2011-05-01

The transport of colloids suspended in natural saline solutions with a wide range of ionic strengths, up to that of Dead Sea brines (10(0.9) M) was explored. Migration of microspheres through saturated sand columns of different sizes was studied in laboratory experiments and simulated with mathematical models. Colloid transport was found to be related to the solution salinity as expected. The relative concentration of colloids at the columns outlet decreased (after 2-3 pore volumes) as the solution ionic strength increased until a critical value was reached (ionic strength > 10(-1.8) M) and then remained constant above this level of salinity. The colloids were found to be mobile even in the extremely saline brines of the Dead Sea. At such high ionic strength no energetic barrier to colloid attachment was presumed to exist and colloid deposition was expected to be a favorable process. However, even at these salinity levels, colloid attachment was not complete and the transport of ∼ 30% of the colloids through the 30-cm long columns was detected. To further explore the deposition of colloids on sand surfaces in Dead Sea brines, transport was studied using 7-cm long columns through which hundreds of pore volumes were introduced. The resulting breakthrough curves exhibited a bimodal shape whereby the relative concentration (C/C(0)) of colloids at the outlet rose to a value of 0.8, and it remained relatively constant (for the ∼ 18 pore volumes during which the colloid suspension was flushed through the column) and then the relative concentration increased to a value of one. The bimodal nature of the breakthrough suggests different rates of colloid attachment. Colloid transport processes were successfully modeled using the limited entrapment model, which assumes that the colloid attachment rate is dependent on the concentration of the attached colloids. Application of this model provided confirmation of the colloid aggregation and their accelerated attachment during

Used Fuel Logistics: Decades of Experience with transportation and Interim storage solutions

Energy Technology Data Exchange (ETDEWEB)

Orban, G.; Shelton, C.

2015-07-01

Used fuel inventories are growing worldwide. While some countries have opted for a closed cycle with recycling, numerous countries must expand their interim storage solutions as implementation of permanent repositories is taking more time than foreseen. In both cases transportation capabilities will have to be developed. AREVA TN has an unparalleled expertise with transportation of used fuel. For more than 50 years AREVA TN has safely shipped more than 7,000 used fuel transport casks. The transportation model that was initially developed in the 1970s has been adapted and enhanced over the years to meet more restrictive regulatory requirements and evolving customer needs, and to address public concerns. The numerous “lessons learned” have offered data and guidance that have allowed for also efficient and consistent improvement over the decades. AREVA TN has also an extensive experience with interim dry storage solutions in many countries on-site but also is working with partners to developed consolidated interim storage facility. Both expertise with storage and transportation contribute to safe, secure and smooth continuity of the operations. This paper will describe decades of experience with a very successful transportation program as well as interim storage solutions. (Author)

Mechanistic analysis of solute transport in an in vitro physiological two-phase dissolution apparatus.

Science.gov (United States)

Mudie, Deanna M; Shi, Yi; Ping, Haili; Gao, Ping; Amidon, Gordon L; Amidon, Gregory E

2012-10-01

In vitro dissolution methodologies that adequately capture the oral bioperformance of solid dosage forms are critical tools needed to aid formulation development. Such methodologies must encompass important physiological parameters and be designed with drug properties in mind. Two-phase dissolution apparatuses, which contain an aqueous phase in which the drug dissolves (representing the dissolution/solubility component) and an organic phase into which the drug partitions (representing the absorption component), have the potential to provide meaningful predictions of in vivo oral bioperformance for some BCS II, and possibly some BCS IV drug products. Before such an apparatus can be evaluated properly, it is important to understand the kinetics of drug substance partitioning from the aqueous to the organic medium. A mass transport analysis was performed of the kinetics of partitioning of drug substance solutions from the aqueous to the organic phase of a two-phase dissolution apparatus. Major assumptions include pseudo-steady-state conditions, a dilute aqueous solution and diffusion-controlled transport. Input parameters can be measured or estimated a priori. This paper presents the theory and derivation of our analysis, compares it with a recent kinetic approach, and demonstrates its effectiveness in predicting in vitro partitioning profiles of three BCS II weak acids in four different in vitro two-phase dissolution apparatuses. Very importantly, the paper discusses how a two-phase apparatus can be scaled to reflect in vivo absorption kinetics and for which drug substances the two-phase dissolution systems may be appropriate tools for measuring oral bioperformance. Copyright © 2012 John Wiley & Sons, Ltd.

Demographic and transportation parameters in RADTRAN

International Nuclear Information System (INIS)

Brogan, J.D.; Cashwell, J.W.; Neuhauser, K.S.

1989-01-01

This paper describes the default parameters for each of the three major variable categories -- transportation network, land use, and population -- in the current version of the RADTRAN code. Changes in the variable assumptions associated with the release of RADTRAN 4.0 will then be described as will the options for users to supply locally-available, rather than national-level, default values. Finally, long-term enhancements anticipated for the code will be discussed. 17 refs

Semianalytical solutions for contaminant transport under variable velocity field in a coastal aquifer

Science.gov (United States)

Koohbor, Behshad; Fahs, Marwan; Ataie-Ashtiani, Behzad; Simmons, Craig T.; Younes, Anis

2018-05-01

Existing closed-form solutions of contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. These solutions cannot be used to investigate contaminant transport in coastal aquifers where seawater intrusion induces a variable velocity field. An adaptation of the Fourier-Galerkin method is introduced to obtain semi-analytical solutions for contaminant transport in a confined coastal aquifer in which the saltwater wedge is in equilibrium with a freshwater discharge flow. Two scenarios dealing with contaminant leakage from the aquifer top surface and contaminant migration from a source at the landward boundary are considered. Robust implementation of the Fourier-Galerkin method is developed to efficiently solve the coupled flow, salt and contaminant transport equations. Various illustrative examples are generated and the semi-analytical solutions are compared against an in-house numerical code. The Fourier series are used to evaluate relevant metrics characterizing contaminant transport such as the discharge flux to the sea, amount of contaminant persisting in the groundwater and solute flux from the source. These metrics represent quantitative data for numerical code validation and are relevant to understand the effect of seawater intrusion on contaminant transport. It is observed that, for the surface contamination scenario, seawater intrusion limits the spread of the contaminant but intensifies the contaminant discharge to the sea. For the landward contamination scenario, moderate seawater intrusion affects only the spatial distribution of the contaminant plume while extreme seawater intrusion can increase the contaminant discharge to the sea. The developed semi-analytical solution presents an efficient tool for the verification of numerical models. It provides a clear interpretation of the contaminant transport processes in coastal aquifers subject to seawater intrusion. For practical usage in further studies, the full

Green transportation logistics: the quest for win-win solutions

DEFF Research Database (Denmark)

measures and speed and route optimization; Sulphur emissions; Lifecycle emissions; Green rail transportation; Green air transportation; Green inland navigation and possible areas for further research. Throughout, the book pursues the goal of “win-win” solutions and analyzes the phenomenon of “push......This book examines the state of the art in green transportation logistics from the perspective of balancing environmental performance in the transportation supply chain while also satisfying traditional economic performance criteria. Part of the book is drawn from the recently completed European...... Union project Super Green, a three-year project intended to promote the development of European freight corridors in an environmentally friendly manner. Additional chapters cover both the methodological base and the application context of green transportation logistics. Individual chapters look...

Finite medium Green's function solutions to nuclide transport in porous media

International Nuclear Information System (INIS)

Oston, S.G.

1979-01-01

Current analytical techniques for predicting the transport of nuclides in porous materials center on the Green's function approach - i.e., determining the response characteristics of a geologic pathway to an impulse function input. To data, the analyses all have set the boundary conditions needed to solve the 1-D transport equation as though each pathway were infinite in length. The purpose of this work is to critically examine the effect that this infinite pathway assumption has on Green's function models of nuclide transport in porous media. The work described herein has directly attacked the more difficult problem of obtaining suitable Green's functions for finite pathways whose dimensions, in fact, may not be much greater than the diffusion length. Two different finite media Green's functions describing the nuclide mass flux have been determined, depending on whether the pathway is terminated by a high or a low flow resistance at the outlet end. Pulse shapes and peak amplitudes have been computed for each Green's function over a wide range of geohydrologic parameters. These results have been compared to both infinite and semi-infinite medium solutions. It was found that predicted pulse shapes are quite sensitive to selection of a Green's function model for short pathways only. For long pathways all models tend toward a symmetric Gaussian flux-time history at the outlet. Thus, the results of our previous waste transport studies using the infinite pathway assumption are still generally valid because they always included at least one long pathway. It was also found that finite medium models offer some unique computational advantages for evaluating nuclide transport in a series of connecting pathways

The effect of low-GDP solution on ultrafiltration and solute transport in continuous ambulatory peritoneal dialysis patients.

Science.gov (United States)

Cho, Kyu-Hyang; Do, Jun-Young; Park, Jong-Won; Yoon, Kyung-Woo; Kim, Yong-Lim

2013-01-01

Several studies have reported benefits for human peritoneal mesothelial cell function of a neutral-pH dialysate low in glucose degradation products (GDPs). However, the effects of low-GDP solution on ultrafiltration (UF), transport of solutes, and control of body water remain elusive. We therefore investigated the effect of low-GDP solution on UF, solute transport, and control of body water. Among 79 new continuous ambulatory peritoneal dialysis (CAPD) patients, 60 completed a 12-month protocol (28 in a lactate-based high-GDP solution group, 32 in a lactate-based low-GDP solution group). Clinical indices--including 24-hour UF volume (UFV), 24-hour urine volume (UV), residual renal function, and dialysis adequacy--were measured at months 1, 6, and 12. At months 1, 6, and 12, UFV, glucose absorption, 4-hour dialysate-to-plasma (D/P) creatinine, and 1-hour D/P Na(+) were assessed during a modified 4.25% peritoneal equilibration test (PET). Body composition by bioelectric impedance analysis was measured at months 1 and 12 in 26 CAPD patients. Daily UFV was lower in the low-GDP group. Despite similar solute transport and aquaporin function, the low-GDP group also showed lower UFV and higher glucose absorption during the PET. Factors associated with UFV during the PET were lactate-based high-GDP solution and 1-hour D/P Na(+). No differences in volume status and obesity at month 12 were observed, and improvements in hypervolemia were equal in both groups. Compared with the high-GDP group, the low-GDP group had a lower UFV during a PET and a lower daily UFV during the first year after peritoneal dialysis initiation. Although the low-GDP group had a lower daily UFV, no difficulties in controlling edema were encountered.

Product Lifecycle Management and the Quest for Sustainable Space Transportation Solutions

Science.gov (United States)

Caruso, Pamela W.

2009-01-01

This viewgraph presentation reviews NASA Marshall's effort to sustain space transportation solutions through product lines that include: 1) Propulsion and Transportation Systems; 2) Life Support Systems; and 3) and Earth and Space Science Spacecraft Systems, and Operations.

Modeling of Flow, Transport and Controlled Sedimentation Phenomena during Mixing of Salt Solutions in Complex Porous Formations

Science.gov (United States)

Skouras, Eugene D.; Jaho, Sofia; Pavlakou, Efstathia I.; Sygouni, Varvara; Petsi, Anastasia; Paraskeva, Christakis A.

2015-04-01

The deposition of salts in porous media is a major engineering phenomenon encountered in a plethora of industrial and environmental applications where in some cases is desirable and in other not (oil production, geothermal systems, soil stabilization etc). Systematic approach of these problems requires knowledge of the key mechanisms of precipitating salts within the porous structures, in order to develop new methods to control the process. In this work, the development and the solution of spatiotemporally variable mass balances during salt solution mixing along specific pores were performed. Both analytical models and finite differences CFD models were applied for the study of flow and transport with simultaneous homogeneous and heterogeneous nucleation (by crystal growth on the surface of the pores) in simple geometries, while unstructured finite elements and meshless methods were developed and implemented for spatial discretization, reconstruction, and solution of transport equations and homogeneous / heterogeneous reactions in more complex geometries. At initial stages of this work, critical problem parameters were identified, such as the characteristics of the porosity, the number of dissolved components, etc. The parameters were then used for solving problems which correspond to available experimental data. For each combination of ions and materials, specific data and process characteristics were included: (a) crystal kinetics (nucleation, growth rates or reaction surface rates of crystals, critical suspension concentrations), (b) physico-chemical properties (bulk density, dimensions of generated crystals, ion diffusion coefficients in the solution), (c) operating parameters (macroscopic velocity, flow, or pressure gradient of the solution, ion concentration) (d) microfluidic data (geometry, flow area), (e) porosity data in Darcy description (initial porosity, specific surface area, tortuosity). During the modeling of flow and transport in three

Contaminant transport at a waste residue deposit: 1. Inverse flow and non-reactive transport modelling

DEFF Research Database (Denmark)

Sonnenborg, Torben Obel; Engesgaard, Peter Knudegaard; Rosbjerg, Dan

1996-01-01

An application of an inverse flow and transport model to a contaminated aquifer is presented. The objective of the study is to identify physical and nonreactive flow and transport parameters through an optimization approach. The approach can be classified as a statistical procedure, where a flow...... to steady state versus transient flow conditions and to the amount of hydraulic and solute data used is investigated. The flow parameters, transmissivity and leakage factor, are estimated simultaneously with the transport parameters: source strength, porosity, and longitudinal dispersivity. This paper...

Efficient solution of a multi objective fuzzy transportation problem

Science.gov (United States)

Vidhya, V.; Ganesan, K.

2018-04-01

In this paper we present a methodology for the solution of multi-objective fuzzy transportation problem when all the cost and time coefficients are trapezoidal fuzzy numbers and the supply and demand are crisp numbers. Using a new fuzzy arithmetic on parametric form of trapezoidal fuzzy numbers and a new ranking method all efficient solutions are obtained. The proposed method is illustrated with an example.

Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport

Science.gov (United States)

Leung, Juliana Y.; Srinivasan, Sanjay

2016-09-01

Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It

A Review of Darcy's Law: Limitations and Alternatives for Predicting Solute Transport

Science.gov (United States)

Steenhuis, Tammo; Kung, K.-J. Sam; Jaynes, Dan; Helling, Charles S.; Gish, Tim; Kladivko, Eileen

2016-04-01

Darcy's Law that was derived originally empirically 160 years ago, has been used successfully in calculating the (Darcy) flux in porous media throughout the world. However, field and laboratory experiments have demonstrated that the Darcy flux employed in the convective disperse equation could only successfully predict solute transport under two conditions: (1) uniformly or densely packed porous media; and (2) field soils under relatively dry condition. Employing the Darcy flux for solute transport in porous media with preferential flow pathways was problematic. In this paper we examine the theoretical background behind these field and laboratory observations and then provide an alternative to predict solute movement. By examining the characteristics of the momentum conservation principles on which Darcy's law is based, we show under what conditions Darcy flux can predict solute transport in porous media of various complexity. We find that, based on several case studies with capillary pores, Darcy's Law inherently merges momentum and in that way erases information on pore-scale velocities. For that reason the Darcy flux cannot predict flow in media with preferential flow conduits where individual pore velocities are essential in predicting the shape of the breakthrough curve and especially "the early arrival" of solutes. To overcome the limitations of the assumption in Darcy's law, we use Jury's conceptualization and employ the measured chemical breakthrough curve as input to characterize the impact of individual preferential flow pathways on chemical transport. Specifically, we discuss how best to take advantage of Jury's conceptualization to extract the pore-scale flow velocity to accurately predict chemical transport through soils with preferential flow pathways.

Fluctuation theorem for channel-facilitated membrane transport of interacting and noninteracting solutes.

Science.gov (United States)

Berezhkovskii, Alexander M; Bezrukov, Sergey M

2008-05-15

In this paper, we discuss the fluctuation theorem for channel-facilitated transport of solutes through a membrane separating two reservoirs. The transport is characterized by the probability, P(n)(t), that n solute particles have been transported from one reservoir to the other in time t. The fluctuation theorem establishes a relation between P(n)(t) and P-(n)(t): The ratio P(n)(t)/P-(n)(t) is independent of time and equal to exp(nbetaA), where betaA is the affinity measured in the thermal energy units. We show that the same fluctuation theorem is true for both single- and multichannel transport of noninteracting particles and particles which strongly repel each other.

Radionuclide transport in fractured porous media -- Analytical solutions for a system of parallel fractures with a kinetic solubility-limited dissolution model

International Nuclear Information System (INIS)

Li, S.H.; Chen, C.T.

1997-01-01

Analytical solutions are developed for the problem of radionuclide transport in a system of parallel fractures situated in a porous rock matrix. A kinetic solubility-limited dissolution model is used as the inlet boundary condition. The solutions consider the following processes: (a) advective transport in the fractures, (b) mechanical dispersion and molecular diffusion along the fractures, (c) molecular diffusion from a fracture to the porous matrix, (d) molecular diffusion within the porous matrix in the direction perpendicular to the fracture axis, (e) adsorption onto the fracture wall, (f) adsorption within the porous matrix, and (g) radioactive decay. The solutions are based on the Laplace transform method. The general transient solution is in the form of a double integral that is evaluated using composite Gauss-Legendre quadrature. A simpler transient solution that is in the form of a single integral is also presented for the case that assumes negligible longitudinal dispersion along the fractures. The steady-state solutions are also provided. A number of examples are given to illustrate the effects of the following important parameters: (a) fracture spacings, (b) dissolution-rate constants, (c) fracture dispersion coefficient, (d) matrix retardation factor, and (e) fracture retardation factor

A compartmentalized solute transport model for redox zones in contaminated aquifers: 1. Theory and development

Science.gov (United States)

Abrams , Robert H.; Loague, Keith

2000-01-01

This paper, the first of two parts [see Abrams and Loague, this issue], takes the compartmentalized approach for the geochemical evolution of redox zones presented by Abrams et al. [1998] and embeds it within a solute transport framework. In this paper the compartmentalized approach is generalized to facilitate the description of its incorporation into a solute transport simulator. An equivalent formulation is developed which removes any discontinuities that may occur when switching compartments. Rate‐limited redox reactions are modeled with a modified Monod relationship that allows either the organic substrate or the electron acceptor to be the rate‐limiting reactant. Thermodynamic constraints are used to inhibit lower‐energy redox reactions from occurring under infeasible geochemical conditions without imposing equilibrium on the lower‐energy reactions. The procedure used allows any redox reaction to be simulated as being kinetically limited or thermodynamically limited, depending on local geochemical conditions. Empirical reaction inhibition methods are not needed. The sequential iteration approach (SIA), a technique which allows the number of solute transport equations to be reduced, is adopted to solve the coupled geochemical/solute transport problem. When the compartmentalized approach is embedded within the SIA, with the total analytical concentration of each component as the dependent variable in the transport equation, it is possible to reduce the number of transport equations even further than with the unmodified SIA. A one‐dimensional, coupled geochemical/solute transport simulation is presented in which redox zones evolve dynamically in time and space. The compartmentalized solute transport (COMPTRAN) model described in this paper enables the development of redox zones to be simulated under both kinetic and thermodynamic constraints. The modular design of COMPTRAN facilitates the use of many different, preexisting solute transport and

Control and optimization of solute transport in a thin porous tube

KAUST Repository

Griffiths, I. M.; Howell, P. D.; Shipley, R. J.

2013-01-01

differentials upon the dispersive solute behaviour are investigated. The model is used to explore the control of solute transport across the membrane walls via the membrane permeability, and a parametric expression for the permeability required to generate a

Comparison of analytical transport and stochastic solutions for neutron slowing down in an infinite medium

International Nuclear Information System (INIS)

Jahshan, S.N.; Wemple, C.A.; Ganapol, B.D.

1993-01-01

A comparison of the numerical solutions of the transport equation describing the steady neutron slowing down in an infinite medium with constant cross sections is made with stochastic solutions obtained from tracking successive neutron histories in the same medium. The transport equation solution is obtained using a numerical Laplace transform inversion algorithm. The basis for the algorithm is an evaluation of the Bromwich integral without analytical continuation. Neither the transport nor the stochastic solution is limited in the number of scattering species allowed. The medium may contain an absorption component as well. (orig.)

Solute transport modelling with the variable temporally dependent ...

Indian Academy of Sciences (India)

Pintu Das

2018-02-07

Feb 7, 2018 ... in a finite domain with time-dependent sources and dis- tance-dependent dispersivities. Also, existing ... solute transport in multi-layered porous media using gen- eralized integral transform technique with .... methods for solving the fractional reaction-–sub-diffusion equation. To solve numerically the Eqs.

Exploration of DGVM Parameter Solution Space Using Simulated Annealing: Implications for Forecast Uncertainties

Science.gov (United States)

Wells, J. R.; Kim, J. B.

2011-12-01

Parameters in dynamic global vegetation models (DGVMs) are thought to be weakly constrained and can be a significant source of errors and uncertainties. DGVMs use between 5 and 26 plant functional types (PFTs) to represent the average plant life form in each simulated plot, and each PFT typically has a dozen or more parameters that define the way it uses resource and responds to the simulated growing environment. Sensitivity analysis explores how varying parameters affects the output, but does not do a full exploration of the parameter solution space. The solution space for DGVM parameter values are thought to be complex and non-linear; and multiple sets of acceptable parameters may exist. In published studies, PFT parameters are estimated from published literature, and often a parameter value is estimated from a single published value. Further, the parameters are "tuned" using somewhat arbitrary, "trial-and-error" methods. BIOMAP is a new DGVM created by fusing MAPSS biogeography model with Biome-BGC. It represents the vegetation of North America using 26 PFTs. We are using simulated annealing, a global search method, to systematically and objectively explore the solution space for the BIOMAP PFTs and system parameters important for plant water use. We defined the boundaries of the solution space by obtaining maximum and minimum values from published literature, and where those were not available, using +/-20% of current values. We used stratified random sampling to select a set of grid cells representing the vegetation of the conterminous USA. Simulated annealing algorithm is applied to the parameters for spin-up and a transient run during the historical period 1961-1990. A set of parameter values is considered acceptable if the associated simulation run produces a modern potential vegetation distribution map that is as accurate as one produced by trial-and-error calibration. We expect to confirm that the solution space is non-linear and complex, and that

Development and applications of the channel network model for simulations of flow and solute transport in fractured rock

International Nuclear Information System (INIS)

Gylling, B.

1997-01-01

The Channel Network model and its computer implementation, the code CHAN3D, for simulations of fluid flow and transport of solutes have been developed. The tool may be used for performance and safety assessments of deep lying repositories in fractured rocks for nuclear and other hazardous wastes, e.g. chemical wastes. It may also be used to simulate and interpret field experiments of flow and transport in large or small scale. Fluid flow and solute transport in fractured media are of interest in the performance assessment of a repository for hazardous waste, located at depth in crystalline rock, with potential release of solutes. Fluid flow in fractured rock is found to be very unevenly distributed due to the heterogeneity of the medium. The water will seek the easiest path, channels, under a prevailing pressure gradient. Solutes in the flowing water may be transported through preferential paths and migrate from the water in the fractures into the stagnant water in the rock matrix. There, sorbing solutes may be sorbed on the micro surfaces within the matrix. The diffusion into the matrix and the sorption process may significantly retard the transport of species and increase the time available for radionuclide decay. Channelling and matrix diffusion contribute to the dispersion of solutes in the water. Important for performance assessment is that channeling may cause a portion of the solutes to arrive much faster than the rest of the solutes. Simulations of field experiments at the Aespoe Hard Rock Laboratory using the Channel Network model have been performed. The application of the model to the site and the simulation results of the pumping and tracer tests are presented. The results show that the model is capable of describing the hydraulic gradient and of predicting flow rates and tracer transport obtained in the experiments. The data requirements for the Channel Network model have been investigated to determine which data are the most important for predictions

New numerical method for solving the solute transport equation

International Nuclear Information System (INIS)

Ross, B.; Koplik, C.M.

1978-01-01

The solute transport equation can be solved numerically by approximating the water flow field by a network of stream tubes and using a Green's function solution within each stream tube. Compared to previous methods, this approach permits greater computational efficiency and easier representation of small discontinuities, and the results are easier to interpret physically. The method has been used to study hypothetical sites for disposal of high-level radioactive waste

Environmental Transport Input Parameters for the Biosphere Model

Energy Technology Data Exchange (ETDEWEB)

M. A. Wasiolek

2003-06-27

This analysis report is one of the technical reports documenting the Environmental Radiation Model for Yucca Mountain Nevada (ERMYN), a biosphere model supporting the total system performance assessment (TSPA) for the geologic repository at Yucca Mountain. A graphical representation of the documentation hierarchy for the ERMYN is presented in Figure 1-1. This figure shows relationships among the reports developed for biosphere modeling and biosphere abstraction products for the TSPA, as identified in the ''Technical Work Plan: for Biosphere Modeling and Expert Support'' (TWP) (BSC 2003 [163602]). Some documents in Figure 1-1 may be under development and not available when this report is issued. This figure provides an understanding of how this report contributes to biosphere modeling in support of the license application (LA), but access to the listed documents is not required to understand the contents of this report. This report is one of the reports that develops input parameter values for the biosphere model. The ''Biosphere Model Report'' (BSC 2003 [160699]) describes the conceptual model, the mathematical model, and the input parameters. The purpose of this analysis is to develop biosphere model parameter values related to radionuclide transport and accumulation in the environment. These parameters support calculations of radionuclide concentrations in the environmental media (e.g., soil, crops, animal products, and air) resulting from a given radionuclide concentration at the source of contamination (i.e., either in groundwater or volcanic ash). The analysis was performed in accordance with the TWP (BSC 2003 [163602]). This analysis develops values of parameters associated with many features, events, and processes (FEPs) applicable to the reference biosphere (DTN: M00303SEPFEPS2.000 [162452]), which are addressed in the biosphere model (BSC 2003 [160699]). The treatment of these FEPs is described in BSC (2003 [160699

Environmental Transport Input Parameters for the Biosphere Model

International Nuclear Information System (INIS)

Wasiolek, M. A.

2003-01-01

This analysis report is one of the technical reports documenting the Environmental Radiation Model for Yucca Mountain Nevada (ERMYN), a biosphere model supporting the total system performance assessment (TSPA) for the geologic repository at Yucca Mountain. A graphical representation of the documentation hierarchy for the ERMYN is presented in Figure 1-1. This figure shows relationships among the reports developed for biosphere modeling and biosphere abstraction products for the TSPA, as identified in the ''Technical Work Plan: for Biosphere Modeling and Expert Support'' (TWP) (BSC 2003 [163602]). Some documents in Figure 1-1 may be under development and not available when this report is issued. This figure provides an understanding of how this report contributes to biosphere modeling in support of the license application (LA), but access to the listed documents is not required to understand the contents of this report. This report is one of the reports that develops input parameter values for the biosphere model. The ''Biosphere Model Report'' (BSC 2003 [160699]) describes the conceptual model, the mathematical model, and the input parameters. The purpose of this analysis is to develop biosphere model parameter values related to radionuclide transport and accumulation in the environment. These parameters support calculations of radionuclide concentrations in the environmental media (e.g., soil, crops, animal products, and air) resulting from a given radionuclide concentration at the source of contamination (i.e., either in groundwater or volcanic ash). The analysis was performed in accordance with the TWP (BSC 2003 [163602]). This analysis develops values of parameters associated with many features, events, and processes (FEPs) applicable to the reference biosphere (DTN: M00303SEPFEPS2.000 [162452]), which are addressed in the biosphere model (BSC 2003 [160699]). The treatment of these FEPs is described in BSC (2003 [160699], Section 6.2). Parameter values

Numerical modeling of solute transport in deformable unsaturated layered soil

Directory of Open Access Journals (Sweden)

Sheng Wu

2017-07-01

Full Text Available The effect of soil stratification was studied through numerical investigation based on the coupled model of solute transport in deformable unsaturated soil. The theoretical model implied two-way coupled excess pore pressure and soil deformation based on Biot's consolidation theory as well as a one-way coupled volatile pollutant concentration field developed from the advection-diffusion theory. Embedded in the model, the degree of saturation, fluid compressibility, self-weight of the soil matrix, porosity variance, longitudinal dispersion, and linear sorption were computed. Based on simulation results of a proposed three-layer landfill model using the finite element method, the multi-layer effects are discussed with regard to the hydraulic conductivity, shear modulus, degree of saturation, molecular diffusion coefficient, and thickness of each layer. Generally speaking, contaminants spread faster in a stratified field with a soft and highly permeable top layer; soil parameters of the top layer are more critical than the lower layers but controlling soil thicknesses will alter the results. This numerical investigation showed noticeable impacts of stratified soil properties on solute migration results, demonstrating the importance of correctly modeling layered soil instead of simply assuming the averaged properties across the soil profile.

Petrophysical and transport parameters evolution during acid percolation through structurally different limestones

Science.gov (United States)

Martinez Perez, Laura; Luquot, Linda

2017-04-01

Processes affecting geological media often show complex and unpredictable behavior due to the presence of heterogeneities. This remains problematic when facing contaminant transport problems, in the CO2 storage industry or dealing with the mechanisms underneath natural processes where chemical reactions can be observed during the percolation of rock non-equilibrated fluid (e.g. karst formation, seawater intrusion). To understand the mechanisms taking place in a porous medium as a result of this water-rock interaction, we need to know the flow parameters that control them, and how they evolve with time as a result of that concurrence. This is fundamental to ensure realistic predictions of the behavior of natural systems in response of reactive transport processes. We investigate the coupled influence of structural and hydrodynamic heterogeneities in limestone rock samples tracking its variations during chemical reactions. To do so we use laboratory petrophysical techniques such as helium porosimetry, gas permeability, centrifugue, electrical resistivity and sonic waves measurements to obtain the parameters that characterize flow within rock matrix (porosity, permeability, retention curve and pore size distribution, electrical conductivity, formation factor, cementation index and tortuosity) before and after percolation experiments. We built an experimental setup that allows injection of acid brine into core samples under well controlled conditions, monitor changes in hydrodynamic properties and obtain the chemical composition of the injected solution at different stages. 3D rock images were also acquired before and after the experiments using a micro-CT to locate the alteration processes and perform an acurate analysis of the structural changes. Two limestones with distinct textural classification and thus contrasting transport properties have been used in the laboratory experiments: a crinoid limestone and an oolithic limestone. Core samples dimensions were 1 inch

Simulation of transportation of low enriched uranium solutions

International Nuclear Information System (INIS)

Hope, E.P.; Ades, M.J.

1996-01-01

A simulation of the transportation by truck of low enriched uranium solutions has been completed for NEPA purposes at the Savannah River Site. The analysis involves three distinct source terms, and establishes the radiological risks of shipment to three possible destinations. Additionally, loading accidents were analyzed to determine the radiological consequences of mishaps during handling and delivery. Source terms were developed from laboratory measurements of chemical samples from low enriched uranium feed materials being stored at SRS facilities, and from manufacturer data on transport containers. The transportation simulations were accomplished over the INTERNET using the DOE TRANSNET system at Sandia National Laboratory. The HIGHWAY 3.3 code was used to analyze routing scenarios, and the RADTRAN 4 code was used to analyze incident free and accident risks of transporting radiological materials. Loading accidents were assessed using the Savannah River Site AXAIR89Q and RELEASE 2 codes

Scaling and predicting solute transport processes in streams

Science.gov (United States)

R. González-Pinzón; R. Haggerty; M. Dentz

2013-01-01

We investigated scaling of conservative solute transport using temporal moment analysis of 98 tracer experiments (384 breakthrough curves) conducted in 44 streams located on five continents. The experiments span 7 orders of magnitude in discharge (10-3 to 103 m3/s), span 5 orders of magnitude in...

Hydrogen isotopes transport parameters in fusion reactor materials

International Nuclear Information System (INIS)

Serra, E.; Ogorodnikova, O.V.

1998-01-01

This work presents a review of hydrogen isotopes-materials interactions in various materials of interest for fusion reactors. The relevant parameters cover mainly diffusivity, solubility, trap concentration and energy difference between trap and solution sites. The list of materials includes the martensitic steels (MANET, Batman and F82H-mod.), beryllium, aluminium, beryllium oxide, aluminium oxide, copper, tungsten and molybdenum. Some experimental work on the parameters that describe the surface effects is also mentioned. (orig.)

Solute transport with time-variable flow paths during upward and downward flux in a heterogeneous unsaturated porous medium

Science.gov (United States)

Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel; Vanderborght, Jan

2014-05-01

assumed to stay under liquid-flow dominated evaporation conditions ("stage 1"). Simulations considering dynamic (infiltration-evaporation) and steady (solely infiltration) boundary conditions are carried out. The influence of dynamic boundary conditions (intensity and duration of precipitation and evaporation events) is examined in a multitude of simulations. If flow rates smaller than the saturated hydraulic conductivity of both materials are chosen to be applied as boundary condition, simulation results indicate that the flow field within the domain is exactly reversed. However, if applied flow rates exceed the saturated hydraulic conductivity of one material, the flow field is not just reversed, but different flow paths during downward and upward flow are observed. Results show the tendency of faster solute leaching under dynamic boundary conditions compared to steady infiltration conditions with the same net-infiltration rate. We use a double domain transport method as an upscaled model to reproduce vertically averaged concentration profiles with net flux only and compare the model parameters for information about flow dynamics and soil heterogeneity.

Earliest Results in the Use of Activated Composite Membranes for the Transport of Silver Ions from Aqueous Solutions

Directory of Open Access Journals (Sweden)

Yucundo Mendoza-Tolentino

2014-01-01

Full Text Available This paper presents the results concerning the first use of activated composite membranes (ACMs for the facilitated transport of silver ions containing di-(2-ethylhexyl-dithiophosphoric acid (DTPA as the carrier. DTPA was immobilized by interfacial polymerization in a dense layer that was deposited in a porous layer, which was prepared on a nonwoven fabric support by phase inversion. The influence of fundamental parameters affecting the transport of silver ion as the carrier concentration in the membrane phase and stripping agent variation of the stripping solution have been studied. In the optimal conditions, the amount of silver transported across the ACMs was greater than 50%, whereas if the content of the carrier is modified, more than the 90% of the initial silver is removed from the feed phase.

Analysis of the Sodium Recirculation Theory of Solute Coupled Water Transport in Small Intestine

DEFF Research Database (Denmark)

Larsen, E. H.; Sørensen, Jens Nørkær; Sørensen, J. B.

2002-01-01

Our previous mathematical model of solute-coupled water transport through the intestinal epithelium is extended for dealing with electrolytes rather than electroneutral solutes. A 3Na+-2K+ pump in the lateral membranes provides the energy-requiring step for driving transjunctional and translateral......, computations predict that the concentration differences between lis and bathing solutions are small for all three ions. Nevertheless, the diffusion fluxes of the ions out of lis significantly exceed their mass transports. It is concluded that isotonic transport requires recirculation of all three ions....... The computed sodium recirculation flux that is required for isotonic transport corresponds to that estimated in experiments on toad small intestine. This result is shown to be robust and independent of whether the apical entrance mechanism for the sodium ion is a channel, a SGLT1 transporter driving inward...

Affordable Freight Logistics Transport Information Management Optimisation and Asset Tracking Solution Using Smartphone GPS Capabilities

Science.gov (United States)

Muna, Joseph T.; Prescott, Kevin

2011-08-01

Traditionally, freight transport and telematics solutions that exploit the GPS capabilities of in- vehicle devices to provide innovative Location Based Services (LBS) including track and trace transport systems have been the preserve of a select cluster of transport operators and organisations with the financial resources to develop the requisite custom software and hardware on which they are deployed. The average cost of outfitting a typical transport vehicle or truck with the latest Intelligent Transport System (ITS) increases the cost of the vehicle by anything from a couple to several thousand Euros, depending on the complexity and completeness of the solution. Though this does not generally deter large fleet transport owners since they typically get Return on Investment (ROI) based on economies of scale, it presents a barrier for the smaller independent entities that constitute the majority of freight transport operators [1].The North Sea Freight Intelligent Transport Solution (NS FRITS), a project co-funded by the European Commission Interreg IVB North Sea Region Programme, aims to make acquisition of such transport solutions easier for those organisations that cannot afford the expensive, bespoke systems used by their larger competitors.The project addresses transport security threats by developing a system capable of informing major actors along the freight logistics supply chain, of changing circumstances within the region's major transport corridors and between transport modes. The project also addresses issues of freight volumes, inter-modality, congestion and eco-mobility [2].

Reactive solute transport in acidic streams

Science.gov (United States)

Broshears, R.E.

1996-01-01

Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

Application of preconditioned GMRES to the numerical solution of the neutron transport equation

International Nuclear Information System (INIS)

Patton, B.W.; Holloway, J.P.

2002-01-01

The generalized minimal residual (GMRES) method with right preconditioning is examined as an alternative to both standard and accelerated transport sweeps for the iterative solution of the diamond differenced discrete ordinates neutron transport equation. Incomplete factorization (ILU) type preconditioners are used to determine their effectiveness in accelerating GMRES for this application. ILU(τ), which requires the specification of a dropping criteria τ, proves to be a good choice for the types of problems examined in this paper. The combination of ILU(τ) and GMRES is compared with both DSA and unaccelerated transport sweeps for several model problems. It is found that the computational workload of the ILU(τ)-GMRES combination scales nonlinearly with the number of energy groups and quadrature order, making this technique most effective for problems with a small number of groups and discrete ordinates. However, the cost of preconditioner construction can be amortized over several calculations with different source and/or boundary values. Preconditioners built upon standard transport sweep algorithms are also evaluated as to their effectiveness in accelerating the convergence of GMRES. These preconditioners show better scaling with such problem parameters as the scattering ratio, the number of discrete ordinates, and the number of spatial meshes. These sweeps based preconditioners can also be cast in a matrix free form that greatly reduces storage requirements

Water and solute transport across the peritoneal membrane.

Science.gov (United States)

Morelle, Johann; Devuyst, Olivier

2015-09-01

We review the molecular mechanisms of peritoneal transport and discuss how a better understanding of these mechanisms is relevant for dialysis therapy. Peritoneal dialysis involves diffusion and osmosis through the highly vascularized peritoneal membrane. Computer simulations, expression studies and functional analyses in Aqp1 knockout mice demonstrated the critical role of the water channel aquaporin-1 (AQP1) in water removal during peritoneal dialysis. Pharmacologic regulation of AQP1, either through increased expression or gating, is associated with increased water transport in rodent models of peritoneal dialysis. Water transport is impaired during acute peritonitis, despite unchanged expression of AQP1, resulting from the increased microvascular area that dissipates the osmotic gradient across the membrane. In long-term peritoneal dialysis patients, the fibrotic interstitium also impairs water transport, resulting in ultrafiltration failure. Recent data suggest that stroke and drug intoxications might benefit from peritoneal dialysis and could represent novel applications of peritoneal transport in the future. A better understanding of the regulation of osmotic water transport across the peritoneum offers novel insights into the role of water channels in microvascular endothelia, the functional importance of structural changes in the peritoneal interstitium and the transport of water and solutes across biological membranes in general.

Solute transport along a single fracture in a porous rock: a simple analytical solution and its extension for modeling velocity dispersion

Science.gov (United States)

Liu, Longcheng; Neretnieks, Ivars; Shahkarami, Pirouz; Meng, Shuo; Moreno, Luis

2018-02-01

A simple and robust solution is developed for the problem of solute transport along a single fracture in a porous rock. The solution is referred to as the solution to the single-flow-path model and takes the form of a convolution of two functions. The first function is the probability density function of residence-time distribution of a conservative solute in the fracture-only system as if the rock matrix is impermeable. The second function is the response of the fracture-matrix system to the input source when Fickian-type dispersion is completely neglected; thus, the effects of Fickian-type dispersion and matrix diffusion have been decoupled. It is also found that the solution can be understood in a way in line with the concept of velocity dispersion in fractured rocks. The solution is therefore extended into more general cases to also account for velocity variation between the channels. This leads to a development of the multi-channel model followed by detailed statistical descriptions of channel properties and sensitivity analysis of the model upon changes in the model key parameters. The simulation results obtained by the multi-channel model in this study fairly well agree with what is often observed in field experiments—i.e. the unchanged Peclet number with distance, which cannot be predicted by the classical advection-dispersion equation. In light of the findings from the aforementioned analysis, it is suggested that forced-gradient experiments can result in considerably different estimates of dispersivity compared to what can be found in natural-gradient systems for typical channel widths.

Large time behaviour of oscillatory nonlinear solute transport in porous media

NARCIS (Netherlands)

Duijn, van C.J.; Zee, van der S.E.A.T.M.

2018-01-01

Oscillations in flow occur under many different situations in natural porous media, due to tidal, daily or seasonal patterns. In this paper, we investigate how such oscillations in flow affect the transport of an initially sharp solute front, if the solute undergoes nonlinear sorption and,

Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma.

Science.gov (United States)

Smith, Alex J; Yao, Xiaoming; Dix, James A; Jin, Byung-Ju; Verkman, Alan S

2017-08-21

Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed 'glymphatic' clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma.

Integrated compartmental model for describing the transport of solute in a fractured porous medium. [FRACPORT

Energy Technology Data Exchange (ETDEWEB)

DeAngelis, D.L.; Yeh, G.T.; Huff, D.D.

1984-10-01

This report documents a model, FRACPORT, that simulates the transport of a solute through a fractured porous matrix. The model should be useful in analyzing the possible transport of radionuclides from shallow-land burial sites in humid environments. The use of the model is restricted to transport through saturated zones. The report first discusses the general modeling approach used, which is based on the Integrated Compartmental Method. The basic equations of solute transport are then presented. The model, which assumes a known water velocity field, solves these equations on two different time scales; one related to rapid transport of solute along fractures and the other related to slower transport through the porous matrix. FRACPORT is validated by application to a simple example of fractured porous medium transport that has previously been analyzed by other methods. Then its utility is demonstrated in analyzing more complex cases of pulses of solute into a fractured matrix. The report serves as a user's guide to FRACPORT. A detailed description of data input, along with a listing of input for a sample problem, is provided. 16 references, 18 figures, 3 tables.

Sn approach applied to the solution of transport equation

International Nuclear Information System (INIS)

Lopes, J.P.

1973-09-01

In this work the origin of the Transport Theory is considered and the Transport Equation for the movement of the neutron in a system is established in its more general form, using the laws of nuclear physics. This equation is used as the starting point for development, under adequate assumptions, of simpler models that render the problem suitable for numerical solution. Representation of this model in different geometries is presented. The different processes of nuclear physics are introduced briefly and discussed. In addition, the boundary conditions for the different cases and a general procedure for the application of the Conservation Law are stated. The last chapter deals specifically with the S n method, its development, definitions and generalities. Computational schemes for obtaining the S n solution in spherical and cylindrical geometry, and convergence acceleration methods are also developed. (author)

Can we predict uranium bioavailability based on soil parameters? Part 1: Effect of soil parameters on soil solution uranium concentration

International Nuclear Information System (INIS)

Vandenhove, H.; Hees, M. van; Wouters, K.; Wannijn, J.

2007-01-01

Present study aims to quantify the influence of soil parameters on soil solution uranium concentration for 238 U spiked soils. Eighteen soils collected under pasture were selected such that they covered a wide range for those parameters hypothesised as being potentially important in determining U sorption. Maximum soil solution uranium concentrations were observed at alkaline pH, high inorganic carbon content and low cation exchange capacity, organic matter content, clay content, amorphous Fe and phosphate levels. Except for the significant correlation between the solid-liquid distribution coefficients (K d , L kg -1 ) and the organic matter content (R 2 = 0.70) and amorphous Fe content (R 2 = 0.63), there was no single soil parameter significantly explaining the soil solution uranium concentration (which varied 100-fold). Above pH = 6, log(K d ) was linearly related with pH [log(K d ) = - 1.18 pH + 10.8, R 2 = 0.65]. Multiple linear regression analysis did result in improved predictions of the soil solution uranium concentration but the model was complex. - Uranium solubility in soil can be predicted from organic matter or amorphous iron content and pH or with complex multilinear models considering several soil parameters

Control and optimization of solute transport in a thin porous tube

KAUST Repository

Griffiths, I. M.

2013-03-01

Predicting the distribution of solutes or particles in flows within porous-walled tubes is essential to inform the design of devices that rely on cross-flow filtration, such as those used in water purification, irrigation devices, field-flow fractionation, and hollow-fibre bioreactors for tissue-engineering applications. Motivated by these applications, a radially averaged model for fluid and solute transport in a tube with thin porous walls is derived by developing the classical ideas of Taylor dispersion. The model includes solute diffusion and advection via both radial and axial flow components, and the advection, diffusion, and uptake coefficients in the averaged equation are explicitly derived. The effect of wall permeability, slip, and pressure differentials upon the dispersive solute behaviour are investigated. The model is used to explore the control of solute transport across the membrane walls via the membrane permeability, and a parametric expression for the permeability required to generate a given solute distribution is derived. The theory is applied to the specific example of a hollow-fibre membrane bioreactor, where a uniform delivery of nutrient across the membrane walls to the extra-capillary space is required to promote spatially uniform cell growth. © 2013 American Institute of Physics.

Thermotransport in interstitial solid solutions

International Nuclear Information System (INIS)

Fogel'son, R.L.

1982-01-01

On the basis of literature data the problem of thermotransport of impurities (H, N, O, C) in interstitial solid solutions is considered. It is shown that from experimental data on the thermotransport an important parameter of dissolved atoms can be found which characterizes atom state in these solutions-enthalpy of transport

Solute transport by groundwater flow to wetland ecosystems : the environmental impact of human activities

NARCIS (Netherlands)

Schot, P.P.

1991-01-01

This thesis deals with solute transport by groundwater flow and the way in which solute transport is affected by human activities. This in relation to wetland ecosystems. Wetlands in the eastern part of the Vecht river plain in The Netherlands are historically renown for their great variety of

Multiple and sign-changing solutions for discrete Robin boundary value problem with parameter dependence

Directory of Open Access Journals (Sweden)

Long Yuhua

2017-12-01

Full Text Available In this paper, we study second-order nonlinear discrete Robin boundary value problem with parameter dependence. Applying invariant sets of descending flow and variational methods, we establish some new sufficient conditions on the existence of sign-changing solutions, positive solutions and negative solutions of the system when the parameter belongs to appropriate intervals. In addition, an example is given to illustrate our results.

Solution processed metal oxide thin film hole transport layers for high performance organic solar cells

Science.gov (United States)

Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.

2017-01-10

A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.

Modeling of water flow and solute transport in unsaturated heterogeneous fields

International Nuclear Information System (INIS)

Bresler, E.; Dagan, G.

1982-01-01

A comprehensive model which considers dispersive solute transport, nonsteady moisture flow regimes and complex boundary conditions is described. The main assumptions are: vertical flow; spatial variability which is associated with the saturated hydraulic conductivity K/sub s/ occurs in the horizontal plane, but is constant in the profile, and has a lognormal probability distribution function (PDF); deterministic recharge and solute concentration are applied during infiltration; the soil is at uniform water content and salt concentration prior to infiltration. The problem is to solve, for arbitrary K/sub s/, the Richards' equation of flow simultaneously with the diffusion-convection equation for salt transport, with the boundary and initial conditions appropriate to infiltration-redistribution. Once this is achieved, the expectation and variance of various quantities of interest (solute concentration, moisture content) are obtained by using the statistical averaging procedure and the given PDF of K/sub s/. Since the solution of Richards' equation for the infiltration-redistribution cycle is extremely difficult (for a given K/sub s/), an approxiate solution is derived by using the concept of piston flow type wetting fronts. Similarly, accurate numerical solutions are used as input for the same statistical averaging procedure. The stochastic model is applied to two spatially variable soils by using both accurate numerical solutions and the simplified water and salt transport models. A comparison between the results shows that the approximate simplified models lead to quite accurate values of the expectations and variances of the flow variables for the entire field. It is suggested that in spatially variable fields, stochastic modeling represents the actual flow phenomena realistically, and provides the main statistical moments by using simplified flow models which can be used with confidence in applications

A variational solution of transport equation based on spherical geometry

International Nuclear Information System (INIS)

Liu Hui; Zhang Ben'ai

2002-01-01

A variational method with differential forms gives better precision for numerical solution of transport critical problem based on spherical geometry, and its computation seems simple than other approximate methods

Numerical modelling of coupled fluid, heat, and solute transport in deformable fractured rock

International Nuclear Information System (INIS)

Chan, T.; Reid, J.A.K.

1987-01-01

This paper reports on a three-dimensional (3D) finite-element code, MOTIF (model of transport in fractured/porous media), developed to model the coupled processes of groundwater flow, heat transport, brine transport, and one-species radionuclide transport in geological media. Three types of elements are available: a 3D continuum element, a planar fracture element that can be oriented in any arbitrary direction in 3D space or pipe flow in 3D space, and a line element for simulating fracture flow in 2D space or pipe flow in 3D space. As a quality-assurance measure, the MOTIF code was verified by comparison of its results with analytical solutions and other published numerical solutions

A general polynomial solution to convection–dispersion equation ...

Indian Academy of Sciences (India)

Jiao Wang

concentration profiles and optimal solute transport parameters. Furthermore, the general .... requirement; in other words, if Is(t) is cumulated solute added in the column ..... National Natural Science Foundation of China. (Nos. 41530854 and ...

Transport parameter estimation from lymph measurements and the Patlak equation.

Science.gov (United States)

Watson, P D; Wolf, M B

1992-01-01

Two methods of estimating protein transport parameters for plasma-to-lymph transport data are presented. Both use IBM-compatible computers to obtain least-squares parameters for the solvent drag reflection coefficient and the permeability-surface area product using the Patlak equation. A matrix search approach is described, and the speed and convenience of this are compared with a commercially available gradient method. The results from both of these methods were different from those of a method reported by Reed, Townsley, and Taylor [Am. J. Physiol. 257 (Heart Circ. Physiol. 26): H1037-H1041, 1989]. It is shown that the Reed et al. method contains a systematic error. It is also shown that diffusion always plays an important role for transmembrane transport at the exit end of a membrane channel under all conditions of lymph flow rate and that the statement that diffusion becomes zero at high lymph flow rate depends on a mathematical definition of diffusion.

Technology in rural transportation. Simple solution #6, traveler information on the internet

Science.gov (United States)

1997-01-01

This application was identified as a promising rural Intelligent Transportation Systems (ITS) solution under a project sponsored by the Federal Highway Administration (FHWA) and the ENTERPRISE program. This summary describes the solution as well as o...

Sensitivity Analysis of Unsaturated Flow and Contaminant Transport with Correlated Parameters

Science.gov (United States)

Relative contributions from uncertainties in input parameters to the predictive uncertainties in unsaturated flow and contaminant transport are investigated in this study. The objectives are to: (1) examine the effects of input parameter correlations on the sensitivity of unsaturated flow and conta...

The separation of radionuclide migration by solution and particle transport in LLRW repository buffer material

International Nuclear Information System (INIS)

Torok, J.; Buckley, L.P.; Woods, B.L.

1989-01-01

Laboratory-scale lysimeter experiments were performed with simulated waste forms placed in candidate buffer materials which have been chosen for a low-level radioactive waste repository. Radionuclide releases into the effluent water and radionuclide capture by the buffer material were determined. The results could not be explained by traditional solution transport mechanisms, and transport by particles released from the waste form and/or transport by buffer particles were suspected as the dominant mechanism for radionuclide release from the lysimeters. To elucidate the relative contribution of particle and solution transport, the waste forms were replaced by a wafer of neutron-activated buffer soaked with selected soluble isotopes. Particle transport was determined by the movement of gamma-emitting neutron-activation products through the lysimeter. Solution transport was quantified by comparing the migration of soluble radionuclides relative to the transport of neutron activation products. The new approach for monitoring radionuclide migration in soil is presented. It facilitates the determination of most of the fundamental coefficients required to model the transport process

Effects of sorption and temperature on solute transport in unsaturated steady flow

International Nuclear Information System (INIS)

Fuentes, H.R.; Polzer, W.L.; Essington, E.H.

1986-01-01

It is known that temperature affects physical and chemical processes and that these processes may alter the transport of solutes in the environment. Laboratory column studies were performed in unsaturated flow conditions with a composite pulse containing iodide, cobalt, cesium and strontium each at 10 -3 M. The experiments were performed with Bandelier Tuff and produced breakthrough curves that indicate significant changes in transport due to a temperature change from 25 0 C to 5 0 C for nonconservative solutes. Also, the interpretation of the temperature and sorption data suggest that the differences in transport between 5 0 C and 25 0 C for nonconservative solutes may be predicted in a qualitative manner from batch equilibrium and nonequilibrium sorption data and the theory of sorption used in deriving the modified Freundlich isotherm equation. These effects should be of concern in modeling and management of spills and waste disposal within this range of environmental temperatures

Peritoneal solute transport and inflammation.

Science.gov (United States)

Davies, Simon J

2014-12-01

The speed with which small solutes cross the peritoneal membrane, termed peritoneal solute transport rate (PSTR), is a key measure of individual membrane performance. PSTR can be quantified easily by using the 4-hour dialysate to plasma creatinine ratio, which, although only an approximation to the diffusive characteristics of the membrane, has been well validated clinically in terms of its relationship to patient survival and changes in longitudinal membrane function. This has led to changes in peritoneal dialysis modality use and dialysis prescription. An important determinant of PSTR is intraperitoneal inflammation, as exemplified by local interleukin 6 production, which is largely independent of systemic inflammation and its relationship to comorbid conditions and increased mortality. There is no strong evidence to support the contention that the peritoneal membrane in some individuals with high PSTR is qualitatively different at the start of treatment; rather, it represents a spectrum that is determined in part by genetic factors. Both clinical and experimental evidence support the view that persistent intraperitoneal inflammation, detected as a continuously high or increasing PSTR, may predispose the membrane to progressive fibrosis. Copyright © 2014 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Approximate solution of the transport equation by methods of Galerkin type

International Nuclear Information System (INIS)

Pitkaranta, J.

1977-01-01

Questions of the existence, uniqueness, and convergence of approximate solutions of transport equations by methods of the Galerkin type (where trial and weighting functions are the same) are discussed. The results presented do not exclude the infinite-dimensional case. Two strategies can be followed in the variational approximation of the transport operator: one proceeds from the original form of the transport equation, while the other is based on the partially symmetrized equation. Both principles are discussed in this paper. The transport equation is assumed in a discretized multigroup form

Coupled geochemical and solute transport code development

International Nuclear Information System (INIS)

Morrey, J.R.; Hostetler, C.J.

1985-01-01

A number of coupled geochemical hydrologic codes have been reported in the literature. Some of these codes have directly coupled the source-sink term to the solute transport equation. The current consensus seems to be that directly coupling hydrologic transport and chemical models through a series of interdependent differential equations is not feasible for multicomponent problems with complex geochemical processes (e.g., precipitation/dissolution reactions). A two-step process appears to be the required method of coupling codes for problems where a large suite of chemical reactions must be monitored. Two-step structure requires that the source-sink term in the transport equation is supplied by a geochemical code rather than by an analytical expression. We have developed a one-dimensional two-step coupled model designed to calculate relatively complex geochemical equilibria (CTM1D). Our geochemical module implements a Newton-Raphson algorithm to solve heterogeneous geochemical equilibria, involving up to 40 chemical components and 400 aqueous species. The geochemical module was designed to be efficient and compact. A revised version of the MINTEQ Code is used as a parent geochemical code

Limit Theorems and Their Relation to Solute Transport in Simulated Fractured Media

Science.gov (United States)

Reeves, D. M.; Benson, D. A.; Meerschaert, M. M.

2003-12-01

Solute particles that travel through fracture networks are subject to wide velocity variations along a restricted set of directions. This may result in super-Fickian dispersion along a few primary scaling directions. The fractional advection-dispersion equation (FADE), a modification of the original advection-dispersion equation in which a fractional derivative replaces the integer-order dispersion term, has the ability to model rapid, non-Gaussian solute transport. The FADE assumes that solute particle motions converge to either α -stable or operator stable densities, which are modeled by spatial fractional derivatives. In multiple dimensions, the multi-fractional dispersion derivative dictates the order and weight of differentiation in all directions, which correspond to the statistics of large particle motions in all directions. This study numerically investigates the presence of super- Fickian solute transport through simulated two-dimensional fracture networks. An ensemble of networks is gen

Can we predict uranium bioavailability based on soil parameters? Part 1: effect of soil parameters on soil solution uranium concentration.

Science.gov (United States)

Vandenhove, H; Van Hees, M; Wouters, K; Wannijn, J

2007-01-01

Present study aims to quantify the influence of soil parameters on soil solution uranium concentration for (238)U spiked soils. Eighteen soils collected under pasture were selected such that they covered a wide range for those parameters hypothesised as being potentially important in determining U sorption. Maximum soil solution uranium concentrations were observed at alkaline pH, high inorganic carbon content and low cation exchange capacity, organic matter content, clay content, amorphous Fe and phosphate levels. Except for the significant correlation between the solid-liquid distribution coefficients (K(d), L kg(-1)) and the organic matter content (R(2)=0.70) and amorphous Fe content (R(2)=0.63), there was no single soil parameter significantly explaining the soil solution uranium concentration (which varied 100-fold). Above pH=6, log(K(d)) was linearly related with pH [log(K(d))=-1.18 pH+10.8, R(2)=0.65]. Multiple linear regression analysis did result in improved predictions of the soil solution uranium concentration but the model was complex.

Coupling between solute transport and chemical reactions models. Acoplamiento de modelos de transporte de solutos y de modelos de reacciones quimicas

Energy Technology Data Exchange (ETDEWEB)

Samper, J.; Ajora, C. (Instituto de Ciencias de la Tierra, CSIC, Barcerlona (Spain))

1993-01-01

During subsurface transport, reactive solutes are subject to a variety of hydrodynamic and chemical processes. The major hydrodynamic processes include advection and convection, dispersion and diffusion. The key chemical processes are complexation including hydrolysis and acid-base reactions, dissolution-precipitation, reduction-oxidation, adsorption and ion exchange. The combined effects of all these processes on solute transport must satisfy the principle of conservation of mass. The statement of conservation of mass for N mobile species leads to N partial differential equations. Traditional solute transport models often incorporate the effects of hydrodynamic processes rigorously but oversimplify chemical interactions among aqueous species. Sophisticated chemical equilibrium models, on the other hand, incorporate a variety of chemical processes but generally assume no-flow systems. In the past decade, coupled models accounting for complex hydrological and chemical processes, with varying degrees of sophistication, have been developed. The existing models of reactive transport employ two basic sets of equations. The transport of solutes is described by a set of partial differential equations, and the chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. An important consideration in any approach is the choice of primary dependent variables. Most existing models cannot account for the complete set of chemical processes, cannot be easily extended to include mixed chemical equilibria and kinetics, and cannot handle practical two and three dimensional problems. The difficulties arise mainly from improper selection of the primary variables in the transport equations. (Author) 38 refs.

Functional test of pedotransfer functions to predict water flow and solute transport with the dual-permeability model MACRO

Directory of Open Access Journals (Sweden)

J. Moeys

2012-07-01

Full Text Available Estimating pesticide leaching risks at the regional scale requires the ability to completely parameterise a pesticide fate model using only survey data, such as soil and land-use maps. Such parameterisations usually rely on a set of lookup tables and (pedotransfer functions, relating elementary soil and site properties to model parameters. The aim of this paper is to describe and test a complete set of parameter estimation algorithms developed for the pesticide fate model MACRO, which accounts for preferential flow in soil macropores. We used tracer monitoring data from 16 lysimeter studies, carried out in three European countries, to evaluate the ability of MACRO and this "blind parameterisation" scheme to reproduce measured solute leaching at the base of each lysimeter. We focused on the prediction of early tracer breakthrough due to preferential flow, because this is critical for pesticide leaching. We then calibrated a selected number of parameters in order to assess to what extent the prediction of water and solute leaching could be improved.

Our results show that water flow was generally reasonably well predicted (median model efficiency, ME, of 0.42. Although the general pattern of solute leaching was reproduced well by the model, the overall model efficiency was low (median ME = −0.26 due to errors in the timing and magnitude of some peaks. Preferential solute leaching at early pore volumes was also systematically underestimated. Nonetheless, the ranking of soils according to solute loads at early pore volumes was reasonably well estimated (concordance correlation coefficient, CCC, between 0.54 and 0.72. Moreover, we also found that ignoring macropore flow leads to a significant deterioration in the ability of the model to reproduce the observed leaching pattern, and especially the early breakthrough in some soils. Finally, the calibration procedure showed that improving the estimation of solute transport parameters is

Functional test of pedotransfer functions to predict water flow and solute transport with the dual-permeability model MACRO

Science.gov (United States)

Moeys, J.; Larsbo, M.; Bergström, L.; Brown, C. D.; Coquet, Y.; Jarvis, N. J.

2012-07-01

Estimating pesticide leaching risks at the regional scale requires the ability to completely parameterise a pesticide fate model using only survey data, such as soil and land-use maps. Such parameterisations usually rely on a set of lookup tables and (pedo)transfer functions, relating elementary soil and site properties to model parameters. The aim of this paper is to describe and test a complete set of parameter estimation algorithms developed for the pesticide fate model MACRO, which accounts for preferential flow in soil macropores. We used tracer monitoring data from 16 lysimeter studies, carried out in three European countries, to evaluate the ability of MACRO and this "blind parameterisation" scheme to reproduce measured solute leaching at the base of each lysimeter. We focused on the prediction of early tracer breakthrough due to preferential flow, because this is critical for pesticide leaching. We then calibrated a selected number of parameters in order to assess to what extent the prediction of water and solute leaching could be improved. Our results show that water flow was generally reasonably well predicted (median model efficiency, ME, of 0.42). Although the general pattern of solute leaching was reproduced well by the model, the overall model efficiency was low (median ME = -0.26) due to errors in the timing and magnitude of some peaks. Preferential solute leaching at early pore volumes was also systematically underestimated. Nonetheless, the ranking of soils according to solute loads at early pore volumes was reasonably well estimated (concordance correlation coefficient, CCC, between 0.54 and 0.72). Moreover, we also found that ignoring macropore flow leads to a significant deterioration in the ability of the model to reproduce the observed leaching pattern, and especially the early breakthrough in some soils. Finally, the calibration procedure showed that improving the estimation of solute transport parameters is probably more important than the

Thermally Cross-Linkable Hole Transport Materials for Solution Processed Phosphorescent OLEDs

Science.gov (United States)

Kim, Beom Seok; Kim, Ohyoung; Chin, Byung Doo; Lee, Chil Won

2018-04-01

Materials for unique fabrication of a solution-processed, multi-layered organic light-emitting diode (OLED) were developed. Preparation of a hole transport layer with a thermally cross-linkable chemical structure, which can be processed to form a thin film and then transformed into an insoluble film by using an amine-alcohol condensation reaction with heat treatment, was investigated. Functional groups, such as triplenylamine linked with phenylcarbazole or biphenyl, were employed in the chemical structure of the hole transport layer in order to maintain high triplet energy properties. When phenylcarbazole or biphenyl compounds continuously react with triphenylamine under acid catalysis, a chemically stable thin film material with desirable energy-level properties for a blue OLED could be obtained. The prepared hole transport materials showed excellent surface roughness and thermal stability in comparison with the commercial reference material. On the solution-processed model hole transport layer, we fabricated a device with a blue phosphorescent OLED by using sequential vacuum deposition. The maximum external quantum, 19.3%, was improved by more than 40% over devices with the commercial reference material (11.4%).

The simulation of solute transport: An approach free of numerical dispersion

International Nuclear Information System (INIS)

Carrera, J.; Melloni, G.

1987-01-01

The applicability of most algorithms for simulation of solute transport is limited either by instability or by numerical dispersion, as seen by a review of existing methods. A new approach is proposed that is free of these two problems. The method is based on the mixed Eulerian-Lagrangian formulation of the mass-transport problem, thus ensuring stability. Advection is simulated by a variation of reverse-particle tracking that avoids the accumulation of interpolation errors, thus preventing numerical dispersion. The algorithm has been implemented in a one-dimensional code. Excellent results are obtained, in comparison with an analytical solution. 36 refs., 14 figs., 1 tab

A multi scale approximation solution for the time dependent Boltzmann-transport equation

International Nuclear Information System (INIS)

Merk, B.

2004-03-01

The basis of all transient simulations for nuclear reactor cores is the reliable calculation of the power production. The local power distribution is generally calculated by solving the space, time, energy and angle dependent neutron transport equation known as Boltzmann equation. The computation of exact solutions of the Boltzmann equation is very time consuming. For practical numerical simulations approximated solutions are usually unavoidable. The objective of this work is development of an effective multi scale approximation solution for the Boltzmann equation. Most of the existing methods are based on separation of space and time. The new suggested method is performed without space-time separation. This effective approximation solution is developed on the basis of an expansion for the time derivative of different approximations to the Boltzmann equation. The method of multiple scale expansion is used for the expansion of the time derivative, because the problem of the stiff time behaviour can't be expressed by standard expansion methods. This multiple scale expansion is used in this work to develop approximation solutions for different approximations of the Boltzmann equation, starting from the expansion of the point kinetics equations. The resulting analytic functions are used for testing the applicability and accuracy of the multiple scale expansion method for an approximation solution with 2 delayed neutron groups. The results are tested versus the exact analytical results for the point kinetics equations. Very good agreement between both solutions is obtained. The validity of the solution with 2 delayed neutron groups to approximate the behaviour of the system with 6 delayed neutron groups is demonstrated in an additional analysis. A strategy for a solution with 4 delayed neutron groups is described. A multiple scale expansion is performed for the space-time dependent diffusion equation for one homogenized cell with 2 delayed neutron groups. The result is

Hydrophilic solute transport across the rat blood-brain barrier

International Nuclear Information System (INIS)

Lucchesi, K.J.

1987-01-01

Brain capillary permeability-surface area products (PS) of hydrophilic solutes ranging in size from 180 to 5,500 Daltons were measured in rats according to the method of Ohno, Pettigrew and Rapoport. The distribution volume of 70 KD dextran at 10 minutes after i.v. injection was also measured to determine the residual volume of blood in brain tissue at the time of sacrifice. Small test solutes were injected in pairs in order to elucidate whether their transfer into the brain proceeds by diffusion through water- or lipid-filled channels or by vesicular transport. This issue was examined in rats whose blood-brain barrier (BBB) was presumed to be intact (untreated) and in rats that received intracarotid infusions to open the BBB (isosmotic salt (ISS) and hyperosmolar arabinose). Ohno PS values of 3 H-inulin and 14 C-L-glucose in untreated rats were found to decrease as the labelling time was lengthened. This was evidence that a rapidly equilibrating compartment exists between blood and brain that renders the Ohno two-compartment model inadequate for computing true transfer rate constants. When the data were reanalyzed using a multi-compartment graphical analysis, solutes with different molecular radii were found to enter the brain at approximately equal rates. Furthermore, unidirectional transport is likely to be initiated by solute adsorption to a glycocalyx coat on the luminal surface of brain capillary endothelium. Apparently, more inulin than L-glucose was adsorbed, which may account for its slightly faster transfer across the BBB. After rats were treated with intracarotid infusions of ISS or hyperosmolar arabinose, solute PS values were significantly increased, but the ratio of PS for each of the solute pairs approached that of their free-diffusion coefficients

Mathematical description of adsorption and transport of reactive solutes in soil: a review of selected literature

International Nuclear Information System (INIS)

Travis, C.C.

1978-10-01

This report reviews selected literature related to the mathematical description of the transport of reactive solutes through soil. The primary areas of the literature reviewed are (1) mathematical models in current use for description of the adsorption-desorption interaction between the soil solution and the soil matrix and (2) analytic solutions of the differential equations describing the convective-dispersive transport of reactive solutes through soil

Monte Carlo methods for flux expansion solutions of transport problems

International Nuclear Information System (INIS)

Spanier, J.

1999-01-01

Adaptive Monte Carlo methods, based on the use of either correlated sampling or importance sampling, to obtain global solutions to certain transport problems have recently been described. The resulting learning algorithms are capable of achieving geometric convergence when applied to the estimation of a finite number of coefficients in a flux expansion representation of the global solution. However, because of the nonphysical nature of the random walk simulations needed to perform importance sampling, conventional transport estimators and source sampling techniques require modification to be used successfully in conjunction with such flux expansion methods. It is shown how these problems can be overcome. First, the traditional path length estimators in wide use in particle transport simulations are generalized to include rather general detector functions (which, in this application, are the individual basis functions chosen for the flus expansion). Second, it is shown how to sample from the signed probabilities that arise as source density functions in these applications, without destroying the zero variance property needed to ensure geometric convergence to zero error

GRRR. The EXPECT groundwater model for transport of solutes

NARCIS (Netherlands)

Meijers R; Sauter FJ; Veling EJM; van Grinsven JJM; Leijnse A; Uffink GJM; MTV; CWM; LBG

1994-01-01

In this report the design and first test results are presented of the EXPECT groundwater module for transport of solutes GRRR (GRoundwater source Receptor Relationships). This model is one of the abiotic compartment modules of the EXPECT model. The EXPECT model is a tool for scenario development

Abstracts of the symposium on unsaturated flow and transport modeling

International Nuclear Information System (INIS)

1982-03-01

Abstract titles are: Recent developments in modeling variably saturated flow and transport; Unsaturated flow modeling as applied to field problems; Coupled heat and moisture transport in unsaturated soils; Influence of climatic parameters on movement of radionuclides in a multilayered saturated-unsaturated media; Modeling water and solute transport in soil containing roots; Simulation of consolidation in partially saturated soil materials; modeling of water and solute transport in unsaturated heterogeneous fields; Fluid dynamics and mass transfer in variably-saturated porous media; Solute transport through soils; One-dimensional analytical transport modeling; Convective transport of ideal tracers in unsaturated soils; Chemical transport in macropore-mesopore media under partially saturated conditions; Influence of the tension-saturated zone on contaminant migration in shallow water regimes; Influence of the spatial distribution of velocities in porous media on the form of solute transport; Stochastic vs deterministic models for solute movement in the field; and Stochastic analysis of flow and solute transport

Transport parameters for the modelling of water transport in ionomer membranes for PEM-fuel cells

International Nuclear Information System (INIS)

Meier, Frank; Eigenberger, Gerhart

2004-01-01

The water transport number (drag coefficient) and the hydraulic permeability were measured for Nafion. The results show a significant increase of both parameters with increasing water content indicating that they are strongly influenced by the membrane microstructure. Based on these experimental studies a new model approach to describe water transport in the H 2 -PEFC membrane is presented. This approach considers water transport by electro-osmosis caused by the proton flux through the membrane and by osmosis caused by a gradient in the chemical potential of water. It is parametrized by the measured data for the water transport number and the hydraulic permeability of Nafion. First simulation results applying this approach to a one-dimensional model of the H 2 -PEFC show good agreement with experimental data. Therefore, the developed model can be used for a new insight into the dominating mechanisms of water transport in the membrane

Correlation of Aquaporins and Transmembrane Solute Transporters Revealed by Genome-Wide Analysis in Developing Maize Leaf

Directory of Open Access Journals (Sweden)

Xun Yue

2012-01-01

Full Text Available Aquaporins are multifunctional membrane channels that facilitate the transmembrane transport of water and solutes. When transmembrane mineral nutrient transporters exhibit the same expression patterns as aquaporins under diverse temporal and physiological conditions, there is a greater probability that they interact. In this study, genome-wide temporal profiling of transcripts analysis and coexpression network-based approaches are used to examine the significant specificity correlation of aquaporins and transmembrane solute transporters in developing maize leaf. The results indicate that specific maize aquaporins are related to specific transmembrane solute transporters. The analysis demonstrates a systems-level correlation between aquaporins, nutrient transporters, and the homeostasis of mineral nutrients in developing maize leaf. Our results provide a resource for further studies into the physiological function of these aquaporins.

Complicated problem solution techniques in optimal parameter searching

International Nuclear Information System (INIS)

Gergel', V.P.; Grishagin, V.A.; Rogatneva, E.A.; Strongin, R.G.; Vysotskaya, I.N.; Kukhtin, V.V.

1992-01-01

An algorithm is presented of a global search for numerical solution of multidimentional multiextremal multicriteria optimization problems with complicated constraints. A boundedness of object characteristic changes is assumed at restricted changes of its parameters (Lipschitz condition). The algorithm was realized as a computer code. The algorithm was realized as a computer code. The programme was used to solve in practice the different applied optimization problems. 10 refs.; 3 figs

Homogenization Theory for the Prediction of Obstructed Solute Diffusivity in Macromolecular Solutions.

Science.gov (United States)

Donovan, Preston; Chehreghanianzabi, Yasaman; Rathinam, Muruhan; Zustiak, Silviya Petrova

2016-01-01

The study of diffusion in macromolecular solutions is important in many biomedical applications such as separations, drug delivery, and cell encapsulation, and key for many biological processes such as protein assembly and interstitial transport. Not surprisingly, multiple models for the a-priori prediction of diffusion in macromolecular environments have been proposed. However, most models include parameters that are not readily measurable, are specific to the polymer-solute-solvent system, or are fitted and do not have a physical meaning. Here, for the first time, we develop a homogenization theory framework for the prediction of effective solute diffusivity in macromolecular environments based on physical parameters that are easily measurable and not specific to the macromolecule-solute-solvent system. Homogenization theory is useful for situations where knowledge of fine-scale parameters is used to predict bulk system behavior. As a first approximation, we focus on a model where the solute is subjected to obstructed diffusion via stationary spherical obstacles. We find that the homogenization theory results agree well with computationally more expensive Monte Carlo simulations. Moreover, the homogenization theory agrees with effective diffusivities of a solute in dilute and semi-dilute polymer solutions measured using fluorescence correlation spectroscopy. Lastly, we provide a mathematical formula for the effective diffusivity in terms of a non-dimensional and easily measurable geometric system parameter.

Homogenization Theory for the Prediction of Obstructed Solute Diffusivity in Macromolecular Solutions.

Directory of Open Access Journals (Sweden)

Preston Donovan

Full Text Available The study of diffusion in macromolecular solutions is important in many biomedical applications such as separations, drug delivery, and cell encapsulation, and key for many biological processes such as protein assembly and interstitial transport. Not surprisingly, multiple models for the a-priori prediction of diffusion in macromolecular environments have been proposed. However, most models include parameters that are not readily measurable, are specific to the polymer-solute-solvent system, or are fitted and do not have a physical meaning. Here, for the first time, we develop a homogenization theory framework for the prediction of effective solute diffusivity in macromolecular environments based on physical parameters that are easily measurable and not specific to the macromolecule-solute-solvent system. Homogenization theory is useful for situations where knowledge of fine-scale parameters is used to predict bulk system behavior. As a first approximation, we focus on a model where the solute is subjected to obstructed diffusion via stationary spherical obstacles. We find that the homogenization theory results agree well with computationally more expensive Monte Carlo simulations. Moreover, the homogenization theory agrees with effective diffusivities of a solute in dilute and semi-dilute polymer solutions measured using fluorescence correlation spectroscopy. Lastly, we provide a mathematical formula for the effective diffusivity in terms of a non-dimensional and easily measurable geometric system parameter.

Electron collision cross sections and transport parameters in Cl2

International Nuclear Information System (INIS)

Pinhao, N.; Chouki, A.

1995-01-01

Molecular chlorine, Cl 2 , is a widely used gas with important application in gas discharge physics, namely in plasma etching, UV lasers and gas-filled particle detectors. However, due to experimental difficulties and to a complicated electronic spectrum, only some of the electron collision cross section have been measured and only recently the electronic structure has been resolved. This situation hampered the theoretical analysis of chlorine mixtures by a lack of relevant transport parameters. To our best knowledge there is only one published measurement of electron drift velocity and characteristic energy. Regrettably these data are considered of doubtful quality. There is also only one measurement of attachment and ionisation coefficients and one published set of cross sections. However those authors used the transport data from a He-Cl 2 mixture (80/20) where chlorine's effect can be hidden by the other component. Consequently that set is not completely consistent with the measurements in pure chlorine. This paper presents a new proposal of a consistent set of electron collision cross sections and the corresponding transport parameters and collision frequencies

Solution to the monoenergetic time-dependent neutron transport equation with a time-varying source

International Nuclear Information System (INIS)

Ganapol, B.D.

1986-01-01

Even though fundamental time-dependent neutron transport problems have existed since the inception of neutron transport theory, it has only been recently that a reliable numerical solution to one of the basic problems has been obtained. Experience in generating numerical solutions to time-dependent transport equations has indicated that the multiple collision formulation is the most versatile numerical technique for model problems. The formulation coupled with a moment reconstruction of each collided flux component has led to benchmark-quality (four- to five-digit accuracy) numerical evaluation of the neutron flux in plane infinite geometry for any degree of scattering anisotropy and for both pulsed isotropic and beam sources. As will be shown in this presentation, this solution can serve as a Green's function, thus extending the previous results to more complicated source situations. Here we will be concerned with a time-varying source at the center of an infinite medium. If accurate, such solutions have both pedagogical and practical uses as benchmarks against which other more approximate solutions designed for a wider class of problems can be compared

Conceptual and numerical models of groundwater flow and solute transport in fracture zones: Application to the Aspo Island (Sweden)

International Nuclear Information System (INIS)

Molinero, J.; Samper, J.

2003-01-01

Several countries around the world are considering the final disposal of high-level radioactive waste in deep repositories located in fractured granite formations. Evaluating the long term safety of such repositories requires sound conceptual and numerical models which must consider simultaneously groundwater flow, solute transport and chemical and radiological processes. These models are being developed from data and knowledge gained from in situ experiments carried out at deep underground laboratories such as that of Aspo, Sweden, constructed in fractured granite. The Redox Zone Experiment is one of such experiments performed at Aspo in order to evaluate the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Previous authors interpreted hydrochemical and isotopic data of this experiment using a mass-balance approach based on a qualitative description of groundwater flow conditions. Such an interpretation, however, is subject to uncertainties related to an over-simplified conceptualization of groundwater flow. Here we present numerical models of groundwater flow and solute transport for this fracture zone. The first model is based on previously published conceptual model. It presents noticeable un consistencies and fails to match simultaneously observed draw downs and chloride breakthrough curves. To overcome its limitations, a revised flow and transport model is presented which relies directly on available hydrodynamic and transport parameters, is based on the identification of appropriate flow and transport boundary conditions and uses, when needed, solute data extrapolated from nearby fracture zones. A significant quantitative improvement is achieved with the revised model because its results match simultaneously drawdown and chloride data. Other improvements are qualitative and include: ensuring consistency of hydrodynamic and hydrochemical data and avoiding

SEAWAT-based simulation of axisymmetric heat transport.

Science.gov (United States)

Vandenbohede, Alexander; Louwyck, Andy; Vlamynck, Nele

2014-01-01

Simulation of heat transport has its applications in geothermal exploitation of aquifers and the analysis of temperature dependent chemical reactions. Under homogeneous conditions and in the absence of a regional hydraulic gradient, groundwater flow and heat transport from or to a well exhibit radial symmetry, and governing equations are reduced by one dimension (1D) which increases computational efficiency importantly. Solute transport codes can simulate heat transport and input parameters may be modified such that the Cartesian geometry can handle radial flow. In this article, SEAWAT is evaluated as simulator for heat transport under radial flow conditions. The 1971, 1D analytical solution of Gelhar and Collins is used to compare axisymmetric transport with retardation (i.e., as a result of thermal equilibrium between fluid and solid) and a large diffusion (conduction). It is shown that an axisymmetric simulation compares well with a fully three dimensional (3D) simulation of an aquifer thermal energy storage systems. The influence of grid discretization, solver parameters, and advection solution is illustrated. Because of the high diffusion to simulate conduction, convergence criterion for heat transport must be set much smaller (10(-10) ) than for solute transport (10(-6) ). Grid discretization should be considered carefully, in particular the subdivision of the screen interval. On the other hand, different methods to calculate the pumping or injection rate distribution over different nodes of a multilayer well lead to small differences only. © 2013, National Ground Water Association.

Modeling variably saturated multispecies reactive groundwater solute transport with MODFLOW-UZF and RT3D

Science.gov (United States)

Bailey, Ryan T.; Morway, Eric D.; Niswonger, Richard G.; Gates, Timothy K.

2013-01-01

A numerical model was developed that is capable of simulating multispecies reactive solute transport in variably saturated porous media. This model consists of a modified version of the reactive transport model RT3D (Reactive Transport in 3 Dimensions) that is linked to the Unsaturated-Zone Flow (UZF1) package and MODFLOW. Referred to as UZF-RT3D, the model is tested against published analytical benchmarks as well as other published contaminant transport models, including HYDRUS-1D, VS2DT, and SUTRA, and the coupled flow and transport modeling system of CATHY and TRAN3D. Comparisons in one-dimensional, two-dimensional, and three-dimensional variably saturated systems are explored. While several test cases are included to verify the correct implementation of variably saturated transport in UZF-RT3D, other cases are included to demonstrate the usefulness of the code in terms of model run-time and handling the reaction kinetics of multiple interacting species in variably saturated subsurface systems. As UZF1 relies on a kinematic-wave approximation for unsaturated flow that neglects the diffusive terms in Richards equation, UZF-RT3D can be used for large-scale aquifer systems for which the UZF1 formulation is reasonable, that is, capillary-pressure gradients can be neglected and soil parameters can be treated as homogeneous. Decreased model run-time and the ability to include site-specific chemical species and chemical reactions make UZF-RT3D an attractive model for efficient simulation of multispecies reactive transport in variably saturated large-scale subsurface systems.

Hydro-dynamic Solute Transport under Two-Phase Flow Conditions.

Science.gov (United States)

Karadimitriou, Nikolaos K; Joekar-Niasar, Vahid; Brizuela, Omar Godinez

2017-07-26

There are abundant examples of natural, engineering and industrial applications, in which "solute transport" and "mixing" in porous media occur under multiphase flow conditions. Current state-of-the-art understanding and modelling of such processes are established based on flawed and non-representative models. Moreover, there is no direct experimental result to show the true hydrodynamics of transport and mixing under multiphase flow conditions while the saturation topology is being kept constant for a number of flow rates. With the use of a custom-made microscope, and under well-controlled flow boundary conditions, we visualized directly the transport of a tracer in a Reservoir-on-Chip (RoC) micromodel filled with two immiscible fluids. This study provides novel insights into the saturation-dependency of transport and mixing in porous media. To our knowledge, this is the first reported pore-scale experiment in which the saturation topology, relative permeability, and tortuosity were kept constant and transport was studied under different dynamic conditions in a wide range of saturation. The critical role of two-phase hydrodynamic properties on non-Fickian transport and saturation-dependency of dispersion are discussed, which highlight the major flaws in parametrization of existing models.

Analytical solution for the transport equation for neutral particles in cylindrical and Cartesian geometry

International Nuclear Information System (INIS)

Goncalves, Glenio Aguiar

2003-01-01

In this work, we are reported analytical solutions for the transport equation for neutral particles in cylindrical and cartesian geometry. For the cylindrical geometry, it is applied the Hankel transform of order zero in the S N approximation of the one-dimensional cylindrical transport equation, assuming azimuthal symmetry and isotropic scattering. This procedure is coined HTSN method. The anisotropic problem is handled using the decomposition method, generating a recursive approach, which the HTSN solution is used as initial condition. For cartesian geometry, the one and two dimensional transport equation is derived in the angular variable as many time as the degree of the anisotropic scattering. This procedure leads to set of integro-differential plus one differential equation that can be really solved by the variable separation method. Following this procedure, it was possible to come out with the Case solution for the one-dimensional problem. Numerical simulations are reported for the cylindrical transport problem both isotropic and anisotropic case of quadratic degree. (author)

Analytical solution of electrohydrodynamic flow and transport in rectangular channels: inclusion of double layer effects

KAUST Repository

Joekar-Niasar, V.

2013-01-25

Upscaling electroosmosis in porous media is a challenge due to the complexity and scale-dependent nonlinearities of this coupled phenomenon. "Pore-network modeling" for upscaling electroosmosis from pore scale to Darcy scale can be considered as a promising approach. However, this method requires analytical solutions for flow and transport at pore scale. This study concentrates on the development of analytical solutions of flow and transport in a single rectangular channel under combined effects of electrohydrodynamic forces. These relations will be used in future works for pore-network modeling. The analytical solutions are valid for all regimes of overlapping electrical double layers and have the potential to be extended to nonlinear Boltzmann distribution. The innovative aspects of this study are (a) contribution of overlapping of electrical double layers to the Stokes flow as well as Nernst-Planck transport has been carefully included in the analytical solutions. (b) All important transport mechanisms including advection, diffusion, and electromigration have been included in the analytical solutions. (c) Fully algebraic relations developed in this study can be easily employed to upscale electroosmosis to Darcy scale using pore-network modeling. © 2013 Springer Science+Business Media Dordrecht.

Analytical solution of electrohydrodynamic flow and transport in rectangular channels: inclusion of double layer effects

KAUST Repository

Joekar-Niasar, V.; Schotting, R.; Leijnse, A.

2013-01-01

Upscaling electroosmosis in porous media is a challenge due to the complexity and scale-dependent nonlinearities of this coupled phenomenon. "Pore-network modeling" for upscaling electroosmosis from pore scale to Darcy scale can be considered as a promising approach. However, this method requires analytical solutions for flow and transport at pore scale. This study concentrates on the development of analytical solutions of flow and transport in a single rectangular channel under combined effects of electrohydrodynamic forces. These relations will be used in future works for pore-network modeling. The analytical solutions are valid for all regimes of overlapping electrical double layers and have the potential to be extended to nonlinear Boltzmann distribution. The innovative aspects of this study are (a) contribution of overlapping of electrical double layers to the Stokes flow as well as Nernst-Planck transport has been carefully included in the analytical solutions. (b) All important transport mechanisms including advection, diffusion, and electromigration have been included in the analytical solutions. (c) Fully algebraic relations developed in this study can be easily employed to upscale electroosmosis to Darcy scale using pore-network modeling. © 2013 Springer Science+Business Media Dordrecht.

Quantum solutions for Prisoner's Dilemma game with general parameters

International Nuclear Information System (INIS)

Sun, Z.W.; Jin, H.; Zhao, H.

2008-01-01

The quantum game of the Prisoner's Dilemma with general payoff matrix was studied in L. Marinatto and T. Weber's scheme presented in [Phys. Lett. A 272 (2000) 291, so that the results of two schemes of the quantum game can be compared. The Nash equilibria and the solutions of the game are obtained. They are related to initial state, matrix parameters and the intervals among the parameters. It can be concluded from the results that the quantum PD game in Marinatto and Weber's scheme matches the one in Eisert et al.'s scheme, one with general unitary operations.

Solute transport and extraction by a single root in unsaturated soils: model development and experiment

Energy Technology Data Exchange (ETDEWEB)

Kim, Jaisoo; Sung, Kijune; Corapcioglu, M. Yavuz; Drew, Malcolm C

2004-09-01

A contaminant transport model was developed to simulate the fate and transport of organic compounds such as TNT (2,4,6-trinitrotoluene), using the single-root system. Onions were planted for this system with 50-ml plastic tubes. Mass in the soil, soil solution, root and leaf was monitored using {sup 14}C-TNT. Model parameters were acquired from the experiments in the single-root system and were used to simulate total TNT concentration in soil, providing the average concentrations in the rhizosphere and bulk soil as well as root and leaf compartments. Because the existing RCF (root concentration factor) and TSCF (transpiration stream concentration factor) equations based on log K{sub ow} (octanol-water partition coefficient) were not correlated to TNT uptake, a new term, root uptake rate (R{sub ur}), and a new T{sub scf} equation, based on the experimental data, were introduced in the proposed model. The results from both modeling and experimental studies showed higher concentrations of TNT in the rhizosphere than in the bulk soil, because mass transported from the surrounding soil into the rhizosphere was higher than that by root uptake.

The Governor's Challenge: "Building a Stronger Virginia Today": Transportation Visions and Solutions

Science.gov (United States)

Baker, Susan

2008-01-01

Using STM(Science, Technology, Engineering, Math) education, this emerging workforce will have the chance to creatively solve one of Virginia's biggest challenges: TRANSPORTATION. - Students will be asked to develop alternative transportation systems for the state. This competition will enable teams to work with business mentors to design creative solutions for regional gridlocks and develop other transportation systems to more easily and expediently reach all parts of the Commonwealth.

Importance of hydrological parameters in contaminant transport modeling in a terrestrial environment

International Nuclear Information System (INIS)

Tsuduki, Katsunori; Matsunaga, Takeshi

2007-01-01

A grid type multi-layered distributed parameter model for calculating discharge in a watershed was described. Model verification with our field observation resulted in different sets of hydrological parameter values, all of which reproduced the observed discharge. The effect of those varied hydrological parameters on contaminant transport calculation was examined and discussed by simulation of event water transfer. (author)

TLC scheme for numerical solution of the transport equation on equilateral triangular meshes

International Nuclear Information System (INIS)

Walters, W.F.

1983-01-01

A new triangular linear characteristic TLC scheme for numerically solving the transport equation on equilateral triangular meshes has been developed. This scheme uses the analytic solution of the transport equation in the triangle as its basis. The data on edges of the triangle are assumed linear as is the source representation. A characteristic approach or nodal approach is used to obtain the analytic solution. Test problems indicate that the new TLC is superior to the widely used DITRI scheme for accuracy

VS2DRTI: Simulating Heat and Reactive Solute Transport in Variably Saturated Porous Media.

Science.gov (United States)

Healy, Richard W; Haile, Sosina S; Parkhurst, David L; Charlton, Scott R

2018-01-29

Variably saturated groundwater flow, heat transport, and solute transport are important processes in environmental phenomena, such as the natural evolution of water chemistry of aquifers and streams, the storage of radioactive waste in a geologic repository, the contamination of water resources from acid-rock drainage, and the geologic sequestration of carbon dioxide. Up to now, our ability to simulate these processes simultaneously with fully coupled reactive transport models has been limited to complex and often difficult-to-use models. To address the need for a simple and easy-to-use model, the VS2DRTI software package has been developed for simulating water flow, heat transport, and reactive solute transport through variably saturated porous media. The underlying numerical model, VS2DRT, was created by coupling the flow and transport capabilities of the VS2DT and VS2DH models with the equilibrium and kinetic reaction capabilities of PhreeqcRM. Flow capabilities include two-dimensional, constant-density, variably saturated flow; transport capabilities include both heat and multicomponent solute transport; and the reaction capabilities are a complete implementation of geochemical reactions of PHREEQC. The graphical user interface includes a preprocessor for building simulations and a postprocessor for visual display of simulation results. To demonstrate the simulation of multiple processes, the model is applied to a hypothetical example of injection of heated waste water to an aquifer with temperature-dependent cation exchange. VS2DRTI is freely available public domain software. © 2018, National Ground Water Association.

Modeling particle-facilitated solute transport using the C-Ride module of HYDRUS

Science.gov (United States)

Simunek, Jiri; Bradford, Scott A.

2017-04-01

Strongly sorbing chemicals (e.g., heavy metals, radionuclides, pharmaceuticals, and/or explosives) in soils are associated predominantly with the solid phase, which is commonly assumed to be stationary. However, recent field- and laboratory-scale observations have shown that, in the presence of mobile colloidal particles (e.g., microbes, humic substances, clays and metal oxides), the colloids could act as pollutant carriers and thus provide a rapid transport pathway for strongly sorbing contaminants. Such transport can be further accelerated since these colloidal particles may travel through interconnected larger pores where the water velocity is relatively high. Additionally, colloidal particles have a considerable adsorption capacity for other species present in water because of their large specific surface areas and their high concentrations in soil-water and groundwater. As a result, the transport of contaminants can be significantly, sometimes dramatically, enhanced when they are adsorbed to mobile colloids. To address this problem, we have developed the C-Ride module for HYDRUS-1D. This one-dimensional numerical module is based on the HYDRUS-1D software package and incorporates mechanisms associated with colloid and colloid-facilitated solute transport in variably saturated porous media. This numerical model accounts for both colloid and solute movement due to convection, diffusion, and dispersion in variably-saturated soils, as well as for solute movement facilitated by colloid transport. The colloids transport module additionally considers processes of attachment/detachment to/from the solid phase, straining, and/or size exclusion. Various blocking and depth dependent functions can be used to modify the attachment and straining coefficients. The module additionally considers the effects of changes in the water content on colloid/bacteria transport and attachment/detachment to/from solid-water and air-water interfaces. For example, when the air

Numerical fluid solutions for nonlocal electron transport in hot plasmas: Equivalent diffusion versus nonlocal source

International Nuclear Information System (INIS)

Colombant, Denis; Manheimer, Wallace

2010-01-01

Flux limitation and preheat are important processes in electron transport occurring in laser produced plasmas. The proper calculation of both of these has been a subject receiving much attention over the entire lifetime of the laser fusion project. Where nonlocal transport (instead of simple single flux limit) has been modeled, it has always been with what we denote the equivalent diffusion solution, namely treating the transport as only a diffusion process. We introduce here a new approach called the nonlocal source solution and show it is numerically viable for laser produced plasmas. It turns out that the equivalent diffusion solution generally underestimates preheat. Furthermore, the advance of the temperature front, and especially the preheat, can be held up by artificial 'thermal barriers'. The nonlocal source method of solution, on the other hand more accurately describes preheat and can stably calculate the solution for the temperature even if the heat flux is up the gradient.

Two-dimensional analytical solutions for chemical transport in aquifers. Part 1. Simplified solutions for sources with constant concentration. Part 2. Exact solutions for sources with constant flux rate

International Nuclear Information System (INIS)

Shan, C.; Javandel, I.

1996-05-01

Analytical solutions are developed for modeling solute transport in a vertical section of a homogeneous aquifer. Part 1 of the series presents a simplified analytical solution for cases in which a constant-concentration source is located at the top (or the bottom) of the aquifer. The following transport mechanisms have been considered: advection (in the horizontal direction), transverse dispersion (in the vertical direction), adsorption, and biodegradation. In the simplified solution, however, longitudinal dispersion is assumed to be relatively insignificant with respect to advection, and has been neglected. Example calculations are given to show the movement of the contamination front, the development of concentration profiles, the mass transfer rate, and an application to determine the vertical dispersivity. The analytical solution developed in this study can be a useful tool in designing an appropriate monitoring system and an effective groundwater remediation method

Quantifying the relative contributions of different solute carriers to aggregate substrate transport

Science.gov (United States)

Taslimifar, Mehdi; Oparija, Lalita; Verrey, Francois; Kurtcuoglu, Vartan; Olgac, Ufuk; Makrides, Victoria

2017-01-01

Determining the contributions of different transporter species to overall cellular transport is fundamental for understanding the physiological regulation of solutes. We calculated the relative activities of Solute Carrier (SLC) transporters using the Michaelis-Menten equation and global fitting to estimate the normalized maximum transport rate for each transporter (Vmax). Data input were the normalized measured uptake of the essential neutral amino acid (AA) L-leucine (Leu) from concentration-dependence assays performed using Xenopus laevis oocytes. Our methodology was verified by calculating Leu and L-phenylalanine (Phe) data in the presence of competitive substrates and/or inhibitors. Among 9 potentially expressed endogenous X. laevis oocyte Leu transporter species, activities of only the uniporters SLC43A2/LAT4 (and/or SLC43A1/LAT3) and the sodium symporter SLC6A19/B0AT1 were required to account for total uptake. Furthermore, Leu and Phe uptake by heterologously expressed human SLC6A14/ATB0,+ and SLC43A2/LAT4 was accurately calculated. This versatile systems biology approach is useful for analyses where the kinetics of each active protein species can be represented by the Hill equation. Furthermore, its applicable even in the absence of protein expression data. It could potentially be applied, for example, to quantify drug transporter activities in target cells to improve specificity. PMID:28091567

Identification of key target markets for intermodal freight transport solutions in South Africa

Directory of Open Access Journals (Sweden)

Joubert van Eeden

2010-11-01

Full Text Available The Accelerated and Shared Growth Initiative for South Africa (AsgiSA identified South Africa's freight logistics challenges as among the key binding constraints on the country's growth aspirations. The research presented here points to the structural imbalance between road and rail freight transport as one of the key contributors to this state of affairs. Most long-distance corridor transport has been captured by road. However, long-distance transport is a market segment that is very suitable for intermodal transportation : rail is utilised for the high-density, long-distance component and road for the feeder and distribution services at the corridor end points. A market segmentation approach is developed to identify the corridors and industries that are natural candidates for such solutions, thereby paving the way for role-players and stakeholders to initiate a dialogue on the development of appropriate solutions.

Recommended direct simulation Monte Carlo collision model parameters for modeling ionized air transport processes

Energy Technology Data Exchange (ETDEWEB)

Swaminathan-Gopalan, Krishnan; Stephani, Kelly A., E-mail: ksteph@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2016-02-15

A systematic approach for calibrating the direct simulation Monte Carlo (DSMC) collision model parameters to achieve consistency in the transport processes is presented. The DSMC collision cross section model parameters are calibrated for high temperature atmospheric conditions by matching the collision integrals from DSMC against ab initio based collision integrals that are currently employed in the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) and Data Parallel Line Relaxation (DPLR) high temperature computational fluid dynamics solvers. The DSMC parameter values are computed for the widely used Variable Hard Sphere (VHS) and the Variable Soft Sphere (VSS) models using the collision-specific pairing approach. The recommended best-fit VHS/VSS parameter values are provided over a temperature range of 1000-20 000 K for a thirteen-species ionized air mixture. Use of the VSS model is necessary to achieve consistency in transport processes of ionized gases. The agreement of the VSS model transport properties with the transport properties as determined by the ab initio collision integral fits was found to be within 6% in the entire temperature range, regardless of the composition of the mixture. The recommended model parameter values can be readily applied to any gas mixture involving binary collisional interactions between the chemical species presented for the specified temperature range.

Quantifying solute transport processes: are chemically "conservative" tracers electrically conservative?

Science.gov (United States)

Singha, Kamini; Li, Li; Day-Lewis, Frederick D.; Regberg, Aaron B.

2012-01-01

The concept of a nonreactive or conservative tracer, commonly invoked in investigations of solute transport, requires additional study in the context of electrical geophysical monitoring. Tracers that are commonly considered conservative may undergo reactive processes, such as ion exchange, thus changing the aqueous composition of the system. As a result, the measured electrical conductivity may reflect not only solute transport but also reactive processes. We have evaluated the impacts of ion exchange reactions, rate-limited mass transfer, and surface conduction on quantifying tracer mass, mean arrival time, and temporal variance in laboratory-scale column experiments. Numerical examples showed that (1) ion exchange can lead to resistivity-estimated tracer mass, velocity, and dispersivity that may be inaccurate; (2) mass transfer leads to an overestimate in the mobile tracer mass and an underestimate in velocity when using electrical methods; and (3) surface conductance does not notably affect estimated moments when high-concentration tracers are used, although this phenomenon may be important at low concentrations or in sediments with high and/or spatially variable cation-exchange capacity. In all cases, colocated groundwater concentration measurements are of high importance for interpreting geophysical data with respect to the controlling transport processes of interest.

A lattice Boltzmann model for solute transport in open channel flow

Science.gov (United States)

Wang, Hongda; Cater, John; Liu, Haifei; Ding, Xiangyi; Huang, Wei

2018-01-01

A lattice Boltzmann model of advection-dispersion problems in one-dimensional (1D) open channel flows is developed for simulation of solute transport and pollutant concentration. The hydrodynamics are calculated based on a previous lattice Boltzmann approach to solving the 1D Saint-Venant equations (LABSVE). The advection-dispersion model is coupled with the LABSVE using the lattice Boltzmann method. Our research recovers the advection-dispersion equations through the Chapman-Enskog expansion of the lattice Boltzmann equation. The model differs from the existing schemes in two points: (1) the lattice Boltzmann numerical method is adopted to solve the advection-dispersion problem by meso-scopic particle distribution; (2) and the model describes the relation between discharge, cross section area and solute concentration, which increases the applicability of the water quality model in practical engineering. The model is verified using three benchmark tests: (1) instantaneous solute transport within a short distance; (2) 1D point source pollution with constant velocity; (3) 1D point source pollution in a dam break flow. The model is then applied to a 50-year flood point source pollution accident on the Yongding River, which showed good agreement with a MIKE 11 solution and gauging data.

A mathematical solution for the parameters of three interfering resonances

Science.gov (United States)

Han, X.; Shen, C. P.

2018-04-01

The multiple-solution problem in determining the parameters of three interfering resonances from a fit to an experimentally measured distribution is considered from a mathematical viewpoint. It is shown that there are four numerical solutions for a fit with three coherent Breit-Wigner functions. Although explicit analytical formulae cannot be derived in this case, we provide some constraint equations between the four solutions. For the cases of nonrelativistic and relativistic Breit-Wigner forms of amplitude functions, a numerical method is provided to derive the other solutions from that already obtained, based on the obtained constraint equations. In real experimental measurements with more complicated amplitude forms similar to Breit-Wigner functions, the same method can be deduced and performed to get numerical solutions. The good agreement between the solutions found using this mathematical method and those directly from the fit verifies the correctness of the constraint equations and mathematical methodology used. Supported by National Natural Science Foundation of China (NSFC) (11575017, 11761141009), the Ministry of Science and Technology of China (2015CB856701) and the CAS Center for Excellence in Particle Physics (CCEPP)

Representing solute transport through the multi-barrier disposal system by simplified concepts

International Nuclear Information System (INIS)

Poteri, A.; Nordman, H.; Pulkkanen, V-M.; Kekaelaeinen, P.; Hautojaervi, A.

2012-02-01

The repository system chosen in Finland for spent nuclear fuel is composed of multiple successive transport barriers. If a waste canister is leaking, this multi-barrier system retards and limits the release rates of radionuclides into the biosphere. Analysis of radionuclide migration in the previous performance assessments has largely been based on numerical modelling of the repository system. The simplified analytical approach introduced here provides a tool to analyse the performance of the whole system using simplified representations of the individual transport barriers. This approach is based on the main characteristics of the individual barriers and on the generic nature of the coupling between successive barriers. In the case of underground repository the mass transfer between successive transport barriers is strongly restricted by the interfaces between barriers leading to well-mixed conditions in these barriers. The approach here simplifies the barrier system so that it can be described with a very simple compartment model, where each barrier is represented by a single, or in the case of buffer, by not more than two compartments. This system of compartments could be solved in analogy with a radioactive decay chain. The model of well mixed compartments lends itself to a very descriptive way to represent and analyse the barrier system because the relative efficiency of the different barriers in hindering transport of solutes can be parameterised by the solutes half-times in the corresponding compartments. In a real repository system there will also be a delay between the start of the inflow and the start of the outflow from the barrier. This delay can be important for the release rates of the short lived and sorbing radionuclides, and it was also included in the simplified representation of the barrier system. In a geological multi-barrier system, spreading of the outflowing release pulse is often governed by the typical behaviour of one transport barrier

Representing solute transport through the multi-barrier disposal system by simplified concepts

Energy Technology Data Exchange (ETDEWEB)

Poteri, A.; Nordman, H.; Pulkkanen, V-M. [VTT Technical Research Centre of Finland, Espoo (Finland); Kekaelaeinen, P. [Jyvaeskylae Univ. (Finland). Dept. pf Physics; Hautojaervi, A.

2012-02-15

The repository system chosen in Finland for spent nuclear fuel is composed of multiple successive transport barriers. If a waste canister is leaking, this multi-barrier system retards and limits the release rates of radionuclides into the biosphere. Analysis of radionuclide migration in the previous performance assessments has largely been based on numerical modelling of the repository system. The simplified analytical approach introduced here provides a tool to analyse the performance of the whole system using simplified representations of the individual transport barriers. This approach is based on the main characteristics of the individual barriers and on the generic nature of the coupling between successive barriers. In the case of underground repository the mass transfer between successive transport barriers is strongly restricted by the interfaces between barriers leading to well-mixed conditions in these barriers. The approach here simplifies the barrier system so that it can be described with a very simple compartment model, where each barrier is represented by a single, or in the case of buffer, by not more than two compartments. This system of compartments could be solved in analogy with a radioactive decay chain. The model of well mixed compartments lends itself to a very descriptive way to represent and analyse the barrier system because the relative efficiency of the different barriers in hindering transport of solutes can be parameterised by the solutes half-times in the corresponding compartments. In a real repository system there will also be a delay between the start of the inflow and the start of the outflow from the barrier. This delay can be important for the release rates of the short lived and sorbing radionuclides, and it was also included in the simplified representation of the barrier system. In a geological multi-barrier system, spreading of the outflowing release pulse is often governed by the typical behaviour of one transport barrier

A solution of the monoenergetic neutral particle transport equation for adjacent half-spaces with anisotropic scattering

Energy Technology Data Exchange (ETDEWEB)

Ganapol, B.D., E-mail: ganapol@cowboy.ame.arizona.edu [Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ (United States); Mostacci, D.; Previti, A. [Montecuccolino Laboratory, University of Bologna, Via dei Colli, 16, I-40136 Bologna (Italy)

2016-07-01

We present highly accurate solutions to the neutral particle transport equation in a half-space. While our initial motivation was in response to a recently published solution based on Chandrasekhar's H-function, the presentation to follow has taken on a more comprehensive tone. The solution by H-functions certainly did achieved high accuracy but was limited to isotropic scattering and emission from spatially uniform and linear sources. Moreover, the overly complicated nature of the H-function approach strongly suggests that its extension to anisotropic scattering and general sources is not at all practical. For this reason, an all encompassing theory for the determination of highly precise benchmarks, including anisotropic scattering for a variety of spatial source distributions, is presented for particle transport in a half-space. We illustrate the approach via a collection of cases including tables of 7-place flux benchmarks to guide transport methods developers. The solution presented can be applied to a considerable number of one and two half-space transport problems with variable sources and represents a state-of-the-art benchmark solution.

Chain segmentation for the Monte Carlo solution of particle transport problems

International Nuclear Information System (INIS)

Ragheb, M.M.H.

1984-01-01

A Monte Carlo approach is proposed where the random walk chains generated in particle transport simulations are segmented. Forward and adjoint-mode estimators are then used in conjunction with the firstevent source density on the segmented chains to obtain multiple estimates of the individual terms of the Neumann series solution at each collision point. The solution is then constructed by summation of the series. The approach is compared to the exact analytical and to the Monte Carlo nonabsorption weighting method results for two representative slowing down and deep penetration problems. Application of the proposed approach leads to unbiased estimates for limited numbers of particle simulations and is useful in suppressing an effective bias problem observed in some cases of deep penetration particle transport problems

Transport of reactive and nonreactive solutes

International Nuclear Information System (INIS)

Garabedian, S.P.; Leblanc, D.R.

1990-01-01

A natural-gradient tracer test was conducted on Cape Cod, Massachusetts, to examine the transport and dispersion of solutes in a sand and gravel aquifer. A nonreactive tracer, bromide, and two reactive tracers, lithium and molybdate, were injected as a pulse in July 1985 and monitored in three dimensions for 3 years as they moved 280 meters downgradient through an array of multilevel samplers. The tracer transport was quantified using spatial moments. The calculated total mass of bromide for each sampling date varied from 86 to 105 percent of the injected mass, and the center of mass moved at a nearly constant horizontal velocity of 0.42 meters per day. The bromide cloud also moved downward about 4 meters, probably because of density-induced sinking and accretion of areal recharge from precipitation. After 200 meters of transport, the bromide cloud was more than 80 meters long but only 14 meters wide and 6 meters thick. The change in longitudinal dispersivity had reached a constant value (0.96 meters). The transverse horizontal and transverse vertical dispersivities were much smaller (1.8 centimeters and 1.5 millimeters, respectively) than the longitudinal value. The lithium and molybdate clouds followed the same path as the bromide cloud, but a significant amount of their mass was adsorbed onto the aquifer sediments, and their rates of movement were retarded about 50 percent relative to the bromide movement. (Author) (5 figs., 23 refs.)

Modeling of water and solute transport under variably saturated conditions: state of the art

International Nuclear Information System (INIS)

Lappala, E.G.

1980-01-01

This paper reviews the equations used in deterministic models of mass and energy transport in variably saturated porous media. Analytic, quasi-analytic, and numerical solution methods to the nonlinear forms of transport equations are discussed with respect to their advantages and limitations. The factors that influence the selection of a modeling method are discussed in this paper; they include the following: (1) the degree of coupling required among the equations describing the transport of liquids, gases, solutes, and energy; (2) the inclusion of an advection term in the equations; (3) the existence of sharp fronts; (4) the degree of nonlinearity and hysteresis in the transport coefficients and boundary conditions; (5) the existence of complex boundaries; and (6) the availability and reliability of data required by the models

A closed-form solution for the two-dimensional transport equation by the LTS{sub N} nodal method in the energy range of Compton effect

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, B.D.A., E-mail: barbararodriguez@furg.b [Universidade Federal do Rio Grande, Instituto de Matematica, Estatistica e Fisica, Rio Grande, RS (Brazil); Vilhena, M.T., E-mail: vilhena@mat.ufrgs.b [Universidade Federal do Rio Grande do Sul, Departamento de Matematica Pura e Aplicada, Porto Alegre, RS (Brazil); Hoff, G., E-mail: hoff@pucrs.b [Pontificia Universidade Catolica do Rio Grande do Sul, Faculdade de Fisica, Porto Alegre, RS (Brazil); Bodmann, B.E.J., E-mail: bardo.bodmann@ufrgs.b [Universidade Federal do Rio Grande do Sul, Departamento de Matematica Pura e Aplicada, Porto Alegre, RS (Brazil)

2011-01-15

In the present work we report on a closed-form solution for the two-dimensional Compton transport equation by the LTS{sub N} nodal method in the energy range of Compton effect. The solution is determined using the LTS{sub N} nodal approach for homogeneous and heterogeneous rectangular domains, assuming the Klein-Nishina scattering kernel and a multi-group model. The solution is obtained by two one-dimensional S{sub N} equation systems resulting from integrating out one of the orthogonal variables of the S{sub N} equations in the rectangular domain. The leakage angular fluxes are approximated by exponential forms, which allows to determine a closed-form solution for the photons transport equation. The angular flux and the parameters of the medium are used for the calculation of the absorbed energy in rectangular domains with different dimensions and compositions. In this study, only the absorbed energy by Compton effect is considered. We present numerical simulations and comparisons with results obtained by using the simulation platform GEANT4 (version 9.1) with its low energy libraries.

The plasma transport equations derived by multiple time-scale expansions and turbulent transport. I. General theory

International Nuclear Information System (INIS)

Edenstrasser, J.W.

1995-01-01

A multiple time-scale derivative expansion scheme is applied to the dimensionless Fokker--Planck equation and to Maxwell's equations, where the parameter range of a typical fusion plasma was assumed. Within kinetic theory, the four time scales considered are those of Larmor gyration, particle transit, collisions, and classical transport. The corresponding magnetohydrodynamic (MHD) time scales are those of ion Larmor gyration, Alfven, MHD collision, and resistive diffusion. The solution of the zeroth-order equations results in the force-free equilibria and ideal Ohm's law. The solution of the first-order equations leads under the assumption of a weak collisional plasma to the ideal MHD equations. On the MHD-collision time scale, not only the full set of the MHD transport equations is obtained, but also turbulent terms, where the related transport quantities are one order in the expansion parameter larger than those of classical transport. Finally, at the resistive diffusion time scale the known transport equations are arrived at including, however, also turbulent contributions. copyright 1995 American Institute of Physics

On the Solution of the Neutron Transport Equation

Energy Technology Data Exchange (ETDEWEB)

Depken, S

1962-12-15

The neutron transport equation has occupied the attention of many authors since Placzek, Wick and others made their first attempts to solve it, Even in the simple case of energy independent cross-sections, and disregarding the motion of the scattering nucleons, it is difficult to find a solution in an analytical form which is easily surveyable and fitted for numerical calculations. In Part I of this paper some new viewpoints will be introduced which enable the solution to be presented in its simplest possible form. Part II is devoted to an investigation of some functions introduced in Part I. In Part III the results are applied to the case of large energy lethargy, and the validity of derived formulas is discussed.

Efflux of drugs and solutes from brain: the interactive roles of diffusional transcapillary transport, bulk flow and capillary transporters.

Science.gov (United States)

Groothuis, Dennis R; Vavra, Michael W; Schlageter, Kurt E; Kang, Eric W-Y; Itskovich, Andrea C; Hertzler, Shannon; Allen, Cathleen V; Lipton, Howard L

2007-01-01

We examined the roles of diffusion, convection and capillary transporters in solute removal from extracellular space (ECS) of the brain. Radiolabeled solutes (eight with passive distribution and four with capillary or cell transporters) were injected into the brains of rats (n=497) and multiple-time point experiments measured the amount remaining in brain as a function of time. For passively distributed compounds, there was a relationship between lipid:water solubility and total brain efflux:diffusional efflux, which dominated when k(p), the transcapillary efflux rate constant, was >10(0) h(-1); when 10(-1)transporters. The total efflux rate constant, k(eff), was the sum of a passive component (k(p)=0.0018 h(-1)), a convective component (k(csf)=0.2 h(-1)), and a variable, concentration-dependent component (k(x)=0 to 0.45 h(-1)). Compounds with cell membrane transporters had longer clearance half times as did an oligonucleotide, which interacted with cell surface receptors. Manipulation of physiologic state (n=35) did not affect efflux, but sucrose efflux half time was longer with pentobarbital anesthesia (24 h) than with no anesthesia or ketamine-xylazine anesthesia (2 to 3 h). These results show that solute clearance from normal brain ECS may involve multiple physiologic pathways, may be affected by anesthesia, and suggests that convection-mediated efflux may be manipulated to increase or decrease drug clearance from brain.

Closed-form kinetic parameter estimation solution to the truncated data problem

International Nuclear Information System (INIS)

Zeng, Gengsheng L; Kadrmas, Dan J; Gullberg, Grant T

2010-01-01

In a dedicated cardiac single photon emission computed tomography (SPECT) system, the detectors are focused on the heart and the background is truncated in the projections. Reconstruction using truncated data results in biased images, leading to inaccurate kinetic parameter estimates. This paper has developed a closed-form kinetic parameter estimation solution to the dynamic emission imaging problem. This solution is insensitive to the bias in the reconstructed images that is caused by the projection data truncation. This paper introduces two new ideas: (1) it includes background bias as an additional parameter to estimate, and (2) it presents a closed-form solution for compartment models. The method is based on the following two assumptions: (i) the amount of the bias is directly proportional to the truncated activities in the projection data, and (ii) the background concentration is directly proportional to the concentration in the myocardium. In other words, the method assumes that the image slice contains only the heart and the background, without other organs, that the heart is not truncated, and that the background radioactivity is directly proportional to the radioactivity in the blood pool. As long as the background activity can be modeled, the proposed method is applicable regardless of the number of compartments in the model. For simplicity, the proposed method is presented and verified using a single compartment model with computer simulations using both noiseless and noisy projections.

Specific transport and storage solutions: Waste management facing current and future stakes of the nuclear fuel cycle

International Nuclear Information System (INIS)

Deniau, Helene; Gagner, Laurent; Gendreau, Francoise; Presta, Anne

2006-01-01

With major projects ongoing or being planned, and also with the daily management of radioactive waste from nuclear facilities, the role of transport and/or storage packaging has been often overlooked. Indeed, the packaging development process and transport solutions implemented are a key part of the waste management challenge: protection of people and environment. During over four decades, the AREVA Group has developed a complete and coherent system for the transport of waste produced by nuclear industries. The transport solutions integrate the factors to consider, as industrial transportation needs, various waste forms, associated hazards and current regulations. Thus, COGEMA LOGISTICS has designed, licensed and manufactured a large number of different transport, storage and dual purpose cask models for residues and all kinds of radioactive wastes. The present paper proposes to illustrate how a company acting both as a cask designer and a carrier is key to the waste management issue and how it can support the waste management policy of nuclear producers through their operational choices. We will focus on the COGEMA LOGISTICS technical solutions implemented to guarantee safe and secure transportation and storage solutions. We will describe different aspects of the cask design process, insisting on how it enables to fulfill both customer needs and regulation requirements. We will also mention the associated services developed by the AREVA Business Unit Logistics (COGEMA LOGISTICS, TRANSNUCLEAR, MAINCO, and LEMARECHAL CELESTIN) in order to manage transportation of liquid and solid waste towards interim or final storage sites. The paper has the following contents: About radioactive waste; - Radioactive waste classification; - High level activity waste and long-lived intermediate level waste; - Long-lived low level waste; - Short-lived low- and intermediate level waste; - Very low level waste; - The radioactive waste in nuclear fuel cycle; - Packaging design and

Win-Win transportation solutions price reforms with multiple benefits

International Nuclear Information System (INIS)

Litman, T.

2001-01-01

Reform strategies in the transportation market, such as the Win-Win Transportation Solutions, can provide several economic, social and environmental benefits. The strategies are cost effective, technically feasible reforms based on market principles which help create a more equitable and efficient transportation system that supports sustainable economic development. The benefits they provide include reduced traffic congestion, road and parking facility savings, consumer savings, equity, safety and environmental protection. They also increase economic productivity. If fully implemented, they could reduce motor vehicle impacts by 15 to 30 per cent and could help achieve the Kyoto emission reduction targets. Examples of Win-Win strategies at the federal level include: (1) removal of subsidies to oil production and internalized costs, and (2) tax exempt employer provided transfer benefits. Examples of Win-Win strategies at the state/provincial level include: (1) distance-based vehicle insurance and registration fees, (2) least-coast transportation planning and funding, (3) revenue-neutral tax shifting, (4) road pricing, (5) reform motor carrier regulations for competition and efficiency, (6) local and regional transportation demand management programs, (7) more efficient land use, (8) more flexible zoning requirements, (9) parking cash out, (10) transportation management associations, (11) location-efficient housing and mortgages, (12) school and campus trip management, (13) car sharing, (14) non-motorized transport improvements, and (15) traffic calming. It was noted that any market reform that leads to more efficient use of existing transportation systems can provide better economic development benefits. 9 refs., 1 tab., 1 fig

Sensitivity and uncertainty analyses applied to one-dimensional radionuclide transport in a layered fractured rock: MULTFRAC --Analytic solutions and local sensitivities

International Nuclear Information System (INIS)

Gureghian, A.B.; Wu, Y.T.; Sagar, B.

1992-12-01

Exact analytical solutions based on the Laplace transforms are derived for describing the one-dimensional space-time-dependent, advective transport of a decaying species in a layered, saturated rock system intersected by a planar fracture of varying aperture. These solutions, which account for advection in fracture, molecular diffusion into the rock matrix, adsorption in both fracture and matrix, and radioactive decay, predict the concentrations in both fracture and rock matrix and the cumulative mass in the fracture. The solute migration domain in both fracture and rock is assumed to be semi-infinite with non-zero initial conditions. The concentration of each nuclide at the source is allowed to decay either continuously or according to some periodical fluctuations where both are subjected to either a step or band release mode. Two numerical examples related to the transport of Np-237 and Cm-245 in a five-layered system of fractured rock were used to verify these solutions with several well established evaluation methods of Laplace inversion integrals in the real and complex domain. In addition, with respect to the model parameters, a comparison of the analytically derived local sensitivities for the concentration and cumulative mass of Np-237 in the fracture with the ones obtained through a finite-difference method of approximation is also reported

Modeling reactive geochemical transport of concentrated aqueous solutions in variably saturated media

Energy Technology Data Exchange (ETDEWEB)

Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin

2004-01-28

Concentrated aqueous solutions (CAS) have unique thermodynamic and physical properties. Chemical components in CAS are incompletely dissociated, especially those containing divalent or polyvalent ions. The problem is further complicated by the interaction between CAS flow processes and the naturally heterogeneous sediments. As the CAS migrates through the porous media, the composition may be altered subject to fluid-rock interactions. To effectively model reactive transport of CAS, we must take into account ion-interaction. A combination of the Pitzer ion-interaction and the ion-association model would be an appropriate way to deal with multiple-component systems if the Pitzer' parameters and thermodynamic data of dissolved components and the related minerals are available. To quantify the complicated coupling of CAS flow and transport, as well as the involved chemical reactions in natural and engineered systems, we have substantially extended an existing reactive biogeochemical transport code, BIO-CORE{sup 2D}{copyright}, by incorporating a comprehensive Pitzer ion-interaction model. In the present paper, the model, and two test cases against measured data were briefly introduced. Finally we present an application to simulate a laboratory column experiment studying the leakage of the high alkaline waste fluid stored in Hanford (a site of the U.S. Department of Energy, located in Washington State, USA). With the Pitzer ion-interaction ionic activity model, our simulation captures measured pH evolution. The simulation indicates that all the reactions controlling the pH evolution, including cation exchanges, mineral precipitation and dissolution, are coupled.

Investigating the effect of compression on solute transport through degrading municipal solid waste

Energy Technology Data Exchange (ETDEWEB)

Woodman, N.D., E-mail: n.d.woodman@soton.ac.uk; Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.

2014-11-15

Highlights: • The influence of compression on MSW flushing was evaluated using 13 tracer tests. • Compression has little effect on solute diffusion times in MSW. • Lithium tracer was conservative in non-degrading waste but not in degrading waste. • Bromide tracer was conservative, but deuterium was not. - Abstract: The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to the presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified.

Characterization of a novel organic solute transporter homologue from Clonorchis sinensis.

Directory of Open Access Journals (Sweden)

Yanyan Lu

2018-04-01

Full Text Available Clonorchis sinensis is a liver fluke that can dwell in the bile ducts of mammals. Bile acid transporters function to maintain the homeostasis of bile acids in C. sinensis, as they induce physiological changes or have harmful effects on C. sinensis survival. The organic solute transporter (OST transports mainly bile acid and belongs to the SLC51 subfamily of solute carrier transporters. OST plays a critical role in the recirculation of bile acids in higher animals. In this study, we cloned full-length cDNA of the 480-amino acid OST from C. sinensis (CsOST. Genomic analysis revealed 11 exons and nine introns. The CsOST protein had a 'Solute_trans_a' domain with 67% homology to Schistosoma japonicum OST. For further analysis, the CsOST protein sequence was split into the ordered domain (CsOST-N at the N-terminus and disordered domain (CsOST-C at the C-terminus. The tertiary structure of each domain was built using a threading-based method and determined by manual comparison. In a phylogenetic tree, the CsOST-N domain belonged to the OSTα and CsOST-C to the OSTβ clade. These two domains were more highly conserved with the OST α- and β-subunits at the structure level than at sequence level. These findings suggested that CsOST comprised the OST α- and β-subunits. CsOST was localized in the oral and ventral suckers and in the mesenchymal tissues abundant around the intestine, vitelline glands, uterus, and testes. This study provides fundamental data for the further understanding of homologues in other flukes.

Characterization of a novel organic solute transporter homologue from Clonorchis sinensis

Science.gov (United States)

Dai, Fuhong; Lee, Ji-Yun; Pak, Jhang Ho; Sohn, Woon-Mok

2018-01-01

Clonorchis sinensis is a liver fluke that can dwell in the bile ducts of mammals. Bile acid transporters function to maintain the homeostasis of bile acids in C. sinensis, as they induce physiological changes or have harmful effects on C. sinensis survival. The organic solute transporter (OST) transports mainly bile acid and belongs to the SLC51 subfamily of solute carrier transporters. OST plays a critical role in the recirculation of bile acids in higher animals. In this study, we cloned full-length cDNA of the 480-amino acid OST from C. sinensis (CsOST). Genomic analysis revealed 11 exons and nine introns. The CsOST protein had a ‘Solute_trans_a’ domain with 67% homology to Schistosoma japonicum OST. For further analysis, the CsOST protein sequence was split into the ordered domain (CsOST-N) at the N-terminus and disordered domain (CsOST-C) at the C-terminus. The tertiary structure of each domain was built using a threading-based method and determined by manual comparison. In a phylogenetic tree, the CsOST-N domain belonged to the OSTα and CsOST-C to the OSTβ clade. These two domains were more highly conserved with the OST α- and β-subunits at the structure level than at sequence level. These findings suggested that CsOST comprised the OST α- and β-subunits. CsOST was localized in the oral and ventral suckers and in the mesenchymal tissues abundant around the intestine, vitelline glands, uterus, and testes. This study provides fundamental data for the further understanding of homologues in other flukes. PMID:29702646

Minimal parameter solution of the orthogonal matrix differential equation

Science.gov (United States)

Bar-Itzhack, Itzhack Y.; Markley, F. Landis

1990-01-01

As demonstrated in this work, all orthogonal matrices solve a first order differential equation. The straightforward solution of this equation requires n sup 2 integrations to obtain the element of the nth order matrix. There are, however, only n(n-1)/2 independent parameters which determine an orthogonal matrix. The questions of choosing them, finding their differential equation and expressing the orthogonal matrix in terms of these parameters are considered. Several possibilities which are based on attitude determination in three dimensions are examined. It is shown that not all 3-D methods have useful extensions to higher dimensions. It is also shown why the rate of change of the matrix elements, which are the elements of the angular rate vector in 3-D, are the elements of a tensor of the second rank (dyadic) in spaces other than three dimensional. It is proven that the 3-D Gibbs vector (or Cayley Parameters) are extendable to other dimensions. An algorithm is developed emplying the resulting parameters, which are termed Extended Rodrigues Parameters, and numerical results are presented of the application of the algorithm to a fourth order matrix.

Implementation of Solute Transport in the Vadose Zone into the `HYDRUS Package for MODFLOW'

Science.gov (United States)

Simunek, J.; Beegum, S.; Szymkiewicz, A.; Sudheer, K. P.

2017-12-01

The 'HYDRUS package for MODFLOW' was developed by Seo et al. (2007) and Twarakavi et al. (2008) to simultaneously evaluate transient water flow in both unsaturated and saturated zones. The package, which is based on the HYDRUS-1D model (Šimůnek et al., 2016) simulating unsaturated water flow in the vadose zone, was incorporated into MODFLOW (Harbaugh et al., 2000) simulating saturated groundwater flow. The HYDRUS package in the coupled model can be used to represent the effects of various unsaturated zone processes, including infiltration, evaporation, root water uptake, capillary rise, and recharge in homogeneous or layered soil profiles. The coupled model is effective in addressing spatially-variable saturated-unsaturated hydrological processes at the regional scale, allowing for complex layering in the unsaturated zone, spatially and temporarily variable water fluxes at the soil surface and in the root zone, and with alternating recharge and discharge fluxes (Twarakavi et al., 2008). One of the major limitations of the coupled model was that it could not be used to simulate at the same time solute transport. However, solute transport is highly dependent on water table fluctuations due to temporal and spatial variations in groundwater recharge. This is an important concern when the coupled model is used for analyzing groundwater contamination due to transport through the unsaturated zone. The objective of this study is to integrate the solute transport model (the solute transport part of HYDRUS-1D for the unsaturated zone and MT3DMS (Zheng and Wang, 1999; Zheng, 2009) for the saturated zone) into an existing coupled water flow model. The unsaturated zone component of the coupled model can consider solute transport involving many biogeochemical processes and reactions, including first-order degradation, volatilization, linear or nonlinear sorption, one-site kinetic sorption, two-site sorption, and two-kinetic sites sorption (Šimůnek and van Genuchten, 2008

Solution of the transport equation with account for inelastic collisions

International Nuclear Information System (INIS)

Kalashnikov, N.P.; Remizovich, V.S.; Ryazanov, M.I.

1980-01-01

The theory of charged particle scattering in a matter with account for inelastic collisions is considered. In ''directly-forward'' approximation the transport equation at the absence of elastic collisions is obtained. The solution of the transport equation is made without and with account for fluctuation of energy losses. Formulas for path-energy relation are given. Energy spectrum and distribution of fast charged particles with respect to paths are studied. The problem of quantum mechanical approach to the theory of multiple scattering of fast charged particles in a matter is discussed briefly

Complex step-based low-rank extended Kalman filtering for state-parameter estimation in subsurface transport models

KAUST Repository

El Gharamti, Mohamad; Hoteit, Ibrahim

2014-01-01

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.

Complex step-based low-rank extended Kalman filtering for state-parameter estimation in subsurface transport models

KAUST Repository

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.

TRACKING AND TRACING SOLUTION FOR DANGEROUS GOODS CARRIED BY INTERMODAL TRANSPORT

Directory of Open Access Journals (Sweden)

Marek Kvet

2014-03-01

Full Text Available This paper deals with the problem of designing a complex tracking and tracing solution for dangerous goods transportation with the support of modern information technologies. This research activity presents a part of the “ChemLogTT” [2] project solved at the University of Žilina. The main goal of our contribution is to present basic conception of a complex developed software tool for monitoring and analyzing mentioned dangerous goods transportation.

New solution for transport and industrial noise protection through reflective noise barriers

Directory of Open Access Journals (Sweden)

Kralov Ivan

2017-01-01

Full Text Available A new solution for protection of transportation and industrial noise through reflective noise barriers is proposed and investigated in this study. The new solution combines the advantages of the known barriers and has its own advantages in addition. The preliminary results show a very good level of noise reduction for this type of barriers.

Experimental constraints on transport from dimensionless parameter scaling studies

International Nuclear Information System (INIS)

Petty, C.C.; Luce, T.C.; Baker, D.R.

1998-02-01

The scalings of heat transport with safety factor (q), normalized collisionality (v), plasma beta (β), and relative gyroradius (ρ*) have been measured on the DIII-D tokamak. The measured ρ* β and v scalings of heat transport indicate that E x B transport from drive wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the safety factor was varied at fixed magnetic shear, the effective (or one-fluid) thermal diffusivity was found to scale like χ eff ∝ q 2.3±0.64 , with the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edge. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, τ th ∝ q -2.42±0.31 ; however, when the magnetic shear was allowed to vary to keep q 0 fixed during the (edge) safety factor scan, a weaker global dependence was observed, τ th ∝ q 95 -1.43±0.23 . This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined ρ*, β, v and q scalings of heat transport for H-mode plasmas on DIII-D reproduce the empirical confinement scaling using physical (dimensionless) parameters with the exception of weaker power degradation

Murt user's guide: A hybrid Lagrangian-Eulerian finite element model of multiple-pore-region solute transport through subsurface media

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

Radionuclide Transport Models Under Ambient Conditions

International Nuclear Information System (INIS)

Moridis, G.; Hu, Q.

2000-01-01

The purpose of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada. This is in accordance with the ''AMR Development Plan U0060, Radionuclide Transport Models Under Ambient Conditions'' (CRWMS M and O 1999a). This AMR supports the UZ Flow and Transport Process Model Report (PMR). This AMR documents the UZ Radionuclide Transport Model (RTM). This model considers: the transport of radionuclides through fractured tuffs; the effects of changes in the intensity and configuration of fracturing from hydrogeologic unit to unit; colloid transport; physical and retardation processes and the effects of perched water. In this AMR they document the capabilities of the UZ RTM, which can describe flow (saturated and/or unsaturated) and transport, and accounts for (a) advection, (b) molecular diffusion, (c) hydrodynamic dispersion (with full 3-D tensorial representation), (d) kinetic or equilibrium physical and/or chemical sorption (linear, Langmuir, Freundlich or combined), (e) first-order linear chemical reaction, (f) radioactive decay and tracking of daughters, (g) colloid filtration (equilibrium, kinetic or combined), and (h) colloid-assisted solute transport. Simulations of transport of radioactive solutes and colloids (incorporating the processes described above) from the repository horizon to the water table are performed to support model development and support studies for Performance Assessment (PA). The input files for these simulations include transport parameters obtained from other AMRs (i.e., CRWMS M and O 1999d, e, f, g, h; 2000a, b, c, d). When not available, the parameter values used are obtained from the literature. The results of the simulations are used to evaluate the transport of radioactive solutes and colloids, and

Intelligent Mechatronics Systems for Transport Climate Parameters Optimization Using Fuzzy Logic Control

OpenAIRE

Beinarts, I; Ļevčenkovs, A; Kuņicina, N

2007-01-01

In article interest is concentrated on the climate parameters optimization in passengers’ salon of public electric transportation vehicles. The article presents mathematical problem for using intelligent agents in mechatronics problems for climate parameters optimal control. Idea is to use fuzzy logic and intelligent algorithms to create coordination mechanism for climate parameters control to save electrical energy, and it increases the level of comfort for passengers. A special interest for...

Prolonged river water pollution due to variable-density flow and solute transport in the riverbed

Science.gov (United States)

Jin, Guangqiu; Tang, Hongwu; Li, Ling; Barry, D. A.

2015-04-01

A laboratory experiment and numerical modeling were used to examine effects of density gradients on hyporheic flow and solute transport under the condition of a solute pulse input to a river with regular bed forms. Relatively low-density gradients due to an initial salt pulse concentration of 1.55 kg m-3 applied in the experiment were found to modulate significantly the pore-water flow and solute transport in the riverbed. Such density gradients increased downward flow and solute transport in the riverbed by factors up to 1.6. This resulted in a 12.2% increase in the total salt transfer from the water column to the riverbed over the salt pulse period. As the solute pulse passed, the effect of the density gradients reversed, slowing down the release of the solute back to the river water by a factor of 3.7. Numerical modeling indicated that these density effects intensified as salt concentrations in the water column increased. Simulations further showed that the density gradients might even lead to unstable flow and result in solute fingers in the bed of large bed forms. The slow release of solute from the bed back to the river led to a long tail of solute concentration in the river water. These findings have implications for assessment of impact of pollution events on river systems, in particular, long-term effects on both the river water and riverbed due to the hyporheic exchange.

Inference of reactive transport model parameters using a Bayesian multivariate approach

Science.gov (United States)

Carniato, Luca; Schoups, Gerrit; van de Giesen, Nick

2014-08-01

Parameter estimation of subsurface transport models from multispecies data requires the definition of an objective function that includes different types of measurements. Common approaches are weighted least squares (WLS), where weights are specified a priori for each measurement, and weighted least squares with weight estimation (WLS(we)) where weights are estimated from the data together with the parameters. In this study, we formulate the parameter estimation task as a multivariate Bayesian inference problem. The WLS and WLS(we) methods are special cases in this framework, corresponding to specific prior assumptions about the residual covariance matrix. The Bayesian perspective allows for generalizations to cases where residual correlation is important and for efficient inference by analytically integrating out the variances (weights) and selected covariances from the joint posterior. Specifically, the WLS and WLS(we) methods are compared to a multivariate (MV) approach that accounts for specific residual correlations without the need for explicit estimation of the error parameters. When applied to inference of reactive transport model parameters from column-scale data on dissolved species concentrations, the following results were obtained: (1) accounting for residual correlation between species provides more accurate parameter estimation for high residual correlation levels whereas its influence for predictive uncertainty is negligible, (2) integrating out the (co)variances leads to an efficient estimation of the full joint posterior with a reduced computational effort compared to the WLS(we) method, and (3) in the presence of model structural errors, none of the methods is able to identify the correct parameter values.

Correlation Relation for the Membrane Transport ParametersL(p), σ, and ω.

Science.gov (United States)

Kargol, A; Kargol, M; Przestalski, S

1997-12-01

We derive a formula for the correlation of the three practical transportparameters L(p), σ, and ω appearing in Kedem-Katchalskyequations. It has a form ω = KL(p)/v(s)(1-σ), where K = 0.0306 is a universal constant independent ofthe choice of a membrane and a solute. It can be used to calculate the valueof any of these parameters, provided the other two and the molar volume[Formula: see text] of the solute are known. The formula couldbe very useful, in particular when measurements of the parameters aredifficult or even impossible.

Numerical Solution of the Electron Transport Equation in the Upper Atmosphere

Energy Technology Data Exchange (ETDEWEB)

Woods, Mark Christopher [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Holmes, Mark [Rensselaer Polytechnic Inst., Troy, NY (United States); Sailor, William C [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-07-01

A new approach for solving the electron transport equation in the upper atmosphere is derived. The problem is a very stiff boundary value problem, and to obtain an accurate numerical solution, matrix factorizations are used to decouple the fast and slow modes. A stable finite difference method is applied to each mode. This solver is applied to a simplifieed problem for which an exact solution exists using various versions of the boundary conditions that might arise in a natural auroral display. The numerical and exact solutions are found to agree with each other to at least two significant digits.

The Human Gene SLC25A29, of Solute Carrier Family 25, Encodes a Mitochondrial Transporter of Basic Amino Acids*

Science.gov (United States)

Porcelli, Vito; Fiermonte, Giuseppe; Longo, Antonella; Palmieri, Ferdinando

2014-01-01

The human genome encodes 53 members of the solute carrier family 25 (SLC25), also called the mitochondrial carrier family, many of which have been shown to transport carboxylates, amino acids, nucleotides, and cofactors across the inner mitochondrial membrane, thereby connecting cytosolic and matrix functions. In this work, a member of this family, SLC25A29, previously reported to be a mitochondrial carnitine/acylcarnitine- or ornithine-like carrier, has been thoroughly characterized biochemically. The SLC25A29 gene was overexpressed in Escherichia coli, and the gene product was purified and reconstituted in phospholipid vesicles. Its transport properties and kinetic parameters demonstrate that SLC25A29 transports arginine, lysine, homoarginine, methylarginine and, to a much lesser extent, ornithine and histidine. Carnitine and acylcarnitines were not transported by SLC25A29. This carrier catalyzed substantial uniport besides a counter-exchange transport, exhibited a high transport affinity for arginine and lysine, and was saturable and inhibited by mercurial compounds and other inhibitors of mitochondrial carriers to various degrees. The main physiological role of SLC25A29 is to import basic amino acids into mitochondria for mitochondrial protein synthesis and amino acid degradation. PMID:24652292

The human gene SLC25A29, of solute carrier family 25, encodes a mitochondrial transporter of basic amino acids.

Science.gov (United States)

Porcelli, Vito; Fiermonte, Giuseppe; Longo, Antonella; Palmieri, Ferdinando

2014-05-09

The human genome encodes 53 members of the solute carrier family 25 (SLC25), also called the mitochondrial carrier family, many of which have been shown to transport carboxylates, amino acids, nucleotides, and cofactors across the inner mitochondrial membrane, thereby connecting cytosolic and matrix functions. In this work, a member of this family, SLC25A29, previously reported to be a mitochondrial carnitine/acylcarnitine- or ornithine-like carrier, has been thoroughly characterized biochemically. The SLC25A29 gene was overexpressed in Escherichia coli, and the gene product was purified and reconstituted in phospholipid vesicles. Its transport properties and kinetic parameters demonstrate that SLC25A29 transports arginine, lysine, homoarginine, methylarginine and, to a much lesser extent, ornithine and histidine. Carnitine and acylcarnitines were not transported by SLC25A29. This carrier catalyzed substantial uniport besides a counter-exchange transport, exhibited a high transport affinity for arginine and lysine, and was saturable and inhibited by mercurial compounds and other inhibitors of mitochondrial carriers to various degrees. The main physiological role of SLC25A29 is to import basic amino acids into mitochondria for mitochondrial protein synthesis and amino acid degradation.

Solute carrier transporters: potential targets for digestive system neoplasms.

Science.gov (United States)

Xie, Jing; Zhu, Xiao Yan; Liu, Lu Ming; Meng, Zhi Qiang

2018-01-01

Digestive system neoplasms are the leading causes of cancer-related death all over the world. Solute carrier (SLC) superfamily is composed of a series of transporters that are ubiquitously expressed in organs and tissues of digestive systems and mediate specific uptake of small molecule substrates in facilitative manner. Given the important role of SLC proteins in maintaining normal functions of digestive system, dysregulation of these protein in digestive system neoplasms may deliver biological and clinical significance that deserves systemic studies. In this review, we critically summarized the recent advances in understanding the role of SLC proteins in digestive system neoplasms. We highlighted that several SLC subfamilies, including metal ion transporters, transporters of glucose and other sugars, transporters of urea, neurotransmitters and biogenic amines, ammonium and choline, inorganic cation/anion transporters, transporters of nucleotide, amino acid and oligopeptide organic anion transporters, transporters of vitamins and cofactors and mitochondrial carrier, may play important roles in mediating the initiation, progression, metastasis, and chemoresistance of digestive system neoplasms. Proteins in these SLC subfamilies may also have diagnostic and prognostic values to particular cancer types. Differential expression of SLC proteins in tumors of digestive system was analyzed by extracting data from human cancer database, which revealed that the roles of SLC proteins may either be dependent on the substrates they transport or be tissue specific. In addition, small molecule modulators that pharmacologically regulate the functions of SLC proteins were discussed for their possible application in the treatment of digestive system neoplasms. This review highlighted the potential of SLC family proteins as drug target for the treatment of digestive system neoplasms.

Meta-analysis of the effects of soil properties, site factors and experimental conditions on solute transport

Directory of Open Access Journals (Sweden)

J. K. Koestel

2012-06-01

Full Text Available Preferential flow is a widespread phenomenon that is known to strongly affect solute transport in soil, but our understanding and knowledge is still poor of the site factors and soil properties that promote it. To investigate these relationships, we assembled a database from the peer-reviewed literature containing information on 733 breakthrough curve experiments under steady-state flow conditions. Most of the collected experiments (585 of the 733 datasets had been conducted on undisturbed soil columns, although some experiments on repacked soil, clean sands, and glass beads were also included. In addition to the apparent dispersivity, we focused our attention on three indicators of preferential solute transport: namely the 5%-arrival time, the holdback factor, and the ratio of piston-flow and average transport velocities. Our results suggest that, in contrast to the 5%-arrival time and the holdback factor, the piston-flow to transport velocity ratio is not related to preferential macropore transport but rather to the exclusion or retardation of the applied tracer. Confirming that the apparent longitudinal dispersivity is positively correlated with the travel distance of the tracer, our results also illustrate that this relationship is refined if the normalized 5%-tracer arrival time is also taken into account. In particular, we found that the degree of preferential solute transport increases with apparent dispersivity and decreases with travel distance. A similar but weaker relationship was observed between apparent dispersivity, 5%-tracer arrival time, and lateral observation scale, such that the degree of preferential transport increases with lateral observation scale. However, we also found that the travel distance and the lateral observation scale in the investigated dataset are correlated, which makes it difficult to distinguish their influence on these transport characteristics. We also found that the strength of preferential transport

Model for diffusion and porewater chemistry in compacted bentonite. Theoretical basis and the solution methodology for the transport model

International Nuclear Information System (INIS)

Lehikoinen, J.

1997-01-01

This report describes the progress of the computer model for ionic transport in bentonite. The research is part of the project Microstructural and chemical parameters of bentonite as determinants of waste isolation efficiency within the Nuclear fission safety program organized by The Commission of the European Communities. The study was started by collecting a comprehensive body of available data on space-charge transport modelling and creating a conceptualization of the problem at hand. The numerical discretization of the governing equations by finite differences was also initiated. This report introduces the theoretical basis for the model, somewhat more elaborated than presented in Progress Report 1/1996, and rectifies a few mistakes appearing in that report. It also gives a brief introduction to the solution methodology of the disc retized governing equations. (orig.) (12 refs.)

Modeling solute transport in a heterogeneous unsaturated porous medium under dynamic boundary conditions on different spatial scales

Science.gov (United States)

Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel

2013-04-01

Understanding transport of solutes/contaminants through unsaturated soil in the shallow subsurface is vital to assess groundwater quality, nutrient cycling or to plan remediation projects. Alternating precipitation and evaporation conditions causing upward and downward flux with differing flow paths, changes in saturation and related structural heterogeneity make the description of transport in the unsaturated zone near the soil-surface a complex problem. Preferential flow paths strongly depend, among other things, on the saturation of a medium. Recent studies (e.g. Bechtold et al., 2011) showed lateral flow and solute transport during evaporation conditions (upward flux) in vertically layered sand columns. Results revealed that during evaporation water and solute are redistributed laterally from coarse to fine media deeper in the soil, and towards zones of lowest hydraulic head near to the soil surface. These zones at the surface can be coarse or fine grained depending on saturation status and evaporation flux. However, if boundary conditions are reversed and precipitation is applied, the flow field is not reversed in the same manner, resulting in entirely different transport patterns for downward and upward flow. Therefore, considering net-flow rates alone is misleading when describing transport in the shallow unsaturated zone. In this contribution, we analyze transport of a solute in the shallow subsurface to assess effects resulting from the superposition of heterogeneous soil structures and dynamic flow conditions on various spatial scales. Two-dimensional numerical simulations of unsaturated flow and transport in heterogeneous porous media under changing boundary conditions are carried out using a finite-volume code coupled to a particle tracking algorithm to quantify solute transport and leaching rates. In order to validate numerical simulations, results are qualitatively compared to those of a physical experiment (Bechtold et al., 2011). Numerical

SOLUTIONS AND MEANS OF ALTERNATIVE TRANSPORT IN THE CONCEPT OF SUSTAINABLE DEVELOPMENT

Directory of Open Access Journals (Sweden)

CATALIN POPESCU

2017-12-01

Full Text Available The paper aims to achieve an overview of innovative initiatives on alternative transport in recent years in the context of increasing emissions of greenhouse gases. In this context are presented the main problems caused by motorized traffic in the urban agglomerations. Also, there are mentioned measures that could be implemented in busy urban areas. On this occasion are mentioned both new technical solutions and new means of alternative transport type. Additional, specific projects and programs are highlighted using bicycle transportation. There are mentioned initiatives regarding urban transportation completed in European projects such as: CIVITAS, EFFECTS etc. The examples and figures are mainly focused on Romania.

The reliable solution and computation time of variable parameters Logistic model

OpenAIRE

Pengfei, Wang; Xinnong, Pan

2016-01-01

The reliable computation time (RCT, marked as Tc) when applying a double precision computation of a variable parameters logistic map (VPLM) is studied. First, using the method proposed, the reliable solutions for the logistic map are obtained. Second, for a time-dependent non-stationary parameters VPLM, 10000 samples of reliable experiments are constructed, and the mean Tc is then computed. The results indicate that for each different initial value, the Tcs of the VPLM are generally different...

Parameters estimation for reactive transport: A way to test the validity of a reactive model

Science.gov (United States)

Aggarwal, Mohit; Cheikh Anta Ndiaye, Mame; Carrayrou, Jérôme

The chemical parameters used in reactive transport models are not known accurately due to the complexity and the heterogeneous conditions of a real domain. We will present an efficient algorithm in order to estimate the chemical parameters using Monte-Carlo method. Monte-Carlo methods are very robust for the optimisation of the highly non-linear mathematical model describing reactive transport. Reactive transport of tributyltin (TBT) through natural quartz sand at seven different pHs is taken as the test case. Our algorithm will be used to estimate the chemical parameters of the sorption of TBT onto the natural quartz sand. By testing and comparing three models of surface complexation, we show that the proposed adsorption model cannot explain the experimental data.

Isolated effects of external bath osmolality, solute concentration, and electrical charge on solute transport across articular cartilage.

Science.gov (United States)

Pouran, Behdad; Arbabi, Vahid; Zadpoor, Amir A; Weinans, Harrie

2016-12-01

The metabolic function of cartilage primarily depends on transport of solutes through diffusion mechanism. In the current study, we use contrast enhanced micro-computed tomography to determine equilibrium concentration of solutes through different cartilage zones and solute flux in the cartilage, using osteochondral plugs from equine femoral condyles. Diffusion experiments were performed with two solutes of different charge and approximately equal molecular weight, namely iodixanol (neutral) and ioxaglate (charge=-1) in order to isolate the effects of solute's charge on diffusion. Furthermore, solute concentrations as well as bath osmolality were changed to isolate the effects of steric hindrance on diffusion. Bath concentration and bath osmolality only had minor effects on the diffusion of the neutral solute through cartilage at the surface, middle and deep zones, indicating that the diffusion of the neutral solute was mainly Fickian. The negatively charged solute diffused considerably slower through cartilage than the neutral solute, indicating a large non-Fickian contribution in the diffusion of charged molecules. The numerical models determined maximum solute flux in the superficial zone up to a factor of 2.5 lower for the negatively charged solutes (charge=-1) as compared to the neutral solutes confirming the importance of charge-matrix interaction in diffusion of molecules across cartilage. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Water and Solute Transport in Arid Vadose Zones: Innovations in Measurement and Analysis

International Nuclear Information System (INIS)

Tyler, S W.; Scanlon, Bridget R.; Gee, Glendon W.; Allison, G B.; Parlange, M. B.; Hopmans, J. W.

1999-01-01

Understanding the physics of flow and transport through the vadose zone has advanced significantly in the last three decades. These advances have been made primarily in humid regions or in irrigated agricultural settings. While some of the techniques are useful, many are not suited to arid regions. The fluxes of water and solutes typically found in arid regions are often orders of magnitude smaller than those found in agricultural settings, while the time scales for transport can be orders of magnitude larger. The depth over which transport must be characterized is also often much greater than in humid regions. Rather than relying on advances in applied tracers, arid-zone researchers have developed natural tracer techniques that are capable of quantifying transport over tens to thousands of years. Techniques have been developed to measure the hydraulic properties of sediments at all water contents, including the very dry range and at far greater depths. As arid and semiarid regions come under increased development pressures for such activities as hazardous- and radioactive-waste disposal, the development of techniques and the understanding of water and solute transport have become crucial components in defining the environmental impacts of activities at the landsurface

Lattice parameters and electrical resistivity of Ceria-Yttria solid solutions

International Nuclear Information System (INIS)

Rey, Jose Fernando Queiruga

2002-01-01

Ce0 2 :u mol% Y 2 O 3 (u=0, 4, 6, 8, 10 and 12) solid solutions were prepared by the conventional powder mixture technique. The main purposes of this work are: the study of the dependence of the lattice parameter of the Ceria cubic phase on the Yttria content, comparing the experimental data with data calculated according to the existing theoretical models; to determine the dependence of the ionic conductivity on the Yttria content; and to study the stability of the cubic fluorite phase after extensive thermal treatments (aging) of the Ceria-Yttria specimens. The results show that the lattice parameter of the solid solutions follows the Vegard's law and can be described by the two reported theoretical models. The 8 mol% Yttria-doped Ceria was found to present the largest value of ionic conductivity. Preliminary results show that a large decrease is found for only 1 h aging at 700 deg C and that the ionic conductivity decreases for ceramic specimens aged for times up to 10 h. (author)

Experimental constraints on transport from dimensionless parameter scaling studies

International Nuclear Information System (INIS)

Petty, C.C.; Luce, T.C.; Baker, D.R.; Ballet, B.; Carlstrom, T.N.; Cordey, J.G.; DeBoo, J.C.; Gohil, P.; Groebner, R.J.; Rice, B.W.; Thomas, D.M.; Wade, M.R.; Waltz, R.E.

1998-01-01

The scalings of heat transport with safety factor (q), normalized collisionality (ν), plasma beta (β), and relative gyroradius (ρ * ) have been measured on the DIII-D tokamak [Fusion Technol. 8, 441 (1985)]. The measured ρ * , β and ν scalings of heat transport indicate that ExB transport from drift wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the safety factor was varied at fixed magnetic shear, the effective (or one-fluid) thermal diffusivity was found to scale like χ eff ∝q 2.3±0.64 , with the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edge. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, τ th ∝q -2.42±0.31 ; however, when the magnetic shear was allowed to vary to keep q 0 fixed during the (edge) safety factor scan, a weaker global dependence was observed, τ th ∝q 95 -1.43±0.23 . This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined ρ * , β , ν and q scalings of heat transport for H-mode plasmas on DIII-D reproduce the empirical confinement scaling using physical (dimensional) parameters with the exception of weaker power degradation. copyright 1998 American Institute of Physics

Mathematical modeling and evaluation of radionuclide transport parameters from the ANL Laboratory Analog Program

International Nuclear Information System (INIS)

Chen, B.C.J.; Hull, J.R.; Seitz, M.G.; Sha, W.T.; Shah, V.L.; Soo, S.L.

1984-07-01

Computer model simulation is required to evaluate the performance of proposed or future high-level radioactive waste geological repositories. However, the accuracy of a model in predicting the real situation depends on how well the values of the transport properties are prescribed as input parameters. Knowledge of transport parameters is therefore essential. We have modeled ANL's Experiment Analog Program which was designed to simulate long-term radwaste migration process by groundwater flowing through a high-level radioactive waste repository. Using this model and experimental measurements, we have evaluated neptunium (actinide) deposition velocity and analyzed the complex phenomena of simultaneous deposition, erosion, and reentrainment of bentonite when groundwater is flowing through a narrow crack in a basalt rock. The present modeling demonstrates that we can obtain the values of transport parameters, as added information without any additional cost, from the available measurements of laboratory analog experiments. 8 figures, 3 tables

Semianalytical Solutions for Transport in Aquifer and Fractured Clay Matrix System

Science.gov (United States)

A three-dimensional mathematical model that describes transport of contaminant in a horizontal aquifer with simultaneous diffusion into a fractured clay formation is proposed. A group of analytical solutions is derived based on specific initial and boundary conditions as well as ...

Exact solutions of Fisher and Burgers equations with finite transport memory

International Nuclear Information System (INIS)

Kar, Sandip; Banik, Suman Kumar; Ray, Deb Shankar

2003-01-01

The Fisher and Burgers equations with finite memory transport, describing reaction-diffusion and convection-diffusion processes, respectively have recently attracted a lot of attention in the context of chemical kinetics, mathematical biology and turbulence. We show here that they admit exact solutions. While the speed of the travelling wavefront is dependent on the relaxation time in the Fisher equation, memory effects significantly smoothen out the shock wave nature of the Burgers solution, without any influence on the corresponding wave speed. We numerically analyse the ansatz for the exact solution and show that for the reaction-diffusion system the strength of the reaction term must be moderate enough not to exceed a critical limit to allow a travelling wave solution to exist for appreciable finite memory effect

Exact solutions of Fisher and Burgers equations with finite transport memory

CERN Document Server

Kar, S; Ray, D S

2003-01-01

The Fisher and Burgers equations with finite memory transport, describing reaction-diffusion and convection-diffusion processes, respectively have recently attracted a lot of attention in the context of chemical kinetics, mathematical biology and turbulence. We show here that they admit exact solutions. While the speed of the travelling wavefront is dependent on the relaxation time in the Fisher equation, memory effects significantly smoothen out the shock wave nature of the Burgers solution, without any influence on the corresponding wave speed. We numerically analyse the ansatz for the exact solution and show that for the reaction-diffusion system the strength of the reaction term must be moderate enough not to exceed a critical limit to allow a travelling wave solution to exist for appreciable finite memory effect.

The Method of Manufactured Solutions for RattleSnake A SN Radiation Transport Solver Inside the MOOSE Framework

International Nuclear Information System (INIS)

Wang, Yaqi

2012-01-01

The Method of Manufactured Solutions (MMS) is an accepted technique to verify that a numerical discretization for the radiation transport equation has been implemented correctly. This technique offers a few advantages over other methods such as benchmark problems or analytical solutions. The solution can be manufactured such that properties for the angular flux are either stressed or preserved. For radiation transport, these properties can include desired smoothness, positiveness and arbitrary order of anisotropy in angle. Another advantage is that the angular flux solution can be manufactured for multidimensional problems where analytical solutions are difficult to obtain in general.

Cyclic deformation-induced solute transport in tissue scaffolds with computer designed, interconnected, pore networks: experiments and simulations.

Science.gov (United States)

Den Buijs, Jorn Op; Dragomir-Daescu, Dan; Ritman, Erik L

2009-08-01

Nutrient supply and waste removal in porous tissue engineering scaffolds decrease from the periphery to the center, leading to limited depth of ingrowth of new tissue into the scaffold. However, as many tissues experience cyclic physiological strains, this may provide a mechanism to enhance solute transport in vivo before vascularization of the scaffold. The hypothesis of this study was that pore cross-sectional geometry and interconnectivity are of major importance for the effectiveness of cyclic deformation-induced solute transport. Transparent elastic polyurethane scaffolds, with computer-programmed design of pore networks in the form of interconnected channels, were fabricated using a 3D printing and injection molding technique. The scaffold pores were loaded with a colored tracer for optical contrast, cyclically compressed with deformations of 10 and 15% of the original undeformed height at 1.0 Hz. Digital imaging was used to quantify the spatial distribution of the tracer concentration within the pores. Numerical simulations of a fluid-structure interaction model of deformation-induced solute transport were compared to the experimental data. The results of experiments and modeling agreed well and showed that pore interconnectivity heavily influences deformation-induced solute transport. Pore cross-sectional geometry appears to be of less relative importance in interconnected pore networks. Validated computer models of solute transport can be used to design optimal scaffold pore geometries that will enhance the convective transport of nutrients inside the scaffold and the removal of waste, thus improving the cell survivability deep inside the scaffold.

Local measurement of transport parameters for laser injected trace impurities

Energy Technology Data Exchange (ETDEWEB)

Giannella, R; Lauro-Taroni, L [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

1994-07-01

A procedure has been developed that determines local measurements of transport parameters`s profiles for injected impurities. The measured profiles extend from the plasma centre up to a certain radial position (usually {rho} = 0.6-0.7). In the outer region of the plasma the procedure supplies ``most suitable extensions`` up to the plasma edge of the measured transport profiles. The procedure intrinsically assures consistency and excellent agreement between the simulated and experimental data of local broad band soft X-ray emissivity and intensities of individual emission lines from different ion states of the injected impurities. 4 refs., 3 figs.

Finite element simulation of moisture movement and solute transport in a large caisson

International Nuclear Information System (INIS)

Huyakorn, P.S.; Jones, B.G.; Parker, J.C.; Wadsworth, T.D.; White, H.O. Jr.

1987-01-01

The results of the solute transport experiments performed on compacted, crushed Bandelier Tuff in caisson B of the experimental cluster described by DePoorter (1981) are simulated. Both one- and three-dimensional simulations of solute transport have been performed using two selected finite element codes. Results of bromide and iodide tracer experiments conducted during near-steady flow conditions have been analyzed for pulse additions made on December 6, 1984, and followed over a period of up to 60 days. In addition, a pulse addition of nonconservative strontium tracer on September 28, 1984, during questionably steady flow conditions has been analyzed over a period of 240 days. One-dimensional finite element flow and transport simulations were carried out assuming the porous medium to be homogeneous and the injection source uniformly distributed. To evaluate effects of the nonuniform source distribution and also to investigate effects of inhomogeneous porous medium properties, three dimensional finite element analyses of transport were carried out. Implications of the three-dimensional effects for the design and analysis of future tracer studies are discussed

Correlating Gas Transport Parameters and X-ray Computed Tomography Measurements in Porous Media

DEFF Research Database (Denmark)

Naveed, Muhammad; Hamamoto, Shoichiro; Kawamoto, Ken

2013-01-01

physical processes. The objective of this study was to characterize the relationships between gas transport parameters and soil-pore geometry revealed by X-ray CT. Sands of different shapes with a mean particle diameter (d50) ranging from 0.19 to 1.51 mm were used as porous media under both air...... was found between α and tortuosity calculated from gas transport parameters (Equation (Uncited) Image Tools), indicating that gas dispersivity has a linear and inverse relationship with gas diffusivity. A linear relationship was also found between ka and d50/TUMS2, indicating a strong dependency of ka...

Solute transport in a well under slow-purge and no-purge conditions

Science.gov (United States)

Plummer, M. A.; Britt, S. L.; Martin-Hayden, J. M.

2010-12-01

Non-purge sampling techniques, such as diffusion bags and in-situ sealed samplers, offer reliable and cost-effective groundwater monitoring methods that are a step closer to the goal of real-time monitoring without pumping or sample collection. Non-purge methods are, however, not yet completely accepted because questions remain about how solute concentrations in an unpurged well relate to concentrations in the adjacent formation. To answer questions about how undisturbed well water samples compare to formation concentrations, and to provide the information necessary to interpret results from non-purge monitoring systems, we have conducted a variety of physical experiments and numerical simulations of flow and transport in and through monitoring wells under low-flow and ambient flow conditions. Previous studies of flow and transport in wells used a Darcy’s law - based continuity equation for flow, which is often justified under the strong, forced-convection flow caused by pumping or large vertical hydraulic potential gradients. In our study, we focus on systems with weakly forced convection, where density-driven free convection may be of similar strength. We therefore solved Darcy’s law for porous media domains and the Navier Stokes equations for flow in the well, and coupled solution of the flow equations to that of solute transport. To illustrate expected in-well transport behavior under low-flow conditions, we present results of three particular studies: (1) time-dependent effluent concentrations from a well purged at low-flow pumping rates, (2) solute-driven density effects in a well under ambient horizontal flow and (3) temperature-driven mixing in a shallow well subject to seasonal temperature variations. Results of the first study illustrate that assumptions about the nature of in-well flow have a significant impact on effluent concentration curves even during pumping, with Poiseuille-type flow producing more rapid removal of concentration differences

Positive solutions for a nonlinear periodic boundary-value problem with a parameter

Directory of Open Access Journals (Sweden)

Jingliang Qiu

2012-08-01

Full Text Available Using topological degree theory with a partially ordered structure of space, sufficient conditions for the existence and multiplicity of positive solutions for a second-order nonlinear periodic boundary-value problem are established. Inspired by ideas in Guo and Lakshmikantham [6], we study the dependence of positive periodic solutions as a parameter approaches infinity, $$ lim_{lambdao +infty}|x_{lambda}|=+infty,quadhbox{or}quad lim_{lambdao+infty}|x_{lambda}|=0. $$

One-parameter families of supersymmetric isospectral potentials from Riccati solutions in function composition form

Energy Technology Data Exchange (ETDEWEB)

Rosu, Haret C., E-mail: hcr@ipicyt.edu.mx [IPICYT, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San José 2055, Col. Lomas 4a Sección, 78216 San Luis Potosí, S.L.P. (Mexico); Mancas, Stefan C., E-mail: mancass@erau.edu [Department of Mathematics, Embry–Riddle Aeronautical University, Daytona Beach, FL 32114-3900 (United States); Chen, Pisin, E-mail: pisinchen@phys.ntu.edu.tw [Leung Center for Cosmology and Particle Astrophysics (LeCosPA) and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)

2014-04-15

In the context of supersymmetric quantum mechanics, we define a potential through a particular Riccati solution of the composition form (F∘f)(x)=F(f(x)) and obtain a generalized Mielnik construction of one-parameter isospectral potentials when we use the general Riccati solution. Some examples for special cases of F and f are given to illustrate the method. An interesting result is obtained in the case of a parametric double well potential generated by this method, for which it is shown that the parameter of the potential controls the heights of the localization probability in the two wells, and for certain values of the parameter the height of the localization probability can be higher in the smaller well. -- Highlights: •Function-composition generalization of parametric isospectral potentials is presented. •Mielnik one-parameter family of harmonic potentials is obtained as a particular case. •Graphical discussion of regular and singular regions in the parameter space is given.

Investigation of Transport Parameters of Graphene-Based Nanostructures

Science.gov (United States)

Sergeyev, D. M.; Shunkeyev, K. Sh.

2018-03-01

The paper presents results of computer simulation of the main transport parameters of nanostructures obtained through the row-by-row removal of carbon atoms from graphene ribbon. Research into the electrical parameters is carried out within the density functional theory using the non-equilibrium Green functions in the local-density approximation. Virtual NanoLab based on Atomistix ToolKit is used to construct structures and analyze simulation results. Current-voltage characteristics, differential conductivity and transmittance spectra of nanostructures are calculated at different values of bias voltage. It is found that there is a large region of negative differential resistance in current-voltage characteristics of nanostructures caused by resonant tunneling of quasi-particles. Differential (dI/dV) characteristic also has similar changes. The obtained results can be useful for building novel electronic devices in the field of nanoelectronics.

Study of the transport parameters of cloud lightning plasmas

International Nuclear Information System (INIS)

Chang, Z. S.; Yuan, P.; Zhao, N.

2010-01-01

Three spectra of cloud lightning have been acquired in Tibet (China) using a slitless grating spectrograph. The electrical conductivity, the electron thermal conductivity, and the electron thermal diffusivity of the cloud lightning, for the first time, are calculated by applying the transport theory of air plasma. In addition, we investigate the change behaviors of parameters (the temperature, the electron density, the electrical conductivity, the electron thermal conductivity, and the electron thermal diffusivity) in one of the cloud lightning channels. The result shows that these parameters decrease slightly along developing direction of the cloud lightning channel. Moreover, they represent similar sudden change behavior in tortuous positions and the branch of the cloud lightning channel.

Inference of reactive transport model parameters using a Bayesian multivariate approach

NARCIS (Netherlands)

Carniato, L.; Schoups, G.H.W.; Van de Giesen, N.C.

2014-01-01

Parameter estimation of subsurface transport models from multispecies data requires the definition of an objective function that includes different types of measurements. Common approaches are weighted least squares (WLS), where weights are specified a priori for each measurement, and weighted least

Fibrin structural and diffusional analysis suggests that fibers are permeable to solute transport.

Science.gov (United States)

Leonidakis, Kimon Alexandros; Bhattacharya, Pinaki; Patterson, Jennifer; Vos, Bart E; Koenderink, Gijsje H; Vermant, Jan; Lambrechts, Dennis; Roeffaers, Maarten; Van Oosterwyck, Hans

2017-01-01

Fibrin hydrogels are promising carrier materials in tissue engineering. They are biocompatible and easy to prepare, they can bind growth factors and they can be prepared from a patient's own blood. While fibrin structure and mechanics have been extensively studied, not much is known about the relation between structure and diffusivity of solutes within the network. This is particularly relevant for solutes with a size similar to that of growth factors. A novel methodological approach has been used in this study to retrieve quantitative structural characteristics of fibrin hydrogels, by combining two complementary techniques, namely confocal fluorescence microscopy with a fiber extraction algorithm and turbidity measurements. Bulk rheological measurements were conducted to determine the impact of fibrin hydrogel structure on mechanical properties. From these measurements it can be concluded that variations in the fibrin hydrogel structure have a large impact on the rheological response of the hydrogels (up to two orders of magnitude difference in storage modulus) but only a moderate influence on the diffusivity of dextran solutes (up to 25% difference). By analyzing the diffusivity measurements by means of the Ogston diffusion model we further provide evidence that individual fibrin fibers can be semi-permeable to solute transport, depending on the average distance between individual protofibrils. This can be important for reducing mass transport limitations, for modulating fibrinolysis and for growth factor binding, which are all relevant for tissue engineering. Fibrin is a natural biopolymer that has drawn much interest as a biomimetic carrier in tissue engineering applications. We hereby use a novel combined approach for the structural characterization of fibrin networks based on optical microscopy and light scattering methods that can also be applied to other fibrillar hydrogels, like collagen. Furthermore, our findings on the relation between solute transport

Solution of the within-group multidimensional discrete ordinates transport equations on massively parallel architectures

Science.gov (United States)

Zerr, Robert Joseph

2011-12-01

The integral transport matrix method (ITMM) has been used as the kernel of new parallel solution methods for the discrete ordinates approximation of the within-group neutron transport equation. The ITMM abandons the repetitive mesh sweeps of the traditional source iterations (SI) scheme in favor of constructing stored operators that account for the direct coupling factors among all the cells and between the cells and boundary surfaces. The main goals of this work were to develop the algorithms that construct these operators and employ them in the solution process, determine the most suitable way to parallelize the entire procedure, and evaluate the behavior and performance of the developed methods for increasing number of processes. This project compares the effectiveness of the ITMM with the SI scheme parallelized with the Koch-Baker-Alcouffe (KBA) method. The primary parallel solution method involves a decomposition of the domain into smaller spatial sub-domains, each with their own transport matrices, and coupled together via interface boundary angular fluxes. Each sub-domain has its own set of ITMM operators and represents an independent transport problem. Multiple iterative parallel solution methods have investigated, including parallel block Jacobi (PBJ), parallel red/black Gauss-Seidel (PGS), and parallel GMRES (PGMRES). The fastest observed parallel solution method, PGS, was used in a weak scaling comparison with the PARTISN code. Compared to the state-of-the-art SI-KBA with diffusion synthetic acceleration (DSA), this new method without acceleration/preconditioning is not competitive for any problem parameters considered. The best comparisons occur for problems that are difficult for SI DSA, namely highly scattering and optically thick. SI DSA execution time curves are generally steeper than the PGS ones. However, until further testing is performed it cannot be concluded that SI DSA does not outperform the ITMM with PGS even on several thousand or tens of

Transport of titanium dioxide nanoparticles in saturated porous media under various solution chemistry conditions

International Nuclear Information System (INIS)

Wang Yu; Gao Bin; Morales, Verónica L.; Tian Yuan; Wu Lei; Gao Jie; Bai Wei; Yang Liuyan

2012-01-01

Because of its wide applications, nanosized titanium dioxide may become a potential environmental risk to soil and groundwater system. It is therefore important to improve current understanding of the environmental fate and transport of titanium oxides nanoparticles (TONPs). In this work, the effect of solution chemistry (i.e., pH, ionic strength, and natural organic matter (NOM) concentration) on the deposition and transport of TONPs in saturated porous media was examined in detail. Laboratory columns packed with acid-cleaned quartz sand were used in the experiment as porous media. Transport experiments were conducted with various chemistry combinations, including four ionic strengths, three pH levels, and two NOM concentrations. The results showed that TONP mobility increased with increasing solution pH, but decreased with increasing solution ionic strength. It is also found that the presence of NOM in the system enhanced the mobility of TONPs in the saturated porous media. The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to justify the mobility trends observed in the experimental data. Predictions from the theory agreed excellently with the experimental data.

Influence of hydrostatic pressure on BCC-lattice parameter in molybdenum, niobium and vanadium with rhenium solid solutions

International Nuclear Information System (INIS)

Smol'yaninova, Eh.A.; Stribuk, E.K.; Tyavlovskij, V.I.

1987-01-01

Data on the effect of 1.8GPa hydrostatic pressure on bcc lattice parameters of solid solutions in Mo-Re, Nb-Re, V-re systems are presented. It is shown that after the application hydrostatic pressure a decrease in bcc lattice parameter is observed and the greatest change in the lattice parameter takes place in bcc of solid solutions in the Nb-Re system (DELTA A ∼ 0.0035 nm). Analysis of the experimental data obtained on the basis of calculations made for packing density change in the above-mentioned solid solutions under the pressure is carried out

Applications of stochastic models to solute transport in fractured rocks

International Nuclear Information System (INIS)

Gelhar, L.W.

1987-01-01

A stochastic theory for flow and solute transport in a single variable aperture fracture bounded by sorbing porous matrix into which solutes may diffuse, is developed using a perturbation approximation and spectral solution techniques which assume local statistical homogeneity. The theory predicts that the effective aperture of the fracture for mean solute displacement will be larger than the aperture required to calculate the large-scale flow resistance of the fracture. This ratio of apertures is a function of the variance of the logarithm of the apertures. The theory also predicts the macrodispersion coefficient for large-scale transport in the fracture. The resulting macrodispersivity is proportional to the variance of the logaperture and to its correlation scale. When variable surface sorption is included, it is found that the macrodispersivity is increased significantly, in some cases more than an order of magnitude. It is also shown that the effective retardation coefficient for the sorptively heterogeneous fracture is found by simply taking the arithmetic mean of the local surface sorption coefficient. Matrix diffusion is also shown to increase the fracture macrodispesivity at very large times. A reexamination of the results of four different field tracer tests in crystalline rock in Sweden and Canada shows aperture ratios and dispersivities that are consistent with the stochastic theory. The variance of the natural logarithm of the aperture is found to be in the range of 3 to 6 and the correlation scales for logaperture ranges from .2 to 1.2 meters. Detailed recommendations for additional field investigations at scales ranging from a few meters up to a kilometer are presented. (orig.)

Analytical solution of neutron transport equation in an annular reactor with a rotating pulsed source; Resolucao analitica da equacao de transporte de neutrons em um reator anelar com fonte pulsada rotativa

Energy Technology Data Exchange (ETDEWEB)

Teixeira, Paulo Cleber Mendonca

2002-12-01

In this study, an analytical solution of the neutron transport equation in an annular reactor is presented with a short and rotating neutron source of the type S(x) {delta} (x- Vt), where V is the speed of annular pulsed reactor. The study is an extension of a previous study by Williams [12] carried out with a pulsed source of the type S(x) {delta} (t). In the new concept of annular pulsed reactor designed to produce continuous high flux, the core consists of a subcritical annular geometry pulsed by a rotating modulator, producing local super prompt critical condition, thereby giving origin to a rotating neutron pulse. An analytical solution is obtained by opening up of the annular geometry and applying one energy group transport theory in one dimension using applied mathematical techniques of Laplace transform and Complex Variables. The general solution for the flux consists of a fundamental mode, a finite number of harmonics and a transient integral. A condition which limits the number of harmonics depending upon the circumference of the annular geometry has been obtained. Inverse Laplace transform technique is used to analyse instability condition in annular reactor core. A regenerator parameter in conjunction with perimeter of the ring and nuclear properties is used to obtain stable and unstable harmonics and to verify if these exist. It is found that the solution does not present instability in the conditions stated in the new concept of annular pulsed reactor. (author)

Presentation of some methods for the solution of the monoenergetic neutrons transport equation

International Nuclear Information System (INIS)

Valle G, E. del.

1978-01-01

The neutrons transport theory problems whose solution has been reached were collected in order to show that the transport equation is so complicated that different techniques were developed so as to give approximative numerical solutions to problems concerning the practical application. Such a technique, which had not been investigated in the literature dealing with these problems, is described here. The results which were obtained through this technique in undimensional problems of criticity are satisfactory and speaking in a conceptual way this method is extremely simple because it times. There is no limitation to deal with problems related neutrons sources with an arbitrary distribution and in principle the application of this technique can be extended to unhomogeneous environments. (author)

High frequency longitudinal profiling reveals hydrologic controls on solute sourcing, transport and processing in a karst river

Science.gov (United States)

Hensley, R. T.; Cohen, M. J.; Spangler, M.; Gooseff, M. N.

2017-12-01

The lower Santa Fe River is a large, karst river of north Florida, fed by numerous artesian springs and also containing multiple sink-rise systems. We performed repeated longitudinal profiles collecting very high frequency measurements of multiple stream parameters including temperature, dissolved oxygen, carbon dioxide, pH, dissolved organic matter, nitrate, ammonium, phosphate and turbidity. This high frequency dataset provided a spatially explicit understanding of solute sources and coupled biogeochemical processing rates along the 25 km study reach. We noted marked changes in river profiles as the river transitioned from low to high flow during the onset of the wet season. The role of lateral inflow from springs as the primary solute source was greatly reduced under high flow conditions. Effects of sink-rise systems, which under low flow conditions allow the majority of flow to bypass several kilometer long sections of the main channel, virtually disappeared under high flow conditions. Impeded light transmittance at high flow reduced primary production and by extension assimilatory nutrient uptake. This study demonstrates how high frequency longitudinal profiling can be used to observe how hydrologic conditions can alter groundwater-surface water interactions and modulate the sourcing, transport and biogeochemical processing of stream solutes.

Laboratory experiments on solute transport in bimodal porous media under cyclic precipitation-evaporation boundary conditions

Science.gov (United States)

Cremer, Clemens; Neuweiler, Insa

2016-04-01

Flow and solute transport in the shallow subsurface is strongly governed by atmospheric boundary conditions. Erratically varying infiltration and evaporation cycles lead to alternating upward and downward flow, as well as spatially and temporally varying water contents and associated hydraulic conductivity of the prevailing materials. Thus presenting a highly complicated, dynamic system. Knowledge of subsurface solute transport processes is vital to assess e.g. the entry of, potentially hazardous, solutes to the groundwater and nutrient uptake by plant roots and can be gained in many ways. Besides field measurements and numerical simulations, physical laboratory experiments represent a way to establish process understanding and furthermore validate numerical schemes. With the aim to gain a better understanding and to quantify solute transport in the unsaturated shallow subsurface under natural precipitation conditions in heterogeneous media, we conduct physical laboratory experiments in a 22 cm x 8 cm x 1 cm flow cell that is filled with two types of sand and apply cyclic infiltration-evaporation phases at the soil surface. Pressure at the bottom of the domain is kept constant. Following recent studies (Lehmann and Or, 2009; Bechtold et al., 2011a), heterogeneity is introduced by a sharp vertical interface between coarse and fine sand. Fluorescent tracers are used to i) qualitatively visualize transport paths within the domain and ii) quantify solute leaching at the bottom of the domain. Temporal and spatial variations in water content during the experiment are derived from x-ray radiographic images. Monitored water contents between infiltration and evaporation considerably changed in the coarse sand while the fine sand remained saturated throughout the experiments. Lateral solute transport through the interface in both directions at different depths of the investigated soil columns were observed. This depended on the flow rate applied at the soil surface and

Experimental design for estimating parameters of rate-limited mass transfer: Analysis of stream tracer studies

Science.gov (United States)

Wagner, Brian J.; Harvey, Judson W.

1997-01-01

Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow moving. We present a methodology for (1) evaluating and comparing alternative stream tracer experiment designs and (2) identifying those combinations of stream transport properties that pose limitations to parameter estimation and therefore a challenge to tracer test design. The methodology uses the concept of global parameter uncertainty analysis, which couples solute transport simulation with parameter uncertainty analysis in a Monte Carlo framework. Two general conclusions resulted from this work. First, the solute injection and sampling strategy has an important effect on the reliability of transport parameter estimates. We found that constant injection with sampling through concentration rise, plateau, and fall provided considerably more reliable parameter estimates than a pulse injection across the spectrum of transport scenarios likely encountered in high-gradient streams. Second, for a given tracer test design, the uncertainties in mass transfer and storage-zone parameter estimates are strongly dependent on the experimental Damkohler number, DaI, which is a dimensionless combination of the rates of exchange between the stream and storage zones, the stream-water velocity, and the stream reach length of the experiment. Parameter uncertainties are lowest at DaI values on the order of 1.0. When DaI values are much less than 1.0 (owing to high velocity, long exchange timescale, and/or short reach length), parameter uncertainties are high because only a small amount of tracer interacts with storage zones in the reach. For the opposite conditions (DaI ≫ 1.0), solute

An Overview of Problems and Solutions for Urban Freight Transport in Brazilian Cities

Directory of Open Access Journals (Sweden)

Leise K. Oliveira

2018-04-01

Full Text Available Urban freight transport is a challenge for Brazilian cities due to the lack of adequate planning for freight flow movement. Public managers also show negligence and a lack of awareness when dealing with urban logistics. Decision-support data on urban freight transport are still scarce, despite being of fundamental value to economic development. With this in mind, this paper presents problems and solutions regarding urban freight transport in Brazilian cities. Data were obtained through a survey conducted in nine cities and analysed by means of descriptive statistics and the successive intervals method. Additionally, a cluster analysis was performed to identify patterns regarding the typical characteristics of each city in order to compare and generalise the perception of retailers regarding problems and solutions at the national level. The results indicate divergent opinions among retailers from different cities, even from cities with similar socioeconomic profiles and urban dynamics. The municipalities which demonstrated the most similarities were (i Betim and Niteroi, in the Southeast of Brazil; (ii Palmas and Quixada, in the North and Northeast, respectively; and (iii Palmas and Caruaru, also in the North and Northeast. The results reinforce the importance of studying the local context and involving stakeholders in the process of planning urban logistics solutions.

Evaluation of unsaturated-zone solute-transport models for studies of agricultural chemicals

Science.gov (United States)

Nolan, Bernard T.; Bayless, E. Randall; Green, Christopher T.; Garg, Sheena; Voss, Frank D.; Lampe, David C.; Barbash, Jack E.; Capel, Paul D.; Bekins, Barbara A.

2005-01-01

Seven unsaturated-zone solute-transport models were tested with two data sets to select models for use by the Agricultural Chemical Team of the U.S. Geological Survey's National Water-Quality Assessment Program. The data sets were from a bromide tracer test near Merced, California, and an atrazine study in the White River Basin, Indiana. In this study the models are designated either as complex or simple based on the water flux algorithm. The complex models, HYDRUS2D, LEACHP, RZWQM, and VS2DT, use Richards' equation to simulate water flux and are well suited to process understanding. The simple models, CALF, GLEAMS, and PRZM, use a tipping-bucket algorithm and are more amenable to extrapolation because they require fewer input parameters. The purpose of this report is not to endorse a particular model, but to describe useful features, potential capabilities, and possible limitations that emerged from working with the model input data sets. More rigorous assessment of model applicability involves proper calibration, which was beyond the scope of this study.

A nonequilibrium model for reactive contaminant transport through fractured porous media: Model development and semianalytical solution

Science.gov (United States)

Joshi, Nitin; Ojha, C. S. P.; Sharma, P. K.

2012-10-01

In this study a conceptual model that accounts for the effects of nonequilibrium contaminant transport in a fractured porous media is developed. Present model accounts for both physical and sorption nonequilibrium. Analytical solution was developed using the Laplace transform technique, which was then numerically inverted to obtain solute concentration in the fracture matrix system. The semianalytical solution developed here can incorporate both semi-infinite and finite fracture matrix extent. In addition, the model can account for flexible boundary conditions and nonzero initial condition in the fracture matrix system. The present semianalytical solution was validated against the existing analytical solutions for the fracture matrix system. In order to differentiate between various sorption/transport mechanism different cases of sorption and mass transfer were analyzed by comparing the breakthrough curves and temporal moments. It was found that significant differences in the signature of sorption and mass transfer exists. Applicability of the developed model was evaluated by simulating the published experimental data of Calcium and Strontium transport in a single fracture. The present model simulated the experimental data reasonably well in comparison to the model based on equilibrium sorption assumption in fracture matrix system, and multi rate mass transfer model.

Critically ill neonates displayed stable vital parameters and reduced metabolic acidosis during neonatal emergency airborne transport in Sweden.

Science.gov (United States)

Frid, Ingrid; Ågren, Johan; Kjellberg, Mattias; Normann, Erik; Sindelar, Richard

2018-02-26

This study evaluated the medical quality of acute airborne transports carried out by a neonatal emergency transport service in a Swedish healthcare region from 2012 to 2015. The transport charts and patient records of all infants transported to the regional centre were reviewed for transport indications and vital parameters and outcomes. We identified 187 acute airborne transports and the main indications for referral were therapeutic hypothermia after perinatal asphyxia, extremely preterm birth and respiratory failure. There were 37 deaths, but none of these occurred during transport and none of the deaths that occurred within 24 hours after transport were found to be related to the transport per se. No differences were found in vital parameters or ventilator settings before and after transport, except for an improvement in blood pH (7.22 ± 0.13 versus 7.27 ± 0.13, mean ± SD, p < 0.01), due to a decrease in base deficit (-8.0 ± 6.8 versus -5.4 ± 6.3 mmol, p < 0.001), while the partial pressure of carbon dioxide remained unchanged. During air transport, critically ill neonates displayed stable vital parameters and reduced metabolic acidosis. No transport-related mortality was found, but the high number of extremely preterm infants transported indicates the potential for improving in-utero transport. ©2018 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

Derivation and solution of a time-dependent, nonlinear, Schrodinger-like equation for the superconductivity order parameter

International Nuclear Information System (INIS)

Esrick, M.A.

1981-01-01

A time-dependent, nonlinear, Schrodinger-like equation for the superconductivity order parameter is derived from the Gor'kov equations. Three types of traveling wave solutions of the equation are discussed. The phases and amplitudes of these solutions propagate at different speeds. The first type of solution has an amplitude that propagates as a soliton and it is suggested that this solution might correspond to the recently observed propagating collective modes of the order parameter. The amplitude of the second type of solution propagates as a periodic disturbance in space and time. It is suggested that this type of solution might explain the recently observed multiple values of the superconductor energy gap as well as the spatially inhomogenous superconducting state. The third type of solution, which is of a more general character, might provide some insight into non-periodic, inhomogeneous states occuring in superconductors. It is also proposed that quasiparticle injection and microwave irradiation might generate soliton-like disturbances in superconductors

Control of optical transport parameters of 'porous medium – supercritical fluid' systems

Energy Technology Data Exchange (ETDEWEB)

Zimnyakov, D A; Ushakova, O V; Yuvchenko, S A [Yuri Gagarin State Technical University of Saratov, Saratov (Russian Federation); Bagratashvili, V N [M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

2015-11-30

The possibility of controlling optical transport parameters (in particular, transport scattering coefficient) of porous systems based on polymer fibres, saturated with carbon dioxide in different phase states (gaseous, liquid and supercritical) has been experimentally studied. An increase in the pressure of the saturating medium leads to a rise of its refractive index and, correspondingly, the diffuse-transmission coefficient of the system due to the decrease in the transport scattering coefficient. It is shown that, in the case of subcritical saturating carbon dioxide, the small-angle diffuse transmission of probed porous layers at pressures close to the saturated vapour pressure is determined by the effect of capillary condensation in pores. The immersion effect in 'porous medium – supercritical fluid' systems, where the fluid pressure is used as a control parameter, is considered. The results of reconstructing the values of transport scattering coefficient of probed layers for different refractive indices of a saturating fluid are presented. (radiation scattering)

Solutes transport in unsaturated double-porosity medium. Modelling by homogenization and applications

International Nuclear Information System (INIS)

Tran Ngoc, T.D.

2008-07-01

This Ph.D thesis presents the development of the solute transport models in unsaturated double-porosity medium, by using the asymptotic homogenization method. The obtained macroscopic models concern diffusion, diffusion-convection and dispersion-convection, according to the transport regime which is characterized by the non-dimensional numbers. The models consist of two coupled equations that show the local non-equilibrium of concentrations. The double-porosity transport models were numerically implemented using the code COMSOL Multiphysics (finite elements method), and compared with the solution of the same problem at the fine scale. The implementation allows solving the coupled equations in the macro- and micro-porosity domains (two-scale computations). The calculations of the dispersion tensor as a solution of the local boundary value problems, were also conducted. It was shown that the dispersivity depends on the saturation, the physical properties of the macro-porosity domain and the internal structure of the double-porosity medium. Finally, two series of experiments were performed on a physical model of double-porosity that is composed of a periodic assemblage of sintered clay spheres in Hostun sand HN38. The first experiment was a drainage experiment, which was conducted in order to validate the unsaturated flow model. The second series was a dispersion experiment in permanent unsaturated water flow condition (water content measured by gamma ray attenuation technique). A good agreement between the numerical simulations and the experimental observations allows the validation of the developed models. (author)

Solute transport in fractured rock - applications to radionuclide waste repositories

International Nuclear Information System (INIS)

Neretnieks, I.

1990-12-01

Flow and solute transport in fractured rocks has been intensively studied in the last decade. The increased interest is mainly due to the plans in many countries to site repositories for high level nuclear waste in deep geologic formations. All investigated crystalline rocks have been found to be fractured and most of the water flows in the fractures and fracture zones. The water transports dissolved species and radionuclides. It is thus of interest to be able to understand and to do predictive modelling of the flowrate of water, the flowpaths and the residence times of the water and of the nuclides. The dissolved species including the nuclides will interact with the surrounding rock in different ways and will in many cases be strongly retarded relative to the water velocity. Ionic species may be ion exchanged or sorbed in the mineral surfaces. Charges and neutral species may diffuse into the stagnant waters in the rock matrix and thus be withdrawn from the mobile water. These effects will be strongly dependent on how much rock surface is in contact with the flowing water. It has been found in a set of field experiments and by other observations that not all fractures conduct water. Furthermore it is found that conductive fractures only conduct the water in a small part of the fracture in what is called channels or preferential flowpaths. This report summarizes the present concepts of water flow and solute transport in fractured rocks. The data needs for predictive modelling are discussed and both field and laboratory measurement which have been used to obtain data are described. Several large scale field experiments which have been specially designed to study flow and tracer transport in crystalline rocks are described. In many of the field experients new techniques have been developed and used. (81 refs.) (author)

Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale

DEFF Research Database (Denmark)

Koestel, J. K.; Nørgaard, Trine; Loung, N. M.

2013-01-01

It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables......, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field...... to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column...

Solution of stochastic media transport problems using a numerical quadrature-based method

International Nuclear Information System (INIS)

Pautz, S. D.; Franke, B. C.; Prinja, A. K.; Olson, A. J.

2013-01-01

We present a new conceptual framework for analyzing transport problems in random media. We decompose such problems into stratified subproblems according to the number of material pseudo-interfaces within realizations. For a given subproblem we assign pseudo-interface locations in each realization according to product quadrature rules, which allows us to deterministically generate a fixed number of realizations. Quadrature integration of the solutions of these realizations thus approximately solves each subproblem; the weighted superposition of solutions of the subproblems approximately solves the general stochastic media transport problem. We revisit some benchmark problems to determine the accuracy and efficiency of this approach in comparison to randomly generated realizations. We find that this method is very accurate and fast when the number of pseudo-interfaces in a problem is generally low, but that these advantages quickly degrade as the number of pseudo-interfaces increases. (authors)

Capillary-Driven Solute Transport and Precipitation in Porous Media during Dry-Out

Science.gov (United States)

Ott, Holger; Andrew, Matthew; Blunt, Martin; Snippe, Jeroen

2014-05-01

The injection of dry or under-saturated gases or supercritical (SC) fluids into water bearing formations might lead to a formation dry-out in the vicinity of the injection well. The dry-out is caused by the evaporation/dissolution of formation water into the injected fluid and the subsequent transport of dissolved water in the injected fluid away from the injection well. Dry-out results in precipitation from solutes of the formation brine and consequently leads to a reduction of the rock's pore space (porosity) and eventually to a reduction of permeability near the injection well, or even to the loss of injectivity. Recently evidence has been found that the complexity of the pore space and the respective capillary driven solute transport plays a key role. While no effective-permeability (Keff) reduction was observed in a single-porosity sandstone, multi porosity carbonate rocks responded to precipitation with a strong reduction of Keff. The reason for the different response of Keff to salt precipitation is suspected to be in the exact location of the precipitate (solid salt) in the pore space. In this study, we investigate dry-out and salt precipitation due to supercritical CO2 injection in single and multi-porosity systems under near well-bore conditions. We image fluid saturation changes by means of μCT scanning during desaturation. We are able to observe capillary driven transport of the brine phase and the respective transport of solutes on the rock's pore scale. Finally we have access to the precipitated solid-salt phase and their distribution. The results can proof the thought models behind permeability porosity relationships K(φ) for injectivity modeling. The topic and the mechanisms we show are of general interest for drying processes in porous material such as soils and paper.

Colloid transport in dual-permeability media

Science.gov (United States)

Leij, Feike J.; Bradford, Scott A.

2013-07-01

It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the increased risks for disease caused by microorganisms and colloid-associated contaminants. This study presents a model for colloid transport in dual-permeability media that includes reversible and irreversible retention of colloids and first-order exchange between the aqueous phases of the two regions. The model may also be used to describe transport of other reactive solutes in dual-permeability media. Analytical solutions for colloid concentrations in aqueous and solid phases were obtained using Laplace transformation and matrix decomposition. The solutions proved convenient to assess the effect of model parameters on the colloid distribution. The analytical model was used to describe effluent concentrations for a bromide tracer and 3.2- or 1-μm-colloids that were observed after transport through a composite 10-cm long porous medium made up of a cylindrical lens or core of sand and a surrounding matrix with sand of a different grain size. The tracer data were described very well and realistic estimates were obtained for the pore-water velocity in the two flow domains. An accurate description was also achieved for most colloid breakthrough curves. Dispersivity and retention parameters were typically greater for the larger 3.2-μm-colloids while both reversible and irreversible retention rates tended to be higher for the finer sands than the coarser sand. The relatively small sample size and the complex flow pattern in the composite medium made it difficult to reach definitive conclusions regarding transport parameters for colloid transport.

Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale

Science.gov (United States)

Koestel, J. K.; Norgaard, T.; Luong, N. M.; Vendelboe, A. L.; Moldrup, P.; Jarvis, N. J.; Lamandé, M.; Iversen, B. V.; Wollesen de Jonge, L.

2013-02-01

It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field site in Silstrup (Denmark) at a sampling distance of approximately 15 m (with a few exceptions), covering an area of approximately 1 ha (60 m × 165 m). For 64 of the 65 investigated soil columns, we observed BTC shapes indicating a strong preferential transport. The strength of preferential transport was positively correlated with the bulk density and the degree of water saturation. The latter suggests that preferential macropore transport was the dominating transport process. Increased bulk densities were presumably related with a decrease in near-saturated hydraulic conductivities and as a consequence to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column scale have to be upscaled when applied to the field scale or larger.

Longitudinal dispersion coefficients for numerical modeling of groundwater solute transport in heterogeneous formations.

Science.gov (United States)

Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K

2017-09-15

Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion

Groundwater and solute transport modeling at Hyporheic zone of upper part Citarum River

Science.gov (United States)

Iskandar, Irwan; Farazi, Hendy; Fadhilah, Rahmat; Purnandi, Cipto; Notosiswoyo, Sudarto

2017-06-01

Groundwater and surface water interaction is an interesting topic to be studied related to the water resources and environmental studies. The study of interaction between groundwater and river water at the Upper Part Citarum River aims to know the contribution of groundwater to the river or reversely and also solute transport of dissolved ions between them. Analysis of drill logs, vertical electrical sounding at the selected sections, measurement of dissolved ions, and groundwater modeling were applied to determine the flow and solute transport phenomena at the hyporheic zone. It showed the hyporheic zone dominated by silt and clay with hydraulic conductivity range from 10-4∼10-8 m/s. The groundwater flowing into the river with very low gradient and it shows that the Citarum River is a gaining stream. The groundwater modeling shows direct seepage of groundwater into the Citarum River is only 186 l/s, very small compared to the total discharge of the river. Total dissolved ions of the groundwater ranged from 200 to 480 ppm while the river water range from 200 to 2,000 ppm. Based on solute transport modeling it indicates dissolved ions dispersion of the Citarum River into groundwater may occur in some areas such as Bojongsoang-Dayeuh Kolot and Nanjung. This situation would increase the dissolved ions in groundwater in the region due to the contribution of the Citarum River. The results of the research can be a reference for further studies related to the mechanism of transport of the pollutants in the groundwater around the Citarum River.

Two-dimensional finite element solution for the simultaneous transport of water and solutes through a nonhomogeneous aquifer under transient saturated unsaturated flow conditions

International Nuclear Information System (INIS)

Gureghian, A.B.

1979-01-01

A mathematical model of ground water transport through an aquifer is presented. The solute of interest is a metal tracer or radioactive material which may undergo decay through a sorbing unconfined aquifer. The subject is developed under the following headings: flow equation, solute equation, boundary conditions, finite element formulation, element formulation, solution scheme (flow equation, solute equation), results and discussions, water movement in a ditch drained aquifer under transient state, water and solute movement in a homogeneous and unsaturated soil, transport of 226 Ra in nonhomogeneous aquifer, tailings pond lined, and tailings pond unlined. It is concluded that this mathematical model may have a wide variety of applications. The uranium milling industry may find it useful to evaluate the hydrogeological suitability of their disposal sites. It may prove suited for the design of clay disposal ponds destined to hold hazardous liquids. It may also provide a means of estimating the long-term impact of radionuclides or other pollutants on the quality of ground water. 31 references, 9 figures, 3 tables

Radionuclide transport through heteogeneous media

International Nuclear Information System (INIS)

Hadermann, J.

1980-01-01

One-dimensional radionuclide migration for conevective water transport with sorption and longitudinal dispersion is investigated. A semianalytic solution for layered media with piecewise constant parametes can be written when taking into account mass conservation and approximate flux conservation at interlayer boundaries. The solution is analytic in the first layer and allows for a recursive calculation in the following layers. Scaling laws for the relevant parameters can be formulated. Numerical examples exhibit the importance of at least a single highly sorbing layer. Small values of dispersivity may not lead to a conservative estimate of conservation at the geological column's end

Determination of Transport Properties From Flowing Fluid Temperature Logging In Unsaturated Fractured Rocks: Theory And Semi-Analytical Solution

International Nuclear Information System (INIS)

Mukhopadhyay, Sumit; Tsang, Yvonne W.

2008-01-01

Flowing fluid temperature logging (FFTL) has been recently proposed as a method to locate flowing fractures. We argue that FFTL, backed up by data from high-precision distributed temperature sensors, can be a useful tool in locating flowing fractures and in estimating the transport properties of unsaturated fractured rocks. We have developed the theoretical background needed to analyze data from FFTL. In this paper, we present a simplified conceptualization of FFTL in unsaturated fractured rock, and develop a semianalytical solution for spatial and temporal variations of pressure and temperature inside a borehole in response to an applied perturbation (pumping of air from the borehole). We compare the semi-analytical solution with predictions from the TOUGH2 numerical simulator. Based on the semi-analytical solution, we propose a method to estimate the permeability of the fracture continuum surrounding the borehole. Using this proposed method, we estimated the effective fracture continuum permeability of the unsaturated rock hosting the Drift Scale Test (DST) at Yucca Mountain, Nevada. Our estimate compares well with previous independent estimates for fracture permeability of the DST host rock. The conceptual model of FFTL presented in this paper is based on the assumptions of single-phase flow, convection-only heat transfer, and negligible change in system state of the rock formation. In a sequel paper (Mukhopadhyay et al., 2008), we extend the conceptual model to evaluate some of these assumptions. We also perform inverse modeling of FFTL data to estimate, in addition to permeability, other transport parameters (such as porosity and thermal conductivity) of unsaturated fractured rocks

Transport of a nonneutral electron plasma due to electron collisions with neutral atoms

International Nuclear Information System (INIS)

Douglas, M.H.; O'Neil, T.M.

1978-01-01

Transport of a nonneutral electron plasma across a magnetic field is caused by electron scattering from ambient neutral atoms. A theoretical model of such transport is presented, assuming the plasma is quiescent and the scattering is elastic scattering from infinite mass scattering centers of constant momentum transfer cross section. This model is motivated by recent experiments. A reduced transport equation is obtained by expanding the Boltzmann equation for the electron distribution in inverse powers of the magnetic field. The equation together with Poisson's equation for the radial electric field, which must exist in a nonneutral column, determine the evolution of the system. When these two equations are properly scaled, they contain only a single parameter: the ratio of initial Debye length to initial column radius. For cases where this parameter is either large or small, analytical solutions, or at least partial solutions, are obtained. For intermediate values of the parameter, numerical solutions are obtained

Analytical solution and simplified analysis of coupled parent-daughter steady-state transport with multirate mass transfer

Science.gov (United States)

R. Haggerty

2013-01-01

In this technical note, a steady-state analytical solution of concentrations of a parent solute reacting to a daughter solute, both of which are undergoing transport and multirate mass transfer, is presented. Although the governing equations are complicated, the resulting solution can be expressed in simple terms. A function of the ratio of concentrations, In (daughter...

Application of synthetic diffusion method in the numerical solution of the equations of neutron transport in slab geometry

International Nuclear Information System (INIS)

Valdes Parra, J.J.

1986-01-01

One of the main problems in reactor physics is to determine the neutron distribution in reactor core, since knowing that, it is possible to calculate the rapidity of occurrence of different nuclear reaction inside the reactor core. Within different theories existing in nuclear reactor physics, is neutron transport the one in which equation who govern the exact behavior of neutronic distribution are developed even inside the proper neutron transport theory, there exist different methods of solution which are approximations to exact solution; still more, with the purpose to reach a more precise solution, the majority of methods have been approached to the obtention of solutions in numerical form with the aim of take the advantages of modern computers, and for this reason a great deal of effort is dedicated to numerical solution of the equations of neutron transport. In agreement with the above mentioned, in this work has been developed a computer program which uses a relatively new techniques known as 'acceleration of synthetic diffusion' which has been applied to solve the neutron transport equation with 'classical schemes of spatial integration' obtaining results with a smaller quantity of interactions, if they compare to done without using such equation (Author)

Volume-weighted particle-tracking method for solute-transport modeling; Implementation in MODFLOW–GWT

Science.gov (United States)

Winston, Richard B.; Konikow, Leonard F.; Hornberger, George Z.

2018-02-16

In the traditional method of characteristics for groundwater solute-transport models, advective transport is represented by moving particles that track concentration. This approach can lead to global mass-balance problems because in models of aquifers having complex boundary conditions and heterogeneous properties, particles can originate in cells having different pore volumes and (or) be introduced (or removed) at cells representing fluid sources (or sinks) of varying strengths. Use of volume-weighted particles means that each particle tracks solute mass. In source or sink cells, the changes in particle weights will match the volume of water added or removed through external fluxes. This enables the new method to conserve mass in source or sink cells as well as globally. This approach also leads to potential efficiencies by allowing the number of particles per cell to vary spatially—using more particles where concentration gradients are high and fewer where gradients are low. The approach also eliminates the need for the model user to have to distinguish between “weak” and “strong” fluid source (or sink) cells. The new model determines whether solute mass added by fluid sources in a cell should be represented by (1) new particles having weights representing appropriate fractions of the volume of water added by the source, or (2) distributing the solute mass added over all particles already in the source cell. The first option is more appropriate for the condition of a strong source; the latter option is more appropriate for a weak source. At sinks, decisions whether or not to remove a particle are replaced by a reduction in particle weight in proportion to the volume of water removed. A number of test cases demonstrate that the new method works well and conserves mass. The method is incorporated into a new version of the U.S. Geological Survey’s MODFLOW–GWT solute-transport model.

Parameters of Transportation of Tailings of Metals Lixiviating

Science.gov (United States)

Golik, Vladimir; Dmitrak, Yury

2017-11-01

The article shows that the change in the situation in the metals market with a steady increase in production volumes is intensified against the tendency of the transition of mining production from underground mining to underground mining for a certain group of ores. The possibility of a non-waste metals extraction from not only standard, but also from substandard raw materials, is currently provided only by technology with the lixiviating of metals from developing ores. The regular dependences of the magnitude of hydraulic resistances on the hydro-mixture velocity and its density are determined. The correct values of the experimental data convergence with the calculated values of these parameters are obtained. It is shown that the optimization of the transportation parameters of lixiviating tailings allows reducing the level of chemically dangerous pollution of the environment by leachate products. The direction of obtaining the ecological and technological effect from the use of simultaneously environmental and resource-saving technology for the extraction of the disclosed metals is indicated.

Transcellular movement of hydroxyurea is mediated by specific solute carrier transporters

Science.gov (United States)

Walker, Aisha L.; Franke, Ryan M.; Sparreboom, Alex; Ware, Russell E.

2015-01-01

Objective Hydroxyurea has proven laboratory and clinical therapeutic benefits for sickle cell anemia (SCA) and other diseases, yet many questions remain regarding its in vivo pharmacokinetic and pharmacodynamic profiles. Previous reports suggest that hydroxyurea passively diffuses across cells, but its observed rapid absorption and distribution are more consistent with facilitated or active transport. We investigated the potential role of solute carrier (SLC) transporters in cellular uptake and accumulation of hydroxyurea. Materials and Methods Passive diffusion of hydroxyurea across cell membranes was determined using the parallel artificial membrane permeability assay. SLC transporter screens were conducted using in vitro intracellular drug accumulation and transcellular transport assays in cell lines and oocytes overexpressing SLC transporters. Gene expression of SLC transporters was measured by real-time PCR in human tissues and cell lines. Results Hydroxyurea had minimal diffusion across a lipid bilayer but was a substrate for 5 different SLC transporters belonging to the OCTN and OATP families of transporters and urea transporters A and B. Further characterization of hydroxyurea transport revealed that cellular uptake by OATP1B3 is time and temperature dependent and inhibited by known substrates of OATP1B3. Urea transporters A and B are expressed differentially in human tissues and erythroid cells, and transport hydroxyurea bidirectionally via facilitated diffusion. Conclusions These studies provide new insight into drug transport proteins that may be involved in the in vivo absorption, cellular distribution, and elimination of hydroxyurea. Elucidation of hydroxyurea transcellular movement should improve our understanding of its pharmacokinetics and pharmacodynamics, and may help explain some of the inter-patient drug variability observed in patients with SCA. PMID:21256917

ipole: Semianalytic scheme for relativistic polarized radiative transport

Science.gov (United States)

Moscibrodzka, Monika; Gammie, Charles F.

2018-04-01

ipole is a ray-tracing code for covariant, polarized radiative transport particularly useful for modeling Event Horizon Telescope sources, though may also be used for other relativistic transport problems. The code extends the ibothros scheme for covariant, unpolarized transport using two representations of the polarized radiation field: in the coordinate frame, it parallel transports the coherency tensor, and in the frame of the plasma, it evolves the Stokes parameters under emission, absorption, and Faraday conversion. The transport step is as spacetime- and coordinate- independent as possible; the emission, absorption, and Faraday conversion step is implemented using an analytic solution to the polarized transport equation with constant coefficients. As a result, ipole is stable, efficient, and produces a physically reasonable solution even for a step with high optical depth and Faraday depth.

Engineering solutions of traffic safety problems of road transport

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M. Bogdevičius

2004-02-01

Full Text Available The authors of this paper focus on the simulation of the motor vehicle movement (taking into consideration motor vehicle dynamics, motor vehicle hydraulic brake system influence on motor vehicle movement, interaction between its wheels with road pavements, road guardrail characteristics, interaction between motor vehicle and road guardrail on a certain road section and propose their specific solution of this problem. The presented results, illustrating the motor vehicle movement trajectories (motor vehicle braking and interaction between motor vehicle and road guardrail at various initial conditions and at various certain pavement surface of the road section under investigation and work of a motor vehicle hydraulic brake system. Taking into consideration the presented general mathematical model and computer aided test results it is possible to investigate various road transport traffic situations as well as to investigate various transport traffic safety problems.

Non-cooperative and cooperative solutions of government subsidy on public transportation

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Husniah Hennie

2018-01-01

Full Text Available The paper deals with two models of government subsidy given to a public transport operator: (i the subsidy for buying bus from an appointed public transport manufacturer, and (ii the subsidy for reimbursing reduced ticket price for passengers. The models are developed to determine the maximum profit for both the public transport operator and the manufacturer. Since we consider two parties – the public transport operator and the manufacturer of the bus, then we use game theoretical approach by considering non-cooperative and cooperative solutions. Furthermore, since the bus is repairable we consider virtual age to model the preventive maintenance and we consider minimal repair to model the corrective maintenance. We analyse both type of subsidy models and give some numerical examples which show the effects of different subsidies to the profit of operator and manufacturer. The result of the numerical examples indicates that reducing ticket price would give a higher profit both to the operator and the manufacturer.

Characterization of a novel sialic acid transporter of the sodium solute symporter (SSS) family and in vivo comparison with known bacterial sialic acid transporters.

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Severi, Emmanuele; Hosie, Arthur H F; Hawkhead, Judith A; Thomas, Gavin H

2010-03-01

The function of sialic acids in the biology of bacterial pathogens is reflected by the diverse range of solute transporters that can recognize these sugar acids. Here, we use an Escherichia coliDeltananT strain to characterize the function of known and proposed bacterial sialic acid transporters. We discover that the STM1128 gene from Salmonella enterica serovar Typhimurium, which encodes a member of the sodium solute symporter family, is able to restore growth on sialic acid to the DeltananT strain and is able to transport [(14)C]-sialic acid. Using the DeltananT genetic background, we performed a direct in vivo comparison of the transport properties of the STM1128 protein with those of sialic acid transporters of the major facilitator superfamily and tripartite ATP-independent periplasmic families, E. coli NanT and Haemophilus influenzae SiaPQM, respectively. This revealed that both STM1128 and SiaPQM are sodium-dependent and, unlike SiaPQM, both STM1128 and NanT are reversible secondary carriers, demonstrating qualitative functional differences in the properties of sialic acid transporters used by bacteria that colonize humans.

The composite water and solute transport of barley (Hordeum vulgare) roots: effect of suberized barriers.

Science.gov (United States)

Ranathunge, Kosala; Kim, Yangmin X; Wassmann, Friedrich; Kreszies, Tino; Zeisler, Viktoria; Schreiber, Lukas

2017-03-01

Roots have complex anatomical structures, and certain localized cell layers develop suberized apoplastic barriers. The size and tightness of these barriers depend on the growth conditions and on the age of the root. Such complex anatomical structures result in a composite water and solute transport in roots. Development of apoplastic barriers along barley seminal roots was detected using various staining methods, and the suberin amounts in the apical and basal zones were analysed using gas chromatography-mass spectometry (GC-MS). The hydraulic conductivity of roots ( Lp r ) and of cortical cells ( Lp c ) was measured using root and cell pressure probes. When grown in hydroponics, barley roots did not form an exodermis, even at their basal zones. However, they developed an endodermis. Endodermal Casparian bands first appeared as 'dots' as early as at 20 mm from the apex, whereas a patchy suberin lamellae appeared at 60 mm. The endodermal suberin accounted for the total suberin of the roots. The absolute amount in the basal zone was significantly higher than in the apical zone, which was inversely proportional to the Lp r . Comparison of Lp r and Lp c suggested that cell to cell pathways dominate for water transport in roots. However, the calculation of Lp r from Lp c showed that at least 26 % of water transport occurs through the apoplast. Roots had different solute permeabilities ( P sr ) and reflection coefficients ( σ sr ) for the solutes used. The σ sr was below unity for the solutes, which have virtually zero permeability for semi-permeable membranes. Suberized endodermis significantly reduces Lp r of seminal roots. The water and solute transport across barley roots is composite in nature and they do not behave like ideal osmometers. The composite transport model should be extended by adding components arranged in series (cortex, endodermis) in addition to the currently included components arranged in parallel (apoplastic, cell to cell pathways). © The

Analytical solution for multi-species contaminant transport in finite media with time-varying boundary conditions

Science.gov (United States)

Most analytical solutions available for the equations governing the advective-dispersive transport of multiple solutes undergoing sequential first-order decay reactions have been developed for infinite or semi-infinite spatial domains and steady-state boundary conditions. In this work we present an ...

Molecular dispersion energy parameters for alkali and halide ions in aqueous solution

International Nuclear Information System (INIS)

Reiser, S.; Deublein, S.; Hasse, H.; Vrabec, J.

2014-01-01

Thermodynamic properties of aqueous solutions containing alkali and halide ions are determined by molecular simulation. The following ions are studied: Li + , Na + , K + , Rb + , Cs + , F − , Cl − , Br − , and I − . The employed ion force fields consist of one Lennard-Jones (LJ) site and one concentric point charge with a magnitude of ±1 e. The SPC/E model is used for water. The LJ size parameter of the ion models is taken from Deublein et al. [J. Chem. Phys. 136, 084501 (2012)], while the LJ energy parameter is determined in the present study based on experimental self-diffusion coefficient data of the alkali cations and the halide anions in aqueous solutions as well as the position of the first maximum of the radial distribution function of water around the ions. On the basis of these force field parameters, the electric conductivity, the hydration dynamics of water molecules around the ions, and the enthalpy of hydration is predicted. Considering a wide range of salinity, this study is conducted at temperatures of 293.15 and 298.15 K and a pressure of 1 bar

Solute carrier transporters: potential targets for digestive system neoplasms

OpenAIRE

Xie, Jing; Zhu, Xiao Yan; Liu, Lu Ming; Meng, Zhi Qiang

2018-01-01

Jing Xie,1,2 Xiao Yan Zhu,1,2 Lu Ming Liu,1,2 Zhi Qiang Meng1,2 1Department of Integrative Oncology, Fudan University Shanghai Cancer Center, 2Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, People’s Republic of China Abstract: Digestive system neoplasms are the leading causes of cancer-related death all over the world. Solute carrier (SLC) superfamily is composed of a series of transporters that are ubiquitously expressed in organs and tissues o...

Coupled Transport Phenomena in the Opalinus Clay: Implications for Radionuclide Transport

International Nuclear Information System (INIS)

Soler, J.M.

1999-09-01

Coupled phenomena (thermal and chemical osmosis, hyperfiltration, coupled diffusion, thermal diffusion, thermal filtration, Dufour effect) may play an important role in fluid, solute and heat transport in clay-rich formations, such as the Opalinus Clay (OPA), which are being considered as potential hosts for radioactive waste repositories. In this study, the potential effects of coupled phenomena on radionuclide transport in the vicinity of a repository for vitrified high-level radioactive waste (HLW) and spent nuclear fuel (SF) hosted by the Opalinus Clay, at times equal to or greater than the expected lifetime of the waste canisters (about 1000 years), have been addressed. Firstly, estimates of the solute fluxes associated with chemical osmosis, hyperfiltration, thermal diffusion and thermal osmosis have been calculated. Available experimental data concerning coupled transport phenomena in compacted clays, and the hydrogeological and geochemical conditions to which the Opalinus Clay is subject, have been used for these estimates. These estimates suggest that thermal osmosis is the only coupled transport mechanism that could have a strong impact on solute and fluid transport in the vicinity of the repository. Secondly, estimates of the heat fluxes associated with thermal filtration and the Dufour effect in the vicinity of the repository have been calculated. The calculated heat fluxes are absolutely negligible compared to the heat flux caused by thermal conduction. As a further step to obtain additional insight into the effects of coupled phenomena on solute transport, the solute fluxes associated with advection, chemical diffusion, thermal and chemical osmosis, hyperfiltration and thermal diffusion have been incorporated into a simple one-dimensional transport equation. The analytical solution of this equation, with appropriate parameters, shows again that thermal osmosis is the only coupled transport mechanism that could have a strong effect on repository

Coupled Transport Phenomena in the Opalinus Clay: Implications for Radionuclide Transport

Energy Technology Data Exchange (ETDEWEB)

Soler, J.M.

1999-09-01

Coupled phenomena (thermal and chemical osmosis, hyperfiltration, coupled diffusion, thermal diffusion, thermal filtration, Dufour effect) may play an important role in fluid, solute and heat transport in clay-rich formations, such as the Opalinus Clay (OPA), which are being considered as potential hosts for radioactive waste repositories. In this study, the potential effects of coupled phenomena on radionuclide transport in the vicinity of a repository for vitrified high-level radioactive waste (HLW) and spent nuclear fuel (SF) hosted by the Opalinus Clay, at times equal to or greater than the expected lifetime of the waste canisters (about 1000 years), have been addressed. Firstly, estimates of the solute fluxes associated with chemical osmosis, hyperfiltration, thermal diffusion and thermal osmosis have been calculated. Available experimental data concerning coupled transport phenomena in compacted clays, and the hydrogeological and geochemical conditions to which the Opalinus Clay is subject, have been used for these estimates. These estimates suggest that thermal osmosis is the only coupled transport mechanism that could have a strong impact on solute and fluid transport in the vicinity of the repository. Secondly, estimates of the heat fluxes associated with thermal filtration and the Dufour effect in the vicinity of the repository have been calculated. The calculated heat fluxes are absolutely negligible compared to the heat flux caused by thermal conduction. As a further step to obtain additional insight into the effects of coupled phenomena on solute transport, the solute fluxes associated with advection, chemical diffusion, thermal and chemical osmosis, hyperfiltration and thermal diffusion have been incorporated into a simple one-dimensional transport equation. The analytical solution of this equation, with appropriate parameters, shows again that thermal osmosis is the only coupled transport mechanism that could have a strong effect on repository

A mass conservative numerical solution of vertical water flow and mass transport equations in unsaturated porous media

International Nuclear Information System (INIS)

Lim, S.C.; Lee, K.J.

1993-01-01

The Galerkin finite element method is used to solve the problem of one-dimensional, vertical flow of water and mass transport of conservative-nonconservative solutes in unsaturated porous media. Numerical approximations based on different forms of the governing equation, although they are equivalent in continuous forms, can result in remarkably different solutions in an unsaturated flow problem. Solutions given by a simple Galerkin method based on the h-based Richards equation yield a large mass balance error and an underestimation of the infiltration depth. With the employment of the ROMV (restoration of main variable) concept in the discretization step, the mass conservative numerical solution algorithm for water flow has been derived. The resulting computational schemes for water flow and mass transport are applied to sandy soil. The ROMV method shows good mass conservation in water flow analysis, whereas it seems to have a minor effect on mass transport. However, it may relax the time-step size restriction and so ensure an improved calculation output. (author)

A two-parameter family of exact asymptotically flat solutions to the Einstein-scalar field equations

International Nuclear Information System (INIS)

Nikonov, V V; Tchemarina, Ju V; Tsirulev, A N

2008-01-01

We consider a static spherically symmetric real scalar field, minimally coupled to Einstein gravity. A two-parameter family of exact asymptotically flat solutions is obtained by using the inverse problem method. This family includes non-singular solutions, black holes and naked singularities. For each of these solutions the respective potential is partially negative but positive near spatial infinity. (comments, replies and notes)

A cell transportation solution that preserves live circulating tumor cells in patient blood samples

International Nuclear Information System (INIS)

Stefansson, Steingrimur; Adams, Daniel L.; Ershler, William B.; Le, Huyen; Ho, David H.

2016-01-01

Circulating tumor cells (CTCs) are typically collected into CellSave fixative tubes, which kills the cells, but preserves their morphology. Currently, the clinical utility of CTCs is mostly limited to their enumeration. More detailed investigation of CTC biology can be performed on live cells, but obtaining live CTCs is technically challenging, requiring blood collection into biocompatible solutions and rapid isolation which limits transportation options. To overcome the instability of CTCs, we formulated a sugar based cell transportation solution (SBTS) that stabilizes cell viability at ambient temperature. In this study we examined the long term viability of human cancer cell lines, primary cells and CTCs in human blood samples in the SBTS for transportation purposes. Four cell lines, 5 primary human cells and purified human PBMCs were tested to determine the viability of cells stored in the transportation solution at ambient temperature for up to 7 days. We then demonstrated viability of MCF-7 cells spiked into normal blood with SBTS and stored for up to 7 days. A pilot study was then run on blood samples from 3 patients with metastatic malignancies stored with or without SBTS for 6 days. CTCs were then purified by Ficoll separation/microfilter isolation and identified using CTC markers. Cell viability was assessed using trypan blue or CellTracker™ live cell stain. Our results suggest that primary/immortalized cell lines stored in SBTS remain ~90 % viable for > 72 h. Further, MCF-7 cells spiked into whole blood remain viable when stored with SBTS for up to 7 days. Finally, live CTCs were isolated from cancer patient blood samples kept in SBTS at ambient temperature for 6 days. No CTCs were isolated from blood samples stored without SBTS. In this proof of principle pilot study we show that viability of cell lines is preserved for days using SBTS. Further, this solution can be used to store patient derived blood samples for eventual isolation of viable CTCs

A cell transportation solution that preserves live circulating tumor cells in patient blood samples.

Science.gov (United States)

Stefansson, Steingrimur; Adams, Daniel L; Ershler, William B; Le, Huyen; Ho, David H

2016-05-06

Circulating tumor cells (CTCs) are typically collected into CellSave fixative tubes, which kills the cells, but preserves their morphology. Currently, the clinical utility of CTCs is mostly limited to their enumeration. More detailed investigation of CTC biology can be performed on live cells, but obtaining live CTCs is technically challenging, requiring blood collection into biocompatible solutions and rapid isolation which limits transportation options. To overcome the instability of CTCs, we formulated a sugar based cell transportation solution (SBTS) that stabilizes cell viability at ambient temperature. In this study we examined the long term viability of human cancer cell lines, primary cells and CTCs in human blood samples in the SBTS for transportation purposes. Four cell lines, 5 primary human cells and purified human PBMCs were tested to determine the viability of cells stored in the transportation solution at ambient temperature for up to 7 days. We then demonstrated viability of MCF-7 cells spiked into normal blood with SBTS and stored for up to 7 days. A pilot study was then run on blood samples from 3 patients with metastatic malignancies stored with or without SBTS for 6 days. CTCs were then purified by Ficoll separation/microfilter isolation and identified using CTC markers. Cell viability was assessed using trypan blue or CellTracker™ live cell stain. Our results suggest that primary/immortalized cell lines stored in SBTS remain ~90% viable for > 72 h. Further, MCF-7 cells spiked into whole blood remain viable when stored with SBTS for up to 7 days. Finally, live CTCs were isolated from cancer patient blood samples kept in SBTS at ambient temperature for 6 days. No CTCs were isolated from blood samples stored without SBTS. In this proof of principle pilot study we show that viability of cell lines is preserved for days using SBTS. Further, this solution can be used to store patient derived blood samples for eventual isolation of viable CTCs after

Influence patterns of transportation parameters in suburban traffic on fatigue of passengers during bus waiting

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Тетяна Михайлівна Григорова

2015-05-01

Full Text Available The change of transport fatigue of suburban traffic passengers during waiting transport waiting is investigated. The results of the processing site examinations allow defining the regularities of the influence of parameters of transportation process of passengers to change index activity of regulatory systems in passenger waiting at stopping points of suburban traffic. The discovered patterns were mathematically formalized

Solution of the linearly anisotropic neutron transport problem in a infinite cylinder combining the decomposition and HTSN methods

International Nuclear Information System (INIS)

Goncalves, Glenio A.; Bodmann, Bardo; Bogado, Sergio; Vilhena, Marco T.

2008-01-01

Analytical solutions for neutron transport in cylindrical geometry is available for isotropic problems, but to the best of our knowledge for anisotropic problems are not available, yet. In this work, an analytical solution for the neutron transport equation in an infinite cylinder assuming anisotropic scattering is reported. Here we specialize the solution, without loss of generality, for the linearly anisotropic problem using the combined decomposition and HTS N methods. The key feature of this method consists in the application of the decomposition method to the anisotropic problem by virtue of the fact that the inverse of the operator associated to isotropic problem is well know and determined by the HTS N approach. So far, following the idea of the decomposition method, we apply this operator to the integral term, assuming that the angular flux appearing in the integrand is considered to be equal to the HTS N solution interpolated by polynomial considering only even powers. This leads to the first approximation for an anisotropic solution. Proceeding further, we replace this solution for the angular flux in the integral and apply again the inverse operator for the isotropic problem in the integral term and obtain a new approximation for the angular flux. This iterative procedure yields a closed form solution for the angular flux. This methodology can be generalized, in a straightforward manner, for transport problems with any degree of anisotropy. For the sake of illustration, we report numerical simulations for linearly anisotropic transport problems. (author)

Design approaches and parameters for magnetically levitated transport systems

International Nuclear Information System (INIS)

Danby, G.T.; Powell, J.R.

1988-01-01

Mechanically levitated transport system approaches are assessed with regard to thrust power needs, track cost, suspension stability, and safety. The null flux suspension appears as the favored approach, having the least thrust power requirements, highest stability, and lowest amount of track material. Various null flux configurations are described, together with operating parameters. The Linear Synchronous Motor (LSM) propulsion system is also described for propelling the suspended vehicles. Cryogenics and superconductivity aspects are discussed and the effect of high T/sub c/ superconductors evaluated

Implementation of the Global Parameters Determination in Gaia's Astrometric Solution (AGIS)

Science.gov (United States)

Raison, F.; Olias, A.; Hobbs, D.; Lindegren, L.

2010-12-01

Gaia is ESA’s space astrometry mission with a foreseen launch date in early 2012. Its main objective is to perform a stellar census of the 1000 Million brightest objects in our galaxy (completeness to V=20 mag) from which an astrometric catalog of micro-arcsec level accuracy will be constructed. A key element in this endeavor is the Astrometric Global Iterative Solution (AGIS). A core part of AGIS is to determine the accurate spacecraft attitude, geometric instrument calibration and astrometric model parameters for a well-behaved subset of all the objects (the ‘primary stars’). In addition, a small number of global parameters will be estimated, one of these being PPN γ. We present here the implementation of the algorithms dedicated to the determination of the global parameters.

Probing liquation cracking and solidification through modeling of momentum, heat, and solute transport during welding of aluminum alloys

International Nuclear Information System (INIS)

Mishra, S.; Chakraborty, S.; DebRoy, T.

2005-01-01

A transport phenomena-based mathematical model is developed to understand liquation cracking in weldments during fusion welding. Equations of conservation of mass, momentum, heat, and solute transport are numerically solved considering nonequilibrium solidification and filler metal addition to determine the solid and liquid phase fractions in the solidifying region and the solute distribution in the weld pool. An effective partition coefficient that considers the local interface velocity and the undercooling is used to simulate solidification during welding. The calculations show that convection plays a dominant role in the solute transport inside the weld pool. The predicted weld-metal solute content agreed well with the independent experimental observations. The liquation cracking susceptibility in Al-Cu alloy weldments could be reliably predicted by the model based on the computed solidifying weld-metal composition and solid fraction considering nonequilibrium solidification

A three-dimensional cohesive sediment transport model with data assimilation: Model development, sensitivity analysis and parameter estimation

Science.gov (United States)

Wang, Daosheng; Cao, Anzhou; Zhang, Jicai; Fan, Daidu; Liu, Yongzhi; Zhang, Yue

2018-06-01

Based on the theory of inverse problems, a three-dimensional sigma-coordinate cohesive sediment transport model with the adjoint data assimilation is developed. In this model, the physical processes of cohesive sediment transport, including deposition, erosion and advection-diffusion, are parameterized by corresponding model parameters. These parameters are usually poorly known and have traditionally been assigned empirically. By assimilating observations into the model, the model parameters can be estimated using the adjoint method; meanwhile, the data misfit between model results and observations can be decreased. The model developed in this work contains numerous parameters; therefore, it is necessary to investigate the parameter sensitivity of the model, which is assessed by calculating a relative sensitivity function and the gradient of the cost function with respect to each parameter. The results of parameter sensitivity analysis indicate that the model is sensitive to the initial conditions, inflow open boundary conditions, suspended sediment settling velocity and resuspension rate, while the model is insensitive to horizontal and vertical diffusivity coefficients. A detailed explanation of the pattern of sensitivity analysis is also given. In ideal twin experiments, constant parameters are estimated by assimilating 'pseudo' observations. The results show that the sensitive parameters are estimated more easily than the insensitive parameters. The conclusions of this work can provide guidance for the practical applications of this model to simulate sediment transport in the study area.

The influence of mass transfer on solute transport in column experiments with an aggregated soil

Science.gov (United States)

Roberts, Paul V.; Goltz, Mark N.; Summers, R. Scott; Crittenden, John C.; Nkedi-Kizza, Peter

1987-06-01

The spreading of concentration fronts in dynamic column experiments conducted with a porous, aggregated soil is analyzed by means of a previously documented transport model (DFPSDM) that accounts for longitudinal dispersion, external mass transfer in the boundary layer surrounding the aggregate particles, and diffusion in the intra-aggregate pores. The data are drawn from a previous report on the transport of tritiated water, chloride, and calcium ion in a column filled with Ione soil having an average aggregate particle diameter of 0.34 cm, at pore water velocities from 3 to 143 cm/h. The parameters for dispersion, external mass transfer, and internal diffusion were predicted for the experimental conditions by means of generalized correlations, independent of the column data. The predicted degree of solute front-spreading agreed well with the experimental observations. Consistent with the aggregate porosity of 45%, the tortuosity factor for internal pore diffusion was approximately equal to 2. Quantitative criteria for the spreading influence of the three mechanisms are evaluated with respect to the column data. Hydrodynamic dispersion is thought to have governed the front shape in the experiments at low velocity, and internal pore diffusion is believed to have dominated at high velocity; the external mass transfer resistance played a minor role under all conditions. A transport model such as DFPSDM is useful for interpreting column data with regard to the mechanisms controlling concentration front dynamics, but care must be exercised to avoid confounding the effects of the relevant processes.

An energy-optimal solution for transportation control of cranes with double pendulum dynamics: Design and experiments

Science.gov (United States)

Sun, Ning; Wu, Yiming; Chen, He; Fang, Yongchun

2018-03-01

Underactuated cranes play an important role in modern industry. Specifically, in most situations of practical applications, crane systems exhibit significant double pendulum characteristics, which makes the control problem quite challenging. Moreover, most existing planners/controllers obtained with standard methods/techniques for double pendulum cranes cannot minimize the energy consumption when fulfilling the transportation tasks. Therefore, from a practical perspective, this paper proposes an energy-optimal solution for transportation control of double pendulum cranes. By applying the presented approach, the transportation objective, including fast trolley positioning and swing elimination, is achieved with minimized energy consumption, and the residual oscillations are suppressed effectively with all the state constrains being satisfied during the entire transportation process. As far as we know, this is the first energy-optimal solution for transportation control of underactuated double pendulum cranes with various state and control constraints. Hardware experimental results are included to verify the effectiveness of the proposed approach, whose superior performance is reflected by being experimentally compared with some comparative controllers.

A Modified Method for Evaluating Sustainable Transport Solutions Based on AHP and Dempster–Shafer Evidence Theory

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Luyuan Chen

2018-04-01

Full Text Available With the challenge of transportation environment, a large amount of attention is paid to sustainable mobility worldwide, thus bringing the problem of the evaluation of sustainable transport solutions. In this paper, a modified method based on analytical hierarchy process (AHP and Dempster–Shafer evidence theory (D-S theory is proposed for evaluating the impact of transport measures on city sustainability. AHP is adapted to determine the weight of sustainability criteria while D-S theory is used for data fusion of the sustainability assessment. A Transport Sustainability Index (TSI is presented as a primary measure to determine whether transport solutions have a positive impact on city sustainability. A case study of car-sharing is illustrated to show the efficiency of our proposed method. Our modified method has two desirable properties. One is that the BPA is generated with a new modification framework of evaluation levels, which can flexibly manage uncertain information. The other is that the modified method has excellent performance in sensitivity analysis.

BUILDING CONCEPTUAL AND MATHEMATICAL MODEL FOR WATER FLOW AND SOLUTE TRANSPORT IN THE UNSATURATED ZONE AT KOSNICA SITE

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Stanko Ružičić

2012-12-01

Full Text Available Conceptual model of flow and solute transport in unsaturated zone at Kosnica site, which is the basis for modeling pollution migration through the unsaturated zone to groundwater, is set up. The main characteristics of the unsaturated zone of the Kosnica site are described. Detailed description of investigated profile of unsaturated zone, with all necessary analytical results performed and used in building of conceptual models, is presented. Experiments that are in progress and processes which are modeled are stated. Monitoring of parameters necessary for calibration of models is presented. The ultimate goal of research is risk assessment of groundwater contamination at Kosnica site that has its source in or on unsaturated zone.

External intermittency prediction using AMR solutions of RANS turbulence and transported PDF models

Science.gov (United States)

Olivieri, D. A.; Fairweather, M.; Falle, S. A. E. G.

2011-12-01

External intermittency in turbulent round jets is predicted using a Reynolds-averaged Navier-Stokes modelling approach coupled to solutions of the transported probability density function (pdf) equation for scalar variables. Solutions to the descriptive equations are obtained using a finite-volume method, combined with an adaptive mesh refinement algorithm, applied in both physical and compositional space. This method contrasts with conventional approaches to solving the transported pdf equation which generally employ Monte Carlo techniques. Intermittency-modified eddy viscosity and second-moment turbulence closures are used to accommodate the effects of intermittency on the flow field, with the influence of intermittency also included, through modifications to the mixing model, in the transported pdf equation. Predictions of the overall model are compared with experimental data on the velocity and scalar fields in a round jet, as well as against measurements of intermittency profiles and scalar pdfs in a number of flows, with good agreement obtained. For the cases considered, predictions based on the second-moment turbulence closure are clearly superior, although both turbulence models give realistic predictions of the bimodal scalar pdfs observed experimentally.

Modeling spin magnetization transport in a spatially varying magnetic field

Science.gov (United States)

Picone, Rico A. R.; Garbini, Joseph L.; Sidles, John A.

2015-01-01

We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]).

Modeling study of solute transport in the unsaturated zone. Information and data sets. Volume 1

International Nuclear Information System (INIS)

Polzer, W.L.; Fuentes, H.R.; Springer, E.P.; Nyhan, J.W.

1986-05-01

The Environmental Science Group (HSE-12) is conducting a study to compare various approaches of modeling water and solute transport in porous media. Various groups representing different approaches will model a common set of transport data so that the state of the art in modeling and field experimentation can be discussed in a positive framework with an assessment of current capabilities and future needs in this area of research. This paper provides information and sets of data that will be useful to the modelers in meeting the objectives of the modeling study. The information and data sets include: (1) a description of the experimental design and methods used in obtaining solute transport data, (2) supporting data that may be useful in modeling the data set of interest, and (3) the data set to be modeled

Influence of the P content on the transport parameters of hydrogen in Fe alloys

Energy Technology Data Exchange (ETDEWEB)

Peñalva, I., E-mail: igor.penalva@ehu.es [University of the Basque Country (UPV/EHU), Department of Nuclear Engineering & Fluid Mechanics, Faculty of Engineering, Alda. Urquijo s/n, 48013 Bilbao (Spain); Alberro, G.; Legarda, F. [University of the Basque Country (UPV/EHU), Department of Nuclear Engineering & Fluid Mechanics, Faculty of Engineering, Alda. Urquijo s/n, 48013 Bilbao (Spain); Ortiz, C.J.; Vila, R. [CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain)

2015-10-15

Highlights: • Gas permeation technique was used to study hydrogen diffusive transport parameters. • Four Fe alloys were analyzed to study the influence of the P content. • Increase in the P content leads to smaller values of permeability and diffusivity. • Trapping effects were observed at temperatures below 473 K for alloys containing P. - Abstract: In this work, the hydrogen transport parameters of permeability (ϕ), diffusivity (D) and Sieverts’ constant (K{sub S}) were experimentally measured in four Fe alloys supplied by the European Fusion Development Agreement (EFDA), by means of the gas evolution permeation technique. The samples had controlled chemical alloying element contents and microstructure. The experimental temperature range explored was from 423 K to 823 K and the high purity hydrogen loading pressures from 10{sup 3} Pa to 1.5·10{sup 5} Pa. The main objective of this work was to determine the influence of the P content of the alloy in the transport parameters of hydrogen. Two of the samples, pure Fe and FeC, contained negligible quantities of P (less than 5 ppm in weight), whereas the other two, FeP and FeCP, had the same metallurgical composition as their corresponding pair, with the only difference in the phosphorus content (89 ppm in weight and 88 ppm in weight, respectively). The experimental permeation results were analyzed using a non-linear least square fitting. The final resulting values of the aforementioned transport parameters were paired off in order to determine the effect of the P content: pure Fe versus FeP and FeC versus FeCP. We observed that the permeability obtained for all the samples follows an Arrhenius law in each case. In general terms, the increase of the P content in the alloy leads to smaller values of the permeability showing a decrease in the permeation activation energy. Regarding diffusivity and Sieverts’ constant, trapping effects have been observed for the alloys containing P. This phenomenon was

An approximate analytical solution for describing surface runoff and sediment transport over hillslope

Science.gov (United States)

Tao, Wanghai; Wang, Quanjiu; Lin, Henry

2018-03-01

Soil and water loss from farmland causes land degradation and water pollution, thus continued efforts are needed to establish mathematical model for quantitative analysis of relevant processes and mechanisms. In this study, an approximate analytical solution has been developed for overland flow model and sediment transport model, offering a simple and effective means to predict overland flow and erosion under natural rainfall conditions. In the overland flow model, the flow regime was considered to be transitional with the value of parameter β (in the kinematic wave model) approximately two. The change rate of unit discharge with distance was assumed to be constant and equal to the runoff rate at the outlet of the plane. The excess rainfall was considered to be constant under uniform rainfall conditions. The overland flow model developed can be further applied to natural rainfall conditions by treating excess rainfall intensity as constant over a small time interval. For the sediment model, the recommended values of the runoff erosion calibration constant (cr) and the splash erosion calibration constant (cf) have been given in this study so that it is easier to use the model. These recommended values are 0.15 and 0.12, respectively. Comparisons with observed results were carried out to validate the proposed analytical solution. The results showed that the approximate analytical solution developed in this paper closely matches the observed data, thus providing an alternative method of predicting runoff generation and sediment yield, and offering a more convenient method of analyzing the quantitative relationships between variables. Furthermore, the model developed in this study can be used as a theoretical basis for developing runoff and erosion control methods.

Application of finite element method in the solution of transport equation

International Nuclear Information System (INIS)

Maiorino, J.R.; Vieira, W.J.

1985-01-01

It is presented the application of finite element method in the solution of second order transport equation (self-adjoint) for the even parity flux. The angular component is treated by expansion in Legendre polinomials uncoupled of the spatial component, which is approached by an expansion in base functions, interpolated in each spatial element. (M.C.K.) [pt

An analysis of parameters affecting slapdown of transportation packages

International Nuclear Information System (INIS)

Bergmann, V.L.; Ammerman, D.J.

1991-01-01

Several parameters affecting the accelerations experienced by packages for the transport of nuclear material during eccentric impact are evaluated. Eccentric impact on one end of a cask causes rotation leading to secondary impact, referred to as slapdown, at the other end. In a slapdown event, the rotational acceleration during the primary impact can cause accelerations at the nose and tail which are greater than those during a side-on impact. Slapdown can also cause acceleration at the tail during the secondary impact to be more severe than at the nose during primary impact. Both of these effects are investigated for two casks geometries. Other parameters evaluated are the characteristics of impact limiters and friction between the impact limiter the impacted surface. Results were obtained using SLAPDOWN, a code which models the impact response of deformable bodies. 2 refs., 11 figs

Cadmium uptake from solution by plants and its transport from roots to shoots

Energy Technology Data Exchange (ETDEWEB)

Jarvis, S.C.; Jones, L.H.P.; Hopper, M.J.

1976-02-01

The uptake of cadmium by the roots of plants, and its transport to shoots was examined using solution culture. Uptake by the roots of perennial ryegrass over a period of 4 hours from an aqueous solution containing 0.25 ppm cadmium as CdCl/sub 2/ was (i) enhanced by killing the roots and (ii) depressed when Ca/sup 2 +/, Mn/sup 2 +/ or Zn/sup 2 +/ were added to the solution. The distribution of cadmium between the roots and shoots of 23 species was examined at 4 days after a single, 3-day exposure to a nutrient solution containing 0.01 ppm added Cd. In all except 3 species, i.e. kale, lettuce and watercress, more than 50% of that taken up was retained in the shoot, and in fibrous roots of fodder beet, parsnip, carrot and radish it was greater than in the swollen storage roots. When perennial ryegrass was similarly exposed to solutions containing 0.01, 0.05, and 0.25 ppm added cadmium, uptake, as measured at 3 days after adding cadmium, increased with increasing rates of addition, but the proportion retained in the roots was constant (approximately 88%). There was no further transport from roots to shoots during the next 21 days, with the result that the concentration in the shoots decreased progressively with increasing growth. It is concluded that although the roots of several species can take up large quantities of cadmium from solution there are mechanisms which may restrict the movement of cadmium through plants, and thus to animals. 21 references, 7 tables.

Relationship between application scale and maximum time latency in intelligent transport solutions

NARCIS (Netherlands)

Knoop, V.; Lint, J. van; Vries, J.; Kester, L.J.H.M.; Passchier, I.

2013-01-01

Congestion is a major problem in large, urbanized areas. Intelligent transport solutions aim to reduce this problem. In general, traffic is monitored with the use of sensors, the resulting data are processed, a traffic state is estimated, and a control measure is computed and implemented. The

Two-parameter double-oscillator model of Mathews-Lakshmanan type: Series solutions and supersymmetric partners

International Nuclear Information System (INIS)

Schulze-Halberg, Axel; Wang, Jie

2015-01-01

We obtain series solutions, the discrete spectrum, and supersymmetric partners for a quantum double-oscillator system. Its potential features a superposition of the one-parameter Mathews-Lakshmanan interaction and a one-parameter harmonic or inverse harmonic oscillator contribution. Furthermore, our results are transferred to a generalized Pöschl-Teller model that is isospectral to the double-oscillator system

Two-parameter double-oscillator model of Mathews-Lakshmanan type: Series solutions and supersymmetric partners

Energy Technology Data Exchange (ETDEWEB)

Schulze-Halberg, Axel, E-mail: axgeschu@iun.edu, E-mail: xbataxel@gmail.com [Department of Mathematics and Actuarial Science and Department of Physics, Indiana University Northwest, 3400 Broadway, Gary, Indiana 46408 (United States); Wang, Jie, E-mail: wangjie@iun.edu [Department of Computer Information Systems, Indiana University Northwest, 3400 Broadway, Gary, Indiana 46408 (United States)

2015-07-15

We obtain series solutions, the discrete spectrum, and supersymmetric partners for a quantum double-oscillator system. Its potential features a superposition of the one-parameter Mathews-Lakshmanan interaction and a one-parameter harmonic or inverse harmonic oscillator contribution. Furthermore, our results are transferred to a generalized Pöschl-Teller model that is isospectral to the double-oscillator system.

Preliminary modeling for solute transport in a fractured zone at the Korea underground research tunnel (KURT)