Relating model parameters to basic soil properties

Soil Research ◽  
2004 ◽  
Vol 42 (7) ◽  
pp. 841 ◽  
Author(s):  
Hasan Merdun ◽  
Virgil L. Quisenberry
Keyword(s):  
Soil Properties ◽  
Path Length ◽  
Water Pressure ◽  
Effective Diffusion ◽  
Diffusion Path ◽  
Model Parameters ◽  
Mixing Depth ◽  
Flow And Transport ◽  
Diffusion Path Length ◽  
Parameter Values

Relating model parameters to basic soil characteristics can help to differentiate and classify soils based on their flow and transport characteristics and ultimately helps to develop a sound management tool to protect groundwater from industrial and agricultural contaminants. In this study, the model parameters (effective diffusion path-length or aggregate half-width, boundary soil water pressure, boundary hydraulic conductivity, saturated hydraulic conductivity, tortuosity in macropores, dispersivity, mixing depth) obtained from simulation of water flow and solute transport for 3 soils (Maury, Cecil, Lakeland) with contrasting properties were related to see whether these derived parameters can be related to variation in fundamental soil properties such as texture and structure and thus the flow and transport characteristics of the soils. The boundary is a division point in which the soil porosity is divided into macropores and micropores. The ANOVA test showed that the parameter values of effective diffusion path-length and tortuosity in macropores for 3 soils were not different from each other, but the parameter values of saturated and boundary hydraulic conductivities including the texture (clay content) were statistically different. Moreover, the means of boundary soil water pressure, dispersivity, and mixing depth for 3 soils were significantly different. These results suggest that relating model parameters to basic soil properties in order to differentiate and classify soils based on their flow and transport characteristics is promising and needs further study.

Deconvoluting the Competing Effects of Zeolite Framework Topology and Diffusion Path Length on Methanol to Hydrocarbons Reaction

ACS Catalysis ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 11042-11053 ◽  
Author(s):  
Yufeng Shen ◽  
Thuy T. Le ◽  
Donglong Fu ◽  
Joel E. Schmidt ◽  
Matthias Filez ◽  
...  
Keyword(s):  
Path Length ◽  
Diffusion Path ◽  
Zeolite Framework ◽  
Methanol To Hydrocarbons ◽  
Diffusion Path Length ◽  
And Diffusion

scholarly journals Evaluation of MACRO model by short-term water and solute transport simulation in Maury silt loam soil

2011 ◽  
Vol 51 (No. 3) ◽  
pp. 110-123 ◽  
Author(s):  
H. Merdun ◽  
V.L. Quisenberry
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Chloride Transport ◽  
Effective Diffusion ◽  
Diffusion Path ◽  
Silt Loam ◽  
Short Term ◽  
Silt Loam Soil ◽  
Diffusion Path Length ◽  
Loam Soil

Modeling preferential flow has been a concern of many academic fields in the past 30 years all over the world and helps to prevent groundwater contamination. A dual-porosity model, MACRO, was evaluated for short-term (less than 2 days) simulation of water flow and non-reactive solute (chloride) transport through the profile of six plots in well-structured Maury silt loam soil. Water flow in micropores is calculated by the Richards’ equation while simple gravity flow is assumed in the macropores. Solute transport in the micropores is calculated by the convection-dispersion equation (CDE) while the dispersion and diffusion in the CDE is neglected for the solute transport in the macropores. The applied water and chloride reached the bottom of the profile during the 2 and 1-hour(s) application periods in studies 2 and 3, respectively. There is a strong indication of macropore flow in this soil. Based on the statistical criteria, the model accurately simulated water flow and solute transport with depth and time in all plots. The mean values of three statistical parameters (coefficient of residual mass, model efficiency, and correlation coefficient) for water and chloride transport were –0.0014, 0.791, 0.903 and 0.0333, 0.923, 0.956, respectively. Preliminary studies showed that the model could not simulate flow and transport well enough with the one-domain flow concept. In the two-domain flow, effective diffusion path-length, boundary hydraulic conductivity, and boundary soil water pressure were the three most important parameters that control flow and transport between the two domains. The effective diffusion path-length represented the structural development with depth in the Maury silt loam soil.

scholarly journals Molecular Diffusion Model of Neurotransmitter Homeostasis Around Synapses Supporting Gradients

2011 ◽  
Vol 23 (4) ◽  
pp. 984-1014 ◽  
Author(s):  
Ashwin Mohan ◽  
Sandeep Pendyam ◽  
Peter W. Kalivas ◽  
Satish S. Nair
Keyword(s):  
Diffusion Model ◽  
Path Length ◽  
Molecular Diffusion ◽  
Three Dimensional ◽  
Release Site ◽  
Diffusion Path ◽  
Stochastic Diffusion ◽  
Molecular Binding ◽  
Chronic Cocaine ◽  
Diffusion Path Length

Neurotransmitter homeostasis in and around a synapse involves complex random processes such as diffusion, molecular binding, and uptake by glial transporters. A three-dimensional stochastic diffusion model of a synapse was developed to provide molecular-level details of neurotransmitter homeostasis not predicted by alternative models based on continuum approaches. The development was illustrated through an example case cortico-accumbens synapse that successfully integrated neuroadaptations observed after chronic cocaine. By incorporating cystine-glutamate exchanger as a nonsynaptic release site for glutamate, the stochastic model was used to quantify the relative contributions of synaptic and nonsynaptic sources to extracellular concentration and to estimate molecular influx rates into the perisynapse. A perturbation analysis showed that among the parameters considered, variation in surface density of glial transporters had the largest effect on glutamate concentrations. The stochastic diffusion model of the example synapse was further generalized to characterize glial morphology by studying the role of diffusion path length in supporting neurotransmitter gradients and isolating the synapse. For the same set of parameters, diffusion path length was found to be proportional to the gradient supported.

Simulation of water and solute transport with MACRO model in Cecil loamy sand soil

Soil Research ◽  
2004 ◽  
Vol 42 (8) ◽  
pp. 939 ◽  
Author(s):  
Hasan Merdun ◽  
Virgil L. Quisenberry
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Preferential Flow ◽  
Effective Diffusion ◽  
Loamy Sand ◽  
Model Parameters ◽  
Drainage Flow ◽  
Sand Soil ◽  
Flow And Transport ◽  
Loamy Sand Soil

Modelling preferential flow increases understanding of flow and transport processes in the unsaturated (vadose) zone and, hence, helps prevention of groundwater contamination. A dual-porosity model, MACRO, was evaluated for long-term drainage flow and short-term chloride-tagged water flow simulations in well-structured Cecil loamy sand soil. Water flow in micropores is calculated by the Richards’ equation, and simple gravity flow is assumed in the macropores. Solute transport in the micropores is calculated by the convection–dispersion equation (CDE), and the dispersion and diffusion in the CDE is neglected for the solute transport in the macropores. Based on the statistical criteria, the model accurately simulated drainage flow with depth and time. The average values of 3 statistical parameters (coefficient of residual mass, model efficiency, correlation coefficient) for drainage flow of different plots and times were 0.0057, 0.972, and 0.987, respectively. Similarly, the average values of the 3 statistical parameters in the same order for water flow and chloride transport of 4 plots were 0.097, 0.628, and 0.915, and 0.167, 0.938, and 0.982, respectively. The model simulated long-term drainage flow better than the short-term applied chloride-tagged water. The percentage recovery of measured water and chloride 2 h after the application ceased was 83 and 63 in the 1.05-m-deep profile of plot 1. This was a strong indication of preferential flow in this soil. Two-domain flow concept was required for acceptable simulation of this type of flow. In the 2-domain flow, boundary tension, boundary hydraulic conductivity, and effective diffusion path-length were the 3 most important parameters controlling flow and transport between the 2 domains. The effective diffusion path-length represented the structural development with depth in Cecil loamy sand soil. The relationships between the variability in flow and transport characteristics and fundamental soil properties and, hence, the associated key model parameters suggest that pedotransfer functions can be developed for the estimation of dual-porosity model parameters that control preferential flow.

Stochastic Model of Glutamatergic PFC-NAc Synapse Predicts Cocaine-Induced Changes in Receptor Occupancy

2009 ◽  
Author(s):  
Ashwin Mohan ◽  
Sandeep Pendyam ◽  
Bradley C. Enke ◽  
Peter Kalivas ◽  
Satish S. Nair
Keyword(s):  
Stochastic Model ◽  
Effective Diffusion ◽  
Three Dimensional ◽  
Receptor Occupancy ◽  
Diffusion Path ◽  
Molecular Binding ◽  
Reward Seeking ◽  
Chronic Cocaine ◽  
Diffusion Path Length ◽  
Induced Changes

Neurotransmitter homeostasis in and around synapses involves random processes such as diffusion, molecular binding and unbinding. A three-dimensional stochastic diffusion model of a synapse was developed to provide molecular level details of neurotransmitter homeostasis not predicted by alternative models based on continuum approaches. This framework was used to estimate effective diffusion and provide a more accurate prediction of geometric tortuosity in the perisynaptic region. The stochastic model was used to predict the relative contributions of non-synaptic sources to extracellular concentration in control, natural reward seeking, and chronic cocaine cases; and estimation of molecular influx rates required to maintain tone on presynaptic autoreceptors. Also, this was the first stochastic model to confirm the prediction of down-regulation of glutamate transporters by 40% after chronic cocaine. The model can be further generalized to study the role of diffusion path length in supporting neurotransmitter gradients and isolating the synapse.

Changes in diffusion path length with old age in diffuse optical tomography

2012 ◽  
Vol 17 (5) ◽  
pp. 056002 ◽  
Author(s):  
Clément Bonnéry ◽  
Paul-Olivier Leclerc ◽  
Michèle Desjardins ◽  
Rick Hoge ◽  
Louis Bherer ◽  
...  
Keyword(s):  
Old Age ◽  
Path Length ◽  
Optical Tomography ◽  
Diffuse Optical Tomography ◽  
Diffusion Path ◽  
Diffusion Path Length

scholarly journals Assimilation of Dynamic Combined Finite Discrete Element Methods Using the Ensemble Kalman Filter

2021 ◽  
Vol 11 (7) ◽  
pp. 2898
Author(s):  
Humberto C. Godinez ◽  
Esteban Rougier
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Peak Stress ◽  
Discrete Element ◽  
Material Behavior ◽  
Model Parameters ◽  
Hopkinson Pressure Bar ◽  
Parameter Values

Simulation of fracture initiation, propagation, and arrest is a problem of interest for many applications in the scientific community. There are a number of numerical methods used for this purpose, and among the most widely accepted is the combined finite-discrete element method (FDEM). To model fracture with FDEM, material behavior is described by specifying a combination of elastic properties, strengths (in the normal and tangential directions), and energy dissipated in failure modes I and II, which are modeled by incorporating a parameterized softening curve defining a post-peak stress-displacement relationship unique to each material. In this work, we implement a data assimilation method to estimate key model parameter values with the objective of improving the calibration processes for FDEM fracture simulations. Specifically, we implement the ensemble Kalman filter assimilation method to the Hybrid Optimization Software Suite (HOSS), a FDEM-based code which was developed for the simulation of fracture and fragmentation behavior. We present a set of assimilation experiments to match the numerical results obtained for a Split Hopkinson Pressure Bar (SHPB) model with experimental observations for granite. We achieved this by calibrating a subset of model parameters. The results show a steady convergence of the assimilated parameter values towards observed time/stress curves from the SHPB observations. In particular, both tensile and shear strengths seem to be converging faster than the other parameters considered.

scholarly journals An enhanced set of displacement parameter restraints in CRYSTALS

2018 ◽  
Vol 51 (4) ◽  
pp. 1059-1068 ◽  
Author(s):  
Pascal Parois ◽  
James Arnold ◽  
Richard Cooper
Keyword(s):  
Structural Model ◽  
Rigid Bodies ◽  
Model Parameters ◽  
Coordinate Systems ◽  
Principal Axes ◽  
Anisotropic Displacement Parameters ◽  
Set Up ◽  
Meaningful Relationships ◽  
Parameter Values ◽  
Total Model

Crystallographic restraints are widely used during refinement of small-molecule and macromolecular crystal structures. They can be especially useful for introducing additional observations and information into structure refinements against low-quality or low-resolution data (e.g. data obtained at high pressure) or to retain physically meaningful parameter values in disordered or unstable refinements. However, despite the fact that the anisotropic displacement parameters (ADPs) often constitute more than half of the total model parameters determined in a structure analysis, there are relatively few useful restraints for them, examples being Hirshfeld rigid-bond restraints, direct equivalence of parameters and SHELXL RIGU-type restraints. Conversely, geometric parameters can be subject to a multitude of restraints (e.g. absolute or relative distance, angle, planarity, chiral volume, and geometric similarity). This article presents a series of new ADP restraints implemented in CRYSTALS [Parois, Cooper & Thompson (2015), Chem. Cent. J. 9, 30] to give more control over ADPs by restraining, in a variety of ways, the directions and magnitudes of the principal axes of the ellipsoids in locally defined coordinate systems. The use of these new ADPs results in more realistic models, as well as a better user experience, through restraints that are more efficient and faster to set up. The use of these restraints is recommended to preserve physically meaningful relationships between displacement parameters in a structural model for rigid bodies, rotationally disordered groups and low-completeness data.

Diffusion of Zinc in Two-Phase Mg-Al Alloy

2007 ◽  
Vol 263 ◽  
pp. 189-194
Author(s):  
Ivo Stloukal ◽  
Jiří Čermák
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Residual Activity ◽  
Diffusion Path ◽  
Al Alloy ◽  
Serial Sectioning ◽  
Two Phase ◽  
Interphase Boundaries ◽  
The Mean

Coefficient of 65Zn heterodiffusion in Mg17Al12 intermetallic and in eutectic alloy Mg - 33.4 wt. % Al was measured in the temperature region 598 – 698 K using serial sectioning and residual activity methods. Diffusion coefficient of 65Zn in the intermetallic can be written as DI = 1.7 × 10-2 m2 s-1 exp (-155.0 kJ mol-1 / RT). At temperatures T ≥ 648 K, where the mean diffusion path was greater than the mean interlamellar distance in the eutectic, the effective diffusion coefficient Def = 2.7 × 10-2 m2 s-1 exp (-155.1 kJ mol-1 / RT) was evaluated. At two lower temperatures, the diffusion coefficients 65Zn in interphase boundaries were estimated: Db (623 K) = 1.6 × 10-12 m2 s-1 and Db (598 K) = 4.4 × 10-13 m2 s-1.

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