scholarly journals Monte Carlo ice flow modeling projects a new stable configuration for Columbia Glacier, Alaska, c. 2020

2012 ◽  
Vol 6 (6) ◽  
pp. 1395-1409 ◽  
Author(s):  
W. Colgan ◽  
W. T. Pfeffer ◽  
H. Rajaram ◽  
W. Abdalati ◽  
J. Balog
Keyword(s):  
Monte Carlo ◽  
Dynamic Equilibrium ◽  
Stable Configuration ◽  
Ice Flow ◽  
Wide Range ◽  
Ensemble Mean ◽  
Iceberg Calving ◽  
Calving Rate ◽  
Parameter Values

Abstract. Due to the abundance of observational datasets collected since the onset of its retreat (c. 1983), Columbia Glacier, Alaska, provides an exciting modeling target. We perform Monte Carlo simulations of the form and flow of Columbia Glacier, using a 1-D (depth-integrated) flowline model, over a wide range of parameter values and forcings. An ensemble filter is imposed following spin-up to ensure that only simulations that accurately reproduce observed pre-retreat glacier geometry are retained; all other simulations are discarded. The selected ensemble of simulations reasonably reproduces numerous highly transient post-retreat observed datasets. The selected ensemble mean projection suggests that Columbia Glacier will achieve a new dynamic equilibrium (i.e. "stable") ice geometry c. 2020, at which time iceberg calving rate will have returned to approximately pre-retreat values. Comparison of the observed 1957 and 2007 glacier geometries with the projected 2100 glacier geometry suggests that Columbia Glacier had already discharged ~82% of its projected 1957–2100 sea level rise contribution by 2007. This case study therefore highlights the difficulties associated with the future extrapolation of observed glacier mass loss rates that are dominated by iceberg calving.

scholarly journals Monte Carlo ice flow modeling projects a new stable configuration for Columbia Glacier, Alaska, by c. 2020

2012 ◽  
Vol 6 (2) ◽  
pp. 893-930 ◽  
Author(s):  
W. Colgan ◽  
W. T. Pfeffer ◽  
H. Rajaram ◽  
W. Abdalati
Keyword(s):  
Monte Carlo ◽  
Dynamic Equilibrium ◽  
Stable Configuration ◽  
Ice Flow ◽  
Wide Range ◽  
Ensemble Mean ◽  
Iceberg Calving ◽  
Calving Rate ◽  
Parameter Values

Abstract. Due to the abundance of observational datasets collected since the onset of its retreat (c. 1983), Columbia Glacier, Alaska, provides an exciting modeling target. We perform Monte Carlo simulations of the form and flow of Columbia Glacier, using a 1-D (depth-integrated) flowline model, over a wide range of parameter values and forcings. An ensemble filter is imposed following spin-up to ensure that only simulations which accurately reproduce observed pre-retreat glacier geometry are retained; all other simulations are discarded. The selected ensemble of simulations reasonably reproduces numerous highly transient post-retreat observed datasets with a minimum of parameterizations. The selected ensemble mean projection suggests that Columbia Glacier will achieve a new dynamic equilibrium (i.e. "stable") ice geometry c. 2020, by which time iceberg calving rate will have returned to approximately pre-retreat values. Comparison of the observed 1957 and 2007 glacier geometries with the projected 2100 glacier geometry suggests that, by 2007, Columbia Glacier had already discharged ∼83 % of its total sea level rise contribution expected by 2100. This case study therefore highlights the difficulties associated with the future extrapolation of observed glacier mass loss rates that are dominated by iceberg calving.

Application of A Monte Carlo Approach to Surface Complexation Modelling

2004 ◽  
Vol 824 ◽  
Author(s):  
M.M. Askarieh ◽  
T.G. Heath ◽  
W.M. Tearle
Keyword(s):  
Monte Carlo ◽  
Model Parameters ◽  
Surface Complexes ◽  
Monte Carlo Approach ◽  
Ion Sorption ◽  
Wide Range ◽  
Complex Models ◽  
Chemical Conditions ◽  
Parameter Values

AbstractA Monte Carlo-based approach has been adopted for development of a chemical thermodynamic model to describe the goethite surface in contact with sodium nitrate solutions. The technique involves the calculation of the goethite surface properties for the chemical conditions corresponding to each experimental data point. The representation of the surface was based on a set of model parameters, each of which was either fixed or was randomly sampled from a specified range of values. Thousands of such model representations were generated for different selected sets of parameter values with the use of the standard geochemical speciation computer program, HARPHRQ. The method allowed many combinations of parameter values to be sampled that might not be achieved with a simple least-squares fitting approach. It also allowed the dependence of the quality of fit on each parameter to be analysed. The Monte Carlo approach is most appropriate in the development of complex models involving the fitting of several datasets with several fitting parameters.Introduction of selenate surface complexes allowed the model to be extended to represent selenate ion sorption, selenium being an important radioelement in evaluation of the long-term safety of ILW disposal. The sorption model gave good agreement with a wide range of experimental sorption datasets for selenate.

scholarly journals Produção de dados de tráfego sintéticos através de algoritmo genético e simulação microscópica

TRANSPORTES ◽  
2010 ◽  
Vol 18 (3) ◽  
Author(s):  
José Elievam Bessa Júnior ◽  
José Reynaldo Setti
Keyword(s):  
Monte Carlo ◽  
Simulation Model ◽  
Synthetic Data ◽  
Monte Carlo Sampling ◽  
Sao Paulo ◽  
Model Parameters ◽  
São Paulo ◽  
Traffic Data ◽  
Wide Range

<p><strong>Resumo: </strong>Neste artigo, propõe-se um método para produzir, por meio de um simulador, uma série de dados de tráfego sintéticos que representem diversas condições operacionais e comportamentais, como os fornecidos por sensores instalados nas vias. O método proposto baseia-se num algoritmo genético (AG), que automaticamente calibra um modelo de simulação microscópico. Entre os cromossomos (soluções) gerados pelo AG na calibração do simulador, são escolhidos os que produzem resultados marginalmente inferiores ao ótimo. As distribuições de valores dos parâmetros que formam os cromossomos deste subconjunto são usadas para gerar, através de uma amostragem de Monte Carlo, parâmetros para as replicações da simulação que são usadas para produzir os dados sintéticos. A viabilidade do método proposto é demonstrada através de um estudo de caso, no qual o simulador usado foi o TWOPAS e os dados de tráfego foram obtidos de sensores instalados no km 98 da SP98, uma rodovia de pista simples no estado de São Paulo.</p><strong>Abstract: </strong>The paper proposes a method for generating, by a simulator, synthetic traffic data which represents a wide range of operational and behavioral conditions, such as those obtained from detectors installed on roads. The proposed method uses a genetic algorithm (GA) to calibrate a traffic simulation model automatically. A subset of chromosomes (solutions) generated by the GA during the calibration of the simulator containing those that produce results marginally inferior to the best solution is used to produce distributions of feasible values for the simulation model parameters. The distributions of simulation model parameters contained in the chromosomes of this subset of solutions are used to produce, by Monte Carlo sampling, parameters for the simulations that generate the synthetic data. The feasibility of the proposed approach is demonstrated by a case study using TWOPAS and data from detectors installed on SP98, a two-lane highway in the state of São Paulo, Brazil.

scholarly journals Iceberg calving rates from northern Ellesmere Island ice caps, Canadian Arctic, 1999–2003

2008 ◽  
Vol 54 (186) ◽  
pp. 391-400 ◽  
Author(s):  
Scott Williamson ◽  
Martin Sharp ◽  
Julian Dowdeswell ◽  
Toby Benham
Keyword(s):  
Glacier Surface ◽  
Ice Flow ◽  
Ice Caps ◽  
Ice Cap ◽  
Glacier Terminus ◽  
Devon Ice Cap ◽  
Order Of Magnitude ◽  
Iceberg Calving ◽  
Flow Through ◽  
Calving Rate

AbstractOptical satellite imagery was used to estimate glacier surface velocities and iceberg calving rates from Agassiz and western Grant Ice Caps, Nunavut, Canada, between 1999 and 2003. The largest mean annual surface velocities ranged from ∼400 to 700 m a−1, but velocities in the ∼100–200 m a−1 range were common. Summer velocities were up to an order of magnitude larger than annually averaged velocities. The highest velocity (∼1530 m a−1) was measured on the floating tongue of Lake Tuborg Glacier between 19 July and 19 August 2001. Calving rates from individual glaciers varied by up to a factor of two between successive years. Summer calving rates were ∼2–8 times larger than annual average rates. The average ratio of the calving flux due to terminus-volume change to that due to ice flow through the glacier terminus was ∼0.81 for the annual rates and ∼1.71 for summer rates. The estimated mean annual calving rate from Agassiz Ice Cap in the period 1999–2002 was 0.67 ± 0.15 km3 a−1, of which ∼54% emanated from Eugenie Glacier alone. This total rate is similar to a previously estimated calving rate from Devon Ice Cap.

How to Measure Diffusion Coefficients in Biofilms: A Critical Analysis

2020 ◽  
Author(s):  
Lenno van den Berg ◽  
Mark van Loosdrecht ◽  
Merle de Kreuk
Keyword(s):  
Monte Carlo ◽  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Granular Sludge ◽  
Monte Carlo Analysis ◽  
Propagation Of Uncertainty ◽  
Relative Standard ◽  
Wide Range

&lt;p&gt;Effective diffusion coefficients are often required for kinetic descriptions of biofilms. Many previous studies have measured diffusion coefficients for specific molecule-biofilm combinations. As a result, many biofilm researchers today rely on literature values of diffusion coefficients for their own biofilm system. However, the reported diffusion coefficients in literature fall within a wide range, even for the same molecule. One potential cause of this range is the accuracy of the methods used to measure diffusion coefficients. The objective of this study was to determine the precision (similarity between repeated experiments) and bias (difference between measured and true diffusion coefficient) of six common methods. The six selected methods were based on determining mass balances and on microelectrode measurements. The precision and bias were quantified based on mathematical models of the six methods, with oxygen diffusion in granular sludge as a case study. The precision was assessed by a Monte Carlo uncertainty analysis, which considers the propagation of uncertainty in the input experimental parameters. The bias was determined for six potential sources of error: solute sorption, biomass deactivation, a concentration boundary layer, granule roughness, granule shape, and granule size distribution. From the Monte Carlo analysis, it followed that the precision of the methods ranged from 4-77% relative standard deviation. The microelectrode methods were more accurate than the mass balance methods. The bias due to the combined effect of the six errors was an underestimation of the diffusion coefficient by 74%. This shows that current methods are unable to accurately determine diffusion coefficients. We do not propose improvements to the current methods, but instead discuss why inaccurate diffusion coefficients are sufficient for accurate engineering of biofilm processes.&amp;#160;&lt;/p&gt;

Monte Carlo calculation of the energy parameters and spatial distribution of the cathodic arc ions while passing through the macro-particles filters

2018 ◽  
Vol 1 (1) ◽  
pp. 30-34 ◽  
Author(s):  
Alexey Chernogor ◽  
Igor Blinkov ◽  
Alexey Volkhonskiy
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Monte Carlo ◽  
Monte Carlo Calculation ◽  
Inhomogeneous Magnetic Field ◽  
Flow Energy ◽  
Wide Range ◽  
Field Concentrator ◽  
Cathodic Arc ◽  
The Magnetic Field

The flow, energy distribution and concentrations profiles of Ti ions in cathodic arc are studied by test particle Monte Carlo simulations with considering the mass transfer through the macro-particles filters with inhomogeneous magnetic field. The loss of ions due to their deposition on filter walls was calculated as a function of electric current and number of turns in the coil. The magnetic field concentrator that arises in the bending region of the filters leads to increase the loss of the ions component of cathodic arc. The ions loss up to 80 % of their energy resulted by the paired elastic collisions which correspond to the experimental results. The ion fluxes arriving at the surface of the substrates during planetary rotating of them opposite the evaporators mounted to each other at an angle of 120° characterized by the wide range of mutual overlapping.

Site specific agricultural soil management with the use of new technologies

2013 ◽  
Vol 16 (1) ◽  
pp. 59-67
Keyword(s):  
New Technologies ◽  
Digital Interface ◽  
Appropriate Treatment ◽  
Wide Range ◽  
Soil Variation ◽  
Soil Information ◽  
Remote Sensing Techniques ◽  
Agricultural Areas

<p>The Soil Science Institute of Thessaloniki produces new digitized Soil Maps that provide a useful electronic database for the spatial representation of the soil variation within a region, based on in situ soil sampling, laboratory analyses, GIS techniques and plant nutrition mathematical models, coupled with the local land cadastre. The novelty of these studies is that local agronomists have immediate access to a wide range of soil information by clicking on a field parcel shown in this digital interface and, therefore, can suggest an appropriate treatment (e.g. liming, manure incorporation, desalination, application of proper type and quantity of fertilizer) depending on the field conditions and cultivated crops. A specific case study is presented in the current work with regards to the construction of the digitized Soil Map of the regional unit of Kastoria. The potential of this map can easily be realized by the fact that the mapping of the physicochemical properties of the soils in this region provided delineation zones for differential fertilization management. An experiment was also conducted using remote sensing techniques for the enhancement of the fertilization advisory software database, which is a component of the digitized map, and the optimization of nitrogen management in agricultural areas.</p>

Oxford Studies in Ancient Philosophy, Volume 55

2018 ◽  
Keyword(s):  
Middle Ages ◽  
Ancient Philosophy ◽  
Recent Book ◽  
Loss Of Control ◽  
Ancient Greek ◽  
Original Essays ◽  
Constant Change ◽  
Wide Range ◽  
Metaphysical Principle

Oxford Studies in Ancient Philosophy provides, twice each year, a collection of the best current work in the field of ancient philosophy. Each volume features original essays that contribute to an understanding of a wide range of themes and problems in all periods of ancient Greek and Roman philosophy, from the beginnings to the threshold of the Middle Ages. From its first volume in 1983, OSAP has been a highly influential venue for work in the field, and has often featured essays of substantial length as well as critical essays on books of distinctive importance. Volume LV contains: a methodological examination on how the evidence for Presocratic thought is shaped through its reception by later thinkers, using discussions of a world soul as a case study; an article on Plato’s conception of flux and the way in which sensible particulars maintain a kind of continuity while undergoing constant change; a discussion of J. L. Austin’s unpublished lecture notes on Aristotle’s Nicomachean Ethics and his treatment of loss of control (akrasia); an article on the Stoics’ theory of time and in particular Chrysippus’ conception of the present and of events; and two articles on Plotinus, one that identifies a distinct argument to show that there is a single, ultimate metaphysical principle; and a review essay discussing E. K. Emilsson’s recent book, Plotinus.

scholarly journals Assessing the Relation between Mud Components and Rheology for Loss Circulation Prevention Using Polymeric Gels: A Machine Learning Approach

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1377
Author(s):  
Musaab I. Magzoub ◽  
Raj Kiran ◽  
Saeed Salehi ◽  
Ibnelwaleed A. Hussein ◽  
Mustafa S. Nasser
Keyword(s):  
Machine Learning ◽  
Rheological Properties ◽  
Nearest Neighbor ◽  
Drilling Fluid ◽  
Gradient Boosting ◽  
K Nearest Neighbor ◽  
Wide Range ◽  
Machine Learning Approach ◽  
Drilling Operations

The traditional way to mitigate loss circulation in drilling operations is to use preventative and curative materials. However, it is difficult to quantify the amount of materials from every possible combination to produce customized rheological properties. In this study, machine learning (ML) is used to develop a framework to identify material composition for loss circulation applications based on the desired rheological characteristics. The relation between the rheological properties and the mud components for polyacrylamide/polyethyleneimine (PAM/PEI)-based mud is assessed experimentally. Four different ML algorithms were implemented to model the rheological data for various mud components at different concentrations and testing conditions. These four algorithms include (a) k-Nearest Neighbor, (b) Random Forest, (c) Gradient Boosting, and (d) AdaBoosting. The Gradient Boosting model showed the highest accuracy (91 and 74% for plastic and apparent viscosity, respectively), which can be further used for hydraulic calculations. Overall, the experimental study presented in this paper, together with the proposed ML-based framework, adds valuable information to the design of PAM/PEI-based mud. The ML models allowed a wide range of rheology assessments for various drilling fluid formulations with a mean accuracy of up to 91%. The case study has shown that with the appropriate combination of materials, reasonable rheological properties could be achieved to prevent loss circulation by managing the equivalent circulating density (ECD).

scholarly journals β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 5. Adsorption Isotherm and Equation of State Revisited, Impact of pH

2021 ◽  
Vol 5 (1) ◽  
pp. 14
Author(s):  
Georgi G. Gochev ◽  
Volodymyr I. Kovalchuk ◽  
Eugene V. Aksenenko ◽  
Valentin B. Fainerman ◽  
Reinhard Miller
Keyword(s):  
Theoretical Description ◽  
Fluid Interfaces ◽  
Interfacial Behavior ◽  
Current State ◽  
Air Interface ◽  
Direct Measurements ◽  
Wide Range ◽  
Dilational Viscoelasticity ◽  
Parameter Values ◽  
Β Lactoglobulin

The theoretical description of the adsorption of proteins at liquid/fluid interfaces suffers from the inapplicability of classical formalisms, which soundly calls for the development of more complicated adsorption models. A Frumkin-type thermodynamic 2-d solution model that accounts for nonidealities of interface enthalpy and entropy was proposed about two decades ago and has been continuously developed in the course of comparisons with experimental data. In a previous paper we investigated the adsorption of the globular protein β-lactoglobulin at the water/air interface and used such a model to analyze the experimental isotherms of the surface pressure, Π(c), and the frequency-, f-, dependent surface dilational viscoelasticity modulus, E(c)f, in a wide range of protein concentrations, c, and at pH 7. However, the best fit between theory and experiment proposed in that paper appeared incompatible with new data on the surface excess, Γ, obtained from direct measurements with neutron reflectometry. Therefore, in this work, the same model is simultaneously applied to a larger set of experimental dependences, e.g., Π(c), Γ(c), E(Π)f, etc., with E-values measured strictly in the linear viscoelasticity regime. Despite this ambitious complication, a best global fit was elaborated using a single set of parameter values, which well describes all experimental dependencies, thus corroborating the validity of the chosen thermodynamic model. Furthermore, we applied the model in the same manner to experimental results obtained at pH 3 and pH 5 in order to explain the well-pronounced effect of pH on the interfacial behavior of β-lactoglobulin. The results revealed that the propensity of β-lactoglobulin globules to unfold upon adsorption and stretch at the interface decreases in the order pH 3 > pH 7 > pH 5, i.e., with decreasing protein net charge. Finally, we discuss advantages and limitations in the current state of the model.

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