Extended Long Wave Hindcast inside Port Solutions to Minimize Resonance
Directory of Open Access Journals (Sweden)
Gabriel Diaz-Hernandez
2016-02-01
Full Text Available The present study shows a methodology to carry out a comprehensive study of port agitation and resonance analysis in Geraldton Harbor (Western Australia. The methodology described and applied here extends the short and long wave hindcast outside the harbor and towards the main basin. To perform such an analysis, and as the first stage of the methodology, it is necessary to determine, in detail, both the long and short wave characteristics, through a comprehensive methodology to obtain and to hindcast the full spectral data (short waves + long waves, for frequencies between 0.005 and 1 Hz. Twelve-year spectral hindcast wave data, at a location before the reef, have been modified analytically to include the energy input associated with infragravity waves. A decomposition technique based on the energy balance of the radiation stress of short waves is followed. Predictions for long wave heights and periods at different harbor locations are predicted and validated with data recorded during 2004 to 2009. This new database will ensure an accurate and reliable assessment of long wave hourly data (height, period and currents in any area within the main basin of the Port of Geraldton, for its present geometry. With this information, two main task will be completed: (1 undertake a forensic diagnosis of the present response of the harbor, identifying those forcing characteristics related to inoperability events; and (2 propose any layout solutions to minimize, change, dissipate/fade/vanish or positively modify the effects of long waves in the harbor, proposing different harbor geometry modifications. The goal is to identify all possible combinations of solutions that would minimize the current inoperability in the harbor. Different pre-designs are assessed in this preliminary study in order to exemplify the potential of the methodology.
Output fields from the NOAA WAVEWATCH IIIÂ® wave model monthly hindcasts
National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA WAVEWATCH IIIÂ® hindcast dataset comprises output fields from the monthly WAVEWATCH IIIÂ® hindcast model runs conducted at the National Centers for...
Hindcasting to measure ice sheet model sensitivity to initial states
Directory of Open Access Journals (Sweden)
A. Aschwanden
2013-07-01
Full Text Available Validation is a critical component of model development, yet notoriously challenging in ice sheet modeling. Here we evaluate how an ice sheet system model responds to a given forcing. We show that hindcasting, i.e. forcing a model with known or closely estimated inputs for past events to see how well the output matches observations, is a viable method of assessing model performance. By simulating the recent past of Greenland, and comparing to observations of ice thickness, ice discharge, surface speeds, mass loss and surface elevation changes for validation, we find that the short term model response is strongly influenced by the initial state. We show that the thermal and dynamical states (i.e. the distribution of internal energy and momentum can be misrepresented despite a good agreement with some observations, stressing the importance of using multiple observations. In particular we identify rates of change of spatially dense observations as preferred validation metrics. Hindcasting enables a qualitative assessment of model performance relative to observed rates of change. It thereby reduces the number of admissible initial states more rigorously than validation efforts that do not take advantage of observed rates of change.
Improving coastal wave hindcasts by combining offshore buoy observations with global wave models.
Crosby, S. C.; O'Reilly, W. C.; Guza, R. T.
2014-12-01
Waves conditions in southern California are sensitive to offshore wave directions. Due to blocking by coastal islands and refraction across complex bathymetry, a transform incident offshore swell-spectra to shallow water buoy locations. A nearly continuous 10 yr data set of approximately 14 buoys is used. Comparisons include standard bulk parameters (e.g. significant wave height, peak period), the frequency-dependent energy spectrum (needed for run-up estimation) and radiation stress component Sxy (needed for alongshore current and sediment transport estimation). Global wave model uncertainties are unknown, complicating the formulation of optimum assimilation constraints. Several plausible models for estimating offshore waves are tested. Future work includes assimilating nearshore buoy observations, with the long-term objective of accurate regional wave hindcasts using an efficient mix of global wave models and buoys. This work is supported by the California Department of Parks and Recreation, Division of Boating and Waterways Oceanography Program.
Evaluation of the multi-model CORDEX-Africa hindcast using RCMES
Kim, J.; Waliser, D. E.; Lean, P.; Mattmann, C. A.; Goodale, C. E.; Hart, A.; Zimdars, P.; Hewitson, B.; Jones, C.
2011-12-01
Recent global climate change studies have concluded with a high confidence level that the observed increasing trend in the global-mean surface air temperatures since mid-20th century is triggered by the emission of anthropogenic greenhouse gases (GHGs). The increase in the global-mean temperature due to anthropogenic emissions is nearly monotonic and may alter the climatological norms resulting in a new climate normal. In the presence of anthropogenic climate change, assessing regional impacts of the altered climate state and developing the plans for mitigating any adverse impacts are an important concern. Assessing future climate state and its impact remains a difficult task largely because of the uncertainties in future emissions and model errors. Uncertainties in climate projections propagates into impact assessment models and result in uncertainties in the impact assessments. In order to facilitate the evaluation of model data, a fundamental step for assessing model errors, the JPL Regional Climate Model Evaluation System (RCMES: Lean et al. 2010; Hart et al. 2011) has been developed through a joint effort of the investigators from UCLA and JPL. RCMES is also a regional climate component of a larger worldwide ExArch project. We will present the evaluation of the surface temperatures and precipitation from multiple RCMs participating in the African component of the Coordinated Regional Climate Downscaling Experiment (CORDEX) that has organized a suite of regional climate projection experiments in which multiple RCMs and GCMs are incorporated. As a part of the project, CORDEX organized a 20-year regional climate hindcast study in order to quantify and understand the uncertainties originating from model errors. Investigators from JPL, UCLA, and the CORDEX-Africa team collaborate to analyze the RCM hindcast data using RCMES. The analysis is focused on measuring the closeness between individual regional climate model outputs as well as their ensembles and observed
Directory of Open Access Journals (Sweden)
J. I. Allen
2003-01-01
Full Text Available The purpose of this paper is to examine the use of a complex ecosystem model along with near real-time in situ data and a sequential data assimilation method for state estimation. The ecosystem model used is the European Regional Seas Ecosystem Model (ERSEM; Baretta et al., 1995 and the assimilation method chosen is the Ensemble Kalman Filer (EnKF. Previously, it has been shown that this method captures the nonlinear error evolution in time and is capable of both tracking the observations and providing realistic error estimates for the estimated state. This system has been used to assimilate long time series of in situ chlorophyll taken from a data buoy in the Cretan Sea. The assimilation of this data using the EnKF method results in a marked improvement in the ability of ERSEM to hindcast chlorophyll. The sensitivity of this system to the type of data used for assimilation, the frequency of assimilation, ensemble size and model errors is discussed. The predictability window of the EnKF appears to be at least 2 days. This is an indication that the methodology might be suitable for future operational data assimilation systems using more complex three-dimensional models. Key words. Oceanography: general (numerical modelling; ocean prediction – Oceanography: biological and chemical (plankton
Directory of Open Access Journals (Sweden)
J. I. Allen
Full Text Available The purpose of this paper is to examine the use of a complex ecosystem model along with near real-time in situ data and a sequential data assimilation method for state estimation. The ecosystem model used is the European Regional Seas Ecosystem Model (ERSEM; Baretta et al., 1995 and the assimilation method chosen is the Ensemble Kalman Filer (EnKF. Previously, it has been shown that this method captures the nonlinear error evolution in time and is capable of both tracking the observations and providing realistic error estimates for the estimated state. This system has been used to assimilate long time series of in situ chlorophyll taken from a data buoy in the Cretan Sea. The assimilation of this data using the EnKF method results in a marked improvement in the ability of ERSEM to hindcast chlorophyll. The sensitivity of this system to the type of data used for assimilation, the frequency of assimilation, ensemble size and model errors is discussed. The predictability window of the EnKF appears to be at least 2 days. This is an indication that the methodology might be suitable for future operational data assimilation systems using more complex three-dimensional models.
Key words. Oceanography: general (numerical modelling; ocean prediction – Oceanography: biological and chemical (plankton
Hermann, Albert J.; Stabeno, Phyllis J.; Haidvogel, Dale B.; Musgrave, David L.
2002-12-01
A regional eddy-resolving primitive equation circulation model was used to simulate circulation on the southeastern Bering Sea (SEBS) shelf and basin. This model resolves the dominant observed mean currents, eddies and meanders in the region, and simultaneously includes both tidal and subtidal dynamics. Circulation, temperature, and salinity fields for years 1995 and 1997 were hindcast, using daily wind and buoyancy flux estimates, and tidal forcing derived from a global model. This paper describes the development of the regional model, a comparison of model results with available Eulerian and Lagrangian data, a comparison of results between the two hindcast years, and a sensitivity analysis. Based on these hindcasts and sensitivity analyses, we suggest the following: (1) The Bering Slope Current is a primary source of large ( ˜100 km diameter) eddies in the SEBS basin. Smaller meanders are also formed along the 100 m isobath on the southeastern shelf, and along the 200-m isobath near the shelf break. (2) There is substantial interannual variability in the statistics of eddies within the basin, driven by variability in the strength of the ANSC. (3) The mean flow on the shelf is not strongly sensitive to changes in the imposed strength of the ANSC; rather, it is strongly sensitive to the local wind forcing. (4) Vertical mixing in the SEBS is strongly affected by both tidal and subtidal dynamics. Strongest mixing in the SEBS may in fact occur between the 100- and 400-m isobaths, near the Pribilof Islands, and in Unimak Pass.
Snyder, Abigail C.; Link, Robert P.; Calvin, Katherine V.
2017-11-01
Hindcasting experiments (conducting a model forecast for a time period in which observational data are available) are being undertaken increasingly often by the integrated assessment model (IAM) community, across many scales of models. When they are undertaken, the results are often evaluated using global aggregates or otherwise highly aggregated skill scores that mask deficiencies. We select a set of deviation-based measures that can be applied on different spatial scales (regional versus global) to make evaluating the large number of variable-region combinations in IAMs more tractable. We also identify performance benchmarks for these measures, based on the statistics of the observational dataset, that allow a model to be evaluated in absolute terms rather than relative to the performance of other models at similar tasks. An ideal evaluation method for hindcast experiments in IAMs would feature both absolute measures for evaluation of a single experiment for a single model and relative measures to compare the results of multiple experiments for a single model or the same experiment repeated across multiple models, such as in community intercomparison studies. The performance benchmarks highlight the use of this scheme for model evaluation in absolute terms, providing information about the reasons a model may perform poorly on a given measure and therefore identifying opportunities for improvement. To demonstrate the use of and types of results possible with the evaluation method, the measures are applied to the results of a past hindcast experiment focusing on land allocation in the Global Change Assessment Model (GCAM) version 3.0. The question of how to more holistically evaluate models as complex as IAMs is an area for future research. We find quantitative evidence that global aggregates alone are not sufficient for evaluating IAMs that require global supply to equal global demand at each time period, such as GCAM. The results of this work indicate it is
How realistic are air quality hindcasts driven by forcings from climate model simulations?
Lacressonnière, G.; Peuch, V.-H.; Arteta, J.; Josse, B.; Joly, M.; Marécal, V.; Saint Martin, D.; Déqué, M.; Watson, L.
2012-12-01
Predicting how European air quality could evolve over the next decades in the context of changing climate requires the use of climate models to produce results that can be averaged in a climatologically and statistically sound manner. This is a very different approach from the one that is generally used for air quality hindcasts for the present period; analysed meteorological fields are used to represent specifically each date and hour. Differences arise both from the fact that a climate model run results in a pure model output, with no influence from observations (which are useful to correct for a range of errors), and that in a "climate" set-up, simulations on a given day, month or even season cannot be related to any specific period of time (but can just be interpreted in a climatological sense). Hence, although an air quality model can be thoroughly validated in a "realistic" set-up using analysed meteorological fields, the question remains of how far its outputs can be interpreted in a "climate" set-up. For this purpose, we focus on Europe and on the current decade using three 5-yr simulations performed with the multiscale chemistry-transport model MOCAGE and use meteorological forcings either from operational meteorological analyses or from climate simulations. We investigate how statistical skill indicators compare in the different simulations, discriminating also the effects of meteorology on atmospheric fields (winds, temperature, humidity, pressure, etc.) and on the dependent emissions and deposition processes (volatile organic compound emissions, deposition velocities, etc.). Our results show in particular how differing boundary layer heights and deposition velocities affect horizontal and vertical distributions of species. When the model is driven by operational analyses, the simulation accurately reproduces the observed values of O3, NOx, SO2 and, with some bias that can be explained by the set-up, PM10. We study how the simulations driven by climate
EDgE multi-model hydro-meteorological seasonal hindcast experiments over Europe
Samaniego, Luis; Thober, Stephan; Kumar, Rohini; Rakovec, Oldrich; Wood, Eric; Sheffield, Justin; Pan, Ming; Wanders, Niko; Prudhomme, Christel
2017-04-01
Extreme hydrometeorological events (e.g., floods, droughts and heat waves) caused serious damage to society and infrastructures over Europe during the past decades. Developing a seamless and skillful operational seasonal forecasting system of these extreme events is therefore a key tool for short-term decision making at local and regional scales. The EDgE project funded by the Copernicus programme (C3S) provides an unique opportunity to investigate the skill of a newly created large multi-model hydro-meteorological ensemble for predicting extreme events over the Pan-EU domain at a higher resolution 5×5 km2. Two state-of-the-art seasonal prediction systems were chosen for this project. Two models from the North American MultiModel ensemble (NMME) with 22 realizations, and two models provided by the ECMWF with 30 realizations. All models provide daily forcings (P, Ta, Tmin, Tmax) of the the Pan-EU at 1°. Downscaling has been carried out with the MTCLIM algorithm (Bohn et al. 2013) and external drift Kriging using elevation as drift to induce orographic effects. In this project, four high-resolution seamless hydrologic simulations with the mHM (www.ufz.de/mhm), Noah-MP, VIC and PCR-GLOBWB have been completed for the common hindcast period of 1993-2012 resulting in an ensemble size of 208 realizations. Key indicators are focussing on six terrestrial Essential Climate Variables (tECVs): river runoff, soil moisture, groundwater recharge, precipitation, potential evapotranspiration, and snow water equivalent. Impact Indicators have been co-designed with stakeholders in Norway (hydro-power), UK (water supply), and Spain (river basin authority) to provide an improved information for decision making. The Indicators encompass diverse information such as the occurrence of high and low streamflow percentiles (floods, and hydrological drought) and lower percentiles of top soil moisture (agricultural drought) among others. Preliminary results evaluated at study sites in Norway
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Hung-Ju Shih
2018-02-01
Full Text Available A 12-year sea-state hindcast for Taiwanese waters, covering the period from 2005 to 2016, was conducted using a fully coupled tide-surge-wave model. The hindcasts of significant wave height and peak period were employed to estimate the wave power resources in the waters surrounding Taiwan. Numerical simulations based on unstructured grids were converted to structured grids with a resolution of 25 × 25 km. The spatial distribution maps of offshore annual mean wave power were created for each year and for the 12-year period. Waters with higher wave power density were observed off the northern, northeastern, southeastern (south of Green Island and southeast of Lanyu and southern coasts of Taiwan. Five energetic sea areas with spatial average annual total wave energy density of 60–90 MWh/m were selected for further analysis. The 25 × 25 km square grids were then downscaled to resolutions of 5 × 5 km, and five 5 × 5 km optimal areas were identified for wave energy converter deployments. The spatial average annual total wave energy yields at the five optimal areas (S1–(S5 were estimated to be 64.3, 84.1, 84.5, 111.0 and 99.3 MWh/m, respectively. The prevailing wave directions for these five areas lie between east and northeast.
Sampson, C. C.; Wing, O.; Quinn, N.; Smith, A.; Neal, J. C.; Schumann, G.; Bates, P.
2017-12-01
During an ongoing natural disaster data are required on: (1) the current situation (nowcast); (2) its likely immediate evolution (forecast); and (3) a consistent view post-event of what actually happened (hindcast or reanalysis). We describe methods used to achieve all three tasks for flood inundation during the Harvey and Irma events using a continental scale 2D hydrodynamic model (Wing et al., 2017). The model solves the local inertial form of the Shallow Water equations over a regular grid of 1 arcsecond ( 30m). Terrain data are taken from the USGS National Elevation Dataset with known flood defences represented using the U.S. Army Corps of Engineers National Levee Dataset. Channels are treated as sub-grid scale features using the HydroSHEDS global hydrography data set. The model is driven using river flows, rainfall and coastal water levels. It simulates river flooding in basins > 50 km2, and fluvial and coastal flooding everywhere. Previous wide area validation tests show this model to be capable of matching FEMA maps and USGS local models built with bespoke data with hit rates of 86% and 92% respectively (Wing et al., 2017). Boundary conditions were taken from NOAA QPS data to produce nowcast and forecast simulations in near real time, before updating with NOAA observations to produce the hindcast. During the event simulation results were supplied to major insurers and multi-nationals who used them to estimate their likely capital exposure and to mitigate flood damage to their infrastructure whilst the event was underway. Simulations were validated against modelled flood footprints computed by FEMA and USACE, and composite satellite imagery produced by the Dartmouth Flood Observatory. For the Harvey event, hit rates ranged from 60-84% against these data sources, but a lack of metadata meant it was difficult to perform like-for-like comparisons. The satellite data also appeared to miss known flooding in urban areas that was picked up in the models. Despite
Krajewski, W. F.; Della Libera Zanchetta, A.; Mantilla, R.; Demir, I.
2017-12-01
This work explores the use of hydroinformatics tools to provide an user friendly and accessible interface for executing and assessing the output of realtime flood forecasts using distributed hydrological models. The main result is the implementation of a web system that uses an Iowa Flood Information System (IFIS)-based environment for graphical displays of rainfall-runoff simulation results for both real-time and past storm events. It communicates with ASYNCH ODE solver to perform large-scale distributed hydrological modeling based on segmentation of the terrain into hillslope-link hydrologic units. The cyber-platform also allows hindcast of model performance by testing multiple model configurations and assumptions of vertical flows in the soils. The scope of the currently implemented system is the entire set of contributing watersheds for the territory of the state of Iowa. The interface provides resources for visualization of animated maps for different water-related modeled states of the environment, including flood-waves propagation with classification of flood magnitude, runoff generation, surface soil moisture and total water column in the soil. Additional tools for comparing different model configurations and performing model evaluation by comparing to observed variables at monitored sites are also available. The user friendly interface has been published to the web under the URL http://ifis.iowafloodcenter.org/ifis/sc/modelplus/.
Energy Technology Data Exchange (ETDEWEB)
Sullivan, T.J.; Bernert, J.A.; Eliers, J.M. (E and S Environmental Chemistry, Corvallis, OR (USA)); Jenne, E.A. (Pacific Northwest Lab., Richland, WA (USA)); Cosby, B.J. (Duke Univ., Durham, NC (USA). School of Forestry and Environmental Studies); Charles, D.F.; Selle, A.R. (Environmental Protection Agency, Corvallis, OR (USA). Environmental Research Lab.)
1991-03-01
Thirty-three lakes that had been statistically selected as part of the US Environmental Protection Agency's Eastern Lake Survey and Direct Delayed Response Project (DDRP) were used to compare the MAGIC (watershed) and Diatom (paleolimnological) models. The study lakes represented a well-defined group of Adirondack lakes, each larger than 4 ha in area and having acid-neutralizing capacity (ANC) <400 {mu}eq L{sup {minus}1}. The study first compared current and pre-industrial (before 1850) pH and ANC estimates from Diatom and MAGIC as they were calibrated in the preceding Paleocological Investigation of Recent Lake Acidification (PIRLA) and DDRP studies, respectively. Initially, the comparison of hindcasts of pre-industrial chemistry was confounded by seasonal and methodological differences in lake chemistry data used in calibration of the model. Although certain differences proved to be of little significance for comparison, MAGIC did predict significantly higher pre-industrial ANC and pH values than did Diatom, using calibrations in the preceding studies. Both models suggest acidification of low ANC Adirondack region lakes since preindustrial times, but differ primarily in that MAGIC inferred greater acidification and that acidification has occurred in all lakes in the comparison, whereas Diatom inferred that acidification has been restricted to low ANC lakes (
Directory of Open Access Journals (Sweden)
Takvor Soukissian
2017-03-01
Full Text Available In this study long-term wind data obtained from high-resolution hindcast simulations is used to analytically assess offshore wind power potential in the Aegean and Ionian Seas and provide wind climate and wind power potential characteristics at selected locations, where offshore wind farms are at the concept/planning phase. After ensuring the good model performance through detailed validation against buoy measurements, offshore wind speed and wind direction at 10 m above sea level are statistically analyzed on the annual and seasonal time scale. The spatial distribution of the mean wind speed and wind direction are provided in the appropriate time scales, along with the mean annual and the inter-annual variability; these statistical quantities are useful in the offshore wind energy sector as regards the preliminary identification of favorable sites for exploitation of offshore wind energy. Moreover, the offshore wind power potential and its variability are also estimated at 80 m height above sea level. The obtained results reveal that there are specific areas in the central and the eastern Aegean Sea that combine intense annual winds with low variability; the annual offshore wind power potential in these areas reach values close to 900 W/m2, suggesting that a detailed assessment of offshore wind energy would be worth noticing and could lead in attractive investments. Furthermore, as a rough estimate of the availability factor, the equiprobable contours of the event [4 m/s ≤ wind speed ≤ 25 m/s] are also estimated and presented. The selected lower and upper bounds of wind speed correspond to typical cut-in and cut-out wind speed thresholds, respectively, for commercial offshore wind turbines. Finally, for seven offshore wind farms that are at the concept/planning phase the main wind climate and wind power density characteristics are also provided.
Chemical spill model (CHEMMAP) for forecasts/hindcasts and environmental risk assessment
International Nuclear Information System (INIS)
French McCay, D.P.
2001-01-01
CHEMMAP is a newly developed three-dimensional, chemical spill model that is used to predict the trajectory and fate of a wide variety of chemical products including floating, sinking, soluble and insoluble chemicals and product mixtures. The model, which was developed by Applied Science Associates Inc., also provides a powerful quantitative tool for estimating the potential impacts of chemical releases. The model incorporates the following components: (1) simulation of the initial release for surface and subsurface spills, (2) slick spreading, transport and entrainment of floating materials, (3) transport of dissolved and particulate materials in three dimensions, (4) evaporation and volatilization, (5) dissolution and adsorption, (6) sedimentation and resuspension, and (7) degradation. The fate of chemical spills are predicted by analyzing physical-chemical properties such as density, vapor pressure, water solubility, environmental degradation rates, adsorbed/dissolved partitioning coefficients, viscosity and surface tension. The distribution of chemicals on the water surface, on shorelines, in the water column and in the sediments can also be estimated. The model can separately track surface slicks, entrained droplets or particles of pure chemical, chemical adsorbed to suspended particulates, and dissolved chemicals. It can be used for forecasting expected water concentrations and atmospheric flux for real events and stochastic applications for ecological risk assessment of chemical spills associated with oil and gas operations in the Gulf of Mexico. 16 refs., 4 tabs., 16 figs
Investigation of Spatial Variation of Sea States Offshore of Humboldt Bay CA Using a Hindcast Model.
Energy Technology Data Exchange (ETDEWEB)
Dallman, Ann Renee; Neary, Vincent Sinclair
2014-10-01
Spatial variability of sea states is an important consideration when performing wave resource assessments and wave resource characterization studies for wave energy converter (WEC) test sites and commercial WEC deployments. This report examines the spatial variation of sea states offshore of Humboldt Bay, CA, using the wave model SWAN . The effect of depth and shoaling on bulk wave parameters is well resolved using the model SWAN with a 200 m grid. At this site, the degree of spatial variation of these bulk wave parameters, with shoaling generally perpendicular to the depth contours, is found to depend on the season. The variation in wave height , for example, was higher in the summer due to the wind and wave sheltering from the protruding land on the coastline north of the model domain. Ho wever, the spatial variation within an area of a potential Tier 1 WEC test site at 45 m depth and 1 square nautical mile is almost negligible; at most about 0.1 m in both winter and summer. The six wave characterization parameters recommended by the IEC 6 2600 - 101 TS were compared at several points along a line perpendicular to shore from the WEC test site . As expected, these parameters varied based on depth , but showed very similar seasonal trends.
Toll, Velle; Männik, Aarne; Luhamaa, Andres; Rõõm, Rein
2015-05-01
On August 8, 2010, a derecho swept over Northern Europe, causing widespread wind damage and more than 2 million Euros in economic loss in Estonia during its most destructive stage. This paper presents a modelling study of the derecho-producing storm utilising the Hirlam Aladin Research for Mesoscale Operational Numerical Weather Prediction in Europe (HARMONIE) model. The model setup is chosen to mimic near-future, nearly kilometre-scale, operational environments in European national weather services. The model simulations are compared to remote sensing and in situ observations. The HARMONIE model is capable of reproducing the wind gust severity and precipitation intensity. Moreover, 2.5-km grid spacing is shown to be sufficient for producing a reliable signal of the severe convective storm. Storm dynamics are well simulated, including the rear inflow jet. Although the model performance is promising, a strong dependence on the initial data, a weak trailing stratiform precipitation region and an incorrect timing of the storm are identified.
Brune, Sebastian; Düsterhus, André; Pohlmann, Holger; Müller, Wolfgang A.; Baehr, Johanna
2017-11-01
We analyze the time dependency of decadal hindcast skill in the North Atlantic subpolar gyre within the time period 1961-2013. We compare anomaly correlation coefficients and temporal interquartile ranges of total upper ocean heat content and sea surface temperature for three differently initialized sets of hindcast simulations with the global coupled model MPI-ESM. All initializations use weakly coupled assimilation with the same full value nudging in the atmospheric component and different assimilation techniques for oceanic temperature and salinity: (1) ensemble Kalman filter assimilating EN4 observations and HadISST data, (2) nudging of anomalies to ORAS4 reanalysis, (3) nudging of full values to ORAS4 reanalysis. We find that hindcast skill depends strongly on the evaluation time period, with higher hindcast skill during strong multiyear trends, especially during the warming in the 1990s and lower hindcast skill in the absence of such trends. Differences between the prediction systems are more pronounced when investigating any 20-year subperiod within the entire hindcast period. In the ensemble Kalman filter initialized hindcasts, we find significant correlation skill for up to 5-8 lead years, albeit along with an overestimation of the temporal interquartile range. In the hindcasts initialized by anomaly nudging, significant correlation skill for lead years greater than two is only found in the 1980s and 1990s. In the hindcasts initialized by full value nudging, correlation skill is consistently lower than in the hindcasts initialized by anomaly nudging in the first lead years with re-emerging skill thereafter. The Atlantic meridional overturning circulation reacts on the density changes introduced by oceanic nudging, this limits the predictability in the subpolar gyre in the first lead years. Overall, we find that a model-consistent assimilation technique can improve hindcast skill. Further, the evaluation of 20 year subperiods within the full hindcast period
Hindcasting of storm waves using neural networks
Digital Repository Service at National Institute of Oceanography (India)
Rao, S.; Mandal, S.
Department NN neural network net i weighted sum of the inputs of neuron i o k network output at kth output node P total number of training pattern s i output of neuron i t k target output at kth output node 1. Introduction Severe storms occur in Bay of Bengal... useful in the planning and maintenance of marine activities. Wave hindcasting is a non-real time application of numerical wave models in the broad field of climatology. Just as weather conditions, w ij weight from neuron j to neuron i YM Young’s model h a...
EURODELTA-Trends, a multi-model experiment of air quality hindcast in Europe over 1990-2010
Colette, Augustin; Andersson, Camilla; Manders, Astrid; Mar, Kathleen; Mircea, Mihaela; Pay, Maria-Teresa; Raffort, Valentin; Tsyro, Svetlana; Cuvelier, Cornelius; Adani, Mario; Bessagnet, Bertrand; Bergström, Robert; Briganti, Gino; Butler, Tim; Cappelletti, Andrea; Couvidat, Florian; D'Isidoro, Massimo; Doumbia, Thierno; Fagerli, Hilde; Granier, Claire; Heyes, Chris; Klimont, Zig; Ojha, Narendra; Otero, Noelia; Schaap, Martijn; Sindelarova, Katarina; Stegehuis, Annemiek I.; Roustan, Yelva; Vautard, Robert; van Meijgaard, Erik; Garcia Vivanco, Marta; Wind, Peter
2017-09-01
The EURODELTA-Trends multi-model chemistry-transport experiment has been designed to facilitate a better understanding of the evolution of air pollution and its drivers for the period 1990-2010 in Europe. The main objective of the experiment is to assess the efficiency of air pollutant emissions mitigation measures in improving regional-scale air quality. The present paper formulates the main scientific questions and policy issues being addressed by the EURODELTA-Trends modelling experiment with an emphasis on how the design and technical features of the modelling experiment answer these questions. The experiment is designed in three tiers, with increasing degrees of computational demand in order to facilitate the participation of as many modelling teams as possible. The basic experiment consists of simulations for the years 1990, 2000, and 2010. Sensitivity analysis for the same three years using various combinations of (i) anthropogenic emissions, (ii) chemical boundary conditions, and (iii) meteorology complements it. The most demanding tier consists of two complete time series from 1990 to 2010, simulated using either time-varying emissions for corresponding years or constant emissions. Eight chemistry-transport models have contributed with calculation results to at least one experiment tier, and five models have - to date - completed the full set of simulations (and 21-year trend calculations have been performed by four models). The modelling results are publicly available for further use by the scientific community. The main expected outcomes are (i) an evaluation of the models' performances for the three reference years, (ii) an evaluation of the skill of the models in capturing observed air pollution trends for the 1990-2010 time period, (iii) attribution analyses of the respective role of driving factors (e.g. emissions, boundary conditions, meteorology), (iv) a dataset based on a multi-model approach, to provide more robust model results for use in impact
EURODELTA-Trends, a multi-model experiment of air quality hindcast in Europe over 1990–2010
Directory of Open Access Journals (Sweden)
A. Colette
2017-09-01
Full Text Available The EURODELTA-Trends multi-model chemistry-transport experiment has been designed to facilitate a better understanding of the evolution of air pollution and its drivers for the period 1990–2010 in Europe. The main objective of the experiment is to assess the efficiency of air pollutant emissions mitigation measures in improving regional-scale air quality. The present paper formulates the main scientific questions and policy issues being addressed by the EURODELTA-Trends modelling experiment with an emphasis on how the design and technical features of the modelling experiment answer these questions. The experiment is designed in three tiers, with increasing degrees of computational demand in order to facilitate the participation of as many modelling teams as possible. The basic experiment consists of simulations for the years 1990, 2000, and 2010. Sensitivity analysis for the same three years using various combinations of (i anthropogenic emissions, (ii chemical boundary conditions, and (iii meteorology complements it. The most demanding tier consists of two complete time series from 1990 to 2010, simulated using either time-varying emissions for corresponding years or constant emissions. Eight chemistry-transport models have contributed with calculation results to at least one experiment tier, and five models have – to date – completed the full set of simulations (and 21-year trend calculations have been performed by four models. The modelling results are publicly available for further use by the scientific community. The main expected outcomes are (i an evaluation of the models' performances for the three reference years, (ii an evaluation of the skill of the models in capturing observed air pollution trends for the 1990–2010 time period, (iii attribution analyses of the respective role of driving factors (e.g. emissions, boundary conditions, meteorology, (iv a dataset based on a multi-model approach, to provide more robust model
Directory of Open Access Journals (Sweden)
Andrzej Jankowski
2002-12-01
Full Text Available This paper presents the results of an attempt to reproduce, with theaid of a numerical circulation model, the hydrological conditions observedin the coastal area of the southern Baltic in September 1989.A large fall in surface layer seawater temperature was recordedin September 1989 at two coastal stations in the vicinity ofKolobrzeg and Wladyslawowo. This upwelling-like phenomenon was assumed tobe related to the specific anemobaric situation in September 1989,however typical of this phenomenon to occur along the Polish Baltic coast(Malicki & Mietus 1994. A three-dimensional (3-D sigma-coordinatebaroclinic model of the Baltic Sea, with a horizontal resolution of~5 km and 24 sigma-levels in the vertical, was applied to investigatewater circulation and thermohaline variability. Hindcastnumerical simulation showed that the model provided a good reproductionof the temporal history of the surface seawater temperature and theduration of the upwelling-like fall, but that the model results wereunderestimated. The maxima of this large fall in the surface layertemperature at both coastal stations are closely related to the phase ofchange of the upwelling-favourable wind direction to the opposite one.The results of simulation runs showed details of upwelling developmentdue to wind field fluctuations in time and differences in shaping thetemperature and current patterns in conjunction with the variations intopography and coastline features in some areas along the Polish coast.Two different hydrodynamic regimes of water movements along the coastresulting from topographical features (the Slupsk Bank can be distinguished.From the model simulation the specific conditions for the occurrence anddevelopment of upwelling at the eastern end of the Polish coast(in the vicinity of Wladyslawowo can be deduced.
Wave hindcast experiments in the Indian Ocean using MIKE 21 SW
Indian Academy of Sciences (India)
Wave prediction and hindcast studies are important in ocean engineering, coastal infrastructure development and management. In view of sparse and infrequent in-situ observations, model derived hindcast wave data can be used for the assessment of wave climate in offshore and coastal areas. In the present study, MIKE ...
Wave hindcast experiments in the Indian Ocean using MIKE 21 SW ...
Indian Academy of Sciences (India)
Wave prediction and hindcast studies are important in ocean engineering, coastal infrastructure devel- opment and management. In view of sparse and infrequent in-situ observations, model derived hindcast wave data can be used for the assessment of wave climate in offshore and coastal areas. In the present study, MIKE ...
Improvement of wind field hindcasts for tropical cyclones
Directory of Open Access Journals (Sweden)
Yi Pan
2016-01-01
Full Text Available This paper presents a study on the improvement of wind field hindcasts for two typical tropical cyclones, i.e., Fanapi and Meranti, which occurred in 2010. The performance of the three existing models for the hindcasting of cyclone wind fields is first examined, and then two modification methods are proposed to improve the hindcasted results. The first one is the superposition method, which superposes the wind field calculated from the parametric cyclone model on that obtained from the Cross-Calibrated Multi-Platform (CCMP reanalysis data. The radius used for the superposition is based on an analysis of the minimum difference between the two wind fields. The other one is the direct modification method, which directly modifies the CCMP reanalysis data according to the ratio of the measured maximum wind speed to the reanalyzed value as well as the distance from the cyclone center. Using these two methods, the problem of underestimation of strong winds in reanalysis data can be overcome. Both methods show considerable improvements in the hindcasting of tropical cyclone wind fields, compared with the cyclone wind model and the reanalysis data.
Improvement of wind field hindcasts for tropical cyclones
Directory of Open Access Journals (Sweden)
Yi Pan
2016-01-01
Full Text Available This paper presents a study on the improvement of wind field hindcasts for two typical tropical cyclones, i.e., Fanapi and Meranti, which occurred in 2010. The performance of the three existing models for the hindcasting of cyclone wind fields is first examined, and then two modification methods are proposed to improve the hindcasted results. The first one is the superposition method, which superposes the wind field calculated from the parametric cyclone model on that obtained from the cross-calibrated multi-platform (CCMP reanalysis data. The radius used for the superposition is based on an analysis of the minimum difference between the two wind fields. The other one is the direct modification method, which directly modifies the CCMP reanalysis data according to the ratio of the measured maximum wind speed to the reanalyzed value as well as the distance from the cyclone center. Using these two methods, the problem of underestimation of strong winds in reanalysis data can be overcome. Both methods show considerable improvements in the hindcasting of tropical cyclone wind fields, compared with the cyclone wind model and the reanalysis data.
Continuously on-going hindcast simulations for impact applications
Anders, Ivonne; Geyer, Beate
2016-04-01
Observations for e.g. temperature, precipitation, radiation, or wind are often used as meteorological forcing for different impact models, like e.g. crop models, urban models, economic models and energy system models. To assess a climate signal, the time period covered by the observation is often too short, they have gaps in between, and are inhomogeneous over time, due to changes in the measurements itself or in the near surrounding. Thus output from global and regional climate models can close the gap and provide homogeneous and physically consistent time series of meteorological parameters. CORDEX evaluation runs performed for the IPCC-AR5 provide a good base for the regional scale. However, with respect to climate services, continuously on-going hindcast simulations are required for regularly updated applications. In this study two projects are presented where hindcast-simulations optimized for a region of interest are performed continuously. The hindcast simulation performed by HZG covering Europe includes the EURO-CORDEX domain with a wider extend to the north to cover the ice edge. The simulation under consideration of the coastDat-experiences is available for the period of 1979 - 2015, prolonged ongoing and fulfills the customer's needs with respect of output variables, levels, intervals and statistical measures. CoastDat - customers are dealing e.g. with naval architecture, renewable energies, offshore wind farming, shipping emissions, coastal flood risk and others. The evaluation of the hindcast is done for Europe by using the EVAL-tool of the CCLM community and by comparison with HYRAS - data for Germany and neighbouring countries. The Climate Research group at the national Austrian weather service, ZAMG, is focusing on high mountain regions and, especially on the Alps. The hindcast-simulation is forced by ERA-interim and optimized for the Alpine Region. One of the main tasks is to capture strong precipitation events which often occur during summer when
Boulder-based wave hindcasting underestimates storm size
Kennedy, David; Woods, Joesphine; Rosser, Nick; Hansom, James; Naylor, Larissa
2017-04-01
Large boulder-size clasts represent an important archive of erosion and wave activity on the coast. From tropical coral reefs to eroding cliffs in the high-latitudes, boulders have been used to hindcast the frequency and magnitude of cyclones and tsunami. Such reconstructions are based on the balance between the hydrodynamic forces acting on individual clasts and the counteracting resistive forces of friction and gravity. Here we test the three principle hindcasting relationships on nearly 1000 intertidal boulders in North Yorkshire, U.K using a combination of field and airborne terrestrial LiDAR data. We quantify the predicted versus actual rates of movement and the degree to which local geomorphology can retard or accelerate transport. Actual clast movement is significantly less than predicted values, regardless of boulder volume, shape or location. In situ cementation of clasts to the substrate by marine organisms and clustering of clasts increases friction thereby preventing transport. The implication is that boulders do not always provide a reliable estimation of wave height on the coast and reliance solely on hindcasting relationships leads to an under prediction of the frequency and magnitude of past storm wave activity. The crucial need for process field studies to refine boulder transport models is thus demonstrated.
Evaluation of decadal hindcasts using satellite simulators
Spangehl, Thomas; Mazurkiewicz, Alex; Schröder, Marc
2013-04-01
hydrometeor types. Therefore, testing is performed to determine the extent to which the quality of the simulator results depends on the applied methods used to generate sub-grid variability (e.g. sub-grid resolution). Moreover, the sensitivity of results to the choice of different distributions of hydrometeors is explored. The model evaluation is carried out in a statistical manner using histograms of radar reflectivities (TRMM PR) and brightness temperatures (IASI). Finally, methods to deduce data suitable for probabilistic evaluation of decadal hindcasts such as simple indices are discussed.
National Oceanic and Atmospheric Administration, Department of Commerce — Weekly biophysical and fish model output of FEAST. Part of The Bering Sea Project, FEAST is a high resolution (~10km2) spatial model that uses a Regional Ocean...
Assessment of Arctic and Antarctic sea ice predictability in CMIP5 decadal hindcasts
Directory of Open Access Journals (Sweden)
C.-Y. Yang
2016-10-01
Full Text Available This paper examines the ability of coupled global climate models to predict decadal variability of Arctic and Antarctic sea ice. We analyze decadal hindcasts/predictions of 11 Coupled Model Intercomparison Project Phase 5 (CMIP5 models. Decadal hindcasts exhibit a large multi-model spread in the simulated sea ice extent, with some models deviating significantly from the observations as the predicted ice extent quickly drifts away from the initial constraint. The anomaly correlation analysis between the decadal hindcast and observed sea ice suggests that in the Arctic, for most models, the areas showing significant predictive skill become broader associated with increasing lead times. This area expansion is largely because nearly all the models are capable of predicting the observed decreasing Arctic sea ice cover. Sea ice extent in the North Pacific has better predictive skill than that in the North Atlantic (particularly at a lead time of 3–7 years, but there is a re-emerging predictive skill in the North Atlantic at a lead time of 6–8 years. In contrast to the Arctic, Antarctic sea ice decadal hindcasts do not show broad predictive skill at any timescales, and there is no obvious improvement linking the areal extent of significant predictive skill to lead time increase. This might be because nearly all the models predict a retreating Antarctic sea ice cover, opposite to the observations. For the Arctic, the predictive skill of the multi-model ensemble mean outperforms most models and the persistence prediction at longer timescales, which is not the case for the Antarctic. Overall, for the Arctic, initialized decadal hindcasts show improved predictive skill compared to uninitialized simulations, although this improvement is not present in the Antarctic.
A multi-decadal wind-wave hindcast for the North Sea 1949-2014: coastDat2
Groll, Nikolaus; Weisse, Ralf
2017-12-01
Long and consistent wave data are important for analysing wave climate variability and change. Moreover, such wave data are also needed in coastal and offshore design and for addressing safety-related issues at sea. Using the third-generation spectral wave model WAM a multi-decadal wind-wave hindcast for the North Sea covering the period 1949-2014 was produced. The hindcast is part of the coastDat database representing a consistent and homogeneous met-ocean data set. It is shown that despite not being perfect, data from the wave hindcast are generally suitable for wave climate analysis. In particular, comparisons of hindcast data with in situ and satellite observations show on average a reasonable agreement, while a tendency towards overestimation of the highest waves could be inferred. Despite these limitations, the wave hindcast still provides useful data for assessing wave climate variability and change as well as for risk analysis, in particular when conservative estimates are needed. Hindcast data are stored at the World Data Center for Climate (WDCC) and can be freely accessed using the doi:10.1594/WDCC/coastDat-2_WAM-North_Sea Groll and Weisse(2016) or via the coastDat web-page http://www.coastdat.de.
Identifying causes of Western Pacific ITCZ drift in ECMWF System 4 hindcasts
Shonk, Jonathan K. P.; Guilyardi, Eric; Toniazzo, Thomas; Woolnough, Steven J.; Stockdale, Tim
2018-02-01
The development of systematic biases in climate models used in operational seasonal forecasting adversely affects the quality of forecasts they produce. In this study, we examine the initial evolution of systematic biases in the ECMWF System 4 forecast model, and isolate aspects of the model simulations that lead to the development of these biases. We focus on the tendency of the simulated intertropical convergence zone in the western equatorial Pacific to drift northwards by between 0.5° and 3° of latitude depending on season. Comparing observations with both fully coupled atmosphere-ocean hindcasts and atmosphere-only hindcasts (driven by observed sea-surface temperatures), we show that the northward drift is caused by a cooling of the sea-surface temperature on the Equator. The cooling is associated with anomalous easterly wind stress and excessive evaporation during the first twenty days of hindcast, both of which occur whether air-sea interactions are permitted or not. The easterly wind bias develops immediately after initialisation throughout the lower troposphere; a westerly bias develops in the upper troposphere after about 10 days of hindcast. At this point, the baroclinic structure of the wind bias suggests coupling with errors in convective heating, although the initial wind bias is barotropic in structure and appears to have an alternative origin.
SOFTWARE SOLUTIONS FOR ARDL MODELS
Directory of Open Access Journals (Sweden)
Nicolae-Marius JULA
2015-07-01
Full Text Available VAR type models can be used only for stationary time series. Causality analyses through econometric models need that series to have the same integrated order. Usually, when constraining the series to comply these restrictions (e.g. by differentiating, economic interpretation of the outcomes may become difficult. Recent solution for mitigating these problems is the use of ARDL (autoregressive distributed lag models. We present implementation in E-Views of these models and we test the impact of exchange rate on consumer price index.
Application of Bayesian Networks to hindcast barrier island morphodynamics
Wilson, Kathleen E.; Adams, Peter N.; Hapke, Cheryl J.; Lentz, Erika E.; Brenner, Owen T.
2015-01-01
Prediction of coastal vulnerability is of increasing concern to policy makers, coastal managers and other stakeholders. Coastal regions and barrier islands along the Atlantic and Gulf coasts are subject to frequent, large storms, whose waves and storm surge can dramatically alter beach morphology, threaten infrastructure, and impact local economies. Given that precise forecasts of regional hazards are challenging, because of the complex interactions between processes on many scales, a range of probable geomorphic change in response to storm conditions is often more helpful than deterministic predictions. Site-specific probabilistic models of coastal change are reliable because they are formulated with observations so that local factors, of potentially high influence, are inherent in the model. The development and use of predictive tools such as Bayesian Networks in response to future storms has the potential to better inform management decisions and hazard preparation in coastal communities. We present several Bayesian Networks designed to hindcast distinct morphologic changes attributable to the Nor'Ida storm of 2009, at Fire Island, New York. Model predictions are informed with historical system behavior, initial morphologic conditions, and a parameterized treatment of wave climate.
UTLS temperature validation of MPI-ESM decadal hindcast experiments with GPS radio occultations
Directory of Open Access Journals (Sweden)
Torsten Schmidt
2016-12-01
Full Text Available Global Positioning System (GPS radio occultation (RO temperature data are used to validate MPI-ESM (Max Planck Institute – Earth System Model decadal hindcast experiments in the upper troposphere and lower stratosphere (UTLS region between 300 hPa and 10 hPa (8 km and 32 km for the time period between 2002 and 2011. The GPSRO dataset is unique since it is very precise, calibration independent and covers the globe better than the usual radiosonde dataset. In addition it is vertically finer resolved than any of the existing satellite temperature measurements available for the UTLS and provides now a unique one decade long temperature validation dataset. The initialization of the MPI-ESM decadal hindcast runs mostly increases the skill of the atmospheric temperatures when compared to uninitialized climate projections with very high skill scores for lead-year one, and gradually decreases for the later lead-years. A comparison between two different initialization sets (b0, b1 of the low-resolution (LR MPI-ESM shows increased skills in b1-LR in most parts of the UTLS in particular in the tropics. The medium resolution (MR MPI-ESM initializations are characterized by reduced temperature biases in the uninitialized runs as compared to observations and a better capturing of the high latitude northern hemisphere interannual polar vortex variability as compared to the LR model version. Negative skills are found for the b1-MR hindcasts however in the regions around the mid-latitude tropospheric jets on both hemispheres and in the vicinity of the tropical tropopause in comparison to the b1-LR variant. It is interesting to highlight that none of the model experiments can reproduce the observed positive temperature trend in the tropical tropopause region since 2001 as seen by GPSRO data.
Hindcasting morphodynamic evolution with sand–mud interactions in the Yangtze Estuary
Directory of Open Access Journals (Sweden)
H. Jie
2015-05-01
Full Text Available Previous work on morphodynamic evolution in the Yangtze Estuary (YE is based on measured historical bathymetries. To evaluate the sensitivity of sand–mud interaction in the estuarine morpho-dynamics, a process-based morphodynamic model, Delft3D, is used to examine the morphodynamic behaviour from 1958 to 1997. Different scenarios concerning sand and mud and their combination are designed systematically. The scenarios considering multiple fractions, and especially with four fractions, improve the hindcasting evolution, suggesting the importance of including both sand and mud fractions and a sediment gradient setting of medium grain.
A hindcast archive to assess forecast uncertainty of seasonal forecasts for the Columbia River Basin
Nijssen, B.
2006-12-01
More than half of the electricity in the northwestern United States is generated by hydropower facilities in the Columbia River Basin. Consequently, seasonal hydrologic forecasts of naturalized streamflow are of interest to system operators, energy traders and financial institutions. Much of the seasonal streamflow predictability is derived from the importance of snow melt in the Columbia River Basin. Further predictability is derived from the ENSO-state (El Niño Southern Oscillation), which affects precipitation patterns in the basin. Typically, the Pacific Northwest experiences a greater likelihood of reduced precipitation during El Niño episodes, and a greater likelihood of increased precipitation during La Niña episodes. For the 2006 water year, we created long-range operational hydrologic forecasts for selected locations in the basin using a macroscale hydrologic model and an ensemble streamflow prediction (ESP) methodology. Although our ESP approach provided a measure of the range of expected streamflow conditions, it did not account for the uncertainty in forecast initial conditions, parameter uncertainty or model uncertainty. To assess the total uncertainty associated with our hydrologic forecasts, we have created a hindcast database for the period 1950-2005, which includes 12-month forecasts made on the start of each month during the period November May. This hindcast archive enables us to assess the total uncertainty associated with our seasonal forecasts. We will present forecast verification results for selected locations in the Columbia River Basin as a function of lead time and ENSO condition.
Continuously on-going regional climate hindcast simulations for impact applications
Anders, Ivonne; Piringer, Martin; Kaufmann, Hildegard; Knauder, Werner; Resch, Gernot; Andre, Konrad
2017-04-01
Observational data for e.g. temperature, precipitation, radiation, or wind are often used as meteorological forcing for different impact models, like e.g. crop models, urban models, economic models and energy system models. To assess a climate signal, the time period covered by the observation is often too short, they have gaps in between, and are inhomogeneous over time, due to changes in the measurements itself or in the near surrounding. Thus output from global and regional climate models can close the gap and provide homogeneous and physically consistent time series of meteorological parameters. CORDEX evaluation runs performed for the IPCC-AR5 provide a good base for the regional scale. However, with respect to climate services, continuously on-going hindcast simulations are required for regularly updated applications. The Climate Research group at the national Austrian weather service, ZAMG, is focusing on high mountain regions and, especially on the Alps. The hindcast-simulation performed with the regional climate model COSMO-CLM is forced by ERAinterim and optimized for the Alpine Region. The simulation available for the period of 1979-2015 in a spatial resolution of about 10km is prolonged ongoing and fullfils the customer's needs with respect of output variables, levels, intervals and statistical measures. One of the main tasks is to capture strong precipitation events which often occur during summer when low pressure systems develop over the Golf of Genoa, moving to the Northeast. This leads to floods and landslide events in Austria, Czech Republic and Germany. Such events are not sufficiently represented in the CORDEX-evaluation runs. ZAMG use high quality gridded precipitation and temperature data for the Alpine Region (1-6km) to evaluate the model performance. Data is provided e.g. to hydrological modellers (high water, low water), but also to assess icing capability of infrastructure or the calculation the separation distances between livestock
Pseudoclassical fermionic model and classical solutions
International Nuclear Information System (INIS)
Smailagic, A.
1981-08-01
We study classical limit of fermionic fields seen as Grassmann variables and deduce the proper quantization prescription using Dirac's method for constrained systems and investigate quantum meaning of classical solutions for the Thirring model. (author)
The quantum Rabi model: solution and dynamics
International Nuclear Information System (INIS)
Xie, Qiongtao; Zhong, Honghua; Lee, Chaohong; Batchelor, Murray T
2017-01-01
This article presents a review of recent developments on various aspects of the quantum Rabi model. Particular emphasis is given on the exact analytic solution obtained in terms of confluent Heun functions. The analytic solutions for various generalisations of the quantum Rabi model are also discussed. Results are also reviewed on the level statistics and the dynamics of the quantum Rabi model. The article concludes with an introductory overview of several experimental realisations of the quantum Rabi model. An outlook towards future developments is also given. (topical review)
Applied Integer Programming Modeling and Solution
Chen, Der-San; Dang, Yu
2011-01-01
An accessible treatment of the modeling and solution of integer programming problems, featuring modern applications and software In order to fully comprehend the algorithms associated with integer programming, it is important to understand not only how algorithms work, but also why they work. Applied Integer Programming features a unique emphasis on this point, focusing on problem modeling and solution using commercial software. Taking an application-oriented approach, this book addresses the art and science of mathematical modeling related to the mixed integer programming (MIP) framework and
Hoteit, Ibrahim
2010-03-02
An eddy-permitting adjoint-based assimilation system has been implemented to estimate the state of the tropical Pacific Ocean. The system uses the Massachusetts Institute of Technology\\'s general circulation model and its adjoint. The adjoint method is used to adjust the model to observations by controlling the initial temperature and salinity; temperature, salinity, and horizontal velocities at the open boundaries; and surface fluxes of momentum, heat, and freshwater. The model is constrained with most of the available data sets in the tropical Pacific, including Tropical Atmosphere and Ocean, ARGO, expendable bathythermograph, and satellite SST and sea surface height data, and climatologies. Results of hindcast experiments in 2000 suggest that the iterated adjoint-based descent is able to significantly improve the model consistency with the multivariate data sets, providing a dynamically consistent realization of the tropical Pacific circulation that generally matches the observations to within specified errors. The estimated model state is evaluated both by comparisons with observations and by checking the controls, the momentum balances, and the representation of small-scale features that were not well sampled by the observations used in the assimilation. As part of these checks, the estimated controls are smoothed and applied in independent model runs to check that small changes in the controls do not greatly change the model hindcast. This is a simple ensemble-based uncertainty analysis. In addition, the original and smoothed controls are applied to a version of the model with doubled horizontal resolution resulting in a broadly similar “downscaled” hindcast, showing that the adjustments are not tuned to a single configuration (meaning resolution, topography, and parameter settings). The time-evolving model state and the adjusted controls should be useful for analysis or to supply the forcing, initial, and boundary conditions for runs of other models.
Aqueous Solution Vessel Thermal Model Development II
Energy Technology Data Exchange (ETDEWEB)
Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-10-28
The work presented in this report is a continuation of the work described in the May 2015 report, “Aqueous Solution Vessel Thermal Model Development”. This computational fluid dynamics (CFD) model aims to predict the temperature and bubble volume fraction in an aqueous solution of uranium. These values affect the reactivity of the fissile solution, so it is important to be able to calculate them and determine their effects on the reaction. Part A of this report describes some of the parameter comparisons performed on the CFD model using Fluent. Part B describes the coupling of the Fluent model with a Monte-Carlo N-Particle (MCNP) neutron transport model. The fuel tank geometry is the same as it was in the May 2015 report, annular with a thickness-to-height ratio of 0.16. An accelerator-driven neutron source provides the excitation for the reaction, and internal and external water cooling channels remove the heat. The model used in this work incorporates the Eulerian multiphase model with lift, wall lubrication, turbulent dispersion and turbulence interaction. The buoyancy-driven flow is modeled using the Boussinesq approximation, and the flow turbulence is determined using the k-ω Shear-Stress-Transport (SST) model. The dispersed turbulence multiphase model is employed to capture the multiphase turbulence effects.
First Successful Hindcasts of the 2016 Disruption of the Stratospheric Quasi-biennial Oscillation
Watanabe, S.; Hamilton, K.; Osprey, S.; Kawatani, Y.; Nishimoto, E.
2018-02-01
In early 2016 the quasi-biennial oscillation in tropical stratospheric winds was disrupted by an anomalous easterly jet centered at 40 hPa, a development that was completely missed by all operational extended range weather forecast systems. This event and its predictability are investigated through 40 day ensemble hindcasts using a global model notable for its sophisticated representation of the upper atmosphere. Integrations starting at different times throughout January 2016—just before and during the initial development of the easterly jet—were performed. All integrations simulated the unusual developments in the stratospheric mean wind, despite considerable differences in other aspects of the flow evolution among the ensemble members, notably in the evolution of the winter polar vortex and the day-to-day variations in extratropical Rossby waves. Key to prediction of this event is simulating the slowly evolving mean winds in the winter subtropics that provide a waveguide for Rossby waves propagating from the winter hemisphere.
Smooth solutions for the dyadic model
International Nuclear Information System (INIS)
Barbato, David; Morandin, Francesco; Romito, Marco
2011-01-01
We consider the dyadic model, which is a toy model to test issues of well-posedness and blow-up for the Navier–Stokes and Euler equations. We prove well-posedness of positive solutions of the viscous problem in the relevant scaling range which corresponds to Navier–Stokes. Likewise we prove well-posedness for the inviscid problem (in a suitable regularity class) when the parameter corresponds to the strongest transport effect of the nonlinearity
Brune, Sebastian; Pohlmann, Holger; Düsterhus, Andre; Kröger, Jürgen; Müller, Wolfgang; Baehr, Johanna
2016-04-01
We investigate hindcast skill for surface air temperature and upper ocean heat content (0-700m) in the North Atlantic for yearly mean values from 1960 to 2014 in four prediction systems based on the global coupled Max Planck Institute for Meteorology Earth System Model (MPI-ESM). We find that in the North Atlantic and within the four prediction systems under consideration only the EnKF initialized hindcasts reproduce the variability of the reference data well both in terms of anomaly correlation and representation of the probability density function. The systems under consideration only differ in the method how they incorporate surface and sub-surface oceanic temperatures and salinities during assimilation: ensemble Kalman Filter (EnKF), anomaly nudging of ORA reanalysis (BS-1), full field nudging of ORA and GECCO reanalysis, respectively (PT-ORA, PT-GEC). We assess the hindcast skill of each prediction system with reference to HadCRUT4 near surface air temperature data (Morice et al. 2012) and NOAA OC5 upper ocean heat content data (Levitus et al. 2012) using anomaly correlation (ACC) and by analysing the interquartile range (IQR) of the probability density function (PDF). Firstly, we calculate hindcast skill in terms of ACC and IQR against reference data over the whole time period. Here, the hindcast skills of EnKF and BS-1 are better for both ACC and IQR in lead years 2 to 5 when compared to PT-ORA and PT-GEC, their hindcast skill drops off after lead year 1. Secondly, the PDF of the reference data is not uniformly distributed over time. We therefore calculate ACC and IQR for a 20 year moving window. We find hindcast skill in terms of ACC for EnKF and BS-1 in the 1960s and from the 1990s onwards, up to eight lead years in advance, with almost no skill for the time period inbetween. In contrast, there is no skill for PT-ORA and PT-GEC in any period after lead year one. The IQR of reference data is best captured by the EnKF, in the 1960s and 1990s up to lead year
Coarse-Grained Modeling of Polyelectrolyte Solutions
Denton, Alan R.; May, Sylvio
2014-03-01
Ionic mixtures, such as electrolyte and polyelectrolyte solutions, have attracted much attention recently for their rich and challenging combination of electrostatic and non-electrostatic interparticle forces and their practical importance, from battery technologies to biological systems. Hydration of ions in aqueous solutions is known to entail ion-specific effects, including variable solubility of organic molecules, as manifested in the classic Hofmeister series for salting-in and salting-out of proteins. The physical mechanism by which the solvent (water) mediates effective interactions between ions, however, is still poorly understood. Starting from a microscopic model of a polyelectrolyte solution, we apply a perturbation theory to derive a coarse-grained model of ions interacting through both long-range electrostatic and short-range solvent-induced pair potentials. Taking these effective interactions as input to molecular dynamics simulations, we calculate structural and thermodynamic properties of aqueous ionic solutions. This work was supported by the National Science Foundation under Grant No. DMR-1106331.
An evaporation model of multicomponent solution drops
Sartori, Silvana; Liñán, Amable; Lasheras, Juan C.
2010-11-01
Solutions of polymers are widely used in the pharmaceutical industry as tablets coatings. These allow controlling the rate at which the drug is delivered, taste or appearance. The coating is performed by spraying and drying the tablets at moderate temperatures. The wetting of the coating solution on the pill's surface depends on the droplet Webber and Re numbers, angle of impact and on the rheological properties of the droplet. We present a model for the evaporation of multicomponent solutions droplets in a hot air environment with temperatures substantially lower than the boiling temperature of the solvent. As the liquid vaporizes from the surface the fluid in the drop increases in concentration, until reaching its saturation point. After saturation, precipitation occurs uniformly within the drop. As the surface regresses, a compacting front formed by the precipitate at its maximum packing density advances into the drop, while the solute continues precipitating uniformly. This porous shell grows fast due to the double effect of surface regression and precipitation. The evaporation rate is determined by the rates at which heat is transported to the droplet surface and at which liquid vapor diffuses away from it. When the drop is fully compacted, the evaporation is drastically reduced.
Li, Shuiqing; Guan, Shoude; Hou, Yijun; Liu, Yahao; Bi, Fan
2018-05-01
A long-term trend of significant wave height (SWH) in China's coastal seas was examined based on three datasets derived from satellite measurements and numerical hindcasts. One set of altimeter data were obtained from the GlobWave, while the other two datasets of numerical hindcasts were obtained from the third-generation wind wave model, WAVEWATCH III, forced by wind fields from the Cross-Calibrated Multi-Platform (CCMP) and NCEP's Climate Forecast System Reanalysis (CFSR). The mean and extreme wave trends were estimated for the period 1992-2010 with respect to the annual mean and the 99th-percentile values of SWH, respectively. The altimeter wave trend estimates feature considerable uncertainties owing to the sparse sampling rate. Furthermore, the extreme wave trend tends to be overestimated because of the increasing sampling rate over time. Numerical wave trends strongly depend on the quality of the wind fields, as the CCMP waves significantly overestimate the wave trend, whereas the CFSR waves tend to underestimate the trend. Corresponding adjustments were applied which effectively improved the trend estimates from the altimeter and numerical data. The adjusted results show generally increasing mean wave trends, while the extreme wave trends are more spatially-varied, from decreasing trends prevailing in the South China Sea to significant increasing trends mainly in the East China Sea.
Hindcasting of Storm Surges, Currents, and Waves at Lower Delaware Bay during Hurricane Isabel
Salehi, M.
2017-12-01
Hurricanes are a major threat to coastal communities and infrastructures including nuclear power plants located in low-lying coastal zones. In response, their sensitive elements should be protected by smart design to withstand against drastic impact of such natural phenomena. Accurate and reliable estimate of hurricane attributes is the first step to that effort. Numerical models have extensively grown over the past few years and are effective tools in modeling large scale natural events such as hurricane. The impact of low probability hurricanes on the lower Delaware Bay is investigated using dynamically coupled meteorological, hydrodynamic, and wave components of Delft3D software. Efforts are made to significantly reduce the computational overburden of performing such analysis for the industry, yet keeping the same level of accuracy at the area of study (AOS). The model is comprised of overall and nested domains. The overall model domain includes portion of Atlantic Ocean, Delaware, and Chesapeake bays. The nested model domain includes Delaware Bay, its floodplain, and portion of the continental shelf. This study is portion of a larger modeling effort to study the impact of low probability hurricanes on sensitive infrastructures located at the coastal zones prone to hurricane activity. The AOS is located on the east bank of Delaware Bay almost 16 miles upstream of its mouth. Model generated wind speed, significant wave height, water surface elevation, and current are calibrated for hurricane Isabel (2003). The model calibration results agreed reasonably well with field observations. Furthermore, sensitivity of surge and wave responses to various hurricane parameters was tested. In line with findings from other researchers, accuracy of wind field played a major role in hindcasting the hurricane attributes.
Energy Technology Data Exchange (ETDEWEB)
Sotillo, M.G. [Area de Medio Fisico, Puertos del Estado, Madrid (Spain); Martin, M.L. [Universidad de Valladolid, Dpto. Matematica Aplicada, Escuela Universitaria de Informatica, Campus de Segovia, Segovia (Spain); Valero, F. [Universidad Complutense de Madrid, Dpto. Astrofisica y CC. de la Atmosfera, Facultad de CC Fisicas, Madrid (Spain); Luna, M.Y. [Instituto Nacional de Meteorologia, Madrid (Spain)
2006-11-15
A 44-year (1958-2001) homogeneous, Mediterranean, high-resolution atmospheric database was generated through dynamical downscaling within the HIPOCAS (Hindcast of Dynamic Processes of the Ocean and Coastal Areas of Europe) Project framework. This work attempts to provide a validation of the monthly winter HIPOCAS precipitation over the Iberian Peninsula and the Balearic Islands and to evaluate the potential improvement of these new hindcasted data versus global reanalysis datasets. The validation was performed through the comparative analysis with a precipitation database derived from 4,617 in situ stations located over Iberia and the Balearics. The statistical comparative analysis between the observed and the HIPOCAS fields highlights their very good agreement not only in terms of spatial and time distribution, but also in terms of total amount of precipitation. A principal component analysis is carried out, showing that the patterns derived from the HIPOCAS data largely capture the main characteristics of the observed field. Moreover, it is worth to note that the HIPOCAS patterns reproduce accurately the observed regional characteristics linked to the main orographic features of the study domain. The existence of high correlations between the hindcasted and observed principal component time series gives a measure of the model performance ability. An additional comparative study of the HIPOCAS winter precipitation with global reanalysis data (NCEP and ERA) is performed. This study reveals the important regional improvement in the characterization of the observed precipitation introduced by the HIPOCAS hindcast relative to the above global reanalyses. Such improvement is effective not only in terms of total amount values, but also in the spatial distribution, the observed field being much more realistically reproduced by HIPOCAS than by the global reanalysis data. (orig.)
Solute transport modelling with the variable temporally dependent ...
Indian Academy of Sciences (India)
Pintu Das
2018-02-07
Feb 7, 2018 ... In this present study, analytical and numerical solutions are obtained for solute transport modelling in homogeneous ..... Clay (0.40). Analytical solution. Numerical solution. Figure 3. Comparison of concentration distribution for sinu- soidal velocity pattern for boundary condition c0. 2 1 ю sec wt р. Ю.
Traveling Wave Solutions in a Reaction-Diffusion Epidemic Model
Wang, Sheng; Liu, Wenbin; Guo, Zhengguang; Wang, Weiming
2013-01-01
We investigate the traveling wave solutions in a reaction-diffusion epidemic model. The existence of the wave solutions is derived through monotone iteration of a pair of classical upper and lower solutions. The traveling wave solutions are shown to be unique and strictly monotonic. Furthermore, we determine the critical minimal wave speed.
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 ...
Periodic Solutions for a Delayed Population Model on Time Scales
Kejun Zhuang; Zhaohui Wen
2010-01-01
This paper deals with a delayed single population model on time scales. With the assistance of coincidence degree theory, sufficient conditions for existence of periodic solutions are obtained. Furthermore, the better estimations for bounds of periodic solutions are established.
Classical and Weak Solutions for Two Models in Mathematical Finance
Gyulov, Tihomir B.; Valkov, Radoslav L.
2011-12-01
We study two mathematical models, arising in financial mathematics. These models are one-dimensional analogues of the famous Black-Scholes equation on finite interval. The main difficulty is the degeneration at the both ends of the space interval. First, classical solutions are studied. Positivity and convexity properties of the solutions are discussed. Variational formulation in weighted Sobolev spaces is introduced and existence and uniqueness of the weak solution is proved. Maximum principle for weak solution is discussed.
Optimisation-Based Solution Methods for Set Partitioning Models
DEFF Research Database (Denmark)
Rasmussen, Matias Sevel
The scheduling of crew, i.e. the construction of work schedules for crew members, is often not a trivial task, but a complex puzzle. The task is complicated by rules, restrictions, and preferences. Therefore, manual solutions as well as solutions from standard software packages are not always su......_cient with respect to solution quality and solution time. Enhancement of the overall solution quality as well as the solution time can be of vital importance to many organisations. The _elds of operations research and mathematical optimisation deal with mathematical modelling of di_cult scheduling problems (among...... other topics). The _elds also deal with the development of sophisticated solution methods for these mathematical models. This thesis describes the set partitioning model which has been widely used for modelling crew scheduling problems. Integer properties for the set partitioning model are shown...
Hindcasting the Continuum of Dansgaard-Oeschger variability: Mechanisms, Patterns and Timing
Timmermann, A.; Menviel, L.; Friedrich, T.; England, M. H.
2013-12-01
Millennial-scale variability associated with Dansgaard-Oeschger (DO) and Heinrich events (HE) is arguably one of the most puzzling climate phenomena ever discovered in paleoclimate archives of the last glacial period. With similar variability occurring during other glacial periods, it is very timely to identify the underlying mechanisms. Here, we set out to elucidate the dynamics of millennial-scale climate variability by conducting a transient global hindcast simulation with a 3-dimensional intermediate complexity Earth system model covering the period 50 ka B.P. to 30 ka B.P. The model is forced by time-varying external boundary conditions (greenhouse gases, orbital forcing, and ice-sheet orography and albedo) and anomalous North Atlantic freshwater fluxes, which capture the effects of Northern Hemisphere ice-sheet calving on millennial timescales. Together these forcings generate a realistic global climate trajectory, as demonstrated by an extensive model/paleo data comparison. Our analysis is consistent with the simple idea that variations in ice-sheet calving and related changes of the Atlantic Meridional Overturning Circulation were the main driver for the continuum of MIS3 DO and HE variability seen in paleorecords across the globe. According to this scenario, timescale and abruptness of millennial-scale variability are primarily determined by the ice-sheet/ice-shelf calving processes, rather than by the thermohaline circulation. Using a number of high-resolution paleo records from other glacial periods we demonstrate that the proposed ice-sheet calving/AMOC response mechanism can universally explain the continuum of millennial-scale glacial variability during the Late Pleistocene.
Correction: MurCSS: A Tool for Standardized Evaluation of Decadal Hindcast Systems
Directory of Open Access Journals (Sweden)
Sebastian Illing
2016-06-01
Full Text Available This article details a correction to the article: Illing S, Kadow C, Oliver K, Cubasch U. MurCSS: A Tool for Standardized Evaluation of Decadal Hindcast Systems. Journal of Open Research Software. 2014; 2(1: e24. DOI: http://doi.org/10.5334/jors.bf
Theoretical modelling of actinide spectra in solution
International Nuclear Information System (INIS)
Danilo, Cecile
2009-01-01
The framework of this PhD is the interpretation of Nuclear Magnetic Relaxation Dispersion experiments performed on solvated U 4+ , NpO 2 + and PuO 2 2+ , which all have a f 2 configuration. Unexpectedly the two actinyl ions have a much higher relaxivity than U 4+ ,. One possible explanation is that the electronic relaxation rate is faster for Uranium(IV) than for the actinyl ions. We address this problem by exploring the electronic spectrum of the three compounds in gas phase and in solution with a two-step SOCI (Spin-Orbit Configuration-Interaction) method. The influence of electron correlation (treated in the first step) and spin-orbit relaxation effects (considered in the second step) has been discussed thoroughly. Solvent effects have been investigated as well. Another issue that has been questioned is the accuracy of Density Functional Theory for the study of actinide species. This matter has been discussed by comparing its performance to wave-function based correlated methods. The chemical problem chosen was the water exchange in [UO 2 2+ (H 2 O) 5 ]. We looked at the associative and at the dissociative mechanisms using a model with one additional water in the second hydration sphere. The last part of the thesis dealt with the spectroscopy of coordinated Uranyl(V). Absorption spectrum of Uranyl(V) with various ligands has been recorded. The first sharp absorption bands in the Near-Infrared region were assigned to the Uranium centered 5f-5f transitions, but uncertainties remained for the assignment of transitions observed in the Visible region. We computed the spectra of naked UO 2 + and [UO 2 (CO 3 ) 3 ] 5- to elucidate the spectral changes induced by the carbonate ligands. (author) [fr
An approximate method of short-term tsunami forecast and the hindcasting of some recent events
Directory of Open Access Journals (Sweden)
Yu. P. Korolev
2011-11-01
Full Text Available The paper presents a method for a short-term tsunami forecast based on sea level data from remote sites. This method is based on Green's function for the wave equation possessing the fundamental property of symmetry. This property is well known in acoustics and seismology as the reciprocity principle. Some applications of this principle on tsunami research are considered in the current study. Simple relationships and estimated transfer functions enabled us to simulate tsunami waveforms for any selected oceanic point based only on the source location and sea level data from a remote reference site. The important advantage of this method is that it is irrespective of the actual source mechanism (seismic, submarine landslide or other phenomena. The method was successfully applied to hindcast several recent tsunamis observed in the Northwest Pacific. The locations of the earthquake epicenters and the tsunami records from one of the NOAA DART sites were used as inputs for the modelling, while tsunami observations at other DART sites were used to verify the model. Tsunami waveforms for the 2006, 2007 and 2009 earthquake events near Simushir Island were simulated and found to be in good agreement with the observations. The correlation coefficients between the predicted and observed tsunami waveforms were from 0.50 to 0.85. Thus, the proposed method can be effectively used to simulate tsunami waveforms for the entire ocean and also for both regional and local tsunami warning services, assuming that they have access to the real-time sea level data from DART stations.
Periodic solutions of nonautonomous differential systems modeling obesity population
International Nuclear Information System (INIS)
Arenas, Abraham J.; Gonzalez-Parra, Gilberto; Jodar, Lucas
2009-01-01
In this paper we study the periodic behaviour of the solutions of a nonautonomous model for obesity population. The mathematical model represented by a nonautonomous system of nonlinear ordinary differential equations is used to model the dynamics of obese populations. Numerical simulations suggest periodic behaviour of subpopulations solutions. Sufficient conditions which guarantee the existence of a periodic positive solution are obtained using a continuation theorem based on coincidence degree theory.
Periodic solutions of nonautonomous differential systems modeling obesity population
Energy Technology Data Exchange (ETDEWEB)
Arenas, Abraham J. [Departamento de Matematicas y Estadistica, Universidad de Cordoba Monteria (Colombia)], E-mail: aarenas@sinu.unicordoba.edu.co; Gonzalez-Parra, Gilberto [Departamento de Calculo, Universidad de los Andes, Merida (Venezuela, Bolivarian Republic of)], E-mail: gcarlos@ula.ve; Jodar, Lucas [Instituto de Matematica Multidisciplinar, Universidad Politecnica de Valencia Edificio 8G, 2o, 46022 Valencia (Spain)], E-mail: ljodar@imm.upv.es
2009-10-30
In this paper we study the periodic behaviour of the solutions of a nonautonomous model for obesity population. The mathematical model represented by a nonautonomous system of nonlinear ordinary differential equations is used to model the dynamics of obese populations. Numerical simulations suggest periodic behaviour of subpopulations solutions. Sufficient conditions which guarantee the existence of a periodic positive solution are obtained using a continuation theorem based on coincidence degree theory.
Travelling wave solutions to nonlinear physical models by means of ...
Indian Academy of Sciences (India)
On the other hand, considerable attention has been given to problem of finding spe- cial types of analytic solutions to understand biological, physical and chemical phenomena modelled by NPDEs. Among the possible solutions, certain solutions may depend only on a single combination of variables such as travelling wave ...
General classical solutions in the noncommutative CPN-1 model
International Nuclear Information System (INIS)
Foda, O.; Jack, I.; Jones, D.R.T.
2002-01-01
We give an explicit construction of general classical solutions for the noncommutative CP N-1 model in two dimensions, showing that they correspond to integer values for the action and topological charge. We also give explicit solutions for the Dirac equation in the background of these general solutions and show that the index theorem is satisfied
Multi-cut solutions in Chern-Simons matrix models
Morita, Takeshi; Sugiyama, Kento
2018-04-01
We elaborate the Chern-Simons (CS) matrix models at large N. The saddle point equations of these matrix models have a curious structure which cannot be seen in the ordinary one matrix models. Thanks to this structure, an infinite number of multi-cut solutions exist in the CS matrix models. Particularly we exactly derive the two-cut solutions at finite 't Hooft coupling in the pure CS matrix model. In the ABJM matrix model, we argue that some of multi-cut solutions might be interpreted as a condensation of the D2-brane instantons.
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.
Solutions of ward's modified chiral model
International Nuclear Information System (INIS)
Ioannidou, T.; Zakrzewski, W.J.
1997-01-01
We discuss the adaptation of Uhlenbeck's method of solving the chiral model in 2 Euclidean dimensions to Ward's modified chiral model in (2+1) dimensions. We show that the method reduces the problem of solving the second-order partial differential equations for the chiral field to solving a sequence of first-order partial differential equations for time dependent projector valued fields
Modelling environmental dynamics. Advances in goematic solutions
Energy Technology Data Exchange (ETDEWEB)
Paegelow, Martin [Toulouse-2 Univ., 31 (France). GEODE UMR 5602 CNRS; Camacho Olmedo, Maria Teresa (eds.) [Granada Univ (Spain). Dpto. de Analisis Geografico Regional y Geografia Fisica
2008-07-01
Modelling environmental dynamics is critical to understanding and predicting the evolution of the environment in response to the large number of influences including urbanisation, climate change and deforestation. Simulation and modelling provide support for decision making in environmental management. The first chapter introduces terminology and provides an overview of methodological modelling approaches which may be applied to environmental and complex dynamics. Based on this introduction this book illustrates various models applied to a large variety of themes: deforestation in tropical regions, fire risk, natural reforestation in European mountains, agriculture, biodiversity, urbanism, climate change and land management for decision support, etc. These case studies, provided by a large international spectrum of researchers and presented in a uniform structure, focus particularly on methods and model validation so that this book is not only aimed at researchers and graduates but also at professionals. (orig.)
The WITCH Model. Structure, Baseline, Solutions.
Energy Technology Data Exchange (ETDEWEB)
Bosetti, V.; Massetti, E.; Tavoni, M.
2007-07-01
WITCH - World Induced Technical Change Hybrid - is a regionally disaggregated hard link hybrid global model with a neoclassical optimal growth structure (top down) and an energy input detail (bottom up). The model endogenously accounts for technological change, both through learning curves affecting prices of new vintages of capital and through R and D investments. The model features the main economic and environmental policies in each world region as the outcome of a dynamic game. WITCH belongs to the class of Integrated Assessment Models as it possesses a climate module that feeds climate changes back into the economy. In this paper we provide a thorough discussion of the model structure and baseline projections. We report detailed information on the evolution of energy demand, technology and CO2 emissions. Finally, we explicitly quantifiy the role of free riding in determining the emissions scenarios. (auth)
Regularity of solutions of a phase field model
Amler, Thomas
2013-01-01
Phase field models are widely-used for modelling phase transition processes such as solidification, freezing or CO2 sequestration. In this paper, a phase field model proposed by G. Caginalp is considered. The existence and uniqueness of solutions are proved in the case of nonsmooth initial data. Continuity of solutions with respect to time is established. In particular, it is shown that the governing initial boundary value problem can be considered as a dynamical system. © 2013 International Press.
Global Solution of Atmospheric Circulation Models with Humidity Effect
Luo, Hong
2014-01-01
The atmospheric circulation models are deduced from the very complex atmospheric circulation models based on the actual background and meteorological data. The models are able to show features of atmospheric circulation and are easy to be studied. It is proved that existence of global solutions to atmospheric circulation models with the use of the $T$-weakly continuous operator.
Analytic solution of a five-direction radiation transport model
International Nuclear Information System (INIS)
Cramer, S.N.
1988-01-01
In order to test certain spatial and angular dependent Monte Carlo biasing techniques, a one-dimensional, one energy, two-media, five-direction radiation transport model has been devised for which an analytic solution exists. Although this solution is too long to be conveniently expressed in an explicit form, it can be easily evaluated on the smallest of computers. This solution is discussed in this paper. 1 ref
Solutions manual to accompany finite mathematics models and applications
Morris, Carla C
2015-01-01
A solutions manual to accompany Finite Mathematics: Models and Applications In order to emphasize the main concepts of each chapter, Finite Mathematics: Models and Applications features plentiful pedagogical elements throughout such as special exercises, end notes, hints, select solutions, biographies of key mathematicians, boxed key principles, a glossary of important terms and topics, and an overview of use of technology. The book encourages the modeling of linear programs and their solutions and uses common computer software programs such as LINDO. In addition to extensive chapters on pr
Anisotropic static solutions in modelling highly compact bodies
Indian Academy of Sciences (India)
Einstein field equations for static anisotropic spheres are solved and exact interior solutions obtained. This paper extends earlier treatments to include anisotropic models which accommodate a wider variety of physically viable energy densities. Two classes of solutions are possible. The first class contains the limiting case ...
Solute transport modelling with the variable temporally dependent ...
Indian Academy of Sciences (India)
Pintu Das
2018-02-07
Feb 7, 2018 ... Abstract. In this present study, analytical and numerical solutions are obtained for solute transport modelling in homogeneous semi-infinite porous medium. The dispersion coefficient is assumed to be initial dispersion and velocity is assumed to be temporally dependent with initial seepage velocity. Also ...
Modeling solutions to Tanzania's physician workforce challenge
Directory of Open Access Journals (Sweden)
Alex J. Goodell
2016-06-01
Full Text Available Background: There is a great need for physicians in Tanzania. In 2012, there were approximately 0.31 physicians per 10,000 individuals nationwide, with a lower ratio in the rural areas, where the majority of the population resides. In response, universities across Tanzania have greatly increased the enrollment of medical students. Yet evidence suggests high attrition of medical graduates to other professions and emigration from rural areas where they are most needed. Objective: To estimate the future number of physicians practicing in Tanzania and the potential impact of interventions to improve retention, we built a model that tracks medical students from enrollment through clinical practice, from 1990 to 2025. Design: We designed a Markov process with 92 potential states capturing the movement of 25,000 medical students and physicians from medical training through employment. Work possibilities included clinical practice (divided into rural or urban, public or private, non-clinical work, and emigration. We populated and calibrated the model using a national 2005/2006 physician mapping survey, as well as graduation records, graduate tracking surveys, and other available data. Results: The model projects massive losses to clinical practice between 2016 and 2025, especially in rural areas. Approximately 56% of all medical school students enrolled between 2011 and 2020 will not be practicing medicine in Tanzania in 2025. Even with these losses, the model forecasts an increase in the physician-to-population ratio to 1.4 per 10,000 by 2025. Increasing the absorption of recent graduates into the public sector and/or developing a rural training track would ameliorate physician attrition in the most underserved areas. Conclusions: Tanzania is making significant investments in the training of physicians. Without linking these doctors to employment and ensuring their retention, the majority of this investment in medical education will be jeopardized.
Modeling Complex Chemical Systems: Problems and Solutions
van Dijk, Jan
2016-09-01
Non-equilibrium plasmas in complex gas mixtures are at the heart of numerous contemporary technologies. They typically contain dozens to hundreds of species, involved in hundreds to thousands of reactions. Chemists and physicists have always been interested in what are now called chemical reduction techniques (CRT's). The idea of such CRT's is that they reduce the number of species that need to be considered explicitly without compromising the validity of the model. This is usually achieved on the basis of an analysis of the reaction time scales of the system under study, which identifies species that are in partial equilibrium after a given time span. The first such CRT that has been widely used in plasma physics was developed in the 1960's and resulted in the concept of effective ionization and recombination rates. It was later generalized to systems in which multiple levels are effected by transport. In recent years there has been a renewed interest in tools for chemical reduction and reaction pathway analysis. An example of the latter is the PumpKin tool. Another trend is that techniques that have previously been developed in other fields of science are adapted as to be able to handle the plasma state of matter. Examples are the Intrinsic Low Dimension Manifold (ILDM) method and its derivatives, which originate from combustion engineering, and the general-purpose Principle Component Analysis (PCA) technique. In this contribution we will provide an overview of the most common reduction techniques, then critically assess the pros and cons of the methods that have gained most popularity in recent years. Examples will be provided for plasmas in argon and carbon dioxide.
Solutions of matrix models in the DIII generator ensemble
Roussel, Harold
1994-01-01
In this paper we solve two matrix models, using standard and new techniques. The two models are represented by special form of antisymmetric matrices and are classified in the DIII generator ensemble. It is shown that, in the double scaling limit, their free energy has the same behavior as previous models describing oriented and unoriented surfaces. We also found an additional solution for the first model.
An asymptotic solution to a passive biped walker model
Yudaev, Sergey A.; Rachinskii, Dmitrii; Sobolev, Vladimir A.
2017-02-01
We consider a simple model of a passive dynamic biped robot walker with point feet and legs without knee. The model is a switched system, which includes an inverted double pendulum. Robot’s gait and its stability depend on parameters such as the slope of the ramp, the length of robot’s legs, and the mass distribution along the legs. We present an asymptotic solution of the model. The first correction to the zero order approximation is shown to agree with the numerical solution for a limited parameter range.
Thermodynamic Models from Fluctuation Solution Theory Analysis of Molecular Simulations
DEFF Research Database (Denmark)
Christensen, Steen; Peters, Günther H.j.; Hansen, Flemming Yssing
2007-01-01
Fluctuation solution theory (FST) is employed to analyze results of molecular dynamics (MD) simulations of liquid mixtures. The objective is to generate parameters for macroscopic GE-models, here the modified Margules model. We present a strategy for choosing the number of parameters included...
Modeling of CO2 absorber using an AMP solution
DEFF Research Database (Denmark)
Gabrielsen, Jostein; Michelsen, Michael Locht; Stenby, Erling Halfdan
2006-01-01
Abstract: An explicit model for carbon dioxide (CO2) solubility in an aqueous solution of 2-amino-2-methyl-1-propanol (AMP) has been proposed and an expression for the heat of absorption of CO2 has been developed as a function of loading and temperature. A rate-based steady-state model for CO2...
A GROOVE Solution for the BPMN to BPEL Model Transformation
de Mol, M.J.; Zimakova, M.V.
In this paper we present a solution of a model transformation between two standard languages for business process modeling BPMN and BPEL, using the GROOVE tool set. GROOVE is a tool for graph transformations that uses directed, edge labelled simple graphs and the SPO approach [Ren04]. Given a graph
Large time periodic solutions to coupled chemotaxis-fluid models
Jin, Chunhua
2017-12-01
In this paper, we deal with the time periodic problem to coupled chemotaxis-fluid models. We prove the existence of large time periodic strong solutions for the full chemotaxis-Navier-Stokes system in spatial dimension N=2, and the existence of large time periodic strong solutions for the chemotaxis-Stokes system in spatial dimension N=3. On the basis of these, the regularity of the solutions can be further improved. More precisely speaking, if the time periodic source g and the potential force \
A Mesoscopic Model for Protein-Protein Interactions in Solution
Lund, Mikael; Jönsson, Bo
2003-01-01
Protein self-association may be detrimental in biological systems, but can be utilized in a controlled fashion for protein crystallization. It is hence of considerable interest to understand how factors like solution conditions prevent or promote aggregation. Here we present a computational model describing interactions between protein molecules in solution. The calculations are based on a molecular description capturing the detailed structure of the protein molecule using x-ray or nuclear ma...
Jacobian elliptic wave solutions in an anharmonic molecular crystal model
International Nuclear Information System (INIS)
Teh, C.G.R.; Lee, B.S.; Koo, W.K.
1997-07-01
Explicit Jacobian elliptic wave solutions are found in the anharmonic molecular crystal model for both the continuum limit and discrete modes. This class of wave solutions include the famous pulse-like and kink-like solitary modes. We would also like to report on the existence of some highly discrete staggered solitary wave modes not found in the continuum limit. (author). 9 refs, 1 fig
A molecular-thermodynamic model for polyelectrolyte solutions
Energy Technology Data Exchange (ETDEWEB)
Jiang, J.; Liu, H.; Hu, Y. [Thermodynamics Research Laboratory, East China University of Science and Technology, Shanghai 200237 (China); Prausnitz, J.M. [Department of Chemical Engineering, University of California, Berkeley, and Chemical Sciences Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 (United States)
1998-01-01
Polyelectrolyte solutions are modeled as freely tangent-jointed, charged hard-sphere chains and corresponding counterions in a continuum medium with permitivity {var_epsilon}. By adopting the sticky-point model, the Helmholtz function for polyelectrolyte solutions is derived through the r-particle cavity-correlation function (CCF) for chains of sticky, charged hard spheres. The r-CCF is approximated by a product of effective nearest-neighbor two-particle CCFs; these are determined from the hypernetted-chain and mean-spherical closures (HNC/MSA) inside and outside the hard core, respectively, for the integral equation theory for electrolytes. The colligative properties are given as explicit functions of a scaling parameter {Gamma} that can be estimated by a simple iteration procedure. Osmotic pressures, osmotic coefficients, and activity coefficients are calculated for model solutions with various chain lengths. They are in good agreement with molecular simulation and experimental results. {copyright} {ital 1998 American Institute of Physics.}
Global solution for a chemotactic haptotactic model of cancer invasion
Tao, Youshan; Wang, Mingjun
2008-10-01
This paper deals with a mathematical model of cancer invasion of tissue recently proposed by Chaplain and Lolas. The model consists of a reaction-diffusion-taxis partial differential equation (PDE) describing the evolution of tumour cell density, a reaction-diffusion PDE governing the evolution of the proteolytic enzyme concentration and an ordinary differential equation modelling the proteolysis of the extracellular matrix (ECM). In addition to random motion, the tumour cells are directed not only by haptotaxis (cellular locomotion directed in response to a concentration gradient of adhesive molecules along the ECM) but also by chemotaxis (cellular locomotion directed in response to a concentration gradient of the diffusible proteolytic enzyme). In one space dimension, the global existence and uniqueness of a classical solution to this combined chemotactic-haptotactic model is proved for any chemotactic coefficient χ > 0. In two and three space dimensions, the global existence is proved for small χ/μ (where μ is the logistic growth rate of the tumour cells). The fundamental point of proof is to raise the regularity of a solution from L1 to Lp (p > 1). Furthermore, the existence of blow-up solutions to a sub-model in two space dimensions for large χ shows, to some extent, that the condition that χ/μ is small is necessary for the global existence of a solution to the full model.
Long Term Wave Climate at the Danish Test Site DanWEC Based on 35 Years Hindcast Data
DEFF Research Database (Denmark)
Tetu, Amélie; Jensen, Palle Martin; Kramer, Morten Mejlhede
2017-01-01
This paper presents an analysis of the wave climate of the DanWEC test site based on the 35 years hindcast data. This includes monthly and annual variation of the wave climate at the site together with an analysis of extreme events. This work includees results from the project “Resource Assessment...... and reduce WEC’s costs. The work so far has been concentrated on establishing the base for gaining detailed information on the wave and current climate at DanWEC. In this paper an analysis of the wave climate at the DanWEC test site based on 35 years modelled data will be presented. Relevant characteristics...... of the test site, such as scatter tables in terms of wave height and energy period (Hm0, Te) and weather window characteristics will be given. Based on 35 years of data gathered so far, an analysis of extreme events at the DanWEC test site is also included in this work....
Stability of subsystem solutions in agent-based models
Perc, Matjaž
2018-01-01
The fact that relatively simple entities, such as particles or neurons, or even ants or bees or humans, give rise to fascinatingly complex behaviour when interacting in large numbers is the hallmark of complex systems science. Agent-based models are frequently employed for modelling and obtaining a predictive understanding of complex systems. Since the sheer number of equations that describe the behaviour of an entire agent-based model often makes it impossible to solve such models exactly, Monte Carlo simulation methods must be used for the analysis. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among agents that describe systems in biology, sociology or the humanities often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. This begets the question: when can we be certain that an observed simulation outcome of an agent-based model is actually stable and valid in the large system-size limit? The latter is key for the correct determination of phase transitions between different stable solutions, and for the understanding of the underlying microscopic processes that led to these phase transitions. We show that a satisfactory answer can only be obtained by means of a complete stability analysis of subsystem solutions. A subsystem solution can be formed by any subset of all possible agent states. The winner between two subsystem solutions can be determined by the average moving direction of the invasion front that separates them, yet it is crucial that the competing subsystem solutions are characterised by a proper composition and spatiotemporal structure before the competition starts. We use the spatial public goods game with diverse tolerance as an example, but the approach has relevance for a wide variety of agent-based models.
ADVAN-style analytical solutions for common pharmacokinetic models.
Abuhelwa, Ahmad Y; Foster, David J R; Upton, Richard N
2015-01-01
The analytical solutions to compartmental pharmacokinetic models are well known, but have not been presented in a form that easily allows for complex dosing regimen and changes in covariate/parameter values that may occur at discrete times within and/or between dosing intervals. Laplace transforms were used to derive ADVAN-style analytical solutions for 1, 2, and 3 compartment pharmacokinetic linear models of intravenous and first-order absorption drug administration. The equations calculate the change in drug amounts in each compartment of the model over a time interval (t; t = t2 - t1) accounting for any dose or covariate events acting in the time interval. The equations were coded in the R language and used to simulate the time-course of drug amounts in each compartment of the systems. The equations were validated against commercial software [NONMEM (Beal, Sheiner, Boeckmann, & Bauer, 2009)] output to assess their capability to handle both complex dosage regimens and the effect of changes in covariate/parameter values that may occur at discrete times within or between dosing intervals. For all tested pharmacokinetic models, the time-course of drug amounts using the ADVAN-style analytical solutions were identical to NONMEM outputs to at least four significant figures, confirming the validity of the presented equations. To our knowledge, this paper presents the ADVAN-style equations for common pharmacokinetic models in the literature for the first time. The presented ADVAN-style equations overcome obstacles to implementing the classical analytical solutions in software, and have speed advantages over solutions using differential equation solvers. The equations presented in this paper fill a gap in the pharmacokinetic literature, and it is expected that these equations will facilitate the investigation of useful open-source software for modelling pharmacokinetic data. Copyright © 2015 Elsevier Inc. All rights reserved.
Pole solution in six dimensions as a dimensional reduction model
Ichinose, Shoichi
2002-01-01
A solution with the pole configuration in six dimensions is analyzed. It is a dimensional reduction model of Randall-Sundrum type. The soliton configuration is induced by the bulk Higgs mechanism. The boundary condition is systematically solved up to the 6th order. The Riemann curvature is finite everywhere.
LED-based Photometric Stereo: Modeling, Calibration and Numerical Solutions
DEFF Research Database (Denmark)
Quéau, Yvain; Durix, Bastien; Wu, Tao
2018-01-01
We conduct a thorough study of photometric stereo under nearby point light source illumination, from modeling to numerical solution, through calibration. In the classical formulation of photometric stereo, the luminous fluxes are assumed to be directional, which is very difficult to achieve in pr...
Approximate Solutions of Interactive Dynamic Influence Diagrams Using Model Clustering
DEFF Research Database (Denmark)
Zeng, Yifeng; Doshi, Prashant; Qiongyu, Cheng
2007-01-01
Interactive dynamic influence diagrams (I-DIDs) offer a transparent and semantically clear representation for the sequential decision-making problem over multiple time steps in the presence of other interacting agents. Solving I-DIDs exactly involves knowing the solutions of possible models...
Stationary solutions of multicomponent chiral and gauge models
International Nuclear Information System (INIS)
Chudnovsky, D.V.; Chudnovsky, G.V.
1979-01-01
The authors examine stationary solutions of completely integrable systems in (x, t) dimensions having infinitely many components. Among the cases under investigation are: (1) the infinite-component non-linear Schroedinger equation; (2) infinite component CPsup(Ω) or SU(N) sigma-models; (3) general gauge and chiral completely integrable systems. (Auth.)
Interpolation solution of the single-impurity Anderson model
International Nuclear Information System (INIS)
Kuzemsky, A.L.
1990-10-01
The dynamical properties of the single-impurity Anderson model (SIAM) is studied using a novel Irreducible Green's Function method (IGF). The new solution for one-particle GF interpolating between the strong and weak correlation limits is obtained. The unified concept of relevant mean-field renormalizations is indispensable for strong correlation limit. (author). 21 refs
Analysis and modeling of alkali halide aqueous solutions
DEFF Research Database (Denmark)
Kim, Sun Hyung; Anantpinijwatna, Amata; Kang, Jeong Won
2016-01-01
on calculations for various electrolyte properties of alkali halide aqueous solutions such as mean ionic activity coefficients, osmotic coefficients, and salt solubilities. The model covers highly nonideal electrolyte systems such as lithium chloride, lithium bromide and lithium iodide, that is, systems...
Foam for Enhanced Oil Recovery : Modeling and Analytical Solutions
Ashoori, E.
2012-01-01
Foam increases sweep in miscible- and immiscible-gas enhanced oil recovery by decreasing the mobility of gas enormously. This thesis is concerned with the simulations and analytical solutions for foam flow for the purpose of modeling foam EOR in a reservoir. For the ultimate goal of upscaling our
Small-scale engagement model with arrivals: analytical solutions
International Nuclear Information System (INIS)
Engi, D.
1977-04-01
This report presents an analytical model of small-scale battles. The specific impetus for this effort was provided by a need to characterize hypothetical battles between guards at a nuclear facility and their potential adversaries. The solution procedure can be used to find measures of a number of critical parameters; for example, the win probabilities and the expected duration of the battle. Numerical solutions are obtainable if the total number of individual combatants on the opposing sides is less than 10. For smaller force size battles, with one or two combatants on each side, symbolic solutions can be found. The symbolic solutions express the output parameters abstractly in terms of symbolic representations of the input parameters while the numerical solutions are expressed as numerical values. The input parameters are derived from the probability distributions of the attrition and arrival processes. The solution procedure reduces to solving sets of linear equations that have been constructed from the input parameters. The approach presented in this report does not address the problems associated with measuring the inputs. Rather, this report attempts to establish a relatively simple structure within which small-scale battles can be studied
Analytic solution of the Starobinsky model for inflation
Energy Technology Data Exchange (ETDEWEB)
Paliathanasis, Andronikos [Universidad Austral de Chile, Instituto de Ciencias Fisicas y Matematicas, Valdivia (Chile); Durban University of Technology, Institute of Systems Science, Durban (South Africa)
2017-07-15
We prove that the field equations of the Starobinsky model for inflation in a Friedmann-Lemaitre-Robertson-Walker metric constitute an integrable system. The analytical solution in terms of a Painleve series for the Starobinsky model is presented for the case of zero and nonzero spatial curvature. In both cases the leading-order term describes the radiation era provided by the corresponding higher-order theory. (orig.)
Numerical solution of dynamic equilibrium models under Poisson uncertainty
DEFF Research Database (Denmark)
Posch, Olaf; Trimborn, Timo
2013-01-01
We propose a simple and powerful numerical algorithm to compute the transition process in continuous-time dynamic equilibrium models with rare events. In this paper we transform the dynamic system of stochastic differential equations into a system of functional differential equations...... of the retarded type. We apply the Waveform Relaxation algorithm, i.e., we provide a guess of the policy function and solve the resulting system of (deterministic) ordinary differential equations by standard techniques. For parametric restrictions, analytical solutions to the stochastic growth model and a novel...... solution to Lucas' endogenous growth model under Poisson uncertainty are used to compute the exact numerical error. We show how (potential) catastrophic events such as rare natural disasters substantially affect the economic decisions of households....
Travelling Wave Solutions in Multigroup Age-Structured Epidemic Models
Ducrot, Arnaut; Magal, Pierre; Ruan, Shigui
2010-01-01
Age-structured epidemic models have been used to describe either the age of individuals or the age of infection of certain diseases and to determine how these characteristics affect the outcomes and consequences of epidemiological processes. Most results on age-structured epidemic models focus on the existence, uniqueness, and convergence to disease equilibria of solutions. In this paper we investigate the existence of travelling wave solutions in a deterministic age-structured model describing the circulation of a disease within a population of multigroups. Individuals of each group are able to move with a random walk which is modelled by the classical Fickian diffusion and are classified into two subclasses, susceptible and infective. A susceptible individual in a given group can be crisscross infected by direct contact with infective individuals of possibly any group. This process of transmission can depend upon the age of the disease of infected individuals. The goal of this paper is to provide sufficient conditions that ensure the existence of travelling wave solutions for the age-structured epidemic model. The case of two population groups is numerically investigated which applies to the crisscross transmission of feline immunodeficiency virus (FIV) and some sexual transmission diseases.
Mesoscale modeling of solute precipitation and radiation damage
Energy Technology Data Exchange (ETDEWEB)
Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States); Schwen, Daniel [Idaho National Lab. (INL), Idaho Falls, ID (United States); Ke, Huibin [Idaho National Lab. (INL), Idaho Falls, ID (United States); Univ. of Wisconsin, Madison, WI (United States); Bai, Xianming [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hales, Jason [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-09-01
This report summarizes the low length scale effort during FY 2014 in developing mesoscale capabilities for microstructure evolution in reactor pressure vessels. During operation, reactor pressure vessels are subject to hardening and embrittlement caused by irradiation-induced defect accumulation and irradiation-enhanced solute precipitation. Both defect production and solute precipitation start from the atomic scale, and manifest their eventual effects as degradation in engineering-scale properties. To predict the property degradation, multiscale modeling and simulation are needed to deal with the microstructure evolution, and to link the microstructure feature to material properties. In this report, the development of mesoscale capabilities for defect accumulation and solute precipitation are summarized. Atomic-scale efforts that supply information for the mesoscale capabilities are also included.
Ruthenium speciation in model nuclear fuel process solutions
International Nuclear Information System (INIS)
Koster, Anne L.; May, Iain; Sharrad, Clint A.; Wright, Des; Owens, Ivan F.; Charnock, John M.; Hennig, Christoph
2004-01-01
Ru speciation is being investigated systematically from models of high level waste solutions right through to the calcination process and the vitrified glass product. The characterisation of these species is complicated due to the fact that a wide range of ruthenium nitrosyl/nitrite/nitrate complexes can be present in nitric acid waste solutions. The general formula for these complexes is RuNO(NO 3 ) x (NO 2 ) y (OH) z (H 2 O) 5-x-y-z +3-x-y-z . A range of different techniques has been used for the characterisation of these species in solution, including electron absorption spectroscopy, vibrational spectroscopy, multi-nuclear magnetic resonance spectroscopy and X-ray absorption spectroscopy. (authors)
Data mining with SPSS modeler theory, exercises and solutions
Wendler, Tilo
2016-01-01
Introducing the IBM SPSS Modeler, this book guides readers through data mining processes and presents relevant statistical methods. There is a special focus on step-by-step tutorials and well-documented examples that help demystify complex mathematical algorithms and computer programs. The variety of exercises and solutions as well as an accompanying website with data sets and SPSS Modeler streams are particularly valuable. While intended for students, the simplicity of the Modeler makes the book useful for anyone wishing to learn about basic and more advanced data mining, and put this knowledge into practice.
Gallagher, Sarah; Tiron, Roxana; Dias, Frédéric
2014-08-01
The Northeast Atlantic possesses some of the highest wave energy levels in the world. The recent years have witnessed a renewed interest in harnessing this vast energy potential. Due to the complicated geomorphology of the Irish coast, there can be a significant variation in both the wave and wind climate. Long-term hindcasts with high spatial resolution, properly calibrated against available measurements, provide vital information for future deployments of ocean renewable energy installations. These can aid in the selection of adequate locations for potential deployment and for the planning and design of those marine operations. A 34-year (from 1979 to 2012), high-resolution wave hindcast was performed for Ireland including both the Atlantic and Irish Sea coasts, with a particular focus on the wave energy resource. The wave climate was estimated using the third-generation spectral wave model WAVEWATCH III®; version 4.11, the unstructured grid formulation. The wave model was forced with directional wave spectral data and 10-m winds from the European Centre for Medium Range Weather Forecasts (ECMWF) ERA-Interim reanalysis, which is available from 1979 to the present. The model was validated against available observed satellite altimeter and buoy data, particularly in the nearshore, and was found to be excellent. A strong spatial and seasonal variability was found for both significant wave heights, and the wave energy flux, particularly on the north and west coasts. A strong correlation between the North Atlantic Oscillation (NAO) teleconnection pattern and wave heights, wave periods, and peak direction in winter and also, to a lesser extent, in spring was identified.
Solution-focused therapy. Counseling model for busy family physicians.
Greenberg, G.; Ganshorn, K.; Danilkewich, A.
2001-01-01
OBJECTIVE: To provide family doctors in busy office practices with a model for counseling compatible with patient-centred medicine, including the techniques, strategies, and questions necessary for implementation. QUALITY OF EVIDENCE: The MEDLINE database was searched from 1984 to 1999 using the terms psychotherapy in family practice, brief therapy in family practice, solution-focused therapy, and brief psychotherapy. A total of 170 relevant articles were identified; 75 abstracts were retriev...
Kadow, Christopher; Illing, Sebastian; Schartner, Thomas; Ulbrich, Uwe; Cubasch, Ulrich
2017-04-01
Operationalization processes are important for Weather and Climate Services. Complex data and work flows need to be combined fast to fulfill the needs of service centers. Standards in data and software formats help in automatic solutions. In this study we show a software solution in between hindcasts, forecasts, and validation to be operationalized. Freva (see below) structures data and evaluation procedures and can easily be monitored. Especially in the development process of operationalized services, Freva supports scientists and project partners. The showcase of the decadal climate prediction project MiKlip (fona-miklip.de) shows such a complex development process. Different predictions, scientists input, tasks, and time evolving adjustments need to be combined to host precise climate informations in a web environment without losing track of its evolution. The Freie Univ Evaluation System Framework (Freva - freva.met.fu-berlin.de) is a software infrastructure for standardized data and tool solutions in Earth system science. Freva runs on high performance computers to handle customizable evaluation systems of research projects, institutes or universities. It combines different software technologies into one common hybrid infrastructure, including all features present in the shell and web environment. The database interface satisfies the international standards provided by the Earth System Grid Federation (ESGF). Freva indexes different data projects into one common search environment by storing the meta data information of the self-describing model, reanalysis and observational data sets in a database. This implemented meta data system with its advanced but easy-to-handle search tool supports users, developers and their plugins to retrieve the required information. A generic application programming interface (API) allows scientific developers to connect their analysis tools with the evaluation system independently of the programming language used. Users of the
Numerical solution of a model for a superconductor field problem
International Nuclear Information System (INIS)
Alsop, L.E.; Goodman, A.S.; Gustavson, F.G.; Miranker, W.L.
1979-01-01
A model of a magnetic field problem occurring in connection with Josephson junction devices is derived, and numerical solutions are obtained. The model is of mathematical interest, because the magnetic vector potential satisfies inhomogeneous Helmholtz equations in part of the region, i.e., the superconductors, and the Laplace equation elsewhere. Moreover, the inhomogeneities are the guage constants for the potential, which are different for each superconductor, and their magnitudes are proportional to the currents flowing in the superconductors. These constants are directly related to the self and mutual inductances of the superconducting elements in the device. The numerical solution is obtained by the iterative use of a fast Poisson solver. Chebyshev acceleration is used to reduce the number of iterations required to obtain a solution. A typical problem involves solving 100,000 simultaneous equations, which the algorithm used with this model does in 20 iterations, requiring three minutes of CPU time on an IBM VM/370/168. Excellent agreement is obtained between calculated and observed values for the inductances
Asymptotically exact solution of a local copper-oxide model
International Nuclear Information System (INIS)
Zhang Guangming; Yu Lu.
1994-03-01
We present an asymptotically exact solution of a local copper-oxide model abstracted from the multi-band models. The phase diagram is obtained through the renormalization-group analysis of the partition function. In the strong coupling regime, we find an exactly solved line, which crosses the quantum critical point of the mixed valence regime separating two different Fermi-liquid (FL) phases. At this critical point, a many-particle resonance is formed near the chemical potential, and a marginal-FL spectrum can be derived for the spin and charge susceptibilities. (author). 15 refs, 1 fig
Exact solutions for the spin tune for model storage rings
Mane, S R
2002-01-01
We present exact analytical expressions for the spin tune for arbitrary values of the orbital action for several storage ring models. The models we treat contain Siberian Snakes, the use of which is essential to preserve the polarization of beams in high-energy proton storage rings. Our solutions contain some novel features. We also prove a previously conjectured claim about the behavior of spin tuneshifts in rings with multiple Snakes. The conjecture is based on numerical simulations, but our proof is analytical, and also nonperturbative.
Bessel collocation approach for approximate solutions of Hantavirus infection model
Directory of Open Access Journals (Sweden)
Suayip Yuzbasi
2017-11-01
Full Text Available In this study, a collocation method is introduced to find the approximate solutions of Hantavirus infection model which is a system of nonlinear ordinary differential equations. The method is based on the Bessel functions of the first kind, matrix operations and collocation points. This method converts Hantavirus infection model into a matrix equation in terms of the Bessel functions of first kind, matrix operations and collocation points. The matrix equation corresponds to a system of nonlinear equations with the unknown Bessel coefficients. The reliability and efficiency of the suggested scheme are demonstrated by numerical applications and all numerical calculations have been done by using a program written in Maple.
Asymptotic solutions of diffusion models for risk reserves
Directory of Open Access Journals (Sweden)
S. Shao
2003-01-01
Full Text Available We study a family of diffusion models for risk reserves which account for the investment income earned and for the inflation experienced on claim amounts. After we defined the process of the conditional probability of ruin over finite time and imposed the appropriate boundary conditions, classical results from the theory of diffusion processes turn the stochastic differential equation to a special class of initial and boundary value problems defined by a linear diffusion equation. Armed with asymptotic analysis and perturbation theory, we obtain the asymptotic solutions of the diffusion models (possibly degenerate governing the conditional probability of ruin over a finite time in terms of interest rate.
Spectroscopic properties of vitamin E models in solution
Oliveira, L. B. A.; Colherinhas, G.; Fonseca, T. L.; Castro, M. A.
2015-05-01
We investigate the first absorption band and the 13C and 17O magnetic shieldings of vitamin E models in chloroform and in water using the S-MC/QM methodology in combination with the TD-DFT and GIAO approaches. The results show that the solvent effects on these spectroscopic properties are small but a proper description of the solvent shift for 17O magnetic shielding of the hydroxyl group in water requires the use of explicit solute-solvent hydrogen bonds. In addition, the effect of the replacement of hydrogen atoms by methyl groups in the vitamin E models only affects magnetic shieldings.
Microfluidic model experiments on the injectability of monoclonal antibody solutions
Duchene, Charles; Filipe, Vasco; Nakach, Mostafa; Huille, Sylvain; Lindner, Anke
2017-11-01
Autoinjection devices that allow patients to self-administer medicine are becoming used more frequently; however, this advance comes with an increased need for precision in the injection process. The rare occurrence of protein aggregates in solutions of monoclonal antibodies constitutes a threat to the reliability of such devices. Here we study the flow of protein solutions containing aggregates in microfluidic model systems, mimicking injection devices, to gain fundamental understanding of the catastrophic clogging of constrictions of given size. We form aggregates by mechanically shaking or heating antibody solutions and then inject these solutions into microfluidic channels with varying types of constrictions. Geometrical clogging occurs when aggregates reach the size of the constriction and can in some cases be undone by increasing the applied pressure. We perform systematic experiments varying the relative aggregate size and the flow rate or applied pressure. The mechanical deformation of aggregates during their passage through constrictions is investigated to gain a better understanding of the clogging and unclogging mechanisms.
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
Transition towards Sustainable Solutions: Product, Service, Technology, and Business Model
Directory of Open Access Journals (Sweden)
Mina Nasiri
2018-01-01
Full Text Available Nowadays, the horse industry can be considered as an important industry in European countries and has a major role in agricultural industry throughout the world. Although today the diversity of the horse-related companies provides new markets and business opportunities, there are also some sustainable issues which needs to be addressed. Therefore, this study contributes to this research gap by reviewing the concept of sustainability and existing approaches to find sustainable solutions for companies. These sustainable approaches can be applied to products, services and technologies as well as business models, such as the product-service-system (PSS, circular economy (CE and industrial symbiosis (IS. Although there seems to be a growing understanding of sustainable approaches and their role in sustainable development, there is a lack of research at the empirical level regarding the types of sustainability approaches (i.e., technologies, services, products and business models that evolve in specific industries. The empirical data in this research have been collected from a cross-section of Finnish horse industry operators to determine how willing companies are to exploit approaches to sustainable solutions, as well as what the existing sustainable solutions are in this industry. The response rate of this study is approximately 24 percent, including 139 received valid responses among the sample of 580 operators.
ELVIS: Multi-Electrolyte Aqueous Activity Model for Geothermal Solutions
Hingerl, F. F.; Wagner, T.; Driesner, T.; Kulik, D. A.; Kosakowski, G.
2011-12-01
High temperature, pressure, and fluid salinities render geochemical modeling of fluid-rock interactions in Enhanced Geothermal Systems a demanding task. Accurate prediction of fluid-mineral equilibria strongly depends on the availability of thermodynamic data and activity models. Typically, the Pitzer activity model is applied for geothermal fluids. A drawback of this model is the large number of parameters required to account for temperature and pressure dependencies, which significantly reduces computational efficiency of reactive transport simulations. In addition, most available parameterizations are valid only at vapor-saturated conditions. As an alternative we implemented the EUNIQUAC local composition model [2] that needs substantially fewer fitting parameters. However, the current EUNIQUAC model design does not include provision for high temperature (>150°C) applications and lacks a formulation for pressure dependence. Therefore, its application to geothermal conditions requires a re-formulation and re-fitting of the model. We developed a new tool termed GEMSFIT that allows generic fitting of activity models (for aqueous electrolyte and non-electrolyte solutions) and equations of state implemented in our geochemical equilibrium solver GEM-Selektor (http://gems.web.psi.ch). GEMSFIT combines a PostgreSQL database for storing and managing the datasets of experimental measurements and interaction parameters, the parallelized genetic algorithm toolbox of MATLAB° for the parameter fitting, and an interface to the numerical kernel of GEM-Selektor to access activity models and perform chemical equilibrium calculations. Benchmarking of the partly re-parameterized EUNIQUAC model against Pitzer revealed that the former is less accurate, which can result in incorrect predictions of mineral precipitation/dissolution. Consequently, we modified the EUNIQUAC model and concurrently introduced a pressure dependence to be able to fit experimental data over wide ranges of
DEM Solutions Develops Answers to Modeling Lunar Dust and Regolith
Dunn, Carol Anne; Calle, Carlos; LaRoche, Richard D.
2010-01-01
With the proposed return to the Moon, scientists like NASA-KSC's Dr. Calle are concerned for a number of reasons. We will be staying longer on the planet's surface, future missions may include dust-raising activities, such as excavation and handling of lunar soil and rock, and we will be sending robotic instruments to do much of the work for us. Understanding more about the chemical and physical properties of lunar dust, how dust particles interact with each other and with equipment surfaces and the role of static electricity build-up on dust particles in the low-humidity lunar environment is imperative to the development of technologies for removing and preventing dust accumulation, and successfully handling lunar regolith. Dr. Calle is currently working on the problems of the electrostatic phenomena of granular and bulk materials as they apply to planetary surfaces, particularly to those of Mars and the Moon, and is heavily involved in developing instrumentation for future planetary missions. With this end in view, the NASA Kennedy Space Center's Innovative Partnerships Program Office partnered with OEM Solutions, Inc. OEM Solutions is a global leader in particle dynamics simulation software, providing custom solutions for use in tackling tough design and process problems related to bulk solids handling. Customers in industries such as pharmaceutical, chemical, mineral, and materials processing as well as oil and gas production, agricultural and construction, and geo-technical engineering use OEM Solutions' EDEM(TradeMark) software to improve the design and operation of their equipment while reducing development costs, time-to-market and operational risk. EDEM is the world's first general-purpose computer-aided engineering (CAE) tool to use state-of-the-art discrete element modeling technology for the simulation and analysis of particle handling and manufacturing operations. With EDEM you'can quickly and easily create a parameterized model of your granular solids
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
Exact solutions in a model of vertical gas migration
Energy Technology Data Exchange (ETDEWEB)
Silin, Dmitriy B.; Patzek, Tad W.; Benson, Sally M.
2006-06-27
This work is motivated by the growing interest in injectingcarbon dioxide into deep geological formations as a means of avoidingatmospheric emissions of carbon dioxide and consequent global warming.One of the key questions regarding the feasibility of this technology isthe potential rate of leakage out of the primary storage formation. Weseek exact solutions in a model of gas flow driven by a combination ofbuoyancy, viscous and capillary forces. Different combinations of theseforces and characteristic length scales of the processes lead todifferent time scaling and different types of solutions. In the case of athin, tight seal, where the impact of gravity is negligible relative tocapillary and viscous forces, a Ryzhik-type solution implies square-rootof time scaling of plume propagation velocity. In the general case, a gasplume has two stable zones, which can be described by travelling-wavesolutions. The theoretical maximum of the velocity of plume migrationprovides a conservative estimate for the time of vertical migration.Although the top of the plume has low gas saturation, it propagates witha velocity close to the theoretical maximum. The bottom of the plumeflows significantly more slowly at a higher gas saturation. Due to localheterogeneities, the plume can break into parts. Individual plumes alsocan coalesce and from larger plumes. The analytical results are appliedto studying carbon dioxide flow caused by leaks from deep geologicalformations used for CO2 storage. The results are also applicable formodeling flow of natural gas leaking from seasonal gas storage, or formodeling of secondary hydrocarbon migration.
Mathematical Model of Suspension Filtration and Its Analytical Solution
Directory of Open Access Journals (Sweden)
Normahmad Ravshanov
2013-01-01
Full Text Available The work develops advanced mathematical model and computing algorithm to analyze, predict and identify the basic parameters of filter units and their variation ranges. Numerical analytic solution of liquid ionized mixtures filtration was got on their basis. Computing experiments results are presented in graphics form. Calculation results analysis enables to determine the optimum performance of filter units, used for liquid ionized mixtures filtration, food preparation, drug production and water purification. Selection of the most suitable parameters contributes to the improvement of economic and technological efficiency of production and filter units working efficiency.
Nonzero solutions of nonlinear integral equations modeling infectious disease
Energy Technology Data Exchange (ETDEWEB)
Williams, L.R. (Indiana Univ., South Bend); Leggett, R.W.
1982-01-01
Sufficient conditions to insure the existence of periodic solutions to the nonlinear integral equation, x(t) = ..integral../sup t//sub t-tau/f(s,x(s))ds, are given in terms of simple product and product integral inequalities. The equation can be interpreted as a model for the spread of infectious diseases (e.g., gonorrhea or any of the rhinovirus viruses) if x(t) is the proportion of infectives at time t and f(t,x(t)) is the proportion of new infectives per unit time.
Survival of Lactobacillus plantarum in model solutions and fruit juices.
Nualkaekul, Sawaminee; Charalampopoulos, Dimitris
2011-03-30
The aim of the work was to study the survival of Lactobacillus plantarum NCIMB 8826 in model solutions and develop a mathematical model describing its dependence on pH, citric acid and ascorbic acid. A Central Composite Design (CCD) was developed studying each of the three factors at five levels within the following ranges, i.e., pH (3.0-4.2), citric acid (6-40 g/L), and ascorbic acid (100-1000 mg/L). In total, 17 experimental runs were carried out. The initial cell concentration in the model solutions was approximately 1 × 10(8)CFU/mL; the solutions were stored at 4°C for 6 weeks. Analysis of variance (ANOVA) of the stepwise regression demonstrated that a second order polynomial model fits well the data. The results demonstrated that high pH and citric acid concentration enhanced cell survival; one the other hand, ascorbic acid did not have an effect. Cell survival during storage was also investigated in various types of juices, including orange, grapefruit, blackcurrant, pineapple, pomegranate, cranberry and lemon juice. The model predicted well the cell survival in orange, blackcurrant and pineapple, however it failed to predict cell survival in grapefruit and pomegranate, indicating the influence of additional factors, besides pH and citric acid, on cell survival. Very good cell survival (less than 0.4 log decrease) was observed after 6 weeks of storage in orange, blackcurrant and pineapple juice, all of which had a pH of about 3.8. Cell survival in cranberry and pomegranate decreased very quickly, whereas in the case of lemon juice, the cell concentration decreased approximately 1.1 logs after 6 weeks of storage, albeit the fact that lemon juice had the lowest pH (pH~2.5) among all the juices tested. Taking into account the results from the compositional analysis of the juices and the model, it was deduced that in certain juices, other compounds seemed to protect the cells during storage; these were likely to be proteins and dietary fibre In contrast, in
Advanced techniques in reliability model representation and solution
Palumbo, Daniel L.; Nicol, David M.
1992-01-01
The current tendency of flight control system designs is towards increased integration of applications and increased distribution of computational elements. The reliability analysis of such systems is difficult because subsystem interactions are increasingly interdependent. Researchers at NASA Langley Research Center have been working for several years to extend the capability of Markov modeling techniques to address these problems. This effort has been focused in the areas of increased model abstraction and increased computational capability. The reliability model generator (RMG) is a software tool that uses as input a graphical object-oriented block diagram of the system. RMG uses a failure-effects algorithm to produce the reliability model from the graphical description. The ASSURE software tool is a parallel processing program that uses the semi-Markov unreliability range evaluator (SURE) solution technique and the abstract semi-Markov specification interface to the SURE tool (ASSIST) modeling language. A failure modes-effects simulation is used by ASSURE. These tools were used to analyze a significant portion of a complex flight control system. The successful combination of the power of graphical representation, automated model generation, and parallel computation leads to the conclusion that distributed fault-tolerant system architectures can now be analyzed.
Fast Proton Titration Scheme for Multiscale Modeling of Protein Solutions.
Teixeira, Andre Azevedo Reis; Lund, Mikael; da Silva, Fernando Luís Barroso
2010-10-12
Proton exchange between titratable amino acid residues and the surrounding solution gives rise to exciting electric processes in proteins. We present a proton titration scheme for studying acid-base equilibria in Metropolis Monte Carlo simulations where salt is treated at the Debye-Hückel level. The method, rooted in the Kirkwood model of impenetrable spheres, is applied on the three milk proteins α-lactalbumin, β-lactoglobulin, and lactoferrin, for which we investigate the net-charge, molecular dipole moment, and charge capacitance. Over a wide range of pH and salt conditions, excellent agreement is found with more elaborate simulations where salt is explicitly included. The implicit salt scheme is orders of magnitude faster than the explicit analog and allows for transparent interpretation of physical mechanisms. It is shown how the method can be expanded to multiscale modeling of aqueous salt solutions of many biomolecules with nonstatic charge distributions. Important examples are protein-protein aggregation, protein-polyelectrolyte complexation, and protein-membrane association.
Trends in marine plankton composition and export production in a CCSM-BEC hindcast (1960-2006)
Laufkoetter, Charlotte; Vogt, Meike; Gruber, Nicolas
2013-04-01
Climate-driven changes in marine plankton distribution are assumed to influence primary production, export production and export efficiency. We analyse trends in marine primary and particle export production and their relation to marine phytoplankton community composition using a hindcast simulation of the Biogeochemical Elemental Cycling Model (BEC) coupled to the Community Climate System Model over the period 1960-2006. The BEC models one generic zooplankton type and three phytoplankton types, diatoms, diazotrophs and small phytoplankton. In our simulation, small phytoplankton biomass, diatom biomass and zooplankton biomass decrease by 8%, 3% and 5%, respectively over the last 50 years. This decrease in plankton biomass is followed by a decrease in global primary and export production by 6% and 7%. Primary and export production decrease strongest in the Western Pacific (-18% and -23% respectively), where increased stratification leads to a decrease in total phytoplankton (-10%) and a decrease in diatom fraction (-12x%). The effect is a decrease in zooplankton biomass (-14%) and a lower export efficiency (-5%). Strong phytoplankton composition changes occur in the Southern Ocean and North Atlantic, where increased wind stress leads to stronger mixing, which reduces the biomass of small phytoplankton (-5% in the North Atlantic, -28% in the Southern Ocean), while diatoms profit from higher nutrient inputs and lower grazing pressure (+40% in the North Atlantic, + 22% in the Southern Ocean). The export efficiency and the relative fraction of diatoms are positively correlated (r=0.8) in most areas except the Northern Pacific and Antarctic Circumpolar Current, where the correlation is negative (r=-0.5). In areas where the correlation between diatom fraction and export efficiency is negative, small phytoplankton are simulated to consist of a high fraction of calcifiers, which are parameterized to produce faster sinking particles than diatoms in our model
Comparison of the modeling solutions with the hydrogen discharge data
International Nuclear Information System (INIS)
Hiskes, J.R.
1992-01-01
With the availability of experimental values for H 2 vibrational population distributions up to v=8 and measured distributions up to v=5 with simultaneous measurements of the H - concentration, it has become possible to test some features of the full-spectrum model of H - generation. The application of the code developed by Gorse et al. to these discharges by the groups at both Bari and at the Ecole Polytechnique has extended the vibrational distribution calculation to include also the H - concentration. Comparing the vibrational population calculated by these two groups at the higher levels, where the onset of H - production occurs, one finds populations for the υ=5 level that are a factor of eight to ten larger than the experimental values. Since these workers have omitted the role of the H 3 + ions known to be present in the discharge, the inclusion of the appropriate S-V process should increase the population discrepancies another factor of two or three. This excess population poses something of a dilemma: Since the Bari code simultaneously reproduces the observed H - concentration but overestimates the vibrational population by a large factor, the standard model of vibrational excitation followed by dissociative attachment is open to question. If measured rather than calculated distributions were used in the H - calculation, the calculated H - concentration would presumably be an order-of-magnitude smaller than the observed value. The measured population distributions taken against the background of the modelling solutions would seem to imply alternate sources of H - production other than dissociative attachment. To examine this problem, we have generated new modelling solutions for comparison with the data of Eenshuistra et al
DEFF Research Database (Denmark)
Larsen, Erik Hviid; Sørensen, Jakob Balslev; Sørensen, Jens Nørkær
2000-01-01
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...
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...... concentration of fluid emerging from lis is then significantly larger than the concentration in lis. Thus, in absence of external driving forces the model generates isotonic transport provided a component of the solute flux emerging downstream lis is taken up by cells through the serosal membrane and pumped...
Directory of Open Access Journals (Sweden)
Maria de Hoyos Guajardo, Ph.D. Candidate, M.Sc., B.Eng.
2004-11-01
Full Text Available The theory that is presented below aims to conceptualise how a group of undergraduate students tackle non-routine mathematical problems during a problem-solving course. The aim of the course is to allow students to experience mathematics as a creative process and to reflect on their own experience. During the course, students are required to produce a written ‘rubric’ of their work, i.e., to document their thoughts as they occur as well as their emotionsduring the process. These ‘rubrics’ were used as the main source of data.Students’ problem-solving processes can be explained as a three-stage process that has been called ‘solutioning’. This process is presented in the six sections below. The first three refer to a common area of concern that can be called‘generating knowledge’. In this way, generating knowledge also includes issues related to ‘key ideas’ and ‘gaining understanding’. The third and the fourth sections refer to ‘generating’ and ‘validating a solution’, respectively. Finally, once solutions are generated and validated, students usually try to improve them further before presenting them as final results. Thus, the last section deals with‘improving a solution’. Although not all students go through all of the stages, it may be said that ‘solutioning’ considers students’ main concerns as they tackle non-routine mathematical problems.
Development of solution-gated graphene transistor model for biosensors
Karimi, Hediyeh; Yusof, Rubiyah; Rahmani, Rasoul; Hosseinpour, Hoda; Ahmadi, Mohammad T.
2014-02-01
The distinctive properties of graphene, characterized by its high carrier mobility and biocompatibility, have stimulated extreme scientific interest as a promising nanomaterial for future nanoelectronic applications. In particular, graphene-based transistors have been developed rapidly and are considered as an option for DNA sensing applications. Recent findings in the field of DNA biosensors have led to a renewed interest in the identification of genetic risk factors associated with complex human diseases for diagnosis of cancers or hereditary diseases. In this paper, an analytical model of graphene-based solution gated field effect transistors (SGFET) is proposed to constitute an important step towards development of DNA biosensors with high sensitivity and selectivity. Inspired by this fact, a novel strategy for a DNA sensor model with capability of single-nucleotide polymorphism detection is proposed and extensively explained. First of all, graphene-based DNA sensor model is optimized using particle swarm optimization algorithm. Based on the sensing mechanism of DNA sensors, detective parameters ( I ds and V gmin) are suggested to facilitate the decision making process. Finally, the behaviour of graphene-based SGFET is predicted in the presence of single-nucleotide polymorphism with an accuracy of more than 98% which guarantees the reliability of the optimized model for any application of the graphene-based DNA sensor. It is expected to achieve the rapid, quick and economical detection of DNA hybridization which could speed up the realization of the next generation of the homecare sensor system.
A potential model for sodium chloride solutions based on the TIP4P/2005 water model
Benavides, A. L.; Portillo, M. A.; Chamorro, V. C.; Espinosa, J. R.; Abascal, J. L. F.; Vega, C.
2017-09-01
Despite considerable efforts over more than two decades, our knowledge of the interactions in electrolyte solutions is not yet satisfactory. Not even one of the most simple and important aqueous solutions, NaCl(aq), escapes this assertion. A requisite for the development of a force field for any water solution is the availability of a good model for water. Despite the fact that TIP4P/2005 seems to fulfill the requirement, little work has been devoted to build a force field based on TIP4P/2005. In this work, we try to fill this gap for NaCl(aq). After unsuccessful attempts to produce accurate predictions for a wide range of properties using unity ionic charges, we decided to follow recent suggestions indicating that the charges should be scaled in the ionic solution. In this way, we have been able to develop a satisfactory non-polarizable force field for NaCl(aq). We evaluate a number of thermodynamic properties of the solution (equation of state, maximum in density, enthalpies of solution, activity coefficients, radial distribution functions, solubility, surface tension, diffusion coefficients, and viscosity). Overall the results for the solution are very good. An important achievement of our model is that it also accounts for the dynamical properties of the solution, a test for which the force fields so far proposed failed. The same is true for the solubility and for the maximum in density where the model describes the experimental results almost quantitatively. The price to pay is that the model is not so good at describing NaCl in the solid phase, although the results for several properties (density and melting temperature) are still acceptable. We conclude that the scaling of the charges improves the overall description of NaCl aqueous solutions when the polarization is not included.
Numerical Solution of a Model Equation of Price Formation
Chernogorova, T.; Vulkov, L.
2009-10-01
The paper [2] is devoted to the effect of reconciling the classical Black-Sholes theory of option pricing and hedging with various phenomena observed in the markets such as the influence of trading and hedging on the dynamics of an asset. Here we will discuss the numerical solution of initial boundary-value problems to a model equation of the theory. The lack of regularity in the solution as a result from Dirac delta coefficient reduces the accuracy in the numerical computations. First, we apply the finite volume method to discretize the differential problem. Second, we implement a technique of local regularization introduced by A-K. Tornberg and B. Engquist [7] for handling this equation. We derived the numerical regularization process into two steps: the Dirac delta function is regularized and then the regularized differential equation is discretized by difference schemes. Using the discrete maximum principle a priori bounds are obtained for the difference equations that imply stability and convergence of difference schemes for the problem under consideration. Numerical experiments are discussed.
Wegen, M. V.; Jaffe, B. E.; Roelvink, J.
2009-12-01
The objective of the current research is to hindcast decadal morphodynamic development in San Pablo Bay, California, USA using a process-based, numerical model, Delft3D. Experience gained in the current research will be ultimately used to model future morphodynamic changes in San Pablo Bay under different scenarios of climate change. Delft3D is run in 3D mode including wind waves, salt and fresh water interaction, sand and mud fractions and applies a sophisticated morphodynamic update scheme [Roelvink (2006)]. Model outcomes are evaluated against measured bathymetric developments [Cappiella (1999), Jaffe et al (2007)] and include an extensive sensitivity analysis on model parameter settings. In the 19th century more than 250 million cubic meters of sediment was deposited in San Pablo Bay because of the increased sediment load associated with hydraulic gold mining activities. When mining stopped and dam construction regulated river flows and trapped sediment upstream early 20th century, San Pablo Bay showed an eroding trend. Focus of the hindcast is on the 1856 to 1887 depositional period and on the 1951 to 1983 erosional period. The results of the model heavily depend on parameter settings related to sediment transport, bed composition and boundary conditions schematization. A major handicap is that the (historic) values of these parameters are not known in detail. Recommendations by Ganju et al. (2008) are used to overcome this problem. The results show, however, that applying best-guess model parameter settings can predict decadal morphodynamic developments reasonably well in San Pablo Bay. From all varied settings sediment concentration, river discharge and waves have the most significant effect on deposition volumes, whereas waves have the most impact on sediment distribution within San Pablo Bay. For the depositional period Brier Skill Scores have values around 0.25 with a maximum of 0.43 (qualified as ‘good’) although higher values (up to 0.65) were
Classical solutions for the super symmetric Grassmannian sigma models in two dimensions, (2)
International Nuclear Information System (INIS)
Fujii, K.; Sasaki, R.
1983-11-01
Classical solutions of the supersymmetric Grassmannian sigma models in two euclidean dimensions are investigated. In the equations of motion of the supersymmetric model we interpret the classical fermion solutions as ordinary c-number fields. A quite general class of solutions is constructed explicitly and elementarily in an analogous way with the pure bosonic Grassmannian sigma models and the linearized supersymmetric Dirac equations. (author)
Nonperturbative Time Dependent Solution of a Simple Ionization Model
Costin, Ovidiu; Costin, Rodica D.; Lebowitz, Joel L.
2018-02-01
We present a non-perturbative solution of the Schrödinger equation {iψ_t(t,x)=-ψ_{xx}(t,x)-2(1 +α sinω t) δ(x)ψ(t,x)} , written in units in which \\hbar=2m=1, describing the ionization of a model atom by a parametric oscillating potential. This model has been studied extensively by many authors, including us. It has surprisingly many features in common with those observed in the ionization of real atoms and emission by solids, subjected to microwave or laser radiation. Here we use new mathematical methods to go beyond previous investigations and to provide a complete and rigorous analysis of this system. We obtain the Borel-resummed transseries (multi-instanton expansion) valid for all values of α, ω, t for the wave function, ionization probability, and energy distribution of the emitted electrons, the latter not studied previously for this model. We show that for large t and small α the energy distribution has sharp peaks at energies which are multiples of ω, corresponding to photon capture. We obtain small α expansions that converge for all t, unlike those of standard perturbation theory. We expect that our analysis will serve as a basis for treating more realistic systems revealing a form of universality in different emission processes.
a Procedural Solution to Model Roman Masonry Structures
Cappellini, V.; Saleri, R.; Stefani, C.; Nony, N.; De Luca, L.
2013-07-01
The paper will describe a new approach based on the development of a procedural modelling methodology for archaeological data representation. This is a custom-designed solution based on the recognition of the rules belonging to the construction methods used in roman times. We have conceived a tool for 3D reconstruction of masonry structures starting from photogrammetric surveying. Our protocol considers different steps. Firstly we have focused on the classification of opus based on the basic interconnections that can lead to a descriptive system used for their unequivocal identification and design. Secondly, we have chosen an automatic, accurate, flexible and open-source photogrammetric pipeline named Pastis Apero Micmac - PAM, developed by IGN (Paris). We have employed it to generate ortho-images from non-oriented images, using a user-friendly interface implemented by CNRS Marseille (France). Thirdly, the masonry elements are created in parametric and interactive way, and finally they are adapted to the photogrammetric data. The presented application, currently under construction, is developed with an open source programming language called Processing, useful for visual, animated or static, 2D or 3D, interactive creations. Using this computer language, a Java environment has been developed. Therefore, even if the procedural modelling reveals an accuracy level inferior to the one obtained by manual modelling (brick by brick), this method can be useful when taking into account the static evaluation on buildings (requiring quantitative aspects) and metric measures for restoration purposes.
Numerical solution of High-kappa model of superconductivity
Energy Technology Data Exchange (ETDEWEB)
Karamikhova, R. [Univ. of Texas, Arlington, TX (United States)
1996-12-31
We present formulation and finite element approximations of High-kappa model of superconductivity which is valid in the high {kappa}, high magnetic field setting and accounts for applied magnetic field and current. Major part of this work deals with steady-state and dynamic computational experiments which illustrate our theoretical results numerically. In our experiments we use Galerkin discretization in space along with Backward-Euler and Crank-Nicolson schemes in time. We show that for moderate values of {kappa}, steady states of the model system, computed using the High-kappa model, are virtually identical with results computed using the full Ginzburg-Landau (G-L) equations. We illustrate numerically optimal rates of convergence in space and time for the L{sup 2} and H{sup 1} norms of the error in the High-kappa solution. Finally, our numerical approximations demonstrate some well-known experimentally observed properties of high-temperature superconductors, such as appearance of vortices, effects of increasing the applied magnetic field and the sample size, and the effect of applied constant current.
Directory of Open Access Journals (Sweden)
Mohamad Javad Kamali
2015-01-01
Full Text Available Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other temperatures in binary and ternary system of aqueous electrolyte solution are predicted. The average absolute deviations for calculation of surface tension of binary and mixed electrolyte systems by new model are 1.98 and 1.70%, respectively.
Physical Property Modeling of Concentrated Cesium Eluate Solutions, Part I - Derivation of Models
Energy Technology Data Exchange (ETDEWEB)
Choi, A.S.; Pierce, R. A.; Edwards, T. B.; Calloway, T. B.
2005-09-15
Major analytes projected to be present in the Hanford Waste Treatment Plant cesium ion-exchange eluate solutions were identified from the available analytical data collected during radioactive bench-scale runs, and a test matrix of cesium eluate solutions was designed within the bounding concentrations of those analytes. A computer model simulating the semi-batch evaporation of cesium eluate solutions was run in conjunction with a multi-electrolyte aqueous system database to calculate the physical properties of each test matrix solution concentrated to the target endpoints of 80% and 100% saturation. The calculated physical properties were analyzed statistically and fitted into mathematical expressions for the bulk solubility, density, viscosity, heat capacity and volume reduction factor as a function of temperature and concentration of each major analyte in the eluate feed. The R{sup 2} of the resulting physical property models ranged from 0.89 to 0.99.
Modelling Difficulties and Their Overcoming Strategies in the Solution of a Modelling Problem
Dede, Ayse Tekin
2016-01-01
The purpose of the study is to reveal the elementary mathematics student teachers' difficulties encountered in the solution of a modelling problem, the strategies to overcome those difficulties and whether the strategies worked or not. Nineteen student teachers solved the modelling problem in their four or five-person groups, and the video records…
New analytical solutions for nonlinear physical models of the ...
Indian Academy of Sciences (India)
2016-10-18
expansion method is implemented to find exact solutions of ... and can be used as an alternative for finding exact solutions of nonlinear equations in mathematical physics. A ... engineering, such as, solid mechanics, plasma physics,.
Self-similar solution for coupled thermal electromagnetic model ...
African Journals Online (AJOL)
An investigation into the existence and uniqueness solution of self-similar solution for the coupled Maxwell and Pennes Bio-heat equations have been done. Criteria for existence and uniqueness of self-similar solution are revealed in the consequent theorems. Journal of the Nigerian Association of Mathematical Physics ...
Malakpoor, K.; Kaasschieter, E.F.; Huyghe, J.M.
2007-01-01
Abstract: The swelling and shrinkage of biological tissues are modelled by a four-component mixture theory [J.M. Huyghe and J.D. Janssen, Int. J. Engng. Sci. 35 (1997) 793-802; K. Malakpoor, E.F. Kaasschieter and J.M. Huyghe, Mathematical modelling and numerical solution of swelling of cartilaginous
Biosorption of chromium (VI) from aqueous solutions and ANN modelling.
Nag, Soma; Mondal, Abhijit; Bar, Nirjhar; Das, Sudip Kumar
2017-08-01
The use of sustainable, green and biodegradable natural wastes for Cr(VI) detoxification from the contaminated wastewater is considered as a challenging issue. The present research is aimed to assess the effectiveness of seven different natural biomaterials, such as jackfruit leaf, mango leaf, onion peel, garlic peel, bamboo leaf, acid treated rubber leaf and coconut shell powder, for Cr(VI) eradication from aqueous solution by biosorption process. Characterizations were conducted using SEM, BET and FTIR spectroscopy. The effects of operating parameters, viz., pH, initial Cr(VI) ion concentration, adsorbent dosages, contact time and temperature on metal removal efficiency, were studied. The biosorption mechanism was described by the pseudo-second-order model and Langmuir isotherm model. The biosorption process was exothermic, spontaneous and chemical (except garlic peel) in nature. The sequence of adsorption capacity was mango leaf > jackfruit leaf > acid treated rubber leaf > onion peel > bamboo leaf > garlic peel > coconut shell with maximum Langmuir adsorption capacity of 35.7 mg g -1 for mango leaf. The treated effluent can be reused. Desorption study suggested effective reuse of the adsorbents up to three cycles, and safe disposal method of the used adsorbents suggested biodegradability and sustainability of the process by reapplication of the spent adsorbent and ultimately leading towards zero wastages. The performances of the adsorbents were verified with wastewater from electroplating industry. The scale-up study reported for industrial applications. ANN modelling using multilayer perception with gradient descent (GD) and Levenberg-Marquart (LM) algorithm had been successfully used for prediction of Cr(VI) removal efficiency. The study explores the undiscovered potential of the natural waste materials for sustainable existence of small and medium sector industries, especially in the third world countries by protecting the environment by eco-innovation.
Computational model for simulation small testing launcher, technical solution
Chelaru, Teodor-Viorel; Cristian, Barbu; Chelaru, Adrian
2014-12-01
The purpose of this paper is to present some aspects regarding the computational model and technical solutions for multistage suborbital launcher for testing (SLT) used to test spatial equipment and scientific measurements. The computational model consists in numerical simulation of SLT evolution for different start conditions. The launcher model presented will be with six degrees of freedom (6DOF) and variable mass. The results analysed will be the flight parameters and ballistic performances. The discussions area will focus around the technical possibility to realize a small multi-stage launcher, by recycling military rocket motors. From technical point of view, the paper is focused on national project "Suborbital Launcher for Testing" (SLT), which is based on hybrid propulsion and control systems, obtained through an original design. Therefore, while classical suborbital sounding rockets are unguided and they use as propulsion solid fuel motor having an uncontrolled ballistic flight, SLT project is introducing a different approach, by proposing the creation of a guided suborbital launcher, which is basically a satellite launcher at a smaller scale, containing its main subsystems. This is why the project itself can be considered an intermediary step in the development of a wider range of launching systems based on hybrid propulsion technology, which may have a major impact in the future European launchers programs. SLT project, as it is shown in the title, has two major objectives: first, a short term objective, which consists in obtaining a suborbital launching system which will be able to go into service in a predictable period of time, and a long term objective that consists in the development and testing of some unconventional sub-systems which will be integrated later in the satellite launcher as a part of the European space program. This is why the technical content of the project must be carried out beyond the range of the existing suborbital vehicle
Cosmological solutions in multidimensional model with multiple exponential potential
International Nuclear Information System (INIS)
Ivashchuk, Vladimir D.; Melnikov, Vitaly N.; Selivanov, Alexey B.
2003-01-01
A family of cosmological solutions with (n+1) Ricci-flat spaces in the theory with several scalar fields and multiple exponential potential is obtained when coupling vectors in exponents obey certain relations. Two subclasses of solutions with power-law and exponential behaviour of scale factors are singled out. It is proved that power-law solutions may take place only when coupling vectors are linearly independent and exponential dependence occurs for linearly dependent set of coupling vectors. A subfamily of solutions with accelerated expansion is singled out. A generalized isotropization behaviours of certain classes of general solutions are found. In quantum case exact solutions to Wheeler-DeWitt equation are obtained and special 'ground state' wave functions are considered. (author)
Stability of core–shell nanowires in selected model solutions
Energy Technology Data Exchange (ETDEWEB)
Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl; Wykowska, U.; Basa, A.; Zambrzycka, E.
2015-03-30
Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.
Stability of core–shell nanowires in selected model solutions
International Nuclear Information System (INIS)
Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.
2015-01-01
Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods
Understanding quantum measurement from the solution of dynamical models
International Nuclear Information System (INIS)
Allahverdyan, Armen E.; Balian, Roger; Nieuwenhuizen, Theo M.
2013-01-01
The quantum measurement problem, to wit, understanding why a unique outcome is obtained in each individual experiment, is currently tackled by solving models. After an introduction we review the many dynamical models proposed over the years for elucidating quantum measurements. The approaches range from standard quantum theory, relying for instance on quantum statistical mechanics or on decoherence, to quantum–classical methods, to consistent histories and to modifications of the theory. Next, a flexible and rather realistic quantum model is introduced, describing the measurement of the z-component of a spin through interaction with a magnetic memory simulated by a Curie–Weiss magnet, including N≫1 spins weakly coupled to a phonon bath. Initially prepared in a metastable paramagnetic state, it may transit to its up or down ferromagnetic state, triggered by its coupling with the tested spin, so that its magnetization acts as a pointer. A detailed solution of the dynamical equations is worked out, exhibiting several time scales. Conditions on the parameters of the model are found, which ensure that the process satisfies all the features of ideal measurements. Various imperfections of the measurement are discussed, as well as attempts of incompatible measurements. The first steps consist in the solution of the Hamiltonian dynamics for the spin-apparatus density matrix D -hat (t). Its off-diagonal blocks in a basis selected by the spin–pointer coupling, rapidly decay owing to the many degrees of freedom of the pointer. Recurrences are ruled out either by some randomness of that coupling, or by the interaction with the bath. On a longer time scale, the trend towards equilibrium of the magnet produces a final state D -hat (t f ) that involves correlations between the system and the indications of the pointer, thus ensuring registration. Although D -hat (t f ) has the form expected for ideal measurements, it only describes a large set of runs. Individual runs are
Understanding quantum measurement from the solution of dynamical models
Energy Technology Data Exchange (ETDEWEB)
Allahverdyan, Armen E. [Laboratoire de Physique Statistique et Systèmes Complexes, ISMANS, 44 Av. Bartholdi, 72000 Le Mans (France); Balian, Roger [Institut de Physique Théorique, CEA Saclay, 91191 Gif-sur-Yvette cedex (France); Nieuwenhuizen, Theo M., E-mail: T.M.Nieuwenhuizen@uva.nl [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)
2013-04-15
The quantum measurement problem, to wit, understanding why a unique outcome is obtained in each individual experiment, is currently tackled by solving models. After an introduction we review the many dynamical models proposed over the years for elucidating quantum measurements. The approaches range from standard quantum theory, relying for instance on quantum statistical mechanics or on decoherence, to quantum–classical methods, to consistent histories and to modifications of the theory. Next, a flexible and rather realistic quantum model is introduced, describing the measurement of the z-component of a spin through interaction with a magnetic memory simulated by a Curie–Weiss magnet, including N≫1 spins weakly coupled to a phonon bath. Initially prepared in a metastable paramagnetic state, it may transit to its up or down ferromagnetic state, triggered by its coupling with the tested spin, so that its magnetization acts as a pointer. A detailed solution of the dynamical equations is worked out, exhibiting several time scales. Conditions on the parameters of the model are found, which ensure that the process satisfies all the features of ideal measurements. Various imperfections of the measurement are discussed, as well as attempts of incompatible measurements. The first steps consist in the solution of the Hamiltonian dynamics for the spin-apparatus density matrix D{sup -hat} (t). Its off-diagonal blocks in a basis selected by the spin–pointer coupling, rapidly decay owing to the many degrees of freedom of the pointer. Recurrences are ruled out either by some randomness of that coupling, or by the interaction with the bath. On a longer time scale, the trend towards equilibrium of the magnet produces a final state D{sup -hat} (t{sub f}) that involves correlations between the system and the indications of the pointer, thus ensuring registration. Although D{sup -hat} (t{sub f}) has the form expected for ideal measurements, it only describes a large set of
SU-F-R-10: Selecting the Optimal Solution for Multi-Objective Radiomics Model
International Nuclear Information System (INIS)
Zhou, Z; Folkert, M; Wang, J
2016-01-01
Purpose: To develop an evidential reasoning approach for selecting the optimal solution from a Pareto solution set obtained by a multi-objective radiomics model for predicting distant failure in lung SBRT. Methods: In the multi-objective radiomics model, both sensitivity and specificity are considered as the objective functions simultaneously. A Pareto solution set with many feasible solutions will be resulted from the multi-objective optimization. In this work, an optimal solution Selection methodology for Multi-Objective radiomics Learning model using the Evidential Reasoning approach (SMOLER) was proposed to select the optimal solution from the Pareto solution set. The proposed SMOLER method used the evidential reasoning approach to calculate the utility of each solution based on pre-set optimal solution selection rules. The solution with the highest utility was chosen as the optimal solution. In SMOLER, an optimal learning model coupled with clonal selection algorithm was used to optimize model parameters. In this study, PET, CT image features and clinical parameters were utilized for predicting distant failure in lung SBRT. Results: Total 126 solution sets were generated by adjusting predictive model parameters. Each Pareto set contains 100 feasible solutions. The solution selected by SMOLER within each Pareto set was compared to the manually selected optimal solution. Five-cross-validation was used to evaluate the optimal solution selection accuracy of SMOLER. The selection accuracies for five folds were 80.00%, 69.23%, 84.00%, 84.00%, 80.00%, respectively. Conclusion: An optimal solution selection methodology for multi-objective radiomics learning model using the evidential reasoning approach (SMOLER) was proposed. Experimental results show that the optimal solution can be found in approximately 80% cases.
Robust and efficient solution procedures for association models
DEFF Research Database (Denmark)
Michelsen, Michael Locht
2006-01-01
Equations of state that incorporate the Wertheim association expression are more difficult to apply than conventional pressure explicit equations, because the association term is implicit and requires solution for an internal set of composition variables. In this work, we analyze the convergence ...... behavior of different solution methods and demonstrate how a simple and efficient, yet globally convergent, procedure for the solution of the equation of state can be formulated....
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.
Travelling wave solutions to nonlinear physical models by means of ...
Indian Academy of Sciences (India)
This paper presents the ﬁrst integral method to carry out the integration of nonlinear partial differential equations in terms of travelling wave solutions. For illustration, three important equations of mathematical physics are analytically investigated. Through the established ﬁrst integrals, exact solutions are successfully ...
New analytical solutions for nonlinear physical models of the ...
Indian Academy of Sciences (India)
2016-10-18
Oct 18, 2016 ... Abstract. In this article, a variety of solitary wave solutions are found for some nonlinear equations. In math- ematical physics, we studied two complex systems, the Maccari system and the coupled Higgs field equation. We construct sufficient exact solutions for nonlinear evolution equations. To study ...
Calcite growth kinetics: Modeling the effect of solution stoichiometry
Wolthers, M.; Nehrke, G.; Gustafsson, J.P.; Van Cappellen, P.
2012-01-01
Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth
New analytical solutions for nonlinear physical models of the ...
Indian Academy of Sciences (India)
In mathematical physics, we studied two complex systems, the Maccari system and the coupled Higgs field equation. We construct sufficient exact solutions for nonlinear evolution equations. To study travelling wave solutions, we used a fractional complex transform to convert the particular partial differential equation of ...
Travelling wave solutions to nonlinear physical models by means
Indian Academy of Sciences (India)
This paper presents the ﬁrst integral method to carry out the integration of nonlinear partial differential equations in terms of travelling wave solutions. For illustration, three important equations of mathematical physics are analytically investigated. Through the established ﬁrst integrals, exact solutions are successfully ...
Segment-based Eyring-Wilson viscosity model for polymer solutions
International Nuclear Information System (INIS)
Sadeghi, Rahmat
2005-01-01
A theory-based model is presented for correlating viscosity of polymer solutions and is based on the segment-based Eyring mixture viscosity model as well as the segment-based Wilson model for describing deviations from ideality. The model has been applied to several polymer solutions and the results show that it is reliable both for correlation and prediction of the viscosity of polymer solutions at different molar masses and temperature of the polymer
Expansion of thermodynamic model of solute permeation through reverse osmosis membrane
International Nuclear Information System (INIS)
Nishimaki, Kenzo; Koyama, Akio
1994-01-01
Many studies have been performed on permeation mechanism of solute and solvent in membrane separation process like reverse osmosis or ultrafiltration, and several models of solute/solvent permeation through membrane are proposed. Among these models, Kedem and Katchalsky, based on the theory of thermodynamics of irreversible processes, formulated the one-solute permeation process in their mathematical model, which treats membrane as a black box, not giving consideration to membrane structure and to interaction between membrane material and permeates, viz. solute and solvent. According to this theory, the driving force of solute/solvent permeation through membrane is the difference of their chemical potential between both sides of membrane, and the linear phenomenological equation is applied to describing the relation between driving force and flux of solute/solvent. This equation can be applied to the irreversible process only when the process is almost in equilibrium. This condition is supposed to be satisfied in the solute/solvent permeation process through compact membrane with fine pores like reverse osmosis membrane. When reverse osmosis is applied to treatment process for liquid waste, which usually contains a lot of solutes as contaminants, we can not predict the behavior of contaminants by the above one-solute process model. In the case of multi-solutes permeation process for liquid waste, the number of parameter in thermodynamic model increases rapidly with the number of solute, because of coupling phenomenon among solutes. In this study, we expanded the above thermodynamic model to multi-solute process applying operational calculus to the differential equations which describe the irreversible process of the system, and expressed concisely solute concentration vector as a matrix product. In this way, we predict the behavior of solutes in multi-solutes process, using values of parameters obtained in two-solutes process. (author)
Random geometry model in criticality calculations of solutions containing Raschig rings
International Nuclear Information System (INIS)
Teng, S.P.; Lindstrom, D.G.
1979-01-01
The criticality constants of fissile solutions containing borated Raschig rings are evaluated using the Monte Carlo code KENO IV with various geometry models. In addition to those used by other investigators, a new geometry model, the random geometry model, is presented to simulate the system of randomly oriented Raschig rings in solution. A technique to obtain the material thickness distribution functions of solution and rings for use in the random geometry model is also presented. Comparison between the experimental data and the calculated results using Monte Carlo method with various geometry models indicates that the random geometry model is a reasonable alternative to models previously used in describing the system of Raschig-ring-filled solution. The random geometry model also provides a solution to the problem of describing an array containing Raschig-ring-filled tanks that is not available to techniques using other models
Plasmoid solutions of the Hahm–Kulsrud–Taylor equilibrium model
Energy Technology Data Exchange (ETDEWEB)
Dewar, R. L. [Plasma Research Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200, Australia and Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8561 (Japan); Bhattacharjee, A.; Kulsrud, R. M. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Wright, A. M. [The Australian National University, Canberra ACT 0200 (Australia)
2013-08-15
The Hahm–Kulsrud (HK) [T. S. Hahm and R. M. Kulsrud, Phys. Fluids 28, 2412 (1985)] solutions for a magnetically sheared plasma slab driven by a resonant periodic boundary perturbation illustrate fully shielded (current sheet) and fully reconnected (magnetic island) responses. On the global scale, reconnection involves solving a magnetohydrodynamic (MHD) equilibrium problem. In systems with a continuous symmetry, such MHD equilibria are typically found by solving the Grad–Shafranov equation, and in slab geometry the elliptic operator in this equation is the 2-D Laplacian. Thus, assuming appropriate pressure and poloidal current profiles, a conformal mapping method can be used to transform one solution into another with different boundary conditions, giving a continuous sequence of solutions in the form of partially reconnected magnetic islands (plasmoids) separated by Syrovatsky current sheets. The two HK solutions appear as special cases.
Exact solutions to a nonlinear dispersive model with variable coefficients
International Nuclear Information System (INIS)
Yin Jun; Lai Shaoyong; Qing Yin
2009-01-01
A mathematical technique based on an auxiliary differential equation and the symbolic computation system Maple is employed to investigate a prototypical and nonlinear K(n, n) equation with variable coefficients. The exact solutions to the equation are constructed analytically under various circumstances. It is shown that the variable coefficients and the exponent appearing in the equation determine the quantitative change in the physical structures of the solutions.
Mathematical modeling of fluid and solute transport in peritoneal dialysis
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...
Positive global solutions for a general model of size-dependent population dynamics
Kato, Nobuyuki
2000-01-01
We study size-structured population models of general type which have the growth rate depending on the size and time. The local existence and uniqueness of the solution have been shown by Kato and Torikata (1997). Here, we discuss the positivity of the solution and global existence as well as $L^\\infty$ solutions.
International Nuclear Information System (INIS)
Portugal, R.; Soares, I.D.
1985-01-01
Two new classes of spatially homogeneous cosmological solutions of Einstein-Maxwell equations are obtained by considering a class of exact perturbations of the static Bertotti-Robinson (BR) model. The BR solution is shown to be unstable under these perturbations, being perturbed into exact cosmological solutions with perfect fluid (equations of state p = lambda rho, O [pt
General classical solutions in the noncommutative CP{sup N-1} model
Energy Technology Data Exchange (ETDEWEB)
Foda, O.; Jack, I.; Jones, D.R.T
2002-10-31
We give an explicit construction of general classical solutions for the noncommutative CP{sup N-1} model in two dimensions, showing that they correspond to integer values for the action and topological charge. We also give explicit solutions for the Dirac equation in the background of these general solutions and show that the index theorem is satisfied.
Stability of core-shell nanowires in selected model solutions
Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.
2015-03-01
This paper presents the studies of stability of magnetic core-shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.
Ganguly, Moumita; Chakraborty, Aniruddha
2017-10-01
A diffusion theory for intramolecular reactions of polymer chain in dilute solution is formulated. We give a detailed analytical expression for calculation of rate of polymer looping in solution. The physical problem of looping can be modeled mathematically with the use of a Smoluchowski-like equation with a Dirac delta function sink of finite strength. The solution of this equation is expressed in terms of Laplace Transform of the Green's function for end-to-end motion of the polymer in absence of the sink. We have defined two different rate constants, the long term rate constant and the average rate constant. The average rate constant and long term rate constant varies with several parameters such as length of the polymer (N), bond length (b) and the relaxation time τR. The long term rate constant is independent of the initial probability distribution.
Thermodynamic modeling of iodine and selenium retention in solutions with high salinity
International Nuclear Information System (INIS)
Hagemann, Sven; Moog, Helge C.; Herbert, Horst-Juergen; Erich, Agathe
2012-04-01
The report on iodine and selenium retention in saline solutions includes the following chapters: (1) Introduction and scope of the work. (2) Actual status of knowledge. (3) Experimental and numerical models. (4) Thermodynamic properties of selenite and hydrogen selenite in solutions of oceanic salts. (5) Thermodynamic properties of selenate in solutions of oceanic salts. (6) Thermodynamic properties of iodide in solutions of oceanic salts. (7) Experimental studies on the retention of iodine and selenium in selected sorbents. (8) Summary and conclusions.
Investigating conceptual models for physical property couplings in solid solution models of cement
International Nuclear Information System (INIS)
Benbow, Steven; Watson, Claire; Savage, David
2005-11-01
The long-term behaviour of cementitious engineered barriers is an important process to consider when modelling the migration of radionuclides from a geological repository for nuclear waste. The modelling of cement is complicated by the fact that the cement is dominated by the behaviour of calcium silicate hydrate (CSH) gel which is a complex solid exhibiting incongruent dissolution behaviour. In this report, we have demonstrated the implementation of a solid-solution CSH gel model within a geochemical transport modelling framework using the Raiden computer code to investigate cement/concrete-groundwater interactions. The modelling conducted here shows that it is possible to couple various conceptual models for the evolution of physical properties of concrete with a solid solution model for cement degradation in a fully coupled geochemical transport model to describe the interaction of cement/concrete engineered barriers with groundwater. The results show that changes to the conceptual models and flow rates can give rise to very different evolutions. Most simulations were carried out at a reduced 'experimental' scale rather than full repository scale. The work has shown the possibility to investigate also the changing physical properties of degrading cement. To further develop the model more emphasis is needed on kinetics and the detailed development of a nearly clogged pore space. Modelling of the full repository scale could be another way forward to understand the behaviour of degrading concrete. A general conclusion is that the combined effects of chemical evolution and physical degradation should be analysed in performance assessments of cementitious repositories. Moreover, the project results will be used as one basis in coming reviews of SKB's safety assessments of repositories for spent fuel and low-and intermediate level waste
Investigating conceptual models for physical property couplings in solid solution models of cement
Energy Technology Data Exchange (ETDEWEB)
Benbow, Steven; Watson, Claire; Savage, David [Quintesssa Ltd., Henley-on-Thames (United Kingdom)
2005-11-15
The long-term behaviour of cementitious engineered barriers is an important process to consider when modelling the migration of radionuclides from a geological repository for nuclear waste. The modelling of cement is complicated by the fact that the cement is dominated by the behaviour of calcium silicate hydrate (CSH) gel which is a complex solid exhibiting incongruent dissolution behaviour. In this report, we have demonstrated the implementation of a solid-solution CSH gel model within a geochemical transport modelling framework using the Raiden computer code to investigate cement/concrete-groundwater interactions. The modelling conducted here shows that it is possible to couple various conceptual models for the evolution of physical properties of concrete with a solid solution model for cement degradation in a fully coupled geochemical transport model to describe the interaction of cement/concrete engineered barriers with groundwater. The results show that changes to the conceptual models and flow rates can give rise to very different evolutions. Most simulations were carried out at a reduced 'experimental' scale rather than full repository scale. The work has shown the possibility to investigate also the changing physical properties of degrading cement. To further develop the model more emphasis is needed on kinetics and the detailed development of a nearly clogged pore space. Modelling of the full repository scale could be another way forward to understand the behaviour of degrading concrete. A general conclusion is that the combined effects of chemical evolution and physical degradation should be analysed in performance assessments of cementitious repositories. Moreover, the project results will be used as one basis in coming reviews of SKB's safety assessments of repositories for spent fuel and low-and intermediate level waste.
The Lunar Internal Structure Model: Problems and Solutions
Nefedyev, Yuri; Gusev, Alexander; Petrova, Natalia; Varaksina, Natalia
decomposition of gravitational field of the Moon of members up to 165th order with a high degree of accuracy. Judging from the given data, the distinctive feature of the Moon’s gravitational field is that harmonics of the third and even the fourth order are comparable with harmonics of the second order, except for member J2. General conclusion: according to recent data, the true figure of the Moon is much more complex than a three-axis ellipsoid. Gravitational field and dynamic figure of the multilayered Moon: One of the main goals of selenodesy is the study of a dynamic figure of the Moon which determines distribution of the mass within the Moon’s body. A dynamic figure is shaped by the inertia ellipsoid set by values of resultant moments of inertia of the Moon A, B, C and their orientation in space. Selenoid satellites (SS) open new and most perspective opportunities in the study of gravitational field and the Moon’s figure. SSs “Moon 10”, “Apollo”, “Clementine”, “Lunar Prospector” trajectory tracking data processing has allowed for identification of coefficients in decomposition of gravitational field of the Moon of members up to 165th order with a high degree of accuracy. Judging from the given data, the distinctive feature of the Moon’s gravitational field is that harmonics of the third and even the fourth order are comparable with harmonics of the second order. Difference from zero of c-coefficients proves asymmetry of gravitational fields on the visible and invisible sides of the Moon. As a first attempt at solving the problem, the report presents the survey of internal structure of the Moon, tabulated values of geophysical parameters and geophysical profile of the Moon, including liquid lunar core, analytical solution of Clairaut’s equation for the two-layer model of the Moon; mathematical and bifurcational analysis of solution based on physically justified task options; original debugged software in VBA programming language for computer
Ocean wave prediction using numerical and neural network models
Digital Repository Service at National Institute of Oceanography (India)
Mandal, S.; Prabaharan, N.
This paper presents an overview of the development of the numerical wave prediction models and recently used neural networks for ocean wave hindcasting and forecasting. The numerical wave models express the physical concepts of the phenomena...
Delaney, Declan T.; O’Hare, Gregory M. P.
2016-01-01
No single network solution for Internet of Things (IoT) networks can provide the required level of Quality of Service (QoS) for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number and complexity of solutions available, it becomes difficult for an application developer to choose the solution which is best suited for an application. This article introduces a framework which autonomously chooses the best solution for the application given the current deployed environment. The framework utilises a performance model to predict the expected performance of a particular solution in a given environment. The framework can then choose an apt solution for the application from a set of available solutions. This article presents the framework with a set of models built using data collected from simulation. The modelling technique can determine with up to 85% accuracy the solution which performs the best for a particular performance metric given a set of solutions. The article highlights the fractured and disjointed practice currently in place for examining and comparing communication solutions and aims to open a discussion on harmonising testing procedures so that different solutions can be directly compared and offers a framework to achieve this within IoT networks. PMID:27916929
Delaney, Declan T; O'Hare, Gregory M P
2016-12-01
No single network solution for Internet of Things (IoT) networks can provide the required level of Quality of Service (QoS) for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number and complexity of solutions available, it becomes difficult for an application developer to choose the solution which is best suited for an application. This article introduces a framework which autonomously chooses the best solution for the application given the current deployed environment. The framework utilises a performance model to predict the expected performance of a particular solution in a given environment. The framework can then choose an apt solution for the application from a set of available solutions. This article presents the framework with a set of models built using data collected from simulation. The modelling technique can determine with up to 85% accuracy the solution which performs the best for a particular performance metric given a set of solutions. The article highlights the fractured and disjointed practice currently in place for examining and comparing communication solutions and aims to open a discussion on harmonising testing procedures so that different solutions can be directly compared and offers a framework to achieve this within IoT networks.
A Framework to Implement IoT Network Performance Modelling Techniques for Network Solution Selection
Directory of Open Access Journals (Sweden)
Declan T. Delaney
2016-12-01
Full Text Available No single network solution for Internet of Things (IoT networks can provide the required level of Quality of Service (QoS for all applications in all environments. This leads to an increasing number of solutions created to fit particular scenarios. Given the increasing number and complexity of solutions available, it becomes difficult for an application developer to choose the solution which is best suited for an application. This article introduces a framework which autonomously chooses the best solution for the application given the current deployed environment. The framework utilises a performance model to predict the expected performance of a particular solution in a given environment. The framework can then choose an apt solution for the application from a set of available solutions. This article presents the framework with a set of models built using data collected from simulation. The modelling technique can determine with up to 85% accuracy the solution which performs the best for a particular performance metric given a set of solutions. The article highlights the fractured and disjointed practice currently in place for examining and comparing communication solutions and aims to open a discussion on harmonising testing procedures so that different solutions can be directly compared and offers a framework to achieve this within IoT networks.
Modelling of flame temperature of solution combustion synthesis of ...
Indian Academy of Sciences (India)
Hydroxyapatite (HAp), an important bio-ceramic was successfully synthesized by combustion in the aqueous system containing calcium nitrate-di-ammonium hydrogen orthophosphate-urea. The combustion flame temperature of solution combustion reaction depends on various process parameters, and it plays a significant ...
Some exact solutions of magnetized viscous model in string ...
Indian Academy of Sciences (India)
Abstract. In this paper, we study anisotropic Bianchi-V Universe with magnetic field and bulk viscous fluid in string cosmology. Exact solutions of the field equations are obtained by using the equation of state (EoS) for a cloud of strings, and a relationship between bulk viscous coefficient and scalar expansion. The bulk ...
Some exact solutions of magnetized viscous model in string ...
Indian Academy of Sciences (India)
In this paper, we study anisotropic Bianchi-V Universe with magnetic field and bulk viscous fluid in string cosmology. Exact solutions of the field equations are obtained by using the equation of state (EoS) for a cloud of strings, and a relationship between bulk viscous coefficient and scalar expansion. The bulk viscous ...
New analytical solutions for nonlinear physical models of the ...
Indian Academy of Sciences (India)
A comparative study with the other methods gives validity to the technique and shows that the method providesadditional solutions. Graphical representations along with the numerical data reinforce the efficacy of the procedure used. The specified idea is very effective, pragmatic for partial differential equations of fractional ...
Liu, Qun; Jiang, Daqing; Hayat, Tasawar; Ahmad, Bashir
2017-09-01
In this paper, we investigate two stochastic SIR epidemic models with higher order perturbation. For the nonautonomous periodic case of the model, by using Has'minskii's theory of periodic solution, we show that the system has at least one nontrivial positive T-periodic solution. For the system disturbed by both the white noise and telephone noise, we establish sufficient conditions for positive recurrence and the existence of ergodic stationary distribution of the positive solution.
Connection between the Affine and conformal Affine Toda models and their Hirota's solution
International Nuclear Information System (INIS)
Constantinidis, C.P.; Ferreira, L.A.; Gomes, J.F.; Zimerman, A.H.
1992-01-01
It is shown that the Affine Toda models (AT) constitute a gauge fixed version of the Conformal Affine Toda model (CAT). This result enables one to map every solution of the AT models into an infinite number of solutions of the corresponding CAT models, each one associated to a point of the orbit of the conformal group. The Hirota's τ-function are introduced and soliton solutions for the AT and CAT models associated to SL (r+1) and SP (r) are constructed. (author)
Local martingale and pathwise solutions for an abstract fluids model
Debussche, Arnaud; Glatt-Holtz, Nathan; Temam, Roger
2011-07-01
We establish the existence and uniqueness of both local martingale and local pathwise solutions of an abstract nonlinear stochastic evolution system. The primary application of this abstract framework is to infer the local existence of strong, pathwise solutions to the 3D primitive equations of the oceans and atmosphere forced by a nonlinear multiplicative white noise. Instead of developing our results, specifically for the 3D primitive equations we choose to develop them in a slightly abstract framework which covers many related forms of these equations (atmosphere, oceans, coupled atmosphere-ocean, on the sphere, on the β-plane approximation etc. and the incompressible Navier-Stokes equations). In applications, all the details are given for the β-plane approximation of the equations of the ocean.
Solutions of several coupled discrete models in terms of Lamé ...
Indian Academy of Sciences (India)
Vol. 78, No. 2. — journal of. February 2012 physics pp. 187–213. Solutions of several coupled discrete models in terms of Lamé polynomials of order one and two ... paper is to carry out a similar study for a number of coupled discrete field theory models. ..... For the solution (23), un,vn satisfy the boundary condition.
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 s...
Steel corrosion resistance in model solutions and reinforced mortar containing wastes
Koleva, D.A.; Van Breugel, K.
2012-01-01
This work reports on the corrosion resistance of steel in alkaline model solutions and in cement-based materials (mortar). The model solutions and the mortar specimens were Ordinary Portland Cement (OPC) based. Further, hereby discussed is the implementation of an eco-friendly approach of waste
Nonexistence of nonconstant steady-state solutions in a triangular cross-diffusion model
Lou, Yuan; Tao, Youshan; Winkler, Michael
2017-05-01
In this paper we study the Shigesada-Kawasaki-Teramoto model for two competing species with triangular cross-diffusion. We determine explicit parameter ranges within which the model exclusively possesses constant steady state solutions.
Multi-scale modelling of uranyl chloride solutions
Energy Technology Data Exchange (ETDEWEB)
Nguyen, Thanh-Nghi; Duvail, Magali, E-mail: magali.duvail@icsm.fr; Villard, Arnaud; Dufrêche, Jean-François, E-mail: jean-francois.dufreche@univ-montp2.fr [Institut de Chimie Séparative de Marcoule (ICSM), UMR 5257, CEA-CNRS-Université Montpellier 2-ENSCM, Site de Marcoule, Bâtiment 426, BP 17171, F-30207 Bagnols-sur-Cèze Cedex (France); Molina, John Jairo [Fukui Institute for Fundamental Chemistry, Kyoto University, Takano-Nishihiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103 (Japan); Guilbaud, Philippe [CEA/DEN/DRCP/SMCS/LILA, Marcoule, F-30207 Bagnols-sur-Cèze Cedex (France)
2015-01-14
Classical molecular dynamics simulations with explicit polarization have been successfully used to determine the structural and thermodynamic properties of binary aqueous solutions of uranyl chloride (UO{sub 2}Cl{sub 2}). Concentrated aqueous solutions of uranyl chloride have been studied to determine the hydration properties and the ion-ion interactions. The bond distances and the coordination number of the hydrated uranyl are in good agreement with available experimental data. Two stable positions of chloride in the second hydration shell of uranyl have been identified. The UO{sub 2}{sup 2+}-Cl{sup −} association constants have also been calculated using a multi-scale approach. First, the ion-ion potential averaged over the solvent configurations at infinite dilution (McMillan-Mayer potential) was calculated to establish the dissociation/association processes of UO{sub 2}{sup 2+}-Cl{sup −} ion pairs in aqueous solution. Then, the association constant was calculated from this potential. The value we obtained for the association constant is in good agreement with the experimental result (K{sub UO{sub 2Cl{sup +}}} = 1.48 l mol{sup −1}), but the resulting activity coefficient appears to be too low at molar concentration.
Modeling hydrate formation conditions in the presence of electrolytes and polar inhibitor solutions
International Nuclear Information System (INIS)
Osfouri, Shahriar; Azin, Reza; Gholami, Reza; Izadpanah, Amir Abbas
2015-01-01
Highlights: • A new predictive model is proposed for prediction of hydrate formation pressures. • A new local composition model was used to evaluate water activity in the presence of electrolyte. • MEG, DEG and TEG were used to test ability of the proposed model in the presence of polar inhibitors. • Cage occupancies by methane for the small cage were higher than carbon dioxide for gas mixtures. • The proposed model gives better match with experimental data in mixed electrolyte solutions. - Abstract: In this paper, a new predictive model is proposed for prediction of gas hydrate formation conditions in the presence of single and mixed electrolytes and solutions containing both electrolyte and a polar inhibitor such as monoethylene glycol (MEG), diethylene glycol (DEG) and triethylene glycol (TEG). The proposed model is based on the γ–φ approach, which uses modified Patel–Teja equation of state (VPT EOS) for characterizing the vapor phase, the solid solution theory by van der Waals and Platteeuw for modeling the hydrate phase, the non-electrolyte NRTL-NRF local composition model and Pitzer–Debye–Huckel equation as short-range and long-range contributions to calculate water activity in single electrolyte solutions. Also, the Margules equation was used to determine the activity of water in solutions containing polar inhibitor (glycols). The model predictions are in acceptable agreement with experimental data. For single electrolyte solutions, the model predictions are similar to available models, while for mixtures of electrolytes and mixtures of electrolytes and inhibitors, the proposed model gives significantly better predictions. In addition, the absolute average deviation of hydrate formation pressures (AADP) for 144 experimental data in solutions containing single electrolyte is 5.86% and for 190 experimental data in mixed electrolytes solutions is 5.23%. Furthermore, the proposed model has an AADP of 14.13%, 5.82% and 5.28% in solutions
Stochastic forward and inverse groundwater flow and solute transport modeling
Janssen, G.M.C.M.
2008-01-01
Keywords: calibration, inverse modeling, stochastic modeling, nonlinear biodegradation, stochastic-convective, advective-dispersive, travel time, network design, non-Gaussian distribution, multimodal distribution, representers
This thesis offers three new approaches that contribute
Exact solution of generalized Schulz-Shastry type models
International Nuclear Information System (INIS)
Osterloh, Andreas; Amico, Luigi; Eckern, Ulrich
2000-01-01
A class of integrable one-dimensional models presented by Shastry and Schulz is consequently extended to the whole class of one-dimensional Hubbard- or XXZ-type models with correlated gauge-like hopping. A complete characterization concerning solvability by coordinate Bethe ansatz of this class of models is found
Toward a Mesoscale Model for the Dynamics of Polymer Solutions
Energy Technology Data Exchange (ETDEWEB)
Miller, G H; Trebotich, D
2006-10-02
To model entire microfluidic systems containing solvated polymers we argue that it is necessary to have a numerical stability constraint governed only by the advective CFL condition. Advancements in the treatment of Kramers bead-rod polymer models are presented to enable tightly-coupled fluid-particle algorithms in the context of system-level modeling.
Does a peer model's task proficiency influence children's solution choice and innovation?
Wood, Lara A; Kendal, Rachel L; Flynn, Emma G
2015-11-01
The current study investigated whether 4- to 6-year-old children's task solution choice was influenced by the past proficiency of familiar peer models and the children's personal prior task experience. Peer past proficiency was established through behavioral assessments of interactions with novel tasks alongside peer and teacher predictions of each child's proficiency. Based on these assessments, one peer model with high past proficiency and one age-, sex-, dominance-, and popularity-matched peer model with lower past proficiency were trained to remove a capsule using alternative solutions from a three-solution artificial fruit task. Video demonstrations of the models were shown to children after they had either a personal successful interaction or no interaction with the task. In general, there was not a strong bias toward the high past-proficiency model, perhaps due to a motivation to acquire multiple methods and the salience of other transmission biases. However, there was some evidence of a model-based past-proficiency bias; when the high past-proficiency peer matched the participants' original solution, there was increased use of that solution, whereas if the high past-proficiency peer demonstrated an alternative solution, there was increased use of the alternative social solution and novel solutions. Thus, model proficiency influenced innovation. Copyright © 2015 Elsevier Inc. All rights reserved.
Fujita, Yasutaka; Doi, Kazuhisa; Harada, Daisuke; Kamikawa, Shuji
2010-04-01
Intraoperative bleeding often obscures the surgical field and may cause neurological damage. The irrigation fluids used during surgery might affect physiological hemostasis because they modulate the extracellular fluid composition of the bleeding area directly. The authors therefore investigated the influence of irrigation fluid on hemostasis in a mouse brain surface bleeding model. The cerebral cortices of ddY strain mice were exposed under irrigation with normal saline, lactated Ringer (LR) solution, or artificial CSF (ACF-95). To investigate the influence of electrolytes, calcium, potassium, or both were also added to the saline. After 10 minutes of irrigation at 100 ml/hour, sequential photographs of the surgical area were taken with a microscope, and the number of bleeding points was counted visually. Irrigation and counting were performed in a masked manner. There were significantly more bleeding points after irrigation with normal saline than with ACF-95; LR solution had a similar effect on physiological hemostasis as ACF-95. Saline augmented with calcium or potassium and calcium was superior to normal saline in terms of hemostasis. The authors demonstrated that the irrigation fluid used in neurosurgery affects bleeding at the surgical site. To avoid surgical site bleeding, ACF-95 and LR solution should be used as irrigation fluids instead of normal saline. The calcium and potassium content of irrigation solutions seems to be important in hemostasis.
New analytical solution for pyle-popovich's peritoneal dialysis model
Energy Technology Data Exchange (ETDEWEB)
Hamada, Hiroyuki; Sakiyama, Ryoichi; Okamoto, Masahiro; Tojo, Kakuji [Kyushi Institute of Technology, Fukuoka (Japan); Yamashita, Akihiro [Shonan Institute of Technology, Kanagwa (Japan)
1999-08-01
Continuous Ambulatory Peritoneal Dialysis (CAPD) is one of the standard treatments for kidney disease patients. A washing solution, called dialysate, is put into the peritoneal cavity to remove waste products and excess amounts of water in CAPD. The dialysate is exchanged four to five times a day by the patient. However, it is not easy to prescribe CAPD therapy, which may have precluded popularization of CAPD therapy. Popovich et al. constructed a mathematical model (P-P model) that applies to the prescription of the treatment schedule. It requires, however, a number of iterative calculations to obtain a exact numerical solution because the model is a set of nonlinear simultaneous ordinary differential equations. In this paper, the authors derived a new approximated analytical solution by employing a time-discrete technique, assuming all the parameters to be constant within each piecewise period of time for the P-P model. We have also described an algorithm of a numerical calculation with the new solution for clinical use with another analytical solution (Vonesh's solution). The new analytical solution consists of a forward solution (FW solution). The new analytical solution consists of a forward solution (FW solution), that is the solution for the plasma and dialysate concentrations from t{sub i} to t{sub i+1}(t{sub i}
The elastic solid solution model for minerals at high pressures and temperatures
Myhill, R.
2018-02-01
Non-ideality in mineral solid solutions affects their elastic and thermodynamic properties, their thermobaric stability, and the equilibrium phase relations in multiphase assemblages. At a given composition and state of order, non-ideality in minerals is typically modelled via excesses in Gibbs free energy which are either constant or linear with respect to pressure and temperature. This approach has been extremely successful when modelling near-ideal solutions. However, when the lattice parameters of the solution endmembers differ significantly, extrapolations of thermodynamic properties to high pressures using these models may result in significant errors. In this paper, I investigate the effect of parameterising solution models in terms of the Helmholtz free energy, treating volume (or lattice parameters) rather than pressure as an independent variable. This approach has been previously applied to models of order-disorder, but the implications for the thermodynamics and elasticity of solid solutions have not been fully explored. Solid solution models based on the Helmholtz free energy are intuitive at a microscopic level, as they automatically include the energetic contribution from elastic deformation of the endmember lattices. A chemical contribution must also be included in such models, which arises from atomic exchange within the solution. Derivations are provided for the thermodynamic properties of n-endmember solutions. Examples of the use of the elastic model are presented for the alkali halides, pyroxene, garnet, and bridgmanite solid solutions. Elastic theory provides insights into the microscopic origins of non-ideality in a range of solutions, and can make accurate predictions of excess enthalpies, entropies, and volumes as a function of volume and temperature. In solutions where experimental data are sparse or contradictory, the Helmholtz free energy approach can be used to assess the magnitude of excess properties and their variation as a function
Ziegler, Erik; Chellappa, Sarah L; Gaggioni, Giulia; Ly, Julien Q M; Vandewalle, Gilles; André, Elodie; Geuzaine, Christophe; Phillips, Christophe
2014-12-01
We present a finite element modeling (FEM) implementation for solving the forward problem in electroencephalography (EEG). The solution is based on Helmholtz's principle of reciprocity which allows for dramatically reduced computational time when constructing the leadfield matrix. The approach was validated using a 4-shell spherical model and shown to perform comparably with two current state-of-the-art alternatives (OpenMEEG for boundary element modeling and SimBio for finite element modeling). We applied the method to real human brain MRI data and created a model with five tissue types: white matter, gray matter, cerebrospinal fluid, skull, and scalp. By calculating conductivity tensors from diffusion-weighted MR images, we also demonstrate one of the main benefits of FEM: the ability to include anisotropic conductivities within the head model. Root-mean square deviation between the standard leadfield and the leadfield including white-matter anisotropy showed that ignoring the directional conductivity of white matter fiber tracts leads to orientation-specific errors in the forward model. Realistic head models are necessary for precise source localization in individuals. Our approach is fast, accurate, open-source and freely available online. Copyright © 2014 Elsevier Inc. All rights reserved.
Ackleh, Azmy S; Chellamuthu, Vinodh K; Ito, Kazufumi
2015-04-01
We study a quasilinear hierarchically size-structured population model presented in [4]. In this model the growth, mortality and reproduction rates are assumed to depend on a function of the population density. In [4] we showed that solutions to this model can become singular (measure-valued) in finite time even if all the individual parameters are smooth. Therefore, in this paper we develop a first order finite difference scheme to compute these measure-valued solutions. Convergence analysis for this method is provided. We also develop a high resolution second order scheme to compute the measure-valued solution of the model and perform a comparative study between the two schemes.
Algebraic Traveling Wave Solutions of a Non-local Hydrodynamic-type Model
International Nuclear Information System (INIS)
Chen, Aiyong; Zhu, Wenjing; Qiao, Zhijun; Huang, Wentao
2014-01-01
In this paper we consider the algebraic traveling wave solutions of a non-local hydrodynamic-type model. It is shown that algebraic traveling wave solutions exist if and only if an associated first order ordinary differential system has invariant algebraic curve. The dynamical behavior of the associated ordinary differential system is analyzed. Phase portraits of the associated ordinary differential system is provided under various parameter conditions. Moreover, we classify algebraic traveling wave solutions of the model. Some explicit formulas of smooth solitary wave and cuspon solutions are obtained
Mehl, S.; Hill, M.C.
2001-01-01
Five common numerical techniques for solving the advection-dispersion equation (finite difference, predictor corrector, total variation diminishing, method of characteristics, and modified method of characteristics) were tested using simulations of a controlled conservative tracer-test experiment through a heterogeneous, two-dimensional sand tank. The experimental facility was constructed using discrete, randomly distributed, homogeneous blocks of five sand types. This experimental model provides an opportunity to compare the solution techniques: the heterogeneous hydraulic-conductivity distribution of known structure can be accurately represented by a numerical model, and detailed measurements can be compared with simulated concentrations and total flow through the tank. The present work uses this opportunity to investigate how three common types of results - simulated breakthrough curves, sensitivity analysis, and calibrated parameter values - change in this heterogeneous situation given the different methods of simulating solute transport. The breakthrough curves show that simulated peak concentrations, even at very fine grid spacings, varied between the techniques because of different amounts of numerical dispersion. Sensitivity-analysis results revealed: (1) a high correlation between hydraulic conductivity and porosity given the concentration and flow observations used, so that both could not be estimated; and (2) that the breakthrough curve data did not provide enough information to estimate individual values of dispersivity for the five sands. This study demonstrates that the choice of assigned dispersivity and the amount of numerical dispersion present in the solution technique influence estimated hydraulic conductivity values to a surprising degree.
Analysis and synthesis of solutions for the agglomeration process modeling
Babuk, V. A.; Dolotkazin, I. N.; Nizyaev, A. A.
2013-03-01
The present work is devoted development of model of agglomerating process for propellants based on ammonium perchlorate (AP), ammonium dinitramide (ADN), HMX, inactive binder, and nanoaluminum. Generalization of experimental data, development of physical picture of agglomeration for listed propellants, development and analysis of mathematical models are carried out. Synthesis of models of various phenomena taking place at agglomeration implementation allows predicting of size and quantity, chemical composition, structure of forming agglomerates and its fraction in set of condensed combustion products. It became possible in many respects due to development of new model of agglomerating particle evolution on the surface of burning propellant. Obtained results correspond to available experimental data. It is supposed that analogical method based on analysis of mathematical models of particular phenomena and their synthesis will allow implementing of the agglomerating process modeling for other types of metalized solid propellants.
Approximate Solutions of Interactive Dynamic Influence Diagrams Using Model Clustering
DEFF Research Database (Denmark)
Zeng, Yifeng; Doshi, Prashant; Qiongyu, Cheng
2007-01-01
of the other agents, which increase exponentially with the number of time steps. We present a method of solving I-DIDs approximately by limiting the number of other agents' candidate models at each time step to a constant. We do this by clustering the models and selecting a representative set from the clusters...
Theoretical bases of modeling decision-marketing solutions
Grigoruk Pavel Mikhaylovych
2012-01-01
The paper deals with issues related with theoretical aspects of modelling of marketing decision making process. According to system approach marketing decision making process is seen as a set of related subprocesses. Provided an opportunity to use the economic and mathematical modelling at each stage of the decision making process.
The PRIME model: a management solution in academic medicine
African Journals Online (AJOL)
pandemic and tuberculosis. Emphasis has shifted from hospital-based care to primary health care adding another dimension to the management strategy of academic institutions. A management model, the PRIME model, was developed that is simple, flex- ible, allows for individuality, integration and efficiency and should ...
Modelling the exposure induced by a criticality excursion in solution
International Nuclear Information System (INIS)
Kerouanton, David; Delgovea, Laure; Castaniera, Eric; Raimondia, Nicolas
2008-01-01
During a criticality accident, significant exposure is generated by 4 radiation origins: radiation directly induced by fissions (prompt neutrons and gamma), gamma radiations induced by (n, γ) reactions in crossed materials (capture gamma) and gamma radiations emitted by fission products. Due to boiling of the solution, a fraction of fissions products is airborne and is deposited in the ventilation shafts. 5.10 18 fissions are considered in a dissolution tank containing uranyl nitrate by using the deterministic ATTILA radiation transport code. Instantaneous radiations rates are evaluated as a function of the distance and compared with data available in the literature. Dose rates induced behind various shielding materials such as concrete, steel or glass are assessed. In all cases, relative contributions of prompt or capture radiations is detailed. (author)
Modeling of Solute transport in a fractured rock zone at KURT
International Nuclear Information System (INIS)
Park, Chung Kyun; Lee, Jae Kwang; Baik, Min Hoon; Jeong, Jong Tae
2010-01-01
A solute transport model has developed to simulate migration of tracers which has tested in KURT. KAERI built an underground research laboratory so called KURT, which stands for Korea Underground Research Tunnel. Dipole tests has performed with some nonradioactive conservative tracers in a fractured zone which having a single fracture at KURT. The objectives of this study are not only developing a migration model of solutes for in-situ open environments but also validating the model by comparing and estimating experimental results
Development of Three-Layer Simulation Model for Freezing Process of Food Solution Systems
Kaminishi, Koji; Araki, Tetsuya; Shirakashi, Ryo; Ueno, Shigeaki; Sagara, Yasuyuki
A numerical model has been developed for simulating freezing phenomena of food solution systems. The cell model was simplified to apply to food solution systems, incorporating with the existence of 3 parts such as unfrozen, frozen and moving boundary layers. Moreover, the moving rate of freezing front model was also introduced and calculated by using the variable space network method proposed by Murray and Landis (1957). To demonstrate the validity of the model, it was applied to the freezing processes of coffee solutions. Since the model required the phase diagram of the material to be frozen, the initial freezing temperatures of 1-55 % coffee solutions were measured by the DSC method. The effective thermal conductivity for coffee solutions was determined as a function of temperature and solute concentration by using the Maxwell - Eucken model. One-dimensional freezing process of 10 % coffee solution was simulated based on its phase diagram and thermo-physical properties. The results were good agreement with the experimental data and then showed that the model could accurately describe the change in the location of the freezing front and the distributions of temperature as well as ice fraction during a freezing process.
Improved numerical solutions for chaotic-cancer-model
Directory of Open Access Journals (Sweden)
Muhammad Yasir
2017-01-01
Full Text Available In biological sciences, dynamical system of cancer model is well known due to its sensitivity and chaoticity. Present work provides detailed computational study of cancer model by counterbalancing its sensitive dependency on initial conditions and parameter values. Cancer chaotic model is discretized into a system of nonlinear equations that are solved using the well-known Successive-Over-Relaxation (SOR method with a proven convergence. This technique enables to solve large systems and provides more accurate approximation which is illustrated through tables, time history maps and phase portraits with detailed analysis.
A Local Composition Model for Paraffinic Solid Solutions
DEFF Research Database (Denmark)
Coutinho, A.P. João; Knudsen, Kim; Andersen, Simon Ivar
1996-01-01
The description of the solid-phase non-ideality remains the main obstacle in modelling the solid-liquid equilibrium of hydrocarbons. A theoretical model, based on the local composition concept, is developed for the orthorhombic phase of n-alkanes and tested against experimental data for binary sy...... systems. It is shown that it can adequately predict the experimental phase behaviour of paraffinic mixtures. This work extends the applicability of local composition models to the solid phase. Copyright (C) 1996 Elsevier Science Ltd....
Linear regression crash prediction models : issues and proposed solutions.
2010-05-01
The paper develops a linear regression model approach that can be applied to : crash data to predict vehicle crashes. The proposed approach involves novice data aggregation : to satisfy linear regression assumptions; namely error structure normality ...
Probabilistic Compositional Models: solution of an equivalence problem
Czech Academy of Sciences Publication Activity Database
Kratochvíl, Václav
2013-01-01
Roč. 54, č. 5 (2013), s. 590-601 ISSN 0888-613X R&D Projects: GA ČR GA13-20012S Institutional support: RVO:67985556 Keywords : Probabilistic model * Compositional model * Independence * Equivalence Subject RIV: BA - General Mathematics Impact factor: 1.977, year: 2013 http://library.utia.cas.cz/separaty/2013/MTR/kratochvil-0391079.pdf
Empirical agent-based modelling challenges and solutions
Barreteau, Olivier
2014-01-01
This instructional book showcases techniques to parameterise human agents in empirical agent-based models (ABM). In doing so, it provides a timely overview of key ABM methodologies and the most innovative approaches through a variety of empirical applications. It features cutting-edge research from leading academics and practitioners, and will provide a guide for characterising and parameterising human agents in empirical ABM. In order to facilitate learning, this text shares the valuable experiences of other modellers in particular modelling situations. Very little has been published in the area of empirical ABM, and this contributed volume will appeal to graduate-level students and researchers studying simulation modeling in economics, sociology, ecology, and trans-disciplinary studies, such as topics related to sustainability. In a similar vein to the instruction found in a cookbook, this text provides the empirical modeller with a set of 'recipes' ready to be implemented. Agent-based modeling (AB...
Analytic solution for a static black hole in the RSII model
Energy Technology Data Exchange (ETDEWEB)
Dai Dechang [Department of Physics, SUNY at Buffalo, Buffalo, NY 14260-1500 (United States); Stojkovic, Dejan, E-mail: ds77@buffalo.edu [Department of Physics, SUNY at Buffalo, Buffalo, NY 14260-1500 (United States)
2011-10-19
We present here a static solution for a large black hole (whose horizon radius is larger than the AdS radius) located on the brane in RSII model. According to some arguments based on the AdS/CFT conjecture, a solution for the black hole located on the brane in RSII model must encode quantum gravitational effects and therefore cannot be static. We demonstrated that a static solution can be found if the bulk is not empty. The stress energy tensor of the matter distribution in the bulk for the solution we found is physical (i.e. it is non-singular with the energy density and pressure not violating any energy conditions). The scale of the solution is given by a parameter 'a'. For large values of the parameter 'a' we have a limit of an almost empty AdS bulk. It is interesting that the solution cannot be transformed into the Schwarzschild-like form and does not reduce to the Schwarzschild solution on the brane. We also present two other related static solutions. At the end, we discuss why the numerical methods failed so far in finding static solutions in this context, including the solutions we found analytically here.
Regional Ocean Modeling System (ROMS): Main Hawaiian Islands: Data Assimilating
National Oceanic and Atmospheric Administration, Department of Commerce — Regional Ocean Modeling System (ROMS) 3-day, 3-hourly data assimilating hindcast for the region surrounding the main Hawaiian islands at approximately 4-km...
Experimental study and new three-dimensional kinetic modeling of foamy solution-gas drive processes.
Sun, Xiaofei; Zhang, Yanyu; Wang, Shilin; Song, Zhaoyao; Li, Peng; Wang, Changfa
2018-03-12
Foamy solution-gas drive processes in heavy oil reservoirs are very complex. The influence of some microscopic factors on this process is not fully understood due to limitations of traditional depletion tests. This study aims to investigate foamy solution-gas drive by experiments and simulations. First, the effects of the pressure depletion rate on critical gas saturation and foamy solution-gas drive processes were investigated by laboratory experiments. Second, a new three-dimensional foamy oil model that captures many important characteristics of foamy solution-gas drive, such as non-equilibrium behavior, gas evolution kinetics, and the effect of viscous forces on gas mobility, was developed. Last, the effects of some important parameters on foamy solution-gas drive were systematically investigated,and a model application was conducted in a typical foamy oil reservoir. The results indicate that the new model is capble of simulating many of the unusual behaviors observed in foamy solution-gas drive on a laboratory and field scales. High oil recoveries were obtained with a high oil viscosity, high depletion rate, long sandpack, and low solution gas-oil ratio. Foamy solution-gas drive processes are sensitive to the depletion rate, length, and critical gas saturation. The oil viscosity, solution GOR and diffusion coefficient are not sensitive factors.
A residue level protein-protein interaction model in electrolyte solutions
Song, Xueyu
2014-03-01
The osmotic second virial coefficients B2 are directly related to the solubility of protein molecules in electrolyte solutions and can be useful to narrow down the search parameter space of protein crystallization conditions. Using a residue level model of protein-protein interaction in electrolyte solutions B2 of bovine pancreatic trypsin inhibitor and lysozyme in various solution conditions such as salt concentration, pH and temperature are calculated using an extended Fast Multipole Methods in combination with the boundary element formulation. Overall, the calculated B2 are well correlated with the experimental observations for various solution conditions. In combination with our previous work on the binding affinity calculations of protein complexes it is demonstrated that our residue level model can be used as a reliable model to describe protein-protein interaction in solutions.
Gómez-Aguilar, J. F.
2018-03-01
In this paper, we analyze an alcoholism model which involves the impact of Twitter via Liouville-Caputo and Atangana-Baleanu-Caputo fractional derivatives with constant- and variable-order. Two fractional mathematical models are considered, with and without delay. Special solutions using an iterative scheme via Laplace and Sumudu transform were obtained. We studied the uniqueness and existence of the solutions employing the fixed point postulate. The generalized model with variable-order was solved numerically via the Adams method and the Adams-Bashforth-Moulton scheme. Stability and convergence of the numerical solutions were presented in details. Numerical examples of the approximate solutions are provided to show that the numerical methods are computationally efficient. Therefore, by including both the fractional derivatives and finite time delays in the alcoholism model studied, we believe that we have established a more complete and more realistic indicator of alcoholism model and affect the spread of the drinking.
Leij, Feike J; Bradford, Scott A
2009-11-20
The transport of solutes and colloids in porous media is influenced by a variety of physical and chemical nonequilibrium processes. A combined physical-chemical nonequilibrium (PCNE) model was therefore used to describe general mass transport. The model partitions the pore space into "mobile" and "immobile" flow regions with first-order mass transfer between these two regions (i.e, "physical" nonequilibrium or PNE). Partitioning between the aqueous and solid phases can either proceed as an equilibrium or a first-order process (i.e, "chemical" nonequilibrium or CNE) for both the mobile and immobile regions. An analytical solution for the PCNE model is obtained using iterated Laplace transforms. This solution complements earlier semi-analytical and numerical approaches to model solute transport with the PCNE model. The impact of selected model parameters on solute breakthrough curves is illustrated. As is well known, nonequilibrium results in earlier solute breakthrough with increased tailing. The PCNE model allows greater flexibility to describe this trend; for example, a closer resemblance between solute input and effluent pulse. Expressions for moments and transfer functions are presented to facilitate the analytical use of the PCNE model. Contours of mean breakthrough time, variance, and spread of the colloid breakthrough curves as a function of PNE and CNE parameters demonstrate the utility of a model that accounts for both physical and chemical nonequilibrium processes. The model is applied to describe representative colloid breakthrough curves in Ottawa sands reported by Bradford et al. (2002). An equilibrium model provided a good description of breakthrough curves for the bromide tracer but could not adequately describe the colloid data. A considerably better description was provide by the simple CNE model but the best description, especially for the larger 3.2-microm colloids, was provided by the PCNE model.
Theory, Solution Methods, and Implementation of the HERMES Model
Energy Technology Data Exchange (ETDEWEB)
Reaugh, John E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); White, Bradley W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Curtis, John P. [Atomic Weapons Establishment (AWE), Reading, Berkshire (United Kingdom); Univ. College London (UCL), Gower Street, London (United Kingdom); Springer, H. Keo [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2017-07-13
The HERMES (high explosive response to mechanical stimulus) model was developed over the past decade to enable computer simulation of the mechanical and subsequent energetic response of explosives and propellants to mechanical insults such as impacts, perforations, drops, and falls. The model is embedded in computer simulation programs that solve the non-linear, large deformation equations of compressible solid and fluid flow in space and time. It is implemented as a user-defined model, which returns the updated stress tensor and composition that result from the simulation supplied strain tensor change. Although it is multi-phase, in that gas and solid species are present, it is single-velocity, in that the gas does not flow through the porous solid. More than 70 time-dependent variables are made available for additional analyses and plotting. The model encompasses a broad range of possible responses: mechanical damage with no energetic response, and a continuous spectrum of degrees of violence including delayed and prompt detonation. This paper describes the basic workings of the model.
New integrable models and analytical solutions in f (R ) cosmology with an ideal gas
Papagiannopoulos, G.; Basilakos, Spyros; Barrow, John D.; Paliathanasis, Andronikos
2018-01-01
In the context of f (R ) gravity with a spatially flat FLRW metric containing an ideal fluid, we use the method of invariant transformations to specify families of models which are integrable. We find three families of f (R ) theories for which new analytical solutions are given and closed-form solutions are provided.
Path integrals and the solution of the Schwinger model in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Barcelos-Neto, J.; Das, A.
1986-04-15
We use the path-integral formalism to derive the solution of the Schwinger model in curved space-time. We show that the nature of flat--space-time solutions persists even in the presence of a background gravitational field.
Relationships between Visual Static Models and Students' Written Solutions to Fraction Tasks
Anderson-Pence, Katie L.; Moyer-Packenham, Patricia S.; Westenskow, Arla; Shumway, Jessica; Jordan, Kerry
2014-01-01
The purpose of this study was to deconstruct the relationship between visual static models and students' written solutions to fraction problems using a large sample of students' solutions. Participants in the study included 162 third-grade and 209 fourth-grade students from 17 different classrooms. Students' written responses to open-ended tasks…
Decay estimate of global solutions to the generalized double dispersion model in Morrey spaces
Wang, Yu-Zhu; Gu, Liuxin; Wang, Yinxia
2017-08-01
In this paper, we investigate the initial value problem for the generalized double dispersion model in Morrey spaces. Based on the decay properties of the solution operator in Morrey spaces, global existence and decay estimates of solutions are proved by Banach fixed point theorem.
A nonlinear model for surface segregation and solute trapping during planar film growth
International Nuclear Information System (INIS)
Han, Xiaoying; Spencer, Brian J.
2007-01-01
Surface segregation and solute trapping during planar film growth is one of the important issues in molecular beam epitaxy, yet the study on surface composition has been largely restricted to experimental work. This paper introduces some mathematical models of surface composition during planar film growth. Analytical solutions are obtained for the surface composition during growth
Concepts and dimensionality in modeling unsaturated water flow and solute transport
Dam, van J.C.; Rooij, de G.H.; Heinen, M.; Stagnitti, F.
2004-01-01
Many environmental studies require accurate simulation of waterand solute fluxes in the unsaturated zone. This paper evaluatesone- and multi-dimensional approaches for soil water flow as wellas different spreading mechanisms to model solute behavior atdifferent scales. For quantification of soil
Model-based fuzzy control solutions for a laboratory Antilock Braking System
DEFF Research Database (Denmark)
Precup, Radu-Emil; Spataru, Sergiu; Rǎdac, Mircea-Bogdan
2010-01-01
This paper gives two original model-based fuzzy control solutions dedicated to the longitudinal slip control of Antilock Braking System laboratory equipment. The parallel distributed compensation leads to linear matrix inequalities which guarantee the global stability of the fuzzy control systems....... Real-time experimental results validate the new fuzzy control solutions....
Queueing-theoretic solution methods for models of parallel and distributed systems
O.J. Boxma (Onno); G.M. Koole (Ger); Z. Liu
1994-01-01
textabstractThis paper aims to give an overview of solution methods for the performance analysis of parallel and distributed systems. After a brief review of some important general solution methods, we discuss key models of parallel and distributed systems, and optimization issues, from the
Effect of PLISSIT Model on Solution of Sexual Problems
Directory of Open Access Journals (Sweden)
Esra Uslu
2016-03-01
Full Text Available This systematic review study aims to determine the effect of PLISSIT model (permission, limited information, special suggestions, intensive therapy in the care of individuals having sexual problems. Two of the studies included in the systematic review have been carried out in Iran and one of them in Turkey. These studies were limited to the patients with stoma and women having sexual problems. Results presented that care via PLISSIT model improves the sexual functions and reduces sexual stress, increases the sexual desire, sexual arousal, lubrication, orgasm, sexual satisfaction and frequency of sexual activity. [Psikiyatride Guncel Yaklasimlar - Current Approaches in Psychiatry 2016; 8(1: 52-63
Challenges and potential solutions for European coastal ocean modelling
She, Jun; Stanev, Emil
2017-04-01
Coastal operational oceanography is a science and technological platform to integrate and transform the outcomes in marine monitoring, new knowledge generation and innovative technologies into operational information products and services in the coastal ocean. It has been identified as one of the four research priorities by EuroGOOS (She et al. 2016). Coastal modelling plays a central role in such an integration and transformation. A next generation coastal ocean forecasting system should have following features: i) being able to fully exploit benefits from future observations, ii) generate meaningful products in finer scales e.g., sub-mesoscale and in estuary-coast-sea continuum, iii) efficient parallel computing and model grid structure, iv) provide high quality forecasts as forcing to NWP and coastal climate models, v) resolving correctly inter-basin and inter-sub-basin water exchange, vi) resolving synoptic variability and predictability in marine ecosystems, e.g., for algae bloom, vi) being able to address critical and relevant issues in coastal applications, e.g., marine spatial planning, maritime safety, marine pollution protection, disaster prevention, offshore wind energy, climate change adaptation and mitigation, ICZM (integrated coastal zone management), the WFD (Water Framework Directive), and the MSFD (Marine Strategy Framework Directive), especially on habitat, eutrophication, and hydrographic condition descriptors. This presentation will address above challenges, identify limits of current models and propose correspondent research needed. The proposed roadmap will address an integrated monitoring-modelling approach and developing Unified European Coastal Ocean Models. In the coming years, a few new developments in European Sea observations can expected, e.g., more near real time delivering on profile observations made by research vessels, more shallow water Argo floats and bio-Argo floats deployed, much more high resolution sea level data from SWOT
African wildlife and people : finding solutions where equilibrium models fail
Poshiwa, X.
2013-01-01
Grazing systems, covering about half of the terrestrial surface, tend to be either equilibrial or non-equilibrial in nature, largely depending on the environmental stochasticity.The equilibrium model perspective stresses the importance of biotic feedbacks between herbivores and
Water and Aqueous Solutions: Simple Non-Speculative Model Approach
Czech Academy of Sciences Publication Activity Database
Nezbeda, Ivo; Jirsák, Jan
2011-01-01
Roč. 13, č. 44 (2011), s. 19689-19703 ISSN 1463-9076 R&D Projects: GA AV ČR IAA400720802; GA AV ČR IAA200760905 Institutional research plan: CEZ:AV0Z40720504 Keywords : molecular modeling of water * separation * perturbation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.573, year: 2011
Stochastic models of solute transport in highly heterogeneous geologic media
Energy Technology Data Exchange (ETDEWEB)
Semenov, V.N.; Korotkin, I.A.; Pruess, K.; Goloviznin, V.M.; Sorokovikova, O.S.
2009-09-15
A stochastic model of anomalous diffusion was developed in which transport occurs by random motion of Brownian particles, described by distribution functions of random displacements with heavy (power-law) tails. One variant of an effective algorithm for random function generation with a power-law asymptotic and arbitrary factor of asymmetry is proposed that is based on the Gnedenko-Levy limit theorem and makes it possible to reproduce all known Levy {alpha}-stable fractal processes. A two-dimensional stochastic random walk algorithm has been developed that approximates anomalous diffusion with streamline-dependent and space-dependent parameters. The motivation for introducing such a type of dispersion model is the observed fact that tracers in natural aquifers spread at different super-Fickian rates in different directions. For this and other important cases, stochastic random walk models are the only known way to solve the so-called multiscaling fractional order diffusion equation with space-dependent parameters. Some comparisons of model results and field experiments are presented.
Infrastructure Suitability Assessment Modeling for Cloud Computing Solutions
2011-09-01
Figure 5. Citrix HDX components/architecture. After [40]. ...........................................17 Figure 6. NComputing UXP deployment...a proprietary, purpose built protocol utilized for VDI ( Citrix ®) IaaS Infrastructure as a Service (cloud service model) IANA Internet Assigned...The open source project Xen, strongly supported by Citrix and other IT enterpris- es, maintains the Xen hypervisor, targeted at the enterprise level
Solutions of two-mode Jaynes–Cummings models
Indian Academy of Sciences (India)
Cummings models. SUDHA SINGH1,∗ and ASHALATA SINHA2. 1University Department of Physics, Ranchi University, Ranchi 834 008, India ... been analysed when one of the field modes is prepared initially in a coherent state while the other ...
Non-perturbative solution of metastable scalar models
Czech Academy of Sciences Publication Activity Database
Šauli, Vladimír
2003-01-01
Roč. 36, - (2003), s. 8703-8722 ISSN 0022-3727 R&D Projects: GA ČR GA202/03/0210 Institutional research plan: CEZ:AV0Z1048901 Keywords : scalar models Subject RIV: BE - Theoretical Physics http://arxiv.org/abs/hep-ph/0211221
Molecular Thermodynamic Modeling of Fluctuation Solution Theory Properties
DEFF Research Database (Denmark)
O’Connell, John P.; Abildskov, Jens
2013-01-01
for densities and gas solubilities, including ionic liquids and complex mixtures such as coal liquids. The approach is especially useful in systems with strong nonidealities. This chapter describes successful application of such modeling to a wide variety of systems treated over several decades and suggests how...
MODELS AND SOLUTIONS FOR THE IMPLEMENTATION OF DISTRIBUTED SYSTEMS
Directory of Open Access Journals (Sweden)
Tarca Naiana
2011-07-01
Full Text Available Software applications may have different degrees of complexity depending on the problems they try to solve and can integrate very complex elements that bring together functionality that sometimes are competing or conflicting. We can take for example a mobile communications system. Functionalities of such a system are difficult to understand, and they add to the non-functional requirements such as the use in practice, performance, cost, durability and security. The transition from local computer networks to cover large networks that allow millions of machines around the world at speeds exceeding one gigabit per second allowed universal access to data and design of applications that require simultaneous use of computing power of several interconnected systems. The result of these technologies has enabled the evolution from centralized to distributed systems that connect a large number of computers. To enable the exploitation of the advantages of distributed systems one had developed software and communications tools that have enabled the implementation of distributed processing of complex solutions. The objective of this document is to present all the hardware, software and communication tools, closely related to the possibility of their application in integrated social and economic level as a result of globalization and the evolution of e-society. These objectives and national priorities are based on current needs and realities of Romanian society, while being consistent with the requirements of Romania's European orientation towards the knowledge society, strengthening the information society, the target goal representing the accomplishment of e-Romania, with its strategic e-government component. Achieving this objective repositions Romania and gives an advantage for sustainable growth, positive international image, rapid convergence in Europe, inclusion and strengthening areas of high competence, in line with Europe 2020, launched by the
International Nuclear Information System (INIS)
Sadeghi, Rahmat
2005-01-01
The polymer Wilson model and the polymer NRTL model have been extended for the representation of the excess enthalpy of multicomponent polymer solutions. Applicability of obtained equations in the correlation of the excess enthalpies of polymer solutions has been examined. It is found that the both models are suitable models in representing the published excess enthalpy data for the tested polymer solutions
MODEL 9975 SHIPPING PACKAGE FABRICATION PROBLEMS AND SOLUTIONS
Energy Technology Data Exchange (ETDEWEB)
May, C; Allen Smith, A
2008-05-07
The Model 9975 Shipping Package is the latest in a series (9965, 9968, etc.) of radioactive material shipping packages that have been the mainstay for shipping radioactive materials for several years. The double containment vessels are relatively simple designs using pipe and pipe cap in conjunction with the Chalfont closure to provide a leak-tight vessel. The fabrication appears simple in nature, but the history of fabrication tells us there are pitfalls in the different fabrication methods and sequences. This paper will review the problems that have arisen during fabrication and precautions that should be taken to meet specifications and tolerances. The problems and precautions can also be applied to the Models 9977 and 9978 Shipping Packages.
International Nuclear Information System (INIS)
Qian Tianwei; Chen Fanrong
2003-01-01
The influence of solution chemical action in groundwater on solute migration has attracted increasing public attention, especially adsorption action occurring on surface of solid phase and liquid phase, which has play a great role in solute migration. There are various interpretations on adsorption mechanism, in which surface complexion is one of successful hypothesis. This paper first establishes a geochemical model based on surface complexion and then coupled it with traditional advection-dispersion model to constitute a solute migration model, which can deal with surface complexion action. The simulated results fit very well with those obtained by the precursors, as compared with a published famous example, which indicates that the model set up by this paper is successful. (authors)
Positive Almost Periodic Solutions for a Time-Varying Fishing Model with Delay
Directory of Open Access Journals (Sweden)
Xia Li
2011-01-01
Full Text Available This paper is concerned with a time-varying fishing model with delay. By means of the continuation theorem of coincidence degree theory, we prove that it has at least one positive almost periodic solution.
Modelling size and structure of nanoparticles formed from drying of submicron solution aerosols
Energy Technology Data Exchange (ETDEWEB)
Bandyopadhyay, Arpan A.; Pawar, Amol A.; Venkataraman, Chandra; Mehra, Anurag, E-mail: mehra@iitb.ac.in [Indian Institute of Technology Bombay, Department of Chemical Engineering (India)
2015-01-15
Drying of submicron solution aerosols, under controlled conditions, has been explored to prepare nanoparticles for drug delivery applications. A computational model of solution drop evaporation is developed to study the evolution of solute gradients inside the drop and predict the size and shell thickness of precipitating nanoparticles. The model considers evaporation as a two-stage process involving droplet shrinkage and shell growth. It was corroborated that droplet evaporation rate controls the solute distribution within a droplet and the resulting particle structure (solid or shell type). At higher gas temperatures, rapid build-up of solute near drop surface from high evaporation rates results in early attainment of critical supersaturation solubility and a steeper solute gradient, which favours formation of larger, shell-type particles. At lower gas temperatures, formation of smaller, solid nanoparticles is indicated. The computed size and shell thickness are in good agreement with experimentally prepared lipid nanoparticles. This study indicates that solid or shell structure of precipitated nanoparticles is strongly affected by evaporation rate, while initial solute concentration in the precursor solution and atomized droplet size affect shell thickness. For the gas temperatures considered, evaporative cooling leads to droplet temperature below the melting point of the lipid solute. Thus, we conclude that control over nanoparticle size and structure, of thermolabile precursor materials suitable for drug delivery, can be achieved by controlling evaporation rates, through selection of aerosol processing conditions.
Directory of Open Access Journals (Sweden)
Magdy A. El-Tawil
2012-07-01
Full Text Available The homotopy analysis method (HAM is used to find approximate analytical solutions of continuous population models for single and interacting species. The homotopy analysis method contains the auxiliary parameter $hbar,$ which provides us with a simple way to adjust and control the convergence region of series solution. the solutions are compared with the numerical results obtained using NDSolve, an ordinary differential equation solver found in the Mathematica package and a good agreement is found. Also the solutions are compared with the available analytic results obtained by other methods and more accurate and convergent series solution found. The convergence region is also computed which shows the validity of the HAM solution. This method is reliable and manageable.
Fast Wideband Solutions Obtained Using Model Based Parameter Estimation with Method of Moments
Directory of Open Access Journals (Sweden)
F. Kaburcuk
2017-10-01
Full Text Available Integration of the Model Based Parameter Estimation (MBPE technique into Method of Moments (MOM provides fast solutions over a wide frequency band to solve radiation and scattering problems. The MBPE technique uses the Padé rational function to approximate solutions over a wide frequency band from a solution at a fixed frequency. In this paper, the MBPE technique with MOM is applied to a thin-wire antenna. The solutions obtained by repeated simulations of MOM agree very well with the solutions obtained by MBPE technique in a single simulation. Therefore, MBPE technique according to MOM provides a remarkable saving in the computation time. Computed results show that solutions at a wider frequency band of interest are achieved in a single simulation.
Krishnan, M.
2017-01-01
We present a model for calculating the net and effective electrical charge of globular macromolecules and linear polyelectrolytes such as proteins and DNA, given the concentration of monovalent salt and pH in solution. The calculation is based on a numerical solution of the non-linear Poisson-Boltzmann equation using a finite element discretized continuum approach. The model simultaneously addresses the phenomena of charge regulation and renormalization, both of which underpin the electrostat...
Numerical Modeling for the Solute Uptake from Groundwater by Plants-Plant Uptake Package
El-Sayed, Amr A.
2006-01-01
A numerical model is presented to describe solute transport in groundwater coupled to sorption by plant roots, translocation into plant stems, and finally evapotranspiration. The conceptual model takes into account both Root Concentration Factor, RCF, and Transpiration Stream Concentration Factor, TSCF for chemicals which are a function of Kow. A similar technique used to simulate the solute transport in groundwater to simulate sorption and plant uptake is used. The mathematical equation is s...
Algebraic solution of the Stein-Stein model for stochastic volatility
Sophocleous, C.; O'Hara, J. G.; Leach, P. G. L.
2011-04-01
We provide an algebraic approach to the solution of the Stein-Stein model for stochastic volatility which arises in the determination of the Radon-Nikodym density of the minimal entropy of the martingale measure. We extend our investigation to the case in which the parameters of the model are time-dependent. Our algorithmic approach obviates the need for Ansätze for the structure of the solution.
[Antifungal Activity of Luliconazole Nail Solution on in vitro and in vivo Onychomycosis Model].
Shimamura, Tsuyoshi; Hasegawa, Nami; Kubota, Nobuo
2016-01-01
We evaluated luliconazole nail solution, originally generated formulation, for the topical treatment of onychomycosis by two infection models. First, a suspension of Trichophyton mentagrophytes was dropped onto the ventral layer of human nail plate and these nails were set in Franz diffusion cells. After 9-day culture, luliconazole nail solutions (1, 3, and 5%) were applied to the dorsal surface of the nails once a day for 7 days. After application, fungal viability was assessed by measuring the ATP contents of the samples. The dose-dependent efficacy was confirmed, with 3% and 5% luliconazole nail solutions producing significantly lower ATP levels at 7-day treatment. When 3% and 5% luliconazole nail solutions were evaluated in a rabbit model of onychomycosis, both concentrations completely inhibited the recovery of fungi on culture after 4-week treatment. We therefore think these results indicate that 5% luliconazole nail solution is sufficiently potent for treatment of onychomycosis.
A Series Solution of the Cauchy Problem for Turing Reaction-diffusion Model
Directory of Open Access Journals (Sweden)
L. Päivärinta
2011-12-01
Full Text Available In this paper, the series pattern solution of the Cauchy problem for Turing reaction-diffusion model is obtained by using the homotopy analysis method (HAM. Turing reaction-diffusion model is nonlinear reaction-diffusion system which usually has power-law nonlinearities or may be rewritten in the form of power-law nonlinearities. Using the HAM, it is possible to find the exact solution or an approximate solution of the problem. This technique provides a series of functions which converges rapidly to the exact solution of the problem. The efficiency of the approach will be shown by applying the procedure on two problems. Furthermore, the so-called homotopy-Pade technique (HPT is applied to enlarge the convergence region and rate of solution series given by the HAM.
The affine constrained GNSS attitude model and its multivariate integer least-squares solution
Teunissen, P.J.G.
2012-01-01
A new global navigation satellite system (GNSS) carrier-phase attitude model and its solution are introduced in this contribution. This affine-constrained GNSS attitude model has the advantage that it avoids the computational complexity of the orthonormality-constrained GNSS attitude model, while it
Tsunami Simulators in Physical Modelling - Concept to Practical Solutions
Chandler, Ian; Allsop, William; Robinson, David; Rossetto, Tiziana; McGovern, David; Todd, David
2017-04-01
Whilst many researchers have conducted simple 'tsunami impact' studies, few engineering tools are available to assess the onshore impacts of tsunami, with no agreed methods available to predict loadings on coastal defences, buildings or related infrastructure. Most previous impact studies have relied upon unrealistic waveforms (solitary or dam-break waves and bores) rather than full-duration tsunami waves, or have used simplified models of nearshore and over-land flows. Over the last 10+ years, pneumatic Tsunami Simulators for the hydraulic laboratory have been developed into an exciting and versatile technology, allowing the forces of real-world tsunami to be reproduced and measured in a laboratory environment for the first time. These devices have been used to model generic elevated and N-wave tsunamis up to and over simple shorelines, and at example coastal defences and infrastructure. They have also reproduced full-duration tsunamis including Mercator 2004 and Tohoku 2011, both at 1:50 scale. Engineering scale models of these tsunamis have measured wave run-up on simple slopes, forces on idealised sea defences, pressures / forces on buildings, and scour at idealised buildings. This presentation will describe how these Tsunami Simulators work, demonstrate how they have generated tsunami waves longer than the facilities within which they operate, and will present research results from three generations of Tsunami Simulators. Highlights of direct importance to natural hazard modellers and coastal engineers include measurements of wave run-up levels, forces on single and multiple buildings and comparison with previous theoretical predictions. Multiple buildings have two malign effects. The density of buildings to flow area (blockage ratio) increases water depths and flow velocities in the 'streets'. But the increased building densities themselves also increase the cost of flow per unit area (both personal and monetary). The most recent study with the Tsunami
Models for enzyme superactivity in aqueous solutions of surfactants.
Viparelli, P; Alfani, F; Cantarella, M
1999-01-01
Theoretical models are developed here for enzymic activity in the presence of direct micellar aggregates. An approach similar to that of Bru et al. [Bru, Sánchez-Ferrer and Garcia-Carmona (1989) Biochem. J. 259, 355-361] for reverse micelles has been adopted. The system is considered to consist of three pseudo-phases: free water, bound water and surfactant tails. The substrate concentration in each pseudo-phase is related to the total substrate concentration in the reaction medium. In the abs...
Thermodynamic study on some alkanediol solutions: Measurement and modeling
International Nuclear Information System (INIS)
Moosavi, Mehrdad; Motahari, Ahmad; Omrani, Abdollah; Rostami, Abbas Ali
2013-01-01
Highlights: • Measuring densities and viscosities for binary mixtures of some alkanediols. • Finding excess molar volume, partial molar volume and thermal expansion coefficient. • Fitting excess molar volume values with PFP and Redlich–Kister polynomial equations. • Deducing excess Gibbs free energy of activation and other thermodynamic parameters. • Predicting viscosity values with different single parameter semi empirical equations. - Abstract: The densities ρ and viscosities η of 1,2-ethanediol with 1,2-propanediol or 1,3-propanediol, and 1,2-propanediol with 1,3-propanediol binary liquid mixtures over the entire concentration range at temperatures (298.15 to 308.15) K with 5 K interval were measured. The experimental data were used to calculate the excess molar volume V m E , partial molar volume V ¯ m,i , partial molar volume at infinite dilution V ¯ i ∞ , apparent molar volume V φi , coefficient of thermal expansion α p , excess coefficient of thermal expansion α p E , excess viscosity η E , excess Gibbs energy of activation ΔG *E , and other thermodynamic parameters. A Redlich–Kister equation and Prigogine–Flory–Patterson (PFP) model was applied to correlate the excess molar volume results. Moreover, the viscosity data were correlated with the Grunberg–Nissan, Tamura–Kurata, Hind–Ubbelohde and Katti–Chaudhary equations. Good agreement was found between experimental data and modeling results
Exact Riemann solutions of the Ripa model for flat and non-flat bottom topographies
Rehman, Asad; Ali, Ishtiaq; Qamar, Shamsul
2018-03-01
This article is concerned with the derivation of exact Riemann solutions for Ripa model considering flat and non-flat bottom topographies. The Ripa model is a system of shallow water equations accounting for horizontal temperature gradients. In the case of non-flat bottom topography, the mass, momentum and energy conservation principles are utilized to relate the left and right states across the step-type bottom topography. The resulting system of algebraic equations is solved iteratively. Different numerical case studies of physical interest are considered. The solutions obtained from developed exact Riemann solvers are compared with the approximate solutions of central upwind scheme.
Existence and regularity of solutions to the Leray-alpha model with Navier slip boundary conditions
Directory of Open Access Journals (Sweden)
Hani Ali
2016-08-01
Full Text Available We establish the existence and regularity of a unique weak solution to turbulent flows in a bounded domain $\\Omega\\subset\\mathbb R^3$ governed by the Leray-$\\alpha$ model with Navier slip boundary condition for the velocity. Furthermore, we show that when the filter coefficient $\\alpha$ tends to zero, these weak solutions converge to a suitable weak solution to the incompressible Navier Stokes equations subject to the Navier boundary conditions. Finally, we discuss the relation between the Leray-$\\alpha$ model and the Navier-Stokes equations with homogeneous Dirichlet boundary condition.
Modeling of Dilute Polymer Solutions in Confined Space
DEFF Research Database (Denmark)
Wang, Yanwei
2009-01-01
This thesis deals with modeling of a polymer chain subject to spatial confinement. The properties of confined macromolecules are both of fundamental interest in polymer physics and of practical importance in a variety of applications including chromatographic separation of polymers, and the use...... method, hereafter referred to as the method of confinement analysis from bulk structures (CABS), has the computational advantage of supplying properties as a function of the confinement size solely based on sampling the configuration space of a polymer chain in bulk alone. CABS is highly adaptable...... to studies of the effects of excluded volume, finite persistent length and nonlinear chain architectures in slit, channel and box confining geometries. Superior in computational efficiency to previous simulation studies, CABS has also the unique theoretical advantage of providing new physical insights only...
Projection methods for the numerical solution of Markov chain models
Saad, Youcef
1989-01-01
Projection methods for computing stationary probability distributions for Markov chain models are presented. A general projection method is a method which seeks an approximation from a subspace of small dimension to the original problem. Thus, the original matrix problem of size N is approximated by one of dimension m, typically much smaller than N. A particularly successful class of methods based on this principle is that of Krylov subspace methods which utilize subspaces of the form span(v,av,...,A(exp m-1)v). These methods are effective in solving linear systems and eigenvalue problems (Lanczos, Arnoldi,...) as well as nonlinear equations. They can be combined with more traditional iterative methods such as successive overrelaxation, symmetric successive overrelaxation, or with incomplete factorization methods to enhance convergence.
Diabetes Care in Malaysia: Problems, New Models, and Solutions.
Hussein, Zanariah; Taher, Sri Wahyu; Gilcharan Singh, Harvinder Kaur; Chee Siew Swee, Winnie
2015-01-01
Diabetes is a major public health concern in Malaysia, and the prevalence of type 2 diabetes (T2D) has escalated to 20.8% in adults above the age of 30, affecting 2.8 million individuals. The burden of managing diabetes falls on primary and tertiary health care providers operating in various settings. This review focuses on the current status of diabetes in Malaysia, including epidemiology, complications, lifestyle, and pharmacologic treatments, as well as the use of technologies in its management and the adoption of the World Health Organization chronic care model in primary care clinics. A narrative review based on local available health care data, publications, and observations from clinic experience. The prevalence of diabetes varies among the major ethnic groups in Malaysia, with Asian Indians having the highest prevalence of T2D, followed by Malays and Chinese. The increase prevalence of overweight and obesity has accompanied the rise in T2D. Multidisciplinary care is available in tertiary and primary care settings with integration of pharmacotherapy, diet, and lifestyle changes. Poor dietary adherence, high consumption of carbohydrates, and sedentary lifestyle are prevalent in patients with T2D. The latest medication options are available with increasing use of intensive insulin regimens, insulin pumps, and continuous glucose monitoring systems for managing glycemic control. A stepwise approach is proposed to expand the chronic care model into an Innovative Care for Chronic Conditions framework to facilitate implementation and realize better outcomes in primary care settings. A comprehensive strategy and approach has been established by the Malaysian government to improve prevention, treatment, and control of diabetes as an urgent response to this growing chronic disease. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
Model based analysis of the drying of a single solution droplet in an ultrasonic levitator
DEFF Research Database (Denmark)
Sloth, Jakob; Kiil, Søren; Jensen, Anker
2006-01-01
A model for the drying of a single solution droplet into a solid, dense particle is presented and simulations are made to achieve a more fundamental understanding of the single droplet drying process relevant in connection with spray drying processes. Model predictions of drying behaviour...... are compared to data for the drying of aqueous solutions of maltodextrin DE 15 and trehalose from experiments conducted using an ultrasonic levitator. Model predictions are in good agreement with the experimental data, indicating that the model describes the most important physical phenomena of the process....
International Nuclear Information System (INIS)
Park, Chung Kyun; Lee, Jaek Wang; Baik, Min Hoon; Jeong, Jong Tae
2012-01-01
Migration tests were performed with conservative tracers in a fractured zone that had a single fracture of about 2.5 m distance at the KURT. To interpret the migration of the tracers in the fractured rock, a solute transport model was developed. A two dimensional variable aperture channel model was adopted to describe the fractured path and hydrology, and a particle tracking method was used for solute transport. The simulation tried not only to develop a migration model of solutes for open flow environments but also to produce ideas for a better understanding of solute behaviours in indefinable fracture zones by comparing them to experimental results. The results of our simulations and experiments are described as elution and breakthrough curves, and are quantified by momentum analysis. The main retardation mechanism of nonsorbing tracers, including matrixdiffusion, was investigated.
Study of heavy metals removal from model solutions by wooden materials
Demcak, S.; Balintova, M.; Demcakova, M.
2017-10-01
The paper deals with the heavy metals removal by wooden material. The adsorption experiments were carried out using of wood sawdust and bark from poplar tree for the removal of copper and zinc cations from model solutions with initial concentration of 10 mg.L-1. The FTIR was used for functional groups determination not for analysis of hemicelluloses, cellulose and lignin in structure of wood sawdust and bark were studied by infrared spectrometry. Poplar sawdust efficiency for Cu(II) and Zn(II) removal from aquatic model solutions reached approximately 80.0%. Changes of pH values were also observed in model solutions that were probably caused by ion exchange between the ions of sorbents and the ions in solutions.
Energy Technology Data Exchange (ETDEWEB)
Janvier, C.
1998-04-02
The oxides-gaseous dioxygen equilibria and the textural thermal stability of six zirconium-cerin solutions Ce{sub 1-x}Zr{sub x}O{sub 2} (0
Optimisation models and solution methods for load management
International Nuclear Information System (INIS)
Gustafsson, Stig-Inge; Roennqvist, Mikael; Claesson, Marcus
2001-02-01
The electricity market in Sweden has changed during recent years. Electricity for industrial use can nowadays be purchased from a number of competing electricity suppliers. Hence, the price for each kilowatt-hour is significantly lower than just two years ago and the interest for electricity conservation measures has declined. Part of the electricity tariff is, however, almost the same as before, i.e. the demand cost expressed in Swedish Kronor, SEK, for each kilowatt. This has put focus on load management measures in order to decrease this specific cost. Saving one kWh might lead to monetary savings between 0.22 to 914 SEK and this paper shows how to save only those kWh which really save money. A load management system has been installed in a small carpentry factory and the device can turn off equipment due to a certain priority and for a number of minutes each hour. The question is now, what level on the electricity load is optimal in a strict mathematical sense, i.e. how many kW should be set in the load management computer in order to get the best profitability? In this paper we develop a mathematical model which can be used both as a tool to find a best profitable subscription level and as a tool to control the turn of choices. Numerical results from a case study are presented
Burov, S V; Shchekin, A K
2010-12-28
General thermodynamic relations for the work of polydisperse micelle formation in the model of ideal solution of molecular aggregates in nonionic surfactant solution and the model of "dressed micelles" in ionic solution have been considered. In particular, the dependence of the aggregation work on the total concentration of nonionic surfactant has been analyzed. The analogous dependence for the work of formation of ionic aggregates has been examined with regard to existence of two variables of a state of an ionic aggregate, the aggregation numbers of surface active ions and counterions. To verify the thermodynamic models, the molecular dynamics simulations of micellization in nonionic and ionic surfactant solutions at two total surfactant concentrations have been performed. It was shown that for nonionic surfactants, even at relatively high total surfactant concentrations, the shape and behavior of the work of polydisperse micelle formation found within the model of the ideal solution at different total surfactant concentrations agrees fairly well with the numerical experiment. For ionic surfactant solutions, the numerical results indicate a strong screening of ionic aggregates by the bound counterions. This fact as well as independence of the coefficient in the law of mass action for ionic aggregates on total surfactant concentration and predictable behavior of the "waterfall" lines of surfaces of the aggregation work upholds the model of "dressed" ionic aggregates.
Allen, Phillip A.; Wells, Douglas N.
2013-01-01
No closed form solutions exist for the elastic-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear finite element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear finite element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (elastic modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full elastic-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without elastic-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.
Multigrid solution of incompressible turbulent flows by using two-equation turbulence models
Energy Technology Data Exchange (ETDEWEB)
Zheng, X.; Liu, C. [Front Range Scientific Computations, Inc., Denver, CO (United States); Sung, C.H. [David Taylor Model Basin, Bethesda, MD (United States)
1996-12-31
Most of practical flows are turbulent. From the interest of engineering applications, simulation of realistic flows is usually done through solution of Reynolds-averaged Navier-Stokes equations and turbulence model equations. It has been widely accepted that turbulence modeling plays a very important role in numerical simulation of practical flow problem, particularly when the accuracy is of great concern. Among the most used turbulence models today, two-equation models appear to be favored for the reason that they are more general than algebraic models and affordable with current available computer resources. However, investigators using two-equation models seem to have been more concerned with the solution of N-S equations. Less attention is paid to the solution method for the turbulence model equations. In most cases, the turbulence model equations are loosely coupled with N-S equations, multigrid acceleration is only applied to the solution of N-S equations due to perhaps the fact the turbulence model equations are source-term dominant and very stiff in sublayer region.
On the Dagan Model of Solute Transport in Groundwater: Foundational Aspects
Sposito, Garrison; Barry, D. A.
1987-10-01
The convection-dispersion equation (CDE) developed by Dagan [1984] to predict the ensemble-average concentration of a conservative solute in groundwater has been used successfully to interpret recent tracer experiments in a sand aquifer at the Borden site in Canada. This successful application encouraged further investigation of the Dagan model in respect to its physical basis and predictive characteristics. It is shown in the present paper, which deals with the first topic, that the Dagan model CDE can be derived through an extension of the cumulant expansion technique applied previously by Chu and Sposito [1980] to develop a mean CDE for solute transport in homogeneous porous media. This technique also leads directly to the mean CDE developed by Gelhar and Axness [1983] as an asymptotic (large time) limit and to model dispersion coefficients derived by Mather on and de Marsily [1980] and Güven and MoIz [1986]. The Dagan CDE then is considered in detail in respect to which conceptualization of the solute concentration, resident or flux, the model may utilize in predictive applications. General mathematical expressions relating the two conceptualizations are derived for an arbitrary solute transport problem and then are applied to the Dagan model for point and prism source inputs. Finally, the Dagan model is interpreted physically using data from the recent tracer experiments of Roberts and Mackay [1986] at the Borden site. It is shown that model predictions of resident and flux concentrations are numerically indistinguishable on any time scale over which field solute concentration measurements typically are made. The model prediction of dispersion coefficients, on the other hand, leads to dramatic differences in predicted plume behavior depending on whether finite time expressions or their asymptotic limits are used. According to the Dagan model, the asymptotic transverse dispersion coefficient cannot replace the time-dependent coefficient on any realistic time
Dual-porosity model of solute diffusion in biological tissue modified by electroporation.
Mahnič-Kalamiza, Samo; Miklavčič, Damijan; Vorobiev, Eugène
2014-07-01
In many electroporation applications mass transport in biological tissue is of primary concern. This paper presents a theoretical advancement in the field and gives some examples of model use in electroporation applications. The study focuses on post-treatment solute diffusion. We use a dual-porosity approach to describe solute diffusion in electroporated biological tissue. The cellular membrane presents a hindrance to solute transport into the extracellular space and is modeled as electroporation-dependent porosity, assigned to the intracellular space (the finite rate of mass transfer within an individual cell is not accounted for, for reasons that we elaborate on). The second porosity is that of the extracellular space, through which solute vacates a block of tissue. The model can be used to study extraction out of or introduction of solutes into tissue, and we give three examples of application, a full account of model construction, validation with experiments, and a parametrical analysis. To facilitate easy implementation and experimentation by the reader, the complete derivation of the analytical solution for a simplified example is presented. Validation is done by comparing model results to experimentally-obtained data; we modeled kinetics of sucrose extraction by diffusion from sugar beet tissue in laboratory-scale experiments. The parametrical analysis demonstrates the importance of selected physicochemical and geometrical properties of the system, illustrating possible outcomes of applying the model to different electroporation applications. The proposed model is a new platform that supports rapid extension by state-of-the-art models of electroporation phenomena, developed as latest achievements in the field of electroporation. Copyright © 2014 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Bart W. Hoogenboom
2012-05-01
Full Text Available Micromechanic resonators provide a small-volume and potentially high-throughput method to determine rheological properties of fluids. Here we explore the accuracy in measuring mass density and viscosity of ethanol-water and glycerol-water model solutions, using a simple and easily implemented model to deduce the hydrodynamic effects on resonating cantilevers of various length-to-width aspect ratios. We next show that these measurements can be extended to determine the alcohol percentage of both model solutions and commercial beverages such as beer, wine and liquor. This demonstrates how micromechanical resonators can be used for quality control of every-day drinks.
An Activity-Based Dissolution Model for Solute-Containing Microdroplets
DEFF Research Database (Denmark)
Bitterfield, Deborah L; Madsen, Anders Utoft; Needham, D.
2016-01-01
activity and chemical potential, at the droplet interface. This work addresses the importance of understanding how water activity changes during solution droplet dissolution. A model for dissolution rate is presented that accounts for the kinetic effects of changing water activity at the droplet interface...... is sufficient to account for the kinetics of dissolution. The dissolution model is based on the Epstein-Plesset equation, which has previously been applied to pure gas (bubble) and liquid (droplet) dissolution into liquid phases, but not to salt solutions. The model is tested by using the micropipet technique...... to form and observe the dehydration of single NaCl solution microdroplets in octanol or butyl acetate. The model successfully predicts the droplet diameter as a function of time in both organic solvents. The NaCl concentration in water is measured well into the supersaturated area >5.4 M...
Directory of Open Access Journals (Sweden)
Sie Long Kek
2015-01-01
Full Text Available A computational approach is proposed for solving the discrete time nonlinear stochastic optimal control problem. Our aim is to obtain the optimal output solution of the original optimal control problem through solving the simplified model-based optimal control problem iteratively. In our approach, the adjusted parameters are introduced into the model used such that the differences between the real system and the model used can be computed. Particularly, system optimization and parameter estimation are integrated interactively. On the other hand, the output is measured from the real plant and is fed back into the parameter estimation problem to establish a matching scheme. During the calculation procedure, the iterative solution is updated in order to approximate the true optimal solution of the original optimal control problem despite model-reality differences. For illustration, a wastewater treatment problem is studied and the results show the efficiency of the approach proposed.
Scientific Approach and Inquiry Learning Model in the Topic of Buffer Solution: A Content Analysis
Kusumaningrum, I. A.; Ashadi, A.; Indriyanti, N. Y.
2017-09-01
Many concepts in buffer solution cause student’s misconception. Understanding science concepts should apply the scientific approach. One of learning models which is suitable with this approach is inquiry. Content analysis was used to determine textbook compatibility with scientific approach and inquiry learning model in the concept of buffer solution. By using scientific indicator tools (SIT) and Inquiry indicator tools (IIT), we analyzed three chemistry textbooks grade 11 of senior high school labeled as P, Q, and R. We described how textbook compatibility with scientific approach and inquiry learning model in the concept of buffer solution. The results show that textbook P and Q were very poor and book R was sufficient because the textbook still in procedural level. Chemistry textbooks used at school are needed to be improved in term of scientific approach and inquiry learning model. The result of these analyses might be of interest in order to write future potential textbooks.
Smooth Solutions to Optimal Investment Models with Stochastic Volatilities and Portfolio Constraints
International Nuclear Information System (INIS)
Pham, H.
2002-01-01
This paper deals with an extension of Merton's optimal investment problem to a multidimensional model with stochastic volatility and portfolio constraints. The classical dynamic programming approach leads to a characterization of the value function as a viscosity solution of the highly nonlinear associated Bellman equation. A logarithmic transformation expresses the value function in terms of the solution to a semilinear parabolic equation with quadratic growth on the derivative term. Using a stochastic control representation and some approximations, we prove the existence of a smooth solution to this semilinear equation. An optimal portfolio is shown to exist, and is expressed in terms of the classical solution to this semilinear equation. This reduction is useful for studying numerical schemes for both the value function and the optimal portfolio. We illustrate our results with several examples of stochastic volatility models popular in the financial literature
An accurate two-phase approximate solution to the acute viral infection model
Energy Technology Data Exchange (ETDEWEB)
Perelson, Alan S [Los Alamos National Laboratory
2009-01-01
During an acute viral infection, virus levels rise, reach a peak and then decline. Data and numerical solutions suggest the growth and decay phases are linear on a log scale. While viral dynamic models are typically nonlinear with analytical solutions difficult to obtain, the exponential nature of the solutions suggests approximations can be found. We derive a two-phase approximate solution to the target cell limited influenza model and illustrate the accuracy using data and previously established parameter values of six patients infected with influenza A. For one patient, the subsequent fall in virus concentration was not consistent with our predictions during the decay phase and an alternate approximation is derived. We find expressions for the rate and length of initial viral growth in terms of the parameters, the extent each parameter is involved in viral peaks, and the single parameter responsible for virus decay. We discuss applications of this analysis in antiviral treatments and investigating host and virus heterogeneities.
Balanced growth path solutions of a Boltzmann mean field game model for knowledge growth
Burger, Martin
2016-11-18
In this paper we study balanced growth path solutions of a Boltzmann mean field game model proposed by Lucas and Moll [15] to model knowledge growth in an economy. Agents can either increase their knowledge level by exchanging ideas in learning events or by producing goods with the knowledge they already have. The existence of balanced growth path solutions implies exponential growth of the overall production in time. We prove existence of balanced growth path solutions if the initial distribution of individuals with respect to their knowledge level satisfies a Pareto-tail condition. Furthermore we give first insights into the existence of such solutions if in addition to production and knowledge exchange the knowledge level evolves by geometric Brownian motion.
Modeling of critical experiments employing Raschig rings in uranyl nitrate solution
International Nuclear Information System (INIS)
Tanner, J.E.
1989-01-01
Four critical experiments employing borated glass rings in concentrated uranyl nitrate solution yielded k eff higher by 0. 04 when modeled with a flux-weighted, homogenized cross section set than when modeled with discrete rings. k eff varied by 0.014 for a 10% boron uncertainty and by up to 0.04 for a 10% packing fraction uncertainty
Characterization of positive solution to stochastic competitor-competitor-cooperative model
Directory of Open Access Journals (Sweden)
Partha Sarathi Mandal
2013-04-01
Full Text Available In this article we study a randomized three-dimensional Lotka-Volterra model with competitor-competitor-mutualist interaction. We show the existence, uniqueness, moment boundedness, stochastic boundedness and global asymptotic stability of positive global solutions for this stochastic model. Analytical results are validated by numerical examples.
Chernyshev, A.V.; Tarasov, P.A.; Semianov, K.A.; Nekrasov, V.M.; Hoekstra, A.G.; Maltsev, V.P.
2008-01-01
A mathematical model of erythrocyte lysis in isotonic solution of ammonium chloride is presented in frames of a statistical approach. The model is used to evaluate several parameters of mature erythrocytes (volume, surface area, hemoglobin concentration, number of anionic exchangers on membrane,
Review and Application of Time Nonlocal Transport Models to Capture Solute Retention
LU, B.; Zhang, Y.; Sun, H.; Green, C. T.; Wei, S.; Qian, J.
2016-12-01
Multiple time nonlocal transport models had long been used to capture solute retention in natural geologic media with intrinsic physical and chemical heterogeneity, but systematical comparison of these models was rather rare. This presentation reviewed four major time nonlocal transport models, which are the matrix diffusion (MD) model, the continuous time random walk (CTRW) framework, the multi-rate mass transfer (MRMT) model, and the time fractional advection-dispersion (fADE) model, by focusing on the physical description and parameter correlation The four models were then applied to quantify solute transport observed in laboratory sand columns to further evaluate their data needs and ability to represent real-world non-Fickian dispersion due to retention process.
Shirmin, G. I.
1980-08-01
In the present paper, an averaging on the basis of Fatou's (1931) scheme is obtained within the framework of a version of the doubly restricted problem of four bodies. A proof is obtained for the existence of particular solutions that are analogous to the Eulerian and Lagrangian solutions. The solutions are applied to an analysis of first-order secular disturbances in the positions of libration points, caused by the influence of a body whose attraction is neglected in the classical model of the restricted three-body problem. These disturbances are shown to lead to continuous displacements of the libration points.
On the iterative solution of the gap equation in the Nambu-Jona-Lasinio model
Martinez, A.; Raya, A.
2017-10-01
In this work we revise the standard iterative procedure to find the solution of the gap equation in the Nambu-Jona-Lasinio model within the most popular regularization schemes available in literature in the super-strong coupling regime. We observe that whereas for the hard cut-off regularization schemes, the procedure smoothly converges to the physically relevant solution, Pauli-Villars and Proper-Time regularization schemes become chaotic in the sense of discrete dynamical systems. We call for the need of an appropriate interpretation of the non-convergence of this procedure to the solution of the gap equation.
Homoclinic orbit solutions of a one Dimensional Wilson-Cowan type model
Directory of Open Access Journals (Sweden)
Edward P. Krisner
2008-08-01
Full Text Available We analyze a time independent integral equation defined on a spatially extended domain which arises in the modelling of neuronal networks. In this paper, the coupling function is oscillatory and the firing rate is a smooth "heaviside-like" function. We will derive an associated fourth order ODE and establish that any bounded solution of the ODE is also a solution of the integral equation. We will then apply shooting arguments to prove that the ODE has N-bump homoclinic orbit solutions for any even-valued N>0. homoclinic orbit.
Generalized dynamics of soft-matter quasicrystals mathematical models and solutions
Fan, Tian-You
2017-01-01
The book systematically introduces the mathematical models and solutions of generalized hydrodynamics of soft-matter quasicrystals (SMQ). It provides methods for solving the initial-boundary value problems in these systems. The solutions obtained demonstrate the distribution, deformation and motion of the soft-matter quasicrystals, and determine the stress, velocity and displacement fields. The interactions between phonons, phasons and fluid phonons are discussed in some fundamental materials samples. Mathematical solutions for solid and soft-matter quasicrystals are compared, to help readers to better understand the featured properties of SMQ.
Analytical solution for two-phase flow in a wellbore using the drift-flux model
Energy Technology Data Exchange (ETDEWEB)
Pan, L.; Webb, S.W.; Oldenburg, C.M.
2011-11-01
This paper presents analytical solutions for steady-state, compressible two-phase flow through a wellbore under isothermal conditions using the drift flux conceptual model. Although only applicable to highly idealized systems, the analytical solutions are useful for verifying numerical simulation capabilities that can handle much more complicated systems, and can be used in their own right for gaining insight about two-phase flow processes in wells. The analytical solutions are obtained by solving the mixture momentum equation of steady-state, two-phase flow with an assumption that the two phases are immiscible. These analytical solutions describe the steady-state behavior of two-phase flow in the wellbore, including profiles of phase saturation, phase velocities, and pressure gradients, as affected by the total mass flow rate, phase mass fraction, and drift velocity (i.e., the slip between two phases). Close matching between the analytical solutions and numerical solutions for a hypothetical CO{sub 2} leakage problem as well as to field data from a CO{sub 2} production well indicates that the analytical solution is capable of capturing the major features of steady-state two-phase flow through an open wellbore, and that the related assumptions and simplifications are justified for many actual systems. In addition, we demonstrate the utility of the analytical solution to evaluate how the bottomhole pressure in a well in which CO{sub 2} is leaking upward responds to the mass flow rate of CO{sub 2}-water mixture.
Manufactured analytical solutions for isothermal full-Stokes ice sheet models
Directory of Open Access Journals (Sweden)
A. Sargent
2010-08-01
Full Text Available We present the detailed construction of a manufactured analytical solution to time-dependent and steady-state isothermal full-Stokes ice sheet problems. The solutions are constructed for two-dimensional flowline and three-dimensional full-Stokes ice sheet models with variable viscosity. The construction is done by choosing for the specified ice surface and bed a velocity distribution that satisfies both mass conservation and the kinematic boundary conditions. Then a compensatory stress term in the conservation of momentum equations and their boundary conditions is calculated to make the chosen velocity distributions as well as the chosen pressure field into exact solutions. By substituting different ice surface and bed geometry formulas into the derived solution formulas, analytical solutions for different geometries can be constructed.
The boundary conditions can be specified as essential Dirichlet conditions or as periodic boundary conditions. By changing a parameter value, the analytical solutions allow investigation of algorithms for a different range of aspect ratios as well as for different, frozen or sliding, basal conditions. The analytical solutions can also be used to estimate the numerical error of the method in the case when the effects of the boundary conditions are eliminated, that is, when the exact solution values are specified as inflow and outflow boundary conditions.
A new modeling and solution approach for the number partitioning problem
Directory of Open Access Journals (Sweden)
Bahram Alidaee
2005-01-01
Full Text Available The number partitioning problem has proven to be a challenging problem for both exact and heuristic solution methods. We present a new modeling and solution approach that consists of recasting the problem as an unconstrained quadratic binary program that can be solved by efficient metaheuristic methods. Our approach readily accommodates both the common two-subset partition case as well as the more general case of multiple subsets. Preliminary computational experience is presented illustrating the attractiveness of the method.
On the Dagan Model of solute transport in groundwater: Application to the Borden Site
Barry, D. A.; Coves, J.; Sposito, Garrison
1988-10-01
In the first part of this study, Sposito and Barry (1987) derived an ensemble-mean convection-dispersion equation (CDE) for tracer solute transport subject to a random velocity field. It was shown that the model dispersion coefficients originally presented by Dagan (1984) could be derived from the general expression for the dispersion coefficients in this mean CDE. Under the assumption of ergodicity, the Dagan model is used in this paper to predict chloride and bromide concentrations in the well-documented Borden aquifer experiment reported by Roberts and Mackay (1986). Because of a possible influence on the solute from the upper aquifer boundary, it was appropriate to apply the two-dimensional form of the model. A number of steps was necessary to reduce the three-dimensional raw data to a two-dimensional form, the main ones being integration over the vertical axis and the use of a gridding algorithm to form a two-dimensional solute concentration surface. Incomplete sampling of the solute plume during the early sampling sessions, as well as the assumptions made with respect to the data analysis, produce a rather large degree of uncertainty in the specification of the initial solute plume. These factors hinder a thorough experimental evaluation of the Dagan model. Data from some of the later sampling sessions were more complete, however, and the model predictions appeared to agree well with the field concentration data, especially in the preasymptotic region for the longitudinal dispersion coefficient.
Energy Technology Data Exchange (ETDEWEB)
Duffet, C.
2004-12-01
Reflection tomography allows the determination of a velocity model that fits the travel time data associated with reflections of seismic waves propagating in the subsurface. A least-square formulation is used to compare the observed travel times and the travel times computed by the forward operator based on a ray tracing. This non-linear optimization problem is solved classically by a Gauss-Newton method based on successive linearization of the forward operator. The obtained solution is only one among many possible models. Indeed, the uncertainties on the observed travel times (resulting from an interpretative event picking on seismic records) and more generally the under-determination of the inverse problem lead to uncertainties on the solution. An a posteriori uncertainty analysis is then crucial to delimit the range of possible solutions that fit, with the expected accuracy, the data and the a priori information. A linearized a posteriori analysis is possible by an analysis of the a posteriori covariance matrix, inverse of the Gauss-Newton approximation of the matrix. The computation of this matrix is generally expensive (the matrix is huge for 3D problems) and the physical interpretation of the results is difficult. Then we propose a formalism which allows to compute uncertainties on relevant geological quantities for a reduced computational time. Nevertheless, this approach is only valid in the vicinity of the solution model (linearized framework) and complex cases may require a non-linear approach. An experimental approach consists in solving the inverse problem under constraints to test different geological scenarios. (author)
A lattice Boltzmann model for solute transport in open channel flow
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.
Application of Harmony Search algorithm to the solution of groundwater management models
Tamer Ayvaz, M.
2009-06-01
This study proposes a groundwater resources management model in which the solution is performed through a combined simulation-optimization model. A modular three-dimensional finite difference groundwater flow model, MODFLOW is used as the simulation model. This model is then combined with a Harmony Search (HS) optimization algorithm which is based on the musical process of searching for a perfect state of harmony. The performance of the proposed HS based management model is tested on three separate groundwater management problems: (i) maximization of total pumping from an aquifer (steady-state); (ii) minimization of the total pumping cost to satisfy the given demand (steady-state); and (iii) minimization of the pumping cost to satisfy the given demand for multiple management periods (transient). The sensitivity of HS algorithm is evaluated by performing a sensitivity analysis which aims to determine the impact of related solution parameters on convergence behavior. The results show that HS yields nearly same or better solutions than the previous solution methods and may be used to solve management problems in groundwater modeling.
Constructing set-valued fundamental diagrams from jamiton solutions in second order traffic models
Seibold, Benjamin
2013-09-01
Fundamental diagrams of vehicular traiic ow are generally multivalued in the congested ow regime. We show that such set-valued fundamental diagrams can be constructed systematically from simple second order macroscopic traiic models, such as the classical Payne-Whitham model or the inhomogeneous Aw-Rascle-Zhang model. These second order models possess nonlinear traveling wave solutions, called jamitons, and the multi-valued parts in the fundamental diagram correspond precisely to jamiton-dominated solutions. This study shows that transitions from function-valued to set-valued parts in a fundamental diagram arise naturally in well-known second order models. As a particular consequence, these models intrinsically reproduce traiic phases. © American Institute of Mathematical Sciences.
Breeding novel solutions in the brain: a model of Darwinian neurodynamics.
Szilágyi, András; Zachar, István; Fedor, Anna; de Vladar, Harold P; Szathmáry, Eörs
2016-01-01
Background : The fact that surplus connections and neurons are pruned during development is well established. We complement this selectionist picture by a proof-of-principle model of evolutionary search in the brain, that accounts for new variations in theory space. We present a model for Darwinian evolutionary search for candidate solutions in the brain. Methods : We combine known components of the brain - recurrent neural networks (acting as attractors), the action selection loop and implicit working memory - to provide the appropriate Darwinian architecture. We employ a population of attractor networks with palimpsest memory. The action selection loop is employed with winners-share-all dynamics to select for candidate solutions that are transiently stored in implicit working memory. Results : We document two processes: selection of stored solutions and evolutionary search for novel solutions. During the replication of candidate solutions attractor networks occasionally produce recombinant patterns, increasing variation on which selection can act. Combinatorial search acts on multiplying units (activity patterns) with hereditary variation and novel variants appear due to (i) noisy recall of patterns from the attractor networks, (ii) noise during transmission of candidate solutions as messages between networks, and, (iii) spontaneously generated, untrained patterns in spurious attractors. Conclusions : Attractor dynamics of recurrent neural networks can be used to model Darwinian search. The proposed architecture can be used for fast search among stored solutions (by selection) and for evolutionary search when novel candidate solutions are generated in successive iterations. Since all the suggested components are present in advanced nervous systems, we hypothesize that the brain could implement a truly evolutionary combinatorial search system, capable of generating novel variants.
Lee, Ping I
2011-10-10
The purpose of this review is to provide an overview of approximate analytical solutions to the general moving boundary diffusion problems encountered during the release of a dispersed drug from matrix systems. Starting from the theoretical basis of the Higuchi equation and its subsequent improvement and refinement, available approximate analytical solutions for the more complicated cases involving heterogeneous matrix, boundary layer effect, finite release medium, surface erosion, and finite dissolution rate are also discussed. Among various modeling approaches, the pseudo-steady state assumption employed in deriving the Higuchi equation and related approximate analytical solutions appears to yield reasonably accurate results in describing the early stage release of a dispersed drug from matrices of different geometries whenever the initial drug loading (A) is much larger than the drug solubility (C(s)) in the matrix (or A≫C(s)). However, when the drug loading is not in great excess of the drug solubility (i.e. low A/C(s) values) or when the drug loading approaches the drug solubility (A→C(s)) which occurs often with drugs of high aqueous solubility, approximate analytical solutions based on the pseudo-steady state assumption tend to fail, with the Higuchi equation for planar geometry exhibiting a 11.38% error as compared with the exact solution. In contrast, approximate analytical solutions to this problem without making the pseudo-steady state assumption, based on either the double-integration refinement of the heat balance integral method or the direct simplification of available exact analytical solutions, show close agreement with the exact solutions in different geometries, particularly in the case of low A/C(s) values or drug loading approaching the drug solubility (A→C(s)). However, the double-integration heat balance integral approach is generally more useful in obtaining approximate analytical solutions especially when exact solutions are not
A Control Volume Model of Solute Transport in a Single Fracture
Kennedy, Christopher A.; Lennox, William C.
1995-02-01
A control volume model of solute transport through a single fracture in a porous matrix is developed. Application to problems of contaminant transport through fractured clay demonstrates several strong features of the method. The control volume approach inherently conserves mass and treats dispersivity at interfaces in a physically correct manner. By employing an upstream weighting scheme, based on the exact solution to the one-dimensional steady state advection-dispersion equation, the model proves to be more efficient than previous single-fracture models. The significance of matrix diffusion in the direction parallel to the fracture axis is investigated. For the transport of a nonreactive tracer through a 20-micrometer-wide fracture in clay material, analytical solutions based on one-dimensional matrix diffusion are erroneous for flow velocities of less than 1 m/day. The influence of boundary conditions on two-dimensional matrix diffusion is considered, and the clean-up of a contaminated fracture is simulated.
Reliable and efficient solution of genome-scale models of Metabolism and macromolecular Expression
DEFF Research Database (Denmark)
Ma, Ding; Yang, Laurence; Fleming, Ronan M. T.
2017-01-01
Constraint-Based Reconstruction and Analysis (COBRA) is currently the only methodology that permits integrated modeling of Metabolism and macromolecular Expression (ME) at genome-scale. Linear optimization computes steady-state flux solutions to ME models, but flux values are spread over many ord...... problems tested here. DQQ will enable extensive use of large linear and nonlinear models in systems biology and other applications involving multiscale data....... orders of magnitude. Data values also have greatly varying magnitudes. Standard double-precision solvers may return inaccurate solutions or report that no solution exists. Exact simplex solvers based on rational arithmetic require a near-optimal warm start to be practical on large problems (current ME...
Xie, Dexuan; Volkmer, Hans W.; Ying, Jinyong
2016-04-01
The nonlocal dielectric approach has led to new models and solvers for predicting electrostatics of proteins (or other biomolecules), but how to validate and compare them remains a challenge. To promote such a study, in this paper, two typical nonlocal dielectric models are revisited. Their analytical solutions are then found in the expressions of simple series for a dielectric sphere containing any number of point charges. As a special case, the analytical solution of the corresponding Poisson dielectric model is also derived in simple series, which significantly improves the well known Kirkwood's double series expansion. Furthermore, a convolution of one nonlocal dielectric solution with a commonly used nonlocal kernel function is obtained, along with the reaction parts of these local and nonlocal solutions. To turn these new series solutions into a valuable research tool, they are programed as a free fortran software package, which can input point charge data directly from a protein data bank file. Consequently, different validation tests can be quickly done on different proteins. Finally, a test example for a protein with 488 atomic charges is reported to demonstrate the differences between the local and nonlocal models as well as the importance of using the reaction parts to develop local and nonlocal dielectric solvers.
CRACK2 - Modelling calcium carbonate deposition from bicarbonate solution in cracks in concrete
International Nuclear Information System (INIS)
Brodersen, K.
2003-03-01
The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description of the model. Hydroxyl ions are transported by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. The cementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide dissolved in the pore solution. Diffusive migration of cesium as radioactive isotope is also considered. Electrical interaction of the migrating ions is taken into account. Example calculations demonstrate effects of parameter variations on distribution of precipitated calcite in the crack and on the composition of the outflowing solution, which can be compared directly with experimental results. Leaching behavior of sodium can be used to tune the model to experimental observations. The calcite is mostly precipitated on top of the original crack surface and may under certain circumstances fill the crack. The produced thin layers of low porosity calcite act as a diffusion barrier limiting contact between cement and solution. Pore closure mechanisms in such layers are discussed. Implications for safety assessment of radioactive waste disposal are shortly mentioned. The model is also relevant for conventional uses of concrete. (au)
An accurate analytical solution of a zero-dimensional greenhouse model for global warming
International Nuclear Information System (INIS)
Foong, S K
2006-01-01
In introducing the complex subject of global warming, books and papers usually use the zero-dimensional greenhouse model. When the ratio of the infrared radiation energy of the Earth's surface that is lost to outer space to the non-reflected average solar radiation energy is small, the model admits an accurate approximate analytical solution-the resulting energy balance equation of the model is a quartic equation that can be solved analytically-and thus provides an alternative solution and instructional strategy. A search through the literature fails to find an analytical solution, suggesting that the solution may be new. In this paper, we review the model, derive the approximation and obtain its solution. The dependence of the temperature of the surface of the Earth and the temperature of the atmosphere on seven parameters is made explicit. A simple and convenient formula for global warming (or cooling) in terms of the percentage change of the parameters is derived. The dependence of the surface temperature on the parameters is illustrated by several representative graphs
A comparison of numerical methods for the solution of continuous-time DSGE models
DEFF Research Database (Denmark)
Parra-Alvarez, Juan Carlos
This paper evaluates the accuracy of a set of techniques that approximate the solution of continuous-time DSGE models. Using the neoclassical growth model I compare linear-quadratic, perturbation and projection methods. All techniques are applied to the HJB equation and the optimality conditions...... parameters of the model and suggest the use of projection methods when a high degree of accuracy is required....
Krishnan, M.
2017-05-01
We present a model for calculating the net and effective electrical charge of globular macromolecules and linear polyelectrolytes such as proteins and DNA, given the concentration of monovalent salt and pH in solution. The calculation is based on a numerical solution of the non-linear Poisson-Boltzmann equation using a finite element discretized continuum approach. The model simultaneously addresses the phenomena of charge regulation and renormalization, both of which underpin the electrostatics of biomolecules in solution. We show that while charge regulation addresses the true electrical charge of a molecule arising from the acid-base equilibria of its ionizable groups, charge renormalization finds relevance in the context of a molecule's interaction with another charged entity. Writing this electrostatic interaction free energy in terms of a local electrical potential, we obtain an "interaction charge" for the molecule which we demonstrate agrees closely with the "effective charge" discussed in charge renormalization and counterion-condensation theories. The predictions of this model agree well with direct high-precision measurements of effective electrical charge of polyelectrolytes such as nucleic acids and disordered proteins in solution, without tunable parameters. Including the effective interior dielectric constant for compactly folded molecules as a tunable parameter, the model captures measurements of effective charge as well as published trends of pKa shifts in globular proteins. Our results suggest a straightforward general framework to model electrostatics in biomolecules in solution. In offering a platform that directly links theory and experiment, these calculations could foster a systematic understanding of the interrelationship between molecular 3D structure and conformation, electrical charge and electrostatic interactions in solution. The model could find particular relevance in situations where molecular crystal structures are not available or
Energy Technology Data Exchange (ETDEWEB)
Merkin, V. G. [The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723 (United States); Lionello, R.; Linker, J.; Török, T.; Downs, C. [Predictive Science, Inc., San Diego, CA 92121 (United States); Lyon, J. G., E-mail: slava.merkin@jhuapl.edu [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States)
2016-11-01
Two well-established magnetohydrodynamic (MHD) codes are coupled to model the solar corona and the inner heliosphere. The corona is simulated using the MHD algorithm outside a sphere (MAS) model. The Lyon–Fedder–Mobarry (LFM) model is used in the heliosphere. The interface between the models is placed in a spherical shell above the critical point and allows both models to work in either a rotating or an inertial frame. Numerical tests are presented examining the coupled model solutions from 20 to 50 solar radii. The heliospheric simulations are run with both LFM and the MAS extension into the heliosphere, and use the same polytropic coronal MAS solutions as the inner boundary condition. The coronal simulations are performed for idealized magnetic configurations, with an out-of-equilibrium flux rope inserted into an axisymmetric background, with and without including the solar rotation. The temporal evolution at the inner boundary of the LFM and MAS solutions is shown to be nearly identical, as are the steady-state background solutions, prior to the insertion of the flux rope. However, after the coronal mass ejection has propagated through the significant portion of the simulation domain, the heliospheric solutions diverge. Additional simulations with different resolution are then performed and show that the MAS heliospheric solutions approach those of LFM when run with progressively higher resolution. Following these detailed tests, a more realistic simulation driven by the thermodynamic coronal MAS is presented, which includes solar rotation and an azimuthally asymmetric background and extends to the Earth’s orbit.
Exact Solution of the Six-Vertex Model with Domain Wall Boundary Conditions. Disordered Phase
Bleher, P M
2005-01-01
The six-vertex model, or the square ice model, with domain wall boundary conditions (DWBC) has been introduced and solved for finite $N$ by Korepin and Izergin. The solution is based on the Yang-Baxter equations and it represents the free energy in terms of an $N\\times N$ Hankel determinant. Paul Zinn-Justin observed that the Izergin-Korepin formula can be re-expressed in terms of the partition function of a random matrix model with a nonpolynomial interaction. We use this observation to obtain the large $N$ asymptotics of the six-vertex model with DWBC in the disordered phase. The solution is based on the Riemann-Hilbert approach and the Deift-Zhou nonlinear steepest descent method. As was noticed by Kuperberg, the problem of enumeration of alternating sign matrices (the ASM problem) is a special case of the the six-vertex model. We compare the obtained exact solution of the six-vertex model with known exact results for the 1, 2, and 3 enumerations of ASMs, and also with the exact solution on the so-called f...
Benchmarking the invariant embedding method against analytical solutions in model transport problems
International Nuclear Information System (INIS)
Malin, Wahlberg; Imre, Pazsit
2005-01-01
The purpose of this paper is to demonstrate the use of the invariant embedding method in a series of model transport problems, for which it is also possible to obtain an analytical solution. Due to the non-linear character of the embedding equations, their solution can only be obtained numerically. However, this can be done via a robust and effective iteration scheme. In return, the domain of applicability is far wider than the model problems investigated in this paper. The use of the invariant embedding method is demonstrated in three different areas. The first is the calculation of the energy spectrum of reflected (sputtered) particles from a multiplying medium, where the multiplication arises from recoil production. Both constant and energy dependent cross sections with a power law dependence were used in the calculations. The second application concerns the calculation of the path length distribution of reflected particles from a medium without multiplication. This is a relatively novel and unexpected application, since the embedding equations do not resolve the depth variable. The third application concerns the demonstration that solutions in an infinite medium and a half-space are interrelated through embedding-like integral equations, by the solution of which the reflected flux from a half-space can be reconstructed from solutions in an infinite medium or vice versa. In all cases the invariant embedding method proved to be robust, fast and monotonically converging to the exact solutions. (authors)
Saltas, V.; Horlait, D.; Sgourou, E. N.; Vallianatos, F.; Chroneos, A.
2017-12-01
Modelling solid solutions is fundamental in understanding the properties of numerous materials which are important for a range of applications in various fields including nanoelectronics and energy materials such as fuel cells, nuclear materials, and batteries, as the systematic understanding throughout the composition range of solid solutions for a range of conditions can be challenging from an experimental viewpoint. The main motivation of this review is to contribute to the discussion in the community of the applicability of methods that constitute the investigation of solid solutions computationally tractable. This is important as computational modelling is required to calculate numerous defect properties and to act synergistically with experiment to understand these materials. This review will examine in detail two examples: silicon germanium alloys and MAX phase solid solutions. Silicon germanium alloys are technologically important in nanoelectronic devices and are also relevant considering the recent advances in ternary and quaternary groups IV and III-V semiconductor alloys. MAX phase solid solutions display a palette of ceramic and metallic properties and it is anticipated that via their tuning they can have applications ranging from nuclear to aerospace industries as well as being precursors for particular MXenes. In the final part, a brief summary assesses the limitations and possibilities of the methodologies discussed, whereas there is discussion on the future directions and examples of solid solution systems that should prove fruitful to consider.
Classical solutions for the ellipsoidal BGK model with fixed collision frequency
Yun, Seok-Bae
2015-12-01
We establish the existence of global in time smooth solutions for the ellipsoidal BGK model, which is a variant of the BGK model for the Boltzmann equation designed to yield the correct Prandtl number in the hydrodynamic approximation at the Navier-Stokes level. For this, we carefully design a function space which captures the growth of the solution in a weighted Sobolev norm, and show that the ellipsoidal relaxation operator is Lipschitz continuous in the induced metric. This approach is restricted to the case when the collision frequency does not depend on the macroscopic field, but no smallness on the initial data is required.
CRACK2. Modelling calcium carbonate deposition from bicarbonate solutions in cracks in concrete
DEFF Research Database (Denmark)
Brodersen, Knud Erik
2003-01-01
The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description ofthe model. Hydroxyl ions are transported...... by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. Thecementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide...
Numerical Modeling Tools for the Prediction of Solution Migration Applicable to Mining Site
International Nuclear Information System (INIS)
Martell, M.; Vaughn, P.
1999-01-01
Mining has always had an important influence on cultures and traditions of communities around the globe and throughout history. Today, because mining legislation places heavy emphasis on environmental protection, there is great interest in having a comprehensive understanding of ancient mining and mining sites. Multi-disciplinary approaches (i.e., Pb isotopes as tracers) are being used to explore the distribution of metals in natural environments. Another successful approach is to model solution migration numerically. A proven method to simulate solution migration in natural rock salt has been applied to project through time for 10,000 years the system performance and solution concentrations surrounding a proposed nuclear waste repository. This capability is readily adaptable to simulate solution migration around mining
Choi, Nari; Han, Jongmin
2018-04-01
In this paper, we study an elliptic equation arising from the self-dual Maxwell gauged O (3) sigma model coupled with gravity. When the parameter τ equals 1 and there is only one singular source, we consider radially symmetric solutions. There appear three important constants: a positive parameter a representing a scaled gravitational constant, a nonnegative integer N1 representing the total string number, and a nonnegative integer N2 representing the total anti-string number. The values of the products aN1 , aN2 ∈ [ 0 , ∞) play a crucial role in classifying radial solutions. By using the decay rates of solutions at infinity, we provide a complete classification of solutions for all possible values of aN1 and aN2. This improves previously known results.
On the stability of soliton solution in NLS-type general field model
International Nuclear Information System (INIS)
Chakrabarti, S.; Nayyar, A.H.
1982-08-01
A model incorporating the nonlinear Schroedinger equation and its generalizations is considered and the stability of its periodic-in-time solutions under the restriction of a fixed charge Q is analysed. It is shown that the necessary condition for the stability is given by the inequality deltaQ/deltaν<0, where ν is the parameter of periodicity of the solution in time. In particular, one specific class of Lagrangians is considered and, in addition, the sufficient conditions for the stability of the soliton solutions are also determined. This study thus examines both the necessary and the sufficient conditions for the stability of the solutions of nonlinear Schroedinger equation and some of its generalizations. (author)
Classical and recent free-volume models for polymer solutions: A comparative evaluation
DEFF Research Database (Denmark)
Radfarnia, H.R.; Kontogeorgis, Georgios; Ghotbi, C.
2007-01-01
In this work, two "classical" (UNIFAC-FV, Entropic-FV) and two "recent" free-volume (FV) models (Kannan-FV, Freed-FV) are comparatively evaluated for polymer-solvent vapor-liquid equilibria including both aqueous and non-aqueous solutions. Moreover, some further developments are presented here...... by the modified Freed-FV model for athermal and non-athermal polymer systems are compared to other "recent" and "classical" FV models, indicating an improvement for the modified Freed-FV model for aqueous polymer solutions. Second, for the original Freed-FV model, new UNIFAC group energy parameters are regressed...... to using the classical UNIFAC parameters, for VLE of aqueous and alcohol polymer systems....
CO2 Mass transfer model for carbonic anhydrase-enhanced aqueous MDEA solutions
DEFF Research Database (Denmark)
Gladis, Arne Berthold; Deslauriers, Maria Gundersen; Neerup, Randi
2018-01-01
In this study a CO2 mass transfer model was developed for carbonic anhydrase-enhanced MDEA solutions based on a mechanistic kinetic enzyme model. Four different enzyme models were compared in their ability to predict the liquid side mass transfer coefficient at temperatures in the range of 298...... the SP model is limited to applications with low CO2 partial pressure such as CCS from coal burning power plants. Two other models that were also investigated are not suitable for implementation into an absorber column simulation, as they cannot describe the influence of changing solvent loading...
Yamazaki, Kendi; Maluf-Filho, Fauze; da Costa, Vitor Alves Pessoa; Pessorrusso, Fernanda Cristina Simões; Hondo, Fabio Yuji; Sakai, Paulo; de Figueiredo, Luis Francisco Poli
2015-01-01
Endoscopic submucosal dissection carries an increased risk of bleeding and perforation. The creation of a long lasting submucosal cushion is essential for the safe and complete removal of the lesion. There is not a suitable experimental model for evaluation of the durability of the cushioning effect of different solutions. To describe an improved experimental model to evaluate submucosal injection solutions. A total of four domestic pigs were employed to evaluate two different submucosal fluid solutions in the gastric submucosa. After midline laparotomy, the anterior gastric wall was incised from the gastric body to the antrum and its mucosal surface was exposed by flipping inside out the incised gastric wall. Two different solutions (10% mannitol and normal saline) were injected in the submucosa of the anterior wall of the distal gastric body. All submucosal cushions were injected until they reach the same size, standardized as 1.0 cm in height and 2.0 cm in diameter. A caliper and a ruler were employed to guarantee accuracy of the measurements. All four animal experiments were completed. All submucosal cushions had the exact same size measured with caliper and a ruler. By using the mannitol solution, the mean duration of the submucosal cushion was longer than the saline solution: 20 and 22 min (mean, 21 min) vs 5 and 6 min (mean, 5.5 min) This experimental model is simple and evaluate the duration, size, and effect of the submucosal cushion, making it more reliable than other models that employ resected porcine stomachs or endoscopic images in live porcine models.
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.
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.
Hindcast storm events in the Bering Sea for the St. Lawrence Island and Unalakleet Regions, Alaska
Erikson, Li H.; McCall, Robert T.; van Rooijen, Arnold; Norris, Benjamin
2015-01-01
This study provides viable estimates of historical storm-induced water levels in the coastal communities of Gambell and Savoonga situated on St. Lawrence Island in the Bering Sea, as well as Unalakleet located at the head of Norton Sound on the western coast of Alaska. Gambell, Savoonga, and Unalakleet are small Native Villages that are regularly impacted by coastal storms but where little quantitative information about these storms exists. The closest continuous water-level gauge is at Nome, located more than 200 kilometers from both St. Lawrence Island and Unalakleet. In this study, storms are identified and quantified using historical atmospheric and sea-ice data and then used as boundary conditions for a suite of numerical models. The work includes storm-surge (temporary rise in water levels due to persistent strong winds and low atmospheric pressures) modeling in the Bering Strait region, as well as modeling of wave runup along specified sections of the coast in Gambell and Unalakleet. Modeled historical water levels are used to develop return periods of storm surge and storm surge plus wave runup at key locations in each community. It is anticipated that the results will fill some of the data void regarding coastal flood data in western Alaska and be used for production of coastal vulnerability maps and community planning efforts.
Zhu, Shichen; Yu, Xiaoyue; Xiong, Shanbai; Liu, Ru; Gu, Zhipeng; You, Juan; Yin, Tao; Hu, Yang
2017-09-01
The elaboration of the rheological behaviors of alginate dialdehyde (ADA) crosslinked collagen solutions, along with the quantitative analysis via numerical models contribute to the controllable design of ADA crosslinked solution system's fluid mechanics performance during manufacturing process for collagen biomaterials. In the present work, steady shear flow, dynamical viscoelasticity, creep-recovery, thixotropy tests were performed to characterize the rheological behaviors of the collagen solutions incorporating of ADA from the different aspects and fitted with corresponding numerical models. It was found that pseudoplastic properties of all samples enhanced with increasing amounts of ADA, which was confirmed by the parameters calculated from the Ostwald-de Waele model, Carreau and Cross model, for instance, the non-Newtonian index (n) decreased from 0.786 to 0.201 and a great increase by 280 times in value of viscosity index (K) was obtained from Ostwald-de Waele model. The forth-mode Leonov model was selected to fit all dynamic modulus-frequency curves due to its higher fitting precision (R 2 >0.99). It could be found that the values of correlation shear viscosity (η k ) increased and the values of relaxation time (θ k ) decreased with increasing ADA at the fixed k value, suggesting that the incorporation of ADA accelerated the transformation of the collagen solutions from liquid-like to gel-like state due to more formation of CN linkages between aldehyde groups and lysine residues. Also, the curves of creep and recovery phase of the native and crosslinked collagen solutions were simulated well using Burger model and a semi-empirical model, respectively. The ability to resist to deformation and elasticity strengthened for the samples with higher amounts of ADA, accompanied with the important fact that compliance value (J 50 ) decreased from 56.317Pa -1 to 2.135Pa -1 and the recovery percentage (R creep ) increased from 2.651% to 28.217%. Finally, it was found
Zheng, Zhenzhen; Chou, Ching-Shan; Yi, Tau-Mu; Nie, Qing
2011-10-01
Cell polarization, in which substances previously uniformly distributed become asymmetric due to external or/and internal stimulation, is a fundamental process underlying cell mobility, cell division, and other polarized functions. The yeast cell S. cerevisiae has been a model system to study cell polarization. During mating, yeast cells sense shallow external spatial gradients and respond by creating steeper internal gradients of protein aligned with the external cue. The complex spatial dynamics during yeast mating polarization consists of positive feedback, degradation, global negative feedback control, and cooperative effects in protein synthesis. Understanding such complex regulations and interactions is critical to studying many important characteristics in cell polarization including signal amplification, tracking dynamic signals, and potential trade-off between achieving both objectives in a robust fashion. In this paper, we study some of these questions by analyzing several models with different spatial complexity: two compartments, three compartments, and continuum in space. The step-wise approach allows detailed characterization of properties of the steady state of the system, providing more insights for biological regulations during cell polarization. For cases without membrane diffusion, our study reveals that increasing the number of spatial compartments results in an increase in the number of steady-state solutions, in particular, the number of stable steady-state solutions, with the continuum models possessing infinitely many steady-state solutions. Through both analysis and simulations, we find that stronger positive feedback, reduced diffusion, and a shallower ligand gradient all result in more steady-state solutions, although most of these are not optimally aligned with the gradient. We explore in the different settings the relationship between the number of steady-state solutions and the extent and accuracy of the polarization. Taken together
Casabán, M.-C.; Cortés, J.-C.; Romero, J.-V.; Roselló, M.-D.
2015-07-01
This paper presents a full probabilistic description of the solution of random SI-type epidemiological models which are based on nonlinear differential equations. This description consists of determining: the first probability density function of the solution in terms of the density functions of the diffusion coefficient and the initial condition, which are assumed to be independent random variables; the expectation and variance functions of the solution as well as confidence intervals and, finally, the distribution of time until a given proportion of susceptibles remains in the population. The obtained formulas are general since they are valid regardless the probability distributions assigned to the random inputs. We also present a pair of illustrative examples including in one of them the application of the theoretical results to model the diffusion of a technology using real data.
Comparison of Model-Based Control Solutions for Severe Riser-Induced Slugs
DEFF Research Database (Denmark)
Pedersen, Simon; Jahanshahi, Esmaiel; Yang, Zhenyu
2017-01-01
Control solutions for eliminating severe riser-induced slugs in offshore oil & gas pipeline installations are key topics in offshore Exploration and Production (E&P) processes. This study describes the identification, analysis and control of a low-dimensional control-oriented model of a lab......-scaled slug testing facility. The model is analyzed and used for anti-slug control development for both lowpoint and topside transmitter solutions. For the controlled variables’ comparison it is concluded that the topside pressure transmitter (Pt) is the most difficult output to apply directly for anti-slug...... control due to the inverse response. However, as Pt often is the only accessible measurement on offshore platforms this study focuses on the controller development for both Pt and the lowpoint pressure transmitter (Pb). All the control solutions are based on linear control schemes and the performance...
Irving, J.; Koepke, C.; Elsheikh, A. H.
2017-12-01
Bayesian solutions to geophysical and hydrological inverse problems are dependent upon a forward process model linking subsurface parameters to measured data, which is typically assumed to be known perfectly in the inversion procedure. However, in order to make the stochastic solution of the inverse problem computationally tractable using, for example, Markov-chain-Monte-Carlo (MCMC) methods, fast approximations of the forward model are commonly employed. This introduces model error into the problem, which has the potential to significantly bias posterior statistics and hamper data integration efforts if not properly accounted for. Here, we present a new methodology for addressing the issue of model error in Bayesian solutions to hydrogeophysical inverse problems that is geared towards the common case where these errors cannot be effectively characterized globally through some parametric statistical distribution or locally based on interpolation between a small number of computed realizations. Rather than focusing on the construction of a global or local error model, we instead work towards identification of the model-error component of the residual through a projection-based approach. In this regard, pairs of approximate and detailed model runs are stored in a dictionary that grows at a specified rate during the MCMC inversion procedure. At each iteration, a local model-error basis is constructed for the current test set of model parameters using the K-nearest neighbour entries in the dictionary, which is then used to separate the model error from the other error sources before computing the likelihood of the proposed set of model parameters. We demonstrate the performance of our technique on the inversion of synthetic crosshole ground-penetrating radar traveltime data for three different subsurface parameterizations of varying complexity. The synthetic data are generated using the eikonal equation, whereas a straight-ray forward model is assumed in the inversion
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)
Solution-diffusion with defects model for pressure-assisted forward osmosis
Duan, Jintang
2014-11-01
An osmosis transport model is presented that combines the standard internal and external concentration polarization equations in the forward osmosis (FO) field with the selective layer transport equations first proposed by Sherwood in 1967. The Sherwood model describes water flux as the sum of a solute-selective, diffusive component driven by the sum of osmotic pressure and hydraulic pressure differences, and a nonselective, convective component driven by hydraulic pressure difference only. This solution-diffusion with defects (SDWD) model and the solution-diffusion (SD) model were compared against data collected using polyamide thin-film-composite (PA-TFC) and integrally-skinned asymmetric cellulose triacetate (CTA) membranes, evaluated in various configurations. When tested with pure water on the porous support side and 1.5. M (π=72.7. bar) sodium chloride solution on the selective layer side, applying 1.25. bar of hydraulic pressure to the porous support side increased water flux by an order of magnitude for PA-TFC membranes, but had negligible effect on CTA membrane flux. These large flux variations can be explained by the SDWD model, but not the SD model. To confirm the existence of defects, a PA-TFC membrane was coated with a uniform, highly water-permeable, nonselective polymer. After coating to block convection through defects, the influence of hydraulic pressure on water flux through this membrane essentially disappeared. Water flux through these defects is low (<1% of total water flux for PA-TFC membranes) and of little consequence in practical FO or reverse osmosis (RO) applications. But in pressure-assisted forward osmosis (PAFO) or pressure-retarded osmosis (PRO), convective transport through defects affects the solute concentration difference across the membrane selective layer, increasing or decreasing water flux through defect-free regions. The presence of defects may explain why membrane power density in PRO is lower than that predicted based on
On the degree of generality of inflationary solutions in cosmological models with a scalar field
International Nuclear Information System (INIS)
Belinsky, V.A.; Khalatnikov, I.M.
1986-11-01
Homogeneous cosmological models of Bianchi I and Friedmann type in the presence of the massive scalar field are studied. Using qualitative theory of dynamical systems we show that the majority of solutions undergoes the inflationary stage. This study is the direct continuation of a previous paper. (author)
Pore-network modeling of solute transport and biofilm growth in porous media
Qin, Chao Zhong; Hassanizadeh, S. Majid
2015-01-01
In this work, a pore-network (PN) model for solute transport and biofilm growth in porous media was developed. Compared to previous studies of biofilm growth, it has two new features. First, the constructed pore network gives a better representation of a porous medium. Second, instead of using a
DEFF Research Database (Denmark)
Sloth, Peter
1988-01-01
Calculations of activity coefficients by application of the zero separation theorem is discussed for the restricted primitive model of electrolyte solutions. Numerical results within the framework of the hypernetted chain approximation are given. These indicate that the bridge functions—at zero s...
Koleva, D.A.; Hu, J.; De Wit, J.H.W.; Boshkov, N.; Radeva, T.; Milkova, V.; Van Breugel, K.
2010-01-01
This work reports on the electrochemical performance of low-carbon steel electrodes in model alkaline solutions in the presence of 4.9.10-4 g/l hybrid aggregates i.e. cement extract, containing PDADMAC (poly (diallyl, dimethyl ammonium chloride) / PAA (Poly (acrylic acid)/ PDADMAC over a CaO core.
McGuire, David; By, Rune Todnem; Hutchings, Kate
2007-01-01
Purpose: Achieving intergenerational interaction and avoiding conflict is becoming increasingly difficult in a workplace populated by three generations--Baby Boomers, Generation X-ers and Generation Y-ers. This paper presents a model and proposes HR solutions towards achieving co-operative generational interaction. Design/methodology/approach:…
Informed Conjecturing of Solutions for Differential Equations in a Modeling Context
Winkel, Brian
2015-01-01
We examine two differential equations. (i) first-order exponential growth or decay; and (ii) second order, linear, constant coefficient differential equations, and show the advantage of learning differential equations in a modeling context for informed conjectures of their solution. We follow with a discussion of the complete analysis afforded by…
An accurate coarse-grained model for chitosan polysaccharides in aqueous solution.
Directory of Open Access Journals (Sweden)
Levan Tsereteli
Full Text Available Computational models can provide detailed information about molecular conformations and interactions in solution, which is currently inaccessible by other means in many cases. Here we describe an efficient and precise coarse-grained model for long polysaccharides in aqueous solution at different physico-chemical conditions such as pH and ionic strength. The Model is carefully constructed based on all-atom simulations of small saccharides and metadynamics sampling of the dihedral angles in the glycosidic links, which represent the most flexible degrees of freedom of the polysaccharides. The model is validated against experimental data for Chitosan molecules in solution with various degree of deacetylation, and is shown to closely reproduce the available experimental data. For long polymers, subtle differences of the free energy maps of the glycosidic links are found to significantly affect the measurable polymer properties. Therefore, for titratable monomers the free energy maps of the corresponding links are updated according to the current charge of the monomers. We then characterize the microscopic and mesoscopic structural properties of large chitosan polysaccharides in solution for a wide range of solvent pH and ionic strength, and investigate the effect of polymer length and degree and pattern of deacetylation on the polymer properties.
Bowron, D T; Diaz-Moreno, S
2007-10-04
Hydrogen/deuterium isotopic neutron diffraction techniques have been used to investigate the structure of a 1 m aqueous solution of YCl3 at room temperature. Empirical potential structure refinement (EPSR) has been used to build a three-dimensional model of the solution structure that is consistent with the bulk solvent correlations strongly probed by the neutron scattering technique. Optimization of the local structural environment of the Y3+ ion sites within the model has been performed through calculations of the yttrium K-edge, extended X-ray absorption fine structure (EXAFS) spectrum of the solution, and detailed information has been extracted on the structure of the ion hydration shell and the extent of inner-sphere ion pairing within the solution. The results demonstrate the significant potential of this hybrid data analysis approach to circumvent the limitations of the individual experimental methods, to refine atomic potential models, and to produce accurate, quantitative structural models of the local environment of dilute atomic species within tightly constrained bulk network structures.
Bifurcating Solutions to the Monodomain Model Equipped with FitzHugh-Nagumo Kinetics
Directory of Open Access Journals (Sweden)
Robert Artebrant
2009-01-01
cells surrounded by collections of normal cells. Thus, the cell model features a discontinuous coefficient. Analytical techniques are applied to approximate the time-periodic solution that arises at the Hopf bifurcation point. Accurate numerical experiments are employed to complement our findings.
Additional disinfection with a modified salt solution in a root canal model
van der Waal, S.V.; Oonk, C.A.M.; Nieman, S.H.; Wesselink, P.R.; de Soet, J.J.; Crielaard, W.
2015-01-01
Objectives The aim of this study is to investigate the disinfecting properties of a modified salt solution (MSS) and calcium hydroxide (Ca(OH)2) in a non-direct-contact ex-vivo model. Methods Seventy-four single-canal roots infected with Enterococcus faecalis were treated with 1% sodium hypochlorite
Periodic solution of a stochastic SIRS epidemic model with seasonal variation.
Jin, Manli; Lin, Yuguo
2018-12-01
In this paper, we consider a stochastic SIRS epidemic model with seasonal variation and saturated incidence. Firstly, we obtain the threshold of stochastic system which determines whether the epidemic occurs or not. Secondly, we prove that there is a non-trivial positive periodic solution if [Formula: see text].
An explicit solution of the (quantum) elliptic Calogero-Sutherland model
Langmann, Edwin
2004-01-01
We present explicit formulas for the eigenvalues and eigenfunctions of the elliptic Calogero-Sutherland (eCS) model as formal power series to all orders in the nome of the elliptic functions, for arbitrary values of the (positive) coupling constant and particle number. Our solution gives explicit formulas for an elliptic deformation of the Jack polynomials.
Data collapse, scaling functions, and analytical solutions of generalized growth models.
Cabella, Brenno Caetano Troca; Martinez, Alexandre Souto; Ribeiro, Fabiano
2011-06-01
We consider a nontrivial one-species population dynamics model with finite and infinite carrying capacities. Time-dependent intrinsic and extrinsic growth rates are considered in these models. Through the model per capita growth rate we obtain a heuristic general procedure to generate scaling functions to collapse data into a simple linear behavior even if an extrinsic growth rate is included. With this data collapse, all the models studied become independent from the parameters and initial condition. Analytical solutions are found when time-dependent coefficients are considered. These solutions allow us to perceive nontrivial transitions between species extinction and survival and to calculate the transition's critical exponents. Considering an extrinsic growth rate as a cancer treatment, we show that the relevant quantity depends not only on the intensity of the treatment, but also on when the cancerous cell growth is maximum.
Directory of Open Access Journals (Sweden)
Jiang-Tao Li
2015-01-01
Full Text Available The nonlinear dual-porosity flow model, specifically considering the quadratic pressure gradient term, wellbore storage coefficient, well skin factor, and interporosity flow of matrix to natural fractures, was established for well production in a naturally fractured formation and then solved using a semianalytical method, including Laplace transform and a transformation of the pressure function. Analytical solution of the model in Laplace space was converted to numerical solution in real space using Stehfest numerical inversion. Nonlinear flow process for well production in a naturally fractured formation with different external boundaries was simulated and analyzed using standard pressure curves. Influence of the quadratic pressure gradient coefficient on pressure curves was studied qualitatively and quantitatively in conditions of a group of fixed model parameters. The research results show that the semianalytical modelling method is applicable in simulating the nonlinear dual-porosity flow behavior.
Hindcast of breaking waves and its impact at an island sheltered coast, Karwar
Dora, G. Udhaba; Kumar, V. Sanil
2018-01-01
Variability in the characteristics of depth-induced wave breakers along a non-uniform coastal topography and its impact on the morpho-sedimentary processes is examined at the island sheltered wave-dominated micro-tidal coast, Karwar, west coast of India. Waves are simulated using the coupled wind wave model, SWAN nested in WAVEWATCH III, forced by the reanalysis winds from different sources (NCEP/NCAR, ECMWF, and NCEP/CFSR). Impact of the wave breakers is evaluated through mean longshore current and sediment transport for various wave energy conditions across different coastal morphology. Study revealed that the NCEP/CFSR wind is comparatively reasonable in simulation of nearshore waves using the SWAN model nested by 2D wave spectra generated from WAVEWATCH III. The Galvin formula for estimating mean longshore current using the crest wave period and the Kamphuis approximation for longshore sediment transport is observed realistically at the sheltered coastal environment while the coast interacts with spilling and plunging breakers.
Asymptotic solution for the El Niño time delay sea—air oscillator model
International Nuclear Information System (INIS)
Mo Jia-Qi; Lin Wan-Tao; Lin Yi-Hua
2011-01-01
A sea—air oscillator model is studied using the time delay theory. The aim is to find an asymptotic solving method for the El Niño-southern oscillation (ENSO) model. Employing the perturbed method, an asymptotic solution of the corresponding problem is obtained. Thus we can obtain the prognoses of the sea surface temperature (SST) anomaly and the related physical quantities. (general)
Traveling Wave Solutions of Reaction-Diffusion Equations Arising in Atherosclerosis Models
Directory of Open Access Journals (Sweden)
Narcisa Apreutesei
2014-05-01
Full Text Available In this short review article, two atherosclerosis models are presented, one as a scalar equation and the other one as a system of two equations. They are given in terms of reaction-diffusion equations in an infinite strip with nonlinear boundary conditions. The existence of traveling wave solutions is studied for these models. The monostable and bistable cases are introduced and analyzed.
A hepatitis C virus infection model with time-varying drug effectiveness: solution and analysis.
Directory of Open Access Journals (Sweden)
Jessica M Conway
2014-08-01
Full Text Available Simple models of therapy for viral diseases such as hepatitis C virus (HCV or human immunodeficiency virus assume that, once therapy is started, the drug has a constant effectiveness. More realistic models have assumed either that the drug effectiveness depends on the drug concentration or that the effectiveness varies over time. Here a previously introduced varying-effectiveness (VE model is studied mathematically in the context of HCV infection. We show that while the model is linear, it has no closed-form solution due to the time-varying nature of the effectiveness. We then show that the model can be transformed into a Bessel equation and derive an analytic solution in terms of modified Bessel functions, which are defined as infinite series, with time-varying arguments. Fitting the solution to data from HCV infected patients under therapy has yielded values for the parameters in the model. We show that for biologically realistic parameters, the predicted viral decay on therapy is generally biphasic and resembles that predicted by constant-effectiveness (CE models. We introduce a general method for determining the time at which the transition between decay phases occurs based on calculating the point of maximum curvature of the viral decay curve. For the parameter regimes of interest, we also find approximate solutions for the VE model and establish the asymptotic behavior of the system. We show that the rate of second phase decay is determined by the death rate of infected cells multiplied by the maximum effectiveness of therapy, whereas the rate of first phase decline depends on multiple parameters including the rate of increase of drug effectiveness with time.
A Novel Solution to Sieving Model for a Drilling Fluid Shale Shaker
HeShun Wang; Xu Hao; WaNi Wu; WeiBing Zhu
2012-01-01
According to the principle of hydromechanics, the flow characteristic of drilling fluid on the screen is studied. In consideration of affecting factors, sieving model equations including kinematic equations and continuity equation for drilling fluid shale shaker are established. This paper shows a novel solution to the sieving model equations by using average energy principle and finite differential method. The computer simulation program of flow capacity of the shaker is developed. The mo...
SOLUTION OF MATHEMATICAL MODEL FOR TRACKED VEHICLE MOVEMENT UNDER DIFFERENT CONTROL ACTIONS
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S. Volosnikov
2017-06-01
Full Text Available The paper presents a solution to the mathematical model of the caterpillar platform motion in the process of going into corner at various speed of movement. The presented model made it possible to obtain characteristic trajectories of a caterpillar platform in a turn for different road conditions and control actions. The «steering wheel» and «levers», which are most widely used in turn control systems, are considered as controls for the caterpillar platform.
Evaluation of intraoperative infusion solution using a complete anhepatic model in baby pigs.
Komiya, K; Sato, Y; Wainai, T; Murayama, T; Yamada, M; Hiruta, A; Seo, N; Yoshino, H; Tanaka, H; Kobayashi, E
2005-06-01
Compared to cadaveric liver transplantation, living-related liver transplantation (LRLT) has the physiological advantage of avoiding hemodynamic changes due to the nonsystemic clamping of the inferior vena cava (IVC). However, metabolic changes in the level of blood glucose and lactate usually occur during the anhepatic phase in LRLT. For pediatric patients, intraoperative infusions have the potential to maintain immature homeostasis during LRLT. In the present study, a complete anhepatic model of baby pigs with nonsystemic clamping of IVC, which mimics the procedure of pediatric LRLT, was established using a heparin-coated tube as an internal shunt lactate Ringer solution (LR, Lactec), acetate Ringer solution (AR, VeenF), and a solution comprising acetate Ringer with 1% glucose (AR-G, Phisio140) were tested using piglets. Hemodynamic and metabolic (blood gas analysis, electrolytes, blood lactate, and glucose) changes were observed during the anhepatic phase. Although no major difference was observed in hemodynamic parameters, arterial blood gas data, or concentration of electrolytes among the three solution groups, significant progressive hyperlactatemia was observed in the LR group. Also, though severe hypoglycemia was found in the LR and AR groups, the AR-G group maintained blood glucose levels throughout the anhepatic phase. To conclude, using the simplified pig anhepatic model, we evaluated various solutions for pediatric LRLT.
Numerical Solution of Fractional Neutron Point Kinetics Model in Nuclear Reactor
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Nowak Tomasz Karol
2014-06-01
Full Text Available This paper presents results concerning solutions of the fractional neutron point kinetics model for a nuclear reactor. Proposed model consists of a bilinear system of fractional and ordinary differential equations. Three methods to solve the model are presented and compared. The first one entails application of discrete Grünwald-Letnikov definition of the fractional derivative in the model. Second involves building an analog scheme in the FOMCON Toolbox in MATLAB environment. Third is the method proposed by Edwards. The impact of selected parameters on the model’s response was examined. The results for typical input were discussed and compared.
A comparison of two- and three-dimensional stochastic models of regional solute movement
Shapiro, A.M.; Cvetkovic, V.D.
1990-01-01
Recent models of solute movement in porous media that are based on a stochastic description of the porous medium properties have been dedicated primarily to a three-dimensional interpretation of solute movement. In many practical problems, however, it is more convenient and consistent with measuring techniques to consider flow and solute transport as an areal, two-dimensional phenomenon. The physics of solute movement, however, is dependent on the three-dimensional heterogeneity in the formation. A comparison of two- and three-dimensional stochastic interpretations of solute movement in a porous medium having a statistically isotropic hydraulic conductivity field is investigated. To provide an equitable comparison between the two- and three-dimensional analyses, the stochastic properties of the transmissivity are defined in terms of the stochastic properties of the hydraulic conductivity. The variance of the transmissivity is shown to be significantly reduced in comparison to that of the hydraulic conductivity, and the transmissivity is spatially correlated over larger distances. These factors influence the two-dimensional interpretations of solute movement by underestimating the longitudinal and transverse growth of the solute plume in comparison to its description as a three-dimensional phenomenon. Although this analysis is based on small perturbation approximations and the special case of a statistically isotropic hydraulic conductivity field, it casts doubt on the use of a stochastic interpretation of the transmissivity in describing regional scale movement. However, by assuming the transmissivity to be the vertical integration of the hydraulic conductivity field at a given position, the stochastic properties of the hydraulic conductivity can be estimated from the stochastic properties of the transmissivity and applied to obtain a more accurate interpretation of solute movement. ?? 1990 Kluwer Academic Publishers.
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
Directory of Open Access Journals (Sweden)
Petráš Ivo
2011-01-01
Full Text Available This paper deals with the fractional-order linear and nonlinear models used in bioengineering applications and an effective method for their numerical solution. The proposed method is based on the power series expansion of a generating function. Numerical solution is in the form of the difference equation, which can be simply applied in the Matlab/Simulink to simulate the dynamics of system. Several illustrative examples are presented, which can be widely used in bioengineering as well as in the other disciplines, where the fractional calculus is often used.
The Complete Solution of the Core-Periphery Model for two Regions using Successive Approximations
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Catalin Angelo Ioan
2012-02-01
Full Text Available In this paper it is give the complete solution, using the Newton’s method of approximation,for the well known Krugman’s Core-Periphery model for two regions. After the process of reductionof the system of conditions, using appropriate substitutions, it is obtained one equation which is thekey of the problem’s solving. After the presentation of the iterative formula which gives the solution,the principal indicators (regional incomes, the prices indexes of manufactured goods and the realwage of workers are calculated.
Constructing Soliton and Kink Solutions of PDE Models in Transport and Biology
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Vsevolod A. Vladimirov
2006-06-01
Full Text Available We present a review of our recent works directed towards discovery of a periodic, kink-like and soliton-like travelling wave solutions within the models of transport phenomena and the mathematical biology. Analytical description of these wave patterns is carried out by means of our modification of the direct algebraic balance method. In the case when the analytical description fails, we propose to approximate invariant travelling wave solutions by means of an infinite series of exponential functions. The effectiveness of the method of approximation is demonstrated on a hyperbolic modification of Burgers equation.
The Train Driver Recovery Problem - a Set Partitioning Based Model and Solution Method
DEFF Research Database (Denmark)
Rezanova, Natalia Jurjevna; Ryan, David
2010-01-01
The need to recover a train driver schedule occurs during major disruptions in the daily railway operations. Based on data from the Danish passenger railway operator DSB S-tog A/S, a solution method to the train driver recovery problem (TDRP) is developed. The TDRP is formulated as a set...... partitioning problem. We define a disruption neighbourhood by identifying a small set of drivers and train tasks directly affected by the disruption. Based on the disruption neighbourhood, the TDRP model is formed and solved. If the TDRP solution provides a feasible recovery for the drivers within...
An integrated radar model solution for mission level performance and cost trades
Hodge, John; Duncan, Kerron; Zimmerman, Madeline; Drupp, Rob; Manno, Mike; Barrett, Donald; Smith, Amelia
2017-05-01
A fully integrated Mission-Level Radar model is in development as part of a multi-year effort under the Northrop Grumman Mission Systems (NGMS) sector's Model Based Engineering (MBE) initiative to digitally interconnect and unify previously separate performance and cost models. In 2016, an NGMS internal research and development (IR and D) funded multidisciplinary team integrated radio frequency (RF), power, control, size, weight, thermal, and cost models together using a commercial-off-the-shelf software, ModelCenter, for an Active Electronically Scanned Array (AESA) radar system. Each represented model was digitally connected with standard interfaces and unified to allow end-to-end mission system optimization and trade studies. The radar model was then linked to the Air Force's own mission modeling framework (AFSIM). The team first had to identify the necessary models, and with the aid of subject matter experts (SMEs) understand and document the inputs, outputs, and behaviors of the component models. This agile development process and collaboration enabled rapid integration of disparate models and the validation of their combined system performance. This MBE framework will allow NGMS to design systems more efficiently and affordably, optimize architectures, and provide increased value to the customer. The model integrates detailed component models that validate cost and performance at the physics level with high-level models that provide visualization of a platform mission. This connectivity of component to mission models allows hardware and software design solutions to be better optimized to meet mission needs, creating cost-optimal solutions for the customer, while reducing design cycle time through risk mitigation and early validation of design decisions.
Extremal solutions of the S3 model and nilpotent orbits of G2(2)
Kim, Sung-Soo; Lindman Hörnlund, Josef; Palmkvist, Jakob; Virmani, Amitabh
2010-08-01
We study extremal black hole solutions of the S3 model (obtained by setting S=T=U in the STU model) using group theoretical methods. Upon dimensional reduction over time, the S3 model exhibits the pseudo-Riemannian coset structure {{G} left/ {{tilde{K}}} right.} with G = G2(2) and tilde{K} = {text{S}}{{text{O}}_0}left( {2,2} right) . We study nilpotent tilde{K} -orbits of G2(2) corresponding to non-rotating single-center extremal solutions. We find six such distinct tilde{K} -orbits. Three of these orbits are supersymmetric, one is non-supersymmetric, and two are unphysical. We write general solutions and discuss examples in all four physical orbits. We show that all solutions in supersymmetric orbits when uplifted to five-dimensional minimal supergravity have single-center Gibbons-Hawking space as their four-dimensional Euclidean hyper-Kähler base space. We construct hitherto unknown extremal (supersymmetric as well as non-supersymmetric) pressureless black strings of minimal five-dimensional supergravity and briefly discuss their relation to black rings.
A three-dimensional spectral element model for the solution of the hydrostatic primitive equations
International Nuclear Information System (INIS)
Iskandarani, M.; Haidvogel, D.B.; Levin, J.C.
2003-01-01
We present a spectral element model to solve the hydrostatic primitive equations governing large-scale geophysical flows. The highlights of this new model include unstructured grids, dual h-p paths to convergence, and good scalability characteristics on present day parallel computers including Beowulf-class systems. The behavior of the model is assessed on three process-oriented test problems involving wave propagation, gravitational adjustment, and nonlinear flow rectification, respectively. The first of these test problems is a study of the convergence properties of the model when simulating the linear propagation of baroclinic Kelvin waves. The second is an intercomparison of spectral element and finite-difference model solutions to the adjustment of a density front in a straight channel. Finally, the third problem considers the comparison of model results to measurements obtained from a laboratory simulation of flow around a submarine canyon. The aforementioned tests demonstrate the good performance of the model in the idealized/process-oriented limits
Existence, uniqueness and positivity of solutions for BGK models for mixtures
Klingenberg, C.; Pirner, M.
2018-01-01
We consider kinetic models for a multi component gas mixture without chemical reactions. In the literature, one can find two types of BGK models in order to describe gas mixtures. One type has a sum of BGK type interaction terms in the relaxation operator, for example the model described by Klingenberg, Pirner and Puppo [20] which contains well-known models of physicists and engineers for example Hamel [16] and Gross and Krook [15] as special cases. The other type contains only one collision term on the right-hand side, for example the well-known model of Andries, Aoki and Perthame [1]. For each of these two models [20] and [1], we prove existence, uniqueness and positivity of solutions in the first part of the paper. In the second part, we use the first model [20] in order to determine an unknown function in the energy exchange of the macroscopic equations for gas mixtures described by Dellacherie [11].
Exact solutions to a schematic nuclear quark model and colorless superconductivity
DEFF Research Database (Denmark)
Bohr, Henrik; da Providencia, Joao
2008-01-01
Exact solutions are found to the equations of a standard nuclear quark model exemplified by the Bonn model which is defined in terms of an effective pairing force. We show, by symmetry arguments, that, in general, the ground state of this model is not color neutral. In particular, color......-neutral states have, in general, higher energy than the ground state. A novel BCS-type formalism, which is able to describe exactly color symmetrical BCS states, is used to show that the model admits, but only as excited states, color-neutral superconductivity. Therefore, such a model, with just a pairing force......, is unrealistic as a model for the color-neutral confined phase which prevails at normal nuclear densities. Finally, the paper shows that there exists a color-neutral superconducting phase independently of whether the model is based on the pairing force or a more realistic three-body string force....
Elqotbi, Mohammed; Vlaev, S.D.; Montastruc, Ludovic; Nikov, Iordan
2013-01-01
International audience; An advanced study of a bioreactor system involving a Navier-Stokes based model has been accomplished. The model allows a more realistic impeller induced flow image to be combined with the Monod bioreaction kinetics reported previously. The time-course of gluconic acid production by Aspergillus niger strain is simulated at kinetic conditions proposed in the literature. The simulation is based on (1) a stepwise solution strategy resolving first the fluid flow field, furt...
Exact solution of the O(n) model on a random lattice
DEFF Research Database (Denmark)
Eynard, B.; Kristjansen, C.
1995-01-01
We present an exact solution of the O(n) model on a random lattice. The coupling constant space of our model is parametrized in terms of a set of moment variables and the same type of universality with respect to the potential as observed for the one-matrix model is found. In addition we find...... a large degree of universality with respect to n; namely for n gE ] - 2,2[ the solution can be presented in a form which is valid not only for any potential, but also for any n (not necessarily rational). The cases n = ±2 are treated separately. We give explicit expressions for the genus-zero contribution...
Boroujeni, Mahdi K.; Goodarzi, F.
2011-09-01
In present study, a special mathematical model for membrane separation processes was studied. Mathematical model was developed for propylene/propane system and was solved using finite difference solution approach. In this study, membrane length is shared into a number of nodes and required equations are written for each node, separately. Also, golden section method was used for suitable step size selection. It is prescience that the results accuracy and calculation time, depend on number of meshes. Therefore 20 meshes were obtained as an optimum number. The effect of pressure drop equation on solution procedure of the model was also investigated and it was found that the pressure drop equation has a negligible effect on it.
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
Hydrodynamics with strength: scaling-invariant solutions for elastic-plastic cavity expansion models
Albright, Jason; Ramsey, Scott; Baty, Roy
2017-11-01
Spherical cavity expansion (SCE) models are used to describe idealized detonation and high-velocity impact in a variety of materials. The common theme in SCE models is the presence of a pressure-driven cavity or void within a domain comprised of plastic and elastic response sub-regions. In past work, the yield criterion characterizing material strength in the plastic sub-region is usually taken for granted and assumed to take a known functional form restrictive to certain classes of materials, e.g. ductile metals or brittle geologic materials. Our objective is to systematically determine a general functional form for the yield criterion under the additional requirement that the SCE admits a similarity solution. Solutions determined under this additional requirement have immediate implications toward development of new compressible flow algorithm verification test problems. However, more importantly, these results also provide novel insight into modeling the yield criteria from the perspective of hydrodynamic scaling.
Reed, H; Leckey, Cara A C; Dick, A; Harvey, G; Dobson, J
2018-01-01
Ultrasonic damage detection and characterization is commonly used in nondestructive evaluation (NDE) of aerospace composite components. In recent years there has been an increased development of guided wave based methods. In real materials and structures, these dispersive waves result in complicated behavior in the presence of complex damage scenarios. Model-based characterization methods utilize accurate three dimensional finite element models (FEMs) of guided wave interaction with realistic damage scenarios to aid in defect identification and classification. This work describes an inverse solution for realistic composite damage characterization by comparing the wavenumber-frequency spectra of experimental and simulated ultrasonic inspections. The composite laminate material properties are first verified through a Bayesian solution (Markov chain Monte Carlo), enabling uncertainty quantification surrounding the characterization. A study is undertaken to assess the efficacy of the proposed damage model and comparative metrics between the experimental and simulated output. The FEM is then parameterized with a damage model capable of describing the typical complex damage created by impact events in composites. The damage is characterized through a transdimensional Markov chain Monte Carlo solution, enabling a flexible damage model capable of adapting to the complex damage geometry investigated here. The posterior probability distributions of the individual delamination petals as well as the overall envelope of the damage site are determined. Copyright © 2017 Elsevier B.V. All rights reserved.
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Mohammad Golriz
2017-03-01
Conclusion: Although the new preservation HTK solution is in several points a well-thought-out modification of the standard HTK solution, its preservation efficacy, at least for kidney preservation in a pig model for 30 hours, seems to be comparable to the current used solutions. A real advantage, however, could be confirmed in clinical settings, where marginal organs may influence the clinical outcome.
Constantin, Julian Gelman; Schneider, Matthias; Corti, Horacio R
2016-06-09
The glass transition temperature of trehalose, sucrose, glucose, and fructose aqueous solutions has been predicted as a function of the water content by using the free volume/percolation model (FVPM). This model only requires the molar volume of water in the liquid and supercooled regimes, the molar volumes of the hypothetical pure liquid sugars at temperatures below their pure glass transition temperatures, and the molar volumes of the mixtures at the glass transition temperature. The model is simplified by assuming that the excess thermal expansion coefficient is negligible for saccharide-water mixtures, and this ideal FVPM becomes identical to the Gordon-Taylor model. It was found that the behavior of the water molar volume in trehalose-water mixtures at low temperatures can be obtained by assuming that the FVPM holds for this mixture. The temperature dependence of the water molar volume in the supercooled region of interest seems to be compatible with the recent hypothesis on the existence of two structure of liquid water, being the high density liquid water the state of water in the sugar solutions. The idealized FVPM describes the measured glass transition temperature of sucrose, glucose, and fructose aqueous solutions, with much better accuracy than both the Gordon-Taylor model based on an empirical kGT constant dependent on the saccharide glass transition temperature and the Couchman-Karasz model using experimental heat capacity changes of the components at the glass transition temperature. Thus, FVPM seems to be an excellent tool to predict the glass transition temperature of other aqueous saccharides and polyols solutions by resorting to volumetric information easily available.
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.
He, E.; Qiu, Hao; van Gestel, C.A.M.
2014-01-01
Protons and other cations may inhibit metal uptake and alleviate metal toxicity in aquatic organisms, but less is known about these interactions in soil organisms. The present study investigated the influence of solution chemistry on uptake and toxicity of Ni in Enchytraeus crypticus after 14 days
Modeling the liquid-liquid interface and the transfer of a solute by molecular dynamics simulation
International Nuclear Information System (INIS)
Hayoun, Marc
1990-11-01
Molecular Dynamics method and Lennard-Jones potential functions have been employed to model Liquid-Liquid Interfaces. The variation of the miscibilities between the two liquids is obtained by changing the interaction between the two atomic species. The resulting interfaces have a thickness of about three atomic diameters and are stable on the time scale of the simulation. They have been characterized by the density and pressure profiles. The interfacial tension has also been computed and is of the order of magnitude of experimental values. The diffusion process is anisotropic in the interfacial region: the transverse diffusion coefficient (parallelly to the interface) is higher than the normal one. A qualitative explanation of this behaviour is suggested by considering the pressure tensor. The second part of this work, performed by Molecular Dynamics in the canonical ensemble, is devoted to the kinetic study of the transfer of a solute through the interface. A model of a symmetric interface with an atomic solute has been used. The interaction potential between the solute and the solvents has been built in order to obtain an activation barrier to the transfer. We have computed the mean force exerted by the solvent on the solute as a function of its distance to the interface. The resulting mean force potential corresponds to a free energy difference. The height of the energy barrier involved is about 4 kT. The potential energy and entropy profiles have also been calculated and discussed. The diffusion coefficient of the solute has been computed by equilibrium and non-equilibrium methods. We deduced the friction coefficient of the solvent, which is essential to determine the Kramers transmission coefficient. This coefficient is compared to the one obtained by simulation. Finally, the solute transfer rate constant has been calculated. (author) [fr
Symmetry-dictated trucation: Solutions of the spherical shell model for heavy nuclei
International Nuclear Information System (INIS)
Guidry, M.W.
1992-01-01
Principles of dynamical symmetry are used to simplify the spherical shell model. The resulting symmetry-dictated truncation leads to dynamical symmetry solutions that are often in quantitative agreement with a variety of observables. Numerical calculations, including terms that break the dynamical symmetries, are shown that correspond to shell model calculations for heavy deformed nuclei. The effective residual interaction is simple, well-behaved, and can be determined from basic observables. With this approach, we intend to apply the shell model in systematic fashion to all nuclei. The implications for nuclear structure far from stability and for nuclear masses and other quantities of interest in astrophysics are discussed
Original analytic solution of a half-bridge modelled as a statically indeterminate system
Oanta, Emil M.; Panait, Cornel; Raicu, Alexandra; Barhalescu, Mihaela
2016-12-01
The paper presents an original computer based analytical model of a half-bridge belonging to a circular settling tank. The primary unknown is computed using the force method, the coefficients of the canonical equation being calculated using either the discretization of the bending moment diagram in trapezoids, or using the relations specific to the polygons. A second algorithm based on the method of initial parameters is also presented. Analyzing the new solution we came to the conclusion that most of the computer code developed for other model may be reused. The results are useful to evaluate the behavior of the structure and to compare with the results of the finite element models.
Global stability, periodic solutions, and optimal control in a nonlinear differential delay model
Directory of Open Access Journals (Sweden)
Anatoli F. Ivanov
2010-09-01
Full Text Available A nonlinear differential equation with delay serving as a mathematical model of several applied problems is considered. Sufficient conditions for the global asymptotic stability and for the existence of periodic solutions are given. Two particular applications are treated in detail. The first one is a blood cell production model by Mackey, for which new periodicity criteria are derived. The second application is a modified economic model with delay due to Ramsey. An optimization problem for a maximal consumption is stated and solved for the latter.
Benchmarking the invariant embedding method against analytical solutions in model transport problems
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Wahlberg Malin
2006-01-01
Full Text Available The purpose of this paper is to demonstrate the use of the invariant embedding method in a few model transport problems for which it is also possible to obtain an analytical solution. The use of the method is demonstrated in three different areas. The first is the calculation of the energy spectrum of sputtered particles from a scattering medium without absorption, where the multiplication (particle cascade is generated by recoil production. Both constant and energy dependent cross-sections with a power law dependence were treated. The second application concerns the calculation of the path length distribution of reflected particles from a medium without multiplication. This is a relatively novel application, since the embedding equations do not resolve the depth variable. The third application concerns the demonstration that solutions in an infinite medium and in a half-space are interrelated through embedding-like integral equations, by the solution of which the flux reflected from a half-space can be reconstructed from solutions in an infinite medium or vice versa. In all cases, the invariant embedding method proved to be robust, fast, and monotonically converging to the exact solutions.
Multidimensional Gravitational Models: Fluxbrane and S-Brane Solutions with Polynomials
International Nuclear Information System (INIS)
Ivashchuk, V. D.; Melnikov, V. N.
2007-01-01
Main results in obtaining exact solutions for multidimensional models and their application to solving main problems of modern cosmology and black hole physics are described. Some new results on composite fluxbrane and S-brane solutions for a wide class of intersection rules are presented. These solutions are defined on a product manifold R* x M1 x ... x Mn which contains n Ricci-flat spaces M1,...,Mn with 1-dimensional R* and M1. They are defined up to a set of functions obeying non-linear differential equations equivalent to Toda-type equations with certain boundary conditions imposed. Exact solutions corresponding to configurations with two branes and intersections related to simple Lie algebras C2 and G2 are obtained. In these cases the functions Hs(z), s = 1, 2, are polynomials of degrees: (3, 4) and (6, 10), respectively, in agreement with a conjecture suggested earlier. Examples of simple S-brane solutions describing an accelerated expansion of a certain factor-space are given explicitely
Dilatonic dyon-like black hole solutions in the model with two Abelian gauge fields
Energy Technology Data Exchange (ETDEWEB)
Abishev, M.E. [Institute of Experimental and Theoretical Physics, Al-Farabi Kazakh National University, Almaty (Kazakhstan); Institute of Gravitation and Cosmology, RUDN University, Moscow (Russian Federation); Boshkayev, K.A. [Institute of Experimental and Theoretical Physics, Al-Farabi Kazakh National University, Almaty (Kazakhstan); Ivashchuk, V.D. [Center for Gravitation and Fundamental Metrology, VNIIMS, Moscow (Russian Federation); Institute of Gravitation and Cosmology, RUDN University, Moscow (Russian Federation)
2017-03-15
Dilatonic black hole dyon-like solutions in the gravitational 4d model with a scalar field, two 2-forms, two dilatonic coupling constants λ{sub i} ≠ 0, i = 1,2, obeying λ{sub 1} ≠ -λ{sub 2} and the sign parameter ε = ±1 for scalar field kinetic term are considered. Here ε = -1 corresponds to a ghost scalar field. These solutions are defined up to solutions of two master equations for two moduli functions, when λ{sup 2}{sub i} ≠ 1/2 for ε = -1. Some physical parameters of the solutions are obtained: gravitational mass, scalar charge, Hawking temperature, black hole area entropy and parametrized post-Newtonian (PPN) parameters β and γ. The PPN parameters do not depend on the couplings λ{sub i} and ε. A set of bounds on the gravitational mass and scalar charge are found by using a certain conjecture on the parameters of solutions, when 1 + 2λ{sub i}{sup 2} ε > 0, i = 1,2. (orig.)
(Liquid plus liquid) equilibria of binary polymer solutions using a free-volume UNIQUAC-NRF model
DEFF Research Database (Denmark)
Radfarnia, H.R.; Ghotbi, C.; Taghikhani, V.
2006-01-01
+ liquid) equilibria (LLE) for a number of binary polymer solutions at various temperatures. The values for the binary characteristic energy parameters for the proposed model and the FV-UNIQUAC model along with their average relative deviations from the experimental data were reported. It should be stated...... that the binary polymer solutions studied in this work were considered as monodisperse. The results obtained from the FV-UNIQUAC-NRF model were compared with those obtained from the FV-UNIQUAC model. The results of the proposed model show that the FV-UNIQUAC-NRF model can accurately correlate the experimental...... in predicting the LCST for binary polymer solutions....
Modelling the Hydraulic Behaviour of Growing Media with the Explicit Finite Volume Solution
Directory of Open Access Journals (Sweden)
Marco Carbone
2015-02-01
Full Text Available The increasing imperviousness of urban areas reduces the infiltration and evapotranspiration capacity of urban catchments and results in increased runoff. In the last few decades, several solutions and techniques have been proposed to prevent such impacts by restoring the hydrological cycle. A limiting factor in spreading the use of such systems is the lack of proper modelling tools for design, especially for the infiltration processes in a growing medium. In this research, a physically-based model, employing the explicit Finite Volume Method (FVM, is proposed for modelling infiltration into growing media. The model solves a modified version of the Richards equation using a formulation which takes into account the main characteristics of green infrastructure substrates. The proposed model was verified against the HYDRUS-1D software and the comparison of results confirmed the suitability of the proposed model for correctly describing the hydraulic behaviour of soil substrates.
On distinguishing different models of a class of emergent Universe solutions
Ghose, Souvik
2018-03-01
A specific class of singularity-free cosmological model has recently been considered in light of different observational data such as observed Hubble data, BAO data from luminous red galaxy survey by Slowan digital sky survey (SDSS) and CMB data from WMAP. However, it is observed that only 12-14 data points are used to study the viability of the model in late time. In this paper, we discuss the viability of all the models belonging to the same class of EU in light of union compilation data (SNIa) which consists of over a hundred data points, thus getting a more robust test for viability. More importantly, it is crucial that we can distinguish between the various models proposed in the class of solution obtained. We discuss here why with the present observational data it is difficult to distinguish between all of them. We show that the late-time behaviour of the model is typical to any asymptotically de Sitter model.
A three-dimensional spectral element model for the solution of the hydrostatic primitive equations
Iskandarani, M; Levin, J C
2003-01-01
We present a spectral element model to solve the hydrostatic primitive equations governing large-scale geophysical flows. The highlights of this new model include unstructured grids, dual h-p paths to convergence, and good scalability characteristics on present day parallel computers including Beowulf-class systems. The behavior of the model is assessed on three process-oriented test problems involving wave propagation, gravitational adjustment, and nonlinear flow rectification, respectively. The first of these test problems is a study of the convergence properties of the model when simulating the linear propagation of baroclinic Kelvin waves. The second is an intercomparison of spectral element and finite-difference model solutions to the adjustment of a density front in a straight channel. Finally, the third problem considers the comparison of model results to measurements obtained from a laboratory simulation of flow around a submarine canyon. The aforementioned tests demonstrate the good performance of th...
Quesnel, Kimberly J.; Ajami, Newsha K.; Wyss, Noemi
2017-11-01
Modern challenges require new approaches to urban water management. One solution in the portfolio of potential strategies is the integration of distributed water infrastructure, practices, and technologies into existing systems. However, many practical barriers have prevented the widespread adoption of these systems in the US. The objective of this paper is to address these challenges by developing a conceptual model encompassing regulatory, financial, and governance components that can be used to incorporate new distributed water solutions into our current network. To construct the model, case studies of successfully implemented distributed electricity systems, specifically energy efficiency and renewable energy technologies, were examined to determine how these solutions have become prominent in recent years and what lessons can be applied to the water sector in a similar pursuit. The proposed model includes four action-oriented elements: catalyzing change, establishing funding sources, using resource pathways, and creating innovative governance structures. As illustrated in the model, the water sector should use suite of coordinated policies to promote change, engage end users through fiscal incentives, and encourage research, development and dissemination of new technologies over time.
Solution chemistry of Mo(III) and Mo(IV): Thermodynamic foundation for modeling localized corrosion
International Nuclear Information System (INIS)
Wang Peiming; Wilson, Leslie L.; Wesolowski, David J.; Rosenqvist, Joergen; Anderko, Andrzej
2010-01-01
To investigate the behavior of molybdenum dissolution products in systems that approximate localized corrosion environments, solubility of Mo(III) in equilibrium with solid MoO 2 has been determined at 80 deg. C as a function of solution acidity, chloride concentration and partial pressure of hydrogen. The measurements indicate a strong increase in solubility with acidity and chloride concentration and a weak effect of hydrogen partial pressure. The obtained results have been combined with literature data for systems containing Mo(III), Mo(IV), and Mo(VI) in solutions to develop a comprehensive thermodynamic model of aqueous molybdenum chemistry. The model is based on a previously developed framework for simulating the properties of electrolyte systems ranging from infinite dilution to solid saturation or fused salt limit. To reproduce the measurements, the model assumes the presence of a chloride complex of Mo(III) (i.e., MoCl 2+ ) and hydrolyzed species (MoOH 2+ , Mo(OH) 2 + , and Mo(OH) 3 0 ) in addition to the Mo 3+ ion. The model generally reproduces the experimental data within experimental scattering and provides a tool for predicting the phase behavior and speciation in complex, concentrated aqueous solutions. Thus, it provides a foundation for simulating the behavior of molybdenum species in localized corrosion environments.
Modeling IoT-Based Solutions Using Human-Centric Wireless Sensor Networks
Directory of Open Access Journals (Sweden)
Álvaro Monares
2014-08-01
Full Text Available The Internet of Things (IoT has inspired solutions that are already available for addressing problems in various application scenarios, such as healthcare, security, emergency support and tourism. However, there is no clear approach to modeling these systems and envisioning their capabilities at the design time. Therefore, the process of designing these systems is ad hoc and its real impact is evaluated once the solution is already implemented, which is risky and expensive. This paper proposes a modeling approach that uses human-centric wireless sensor networks to specify and evaluate models of IoT-based systems at the time of design, avoiding the need to spend time and effort on early implementations of immature designs. It allows designers to focus on the system design, leaving the implementation decisions for a next phase. The article illustrates the usefulness of this proposal through a running example, showing the design of an IoT-based solution to support the first responses during medium-sized or large urban incidents. The case study used in the proposal evaluation is based on a real train crash. The proposed modeling approach can be used to design IoT-based systems for other application scenarios, e.g., to support security operatives or monitor chronic patients in their homes.
Quesnel, Kimberly J; Ajami, Newsha K; Wyss, Noemi
2017-11-01
Modern challenges require new approaches to urban water management. One solution in the portfolio of potential strategies is the integration of distributed water infrastructure, practices, and technologies into existing systems. However, many practical barriers have prevented the widespread adoption of these systems in the US. The objective of this paper is to address these challenges by developing a conceptual model encompassing regulatory, financial, and governance components that can be used to incorporate new distributed water solutions into our current network. To construct the model, case studies of successfully implemented distributed electricity systems, specifically energy efficiency and renewable energy technologies, were examined to determine how these solutions have become prominent in recent years and what lessons can be applied to the water sector in a similar pursuit. The proposed model includes four action-oriented elements: catalyzing change, establishing funding sources, using resource pathways, and creating innovative governance structures. As illustrated in the model, the water sector should use suite of coordinated policies to promote change, engage end users through fiscal incentives, and encourage research, development and dissemination of new technologies over time.
Exact solution of the p + ip pairing Hamiltonian and a hierarchy of integrable models
International Nuclear Information System (INIS)
Dunning, Clare; Ibañez, Miguel; Sierra, Germán; Links, Jon; Zhao, Shao-You
2010-01-01
Using the well-known trigonometric six-vertex solution of the Yang–Baxter equation we derive an integrable pairing Hamiltonian with anyonic degrees of freedom. The exact algebraic Bethe ansatz solution is obtained using standard techniques. From this model we obtain several limiting models, including the pairing Hamiltonian with p + ip-wave symmetry. An in-depth study of the p + ip model is then undertaken, including a mean-field analysis, analytical and numerical solutions of the Bethe ansatz equations and an investigation of the topological properties of the ground-state wavefunction. Our main result is that the ground-state phase diagram of the p + ip model consists of three phases. There is the known boundary line with gapless excitations that occurs for vanishing chemical potential, separating the topologically trivial strong pairing phase and the topologically non-trivial weak pairing phase. We argue that a second boundary line exists separating the weak pairing phase from a topologically trivial weak coupling BCS phase, which includes the Fermi sea in the limit of zero coupling. The ground state on this second boundary line is the Moore–Read state
Modeling IoT-based solutions using human-centric wireless sensor networks.
Monares, Álvaro; Ochoa, Sergio F; Santos, Rodrigo; Orozco, Javier; Meseguer, Roc
2014-08-25
The Internet of Things (IoT) has inspired solutions that are already available for addressing problems in various application scenarios, such as healthcare, security, emergency support and tourism. However, there is no clear approach to modeling these systems and envisioning their capabilities at the design time. Therefore, the process of designing these systems is ad hoc and its real impact is evaluated once the solution is already implemented, which is risky and expensive. This paper proposes a modeling approach that uses human-centric wireless sensor networks to specify and evaluate models of IoT-based systems at the time of design, avoiding the need to spend time and effort on early implementations of immature designs. It allows designers to focus on the system design, leaving the implementation decisions for a next phase. The article illustrates the usefulness of this proposal through a running example, showing the design of an IoT-based solution to support the first responses during medium-sized or large urban incidents. The case study used in the proposal evaluation is based on a real train crash. The proposed modeling approach can be used to design IoT-based systems for other application scenarios, e.g., to support security operatives or monitor chronic patients in their homes.
Effect of heat/pressure on cyanidin-3-glucoside ethanol model solutions
International Nuclear Information System (INIS)
Corrales, M; Lindauer, R; Butz, P; Tauscher, B
2008-01-01
The stability of cyanidin-3-glucoside (Cy3gl) in 50% ethanol model solutions under heat/pressure treatments was investigated. Cy3gl was rapidly degraded when solutions were subjected to a heat/pressure treatment. The higher the pressure and the temperature used, the higher the degradation. Moreover, the degradation was increased according to increasing holding times. Parallel to the degradation of Cy3gl several hydrolytic products were formed and identified by LC-DAD/ESI-MS. The degradation of Cy3gl was well fitted to a first order reaction (R=0.99). This study pointed out the rate of susceptibility of Cy3gl in model solutions to degrade when exposed to a heat/pressure treatment and the trigger effect of high hydrostatic pressure to hydrolyse Cy3gl. By contrast, the degradation of anthocyanins in a food matrix (red grape extract solutions) was negligible after a heat/pressure process at 600MPa, 70 deg. C during 1h (P >0.05)
An analytic solution for numerical modeling validation in electromagnetics: the resistive sphere
Swidinsky, Andrei; Liu, Lifei
2017-11-01
We derive the electromagnetic response of a resistive sphere to an electric dipole source buried in a conductive whole space. The solution consists of an infinite series of spherical Bessel functions and associated Legendre polynomials, and follows the well-studied problem of a conductive sphere buried in a resistive whole space in the presence of a magnetic dipole. Our result is particularly useful for controlled-source electromagnetic problems using a grounded electric dipole transmitter and can be used to check numerical methods of calculating the response of resistive targets (such as finite difference, finite volume, finite element and integral equation). While we elect to focus on the resistive sphere in our examples, the expressions in this paper are completely general and allow for arbitrary source frequency, sphere radius, transmitter position, receiver position and sphere/host conductivity contrast so that conductive target responses can also be checked. Commonly used mesh validation techniques consist of comparisons against other numerical codes, but such solutions may not always be reliable or readily available. Alternatively, the response of simple 1-D models can be tested against well-known whole space, half-space and layered earth solutions, but such an approach is inadequate for validating models with curved surfaces. We demonstrate that our theoretical results can be used as a complementary validation tool by comparing analytic electric fields to those calculated through a finite-element analysis; the software implementation of this infinite series solution is made available for direct and immediate application.
Simulation of solute transport in a mountain pool-and-riffle stream: A transient storage model
Bencala, Kenneth E.; Walters, Roy A.
1983-01-01
The physical characteristics of mountain streams differ from the uniform and conceptually well- defined open channels for which the analysis of solute transport has been oriented in the past and is now well understood. These physical conditions significantly influence solute transport behavior, as demonstrated by a transient storage model simulation of solute transport in a very small (0.0125 m3s−1) mountain pool-and-riffle stream. The application is to a carefully controlled and intensively monitored chloride injection experiment. The data from the experiment are not explained by the standard convection-dispersion mechanisms alone. A transient storage model, which couples dead zones with the one-dimensional convection-dispersion equation, simulates the general characteristics of the solute transport behavior and a set of simulation parameters were determined that yield an adequate fit to the data. However, considerable uncertainty remains in determining physically realistic values of these parameters. The values of the simulation parameters used are compared to values used by other authors for other streams. The comparison supports, at least qualitatively, the determined parameter values.
Analytical Solutions for Rumor Spreading Dynamical Model in a Social Network
Fallahpour, R.; Chakouvari, S.; Askari, H.
2015-03-01
In this paper, Laplace Adomian decomposition method is utilized for evaluating of spreading model of rumor. Firstly, a succinct review is constructed on the subject of using analytical methods such as Adomian decomposion method, Variational iteration method and Homotopy Analysis method for epidemic models and biomathematics. In continue a spreading model of rumor with consideration of forgetting mechanism is assumed and subsequently LADM is exerted for solving of it. By means of the aforementioned method, a general solution is achieved for this problem which can be readily employed for assessing of rumor model without exerting any computer program. In addition, obtained consequences for this problem are discussed for different cases and parameters. Furthermore, it is shown the method is so straightforward and fruitful for analyzing equations which have complicated terms same as rumor model. By employing numerical methods, it is revealed LADM is so powerful and accurate for eliciting solutions of this model. Eventually, it is concluded that this method is so appropriate for this problem and it can provide researchers a very powerful vehicle for scrutinizing rumor models in diverse kinds of social networks such as Facebook, YouTube, Flickr, LinkedIn and Tuitor.
International Nuclear Information System (INIS)
Fang Zheng; Qiu Guanzhou
2007-01-01
A metallic solution model with adjustable parameter k has been developed to predict thermodynamic properties of ternary systems from those of its constituent three binaries. In the present model, the excess Gibbs free energy for a ternary mixture is expressed as a weighted probability sum of those of binaries and the k value is determined based on an assumption that the ternary interaction generally strengthens the mixing effects for metallic solutions with weak interaction, making the Gibbs free energy of mixing of the ternary system more negative than that before considering the interaction. This point is never considered in the models currently reported, where the only difference in a geometrical definition of molar values of components is considered that do not involve thermodynamic principles but are completely empirical. The current model describes the results of experiments very well, and by adjusting the k value also agrees with those from models used widely in the literature. Three ternary systems, Mg-Cu-Ni, Zn-In-Cd, and Cd-Bi-Pb are recalculated to demonstrate the method of determining k and the precision of the model. The results of the calculations, especially those in Mg-Cu-Ni system, are better than those predicted by the current models in the literature
PREDICTING WATER ACTIVITY IN ELECTROLYTE SOLUTIONS WITH THE CISTERNAS-LAM MODEL
Energy Technology Data Exchange (ETDEWEB)
REYNOLDS JG; GREER DA; DISSELKAMP RL
2011-03-01
Water activity is an important parameter needed to predict the solubility of hydrated salts in Hanford nuclear waste supernatants. A number of models available in the scientific literature predict water activity from electrolyte solution composition. The Cisternas-Lam model is one of those models and has several advantages for nuclear waste application. One advantage is that it has a single electrolyte specific parameter that is temperature independent. Thus, this parameter can be determined from very limited data and extrapolated widely. The Cisternas-Lam model has five coefficients that are used for all aqueous electrolytes. The present study aims to determine if there is a substantial improvement in making all six coefficients electrolyte specific. The Cisternas-Lam model was fit to data for six major electrolytes in Hanford nuclear waste supernatants. The model was first fit to all data to determine the five global coefficients, when they were held constant for all electrolytes it yielded a substantially better fit. Subsequently, the model was fit to each electrolyte dataset separately, where all six coefficients were allowed to be electrolyte specific. Treating all six coefficients as electrolyte specific did not make sufficient difference, given the complexity of applying the electrolyte specific parameters to multi-solute systems. Revised water specific parameters, optimized to the electrolytes relevant to Hanford waste, are also reported.
Predicting Water Activity In Electrolyte Solutions With The Cisternas-Lam Model
International Nuclear Information System (INIS)
Reynolds, J.G.; Greer, D.A.; Disselkamp, R.L.
2011-01-01
Water activity is an important parameter needed to predict the solubility of hydrated salts in Hanford nuclear waste supernatants. A number of models available in the scientific literature predict water activity from electrolyte solution composition. The Cisternas-Lam model is one of those models and has several advantages for nuclear waste application. One advantage is that it has a single electrolyte specific parameter that is temperature independent. Thus, this parameter can be determined from very limited data and extrapolated widely. The Cisternas-Lam model has five coefficients that are used for all aqueous electrolytes. The present study aims to determine if there is a substantial improvement in making all six coefficients electrolyte specific. The Cisternas-Lam model was fit to data for six major electrolytes in Hanford nuclear waste supernatants. The model was first fit to all data to determine the five global coefficients, when they were held constant for all electrolytes it yielded a substantially better fit. Subsequently, the model was fit to each electrolyte dataset separately, where all six coefficients were allowed to be electrolyte specific. Treating all six coefficients as electrolyte specific did not make sufficient difference, given the complexity of applying the electrolyte specific parameters to multi-solute systems. Revised water specific parameters, optimized to the electrolytes relevant to Hanford waste, are also reported.
Directory of Open Access Journals (Sweden)
Sana Guetat
2013-01-01
Full Text Available The concept of Information Systems urbanization has been proposed since the late 1990’s in order to help organizations building agile information systems. Nevertheless, despite the advantages of this concept, it remains too descriptive and presents many weaknesses. In particular, there is a lack of useful architecture models dedicated to defining software solutions compliant with information systems urbanization principles and rules. Moreover, well-known software architecture models do not provide sufficient resources to address the requirements and constraints of urbanized information systems. In this paper, we draw on the “information city” framework to propose a model of software architecture - called the 5+1 Software Architecture Model - which is compliant with information systems urbanization principles and helps organizations building urbanized software solutions. This framework improves the well-established software architecture models and allows the integration of new architectural paradigms. Furthermore, the proposed model contributes to the implementation of information systems urbanization in several ways. On the one hand, this model devotes a specific layer to applications integration and software reuse. On the other hand, it contributes to the information system agility and scalability due to its conformity to the separation of concerns principle.
Chevuturi, A.; Turner, A. G.; Woolnough, S. J.
2016-12-01
In this study we investigate the development of biases in the Indian Ocean region in summer hindcasts of the UK Met Office coupled initialised global seasonal forecasting system, GloSea5-GC2. Previous work has demonstrated the rapid evolution of strong monsoon circulation biases over India from seasonal forecasts initialised in early May, together with coupled strong easterly wind biases on the equator. We analyse a set of three springtime start dates for the 20-year hindcast period (1992-2011) and fifteen total ensemble members for each year. We use comparisons with a variety of observations to test the rate of evolving mean-state biases in the Arabian Sea, over India, and over the equatorial Indian Ocean. Biases are all shown to develop rapidly, particularly for the circulation bias over India that is connected to convection. These circulation biases later reach the surface and lead to responses in Arabian Sea SST in accordance with coastal and Ekman upwelling processes. We also assess the evolution of radiation and turbulent heat fluxes at the surface. Meanwhile at the equator, easterly biases in surface winds are shown to develop rapidly, consistent with an SST pattern that is consistent with positive-Indian Ocean dipole mean state conditions (warm western equatorial Indian Ocean, cold east). This bias develops consistent with coupled ocean-atmosphere exchanges and Bjerknes feedback. We hypothesize that lower tropospheric easterly wind biases developing in the equatorial region originate from the surface, and also that signals of the cold bias in the eastern equatorial Indian Ocean propagate to the Bay of Bengal via coastal Kelvin waves. Earlier work has shown the utility of wind-stress corrections in the Indian Ocean for correcting the easterly winds bias there and ultimately improving the evolution of the Indian Ocean Dipole. We identify and test this wind-stress correction technique in case study years from the hindcast period to see their impact on seasonal
In-core LOCA-s: analytical solution for the delayed mixing model for moderator poison concentration
International Nuclear Information System (INIS)
Firla, A.P.
1995-01-01
Solutions to dynamic moderator poison concentration model with delayed mixing under single pressure tube / calandria tube rupture scenario are discussed. Such a model is described by a delay differential equation, and for such equations the standard ways of solution are not directly applicable. In the paper an exact, direct time-domain analytical solution to the delayed mixing model is presented and discussed. The obtained solution has a 'marching' form and is easy to calculate numerically. Results of the numerical calculations based on the analytical solution indicate that for the expected range of mixing times the existing uniform mixing model is a good representation of the moderator poison mixing process for single PT/CT breaks. However, for postulated multi-pipe breaks ( which is very unlikely to occur ) the uniform mixing model is not adequate any more; at the same time an 'approximate' solution based on Laplace transform significantly overpredicts the rate of poison concentration decrease, resulting in excessive increase in the moderator dilution factor. In this situation the true, analytical solution must be used. The analytical solution presented in the paper may also serve as a bench-mark test for the accuracy of the existing poison mixing models. Moreover, because of the existing oscillatory tendency of the solution, special care must be taken in using delay differential models in other applications. (author). 3 refs., 3 tabs., 8 figs
Thermodynamically Consistent Algorithms for the Solution of Phase-Field Models
Vignal, Philippe
2016-02-11
Phase-field models are emerging as a promising strategy to simulate interfacial phenomena. Rather than tracking interfaces explicitly as done in sharp interface descriptions, these models use a diffuse order parameter to monitor interfaces implicitly. This implicit description, as well as solid physical and mathematical footings, allow phase-field models to overcome problems found by predecessors. Nonetheless, the method has significant drawbacks. The phase-field framework relies on the solution of high-order, nonlinear partial differential equations. Solving these equations entails a considerable computational cost, so finding efficient strategies to handle them is important. Also, standard discretization strategies can many times lead to incorrect solutions. This happens because, for numerical solutions to phase-field equations to be valid, physical conditions such as mass conservation and free energy monotonicity need to be guaranteed. In this work, we focus on the development of thermodynamically consistent algorithms for time integration of phase-field models. The first part of this thesis focuses on an energy-stable numerical strategy developed for the phase-field crystal equation. This model was put forward to model microstructure evolution. The algorithm developed conserves, guarantees energy stability and is second order accurate in time. The second part of the thesis presents two numerical schemes that generalize literature regarding energy-stable methods for conserved and non-conserved phase-field models. The time discretization strategies can conserve mass if needed, are energy-stable, and second order accurate in time. We also develop an adaptive time-stepping strategy, which can be applied to any second-order accurate scheme. This time-adaptive strategy relies on a backward approximation to give an accurate error estimator. The spatial discretization, in both parts, relies on a mixed finite element formulation and isogeometric analysis. The codes are
Schuck, Peter
2004-03-01
Macromolecular sedimentation in inhomogeneous media is of great practical importance. Dynamic density gradients have a long tradition in analytical ultracentrifugation, and are frequently used in preparative ultracentrifugation. In this paper, a new theoretical model for sedimentation in inhomogeneous media is presented, based on finite element solutions of the Lamm equation with spatial and temporal variation of the local solvent density and viscosity. It is applied to macromolecular sedimentation in the presence of a dynamic density gradient formed by the sedimentation of a co-solute at high concentration. It is implemented in the software SEDFIT for the analysis of experimental macromolecular concentration distributions. The model agrees well with the measured sedimentation profiles of a protein in a dynamic cesium chloride gradient, and may provide a measure for the effects of hydration or preferential solvation parameters. General features of protein sedimentation in dynamic density gradients are described.
DEFF Research Database (Denmark)
Boyd, Britta; Brem, Alexander; Bogers, Marcel
, Amit, & Massa, 2011). Especially in the face of the grand challenge of climate change, looking for energy efficient solutions offers particular opportunities to businesses to stay competitive. This is an opportunity not only for big companies in metropolitan areas, but also for small and medium sized......The growing dynamics of innovation and productivity affect businesses in most industries and countries. Companies face these challenges by constantly developing new technologies and business models - the logic with which they create and capture value (Afuah, 2014; Osterwalder & Pigneur, 2010; Zott...... more energy efficient solutions seems to pay off. News items in media like “The Guardian” show at least that there is supraregional attention (Guardian, 2015). We tap into these developments through a study of exploring collaborations and business models that have the potential to increase energy...
Efficacy of chitosan in inhibiting the oxidation of (+)-catechin in white wine model solutions.
Chinnici, Fabio; Natali, Nadia; Riponi, Claudio
2014-10-08
The efficacy of chitosan and sulfites in inhibiting the oxidation of (+)-catechin in aerated model white wines has been compared by monitoring the browning development and the generation of oxidized phenolic compounds. In addition, the protecting effects of these two additives toward the oxidative decay of varietal thiols were investigated. Chitosan effectively contrasted the browning onset in model solutions all along the entire duration of the experimentation. Color development was limited and comparable in both the sulfite and chitosan added samples. Thanks to its polyelectrolyte behavior, chitosan adsorbed up to 80% of the more hydrophilic oxidized phenolic species and chelated 70 and 30% of Fe and Cu added to the solutions, respectively. Thiol oxidation was significantly lowered by chitosan, suggesting that this additive could contribute to maintain the varietal character of wines coming from aromatic grapes and vinified with reduced sulfite amounts.
Utilization of poplar wood sawdust for heavy metals removal from model solutions
Directory of Open Access Journals (Sweden)
Demcak Stefan
2017-06-01
Full Text Available Some kinds of natural organic materials have a potential for removal of heavy metal ions from wastewater. It is well known that cellulosic waste materials or by-products can be used as cheap adsorbents in chemical treatment process. In this paper, poplar wood sawdust were used for removal of Cu(II, Zn(II and Fe(II ions from model solutions with using the static and dynamic adsorption experiments. Infrared spectrometry of poplar wood sawdust confirmed the presence of the functional groups which correspond with hemicelluloses, cellulose and lignin. At static adsorption was achieved approximately of 80 % efficiency for all treated model solutions. Similar efficiency of the adsorption processes was reached after 5 min at dynamic condition. The highest efficiency of Cu(II removal (98 % was observed after 30 min of dynamic adsorption. Changes of pH values confirmed a mechanism of ion exchange on the beginning of the adsorption process.
Modelling with the master equation solution methods and applications in social and natural sciences
Haag, Günter
2017-01-01
This book presents the theory and practical applications of the Master equation approach, which provides a powerful general framework for model building in a variety of disciplines. The aim of the book is to not only highlight different mathematical solution methods, but also reveal their potential by means of practical examples. Part I of the book, which can be used as a toolbox, introduces selected statistical fundamentals and solution methods for the Master equation. In Part II and Part III, the Master equation approach is applied to important applications in the natural and social sciences. The case studies presented mainly hail from the social sciences, including urban and regional dynamics, population dynamics, dynamic decision theory, opinion formation and traffic dynamics; however, some applications from physics and chemistry are treated as well, underlining the interdisciplinary modelling potential of the Master equation approach. Drawing upon the author’s extensive teaching and research experience...
Owens, Brett D; White, Daniel W; Wenke, Joseph C
2009-01-01
There is much to learn about the effectiveness of different methods currently used for the irrigation of open wounds. The purpose of this study was to compare various approaches in a survival animal model. We used an established goat model involving the creation of a reproducible complex musculoskeletal wound followed by inoculation with Pseudomonas aeruginosa (lux) bacteria. This genetically altered luminescent bacterium provides the ability for quantitative analysis with a photon-counting camera system. For Study 1, wound irrigation was performed six hours after the injury and inoculation; the goats were assigned to four treatment groups: normal saline solution, bacitracin solution, castile soap, and benzalkonium chloride. All wounds received sharp débridement and irrigation with use of a pulsatile lavage device (19 psi). Images and photon counts were obtained prior to irrigation, after irrigation, and forty-eight hours after injury and inoculation. For Study 2, we used the same animal model and compared bulb syringe and pulsatile lavage irrigation with saline solution. In Study 1, the irrigation treatment lowered the bacterial counts in all treatment groups. The greatest reduction was seen with castile soap, which lowered the photon count to 13% of the pretreatment level. This was followed by benzalkonium chloride, bacitracin, and saline solution at 18%, 22%, and 29%, respectively. At forty-eight hours, imaging showed a rebound in bacterial counts in every group. The highest rebound was measured in the castile soap group, which rebounded to 120% of the pretreatment level. The benzalkonium chloride group experienced a rebound to 94% of the pretreatment level. These were followed by bacitracin solution (89%) and normal saline solution (68%). In Study 2, both treatment methods were effective in removing 75% of the bacteria initially. At forty-eight hours, the bacterial levels in the pulsed lavage group rebounded to 94% of the original levels (compared with 48% in
International Nuclear Information System (INIS)
Souto, F.J.; Heger, A.S.
2001-01-01
To investigate the effects of radiolytic gas bubbles and thermal expansion on the steady-state operation of solution reactors at the power level required for the production of medical isotopes, a calculational model has been developed. To validate this model, including its principal hypotheses, specific experiments at the Los Alamos National Laboratory SHEBA uranyl fluoride solution reactor were conducted. The following sections describe radiolytic gas generation in solution reactors, the equations to estimate the fuel solution volume change due to radiolytic gas bubbles and thermal expansion, the experiments conducted at SHEBA, and the comparison of experimental results and model calculations. (author)
Energy Technology Data Exchange (ETDEWEB)
Souto, F.J. [NIS-6: Advanced Nuclear Technology, Los Alamos National Lab., Los Alamos, NM (United States); Heger, A.S. [ESA-EA: Engineering Sciences and Application, Los Alamos National Lab., Los Alamos, NM (United States)
2001-07-01
To investigate the effects of radiolytic gas bubbles and thermal expansion on the steady-state operation of solution reactors at the power level required for the production of medical isotopes, a calculational model has been developed. To validate this model, including its principal hypotheses, specific experiments at the Los Alamos National Laboratory SHEBA uranyl fluoride solution reactor were conducted. The following sections describe radiolytic gas generation in solution reactors, the equations to estimate the fuel solution volume change due to radiolytic gas bubbles and thermal expansion, the experiments conducted at SHEBA, and the comparison of experimental results and model calculations. (author)
Directory of Open Access Journals (Sweden)
Xin Liang
2018-01-01
Full Text Available In this paper, an anomalous advection-dispersion model involving a new general Liouville–Caputo fractional-order derivative is addressed for the first time. The series solutions of the general fractional advection-dispersion equations are obtained with the aid of the Laplace transform. The results are given to demonstrate the efficiency of the proposed formulations to describe the anomalous advection dispersion processes.
On weak solutions to a diffuse interface model of a binary mixture of compressible fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2016-01-01
Roč. 9, č. 1 (2016), s. 173-183 ISSN 1937-1632 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : Euler-Cahn-Hilliard system * weak solution * diffuse interface model Subject RIV: BA - General Mathematics Impact factor: 0.781, year: 2016 http://aimsciences.org/ journals /displayArticlesnew.jsp?paperID=12093
On weak solutions to a diffuse interface model of a binary mixture of compressible fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2016-01-01
Roč. 9, č. 1 (2016), s. 173-183 ISSN 1937-1632 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : Euler-Cahn-Hilliard system * weak solution * diffuse interface model Subject RIV: BA - General Mathematics Impact factor: 0.781, year: 2016 http://aimsciences.org/journals/displayArticlesnew.jsp?paperID=12093
Directory of Open Access Journals (Sweden)
Olumoye Ajao
2017-12-01
Full Text Available Prehydrolysate, a dilute solution consisting mainly of pentoses, hexoses, and lesser quantities of organic acids, furfural and phenolics, is generated in the Kraft dissolving pulp process. An obstacle facing the valorization of the solution in hemicellulose biorefineries, by conversion of the sugars into bioproducts such as furfural, is the low sugar concentration. Membrane filtration is typically proposed in several hemicellulose based biorefineries for concentrating the solution, although they are usually generated using different wood species, pretreatment methods, and operating conditions. However, the chemical composition of the solutions is generally not considered. Also, the combined effect of composition and operating conditions is rarely investigated for biorefinery applications. The purpose of this work was to determine the impact of the prehydrolysate composition and operating parameters on the component separation and permeate flux during membrane filtration. Using model prehydrolysate solutions, two commercial reverse osmosis (RO membranes were screened, and one was selected for use, based on its higher sugar and acetic acid retention. A Taguchi L18 experimental design array was then applied to determine the dominant parameters and limiting factors. Results showed that the feed pressure and temperature have the highest impact on permeate flux, but the least effect on sugar retention. Further experiments to quantify flux decline, due to fouling and osmotic pressure, showed that furfural has the highest membrane fouling tendency, and can limit the lifetime of the membrane. Regeneration of the membrane by cleaning with a sodium hydroxide solution is also effective for reversing fouling. It has been demonstrated that RO can efficiently and sustainably concentrate wood prehydrolysate.
International Nuclear Information System (INIS)
Guo, Haojie; Zheng, Sining; Liang, Bo
2013-01-01
This paper deals with the Keller–Segel chemotaxis model of parabolic–elliptic type with the volume-filling effect studied by Burger et al (2006 The Keller–Segel model for chemotaxis with prevention of overcrowding: linear versus nonlinear diffusion SIAM J. Math. Anal. 38 1288–315). In their discussion on the large time asymptotic behaviour of solutions, the diffusion rate of ρ (the density of cells) had to be assumed to be large with ε> 1/4 . While for the nonlinear diffusion model, it was proved that the asymptotic behaviour of solutions is fully determined by the diffusion constant being larger or smaller than the threshold value ε = 1. The same ‘large ε-restriction’ (ε> 1/4 ) was also made for studying the parallel parabolic–parabolic model in Di Francesco and Rosado (2008 Fully parabolic Keller–Segel model for chemotaxis with prevention of overcrowding Nonlinearity 21 2715–30), where it was pointed out that ‘Whether this condition is necessary to have large time decay (and consequently a self-similar behaviour) for ρ is still an open problem even in the (simpler) parabolic–elliptic case’. The aim of the paper is to answer this problem for the parabolic–elliptic model. We prove the mentioned time decay estimate without the restriction ε> 1/4 . The main technique used in this paper is the L p -L q estimate method. (paper)
Solution algorithm of dwell time in slope-based figuring model
Li, Yong; Zhou, Lin
2017-10-01
Surface slope profile is commonly used to evaluate X-ray reflective optics, which is used in synchrotron radiation beam. Moreover, the measurement result of measuring instrument for X-ray reflective optics is usually the surface slope profile rather than the surface height profile. To avoid the conversion error, the slope-based figuring model is introduced introduced by processing the X-ray reflective optics based on surface height-based model. However, the pulse iteration method, which can quickly obtain the dell time solution of the traditional height-based figuring model, is not applied to the slope-based figuring model because property of the slope removal function have both positive and negative values and complex asymmetric structure. To overcome this problem, we established the optimal mathematical model for the dwell time solution, By introducing the upper and lower limits of the dwell time and the time gradient constraint. Then we used the constrained least squares algorithm to solve the dwell time in slope-based figuring model. To validate the proposed algorithm, simulations and experiments are conducted. A flat mirror with effective aperture of 80 mm is polished on the ion beam machine. After iterative polishing three times, the surface slope profile error of the workpiece is converged from RMS 5.65 μrad to RMS 1.12 μrad.
Multi-scale modelling of ions in solution: from atomistic descriptions to chemical engineering
International Nuclear Information System (INIS)
Molina, J.J.
2011-01-01
Ions in solution play a fundamental role in many physical, chemical, and biological processes. The PUREX process used in the nuclear industry to the treatment of spent nuclear fuels is considered as an example. For industrial applications these systems are usually described using simple analytical models which are fitted to reproduce the available experimental data. In this work, we propose a multi-scale coarse graining procedure to derive such models from atomistic descriptions. First, parameters for classical force-fields of ions in solution are extracted from ab-initio calculations. Effective (McMillan-Mayer) ion-ion potentials are then derived from radial distribution functions measured in classical molecular dynamics simulations, allowing us to define an implicit solvent model of electrolytes. Finally, perturbation calculations are performed to define the best possible representation for these systems, in terms of charged hard-sphere models. Our final model is analytical and contains no free 'fitting' parameters. It shows good agreement with the exact results obtained from Monte-Carlo simulations for the thermodynamic and structural properties. Development of a similar model for the electrolyte viscosity, from information derived from atomistic descriptions, is also introduced. (author)
Formal Modelling of a Usable Identity Management Solution for Virtual Organisations
Directory of Open Access Journals (Sweden)
Ali N. Haidar
2010-01-01
Full Text Available This paper attempts to accurately model security requirements for computational grid environments with particular focus on authentication. We introduce the Audited Credential Delegation (ACD architecture as a solution to some of the virtual organisations identity management usability problems. The approach uses two complementary models: one is state based, described in Z notation, and the other is event-based, expressed in the Process Algebra of Hoare's Communicating Sequential Processes (CSP. The former will be used to capture the state of the WS and to model back-end operations on it whereas the latter will be used to model behavior, and in particular, front-end interactions and communications. The modelling helps to clearly and precisely understand functional and security requirements and provide a basis for verifying that the system meets its intended requirements.
Mathematical models and heuristic solutions for container positioning problems in port terminals
DEFF Research Database (Denmark)
Kallehauge, Louise Sibbesen
2008-01-01
, and conclusive remarks. The introduction provides a basis for appreciating the presented work and sets out the scope, motivation, purpose, and contributions of the thesis. Furthermore, the CPP is defined and described, an overview of port container terminal issues in general is provided, and relevant literature...... mathematical programming formulations. First, a conceptual mixed integer linear programming (MIP) model for the entire port container terminal is presented. Subsequently, two models for the CPP are suggested: A MIP model and a binary integer linear programming (BIP) model. The models provide a basis...... in parameters and input data. Two improvement routines are presented, one imbedded in the basic heuristic and the other constituting a repair algorithm with the purpose of improving an initial heuristic solution. The heuristic algorithm performance and a wide range of different planning strategies...
Modeling study of solute transport in the unsaturated zone: Workshop proceedings
International Nuclear Information System (INIS)
Springer, E.P.; Fuentes, H.R.
1987-04-01
Issues addressed were the adequacy of the data for the various models, effectiveness of the models to represent the data, particular information provided by the models, the role of caisson experiments in providing fundamental knowledge of porous-media water flow and solute transport, and the importance of geochemistry to the transport of nonconservative tracers. These proceedings include the presentations made by each of the modelers; the summary document written by the panel; and a transcript of the discussions, both the discussions that followed individual presentations and the general discussion held on the second day. This publication completes the series on the workshop. Volume I in the series (NUREG/CR-4615, Vol. I) contains background information and the data sets provided each modeler
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
Bajul, Audrey; Gerbaud, Vincent; Teychene, Sébastien; Devatine, Audrey; Bajul, Gilles
2017-08-01
Instability in bottled wines refer to tartaric salts crystallization such as potassium bitartrate (KHT). It is not desirable as consumers see the settled salts as an evidence of a poor quality control. In some cases, it causes excessive gushing in sparkling wine. We investigate the effect of two oenological carboxymethylcellulose (CMC) for KHT inhibition in a model solution of white wine by studying the impact of some properties of CMC such as the degree of polymerization, the degree of substitution, and the apparent dissociation constant determined by potentiometric titration. Polyelectrolyte adsorption is used for determining the surface and total charge and for providing information about the availability of CMC charged groups for interacting with KHT crystal faces. The inhibitory efficiency of CMC on model solution is evaluated by measuring the induction time with the help of conductimetric methods. Crystals growth with and without CMC are studied by observation with MEB and by thermal analysis using DSC. The results confirm the effectiveness of CMC as an inhibitor of KHT crystallization in a model solution. The main hypothesis of the mechanism lies in the interaction of dissociated anionic carboxymethyl groups along the cellulose backbone with positively charged layers on KHT faces like the {0 1 0} face. Key factors such as pH, CMC chain length and total charge are discusses.
Energy Technology Data Exchange (ETDEWEB)
Laroche, L.; Henner, P.; Camilleri, V.; Garnier-Laplace, J. [CEA Cadarache (DEI/SECRE/LRE), Laboratory of Radioecology and Ecotoxicology, Institute for Radioprotection and Nuclear Safety, 13 - Saint-Paul-lez-Durance (France)
2004-07-01
Uranium behaviour in soils is controlled by actions and interactions between physicochemical and biological processes that also determine its bioavailability. In soil solution, uranium(+VI) aqueous speciation undergoes tremendous changes mainly depending on pH, carbonates, phosphates and organic matter. In a first approach to identify bioavailable species of U to plants, cultures were performed using hydroponics, to allow an easy control of the composition of the exposure media. The latter, here an artificial soil solution, was designed to control the uranium species in solution. The geochemical speciation code JCHESS using a database compiled from the OECD/NEA thermochemical database project and verified was used to perform the solution speciation calculations. On this theoretical basis, three domains were defined for short-duration well-defined laboratory experiments in simplified conditions: pH 4.9, 5.8 and 7 where predicted dominant species are uranyl ions, hydroxyl complexes and carbonates respectively. For these domains, biokinetics and characterization of transmembrane transport according to a classical Michaelis Menten approach were investigated. The Free Ion Model (or its derived Biotic Ligand Model) was tested to determine if U uptake is governed by the free uranyl species or if other metal complexes can be assimilated. The effect of different variables on root assimilation efficiency and phyto-toxicity was explored: presence of ligands such as phosphates or carbonates and competitive ions such as Ca{sup 2+} at the 3 pH. According to previous experiments, uranium was principally located in roots whatever the pH and no difference in uranium uptake was evidenced between the main growth stages of the plant. Within the 3 studied chemical domains, results from short-term kinetics evidenced a linear correlation between total uranium concentration in bean roots and that in exposure media, suggesting that total uranium in soil solution could be a good predictor
Zhao, Gang; Takamatsu, Hiroshi; He, Xiaoming
2014-04-01
A new model was developed to predict transmembrane water transport and diffusion-limited ice formation in cells during freezing without the ideal-solution assumption that has been used in previous models. The model was applied to predict cell dehydration and intracellular ice formation (IIF) during cryopreservation of mouse oocytes and bovine carotid artery endothelial cells in aqueous sodium chloride (NaCl) solution with glycerol as the cryoprotectant or cryoprotective agent. A comparison of the predictions between the present model and the previously reported models indicated that the ideal-solution assumption results in under-prediction of the amount of intracellular ice at slow cooling rates (cryopreservation for practical applications.
Energy Technology Data Exchange (ETDEWEB)
Bagheri, Saman; Nikkar, Ali [University of Tabriz, Tabriz (Iran, Islamic Republic of)
2014-11-15
This paper deals with the determination of approximate solutions for a model of column buckling using two efficient and powerful methods called He's variational approach and variational iteration algorithm-II. These methods are used to find analytical approximate solution of nonlinear dynamic equation of a model for the column buckling. First and second order approximate solutions of the equation of the system are achieved. To validate the solutions, the analytical results have been compared with those resulted from Runge-Kutta 4th order method. A good agreement of the approximate frequencies and periodic solutions with the numerical results and the exact solution shows that the present methods can be easily extended to other nonlinear oscillation problems in engineering. The accuracy and convenience of the proposed methods are also revealed in comparisons with the other solution techniques.
Global weak solutions for a gas liquid model with external forces and general pressure law
Evje, Steinar; Friis, Helmer André
2011-01-01
This is a copy of an article previously published in; SIAM journal on applied mathematics, which has been made available here with permission. Original article; http://dx.doi.org/10.1137/100813336. In this work we show existence of global weak solutions for a two-phase gas-liquid model where the gas phase is represented by a general isothermal pressure law, whereas the liquid is assumed to be incompressible. To make the model relevant for pipe and well-flow applications we have included ex...
Radiolysis study of the oxidation of a vitamin K model compound in ethanolic solution
International Nuclear Information System (INIS)
Fackir, L.; Jore, D.; Gardes-Albert, M.; Ferradini, C.; Acher, F.; Azerad, R.
1993-01-01
It seems that the biological action of vitamin K (with its important role in carboxylating processes) may involve monoelectronic exchanges. Therefore radical mechanisms of a vitamin K model molecule KHp have been studied in ethanolic solution by mean of steady state radiolysis method. The oxidation of KHp by H 3 C-CH(OH)OO . model peroxyl radicals leads to the formation of a 'dimeric' form of vitamin K. The superoxide anions seem not to be reactive towards KHp in the chosen irradiation conditions
On solutions of boundary value problems for model of axially symmetric quantum dots
International Nuclear Information System (INIS)
Gusev, A.A.; Chvluunbaatar, O.; Vinitsky, S.I.; Dvoyan, K.G.; Kazaryan, E.M.; Sarkisyan, H.A.
2010-01-01
Full text: (author)In the framework of effective mass approximation we have considered solutions of boundary value problems with separated and nonseparated variables for models of quantum dots with axial-symmetric potentials of harmonic oscillators and confinement potentials with infinite and finite walls. For considered problems we have made comparisons of levels with low energy of discrete spectra and eigenfunctions nodes by using exact and adiabatic classification of states. Critical values of the spheroidal aspect ratio, at which the discrete spectrum of models with finite-wall potentials is transformed into a continuous one in strong dimensional quantization regime, were revealed
Parallel shooting methods for finding steady state solutions to engine simulation models
DEFF Research Database (Denmark)
Andersen, Stig Kildegård; Thomsen, Per Grove; Carlsen, Henrik
2007-01-01
Parallel single- and multiple shooting methods were tested for finding periodic steady state solutions to a Stirling engine model. The model was used to illustrate features of the methods and possibilities for optimisations. Performance was measured using simulation of an experimental data set...... as test case. A parallel speedup factor of 23 on 33 processors was achieved with multiple shooting. But fast transients at the beginnings of sub intervals caused significant overhead for the multiple shooting methods and limited the best speedup to 3.8 relative to the fastest sequential method: Single...
Hyperosmolar irrigation compared with a standard solution in a canine shoulder arthroscopy model.
Capito, Nicholas M; Smith, Matthew J; Stoker, Aaron M; Werner, Nikki; Cook, James L
2015-08-01
A hyperosmolar irrigation solution may decrease fluid extravasation during arthroscopic procedures. Demonstrating the safety of a hyperosmolar irrigation solution with respect to chondrocyte viability and cartilage water content was deemed necessary before designing a clinical efficacy study. We designed a translational animal model study in which hyperosmolar arthroscopy irrigation fluid (1.8%, 600 mOsm/L) was compared with normal saline (0.9%, 300 mOsm/L). Purpose-bred research dogs (n = 5) underwent bilateral shoulder arthroscopy. Irrigation fluid was delivered to each shoulder joint (n = 10) at 40 mm Hg for 120 minutes using standard ingress and egress portals. The percentage change in shoulder girth was documented at the completion of 120 minutes. Articular cartilage sections from the glenoid and humeral head were harvested from both shoulders. Chondrocyte viability and tissue water content were evaluated. Differences between groups and compared with time 0 controls were determined, with significance set at P irrigation solution used for arthroscopy was not associated with any detrimental effects on chondrocyte viability or tissue water content after 2 hours of arthroscopic irrigation. On the basis of potential benefits in conjunction with the safety demonstrated in these data, clinical evaluation of a hyperosmolar solution for irrigation during shoulder arthroscopy appears warranted. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.
Bradbury, Robert; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Jones, Craig
2013-03-12
The adsorption of the model perfumes phenyl ethanol, PE, and linalool, LL, at the air-solution interface by coadsorption with the anionic surfactant sodium dodecyl 6-benezene sulfonate, LAS-6, has been studied primarily by neutron reflectivity, NR. The variation in the mixed surface adsorption with solution composition is highly nonideal, and the more hydrophobic LL is more surface active. At a LAS-6 concentration of 0.5 mM the adsorption of PE and LL is broadly similar but with the LL systematically more surface active, and at 2 mM the LL completes more effectively for the surface than the PE. The variation in surface composition with solution composition and concentration reflect the greater hydrophobicity and hence surface activity of LL, and the greater solubility of PE in aqueous solution. Changing the geometry of the LAS isomer, from the symmetrical LAS-6 geometry to the more asymmetrical LAS-4, results in the LL competing more effectively for the surface due to changes in the packing constraints associated with the hydrophobic region. The results provide insights into the factors that affect coadsorption that can be more broadly applied to the surface delivery of a wide range of molecules other than perfumes.
Directory of Open Access Journals (Sweden)
D. A. Eliseev
2015-01-01
Full Text Available The solution stability of an initial boundary problem for a linear hybrid system of differential equations, which models the rotation of a rigid body with two elastic rods located in the same plane is studied in the paper. To an axis passing through the mass center of the rigid body perpendicularly to the rods location plane is applied the stabilizing moment proportional to the angle of the system rotation, derivative of the angle, integral of the angle. The external moment provides a feedback. A method of studying the behavior of solutions of the initial boundary problem is proposed. This method allows to exclude from the hybrid system of differential equations partial differential equations, which describe the dynamics of distributed elements of a mechanical system. It allows us to build one equation for an angle of the system rotation. Its characteristic equation defines the stability of solutions of all the system. In the space of feedback-coefficients the areas that provide the asymptotic stability of solutions of the initial boundary problem are built up.
International Nuclear Information System (INIS)
Sasahira, Akira; Hoshikawa, Tadahiro; Kamoshida, Mamoru; Kawamura, Fumio
1994-01-01
In order to evaluate the amounts of gas phase transferred ruthenium (Ru), and technetium (Tc), simulations were made for the continuous evaporator used in a reprocessing plant to concentrate high level liquid waste. The concentrations and activities of nitric acid and water, which controlled the reaction rate and gas-liquid equilibrium in the evaporator solution, were evaluated using the previously developed 'Hydration Model'. When the feed solution contained 2.7 M (=mol/dm 3 ) of nitric acid, the nitric acid concentration in the evaporator solution reached its maximum at the concentration factor (CF) of 6 (CF: concentration ratio of FPs in evaporator and feed solutions). The activities of nitric acid and water were saturated at values of 0.01 and 0.43, respectively, after the CF reached 6. The simulation predicted decontamination factors DFs of 2x10 5 and 8x10 3 for Ru and Tc, respectively, for a typical evaporation conditions with an operational pressure of 6,700 Pa, and FPs of 0.02 to 1.4 M. The simulation results agreed with the verification experiment within a factor of 2 for the amount of gas-phase transferred Ru during evaporation. The factor for the amount of gas-phase transferred Tc was estimated as 5 from the measurement error in the gas-liquid equilibrium constant. (author)
Measuring and modeling aqueous electrolyte/amino-acid solutions with ePC-SAFT
International Nuclear Information System (INIS)
Held, Christoph; Reschke, Thomas; Müller, Rainer; Kunz, Werner; Sadowski, Gabriele
2014-01-01
Highlights: • Amino-acid solubilities and osmotic coefficients in ternary solutions containing one amino acids and one salt measured. • Weak salt influence on amino-acid solubilities except for salts containing Mg [2+] or NO 3 [−] (salting-in behavior). • Osmotic coefficients dominated by the solute with the highest molality. • Amino-acid solubilities and osmotic coefficients predicted reasonably with ePC-SAFT with deviations of 3.7% and 9.3%. • Predictions based on pure-component parameters for ions and amino acids using no ion/amino-acid fitting parameters. -- Abstract: In this work thermodynamic properties of electrolyte/amino acid/water solutions were measured and modeled. Osmotic coefficients at 298.15 K were measured by means of vapor-pressure osmometry. Amino-acid solubility at 298.15 K was determined gravimetrically. Considered aqueous systems contained one of the four amino acids: glycine, L-/DL-alanine, L-/DL-valine, and L-proline up to the respective amino-acid solubility limit and one of 13 salts composed of the ions Li + , Na + , K + , NH 4 + , Cl − , Br − , I − , NO 3 − , and SO 4 2− at salt molalities of 0.5, 1.0, and 3.0 mol · kg −1 , respectively. The data show that the salt influence is more pronounced on osmotic coefficients than on amino-acid solubility. The electrolyte Perturbed-Chain Statistical Association Theory (ePC-SAFT) was applied to model thermodynamic properties in aqueous electrolyte/amino-acid solutions. In previous works, this model had been applied to binary salt/water and binary amino acid/water systems. Without fitting any additional parameters, osmotic coefficients and amino-acid solubility in the ternary electrolyte/amino acid/water systems could be predicted with overall deviations of 3.7% and 9.3%, respectively, compared to the experimental data
ter Wee, P M; Beelen, R H J; van den Born, J
2003-12-01
The application of animal models to study the biocompatibility of bicarbonate-buffered peritoneal dialysis solutions. Patients treated with peritoneal dialysis (PD) are at risk for development of ultrafiltration failure and peritonitis. These two significant complications can result in the termination of PD treatment. The relative unphysiologic composition of the currently used standard peritoneal dialysis fluids (PDF) is considered to be a major cause for the development of morphologic changes of the peritoneal membrane, ultimately resulting in ultrafiltration failure and probably contributing to changes in local defense mechanisms with the associated increased risk of peritonitis. In recent years, a major research focus has become the development of new and improved PD solutions. This has resulted in the development of an amino-acid-based PDF, a glucose polymer-based PDF, and several bicarbonate-buffered PDF. Typically, the first phase of biocompatibility testing of new PD solutions involves in vitro testing, employing isolated cells such as peritoneal macrophages or cell culture systems using human peritoneal mesothelial cells. The results of such evaluations are useful in providing insights into the biocompatibility performance of any given formulation, but suffer from several disadvantages, which can be better addressed using animal models. In vivo studies using animals permit the analysis of biocompatibility under conditions that allow for cell-to-cell interactions and dynamic changes in solution composition that more closely mimic the clinical situation. In this paper, we will review the use of animal models for the study of PDF biocompatibility and their application to the assessment of bicarbonate-buffered PDF.
Assessment of applications of transport models on regional scale solute transport
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.
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.
Huber, F. M.; Enzmann, F.; Wenka, A.; Dentz, M.; Schaefer, T.
2010-12-01
Fluid flow and solute transport through fractures are a key process in both industrial and scientific issues ranging from e.g. geothermal energy production to the disposal of nuclear waste in deep geologic formations. Therefore, a fundamental understanding of the various interdependent processes governing fluid flow and solute transport in fractures over a broad range of length and time scales is of utmost importance. Numerous studies have shown the importance of fracture geometry on flow and solute transport. More recently, significance of so called recirculation zones which are accessible for solutes and colloids through hydrodynamic dispersion and molecular diffusion have been identified [1,2] which can be responsible for pronounced late time solute breakthrough (tailing). Unfortunately, these studies are mostly focused on 2D. Thus, the intention of the prevailing study is to investigate the influence of fracture geometry on solute transport under a broad range of flow conditions (Pe number from 0.1 up to 1000) and as a function of flow direction (that is, reversed flow direction) both in 2D and 3D. We present µXCT measurements with a spatial resolution of 80 µm of a natural single fracture in a diorite drill core from Äspö, Sweden, which serves as direct input for computational mesh generation in order to obtain a realistic 3D model. Besides, a 2D model was produced by projecting the 3D mesh into the x-y-plane to completely exclude the fracture aperture information. Computational fluid dynamic simulations in 2D and 3D have been conducted to study fluid flow and conservative tracer (HTO) transport by means of the finite volume code FLUENT. The natural fracture exhibits a very complex geometry with asperities, rough side walls and a heterogenous aperture distribution. Furthermore, the µXCT data clearly shows that the fracture is not filled with fault gauge material. Simulation results confirm the impact of fracture geometry/roughness on fluid flow causing
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
Eggers, Daryl K.
2011-01-01
A new phenomenological model for interpreting solute effects on biological equilibria is presented. The model attributes changes in equilibria to differences in the desolvation energy of the reacting species which, in turn, reflect changes in the free energy of the bulk water on addition of secondary solutes. The desolvation approach differs notably from other solute models by treating the free energy of bulk water as a variable and by not ascribing the observed shifts in reaction equilibria to accumulation or depletion of solutes next to the surfaces of the reacting species. On the contrary, the partitioning of solutes is viewed as a manifestation of the different subpopulations of water that arise in response to the surface boundary conditions. A thermodynamic framework consistent with the proposed model is used to derive a relationship for a specific reaction, an aqueous solubility equilibrium, in two or more solutions. The resulting equation reconciles some potential issues with the transfer free energy model of Tanford. Application of the desolvation energy model to the analysis of a two-state protein folding equilibrium is discussed and contrasted to the application of two other solute models developed by Timasheff and by Parsegian. Future tabulation of solvation energies and bulk water energies may allow biophysical chemists to confirm the mechanism by which secondary solutes influence binding and conformational equilibria and may provide a common ground for experimentalists and theoreticians to compare and evaluate their results. PMID:21284393
Starn, J. J.
2013-12-01
Particle tracking often is used to generate particle-age distributions that are used as impulse-response functions in convolution. A typical application is to produce groundwater solute breakthrough curves (BTC) at endpoint receptors such as pumping wells or streams. The commonly used semi-analytical particle-tracking algorithm based on the assumption of linear velocity gradients between opposing cell faces is computationally very fast when used in combination with finite-difference models. However, large gradients near pumping wells in regional-scale groundwater-flow models often are not well represented because of cell-size limitations. This leads to inaccurate velocity fields, especially at weak sinks. Accurate analytical solutions for velocity near a pumping well are available, and various boundary conditions can be imposed using image-well theory. Python can be used to embed these solutions into existing semi-analytical particle-tracking codes, thereby maintaining the integrity and quality-assurance of the existing code. Python (and associated scientific computational packages NumPy, SciPy, and Matplotlib) is an effective tool because of its wide ranging capability. Python text processing allows complex and database-like manipulation of model input and output files, including binary and HDF5 files. High-level functions in the language include ODE solvers to solve first-order particle-location ODEs, Gaussian kernel density estimation to compute smooth particle-age distributions, and convolution. The highly vectorized nature of NumPy arrays and functions minimizes the need for computationally expensive loops. A modular Python code base has been developed to compute BTCs using embedded analytical solutions at pumping wells based on an existing well-documented finite-difference groundwater-flow simulation code (MODFLOW) and a semi-analytical particle-tracking code (MODPATH). The Python code base is tested by comparing BTCs with highly discretized synthetic steady
Modeling of carbon dioxide absorption by aqueous ammonia solutions using the Extended UNIQUAC model
DEFF Research Database (Denmark)
Darde, Victor Camille Alfred; van Well, Willy J. M.; Stenby, Erling Halfdan
2010-01-01
An upgraded version of the Extended UNIQUAC thermodynamic model for the carbon dioxide-ammonia-water system has been developed, based on the original version proposed by Thomsen and Rasmussen. The original model was valid in the temperature range 0-110°C, the pressure range 0-10 MPa and the conce......An upgraded version of the Extended UNIQUAC thermodynamic model for the carbon dioxide-ammonia-water system has been developed, based on the original version proposed by Thomsen and Rasmussen. The original model was valid in the temperature range 0-110°C, the pressure range 0-10 MPa...
Global existence of solutions to a tear film model with locally elevated evaporation rates
Gao, Yuan; Ji, Hangjie; Liu, Jian-Guo; Witelski, Thomas P.
2017-07-01
Motivated by a model proposed by Peng et al. (2014) for break-up of tear films on human eyes, we study the dynamics of a generalized thin film model. The governing equations form a fourth-order coupled system of nonlinear parabolic PDEs for the film thickness and salt concentration subject to non-conservative effects representing evaporation. We analytically prove the global existence of solutions to this model with mobility exponents in several different ranges and present numerical simulations that are in agreement with the analytic results. We also numerically capture other interesting dynamics of the model, including finite-time rupture-shock phenomenon due to the instabilities caused by locally elevated evaporation rates, convergence to equilibrium and infinite-time thinning.
Numerical solution of continuous-time DSGE models under Poisson uncertainty
DEFF Research Database (Denmark)
Posch, Olaf; Trimborn, Timo
We propose a simple and powerful method for determining the transition process in continuous-time DSGE models under Poisson uncertainty numerically. The idea is to transform the system of stochastic differential equations into a system of functional differential equations of the retarded type. We...... then use the Waveform Relaxation algorithm to provide a guess of the policy function and solve the resulting system of ordinary differential equations by standard methods and fix-point iteration. Analytical solutions are provided as a benchmark from which our numerical method can be used to explore broader...... classes of models. We illustrate the algorithm simulating both the stochastic neoclassical growth model and the Lucas model under Poisson uncertainty which is motivated by the Barro-Rietz rare disaster hypothesis. We find that, even for non-linear policy functions, the maximum (absolute) error is very...
Directory of Open Access Journals (Sweden)
L. Toledo Sesma
2016-01-01
Full Text Available We construct an effective four-dimensional model by compactifying a ten-dimensional theory of gravity coupled with a real scalar dilaton field on a time-dependent torus. This approach is applied to anisotropic cosmological Bianchi type I model for which we study the classical coupling of the anisotropic scale factors with the two real scalar moduli produced by the compactification process. Under this approach, we present an isotropization mechanism for the Bianchi I cosmological model through the analysis of the ratio between the anisotropic parameters and the volume of the Universe which in general keeps constant or runs into zero for late times. We also find that the presence of extra dimensions in this model can accelerate the isotropization process depending on the momenta moduli values. Finally, we present some solutions to the corresponding Wheeler-DeWitt (WDW equation in the context of standard quantum cosmology.
Scheuerell, Mark D
2016-01-01
Stock-recruitment models have been used for decades in fisheries management as a means of formalizing the expected number of offspring that recruit to a fishery based on the number of parents. In particular, Ricker's stock recruitment model is widely used due to its flexibility and ease with which the parameters can be estimated. After model fitting, the spawning stock size that produces the maximum sustainable yield (S MSY) to a fishery, and the harvest corresponding to it (U MSY), are two of the most common biological reference points of interest to fisheries managers. However, to date there has been no explicit solution for either reference point because of the transcendental nature of the equation needed to solve for them. Therefore, numerical or statistical approximations have been used for more than 30 years. Here I provide explicit formulae for calculating both S MSY and U MSY in terms of the productivity and density-dependent parameters of Ricker's model.
Automated search-model discovery and preparation for structure solution by molecular replacement.
Keegan, Ronan M; Winn, Martyn D
2007-04-01
A novel automation pipeline for macromolecular structure solution by molecular replacement is described. There is a special emphasis on the discovery and preparation of a large number of search models, all of which can be passed to the core molecular-replacement programs. For routine molecular-replacement problems, the pipeline automates what a crystallographer might do and its value is simply one of convenience. For more difficult cases, the pipeline aims to discover the particular template structure and model edits required to produce a viable search model and may succeed in finding an efficacious combination that would be missed otherwise. The pipeline is described in detail and a number of examples are given. The examples are chosen to illustrate successes in real crystallography problems and also particular features of the pipeline. It is concluded that exploring a range of search models automatically can be valuable in many cases.
solveME: fast and reliable solution of nonlinear ME models
DEFF Research Database (Denmark)
Yang, Laurence; Ma, Ding; Ebrahim, Ali
2016-01-01
Background: Genome-scale models of metabolism and macromolecular expression (ME) significantly expand the scope and predictive capabilities of constraint-based modeling. ME models present considerable computational challenges: they are much (>30 times) larger than corresponding metabolic reconstr...... methods will accelerate the wide-spread adoption of ME models for researchers in these fields. Electronic supplementary material The online version of this article (doi:10.1186/s12859-016-1240-1) contains supplementary material, which is available to authorized users.......Background: Genome-scale models of metabolism and macromolecular expression (ME) significantly expand the scope and predictive capabilities of constraint-based modeling. ME models present considerable computational challenges: they are much (>30 times) larger than corresponding metabolic...... reconstructions (M models), are multiscale, and growth maximization is a nonlinear programming (NLP) problem, mainly due to macromolecule dilution constraints. Results: Here, we address these computational challenges. We develop a fast and numerically reliable solution method for growth maximization in ME models...
Spike solutions in Gierer#x2013;Meinhardt model with a time dependent anomaly exponent
Nec, Yana
2018-01-01
Experimental evidence of complex dispersion regimes in natural systems, where the growth of the mean square displacement in time cannot be characterised by a single power, has been accruing for the past two decades. In such processes the exponent γ(t) in ⟨r2⟩ ∼ tγ(t) at times might be approximated by a piecewise constant function, or it can be a continuous function. Variable order differential equations are an emerging mathematical tool with a strong potential to model these systems. However, variable order differential equations are not tractable by the classic differential equations theory. This contribution illustrates how a classic method can be adapted to gain insight into a system of this type. Herein a variable order Gierer-Meinhardt model is posed, a generic reaction- diffusion system of a chemical origin. With a fixed order this system possesses a solution in the form of a constellation of arbitrarily situated localised pulses, when the components' diffusivity ratio is asymptotically small. The pattern was shown to exist subject to multiple step-like transitions between normal diffusion and sub-diffusion, as well as between distinct sub-diffusive regimes. The analytical approximation obtained permits qualitative analysis of the impact thereof. Numerical solution for typical cross-over scenarios revealed such features as earlier equilibration and non-monotonic excursions before attainment of equilibrium. The method is general and allows for an approximate numerical solution with any reasonably behaved γ(t).
Experiment and model for the surface tension of amine–ionic liquids aqueous solutions
International Nuclear Information System (INIS)
Zhang, Pan; Du, LeiXia; Fu, Dong
2014-01-01
Highlights: • The surface tensions of MEA/DEA–ionic liquids aqueous solutions were measured. • The experiments were modeled satisfactorily by using a thermodynamic equation. • The temperature dependence of the surface tension was illustrated. • The effects of the mass fractions of MEA/DEA and ionic liquids were demonstrated. - Abstract: The surface tension (γ) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF 4 ])–monoethanolamine (MEA), 1-butyl-3-methylimidazolium bromide ([Bmim][Br])–MEA, [Bmim][BF 4 ]–diethanolamine (DEA) and [Bmim][Br]–DEA aqueous solutions was measured by using the BZY-1 surface tension meter. The temperature ranged from (293.2 to 323.2) K. The mass fraction of amines and ionic liquids (ILS) respectively ranged from 0.15 to 0.30 and 0.05 to 0.10. A thermodynamic equation was proposed to model the surface tension of amines–ILS aqueous solutions and the calculated results agreed well with the experiments. The effects of temperature, mass fraction of amines and ILS on the surface tension were demonstrated on the basis of experiments and calculations
Ferlemann, Paul G.
2000-01-01
A solution methodology has been developed to efficiently model multi-specie, chemically frozen, thermally perfect gas mixtures. The method relies on the ability to generate a single (composite) set of thermodynamic and transport coefficients prior to beginning a CFD solution. While not fundamentally a new concept, many applied CFD users are not aware of this capability nor have a mechanism to easily and confidently generate new coefficients. A database of individual specie property coefficients has been created for 48 species. The seven coefficient form of the thermodynamic functions is currently used rather then the ten coefficient form due to the similarity of the calculated properties, low temperature behavior and reduced CPU requirements. Sutherland laminar viscosity and thermal conductivity coefficients were computed in a consistent manner from available reference curves. A computer program has been written to provide CFD users with a convenient method to generate composite specie coefficients for any mixture. Mach 7 forebody/inlet calculations demonstrated nearly equivalent results and significant CPU time savings compared to a multi-specie solution approach. Results from high-speed combustor analysis also illustrate the ability to model inert test gas contaminants without additional computational expense.
Bayesian reliability modeling and assessment solution for NC machine tools under small-sample data
Yang, Zhaojun; Kan, Yingnan; Chen, Fei; Xu, Binbin; Chen, Chuanhai; Yang, Chuangui
2015-11-01
Although Markov chain Monte Carlo(MCMC) algorithms are accurate, many factors may cause instability when they are utilized in reliability analysis; such instability makes these algorithms unsuitable for widespread engineering applications. Thus, a reliability modeling and assessment solution aimed at small-sample data of numerical control(NC) machine tools is proposed on the basis of Bayes theories. An expert-judgment process of fusing multi-source prior information is developed to obtain the Weibull parameters' prior distributions and reduce the subjective bias of usual expert-judgment methods. The grid approximation method is applied to two-parameter Weibull distribution to derive the formulas for the parameters' posterior distributions and solve the calculation difficulty of high-dimensional integration. The method is then applied to the real data of a type of NC machine tool to implement a reliability assessment and obtain the mean time between failures(MTBF). The relative error of the proposed method is 5.8020×10-4 compared with the MTBF obtained by the MCMC algorithm. This result indicates that the proposed method is as accurate as MCMC. The newly developed solution for reliability modeling and assessment of NC machine tools under small-sample data is easy, practical, and highly suitable for widespread application in the engineering field; in addition, the solution does not reduce accuracy.
Moreno Chaparro, Nicolas
2015-06-30
We introduce a framework for model reduction of polymer chain models for dissipative particle dynamics (DPD) simulations, where the properties governing the phase equilibria such as the characteristic size of the chain, compressibility, density, and temperature are preserved. The proposed methodology reduces the number of degrees of freedom required in traditional DPD representations to model equilibrium properties of systems with complex molecules (e.g., linear polymers). Based on geometrical considerations we explicitly account for the correlation between beads in fine-grained DPD models and consistently represent the effect of these correlations in a reduced model, in a practical and simple fashion via power laws and the consistent scaling of the simulation parameters. In order to satisfy the geometrical constraints in the reduced model we introduce bond-angle potentials that account for the changes in the chain free energy after the model reduction. Following this coarse-graining process we represent high molecular weight DPD chains (i.e., ≥200≥200 beads per chain) with a significant reduction in the number of particles required (i.e., ≥20≥20 times the original system). We show that our methodology has potential applications modeling systems of high molecular weight molecules at large scales, such as diblock copolymer and DNA.
Singular solutions for the rigid plastic double slip and rotation model under plane strain
Alexandrov, S.; Lyamina, E.
2018-02-01
In the mechanics of granular and other materials the system of equations comprising the rigid plastic double slip and rotation model together with the stress equilibrium equations under plane strain conditions forms a hyperbolic system. Boundary value problems for this system of equations can involve a frictional interface. An envelope of characteristics may coincide with this interface. In this case, the solution is singular. In particular, some components of the strain rate tensor approach infinity in the vicinity of the frictional interface. Such behavior of solutions is in qualitative agreement with experimental data that show that a narrow layer of localized plastic deformation is often generated near frictional interfaces. The present paper deals with asymptotic analysis of the aforementioned system of equations in the vicinity of an envelope of characteristics. It is shown that the shear strain rate and the spin component in a local coordinate system connected to the envelope follow an inverse square root rule in its vicinity.
First-Principles Modeling of ThO2 Solid Solutions with Oxides of Trivalent Cations
Alexandrov, Vitaly; Asta, Mark; Gronbech-Jensen, Niels
2010-03-01
Solid solutions formed by doping ThO2 with oxides of trivalent cations, such as Y2O3 and La2O3, are suitable for solid electrolyte applications, similar to doped zirconia and ceria. ThO2 has also been gaining much attention as an alternative to UO2 in nuclear energy applications, the aforementioned trivalent cations being important fission products. In both cases the mixing energetics and short-range ordering/clustering are key to understanding structural and transport properties. Using first-principles atomistic calculations, we address intra- and intersublattice interactions for both cation and anion sublattices in ThO2-based fluorite-type solid solutions and compare the results with similar modeling studies for related trivalent-doped zirconia systems.
Landau-Zener extension of the Tavis-Cummings model: structure of the solution
Sun, Chen; Sinitsyn, Nikolai
We explore the recently discovered solution of the driven Tavis-Cummings model (DTCM). It describes interaction of arbitrary number of two-level systems with a bosonic mode that has linearly time-dependent frequency. We derive compact and tractable expressions for transition probabilities in terms of the well known special functions. In the new form, our formulas are suitable for fast numerical calculations and analytical approximations. As an application, we obtain the semiclassical limit of the exact solution and compare it to prior approximations. We also reveal connection between DTCM and q-deformed binomial statistics. Under the auspices of the National Nuclear Security Administration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Authors also thank the support from the LDRD program at LANL.
On new traveling wave solutions and conserved densities for the 2D Ricci flow model
Cimpoiasu, Rodica
2018-01-01
In this paper some travelling wave solutions and conservation laws for the 2D Ricci flow model in conformal gauge are investigated. A guideline able to classify the types of solutions according to the values of some parameters is provided by making use of two versions of the auxiliary equation method. The key feature of these approaches is to take a second order linear ordinary differential equation (ODE), respectively a first order nonlinear ODE with at most an eighth-degree nonlinear term as auxiliary equations. Conserved forms of the travelling wave equation for the Ricci flow are derived through three specific approaches, namely the variational approach, the Ibragimov method for nonlinear self-adjoint differential equations and the one based upon a relationship between conserved forms and their associated symmetries. The former two methods generated similar results, while the latter one has revealed new conserved densities.
A Numerical Algorithm for the Solution of a Phase-Field Model of Polycrystalline Materials
Energy Technology Data Exchange (ETDEWEB)
Dorr, M R; Fattebert, J; Wickett, M E; Belak, J F; Turchi, P A
2008-12-04
We describe an algorithm for the numerical solution of a phase-field model (PFM) of microstructure evolution in polycrystalline materials. The PFM system of equations includes a local order parameter, a quaternion representation of local orientation and a species composition parameter. The algorithm is based on the implicit integration of a semidiscretization of the PFM system using a backward difference formula (BDF) temporal discretization combined with a Newton-Krylov algorithm to solve the nonlinear system at each time step. The BDF algorithm is combined with a coordinate projection method to maintain quaternion unit length, which is related to an important solution invariant. A key element of the Newton-Krylov algorithm is the selection of a preconditioner to accelerate the convergence of the Generalized Minimum Residual algorithm used to solve the Jacobian linear system in each Newton step. Results are presented for the application of the algorithm to 2D and 3D examples.
International Nuclear Information System (INIS)
Milioli, F.E.
1985-01-01
In this research work a numerical model for the solution of two-dimensional natural convection problems in arbitrary cavities of a Boussinesq fluid is presented. The conservation equations are written in a general curvilinear coordinate system which matches the irregular boundaries of the domain. The nonorthogonal system is generated by a suitable system of elliptic equations. The momentum and continuity equations are transformed from the Cartesian system to the general curvilinear system keeping the Cartesian velocity components as the dependent variables in the transformed domain. Finite difference equations are obtained for the contravariant velocity components in the transformed domain. The numerical calculations are performed in a fixed rectangular domain and both the Cartesian and the contravariant velocity components take part in the solutiomn procedure. The dependent variables are arranged on the grid in a staggered manner. The numerical model is tested by solving the driven flow in a square cavity with a moving side using a nonorthogoanl grid. The natural convenction in a square cavity, using an orthogonal and a nonorthogonal grid, is also solved for the model test. Also, the solution for the buoyancy flow between a square cylinder placed inside a circular cylinder is presented. The results of the test problems are compared with those available in the specialized literature. Finally, in order to show the generality of the model, the natural convection problem inside a very irregular cavity is presented. (Author) [pt
International Nuclear Information System (INIS)
Vazquez-Arenas, Jorge; Pritzker, Mark
2011-01-01
A comprehensive physicochemical model for cobalt deposition onto a cobalt rotating disk electrode in sulfate-borate (pH 3) solutions is derived and statistically fit to experimental EIS spectra obtained over a range of CoSO 4 concentrations, overpotentials and rotation speeds. The model accounts for H + and water reduction, homogeneous reactions and mass transport within the boundary layer. Based on a thermodynamic analysis, the species CoSO 4(aq) , B(OH) 3(aq) , B 3 O 3 (OH) 4 - , H + and OH - and two homogeneous reactions (B(OH) 3(aq) hydrolysis and water dissociation) are included in the model. Kinetic and transport parameters are estimated by minimizing the sum-of-squares error between the model and experimental measurements using a simplex method. The electrode response is affected most strongly by parameters associated with the first step of Co(II) reduction, reflecting its control of the rate of Co deposition, and is moderately sensitive to the parameters for H + reduction and the Co(II) diffusion coefficient. Water reduction is found not to occur to any significant extent under the conditions studied. These trends are consistent with that obtained by fitting equivalent electrical circuits to the experimental spectra. The simplest circuit that best fits the data consists of two RQ elements (resistor-constant phase element) in parallel or series with the solution resistance.
An Integrated Numerical Hydrodynamic Shallow Flow-Solute Transport Model for Urban Area
Alias, N. A.; Mohd Sidek, L.
2016-03-01
The rapidly changing on land profiles in the some urban areas in Malaysia led to the increasing of flood risk. Extensive developments on densely populated area and urbanization worsen the flood scenario. An early warning system is really important and the popular method is by numerically simulating the river and flood flows. There are lots of two-dimensional (2D) flood model predicting the flood level but in some circumstances, still it is difficult to resolve the river reach in a 2D manner. A systematic early warning system requires a precisely prediction of flow depth. Hence a reliable one-dimensional (1D) model that provides accurate description of the flow is essential. Research also aims to resolve some of raised issues such as the fate of pollutant in river reach by developing the integrated hydrodynamic shallow flow-solute transport model. Presented in this paper are results on flow prediction for Sungai Penchala and the convection-diffusion of solute transports simulated by the developed model.
The Wigner solution and QCD phase transitions in a modified PNJL model
Energy Technology Data Exchange (ETDEWEB)
Cui, Zhu-fang [Nanjing University, Department of Physics, Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Nanjing (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing (China); Shi, Chao [Nanjing University, Department of Physics, Nanjing (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing (China); Sun, Wei-min; Zong, Hong-shi [Nanjing University, Department of Physics, Nanjing (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing (China); Wang, Yong-long [Nanjing University, Department of Physics, Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Nanjing (China); Linyi University, Department of Physics, School of Science, Linyi (China); Massachusetts Institute of Technology, Center for Theoretical Physics, Cambridge, MA (United States)
2014-02-15
By employing some modification to the widely used two-flavor Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model, we discuss the Wigner solution of the quark gap equation at finite temperature and zero quark chemical potential beyond the chiral limit, and then we try to explore its influence on the chiral and deconfinement phase transitions of QCD at finite temperature and zero chemical potential. The discovery of the coexistence of the Nambu and the Wigner solutions of the quark gap equation with nonzero current quark mass at zero temperature and zero chemical potential, as well as their evolutions with temperature, is very interesting for the studies of the phase transitions of QCD. According to our results, the chiral phase transition might be of first order (while the deconfinement phase transition is still a crossover, as in the normal PNJL model), and the corresponding phase transition temperature is lower than that of the deconfinement phase transition, instead of coinciding with each other, which are not the same as the conclusions obtained from the normal PNJL model. In addition, we also discuss the sensibility of our final results on the choice of model parameters. (orig.)
Ma, Ning
2005-11-01
To accurately predict microstructure evolution and, hence, to synthesis metal and ceramic alloys with desirable properties involves many fundamental as well as practical issues. In the present study, novel theoretical and phase field approaches have been developed to address some of these issues including solute drag and segregation transition at grain boundaries and dislocations, grain growth in systems of anisotropic boundary properties, and precipitate microstructure development in polycrystalline materials. The segregation model has allowed for the prediction of a first-order segregation transition, which could be related to the sharp transition of solute concentration of grain boundary as a function of temperature. The incorporating of interfacial energy and mobility as functions of misorientation and inclination in the phase field model has allowed for the study of concurrent grain growth and texture evolution. The simulation results were analyzed using the concept of local grain boundary energy density, which simplified significantly the development of governing equations for texture controlled grain growth in Ti-6Al-4V. Quantitative phase field modeling techniques have been developed by incorporating thermodynamic and diffusivity databases. The models have been validated against DICTRA simulations in simple 1D problems and applied to simulate realistic microstructural evolutions in Ti-6Al-4V, including grain boundary a and globular a growth and sideplate development under both isothermal aging and continuous cooling conditions. The simulation predictions agree well with experimental observations.
Atlabachew, Abunu; Shu, Longcang; Wu, Peipeng; Zhang, Yongjie; Xu, Yang
2018-03-01
This laboratory study improves the understanding of the impacts of horizontal hydraulic gradient, artificial recharge, and groundwater pumping on solute transport through aquifers. Nine experiments and numerical simulations were carried out using a sand tank. The variable-density groundwater flow and sodium chloride transport were simulated using the three-dimensional numerical model SEAWAT. Numerical modelling results successfully reproduced heads and concentrations observed in the sand tank. A higher horizontal hydraulic gradient enhanced the migration of sodium chloride, particularly in the groundwater flow direction. The application of constant artificial recharge increased the spread of the sodium chloride plume in both the longitudinal and lateral directions. In addition, groundwater pumping accelerated spreading of the sodium chloride plume towards the pumping well. Both higher hydraulic gradient and pumping rate generated oval-shaped plumes in the horizontal plane. However, the artificial recharge process produced stretched plumes. These effects of artificial recharge and groundwater pumping were greater under higher hydraulic gradient. The concentration breakthrough curves indicated that emerging solutions never attained the concentration of the originally injected solution. This is probably because of sorption of sodium chloride onto the silica sand and/or the exchange of sodium chloride between the mobile and immobile liquid domains. The fingering and protruding plume shapes in the numerical models constitute instability zones produced by buoyancy-driven flow. Overall, the results have substantiated the influences of hydraulic gradient, boundary condition, artificial recharge, pumping rate and density differences on solute transport through a homogeneous unconfined aquifer. The implications of these findings are important for managing liquid wastes.
Dual-permeability model for water flow and solute transport in shrinking soils
Coppola, Antonio; Gerke, Horst; Comegna, Alessandro; Basile, Angelo
2014-05-01
A dual-permeability approach was extended to describe preferential water flow and solute transport in shrinking soils. In the approach, the soil is treated as a dual-permeability bulk porous medium consisting of dynamic interacting matrix and fractures pore domains. Water flow and solute transport in both the domains are described by the Richards' equation and advection-dispersion equation, respectively. In the model the contributions of the two regions to water flow and solute transport is changed dynamically according to the shrinkage characteristic exhibited under soil drying. Aggregate deformation during wetting/drying cycles is assumed to change only the relative proportions of voids in the fractures and in the aggregates, while the total volume of pores (and thus the layer thickness) remains unchanged. Thus, the partial contributions of the fracture and aggregate domains, are now a function of the water content (or the pressure head h), while their sum, the bulk porosity, is assumed to be constant. Any change in the aggregate contribution to total porosity is directly converted into a proportional change in the fracture porosity. This means that bulk volume change during shrinkage is mainly determined by change in crack volume rather than by change in layer thickness. This simplified approach allows dealing with an expansive soil as with a macroscopically rigid soil. The model was already tested by investigating whether and how well hydraulic characteristics obtained under the assumption of "dynamic" dual-permeability hydraulic parameterizations, or, alternatively, assuming the rigidity of the porous medium, reproduced measured soil water contents in a shrinking soil. Here we will discuss theoretical implications of the model in terms of relative importance of the parameters involved. The relative importance will be evaluated for different flow and transport processes and for different initial and top boundary conditions. Key words: Preferential flow and
C4: Exploring Multiple Solutions in Graphical Models by Cluster Sampling.
Porway, Jake; Zhu, Song-Chun
2011-09-01
This paper presents a novel Markov Chain Monte Carlo (MCMC) inference algorithm called C(4)--Clustering with Cooperative and Competitive Constraints--for computing multiple solutions from posterior probabilities defined on graphical models, including Markov random fields (MRF), conditional random fields (CRF), and hierarchical models. The graphs may have both positive and negative edges for cooperative and competitive constraints. C(4) is a probabilistic clustering algorithm in the spirit of Swendsen-Wang. By turning the positive edges on/off probabilistically, C(4) partitions the graph into a number of connected components (ccps) and each ccp is a coupled subsolution with nodes connected by positive edges. Then, by turning the negative edges on/off probabilistically, C(4) obtains composite ccps (called cccps) with competing ccps connected by negative edges. At each step, C(4) flips the labels of all nodes in a cccp so that nodes in each ccp keep the same label while different ccps are assigned different labels to observe both positive and negative constraints. Thus, the algorithm can jump between multiple competing solutions (or modes of the posterior probability) in a single or a few steps. It computes multiple distinct solutions to preserve the intrinsic ambiguities and avoids premature commitments to a single solution that may not be valid given later context. C(4) achieves a mixing rate faster than existing MCMC methods, such as various Gibbs samplers and Swendsen-Wang cuts. It is also more "dynamic" than common optimization methods such as ICM, LBP, and graph cuts. We demonstrate the C(4) algorithm in line drawing interpretation, scene labeling, and object recognition.
Evaluation of unsaturated-zone solute-transport models for studies of agricultural chemicals
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.
The effect of re-solution models on fission gas disposition in irradiated UO2 fuel
International Nuclear Information System (INIS)
Wazzan, A.R.; Orkent, D.; Villalobos, A.
1985-01-01
A computer code developed earlier by Villalobos et al. to predict fission gas behavior in uranium oxide fuel under steady-state irradiation conditions and where bubble gas resolution is represented with the single knock-on model (SKO) is modified to replace the SKO model with the complete bubble destruction model (CBD). The CBD model required that bubble nucleation be included in the analysis. The revised code is used to compute gas release and total swelling. Both are found to be insensitive to whether they are obtained with the CBD or the SKO option. This is mainly because at low atomic percent of burnup, total swelling is dominated by the grain-edge bubble gas contribution, and release is dependent on the formation of a complete grainface/grain-edge tunnel network - factors that are not much affected by either the SKO or CBD models. At higher atomic percent of burnup, intragranular swelling, which can be sensitive to the re-solution model, contributes more to swelling. But even then, computations at 1.0 at .% burnup suggest total swelling will continue to be dominated by grain-edge gas. These results suggest that in modeling swelling and release in irradiated uranium dioxide fuel, the simpler SKO resolution model is satisfactory
Exact solutions to plaquette Ising models with free and periodic boundaries
International Nuclear Information System (INIS)
Mueller, Marco; Johnston, Desmond A.; Janke, Wolfhard
2017-01-01
An anisotropic limit of the 3d plaquette Ising model, in which the plaquette couplings in one direction were set to zero, was solved for free boundary conditions by Suzuki (1972) , who later dubbed it the fuki-nuke, or “no-ceiling”, model. Defining new spin variables as the product of nearest-neighbour spins transforms the Hamiltonian into that of a stack of (standard) 2d Ising models and reveals the planar nature of the magnetic order, which is also present in the fully isotropic 3d plaquette model. More recently, the solution of the fuki-nuke model was discussed for periodic boundary conditions, which require a different approach to defining the product spin transformation, by Castelnovo et al. (2010) . We clarify the exact relation between partition functions with free and periodic boundary conditions expressed in terms of original and product spin variables for the 2d plaquette and 3d fuki-nuke models, noting that the differences are already present in the 1d Ising model. In addition, we solve the 2d plaquette Ising model with helical boundary conditions. The various exactly solved examples illustrate how correlations can be induced in finite systems as a consequence of the choice of boundary conditions.
Eshagh, Mehdi; Steinberger, Bernhard; Tenzer, Robert; Tassara, Andrés
2018-01-01
Based on Hager and O'Connell's solution to mantle flow equations the stresses induced by mantle convection are determined using the density and viscosity structure in addition to topographic data and a plate velocity model. The solution to mantle flow equations requires the knowledge of mantle properties that are typically retrieved from seismic information. Large parts of the world are, however, not yet covered sufficiently by seismic surveys. An alternative method of modelling the stress field was introduced by Runcorn. He formulated a direct relation between the stress field and gravity data while adopting several assumptions, particularly disregarding the toroidal mantle flow component and mantle viscosity variations. A possible way to overcome theoretical deficiencies of Runcorn's theory as well as some practical limitations of applying Hager and O'Connell's theory (in the absence of seismic data) is to combine these two methods. In this study we apply a least-squares analysis to combine these two methods based on the gravity data inversion constraint on mantle flow equations. In particular, we use vertical gravity gradients from the Gravity field and steady state Ocean Circulation Explorer (GOCE) that are corrected for the gravitational contribution of crustal density heterogeneities prior to applying a localized gravity-gradient inversion. This gravitational contribution is estimated based on combining the Vening Meinesz-Moritz (VMM) and flexural isostatic theories. Moreover, we treat the non-isostatic effect implicitly by applying a band-limited kernel of the integral equation during the inversion. In numerical studies of modelling the stress field within the South American continental lithosphere we compare the results obtained after applying Runcorn and Hager and O'Connell's methods as well as their combination. The results show that, according to Hager and O'Connell's (mantle flow) solution, the maximum stress intensity is inferred under the northern
Location-allocation models and new solution methodologies in telecommunication networks
Dinu, S.; Ciucur, V.
2016-08-01
When designing a telecommunications network topology, three types of interdependent decisions are combined: location, allocation and routing, which are expressed by the following design considerations: how many interconnection devices - consolidation points/concentrators should be used and where should they be located; how to allocate terminal nodes to concentrators; how should the voice, video or data traffic be routed and what transmission links (capacitated or not) should be built into the network. Including these three components of the decision into a single model generates a problem whose complexity makes it difficult to solve. A first method to address the overall problem is the sequential one, whereby the first step deals with the location-allocation problem and based on this solution the subsequent sub-problem (routing the network traffic) shall be solved. The issue of location and allocation in a telecommunications network, called "The capacitated concentrator location- allocation - CCLA problem" is based on one of the general location models on a network in which clients/demand nodes are the terminals and facilities are the concentrators. Like in a location model, each client node has a demand traffic, which must be served, and the facilities can serve these demands within their capacity limit. In this study, the CCLA problem is modeled as a single-source capacitated location-allocation model whose optimization objective is to determine the minimum network cost consisting of fixed costs for establishing the locations of concentrators, costs for operating concentrators and costs for allocating terminals to concentrators. The problem is known as a difficult combinatorial optimization problem for which powerful algorithms are required. Our approach proposes a Fuzzy Genetic Algorithm combined with a local search procedure to calculate the optimal values of the location and allocation variables. To confirm the efficiency of the proposed algorithm with respect
Modeling of Dielectric Properties of Aqueous Salt Solutions with an Equation of State
DEFF Research Database (Denmark)
Maribo-Mogensen, Bjørn; Kontogeorgis, Georgios; Thomsen, Kaj
2013-01-01
The static permittivity is the most important physical property for thermodynamic models that account for the electrostatic interactions between ions. The measured static permittivity in mixtures containing electrolytes is reduced due to kinetic depolarization and reorientation of the dipoles...... in the electrical field surrounding ions. Kinetic depolarization may explain 25–75% of the observed decrease in the permittivity of solutions containing salts, but since this is a dynamic property, this effect should not be included in the thermodynamic modeling of electrolytes. Kinetic depolarization has, however......, been ignored in relation to thermodynamic modeling, and authors have either neglected the effect of salts on permittivity or used empirical correlations fitted to the measured static permittivity, leading to an overestimation of the reduction in the thermodynamic static permittivity. We present a new...
Energy Technology Data Exchange (ETDEWEB)
Nourtier-Mazauric, E.
2003-03-15
This thesis presents a thermodynamic and kinetic model of interactions between a fluid and ideal solid solutions represented by several end-members. The reaction between a solid solution and the aqueous solution results from the competition between the stoichiometric dissolution of the initial solid solution and the co-precipitation of the least soluble solid solution in the fluid at considered time. This model was implemented in ARCHIMEDE, a computer code of reactive transport in porous media, then applied to various examples. In the case of binary solid solutions, a graphical method allowed to determine the compositions of the precipitating solid solutions, with the aid of the end-member chemical potentials. The obtained program could be used to notably model the diagenesis of clayey or carbonated oil reservoirs, or the ground pollutant dispersion. (author)
Structural model of the 50S subunit of E.Coli ribosomes from solution scattering
International Nuclear Information System (INIS)
Svergun, D.I.; Koch, M.H.J.; Pedersen, J.S.; Serdyuk, I.N.
1994-01-01
The application of new methods of small-angle scattering data interpretation to a contrast variation study of the 50S ribosomal subunit of Escherichia coli in solution is described. The X-ray data from contrast variation with sucrose are analyzed in terms of the basic scattering curves from the volume inaccessible to sucrose and from the regions inside this volume occupied mainly by RNA and by proteins. From these curves models of the shape of the 50S and its RNA-rich core are evaluated and positioned so that their difference produces a scattering curve which is in good agreement with the scattering from the protein moiety. Basing on this preliminary model, the X-ray and neutron contrast variation data of the 50S subunit in aqueous solutions are interpreted in the frame of the advanced two-phase model described by the shapes of the 50S subunit and its RNA-rich core taking into account density fluctuations inside the RNA and the protein moiety. The shape of the envelope of the 50S subunit and of the RNA-rich core are evaluated with a resolution of about 40A. The shape of the envelope is in good agreement with the models of the 50S subunit obtained from electron microscopy on isolated particles. The shape of the RNA-rich core correlates well with the model of the entire particle determined by the image reconstruction from ordered sheets indicating that the latter model which is based on the subjective contouring of density maps is heavily biased towards the RNA
Directory of Open Access Journals (Sweden)
Rasheed Uthman Owolabi
2018-01-01
Full Text Available A satisfactory model for predicting monomer conversion in free radical polymerization has been a challenge due to the complexity and rigors associated with classical kinetic models. This renders the usage of such model an exciting endeavour in the academia but not exactly so in industrial practice. In this study, the individual and interactive effects of three processing conditions (reaction temperature, reaction time and initiator concentration on monomer conversion in the solution polymerization of styrene using acetone as solvent was investigated in a batch reactor through the central composite design (CCD model of response surface methodology (RSM for experimental design, modelling and process optimization. The modelled optimization conditions are: reaction time of 30 min, reaction temperature of 120 °C, and initiator concentration of 0.1135 mol/l, with the corresponding monomer conversion of 76.82% as compared to the observed conversion of 70.86%. A robust model for predicting monomer conversion that is very suitable for routine industrial usage is thus obtained.
On the formulation of environmental fugacity models and their numerical solutions.
Bates, Michael L; Bigot, Marie; Cropp, Roger A; Engwirda, Darren; Friedman, Carey L; Hawker, Darryl W
2016-09-01
Multimedia models based on chemical fugacity, solved numerically, play an important role in investigating and quantifying the environmental fate of chemicals such as persistent organic pollutants. These models have been used extensively in studying the local and global distribution of chemicals in the environment. The present study describes potential sources of error that may arise from the formulation and numerical solution of environmental fugacity models. The authors derive a general fugacity equation for the rate of change of mass in an arbitrary volume (e.g., an environmental phase). Deriving this general equation makes clear several assumptions that are often not articulated but can be important for successfully applying multimedia fugacity models. It shows that the homogeneity of fugacity and fugacity capacity in a volume (the homogeneity assumption) is fundamental to formulating discretized fugacity models. It also shows that when using the fugacity rather than mass as the state-variable, correction terms may be necessary to accommodate environmental factors such as varying phase temperatures and volume. Neglecting these can lead to conservation errors. The authors illustrate the manifestation of these errors using heuristic multimedia fugacity models. The authors also show that there are easily avoided errors that can arise in mass state-variable models if variables are not updated appropriately in the numerical integration scheme. Environ Toxicol Chem 2016;35:2182-2191. © 2016 SETAC. © 2016 SETAC.
International Nuclear Information System (INIS)
Vrba, J; Robinson, S E; McCubbin, J; Lowery, C L; Eswaran, H; Murphy, P; Preissl, H
2007-01-01
Fetal brain signals produce weak magnetic fields at the maternal abdominal surface. In the presence of much stronger interference these weak fetal fields are often nearly indistinguishable from noise. Our initial objective was to validate these weak fetal brain fields by demonstrating that they agree with the electromagnetic model of the fetal brain. The fetal brain model is often not known and we have attempted to fit the data to not only the brain source position, orientation and magnitude, but also to the brain model position. Simulation tests of this extended model search on fetal MEG recordings using dipole fit and beamformers revealed a region of ambiguity. The region of ambiguity consists of a family of models which are not distinguishable in the presence of noise, and which exhibit large and comparable SNR when beamformers are used. Unlike the uncertainty of a dipole fit with known model plus noise, this extended ambiguity region yields nearly identical forward solutions, and is only weakly dependent on noise. The ambiguity region is located in a plane defined by the source position, orientation, and the true model centre, and will have a diameter approximately 0.67 of the modelled fetal head diameter. Existence of the ambiguity region allows us to only state that the fetal brain fields do not contradict the electromagnetic model; we can associate them with a family of models belonging to the ambiguity region, but not with any specific model. In addition to providing a level of confidence in the fetal brain signals, the ambiguity region knowledge in combination with beamformers allows detection of undistorted temporal waveforms with improved signal-to-noise ratio, even though the source position cannot be uniquely determined
Comparison of Model-Based Control Solutions for Severe Riser-Induced Slugs
Directory of Open Access Journals (Sweden)
Simon Pedersen
2017-12-01
Full Text Available Control solutions for eliminating severe riser-induced slugs in offshore oil & gas pipeline installations are key topics in offshore Exploration and Production (E&P processes. This study describes the identification, analysis and control of a low-dimensional control-oriented model of a lab-scaled slug testing facility. The model is analyzed and used for anti-slug control development for both lowpoint and topside transmitter solutions. For the controlled variables’ comparison it is concluded that the topside pressure transmitter ( P t is the most difficult output to apply directly for anti-slug control due to the inverse response. However, as P t often is the only accessible measurement on offshore platforms this study focuses on the controller development for both P t and the lowpoint pressure transmitter ( P b . All the control solutions are based on linear control schemes and the performance of the controllers are evaluated from simulations with both the non-linear MATLAB and OLGA models. Furthermore, the controllers are studied with input disturbances and parametric variations to evaluate their robustness. For both pressure transmitters the H ∞ loop-shaping controller gives the best performance as it is relatively robust to disturbances and has a fast convergence rate. However, P t does not increase the closed-loop bifurcation point significantly and is also sensitive to disturbances. Thus the study concludes that the best option for single-input-single-output (SISO systems is to control P b with a H ∞ loop-shaping controller. It is suggested that for cases where only topside transmitters are available a cascaded combination of the outlet mass flow and P t could be considered to improve the performance.
A Decomposition Model for HPLC-DAD Data Set and Its Solution by Particle Swarm Optimization
Directory of Open Access Journals (Sweden)
Lizhi Cui
2014-01-01
Full Text Available This paper proposes a separation method, based on the model of Generalized Reference Curve Measurement and the algorithm of Particle Swarm Optimization (GRCM-PSO, for the High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD data set. Firstly, initial parameters are generated to construct reference curves for the chromatogram peaks of the compounds based on its physical principle. Then, a General Reference Curve Measurement (GRCM model is designed to transform these parameters to scalar values, which indicate the fitness for all parameters. Thirdly, rough solutions are found by searching individual target for every parameter, and reinitialization only around these rough solutions is executed. Then, the Particle Swarm Optimization (PSO algorithm is adopted to obtain the optimal parameters by minimizing the fitness of these new parameters given by the GRCM model. Finally, spectra for the compounds are estimated based on the optimal parameters and the HPLC-DAD data set. Through simulations and experiments, following conclusions are drawn: (1 the GRCM-PSO method can separate the chromatogram peaks and spectra from the HPLC-DAD data set without knowing the number of the compounds in advance even when severe overlap and white noise exist; (2 the GRCM-PSO method is able to handle the real HPLC-DAD data set.
Numerical solutions of the semiclassical Boltzmann ellipsoidal-statistical kinetic model equation
Yang, Jaw-Yen; Yan, Chin-Yuan; Huang, Juan-Chen; Li, Zhihui
2014-01-01
Computations of rarefied gas dynamical flows governed by the semiclassical Boltzmann ellipsoidal-statistical (ES) kinetic model equation using an accurate numerical method are presented. The semiclassical ES model was derived through the maximum entropy principle and conserves not only the mass, momentum and energy, but also contains additional higher order moments that differ from the standard quantum distributions. A different decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. The numerical method in phase space combines the discrete-ordinate method in momentum space and the high-resolution shock capturing method in physical space. Numerical solutions of two-dimensional Riemann problems for two configurations covering various degrees of rarefaction are presented and various contours of the quantities unique to this new model are illustrated. When the relaxation time becomes very small, the main flow features a display similar to that of ideal quantum gas dynamics, and the present solutions are found to be consistent with existing calculations for classical gas. The effect of a parameter that permits an adjustable Prandtl number in the flow is also studied. PMID:25104904
Structure of Aqueous Trehalose Solution by Neutron Diffraction and Structural Modeling.
Olsson, Christoffer; Jansson, Helén; Youngs, Tristan; Swenson, Jan
2016-12-15
The molecular structure of an aqueous solution of the disaccharide trehalose (C 12 H 22 O 11 ) has been studied by neutron diffraction and empirical potential structure refinement modeling. Six different isotope compositions with 33 wt % trehalose (corresponding to 38 water molecules per trehalose molecule) were measured to ensure that water-water, trehalose-water, and trehalose-trehalose correlations were accurately determined. In fact, this is the first neutron diffraction study of an aqueous trehalose solution in which also the nonexchangeable hydrogen atoms in trehalose are deuterated. With this approach, it was possible to determine that (1) there is a substantial hydrogen bonding between trehalose and water (∼11 hydrogen bonds per trehalose molecule), which is in contrast to previous neutron diffraction studies, and (2) there is no tendency of clustering of trehalose, in contrast to what is generally observed by molecular dynamics simulations and experimentally found for other disaccharides. Thus, the results give the structural picture that trehalose prefers to interact with water and participate in a hydrogen-bonded network. This strong network character of the solution might be one of the key reasons for its extraordinary stabilization effect on biological materials.
Abdrassilova, Gulnara S.
2017-09-01
In the context of development of the agriculture as the driver of the economy of Kazakhstan it is imperative to study new types of agrarian constructions (agroparks, agrotourists complexes, "vertical" farms, conservatories, greenhouses) that can be combined into complexes - agrarian technoparks. Creation of agrarian technoparks as elements of the infrastructure of the agglomeration shall ensure the breakthrough in the field of agrarian goods production, storing and recycling. Modeling of architectural-planning solutions of agrarian technoparks supports development of the theory and practice of designing objects based on innovative approaches.
Exact solution to the 'auxiliary extra-dimension' model of massive gravity
International Nuclear Information System (INIS)
Hassan, S.F.; Rosen, Rachel A.
2011-01-01
The 'auxiliary extra-dimension' model was proposed in order to provide a geometrical interpretation to modifications of general relativity, in particular to non-linear massive gravity. In this context, the theory was shown to be ghost free to third order in perturbations, in the decoupling limit. In this work, we exactly solve the equation of motion in the extra dimension, to obtain a purely 4-dimensional theory. Using this solution, it is shown that the ghost appears at the fourth order and beyond. We explore potential modifications to address the ghost issue and find that their consistent implementation requires going beyond the present framework.
NEW SOLUTION AND ITS IMPACT ON INCREASING, DECREASING AND BATHTUB SHAPED FAILURE RATE MODEL
Directory of Open Access Journals (Sweden)
Mahmudul Alam
2009-01-01
Full Text Available The maximum likelihood equations of IDB distribution can’t be solved analytically. Solutions of the MLE equations can be obtained numerically. But the problem is to detect the initial value of the parameters to solve the nonlinear MLE equations. A technique is developed for formulating the initial value of the parameter to solve the MLE equations of IDB distribution. Considering all the facts, though IDB distribution is not suitable for graduating mortality data but the model can graduate mortality data of Bangladesh in the age range of 0-8 very well.
Falling paper: Navier-Stokes solutions, model of fluid forces, and center of mass elevation.
Pesavento, Umberto; Wang, Z Jane
2004-10-01
We investigate the problem of falling paper by solving the two dimensional Navier-Stokes equations subject to the motion of a free-falling body at Reynolds numbers around 10(3). The aerodynamic lift on a tumbling plate is found to be dominated by the product of linear and angular velocities rather than velocity squared, as appropriate for an airfoil. This coupling between translation and rotation provides a mechanism for a brief elevation of center of mass near the cusplike turning points. The Navier-Stokes solutions further provide the missing quantity in the classical theory of lift, the instantaneous circulation, and suggest a revised model for the fluid forces.
Global existence of periodic solutions on a simplified BAM neural network model with delays
International Nuclear Information System (INIS)
Zheng Baodong; Zhang Yazhuo; Zhang Chunrui
2008-01-01
A simplified n-dimensional BAM neural network model with delays is considered. Some results of Hopf bifurcations occurring at the zero equilibrium as the delay increases are exhibited. Global existence of periodic solutions are established using a global Hopf bifurcation result of Wu [Wu J. Symmetric functional-differential equations and neural networks with memory. Trans Am Math Soc 1998;350:4799-838], and a Bendixson criterion for higher dimensional ordinary differential equations due to Li and Muldowney [Li MY, Muldowney J. On Bendixson's criterion. J Differ Equations 1994;106:27-39]. Finally, computer simulations are performed to illustrate the analytical results found
Validation of ANUGA hydraulic model using exact solutions to shallow water wave problems
International Nuclear Information System (INIS)
Mungkasi, S; Roberts, S G
2013-01-01
ANUGA is an open source and free software developed by the Australian National University (ANU) and Geoscience Australia (GA). This software is a hydraulic numerical model used to solve the two-dimensional shallow water equations. The numerical method underlying it is a finite volume method. This paper presents some validation results of ANUGA with respect to exact solutions to shallow water flow problems. We identify the strengths of ANUGA and comment on future work that may be taken into account for ANUGA development.
Directory of Open Access Journals (Sweden)
Alok Dhaundiyal
2016-10-01
Full Text Available This article focuses on the influence of relevant parameters of biomass pyrolysis on the numerical solution of the isothermal nth-order distributed activation energy model (DAEM using the Rayleigh distribution as the initial distribution function F(E of the activation energies. In this study, the integral upper limit, the frequency factor, the reaction order and the scale parameters are investigated. This paper also derived the asymptotic approximation for the DAEM. The influence of these parameters is used to calculate the kinetic parameters of the isothermal nth-order DAEM with the help of thermo-analytical results of TGA/DTG analysis.
Turchi, Patrice E. A.; Fattebert, Jean-Luc; Dorr, Milo R.; Wickett, Michael E.; Belak, James F.
2011-03-01
We describe an algorithm for the numerical solution of a phase-field model (PFM) of microstructure evolution in alloys using physical parameters from thermodynamic (CALPHAD) and kinetic databases. The coupled system of PFM equations includes a local order parameter, a quaternion representation of local crystal orientation and a species composition parameter. Time evolution of microstructures and alloy composition is obtained using an implicit time integration of the system. Physical parameters in databases can be obtained either through experiment or first-principles calculations. Application to coring studies and microstructure evolution of Au-Ni will be presented. Prepared by LLNL under Contract DE-AC52-07NA27344
The Train Driver Recovery Problem - a Set Partitioning Based Model and Solution Method
DEFF Research Database (Denmark)
Rezanova, Natalia Jurjevna; Ryan, David
The need to recover a train driver schedule occurs during major disruptions in the daily railway operations. Using data from the train driver schedule of the Danish passenger railway operator DSB S-tog A/S, a solution method to the Train Driver Recovery Problem (TDRP) is developed. The TDRP...... is formulated as a set partitioning problem. The LP relaxation of the set partitioning formulation of the TDRP possesses strong integer properties. The proposed model is therefore solved via the LP relaxation and Branch & Price. Starting with a small set of drivers and train tasks assigned to the drivers within...
A self-consistent model for thermodynamics of multicomponent solid solutions
International Nuclear Information System (INIS)
Svoboda, J.; Fischer, F.D.
2016-01-01
The self-consistent concept recently published in this journal (108, 27–30, 2015) is extended from a binary to a multicomponent system. This is possible by exploiting the trapping concept as basis for including the interaction of atoms in terms of pairs (e.g. A–A, B–B, C–C…) and couples (e.g. A–B, B–C, …) in a multicomponent system with A as solvent and B, C, … as dilute solutes. The model results in a formulation of Gibbs-energy, which can be minimized. Examples show that the couple and pair formation may influence the equilibrium Gibbs energy markedly.
Modeling radical edge-site reactions of biochar in CO2/water solution under ultrasonic treatment
Zubatiuk, Tetiana; Sajjadi, Baharak; Hill, Glake; Leszczynska, Danuta; Chen, Wei-Yin; Leszczynski, Jerzy
2017-12-01
We report results of theoretical evaluation of the mechanisms of possible radical reactions on the edge-site of biochar with CO2,SUP>·-, OH ˙ , and H ˙ in irradiated aqueous solution. The computational studies were performed for model poly aromatic systems. Obtained mechanisms reflect one of the routes of the oxygen loss accompanied by increase of hydrogen content, as observed in photochemical experiment. The reaction of CO2·- with the edge site of biochar mainly leads to reduced rather than oxidized products. The mechanism of CO2 capturing is mapped by different routes of one-electron reduction and radical addition to the aromatic ring.
Frampton, Andrew; Destouni, Georgia
2016-04-01
In cold regions, flow in the unsaturated zone is highly dynamic with seasonal variability and changes in temperature, moisture, and heat and water fluxes, all of which affect ground freeze-thaw processes and influence transport of inert and reactive waterborne substances. In arctic permafrost environments, near-surface groundwater flow is further restricted to a relatively shallow and seasonally variable active layer, confined by perennially frozen ground below. The active layer is typically partially saturated with ice, liquid water and air, and is strongly dependent on seasonal temperature fluctuations, thermal forcing and infiltration patterns. Here there is a need for improved understanding of the mechanisms controlling subsurface solute transport in the partially saturated active layer zone. Studying solute transport in cold regions is relevant to improve the understanding of how natural and anthropogenic pollution may change as activities in arctic and sub-arctic regions increase. It is also particularly relevant for understanding how dissolved carbon is transported in coupled surface and subsurface hydrological systems under climate change, in order to better understand the permafrost-hydrological-carbon climate feedback. In this contribution subsurface solute transport under surface warming and degrading permafrost conditions is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in subsurface water flows and solute transport travel times are analysed for different modelled geological configurations during a 100-year warming period. Results show that for all simulated cases, the minimum and mean travel times increase non-linearly with warming irrespective of geological configuration and heterogeneity structure. The travel time changes are shown to depend on combined warming effects of increase in pathway length due to deepening of the active layer, reduced transport
Equilibrium and kinetic models for colloid release under transient solution chemistry conditions.
Bradford, Scott A; Torkzaban, Saeed; Leij, Feike; Simunek, Jiri
2015-10-01
We present continuum models to describe colloid release in the subsurface during transient physicochemical conditions. Our modeling approach relates the amount of colloid release to changes in the fraction of the solid surface area that contributes to retention. Equilibrium, kinetic, equilibrium and kinetic, and two-site kinetic models were developed to describe various rates of colloid release. These models were subsequently applied to experimental colloid release datasets to investigate the influence of variations in ionic strength (IS), pH, cation exchange, colloid size, and water velocity on release. Various combinations of equilibrium and/or kinetic release models were needed to describe the experimental data depending on the transient conditions and colloid type. Release of Escherichia coli D21g was promoted by a decrease in solution IS and an increase in pH, similar to expected trends for a reduction in the secondary minimum and nanoscale chemical heterogeneity. The retention and release of 20nm carboxyl modified latex nanoparticles (NPs) were demonstrated to be more sensitive to the presence of Ca(2+) than D21g. Specifically, retention of NPs was greater than D21g in the presence of 2mM CaCl2 solution, and release of NPs only occurred after exchange of Ca(2+) by Na(+) and then a reduction in the solution IS. These findings highlight the limitations of conventional interaction energy calculations to describe colloid retention and release, and point to the need to consider other interactions (e.g., Born, steric, and/or hydration forces) and/or nanoscale heterogeneity. Temporal changes in the water velocity did not have a large influence on the release of D21g for the examined conditions. This insensitivity was likely due to factors that reduce the applied hydrodynamic torque and/or increase the resisting adhesive torque; e.g., macroscopic roughness and grain-grain contacts. Our analysis and models improve our understanding and ability to describe the amounts
Bu, Sunyoung; Huang, Jingfang; Boyer, Treavor H; Miller, Cass T
2010-07-01
The focus of this work is on the modeling of an ion exchange process that occurs in drinking water treatment applications. The model formulation consists of a two-scale model in which a set of microscale diffusion equations representing ion exchange resin particles that vary in size and age are coupled through a boundary condition with a macroscopic ordinary differential equation (ODE), which represents the concentration of a species in a well-mixed reactor. We introduce a new age-averaged model (AAM) that averages all ion exchange particle ages for a given size particle to avoid the expensive Monte-Carlo simulation associated with previous modeling applications. We discuss two different numerical schemes to approximate both the original Monte Carlo algorithm and the new AAM for this two-scale problem. The first scheme is based on the finite element formulation in space coupled with an existing backward-difference-formula-based ODE solver in time. The second scheme uses an integral equation based Krylov deferred correction (KDC) method and a fast elliptic solver (FES) for the resulting elliptic equations. Numerical results are presented to validate the new AAM algorithm, which is also shown to be more computationally efficient than the original Monte Carlo algorithm. We also demonstrate that the higher order KDC scheme is more efficient than the traditional finite element solution approach and this advantage becomes increasingly important as the desired accuracy of the solution increases. We also discuss issues of smoothness, which affect the efficiency of the KDC-FES approach, and outline additional algorithmic changes that would further improve the efficiency of these developing methods for a wide range of applications.
Modelling The Transport Of Solutes And Colloids In The Grimsel Migration Shear Zone
Energy Technology Data Exchange (ETDEWEB)
Kosakowski, G.; Smith, P
2005-02-01
This report describes modelling of the transport of solutes and colloids in an experimental system comprising an artificial dipole flow field in a water-conducting shear zone at Nagra's Grimsel Test Site (GTS) in the central Swiss Alps. The modelling work forms part of the Colloid and Radionuclide Retardation Project (CRR), which includes a series of field transport experiments and a supporting laboratory programme, as well as modelling studies. Four independent groups representing different organisations or research institutes have conducted the modelling, with each group employing its own modelling approach or approaches. Only the work conducted at the Paul Scherrer Institute (PSI) is described in the present report. The modelling approaches used in the present study may not be directly applicable to safety assessment problems and the direct implications of the results of this study for safety assessment are limited. It can, however, be said that the study has demonstrated the high degree of mobility of bentonite and other colloids in a system that is at least in some ways comparable to those of interest in safety assessment, and has shown that bentonite colloids can at least potentially affect the transport of some safety relevant radionuclides over longer temporal and spatial scales than those addressed here. (author)
Directory of Open Access Journals (Sweden)
T. S. Steenhuis
1997-01-01
Full Text Available Agricultural tile drainage lines have been implicated as a source of pesticide contamination of surface waters. Field experiments were conducted and a simple model was developed to examine preferential transport of applied chemicals to agricultural tile lines. The conceptual model consists of two linear reservoirs, one near the soil surface and one near the tile drain. The connection between the two reservoirs is via preferential flow paths with very little interaction with the soil matrix. The model assumes that only part of the field contributes solutes to the tile drain. The model was evaluated with data from the field experiments in which chloride, 2,4-D, and atrazine concentrations were measured on eight tile-drained plots that were irrigated twice. Atrazine was applied two months prior to the experiment, 2,4-D was sprayed just before the first irrigation, and chloride before the second irrigation. All three chemicals were found in the tile effluent shortly after the rainfall began. Generally, the concentration increased with increased flow rates and decreased exponentially after the rainfall ceased. Although the simple model could simulate the observed chloride concentration patterns in the tile outflow for six of the eight plots, strict validation was not possible because of the difficulty with independent measurement of the data needed for a preferential flow model applied to field conditions. The results show that, to simulate pesticide concentration in tile lines, methods that can measure field averaged preferential flow characteristics need to be developed.
Pseudolinear Model Based Solution to the SLAM Problem of Nonholonomic Mobile Robots
Pathiranage, Chandima Dedduwa; Watanabe, Keigo; Izumi, Kiyotaka
This paper describes an improved solution to the simultaneous localization and mapping (SLAM) problem based on pseudolinear models. Accurate estimation of vehicle and landmark states is one of the key issues for successful mobile robot navigation if the configuration of the environment and initial robot location are unknown. A state estimator which can be designed to use the nonlinearity as it is coming from the original model has always been invaluable in which high accuracy is expected. Thus to accomplish the above highlighted point, pseudolinear model based Kalman filter (PLKF) state estimator is introduced. A less error prone vehicle process model is proposed to improve the accuracy and the faster convergence of state estimation. Evolution of vehicle motion is modeled using vehicle frame translation derived from successive dead reckoned poses as a control input. A measurement model with two sensor frames is proposed to improve the data association. The PLKF-based SLAM algorithm is simulated using Matlab for vehicle-landmarks system and results show that the proposed approach performs much accurately compared to the well known extended Kalman filter (EKF).
Thermodiffusive behaviour of NaCl and KCl aqueous solutions a model for the Na-K pump
International Nuclear Information System (INIS)
Gaeta, F.S.; Mita, D.G.; Perna, G.; Scala, G.
1975-01-01
In NaCl and KCl aqueous nonisothermal solutions K + inverts its sense of migration within the physiological concentration range; Na + behaves similarly at much lower concentrations. These findings are discussed in relation to solute induced modifications of water structure and of their influence on thermal diffusion. A possible evolutionary model of a thermodiffusive mechanism for the sodium potassium pump is also suggested
Meso-scale Modeling of Block Copolymers Self-Assembly in Casting Solutions for Membrane Manufacture
Moreno Chaparro, Nicolas
2016-05-01
Isoporous membranes manufactured from diblock copolymer are successfully produced at laboratory scale under controlled conditions. Because of the complex phenomena involved, membrane preparation requires trial and error methodologies to find the optimal conditions, leading to a considerable demand of resources. Experimental insights demonstrate that the self-assembly of the block copolymers in solution has an effect on the final membrane structure. Nevertheless, the complete understanding of these multi-scale phenomena is elusive. Herein we use the coarse-grained method Dissipative Particle Dynamics to study the self-assembly of block copolymers that are used for the preparation of the membranes. To simulate representative time and length scales, we introduce a framework for model reduction of polymer chain representations for dissipative particle dynamics, which preserves the properties governing the phase equilibria. We reduce the number of degrees of freedom by accounting for the correlation between beads in fine-grained models via power laws and the consistent scaling of the simulation parameters. The coarse-graining models are consistent with the experimental evidence, showing a morphological transition of the aggregates as the polymer concentration and solvent affinity change. We show that hexagonal packing of the micelles can occur in solution within different windows of polymer concentration depending on the solvent affinity. However, the shape and size dispersion of the micelles determine the characteristic arrangement. We describe the order of crew-cut micelles using a rigid-sphere approximation and propose different phase parameters that characterize the emergence of monodisperse-spherical micelles in solution. Additionally, we investigate the effect of blending asymmetric diblock copolymers (AB/AC) over the properties of the membranes. We observe that the co-assembly mechanism localizes the AC molecules at the interface of A and B domains, and induces
Study of Research and Development Processes through Fuzzy Super FRM Model and Optimization Solutions
Directory of Open Access Journals (Sweden)
Flavius Aurelian Sârbu
2015-01-01
Full Text Available The aim of this study is to measure resources for R&D (research and development at the regional level in Romania and also obtain primary data that will be important in making the right decisions to increase competitiveness and development based on an economic knowledge. As our motivation, we would like to emphasize that by the use of Super Fuzzy FRM model we want to determine the state of R&D processes at regional level using a mean different from the statistical survey, while by the two optimization methods we mean to provide optimization solutions for the R&D actions of the enterprises. Therefore to fulfill the above mentioned aim in this application-oriented paper we decided to use a questionnaire and for the interpretation of the results the Super Fuzzy FRM model, representing the main novelty of our paper, as this theory provides a formalism based on matrix calculus, which allows processing of large volumes of information and also delivers results difficult or impossible to see, through statistical processing. Furthermore another novelty of the paper represents the optimization solutions submitted in this work, given for the situation when the sales price is variable, and the quantity sold is constant in time and for the reverse situation.
Importance analysis for models with correlated variables and its sparse grid solution
International Nuclear Information System (INIS)
Li, Luyi; Lu, Zhenzhou
2013-01-01
For structural models involving correlated input variables, a novel interpretation for variance-based importance measures is proposed based on the contribution of the correlated input variables to the variance of the model output. After the novel interpretation of the variance-based importance measures is compared with the existing ones, two solutions of the variance-based importance measures of the correlated input variables are built on the sparse grid numerical integration (SGI): double-loop nested sparse grid integration (DSGI) method and single loop sparse grid integration (SSGI) method. The DSGI method solves the importance measure by decreasing the dimensionality of the input variables procedurally, while SSGI method performs importance analysis through extending the dimensionality of the inputs. Both of them can make full use of the advantages of the SGI, and are well tailored for different situations. By analyzing the results of several numerical and engineering examples, it is found that the novel proposed interpretation about the importance measures of the correlated input variables is reasonable, and the proposed methods for solving importance measures are efficient and accurate. -- Highlights: •The contribution of correlated variables to the variance of the output is analyzed. •A novel interpretation for variance-based indices of correlated variables is proposed. •Two solutions for variance-based importance measures of correlated variables are built
Eric, L.; Vrugt, J. A.
2010-12-01
Spatially distributed hydrologic models potentially contain hundreds of parameters that need to be derived by calibration against a historical record of input-output data. The quality of this calibration strongly determines the predictive capability of the model and thus its usefulness for science-based decision making and forecasting. Unfortunately, high-dimensional optimization problems are typically difficult to solve. Here we present our recent developments to the Differential Evolution Adaptive Metropolis (DREAM) algorithm (Vrugt et al., 2009) to warrant efficient solution of high-dimensional parameter estimation problems. The algorithm samples from an archive of past states (Ter Braak and Vrugt, 2008), and uses multiple-try Metropolis sampling (Liu et al., 2000) to decrease the required burn-in time for each individual chain and increase efficiency of posterior sampling. This approach is hereafter referred to as MT-DREAM. We present results for 2 synthetic mathematical case studies, and 2 real-world examples involving from 10 to 240 parameters. Results for those cases show that our multiple-try sampler, MT-DREAM, can consistently find better solutions than other Bayesian MCMC methods. Moreover, MT-DREAM is admirably suited to be implemented and ran on a parallel machine and is therefore a powerful method for posterior inference.