Atmospheric dispersion modeling: Challenges of the Fukushima Daiichi response
Energy Technology Data Exchange (ETDEWEB)
Sugiyama, Gayle [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nasstrom, John [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pobanz, Brenda [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Foster, Kevin [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Simpson, Matthew [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Vogt, Phil [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Aluzzi, Fernando [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Homann, Steve [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2012-05-01
In this research, the U.S. Department of Energy’s (DOE) National Atmospheric Release Advisory Center (NARAC) provided a wide range of predictions and analyses as part of the response to the Fukushima Daiichi Nuclear Power Plant accident including: daily Japanese weather forecasts and atmospheric transport predictions to inform planning for field monitoring operations and to provide U.S. government agencies with ongoing situational awareness of meteorological conditions; estimates of possible dose in Japan based on hypothetical U.S. Nuclear Regulatory Commission scenarios of potential radionuclide releases to support protective action planning for U.S. citizens; predictions of possible plume arrival times and dose levels at U.S. locations; and source estimation and plume model refinement based on atmospheric dispersion modeling and available monitoring data.
Ensemble atmospheric dispersion modeling for emergency response consequence assessments
International Nuclear Information System (INIS)
Addis, R.P.; Buckley, R.L.
2003-01-01
models. This provides a better understanding of the atmosphere and plume behavior than would a single model output. Atmospheric models often give the impression of greater accuracy than the science is capable of delivering. The ensemble approach is a powerful way to reassert the concept of having a family of equally valid solutions, while enabling outliers to be identified. The U.S. Department of Energy's Savannah River Technology Center (SRTC) has participated in RTMOD and ENSEMBLE. SRTC uses the Regional Atmospheric Modeling System (RAMS) and Lagrangian Particle Dispersion Model (LPDM) to provide plume forecasts in real-time for the European grid as described in the figure. The NOAA northern hemispheric model, Global Forecast System (a combination of the medium range forecast and aviation forecast models), is used to provide the initial and boundary conditions for RAMS. The model plume forecast data are sent to the ENSEMBLE WEB page in real-time where they may be compared with other model outputs. SRTC has participated in all the ENSEMBLE exercises in real-time. An example of the ensemble output is shown in the figure, which shows an overlay of the SRTC (crosshatched) initial 60-hour forecast for the plume overlaid on an ensemble of 5 other model outputs. The plume shadings show the level of consensus for a minimum threshold, enabling modelers to determine consensus between models and identify possible outliers. The traditional approach to provide atmospheric consequence assessment tools to aid decision-makers in response to a release from a nuclear facility is to provide a plume output from a particular model. However, the non-unique nature of solutions to the non-linear equations that govern the atmosphere, and the sensitivity of such equations to perturbations in the initial and boundary conditions, results in any single model output being simply one of many viable solutions. As such, the traditional approach does a disservice to decision-makers by inferring greater
MESOI, an interactive atmospheric dispersion model for emergency response applications
International Nuclear Information System (INIS)
Ramsdell, J.V.; Athey, G.F.; Glantz, C.S.
1984-01-01
MESOI is an interactive atmospheric dispersion model that has been developed for use by the U.S. Department of Energy, and the U.S. Nuclear Regulatory Commission in responding to emergencies at nuclear facilities. MESOI uses both straight-line Gaussian plume and Lagrangian trajectory Gaussian puff models to estimate time-integrated ground-level air and surface concentrations. Puff trajectories are determined from temporally and spatially varying horizontal wind fields that are defined in 3 dimensions. Other processes treated in MESOI include dry deposition, wet deposition and radioactive decay
MESOI, an interactive atmospheric dispersion model for emergency response applications
International Nuclear Information System (INIS)
Ramsdell, J.V.; Athey, G.F.; Glantz, C.S.
1983-12-01
MESOI is an interactive atmospheric despersion model that has been developed for use by the US Department of Energy, and the US Nuclear Regulatory Commission in responding to emergencies at nuclear facilities. MESOI uses both straight-line Gaussian plume and Lagrangian trajectory Gaussian puff models to estimate time-integrated ground-level air and surface concentrations. Puff trajectories are determined from temporally and spatially varying horizontal wind fields that are defined in 3 dimensions. Other processes treated in MESOI include dry deposition, wet deposition and radioactive decay. 9 references
A set of rapid-response models for pollutant dispersion assessments in southern Spain coastal waters
International Nuclear Information System (INIS)
Perianez, R.; Caravaca, F.
2010-01-01
Three rapid-response Lagrangian particle-tracking dispersion models have been developed for southern Spain coastal waters. The three domains cover the Gulf of Cadiz (Atlantic Ocean), the Alboran Sea (Mediterranean), and the Strait of Gibraltar with higher spatial resolution. The models are based on different hydrodynamic submodels, which are run in advance. Tides are calculated using a 2D barotropic model in the three cases. Models used to obtain the residual circulation depend on the physical oceanography of each region. Thus, two-layer models are applied to Gibraltar Strait and Alboran Sea and a 3D baroclinic model is used in the Gulf of Cadiz. Results from these models have been compared with observations to validate them and are then used by the particle-tracking models to calculate dispersion. Chemical, radioactive and oil spills may be simulated, incorporating specific processes for each kind of pollutant. Several application examples are provided.
International Nuclear Information System (INIS)
Uliasz, M.
1990-01-01
The mesoscale dispersion modeling system is under continuous development. The included numerical models require further improvements and evaluation against data from meteorological and tracer field experiments. The system can not be directly applied to real time predictions. However, it seems to be a useful simulation tool for solving several problems related to planning the monitoring network and development of the emergency response system for the nuclear power plant located in a coastal area. The modeling system can be also applied to another environmental problems connected with air pollution dispersion in complex terrain. The presented numerical models are designed for the use on personal computers and are relatively fast in comparison with the similar mesoscale models developed on mainframe computers
International Nuclear Information System (INIS)
Sims, J.; Lee, R.; McCallen, R.; Lawver, B.; Clark, J.; Rueppel, D.; Sullivan, T.
1992-07-01
We have developed a stand-alone, real-time emergency response system to assess and predict the offsite dispersion of particulate releases. We have also developed advanced modeling tools that win expand the capability of the emergency response system to predict nearfield dispersion over complex terrain and around buildings
International Nuclear Information System (INIS)
Greenly, G.D.; Dickerson, M.H.
1983-03-01
Numerical models on several levels of complexity should be available to the emergency response planner. They are a basic tool but must be used in conjunction with both measurements and experience. When these tools are used in a complimentary fashion they greatly enhance the capability of the consequence manager to respond in an emergency situation. Because each accident or incident develops it's own characteristics and requirements the system must be capable of a flexible response. Interaction and feedback between model results from a suite of models and measurements (including airborne measurements) serve the emergency response planner's spectrum of needs, ranging from planning exercises and emergency precalculations to a real-time emergency response
International Nuclear Information System (INIS)
Rahm, L.; Nyberg, L.; Gidhagen, L.
1990-01-01
A dispersion model to be used off costal waters has been developed. The model has been applied to describe the migration of radionuclides in the Baltic sea. A summary of the results is presented here. (K.A.E)
Working document dispersion models
International Nuclear Information System (INIS)
Dop, H. van
1988-01-01
This report is a summary of the most important results from June 1985 of the collaboration of the RIVM (Dutch National Institute for Public Health and Environment Hygiene) and KNMI (Royal Dutch Meteorologic Institute) on the domain of dispersion models. It contains a short description of the actual SO x /NO x -model. Furthermore it contains recommendations for modifications of some numerical-mathematical aspects and an impulse to a more complete description of chemical processes in the atmosphere and the (wet) deposition process. A separate chapter is devoted to the preparation of meteorologic data which are relevant for dispersion as well as atmospheric chemistry and deposition. This report serves as working document for the final formulation of a acidifying- and oxidant-model. (H.W.). 69 refs.; 51 figs.; 13 tabs.; 3 schemes
Distributed emergency response system to model dispersion and deposition of atmospheric releases
International Nuclear Information System (INIS)
Taylor, S.S.
1985-04-01
Aging hardware and software and increasing commitments by the Departments of Energy and Defense have led us to develop a new, expanded system to replace the existing Atmospheric Release Advisory Capability (ARAC) system. This distributed, computer-based, emergency response system is used by state and federal agencies to assess the environmental health hazards resulting from an accidental release of radioactive material into the atmosphere. Like its predecessor, the expanded system uses local meteorology (e.g., wind speed and wind direction), as well as terrain information, to simulate the transport and dispersion of the airborne material. The system also calculates deposition and dose and displays them graphically over base maps of the local geography for use by on-site authorities. This paper discusses the limitations of the existing ARAC system. It also discusses the components and functionality of the new system, the technical difficulties encountered and resolved in its design and implementation, and the software methodologies and tools employed in its development
Resuspension parameters for TRAC dispersion model
International Nuclear Information System (INIS)
Langer, G.
1987-01-01
Resuspension factors for the wind erosion of soil contaminated with plutonium are necessary to run the Rocky Flats Plant Terrain Responsive Atmospheric Code (TRAC). The model predicts the dispersion and resulting population dose due to accidental plutonium releases
The Dangers of Dispersal of Responsibilities
Directory of Open Access Journals (Sweden)
Adriana Schiopoiu Burlea
2017-05-01
Full Text Available Taking into account that it is in the nature of the modern corporation that risks are distributed over several agents, we discuss in this paper the organisational behaviour as it results from such dispersal of responsibilities for both the principal and the agent. We explore the hypothesis that dispersal of responsibilities could be the result or a cause of a lack of consensus between the principal and the agent. Our findings suggest that a dispersal of responsibilities has a negative impact on the principal-agent relationship and that it represents a foundation for theoretical and empirical approaches to organisational behaviour. We find that agent perceptions of a dispersal of responsibilities are linked to his/her resistance to the principal’s interests, but this relationship is deeper than was suggested by previous research. However, if the sharing of responsibilities does not run parallel to that, we may have as a result what we call an agency problem.
Modeling volcanic ash dispersal
CERN. Geneva
2010-01-01
The assessment of volcanic fallout hazard is an important scientific, economic, and political issue, especially in densely populated areas. From a scientific point of view, considerable progress has been made during the last two decades through the use of increasingly powerful computational models and capabilities. Nowadays, models are used to quantify hazard...
Improving practical atmospheric dispersion models
International Nuclear Information System (INIS)
Hunt, J.C.R.; Hudson, B.; Thomson, D.J.
1992-01-01
The new generation of practical atmospheric dispersion model (for short range ≤ 30 km) are based on dispersion science and boundary layer meteorology which have widespread international acceptance. In addition, recent improvements in computer skills and the widespread availability of small powerful computers make it possible to have new regulatory models which are more complex than the previous generation which were based on charts and simple formulae. This paper describes the basis of these models and how they have developed. Such models are needed to satisfy the urgent public demand for sound, justifiable and consistent environmental decisions. For example, it is preferable that the same models are used to simulate dispersion in different industries; in many countries at present different models are used for emissions from nuclear and fossil fuel power stations. The models should not be so simple as to be suspect but neither should they be too complex for widespread use; for example, at public inquiries in Germany, where simple models are mandatory, it is becoming usual to cite the results from highly complex computational models because the simple models are not credible. This paper is written in a schematic style with an emphasis on tables and diagrams. (au) (22 refs.)
1993-03-01
the HDA . The model will 89 explicitly account for initial dilution, aerosol evaporation, and entrainment for turbulent jets, which simplifies...D.N., Yohn, J.F., Koopman R.P. and Brown T.C., "Conduct of Anhydrous Hydrofluoric Acid Spill Experiments," Proc. Int. Cqnf. On Vapor Cloud Modeling
Stochastic models for atmospheric dispersion
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager
2003-01-01
Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... positions close to the boundaries. Different rules have been suggested in the literature with justifications based on simulation studies. Herein the relevant stochastic differential equation model is formulated in a particular way. The formulation is based on the marginal transformation of the position...... velocity distributions that depend on height above the ground both with respect to standard deviation and skewness are substituted into the stationary Fokker/Planck equation. The particle position distribution is taken to be uniform *the well/mixed condition( and also a given dispersion coefficient...
Dispersion modeling by kinematic simulation: Cloud dispersion model
International Nuclear Information System (INIS)
Fung, J C H; Perkins, R J
2008-01-01
A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows (tidal current near a coast and deep ocean). An initial distribution of material is discretized into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by kinematic simulation (KS) or direct numerical simulation. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by KS. The ensemble of discrete clouds is periodically re-discretized, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow, and the results are compared with analytic, steady state solutions. The aim of this study is to understand how pollutants disperses in a turbulent flow through a numerical simulation of fluid particle motion in a random flow field generated by Fourier modes. Although this homogeneous turbulent is rather a 'simple' flow, it represents a building block toward understanding pollutant dispersion in more complex flow. The results presented here are preliminary in nature, but we expect that similar qualitative results should be observed in a genuine turbulent flow.
Utilities for high performance dispersion model PHYSIC
International Nuclear Information System (INIS)
Yamazawa, Hiromi
1992-09-01
The description and usage of the utilities for the dispersion calculation model PHYSIC were summarized. The model was developed in the study of developing high performance SPEEDI with the purpose of introducing meteorological forecast function into the environmental emergency response system. The procedure of PHYSIC calculation consists of three steps; preparation of relevant files, creation and submission of JCL, and graphic output of results. A user can carry out the above procedure with the help of the Geographical Data Processing Utility, the Model Control Utility, and the Graphic Output Utility. (author)
Gold Nanospheres Dispersed Light Responsive Epoxy Vitrimers
Directory of Open Access Journals (Sweden)
Zhenhua Wang
2018-01-01
Full Text Available Vitrimers represent a new class of smart materials. They are covalently crosslinked like thermosets, yet they can be reprocessed like thermoplastics. The underlying mechanism is the rapid exchange reactions which form new bonds while breaking the old ones. So far, heating is the most widely used stimulus to activate the exchange reaction. Compared to heating, light not only is much more convenient to achieve remote and regional control, but can also offer fast healing. Gold nanospheres are excellent photothermal agents, but they are difficult to disperse into vitrimers as they easily aggregate. In this paper, we use polydopamine to prepare gold nanospheres. The resultant polydopamine-coated gold nanospheres (GNS can be well dispersed into epoxy vitrimers, endowing epoxy vitrimers with light responsivity. The composites can be reshaped permanently and temporarily with light at different intensity. Efficient surface patterning and healing are also demonstrated.
Pollen Forecast and Dispersion Modelling
Costantini, Monica; Di Giuseppe, Fabio; Medaglia, Carlo Maria; Travaglini, Alessandro; Tocci, Raffaella; Brighetti, M. Antonia; Petitta, Marcello
2014-05-01
The aim of this study is monitoring, mapping and forecast of pollen distribution for the city of Rome using in-situ measurements of 10 species of common allergenic pollens and measurements of PM10. The production of daily concentration maps, associated to a mobile phone app, are innovative compared to existing dedicated services to people who suffer from respiratory allergies. The dispersal pollen is one of the most well-known causes of allergic disease that is manifested by disorders of the respiratory functions. Allergies are the third leading cause of chronic disease and it is estimated that tens millions of people in Italy suffer from it. Recent works reveal that during the last few years there was a progressive increase of affected subjects, especially in urban areas. This situation may depend: on the ability to transport of pollutants, on the ability to react between pollutants and pollen and from a combination of other irritants, existing in densely populated and polluted urban areas. The methodology used to produce maps is based on in-situ measurements time series relative to 2012, obtained from networks of air quality and pollen stations in the metropolitan area of Rome. The monitoring station aerobiological of University of Rome "Tor Vergata" is located at the Department of Biology. The instrument used to pollen monitoring is a volumetric sampler type Hirst (Hirst 1952), Model 2000 VPPS Lanzoni; the data acquisition is carried out as reported in Standard UNI 11008:2004 - "Qualità dell'aria - Metodo di campionamento e conteggio dei granuli pollinici e delle spore fungine aerodisperse" - the protocol that describes the procedure for measuring of the concentration of pollen grains and fungal spores dispersed into the atmosphere, and reported in the "Manuale di gestione e qualità della R.I.M.A" (Travaglini et. al. 2009). All 10 allergenic pollen are monitored since 1996. At Tor Vergata university is also operating a meteorological station (SP2000, CAE
Discrete dispersion models and their Tweedie asymptotics
DEFF Research Database (Denmark)
Jørgensen, Bent; Kokonendji, Célestin C.
2016-01-01
The paper introduce a class of two-parameter discrete dispersion models, obtained by combining convolution with a factorial tilting operation, similar to exponential dispersion models which combine convolution and exponential tilting. The equidispersed Poisson model has a special place in this ap......The paper introduce a class of two-parameter discrete dispersion models, obtained by combining convolution with a factorial tilting operation, similar to exponential dispersion models which combine convolution and exponential tilting. The equidispersed Poisson model has a special place...... in this approach, whereas several overdispersed discrete distributions, such as the Neyman Type A, Pólya-Aeppli, negative binomial and Poisson-inverse Gaussian, turn out to be Poisson-Tweedie factorial dispersion models with power dispersion functions, analogous to ordinary Tweedie exponential dispersion models...... with power variance functions. Using the factorial cumulant generating function as tool, we introduce a dilation operation as a discrete analogue of scaling, generalizing binomial thinning. The Poisson-Tweedie factorial dispersion models are closed under dilation, which in turn leads to a Poisson...
Modelling airborne dispersion of coarse particulate material
International Nuclear Information System (INIS)
Apsley, D.D.
1989-03-01
Methods of modelling the airborne dispersion and deposition of coarse particulates are presented, with the emphasis on the heavy particles identified as possible constituents of releases from damaged AGR fuel. The first part of this report establishes the physical characteristics of the irradiated particulate in airborne emissions from AGR stations. The second part is less specific and describes procedures for extending current dispersion/deposition models to incorporate a coarse particulate component: the adjustment to plume spread parameters, dispersion from elevated sources and dispersion in conjunction with building effects and plume rise. (author)
An expert system for dispersion model interpretation
International Nuclear Information System (INIS)
Skyllingstad, E.D.; Ramsdell, J.V.
1988-10-01
A prototype expert system designed to diagnose dispersion model uncertainty is described in this paper with application to a puff transport model. The system obtains qualitative information from the model user and through an expert-derived knowledge base, performs a rating of the current simulation. These results can then be used in combination with dispersion model output for deciding appropriate evacuation measures. Ultimately, the goal of this work is to develop an expert system that may be operated accurately by an individual uneducated in meteorology or dispersion modeling. 5 refs., 3 figs
Wamelink, G.W.W.; Jochem, R.; Greft, van der J.G.M.; Franke, J.; Malinowska, A.H.; Geertsema, W.; Prins, A.H.; Ozinga, W.A.; Hoek, van der D.C.J.; Grashof-Bokdam, C.J.
2014-01-01
Due to human activities many natural habitats have become isolated. As a result the dispersal of many plant species is hampered. Isolated populations may become extinct and have a lower probability to become reestablished in a natural way. Moreover, plant species may be forced to migrate to new
Modeling of atmospheric dispersion of radionuclides
International Nuclear Information System (INIS)
Baklouti, Nada
2010-01-01
This work is a prediction of atmospheric dispersion of radionuclide from a chronic rejection of the nuclear power generating plant that can be located in one of the Tunisian sites: Skhira or Bizerte. Also it contains a study of acute rejection 'Chernobyl accident' which was the reference for the validation of GENII the code of modeling of atmospheric dispersion.
Modeling electrical dispersion phenomena in Earth materials
Directory of Open Access Journals (Sweden)
D. Patella
2008-06-01
Full Text Available It is illustrated that IP phenomena in rocks can be described using conductivity dispersion models deduced as solutions to a 2nd-order linear differential equation describing the motion of a charged particle immersed in an external electrical field. Five dispersion laws are discussed, namely: the non-resonant positive IP model, which leads to the classical Debye-type dispersion law and by extension to the Cole-Cole model, largely used in current practice; the non-resonant negative IP model, which allows negative chargeability values, known in metals at high frequencies, to be explained as an intrinsic physical property of earth materials in specific field cases; the resonant flat, positive or negative IP models, which can explain the presence of peak effects at specific frequencies superimposed on flat, positive or negative dispersion spectra.
Modelling of pollution dispersion in atmosphere
International Nuclear Information System (INIS)
Borysiewicz, M.; Stankiewicz, R.
1994-01-01
The paper contains the review of the mathematical foundation of atmospheric dispersion models. The atmospheric phenomena relevant to atmospheric dispersion model are discussed. In particular the parametrization of processes with time and space scales smaller than numerical grid size, limited by available computer power, is presented. The special attention was devoted to similarity theory and parametrization of boundary layer. The numerical methods are analysed and the drawbacks of the method are presented. (author). 99 refs, 15 figs, 3 tabs
Atmospheric dispersion models of radioactivity releases
International Nuclear Information System (INIS)
Oza, R.B.
2016-01-01
In view of the rapid industrialization in recent time, atmospheric dispersion models have become indispensible 'tools' to ensure that the effects of releases are well within the acceptable limits set by the regulatory authority. In the case of radioactive releases from the nuclear facility, though negligible in quantity and many a times not even measurable, it is required to demonstrate the compliance of these releases to the regulatory limits set by the regulatory authority by carrying out radiological impact assessment. During routine operations of nuclear facility, the releases are so low that environmental impact is usually assessed with the help of atmospheric dispersion models as it is difficult to distinguish negligible contribution of nuclear facility to relatively high natural background radiation. The accidental releases from nuclear facility, though with negligible probability of occurrence, cannot be ruled out. In such cases, the atmospheric dispersion models are of great help to emergency planners for deciding the intervention actions to minimize the consequences in public domain and also to workout strategies for the management of situation. In case of accidental conditions, the atmospheric dispersion models are also utilized for the estimation of probable quantities of radionuclides which might have got released to the atmosphere. Thus, atmospheric dispersion models are an essential tool for nuclear facility during routine operation as well as in the case of accidental conditions
Spatially varying dispersion to model breakthrough curves.
Li, Guangquan
2011-01-01
Often the water flowing in a karst conduit is a combination of contaminated water entering at a sinkhole and cleaner water released from the limestone matrix. Transport processes in the conduit are controlled by advection, mixing (dilution and dispersion), and retention-release. In this article, a karst transport model considering advection, spatially varying dispersion, and dilution (from matrix seepage) is developed. Two approximate Green's functions are obtained using transformation of variables, respectively, for the initial-value problem and for the boundary-value problem. A numerical example illustrates that mixing associated with strong spatially varying conduit dispersion can cause strong skewness and long tailing in spring breakthrough curves. Comparison of the predicted breakthrough curve against that measured from a dye-tracing experiment between Ames Sink and Indian Spring, Northwest Florida, shows that the conduit dispersivity can be as large as 400 m. Such a large number is believed to imply strong solute interaction between the conduit and the matrix and/or multiple flow paths in a conduit network. It is concluded that Taylor dispersion is not dominant in transport in a karst conduit, and the complicated retention-release process between mobile- and immobile waters may be described by strong spatially varying conduit dispersion. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.
Modeling of corium dispersion in DCH accidents
International Nuclear Information System (INIS)
Wu, Q.
1996-01-01
A model that governs the dispersion process in the direct containment heating (DCH) reactor accident scenario is developed by a stepwise approach. In this model, the whole transient is subdivided into four phases with an isothermal assumption. These are the liquid and gas discharge, the liquid film flow in the cavity before gas blowdown, the liquid and gas flow in the cavity with droplet entrainment, and the liquid transport and re-entrainment in the subcompartment. In each step, the dominant driving mechanisms are identified to construct the governing equations. By combining all the steps together, the corium dispersion information is obtained in detail. The key parameters are predicted quantitatively. These include the fraction of liquid that flows out of the cavity before gas blowdown, the dispersion fraction and the mean droplet diameter in the cavity, the cavity pressure rise due to the liquid friction force, and the dispersion fractions in the containment via different paths. Compared with the data of the 1:10 scale experiments carried out at Purdue University, fairly good agreement is obtained. A stand-alone prediction of the corium dispersion under prototypic Zion reactor conditions is carried out by assuming an isothermal process without chemical reactions. (orig.)
Modeling the dispersion effects of contractile fibers in smooth muscles
Murtada, Sae-Il; Kroon, Martin; Holzapfel, Gerhard A.
2010-12-01
Micro-structurally based models for smooth muscle contraction are crucial for a better understanding of pathological conditions such as atherosclerosis, incontinence and asthma. It is meaningful that models consider the underlying mechanical structure and the biochemical activation. Hence, a simple mechanochemical model is proposed that includes the dispersion of the orientation of smooth muscle myofilaments and that is capable to capture available experimental data on smooth muscle contraction. This allows a refined study of the effects of myofilament dispersion on the smooth muscle contraction. A classical biochemical model is used to describe the cross-bridge interactions with the thin filament in smooth muscles in which calcium-dependent myosin phosphorylation is the only regulatory mechanism. A novel mechanical model considers the dispersion of the contractile fiber orientations in smooth muscle cells by means of a strain-energy function in terms of one dispersion parameter. All model parameters have a biophysical meaning and may be estimated through comparisons with experimental data. The contraction of the middle layer of a carotid artery is studied numerically. Using a tube the relationships between the internal pressure and the stretches are investigated as functions of the dispersion parameter, which implies a strong influence of the orientation of smooth muscle myofilaments on the contraction response. It is straightforward to implement this model in a finite element code to better analyze more complex boundary-value problems.
Advection models of longitudinal dispersion in rivers
Kranenburg, C.
1996-01-01
A derivation is presented of a general cross-section averaged model of longitudinal dispersion, which is based on the notion of the advection of tracer particles. Particle displacement length and particle travel time are conceived as stochastic variables, and a joint probability density function is
Chaotic Lagrangian models for turbulent relative dispersion.
Lacorata, Guglielmo; Vulpiani, Angelo
2017-04-01
A deterministic multiscale dynamical system is introduced and discussed as a prototype model for relative dispersion in stationary, homogeneous, and isotropic turbulence. Unlike stochastic diffusion models, here trajectory transport and mixing properties are entirely controlled by Lagrangian chaos. The anomalous "sweeping effect," a known drawback common to kinematic simulations, is removed through the use of quasi-Lagrangian coordinates. Lagrangian dispersion statistics of the model are accurately analyzed by computing the finite-scale Lyapunov exponent (FSLE), which is the optimal measure of the scaling properties of dispersion. FSLE scaling exponents provide a severe test to decide whether model simulations are in agreement with theoretical expectations and/or observation. The results of our numerical experiments cover a wide range of "Reynolds numbers" and show that chaotic deterministic flows can be very efficient, and numerically low-cost, models of turbulent trajectories in stationary, homogeneous, and isotropic conditions. The mathematics of the model is relatively simple, and, in a geophysical context, potential applications may regard small-scale parametrization issues in general circulation models, mixed layer, and/or boundary layer turbulence models as well as Lagrangian predictability studies.
Debris Dispersion Model Using Java 3D
Thirumalainambi, Rajkumar; Bardina, Jorge
2004-01-01
This paper describes web based simulation of Shuttle launch operations and debris dispersion. Java 3D graphics provides geometric and visual content with suitable mathematical model and behaviors of Shuttle launch. Because the model is so heterogeneous and interrelated with various factors, 3D graphics combined with physical models provides mechanisms to understand the complexity of launch and range operations. The main focus in the modeling and simulation covers orbital dynamics and range safety. Range safety areas include destruct limit lines, telemetry and tracking and population risk near range. If there is an explosion of Shuttle during launch, debris dispersion is explained. The shuttle launch and range operations in this paper are discussed based on the operations from Kennedy Space Center, Florida, USA.
Air quality dispersion models from energy sources
International Nuclear Information System (INIS)
Lazarevska, Ana
1996-01-01
Along with the continuing development of new air quality models that cover more complex problems, in the Clean Air Act, legislated by the US Congress, a consistency and standardization of air quality model applications were encouraged. As a result, the Guidelines on Air Quality Models were published, which are regularly reviewed by the Office of Air Quality Planning and Standards, EPA. These guidelines provide a basis for estimating the air quality concentrations used in accessing control strategies as well as defining emission limits. This paper presents a review and analysis of the recent versions of the models: Simple Terrain Stationary Source Model; Complex Terrain Dispersion Model; Ozone,Carbon Monoxide and Nitrogen Dioxide Models; Long Range Transport Model; Other phenomenon Models:Fugitive Dust/Fugitive Emissions, Particulate Matter, Lead, Air Pathway Analyses - Air Toxic as well as Hazardous Waste. 8 refs., 4 tabs., 2 ills
Modelling Pollutant Dispersion in a Street Network
Salem, N. Ben; Garbero, V.; Salizzoni, P.; Lamaison, G.; Soulhac, L.
2015-04-01
This study constitutes a further step in the analysis of the performances of a street network model to simulate atmospheric pollutant dispersion in urban areas. The model, named SIRANE, is based on the decomposition of the urban atmosphere into two sub-domains: the urban boundary layer, whose dynamics is assumed to be well established, and the urban canopy, represented as a series of interconnected boxes. Parametric laws govern the mass exchanges between the boxes under the assumption that the pollutant dispersion within the canopy can be fully simulated by modelling three main bulk transfer phenomena: channelling along street axes, transfers at street intersections, and vertical exchange between street canyons and the overlying atmosphere. Here, we aim to evaluate the reliability of the parametrizations adopted to simulate these phenomena, by focusing on their possible dependence on the external wind direction. To this end, we test the model against concentration measurements within an idealized urban district whose geometrical layout closely matches the street network represented in SIRANE. The analysis is performed for an urban array with a fixed geometry and a varying wind incidence angle. The results show that the model provides generally good results with the reference parametrizations adopted in SIRANE and that its performances are quite robust for a wide range of the model parameters. This proves the reliability of the street network approach in simulating pollutant dispersion in densely built city districts. The results also show that the model performances may be improved by considering a dependence of the wind fluctuations at street intersections and of the vertical exchange velocity on the direction of the incident wind. This opens the way for further investigations to clarify the dependence of these parameters on wind direction and street aspect ratios.
Energy Technology Data Exchange (ETDEWEB)
Gowardhan, Akshay [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Neuscamman, Stephanie [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Donetti, John [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Walker, Hoyt [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Belles, Rich [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Eme, Bill [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Homann, Steven [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Simpson, Matthew [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Nasstrom, John [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC)
2017-05-24
Aeolus is an efficient three-dimensional computational fluid dynamics code based on finite volume method developed for predicting transport and dispersion of contaminants in a complex urban area. It solves the time dependent incompressible Navier-Stokes equation on a regular Cartesian staggered grid using a fractional step method. It also solves a scalar transport equation for temperature and using the Boussinesq approximation. The model also includes a Lagrangian dispersion model for predicting the transport and dispersion of atmospheric contaminants. The model can be run in an efficient Reynolds Average Navier-Stokes (RANS) mode with a run time of several minutes, or a more detailed Large Eddy Simulation (LES) mode with run time of hours for a typical simulation. This report describes the model components, including details on the physics models used in the code, as well as several model validation efforts. Aeolus wind and dispersion predictions are compared to field data from the Joint Urban Field Trials 2003 conducted in Oklahoma City (Allwine et al 2004) including both continuous and instantaneous releases. Newly implemented Aeolus capabilities include a decay chain model and an explosive Radiological Dispersal Device (RDD) source term; these capabilities are described. Aeolus predictions using the buoyant explosive RDD source are validated against two experimental data sets: the Green Field explosive cloud rise experiments conducted in Israel (Sharon et al 2012) and the Full-Scale RDD Field Trials conducted in Canada (Green et al 2016).
Modeling of Rayleigh wave dispersion in Iberia
Directory of Open Access Journals (Sweden)
José Badal
2011-01-01
Full Text Available Phase and group velocities of 15–70 s Rayleigh waves propagating across the Iberian Peninsula have been transformed into local dispersion curves by linear inversion of travel times. The procedure permits that the waveform dispersion to be obtained as a continuous period-dependent velocity function at grid points belonging to the area probed by the waves, thus providing phase- and group-velocity contour maps for several periods within the interval of interest. The regionalization process rests on a homogeneous initial data set in which the number of observations remains almost constant for all periods of reference. Damped least-squares inversion of the local dispersion curves for shear-wave velocity structure is performed to obtain depth-dependent S-wave velocity profiles at the grid points covering the model region. The reliability of the results should improve significantly owing to the use of phase and group velocities simultaneously. On this basis, we have built horizontal depth sections that give an updated view of the seismic velocity structure of the peninsula at lithospheric and upper mantle depths (20–200 km. After averaging all the pure-path S-wave velocities previously determined at each grid point, the velocity-depth models so obtained for major tectonic units allow the comparison between the Hercynian basement and other areas of Mesozoic folding and Tertiary basins.
Modeling pollutant dispersion within a tornadic thunderstorm
Energy Technology Data Exchange (ETDEWEB)
Pepper, D W
1982-01-01
A three-dimensional numerical model has been developed to calculate ground-level air concentration and deposition of particles entrained in a tornadic thunderstorm. The rotational characteristics of the tornadic storm are within the larger mesoscale flow of the storm system and transported with the vortex. Turbulence exchange coefficients are based on empirical values. The quasi-Lagrangian method of moments is used to model the transport of concentration within a grid cell volume. Results indicate that updrafts and downdrafts, coupled with scavenging of particles by precipitation, account for most of the material being deposited closer to the site than anticipated. Approximately 5% of the pollutant is dispersed into the stratosphere.
Air Quality Dispersion Modeling - Alternative Models
Models, not listed in Appendix W, that can be used in regulatory applications with case-by-case justification to the Reviewing Authority as noted in Section 3.2, Use of Alternative Models, in Appendix W.
Modelling airborne dispersion for disaster management
Musliman, I. A.; Yohnny, L.
2017-05-01
Industrial disasters, like any other disasters, can happen anytime, anywhere and in any form. Airborne industrial disaster is a kind of catastrophic event involving the release of particles such as chemicals and industrial wastes into environment in gaseous form, for instance gas leakages. Unlike solid and liquid materials, gases are often colourless and odourless, the particles are too tiny to be visible to the naked eyes; hence it is difficult to identify the presence of the gases and to tell the dispersion and location of the substance. This study is to develop an application prototype to perform simulation modelling on the gas particles to determine the dispersion of the gas particles and to identify the coverage of the affected area. The prototype adopted Lagrangian Particle Dispersion (LPD) model to calculate the position of the gas particles under the influence of wind and turbulent velocity components, which are the induced wind due to the rotation of the Earth, and Convex Hull algorithm to identify the convex points of the gas cloud to form the polygon of the coverage area. The application performs intersection and overlay analysis over a set of landuse data at Pasir Gudang, Johor industrial and residential area. Results from the analysis would be useful to tell the percentage and extent of the affected area, and are useful for the disaster management to evacuate people from the affected area. The developed application can significantly increase efficiency of emergency handling during a crisis. For example, by using a simulation model, the emergency handling can predict what is going to happen next, so people can be well informed and preparations works can be done earlier and better. Subsequently, this application helps a lot in the decision making process.
Modelling airborne dispersion for disaster management
International Nuclear Information System (INIS)
Musliman, I A; Yohnny, L
2017-01-01
Industrial disasters, like any other disasters, can happen anytime, anywhere and in any form. Airborne industrial disaster is a kind of catastrophic event involving the release of particles such as chemicals and industrial wastes into environment in gaseous form, for instance gas leakages. Unlike solid and liquid materials, gases are often colourless and odourless, the particles are too tiny to be visible to the naked eyes; hence it is difficult to identify the presence of the gases and to tell the dispersion and location of the substance. This study is to develop an application prototype to perform simulation modelling on the gas particles to determine the dispersion of the gas particles and to identify the coverage of the affected area. The prototype adopted Lagrangian Particle Dispersion (LPD) model to calculate the position of the gas particles under the influence of wind and turbulent velocity components, which are the induced wind due to the rotation of the Earth, and Convex Hull algorithm to identify the convex points of the gas cloud to form the polygon of the coverage area. The application performs intersection and overlay analysis over a set of landuse data at Pasir Gudang, Johor industrial and residential area. Results from the analysis would be useful to tell the percentage and extent of the affected area, and are useful for the disaster management to evacuate people from the affected area. The developed application can significantly increase efficiency of emergency handling during a crisis. For example, by using a simulation model, the emergency handling can predict what is going to happen next, so people can be well informed and preparations works can be done earlier and better. Subsequently, this application helps a lot in the decision making process. (paper)
Hrycik, Janelle M.; Chassé, Joël; Ruddick, Barry R.; Taggart, Christopher T.
2013-11-01
Early life-stage dispersal influences recruitment and is of significance in explaining the distribution and connectivity of marine species. Motivations for quantifying dispersal range from biodiversity conservation to the design of marine reserves and the mitigation of species invasions. Here we compare estimates of real particle dispersion in a coastal marine environment with similar estimates provided by hydrodynamic modelling. We do so by using a system of magnetically attractive particles (MAPs) and a magnetic-collector array that provides measures of Lagrangian dispersion based on the time-integration of MAPs dispersing through the array. MAPs released as a point source in a coastal marine location dispersed through the collector array over a 5-7 d period. A virtual release and observed (real-time) environmental conditions were used in a high-resolution three-dimensional hydrodynamic model to estimate the dispersal of virtual particles (VPs). The number of MAPs captured throughout the collector array and the number of VPs that passed through each corresponding model location were enumerated and compared. Although VP dispersal reflected several aspects of the observed MAP dispersal, the comparisons demonstrated model sensitivity to the small-scale (random-walk) particle diffusivity parameter (Kp). The one-dimensional dispersal kernel for the MAPs had an e-folding scale estimate in the range of 5.19-11.44 km, while those from the model simulations were comparable at 1.89-6.52 km, and also demonstrated sensitivity to Kp. Variations among comparisons are related to the value of Kp used in modelling and are postulated to be related to MAP losses from the water column and (or) shear dispersion acting on the MAPs; a process that is constrained in the model. Our demonstration indicates a promising new way of 1) quantitatively and empirically estimating the dispersal kernel in aquatic systems, and 2) quantitatively assessing and (or) improving regional hydrodynamic
mathematical modelling of atmospheric dispersion of pollutants
International Nuclear Information System (INIS)
Mohamed, M.E.
2002-01-01
the main objectives of this thesis are dealing with environmental problems adopting mathematical techniques. in this respect, atmospheric dispersion processes have been investigated by improving the analytical models to realize the realistic physical phenomena. to achieve these aims, the skeleton of this work contained both mathematical and environmental topics,performed in six chapters. in chapter one we presented a comprehensive review study of most important informations related to our work such as thermal stability , plume rise, inversion, advection , dispersion of pollutants, gaussian plume models dealing with both radioactive and industrial contaminants. chapter two deals with estimating the decay distance as well as the decay time of either industrial or radioactive airborne pollutant. further, highly turbulent atmosphere has been investigated as a special case in the three main thermal stability classes namely, neutral, stable, and unstable atmosphere. chapter three is concerned with obtaining maximum ground level concentration of air pollutant. the variable effective height of pollutants has been considered throughout the mathematical treatment. as a special case the constancy of effective height has been derived mathematically and the maximum ground level concentration as well as its location have been established
Meteorological Uncertainty of atmospheric Dispersion model results (MUD)
DEFF Research Database (Denmark)
Havskov Sørensen, Jens; Amstrup, Bjarne; Feddersen, Henrik
The MUD project addresses assessment of uncertainties of atmospheric dispersion model predictions, as well as optimum presentation to decision makers. Previously, it has not been possible to estimate such uncertainties quantitatively, but merely to calculate the 'most likely' dispersion scenario....
Response surface analysis to improve dispersed crude oil biodegradation
Energy Technology Data Exchange (ETDEWEB)
Zahed, Mohammad A.; Aziz, Hamidi A.; Mohajeri, Leila [School of Civil Engineering, Universiti Sains Malaysia, Nibong Tebal, Penang (Malaysia); Isa, Mohamed H. [Civil Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Perak (Malaysia)
2012-03-15
In this research, the bioremediation of dispersed crude oil, based on the amount of nitrogen and phosphorus supplementation in the closed system, was optimized by the application of response surface methodology and central composite design. Correlation analysis of the mathematical-regression model demonstrated that a quadratic polynomial model could be used to optimize the hydrocarbon bioremediation (R{sup 2} = 0.9256). Statistical significance was checked by analysis of variance and residual analysis. Natural attenuation was removed by 22.1% of crude oil in 28 days. The highest removal on un-optimized condition of 68.1% were observed by using nitrogen of 20.00 mg/L and phosphorus of 2.00 mg/L in 28 days while optimization process exhibited a crude oil removal of 69.5% via nitrogen of 16.05 mg/L and phosphorus 1.34 mg/L in 27 days therefore optimization can improve biodegradation in shorter time with less nutrient consumption. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Biophysical models of larval dispersal in the Benguela Current ...
African Journals Online (AJOL)
We synthesise and update results from the suite of biophysical, larval-dispersal models developed in the Benguela Current ecosystem. Biophysical models of larval dispersal use outputs of physical hydrodynamic models as inputs to individual-based models in which biological processes acting during the larval life are ...
Atmospheric dispersion modelling over complex terrain at small scale
Nosek, S.; Janour, Z.; Kukacka, L.; Jurcakova, K.; Kellnerova, R.; Gulikova, E.
2014-03-01
Previous study concerned of qualitative modelling neutrally stratified flow over open-cut coal mine and important surrounding topography at meso-scale (1:9000) revealed an important area for quantitative modelling of atmospheric dispersion at small-scale (1:3300). The selected area includes a necessary part of the coal mine topography with respect to its future expansion and surrounding populated areas. At this small-scale simultaneous measurement of velocity components and concentrations in specified points of vertical and horizontal planes were performed by two-dimensional Laser Doppler Anemometry (LDA) and Fast-Response Flame Ionization Detector (FFID), respectively. The impact of the complex terrain on passive pollutant dispersion with respect to the prevailing wind direction was observed and the prediction of the air quality at populated areas is discussed. The measured data will be used for comparison with another model taking into account the future coal mine transformation. Thus, the impact of coal mine transformation on pollutant dispersion can be observed.
Modeling the dispersal of spiny lobster (
Whomersley, P.; van der Molen, J.; Holt, D.; Trundle, C.; Clark, S.; Fletcher, D.
2018-01-01
Knowledge of larval dispersal, population dynamics and connectivity in relation to the management and conservation of commercially important species is vital if existing fisheries are to remain sustainable into the future. Larval dispersal of the commercially exploited spiny lobster, Palinurus
Novel applications of the dispersive optical model
Dickhoff, W. H.; Charity, R. J.; Mahzoon, M. H.
2017-03-01
A review of recent developments of the dispersive optical model (DOM) is presented. Starting from the original work of Mahaux and Sartor, several necessary steps are developed and illustrated which increase the scope of the DOM allowing its interpretation as generating an experimentally constrained functional form of the nucleon self-energy. The method could therefore be renamed as the dispersive self-energy method. The aforementioned steps include the introduction of simultaneous fits of data for chains of isotopes or isotones allowing a data-driven extrapolation for the prediction of scattering cross sections and level properties in the direction of the respective drip lines. In addition, the energy domain for data was enlarged to include results up to 200 MeV where available. An important application of this work was implemented by employing these DOM potentials to the analysis of the (d, p) transfer reaction using the adiabatic distorted wave approximation. We review these calculations which suggest that physically meaningful results are easier to obtain by employing DOM ingredients as compared to the traditional approach which relies on a phenomenologically-adjusted bound-state wave function combined with a global (nondispersive) optical-model potential. Application to the exotic 132Sn nucleus also shows great promise for the extrapolation of DOM potentials towards the drip line with attendant relevance for the physics of FRIB. We note that the DOM method combines structure and reaction information on the same footing providing a unique approach to the analysis of exotic nuclei. We illustrate the importance of abandoning the custom of representing the non-local Hartree-Fock (HF) potential in the DOM by an energy-dependent local potential as it impedes the proper normalization of the solution of the Dyson equation. This important step allows for the interpretation of the DOM potential as representing the nucleon self-energy permitting the calculations of
Sensitivity of numerical dispersion modeling to explosive source parameters
International Nuclear Information System (INIS)
Baskett, R.L.; Cederwall, R.T.
1991-01-01
The calculation of downwind concentrations from non-traditional sources, such as explosions, provides unique challenges to dispersion models. The US Department of Energy has assigned the Atmospheric Release Advisory Capability (ARAC) at the Lawrence Livermore National Laboratory (LLNL) the task of estimating the impact of accidental radiological releases to the atmosphere anywhere in the world. Our experience includes responses to over 25 incidents in the past 16 years, and about 150 exercises a year. Examples of responses to explosive accidents include the 1980 Titan 2 missile fuel explosion near Damascus, Arkansas and the hydrogen gas explosion in the 1986 Chernobyl nuclear power plant accident. Based on judgment and experience, we frequently estimate the source geometry and the amount of toxic material aerosolized as well as its particle size distribution. To expedite our real-time response, we developed some automated algorithms and default assumptions about several potential sources. It is useful to know how well these algorithms perform against real-world measurements and how sensitive our dispersion model is to the potential range of input values. In this paper we present the algorithms we use to simulate explosive events, compare these methods with limited field data measurements, and analyze their sensitivity to input parameters. 14 refs., 7 figs., 2 tabs
Accident consequence assessments with different atmospheric dispersion models
International Nuclear Information System (INIS)
Panitz, H.J.
1989-11-01
An essential aim of the improvements of the new program system UFOMOD for Accident Consequence Assessments (ACAs) was to substitute the straight-line Gaussian plume model conventionally used in ACA models by more realistic atmospheric dispersion models. To identify improved models which can be applied in ACA codes and to quantify the implications of different dispersion models on the results of an ACA, probabilistic comparative calculations with different atmospheric dispersion models have been performed. The study showed that there are trajectory models available which can be applied in ACAs and that they provide more realistic results of ACAs than straight-line Gaussian models. This led to a completely novel concept of atmospheric dispersion modelling in which two different distance ranges of validity are distinguished: the near range of some ten kilometres distance and the adjacent far range which are assigned to respective trajectory models. (orig.) [de
Fused deposition modelling of sodium caseinate dispersions
Schutyser, M.A.I.; Houlder, S.; Wit, de Martin; Buijsse, C.A.P.; Alting, A.C.
2018-01-01
Only recently, researchers have started experimenting with 3D printing of foods. The aim of this study was to investigate 3D printed objects from sodium caseinate dispersions, exhibiting reversible gelation behaviour. Gelation and dispensing behaviour were explored and structures of different
International Nuclear Information System (INIS)
Milinkovitch, Thomas; Godefroy, Joachim; Theron, Michael; Thomas-Guyon, Helene
2011-01-01
Dispersant use in nearshore areas is likely to increase the exposure of aquatic organisms to petroleum. To measure the toxicity of this controversial response technique, golden grey mullets (Liza aurata) were exposed to mechanically dispersed oil, chemically dispersed oil, dispersant alone in seawater, water-soluble fraction of oil and to seawater as a control treatment. Several biomarkers were assessed in the gills (enzymatic antioxidant activities, glutathione content, lipid peroxidation) and in the gallbladder (polycylic aromatic hydrocarbons metabolites). The significant differences between chemically dispersed oil and water soluble fraction of oil highlight the environmental risk to disperse an oil slick when containment and recovery can be conducted. The lack of significance between chemically and mechanically dispersed oil suggests that dispersant application is no more toxic than the natural dispersion of the oil slick. The results of this study are of interest in order to establish dispersant use policies in nearshore areas. - Highlights: → This study simulates and evaluates the toxicity of dispersant use in nearshore area. → Dispersant use toxicity is assessed through biomarkers measurement in a fish species. → Chemical dispersion of an oil slick increases the petroleum toxicity. → Dispersant use does not enhance the toxicity of a mechanically dispersed oil slick. → This work leads to conclusions concerning dispersant use policies in nearshore area. - When the meteorological conditions induce the dispersion of the oil slick (e.g. wave), the application of dispersant does not increase the toxicity of petroleum.
Computer modelling of contaminant migration in natural disperse media
International Nuclear Information System (INIS)
Kundas, S.P.; Gishkelyuk, I.A.; Khil'ko, O.S.
2012-01-01
The theoretical foundations for modeling of the contaminants migration in natural disperses media taking into account interconnected heat and moisture transport are developed. The calculation of mass transfer parameters based on adsorption isotherms of water and thermodynamic equations in the developed mathematical models. The artificial neural networks use to predict migration of contaminants in natural disperse media is proposed. The developed software package is presented and results of practical application of models and software are discussed. (authors)
Modelling long-distance seed dispersal in heterogeneous landscapes.
Energy Technology Data Exchange (ETDEWEB)
Levey, Douglas, J.; Tewlsbury, Joshua, J.; Bolker, Benjamin, M.
2008-01-01
1. Long-distance seed dispersal is difficult to measure, yet key to understanding plant population dynamics and community composition. 2. We used a spatially explicit model to predict the distribution of seeds dispersed long distances by birds into habitat patches of different shapes. All patches were the same type of habitat and size, but varied in shape. They occurred in eight experimental landscapes, each with five patches of four different shapes, 150 m apart in a matrix of mature forest. The model was parameterized with smallscale movement data collected from field observations of birds. In a previous study we validated the model by testing its predictions against observed patterns of seed dispersal in real landscapes with the same types and spatial configuration of patches as in the model. 3. Here we apply the model more broadly, examining how patch shape influences the probability of seed deposition by birds into patches, how dispersal kernels (distributions of dispersal distances) vary with patch shape and starting location, and how movement of seeds between patches is affected by patch shape. 4. The model predicts that patches with corridors or other narrow extensions receive higher numbers of seeds than patches without corridors or extensions. This pattern is explained by edgefollowing behaviour of birds. Dispersal distances are generally shorter in heterogeneous landscapes (containing patchy habitat) than in homogeneous landscapes, suggesting that patches divert the movement of seed dispersers, ‘holding’ them long enough to increase the probability of seed defecation in the patches. Dispersal kernels for seeds in homogeneous landscapes were smooth, whereas those in heterogenous landscapes were irregular. In both cases, long-distance (> 150 m) dispersal was surprisingly common, usually comprising approximately 50% of all dispersal events. 5. Synthesis . Landscape heterogeneity has a large influence on patterns of long-distance seed dispersal. Our
Modelling surface radioactive spill dispersion in the Alboran Sea
International Nuclear Information System (INIS)
Perianez, R.
2006-01-01
The Strait of Gibraltar and the Alboran Sea are the only connection between the Atlantic Ocean and the Mediterranean Sea. Intense shipping activities occur in the area, including transport of waste radionuclides and transit of nuclear submarines. Thus, it is relevant to have a dispersion model that can be used in an emergency situation after an accident, to help the decision-making process. Such dispersion model requires an appropriate description of the physical oceanography of the region of interest, with simulations of tides and residual (average) circulation. In this work, a particle-tracking dispersion model that can be used to simulate the dispersion of radionuclides in the system Strait of Gibraltar-Alboran Sea is described. Tides are simulated using a barotropic model and for the average circulation a reduced-gravity model is applied. This model is able to reproduce the main features of the Alboran circulation (the well known Western Alboran Gyre, WAG, and the coastal circulation mode). The dispersion model is run off-line, using previously computed tidal and residual currents. The contamination patch is simulated by a number of particles whose individual paths are computed; diffusion and decay being modelled using a Monte Carlo method. Radionuclide concentrations may be obtained from the density of particles per water volume unit. Results from the hydrodynamic models have been compared with observations in the area. Several examples of dispersion computations under different wind and circulation conditions are presented
Presentation of Austrians recommended dispersion model for tunnel portals
Energy Technology Data Exchange (ETDEWEB)
Oettl, D.; Sturm, P.; Almbauer, R. [Inst. for Internal Combustion Engines and Thermodynamics, Graz Univ. of Technology (Austria)
2004-07-01
Street tunnels in cities are often suggested as solution to avoid daily congestions but also to prevent residential areas from high noise and air pollution emissions. In case of longitudinal ventilated tunnels high pollution levels may occur in the vicinity of the portals. The dispersion of pollutants from tunnel portals is considered to differ significantly from those of other sources, such as line or point sources. To the best of the authors knowledge, there exist currently two distinct dispersion models, which are especially designed to treat dispersion from tunnel portals. Okamoto et al proposed a diagnostic wind field model, where the dispersion is modelled using a Taylor-Galerkin-Forester filter method. Oettl et al. developed a Lagrangian-type model (GRAL TM 3.5=Graz Lagrangian model Tunnel Module version 3.5), which is briefly described in the next section. (orig.)
NARAC Dispersion Model Product Integration With RadResponder
Energy Technology Data Exchange (ETDEWEB)
Aluzzi, Fernando [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-09-30
Work on enhanced cooperation and interoperability of Nuclear Incident Response Teams (NIRT) is a joint effort between DHS/FEMA, DOE/NNSA and EPA. One such effort was the integration between the RadResponder Network, a resource sponsored by FEMA for the management of radiological data during an emergency, and the National Atmospheric Advisory Center (NARAC), a DOE/NNSA modeling resource whose predictions are used to aid radiological emergency preparedness and response. Working together under a FEMA-sponsored project these two radiological response assets developed a capability to read and display plume model prediction results from the NARAC computer system in the RadResponder software tool. As a result of this effort, RadResponder users have been provided with NARAC modeling predictions of contamination areas, radiological dose levels, and protective action areas (e.g., areas warranting worker protection or sheltering/evacuation) to help guide protective action decisions and field monitoring surveys, and gain key situation awareness following a radiological/nuclear accident or incident (e.g., nuclear power plant accident, radiological dispersal device incident, or improvised nuclear detonation incident). This document describes the details of this integration effort.
Air Dispersion Modeling for Building 3026C/D Demolition
Energy Technology Data Exchange (ETDEWEB)
Ward, Richard C [ORNL; Sjoreen, Andrea L [ORNL; Eckerman, Keith F [ORNL
2010-06-01
This report presents estimates of dispersion coefficients and effective dose for potential air dispersion scenarios of uncontrolled releases from Oak Ridge National Laboratory (ORNL) buildings 3026C, 3026D, and 3140 prior to or during the demolition of the 3026 Complex. The Environmental Protection Agency (EPA) AERMOD system1-6 was used to compute these estimates. AERMOD stands for AERMIC Model, where AERMIC is the American Meteorological Society-EPA Regulatory Model Improvement Committee. Five source locations (three in building 3026D and one each in building 3026C and the filter house 3140) and associated source characteristics were determined with the customer. In addition, the area of study was determined and building footprints and intake locations of air-handling systems were obtained. In addition to the air intakes, receptor sites consisting of ground level locations on four polar grids (50 m, 100 m, 200 m, and 500 m) and two intersecting lines of points (50 m separation), corresponding to sidewalks along Central Avenue and Fifth Street. Three years of meteorological data (2006 2008) were used each consisting of three datasets: 1) National Weather Service data; 2) upper air data for the Knoxville-Oak Ridge area; and 3) local weather data from Tower C (10 m, 30 m and 100 m) on the ORNL reservation. Annual average air concentration, highest 1 h average and highest 3 h average air concentrations were computed using AERMOD for the five source locations for the three years of meteorological data. The highest 1 h average air concentrations were converted to dispersion coefficients to characterize the atmospheric dispersion as the customer was interested in the most significant response and the highest 1 h average data reflects the best time-averaged values available from the AERMOD code. Results are presented in tabular and graphical form. The results for dose were obtained using radionuclide activities for each of the buildings provided by the customer.7
Offshore and coastal dispersion (OCD) model. Users guide
International Nuclear Information System (INIS)
Hanna, S.R.; Schulman, L.L.; Paine, R.J.; Pleim, J.E.
1984-09-01
The Offshore and Coastal Dispersion (OCD) model was adapted from the EPA guideline model MPTER to simulate the effect of offshore emissions from point sources in coastal regions. Modifications were made to incorporate overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. Hourly meteorological data are needed from overwater and overland locations. Turbulence intensities are used but are not mandatory. For overwater dispersion, the turbulence intensities are parameterized from boundary-layer similarity relationships if they are not measured. Specifications of emission characteristics and receptor locations are the same as for MPTER; 250 point sources and 180 receptors may be used
Essays on pricing dynamics, price dispersion, and nested logit modelling
Verlinda, Jeremy Alan
The body of this dissertation comprises three standalone essays, presented in three respective chapters. Chapter One explores the possibility that local market power contributes to the asymmetric relationship observed between wholesale costs and retail prices in gasoline markets. I exploit an original data set of weekly gas station prices in Southern California from September 2002 to May 2003, and take advantage of highly detailed station and local market-level characteristics to determine the extent to which spatial differentiation influences price-response asymmetry. I find that brand identity, proximity to rival stations, bundling and advertising, operation type, and local market features and demographics each influence a station's predicted asymmetric relationship between prices and wholesale costs. Chapter Two extends the existing literature on the effect of market structure on price dispersion in airline fares by modeling the effect at the disaggregate ticket level. Whereas past studies rely on aggregate measures of price dispersion such as the Gini coefficient or the standard deviation of fares, this paper estimates the entire empirical distribution of airline fares and documents how the shape of the distribution is determined by market structure. Specifically, I find that monopoly markets favor a wider distribution of fares with more mass in the tails while duopoly and competitive markets exhibit a tighter fare distribution. These findings indicate that the dispersion of airline fares may result from the efforts of airlines to practice second-degree price discrimination. Chapter Three adopts a Bayesian approach to the problem of tree structure specification in nested logit modelling, which requires a heavy computational burden in calculating marginal likelihoods. I compare two different techniques for estimating marginal likelihoods: (1) the Laplace approximation, and (2) reversible jump MCMC. I apply the techniques to both a simulated and a travel mode
A 'Puff' dispersion model for routine and accidental releases
International Nuclear Information System (INIS)
Grsic, Z.; Rajkovic, B.; Milutinovic, P.
1999-01-01
A Puff dispersion model for accidental or routine releases is presented. This model was used as a constitutive part of an automatic meteorological station.All measured quantities are continuously displayed on PC monitor in a digital and graphical form, they are averaging every 10 minutes and sending to the civil information center of Belgrade. In the paper simulation of a pollutant plume dispersion from The oil refinery 'Pancevo', on April 18 th 1999 is presented. (author)
Milinkovitch, Thomas; Godefroy, Joachim; Théron, Michaël; Thomas-Guyon, Hélène
2011-10-01
Dispersant use in nearshore areas is likely to increase the exposure of aquatic organisms to petroleum. To measure the toxicity of this controversial response technique, golden grey mullets (Liza aurata) were exposed to mechanically dispersed oil, chemically dispersed oil, dispersant alone in seawater, water-soluble fraction of oil and to seawater as a control treatment. Several biomarkers were assessed in the gills (enzymatic antioxidant activities, glutathione content, lipid peroxidation) and in the gallbladder (polycylic aromatic hydrocarbons metabolites). The significant differences between chemically dispersed oil and water soluble fraction of oil highlight the environmental risk to disperse an oil slick when containment and recovery can be conducted. The lack of significance between chemically and mechanically dispersed oil suggests that dispersant application is no more toxic than the natural dispersion of the oil slick. The results of this study are of interest in order to establish dispersant use policies in nearshore areas. Copyright © 2011 Elsevier Ltd. All rights reserved.
Aquatic dispersion modelling of a tritium plume in Lake Ontario
International Nuclear Information System (INIS)
Klukas, M.H.; Moltyaner, G.L.
1996-05-01
Approximately 2900 kg of tritiated water, containing 2.3E+15 Bq of tritium, were released to Lake Ontario via the cooling water discharge when a leak developed in a moderator heat exchanger in Unit 1 at the Pickering Nuclear Generating Station (PNGS) on 1992 August 2. The release provided the opportunity to study the dispersion of a tritium plume in the coastal zone of Lake Ontario. Current direction over the two-week period following the release was predominantly parallel to the shore, and elevated tritium concentrations were observed up to 20 km east and 85 km west of the PNGS. Predictions of the tritium plume movement were made using current velocity measurements taken at 8-m depth, 2.5 km offshore from Darlington and using a empirical relationship where alongshore current speed is assumed to be proportional to the alongshore component of the wind speed. The tritium migration was best described using current velocity measurements. The tritium plume dispersion is modelled using the one-dimensional advection-dispersion equation. Transport parameters are the alongshore current speed and longitudinal dispersion coefficient. Longitudinal dispersion coefficients, estimated by fitting the solution of the advection-dispersion equation to measured concentration distance profiles ranged from 3.75 to 10.57 m 2 s -1 . Simulations using the fitted values of the dispersion coefficient were able to describe maximum tritium concentrations measured at water supply plants located within 25 km of Pickering to within a factor of 3. The dispersion coefficient is a function of spatial and temporal variability in current velocity and the fitted dispersion coefficients estimated here may not be suitable for predicting tritium plume dispersion under different current conditions. The sensitivity of the dispersion coefficient to variability in current conditions should be evaluated in further field experiments. (author). 13 refs., 7 tabs., 12 figs
Dispersive processes in models of regional radionuclide migration. Technical memorandum
International Nuclear Information System (INIS)
Evenson, D.E.; Dettinger, M.D.
1980-05-01
Three broad areas of concern in the development of aquifer scale transport models will be local scale diffusion and dispersion processes, regional scale dispersion processes, and numerical problems associated with the advection-dispersion equation. Local scale dispersion processes are fairly well understood and accessible to observation. These processes will generally be dominated in large scale systems by regional processes, or macro-dispersion. Macro-dispersion is primarily the result of large scale heterogeneities in aquifer properties. In addition, the effects of many modeling approximations are often included in the process. Because difficulties arise in parameterization of this large scale phenomenon, parameterization should be based on field measurements made at the same scale as the transport process of interest or else partially circumvented through the application of a probabilistic advection model. Other problems associated with numerical transport models include difficulties with conservation of mass, stability, numerical dissipation, overshoot, flexibility, and efficiency. We recommend the random-walk model formulation for Lawrence Livermore Laboratory's purposes as the most flexible, accurate and relatively efficient modeling approach that overcomes these difficulties
Comparative calculations and validation studies with atmospheric dispersion models
International Nuclear Information System (INIS)
Paesler-Sauer, J.
1986-11-01
This report presents the results of an intercomparison of different mesoscale dispersion models and measured data of tracer experiments. The types of models taking part in the intercomparison are Gaussian-type, numerical Eulerian, and Lagrangian dispersion models. They are suited for the calculation of the atmospherical transport of radionuclides released from a nuclear installation. For the model intercomparison artificial meteorological situations were defined and corresponding arithmetical problems were formulated. For the purpose of model validation real dispersion situations of tracer experiments were used as input data for model calculations; in these cases calculated and measured time-integrated concentrations close to the ground are compared. Finally a valuation of the models concerning their efficiency in solving the problems is carried out by the aid of objective methods. (orig./HP) [de
International Nuclear Information System (INIS)
Saint Yves, Thalis Leon de Avila; Lauria, Dejanira da Costa; Maia, Arlei; Andrade, Edson Ramos de
2011-01-01
Since the terrorist attacks on September 11, 2001, the assessment of radiological impacts for the public and the environment due to radionuclides being scattered by a radiological malevolent event has been a central focus. Models and computational codes have been developed and hypothetical scenarios have been formulated for establishing priority of countermeasures and protective actions; determining of generic operational guidelines; and assessment of risks for exposure population. In this study, a likely scenario was considered for evaluation of radiation exposures after a hypothetical radiological explosion of a 137 Cs device event in an urban environment. Joining to that, the main goal of this study is evaluating the usefulness of the sequential use of two codes for assessment of radiological consequence, and supporting decision making related to a RDD. A summary of the approaches of the two different codes, of their key inputs and outputs are presented. (author)
Federal Response Assets for a Radioactive Dispersal Device Incident
Energy Technology Data Exchange (ETDEWEB)
Sullivan,T.
2009-06-30
If a large scale RDD event where to occur in New York City, the magnitude of the problem would likely exceed the capabilities of City and State to effectively respond to the event. New York State could request Federal Assistance if the United States President has not already made the decision to provide it. The United States Federal Government has a well developed protocol to respond to emergencies. The National Response Framework (NRF) describes the process for responding to all types of emergencies including RDD incidents. Depending on the location and type of event, the NRF involves appropriate Federal Agencies, e.g., Department of Homeland Security (DHS), the Department of Energy (DOE), Environmental Protection Agency (EPA), United States Coast Guard (USCG), Department of Defense (DOD), Department of Justice (DOJ), Department of Agriculture (USDA), and Nuclear Regulatory Commission (NRC). The Federal response to emergencies has been refined and improved over the last thirty years and has been tested on natural disasters (e.g. hurricanes and floods), man-made disasters (oil spills), and terrorist events (9/11). However, the system has never been tested under an actual RDD event. Drills have been conducted with Federal, State, and local agencies to examine the initial (early) phases of such an event (TopOff 2 and TopOff 4). The Planning Guidance for Protection and Recovery Following Radiological Dispersal Device (RDD) and Improvised Nuclear Device (IND) incidents issued by the Department of Homeland Security (DHS) in August 2008 has never been fully tested in an interagency exercise. Recently, another exercise called Empire 09 that was situated in Albany, New York was conducted. Empire 09 consists of 3 different exercises be held in May and June, 2009. The first exercise, May 2009, involved a table top exercise for phase 1 (0-48 hours) of the response to an RDD incident. In early June, a full-scale 3- day exercise was conducted for the mid-phase response (48
Zhang, Hai-Mei; Chen, Shi-Lu
2015-06-09
The lack of dispersion in the B3LYP functional has been proposed to be the main origin of big errors in quantum chemical modeling of a few enzymes and transition metal complexes. In this work, the essential dispersion effects that affect quantum chemical modeling are investigated. With binuclear zinc isoaspartyl dipeptidase (IAD) as an example, dispersion is included in the modeling of enzymatic reactions by two different procedures, i.e., (i) geometry optimizations followed by single-point calculations of dispersion (approach I) and (ii) the inclusion of dispersion throughout geometry optimization and energy evaluation (approach II). Based on a 169-atom chemical model, the calculations show a qualitative consistency between approaches I and II in energetics and most key geometries, demonstrating that both approaches are available with the latter preferential since both geometry and energy are dispersion-corrected in approach II. When a smaller model without Arg233 (147 atoms) was used, an inconsistency was observed, indicating that the missing dispersion interactions are essentially responsible for determining equilibrium geometries. Other technical issues and mechanistic characteristics of IAD are also discussed, in particular with respect to the effects of Arg233.
A linearized dispersion relation for orthorhombic pseudo-acoustic modeling
Song, Xiaolei; Alkhalifah, Tariq Ali
2012-01-01
Wavefield extrapolation in acoustic orthorhombic anisotropic media suffers from wave-mode coupling and stability limitations in the parameter range. We introduce a linearized form of the dispersion relation for acoustic orthorhombic media to model acoustic wavefields. We apply the lowrank approximation approach to handle the corresponding space-wavenumber mixed-domain operator. Numerical experiments show that the proposed wavefield extrapolator is accurate and practically free of dispersions. Further, there is no coupling of qSv and qP waves, because we use the analytical dispersion relation. No constraints on Thomsen's parameters are required for stability. The linearized expression may provide useful application for parameter estimation in orthorhombic media.
A dispersion modelling system for urban air pollution
Energy Technology Data Exchange (ETDEWEB)
Karppinen, A.; Kukkonen, J.; Nordlund, G.; Rantakrans, E.; Valkama, I.
1998-10-01
An Urban Dispersion Modelling system UDM-FMI, developed at the Finnish Meteorological Institute is described in the report. The modelling system includes a multiple source Gaussian plume model and a meteorological pre-processing model. The dispersion model is an integrated urban scale model, taking into account of all source categories (point, line, area and volume sources). It includes a treatment of chemical transformation (for NO{sub 2}) wet and dry deposition (for SO{sub 2}) plume rise, downwash phenomena and dispersion of inert particles. The model allows also for the influence of a finite mixing height. The model structure is mainly based on the state-of-the-art methodology. The system also computes statistical parameters from the time series, which can be compared to air quality guidelines. The relevant meteorological parameters for the dispersion model are evaluated using data produced by a meteorological pre-processor. The model is based mainly on the energy budget method. Results of national investigations have been used for evaluating climate-dependent parameters. The model utilises the synoptic meteorological observations, radiation records and aerological sounding observations. The model results include the hourly time series of the relevant atmospheric turbulence 51 refs.
Unstructured Spectral Element Model for Dispersive and Nonlinear Wave Propagation
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Eskilsson, Claes; Bigoni, Daniele
2016-01-01
We introduce a new stabilized high-order and unstructured numerical model for modeling fully nonlinear and dispersive water waves. The model is based on a nodal spectral element method of arbitrary order in space and a -transformed formulation due to Cai, Langtangen, Nielsen and Tveito (1998). In...
Uncertainty modelling of atmospheric dispersion by stochastic ...
Indian Academy of Sciences (India)
by stochastic response surface method under aleatory ... 3Health Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India e-mail: ...... Brandimarte P 2011 Quantitative methods: An introduction for business management.
Evaluation of uncertainties in selected environmental dispersion models
International Nuclear Information System (INIS)
Little, C.A.; Miller, C.W.
1979-01-01
Compliance with standards of radiation dose to the general public has necessitated the use of dispersion models to predict radionuclide concentrations in the environment due to releases from nuclear facilities. Because these models are only approximations of reality and because of inherent variations in the input parameters used in these models, their predictions are subject to uncertainty. Quantification of this uncertainty is necessary to assess the adequacy of these models for use in determining compliance with protection standards. This paper characterizes the capabilities of several dispersion models to predict accurately pollutant concentrations in environmental media. Three types of models are discussed: aquatic or surface water transport models, atmospheric transport models, and terrestrial and aquatic food chain models. Using data published primarily by model users, model predictions are compared to observations
A numerical model of heavy gas dispersion
International Nuclear Information System (INIS)
Bidokhtti, A.A.
1993-01-01
A simple mathematical model describing the motion of a dense gas released continuously into and environment is presented. The model correctly predicts the laboratory experiments which were carried out by Britter and Snyder (1987). It is an entrainment model better known as box model. In this model, the effects of temperature change and phase change are not considered and it is for a steady-state case. Further work is required for including these effects which are often associated with the mechanisms involved in accidental or natural release of heavy gases in the environment. The results of such a model will be extended to the practical situations which are and will be common to the nuclear industry at the Atomic Energy Organization of Iran. The applicability of such studies to these situations will be discussed
Evaluation of atmospheric dispersion/consequence models supporting safety analysis
International Nuclear Information System (INIS)
O'Kula, K.R.; Lazaro, M.A.; Woodard, K.
1996-01-01
Two DOE Working Groups have completed evaluation of accident phenomenology and consequence methodologies used to support DOE facility safety documentation. The independent evaluations each concluded that no one computer model adequately addresses all accident and atmospheric release conditions. MACCS2, MATHEW/ADPIC, TRAC RA/HA, and COSYMA are adequate for most radiological dispersion and consequence needs. ALOHA, DEGADIS, HGSYSTEM, TSCREEN, and SLAB are recommended for chemical dispersion and consequence applications. Additional work is suggested, principally in evaluation of new models, targeting certain models for continued development, training, and establishing a Web page for guidance to safety analysts
Dispersion Modeling Using Ensemble Forecasts Compared to ETEX Measurements.
Straume, Anne Grete; N'dri Koffi, Ernest; Nodop, Katrin
1998-11-01
Numerous numerical models are developed to predict long-range transport of hazardous air pollution in connection with accidental releases. When evaluating and improving such a model, it is important to detect uncertainties connected to the meteorological input data. A Lagrangian dispersion model, the Severe Nuclear Accident Program, is used here to investigate the effect of errors in the meteorological input data due to analysis error. An ensemble forecast, produced at the European Centre for Medium-Range Weather Forecasts, is then used as model input. The ensemble forecast members are generated by perturbing the initial meteorological fields of the weather forecast. The perturbations are calculated from singular vectors meant to represent possible forecast developments generated by instabilities in the atmospheric flow during the early part of the forecast. The instabilities are generated by errors in the analyzed fields. Puff predictions from the dispersion model, using ensemble forecast input, are compared, and a large spread in the predicted puff evolutions is found. This shows that the quality of the meteorological input data is important for the success of the dispersion model. In order to evaluate the dispersion model, the calculations are compared with measurements from the European Tracer Experiment. The model manages to predict the measured puff evolution concerning shape and time of arrival to a fairly high extent, up to 60 h after the start of the release. The modeled puff is still too narrow in the advection direction.
Real-time dispersion calculation using the Lagrange model LASAT
International Nuclear Information System (INIS)
Janicke, L.
1987-01-01
The LASAT (Lagrange Simulation of Aerosol Transport) dispersion model demonstrates pollutant transport in the atmosphere by simulating the paths of representative random samples of pollutant particles on the computer as natural as possible. The author demonstrates the generated particle paths and refers to literature for details of the model algorithm. (DG) [de
Modeling atmospheric dispersion for reactor accident consequence evaluation
International Nuclear Information System (INIS)
Alpert, D.J.; Gudiksen, P.H.; Woodard, K.
1982-01-01
Atmospheric dispersion models are a central part of computer codes for the evaluation of potential reactor accident consequences. A variety of ways of treating to varying degrees the many physical processes that can have an impact on the predicted consequences exists. The currently available models are reviewed and their capabilities and limitations, as applied to reactor accident consequence analyses, are discussed
Mathematical modeling of disperse two-phase flows
Morel, Christophe
2015-01-01
This book develops the theoretical foundations of disperse two-phase flows, which are characterized by the existence of bubbles, droplets or solid particles finely dispersed in a carrier fluid, which can be a liquid or a gas. Chapters clarify many difficult subjects, including modeling of the interfacial area concentration. Basic knowledge of the subjects treated in this book is essential to practitioners of Computational Fluid Dynamics for two-phase flows in a variety of industrial and environmental settings. The author provides a complete derivation of the basic equations, followed by more advanced subjects like turbulence equations for the two phases (continuous and disperse) and multi-size particulate flow modeling. As well as theoretical material, readers will discover chapters concerned with closure relations and numerical issues. Many physical models are presented, covering key subjects including heat and mass transfers between phases, interfacial forces and fluid particles coalescence and breakup, a...
Model-based dispersive wave processing: A recursive Bayesian solution
International Nuclear Information System (INIS)
Candy, J.V.; Chambers, D.H.
1999-01-01
Wave propagation through dispersive media represents a significant problem in many acoustic applications, especially in ocean acoustics, seismology, and nondestructive evaluation. In this paper we propose a propagation model that can easily represent many classes of dispersive waves and proceed to develop the model-based solution to the wave processing problem. It is shown that the underlying wave system is nonlinear and time-variable requiring a recursive processor. Thus the general solution to the model-based dispersive wave enhancement problem is developed using a Bayesian maximum a posteriori (MAP) approach and shown to lead to the recursive, nonlinear extended Kalman filter (EKF) processor. The problem of internal wave estimation is cast within this framework. The specific processor is developed and applied to data synthesized by a sophisticated simulator demonstrating the feasibility of this approach. copyright 1999 Acoustical Society of America.
Computer Models Simulate Fine Particle Dispersion
2010-01-01
Through a NASA Seed Fund partnership with DEM Solutions Inc., of Lebanon, New Hampshire, scientists at Kennedy Space Center refined existing software to study the electrostatic phenomena of granular and bulk materials as they apply to planetary surfaces. The software, EDEM, allows users to import particles and obtain accurate representations of their shapes for modeling purposes, such as simulating bulk solids behavior, and was enhanced to be able to more accurately model fine, abrasive, cohesive particles. These new EDEM capabilities can be applied in many industries unrelated to space exploration and have been adopted by several prominent U.S. companies, including John Deere, Pfizer, and Procter & Gamble.
Low Frequency Dispersion Mechanism of Dielectric Response for Oil-paper Insulation Diagnosis
Institute of Scientific and Technical Information of China (English)
ZHOU Lijun; LI Xianlang; WU Guangning
2013-01-01
Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low frequencies,especially at ultra-low frequencies under conditions of different moisture concentrations and temperatures,which is recognized as the low frequency dispersion (LFD).In order to explain this dispersion,a new mechanism of dielectric response of LFD of oil-paper insulation is proposed.A simplified one-dimensional mathematical model of concentration polarization carrier caused by slow migration is developed and solved,which indicates that ion mobility is closely related to the size of gap and the adsorption capacity of cellulose molecular chains to ions.A stochastic statistical model of the carrier mobility induced LFD is also developed.Moreover,actual tests under 50 ℃and 2％ moisture content were put forward,as well as simulations with according current waveforms.The simulation results agreed well with the experimental data in that concentration polarization of carriers caused by slow migration is the probable cause of low frequency dispersion ofdielectric response for oil-paper insulation diagnosis.
A model for dispersion of contaminants in the subway environment
Energy Technology Data Exchange (ETDEWEB)
Coke, L. R.; Sanchez, J. G.; Policastro, A. J.
2000-05-03
Although subway ventilation has been studied extensively, very little has been published on dispersion of contaminants in the subway environment. This paper presents a model that predicts dispersion of contaminants in a complex subway system. It accounts for the combined transient effects of train motion, station airflows, train car air exchange rates, and source release properties. Results are presented for a range of typical subway scenarios. The effects of train piston action and train car air exchange are discussed. The model could also be applied to analyze the environmental impact of hazardous materials releases such as chemical and biological agents.
Atmospheric dispersion models for environmental pollution applications
International Nuclear Information System (INIS)
Gifford, F.A.
1976-01-01
Pollutants are introduced into the air by many of man's activities. The potentially harmful effects these can cause are, broadly speaking, of two kinds: long-term, possibly large-scale and wide-spread chronic effects, including long-term effects on the earth's climate; and acute, short-term effects such as those associated with urban air pollution. This section is concerned with mathematical cloud or plume models describing the role of the atmosphere, primarily in relation to the second of these, the acute effects of air pollution, i.e., those arising from comparatively high concentration levels. The need for such air pollution modeling studies has increased spectacularly as a result of the National Environmental Policy Act of 1968 and, especially, two key court decisions; the Calvert Cliffs decision, and the Sierra Club ruling on environmental non-degradation
Stress modeling in colloidal dispersions undergoing non-viscometric flows
Dolata, Benjamin; Zia, Roseanna
2017-11-01
We present a theoretical study of the stress tensor for a colloidal dispersion undergoing non-viscometric flow. In such flows, the non-homogeneous suspension stress depends on not only the local average total stresslet-the sum of symmetric first moments of both the hydrodynamic traction and the interparticle force-but also on the average quadrupole, octupole, and higher-order moments. To compute the average moments, we formulate a six dimensional Smoluchowski equation governing the microstructural evolution of a suspension in an arbitrary fluid velocity field. Under the conditions of rheologically slow flow, where the Brownian relaxation of the particles is much faster than the spatiotemporal evolution of the flow, the Smoluchowski equation permits asymptotic solution, revealing a suspension stress that follows a second-order fluid constitutive model. We obtain a reciprocal theorem and utilize it to show that all constitutive parameters of the second-order fluid model may be obtained from two simpler linear-response problems: a suspension undergoing simple shear and a suspension undergoing isotropic expansion. The consequences of relaxing the assumption of rheologically slow flow, including the appearance of memory and microcontinuum behaviors, are discussed.
A hybrid plume model for local-scale dispersion
Energy Technology Data Exchange (ETDEWEB)
Nikmo, J.; Tuovinen, J.P.; Kukkonen, J.; Valkama, I.
1997-12-31
The report describes the contribution of the Finnish Meteorological Institute to the project `Dispersion from Strongly Buoyant Sources`, under the `Environment` programme of the European Union. The project addresses the atmospheric dispersion of gases and particles emitted from typical fires in warehouses and chemical stores. In the study only the `passive plume` regime, in which the influence of plume buoyancy is no longer important, is addressed. The mathematical model developed and its numerical testing is discussed. The model is based on atmospheric boundary-layer scaling theory. In the vicinity of the source, Gaussian equations are used in both the horizontal and vertical directions. After a specified transition distance, gradient transfer theory is applied in the vertical direction, while the horizontal dispersion is still assumed to be Gaussian. The dispersion parameters and eddy diffusivity are modelled in a form which facilitates the use of a meteorological pre-processor. Also a new model for the vertical eddy diffusivity (K{sub z}), which is a continuous function of height in the various atmospheric scaling regions is presented. The model includes a treatment of the dry deposition of gases and particulate matter, but wet deposition has been neglected. A numerical solver for the atmospheric diffusion equation (ADE) has been developed. The accuracy of the numerical model was analysed by comparing the model predictions with two analytical solutions of ADE. The numerical deviations of the model predictions from these analytic solutions were less than two per cent for the computational regime. The report gives numerical results for the vertical profiles of the eddy diffusivity and the dispersion parameters, and shows spatial concentration distributions in various atmospheric conditions 39 refs.
Meteorological uncertainty of atmospheric dispersion model results (MUD)
Energy Technology Data Exchange (ETDEWEB)
Havskov Soerensen, J.; Amstrup, B.; Feddersen, H. [Danish Meteorological Institute, Copenhagen (Denmark)] [and others
2013-08-15
The MUD project addresses assessment of uncertainties of atmospheric dispersion model predictions, as well as possibilities for optimum presentation to decision makers. Previously, it has not been possible to estimate such uncertainties quantitatively, but merely to calculate the 'most likely' dispersion scenario. However, recent developments in numerical weather prediction (NWP) include probabilistic forecasting techniques, which can be utilised also for long-range atmospheric dispersion models. The ensemble statistical methods developed and applied to NWP models aim at describing the inherent uncertainties of the meteorological model results. These uncertainties stem from e.g. limits in meteorological observations used to initialise meteorological forecast series. By perturbing e.g. the initial state of an NWP model run in agreement with the available observational data, an ensemble of meteorological forecasts is produced from which uncertainties in the various meteorological parameters are estimated, e.g. probabilities for rain. Corresponding ensembles of atmospheric dispersion can now be computed from which uncertainties of predicted radionuclide concentration and deposition patterns can be derived. (Author)
Meteorological uncertainty of atmospheric dispersion model results (MUD)
International Nuclear Information System (INIS)
Havskov Soerensen, J.; Amstrup, B.; Feddersen, H.
2013-08-01
The MUD project addresses assessment of uncertainties of atmospheric dispersion model predictions, as well as possibilities for optimum presentation to decision makers. Previously, it has not been possible to estimate such uncertainties quantitatively, but merely to calculate the 'most likely' dispersion scenario. However, recent developments in numerical weather prediction (NWP) include probabilistic forecasting techniques, which can be utilised also for long-range atmospheric dispersion models. The ensemble statistical methods developed and applied to NWP models aim at describing the inherent uncertainties of the meteorological model results. These uncertainties stem from e.g. limits in meteorological observations used to initialise meteorological forecast series. By perturbing e.g. the initial state of an NWP model run in agreement with the available observational data, an ensemble of meteorological forecasts is produced from which uncertainties in the various meteorological parameters are estimated, e.g. probabilities for rain. Corresponding ensembles of atmospheric dispersion can now be computed from which uncertainties of predicted radionuclide concentration and deposition patterns can be derived. (Author)
Mixing height derived from the DMI-HIRLAM NWP model, and used for ETEX dispersion modelling
Energy Technology Data Exchange (ETDEWEB)
Soerensen, J.H.; Rasmussen, A. [Danish Meteorological Inst., Copenhagen (Denmark)
1997-10-01
For atmospheric dispersion modelling it is of great significance to estimate the mixing height well. Mesoscale and long-range diffusion models using output from numerical weather prediction (NWP) models may well use NWP model profiles of wind, temperature and humidity in computation of the mixing height. This is dynamically consistent, and enables calculation of the mixing height for predicted states of the atmosphere. In autumn 1994, the European Tracer Experiment (ETEX) was carried out with the objective to validate atmospheric dispersion models. The Danish Meteorological Institute (DMI) participates in the model evaluations with the Danish Emergency Response Model of the Atmosphere (DERMA) using NWP model data from the DMI version of the High Resolution Limited Area Model (HIRLAM) as well as from the global model of the European Centre for Medium-Range Weather Forecast (ECMWF). In DERMA, calculation of mixing heights are performed based on a bulk Richardson number approach. Comparing with tracer gas measurements for the first ETEX experiment, a sensitivity study is performed for DERMA. Using DMI-HIRLAM data, the study shows that optimum values of the critical bulk Richardson number in the range 0.15-0.35 are adequate. These results are in agreement with recent mixing height verification studies against radiosonde data. The fairly large range of adequate critical values is a signature of the robustness of the method. Direct verification results against observed missing heights from operational radio-sondes released under the ETEX plume are presented. (au) 10 refs.
Review of potential models for UF6 dispersion
International Nuclear Information System (INIS)
Sykes, R.I.; Lewellen, W.S.
1992-07-01
A survey of existing atmospheric dispersion models has been conducted to determine the most appropriate basis for the development of a model for predicting the consequences of an accidental UF 6 release. The model is required for safety analysis studies and should therefore be computationally efficient. The release of UF 6 involves a number of physical phenomena which make the situation more complicated than passive dispersion of a trace gas. The safety analysis must consider the density variations in the UF 6 cloud, which can be heavier or lighter than the ambient air. The release also involves rapid chemical reactions and associated heat release, which must be modeled. Other Department of Energy storage facilities require a dense gas prediction capability, so the model must be sufficiently general for use with a variety of release scenarios. The special problems associated with UF 6 make it unique, so there are very few models with existing capability for the problem. There are, however, a large number of dense gas dispersion models, some with relevant chemical reaction modeling, that could potentially form the basis of an advanced UF 6 model. We have examined a large selection of possible candidates, and selected 5 models for detailed consideration
Meteorological Uncertainty of atmospheric Dispersion model results (MUD)
DEFF Research Database (Denmark)
Havskov Sørensen, Jens; Amstrup, Bjarne; Feddersen, Henrik
The MUD project addresses assessment of uncertainties of atmospheric dispersion model predictions, as well as possibilities for optimum presentation to decision makers. Previously, it has not been possible to estimate such uncertainties quantitatively, but merely to calculate the ‘most likely’ di...
Mechanistic model for dispersion coefficients in bubble column
CSIR Research Space (South Africa)
Skosana, PJ
2015-05-01
Full Text Available predicts axial and radial dispersion coefficients that are of the same order of magnitude as the reported data. Whereas the model is based on a description of the underlying physical phenomena, its validity and extrapolation is expected to be more reliable...
Pollutant dispersion models for issues of air pollution control
International Nuclear Information System (INIS)
1985-01-01
14 papers entered separately into the data base were presented at the meeting for application-oriented dispersion models for issues of air pollution control. These papers focus on fields of application, availability of required input data relevant to emissions and meteorology, performance and accuracy of these methods and their practicability. (orig./PW) [de
Variational Boussinesq model for strongly nonlinear dispersive waves
Lawrence, C.; Adytia, D.; van Groesen, E.
2018-01-01
For wave tank, coastal and oceanic applications, a fully nonlinear Variational Boussinesq model with optimized dispersion is derived and a simple Finite Element implementation is described. Improving a previous weakly nonlinear version, high waves over flat and varying bottom are shown to be
Equilibrium Price Dispersion in a Matching Model with Divisible Money
Kamiya, K.; Sato, T.
2002-01-01
The main purpose of this paper is to show that, for any given parameter values, an equilibrium with dispersed prices (two-price equilibrium) exists in a simple matching model with divisible money presented by Green and Zhou (1998).We also show that our two-price equilibrium is unique in certain
PHYSICAL AND NUMERICAL MODELING OF ASD EXHAUST DISPERSION AROUND HOUSES
The report discusses the use of a wind tunnel to physically model the dispersion of exhaust plumes from active soil depressurization (ASD) radon mitigation systems in houses. he testing studied the effects of exhaust location (grade level vs. above the eave), as house height, roo...
A linearized dispersion relation for orthorhombic pseudo-acoustic modeling
Song, Xiaolei
2012-11-04
Wavefield extrapolation in acoustic orthorhombic anisotropic media suffers from wave-mode coupling and stability limitations in the parameter range. We introduce a linearized form of the dispersion relation for acoustic orthorhombic media to model acoustic wavefields. We apply the lowrank approximation approach to handle the corresponding space-wavenumber mixed-domain operator. Numerical experiments show that the proposed wavefield extrapolator is accurate and practically free of dispersions. Further, there is no coupling of qSv and qP waves, because we use the analytical dispersion relation. No constraints on Thomsen\\'s parameters are required for stability. The linearized expression may provide useful application for parameter estimation in orthorhombic media.
Rossel, F.; Gironas, J. A.
2012-12-01
The link between stream network structure and hydrologic response for natural basins has been extensively studied. It is well known that stream network organization and flow dynamics in the reaches combine to shape the hydrologic response of natural basins. Geomorphologic dispersion and hydrodynamic dispersion along with hillslope processes control to a large extent the overall variance of the hydrograph, particularly under the assumption of constant celerity throughout the basin. In addition, a third mechanism referred as to kinematic dispersion becomes relevant when considering spatial variations of celerity. On contrary, the link between the drainage network structure and overall urban terrain, and the hydrologic response in urban catchments has been much less studied. In particular, the characterization of the different dispersion mechanisms within urban areas remains to be better understood. In such areas artificial elements are expected to contribute to the total dispersion due to the variety of geometries and the spatial distribution of imperviousness. This work quantifies the different dispersion mechanisms in an urban catchment, focusing on their relevance and the spatial scales involved. For this purpose we use the Urban Morpho-climatic Instantaneous Unit Hydrograph model, a deterministic spatially distributed direct hydrograph travel time model, which computes travel times in hillslope, pipe, street and channel cells using formulations derived from kinematic wave theory. The model was applied to the Aubeniere catchment, located in Nantes, France. Unlike stochastic models, this deterministic model allows the quantification of dispersion mechanism at the local scale (i.e. the grid-cell). We found that kinematic dispersion is more relevant for small storm events, whereas geomorphologic dispersion becomes more significant for larger storms, as the mean celerity within the catchment increases. In addition, the total dispersion relates to the drainage area in
Application of GIS to modified models of vehicle emission dispersion
Jin, Taosheng; Fu, Lixin
This paper reports on a preliminary study of the forecast and evaluation of transport-related air pollution dispersion in urban areas. Some modifications of the traditional Gauss dispersion models are provided, and especially a crossroad model is built, which considers the great variation of vehicle emission attributed to different driving patterns at the crossroad. The above models are combined with a self-developed geographic information system (GIS) platform, and a simulative system with graphical interfaces is built. The system aims at visually describing the influences on the urban environment by urban traffic characteristics and therefore gives a reference to the improvement of urban air quality. Due to the introduction of a self-developed GIS platform and a creative crossroad model, the system is more effective, flexible and accurate. Finally, a comparison of the simulated (predicted) and observed hourly concentration is given, which indicates a good simulation.
Unconfined Groundwater Dispersion Model On Sand Layers In Coral Island
Sultan
2016-01-01
The research objective is to analyze the sand layer to determine the characteristics of the unconfined groundwater aquifer on coral island and found the dispersion model of unconfined groundwater in the sand layer in the coral island. The method used is direct research in the field, laboratory analysis and secondary data. Observations geological conditions, as well as the measurement and interpretation of geoelectrical potential groundwater models based on the value of the conductivity of gro...
Analytical solution of dispersion relations for the nuclear optical model
Energy Technology Data Exchange (ETDEWEB)
VanderKam, J.M. [Center for Communications Research, Thanet Road, Princeton, NJ 08540 (United States); Weisel, G.J. [Triangle Universities Nuclear Laboratory, and Duke University, Box 90308, Durham, NC 27708-0308 (United States); Penn State Altoona, 3000 Ivyside Park, Altoona, PA 16601-3760 (United States); Tornow, W. [Triangle Universities Nuclear Laboratory, and Duke University, Box 90308, Durham, NC 27708-0308 (United States)
2000-12-01
Analytical solutions of dispersion integral relations, linking the real and imaginary parts of the nuclear optical model, have been derived. These are displayed for some widely used forms of the volume- and surface-absorptive nuclear potentials. When the analytical solutions are incorporated into the optical-model search code GENOA, replacing a numerical integration, the code runs three and a half to seven times faster, greatly aiding the analysis of direct-reaction, elastic scattering data. (author)
Czech Academy of Sciences Publication Activity Database
Sáňka, O.; Melymuk, L.; Čupr, P.; Dvorská, Alice; Klánová, J.
2014-01-01
Roč. 90, oct (2014), s. 88-95 ISSN 1352-2310 Institutional support: RVO:67179843 Keywords : passive air sampling * air dispersion modeling * GIS * polycyclic aromatic hydrocarbons * emission inventories Subject RIV: DI - Air Pollution ; Quality Impact factor: 3.281, year: 2014
Comparison of marine dispersion model predictions with environmental radionuclide concentrations
International Nuclear Information System (INIS)
Johnson, C.E.; McKay, W.A.
1988-01-01
The comparison of marine dispersion model results with measurements is an essential part of model development and testing. The results from two residual flow models are compared with seawater concentrations, and in one case with concentrations measured in marine molluscs. For areas with short turnover times, seawater concentrations respond rapidly to variations in discharge rate and marine currents. These variations are difficult to model, and comparison with concentrations in marine animals provides an alternative and complementary technique for model validation with the advantages that the measurements reflect the mean conditions and frequently form a useful time series. (author)
Comparison of turbulent particle dispersion models in turbulent shear flows
Directory of Open Access Journals (Sweden)
S. Laín
2007-09-01
Full Text Available This work compares the performance of two Lagrangian turbulent particle dispersion models: the standard model (e.g., that presented in Sommerfeld et al. (1993, in which the fluctuating fluid velocity experienced by the particle is composed of two components, one correlated with the previous time step and a second one randomly sampled from a Wiener process, and the model proposed by Minier and Peirano (2001, which is based on the PDF approach and performs closure at the level of acceleration of the fluid experienced by the particle. Formulation of a Langevin equation model for the increments of fluid velocity seen by the particle allows capturing some underlying physics of particle dispersion in general turbulent flows while keeping the mathematical manipulation of the stochastic model simple, thereby avoiding some pitfalls and simplifying the derivation of macroscopic relations. The performance of both dispersion models is tested in the configurations of grid-generated turbulence (Wells and Stock (1983 experiments, simple shear flow (Hyland et al., 1999 and confined axisymmetric jet flow laden with solids (Hishida and Maeda (1987 experiments.
Physical modelling of flow and dispersion over complex terrain
Cermak, J. E.
1984-09-01
Atmospheric motion and dispersion over topography characterized by irregular (or regular) hill-valley or mountain-valley distributions are strongly dependent upon three general sets of variables. These are variables that describe topographic geometry, synoptic-scale winds and surface-air temperature distributions. In addition, pollutant concentration distributions also depend upon location and physical characteristics of the pollutant source. Overall fluid-flow complexity and variability from site to site have stimulated the development and use of physical modelling for determination of flow and dispersion in many wind-engineering applications. Models with length scales as small as 1:12,000 have been placed in boundary-layer wind tunnels to study flows in which forced convection by synoptic winds is of primary significance. Flows driven primarily by forces arising from temperature differences (gravitational or free convection) have been investigated by small-scale physical models placed in an isolated space (gravitational convection chamber). Similarity criteria and facilities for both forced and gravitational-convection flow studies are discussed. Forced-convection modelling is illustrated by application to dispersion of air pollutants by unstable flow near a paper mill in the state of Maryland and by stable flow over Point Arguello, California. Gravitational-convection modelling is demonstrated by a study of drainage flow and pollutant transport from a proposed mining operation in the Rocky Mountains of Colorado. Other studies in which field data are available for comparison with model data are reviewed.
Czech Academy of Sciences Publication Activity Database
Nakayama, H.; Jurčáková, Klára; Nagai, H.
2013-01-01
Roč. 50, č. 5 (2013), s. 503-519 ISSN 0022-3131 Institutional support: RVO:61388998 Keywords : local-scale high-resolution dispersion model * nuclear emergency response system * large-eddy simulation * spatially developing turbulent boundary layer flow Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.452, year: 2013
A computer model for dispersed fluid-solid turbulent flows
International Nuclear Information System (INIS)
Liu, C.H.; Tulig, T.J.
1985-01-01
A computer model is being developed to simulate two-phase turbulent flow phenomena in fluids containing finely dispersed solids. The model is based on a dual-continuum picture of the individual phases and an extension of a two-equation turbulence closure theory. The resulting set of nonlinear partial differential equations are solved using a finite difference procedure with special treatment to promote convergence. The model has been checked against a number of idealized flow problems with known solutions. The authors are currently comparing model predictions with measurements to determine a proper set of turbulence parameters needed for simulating two-phase turbulent flows
Difficulties in modeling dispersed-flow film boiling
International Nuclear Information System (INIS)
Andreani, M.; Yadigaroglu, G.
1991-01-01
Dispersed Flow Film Boiling (DFFB) is characterized by important departures from thermal and velocity equilibrium that make it suitable for modeling with two-fluid models. The fundamental limitations and difficulties imposed by the one-dimensional nature of these models are extensively discussed. The validity of the assumptions and empirical laws used to close the system of conservation equations is critically reviewed, in light of the multidimensional aspects of the problem. Modifications that could improve the physics of the models are identified. (orig.) [de
Radiation response of vitamin A in aqueous dispersions
International Nuclear Information System (INIS)
Bhushan, B.; Kumta, U.S.
1977-01-01
The radiation destruction of vitamin A acetate was monitored in isooctane, coconut oil, and aqueous dispersions. The G(-vit. A), i.e., the number of vitamin A molecules destroyed per 100 eV of energy absorbed in lipid solvents and aqueous preparations, increased with the concentrations of vitamin A used. In the freely dissolved state, as in isooctane or coconut oil, the extent of destruction of vitamin A was more or less identical. However, a marked reduction in the radiation destruction of vitamin A was observed in aqueous dispersions at all concentrations except at 1 x 10 -4 M. Incorporation of sugars, starch, and egg albumin in aqueous preparations offered considerable protection to vitamin A from radiation damage which could be discerned even at the lowest concentration (1 x 10 -4 M). The protective influence of aqueous dispersion as noted for vitamin A was also observed for β-carotene, vitamin A alcohol, and ubiquinone-30. The significance of the above findings in radiation processing of foods has been discussed
International Nuclear Information System (INIS)
Colli, A.N.; Bisang, J.M.
2011-01-01
Highlights: · The type of turbulence promoters has a strong influence on the hydrodynamics. · The dispersion model is appropriate for expanded plastic turbulence promoters. · The dispersion model is appropriate for glass beads turbulence promoters. - Abstract: The hydrodynamic behaviour of electrochemical reactors with parallel plate electrodes is experimentally studied using the stimulus-response method either with an empty reactor or with different turbulence promoters. Theoretical results which are in accordance with the analytical and numerical resolution of the dispersion model for a closed system are compared with the classical relationships of the normalized outlet concentration for open systems and the validity range of the equations is discussed. The experimental results were well correlated with the dispersion model using glass beads or expanded plastic meshes as turbulence promoters, which have shown the most advantageous performance. The Peclet number was higher than 63. The dispersion coefficient was found to increase linearly with flow velocity in these cases.
Energy Technology Data Exchange (ETDEWEB)
Martin, F.
2013-07-01
One of the main challenges of the atmospheric sciences is to reproduce as well as possible the phenomena and processes of pollutants in the atmosphere. To do it, mathematical models based in this case on fluid dynamics and mass and energy conservation equations, equations that govern the atmospheric chemistry, etc., adapted to the spatial scales to be simulated, are developed. The dispersion models simulate the processes of transport, dispersion, chemical transformation and elimination by deposition that air pollutants undergo once they are emitted. Atmospheric dispersion models with their multiple applications have become essential tools for the air quality management. (Author)
Implementation of meso-scale radioactive dispersion model for GPU
Energy Technology Data Exchange (ETDEWEB)
Sunarko [National Nuclear Energy Agency of Indonesia (BATAN), Jakarta (Indonesia). Nuclear Energy Assessment Center; Suud, Zaki [Bandung Institute of Technology (ITB), Bandung (Indonesia). Physics Dept.
2017-05-15
Lagrangian Particle Dispersion Method (LPDM) is applied to model atmospheric dispersion of radioactive material in a meso-scale of a few tens of kilometers for site study purpose. Empirical relationships are used to determine the dispersion coefficient for various atmospheric stabilities. Diagnostic 3-D wind-field is solved based on data from one meteorological station using mass-conservation principle. Particles representing radioactive pollutant are dispersed in the wind-field as a point source. Time-integrated air concentration is calculated using kernel density estimator (KDE) in the lowest layer of the atmosphere. Parallel code is developed for GTX-660Ti GPU with a total of 1 344 scalar processors using CUDA. A test of 1-hour release discovers that linear speedup is achieved starting at 28 800 particles-per-hour (pph) up to about 20 x at 14 4000 pph. Another test simulating 6-hour release with 36 000 pph resulted in a speedup of about 60 x. Statistical analysis reveals that resulting grid doses are nearly identical in both CPU and GPU versions of the code.
Dispersion Relations for Electroweak Observables in Composite Higgs Models
Contino, Roberto
2015-12-14
We derive dispersion relations for the electroweak oblique observables measured at LEP in the context of $SO(5)/SO(4)$ composite Higgs models. It is shown how these relations can be used and must be modified when modeling the spectral functions through a low-energy effective description of the strong dynamics. The dispersion relation for the parameter $\\epsilon_3$ is then used to estimate the contribution from spin-1 resonances at the 1-loop level. Finally, it is shown that the sign of the contribution to the $\\hat S$ parameter from the lowest-lying spin-1 states is not necessarily positive definite, but depends on the energy scale at which the asymptotic behavior of current correlators is attained.
Plutonium explosive dispersal modeling using the MACCS2 computer code
International Nuclear Information System (INIS)
Steele, C.M.; Wald, T.L.; Chanin, D.I.
1998-01-01
The purpose of this paper is to derive the necessary parameters to be used to establish a defensible methodology to perform explosive dispersal modeling of respirable plutonium using Gaussian methods. A particular code, MACCS2, has been chosen for this modeling effort due to its application of sophisticated meteorological statistical sampling in accordance with the philosophy of Nuclear Regulatory Commission (NRC) Regulatory Guide 1.145, ''Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants''. A second advantage supporting the selection of the MACCS2 code for modeling purposes is that meteorological data sets are readily available at most Department of Energy (DOE) and NRC sites. This particular MACCS2 modeling effort focuses on the calculation of respirable doses and not ground deposition. Once the necessary parameters for the MACCS2 modeling are developed and presented, the model is benchmarked against empirical test data from the Double Tracks shot of project Roller Coaster (Shreve 1965) and applied to a hypothetical plutonium explosive dispersal scenario. Further modeling with the MACCS2 code is performed to determine a defensible method of treating the effects of building structure interaction on the respirable fraction distribution as a function of height. These results are related to the Clean Slate 2 and Clean Slate 3 bunkered shots of Project Roller Coaster. Lastly a method is presented to determine the peak 99.5% sector doses on an irregular site boundary in the manner specified in NRC Regulatory Guide 1.145 (1983). Parametric analyses are performed on the major analytic assumptions in the MACCS2 model to define the potential errors that are possible in using this methodology
Plutonium explosive dispersal modeling using the MACCS2 computer code
Energy Technology Data Exchange (ETDEWEB)
Steele, C.M.; Wald, T.L.; Chanin, D.I.
1998-11-01
The purpose of this paper is to derive the necessary parameters to be used to establish a defensible methodology to perform explosive dispersal modeling of respirable plutonium using Gaussian methods. A particular code, MACCS2, has been chosen for this modeling effort due to its application of sophisticated meteorological statistical sampling in accordance with the philosophy of Nuclear Regulatory Commission (NRC) Regulatory Guide 1.145, ``Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants``. A second advantage supporting the selection of the MACCS2 code for modeling purposes is that meteorological data sets are readily available at most Department of Energy (DOE) and NRC sites. This particular MACCS2 modeling effort focuses on the calculation of respirable doses and not ground deposition. Once the necessary parameters for the MACCS2 modeling are developed and presented, the model is benchmarked against empirical test data from the Double Tracks shot of project Roller Coaster (Shreve 1965) and applied to a hypothetical plutonium explosive dispersal scenario. Further modeling with the MACCS2 code is performed to determine a defensible method of treating the effects of building structure interaction on the respirable fraction distribution as a function of height. These results are related to the Clean Slate 2 and Clean Slate 3 bunkered shots of Project Roller Coaster. Lastly a method is presented to determine the peak 99.5% sector doses on an irregular site boundary in the manner specified in NRC Regulatory Guide 1.145 (1983). Parametric analyses are performed on the major analytic assumptions in the MACCS2 model to define the potential errors that are possible in using this methodology.
International Nuclear Information System (INIS)
Srinivas, C.V.; Venkatesan, R.; Muralidharan, N.V.; Das, Someshwar; Dass, Hari; Eswara Kumar, P.
2005-08-01
An operational atmospheric dispersion prediction system is implemented on a cluster super computer for 'Online Emergency Response' for Kalpakkam nuclear site. The numerical system constitutes a parallel version of a nested grid meso-scale meteorological model MM5 coupled to a random walk particle dispersion model FLEXPART. The system provides 48 hour forecast of the local weather and radioactive plume dispersion due to hypothetical air borne releases in a range of 100 km around the site. The parallel code was implemented on different cluster configurations like distributed and shared memory systems. Results of MM5 run time performance for 1-day prediction are reported on all the machines available for testing. A reduction of 5 times in runtime is achieved using 9 dual Xeon nodes (18 physical/36 logical processors) compared to a single node sequential run. Based on the above run time results a cluster computer facility with 9-node Dual Xeon is commissioned at IGCAR for model operation. The run time of a triple nested domain MM5 is about 4 h for 24 h forecast. The system has been operated continuously for a few months and results were ported on the IMSc home page. Initial and periodic boundary condition data for MM5 are provided by NCMRWF, New Delhi. An alternative source is found to be NCEP, USA. These two sources provide the input data to the operational models at different spatial and temporal resolutions and using different assimilation methods. A comparative study on the results of forecast is presented using these two data sources for present operational use. Slight improvement is noticed in rainfall, winds, geopotential heights and the vertical atmospheric structure while using NCEP data probably because of its high spatial and temporal resolution. (author)
Dispersion Models to Forecast Traffic-related Emissions in Urban Areas
Directory of Open Access Journals (Sweden)
Davide Scannapieco
2011-11-01
Full Text Available Down the centuries, a direct link had been developed between increase in mobility and increase in wealth. On the other hand, air emission of greenhouse gases (GHG due to vehicles equipped with internal combustion engines can be regarded as a negative pressure over the environment. In the coming decades, road transport is likely to remain a significant contributor to air pollution in cities. Many urban trips cover distances of less than 6 km. Since the effectiveness of catalytic converters in the initial minutes of engine operation is small, the average emission per distance driven is very high in urban areas. Also, poorly maintained vehicles that lack exhaust aftertreatment systems are responsible for a major part of pollutant emissions. Therefore in urban areas, where higher concentrations of vehicles can be easily found, air pollution represents a critical issue, being it related with both environment and human health protection: in truth, research in recent decades consistently indicates the adverse effects of outdoor air pollution on human health, and the evidence points to air pollution stemming from transport as an important contributor to these effects. Several institutions (EEA, USEPA, etc. focused their interest in dispersion models because of their potential effectiveness to forecast atmospheric pollution. Furthermore, air micropollutants such as Polycyclic Aromatic Compounds (PAH and Metallic Trace Elements (MTE are traffic-related and although very low concentrations their dispersion is a serious issue. However, dispersion models are usefully implemented to better manage this estimation problem. Nonetheless, policy makers and land managers have to deal with model selection, taking into account that several dispersion models are available, each one of them focused on specific goals (e.g., wind transport of pollutants, land morphology implementation, evaluation of micropollutants transport, etc.; a further aspect to be considered is
Landau fluid model for weakly nonlinear dispersive magnetohydrodynamics
International Nuclear Information System (INIS)
Passot, T.; Sulem, P. L.
2005-01-01
In may astrophysical plasmas such as the solar wind, the terrestrial magnetosphere, or in the interstellar medium at small enough scales, collisions are negligible. When interested in the large-scale dynamics, a hydrodynamic approach is advantageous not only because its numerical simulations is easier than of the full Vlasov-Maxwell equations, but also because it provides a deep understanding of cross-scale nonlinear couplings. It is thus of great interest to construct fluid models that extended the classical magnetohydrodynamic (MHD) equations to collisionless situations. Two ingredients need to be included in such a model to capture the main kinetic effects: finite Larmor radius (FLR) corrections and Landau damping, the only fluid-particle resonance that can affect large scales and can be modeled in a relatively simple way. The Modelization of Landau damping in a fluid formalism is hardly possible in the framework of a systematic asymptotic expansion and was addressed mainly by means of parameter fitting in a linearized setting. We introduced a similar Landau fluid model but, that has the advantage of taking dispersive effects into account. This model properly describes dispersive MHD waves in quasi-parallel propagation. Since, by construction, the system correctly reproduces their linear dynamics, appropriate tests should address the nonlinear regime. In a first case, we show analytically that the weakly nonlinear modulational dynamics of quasi-parallel propagating Alfven waves is well captured. As a second test we consider the parametric decay instability of parallel Alfven waves and show that numerical simulations of the dispersive Landau fluid model lead to results that closely match the outcome of hybrid simulations. (Author)
Dispersion of tracers by the oceanic eddy field modelling programme
International Nuclear Information System (INIS)
Richards, K.J.; O'Farrell, S.P.
1987-01-01
A numerical model has been developed to study the dispersion of tracers by the oceanic eddy field. The present study is designed to study the dispersion of particles in a mesoscale eddy field produced by the numerical model. Dispersion rates are calculated for flows above three types of topography, a flat bottom, a random collection of hills and a ridge. The presence of topography is found to significantly affect the flow. The effective diffusion coefficient of the flow near the bottom is reduced by 20% for the random topography and 60% for the ridge from that for the flat bottom case. Estimates are given of the number of float years required to obtain a given accuracy for the diffusion coefficient. At the surface a modest number of floats (order 5) are required to obtain a 50% accuracy. However at the bottom, to be within a factor of 2 of the true value for the flows considered requires respectively 26, 42 and 103 float years for the flat, random and ridge cases. (author)
Dispersion in the wake of a model industrial complex
International Nuclear Information System (INIS)
Hatcher, R.V.; Meroney, R.N.; Peterka, J.A.; Kothari, K.
1977-06-01
Models (1:200 scale) of the EOCR reactor building and surrounding silo and tank buildings at the Idaho National Engineering Laboratory, Idaho Falls, Idaho were put into the Meteorological Wind Tunnel at Colorado State University for the purpose of studying the effects of building wakes on dispersion. Flow visualization was done and concentration measurements were taken. The test program consisted of systematic releases from ground, building height, and stack height sources with no appreciable plume rise. The program was repeated for cases of moderately unstable, neutral, moderately stable, and stable conditions in the wind tunnel. Results show that the buildings significantly alter the dispersion patterns and the addition of any extra buildings or slight terrain change in the immediate vicinity of the building has a major effect. In the near wake region the effects of stratification were still evident causing slightly higher concentrations for stable conditions and slightly lower for unstable. Current dispersion models are discussed and evaluated that predict concentrations in the building wake region
Viscoelasticity and diffusional properties of colloidal model dispersions
Naegele, G
2003-01-01
We examine linear viscoelastic, and translational and rotational diffusion properties of colloidal model dispersions. Theoretical results are discussed, in comparison with experiments, for monodisperse suspensions of charged and neutral colloidal spheres, and for binary dispersions of differently sized tracer and host particles. The theoretical methods employed comprise a mode-coupling scheme for Brownian particles, and a rooted cluster expansion scheme of tracer diffusion with two- and three-body hydrodynamic interactions included. We analyse in particular the validity of various empirical generalized Stokes-Einstein-Debye (SED) relations between the (dynamic) shear viscosity and translational/rotational diffusion coefficients. Some of these generalized SED relations are basic to microrheological measurements aimed at characterizing the viscoelasticity of complex fluids on the basis of the diffusional properties of immersed tracer particles.
Viscoelasticity and diffusional properties of colloidal model dispersions
International Nuclear Information System (INIS)
Naegele, Gerhard
2003-01-01
We examine linear viscoelastic, and translational and rotational diffusion properties of colloidal model dispersions. Theoretical results are discussed, in comparison with experiments, for monodisperse suspensions of charged and neutral colloidal spheres, and for binary dispersions of differently sized tracer and host particles. The theoretical methods employed comprise a mode-coupling scheme for Brownian particles, and a rooted cluster expansion scheme of tracer diffusion with two- and three-body hydrodynamic interactions included. We analyse in particular the validity of various empirical generalized Stokes-Einstein-Debye (SED) relations between the (dynamic) shear viscosity and translational/rotational diffusion coefficients. Some of these generalized SED relations are basic to microrheological measurements aimed at characterizing the viscoelasticity of complex fluids on the basis of the diffusional properties of immersed tracer particles
Jin, Xin; Zhang, Zhen-Hai; Zhu, Jing; Sun, E; Yu, Dan-Hong; Chen, Xiao-Yun; Liu, Qi-Yuan; Ning, Qing; Jia, Xiao-Bin
2012-04-01
This article reports that nano-silica solid dispersion technology was used to raise genistein efficiency through increasing the enzymatic hydrolysis rate. Firstly, genistin-nano-silica solid dispersion was prepared by solvent method. And differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) were used to verify the formation of solid dispersion, then enzymatic hydrolysis of solid dispersion was done by snailase to get genistein. With the conversion of genistein as criteria, single factor experiments were used to study the different factors affecting enzymatic hydrolysis of genistin and its solid dispersion. And then, response surface method was used to optimize of nano-silica solid dispersion technology assistant enzymatic hydrolysis. The optimum condition to get genistein through enzymatic hydrolysis of genistin-nano-silica solid dispersion was pH 7.1, temperature 52.2 degrees C, enzyme concentration 5.0 mg x mL(-1) and reaction time 7 h. Under this condition, the conversion of genistein was (93.47 +/- 2.40)%. Comparing with that without forming the genistin-nano-silica solid dispersion, the conversion increased 2.62 fold. At the same time, the product of hydrolysis was purified to get pure genistein. The method of enzymatic hydrolysis of genistin-nano-silica solid dispersion by snailase to obtain genistein is simple, efficiency and suitable for the modern scale production.
CRUNCH, Dispersion Model for Continuous Dense Vapour Release in Atmosphere
International Nuclear Information System (INIS)
Jagger, S.F.
1987-01-01
1 - Description of program or function: The situation modelled is as follows. A dense gas emerges from a source such that it can be considered to emerge through a rectangular area, placed in the vertical plane and perpendicular to the plume direction, which assumes that of the ambient wind. The gas flux at the source, and in every plane perpendicular to the plume direction, is constant in time and a stationary flow field has been attained. For this to apply, the characteristic time of release must be much larger than that for dispersal of the contaminant. The plume can be thought to consist of a number of rectangular elements or 'puffs' emerging from the source at regular time intervals. The model follows the development of these puffs at a series of downwind points. These puffs are immediately assumed to advect with the ambient wind at their half-height. The plume also slumps due to the action of gravity and is allowed to entrain air through its sides and top surface. Spreading of a fluid element is caused by pressure differences across this element and since the pressure gradient in the wind direction is small, the resulting pressure differences and slumping velocities are small also, thus permitting this convenient approximation. Initially, as the plume slumps, its vertical dimension decreases and with it the slumping velocity and advection velocity. Thus the plume advection velocity varies as a function of downwind distance. With the present steady state modelling, and to satisfy continuity constraints, there must be consequent adjustment of plume height. Calculation of this parameter from the volume flux ensures this occurs. As the cloud height begins to grow, the advection velocity increases and the plume height decreases accordingly. With advection downwind, the cloud gains buoyancy by entraining air and, if the cloud is cold, by absorbing heat from the ground. Eventually the plume begins to disperse as would a passive pollutant, through the action of
DEFF Research Database (Denmark)
Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K.
2018-01-01
Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and conc...
On unitarity of the particle-hole dispersive optical model
Gorelik, M. L.; Shlomo, S.; Tulupov, B. A.; Urin, M. H.
2018-02-01
For the recently developed particle-hole dispersive optical model, weak violations of unitarity due to a phenomenological description of the spreading effect are considered. Methods for unitarity restoration are proposed and implemented for the 208Pb nucleus in the description of the energy-averaged isoscalar monopole double transition density and strength functions in a wide excitation energy interval that includes the isoscalar giant monopole resonance and its overtone. To illustrate abilities of the model, direct neutron decay of the mentioned giant resonance is also considered.
International Nuclear Information System (INIS)
Carpentieri, Matteo; Kumar, Prashant; Robins, Alan
2011-01-01
Understanding the transformation of nanoparticles emitted from vehicles is essential for developing appropriate methods for treating fine scale particle dynamics in dispersion models. This article provides an overview of significant research work relevant to modelling the dispersion of pollutants, especially nanoparticles, in the wake of vehicles. Literature on vehicle wakes and nanoparticle dispersion is reviewed, taking into account field measurements, wind tunnel experiments and mathematical approaches. Field measurements and modelling studies highlighted the very short time scales associated with nanoparticle transformations in the first stages after the emission. These transformations strongly interact with the flow and turbulence fields immediately behind the vehicle, hence the need of characterising in detail the mixing processes in the vehicle wake. Very few studies have analysed this interaction and more research is needed to build a basis for model development. A possible approach is proposed and areas of further investigation identified. - Research highlights: → Nanoparticle emissions experience very short transformation time scales. → Vehicle wakes need to be characterised to analyse nanoparticle dispersion. → Fast response measurements of nanoparticle evolution in vehicle wakes are very rare. → Wind tunnel methodologies can be further improved to include nanoparticle dynamics. → A simple mathematical approach has been proposed for future development. - The transformation of nanoparticles and the flow characteristics in both the near and far wake regions must be understood in order to develop mathematical models.
A modeling framework was developed to investigate the interactive effects of life history characteristics and landscape heterogeneity on dispersal success. An individual-based model was used to examine how dispersal between resource patches is affected by four landscape characte...
Field-dependent dynamic responses from dilute magnetic nanoparticle dispersions
DEFF Research Database (Denmark)
Fock, Jeppe; Balceris, Christoph; Costo, Rocio
2018-01-01
The response of magnetic nanoparticles (MNPs) to an oscillating magnetic field outside the linear response region is important for several applications including magnetic hyperthermia, magnetic resonance imaging and biodetection. The size and magnetic moment are two critical parameters for the pe...
Applying Dispersive Changes to Lagrangian Particles in Groundwater Transport Models
Konikow, Leonard F.
2010-01-01
Method-of-characteristics groundwater transport models require that changes in concentrations computed within an Eulerian framework to account for dispersion be transferred to moving particles used to simulate advective transport. A new algorithm was developed to accomplish this transfer between nodal values and advecting particles more precisely and realistically compared to currently used methods. The new method scales the changes and adjustments of particle concentrations relative to limiting bounds of concentration values determined from the population of adjacent nodal values. The method precludes unrealistic undershoot or overshoot for concentrations of individual particles. In the new method, if dispersion causes cell concentrations to decrease during a time step, those particles in the cell having the highest concentration will decrease the most, and those with the lowest concentration will decrease the least. The converse is true if dispersion is causing concentrations to increase. Furthermore, if the initial concentration on a particle is outside the range of the adjacent nodal values, it will automatically be adjusted in the direction of the acceptable range of values. The new method is inherently mass conservative. ?? US Government 2010.
Dense-gas dispersion advection-diffusion model
International Nuclear Information System (INIS)
Ermak, D.L.
1992-07-01
A dense-gas version of the ADPIC particle-in-cell, advection- diffusion model was developed to simulate the atmospheric dispersion of denser-than-air releases. In developing the model, it was assumed that the dense-gas effects could be described in terms of the vertically-averaged thermodynamic properties and the local height of the cloud. The dense-gas effects were treated as a perturbation to the ambient thermodynamic properties (density and temperature), ground level heat flux, turbulence level (diffusivity), and windfield (gravity flow) within the local region of the dense-gas cloud. These perturbations were calculated from conservation of energy and conservation of momentum principles along with the ideal gas law equation of state for a mixture of gases. ADPIC, which is generally run in conjunction with a mass-conserving wind flow model to provide the advection field, contains all the dense-gas modifications within it. This feature provides the versatility of coupling the new dense-gas ADPIC with alternative wind flow models. The new dense-gas ADPIC has been used to simulate the atmospheric dispersion of ground-level, colder-than-ambient, denser-than-air releases and has compared favorably with the results of field-scale experiments
Modeling skull's acoustic attenuation and dispersion on photoacoustic signal
Mohammadi, L.; Behnam, H.; Nasiriavanaki, M. R.
2017-03-01
Despite the great promising results of a recent new transcranial photoacoustic brain imaging technology, it has been shown that the presence of the skull severely affects the performance of this imaging modality. In this paper, we investigate the effect of skull on generated photoacoustic signals with a mathematical model. The developed model takes into account the frequency dependence attenuation and acoustic dispersion effects occur with the wave reflection and refraction at the skull surface. Numerical simulations based on the developed model are performed for calculating the propagation of photoacoustic waves through the skull. From the simulation results, it was found that the skull-induced distortion becomes very important and the reconstructed image would be strongly distorted without correcting these effects. In this regard, it is anticipated that an accurate quantification and modeling of the skull transmission effects would ultimately allow for skull aberration correction in transcranial photoacoustic brain imaging.
Dispersion of tracers by the oceanic eddy field modelling programme
International Nuclear Information System (INIS)
Richards, K.J.
1986-01-01
A numerical model has been developed to study the dispersion of tracers by the oceanic eddy field. The study is designed to investigate the horizontal and vertical structure of the eddies and how this structure is influenced by the bottom topography. It is found that hills and valleys have a strong effect on the eddies above them. The flow close to the bottom has a tendency to be steered by the height contours. The surface and bottom flows become decorrelated and the vertical variation of the kinetic energy of the eddies is increased with higher topographic features. (author)
User manual of nuclide dispersion in phreatic aquifers model
International Nuclear Information System (INIS)
Rives, D.E.
1999-01-01
The Nuclide Dispersion in Phreatic Aquifers (DRAF) model was developed in the 'Division Estudios Ambientales' of the 'Gerencia de Seguridad Radiologica y Nuclear, Comision Nacional de Energia Atomica' (1991), for the Safety Assessment of Near Surface Radioactive Waste Disposal Facilities. Afterwards, it was modified in several opportunities, adapting it to a number of application conditions. The 'Manual del usuario del codigo DRAF' here presented is a reference document for the use of the last three versions of the code developed for the 'Autoridad Regulatoria Nuclear' between 1995 and 1996. The DRAF model solves the three dimension's solute transport equation for porous media by the finite differences method. It takes into account the advection, dispersion, radioactive decay, and retention in the solid matrix processes, and has multiple possibilities for the source term. There are three versions of the model, two of them for the saturated zone and one for the unsaturated zone. All the versions have been verified in different conditions, and have been applied in exercises of the International Atomic Energy Agency and also in real cases. (author)
Majdalani, Samer; Guinot, Vincent; Delenne, Carole; Gebran, Hicham
2018-06-01
This paper is devoted to theoretical and experimental investigations of solute dispersion in heterogeneous porous media. Dispersion in heterogenous porous media has been reported to be scale-dependent, a likely indication that the proposed dispersion models are incompletely formulated. A high quality experimental data set of breakthrough curves in periodic model heterogeneous porous media is presented. In contrast with most previously published experiments, the present experiments involve numerous replicates. This allows the statistical variability of experimental data to be accounted for. Several models are benchmarked against the data set: the Fickian-based advection-dispersion, mobile-immobile, multirate, multiple region advection dispersion models, and a newly proposed transport model based on pure advection. A salient property of the latter model is that its solutions exhibit a ballistic behaviour for small times, while tending to the Fickian behaviour for large time scales. Model performance is assessed using a novel objective function accounting for the statistical variability of the experimental data set, while putting equal emphasis on both small and large time scale behaviours. Besides being as accurate as the other models, the new purely advective model has the advantages that (i) it does not exhibit the undesirable effects associated with the usual Fickian operator (namely the infinite solute front propagation speed), and (ii) it allows dispersive transport to be simulated on every heterogeneity scale using scale-independent parameters.
Dispersion model for airborne radioactive particulates inside a process building
International Nuclear Information System (INIS)
Perkins, W.C.; Stoddard, D.H.
1984-02-01
An empirical model, predicting the spread of airborne radioactive particles after they are released inside a building, has been developed. The basis for this model is a composite of data for dispersion of airborne activity recorded during 12 case incidents. These incidents occurred at the Savannah River Plant (SRP) during approximately 90 plant-years of experience with the chemical and metallurgical processing of purified neptunium and plutonium. The model illustrates that the multiple-air-zone concept, used in the designs of many nuclear facilities, can be an efficient safety feature to limit the spread of airborne activity from a release. This study also provides some insight into an apparently anomalous behavior of airborne particulates, namely, their migration against the prevailing flow of ventilation air. 2 references, 12 figures, 4 tables
International Nuclear Information System (INIS)
Havens, J.; Spicer, T.
1990-09-01
The topical report is one of a series on the development of methods for LNG vapor dispersion prediction for regulatory application. The results indicate that the DEGADIS model is superior both phenomenologically and in performance to the Gaussian line source model promulgated in 49 CFR 193 for LNG vapor dispersion simulation. Availability of the DEGADIS model for VAX and IBM-PC formats provides for wider use of the model and greater potential for industry and regulatory acceptance. The acceptance is seen as an important interim objective while research continues on vapor dispersion estimation methods which provide for effects of vapor detention systems, turbulence induced by plant structure, and plant/area topographical features
Mescia, L.; Bia, P.; Caratelli, D.
2017-01-01
A novel two-dimensional (2-D) finite-difference timedomain algorithm for modeling ultrawideband pulse propagation in arbitrary dispersive soils is presented. The soil dispersion is modeled by general power law series representation, accounting for multiple higher order dispersive relaxation
Validation and comparison of dispersion models of RTARC DSS
International Nuclear Information System (INIS)
Duran, J.; Pospisil, M.
2004-01-01
RTARC DSS (Real Time Accident Release Consequences - Decision Support System) is a computer code developed at the VUJE Trnava, Inc. (Stubna, M. et al, 1993). The code calculations include atmospheric transport and diffusion, dose assessment, evaluation and displaying of the affected zones, evaluation of the early health effects, concentration and dose rate time dependence in the selected sites etc. The simulation of the protective measures (sheltering, iodine administration) is involved. The aim of this paper is to present the process of validation of the RTARC dispersion models. RTARC includes models for calculations of release for very short (Method Monte Carlo - MEMOC), short (Gaussian Straight-Line Model) and long distances (Puff Trajectory Model - PTM). Validation of the code RTARC was performed using the results of comparisons and experiments summarized in the Table 1.: 1. Experiments and comparisons in the process of validation of the system RTARC - experiments or comparison - distance - model. Wind tunnel experiments (Universitaet der Bundeswehr, Muenchen) - Area of NPP - Method Monte Carlo. INEL (Idaho National Engineering Laboratory) - short/medium - Gaussian model and multi tracer atmospheric experiment - distances - PTM. Model Validation Kit - short distances - Gaussian model. STEP II.b 'Realistic Case Studies' - long distances - PTM. ENSEMBLE comparison - long distances - PTM (orig.)
Vapor generation rate model for dispersed drop flow
International Nuclear Information System (INIS)
Unal, C.; Tuzla, K.; Cokmez-Tuzla, A.F.; Chen, J.C.
1991-01-01
A comparison of predictions of existing nonequilibrium post-CHF heat transfer models with the recently obtained rod bundle data has been performed. The models used the experimental conditions and wall temperatures to predict the heat flux and vapor temperatures at the location of interest. No existing model was able to reasonably predict the vapor superheat and the wall heat flux simultaneously. Most of the models, except Chen-Sundaram-Ozkaynak, failed to predict the wall heat flux, while all of the models could not predict the vapor superheat data or trends. A recently developed two-region heat transfer model, the Webb-Chen two-region model, did not give a reasonable prediction of the vapor generation rate in the far field of the CHF point. A new correlation was formulated to predict the vapor generation rate in convective dispersed droplet flow in terms of thermal-hydraulic parameters and thermodynamic properties. A comparison of predictions of the two-region heat transfer model, with the use of a presently developed correlation, with all the existing post-CHF data, including single-tube and rod bundle, showed significant improvements in predicting the vapor superheat and tube wall heat flux trends. (orig.)
Lagrangian Stochastic Dispersion Model IMS Model Suite and its Validation against Experimental Data
International Nuclear Information System (INIS)
Bartok, J.
2010-01-01
The dissertation presents IMS Lagrangian Dispersion Model, which is a 'new generation' Slovak dispersion model of long-range transport, developed by MicroStep-MIS. It solves trajectory equation for a vast number of Lagrangian 'particles' and stochastic equation that simulates the effects of turbulence. Model contains simulation of radioactive decay (full decay chains of more than 300 nuclides), and dry and wet deposition. Model was integrated into IMS Model Suite, a system in which several models and modules can run and cooperate, e.g. LAM model WRF preparing fine resolution meteorological data for dispersion. The main theme of the work is validation of dispersion model against large scale international campaigns CAPTEX and ETEX, which are two of the largest tracer experiments. Validation addressed treatment of missing data, data interpolation into comparable temporal and spatial representation. The best model results were observed for ETEX I, standard results for CAPTEXes and worst results for ETEX II, known in modelling community for its meteorological conditions that can be hardly resolved by models. The IMS Lagrangian Dispersion Model was identified as capable long range dispersion model for slowly- or nonreacting chemicals and radioactive matter. Influence of input data on simulation quality is discussed within the work. Additional modules were prepared according to praxis requirement: a) Recalculation of concentrations of radioactive pollutant into effective doses form inhalation, immersion in the plume and deposition. b) Dispersion of mineral dust was added and tested in desert locality, where wind and soil moisture were firstly analysed and forecast by WRF. The result was qualitatively verified in case study against satellite observations. (author)
Open Burn/Open Detonation Dispersion Model (OBODM) User's Guide. Volume I. User's Instructions
National Research Council Canada - National Science Library
Bjorklund, Jay
1998-01-01
...) of obsolete munitions and solid propellants. OBODM uses loud/plume rise, dispersion, and deposition algorithms taken from existing models for instantaneous and quasi-continuous sources to predict the downwind transport and dispersion...
2-D model for pollutant dispersion at the coastal outfall off Paradip
Digital Repository Service at National Institute of Oceanography (India)
Suryanarayana, A.; Babu, M.T.; Vethamony, P.; Gouveia, A.D.
Simulation of dispersion of the effluent discharge has been carried out using 2-D Model to verify the advection and diffusion of the pollutant patch of the proposed effluent disposal off Paradip, Orissa, India. The simulation of dispersion...
An Empirical Model of Wage Dispersion with Sorting
DEFF Research Database (Denmark)
Bagger, Jesper; Lentz, Rasmus
(submodular). The model is estimated on Danish matched employer-employee data. We find evidence of positive assortative matching. In the estimated equilibrium match distribution, the correlation between worker skill and firm productivity is 0.12. The assortative matching has a substantial impact on wage......This paper studies wage dispersion in an equilibrium on-the-job-search model with endogenous search intensity. Workers differ in their permanent skill level and firms differ with respect to productivity. Positive (negative) sorting results if the match production function is supermodular...... to mismatch by asking how much greater output would be if the estimated population of matches were perfectly positively assorted. In this case, output would increase by 7.7%....
Dispersion model computations of urban air pollution in Espoo, Finland
Energy Technology Data Exchange (ETDEWEB)
Valkonen, E.; Haerkoenen, J.; Kukkonen, J.; Rantakrans, E.; Jalkanen, L.
1997-12-31
This report presents the numerical results of air quality studies of the city of Espoo in southern Finland. This city is one of the four cities in the Helsinki metropolitan area, having a total population of 850 000. A thorough emission inventory was made of both mobile and stationary sources in the Helsinki metropolitan area. The atmospheric dispersion was evaluated using an urban dispersion modelling system, including a Gaussian multiple-source plume model and a meteorological pre-processing model. The hourly time series of CO, NO{sub 2} and SO{sub 2} concentrations were predicted, using the emissions and meteorological data for the year 1990. The predicted results show a clear decrease in the yearly mean concentrations from southeast to northwest. This is due in part to the denser traffic in the southern parts of Espoo, and in part to pollution from the neighbouring cities of Helsinki and Vantaa, located east of Espoo. The statistical concentration parameters found for Espoo were lower than the old national air quality guidelines (1984); however, some occurrences of above-threshold values were found for NO{sub 2} in terms of the new guidelines (1996). The contribution of traffic to the total concentrations varies spatially from 30 to 90 % for NO{sub 2} from 1 to 65 % for SO{sub 2} while for CO it is nearly 100 %. The concentrations database will be further utilised to analyse the influence of urban air pollution on the health of children attending selected day nurseries in Espoo. The results of this study can also be applied in traffic and city planning. In future work the results will also be compared with data from the urban measurement network of the Helsinki Metropolitan Area Council. (orig.) 19 refs.
Modeling of dilute and dense dispersed fluid-particle flow
Energy Technology Data Exchange (ETDEWEB)
Laux, Harald
1998-08-01
A general two-fluid model is derived and applied in CFD computations to various test cases of important industrial multiphase flows. It is general in the sense of its applicability to dilute and dense dispersed fluid-particle flows. The model is limited to isothermal flow without mass transfer and only one particle phase is described. The instantaneous fluid phase equations, including the phase interaction terms, are derived from a volume averaging technique, and the instantaneous particle phase equations are derived from the kinetic theory of granular material. Whereas the averaging procedure, the treatment of the interaction terms, and the kinetic theory approach have been reported in literature prior to this work the combination of the approaches is new. The resulting equations are derived without ambiguity in the interpretation of the particle phase pressure (equation-of-state of particle phase). The basic modeling for the particle phase is improved in two steps. Because in the basic modeling only stresses due to kinetic and collisional interactions are included, a simple model for an effective viscosity is developed in order to allow also frictional stresses within the particle phase. Moreover, turbulent stresses and turbulent dispersion of particles play often an important role for the transport processes. Therefore in a second step, a two-equation turbulence model for both fluid and particle phase turbulence is derived by applying the phasic average to the instantaneous equations. The resulting k-{epsilon}-k{sup d}-{epsilon}{sup d} model is new. Mathematical closure is attempted such that the resulting set of equations is valid for both dilute arid dense flows. During the development of the closure relations a clear distinction is made between granular or ''viscous'' microscale fluctuations and turbulent macro scale fluctuations (true particle turbulence) within the particle phase. The set of governing equations is discretized by using a
Modeling of dilute and dense dispersed fluid-particle flow
Energy Technology Data Exchange (ETDEWEB)
Laux, Harald
1998-08-01
A general two-fluid model is derived and applied in CFD computations to various test cases of important industrial multiphase flows. It is general in the sense of its applicability to dilute and dense dispersed fluid-particle flows. The model is limited to isothermal flow without mass transfer and only one particle phase is described. The instantaneous fluid phase equations, including the phase interaction terms, are derived from a volume averaging technique, and the instantaneous particle phase equations are derived from the kinetic theory of granular material. Whereas the averaging procedure, the treatment of the interaction terms, and the kinetic theory approach have been reported in literature prior to this work the combination of the approaches is new. The resulting equations are derived without ambiguity in the interpretation of the particle phase pressure (equation-of-state of particle phase). The basic modeling for the particle phase is improved in two steps. Because in the basic modeling only stresses due to kinetic and collisional interactions are included, a simple model for an effective viscosity is developed in order to allow also frictional stresses within the particle phase. Moreover, turbulent stresses and turbulent dispersion of particles play often an important role for the transport processes. Therefore in a second step, a two-equation turbulence model for both fluid and particle phase turbulence is derived by applying the phasic average to the instantaneous equations. The resulting k-{epsilon}-k{sup d}-{epsilon}{sup d} model is new. Mathematical closure is attempted such that the resulting set of equations is valid for both dilute arid dense flows. During the development of the closure relations a clear distinction is made between granular or ''viscous'' microscale fluctuations and turbulent macro scale fluctuations (true particle turbulence) within the particle phase. The set of governing equations is discretized by using a finite volume method
MESOILT2, a Lagrangian trajectory climatological dispersion model
International Nuclear Information System (INIS)
Ramsdell, J.V. Jr.; Burk, K.W.
1991-03-01
The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation dose that individuals could have received as a result of emissions from nuclear operations at the Hanford Site. An independent Technical Steering Panel (TSP) directs the project, which is conducted by the Pacific Northwest Laboratory (PNL). The TSP directed PNL to demonstrate that its recommended approach for dose reconstruction is technically feasible and practical. This demonstration was Phase 1 of the project. This report is specifically concerned with the approach that PNL recommends for dealing with the atmospheric pathway. The TSP established a model domain for the atmospheric pathway for Phase 1 that includes 10 counties in Washington and Oregon and covers several thousand square miles. It is unrealistic to assume that atmospheric models which estimate transport and diffusion based on the meteorological conditions near the point of release of material at the time of release are adequate for a region this large. As a result, PNL recommended use of a Lagrangian trajectory, puff dispersion model for the Phase I study. This report describes the MESOILT2 computer code and the atmospheric transport, diffusion, deposition, and depletion models used in Phase I. The contents of the report include a technical description of the models, a user's guide for the codes, and descriptions of the individual code elements. 53 refs., 17 figs., 5 tabs
Dispersion model for airborne particulates inside a building
International Nuclear Information System (INIS)
Perkins, W.C.; Stoddard, D.H.
1985-01-01
An empirical model has been developed for the spread of airborne radioactive particles after they are released inside a building. The model has been useful in performing safety analyses of actinide materials facilities at the Savannah River Plant (SRP). These facilities employ the multiple-air-zone concept; that is, ventilation air flows from rooms or areas of least radioactive material hazard, through zones of increasing hazard, to a treatment system. A composite of the data for dispersion of airborne activity during 12 actual case incidents at SRP forms the basis for this model. These incidents occurred during approximately 90 plant-years of experience at SRP with the chemical and metallurgical processing of purified neptunium and plutonium after their recovery from irradiated uranium. The model gives ratios of the airborne activity concentrations in rooms and corridors near the site of the release. The multiple-air-zone concept has been applied to many designs of nuclear facilities as a safety feature to limit the spread of airborne activity from a release. The model illustrates the limitations of this concept: it predicts an apparently anomalous behavior of airborne particulates; namely, a small migration against the flow of the ventilation air
Turbulent diffusion modelling for windflow and dispersion analysis
International Nuclear Information System (INIS)
Bartzis, J.G.
1988-01-01
The need for simple but reliable models for turbulent diffusion for windflow and atmospheric dispersion analysis is a necessity today if one takes into consideration the relatively high demand in computer time and costs for such an analysis, arising mainly from the often large solution domains needed, the terrain complexity and the transient nature of the phenomena. In the accident consequence assessment often there is a need for a relatively large number of cases to be analysed increasing further the computer time and costs. Within the framework of searching for relatively simple and universal eddy viscosity/diffusivity models, a new three dimensional non isotropic model is proposed applicable to any domain complexity and any atmospheric stability conditions. The model utilizes the transport equation for turbulent kinetic energy but introduces a new approach in effective length scale estimation based on the flow global characteristics and local atmospheric stability. The model is discussed in detail and predictions are given for flow field and boundary layer thickness. The results are compared with experimental data with satisfactory results
International Nuclear Information System (INIS)
Macdonald, J Ross
2005-01-01
Analysis by D L Sidebottom of the dispersive frequency response of the real-part of the conductivity, σ'(ω), for many alkali phosphate and metaphosphate glasses, using a fitting model involving a 'universal dynamic response' power law with an exponent n and a constant-loss term, led to anomalous n behaviour that he explained as arising from variable constriction of the local cation conduction space. In order to obtain adequate fits, he eliminated from the data all low-frequency decreases of σ'(ω) below the dc plateau, ones actually associated with electrode effects. Such a cut-off does not, however, eliminate electrode effects possibly present in the high-frequency part of the data range. The results of the present detailed analysis and fitting of both synthetic data and several of his experimental data sets show unequivocally that his anomalous n behaviour arose from neglecting electrode effects. Their inclusion, with or without data cut-off in the fitting model, leads to the expected high-frequency slope value of n = 2/3 associated with bulk conduction, as required by recently published topological effective-dimension considerations for dielectric relaxation in conductive systems. Further, the effects of the inclusion in a full fitting model of series and possibly parallel complex constant-phase-element contributions, representing electrode and nearly constant loss effects, respectively, have been investigated in detail. Such composite models usually lead to best fitting of either the full or cut-off complex data when they include the semi-universal, topologically based K1 bulk model, one indirectly derived from the assumption of stretched-exponential temporal behaviour
radionuclides modelling dispersion of in the atmosphere for continuous discharges and accidental
International Nuclear Information System (INIS)
Teyeb, Malika
2011-01-01
The study of the dispersion of radionuclides in the atmosphere is the subject of a physical and numerical modeling of the phenomenon of dispersion. This work aims to study the atmospheric dispersion of accidental releases and continuous, from the possible establishment of a nuclear pressurized water reactor in the potential in Bizerte and Skhira.
International Nuclear Information System (INIS)
Baskett, R.L.; Vogt, P.J.; Schalk, W.W. III; Pobanz, B.M.; Foster, C.S.; Ellis, J.S.
1995-01-01
Atmospheric modeling of accidental toxic chemical releases requires accurate simulation of wind flows on the 1 to 25 km (meso-γ) scale. Complex meteorological fields have been a challenge to real-time emergency response models for decades especially when,wind observations are sparse. 'ne Gaussian model is a reasonable tool for the first few kilometers if the terrain is relatively flat, the wind flow is simple (no vertical structure), and meteorological data are available at the source. Most other situations demand three-dimensional models. Three-dimensional diagnostic wind field models depend on available meteorological observations which are subsequently adjusted by mass conservation to create a wind field over the terrain. Even in urban areas with multiple meteorological stations, 3-D diagnostic models may suffer from a lack of sufficient real-time observations. Deterministic models are stressed even more during variable low wind speed or stable atmospheric conditions, especially if the release is denser-than-air. Furthermore, typical wind direction measurement errors of 5 to 10 degrees extrapolated 10 or 20 km cause significant dislocations of downwind concentrations. This paper presents a recent case study that illustrates the difficulty of modeling accidental toxic releases in urban areas
A CFD model for pollutant dispersion in rivers
Directory of Open Access Journals (Sweden)
Modenesi K.
2004-01-01
Full Text Available Studies have shown that humankind will experience a water shortage in the coming decades. It is therefore paramount to develop new techniques and models with a view to minimizing the impact of pollution. It is important to predict the environmental impact of new emissions in rivers, especially during periods of drought. Computational fluid dynamics (CFD has proved to be an invaluable tool to develop models able to analyze in detail particle dispersion in rivers. However, since these models generate grids with thousands (even millions of points to evaluate velocities and concentrations, they still require powerful machines. In this context, this work contributes by presenting a new three-dimensional model based on CFD techniques specifically developed to be fast, providing a significant improvement in performance. It is able to generate predictions in a couple of hours for a one-thousand-meter long section of river using Pentium IV computers. Commercial CFD packages would require weeks to solve the same problem. Another innovation inb this work is that a half channel with a constant elliptical cross section represents the river, so the Navier Stokes equations were derived for the elliptical system. Experimental data were obtained from REPLAN (PETROBRAS refining unit on the Atibaia River in São Paulo, Brazil. The results show good agreement with experimental data.
Skull's acoustic attenuation and dispersion modeling on photoacoustic signal
Mohammadi, Leila; Behnam, Hamid; Tavakkoli, Jahan; Nasiriavanaki, Mohammadreza
2018-02-01
Despite the promising results of the recent novel transcranial photoacoustic (PA) brain imaging technology, it has been demonstrated that the presence of the skull severely affects the performance of this imaging modality. We theoretically investigate the effects of acoustic heterogeneity induced by skull on the PA signals generated from single particles, with firstly developing a mathematical model for this phenomenon and then explore experimental validation of the results. The model takes into account the frequency dependent attenuation and dispersion effects occur with wave reflection, refraction and mode conversion at the skull surfaces. Numerical simulations based on the developed model are performed for calculating the propagation of photoacoustic waves through the skull. The results show a strong agreement between simulation and ex-vivo study. The findings are as follow: The thickness of the skull is the most PA signal deteriorating factor that affects both its amplitude (attenuation) and phase (distortion). Also we demonstrated that, when the depth of target region is low and it is comparable to the skull thickness, however, the skull-induced distortion becomes increasingly severe and the reconstructed image would be strongly distorted without correcting these effects. It is anticipated that an accurate quantification and modeling of the skull transmission effects would ultimately allow for aberration correction in transcranial PA brain imaging.
Székely, Anna J; Langenheder, Silke
2017-08-01
The extent and frequency of drought episodes is expected to increase in the following decades making it a crucial stress factor for smaller water bodies. However, very little is known about how bacterioplankton is affected by increased evaporation and how these communities reassemble after rewetting. Here, we present results from a microcosm experiment that assessed the effect of drying-rewetting stress on bacterioplankton in the light of the stress history and the rate and timing of dispersal after the rewetting. We found that the drying phase resulted mainly in a change of function, whereas the complete desiccation and rewetting processes strongly affected both composition and function, which were, however, influenced by the initial conditions and stress history of the communities. Effects of dispersal were generally stronger when it occurred at an early stage after the rewetting. At this stage, selective establishment of dispersed bacteria coupled with enhanced compositional and functional recovery was found, whereas effects of dispersal were neutral, that is, predictable by dispersal rates, at later stages. Our studies therefore show that both the stress history and the timing of dispersal are important factors that influence the response of bacterial communities to environmental change and stress events.
Applications of the PUFF model to forecasts of volcanic clouds dispersal from Etna and Vesuvio
Daniele, P.; Lirer, L.; Petrosino, P.; Spinelli, N.; Peterson, R.
2009-05-01
PUFF is a numerical volcanic ash tracking model developed to simulate the behaviour of ash clouds in the atmosphere. The model uses wind field data provided by meteorological models and adds dispersion and sedimentation physics to predict the evolution of the cloud once it reaches thermodynamic equilibrium with the atmosphere. The software is intended for use in emergency response situations during an eruption to quickly forecast the position and trajectory of the ash cloud in the near (˜1-72 h) future. In this paper, we describe the first application of the PUFF model in forecasting volcanic ash dispersion from the Etna and Vesuvio volcanoes. We simulated the daily occurrence of an eruptive event of Etna utilizing ash cloud parameters describing the paroxysm of 22nd July 1998 and wind field data for the 1st September 2005-31st December 2005 time span from the Global Forecast System (GFS) model at the approximate location of the Etna volcano (38N 15E). The results show that volcanic ash particles are dispersed in a range of directions in response to changing wind field at various altitudes and that the ash clouds are mainly dispersed toward the east and southeast, although the exact trajectory is highly variable, and can change within a few hours. We tested the sensitivity of the model to the mean particle grain size and found that an increased concentration of ash particles in the atmosphere results when the mean grain size is decreased. Similarly, a dramatic variation in dispersion results when the logarithmic standard deviation of the particle-size distribution is changed. Additionally, we simulated the occurrence of an eruptive event at both Etna and Vesuvio, using the same parameters describing the initial volcanic plume, and wind field data recorded for 1st September 2005, at approximately 38N 15E for Etna and 41N 14E for Vesuvio. The comparison of the two simulations indicates that identical eruptions occurring at the same time at the two volcanic centres
Plume dispersion in four pine thinning scenarios: development of a simple pheromone dispersion model
Holly Peterson; Harold Thistle; Brian Lamb; Gene Allwine; Steve Edburg; Brian Strom
2010-01-01
A unique field campaign was conducted in 2004 to examine how changes in stand density may affect dispersion of insect pheromones in forest canopies. Over a l4-day period, 126 tracer tests were performed, and conditions ranged from an unthinned loblolly pine (Pinus taeda) canopy through a series of thinning scenarios with basal areas of32.l, 23.0, and 16.1 m2ha-l.ln...
Two-patch population models with adaptive dispersal: the effects of varying dispersal speeds
Czech Academy of Sciences Publication Activity Database
Cressman, R.; Křivan, Vlastimil
2013-01-01
Roč. 67, č. 2 (2013), s. 329-358 ISSN 0303-6812 Grant - others:The University of Tennessee(US) EF-0832858; National Science Foundation(US) DMS 0931642 Institutional support: RVO:60077344 Keywords : competition * dispersal * evolution Subject RIV: EH - Ecology, Behaviour Impact factor: 2.388, year: 2013 http://link.springer.com/content/pdf/10.1007%2Fs00285-012-0548-3.pdf
Global atmospheric dispersion modelling after the Fukushima accident
Energy Technology Data Exchange (ETDEWEB)
Suh, K.S.; Youm, M.K.; Lee, B.G.; Min, B.I. [Korea Atomic Energy Research Institute (Korea, Republic of); Raul, P. [Universidad de Sevilla (Spain)
2014-07-01
A large amount of radioactive material was released to the atmosphere due to the Fukushima nuclear accident in March 2011. The radioactive materials released into the atmosphere were mostly transported to the Pacific Ocean, but some of them were fallen on the surface due to dry and wet depositions in the northwest area from the Fukushima nuclear site. Therefore, northwest part of the nuclear site was seriously contaminated and it was designated with the restricted zone within a radius of 20 ∼ 30 km around the Fukushima nuclear site. In the early phase of the accident from 11 March to 30 March, the radioactive materials were dispersed to an area of the inland and offshore of the nuclear site by the variations of the wind. After the Fukushima accident, the radionuclides were detected through the air monitoring in the many places over the world. The radioactive plume was transported to the east part off the site by the westerly jet stream. It had detected in the North America during March 17-21, in European countries during March 23-24, and in Asia during from March 24 to April 6, 2011. The radioactive materials were overall detected across the northern hemisphere passed by 15 ∼ 20 days after the accident. Three dimensional numerical model was applied to evaluate the dispersion characteristics of the radionuclides released into the air. Simulated results were compared with measurements in many places over the world. Comparative results had good agreements in some places, but they had a little differences in some locations. The difference between the calculations and measurements are due to the meteorological data and relatively coarse resolutions in the model. Some radioactive materials were measured in Philippines, Taiwan, Hon Kong and South Korea during from March 23-28. It inferred that it was directly transported from the Fukushima by the northeastern monsoon winds. This event was well represented in the numerical model. Generally, the simulations had a good
Radiation environmental real-time monitoring and dispersion modeling
International Nuclear Information System (INIS)
Kovacik, A.; Bartokova, I.; Omelka, J.; Melicherova, T.
2014-01-01
The system of real-time radiation monitoring provided by MicroStep-MIS is a turn-key solution for measurement, acquisition, processing, reporting, archiving and displaying of various radiation data. At the level of measurements, the monitoring stations can be equipped with various devices from radiation probes, measuring the actual ambient gamma dose rate, to fully automated aerosol monitors, returning analysis results of natural and manmade radionuclides concentrations in the air. Using data gathered by our radiation probes RPSG-05 integrated into monitoring network of Crisis Management of the Slovak Republic and into monitoring network of Slovak Hydrometeorological Institute, we demonstrate its reliability and long-term stability of measurements. Data from RPSG-05 probes and GammaTracer probes, both of these types are used in the SHI network, are compared. The sensitivity of RPSG-05 is documented on data where changes of dose rate are caused by precipitation. Qualities of RPSG-05 probe are illustrated also on example of its use in radiation monitoring network in the United Arab Emirates. A more detailed information about radioactivity of the atmosphere can be obtained by using spectrometric detectors (e.g. scintillation detectors) which, besides gamma dose rate values, offer also a possibility to identify different radionuclides. However, this possibility is limited by technical parameters of detector like energetic resolution and detection efficiency in given geometry of measurement. A clearer information with less doubts can be obtained from aerosol monitors with a built-in silicon detector of alpha and beta particles and with an electrically cooled HPGe detector dedicated for gamma-ray spectrometry, which is performed during the sampling. Data from a complex radiation monitoring network can be used, together with meteorological data, in radiation dispersion model by MicroStep-MIS. This model serves for simulation of atmospheric propagation of radionuclides
Advances and Problems in Mathematical Modelling of Dispersion of ...
African Journals Online (AJOL)
Most expressions for dispersion of pollutants have failed to give accurate predictions in both channel and natural stream flows. This paper outlines the basic concepts on which the fundamental dispersion equations have been derived. Some of the advances on these equations are examined and their deficiencies pointed ...
A model for evaluating dispersed outdoor recreation use estimation
Stanley J. Zarnoch; Donald B. K. English; Susan M. Kocis
2004-01-01
An outdoor recreation use simulator (ORUS) has been developed to simulate dispersed recreation survey data similar to that collected by the National Visitor Use Monitoring (NVUM) Project's survey of the national forests of the U.S.A. Statistical distributions are used to represent the various behaviors of recreationists during their visit to a dispersed area. The...
International Nuclear Information System (INIS)
Hodgin, C.R.
1986-01-01
The Rocky Flats Plant applies atmospheric dispersion modeling as a tool for Emergency Response, Risk Assessment, and Regulatory Compliance. Extreme variations in terrain around the facility have necessitated the development of an advanced modeling approach. The Terrain-Responsive Atmospheric Code (TRAC) was developed to treat realistically the changing wind, stability, dispersion, and deposition patterns that are experienced in mountainous areas. The result is a detailed picture of dose and deposition patterns associated with postulated or actual releases. A unified approach was taken to modeling needs at Rocky Flats. This produces consistent dose projections for all applications. A Risk Assessment version of TRAC is now operational. A high-speed version of the code is being implemented for Emergency Response, and development of a regulatory version is under way. Public, scientific, and governmental acceptance of TRAC is critical to successful applications at the Rocky Flats Plant. A program of peer review and regulatory approval was initiated to provide a full outside evaluation of our techniques. Full field validation (tracer testing) is key to demonstrating reliability of the TRAC model. A validation study was planned for implementation beginning in early CY-1986. The necessary funding ($500,000) is being sought. Although the TRAC model development and approval program was developed for site-specific needs at the Rocky Flats Plant, potential exists for wider application within the Department of Energy (DOE). The TRAC model can be easily applied at other sites in complex terrain. A coordinated approach to model validation throughout the Albquerque Operations Office (AL) or DOE complexes could prove more cost effective than site-by-site evaluations. Finally, the model approval procedure developed jointly by Rocky Flats and the Environmental Protection Agency (EPA) is general and could be applied to other models or as the basis for a DOE-wide program
Modelling substorm chorus events in terms of dispersive azimuthal drift
Directory of Open Access Journals (Sweden)
A. B. Collier
2004-12-01
Full Text Available The Substorm Chorus Event (SCE is a radio phenomenon observed on the ground after the onset of the substorm expansion phase. It consists of a band of VLF chorus with rising upper and lower cutoff frequencies. These emissions are thought to result from Doppler-shifted cyclotron resonance between whistler mode waves and energetic electrons which drift into a ground station's field of view from an injection site around midnight. The increasing frequency of the emission envelope has been attributed to the combined effects of energy dispersion due to gradient and curvature drifts, and the modification of resonance conditions and variation of the half-gyrofrequency cutoff resulting from the radial component of the ExB drift.
A model is presented which accounts for the observed features of the SCE in terms of the growth rate of whistler mode waves due to anisotropy in the electron distribution. This model provides an explanation for the increasing frequency of the SCE lower cutoff, as well as reproducing the general frequency-time signature of the event. In addition, the results place some restrictions on the injected particle source distribution which might lead to a SCE.
Key words. Space plasma physics (Wave-particle interaction – Magnetospheric physics (Plasma waves and instabilities; Storms and substorms
Modelling substorm chorus events in terms of dispersive azimuthal drift
Directory of Open Access Journals (Sweden)
A. B. Collier
2004-12-01
Full Text Available The Substorm Chorus Event (SCE is a radio phenomenon observed on the ground after the onset of the substorm expansion phase. It consists of a band of VLF chorus with rising upper and lower cutoff frequencies. These emissions are thought to result from Doppler-shifted cyclotron resonance between whistler mode waves and energetic electrons which drift into a ground station's field of view from an injection site around midnight. The increasing frequency of the emission envelope has been attributed to the combined effects of energy dispersion due to gradient and curvature drifts, and the modification of resonance conditions and variation of the half-gyrofrequency cutoff resulting from the radial component of the ExB drift. A model is presented which accounts for the observed features of the SCE in terms of the growth rate of whistler mode waves due to anisotropy in the electron distribution. This model provides an explanation for the increasing frequency of the SCE lower cutoff, as well as reproducing the general frequency-time signature of the event. In addition, the results place some restrictions on the injected particle source distribution which might lead to a SCE. Key words. Space plasma physics (Wave-particle interaction – Magnetospheric physics (Plasma waves and instabilities; Storms and substorms
A regulator's perspective on the use of atmospheric dispersion models
International Nuclear Information System (INIS)
Williams, C.R.
1992-01-01
On 1 April 1991 a new regime for industrial pollution control was introduced in England and Wales: Integrated Pollution Regulation (IPR). For those industrial processes which involve releases of pollutants into the atmosphere, the relevant primary legislation includes: the Environmental Protection Act 1990, which established a system of Integrated Pollution Control for those industries which have the greatest potential to cause pollution, and the Radioactive Substances Act 1960, which is concerned with the regulation of radioactive releases. There is a requirement for the operator of a process to make an application to HMIP for authorization to operate the process and dispose of waste arisings, and an environmental impact assessment must form part of that application. HMIP does not prescribe the type of assessment techniques that the applicant should use. But the Inspectorate will audit the applicant's assessment, and also carry out its own calculations if appropriate. The assessment standards used by HMIP are being published in the form of ''Chief Inspector's Guidance to Inspectors'', which can be referred to by applicants. HMIP makes use of both short-range and longer-range atmospheric dispersion models to fulfill its regulatory duties. Within the former category, the Inspectorate is one of the UK organisations which is sponsoring the development of the UK-ADMS model. (AB)
Revisiting the advection-dispersion model - Testing an alternative
International Nuclear Information System (INIS)
Neretnieks, I.
2001-01-01
Some of the basic assumptions of the Advection-Dispersion model, AD-model, are revisited. That model assumes a continuous mixing along the flowpath similar to Fickian diffusion. This implies that there is a constant dispersion length irrespective of observation distance. This is contrary to most field observations. The properties of an alternative model based on the assumption that individual water packages can retain their identity over long distances are investigated. The latter model is called the Multi-Channel model, MChM. Inherent in the latter model is that if the waters in the different pathways are collected and mixed, the 'dispersion length' is proportional to observation distance. Using diffusion theory it is investigated over which distances or contact times, adjacent water packages will keep their identity. It is found that for a contact time of 10 hours, two streams, each wider than 6 mm, that flow side by side, will not have lost their identity. For 1000 hours contact time the minimum width is 6 cm. The MChM and AD-models were found to have very similar Residence Time Distributions, RTD, for Peclet numbers larger than 3. A generalised relation between flowrate and residence time is developed, including the so-called cubic law and constant aperture assumptions. Using the generalised relation, surprisingly it is found that for a system that has the same average flow volume and average flowrate the form of the RTD curves are the same irrespective of the form of the relation. Both models are also compared for a system where there is strong interaction of the solute with the rock matrix. In this case it is assumed that the solute can diffuse into and out of the fracture walls and also to sorb on the micro-fractures of the matrix. The so-called Flow Wetted Surface, FWS, between the flowing water in the fracture and the rock is a key entity in such systems. It is found that the AD-model predicts much later arrivals and lower concentrations than does the MCh-model
Kalyuzhnyi, S.V.; Fedorovich, V.V.; Lens, P.N.L.
2006-01-01
A new approach to model upflow anaerobic sludge bed (UASB)-reactors, referred to as a one-dimensional dispersed plug flow model, was developed. This model focusses on the granular sludge dynamics along the reactor height, based on the balance between dispersion, sedimentation and convection using
Atmospheric mercury dispersion modelling from two nearest hypothetical point sources
Energy Technology Data Exchange (ETDEWEB)
Al Razi, Khandakar Md Habib; Hiroshi, Moritomi; Shinji, Kambara [Environmental and Renewable Energy System (ERES), Graduate School of Engineering, Gifu University, Yanagido, Gifu City, 501-1193 (Japan)
2012-07-01
The Japan coastal areas are still environmentally friendly, though there are multiple air emission sources originating as a consequence of several developmental activities such as automobile industries, operation of thermal power plants, and mobile-source pollution. Mercury is known to be a potential air pollutant in the region apart from SOX, NOX, CO and Ozone. Mercury contamination in water bodies and other ecosystems due to deposition of atmospheric mercury is considered a serious environmental concern. Identification of sources contributing to the high atmospheric mercury levels will be useful for formulating pollution control and mitigation strategies in the region. In Japan, mercury and its compounds were categorized as hazardous air pollutants in 1996 and are on the list of 'Substances Requiring Priority Action' published by the Central Environmental Council of Japan. The Air Quality Management Division of the Environmental Bureau, Ministry of the Environment, Japan, selected the current annual mean environmental air quality standard for mercury and its compounds of 0.04 ?g/m3. Long-term exposure to mercury and its compounds can have a carcinogenic effect, inducing eg, Minamata disease. This study evaluates the impact of mercury emissions on air quality in the coastal area of Japan. Average yearly emission of mercury from an elevated point source in this area with background concentration and one-year meteorological data were used to predict the ground level concentration of mercury. To estimate the concentration of mercury and its compounds in air of the local area, two different simulation models have been used. The first is the National Institute of Advanced Science and Technology Atmospheric Dispersion Model for Exposure and Risk Assessment (AIST-ADMER) that estimates regional atmospheric concentration and distribution. The second is the Hybrid Single Particle Lagrangian Integrated trajectory Model (HYSPLIT) that estimates the atmospheric
Brixey, Laurie A; Heist, David K; Richmond-Bryant, Jennifer; Bowker, George E; Perry, Steven G; Wiener, Russell W
2009-12-01
This article is the second in a two-paper series presenting results from wind tunnel and computational fluid dynamics (CFD) simulations of flow and dispersion in an idealized model urban neighborhood. Pollutant dispersion results are presented and discussed for a model neighborhood that was characterized by regular city blocks of three-story row houses with a single 12-story tower located at the downwind edge of one of these blocks. The tower had three significant effects on pollutant dispersion in the surrounding street canyons: drawing the plume laterally towards the tower, greatly enhancing the vertical dispersion of the plume in the wake of the tower, and significantly decreasing the residence time of pollutants in the wake of the tower. In the wind tunnel, tracer gas released in the avenue lee of the tower, but several blocks away laterally, was pulled towards the tower and lifted in the wake of the tower. The same lateral movement of the pollutant was seen in the next avenue, which was approximately 2.5 tower heights downwind of the tower. The tower also served to ventilate the street canyon directly in its wake more rapidly than the surrounding areas. This was evidenced by CFD simulations of concentration decay where the residence time of pollutants lee of the 12-story tower was found to be less than half the residence time behind a neighboring three-story building. This same phenomenon of rapid vertical dispersion lee of a tower among an array of smaller buildings was also demonstrated in a separate set of wind tunnel experiments using an array of cubical blocks. A similar decrease in the residence time was observed when the height of one block was increased.
Measuring and modeling the magnetic settling of superparamagnetic nanoparticle dispersions.
Prigiobbe, Valentina; Ko, Saebom; Huh, Chun; Bryant, Steven L
2015-06-01
In this paper, we present settling experiments and mathematical modeling to study the magnetic separation of superparamagnetic iron-oxide nanoparticles (SPIONs) from a brine. The experiments were performed using SPIONs suspensions of concentration between 3 and 202g/L dispersed in water and separated from the liquid under the effect of a permanent magnet. A 1D model was developed in the framework of the sedimentation theory with a conservation law for SPIONs and a mass flux function based on the Newton's law for motion in a magnetic field. The model describes both the hindering effect of suspension concentration (n) during settling due to particle collisions and the increase in settling rate due to the attraction of the SPIONs towards the magnet. The flux function was derived from the settling experiments and the numerical model validated against the analytical solution and the experimental data. Suspensions of SPIONs were of 2.8cm initial height, placed on a magnet, and monitored continuously with a digital camera. Applying a magnetic field of 0.5T of polarization, the SPION's velocity was of approximately 3·10(-5)m/s close to the magnet and decreases of two orders of magnitude across the domain. The process was characterized initially by a classical sedimentation behavior, i.e., an upper interface between the clear water and the suspension slowly moving towards the magnet and a lower interface between the sediment layer and the suspension moving away from the magnet. Subsequently, a rapid separation of nanoparticle occured suggesting a non-classical settling phenomenon induced by magnetic forces which favor particle aggregation and therefore faster settling. The rate of settling decreased with n and an optimal condition for fast separation was found for an initial n of 120g/L. The model agrees well with the measurements in the early stage of the settling, but it fails to describe the upper interface movement during the later stage, probably because of particle
Quantal Response: Nonparametric Modeling
2017-01-01
capture the behavior of observed phenomena. Higher-order polynomial and finite-dimensional spline basis models allow for more complicated responses as the...flexibility as these are nonparametric (not constrained to any particular functional form). These should be useful in identifying nonstandard behavior via... deviance ∆ = −2 log(Lreduced/Lfull) is defined in terms of the likelihood function L. For normal error, Lfull = 1, and based on Eq. A-2, we have log
DEFF Research Database (Denmark)
Kiil, Søren
2017-01-01
The purpose of this work is to develop a mathematical model that can quantify the dispersion of pigments, with a focus on the mechanical breakage of pigment agglomerates. The underlying physical mechanism was assumed to be surface erosion of spherical pigment agglomerates. The full agglomerate pa.......g., in the development of novel dispersion principles and for analysis of dispersion failures. The general applicability of the model, beyond the three pigments considered, needs to be confirmed....
International Nuclear Information System (INIS)
Panitz, H.J.
1988-01-01
An essential aim of the improvements of the new program system UFOMOD for Accident Consequence Assessments (ACAs) was to substitute the straightline Gaussian plume model conventionally used in ACA models by more realistic atmospheric dispersion models. To identify improved models which can be applied in ACA codes and to quantify the implications of different concepts of dispersion modelling on the results of an ACA, probabilistic comparative calculations with different atmospheric dispersion models have been carried out. The study showed that there are trajectory models available which can be applied in ACAs and that these trajectory models provide more realistic results of ACAs than straight-line Gaussian models. This led to a completly novel concept of atmospheric dispersion modelling which distinguish between two different distance ranges of validity: the near range ( 50 km). The two ranges are assigned to respective trajectory models
International Nuclear Information System (INIS)
Yambert, M.W.; Lombardi, D.A.; Goode, W.D. Jr.; Bloom, S.G.
1998-08-01
The original WAKE dispersion model a component of the HGSYSTEM/UF 6 model suite, is based on Shell Research Ltd.'s HGSYSTEM Version 3.0 and was developed by the US Department of Energy for use in estimating downwind dispersion of materials due to accidental releases from gaseous diffusion plant (GDP) process buildings. The model is applicable to scenarios involving both ground-level and elevated releases into building wake cavities of non-reactive plumes that are either neutrally or positively buoyant. Over the 2-year period since its creation, the WAKE model has been used to perform consequence analyses for Safety Analysis Reports (SARs) associated with gaseous diffusion plants in Portsmouth (PORTS), Paducah (PGDP), and Oak Ridge. These applications have identified the need for additional model capabilities (such as the treatment of complex terrain and time-variant releases) not present in the original utilities which, in turn, has resulted in numerous modifications to these codes as well as the development of additional, stand-alone postprocessing utilities. Consequently, application of the model has become increasingly complex as the number of executable, input, and output files associated with a single model run has steadily grown. In response to these problems, a streamlined version of the WAKE model has been developed which integrates all calculations that are currently performed by the existing WAKE, and the various post-processing utilities. This report summarizes the efforts involved in developing this revised version of the WAKE model
de'Michieli Vitturi, Mattia; Pardini, Federica; Spanu, Antonio; Neri, Augusto; Vittoria Salvetti, Maria
2015-04-01
Volcanic ash clouds represent a major hazard for populations living nearby volcanic centers producing a risk for humans and a potential threat to crops, ground infrastructures, and aviation traffic. Lagrangian particle dispersal models are commonly used for tracking ash particles emitted from volcanic plumes and transported under the action of atmospheric wind fields. In this work, we present the results of an uncertainty propagation analysis applied to volcanic ash dispersal from weak plumes with specific focus on the uncertainties related to the grain-size distribution of the mixture. To this aim, the Eulerian fully compressible mesoscale non-hydrostatic model WRF was used to generate the driving wind, representative of the atmospheric conditions occurring during the event of November 24, 2006 at Mt. Etna. Then, the Lagrangian particle model LPAC (de' Michieli Vitturi et al., JGR 2010) was used to simulate the transport of mass particles under the action of atmospheric conditions. The particle motion equations were derived by expressing the Lagrangian particle acceleration as the sum of the forces acting along its trajectory, with drag forces calculated as a function of particle diameter, density, shape and Reynolds number. The simulations were representative of weak plume events of Mt. Etna and aimed to quantify the effect on the dispersal process of the uncertainty in the particle sphericity and in the mean and variance of a log-normal distribution function describing the grain-size of ash particles released from the eruptive column. In order to analyze the sensitivity of particle dispersal to these uncertain parameters with a reasonable number of simulations, and therefore with affordable computational costs, response surfaces in the parameter space were built by using the generalized polynomial chaos technique. The uncertainty analysis allowed to quantify the most probable values, as well as their pdf, of the number of particles as well as of the mean and
Energy Technology Data Exchange (ETDEWEB)
Connan, O.; Hebert, D.; Solier, L.; Voiseux, C.; Lamotte, M.; Laguionie, P.; Maro, D.; Thomas, L. [IRSN/PRP-ENV/SERIS/LRC (France)
2014-07-01
Atmospheric dispersion of pollutant or radionuclides in stratified meteorological condition, i.e. especially when weather conditions are very stable, mainly at night, is still poorly understood and not well apprehended by the operational atmospheric dispersion models. However, correctly predicting the dispersion of a radioactive plume, and estimating the radiological consequences for the population, following an unplanned atmospheric release of radionuclides are crucial steps in an emergency response. To better understand dispersion in these special weather conditions, IRSN performed a series of 22 air sampling campaigns between 2010 and 2013 in the vicinity of the La Hague nuclear reprocessing plant (AREVA - NC, France), at distances between 200 m and 3000 m from the facility. Krypton-85 ({sup 85}Kr), a b-and g-emitting radionuclide, released during the reprocessing of spent nuclear fuel was used as a non-reactive tracer of radioactive plumes. Experimental campaigns were realized in stability class stable or very stable (E or F according to Pasquill classification) 18 times, and in neutral conditions (D according to Pasquill classification) 4 times. During each campaign, Krypton-85 real time measurement were made to find the plume around the plant, and then integrated samples (30 min) were collected in bag perpendicularly to the assumed wind direction axis. After measurement by gamma spectrometry, we have, when it was possible, estimate the point of impact and the width of the plume. The objective was to estimate the horizontal dispersion (width) of the plume at ground level in function of the distance and be able to calculate atmospheric transfer coefficients. In a second step, objective was to conclude on the use of common model and on their uncertainties. The results will be presented in terms of impact on the near-field. They will be compared with data obtained in previous years in neutral atmospheric conditions, and finally the results will be confronted with
RANS modeling of scalar dispersion from localized sources within a simplified urban-area model
Rossi, Riccardo; Capra, Stefano; Iaccarino, Gianluca
2011-11-01
The dispersion of a passive scalar downstream a localized source within a simplified urban-like geometry is examined by means of RANS scalar flux models. The computations are conducted under conditions of neutral stability and for three different incoming wind directions (0°, 45°, 90°) at a roughness Reynolds number of Ret = 391. A Reynolds stress transport model is used to close the flow governing equations whereas both the standard eddy-diffusivity closure and algebraic flux models are employed to close the transport equation for the passive scalar. The comparison with a DNS database shows improved reliability from algebraic scalar flux models towards predicting both the mean concentration and the plume structure. Since algebraic flux models do not increase substantially the computational effort, the results indicate that the use of tensorial-diffusivity can be promising tool for dispersion simulations for the urban environment.
State of the art atmospheric dispersion modelling. Should the Gaussian plume model still be used?
Energy Technology Data Exchange (ETDEWEB)
Richter, Cornelia [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH, Koeln (Germany)
2016-11-15
For regulatory purposes with respect to licensing and supervision of airborne releases of nuclear installations, the Gaussian plume model is still in use in Germany. However, for complex situations the Gaussian plume model is to be replaced by a Lagrangian particle model. Now the new EU basic safety standards for protection against the dangers arising from exposure to ionising radiation (EU BSS) [1] asks for a realistic assessment of doses to the members of the public from authorised practices. This call for a realistic assessment raises the question whether dispersion modelling with the Gaussian plume model is an adequate approach anymore or whether the use of more complex models is mandatory.
Polster, Christopher S; Wu, Sy-Juen; Gueorguieva, Ivelina; Sperry, David C
2015-04-06
An artificial stomach duodenum (ASD) model has been used to demonstrate the performance difference between two formulations of LY2300559, a low-solubility acidic developmental drug. The two formulations investigated were a conventional high-shear wet granulation (HSWG) formulation and a solid dispersion formulation. A pharmacokinetic study in humans demonstrated the enhanced performance of the solid dispersion formulation relative to the HSWG formulation. The Cmax and AUC of the solid dispersion was 2.6 and 1.9 times greater, respectively, compared to the HSWG formulation. In the ASD, the solid dispersion formulation performance was characterized by three main phases: (1) rapid release in the stomach, creating a supersaturated concentration of drug, (2) precipitation in the stomach, and (3) rapid redissolution of the precipitate in the duodenum to concentration levels that are supersaturated relative to crystalline drug. A series of complementary experiments were employed to describe this performance behavior mechanistically. Imaging experiments with a pH indicating dye showed that local pH gradients from meglumine in the solid dispersion formulation were responsible for creating a high initial supersaturation concentration in the stomach. Upon dissipation of meglumine, the drug precipitated in the stomach as an amorphous solid. Because the precipitated drug is in an amorphous form, it can then rapidly redissolve as it transits to the more neutral environment of the duodenum. This unexpected sequence of physical state changes gives a mechanistic explanation for the enhanced in vivo performance of the solid dispersion formulation relative to the HSWG formulation.
One-dimensional Analytical Modelling of Floating Seed Dispersal in Tidal Channels
Shi, W.; Purnama, A.; Shao, D.; Cui, B.; Gao, W.
2017-12-01
Seed dispersal is a primary factor influencing plant community development, and thus plays a critical role in maintaining wetland ecosystem functioning. However, compared with fluvial seed dispersal of riparian plants, dispersal of saltmarsh plant seeds in tidal channels is much less studied due to its complex behavior, and relevant mathematical modelling is particularly lacking. In this study, we developed a one-dimensional advection-dispersion model to explore the patterns of tidal seed dispersal. Oscillatory tidal current and water depth were assumed to represent the tidal effects. An exponential decay coefficient λ was introduced to account for seed deposition and retention. Analytical solution in integral form was derived using Green's function and further evaluated using numerical integration. The developed model was applied to simulate Spartina densiflora seed dispersal in a tidal channel located at the Mad River Slough in North Humboldt Bay, California, USA, to demonstrate its practical applicability. Model predictions agree satisfactorily with field observation and simulation results from Delft3D numerical model. Sensitivity analyses were also conducted to evaluate the effects of varying calibrated parameters on model predictions. The range of the seed dispersion as well as the distribution of the seed concentration were further analyzed through statistical parameters such as centroid displacement and variance of the seed cloud together with seed concentration contours. Implications of the modelling results on tidal marsh restoration and protection, e.g., revegetation through seed addition, were also discussed through scenario analysis. The developed analytical model provides a useful tool for ecological management of tidal marshes.
Directory of Open Access Journals (Sweden)
Dannise V. Ruiz-Ramos
2017-12-01
Full Text Available The 2010 Deep Water Horizon oil well failure released billions of gallons of crude oil into the deep Gulf of Mexico, and, combined with chemical dispersants, this oil caused significant coral mortality. However, the mechanisms by which oil and dispersed oil impact deep marine fauna are not well understood. Here, we investigate the effects of oil and dispersed oil on a black coral common in the deep Gulf of Mexico, 'Leiopathes glaberrima. 'This coral occurs in several color morphs that show ecological and genetic differences. We hypothesized that dispersed oil would be more detrimental to coral health than oil alone and that this difference would be detectable in the gene expression response of the colonies even at sub-lethal concentrations. In two experiments, four and six colonies of red and white color morphs were exposed to oil, dispersant, and dispersed oil for a minimum of 96 hours. Visual assessment indicated that indeed dispersant and dispersed oil treatments were more damaging than oil alone, for target concentrations of 25 mg L–1. Decline in health was observed for all treatments, independently of color morphotype, but the decline was faster in the white colonies exposed to dispersant. The responses to the treatments were also investigated by monitoring gene expression after 24 hours of sub-lethal chemical exposure. Coral gene expression differed by chemical stressor. Interestingly, the polycyclic aromatic hydrocarbon biomarker gene, cytochrome P450, was only up-regulated in dispersed oil but not oil alone, suggesting that the dispersant increased the availability of such hydrocarbons in the tissue. The gene expression response was apparent at 24 hours when visual impacts were not (yet detectable. The use of chemical dispersants in oil-spill remediation may cause health declines in deep-water corals and deserves further study.
Dispersion of conservative properties for SGD effects by numerical modeling
Gallegos, G.; Marino-Tapia, I.; Enriquez, C.
2013-05-01
The submarine groundwater discharges around de coasts of theYucatán Peninsula are very common because of its karstic nature. These discharges of fresh water into the sea can change the thermohaline conditions of the region. There are several studies that demonstrate that point submarine groundwater discharges can change the superficial temperature and haline conditions near the point-SGD. Furthermore, there is evidence that considerable concentrations of nutrients are transported to the sea via SGDs. In order to quantify the area of influence of a point-SGD and the ability of the coastal system to dissipate the ground water, this study presents a numerical simulation of a point-SGD on the north coast of Yucatán, Dzilam Bravo. Teh flow recorded for this SGD is ~1m^3/s and it is located 200m offshore in waters of less than 2m detph.. The numerical simulation was carried out in the model DELFT-3D which has been calibrated with water level and hydrodynamics data for the region with a grid of 486 x 243 nodes that cover an area of 6 km alongshore by 2 km crosshore with a resolution of 14 m. Three ideal numerical scenarios were simulated: only wind forcing, only tidal forcing and wind-tide forcing. The real cases are for two different wind conditions, the first is a southeast wind, and the second is a breeze with an easterly component; the dominant winds in the region are easterly. Seasonal variation was also simulated; the two conditions that exist in the region are the rainy and dry seasons. The extreme events of ENSO and northerly storms locally known as "nortes" were also simulated. The results of the ideal set of scenarios shows wind as the principal forcing for dispersion and it governs the direction of the salinity gradient. The seasonal variations show that the area of influence in terms of salinity is also a function of the contrast between fresh and sea water, and finally the set of extreme condition simulations shows, in case of the northerly storms, that the
Zhou, Yixuan; Yiwen, E.; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li
2016-12-01
Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.
Leverett, Lindsay D.; Auge, Gabriela A.; Bali, Aman; Donohue, Kathleen
2016-01-01
Background Seeds adjust their germination based on conditions experienced before and after dispersal. Post-dispersal cues are expected to be more accurate predictors of offspring environments, and thus offspring success, than pre-dispersal cues. Therefore, germination responses to conditions experienced during seed maturation may be expected to be superseded by responses to conditions experienced during seed imbibition. In taxa of disturbed habitats, neighbours frequently reduce the performance of germinants. This leads to the hypotheses that a vegetative canopy will reduce germination in such taxa, and that a vegetative canopy experienced during seed imbibition will over-ride germination responses to a canopy experienced during seed maturation, since it is a more proximal cue of immediate competition. These hypotheses were tested here in Arabidopsis thaliana. Methods Seeds were matured under a simulated canopy (green filter) or white light. Fresh (dormant) seeds were imbibed in the dark, white light or canopy at two temperatures (10 or 22 °C), and germination proportions were recorded. Germination was also recorded in after-ripened (less dormant) seeds that were induced into secondary dormancy and imbibed in the dark at each temperature, either with or without brief exposure to red and far-red light. Key Results Unexpectedly, a maturation canopy expanded the conditions that elicited germination, even as seeds lost and regained dormancy. In contrast, an imbibition canopy impeded or had no effect on germination. Maturation under a canopy did not modify germination responses to red and far-red light. Seed maturation under a canopy masked genetic variation in germination. Conclusions The results challenge the hypothesis that offspring will respond more strongly to their own environment than to that of their parents. The observed relaxation of germination requirements caused by a maturation canopy could be maladaptive for offspring by disrupting germination responses
DEFF Research Database (Denmark)
Christiansen, Peter Leth; Gaididei, Yuri Borisovich; Johansson, M.
1998-01-01
The dynamics of discrete two-dimensional nonlinear Schrodinger models with long-range dispersive interactions is investigated. In particular, we focus on the cases where the dispersion arises from a dipole-dipole interaction, assuming the dipole moments at each lattice site to be aligned either...
Directory of Open Access Journals (Sweden)
Luis J. Perez Calderon
2018-05-01
Full Text Available Deep sea oil exploration is increasing and presents environmental challenges for deep ocean ecosystems. Marine oil spills often result in contamination of sediments with oil; following the Deepwater Horizon (DwH disaster up to 31% of the released oil entrained in the water column was deposited as oily residues on the seabed. Although the aftermath of DwH was studied intensely, lessons learned may not be directly transferable to other deep-sea hydrocarbon exploration areas, such as the Faroe-Shetland Channel (FSC which comprises cold temperatures and a unique hydrodynamic regime. Here, transport of hydrocarbons into deep FSC sediments, subsequent responses in benthic microbial populations and effects of dispersant application on hydrocarbon fate and microbial communities were investigated. Sediments from 1,000 m in the FSC were incubated at 0°C for 71 days after addition of a 20-hydrocarbon component oil-sediment aggregate. Dispersant was added periodically from day 4. An additional set of cores using sterilized and homogenized sediment was analyzed to evaluate the effects of sediment matrix modification on hydrocarbon entrainment. Sediment layers were independently analyzed for hydrocarbon content by gas chromatography with flame ionization detection and modeled with linear mixed effects models. Oil was entrained over 4 cm deep into FSC sediments after 42 days and dispersant effectiveness on hydrocarbon removal from sediment to the water column decreased with time. Sterilizing and homogenizing sediment resulted in hydrocarbon transport over 4 cm into sediments after 7 days. Significant shifts in bacterial populations were observed (DGGE profiling in response to hydrocarbon exposure after 42 days and below 2 cm deep. Dispersant application resulted in an accelerated and modified shift in bacterial communities. Bacterial 16S rRNA gene sequencing of oiled sediments revealed dominance of Colwellia and of Fusibacter when dispersant was applied over
International Nuclear Information System (INIS)
Ramsdell, J.V.
1991-07-01
Radiation doses that may have resulted from operations at the Hanford Site are being estimated in the Hanford Environmental Dose Reconstruction (HEDR) Project. One of the project subtasks, atmospheric transport, is responsible for estimating the transport, diffusion and deposition of radionuclides released to the atmosphere. This report discusses modeling transport and diffusion in the atmospheric pathway. It is divided into three major sections. The first section of the report presents the atmospheric modeling approach selected following discussion with the Technical Steering Panel that directs the HEDR Project. In addition, the section discusses the selection of the MESOI/MESORAD suite of atmospheric dispersion models that form the basis for initial calculations and future model development. The second section of the report describes alternative modeling approaches that were considered. Emphasis is placed on the family of plume and puff models that are based on Gaussian solution to the diffusion equations. The final portion of the section describes the performance of various models. The third section of the report discusses factors that bear on the selection of an atmospheric transport modeling approach for HEDR. These factors, which include the physical setting of the Hanford Site and the available meteorological data, serve as constraints on model selection. Five appendices are included in the report. 39 refs., 4 figs., 2 tabs
Lovreglio, Ruggiero; Ronchi, Enrico; Maragkos, Georgios; Beji, Tarek; Merci, Bart
2016-11-15
The release of toxic gases due to natural/industrial accidents or terrorist attacks in populated areas can have tragic consequences. To prevent and evaluate the effects of these disasters different approaches and modelling tools have been introduced in the literature. These instruments are valuable tools for risk managers doing risk assessment of threatened areas. Despite the significant improvements in hazard assessment in case of toxic gas dispersion, these analyses do not generally include the impact of human behaviour and people movement during emergencies. This work aims at providing an approach which considers both modelling of gas dispersion and evacuation movement in order to improve the accuracy of risk assessment for disasters involving toxic gases. The approach is applied to a hypothetical scenario including a ship releasing Nitrogen dioxide (NO2) on a crowd attending a music festival. The difference between the results obtained with existing static methods (people do not move) and a dynamic approach (people move away from the danger) which considers people movement with different degrees of sophistication (either a simple linear path or more complex behavioural modelling) is discussed. Copyright © 2016 Elsevier B.V. All rights reserved.
Evaluation of hydrodynamic ocean models as a first step in larval dispersal modelling
Vasile, Roxana; Hartmann, Klaas; Hobday, Alistair J.; Oliver, Eric; Tracey, Sean
2018-01-01
Larval dispersal modelling, a powerful tool in studying population connectivity and species distribution, requires accurate estimates of the ocean state, on a high-resolution grid in both space (e.g. 0.5-1 km horizontal grid) and time (e.g. hourly outputs), particularly of current velocities and water temperature. These estimates are usually provided by hydrodynamic models based on which larval trajectories and survival are computed. In this study we assessed the accuracy of two hydrodynamic models around Australia - Bluelink ReANalysis (BRAN) and Hybrid Coordinate Ocean Model (HYCOM) - through comparison with empirical data from the Australian National Moorings Network (ANMN). We evaluated the models' predictions of seawater parameters most relevant to larval dispersal - temperature, u and v velocities and current speed and direction - on the continental shelf where spawning and nursery areas for major fishery species are located. The performance of each model in estimating ocean parameters was found to depend on the parameter investigated and to vary from one geographical region to another. Both BRAN and HYCOM models systematically overestimated the mean water temperature, particularly in the top 140 m of water column, with over 2 °C bias at some of the mooring stations. HYCOM model was more accurate than BRAN for water temperature predictions in the Great Australian Bight and along the east coast of Australia. Skill scores between each model and the in situ observations showed lower accuracy in the models' predictions of u and v ocean current velocities compared to water temperature predictions. For both models, the lowest accuracy in predicting ocean current velocities, speed and direction was observed at 200 m depth. Low accuracy of both model predictions was also observed in the top 10 m of the water column. BRAN had more accurate predictions of both u and v velocities in the upper 50 m of water column at all mooring station locations. While HYCOM
Energy Technology Data Exchange (ETDEWEB)
French McCay, D.; Mueller, C.; Jayko, K.; Longval, B.; Schroeder, M. [Applied Science Associates Inc., Narragansett, RI (United States); Terrill, E.; Carter, M.; Otero, M.; Kim, S.Y. [Scripps Inst. of Oceanography, La Jolla, CA (United States); Nordhausen, W.; Lampinen, M. [California Dept. of Fish and Game, San Diego, CA (United States). Office of Spill Prevention and Response; Payne, J.R. [Payne Environmental Consultants Inc., Encinitas, CA (United States); Ohlmann, C. [California Univ., Santa Barbara, CA (United States)
2007-07-01
In the event of on oil spill at sea, the concentration of hydrocarbons in the water column can be evaluated using oil spill fate and transport modeling. Such modeling can also determine the potential exposure to zooplankton, and the impacts of oil spills with and without the use of dispersants. This paper reported on fluorescein dye studies that were conducted off Sand Diego, California to evaluate the ability of transport models to hindcast movement and dispersion of dye using data such as surface currents calculated from high-frequency radar; near surface currents from drifter measurements drogued at several depths; dye concentrations measured by fluorescence; spreading and dye intensity measurements based on aerial photography; and, water density profiles from conductivity-temperature-depth (CTD) casts. This paper presented modeling issues that remain to be addressed, such as the need to resolve small-scale transport processes in order to evaluate effects on water column biota. Since these processes determining current velocities are complex, it is not feasible to include most of the complexities at appropriately small scales in oil spill modeling applications. The difficulty in predicting currents that transport oil components and organisms with a hydrodynamic model application that does not include temporal details in the forcing function was also discussed. This paper demonstrated that the SIMAP spill trajectory model, using the drifter velocities as current input, successfully reproduced trajectories of the dye. The effect of wind drift transporting the surface material faster than the subsurface materials was identified as a spreading mechanism. Therefore, subtraction of the wind drift from the shallower drifter velocities, and inclusion of wind drift in SIMAP would allow those velocities to be used for depths other than those tracked by the drifters. 57 refs., 8 tabs., 17 figs.
International Nuclear Information System (INIS)
Norden, C.E.
1981-11-01
An indium tracer aerosol generating apparatus based on an alcohol/oxygen burner, and an analytical procedure by which filter samples containing tracer material could be analysed quantitatively by means of neutron activation analysis, were developed for use in atmospheric dispersion and deposition studies. A number of series of atmospheric dispersion experiments were conducted in the Richards Bay and Koeberg- Cape Town areas. The results are given, comparing the airbone tracer concentrations measured at ground level with values predicted by means of a numerical model, utilising two to three schemes, varying in sophistication, for calculating the dispersion coefficients. Recommendations are given regarding a dispersion model and dispersion coefficients for regular use in the Koeberg area, and ways for estimating plume trajectories
Modelling surface radioactive spill dispersion in the Alborán Sea.
Periáñez, R
2006-01-01
The Strait of Gibraltar and the Alborán Sea are the only connection between the Atlantic Ocean and the Mediterranean Sea. Intense shipping activities occur in the area, including transport of waste radionuclides and transit of nuclear submarines. Thus, it is relevant to have a dispersion model that can be used in an emergency situation after an accident, to help the decision-making process. Such dispersion model requires an appropriate description of the physical oceanography of the region of interest, with simulations of tides and residual (average) circulation. In this work, a particle-tracking dispersion model that can be used to simulate the dispersion of radionuclides in the system Strait of Gibraltar-Alborán Sea is described. Tides are simulated using a barotropic model and for the average circulation a reduced-gravity model is applied. This model is able to reproduce the main features of the Alborán circulation (the well known Western Alborán Gyre, WAG, and the coastal circulation mode). The dispersion model is run off-line, using previously computed tidal and residual currents. The contamination patch is simulated by a number of particles whose individual paths are computed; diffusion and decay being modelled using a Monte Carlo method. Radionuclide concentrations may be obtained from the density of particles per water volume unit. Results from the hydrodynamic models have been compared with observations in the area. Several examples of dispersion computations under different wind and circulation conditions are presented.
Estimating sub-surface dispersed oil concentration using acoustic backscatter response.
Fuller, Christopher B; Bonner, James S; Islam, Mohammad S; Page, Cheryl; Ojo, Temitope; Kirkey, William
2013-05-15
The recent Deepwater Horizon disaster resulted in a dispersed oil plume at an approximate depth of 1000 m. Several methods were used to characterize this plume with respect to concentration and spatial extent including surface supported sampling and autonomous underwater vehicles with in situ instrument payloads. Additionally, echo sounders were used to track the plume location, demonstrating the potential for remote detection using acoustic backscatter (ABS). This study evaluated use of an Acoustic Doppler Current Profiler (ADCP) to quantitatively detect oil-droplet suspensions from the ABS response in a controlled laboratory setting. Results from this study showed log-linear ABS responses to oil-droplet volume concentration. However, the inability to reproduce ABS response factors suggests the difficultly in developing meaningful calibration factors for quantitative field analysis. Evaluation of theoretical ABS intensity derived from the particle size distribution provided insight regarding method sensitivity in the presence of interfering ambient particles. Copyright © 2013 Elsevier Ltd. All rights reserved.
Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K
2017-09-15
Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion
Modelling drivers of mangrove propagule dispersal and restoration of abandoned shrimp farms
Directory of Open Access Journals (Sweden)
D. Di Nitto
2013-07-01
Full Text Available Propagule dispersal of four mangrove species Rhizophora mucronata, R. apiculata, Ceriops tagal and Avicennia officinalis in the Pambala–Chilaw Lagoon Complex (Sri Lanka was studied by combining a hydrodynamic model with species-specific knowledge on propagule dispersal behaviour. Propagule transport was simulated using a finite-volume advection-diffusion model to investigate the effect of dispersal vectors (tidal flow, freshwater discharge and wind, trapping agents (retention by vegetation and seed characteristics (buoyancy on propagule dispersal patterns. Sensitivity analysis showed that smaller propagules, like the oval-shaped propagules of Avicennia officinalis, dispersed over larger distances and were most sensitive to changing values of retention by mangrove vegetation compared to larger, torpedo-shaped propagules of Rhizophora spp. and C. tagal. Directional propagule dispersal in this semi-enclosed lagoon with a small tidal range was strongly concentrated towards the edges of the lagoon and channels. Short distance dispersal appeared to be the main dispersal strategy for all four studied species, with most of the propagules being retained within the vegetation. Only a small proportion (max. 5% of propagules left the lagoon through a channel connecting the lagoon with the open sea. Wind significantly influenced dispersal distance and direction once propagules entered the lagoon or adjacent channels. Implications of these findings for mangrove restoration were tested by simulating partial removal in the model of dikes around abandoned shrimp ponds to restore tidal hydrology and facilitate natural recolonisation by mangroves. The specific location of dike removal, (with respect to the vicinity of mangroves and independently suitable hydrodynamic flows, was found to significantly affect the resultant quantities and species of inflowing propagules and hence the potential effectiveness of natural regeneration. These results demonstrate the
International Nuclear Information System (INIS)
Damjanovic, D.; Bharadwaja, S.S.N.; Setter, N.
2005-01-01
A phenomenological approach is proposed describing both nonlinearity and frequency dispersion in dielectric and piezoelectric properties of lead zirconate titanate, Pb(Zr,Ti)O 3 (PZT), thin films and ceramics. The approach couples the frequency dependent response in form of the power law, 1/ω β , with the rate-independent nonlinear response described by the Rayleigh law. The main experimental trends are well described by the model
User assessment of smoke-dispersion models for wildland biomass burning.
Steve Breyfogle; Sue A. Ferguson
1996-01-01
Several smoke-dispersion models, which currently are available for modeling smoke from biomass burns, were evaluated for ease of use, availability of input data, and output data format. The input and output components of all models are listed, and differences in model physics are discussed. Each model was installed and run on a personal computer with a simple-case...
Modelling sequentially scored item responses
Akkermans, W.
2000-01-01
The sequential model can be used to describe the variable resulting from a sequential scoring process. In this paper two more item response models are investigated with respect to their suitability for sequential scoring: the partial credit model and the graded response model. The investigation is
Wind field and dispersion modelling in complex terrain
International Nuclear Information System (INIS)
Bartzis, J.G.; Varvayanni, M.; Catsaros, N.; Konte, K.; Amanatidis, G.
1991-01-01
Dispersion of airborne radioactive material can have an important environmental impact. Its prediction remains a difficult problem, especially over complex and inhomogeneous terrain, or under complicated atmospheric conditions. The ADREA-I code, a three-dimensional transport code especially designed for terrains of high complexity can be considered as contribution to the solution of the above problem. The code development has been initiated within the present CEC Radiation Program. New features are introduced into the code to describe the anomalous topography, the turbulent diffusion and numerical solution procedures. In this work besides a brief presentation of the main features of the code, a number of applications will be presented with the aim on one hand to illustrate the capability and reliability of the code and on the other hand to clarify the effects on windfield and dispersion in special cases of interest. Within the framework of ADREA-I verification studies, a I-D simulation of the experimental Wangara Day-33 mean boundary layer was attempted, reproducing the daytime wind speeds, temperatures, specific humidities and mixing depths. In order to address the effect of surface irregularities and inhomogeneities on contamination patterns, the flow field and dispersion were analyzed over a 2-D, 1000m high mountain range, surrounded by sea, with a point source assumed 40km offshore from one coastline. This terrain was studied as representing a greater Athens area idealization. The effects of a 2-D, 1000m high mountain range of Gaussian shape on long range transport has also been studied in terms of influence area, wind and concentration profile distortions and dry deposition patterns
Lagrangian modelling of dispersion, sedimentation and resuspension processes in marine environments
International Nuclear Information System (INIS)
Gidhagen, L.; Rahm, L.; Nyberg, L.
1989-01-01
The model is based on a modified Langevin's equation which simulates the turbulent crossflow velocity fluctuations in shear flows. The velocity and turbulence fields used are generated by a 2-dimensional hydrodynamical model including a k-ε turbulence scheme. Since the dispersion model is formulated for only low particle concentrations, it is decoupled from the hydrodynamical model calculations. A great drawback in conventional dispersion modelling is the more or less unavoidable numerical diffusion. The use of a Lagrangian particle model will avoid this effect and the resulting too low concentrations for a given release. One consequence is a more realistic distribution of deposited particles. However, with regard to the overall deposition rates the simulated sedimentation process agrees well with well-established advection/diffusion model formulations. With a modified hydrodynamic model, the dispersion model can directly be applied to stratified 3D simulations. (orig./HP) [de
Lestage, David Jackson
These studies were undertaken to further understand the design of colloidal dispersions containing bio-active phospholipids (PL) as stabilizing agents and their stimuli-responsive behaviors during film formation. Methyl methacrylate (MMA) and n-butyl acrylate (nBA) dispersions were synthesized using anionic surfactants and PL, and the surface-responsiveness of coalesced films was monitored at the film-air (F-A) and film-substrate (F-S) interfaces after exposure to temperature, UV, pH, ionic strength, and enzymatic stimuli. Using spectroscopic molecular-level probes such as attenuated total reflectance (ATR) and internal reflection IR imaging (IRIRI), these studies show that structural features of PL and surfactants significantly affect stimuli-responsiveness of polymeric films. MMA/nBA homopolymer, blend, copolymer, and core-shell particle coalescence studies indicated that controlled permeability is influenced by particle composition and sodium dioctyl sulfosuccinate (SDOSS) mobility to the F-A interface is enhanced in response to temperature. Utilization of hydrogenated soybean phosphocholine (HSPC) as a co-surfactant with SDOSS resulted in bimodal p-MMA/nBA colloidal particles, and experiments showed that ionic interactions with HSPC inhibit SDOSS mobility. However, the controlled release of individual species is detected in the presence of Ca2+ ionic strength stimuli. Utilizing 1,2-bis(10,12-tricosadiynoyl)- sn-glycero-3-phosphocholine (DCPC), cocklebur-shape particle morphologies were obtained and using transmission electron microscopy (TEM), self-assembled tubules were detected at particle interfaces, but not in the presence of Ca 2+. At altered concentration levels of DCPC, surface localized ionic clusters (SLICs) composed of SDOSS and DCPC form at the F-A and F-S interfaces in response to temperature and ionic strength stimuli. Micelle formation of 1-myristoyl-2-hydroxy-sn-glycero-phosphocholine (MHPC) stabilizes unimodal p-MMA/nBA colloidal particles
Witte, L.
2014-06-01
To support landing site assessments for HDA-capable flight systems and to facilitate trade studies between the potential HDA architectures versus the yielded probability of safe landing a stochastic landing dispersion model has been developed.
Marine radioactivity studies in the Suez Canal: Modelling hydrodynamics and dispersion
International Nuclear Information System (INIS)
Abril, J.M.; Abdel-Aal, M.M.
1999-01-01
This paper comprises the work carried out under the IAEA Technical Co-operation Project EGY/07/002. The main goal was to develop a modelling study on the dispersion of radioactive pollution in the Suez Canal
Benchmarking of numerical models describing the dispersion of radionuclides in the Arctic Seas
DEFF Research Database (Denmark)
Scott, E.M.; Gurbutt, P.; Harms, I.
1997-01-01
As part of the International Arctic Seas Assessment Project (IASAP) of the International Atomic Energy Agency (IAEA), a working group was created to model the dispersal and transfer of radionuclides released from radioactive waste disposed of in the Kara Sea. The objectives of this group are: (1......) development of realistic and reliable assessment models for the dispersal of radioactive contaminants both within, and from, the Arctic ocean; and (2) evaluation of the contributions of different transfer mechanisms to contaminant dispersal and hence, ultimately, to the risks to human health and environment...
Modelling of pollution dispersion in atmosphere; Modelowanie procesow propagacji skazen w atmosferze
Energy Technology Data Exchange (ETDEWEB)
Borysiewicz, M; Stankiewicz, R
1994-12-31
The paper contains the review of the mathematical foundation of atmospheric dispersion models. The atmospheric phenomena relevant to atmospheric dispersion model are discussed. In particular the parametrization of processes with time and space scales smaller than numerical grid size, limited by available computer power, is presented. The special attention was devoted to similarity theory and parametrization of boundary layer. The numerical methods are analysed and the drawbacks of the method are presented. (author). 99 refs, 15 figs, 3 tabs.
Numerical models for computation of pollutant-dispersion in the atmosphere
International Nuclear Information System (INIS)
Leder, S.M.; Biesemann-Krueger, A.
1985-04-01
The report describes some models which are used to compute the concentration of emitted pollutants in the lower atmosphere. A dispersion model, developed at the University of Hamburg, is considered in more detail and treated with two different numerical methods. The convergence of the methods is investigated and a comparison of numerical results and dispersion experiments carried out at the Nuclear Research Center Karlsruhe is given. (orig.) [de
Absorptive and dispersive optical profiles in fluctuating environments: A stochastic model
International Nuclear Information System (INIS)
Paz, J.L.; Mendoza-Garcia, A.; Mastrodomenico, A.
2011-01-01
In this study, we determined the absorptive and dispersive optical profiles of a molecular system coupled with a thermal bath. Solvent effects were explicitly considered by modelling the non-radiative interaction with the solute as a random variable. The optical stochastical Bloch equations (OSBE) were solved using a time-ordered cumulant expansion with white noise as a correlation function. We found a solution for the Fourier component of coherence at the third order of perturbation for the nonlinear Four-wave mixing signal and produced analytical expressions for the optical responses of the system. Finally, we examined the behaviour of these properties with respect to the noise parameter, frequency detuning of the dynamic perturbation, and relaxation times.
International Nuclear Information System (INIS)
Zhang Fen; Ding Huan-Da; Duan Chao; Tong Chao-Hui; Zhao Shuang-Liang
2017-01-01
Langevin dynamics simulations have been performed to investigate the response of bi-disperse and strong polyacid chains grafted on an electrode to electric fields generated by opposite surface charges on the polyelectrolyte (PE)-grafted electrode and a second parallel electrode. Simulation results clearly show that, under a negative external electric field, the longer grafted PE chains are more strongly stretched than the shorter ones in terms of the relative change in their respective brush heights. Whereas under a positive external electric field, the grafted shorter chains collapse more significantly than the longer ones. It was found that, under a positive external electric field, the magnitude of the total electric force acting on one shorter PE chain is larger than that on one longer PE chain, or vice versa. The effects of smeared and discrete charge distributions of grafted PE chains on the response of PE brushes to external electric fields were also examined. (paper)
MODELING DISPERSION FROM CHEMICALS RELEASED AFTER A TRAIN COLLISION IN GRANITEVILLE, SOUTH CAROLINA
Energy Technology Data Exchange (ETDEWEB)
Buckley, R; Chuck Hunter, C; Robert Addis, R; Matt Parker, M
2006-08-07
The Savannah River National Laboratory's (SRNL) Weather INformation and Display (WIND) System was used to provide meteorological and atmospheric modeling/consequence assessment support to state and local agencies following the collision of two Norfolk Southern freight trains on the morning of January 6, 2005. This collision resulted in the release of several toxic chemicals to the environment, including chlorine. The dense and highly toxic cloud of chlorine gas that formed in the vicinity of the accident was responsible for nine fatalities, and caused injuries to more than five hundred others. Transport model results depicting the forecast path of the ongoing release were made available to emergency managers in the county's Unified Command Center shortly after SRNL received a request for assistance. Support continued over the ensuing two days of the active response. The SRNL also provided weather briefings and transport/consequence assessment model results to responders from South Carolina Department of Health and Environmental Control (SCDHEC), the Savannah River Site's (SRS) Emergency Operations Center (EOC), Department of Energy Headquarters, and hazmat teams dispatched from the SRS. Although model-generated forecast winds used in consequence assessments conducted during the incident were provided at 2-km horizontal grid spacing during the accident response, a high-resolution Regional Atmospheric Modeling System (RAMS, version 4.3.0) simulation was later performed to examine potential influences of local topography on plume migration. The detailed RAMS simulation was used to determine meteorology using multiple grids with an innermost grid spacing of 125 meters. Results from the two simulations are shown to generally agree with meteorological observations at the time; consequently, local topography did not significantly affect wind in the area. Use of a dense gas dispersion model to simulate localized plume behavior using the higher resolution
Modelling the atmospheric dispersion of foot-and-mouth disease virus for emergency preparedness
DEFF Research Database (Denmark)
Sørensen, J.H.; Jensen, C.O.; Mikkelsen, T.
2001-01-01
A model system for simulating airborne spread of foot-and-mouth disease (FMD) is described. The system includes a virus production model and the local- and mesoscale atmospheric dispersion model RIMPUFF linked to the LINCOM local-scale Row model. LINCOM is used to calculate the sub-grid scale Row...
International Nuclear Information System (INIS)
Musolino, S.V.; Harper, F.T.
2016-01-01
The first 100 minutes of a response to a radiological dispersal device are critical as this period will set the stage for how the overall response will be executed. First responders will be tasked with multiple activities such as confirming a radiological release, conducting lifesaving rescue operations, issuing protective actions, and beginning characterization of the scene. These activities need to take place as soon as the responders arrive on the scene (the first few minutes). The effectiveness of these early activities will define how well or how poorly the response will be in the emergency phase. The document which is under development provides guidance that can be used for planning an effective response to an RDD that will result in protection of the responders and the members of the public. The information is based on research and results of extensive experiments conducted by the Department of Energy National Laboratories. This guidance provides a realistic estimate of the possible consequences of an RDD detonation and delineates five missions and ten tactics that should be executed by the first responders and local response agencies in the first 100 minutes of a response. The guidance includes recommendations on how to execute the strategy, equipment requirements including personal protective equipment and public messaging
Energy Technology Data Exchange (ETDEWEB)
Torres Astorga, Romina; Velasco, Hugo; Valladares, Diego L.; Lohaiza, Flavia; Ayub, Jimena Juri; Rizzotto, Marcos [Grupo de Estudios Ambientales. Instituto de Matematica Aplicada San Luis - Universidad Nacional de San Luis - CONICET, San Luis (Argentina)
2014-07-01
{sup 7}Be is a short-lived environmental radionuclide, produced in the upper atmosphere by spallation of nitrogen and oxygen by cosmic rays. After of the production by the nuclear reaction, {sup 7}Be diffuses through the atmosphere until it attaches to atmospheric aerosols. Subsequently, it is deposited on the earth surface mainly as wet fallout. The main physical processes which transport {sup 7}Be in soil are diffusion and advection by water. Migration parameters and measurements confirm that sorption is the main physical process, which confines {sup 7}Be concentration to soil surface. The literature data show that in soils, {sup 7}Be is concentrated near the surface (0-2 cm) as it is adsorbed onto clay minerals after its deposition on the soil surface and does not penetrate deeper into soils due to its short half-life. The maximum mass activity density of {sup 7}Be is found at the point of input of the radionuclide, i.e. at the surface of the soil column, showing a exponential distribution profile typical of a purely diffusive transport. Many studies applying the advection dispersion models have been reported in the literature in order to modelling the transport of {sup 137}Cs in soils. On them, the models are used to achieve information of the mechanisms that govern the transport, i. e. the model is used to explain the soil profile of radionuclide. The effective dispersion coefficient and the apparent advection velocity of radionuclide in soil are also obtained by fitting the analytical solution of the model equation to measured depth distributions of the radionuclide. In this work, the advective dispersive transport model with linear sorption is used to analyze the vertical migration process of {sup 7}Be in soils of undisturbed or reference sites. The deposition history is approximated by pulse-like input functions and time dependent analytical solution of equation model is obtained. The values of dispersion coefficient and apparent advection velocity obtained
Model independent dispersion approach to proton Compton scattering
International Nuclear Information System (INIS)
Caprini, I.; Radescu, E.E.
1980-12-01
The proton Compton scattering at low and intermediate energies is studied by means of a dispersion framework which exploits in an optimal way the (fixed momentum transfer) analyticity properties of the amplitudes in conjunction with the consequences of the (s-channel) unitarity. The mathematical background of the work consists of methods specific to boundary value problems for analytic vector-valued functions and interpolation theory. In comparison with previous related work, the external problems to be solved now are much more difficult because of the inclusion of the photoproduction input and also lead to additional computational complications. The lower bounds on the differential cross-section, obtained without any reference to subtractions and annihilation channel contributions, appear sufficiently restrictive to evidentiate rigorously some inconsistencies between results of single pion photoproduction multipole extractions and proton Compton scattering data. (author)
Modeling compressible multiphase flows with dispersed particles in both dense and dilute regimes
McGrath, T.; St. Clair, J.; Balachandar, S.
2018-05-01
Many important explosives and energetics applications involve multiphase formulations employing dispersed particles. While considerable progress has been made toward developing mathematical models and computational methodologies for these flows, significant challenges remain. In this work, we apply a mathematical model for compressible multiphase flows with dispersed particles to existing shock and explosive dispersal problems from the literature. The model is cast in an Eulerian framework, treats all phases as compressible, is hyperbolic, and satisfies the second law of thermodynamics. It directly applies the continuous-phase pressure gradient as a forcing function for particle acceleration and thereby retains relaxed characteristics for the dispersed particle phase that remove the constituent material sound velocity from the eigenvalues. This is consistent with the expected characteristics of dispersed particle phases and can significantly improve the stable time-step size for explicit methods. The model is applied to test cases involving the shock and explosive dispersal of solid particles and compared to data from the literature. Computed results compare well with experimental measurements, providing confidence in the model and computational methods applied.
Calibration of Discrete Random Walk (DRW) Model via G.I Taylor's Dispersion Theory
Javaherchi, Teymour; Aliseda, Alberto
2012-11-01
Prediction of particle dispersion in turbulent flows is still an important challenge with many applications to environmental, as well as industrial, fluid mechanics. Several models of dispersion have been developed to predict particle trajectories and their relative velocities, in combination with a RANS-based simulation of the background flow. The interaction of the particles with the velocity fluctuations at different turbulent scales represents a significant difficulty in generalizing the models to the wide range of flows where they are used. We focus our attention on the Discrete Random Walk (DRW) model applied to flow in a channel, particularly to the selection of eddies lifetimes as realizations of a Poisson distribution with a mean value proportional to κ / ɛ . We present a general method to determine the constant of this proportionality by matching the DRW model dispersion predictions for fluid element and particle dispersion to G.I Taylor's classical dispersion theory. This model parameter is critical to the magnitude of predicted dispersion. A case study of its influence on sedimentation of suspended particles in a tidal channel with an array of Marine Hydrokinetic (MHK) turbines highlights the dependency of results on this time scale parameter. Support from US DOE through the Northwest National Marine Renewable Energy Center, a UW-OSU partnership.
Simulation of atmospheric dispersion of radionuclides using an Eulerian-Lagrangian modelling system.
Basit, Abdul; Espinosa, Francisco; Avila, Ruben; Raza, S; Irfan, N
2008-12-01
In this paper we present an atmospheric dispersion scenario for a proposed nuclear power plant in Pakistan involving the hypothetical accidental release of radionuclides. For this, a concept involving a Lagrangian stochastic particle model (LSPM) coupled with an Eulerian regional atmospheric modelling system (RAMS) is used. The atmospheric turbulent dispersion of radionuclides (represented by non-buoyant particles/neutral traces) in the LSPM is modelled by applying non-homogeneous turbulence conditions. The mean wind velocities governed by the topography of the region and the surface fluxes of momentum and heat are calculated by the RAMS code. A moving least squares (MLS) technique is introduced to calculate the concentration of radionuclides at ground level. The numerically calculated vertical profiles of wind velocity and temperature are compared with observed data. The results obtained demonstrate that in regions of complex terrain it is not sufficient to model the atmospheric dispersion of particles using a straight-line Gaussian plume model, and that by utilising a Lagrangian stochastic particle model and regional atmospheric modelling system a much more realistic estimation of the dispersion in such a hypothetical scenario was ascertained. The particle dispersion results for a 12 h ground release show that a triangular area of about 400 km(2) situated in the north-west quadrant of release is under radiological threat. The particle distribution shows that the use of a Gaussian plume model (GPM) in such situations will yield quite misleading results.
Modeling the generation and dispersion of odors from mushroom composting facilities
International Nuclear Information System (INIS)
Heinemann, P.; Wahanik, D.
1998-01-01
An odor source generation model and an odor dispersion model were developed to predict the local distribution of odors emanating from mushroom composting facilities. The odor source generation model allowed for simulation of various composting wharf configurations and odor source strengths. This model was linked to a Gaussian plume diffusion model that predicted odor dispersion. Dimethyl disulfide production at a rate of 1760 micrograms/h was simulated by the source generation model and six different atmospheric conditions were analyzed to demonstrate the effect of wind speed, atmospheric stability, and source generation on the dispersion of this odor producing compound. Detectable levels of dimethyl disulfide were predicted to range from less than 100 m from the source during very unstable conditions to almost 5000 m during very stable conditions
International Nuclear Information System (INIS)
Galmarini, S.; Bianconi, R.; Bellasio, R.; Graziani, G.
2001-01-01
The RTMOD system is presented as a tool for the intercomparison of long-range dispersion models as well as a system for support of decision making. RTMOD is an internet-based procedure that collects the results of more than 20 models used around the world to predict the transport and deposition of radioactive releases in the atmosphere. It allows the real-time acquisition of model results and their intercomparison. Taking advantage of the availability of several model results, the system can also be used as a tool to support decision making in case of emergency. The new concept of ensemble dispersion modelling is introduced which is the basis for the decision-making application of RTMOD. New statistical parameters are presented that allow gathering the results of several models to produce a single dispersion forecast. The devised parameters are presented and tested on the results of RTMOD exercises
Dussauze, Matthieu; Pichavant-Rafini, Karine; Belhomme, Marc; Buzzacott, Peter; Privat, Killian; Le Floch, Stéphane; Lemaire, Philippe; Theron, Michaël
2017-01-01
Data on the biological impact of oil dispersion in deep-sea environment are scarce. Hence, the aim of this study was to evaluate the potential interest of a pressure challenge as a new experimental approach for the assessment of consequences of chemically dispersed oil, followed by a high hydrostatic pressure challenge. This work was conducted on a model fish: juvenile Dicentrarchus labrax. Seabass were exposed for 48 h to dispersant alone (nominal concentration (NC) = 4 mg L -1 ), mechanically dispersed oil (NC = 80 mg L -1 ), two chemically dispersed types of oil (NC = 50 and 80 mg L -1 with a dispersant/oil ratio of 1/20), or kept in clean seawater. Fish were then exposed for 30 min at a simulated depth of 1350 m, corresponding to pressure of 136 absolute atmospheres (ATA). The probability of fish exhibiting normal activity after the pressure challenge significantly increased from 0.40 to 0.55 when they were exposed to the dispersant but decreased to 0.26 and 0.11 in the case of chemical dispersion of oil (at 50 and 80 mg L -1 , respectively). The chemical dispersion at 80 mg L -1 also induced an increase in probability of death after the pressure challenge (from 0.08 to 0.26). This study clearly demonstrates the ability of a pressure challenge test to give evidence of the effects of a contaminant on the capacity of fish to face hydrostatic pressure. It opens new perspectives on the analysis of the biological impact of chemical dispersion of oil at depth, especially on marine species performing vertical migrations.
Micro-meteorological modelling in urban areas: pollutant dispersion and radiative effects modelling
International Nuclear Information System (INIS)
Milliez, Maya
2006-01-01
Atmospheric pollution and urban climate studies require to take into account the complex processes due to heterogeneity of urban areas and the interaction with the buildings. In order to estimate the impact of buildings on flow and pollutant dispersion, detailed numerical simulations were performed over an idealized urban area, with the three-dimensional model Mercure-Saturne, modelling both concentration means and their fluctuations. To take into account atmospheric radiation in built up areas and the thermal effects of the buildings, we implemented a three-dimensional radiative model adapted to complex geometry. This model, adapted from a scheme used for thermal radiation, solves the radiative transfer equation in a semi-transparent media, using the discrete ordinate method. The new scheme was validated with idealized cases and compared to a complete case. (author) [fr
International Nuclear Information System (INIS)
Klukas, M.H.; Davis, P.A.
2000-01-01
AECL is undertaking the validation of ADDAM, an atmospheric dispersion and dose code based on the Canadian Standards Association model CSA N288.2. The key component of the validation program involves comparison of model predicted and measured vertical and lateral dispersion parameters, effective release height and air concentrations. A wind tunnel study of the dispersion of exhaust gases from the CANDU complex at Wolsong, Korea provides test data for dispersion over uniform and complex terrain. The test data are for distances close enough to the release points to evaluate the model for exclusion area boundaries (EAB) as small as 500 m. Lateral and vertical dispersion is described well for releases over uniform terrain but the model tends to over-predict these parameters for complex terrain. Both plume rise and entrainment are modelled conservatively and the way they are combined in the model produces conservative estimates of the effective release height for low and high wind speeds. Estimates for the medium wind speed case (50-m wind speed, 3.8 ms -1 ) are conservative when the correction for entrainment is made. For the highest ground-level concentrations, those of greatest interest in a safety analysis, 82% of the predictions were within a factor 2 of the observed values. The model can be used with confidence to predict air concentrations of exhaust gases at the Wolsong site for neutral conditions, even for flows over the hills to the west, and is unlikely to substantially under-predict concentrations. (author)
Modeling Smoke Plume-Rise and Dispersion from Southern United States Prescribed Burns with Daysmoke
G L Achtemeier; S L Goodrick; Y Liu; F Garcia-Menendez; Y Hu; M. Odman
2011-01-01
We present Daysmoke, an empirical-statistical plume rise and dispersion model for simulating smoke from prescribed burns. Prescribed fires are characterized by complex plume structure including multiple-core updrafts which makes modeling with simple plume models difficult. Daysmoke accounts for plume structure in a three-dimensional veering/sheering atmospheric...
Traveling waves in a delayed SIR model with nonlocal dispersal and nonlinear incidence
Zhang, Shou-Peng; Yang, Yun-Rui; Zhou, Yong-Hui
2018-01-01
This paper is concerned with traveling waves of a delayed SIR model with nonlocal dispersal and a general nonlinear incidence. The existence and nonexistence of traveling waves of the system are established respectively by Schauder's fixed point theorem and two-sided Laplace transform. It is also shown that the spread speed c is influenced by the dispersal rate of the infected individuals and the delay τ.
Pillai, Rajesh S.; Brakenhoff, G. J.; Müller, M.
2006-09-01
The third harmonic generation (THG) axial response in the vicinity of an interface formed by two isotropic materials of normal dispersion is typically single peaked, with the maximum intensity at the interface position. Here it is shown experimentally that this THG z response may show anomalous behavior—being double peaked with a dip coinciding with the interface position—when the THG contributions from both materials are of similar magnitude. The observed anomalous behavior is explained, using paraxial Gaussian theory, by considering dispersion induced shape changes in the THG z response.
Cai, Hongzhu; Hu, Xiangyun; Xiong, Bin; Zhdanov, Michael S.
2017-12-01
The induced polarization (IP) method has been widely used in geophysical exploration to identify the chargeable targets such as mineral deposits. The inversion of the IP data requires modeling the IP response of 3D dispersive conductive structures. We have developed an edge-based finite-element time-domain (FETD) modeling method to simulate the electromagnetic (EM) fields in 3D dispersive medium. We solve the vector Helmholtz equation for total electric field using the edge-based finite-element method with an unstructured tetrahedral mesh. We adopt the backward propagation Euler method, which is unconditionally stable, with semi-adaptive time stepping for the time domain discretization. We use the direct solver based on a sparse LU decomposition to solve the system of equations. We consider the Cole-Cole model in order to take into account the frequency-dependent conductivity dispersion. The Cole-Cole conductivity model in frequency domain is expanded using a truncated Padé series with adaptive selection of the center frequency of the series for early and late time. This approach can significantly increase the accuracy of FETD modeling.
A model for the dispersion of pollution from a road network
Energy Technology Data Exchange (ETDEWEB)
Haerkoenen, J.; Valkonen, E.; Kukkonen, J.; Rantakarans, E.; Lahtinen, K.; Karppinen, A.; Jalkanen, L.
1996-12-31
A mathematical model for predicting the dispersion of pollution from a road network, for use in a regulatory context is presented in the report. The model includes an emission model a treatment of the meteorological and background concentration time series, a dispersion model statistical analysis of the computed time series of concentrations and a Windows-based user interface. The dispersion model is based on a partly analytical solution of the Gaussian diffusion equation for a finite dine source. It allows for any wind direction with respect to the road. The dispersion parameters are modelled in a form which facilitates the use of the meteorological preprocessor. The chemical transformation is modelled by using a modified form of the discrete parcel method, developed in this study. The chemistry model contains the basic reactions of nitrogen oxides, oxygen and ozone. An operational model for evaluating the meteorological and background concentration data for the model applications is also presented. The model does not take into account the influence of buildings and inhomogeneous terrain on the dispersion processes. The validity of the mathematical solution presented has been tested against a more detailed numerical model. The overall differences are reasonable, and the solution can be used with confidence in an operational model. The program has been implemented on a personal computer and on a main-frame computer, and in the later case also executed on a Cray C94 supercomputer. The validation of the model against experimental data is reported elsewhere. Testing of the model near a major road Turunvaeylae Finland 1994 showed that the overall agreement of the measured and predicted values for NO{sub x} and NO{sub 2} concentrations was fairly good 30 refs.
International Nuclear Information System (INIS)
Benamrane, Y.; Wybo, J.-L.; Armand, P.
2013-01-01
The threat of a major accidental or deliberate event that would lead to hazardous materials emission in the atmosphere is a great cause of concern to societies. This is due to the potential large scale of casualties and damages that could result from the release of explosive, flammable or toxic gases from industrial plants or transport accidents, radioactive material from nuclear power plants (NPPs), and chemical, biological, radiological or nuclear (CBRN) terrorist attacks. In order to respond efficiently to such events, emergency services and authorities resort to appropriate planning and organizational patterns. This paper focuses on the use of atmospheric dispersion modeling (ADM) as a support tool for emergency planning and response, to assess the propagation of the hazardous cloud and thereby, take adequate counter measures. This paper intends to illustrate the noticeable evolution in the operational use of ADM tools over 25 y and especially in emergency situations. This study is based on data available in scientific publications and exemplified using the two most severe nuclear accidents: Chernobyl (1986) and Fukushima (2011). It appears that during the Chernobyl accident, ADM were used few days after the beginning of the accident mainly in a diagnosis approach trying to reconstruct what happened, whereas 25 y later, ADM was also used during the first days and weeks of the Fukushima accident to anticipate the potentially threatened areas. We argue that the recent developments in ADM tools play an increasing role in emergencies and crises management, by supporting stakeholders in anticipating, monitoring and assessing post-event damages. However, despite technological evolutions, its prognostic and diagnostic use in emergency situations still arise many issues. -- Highlights: • Study of atmospheric dispersion modeling use during nuclear accidents. • ADM tools were mainly used in a diagnosis approach during Chernobyl accident. • ADM tools were also used
Carpentieri, Matteo; Kumar, Prashant; Robins, Alan
2011-03-01
Understanding the transformation of nanoparticles emitted from vehicles is essential for developing appropriate methods for treating fine scale particle dynamics in dispersion models. This article provides an overview of significant research work relevant to modelling the dispersion of pollutants, especially nanoparticles, in the wake of vehicles. Literature on vehicle wakes and nanoparticle dispersion is reviewed, taking into account field measurements, wind tunnel experiments and mathematical approaches. Field measurements and modelling studies highlighted the very short time scales associated with nanoparticle transformations in the first stages after the emission. These transformations strongly interact with the flow and turbulence fields immediately behind the vehicle, hence the need of characterising in detail the mixing processes in the vehicle wake. Very few studies have analysed this interaction and more research is needed to build a basis for model development. A possible approach is proposed and areas of further investigation identified. Copyright Â© 2010 Elsevier Ltd. All rights reserved.
A model for long-distance dispersal of boll weevils (Coleoptera: Curculionidae)
Westbrook, John K.; Eyster, Ritchie S.; Allen, Charles T.
2011-07-01
The boll weevil, Anthonomus grandis (Boheman), has been a major insect pest of cotton production in the US, accounting for yield losses and control costs on the order of several billion US dollars since the introduction of the pest in 1892. Boll weevil eradication programs have eliminated reproducing populations in nearly 94%, and progressed toward eradication within the remaining 6%, of cotton production areas. However, the ability of weevils to disperse and reinfest eradicated zones threatens to undermine the previous investment toward eradication of this pest. In this study, the HYSPLIT atmospheric dispersion model was used to simulate daily wind-aided dispersal of weevils from the Lower Rio Grande Valley (LRGV) of southern Texas and northeastern Mexico. Simulated weevil dispersal was compared with weekly capture of weevils in pheromone traps along highway trap lines between the LRGV and the South Texas / Winter Garden zone of the Texas Boll Weevil Eradication Program. A logistic regression model was fit to the probability of capturing at least one weevil in individual pheromone traps relative to specific values of simulated weevil dispersal, which resulted in 60.4% concordance, 21.3% discordance, and 18.3% ties in estimating captures and non-captures. During the first full year of active eradication with widespread insecticide applications in 2006, the dispersal model accurately estimated 71.8%, erroneously estimated 12.5%, and tied 15.7% of capture and non-capture events. Model simulations provide a temporal risk assessment over large areas of weevil reinfestation resulting from dispersal by prevailing winds. Eradication program managers can use the model risk assessment information to effectively schedule and target enhanced trapping, crop scouting, and insecticide applications.
International Nuclear Information System (INIS)
Boust, D.; Fraizier, A.; Hairie, A.; Baron, Y.
1995-01-01
This work presents analysis and prediction of the dispersion of radioelements in the marine environment based on the pulse response theory. The analysis is made on three data sets over the period 1984-1988: the amounts of gamma-emitting radioelements contained in controlled releases from the nuclear reprocessing plant of La Hague (=signal emission point), and gamma-emitting radionuclide concentrations in sea water at two stations (signal reception points), situated at 8 and 35 km distance from the release point. Using this data base, the pulse response is determined for each station and for each element. This allows us to estimate the mean delay and the amplitude of the reception signal (i.e. the concentrations of radioelements) and its sensitivity to wind forcing. We then demonstrate that the convolution of the pulse response and released radionuclide time-series is capable of yielding a fairly good prediction of the concentrations at each station. Some particularities of the behaviour of 137 Cs, 106 Ru and 60 Co are evidenced by comparison with that of 125 Sb, assumed to be a conservative element in sea water: adsorption of 106 Ru and 60 Co on to particles, additional sources of 137 Cs. The mean delays calculated for 125 Sb at each station are close to each other (28-30 days) despite their different distances from the release point, and are explained by the specific hydrodynamics of the studied area. (Authors). 16 refs., 9 figs
Visual plumes coastal dispersion modeling in southwest Sabah ...
African Journals Online (AJOL)
In theory, the dilution capacity of open waters, particularly coastal areas, straits and oceans are enormous. This means that for surface and sub-merged ... Prior to the modeling exercise, field data pertaining to ambient water quality, hydraulic characteristics and tide patterns were collected. The modeling results indicated that ...
A water wave model with horizontal circulation and accurate dispersion
Cotter, C.; Bokhove, Onno
We describe a new water wave model which is variational, and combines a depth-averaged vertical (component of) vorticity with depth-dependent potential flow. The model facilitates the further restriction of the vertical profile of the velocity potential to n-th order polynomials or a finite element
Numerical Models of Sewage Dispersion and Statistica Bathing Water Standards
DEFF Research Database (Denmark)
Petersen, Ole; Larsen, Torben
1991-01-01
As bathing water standards usually are founded in statistical methods, the numerical models used in outfall design should reflect this. A statistical approach, where stochastic variations in source strength and bacterial disappearance is incorporated into a numerical dilution model is presented. ...
International Nuclear Information System (INIS)
Bustamante C, Paula M.; Ortiz R, Marcela A.
1996-01-01
Based on a dispersion model, an accidental release of radioactive material to the atmosphere was simulated. To evaluate the consequences of the accidental release it was used the P C COSYMA program (KfK and NRPB). The atmospheric dispersion model was MUSEMET, a segmented Gaussian plume model which requires information on meteorological conditions for a period of one year. This study was carried out to determine the plume's behavior and path, and to define protective actions. The meteorological analysis shows an airflow from the WSW and a channeling flow from the S E at night, due to topographical influences. (author)
International Nuclear Information System (INIS)
Edwards, L.L.; Freis, R.P.; Peters, L.G.; Gudiksen, P.H.; Pitovranov, S.E.
1993-01-01
The accuracy associated with assessing the environmental consequences of an accidental release of radioactivity is highly dependent on the knowledge of the source term characteristics, which are generally poorly known. The development of an automated numerical technique that integrates the radiological measurements with atmospheric dispersion modeling for more accurate source term estimation is reported. Often, this process of parameter estimation is performed by an emergency response assessor, who takes an intelligent first guess at the model parameters, then, comparing the model results with whatever measurements are available, makes an intuitive, informed next guess of the model parameters. This process may be repeated any number of times until the assessor feels that the model results are reasonable in terms of the measured observations. A new approach, based on a nonlinear least-squares regression scheme coupled with the existing Atmospheric Release Advisory Capability three-dimensional atmospheric dispersion models, is to supplement the assessor's intuition with automated mathematical methods that do not significantly increase the response time of the existing predictive models. The viability of the approach is evaluated by estimation of the known SF 6 tracer release rates associated with the Mesoscale Atmospheric Transport Studies tracer experiments conducted at the Savannah River Laboratory during 1983. These 19 experiments resulted in 14 successful, separate tracer releases with sampling of the tracer plumes along the cross-plume arc situated ∼30 km from the release site
Scaling and modeling in the analysis of dispersive relaxation of ionic materials
International Nuclear Information System (INIS)
Macdonald, J. Ross
2001-01-01
Problems with scaling of conductive-system experimental M dat # double p rime#(ω) and σ dat prime(ω) data are considered and resolved by dispersive-relaxation-model fitting and comparison. Scaling is attempted for both synthetic and experimental M # double p rime#(ω) data sets. A crucial element in all experimental frequency-response data is the influence of the high-frequency-limiting dipolar-and-vibronic dielectric constant var-epsilon D∞ , often designated var-epsilon ∞ , and not related to ionic transport. It is shown that var-epsilon D∞ precludes scaling of M dat # double p rime#(ω) for ionic materials when the mobile-charge concentration varies. When the effects of var-epsilon D∞ are properly removed from the data, however, such scaling is viable. Only the σprime(ω) and var-epsilon # double p rime#(ω) parts of immittance response are uninfluenced by var-epsilon D∞ . Thus, scaling is possible for experimental σprime(ω) data sets under concentration variation if the shape parameter of a well-fitting model remains constant and if any parts of the response not associated with bulk ionic transport are eliminated. Comparison between the predictions of the original-modulus-formalism (OMF) response model of 1972 - 1973 and a corrected version of it that takes proper account of var-epsilon D∞ , the corrected modulus formalism (CMF), demonstrates that the role played by var-epsilon D∞ (or var-epsilon ∞ ) in the OMF is incorrect. Detailed fitting of data for three different ionic glasses using a Kohlrausch - Williams - Watts response model, the KWW 1 , for OMF and CMF analysis clearly demonstrates that the OMF leads to inconsistent shape-parameter (β 1 ) estimates and the CMF does not. The CMF KWW 1 model is shown to subsume, correct, and generalize the recent disparate scaling/fitting approaches of Sidebottom, Leon, Roling, and Ngai. [copyright] 2001 American Institute of Physics
A Semi-Analytical Model for Dispersion Modelling Studies in the Atmospheric Boundary Layer
Gupta, A.; Sharan, M.
2017-12-01
The severe impact of harmful air pollutants has always been a cause of concern for a wide variety of air quality analysis. The analytical models based on the solution of the advection-diffusion equation have been the first and remain the convenient way for modeling air pollutant dispersion as it is easy to handle the dispersion parameters and related physics in it. A mathematical model describing the crosswind integrated concentration is presented. The analytical solution to the resulting advection-diffusion equation is limited to a constant and simple profiles of eddy diffusivity and wind speed. In practice, the wind speed depends on the vertical height above the ground and eddy diffusivity profiles on the downwind distance from the source as well as the vertical height. In the present model, a method of eigen-function expansion is used to solve the resulting partial differential equation with the appropriate boundary conditions. This leads to a system of first order ordinary differential equations with a coefficient matrix depending on the downwind distance. The solution of this system, in general, can be expressed in terms of Peano-baker series which is not easy to compute, particularly when the coefficient matrix becomes non-commutative (Martin et al., 1967). An approach based on Taylor's series expansion is introduced to find the numerical solution of first order system. The method is applied to various profiles of wind speed and eddy diffusivities. The solution computed from the proposed methodology is found to be efficient and accurate in comparison to those available in the literature. The performance of the model is evaluated with the diffusion datasets from Copenhagen (Gryning et al., 1987) and Hanford (Doran et al., 1985). In addition, the proposed method is used to deduce three dimensional concentrations by considering the Gaussian distribution in crosswind direction, which is also evaluated with diffusion data corresponding to a continuous point source.
Operational evaluation of the RLINE dispersion model for studies of traffic-related air pollutants
Milando, Chad W.; Batterman, Stuart A.
2018-06-01
Exposure to traffic-related air pollutants (TRAP) remains a key public health issue, and improved exposure measures are needed to support health impact and epidemiologic studies and inform regulatory responses. The recently developed Research LINE source model (RLINE), a Gaussian line source dispersion model, has been used in several epidemiologic studies of TRAP exposure, but evaluations of RLINE's performance in such applications have been limited. This study provides an operational evaluation of RLINE in which predictions of NOx, CO and PM2.5 are compared to observations at air quality monitoring stations located near high traffic roads in Detroit, MI. For CO and NOx, model performance was best at sites close to major roads, during downwind conditions, during weekdays, and during certain seasons. For PM2.5, the ability to discern local and particularly the traffic-related portion was limited, a result of high background levels, the sparseness of the monitoring network, and large uncertainties for certain processes (e.g., formation of secondary aerosols) and non-mobile sources (e.g., area, fugitive). Overall, RLINE's performance in near-road environments suggests its usefulness for estimating spatially- and temporally-resolved exposures. The study highlights considerations relevant to health impact and epidemiologic applications, including the importance of selecting appropriate pollutants, using appropriate monitoring approaches, considering prevailing wind directions during study design, and accounting for uncertainty.
Objectives for next generation of practical short-range atmospheric dispersion models
International Nuclear Information System (INIS)
Olesen, H.R.; Mikkelsen, T.
1992-01-01
The proceedings contains papers from the workshop ''Objectives for Next Generation of Practical Short-Range Atmospheric Dispersion Models''. They deal with two types of models, namely models for regulatory purposes and models for real-time applications. The workshop was the result of an action started in 1991 for increased cooperation and harmonization within atmospheric dispersion modelling. The focus of the workshop was on the management of model development and the definition of model objectives, rather than on detailed model contents. It was the intention to identify actions that can be taken in order to improve the development and use of atmospheric dispersion models. The papers in the proceedings deal with various topics within the broad spectrum of matters related to up-to-date practical models, such as their scientific basis, requirements for model input and output, meteorological preprocessing, standardisation within modelling, electronic information exchange as a potentially useful tool, model evaluation and data bases for model evaluation. In addition to the papers, the proceedings contain summaries of the discussions at the workshop. These summaries point to a number of recommended actions which can be taken in order to improve ''modelling culture''. (AB)
Mariani, Patrizio; MacKenzie, Brian R.; Iudicone, Daniele; Bozec, Alexandra
2010-07-01
Knowledge of early life history of most fish species in the Mediterranean Sea is sparse and processes affecting their recruitment are poorly understood. This is particularly true for bluefin tuna, Thunnus thynnus, even though this species is one of the world’s most valued fish species. Here we develop, apply and validate an individually based coupled biological-physical oceanographic model of fish early life history in the Mediterranean Sea. We first validate the general structure of the coupled model with a 12-day Lagrangian drift study of anchovy ( Engraulis encrasicolus) larvae in the Catalan Sea. The model reproduced the drift and growth of anchovy larvae as they drifted along the Catalan coast and yielded similar patterns as those observed in the field. We then applied the model to investigate transport and retention processes affecting the spatial distribution of bluefin tuna eggs and larvae during 1999-2003, and we compared modelled distributions with available field data collected in 2001 and 2003. Modelled and field distributions generally coincided and were patchy at mesoscales (10s-100s km); larvae were most abundant in eddies and along frontal zones. We also identified probable locations of spawning bluefin tuna using hydrographic backtracking procedures; these locations were situated in a major salinity frontal zone and coincided with distributions of an electronically tagged bluefin tuna and commercial bluefin tuna fishing vessels. Moreover, we hypothesized that mesoscale processes are responsible for the aggregation and dispersion mechanisms in the area and showed that these processes were significantly correlated to atmospheric forcing processes over the NW Mediterranean Sea. Interannual variations in average summer air temperature can reduce the intensity of ocean mesoscale processes in the Balearic area and thus potentially affect bluefin tuna larvae. These modelling approaches can increase understanding of bluefin tuna recruitment processes and
A Deformation Model of TRU Metal Dispersion Fuel Rod for HYPER
International Nuclear Information System (INIS)
Lee, Byoung Oon; Hwang, Woan; Park, Won S.
2002-01-01
Deformation analysis in fuel rod design is essential to assure adequate fuel performance and integrity under irradiation conditions. An in-reactor performance computer code for a dispersion fuel rod is being developed in the conceptual design stage of blanket fuel for HYPER. In this paper, a mechanistic deformation model was developed and the model was installed into the DIMAC program. The model was based on the elasto-plasticity theory and power-law creep theory. The preliminary deformation calculation results for (TRU-Zr)-Zr dispersion fuel predicted by DIMAC were compared with those of silicide dispersion fuel predicted by DIFAIR. It appeared that the deformation levels for (TRU-Zr)-Zr dispersion fuel were relatively higher than those of silicide fuel. Some experimental tests including in-pile and out-pile experiments are needed for verifying the predictive capability of the DIMAC code. An in-reactor performance analysis computer code for blanket fuel is being developed at the conceptual design stage of blanket fuel for HYPER. In this paper, a mechanistic deformation model was developed and the model was installed into the DIMAC program. The model was based on the elasto-plasticity theory and power-law creep theory. The preliminary deformation calculation results for (TRUZr)- Zr dispersion fuel predicted by DIMAC were compared with those of silicide dispersion fuel predicted by DIFAIR. It appears that the deformation by swelling within fuel meat is very large for both fuels, and the major deformation mechanism at cladding is creep. The swelling strain is almost constant within the fuel meat, and is assumed to be zero in the cladding made of HT9. It is estimated that the deformation levels for (TRU-Zr)-Zr dispersion fuel were relatively higher than those of silicide fuel, and the dispersion fuel performance may be limited by swelling. But the predicted volume change of the (TRU-Zr)-Zr dispersion fuel models is about 6.1% at 30 at.% burnup. The value of cladding
DART model for thermal conductivity of U3Si2 Aluminum dispersion fuel
International Nuclear Information System (INIS)
Rest, J.; Snelgrove, J.L.; Hofman, G.L.
2004-01-01
This paper describes the primary physical models that form the basis of the DART model for calculating irradiation-induced changes in the thermal conductivity of aluminum dispersion fuel. DART calculations of fuel swelling, pore closure, and thermal conductivity are compared with measured values. (author)
DART model for thermal conductivity of U3Si2 aluminum dispersion fuel
International Nuclear Information System (INIS)
Rest, J.; Snelgrove, J.L.; Hofman, G.L.
1995-09-01
This paper describes the primary physical models that form the basis of the DART model for calculating irradiation-induced changes in the thermal conductivity of aluminium dispersion fuel. DART calculations of fuel swelling, pore closure, and thermal conductivity are compared with measured values
Modeling Dispersion of Chemical-Biological Agents in Three Dimensional Living Space
International Nuclear Information System (INIS)
William S. Winters
2002-01-01
This report documents a series of calculations designed to demonstrate Sandia's capability in modeling the dispersal of chemical and biological agents in complex three-dimensional spaces. The transport of particles representing biological agents is modeled in a single room and in several connected rooms. The influence of particle size, particle weight and injection method are studied
Development of numerical dispersion model for radioactive nuclei including resuspension processes
International Nuclear Information System (INIS)
Chiba, Masaru; Kurita, Susumu; Sasaki, Hidetaka
2003-01-01
Global-scale and local-scale dispersion model are developed combining to global and local scale meteorological forecasting model. By applying this system to another miner constituent such as mineral dust blowing by strong wind in arid region, this system shows very good performance to watch and predict the distribution of it. (author)
Randomly dispersed particle fuel model in the PSG Monte Carlo neutron transport code
International Nuclear Information System (INIS)
Leppaenen, J.
2007-01-01
High-temperature gas-cooled reactor fuels are composed of thousands of microscopic fuel particles, randomly dispersed in a graphite matrix. The modelling of such geometry is complicated, especially using continuous-energy Monte Carlo codes, which are unable to apply any deterministic corrections in the calculation. This paper presents the geometry routine developed for modelling randomly dispersed particle fuels using the PSG Monte Carlo reactor physics code. The model is based on the delta-tracking method, and it takes into account the spatial self-shielding effects and the random dispersion of the fuel particles. The calculation routine is validated by comparing the results to reference MCNP4C calculations using uranium and plutonium based fuels. (authors)
Sensitivity model study of regional mercury dispersion in the atmosphere
Gencarelli, Christian N.; Bieser, Johannes; Carbone, Francesco; De Simone, Francesco; Hedgecock, Ian M.; Matthias, Volker; Travnikov, Oleg; Yang, Xin; Pirrone, Nicola
2017-01-01
Atmospheric deposition is the most important pathway by which Hg reaches marine ecosystems, where it can be methylated and enter the base of food chain. The deposition, transport and chemical interactions of atmospheric Hg have been simulated over Europe for the year 2013 in the framework of the Global Mercury Observation System (GMOS) project, performing 14 different model sensitivity tests using two high-resolution three-dimensional chemical transport models (CTMs), varying the anthropogenic emission datasets, atmospheric Br input fields, Hg oxidation schemes and modelling domain boundary condition input. Sensitivity simulation results were compared with observations from 28 monitoring sites in Europe to assess model performance and particularly to analyse the influence of anthropogenic emission speciation and the Hg0(g) atmospheric oxidation mechanism. The contribution of anthropogenic Hg emissions, their speciation and vertical distribution are crucial to the simulated concentration and deposition fields, as is also the choice of Hg0(g) oxidation pathway. The areas most sensitive to changes in Hg emission speciation and the emission vertical distribution are those near major sources, but also the Aegean and the Black seas, the English Channel, the Skagerrak Strait and the northern German coast. Considerable influence was found also evident over the Mediterranean, the North Sea and Baltic Sea and some influence is seen over continental Europe, while this difference is least over the north-western part of the modelling domain, which includes the Norwegian Sea and Iceland. The Br oxidation pathway produces more HgII(g) in the lower model levels, but overall wet deposition is lower in comparison to the simulations which employ an O3 / OH oxidation mechanism. The necessity to perform continuous measurements of speciated Hg and to investigate the local impacts of Hg emissions and deposition, as well as interactions dependent on land use and vegetation, forests, peat
Biphasic poly-dispersions modelling with applications in nuclear safety
International Nuclear Information System (INIS)
Gimenez, Marcelo
2005-01-01
Many technological, scientific and environmental areas require of the understanding of multiple-phase, polydisperse systems.Particularly, in nuclear safety area, under hypothetical severe accident conditions, the fission products are released as gases and airborne particles.In the present thesis a contribution to the modeling of confined polydisperse systems (aerosols and liquid-gas) is presented. A family of one and two dimensional models was developed, describing the impact of the particles size on the aerosol evolution, taking into account the transport mechanisms by the carrying media, settling, lift, thermophoresis, diffusion, coagulation and condensation, considering the spatial dependence. The aerosol general dynamic balance equation -no-linear integral-differential equation-, is treated by means of the Moments Method, imposing a prescribed volume size distribution, and obtaining a model based in the first few moments.This yields to a relatively simple convection-diffusion set of coupled equations, that describes the evolution of the parameters that characterize the size distribution, with a low computational cost that allows to deal the heterogeneities of the spatial distribution of the aerosol.A complementary model, based also on the Moments Method, is developed to perform sensitivity analysis due to uncertainties in the constitutive equations and in the input parameters.The Perturbative Method, Differential-formalism, is used to develop a set of sensitivity equations, which are useful for designing experiments and theoretical studies.The model results are compared with exact solutions and numerical and experimental data extracted from the open literature.Various physical phenomena involved in different simulated case are analysed in detail.Particularly, the study is oriented to the analysis of the concentration gradients and the validation of the aerosol well-mixed hypothesis, typically used in present numerical codes.Deviations were observed from the
International Nuclear Information System (INIS)
Oyabu, Takako; Morimoto, Yasuo; Hirohashi, Masami; Horie, Masanori; Kambara, Tatsunori; Lee, Byeong Woo; Hashiba, Masayoshi; Mizuguchi, Yohei; Myojo, Toshihiko; Kuroda, Etsushi
2013-01-01
In order to investigate the relationship between pulmonary inflammation and particle clearance of nanoparticles, and also their dose dependency, we performed an instillation study of well-dispersed TiO 2 nanoparticles and examined the pulmonary inflammations, the particle clearance rate and histopathological changes. Wistar rats were intratracheally administered 0.1 mg (0.33 mg/kg), 0.2 mg (0.66 mg/kg), 1 mg (3.3 mg/kg), and 3 mg (10 mg/kg) of well-dispersed TiO 2 nanoparticles (diameter of agglomerates: 25 nm), and the pulmonary inflammation response and the amount of TiO 2 in the lung were determined from 3 days up to 12 months sequentially after the instillation. There were no increases of total cell or neutrophil counts in bronchoalveolar lavage fluid (BALF) in the 0.1 and the 0.2 mg-administered groups. On the other hand, mild infiltration of neutrophils was observed in the 1 and 3 mg-administered groups. Histopathological findings showed infiltration of neutrophils in the 1 and 3 mg-administered groups. Of special note, a granulomatous lesion including a local accumulation of TiO 2 was observed in the bronchioli-alveolar space in the 3 mg-administered group. The biological half times of the TiO 2 in the lung were 4.2, 4.4, 6.7, and 10.8 months in the 0.1, 0.2, 1, and 3 mg-administered groups, respectively. Neutrophil infiltration was observed as the particle clearance was delayed, suggesting that an excessive dose of TiO 2 nanoparticles may induce pulmonary inflammation and clearance delay.
Energy Technology Data Exchange (ETDEWEB)
Oyabu, Takako [Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Department of Environmental Health Engineering (Japan); Morimoto, Yasuo, E-mail: yasuom@med.uoeh-u.ac.jp; Hirohashi, Masami; Horie, Masanori; Kambara, Tatsunori [Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Department of Occupational Pneumology (Japan); Lee, Byeong Woo [Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Department of Environmental Health Engineering (Japan); Hashiba, Masayoshi [Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Department of Occupational Pneumology (Japan); Mizuguchi, Yohei; Myojo, Toshihiko [Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Department of Environmental Health Engineering (Japan); Kuroda, Etsushi [Osaka University, Laboratory of Vaccine Science, WPI Immunology Frontier Research Center (Japan)
2013-04-15
In order to investigate the relationship between pulmonary inflammation and particle clearance of nanoparticles, and also their dose dependency, we performed an instillation study of well-dispersed TiO{sub 2} nanoparticles and examined the pulmonary inflammations, the particle clearance rate and histopathological changes. Wistar rats were intratracheally administered 0.1 mg (0.33 mg/kg), 0.2 mg (0.66 mg/kg), 1 mg (3.3 mg/kg), and 3 mg (10 mg/kg) of well-dispersed TiO{sub 2} nanoparticles (diameter of agglomerates: 25 nm), and the pulmonary inflammation response and the amount of TiO{sub 2} in the lung were determined from 3 days up to 12 months sequentially after the instillation. There were no increases of total cell or neutrophil counts in bronchoalveolar lavage fluid (BALF) in the 0.1 and the 0.2 mg-administered groups. On the other hand, mild infiltration of neutrophils was observed in the 1 and 3 mg-administered groups. Histopathological findings showed infiltration of neutrophils in the 1 and 3 mg-administered groups. Of special note, a granulomatous lesion including a local accumulation of TiO{sub 2} was observed in the bronchioli-alveolar space in the 3 mg-administered group. The biological half times of the TiO{sub 2} in the lung were 4.2, 4.4, 6.7, and 10.8 months in the 0.1, 0.2, 1, and 3 mg-administered groups, respectively. Neutrophil infiltration was observed as the particle clearance was delayed, suggesting that an excessive dose of TiO{sub 2} nanoparticles may induce pulmonary inflammation and clearance delay.
Modeling Neolithic dispersal in Central Europe: demographic implications
Czech Academy of Sciences Publication Activity Database
Galeta, P.; Sládek, Vladimír; Sosna, D.; Brůžek, J.
2011-01-01
Roč. 146, č. 1 (2011), s. 104-115 ISSN 0002-9483 R&D Projects: GA ČR GA206/09/0589 Institutional research plan: CEZ:AV0Z60930519 Keywords : population projections * stochastic modeling * total fertility rate * growth rate Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 2.824, year: 2011
International Nuclear Information System (INIS)
Burkes, Douglas E.; Casella, Andrew M.; Huber, Tanja K.
2015-01-01
Highlights: • Hsu equation provides best thermal conductivity estimate of U–Mo dispersion fuel. • Simple model considering interaction layer formation was coupled with Hsu equation. • Interaction layer thermal conductivity is not the most important attribute. • Effective thermal conductivity is mostly influenced by interaction layer formation. • Fuel particle distribution also influences the effective thermal conductivity. - Abstract: The Global Threat Reduction Initiative Program continues to develop existing and new test reactor fuels to achieve the maximum attainable uranium loadings to support the conversion of a number of the world’s remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Currently, the program is focused on assisting with the development and qualification of a fuel design that consists of a uranium–molybdenum (U–Mo) alloy dispersed in an aluminum matrix. Thermal conductivity is an important consideration in determining the operational temperature of the fuel and can be influenced by interaction layer formation between the dispersed phase and matrix, porosity that forms during fabrication of the fuel plates or rods, and upon the concentration of the dispersed phase within the matrix. This paper develops and validates a simple model to study the influence of interaction layer formation, dispersed particle size, and volume fraction of dispersed phase in the matrix on the effective conductivity of the composite. The model shows excellent agreement with results previously presented in the literature. In particular, the thermal conductivity of the interaction layer does not appear to be as important in determining the effective conductivity of the composite, while formation of the interaction layer and subsequent consumption of the matrix reveals a rather significant effect. The effective thermal conductivity of the composite can be influenced by the dispersed particle distribution by minimizing interaction
Modelling of atmospheric dispersion in a complex medium and associated uncertainties
International Nuclear Information System (INIS)
Demael, Emmanuel
2007-01-01
This research thesis addresses the study of the digital modelling of atmospheric dispersions. It aimed at validating the Mercure-Saturne tool used with a RANS (Reynolds Averaged Navier-Stokes) approach within the frame of an impact study or of an accidental scenario on a nuclear site while taking buildings and ground relief into account, at comparing the Mercure-Saturne model with a more simple and less costly (in terms of computation time) Gaussian tool (the ADMS software, Atmospheric Dispersion Modelling System), and at quantifying uncertainties related to the use of the Mercure-Saturne model. The first part introduces theoretical elements of atmosphere physics and of the atmospheric dispersion in a boundary layer, presents the Gaussian model and the Mercure-Saturne tool and its associated RANS approach. The second part reports the comparison of the Mercure-Saturne model with conventional Gaussian plume models. The third part reports the study of the atmospheric flow and dispersion about the Bugey nuclear site, based on a study performed in a wind tunnel. The fourth part reports the same kind of study for the Flamanville site. The fifth part reports the use of different approaches for the study of uncertainties in the case of the Bugey site: application of the Morris method (a screening method), and of the Monte Carlo method (quantification of the uncertainty and of the sensitivity of each uncertainty source) [fr
Rogers, M Brooke; Amlôt, Richard; Rubin, G James
2013-03-01
It is a common assumption that, in the event of a chemical, biological, radiological, or nuclear (CBRN) attack, a well-prepared and informed public is more likely to follow official recommendations regarding the appropriate safety measures to take. We present findings from a UK study investigating the ability of crisis communication to influence perceptions of risk and behavioral intentions in the general public in response to CBRN terrorism. We conducted a focus group study involving a scenario presented in mock news broadcasts to explore levels of public knowledge, information needs, and intended behavioral reactions to an attack involving an overt radiological dispersal device (RDD), or dirty bomb. We used the findings from these focus groups to design messages for the public that could be presented in a short leaflet. We then tested the effects of the leaflet on reactions to the same scenario in 8 further focus groups. The impact of the new messages on levels of knowledge, information needs, and intended compliance with official recommendations was assessed. The provision of information increased the perceived credibility of official messages and increased reported levels of intended compliance with advice to return to normal/stop sheltering, attend a facility for assessment and treatment, and return to a previously contaminated area after decontamination of the environment has taken place. Should a real attack with an RDD occur, having pretested messages available to address common concerns and information needs should facilitate the public health response to the attack.
International Nuclear Information System (INIS)
Fields, D.E.; Miller, C.W.
1980-05-01
The most commonly used approach for estimating the atmospheric concentration and deposition of material downwind from its point of release is the Gaussian plume atmospheric dispersion model. Two of the critical parameters in this model are sigma/sub y/ and sigma/sub z/, the horizontal and vertical dispersion parameters, respectively. A number of different sets of values for sigma/sub y/ and sigma/sub z/ have been determined empirically for different release heights and meteorological and terrain conditions. The computer code DWNWND, described in this report, is an interactive implementation of the Gaussian plume model. This code allows the user to specify any one of eight different sets of the empirically determined dispersion paramters. Using the selected dispersion paramters, ground-level normalized exposure estimates are made at any specified downwind distance. Computed values may be corrected for plume depletion due to deposition and for plume settling due to gravitational fall. With this interactive code, the user chooses values for ten parameters which define the source, the dispersion and deposition process, and the sampling point. DWNWND is written in FORTRAN for execution on a PDP-10 computer, requiring less than one second of central processor unit time for each simulation
International Nuclear Information System (INIS)
Rest, J.; Hofman, G.L.
1997-01-01
The Dispersion Analysis Research Tool (DART) contains models for fission-gas-induced fuel swelling, interaction of fuel with the matrix aluminum, for the resultant reaction-product swelling, and for the calculation of the stress gradient within the fuel particle. The effects of an aluminide shell on fuel particle swelling are evaluated. Validation of the model is demonstrated by a comparison of DART calculations of fuel swelling of U 3 SiAl-Al and U 3 Si 2 -Al for various dispersion fuel element designs with the data
''POSEIDON'': one radioactive matter dispersion model in maritime environment
International Nuclear Information System (INIS)
Raffestin, D.; Lepicard, S.
1995-02-01
The radio element filiation effect respect, during a spoil in maritime environment was necessary to implement the mathematical integration technologies aiming to optimize the speed calculation and memory. These choices allowed to treat the filiation on several descent levels with compartmental more exact models. Recent data on the fishing product sources and their destinations allow now to sharpen the results by radiological shock decomposition on the European Community countries. 2 refs., 20 figs., 11 tabs., 4 Appendixes
Atmospheric Dispersion Simulation for Level 3 PSA at Ulchin Nuclear Site using a PUFF model
Energy Technology Data Exchange (ETDEWEB)
Lee, Seung Jun; Han, Seok-Jung; Jeong, Hyojoon; Jang, Seung-Cheol [KAERI, Daejeon (Korea, Republic of)
2015-05-15
Air dispersion prediction is a key in the level 3 PSA to predict radiation releases into the environment for preparing an effective strategy for an evacuation as a basis of the emergency preparedness. To predict the atmospheric dispersion accurately, the specific conditions of the radiation release location should be considered. There are various level 3 PSA tools and MACSS2 is one of the widely used level 3 PSA tools in many countries including Korea. Due to the characteristics of environmental conditions in Korea, it should be demonstrated that environmental conditions of Korea nuclear sites can be appropriately illustrated by the tool. In Korea, because all nuclear power plants are located on coasts, sea and land breezes might be a significant factor. The objectives of this work is to simulate the atmospheric dispersion for Ulchin nuclear site in Korea using a PUFF model and to generate the data which can be used for the comparison with that of PLUME model. A nuclear site has own atmospheric dispersion characteristics. Especially in Korea, nuclear sites are located at coasts and it is expected that see and land breeze effects are relatively high. In this work, the atmospheric dispersion at Ulchin nuclear site was simulated to evaluate the effect of see and land breezes in four seasons. In the simulation results, it was observed that the wind direction change with time has a large effect on atmospheric dispersion. If the result of a PLUME model is more conservative than most severe case of a PUFF model, then the PLUME model could be used for Korea nuclear sites in terms of safety assessment.
Dispersive versus constant-geometry models of the neutron-208Pb mean field
International Nuclear Information System (INIS)
Mahaux, C.; Sartor, R.
1990-01-01
Phenomenological optical-model analyses of differential elastic scattering cross sections of neutrons by 208 Pb indicate that the radius of the real part of the potential decreases with increasing energy in the domain 4< E<40 MeV. On the other hand, the experimental total cross section is compatible with a real potential whose radial shape is energy independent. In order to clarify this situation, we compare a 'constant geometry' model whose real part has an energy-independent radial shape with a 'dispersive model' whose real part has an energy-dependent radial shape calculated from the dispersion relation which connects the real and imaginary parts of the field. The following three main features are considered. (i) The junction of the optical-model potential with the shell-model potential at negative energy. (ii) The agreement between the calculated total and differential cross sections and their experimental values. (iii) The extent to which the real part of the optical-model potential can be accurately determined by analyzing the total cross section only. It is concluded that the presently available experimental data support the existence of an energy dependence of the radial shape of the real potential, in keeping with the dispersion relation. A new parametrization of a 'dispersive' mean field is also presented. It does not involve more parameters than the previously published one but takes better account of the physical properties of the spectral functions; it is shown to improve the agreement between predicted and experimental scattering data. (orig.)
Fridgeirsdottir, Gudrun A; Harris, Robert J; Dryden, Ian L; Fischer, Peter M; Roberts, Clive J
2018-03-29
Solid dispersions can be a successful way to enhance the bioavailability of poorly soluble drugs. Here 60 solid dispersion formulations were produced using ten chemically diverse, neutral, poorly soluble drugs, three commonly used polymers, and two manufacturing techniques, spray-drying and melt extrusion. Each formulation underwent a six-month stability study at accelerated conditions, 40 °C and 75% relative humidity (RH). Significant differences in times to crystallization (onset of crystallization) were observed between both the different polymers and the two processing methods. Stability from zero days to over one year was observed. The extensive experimental data set obtained from this stability study was used to build multiple linear regression models to correlate physicochemical properties of the active pharmaceutical ingredients (API) with the stability data. The purpose of these models is to indicate which combination of processing method and polymer carrier is most likely to give a stable solid dispersion. Six quantitative mathematical multiple linear regression-based models were produced based on selection of the most influential independent physical and chemical parameters from a set of 33 possible factors, one model for each combination of polymer and processing method, with good predictability of stability. Three general rules are proposed from these models for the formulation development of suitably stable solid dispersions. Namely, increased stability is correlated with increased glass transition temperature ( T g ) of solid dispersions, as well as decreased number of H-bond donors and increased molecular flexibility (such as rotatable bonds and ring count) of the drug molecule.
Randomized Item Response Theory Models
Fox, Gerardus J.A.
2005-01-01
The randomized response (RR) technique is often used to obtain answers on sensitive questions. A new method is developed to measure latent variables using the RR technique because direct questioning leads to biased results. Within the RR technique is the probability of the true response modeled by
A Platoon Dispersion Model Based on a Truncated Normal Distribution of Speed
Directory of Open Access Journals (Sweden)
Ming Wei
2012-01-01
Full Text Available Understanding platoon dispersion is critical for the coordination of traffic signal control in an urban traffic network. Assuming that platoon speed follows a truncated normal distribution, ranging from minimum speed to maximum speed, this paper develops a piecewise density function that describes platoon dispersion characteristics as the platoon moves from an upstream to a downstream intersection. Based on this density function, the expected number of cars in the platoon that pass the downstream intersection, and the expected number of cars in the platoon that do not pass the downstream point are calculated. To facilitate coordination in a traffic signal control system, dispersion models for the front and the rear of the platoon are also derived. Finally, a numeric computation for the coordination of successive signals is presented to illustrate the validity of the proposed model.
Model Equation for Acoustic Nonlinear Measurement of Dispersive Specimens at High Frequency
Zhang, Dong; Kushibiki, Junichi; Zou, Wei
2006-10-01
We present a theoretical model for acoustic nonlinearity measurement of dispersive specimens at high frequency. The nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation governs the nonlinear propagation in the SiO2/specimen/SiO2 multi-layer medium. The dispersion effect is considered in a special manner by introducing the frequency-dependant sound velocity in the KZK equation. Simple analytic solutions are derived by applying the superposition technique of Gaussian beams. The solutions are used to correct the diffraction and dispersion effects in the measurement of acoustic nonlinearity of cottonseed oil in the frequency range of 33-96 MHz. Regarding two different ultrasonic devices, the accuracies of the measurements are improved to ±2.0% and ±1.3% in comparison with ±9.8% and ±2.9% obtained from the previous plane wave model.
Energy Technology Data Exchange (ETDEWEB)
Payne, J.R. [Payne Environmental Consultants Inc., Encinitas, CA (United States); Terrill, E.; Carter, M.; Otero, M.; Middleton, W.; Chen, A. [Scripps Inst. of Oceanography, La Jolla, CA (United States); French McCay, D.; Mueller, C.; Jayko, K. [Applied Science Associates Inc., Narragansett, RI (United States); Nordhausen, W.; Lewis, R.; Lampinen, M.; Evans, T. [California Dept. of Fish and Game, San Diego, CA (United States). Office of Spill Prevention and Response; Ohlmann, C. [California Univ., Santa Barbara, CA (United States); Via, G.L.; Ruiz-Santana, H.; Maly, M.; Willoughby, B.; Varela, C. [United States Coast Guard Pacific Strike Team, Novato, CA (United States); Lynch, P.; Sanchez, P. [Marine Spill Response Corp., San Diego, CA (United States)
2007-07-01
Extensive coastal areas in the United States have been designated as pre-approved zones for dispersant applications in the event of an oil spill. Although the use of dispersants may reduce impacts to wildlife and shoreline habitats, it is recognized that the dispersed oil may cause impacts to organisms in the water column. The State of California Department of Fish and Game Office of Spill Prevention and Response is currently using oil spill fate and transport modeling to address this issue. The purpose is to develop the time and spatial scales, and equipment needs for a formal dispersed oil monitoring plan (DOMP) to document hydrocarbon water column concentrations, potentially exposed zooplankton, and the impact of the oil spills with and without dispersant use. A series of 7 fluorescein dye releases were completed off the coast of San Diego, California in order to test the operational framework for repeated sampling of dispersed oil plumes as outlined in the DOMP. The ability of high-frequency radar to provide surface current input data to oil spill models was also evaluated. The dye concentrations were measured over three spatial dimensions and time in order to verify the model-predicted movement of subsurface dye. Surface current fields at varying depths were also measured and the subsurface dye plume structure was mapped using a GPS coupled towed-fluorometer equipped with pressure sensors. Measurements were compared with data from traditional special monitoring of applied response technology (SMART). The database acquired through this program represents a technical resource that can help physical and chemical oceanographers, modelers, spill response and contingency planners involved in the debate of whether or not to use dispersants to mitigate near shore and open ocean marine oil spills. 14 refs., 2 tabs., 14 figs.
Design basis for the operational modelling of the atmospheric dispersion
International Nuclear Information System (INIS)
Doury, A.
1987-10-01
Based on the latest practices at the Institut de Protection et de Surete Nucleaire of the Commissariat a l'Energie Atomique (CEA), we shall first present the basis elements used for a simple and adequate modelling method for assessing hypothetical atmospheric pollution from transient or continuous discharge with any given kinetics under various weather conditions which are not necessarily stationary or uniform, which are likely to occur even with little or no wind. Discharges shall be considered as sequences of instantaneous successive puffs. The parameters deduced experimentally or from observations are functions of the transfer time and cover all time and space scales. The restrictions of use are indicated, especially concerning heavy gases. Finally, simple formulas are proposed for concentrations and depositions so as to be able to make a rapid estimation of the orders of magnitude with almost no computation [fr
Design basis for the operational modelling of the atmospheric dispersion
International Nuclear Information System (INIS)
Doury, A.
1987-11-01
Based on the latest practices at the Institut de Protection et de Surete Nucleaire of the Commissariat a l'Energie Atomique (CEA), we shall first present the basis elements used for a simple and adequate modelling method for assessing hypothetical atmospheric pollution from transient or continuous discharge with any given kinetics under various weather conditions which are not necessarily stationary or uniform, which are likely to occur even with little or no wind. Discharges shall be considered as sequences of instantaneous successive puffs. The parameters deduced experimentally or from observations are functions of the transfer time and cover all time and space scales. The restrictions of use are indicated, especially concerning heavy gases. Finally, simple formulas are proposed for concentrations and depositions so as to be able to make a rapid estimation of the orders of magnitude with almost no computation [fr
Silvestro, Daniele; Zizka, Alexander; Bacon, Christine D; Cascales-Miñana, Borja; Salamin, Nicolas; Antonelli, Alexandre
2016-04-05
Methods in historical biogeography have revolutionized our ability to infer the evolution of ancestral geographical ranges from phylogenies of extant taxa, the rates of dispersals, and biotic connectivity among areas. However, extant taxa are likely to provide limited and potentially biased information about past biogeographic processes, due to extinction, asymmetrical dispersals and variable connectivity among areas. Fossil data hold considerable information about past distribution of lineages, but suffer from largely incomplete sampling. Here we present a new dispersal-extinction-sampling (DES) model, which estimates biogeographic parameters using fossil occurrences instead of phylogenetic trees. The model estimates dispersal and extinction rates while explicitly accounting for the incompleteness of the fossil record. Rates can vary between areas and through time, thus providing the opportunity to assess complex scenarios of biogeographic evolution. We implement the DES model in a Bayesian framework and demonstrate through simulations that it can accurately infer all the relevant parameters. We demonstrate the use of our model by analysing the Cenozoic fossil record of land plants and inferring dispersal and extinction rates across Eurasia and North America. Our results show that biogeographic range evolution is not a time-homogeneous process, as assumed in most phylogenetic analyses, but varies through time and between areas. In our empirical assessment, this is shown by the striking predominance of plant dispersals from Eurasia into North America during the Eocene climatic cooling, followed by a shift in the opposite direction, and finally, a balance in biotic interchange since the middle Miocene. We conclude by discussing the potential of fossil-based analyses to test biogeographic hypotheses and improve phylogenetic methods in historical biogeography. © 2016 The Author(s).
Dispersion-convolution model for simulating peaks in a flow injection system.
Pai, Su-Cheng; Lai, Yee-Hwong; Chiao, Ling-Yun; Yu, Tiing
2007-01-12
A dispersion-convolution model is proposed for simulating peak shapes in a single-line flow injection system. It is based on the assumption that an injected sample plug is expanded due to a "bulk" dispersion mechanism along the length coordinate, and that after traveling over a distance or a period of time, the sample zone will develop into a Gaussian-like distribution. This spatial pattern is further transformed to a temporal coordinate by a convolution process, and finally a temporal peak image is generated. The feasibility of the proposed model has been examined by experiments with various coil lengths, sample sizes and pumping rates. An empirical dispersion coefficient (D*) can be estimated by using the observed peak position, height and area (tp*, h* and At*) from a recorder. An empirical temporal shift (Phi*) can be further approximated by Phi*=D*/u2, which becomes an important parameter in the restoration of experimental peaks. Also, the dispersion coefficient can be expressed as a second-order polynomial function of the pumping rate Q, for which D*(Q)=delta0+delta1Q+delta2Q2. The optimal dispersion occurs at a pumping rate of Qopt=sqrt[delta0/delta2]. This explains the interesting "Nike-swoosh" relationship between the peak height and pumping rate. The excellent coherence of theoretical and experimental peak shapes confirms that the temporal distortion effect is the dominating reason to explain the peak asymmetry in flow injection analysis.
A random walk model to simulate the atmospheric dispersion of radionuclide
Zhuo, Jun; Huang, Liuxing; Niu, Shengli; Xie, Honggang; Kuang, Feihong
2018-01-01
To investigate the atmospheric dispersion of radionuclide in large-medium scale, a numerical simulation method based on random walk model for radionuclide atmospheric dispersion was established in the paper. The route of radionuclide migration and concentration distribution of radionuclide can be calculated out by using the method with the real-time or historical meteorological fields. In the simulation, a plume of radionuclide is treated as a lot of particles independent of each other. The particles move randomly by the fluctuations of turbulence, and disperse, so as to enlarge the volume of the plume and dilute the concentration of radionuclide. The dispersion of the plume over time is described by the variance of the particles. Through statistical analysis, the relationships between variance of the particles and radionuclide dispersion characteristics can be derived. The main mechanisms considered in the physical model are: (1) advection of radionuclide by mean air motion, (2) mixing of radionuclide by atmospheric turbulence, (3) dry and wet deposition, (4) disintegration. A code named RADES was developed according the method. And then, the European Tracer Experiment (ETEX) in 1994 is simulated by the RADES and FLEXPART codes, the simulation results of the concentration distribution of tracer are in good agreement with the experimental data.
Numerical simulations of atmospheric dispersion of iodine-131 by different models.
Directory of Open Access Journals (Sweden)
Ádám Leelőssy
Full Text Available Nowadays, several dispersion models are available to simulate the transport processes of air pollutants and toxic substances including radionuclides in the atmosphere. Reliability of atmospheric transport models has been demonstrated in several recent cases from local to global scale; however, very few actual emission data are available to evaluate model results in real-life cases. In this study, the atmospheric dispersion of 131I emitted to the atmosphere during an industrial process was simulated with different models, namely the WRF-Chem Eulerian online coupled model and the HYSPLIT and the RAPTOR Lagrangian models. Although only limited data of 131I detections has been available, the accuracy of modeled plume direction could be evaluated in complex late autumn weather situations. For the studied cases, the general reliability of models has been demonstrated. However, serious uncertainties arise related to low level inversions, above all in case of an emission event on 4 November 2011, when an important wind shear caused a significant difference between simulated and real transport directions. Results underline the importance of prudent interpretation of dispersion model results and the identification of weather conditions with a potential to cause large model errors.
Adaptive hierarchical grid model of water-borne pollutant dispersion
Borthwick, A. G. L.; Marchant, R. D.; Copeland, G. J. M.
Water pollution by industrial and agricultural waste is an increasingly major public health issue. It is therefore important for water engineers and managers to be able to predict accurately the local behaviour of water-borne pollutants. This paper describes the novel and efficient coupling of dynamically adaptive hierarchical grids with standard solvers of the advection-diffusion equation. Adaptive quadtree grids are able to focus on regions of interest such as pollutant fronts, while retaining economy in the total number of grid elements through selective grid refinement. Advection is treated using Lagrangian particle tracking. Diffusion is solved separately using two grid-based methods; one is by explicit finite differences, the other a diffusion-velocity approach. Results are given in two dimensions for pure diffusion of an initially Gaussian plume, advection-diffusion of the Gaussian plume in the rotating flow field of a forced vortex, and the transport of species in a rectangular channel with side wall boundary layers. Close agreement is achieved with analytical solutions of the advection-diffusion equation and simulations from a Lagrangian random walk model. An application to Sepetiba Bay, Brazil is included to demonstrate the method with complex flows and topography.
ERUPTION TO DOSE: COUPLING A TEPHRA DISPERSAL MODEL WITHIN A PERFORMANCE ASSESSMENT FRAMEWORK
International Nuclear Information System (INIS)
G. N. Keating, J. Pelletier
2005-01-01
The tephra dispersal model used by the Yucca Mountain Project (YMP) to evaluate the potential consequences of a volcanic eruption through the waste repository must incorporate simplifications in order to function within a large Monte-Carlo style performance assessment framework. That is, the explicit physics of the conduit, vent, and eruption column processes are abstracted to a 2-D, steady-state advection-dispersion model (ASHPLUME) that can be run quickly over thousands of realizations of the overall system model. Given the continuous development of tephra dispersal modeling techniques in the last few years, we evaluated the adequacy of this simplified model for its intended purpose within the YMP total system performance assessment (TSPA) model. We evaluated uncertainties inherent in model simplifications including (1) instantaneous, steady-state vs. unsteady eruption, which affects column height, (2) constant wind conditions, and (3) power-law distribution of the tephra blanket; comparisons were made to other models and published ash distributions. Spatial statistics are useful for evaluating differences in these model output vs. results using more complex wind, column height, and tephra deposition patterns. However, in order to assess the adequacy of the model for its intended use in TSPA, we evaluated the propagation of these uncertainties through FAR, the YMP ash redistribution model, which utilizes ASHPLUME tephra deposition results to calculate the concentration of nuclear waste-contaminated tephra at a dose-receptor population as a result of sedimentary transport and mixing processes on the landscape. Questions we sought to answer include: (1) what conditions of unsteadiness, wind variability, or departure from simplified tephra distribution result in significant effects on waste concentration (related to dose calculated for the receptor population)? (2) What criteria can be established for the adequacy of a tephra dispersal model within the TSPA
Harmonisation within atmospheric dispersion modelling for regulatory purposes. Proceedings. Vol. 2
International Nuclear Information System (INIS)
Suppan, P.
2004-01-01
Dispersion modelling has proved to be a very effective tool to assess the environmental impact of human activities on air quality already at the early planning stage. Environmental assessments during planning are required by the EU directive 85/337/EEC. Only models can give detailed information on the distribution of pollutants with high spatial and temporal resolution, while they allow the decision-maker to devise a range of scenarios, in which the various processes determining the environmental impact can be easily simulated and changed. In June 1991, the Joint Research Centre of the European Commission started an initiative on the sharing of information and possible harmonisation of new approaches to atmospheric dispersion modelling and model evaluation. This initiative has fostered a series of conferences that have been concerned with improvement of ''modelling culture'' in Europe. The 9 th International Conference on Harmonisation within atmospheric dispersion modelling for regulatory purposes in Garmisch-Partenkirchen, in Germany/ Bavaria, 1-4 June, 2004, will continue the efforts of the previous conferences. The conference has a role as a forum where users and decision-makers can bring their requirements to the attention of scientists. It is also a natural forum for discussing environmental issues related to the European union enlargement process. The scope of this conference is covered by the following topics: Validation and inter-comparison of models: Model evaluation methodology, experiences with implementation of EU directives; regulatory modelling, short distance dispersion modelling, urban scale and street canyon modelling: Meteorology and air quality, mesoscale meteorology and air quality modelling, environmental impact assessment: Air pollution management and decision support systems. (orig.)
Biomass burning aerosol over Romania using dispersion model and Calipso data
Nicolae, Victor; Dandocsi, Alexandru; Marmureanu, Luminita; Talianu, Camelia
2018-04-01
The purpose of the study is to analyze the seasonal variability, for the hot and cold seasons, of biomass burning aerosol observed over Romania using forward dispersion calculations based on FLEXPART model. The model was set up to use as input the MODIS fire data with a degree of confidence over 25% after transforming the emitted power in emission rate. The modelled aerosols in this setup was black carbon coated by organics. Distribution in the upper layers were compared to Calipso retrieval.
Kwak, Kyung-Hwan; Baik, Jong-Jin
2012-01-01
A computational fluid dynamics (CFD) model that includes the carbon bond mechanism IV (CBM-IV) is developed and used to investigate reactive pollutant dispersion in and above a street canyon with an aspect ratio of 1. Fourteen emission scenarios of NO x and volatile organic compounds (VOCs) are considered. Dispersion types are classified into NO-type, NO 2-type, and O 3-type dispersion that exhibit concentration maxima at the street bottom, near the center of the street canyon, and above the street canyon, respectively. For the base emission scenario, the number of reactive species is 9 in the NO-type dispersion, 10 in the NO 2-type dispersion, and 15 in the O 3-type dispersion. As the NO x emission level decreases or the VOC emission level increases, some species in the O 3-type dispersion are shifted to the NO 2-type dispersion. The VOC-to-NO x emission ratio is found to be an important factor in determining the transition of dispersion type. In this transition process, OH plays a key role through a radical chain including HO 2, RO, and RO 2. Because of their high OH reactivities, XYL (xylene) and OLE (olefin carbon bond) among VOCs are largely responsible for the transition of dispersion type. The O 3 sensitivity is examined by reducing NO x or VOC emission level by a half. Because the NO titration of O 3 is more pronounced than the NO 2 photolysis and the radical chain process in the street canyon, the O 3 concentration therein is negatively correlated with the NO x emission level and weakly correlated with the VOC emission level. As a result, the street canyon is a negatively NO x-sensitive regime.
CFD modelling of the aerodynamic effect of trees on urban air pollution dispersion.
Amorim, J H; Rodrigues, V; Tavares, R; Valente, J; Borrego, C
2013-09-01
The current work evaluates the impact of urban trees over the dispersion of carbon monoxide (CO) emitted by road traffic, due to the induced modification of the wind flow characteristics. With this purpose, the standard flow equations with a kε closure for turbulence were extended with the capability to account for the aerodynamic effect of trees over the wind field. Two CFD models were used for testing this numerical approach. Air quality simulations were conducted for two periods of 31h in selected areas of Lisbon and Aveiro, in Portugal, for distinct relative wind directions: approximately 45° and nearly parallel to the main avenue, respectively. The statistical evaluation of modelling performance and uncertainty revealed a significant improvement of results with trees, as shown by the reduction of the NMSE from 0.14 to 0.10 in Lisbon, and from 0.14 to 0.04 in Aveiro, which is independent from the CFD model applied. The consideration of the plant canopy allowed to fulfil the data quality objectives for ambient air quality modelling established by the Directive 2008/50/EC, with an important decrease of the maximum deviation between site measurements and CFD results. In the non-aligned wind situation an average 12% increase of the CO concentrations in the domain was observed as a response to the aerodynamic action of trees over the vertical exchange rates of polluted air with the above roof-level atmosphere; while for the aligned configuration an average 16% decrease was registered due to the enhanced ventilation of the street canyon. These results show that urban air quality can be optimised based on knowledge-based planning of green spaces. Copyright © 2013 Elsevier B.V. All rights reserved.
Response of the REWARD detection system to the presence of a Radiological Dispersal Device
International Nuclear Information System (INIS)
Luís, R.; Fleta, C.; Balbuena, J.; Baptista, M.; Barros, S.; Disch, C.; Jumilla, C.; Lozano, M.; Marques, J.G.; Vaz, P.
2016-01-01
The objective of the REWARD project consisted in building a mobile system for real time, wide area radiation surveillance, using a CdZnTe detector for gamma radiation and a neutron detector based on novel silicon technologies. The sensing unit includes a GPS system and a wireless communication interface to send the data remotely to a monitoring base station, where it will be analyzed in real time and correlated with historical data from the tag location, in order to generate an alarm when an abnormal situation is detected. The main objective of this work consisted in making predictions regarding the behavior of the REWARD system in the presence of a Radiological Dispersion Device (RDD), one of the reference scenarios foreseen for REWARD, using experimental data and the Monte Carlo simulation program MCNP6. Experimental tests were performed at the Fire Brigades Facilities in Rome and at the Naples Fire Brigades. The response of the REWARD detection system to the presence of an RDD is predicted and discussed. - Highlights: • A prototype mobile system for real-time, wide-area radiation surveillance was built. • Experimental measurements and Monte Carlo simulations were used to test the system. • The system is suitable to detect and identify radiation sources in threat scenarios.
Improving long-range dispersion predictions with ETEX real-time and a-posteriori model evaluations
International Nuclear Information System (INIS)
Desiato, F.
1997-01-01
The Italian environmental Protection Agency (ANPA), which is responsible for the evaluation of the consequences of accidental releases into the atmosphere, has participated to both the real-time (phase-1) and a-posteriori (phase-2) ETEX model evaluations. The double benchmark actually constituted an invaluable experience for better understanding the skill and limits of the present long-range dispersion modelling capabilities. In particular, the strong difference between phase-1 and phase-2 model performance emphasised the opportunity to modify, improve or tune a number of specific aspects of the overall simulation. ETEX model runs were carried out with the Lagrangian particle model APOLLO. The meteorological input was constituted by ECMWF fields. Three-hourly average concentrations paired in space and time and time-integrated concentrations were used in the evaluation of the results, based on a set of statistical indexes and concentration contour lines and scatter diagrams
Litchford, Ron J.; Jeng, San-Mou
1992-01-01
The performance of a recently introduced statistical transport model for turbulent particle dispersion is studied here for rigid particles injected into a round turbulent jet. Both uniform and isosceles triangle pdfs are used. The statistical sensitivity to parcel pdf shape is demonstrated.
Numerical modeling of flow and pollutant dispersion in street canyons with tree planting
Balczó, M.; Gromke, C.B.; Ruck, B.
2009-01-01
Numerical simulations of the impact of tree planting on airflow and traffic pollutant dispersion in urban street canyons have been performed using the commercial CFD (Computational Fluid Dynamics) code MISKAM. A k-e turbulence model including additional terms for the treatment of vegetation, has
A collection of mathematical models for dispersion in surface water and groundwater
International Nuclear Information System (INIS)
Codell, R.B.; Key, K.T.; Whelan, G.
1982-06-01
This report represents a collection of some of the manual procedures and simple computer programs used by the Hydrologic Engineering Section of the Division of Engineering, Office of Nuclear Reactor Regulation, for computing the fate of routinely or accidentally released radionuclides in surface water and groundwater. All models are straightforward simulations of dispersion with constant coefficients in simple geometries
DEFF Research Database (Denmark)
Falk, Anne Katrine Vinther; Gryning, Sven-Erik
1997-01-01
In this model for atmospheric dispersion particles are simulated by the Langevin Equation, which is a stochastic differential equation. It uses the probability density function (PDF) of the vertical velocity fluctuations as input. The PDF is constructed as an expansion after Hermite polynomials...
When Lagrangian stochastic models for turbulent dispersion are applied to complex flows, some type of ad hoc intervention is almost always necessary to eliminate unphysical behavior in the numerical solution. This paper discusses numerical considerations when solving the Langevin-based particle velo...
Energy Technology Data Exchange (ETDEWEB)
Mistarhi, Qusai M.; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of)
2016-05-15
U-Mo/Al dispersion fuel performed well at a low burn-up. However, higher burn-up and higher fission rate irradiation testing showed enhanced fuel meat swelling which was caused by high interaction layer growth and pore formation. The performance of the dispersion type fuel in the irradiation and un-irradiation environment is very important. During the fabrication of the dispersion type fuel an Interaction Layer (IL) is formed due to the inter-diffusion between the U-Mo fuel particles and the Al matrix which is an intermetallic compound (U,Mo)Alx. During irradiation, the IL becomes amorphous causing a further decrease in the thermal conductivity and an increase in the centerline temperature of the fuel meat. Several analytical models and numerical methods were developed to study the performance of the unirradiated U-Mo/Al dispersion fuel. Two analytical models were developed to study the performance of the irradiated U-Mo/Al dispersion fuel. In these models, the thermal conductivity of the IL was assumed to be constant. The properties of the irradiated U-Mo dispersion fuel have been investigated recently by Huber et al. The objective of this study is to develop a correlation for IL thermal conductivity during irradiation as a function of the temperature and fission density from the experimentally measured thermal conductivity of the irradiated U-Mo/Al dispersion fuel. The thermal conductivity of IL during irradiation was calculated from the experimentally measured data and a correlation was developed from the thermal conductivity of IL as a function of T and fission density.
Atmospheric aerosol dispersion models and their applications to environmental risk assessment
Directory of Open Access Journals (Sweden)
Andrzej Mazur
2014-03-01
Full Text Available Introduction. Numerical models of dispersion of atmospheric pollutants are widely used to forecast the spread of contaminants in the air and to analyze the effects of this phenomenon. The aim of the study is to investigate the possibilities and the quality of diagnosis and prediction of atmospheric transport of aerosols in the air using the dispersion model of atmospheric pollutants, developed at the Institute of Meteorology and Water Management (IMWM in Warsaw. Material and methods. A model of the dispersion of atmospheric pollutants, linked with meteorological models in a diagnostic mode, was used to simulate the transport of the cloud of aerosols released during the crash near the town of Ożydiw (Ukraine and of volcanic ash – during the volcanic eruption of Eyjafjallajökull in Iceland. Results. Possible directions of dispersion of pollutants in the air and its concentration in the atmosphere and deposition to the soil were assessed. The analysis of temporal variability of concentrations of aerosols in the atmosphere confirmed that the model developed at IMWM is an effective tool for diagnosis of air quality in the area of Poland as well as for determination of exposure duration to the aerosol clouds for different weather scenarios. Conclusions. The results are a confirmation of the thesis, that because in the environmental risk assessment, an important element is not only current information on the level of pollution concentrations, but also the time of exposure to pollution and forecast of these elements, and consequently the predicted effects on man or the environment in general; so it is necessary to use forecasting tools, similar to presented application. The dispersion model described in the paper is an operational tool for description, analysis and forecasting of emergency situations in case of emissions of hazardous substances.
Pollutant Dispersion Modeling in Natural Streams Using the Transmission Line Matrix Method
Directory of Open Access Journals (Sweden)
Safia Meddah
2015-09-01
Full Text Available Numerical modeling has become an indispensable tool for solving various physical problems. In this context, we present a model of pollutant dispersion in natural streams for the far field case where dispersion is considered longitudinal and one-dimensional in the flow direction. The Transmission Line Matrix (TLM, which has earned a reputation as powerful and efficient numerical method, is used. The presented one-dimensional TLM model requires a minimum input data and provides a significant gain in computing time. To validate our model, the results are compared with observations and experimental data from the river Severn (UK. The results show a good agreement with experimental data. The model can be used to predict the spatiotemporal evolution of a pollutant in natural streams for effective and rapid decision-making in a case of emergency, such as accidental discharges in a stream with a dynamic similar to that of the river Severn (UK.
A comprehensive experimental databank for the verification of urban car emission dispersion models
Energy Technology Data Exchange (ETDEWEB)
Pavageau, M.; Rafailidis, S.; Schatzmann, M. [Universitaet Hamburg (Germany). Meteorologisches Inst.
2001-07-01
A summary presentation is made of representative samples from a comprehensive experimental databank on car exhaust dispersion in urban street canyons. Physical modelling, under neutral stratification conditions, was used to provide visualisation, pollutant concentration and velocity measurements above and inside test canyons amidst surrounding urban roughness. The study extended to two different canyon aspects ratios, in combination with different roof configurations on the surrounding buildings. To serve as a reliable basis for validation and testing of urban pollution dispersion codes, special emphasis was placed in this work on data quality assurance. (Author)
Chattopadhyay, Ankur; Rani, Poonam; Srivastava, Rajendra; Dhar, Purbarun
2018-06-01
The present article discusses the typical influence of grafted conducting polymers in the mesoscale pores of dielectric particles on the static and dynamic electrorheology and electro-viscoelastic behavior of corresponding colloids. Nanocrystalline meso-nanoporous zeolite has been prepared by chemical synthesis and subsequently polyaniline (PANI) coating has been implemented. Electrorheological (ER) suspensions have been formed by dispersing the nanoparticles in silicone oil and their viscoelastic behaviors are examined to understand the nature of such complex colloidal systems under electric fields. PANI-Zeolite ER fluids demonstrate higher static electroviscous effects and yield stress potential than untreated Zeolite, typically studied in literature. Transient electro-viscous characterizations show a stable and negligible hysteresis behavior when both the fluids are exposed to constant as well as time varying electric field intensities. Further oscillatory shear experiments of frequency and strain sweeps exhibit predominant elastic behavior in case of Zeolite based ER suspensions as compared to PANI systems. Detailed investigations reveal Zeolite based ER suspensions display enhanced relative yielding as well as electro-viscoelastic stability than the PANI-Zeolite. The steady state viscous behaviors are scaled against the non-dimensional Mason number to model the system behavior for both fluids. Experimental data of flow behaviors of both the ER fluids are compared with semi-classical models and it is found that the CCJ model possesses a closer proximity than traditional Bingham model, thereby revealing the fluids to be generic pseudo-linear fluids. The present article reveals that while the PANI based fluids are typically hailed superior in literature, it is only restricted to steady shear utilities. In case of dynamic and oscillatory systems, the traditional Zeolite based fluids exhibit superior ER caliber. Copyright © 2018 Elsevier Inc. All rights reserved.
FIREPLUME model for plume dispersion from fires: Application to uranium hexafluoride cylinder fires
International Nuclear Information System (INIS)
Brown, D.F.; Dunn, W.E.
1997-06-01
This report provides basic documentation of the FIREPLUME model and discusses its application to the prediction of health impacts resulting from releases of uranium hexafluoride (UF 6 ) in fires. The model application outlined in this report was conducted for the Draft Programmatic Environmental Impact Statement for Alternative Strategies for the Long-Term Management and Use of Depleted UF 6 . The FIREPLUME model is an advanced stochastic model for atmospheric plume dispersion that predicts the downwind consequences of a release of toxic materials from an explosion or a fire. The model is based on the nonbuoyant atmospheric dispersion model MCLDM (Monte Carlo Lagrangian Dispersion Model), which has been shown to be consistent with available laboratory and field data. The inclusion of buoyancy and the addition of a postprocessor to evaluate time-varying concentrations lead to the current model. The FIREPLUME model, as applied to fire-related UF 6 cylinder releases, accounts for three phases of release and dispersion. The first phase of release involves the hydraulic rupture of the cylinder due to heating of the UF 6 in the fire. The second phase involves the emission of material into the burning fire, and the third phase involves the emission of material after the fire has died during the cool-down period. The model predicts the downwind concentration of the material as a function of time at any point downwind at or above the ground. All together, five fire-related release scenarios are examined in this report. For each scenario, downwind concentrations of the UF 6 reaction products, uranyl fluoride and hydrogen fluoride, are provided for two meteorological conditions: (1) D stability with a 4-m/s wind speed, and (2) F stability with a 1-m/s wind speed
Contributions of chemical exchange to T1ρ dispersion in a tissue model.
Cobb, Jared G; Xie, Jingping; Gore, John C
2011-12-01
Variations in T(1ρ) with locking-field strength (T(1ρ) dispersion) may be used to estimate proton exchange rates. We developed a novel approach utilizing the second derivative of the dispersion curve to measure exchange in a model system of cross-linked polyacrylamide gels. These gels were varied in relative composition of comonomers, increasing stiffness, and in pH, modifying exchange rates. Magnetic resonance images were recorded with a spin-locking sequence as described by Sepponen et al. These measurements were fit to a mono-exponential decay function yielding values for T(1ρ) at each locking-field measured. These values were then fit to a model by Chopra et al. for estimating exchange rates. For low stiffness gels, the calculated exchange values increased by a factor of 4 as pH increased, consistent with chemical exchange being the dominant contributor to T(1ρ) dispersion. Interestingly, calculated chemical exchange rates also increased with stiffness, likely due to modified side-chain exchange kinetics as the composition varied. This article demonstrates a new method to assess the structural and chemical effects on T(1ρ) relaxation dispersion with a suitable model. These phenomena may be exploited in an imaging context to emphasize the presence of nuclei of specific exchange rates, rather than chemical shifts. Copyright © 2011 Wiley Periodicals, Inc.
A model for short and medium range dispersion of radionuclides released to the atmosphere
International Nuclear Information System (INIS)
Clarke, R.H.
1979-09-01
A Working Group was established to give practical guidance on the estimation of the dispersion of radioactive releases to the atmosphere. The dispersion is estimated in the short and medium range, that is from about 100 m to a few tens of kilometres from the source, and is based upon a Gaussian plume model. A scheme is presented for categorising atmospheric conditions and values of the associated dispersion parameters are given. Typical results are presented for releases in specific meteorological conditions and a scheme is included to allow for durations of release of up to 24 hours. Consideration has also been given to predicting longer term average concentrations, typically annual averages, and results are presented which facilitate site specific calculations. The results of the models are extended to 100 km from the source, but the increasing uncertainty with which results may be predicted beyond a few tens of kilometres from the source is emphasised. Three technical appendices provide some of the rationale behind the decisions made in adopting the various models in the proposed dispersion scheme. (author)
The formulations of the AMS/EPA Regulatory Model Improvement Committee's applied air dispersion model (AERMOD) as related to the characterization of the planetary boundary layer are described. This is the first in a series of three articles. Part II describes the formulation of...
Mixed Platoon Flow Dispersion Model Based on Speed-Truncated Gaussian Mixture Distribution
Directory of Open Access Journals (Sweden)
Weitiao Wu
2013-01-01
Full Text Available A mixed traffic flow feature is presented on urban arterials in China due to a large amount of buses. Based on field data, a macroscopic mixed platoon flow dispersion model (MPFDM was proposed to simulate the platoon dispersion process along the road section between two adjacent intersections from the flow view. More close to field observation, truncated Gaussian mixture distribution was adopted as the speed density distribution for mixed platoon. Expectation maximum (EM algorithm was used for parameters estimation. The relationship between the arriving flow distribution at downstream intersection and the departing flow distribution at upstream intersection was investigated using the proposed model. Comparison analysis using virtual flow data was performed between the Robertson model and the MPFDM. The results confirmed the validity of the proposed model.
The Lagrangian particle dispersion model FLEXPART-WRF VERSION 3.1
Energy Technology Data Exchange (ETDEWEB)
Brioude, J.; Arnold, D.; Stohl, A.; Cassiani, M.; Morton, Don; Seibert, P.; Angevine, W. M.; Evan, S.; Dingwell, A.; Fast, Jerome D.; Easter, Richard C.; Pisso, I.; Bukhart, J.; Wotawa, G.
2013-11-01
The Lagrangian particle dispersion model FLEXPART was originally designed for cal- culating long-range and mesoscale dispersion of air pollutants from point sources, such as after an accident in a nuclear power plant. In the meantime FLEXPART has evolved into a comprehensive tool for atmospheric transport modeling and analysis at different scales. This multiscale need from the modeler community has encouraged new developments in FLEXPART. In this document, we present a version that works with the Weather Research and Forecasting (WRF) mesoscale meteoro- logical model. Simple procedures on how to run FLEXPART-WRF are presented along with special options and features that differ from its predecessor versions. In addition, test case data, the source code and visualization tools are provided to the reader as supplementary material.
Homogenization of a Directed Dispersal Model for Animal Movement in a Heterogeneous Environment.
Yurk, Brian P
2016-10-01
The dispersal patterns of animals moving through heterogeneous environments have important ecological and epidemiological consequences. In this work, we apply the method of homogenization to analyze an advection-diffusion (AD) model of directed movement in a one-dimensional environment in which the scale of the heterogeneity is small relative to the spatial scale of interest. We show that the large (slow) scale behavior is described by a constant-coefficient diffusion equation under certain assumptions about the fast-scale advection velocity, and we determine a formula for the slow-scale diffusion coefficient in terms of the fast-scale parameters. We extend the homogenization result to predict invasion speeds for an advection-diffusion-reaction (ADR) model with directed dispersal. For periodic environments, the homogenization approximation of the solution of the AD model compares favorably with numerical simulations. Invasion speed approximations for the ADR model also compare favorably with numerical simulations when the spatial period is sufficiently small.
Modelling of pollen dispersion in the atmosphere: evaluation with a continuous 1β+1δ lidar
Sicard, Michaël; Izquierdo, Rebeca; Jorba, Oriol; Alarcón, Marta; Belmonte, Jordina; Comerón, Adolfo; De Linares, Concepción; Baldasano, José Maria
2018-04-01
Pollen allergenicity plays an important role on human health and wellness. It is thus of large public interest to increase our knowledge of pollen grain behavior in the atmosphere (source, emission, processes involved during their transport, etc.) at fine temporal and spatial scales. First simulations with the Barcelona Supercomputing Center NMMB/BSC-CTM model of Platanus and Pinus dispersion in the atmosphere were performed during a 5-day pollination event observed in Barcelona, Spain, between 27 - 31 March, 2015. The simulations are compared to vertical profiles measured with the continuous Barcelona Micro Pulse Lidar system. First results show that the vertical distribution is well reproduced by the model in shape, but not in intensity, the model largely underestimating in the afternoon. Guidelines are proposed to improve the dispersion of airborne pollen by numerical prediction models.
International Nuclear Information System (INIS)
Buske, D.
2011-01-01
The present contribution focuses on the question of radioactive material dispersion after discharge from a nuclear power plant in the context of micro-meteorology, i.e. an atmospheric dispersion model. The advection-diffusion equation with Fickian closure for the turbulence is solved for the atmospheric boundary layer where the eddy diffusivity coefficients and the wind profile are assumed to be space dependent. The model is solved in closed form using integral transform and spectral theory. Convergence of the solution is discussed in terms of a convergence criterion using a new interpretation of the Cardinal Theorem of Interpolation theory and Parseval's theorem. The solution is compared to other methods and model adequacy is analyzed. Model validation is performed against experimental data from a controlled release of radioactive material at the Itaorna Beach (Angra dos Reis, Rio de Janeiro state, Brazil, 1985). (author)
International Nuclear Information System (INIS)
Zhang, Bin; Yang, Gang
2014-01-01
A two dimensional (2D) micromorphic model is developed for monolayer hexagonal boron nitride (h-BN). Theoretical expressions of phonon dispersions for 2D crystals are derived based on the simplified governing equations of specialized three dimensional micromorphic crystals. The constitutive constants of governing equations of the h-BN micromorphic model are determined, which is performed by fitting the available phonon dispersions data of experimental measurements and first-principles calculations with our theoretical expressions. The obtained Young’s modulus and Poisson’s ratio of h-BN are comparable with the results of ab initio calculations and inelastic x-ray scattering experiments, thus the constitutive relations of the h-BN model are verified, which also indicates that mechanical properties of monolayer h-BN could be characterized by our 2D micromorphic model
Energy Technology Data Exchange (ETDEWEB)
Ma, Denglong [Fuli School of Food Equipment Engineering and Science, Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an 710049 (China); Zhang, Zaoxiao, E-mail: zhangzx@mail.xjtu.edu.cn [State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an 710049 (China); School of Chemical Engineering and Technology, Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an 710049 (China)
2016-07-05
Highlights: • The intelligent network models were built to predict contaminant gas concentrations. • The improved network models coupled with Gaussian dispersion model were presented. • New model has high efficiency and accuracy for concentration prediction. • New model were applied to indentify the leakage source with satisfied results. - Abstract: Gas dispersion model is important for predicting the gas concentrations when contaminant gas leakage occurs. Intelligent network models such as radial basis function (RBF), back propagation (BP) neural network and support vector machine (SVM) model can be used for gas dispersion prediction. However, the prediction results from these network models with too many inputs based on original monitoring parameters are not in good agreement with the experimental data. Then, a new series of machine learning algorithms (MLA) models combined classic Gaussian model with MLA algorithm has been presented. The prediction results from new models are improved greatly. Among these models, Gaussian-SVM model performs best and its computation time is close to that of classic Gaussian dispersion model. Finally, Gaussian-MLA models were applied to identifying the emission source parameters with the particle swarm optimization (PSO) method. The estimation performance of PSO with Gaussian-MLA is better than that with Gaussian, Lagrangian stochastic (LS) dispersion model and network models based on original monitoring parameters. Hence, the new prediction model based on Gaussian-MLA is potentially a good method to predict contaminant gas dispersion as well as a good forward model in emission source parameters identification problem.
International Nuclear Information System (INIS)
Ma, Denglong; Zhang, Zaoxiao
2016-01-01
Highlights: • The intelligent network models were built to predict contaminant gas concentrations. • The improved network models coupled with Gaussian dispersion model were presented. • New model has high efficiency and accuracy for concentration prediction. • New model were applied to indentify the leakage source with satisfied results. - Abstract: Gas dispersion model is important for predicting the gas concentrations when contaminant gas leakage occurs. Intelligent network models such as radial basis function (RBF), back propagation (BP) neural network and support vector machine (SVM) model can be used for gas dispersion prediction. However, the prediction results from these network models with too many inputs based on original monitoring parameters are not in good agreement with the experimental data. Then, a new series of machine learning algorithms (MLA) models combined classic Gaussian model with MLA algorithm has been presented. The prediction results from new models are improved greatly. Among these models, Gaussian-SVM model performs best and its computation time is close to that of classic Gaussian dispersion model. Finally, Gaussian-MLA models were applied to identifying the emission source parameters with the particle swarm optimization (PSO) method. The estimation performance of PSO with Gaussian-MLA is better than that with Gaussian, Lagrangian stochastic (LS) dispersion model and network models based on original monitoring parameters. Hence, the new prediction model based on Gaussian-MLA is potentially a good method to predict contaminant gas dispersion as well as a good forward model in emission source parameters identification problem.
Directory of Open Access Journals (Sweden)
Christoph Häni
2018-04-01
Full Text Available A controlled ammonia (NH3 release experiment was performed at a grassland site. The aim was to quantify the effect of dry deposition between the source and the receptors (NH3 measurement locations on emission rate estimates by means of inverse dispersion modelling. NH3 was released for three hours at a constant rate of Q = 6.29 mg s−1 from a grid of 36 orifices spread over an area of 250 m2. The increase in line-integrated NH3 concentration was measured with open-path optical miniDOAS devices at different locations downwind of the artificial source. Using a backward Lagrangian stochastic (bLS dispersion model (bLSmodelR, the fraction of the modelled release rate to the emitted NH3 ( Q bLS / Q was calculated from the measurements of the individual instruments. Q bLS / Q was found to be systematically lower than 1, on average between 0.69 and 0.91, depending on the location of the receptor. We hypothesized that NH3 dry deposition to grass and soil surfaces was the main factor responsible for the observed depletion of NH3 between source and receptor. A dry deposition algorithm based on a deposition velocity approach was included in the bLS modelling. Model deposition velocities were evaluated from a ‘big-leaf’ canopy resistance analogy. Canopy resistances (generally termed R c that provided Q bLS / Q = 1 ranged from 75 to 290 s m−1, showing that surface removal of NH3 by dry deposition can plausibly explain the original underestimation of Q bLS / Q . The inclusion of a dry deposition process in dispersion modelling is crucial for emission estimates, which are based on concentration measurements of depositing tracers downwind of homogeneous area sources or heterogeneously-distributed hot spots, such as, e.g., urine patches on pastures in the case of NH3.
Frequency dispersion analysis of thin dielectric MOS capacitor in a five-element model
Zhang, Xizhen; Zhang, Sujuan; Zhu, Huichao; Pan, Xiuyu; Cheng, Chuanhui; Yu, Tao; Li, Xiangping; Cheng, Yi; Xing, Guichao; Zhang, Daming; Luo, Xixian; Chen, Baojiu
2018-02-01
An Al/ZrO2/IL/n-Si (IL: interface layer) MOS capacitor has been fabricated by metal organic decomposition of ZrO2 and thermal deposition Al. We have measured parallel capacitance (C m) and parallel resistance (R m) versus bias voltage curves (C m, R m-V) at different AC signal frequency (f), and C m, R m-f curves at different bias voltage. The curves of C m, R m-f measurements show obvious frequency dispersion in the range of 100 kHz-2 MHz. The energy band profile shows that a large voltage is applied on the ZrO2 layer and IL at accumulation, which suggests possible dielectric polarization processes by some traps in ZrO2 and IL. C m, R m-f data are used for frequency dispersion analysis. To exclude external frequency dispersion, we have extracted the parameters of C (real MOS capacitance), R p (parallel resistance), C IL (IL capacitance), R IL (IL resistance) and R s (Si resistance) in a five-element model by using a three-frequency method. We have analyzed intrinsic frequency dispersion of C, R p, C IL, R IL and R s by studying the dielectric characteristics and Si surface layer characteristics. At accumulation, the dispersion of C and R p is attributed to dielectric polarization such as dipolar orientation and oxide traps. The serious dispersion of C IL and R IL are relative to other dielectric polarization, such as border traps and fixed oxide traps. The dispersion of R s is mainly attributed to contact capacitance (C c) and contact resistance (R c). At depletion and inversion, the frequency dispersion of C, R p, C IL, R IL, and R s are mainly attributed to the depletion layer capacitance (C D). The interface trap capacitance (C it) and interface trap resistance (R it) are not dominant for the dispersion of C, R p, C IL, R IL, and R s.
Modeling Solution of Nonlinear Dispersive Partial Differential Equations using the Marker Method
International Nuclear Information System (INIS)
Lewandowski, Jerome L.V.
2005-01-01
A new method for the solution of nonlinear dispersive partial differential equations is described. The marker method relies on the definition of a convective field associated with the underlying partial differential equation; the information about the approximate solution is associated with the response of an ensemble of markers to this convective field. Some key aspects of the method, such as the selection of the shape function and the initial loading, are discussed in some details
Modelling of U-Mo/Al Dispersion fuel fission induced swelling and creep
International Nuclear Information System (INIS)
Jeong, Gwan Yoon; Sohn, Dong Seong; Kim, Yeon Soo
2014-01-01
In a Dispersion fuel which U-Mo particles are dispersed in Al metal matrix, a similar phenomenon forming a bulge region was observed but it is difficult to quantify and construct a model for explaining creep and swelling because of its complex microstructure change during irradiation including interaction layer (IL) and porosity formation. In a Dispersion fuel meat, fission product induces fuel particles swelling and it has to be accommodated by the deformation of the Al matrix and newly formed IL during irradiation. Then, it is reasonable that stress from fuel swelling in the complex structure should be relaxed by local adjustments of particles, Al matrix, and IL. For analysis of U-Mo/Al Dispersion fuel creep, the creep of U-Mo particle, Al matrix, and IL should be considered. Moreover, not only fuel particle swelling and IL growth, but also fuel and Al matrix consumptions due to IL formation are accounted in terms of their volume fraction changes during irradiation. In this work, fuel particles, Al matrix and IL are treated in a way of homogenized constituents: Fuel particles, Al matrix and IL consist of an equivalent meat during irradiation. Meat volume swelling of two representative plates was measured: One (Plate A) was a pure Al matrix with 6g/cc uranium loading, the other (Plate B) a silicon added Al matrix with 8g/cc uranium loading. The meat swelling of calculated as a function of burnup. The meat swelling of calculation and measurement was compared and the creep rate coefficients for Al and IL were estimated by repetitions. Based on assumption that only the continuous phase of Al-IL combined matrix accommodated the stress from fuel particle swelling and it was allowed to have creep deformation, the homogenization modeling was performed. The meat swelling of two U-Mo/Al Dispersion fuel plates was modeled by using homogenization model
Modelling of U-Mo/Al Dispersion fuel fission induced swelling and creep
Energy Technology Data Exchange (ETDEWEB)
Jeong, Gwan Yoon; Sohn, Dong Seong [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Kim, Yeon Soo [Argonne National Laboratory, Argonne (United States)
2014-05-15
In a Dispersion fuel which U-Mo particles are dispersed in Al metal matrix, a similar phenomenon forming a bulge region was observed but it is difficult to quantify and construct a model for explaining creep and swelling because of its complex microstructure change during irradiation including interaction layer (IL) and porosity formation. In a Dispersion fuel meat, fission product induces fuel particles swelling and it has to be accommodated by the deformation of the Al matrix and newly formed IL during irradiation. Then, it is reasonable that stress from fuel swelling in the complex structure should be relaxed by local adjustments of particles, Al matrix, and IL. For analysis of U-Mo/Al Dispersion fuel creep, the creep of U-Mo particle, Al matrix, and IL should be considered. Moreover, not only fuel particle swelling and IL growth, but also fuel and Al matrix consumptions due to IL formation are accounted in terms of their volume fraction changes during irradiation. In this work, fuel particles, Al matrix and IL are treated in a way of homogenized constituents: Fuel particles, Al matrix and IL consist of an equivalent meat during irradiation. Meat volume swelling of two representative plates was measured: One (Plate A) was a pure Al matrix with 6g/cc uranium loading, the other (Plate B) a silicon added Al matrix with 8g/cc uranium loading. The meat swelling of calculated as a function of burnup. The meat swelling of calculation and measurement was compared and the creep rate coefficients for Al and IL were estimated by repetitions. Based on assumption that only the continuous phase of Al-IL combined matrix accommodated the stress from fuel particle swelling and it was allowed to have creep deformation, the homogenization modeling was performed. The meat swelling of two U-Mo/Al Dispersion fuel plates was modeled by using homogenization model.
Faroughi, S. A.; Huber, C.
2015-12-01
Crystal settling and bubbles migration in magmas have significant effects on the physical and chemical evolution of magmas. The rate of phase segregation is controlled by the force balance that governs the migration of particles suspended in the melt. The relative velocity of a single particle or bubble in a quiescent infinite fluid (melt) is well characterized; however, the interplay between particles or bubbles in suspensions and emulsions and its effect on their settling/rising velocity remains poorly quantified. We propose a theoretical model for the hindered velocity of non-Brownian emulsions of nondeformable droplets, and suspensions of spherical solid particles in the creeping flow regime. The model is based on three sets of hydrodynamic corrections: two on the drag coefficient experienced by each particle to account for both return flow and Smoluchowski effects and a correction on the mixture rheology to account for nonlocal interactions between particles. The model is then extended for mono-disperse non-spherical solid particles that are randomly oriented. The non-spherical particles are idealized as spheroids and characterized by their aspect ratio. The poly-disperse nature of natural suspensions is then taken into consideration by introducing an effective volume fraction of particles for each class of mono-disperse particles sizes. Our model is tested against new and published experimental data over a wide range of particle volume fraction and viscosity ratios between the constituents of dispersions. We find an excellent agreement between our model and experiments. We also show two significant applications for our model: (1) We demonstrate that hindered settling can increase mineral residence time by up to an order of magnitude in convecting magma chambers. (2) We provide a model to correct for particle interactions in the conventional hydrometer test to estimate the particle size distribution in soils. Our model offers a greatly improved agreement with
Pratt, D. T.
1984-01-01
An interactive computer code for simulation of a high-intensity turbulent combustor as a single point inhomogeneous stirred reactor was developed from an existing batch processing computer code CDPSR. The interactive CDPSR code was used as a guide for interpretation and direction of DOE-sponsored companion experiments utilizing Xenon tracer with optical laser diagnostic techniques to experimentally determine the appropriate mixing frequency, and for validation of CDPSR as a mixing-chemistry model for a laboratory jet-stirred reactor. The coalescence-dispersion model for finite rate mixing was incorporated into an existing interactive code AVCO-MARK I, to enable simulation of a combustor as a modular array of stirred flow and plug flow elements, each having a prescribed finite mixing frequency, or axial distribution of mixing frequency, as appropriate. Further increase the speed and reliability of the batch kinetics integrator code CREKID was increased by rewriting in vectorized form for execution on a vector or parallel processor, and by incorporating numerical techniques which enhance execution speed by permitting specification of a very low accuracy tolerance.
Stenzel, S.; Baumann-Stanzer, K.
2009-04-01
Dispersion modeling of accidental releases of toxic gases - Comparison of the models and their utility for the fire brigades. Sirma Stenzel, Kathrin Baumann-Stanzer In the case of accidental release of hazardous gases in the atmosphere, the emergency responders need a reliable and fast tool to assess the possible consequences and apply the optimal countermeasures. For hazard prediction and simulation of the hazard zones a number of air dispersion models are available. The most model packages (commercial or free of charge) include a chemical database, an intuitive graphical user interface (GUI) and automated graphical output for display the results, they are easy to use and can operate fast and effective during stress situations. The models are designed especially for analyzing different accidental toxic release scenarios ("worst-case scenarios"), preparing emergency response plans and optimal countermeasures as well as for real-time risk assessment and management. There are also possibilities for model direct coupling to automatic meteorological stations, in order to avoid uncertainties in the model output due to insufficient or incorrect meteorological data. Another key problem in coping with accidental toxic release is the relative width spectrum of regulations and values, like IDLH, ERPG, AEGL, MAK etc. and the different criteria for their application. Since the particulate emergency responders and organizations require for their purposes unequal regulations and values, it is quite difficult to predict the individual hazard areas. There are a quite number of research studies and investigations coping with the problem, anyway the end decision is up to the authorities. The research project RETOMOD (reference scenarios calculations for toxic gas releases - model systems and their utility for the fire brigade) was conducted by the Central Institute for Meteorology and Geodynamics (ZAMG) in cooperation with the Vienna fire brigade, OMV Refining & Marketing GmbH and
Li, Ping; Jiang, Li Jun; Bagci, Hakan
2018-01-01
It is well known that graphene demonstrates spatial dispersion properties, i.e., its conductivity is nonlocal and a function of spectral wave number (momentum operator) q. In this paper, to account for effects of spatial dispersion on transmission of high speed signals along graphene nano-ribbon (GNR) interconnects, a discontinuous Galerkin time-domain (DGTD) algorithm is proposed. The atomically-thick GNR is modeled using a nonlocal transparent surface impedance boundary condition (SIBC) incorporated into the DGTD scheme. Since the conductivity is a complicated function of q (and one cannot find an analytical Fourier transform pair between q and spatial differential operators), an exact time domain SIBC model cannot be derived. To overcome this problem, the conductivity is approximated by its Taylor series in spectral domain under low-q assumption. This approach permits expressing the time domain SIBC in the form of a second-order partial differential equation (PDE) in current density and electric field intensity. To permit easy incorporation of this PDE with the DGTD algorithm, three auxiliary variables, which degenerate the second-order (temporal and spatial) differential operators to first-order ones, are introduced. Regarding to the temporal dispersion effects, the auxiliary differential equation (ADE) method is utilized to eliminates the expensive temporal convolutions. To demonstrate the applicability of the proposed scheme, numerical results, which involve characterization of spatial dispersion effects on the transfer impedance matrix of GNR interconnects, are presented.
Combining a dispersal model with network theory to assess habitat connectivity.
Lookingbill, Todd R; Gardner, Robert H; Ferrari, Joseph R; Keller, Cherry E
2010-03-01
Assessing the potential for threatened species to persist and spread within fragmented landscapes requires the identification of core areas that can sustain resident populations and dispersal corridors that can link these core areas with isolated patches of remnant habitat. We developed a set of GIS tools, simulation methods, and network analysis procedures to assess potential landscape connectivity for the Delmarva fox squirrel (DFS; Sciurus niger cinereus), an endangered species inhabiting forested areas on the Delmarva Peninsula, USA. Information on the DFS's life history and dispersal characteristics, together with data on the composition and configuration of land cover on the peninsula, were used as input data for an individual-based model to simulate dispersal patterns of millions of squirrels. Simulation results were then assessed using methods from graph theory, which quantifies habitat attributes associated with local and global connectivity. Several bottlenecks to dispersal were identified that were not apparent from simple distance-based metrics, highlighting specific locations for landscape conservation, restoration, and/or squirrel translocations. Our approach links simulation models, network analysis, and available field data in an efficient and general manner, making these methods useful and appropriate for assessing the movement dynamics of threatened species within landscapes being altered by human and natural disturbances.
Li, Ping
2018-04-13
It is well known that graphene demonstrates spatial dispersion properties, i.e., its conductivity is nonlocal and a function of spectral wave number (momentum operator) q. In this paper, to account for effects of spatial dispersion on transmission of high speed signals along graphene nano-ribbon (GNR) interconnects, a discontinuous Galerkin time-domain (DGTD) algorithm is proposed. The atomically-thick GNR is modeled using a nonlocal transparent surface impedance boundary condition (SIBC) incorporated into the DGTD scheme. Since the conductivity is a complicated function of q (and one cannot find an analytical Fourier transform pair between q and spatial differential operators), an exact time domain SIBC model cannot be derived. To overcome this problem, the conductivity is approximated by its Taylor series in spectral domain under low-q assumption. This approach permits expressing the time domain SIBC in the form of a second-order partial differential equation (PDE) in current density and electric field intensity. To permit easy incorporation of this PDE with the DGTD algorithm, three auxiliary variables, which degenerate the second-order (temporal and spatial) differential operators to first-order ones, are introduced. Regarding to the temporal dispersion effects, the auxiliary differential equation (ADE) method is utilized to eliminates the expensive temporal convolutions. To demonstrate the applicability of the proposed scheme, numerical results, which involve characterization of spatial dispersion effects on the transfer impedance matrix of GNR interconnects, are presented.
DFT Modeling of Cross-Linked Polyethylene: Role of Gold Atoms and Dispersion Interactions.
Blaško, Martin; Mach, Pavel; Antušek, Andrej; Urban, Miroslav
2018-02-08
Using DFT modeling, we analyze the concerted action of gold atoms and dispersion interactions in cross-linked polyethylene. Our model consists of two oligomer chains (PEn) with 7, 11, 15, 19, or 23 carbon atoms in each oligomer cross-linked with one to three Au atoms through C-Au-C bonds. In structures with a single gold atom the C-Au-C bond is located in the central position of the oligomer. Binding energies (BEs) with respect to two oligomer radical fragments and Au are as high as 362-489 kJ/mol depending on the length of the oligomer chain. When the dispersion contribution in PEn-Au-PEn oligomers is omitted, BE is almost independent of the number of carbon atoms, lying between 293 and 296 kJ/mol. The dispersion energy contributions to BEs in PEn-Au-PEn rise nearly linearly with the number of carbon atoms in the PEn chain. The carbon-carbon distance in the C-Au-C moiety is around 4.1 Å, similar to the bond distance between saturated closed shell chains in the polyethylene crystal. BEs of pure saturated closed shell PEn-PEn oligomers are 51-187 kJ/mol. Both Au atoms and dispersion interactions contribute considerably to the creation of nearly parallel chains of oligomers with reasonably high binding energies.
Generation of shrimp waste-based dispersant for oil spill response.
Zhang, Kedong; Zhang, Baiyu; Song, Xing; Liu, Bo; Jing, Liang; Chen, Bing
2018-04-01
In this study, shrimp waste was enzymatically hydrolyzed to generate a green dispersant and the product was tested for crude oil dispersion in seawater. The hydrolysis process was first optimized based on the dispersant effectiveness (DE) of the product. The functional properties of the product were identified including stability, critical micelle concentration, and emulsification activity. Water was confirmed as a good solvent for dispersant generation when compared with three chemical solvents. The effects of salinity, mixing energy, and temperature on the dispersion of the Alaska North Slope (ANS) crude oil were examined. Microtox acute toxicity test was also conducted to evaluate the toxicity of the produced dispersant. In addition, DE of the product on three different types of crude oil, including ANS crude oil, Prudhoe Bay crude oil (PBC), and Arabian Light crude oil (ALC) was compared with that of the Corexit 9500, respectively. The research output could lead to a promising green solution to the oil spill problem and might result in many other environmental applications.
Response of the REWARD detection system to the presence of a Radiological Dispersal Device
International Nuclear Information System (INIS)
Luis, R.; Baptista, M.; Barros, S.; Marques, J.; Vaz, P.; Balbuena, J.; Disch, C.; Fleta, C.; Jumilla, C.; Lozano, M.
2015-01-01
In recent years an increased international concern has emerged about the radiological and nuclear (RN) threats associated with the illicit trafficking of nuclear and radioactive materials that could be potentially used for terrorist attacks. The objective of the REWARD (Real Time Wide Area Radiation Surveillance System) project, co-funded by the European Union 7. Framework Programme Security, consisted in building a mobile system for real time, wide area radiation surveillance, using a CdZnTe detector for gamma radiation and a neutron detector based on novel silicon technologies. The sensing unit includes a GPS system and a wireless communication interface to send the data remotely to a monitoring base station, where it will be analyzed in real time and correlated with historical data from the tag location, in order to generate an alarm when an abnormal situation is detected. Due to its portability and accuracy, the system will be extremely useful in many different scenarios such as nuclear terrorism, lost radioactive sources, radioactive contamination or nuclear accidents. This paper shortly introduces the REWARD detection system, depicts some terrorist threat scenarios involving radioactive sources and special nuclear materials and summarizes the simulation work undertaken during the past three years in the framework of the REWARD project. The main objective consisted in making predictions regarding the behavior of the REWARD system in the presence of a Radiological Dispersion Device (RDD), one of the reference scenarios foreseen for REWARD, using the Monte Carlo simulation program MCNP6. The reference scenario is characterized in detail, from the i) radiological protection, ii) radiation detection requirements and iii) communications points of view. Experimental tests were performed at the Fire Brigades Facilities in Rome and at the Naples Fire Brigades, and the results, which validate the simulation work, are presented and analyzed. The response of the REWARD
Response of the REWARD detection system to the presence of a Radiological Dispersal Device
Energy Technology Data Exchange (ETDEWEB)
Luis, R.; Baptista, M.; Barros, S.; Marques, J.; Vaz, P. [IST - Campus Tecnologico e Nuclear, Estrada Nacional 10 - km 139.7, 2695-066, Bobadela LRS (Portugal); Balbuena, J.; Disch, C. [Physical Institut, University of Freiburg Hermann-Herder-Str. 3 D-79104 Freiburg (Germany); Fleta, C.; Jumilla, C.; Lozano, M. [Instituto de Microelectronica de Barcelona - IMB-CNM, CSIC, E-08193 Bellaterra, Barcelona (Spain)
2015-07-01
In recent years an increased international concern has emerged about the radiological and nuclear (RN) threats associated with the illicit trafficking of nuclear and radioactive materials that could be potentially used for terrorist attacks. The objective of the REWARD (Real Time Wide Area Radiation Surveillance System) project, co-funded by the European Union 7. Framework Programme Security, consisted in building a mobile system for real time, wide area radiation surveillance, using a CdZnTe detector for gamma radiation and a neutron detector based on novel silicon technologies. The sensing unit includes a GPS system and a wireless communication interface to send the data remotely to a monitoring base station, where it will be analyzed in real time and correlated with historical data from the tag location, in order to generate an alarm when an abnormal situation is detected. Due to its portability and accuracy, the system will be extremely useful in many different scenarios such as nuclear terrorism, lost radioactive sources, radioactive contamination or nuclear accidents. This paper shortly introduces the REWARD detection system, depicts some terrorist threat scenarios involving radioactive sources and special nuclear materials and summarizes the simulation work undertaken during the past three years in the framework of the REWARD project. The main objective consisted in making predictions regarding the behavior of the REWARD system in the presence of a Radiological Dispersion Device (RDD), one of the reference scenarios foreseen for REWARD, using the Monte Carlo simulation program MCNP6. The reference scenario is characterized in detail, from the i) radiological protection, ii) radiation detection requirements and iii) communications points of view. Experimental tests were performed at the Fire Brigades Facilities in Rome and at the Naples Fire Brigades, and the results, which validate the simulation work, are presented and analyzed. The response of the REWARD
Sarout, Joel; Cazes, Emilie; Delle Piane, Claudio; Arena, Alessio; Esteban, Lionel
2017-08-01
We experimentally assess the impact of microstructure, pore fluid, and frequency on wave velocity, wave dispersion, and permeability in thermally cracked Carrara marble under effective pressure up to 50 MPa. The cracked rock is isotropic, and we observe that (1) P and S wave velocities at 500 kHz and the low-strain (S waves and 9% for P waves at 1 MPa, and (4) wave dispersion virtually vanishes above 30 MPa. Assuming no interactions between the cracks, effective medium theory is used to model the rock's elastic response and its permeability. P and S wave velocity data are jointly inverted to recover the crack density and effective aspect ratio. The permeability data are inverted to recover the cracks' effective radius. These parameters lead to a good agreement between predicted and measured wave velocities, dispersion and permeability up to 50 MPa, and up to a crack density of 0.5. The evolution of the crack parameters suggests that three deformation regimes exist: (1) contact between cracks' surface asperities up to 10 MPa, (2) progressive crack closure between 10 and 30 MPa, and (3) crack closure effectively complete above 30 MPa. The derived crack parameters differ significantly from those obtained by analysis of 2-D electron microscope images of thin sections or 3-D X-ray microtomographic images of millimeter-size specimens.
Hydrodynamic dispersion characteristics of lateral inflow into a river tested by a laboratory model
Directory of Open Access Journals (Sweden)
P. Y. Chou
2009-02-01
Full Text Available Groundwater and river-water have a different composition and interact in and below the riverbed. The riverbed-aquifer flux interactions have received growing interest because of their role in the exchange and transformation of nutrients and pollutants between rivers and the aquifer. In this research our main purpose is to identify the physical processes and characteristics needed for a numerical transport model, which includes the unsaturated recharge zone, the aquifer and the riverbed. In order to investigate such lateral groundwater inflow process, a laboratory J-shaped column experiment was designed. This study determined the transport parameters of the J-shaped column by fitting an analytical solution of the convective-dispersion equation for every flux on individual segments to the observed breakthrough curves of the resident concentration, and by inverse modelling for every flux simultaneously over the entire flow domain. The obtained transport-parameter relation was tested by numerical simulation using HYDRUS 2-D/3-D.
Four steady-state flux conditions (i.e. 0.5 cm hr^{−1}, 1 cm hr^{−1}, 1.5 cm hr^{−1} and 2 cm hr^{−1} were applied, transport parameters including pore water velocity and dispersivity were determined for both unsaturated and saturated sections along the column. Results showed that under saturated conditions the dispersivity was fairly constant and independent of the flux. In contrast, dispersivity under unsaturated conditions was flux dependent and increased at lower flux. For our porous medium the dispersion coefficient related best to the quotient of the pore water velocity divided by the water content. A simulation model of riverbed-aquifer flux interaction should take this into account.
Sutherland, Richard L.
2002-12-01
Polarization properties and electro-optical switching behavior of holographic polymer-dispersed liquid-crystal (HPDLC) reflection and transmission gratings are studied. A theoretical model is developed that combines anisotropic coupled-wave theory with an elongated liquid-crystal-droplet switching model and includes the effects of a statistical orientational distribution of droplet-symmetry axes. Angle- and polarization-dependent switching behaviors of HPDLC gratings are elucidated, and the effects on dynamic range are described. A new type of electro-optical switching not seen in ordinary polymer-dispersed liquid crystals, to the best of the author's knowledge, is presented and given a physical interpretation. The model provides valuable insight to the physics of these gratings and can be applied to the design of HPDLC holographic optical elements.
A numerical three-dimensional ocean general circulation and radionuclides dispersion model
International Nuclear Information System (INIS)
Chartier, M.; Marti, O.
1988-01-01
The dispersion of radioactive waste disposed of in the deep-sea or transferred from the atmosphere is a complex hydrodynamic problem concerned by space scales as large as the world ocean. The recent development in the high-speed computers has led to significant progress in ocean modelling and now allows a thorough improvement in the accuracy of the simulations of the nuclides dispersion in the sea. A three-dimensional ocean general circulation model has been recently developed in France for research and engineering purposes. The model solves the primitive equation of the ocean hydrodynamics and the advection-diffusion equation for any dissolved tracer. The code has been fully vectorized and multitasked on 1 to 4 processors of the CRAY-2
Description and validation of ERAD: An atmospheric dispersion model for high explosive detonations
Energy Technology Data Exchange (ETDEWEB)
Boughton, B.A.; DeLaurentis, J.M.
1992-10-01
The Explosive Release Atmospheric Dispersion (ERAD) model is a three-dimensional numerical simulation of turbulent atmospheric transport and diffusion. An integral plume rise technique is used to provide a description of the physical and thermodynamic properties of the cloud of warm gases formed when the explosive detonates. Particle dispersion is treated as a stochastic process which is simulated using a discrete time Lagrangian Monte Carlo method. The stochastic process approach permits a more fundamental treatment of buoyancy effects, calm winds and spatial variations in meteorological conditions. Computational requirements of the three-dimensional simulation are substantially reduced by using a conceptualization in which each Monte Carlo particle represents a small puff that spreads according to a Gaussian law in the horizontal directions. ERAD was evaluated against dosage and deposition measurements obtained during Operation Roller Coaster. The predicted contour areas average within about 50% of the observations. The validation results confirm the model`s representation of the physical processes.
International Nuclear Information System (INIS)
Kim, Joo Yeon; Ryu, Hyung Joon; Jung, Gyu Hwan; Lee, Jai Ki
2011-01-01
The dependency within the sequential realizations in the generated Markov chains and their reliabilities are monitored by introducing the autocorrelation and the potential scale reduction factor (PSRF) by model parameters in the atmospheric dispersion. These two diagnostics have been applied for the posterior quantities of the release point and the release rate inferred through the inverse tracking of unknown model parameters for the Yonggwang atmospheric tracer experiment in Korea. The autocorrelations of model parameters are decreasing to low values approaching to zero with increase of lag, resulted in decrease of the dependencies within the two sequential realizations. Their PSRFs are reduced to within 1.2 and the adequate simulation number recognized from these results. From these two convergence diagnostics, the validation of Markov chains generated have been ensured and PSRF then is especially suggested as the efficient tool for convergence monitoring for the source reconstruction in atmospheric dispersion. (author)
Harmonisation within atmospheric dispersion modelling for regulatory purposes. Proceedings. Vol. 1
International Nuclear Information System (INIS)
Suppan, P.
2004-01-01
Dispersion modelling has proved to be a very effective tool to assess the environmental impact of human activities to be a very effective tool to assess the environmental impact of human activities on air quality already at the early planning stage. Environmental assessments during planning are required by the EU directive 85/337/EEC. Only models can give detailed information on the distribution of pollutants with high spatial and temporal resolution, while they allow the decision-maker to devise a range of scenarios, in which the various processes determining the environmental impact can be easily simulated and changed. In June 1991, the Joint Research Centre of the European Commission started an initiative on the sharing of information and possible harmonisation of new approaches to atmospheric disperion modelling and model evaluation. This initiative has fostered a series of conferences that have be concerned with improvement of ''modelling culture'' in Europe. The 9th International Conference on Harmonisation within Atmospheric dispersion Modelling for Regulatory Purposes in Garmisch-Partenkirchen, in Germany/Bavaria, 1-4 June, 2004, will continue the efforts of the previous conferences. The conference has a role as a forum where users and decision-makers can bring their requirements to the attention of scientists. It is also a natural forum for discussing environmental issues related to the European Union enlargement process. The scope of this conference is covered by the following topics: 1. Validation and inter-comparison of models: Model evaluation methodology - 2. Experiences with implementation of EU directives: regulatory modelling - 3. Short distance dispersion modelling - 4. Urban scale and street canyon modelling: Meteorology and air quality - 5. Mesoscale meteorology and air quality modelling - 6. Environmental impact assessment: Air pollution management and decision support systems. (orig.)
Model calculating annual mean atmospheric dispersion factor for coastal site of nuclear power plant
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper describes an atmospheric dispersion field experiment performed on the coastal site of nuclear power plant in the east part of China during 1995 to 1996. The three-dimension joint frequency are obtained by hourly observation of wind and temperature on a 100m high tower; the frequency of the “event day of land and sea breezes” are given by observation of surface wind and land and sea breezes; the diffusion parameters are got from measurements of turbulent and wind tunnel simulation test.A new model calculating the annual mean atmospheric dispersion factor for coastal site of nuclear power plant is developed and established.This model considers not only the effect from mixing release and mixed layer but also the effect from the internal boundary layer and variation of diffusion parameters due to the distance from coast.The comparison between results obtained by the new model and current model shows that the ratio of annual mean atmospheric dispersion factor gained by the new model and the current one is about 2.0.
Comparison of the local-scale atmospheric dispersion model Cedrat with 85KR measurements
International Nuclear Information System (INIS)
Rennesson, M.; Devin, P.; Maro, D.; Fitamant, M.L.; Bouland, P.
2004-01-01
An accurate model of atmospheric dispersion of radionuclides over the complex terrain of the La Hague reprocessing plant (North Cotentin, France) has been developed by COGEMA, in partnership with Paris VI University. This model, called CEDRAT 1.0.1 (operational since October 2002), takes into account areas typically outside the validity limits of Gaussian models: relief and building influence, short-distance (beyond 500 m from the release point) and stable atmospheric conditions. The modelling tool is based on an original method: a 2D-meshed model for flow resolution at permanent rate in the prevailing wind direction, and a 3D description of the dispersion phenomena, taking into account wet and dry deposits, at permanent or transitory rate. This leads to an effective compromise between rapidity (45 min on a 6000 nodes grid, with a standard PC), robustness and accuracy, coupled with a user-friendly interface. Primarily the validation process consisted of a comparison with the 3D complex dispersion reference model MERCURE, developed by EDF. Then, MERCURE and CEDRAT results were compared on real release scenario basis, for which actual meteorological conditions and tracer data collected at monitoring stations around the site were known. To enlarge this validation process, a second level of comparison was made in collaboration with a IRSN Cherbourg team, through different field experiments, which provided both ground and elevated level measurements (collected with a captive balloon), for different stability classes of the atmosphere. The plume tracer is krypton 85, an inert gas released from a height of 100 m. Thus, the aim of this paper is to present the original method to describe short distance dispersion over complex terrain and its validation enrichment for stability conditions and areas not yet observed, through wind and cross-wind Atmospheric Transfer Coefficients comparisons, at both ground and elevated levels. (author)
Spatially-varying surface roughness and ground-level air quality in an operational dispersion model
International Nuclear Information System (INIS)
Barnes, M.J.; Brade, T.K.; MacKenzie, A.R.; Whyatt, J.D.; Carruthers, D.J.; Stocker, J.; Cai, X.; Hewitt, C.N.
2014-01-01
Urban form controls the overall aerodynamic roughness of a city, and hence plays a significant role in how air flow interacts with the urban landscape. This paper reports improved model performance resulting from the introduction of variable surface roughness in the operational air-quality model ADMS-Urban (v3.1). We then assess to what extent pollutant concentrations can be reduced solely through local reductions in roughness. The model results suggest that reducing surface roughness in a city centre can increase ground-level pollutant concentrations, both locally in the area of reduced roughness and downwind of that area. The unexpected simulation of increased ground-level pollutant concentrations implies that this type of modelling should be used with caution for urban planning and design studies looking at ventilation of pollution. We expect the results from this study to be relevant for all atmospheric dispersion models with urban-surface parameterisations based on roughness. -- Highlights: • Spatially variable roughness improved performance of an operational model. • Scenario modelling explored effect of reduced roughness on air pollution. • Reducing surface roughness can increase modelled ground-level pollution. • Damped vertical mixing outweighs increased horizontal advection in model study. • Result should hold for any model with a land-surface coupling based on roughness. -- Spatially varying roughness improves model simulations of urban air pollutant dispersion. Reducing roughness does not always decrease ground-level pollution concentrations
Comparison of numerical models for calculating dispersion from accidental releases of pollutants
Energy Technology Data Exchange (ETDEWEB)
Pepper, D W [Savannah River Lab., Aiken, SC; Cooper, R E; Baker, A J
1982-01-01
A modular, data-based system approach has been developed to facilitate computational simulation of multi-dimensional pollutant dispersion in atmospheric, steam, estuary, and groundwater applications. This system is used to assess effects of accidental releases of pollutants to the environment. Model sophistication ranges from simple statistical to complex three-dimensional numerical methods. The system used specifies desired degree of model sophistication from a terminal. The model used depends on the particular type of problem being solved, and on a basis of merit related to computer cost. The results of prediction for several model problems are presented.
Development and application of dispersive soft ferrite models for time-domain simulation
International Nuclear Information System (INIS)
DeFord, J.F.; Kamin, G.; Craig, G.D.; Walling, L.
1992-01-01
Ferrite has a variety of applications in accelerator components, and the capability to model this magnetic material in the time domain is an important adjunct to currently available accelerator modeling tool. We describe in this report a material model we have developed for the magnetic characteristics of PE11BL, the ferrite found in the ETA-II (Experimental Test Accelerator-II) induction module. This model, which includes the important magnetic dispersion effects found in most soft ferrites, has been implemented in 1-D and 2-D finite-difference time-domain (FDTD) electromagnetic simulators, and comparisons with analytic and experimental results are presented
Energy Technology Data Exchange (ETDEWEB)
Banerjee, T., E-mail: tirthankaronline@gmail.com [Department of Environmental Science, G.B. Pant University of Agriculture and Technology, Pantnagar, U.S. Nagar, Uttarakhand 263 145 (India); Barman, S.C., E-mail: scbarman@yahoo.com [Department of Environmental Monitoring, Indian Institute of Toxicology Research, Post Box No. 80, Mahatma Gandhi Marg, Lucknow-226 001, Uttar Pradesh (India); Srivastava, R.K., E-mail: rajeevsrivastava08@gmail.com [Department of Environmental Science, G.B. Pant University of Agriculture and Technology, Pantnagar, U.S. Nagar, Uttarakhand 263 145 (India)
2011-04-15
Source-contribution assessment of ambient NO{sub 2} concentration was performed at Pantnagar, India through simulation of two urban mathematical dispersive models namely Gaussian Finite Line Source Model (GFLSM) and Industrial Source Complex Model (ISCST-3) and model performances were evaluated. Principal approaches were development of comprehensive emission inventory, monitoring of traffic density and regional air quality and conclusively simulation of urban dispersive models. Initially, 18 industries were found responsible for emission of 39.11 kg/h of NO{sub 2} through 43 elevated stacks. Further, vehicular emission potential in terms of NO{sub 2} was computed as 7.1 kg/h. Air quality monitoring delineates an annual average NO{sub 2} concentration of 32.6 {mu}g/m{sup 3}. Finally, GFLSM and ISCST-3 were simulated in conjunction with developed emission inventories and existing meteorological conditions. Models simulation indicated that contribution of NO{sub 2} from industrial and vehicular source was in a range of 45-70% and 9-39%, respectively. Further, statistical analysis revealed satisfactory model performance with an aggregate accuracy of 61.9%. - Research highlights: > Application of dispersion modeling for source-contribution assessment of ambient NO{sub 2}. > Inventorization revealed emission from industry and vehicles was 39.11 and 7.1 kg/h. > GFLSM revealed that vehicular pollution contributes a range of 9.0-38.6%. > Source-contribution of 45-70% was found for industrial emission through ISCST-3. > Aggregate performance of both models shows good agreement with an accuracy of 61.9%. - Development of industrial and vehicular inventory in terms of ambient NO{sub 2} for model simulation at Pantnagar, India and model validation revealed satisfactory outcome.
International Nuclear Information System (INIS)
Uwaba, Tomoyuki; Ukai, Shigeharu; Asaga, Takeo
2002-03-01
Bundle Duct Interaction (BDI) is one of the life limiting factors of a FBR fuel subassembly. Under the BDI condition, the fuel pin dispersion would occur mainly by the deviation of the wire position due to the irradiation. In this study the effect of the dispersion on the bundle deformation was evaluated by using the BAMBOO code and following results were obtained. (1) A new contact analysis model was introduced in BAMBOO code. This model considers the contact condition at the axial position other than the nodal point of the beam element that composes the fuel pin. This improvement made it possible in the bundle deformation analysis to cause fuel pin dispersion due to the deviations of the wire position. (2) This model was validated with the results of the out-of-pile compression test with the wire deviation. The calculated pin-to-duct and pin-to-pin clearances with the dispersion model almost agreed with the test results. Therefore it was confirmed that the BAMBOO code reasonably predicts the bundle deformation with the dispersion. (3) In the dispersion bundle the pin-to-pin clearances widely scattered. And the minimum pin-to-duct clearance increased or decreased depending on the dispersion condition compared to the no-dispersion bundle. This result suggests the possibility that the considerable dispersion would affect the thermal integrity of the bundle. (author)
Directory of Open Access Journals (Sweden)
Anjaneyulu Yerramilli
2008-12-01
Full Text Available Coastal atmospheric conditions widely vary from those over inland due to the land-sea interface, temperature contrast and the consequent development of local circulations. In this study a field meteorological experiment was conducted to measure vertical structure of boundary layer during the period 25-29 June, 2007 at three locations Seabee base, Harrison and Wiggins sites in the Mississippi coast. A GPS Sonde along with slow ascent helium balloon and automated weather stations equipped with slow and fast response sensors were used in the experiment. GPS sonde were launched at three specific times (0700 LT, 1300 LT and 1800 LT during the experiment days. The observations indicate shallow boundary layer near the coast which gradually develops inland. The weather research and forecasting (WRF meso-scale atmospheric model and a Lagrangian particle dispersion model (HYSPLIT are used to simulate the lower atmospheric flow and dispersion in a range of 100 km from the coast for 28-30 June, 2007. The simulated meteorological parameters were compared with the experimental observations. The meso-scale model results show significant temporal and spatial variations in the meteorological fields as a result of development of sea breeze flow, its coupling with the large scale flow field and the ensuing alteration in the mixing depth across the coast. Simulated ground-level concentrations of SO2 from four elevated point sources located along the coast indicate diurnal variation and impact of the local sea-land breeze on the direction of the plume. Model concentration levels were highest during the stable morning condition and during the sea-breeze time in the afternoon. The highest concentrations were found up to 40 km inland during sea breeze time. The study illustrates the application of field meteorological observations for the validation of WRF which is coupled to HYSPLIT for dispersion assessment in the coastal region.
Radiogenomics and radiotherapy response modeling
El Naqa, Issam; Kerns, Sarah L.; Coates, James; Luo, Yi; Speers, Corey; West, Catharine M. L.; Rosenstein, Barry S.; Ten Haken, Randall K.
2017-08-01
Advances in patient-specific information and biotechnology have contributed to a new era of computational medicine. Radiogenomics has emerged as a new field that investigates the role of genetics in treatment response to radiation therapy. Radiation oncology is currently attempting to embrace these recent advances and add to its rich history by maintaining its prominent role as a quantitative leader in oncologic response modeling. Here, we provide an overview of radiogenomics starting with genotyping, data aggregation, and application of different modeling approaches based on modifying traditional radiobiological methods or application of advanced machine learning techniques. We highlight the current status and potential for this new field to reshape the landscape of outcome modeling in radiotherapy and drive future advances in computational oncology.
Campo, Jochen; Wenseleers, Wim; Hales, Joel M; Makarov, Nikolay S; Perry, Joseph W
2012-08-16
A practical yet accurate dispersion model for the molecular first hyperpolarizability β is presented, incorporating both homogeneous and inhomogeneous line broadening because these affect the β dispersion differently, even if they are indistinguishable in linear absorption. Consequently, combining the absorption spectrum with one free shape-determining parameter Ginhom, the inhomogeneous line width, turns out to be necessary and sufficient to obtain a reliable description of the β dispersion, requiring no information on the homogeneous (including vibronic) and inhomogeneous line broadening mechanisms involved, providing an ideal model for practical use in extrapolating experimental nonlinear optical (NLO) data. The model is applied to the efficient NLO chromophore picolinium quinodimethane, yielding an excellent fit of the two-photon resonant wavelength-dependent data and a dependable static value β0 = 316 × 10(-30) esu. Furthermore, we show that including a second electronic excited state in the model does yield an improved description of the NLO data at shorter wavelengths but has only limited influence on β0.
Abril, Gabriela A.; Wannaz, Eduardo D.; Mateos, Ana C.; Pignata, María L.
2014-01-01
The influence of a cement plant that incinerates industrial waste on the air quality of a region in the province of Córdoba, Argentina, was assessed by means of biomonitoring studies (effects of immission) and atmospheric dispersion (effects of emission) of PM10 with the application of the ISC3 model (Industrial Source Complex) developed by the USEPA (Environmental Protection Agency). For the biomonitoring studies, samples from the epiphyte plant Tillandsia capillaris Ruíz & Pav. f. capillaris were transplanted to the vicinities of the cement plant in order to determine the physiological damage and heavy metal accumulation (Ca, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb). For the application of the ISC3 model, point and area sources from the cement plant were considered to obtain average PM10 concentration results from the biomonitoring exposure period. This model permitted it to be determined that the emissions from the cement plant (point and area sources) were confined to the vicinities, without significant dispersion in the study area. This was also observed in the biomonitoring study, which identified Ca, Cd and Pb, pH and electric conductivity (EC) as biomarkers of this cement plant. Vehicular traffic emissions and soil re-suspension could be observed in the biomonitors, giving a more complete scenario. In this study, biomonitoring studies along with the application of atmospheric dispersion models, allowed the atmospheric pollution to be assessed in more detail.
Modelling larval dispersal dynamics of common sole (Solea solea) along the western Iberian coast
Tanner, Susanne E.; Teles-Machado, Ana; Martinho, Filipe; Peliz, Álvaro; Cabral, Henrique N.
2017-08-01
Individual-based coupled physical-biological models have become the standard tool for studying ichthyoplankton dynamics and assessing fish recruitment. Here, common sole (Solea solea L.), a flatfish of high commercial importance in Europe was used to evaluate transport of eggs and larvae and investigate the connectivity between spawning and nursery areas along the western Iberian coast as spatio-temporal variability in dispersal and recruitment patterns can result in very strong or weak year-classes causing large fluctuations in stock size. A three-dimensional particle tracking model coupled to Regional Ocean Modelling System model was used to investigate variability of sole larvae dispersal along the western Iberian coast over a five-year period (2004-2009). A sensitivity analysis evaluating: (1) the importance of diel vertical migrations of larvae and (2) the size of designated recruitment areas was performed. Results suggested that connectivity patterns of sole larvae dispersal and their spatio-temporal variability are influenced by the configuration of the coast with its topographical structures and thus the suitable recruitment area available as well as the wind-driven mesoscale circulation along the Iberian coast.
Short-term dispersal response of an endangered Australian lizard varies with time of year.
Directory of Open Access Journals (Sweden)
Mehregan Ebrahimi
Full Text Available Dispersal is an important component in the demography of animal populations. Many animals show seasonal changes in their tendency to disperse, reflecting changes in resource availability, mating opportunities, or in population age structure at the time when new offspring enter the population. Understanding when and why dispersal occurs can be important for the management of endangered species. The pygmy bluetongue lizard is an endangered Australian species that occupies and defends single burrow refuges for extended periods of time, rarely moving far from the burrow entrance. However, previous pitfall trapping data have suggested movement of adult males in spring and of juveniles in autumn of each year. In the current study we compared behaviours of adult lizards each month, over the spring-summer activity period over two consecutive field seasons, to provide deeper understanding of the seasonal dispersal pattern. We released adult pygmy bluetongue lizards into a central area, provided with artificial burrows, within large enclosures, and monitored the behaviour and movements of the released lizards over a four day period. There was a consistent decline in time spent basking, amount of movement around burrow entrances, and rates of dispersal from the central release area from early spring to late summer. Results could be relevant to understanding and managing natural populations and for any translocation attempts of this endangered lizard species.
Tuma, M. Carolina; Zill, Andrew; Le Bot, Nathalie; Vernos, Isabelle; Gelfand, Vladimir
1998-01-01
Melanophores move pigment organelles (melanosomes) from the cell center to the periphery and vice-versa. These bidirectional movements require cytoplasmic microtubules and microfilaments and depend on the function of microtubule motors and a myosin. Earlier we found that melanosomes purified from Xenopus melanophores contain the plus end microtubule motor kinesin II, indicating that it may be involved in dispersion (Rogers, S.L., I.S. Tint, P.C. Fanapour, and V.I. Gelfand. 1997. Proc. Natl. Acad. Sci. USA. 94: 3720–3725). Here, we generated a dominant-negative construct encoding green fluorescent protein fused to the stalk-tail region of Xenopus kinesin-like protein 3 (Xklp3), the 95-kD motor subunit of Xenopus kinesin II, and introduced it into melanophores. Overexpression of the fusion protein inhibited pigment dispersion but had no effect on aggregation. To control for the specificity of this effect, we studied the kinesin-dependent movement of lysosomes. Neither dispersion of lysosomes in acidic conditions nor their clustering under alkaline conditions was affected by the mutant Xklp3. Furthermore, microinjection of melanophores with SUK4, a function-blocking kinesin antibody, inhibited dispersion of lysosomes but had no effect on melanosome transport. We conclude that melanosome dispersion is powered by kinesin II and not by conventional kinesin. This paper demonstrates that kinesin II moves membrane-bound organelles. PMID:9852150
Pavement Aging Model by Response Surface Modeling
Directory of Open Access Journals (Sweden)
Manzano-Ramírez A.
2011-10-01
Full Text Available In this work, surface course aging was modeled by Response Surface Methodology (RSM. The Marshall specimens were placed in a conventional oven for time and temperature conditions established on the basis of the environment factors of the region where the surface course is constructed by AC-20 from the Ing. Antonio M. Amor refinery. Volatilized material (VM, load resistance increment (ΔL and flow resistance increment (ΔF models were developed by the RSM. Cylindrical specimens with real aging were extracted from the surface course pilot to evaluate the error of the models. The VM model was adequate, in contrast (ΔL and (ΔF models were almost adequate with an error of 20 %, that was associated with the other environmental factors, which were not considered at the beginning of the research.
Ahmad, H.; Karim, M. R.; Rahman, B. M. A.
2018-03-01
A rigorous numerical investigation has been carried out through dispersion engineering of chalcogenide rib waveguide for near-infrared to mid-infrared ultraflat broadband supercontinuum generation in all-normal group-velocity dispersion regime. We propose a novel design of a 1-cm-long air-clad rib waveguide which is made from {Ge}_{11.5} {As}_{24} {Se}_{64.5} chalcogenide glass as the core with either silica or {Ge}_{11.5} {As}_{24} {S}_{64.5} chalcogenide glass as a lower cladding separately. A broadband ultraflat supercontinuum spanning from 1300 to 1900 nm could be generated when pumped at 1.55 μ {m} with a low input peak power of 100 W. Shifting the pump to 2 μ {m}, the supercontinuum spectra extended in the mid-infrared region up to 3400 nm with a moderate-input peak power of 500 W. To achieve further extension in mid-infrared, we excite our optimized rib waveguide in both the anomalous and all-normal dispersion pumping regions at 3.1 μ {m} with a largest input peak power of 3 kW. In the case of anomalous dispersion region pumping, numerical analysis shows that supercontinuum spectrum can be extended in the mid-infrared up to 10 μ {m}, although this contains high spectral amplitude fluctuations over the entire bandwidth which limits the supercontinuum sources in the field of high precision measurement applications. On the other hand, by optimizing a rib waveguide geometry for pumping in all-normal dispersion region, we are able to generate a smooth and flat-top coherent supercontinuum spectrum with a moderate bandwidth spanning the wavelength range 2-5.5 μ {m} with less than 5 dB spectral fluctuation over the entire output bandwidth. Our proposed design is highly suitable for making on-chip SC light sources for a variety of applications such as biomedical imaging, and environmental and industrial sensing in the mid-infrared region.
Modeling a failure criterion for U-Mo/Al dispersion fuel
Oh, Jae-Yong; Kim, Yeon Soo; Tahk, Young-Wook; Kim, Hyun-Jung; Kong, Eui-Hyun; Yim, Jeong-Sik
2016-05-01
The breakaway swelling in U-Mo/Al dispersion fuel is known to be caused by large pore formation enhanced by interaction layer (IL) growth between fuel particles and Al matrix. In this study, a critical IL thickness was defined as a criterion for the formation of a large pore in U-Mo/Al dispersion fuel. Specifically, the critical IL thickness is given when two neighboring fuel particles come into contact with each other in the developed IL. The model was verified using the irradiation data from the RERTR tests and KOMO-4 test. The model application to full-sized sample irradiations such as IRISs, FUTURE, E-FUTURE, and AFIP-1 tests resulted in conservative predictions. The parametric study revealed that the fuel particle size and the homogeneity of the fuel particle distribution are influential for fuel performance.
Modeling a failure criterion for U–Mo/Al dispersion fuel
Energy Technology Data Exchange (ETDEWEB)
Oh, Jae-Yong, E-mail: tylor@kaeri.re.kr [Korea Atomic Energy Research Institute, 111, Daedeok-Daero 989 Beon-Gil, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Kim, Yeon Soo [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Tahk, Young-Wook; Kim, Hyun-Jung; Kong, Eui-Hyun; Yim, Jeong-Sik [Korea Atomic Energy Research Institute, 111, Daedeok-Daero 989 Beon-Gil, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of)
2016-05-15
The breakaway swelling in U–Mo/Al dispersion fuel is known to be caused by large pore formation enhanced by interaction layer (IL) growth between fuel particles and Al matrix. In this study, a critical IL thickness was defined as a criterion for the formation of a large pore in U–Mo/Al dispersion fuel. Specifically, the critical IL thickness is given when two neighboring fuel particles come into contact with each other in the developed IL. The model was verified using the irradiation data from the RERTR tests and KOMO-4 test. The model application to full-sized sample irradiations such as IRISs, FUTURE, E-FUTURE, and AFIP-1 tests resulted in conservative predictions. The parametric study revealed that the fuel particle size and the homogeneity of the fuel particle distribution are influential for fuel performance.
Dispersion modeling of accidental releases of toxic gases - utility for the fire brigades.
Stenzel, S.; Baumann-Stanzer, K.
2009-09-01
Several air dispersion models are available for prediction and simulation of the hazard areas associated with accidental releases of toxic gases. The most model packages (commercial or free of charge) include a chemical database, an intuitive graphical user interface (GUI) and automated graphical output for effective presentation of results. The models are designed especially for analyzing different accidental toxic release scenarios ("worst-case scenarios”), preparing emergency response plans and optimal countermeasures as well as for real-time risk assessment and management. The research project RETOMOD (reference scenarios calculations for toxic gas releases - model systems and their utility for the fire brigade) was conducted by the Central Institute for Meteorology and Geodynamics (ZAMG) in cooperation with the Viennese fire brigade, OMV Refining & Marketing GmbH and Synex Ries & Greßlehner GmbH. RETOMOD was funded by the KIRAS safety research program of the Austrian Ministry of Transport, Innovation and Technology (www.kiras.at). The main tasks of this project were 1. Sensitivity study and optimization of the meteorological input for modeling of the hazard areas (human exposure) during the accidental toxic releases. 2. Comparison of several model packages (based on reference scenarios) in order to estimate the utility for the fire brigades. For the purpose of our study the following models were tested and compared: ALOHA (Areal Location of Hazardous atmosphere, EPA), MEMPLEX (Keudel av-Technik GmbH), Trace (Safer System), Breeze (Trinity Consulting), SAM (Engineering office Lohmeyer). A set of reference scenarios for Chlorine, Ammoniac, Butane and Petrol were proceed, with the models above, in order to predict and estimate the human exposure during the event. Furthermore, the application of the observation-based analysis and forecasting system INCA, developed in the Central Institute for Meteorology and Geodynamics (ZAMG) in case of toxic release was
Comparison of different passive dispersion models for the simulation of a given release
International Nuclear Information System (INIS)
Wendum, D.; Musson-Genon, L.
1996-01-01
For internal needs of Electricite de France (dispersion computations of radioactive effluents during nuclear emergency situations, simulations of chemical pollution on the vicinity of thermal power plants), different models of passive dispersion in the atmosphere have been developed at the R and D D. This report presents the comparison of the performances of three such models: DIFTRA (Lagrangian puff model, with operational goal), DIFEUL (three dimensional Eulerian) and DiFPAR (Monte-Carlo particle model). The aim of this intercomparison is to assess the model differences of concentration values computed during an academic release in real meteorological conditions. The obtained results give inter-model differences of the same order as the model vs. experience differences observed during an international model comparison experiment using data of the Chernobyl release, the ATMES exercise. In a future study we plan to compare the results of these models to the results of an international tracer campaign named ETEX95, during which a passive tracer cloud has been followed over Europe. (author). 13 refs., 8 figs
Experimental and Numerical Modelling of CO2 Atmospheric Dispersion in Hazardous Gas Emission Sites.
Gasparini, A.; sainz Gracia, A. S.; Grandia, F.; Bruno, J.
2015-12-01
Under stable atmospheric conditions and/or in presence of topographic depressions, CO2 concentrations can reach high values resulting in lethal effect to living organisms. The distribution of denser than air gases released from the underground is governed by gravity, turbulence and dispersion. Once emitted, the gas distribution is initially driven by buoyancy and a gas cloud accumulates on the ground (gravitational phase); with time the density gradient becomes less important due to dispersion or mixing and gas distribution is mainly governed by wind and atmospheric turbulence (passive dispersion phase). Natural analogues provide evidences of the impact of CO2 leakage. Dangerous CO2 concentration in atmosphere related to underground emission have been occasionally reported although the conditions favouring the persistence of such a concentration are barely studied.In this work, the dynamics of CO2 in the atmosphere after ground emission is assessed to quantify their potential risk. Two approaches have been followed: (1) direct measurement of air concentration in a natural emission site, where formation of a "CO2 lake" is common and (2) numerical atmospheric modelling. Two sites with different morphology were studied: (a) the Cañada Real site, a flat terrain in the Volcanic Field of Campo de Calatrava (Spain); (b) the Solforata di Pomezia site, a rough terrain in the Alban Hills Volcanic Region (Italy). The comparison between field data and model calculations reveal that numerical dispersion models are capable of predicting the formation of CO2 accumulation over the ground as a consequence of underground gas emission. Therefore, atmospheric modelling could be included as a valuable methodology in the risk assessment of leakage in natural degassing systems and in CCS projects. Conclusions from this work provide clues on whether leakage may be a real risk for humans and under which conditions this risk needs to be included in the risk assessment.
International Nuclear Information System (INIS)
Klotz, D.; Moser, H.
1980-01-01
The object of the research project is to assess the hydrodynamic dispersion of labelling material solutions in special ground water lines based on measurements of the ground water flow rate and on the sedimentological properties of the natural ground water line present. The investigations were carried out in the laboratory in a three-dimensional ground water flow model and in column systems with HTO as tracer. (orig./HP) [de
Two-Fluid Models for Simulating Dispersed Multiphase Flows-A Review
Directory of Open Access Journals (Sweden)
L.X. Zhou
2009-01-01
Full Text Available The development of two-fluid models for simulating dispersed multiphase flows (gas-particle, gas-droplet, bubble-liquid, liquid-particle flows by the present author within the last 20 years is systematically reviewed. The two-fluid models based on Reynolds expansion, time averaging and mass-weighed averaging, and also PDF transport equations are described. Different versions of two-phase turbulence models, including the unified second-order moment (USM and k-ε-kp models, the DSM-PDF model, the SOM-MC model, the nonlinear k-e-kp model, and the USM-Θ model for dense gas-particle flows and their application and experimental validation are discussed.
Applications of complex terrain meteorological models to emergency response management
International Nuclear Information System (INIS)
Yamada, Tetsuji; Leone, J.M. Jr.; Rao, K.S.; Dickerson, M.H.; Bader, D.C.; Williams, M.D.
1989-01-01
The Office of Health and Environmental Research (OHER), US Department of Energy (DOE), has supported the development of mesoscale transport and diffusion and meteorological models for several decades. The model development activities are closely tied to the OHER field measurement program which has generated a large amount of meteorological and tracer gas data that have been used extensively to test and improve both meteorological and dispersion models. This paper briefly discusses the history of the model development activities associated with the OHER atmospheric science program. The discussion will then focus on how results from this program have made their way into the emergency response community in the past, and what activities are presently being pursued to improve real-time emergency response capabilities. Finally, fruitful areas of research for improving real-time emergency response modeling capabilities are suggested. 35 refs., 5 figs
Sea Outfall Design Based on a Stochastic Transport/Dispersion Model
DEFF Research Database (Denmark)
Larsen, Torben
1983-01-01
/dispersion phenomena can easily be modelled by the stochastic approach without going into advanced methods as finite differences or elements. The advantage of this approach is the simple programming and Iow need of computer memory. The disadvantage could be the need for excessive computing time.......This paper describes a numerical model of the dilution and disappearance of sewage discharged to the coastal zone. The model is based on the Monte Carlo (or random walk) principle. A cloud of particles is released at discrete time steps and the 3-dimensional path of every particle is simulated...
MAFALDA: An early warning modeling tool to forecast volcanic ash dispersal and deposition
Barsotti, S.; Nannipieri, L.; Neri, A.
2008-12-01
Forecasting the dispersal of ash from explosive volcanoes is a scientific challenge to modern volcanology. It also represents a fundamental step in mitigating the potential impact of volcanic ash on urban areas and transport routes near explosive volcanoes. To this end we developed a Web-based early warning modeling tool named MAFALDA (Modeling and Forecasting Ash Loading and Dispersal in the Atmosphere) able to quantitatively forecast ash concentrations in the air and on the ground. The main features of MAFALDA are the usage of (1) a dispersal model, named VOL-CALPUFF, that couples the column ascent phase with the ash cloud transport and (2) high-resolution weather forecasting data, the capability to run and merge multiple scenarios, and the Web-based structure of the procedure that makes it suitable as an early warning tool. MAFALDA produces plots for a detailed analysis of ash cloud dynamics and ground deposition, as well as synthetic 2-D maps of areas potentially affected by dangerous concentrations of ash. A first application of MAFALDA to the long-lasting weak plumes produced at Mt. Etna (Italy) is presented. A similar tool can be useful to civil protection authorities and volcanic observatories in reducing the impact of the eruptive events. MAFALDA can be accessed at http://mafalda.pi.ingv.it.
Sharifian, Mohammad Kazem; Kesserwani, Georges; Hassanzadeh, Yousef
2018-05-01
This work extends a robust second-order Runge-Kutta Discontinuous Galerkin (RKDG2) method to solve the fully nonlinear and weakly dispersive flows, within a scope to simultaneously address accuracy, conservativeness, cost-efficiency and practical needs. The mathematical model governing such flows is based on a variant form of the Green-Naghdi (GN) equations decomposed as a hyperbolic shallow water system with an elliptic source term. Practical features of relevance (i.e. conservative modeling over irregular terrain with wetting and drying and local slope limiting) have been restored from an RKDG2 solver to the Nonlinear Shallow Water (NSW) equations, alongside new considerations to integrate elliptic source terms (i.e. via a fourth-order local discretization of the topography) and to enable local capturing of breaking waves (i.e. via adding a detector for switching off the dispersive terms). Numerical results are presented, demonstrating the overall capability of the proposed approach in achieving realistic prediction of nearshore wave processes involving both nonlinearity and dispersion effects within a single model.
Benamrane, Y; Wybo, J-L; Armand, P
2013-12-01
The threat of a major accidental or deliberate event that would lead to hazardous materials emission in the atmosphere is a great cause of concern to societies. This is due to the potential large scale of casualties and damages that could result from the release of explosive, flammable or toxic gases from industrial plants or transport accidents, radioactive material from nuclear power plants (NPPs), and chemical, biological, radiological or nuclear (CBRN) terrorist attacks. In order to respond efficiently to such events, emergency services and authorities resort to appropriate planning and organizational patterns. This paper focuses on the use of atmospheric dispersion modeling (ADM) as a support tool for emergency planning and response, to assess the propagation of the hazardous cloud and thereby, take adequate counter measures. This paper intends to illustrate the noticeable evolution in the operational use of ADM tools over 25 y and especially in emergency situations. This study is based on data available in scientific publications and exemplified using the two most severe nuclear accidents: Chernobyl (1986) and Fukushima (2011). It appears that during the Chernobyl accident, ADM were used few days after the beginning of the accident mainly in a diagnosis approach trying to reconstruct what happened, whereas 25 y later, ADM was also used during the first days and weeks of the Fukushima accident to anticipate the potentially threatened areas. We argue that the recent developments in ADM tools play an increasing role in emergencies and crises management, by supporting stakeholders in anticipating, monitoring and assessing post-event damages. However, despite technological evolutions, its prognostic and diagnostic use in emergency situations still arise many issues. Copyright © 2013 Elsevier Ltd. All rights reserved.
Dispersion bias, dispersion effect, and the aerosol-cloud conundrum
International Nuclear Information System (INIS)
Liu Yangang; Daum, Peter H; Guo Huan; Peng Yiran
2008-01-01
This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO 2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo.
Evaluation of a mesoscale dispersion modelling tool during the CAPITOUL experiment
Lac, C.; Bonnardot, F.; Connan, O.; Camail, C.; Maro, D.; Hebert, D.; Rozet, M.; Pergaud, J.
2008-12-01
Atmospheric transport and dispersion were investigated during the CAPITOUL campaign using measurements of sulphur hexafluoride (SF6) tracer. Six releases of SF6 tracer were performed (March 9-11 and July 1-3, 2004) in the same suburban area of Toulouse conurbation, during the Intensive Observing Periods (IOP) of CAPITOUL. Concentration data were collected both at ground-level along axes perpendicular to the wind direction (at distances ranging between 280 m and 5000 m from the release point), and above the ground at 100 m and 200 m height using aircraft flights. Meteorological conditions were all associated with daytime anticyclonic conditions with weak winds and convective clear and cloudy boundary layers. A meso-scale dispersion modelling system, PERLE, developed at Meteo-France for environmental emergencies in case of atmospheric accidental release, was evaluated in terms of meteorology and dispersion, for the different tracer experiments, in its operational configuration. PERLE is based on the combination of the non-hydrostatic meso-scale MESO-NH model, running at 2 km horizontal resolution, and the Lagrangian particle model SPRAY. The statistical meteorological evaluation includes two sets of simulations with initialisation from ECMWF or ALADIN. The meteorological day-to-day error statistics show fairly good Meso-NH predictions, in terms of wind speed, wind direction and near-surface temperature. A strong sensitivity to initial fields concerns the surface fluxes, crucial for dispersion, with an excessive drying of the convective boundary layer with ALADIN initial fields, leading to an overprediction of surface sensible heat fluxes. A parameterization of dry and shallow convection according to the Eddy-Diffusivity-Mass-Flux (EDMF) approach (Pergaud et al. 2008) allows an efficient mixing in the Convective Boundary Layer (CBL) and improves significantly the wind fields. A statistical evaluation of the dispersion prediction was then performed and shows a
Pseudospectral modeling and dispersion analysis of Rayleigh waves in viscoelastic media
Zhang, K.; Luo, Y.; Xia, J.; Chen, C.
2011-01-01
Multichannel Analysis of Surface Waves (MASW) is one of the most widely used techniques in environmental and engineering geophysics to determine shear-wave velocities and dynamic properties, which is based on the elastic layered system theory. Wave propagation in the Earth, however, has been recognized as viscoelastic and the propagation of Rayleigh waves presents substantial differences in viscoelastic media as compared with elastic media. Therefore, it is necessary to carry out numerical simulation and dispersion analysis of Rayleigh waves in viscoelastic media to better understand Rayleigh-wave behaviors in the real world. We apply a pseudospectral method to the calculation of the spatial derivatives using a Chebyshev difference operator in the vertical direction and a Fourier difference operator in the horizontal direction based on the velocity-stress elastodynamic equations and relations of linear viscoelastic solids. This approach stretches the spatial discrete grid to have a minimum grid size near the free surface so that high accuracy and resolution are achieved at the free surface, which allows an effective incorporation of the free surface boundary conditions since the Chebyshev method is nonperiodic. We first use an elastic homogeneous half-space model to demonstrate the accuracy of the pseudospectral method comparing with the analytical solution, and verify the correctness of the numerical modeling results for a viscoelastic half-space comparing the phase velocities of Rayleigh wave between the theoretical values and the dispersive image generated by high-resolution linear Radon transform. We then simulate three types of two-layer models to analyze dispersive-energy characteristics for near-surface applications. Results demonstrate that the phase velocity of Rayleigh waves in viscoelastic media is relatively higher than in elastic media and the fundamental mode increases by 10-16% when the frequency is above 10. Hz due to the velocity dispersion of P
Non-Fickian dispersive transport of strontium in laboratory-scale columns: Modelling and evaluation
Liu, Dongxu; Jivkov, Andrey P.; Wang, Lichun; Si, Gaohua; Yu, Jing
2017-06-01
In the context of environmental remediation of contaminated sites and safety assessment of nuclear waste disposal in the near-surface zone, we investigate the leaching and non-Fickian dispersive migration with sorption of strontium (mocking strontium-90) through columns packed with sand and clay. Analysis is based on breakthrough curves (BTCs) from column experiments, which simulated rainfall infiltration and source term release scenario, rather than applying constant tracer solution at the inlet as commonly used. BTCs are re-evaluated and transport parameters are estimated by inverse modelling using two approaches: (1) equilibrium advection-dispersion equation (ADE); and (2) continuous time random walk (CTRW). Firstly, based on a method for calculating leach concentration, the inlet condition with an exponential decay input is identified. Secondly, the results show that approximately 39%-58% of Br- and 16%-49% of Sr2+ are eluted from the columns at the end of the breakthrough experiments. This suggests that trapping mechanisms, including diffusion into immobile zones and attachment of tracer on mineral surfaces, are more pronounced for Sr2+ than for Br-. Thirdly, we demonstrate robustness of CTRW-based truncated power-law (TPL) model in capturing non-Fickian reactive transport with 0 2. The non-Fickian dispersion observed experimentally is explained by variations of local flow field from preferential flow paths due to physical heterogeneities. Particularly, the additional sorption process of strontium on clay minerals contributes to the delay of the peak concentration and the tailing features, which leads to an enhanced non-Fickian transport for strontium. Finally, the ADE and CTRW approaches to environmental modelling are evaluated. It is shown that CTRW with a sorption term can describe non-Fickian dispersive transport of strontium at laboratory scale by identifying appropriate parameters, while the traditional ADE with a retardation factor fails to reproduce
Validation of dispersion model of RTARC-DSS based on ''KIT'' field experiments
International Nuclear Information System (INIS)
Duran, J.
2000-01-01
The aim of this study is to present the performance of the Gaussian dispersion model RTARC-DSS (Real Time Accident Release Consequences - Decision Support System) at the 'Kit' field experiments. The Model Validation Kit is a collection of three experimental data sets from Kincaid, Copenhagen, Lillestrom and supplementary Indianopolis experimental campaigns accompanied by software for model evaluation. The validation of the model has been performed on the basis of the maximum arc-wise concentrations using the Bootstrap resampling procedure the variation of the model residuals. Validation was performed for the short-range distances (about 1 - 10 km, maximum for Kincaid data set - 50 km from source). Model evaluation procedure and amount of relative over- or under-prediction are discussed and compared with the model. (author)
International Nuclear Information System (INIS)
Wittek, P.
1985-09-01
Atmospheric dispersion models are reviewed with respect to their application to the consequence assessment within risk studies for nuclear power plants located in complex terrain. This review comprises: seven straight-line Gaussian models, which have been modified in order to take into account in a crude way terrain elevations, enhanced turbulence and some others effects; three trajectory/puff-models, which can handle wind direction changes and the resulting plume or puff trajectories; five three-dimensional wind field models, which calculate the wind field in complex terrain for the application in a grid model; three grid models; one Monte-Carlo-model. The main features of the computer codes are described, along with some informations on the necessary computer time and storage capacity. (orig.) [de
All dispersal functions are wrong, but many are useful: A response to Cousens etal.
Czech Academy of Sciences Publication Activity Database
Bullock, J. M.; Hooftman, D. A. P.; Tamme, R.; Götzenberger, Lars; Pärtel, M.; González, L. M.; White, S. M.
2018-01-01
Roč. 106, č. 3 (2018), s. 907-910 ISSN 0022-0477 Institutional support: RVO:67985939 Keywords : seed dispersal * probability density function * prediction Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 5.813, year: 2016
Long-range transmission of pollutants simulated by a two-dimensional pseudospectral dispersion model
International Nuclear Information System (INIS)
Prahm, L.P.; Christensen, O.
1977-01-01
The pseudospectral dispersion model (Christensen and Prahm, 1976) is adapted for simulation of the long-range transmission of sulphur pollutants in the European region, covering an area of about 4000 km x 4000 km. Regional ''background'' concentrations of sulphur oxides are found to be highly dependent on distant sources and to correlate poorly with local source strength during the considered three- and four-day episodes. The simulation is based on emission data, given in squares of about 50 km x 50 km and on synoptic wind fields derived from observed wind velocities of the 850 mb level and the surface level. The two-dimensional model includes a constant vertical mixing depth. Appropriate values for the deposition and the transformation rates of SO 2 and SO/sup 4 are used. The concentration of pollutants computed from the two-dimensional pseudospectral dispersion model reflects the variable meteorological conditions. Computed concentrations are compared with measurements, giving spatial correlations between 0.4 and 0.8 for more than 400 ground-based 24 h mean values, and a spatial correlation of 0.9 for eight aircraft samples averaged over approx.30 min. A discussion of the influence of different sources of error in the model simulation is given. The high numerical accuracy of the pseudospectral model is combined with a modest consumption of CPU computer time. This study is the first application of the pseudospectral dispersion model which compares computed concentrations with measured field data. The model has possible applications as a tool for assessment of the impact of both national and international emission regulation strategies
Robin A. J. Taylor; Daniel A. Herms; Louis R. Iverson
2008-01-01
The dispersal of organisms is rarely random, although diffusion processes can be useful models for movement in approximately homogeneous environments. However, the environments through which all organisms disperse are far from uniform at all scales. The emerald ash borer (EAB), Agrilus planipennis, is obligate on ash (Fraxinus spp...
Moonen, P.; Gromke, C.B.; Dorer, V.
2013-01-01
The potential of a Large Eddy Simulation (LES) model to reliably predict near-field pollutant dispersion is assessed. To that extent, detailed time-resolved numerical simulations of coupled flow and dispersion are conducted for a street canyon with tree planting. Different crown porosities are
Validation of a two-dimensional pollutant dispersion model in an isolated street canyon
Energy Technology Data Exchange (ETDEWEB)
Chan, T.L.; Dong, G.; Leung, C.W.; Cheung, C.S. [The Hong Kong Polytechnic University, Kowloon (Hong Kong). Research Centre for Combustion and Pollution Control, Department of Mechanical Engineering; Hung, W.T. [The Hong Kong Polytechnic University, Kowloon (Hong Kong). Department of Civil and Structural Engineering
2002-07-01
A two-dimensional numerical model based on Reynolds-averaged Navier-Stokes equations coupled with a series of standard, Renormalization Group (RNG) and realizable k-{epsilon} turbulence models was developed to simulate the fluid-flow development and pollutant dispersion within an isolated street canyon using the FLUENT code. In the present study, the validation of the numerical model was evaluated using an extensive experimental database obtained from the atmospheric boundary layer wind tunnel at the Meteorological Institute of Hamburg University, Germany (J. Wind Eng. Ind. Aerodyn. 62 (1996) 37). Among the studied turbulence models, the RNG k-{epsilon} turbulence model was found to be the most optimum turbulence model coupled with the two-dimensional street canyon model developed in the present study. Both the calculated and measured dimensionless pollutant concentrations have been shown to be less dependent on the variation of wind speed and source strength conditions for the studied street canyon aspect ratio of the B/H=1 case. However, the street canyon configuration has significant influence on the pollutant dispersion. The wider street and lower height of the buildings are favorable to pollutant dilution within the street canyon. The fluid-flow development has demonstrated that the rotative vortex or vortices generated within the urban street canyon can transport the pollutants from a line source to the wall surfaces of the buildings. (author)
Annular dispersed flow analysis model by Lagrangian method and liquid film cell method
International Nuclear Information System (INIS)
Matsuura, K.; Kuchinishi, M.; Kataoka, I.; Serizawa, A.
2003-01-01
A new annular dispersed flow analysis model was developed. In this model, both droplet behavior and liquid film behavior were simultaneously analyzed. Droplet behavior in turbulent flow was analyzed by the Lagrangian method with refined stochastic model. On the other hand, liquid film behavior was simulated by the boundary condition of moving rough wall and liquid film cell model, which was used to estimate liquid film flow rate. The height of moving rough wall was estimated by disturbance wave height correlation. In each liquid film cell, liquid film flow rate was calculated by considering droplet deposition and entrainment flow rate. Droplet deposition flow rate was calculated by Lagrangian method and entrainment flow rate was calculated by entrainment correlation. For the verification of moving rough wall model, turbulent flow analysis results under the annular flow condition were compared with the experimental data. Agreement between analysis results and experimental results were fairly good. Furthermore annular dispersed flow experiments were analyzed, in order to verify droplet behavior model and the liquid film cell model. The experimental results of radial distribution of droplet mass flux were compared with analysis results. The agreement was good under low liquid flow rate condition and poor under high liquid flow rate condition. But by modifying entrainment rate correlation, the agreement become good even under high liquid flow rate. This means that basic analysis method of droplet and liquid film behavior was right. In future work, verification calculation should be carried out under different experimental condition and entrainment ratio correlation also should be corrected
Directory of Open Access Journals (Sweden)
Yuhui Jiang
2018-04-01
Full Text Available Hexachlorobenzene (HCB contamination of soils remains a significant environmental challenge all over the world. Reductive stabilization is a developing technology that can decompose the HCB with a dechlorination process. A nanometallic Al/CaO (n-Al/CaO dispersion mixture was developed utilizing ball-milling technology in this study. The dechlorination efficiency of HCB in contaminated soils by the n-Al/CaO grinding treatment was evaluated. Response surface methodology (RSM was employed to investigate the effects of three variables (soil moisture content, n-Al/CaO dosage and grinding time and the interactions between these variables under the Box-Behnken Design (BBD. A high regression coefficient value (R2 = 0.9807 and low p value (<0.0001 of the quadratic model indicated that the model was accurate in predicting the experimental results. The optimal soil moisture content, n-Al/CaO dosage, and grinding time were found to be 7% (m/m, 17.7% (m/m, and 24 h, respectively, in the experimental ranges and levels. Under optimal conditions, the dechlorination efficiency was 80%. The intermediate product analysis indicated that dechlorination was the process by stepwise loss of chloride atoms. The main pathway observed within 24 h was HCB → pentachlorobenzene (PeCB → 1,2,3,4-tetrachlorobenzene (TeCB and 1,2,4,5-TeCB. The results indicated that the moderate soil moisture content was crucial for the hydrodechlorination of HCB. A probable mechanism was proposed wherein water acted like a hydrogen donor and promoted the hydrodechlorination process. The potential application of n-Al/CaO is an environmentally-friendly and cost-effective option for decontamination of HCB-contaminated soils.
O'Doherty, Jim; Chilcott, Anna; Dunn, Joel
2015-11-01
Arterial sampling with dispersion correction is routinely performed for kinetic analysis of PET studies. Because of the the advent of PET-MRI systems, non-MR safe instrumentation will be required to be kept outside the scan room, which requires the length of the tubing between the patient and detector to increase, thus worsening the effects of dispersion. We examined the effects of dispersion in idealized radioactive blood studies using various lengths of tubing (1.5, 3, and 4.5 m) and applied a well-known transmission-dispersion model to attempt to correct the resulting traces. A simulation study was also carried out to examine noise characteristics of the model. The model was applied to patient traces using a 1.5 m acquisition tubing and extended to its use at 3 m. Satisfactory dispersion correction of the blood traces was achieved in the 1.5 m line. Predictions on the basis of experimental measurements, numerical simulations and noise analysis of resulting traces show that corrections of blood data can also be achieved using the 3 m tubing. The effects of dispersion could not be corrected for the 4.5 m line by the selected transmission-dispersion model. On the basis of our setup, correction of dispersion in arterial sampling tubing up to 3 m by the transmission-dispersion model can be performed. The model could not dispersion correct data acquired using a 4.5 m arterial tubing.
Dispersion analysis of the Pn -Pn-1DG mixed finite element pair for atmospheric modelling
Melvin, Thomas
2018-02-01
Mixed finite element methods provide a generalisation of staggered grid finite difference methods with a framework to extend the method to high orders. The ability to generate a high order method is appealing for applications on the kind of quasi-uniform grids that are popular for atmospheric modelling, so that the method retains an acceptable level of accuracy even around special points in the grid. The dispersion properties of such schemes are important to study as they provide insight into the numerical adjustment to imbalance that is an important component in atmospheric modelling. This paper extends the recent analysis of the P2 - P1DG pair, that is a quadratic continuous and linear discontinuous finite element pair, to higher polynomial orders and also spectral element type pairs. In common with the previously studied element pair, and also with other schemes such as the spectral element and discontinuous Galerkin methods, increasing the polynomial order is found to provide a more accurate dispersion relation for the well resolved part of the spectrum but at the cost of a number of unphysical spectral gaps. The effects of these spectral gaps are investigated and shown to have a varying impact depending upon the width of the gap. Finally, the tensor product nature of the finite element spaces is exploited to extend the dispersion analysis into two-dimensions.
Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.
2016-01-01
Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil
Modeling of laser radiation transport in powder beds with high-dispersive metal particles
Energy Technology Data Exchange (ETDEWEB)
Kharanzhevskiy, Evgeny, E-mail: eh@udsu.ru [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation); Kostenkov, Sergey [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation)
2014-02-15
Highlights: ► Transport of laser energy in dispersive powder beds was numerically simulated. ► The results of simulating are compared with physicals experiments. ► We established the dependence of the extinction coefficient from powder properties. ► A confirmation of a geometric optic approach for monodisperse powders was proposed. -- Abstract: Two-dimensional transfer of laser radiation in a high-dispersive powder heterogeneous media is numerically calculated. The size of particles is comparable with the wave length of laser radiation so the model takes into account all known physical effects that are occurred on the vacuum–metal surface interface. It is shown that in case of small particles size both morphology of powder particles and porosity of beds influence on absorptance by the solid phase and laser radiation penetrate deep into the area of geometric shadow. Intensity of laser radiation may be described as a function corresponded to the Beer–Lambert–Bouguer law.
Modeling of laser radiation transport in powder beds with high-dispersive metal particles
International Nuclear Information System (INIS)
Kharanzhevskiy, Evgeny; Kostenkov, Sergey
2014-01-01
Highlights: ► Transport of laser energy in dispersive powder beds was numerically simulated. ► The results of simulating are compared with physicals experiments. ► We established the dependence of the extinction coefficient from powder properties. ► A confirmation of a geometric optic approach for monodisperse powders was proposed. -- Abstract: Two-dimensional transfer of laser radiation in a high-dispersive powder heterogeneous media is numerically calculated. The size of particles is comparable with the wave length of laser radiation so the model takes into account all known physical effects that are occurred on the vacuum–metal surface interface. It is shown that in case of small particles size both morphology of powder particles and porosity of beds influence on absorptance by the solid phase and laser radiation penetrate deep into the area of geometric shadow. Intensity of laser radiation may be described as a function corresponded to the Beer–Lambert–Bouguer law
Dispersion of radionuclides in the European north-western seas: observations and modelling
International Nuclear Information System (INIS)
Bailly du Bois, Pascal
2013-01-01
In this report for an Accreditation to supervise research (HDR), the author reports the use over 30 years by the Cherbourg-Octeville IRSN Laboratory of artificial radionuclides in solution in sea water as oceanographic markers. Such measurements on radio-markers which are soluble in sea water, enabled a better knowledge of dissolved substance displacements in north-western seas of Europe, notably the Channel, the North Sea, the Celtic Sea, and the Irish Sea. The author reports researches which aimed at studying the dispersion of radionuclides in seawater and their use as water mass markers, at validating hydrodynamic models of dispersion at different time-space scales, at the understanding and simulation of the sedimentary transport, and at studying the transfer to living species. These different topics give the document its structure [fr
Modeling non-Fickian dispersion by use of the velocity PDF on the pore scale
Kooshapur, Sheema; Manhart, Michael
2015-04-01
For obtaining a description of reactive flows in porous media, apart from the geometrical complications of resolving the velocities and scalar values, one has to deal with the additional reactive term in the transport equation. An accurate description of the interface of the reacting fluids - which is strongly influenced by dispersion- is essential for resolving this term. In REV-based simulations the reactive term needs to be modeled taking sub-REV fluctuations and possibly non-Fickian dispersion into account. Non-Fickian dispersion has been observed in strongly heterogeneous domains and in early phases of transport. A fully resolved solution of the Navier-Stokes and transport equations which yields a detailed description of the flow properties, dispersion, interfaces of fluids, etc. however, is not practical for domains containing more than a few thousand grains, due to the huge computational effort required. Through Probability Density Function (PDF) based methods, the velocity distribution in the pore space can facilitate the understanding and modelling of non-Fickian dispersion [1,2]. Our aim is to model the transition between non-Fickian and Fickian dispersion in a random sphere pack within the framework of a PDF based transport model proposed by Meyer and Tchelepi [1,3]. They proposed a stochastic transport model where velocity components of tracer particles are represented by a continuous Markovian stochastic process. In addition to [3], we consider the effects of pore scale diffusion and formulate a different stochastic equation for the increments in velocity space from first principles. To assess the terms in this equation, we performed Direct Numerical Simulations (DNS) for solving the Navier-Stokes equation on a random sphere pack. We extracted the PDFs and statistical moments (up to the 4th moment) of the stream-wise velocity, u, and first and second order velocity derivatives both independent and conditioned on velocity. By using this data and
Numerical predictions of particle dispersed two-phase flows, using the LSD and SSF models
International Nuclear Information System (INIS)
Avila, R.; Cervantes de Gortari, J.; Universidad Nacional Autonoma de Mexico, Mexico City. Facultad de Ingenieria)
1988-01-01
A modified version of a numerical scheme which is suitable to predict parabolic dispersed two-phase flow, is presented. The original version of this scheme was used to predict the test cases discussed during the 3rd workshop on TPF predictions in Belgrade, 1986. In this paper, two particle dispersion models are included which use the Lagrangian approach predicting test case 1 and 3 of the 4th workshop. For the prediction of test case 1 the Lagrangian Stochastic Deterministic model (LSD) is used providing acceptable good results of mean and turbulent quantities for both solid and gas phases; however, the computed void fraction distribution is not in agreement with the measurements at locations away from the inlet, especially near the walls. Test case 3 is predicted using both the LSD and the Stochastic Separated Flow (SSF) models. It was found that the effects of turbulence modulation are large when the LSD model is used, whereas the particles have a negligible influence on the continuous phase if the SSF model is utilized for the computations. Predictions of gas phase properties based on both models agree well with measurements; however, the agreement between calculated and measured solid phase properties is less satisfactory. (orig.)
Parametric laws to model urban pollutant dispersion with a street network approach
Soulhac, L.; Salizzoni, P.; Mejean, P.; Perkins, R. J.
2013-03-01
This study discusses the reliability of the street network approach for pollutant dispersion modelling in urban areas. This is essentially based on a box model, with parametric relations that explicitly model the main phenomena that contribute to the street canyon ventilation: the mass exchanges between the street and the atmosphere, the pollutant advection along the street axes and the pollutant transfer at street intersections. In the first part of the paper the focus is on the development of a model for the bulk transfer street/atmosphere, which represents the main ventilation mechanisms for wind direction that are almost perpendicular to the axis of the street. We then discuss the role of the advective transfer along the street axis on its ventilation, depending on the length of the street and the direction of the external wind. Finally we evaluate the performances of a box model integrating parametric exchange laws for these transfer phenomena. To that purpose we compare the prediction of the model to wind tunnel experiments of pollutant dispersion within a street canyon placed in an idealised urban district.
Carotenuto, Federico; Gualtieri, Giovanni; Miglietta, Franco; Riccio, Angelo; Toscano, Piero; Wohlfahrt, Georg; Gioli, Beniamino
2018-02-22
CO 2 remains the greenhouse gas that contributes most to anthropogenic global warming, and the evaluation of its emissions is of major interest to both research and regulatory purposes. Emission inventories generally provide quite reliable estimates of CO 2 emissions. However, because of intrinsic uncertainties associated with these estimates, it is of great importance to validate emission inventories against independent estimates. This paper describes an integrated approach combining aircraft measurements and a puff dispersion modelling framework by considering a CO 2 industrial point source, located in Biganos, France. CO 2 density measurements were obtained by applying the mass balance method, while CO 2 emission estimates were derived by implementing the CALMET/CALPUFF model chain. For the latter, three meteorological initializations were used: (i) WRF-modelled outputs initialized by ECMWF reanalyses; (ii) WRF-modelled outputs initialized by CFSR reanalyses and (iii) local in situ observations. Governmental inventorial data were used as reference for all applications. The strengths and weaknesses of the different approaches and how they affect emission estimation uncertainty were investigated. The mass balance based on aircraft measurements was quite succesful in capturing the point source emission strength (at worst with a 16% bias), while the accuracy of the dispersion modelling, markedly when using ECMWF initialization through the WRF model, was only slightly lower (estimation with an 18% bias). The analysis will help in highlighting some methodological best practices that can be used as guidelines for future experiments.
International Nuclear Information System (INIS)
Alvarez, M.C.; Garzon, L.
1990-01-01
In this paper a practical dispersion model is presented, which permits to calculate, in Spain, the concentration of natural radionuclides released to the atmosphere from coal power plants. To apply the model it is necessary to know the following data: emission rates, dry deposition velocity, scavenging coefficient, mixing layer height, together with climatological frequency data relating to wind speed and wind direction (to determinate trajectories from a given source) in the areas examined. Meteorological data can be obtained from meteorological stations across Spain. (Author)
Experimental modelling of core debris dispersion from the vault under a PWR pressure vessel: Part 1
International Nuclear Information System (INIS)
Macbeth, R.V.; Trenberth, R.
1987-12-01
Modelling experiments have been done on a 1/25 scale model in Perspex of the vault under a PWR pressure vessel. Various liquids have been used to simulate molten core debris assumed to have fallen on to the vault floor from a breach at the bottom of the pressure vessel. High pressure air and helium have been used to simulate the discharge of steam and gas from the breach. The dispersion of liquid via the vault access shafts has been measured. Photographs have been taken of fluid flow patterns and velocity profiles have been obtained. The requirements for further experiments are indicated. (author)
Directory of Open Access Journals (Sweden)
Joel K Kelso
Full Text Available The spread of Bluetongue virus (BTV among ruminants is caused by movement of infected host animals or by movement of infected Culicoides midges, the vector of BTV. Biologically plausible models of Culicoides dispersal are necessary for predicting the spread of BTV and are important for planning control and eradication strategies.A spatially-explicit simulation model which captures the two underlying population mechanisms, population dynamics and movement, was developed using extensive data from a trapping program for C. brevitarsis on the east coast of Australia. A realistic midge flight sub-model was developed and the annual incursion and population establishment of C. brevitarsis was simulated. Data from the literature was used to parameterise the model.The model was shown to reproduce the spread of C. brevitarsis southwards along the east Australian coastline in spring, from an endemic population to the north. Such incursions were shown to be reliant on wind-dispersal; Culicoides midge active flight on its own was not capable of achieving known rates of southern spread, nor was re-emergence of southern populations due to overwintering larvae. Data from midge trapping programmes were used to qualitatively validate the resulting simulation model.The model described in this paper is intended to form the vector component of an extended model that will also include BTV transmission. A model of midge movement and population dynamics has been developed in sufficient detail such that the extended model may be used to evaluate the timing and extent of BTV outbreaks. This extended model could then be used as a platform for addressing the effectiveness of spatially targeted vaccination strategies or animal movement bans as BTV spread mitigation measures, or the impact of climate change on the risk and extent of outbreaks. These questions involving incursive Culicoides spread cannot be simply addressed with non-spatial models.
Dispersion coefficients for coastal regions
International Nuclear Information System (INIS)
MacRae, B.L.; Kaleel, R.J.; Shearer, D.L.
1983-03-01
The Nuclear Regulatory Commission (NRC) has undertaken an extensive atmospheric dispersion research and measurement program from which it is intended will emerge improved predictive techniques for employment in licensing decisions and for emergency planning and response. Through this program the NRC has conducted field measurement programs over a wide range of geographic and topographic locations, and are using the acquired tracer and meteorological measurements to evaluate existing dispersion models and prediction techniques, and to develop new techniques when necessary
Sensitivity analysis of the near-road dispersion model RLINE - An evaluation at Detroit, Michigan
Milando, Chad W.; Batterman, Stuart A.
2018-05-01
The development of accurate and appropriate exposure metrics for health effect studies of traffic-related air pollutants (TRAPs) remains challenging and important given that traffic has become the dominant urban exposure source and that exposure estimates can affect estimates of associated health risk. Exposure estimates obtained using dispersion models can overcome many of the limitations of monitoring data, and such estimates have been used in several recent health studies. This study examines the sensitivity of exposure estimates produced by dispersion models to meteorological, emission and traffic allocation inputs, focusing on applications to health studies examining near-road exposures to TRAP. Daily average concentrations of CO and NOx predicted using the Research Line source model (RLINE) and a spatially and temporally resolved mobile source emissions inventory are compared to ambient measurements at near-road monitoring sites in Detroit, MI, and are used to assess the potential for exposure measurement error in cohort and population-based studies. Sensitivity of exposure estimates is assessed by comparing nominal and alternative model inputs using statistical performance evaluation metrics and three sets of receptors. The analysis shows considerable sensitivity to meteorological inputs; generally the best performance was obtained using data specific to each monitoring site. An updated emission factor database provided some improvement, particularly at near-road sites, while the use of site-specific diurnal traffic allocations did not improve performance compared to simpler default profiles. Overall, this study highlights the need for appropriate inputs, especially meteorological inputs, to dispersion models aimed at estimating near-road concentrations of TRAPs. It also highlights the potential for systematic biases that might affect analyses that use concentration predictions as exposure measures in health studies.
A Generalized turbulent dispersion model for bubbly flow numerical simulation in NEPTUNE-CFD
Energy Technology Data Exchange (ETDEWEB)
Laviéville, Jérôme, E-mail: Jerome-marcel.lavieville@edf.fr; Mérigoux, Nicolas, E-mail: nicolas.merigoux@edf.fr; Guingo, Mathieu, E-mail: mathieu.guingo@edf.fr; Baudry, Cyril, E-mail: Cyril.baudry@edf.fr; Mimouni, Stéphane, E-mail: stephane.mimouni@edf.fr
2017-02-15
The NEPTUNE-CFD code, based upon an Eulerian multi-fluid model, is developed within the framework of the NEPTUNE project, financially supported by EDF (Electricité de France), CEA (Commissariat à l’Energie Atomique et aux Energies Alternatives), IRSN (Institut de Radioprotection et de Sûreté Nucléaire) and AREVA-NP. NEPTUNE-CFD is mainly focused on Nuclear Safety applications involving two-phase water-steam flows, like two-phase Pressurized Shock (PTS) and Departure from Nucleate Boiling (DNB). Many of these applications involve bubbly flows, particularly, for application to flows in PWR fuel assemblies, including studies related to DNB. Considering a very usual model for interfacial forces acting on bubbles, including drag, virtual mass and lift forces, the turbulent dispersion force is often added to moderate the lift effect in orthogonal directions to the main flow and get the right dispersion shape. This paper presents a formal derivation of this force, considering on the one hand, the fluctuating part of drag and virtual mass, and on the other hand, Turbulent Pressure derivation obtained by comparison between Lagrangian and Eulerian description of bubbles motion. An extension of the Tchen’s theory is used to express the turbulent kinetic energy of bubbles and the two-fluid turbulent covariance tensor in terms of liquid turbulent velocities and time scale. The model obtained by this way, called Generalized Turbulent Dispersion Model (GTD), does not require any user parameter. The model is validated against Liu & Bankoff air-water experiment, Arizona State University (ASU) experiment, DEBORA experiment and Texas A&M University (TAMU) boiling flow experiments.
International Nuclear Information System (INIS)
Perianez, R.; Abril, J.M.; Garcia-Leon, M.
1996-01-01
A 2D four-phase model to study the dispersion of non-conservative radionuclides in tidal waters, in conditions of disequilibrium for ionic exchanges, has been developed. At disequilibrium conditions, ionic exchanges cannot be formulated using distribution coefficients k d . Thus, kinetic transfer coefficients have been used. The model includes ionic exchanges among water and the solid phases (suspended matter and two grain size fractions of sediments), the deposition and resuspension of suspended matter and advective plus diffusive transport. In the second part of this work, which is presented in a separate paper, the model is applied to simulate 226 Ra dispersion, discharged from a fertilizer processing plant, in an estuarine system in the south-west of Spain. (Author)
Evaluation of three atmospheric dispersion models using tracer release experiment data
International Nuclear Information System (INIS)
Daoo, V.J.; Oza, R.B.; Pandit, G.G.; Sadasivan, S.; Venkat Raj, V.
2004-01-01
Performance of three atmospheric dispersion models viz: (1) Gaussian Plume Model (GPM), (2) Equi-Distance PUFF Model (EDPUFFM) and (3) Particle Trajectory Model (PTM) is evaluated using field data collected from a tracer (SF 6 ) release experiment. The experiment was conducted within the campus of the Bhabha Atomic Research Centre (BARC), located at Trombay, Mumbai, India. The three models used are currently in operation at the BARC. The first one is a standard, well-documented empirical model while the other two models have been developed at the Bhabha Atomic Research Centre. The PTM is a numerical model while the EDPUFFM is a hybrid model combining both the numerical and analytical techniques. The procedure for evaluation is as per the recommendations of 1980 AMS (American Meteorological Society) workshop on atmospheric dispersion models performance evaluation. In addition, linear regression analysis has also been carried out. The regression analysis reveals that on an average, the EDPUFFM and the GPM predictions are higher by a factor of about 1.5 while the PTM predictions are lower by a factor of about 4. Comparison of various performance measures reveals that the performance of the EDPUFFM is marginally better than that of the GPM while the PTM performance is comparatively poor. The uncertainty factors obtained in this study, especially for higher concentration range ( > 100 ppt) are similar to those obtained in other validation study carried out elsewhere to validate the GPM predictions. However, for lower concentration range and for the conditions after the source is switched off, all the three models perform poorly in predicting the concentration. (author)
Energy Technology Data Exchange (ETDEWEB)
Rossi, R., E-mail: riccardo.rossi12@unibo.i [Laboratorio di Termofluidodinamica Computazionale Seconda Facolta di Ingegneria di Forli, Universita di Bologna Via Fontanelle 40, 47100 Forli (Italy); Center for Turbulence Research Department of Mechanical Engineering Stanford University, CA 94305 (United States); Philips, D.A.; Iaccarino, G. [Center for Turbulence Research Department of Mechanical Engineering Stanford University, CA 94305 (United States)
2010-10-15
Research highlights: {yields} The computed DNS statistics indicate that a gradient-transport scheme can be applied to the vertical and spanwise scalar flux components. {yields} The streamwise scalar flux is characterized by a counter-gradient transport mechanism in the wake region close to the obstacle. {yields} The wake profiles of scalar fluctuations and the shape of probability density functions do not suggest a significant flapping movement of the scalar plume. {yields} The evaluation of scalar dispersion models must include a careful assessment of the computed mean velocity field and Reynolds stress tensor. {yields} Algebraic models provide an improved prediction of the mean concentration field as compared to the standard eddy-diffusivity model. -- Abstract: The dispersion of a passive scalar downstream of a wall-mounted cube is examined using direct numerical simulations and turbulence models applied to the Reynolds equations. The scalar is released from a circular source located on top of the obstacle, which is immersed in a developing boundary-layer flow. Direct simulations are performed to give insight into the mixing process and to provide a reference database for turbulence closures. Algebraic flux models are evaluated against the standard eddy-diffusivity representation. Coherent structures periodically released from the cube top are responsible for a counter-diffusion mechanism appearing in the streamwise scalar flux. Alternating vortex pairs form from the lateral edges of the cube, but the intensity profiles and probability density functions of scalar fluctuations suggest that they do not cause a significant flapping movement of the scalar plume. The gradient-transport scheme is consistent with the vertical and spanwise scalar flux components. From the comparative study with our direct simulations, we further stress that Reynolds stress predictions must be carefully evaluated along with scalar flux closures in order to establish the reliability of
International Nuclear Information System (INIS)
Rossi, R.; Philips, D.A.; Iaccarino, G.
2010-01-01
Research highlights: → The computed DNS statistics indicate that a gradient-transport scheme can be applied to the vertical and spanwise scalar flux components. → The streamwise scalar flux is characterized by a counter-gradient transport mechanism in the wake region close to the obstacle. → The wake profiles of scalar fluctuations and the shape of probability density functions do not suggest a significant flapping movement of the scalar plume. → The evaluation of scalar dispersion models must include a careful assessment of the computed mean velocity field and Reynolds stress tensor. → Algebraic models provide an improved prediction of the mean concentration field as compared to the standard eddy-diffusivity model. -- Abstract: The dispersion of a passive scalar downstream of a wall-mounted cube is examined using direct numerical simulations and turbulence models applied to the Reynolds equations. The scalar is released from a circular source located on top of the obstacle, which is immersed in a developing boundary-layer flow. Direct simulations are performed to give insight into the mixing process and to provide a reference database for turbulence closures. Algebraic flux models are evaluated against the standard eddy-diffusivity representation. Coherent structures periodically released from the cube top are responsible for a counter-diffusion mechanism appearing in the streamwise scalar flux. Alternating vortex pairs form from the lateral edges of the cube, but the intensity profiles and probability density functions of scalar fluctuations suggest that they do not cause a significant flapping movement of the scalar plume. The gradient-transport scheme is consistent with the vertical and spanwise scalar flux components. From the comparative study with our direct simulations, we further stress that Reynolds stress predictions must be carefully evaluated along with scalar flux closures in order to establish the reliability of Reynolds
Catchment Dispersion Mechanisms in an Urban Context
Gironas, J. A.; Mejia, A.; Rossel, F.; Rinaldo, A.; Rodriguez, F.
2014-12-01
Dispersion mechanisms have been examined in-depth in natural catchments in previous studies. However, these dispersion mechanisms have been studied little in urban catchments, where artificial transport elements and morphological arrangements are expected to modify travel times and mobilize excess rainfall from spatially distributed impervious sites. Thus, these features can modify the variance of the catchment's travel times and hence the total dispersion. This work quantifies the dispersion mechanisms in an urban catchment using the theory of transport by travel times as represented by the Urban Morpho-climatic Instantaneous Unit Hydrograph (U-McIUH) model. This model computes travel times based on kinematic wave theory and accounts explicitly for the path heterogeneities and altered connectivity patterns characteristic of an urban drainage network. The analysis is illustrated using the Aubinière urban catchment (France) as a case study. We found that kinematic dispersion is dominant for small rainfall intensities, whereas geomorphologic dispersion becomes more dominant for larger intensities. The total dispersion scales with the drainage area in a power law fashion. The kinematic dispersion is dominant across spatial scales up to a threshold of approximately 2-3 km2, after which the geomorphologic dispersion becomes more dominant. Overall, overland flow is responsible for most of the dispersion, while conduits tend to counteract the increase of the geomorphologic dispersion with a negative kinematic dispersion. Further studies with other catchments are needed to assess whether the latter is a general feature of urban drainage networks.
Baird, Jared A; Taylor, Lynne S
2011-06-01
The purpose of this study was to gain a better understanding of which factors contribute to the eutectic composition of drug-polyethylene glycol (PEG) blends and to compare experimental values with predictions from the semi-empirical model developed by Lacoulonche et al. Eutectic compositions of various drug-PEG 3350 solid dispersions were predicted, assuming athermal mixing, and compared to experimentally determined eutectic points. The presence or absence of specific interactions between the drug and PEG 3350 were investigated using Fourier transform infrared (FT-IR) spectroscopy. The eutectic composition for haloperidol-PEG and loratadine-PEG solid dispersions was accurately predicted using the model, while predictions for aceclofenac-PEG and chlorpropamide-PEG were very different from those experimentally observed. Deviations in the model prediction from ideal behavior for the systems evaluated were confirmed to be due to the presence of specific interactions between the drug and polymer, as demonstrated by IR spectroscopy. Detailed analysis showed that the eutectic composition prediction from the model is interdependent on the crystal lattice energy of the drug compound (evaluated from the melting temperature and the heat of fusion) as well as the nature of the drug-polymer interactions. In conclusion, for compounds with melting points less than 200°C, the model is ideally suited for predicting the eutectic composition of systems where there is an absence of drug-polymer interactions.
Equilibrium-eulerian les model for turbulent poly-dispersed particle-laden flow
Icardi, Matteo
2013-04-01
An efficient Eulerian method for poly-dispersed particles in turbulent flows is implemented, verified and validated for a channel flow. The approach couples a mixture model with a quadrature-based moment method for the particle size distribution in a LES framework, augmented by an approximate deconvolution method to reconstructs the unfiltered velocity. The particle velocity conditioned on particle size is calculated with an equilibrium model, valid for low Stokes numbers. A population balance equation is solved with the direct quadrature method of moments, that efficiently represents the continuous particle size distribution. In this first study particulate processes are not considered and the capability of the model to properly describe particle transport is investigated for a turbulent channel flow. First, single-phase LES are validated through comparison with DNS. Then predictions for the two-phase system, with particles characterised by Stokes numbers ranging from 0.2 to 5, are compared with Lagrangian DNS in terms of particle velocity and accumulation at the walls. Since this phenomenon (turbophoresis) is driven by turbulent fluctuations and depends strongly on the particle Stokes number, the approximation of the particle size distribution, the choice of the sub-grid scale model and the use of an approximate deconvolution method are important to obtain good results. Our method can be considered as a fast and efficient alternative to classical Lagrangian methods or Eulerian multi-fluid models in which poly-dispersity is usually neglected.
Equilibrium-eulerian les model for turbulent poly-dispersed particle-laden flow
Icardi, Matteo; Marchisio, Daniele Luca; Chidambaram, Narayanan; Fox, Rodney O.
2013-01-01
An efficient Eulerian method for poly-dispersed particles in turbulent flows is implemented, verified and validated for a channel flow. The approach couples a mixture model with a quadrature-based moment method for the particle size distribution in a LES framework, augmented by an approximate deconvolution method to reconstructs the unfiltered velocity. The particle velocity conditioned on particle size is calculated with an equilibrium model, valid for low Stokes numbers. A population balance equation is solved with the direct quadrature method of moments, that efficiently represents the continuous particle size distribution. In this first study particulate processes are not considered and the capability of the model to properly describe particle transport is investigated for a turbulent channel flow. First, single-phase LES are validated through comparison with DNS. Then predictions for the two-phase system, with particles characterised by Stokes numbers ranging from 0.2 to 5, are compared with Lagrangian DNS in terms of particle velocity and accumulation at the walls. Since this phenomenon (turbophoresis) is driven by turbulent fluctuations and depends strongly on the particle Stokes number, the approximation of the particle size distribution, the choice of the sub-grid scale model and the use of an approximate deconvolution method are important to obtain good results. Our method can be considered as a fast and efficient alternative to classical Lagrangian methods or Eulerian multi-fluid models in which poly-dispersity is usually neglected.
A model for the calculation of dispersion, advection and deposition of polluants in the atmosphere
International Nuclear Information System (INIS)
Doron, E.
1981-08-01
A numerical model for the prediction of atmospheric pollutants concentrations as a function of time and location is described. The model includes effects of dispersion, advection and deposition of the pollutant. Topographic influences are included through the introduction of a terrain following vertical coordinate. The wind field, needed for the calculation of the advection, is obtained from a time series of objective analysis of actual wind measurements. A unique feature of the model is the use of the logarithm of the concentration as the predicted variable. For a concentration distribution close to Gaussian, the distribution of this variable is close to parabolic. Thus, a polynomial of low order can be fitted to the distribution and then used for the calculation of derivatives of the advection and diffusion terms with great accuracy. The fitting method used was the cubic splines method. Initial experiments with the method included tests of the interpolation methods, which were found to be very accurate, and a few dispersion and advection experiments designed for an initial check of the influence of vertical wind shear, topography and changes of wind speed and direction with time. The results of these experiments show that the model has a marked advantage over the Gaussian model but its use requires more advanced computing facilities. (author)
International Nuclear Information System (INIS)
Sri Kuntjoro
2010-01-01
Additional of electrical power especially Nuclear Power Plant will give radiological consequence sto population and environment due to radioactive release in normal and abnormal condition. In consequence the management of nuclear power plant must supply data and strong argumentation to clarify the safety of nuclear power plant to environment. For that purpose it needs to be carried out an analysis of abnormal condition in nuclear power plant and its radiological consequences to the environment. That analysis is done using abnormal condition simulation model postulated on 1000 MWe nuclear power plant.That simulation model is used also to evaluate environmental potential as site capability in supporting the radiological consequences. Radionuclide transport modeling from reactor core to containment uses EMERALD computer code. Other computer codes are Wind rose, PC-COSYMA and Arc View are used to simulate meteorology condition, radionuclide release to population distribution of food production and consumption and distribution of radiation dose received to population around nuclear power plant. Application of that simulation is carried out to NPP candidate site in Bojanegara-Kramatwatu, Serang Banten peninsula. Using source term data, meteorology data, dispersion data and pathways modeling are resulting radionuclide dispersion model and radiation pathway acceptance at the surrounding nuclear power plant site (Bojanegara-Serang peninsula). The result shows that maximum radiation dose received is lower than dose permitted in accordance with regulatory body (BAPETEN). (author)
International Nuclear Information System (INIS)
Barros, Felipe Pereira Jorge de
2004-05-01
The aims of the present work were to use the Generalized Integral Transform Technique (GITT) to solve steady state multidimensional models for contaminants dispersion in rivers and channels, as well as to analyze the reduction of computational costs associated with convection-diffusion models that contains more than one space variable. The main focus of this work is the development of models that include variable coefficients such as variable velocity fields along and across the channel. The mathematical formulations also allow the use of different inlet conditions such as point sources, linear sources and plane sources. Several test cases were simulated and the models were validated numerically and with experimental data taken from the literature. The models were implemented in the symbolic computation platform, Mathematica 4.2. (author)
Edwards, L. L.; Harvey, T. F.; Freis, R. P.; Pitovranov, S. E.; Chernokozhin, E. V.
1992-10-01
The accuracy associated with assessing the environmental consequences of an accidental release of radioactivity is highly dependent on our knowledge of the source term characteristics and, in the case when the radioactivity is condensed on particles, the particle size distribution, all of which are generally poorly known. This paper reports on the development of a numerical technique that integrates the radiological measurements with atmospheric dispersion modeling. This results in a more accurate particle-size distribution and particle injection height estimation when compared with measurements of high explosive dispersal of (239)Pu. The estimation model is based on a non-linear least squares regression scheme coupled with the ARAC three-dimensional atmospheric dispersion models. The viability of the approach is evaluated by estimation of ADPIC model input parameters such as the ADPIC particle size mean aerodynamic diameter, the geometric standard deviation, and largest size. Additionally we estimate an optimal 'coupling coefficient' between the particles and an explosive cloud rise model. The experimental data are taken from the Clean Slate 1 field experiment conducted during 1963 at the Tonopah Test Range in Nevada. The regression technique optimizes the agreement between the measured and model predicted concentrations of (239)Pu by varying the model input parameters within their respective ranges of uncertainties. The technique generally estimated the measured concentrations within a factor of 1.5, with the worst estimate being within a factor of 5, very good in view of the complexity of the concentration measurements, the uncertainties associated with the meteorological data, and the limitations of the models. The best fit also suggest a smaller mean diameter and a smaller geometric standard deviation on the particle size as well as a slightly weaker particle to cloud coupling than previously reported.
International Nuclear Information System (INIS)
Edwards, L.L.; Harvey, T.F.; Freis, R.P.; Pitovranov, S.E.; Chernokozhin, E.V.
1992-10-01
The accuracy associated with assessing the environmental consequences of an accidental release of radioactivity is highly dependent on our knowledge of the source term characteristics and, in the case when the radioactivity is condensed on particles, the particle size distribution, all of which are generally poorly known. This paper reports on the development of a numerical technique that integrates the radiological measurements with atmospheric dispersion modeling. This results in a more accurate particle-size distribution and particle injection height estimation when compared with measurements of high explosive dispersal of 239 Pu. The estimation model is based on a non-linear least squares regression scheme coupled with the ARAC three-dimensional atmospheric dispersion models. The viability of the approach is evaluated by estimation of ADPIC model input parameters such as the ADPIC particle size mean aerodynamic diameter, the geometric standard deviation, and largest size. Additionally we estimate an optimal ''coupling coefficient'' between the particles and an explosive cloud rise model. The experimental data are taken from the Clean Slate 1 field experiment conducted during 1963 at the Tonopah Test Range in Nevada. The regression technique optimizes the agreement between the measured and model predicted concentrations of 239 Pu by varying the model input parameters within their respective ranges of uncertainties. The technique generally estimated the measured concentrations within a factor of 1.5, with the worst estimate being within a factor of 5, very good in view of the complexity of the concentration measurements, the uncertainties associated with the meteorological data, and the limitations of the models. The best fit also suggest a smaller mean diameter and a smaller geometric standard deviation on the particle size as well as a slightly weaker particle to cloud coupling than previously reported
Modeling blast waves, gas and particles dispersion in urban and hilly ground areas
International Nuclear Information System (INIS)
Hank, S.; Saurel, R.; Le Metayer, O.; Lapebie, E.
2014-01-01
The numerical simulation of shock and blast waves as well as particles dispersion in highly heterogeneous media such as cities, urban places, industrial plants and part of countries is addressed. Examples of phenomena under study are chemical gas products dispersion from damaged vessels, gas dispersion in urban places under explosion conditions, shock wave propagation in urban environment. A three-dimensional simulation multiphase flow code (HI2LO) is developed in this aim. To simplify the consideration of complex geometries, a heterogeneous discrete formulation is developed. When dealing with large scale domains, such as countries, the topography is considered with the help of elevation data. Meteorological conditions are also considered, in particular regarding complex temperature and wind profiles. Heat and mass transfers on sub-scale objects, such as buildings, trees and other obstacles are considered as well. Particles motion is addressed through a new turbulence model involving a single parameter to describe accurately plumes. Validations against experiments in basic situations are presented as well as examples of industrial and environmental computations. (authors)
International Nuclear Information System (INIS)
Bhattacharya, Sayak; Shah, Kushal
2015-01-01
The analytical dispersion relation of spoof surface plasmon (SSP) is known only in the low-frequency limit and thus cannot be used to describe various practically important characteristics of SSP in the high-frequency limit (such as multimodal nature, anisotropic propagation, self-collimation). In this article, we consider a square lattice of holes made on a perfect electric conductor and derive a closed form expression of the SSP dispersion relation in the high-frequency limit using a tight binding model. Instead of using prior knowledge of the band diagram along the entire first Brillouin zone (BZ) edge, we analytically determine the hopping parameters by using the eigenfrequencies only at the three high-symmetry points of the square lattice. Using this dispersion relation, we derive an expression for the self-collimation frequency of SSP. We show that this analytical formulation is also applicable to dielectric photonic crystals and can be used to predict the frequencies corresponding to centimetre-scale supercollimation and second band self-collimation in these structures. Finally, we show that our analytical results are in agreement with the simulation results for both SSP and photonic crystals. (paper)
Modelling electro-active polymers with a dispersion-type anisotropy
Hossain, Mokarram; Steinmann, Paul
2018-02-01
We propose a novel constitutive framework for electro-active polymers (EAPs) that can take into account anisotropy with a chain dispersion. To enhance actuation behaviour, particle-filled EAPs become promising candidates nowadays. Recent studies suggest that particle-filled EAPs, which can be cured under an electric field during the manufacturing time, do not necessarily form perfect anisotropic composites, rather they create composites with dispersed chains. Hence in this contribution, an electro-mechanically coupled constitutive model is devised that considers the chain dispersion with a probability distribution function in an integral form. To obtain relevant quantities in discrete form, numerical integration over the unit sphere is utilized. Necessary constitutive equations are derived exploiting the basic laws of thermodynamics that result in a thermodynamically consistent formulation. To demonstrate the performance of the proposed electro-mechanically coupled framework, we analytically solve a non-homogeneous boundary value problem, the extension and inflation of an axisymmetric cylindrical tube under electro-mechanically coupled load. The results capture various electro-mechanical couplings with the formulation proposed for EAP composites.
International Nuclear Information System (INIS)
Gromke, Christof
2011-01-01
A new vegetation modeling concept for Building and Environmental Aerodynamics wind tunnel investigations was developed. The modeling concept is based on fluid dynamical similarity aspects and allows the small-scale modeling of various kinds of vegetation, e.g. field crops, shrubs, hedges, single trees and forest stands. The applicability of the modeling concept was validated in wind tunnel pollutant dispersion studies. Avenue trees in urban street canyons were modeled and their implications on traffic pollutant dispersion were investigated. The dispersion experiments proved the modeling concept to be practicable for wind tunnel studies and suggested to provide reliable concentration results. Unfavorable effects of trees on pollutant dispersion and natural ventilation in street canyons were revealed. Increased traffic pollutant concentrations were found in comparison to the tree-free reference case. - Highlights: → A concept for aerodynamic modelling of vegetation in small scale wind tunnel studies is presented. → The concept was applied to study pollutant dispersion in urban street canyons with avenue tress. → The wind tunnel studies show that modelling the aerodynamic effects of vegetation is important. → Avenue trees give rise to increased pollutant concentrations in urban street canyons. - Avenue trees in urban street canyons affect the pollutant dispersion and result in increased traffic exhaust concentrations.
NOx dispersion modelling around roundabout in a small city, example from Hungary
Farkas, Orsolya; Rákai, Anikó; Czáder, Károly; Török, Ákos
2013-04-01
The present paper focuses on the modelling of pollutant distribution and dispersion in an urban region that is located in a moderately industrialized town of Hungary, Székesfehérvár, with a population of 100,000. The study area is located close to the city centre, with different housing styles and different building elevations. High-rise buildings with 10 floors to small houses with gardens are found in the modelled area. The roundabout has 5 access roads; three major ones and two minor ones with different geometries and traffic load. The traffic load of the roads was defined by traffic count, while for the meteorological characteristics wind-statistics were created. Additional input parameters were the ground plan and the elevation of buildings. To simulate the airflow and the dispersion of pollutants a Computational Fluid Dynamics code called MISKAM was used. The background concentration was taken from the dataset of a nearby air quality monitoring station. According to vehicle counting the 5 roads of the roundabout have very different loads from 12 vehicles to more than 412 vehicles/hour. Three different grid systems were applied ranging from half million to 5 million cells. The difference in the results related to grid density was also evaluated. Wind speed distribution, wind turbulence and building wake flow patterns were identified by using the model. With the help of the simulation the NOx flow and dispersion of pollutants around the roundabout can be estimated and the critical locations with higher pollution concentration are presented. The results of the modelling can be more generalized and used in the design of the layout, development, traffic-control and environmental aspects of roundabouts located in small urban areas.
The Dynamics of M15: Observations of the Velocity Dispersion Profile and Fokker-Planck Models
Dull, J. D.; Cohn, H. N.; Lugger, P. M.; Murphy, B. W.; Seitzer, P. O.; Callanan, P. J.; Rutten, R. G. M.; Charles, P. A.
1997-05-01
We report a new measurement of the velocity dispersion profile within 1' (3 pc) of the center of the globular cluster M15 (NGC 7078), using long-slit spectra from the 4.2 m William Herschel Telescope at La Palma Observatory. We obtained spatially resolved spectra for a total of 23 slit positions during two observing runs. During each run, a set of parallel slit positions was used to map out the central region of the cluster; the position angle used during the second run was orthogonal to that used for the first. The spectra are centered in wavelength near the Ca II infrared triplet at 8650 Å, with a spectral range of about 450 Å. We determined radial velocities by cross-correlation techniques for 131 cluster members. A total of 32 stars were observed more than once. Internal and external comparisons indicate a velocity accuracy of about 4 km s-1. The velocity dispersion profile rises from about σ = 7.2 +/- 1.4 km s-1 near 1' from the center of the cluster to σ = 13.9 +/- 1.8 km s-1 at 20". Inside of 20", the dispersion remains approximately constant at about 10.2 +/- 1.4 km s-1 with no evidence for a sharp rise near the center. This last result stands in contrast with that of Peterson, Seitzer, & Cudworth who found a central velocity dispersion of 25 +/- 7 km s-1, based on a line-broadening measurement. Our velocity dispersion profile is in good agreement with those determined in the recent studies of Gebhardt et al. and Dubath & Meylan. We have developed a new set of Fokker-Planck models and have fitted these to the surface brightness and velocity dispersion profiles of M15. We also use the two measured millisecond pulsar accelerations as constraints. The best-fitting model has a mass function slope of x = 0.9 (where 1.35 is the slope of the Salpeter mass function) and a total mass of 4.9 × 105 M⊙. This model contains approximately 104 neutron stars (3% of the total mass), the majority of which lie within 6" (0.2 pc) of the cluster center. Since the
Assessment of Safety Parameters for Radiological Explosion Based on Gaussian Dispersion Model
Energy Technology Data Exchange (ETDEWEB)
Pandey, Alok [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Yu, Hyungjoon; Kim, Hong Suk [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)
2014-10-15
These sources if used with explosive (called RDD - radiological dispersion device), can cause dispersion of radioactive material resulting in public exposure and contamination of the environment. Radiological explosion devices are not weapons for the mass destruction like atom bombs, but can cause the death of few persons and contamination of large areas. The reduction of the threat of radiological weapon attack by terrorist groups causing dispersion of radioactive material is one of the priority tasks of the IAEA Nuclear Safety and Security Program.Emergency preparedness is an essential part for reducing and mitigating radiological weapon threat. Preliminary assessment of dispersion study followed by radiological explosion and its quantitative effect will be helpful for the emergency preparedness team for an early response. The effect of the radiological dispersion depends on various factors like radioisotope, its activity, physical form, amount of explosive used and meteorological factors at the time of an explosion. This study aim to determine the area affected by the radiological explosion as pre assessment to provide feedback to emergency management teams for handling and mitigation the situation after an explosion. Most practical scenarios of radiological explosion are considered with conservative approach for the assessment of the area under a threat for emergency handling and management purpose. Radioisotopes under weak security controls can be used for a radiological explosion to create terror and socioeconomic threat for the public. Prior assessment of radiological threats is helpful for emergency management teams to take prompt decision about evacuation of the affected area and other emergency handling actions. Comparable activities of Co-60 source used in radiotherapy and Sr-90 source of disused and orphaned RTGs with two different quantities of TNT were used for the scenario development of radiological explosion. In the Basic Safety Standard (BSS
Assessment of Safety Parameters for Radiological Explosion Based on Gaussian Dispersion Model
International Nuclear Information System (INIS)
Pandey, Alok; Yu, Hyungjoon; Kim, Hong Suk
2014-01-01
These sources if used with explosive (called RDD - radiological dispersion device), can cause dispersion of radioactive material resulting in public exposure and contamination of the environment. Radiological explosion devices are not weapons for the mass destruction like atom bombs, but can cause the death of few persons and contamination of large areas. The reduction of the threat of radiological weapon attack by terrorist groups causing dispersion of radioactive material is one of the priority tasks of the IAEA Nuclear Safety and Security Program.Emergency preparedness is an essential part for reducing and mitigating radiological weapon threat. Preliminary assessment of dispersion study followed by radiological explosion and its quantitative effect will be helpful for the emergency preparedness team for an early response. The effect of the radiological dispersion depends on various factors like radioisotope, its activity, physical form, amount of explosive used and meteorological factors at the time of an explosion. This study aim to determine the area affected by the radiological explosion as pre assessment to provide feedback to emergency management teams for handling and mitigation the situation after an explosion. Most practical scenarios of radiological explosion are considered with conservative approach for the assessment of the area under a threat for emergency handling and management purpose. Radioisotopes under weak security controls can be used for a radiological explosion to create terror and socioeconomic threat for the public. Prior assessment of radiological threats is helpful for emergency management teams to take prompt decision about evacuation of the affected area and other emergency handling actions. Comparable activities of Co-60 source used in radiotherapy and Sr-90 source of disused and orphaned RTGs with two different quantities of TNT were used for the scenario development of radiological explosion. In the Basic Safety Standard (BSS
Li, Kewei; Ogden, Ray W; Holzapfel, Gerhard A
2018-01-01
Recently, micro-sphere-based methods derived from the angular integration approach have been used for excluding fibres under compression in the modelling of soft biological tissues. However, recent studies have revealed that many of the widely used numerical integration schemes over the unit sphere are inaccurate for large deformation problems even without excluding fibres under compression. Thus, in this study, we propose a discrete fibre dispersion model based on a systematic method for discretizing a unit hemisphere into a finite number of elementary areas, such as spherical triangles. Over each elementary area, we define a representative fibre direction and a discrete fibre density. Then, the strain energy of all the fibres distributed over each elementary area is approximated based on the deformation of the representative fibre direction weighted by the corresponding discrete fibre density. A summation of fibre contributions over all elementary areas then yields the resultant fibre strain energy. This treatment allows us to exclude fibres under compression in a discrete manner by evaluating the tension-compression status of the representative fibre directions only. We have implemented this model in a finite-element programme and illustrate it with three representative examples, including simple tension and simple shear of a unit cube, and non-homogeneous uniaxial extension of a rectangular strip. The results of all three examples are consistent and accurate compared with the previously developed continuous fibre dispersion model, and that is achieved with a substantial reduction of computational cost. © 2018 The Author(s).
Invariant Theory for Dispersed Transverse Isotropy: An Efficient Means for Modeling Fiber Splay
Freed, alan D.; Einstein, Daniel R.; Vesely, Ivan
2004-01-01
Most soft tissues possess an oriented architecture of collagen fiber bundles, conferring both anisotropy and nonlinearity to their elastic behavior. Transverse isotropy has often been assumed for a subset of these tissues that have a single macroscopically-identifiable preferred fiber direction. Micro-structural studies, however, suggest that, in some tissues, collagen fibers are approximately normally distributed about a mean preferred fiber direction. Structural constitutive equations that account for this dispersion of fibers have been shown to capture the mechanical complexity of these tissues quite well. Such descriptions, however, are computationally cumbersome for two-dimensional (2D) fiber distributions, let alone for fully three-dimensional (3D) fiber populations. In this paper, we develop a new constitutive law for such tissues, based on a novel invariant theory for dispersed transverse isotropy. The invariant theory is based on a novel closed-form splay invariant that can easily handle 3D fiber populations, and that only requires a single parameter in the 2D case. The model is polyconvex and fits biaxial data for aortic valve tissue as accurately as the standard structural model. Modification of the fiber stress-strain law requires no re-formulation of the constitutive tangent matrix, making the model flexible for different types of soft tissues. Most importantly, the model is computationally expedient in a finite-element analysis.
Marcello Falcieri, Francesco; Laforsch, Christian; Piehl, Sarah; Ricchi, Antonio; Atwood, Elizabeth C.; Carniel, Sandro; Sclavo, Mauro
2017-04-01
The Chiemsee (measuring about 80 km2 and a maximum depth of 73 m) is a NATURA 2000 site and one of the major German lakes and plays a significant environmental role for the region. Moreover it is an important touristic destination, making its beaches and water quality highly valuable from a socio-economical viewpoint. As for most inland European aquatic environments, the Chiemsee was recently found to be contaminated by microplastic (i.e. plastic fragments smaller than 0.5 mm). Two main microplastics sources were identified in the Chiemsee: riverine inputs, and degradation of litter from touristic beaches. Hence, it is of interest to study lake circulation and the resulting microplastic dispersion from these sources in order to support activities to achieve a good environmental status. Here we present the first attempt to characterize the hydrodynamic processes of the Chiemsee with a high resolution 3D implementation of the Regional Ocean Modeling System (ROMS). The simulations were forced with observed riverine inputs and modeled atmospherical fields computed with a local implementation of the Weather Research and Forecasting (WRF) model. Modeling results provide a first insight into the Chiemsee circulation system and contribute to understanding the dispersion pathways of microplastic particles from different sources. Furthermore, results can be used to highlight coastlines with higher risk of microplastic accumulation, identified using a set of Lagrangian simulations. The work was partially supported by the CNR Short Term Mobility grant.
Advanced modeling of the size poly-dispersion of boiling flows
International Nuclear Information System (INIS)
Ruyer, Pierre; Seiler, Nathalie
2008-01-01
Full text of publication follows: This work has been performed within the Institut de Radioprotection et de Surete Nucleaire that leads research programs concerning safety analysis of nuclear power plants. During a LOCA (Loss Of Coolant Accident), in-vessel pressure decreases and temperature increases, leading to the onset of nucleate boiling. The present study focuses on the numerical simulation of the local topology of the boiling flow. There is experimental evidence of a local and statistical large spectra of possible bubble sizes. The relative importance of the correct description of this poly-dispersion in size is due to the dependency of (i) main hydrodynamic forces, like lift, as well as of (ii) transfer area with respect to the individual bubble size. We study the corresponding CFD model in the framework of an ensemble averaged description of the dispersed two-phase flow. The transport equations of the main statistical moment densities of the population size distribution are derived and models for the mass, momentum and heat transfers at the bubble scale as well as for bubble coalescence are achieved. This model introduced within NEPTUNE-CFD code of the NEPTUNE thermal-hydraulic platform, a joint project of CEA, EDF, IRSN and AREVA, has been tested on boiling flows obtained on the DEBORA facility of the CEA at Grenoble. These numerical simulations provide a validation and attest the impact of the proposed model. (authors) [fr
Habilomatis, George; Chaloulakou, Archontoula
2013-10-01
Recently, a branch of particulate matter research concerns on ultrafine particles found in the urban environment, which originate, to a significant extent, from traffic sources. In urban street canyons, dispersion of ultrafine particles affects pedestrian's short term exposure and resident's long term exposure as well. The aim of the present work is the development and the evaluation of a composite lattice Boltzmann model to study the dispersion of ultrafine particles, in urban street canyon microenvironment. The proposed model has the potential to penetrate into the physics of this complex system. In order to evaluate the model performance against suitable experimental data, ultrafine particles levels have been monitored on an hourly basis for a period of 35 days, in a street canyon, in Athens area. The results of the comparative analysis are quite satisfactory. Furthermore, our modeled results are in a good agreement with the results of other computational and experimental studies. This work is a first attempt to study the dispersion of an air pollutant by application of the lattice Boltzmann method. Copyright © 2013 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Lee, B. W.; Hwang, W.; Lee, B. S.; Park, W. S.
2000-01-01
Either TRU-Zr metal alloy or (TRU-Zr)-Zr dispersion fuel is considered as a blanket fuel for HYPER(Hybrid Power Extraction Reactor). In order to develop the code for dispersion fuel rod performance analysis under steady state condition, the fuel temperature distribution model which is the one of the most important factors in a fuel performance code has been developed in this paper,. This developed model computes the one dimensional radial temperature distribution of a cylindrical fuel rod. The temperature profile results by this model are compared with the temperature distributions of U 3 Si-A1 dispersion fuel and TRU-Zr metal alloy fuel. This model will be installed in performance analysis code for dispersion fuel
Put, van der A.G.
1980-01-01
This thesis presents a systematic experimental and theoretical study on electrokinetic and electroconducting properties of disperse systems. The increasing interest in transport processes through charged porous systems has recently brought about a corresponding growth of models and theories since
Parameterizing Urban Canopy Layer transport in an Lagrangian Particle Dispersion Model
Stöckl, Stefan; Rotach, Mathias W.
2016-04-01
The percentage of people living in urban areas is rising worldwide, crossed 50% in 2007 and is even higher in developed countries. High population density and numerous sources of air pollution in close proximity can lead to health issues. Therefore it is important to understand the nature of urban pollutant dispersion. In the last decades this field has experienced considerable progress, however the influence of large roughness elements is complex and has as of yet not been completely described. Hence, this work studied urban particle dispersion close to source and ground. It used an existing, steady state, three-dimensional Lagrangian particle dispersion model, which includes Roughness Sublayer parameterizations of turbulence and flow. The model is valid for convective and neutral to stable conditions and uses the kernel method for concentration calculation. As most Lagrangian models, its lower boundary is the zero-plane displacement, which means that roughly the lower two-thirds of the mean building height are not included in the model. This missing layer roughly coincides with the Urban Canopy Layer. An earlier work "traps" particles hitting the lower model boundary for a recirculation period, which is calculated under the assumption of a vortex in skimming flow, before "releasing" them again. The authors hypothesize that improving the lower boundary condition by including Urban Canopy Layer transport could improve model predictions. This was tested herein by not only trapping the particles, but also advecting them with a mean, parameterized flow in the Urban Canopy Layer. Now the model calculates the trapping period based on either recirculation due to vortex motion in skimming flow regimes or vertical velocity if no vortex forms, depending on incidence angle of the wind on a randomly chosen street canyon. The influence of this modification, as well as the model's sensitivity to parameterization constants, was investigated. To reach this goal, the model was
Testing the atmospheric dispersion model of CSA N288.1 with site-specific data
Chouhan, S L
2001-01-01
The atmospheric dispersion component of CSA Standard N288. 1, which provides guidelines for calculating derived release limits, has been tested. Long-term average concentrations of tritium in air were predicted using site-specific release rates and meteorological data and compared with measured concentrations at 43 monitoring sites at all CANDU stations in Canada. The predictions correlate well with the observations but were found to be conservative, overestimating by about 50% on average. The model overpredicted 84% of the time, with the highest prediction lying a factor of 5.5 above the corresponding observation. The model underpredicted the remaining 16% of the time, with the lowest prediction about one-half of the corresponding measurement. Possible explanations for this bias are discussed but no single reason appears capable of accounting for the discrepancy. Rather, the tendency to overprediction seems to result from the cumulative effects of a number of small conservatisms in the model. The model predi...
A new percolation model for composite solid electrolytes and dispersed ionic conductors
Risyad Hasyim, Muhammad; Lanagan, Michael T.
2018-02-01
Composite solid electrolytes (CSEs) including conductor/insulator composites known as dispersed ionic conductors (DICs) have motivated the development of novel percolation models that describe their conductivity. Despite the long history, existing models lack in one or more key areas: (1) rigorous foundation for their physical theory, (2) explanation for non-universal conductor-insulator transition, (3) classification of DICs, and (4) extension to frequency-domain. This work describes a frequency-domain effective medium approximation (EMA) of a bond percolation model for CSEs. The EMA is derived entirely from Maxwell’s equations and contains basic microstructure parameters. The model was applied successfully to several composite systems from literature. Simulations and fitting of literature data address these key areas and illustrate the interplay between space charge layer properties and bulk microstructure.
Atmospheric Dispersion Models for the Calculation of Environmental Impact: A Comparative Study
International Nuclear Information System (INIS)
Caputo, Marcelo; Gimenez, Marcelo; Felicelli, Sergio; Schlamp, Miguel
2000-01-01
In this paper some new comparisons are presented between the codes AERMOD, HPDM and HYSPLIT.The first two are Gaussian stationary plume codes and they were developed to calculate environmental impact produced by chemical contaminants.HYSPLIT is a hybrid code because it uses a Lagrangian reference system to describe the transport of a puff center of mass and uses an Eulerian system to describe the dispersion within the puff.The meteorological and topographic data used in the present work were obtained from runs of the prognostic code RAMS, provided by NOAA. The emission was fixed in 0.3 g/s , 284 K and 0 m/s .The surface rough was fixed in 0.1m and flat terrain was considered.In order to analyze separate effects and to go deeper in the comparison, the meteorological data was split into two, depending on the atmospheric stability class (F to B), and the wind direction was fixed to neglect its contribution to the contaminant dispersion.The main contribution of this work is to provide recommendations about the validity range of each code depending on the model used.In the case of Gaussian models the validity range is fixed by the distance in which the atmospheric condition can be consider homogeneous.In the other hand the validity range of HYSPLIT's model is determined by the spatial extension of the meteorological data.The results obtained with the three codes are comparable if the emission is in equilibrium with the environment.This means that the gases were emitted at the same temperature of the medium with zero velocity.There was an important difference between the dispersion parameters used by the Gaussian codes
International Nuclear Information System (INIS)
Rossi, R.; Iaccarino, G.
2013-01-01
Highlights: • Scalar dispersion downstream of a wall-mounted cube is examined by DNS and RANS models. • Vortex-shedding and plume meandering are established in the wake of the cube. • Low-frequency modulation is observed in the vortex-shedding and plume meandering. • Counter-gradient transport takes place in the streamwise component of the scalar flux. • Concentration decay and plume spread improved by the unsteady RANS model. -- Abstract: A DNS database is employed to examine the onset of plume meandering downstream of a wall-mounted cube and to address the impact of large-scale unsteadiness in modeling dispersion using the RANS equations. The cube is immersed in a uniform stream where the thin boundary-layer developing over the flat plate is responsible for the onset of vortex-shedding in the wake of the bluff-body. Spectra of velocity and concentration fluctuations exhibit a prominent peak in the energy content at the same frequency, showing that the plume meandering is established by the action of the vortex-shedding. The vortex-shedding and plume meandering display a low-frequency modulation where coherent fluctuations are suppressed at times with a quasi-regular period. The onset of the low-frequency modulation is indicated by a secondary peak in the energy spectrum and confirmed by the autocorrelation of velocity and scalar fluctuations. Unsteady RANS simulations performed with the v 2 − f model are able to detect the onset of the plume meandering and show remarkable improvement of the predicted decay rate and rate of spread of the scalar plume when compared to steady RANS solutions. By computing explicitly the periodic component of velocity and scalar fluctuations, the unsteady v 2 − f model is able to provide a representation of scalar flux components consistent with DNS statistics, where the counter-gradient transport mechanism that takes place in the streamwise component is also captured by URANS results. Nonetheless, the agreement with DNS
Neutron-/sup 90/Zr mean field from a dispersive optical model analysis
International Nuclear Information System (INIS)
Delaroche, J.P.; Wang, Y.; Rapaport, J.
1989-01-01
Elastic scattering cross sections have been measured for 8, 10, and 24 MeV neutrons incident on /sup 90/Zr. These measurements, together with other neutron elastic scattering and total cross section data available up to 29 MeV, are used in grid searches to obtain an optical model potential which contains a dispersion relation term. This potential is then extrapolated toward negative energies to predict bound single-particle state properties. An overall good description of the data at positive and negative energies is achieved
Wind rose and Radionuclide Dispersion Modelling for Nuclear Malaysia Research Reactor
International Nuclear Information System (INIS)
Mohd Nahar Othman
2015-01-01
After the incident of radioactive gasses released to the environment because of unusual earthquake and tsunamis happen in Fukushima, Japan. The problem of release of radiological radionuclide became deep concern and serious problem to the world community. The incident course almost all nuclear power plant in Japan cannot operate because opposition from local people. From this point of view Malaysian Nuclear agency don't left behind in doing it research in release of radionuclide from it research reactor, in the meantime new wind rose data had been collected from 2013 to 2014. This paper will present the new radionuclide release including the new dispersion modelling that had been developed. (author)
Report of the Nordic dispersion-/trajectory model comparison with the ETEX-1 fullscale experiment
International Nuclear Information System (INIS)
Tveten, U.; Mikkelsen, T.
1995-12-01
On the 6th and 7th June 1995 a meeting was held at Risoe, where calculations of the atmospheric transportation and dispersion of the ETEX-1 release carried out by a number of institutions in the Nordic countries were presented. Also presented were the results of the measurements carried out by the National Environmental Research Institute of Denmark, information previously not known to the participants in the meeting. This provided not only an opportunity of intercomparing the models, but also of carrying out a validation exercise. The main points form the concluding discussions are also included in this report. (au) 7 tabs., 75 ills
International Nuclear Information System (INIS)
Sittel, Wiebke; Basuki, Widodo W.; Aktaa, Jarir
2015-01-01
A modeling based optimization process of the solid state diffusion bonding is presented for joining ferritic oxide dispersion strengthened steels PM2000. An optimization study employing varying bonding temperatures and pressures results in almost the same strength and toughness of the bonded compared to the as received material. TEM investigations of diffusion bonded samples show a homogeneous distribution of oxide particles at the bonding seam similar to that in the bulk. Hence, no loss in strength or creep resistance due to oxide particle agglomeration is found, as verified by the mechanical properties observed for the joint.
National Research Council Canada - National Science Library
McKinney, Jason D; Diehl, John
2007-01-01
In this work we demonstrate a new technique for measuring the chromatic dispersion of an optical fiber using the baseband RF response of a phase-modulated analog optical link in concert with a well...
Dispersive Sachdev-Ye-Kitaev model: Band structure and quantum chaos
Zhang, Pengfei
2017-11-01
The Sachdev-Ye-Kitaev (SYK) model is a concrete model for a non-Fermi liquid with maximally chaotic behavior in (0 +1 ) dimensions. In order to gain some insights into real materials in higher dimensions where fermions could hop between different sites, here we consider coupling a SYK lattice by constant hopping. We call this the dispersive SYK model. Focusing on (1 +1 ) -dimensional homogeneous hopping, by either tuning the temperature or the relative strength of the random interaction (hopping) and constant hopping, we find a crossover between a dispersive metal to an incoherent metal, where the dynamic exponent z changes from 1 to ∞ . We study the crossover by calculating the spectral function, charge density correlator, and the Lyapunov exponent. We further find the Lyapunov exponent becomes larger when the chemical potential is tuned to approach a van Hove singularity because of the large density of states near the Fermi surface. The effect of the topological nontrivial bands is also discussed.
Dispersion modeling in assessing air quality of industrial projects under Indian regulatory regime
Energy Technology Data Exchange (ETDEWEB)
Bandyopadhyay, Amitava [Department of Chemical Engineering, University of Calcutta, 92, A.P.C.Road, Kolkata 700 009 (India)
2010-07-01
Environmental impact assessment (EIA) studies conducted over the years as a part of obtaining environmental clearance in accordance with Indian regulation have been given significant attention towards carrying out Gaussian dispersion modeling for predicting the ground level concentration (GLC) of pollutants, especially for SO{sub 2}. Making any adhoc decision towards recommending flue gas desulfurization (FGD) system in Indian fossil fuel combustion operations is not realistic considering the usage of fuel with low sulfur content. Thus a predictive modeling is imperative prior to making any conclusive decision. In the light of this finding, dispersion modeling has been accorded in Indian environmental regulations. This article aims at providing approaches to ascertain pollution potential for proposed power plant operation either alone or in presence of other industrial operations under different conditions. In order to assess the performance of the computational work four different cases were analyzed based on worst scenario. Results obtained through predictions were compared with National Ambient Air Quality Standards (NAAQS) of India. One specific case found to overshoot the ambient air quality adversely in respect of SO2 and was therefore, suggested to install a FGD system with at least 80 % SO2 removal efficiency. With this recommendation, the cumulative prediction yielded a very conservative resultant value of 24 hourly maximum GLC of SO2 as against a value that exceeded well above the stipulated value without considering the FGD system. The computational algorithm developed can therefore, be gainfully utilized for the purpose of EIA analysis in Indian condition.
Haupt, Sue Ellen; Beyer-Lout, Anke; Long, Kerrie J.; Young, George S.
Assimilating concentration data into an atmospheric transport and dispersion model can provide information to improve downwind concentration forecasts. The forecast model is typically a one-way coupled set of equations: the meteorological equations impact the concentration, but the concentration does not generally affect the meteorological field. Thus, indirect methods of using concentration data to influence the meteorological variables are required. The problem studied here involves a simple wind field forcing Gaussian dispersion. Two methods of assimilating concentration data to infer the wind direction are demonstrated. The first method is Lagrangian in nature and treats the puff as an entity using feature extraction coupled with nudging. The second method is an Eulerian field approach akin to traditional variational approaches, but minimizes the error by using a genetic algorithm (GA) to directly optimize the match between observations and predictions. Both methods show success at inferring the wind field. The GA-variational method, however, is more accurate but requires more computational time. Dynamic assimilation of a continuous release modeled by a Gaussian plume is also demonstrated using the genetic algorithm approach.
International Nuclear Information System (INIS)
Aluzzi, F J; Pace, J C; Pobanz, B M; Vogt, P J
1999-01-01
On May 30, 1998 scrap metal containing radioactive Cesium-137 (Cs-137) was accidentally melted in a furnace at the Acerinox steel mill in Algeciras, Spain. Cs-137 was released from the mill's smokestack, and spread across the western Mediterranean Sea to France and Italy and beyond. The first indication of the release was radiation levels up to 1000 times background reported by Swiss, French, and Italian authorities during the following two weeks. Initially no elevated radiation levels were detected over Spain. A release of hazardous material to the atmosphere is the type of situation the Atmospheric Release Advisory Capability (ARAC) emergency response organization was designed to address. The amount and exact time of the release were unknown, though the incident was thought to have taken place during the last week in May. Using air concentration measurements supplied by colleagues of ARAC in Spain, France, Switzerland, Italy, Sweden, Russia and the European Union, ARAC meteorologists estimated the magnitude and timing of the release (Vogt, 1999). Correctly locating the downwind footprint is the most important goal of emergency response modeling. In this study, we compare predicted results for the Algeciras event based on four wind data sources: (1) US Navy Operational Global Atmospheric Prediction System (NOGAPS) data alone, (2) surface and upper air observations alone, (3) NOGAPS data together with surface and upper air observations, and (4) forecasts from ARAC's in-house execution of the U.S. Navy Operational Regional Atmospheric Prediction System (NORAPS) (without surface or upper air observations). We compare the resulting dispersion predictions from ARAC's diagnostic dispersion modeling system to the measurements supplied by our European colleagues to determine which data source produced the best results
International Nuclear Information System (INIS)
Moles, A.
2009-01-01
Very little is known about fish behaviour in relation to oil spill contamination. In this study, out-migrant pink salmon fry Oncorhynchus gorbuscha were subjected to varying concentrations of oil and sea water solutions, or uncontaminated sea water at a temperature of 7 degrees C. Fresh oil, artificially weathered oil, and dispersed oil samples were used. Twenty trials were run for concentrations of 48 aromatic and 30alkane hydrocarbons. The number of minutes spent in the uncontaminated water was significantly higher than sample areas. Fry avoided water-accommodated mixtures of Alaska North Slope crude oil in sea water at concentrations of 960 mg/L total aromatic hydrocarbon fresh oil and 873 mg/L total aromatic hydrocarbon dispersed oil. Concentrations corresponded to 75 per cent and 68 per cent of the median lethal concentration level. However, the fry did not avoid the weathered oil, which indicated that the fry may be sensitive to monoaromatic hydrocarbon components in the oil. It was concluded that oil pollution may alter pink salmon migration behaviour. 28 refs., 1 tab., 2 figs
Meneguz, Elena; Thomson, David; Witham, Claire; Kusmierczyk-Michulec, Jolanta
2015-04-01
NAME is a Lagrangian atmospheric dispersion model used by the Met Office to predict the dispersion of both natural and man-made contaminants in the atmosphere, e.g. volcanic ash, radioactive particles and chemical species. Atmospheric convection is responsible for transport and mixing of air resulting in a large exchange of heat and energy above the boundary layer. Although convection can transport material through the whole troposphere, convective clouds have a small horizontal length scale (of the order of few kilometres). Therefore, for large-scale transport the horizontal scale on which the convection exists is below the global NWP resolution used as input to NAME and convection must be parametrized. Prior to the work presented here, the enhanced vertical mixing generated by non-resolved convection was reproduced by randomly redistributing Lagrangian particles between the cloud base and cloud top with probability equal to 1/25th of the NWP predicted convective cloud fraction. Such a scheme is essentially diffusive and it does not make optimal use of all the information provided by the driving meteorological model. To make up for these shortcomings and make the parametrization more physically based, the convection scheme has been recently revised. The resulting version, presented in this paper, is now based on the balance equation between upward, entrainment and detrainment fluxes. In particular, upward mass fluxes are calculated with empirical formulas derived from Cloud Resolving Models and using the NWP convective precipitation diagnostic as closure. The fluxes are used to estimate how many particles entrain, move upward and detrain. Lastly, the scheme is completed by applying a compensating subsidence flux. The performance of the updated convection scheme is benchmarked against available observational data of passive tracers. In particular, radioxenon is a noble gas that can undergo significant long range transport: this study makes use of observations of
A model to predict failure of irradiated U–Mo dispersion fuel
Energy Technology Data Exchange (ETDEWEB)
Burkes, Douglas E., E-mail: Douglas.Burkes@pnnl.gov; Senor, David J.; Casella, Andrew M.
2016-12-15
Highlights: • Simple model to predict failure of dispersion fuel meat designs. • Evaluated as a function of fabrication parameters and irradiation conditions. • Predictions compare well with experimental measurements of miniature fuel plates. • Interaction layer formation reduces matrix strength and increases temperature. • Si additions to the matrix appear effective only at moderate heat flux and burnup. - Abstract: Numerous global programs are focused on the continued development of existing and new research and test reactor fuels to achieve maximum attainable uranium loadings to support the conversion of a number of the world’s remaining high-enriched uranium fueled reactors to low-enriched uranium fuel. Some of these programs are focused on development and qualification of a fuel design that consists of a uranium–molybdenum (U–Mo) alloy dispersed in an aluminum matrix as one option for reactor conversion. The current paper extends a failure model originally developed for UO{sub 2}-stainless steel dispersion fuels and uses currently available thermal–mechanical property information for the materials of interest in the currently proposed design. A number of fabrication and irradiation parameters were investigated to understand the conditions at which failure of the matrix, classified as onset of pore formation in the matrix, might occur. The results compared well with experimental observations published as part of the Reduced Enrichment for Research and Test Reactors (RERTR)-6 and -7 mini-plate experiments. Fission rate, a function of the {sup 235}U enrichment, appeared to be the most influential parameter in premature failure, mainly as a result of increased interaction layer formation and operational temperature, which coincidentally decreased the strength of the matrix and caused more rapid fission gas production and recoil into the surrounding matrix material. Addition of silicon to the matrix appeared effective at reducing the rate of
The dispersive optical model for n + [sup 208]Pb and n + [sup 209]Bi
Energy Technology Data Exchange (ETDEWEB)
Walter, R.L. (Dept. of Physics, Duke Univ., Durham, NC (United States) Triangle Univ. Nuclear Lab., Durham, NC (United States)); Weisel, G.J. (Dept. of Physics, Duke Univ., Durham, NC (United States) Triangle Univ. Nuclear Lab., Durham, NC (United States)); Das, R.K. (Dept. of Physics, Duke Univ., Durham, NC (United States) Triangle Univ. Nuclear Lab., Durham, NC (United States)); Tornow, W. (Dept. of Physics, Duke Univ., Durham, NC (United States) Triangle Univ. Nuclear Lab., Durham, NC (United States)); Howell, C.R. (Dept. of Physics, Duke Univ., Durham, NC (United States) Triangle Univ. Nuclear Lab., Durham, NC (United States))
1993-06-01
The dispersive optical model (DOM) provides a natural connection between the shell model potential for bound states and the optical model for nucleon scattering at positive energies. At TUNL we have developed DOMs for neutron scattering for ten nuclei between [sup 27]Al and [sup 209]Bi. In these studies we rely on TUNL measurements of differential cross-section ([sigma]([theta])) and analyzing power, as well as a wealth of [sigma]([theta]) and total cross section measurements from numerous other laboratories. In this paper we briefly outline the DOM method and the achievements in describing scattering data for n + [sup 208]Pb and n + [sup 209]Bi and single-particle bound-state data for neutrons in [sup 208]Pb. (orig.)
Modeling for pollution dispersion and air quality. 3.: meteorological data and emissions
International Nuclear Information System (INIS)
Bertagna, Silvia
2005-01-01
To better and correctly choose the suitable modeling system to use, it is necessary previously to define with objective criteria the characteristic of the problem to be studied and to gather together a great amount of input data and information, needed by the model, regarding, namely, the meteorological diffusive conditions of the atmosphere, the characteristic of the emission source (type, number, site etc.) and the characteristic of the area of interest (as land use and orography). In this work, the main different typologies of input data, which occur to simulate the air pollutant dispersion, are described, together with the instruments to obtain them: they include the consultation and the elaboration of information coming from databases and inventories appositely built and often also the use of other models or dedicated SW programs [it
A mechanistic Eulerian-Lagrangian model for dispersed flow film boiling
International Nuclear Information System (INIS)
Andreani, M.; Yadigaroglu, G.
1991-01-01
In this paper a new mechanistic model of heat transfer in the dispersed flow regime is presented. The usual assumptions that render most of the available models unsuitable for the analysis of the reflooding phase of the LOCA are discussed, and a two-dimensional time-independent numerical model is developed. The gas temperature field is solved in a fixed-grid (Eulerian) mesh, with the droplets behaving as mass and energy sources. The histories of a large number of computational droplets are followed in a Lagrangian frame, considering evaporation, break-up and interactions with the vapor and with the wall. comparisons of calculated wall and vapor temperatures with experimental data are shown for two reflooding tests
DEFF Research Database (Denmark)
Bigoni, Daniele; Engsig-Karup, Allan Peter; Eskilsson, Claes
2016-01-01
A major challenge in next-generation industrial applications is to improve numerical analysis by quantifying uncertainties in predictions. In this work we present a formulation of a fully nonlinear and dispersive potential flow water wave model with random inputs for the probabilistic description...... at different points in the parameter space, allowing for the reuse of existing simulation software. The choice of the applied methods is driven by the number of uncertain input parameters and by the fact that finding the solution of the considered model is computationally intensive. We revisit experimental...... benchmarks often used for validation of deterministic water wave models. Based on numerical experiments and assumed uncertainties in boundary data, our analysis reveals that some of the known discrepancies from deterministic simulation in comparison with experimental measurements could be partially explained...
International Nuclear Information System (INIS)
Kobayashi, Takuya; Otosaka, Shigeyoshi; Togawa, Orihiko; Hayashi, Keisuke
2007-01-01
A numerical simulation model system that consists of an ocean current model, Princeton Ocean Model (POM), and a particle random-walk model, SEA-GEARN, has been developed to describe the migration behavior of non-conservative radionuclides in a shallow water region. Radionuclides in the ocean are modeled in three phases, i.e., the dissolved phase in seawater, the adsorbed with large particulate matter (LPM) and the adsorbed with active bottom sediment. The adsorption and desorption processes between the dissolved and solid phases are solved by the stochastic method with the kinetic transfer coefficients. Deposition of the LPM and re-suspension from bottom sediment are also considered. The system was applied to simulate the long-term (24-year) dispersion of 137 Cs actually released from the BNFL spent nuclear fuel reprocessing plant at Sellafield in United Kingdom. The calculation well reproduced the main characteristics of migration of dissolved 137 Cs concentration in the Irish Sea. (author)
Roustan, Yelva; Duhanyan, Nora; Bocquet, Marc; Winiarek, Victor
2013-04-01
A sensitivity study of the numerical model, as well as, an inverse modelling approach applied to the atmospheric dispersion issues after the Chernobyl disaster are both presented in this paper. On the one hand, the robustness of the source term reconstruction through advanced data assimilation techniques was tested. On the other hand, the classical approaches for sensitivity analysis were enhanced by the use of an optimised forcing field which otherwise is known to be strongly uncertain. The POLYPHEMUS air quality system was used to perform the simulations of radionuclide dispersion. Activity concentrations in air and deposited to the ground of iodine-131, caesium-137 and caesium-134 were considered. The impact of the implemented parameterizations of the physical processes (dry and wet depositions, vertical turbulent diffusion), of the forcing fields (meteorology and source terms) and of the numerical configuration (horizontal resolution) were investigated for the sensitivity study of the model. A four dimensional variational scheme (4D-Var) based on the approximate adjoint of the chemistry transport model was used to invert the source term. The data assimilation is performed with measurements of activity concentrations in air extracted from the Radioactivity Environmental Monitoring (REM) database. For most of the investigated configurations (sensitivity study), the statistics to compare the model results to the field measurements as regards the concentrations in air are clearly improved while using a reconstructed source term. As regards the ground deposited concentrations, an improvement can only be seen in case of satisfactorily modelled episode. Through these studies, the source term and the meteorological fields are proved to have a major impact on the activity concentrations in air. These studies also reinforce the use of reconstructed source term instead of the usual estimated one. A more detailed parameterization of the deposition process seems also to be
International Nuclear Information System (INIS)
Amokrane, Abdenour
2014-01-01
The thesis focuses on the study and modeling of a pulsed column used in liquid-liquid extraction operations in the nuclear industry and which is otherwise considered for continuous precipitation operations in emulsion. Modeling the behavior of the dispersed phase in the column is undertaken in this manuscript. First, we began by modeling the continuous phase mean velocity and turbulence fields, which are responsible for transport, breakage and coalescence of the drops. The model developed, validated by PIV measurements, predicts turbulence in a satisfying way. Modeling the residence time distribution (RTD) of the drops by a Lagrangian approach is then achieved. This model is validated on measurements taken by a shadow-graph technique. The simulation results are in good agreement with the experimental ones. To model the droplet size distributions (DSD) in the column, we used the population balance equations (PBE) that we have coupled with the computational fluid dynamics equations (CFD). A continuously stirred tank reactor (CSTR) with an optical sensor is used, at first, to acquire the DSD representative of our liquid-liquid system. Through a 0D modeling of the flow in the CSTR, and solving the inverse problem, we have determined the breakage and coalescence kernels relevant for our system, to be used in the PBE. These kernels were then used to predict the DSD in the pulsed column by a coupled CFD-PBE model based on the QMOM method. Finally, a validation of the coupled CFD-PBE model is made from DSD in good agreement with the experimental data both qualitatively and quantitatively. The validated model is then used to study the emulsion sensitivity to the column operating conditions. (author) [fr
Dave, Rutesh H; Patel, Hardikkumar H; Donahue, Edward; Patel, Ashwinkumar D
2013-10-01
The solubility of drugs remains one of the most challenging aspects of formulation development. There are numerous ways to improve the solubility of drugs amongst which the most promising strategy is solid dispersion. Different ratios of sulfathiazole: PVP-K29/32: sodium lauryl sulfate (SLS) were prepared (1:1:0.1, 1:1:0.5, 1:1:1) and various methods were employed to characterize the prepared solid dispersions, namely modulated differential scanning calorimeter, X-ray powder diffraction, Fourier Transformed Infrared Spectroscopy and dissolution studies. Lack of crystallinity was observed in internal and external systems suggesting a loss of crystallinity, whereas the physical mixtures showed a characteristic peak of sulfathiazole. In vitro dissolution results clearly showed that the incorporation of a relatively small amount of surfactants (5, 20 or 33% w/w) into a solid dispersion can improve its dissolution rates compared to binary solid dispersion (SD) alone and pure sulfathiazole. In all ratios solid dispersion internal shows a higher dissolution rate compared to a physical mixture and solid dispersion external which suggests that the way that the surfactant is incorporated into the solid dispersion plays an important role in changing the solubility of a drug. The solubilization mechanism is mainly responsible for this higher dissolution rate when we incorporate the SLS in SD.
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.
Numerical modeling of disperse material evaporation in axisymmetric thermal plasma reactor
Directory of Open Access Journals (Sweden)
Stefanović Predrag Lj.
2003-01-01
Full Text Available A numerical 3D Euler-Lagrangian stochastic-deterministic (LSD model of two-phase flow laden with solid particles was developed. The model includes the relevant physical effects, namely phase interaction, panicle dispersion by turbulence, lift forces, particle-particle collisions, particle-wall collisions, heat and mass transfer between phases, melting and evaporation of particles, vapour diffusion in the gas flow. It was applied to simulate the processes in thermal plasma reactors, designed for the production of the ceramic powders. Paper presents results of extensive numerical simulation provided (a to determine critical mechanism of interphase heat and mass transfer in plasma flows, (b to show relative influence of some plasma reactor parameters on solid precursor evaporation efficiency: 1 - inlet plasma temperature, 2 - inlet plasma velocity, 3 - particle initial diameter, 4 - particle injection angle a, and 5 - reactor wall temperature, (c to analyze the possibilities for high evaporation efficiency of different starting solid precursors (Si, Al, Ti, and B2O3 powder, and (d to compare different plasma reactor configurations in conjunction with disperse material evaporation efficiency.
Physically Inspired Models for the Synthesis of Stiff Strings with Dispersive Waveguides
Directory of Open Access Journals (Sweden)
Testa I
2004-01-01
Full Text Available We review the derivation and design of digital waveguides from physical models of stiff systems, useful for the synthesis of sounds from strings, rods, and similar objects. A transform method approach is proposed to solve the classic fourth-order equations of stiff systems in order to reduce it to two second-order equations. By introducing scattering boundary matrices, the eigenfrequencies are determined and their dependency is discussed for the clamped, hinged, and intermediate cases. On the basis of the frequency-domain physical model, the numerical discretization is carried out, showing how the insertion of an all-pass delay line generalizes the Karplus-Strong algorithm for the synthesis of ideally flexible vibrating strings. Knowing the physical parameters, the synthesis can proceed using the generalized structure. Another point of view is offered by Laguerre expansions and frequency warping, which are introduced in order to show that a stiff system can be treated as a nonstiff one, provided that the solutions are warped. A method to compute the all-pass chain coefficients and the optimum warping curves from sound samples is discussed. Once the optimum warping characteristic is found, the length of the dispersive delay line to be employed in the simulation is simply determined from the requirement of matching the desired fundamental frequency. The regularization of the dispersion curves by means of optimum unwarping is experimentally evaluated.
International Nuclear Information System (INIS)
Mora, V.R.; Sosa, G.; Molina, M.M.; Palmerin-ruiz, M.E.; Melgarejo-flores, L.E.
2009-01-01
Major sulphur dioxide emissions in Mexico are due largely to fuel of oil refining and coal combustion. In Tula-Vito-Apasco industrial corridor (TVA) are located two important sources of SO/sub 2/: the 'Miguel Hidalgo' refinery and the 'Francisco Perez Rios' power plant. Due to from March 25 to April 22 of 2006 a major field campaign took place as part of a collaborative research program called MILAGRO. Data collected around the Industrial Complex were used to: a) evaluate the air quality to local and regional scale; b) study the structure of the atmospheric boundary layer (BL); and c) validate meteorological and dispersion models. In this study we presented the behaviour of daytime BL, and the results of meteorological and dispersion modelling for selected episodes of high sulfur dioxide (SO/sub 2/). The Regional Atmospheric Modeling System (RAMS) and the Hybrid and Particle Concentration Transport Model (HYPACT) were used to evaluate the impact of SO/sub 2/ emissions to regional scale. For modelling, we selected the days where higher mean daily levels of SO/sub 2 /surface concentrations were observed, these corresponded to March 31 and April 6. The results indicate that: The daytime BL in TVA, exhibited a normal behavior, a stable layer or thermal inversion close to surface was observed at 0800 LST (up to 80% of the cases), then the mixing height (MH) growths, with a growth rate of 313 m h-1 (between 0800 to 1200 LST). The most rapid MH growth happened between 1200 to 1500 LST;. The maximum MH was observed at 1500 LST (90% of the cases); the mean maximum MH was close to 2794 m AGL; Potential temperature and humidity profiles showed a normal behavior; High persistence in wind direction (> 0.6) close to surface up to 500 m AGL, was observed at 1500, and 1800 LST, at the same time, a low level jet, penetrating from the NE, with wind speed between 6 to 8 m s/sup -1/ was observed. Meteorological modelling was used to determine the circulation patterns in the region
Optically induced anisotropy in photo responsive sol-gel matrix bearing a silylated disperse red 1
International Nuclear Information System (INIS)
Choi, Dong Hoon; Cho, Kang Jin; Cha, Young Kwan; Oh, Sang Joon
2000-01-01
We synthesized the simple triethoxysilanes (SGDR1) bearing a disperse red 1 for thin film fabrication. The thin films were prepared using the solution of SGDR1 after hydrolysis and condensation. The films were annealed at two different temperatures such as 150.deg.C and 200.deg.C. Trans-to-cis photoisomerization was observed under the exposure of 532 nm light with UV-Vis absorption spectroscopy. The kinetic study of photoisomerization was performed in the film. Reorientation of the polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532 nm. The effect of aggregation of the chromophores and annealing of the silicon oxide in the matrix were studied on the dynamic properties of isomerization and induced birefringence
Sensing response of copper phthalocyanine salt dispersed glass with organic vapours
Energy Technology Data Exchange (ETDEWEB)
Ridhi, R.; Sachdeva, Sheenam; Saini, G. S. S.; Tripathi, S. K., E-mail: surya@pu.ac.in [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh-160 014 (INDIA) Fax: +91-172-2783336; Tel.:+91-172-2544362 (India)
2016-05-06
Copper Phthalocyanine and other Metal Phthalocyanines are very flexible and tuned easily to modify their structural, spectroscopic, optical and electrical properties by either functionalizing them with various substituent groups or by replacing or adding a ligand to the central metal atom in the phthalocyanine ring and accordingly can be made sensitive and selective to various organic species or gaseous vapours. In the present work, we have dispersed Copper Phthalocyanine Salt (CuPcS) in sol-gel glass form using chemical route sol-gel method and studied its sensing mechanism with organic vapours like methanol and benzene and found that current increases onto their exposure with vapours. A variation in the activation energies was also observed with exposure of vapours.
Dispersive FDTD analysis of induced electric field in human models due to electrostatic discharge.
Hirata, Akimasa; Nagai, Toshihiro; Koyama, Teruyoshi; Hattori, Junya; Chan, Kwok Hung; Kavet, Robert
2012-07-07
Contact currents flow from/into a charged human body when touching a grounded conductive object. An electrostatic discharge (ESD) or spark may occur just before contact or upon release. The current may stimulate muscles and peripheral nerves. In order to clarify the difference in the induced electric field between different sized human models, the in-situ electric fields were computed in anatomically based models of adults and a child for a contact current in a human body following ESD. A dispersive finite-difference time-domain method was used, in which biological tissue is assumed to obey a four-pole Debye model. From our computational results, the first peak of the discharge current was almost identical across adult and child models. The decay of the induced current in the child was also faster due mainly to its smaller body capacitance compared to the adult models. The induced electric fields in the forefingers were comparable across different models. However, the electric field induced in the arm of the child model was found to be greater than that in the adult models primarily because of its smaller cross-sectional area. The tendency for greater doses in the child has also been reported for power frequency sinusoidal contact current exposures as reported by other investigators.
Dispersive FDTD analysis of induced electric field in human models due to electrostatic discharge
International Nuclear Information System (INIS)
Hirata, Akimasa; Nagai, Toshihiro; Koyama, Teruyoshi; Hattori, Junya; Chan, Kwok Hung; Kavet, Robert
2012-01-01
Contact currents flow from/into a charged human body when touching a grounded conductive object. An electrostatic discharge (ESD) or spark may occur just before contact or upon release. The current may stimulate muscles and peripheral nerves. In order to clarify the difference in the induced electric field between different sized human models, the in-situ electric fields were computed in anatomically based models of adults and a child for a contact current in a human body following ESD. A dispersive finite-difference time-domain method was used, in which biological tissue is assumed to obey a four-pole Debye model. From our computational results, the first peak of the discharge current was almost identical across adult and child models. The decay of the induced current in the child was also faster due mainly to its smaller body capacitance compared to the adult models. The induced electric fields in the forefingers were comparable across different models. However, the electric field induced in the arm of the child model was found to be greater than that in the adult models primarily because of its smaller cross-sectional area. The tendency for greater doses in the child has also been reported for power frequency sinusoidal contact current exposures as reported by other investigators. (paper)
Directory of Open Access Journals (Sweden)
Sofia Costanzini
2018-01-01
Full Text Available This work originates from an epidemiological study aimed to assess the correlation between population exposure to pesticides used in agriculture and adverse health effects. In support of the population exposure evaluation two models implemented by the authors were applied: a GIS-based proximity model and the CAREA atmospheric dispersion model. In this work, the results of the two models are presented and compared. Despite the proximity analysis is widely used for these kinds of studies, it was investigated how meteorology could affect the exposure assessment. Both models were applied to pesticides emitted by 1519 agricultural fields and considering 2584 receptors distributed over an area of 8430 km2. CAREA output shows a considerable enhancement in the percentage of exposed receptors, from the 4% of the proximity model to the 54% of the CAREA model. Moreover, the spatial analysis of the results on a specific test site showed that the effects of meteorology considered by CAREA led to an anisotropic exposure distribution that differs considerably from the symmetric distribution resulting by the proximity model. In addition, the results of a field campaign for the definition and planning of ground measurement of concentration for the validation of CAREA are presented. The preliminary results showed how, during treatments, pesticide concentrations distant from the fields are significantly higher than background values.
International Nuclear Information System (INIS)
Srinivas, C.V; Venkatesan, R.; Bagavath Singh, A.; Somayaji, K.M.
2003-11-01
Environmental concentrations and radioactive doses within and beyond the site boundary for the CDA situation of PFBR have been estimated using an Advanced Radiological Impact Prediction system for a real atmospheric situation on a typical summer day in the month of May 2003. The system consists of a meso-scale atmospheric prognostic model MM5 coupled with a random walk Lagrangian particle dispersion model FLEXPART for the simulation of transport, diffusion and deposition of radio nuclides. The details of the modeling system, its capabilities and various features are presented. The model has been validated for the simulated coastal atmospheric features of land-sea breeze, development of TIBL etc., with site and regional meteorological observations from IMD. Analysis of the dose distribution in a situation that corresponds to the atmospheric conditions on the chosen day shows that the doses for CDA through different pathways are 8 times less than the earlier estimations made according to regulatory requirements using the Gaussian Plume Model (GPM) approach. However for stack releases a higher dose than was reported earlier occurred beyond the site boundary at 2-4 km range under stable and fumigation conditions. The doses due to stack releases under these conditions maintained almost the same value in 3 to 10 km range and decreased there after. Deposition velocities computed from radionuclide species, wind speed, surface properties were 2 orders lower than the values used earlier and hence gave more realistic estimates of ground deposited activity. The study has enabled to simulate the more complex meteorological situation that actually is present at the site of interest and the associated spatial distribution of radiological impact around Kalpakkam. In order to draw meaningful conclusion that can be compared with regulatory estimates future study would be undertaken to simulate the dispersion under extreme meteorological situations which could possibly be worse than
Chai, Tianfeng; Crawford, Alice; Stunder, Barbara; Pavolonis, Michael J.; Draxler, Roland; Stein, Ariel
2017-02-01
Currently, the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) runs the HYSPLIT dispersion model with a unit mass release rate to predict the transport and dispersion of volcanic ash. The model predictions provide information for the Volcanic Ash Advisory Centers (VAAC) to issue advisories to meteorological watch offices, area control centers, flight information centers, and others. This research aims to provide quantitative forecasts of ash distributions generated by objectively and optimally estimating the volcanic ash source strengths, vertical distribution, and temporal variations using an observation-modeling inversion technique. In this top-down approach, a cost functional is defined to quantify the differences between the model predictions and the satellite measurements of column-integrated ash concentrations weighted by the model and observation uncertainties. Minimizing this cost functional by adjusting the sources provides the volcanic ash emission estimates. As an example, MODIS (Moderate Resolution Imaging Spectroradiometer) satellite retrievals of the 2008 Kasatochi volcanic ash clouds are used to test the HYSPLIT volcanic ash inverse system. Because the satellite retrievals include the ash cloud top height but not the bottom height, there are different model diagnostic choices for comparing the model results with the observed mass loadings. Three options are presented and tested. Although the emission estimates vary significantly with different options, the subsequent model predictions with the different release estimates all show decent skill when evaluated against the unassimilated satellite observations at later times. Among the three options, integrating over three model layers yields slightly better results than integrating from the surface up to the observed volcanic ash cloud top or using a single model layer. Inverse tests also show that including the ash-free region to constrain the model is not
International Nuclear Information System (INIS)
Steckmeyer, A.
2012-01-01
The strength of metals, and therefore their maximum operating temperature, can be improved by oxide dispersion strengthening (ODS). Numerous research studies are carried out at the French Atomic Energy Commission (CEA) in order to develop a cladding tube material for Gen IV nuclear power reactors. Oxide dispersion strengthened steels appear to be the most promising candidates for such application, which demands a minimum operating temperature of 650 C. The present dissertation intends to improve the understanding of the mechanical properties of ODS steels, in terms of creep lifetime and mechanical anisotropy. The methodology of this work includes mechanical tests between room temperature and 900 C as well as macroscopic and polycrystalline modelling. These tests are carried out on a Fe-14Cr1W0,26Ti + 0,3 Y 2 O 3 ODS ferritic steel processed at CEA by mechanical alloying and hot extrusion. The as-received material is a bar with a circular section. The mechanical tests reveal the high mechanical strength of this steel at high temperature. A strong influence of the strain rate on the ductility and the mechanical strength is also observed. A macroscopic mechanical model has been developed on the basis of some experimental statements such as the high kinematic contribution to the flow stress. This model has a strong ability to reproduce the mechanical behaviour of the studied material. Two different polycrystalline models have also been developed in order to reproduce the mechanical anisotropy of the material. They are based on its specific grain morphology and crystallographic texture. The discrepancy between the predictions of both models and experimental results reveal the necessity to formulate alternate assumptions on the deformation mechanisms of ODS ferritic steels. (author) [fr
Energy Technology Data Exchange (ETDEWEB)
Berlowitz, D.R.
1996-11-01
In the last few decades the negative impact by humans on the thin atmospheric layer enveloping the earth, the basis for life on this planet, has increased steadily. In order to halt, or at least slow down this development, the knowledge and study of these anthropogenic influence has to be increased and possible remedies have to be suggested. An important tool for these studies are computer models. With their help the atmospheric system can be approximated and the various processes, which have led to the current situation can be quantified. They also serve as an instrument to assess short or medium term strategies to reduce this human impact. However, to assure efficiency as well as accuracy, a careful analysis of the numerous processes involved in the dispersion of pollutants in the atmosphere is called for. This should help to concentrate on the essentials and also prevent excessive usage of sometimes scarce computing resources. The basis of the presented work is the EUMAC Zooming Model (ETM), and particularly the component calculating the dispersion of pollutants in the atmosphere, the model MARS. The model has two main parts: an explicit solver, where the advection and the horizontal diffusion of pollutants are calculated, and an implicit solution mechanism, allowing the joint computation of the change of concentration due to chemical reactions, coupled with the respective influence of the vertical diffusion of the species. The aim of this thesis is to determine particularly the influence of the horizontal components of the turbulent diffusion on the existing implicit solver of the model. Suggestions for a more comprehensive inclusion of the full three dimensional diffusion operator in the implicit solver are made. This is achieved by an appropriate operator splitting. A selection of numerical approaches to tighten the coupling of the diffusion processes with the calculation of the applied chemical reaction mechanisms are examined. (author) figs., tabs., refs.
International Nuclear Information System (INIS)
Fukuda, Ryo; Fujita, Yuko; Yoneda, Jiro; Okabayashi, Kazuki; Tabuse, Shigehiko; Watada, Masayuki
2009-01-01
dispersion effect exists behind a building. Regarding the degree of meandering effect with dispersion by a building, however, the further investigation would still be necessary for a conclusion. At an additional experiment with a model of a higher release point similar to BWR LOCA showed no significant dispersion effect behind a building. The prediction of both of past and recent prediction models did not show an enough good agreement with this experimental data. The configuration coefficient by Gifford model, only predicting the experiment with PWR LOCA, was widely ranged between 0.1 and 1.0 on the roof of the building. (author)
Liu, Yun; Li, Hong; Sun, Sida; Fang, Sheng
2017-09-01
An enhanced air dispersion modelling scheme is proposed to cope with the building layout and complex terrain of a typical Chinese nuclear power plant (NPP) site. In this modelling, the California Meteorological Model (CALMET) and the Stationary Wind Fit and Turbulence (SWIFT) are coupled with the Risø Mesoscale PUFF model (RIMPUFF) for refined wind field calculation. The near-field diffusion coefficient correction scheme of the Atmospheric Relative Concentrations in the Building Wakes Computer Code (ARCON96) is adopted to characterize dispersion in building arrays. The proposed method is evaluated by a wind tunnel experiment that replicates the typical Chinese NPP site. For both wind speed/direction and air concentration, the enhanced modelling predictions agree well with the observations. The fraction of the predictions within a factor of 2 and 5 of observations exceeds 55% and 82% respectively in the building area and the complex terrain area. This demonstrates the feasibility of the new enhanced modelling for typical Chinese NPP sites. Copyright © 2017 Elsevier Ltd. All rights reserved.
A source term estimation method for a nuclear accident using atmospheric dispersion models
DEFF Research Database (Denmark)
Kim, Minsik; Ohba, Ryohji; Oura, Masamichi
2015-01-01
The objective of this study is to develop an operational source term estimation (STE) method applicable for a nuclear accident like the incident that occurred at the Fukushima Dai-ichi nuclear power station in 2011. The new STE method presented here is based on data from atmospheric dispersion...... models and short-range observational data around the nuclear power plants.The accuracy of this method is validated with data from a wind tunnel study that involved a tracer gas release from a scaled model experiment at Tokai Daini nuclear power station in Japan. We then use the methodology developed...... and validated through the effort described in this manuscript to estimate the release rate of radioactive material from the Fukushima Dai-ichi nuclear power station....
International Nuclear Information System (INIS)
Lazaro, M.
1989-06-01
The US Department of Energy is conducting the Weldon Spring Site Remedial Action Project under the Surplus Facilities Management Program (SFMP). The major goals of the SFMP are to eliminate potential hazards to the public and the environment that associated with contamination at SFMP sites and to make surplus property available for other uses to the extent possible. This report presents the results of analysis of available meteorological data from stations near the Weldon Spring site. Data that are most representative of site conditions are needed to accurately model the transport and dispersion of air pollutants associated with remedial activities. Such modeling will assist the development of mitigative measures. 17 refs., 12 figs., 6 tabs
Mercury Dispersion Modeling And Purge Ventilation Stack Height Determination For Tank 40H
Energy Technology Data Exchange (ETDEWEB)
Rivera-Giboyeaux, A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2017-05-19
The SRNL Atmospheric Technologies Group performed an analysis for mercury emissions from H-Tank Farm - Tank 40 ventilation system exhaust in order to assess whether the Short Term Exposure Limit (STEL), or Threshold Limit Value (TLV) levels for mercury will be exceeded during bulk sludge slurry mixing and sludge removal operations. The American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) was used as the main dispersion modelling tool for this analysis. The results indicated that a 45-foot stack is sufficient to raise the plume centerline from the Tank 40 release to prevent mercury exposure problems for any of the stack discharge scenarios provided. However, a 42-foot stack at Tank 40 is sufficient to prevent mercury exposure concerns in all emission scenarios except the 50 mg/m^{3} release. At a 42-foot stack height, values exceeding the exposure standards are only measured on receptors located above 34 feet.
International Nuclear Information System (INIS)
Emad, A.A.; El Shazly, S.M.; Kassem, Kh.O.
2010-01-01
A line source model, developed in laboratory of environmental physics, faculty of science at Qena, Egypt is proposed to describe the downwind dispersion of pollutants near roadways, at different cities in Egypt. The model is based on the Gaussian plume methodology and is used to predict air pollutants' concentrations near roadways. In this direction, simple software has been presented in this paper, developed by authors, adopted completely Graphical User Interface (GUI) technique for operating in various windows-based microcomputers. The software interface and code have been designed by Microsoft Visual basic 6.0 based on the Gaussian diffusion equation. This software is developed to predict concentrations of gaseous pollutants (eg. CO, SO 2 , NO 2 and particulates) at a user specified receptor grid
Application of the annular dispersed flow model to two-phase critical flow calculation
International Nuclear Information System (INIS)
Ivandaev, A.I.; Nigmatulin, B.I.
1977-01-01
The application of the annular dispersed flow model with an effective monodisperse core to the calculation of vapour-liquid mixture maximum rates through long pipes is discussed. An effect of the main dominant parameters such as evaporation intensity, diameter of drops picked out from the film surface and initial drop diameter at the pipe inlet on the outlet critical condition formation process has been investigated. The corresponding model constants have been determined. The calculated and experimental values of critical rates and pressure profiles along the channel have been found to be in a satisfactory agreement in the studied range of parameters. The observed non-conformity of the calculated and experimental values of critical pressures and vapour contents can be due to inadequate accuracy of the experimental techniques
Testing the atmospheric dispersion model of CSA N288.1 with site-specific data
International Nuclear Information System (INIS)
Chouhan, S.L.; Davis, P.A.
2001-01-01
The atmospheric dispersion component of CSA Standard N288. 1, which provides guidelines for calculating derived release limits, has been tested. Long-term average concentrations of tritium in air were predicted using site-specific release rates and meteorological data and compared with measured concentrations at 43 monitoring sites at all CANDU stations in Canada. The predictions correlate well with the observations but were found to be conservative, overestimating by about 50% on average. The model overpredicted 84% of the time, with the highest prediction lying a factor of 5.5 above the corresponding observation. The model underpredicted the remaining 16% of the time, with the lowest prediction about one-half of the corresponding measurement. Possible explanations for this bias are discussed but no single reason appears capable of accounting for the discrepancy. Rather, the tendency to overprediction seems to result from the cumulative effects of a number of small conservatisms in the model. The model predictions were slightly better when site-specific meteorological data were used in the calculations in place of the default data of N288.1. Some large discrepancies between predictions and observations at specific monitoring sites suggest that it is the measurements rather than the model that are at fault. The testing has therefore provided a check on the observations as well as on the model. Recommendations on model use and data collection are made to improve the level of agreement between predictions and observations in the future. (author)
Transport and dispersion of pollutants in surface impoundments: a finite element model
International Nuclear Information System (INIS)
Yeh, G.T.
1980-07-01
A surface impoundment model in finite element (SIMFE) is presented to enable the simulation of flow circulations and pollutant transport and dispersion in natural or artificial lakes, reservoirs or ponds with any number of islands. This surface impoundment model consists of two sub-models: hydrodynamic and pollutant transport models. Both submodels are simulated by the finite element method. While the hydrodynamic model is solved by the standard Galerkin finite element scheme, the pollutant transport model can be solved by any of the twelve optional finite element schemes built in the program. Theoretical approximations and the numerical algorithm of SIMFE are described. Detail instruction of the application are given and listing of FORTRAN IV source program are provided. Two sample problems are given. One is for an idealized system with a known solution to show the accuracy and partial validation of the models. The other is applied to Prairie Island for a set of hypothetical input data, typifying a class of problems to which SIMFE may be applied
Development of Air Dispersion Modeling for Future Nuclear Plant in Malaysia
International Nuclear Information System (INIS)
Mohd Nahar Othman
2011-01-01
The impact development of Nuclear power plant in Malaysia, can be very negative to the nearby population, causing public restlessness and consequently affecting the image of the authorities in the countries. The precise source of the pollution from the nuclear power plant must be determined, pollution emission level and the meteorological conditions are needed to predict and established the ambient air to the save level at the perimeter fence of the plant and address it with respect to the radiological ambient standards. Upon modeling using an established package as well as site measurements, the radiological level at the perimeter fence of the plant must deduced and lower than the normal ambient level. Based on this issue, a modeling study was made in vicinity of Malaysian Nuclear Agency TRIGA reactor in the area of Bangi, Selangor to evaluate the possibility of movement of air around the area and their impact. This paper will address and discuss the modeling base on the data getting from Meteorological Department such as measurement of wind speed, temperature, humidity, ambient air radiological concentration and ect. The purpose of Air Dispersion Modeling is to establish the critical ambient emission level, as well as radiological modeling. The focus will be made on exploring the use of Ausplume modeling to develop correlations between the radiological concentrations, chemical compositions and ambient model for emission controls. (author)
Transport and dispersion of pollutants in surface impoundments: a finite element model
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.
1980-07-01
A surface impoundment model in finite element (SIMFE) is presented to enable the simulation of flow circulations and pollutant transport and dispersion in natural or artificial lakes, reservoirs or ponds with any number of islands. This surface impoundment model consists of two sub-models: hydrodynamic and pollutant transport models. Both submodels are simulated by the finite element method. While the hydrodynamic model is solved by the standard Galerkin finite element scheme, the pollutant transport model can be solved by any of the twelve optional finite element schemes built in the program. Theoretical approximations and the numerical algorithm of SIMFE are described. Detail instruction of the application are given and listing of FORTRAN IV source program are provided. Two sample problems are given. One is for an idealized system with a known solution to show the accuracy and partial validation of the models. The other is applied to Prairie Island for a set of hypothetical input data, typifying a class of problems to which SIMFE may be applied.
Dispersion relations in the noncommutative φ3 and Wess-Zumino model in the Yang-Feldman formalism
International Nuclear Information System (INIS)
Doescher, C.; Zahn, J.
2006-05-01
We study dispersion relations in the noncommutative φ 3 and Wess-Zumino model in the Yang-Feldman formalism at one-loop order. Non-planar graphs lead to a distortion of the dispersion relation. We find that this effect is small if the scale of noncommutativity is identified with the Planck scale and parameters typical for a Higgs field are employed. (Orig.)
Kinetics of release of a model disperse dye from supersaturated cellulose acetate matrices.
Papadokostaki, K G; Petropoulos, J H
1998-08-14
A study has been made of the kinetics of release into water of a model disperse dye (4-aminoazobenzene) from supersaturated solvent-cast cellulose acetate films at room temperature. Excess dye was introduced into the polymer matrix by: (i) sorption from aqueous solution at 100 degrees C; (ii) sorption from the vapour phase at 110 degrees C; or (iii) prior dissolution in the casting solvent. The effect of the method of introduction of the dye, the degree of supersaturation and the rate of agitation of the bath were investigated. Under conditions of strong agitation, the release kinetics from films dyed by method (i) or (iii) were in general accord with the theoretical model which assumes solute in the film in excess of the saturation limit to be in the form of immobile aggregates at equilibrium with mobile dye; although the value of the diffusion coefficient of the solute in the film was found to be substantially higher than that in the unsaturated film. On the other hand, when dyeing had been effected from the vapour phase, Fickian kinetics was followed and the diffusion coefficient was found to be equal to that observed in unsaturated film. It was concluded that under these conditions, the excess dye in the film tends to remain molecularly dispersed. Under conditions of slow agitation, the square root of t kinetics was not attained in many instances. General and early-time approximate expressions based on the Roseman-Higuchi model proved useful for the interpretation of the results in such cases; while the said model was extended to include the effect of significant variation of the partition coefficient of the solute with concentration.
Modeling of high-density U-MO dispersion fuel plate performance
International Nuclear Information System (INIS)
Hayes, S.L.; Meyer, M.K.; Hofman, G.L.; Rest, J.; Snelgrove, J.L.
2002-01-01
Results from postirradiation examinations (PIE) of highly loaded U-Mo/Al dispersion fuel plates over the past several years have shown that the interaction between the metallic fuel particles and the matrix aluminum can be extensive, reducing the volume of the high-conductivity matrix phase and producing a significant volume of low-conductivity reaction-product phase. This phenomenon results in a significant decrease in fuel meat thermal conductivity during irradiation. PIE has further shown that the fuel-matrix interaction rate is a sensitive function of irradiation temperature. The interplay between fuel temperature and fuel-matrix interaction makes the development of a simple empirical correlation between the two difficult. For this reason a comprehensive thermal model has been developed to calculate temperatures throughout the fuel plate over its lifetime, taking into account the changing volume fractions of fuel, matrix and reaction-product phases within the fuel meat owing to fuel-matrix interaction; this thermal model has been incorporated into the dispersion fuel performance code designated PLATE. Other phenomena important to fuel thermal performance that are also treated in PLATE include: gas generation and swelling in the fuel and reaction-product phases, incorporation of matrix aluminum into solid solution with the unreacted metallic fuel particles, matrix extrusion resulting from fuel swelling, and cladding corrosion. The phenomena modeled also make possible a prediction of fuel plate swelling. This paper presents a description of the models and empirical correlations employed within PLATE as well as validation of code predictions against fuel performance data for U-Mo experimental fuel plates from the RERTR-3 irradiation test. (author)
Evaluation of a coupled dispersion and aerosol process model against measurements near a major road
Pohjola, M. A.; Pirjola, L.; Karppinen, A.; Härkönen, J.; Ketzel, M.; Kukkonen, J.
2007-02-01
A field measurement campaign was conducted near a major road "Itäväylä" in an urban area in Helsinki in 17-20 February 2003. Aerosol measurements were conducted using a mobile laboratory "Sniffer" at various distances from the road, and at an urban background location. Measurements included particle size distribution in the size range of 7 nm-10 μm (aerodynamic diameter) by the Electrical Low Pressure Impactor (ELPI) and in the size range of 3-50 nm (mobility diameter) by Scanning Mobility Particle Sizer (SMPS), total number concentration of particles larger than 3 nm detected by an ultrafine condensation particle counter (UCPC), temperature, relative humidity, wind speed and direction, driving route of the mobile laboratory, and traffic density on the studied road. In this study, we have compared measured concentration data with the predictions of the road network dispersion model CAR-FMI used in combination with an aerosol process model MONO32. The vehicular exhaust emissions, and atmospheric dispersion and transformation of fine and ultrafine particles was evaluated within the distance scale of 200 m (corresponding to a time scale of a couple of minutes). We computed the temporal evolution of the number concentrations, size distributions and chemical compositions of various particle size classes. The atmospheric dilution rate of particles is obtained from the roadside dispersion model CAR-FMI. Considering the evolution of total number concentration, dilution was shown to be the most important process. The influence of coagulation and condensation on the number concentrations of particle size modes was found to be negligible at this distance scale. Condensation was found to affect the evolution of particle diameter in the two smallest particle modes. The assumed value of the concentration of condensable organic vapour of 1012 molecules cm-3 was shown to be in a disagreement with the measured particle size evolution, while the modelling runs with the
Meteorological monitoring for dose assessment and emergency response modeling - how much is enough?
International Nuclear Information System (INIS)
Glantz, C.S.
1990-01-01
Individuals responsible for emergency response or environmental/dose assessment routinely ask if there are enough meteorological data to adequately support their objectives. The answer requires detailed consideration of the intended applications, capabilities of the atmospheric dispersion model data, pollutant release characteristics, terrain in the modeling region, and size and distribution of the human population in the modeling domain. The meteorologist's detailed knowledge of, and experience in, studying atmospheric transport and diffusion can assist in determining the appropriate level of meteorological monitoring
Directory of Open Access Journals (Sweden)
Tony Gutierrez
2017-04-01
Full Text Available In this study we report the formation of marine oil snow (MOS, its associated microbial community, the factors influencing its formation, and the microbial response to crude oil in surface waters of the Faroe-Shetland Channel (FSC. The FSC is a subarctic region that is hydrodynamically complex located in the northeast Atlantic where oil extraction is currently occurring and where exploration is likely to expand into its deeper waters (>500 m. A major oil spill in this region may mirror the aftermath that ensued following the Deepwater Horizon (DWH blowout in the Gulf of Mexico, where the massive influx of Macondo crude oil triggered the formation of copious quantities of rapidly sinking MOS and successional blooms of opportunistic oil-degrading bacteria. In laboratory experiments, we simulated environmental conditions in sea surface waters of the FSC using water collected from this site during the winter of 2015. We demonstrated that the presence of dispersant triggers the formation of MOS, and that nutrient amendments magnify this. Illumina MiSeq sequencing revealed the enrichment on MOS of associated oil-degrading (Cycloclasticus, Thalassolituus, Marinobacter and EPS-producing (Halomonas, Pseudoalteromonas, Alteromonas bacteria, and included major representation by Psychrobacter and Cobetia with putative oil-degrading/EPS-producing qualities. The formation of marine snow, in the absence of crude oil and dispersant, in seawater amended with nutrients alone indicated that the de novo synthesis of bacterial EPS is a key factor in MOS formation, and the glycoprotein composition of the MOS aggregates confirmed that its amorphous biopolymeric matrix was of microbial (likely bacterial origin. The presence of dispersants and crude oil with/without nutrients resulted in distinct microbial responses marked by intermittent, and in some cases short-lived, blooms of opportunistic heterotrophs, principally obligate hydrocarbonoclastic (Alcanivorax
DEFF Research Database (Denmark)
Thiessen, K.M.; Andersson, Kasper Grann; Batandjieva, B.
2009-01-01
The Urban Remediation Working Group of the International Atomic Energy Agency's EMRAS (Environmental Modelling for Radiation Safety) program was organized to address issues of remediation assessment modelling for urban areas contaminated with dispersed radionuclides. The present paper describes...... the second of two modelling exercises. This exercise was based on a hypothetical dispersal of radioactivity in an urban area from a radiological dispersal device, with reference surface contamination at selected sites used as the primary input information. Modelling endpoints for the exercise included...... radionuclide concentrations and external dose rates at specified locations, contributions to the dose rates from individual surfaces, and annual and cumulative external doses to specified reference individuals. Model predictions were performed for a "no action" situation (with no remedial measures...
Ismail, Sascha A; Ghazoul, Jaboury; Ravikanth, Gudasalamani; Kushalappa, Cheppudira G; Uma Shaanker, Ramanan; Kettle, Chris J
2017-05-01
Despite the importance of seed dispersal for survival of plant species in fragmented landscapes, data on seed dispersal at landscape scales remain sparse. Effective seed dispersal among fragments determines recolonization and plant species persistence in such landscapes. We present the first large-scale (216-km 2 ) direct estimates of realized seed dispersal of a high-value timber tree (Dysoxylum malabaricum) across an agro-forest landscape in the Western Ghats, India. Based upon an exhaustive inventory of adult trees and a sample of 488 seedlings all genotyped at 10 microsatellite loci, we estimated realized seed dispersal using parentage analysis and the neighbourhood model. Our estimates found that most realized seed dispersal was within 200 m, which is insufficient to effectively bridge the distances between forest patches. We conclude that using mobility of putative animal dispersers can be misleading when estimating tropical tree species vulnerability to habitat fragmentation. This raises serious concerns about the potential of many tropical trees to recolonize isolated forest patches where high-value tree species have already been removed. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.
A nonlocal application of the dispersive optical model to 208Pb
Keim, M. A.; Mahzoon, M. H.; Atkinson, M. C.; Charity, R. J.; Dickhoff, W. H.
2017-09-01
A nonlocal application of the dispersive optical model to neutrons and protons in 208Pb is presented. A nucleon self-energy is described by parametrized real and imaginary parts connected through a dispersion relation. This parametrization includes nonlocal Hartree-Fock and local Coulomb and spin-orbit real terms, and nonlocal volume and surface and local spin-orbit imaginary terms. A simple Gaussian nonlocality is employed, and appropriate asymmetry parameters are included to describe the N-Z dependence of the nucleus. These parameters are constrained by fitting to experimental data, including particle numbers, energy levels, the charge density, elastic-scattering angular distributions, reaction cross sections, and the neutron total reaction cross section. From the resulting nucleon self-energy, the neutron matter distribution and neutron skin are deduced. This work was supported by the US Department of Energy, Division of Nuclear Physics under Grant DE-FG02-87ER-40316, the US National Science Foundation under Grants PHY-1304242 and PHY-1613362, and the Washington University Office of Undergraduate Research.
International Nuclear Information System (INIS)
Taylor, J.M.; Daniel, S.L.
1978-01-01
The analysis of accidental releases of radioactive material which may result from transportation accidents in high-density urban areas is influenced by several urban characteristics which make computer simulation the calculational method of choice. These urban features fall into four categories. Each of these categories contains time- and location-dependent parameters which must be coupled to the actual time and location of the release in the calculation of the anticipated radiological consequences. Due to the large number of dependent parameters a computer model, METRAN, has been developed to quantify these radiological consequences. Rather than attempt to describe an urban area as a single entity, a specific urban area is subdivided into a set of cells of fixed size to permit more detailed characterization. Initially, the study area is subdivided into a set of 2-dimensional cells. A uniform set of time-dependent physical characteristics which describe the land use, population distribution, traffic density, etc., within that cell are then computed from various data sources. The METRAN code incorporates several details of urban areas. A principal limitation of the analysis is the limited availability of accurate information to use as input data. Although the code was originally developed to analyze dispersal of radioactive material, it is currently being evaluated for use in analyzing the effects of dispersal of other hazardous materials in both urban and rural areas
Comparison of the 1981 INEL dispersion data with results from a number of different models
Energy Technology Data Exchange (ETDEWEB)
Lewellen, W S; Sykes, R I; Parker, S F
1985-05-01
The results from simulations by 12 different dispersion models are compared with observations from an extensive field experiment conducted by the Nuclear Regulatory Commission at the Idaho National Engineering Laboratory in July, 1981. Comparisons were made on the bases of hourly SF/sub 6/ samples taken at the surface, out to approximately 10 km from the 46 m release tower, both during and following 7 different 8-hour releases. Comparisons are also made for total integrated doses collected out to approximately 40 km. Three classes of models are used. Within the limited range appropriate for Class A models this data comparison shows that neither the puff models or the transport and diffusion models agree with the data any better than the simple Gaussian plume models. The puff and transport and diffusion models do show a slight edge in performance in comparison with the total dose over the extended range approximate for class B models. The best model results for the hourly samples show approximately 40% calculated within a factor of two when a 15/sup 0/ uncertainty in plume position is permitted and it is assumed that higher data samples may occur at stations between the actual sample sites. This is increased to 60% for the 12 hour integrated dose and 70% for the total integrated dose when the same performance measure is used. None of the models reproduce the observed patchy dose patterns. This patchiness is consistent with the discussion of the inherent uncertainty associated with time averaged plume observations contained in our companion reports on the scientific critique of available models.
Modelling of Dispersed Gas-Liquid Flow using LBGK and LPT Approach
Agarwal, Alankar; Prakash, Akshay; Ravindra, B.
2017-11-01
The dynamics of gas bubbles play a significant, if not crucial, role in a large variety of industrial process that involves using reactors. Many of these processes are still not well understood in terms of optimal scale-up strategies.An accurate modeling of bubbles and bubble swarms become important for high fidelity bioreactor simulations. This study is a part of the development of robust bubble fluid interaction modules for simulation of industrial-scale reactors. The work presents the simulation of a single bubble rising in a quiescent water tank using current models presented in the literature for bubble-fluid interaction. In this multiphase benchmark problem, the continuous phase (water) is discretized using the Lattice Bhatnagar-Gross and Krook (LBGK) model of Lattice Boltzmann Method (LBM), while the dispersed gas phase (i.e. air-bubble) modeled with the Lagrangian particle tracking (LPT) approach. The cheap clipped fourth order polynomial function is used to model the interaction between two phases. The model is validated by comparing the simulation results for terminal velocity of a bubble at varying bubble diameter and the influence of bubble motion in liquid velocity with the theoretical and previously available experimental data. This work is supported by the ``Centre for Development of Advanced Computing (C-DAC), Pune'' by providing the advanced computational facility in PARAM Yuva-II.
Dzwinel, Witold; Yuen, David A
2002-03-15
The dispersion of the agglomerating fluid process involving colloids has been investigated at the mesoscale level by a discrete particle approach--the hybrid fluid-particle model (FPM). Dynamical processes occurring in the granulation of colloidal agglomerate in solvents are severely influenced by coupling between the dispersed microstructures and the global flow. On the mesoscale this coupling is further exacerbated by thermal fluctuations, particle-particle interactions between colloidal beds, and hydrodynamic interactions between colloidal beds and the solvent. Using the method of FPM, we have tackled the problem of dispersion of a colloidal slab being accelerated in a long box filled with a fluid. Our results show that the average size of the agglomerated fragments decreases with increasing shearing rate gamma, according to the power law A x gamma(k), where k is around 2. For larger values of gamma, the mean size of the agglomerate S(avg) increases slowly with gamma from the collisions between the aggregates and the longitudinal stretching induced by the flow. The proportionality constant A increases exponentially with the scaling factor of the attractive forces acting between the colloidal particles. The value of A shows a rather weak dependence on the solvent viscosity. But A increases proportionally with the scaling factor of the colloid-solvent dissipative interactions. Similar type of dependence can be found for the mixing induced by Rayleigh-Taylor instabilities involving the colloidal agglomerate and the solvent. Three types of fragmentation structures can be identified, which are called rupture, erosion, and shatter. They generate very complex structures with multiresolution character. The aggregation of colloidal beds is formed by the collisions between aggregates, which are influenced by the flow or by the cohesive forces for small dispersion energies. These results may be applied to enhance our understanding concerning the nonlinear complex
A Conway-Maxwell-Poisson (CMP) model to address data dispersion on positron emission tomography.
Santarelli, Maria Filomena; Della Latta, Daniele; Scipioni, Michele; Positano, Vincenzo; Landini, Luigi
2016-10-01
Positron emission tomography (PET) in medicine exploits the properties of positron-emitting unstable nuclei. The pairs of γ- rays emitted after annihilation are revealed by coincidence detectors and stored as projections in a sinogram. It is well known that radioactive decay follows a Poisson distribution; however, deviation from Poisson statistics occurs on PET projection data prior to reconstruction due to physical effects, measurement errors, correction of deadtime, scatter, and random coincidences. A model that describes the statistical behavior of measured and corrected PET data can aid in understanding the statistical nature of the data: it is a prerequisite to develop efficient reconstruction and processing methods and to reduce noise. The deviation from Poisson statistics in PET data could be described by the Conway-Maxwell-Poisson (CMP) distribution model, which is characterized by the centring parameter λ and the dispersion parameter ν, the latter quantifying the deviation from a Poisson distribution model. In particular, the parameter ν allows quantifying over-dispersion (ν1) of data. A simple and efficient method for λ and ν parameters estimation is introduced and assessed using Monte Carlo simulation for a wide range of activity values. The application of the method to simulated and experimental PET phantom data demonstrated that the CMP distribution parameters could detect deviation from the Poisson distribution both in raw and corrected PET data. It may be usefully implemented in image reconstruction algorithms and quantitative PET data analysis, especially in low counting emission data, as in dynamic PET data, where the method demonstrated the best accuracy. Copyright © 2016 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Tachi, Yukio; Suyama, Tadahiro; Ochs, Michael
2014-01-01
To predict the long-term migration of radionuclides (RNs) under variable conditions within the framework of safety analyses for geological disposal, thermodynamic sorption models are very powerful tools. The integrated sorption and diffusion (ISD) model for compacted bentonite was developed to achieve a consistent combination of clay–water interaction, sorption, and diffusion models. The basic premise considered in the ISD model was to consistently use the same simple surface model design and parameters for describing RNs sorption/diffusion as well as clay surface and porewater chemistry. A simple 1-site non-electrostatic surface complexation model in combination with a 1-site ion exchange model was selected to keep sorption model characteristics relatively robust for compacted systems. Fundamental parameters for the proposed model were evaluated from surface titration data for purified montmorillonite. The resulting basic model was then parameterized on the basis of selected published sorption data-sets for Np(V), Am(III), and U(VI) in dispersed systems, which cover a range of key geochemical conditions such as pH, ionic strength, and carbonate concentration. The sorption trends for these RNs can be quantitatively described by the model considering a full suite of surface species including hydrolytic and carbonate species. The application of these models to the description of diffusive-sorptive transport in compacted bentonites is presented in Part 2. (author)