WorldWideScience

Sample records for atmospheric diffusion

  1. Atmospheric turbulence and diffusion research

    International Nuclear Information System (INIS)

    The Atmospheric Turbulence and Diffusion Division (well known in the atmospheric dispersion community as the Atmospheric Turbulence and Diffusion Laboratory, ATDL) is one of several field facilities of NOAAs Air Resources Laboratory, headquartered in Silver Spring, Maryland. The laboratory conducts research on matters of atmospheric diffusion and turbulent exchange, concerning air quality. ATDD focuses attention on the physics of the lower atmosphere, with special emphasis on the processes contributing to atmospheric transport, dispersion, deposition, and air-surface exchange, and on the development of predictive capabilities using the results of this research. Research is directed toward issues of national and global importance related to the missions of DOE, to DOE's Oak Ridge Field Office, and to NOAA. The program is divided into four major projects: plume transport and diffusion in the planetary boundary layer, complex topography, canopy micrometeorology, and air-surface exchange

  2. Evaluation of empirical atmospheric diffusion data

    International Nuclear Information System (INIS)

    A study has been made of atmospheric diffusion over level, homogeneous terrain of contaminants released from non-buoyant point sources up to 100 m in height. Current theories of diffusion are compared to empirical diffusion data, and specific dispersion estimation techniques are recommended which can be implemented with the on-site meteorological instrumentation required by the Nuclear Regulatory Commission. A comparison of both the recommended diffusion model and the NRC diffusion model with the empirical data demonstrates that the predictions of the recommended model have both smaller scatter and less bias, particularly for groundlevel sources

  3. Particle diffusion in atmospheres of CP stars

    OpenAIRE

    Aret, A.; Sapar, A.

    1998-01-01

    We give concisely the formulae governing diffusion of chemical elements and their isotopes in quiescent stellar atmospheres, due to electrostatic, gravitational and radiation fields and to impacts between particles. Isotope segregation of heavy elements due to light-induced drift is emphasized.

  4. Atmospheric transport, diffusion, and deposition of radioactivity

    International Nuclear Information System (INIS)

    From a meteorological standpoint there are two types of initial sources for atmospheric diffusion from Plowshare applications. One is the continuous point-source plume - a slow, small leak from an underground engineering application. The other is the large cloud produced almost instantaneously from a cratering application. For the purposes of this paper the effluent from neither type has significant fall speed. Both are carried by the prevailing wind, but the statistics of diffusion for each type are different. The use of constant altitude, isobaric and isentropic techniques for predicting the mean path of the effluent is briefly discussed. Limited data are used to assess the accuracy of current trajectory forecast techniques. Diffusion of continuous point-source plumes has been widely studied; only a brief review is given of the technique used and the variability of their results with wind speed and atmospheric stability. A numerical model is presented for computing the diffusion of the 'instantaneously-produced' large clouds. This model accounts for vertical and diurnal changes in atmospheric turbulence, wet and dry deposition, and radioactivity decay. Airborne concentrations, cloud size, and deposition on the ground are calculated. Pre- and post-shot calculations of cloud center, ground level concentration of gross radioactivity, and dry and wet deposition of iodine-131 are compared with measurements on Cabriolet and Buggy. (author)

  5. Atmospheric diffusion of radioactive substances. Report 2

    International Nuclear Information System (INIS)

    This part of the survey deals with the air path, i.e. the emission to the atmosphere, diffusion and immission. For the model calculations it includes in particular the variation of wind direction with height, weather situations with little exchange and inversion weather situations, a roundup of diffusion parameters elaborated in the FRG (e.g. roughness of the ground), initial dilutions, environmental impacts of radionuclides in the surface air, as well as the most recent calculation fundamentals for handling the environmental impacts of γ-submersion (γ-dose from the waste air plume). (DG)

  6. Diffusion impact on atmospheric moisture transport

    Science.gov (United States)

    Moseley, C.; Haerter, J.; Göttel, H.; Hagemann, S.; Jacob, D.

    2009-04-01

    To ensure numerical stability, many global and regional climate models employ numerical diffusion to dampen short wavelength modes. Terrain following sigma diffusion is known to cause unphysical effects near the surface in orographically structured regions. They can be reduced by applying z-diffusion on geopotential height levels. We investigate the effect of the diffusion scheme on atmospheric moisture transport and precipitation formation at different resolutions in the European region. With respect to a better understanding of diffusion in current and future grid-space global models, current day regional models may serve as the appropriate tool for studies of the impact of diffusion schemes: Results can easily be constrained to a small test region and checked against reliable observations, which often are unavailable on a global scale. Special attention is drawn to the Alps - a region of strong topographic gradients and good observational coverage. Our study is further motivated by the appearance of the "summer drying problem" in South Eastern Europe. This too warm and too dry simulation of climate is common to many regional climate models and also to some global climate models, and remains a permanent unsolved problem in the community. We perform a systematic comparison of the two diffusion-schemes with respect to the hydrological cycle. In particular, we investigate how local meteorological quantities - such as the atmospheric moisture in the region east of the Alps - depend on the spatial model resolution. Higher model resolution would lead to a more accurate representation of the topography and entail larger gradients in the Alps. This could lead to consecutively stronger transport of moisture along the slopes in the case of sigma-diffusion with subsequent orographic precipitation, whereas the effect could be qualitatively different in the case of z-diffusion. For our study, we analyse a sequence of simulations of the regional climate model REMO employing

  7. Diffuse Sky Radiation in a Dry Turbid Atmosphere

    OpenAIRE

    R. A. Gupta; B. K. Agarwal

    1984-01-01

    Development of a simple method for the assessment of atmospheric turbidity all over the country in all seasons has been attempted. We have been able to derive a reasonably reliable equation relating diffuse sky radiation Dr on a horizontal surface to air mass mr and Angstrom Schuepp turbidity coefficient B, in a dry atmosphere with constant albedo (A = 0.25) of the terrain.

  8. Measurement of the dynamic characteristics of atmospheric diffusion

    International Nuclear Information System (INIS)

    A new method is proposed for studying the diffusion of atmospheric pollutants above real sites which considers the actual magnitudes encountered. The dynamic application of this method yields original information. In view of justifying the method, fundamental theories concerning diffusion are presented together with different models for the atmosphere. The atmosphere is then considered as a linear filter to which the process identification method is applied. The pulse response of the filter is examined in the pollutant - time plane. The limits of the method and its field of application are discussed. The concept of ergodism and stationariness are introduced. Various diffusion experiments carried out under different conditions are reviewed. Information on the effect of obstacles, and the roughness of the ground is given together with calculations of the longitudinal diffusion and the transport velocity. A brief description is then given of the apparatus used to measure the concentrations and the meteorological conditions. The correlation calculation is also briefly presented. (author)

  9. Diffusion of Radioactive Materials in the Atmosphere

    Directory of Open Access Journals (Sweden)

    Abdul-Wali Ajlouni

    2009-01-01

    Full Text Available Problem statement: The dispersion of radioactive materials in the environment related to escaping of noble gases, halogens and aerosols of non-volatile radioactive materials, from the reactor containment during normal operations, or in the event of a sever reactor accident. Approach: radionuclide dispersion in the environment is demonstrated by mathematical tools which are the partial differential equations, mainly the diffusion equation. A mathematical model to calculate the concentration of nuclear pollutants (radioactivity with certain boundary conditions is constructed. Results: Solving the mathematical model and using some approximations lead to a distribution represents a model for plume of radioactive pollutants dispersed in two dimensions normal to the wind direction in which the plume moves as an entire non-dispersible unit. Conclusion: The obtained result theoretically are very close to those achieved experimentally.

  10. Diffuse Sky Radiation in a Dry Turbid Atmosphere

    Directory of Open Access Journals (Sweden)

    R. A. Gupta

    1984-07-01

    Full Text Available Development of a simple method for the assessment of atmospheric turbidity all over the country in all seasons has been attempted. We have been able to derive a reasonably reliable equation relating diffuse sky radiation Dr on a horizontal surface to air mass mr and Angstrom Schuepp turbidity coefficient B, in a dry atmosphere with constant albedo (A = 0.25 of the terrain.

  11. Simplified atmospheric diffusion calculations with slide-rule gage points

    International Nuclear Information System (INIS)

    Gage points are given with the help of which the most commonly required atmospheric diffusion calculations can be carried out rapidly using a simple slide-rule setting; e.g. maximum ground concentration, its distance, and the corresponding effective stack height as functions of the prevailing type of meteorological condition. (author)

  12. An atmospheric electrical method to determine the eddy diffusion coefficient

    Indian Academy of Sciences (India)

    M N Kulkarni; A K Kamra

    2010-02-01

    The ion–aerosol balance equations are solved to get the profiles of atmospheric electric parameters over the ground surface in an aerosol-rich environment under the conditions of surface radioactivity. Combining the earlier results for low aerosol concentrations and the present results for high aerosol concentrations, a relation is obtained between the average value of atmospheric electric space charge in the lowest ∼2m, the surface electric field and eddy diffusivity/aerosol concentration. The values of eddy diffusivity estimated from this method using some earlier measurements of space charge and surface electric field are in reasonably good agreement with those calculated from other standard methods using meteorological or electrical variables.

  13. Measurements and theoretical calculations of diffused radiation and atmosphere lucidity

    International Nuclear Information System (INIS)

    Align with other environment friendly renewable energy sources solar energy is widely used in the world. Also in Latvia solar collectors are used. However, in Latvia because of its geographical and climatic conditions there are some specific features in comparison with traditional solar energy using countries. These features lead to the necessity to pay more attention to diffused irradiance. Another factor affecting the received irradiance of any surface is lucidity of atmosphere. This factor has not been studied in Latvia yet. This article deals with evaluation of diffused irradiance, and also of lucidity of atmosphere. The diffused irradiance can be measured directly or as a difference between the global irradiance and the beam one. The lucidity of atmosphere can be calculated from the measurements of both global and beam irradiance, if the height of the sun is known. Therefore, measurements of both global and beam irradiance have been carried out, and the diffused irradiance calculated as a difference between the global irradiance and the beam one. For measuring of the global irradiance the dome solarimeter has been used. For measuring of the direct irradiance tracking to sun pirheliometer has been used. The measurements were performed in Riga from October 2008 till March 2009. The measurements were executed automatically after every 5 minutes. The obtained results have been analyzed taking into account also the data on nebulosity from the State agency Latvian Environment, Geology and Meteorology Agency. Also efforts to calculate theoretically the diffused irradiance from the height of the sun and the data of the nebulosity have been done. These calculated values have been compared with the measured ones. Good accordance is obtained. (author)

  14. Behaviour of tracer diffusion in simple atmospheric boundary layer models

    Directory of Open Access Journals (Sweden)

    P. S. Anderson

    2006-12-01

    Full Text Available 1-D profiles and time series from an idealised atmospheric boundary layer model are presented, which show agreement with measurements of polar photogenic NO and NO2. Diffusion models are increasingly being used as the framework for studying tropospheric air chemistry dynamics. Models based on standard boundary layer diffusivity profiles have an intrinsic behaviour that is not necessarily intuitive, due to the variation of turbulent diffusivity with height. The relatively simple model provides both a programming and a conceptual tool in the analysis of observed trace gas evolution. A time scale inherent in the model can be tuned by fitting model time series to observations. This scale is then applicable to the more physically simple but chemically complex zeroth order or box models of chemical interactions.

  15. Behaviour of tracer diffusion in simple atmospheric boundary layer models

    Directory of Open Access Journals (Sweden)

    P. S. Anderson

    2007-10-01

    Full Text Available 1-D profiles and time series from an idealised atmospheric boundary layer model are presented, which show agreement with boundary layer measurements of polar NOx. Diffusion models are increasingly being used as the framework for studying tropospheric air chemistry dynamics. Models based on standard boundary layer diffusivity profiles have an intrinsic behaviour that is not necessarily intuitive, due to the variation of turbulent diffusivity with height. The simple model presented captures the essence of the evolution of a trace gas released at the surface, and thereby provides both a programming and a conceptual tool in the analysis of observed trace gas evolution. A time scale inherent in the model can be tuned by fitting model time series to observations. This scale is then applicable to the more physically simple but chemically complex zeroth order or box models of chemical interactions.

  16. Persistency of atmospheric diffusion conditions in Angra dos Reis - Brazil

    International Nuclear Information System (INIS)

    Based on a 2 year observation period, the diffusion conditions at the Almirante Alvaro Alberto N.P.P. site, in Angra dos Reis, are analized with respect to persistency as a function of the wind direction, the Pasquill stability class and the time of the day. The Pasquill stability class relates to the bulk vertical temperature gradient measured between 2m and 50m in the atmosphere; the wind direction is measured at 50m height. The persistency is defined in this report as the probability that the wind direction will remain longer than a given time in a sector without change in the diffusion category by more than a certain stage. During the day the persistency is mostly affected by the sea breeze with predominance of the unstable and neutral categories. At night the stable categories dominate. The alternating sea and land breezes disturb daily the trade wind field resulting in low persistency of the diffusion conditions. (Author)

  17. A comparison of Gaussian and diffusivity models of atmospheric dispersion

    International Nuclear Information System (INIS)

    The Gaussian plume diffusion model of Smith and a diffusivity model by Maul are compared over the full range of atmospheric stability. The models' predictions for ground level concentration are found to agree well a) for ground level releases of materials, and b) for elevated releases of material at distances comparable to or greater than the distance of maximum ground level concentration. Surface layer, ground roughness, and dry deposition effects are examined and a simple ground deposition model used in the Gaussian plume model is found to be adequate over most of the stability range. Uncertainties due to the models themselves and the meteorological input data are estimated and the advantages and limitations of both types of model are discussed. It is concluded that the models are suitable for a variety of applications and that they are fast and inexpensive to run as computer models. (author)

  18. Green's Method Approach for Solving the Hermitized Atmospheric Diffusion Equation with Multiple Sources and Eddy Diffusivities

    International Nuclear Information System (INIS)

    The three-dimensional generalized (self-adjoint) atmospheric diffusion equation can be solved analytically. Where the source strength is located at any where within the region of interest, and with arbitrary power- law function of wind speed and eddy diffusivities. The Greens method approach is utilized, where the Green's function is splitting into two factors, As a result of the hermeticity the solution of the diffusion equation can be expressed exact, as a multiple of source and the two factors of the Green's function, vertical dispersion factor, and cross wind dispersion factor. The two factors of the Green's function are derived analytically in which, the Green's of the diffusion equation is splitting into two pair of two-dimensional differential equations, by using: separation of variables, Bessel equation, and transform the dependent and independent variables, and the cosine transformation. All amenable cases are adopted such as: Neumann (total reflection), Dirichlet (total adsorption), and mixed boundary conditions. Gaussian plume model is extracted in all the previously cases

  19. Introducing atmospheric attenuation within a diffusion model for room-acoustic predictions (L)

    OpenAIRE

    Billon, Alexis; Picaut, Judicaël; FOY, Cédric; Valeau, Vincent; SAKOUT, Anas

    2008-01-01

    This paper presents an extension of a diffusion model for room acoustics to handle the atmospheric attenuation. This phenomenon is critical at high frequencies and in large rooms to obtain correct acoustic predictions. An additional term is introduced in the diffusion equation as well as in the diffusion constant, in order to take the atmospheric attenuation into account. The modified diffusion model is then compared with the statistical theory and a cone-tracing software. Three typical room-...

  20. Development and application of random walk model of atmospheric diffusion in emergency response of nuclear accidents

    International Nuclear Information System (INIS)

    Plume concentration prediction is one of the main contents of radioactive consequence assessment for early emergency to nuclear accidents. This paper describes random characteristics of atmospheric diffusion itself, introduces random walk model of atmospheric diffusion (Random Walk), and compare with Lagrangian puff model (RIMPUFF) in the nuclear emergency decision support system (RODOS) developed by European Community for verification. The results show the concentrations calculated by the two models are quite close except that plume area calculated by Random Walk is a little smaller than that by RIMPUFF. The random walk model for atmospheric diffusion can simulate the atmospheric diffusion in case of nuclear accidents and provide more actual information for early emergency and consequence assessment as one atmospheric diffusion module of the nuclear emergency decision support system. (authors)

  1. Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Jie, E-mail: tangjie1979@opt.ac.cn; Jiang, Weiman; Wang, Yishan; Zhao, Wei [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics of CAS, Xi' an 710119 (China); Li, Jing [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics of CAS, Xi' an 710119 (China); Faculty of Mathematics and Physics, Huaiyin Institute of Technology, Huaian 223003 (China); Duan, Yixiang [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics of CAS, Xi' an 710119 (China); Research Center of Analytical Instrumentation, Sichuan University, Chengdu 610064 (China)

    2015-08-24

    A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.

  2. Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

    International Nuclear Information System (INIS)

    A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation

  3. Statistical analysis of meteorological data above a given site applied to atmospheric diffusion problems

    International Nuclear Information System (INIS)

    This paper presents a method for clarifying the meteorological conditions above a given site and objectively distinguishes a number of predominant weather types. For each weather type atmospheric diffusion coefficients are estimated and numerical solutions of the diffusion equation are compared with observed experimental data

  4. Effects on atmospheric diffusion of meterological processes in coastal zones

    International Nuclear Information System (INIS)

    Meteorological processes in coastal zones differ from those inland because of the surface discontinuity between land and water. The difference in heating between the two surfaces gives rise to sea or lake breeze circulations which can transport pollutants in nongradient directions and recirculate them over source areas. The step change in surface characteristics at the land-water interface also causes formation of internal boundary layers having different transport velocities and diffusion rates than unmodified air upwind or above the boundary. These features require a more extensive measurement program and more versatile diffusion models than at inland sites

  5. Evaluation of carbon diffusion in heat treatment of H13 tool steel under different atmospheric conditions

    OpenAIRE

    Maziar Ramezani; Timotius Pasang; Zhan Chen; Thomas Neitzert; Dominique Au

    2015-01-01

    Although the cost of the heat treatment process is only a minor portion of the total production cost, it is arguably the most important and crucial stage on the determination of material quality. In the study of the carbon diffusion in H13 steel during austenitization, a series of heat treatment experiments had been conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied, i.e., heat treatment without atmospheric contro...

  6. Applications of advanced atmospheric diffusion models in complex terrain

    International Nuclear Information System (INIS)

    The recalculation of a single diffusion pattern experimentally determined in the field near an artificial hill in a brown coal mining area serves as an example to show the performance of the MOSES modular modelling system. The other example presented refers to the determination of the large-area, mean wind direction distribution in the large, orographically structured region of North-Rhine Westfalia. (DG)

  7. EOCR building wake effects on atmospheric diffusion. Technical memo

    Energy Technology Data Exchange (ETDEWEB)

    Start, G.E.; Hukari, N.F.; Sagendorf, J.F.; Cate, J.H.; Dickson, C.R.

    1981-01-01

    A series of 22 simultaneous releases of three gaseous tracers was conducted around the EOCR test reactor building at the Idaho National Engineering Laboratory in SE Idaho. Hourly average gaseous tracer concentrations were sampled on several concentric sampling arcs and at a limited number of elevated locations. Winds and temperatures were measured on a nearby 30mm tower. Complete data appendices provide tracer concentration measurements, temperatures, winds and detailed wind statistics, derived diffusion statistics, and plots and analyses.

  8. A study of atmospheric diffusion from the LANDSAT imagery. [pollution transport over the ocean

    Science.gov (United States)

    Dejesusparada, N. (Principal Investigator); Viswanadham, Y.; Torsani, J. A.

    1981-01-01

    LANDSAT multispectral scanner data of the smoke plumes which originated in eastern Cabo Frio, Brazil and crossed over into the Atlantic Ocean, are analyzed to illustrate how high resolution LANDSAT imagery can aid meteorologists in evaluating specific air pollution events. The eleven LANDSAT images selected are for different months and years. The results show that diffusion is governed primarily by water and air temperature differences. With colder water, low level air is very stable and the vertical diffusion is minimal; but water warmer than the air induces vigorous diffusion. The applicability of three empirical methods for determining the horizontal eddy diffusivity coefficient in the Gaussian plume formula was evaluated with the estimated standard deviation of the crosswind distribution of material in the plume from the LANDSAT imagery. The vertical diffusion coefficient in stable conditions is estimated using Weinstock's formulation. These results form a data base for use in the development and validation of meso scale atmospheric diffusion models.

  9. Atmospheric diffusion at coastal site in presence of sea-breeze

    International Nuclear Information System (INIS)

    The coastal sites present special features so much by the dominant wind system then by the lower layers of the atmosphere. Two types of experiments were handled on a coastal site in presence of sea breeze. First, vertical atmospheric sounding by radiosounding and by throwing experimental balloons; then the discharge of tracer: the SF6. The first experiment lead us to put in a prominent position the Internal Boundary Layer and the determination of its height. Whereas the second experiment allowed us to estimate the diffusion parameters of the site as well as to obtain interesting conclusions on diffusivity of the environment studied and the influence of certain factors

  10. Solution of the Atmospheric Diffusion Equation with Longitudinal Wind Speed Depending on Source Distance

    OpenAIRE

    Davidson Martins Moreira; Taciana Toledo de Almeida Albuquerque

    2016-01-01

    Abstract An integral semi-analytical solution of the atmospheric diffusion equation considering wind speed as a function of both downwind distance from a pollution source and vertical height is presented. The model accounts for transformation and removal mechanisms via both chemical reaction and dry deposition processes. A hypothetical dispersion of contaminants emitted from an urban pollution source in the presence of mesoscale winds in an unstable atmospheric boundary layer is showed. The r...

  11. Low-temperature hydrogenation of diamond nanoparticles using diffuse coplanar surface barrier discharge at atmospheric pressure

    Czech Academy of Sciences Publication Activity Database

    Kromka, Alexander; Čech, J.; Kozak, Halyna; Artemenko, Anna; Ižák, Tibor; Čermák, Jan; Rezek, Bohuslav; Černák, M.

    2015-01-01

    Roč. 252, č. 11 (2015), s. 2602-2607. ISSN 0370-1972 R&D Projects: GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:68378271 Keywords : atmospheric plasma * diamond nanoparticles * diffuse coplanar surface barrier discharge * FTIR * XPS Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.489, year: 2014

  12. Development and application of a random walk model of atmospheric diffusion in the emergency response of nuclear accidents

    Institute of Scientific and Technical Information of China (English)

    CHI Bing; LI Hong; FANG Dong

    2007-01-01

    Plume concentration prediction is one of the main contents of radioactive consequence assessment for early emergency response to nuclear accidents. Random characteristics of atmospheric diffusion itself was described, a random walk model of atmospheric diffusion (Random Walk) was introduced and compared with the Lagrangian puff model (RIMPUFF) in the nuclear emergency decision support system (RODOS) developed by the European Community for verification. The results show the concentrations calculated by the two models are quite close except that the plume area calculated by Random Walk is a little smaller than that by RIMPUFF. The random walk model for atmospheric diffusion can simulate the atmospheric diffusion in case of nuclear accidents, and provide more actual information for early emergency and consequence assessment as one of the atmospheric diffusion module of the nuclear emergency decision support system.

  13. Implicit coupling of turbulent diffusion with chemical reaction mechanisms for prognostic atmospheric dispersion models

    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.

  14. Atmospheric Escape by Magnetically Driven Wind from Gaseous Planets II --Effects of Magnetic Diffusion--

    CERN Document Server

    Tanaka, Yuki A; Inutsuka, Shu-ichiro

    2015-01-01

    We investigate roles of Alfvenic waves in the weakly-ionized atmosphere of hot Jupiters by carrying out non-ideal magnetohydrodynamic (MHD) simulations with Ohmic diffusion in one-dimensional magnetic flux tubes. Turbulence at the surface excites Alfven waves and they propagate upward to drive hot (~ 10^4 K) outflows. The magnetic diffusion plays an important role in the dissipation of the Alfvenic waves in the weakly ionized atmosphere of hot Jupiters. The mass-loss rate of the spontaneously driven planetary wind is considerably reduced, in comparison with that obtained from ideal MHD simulations because the Alfvenic waves are severely damped at low altitudes in the atmosphere, whereas the wave heating is still important in the heating of the upper atmosphere. Dependence on the surface temperature, planetary radius, and velocity dispersion at the surface is also investigated. We find an inversion phenomenon of the transmitted wave energy flux; the energy flux carried by Alfven waves in the upper atmosphere h...

  15. Strong atmospheric disturbances as a possible origin of inner zone particle diffusion

    Directory of Open Access Journals (Sweden)

    O. A. Pokhotelov

    Full Text Available A new mechanism of the atmosphere-magnetosphere interaction, which might be called "acoustic-magnetospheric cyclotron accelerator", is proposed. The idea of this mechanism stems from the fact that strong acoustical perturbations in the ionosphere (e.g., due to earthquakes, thunderstorms, etc. may generate magnetic disturbances in the magnetosphere. Then, the latter will induce local resonant acceleration and subsequent inward diffusion of trapped particles. This idea may be fruitful in the interpretation of some occasional increases in inner zone particle fluxes which do not correlate with the solar or magnetospheric activities.

    Key words. Ionosphere (active experiments; ionosphere-atmosphere interactions; particle acceleration

  16. Solution of the Atmospheric Diffusion Equation with Longitudinal Wind Speed Depending on Source Distance

    Directory of Open Access Journals (Sweden)

    Davidson Martins Moreira

    2016-06-01

    Full Text Available Abstract An integral semi-analytical solution of the atmospheric diffusion equation considering wind speed as a function of both downwind distance from a pollution source and vertical height is presented. The model accounts for transformation and removal mechanisms via both chemical reaction and dry deposition processes. A hypothetical dispersion of contaminants emitted from an urban pollution source in the presence of mesoscale winds in an unstable atmospheric boundary layer is showed. The results demonstrate that the mesoscale winds generated by urban heat islands advect contaminants upward, which increases the intensity of air pollution in urban areas.

  17. Developing a passive trap for diffusive atmospheric 14CO2 sampling

    Science.gov (United States)

    Walker, Jennifer C.; Xu, Xiaomei; Fahrni, Simon M.; Lupascu, Massimo; Czimczik, Claudia I.

    2015-10-01

    14C-CO2 measurement is an unique tool to quantify source-based emissions of CO2 for both the urban and natural environments. Acquiring a sample that temporally integrates the atmospheric 14C-CO2 signature that allows for precise 14C analysis is often necessary, but can require complex sampling devices, which can be difficult to deploy and maintain, especially for multiple locations. Here we describe our progress in developing a diffusive atmospheric CO2 molecular sieve trap, which requires no power to operate. We present results from various cleaning procedures, and rigorously tested for blank and memory effects. Traps were tested in the environment along-side conventional sampling flasks for accuracy. Results show that blank and memory effects can be minimized with thorough cleaning and by avoiding overheating, and that diffusively collected air samples agree well with traditionally canister-sampled air.

  18. Effect of growth regulators on 'Brookfield' apple gas diffusion and metabolism under controlled atmosphere storage

    OpenAIRE

    Auri Brackmann; Fabio Rodrigo Thewes; Rogerio de Oliveira Anese; Vanderlei Both

    2014-01-01

    The objective of this work was to evaluate the effect of growth regulators on gas diffusion and on metabolism of 'Brookfield' apple, and to determine their correlation with quality characteristics of fruit stored in controlled atmosphere. A completely randomized design was used with four replicates. After eight months of storage, the effects of water (control), aminoethoxyvinylglycine (AVG), AVG + ethephon, AVG + naphthaleneacetic acid (NAA), ethephon + NAA, sole NAA, 1-MCP, ethylene absorpti...

  19. Development and field validation of a new diffusive sampler for determination of atmospheric volatile organic compounds

    Science.gov (United States)

    Özden Üzmez, Özlem; Gaga, Eftade O.; Döğeroğlu, Tuncay

    2015-04-01

    A tailor-made diffusive sampler was developed for the determination of atmospheric Volatile Organic Compounds (VOCs) and the validation of the sampler was carried out under field conditions. All parts of the diffusive sampler which are reusable after a proper cleaning process were made of plastic material (delrin). The reusability of the sampler brings an important advantage considering its lower cost. Activated carbon was used as adsorbent and VOCs adsorbed on the activated carbon were analyzed by GC-MS (gas chromatography equipped with mass selective detector). A comprehensive validation study including detection limit, precision, bias, recovery, self-consistency, shelf life, storage stability, reusability was carried out in accordance with the related European standards ((EN) 13528-1 (2000) and 13528-2 (2000)). Also, a comparison was performed with some commercial diffusive samplers such as 3 M OVM 3500 and Radiello to test the performance of the new diffusive sampler in different environments such as urban area and road tunnel. Uptake rates for the measured VOCs were determined and they were evaluated together with the meteorological parameters (temperature, humidity, wind speed). According to the validation results; all the parameters evaluated for the sampler comply with the related standards and this is an indication of the reliability of the sampler for the sampling of VOCs in the atmosphere.

  20. Evaluation of carbon diffusion in heat treatment of H13 tool steel under different atmospheric conditions

    Directory of Open Access Journals (Sweden)

    Maziar Ramezani

    2015-04-01

    Full Text Available Although the cost of the heat treatment process is only a minor portion of the total production cost, it is arguably the most important and crucial stage on the determination of material quality. In the study of the carbon diffusion in H13 steel during austenitization, a series of heat treatment experiments had been conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied, i.e., heat treatment without atmospheric control, heat treatment with stainless steel foil wrapping, pack carburization heat treatment and vacuum heat treatment. The results showed that stainless steel foil wrapping could restrict decarburization process, resulting in a constant hardness profile as vacuum heat treatment does. However, the tempering characteristic between these two heat treatment methods is different. Results from the gas nitrided samples showed that the thickness and the hardness of the nitrided layer is independent of the carbon content in H13 steel.

  1. Effect of growth regulators on 'Brookfield' apple gas diffusion and metabolism under controlled atmosphere storage

    Directory of Open Access Journals (Sweden)

    Auri Brackmann

    2014-05-01

    Full Text Available The objective of this work was to evaluate the effect of growth regulators on gas diffusion and on metabolism of 'Brookfield' apple, and to determine their correlation with quality characteristics of fruit stored in controlled atmosphere. A completely randomized design was used with four replicates. After eight months of storage, the effects of water (control, aminoethoxyvinylglycine (AVG, AVG + ethephon, AVG + naphthaleneacetic acid (NAA, ethephon + NAA, sole NAA, 1-MCP, ethylene absorption by potassium permanganate (ABS, AVG + ABS, and of AVG + 1-MCP - applied at different rates and periods - were evaluated on: gas diffusion rate, ethylene production, respiratory rate, internal ethylene concentration, internal CO2 content, mealiness, and intercellular space. Fruit from the control and sole NAA treatments had the highest mealiness occurrence. Growth regulators significantly changed the gaseous diffusion through the pulp of 'Brookfield' apple, mainly in the treatment AVG + ABS, which kept the highest gas diffusion rate. NAA spraying in the field, with or without another growth regulator, increased ripening metabolism by rising ethylene production and respiration rate, and reduced gas diffusion during shelf life. AVG spraying cannot avoid the ethephon effect during the ripening process, and reduces both the internal space and mealiness incidence, but it is not able to induce ethylene production or to increase respiration rates.

  2. Diffuse plasma treatment of polyamide 66 fabric in atmospheric pressure air

    Science.gov (United States)

    Li, Lee; Peng, Ming-yang; Teng, Yun; Gao, Guozhen

    2016-01-01

    The polyamide 66 (PA66) fabrics are hard to be colored or glued in industrial production due to the poor hydrophily. Diffuse plasma is a kind of non-thermal plasma generated at atmospheric pressure in air. This paper proposes that large-scale diffuse plasma generated between wire electrodes can be employed for improving the hydrophily of PA66 fabrics. A repetitive nanosecond-pulse diffuse-discharge reactor using a cylindrical wire electrode configuration is presented, which can generate large-scale non-thermal plasmas steadily at atmospheric pressure without any barrier dielectric. Then the reactor is used to treat PA66 fabrics in different discharge conditions. The hydrophilicity property of modified PA66 is measured by wicking test method. The modified PA66 is also analyzed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) to prove the surface changes in physical microstructure and chemical functional groups, respectively. What's more, the effects of treatment time and treatment frequency on surface modification are investigated and discussed.

  3. Diffuse and spot mode of cathode arc attachments in an atmospheric magnetically rotating argon arc

    International Nuclear Information System (INIS)

    A model including the cathode, near-cathode region, and arc column was constructed. Specifically, a thermal perturbation layer at the arc fringe was calculated in order to couple sheath/presheath modelling with typical arc column modelling. Comparative investigation of two modes of attachment of a dc (100, 150, 200 A) atmospheric-pressure arc in argon to a thermionic cathode made of pure tungsten was conducted. Computational data revealed that there exists two modes of arc discharge: the spot mode, which has an obvious cathode surface temperature peak in the arc attachment centre; and the diffuse mode, which has a flat cathode surface temperature distribution and a larger arc attachment area. The modelling results of the arc attachment agree with previous experimental observations for the diffuse mode. A further 3D simulation is obviously needed to investigate the non-axisymmetrical features, especially for the spot mode. (paper)

  4. Atmospheric pressure diffuse plasma in ambient air for ITO surface cleaning

    International Nuclear Information System (INIS)

    Effects of atmospheric filament-free diffuse plasma in ambient air and oxygen by Diffuse Coplanar Surface Barrier Discharge (DCSBD) on surface of indium tin oxide (ITO) were studied. The DCSBD plasma treatment resulted in significant reduction of water contact angles (even for 1 s long treatment). The decrease can be explained by the chemical changes on surface. These were studied by XPS which shows considerable decrease in the carbon surface concentration. The detailed analysis of C1s peak indicates the increase of the highest binding energy component of the C1s peak that corresponds to polar bonds with oxygen, which may be also related to decrease of water contact angle. AFM measurement showed no significant effect of plasma on ITO surface morphology.

  5. assessment of concentration of air pollutants using analytical and numerical solution of the atmospheric diffusion equation

    International Nuclear Information System (INIS)

    The mathematical formulation of numerous physical problems a results in differential equations actually partial or ordinary differential equations.In our study we are interested in solutions of partial differential equations.The aim of this work is to calculate the concentrations of the pollution, by solving the atmospheric diffusion equation(ADE) using different mathematical methods of solution. It is difficult to solve the general form of ADE analytically, so we use some assumptions to get its solution.The solutions of it depend on the eddy diffusivity profiles(k) and the wind speed u. We use some physical assumptions to simplify its formula and solve it. In the present work, we solve the ADE analytically in three dimensions using Green's function method, Laplace transform method, normal mode method and these separation of variables method. Also, we use ADM as a numerical method. Finally, comparisons are made with the results predicted by the previous methods and the observed data.

  6. Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air

    DEFF Research Database (Denmark)

    Zhu, Jiajian; Gao, Jinlong; Li, Zhongshan;

    2014-01-01

    Rapid transition from glow discharge to thermal arc has been a common problem in generating stable high-power non-thermal plasmas especially at ambient conditions. A sustained diffusive gliding arc discharge was generated in a large volume in atmospheric pressure air, driven by an alternating......, synchronized with simultaneously recorded current and voltage waveforms. Dynamic details of the novel non-equilibrium discharge are revealed, which is characterized by a sinusoidal current waveform with amplitude stabilized at around 200 mA intermediate between thermal arc and glow discharge, shedding light to...

  7. Diffuse α-mode atmospheric pressure radio-frequency discharge in neon

    International Nuclear Information System (INIS)

    In this work, a radio-frequency (RF) atmospheric pressure glow discharge burning in neon between planar metal electrodes is achieved for the first time. The RF discharge can operate in two stable modes: in a diffuse α-mode with uniformly covered electrode surfaces and in a constricted γ-mode. Similarities are revealed when the discharge is compared against the RF atmospheric pressure glow discharge in helium, namely both discharges show a discontinuity and a hysteresis in the current–voltage characteristic at the mode transition; the spatio-temporal profiles of the light emission in the α-mode from neon, helium and atomic oxygen are also similar. (fast track communication)

  8. Interplay between diffusion, accretion and nuclear reactions in the atmospheres of Sirius and Przybylski's star

    CERN Document Server

    Yushchenko, A; Goriely, S; Shavrina, A; Kang, Y W; Rostopchin, S; Valyavin, G; Mkrtichian, D; Hatzes, A; Lee, B C; Kim, C; Yushchenko, Alexander; Gopka, Vera; Goriely, Stephane; Shavrina, Angelina; Kang, Young Woon; Rostopchin, Sergey; Valyavin, Gennady; Mkrtichian, David; Hatzes, Artie; Lee, Byeong-Cheol; Kim, Chulhee

    2006-01-01

    The abundance anomalies in chemically peculiar B-F stars are usually explained by diffusion of chemical elements in the stable atmospheres of these stars. But it is well known that Cp stars with similar temperatures and gravities show very different chemical compositions. We show that the abundance patterns of several stars can be influenced by accretion and (or) nuclear reactions in stellar atmospheres. We report the result of determination of abundances of elements in the atmosphere of hot Am star: Sirius A and show that Sirius A was contaminated by s-process enriched matter from Sirius B (now a white dwarf). The second case is Przybylski's star. The abundance pattern of this star is the second most studied one after the Sun with the abundances determined for about 60 chemical elements. Spectral lines of radioactive elements with short decay times were found in the spectrum of this star. We report the results of investigation on the stratification of chemical elements in the atmosphere of Przybylski's star ...

  9. A numerical model of the transport and diffusion of Peronospora tabacina spores in the evolving atmospheric boundary layer

    Science.gov (United States)

    Yao, Chengwei; Pal Arya, S.; Davis, Jerry; Main, Charles E.

    Numerical solutions of the diffusion equation of Peronospora tabacina spores from a finite-area source over flat terrain in the evolving convective boundary layer are presented. Temporal variations in the release of spores, atmospheric stability, wind speed, and eddy diffusivity are considered. The model also includes the vertical variations of wind and eddy diffusivity. The model results indicate that ground level concentrations decrease with time as wind speed and eddy diffusivity increase in the evolving convective boundary layer. The loss of P. tabacina spores due to deposition at the surface also decrease with increasing instability and wind speed. Deposition is found to be particularly important close to the source area.

  10. Generating diffuse discharge via repetitive nanosecond pulses and line-line electrodes in atmospheric air

    Science.gov (United States)

    Li, Lee; Liu, Yun-Long; Ge, Ya-Feng; Bin, Yu; Huang, Jia-Jia; Lin, Fo-Chan

    2013-10-01

    Diffuse discharge in atmospheric air can generate extremely high power density and large-scale non-thermal plasma. An achievable method of generating diffuse discharge is reported in this paper. Based on the resonance theory, a compact high-voltage repetitive nanosecond pulse generator (HRNPG) has been developed as discharge excitation source. The HRNPG mainly consists of repetitive charging circuit, Tesla transformer and sharpening switch. With the voltage lower than 1.0 kV, the primary repetitive charging circuit comprises two fast thyristors as low-voltage switches. A spiral Tesla transformer is designed to provide a peak transformation ratio of more than 100. The HRNPG prototype is capable of generating a pulse with over 100 kV peak voltage and ˜30 ns rise-time at the repetition frequency of 500 Hz. Using the copper line electrodes with a diameter of 0.4 mm, the gaps with highly non-uniform electric field are structured. With the suitable gap spacing and applied pulse, the glow-like diffuse discharge has been generated in line-type and ring-type electrode pairs. Some typical images are presented.

  11. Study on fitness functions of genetic algorithm for dynamically correcting nuclide atmospheric diffusion model

    International Nuclear Information System (INIS)

    Background: In radioactive nuclides atmospheric diffusion models, the empirical dispersion coefficients were deduced under certain experiment conditions, whose difference with nuclear accident conditions is a source of deviation. A better estimation of the radioactive nuclide's actual dispersion process could be done by correcting dispersion coefficients with observation data, and Genetic Algorithm (GA) is an appropriate method for this correction procedure. Purpose: This study is to analyze the fitness functions' influence on the correction procedure and the forecast ability of diffusion model. Methods: GA, coupled with Lagrange dispersion model, was used in a numerical simulation to compare 4 fitness functions' impact on the correction result. Results: In the numerical simulation, the fitness function with observation deviation taken into consideration stands out when significant deviation exists in the observed data. After performing the correction procedure on the Kincaid experiment data, a significant boost was observed in the diffusion model's forecast ability. Conclusion: As the result shows, in order to improve dispersion models' forecast ability using GA, observation data should be given different weight in the fitness function corresponding to their error. (authors)

  12. Local scale atmospheric diffusion at a coastal site in the presence of breeze effect

    International Nuclear Information System (INIS)

    The aim of this work is the characterization, from the thermal and anemological point of view, of the lower layers of the atmosphere at a coastal site, affected by breeze circulation, in order to set up possible diffusion models for accidental releases of airborne materials, both of short and prolonged duration. Five inland meteorological campaigns, starting from April '82 (Apr., Jul., Oct. 1982, Jan. 1983), have been carried out. An appropriate extension of the research allowed the execution of two more campaigns in the open sea (Apr., Jul. 1983), utilizing the oceanographic ship ''Bannock'' supplied by CNR. The analysis of the data showed the development of a well defined IBL during on-shore flow only in Spring and Summer, while an inversion layer was detectable aloft independently of the season (provided that an anticyclonic situation was present). According to those relevant features a simple diffusion model has been developed for short duration releases at local scale. Finally, the analysis and elaboration of the data collected on site by a meteorological automatic station, allowed the extension of the model to prolonged releases. (author)

  13. Investigation of atmospheric diffusion by immission measurements of xenon-133 from Fessenheim nuclear power station

    International Nuclear Information System (INIS)

    The atmospheric xenon radioactivity was measured from mid 1983 to the end of 1984 in the surroundings of Fessenheim nuclear power station on the right bank of the Rhine. The level of activity (annual mean at Hartheim 1.6 pCi/m3 against a background of about 0.2 pCi/m3) makes it possible to carry out a diffusion study. Using a one-dimensional Gauss model, expected values of immission were calculated, taking into account the average strength of the source. Radiation balance, degree of cover or global radiation/degree of cover and wind speed, were used as parameters for atmospheric stability. The agreement between the calculated and measured immission based on weekly averages is satisfactory: about 2/3 of all calculated immissions deviate by less than a factor of 3.5 from the measured values. The accuracy of prediction of the model rises for longer averaging periods; for three months averaging, there is a factor of 1.5 deviation. The drop in concentration between the stations at different distances from the source is predicted too steeply by a factor of 1.5 by the model. (orig.)

  14. Investigation of atmospheric diffusion by immission measurements of xenon-133 from Fessenheim nuclear power station

    International Nuclear Information System (INIS)

    The atmospheric xenon radioactivity was measured from mid 1983 to the end of 1984 in the surroundings of Fessenheim nuclear power station on the right bank of the Rhine. The level of activity (annual mean at Hartheim 1.6 pCi/m3 against a background of about 0.2 pCi/m3) makes it possible to carry out a diffusion study. Using a one-dimensional Gauss model, expected values of immission were calculated, taking into account the average strength of the source. Radiation balance, degree of cover or global radiation/ degree of cover and wind speed, were used as parameters for atmospheric stability. The agreement between the calculated and measured immission based on weekly averages is satisfactory: about 2/3 of all calculated immissions deviate by less than a factor of 3.5 from the measured values. The accuracy of prediction of the model rises for longer averaging periods; for three months averaging, there is a factor of 1.5 deviation. The drop in concentration between the stations at different distances from the source is predicted too steeply by a factor of 1.5 by the model. (orig./HP)

  15. Evaluation of the impact of atmospheric ozone and aerosols on the horizontal global/diffuse UV Index at Livorno (Italy)

    Science.gov (United States)

    Scaglione, Daniele; Giulietti, Danilo; Morelli, Marco

    2016-08-01

    A study was conducted at Livorno (Italy) to evaluate the impact of atmospheric aerosols and ozone on the solar UV radiation and its diffuse component at ground in clear sky conditions. Solar UV radiation has been quantified in terms of UV Index (UVI), following the ISO 17166:1999/CIE S007/E-1998 international standard. UVI has been calculated by exploiting the libRadtran radiative transfer modelling software as a function of both the Aerosols Optical Depth (AOD) and the Total Ozone Column (TOC). In particular AOD and TOC values have been remotely sensed by the Ozone Monitoring Instrument (OMI) on board the NASA's EOS (Earth Observing System) satellites constellation. An experimental confirmation was also obtained by exploiting global UVI ground-based measurements from the 26/9/14 to 12/8/15 and diffuse UVI ground-based measurements from the 17/5/15 to 12/8/15. For every considered value of Solar Zenith Angle (SZA) and atmospheric condition, estimates and measurements confirm that the diffuse component contributes for more than 50% on the global UV radiation. Therefore an exposure of human skin also to diffuse solar UV radiation can be potentially harmful for health and need to be accurately monitored, e.g. by exploiting innovative applications such as a mobile app with a satellite-based UV dosimeter that has been developed. Global and diffuse UVI variations due to the atmosphere are primarily caused by the TOC variations (typically cyclic): the maximum TOC variation detected by OMI in the area under study leads to a corresponding variation in global and diffuse UVI of about 50%. Aerosols in the area concerned, mainly of maritime nature, have instead weaker effects causing a maximum variation of the global and diffuse UVI respectively of 9% and 35% with an SZA of 20° and respectively of 13% and 10% with an SZA of 60°.

  16. Surface diffuse discharge mechanism of well-aligned atmospheric pressure microplasma arrays

    Science.gov (United States)

    Ren-Wu, Zhou; Ru-Sen, Zhou; Jin-Xing, Zhuang; Jiang-Wei, Li; Mao-Dong, Chen; Xian-Hui, Zhang; Dong-Ping, Liu; Kostya (Ken, Ostrikov; Si-Ze, Yang

    2016-04-01

    A stable and homogeneous well-aligned air microplasma device for application at atmospheric pressure is designed and its electrical and optical characteristics are investigated. Current-voltage measurements and intensified charge coupled device (ICCD) images show that the well-aligned air microplasma device is able to generate a large-area and homogeneous discharge at the applied voltages ranging from 12 kV to 14 kV, with a repetition frequency of 5 kHz, which is attributed to the diffusion effect of plasma on dielectric surface. Moreover, this well-aligned microplasma device may result in the uniform and large-area surface modification of heat-sensitive PET polymers without damage, such as optimization in hydrophobicity and biocompatibility. In the biomedical field, the utility of this well-aligned microplasma device is further testified. It proves to be very efficient for the large-area and uniform inactivation of E. coli cells with a density of 103/cm2 on LB agar plate culture medium, and inactivation efficiency can reach up to 99% for 2-min treatment. Project supported by the Natural Science Foundation of Fujian Province, China (Grant No. 2014J01025), the National Natural Science Foundation of China (Grant No. 11275261), the Natural Science Foundation of Guangdong Province, China (Grant No. 2015A030313005), and the Fund from the Fujian Provincial Key Laboratory for Plasma and Magnetic Resonance, China.

  17. Graphic displays on PCs of gaseous diffusion models of radionuclide releases to the atmosphere

    International Nuclear Information System (INIS)

    The well-known MESOI program has been modified and improved to adapt it to a PC/AT with VGA colour monitor. Far from losing any of its powerful characteristics to calculate the transport, diffusion, deposition and decay of gaseous radioactive effluents discharged to the atmosphere, it has been enhanced to allow graphic viewing of concentrations, wind speed and direction and puff locations in colour, all on a background map of the site. The background covers a 75 x 75 km square and has a graphic grid density of 421 x 421 pixels. This means that effluent concentration is represented approximately every 170 metres in the 'clouded-area'. Among the modifications and enhancements made, the following are of particular interest: 1. A new subroutine called NUBE has been added, which calculates the distribution of effluent concentration of activity in a grid of 421 x 421 pixels. 2. Several subroutines have been added to obtain graphic displays and printouts of the cloud, wind field and puff locations. 3. Graphic display of the geographic plane of the area surrounding the effluent release point. 4. Off-line preparation of meteorological and topographical data files necessary for program execution. (author)

  18. Influence of air diffusion on the OH radicals and atomic O distribution in an atmospheric Ar (bio)plasma jet

    OpenAIRE

    Nikiforov, Anton; Li, L.; Britun, N; Snyders, R; Vanraes, Patrick; Leys, Christophe

    2014-01-01

    Treatment of samples with plasmas in biomedical applications often occurs in ambient air. Admixing air into the discharge region may severely affect the formation and destruction of the generated oxidative species. Little is known about the effects of air diffusion on the spatial distribution of OH radicals and O atoms in the afterglow of atmospheric-pressure plasma jets. In our work, these effects are investigated by performing and comparing measurements in ambient air with measurements in a...

  19. Consequences of Windscale accident (October 1957) and study of the validity of the Sutton's mathematical model of atmospheric diffusion (1960)

    International Nuclear Information System (INIS)

    The reactor accident that happens at the number 1 pile of Windscale in 1957 was followed by a discharge of radioactive products into the atmosphere from the 1.X.1957 at 4.30 PM to the 12.X.1957 at 3.10 PM. On october the 11th it was possible to say that there was no more risk either of external irradiation or inhalation. But in adopting a M.A.C. of 0,1 μcurie of iodine 131 per litre of milk, the Authority had to control the milk delivery till november 23rd on a 500 km2 area. On the other hand, this exceptional accident permit to verify that Sutton's atmospheric diffusion model could give an easy means to foresee, with a sufficient approximation, the consequences of a dispersion of radioactive products into the atmosphere. (author)

  20. Diffusive transport and evaporation to the atmosphere from a NAPL source in the vadose zone

    DEFF Research Database (Denmark)

    Holtegaard, L.E.; Bjerre, T.; Christophersen, Mette;

    2002-01-01

    To evaluate the risks concerned with the presence of volatile organic compounds in the unsaturated zone it is important to know how the compounds are transported in the soil. In this project the effective diffusion coefficient of 3-methylpentane, hexane, methyl-cyclopentane, iso-octane and methyl-cyclo-hexane...... has been measured in-situ using a diffusive tracer test (DTT). Furthermore the flux from a NAPL source has been measured in flux chambers. From these results the effective diffusion coefficient has been calculated for CFC113, methyl-cyclo-pentane, benzene, iso-octane, and methyl-cyclo-hexane, but...

  1. Observation of Diffuse Cosmic and Atmospheric Gamma Rays at Balloon Altitudes with an Electron-tracking Compton Camera

    CERN Document Server

    Takada, Atsushi; Nishimura, Hironobu; Ueno, Kazuki; Hattori, Kaori; Kabuki, Shigeto; Kurosawa, Shunsuke; Miuchi, Kentaro; Mizuta, Eiichi; Nagayoshi, Tsutomu; Nonaka, Naoki; Okada, Yoko; Orito, Reiko; Sekiya, Hiroyuki; Takeda, Atsushi; Tanimori, Toru

    2011-01-01

    We observed diffuse cosmic and atmospheric gamma rays at balloon altitudes with the Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I (SMILE-I) as the first step toward a future all-sky survey with a high sensitivity. SMILE-I employed an electron-tracking Compton camera comprised of a gaseous electron tracker as a Compton-scattering target and a scintillation camera as an absorber. The balloon carrying the SMILE-I detector was launched from the Sanriku Balloon Center of the Institute of Space and Astronomical Science/Japan Space Exploration Agency on September 1, 2006, and the flight lasted for 6.8 hr, including level flight for 4.1 hr at an altitude of 32-35 km. During the level flight, we successfully detected 420 downward gamma rays between 100 keV and 1 MeV at zenith angles below 60 degrees. To obtain the flux of diffuse cosmic gamma rays, we first simulated their scattering in the atmosphere using Geant4, and for gamma rays detected at an atmospheric depth of 7.0 g cm-2, we found that 50% and 21% ...

  2. Isotopic composition of carbon in atmospheric air; use of a diffusion model at the water/atmosphere interface in Velenje Basin

    Directory of Open Access Journals (Sweden)

    Tjaša Kanduč

    2015-07-01

    Full Text Available CO2 concentrations (partial pressure of CO2, pCO2, and isotope compositions of carbon dioxide in air (δ13CCO2, temperature (T and relative humidity (H have been measured in the atmosphere in the Velenje Basin. Samples were collected monthly in the calendar year 2011 from 9 locations in the area where the largest thermal power plant in Slovenia with the greatest emission of CO2 to the atmosphere (around 4M t/year is located. Values of pCO2 ranged from 239 to 460 ppm with an average value of 294 ppm, which is below the average atmospheric CO2 pressure (360 ppm. δ13CCO2 ranged from -18.0 to -6.4 ‰, with an average value of -11.7 ‰. These values are similar to those measured in Wroclaw, Poland. We performed the comparison of δ13CCO2 values in atmospheric air with Wroclaw since researchers used similar approach to trace δ13CCO2 around anthropogenic sources. The isotopic composition of dissolved inorganic carbon (δ13CDIC in rivers and lakes from the Velenje basin changes seasonally from -13.5 to -7.1‰. The values of δ13CDIC indicate the occurrence of biogeochemical processes in the surface waters, with dissolution of carbonates and degradation of organic matter being the most important. A concentration and diffusion model was used to calculate the time of equilibration between dissolved inorganic carbon in natural sources (rivers and atmospheric CO2.

  3. Development of a diffuse air-argon plasma source using a dielectric-barrier discharge at atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Tang Jie; Jiang Weiman; Zhao Wei; Wang Yishan; Li Shibo; Wang Haojing [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics of CAS, Xi' an 710119 (China); Duan Yixiang [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics of CAS, Xi' an 710119 (China); Research Center of Analytical Instrumentation, Sichuan University, Chengdu 610064 (China)

    2013-01-21

    A stable diffuse large-volume air plasma source was developed by using argon-induced dielectric-barrier discharges at atmospheric pressure. This plasma source can be operated in a filamentary discharge with the average areal power density of 0.27 W/cm{sup 2} and the gas temperature of 315{+-}3 K. Spatial measurement of emission spectrum and temperature indicates that this plasma is uniform in the central region along the transverse direction. It is also found that the formation of diffuse air plasma mainly lies in the creation of sufficient seed electrons by the Penning effect through collisions between two argon or nitrogen metastables at low electric fields.

  4. Application of diffuse discharges of atmospheric pressure formed by runaway electrons for modification of copper and stainless steel surface

    Energy Technology Data Exchange (ETDEWEB)

    Tarasenko, V. F., E-mail: VFT@loi.hcei.tsc.ru; Shulepov, M. A.; Erofeev, M. V. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation)

    2015-12-15

    The results of studies devoted to the influence of a runaway electron pre-ionized diffuse discharge (REP DD) formed in air and nitrogen at atmospheric pressure on the surface of copper and stainless steel are presented. Nanosecond high-voltage pulses were used to obtain REP DD in different gases at high pressures in a chamber with a flat anode and a cathode possessing a small radius of curvature. This mode of discharge was implemented owing to the generation of runaway electrons and X-rays. The conditions under which the surface of copper and stainless steel was cleaned from carbon and oxidized are described.

  5. Compilation and evaluation of gas-phase diffusion coefficients of reactive trace gases in the atmosphere: volume 2. Organic compounds and Knudsen numbers for gas uptake calculations

    Directory of Open Access Journals (Sweden)

    M. J. Tang

    2015-02-01

    Full Text Available Diffusion of organic vapours to the surface of aerosol or cloud particles is an important step for the formation and transformation of atmospheric particles. So far, however, a database of gas phase diffusion coefficients for organic compounds of atmospheric interest has not been available. In this work we have compiled and evaluated gas phase diffusivities (pressure-independent diffusion coefficients of organic compounds reported by previous experimental studies, and we compare the measurement data to estimates obtained with Fuller's semi-empirical method. The difference between measured and estimated diffusivities are mostly Kn although their gas phase diffusivities may vary over a wide range. Knudsen numbers of gases with unknown diffusivity can be approximated by a simple function of particle diameter and pressure and can be used to characterize the influence of diffusion on gas uptake by aerosol or cloud particles. We use a kinetic multi-layer model of gas-particle interaction to illustrate the effects of gas phase diffusion on the condensation of organic compounds with different volatilities. The results show that gas-phase diffusion can play a major role in determining the growth of secondary organic aerosol particles by condensation of low-volatility organic vapours.

  6. Soil atmosphere exchange of Carbonyl Sulfide (COS regulated by diffusivity depending on water-filled pore space

    Directory of Open Access Journals (Sweden)

    H. Van Diest

    2007-10-01

    Full Text Available The exchange of carbonyl sulfide (COS between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS concentration, soil water content (WC and air temperature. All investigated soils acted as significant sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil WC, respectively, indicating that the soil WC acts as an important biological and physical parameter for characterizing the exchange of COS between soils and the atmosphere. Different optima of deposition velocities (Vd as observed for the Chinese, Finnish and Siberian boreal soil types in relation to their soil WC, aligned at 19% in relation to the water-filled pore space (WFPS, indicating the dominating role of gas diffusion. This interpretation was supported by the linear correlation between Vd and bulk density. We suggest that the uptake of COS depends on the diffusivity dominated by WFPS, a parameter depending on soil WC, soil structure and porosity of the soil.

  7. Soil atmosphere exchange of carbonyl sulfide (COS regulated by diffusivity depending on water-filled pore space

    Directory of Open Access Journals (Sweden)

    H. Van Diest

    2008-04-01

    Full Text Available The exchange of carbonyl sulfide (COS between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS concentration, soil water content (WC and air temperature. All investigated soils acted as sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil WC, respectively, indicating that the soil WC acts as an important biological and physical parameter for characterizing the exchange of COS between soils and the atmosphere. Different optima of deposition velocities (Vd as observed for the Chinese, Finnish and Siberian boreal soil types in relation to their soil WC, aligned at 19% in relation to the water-filled pore space (WFPS, indicating the dominating role of gas diffusion. This interpretation was supported by the linear correlation between Vd and bulk density. We suggest that the uptake of COS depends on the diffusivity dominated by WFPS, a parameter depending on soil WC, soil structure and porosity of the soil.

  8. Modelling of anthropogenic pollutant diffusion in the atmosphere and applications to civil protection monitoring

    CERN Document Server

    Tessarotto, Marco

    2008-01-01

    A basic feature of fluid mechanics concerns the frictionless phase-space dynamics of particles in an incompressible fluid. The issue, besides its theoretical interest in turbulence theory, is important in many applications, such as the pollutant dynamics in the atmosphere, a problem relevant for civil protection monitoring of air quality. Actually, both the numerical simulation of the ABL (atmospheric boundary layer) portion of the atmosphere and that of pollutant dynamics may generally require the correct definition of the Lagrangian dynamics which characterizes arbitrary fluid elements of incompressible thermofluids. We claim that particularly important for applications would be to consider these trajectories as phase-space trajectories. This involves, however, the unfolding of a fundamental theoretical problem up to now substantially unsolved: {\\it namely the determination of the exact frictionless dynamics of tracer particles in an incompressible fluid, treated either as a deterministic or a turbulent (i....

  9. Some discussions on micrometeorology and atmospheric diffusion of classic and radioactive industrial pollutions. 1

    International Nuclear Information System (INIS)

    The fundamental static equations are given describing the atmosphere. Relations are derived for the description of dynamic phenomena, such as changes in temperature, pressure and density of the air in the lower part of the atmosphere. The effect of wind is considered and the expressions are presented for the vertical profile of wind velocity. The properties of flow are discussed in the fully developed boundary layer, such as stress, viscous stress and dynamic viscosity. The concept of surface roughness and its significance for micrometeorology is dealt with. (L.O.)

  10. Influence of air diffusion on the OH radicals and atomic O distribution in an atmospheric Ar (bio)plasma jet

    International Nuclear Information System (INIS)

    Treatment of samples with plasmas in biomedical applications often occurs in ambient air. Admixing air into the discharge region may severely affect the formation and destruction of the generated oxidative species. Little is known about the effects of air diffusion on the spatial distribution of OH radicals and O atoms in the afterglow of atmospheric-pressure plasma jets. In our work, these effects are investigated by performing and comparing measurements in ambient air with measurements in a controlled argon atmosphere without the admixture of air, for an argon plasma jet. The spatial distribution of OH is detected by means of laser-induced fluorescence diagnostics (LIF), whereas two-photon laser-induced fluorescence (TALIF) is used for the detection of atomic O. The spatially resolved OH LIF and O TALIF show that, due to the air admixture effects, the reactive species are only concentrated in the vicinity of the central streamline of the afterglow of the jet, with a characteristic discharge diameter of ∼1.5 mm. It is shown that air diffusion has a key role in the recombination loss mechanisms of OH radicals and atomic O especially in the far afterglow region, starting up to ∼4 mm from the nozzle outlet at a low water/oxygen concentration. Furthermore, air diffusion enhances OH and O production in the core of the plasma. The higher density of active species in the discharge in ambient air is likely due to a higher electron density and a more effective electron impact dissociation of H2O and O2 caused by the increasing electrical field, when the discharge is operated in ambient air. (paper)

  11. Some discussions on micrometeorology and atmospheric diffusion of classic and radioactive industrial sollutions. 7

    International Nuclear Information System (INIS)

    The effects are shown of small horizontal wind fluctuations on the dispersion parameters, which will acquire higher values. This will cause more intense diffusion in the horizontal direction perpendicular to the main wind direction. Thus the plume will get more spread in lower concentrations. Some measurement methods of the dispersion parameters take this influence into consideration during the experimental stage - in these cases the data need not be corrected. (author)

  12. Atmospheric corrosion mapping of copper surfaces from diffuse light scattering measurements by an optoelectronic sensor system

    Institute of Scientific and Technical Information of China (English)

    Marimuthu PAULVANNA NAYAKI; Arunachalam P. KABILAN

    2009-01-01

    A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprising a thin beam light emitting diode (LED) illuminating a small spot on the metal surface, and a matched pair of photodetectors, one for capturing the reflected light and the other for sampling the scattered light. The analog photocurrent signals are digitized and processed online by a personal computer (PC) to determine the corrosion factor defined in terms of the two current values. By scanning the sample surface using the light beam and by computing the corrosion factor values simultaneously, a three dimensional graph and a two dimensional contour map are generated in the PC using Matlab tools. The values of the corrosion factor measured in different durations of exposure to atmosphere, which obey a bilogarithmic law, testify to the validity of our mathematical model.

  13. Programs to calculate human radiation exposure caused by atmospheric diffusion of radioactive substances

    International Nuclear Information System (INIS)

    This report describes - with a discussion on the mathematical background of transport processes near the ground - a program system START which make possible the interactive calculation of human radiation exposure resulting from the accidental release of radioactivity from nuclear facilities into the atmosphere. The system supplies data relevant immediately after the release on the whole-body and thyroid exposure of adults caused by inhalation and γ-submersion. (orig./HP)

  14. Atmospheric response in aurora experiment: Observations of E and F region neutral winds in a region of postmidnight diffuse aurora

    Science.gov (United States)

    Larsen, M. F.; Marshall, T. R.; Mikkelsen, I. S.; Emery, B. A.; Christensen, A.; Kayser, D.; Hecht, J.; Lyons, L.; Walterscheid, R.

    1995-01-01

    The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the post midnight sector. A combination of chemical release rocket wind measurements, instrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of approximately 100 m/s developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of approximately 150 m/s developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nominally unstable with a Richardson number of approximately 0.08.

  15. Contribution of emission control and atmospheric diffusion ability to the improved air quality in 2015 of China

    Science.gov (United States)

    Wang, X.; Wang, K.

    2015-12-01

    China experiences extremely severe and frequent PM2.5 (fine particulate matters with diameters less than 2.5 µm) pollution in recent years, arousing unprecedented public concern. Tough targets have been set for three particularly smog-ridden regions: JingJinJi area, the Yangtze River Delta and Pearl River Delta, requiring these regions to reduce their atmospheric levels of PM2.5 by 25%, 20% and 15% respectively by the year 2017. A lot of mitigation actions have been taken to improve the air quality in China. In January 2013, China began to deploy instruments to measure PM2.5 nationally and released hourly observational data to the public. Observed PM2.5 concentrations showed a significant decrease in 2015 comparing to that of 2014 as shown in Fig.1. Many studies have attributed this kind of air quality improvement to the effect of emission control. However, air quality not only depends on the original emission, the atmospheric abilities of contaminant transfer, spread and wet deposition play a big role in reducing the ambient air pollutants and directly determined by the occurrence of pollution episodes. Here we used the first 2 years PM2.5 observation data in China to quantify the contribution of the effect of emission control and atmospheric ability of diffusing on reducing ambient PM2.5 concentrations. We found that PM2.5 decreased by 24% in 2015 winter (Dec. 2014-Feb. 2015) comparing to that in 2014; and 12% of decrease occurred for the spring time. The inconsistent seasonal improvement of air quality is mainly due to the favorable atmospheric background in 2015, with its frequent precipitation, infrequency of surface calm wind during the wintertime.

  16. Radon-222 measurements aboard an airplane for the description of atmospheric diffusion

    International Nuclear Information System (INIS)

    Radon-222 is absorbed aboard an airplane in tubes filled with 50 g of selected charcoal and cooked in Dewars by carbon dioxide and freon. After air collection at different heights up to 5 km, the tubes are evacuated and heated in the laboratory for desorption of the gas molecules and for transfer into a decay chamber covered with zinc-sulfide serving as a scintillator for the detection of alpha activity from radon-222 and its daughters. In general, the measurements show an exponential decrease of the concentration up to 5 km in height, if there is no cloud layer. The height for a reduction by a factor of two is about 900 meters. Assuming a constant diffusion coefficient K0 up to 5 km, the measurements yield a K0 of approximately 3.7 x 104 cm2s-1. For flights in stratiform clouds a decrease is observed of the concentration up to a certain height, then radon-222 is again increasing or remains constant. This must be explained with respect to the meteorological situation. Assuming only a constant value for K0 between the different flying heights, it was possible to appraise the development of the eddy diffusion coefficient with height

  17. Some discussions on micrometeorology and atmospheric diffusion of classic and radioactive industrial pollutions. 10

    International Nuclear Information System (INIS)

    Relations are shown used for calculating air and surface pollution in the METEO-2 computer programme. The programme may be used for computing both short-term and long-term stack emissions of conventional and radioactive industrial wastes into the atmosphere and their deposition in the neighbouring environment. The factors for pollution computation comprise vertical plume dynamics and heat capacity. Methods of dispersion data determination are given. The practical choice of a mesh point system used in the computations is discussed. (J.B.)

  18. Atmospheric diffusion and fallout and alkaline materials produced by sodium fires

    International Nuclear Information System (INIS)

    The present works deals with a theoretic approach of the diffusion in air of colloidal Na2O coming out of sodium fires, consequent to sodium losses from the cooling circuit of a fast breeder reactor, in case of accident. The theoretical pattern has subsequently been applied to a numerical assessment of the Na2O concentration in air and on the ground (due to fallout), either inside or outside the sodium hall of the Cpv-1 facility at the Brasimone site. The assessment refers to the maximum credible accident 'pool burning', in the most unfavourable meteorological conditions. Protectionistic recomendations are given, and emergency procedures are described, in that concerns boot people professionally employed within the reactor site and the external population

  19. Passive Effluent Diffusion in a Convective Atmospheric Boundary Layer: An Airborne Approach to Locating Sources and Estimating Their Emission Rates

    Science.gov (United States)

    Suard, Maxime

    We studied the near field dispersion of natural gas plumes leaking from transmission lines and diffusing in a convective Atmospheric Boundary Layer (ABL), with the intent of providing an aerial system of leak detection and pinpointing, as well as quantitative leak rate estimation. We used high frequency measurements of methane and ethane concentrations on a fixed wing aircraft using high rate spectroscopic gas concentration measurements. We looked for characteristics of the effluent concentration field which can be related to the distance from the effluent source, and developed an empirical approach to effluent source position estimation from airborne effluent concentration measurements. From a mass-balance approach we developed a practical method of effluent leak rate estimation based on airborne effluent concentration measurements. Since gathering experimental data was costly and time-expensive, Large Eddy Simulation (LES) results were also investigated. Results showed that analysis of effluent concentration variability is likely to provide information about the position of the effluent source. The developed leak rate estimation method provided encouraging results showing that such an approach is able to yield relatively accurate leak rate estimates. LES results proved to be very useful as they helped to provide guidelines for experiments as well as to deepen our understanding of the diffusion dynamics of turbulent effluent plumes.

  20. Thermally Induced Chemistry of Meteoritic Complex Organic Molecules: A New Heat-Diffusion Model for the Atmospheric Entry of Meteorites

    CERN Document Server

    Shingledecker, Christopher N

    2014-01-01

    Research over the past four decades has shown a rich variety of complex organic molecular content in some meteorites. This current study is an attempt to gain a better insight into the thermal conditions experienced by these molecules inside meteorites during atmospheric entry. In particular, we wish to understand possible chemical processes that can occur during entry and that might have had an effect on complex organic or prebiotic species that were delivered in this way to the early Earth. A simulation was written in Fortran to model heating by the shock generated during entry and the subsequent thermal diffusion inside the body of a meteorite. Experimental data was used for the thermal parameters of several types of meteorites, including iron-nickel and several classes of chondrites. A Sutton-Graves model of stagnation-point heating was used to calculate peak surface temperatures and an explicit difference formula was used to generate thermal diffusion profiles for both chondrites and iron-nickel type met...

  1. The influence of clouds and diffuse radiation on ecosystem-atmosphere CO2 and CO18O exhanges

    Energy Technology Data Exchange (ETDEWEB)

    Still, C.J.; Riley, W.J.; Biraud, S.C.; Noone, D.C.; Buenning, N.H.; Randerson, J.T.; Torn, M.S.; Welker, J.; White, J.W.C.; Vachon, R.; Farquhar, G.D.; Berry, J.A.

    2009-05-01

    This study evaluates the potential impact of clouds on ecosystem CO{sub 2} and CO{sub 2} isotope fluxes ('isofluxes') in two contrasting ecosystems (a broadleaf deciduous forest and a C{sub 4} grassland), in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope-enabled land surface model, ISOLSM. Our model results indicate a large impact of clouds on ecosystem CO{sub 2} fluxes and isofluxes. Despite lower irradiance on partly cloudy and cloudy days, predicted forest canopy photosynthesis was substantially higher than on clear, sunny days, and the highest carbon uptake was achieved on the cloudiest day. This effect was driven by a large increase in light-limited shade leaf photosynthesis following an increase in the diffuse fraction of irradiance. Photosynthetic isofluxes, by contrast, were largest on partly cloudy days, as leaf water isotopic composition was only slightly depleted and photosynthesis was enhanced, as compared to adjacent clear sky days. On the cloudiest day, the forest exhibited intermediate isofluxes: although photosynthesis was highest on this day, leaf-to-atmosphere isofluxes were reduced from a feedback of transpiration on canopy relative humidity and leaf water. Photosynthesis and isofluxes were both reduced in the C{sub 4} grass canopy with increasing cloud cover and diffuse fraction as a result of near-constant light limitation of photosynthesis. These results suggest that some of the unexplained variation in global mean {delta}{sup 18}O of CO{sub 2} may be driven by large-scale changes in clouds and aerosols and their impacts on diffuse radiation, photosynthesis, and relative humidity.

  2. A novel approach to control atmospheric methane emissions from low-volume point sources and diffused area sources

    Energy Technology Data Exchange (ETDEWEB)

    Hettiaratchi, J.P.A.; Pokhrel, D.; Chandrakanthi, M. [Calgary Univ., AB (Canada)

    2003-07-01

    Over the past one hundred years, the atmospheric concentration of methane has significantly increased. The search for inexpensive techniques for reducing anthropogenic methane gas emissions into the atmosphere have led the authors to propose a technique called methanobiofiltration (MBF), which utilizes a naturally occurring bacterium to convert methane into carbon dioxide. It was shown that this method can be applied where conventional methods to extract methane for energy recovery may not be viable, such as controlling methane emissions from low volume, but numerous, or spatially diffused sources. A long-term research program, which involved laboratory based experimental studies, pilot-scale field studies and mathematical modeling was carried out. Several filter media were tested using passively aerated biofilter columns. The highest oxidation rate was obtained with compost. A decrease in the rate of oxidation was noted after reaching a maximum value within 100 days of continuous operation. Passively aerated biofilter columns did not perform as well as actively aerated columns. The authors presented the preliminary results obtained from two passively aerated pilot-scale field MBFs. The MBF design curves were developed using a series of 480 model simulations performed under a one-dimensional reactive transport model. 5 refs., 10 figs.

  3. Atmospheric tracer investigation of transport and diffusion around a large isolated hill

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, W.; Lamb, B.; Robinson, E.

    1984-01-01

    Twenty-one single and dual tracer tests were conducted during May and June 1981, at Steptoe Butte (335 m), an isolated hill located in eastern Washington state. SF/sub 6/ and CBrF/sub 3/ tracer released from upwind of the hill at heights ranging from near the surface to approximately 190 m were used to study plume transport over and around the hill during unstable, neutral, and stable atmospheric conditions. Plumes releases upwind during daytime near-neutral conditions traveled up and over the hill with maximum concentrations on the windward side at receptor elevations between 0.5 and 1.5 times the source height. Maximum concentrations were in the same range as calculated from models for neutral flow over a hemisphere. Plumes released upwind during transitional day-to-night conditions exhibited maximum concentrations similar to the daytime releases, buth the tracer isopleths indicated some plume bifurcation. The concept of a critical streamline height to predict whether plumes impinge upon the hill and pass round it or travel up and over the hill was found to be valid at Steptoe Butte. The position of the maximum concentrations tended to shift toward the side of the hill as the horizontal displacement of the source from the flow centerline increased. The largest maximum concentration was in a range calculated previously with an impingement model of a turbulent plume embedded in a potential flow around a cyclinder, while the remainder of the maxima were in a range predicted with a similar model of potential flow over a hemisphere. 17 references, 15 figures, 1 table.

  4. Optimum modellings of atmospheric diffusion of radioactive effluents and exposure doses in the accident consequence assessment (Level 3 PSA)

    International Nuclear Information System (INIS)

    Atmospheric diffusion and exposure strongly dependent on the environment were firstly considered in the full spectrum of accident consequence assessment to establish based on Korean conditions. An optimum weather category based on Korean climate and site-specific meteorology of Kori region was established by statistical analysis of measured data for 10 years. And a trajectory model was selected as the optimal one in the ACA by reviewing several existing diffusion models. Following aspects were considered in this selection as availability of meteorological data, ability to treat the change to wind direction, easy applicability of the model, and restriction of CPU time and core memory in current computers. Numerical integration method of our own was selected as the optimal dose assessment tool of external exposure. Unit dose rate was firstly computed with this method as the function of energy level of radionuclide, size of lattice, and distance between source and receptor, and then the results were rearranged as the data library for the rapid access to the ACA run. Dynamic ecosystem modelling has been done in order to estimate the seasonal variation of radioactivity for the assessment of ingestion exposure, considering Korean ingestion behavior, agricultural practice and the transportation. There is a lot of uncertainty in a countermeasure model due to the assumed values of parameters such as fraction of population with different shielding factor and driving speed. A new countermeasure model was developed using the concept of fuzzy set theory, since it provided the mathematical tools which could characterize the uncertainty involved in countermeasure modelling. (Author)

  5. Continuous on-line calibration of diffusive soil-atmosphere trace gas transport using vertical 220Rn- and 222Rn-activity profiles

    International Nuclear Information System (INIS)

    Continuous monitoring of 220Rn- and 222Rn-activities above and below the soil surface combined with sporadic direct 222Rn-flux measurements is used to quantify diffusive trace gas transport in the air-filled pore space of soil, through the soil-atmosphere interface and in the lowest layers of the atmosphere. In a calm night, 222Rn-activities above the surface first build-up near the ground (z 222Rn-flux from activity profiles measured in soil gas, (2) from direct flux determinations and (3) using information about atmospheric diffusion parameters from 220Rn-activities measured near the surface it is possible to model the temporal evolution of the vertical 222Rn-profiles in a night with stable weather and constant soil conditions. The system operates automatically for extended periods of time in the field enabling a better understanding of transport processes in response to changing environmental conditions (wind, rain, soil humidity). (orig.)

  6. Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

    Science.gov (United States)

    Li, Lee; Liu, Lun; Liu, Yun-Long; Bin, Yu; Ge, Ya-Feng; Lin, Fo-Chang

    2014-01-01

    Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

  7. Diffusion-type model of the global carbon cycle for the estimation of dose to the world population from releases of carbon-14 to the atmosphere

    International Nuclear Information System (INIS)

    A nonlinear dynamic model of the exchange of carbon among the atmosphere, terrestrial biosphere, and ocean is described and applied to estimating the radiation dose to the world's population from the release of 14C to the atmosphere from the nuclear power industry. A computer implementation of the model, written in the IBM Continuous System Modeling Program III (CSMP III) simulation language, is presented. The model treats the ocean as a diffusive medium with respect to vertical transport of carbon, and the nonlinear variation of CO2 partial pressure with the total inorganic carbon concentration in surface waters is taken into account in calculating the transfer rate from ocean to atmosphere. Transfers between the atmosphere and terrestrial biosphere are represented by nonlinear equations which consider CO2 fertilization and impose a constraint on the ultimate total carbon mass in the biosphere

  8. Determination of the safety zones of Angra dos Reis Nuclear Power Plant, according to the model of radion diffusion in the atmosphere

    International Nuclear Information System (INIS)

    The safety distance for Angra dos Reis Nuclear Power Plant are calculated, based on the model of the maximum credible accident for PWR power reactors and on the calculation of the dose due to hypothetical accidental release of radioactivity, using the model of radiation dispersion in the atmosphere. The safety distances for the Angra dos Reis reactors are also calculated using the model of the nine accident categories of the Rasmussen Report. The values of probability associated to each type of accident are used with the respective fractions of radiation release to the atmosphere. The soil contamination is also calculated for all the accidents considered and for several conditions of atmospheric stability, according to the model developed by Chamberlain. The program ACRA-II is used for calculation of the diffusion of radiation in the atmosphere, and the doses associated to it

  9. Multiple tree-ring isotopes as environmental indicators of diffuse atmospheric pollution in a peri-urban area

    Science.gov (United States)

    Doucet, A.; Savard, M. M.; Bégin, C.; Ouarda, T. B.; Marion, J.

    2010-12-01

    The combined analyses of tree-ring δ13C, δ18O, δ15N, 206Pb/207Pb, 206Pb/204Pb and 206Pb/208Pb isotope ratios of three red spruce specimens from the Tantaré ecological reserve located 40 km northwest of Québec City (Canada) were studied with the aim of reconstructing environmental conditions and unravel past air-quality changes of the 1880-2007 period. To separate the tree-ring δ18O and δ13C patterns induced by natural conditions from those generated by anthropogenic perturbations, a linear regression was applied between the most explicative meteorological parameters and the isotopic series for the period of low pollution (1880 to 1909). The model equations were then applied to the most recent part of the series (1910-2007) to verify if climatic conditions have remained the main driver of the tree-ring isotopic variations. The good fit between the modeled and measured δ18O series for the entire studied period suggests that the assimilation of oxygen by red spruce trees is not significantly affected by pollution stress near Québec City. However, the deviation between the measured and modeled δ13C values for the 1944-2007 period indicates that diffuse pollution affected carbon assimilation by the investigated trees. To independently validate if atmospheric pollution could have generated the deviation between the measured and the estimated δ13C values, a linear regression was applied between the portion of the residual δ13C values and atmospheric pollution (Canadian fossil fuel proxy from 1958 to 2000). The nice fit between the modeled δ13C values from the combination of the two regression analyses based on climate and emission proxy strongly supports the hypothesis that there is a natural and an anthropogenic portion in the δ13C variations of the studied specimens. The short-term variations of the red spruce δ15N series are correlated with the instrumentally measured amounts of provincial N emissions for the 1990 to 2006 period (longest measurements

  10. Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure

    Science.gov (United States)

    Tang, Kai; Wang, Wenchun; Yang, Dezheng; Zhang, Shuai; Yang, Yang; Liu, Zhijie

    2013-08-01

    In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C3Πu → B3Πg 1-3) and N2 (C3Πu → B3Πg 0-2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C3Πu → B3Πg, 0-0, 337.1 nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C3Πu → B3Πg, 0-0, 337.1 nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material.

  11. DIFFUSION IN THE VICINITY OF STANDARD-DESIGN NUCLEAR POWER PLANTS-I. WIND-TUNNEL EVALUATION OF DIFFUSIVE CHARACTERISTICS OF A SIMULATED SUBURBAN NEUTRAL ATMOSPHERIC BOUNDARY LAYER

    Science.gov (United States)

    A large meteorological wind tunnel was used to simulate a suburban atmospheric boundary layer. The model-prototype scale was 1:300 and the roughness length was approximately 1.0 m full scale. The model boundary layer simulated full scale dispersion from ground-level and elevated ...

  12. Contribution of CO2 and H2S emitted to the atmosphere by plume and diffuse degassing from volcanoes: the Etna volcano case study

    Science.gov (United States)

    Hernández, Pedro A.; Melián, Gladys; Giammanco, Salvatore; Sortino, Francesco; Barrancos, José; Pérez, Nemesio M.; Padrón, Eleazar; López, Manuela; Donovan, Amy; Mori, Toshiya; Notsu, Kenji

    2015-05-01

    Active subaerial volcanoes often discharge large amounts of CO2 and H2S to the atmosphere, not only during eruptions but also during periods of quiescence. These gases are discharged through focused (plumes, fumaroles, etc.) and diffuse emissions. Several studies have been carried out to estimate the global contribution of CO2 and H2S emitted to the atmosphere by subaerial volcanism, but additional volcanic degassing studies will help to improve the current estimates of both CO2 and H2S discharges. In October 2008, a wide-scale survey was carried out at Mt. Etna volcano, one the world's most actively degassing volcanoes on Earth, for the assessment of the total budget of volcanic/hydrothermal discharges of CO2 and H2S, both from plume and diffuse emissions. Surface CO2 and H2S effluxes were measured by means of the accumulation chamber method at 4075 sites, covering an area of about 972.5 km2. Concurrently, plume SO2 emission at Mt. Etna was remotely measured by a car-borne Differential Optical Absorption Spectrometry (DOAS) instrument. Crater emissions of H2O, CO2 and H2S were estimated by multiplying the plume SO2 emission times the H2O/SO2, CO2/SO2 and H2S/SO2 gas plume mass ratios measured in situ using a portable multisensor. The total output of diffuse CO2 emission from Mt. Etna was estimated to be 20,000 ± 400 t day-1 with 4520 t day-1 of deep-seated CO2. Diffuse H2S output was estimated to be 400 ± 20 kg day-1, covering an area of 9.1 km2 around the summit craters of the volcano. Diffuse H2S emission on the volcano flanks was either negligible or null, probably due to scrubbing of this gas before reaching the surface. During this study, the average crater SO2 emission rate was ~2100 t day-1. Based on measured SO2 emission rates, the estimated H2O, CO2 and H2S emission rates from Etna's crater degassing were 220,000 ± 100,000, 35,000 ± 16,000 and 510 ± 240 t day-1, respectively. These high values are explained in terms of intense volcanic activity at

  13. Dynamics of the atmospheric pressure diffuse dielectric barrier discharge between cylindrical electrodes in roll-to-roll PECVD reactor

    Science.gov (United States)

    Starostin, Sergey A.; Welzel, Stefan; Liu, Yaoge; van der Velden-Schuermans, Bernadette; Bouwstra, Jan B.; van de Sanden, Mauritius C. M.; de Vries, Hindrik W.

    2015-07-01

    The high current diffuse dielectric barrier discharge (DBD) was operated in a bi-axial cylindrical electrode configuration using nitrogen, oxygen and argon gas flow with the addition of tetraethyl orthosilicate as precursor for silica-like film deposition. The behaviour of the transient plasma was visualized by means of fast imaging from two orthogonal directions. The formation and propagation (~3 × 104 m s-1) of lateral ionization waves with the transverse light emission structure similar to the low pressure glow discharge was observed at time scales below 1 µs. Despite plasma non-uniformity at nanosecond time scale the deposition process on the web-rolled polymer results in smooth well adherent films with good film uniformity and excellent gas diffusion barrier properties. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark

  14. Derivation of upward muon energy spectra in the TeV range produced by neutrinos from 3C273 AGN and diffuse atmospheric sources

    International Nuclear Information System (INIS)

    The neutrino-induced upward muon energy spectrum on Earth at the TeV energy range emitted by the point source 3C273 AGN has been calculated using the AGN-emitted neutrino spectrum of Szabo and Protheroe and the result has been compared with that expected from background neutrinos. The QCD-based model of Berezinsky et al. has been fairly employed to estimate the muon contribution due to the charge current interactions in rock. The diffuse neutrino-induced upward muon energy spectrum from AGN sources has also been estimated and compared with the expected results from the spectra of prompt neutrinos and atmospheric backgrounds. It is found that the upward muon fluxes generated by AGN neutrinos are dominating the Universe beyond 10 TeV muon energy

  15. Derivation of upward muon energy spectra in the TeV range produced by neutrinos from 3C273 AGN and diffuse atmospheric sources

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, D.P. [Indian Association for the Cultivation of Science, Calcutta (India). Dept. of Theoretical Physics

    1998-01-01

    The neutrino-induced upward muon energy spectrum on Earth at the TeV energy range emitted by the point source 3C273 AGN has been calculated using the AGN-emitted neutrino spectrum of Szabo and Protheroe and the result has been compared with that expected from background neutrinos. The QCD-based model of Berezinsky et al. has been fairly employed to estimate the muon contribution due to the charge current interactions in rock. The diffuse neutrino-induced upward muon energy spectrum from AGN sources has also been estimated and compared with the expected results from the spectra of prompt neutrinos and atmospheric backgrounds. It is found that the upward muon fluxes generated by AGN neutrinos are dominating the Universe beyond 10 TeV muon energy.

  16. On the formation mechanisms of the diffuse atmospheric pressure dielectric barrier discharge in CVD processes of thin silica-like films

    International Nuclear Information System (INIS)

    Pathways of formation and temporal evolution of the diffuse dielectric barrier discharge at atmospheric pressure were experimentally studied in this work by means of optical (fast imaging camera) and electrical diagnostics. The chosen model system is relevant for applications of plasma-enhanced chemical vapor deposition of thin silica-like film on the polymeric substrate, from cost-efficient gas mixtures of Ar/N2/O2/hexamethyldisiloxane. It was found that the discharge can gradually experience the phases of homogeneous low current Townsend-like mode, local Townsend to glow transition and expanding high current density (∼0.7 A cm-2) glow-like mode. While the glow-like current spot occupies momentarily only a small part of the electrode area, its expanding behavior provides uniform treatment of the whole substrate surface. Alternatively, it was observed that a visually uniform discharge can be formed by the numerous microdischarges overlapping over the large electrode area.

  17. An atmospheric transmittance model for the calculation of the clear sky beam, diffuse and global photosynthetically active radiation

    International Nuclear Information System (INIS)

    A physical model is proposed for the estimation of the photosynthetically-active-radiation (PAR) components. Transmittances corresponding to ozone absorption, Rayleigh scattering and aerosol extinction are parameterized after numerical integration of spectral formulae. The parameters used in the model are station pressure, ozone amount, Angström turbidity coefficients, single-scattering albedo, ground albedo and solar elevation. Knowledge of these parameters is necessary if the beam and diffuse PAR are to be estimated accurately; while the global PAR is essentially a function of solar elevation. Model estimates compare well with predictions obtained with rigorous spectral codes (LOWTRAN and BRITE) and to measurements in Uccle, Belgium. It may be used in any area where the turbidity climatology is sufficiently known, to compute instantaneous, hourly or daily PAR clear sky values, even if simultaneous solar radiation measurements are not available

  18. Local scale atmospheric diffusion at a coastal site in the presence of breeze effect (Phase I and II: data collection at a coastal site and off shore)

    International Nuclear Information System (INIS)

    The aim of this contract is the characterization, from the thermal and anemological point of view of the lower layers of the atmosphere at a coastal site, affected by breeze circulation. Data are utilized to set up diffusion models for accidental releases of airborne materials, both of short and prolonged duration. Five inland meteorological campaigns, starting from Jan. 82 (Jan., Apr., Jul., Oct. 1982, Jan. 1983), have been carried out; an appropriate extension of the contract allowed the execution of two more campaigns in the open sea (Apr., Jul. 1983), utilizing the oceanographic ship ''Bannock'' kindly supplied by CNR. The analysis of the data showed the development of a well defined IBL during on-shore flow only in Spring and Summer, while an inversion layer was detectable aloft independently of the season (provided that an anticyclonic situation was present). According to those relevant features a simple diffusion model has been developed for short duration releases at local scale. Finally, the analysis and elaboration of the data, collected on site by a meteorological automatic station, allowed the extension of the model to prolonged releases

  19. Atmospheric air diffuse array-needles dielectric barrier discharge excited by positive, negative, and bipolar nanosecond pulses in large electrode gap

    Science.gov (United States)

    Zhang, Li; Yang, De-zheng; Wang, Wen-chun; Liu, Zhi-jie; Wang, Sen; Jiang, Peng-chao; Zhang, Shuai

    2014-09-01

    In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6 mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10-20 K lower than the unipolar discharge plasma.

  20. Local scale atmospheric diffusion at a coastal site in the presence of breeze effect (phase III: data elaboration and model development). Volume 1

    International Nuclear Information System (INIS)

    The aim of this contract is the characterization, from the thermal and anemological point of view, of the lower layers of the atmosphere at a coastal site, affected by breeze circulation. Data are utilized to set up diffusion models for accidental releases of airborne materials, both of short and prolonged duration. Five inland meteorological campaigns, starting from Jan. 82 (Jan., Apr., Jul., Oct. 1982, Jan. 1983), have been carried out; an appropriate extension of the contract allowed the execution of two more campaigns in the open sea (Apr., Jul. 1983), utilizing the oceanographic ship ''Bannock'' kindly supplied by CNR. The analysis of the data showed the development of a well defined IBL during on-shore flow only in Spring and Summer, while an inversion layer was detectable aloft independently of the season (provided that an anticyclonic situation was present). According to those relevant features a simple diffusion model has been developed for short duration releases at local scale. Finally, the analysis and elaboration of the data, collected on site by a meteorological automatic station, allowed the extension of the model to prolonged releases

  1. Absolute OH density measurements by broadband UV absorption in diffuse atmospheric-pressure He–H2O RF glow discharges

    International Nuclear Information System (INIS)

    The measurement of radical densities in atmospheric-pressure plasmas has gained increasing importance in recent years in view of their crucial role in many applications. In this paper we present absolute OH density measurements by broadband UV absorption in diffuse atmospheric-pressure RF glow discharges in mixtures of He and H2O. The use of a 310 nm light-emitting diode as a light source and a very high resolution spectrometer (2.6 pm resolution) made the estimation of the total OH density possible by simultaneously measuring the absorption rates of different spectrally resolved rotational lines of the OH(A–X) transition. For different RF powers and water concentrations, OH densities and gas temperatures ranging between 6 × 1019and 4 × 1020 m−3 and 345 and 410 K, respectively, were obtained. The gas temperature Tg was also measured by three different methods. Tg deduced from the rotational temperature of N2(C–B) emission, nitrogen being present as a trace impurity, provided the most reliable value. The rotational temperature Tr of the ground state OH(X) presented values with a maximum deviation of 25 K compared with Tg. To obtain the gas temperature from the emission intensities of OH(A–X) rotational lines, the recorded intensities of different lines must be corrected for the effect of self-absorption inside the plasma. (paper)

  2. The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes

    International Nuclear Information System (INIS)

    Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform α mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work

  3. The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Sun Wenting; Liang Tianran; Wang Huabo; Li Heping; Bao Chengyu [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

    2007-05-15

    Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform {alpha} mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work.

  4. The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes

    Science.gov (United States)

    Sun, Wen-Ting; Liang, Tian-Ran; Wang, Hua-Bo; Li, He-Ping; Bao, Cheng-Yu

    2007-05-01

    Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform α mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work.

  5. Sensitivity of the photodissociation of NO2, NO3, HNO3 and H2O2 to the solar radiation diffused by the ground and by atmospheric particles

    International Nuclear Information System (INIS)

    The diffusion of solar radiation by atmospheric molecules and aerosols and by ground albedo affects the photodissociation rates of atmospheric species relevant to the ozone chemistry. In this paper, a previous investigation on the photodissociation of O3 is extended to NO2, NO3, HNO3, H2O2. Because of the different character of the absorption spectra of these species, the behaviour of photodissociation profiles with height and their sensitivity to such factors as ground albedo, aerosol loads, solar zenith angle are somewhat different. The results show that the presence of the aerosols usually enhances the photodissociation in the upper troposphere and in the stratosphere, because of scattering, but tends to reduce it at low heights because of the increased extinction. Enhancements in the photodissociation coefficients are as high as 20 to 40% for low values of the albedo and large aerosol loads such as those obtained after a volcanic eruption. On the other hand, at large values of the albedo, the effect of aerosols is mainly in attenuating the radiation going into and coming from the ground and their presence can lead to reduced photolysis even in the stratosphere. (author)

  6. Improved retrieval of direct and diffuse downwelling surface shortwave flux in cloudless atmosphere using dynamic estimates of aerosol content and type: application to the LSA-SAF project

    Directory of Open Access Journals (Sweden)

    X. Ceamanos

    2014-03-01

    Full Text Available Downwelling surface shortwave flux (DSSF is a key parameter to address many climate, meteorological, and solar energy issues. Under clear sky conditions, DSSF is particularly sensitive to the variability both in time and space of the aerosol load and chemical composition. Hitherto, this dependence has not been properly addressed by the Satellite Application Facility on Land Surface Analysis (LSA-SAF, which operationally disseminates instantaneous DSSF products over the continents since 2005 considering unchanging aerosol conditions. In the present study, an efficient method is proposed for DSSF retrieval that will overcome the limitations of the current LSA-SAF product. This method referred to as SIRAMix (Surface Incident Radiation estimation using Aerosol Mixtures is based on an accurate physical parameterization that is coupled with a radiative transfer-based look up table of aerosol properties. SIRAMix considers an aerosol layer constituted of several major aerosol species that are conveniently mixed to match real aerosol conditions. This feature of SIRAMix allows it to provide not only accurate estimates of global DSSF but also the direct and diffuse DSSF components, which are crucial radiative terms in many climatological applications. The implementation of SIRAMix is tested in the present article using atmospheric inputs from the European Center for Medium-Range Weather Forecasts (ECMWF. DSSF estimates provided by SIRAMix are compared against instantaneous DSSF measurements taken at several ground stations belonging to several radiation measurement networks. Results show an average root mean square error (RMSE of 23.6 W m−2, 59.1 W m−2, and 44.9 W m−2 for global, direct, and diffuse DSSF, respectively. These scores decrease the average RMSE obtained for the current LSA-SAF product by 18.6%, which only provides global DSSF for the time being, and, to a lesser extent, for the state of the art in matter of DSSF retrieval (RMSE decrease

  7. Identification of the different diffuse dielectric barrier discharges obtained between 50 kHz to 9 MHz in Ar/NH3 at atmospheric pressure

    International Nuclear Information System (INIS)

    The aim of this work was to identify the different diffuse dielectric barrier discharges (DBDs) obtained in the same electrode configuration and in the same gas for an excitation frequency ranging from 50 kHz to 9 MHz. The gas mixture was argon with 133 ppm of NH3. This Penning mixture is useful to obtain both low-frequency glow DBDs (GDBDs) and diffuse radio-frequency (RF) discharges. Electrical measurements and short exposure time photographs showed that whatever the frequency, a discharge free of micro-discharge was obtained. In the same configuration, the discharge was a GDBD up to 200 kHz. For frequencies higher than 250 kHz, the discharge behavior was that of a Townsend-like discharge associated with a maximum energy transfer close to the anode and a higher power (about twice that of the GDBD). The cathode fall formation was no longer observed during the discharge current increase because of ion trapping in the gas gap by the rapid electric field oscillations. In the same configuration, the alpha RF mode was observed from 1.3 MHz. Gamma secondary electron emission gave way to electron acceleration by the cathode sheath formation. Bulk ionization was important due to the high electron collision rate at atmospheric pressure. One consequence of the transition from low-frequency to high-frequency discharge was a significant increase in the power (factor ≈30), which reached 35 W cm−3, while the breakdown voltage decreased from 900 V to less than 200 V. (paper)

  8. An Experimental Field Dataset with Buoyant, Neutral, and Dense Gas Atmospheric Releases and Model Comparisons in Low-Wind Speed (Diffusion) Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Veronica E. Wannberg, Gustavious Williams, Patrick Sawyer, and Richard Venedam

    2010-09-01

    Aunique field dataset from a series of low–wind speed experiments, modeling efforts using three commonly used models to replicate these releases, and statistical analysis of how well these models were able to predict the plume concentrations is presented. The experiment was designed to generate a dataset to describe the behavior of gaseous plumes under low-wind conditions and the ability of current, commonly used models to predict these movements. The dataset documents the release and transport of three gases: ammonia (buoyant), ethylene (neutral), and propylene (dense) in low–wind speed (diffusion) conditions. Release rates ranged from 1 to 20 kg h21. Ammonia and ethylene had five 5-min releases each to represent puff releases and five 20-min releases each to represent plume releases. Propylene had five 5-min puffs, six 20-min plumes, and a single 30-min plume. Thirty-two separate releases ranging from 6 to 47 min were conducted, of which only 30 releases generated useful data. The data collected included release rates, atmospheric concentrations to 100 m from the release point, and local meteorological conditions. The diagnostics included nine meteorological stations on 100-m centers and 36 photoionization detectors in a radial pattern. Three current stateof- the-practice models, Aerial locations of Hazardous Atmospheres (ALOHA), Emergency Prediction Information code (EPIcode), and Second-Order Closure Integrated Puff (SCIPUFF), were used to try to duplicate the measured field results. Low wind speeds are difficult to model, and all of the models had difficulty replicating the field measurements. However, the work does show that these models, if used correctly, are conservative (overpredict concentrations) and can be used for safety and emergency planning.

  9. Diffusion bonding

    Science.gov (United States)

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  10. Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses

    Science.gov (United States)

    Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

    2014-10-01

    This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

  11. In-depth diffusion of oxygen into LDPE exposed to an Ar--O2 atmospheric post-discharge: a complementary approach between AR-XPS and Tof-SIMS techniques

    CERN Document Server

    Rich, Sami Abou; Dufour, Thierry; Wehbe, Nimer; Houssiau, Laurent; Reniers, François

    2016-01-01

    The in-depth oxygen diffusion into a low density polyethylene film is performed in the post-discharge of an atmospheric plasma torch, supplied in argon as carrier gas and with or without oxygen as reactive gas. The chemical and structural properties of the polymer surface and bulk are studied in terms of plasma parameters (treatment time, power, and reactive gas flow rate). A good correlation between XPS and Fourier transform infrared spectroscopy analyses is demonstrated. The penetration depth of oxygen into the bulk of the polymer is investigated by angle resolved-XPS and time-of-flight SIMS. It is shown that, depending on the plasma conditions, oxygen could penetrate up to 20--40 nm into the low density polyethylene during the atmospheric plasma treatment.

  12. Regulation of N2O and NOx emission patterns in six acid temperate beech forest soils by soil gas diffusivity, N turnover, and atmospheric NOx concentrations

    OpenAIRE

    Eickenscheidt, Nadine; Brumme, Rainer

    2013-01-01

    Low gas diffusivity of the litter layer is held responsible for high seasonal nitrous oxide (N2O) and low nitric oxide (NO) emissions from acid beech forest soils with moder type humus. The objectives were (i) to evaluate whether these beech forest soils generally exhibit high seasonal N2O emissions and (ii) to assess the influence of gas diffusivity and nitrogen (N) mineralisation on N oxide fluxes.We measured N2O and NOx (NO + NO2) fluxes in six German beech stands and determined net N turn...

  13. Consequences of Windscale accident (October 1957) and study of the validity of the Sutton's mathematical model of atmospheric diffusion (1960); Etude des consequences de l'accident de Windscale (Octobre 1957) et de la validite du modele mathematique de diffusion atmospherique de Sutton (1960)

    Energy Technology Data Exchange (ETDEWEB)

    Doury, A. [Commissariat a l' Energie Atomique (S.C.R.G.R.) Saclay (France).Centre d' Etudes Nucleaires; Martin, J.J. [Electricite de France (EDF)(S.L.P.R.), 37 - Chinon (France)

    1960-07-01

    The reactor accident that happens at the number 1 pile of Windscale in 1957 was followed by a discharge of radioactive products into the atmosphere from the 1.X.1957 at 4.30 PM to the 12.X.1957 at 3.10 PM. On october the 11{sup th} it was possible to say that there was no more risk either of external irradiation or inhalation. But in adopting a M.A.C. of 0,1 {mu}curie of iodine 131 per litre of milk, the Authority had to control the milk delivery till november 23{sup rd} on a 500 km{sup 2} area. On the other hand, this exceptional accident permit to verify that Sutton's atmospheric diffusion model could give an easy means to foresee, with a sufficient approximation, the consequences of a dispersion of radioactive products into the atmosphere. (author) [French] L'accident survenu a la pile numero 1 de Windscale en 1957 a entraine l'emission de matieres radioactives dans l'atmosphere du 10 octobre a 16h30 au 12 octobre a 15h10. Le 11 octobre, on pouvait dire qu'il n'y avait plus de risque d'irradiation externe ni de danger par inhalation. Mais en adoptant une C.M.A. de 0,1 {mu}curie d'iode 131 par litre de lait, les autorites ont du reglementer la consommation du lait jusqu'au 23 novembre sur une etendue d'environ 500 km{sup 2}. D'autre part, cet accident exceptionnel a permis de verifier que le modele de diffusion atmospherique de Sutton pouvait fournir un moyen commode de prevoir avec une approximation suffisante les consequences d'une dispersion de produits radioactifs dans l'atmosphere. (auteur)

  14. On the modeling of electrical boundary layer (electrode layer) and derivation of atmospheric electrical profiles, eddy diffusion coeffcient and scales of electrode layer

    Indian Academy of Sciences (India)

    Madhuri N Kulkarni

    2010-02-01

    Electrode layer or electrical boundary layer is one of the charge generators in the global atmospheric electric circuit. In spite of this we find very few model studies and few measurements of it in the literature. Using a new technique it is shown that in this layer, the space charge density varies exponentially in vertical. A new experimental method based on the surface measurements is discussed to determine all the characteristic scales and an average electrical and meteorological state of an electrode layer. The results obtained are in good agreement with the previous studies. So, it is suggested that an exponential space charge density profile will no longer be an assumption in the case of electrode layer studies. The profiles of atmospheric electric field and electrical conductivity are also derived and a new term named as electrode layer constant is introduced.

  15. Atomic diffusion in stars

    CERN Document Server

    Michaud, Georges; Richer, Jacques

    2015-01-01

    This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

  16. Diffusion fundamentals

    OpenAIRE

    2015-01-01

    Diffusion Fundamentals is a peer-reviewed interdisciplinary open-access online journal published as a part of the website Diffusion-Fundamentals.org. It publishes original research articles in the field of diffusion and transport. Main research areas include theory, experiments applications, methods and diffusion-like phenomena. The readers of Diffusion Fundamentals are academic or industrial scientists in all research disciplines. The journal aims at providing a broad forum for their c...

  17. Accurate gamma and MeV-electron track reconstruction with an ultra-low diffusion Xenon/TMA TPC at 10 atmospheres

    CERN Document Server

    Gonzalez-Diaz, Diego; Borges, F I G; Camargo, M; Cárcel, S; Cebrián, S; Cervera, A; Conde, C A N; Dafni, T; Díaz, J; Esteve, R; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Gehman, V M; Goldschmidt, A; Gómez-Cadenas, J J; Gutiérrez, R M; Hauptman, J; Hernando Morata, J A; Herrera, D C; Irastorza, I G; Labarga, L; Laing, A; Liubarsky, I; Lopez-March, N; Lorca, D; Losada, M; Luzón, G; Marí, A; Martín-Albo, J; Martínez-Lema, G; Martínez, A; Miller, T; Monrabal, F; Monserrate, M; Monteiro, C M B; Mora, F J; Moutinho, L M; Muñoz Vidal, J; Nebot-Guinot, M; Nygren, D; Oliveira, C A B; Pérez, J; Pérez Aparicio, J L; Querol, M; Renner, J; Ripoll, L; Rodríguez, J; Santos, F P; dos Santos, J M F; Serra, L; Shuman, D; Simón, A; Sofka, C; Sorel, M; Toledo, J F; Torrent, J; Tsamalaidze, Z; Veloso, J F C A; Villar, J A; Webb, R; White, J T; Yahlali, N; Azevedo, C; Aznar, F; Calvet, D; Castel, J; Ferrer-Ribas, E; García, J A; Giomataris, I; Gómez, H; Iguaz, F J; Lagraba, A; Le Coguie, A; Mols, J P; Şahin, Ö; Rodríguez, A; Ruiz-Choliz, E; Segui, L; Tomás, A; Veenhof, R

    2015-01-01

    We report the performance of a 10 atm Xenon/trimethylamine time projection chamber (TPC) for the detection of X-rays (30 keV) and gamma-rays (0.511-1.275 MeV) in conjunction with the accurate tracking of the associated electrons. When operated at such a high pressure and in 1%-admixtures, trimethylamine (TMA) endows Xenon with an extremely low electron diffusion (1.3 +-0.13 mm-sigma (longitudinal), 0.8 +-0.15 mm-sigma (transverse) along 1 m drift) besides forming a convenient Penning-Fluorescent mixture. The TPC, that houses 1.1 kg of gas in its active volume, operated continuously for 100 live-days in charge amplification mode. The readout was performed through the recently introduced microbulk Micromegas technology and the AFTER chip, providing a 3D voxelization of 8mm x 8mm x 1.2mm for approximately 10 cm/MeV-long electron tracks. This work was developed as part of the R&D program of the NEXT collaboration for future detector upgrades in the search of the 0bbnu decay in 136Xe, specifically those based ...

  18. CONTROLLING DIFFUSION

    NARCIS (Netherlands)

    WESSELINGH, JA

    1993-01-01

    In this paper I first briefly look at diffusion in several controlled release devices. I have found that these exploit complicated diffusional mechanisms. These cannot be understood using the conventional description of diffusion. So, a general theory of multicomponent diffusion which can describe t

  19. Diffusion MRI

    Science.gov (United States)

    Fukuyama, Hidenao

    Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

  20. Atmospheric contamination

    International Nuclear Information System (INIS)

    It is about the levels of contamination in center America, the population's perception on the problem, effects of the atmospheric contamination, effects in the environment, causes of the atmospheric contamination, possibilities to reduce the atmospheric contamination and list of Roeco Swisscontac in atmospheric contamination

  1. Diffuse scattering

    Energy Technology Data Exchange (ETDEWEB)

    Kostorz, G. [Eidgenoessische Technische Hochschule, Angewandte Physik, Zurich (Switzerland)

    1996-12-31

    While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs.

  2. Diffuse scattering

    International Nuclear Information System (INIS)

    While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs

  3. Defusing Diffusion

    Science.gov (United States)

    Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

  4. Description of the Risoe puff diffusion model

    International Nuclear Information System (INIS)

    The Risoe National Laboratory, Roskilde, Denmark, atmospheric puff dispersion model is described. This three-dimensional model simulates the release of Gaussian pullutant puffs and predicts their concentration as they are diffused and advected downwind by a horizontally homogeneous, time-dependent wind. Atmospheric characteristics such as turbulence intensity, potential temperature gradient, buoyant heat flux and maximum mixing depth have been considered. (author)

  5. Atmosphere and Ambient Space

    DEFF Research Database (Denmark)

    Schmidt, Ulrik

    Atmosphere and Ambient Space This paper explores the relation between atmosphere and ambient space. Atmosphere and ambient space share many salient properties. They are both ontologically indeterminate, constantly varying and formally diffuse and they are both experienced as a subtle, non......-signifying property of a given space. But from a certain point of view, the two concepts also designate quite dissimilar experiences of space. To be ’ambient’ means to surround. Accordingly, ambient space is that space, which surrounds something or somebody. (Gibson 1987: 65) Since space is essentially...... of a surrounding character, all space can thus be described as having a fundamentally ambient character. So what precisely is an ambient space, then? As I will argue in my presentation, ambient space is a sensory effect of spatiality when a space is experienced as being particularly surrounding: a ‘space effect...

  6. Phenomenology of atmospheric neutrinos

    Science.gov (United States)

    Fedynitch, Anatoli

    2016-04-01

    The detection of astrophysical neutrinos, certainly a break-through result, introduced new experimental challenges and fundamental questions about acceleration mechanisms of cosmic rays. On one hand IceCube succeeded in finding an unambiguous proof for the existence of a diffuse astrophysical neutrino flux, on the other hand the precise determination of its spectral index and normalization requires a better knowledge about the atmospheric background at hundreds of TeV and PeV energies. Atmospheric neutrinos in this energy range originate mostly from decays of heavy-flavor mesons, which production in the phase space relevant for prompt leptons is uncertain. Current accelerator-based experiments are limited by detector acceptance and not so much by the collision energy. This paper recaps phenomenological aspects of atmospheric leptons and calculation methods, linking recent progress in flux predictions with particle physics at colliders, in particular the Large Hadron Collider.

  7. Phenomenology of atmospheric neutrinos

    Directory of Open Access Journals (Sweden)

    Fedynitch Anatoli

    2016-01-01

    Full Text Available The detection of astrophysical neutrinos, certainly a break-through result, introduced new experimental challenges and fundamental questions about acceleration mechanisms of cosmic rays. On one hand IceCube succeeded in finding an unambiguous proof for the existence of a diffuse astrophysical neutrino flux, on the other hand the precise determination of its spectral index and normalization requires a better knowledge about the atmospheric background at hundreds of TeV and PeV energies. Atmospheric neutrinos in this energy range originate mostly from decays of heavy-flavor mesons, which production in the phase space relevant for prompt leptons is uncertain. Current accelerator-based experiments are limited by detector acceptance and not so much by the collision energy. This paper recaps phenomenological aspects of atmospheric leptons and calculation methods, linking recent progress in flux predictions with particle physics at colliders, in particular the Large Hadron Collider.

  8. Radionuclide dispersion in the atmosphere

    International Nuclear Information System (INIS)

    The instantaneous liberation of radionuclides in the atmosphere is studied in three dimensions, according to the formalism of the diffusion theory. The analytical solution, expose to gravitational and an atmospherical effects, is combined with the discretization of space and time in the calculation of levels of exposure. A typical inventory (for a PWR) was considered in the calculation of immersion doses, and the results permitted a comparative analysis among the different existing models. (Author)

  9. Diffuse solar radiation correlations: applications to Turkey and Australia

    International Nuclear Information System (INIS)

    In order to obtain the diffuse radiation for practical application at various locations, 12 theoretical models for calculating the monthly-average, daily, diffuse radiation as a function of atmospheric parameters were applied to measured data in Turkey and Australia. Results of error analyses and calculated monthly-average, daily, diffuse estimates are given

  10. DIFFUSION PUMP

    Science.gov (United States)

    Levenson, L.

    1963-09-01

    A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

  11. Exoplanet Atmospheres

    CERN Document Server

    Seager, S

    2010-01-01

    At the dawn of the first discovery of exoplanets orbiting sun-like stars in the mid-1990s, few believed that observations of exoplanet atmospheres would ever be possible. After the 2002 Hubble Space Telescope detection of a transiting exoplanet atmosphere, many skeptics discounted it as a one-object, one-method success. Nevertheless, the field is now firmly established, with over two dozen exoplanet atmospheres observed today. Hot Jupiters are the type of exoplanet currently most amenable to study. Highlights include: detection of molecular spectral features; observation of day-night temperature gradients; and constraints on vertical atmospheric structure. Atmospheres of giant planets far from their host stars are also being studied with direct imaging. The ultimate exoplanet goal is to answer the enigmatic and ancient question, "Are we alone?" via detection of atmospheric biosignatures. Two exciting prospects are the immediate focus on transiting super Earths orbiting in the habitable zone of M-dwarfs, and u...

  12. Pluto's atmosphere

    International Nuclear Information System (INIS)

    Airborne CCD photometer observations of Pluto's June 9, 1988 stellar occultation have yielded an occultation lightcurve, probing two regions on the sunrise limb 2000 km apart, which reveals an upper atmosphere overlying an extinction layer with an abrupt upper boundary. The extinction layer may surround the entire planet. Attention is given to a model atmosphere whose occultation lightcurve closely duplicates observations; fits of the model to the immersion and emersion lightcurves exhibit no significant derived atmosphere-structure differences. Assuming a pure methane atmosphere, surface pressures of the order of 3 microbars are consistent with the occultation data. 43 references

  13. Atmospheric electricity

    CERN Document Server

    Chalmers, J Alan

    1957-01-01

    Atmospheric Electricity brings together numerous studies on various aspects of atmospheric electricity. This book is composed of 13 chapters that cover the main problems in the field, including the maintenance of the negative charge on the earth and the origin of the charges in thunderstorms. After a brief overview of the historical developments of atmospheric electricity, this book goes on dealing with the general principles, results, methods, and the MKS system of the field. The succeeding chapters are devoted to some aspects of electricity in the atmosphere, such as the occurrence and d

  14. Diffusion coefficient in photon diffusion theory

    NARCIS (Netherlands)

    Graaff, R; Ten Bosch, JJ

    2000-01-01

    The choice of the diffusion coefficient to be used in photon diffusion theory has been a subject of discussion in recent publications on tissue optics. We compared several diffusion coefficients with the apparent diffusion coefficient from the more fundamental transport theory, D-app. Application to

  15. On physical diffusion and stochastic diffusion

    OpenAIRE

    Narasimhan, T.N.

    2010-01-01

    Although the same mathematical expression is used to describe physical diffusion and stochastic diffusion, there are intrinsic similarities and differences in their nature. A comparative study shows that characteristic terms of physical and stochastic diffusion cannot be placed exactly in one-to-one correspondence. Therefore, judgment needs to be exercised in transferring ideas between physical and stochastic diffusion.

  16. Is Arnold diffusion relevant to global diffusion?

    OpenAIRE

    Honjo, Seiichiro; Kaneko, Kunihiko

    2003-01-01

    Global diffusion of Hamiltonian dynamical systems is investigated by using a coupled standard maps. Arnold web is visualized in the frequency space, using local rotation numbers, while Arnold diffusion and resonance overlaps are distinguished by the residence time distributions at resonance layers. Global diffusion in the phase space is shown to be accelerated by diffusion across overlapped resonances generated by the coupling term, rather than Arnold diffusion along the lower-order resonance...

  17. Diffusion zinc plating of structural steels

    International Nuclear Information System (INIS)

    The report deals with the research on diffusion zinc plating of structural steels when replacing their cyanide cadmium plating. The results of the experiments in the open air, in vacuum, in the inert atmosphere, under various temperatures (300 - 500 deg.C) for different steel brands are presented. It is shown that diffusion zinc plating in argon or nitrogen atmosphere ensures obtaining the qualitative anticorrosion coating with insignificant change of mechanical properties of steels. The process is simple, reliable, ecology pure and cost-effective. (authors)

  18. Articulating Atmospheres

    DEFF Research Database (Denmark)

    Kinch, Sofie

    2011-01-01

    This paper presents an architectural approach to designing computational interfaces by articulating the notion of atmosphere in the field of interaction design. It draws upon the concept of kinesthetic interaction and a philosophical notion on atmosphere emphasizing the importance of bodily...... experience in space, presented as middle ground experience. In the field of HCI, middle ground experiences complete the unarticulated spectrum between designing for foreground of attention or background awareness. When “Articulating Atmospheres through Middle Ground Experiences in Interaction Design......” implications and qualities of the approach are identified through concrete examples of a design case, which also investigates the qualities and implications of addressing atmospheres both as design concern and user experience....

  19. Exoplanetary Atmospheres

    CERN Document Server

    Madhusudhan, Nikku; Fortney, Jonathan; Barman, Travis

    2014-01-01

    The study of exoplanetary atmospheres is one of the most exciting and dynamic frontiers in astronomy. Over the past two decades ongoing surveys have revealed an astonishing diversity in the planetary masses, radii, temperatures, orbital parameters, and host stellar properties of exoplanetary systems. We are now moving into an era where we can begin to address fundamental questions concerning the diversity of exoplanetary compositions, atmospheric and interior processes, and formation histories, just as have been pursued for solar system planets over the past century. Exoplanetary atmospheres provide a direct means to address these questions via their observable spectral signatures. In the last decade, and particularly in the last five years, tremendous progress has been made in detecting atmospheric signatures of exoplanets through photometric and spectroscopic methods using a variety of space-borne and/or ground-based observational facilities. These observations are beginning to provide important constraints...

  20. Staging atmospheres

    DEFF Research Database (Denmark)

    Bille, Mikkel; Bjerregaard, Peter; Sørensen, Tim Flohr

    2015-01-01

    . Nevertheless, people’s experience of the environment is sought manipulated in a variety of contexts, often without offering a less ‘true’ experience of a situation than if it had not been manipulated by people. In fact, orchestrations of space are often central to sociality, politics and aesthetics. This...... introduction seeks to outline how a number of scholars have addressed the relationship between staged atmospheres and experience, and thus highlight both the philosophical, social and political aspects of atmospheres...

  1. Radiative equilibrium and escape of Pluto's atmosphere

    Science.gov (United States)

    Erwin, Justin; Koskinen, Tommi T.; Yelle, Roger V.

    2015-11-01

    Observations of Pluto’s extend atmosphere by the New Horizons spacecraft motivate an update to our modeling effort on Pluto’s atmosphere. New Horizons observations have already improved our constraints on planet radius and surface pressure, which are key to modeling the atmospheric structure. We model the radiative conductive equilibrium in the lower atmosphere combined with the UV driven escape model of the upper atmosphere. The non-LTE radiative transfer model in the lower atmosphere include heating and cooling by CH4, CO, and HCN. The escape model of the upper atmosphere is updated to include diffusion and escape of each molecular component. These results will be used to aid in the analysis and better understanding of the full atmospheric structure.

  2. Quantifying water diffusion in secondary organic material

    Science.gov (United States)

    Price, Hannah; Murray, Benjamin; Mattsson, Johan; O'Sullivan, Daniel; Wilson, Theodore; Zhang, Yue; Martin, Scot

    2014-05-01

    Recent research suggests that some secondary organic aerosol (SOA) is highly viscous under certain atmospheric conditions. This may have important consequences for equilibration timescales, SOA growth, heterogeneous chemistry and ice nucleation. In order to quantify these effects, knowledge of the diffusion coefficients of relevant gas species within aerosol particles is vital. In this work, a Raman isotope tracer method is used to quantify water diffusion coefficients over a range of atmospherically relevant humidity and temperature conditions. D2O is observed as it diffuses from the gas phase into a disk of aqueous solution, without the disk changing in size or viscosity. An analytical solution of Fick's second law is then used with a fitting procedure to determine water diffusion coefficients in reference materials for method validation. The technique is then extended to compounds of atmospheric relevance and α-pinene secondary organic material. We produce water diffusion coefficients from 20 to 80 % RH at 23.5° C for sucrose, levoglucosan, M5AS and MgSO4. For levoglucosan we show that under conditions where a particle bounces, water diffusion in aqueous solutions can be fast (a fraction of a second for a 100 nm radius). For sucrose solutions, we also show that the Stokes-Einstein relation breaks down at high viscosity and cannot be used to predict water diffusion timescales with accuracy. In addition, we also quantify water diffusion coefficients in α-pinene SOM from 20-80% RH and over temperatures from 6 to -30° C. Our results suggest that, at 6° C, water diffusion in α-pinene SOA is not kinetically limited on the second timescale, even at 20% RH. As temperatures decrease, however, diffusion slows and may become an increasingly limiting factor for atmospheric processes. A parameterization for the diffusion coefficient of water in α-pinene secondary organic material, as a function of relative humidity and temperature, is presented. The implications for

  3. Parallel flow diffusion battery

    Science.gov (United States)

    Yeh, Hsu-Chi; Cheng, Yung-Sung

    1984-08-07

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  4. NIST Diffusion Data Center

    Science.gov (United States)

    NIST Diffusion Data Center (Web, free access)   The NIST Diffusion Data Center is a collection of over 14,100 international papers, theses, and government reports on diffusion published before 1980.

  5. Atmospheric thermodynamics

    CERN Document Server

    Iribarne, J V

    1973-01-01

    The thermodynamics of the atmosphere is the subject of several chapters in most textbooks on dynamic meteorology, but there is no work in English to give the subject a specific and more extensive treatment. In writing the present textbook, we have tried to fill this rather remarkable gap in the literature related to atmospheric sciences. Our aim has been to provide students of meteorology with a book that can playa role similar to the textbooks on chemical thermodynamics for the chemists. This implies a previous knowledge of general thermodynamics, such as students acquire in general physics courses; therefore, although the basic principles are reviewed (in the first four chapters), they are only briefly discussed, and emphasis is laid on those topics that will be useful in later chapters, through their application to atmospheric problems. No attempt has been made to introduce the thermodynamics of irreversible processes; on the other hand, consideration of heterogeneous and open homogeneous systems permits a...

  6. Atmospheric Smell

    DEFF Research Database (Denmark)

    Stenslund, Anette

    awareness. Subsequently, visitor interviews revealed how a museum-staged hospital atmosphere of an art installation was directly addressed owing to its smell. Curiously, this observation speaks against prevailing literature portraying smell as the ‘mute sense’, and what is more, the museum display did not...... alter smell curatorially. Rather, smell was gestured through non-olfactory effects and it was put in words metonymically, gesturing a reversibly synaesthetic atmosphere of a hospital. Visitor conversations revealed how smell could be poignantly picked up in situ, yet not until frequenting the museum...

  7. Alarming atmospheres

    DEFF Research Database (Denmark)

    Højlund, Marie; Kinch, Sofie

    2014-01-01

    . As a response to this situation, our design artefact, the interactive furniture Kidkit, invites children to become accustomed to the alarming sounds sampled from the ward while they are waiting in the waiting room. Our design acknowledges how atmospheres emerge as temporal negotiations between the...

  8. Diffusion-driven evaporation of sessile drops

    International Nuclear Information System (INIS)

    The evaporation of wetting drops deposited on a substrate at thermal equilibrium under normal atmosphere is discussed. The evaporation rate appears to be controlled by the stationary diffusion of vapour molecules in the gas phase. Experiments with alkanes and water drops are fairly well accounted for by an isothermal model, taking into account the specific properties of thin films

  9. Vulnerability to diffuse pollution of European soils and groundwater

    NARCIS (Netherlands)

    Meinardi CR; Beusen AHW; Bollen MJS; Klepper O; LBG; CWM

    1994-01-01

    From the Atlantic Ocean to the Ural Mountains, European soils and groundwater are threatened by diffuse pollution derived from various chemicals used in modern agriculture and by increased atmospheric deposition of pollutants. The investigated vulnerability of soils (including groundwater) to diffus

  10. A Method for Generating Diffuse Discharge via Repetitive Nanosecond Pulses and Wire Electrodes in Room-temperature Atmospheric Air%利用重复频率纳秒脉冲和线电极产生常温常压下的大气压弥散放电

    Institute of Scientific and Technical Information of China (English)

    李黎; 刘云龙; 俞斌; 葛亚峰; 林福昌

    2014-01-01

    The non-equilibrium plasmas produced by diffuse discharges have a great potential of application in many high technology fields. In room-temperature atmospheric air, the formation mechanism of non-equilibrium plasma is discussed and analysed. It is concluded that generating diffuse discharge in open air should meet the three conditions: low-voltage excitation, plentiful electron avalanches and temperature inhibition of spatial charge particles. A method of generating diffuse discharge is proposed and implemented. Based on runaway electrons breakdown theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform electrical field are structured. The experiments are performed in linear-type and ring-type electrode pairs. The results prove that the proposed method can generate typical diffuse discharges in cm. gaps via nanosecond pluses with less than 100kV peak voltage, hundreds of Hz repetitive frequency.%大气压弥散放电产生非热平衡等离子体在诸多高新技术领域具有较大应用潜力。分析了在常温常压的大气压条件下,形成和维持非热平衡等离子体的机制,提出了实现弥散放电应设法满足低放电电压、多电子崩发展和带电粒子温度抑制的条件。由此设计了在开放的大气压空气环境中实现大面积弥散放电的装置。根据逃逸电子击穿理论,选择重复频率、较低占空比的纳秒脉冲电激励方式作为弥散放电的低电压驱动源。利用线型电极的小曲率半径,构成极不均匀电场间隙。弥散放电分别在直线型电极和圆环型电极中进行。实验结果表明,所研制的放电装置能够以百kV以内峰值纳秒脉冲电压、数百Hz的频率激励若干厘米等级间距的大气压弥散放电。

  11. Atmospheric Neutrinos

    CERN Document Server

    Gaisser, Thomas K

    2016-01-01

    In view of the observation by IceCube of high-energy astrophysical neutrinos, it is important to quantify the uncertainty in the background of atmospheric neutrinos. There are two sources of uncertainty, the imperfect knowledge of the spectrum and composition of the primary cosmic rays that produce the neutrinos and the limited understanding of hadron production, including charm, at high energy. This paper is an overview of both aspects.

  12. Microfabricated diffusion source

    Science.gov (United States)

    Oborny, Michael C.; Frye-Mason, Gregory C.; Manginell, Ronald P.

    2008-07-15

    A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.

  13. Diffusion on spatial network

    Science.gov (United States)

    Hui, Zi; Tang, Xiaoyue; Li, Wei; Greneche, Jean-Marc; Wang, Qiuping A.

    2015-04-01

    In this work, we study the problem of diffusing a product (idea, opinion, disease etc.) among agents on spatial network. The network is constructed by random addition of nodes on the planar. The probability for a previous node to be connected to the new one is inversely proportional to their spatial distance to the power of α. The diffusion rate between two connected nodes is inversely proportional to their spatial distance to the power of β as well. Inspired from the Fick's first law, we introduce the diffusion coefficient to measure the diffusion ability of the spatial network. Using both theoretical analysis and Monte Carlo simulation, we get the fact that the diffusion coefficient always decreases with the increasing of parameter α and β, and the diffusion sub-coefficient follows the power-law of the spatial distance with exponent equals to -α-β+2. Since both short-range diffusion and long-range diffusion exist, we use anomalous diffusion method in diffusion process. We get the fact that the slope index δ in anomalous diffusion is always smaller that 1. The diffusion process in our model is sub-diffusion.

  14. Microgravity Turbulent Gas-Jet Diffusion Flames

    Science.gov (United States)

    1996-01-01

    A gas-jet diffusion flame is similar to the flame on a Bunsen burner, where a gaseous fuel (e.g., propane) flows from a nozzle into an oxygen-containing atmosphere (e.g., air). The difference is that a Bunsen burner allows for (partial) premixing of the fuel and the air, whereas a diffusion flame is not premixed and gets its oxygen (principally) by diffusion from the atmosphere around the flame. Simple gas-jet diffusion flames are often used for combustion studies because they embody the mechanisms operating in accidental fires and in practical combustion systems. However, most practical combustion is turbulent (i.e., with random flow vortices), which enhances the fuel/air mixing. These turbulent flames are not well understood because their random and transient nature complicates analysis. Normal gravity studies of turbulence in gas-jet diffusion flames can be impeded by buoyancy-induced instabilities. These gravitycaused instabilities, which are evident in the flickering of a candle flame in normal gravity, interfere with the study of turbulent gas-jet diffusion flames. By conducting experiments in microgravity, where buoyant instabilities are avoided, we at the NASA Lewis Research Center hope to improve our understanding of turbulent combustion. Ultimately, this could lead to improvements in combustor design, yielding higher efficiency and lower pollutant emissions. Gas-jet diffusion flames are often researched as model flames, because they embody mechanisms operating in both accidental fires and practical combustion systems (see the first figure). In normal gravity laboratory research, buoyant air flows, which are often negligible in practical situations, dominate the heat and mass transfer processes. Microgravity research studies, however, are not constrained by buoyant air flows, and new, unique information on the behavior of gas-jet diffusion flames has been obtained.

  15. Computational investigations of atmospheric pressure discharges

    OpenAIRE

    Iqbal, Muhammad Munawar

    2010-01-01

    This research work presents the numerical simulations of multispecies multi-dimensional fluid model of atmospheric pressure discharge. The semi-implicit sequential iterative scheme is used to solve the coupled system of plasma fluid model equations with a proper set of boundary conditions. A one- dimensional self consistent drift-diffusion fluid model is developed to investigate the characteristics of atmospheric pressure discharge in pure helium and He-N2 gases. The uniform atmos...

  16. Lung diffusion testing

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003854.htm Lung diffusion testing To use the sharing features on this page, please enable JavaScript. Lung diffusion testing measures how well the lungs exchange ...

  17. Atmospheric sciences annual progress report, 1974

    International Nuclear Information System (INIS)

    Activities in atmospheric sciences in the Department of Applied Science at Brookhaven National Laboratory carried out during 1974 are described. Included are contributions from the Meteorology, Atmospheric Diagnostics, Atmospheric Chemistry Research, and Atmospheric Instrumentation Groups. Programs in Meteorology reported on include diffusion from an off-shore source, plume dynamics studies, modeling of coastal effects on wind and temperature fields and pollutant distributions, effects of indoor shelter on inhalation of airborne radionuclides, chemical-dynamical interactions, techniques for determining acid-rain impact upon the ecology of the eastern U.S., and climatology. Work under Atmospheric Chemistry Research was concentrated on atmospheric aerosol studies, including formation by free radical and neutral association reactions, identification of reactive systems leading to aerosol formation, growth of sodium aerosols under atmospheric conditions and clustering reactions. Atmospheric Diagnostics presents work on field sampling and analytical technology for atmospheric pollutants, airborne sampling systems, atmospheric sulfate particulates methodology, and on a pyroturbidometric method for particulate sulfate discrimination and determination. Methodology for the use of sulfur hexafluoride in field tracer studies is discussed under Atmospheric Instrumentation. A list of publications is included

  18. Diffusion of Wilson Loops

    OpenAIRE

    Brzoska, A. M.; Lenz, F.; Negele, J. W.; Thies, M.

    2004-01-01

    A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops i...

  19. Nuclear Isospin Diffusivity

    OpenAIRE

    Shi, L; Danielewicz, P

    2003-01-01

    The isospin diffusion and other irreversible phenomena are discussed for a two-component nuclear Fermi system. The set of Boltzmann transport equations, such as employed for reactions, are linearized, for weak deviations of a system from uniformity, in order to arrive at nonreversible fluxes linear in the nonuniformities. Besides the diffusion driven by a concentration gradient, also the diffusion driven by temperature and pressure gradients is considered. Diffusivity, conductivity, heat cond...

  20. Hydrogen diffusion in tantalum

    International Nuclear Information System (INIS)

    Using resistivity technique, the diffusion of hydrogen in tantalum has been studied in the temperature range of 298-373 K. The diffusivity values obtained obey the following Arrhenius equation: D=4.38x10-4 exp(-0.142/kT) cm2/sec. The diffusion parameters agree with those obtained by others. The data has been interpreted in terms of modified over barrier diffusion mechanism. (author). 8 refs., 1 table, 4 figures

  1. Diffusion of uranium hexafluoride

    Science.gov (United States)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of uranium hexafluoride

  2. Test emission of uranium hexafluoride in atmosphere. Results interpretation

    International Nuclear Information System (INIS)

    To permit the modelization of gaseous uranium hexafluoride behaviour in atmosphere, a validation test has been executed the 10 April 1987. The experimental conditions, the main results and a comparison with a diffusion model are given in this report

  3. Diffusion in heterogeneous media

    Science.gov (United States)

    Zhang, Y.; Liu, L.

    2012-12-01

    Diffusion in heterogeneous media has been investigated for over forty years. However, the fundamental equations for bulk (effective) diffusivity in multi-phase systems were incorrect because of the use of an inappropriate similarity between diffusion and other physical properties such as thermal conductivity. The mistake has permeated through the literature and textbooks. Specifically, the role of concentration partitioning between different phases in diffusion was not considered in such similarity relations. In this work, we present the correct method to derive such relations in heterogeneous media. Barrer [1] used the similarity between diffusivity and thermal conductivity to derive the relation between the bulk (effective) diffusivity and the individual-phase diffusivities. The approach was followed by many others [2-4]. Unfortunately the similarity approach by Barrer [1] is incorrect because there is also dissimilarity. The key difference is that, even though heat conduction and mass diffusion are characterized by a similar flux equation, in heat conduction, T is continuous across phase boundaries, whereas in diffusion, C is usually not continuous across phase boundaries. The concentration in each phase plays a major role in controlling the contribution by the phase to the bulk diffusive flux and hence the bulk diffusivity. For example, if the concentration of a component in a phase is very low, even if the diffusivity in the phase is high, the contribution of diffusion in that phase to the bulk diffusion flux can still be negligible. Hence, previous models for diffusivity in composite materials or multi-mineral rocks, no matter how sophisticated, are fundamentally wrong because the foundation is a mistake. Correcting the mistake is straightforward. The mass flux can be written in terms of chemical potential and mobility [5,6]. Because chemical potential is continuous across phase boundaries, the relation between bulk mobility and individual-phase mobilities is

  4. On the influence of neutral turbulence on ambipolar diffusivities deduced from meteor trail expansion

    Directory of Open Access Journals (Sweden)

    C. M. Hall

    Full Text Available By measuring fading times of radar echoes from underdense meteor trails, it is possible to deduce the ambipolar diffusivities of the ions responsible for these radar echoes. It could be anticipated that these diffusivities increase monotonically with height akin to neutral viscosity. In practice, this is not always the case. Here, we investigate the capability of neutral turbulence to affect the meteor trail diffusion rate.

    Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence

  5. Diffusion in disordered media

    Science.gov (United States)

    Havlin, Shlomo; Ben-Avraham, Daniel

    2002-01-01

    Diffusion in disordered systems does not follow the classical laws which describe transport in ordered crystalline media, and this leads to many anomalous physical properties. Since the application of percolation theory, the main advances in the understanding of these processes have come from fractal theory. Scaling theories and numerical simulations are important tools to describe diffusion processes (random walks: the 'ant in the labyrinth') on percolation systems and fractals. Different types of disordered systems exhibiting anomalous diffusion are presented (the incipient infinite percolation cluster, diffusion-limited aggregation clusters, lattice animals, and random combs), and scaling theories as well as numerical simulations of greater sophistication are described. Also, diffusion in the presence of singular distributions of transition rates is discussed and related to anomalous diffusion on disordered structures.

  6. Multinomial diffusion equation

    Science.gov (United States)

    Balter, Ariel; Tartakovsky, Alexandre M.

    2011-06-01

    We describe a new, microscopic model for diffusion that captures diffusion induced fluctuations at scales where the concept of concentration gives way to discrete particles. We show that in the limit as the number of particles N→∞, our model is equivalent to the classical stochastic diffusion equation (SDE). We test our new model and the SDE against Langevin dynamics in numerical simulations, and show that our model successfully reproduces the correct ensemble statistics, while the classical model fails.

  7. Primary Diffuse Leptomeningeal Gliosarcomatosis

    OpenAIRE

    Moon, Ju Hyung; Kim, Se Hoon; Kim, Eui Hyun; Kang, Seok-Gu; Chang, Jong Hee

    2015-01-01

    Primary diffuse leptomeningeal gliomatosis (PDLG) is a rare condition with a fatal outcome, characterized by diffuse infiltration of the leptomeninges by neoplastic glial cells without evidence of primary tumor in the brain or spinal cord parenchyma. In particular, PDLG histologically diagnosed as gliosarcoma is extremely rare, with only 2 cases reported to date. We report a case of primary diffuse leptomeningeal gliosarcomatosis. A 68-year-old man presented with fever, chilling, headache, an...

  8. Diffusion of Asymmetric Swimmers

    OpenAIRE

    Rutenberg, Andrew D.; Richardson, Andrew J.; Montgomery, Claire J.

    2003-01-01

    Particles moving along curved trajectories will diffuse if the curvature fluctuates sufficiently in either magnitude or orientation. We consider particles moving at a constant speed with either a fixed or with a Gaussian distributed curvature magnitude. At small speeds the diffusivity is independent of the speed. At larger particle speeds, the diffusivity depends on the speed through a novel exponent. We apply our results to intracellular transport of vesicles. In sharp contrast to thermal di...

  9. Diffusers for holographic stereography

    OpenAIRE

    Helseth, L.E.; Singstad, I.

    2001-01-01

    Holographic diffusers have long been recognized as versatile components with a broad number of applications. In this work we discuss holographic diffusers for projection of laser light from a Liquid Crystal Display(LCD) onto a holographic recording medium. In holographic stereography, projection of the information from a LCD onto a holographic recording medium has traditionally been done by a lens or a ground glass. It is suggested that the holographic diffusers can replace these elements and...

  10. Review of Diffusion Research

    OpenAIRE

    Sriwannawit, Pranpreya; Sandström, Ulf

    2013-01-01

    Despite the fact that diffusion research has existed for more than one century, there is no quantitative review study that covers this subject in a broad and general context. This article reviews diffusion research by providing an extensive bibliometric and clustering analysis. We identify research trails and explain the characteristics of diffusion research using new methods. We contribute a methodology for the use of advanced mapping and clustering techniques in order to describe the resear...

  11. Diffusion of Classical Solitons

    OpenAIRE

    Dziarmaga, J.; Zakrzewski, W.

    1998-01-01

    We study the diffusion and deformation of classical solitons coupled to thermal noise. The diffusion coefficient for kinks in the $\\phi^4$ theory is predicted up to the second order in $kT$. The prediction is verified by numerical simulations. Multiskyrmions in the vector O(3) sigma model are studied within the same formalism. Thermal noise results in a diffusion on the multisoliton collective coordinate space (moduli space). There are entropic forces which tend, for example, to bind pairs of...

  12. Relativistic diffusive transport

    OpenAIRE

    Haba, Z.

    2009-01-01

    We discuss transport equations resulting from relativistic diffusions in the proper time. We show that a solution of the transport equation can be obtained from the solution of the diffusion equation by means of an integration over the proper time. We study the stochastic processes solving the relativistic diffusion equation and the relativistic transport equation. We show that the relativistic transport equation for massive particles in the light cone coordinates and for massless particles i...

  13. Atmospheric neutrinos and the νe/νμ ratio

    International Nuclear Information System (INIS)

    This work calculates analytically the atmospheric neutrino flux by solving the one-dimensional equations which describe the hadrons and leptons diffusion in the atmosphere, and compares the results with those obtained by using simulation calculations performed by Gaisser and coworkers, and analytically obtained by Bugaev and Naumov

  14. Experimental study of vortex diffusers

    Energy Technology Data Exchange (ETDEWEB)

    Shakerin, S.; Miller, P.L. [National Renewable Energy Lab., Golden, CO (United States)

    1995-11-01

    This report documents experimental research performed on vortex diffusers used in ventilation and air-conditioning systems. The main objectives of the research were (1) to study the flow characteristics of isothermal jets issuing from vortex diffusers, (2) to compare the vortex diffuser`s performance with that of a conventional diffuser, and (3) to prepare a report that disseminates the results to the designers of ventilation and air-conditioning systems. The researchers considered three diffusers: a conventional round ceiling diffuser and two different styles of vortex diffusers. Overall, the vortex diffusers create slightly more induction of ambient air in comparison to the conventional diffuser.

  15. Origins of the Earth's Diffuse Auroral Precipitation

    Science.gov (United States)

    Ni, Binbin; Thorne, Richard M.; Zhang, Xiaojia; Bortnik, Jacob; Pu, Zuyin; Xie, Lun; Hu, Ze-jun; Han, Desheng; Shi, Run; Zhou, Chen; Gu, Xudong

    2016-02-01

    The Earth's diffuse auroral precipitation provides the major source of energy input into the nightside upper atmosphere and acts as an essential linkage of the magnetosphere-ionosphere coupling. Resonant wave-particle interactions play a dominant role in the scattering of injected plasma sheet electrons, leading to the diffuse auroral precipitation. We review the recent advances in understanding the origin of the diffuse aurora and in quantifying the exact roles of various magnetospheric waves in producing the global distribution of diffuse auroral precipitation and its variability with the geomagnetic activity. Combined scattering by upper-and lower-band chorus accounts for the most intense inner magnetospheric electron diffuse auroral precipitation on the nightside. Dayside chorus can be responsible for the weaker dayside electron diffuse auroral precipitation. Pulsating auroras, the dynamic auroral structures embedded in the diffuse aurora, can be mainly caused by modulation of the excitation of lower band chorus due to macroscopic density variations in the magnetosphere. Electrostatic electron cyclotron harmonic waves are an important or even dominant cause for the nightside electron diffuse auroral precipitation beyond {˜}8Re and can also contribute to the occurrence of the pulsating aurora at high L-shells. Scattering by electromagnetic ion cyclotron waves could quite possibly be the leading candidate responsible for the ion precipitation (especially the reversed-type events of the energy-latitude dispersion) in the regions of the central plasma sheet and ring current. We conclude the review with a summary of current understanding, outstanding questions, and a number of suggestions for future research.

  16. Origins of the Earth's Diffuse Auroral Precipitation

    Science.gov (United States)

    Ni, Binbin; Thorne, Richard M.; Zhang, Xiaojia; Bortnik, Jacob; Pu, Zuyin; Xie, Lun; Hu, Ze-jun; Han, Desheng; Shi, Run; Zhou, Chen; Gu, Xudong

    2016-04-01

    The Earth's diffuse auroral precipitation provides the major source of energy input into the nightside upper atmosphere and acts as an essential linkage of the magnetosphere-ionosphere coupling. Resonant wave-particle interactions play a dominant role in the scattering of injected plasma sheet electrons, leading to the diffuse auroral precipitation. We review the recent advances in understanding the origin of the diffuse aurora and in quantifying the exact roles of various magnetospheric waves in producing the global distribution of diffuse auroral precipitation and its variability with the geomagnetic activity. Combined scattering by upper-and lower-band chorus accounts for the most intense inner magnetospheric electron diffuse auroral precipitation on the nightside. Dayside chorus can be responsible for the weaker dayside electron diffuse auroral precipitation. Pulsating auroras, the dynamic auroral structures embedded in the diffuse aurora, can be mainly caused by modulation of the excitation of lower band chorus due to macroscopic density variations in the magnetosphere. Electrostatic electron cyclotron harmonic waves are an important or even dominant cause for the nightside electron diffuse auroral precipitation beyond {˜}8Re and can also contribute to the occurrence of the pulsating aurora at high L-shells. Scattering by electromagnetic ion cyclotron waves could quite possibly be the leading candidate responsible for the ion precipitation (especially the reversed-type events of the energy-latitude dispersion) in the regions of the central plasma sheet and ring current. We conclude the review with a summary of current understanding, outstanding questions, and a number of suggestions for future research.

  17. Turbulence and diffusion fossil turbulence

    CERN Document Server

    Gibson, C H

    2000-01-01

    Fossil turbulence processes are central to turbulence, turbulent mixing, and turbulent diffusion in the ocean and atmosphere, in astrophysics and cosmology, and in most other natural flows. George Gamov suggested in 1954 that galaxies might be fossils of primordial turbulence produced by the Big Bang. John Woods showed that breaking internal waves on horizontal dye sheets in the interior of the stratified ocean form highly persistent remnants of these turbulent events, which he called fossil turbulence. The dark mixing paradox of the ocean refers to undetected mixing that must exist somewhere to explain why oceanic scalar fields like temperature and salinity are so well mixed, just as the dark matter paradox of galaxies refers to undetected matter that must exist to explain why rotating galaxies don't fly apart by centrifugal forces. Both paradoxes result from sampling techniques that fail to account for the extreme intermittency of random variables involved in self-similar, nonlinear, cascades over a wide ra...

  18. Atmospheric diffusion and dose estimation for habitability assessments

    International Nuclear Information System (INIS)

    The assessment of Emergency Centre has a bearing on the implementing of Emergency plan, and is of great significance. So the calculation procedure and models concerning the normalized concentration (X/Q) in the building wakes are becoming very important. A model which is different from the currently used is used to assess the habitability of Emergency Centre of a certain power plant in China. (4 figs., 3 tabs.)

  19. Acoustics in the Martian Atmosphere

    Science.gov (United States)

    Williams, J.-P.

    2000-10-01

    With the advent of the first attempt to deliver an acoustic microphone to the Martian surface aboard the failed Mars Polar Lander, there has been growing interests in the development of acoustic sensors to compliment scientific payloads on future spacecraft. Terrestrial scientist have been very successful in using infrasound (sound at frequencies below human detection, detect and monitor atmospheric phenomena related to weather, tornadoes, mountain waves, microbaroms, ionospheric and auroral disturbances, and meteror/fireballs, as well as anthropogenic sources such as aircraft and nuclear explosions. Sounds on Mars at the audible frequencies (20 Hz to 20 kHz) will be severely attenuated due to viscous relaxation and thermal diffusion (collectively referred to as classical attenuation) which will be much more severe in the colder, less dense Martian atmosphere. Molecular relaxation of carbon dioxide will also contribute to the sound absorption in the lower audible frequencies. Since classical attenuation increases as a function of the frequency squared, at low infrasonic frequencies ( < 10 Hz), classical attenuation becomes less significant and sound absorption in the Martian atmosphere becomes more similar to that of the terrestrial atmosphere for the same frequencies. At these longer wavelengths, geometric spreading will dominate as the source of attenuation as the acoustic energy is spread out over an ever increasing spherical wave front. This implies that infrasound (10 to 0.01 Hz) will be a useful frequency range for future acoustic sensors developed for scientific payloads delivered to the Martian surface.

  20. The Diffusion of Innovation

    Science.gov (United States)

    Earabino, Gerard J.; Heyl, G. Christopher; Percorini, Thomas J.

    1987-01-01

    New ideas encounter obstacles on way to becoming products. Report examines process by which new ideas become products, processes, or accepted standards. Sequence of events called "the diffusion of innovation." Focuses on development of material processing in low gravity as case study in diffusion of innovation.

  1. Galactic Diffuse Emissions

    Energy Technology Data Exchange (ETDEWEB)

    Digel, Seth W.; /SLAC

    2007-10-25

    Interactions of cosmic rays with interstellar nucleons and photons make the Milky Way a bright, diffuse source of high-energy {gamma}-rays. Observationally, the results from EGRET, COMPTEL, and OSSE have now been extended to higher energies by ground-based experiments, with detections of diffuse emission in the Galactic center reported by H.E.S.S. in the range above 100 GeV and of diffuse emission in Cygnus by MILAGRO in the TeV range. In the range above 100 keV, INTEGRAL SPI has found that diffuse emission remains after point sources are accounted for. I will summarize current knowledge of diffuse {gamma}-ray emission from the Milky Way and review some open issues related to the diffuse emission -- some old, like the distribution of cosmic-ray sources and the origin of the 'excess' of GeV emission observed by EGRET, and some recently recognized, like the amount and distribution of molecular hydrogen not traced by CO emission -- and anticipate some of the advances that will be possible with the Large Area Telescope on GLAST. We plan to develop an accurate physical model for the diffuse emission, which will be useful for detecting and accurately characterizing emission from Galactic point sources as well as any Galactic diffuse emission from exotic processes, and for studying the unresolved extragalactic emission.

  2. Diffusion Based Photon Mapping

    DEFF Research Database (Denmark)

    Schjøth, Lars; Fogh Olsen, Ole; Sporring, Jon

    2007-01-01

    . To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination...... features, while eliminating noise. We call our method diffusion based photon mapping....

  3. Diffusion Based Photon Mapping

    DEFF Research Database (Denmark)

    Schjøth, Lars; Olsen, Ole Fogh; Sporring, Jon

    2006-01-01

    . To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination...... features, while eliminating noise. We call our method diffusion based photon mapping....

  4. Discrimination of thermal diffusivity

    NARCIS (Netherlands)

    Bergmann Tiest, W.M.; Kappers, A.M.L.

    2009-01-01

    Materials such as wood or metal which are at equal temperatures are perceived to be of different ‘coldness’ due to differences in thermal properties, such as the thermal diffusivity. The thermal diffusivity of a material is a parameter that controls the rate with which heat is extracted from the han

  5. Investigating Diffusion with Technology

    Science.gov (United States)

    Miller, Jon S.; Windelborn, Augden F.

    2013-01-01

    The activities described here allow students to explore the concept of diffusion with the use of common equipment such as computers, webcams and analysis software. The procedure includes taking a series of digital pictures of a container of water with a webcam as a dye slowly diffuses. At known time points, measurements of the pixel densities…

  6. Anatomy of Particle Diffusion

    Science.gov (United States)

    Bringuier, E.

    2009-01-01

    The paper analyses particle diffusion from a thermodynamic standpoint. The main goal of the paper is to highlight the conceptual connection between particle diffusion, which belongs to non-equilibrium statistical physics, and mechanics, which deals with particle motion, at the level of third-year university courses. We start out from the fact…

  7. Diffuse solar radiation and associated meteorological parameters in India

    Directory of Open Access Journals (Sweden)

    A. B. Bhattacharya

    Full Text Available Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another.

  8. Nuclear Isospin Diffusivity

    CERN Document Server

    Shi, L

    2003-01-01

    The isospin diffusion and other irreversible phenomena are discussed for a two-component nuclear Fermi system. The set of Boltzmann transport equations, such as employed for reactions, are linearized, for weak deviations of a system from uniformity, in order to arrive at nonreversible fluxes linear in the nonuniformities. Besides the diffusion driven by a concentration gradient, also the diffusion driven by temperature and pressure gradients is considered. Diffusivity, conductivity, heat conduction and shear viscosity coefficients are formally expressed in terms of the responses of distribution functions to the nonuniformities. The linearized Boltzmann-equation set is solved, under the approximation of constant form-factors in the distribution-function responses, to find concrete expressions for the transport coefficients in terms of weighted collision integrals. The coefficients are calculated numerically for nuclear matter, using experimental nucleon-nucleon cross sections. The isospin diffusivity is invers...

  9. An Analytical Air Pollution Model with Time Dependent Eddy Diffusivity

    OpenAIRE

    Tiziano Tirabassi; Marco Túllio Vilhena; Daniela Buske; Gervásio Annes Degrazia

    2013-01-01

    Air pollution transport and dispersion in the atmospheric boundary layer are modeled by the advection-diffusion equation, that is, essentially, a statement of conservation of the suspended material in an incompressible flow. Many models simulating air pollution dispersion are based upon the solution (numerical or analytical) of the advection-diffusion equation assuming turbulence parameterization for realistic physical scenarios. We present the general time dependent three-dimensional soluti...

  10. Thermal diffusivity of seasonal snow determined from temperature profiles

    OpenAIRE

    Oldroyd, Holly Jayne; Higgins, Chad; Huwald, Hendrik; Selker, John; Parlange, Marc

    2013-01-01

    Thermal diffusivity of snow is an important thermodynamic property associated with key hydrological phenomena such as snow melt and heat and water vapor exchange with the atmosphere. Direct determination of snow thermal diffusivity requires coupled point measurements of thermal conductivity and density, which continually change due to snow metamorphism. Traditional methods for determining these two quantities are generally limited by temporal resolution. In this study we present a method to d...

  11. Quantitative Microplate-Based Respirometry with Correction for Oxygen Diffusion

    OpenAIRE

    Gerencser, Akos A.; Neilson, Andy; Choi, Sung W.; Edman, Ursula; Yadava, Nagendra; Oh, Richard J.; Ferrick, David A.; Nicholls, David G.; Brand, Martin D.

    2009-01-01

    Respirometry using modified cell culture microplates offers an increase in throughput and a decrease in biological material required for each assay. Plate based respirometers are susceptible to a range of diffusion phenomena; as O2 is consumed by the specimen, atmospheric O2 leaks into the measurement volume. Oxygen also dissolves in and diffuses passively through the polystyrene commonly used as a microplate material. Consequently the walls of such respirometer chambers are not just permeabl...

  12. Study of radon diffusion through clay bricks

    International Nuclear Information System (INIS)

    Radon is a naturally occurring radioactive gas that is generated in the earth's crust and is free to migrate through soil and be released to the indoor and outdoor atmosphere. Much attention has been given to the radiological health hazard posed by increased radon concentrations in the living and working environment. In order to study radon profiles for geophysical purposes and to predict its entry indoors, it is necessary to study its transport through building materials. The most common way of modeling radon flow through building materials is the advective transport by pressure-driven air flow from the source. The transport phenomenon of radon through diffusion is a significant contributor to indoor radon entry. The diffusion coefficient of radon gas in building materials is often used as an indication for radon transportability through a porous medium and, furthermore, as an essential tool for quantitative predictions of radon concentrations in dwellings by estimating the exhalation rates of the wall surfaces. Radon diffusion coefficients in bricks were determined by employing the two compartment method in which one compartment is kept at a high radon concentration while the other is initially at low concentration. The radon diffusion coefficient is then deduced by monitoring the radon in the second compartment by measuring the steady state radon flux into the compartment. In this case, a steady-state solution was used to calculate the diffusion coefficient. The radon diffusion coefficients were found to vary from 0.32x10-6 m2/s to 0.48 x10-6 m2/s and the diffusion length were from 36x10-2 m to 42 x102 m in bricks. The results indicate that the bricks analyzed are fairly radon tight. (author)

  13. Diffusion Flame Stabilization

    Science.gov (United States)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2007-01-01

    Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm) (Fig. 1, left). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated (Fig. 1, right). A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

  14. Inner zone electron radial diffusion coefficients - An update with Van Allen Probes MagEIS data

    Science.gov (United States)

    O'Brien, Paul; Fennell, Joseph; Guild, Timothy; Mazur, Joseph; Claudepierre, Seth; Clemmons, James; Turner, Drew; Blake, Bernard; Roeder, James

    2016-07-01

    Using MagEIS data from NASA's recent Van Allen Probes mission, we estimate the quiet-time radial diffusion coefficients for electrons in the inner radiation belt and slot, for energies up to ~700 keV. We provide observational evidence that energy diffusion is negligible. The main dynamic processes, then, are radial diffusion and elastic pitch angle scattering. We use a coordinate system in which these two modes of diffusion are separable. Then we integrate over pitch angle to obtain a field line content whose dynamics consist of radial diffusion and loss to the atmosphere. We estimate the loss timescale from periods of exponential decay in the time series. We then estimate the radial diffusion coefficient from the temporal and radial variation of the field line content. We show that our diffusion coefficients agree well with previously determined values. Our coefficients are consistent with diffusion by electrostatic impulses, whereas outer zone radial diffusion is thought to be dominated by electromagnetic fluctuations.

  15. On the relationship between Red Rectangle and diffuse interstellar bands

    CERN Document Server

    Zagury, Frederic

    2009-01-01

    A careful examination of Red Rectangle bands which have been considered as diffuse interstellar bands (DIBs) in emission shows that a few are likely to be artifacts in the spectrum. Some others result from atmospheric extinction. Consequences for the Red Rectangle band/DIB associations are examined. I will also comment a striking resemblance between the DIB spectrum and the spectrum of NO2 in the 6150-6250A region. This suggests that some DIBs could be provoked by atmospheric molecules.

  16. Diffusion of radionuclides through deep-sea sediments

    International Nuclear Information System (INIS)

    Methods for the direct determination of diffusion coefficients in deep-sea sediments were developed and compared. Diffusion coefficients were determined for the nuclides Am, Pu, Np, U, Tc, I, and Cs and the results were compared with values calculated from distribution ratio measurements. Diffusion coefficient and distribution ratio determinations were carried out in a nitrogen-filled glove box on postoxic sediments that had been kept in a nitrogen atmosphere from the time of collection. The values obtained were compared with those for oxic sediments in air. (author)

  17. Theories on diffusion of technology

    DEFF Research Database (Denmark)

    Munch, Birgitte

    Tracing the body of the diffusion proces by analysing the diffusion process from historical, sociological, economic and technical approaches. Discussing central characteristics of the proces of diffusion og CAD/CAM in Denmark.......Tracing the body of the diffusion proces by analysing the diffusion process from historical, sociological, economic and technical approaches. Discussing central characteristics of the proces of diffusion og CAD/CAM in Denmark....

  18. Carbon diffusion in niobium

    International Nuclear Information System (INIS)

    An attempt is made to find out the reasons for deviations in the literary data on carbon diffusion in niobium. Methods of layer-by-layer radiometric analysis and measuring the internal friction are applied for this purpose. It is shown that penetration curves can be presented as a sum of two exponents which describe the distribution of active carbon in the surface and depth layers. Carbon diffusion parameters calculated in the above two regions are noticeably different, which can be the reason for deviations in the literary data. The temperature dependence of carbon diffusion coefficients in niobium at 677-1300 deg C in found which corresponds to the interstitial diffusion coe icient

  19. Hereditary diffuse gastric cancer

    DEFF Research Database (Denmark)

    van der Post, Rachel S; Vogelaar, Ingrid P; Carneiro, Fátima;

    2015-01-01

    Germline CDH1 mutations confer a high lifetime risk of developing diffuse gastric (DGC) and lobular breast cancer (LBC). A multidisciplinary workshop was organised to discuss genetic testing, surgery, surveillance strategies, pathology reporting and the patient's perspective on multiple aspects...

  20. Seismic Fault Preserving Diffusion

    CERN Document Server

    Lavialle, Olivier; Germain, Christian; Donias, Marc; Guillon, Sebastien; Keskes, Naamen; Berthoumieu, Yannick

    2007-01-01

    This paper focuses on the denoising and enhancing of 3-D reflection seismic data. We propose a pre-processing step based on a non linear diffusion filtering leading to a better detection of seismic faults. The non linear diffusion approaches are based on the definition of a partial differential equation that allows us to simplify the images without blurring relevant details or discontinuities. Computing the structure tensor which provides information on the local orientation of the geological layers, we propose to drive the diffusion along these layers using a new approach called SFPD (Seismic Fault Preserving Diffusion). In SFPD, the eigenvalues of the tensor are fixed according to a confidence measure that takes into account the regularity of the local seismic structure. Results on both synthesized and real 3-D blocks show the efficiency of the proposed approach.

  1. Hereditary Diffuse Gastric Cancer

    Science.gov (United States)

    ... procedure done in conjunction with in-vitro fertilization (IVF). It allows people who carry a specific known ... gastric cancer before age 40 Personal or family history of both diffuse gastric cancer and lobular breast ...

  2. Diffusion Adaptation over Networks

    CERN Document Server

    Sayed, Ali H

    2012-01-01

    Adaptive networks are well-suited to perform decentralized information processing and optimization tasks and to model various types of self organized and complex behavior encountered in nature. Adaptive networks consist of a collection of agents with processing and learning abilities. The agents are linked together through a connection topology, and they cooperate with each other through local interactions to solve distributed inference problems in real-time. The continuous diffusion of information across the network enables agents to adapt their performance in relation to changing data and network conditions; it also results in improved adaptation and learning performance relative to non-cooperative networks. This article provides an overview of diffusion strategies for adaptation and learning over networks. The article is divided into several sections: 1. Motivation; 2. Mean-Square-Error Estimation; 3. Distributed Optimization via Diffusion Strategies; 4. Adaptive Diffusion Strategies; 5. Performance of Ste...

  3. On Diffusion and Permeation

    KAUST Repository

    Peppin, Stephen S. L.

    2009-01-01

    Diffusion and permeation are discussed within the context of irreversible thermodynamics. A new expression for the generalized Stokes-Einstein equation is obtained which links the permeability to the diffusivity of a two-component solution and contains the poroelastic Biot-Willis coefficient. The theory is illustrated by predicting the concentration and pressure profiles during the filtration of a protein solution. At low concentrations the proteins diffuse independently while at higher concentrations they form a nearly rigid porous glass through which the fluid permeates. The theoretically determined pressure drop is nonlinear in the diffusion regime and linear in the permeation regime, in quantitative agreement with experimental measurements. © 2009 Walter de Gruyter, Berlin, New York.

  4. Mastocytosis, diffuse cutaneous (image)

    Science.gov (United States)

    This is a picture of diffuse, cutaneous mastocytosis. Abnormal collections of cells in the skin (mast cells) produce this rash. Unlike bullous mastocytosis, rubbing will not lead to formation of blisters ( ...

  5. Diffusing Best Practices

    DEFF Research Database (Denmark)

    Pries-Heje, Jan; Baskerville, Richard

    2014-01-01

    approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...... resulting from the design were two-day training workshops conceptually anchored to TBP. The design theory was evaluated through execution of eight diffusion workshops involving three different groups in the same company. The findings indicate that the match between the practice and the context materialized...... that the behavior will be effective). These two factors were especially critical if the source context of the best practice is qualitatively different from the target context into which the organization is seeking to diffuse the best practice....

  6. Direct measurement of VOC diffusivities in tree tissues

    DEFF Research Database (Denmark)

    Baduru, K.K.; Trapp, Stefan; Burken, Joel G.

    2008-01-01

    Recent discoveries in the phytoremediation of volatile organic compounds (VOCs) show that vapor-phase transport into roots leads to VOC removal from the vadose zone and diffusion and volatilization out of plants is an important fate following uptake. Volatilization to the atmosphere constitutes one...... in numerous vegetation−VOC interactions, including the phytoremediation of soil vapors and dissolved aqueous-phase contaminants. The diffusion of VOCs through freshly excised tree tissue was directly measured for common groundwater contaminants, chlorinated compounds such as trichloroethylene, perchloroethene......, and tetrachloroethane and aromatic hydrocarbons such as benzene, toluene, and methyl tert-butyl ether. All compounds tested are currently being treated at full scale with tree-based phytoremediation. Diffusivities were determined by modeling the diffusive transport data with a one-dimensional diffusive flux model...

  7. Seismic Fault Preserving Diffusion

    OpenAIRE

    Lavialle, Olivier; Pop, Sorin; Germain, Christian; Donias, Marc; Guillon, Sebastien; Keskes, Naamen; Berthoumieu, Yannick

    2007-01-01

    This paper focuses on the denoising and enhancing of 3-D reflection seismic data. We propose a pre-processing step based on a non linear diffusion filtering leading to a better detection of seismic faults. The non linear diffusion approaches are based on the definition of a partial differential equation that allows us to simplify the images without blurring relevant details or discontinuities. Computing the structure tensor which provides information on the local orientation of the geological...

  8. Advanced manufacturing: Technology diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Tesar, A.

    1995-12-01

    In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.

  9. Atmosphere and ocean in radioactive balance

    International Nuclear Information System (INIS)

    The article describes an extension of a classical model in the theory of radioactive equilibrium of planetary layers. it is elaborated in the spirit of the Eddington approximation, by virtue of which analytical solutions become feasible. The extension consists in allowing for the (isotropically diffuse) reflection of solar radiation at the interface between a planet's atmosphere and its surface layer. Since the model also incorporates absorption of short-wave radiation, it l encompasses earlier models of the same kind. As an illustration, it is applied to calculating the 11 temperature profiles of both the earth's atmosphere and its ocean

  10. Nucleation of atmospheric particles

    OpenAIRE

    Curtius J

    2009-01-01

    Two types of particles exist in the atmosphere, primary and secondary particles. While primary particles such as soot, mineral dust, sea salt particles or pollen are introduced directly as particles into the atmosphere, secondary particles are formed in the atmosphere by condensation of gases. The formation of such new aerosol particles takes place frequently and at a broad variety of atmospheric conditions and geographic locations. A considerable fraction of the atmospheric particles is form...

  11. Multispecies diffusion models: A study of uranyl species diffusion

    International Nuclear Information System (INIS)

    Rigorous numerical description of multi-species diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication for imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multi-species diffusion in groundwater. Diffusion of uranyl (U(VI)) species was used as an example in demonstrating the effectiveness of the models in describing multi-species diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multi-species U(VI) diffusion under steady-state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that a fully coupled diffusion model can be well approximated by a component-based diffusion model, which considers difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be rigorously enforced, if necessary, by adding an artificial kinetic reaction term induced by the charge separation. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from US Department of Energy's Hanford 300A where intragrain diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that has been described using a semi-empirical, multi-rate model

  12. Diffusion limited aggregation with directed and anisotropic diffusion

    OpenAIRE

    Jullien, R.; Kolb, M.; Botet, R.

    1984-01-01

    Fractal aggregates obtained from diffusion limited growth processes are studied. Numerical simulations are reported for a two-dimensional cluster growing on a basal line. For isotropic diffusion this model behaves as the spherically growing model of Witten and Sander. It is found that directed diffusion renders the cluster compact while anisotropic diffusion apparently yields a continuously varying fractal dimension.

  13. Diffuse Attenuation Coef. K490, Aqua MODIS, 0.125 degrees, Indonesia

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — OSU distributes Diffuse Attenuation Coefficient at 490 nm Wavelength data from NASA's Aqua satellite. Measurements are gathered by the Moderate Resolution Imaging...

  14. Diffuse Attenuation Coef. K490, Aqua MODIS, NPP, 0.125 degrees, East US

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NASA distributes Diffuse Attenuation Coefficient at 490 nm Wavelength data from NASA's Aqua satellite. Measurements are gathered by the Moderate Resolution Imaging...

  15. MODISA Level-3 Standard Mapped Image, Diffuse Attenuation Coef. KD490, Daily, 4km

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes Diffuse Attenuation Coef. KD490 derived from NASA's Aqua Spacecraft. Measurements are gathered by the Moderate Resolution Imaging...

  16. Lead diffusion in monazite

    International Nuclear Information System (INIS)

    Proper knowledge of the diffusion rates of lead in monazite is necessary to understand the U-Th-Pb age anomalies of this mineral, which is one of the most used in geochronology after zircon. Diffusion experiments were performed in NdPO4 monocrystals and in Nd0.66Ca0.17Th0.17PO4 polycrystals from Nd0.66Pb0.17Th0.17PO4 thin films to investigate Pb2+ + Th4+ ↔ 2 Nd3+ and Pb2+ ↔ Ca2+ exchanges. Diffusion annealings were run between 1200 and 1500 Celsius degrees, at room pressure, for durations ranging from one hour to one month. The diffusion profiles were analysed using TEM (transmission electronic microscopy) and RBS (Rutherford backscattering spectroscopy). The diffusivities extracted for Pb2+ + Th4+ ↔ 2 Nd3+ exchange follow an Arrhenius law with parameters E equals 509 ± 24 kJ mol-1 and log(D0 (m2s-1)) equals -3.41 ± 0.77. Preliminary data for Pb2+ ↔ Ca2+ exchange are in agreement with this result. The extrapolation of our data to crustal temperatures yields very slow diffusivities. For instance, the time necessary for a 50 μm grain to lose all of its lead at 800 Celsius degrees is greater than the age of the Earth. From these results and other evidence from the literature, we conclude that most of the perturbations in U-Th-Pb ages of monazite cannot be attributed to lead diffusion, but rather to interactions with fluids. (author)

  17. International Trade, Technology Diffusion, and the Role of Diffusion Barriers

    OpenAIRE

    Li, Yao Amber

    2010-01-01

    This paper assesses the welfare impact of trade and technology diffusion as well as the change in the cross-country distribution of GDP due to removal of trade costs and diffusion barriers. The model extends the multi-country Ricardian trade model of Alvarez and Lucas (2007) to include technology diffusion with diffusion barriers. A key feature of the model is that some countries export goods produced by foreign technology via diffusion. The model is calibrated to match the world GDP distribu...

  18. Dispersion of effluents in the atmosphere; Dispersion des effluents dans l`atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-31

    This conference day was organized by the `convection` section of the French association of thermal engineers with the support of the environment and energy mastery agency (ADEME). This book of proceedings contains 10 papers entitled: `physical modeling of atmospheric dispersion in wind tunnels. Some industrial examples`; `modeling of the noxious effects of a fire on the environment of an industrial site: importance of thermal engineering related hypotheses`; `atmospheric diffusion of a noxious cloud: fast evaluation method of safety areas around refrigerating installations that use ammonia`; `modeling of atmospheric flows in urban areas in order to study the dispersion of pollutants`; `use of a dispersion parameter to characterize the evolution of a diffusion process downstream of a linear source of passive contaminant placed inside a turbulent boundary layer`; `elements of reflexion around the development of an analytical methodology applied to the elaboration of measurement strategies of air quality in ambient and outdoor atmospheres around industrial sites`; `state-of-the-art about treatment techniques for VOC-rich gaseous effluents`; `characteristics of the time variation of the atmospheric pollution in the Paris region and visualization of its space distribution`; `mass-spectrometry for the measurement of atmospheric pollutants`; `volume variations in natural convection turbulence`. (J.S.)

  19. Atmospheric composition change: Ecosystems–Atmosphere interactions

    DEFF Research Database (Denmark)

    Fowler, D.; Pilegaard, Kim; Sutton, M.A.;

    2009-01-01

    Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth's surface and the atmosphere. The gases covered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O3, CH4, N2O and particles...

  20. Diffusive Nuclear Burning on Neutron Star Envelopes

    CERN Document Server

    Chang, P

    2003-01-01

    We calculate the rate of hydrogen burning for neutron stars (NSs) with hydrogen atmospheres and an underlying reservoir of nuclei capable of proton capture. This burning occurs in the exponentially suppressed diffusive tail of H that extends to the hotter depths of the envelope where protons are rapidly captured. This process, which we call diffusive nuclear burning (DNB), can change the H abundance at the NS photosphere on timescales as short as $10^{2-4}$ years. In the absence of diffusion, the hydrogen at the photosphere (where $T\\approx 10^6 {\\rm K}$ and $\\rho\\sim 0.1 {\\rm g cm^{-2}}$) would last for far longer than a Hubble time. Our work impacts the understanding of the evolution of surface abundances of isolated NSs, which is important to their thermal spectrum and their effective temperature-core temperature relation. In this paper, we calculate the rate of H burning when the overall consumption rate is controlled by the nuclear timescales, rather than diffusion timescales. The immediate application i...

  1. Diffusion studies in sintered iron

    International Nuclear Information System (INIS)

    In the temperature range investigated, tracer diffusion in powder compacts occurs by high diffusivity paths, composed of at least grain boundary and surface diffusion. It was shown that effective grain boundary diffusion coefficient increase with temperature for the same density of specimens and decrease with increasing density of specimens for the same temperature. Tracer diffusion is slowest in powder specimens pre-sintered at the highest diffusion annealing temperature, but for all specimens investigated, it is faster than grain boundary diffusion in massive specimens

  2. Study on influence of native oxide and corrosion products on atmospheric corrosion of pure Al

    International Nuclear Information System (INIS)

    Highlights: •Corrosion products layer is only formed in coastal atmosphere. •In coastal atmosphere, rate controlling step is diffusion process. •In rural atmosphere, rate controlling step is charge transfer process. •Pitting area increases greatly in coastal site, but slightly in rural site. -- Abstract: Effects of native oxide and corrosion products on atmospheric corrosion of aluminium in rural and coastal sites were studied by electrochemical impedance spectroscopy (EIS), open-circuit potential (OCP) and scanning electron microscope (SEM) techniques after outdoor exposure. In the rural atmosphere, only the compact, adhesive native oxide layer exists, and the rate controlling step is diffusion process, while in the coastal atmosphere, another loose, inadhesive corrosion products layer exists, and a charge transfer process controls the corrosion process. The pitting area in the coastal atmosphere increases over time more obviously than that in the rural atmosphere

  3. Diffusion in flexible pipes

    Energy Technology Data Exchange (ETDEWEB)

    Brogaard Kristensen, S.

    2000-06-01

    This report describes the work done on modelling and simulation of the complex diffusion of gas through the wall of a flexible pipe. The diffusion and thus the pressure in annulus depends strongly on the diffusion and solubility parameters of the gas-polymer system and on the degree of blocking of the outer surface of the inner liner due to pressure reinforcements. The report evaluates the basis modelling required to describe the complex geometries and flow patterns. Qualitatively results of temperature and concentration profiles are shown in the report. For the program to serve any modelling purpose in 'real life' the results need to be validated and possibly the model needs corrections. Hopefully, a full-scale test of a flexible pipe will provide the required temperatures and pressures in annulus to validate the models. (EHS)

  4. Diffusion and mass transfer

    CERN Document Server

    Vrentas, James S

    2013-01-01

    The book first covers the five elements necessary to formulate and solve mass transfer problems, that is, conservation laws and field equations, boundary conditions, constitutive equations, parameters in constitutive equations, and mathematical methods that can be used to solve the partial differential equations commonly encountered in mass transfer problems. Jump balances, Green’s function solution methods, and the free-volume theory for the prediction of self-diffusion coefficients for polymer–solvent systems are among the topics covered. The authors then use those elements to analyze a wide variety of mass transfer problems, including bubble dissolution, polymer sorption and desorption, dispersion, impurity migration in plastic containers, and utilization of polymers in drug delivery. The text offers detailed solutions, along with some theoretical aspects, for numerous processes including viscoelastic diffusion, moving boundary problems, diffusion and reaction, membrane transport, wave behavior, sedime...

  5. Anomalous diffusion in geophysical and laboratory turbulence

    Directory of Open Access Journals (Sweden)

    A. Tsinober

    1994-01-01

    Full Text Available We present an overview and some new results on anomalous diffusion of passive scalar in turbulent flows (including those used by Richardson in his famous paper in 1926. The obtained results are based on the analysis of the properties of invariant quantities (energy, enstrophy, dissipation, enstrophy generation, helicity density, etc. - i.e. independent of the choice of the system of reference as the most appropriate to describe physical processes - in three different turbulent laboratory flows (grid-flow, jet and boundary layer, see Tsinober et al. (1992 and Kit et al. (1993. The emphasis is made on the relations between the asymptotic properties of the intermittency exponents of higher order moments of different turbulent fields (energy, dissipation, helicity, spontaneous breaking of isotropy and reflexional symmetry and the variability of turbulent diffusion in the atmospheric boundary layer, in the troposphere and in the stratosphere. It is argued that local spontaneous breaking of isotropy of turbulent flow results in anomalous scaling laws for turbulent diffusion (as compared to the scaling law of Richardson which are observed, as a rule, in different atmospheric layers from the atmospheric boundary layer (ABL to the stratosphere. Breaking of rotational symmetry is important in the ABL, whereas reflexional symmetry breaking is dominating in the troposphere locally and in the stratosphere globally. The results are of speculative nature and further analysis is necessary to validate or disprove the claims made, since the correspondence with the experimental results may occur for the wrong reasons as happens from time to time in the field of turbulence.

  6. Diffusion imaging concepts for clinicians.

    Science.gov (United States)

    Neil, Jeffrey J

    2008-01-01

    This review covers the fundamentals of diffusion tensor imaging. It is written with the clinician in mind and assumes the reader has a passing familiarity with magnetic resonance imaging (MRI). Topics covered include comparison of diffusion MRI with conventional MRI, water apparent diffusion coefficient (ADC), diffusion anisotropy, tract tracing, and changes of water apparent diffusion in response to injury. The discussion centers primarily on applications to the central nervous system, but examples from other tissues are included. PMID:18050325

  7. Double-Diffusive Convection

    CERN Document Server

    Garaud, Pascale

    2014-01-01

    Much progress has recently been made in understanding and quantifying vertical mixing induced by double-diffusive instabilities such as fingering convection (usually called thermohaline convection) and oscillatory double-diffusive convection (a process closely related to semiconvection). This was prompted in parts by advances in supercomputing, which allow us to run Direct Numerical Simulations of these processes at parameter values approaching those relevant in stellar interiors, and in parts by recent theoretical developments in oceanography where such instabilities also occur. In this paper I summarize these recent findings, and propose new mixing parametrizations for both processes that can easily be implemented in stellar evolution codes.

  8. Phase transformation and diffusion

    CERN Document Server

    Kale, G B; Dey, G K

    2008-01-01

    Given that the basic purpose of all research in materials science and technology is to tailor the properties of materials to suit specific applications, phase transformations are the natural key to the fine-tuning of the structural, mechanical and corrosion properties. A basic understanding of the kinetics and mechanisms of phase transformation is therefore of vital importance. Apart from a few cases involving crystallographic martensitic transformations, all phase transformations are mediated by diffusion. Thus, proper control and understanding of the process of diffusion during nucleation, g

  9. Mass diffusion in liquids

    Science.gov (United States)

    Walter, H. U.

    Dimensionless number analysis indicates that diffusion-controlled conditions with liquid samples having characteristic dimensions larger than one millimetre can only be established under microgravity conditions.Consequently, heat and mass transport properties of fluids can only be quantitatively investigated in space.Results obtained from experiments on selfdiffusion, interdiffusion and thermodiffusion carried out during the SL-1 and D-1 Spacelab missions clearly demonstrate the potential of space platforms to determine such properties with a precision unattainable on earth. These results imply also that crystal growth from solutions, vapours and melts in the diffusive regime can be realised in space only.

  10. Radon diffusion modelling.

    Science.gov (United States)

    Wilkinson, P; Dimbylow, P J

    1985-10-01

    A mathematical model has been developed that examines the ingress of radon into houses, through a vertical crack in an otherwise impervious concrete floor. Initially, the model considered the diffusive flow of radon from its soil source and this simulation has highlighted the dependency of the flux of radon into the house on the magnitude of various parameters, such as the diffusion coefficient of radon in soil. A preliminary investigation of the modelling of pressure-driven flow into a building is presented, and the potential of this type of analysis is discussed. PMID:4081719

  11. Diffusion in advanced materials

    CERN Document Server

    Murch, Graeme; Belova, Irina

    2014-01-01

    In the first chapter Prof. Kozubski and colleagues present atomisticsimulations of superstructure transformations of intermetallic nanolayers.In Chapter 2, Prof. Danielewski and colleagues discuss a formalism for themorphology of the diffusion zone in ternary alloys. In Chapter 3, ProfessorsSprengel and Koiwa discuss the classical contributions of Boltzmann andMatano for the analysis of concentration-dependent diffusion. This isfollowed by Chapter 4 by Professor Cserháti and colleagues on the use of Kirkendall porosity for fabricating hollow hemispheres. In Chapter 5,Professor Morton-Blake rep

  12. Ambipolar diffusion in plasma

    International Nuclear Information System (INIS)

    Is this thesis, a numerical method for the solution of the linear diffusion equation for a plasma containing two types of ions, with the possibility of charge exchange, has been developed. It has been shown that the decay time of the electron and ion densities is much smaller than that in a plasma containing only a single type of ion. A non-linear diffusion equation, which includes the effects of an external electric field varying linearly in time, to describe a slightly ionized plasma has also been developed. It has been verified that the decay of the electron density in the presence of such an electric field is very slow. (author)

  13. Anticorrosion diffusion coatings

    International Nuclear Information System (INIS)

    The effect of chemical- and heat treatment on corrosion resistance of steels in aqueous solutions of acids, salts and alkalies has been investigated to find a possibility of replacing stainless steel by carbon or low-alloyed steels with diffusion coatings. Data on corrosion resistance of steels with diffusion coatings such as Cr, Cr-Si, Cr-Ti, Cr-Al, Zr-Al, V-Al are presented. The mechanism of fracture of steels with coatings prepared under optimum conditions is studied

  14. The Trouble with Diffusion

    Directory of Open Access Journals (Sweden)

    R.T. DeHoff

    2002-09-01

    Full Text Available The phenomenological formalism, which yields Fick's Laws for diffusion in single phase multicomponent systems, is widely accepted as the basis for the mathematical description of diffusion. This paper focuses on problems associated with this formalism. This mode of description of the process is cumbersome, defining as it does matrices of interdiffusion coefficients (the central material properties that require a large experimental investment for their evaluation in three component systems, and, indeed cannot be evaluated for systems with more than three components. It is also argued that the physical meaning of the numerical values of these properties with respect to the atom motions in the system remains unknown. The attempt to understand the physical content of the diffusion coefficients in the phenomenological formalism has been the central fundamental problem in the theory of diffusion in crystalline alloys. The observation by Kirkendall that the crystal lattice moves during diffusion led Darken to develop the concept of intrinsic diffusion, i.e., atom motion relative to the crystal lattice. Darken and his successors sought to relate the diffusion coefficients computed for intrinsic fluxes to those obtained from the motion of radioactive tracers in chemically homogeneous samples which directly report the jump frequencies of the atoms as a function of composition and temperature. This theoretical connection between tracer, intrinsic and interdiffusion behavior would provide the basis for understanding the physical content of interdiffusion coefficients. Definitive tests of the resulting theoretical connection have been carried out for a number of binary systems for which all three kinds of observations are available. In a number of systems predictions of intrinsic coefficients from tracer data do not agree with measured values although predictions of interdiffusion coefficients appear to give reasonable agreement. Thus, the complete

  15. Discovery of diffuse aurora on Mars.

    Science.gov (United States)

    Schneider, N M; Deighan, J I; Jain, S K; Stiepen, A; Stewart, A I F; Larson, D; Mitchell, D L; Mazelle, C; Lee, C O; Lillis, R J; Evans, J S; Brain, D; Stevens, M H; McClintock, W E; Chaffin, M S; Crismani, M; Holsclaw, G M; Lefevre, F; Lo, D Y; Clarke, J T; Montmessin, F; Jakosky, B M

    2015-11-01

    Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment. We report the discovery of low-altitude, diffuse auroras spanning much of Mars' northern hemisphere, coincident with a solar energetic particle outburst. The Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, detected auroral emission in virtually all nightside observations for ~5 days, spanning nearly all geographic longitudes. Emission extended down to ~60 kilometer (km) altitude (1 microbar), deeper than confirmed at any other planet. Solar energetic particles were observed up to 200 kilo--electron volts; these particles are capable of penetrating down to the 60 km altitude. Given minimal magnetic fields over most of the planet, Mars is likely to exhibit auroras more globally than Earth. PMID:26542577

  16. Statistics in Atmospheric Science

    OpenAIRE

    Solow, Andrew R.

    2003-01-01

    This paper reviews the use of statistical methods in atmospheric science. The applications covered include the development, assessment and use of numerical physical models of the atmosphere and more empirical analysis unconnected to physical models.

  17. Our shared atmosphere

    Science.gov (United States)

    Our atmosphere is a precious and fascinating resource, providing air to breath, shielding us from harmful ultraviolet radiation (UV), and maintaining a comfortable climate. Since the industrial revolution, people have significantly altered the composition of the atmosphere throu...

  18. Planetary Atmospheric Electricity

    CERN Document Server

    Leblanc, F; Yair, Y; Harrison, R. G; Lebreton, J. P; Blanc, M

    2008-01-01

    This volume presents our contemporary understanding of atmospheric electricity at Earth and in other solar system atmospheres. It is written by experts in terrestrial atmospheric electricity and planetary scientists. Many of the key issues related to planetary atmospheric electricity are discussed. The physics presented in this book includes ionisation processes in planetary atmospheres, charge generation and separation, and a discussion of electromagnetic signatures of atmospheric discharges. The measurement of thunderstorms and lightning, including its effects and hazards, is highlighted by articles on ground and space based instrumentation, and new missions.Theory and modelling of planetary atmospheric electricity complete this review of the research that is undertaken in this exciting field of space science. This book is an essential research tool for space scientists and geoscientists interested in electrical effects in atmospheres and planetary systems. Graduate students and researchers who are new to t...

  19. Earth's changeable atmosphere

    Science.gov (United States)

    2016-06-01

    Billions of years ago, high atmospheric greenhouse gas concentrations were vital to life's tenuous foothold on Earth. Despite new constraints, the composition and evolution of Earth's early atmosphere remains hazy.

  20. Atmospheric Lepton Fluxes

    CERN Document Server

    Gaisser, Thomas K

    2014-01-01

    This review of atmospheric muons and neutrinos emphasizes the high energy range relevant for backgrounds to high-energy neutrinos of astrophysical origin. After a brief historical introduction, the main distinguishing features of atmospheric $\

  1. Mirador - Atmospheric Composition

    Data.gov (United States)

    National Aeronautics and Space Administration — Earth Science data access made simple. Atmospheric Composition is focused on the composition of Earth's atmosphere in relation to climate prediction, solar effects,...

  2. Diffuse axonal injury: detection of changes in anisotropy of water diffusion by diffusion-weighted imaging

    Energy Technology Data Exchange (ETDEWEB)

    Chan, J.H.M.; Tsui, E.Y.K.; Yuen, M.K. [Department of Diagnostic Radiology, Tuen Mun Hospital, Tsing Chung Koon Road, Tuen Mun, N.T., Hong Kong (China); Peh, W.C.G. [Department of Diagnostic Radiology, Singapore General Hospital (Singapore); Fong, D.; Fok, K.F.; Leung, K.M. [Department of Neurosurgery, Tuen Mun Hospital (Hong Kong); Fung, K.K.L. [Department of Optometry and Radiography, Hong Kong Polytechnic University (China)

    2003-01-01

    Myelinated axons of white matter demonstrate prominent directional differences in water diffusion. We performed diffusion-weighted imaging on ten patients with head injury to explore the feasibility of using water diffusion anisotropy for quantitating diffuse axonal injury. We showed significant decrease in diffusion anisotropy indices in areas with or without signal abnormality on T2 and T2*-weighted images. We conclude that the water diffusion anisotropy index a potentially useful, sensitive and quantitative way of diagnosing and assessing patients with diffuse axonal injury. (orig.)

  3. Diffuse axonal injury: detection of changes in anisotropy of water diffusion by diffusion-weighted imaging

    International Nuclear Information System (INIS)

    Myelinated axons of white matter demonstrate prominent directional differences in water diffusion. We performed diffusion-weighted imaging on ten patients with head injury to explore the feasibility of using water diffusion anisotropy for quantitating diffuse axonal injury. We showed significant decrease in diffusion anisotropy indices in areas with or without signal abnormality on T2 and T2*-weighted images. We conclude that the water diffusion anisotropy index a potentially useful, sensitive and quantitative way of diagnosing and assessing patients with diffuse axonal injury. (orig.)

  4. Atmospheric scattering and decay of inner radiation belt electrons

    Science.gov (United States)

    Selesnick, R. S.

    2012-08-01

    The dynamics of inner radiation belt electrons are governed by competing source, loss, and transport processes. However, during the recent extended solar minimum period the source was inactive and electron intensity was characterized by steady decay. This provided an opportunity to determine contributions to the decay rate of losses by precipitation into the atmosphere and of diffusive radial transport. To this end, a stochastic simulation of inner radiation belt electron transport is compared to data taken by the IDP instrument on the DEMETER satellite during 2009. For quasi-trapped, 200 keV electrons atL= 1.3, observed in the drift loss cone (DLC), results are consistent with electron precipitation losses by atmospheric scattering alone, provided account is taken of non-diffusive wide-angle scattering. Such scattering is included in the stochastic simulation using a Markov jump process. Diffusive small-angle atmospheric scattering, while causing most of the precipitation losses, is too slow relative to azimuthal drift to contribute significantly to DLC intensity. Similarly there is no contribution from scattering by VLF plasma waves. Energy loss, energy diffusion, and azimuthal drift are also included in the model. Even so, observed decay rates of stably-trapped electrons withL diffusion with coefficient DLL ˜ 3 × 10-10 s-1 to replenish electrons lost to the atmosphere at low L values.

  5. An Atmospheric Cloud Physics Laboratory for the Space Laboratory

    Science.gov (United States)

    Smith, R.; Anderson, J.; Schrick, B.; Ellsworth, C.; Davis, M.

    1976-01-01

    Results of research and engineering analyses to date show that it is feasible to develop and fly on the first Spacelab mission a multipurpose laboratory in which experiments can be performed on the microphysical processes in atmospheric clouds. The paper presents a series of tables on the Atmospheric Cloud Physics Laboratory, with attention given to experiment classes, the preliminary equipment list (particle generators, optical and imaging devices, particle detectors and characterizers, etc.), initial equipment (scientific equipment subsystems and flight support subsystems), and scientific functional requirements (the expansion chamber, the continuous flow diffusion chamber, the static diffusion chamber, the humidifier, and particle generators).

  6. Intensifying the Atmospheric

    DEFF Research Database (Denmark)

    Liebst, Lasse Suonperä

    2012-01-01

    understanding of atmospheres as aesthetically ‘radiating’ from the surfaces of space, thinks physiognomically, the article argues for a spatial morphological perspective on atmospheres. Thus, post-phenomeno¬logically, it is argued that the atmospheric given is given by the density of pedestrians, which are...

  7. Diffusion Based Photon Mapping

    DEFF Research Database (Denmark)

    Schjøth, Lars; Sporring, Jon; Fogh Olsen, Ole

    2008-01-01

    . To address this problem, we introduce a photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way, we preserve important illumination features...

  8. Model of information diffusion

    CERN Document Server

    Lande, D V

    2008-01-01

    The system of cellular automata, which expresses the process of dissemination and publication of the news among separate information resources, has been described. A bell-shaped dependence of news diffusion on internet-sources (web-sites) coheres well with a real behavior of thematic data flows, and at local time spans - with noted models, e.g., exponential and logistic ones.

  9. Diffusion in ceramics

    CERN Document Server

    Pelleg, Joshua

    2016-01-01

    This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. Solutions of Fick’s second law for constant D, diffusion in grain boundaries and dislocations are presented along with a look at the atomistic approach for the random motion of atoms. In the second part, the author discusses diffusion in several technologically important ceramics. The ceramics selected are monolithic single phase ones, including: A12O3, SiC, MgO, ZrO2 and Si3N4. Of these, three refer to oxide ceramics (alumina, magnesia and zirconia). Carbide based ceramics are represented by the technologically very important Si-ca...

  10. Diffusion in aggregated soil.

    NARCIS (Netherlands)

    Rappoldt, C.

    1992-01-01

    The structure of an aggregated soil is characterized by the distribution of the distance from an arbitrary point in the soil to the nearest macropore or crack. From this distribution an equivalent model system is derived to which a diffusion model can be more easily applied. The model system consist

  11. Bronnen van diffuse bodembelasting

    NARCIS (Netherlands)

    Lijzen JPA; Ekelenkamp A; LBG; DGM/BO

    1995-01-01

    The aim of this study was to support the policy on preventive soil protection with information on the diffuse (non-local) emissions to soil and the influence on future soil quality. This study is related to inventories on (potential) sources of local soil pollution (e.g. industrial areas, landfills

  12. A white dwarf with an oxygen atmosphere.

    Science.gov (United States)

    Kepler, S O; Koester, Detlev; Ourique, Gustavo

    2016-04-01

    Stars born with masses below around 10 solar masses end their lives as white dwarf stars. Their atmospheres are dominated by the lightest elements because gravitational diffusion brings the lightest element to the surface. We report the discovery of a white dwarf with an atmosphere completely dominated by oxygen, SDSS J124043.01+671034.68. After oxygen, the next most abundant elements in its atmosphere are neon and magnesium, but these are lower by a factor of ≥25 by number. The fact that no hydrogen or helium are observed is surprising. Oxygen, neon, and magnesium are the products of carbon burning, which occurs in stars at the high-mass end of pre-white dwarf formation. This star, a possible oxygen-neon white dwarf, will provide a rare observational test of the evolutionary paths toward white dwarfs. PMID:27034367

  13. Magnetic Effects in Hot Jupiter Atmospheres

    CERN Document Server

    Rogers, Tamara M

    2014-01-01

    We present magnetohydrodynamic (MHD) simulations of the atmospheres of hot Jupiters ranging in temperature from 1100-1800K. Magnetic effects are negligible in atmospheres with temperatures $\\lesssim$ 1400K. At higher temperatures winds are variable and in many cases, mean equatorial flows can become westward, opposite to their hydrodynamic counterparts. Ohmic dissipation peaks at temperatures $\\sim$1500-1600K, depending on field strength, with maximum values $\\sim 10^{18}$W at 10bar, substantially lower than previous estimates. Based on the limited parameter study done, this value can not be increased substantially with increasing winds, higher temperatures, higher field strengths, different boundary conditions or lower diffusivities. Although not resolved in these simulations there is modest evidence that a magnetic buoyancy instability may proceed in hot atmospheres.

  14. A white dwarf with an oxygen atmosphere

    Science.gov (United States)

    Kepler, S. O.; Koester, Detlev; Ourique, Gustavo

    2016-04-01

    Stars born with masses below around 10 solar masses end their lives as white dwarf stars. Their atmospheres are dominated by the lightest elements because gravitational diffusion brings the lightest element to the surface. We report the discovery of a white dwarf with an atmosphere completely dominated by oxygen, SDSS J124043.01+671034.68. After oxygen, the next most abundant elements in its atmosphere are neon and magnesium, but these are lower by a factor of ≥25 by number. The fact that no hydrogen or helium are observed is surprising. Oxygen, neon, and magnesium are the products of carbon burning, which occurs in stars at the high-mass end of pre-white dwarf formation. This star, a possible oxygen-neon white dwarf, will provide a rare observational test of the evolutionary paths toward white dwarfs.

  15. Diffuse mode and diffuse-to-filamentary transition in a high pressure nanosecond scale corona discharge under high voltage

    Energy Technology Data Exchange (ETDEWEB)

    Tardiveau, P; Moreau, N; Bentaleb, S; Postel, C; Pasquiers, S, E-mail: pierre.tardiveau@u-psud.f [Laboratoire de Physique des Gaz et des Plasmas, Bat 210, Universite Paris-Sud, 91405 Orsay Cedex (France)

    2009-09-07

    The dynamics of a point-to-plane corona discharge induced in high pressure air under nanosecond scale high overvoltage is investigated. The electrical and optical properties of the discharge can be described in space and time with fast and precise current measurements coupled to gated and intensified imaging. Under atmospheric pressure, the discharge exhibits a diffuse pattern like a multielectron avalanche propagating through a direct field ionization mechanism. The diffuse regime can exist since the voltage rise time is much shorter than the characteristic time of the field screening effects, and as long as the local field is higher than the critical ionization field in air. As one of these conditions is not fulfilled, the discharge turns into a multi-channel regime and the diffuse-to-filamentary transition strongly depends on the overvoltage, the point-to-plane gap length and the pressure. When pressure is increased above atmospheric pressure, the diffuse stage and its transition to streamers seem to satisfy similarity rules as the key parameter is the reduced critical ionization field only. However, above 3 bar, neither diffuse avalanche nor streamer filaments are observed but a kind of streamer-leader regime, due to the fact that mechanisms such as photoionization and heat diffusion are not similar to pressure.

  16. Nonisothermal Pluto atmosphere models

    International Nuclear Information System (INIS)

    The present thermal profile calculation for a Pluto atmosphere model characterized by a high number fraction of CH4 molecules encompasses atmospheric heating by solar UV flux absorption and conductive transport cooling to the surface of Pluto. The stellar occultation curve predicted for an atmosphere of several-microbar surface pressures (which entail the existence of a substantial temperature gradient close to the surface) agrees with observations and implies that the normal and tangential optical depth of the atmosphere is almost negligible. The minimum period for atmospheric methane depletion is calculated to be 30 years. 29 refs

  17. PERFORMANCE OF A NEW DIFFUSIVE SAMPLER FOR HG0 DETERMINATION IN THE TROPOSPHERE

    Science.gov (United States)

    Mercury behaves uniquely in the atmosphere due to its volatility and long lifetime. The existing methods for measuring atmospheric mercury are either expensive or labour intensive. The present paper presents a new measurement technique, the diffusive sampler, that is portable, in...

  18. Erbium diffusion in silicon dioxide

    International Nuclear Information System (INIS)

    Erbium diffusion in silicon dioxide layers prepared by magnetron sputtering, chemical vapor deposition, and thermal growth has been investigated by secondary ion mass spectrometry, and diffusion coefficients have been extracted from simulations based on Fick's second law of diffusion. Erbium diffusion in magnetron sputtered silicon dioxide from buried erbium distributions has in particular been studied, and in this case a simple Arrhenius law can describe the diffusivity with an activation energy of 5.3±0.1 eV. Within a factor of two, the erbium diffusion coefficients at a given temperature are identical for all investigated matrices.

  19. Instrumentation in Diffuse Optical Imaging

    Directory of Open Access Journals (Sweden)

    Xiaofeng Zhang

    2014-03-01

    Full Text Available Diffuse optical imaging is highly versatile and has a very broad range of applications in biology and medicine. It covers diffuse optical tomography, fluorescence diffuse optical tomography, bioluminescence and a number of other new imaging methods. These methods of diffuse optical imaging have diversified instrument configurations, but share the same core physical principle: light propagation in highly diffusive media, i.e., biological tissue. In this review, the author summarizes the latest development in instrumentation and methodology available to diffuse optical imaging in terms of system architecture, light source, photo-detection, spectral separation, signal modulation and, lastly, imaging contrast.

  20. Uncertainty for calculating transport on Titan: A probabilistic description of bimolecular diffusion parameters

    Science.gov (United States)

    Plessis, S.; McDougall, D.; Mandt, K.; Greathouse, T.; Luspay-Kuti, A.

    2015-11-01

    Bimolecular diffusion coefficients are important parameters used by atmospheric models to calculate altitude profiles of minor constituents in an atmosphere. Unfortunately, laboratory measurements of these coefficients were never conducted at temperature conditions relevant to the atmosphere of Titan. Here we conduct a detailed uncertainty analysis of the bimolecular diffusion coefficient parameters as applied to Titan's upper atmosphere to provide a better understanding of the impact of uncertainty for this parameter on models. Because temperature and pressure conditions are much lower than the laboratory conditions in which bimolecular diffusion parameters were measured, we apply a Bayesian framework, a problem-agnostic framework, to determine parameter estimates and associated uncertainties. We solve the Bayesian calibration problem using the open-source QUESO library which also performs a propagation of uncertainties in the calibrated parameters to temperature and pressure conditions observed in Titan's upper atmosphere. Our results show that, after propagating uncertainty through the Massman model, the uncertainty in molecular diffusion is highly correlated to temperature and we observe no noticeable correlation with pressure. We propagate the calibrated molecular diffusion estimate and associated uncertainty to obtain an estimate with uncertainty due to bimolecular diffusion for the methane molar fraction as a function of altitude. Results show that the uncertainty in methane abundance due to molecular diffusion is in general small compared to eddy diffusion and the chemical kinetics description. However, methane abundance is most sensitive to uncertainty in molecular diffusion above 1200 km where the errors are nontrivial and could have important implications for scientific research based on diffusion models in this altitude range.

  1. Multidecadal variations in the direct and diffuse solar irradiance

    Science.gov (United States)

    Liepert, B. G.

    2005-12-01

    It has been reported that diffuse radiation plays a relatively more important role in photosynthesis and hence in carbon uptake by plants than the total solar irradiance reaching the canopy. Clouds scatter sunlight and also are responsible for the rainfall patterns. Many sites worldwide exist where diffuse solar irradiance has been measured at the ground for several decades. Here we plan to present an overview of existing data sets and their possible temporal variability. The possible causes of this variability will be discussed together with the possible impacts on the water and carbon cycle. Clouds scatter sunlight and increase diffuse light but also form rain whereas aerosols scatter sunlight and potentially dry the atmosphere. An assessment of the magnitude of diffuse radiative variability and the impacts of various natural (volcanic eruptions, clouds) and anthropogenic disturbances will be discussed.

  2. Helium Atmospheres on Warm Neptune- and Sub-Neptune-Sized Exoplanets and Applications to GJ 436 b

    OpenAIRE

    Hu, Renyu; Seager, Sara; Yung, Yuk L.

    2015-01-01

    Warm Neptune- and sub-Neptune-sized exoplanets in orbits smaller than Mercury's are thought to have experienced extensive atmospheric evolution. Here we propose that a potential outcome of this atmospheric evolution is the formation of helium-dominated atmospheres. The hydrodynamic escape rates of Neptune- and sub-Neptune-sized exoplanets are comparable to the diffusion-limited escape rate of hydrogen, and therefore the escape is heavily affected by diffusive separation between hydrogen and h...

  3. The Pearson diffusions: A class of statistically tractable diffusion processes

    DEFF Research Database (Denmark)

    Forman, Julie Lyng; Sørensen, Michael

    The Pearson diffusions is a flexible class of diffusions defined by having linear drift and quadratic squared diffusion coefficient. It is demonstrated that for this class explicit statistical inference is feasible. Explicit optimal martingale estimating func- tions are found, and the corresponding...

  4. Puff-plume atmospheric deposition model for use at SRP in emergency-response situations

    International Nuclear Information System (INIS)

    An atmospheric transport and diffusion model developed for real-time calculation of the location and concentration of toxic or radioactive materials during an accidental release was improved by including deposition calculations

  5. [Diffuse Pulmonary Ossification].

    Science.gov (United States)

    Avsar, K; Behr, J; Morresi-Hauf, A

    2016-04-01

    Diffuse pulmonary ossification (DPO) represents an uncommon condition usually associated with different underlying pulmonary and extrapulmonary diseases. In this work, we discuss eleven patients of our clinic with the diagnosis of a diffuse pulmonary ossification. We focus on histological changes in the surrounding lung tissue. Clinical and radiological findings were analysed. The aim of the study is to collect data for a better understanding of this condition, especially in association with interstitial lung disease.Three patients with interstitial lung disease had histological findings of UIP. The follow-up data of these patients showed a benign course of the disease.The analysis of the clinical data yielded a very heterogenous group. Regarding these fact we assume, that DPO is not an own entity, but a pathological epiphenomenon in the context of different conditions, possibly with pathogenetic overlap. PMID:26829606

  6. Diffused Religion and Prayer

    Directory of Open Access Journals (Sweden)

    Roberto Cipriani

    2011-06-01

    Full Text Available It is quite likely that the origins of prayer are to be found in ancient mourning and bereavement rites. Primeval ritual prayer was codified and handed down socially to become a deep-rooted feature of people’s cultural behavior, so much so, that it may surface again several years later, in the face of death, danger, need, even in the case of relapse from faith and religious practice. Modes of prayer depend on religious experience, on relations between personal prayer and political action, between prayer and forgiveness, and between prayer and approaches to religions. Various forms of prayer exist, from the covert-hidden to the overt-manifest kind. How can they be investigated? How can one, for instance, explore mental prayer? These issues regard the canon of diffused religion and, therefore, of diffused prayer.

  7. Galactic Diffuse Polarized Emission

    Indian Academy of Sciences (India)

    Ettore Carretti

    2011-12-01

    Diffuse polarized emission by synchrotron is a key tool to investigate magnetic fields in the Milky Way, particularly the ordered component of the large scale structure. Key observables are the synchrotron emission itself and the RM is by Faraday rotation. In this paper the main properties of the radio polarized diffuse emission and its use to investigate magnetic fields will be reviewed along with our current understanding of the galactic magnetic field and the data sets available. We will then focus on the future perspective discussing RM-synthesis – the new powerful instrument devised to unlock the information encoded in such an emission – and the surveys currently in progress like S-PASS and GMIMS.

  8. Diffuse Ceiling Ventilation

    DEFF Research Database (Denmark)

    Zhang, Chen; Heiselberg, Per; Nielsen, Peter V.

    2014-01-01

    and numerical studies on diffuse ceiling ventilation. Performance in terms of thermal comfort, air quality, pressure drop as well as radiant cooling potential are examined. Finally, a discussion on the proper design of the suspended ceiling and plenum to achieve a uniform air distribution and surface......As a novel air distribution system, diffuse ceiling ventilation combines the suspended acoustic ceiling with ventilation supply. Due to the low-impulse supply from the large ceiling area, the system does not generate draught when supplying cold air. However, heat sources play an important role on...... thermal comfort in the occupant zone. Another characteristic of this system is its lower pressure drop compared with conventional ventilation systems, which reduces the noise problem and, at the same time, the energy consumption of the fan can be reduced. This review is based on a number of experimental...

  9. Controlled diffusion processes

    CERN Document Server

    Krylov, Nicolai V

    1980-01-01

    This book deals with the optimal control of solutions of fully observable Itô-type stochastic differential equations. The validity of the Bellman differential equation for payoff functions is proved and rules for optimal control strategies are developed. Topics include optimal stopping; one dimensional controlled diffusion; the Lp-estimates of stochastic integral distributions; the existence theorem for stochastic equations; the Itô formula for functions; and the Bellman principle, equation, and normalized equation.

  10. Diffuse Ceiling Ventilation

    DEFF Research Database (Denmark)

    Zhang, Chen; Heiselberg, Per; Nielsen, Peter V.

    2014-01-01

    As a novel air distribution system, diffuse ceiling ventilation combines the suspended acoustic ceiling with ventilation supply. Due to the low-impulse supply from the large ceiling area, the system does not generate draught when supplying cold air. However, heat sources play an important role on...... temperature as well as optimizing the radiant cooling potential by combining with thermal mass is conducted and gives a direction for further investigation....

  11. Diffusion in hydrogeology

    OpenAIRE

    Barker, John A.

    2016-01-01

    The field of hydrogeology is primarily concerned with the flow of water below the ground surface and with transport, normally of solutes and heat, within that water. Many disciplines have contributed to this endeavor which requires skills from across the spectrum of science, engineering and beyond. The diffusion equation describes not only solute transport but also the flow of water, via Darcy’s law. Of particular interest is transport in fractured rock where most of the flow is through th...

  12. Teaching neutron diffusion theory

    International Nuclear Information System (INIS)

    A method has been developed of introducing to, in particular, engineering students, neutron diffusion theory and the relevant one-group neutron equations. This new approach to Fick's law suggests a concise, speedy and physically-based method of introducing the subject which is seen to encompass a wider class of spatially dependent problems and which offers an alternative method of introducing boundary continuity conditions. (U.K.)

  13. Diffusion in aggregated soil.

    OpenAIRE

    Rappoldt, C.

    1992-01-01

    The structure of an aggregated soil is characterized by the distribution of the distance from an arbitrary point in the soil to the nearest macropore or crack. From this distribution an equivalent model system is derived to which a diffusion model can be more easily applied. The model system consists of spherical, or cylindrical or plane aggregates, which do not represent the individual aggregates of the soil, however. The radii of the spheres, cylinders or plane sheets represent different le...

  14. Peridynamic thermal diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Oterkus, Selda [Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ 85721 (United States); Madenci, Erdogan, E-mail: madenci@email.arizona.edu [Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, AZ 85721 (United States); Agwai, Abigail [Intel Corporation, Chandler, AZ 85226 (United States)

    2014-05-15

    This study presents the derivation of ordinary state-based peridynamic heat conduction equation based on the Lagrangian formalism. The peridynamic heat conduction parameters are related to those of the classical theory. An explicit time stepping scheme is adopted for numerical solution of various benchmark problems with known solutions. It paves the way for applying the peridynamic theory to other physical fields such as neutronic diffusion and electrical potential distribution.

  15. MAVEN Imaging UV Spectrograph Results on the Mars Atmosphere and Atmospheric Escape

    Science.gov (United States)

    Chaffin, Michael; Schneider, Nick; McClintock, Bill; Stewart, Ian; Deighan, Justin; Jain, Sonal; Clarke, John; Holsclaw, Greg; Montmessin, Franck; Lefevre, Franck; Chaufray, Jean-Yves; Stiepen, Arnaud; Crismani, Matteo; Mayyasi, Majd; Evans, Scott; Stevens, Mike; Yelle, Roger; Jakosky, Bruce

    2016-04-01

    The Imaging Ultraviolet Spectrograph (IUVS) is one of nine science instruments aboard the Mars Atmosphere and Volatile and EvolutioN (MAVEN) spacecraft, whose payload is dedicated to exploring the upper atmosphere of Mars and understanding the magnitude and drivers of Mars' atmospheric escape rate. IUVS uses ultraviolet light to investigate the lower and upper atmosphere and ionosphere of Mars. The instrument is among the most powerful spectrographs sent to another planet, with several key capabilities: (1) separate Far-UV & Mid-UV channels for stray light control, (2) a high resolution echelle mode to resolve deuterium and hydrogen emission, (3) internal instrument pointing and scanning capabilities to allow complete mapping and nearly continuous operation, and (4) optimization for airglow studies. IUVS, along with other MAVEN instruments, obtains a comprehensive picture of the current state of the Mars upper atmosphere and ionosphere and the processes that control atmospheric escape. We present an overview of selected IUVS results, including (1) the discovery of diffuse aurora at Mars, and its contrast with previously detected discrete aurora localized near crustal magnetic fields; (2) widespread detection of mesospheric clouds; (3) Significant seasonal and short-timescale variability in thermospheric composition; (4) Global ozone maps spanning six months of seasonal evolution; and (5) mapping of the Mars H and O coronas, deriving the escape rates of H and O and their variability. This last is of particular importance for understanding the long term evolution of Mars and its atmosphere, with the observed preset escape of H potentially capable of removing a large fraction of Mars' initial water inventory, and the differential escape of O relative to H potentially providing a net source of oxidizing power to the atmosphere and planet at present, in contrast with a photochemical theory that predicts stoichiometrically balanced escape. The atmospheric and escape

  16. Entropy, Duality and Cross Diffusion

    OpenAIRE

    Desvillettes, Laurent; Lepoutre, Thomas; Moussa, Ayman

    2013-01-01

    This paper is devoted to the use of the entropy and duality methods for the existence theory of reaction-cross diffusion systems consisting of two equations, in any dimension of space. Those systems appear in population dynamics when the diffusion rates of individuals of two species depend on the concentration of individuals of the same species (self-diffusion), or of the other species (cross diffusion).

  17. Diffusion-Exchange Weighted Imaging

    OpenAIRE

    Saadallah Ramadan

    2009-01-01

    A method has been developed whereby diffusion and exchange in micro cellular structures in the human brain are correlated to produce a new type of image contrast leading to determination of water exchange rates in vivo. The diffusion method relies on differential apparent diffusion coefficients as detectable nuclei exchange between adjacent compartments marked with different apparent diffusion coefficient values (e.g. intra- and extra-cellular compartments). A new pulse sequence was developed...

  18. Helium Atmospheres on Warm Neptune- and Sub-Neptune-Sized Exoplanets and Applications to GJ 436 b

    CERN Document Server

    Hu, Renyu; Yung, Yuk L

    2015-01-01

    Warm Neptune- and sub-Neptune-sized exoplanets in orbits smaller than Mercury's are thought to have experienced extensive atmospheric evolution. Here we propose that a potential outcome of this atmospheric evolution is the formation of helium-dominated atmospheres. The hydrodynamic escape rates of Neptune- and sub-Neptune-sized exoplanets are comparable to the diffusion-limited escape rate of hydrogen, and therefore the escape is heavily affected by diffusive separation between hydrogen and helium. A helium atmosphere can thus be formed -- from a primordial hydrogen-helium atmosphere -- via atmospheric hydrodynamic escape from the planet. The helium atmosphere has very different abundances of major carbon and oxygen species from those of a hydrogen atmosphere, leading to distinctive transmission and thermal emission spectral features. In particular, the hypothesis of a helium-dominated atmosphere can explain the thermal emission spectrum of GJ 436 b, a warm Neptune-sized exoplanet, while also consistent with ...

  19. Uncertainty for calculating transport on Titan: a probabilistic description of bimolecular diffusion parameters

    CERN Document Server

    Plessis, Sylvain; Mandt, Kathy; Greathouse, Thomas; Luspay-Kuti, Adrienn

    2015-01-01

    Bimolecular diffusion coefficients are important parameters used by atmospheric models to calculate altitude profiles of minor constituents in an atmosphere. Unfortunately, laboratory measurements of these coefficients were never conducted at temperature conditions relevant to the atmosphere of Titan. Here we conduct a detailed uncertainty analysis of the bimolecular diffusion coefficient parameters as applied to Titan's upper atmosphere to provide a better understanding of the impact of uncertainty for this parameter on models. Because temperature and pressure conditions are much lower than the laboratory conditions in which bimolecular diffusion parameters were measured, we apply a Bayesian framework, a problem-agnostic framework, to determine parameter estimates and associated uncertainties. We solve the Bayesian calibration problem using the open-source QUESO library which also performs a propagation of uncertainties in the calibrated parameters to temperature and pressure conditions observed in Titan's u...

  20. Pluto's atmosphere near perihelion

    International Nuclear Information System (INIS)

    A recent stellar occultation has confirmed predictions that Pluto has an atmosphere which is sufficiently thick to uniformly envelope the planet and to extend far above the surface. Pluto's atmosphere consists of methane and perhaps other volatile gases at temperatures below their freezing points; it should regulate the surface temperature of its volatile ices to a globally uniform value. As Pluto approaches and passes through perihelion, a seasonal maximum in the atmospheric bulk and a corresponding minimum in the exposed volatile ice abundance is expected to occur. The lag in maximum atmospheric bulk relative to perihelion will be diagnostic of the surface thermal properties. An estimate of Pluto's atmospheric bulk may result if a global darkening (resulting from the disappearance of the seasonally deposited frosts) occurs before the time of maximum atmospheric bulk. The ice deposited shortly after perihelion may be diagnostic of the composition of Pluto's volatile reservoir

  1. Measurement of the Atmospheric $\

    CERN Document Server

    Aartsen, M G; Abdou, Y; Ackermann, M; Adams, J; Aguilar, J A; Ahlers, M; Altmann, D; Andeen, K; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Baum, V; Bay, R; Beattie, K; Beatty, J J; Bechet, S; Tjus, J Becker; Becker, K -H; Bell, M; Benabderrahmane, M L; BenZvi, S; Berdermann, J; Berghaus, P; Berley, D; Bernardini, E; Bertrand, D; Besson, D Z; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohaichuk, S; Bohm, C; Bose1, D; Boser, S; Botner, O; Brayeur, L; Brown, A M; Bruijn, R; Brunner, J; Buitink, S; Carson, M; Casey, J; Casier, M; Chirkin, D; Christy, B; Clark, K; Clevermann, F; Cohen, S; Cowen, D F; Silva, A H Cruz; Danninger, M; Daughhetee, J; Davis, J C; De Clercq, C; De Ridder, S; Descamps, F; Desiati, P; de Vries-Uiterweerd, G; DeYoung, T; Diaz-Velez, J C; Dreyer, J; Dumm, J P; Dunkman, M; Eagan, R; Eberhardt, B; Eisch, J; Ellsworth, R W; Engdegard, O; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Feusels, T; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Franckowiak, A; Franke, R; Frantzen, K; Fuchs, T; Gaisser, T K; Gallagher, J; Gerhardt, L; Gladstone, L; Glusenkamp, T; Goldschmidt, A; Golup, G; Goodman, J A; Gora, D; Grant, D; Gross, A; Grullon, S; Gurtner, M; Ha, C; Ismail, A Haj; Hallgren, A; Halzen, F; Hanson, K; Heereman, D; Heimann, P; Heinen, D; Helbing, K; Hellauer, R; Hickford, S; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huelsnitz, W; Hulth, P O; Hultqvist, K; Hussain, S; Ishihara, A; Jacobi, E; Jacobsen, J; Japaridze, G S; Jlelati, O; Kappes, A; Karg, T; Karle, A; Kiryluk, J; Kislat, F; Klas, J; Klein, S R; Kohne, J -H; Kohnen, G; Kolanoski, H; Kopke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Krasberg, M; Kroll, G; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Landsman, H; Larson, M J; Lauer, R; Lesiak-Bzdak, M; Lunemann, J; Madsen, J; Maruyama, R; Mase, K; Matis, H S; McNally, F; Meagher, K; Merck, M; Meszaros, P; Meures, T; Miarecki, S; Middell, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Nahnhauer, R; Naumann, U; Nowicki, S C; Nygren, D R; Obertacke, A; Odrowski, S; Olivas, A; Olivo, M; O'Murchadha, A; Panknin, S; Paul, L; Pepper, J A; Heros, C Perez de los; Pieloth, D; Pirk, N; Posselt, J; Price, P B; Przybylski, G T; Radel, L; Rawlins, K; Redl, P; Resconi, E; Rhode, W; Ribordy, M; Richman, M; Riedel, B; Rodrigues, J P; Rott, C; Ruhe, T; Ruzybayev, B; Ryckbosch, D; Saba, S M; Salameh, T; Sander, H -G; Santander, M; Sarkar, S; Schatto, K; Scheel, M; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schoneberg, S; Schonherr, L; Schonwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Seo, S H; Sestayo, Y; Seunarine, S; Sheremata, C; Smith, M W E; Soiron, M; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stasik, A; Stezelberger, T; Stokstad, R G; Stoss, A; Strahler, E A; Strom, R; Sullivan, G W; Taavola, H; Taboada, I; Tamburro, A; Ter-Antonyan, S; Tilav, S; Toale, P A; Toscano, S; Usner, M; van der Drift, D; van Eijndhoven, N; Van Overloop, A; van Santen, J; Vehring, M; Voge1, M; Vraeghe, M; Walck, C; Waldenmaier, T; Wallraff, M; Walter, M; Wasserman, R; Weaver, Ch; Wendt, C; Westerhoff, S; Whitehorn, N; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, C; Xu, D L; Xu, X W; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zierke, S; Zilles, A; Zoll, M

    2012-01-01

    We report the first observation in a high energy neutrino telescope of cascades induced by atmospheric electron neutrinos and by neutral current interactions of atmospheric neutrinos of all flavors. Using data recorded during the first year of operation of IceCube's DeepCore low energy extension, a sample of 1029 events is observed in 281 days of data. The number of observed cascades is $N_{\\rm cascade} = 496 \\pm 66 (stat.) \\pm 88(syst.)$ and the rest of the sample consists of residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is determined in the energy range between approximately 80 GeV and 6 TeV and is consistent with models of atmospheric neutrinos.

  2. Atmospheric Circulation of Exoplanets

    CERN Document Server

    Showman, Adam P; Menou, Kristen

    2009-01-01

    We survey the basic principles of atmospheric dynamics relevant to explaining existing and future observations of exoplanets, both gas giant and terrestrial. Given the paucity of data on exoplanet atmospheres, our approach is to emphasize fundamental principles and insights gained from Solar-System studies that are likely to be generalizable to exoplanets. We begin by presenting the hierarchy of basic equations used in atmospheric dynamics, including the Navier-Stokes, primitive, shallow-water, and two-dimensional nondivergent models. We then survey key concepts in atmospheric dynamics, including the importance of planetary rotation, the concept of balance, and scaling arguments to show how turbulent interactions generally produce large-scale east-west banding on rotating planets. We next turn to issues specific to giant planets, including their expected interior and atmospheric thermal structures, the implications for their wind patterns, and mechanisms to pump their east-west jets. Hot Jupiter atmospheric d...

  3. Fair weather atmospheric electricity

    International Nuclear Information System (INIS)

    Not long after Franklin's iconic studies, an atmospheric electric field was discovered in 'fair weather' regions, well away from thunderstorms. The origin of the fair weather field was sought by Lord Kelvin, through development of electrostatic instrumentation and early data logging techniques, but was ultimately explained through the global circuit model of C.T.R. Wilson. In Wilson's model, charge exchanged by disturbed weather electrifies the ionosphere, and returns via a small vertical current density in fair weather regions. New insights into the relevance of fair weather atmospheric electricity to terrestrial and planetary atmospheres are now emerging. For example, there is a possible role of the global circuit current density in atmospheric processes, such as cloud formation. Beyond natural atmospheric processes, a novel practical application is the use of early atmospheric electrostatic investigations to provide quantitative information on past urban air pollution.

  4. Photochemistry in planetary atmospheres

    Science.gov (United States)

    Levine, J. S.; Graedel, T. E.

    1981-01-01

    Widely varying paths of evolutionary history, atmospheric processes, solar fluxes, and temperatures have produced vastly different planetary atmospheres. The similarities and differences between the earth atmosphere and those of the terrestrial planets (Venus and Mars) and of the Jovian planets are discussed in detail; consideration is also given to the photochemistry of Saturn, Uranus, Pluto, Neptune, Titan, and Triton. Changes in the earth's ancient atmosphere are described, and problems of interest in the earth's present troposphere are discussed, including the down wind effect, plume interactions, aerosol nucleation and growth, acid rain, and the fate of terpenes. Temperature fluctuations in the four principal layers of the earth's atmosphere, predicted decreases in the ozone concentration as a function of time, and spectra of particles in the earth's upper atmosphere are also presented. Finally, the vertical structure of the Venus cloud system and the thermal structure of the Jovian planets are shown graphically.

  5. Oxygen transport in waterlogged soils, Part II. Diffusion coefficients

    International Nuclear Information System (INIS)

    Several equations are available for Oxygen Transport in Waterlogged Soils and have been used for soils and plants. All of them are some form of first Fick's law as given by dQ = - DA(dc/dx)/dt. This equation illustrates some important aspects of aeration in waterlogged soils; first, D is a property of the medium and the gas, and is affected by temperature T. Likewise, the amount of diffusing substance dQ in dt is a direct function of the cross sectional area A and inversely proportional to the distance x. In fact, increasing the water content of air-dry soil, drastically decreases A and creates a further resistance for the flow of oxygen through water films around root plants, soil micro organisms and soil aggregates. The solid phase is also limiting the cross-section of surface of the free gaseous diffusion and the length and tortuosity of diffusion path in soil. In most of cases, soil gas porosity and tortuosity of soil voids are expressed in the equations of diffusion as a broad 'diffusion coefficient' (apparent coefficient diffusion). The process of soil respiration is complicated, involves many parameters, and is difficult to realistically quantify. With regard to the oxygen supply, it is convenient to distinguish macro and micro models, and hence, the flux of oxygen is assumed to have two steps. The first step is related to oxygen diffusion from the atmosphere and the air-filled porosity. The second step is related to the oxygen diffusion through water-films in and around plant roots, soil micro organisms and aggregates. Because of these models we obtain coefficients of macro or micro diffusion, rates of macro or micro diffusion, etc. In the macro diffusion process oxygen is transferred in the soil profile, mainly from the soil surface to a certain depth of the root zone, while micro diffusion deals with the flux over very short distances. Both processes, macro and micro diffusion are highly influenced by soil water content. Of course, if water is added to

  6. Energy balance and plume dynamics in Triton's lower atmosphere

    Science.gov (United States)

    Yelle, Roger V.; Lunine, Jonathan I.; Hunten, Donald M.

    1991-01-01

    The present study of the thermal balance-affecting relationships among Triton lower atmosphere thermal conduction, eddy mixing, condensation, and radiative heating indicates that, while the temperature gradient is negative in the lower atmosphere, it becomes positive at higher altitudes due to the downward conduction of ionospheric heat. This temperature profile is essentially consistent with radio-occultation experiment data; the geyser-like plumes observed by Voyager suggest that the Trioton atmosphere's convective and conductive regions join near 10-km altitude, and that the values inferred for the eddy diffusion and heat-transport coefficients indicate a profile reminiscent of the earth's.

  7. Designing Dynamic Atmospheres

    DEFF Research Database (Denmark)

    Højlund, Marie; Kinch, Sofie

    2012-01-01

    This paper addresses the notion of atmospheres from a designerly perspective, and discusses temporal challenges facing interaction designers when acknowledging the dynamic character of it. As atmospheres are created in the relation between body, space, and time, a pragmatic approach seems useful......, in order to encompass dynamic atmospheres as intertwined, constantly shifting negotiations between the rhythms of the environment and of the body. The contribution of this paper is to unravel these negotiations of diverse rhythms, in order to approach dynamic atmospheres from an operational...

  8. Atmospheric Measurements Laboratory (AML)

    Data.gov (United States)

    Federal Laboratory Consortium — The Atmospheric Measurements Laboratory (AML) is one of the nation's leading research facilities for understanding aerosols, clouds, and their interactions. The AML...

  9. Measuring methods of matrix diffusion

    International Nuclear Information System (INIS)

    In Finland the spent nuclear fuel is planned to be disposed of at large depths in crystalline bedrock. The radionuclides which are dissolved in the groundwater may be able to diffuse into the micropores of the porous rock matrix and thus be withdrawn from the flowing water in the fractures. This phenomenon is called matrix diffusion. A review over matrix diffusion is presented in the study. The main interest is directed to the diffusion of non-sorbing species. The review covers diffusion experiments and measurements of porosity, pore size, specific surface area and water permeability

  10. Advanced diffusion processes and phenomena

    CERN Document Server

    Öchsner, Andreas; Belova, Irina

    2014-01-01

    This topical volume on Advanced Diffusion Processes and Phenomena addresses diffusion in a wider sense of not only mass diffusion but also heat diffusion in fluids and solids. Both diffusion phenomena play an important role in the characterization of engineering materials and corresponding structures. Understanding these different transport phenomena at many levels, from atomistic to macro, has therefore long attracted the attention of many researchers in materials science and engineering and related disciplines. The present topical volume captures a representative cross-section of some of the

  11. Search for a diffuse flux of high-energy $\

    CERN Document Server

    Aguilar, J A; Albert, A; André, M; Anghinolfi, M; Anton, G; Anvar, S; Ardid, M; Jesus, A C Assis; Astraatmadja, T; Aubert, J-J; Auer, R; Baret, B; Basa, S; Bazzotti, M; Bertin, V; Biagi, S; Bigongiari, C; Bogazzi, C; Bou-Cabo, M; Bouwhuis, M C; Brown, A M; Brunner, J; Busto, J; Camarena, F; Capone, A; Carloganu, C; Carminati, G; Carr, J; Cecchini, S; Charvis, Ph; Chiarusi, T; Circella, M; Coniglione, R; Costantini, H; Cottini, N; Coyle, P; Curtil, C; Decowski, M P; Dekeyser, I; Deschamps, A; Donzaud, C; Dornic, D; Dorosti, Q; Drouhin, D; Eberl, T; Emanuele, U; Ernenwein, J-P; Escoffier, S; Fehr, F; Flaminio, V; Folger, F; Fritsch, U; Fuda, J-L; Galata, S; Gay, P; Giacomelli, G; Gomez-Gonzalez, J P; Graf, K; Guillard, G; Halladjian, G; Hallewell, G; van Haren, H; Heijboer, A J; Hello, Y; Hernandez-Rey, J J; Herold, B; Hossl, J; Hsu, C C; de Jong, M; Kadler, M; Kalantar-Nayestanaki, N; Kalekin, O; Kappes, A; Katz, U; Kooijman, P; Kopper, C; Kouchner, A; Kulikovskiy, V; Lahmann, R; Lamare, P; Larosa, G; Lefèvre, D; Lim, G; Presti, D Lo; Loehner, H; Loucatos, S; Lucarelli, F; Mangano, S; Marcelin, M; Margiotta, A; Martinez-Mora, J A; Mazure, A; Meli, A; Montaruli, T; Morganti, M; Moscoso, L; Motz, H; Naumann, C; Neff, M; Palioselitis, D; Pavalas, G E; Payre, P; Petrovic, J; Piattelli, P; Picot-Clemente, N; Picq, C; Popa, V; Pradier, T; Presani, E; Racca, C; Reed, C; Riccobene, G; Richardt, C; Roensch, K; Rostovtsev, A; Rujoiu, M; Russo, G V; Salesa, F; Sapienza, P; Schock, F; Schuller, J-P; Shanidze, R; Simeone, F; Spies, A; Spurio, M; Steijger, J J M; Stolarczyk, Th; Taiuti, M; Tamburini, C; Tasca, L; Toscano, S; Vallage, B; Van Elewyck, V; Vannoni, G; Vecchi, M; Vernin, P; Wijnker, G; de Wolf, E; Yepes, H; Zaborov, D; Zornoza, J D; Zuniga, J

    2010-01-01

    A search for a diffuse flux of astrophysical muon neutrinos, using data collected by the ANTARES neutrino telescope is presented. A $(0.83\\times 2\\pi)$ sr sky was monitored for a total of 334 days of equivalent live time. The searched signal corresponds to an excess of events, produced by astrophysical sources, over the expected atmospheric neutrino background. The observed number of events is found compatible with the background expectation. Assuming an $E^{-2}$ flux spectrum, a 90% c.l. upper limit on the diffuse $\

  12. Atmospheric corrosion model and monitor for low cost solar arrays

    Science.gov (United States)

    Kaelble, D. H.; Mansfeld, F. B.; Jeanjaquet, S. L.; Kendig, M.

    1981-01-01

    An atmospheric corrosion model and corrosion monitoring system has been developed for low cost solar arrays (LSA). The corrosion model predicts that corrosion rate is the product of the surface condensation probability of water vapor and the diffusion controlled corrosion current. This corrosion model is verified by simultaneous monitoring of weather conditions and corrosion rates at the solar array test site at Mead, Nebraska.

  13. Use and abuse of diffusion

    International Nuclear Information System (INIS)

    Diffusion in a bounded region (or diffusive mass transport) can be seen from at least three platforms: - chemistry of he Fick's equation; - chemical engineering. To pose a particular problem we have to provide some additional conditions (initial conditions, boundary conditions and further). As we understood it in all cases diffusion is considered in an open region (in other words in one phase). Chemical engineering however brings an idea of 'diffusion' between phases. We claim that there isn't diffusion between phases. One can only consider mass transport between phases. Mass transport (or transfer in chemical engineering jargon) from one phase to another composes of: diffusion in first phase partition at an interface diffusion in second phase. (author)

  14. Coupled Diffusion Processes

    Institute of Scientific and Technical Information of China (English)

    章复熹

    2004-01-01

    @@ Coupled diffusion processes (or CDP for short) model the systems of molecular motors,which attract much interest from physicists and biologists in recent years[1,2,9,14,4,7,21]. The protein moves along a filament called the track, and it is crucial that there are several inner states of the protein and the underlying chemical reaction causes transitions among different inner states,while chemical energy can be converted to mechanical energy by rachet effects[5,3,2,14,12].

  15. Diffuse esophageal spasm

    International Nuclear Information System (INIS)

    Radiologic and manometric findings were correlated in 17 patients with diffuse esophageal spasm (DES). All patients initially had chest pain and/or dysphagia and had a manometric diagnosis of DES. Mean percentage of normal peristalsis manometrically was 46% (range, 20%-80%). Based on radiologic examination, an esophageal motor disorder consistent with DES was diagnosed in 12 of 17 patients, and there was one misinterpretation of achalasia. Radiologic detection was not related significantly to the percentage of peristalsis seen on manometric examination. Mean esophageal wall thickness as measured radiographically in patients with DES was 2.6 mm, compared with 2.5 mm in 17 individuals with normal results of manometry

  16. Hydrogen diffusion in aluminum

    International Nuclear Information System (INIS)

    Recent findings on the H-Al system are discussed in terms of the kinetic behavior predicted for solutions of H in metals where there is a high concentration of vacancies in thermal equilibrium. Solubility and diffusivity plots for H in Al are presented together with the corresponding equations. An analysis of the results obtained suggests that direct thermodynamic measurement of the i-vacancy binding energy may be possible through equilibrating with a second phase where the chemical potential of i is such that all the vacancy-related sites are occupied

  17. Distributed Control Diffusion

    DEFF Research Database (Denmark)

    Schultz, Ulrik Pagh

    2007-01-01

    . Programming a modular, self-reconfigurable robot is however a complicated task: the robot is essentially a real-time, distributed embedded system, where control and communication paths often are tightly coupled to the current physical configuration of the robot. To facilitate the task of programming modular....... The prototype relies on a simple virtual machine with a dedicated instruction set, allowing mobile programs to migrate between the modules that constitute a robot. Through a number of simulated experiments, we should how a single rule-based controller program implemented using distributed control diffusion can...

  18. Planar Dirac diffusion

    CERN Document Server

    De Leo, Stefano

    2010-01-01

    We present the results of the planar diffusion of a Dirac particle by step and barrier potentials, when the incoming wave impinges at an arbitrary angle with the potential. Except for right-angle incidence this process is characterized by the appearance of spin flip terms. For the step potential, spin flip occurs for both transmitted and reflected waves. However, we find no spin flip in the transmitted barrier result. This is surprising because the barrier result may be derived directly from a two-step calculation. We demonstrate that the spin flip cancellation indeed occurs for each particle (wave packet) contribution.

  19. Kuiper Prize Lecture - Escape of atmospheres, ancient and modern

    Energy Technology Data Exchange (ETDEWEB)

    Hunten, D.M. (Arizona Univ., Tucson (USA))

    1990-05-01

    A development history is presented for theories concerning planetary atmosphere gas-escape phenomena, which although firmly grounded in the kinetics of gases achieved truly productive results only after spacecraft remote sensing data for both the earth atmosphere and the planets became widely available. The most significant initial advances, encompassing diffusion-limited flow, nonthermal escape mechanisms, bound nonthermal coronas, and mass fractionation during early blowoff, followed from sounding rocket studies of the earth upper atmosphere, Mariner 5 results on hydrogen near Venus, and the nitrogen isotopic composition discovered by Viking in Mars. Attention has more recently been given to the xenon isotopic patterns in various atmospheres, as well as to the puzzling behavior of the Io atmosphere and plasma torus. 126 refs.

  20. Kuiper Prize Lecture - Escape of atmospheres, ancient and modern

    International Nuclear Information System (INIS)

    A development history is presented for theories concerning planetary atmosphere gas-escape phenomena, which although firmly grounded in the kinetics of gases achieved truly productive results only after spacecraft remote sensing data for both the earth atmosphere and the planets became widely available. The most significant initial advances, encompassing diffusion-limited flow, nonthermal escape mechanisms, bound nonthermal coronas, and mass fractionation during early blowoff, followed from sounding rocket studies of the earth upper atmosphere, Mariner 5 results on hydrogen near Venus, and the nitrogen isotopic composition discovered by Viking in Mars. Attention has more recently been given to the xenon isotopic patterns in various atmospheres, as well as to the puzzling behavior of the Io atmosphere and plasma torus. 126 refs

  1. Update on Atmospheric Neutrinos

    CERN Document Server

    González-Garciá, M Concepción; Peres, O L G; Stanev, T; Valle, José W F

    1998-01-01

    We discuss the impact of recent experimental results on the determination of atmospheric neutrino oscillation parameters. We use all published results on atmospheric neutrinos, including the preliminary large statistics data of Super-Kamiokande. We re-analyze the data in terms of both $\

  2. Atmosphere and Heritage

    DEFF Research Database (Denmark)

    Ventzel Riis, Nina

    2012-01-01

    -between of the materials. This is what we identify as atmosphere, an enveloping phenomenon that surrounds and affects our sensuous system and well-being when we approach, enter, stay or move in a building. When we leave the building again we carry this atmospheric multi-sensory experience with us without adequate methods...

  3. Urban atmospheric contamination

    International Nuclear Information System (INIS)

    The problems of contamination are not only limited to this century, pale pathology evidences of the effects of the contamination of the air exist in interiors in the health of the old ones; the article mention the elements that configure the problem of the atmospheric contamination, atmospheric pollutants and emission sources, orography condition and effects induced by the urbanization process

  4. Turbulent transport in the atmospheric surface layer

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern [Dept. of Physical Geography and Ecosystem Science, Lund Univ., Lund (Sweden)

    2012-04-15

    In the modelling of transport and accumulation of the radioactive isotope carbon-14 (C-14) in the case of a potential release from a future repository of radioactive waste, it is important to describe the transport of the isotope in the atmosphere. This report aims to describe the turbulent transport within the lower part of the atmosphere; the inertial surface layer and the roughness sublayer. Transport in the inertial surface layer is dependent on several factors, whereof some can be neglected under certain circumstances. Under steady state conditions, fully developed turbulent conditions, in flat and horizontal homogeneous areas, it is possible to apply an eddy diffusivity approach for estimating vertical transport of C. The eddy diffusivity model assumes that there is proportionality between the vertical gradient and the transport of C. The eddy diffusivity is depending on the atmospheric turbulence, which is affected by the interaction between mean wind and friction of the ground surface and of the sensible heat flux in the atmosphere. In this report, it is described how eddy diffusivity of the inertial surface layer can be estimated from 3-d wind measurements and measurements of sensible heat fluxes. It is also described how to estimate the eddy diffusivity in the inertial surface layer from profile measurements of temperature and wind speed. Close to the canopy, wind and C profiles are influenced by effects of the surface roughness; this section of the atmosphere is called the roughness sublayer. Its height is up to {approx}3 times the height of the plant canopy. When the mean wind interacts with the canopy, turbulence is not only produced by shear stress and buoyancy, it is additionally created by wakes, which are formed behind the plants. Turbulence is higher than it would be over a flat surface, and the turbulent transport is hereby more efficient. Above the plant canopy, but still within the roughness sublayer, a function that compensates for the effect

  5. Magneto-atmospheric waves

    Science.gov (United States)

    Thomas, J. H.

    1983-01-01

    A theoretical treatment of magneto-atmospheric waves is presented and applied to the modelling of waves in the solar atmosphere. The waves arise in compressible, stratified, electrically conductive atmospheres within gravitational fields when permeated by a magnetic field. Compression, buoyancy, and distortion of the magnetic field all contribute to the existence of the waves. Basic linearized equations are introduced to describe the waves and attention is given to plane-stratified atmospheres and their stability. A dispersion relation is defined for wave propagation in a plane-stratified atmosphere when there are no plane-wave solutions. Solutions are found for the full wave equation in the presence of either a vertical or a horizontal magnetic field. The theory is applied to describing waves in sunspots, in penumbrae, and flare-induced coronal disturbances.

  6. Diffusion in Solids Fundamentals, Methods, Materials, Diffusion-Controlled Processes

    CERN Document Server

    Mehrer, Helmut

    2007-01-01

    Diffusion is a vital topic in solid-state physics and chemistry, physical metallurgy and materials science. Diffusion processes are ubiquitous in solids at elevated temperatures. A thorough understanding of diffusion in materials is crucial for materials development and engineering. This book first gives an account of the central aspects of diffusion in solids, for which the necessary background is a course in solid state physics. It then provides easy access to important information about diffuson in metals, alloys, semiconductors, ion-conducting materials, glasses and nanomaterials. Several diffusion-controlled phenomena, including ionic conduction, grain-boundary and dislocation pipe diffusion, are considered as well. Graduate students in solid-state physics, physical metallurgy, materials science, physical and inorganic chemistry or geophysics will benefit from this book as will physicists, chemists, metallurgists, materials engineers in academic and industrial research laboratories.

  7. A simple flow analysis of diffuser-getter-diffuser systems

    International Nuclear Information System (INIS)

    Tritium clean-up systems typically deploy gas processing technologies between stages of palladium-silver (Pd/Ag) diffusers/permeators. The number of diffusers positioned before and after a gas clean-up process to obtain optimal system performance will vary with feed gas inert composition. A simple method to analyze optimal diffuser configuration is presented. The method assumes equilibrium across the Pd/Ag tubes and system flows are limited by diffuser vacuum pump speeds preceding or following the clean-up process. A plot of system feed as a function of inert feed gas composition for various diffuser configuration allows selection of a diffuser configuration for maximum throughput based on feed gas composition. (authors)

  8. The diffusion of microfinance.

    Science.gov (United States)

    Banerjee, Abhijit; Chandrasekhar, Arun G; Duflo, Esther; Jackson, Matthew O

    2013-07-26

    To study the impact of the choice of injection points in the diffusion of a new product in a society, we developed a model of word-of-mouth diffusion and then applied it to data on social networks and participation in a newly available microfinance loan program in 43 Indian villages. Our model allows us to distinguish information passing among neighbors from direct influence of neighbors' participation decisions, as well as information passing by participants versus nonparticipants. The model estimates suggest that participants are seven times as likely to pass information compared to informed nonparticipants, but information passed by nonparticipants still accounts for roughly one-third of eventual participation. An informed household is not more likely to participate if its informed friends participate. We then propose two new measures of how effective a given household would be as an injection point. We show that the centrality of the injection points according to these measures constitutes a strong and significant predictor of eventual village-level participation. PMID:23888042

  9. Diffuse infiltrative lung disease

    International Nuclear Information System (INIS)

    The authors discuss their approach to the diagnosis and management of patients with DILD. Gallium scans play a central role in this process. Not only do they help them decide whom to biopsy, but also where to biopsy. The scans can be used for the early detection of disease in a high-risk population, for following the progression and regression of disease, for the regulation of medication, and for the evaluation of therapy. Bronchoalveolar lung lavage appears to be equally sensitive. However, patients are less willing to undergo repeated fiberoptic bronchoscopies than lung scans. Both tests may prove useful, one complementing the other. Gallium imaging has also been utilized by the authors in select patients with questionable diffuse lung infiltrates roentgenographically or with a normal chest roentgenogram, chronic respiratory symptoms, and abnormal pulmonary function studies. An abnormal gallium lung scan in these clinical situations helps them select which patients have a diffuse active pulmonary process meriting transbronchial biopsies. This has proven to be of particular value in the management of older patients

  10. Apparatus for diffusion separation

    International Nuclear Information System (INIS)

    A diffuser separator apparatus is described which comprises a plurality of flow channels in a single stage. Each of said channels has an inlet port and an outlet port and a constant cross sectional area between said ports. At least a portion of the defining surface of each of said channels is a diffusion separation membrane, and each of said channels is a different cross sectional area. Means are provided for connecting said channels in series so that each successive channel of said series has a smaller cross sectional area than the previous channel of said series. Also provided are a source of gaseous mixture, individual means for flowing said gaseous mixture to the inlet port of each of said channels, gas receiving and analyzing means, individual means for flowing gas passing from each of said outlet ports and means for flowing gas passing through said membranes to said receiving and analyzing means, and individual means for connecting the outlet port of each channel with the inlet port of the channel having the next smaller cross sectional area

  11. Estimation of diffusion parameters for discretely observed diffusion processes

    OpenAIRE

    Sørensen, Helle

    2002-01-01

    We study the estimation of diffusion parameters for one-dimensional, ergodic diffusion processes that are discretely observed. We discuss a method based on a functional relationship between the drift function, the diffusion function and the invariant density and use empirical process theory to show that the estimator is $\\sqrt{n}$-consistent and in certain cases weakly convergent. The Chan-Karolyi-Longstaff-Sanders (CKLS) model is used as an example and a numerical example i...

  12. Diffusion limited aggregation. The role of surface diffusion

    Science.gov (United States)

    García-Ruiz, Juan M.; Otálora, Fermín

    1991-11-01

    We present a growth model in which the hitting particles are able to diffuse to more stable growth sites in the perimeter of a cluster growing by diffusion limited aggregation. By tuning the diffusion path Ls, the morphological output - from disordered fractal to perfect single crystals - can be controlled. Instabilities appear when the mean length of the crystal faces Lf are greater than 2 Ls.

  13. Anisotropic diffusion in confined colloidal dispersions: The evanescent diffusivity

    OpenAIRE

    Swan, James W.; Brady, John F.

    2011-01-01

    We employ an analogy to traditional dynamic light scattering to describe the inhomogeneous and anisotropic diffusion of colloid particles near a solid boundary measured via evanescent wave dynamic light scattering. Following this approach, we generate new expressions for the short-time self- and collective diffusivities of colloidal dispersions with arbitrary volume fraction. We use these expressions in combination with accelerated Stokesian dynamics simulations to calculate the diffusivities...

  14. Numerical simulation of asymmetric particle precipitation by pitch angle diffusion

    Science.gov (United States)

    Thorne, Richard M.; Abel, Robert W.; Summers, Danny

    1996-11-01

    A numerical simulation code is developed to evaluate the loss rate of particles trapped in a mirror magnetic field geometry with asymmetric loss cones. The one-dimensional model can accommodate particle diffusion at any prescribed rate and loss cones of any prescribed sizes, and it incorporates the important effect of atmospheric backscattering. Numerical solutions for the loss cone particle distribution function calculated for the case of equal loss cones provide an acceptable simulation of the well-known modified Bessel function solution. The code provides the first quantitative solutions for any specified rate of pitch angle scattering for the general case of arbitrary asymmetry in loss cone size. In the case of weak or moderate diffusion the ratio of particle precipitation fluxes into the two loss cones can provide a sensitive measurement of the rate of particle scattering, but to utilize this important diagnostic property, one must also have information on the fraction of particles that are backscattered from the atmosphere.

  15. Transport properties in the Jovian atmosphere

    Science.gov (United States)

    Biolsi, L.

    1978-01-01

    Transport properties in a Jupiter-like atmosphere (89 mol % hydrogen and 11 mol % helium) are obtained by using the method of the kinetic theory of gases. The transport collision integrals are calculated by fitting various two-body semiempirical interaction potentials for which the collision integrals are tabulated to ab initio quantum mechanical calculations of the two-body interactions. The collision integrals are used to calculate the binary diffusion coefficients, viscosity, and 'total' thermal conductivity of the pure gases and the gas mixtures at 1-atm pressure from 1000 K to 25,000 K.

  16. Tropical Atmospheric Circulations with Humidity Effects

    CERN Document Server

    Hsia, Chun-Hsiung; Ma, Tian; Wang, Shouhong

    2011-01-01

    The main objective of this article is to study the effect of the moisture on the planetary scale atmospheric circulation over the tropics. The modeling we adopt is the Boussinesq equations coupled with a diffusive equation of humidity and the humidity dependent heat source is modeled by a linear approximation of the humidity. The rigorous mathematical analysis is carried out using the dynamic transition theory. In particular, we obtain the same types of transitions and hence the scenario of the El Ni\\~no mechanism as described in \\cite{MW2,MW3}. The effect of the moisture only lowers slightly the magnitude of the critical thermal Rayleigh number.

  17. Multimodel analysis of anisotropic diffusive tracer-gas transport in a deep arid unsaturated zone

    Science.gov (United States)

    Green, Christopher T.; Walvoord, Michelle Ann; Andraski, Brian J.; Striegl, Rob; Stonestrom, David A.

    2015-01-01

    Gas transport in the unsaturated zone affects contaminant flux and remediation, interpretation of groundwater travel times from atmospheric tracers, and mass budgets of environmentally important gases. Although unsaturated zone transport of gases is commonly treated as dominated by diffusion, the characteristics of transport in deep layered sediments remain uncertain. In this study, we use a multimodel approach to analyze results of a gas-tracer (SF6) test to clarify characteristics of gas transport in deep unsaturated alluvium. Thirty-five separate models with distinct diffusivity structures were calibrated to the tracer-test data and were compared on the basis of Akaike Information Criteria estimates of posterior model probability. Models included analytical and numerical solutions. Analytical models provided estimates of bulk-scale apparent diffusivities at the scale of tens of meters. Numerical models provided information on local-scale diffusivities and feasible lithological features producing the observed tracer breakthrough curves. The combined approaches indicate significant anisotropy of bulk-scale diffusivity, likely associated with high-diffusivity layers. Both approaches indicated that diffusivities in some intervals were greater than expected from standard models relating porosity to diffusivity. High apparent diffusivities and anisotropic diffusivity structures were consistent with previous observations at the study site of rapid lateral transport and limited vertical spreading of gas-phase contaminants. Additional processes such as advective oscillations may be involved. These results indicate that gases in deep, layered unsaturated zone sediments can spread laterally more quickly, and produce higher peak concentrations, than predicted by homogeneous, isotropic diffusion models.

  18. Homogeneous Water Nucleation in a Laminar Flow Diffusion Chamber

    Czech Academy of Sciences Publication Activity Database

    Manka, A.; Brus, David; Hyvärinen, A.-P.; Lihavainen, H.; Wölk, J.; Strey, R.

    Prague : Orgit, 2009 - (Smolík, J.; O'Dowd, C.), s. 480-483 ISBN 978-80-02-12161-2. [International Conference Nucleation and Atmospheric Aerosols /18./. Prague (CZ), 10.08.2009-14.08.2009] Institutional research plan: CEZ:AV0Z40720504 Keywords : water * homogeneous nucleation * laminar flow diffusion chamber Subject RIV: CF - Physical ; Theoretical Chemistry http://www.icnaa.cz/

  19. Diffusion Processes on Complex Networks

    OpenAIRE

    Švarcová, Natálie; Švarc, Petr

    2009-01-01

    In this paper we apply agent-based methodology on an issue that is fundamental for economic prosperity and growth: the diffusion of innovations. The diffusion of innovations is one of the topics where agent-based simulation is an extremely fruitful method allowing not only the observation of stable states but also the process and development of the diffusion. Furthermore, empirical studies revealed that the topological structure of interactions among individuals importantly influences the dif...

  20. Econometric Advances in Diffusion Models

    OpenAIRE

    Peers, Yuri

    2011-01-01

    textabstractThis thesis gives new and important insights in modeling diffusion data in marketing. It addresses modeling multiple series instead of just one series such that one can learn from the differences and similarities across products and countries. Additionally, this thesis addresses the current availability of higher frequency diffusion data. The two issues provide challenges for modeling of diffusion processes. In this thesis we provide solutions to these challenges, and we also sugg...

  1. Reversible Diffusion by Thermal Fluctuations

    OpenAIRE

    Donev, A.; Fai, T. G.; Vanden-Eijnden, and E.

    2013-01-01

    A model for diffusion in liquids that couples the dynamics of tracer particles to a fluctuating Stokes equation for the fluid is investigated in the limit of large Schmidt number. In this limit, the concentration of tracers is shown to satisfy a closed-form stochastic advection-diffusion equation that is used to investigate the collective diffusion of hydrodynamically-correlated tracers through a combination of Eulerian and Lagrangian numerical methods. This analysis indicates that transport ...

  2. Confinement and diffusion in tokamaks

    International Nuclear Information System (INIS)

    The effect of electric field fluctuations on confinement and diffusion in tokamak is discussed. Based on the experimentally determined cross-field turbolent diffusion coefficient, D∼3.7*cTe/eB(δni/ni)rms which is also derived by a simple theory, the cross-field diffusion time, tp=a2/D, is calculated and compared to experimental results from 51 tokamak for standard Ohmic operation

  3. Diffuse alveolar hemorrhages

    International Nuclear Information System (INIS)

    The Diffuse Alveolar Hemorrhage (DAH) it is a clinical syndrome that generally manifests with hemoptysis, anemia and infiltrated in the thorax x-ray. From the anatomical point of view, the DAH is defined as the presence of blood in the distal alveolar spaces without it can identify any endobronchial abnormality. The radiological presentation of the DAH is characterized by the presence of having infiltrated of alveolar occupation in the Rx of thorax of prevalence perihiliar and bilateral that goes converging to configure an image of complete consolidation of the air space, the apexes and the periphery of the lungs are generally respected. These infiltrated are solved in one to two weeks, but with the repeated episodes of having bled it can develop interstitial fibrosis

  4. Nonlocal diffusion and applications

    CERN Document Server

    Bucur, Claudia

    2016-01-01

    Working in the fractional Laplace framework, this book provides models and theorems related to nonlocal diffusion phenomena. In addition to a simple probabilistic interpretation, some applications to water waves, crystal dislocations, nonlocal phase transitions, nonlocal minimal surfaces and Schrödinger equations are given. Furthermore, an example of an s-harmonic function, its harmonic extension and some insight into a fractional version of a classical conjecture due to De Giorgi are presented. Although the aim is primarily to gather some introductory material concerning applications of the fractional Laplacian, some of the proofs and results are new. The work is entirely self-contained, and readers who wish to pursue related subjects of interest are invited to consult the rich bibliography for guidance.

  5. Multilane driven diffusive systems

    International Nuclear Information System (INIS)

    We consider networks made of parallel lanes along which particles hop according to driven diffusive dynamics. The particles also hop transversely from lane to lane, hence indirectly coupling their longitudinal dynamics. We present a general method for constructing the phase diagram of these systems which reveals that in many cases their physics reduce to that of single-lane systems. The reduction to an effective single-lane description legitimizes, for instance, the use of a single TASEP to model the hopping of molecular motors along the many tracks of a single microtubule. Then, we show how, in quasi-2D settings, new phenomena emerge due to the presence of non-zero transverse currents, leading, for instance, to strong ‘shear localization’ along the network. (paper)

  6. Diffuse interstellar absorption bands

    Institute of Scientific and Technical Information of China (English)

    XIANG FuYuan; LIANG ShunLin; LI AiGen

    2009-01-01

    The diffuse interstellar bands (DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s, the exact nature of DIBs still remains unclear. This article reviews the history of the detec-tions of DIBs in the Milky Way and external galaxies, the major observational characteristics of DIBs, the correlations or anti-correlations among DIBs or between DIBs and other interstellar features (e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise), and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.

  7. Diffuse lung disease: Pneumoconioses

    International Nuclear Information System (INIS)

    This paper begins with a discussion of the 1980 International Labour Organization classification of the pneumoconioses. Emphasis is on the common pneumoconioses, that is, silicosis, coalworker's pneumoconiosis, and asbestos-related pleural and parenchymal disease. Examples of the five radiographic forms of silicosis-simple and complicated silicosis, Caplan syndrome, silicotuberculosis, and acute silicosis- are presented, and the differential diagnoses are discussed. Discussion of asbestos-related disease included pleural manifestations such as plaques, diffuse pleural thickening, and asbestos pleural effusion as well as asbestosis and malignancies associated with asbestos exposure, such as bronchogenic carcinoma and malignant mesothelioma. Although the standard radiographic findings are stressed, the use of CT in the diagnosis of pneumoconiosis and the staging of dust-related malignancies is also discussed

  8. Multilane driven diffusive systems

    Science.gov (United States)

    Curatolo, A. I.; Evans, M. R.; Kafri, Y.; Tailleur, J.

    2016-03-01

    We consider networks made of parallel lanes along which particles hop according to driven diffusive dynamics. The particles also hop transversely from lane to lane, hence indirectly coupling their longitudinal dynamics. We present a general method for constructing the phase diagram of these systems which reveals that in many cases their physics reduce to that of single-lane systems. The reduction to an effective single-lane description legitimizes, for instance, the use of a single TASEP to model the hopping of molecular motors along the many tracks of a single microtubule. Then, we show how, in quasi-2D settings, new phenomena emerge due to the presence of non-zero transverse currents, leading, for instance, to strong ‘shear localization’ along the network.

  9. New atmospheric program

    Science.gov (United States)

    The National Science Foundation's Division of Atmospheric Sciences has established an Upper Atmospheric Facilities program within its Centers and Facilities section. The program will support the operation of and the scientific research that uses the longitudinal chain of incoherent scatter radars. The program also will ensure that the chain is maintained as a state-of-the-art research tool available to all interested and qualified scientists.For additional information, contact Richard A. Behnke, Division of Atmospheric Sciences, National Science Foundation, 1800 G Street, N.W., Washington, DC 20550 (telephone: 202-357-7390).

  10. Measurement and Analysis of the Diffusible Hydrogen in Underwater Wet Welding Joint

    Directory of Open Access Journals (Sweden)

    Kong Xiangfeng

    2016-01-01

    Full Text Available The diffusible hydrogen in steel weldments is one of the main reasons that led to hydrogen assisted cracking. In this paper, the results of literatures survey and preliminary tests of the diffusible hydrogen in underwater wet welding joint were presented. A fluid-discharge method of for measuring the diffusible hydrogen in weldment was introduced in detail. Two kinds of underwater welding electrode diffusible hydrogen are 26.5 mL/100g and 35.5 mL/100g by fluid-discharge method, which are high levels. The diffusible hydrogen of underwater welding is higher than atmospheric welding, and the result is closely related to welding material. The best way to control the diffusible hydrogen is adjusting welding material and improving fluidity of slag.

  11. Puff models for simulation of fugitive radioactive emissions in atmosphere

    International Nuclear Information System (INIS)

    A puff model for the dispersion of material from fugitive radioactive emissions is presented. For vertical diffusion the model is based on general techniques for solving time dependent advection-diffusion equation: the ADMM (Advection Diffusion Multilayer Method) and GILTT (Generalized Integral Laplace Transform Technique) techniques. The first one is an analytical solution based on a discretization of the Atmospheric Boundary Layer (ABL) in sub-layers where the advection-diffusion equation is solved by the Laplace transform technique. The solution is given in integral form. The second one is a well-known hybrid method that had solved a wide class of direct and inverse problems mainly in the area of Heat Transfer and Fluid Mechanics and the solution is given in series form. Comparisons between values predicted by the models against experimental ground-level concentrations are shown. (author)

  12. The magnetic diffusion of neutrons

    International Nuclear Information System (INIS)

    The purpose of this report is to examine briefly the diffusion of neutrons by substances, particularly by crystals containing permanent atomic or ionic magnetic moments. In other words we shall deal with ferromagnetic, antiferromagnetic, ferrimagnetic or paramagnetic crystals, but first it is necessary to touch on nuclear diffusion of neutrons. We shall start with the interaction of the neutron with a single diffusion centre; the results will then be applied to the magnetic interactions of the neutron with the satellite electrons of the atom; finally we shall discuss the diffusion of neutrons by crystals. (author)

  13. Replacement of diffusers on JRR-3 secondary cooling tower

    International Nuclear Information System (INIS)

    The secondary cooling tower of JRR-3 is a facility for dissipating/cooling the heat generated in the reactor core by receiving it via heat exchanger, and the secondary cooling tower diffuser is a facility to efficiently dissipate this heat to atmosphere. Since this equipment had passed 25 years since its establishment, and the corrosion due to aging deterioration was significant, the updating of the equipment was planned aimed at contributing to long-term safety and the stable operation of JRR-3. This paper describes the overview of entire reactor cooling system facility, and the inspection maintenance and performance of the secondary cooling tower. As the improvements in the updating of the secondary cooling tower diffuser, this paper describes the consideration of paints and quality of the base material, and the improvement of inspection port and base frame opening. It also reports the fabrication of these devices, dismantling of existing equipment, and installation of the new diffuser. (A.O.)

  14. RETADD: a Regional Trajectory And Diffusion-Deposition model

    Energy Technology Data Exchange (ETDEWEB)

    Begovich, C. L.; Murphy, B. D.; Nappo, Jr., C. J.

    1978-06-01

    The Regional Trajectory and Diffusion-Deposition Model (RETADD) is based upon a version of the National Oceanic and Atmospheric Administration Air Resources Laboratory's Regional-Continental Scale Transport, Diffusion, and Deposition Model. The FORTRAN IV computer model uses a trajectory analysis technique for estimating the transport and long-range diffusion of material emitted from a point source. The wind trajectory portion of the code uses observed upper air winds to compute the transport of the material. Ground level concentrations and depositions are computed by using the Gaussian plume equation for wind trajectories projected forward in time. Options are included to specify an upper bound for the mixed layer and a chemical decomposition rate for the effluent. The limitations to the technique are discussed, the equations and model are described, and listings of the program, input, and output are included.

  15. Tracking Water Diffusion Fronts in a Highly Viscous Aerosol Particle

    Science.gov (United States)

    Bastelberger, Sandra; Krieger, Ulrich; Peter, Thomas

    2016-04-01

    Field measurements indicate that atmospheric secondary aerosol particles can be present in a highly viscous, glassy state [1]. In contrast to liquid state particles, the gas phase equilibration is kinetically limited and governed by condensed phase diffusion. In recent water diffusion experiments on highly viscous single aerosol particles levitated in an electrodynamic balance (EDB) we observed a characteristic shift behavior of the Mie whispering gallery modes (WGM) indicative of the changing radial structure of the particle, thus providing us with an experimental method to track the diffusion process inside the particle. When a highly viscous, homogeneous particle is exposed to an abrupt increase in relative humidity, the rapid gas phase diffusion and strong concentration dependence of the diffusion coefficient in the condensed phase lead to extremely steep water concentration gradients inside the particle, reminiscent of diffusion fronts. The resulting quasi step-like concentration profile motivates the introduction of a simple core-shell model describing the morphology of the non-equilibrium particle during humidification. The subsequent particle growth and reduction of the shell refractive index can be observed as red and blueshift behavior of the WGM, respectively. The shift pattern can be attributed to a core-shell radius ratio and particle radius derived from model calculations [2]. If supplemented with growth information obtained from the WGM redshift and thermodynamic equilibrium data, we can infer a comprehensive picture of the time evolution of the diffusion fronts in the framework of our core-shell model. The measured time dependent concentration profile is then compared with simulations solving the non-linear diffusion equation [3] [1] Virtanen, A., et al., Nature, 467, 824-827, 2010 [2] Kaiser, T., Schweiger, G., Computers in Physics, Vol. 7, No. 6, 682-686, Nov/Dec 1993 [3] Zobrist, B., Soonsin, V., Luo, B.P., Peter, T. et al., Phys. Chem. Chem

  16. Atmospheric Neutrino Status

    CERN Document Server

    O'Sullivan, E

    2016-01-01

    This conference proceeding discusses new results arising from atmospheric neutrino detection in the Super-Kamiokande and IceCube experiments. Super-Kamiokande has measured atmospheric neutrinos in the energy range of 100 MeV-10 TeV and uses this data set to conclusively measure the east-west effect to 8.0 (6.0) $\\sigma$ for electron (muon) neutrinos. IceCube is ideal for measuring high energy atmospheric neutrinos and has explored how different production channels for atmospheric neutrinos contribute to the total overall observed flux. The measurement is consistent with the conventional spectrum, produced by the decay of pions and kaon, while the contribution from the prompt channel (due to charm decay) is consistent with zero.

  17. Unravelling our atmosphere

    Science.gov (United States)

    Caldwell, Martin

    2014-05-01

    A main limiting factor in climate predictions is that we do not understand atmospheric processes as a function of height. An upcoming European and Japanese space mission called EarthCARE seeks to remedy this, as Martin Caldwell explains.

  18. Heterogeneous atmospheric chemistry

    Science.gov (United States)

    Schryer, D. R.

    1982-01-01

    The present conference on heterogeneous atmospheric chemistry considers such topics concerning clusters, particles and microparticles as common problems in nucleation and growth, chemical kinetics, and catalysis, chemical reactions with aerosols, electron beam studies of natural and anthropogenic microparticles, and structural studies employing molecular beam techniques, as well as such gas-solid interaction topics as photoassisted reactions, catalyzed photolysis, and heterogeneous catalysis. Also discussed are sulfur dioxide absorption, oxidation, and oxidation inhibition in falling drops, sulfur dioxide/water equilibria, the evidence for heterogeneous catalysis in the atmosphere, the importance of heterogeneous processes to tropospheric chemistry, soot-catalyzed atmospheric reactions, and the concentrations and mechanisms of formation of sulfate in the atmospheric boundary layer.

  19. The origin of atmosphere

    International Nuclear Information System (INIS)

    The evolution of the atmosphere of the Earth is described. Starting from the hot Universe the main steps of the ''cooling-down'' process as the different states of the condensation of the matter are discussed. After this nuclear evolution the chemical evolution could start on the solid Earth's crust. In the reductive primordial atmosphere mainly due to ultraviolet rays the basic molecules for life as sugars and amino acids were formed. The photosynthesis of the plants has later produced the oxygen being present in the recent atmosphere. The question whether the pollution could affect the auto-stabilization loop of the atmosphere is also discussed. Finally the possibility of life on the Mars is studied. (Sz.Z.)

  20. The invention of atmosphere.

    Science.gov (United States)

    Martin, Craig

    2015-08-01

    The word "atmosphere" was a neologism Willebrord Snellius created for his Latin translation of Simon Stevin's cosmographical writings. Astronomers and mathematical practitioners, such as Snellius and Christoph Scheiner, applying the techniques of Ibn Mu'ādh and Witelo, were the first to use the term in their calculations of the height of vapors that cause twilight. Their understandings of the atmosphere diverged from Aristotelian divisions of the aerial region. From the early years of the seventeenth century, the term was often associated with atomism or corpuscular matter theory. The concept of the atmosphere changed dramatically with the advent of pneumatic experiments in the middle of the seventeenth century. Pierre Gassendi, Walter Charleton, and Robert Boyle transformed the atmosphere of the mathematicians giving it the characteristics of weight, specific gravity, and fluidity, while disputes about its extent and border remained unresolved. PMID:26193787

  1. Students 'Weigh' Atmospheric Pollution.

    Science.gov (United States)

    Caporaloni, Marina

    1998-01-01

    Describes a procedure developed by students that measures the mass concentration of particles in a polluted urban atmosphere. Uses a portable fan and filters of various materials. Compares students' data with official data. (DDR)

  2. Carbon neutron star atmospheres

    CERN Document Server

    Suleimanov, V F; Pavlov, G G; Werner, K

    2013-01-01

    The accuracy of measuring the basic parameters of neutron stars is limited in particular by uncertainties in chemical composition of their atmospheres. For example, atmospheres of thermally - emitting neutron stars in supernova remnants might have exotic chemical compositions, and for one of them, the neutron star in CasA, a pure carbon atmosphere has recently been suggested by Ho & Heinke (2009). To test such a composition for other similar sources, a publicly available detailed grid of carbon model atmosphere spectra is needed. We have computed such a grid using the standard LTE approximation and assuming that the magnetic field does not exceed 10^8 G. The opacities and pressure ionization effects are calculated using the Opacity Project approach. We describe the properties of our models and investigate the impact of the adopted assumptions and approximations on the emergent spectra.

  3. Middle atmospheric electrodynamics

    Science.gov (United States)

    Kelley, M. C.

    1983-01-01

    A review is presented of the advances made during the last few years with respect to the study of the electrodynamics in the earth's middle atmosphere. In a report of the experimental work conducted, attention is given to large middle atmospheric electric fields, the downward coupling of high altitude processes into the middle atmosphere, and upward coupling of tropospheric processes into the middle atmosphere. It is pointed out that new developments in tethered balloons and superpressure balloons should greatly increase the measurement duration of earth-ionospheric potential measurements and of stratospheric electric field measurements in the next few years. Theoretical work considered provides an excellent starting point for study of upward coupling of transient and dc electric fields. Hays and Roble (1979) were the first to construct a model which included orographic features as well as the classical thunderstorm generator.

  4. Proterozoic atmospheric oxygen

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene

    2014-01-01

    This article is concerned with the evolution of atmospheric oxygen concentrations through the Proterozoic Eon. In particular, this article will seek to place the history of atmospheric oxygenation through the Proterozoic Eon in the context of the evolving physical environment including the history...... of continental growth and volcanic outgassing, as well as biogeochemical processing of elements within the oceans. The author will seek to explore constraints on the history of oxygenation and understand which processes have regulated oxygen through this eon....

  5. Atmospheric release advisory capability

    International Nuclear Information System (INIS)

    The ARAC system (Atmospheric Release Advisory Capability) is described. The system is a collection of people, computers, computer models, topographic data and meteorological input data that together permits a calculation of, in a quasi-predictive sense, where effluent from an accident will migrate through the atmosphere, where it will be deposited on the ground, and what instantaneous and integrated dose an exposed individual would receive

  6. Global atmospheric changes.

    OpenAIRE

    Piver, W T

    1991-01-01

    Increasing concentrations of CO2 and other greenhouse gases in the atmosphere can be directly related to global warming. In terms of human health, because a major cause of increasing atmospheric concentrations of CO2 is the increased combustion of fossil fuels, global warming also may result in increases in air pollutants, acid deposition, and exposure to ultraviolet (UV) radiation. To understand better the impacts of global warming phenomena on human health, this review emphasizes the proces...

  7. Atmospheric muons: experimental aspects

    CERN Document Server

    Cecchini, Stefano

    2012-01-01

    We present a review of atmospheric muon flux and energy spectrum measurements over almost six decades of muon momentum. Sea-level and underground/water/ice experiments are considered. Possible sources of systematic errors in the measurements are examinated. The characteristics of underground/water muons (muons in bundle, lateral distribution, energy spectrum) are discussed. The connection between the atmospheric muon and neutrino measurements are also reported.

  8. Dynamics in Atmospheric Physics

    Science.gov (United States)

    Lindzen, Richard A.

    2005-08-01

    Motion is manifest in the atmosphere in an almost infinite variety of ways. In Dynamics in Atmospheric Physics, Dr. Richard Lindzen describes the nature of motion in the atmosphere, develops fluid dynamics relevant to the atmosphere, and explores the role of motion in determining the climate and atmospheric composition. The author presents the material in a lecture note style, and the emphasis throughout is on describing phenomena that are at the frontiers of current research, but due attention is given to the methodology of research and to the historical background of these topics. The author's treatment and choice of topics is didactic. Problems at the end of each chapter will help students assimilate the material. In general the discussions emphasize physical concepts, and throughout Dr. Lindzen makes a concerted effort to avoid the notion that dynamic meteorology is simply the derivation of equations and their subsequent solution. His desire is that interested students will delve further into solution details. The book is intended as a text for first year graduate students in the atmospheric sciences. Although the material in the book is self contained, a familiarity with differential equations is assumed; some background in fluid mechanics is helpful.

  9. THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES OBSERVED WITH AIA/SDO: FRACTAL DIFFUSION, SUB-DIFFUSION, OR LOGISTIC GROWTH?

    Energy Technology Data Exchange (ETDEWEB)

    Aschwanden, Markus J., E-mail: aschwanden@lmsal.com [Lockheed Martin Advanced Technology Center, Solar and Astrophysics Laboratory, Organization ADBS, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

    2012-09-20

    We explore the spatio-temporal evolution of solar flares by fitting a radial expansion model r(t) that consists of an exponentially growing acceleration phase, followed by a deceleration phase that is parameterized by the generalized diffusion function r(t){proportional_to}{kappa}(t - t{sub 1}){sup {beta}/2}, which includes the logistic growth limit ({beta} = 0), sub-diffusion ({beta} = 0-1), classical diffusion ({beta} = 1), super-diffusion ({beta} = 1-2), and the linear expansion limit ({beta} = 2). We analyze all M- and X-class flares observed with Geostationary Operational Environmental Satellite and Atmospheric Imaging Assembly/Solar Dynamics Observatory (SDO) during the first two years of the SDO mission, amounting to 155 events. We find that most flares operate in the sub-diffusive regime ({beta} = 0.53 {+-} 0.27), which we interpret in terms of anisotropic chain reactions of intermittent magnetic reconnection episodes in a low plasma-{beta} corona. We find a mean propagation speed of v = 15 {+-} 12 km s{sup -1}, with maximum speeds of v{sub max} = 80 {+-} 85 km s{sup -1} per flare, which is substantially slower than the sonic speeds expected for thermal diffusion of flare plasmas. The diffusive characteristics established here (for the first time for solar flares) is consistent with the fractal-diffusive self-organized criticality model, which predicted diffusive transport merely based on cellular automaton simulations.

  10. THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES OBSERVED WITH AIA/SDO: FRACTAL DIFFUSION, SUB-DIFFUSION, OR LOGISTIC GROWTH?

    International Nuclear Information System (INIS)

    We explore the spatio-temporal evolution of solar flares by fitting a radial expansion model r(t) that consists of an exponentially growing acceleration phase, followed by a deceleration phase that is parameterized by the generalized diffusion function r(t)∝κ(t – t1)β/2, which includes the logistic growth limit (β = 0), sub-diffusion (β = 0-1), classical diffusion (β = 1), super-diffusion (β = 1-2), and the linear expansion limit (β = 2). We analyze all M- and X-class flares observed with Geostationary Operational Environmental Satellite and Atmospheric Imaging Assembly/Solar Dynamics Observatory (SDO) during the first two years of the SDO mission, amounting to 155 events. We find that most flares operate in the sub-diffusive regime (β = 0.53 ± 0.27), which we interpret in terms of anisotropic chain reactions of intermittent magnetic reconnection episodes in a low plasma-β corona. We find a mean propagation speed of v = 15 ± 12 km s–1, with maximum speeds of vmax = 80 ± 85 km s–1 per flare, which is substantially slower than the sonic speeds expected for thermal diffusion of flare plasmas. The diffusive characteristics established here (for the first time for solar flares) is consistent with the fractal-diffusive self-organized criticality model, which predicted diffusive transport merely based on cellular automaton simulations.

  11. GREAT/SOFIA atmospheric calibration

    OpenAIRE

    Guan, Xin; Stutzki, Jürgen; Graf, Urs U.; Güsten, Rolf; Okada, Yoko; Torres, Miguel Angel Requena; Simon, Robert; Wiesemeyer, Helmut

    2012-01-01

    The GREAT observations need frequency-selective calibration across the passband for the residual atmospheric opacity at flight altitude. At these altitudes the atmospheric opacity has both narrow and broad spectral features. To determine the atmospheric transmission at high spectral resolution, GREAT compares the observed atmospheric emission with atmospheric model predictions, and therefore depends on the validity of the atmospheric models. We discusse the problems identified in this compari...

  12. Image Denoising via Nonlinear Hybrid Diffusion

    OpenAIRE

    Xiaoping Ji; Dazhi Zhang; Zhichang Guo; Boying Wu

    2013-01-01

    A nonlinear anisotropic hybrid diffusion equation is discussed for image denoising, which is a combination of mean curvature smoothing and Gaussian heat diffusion. First, we propose a new edge detection indicator, that is, the diffusivity function. Based on this diffusivity function, the new diffusion is nonlinear anisotropic and forward-backward. Unlike the Perona-Malik (PM) diffusion, the new forward-backward diffusion is adjustable and under control. Then, the existence, uniqueness, and lo...

  13. Helioseismic tests of diffusion theory

    OpenAIRE

    Fiorentini, G; Lissia, M.; B. Ricci

    2014-01-01

    We present a quantitative estimate of the accuracy of the calculated diffusion coefficients, by comparing predictions of solar models with observational data provided by helioseismology. By taking into account the major uncertainties in building solar models we conclude that helioseismology confirms the diffusion efficiency adopted in SSM calculations, to the 10% level.

  14. Molecular dynamics simulation of diffusivity

    Institute of Scientific and Technical Information of China (English)

    Juanfang LIU; Danling ZENG; Qin LI; Hong GAO

    2008-01-01

    Equilibrium molecular dynamics simulation was performed on water to calculate its diffusivity by adopting different potential models. The results show that the potential models have great influence on the simulated results. In addition, the diffusivities obtained by the SPCE model conform well to the experimental values.

  15. Diffusion measurements by Raman spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Shapiro, Alexander; Berg, Rolf W.;

    Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt......Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt...

  16. Osmosis and Diffusion Conceptual Assessment

    Science.gov (United States)

    Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts

    2011-01-01

    Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified…

  17. Group classification of systems of non-linear reaction-diffusion equations with general diffusion matrix. III. Triangular diffusion matrix

    OpenAIRE

    Nikitin, A. G.

    2005-01-01

    Group classification of systems of two coupled nonlinear reaction-diffusion equation with a general diffusion matrix started in papers math-ph/0411027,, math-ph/0411028 is completed in present paper where all non-equivalent equations with triangular diffusion matrix are classified. In addition, symmetries of diffusion systems with nilpotent diffusion matrix and additional first order derivative terms are described.

  18. Modification of the glass surface induced by redox reactions and internal diffusion processes

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Deubener, Joachim; Yue, Yuanzheng

    In this paper we report a novel way to modify the glass surface in favor of some physical performances. The main step is to perform iso-thermal treatments on the selected silicate glasses containing transition metal at temperatures near the glass transition temperature for various durations under...... different gases. As a result, we have observed a striking phenomenon, i.e., the outward diffusion of divalent cations occurs not only under an oxidizing atmosphere of heat-treatment, but also under nitrogen, even under reducing atmospheres like H2/N2 (10/90). The extent of the cationic diffusion depends on...... temperature and duration of heat-treatments. The mechanism of the diffusion depends on the type of the gases used for the heat-treatments. In this paper we propose several possible models describing mechanisms of the cationic diffusion, and hence, of the formation of the nano-layer. We also report the effect...

  19. Performance examination of atmospheric model at seacoast region

    International Nuclear Information System (INIS)

    A three-dimensional numerical atmospheric model (PHYSIC) was developed to apply it to atmospheric transport and diffusion evaluation. The main frame of PHYSIC is made up of momentum equations with the hydrostatic and Boussinesq approximation, the second-order turbulence closure model level 2.5 and other basic equations of physical process in the atmosphere. A terrain following z* coordinate system is used. The calculation results at a coastal plain were examined using meteorological data observed during atmospheric diffusion experiments at Tokai in 1983. The present model successfully predicts the temporal change of wind field within 20 h from evening to next noon and the occurrence and structure of sea breeze are simulated satisfactorily. The model performance concerning the structure of sea breeze and the distribution of eddy diffusivities is thought to be reasonable, although the direct comparison between calculation and observation is restricted to wind and temperature profiles by limited observation data. Further examination of model performance relating to above items, and over mountainous region, will be needed. (author)

  20. Sodium diffusion in boroaluminosilicate glasses

    DEFF Research Database (Denmark)

    Smedskjaer, Morten M.; Zheng, Qiuju; Mauro, John C.;

    2011-01-01

    isothermal sodium diffusion in BAS glasses by ion exchange, inward diffusion, and tracer diffusion experiments. By varying the [SiO2]/[Al2O3] ratio of the glasses, different structural regimes of sodium behavior are accessed. We show that the mobility of the sodium ions decreases with increasing [SiO2]/[Al2O......3] ratio, revealing that sodium is more mobile when it acts as a charge compensator to stabilize network formers than when it acts as a creator of non-bridging oxygens on tetrahedrally-coordinated silicon and trigonal boron. The impacts of both the addition of iron and its redox state on the sodium...... be attributed to the fact that for sodium inward diffusion, the charge compensation for electron holes is a rather slow process that limits the rate of diffusion. (C) 2011 Elsevier B.V. All rights reserved....

  1. Magnetic Diffusion in Star Formation

    CERN Document Server

    Basu, Shantanu

    2010-01-01

    Magnetic diffusion plays a vital role in star formation. We trace its influence from interstellar cloud scales down to star-disk scales. On both scales, we find that magnetic diffusion can be significantly enhanced by the buildup of strong gradients in magnetic field structure. Large scale nonlinear flows can create compressed cloud layers within which ambipolar diffusion occurs rapidly. However, in the flux-freezing limit that may be applicable to photoionized molecular cloud envelopes, supersonic motions can persist for long times if driven by an externally generated magnetic field that corresponds to a subcritical mass-to-flux ratio. In the case of protostellar accretion, rapid magnetic diffusion (through Ohmic dissipation with additional support from ambipolar diffusion) near the protostar causes dramatic magnetic flux loss. By doing so, it also allows the formation of a centrifugal disk, thereby avoiding the magnetic braking catastrophe.

  2. Solute diffusivity in undisturbed soil

    DEFF Research Database (Denmark)

    Lægdsmand, Mette; Møldrup, Per; Schjønning, Per

    2012-01-01

    soil samples from two different tillage treatments (soil from below the depth of a harrow treatment and soil from within a moldboard plowed plow layer) was estimated based on concentration profiles using a newly developed method. The method makes use of multiple tracers (two sets of counterdiffusing......Solute diffusivity in soil plays a major role in many important processes with relation to plant growth and environmental issues. Soil solute diffusivity is affected by the volumetric water content as well as the morphological characteristics of water-filled pores. The solute diffusivity in intact...... tracers) for a better determination of the diffusivity. The diffusivity was higher in the below-till soil than the plowed soil at the same soil water matric potential due to higher water content but also due to higher continuity and lower tortuosity of the soil pores. We measured identical solute...

  3. Diffusion processes and coalescent trees

    CERN Document Server

    Griffiths, Robert C

    2010-01-01

    We dedicate this paper to Sir John Kingman on his 70th Birthday. In modern mathematical population genetics the ancestral history of a population of genes back in time is described by John Kingman's coalescent tree. Classical and modern approaches model gene frequencies by diffusion processes. This paper, which is partly a review, discusses how coalescent processes are dual to diffusion processes in an analytic and probabilistic sense. Bochner (1954) and Gasper (1972) were interested in characterizations of processes with Beta stationary distributions and Jacobi polynomial eigenfunctions. We discuss the connection with Wright--Fisher diffusions and the characterization of these processes. Subordinated Wright--Fisher diffusions are of this type. An Inverse Gaussian subordinator is interesting and important in subordinated Wright--Fisher diffusions and is related to the Jacobi Poisson Kernel in orthogonal polynomial theory. A related time-subordinated forest of non-mutant edges in the Kingman coalescent is nove...

  4. Thermal diffusivity of diamond films

    Science.gov (United States)

    Albin, Sacharia; Winfree, William P.; Crews, B. Scott

    1990-01-01

    A laser pulse technique to measure the thermal diffusivity of diamond films deposited on a silicon substrate is developed. The effective thermal diffusivity of diamond film on silicon was measured by observing the phase and amplitude of the cyclic thermal waves generated by the laser pulses. An analytical model is developed to calculate the effective in-plane (face-parallel) diffusivity of a two layer system. The model is used to reduce the effective thermal diffusivity of the diamond/silicon sample to a value for the thermal diffusivity and conductivity of the diamond film. Phase and amplitude measurements give similar results. The thermal conductivity of the films is found to be better than that of type 1a natural diamond.

  5. Portable vapor diffusion coefficient meter

    Science.gov (United States)

    Ho, Clifford K.

    2007-06-12

    An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

  6. Asymmetric diffusion of cosmic rays

    CERN Document Server

    Medvedev, Mikhail V

    2015-01-01

    Cosmic ray propagation is diffusive because of pitch angle scattering by waves. We demonstrate that if the high-amplitude magnetohydrodynamic turbulence with $\\tilde B/\\langle B\\rangle \\sim 1$ is present on top of the mean field gradient, the diffusion becomes asymmetric. As an example, we consider the vertical transport of cosmic rays in our Galaxy propagating away from a point-like source. We solve this diffusion problem analytically using a one-dimensional Markov chain analysis. We obtained that the cosmic ray density markedly differs from the standard diffusion prediction and has a sizable effect on their distribution throughout the galaxy. The equation for the continuous limit is also derived, which shows limitations of the convection-diffusion equation.

  7. Experimental investigation of the starting process of short diffusers for gas dynamic lasers

    Energy Technology Data Exchange (ETDEWEB)

    Oudekerk, M.M.

    1975-06-01

    The diffuser section of a Gas Dynamic Laser (GDL) is one of the largest components in the system. The purpose of this investigation was to examine the problem of starting supersonic flow in short diffusers with fixed walls, incorporating various bleed arrangements for boundary layer control (BLC). A Mach number of 4, ramp angle of 19 degrees diffuser length of 4.5 in. and a diffuser width of 1.0 in. were used throughout this investigation. Intrusion by the atmosphere into the diffuser causes a separation region or bubble to form. The presence of this 'bubble' could be made to improve the diffuser performance by making a variable area diffuser out of a fixed wall diffuser without the use of any external apparatus. BLC was helpful in increasing the over all pressure recovery of the diffuser. BLC also affects the unsteady flow, which was present in the diffuser, but only when it is applied at a point prior to the converging section of the GDL.

  8. Diffusion in membranes: toward a two-dimensional diffusion map

    International Nuclear Information System (INIS)

    For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasielastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nano-scale membrane permeability. (authors)

  9. Diffusion in membranes: Toward a two-dimensional diffusion map

    Directory of Open Access Journals (Sweden)

    Toppozini Laura

    2015-01-01

    Full Text Available For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.

  10. Multidimensional diffusion processes

    CERN Document Server

    Stroock, Daniel W

    1997-01-01

    From the reviews: "… Both the Markov-process approach and the Itô approach … have been immensely successful in diffusion theory. The Stroock-Varadhan book, developed from the historic 1969 papers by its authors, presents the martingale-problem approach as a more powerful - and, in certain regards, more intrinsic-means of studying the foundations of the subject. […] … the authors make the uncompromising decision not "to proselytise by intimidating the reader with myriad examples demonstrating the full scope of the techniques", but rather to persuade the reader "with a careful treatment of just one problem to which they apply". […] Most of the main tools of stochastic-processes theory are used, ..but it is the formidable combination of probability theory with analysis … which is the core of the work. […] I have emphasized the great importance of the Stroock-Varadhan book. It contains a lot more than I have indicated; in particular, its many exercises conain much interesting material. For immediat...

  11. Diffuse Microwave Emission Survey

    Science.gov (United States)

    Shafer, R. A.; Mather, J.; Kogut, A.; Fixsen, D. J.; Seiffert, M.; Lubin, P. M.; Levin, S. M.

    1996-12-01

    The Diffuse Microwave Emission Survey (DIMES) is a mission concept selected by NASA in 1995 to answer fundamental questions about the content and history of the universe. DIMES will use a set of absolutely calibrated cryogenic radiometers from a space platform to measure the frequency spectrum of the cosmic microwave background (CMB) at wavelengths 15--0.3 cm (frequency 2--100 GHz) to precision 0.1 mK or better. Measurements at centimeter wavelengths probe different physical processes than the COBE-FIRAS spectra at shorter wavelengths, and complement the anisotropy measurements from DMR, balloon and ground-based instruments, and the planned MAP and COBRAS/SAMBA satellites. DIMES will observe the free-free signal from early photoionization to establish the precise epoch of structure formation, and will measure or limit energy release at redshift 10(4) theory and allowed by current measurement limits; even an upper limit at the expected sensitivity 10(-5) MJy/sr will place important constraints on the matter content, structure, and evolution of the universe. Detecting these distortions or showing that they do not exist constitutes the last frontier of CMB observations.

  12. Atmospheric freeze drying assisted by power ultrasound

    International Nuclear Information System (INIS)

    Atmospheric freeze drying (AFD) is considered an alternative to vacuum freeze drying to keep the quality of fresh product. AFD allows continuous drying reducing fix and operating costs, but presents, as main disadvantage, a long drying time required. The application of power ultrasound (US) can accelerate AFD process. The main objective of the present study was to evaluate the application of power ultrasound to improve atmospheric freeze drying of carrot. For that purpose, AFD experiments were carried out with carrot cubes (10 mm side) at constant air velocity (2 ms−1), temperature (−10°C) and relative humidity (10%) with (20.5 kWm−3,USAFD) and without (AFD) ultrasonic application. A diffusion model was used in order to quantify the influence of US in drying kinetics. To evaluate the quality of dry products, rehydration capacity and textural properties were determined. The US application during AFD of carrot involved the increase of drying rate. The effective moisture diffusivity identified in USAFD was 73% higher than in AFD experiments. On the other hand, the rehydration capacity was higher in USAFD than in AFD and the hardness of dried samples did not show significant (p<0.05) differences. Therefore, US application during AFD significantly (p<0.05) sped-up the drying process preserving the quality properties of the dry product.

  13. Air Pollution Steady-State Advection-Diffusion Equation: The General Three-Dimensional Solution

    OpenAIRE

    Bardo Bodmann; Tiziano Tirabassi; Marco Túllio Vilhena; Daniela Buske

    2012-01-01

    Atmospheric air pollution turbulent fluxes can be assumed to be proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection-diffusion equation. Many models simulating air pollution dispersion are based upon the solution (numerical or analytical) of the advection-diffusion equation as- suming turbulence parameterization for realistic physical scenarios. We present the general steady three-dimensional solution of the advection-...

  14. A permeation-diffusion-reaction model of gas transport in cellular tissue of plant materials

    OpenAIRE

    Ho, Quang Tri; Verlinden, Bert; Verboven, Pieter; Vandewalle, Stefan; Nicolai, Bart

    2006-01-01

    Gas transport in fruit tissue is governed by both diffusion and permeation. The latter phenomenon is caused by overall pressure gradients which may develop due to the large difference in O-2 and CO2 diffusivity during controlled atmosphere storage of the fruit. A measurement set-up for tissue permeation based on unsteady-state gas exchange was developed. The gas permeability of pear tissue was determined based on an analytical gas transport model. The overall gas transport in pear tissue samp...

  15. Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

    Abstract. In the present paper various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this end thermogravimetric carburization was simulated for various experimental conditions and the evaluated...... composition dependent diffusivity of carbon derived from the simulated experiments was compared with the input data. The most promising procedure for an accurate determination is shown to be stepwise gaseous carburizing of thin foils in a gaseous atmosphere; the finer the stepsize, the more accurate the...

  16. Transdermal diffusion of xenon in vitro using diffusion cells

    Science.gov (United States)

    Verkhovsky, A.; Petrov, E.

    2015-11-01

    The aim of this research was to study the diffusion rate of xenon through guinea pig skin and how viscosity of cosmetic component capryl/capric triglyceride (CCT) facilitates to deliver xenon to surface of skin patches. They were placed in Franz cell for 24 hours and diffusion rate and permeability of xenon were calculated. Thus diffusion rate was 0.031 mg/hour*cm2 and permeability was 0.003 cm/hour. Using Brookfield viscometer it was shown that viscosity of CCT decreased upon increasing xenon concentration. Obtained results can be utilized in developing of new xenon containing drugs for topical administration.

  17. Acid diffusion through polymer films

    Science.gov (United States)

    Zhang, P. Linda; Eckert, Andrew R.; Willson, C. Grant; Webber, Stephen E.; Byers, Jeffrey D.

    1997-07-01

    In order to perform 0.2 micrometer processes, one needs to study the diffusion of photoacid generators within the photoresist system, since diffusion during post exposure bake time has an influence on the critical dimension (CD). We have developed a new method to study the diffusion of photoacid generators within a polymer film. This new method is based on monitoring the change of the fluorescence intensity of a pH- sensitive fluorescent dye caused by the reaction with photoacid. A simplified version of this experiment has been conducted by introducing acid vapor to quench the fluorescence intensity of this pH sensor. A thin polymer film is spin cast onto the sensor to create a barrier to the acid diffusion process. During the acid diffusion process, the fluorescence intensity of this pH sensor is measured in situ, using excitation and emission wavelengths at 466 nm and 516 nm, respectively. Fluoresceinamine, the pH sensitive fluorescent dye, is covalently bonded onto the treated quartz substrate to form a single dye layer. Poly(hydroxystyrene) (Mn equals 13k, Tg equals 180 degrees Celsius) in PGMEA (5% - 18% by weight) is spin cast onto this quartz substrate to form films with varying thickness. The soft bake time is 60 seconds at 90 degrees Celsius and a typical film has a thickness of 1.4 micrometers. Trifluoroacetic acid is introduced into a small chamber while the fluorescence from this quartz window is observed. Our study focuses on finding the diffusion constant of the vaporized acid (trifluoroacetic acid) in the poly(hydroxystyrene) polymer film. By applying the Fick's second law, (It - Io)/(I(infinity ) - Io) equals erfc [L/(Dt)1/2] is obtained. The change of fluorescence intensity with respect to the diffusion time is monitored. The above equation is used for the data analysis, where L represents the film thickness and t represents the average time for the acid to diffuse through the film. The diffusion constant is calculated to be at the order of 10

  18. Diffusion of dust particles emitted from a fixed source

    Directory of Open Access Journals (Sweden)

    Khaled Al-mashrafi

    2015-09-01

    Full Text Available In this paper, we investigate the mathematical model for the diffusion of dust particles emitted from a fixed source. Mathematically, the time-dependent diffusion equation in the presence of a point source whose strength is dependent on time is solved. The solution in closed form for a source of general time dependence is obtained. A number of special cases, in which the source function of time is explicitly given and special values of the diffusion parameters are taken are examined in detail. The numerical calculations show the strong dependence of the concentration of dust on the speed of the wind, the source, and its position in the vertical direction. It is also found that the diffusion parameters play an important role in the spread of the dust particles in the atmosphere. When diffusion is present only in the vertical direction, it is found that for small times the dust spreads with a front that travels with the speed of the wind.

  19. Diffusion behavior for Se and Zr in sodium-bentonite

    International Nuclear Information System (INIS)

    Apparent diffusion coefficients for Se and Zr in bentonite were measured by in-diffusion method at room temperature using water-saturated sodium-bentonite, Kunigel V1 reg-sign containing 50wt% Na-smectite as a major mineral was used as the bentonite material. The experiments were carried out in the dry density range of 400--1,800 kg/m3. Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N2 atmospheric condition (O2: 2.5ppm). Those for Zr were carried out under aerobic condition. The apparent diffusion coefficients decrease with increasing density of the bentonite. Since dominant species of Se in the pore water is predicted to be SeO32-, Se may be retarded by anion-exclusion because of negative charge on the surface of the bentonite and little sorption. The dominant species of Zr in the porewater is predicted to be Zr(OH)5- or HZrO3-. Distribution coefficient measured for Zr on the bentonite was about 1.0 m3/kg from batch experiments. Therefore, the retardation may be caused by combination of the sorption and the anion-exclusion. A modeling for the diffusion mechanisms in the bentonite were discussed based on an electric double layer theory. Comparison between the apparent diffusion coefficients predicted by the model and the measured ones shows a good agreement

  20. Super-diffusion versus competitive advection: a simulation

    CERN Document Server

    Del Moro, D; Berrilli, F; Consolini, G; Lepreti, F; Gosic, M

    2015-01-01

    Magnetic element tracking is often used to study the transport and diffusion of the magnetic field on the solar photosphere. From the analysis of the displacement spectrum of these tracers, it has been recently agreed that a regime of super-diffusivity dominates the solar surface. Quite habitually this result is discussed in the framework of fully developed turbulence. But the debate whether the super-diffusivity is generated by a turbulent dispersion process, by the advection due to the convective pattern, or by even another process, is still open, as is the question about the amount of diffusivity at the scales relevant to the local dynamo process. To understand how such peculiar diffusion in the solar atmosphere takes places, we compared the results from two different data-sets (ground-based and space-borne) and developed a simulation of passive tracers advection by the deformation of a Voronoi network. The displacement spectra of the magnetic elements obtained by the data-sets are consistent in retrieving...

  1. LSM-YSZ Reactions in Different Atmospheres

    DEFF Research Database (Denmark)

    Chen, Ming; Liu, Yi-Lin; Hagen, Anke;

    2009-01-01

    The influences of the oxygen partial pressure and the LSM/YSZ ratio on the LSM-YSZ interface reactions at 1,000 °C were investigated. Both pellets and diffusion couples were employed in the study. The equilibrium thermodynamics of the LSM-YSZ reactions was clarified based on the pellet study......-powder reaction. LSM reacts differently with YSZ in different atmospheres. In air, m-ZrO2 (monoclinic) is formed; while in N2, SrZrO3 and/or La2Zr2O7 are formed depending on the initial LSM/YSZ ratio. The reactions are reversible with varying P(O2) i.e. treating the sample in air after the heat treatment in N2...... results in a decomposition of the formed La- and Sr-zirconates. The de-stabilisation of the LSM-YSZ interface under long-term annealing at 1,000 °C originates mainly from the inter-diffusion across the interface. Under reduced P(O2), the Mn diffusion from LSM into YSZ is enhanced. High P(O2) (0.21 atm...

  2. Pertechnetate diffusion in GMZ bentonite

    International Nuclear Information System (INIS)

    99Tc is an important radionuclides related to repository safety assessment. The mobility pertechnetate (TcO4-) can be reduced to immobility technetium(IV) hydrous oxides (TcO2 · nH2O) by Fe(II)-bearing minerals. In China, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for the HLW repository, which is contained some FeO. The diffusion behavior of 99Tc was investigated in GMZ bentonite by through- and out-diffusion methods. The effective diffusion coefficient (De), the accessible porosity (εacc), apparent diffusion coefficient (Da) and distribution coefficient (Kd) were decreased with the increasing of dry density. The De values were (2.8 ± 0.2) x 10-11 m2/s and (3.5 ± 0.2) x 10-12 m2/s at dry density of 1,600 and 1,800 kg/m3, respectively. It was indicated that the dominating species was TcO4- during the diffusion processing. While, out-diffusion results showed that part of TcO4- may be reduced by Fe(II). The relationship of De and εacc could be described by Archie's law with exponent n = 2.4 for 99Tc diffusion in GMZ bentonite. Furthermore, the relationship between Da and dry density (ρ) was exponential. (author)

  3. Ion diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, Kd, unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.)

  4. Chemical diffusion during isobaric degassing of magma

    Science.gov (United States)

    von Aulock, Felix W.; Kennedy, Ben M.; Lavallée, Yan; Henton-de Angelis, Sarah; Oze, Christopher; Morgan, Daniel J.; Clesham, Steve

    2014-05-01

    During ascent of magma, volatiles exsolve and bubbles form. Volatiles can either escape through a permeable network of bubbles in an open system or be trapped in non-connected pores during closed system degassing. Geochemical studies have shown that in most cases both- open system and closed system degassing take place at the same time. During cooling of the melt, diffusion slows down and eventually diffusional gradients get frozen in, preserving a history of degassing and rehydration during bubble growth, bubble collapse and crystal growth. We present data from experiments in which natural obsidian was degassed at atmospheric pressures at 950ºC over timescales of 3-24h. During bubble growth, a skin formed, at the outer edge of the sample, effectively prohibiting any degassing of its interior. Diffusion gradients were measured across the glass surrounding vesicles, and across this impermeable skin. Water contents were analyzed with synchrotron sourced Fourier transform infrared spectroscopy and several major, minor and trace elements were mapped using synchrotron sourced X-ray fluorescence spectroscopy. The samples show a dimpled surface, as well as signs of oxidation and growth of submicroscopic crystals. Water contents around bubbles decrease in simple heating experiments (from ~0.13 wt. % down to ~0.1 wt. %), whereas slight rehydration of the vesicle wall can be observed when a second, cooler step at 850ºC follows the initial 950ºC. Water gradients towards the outside of the sample decrease linearly to a minimum of ~0.045 wt. %, far below the solubility of water in melts at these temperatures. We mapped the distribution of K, Ca, Fe, Ti, Mn, Rb, Sr, Y and Zr. Especially the trace elements show a decrease towards the outside of the sample, whereas K, Fe, Ca and Ti generally do not show significant partitioning between melt and gas/crystal phase. Several effects could attribute to the distribution of these elements, such as the crystal growth and exchange with

  5. Observations of Exoplanet Atmospheres

    CERN Document Server

    Crossfield, Ian J M

    2015-01-01

    Detailed characterization of an extrasolar planet's atmosphere provides the best hope for distinguishing the makeup of its outer layers, and the only hope for understanding the interplay between initial composition, chemistry, dynamics & circulation, and disequilibrium processes. In recent years, some areas have seen rapid progress while developments in others have come more slowly and/or have been hotly contested. This article gives an observer's perspective on the current understanding of extrasolar planet atmospheres prior to the considerable advances expected from the next generation of observing facilities. Atmospheric processes of both transiting and directly-imaged planets are discussed, including molecular and atomic abundances, cloud properties, thermal structure, and planetary energy budgets. In the future we can expect a continuing and accelerating stream of new discoveries, which will fuel the ongoing exoplanet revolution for many years to come.

  6. Atmospheric Radiative Transfer

    Science.gov (United States)

    Perliski, Lori

    Because radiative transfer cuts across many scientific disciplines with applications including remote sensing, climate, atmospheric chemistry, and photobiology, there is a need for comprehensive books on this subject that can appeal to a wide readership. While Atmospheric Radiative Transfer takes strides toward filling this niche by addressing a broad range of topics, it is dry reading and suffers from lack of detail. The book was based on a graduate-level course taught at the University of Sciences and Technologies in Lille, France, and indeed, the text reads much like an expanded outline perhaps derived from lecture notes.Part one deals with general radiative transfer, and part two covers Earth's radiation budget, the climate system, and remote sensing techniques. The radiative transfer equation and solutions for absorbing and scattering atmospheres are discussed as are the details of absorption, such as energy levels, line strengths, line intensities, equivalent widths, and weak- and strong-line limits.

  7. Observations of Exoplanet Atmospheres

    Science.gov (United States)

    Crossfield, Ian J. M.

    2015-10-01

    Detailed characterization of an extrasolar planet's atmosphere provides the best hope for distinguishing the makeup of its outer layers, and the only hope for understanding the interplay between initial composition, chemistry, dynamics and circulation, and disequilibrium processes. In recent years, some areas have seen rapid progress, while developments in others have come more slowly and/or have been hotly contested. This article gives an observer's perspective on the current understanding of extrasolar planet atmospheres prior to the considerable advances expected from the next generation of observing facilities. Atmospheric processes of both transiting and directly imaged planets are discussed, including molecular and atomic abundances, cloud properties, thermal structure, and planetary energy budgets. In the future we can expect a continuing and accelerating stream of new discoveries, which will fuel the ongoing exoplanet revolution for many years to come.

  8. Atmospheres of Brown Dwarfs

    CERN Document Server

    Helling, Christiane

    2014-01-01

    Brown Dwarfs are the coolest class of stellar objects known to date. Our present perception is that Brown Dwarfs follow the principles of star formation, and that Brown Dwarfs share many characteristics with planets. Being the darkest and lowest mass stars known makes Brown Dwarfs also the coolest stars known. This has profound implication for their spectral fingerprints. Brown Dwarfs cover a range of effective temperatures which cause brown dwarfs atmospheres to be a sequence that gradually changes from a M-dwarf-like spectrum into a planet-like spectrum. This further implies that below an effective temperature of < 2800K, clouds form already in atmospheres of objects marking the boundary between M-Dwarfs and brown dwarfs. Recent developments have sparked the interest in plasma processes in such very cool atmospheres: sporadic and quiescent radio emission has been observed in combination with decaying Xray-activity indicators across the fully convective boundary.

  9. Photochemistry of Pluto's Atmosphere

    Science.gov (United States)

    Krasnopolsky, Vladimir A.

    1999-01-01

    This work include studies of two problems: (1) Modeling thermal balance, structure. and escape processes in Pluto's upper atmosphere. This study has been completed in full. A new method, of analytic solution for the equation of hydrodynamic flow from in atmosphere been developed. It was found that the ultraviolet absorption by methane which was previously ignored is even more important in Pluto's thermal balance than the extreme ultraviolet absorption by nitrogen. Two basic models of the lower atmosphere have been suggested, with a tropopause and a planetary surface at the bottom of the stellar occultation lightcurve, respectively, Vertical profiles, of temperature, density, gas velocity, and the CH4 mixing ratio have been calculated for these two models at low, mean, and high solar activity (six models). We prove that Pluto' " s atmosphere is restricted to 3060-4500 km, which makes possible a close flyby of future spacecraft. Implication for Pluto's evolution have also been discussed. and (2) Modeling of Pluto's photochemistry. Based on the results of (1), we have made some changes in the basic continuity equation and in the boundary conditions which reflect a unique can of hydrodynamic escape and therefore have not been used in modeling of other planetary atmospheres. We model photochemistry of 44 neutral and 23 ion species. This work required solution of a set of 67 second-order nonlinear ordinary differential equations. Two models have been developed. Each model consists of the vertical profiles for 67 species, their escape and precipitation rates. These models predict the chemical structure and basic chemical processes in the current atmosphere and possible implication of these processes for evolution. This study has also been completed in full.

  10. Composition of Estonian atmosphere

    International Nuclear Information System (INIS)

    Atmospheric study, particularly that of its chemical composition, has a long tradition in Estonia. Since middle of this century, in addition to meteorological observations, some chemical compounds in precipitations have been regularly measured in many meteorological stations. The main aim was to acquire information about the state and dynamics of the atmosphere. Therefore, main attention was paid to monitoring chemical compounds which have a direct impact on the human environment. As energy production developed intensively and SO2 and NOx increased drastically in the atmosphere in acidic rock areas, like Scandinavia, the problem of acid rain became the most important environmental problem in Europe and North-America. As a consequence, monitoring the compounds of sulphur in precipitation was organized in Estonia. In the 1970 s, as related to large operating oil shale-based power plants, Estonia became a country , where emissions of sulphur compounds per capita were extremely high. In 1979, Estonia became a participant in the European Monitoring and Evaluation Programme - the network created to study transboundary air pollution. The aims of the precipitation chemistry study and the related problems of the formation and transformation of the atmospheric composition have varied over the years. But monitoring of pollutant (in particular, sulphur compound) loads has been a central issue. Over recent years, an attempt was made to estimate the spatial regularities of atmospheric impurities and their impact on the pH of mean monthly precipitations. Furthermore, calculations were provided to find out the origin of atmospheric impurities washed out in Estonia. Until the 1990 s, CO2, and some other greenhouse gas (GHG) emissions were not studied in Estonia. The first inventory of GHG for Estonia was provided in 1995 using the Intergovernmental Panel on Climate Change (IPCC) methodology

  11. Propagators and Time-Dependent Diffusion Coefficients for Anomalous Diffusion

    OpenAIRE

    Wu, Jianrong; Berland, Keith M.

    2008-01-01

    Complex diffusive dynamics are often observed when one is investigating the mobility of macromolecules in living cells and other complex environments, yet the underlying physical or chemical causes of anomalous diffusion are often not fully understood and are thus a topic of ongoing research interest. Theoretical models capturing anomalous dynamics are widely used to analyze mobility data from fluorescence correlation spectroscopy and other experimental measurements, yet there is significant ...

  12. Spin diffusion in Fermi gases

    DEFF Research Database (Denmark)

    Bruun, Georg

    2011-01-01

    We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures......, strong correlation effects are included through the Landau parameters which we extract from Monte Carlo results. We show that the spin diffusion coefficient has a minimum for a temperature somewhat below the Fermi temperature with a value that approaches the quantum limit ~/m in the unitarity regime...

  13. Diffusion coefficients for absorbing materials

    International Nuclear Information System (INIS)

    A method to improve the diffusion results for systems containing strong absorbers is described. Each absorbing material is transformed into an equivalent rectangle. Transport and diffusion calculations in slab geometry are performed for both directions of the rectangle, and group-dependent diffusion coefficients are determined by matching the outgoing currents. Test problems comprise a critical slab, a compact PWR fuel element storage pool and two BWR fuel elements with a control rod and a poison cell. The multiplication factors of these systems are calculated with an accuracy of 1 to 2%. (Auth.)

  14. Phosphorus diffusion in polycrystalline silicon

    Science.gov (United States)

    Losee, D. L.; Lavine, J. P.; Trabka, E. A.; Lee, S.-T.; Jarman, C. M.

    1984-02-01

    The diffusion of phosphorus in crystallized amorphous Si layers was studied with secondary-ion mass spectroscopy. A two-dimensional diffusion model is used to find effective grain (Dg) and grain-boundary (Dgb) diffusion coefficients. This simplified model leads to Dgb ≤ 10Dg, which is significantly lower than what has been deduced from conventional, larger grained polysilicon. Our result is consistent with specific-gravity measurements, which found a significantly lower ``mass defect'' for layers deposited amorphous and subsequently crystallized as compared to initially polycrystalline layers.

  15. Anomalous Diffusion with Absorbing Boundary

    OpenAIRE

    Kantor, Yacov; Kardar, Mehran

    2007-01-01

    In a very long Gaussian polymer on time scales shorter that the maximal relaxation time, the mean squared distance travelled by a tagged monomer grows as ~t^{1/2}. We analyze such sub-diffusive behavior in the presence of one or two absorbing boundaries and demonstrate the differences between this process and the sub-diffusion described by the fractional Fokker-Planck equation. In particular, we show that the mean absorption time of diffuser between two absorbing boundaries is finite. Our res...

  16. Atmospheric transport of radionuclides

    International Nuclear Information System (INIS)

    The chairman and contributors are members of the Working Group on Atmospheric Dispersion, Deposition, and Resuspension. This group examined the mathematical approaches for determining the direct and indirect pathways to man of releases of pollutants to the atmosphere. The dose-to-man limitations promulgated by the Nuclear Regulatory Commission, the Environmental Protection Agency, and the Energy Research and Development Administration were presented. The present status of research was discussed, and recommendations for future work were made. Particular emphasis was placed on the need for additional experimental work to develop confidence limits leading to acceptable probability statements of critical pathways for determining the dose-to-man

  17. Exoplanet atmospheres physical processes

    CERN Document Server

    Seager, Sara

    2010-01-01

    Over the past twenty years, astronomers have identified hundreds of extrasolar planets--planets orbiting stars other than the sun. Recent research in this burgeoning field has made it possible to observe and measure the atmospheres of these exoplanets. This is the first textbook to describe the basic physical processes--including radiative transfer, molecular absorption, and chemical processes--common to all planetary atmospheres, as well as the transit, eclipse, and thermal phase variation observations that are unique to exoplanets. In each chapter, Sara Seager offers a conceptual introdu

  18. Atmospheric science and emergency preparedness: the DOE/OHER perspective

    International Nuclear Information System (INIS)

    In the 1950s, Office of Health and Environmental Research (OHER) funded pioneering research on precipitation scavenging and dry deposition as processes removing radioactive particles and gases from the atmosphere. In the early 1970s, the Atmospheric Release Advisory Capability (ARAC) was conceived. This is a system combining knowledge of atmospheric transport and diffusion with hihg-speed computing and modern communications systems. It provides real-time advice on the movement and spread of a radioactive or chemical release to the atmosphere. ARAC has been activated in a variety of threatening situations. Through the lessons learned from real-world accident responses, ARAC has evolved an extensive set of emergency response services. ARAC is now supported by operational groups in the Departments of Defense and Energy. In 1989 there are 73 sites and facilities in the U.S. being served by the ARAC system. In the 1980s, two major programs were launched. The first was a tracer experiment, CAPTEX (Cross-Appalachian Tracer Experiment), which used perfluorocarbons and explored transport and diffusion over distances greater than 1000km. The second is a continuing field and modeling activity, ASCOT (Atmospheric Studies in Complex Terrain), studying the meteorology of transport and dispersion over the rugged terrain that dominates the western energy-rich regions of the U.S. ASCOT is currently focusing its research activities on fundamental meteorological forecasting problems that have generic value to the emergency preparedness planning at key DOE facilities

  19. Re-evaluating the Frankfurt isothermal static diffusion chamber for ice nucleation

    OpenAIRE

    J. Schrod; A. Danielczok; Weber, D.; M. Ebert; Thomson, E. S.; H. G. Bingemer

    2015-01-01

    Recently significant advances have been made in the collection, detection, and characterization of ice nucleating particles (INP). Ice nuclei are particles that facilitate the heterogeneous formation of ice within the atmospheric aerosol by lowering the free energy barrier to spontaneous nucleation and growth of ice from atmospheric water and/or vapor. The Frankfurt isostatic diffusion chamber (FRIDGE) is an INP collection and offline detection system that has become widely deployed and sho...

  20. Re-evaluating the Frankfurt isothermal static diffusion chamber for ice nucleation

    OpenAIRE

    Schrod, Jann; Danielczok, Anja; Weber, Daniel; Ebert, Martin; Thomson, Erik S.; Bingemer, Heinz G.

    2016-01-01

    Recently significant advances have been made in the collection, detection and characterization of ice nucleating particles (INPs). Ice nuclei are particles that facilitate the heterogeneous formation of ice within the atmospheric aerosol by lowering the free energy barrier to spontaneous nucleation and growth of ice from atmospheric water and/or vapor. The Frankfurt isostatic diffusion chamber (FRankfurt Ice nucleation Deposition freezinG Experiment: FRIDGE) is an INP collecti...

  1. APC: A New Code for Atmospheric Polarization Computations

    Science.gov (United States)

    Korkin, Sergey V.; Lyapustin, Alexei I.; Rozanov, Vladimir V.

    2014-01-01

    A new polarized radiative transfer code Atmospheric Polarization Computations (APC) is described. The code is based on separation of the diffuse light field into anisotropic and smooth (regular) parts. The anisotropic part is computed analytically. The smooth regular part is computed numerically using the discrete ordinates method. Vertical stratification of the atmosphere, common types of bidirectional surface reflection and scattering by spherical particles or spheroids are included. A particular consideration is given to computation of the bidirectional polarization distribution function (BPDF) of the waved ocean surface.

  2. Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records

    DEFF Research Database (Denmark)

    Buizert, C.; Sowers, T.; Blunier, T.

    2013-01-01

    cores and firn need to be corrected for this diffusive fractionation artifact. We present a novel, semi-empirical method to accurately estimate the magnitude of the diffusive fractionation in the ice core record. Our method (1) consists of a relatively simple analytical calculation; (2) requires only...... commonly available ice core data; (3) is not subject to the uncertainties inherent to estimating the accumulation rate, temperature, close-off depth and depth-diffusivity relationship back in time; (4) does not require knowledge of the true atmospheric variations, but uses the smoothed records obtained...

  3. Influence of Annealing on the Grain Growth and Thermal Diffusivity of Nanostructured YSZ Thermal Barrier Coating

    Institute of Scientific and Technical Information of China (English)

    Na WANG; Chungen ZHOU; Shengkai GONG; Huibin XU

    2006-01-01

    The nanostructured zirconia coatings were deposited by atmospherically plasma spraying. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction were used to investigate the microstructure of the zirconia coatings. Thermal diffusivity values at normal temperatures have been evaluated by laser flash technique. Effect of annealing on the microstructure evolution of the zirconia coating has been performed. The grains and thermal diffusivity are increased with increasing annealing time and temperature.The grain growth is according to the GRIGC (the grain rotation induced grain coalescence) mechanism. The increase in thermal diffusivity is attributed to the grain growth and the decrease in porosity of nanostructured zirconia coatings.

  4. Atmospheric radon families and environmental radioactivity

    International Nuclear Information System (INIS)

    The Committee on Investigation and Research Regarding the Effect of Radon in the Atmosphere Exerted on Environmental Radioactivity was organized, in 1982, in order to carry out the research and discussion on radon and joint observation. As the results, the following facts were revealed: (1) the effectiveness of various methods of measuring environmental radon and its daughters, for example, Track Etch Detectors for the deposition rate of airborne radon daughters, (2) the analysis of radon family concentration from the viewpoint of geophysical phenomena, for instance, the relationships among the concentration, wind speed, solar radiation, net radiation, atmospheric stability, precipitation snow cover, and diffusion equation. And it was also reveleaed that the exhalation rate of radon at Siberia in winter is not low in spite of low temperature, and that the scavenging effect of snowfall to radon daughters is large, from the comparison between the atmospheric radon daughters concentrations at the Japan Sea and at Fukui located at north part of Central Japan. (J.P.N.)

  5. Inhomogeneous nucleosynthesis with neutron diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Kurki-Suonio, H.; Matzner, R.A.; Centrella, J.M.; Rothman, T.; Wilson, J.R.

    1988-08-15

    It was recently proposed that a critical, i.e., closure, baryon density could be compatible with helium and deuterium observations, if this baryon density were suitably inhomogeneous during cosmic nucleosynthesis. In this scenario, neutrons would diffuse out of the high-density regions, which would lead to a nonstandard nucleosynthesis, with reduced helium production and improved deuterium survival, and could restore the agreement with observations, which is lost in homogeneous closure models. We have used a numerical model which shows that this proposal is not viable. Our model combines inhomogeneous nucleosynthesis and neutron diffusion self-consistently to study element formation in inhomogeneous situations in which diffusion is important. We find that the proposal fails: it is very difficult to lower the helium production significantly or to raise the final deuterium abundance, because the neutrons diffuse back to the high-density region once nucleosynthesis begins there.

  6. Diffusion mechanisms in intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Larikov, L.N. (ANU, Inst. Metallofiziki, Kiev (Ukraine))

    1992-08-01

    Recent research aimed at the identification of the principal mechanisms of diffusion in intermetallics is reviewed. In particular, attention is given to the effect of the type of interatomic bond on the contribution of different mechanisms to diffusion in ordered metallic compounds. Results of an analysis of experimental determinations of diffusion coefficients D(A) and D(B) in binary intermetallics (CuZn, Cu3Sn, AuCd, AgZn, AgMg, InSb, GaSb, AlSb, Fe3Al, FeAl, FeAl3, Ni3Al, Ni3Nb, FeSn, FeSn2, Ni3Sn2, Ni3Sn4, Co3Sn2, CoSn, CoSn2, and CoGa) are presented, and it is shown that the D(A)/D(B) ratio differs substantially for different diffusion mechanisms. 60 refs.

  7. Diffusion from cylindrical waste forms

    International Nuclear Information System (INIS)

    The diffusion of a single component material from a finite cylindrical waste form, initially containing a uniform concentration of the material, is investigated. Under the condition that the cylinder is maintained in a well-stirred bath, expressions for the fractional inventory leached and the leach rate are derived with allowance for the possible permanent immobilization of the diffusant through its decay to a stable product and/or its irreversible reaction with the waste form matrix. The usefulness of the reported results in nuclear waste disposal applications is emphasized. The results reported herein are related to those previously derived at Oak Ridge National Laboratory by Bell and Nestor. A numerical scheme involving the partial decoupling of nested infinite summations and the use of rapidly converging rational approximants is recommended for the efficient implementation of the expressions derived to obtain reliable estimates of the bulk diffusion constant and the rate constant describing the diffusant-waste form interaction from laboratory data

  8. Simulation of multivariate diffusion bridges

    DEFF Research Database (Denmark)

    Bladt, Mogens; Finch, Samuel; Sørensen, Michael

    We propose simple methods for multivariate diffusion bridge simulation, which plays a fundamental role in simulation-based likelihood and Bayesian inference for stochastic differential equations. By a novel application of classical coupling methods, the new approach generalizes a previously...

  9. Diffusive conductors as Andreev interferometers

    OpenAIRE

    Nazarov, Y. V.; Stoof, T. H.

    1995-01-01

    We present a novel mechanism of phase-dependent electric transport in diffusive normal metal-superconductor structures. We provide a detailed theoretical and numerical analysis of recent unexplained experiments essentially explaining them.

  10. Atmospheric and aerosol chemistry

    International Nuclear Information System (INIS)

    This series presents critical reviews of the present position and future trends in modern chemical research. Short and concise reports on chemistry, each written by the world renowned experts. Still valid and useful after 5 or 10 years. More information as well as the electronic version of the whole content available at: springerlink.com. Christian George, Barbara D'Anna, Hartmut Herrmann, Christian Weller, Veronica Vaida, D. J. Donaldson, Thorsten Bartels-Rausch, Markus Ammann Emerging Areas in Atmospheric Photochemistry. Lisa Whalley, Daniel Stone, Dwayne Heard New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory. Neil M. Donahue, Allen L. Robinson, Erica R. Trump, Ilona Riipinen, Jesse H. Kroll Volatility and Aging of Atmospheric Organic Aerosol. P. A. Ariya, G. Kos, R. Mortazavi, E. D. Hudson, V. Kanthasamy, N. Eltouny, J. Sun, C. Wilde Bio-Organic Materials in the Atmosphere and Snow: Measurement and Characterization V. Faye McNeill, Neha Sareen, Allison N. Schwier Surface-Active Organics in Atmospheric Aerosols.

  11. Solar Atmosphere Models

    Science.gov (United States)

    Rutten, R. J.

    2002-12-01

    This contribution honoring Kees de Jager's 80th birthday is a review of "one-dimensional" solar atmosphere modeling that followed on the initial "Utrecht Reference Photosphere" of Heintze, Hubenet & de Jager (1964). My starting point is the Bilderberg conference, convened by de Jager in 1967 at the time when NLTE radiative transfer theory became mature. The resulting Bilderberg model was quickly superseded by the HSRA and later by the VAL-FAL sequence of increasingly sophisticated NLTE continuum-fitting models from Harvard. They became the "standard models" of solar atmosphere physics, but Holweger's relatively simple LTE line-fitting model still persists as a favorite of solar abundance determiners. After a brief model inventory I discuss subsequent work on the major modeling issues (coherency, NLTE, dynamics) listed as to-do items by de Jager in 1968. The present conclusion is that one-dimensional modeling recovers Schwarzschild's (1906) finding that the lower solar atmosphere is grosso modo in radiative equilibrium. This is a boon for applications regarding the solar atmosphere as one-dimensional stellar example - but the real sun, including all the intricate phenomena that now constitute the mainstay of solar physics, is vastly more interesting.

  12. Climate and atmospheric research

    International Nuclear Information System (INIS)

    This issue of the scientific journal of the Humboldt university is dedicated to results of research work carried out to the greatest extent at the meteorological institute in the last two years on the area of climate and atmospheric research. The traditional research areas of the institute are climatology and the dynamics of the atmosphere, in particular the atmospherical boundary layer. Considering the high probability of a global climatic fluctuation due to the anthropogenic change of composition of the atmosphere and other climate-relevant factors imminent in the next century, climatological research today is an important part of global and regional environmental research. From the necessity of determination and evaluation of the effect of climatic fluctuations on nature and society the contours of a new interdisciplinary research area are already visible now. This is suitable as hardly any other area to be the supporting idea of environmental research at universities. The contributions contained in the issue already consider, in addition to results on climate diagnosis, also results on aspects of climate effect research. (orig./KW)

  13. Astronomy and Atmospheric Optics

    Science.gov (United States)

    Cowley, Les; Gaina, Alex

    2011-12-01

    The authors discusse the insuccess of the observation of the Total Eclipse of the Moon from 10 december 2011 in Romania and relate them with meteoconditions. Only a very short part of the last penumbral phase was observed, while the inital part and the totality was not observed due to very dense clouds. The change in color and brightness during this phase was signaled. Meanwhile, there is an area of science where clouds are of great use and interest. This area is Atmospheric optics, while the science which study clouds is meteorology. Clouds in combination with Solar and Moon light could give rise to a variety of strange, rare and unobvious phenomena in the atmosphere (sky), sometimes confused with Unidentified Flying Objects (UFO). The importance of meteorology for astronomy and atmospheric optics is underlined and an invitation to astronomers to use unfavourable days for athmospheric observations was sent. The web address of the site by Les Cowley, designed for atmospheric optics phenomena is contained in the text of the entry.

  14. Results from atmospheric neutrinos

    Indian Academy of Sciences (India)

    J G Learned

    2000-07-01

    With the announcement of new evidence for muon neutrino disappearance observed by the super-Kamiokande experiment, the more than a decade old atmospheric neutrino anomaly moved from a possible indication for neutrino oscillations to an apparently inescapable fact. The evidence is reviewed, and new indications are presented that the oscillations are probably between muon and tau neutrinos. Implications and future directions are discussed.

  15. Vehicle Cabin Atmosphere Monitor

    Science.gov (United States)

    Chutjian, Ara; Darrach, Muray

    2007-01-01

    Vehicle Cabin Atmosphere Monitor (VCAM) identifies gases that are present in minute quantities in the International Space Station (ISS) breathing air that could harm the crew s health. If successful, instruments like VCAM could accompany crewmembers during long-duration exploration missions to the Moon or traveling to Mars.

  16. Contaminants in the Atmosphere

    DEFF Research Database (Denmark)

    Skov, H.; Bossi, R.; Wåhlin, P.;

    This report presents the results of atmospheric monitoring in Nuuk, Greenland. A long series of heavy metals and persistent organic Pollutants (POPs) have been measured and model calculations have been carried out supporting the interpretation of the results. Financially, the Danish Environmental...

  17. Diffusion behaviour of vanadium in GaN thin films studied by secondary ion mass spectrometry

    International Nuclear Information System (INIS)

    A sandwiched multi-structure made of alternatively undoped and vanadium (V) doped GaN layers was grown on SiN-treated (0 0 0 1) sapphire substrates by atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD). The V diffusion in GaN has been investigated in the temperature range of 1000–1100 °C by using secondary ion mass spectroscopy. The diffusion coefficients were obtained through a data-fitting program based on Fick's first law. The results suggest that V diffuses faster near the GaN/sapphire interface. During annealing, V redistributed by both in- and out-diffusion mechanisms. An activation energy of 2.9 ± 0.4 eV is estimated for V diffusion in GaN

  18. Diffusive flux in a model of stochastically gated oxygen transport in insect respiration

    Science.gov (United States)

    Berezhkovskii, Alexander M.; Shvartsman, Stanislav Y.

    2016-05-01

    Oxygen delivery to insect tissues is controlled by transport through a branched tubular network that is connected to the atmosphere by valve-like gates, known as spiracles. In certain physiological regimes, the spiracles appear to be randomly switching between open and closed states. Quantitative analysis of this regime leads a reaction-diffusion problem with stochastically switching boundary condition. We derive an expression for the diffusive flux at long times in this problem. Our approach starts with the derivation of the passage probability for a single particle that diffuses between a stochastically gated boundary, which models the opening and closing spiracle, and the perfectly absorbing boundary, which models oxygen absorption by the tissue. This passage probability is then used to derive an expression giving the diffusive flux as a function of the geometric parameters of the tube and characteristic time scales of diffusion and gate dynamics.

  19. Culture, Diffusion, and Economic Development

    OpenAIRE

    Harutyunyan, Ani; Özak, Ömer

    2016-01-01

    This research explores the effects of culture on technological diffusion and economic development. It shows that culture's direct effects on development and barrier effects to technological diffusion are, in general, observationally equivalent. In particular, using a large set of cultural measures, it establishes empirically that pairwise differences in contemporary development are associated with pairwise cultural differences relative to the technological frontier, only in cases where obse...

  20. Analysis of diffusion battery data

    International Nuclear Information System (INIS)

    A brief review is given of the use of diffusion batteries to obtain size information about ultrafine aerosol particles. Accurate formulas are included for the penetration functions of circular tube and parallel plate diffusion cells. After noting the usefulness of some previously suggested data inversion techniques, a new method for obtaining a 'complete' solution, is outlined. The techniques are illustrated by the analysis of some experimental data. (author)

  1. Active diffusion of motor particles

    OpenAIRE

    Klumpp, Stefan; Lipowsky, Reinhard

    2005-01-01

    The movement of motor particles consisting of one or several molecular motors bound to a cargo particle is studied theoretically. The particles move on patterns of immobilized filaments. Several patterns are described for which the motor particles undergo non-directed but enhanced diffusion. Depending on the walking distance of the particles and the mesh size of the patterns, the active diffusion coefficient exhibits three different regimes. For micrometer-sized motor particles in water, e.g....

  2. Boron diffusion in silicon devices

    Science.gov (United States)

    Rohatgi, Ajeet; Kim, Dong Seop; Nakayashiki, Kenta; Rounsaville, Brian

    2010-09-07

    Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.

  3. Anomalous Diffusion in Velocity Space

    OpenAIRE

    Trigger, S. A.

    2009-01-01

    The problem of anomalous diffusion in the momentum space is considered on the basis of the appropriate probability transition function (PTF). New general equation for description of the diffusion of heavy particles in the gas of the light particles is formulated on basis of the new approach similar to one in coordinate space (S. Trigger et al.). The obtained results permit to describe the various situations when the probability transition function (PTF) has a long tail in the momentum space. ...

  4. Turbulent-diffusion vertical transfer coefficient in relationship to the electrical parameters of air

    International Nuclear Information System (INIS)

    The vertical movement of ions in the lower atmosphere is due to two main causes: the atmospheric electrical field and turbulent diffusion. The vertical current is thus the sum of a conduction current and of a diffusion current. In order to resolve the discrepancies between the theories usually adopted (which neglect the diffusion current) and the experimental results, we propose here a theoretical model which takes into account the turbulent diffusion. This model makes it possible, if it is assumed that the conductivity is independent of the altitude in the exchange layer, to calculate the diffusivity from the three basic electrical parameters: electrical field, space charge, conductivity. The diffusivity values thus obtained have been compared to those deduced from thoron determinations made at different levels, and carried out at the same point and at the same time as the measurements of the electrical parameters. When the diffusivity is greater than 0.05 m2s-1 (this corresponding to adiabatic or super-adiabatic conditions) the values obtained are practically equal. This theoretical model thus appears to be satisfactory. (author)

  5. Time-dependent atomic diffusion in magnetic ApBp stars

    Science.gov (United States)

    Stift, M. J.; Alecian, G.

    2016-03-01

    Numerical modelling of surface abundance distributions in ApBp star atmospheres constitutes a challenging astrophysical problem. This paper is intended to deepen our understanding of how atomic diffusion affects the atmospheric structure of magnetic ApBp stars, and in particular how time-dependent calculations may be compared to the alternative method of estimating equilibrium stratifications. Our numerical calculations - with the stellar atmosphere adjusted self-consistently to the abundance profiles - show that final stationary solutions of the time-dependent diffusion problem (constant particle flux throughout the stellar atmosphere) are seemingly at variance with equilibrium stratifications (zero particle flux). In this work, we will provide some understanding of the origin of these differences and try to elucidate the as yet little explored behaviour of time-dependent atomic diffusion. To this purpose, we assess the influence of the boundary condition at the bottom of the atmosphere, we investigate how the stratifications depend on magnetic field angle and strength, and we have a look at possible interactions between different chemical elements. Based on a grid of atmospheric models and stratifications reflecting dipolar magnetic geometries, we also present predicted line profiles for different oblique rotator models. Finally, we shortly discuss the consequences of our findings for the interpretation of abundance maps of magnetic ApBp stars.

  6. Diffusivity in silicon 1953 to 2009

    CERN Document Server

    Fisher, David J

    2010-01-01

    This work is essentially an update of previous compilations of information on the diffusivity of elements in semiconductor-grade silicon. It subsumes the data contained in B.L.Sharma's monograph on 'Diffusion in Semiconductors' (Trans Tech Publications, 1970), plus the data contained in Diffusion and Defect Data (Diffusion in Silicon) Volume 45 (1986), Defect and Diffusion Forum (Diffusion in Silicon - 10 years of Research) Volumes 153-155 (1998), Defect and Diffusion Forum (Diffusion in Silicon - a Seven-Year Retrospective) Volume 241 (2005) and the latest data from recent Semiconductor Retro

  7. Oxygen diffusion in Bi2O3-doped ZnO

    Directory of Open Access Journals (Sweden)

    Antônio Claret Soares Sabioni

    2008-06-01

    Full Text Available In order to clarify the influence of Bi-doping on oxygen diffusion in ZnO, the bulk and grain boundary oxygen diffusion coefficients were measured in Bi2O3-doped ZnO polycrystals by means of the gas-solid exchange method using the isotope 18O as the oxygen tracer. The experiments were performed on ZnO sintered samples containing 0.1, 0.3 and 0.5 mol% Bi2O3. The diffusion annealings were performed at 942, 1000 and 1092 °C, in an Ar+18O2 atmosphere under an oxygen partial pressure of 0.2 atm. After the diffusion annealings, the 18O diffusion profiles were established by secondary ion mass spectrometry (SIMS. The results show an increase in the oxygen diffusion in the Bi2O3-doped ZnO, when compared to the oxygen diffusion in the undoped ZnO polycrystal under the same experimental conditions, both in bulk and in grain-boundaries. Moreover, it was observed that the higher the Bi2O3 concentration, the higher the oxygen diffusion. These results suggest that the incorporation of Bi2O3 increases the interstitial oxygen concentration which agrees with an interstitial diffusion mechanism both in bulk and in grain-boundaries.

  8. Study of the diffusion of iron, of silver and of carbon in beryllium using radioactive tracers

    International Nuclear Information System (INIS)

    A study has been made of the diffusion of radioactive iron and silver tracers in beryllium. The following values have been found. DFe = 0.53 exp - [51800 / RT], DAg = 62 exp - [46100 / RT]. The values for iron are in good agreement with those found previously for chemical diffusion. A comparison of the diffusion coefficients for iron, silver and nickel shows that the diffusion rate increases with increasing solute atom radius. The existence has been shown of diffusion anisotropy for silver; it has been studied quantitatively on monocrystals. It is found that: Dparallel 0.41 exp - [39100 / RT], Dperpendicular = 1.98 exp - [45700 / RT]. The anisotropy decreases as the temperature increases. The silver diffuses more rapidly along the C axis than in the base plane. This result cannot be explained in terms of the model proposed for the diffusion of foreign atoms in solution in zinc. A greater number of experiments is required before a model can be put forward. An attempt has also been made to determine the diffusion coefficients of carbon in beryllium by treatment in an atmosphere of acetylene marked with C-14. Diffusion coefficients have been obtained but these should not be considered to be very significant since a chemical reaction occurs at the surface of the samples. (author)

  9. Diffusion, confusion and functional MRI

    International Nuclear Information System (INIS)

    Diffusion MRI has been introduced in 1985 and has had a very successful life on its own. While it has become a standard for imaging stroke and white matter disorders, the borders between diffusion MRI and the general field of fMRI have always remained fuzzy. First, diffusion MRI has been used to obtain images of brain function, based on the idea that diffusion MRI could also be made sensitive to blood flow, through the intra-voxel incoherent motion (IVIM) concept. Second, the IVIM concept helped better understand the contribution from different vasculature components to the BOLD fMRI signal. Third, it has been shown recently that a genuine fMRI signal can be obtained with diffusion MRI. This 'DfMRI' signal is notably different from the BOLD fMRI signal, especially for its much faster response to brain activation both at onset and offset, which points out to structural changes in the neural tissues, perhaps such as cell swelling, occurring in activated neural tissue. This short article reviews the major steps which have paved the way for this exciting development, underlying how technical progress with MRI equipment has each time been instrumental to expand the horizon of diffusion MRI toward the field of fMRI. (authors)

  10. Stability of a Diffusing Plasma

    International Nuclear Information System (INIS)

    In the DAPHNIS experiment the plasma produced by a magnetron source diffuses along a static magnetic field B0. There will, therefore, be neither a macroscopic current . nor a flux of fast electrons through the measuring chamber located about a metre from the source. Since the neutral gas pressure in the chamber may vary from 10-2 to 10-5 Torr it is verified first that the plasma in fact behaves as a true diffusing plasma, namely, that its density increases with B0 and decreases as the pressure is increased. However, by measuring Da⊥, the coefficient of ambipolar diffusion perpendicular to B0, it was found that anomalous diffusion takes place. We therefore analysed the noise emitted by the plasma, and determined a distinct emission in two clearly defined regions of the spectrum: a) a UHF noise emitted in two separate bands on either side of the electron cyclotron frequency b) an HF noise from 1 to 10 Mc/s whose amplitude is correlated with density fluctuations of frequency equal to some tens of kilocycles per second. But the coefficient of diffusion Da⊥ varies as a function of B0 similarly to the emitted noise intensity. In order to identify the two types of instability responsible for this emission, we measured the velocity distribution function of the electrons in the source and in the measuring chamber. The influence of these Instabilities on the particle diffusion perpendicular to B0 is analysed in this investigation. (author)

  11. Lead diffusion in monazite; Diffusion du plomb dans la monazite

    Energy Technology Data Exchange (ETDEWEB)

    Gardes, E

    2006-06-15

    Proper knowledge of the diffusion rates of lead in monazite is necessary to understand the U-Th-Pb age anomalies of this mineral, which is one of the most used in geochronology after zircon. Diffusion experiments were performed in NdPO{sub 4} monocrystals and in Nd{sub 0.66}Ca{sub 0.17}Th{sub 0.17}PO{sub 4} polycrystals from Nd{sub 0.66}Pb{sub 0.17}Th{sub 0.17}PO{sub 4} thin films to investigate Pb{sup 2+} + Th{sup 4+} {r_reversible} 2 Nd{sup 3+} and Pb{sup 2+} {r_reversible} Ca{sup 2+} exchanges. Diffusion annealings were run between 1200 and 1500 Celsius degrees, at room pressure, for durations ranging from one hour to one month. The diffusion profiles were analysed using TEM (transmission electronic microscopy) and RBS (Rutherford backscattering spectroscopy). The diffusivities extracted for Pb{sup 2+} + Th{sup 4+} {r_reversible} 2 Nd{sup 3+} exchange follow an Arrhenius law with parameters E equals 509 {+-} 24 kJ mol{sup -1} and log(D{sub 0} (m{sup 2}s{sup -1})) equals -3.41 {+-} 0.77. Preliminary data for Pb{sup 2+} {r_reversible} Ca{sup 2+} exchange are in agreement with this result. The extrapolation of our data to crustal temperatures yields very slow diffusivities. For instance, the time necessary for a 50 {mu}m grain to lose all of its lead at 800 Celsius degrees is greater than the age of the Earth. From these results and other evidence from the literature, we conclude that most of the perturbations in U-Th-Pb ages of monazite cannot be attributed to lead diffusion, but rather to interactions with fluids. (author)

  12. Diffusion Weighted and Trace Images

    Directory of Open Access Journals (Sweden)

    Helen Nayeri

    2009-01-01

    Full Text Available   "nThe signal intensity in MRI depends on the proton density, T1, T2, and T2* relaxation processes of any ensemble of the spins within each imaging element. Another important contrast mechanism in MRI is signal loss caused by proton dephasing in the presence of coherent and incoherent flow. Diffusion refers to the dispersion of molecules from a region of high concentration to one of low concentration by random molecular or “Brownian” motion. "nDWI is based on the microscopic movement (Brownian motion of water molecules. The motion of water molecules, under the influence of diffusion-sensitizing gradient pulses, causes irreversible signal attenuation (hypointensity on DWI. In restricted diffusion (like acute infarction the signal attenuation is decreased (hyperintensity on DWI. "nIn biological tissues, water diffusion is not truly random. Structural barriers such as membranes and cellular elements, as well as chemical interactions, restrict Brownian motion in 3-D space. Additionally, disturbances associated with tissue perfusion and respiration can alter the biological environment. So it is termed “apparent” because the measured value does not indicate pure diffusion, but reflects capillary perfusion and other processes.  ADC (Apparent Diffusion Coefficient maps are typically created by combining at least two DWIs that are differently sensitized to diffusion (different b-values but which remain identical with respect to the other imaging parameters (TR and TE. Diffusion-weighted images are a combination of diffusion information and T2 signal intensity. In order to avoid the hyperintensity effect of T2 signal intensity (T2 shine-through, DW images should be compared with ADC images. ADC maps demonstrate contrast based purely on diffusion differences.   "nThe apparent diffusion in tissue is slowed if the protons are “hindered” or slowed in their random motion by the presence of cell membranes, walls, and macromolecules but are not

  13. Diffuse radiation increases global ecosystem-level water-use efficiency

    Science.gov (United States)

    Moffat, A. M.; Reichstein, M.; Cescatti, A.; Knohl, A.; Zaehle, S.

    2012-12-01

    Current environmental changes lead not only to rising atmospheric CO2 levels and air temperature but also to changes in air pollution and thus the light quality of the solar radiation reaching the land-surface. While rising CO2 levels are thought to enhance photosynthesis and closure of stomata, thus leading to relative water savings, the effect of diffuse radiation on transpiration by plants is less clear. It has been speculated that the stimulation of photosynthesis by increased levels of diffuse light may be counteracted by higher transpiration and consequently water depletion and drought stress. Ultimately, in water co-limited systems, the overall effect of diffuse radiation will depend on the sensitivity of canopy transpiration versus photosynthesis to diffuse light, i.e. whether water-use efficiency changes with relative levels of diffuse light. Our study shows that water-use efficiency increases significantly with higher fractions of diffuse light. It uses the ecosystem-atmosphere gas-exchange observations obtained with the eddy covariance method at 29 flux tower sites. In contrast to previous global studies, the analysis is based directly on measurements of diffuse radiation. Its effect on water-use efficiency was derived by analyzing the multivariate response of carbon and water fluxes to radiation and air humidity using a purely empirical approach based on artificial neural networks. We infer that per unit change of diffuse fraction the water-use efficiency increases up to 40% depending on diffuse fraction levels and ecosystem type. Hence, in regions with increasing diffuse radiation positive effects on primary production are expected even under conditions where water is co-limiting productivity.

  14. A dielectric barrier discharge in neon at atmospheric pressure

    International Nuclear Information System (INIS)

    A dielectric barrier discharge in neon at atmospheric pressure is investigated with electrical measurement and fast photography. It is found that a stable diffuse discharge can be easily generated in a gap with a gap space of 0.5-6 mm and is identified with a glow discharge. The first breakdown voltage of the gap is considerably higher than that of the same gap working in a stable diffuse discharge mode, which indicates that Penning ionization of neon metastables from the previous discharge with inevitable gas impurities plays an important role in the decrease in the breakdown voltage. Discharge patterns are observed in a gap shorter than 1 mm. From the experiments with a wedge-like gap, it is found that the discharge patterns are formed in the area with a higher applied electric field, which suggests that a higher applied electric field may cause a transition from a diffuse glow to discharge patterns.

  15. Modeling short-term concentration fluctuations of semi-volatile pollutants in the soil-plant-atmosphere system.

    Science.gov (United States)

    Bao, Zhongwen; Haberer, Christina M; Maier, Uli; Beckingham, Barbara; Amos, Richard T; Grathwohl, Peter

    2016-11-01

    Temperature changes can drive cycling of semi-volatile pollutants between different environmental compartments (e.g. atmosphere, soil, plants). To evaluate the impact of daily temperature changes on atmospheric concentration fluctuations we employed a physically based model coupling soil, plants and the atmosphere, which accounts for heat transport, effective gas diffusion, sorption and biodegradation in the soil as well as eddy diffusion and photochemical oxidation in the atmospheric boundary layer of varying heights. The model results suggest that temperature-driven re-volatilization and uptake in soils cannot fully explain significant diurnal concentration fluctuations of atmospheric pollutants as for example observed for polychlorinated biphenyls (PCBs). This holds even for relatively low water contents (high gas diffusivity) and high sorption capacity of the topsoil (high organic carbon content and high pollutant concentration in the topsoil). Observed concentration fluctuations, however, can be easily matched if a rapidly-exchanging environmental compartment, such as a plant layer, is introduced. At elevated temperatures, plants release organic pollutants, which are rapidly distributed in the atmosphere by eddy diffusion. For photosensitive compounds, e.g. some polycyclic aromatic hydrocarbons (PAHs), decreasing atmospheric concentrations would be expected during daytime for the bare soil scenario. This decline is buffered by a plant layer, which acts as a ground-level reservoir. The modeling results emphasize the importance of a rapidly-exchanging compartment above ground to explain short-term atmospheric concentration fluctuations. PMID:27341116

  16. Modelling the soil-atmosphere exchange of POPs: Long-term steady state and diurnal fluctuations

    Science.gov (United States)

    Bao, Z.; Beckingham, B.; Maier, U.; Haberer, C.; Grathwohl, P.

    2014-12-01

    Soil-atmosphere exchange is an important transport process influencing environmental fate and transport of many persistent organic pollutants (POPs). This study focuses on modelling the gaseous exchange of a semi-volatile polycyclic aromatic hydrocarbon (phenanthrene) between soil and the atmosphere using the multicomponent reactive transport code MIN3P. MIN3P is typically applied to simulate aqueous and vapor phase subsurface transport and reaction processes. We extended the code to also include an atmospheric boundary layer where eddy diffusion and photodegradation take place. The relevant processes and parameters affecting soil-atmosphere exchange were investigated in several scenarios and at various time scales. We found that phenanthrene is well-mixed in the atmospheric boundary layer under neutral or stable atmospheric conditions due to fast eddy diffusion. Uptake of airborne phenanthrene to soils is limited by the soil properties and initially depends on diffusion in soil gas and sorption to the solids. On the long term seepage water dominates transport into deeper soil layers; biodegradation finally leads to steady-state concentration profiles in the subsurface typically achieved after a few centuries. If concentrations in the atmosphere decrease, e.g. due to environmental legislation, then soils become sources for the POPs for the first two months and function as sinks again for the POPs until new steady state concentrations are reached (after decades to centuries). MIN3P was also used to simulate diurnal soil-atmosphere exchanges of airborne pollutants due to temperature changes and photodegradation, both which cause fluctuations in atmospheric concentrations and therefore affect mass transfer between soil and the atmosphere. The model can further be applied to estimate the environmental fate of other POPs between soil and the atmosphere under different environmental pollution and climate change scenarios.

  17. Ion diffusion in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Lehikoinen, J. [VTT Chemical Technology, Espoo (Finland)

    1999-03-01

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K{sub d}, unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.) 45 refs.

  18. Dreaming of atmospheres

    CERN Document Server

    Waldmann, I P

    2015-01-01

    Here we introduce the RobERt (Robotic Exoplanet Recognition) algorithm for the classification of exoplanetary emission spectra. Spectral retrievals of exoplanetary atmospheres frequently requires the preselection of molecular/atomic opacities to be defined by the user. In the era of open-source, automated and self-sufficient retrieval algorithms, manual input should be avoided. User dependent input could, in worst case scenarios, lead to incomplete models and biases in the retrieval. The RobERt algorithm is based on deep belief neural (DBN) networks trained to accurately recognise molecular signatures for a wide range of planets, atmospheric thermal profiles and compositions. Reconstructions of the learned features, also referred to as `dreams' of the network, indicate good convergence and an accurate representation of molecular features in the DBN. Using these deep neural networks, we work towards retrieval algorithms that themselves understand the nature of the observed spectra, are able to learn from curre...

  19. Atmospheric Release Advisory Capability

    International Nuclear Information System (INIS)

    The Atmospheric Release Advisory Capability (ARAC) project is a Department of Energy (DOE) sponsored real-time emergency response service available for use by both federal and state agencies in case of a potential or actual atmospheric release of nuclear material. The project, initiated in 1972, is currently evolving from the research and development phase to full operation. Plans are underway to expand the existing capability to continuous operation by 1984 and to establish a National ARAC Center (NARAC) by 1988. This report describes the ARAC system, its utilization during the past two years, and plans for its expansion during the next five to six years. An integral part of this expansion is due to a very important and crucial effort sponsored by the Defense Nuclear Agency to extend the ARAC service to approximately 45 Department of Defense (DOD) sites throughout the continental US over the next three years

  20. Atmospheric lepton fluxes

    Directory of Open Access Journals (Sweden)

    Gaisser Thomas K.

    2015-01-01

    Full Text Available This review of atmospheric muons and neutrinos emphasizes the high energy range relevant for backgrounds to high-energy neutrinos of astrophysical origin. After a brief historical introduction, the main distinguishing features of atmospheric νμ and νe are discussed, along with the implications of the muon charge ratio for the νµ / ν̅µ ratio. Methods to account for effects of the knee in the primary cosmic-ray spectrum and the energy-dependence of hadronic interactions on the neutrino fluxes are discussed and illustrated in the context of recent results from IceCube. A simple numerical/analytic method is proposed for systematic investigation of uncertainties in neutrino fluxes arising from uncertainties in the primary cosmic-ray spectrum/composition and hadronic interactions.

  1. Understanding Atmospheric Catastrophes

    Science.gov (United States)

    Chao, Winston C.

    2009-01-01

    The atmosphere, as in other parts of nature, is full of phenomena that involve rapid transitions from one (quasi-) equilibrium state to another--- i.e. catastrophes. These (quasi-) equilibria are the multiple solutions of the same dynamical system. Unlocking the mystery behind a catastrophe reveals not only the physical mechanism responsible for the transition, but also how the (quasi-) equilibria before and after the transition are maintained. Each catastrophe is different, but they do have some common traits. Understanding these common traits is the first step in studying these catastrophes. In this seminar, three examples chosen based on the speaker's research interest--tropical cyclogenesis, stratospheric sudden warming, and monsoon onset--are given to illustrate how atmospheric catastrophes can be studied.

  2. 24. Atmosphere and climate

    International Nuclear Information System (INIS)

    The Earth's atmosphere is changing, and we do not fully understand what the effect of those changes will be on our own lives, much less the lives of our children. It is easy to imagine effects that could be catastrophic for life on this planet. Yet, in the face of these possibilities and our inadequate understanding of Earth processes, anthropogenic emissions of trace gases - pollutants that affect climate, the ozone layer, and human health - continue. Tables give information on the following: CO2 emissions from industrial processes, 1989; Other greenhouse gas emissions, 1989; Atmospheric concentrations of greenhouse and ozone-depleting gases, 1959-90; World CO2 emissions from fossil fuel consumption and cement manufacture, 1950-89; Sulfur and nitrogen emissions, 1970-89; and Common anthropogenic pollutants, 1980-89

  3. Discovering Pluto's atmosphere

    International Nuclear Information System (INIS)

    Observations of the occultation of an obscure 12th-magnitude star in eastern Virgo by Pluto on June 9, 1988 are discussed. The occultation was observed by astronomers aboard NASA's Kuiper Airborne Observatory flying over the Pacific. The prediction of the occultation and the results of the observations are examined. The study demonstrated that Pluto has a thin atmosphere and that its diameter is about two-thirds that of the moon

  4. Tritium in atmospheric hydrogen

    OpenAIRE

    Martin, J. David; Hackett, Joseph P.

    2011-01-01

    The radioactivity of tritiated hydrogen (HT) in the atmosphere in Westwood, New Jersey was measured at approximately weekly intervals from August 1971 to August 1973. The background level remained constant at approximately 80 tritium atoms per milligram of air. Frequent increases in the activity level of up to an order of magnitude were observed until January 1973. The source(s) of HT which was responsible for the frequent increases apparently ceased as a tropospheric source in January 1973. ...

  5. Atmospheric Disturbance Environment Definition

    Science.gov (United States)

    Tank, William G.

    1994-01-01

    Traditionally, the application of atmospheric disturbance data to airplane design problems has been the domain of the structures engineer. The primary concern in this case is the design of structural components sufficient to handle transient loads induced by the most severe atmospheric "gusts" that might be encountered. The concern has resulted in a considerable body of high altitude gust acceleration data obtained with VGH recorders (airplane velocity, V, vertical acceleration, G, altitude, H) on high-flying airplanes like the U-2 (Ehernberger and Love, 1975). However, the propulsion system designer is less concerned with the accelerations of the airplane than he is with the airflow entering the system's inlet. When the airplane encounters atmospheric turbulence it responds with transient fluctuations in pitch, yaw, and roll angles. These transients, together with fluctuations in the free-stream temperature and pressure will disrupt the total pressure, temperature, Mach number and angularity of the inlet flow. For the mixed compression inlet, the result is a disturbed throat Mach number and/or shock position, and in extreme cases an inlet unstart can occur (cf. Section 2.1). Interest in the effects of inlet unstart on the vehicle dynamics of large, supersonic airplanes is not new. Results published by NASA in 1962 of wind tunnel studies of the problem were used in support of the United States Supersonic Transport program (SST) (White, at aI, 1963). Such studies continued into the late 1970's. However, in spite of such interest, there never was developed an atmospheric disturbance database for inlet unstart analysis to compare with that available for the structures load analysis. Missing were data for the free-stream temperature and pressure disturbances that also contribute to the unStart problem.

  6. Atmospheric Science Without Borders

    Science.gov (United States)

    Panday, Arnico; Praveen, Ps; Adhikary, Bhupesh; Bhave, Prakash; Surapipith, Vanisa; Pradhan, Bidya; Karki, Anita; Ghimire, Shreta; Thapa, Alpha; Shrestha, Sujan

    2016-04-01

    The Indo-Gangetic Plains (IGP) in northern South Asia are among the most polluted and most densely populated places in the world, and they are upwind of vulnerable ecosystems in the Himalaya mountains. They are also fragmented across 5 countries between which movement of people, data, instruments and scientific understanding have been very limited. ICIMOD's Atmosphere Initiative has for the past three years been working on filling data gaps in the region, while facilitating collaborations across borders. It has established several atmospheric observatories at low and mid elevations in Bhutan and Nepal that provide new data on the inflow of pollutants from the IGP towards the mountains, as well as quantify the effects of local emissions on air quality in mountain cities. EGU will be the first international conference where these data will be presented. ICIMOD is in the process of setting up data servers through which data from the region will be shared with scientists and the general public across borders. Meanwhile, to promote cross-border collaboration among scientists in the region, while addressing an atmospheric phenomenon that affects the lives of the several hundred million people, ICIMOD' Atmosphere Initiative has been coordinating an interdisciplinary multi-year study of persistent winter fog over the Indo-Gangetic Plains, with participation by researchers from Pakistan, India, China, Nepal, Bhutan and Bangladesh. Using a combination of in-situ measurements and sample collection, remote sensing, modeling and community based research, the researchers are studying how changing moisture availability and air pollution have led to increases in fog frequency and duration, as well as the fog's impacts on local communities and energy demand that may affect air pollution emissions. Preliminary results of the Winter 2015-2016 field campaign will be shown.

  7. Atmospheric pseudohalogen chemistry

    Directory of Open Access Journals (Sweden)

    D. J. Lary

    2004-09-01

    Full Text Available There are at least three reasons why hydrogen cyanide is likely to be significant for atmospheric chemistry. The first is well known, HCN is a product and marker of biomass burning. However, if a detailed ion chemistry of lightning is considered then it is almost certain than in addition to lightning producing NOx, it also produces HOx and HCN. Unlike NOx and HOx, HCN is long-lived and could therefore be a useful marker of lightning activity. Observational evidence is considered to support this view. Thirdly, the chemical decomposition of HCN leads to the production of small amounts of CN and NCO. NCO can be photolyzed in the visible portion of the spectrum yielding N atoms. The production of N atoms is significant as it leads to the titration of nitrogen from the atmosphere via N+N→N2. Normally the only modelled source of N atoms is NO photolysis which happens largely in the UV Schumann-Runge bands. However, NCO photolysis occurs in the visible and so could be involved in titration of atmospheric nitrogen in the lower stratosphere and troposphere. HCN emission inventories are worthy of attention. The CN and NCO radicals have been termed pseudohalogens since the 1920s. They are strongly bound, univalent, radicals with an extensive and varied chemistry. The products of the atmospheric oxidation of HCN are NO, CO and O3. N+CH4 and N+CH3OH are found to be important sources of HCN. Including the pseudohalogen chemistry gives a small increase in ozone and total reactive nitrogen (NOy.

  8. Diffuse and vascular hepatic diseases; Diffuse und vaskulaere Lebererkrankungen

    Energy Technology Data Exchange (ETDEWEB)

    Kreimeyer, S.; Grenacher, L. [Universitaetsklinikum Heidelberg, Abteilung Diagnostische und Interventionelle Radiologie, Heidelberg (Germany)

    2011-08-15

    In addition to focal liver lesions, diffuse and vascular disorders of the liver represent a wide spectrum of liver diseases which are from the radiological point of view often difficult or nearly impossible to diagnose. Classical diagnostic methods are computed tomography and magnetic resonance imaging in addition to ultrasound. Diffuse parenchymal damage caused by diseases of various etiologies is therefore difficult to evaluate because it often lacks characteristic morphological features. For hepatic steatosis, hemochromatosis/siderosis as an example of a diffuse storage disease and sarcoidosis and candidiasis as infectious/inflammatory diseases, an image-based diagnosis is appropriate in some cases. For most diffuse liver diseases, however only nonspecific changes are visualized. Vascular pathologies of the liver, such as the Budd-Chiari syndrome and portal vein thrombosis, however, can usually be diagnosed very clearly using radiology and there is also a very effective interventional radiological treatment. Chronic diseases very often culminate in liver cirrhosis which is highly associated with an increased risk of liver cancer. (orig.) [German] Neben den fokalen Leberlaesionen stellen diffuse und vaskulaere Lebererkrankungen ein weites Spektrum an Erkrankungen der Leber dar, die radiologisch oft schwer oder gar nicht diagnostizierbar sind. Klassische diagnostische Verfahren sind dabei neben dem Ultraschall die Computertomographie und die Magnetresonanztomographie. Diffuse Parenchymschaeden, bedingt durch Erkrankungen unterschiedlichster Aetiologie, sind deshalb schwierig evaluierbar, weil haeufig charakteristische bildmorphologische Merkmale fehlen. Die Steatosis hepatis, die Haemochromatose/Siderose als Beispiel der Speicherkrankheiten sowie die Sarkoidose und die Candidose als infektioes-entzuendliche Erkrankungen sind einer bildbasierten Diagnosestellung z. T. zugaenglich, bei den meisten diffusen Lebererkrankungen jedoch zeigen sich lediglich unspezifische

  9. Dreaming of Atmospheres

    Science.gov (United States)

    Waldmann, I. P.

    2016-04-01

    Here, we introduce the RobERt (Robotic Exoplanet Recognition) algorithm for the classification of exoplanetary emission spectra. Spectral retrieval of exoplanetary atmospheres frequently requires the preselection of molecular/atomic opacities to be defined by the user. In the era of open-source, automated, and self-sufficient retrieval algorithms, manual input should be avoided. User dependent input could, in worst-case scenarios, lead to incomplete models and biases in the retrieval. The RobERt algorithm is based on deep-belief neural (DBN) networks trained to accurately recognize molecular signatures for a wide range of planets, atmospheric thermal profiles, and compositions. Reconstructions of the learned features, also referred to as the “dreams” of the network, indicate good convergence and an accurate representation of molecular features in the DBN. Using these deep neural networks, we work toward retrieval algorithms that themselves understand the nature of the observed spectra, are able to learn from current and past data, and make sensible qualitative preselections of atmospheric opacities to be used for the quantitative stage of the retrieval process.

  10. Titan's surface and atmosphere

    Science.gov (United States)

    Hayes, Alexander G.; Soderblom, Jason M.; Ádámkovics, Máté

    2016-05-01

    Since its arrival in late 2004, the NASA/ESA Cassini-Huygens mission to Saturn has revealed Titan to be a world that is both strange and familiar. Titan is the only extraterrestrial body known to support standing bodies of stable liquid on its surface and, along with Earth and early Mars, is one of three places in the Solar System known to have had an active hydrologic cycle. With atmospheric pressures of 1.5 bar and temperatures of 90-95 K at the surface, methane and ethane condense out of Titan's nitrogen-dominated atmosphere and flow as liquids on the surface. Despite vast differences in environmental conditions and materials from Earth, Titan's methane-based hydrologic cycle drives climatic and geologic processes which generate landforms that are strikingly similar to their terrestrial counterparts, including vast equatorial dunes, well-organized channel networks that route material through erosional and depositional landscapes, and lakes and seas of liquid hydrocarbons. These similarities make Titan a natural laboratory for studying the processes that shape terrestrial landscapes and drive climates, probing extreme conditions impossible to recreate in earthbound laboratories. Titan's exotic environment ensures that even rudimentary measurements of atmospheric/surface interactions, such as wind-wave generation or aeolian dune development, provide valuable data to anchor physical models.

  11. Understanding Diffusion MR Imaging Techniques: From Scalar Diffusion-weighted Imaging to Diffusion Tensor Imaging and Beyond

    OpenAIRE

    Hagmann, P.; Jonasson, L.; Maeder, P; Thiran, Jean-Philippe; Wedeen, V.; Meuli, R

    2006-01-01

    The complex structural organization of the white matter of the brain can be depicted in vivo in great detail with advanced diffusion magnetic resonance (MR) imaging schemes. Diffusion MR imaging techniques are increasingly varied, from the simplest and most commonly used technique —the mapping of apparent diffusion coefficient values— to the more complex, such as diffusion tensor imaging, q-ball imaging, diffusion spectrum imaging, and tractography. The type of structural information obtained...

  12. Diffusion Correlation NMR Spectroscopic Study of Anisotropic Diffusion of Water in Plant Tissues

    OpenAIRE

    Qiao, Y.; Galvosas, P.; Callaghan, P. T.

    2005-01-01

    The anisotropic diffusion of water in chive (Allium schoenoprasum) tissues has been investigated using two-dimensional nuclear magnetic resonance methods: diffusion-diffusion correlation spectroscopy and diffusion-relaxation correlation spectroscopy. Corresponding one-dimensional T2 and diffusion measurements confirm independently the results of the two-dimensional investigations. In particular the diffusion-diffusion correlation spectroscopy method proves to be very powerful in resolving the...

  13. Kramers turnover: From energy diffusion to spatial diffusion using metadynamics

    Science.gov (United States)

    Tiwary, Pratyush; Berne, B. J.

    2016-04-01

    We consider the rate of transition for a particle between two metastable states coupled to a thermal environment for various magnitudes of the coupling strength using the recently proposed infrequent metadynamics approach [P. Tiwary and M. Parrinello, Phys. Rev. Lett. 111, 230602 (2013)]. We are interested in understanding how this approach for obtaining rate constants performs as the dynamics regime changes from energy diffusion to spatial diffusion. Reassuringly, we find that the approach works remarkably well for various coupling strengths in the strong coupling regime, and to some extent even in the weak coupling regime.

  14. Gaseous diffusion -- the enrichment workhorse

    International Nuclear Information System (INIS)

    Construction of the first large-scale gaseous diffusion facility was started as part of the Manhattan Project in Oak Ridge, Tennessee, in 1943. This facility, code named ''K-25,'' began operation in January 1945 and was fully on stream by September 1945. Four additional process buildings were later added in Oak Ridge as the demand for enriched uranium escalated. New gaseous diffusion plants were constructed at Paducah, Kentucky, and Portsmouth, Ohio, during this period. The three gaseous diffusion plants were the ''workhorses'' which provided the entire enriched uranium demand for the United States during the 1950s and 1960s. As the demand for enriched uranium for military purposes decreased during the early 1960s, power to the diffusion plants was curtailed to reduce production. During the 1960s, as plans for the nuclear power industry were formulated, the role of the diffusion plants gradually changed from providing highly-enriched uranium for the military to providing low-enriched uranium for power reactors

  15. A Diffusion Approach to Study Leadership Reform

    Science.gov (United States)

    Adams, Curt M.; Jean-Marie, Gaetane

    2011-01-01

    Purpose: This study aims to draw on elements of diffusion theory to understand leadership reform. Many diffusion studies examine the spread of an innovation across social units but the objective is to examine diffusion of a collective leadership model within school units. Specifically, the strength of reform diffusion is tested to account for…

  16. Diffusion of Responsibility in College Classes

    Institute of Scientific and Technical Information of China (English)

    李珍珍

    2015-01-01

    Diffusion of responsibility takes place in college classes nowadays.The author points out diffusion of responsibility in college classes,analyses psychological reasons of diffusion of responsibility,and gives strategies on avoiding the diffusion of responsibility.The paper aims at doing some contribution to improving teaching quality of college class.

  17. Fast Measurements Of Thermal Diffusivities Of Ceramics

    Science.gov (United States)

    Smith, Marnell; Goldstein, Howard E.

    1988-01-01

    Temperature rises of samples compared with reference sample. Apparatus quickly measures thermal diffusivities of ceramics at high temperatures. Produces data on relative thermal diffusivities of as many as six ceramic specimens per hour. Thermal-diffusivity tester makes it easy to determine thermal diffusivities of ceramics. Pronounced effects of processing parameters on thermal properties of ceramics evaluated quickly.

  18. On diffusion approximation with discontinuous coefficients

    OpenAIRE

    Krylov, N. V.; Liptser, R.

    2002-01-01

    Convergence of stochastic processes with jumps to diffusion processes is investigated in the case when the limit process has discontinuous coefficients. An example is given in which the diffusion approximation of a queueing model yields a diffusion process with discontinuous diffusion and drift coefficients.

  19. Diffusion of Nickel into Ferritic Steel Interconnects of Solid Oxide Fuel/Electrolysis Stacks

    DEFF Research Database (Denmark)

    Molin, Sebastian; Chen, Ming; Bowen, Jacob R.;

    2013-01-01

    a limited number of studies have been devoted to the phenomenon. Here, diffusion of Ni into ferritic Crofer 22 APU steel is studied in a wet hydrogen atmosphere after 250 hours of exposure at 800 °C using Ni-plated (~ 10 micron thick coatings) sheet steel samples as a model system. Even after...

  20. Diffusion of Nickel into Ferritic Steel Interconnects of Solid Oxide Fuel/Electrolysis Stacks

    DEFF Research Database (Denmark)

    Molin, Sebastian; Chen, Ming; Bowen, Jacob R.; Hendriksen, Peter Vang

    2013-01-01

    limited number of studies have been devoted to the phenomenon. Here, diffusion of Ni into ferritic Crofer 22 APU steel is studied in a wet hydrogen atmosphere after 250 hours of exposure at 800 °C using Ni-plated (~ 10 micron thick coatings) sheet steel samples as a model system. Even after this...

  1. NOAA's Tropical Atmosphere Ocean Project

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Realtime El Nino and La Nina data from the tropical Pacific Ocean is provided by the Tropical Atmosphere Ocean / Triangle Trans-Ocean buoy network (TAO/TRITON) of...

  2. Diffusion probe for gas sampling in undisturbed soil

    DEFF Research Database (Denmark)

    Petersen, Søren O

    2014-01-01

    Soil-atmosphere fluxes of trace gases such as methane (CH4) and nitrous oxide (N2O) are determined by complex interactions between biological activity and soil conditions. Soil gas concentration profiles may, in combination with other information about soil conditions, help to understand emission...... controls. This note describes a simple and robust diffusion probe for soil gas sampling as part of flux monitoring programs. It can be deployed with minimum disturbance of in-situ conditions, also at sites with a high or fluctuating water table. Separate probes are used for each sampling depth, in this...... on peat soils used for grazing showed soil gas concentrations of CH4 and N2O as influenced by topography, site conditions, and season. The applicability of the diffusion probe for trace gas monitoring is discussed....

  3. Elastic wave velocities and thermal diffusivities of Apollo 14 rocks.

    Science.gov (United States)

    Mizutani, H.; Fujii, N.; Hamano, Y.; Osako, M.

    1972-01-01

    The compressional- and shear-wave velocities of Apollo 14 lunar rocks 14311,50 and 14313,27 as functions of pressure up to 10 kb and the thermal diffusivity of sample 14311,50 over the temperature range 100 to 550 K have been measured. Both samples 14311 and 14313 are polymict fragmental rocks. The overall elastic and anelastic behavior of the Apollo 14 samples are similar to those of Apollo 11 and 12 samples; low velocity and low Q at pressures below 1 kb and rapid increase of velocity and Q with pressure are also typical of the Apollo 14 rocks. The available data of P- and S-wave velocities of lunar rocks show that Birch's law holds for the lunar rocks. The thermal diffusivity of a lunar rock in vacuum is found to be significantly lower than that in air at one atmospheric pressure.

  4. The Reactive-Diffusive Length of OH Radical in Squalane

    Science.gov (United States)

    Lee, L.; Wilson, K. R.

    2015-12-01

    With the technique of core-shell particle configuration, we have measured the radical penetration length in a reactive matrix by observing the transmission efficiency of OH radical through squalane shell of various thickness ranging from 0 nm (without coating) to 16 nm. The result indicates a penetration depth of 2.2 nm. Our data suggest that the OH concentration profile in squalane as a function of the distance from the squalane/air interface can be satisfactorily described by the analytical solution to diffusion equation with an added chemical loss term experienced by the OH radical. This allowed an almost unambiguous determination of either OH diffusivity or OH reactivity given that one of the value is known in systems where radical chain propagation is not a significant factor and can shed new lights on the lifetime alteration of particulate matters in the atmosphere where possible coating processes are abundant.

  5. Temporal and spatial variations of the concentration of the short-lived decay products of radon in the lower atmosphere

    OpenAIRE

    Servant, J.

    2011-01-01

    The study of natural radioactivity in the lower atmosphere will provide information on turbulent diffusion and transport of air masses in the lower atmosphere. We have, therefore, undertaken a two-part research program. Firstly, we have made a study of natural radioactivity of the atmosphere above a plateau and, secondly, we have taken measurements at different latitudes and longitudes over the continents and the oceans, to obtain the general distribution of the radioactivity in the lower at...

  6. Upscaling diffusion waves in porous media

    Science.gov (United States)

    Valdés-Parada, Francisco J.; Álvarez Ramírez, José; Ochoa-Tapia, J. Alberto

    2016-04-01

    The aim of this work is to derive the effective-medium equations and to estimate the related effective diffusivities for diffusion waves in porous media. Effective diffusivities are estimated within the framework of the volume averaging method, where they are obtained from the solution of the associated closure problems in 2D and 3D periodic unit cells. The results showed that the transport of diffusion waves are governed by the diffusion and co-diffusion mechanisms of harmonic waves. In addition, numerical results showed that the effective diffusivities increase with frequency, while the effective co-diffusivities display a resonance-like behavior. Our results also indicate that geometry plays a more significant effect over the predictions of the co-diffusion coefficient at moderate frequencies and it mainly influences the predictions of the direct diffusivity at low frequencies (i . e .,ω∗ ≪ 1).

  7. Pluto's Atmosphere Does Not Collapse

    OpenAIRE

    Olkin, C. B.; Young, L. A.; Borncamp, D.; Pickles, A; Sicardy, B.; Assafin, M.; Bianco, F. B.; Buie, M. W.; Oliveira, A. Dias de; Gillon, M.; French, R. G.; Gomes Jr., A. Ramos; Jehin, E.; Morales, N.; Opitom, C.

    2013-01-01

    Combining stellar occultation observations probing Pluto's atmosphere from 1988 to 2013 and models of energy balance between Pluto's surface and atmosphere, we conclude that Pluto's atmosphere does not collapse at any point in its 248-year orbit. The occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models with a high thermal inertia and a permanent N2 ice cap at Pluto's north rotational pole.

  8. Atmospheric corrosion of mild steel

    OpenAIRE

    Morcillo, Manuel; Fuente, Daniel de la; Díaz Ocaña, Iván; Cano, Heidis

    2011-01-01

    The atmospheric corrosion of mild steel is an extensive topic that has been studied by many authors in different regions throughout the world. This compilation paper incorporates relevant publications on the subject, in particular about the nature of atmospheric corrosion products, mechanisms of atmospheric corrosion and kinetics of the atmospheric corrosion process, paying special attention to two matters upon which relatively less information has been published: a) the morpholog...

  9. Atmospheric corrosion of mild steel

    OpenAIRE

    Morcillo, M.; de la Fuente, D.; I. Díaz; Cano, H.

    2011-01-01

    The atmospheric corrosion of mild steel is an extensive topic that has been studied by many authors in different regions throughout the world. This compilation paper incorporates relevant publications on the subject, in particular about the nature of atmospheric corrosion products, mechanisms of atmospheric corrosion and kinetics of the atmospheric corrosion process, paying special attention to two matters upon which relatively less information has been published: a) the morphology of steel c...

  10. KAJIAN PUSTAKA MENGENAI RESTAURANT ATMOSPHERE

    OpenAIRE

    Adeline Agoes; Nami Fitricia Pasaribu

    2015-01-01

    Restaurant is one of the businesses that support tourism development. Restaurants nowadays dont only provide food, but also the service and atmosphere to their customers. The purpose of this study is to discover the aspects defining restaurant atmosphere and the implications of restaurant atmosphere to other particular aspects related to restaurant business. This article is written based on a study conducted through a literature review. Through the examination, it is found that the atmosphere...

  11. Water vapor diffusion membranes, 2

    Science.gov (United States)

    Holland, F. F.; Klein, E.; Smith, J. K.; Eyer, C.

    1976-01-01

    Transport mechanisms were investigated for the three different types of water vapor diffusion membranes. Membranes representing porous wetting and porous nonwetting structures as well as dense diffusive membrane structures were investigated for water permeation rate as a function of: (1) temperature, (2) solids composition in solution, and (3) such hydrodynamic parameters as sweep gas flow rate, solution flow rate and cell geometry. These properties were measured using nitrogen sweep gas to collect the effluent. In addition, the chemical stability to chromic acid-stabilized urine was measured for several of each type of membrane. A technology based on the mechanism of vapor transport was developed, whereby the vapor diffusion rates and relative susceptibility of membranes to fouling and failure could be projected for long-term vapor recovery trials using natural chromic acid-stabilized urine.

  12. Nonlinear Diffusion and Transient Osmosis

    Institute of Scientific and Technical Information of China (English)

    Akira Igarashi; Lamberto Rondon; Antonio Botrugno; Marco Pizzi

    2011-01-01

    We investigate both analytically and numerically the concentration dynamics of a solution in two containers connected by a narrow and short channel, in which diffusion obeys a porous medium equation. We also consider the variation of the pressure in the containers due to the flow of matter in the channel. In particular, we identify a phenomenon, which depends on the transport of matter across nano-porous membranes, which we call "transient osmosis". We find that nonlinear diffusion of the porous medium equation type allows numerous different osmotic-like phenomena, which are not present in the case of ordinary Fickian diffusion. Experimental results suggest one possible candidate for transiently osmotic processes.

  13. Quantum Diffusion-Limited Aggregation

    CERN Document Server

    Johnson, David B

    2011-01-01

    Though classical random walks have been studied for many years, research concerning their quantum analogues, quantum random walks, has only come about recently. Numerous simulations of both types of walks have been run and analyzed, and are generally well-understood. Research pertaining to one of the more important properties of classical random walks, namely, their ability to build fractal structures in diffusion-limited aggregation, has been particularly noteworthy. However, only now has research begun in this area in regards to quantum random motion. The study of random walks and the structures they build has various applications in materials science. Since all processes are quantum in nature, it is important to consider the quantum variant of diffusion-limited aggregation. Recognizing that Schr\\"odinger equation and a classical random walk are both diffusion equations, it is possible to connect and compare them. Using similar parameters for both equations, we ran various simulations aggregating particles....

  14. Diffusion inside living human cells

    DEFF Research Database (Denmark)

    Leijnse, N.; Jeon, J. -H.; Loft, Steffen; Metzler, R.; Oddershede, L. B.

    2012-01-01

    Naturally occurring lipid granules diffuse in the cytoplasm and can be used as tracers to map out the viscoelastic landscape inside living cells. Using optical trapping and single particle tracking we found that lipid granules exhibit anomalous diffusion inside human umbilical vein endothelial...... cells. For these cells the exact diffusional pattern of a particular granule depends on the physiological state of the cell and on the localization of the granule within the cytoplasm. Granules located close to the actin rich periphery of the cell move less than those located towards to the center of...... the cell or within the nucleus. Also, granules in cells which are stressed by intense laser illumination or which have attached to a surface for a long period of time move in a more restricted fashion than those within healthy cells. For granules diffusing in healthy cells, in regions away from the...

  15. Monitoring of contamination of atmospheric environment by radiation

    International Nuclear Information System (INIS)

    Atmospheric pollution has become a worldwide problem regardless of developed industrial nations and developing countries. In particular, the pollution due to automobile exhaust gas, the carcinogenic particles in diesel exhaust and their relation to various respiratory diseases are the problems. Nitrogen oxides and sulfur oxides in exhaust gas become the cause of acid rain. Radiation began to be utilized for the measurement of the concentration of floating particles and the amount of fallout dust, the forecast of the generation and diffusion of pollutants, the elucidation of the contribution of generation sources in wide areas and so on. In this report, the circumstances that radiation became to be utilized for monitoring atmospheric environment and the present status and the perspective of the radiation utilization in the field of the preservation of atmospheric environment are described. The progress of the method of measuring floating particles in Japan is explained. The automatic measurement of floating particles by β-ray absorption method and the application of β-ray absorption method to the measurement of the amount of fallout dust, generation source particles and the exposure to floating particles of individuals for health control are described. The utilization of radiation for real time monitoring, the investigation of the generation of blown-up dust, atmospheric diffusion experiment and the elucidation of the contribution of generation sources by PIXE radioactivation analysis are reported. (K.I.)

  16. Atmospheric corrosion of mild steel. Pt. II. Marine atmospheres

    International Nuclear Information System (INIS)

    This paper summarizes the results obtained in the MICAT project for mild steel specimens exposed for 1 to 4 years in 47 marine atmospheres in the Ibero-American region. All these atmospheres were characterized for climatology, pollution and corrosion rates according to ISO standards. Complementary morphological and chemical characterization of the steel corrosion product layers (SCPLs) formed in these atmospheres was carried out. The overall analysis of results contributes to understanding, in a systematic way, how atmospheric corrosivity categories can be correlated with corrosion mechanisms. Special aspects of the atmospheres, from pure to mixed marine, were considered. (orig.)

  17. Absorption of Soluble Gases by Atmospheric Nanoaerosols

    CERN Document Server

    Elperin, Tov; Krasovitov, Boris; Lushnikov, Alexey

    2012-01-01

    We investigate mass transfer during absorption of atmospheric trace soluble gases by a single droplet whose size is comparable to the molecular mean free path in air at normal conditions. It is assumed that the trace reactant diffuses to the droplet surface and then reacts with the substances inside the droplet according to the first order rate law. Our analysis applies a flux-matching theory of transport processes in gases and assumes constant thermophysical properties of the gases and liquids. We derive an integral equation of Volterra type for the transient molecular flux density to a liquid droplet and solve it numerically. Numerical calculations are performed for absorption of sulfur dioxide (SO2), dinitrogen trioxide (N2O3) and chlorine (Cl2) by liquid nanoaerosols accompanied by chemical dissociation reaction. It is shown that during gas absorption by nanoaerosols the kinetic effects play significant role, and neglecting kinetic effects leads to significant overestimation of the soluble gas flux into a...

  18. Analysis of software for modeling atmospheric dispersion

    International Nuclear Information System (INIS)

    During last few years, a number software packages for microcomputes have appeared with the aim to simulate diffusion of atmospheric pollutants. These codes, simplifying the models used for safety analyses of industrial plants are becoming more useful, and are even used for post-accidental conditions. The report presents for the first time in a critical manner, principal models available up to this date. The problem arises in adapting the models to the demanded post-accidental interventions. In parallel to this action an analysis of performance was performed. It means, identifying the need of forecasting the most appropriate actions to be performed having in mind short available time and lack of information. Because of these difficulties, it is possible to simplify the software, which will not include all the options but could deal with a specific situation. This would enable minimisation of data to be collected on the site

  19. Atmospheric transmittance model for photosynthetically active radiation

    Energy Technology Data Exchange (ETDEWEB)

    Paulescu, Marius; Stefu, Nicoleta; Gravila, Paul; Paulescu, Eugenia; Boata, Remus; Pacurar, Angel; Mares, Oana [Physics Department, West University of Timisoara, V Parvan 4, 300223 Timisoara (Romania); Pop, Nicolina [Department of Physical Foundations of Engineering, Politehnica University of Timisoara, V Parvan 2, 300223 Timisoara (Romania); Calinoiu, Delia [Mechanical Engineering Faculty, Politehnica University of Timisoara, Mihai Viteazu 1, 300222 Timisoara (Romania)

    2013-11-13

    A parametric model of the atmospheric transmittance in the PAR band is presented. The model can be straightforwardly applied for calculating the beam, diffuse and global components of the PAR solar irradiance. The required inputs are: air pressure, ozone, water vapor and nitrogen dioxide column content, Ångström's turbidity coefficient and single scattering albedo. Comparison with other models and ground measured data shows a reasonable level of accuracy for this model, making it suitable for practical applications. From the computational point of view the calculus is condensed into simple algebra which is a noticeable advantage. For users interested in speed-intensive computation of the effective PAR solar irradiance, a PC program based on the parametric equations along with a user guide are available online at http://solar.physics.uvt.ro/srms.

  20. Manual of dose evaluation from atmospheric releases

    International Nuclear Information System (INIS)

    The problem of dose evaluation from atmospheric releases is reduced to simple arithmetic by giving tables of concentrations and time integrated concentrations for instantaneous plumes and long time (1 year), sector averaged plumes for distances upto 10 km, effective release heights of upto 200 m and the six Pasquill stability classes. Correction factors for decay, depletion due to deposition and rainout are also given. Inhalation doses, immersion doses and contamination levels can be obtained from these by using multiplicative factors tabulated for various isotopes of significance. Tables of external gamma doses from plume are given separately for various gamma energies. Tables are also given to evaluate external beta and gamma dose rates from contaminated surfaces. The manual also discusses the basic diffusion model relevant to the problem. (author)

  1. Diffusion of polyelectrolytes in polyelectrolyte gels

    Science.gov (United States)

    Rahalkar, Anand; Muthukumar, Murugappan

    2015-03-01

    Using dynamic light scattering, we have investigated the diffusion coefficient of sodium poly(styrene sulfonate) in a matrix of poly(acrylamide-co-acrylate) gels. The diffusion coefficient of the probe polyelectrolyte exhibits a crossover behavior from a particle-diffusion to entropic-barrier dominated diffusion, as the molecular weight is increased. The effect of electrostatics, by varying the charge density of the matrix, on probe diffusion constant will be presented.

  2. Measurement of Diffusion in Flowing Complex Fluids

    OpenAIRE

    Leonard, Edward F.; Aucoin, Christian P.; Nanne, Edgar E.

    2006-01-01

    A microfluidic device for the measurement of solute diffusion as well as particle diffusion and migration in flowing complex fluids is described. The device is particularly suited to obtaining diffusivities in such fluids, which require a desired flow state to be maintained during measurement. A method based on the Loschmidt diffusion theory and short times of exposure is presented to allow calculation of diffusivities from concentration differences in the flow streams leaving the cell.

  3. Correlation structure of fractional Pearson diffusions

    OpenAIRE

    Leonenko, Nikolai N.; Meerschaert, Mark M.; Sikorskii, Alla

    2013-01-01

    The stochastic solution to a diffusion equations with polynomial coefficients is called a Pearson diffusion. If the first time derivative is replaced by a Caputo fractional derivative of order less than one, the stochastic solution is called a fractional Pearson diffusion. This paper develops an explicit formula for the covariance function of a fractional Pearson diffusion in steady state, in terms of Mittag-Leffler functions. That formula shows that fractional Pearson diffusions are long ran...

  4. Deriving scalar maps from Diffusion Spectrum MRI

    OpenAIRE

    Hagmann, P.; Gigandet, X.; Cammoun, L.; Wedeen, V.; Maeder, P; Thiran, J.-P.; Meuli, R.

    2007-01-01

    Whole brain DSI acquisitions are now clinically feasible. It is therefore necessary to have scalar maps available in order to easily visualize summary statistics of the full 3D diffusion pdf available in every voxel. We show how to derive from DSI not only the widely used scalar maps like mean diffusion or fractional anisotropy but also how to extract contrasts reflecting other features of the diffusion pdf shape like the diffusion sharpness, the diffusion coefficient along and perpendicular ...

  5. Zinc self-diffusion, electrical properties, and defect structure of undoped, single crystal zinc oxide

    International Nuclear Information System (INIS)

    Zinc self-diffusion was measured in single crystal zinc oxide using nonradioactive 70Zn as the tracer isotope and secondary ion mass spectrometry for data collection. Crystal mass was closely monitored to measure ZnO evaporation. Diffusion coefficients were isotropic with an activation energy of 372 kJ/mol. Zinc self-diffusion is most likely controlled by a vacancy mechanism. Electrical property measurements exhibit a plateau in conductivity at intermediate pO2 with an increase in reducing atmospheres. An analysis of the defect structure is presented that indicates that oxygen vacancies are probably the intrinsic ionic defects responsible for n-type conductivity in reducing atmospheres. (c) 2000 American Institute of Physics

  6. Innovation Diffusion: Assessment of Strategies within the Diffusion Simulation Game

    Science.gov (United States)

    Enfield, Jacob; Myers, Rodney D.; Lara, Miguel; Frick, Theodore W.

    2012-01-01

    Educators increasingly view the high level of engagement and experiential learning offered by games as a means to promote learning. However, as with any designed learning experience, player experiences should provide an accurate representation of content to be learned. In this study, the authors investigated the DIFFUSION SIMULATION GAME (DSG) to…

  7. Features of ionization of atmospheric air at radioactive pollution

    International Nuclear Information System (INIS)

    One studied the peculiarities of heterogeneous ionization at radioactive contamination of the atmosphere lower layers. When analyzing the radiochemical conversion of the atmosphere one determined that at rather high 0.1-1 MPa pressures the ranges with high concentration of ionized particles, so-called tracks of high-energy corpuscular (protons, α- and β-particles) emissions might be formed in the air. A model of the atmosphere track ionization taking account of the elementary processes within the tracks that was: kinetics, molecular diffusion and ion drift within the electrical field, was proposed. Paper presents all basic elementary ion-molecular processes in the ionized troposphere and determines the application limits of the mentioned model

  8. Diffusion equations and turbulent transport

    International Nuclear Information System (INIS)

    One scrutinized transport equations differing essentially in form from the classical diffusion one. Description of diffusion under strong nonequilibrium and turbulence involved application of equations that took account of transport nonlocality and memory effects. One analyzed ways to derive the mentioned equations starting from quasi-linear approximation and up to equations with fractional derivatives. One points out the generality of the applied theoretical concepts in spite of the essential difference of the exact physical problems. One demonstrated the way of application of the theoretical and probabilistic ideas

  9. Diffusion equations and turbulent transport

    International Nuclear Information System (INIS)

    Diffusion equations are considered that differ substantially in structure from classical ones. A description of diffusion under strongly nonequilibrium conditions in a highly turbulent plasma requires the use of equations that take into account memory effects and the nonlocal nature of transport. Different methods are developed for constructing such equations, ranging from those in the quasilinear approximation to those with fractional derivatives. It is emphasized that the theoretical concepts underlying the equations proposed are common for a very wide variety of specific physical problems. The ways of applying theoretical probabilistic ideas are demonstrated

  10. Diffusion dynamics on multiplex networks

    CERN Document Server

    Gomez, S; Gomez-Gardeñes, J; Perez-Vicente, C J; Moreno, Y; Arenas, A

    2012-01-01

    We study the time scales associated to diffusion processes that take place on multiplex networks (a set of networks structured in interconnected layers). To this end we propose the construction of a supra-Laplacian matrix, which consists of a dimensional lifting of the Laplacian matrix of each layer of the multiplex network. We use perturbative analysis to reveal analytically the structure of eigenvectors and eigenvalues of the complete network in terms of the spectral properties of the individual layers. The spectrum of the supra-Laplacian allows us to understand the physics of diffusion-like processes on top of multiplex networks.

  11. Optimization of hydraulic turbine diffuser

    Science.gov (United States)

    Moravec, Prokop; Hliník, Juraj; Rudolf, Pavel

    2016-03-01

    Hydraulic turbine diffuser recovers pressure energy from residual kinetic energy on turbine runner outlet. Efficiency of this process is especially important for high specific speed turbines, where almost 50% of available head is utilized within diffuser. Magnitude of the coefficient of pressure recovery can be significantly influenced by designing its proper shape. Present paper focuses on mathematical shape optimization method coupled with CFD. First method is based on direct search Nelder-Mead algorithm, while the second method employs adjoint solver and morphing. Results obtained with both methods are discussed and their advantages/disadvantages summarized.

  12. Oxygen diffusion in cuprate superconductors

    International Nuclear Information System (INIS)

    Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La2-xSrxCuO4, YBa2Cu3O7-δ, YBa2Cu4O8, and the Bi2Sr2Can-1CunO2+4 (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible

  13. Dynamics of polymerization in polyacrylamide gel (PAG) dosimeters: (II) modelling oxygen diffusion

    International Nuclear Information System (INIS)

    Oxygen contamination of a polyacrylamide gel (PAG) dosimeter can have a significant detrimental effect upon the performance characteristics of the gel as a dosimeter. Oxygen contamination can occur during preparation, but can also arise from the diffusion of atmospheric oxygen through vessel walls. Even 'trace' amounts of oxygen present in any gaseous space (usually nitrogen filled) between the surface of the PAG and the vessel seal can have a detectable effect. This paper describes a method used to quantify the detrimental effects of a range of oxygen concentrations upon the performance of the PAG. The results of diffusion studies for air and pure oxygen diffusing into the PAG over time are presented and coupled with a novel method of calculating oxygen concentrations in the PAG. Results obtained suggest that the diffusion is Fickian. The coefficient of diffusion D has been calculated to be (8±2)x10-6cm2s-1 for oxygen diffusing into PAG stored at 4 deg. C, under the assumption that the diffusion mechanism is independent of the concentration of the diffusing species. In addition, a quantitative relation has been established between the transverse relaxation rate R2 of the PAG and the concentration of oxygen present. The implications of these findings for polymer gel dosimetry are discussed. (author)

  14. Metal Accretion onto White Dwarfs. I. The Approximate Approach Based on Estimates of Diffusion Timescales

    Science.gov (United States)

    Fontaine, G.; Brassard, P.; Dufour, P.; Tremblay, P.-E.

    2015-06-01

    The accretion-diffusion picture is the model par excellence for describing the presence of planetary debris polluting the atmospheres of relatively cool white dwarfs. Some important insights into the process may be derived using an approximate approach which combines static stellar models with estimates of diffusion timescales at the base of the outer convection zone or, in its absence, at the photosphere. Until recently, and to our knowledge, values of diffusion timescales in white dwarfs have all been obtained on the basis of the same physics as that developed initially by Paquette et al., including their diffusion coefficients and thermal diffusion coefficients. In view of the recent exciting discoveries of a plethora of metals (including some never seen before) polluting the atmospheres of an increasing number of cool white dwarfs, we felt that a new look at the estimates of settling timescales would be worthwhile. We thus provide improved estimates of diffusion timescales for all 27 elements from Li to Cu in the periodic table in a wide range of the surface gravity-effective temperature domain and for both DA and non-DA stars.

  15. Modelling of atmospheric effects on the angular distribution of a backscattering peak

    International Nuclear Information System (INIS)

    If off-nadir satellite sensing of vegetative surfaces is considered, understanding the angular distribution of the radiance exiting the atmosphere in all upward directions is of interest. Of particular interest is the discovery of those reflectance features which are invariant to atmospheric perturbations. When mono-directional radiation is incident on a vegetative scene a characteristic angular signature called the hot-spot is produced in the solar retro-direction. The remotely sensed hot-spot is modified by atmospheric extinction of the direct and reflected solar radiation, atmospheric backscattering, and the diffuse sky irradiance incident on the surface. It is demonstrated, however, by radiative transfer calculations through model atmospheres that at least one parameter which characterizes the canopy hot-spot, namely its angular half width, is invariant to atmospheric perturbations. 7 refs., 4 figs., 1 tab

  16. Atmospheric pseudohalogen chemistry

    OpenAIRE

    Lary, D. J.

    2004-01-01

    There are at least three reasons why hydrogen cyanide is likely to be significant for atmospheric chemistry. The first is well known, HCN is a product and marker of biomass burning. However, if a detailed ion chemistry of lightning is considered then it is almost certain than in addition to lightning producing NOx, it also produces HOx and HCN. Unlike NOx and HOx, HCN is long-lived and could therefore ...

  17. Fair weather terrestrial atmospheric electricity

    Science.gov (United States)

    Harrison, G.

    Atmospheric electricity is one of the oldest experimental topics in atmospheric science. The fair weather aspects, although having less dramatic effects than thunderstorm electrification, link the microscale behaviour of ion clusters to currents flowing on the global scale. This talk will include a survey of some past measurements and measurement methods, as atmospheric electrical data from a variety of sites and eras are now being used to understand changes in atmospheric composition. Potential Gradient data was the original source of information on the global atmospheric electrical circuit, and similar measurements can now be used to reconstruct past air pollution concentrations, and black carbon loading.

  18. VULCAN: an Open-Source, Validated Chemical Kinetics Python Code for Exoplanetary Atmospheres

    OpenAIRE

    Tsai, Shang-Min; Lyons, James R.; Grosheintz, Luc; Rimmer, Paul B.; Kitzmann, Daniel; Heng, Kevin

    2016-01-01

    We present an open-source and validated chemical kinetics code for studying hot exoplanetary atmospheres, which we name VULCAN. It is constructed for gaseous chemistry from 500 to 2500 K using a reduced C- H-O chemical network with about 300 reactions. It uses eddy diffusion to mimic atmospheric dynamics and excludes photochemistry. We have provided a full description of the rate coefficients and thermodynamic data used. We validate VULCAN by reproducing chemical equilibrium and by comparing ...

  19. Millisecond time scale atmospheric light pulses associated with solar and magnetospheric activity.

    Science.gov (United States)

    Ogelman, H.

    1973-01-01

    By using a wide-angle photomultiplier system a class of millisecond time scale diffuse atmospheric light emission of terrestrial origin has been discovered. These fast atmospheric pulsation events also show damped oscillations around 10-kHz frequency, which distinguishes them from ordinary lightning-type events. Evidence is presented for the enhancement in the rate of these events induced by solar flare activity.

  20. The partitioning of excess CO2 in a five-reservoir atmosphere-ocean model

    OpenAIRE

    Crane, A. J.

    2011-01-01

    The two-box-diffusion model of the oceans developed by Oeschger et al. (1975) is extended to include a well-mixed, deep polar reservoir in contact with the atmosphere and a split diffusive deep ocean comprising two reservoirs with characteristics akin to the Atlantic and Pacific oceans. It is shown that the division of the deep ocean has little influence on the airborne fraction of fossil fuel CO2. The partial or complete replacement of the diffusive Atlantic reservoir with the well-mixed pol...