WorldWideScience

Sample records for sand transport calculated

  1. Aeolian transport of sand.

    Science.gov (United States)

    Almeida, M P; Andrade, J S; Herrmann, H J

    2007-03-01

    The airborne transport of particles on a granular surface by the saltation mechanism is studied through numerical simulation of particles dragged by turbulent air flow. We calculate the saturated flux q(s) and show that its dependence on the wind strength u(*) is consistent with several empirical relations obtained from experimental measurements. We propose and explain a new relation for fluxes close to the threshold velocity u(t), namely, q(s)=a(u(*)-u(t))(alpha) with alpha approximately 2. We also obtain the distortion of the velocity profile of the wind due to the drag of the particles and find a novel dynamical scaling relation. We also obtain a new expression for the dependence of the height of the saltation layer as function of the strength of the wind.

  2. Discrete particle simulation of mixed sand transport

    Institute of Scientific and Technical Information of China (English)

    Fengjun Xiao; Liejin Guo; Debiao Li; Yueshe Wang

    2012-01-01

    An Eulerian/Lagrangian numerical simulation is performed on mixed sand transport.Volume averaged Navier-Stokes equations are solved to calculate gas motion,and particle motion is calculated using Newton's equation,involving a hard sphere model to describe particle-to-particle and particle-to-wall collisions.The influence of wall characteristics,size distribution of sand particles and boundary layer depth on vertical distribution of sand mass flux and particle mean horizontal velocity is analyzed,suggesting that all these three factors affect sand transport at different levels.In all cases,for small size groups,sand mass flux first increases with height and then decreases while for large size groups,it decreases exponentially with height and for middle size groups the behavior is in-between.The mean horizontal velocity for all size groups well fits experimental data,that is,increasing logarithmically with height in the middle height region.Wall characteristics greatly affects particle to wall collision and makes the flat bed similar to a Gobi surface and the rough bed similar to a sandy surface.Particle size distribution largely affects the sand mass flux and the highest heights they can reach especially for larger particles.

  3. Nearshore Sand Transport.

    Science.gov (United States)

    1987-01-01

    Born November 19, 1956 - Peoria, Illinois 1978 B.S., Civil Engineering, University of Miami, Coral Gables, Florida 1978 B.S., Physics, University of...Aubrey, 1985, "Theoretical and observational estimates of nearshore bedload transport rates," Marino Geology, v 64, p 91-111. Guza, R.T., N.C. Clifton

  4. Sand transport, erosion and granular electrification

    DEFF Research Database (Denmark)

    Merrison, J.P.

    2012-01-01

    The transport of granular materials by wind has a major impact on our environment through sand/soil erosion and the generation and transport of atmospheric dust aerosols. Terrestrially the transport of dust involves billions of tons of material every year, influencing the global climate and impac......The transport of granular materials by wind has a major impact on our environment through sand/soil erosion and the generation and transport of atmospheric dust aerosols. Terrestrially the transport of dust involves billions of tons of material every year, influencing the global climate...... can affect grain transport through the generation of intense electric fields and processes of electrostatic assembly. Importantly the transport of sand is characterized by saltation, which is known to be an active process for erosion and therefore a source for dust and sand formation. Using novel...... erosion simulation techniques the link between grain transport rates and erosion rates has been quantified. Furthermore this can be linked to production rates for dust and has been associated with chemical and mineral alteration through a process of mechanical activation of fractured surfaces. This work...

  5. Longshore sediment transport at Golden Sands (Bulgaria

    Directory of Open Access Journals (Sweden)

    Hristo Nikolov

    2006-09-01

    Full Text Available The paper presents the results of studies on the qualitative and quantitative features of the littoral drift at Golden Sands (Bulgaria, carried out jointly by Polish and Bulgarian researchers. The mathematical modelling of physical coastal processes took wave transformation (wave diffraction and refraction; the effects of shoaling and wave breaking and longshore sediment transport into account. The computations were carried out for the mean statistical annual wave climate, determined on the basis of IO BAS wave data, simulated using the WAM method from long-term Black Sea wind data. The results of sediment transport computations clearly show that its direction off the Golden Sands shore is from north to south.

  6. A Comparative Study on Sand Transport Modeling for Horizontal Multiphase Pipeline

    Directory of Open Access Journals (Sweden)

    Kan Wai Choong

    2014-02-01

    Full Text Available Presence of sand causes adverse effects on hydrocarbon production, pipeline erosion and problems at wellbore. If the problems persist, production may be stopped and delayed. This imposes workover cost. Hence, operating expenses increase and revenue reduces. There is no explicit calculation algorithm for sand transportation modeling readily available in flow simulators. Therefore, this study aims to develop an Excel-based spreadsheet on sand transportation to predict sand critical velocity and onset of sand deposition based on published literature. The authors reviewed nine sand transportation models in pipelines and made comparisons on the selected models based on various criteria. Four of which were then developed into a sand modeling spreadsheet. The four models are the Turian et al. (1987, Oudeman (1993, Stevenson et al. (2002b Model and Danielson (2007. The spreadsheet presently focuses on sand production prediction in horizontal two-phase flow. The Danielson model can predict sand hold up while the other models estimate grain size transportable and critical velocity of sand. Flowing pipeline properties, sand properties and results of simulations like using OLGA (for flow rate, velocity and superficial velocity of different phases are necessary inputs of the spreadsheet. A user selects any model based on different operating conditions or user preference. The spreadsheet was validated by comparing data extracted from the research papers. Sensitivity analyses can also be performed with the spreadsheet by manipulating the parameters such as grain size and flow rate. This review is useful for flow simulators’ development to include sand transport modeling.

  7. Transport velocities of coal and sand particles

    Energy Technology Data Exchange (ETDEWEB)

    Adanez, J. (Inst. de Carboquimica, Zaragoza (Spain)); Diego, L.F. de (Inst. de Carboquimica, Zaragoza (Spain)); Gayan, P. (Inst. de Carboquimica, Zaragoza (Spain))

    1993-10-01

    Transport velocities of narrow cut sizes of coarse particles of sand and coal were determined at room temperature and atmospheric pressure. These velocities were obtained by four different methods previously utilized by other authors with fine particles. The four methods tested gave good predictions of the transport velocities. The method based on the measurement of the time required for all the solids to leave the bed without feeding in any fresh solid is specially interesting because of its rapidity and simplicity. The determined transport velocities were strongly dependent on the solid particle size and density. The experimental values were fitted to an equation which fitted both the experimental results obtained in this work and other published results obtained with fine particles. (orig.)

  8. A transport-rate model of wind-blown sand

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Sand transport by wind plays an important role in environmental problems.Formulating the sand-transport rate model has been of continuing significance,because the majority of the existing models relate sand-transport rate to the wind-shear velocity.However,the wind-shear velocity readapted to blown sand is difficult to determine from the measured wind profiles when sand movement occurs,especially at high wind velocity.Detailed wind tunnel tests were carried out to reformulate the sand-transport rate model,followed by attempts to relate sand-transport rate to parameters of wind velocity,threshold shear-velocity,and grain size.Finally,we validated the model based on the data from field observations.

  9. Modeling sheet-flow sand transport under progressive surface waves

    NARCIS (Netherlands)

    Kranenburg, W.M.

    2013-01-01

    In the near-shore zone, energetic sea waves generate sheet-flow sand transport. In present day coastal models, wave-induced sheet-flow sand transport rates are usually predicted with semi-empirical transport formulas, based on extensive research on this phenomenon in oscillatory flow tunnels. Howeve

  10. Sand transportation and reverse patterns over leeward face of sand dune

    Science.gov (United States)

    Jiang, Hong; Dun, Hongchao; Tong, Ding; Huang, Ning

    2017-04-01

    Sand saltation has complex interactions with turbulent flow and dune form. Most models of wind-blown sand consider ideal circumstances such as steady wind velocity and a flat surface, and the bulk of data on wind flow and sand transport over an individual dune has focused mostly on the influence of dune shape or inter-dune space on the wind flow, neglecting the effect of morphology on sand saltation, particularly airflow and sand transportation over the leeward slope. Wind flow structures over the leeward slope of sand dunes have a fundamental influence on the organization of sand dunes. In order to understand sand dune dynamics, lee face airflow and sediment transportation should be paid more attention. Previous field observations could not measure turbulent flow structure well because of the limited observation points and the influence of experiment structure on wind field. In addition, the reverse sand particles over leeward face could not be collected by sand trap in field. Numerous field observations could not measure turbulent flow structure because of the limited observation points and the influence of experimental structures on the wind field. In addition, the reverse transport of sand particles over leeward face could not be collected by sand traps in field. Therefore, this paper aims to investigate the turbulent flow structure and sand transport pattern over the leeward slope. A numerical model of sand saltation over slope terrain is constructed, which also considers the coupling effects between air flow and sand particles. The large eddy simulation method is used to model turbulent flow. Sand transport is simulated by tracking the trajectory of each sand particle. The results show that terrain significantly alters the turbulent air flow structure and wind-blown sand movement, especially over the leeward slope. Here, mass flux increases initially and then decreases with height in the reversed flow region in the direction of wind flow, and the mass flux

  11. Sand transport in oscillatory sheet-flow; a literature review

    NARCIS (Netherlands)

    Janssen, C.M.

    1995-01-01

    This literature review is part of the ongoing research on sand transport in oscillatory sheet-flow, as taking place at the coast during storms. Because sheet-flow corresponds to conditions of high shear stress, large amounts of sand are transported. Therefore it is an important part of the total san

  12. Sand transport processes in the surf and swash zones

    NARCIS (Netherlands)

    Zanden, van der Joep

    2016-01-01

    Long-term predictions of beach morphology using numerical models contribute to cost-effective coastal protection strategies. The physics of sand transport in the wave breaking region and the swash zone are not fully understood, leading to poor predictive capability of existing sand transport models

  13. experimental investigation of sand minimum transport velocity in ...

    African Journals Online (AJOL)

    user

    minimum transport velocity models in pipelines, the analytical and empirical methods. Because of the ... identified two niche areas of research such as sand transport in .... operational conditions the limit deposit velocity passes through a ...

  14. Aeolian sand transport and aeolian deposits on Venus: A review

    Science.gov (United States)

    Kreslavsly, Mikhail A.; Bondarenko, Nataliya V.

    2017-06-01

    We review the current state of knowledge about aeolian sand transport and aeolian bedforms on planet Venus. This knowledge is limited by lack of observational data. Among the four planetary bodies of the Solar System with sufficient atmospheres in contact with solid surfaces, Venus has the densest atmosphere; the conditions there are transitional between those for terrestrial subaerial and subaqueous transport. The dense atmosphere causes low saltation threshold and short characteristic saltation length, and short scale length of the incipient dunes. A few lines of evidence indicate that the typical wind speeds exceed the saltation threshold; therefore, sand transport would be pervasive, if sand capable of saltation is available. Sand production on Venus is probably much slower than on the Earth; the major terrestrial sand sinks are also absent, however, lithification of sand through sintering is expected to be effective under Venus' conditions. Active transport is not detectable with the data available. Aeolian bedforms (transverse dunes) resolved in the currently available radar images occupy a tiny area on the planet; however, indirect observations suggest that small-scale unresolved aeolian bedforms are ubiquitous. Aeolian transport is probably limited by sand lithification causing shortage of saltation-capable material. Large impact events likely cause regional short-term spikes in aeolian transport by supplying a large amount of sand-size particles, as well as disintegration and activation of older indurated sand deposits. The data available are insufficient to understand whether the global aeolian sand transport occurs or not. More robust knowledge about aeolian transport on Venus is essential for future scientific exploration of the planet, in particular, for implementation and interpretation of geochemical studies of surface materials. High-resolution orbital radar imaging with local to regional coverage and desirable interferometric capabilities is the

  15. Prediction of sand transport over immobile gravel from supply limited to capacity conditions.

    Science.gov (United States)

    The prediction of the transport of sand in armored gravel reaches downstream of dams is complicated by variable bed conditions ranging from sand transported through gravel to sand in transport over buried gravel. Knowledge of the rate of sand transport in these conditions, however, is necessary for...

  16. Modelling aeolian sand transport using a dynamic mass balancing approach

    Science.gov (United States)

    Mayaud, Jerome R.; Bailey, Richard M.; Wiggs, Giles F. S.; Weaver, Corinne M.

    2017-03-01

    Knowledge of the changing rate of sediment flux in space and time is essential for quantifying surface erosion and deposition in desert landscapes. Whilst many aeolian studies have relied on time-averaged parameters such as wind velocity (U) and wind shear velocity (u*) to determine sediment flux, there is increasing field evidence that high-frequency turbulence is an important driving force behind the entrainment and transport of sand. At this scale of analysis, inertia in the saltation system causes changes in sediment transport to lag behind de/accelerations in flow. However, saltation inertia has yet to be incorporated into a functional sand transport model that can be used for predictive purposes. In this study, we present a new transport model that dynamically balances the sand mass being transported in the wind flow. The 'dynamic mass balance' (DMB) model we present accounts for high-frequency variations in the horizontal (u) component of wind flow, as saltation is most strongly associated with the positive u component of the wind. The performance of the DMB model is tested by fitting it to two field-derived (Namibia's Skeleton Coast) datasets of wind velocity and sediment transport: (i) a 10-min (10 Hz measurement resolution) dataset; (ii) a 2-h (1 Hz measurement resolution) dataset. The DMB model is shown to outperform two existing models that rely on time-averaged wind velocity data (e.g. Radok, 1977; Dong et al., 2003), when predicting sand transport over the two experiments. For all measurement averaging intervals presented in this study (10 Hz-10 min), the DMB model predicted total saltation count to within at least 0.48%, whereas the Radok and Dong models over- or underestimated total count by up to 5.50% and 20.53% respectively. The DMB model also produced more realistic (less 'peaky') time series of sand flux than the other two models, and a more accurate distribution of sand flux data. The best predictions of total sand transport are achieved using

  17. Field Measurements of Influence of Sand Transport Rate on Structure of Wind-sand Flow over Coastal Transverse Ridge

    Institute of Scientific and Technical Information of China (English)

    DONG Yuxiang; S L NAMIKAS; P A HESP; MA Jun

    2008-01-01

    The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province,which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges.The measurement results show that,on the conditions of approximate wind velocities and same surface materials and environments,some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge.First,the sand transport rates of layers at different heights in the wind-sand flow increase,with the maximum increase at the height layer of 4-8cm.Second,the ratios of sand transport rates of layers at different heights to total sand transport rate decrease at the low height layer (0-4cm),but increase at the high height layer (4-60cm).Third,the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm,but it changes fi'om power function model to exponential function model in the whole height layer (0-60cm) and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate.Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.

  18. Comparison of Calculation Models for Bucket Foundation in Sand

    DEFF Research Database (Denmark)

    Vaitkunaite, Evelina; Molina, Salvador Devant; Ibsen, Lars Bo

    The possibility of fast and rather precise preliminary offshore foundation design is desirable. The ultimate limit state of bucket foundation is investigated using three different geotechnical calculation tools: [Ibsen 2001] an analytical method, LimitState:GEO and Plaxis 3D. The study has focused...... on resultant bearing capacity of variously embedded foundation in sand. The 2D models, [Ibsen 2001] and LimitState:GEO can be used for the preliminary design because they are fast and result in a rather similar bearing capacity calculation compared with the finite element models of Plaxis 3D. The 2D models...... and their results are compared to the finite element model in Plaxis 3D in this article....

  19. Influence of silicate on the transport of bacteria in quartz sand and iron mineral-coated sand.

    Science.gov (United States)

    Dong, Zhe; Yang, Haiyan; Wu, Dan; Ni, Jinren; Kim, Hyunjung; Tong, Meiping

    2014-11-01

    The influence of silicate on the transport and deposition of bacteria (Escherichia coli) in packed porous media were examined at a constant 20 mM ionic strength with different silicate concentrations (from 0 to 1 mM) at pH 7. Transport experiments were performed in two types of representative porous media, both bare quartz sand and iron mineral-coated quartz sand. In bare quartz sand, the breakthrough plateaus in the presence of silicate in suspensions were lower and the corresponding retained profiles were higher than those without silicate ions, indicating that the presence of silicate in suspensions decreased cell transport in bare quartz sand. Moreover, the decrease of bacteria transport in quartz sand induced by silicate was more pronounced with increasing silicate concentrations from 0 to 1 mM. However, when EPS was removed from cell surfaces, the presence of silicate in cell suspensions (with different concentrations) did not affect the transport behavior of bacteria in quartz sand. The interaction of silicate with EPS on cell surfaces negatively decreased the zeta potentials of bacteria, resulting in the decreased cell transport in bare quartz sand when silicate was copresent in bacteria suspensions. In contrast, the presence of silicate in suspensions increased cell transport in iron mineral-coated sand. Silicate ions competed with bacteria for the adsorption sites on mineral-coated sand, contributing to the increased cell transport in mineral-coated sand with silicate present in cell suspensions.

  20. Oblique second-order sand transport pathways on an intertidal sand flat in a natural tidal inlet system

    DEFF Research Database (Denmark)

    Ernstsen, Verner Brandbyge; Lefebvre, Alice; Kroon, Aart

    2013-01-01

    . This indicates distinct second-order sand transport pathways oblique to the main tidal transport pathways. A conceptual model for the development of the bedforms and channels is presented, which comprises hypotheses of the hydrodynamic forcing of the different second-order sand transport pathways. During flood...

  1. 2007 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

    Science.gov (United States)

    Draut, Amy E.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.

    2009-01-01

    Weather data constitute an integral part of ecosystem monitoring in the Colorado River corridor and are particularly valuable for understanding processes of landscape change that contribute to the stability of archeological sites. Data collected in 2007 are reported from nine weather stations in the Colorado River corridor through Grand Canyon, Ariz. The stations were deployed in February and March 2007 to measure wind speed and direction, rainfall, air temperature, relative humidity, and barometric pressure. Sand traps near each weather station collect windblown sand, from which daily aeolian sand-transport rates are calculated. The data reported here were collected as part of an ongoing study to test and evaluate methods for quantifying processes that affect the physical integrity of archeological sites along the river corridor; as such, these data can be used to identify rainfall events capable of causing gully incision and to predict likely transport pathways for aeolian sand, two landscape processes integral to the preservation of archeological sites. Weather data also have widespread applications to other studies of physical, cultural, and biological resources in Grand Canyon. Aeolian sand-transport data reported here, collected in the year before the March 2008 High-Flow Experiment (HFE) at Glen Canyon Dam, represent baseline data against which the effects of the 2008 HFE on windblown sand will be compared in future reports.

  2. Experimental investigation on heat transport in gravel-sand materials

    DEFF Research Database (Denmark)

    Maureschat, Gerald; Heller, Alfred

    1997-01-01

    out in a small size experiment. The experiment consists of a highly insulated box filled with two kinds of sand material crossed by a plastic heat pipe. Heat transfer is measured under dry and water satured conditions in a cross-section.The conclusions are clear. To obtain necessary heat conduction......The project is a basic study on the expected thermal behaviour of gravel storage initiated as a part of a research and demonstration gravel storage for seasonal heat storage.The goal of the investigation is to determine the heat transfer between heat pipes and sand-gravel storage media by carrying...... media no convectional heat transport is found. It would be relevant to extend the investigation to media that enables convectional heat transport. A last conclusion is that such experiments, necessary for proper designing of sand-gravel storage types, are a very cheap form of collecting information...

  3. Experimental investigation on heat transport in gravel-sand materials

    DEFF Research Database (Denmark)

    Maureschat, Gerald; Heller, Alfred

    1997-01-01

    out in a small size experiment. The experiment consists of a highly insulated box filled with two kinds of sand material crossed by a plastic heat pipe. Heat transfer is measured under dry and water satured conditions in a cross-section.The conclusions are clear. To obtain necessary heat conduction...... in sand-gravel material, the storage media is to be water satured. In this case, handling of such material on site is rather complex. The conduction is highly dependent on the thermal properties of the storage media and so is the overall thermal performance of a storage applying such media. For sandy...... media no convectional heat transport is found. It would be relevant to extend the investigation to media that enables convectional heat transport. A last conclusion is that such experiments, necessary for proper designing of sand-gravel storage types, are a very cheap form of collecting information...

  4. Batch and column studies of adsorption of Li, Ni and Br by a reference sand for contaminant transport experiments

    Energy Technology Data Exchange (ETDEWEB)

    Seigel, M.D. [Sandia National Labs., Albuquerque, NM (United States); Ward, D.B.; Bryan, C.R. [Univ. of New Mexico, Albuquerque, NM (United States)] [and others

    1995-09-01

    A processed quartz sand (Wedron 510), mined from the St. Peter sandstone, has been characterized by a variety of chemical and physical methods for use as a reference porous media in transport model validation experiments. Wedron 510 sand was used in an intermediate-scale experiment involving migration of Ni, Li and Br through a 6-m high x 3-m diameter caisson. Ni and Li adsorption/desorption, and Li/Ni site-competition experiments yielded information on the importance of the trace mineral phases to adsorption of Li and Ni by the sand. The presence of an iron hydroxide coating similar to goethite on the sand grains is suggested by visual observation and leaching experiments. Kaolinite was identified by SEM and XRD as a significant trace mineral phase in the sand and occurs as small particles coating the sand grains. Quartz, the predominant constituent of the sand by weight, does not appear to contribute significantly to the adsorption properties of the sand. Qualitatively, the adsorption properties of the sand can be adequately modeled as a two-mineral system (goethite and kaolinite). The studies described in this report should provide a basis for understanding transport of Ni, Li and Br through porous media similar to the reference sand. Techniques were developed for obtaining parameter values for surface complexation and kinetic adsorption models for the sand and its mineral components. These constants can be used directly in coupled hydrogeochemical transport codes. The techniques should be useful for characterization of other natural materials and elements in high-level nuclear waste in support of coupled hydrogeochemical transport calculations for Yucca Mountain.

  5. Oblique second-order sand transport pathways on an intertidal sand flat in a natural tidal inlet system

    DEFF Research Database (Denmark)

    Ernstsen, Verner Brandbyge; Lefebvre, Alice; Kroon, Aart

    2013-01-01

    A detailed digital elevation model (DEM) of an intertidal sand flat in the Knudedyb tidal inlet in the Danish Wadden Sea, derived from high-resolution Light Detection And Ranging (LiDAR) data, reveals a large elongated bedform field with complex bedform morphologies and drainage channel networks....... This indicates distinct second-order sand transport pathways oblique to the main tidal transport pathways. A conceptual model for the development of the bedforms and channels is presented, which comprises hypotheses of the hydrodynamic forcing of the different second-order sand transport pathways. During flood...

  6. A new turbulence-based model for sand transport

    Science.gov (United States)

    Mayaud, Jerome; Wiggs, Giles; Bailey, Richard

    2016-04-01

    Knowledge of the changing rate of sediment flux in space and time is essential for quantifying surface erosion and deposition in desert landscapes. While many aeolian studies have relied on time-averaged parameters such as wind velocity (U) and wind shear velocity (u*) to determine sediment flux, there is increasing evidence that high-frequency turbulence is an important driving force behind the entrainment and transport of sand. However, turbulence has yet to be incorporated into a functional sand transport model that can be used for predictive purposes. In this study we present a new transport model (the 'turbulence model') that accounts for high-frequency variations in the horizontal (u) and vertical (w) components of wind flow. The turbulence model is fitted to wind velocity and sediment transport data from a field experiment undertaken in Namibia's Skeleton Coast National Park, and its performance at three temporal resolutions (10 Hz, 1 Hz, 1 min) is compared to two existing models that rely on time-averaged wind velocity data (Radok, 1977; Dong et al., 2003). The validity of the three models is analysed under a variety of saltation conditions, using a 2-hour (1 Hz measurement resolution) dataset from the Skeleton Coast and a 5-hour (1 min measurement resolution) dataset from the southwestern Kalahari Desert. The turbulence model is shown to outperform the Radok and Dong models when predicting total saltation count over the three experimental periods. For all temporal resolutions presented in this study (10 Hz-10 min), the turbulence model predicted total saltation count to within at least 0.34%, whereas the Radok and Dong models over- or underestimated total count by up to 5.50% and 20.53% respectively. The strong performance of the turbulence model can be attributed to a lag in mass flux response built into its formulation, which can be adapted depending on the temporal resolution of investigation. This accounts for the inherent lag within the physical

  7. Influence of Bisphenol A on the transport and deposition behaviors of bacteria in quartz sand.

    Science.gov (United States)

    Wu, Dan; He, Lei; Sun, Ruonan; Tong, Meiping; Kim, Hyunjung

    2017-09-15

    The influence of Bisphenol A (BPA) on the transport and deposition behaviors of bacteria in quartz sand was examined in both NaCl (10 and 25 mM) and CaCl2 solutions (1.2 and 5 mM) by comparing the breakthrough curves and retained profiles of cell with BPA in suspensions versus those without BPA. Gram-negative Escherichia coli and Gram-positive Bacillus subtilis were employed as model cells in the present study. The extended Derjaguin-Landau-Verwey-Overbeek interaction energy calculation revealed that the presence of BPA in cell suspensions led to a lower repulsive interaction between the cells and the quartz sand. This suggests that, theoretically, increased cell deposition on quartz sand would be expected in the presence of BPA. However, under all examined solution conditions, the presence of BPA in cell suspensions increased transport and decreased deposition of bacteria in porous media regardless of cell type, ionic strength, ion valence, the presence or absence of extracellular polymeric substances. We found that competition by BPA through hydrophobicity for deposition sites on the quartz sand surfaces was the sole contributor to the enhanced transport and decreased deposition of bacteria in the presence of BPA. Copyright © 2017. Published by Elsevier Ltd.

  8. The effects of surfactants and solution chemistry on the transport of multiwalled carbon nanotubes in quartz sand-packed columns.

    Science.gov (United States)

    Lu, Yinying; Xu, Xiaopan; Yang, Kun; Lin, Daohui

    2013-11-01

    The effect of different surfactants on the transport of multiwalled carbon nanotubes (MWCNTs) in quartz sand-packed columns was firstly investigated under various conditions. The stable plateau values (C(max)) of the breakthrough curves (BTCs), critical PVs (the number of pore volumes of infusions needed to reach the C(max)), maximum transport distances (L(max)), deposition rate coefficients (kd) and retention rates were calculated to compare the transport and retention of MWCNTs under various conditions. Stability of the MWCNT suspensions as a function of the influencing factors was examined to reveal the underlying mechanism of the MWCNT retention. Results showed that MWCNTs suspended by different surfactants presented different BTCs; the MWCNT transport increased with increasing sand size and MWCNT concentration; high flow velocity was favorable for the MWCNT transport, while high Ca(2+) concentration and low pH were unfavorable for the transport; hetero-aggregation, straining and site blocking occurred during the transport.

  9. The role of suspended load transport in the occurrence of tidal sand waves

    NARCIS (Netherlands)

    Borsje, B.W.; Kranenburg, W.M.; Roos, P.C.; Matthieu, J.; Hulscher, S.J.M.H.

    2014-01-01

    Tidal sand waves are dynamic bed patterns which are formed by the complex interaction between hydrodynamics, sediment transport, and geomorphology. Field data from the southern North Sea reveal that sand waves are absent where suspended load transport is the dominant transport mode. In order to unde

  10. The role of suspended load transport in the occurrence of tidal sand waves

    NARCIS (Netherlands)

    Borsje, Bastiaan Wijnand; Kranenburg, Wouter; Roos, Pieter C.; Matthieu, J.; Hulscher, Suzanne J.M.H.

    2014-01-01

    Tidal sand waves are dynamic bed patterns which are formed by the complex interaction between hydrodynamics, sediment transport, and geomorphology. Field data from the southern North Sea reveal that sand waves are absent where suspended load transport is the dominant transport mode. In order to unde

  11. Radiation transport calculations and simulations.

    Science.gov (United States)

    Fassò, A; Ferrari, A; Sala, P R

    2009-11-01

    This article is an introduction to the Monte Carlo method as used in particle transport. After a description at an elementary level of the mathematical basis of the method, the Boltzmann equation and its physical meaning are presented, followed by Monte Carlo integration and random sampling, and by a general description of the main aspects and components of a typical Monte Carlo particle transport code. In particular, the most common biasing techniques are described, as well as the concepts of estimator and detector. After a discussion of the different types of errors, the issue of quality assurance is briefly considered.

  12. Radiation Transport Calculations and Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Fasso, Alberto; /SLAC; Ferrari, A.; /CERN

    2011-06-30

    This article is an introduction to the Monte Carlo method as used in particle transport. After a description at an elementary level of the mathematical basis of the method, the Boltzmann equation and its physical meaning are presented, followed by Monte Carlo integration and random sampling, and by a general description of the main aspects and components of a typical Monte Carlo particle transport code. In particular, the most common biasing techniques are described, as well as the concepts of estimator and detector. After a discussion of the different types of errors, the issue of Quality Assurance is briefly considered.

  13. Aerolian erosion, transport, and deposition of volcaniclastic sands among the shifting sand dunes, Christmas Lake Valley, Oregon: TIMS image analysis

    Science.gov (United States)

    Edgett, Kenneth S.; Ramsey, Michael S.; Christensen, Philip R.

    1995-01-01

    Remote sensing is a tool that, in the context of aeolian studies, offers a synoptic view of a dune field, sand sea, or entire desert region. Blount et al. (1990) presented one of the first studies demonstrating the power of multispectral images for interpreting the dynamic history of an aeolian sand sea. Blount's work on the Gran Desierto of Mexico used a Landsat TM scene and a linear spectral mixing model to show where different sand populations occur and along what paths these sands may have traveled before becoming incorporated into dunes. Interpretation of sand transport paths and sources in the Gran Desierto led to an improved understanding of the origin and Holocene history of the dunes. With the anticipated advent of the EOS-A platform and ASTER thermal infrared capability in 1998, it will become possible to look at continental sand seas and map sand transport paths using 8-12 mu m bands that are well-suited to tracking silicate sediments. A logical extension of Blount's work is to attempt a similar study using thermal infrared images. One such study has already begun by looking at feldspar, quartz, magnetite, and clay distributions in the Kelso Dunes of southern California. This paper describes the geology and application of TIMS image analysis of a less-well known Holocene dune field in south central Oregon using TIMS data obtained in 1991.

  14. The dune effect on sand-transporting winds on Mars

    Science.gov (United States)

    Jackson, Derek W. T.; Bourke, Mary C.; Smyth, Thomas A. G.

    2015-11-01

    Wind on Mars is a significant agent of contemporary surface change, yet the absence of in situ meteorological data hampers the understanding of surface-atmospheric interactions. Airflow models at length scales relevant to landform size now enable examination of conditions that might activate even small-scale bedforms (ripples) under certain contemporary wind regimes. Ripples have the potential to be used as modern `wind vanes' on Mars. Here we use 3D airflow modelling to demonstrate that local dune topography exerts a strong influence on wind speed and direction and that ripple movement likely reflects steered wind direction for certain dune ridge shapes. The poor correlation of dune orientation with effective sand-transporting winds suggests that large dunes may not be mobile under modelled wind scenarios. This work highlights the need to first model winds at high resolution before inferring regional wind patterns from ripple movement or dune orientations on the surface of Mars today.

  15. The dune effect on sand-transporting winds on Mars.

    Science.gov (United States)

    Jackson, Derek W T; Bourke, Mary C; Smyth, Thomas A G

    2015-11-05

    Wind on Mars is a significant agent of contemporary surface change, yet the absence of in situ meteorological data hampers the understanding of surface-atmospheric interactions. Airflow models at length scales relevant to landform size now enable examination of conditions that might activate even small-scale bedforms (ripples) under certain contemporary wind regimes. Ripples have the potential to be used as modern 'wind vanes' on Mars. Here we use 3D airflow modelling to demonstrate that local dune topography exerts a strong influence on wind speed and direction and that ripple movement likely reflects steered wind direction for certain dune ridge shapes. The poor correlation of dune orientation with effective sand-transporting winds suggests that large dunes may not be mobile under modelled wind scenarios. This work highlights the need to first model winds at high resolution before inferring regional wind patterns from ripple movement or dune orientations on the surface of Mars today.

  16. The dune effect on sand-transporting winds on Mars

    Science.gov (United States)

    Jackson, Derek W. T.; Bourke, Mary C; Smyth, Thomas A. G.

    2015-01-01

    Wind on Mars is a significant agent of contemporary surface change, yet the absence of in situ meteorological data hampers the understanding of surface–atmospheric interactions. Airflow models at length scales relevant to landform size now enable examination of conditions that might activate even small-scale bedforms (ripples) under certain contemporary wind regimes. Ripples have the potential to be used as modern ‘wind vanes' on Mars. Here we use 3D airflow modelling to demonstrate that local dune topography exerts a strong influence on wind speed and direction and that ripple movement likely reflects steered wind direction for certain dune ridge shapes. The poor correlation of dune orientation with effective sand-transporting winds suggests that large dunes may not be mobile under modelled wind scenarios. This work highlights the need to first model winds at high resolution before inferring regional wind patterns from ripple movement or dune orientations on the surface of Mars today. PMID:26537669

  17. Sand, salt and water in the Stampriet Basin, Namibia: Calculating ...

    African Journals Online (AJOL)

    is the first time that substantial direct (diffuse) recharge has been quantified for the Stampriet Basin, and this part ... large-scale drilling at these sites, and borehole level monitoring ..... using a laser granulometer with statistics calculated using.

  18. Transport of citrate-coated silver nanoparticles in unsaturated sand

    Science.gov (United States)

    Kumahor, Samuel; Hron, Pavel; Metreveli, George; Schaumann, Gabriele; Vogel, Hans-Jörg

    2015-04-01

    Chemical factors and physical constraints lead to coupled effects during particle transport in unsaturated porous media. Unlike for saturated transport, studies on unsaturated transport as typical for soil are currently scarce. We investigated the mobility of citrate-coated Ag NPs in unsaturated sand (grain diameter: 0.1-0.3 mm). For three flux rates and a given pore-water ionic strength (1 mM KNO3), the citrate-coated Ag NPs were less mobile at pH = 5 compared to pH = 9. The classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory suggests unfavorable deposition conditions at both, the air-water interface and solid-water interface. Breakthrough curves measured under quasi-steady state unsaturated flow showed retardation of the citrate-coated Ag NPs compared to inert solute (KBr). After flushing with nanoparticle-free 1 mM KNO3 solution (pH-adjusted), retention was much lower in deeper depths compared to the surface where the particles entered the flow field. The results show a non-linear dependence of nanoparticle (NP) mobility on flux rate and water content. Especially the observed retardation similar to equilibrium sorption is in contrast to observations under saturated flow conditions. A convection-dispersion and reaction model that combines a reversible equilibrium process and a non-equilibrium interaction process reproduced the measured breakthrough curves reasonably well. From comparison between saturated and unsaturated experiments we conclude that the air-water interface is responsible for the reversible equilibrium process while the water-solid interface accounts for irreversible soption.

  19. Transport of citrate-coated silver nanoparticles in unsaturated sand

    Energy Technology Data Exchange (ETDEWEB)

    Kumahor, Samuel K., E-mail: samuel.kumahor@ufz.de [Department of Soil Physics, Helmholtz Centre for Environmental Research–UFZ, Theodor-Lieser-Strasse 4, 06120 Halle-Saale (Germany); Hron, Pavel, E-mail: pavel.hron@iwr.uni-heidelberg.de [Interdisciplinary Center for Scientific Computing, University of Heidelberg, Im Neuenheimer Feld 368, Raum 422, 69120 Heidelberg (Germany); Metreveli, George, E-mail: metreveli@uni-landau.de [Universität Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstr. 7, D-76829 Landau (Germany); Schaumann, Gabriele E., E-mail: schaumann@uni-landau.de [Universität Koblenz-Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Fortstr. 7, D-76829 Landau (Germany); Vogel, Hans-Jörg, E-mail: hans-joerg.vogel@ufz.de [Department of Soil Physics, Helmholtz Centre for Environmental Research–UFZ, Theodor-Lieser-Strasse 4, 06120 Halle-Saale (Germany); Institute of Soil Science and Plant Nutrition, Martin-Luther-University Halle-Wittenberg, Von-Seckendorff-Platz 3, 06120 Halle-Saale (Germany)

    2015-12-01

    Chemical factors and physical constraints lead to coupled effects during particle transport in unsaturated porous media. Studies on unsaturated transport as typical for soils are currently scarce. In unsaturated porous media, particle mobility is determined by the existence of an air–water interface in addition to a solid–water interface. To this end, we measured breakthrough curves and retention profiles of citrate-coated Ag nanoparticles in unsaturated sand at two pH values (5 and 9) and three different flow rates corresponding to different water contents with 1 mM KNO{sub 3} as background electrolyte. The classical DLVO theory suggests unfavorable deposition conditions at the air–water and solid–water interfaces. The breakthrough curves indicate modification in curve shapes and retardation of nanoparticles compared to inert solute. Retention profiles show sensitivity to flow rate and pH and this ranged from almost no retention for the highest flow rate at pH = 9 to almost complete retention for the lowest flow rate at pH = 5. Modeling of the breakthrough curves, thus, required coupling two parallel processes: a kinetically controlled attachment process far from equilibrium, responsible for the shape modification, and an equilibrium sorption, responsible for particle retardation. The non-equilibrium process and equilibrium sorption are suggested to relate to the solid–water and air–water interfaces, respectively. This is supported by the DLVO model extended for hydrophobic interactions which suggests reversible attachment, characterized by a secondary minimum (depth 3–5 kT) and a repulsive barrier at the air–water interface. In contrast, the solid–water interface is characterized by a significant repulsive barrier and the absence of a secondary minimum suggesting kinetically controlled and non-equilibrium interaction. This study provides new insights into particle transport in unsaturated porous media and offers a model concept representing the

  20. Blocking effect of colloids on arsenate adsorption during co-transport through saturated sand columns.

    Science.gov (United States)

    Ma, Jie; Guo, Huaming; Lei, Mei; Wan, Xiaoming; Zhang, Hanzhi; Feng, Xiaojuan; Wei, Rongfei; Tian, Liyan; Han, Xiaokun

    2016-06-01

    Transport of environmental pollutants through porous media is influenced by colloids. Co-transport of As(V) and soil colloids at different pH were systematically investigated by monitoring breakthrough curves (BTCs) in saturated sand columns. A solute transport model was applied to characterize transport and retention sites of As(V) in saturated sand in the presence of soil colloids. A colloid transport model and the DLVO theory were used to reveal the mechanism and hypothesis of soil colloid-promoted As(V) transport in the columns. Results showed that rapid transport of soil colloids, regulated by pH and ionic strength, promoted As(V) transport by blocking As(V) adsorption onto sand, although soil colloids had low adsorption for As(V). The promoted transport was more significant at higher concentrations of soil colloids (between 25 mg L(-1) and 150 mg L(-1)) due to greater blocking effect on As(V) adsorption onto the sand surfaces. The blocking effect of colloids was explained by the decreases in both instantaneous (equilibrium) As adsorption and first-order kinetic As adsorption on the sand surface sites. The discovery of this blocking effect improves our understanding of colloid-promoted As transport in saturated porous media, which provides new insights into role of colloids, especially colloids with low As adsorption capacity, in As transport and mobilization in soil-groundwater systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Effect of Different Forcing Processes on the Longshore Sediment Transport at the Sand Motor, The Netherlands

    NARCIS (Netherlands)

    Kaji, A.O.; Luijendijk, A.P.; van Thiel de Vries, J.S.M.; De Schipper, M.A.; Stive, M.J.F.

    2014-01-01

    The Sand Motor is a pilot project of a ‘mega-nourishment’ built in the Dutch coast in 2011. In order to understand which conditions reshape those mega-nourishments the influence of different types of forcing on the longshore sediment transport along the Sand Motor has been assessed in this paper usi

  2. Laser particle counter validation for aeolian sand transport measurements using a highspeed camera

    NARCIS (Netherlands)

    Duarte Campos, Leonardo Andres; Wijnberg, Kathelijne Mariken; Oyarte Galvez, Loreto Alejandra; Hulscher, Suzanne J.M.H.

    2017-01-01

    Measuring aeolian sand transport rates in the field has been a long-standing challenge. In this paper, we present the results of a laboratory experiment to test the ability of a laser particle counter sensor (Wenglor) to accurately count sand grains of various grain size classes and stainless steel

  3. Aeolian sand transport and its effects on the stability of Miramar-Caranzalem beach

    Digital Repository Service at National Institute of Oceanography (India)

    Reddy, G.V.; Sastry, J.S.

    Removal of sand by wind from the beach at Miramar-Caranzalem, Goa, has been found to effect its stability over a relatively longer time scale. This aeolian sand transport has been computed for this strip of the beach utilising the relation between...

  4. Effect of Different Forcing Processes on the Longshore Sediment Transport at the Sand Motor, The Netherlands

    NARCIS (Netherlands)

    Kaji, A.O.; Luijendijk, A.P.; van Thiel de Vries, J.S.M.; De Schipper, M.A.; Stive, M.J.F.

    2014-01-01

    The Sand Motor is a pilot project of a ‘mega-nourishment’ built in the Dutch coast in 2011. In order to understand which conditions reshape those mega-nourishments the influence of different types of forcing on the longshore sediment transport along the Sand Motor has been assessed in this paper

  5. Beach Sand Supply and Transport at Kunduchi in Tanzania and ...

    African Journals Online (AJOL)

    OCEAN. Mombasa. Dar es. Salaam. KUNDUCHI. KENYA. TANZANIA ... Figure 2. a) Reef-platform transects at Bamburi. b) Beach plain sand ..... comprised coral debris covered by turf algae .... and ocean acidification should not be ruled.

  6. Predicting bed load transport of sand and gravel on Goodwin Creek

    Science.gov (United States)

    Bed load transport rates are difficult to predict in channels with bed material composed of sand and gravel mixtures. The transport of bed load was measured on Goodwin Creek, and in a laboratory flume channel with a similar bed material size distribution. The range of bed load transport rates meas...

  7. Sand box experiments to evaluate the influence of subsurface temperature probe design on temperature based water flux calculation

    Directory of Open Access Journals (Sweden)

    M. Munz

    2011-06-01

    Full Text Available Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface temperatures. The influence of temperature probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four temperature probe setups were installed into a sand box experiment to measure temporal highly resolved vertical temperature profiles under controlled water fluxes in the range of ±1.3 m d−1. Pass band filtered time series provided amplitude and phase of the diurnal temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to probe distance, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of temperature probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small probe distances of all setups were found to be insensitive to vertical water flux.

  8. Transport calculations of antiproton-nucleus interactions

    CERN Document Server

    Larionov, A B; Pshenichnov, I A; Satarov, L M; Greiner, W

    2010-01-01

    The Giessen Boltzmann-Uehling-Uhlenbeck transport model is extended and applied to the antiproton-nucleus interactions in a wide beam momentum range. The model calculations are compared with the experimental data on $\\bar p$-absorption cross sections on nuclei with an emphasis on extraction of the real part of an antiproton optical potential. The possibility of the cold compression of a nucleus by an antiproton in-flight is also considered.

  9. Advanced testing and characterization of transportation soils and bituminous sands

    CSIR Research Space (South Africa)

    Anochie-Boateng, Joseph

    2007-12-01

    Full Text Available This research study was intended to develop laboratory test procedures for advance testing and characterization of fine-grained cohesive soils and oil sand materials. The test procedures are based on typical field loading conditions and the loading...

  10. 2008 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

    Science.gov (United States)

    Draut, Amy E.; Sondossi, Hoda A.; Hazel, Joseph E.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.; Vanaman, Karen M.

    2009-01-01

    This report presents measurements of weather parameters and aeolian (windblown) sand transport made in 2008 near selected archaeological sites in the Colorado River corridor through Grand Canyon, Ariz. The quantitative methods and data discussed here form a basis for monitoring ecosystem processes that affect archeological-site stability. Combined with forthcoming work to evaluate landscape evolution at nearby archaeological sites, these data can be used to document the relationship between physical processes, including weather and aeolian sand transport, and their effects on the physical integrity of archaeological sites. Data collected in 2008 reveal event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Broad seasonal changes in aeolian sediment flux are also apparent at most study sites. The continuation of monitoring that began in 2007, and installation of equipment at several new sites in early 2008, allowed evaluation of the effects of the March 2008 high-flow experiment (HFE) on aeolian sand transport. At two of the nine sites studied, spring and summer winds reworked 2008 HFE sandbars to form new aeolian dunes, at which sand moved inland toward larger, well-established dune fields. At the other seven study sites, neither dune formation nor enhanced sand transport after the HFE were observed. At several of those sites, dominant wind directions in spring 2008 were not oriented such that much HFE sand would have moved inland; at other sites, lack of increased inland sand flux is attributable to lack of sandbar enlargement near the study sites or to inhibition of sand movement by vegetation or local topography.

  11. A Multiphase First Order Model for Non-Equilibrium Sand Erosion, Transport and Sedimentation

    CERN Document Server

    Preziosi, Luigi; Bruno, Luca

    2015-01-01

    Three phenomena are involved in sand movement: erosion, wind transport, and sedimentation. This paper presents a comprehensive easy-to-use multiphase model that include all three aspects with a particular attention to situations in which erosion due to wind shear and sedimentation due to gravity are not in equilibrium. The interest is related to the fact that these are the situations leading to a change of profile of the sand bed.

  12. Bedload transport of sand-gravel mixtures with antidunes: flume experiments

    OpenAIRE

    Núñez González, Francisco

    2012-01-01

    In this thesis, the interaction between flow and sediment in alluvial channels is studied from an empirical approach, for conditions close or pertaining to supercritical flow, and for four types of sediment: sand, gravel and two mixtures with sand and gravel in a relative proportion of 70-30 and 55-45, respectively. The objective is to obtain by means of laboratory experiments a data set with the characteristics of flow, sediment transport, bed configurations and sediment sorting patterns in ...

  13. Seismic behavior of tire waste-sand mixtures for transportation infrastructure in cold regions

    Institute of Scientific and Technical Information of China (English)

    Aye Edinliler; Ozgur Yildiz

    2015-01-01

    Tire wastes have many properties that are valuable from a geotechnical engineering perspective, such as low density, high strength, thermal insulation, energy absorption capacity, permeability, durability, compressibility, resilience, and high frictional strength. Thus, tire wastes offer good thermal characteristics in resisting frost penetration and have good drainage characteristics, being as permeable as coarse granular soil for fill materials. The many advantages of tire wastes make the material suitable for transportation infrastructure construction in cold regions. Also, tire wastes with high damping prop-erty make them a preferable admixture with sand for transportation infrastructures in seismic regions. This study aimed to determine the seismic performance of certain tire waste-sand mixtures in cold regions. A 70% sand-30% tire crumb mixture by weight (TC30) with a very high damping property was selected for analysis as an engineering material for transportation infrastructure. Small-scale shake-table tests were conducted on this material as well as on a sand-only sample under two different temperatures, 0 °C and 20 °C, to simulate cold-region and moderate-temperature performance, respectively. The 1999İzmit Earthquake Excitation (EW) (Mw=7.4) was taken as the input motion. Test results showed that the tire waste-sand mixture at 0 °C showed better seismic performance than that at room temperature, suggesting that a tire waste-sand mixture in cold regions may reduce seismic hazards to infrastructure.

  14. Molecular transport calculations with Wannier Functions

    DEFF Research Database (Denmark)

    Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2005-01-01

    We present a scheme for calculating coherent electron transport in atomic-scale contacts. The method combines a formally exact Green's function formalism with a mean-field description of the electronic structure based on the Kohn-Sham scheme of density functional theory. We use an accurate plane...... is applied to a hydrogen molecule in an infinite Pt wire and a benzene-dithiol (BDT) molecule between Au(111) surfaces. We show that the transmission function of BDT in a wide energy window around the Fermi level can be completely accounted for by only two molecular orbitals. (c) 2005 Elsevier B.V. All...

  15. Turbulent Flow and Sand Dune Dynamics: Identifying Controls on Aeolian Sediment Transport

    Science.gov (United States)

    Weaver, C. M.; Wiggs, G.

    2007-12-01

    Sediment transport models are founded on cubic power relationships between the transport rate and time averaged flow parameters. These models have achieved limited success and recent aeolian and fluvial research has focused on the modelling and measurement of sediment transport by temporally varying flow conditions. Studies have recognised turbulence as a driving force in sediment transport and have highlighted the importance of coherent flow structures in sediment transport systems. However, the exact mechanisms are still unclear. Furthermore, research in the fluvial environment has identified the significance of turbulent structures for bedform morphology and spacing. However, equivalent research in the aeolian domain is absent. This paper reports the findings of research carried out to characterise the importance of turbulent flow parameters in aeolian sediment transport and determine how turbulent energy and turbulent structures change in response to dune morphology. The relative importance of mean and turbulent wind parameters on aeolian sediment flux was examined in the Skeleton Coast, Namibia. Measurements of wind velocity (using sonic anemometers) and sand transport (using grain impact sensors) at a sampling frequency of 10 Hz were made across a flat surface and along transects on a 9 m high barchan dune. Mean wind parameters and mass sand flux were measured using cup anemometers and wedge-shaped sand traps respectively. Vertical profile data from the sonic anemometers were used to compute turbulence and turbulent stress (Reynolds stress; instantaneous horizontal and vertical fluctuations; coherent flow structures) and their relationship with respect to sand transport and evolving dune morphology. On the flat surface time-averaged parameters generally fail to characterise sand transport dynamics, particularly as the averaging interval is reduced. However, horizontal wind speed correlates well with sand transport even with short averaging times. Quadrant

  16. Effects of woody vegetation on overbank sand transport during a large flood, Rio Puerco, New Mexico

    Science.gov (United States)

    Griffin, Eleanor R.; Perignon, Mariela C.; Friedman, Jonathan M.; Tucker, Gregory E.

    2014-01-01

    Distributions of woody vegetation on floodplain surfaces affect flood-flow erosion and deposition processes. A large flood along the lower Rio Puerco, New Mexico, in August 2006 caused extensive erosion in a reach that had been sprayed with herbicide in September 2003 for the purpose of saltcedar (Tamarix spp.) control. Large volumes of sediment, including a substantial fraction of sand, were delivered to the reach downstream, which had not been treated with herbicide. We applied physically based, one-dimensional models of flow and suspended-sediment transport to compute volume concentrations of sand in suspension in floodplain flow at a site within the sprayed reach and at a site downstream from the sprayed reach. We computed the effects of drag on woody stems in reducing the skin friction shear stress, velocity of flow, and suspended-sand transport from open paths into patches of dense stems. Total flow and suspended-sand fluxes were computed for each site using well-constrained flood-flow depths, water-surface slopes, and measured shrub characteristics. Results show that flow in open paths carried high concentrations of sand in suspension with nearly uniform vertical distributions. Drag on woody floodplain stems reduced skin friction shear stresses by two orders of magnitude, yet sufficient velocities were maintained to transport sand more than 50 m into fields of dense, free-surface-penetrating stems. An increase in shrub canopy extent from 31% in the sprayed reach site to 49% in the downstream site was found to account for 69% of the computed decrease in discharge between the two sites. The results demonstrate the need to compute the spatial distribution of skin friction shear stress in order to effectively compute suspended-sand transport and to predict the fate of sediment and contaminants carried in suspension during large floods.

  17. Effects of Outer Membrane Proteins (OMPs) on the Transport of Escherichia coli within Saturated Sands

    Science.gov (United States)

    Xu, S.; Bardy, S.; Feriancikova, L.

    2012-12-01

    A thorough understanding of the transport behavior of bacteria within the groundwater system is critical to the protection of groundwater resources from microbial contamination and the reduction of associated public health risks. In this study, we used TolC and Ag43 positive and negative E. coli mutants to evaluate the effects of OMP TolC and Ag43 on the transport behavior of E. coli under a wide range of water chemistry conditions. The surface properties (e.g., zeta potential, contact angles of three probing liquid) of TolC and Ag43 positive and negative E. coli cells were determined and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, which considers Lifshitz-van der Waals (LW) interaction, the electrostatic double layer (EDL) interaction as well as the Lewis acid-base (AB) (i.e., hydrophobic) interaction between E. coli cells and the surface of quartz sands, were used to explain the observed trend in E. coli mobility. In general, good agreements between the experimental observations and XDLVO calculations were observed. Findings from this research suggested that OMPs could significantly impact bacterial mobility in sandy aquifers.

  18. Discrete Element Method simulations of the saturation of aeolian sand transport

    CERN Document Server

    Pähtz, Thomas; Carneiro, Marcus V; Araújo, Nuno A M; Herrmann, Hans J

    2015-01-01

    The saturation length of aeolian sand transport ($L_s$), characterizing the distance needed by wind-blown sand to adapt to changes in the wind shear, is essential for accurate modeling of the morphodynamics of Earth's sandy landscapes and for explaining the formation and shape of sand dunes. In the last decade, it has become a widely-accepted hypothesis that $L_s$ is proportional to the characteristic distance needed by transported particles to reach the wind speed (the ``drag length''). Here we challenge this hypothesis. From extensive numerical Discrete Element Method simulations, we find that, for medium and strong winds, $L_s\\propto V_s^2/g$, where $V_s$ is the saturated value of the average speed of sand particles traveling above the surface and $g$ the gravitational constant. We show that this proportionality is consistent with a recent analytical model, in which the drag length is just one of four similarly important length scales relevant for sand transport saturation.

  19. Modelling and measurement of sand transport processes over full-scale ripples in oscillatory flow

    NARCIS (Netherlands)

    Werf, van der Jebbe J.; Ribberink, Jan S.; O'Donoghue, Tom; Doucette, Jeffrey C.

    2006-01-01

    A new series of laboratory experiments was performed in the Aberdeen Oscillatory Flow Tunnel (AOFT) and the Large Oscillating Water Tunnel (LOWT) to investigate time-averaged suspended sand concentrations and transport rates over rippled beds in regular and irregular oscillatory flow. The wave-induc

  20. The influence of rainfall on transport of beach sand by wind.

    NARCIS (Netherlands)

    Dijk, van P.M.; Stroosnijder, L.; Lima, de J.L.M.P.

    1996-01-01

    This paper deals with the effect of rainfall on the process of wind erosion of beach sands and presents results from both field and wind tunnel experiments. Although sediment transport by splash is of secondary importance on coastal dunes, splash-saltation processes can move sediments in conditions

  1. Modelling of sand transport under wave-generated sheet flows with a RANS diffusion model

    NARCIS (Netherlands)

    Hassan, Wael; Ribberink, Jan S.

    2010-01-01

    A 1DV-RANS diffusion model is used to study sand transport processes in oscillatory flat-bed/sheet flow conditions. The central aim is the verification of the model with laboratory data and to identify processes controlling the magnitude and direction (‘onshore’/‘offshore’) of the net time-averaged

  2. Influence of enterococcal surface protein (esp) on the transport of Enterococcus faecium within saturated quartz sands.

    Science.gov (United States)

    Johanson, Jennifer J; Feriancikova, Lucia; Xu, Shangping

    2012-02-07

    Enterococcus was selected by US EPA as a Gram-positive indicator microorganism for groundwater fecal contamination. It was recently reported that enterococcal surface protein (esp) was more prevalent in Enterococcus from human sources than in Enterococcus from nonhuman sources and esp could potentially be used as a source tracking tool for fecal contamination (Scott et al., 2005). In this research, we performed laboratory column transport experiments to investigate the transport of Enterococcus faecium within saturated quartz sands. Particularly, we used a wild type strain (E1162) and a mutant (E1162Δesp) to examine the influence of esp on the transport behavior of E. faecium. Our results showed that esp could significantly enhance the attachment of E. faecium cells onto the surface of silica sands and thus lower the mobility of E. faecium within sand packs. Cell surface properties (e.g., zeta potential) were determined and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was applied to explain the effects of esp on the retention of E. faecium. Overall, our results suggested that E. faecium strains with esp could display lower mobility within saturated sand packs than E. faecium strains without esp. The disparity in the transport behavior of E. faecium with and without esp could limit the effectiveness of esp as a source tracking tool within the groundwater system.

  3. Transport and retention of bacteria and viruses in biochar-amended sand.

    Science.gov (United States)

    Sasidharan, Salini; Torkzaban, Saeed; Bradford, Scott A; Kookana, Rai; Page, Declan; Cook, Peter G

    2016-04-01

    The transport and retention of Escherichia coli and bacteriophages (PRD1, MS2 and ФX174), as surrogates for human pathogenic bacteria and viruses, respectively, were studied in the sand that was amended with several types of biochar produced from various feedstocks. Batch and column studies were conducted to distinguish between the role of attachment and straining in microbe retention during transport. Batch experiments conducted at various solution chemistries showed negligible attachment of viruses and bacteria to biochar before or after chemical activation. At any given solution ionic strength, the attachment of viruses to sand was significantly higher than that of biochar, whereas bacteria showed no attachment to either sand or biochar. Consistent with batch results, biochar addition (10% w/w) to sand reduced virus retention in the column experiments, suggesting a potential negative impact of biochar application to soil on virus removal. In contrast, the retention of bacteria was enhanced in biochar-amended sand columns. However, elimination of the fine fraction (bacteria retention. Results from batch and column experiments suggest that land application of biochar may only play a role in microbe retention via straining, by alteration of pore size distribution, and not via attachment. Consequently, the particle size distribution of biochar and sediments is a more important factor than type of biochar in determining whether land application of biochar enhances or diminishes microbial retention.

  4. Groundwater Flow and Salt Transport at a Sand Tailings Dam: Field Observations and Modelling Results.

    Science.gov (United States)

    Price, A. C.; Mendoza, C. A.

    2004-05-01

    Large volumes of sand tailings are produced during the extraction of bitumen from the oil sands of Northeastern Alberta. The long-term groundwater response and subsequent movement of water and solutes within the large permeable sand tailings storage areas is uncertain. At the Southwest Sand Storage (SWSS) Facility, located at Syncrude's Mildred Lake operations near Ft. McMurray, there is concern that salts from the tailings water may discharge to newly placed reclamation material that covers the sand tailings. This saline discharge water could destroy the reclamation soil structure and negatively impact vegetation. The steady-state groundwater flow and transient movement of salts at the local (bench and slope) and intermediate (pile) scales in the SWSS are investigated. Water levels, seepage and groundwater quality (including TDS) have been measured for over a year along two transects of piezometers installed in the SWSS. The field data have been used to complete traditional hydrogeological interpretations of the site, and to develop a conceptual model of flow and transport. The local and intermediate flow systems and salt transport in the dam are being evaluated with numerical models. The models will allow possible future hydrogeological behaviour of the structure to be tested. Preliminary results show differences in flow systems and salinity distribution that depend on the deposition of the SWSS. This research will facilitate better long-term environmental management of this and similar sites.

  5. Transport and deposition of suspended soil colloids in saturated sand columns

    DEFF Research Database (Denmark)

    Sharma, Anu; Kawamoto, Ken; Møldrup, Per;

    2011-01-01

    Understanding colloid mobilization, transport and deposition in the subsurface is a prerequisite for predicting colloid‐facilitated transport of strongly adsorbing contaminants and further developing remedial activities. This study investigated the transport behavior of soil‐colloids extracted from...... a red‐yellow soil from Okinawa, Japan. Different concentrations of suspended‐soil colloids (with diameter ....21 mm) sands. The transport and retention of colloids were studied by analyzing colloid effluent breakthrough curves (BTCs), particle size distribution in the effluent, and colloid deposition profiles within the column. The results showed a significant influence of flow velocity: Low flow velocity...

  6. Effects of outer membrane protein TolC on the transport of Escherichia coli within saturated quartz sands.

    Science.gov (United States)

    Feriancikova, Lucia; Bardy, Sonia L; Wang, Lixia; Li, Jin; Xu, Shangping

    2013-06-04

    The outer membrane protein (OMP) TolC is the cell surface component of several drug efflux pumps that are responsible for bacterial resistance against a variety of antibiotics. In this research, we investigated the effects of OMP TolC on E. coli transport within saturated sands through column experiments using a wild-type E. coli K12 strain (with OMP TolC), as well as the corresponding transposon mutant (tolC::kan) and the markerless deletion mutant (ΔtolC). Our results showed OMP TolC could significantly enhance the transport of E. coli when the ionic strength was 20 mM NaCl or higher. The deposition rate coefficients for the wild-type E. coli strain (with OMP TolC) was usually >50% lower than those of the tolC-negative mutants. The measurements of contact angles using three probe liquids suggested that TolC altered the surface tension components of E. coli cells and lead to lower Hamaker constants for the cell-water-sand system. The interaction energy calculations using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory suggested that the deposition of the E. coli cell primarily occurred at the secondary energy minimum. The depth of the secondary energy minimum increased with ionic strength, and was greater for the TolC-deletion strains under high ionic strength conditions. Overall, the transport behavior of three E. coli strains within saturated sands could be explained by the XDLVO calculations. Results from this research suggested that antibiotic resistant bacteria expressing OMP TolC could spread more widely within sandy aquifers.

  7. Influence of Perfluorooctanoic Acid on the Transport and Deposition Behaviors of Bacteria in Quartz Sand.

    Science.gov (United States)

    Wu, Dan; Tong, Meiping; Kim, Hyunjung

    2016-03-01

    The significance of perfluorooctanoic acid (PFOA) on the transport and deposition behaviors of bacteria (Gram-negative Escherichia coli and Gram-positive Bacillus subtilis) in quartz sand is examined in both NaCl and CaCl2 solutions at pH 5.6 by comparing both breakthrough curves and retained profiles with PFOA in solutions versus those without PFOA. All test conditions are found to be highly unfavorable for cell deposition regardless of the presence of PFOA; however, 7%-46% cell deposition is observed depending on the conditions. The cell deposition may be attributed to micro- or nanoscale roughness and/or to chemical heterogeneity of the sand surface. The results show that, under all examined conditions, PFOA in suspensions increases cell transport and decreases cell deposition in porous media regardless of cell type, presence or absence of extracellular polymeric substances, ionic strength, and ion valence. We find that the additional repulsion between bacteria and quartz sand caused by both acid-base interaction and steric repulsion as well as the competition for deposition sites on quartz sand surfaces by PFOA are responsible for the enhanced transport and decreased deposition of bacteria with PFOA in solutions.

  8. Computational fluid dynamics simulation of transport and retention of nanoparticle in saturated sand filters

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Ashraf Aly [U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 W. Martin Luther King Drive, Cincinnati, OH 45268 (United States); Li, Zhen [School of Energy, Environmental, Biological, and Medical Engineering, Environmental Engineering Program, University of Cincinnati, Cincinnati, OH (United States); Sahle-Demessie, Endalkachew, E-mail: sahle-demessie.endalkachew@epa.gov [U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 W. Martin Luther King Drive, Cincinnati, OH 45268 (United States); Sorial, George A. [School of Energy, Environmental, Biological, and Medical Engineering, Environmental Engineering Program, University of Cincinnati, Cincinnati, OH (United States)

    2013-01-15

    Highlights: ► Breakthrough curves used to study fate of NPs in slow sand filters (SSF). ► CFD simulate transport, attachment/detachment of NPs in SSFs. ► CFD predicted spatial and temporal changes for transient concentrations of NPs. ► CFD predicts low concentrations and steady NP influx would not be retained by SSFs. ► Pulse input is retained with outlet concentration of 0.2% of the inlet. -- Abstract: Experimental and computational investigation of the transport parameters of nanoparticles (NPs) flowing through porous media has been made. This work intends to develop a simulation applicable to the transport and retention of NPs in saturated porous media for investigating the effect of process conditions and operating parameters such, as ion strength, and filtration efficiency. Experimental data obtained from tracer and nano-ceria, CeO{sub 2}, breakthrough studies were used to characterize dispersion of nanoparticle with the flow and their interaction with sand packed columns with different heights. Nanoparticle transport and concentration dynamics were solved using the Eulerian computational fluid dynamics (CFD) solver ANSYS/FLUENT{sup ®} based on a scaled down flow model. A numerical study using the Navier–Stokes equation with second order interaction terms was used to simulate the process. Parameters were estimated by fitting tracer, experimental NP transport data, and interaction of NP with the sand media. The model considers different concentrations of steady state inflow of NPs and different amounts of spike concentrations. Results suggest that steady state flow of dispersant-coated NPs would not be retained by a sand filter, while spike concentrations could be dampened effectively. Unlike analytical solutions, the CFD allows estimating flow profiles for structures with complex irregular geometry and uneven packing.

  9. Sediment load calculations from point measurements in sand-bed rivers

    Institute of Scientific and Technical Information of China (English)

    Seema C SHAH-FAIRBANK; Pierre Y JULIEN

    2015-01-01

    Point velocity and suspended sediment concentration measurements are used to calculate the total sediment discharge in sand-bed rivers. Calculations with the Series Expansion of the Modified Einstein Point Procedure (SEMEPP) depend on grain diameterds and settling velocityω, flow depthh, shear velocityu*, and sampling depthhp. This procedure extends the applicability of the Modified Einstein Procedure (MEP) by using point sediment concentration and velocity measurements. This procedure is tested using the laboratory data from Coleman, and field measurements from the Enoree, Middle Rio Grande and Mississippi Rivers. Based on 801 point measurements over 124 verticals at flow depths ranging from 0.17 m to 33.5 m and sediment concentrations less than 0.1 kg L-1, the accuracy of the calculations depends onu*/ω andhp/ds. Point measurement techniques like SEMEPP are well-suited whenu*/ω > 5 where at least 60% of the total sediment load is measured when 90% of the flow depth is sampled. The determination of sediment discharge from point measurements is most accurate in deep rivers whenhp/ds > 10,000, andu*/ω > 10. Point measurements are not well-suited for shallow rivers and laboratory flumes whereh< 0.5 m and whenu*/ω < 2.

  10. Calculation of transport coefficients in an axisymmetric plasma

    Energy Technology Data Exchange (ETDEWEB)

    Shumaker, D.E.

    1977-01-01

    A method of calculating the transport coefficient in an axisymmetric toroidal plasma is presented. This method is useful in calculating the transport coefficients in a Tokamak plasma confinement device. The particle density and temperature are shown to be a constant on a magnetic flux surface. Transport equations are given for the total particle flux and total energy flux crossing a closed toroidal surface. Also transport equations are given for the toroidal magnetic flux. A computer code was written to calculate the transport coefficients for a three species plasma, electrons and two species of ions. This is useful for calculating the transport coefficients of a plasma which contains impurities. It was found that the particle and energy transport coefficients are increased by a large amount, and the transport coefficients for the toroidal magnetic field are reduced by a small amount.

  11. Transport of soil-aged silver nanoparticles in unsaturated sand

    Science.gov (United States)

    Kumahor, Samuel K.; Hron, Pavel; Metreveli, George; Schaumann, Gabriele E.; Klitzke, Sondra; Lang, Friederike; Vogel, Hans-Jörg

    2016-12-01

    Engineered nanoparticles released into soils may be coated with humic substances, potentially modifying their surface properties. Due to their amphiphilic nature, humic coating is expected to affect interaction of nanoparticle at the air-water interface. In this study, we explored the roles of the air-water interface and solid-water interface as potential sites for nanoparticle attachment and the importance of hydrophobic interactions for nanoparticle attachment at the air-water interface. By exposing Ag nanoparticles to soil solution extracted from the upper soil horizon of a floodplain soil, the mobility of the resulting "soil-aged" Ag nanoparticles was investigated and compared with the mobility of citrate-coated Ag nanoparticles as investigated in an earlier study. The mobility was determined as a function of hydrologic conditions and solution chemistry using column breakthrough curves and numerical modeling. Specifically, we compared the mobility of both types of nanoparticles for different unsaturated flow conditions and for pH = 5 and pH = 9. The soil-aged Ag NP were less mobile at pH = 5 than at pH = 9 due to lower electrostatic repulsion at pH = 5 for both types of interfaces. Moreover, the physical flow field at different water contents modified the impact of chemical forces at the solid-water interface. An extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) model did not provide satisfactory explanation of the observed transport phenomena unlike for the citrate-coated case. For instance, the eDLVO model assuming sphere-plate geometry predicts a high energy barrier (> 90 kT) for the solid-water interface, indicating that nanoparticle attachment is less likely. Furthermore, retardation through reversible sorption at the air-water interface was probably less relevant for soil-aged nanoparticles than for citrate-coated nanoparticles. An additional cation bridging mechanism and straining within the flow field may have enhanced nanoparticle retention at the

  12. Transport of soil-aged silver nanoparticles in unsaturated sand.

    Science.gov (United States)

    Kumahor, Samuel K; Hron, Pavel; Metreveli, George; Schaumann, Gabriele E; Klitzke, Sondra; Lang, Friederike; Vogel, Hans-Jörg

    2016-12-01

    Engineered nanoparticles released into soils may be coated with humic substances, potentially modifying their surface properties. Due to their amphiphilic nature, humic coating is expected to affect interaction of nanoparticle at the air-water interface. In this study, we explored the roles of the air-water interface and solid-water interface as potential sites for nanoparticle attachment and the importance of hydrophobic interactions for nanoparticle attachment at the air-water interface. By exposing Ag nanoparticles to soil solution extracted from the upper soil horizon of a floodplain soil, the mobility of the resulting "soil-aged" Ag nanoparticles was investigated and compared with the mobility of citrate-coated Ag nanoparticles as investigated in an earlier study. The mobility was determined as a function of hydrologic conditions and solution chemistry using column breakthrough curves and numerical modeling. Specifically, we compared the mobility of both types of nanoparticles for different unsaturated flow conditions and for pH=5 and pH=9. The soil-aged Ag NP were less mobile at pH=5 than at pH=9 due to lower electrostatic repulsion at pH=5 for both types of interfaces. Moreover, the physical flow field at different water contents modified the impact of chemical forces at the solid-water interface. An extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) model did not provide satisfactory explanation of the observed transport phenomena unlike for the citrate-coated case. For instance, the eDLVO model assuming sphere-plate geometry predicts a high energy barrier (>90 kT) for the solid-water interface, indicating that nanoparticle attachment is less likely. Furthermore, retardation through reversible sorption at the air-water interface was probably less relevant for soil-aged nanoparticles than for citrate-coated nanoparticles. An additional cation bridging mechanism and straining within the flow field may have enhanced nanoparticle retention at the solid

  13. Mixed sand and gravel beaches: accurate measurement of active layer depth and sediment transport volumes using PIT tagged tracer pebbles

    Science.gov (United States)

    Holland, A.; Moses, C.; Sear, D. A.; Cope, S.

    2016-12-01

    As sediments containing significant gravel portions are increasingly used for beach replenishment projects globally, the total number of beaches classified as `mixed sand and gravel' (MSG) increases. Calculations for required replenishment sediment volumes usually assume a uniform layer of sediment transport across and along the beach, but research into active layer (AL) depth has shown variations both across shore and according to sediment size distribution. This study addresses the need for more accurate calculations of sediment transport volumes on MSG beaches by using more precise measurements of AL depth and width, and virtual velocity of tracer pebbles. Variations in AL depth were measured along three main profile lines (from MHWS to MLWN) at Eastoke, Hayling Island (Hampshire, UK). Passive Integrated Transponder (PIT) tagged pebbles were deployed in columns, and their new locations repeatedly surveyed with RFID technology. These data were combined with daily dGPS beach profiles and sediment sampling for detailed analysis of the influence of beach morphodynamics on sediment transport volumes. Data were collected over two consecutive winter seasons: 2014-15 (relatively calm, average wave height sandy lower foreshore reduced the AL to 10% of wave height in this area. The disparity in AL depth across the beach profile indicates that traditional models are not accurately representing bulk sediment transport on MSG beaches. It is anticipated that by improving model inputs, beach managers will be better able to predict necessary volumes and sediment grain size proportions of replenishment material for effective management of MSG beaches.

  14. Influence Of Carboxymethyl Cellulose For The Transport Of Titanium Dioxide Nanoparticles In Clean Silica And Mineral-Coated Sands

    Science.gov (United States)

    The transport properties of titanium dioxide (anatase polymorph) nanoparticles encapsulated by carboxymethyl cellulose (CMC) were evaluated as a function of changes in the solute chemical properties in clean quartz, amorphous aluminum and iron hydroxide-coated sands. While prist...

  15. Uncertainty calculation in transport models and forecasts

    DEFF Research Database (Denmark)

    Manzo, Stefano; Prato, Carlo Giacomo

    in a four-stage transport model related to different variable distributions (to be used in a Monte Carlo simulation procedure), assignment procedures and levels of congestion, at both the link and the network level. The analysis used as case study the Næstved model, referring to the Danish town of Næstved2...... the uncertainty propagation pattern over time specific for key model outputs becomes strategically important. 1 Manzo, S., Nielsen, O. A. & Prato, C. G. (2014). The Effects of uncertainty in speed-flow curve parameters on a large-scale model. Transportation Research Record, 1, 30-37. 2 Manzo, S., Nielsen, O. A...

  16. LDRD Final Review: Radiation Transport Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Goorley, John Timothy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Morgan, George Lake [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lestone, John Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-06-22

    Both high-fidelity & toy simulations are being used to understand measured signals and improve the Area 11 NDSE diagnostic. We continue to gain more and more confidence in the ability for MCNP to simulate neutron and photon transport from source to radiation detector.

  17. Agglomeration of a comprehensive model for the wind-driven sand transport at the Belgian Coast

    Science.gov (United States)

    Strypsteen, Glenn; Rauwoens, Pieter

    2016-04-01

    Although a lot of research has been done in the area of Aeolian transport, it is only during the last years that attention has been drawn to Aeolian transport in coastal areas. In these areas, the physical processes are more complex, due to a large number of transport limiting parameters. In this PhD-project, which is now in its early stage, a model will be developed which relates the wind-driven sand transport at the Belgian coast with physical parameters such as the wind speed, humidity and grain size of the sand, and the slope of beach and dune surface. For the first time, the interaction between beach and dune dynamics is studied at the Belgian coast. The Belgian coastline is only 67km long, but densely populated and therefore subject to coastal protection and safety. The coast mostly consists of sandy beaches and dikes. Although, still 33km of dunes exist, whose dynamics are far less understood. The overall research approach consists of three pathways: (i) field measurements, (ii) physical model tests, and (iii) numerical simulations. Firstly and most importantly, several field campaigns will provide accurate data of meteo-marine conditions, morphology, and sand transport events on a wide beach at the Belgian Coastline. The experimental set-up consists of a monitoring station, which will provide time series of vegetation cover, shoreline position, fetch distances, surficial moisture content, wind speed and direction and transport processes. The horizontal and vertical variability of the event scale Aeolian sand transport is analyzed with 8 MWAC sand traps. Two saltiphones register the intensity and variations of grain impacts over time. Two meteo-masts, each with four anemometers and one wind vane, provide quantitative measurements of the wind flow at different locations on the beach. Surficial moisture is measured with a moisture sensor. The topography measurements are typically done with laser techniques. To start, two sites are selected for measurement

  18. Influence of clay particles on the transport and retention of titanium dioxide nanoparticles in quartz sand.

    Science.gov (United States)

    Cai, Li; Tong, Meiping; Wang, Xueting; Kim, Hyunjung

    2014-07-01

    This study investigated the influence of two representative suspended clay particles, bentonite and kaolinite, on the transport of titanium dioxide nanoparticles (nTiO2) in saturated quartz sand in both NaCl (1 and 10 mM ionic strength) and CaCl2 solutions (0.1 and 1 mM ionic strength) at pH 7. The breakthrough curves of nTiO2 with bentonite or kaolinite were higher than those without the presence of clay particles in NaCl solutions, indicating that both types of clay particles increased nTiO2 transport in NaCl solutions. Moreover, the enhancement of nTiO2 transport was more significant when bentonite was present in nTiO2 suspensions relative to kaolinite. Similar to NaCl solutions, in CaCl2 solutions, the breakthrough curves of nTiO2 with bentonite were also higher than those without clay particles, while the breakthrough curves of nTiO2 with kaolinite were lower than those without clay particles. Clearly, in CaCl2 solutions, the presence of bentonite in suspensions increased nTiO2 transport, whereas, kaolinite decreased nTiO2 transport in quartz sand. The attachment of nTiO2 onto clay particles (both bentonite and kaolinite) were observed under all experimental conditions. The increased transport of nTiO2 in most experimental conditions (except for kaolinite in CaCl2 solutions) was attributed mainly to the clay-facilitated nTiO2 transport. The straining of larger nTiO2-kaolinite clusters yet contributed to the decreased transport (enhanced retention) of nTiO2 in divalent CaCl2 solutions when kaolinite particles were copresent in suspensions.

  19. Hydrophobicity of biofilm coatings influences the transport dynamics of polystyrene nanoparticles in biofilm-coated sand.

    Science.gov (United States)

    Mitzel, Michael R; Sand, Stefanie; Whalen, Joann K; Tufenkji, Nathalie

    2016-04-01

    Engineered nanoparticles (ENPs) are used in the manufacture of over 2000 industrial and consumer products to enhance their material properties and functions or to enable new nanoparticle-dependent functions. The widespread use of ENPs will result in their release to the subsurface and aquatic environments, where they will interact with indigenous biota. Laboratory column experiments were designed to understand the influence of two different Pseudomonas aeruginosa biofilms on the mobility of polystyrene latex nanoparticles in granular porous media representative of groundwater aquifers or riverbank filtration settings. The transport behavior of 20 nm carboxylate-modified (CLPs) and sulfate (SLPs) polystyrene latex ENPs suspended in NaCl or CaCl2 (1 and 10 mM ionic strength, pH 7) was studied in columns packed with quartz sand coated with biofilms formed by two P. aeruginosa strains that differed in cell surface hydrophobicity (P. aeruginosa 9027™, relatively hydrophilic and P. aeruginosa PAO1, relatively hydrophobic). Biofilm-coated quartz sand retained more of the electrostatically-stabilized latex ENPs than clean, uncoated sand, regardless of the serotype. As IS increased, clear differences in the shape of the ENP breakthrough curves were observed for each type of biofilm coating. ENP breakthrough in the P. aeruginosa PAO1 biofilm-coated sand was generally constant with time whereby breakthrough in the P. aeruginosa 9027 biofilm-coated sand showed dynamic behavior. This indicates a fundamental difference in the mechanisms of ENP deposition onto hydrophilic or hydrophobic biofilm coatings due to the hydration properties of these biofilms. The results of this study demonstrate the importance of considering the surface properties of aquifer grain coatings when evaluating ENP fate in natural subsurface environments.

  20. Sequential Subterranean Transport of Excavated Sand and Foraged Seeds in Nests of the Harvester Ant, Pogonomyrmex badius.

    Science.gov (United States)

    Tschinkel, Walter R; Rink, William J; Kwapich, Christina L

    2015-01-01

    During their approximately annual nest relocations, Florida harvester ants (Pogonomyrmex badius) excavate large and architecturally-distinct subterranean nests. Aspects of this process were studied by planting a harvester ant colony in the field in a soil column composed of layers of 12 different colors of sand. Quantifying the colors of excavated sand dumped on the surface by the ants revealed the progress of nest deepening to 2 m and enlargement to 8 L in volume. Most of the excavation was completed within about 2 weeks, but the nest was doubled in volume after a winter lull. After 7 months, we excavated the nest and mapped its structure, revealing colored sand deposited in non-host colored layers, especially in the upper 30 to 40 cm of the nest. In all, about 2.5% of the excavated sediment was deposited below ground, a fact of importance to sediment dating by optically-stimulated luminescence (OSL). Upward transport of excavated sand is carried out in stages, probably by different groups of ants, through deposition, re-transport, incorporation into the nest walls and floors and remobilization from these. This results in considerable mixing of sand from different depths, as indicated in the multiple sand colors even within single sand pellets brought to the surface. Just as sand is transported upward by stages, incoming seeds are transported downward to seed chambers. Foragers collect seeds and deposit them only in the topmost nest chambers from which a separate group of workers rapidly transports them downward in increments detectable as a "wave" of seeds that eventually ends in the seed chambers, 20 to 80 cm below the surface. The upward and downward transport is an example of task-partitioning in a series-parallel organization of work carried out by a highly redundant work force in which each worker usually completes only part of a multi-step process.

  1. Nonlinear acceleration of SN transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Fichtl, Erin D [Los Alamos National Laboratory; Warsa, James S [Los Alamos National Laboratory; Calef, Matthew T [Los Alamos National Laboratory

    2010-12-20

    The use of nonlinear iterative methods, Jacobian-Free Newton-Krylov (JFNK) in particular, for solving eigenvalue problems in transport applications has recently become an active subject of research. While JFNK has been shown to be effective for k-eigenvalue problems, there are a number of input parameters that impact computational efficiency, making it difficult to implement efficiently in a production code using a single set of default parameters. We show that different selections for the forcing parameter in particular can lead to large variations in the amount of computational work for a given problem. In contrast, we present a nonlinear subspace method that sits outside and effectively accelerates nonlinear iterations of a given form and requires only a single input parameter, the subspace size. It is shown to consistently and significantly reduce the amount of computational work when applied to fixed-point iteration, and this combination of methods is shown to be more efficient than JFNK for our application.

  2. Influence of sulfate on the transport of bacteria in quartz sand.

    Science.gov (United States)

    Shen, Xiufang; Han, Peng; Yang, Haiyan; Kim, Hyunjung; Tong, Meiping

    2013-10-01

    The influence of sulfate on the transport of bacteria in packed quartz sand was examined at a constant 25mM ionic strength with the sulfate concentration progressively increased from 0 to 20mM at pH 6.0. Two representative cell types, Escherichia coli BL21 (Gram-negative) and Bacillus subtilis (Gram-positive), were used to determine the effect of sulfate on cell transport behavior. For both examined cell types, the breakthrough plateaus in the presence of sulfate in suspensions were higher and the corresponding retained profiles were lower than those without sulfate ions, indicating that the presence of sulfate in suspensions increased cell transport in packed quartz sand regardless of the examined cell types (Gram-positive or Gram-negative). Moreover, the enhancement of bacteria transport induced by the presence of sulfate was more pronounced with increasing sulfate concentration from 5 to 20mM. In contrast with the results for EPS-present bacteria, the presence of sulfate in solutions did not change the transport behavior for EPS-removed cells. The zeta potentials of EPS-present cells with sulfate were found to be more negative relative to those without sulfate in suspensions, whereas, the zeta potentials for EPS-removed cells in the presence of sulfate were similar as those without sulfate. We proposed that sulfate could interact with EPS on cell surfaces and thus negatively increased the zeta potentials of bacteria, contributing to the increased transport in the presence of sulfate in suspensions.

  3. Facilitated transport of heavy metals by bacterial colloids in sand columns

    Science.gov (United States)

    Guiné, V.; Martins, J.; Gaudet, J. P.

    2003-05-01

    The aim of this work is to evaluate the ability of biotic collois (e.g. bacterial cells) to facilitate the transport of heavy metals in soils. and to identify the main factors influencing colloid transport in order to detelmine the geo-chemical conditions where this secondary transport process may become dominant. The model colloids studied here are living cells of Escherichia coli and Ralstonia metallidurans. We studied the transport of mercury zinc, and cadmium in columns of Fontainebleau sand. The properties (i.e. optical and morphological properties, charge (zeta potential, zeta) and hydrophobia (water/hexadecane distribution parameter, K_{hw})) of the bacterial cells surface were characterised, as well as their potential for heavy metals sorption (kinetic and isotherm). Both surface charge (zeta=-54 and -14 mV) and hydrophobia (K_{hw} = 0.25 and 0.05) differ strongly for the two bacteria. Column studies were conducted with bacteria and heavy metals separately or simultaneously. The cell surface differences led to different transport behaviour of the two bacteria, although the retardation factor is close to 1 for both. We observed that colloid mobility increases when increasing bacterial cells concentration and when decreasing the ionic strength. We also observed that bacterial colloids appeared as excellent vectors for Hg, Zn and Cd. Indeed, heavy metals adsorbed on the Fontainebleau sand when injected alone in columns (retardation factors of 1.4 ; 2.9 and 3.8 for Hg, Zn and Cd, respectively); whereas no retardation (R≈1) is observed when injected in the presence of both bacteria. Moreover, transport of bio-sorbed metal appears to be 4 to 6 times higher than dissolved heavy-metal.

  4. Complexity confers stability: Climate variability, vegetation response and sand transport on longitudinal sand dunes in Australia's deserts

    Science.gov (United States)

    Hesse, Paul P.; Telfer, Matt W.; Farebrother, Will

    2017-04-01

    The relationship between antecedent precipitation, vegetation cover and sand movement on sand dunes in the Simpson and Strzelecki Deserts was investigated by repeated (up to four) surveys of dune crest plots (≈25 × 25 m) over a drought cycle (2002-2012) in both winter (low wind) and spring (high wind). Vegetation varied dramatically between surveys on vegetated and active dune crests. Indices of sand movement had significant correlations with vegetation cover: the depth of loose sand has a strong inverse relationship with crust (cyanobacterial and/or physical) while the area covered by ripples has a strong inverse relationship with the areal cover of vascular plants. However, the relationship between antecedent rainfall and vegetation cover was found to be complex. We tentatively identify two thresholds; (1) >10 mm of rainfall in the preceding 90 days leads to rapid and near total cover of crust and/or small plants 400 mm of rainfall in the preceding three years leads to higher cover of persistent and longer-lived plants >50 cm tall. These thresholds were used to predict days of low vegetation cover on dune crests. The combination of seasonality of predicted bare-crest days, potential sand drift and resultant sand drift direction explains observed patterns of sand drift on these dunes. The complex vegetation and highly variable rainfall regime confer meta-stability on the dunes through the range of responses to different intervals of antecedent rainfall and non-linear growth responses. This suggests that the geomorphic response of dunes to climate variation is complex and non-linear.

  5. Laser particle counter validation for aeolian sand transport measurements using a highspeed camera

    Science.gov (United States)

    Duarte-Campos, Leonardo; Wijnberg, Kathelijne M.; Oyarte-Gálvez, Loreto; Hulscher, Suzanne J. M. H.

    2017-04-01

    Measuring aeolian sand transport rates in the field has been a long-standing challenge. In this paper, we present the results of a laboratory experiment to test the ability of a laser particle counter sensor (Wenglor) to accurately count sand grains of various grain size classes and stainless steel beads. We compared the count data collected by the Wenglor with images from a Highspeed camera which revealed the actual number of grains passing the laser beam. A Silicon photodiode was used to record the laser intensity reduction induced by the sand grain passage through the laser beam to derive the minimal necessary reduction for the Wenglor to count grains. For the two possible settings of the Wenglor, i.e., Minimal Teach-in or Normal Teach-in, a minimum of 18% and 78% blocking of the laser beam was required for recording a count. This implies that the minimum grain size that can be observed by the Wenglor is 210 ± 3 μm and 495 ± 10 μm for the two settings respectively, which is considerably coarser than previously assumed. Due to the non-uniform power distribution of the laser sensor intensity, at the detection limit of 210 μm, only grains passing through the centre of the beam will be counted.

  6. Boltzmann transport calculation of collinear spin transport on short timescales

    Science.gov (United States)

    Nenno, Dennis M.; Kaltenborn, Steffen; Schneider, Hans Christian

    2016-09-01

    A spin-dependent Boltzmann transport equation is used to describe charge and spin dynamics resulting from the excitation of hot electrons in a ferromagnet/normal metal heterostructure. As the microscopic Boltzmann equation works with k -dependent distribution functions, it can describe far-from-equilibrium excitations, which are outside the scope of drift-diffusion theories. We study different scenarios for spin-dependent carrier injection into a nonmagnetic metal using an effectively two-dimensional phase space. While the charge signal is robust for various excitation schemes, the shape of the resulting spin current/density depends critically on the interplay between transport and scattering, and on the energetic distribution of the injected carriers. Our results imply that the energy dependence of the injected hot electrons has a decisive effect on the spin dynamics.

  7. Geomorphology and sediment transport on a submerged back-reef sand apron: One Tree Reef, Great Barrier Reef

    Science.gov (United States)

    Harris, Daniel L.; Vila-Concejo, Ana; Webster, Jody M.

    2014-10-01

    Back-reef sand aprons are conspicuous and dynamic sedimentary features in coral reef systems. The development of these features influences the evolution and defines the maturity of coral reefs. However, the hydrodynamic processes that drive changes on sand aprons are poorly understood with only a few studies directly assessing sediment entrainment and transport. Current and wave conditions on a back-reef sand apron were measured during this study and a digital elevation model was developed through topographic and bathymetric surveying of the sand apron, reef flats and lagoon. The current and wave processes that may entrain and transport sediment were assessed using second order small amplitude (Stokes) wave theory and Shields equations. The morphodynamic interactions between current flow and geomorphology were also examined. The results showed that sediment transport occurs under modal hydrodynamic conditions with waves the main force entraining sediment rather than average currents. A morphodynamic relationship between current flow and geomorphology was also observed with current flow primarily towards the lagoon in shallow areas of the sand apron and deeper channel-like areas directing current off the sand apron towards the lagoon or the reef crest. These results show that the short-term mutual interaction of hydrodynamics and geomorphology in coral reefs can result in morphodynamic equilibrium.

  8. Physical Modeling of the Cross-Shore Sediment Transport on a Sand-Gravel Beach

    Science.gov (United States)

    Xharde, Regis; Brunelle, Corinne; Frandsen, Jannette

    2014-11-01

    The aim of the study is to investigate the cross-shore evolution of a nourished beach profile under storm wave conditions with specific emphasis on sediment transport within the breaking zone. To investigate the underlying mechanisms of the coastal transport processes, a physical model of the beach was built at scale 1:3 in the new Quebec Coastal Physics Laboratory (QCPL), Canada. The modeled beach is 4.2 m high, 5 m wide and 40 m long with a mean slope of 1:10. The beach is formed of a mixture of sediment with grain sizes ranging from 0.65 mm up to 20 mm. The stability of the beach is tested for operational and storm waves. We report on run-up and run-down processes via wave gages, video records of waves and ultrasonic water level measurements. Sediment transport processes within the surf zone and on the beach face are monitored using acoustic Doppler profilers and optical backscattering sensors. The beach profile is surveyed prior and after each test series using a topographic laser scanner. Initial results show that sand is transported off-shore to a breaker bar while cobbles are pushed on the upper beach by run-up. Details of the underlying mechanism of different breaker types and impact on sediment transport will be presented.

  9. Sensitivity of growth characteristics of tidal sand ridges and long bed waves to formulations of bed shear stress, sand transport and tidal forcing: A numerical model study

    Science.gov (United States)

    Yuan, Bing; de Swart, Huib E.; Panadès, Carles

    2016-09-01

    Tidal sand ridges and long bed waves are large-scale bedforms that are observed on continental shelves. They differ in their wavelength and in their orientation with respect to the principal direction of tidal currents. Previous studies indicate that tidal sand ridges appear in areas where tidal currents are above 0.5 m s-1, while long bed waves occur in regions where the maximum tidal current velocity is slightly above the critical velocity for sand erosion and the current is elliptical. An idealized nonlinear numerical model was developed to improve the understanding of the initial formation of these bedforms. The model governs the feedbacks between tidally forced depth-averaged currents and the sandy bed on the outer shelf. The effects of different formulations of bed shear stress and sand transport, tidal ellipticity and different tidal constituents on the characteristics of these bedforms (growth rate, wavelength, orientation of the preferred bedforms) during their initial formation were examined systematically. The results show that the formulations for bed shear stress and slope-induced sand transport are not critical for the initial formation of these bedforms. For tidal sand ridges, under rectilinear tidal currents, increasing the critical bed shear stress for sand erosion decreases the growth rate and the wavelength of the preferred bedforms significantly, while the orientation angle slightly decreases. The dependence of the growth rate, wavelength and the orientation of the preferred bedforms on the tidal ellipticity is non-monotonic. A decrease in tidal frequency results in preferred bedforms with larger wavelength and smaller orientation angle, while their growth rate hardly changes. In the case of joint diurnal and semidiurnal tides, or spring-neap tides, the characteristics of the bedforms are determined by the dominant tidal constituent. For long bed waves, the number of anticyclonically/cyclonically oriented bedforms with respect to the principal

  10. Computer Modeling of Sand Transport on Mars Using a Compart-Mentalized Fluids Algorithm (CFA)

    Science.gov (United States)

    Marshall, J.; Stratton, D.

    1999-01-01

    It has been postulated that aeolian transport on Mars may be significantly different from that on Earth. From laboratory experiments simulating martian grain transport [2], it has been observed that (saltating) grains striking the bed can cause hundreds of secondary reptation trajectories when impact occurs at speeds postulated for Mars. Some of the ballistically induced trajectories "die ouf' and effectively join the ranks on the creep population that is merely nudged along by impact. Many of the induced reptation trajectories, however, are sufficiently high for the grains to become part of the saltation load (it is irrelevant to the boundary layer how a grain attained its initial lift force). When these grains, in turn, strike the surface, they too are capable of inducing more reptating grains. This cascading effect has been discussed in connection with terrestrial aeolian transport in an attempt to dispel the notion that sand motion is divisible only into creep and saltation loads. On Earth, only a few grains are splashed by impact. On Mars, it may be hundreds. We developed a computer model to address this phenomenon because there are some important ramifications: First, this ratio may mean that martian aeolian transport is dominated by reptation flux rather than saltation. On Earth, the flux would be a roughly balanced mixture between reptation/creep and saltation. On Venus, there would be no transport other than by saltation. In other words, an understanding of planetary aeolian processes may not be necessarily understood by extrapolating from the "Earth case", with only gravity and atmospheric density/viscosity being considered as variables. Second, the reptation flux on Mars may be self sustaining, so that little input is required by the wind once transport has been initiated. The number of grains saturating the boundary layer near the bed may mean that average grain speed on Mars might conceivably be less than that on Earth. This would say much for models

  11. Sediment transport and dispersal pathways in the Lower Cretaceous sands of the Britannia Field, derived from magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hailwood, E.; Ding, F. [Core Magnetics, Sedbergh (United Kingdom)

    2000-11-01

    Sediment transport directions and dispersal patterns in the Lower Cretaceous sands of the Britannia Field have been investigated, using magnetic anisotropy and palaeomagnetic core re-orientation methods, to aid understanding of the geometry and architecture of the reservoir sand units. The results indicate that sands were sourced mainly from the north. This applies both to the massive sand bodies with lobate geometry in the lower reservoir zones in the western part of the field and to the laminated slurried beds with tabular geometry in the upper zones in the eastern part. Thus, sediment in this part of the Outer Moray Firth play appears to have been derived largely from a discrete point source to the north rather than from axial flow along the Witch Ground Graben. (Author)

  12. Road Transport Congestion Costs Calculations-Adaptation to Engineering Approach

    Directory of Open Access Journals (Sweden)

    Marjan Lep

    2008-01-01

    Full Text Available The article represents so called “engineering” approach for computing the total road transport congestion costs. According to economic welfare theory, the total costs of transport congestion are defined as dead weight loss (DWL of infrastructure use. With a set of equations DWL could be formulated in a mathematical way. Because such form of equation is not directly applicable for concrete road network calculations it should be transformed into “engineering” form, which comprises transport engineering related data as classified road links, traffic volumes, passenger unit costs, etc. The equation is well applicable on the interurban road network; adaptations are needed for the urban road network cost calculations, where time losses are not so much related to the link travel time. The final equation was derived for the purposes of national road congestion cost calculation.

  13. A 3-Dimensional Simulation of Mixed Sand Transport%三维混合沙输运数值模拟

    Institute of Scientific and Technical Information of China (English)

    肖锋军; 郭烈锦; 王跃社; 李德标

    2012-01-01

    采用计算流体力学和颗粒离散元耦合的方法模拟了三维混合沙输运过程。采用体平均的Navier—stokes方程来描述气相运动,考虑了气相和颗粒相的相互作用。颗粒运动通过求解牛顿运动方程来求解,采用硬球模型描述颗粒和颗粒及颗粒和壁面的碰撞。本模型中,颗粒运动是三维的而气相运动是二维的。计算结果表明:总输沙率沿高度方向在大于2cm以上按照指数衰减,在2cm以下则偏大;各粒径颗粒具有不同的输沙率分布,粗粒径颗粒按指数规律衰减,其它粒径颗粒输沙率随高度先指数增加后减少;各粒径颗粒平均水平速度随高度对数函数增加且同高度时随粒径增大而减小,1cm高度以下则相反;沙粒平均粒径沿高度线性递减,2cm以下粒径偏大。%A combined computational fluid dynamics and discrete particle method approach was proposed to perform numerical simulation on a mixed sand transport. In this paper the volume averaged Navier-stokes equations were solved to calculate the gas motion, taking into account the interaction between gas and particles; the particle motion was calculated using Newton's equation of motion, where a hard sphere model was used to describe the particle-particle and particle-wall collisions. In this model, the motion of individual particle was three-dimensional and the flow of continuous gas was two-dimensional. The results showed that, the total sand mass flux decreased exponentially with height above 2 cm and deviated below 2 cm. The distributions of mass flux of each size group were very different from each other. For the large size group, the sand mass flux decreased exponentially with height, while the sand mass flux increased with height firstly and then decreased for the other size groups. The particle mean horizontal velocity of all sand groups increased logarithmically with height and decreased with particle size at the same height

  14. Estimating bedload transport in a large sand-gravel bed river from direct sampling, dune tracking and empirical formulas

    Science.gov (United States)

    Claude, Nicolas; Rodrigues, Stéphane; Bustillo, Vincent; Bréhéret, Jean-Gabriel; Macaire, Jean-Jacques; Jugé, Philippe

    2012-12-01

    Three methods used to estimate river bedload discharges were compared in a large sand-gravel bed river. The unit and total bedload transport rates estimated by sediment sampling, dune tracking method and the equations of Van Rijn and Meyer-Peter and Müller were compared. The analysis was based on a large data set obtained from field surveys that combined sediment sampling, acoustic doppler profiler (ADP) measurements, and multibeam echosoundings of the middle reach of the River Loire (France) for contrasting flow conditions ranging from low flows to 2-year floods. For transport stages between 2 and 6 (i.e. between the annual mean discharge and the discharge for a 2-year flood), the tested equations predicted fairly well the unit and total bedload discharges and roughly estimated the temporal variability of the bedload during floods. For these transport conditions, the best agreement with the sediment sampling measurements was observed with the Van Rijn formula. For lower flow conditions, the tested formulas provide lower estimates than those sampled. To improve the accuracy of the equations for low flows, potential solutions include integrating near-bed turbulences and non uniformity of bed particles into the models. The ability of the formulas to predict the temporal variability of the bedload can be improved by using the bedform roughness to adjust the estimates. The bedload transport rates calculated with dune tracking method are lower than the fluxes sampled because a substantial fraction of the bedload does not participate to the dune migration. Finally, a first rating curve that was implemented for the River Loire estimates the annual bedload discharge for 2010 to be 480,000 t.

  15. Sand-Mud Sediment Transport induced by tidal currents and wind waves in shallow microtidal basins

    Science.gov (United States)

    Carniello, L.; Defina, A.; D'Alpaos, L.

    2011-12-01

    Field data and mathematical modeling have demonstrated that the morphological evolution of shallow tidal basins is the result of the combined effect of tidal currents and wind waves. Tidal currents, in particular, drive the morphological evolution of shallow tidal systems in proximity of the inlets and within the channel network, whereas in shallow areas tidal current mainly acts enhancing the bottom shear stress due to wind waves and redistributing sediments within the basin. In this study we present a mathematical model for sediment entrainment, transport and deposition due to the combined effect of tidal currents and wind waves. The model is coupled with a hydrodynamic module based on the shallow water equations and with a module for the generation and propagation of wind waves. The sediment transport model describes the sediments by the way of a bi-granular mixtures composed by both cohesive and non-cohesive sediments thus considering the contemporary presence of clay, silt and sand which usually characterizes estuaries and tidal basins. Moreover, the model describes the bed evolution and evaluates the variation of bed sediment composition considering also the transition between cohesive and non-cohesive behavior. Attention is focused on some issues concerning the definition of a reliable initial bed composition and the incipient sediment motion which is treated following a stochastic approach for the bottom shear stress and for the critical shear stress distribution. The model is applied to the Lagoon of Venice (Italy) and the results of different simulations are compared, with good agreement, to a series of turbidity measurements collected inside the lagoon. The application of the model to the present bathymetry of the Venice lagoon allows for a first estimation of the actual net amount of sand and mud flowing through the three inlets and also gives some information on bottom evolution in terms of elevation and composition.

  16. Transport of atrazine versus bromide and δO18 in sand

    Science.gov (United States)

    Tindall, James A.; Friedel, Michael J.

    2016-01-01

    The objective of this research was to determine the process of atrazine transport compared to bromide and δO18 transport in sands near Denver. Three 1.5 × 2 × 1.5-m plots were installed and allowed to equilibrate for 2 years before research initiation and were instrumented with 1.5 × 2-m zero-tension pan lysimeters installed at 1.5-m depths. Additionally, each plot was instrumented with suction lysimeters, tensiometers, time domain reflectometry (TDR) moisture probes, and thermocouples (to measure soil temperature) at 15-cm depth increments. All plots were enclosed with a raised frame (of 8-cm height) to prevent surface runoff. During the 2-year period before research began, all suction and pan lysimeters were purged monthly and were sampled for fluids immediately prior to atrazine and KBr application to obtain background concentrations. Atrazine illustrated little movement until after a significant rainfall event, which peaked concentrations at depths of about 90 to 135 cm. Both Br− and δO18 moved rapidly through the soil, probably owing to soil porosity and anion exclusion for Br−. Concentrations of atrazine exceeding 5.0 μL−1 were observed with depth (90 to 150 cm) after several months. It appears that significant rainfall events were a key factor in the movement of atrazine in the sand, which allowed the chemicals to move to greater depths and thus avoid generally found biodegradation processes.

  17. The effect of EDTA on the groundwater transport of thorium through sand.

    Science.gov (United States)

    May, Colin C; Young, Lindsay; Worsfold, Paul J; Heath, Sarah; Bryan, Nick D; Keith-Roach, Miranda J

    2012-10-01

    The effect of the anthropogenic complexing agent EDTA on thorium transport in groundwater has been studied using sand-packed columns and flow rates in the range of 20-100 m y⁻¹. The concentrations injected into the columns were in the range of 0.4-4 mM for Th and 4-40 mM for EDTA, and with EDTA:Th ratios in the range 1:1 to 10:1. The results show that EDTA can significantly increase Th transport, but two very different behaviours are observed at Th concentrations of 0.4 and 4 mM. At the lower concentration, Th breakthrough is retarded with respect to a conservative tracer, with a peak width that is consistent with a single K(d) value, followed by a longer tail, and the behaviour is very sensitive to the flow rate. However at 4 mM Th, the breakthrough peak appears near to that of the tracer, and the width of the peak is consistent with a distribution of K(d) values and/or a larger dispersivity than the tracer. Speciation and transport modelling have been used to interpret the data, and a model was developed that could explain the 0.4 mM behaviour. This suggests that ternary surface complexes are important in these systems, with at least two different species involved, although the complexity of Th speciation in these systems leads to significant uncertainty in the values of the equilibrium and kinetic parameters. For the 4 mM systems, the rapid transport observed could not be explained by a simple chemical model; instead it is likely that EDTA plays an important role in stabilising and transporting thorium colloids and clusters.

  18. Transport and removal of viruses in saturated sand columns under oxic and anoxic conditions--Potential implications for groundwater protection.

    Science.gov (United States)

    Frohnert, Anne; Apelt, Susann; Klitzke, Sondra; Chorus, Ingrid; Szewzyk, Regine; Selinka, Hans-Christoph

    2014-11-01

    To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered. Copyright © 2014 Elsevier GmbH. All rights reserved.

  19. Eolian sand transport pathways in the southwestern United States: Importance of the Colorado River and local sources

    Science.gov (United States)

    Muhs, D.R.; Reynolds, R.L.; Been, J.; Skipp, G.

    2003-01-01

    Geomorphologists have long recognized that eolian sand transport pathways extend over long distances in desert regions. Along such pathways, sediment transport by wind can surmount topographic obstacles and cross major drainages. Recent studies have suggested that three distinct eolian sand transport pathways exist (or once existed) in the Mojave and Sonoran Desert regions of the southwestern United States. One hypothesized pathway is colian sand transport from the eastern Mojave Desert of California into western Arizona, near Parker, and would require sand movement across what must have been at least a seasonally dry Colorado River valley. We tested this hypothesis by mineralogical, geochemical and magnetic analyses of eolian sands on both sides of the Colorado River, as well as sediment from the river itself. Results indicate that dunes on opposite sides of the Colorado River are mineralogically distinct: eastern California dunes are feldspar-rich whereas western Arizona dunes are quartz-rich, derived from quartz-rich Colorado River sediments. Because of historic vegetation changes, little new sediment from the Colorado River is presently available to supply the Parker dunes. Based on this study and previous work, the Colorado River is now known to be the source of sand for at least three of the major dune fields of the Sonoran Desert of western Arizona and northern Mexico. On the other hand, locally derived alluvium appears to be a more important source of dune fields in the Mojave Desert of California. Although many geomorphologists have stressed the importance of large fluvial systems in the origin of desert dune fields, few empirical data actually exist to support this theory. The results presented here demonstrate that a major river system in the southwestern United States is a barrier to the migration of some dune fields, but essential to the origin of others. Published by Elsevier Science Ltd.

  20. Graphical User Interface for Simplified Neutron Transport Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Randolph; Carter, Leland L

    2011-07-18

    A number of codes perform simple photon physics calculations. The nuclear industry is lacking in similar tools to perform simplified neutron physics shielding calculations. With the increased importance of performing neutron calculations for homeland security applications and defense nuclear nonproliferation tasks, having an efficient method for performing simple neutron transport calculations becomes increasingly important. Codes such as Monte Carlo N-particle (MCNP) can perform the transport calculations; however, the technical details in setting up, running, and interpreting the required simulations are quite complex and typically go beyond the abilities of most users who need a simple answer to a neutron transport calculation. The work documented in this report resulted in the development of the NucWiz program, which can create an MCNP input file for a set of simple geometries, source, and detector configurations. The user selects source, shield, and tally configurations from a set of pre-defined lists, and the software creates a complete MCNP input file that can be optionally run and the results viewed inside NucWiz.

  1. Facilitated transport of Cu with hydroxyapatite nanoparticles in saturated sand: Effects of solution ionic strength and composition

    Science.gov (United States)

    Column experiments were conducted to investigate the facilitated transport of Cu in association with hydroxyapatite nanoparticles (nHAP) in water-saturated quartz sand at different solution concentrations of NaCl (0 to 100 mM) or CaCl2 (0.1 to 1.0 mM). The experimental breakthrough curves and retent...

  2. Modeling Atmospheric Emissions and Calculating Mortality Rates Associated with High Volume Hydraulic Fracturing Transportation

    Science.gov (United States)

    Mathews, Alyssa

    Emissions from the combustion of fossil fuels are a growing pollution concern throughout the global community, as they have been linked to numerous health issues. The freight transportation sector is a large source of these emissions and is expected to continue growing as globalization persists. Within the US, the expanding development of the natural gas industry is helping to support many industries and leading to increased transportation. The process of High Volume Hydraulic Fracturing (HVHF) is one of the newer advanced extraction techniques that is increasing natural gas and oil reserves dramatically within the US, however the technique is very resource intensive. HVHF requires large volumes of water and sand per well, which is primarily transported by trucks in rural areas. Trucks are also used to transport waste away from HVHF well sites. This study focused on the emissions generated from the transportation of HVHF materials to remote well sites, dispersion, and subsequent health impacts. The Geospatial Intermodal Freight Transport (GIFT) model was used in this analysis within ArcGIS to identify roadways with high volume traffic and emissions. High traffic road segments were used as emissions sources to determine the atmospheric dispersion of particulate matter using AERMOD, an EPA model that calculates geographic dispersion and concentrations of pollutants. Output from AERMOD was overlaid with census data to determine which communities may be impacted by increased emissions from HVHF transport. The anticipated number of mortalities within the impacted communities was calculated, and mortality rates from these additional emissions were computed to be 1 in 10 million people for a simulated truck fleet meeting stricter 2007 emission standards, representing a best case scenario. Mortality rates due to increased truck emissions from average, in-use vehicles, which represent a mixed age truck fleet, are expected to be higher (1 death per 341,000 people annually).

  3. Efficient wave-function matching approach for quantum transport calculations

    DEFF Research Database (Denmark)

    Sørensen, Hans Henrik Brandenborg; Hansen, Per Christian; Petersen, Dan Erik;

    2009-01-01

    The wave-function matching (WFM) technique has recently been developed for the calculation of electronic transport in quantum two-probe systems. In terms of efficiency it is comparable to the widely used Green's function approach. The WFM formalism presented so far requires the evaluation of all ...

  4. Inhibited transport of graphene oxide nanoparticles in granular quartz sand coated with Bacillus subtilis and Pseudomonas putida biofilms.

    Science.gov (United States)

    He, Jian-Zhou; Wang, Deng-Jun; Fang, Huan; Fu, Qing-Long; Zhou, Dong-Mei

    2017-02-01

    Increasing production and use of graphene oxide nanoparticles (GONPs) boost their wide dissemination in the subsurface environments where biofilms occur ubiquitously, representative of the physical and chemical heterogeneities. This study aimed at investigating the influence of Gram-positive Bacillus subtilis (BS) and Gram-negative Pseudomonas putida (PP) biofilms on the transport of GONPs under different ionic strengths (0.1, 0.5, and 1.0 mM CaCl2) at neutral pH 7.2 in water-saturated porous media. Particularly, the X-ray micro-computed tomography was used to quantitatively characterize the pore structures of sand columns in the presence and absence of biofilms. Our results indicated that the presence of biofilms reduced the porosity and narrowed down the pore sizes of packed columns. Transport experiments in biofilm-coated sand showed that biofilms, irrespective of bacterial species, significantly inhibited the mobility of GONPs compared to that in cleaned sand. This could be due to the Ca(2+) complexation, increased surface roughness and charge heterogeneities of collectors, and particularly enhanced physical straining caused by biofilms. The two-site kinetic retention model-fitted value of maximum solid-phase concentration (Smax2) for GONPs was higher for biofilm-coated sand than for cleaned sand, demonstrating that biofilms act as favorable sites for GONPs retention. Our findings presented herein are important to deepen our current understanding on the nature of particle-collector interactions.

  5. Influence of gravity on transport and retention of representative engineered nanoparticles in quartz sand.

    Science.gov (United States)

    Cai, Li; Zhu, Jinghan; Hou, Yanglong; Tong, Meiping; Kim, Hyunjung

    2015-10-01

    Four types of NPs: carbon nanotubes and graphene oxide (carbon-based NPs), titanium dioxide and zinc oxide metal-oxide NPs, were utilized to systematically determine the influence of gravity on the transport of NPs in porous media. Packed column experiments for two types of carbon-based NPs were performed under unfavorable conditions in both up-flow (gravity-negative) and down-flow (gravity-positive) orientations, while for two types of metal-oxide NPs, experiments were performed under both unfavorable and favorable conditions in both up-flow and down-flow orientations. Both breakthrough curves and retained profiles of two types of carbon-based NPs in up-flow orientation were equivalent to those in down-flow orientation, indicating that gravity had negligible effect on the transport and retention of carbon-based NPs under unfavorable conditions. In contrast, under both unfavorable and favorable conditions, the breakthrough curves for two types of metal-oxide NPs in down-flow orientation were lower relative to those in up-flow orientation, indicating that gravity could decrease the transport of metal-oxide NPs in porous media. The distinct effect of gravity on the transport and retention of carbon-based and metal-oxide NPs was mainly attributed to the contribution of gravity to the force balance on the NPs in quartz sand. The contribution of gravity was determined by the interplay of the density and sizes of NP aggregates under examined solution conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Simulation of aeolian sand saltation with rotational motion

    Science.gov (United States)

    Huang, Ning; Wang, Cong; Pan, Xiying

    2010-11-01

    In this work, we propose a theoretical model based on the distribution functions of initial liftoff velocity and angular velocity of sand grains to describe a sand saltation process in which both wind field-sand grain coupling and the Magnus force experienced by saltating sand grains have been incorporated. The computation results showed that the Magnus force had significant effects on sand grain saltation. In particular, when the Magnus force was incorporated, the calculated sand transport fluxes and sand transport rate per unit width were closer to the experimental value than when this force was excluded. The sand transport flux is enhanced because the Magnus force owing to particle rotation causes the particles to have higher and longer trajectories, so the particles can get more speed and energy from the wind, which leads to a larger sand transport flux. In addition, it was found that when taking the Magnus force into account, the probability density of the impact velocity and angular velocity of saltating sand grains followed an exponential distribution and a unimodal asymmetric distribution, respectively. Moreover, the sand energy flux increased with the height above the sand surface until the energy flux reached its maximum and then decreased. Furthermore, the energy flux near the ground surface decreased as the grain diameter increased, but beyond a specific height the energy flux increased with the grain diameter. Finally, for the same sand grain diameter, the energy flux increased with the friction velocity.

  7. Effects of Heterogeneous Adsorption Affinity on Natural Organic Matter (NOM) Transport in Laboratory Sand Columns

    Science.gov (United States)

    McInnis, D. P.; Bolster, D.; Maurice, P. A.

    2012-12-01

    Transport of reactive sorbing solutes through porous media is commonly quantified by implementing an effective retardation coefficient in the advection-dispersion equation (ADE), which describes dispersion in accordance with Fick's law. However, anomalous (non-Fickian) transport behavior can be observed in systems with heterogeneous retardation coefficients (Dentz & Castro, 2009). In such systems, the ADE is unable to reproduce the non-Fickian nature of plume shapes and breakthrough curves, motivating the development and application of alternative solute transport theories, such as the continuous time random walk (CTRW) or multi-rate mass transfer (MRMT). Heterogeneity in retardation coefficients in practice arises from variability in the geochemical properties controlling sorption-desorption kinetics between the solute and mineral surfaces. These distributions have been described in the context of heterogeneity of the porous medium, but to date little attention has been given to the potential role of a geochemically heterogeneous solute. In this work, we consider a system in which anomalous transport arises during the passage of natural organic matter (NOM), a polydisperse mixture of compounds derived from the breakdown of plants and microorganisms in the environment, through homogeneous laboratory sand columns. NOM solutions were passed through columns containing either hematite, corundum, or a naturally-coated quartz sand at a variety of pH and ionic strength conditions. Influent and effluent NOM concentration was measured as UV absorbance at 254 nm. The resulting breakthrough curves are non-Fickian, displaying power-law tailing at late times. Such curves cannot be predicted by the ADE model. Reactivity of NOM components is known to be related to their molecular weight (MW), which tends to be log-normally distributed in aquatic NOM isolates (Cabaniss et al., 2000). Low-MW compounds are more water-soluble, have a higher diffusion coefficient, and due to their

  8. Efficient calculation of dissipative quantum transport properties in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Greck, Peter

    2012-11-26

    We present a novel quantum transport method that follows the non-equilibrium Green's function (NEGF) framework but side steps any self-consistent calculation of lesser self-energies by replacing them by a quasi-equilibrium expression. We termed this method the multi-scattering Buettiker-Probe (MSB) method. It generalizes the so-called Buettiker-Probe model but takes into account all relevant individual scattering mechanisms. It is orders of magnitude more efficient than a fully selfconsistent non-equilibrium Green's function calculation for realistic devices, yet accurately reproduces the results of the latter method as well as experimental data. This method is fairly easy to implement and opens the path towards realistic three-dimensional quantum transport calculations. In this work, we review the fundamentals of the non-equilibrium Green's function formalism for quantum transport calculations. Then, we introduce our novel MSB method after briefly reviewing the original Buettiker-Probe model. Finally, we compare the results of the MSB method to NEGF calculations as well as to experimental data. In particular, we calculate quantum transport properties of quantum cascade lasers in the terahertz (THz) and the mid-infrared (MIR) spectral domain. With a device optimization algorithm based upon the MSB method, we propose a novel THz quantum cascade laser design. It uses a two-well period with alternating barrier heights and complete carrier thermalization for the majority of the carriers within each period. We predict THz laser operation for temperatures up to 250 K implying a new temperature record.

  9. Flow and suspended sediment transport through the gravel-sand transition in the Fraser River, British Columbia

    OpenAIRE

    2011-01-01

    The Fraser River, British Columbia is a large alluvial channel that features an abrupt gravel-sand transition that occurs due to a dramatic slope change and the ocean base-level control. There have been no previous observations of the sediment dynamics through transitions in rivers of this scale. I examine the spatial and temporal changes in flow and the suspended sediment transport regime through the transition using hydro-acoustics in an attempt to test the hypothesis that sand in the grave...

  10. Characteristics Of Basaltic Sand: Size, Shape, And Composition As A Function Of Transport Process And Distance

    Science.gov (United States)

    Craddock, R. A.; Needell, Z. A.; Rose, T. R.

    2012-04-01

    quartz, feldspar, and heavy minerals commonly found in most terrestrial sedimentary deposits, basaltic sediments are composed of varying amounts of olivine, pyroxene, plagioclase, and vitric and lithic fragments. One of the few locations on Earth containing such material is the Ka'u Desert of Hawaii. This area is unique in that both eolian and fluvial sediment pathways occur in the same area, thus allowing a direct comparison of particles transported by different processes over identical distances (~20 km). We are currently documenting the physical and chemical changes that take place in basaltic sediments as they are transported by wind and water over increasing distances. This will result in an improvement in our understanding of traditional sedimentological concepts when applying them to Martian surface materials. Process: The Ka'u Desert is ~350 km2 and contains the largest basaltic dune fields on Earth. We have identified several different dune types located in various parts of the desert, including climbing and falling dunes, sand sheets, parabolic dunes (that were initially barchans), and crescentic dunes. Fluvial sediments occur as floodout deposits where ephemeral streams go from confined to unconfined flow outside the continuous Keanakako'i Formation [7]. There are also a number of sand bottom streams and playas that occur along a series of channels that extend from the Keanakako'i Formation ~20 km to the sea. We have collected samples from dunes and fluvial deposits at various locations in the Ka'u Desert, at varying distances from sources and subject to different environmental processes. In the lab, we have begun to use optical and scanning electron microscopic images to assess how grain size, shape, and angularity of individual particles change with increasing transport distances. We are also conducting point counts of particles contained within each sample to better understand how olivine, pyroxene, feldspar, and lithic and vitric fragments weather with

  11. Three dimensions transport calculations for PWR core; Calcul de coeur R.E.P. en transport 3D

    Energy Technology Data Exchange (ETDEWEB)

    Richebois, E

    2000-07-01

    The objective of this work is to define improved 3-D core calculation methods based on the transport theory. These methods can be particularly useful and lead to more precise computations in areas of the core where anisotropy and steep flux gradients occur, especially near interface and boundary conditions and in regions of high heterogeneity (bundle with absorbent rods). In order to apply the transport theory a new method for calculating reflector constants has been developed, since traditional methods were only suited for 2-group diffusion core calculations and could not be extrapolated to transport calculations. In this thesis work, the new method for obtaining reflector constants is derived regardless of the number of energy groups and of the operator used. The core calculations results using the reflector constants thereof obtained have been validated on the EDF's power reactor Saint Laurent B1 with MOX loading. The advantages of a 3-D core transport calculation scheme have been highlighted as opposed to diffusion methods; there are a considerable number of significant effects and potential advantages to be gained in rod worth calculations for instance. These preliminary results obtained with on particular cycle will have to be confirmed by more systematic analysis. Accidents like MSLB (main steam line break) and LOCA (loss of coolant accident) should also be investigated and constitute challenging situations where anisotropy is high and/or flux gradients are steep. This method is now being validated for others EDF's PWRs' reactors, as well as for experimental reactors and other types of commercial reactors. (author)

  12. Direct method for calculating temperature-dependent transport properties

    Science.gov (United States)

    Liu, Yi; Yuan, Zhe; Wesselink, R. J. H.; Starikov, Anton A.; van Schilfgaarde, Mark; Kelly, Paul J.

    2015-06-01

    We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calculated from first principles. For Fe, the agreement with experiment is limited by how well the magnetization (of itinerant ferromagnets) can be calculated as a function of temperature. By introducing a simple Debye-like model of spin disorder parameterized to reproduce the experimental magnetization, the temperature dependence of the average resistivity, the anisotropic magnetoresistance, and the spin polarization of a Ni80Fe20 alloy are calculated and found to be in good agreement with existing data. Extension of the method to complex, inhomogeneous materials as well as to the calculation of other finite-temperature physical properties within the adiabatic approximation is straightforward.

  13. FLOW FIELD CHARACTERISTICS OF THE SAND FUNNEL AND ITS ME-CHANICS OF SEDIMENT TRANSPORT

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The flow in funnel chamber is typical three-di-mensional flow. The experimental results of clear water flowfield and muddy water flow field show that the flow character-istics in the funnel chamber are favorable to the separation ofwater and sand. Tangential velocity sustains the vortexstrength of the funnel chamber, axial velocity is benefit to thesediment sinking, and radial velocity is benefit to sedimentmoving to desilting hole. So the sand funnel is successful insediment disposal. The sand funnel projection has also gooddesilting effectiveness in practice. Its average flushing dis-charge is 3% of inlet canal discharge, the sand disposal rate is100% for the sand with grain diameter of more than 0. 5mm,and is more than 90% for the sand with grain diameter of lessthan 0. 5mm.

  14. Transport of heavy metals and chemical compatibility of hydraulic conductivity of a compacted sand-bentonite mixture

    Directory of Open Access Journals (Sweden)

    Nanthanit Charoenthaisong

    2008-03-01

    Full Text Available Clayey soils are usually used as barrier material in landfill liners because of its low hydraulic conductivity and high sorption capacity. Bentonite, which consists mainly of montmorillonite, has a high cation exchange capacity resulting in a high retention capacity of heavy metals. Sand is a permeable material but its hydraulic conductivity decreases significantly when mixed with bentonite. However, using a sand-bentonite mixture as landfill liners is questionable, because the hydraulic conductivity of the sand-bentonite mixture may increase when permeated with heavy metal solutions, which are normally found in landfill leachates. In this paper, transport of heavy metals through a compacted sand-bentonite mixture and its chemical compatibility were studied through the batch adsorption test, the column test, and the hydraulic conductivity test.Experimental results indicate that the sorption capacity of the bentonite, ranked in descending order, was Cr3+, Pb2+, Cd2+, Zn2+, and Ni2+, respectively. The diffusion coefficients of the sand-bentonite mixture were in the order of 10-5 cm2/s and the retardation factors were 130, 115, 111, and 90 for Pb2+, Ni2+, Zn2+, and Cd2+, respectively. The hydraulic conductivity of thesand-bentonite mixture was only compatible with a chromium solution having a concentration not greater than 0.001 M.

  15. GUIDE TO CALCULATING TRANSPORT EFFICIENCY OF AEROSOLS IN OCCUPATIONAL AIR SAMPLING SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Hogue, M.; Hadlock, D.; Thompson, M.; Farfan, E.

    2013-11-12

    This report will present hand calculations for transport efficiency based on aspiration efficiency and particle deposition losses. Because the hand calculations become long and tedious, especially for lognormal distributions of aerosols, an R script (R 2011) will be provided for each element examined. Calculations are provided for the most common elements in a remote air sampling system, including a thin-walled probe in ambient air, straight tubing, bends and a sample housing. One popular alternative approach would be to put such calculations in a spreadsheet, a thorough version of which is shared by Paul Baron via the Aerocalc spreadsheet (Baron 2012). To provide greater transparency and to avoid common spreadsheet vulnerabilities to errors (Burns 2012), this report uses R. The particle size is based on the concept of activity median aerodynamic diameter (AMAD). The AMAD is a particle size in an aerosol where fifty percent of the activity in the aerosol is associated with particles of aerodynamic diameter greater than the AMAD. This concept allows for the simplification of transport efficiency calculations where all particles are treated as spheres with the density of water (1g cm-3). In reality, particle densities depend on the actual material involved. Particle geometries can be very complicated. Dynamic shape factors are provided by Hinds (Hinds 1999). Some example factors are: 1.00 for a sphere, 1.08 for a cube, 1.68 for a long cylinder (10 times as long as it is wide), 1.05 to 1.11 for bituminous coal, 1.57 for sand and 1.88 for talc. Revision 1 is made to correct an error in the original version of this report. The particle distributions are based on activity weighting of particles rather than based on the number of particles of each size. Therefore, the mass correction made in the original version is removed from the text and the calculations. Results affected by the change are updated.

  16. The Effect of Air Density on Sand Transport Structures and the Adobe Abrasion Profile: A Field Wind-Tunnel Experiment Over a Wide Range of Altitude

    Science.gov (United States)

    Han, Qingjie; Qu, Jianjun; Dong, Zhibao; Zu, Ruiping; Zhang, Kecun; Wang, Hongtao; Xie, Shengbo

    2013-11-01

    Aeolian sand transport results from interactions between the surface and the airflow above. Air density strongly constrains airflow characteristics and the resulting flow of sand, and therefore should not be neglected in sand transport models. In the present study, we quantify the influence of air density on the sand flow structure, sand transport rate, adobe abrasion profiles, and abrasion rate using a portable wind-tunnel in the field. For a given wind speed, the flow's ability to transport sand decreases at low air density, so total sand transport decreases, but the saltation height increases. Thus, the damage to human structures increases compared with what occurs at lower altitudes. The adobe abrasion rate by the cloud of blowing sand decreases exponentially with increasing height above the surface, while the wind erosion and dust emission intensity both increase with increasing air density. Long-term feedback processes between air density and wind erosion suggest that the development of low-altitude areas due to long-term deflation plays a key role in dust emission, and will have a profound significance for surface Aeolian processes and geomorphology.

  17. Accounting for chemical kinetics in field scale transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bryan, N.D. [Manchester Univ. (United Kingdom). Dept. of Chemistry

    2005-04-01

    The modelling of column experiments has shown that the humic acid mediated transport of metal ions is dominated by the non-exchangeable fraction. Metal ions enter this fraction via the exchangeable fraction, and may transfer back again. However, in both directions these chemical reactions are slow. Whether or not a kinetic description of these processes is required during transport calculations, or an assumption of local equilibrium will suffice, will depend upon the ratio of the reaction half-time to the residence time of species within the groundwater column. If the flow rate is sufficiently slow or the reaction sufficiently fast then the assumption of local equilibrium is acceptable. Alternatively, if the reaction is sufficiently slow (or the flow rate fast), then the reaction may be 'decoupled', i.e. removed from the calculation. These distinctions are important, because calculations involving chemical kinetics are computationally very expensive, and should be avoided wherever possible. In addition, column experiments have shown that the sorption of humic substances and metal-humate complexes may be significant, and that these reactions may also be slow. In this work, a set of rules is presented that dictate when the local equilibrium and decoupled assumptions may be used. In addition, it is shown that in all cases to a first approximation, the behaviour of a kinetically controlled species, and in particular its final distribution against distance at the end of a calculation, depends only upon the ratio of the reaction first order rate to the residence time, and hence, even in the region where the simplifications may not be used, the behaviour is predictable. In this way, it is possible to obtain an estimate of the migration of these species, without the need for a complex transport calculation. (orig.)

  18. Sand Transport and Turbulence over Immobile Gravel and Cobble Beds: Similarities and Differences Caused by Roughness Scale

    Science.gov (United States)

    Wren, D. G.; Langendoen, E. J.; Kuhnle, R. A.

    2011-12-01

    Characterizing the turbulence generated by flow over rough beds has become increasingly important in support of efforts to predict sediment transport downstream of dams. The advanced age and impending decommissioning of many dams have brought increased attention to the fate of sediments stored in reservoirs. In many cases, fine sediments are reintroduced to coarse substrates that have large volumes of pore space available for storage after having sediments removed by years of sediment-starved flow. The roughness and porosity of the coarse substrate are both affected by the fine sediment elevation relative to the coarse substrate; therefore, the turbulence characteristics and sediment transport over and through these beds are significantly altered after sediment is reintroduced. Experiments at the USDA-ARS-National Sedimentation Laboratory have focused on sand transport and turbulence over two different rough, immobile, substrates: 35 mm gravel and 150 mm cobbles. Detailed acoustic Doppler-based measurements of turbulence structure over the gravel and cobble beds have allowed the influence of the scale of roughness on both the turbulence and sand transport to be evaluated. It was found that the sand transport in both the gravel and cobble beds showed a strong relationship with bed shear stress scaled by the value of the cumulative distribution of bed elevation at the level of sand within the rough bed. Reynolds stresses near and just below the top of the cobble bed show a region of near constant value with depth, while, for the gravel bed there is a gradual decrease in Reynolds stress beginning just above the gravel and decreasing with increasing depth into the gravel. Dispersive stresses show a very similar patter with a peak at the top of the roughness elements decaying to zero with increasing distance above and below.

  19. Transport, retention, and long-term release behavior of ZnO nanoparticle aggregates in saturated quartz sand: Role of solution pH and biofilm coating.

    Science.gov (United States)

    Han, Yosep; Hwang, Gukhwa; Kim, Donghyun; Bradford, Scott A; Lee, Byoungcheun; Eom, Igchun; Kim, Pil Je; Choi, Siyoung Q; Kim, Hyunjung

    2016-03-01

    The transport, retention, and long-term release of zinc oxide nanoparticle aggregates (denoted below as ZnO-NPs) were investigated in saturated, bare and biofilm (Pseudomonas putida) coated sand packed columns. Almost complete retention of ZnO-NPs occurred in bare and biofilm coated sand when the influent solution pH was 9 and the ionic strength (IS) was 0.1 or 10 mM NaCl, and the retention profiles were always hyper-exponential. Increasing the solution IS and biofilm coating produced enhanced retention of ZnO-NPs near the column inlet. The enhanced NPs retention at high IS was attributed to more favorable NP-silica and NP-NP interactions; this was consistent with the interaction energy calculations. Meanwhile, the greater NPs retention in the presence of biofilm was attributed to larger roughness heights which alter the mass transfer rate, the interaction energy profile, and lever arms associated with the torque balance; e.g., scanning electron and atomic force microscopy was used to determine roughness heights of 33.4 nm and 97.8 nm for bare sand and biofilm-coated sand, respectively. Interactions between NPs and extracellular polymeric substances may have also contributed to enhanced NP retention in biofilm-coated sand at low IS. The long-term release of retained ZnO-NPs was subsequently investigated by continuously injecting NP-free solution at pH 6, 9, or 10 and keeping the IS constant at 10 mM. The amount and rate of retained ZnO-NP removal was strongly dependent on the solution pH. Specifically, almost complete removal of retained ZnO-NPs was observed after 627 pore volumes when the solution pH was 6, whereas much less Zn was recovered when the eluting solution pH was buffered to pH = 9 and especially 10. This long-term removal was attributed to pH-dependent dissolution of retained ZnO-NPs because: (i) the solubility of ZnO-NPs increases with decreasing pH; and (ii) ZnO-NPs were not detected in the effluent. The presence of biofilm also decreased the

  20. Imidacloprid transport and sorption nonequilibrium in single and multilayered columns of Immokalee fine sand.

    Science.gov (United States)

    Leiva, Jorge A; Nkedi-Kizza, Peter; Morgan, Kelly T; Kadyampakeni, Davie M

    2017-01-01

    Imidacloprid (IMD) is a neonicotinoid pesticide soil-drenched to many crops to control piercing-sucking insects such as the Asian citrus psyllid (ACP). Neonicotinoids are persistent in the environment and transport analyses are helpful estimate leaching potential from soils that could result in groundwater pollution. The objective of this study was to analyze IMD breakthrough under saturated water flow in soil columns packed with three horizons (A, E, Bh) of Immokalee Fine Sand (IFS). Also, we used the dimensionless form of the convective-dispersive model (CD-Model) to compare the optimized transport parameters from each column experiment (retardation factor, R; fraction of instantaneous-to-total retardation, β; and mass transfer coefficient, ω) with the parameters obtained from sorption batch equilibria and sorption kinetics. The tracer (Cl-) breakthrough curves (BTCs) were symmetrical and properly described by the CD-Model. IMD BTCs from A, Bh, and multilayered [A+E+Bh] soil columns showed steep fronts and tailing that were well described by the one-site nonequilibrium (OSNE) model, which was an evidence of non-ideal transport due to IMD mass transfer into the soil organic matter. In general, IMD was weakly-sorbed in the A and Bh horizons (R values of 3.72 ± 0.04 and 3.08 ± 0.07, respectively), and almost no retardation was observed in the E horizon (R = 1.20 ± 0.02) due to its low organic matter content (0.3%). Using the HYDRUS-1D package, optimized parameters (R, β, ω) from the individual columns successfully simulated IMD transport in a multilayered column mimicking an IFS soil profile. These column studies and corresponding simulations agreed with previous findings from batch sorption equilibria and kinetics experiments, where IMD showed one-site kinetic mass transfer between soil surfaces and soil solution. Ideally, sandy soils should be maintained unsaturated by crop irrigation systems and rainfall monitoring during and after soil-drench application

  1. Calculations of Bed-Material Transport, Chetco River, Oregon

    Science.gov (United States)

    Anderson, S.; Wallick, R.; Cannon, C.; O'Connor, J. E.

    2009-12-01

    The Chetco River drains 914 square kilometers of the Klamath Mountains in far southwestern Oregon. The lower 18 kilometers of the river are flanked by large and abundant gravel bars, which have been commercially mined for aggregate during most of the last century. Increasing concern regarding the impact of this mining on aquatic habitats motivated an assessment of historical channel change and sediment transport rates along this lower reach. A key component of this research was estimating bed-material transport through the application of sediment transport equations at multiple locations along the study reach. Flow hydraulics were estimated with a 1-D hydraulic model constructed in HEC-RAS, using a combination of LiDAR and bathymetric surveys to characterize the valley morphology. Once calibrated to USGS rating curves, low flow water surfaces, and several high flow photos, this model allowed us to calculate energy slopes for a given cross section at a variety of flows. These flow-energy slope pairs, along with cross sections and sediment data collected from surface pebble counts, were then applied to a number of different modern bedload transport equations. This process was facilitated by the Bedload Assessment in Gravel-bedded Streams Excel macro, or BAGS, which allows users to quickly apply multiple transport equations using a single set of inputs (Pitlick et al., 2009). A review of the literature, along with tests of internal consistency and comparisons to direct bedload measurements taken in the winter of 2008-09, led us to choose the Parker (1991) and Wilcock-Crowe (2003) equations as the two most applicable to the Chetco River. Sediment transport-flow curves for both equations were calculated for seven cross sections spanning the study area. For each of these cross sections, we estimated annual transport fluxes using derived transport rating curves in conjunction with unit flow data from a USGS gage at the upstream end of study reach, with data extending back

  2. An accurate {delta}f method for neoclassical transport calculation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.X.; Nakajima, N.; Murakami, S.; Okamoto, M. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    1999-03-01

    A {delta}f method, solving drift kinetic equation, for neoclassical transport calculation is presented in detail. It is demonstrated that valid results essentially rely on the correct evaluation of marker density g in weight calculation. A general and accurate weighting scheme is developed without using some assumed g in weight equation for advancing particle weights, unlike the previous schemes. This scheme employs an additional weight function to directly solve g from its kinetic equation using the idea of {delta}f method. Therefore the severe constraint that the real marker distribution must be consistent with the initially assumed g during a simulation is relaxed. An improved like-particle collision scheme is presented. By performing compensation for momentum, energy and particle losses arising from numerical errors, the conservations of all the three quantities are greatly improved during collisions. Ion neoclassical transport due to self-collisions is examined under finite banana case as well as zero banana limit. A solution with zero particle and zero energy flux (in case of no temperature gradient) over whole poloidal section is obtained. With the improvement in both like-particle collision scheme and weighting scheme, the {delta}f simulation shows a significantly upgraded performance for neoclassical transport study. (author)

  3. Transport, retention, and long-term release behavior of ZnO nanoparticle aggregates in saturated quartz sand: Role of solution pH and biofilm coating

    Science.gov (United States)

    The transport, retention, and long-term fate of zinc oxide nanoparticles (ZnO-NPs) were investigated in saturated, bare and biofilm (Pseudomonas putida) coated sand packed columns. Almost complete retention of ZnO-NPs occurred in bare and biofilm coated sand when the influent solution pH was 9 and t...

  4. Vertical structure of aeolian turbulence in a boundary layer with sand transport

    Science.gov (United States)

    Lee, Zoe S.; Baas, Andreas C. W.

    2016-04-01

    originating from the top of the boundary layer, indicating a downwards direction of eddy motion. While directionality of turbulence cannot be definitively determined, our results indicate that the top-down turbulence model is a suitable explanation, further supported by the presence of 'incomplete' eddies which originate at higher elevations but fail to extend to the surface. This provides the first evidence in support of a top down turbulence model as observed in aeolian geomorphology, and we present preliminary findings on its relationship to sand transport activity. Lee, Z.S., Baas, A.C.W. (2016) Variable and conflicting shear stress estimates inside a boundary layer with sediment transport. Earth Surface Processes and Landforms; DOI: 10.1002/esp.3829

  5. Deficit of sand in a sediment transport model favors coral reef development in Brazil

    Directory of Open Access Journals (Sweden)

    Abílio C.S.P. Bittencourt

    2008-03-01

    Full Text Available This paper shows that the location of the shoreface bank reefs along the northeastern and eastern coasts of Brazil, in a first order approximation, seem to be controlled by the deficit of sediment in the coastal system. The sediment transport pattern defined by a numerical modeling of wave refraction diagrams, representing circa 2000 km of the northeastern and eastern coasts of Brazil, permitted the regional-scale reproduction of several drift cells of net longshore sediment transport. Those drift cells can reasonably explain the coastal sections that present sediment surplus or sediment deficit, which correspond, respectively, to regions where there is deposition and erosion or little/no deposition of sand. The sediment deficit allows the exposure and maintenance of rocky substrates to be free of sediment, a favorable condition for the fixation and development of coral larvae.Este trabalho mostra que a localização dos recifes de coral ao longo dos litorais leste e nordeste do Brasil, em uma aproximação de primeira ordem, parece ser controlada pelo déficit de sedimentos no sistema costeiro. O padrão de transporte de sedimentos definido por modelagem numérica a partir de diagramas de refração de ondas, representando cerca de 2000 km dos litorais leste e nordeste do Brasil, permitiu a reprodução, em escala regional, de várias células de deriva litorânea efetiva de sedimentos. Essas células de deriva podem razoavelmente explicar os segmentos costeiros que representam superávit, ou deficit de sedimentos que correspondem, respectivamente, a regiões onde existe deposição e erosão ou pouca/nenhuma deposição de areia. O deficit de sedimentos propicia a exposição e manutenção de substratos rochosos livres de sedimento, uma condição favorável para a fixação e desenvolvimento das larvas de coral.

  6. Hydraulic calculation of gravity transportation pipeline system for backfill slurry

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qin-li; HU Guan-yu; WANG Xin-min

    2008-01-01

    Taking cemented coal gangue pipeline transportation system in Suncun Coal Mine, Xinwen Mining Group, Shandong Province, China, as an example, the hydraulic calculation approaches and process about gravity pipeline transportation of backfill slurry were investigated. The results show that the backfill capability of the backfill system should be higher than 74.4m3/h according to the mining production and backfill times in the mine; the minimum velocity (critical velocity) and practical working velocity of the backfill slurry are 1.44 and 3.82m/s, respectively. Various formulae give the maximum ratio of total length to vertical height of pipeline (L/H ratio) of the backfill system of 5.4, and then the reliability and capability of the system can be evaluated.

  7. Assessment of the solubility of thorium and uranium from black sand of Camargue in both simulated lung and gut fluids for dose calculation after internal exposure

    Energy Technology Data Exchange (ETDEWEB)

    Frelon, S.; Chazel, V.; Tourlonias, E.; Paquet, F. [IRSN/ DRPH/ SRBE, LRTOX, BP 166, 26702 Pierrelatte Cedex (France); Blanchardon, E. [IRSN/ DRPH/ SDI, LEDI, BP 17, 92262 Fontenay Aux Roses Cedex (France); Bouisset, P. [IRSN/ DEI/ STEME, LMRE, Bois des rames, 91400 Orsay (France); Pourcelot, L. [IRSN/ DEI/ SESURE, LERCM, BP3, 13 115 St Paul lez Durance Cedex (France)

    2006-07-01

    In the south of France, some beaches of Camargue present a high rate of natural radioactivity due to thorium and uranium from zircon and apatite heavy minerals present in the so-called black sand. These radionuclides may lead to internal exposure consecutive to inhalation or ingestion of this sand. The accurate assessment of radiological risk after internal exposure of public frequenting these beaches requires some information on the human bioavailability of U and Th from the sand. Both routes of intake were studied in this work and the consecutive dose delivered was calculated under two different scenarios for each type of exposure. As far as inhalation is concerned, the first important conclusion is that the inhalable fraction, i.e. particles with aerodynamic diameters below 50 {mu}m, was tiny (0.002%) in this sample of sand. Moreover in vitro assays of solubility were performed for this fraction and showed that U and Th as well as their progeny presented moderate solubility. Then effective doses under several scenarios were calculated and seem to demonstrate a very poor risk of exposure after inhalation. Indeed, a dose of 1 mSv would be received by a babies after inhalation of about 40 Kg of sand, that is impossible, whereas a more realistic scenario of chronic exposure only reached 31 {mu} Sv. In case of ingestion, the solubility of Th and U in the gastrointestinal fluids was found to be very low with a maximum solubility of 0.5% of the initial mass of radioelement in the sample of sand. Then the worst hypothesis studied yields an effective dose of 0.018 mSv./(g-swallowed sand) that is roughly 50 times less than the legal annual dose limit for members of the public. as a conclusion, the possible internal dose after exposure by inhalation or ingestion of black sand of Camargue seems to be very low under the conditions of this study. (N.C.)

  8. Transport and Retention of Toxoplasma gondii Oocysts in Loamy Sand and Sandy Loam Soils

    Science.gov (United States)

    Kinsey, E. N.; Korte, C.; L'Ollivier, C.; Dubey, J. P.; Aurélien, D.; Darnault, C. J. G.

    2016-12-01

    Toxoplasma gondii is one of the most prevalent parasites affecting warm-blooded animals and humans. It has a complex life cycle that involves a wide variety of intermediate hosts with felids as a definitive host. Humans may contract it through consumption of infected, undercooked meat or by water or food sources contaminated with the oocyst form of the parasite. Infection of pregnant women can cause stillbirth, neurological effects or blindness. Because of the prevalence of cats, including on farms where oocyst-contaminated cat feces, animal feed, soil and water have been found, T. gondii is spread almost throughout the entire globe. It has been implicated or suspected in waterborne infections since the 1990s. This study aims to characterize the transport and retention of T. gondii oocysts in field soils. The four soils used were collected from fallow and cultivated fields in Illinois and Utah, USA. They are classified as loamy sands and sandy loams. Soil columns were subjected to continuous artificial rainfall until they reached steady state at which point pulses that included 2.5 million T. gondii oocysts (Me49 strain) and KBr as a tracer were added. After the pulse infiltrated, continuous rainfall was resumed. Rain applied all columns was a 1 mM KCl solution. Leachate samples were collected, analyzed using qPCR for T. gondii and bromide ions and breakthrough curves were produced. Soil was sliced into 1 to 2 cm sections, for which water content and T. gondii concentration were measured to access degree of saturation and oocyst retention.

  9. Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Surf-zone integrated alongshore potential flux for oil-sand balls

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates...

  10. Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Surf-zone integrated alongshore potential flux for oil-sand balls

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates...

  11. Neutron and photon transport calculations in fusion system. 2

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Satoshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    1998-03-01

    On the application of MCNP to the neutron and {gamma}-ray transport calculations for fusion reactor system, the wide range design calculation has been carried out in the engineering design activities for the international thermonuclear fusion experimental reactor (ITER) being developed jointly by Japan, USA, EU and Russia. As the objects of shielding calculation for fusion reactors, there are the assessment of dose equivalent rate for living body shielding and the assessment of the nuclear response for the soundness of in-core structures. In the case that the detailed analysis of complicated three-dimensional shapes is required, the assessment using MCNP has been carried out. Also when the nuclear response of peripheral equipment due to the gap streaming between blanket modules is evaluated with good accuracy, the calculation with MCNP has been carried out. The analyses of the shieldings for blanket modules and NBI port are explained, and the examples of the results of analyses are shown. In the blanket modules, there are penetrating holes and continuous gap. In the case of the NBI port, shielding plug cannot be installed. These facts necessitate the MCNP analysis with high accuracy. (K.I.)

  12. Neutron and gamma ray transport calculations in shielding system

    Energy Technology Data Exchange (ETDEWEB)

    Masukawa, Fumihiro; Sakamoto, Hiroki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    In the shields for radiation in nuclear facilities, the penetrating holes of various kinds and irregular shapes are made for the reasons of operation, control and others. These penetrating holes and gaps are filled with air or the substances with relatively small shielding performance, and radiation flows out through them, which is called streaming. As the calculation techniques for the shielding design or analysis related to the streaming problem, there are the calculations by simplified evaluation, transport calculation and Monte Carlo method. In this report, the example of calculation by Monte Carlo method which is represented by MCNP code is discussed. A number of variance reduction techniques which seem effective for the analysis of streaming problem were tried. As to the investigation of the applicability of MCNP code to streaming analysis, the object of analysis which are the concrete walls without hole and with horizontal hole, oblique hole and bent oblique hole, the analysis procedure, the composition of concrete, and the conversion coefficient of dose equivalent, and the results of analysis are reported. As for variance reduction technique, cell importance was adopted. (K.I.)

  13. 厦门岛东南部海岸演变与泥沙输移%Coast evolution and sand transportation in east-southern Xiamen Island

    Institute of Scientific and Technical Information of China (English)

    陈坚; 蔡锋

    2001-01-01

    By means of coastal morphology and sediment investigation, shore change and littoral sand transportation rate calculation et al., characteristics of beach evolution in east-southern Xiamen Island were analyzed and studied. It is announced that the direction of net littoral sand transportation is from east-north to west-south and from east to west. Coast hereof is divided into 6 types, which are serious erosion type, mild-serious erosion type, mild erosion type, slight erosion type, slight deposit type and undefined type. Moreover, sand mining was defined as one of the most important factors for coast erosion.%通过海岸地貌调查、沉积物分布、岸线对比、沿岸输沙率计算等手段,分析研究了厦门岛东南部海岸海滩的演变特征.认为厦门岛东南部海岸的沿岸净输沙方向是由东北向西南,由东向西;黄厝湾中北部存在反向输沙.文中划分了中-强侵蚀海岸、中侵蚀海岸、中-弱侵蚀海岸、弱侵蚀海岸、弱淤积海岸和不确定海岸等6种类型.人工采沙是引起海岸侵蚀的最重要因素之一.

  14. Hand calculations for transport of radioactive aerosols through sampling systems.

    Science.gov (United States)

    Hogue, Mark; Thompson, Martha; Farfan, Eduardo; Hadlock, Dennis

    2014-05-01

    Workplace air monitoring programs for sampling radioactive aerosols in nuclear facilities sometimes must rely on sampling systems to move the air to a sample filter in a safe and convenient location. These systems may consist of probes, straight tubing, bends, contractions and other components. Evaluation of these systems for potential loss of radioactive aerosols is important because significant losses can occur. However, it can be very difficult to find fully described equations to model a system manually for a single particle size and even more difficult to evaluate total system efficiency for a polydispersed particle distribution. Some software methods are available, but they may not be directly applicable to the components being evaluated and they may not be completely documented or validated per current software quality assurance requirements. This paper offers a method to model radioactive aerosol transport in sampling systems that is transparent and easily updated with the most applicable models. Calculations are shown with the R Programming Language, but the method is adaptable to other scripting languages. The method has the advantage of transparency and easy verifiability. This paper shows how a set of equations from published aerosol science models may be applied to aspiration and transport efficiency of aerosols in common air sampling system components. An example application using R calculation scripts is demonstrated. The R scripts are provided as electronic attachments.

  15. Using the Chebychev expansion in quantum transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, Bogdan; Rahman, Hasan; Kleinekathöfer, Ulrich, E-mail: u.kleinekathoefer@jacobs-university.de [Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany)

    2015-04-21

    Irradiation by laser pulses and a fluctuating surrounding liquid environment can, for example, lead to time-dependent effects in the transport through molecular junctions. From the theoretical point of view, time-dependent theories of quantum transport are still challenging. In one of these existing transport theories, the energy-dependent coupling between molecule and leads is decomposed into Lorentzian functions. This trick has successfully been combined with quantum master approaches, hierarchical formalisms, and non-equilibrium Green’s functions. The drawback of this approach is, however, its serious limitation to certain forms of the molecule-lead coupling and to higher temperatures. Tian and Chen [J. Chem. Phys. 137, 204114 (2012)] recently employed a Chebychev expansion to circumvent some of these latter problems. Here, we report on a similar approach also based on the Chebychev expansion but leading to a different set of coupled differential equations using the fact that a derivative of a zeroth-order Bessel function can again be given in terms of Bessel functions. Test calculations show the excellent numerical accuracy and stability of the presented formalism. The time span for which this Chebychev expansion scheme is valid without any restrictions on the form of the spectral density or temperature can be determined a priori.

  16. Using the Chebychev expansion in quantum transport calculations.

    Science.gov (United States)

    Popescu, Bogdan; Rahman, Hasan; Kleinekathöfer, Ulrich

    2015-04-21

    Irradiation by laser pulses and a fluctuating surrounding liquid environment can, for example, lead to time-dependent effects in the transport through molecular junctions. From the theoretical point of view, time-dependent theories of quantum transport are still challenging. In one of these existing transport theories, the energy-dependent coupling between molecule and leads is decomposed into Lorentzian functions. This trick has successfully been combined with quantum master approaches, hierarchical formalisms, and non-equilibrium Green's functions. The drawback of this approach is, however, its serious limitation to certain forms of the molecule-lead coupling and to higher temperatures. Tian and Chen [J. Chem. Phys. 137, 204114 (2012)] recently employed a Chebychev expansion to circumvent some of these latter problems. Here, we report on a similar approach also based on the Chebychev expansion but leading to a different set of coupled differential equations using the fact that a derivative of a zeroth-order Bessel function can again be given in terms of Bessel functions. Test calculations show the excellent numerical accuracy and stability of the presented formalism. The time span for which this Chebychev expansion scheme is valid without any restrictions on the form of the spectral density or temperature can be determined a priori.

  17. Reactive transport of gentisic acid in a hematite-coated sand column: Experimental study and modeling

    Science.gov (United States)

    Hanna, K.; Rusch, B.; Lassabatere, L.; Hofmann, A.; Humbert, B.

    2010-06-01

    The adsorption of gentisic acid (GA) by hematite nano-particles was examined under static and dynamic conditions by conducting batch and column tests. To simulate natural sediments, the iron oxide was deposited on 10 μm quartz particles. The GA adsorption was described by a surface complexation model fitted to pH-adsorption curves with GA concentrations of 0.1-1 mM in a pH range of 3-10. The surface was described with one type of site ( tbnd FeOH°), while gentisic acid at the surface was described by two surface complexes ( tbnd FeLH 2°, log Kint = 8.9 and tbnd FeLH -, log Kint = -8.2). Modeling was conducted with PHREEQC-2 using the MINTEQ database. From a kinetic point of view, the intrinsic chemical reactions were likely to be the rate-limiting step of sorption (˜10 -3 s -1) while external and internal mass transfer rates (˜10 2 s -1) were much faster. Under flow through conditions (column), adsorption of GA to hematite-coated sand was about 7-times lower than under turbulent mixing (batch). This difference could not be explained by chemical adsorption kinetics as shown by test calculations run with HYDRUS-1D software. Surface complexation model simulations however successfully described the data when the surface area was adjusted, suggesting that under flow conditions the accessibility to the reactive surface sites was reduced. The exact mechanism responsible for the increased mobility of GA could not be determined but some parameters suggested that decreased external mass transfer between solution and surface may play a significant role under flow through conditions.

  18. First Cost Calculation Methods for Road Freight Transport Activity

    Directory of Open Access Journals (Sweden)

    Kovács György

    2017-06-01

    Full Text Available The transport activity is one of the most expensive processes in the supply chain. Forwarding and transport companies focuses on the optimization of transportation and the reduction of transport costs.

  19. Effect of different-sized colloids on the transport and deposition of titanium dioxide nanoparticles in quartz sand.

    Science.gov (United States)

    Cai, Li; Peng, Shengnan; Wu, Dan; Tong, Meiping

    2016-01-01

    Colloids (non-biological and biological) with different sizes are ubiquitous in natural environment. The investigations regarding the influence of different-sized colloids on the transport and deposition behaviors of engineered-nanoparticles in porous media yet are still largely lacking. This study investigated the effects of different-sized non-biological and biological colloids on the transport of titanium dioxide nanoparticles (nTiO2) in quartz sand under both electrostatically favorable and unfavorable conditions. Fluorescent carboxylate-modified polystyrene latex microspheres (CML) with sizes of 0.2-2 μm were utilized as model non-biological colloids, while Gram-negative Escherichia coli (∼ 1 μm) and Gram-positive Bacillus subtilis (∼ 2 μm) were employed as model biological colloids. Under the examined solution conditions, both breakthrough curves and retained profiles of nTiO2 with different-sized CML particles/bacteria were similar as those without colloids under favorable conditions, indicating that the copresence of model colloids in suspensions had negligible effects on the transport and deposition of nTiO2 under favorable conditions. In contrast, higher breakthrough curves and lower retained profiles of nTiO2 with CML particles/bacteria relative to those without copresent colloids were observed under unfavorable conditions. Clearly, the copresence of model colloids increased the transport and decreased the deposition of nTiO2 in quartz sand under unfavorable conditions (solution conditions examined in present study). Both competition of deposition sites on quartz sand surfaces and the enhanced stability/dispersion of nTiO2 induced by copresent colloids were found to be responsible for the increased nTiO2 transport with colloids under unfavorable conditions. Moreover, the smallest colloids had the highest coverage on sand surface and most significant dispersion effect on nTiO2, resulting in the greatest nTiO2 transport. Copyright © 2015. Published

  20. Calculated characteristics of subcritical assembly with anisotropic transport of neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Gorin, N.V.; Lipilina, E.N.; Lyutov, V.D.; Saukov, A.I. [Zababakhin Russian Federal Nuclear Center - All-Russian Scientific Researching Institute of Technical Physics (Russian Federation)

    2003-07-01

    There was considered possibility of creating enough sub-critical system that multiply neutron fluence from a primary source by many orders. For assemblies with high neutron tie between parts, it is impossible. That is why there was developed a construction consisting of many units (cascades) having weak feedback with preceding cascades. The feedback attenuation was obtained placing layers of slow neutron absorber and moderators between the cascades of fission material. Anisotropy of fast neutron transport through the layers was used. The system consisted of many identical cascades aligning one by another. Each cascade consists of layers of moderator, fissile material and absorber of slow neutrons. The calculations were carried out using the code MCNP.4a with nuclear data library ENDF/B5. In this construction neutrons spread predominantly in one direction multiplying in each next fissile layer, and they attenuate considerably in the opposite direction. In a calculated construction, multiplication factor of one cascade is about 1.5 and multiplication factor of whole construction composed of n cascades is 1.5{sup n}. Calculated keff value is 0.9 for one cascade and does not exceed 0.98 for a system containing any number of cascades. Therefore the assembly is always sub-critical and therefore it is safe in respect of criticality. There was considered using such a sub-critical assembly to create a powerful neutron fluence for neutron boron-capturing therapy. The system merits and demerits were discussed. (authors)

  1. First-principles calculations of mass transport in magnesium borohydride

    Science.gov (United States)

    Yu, Chao; Ozolins, Vidvuds

    2013-03-01

    Mg(BH4)2 is a hydrogen storage material which can decompose to release hydrogen in the following reaction: Mg(BH4)2(solid) -->1/6 MgB12H12(solid) + 5/6MgH2(solid) +13/6 H2(gas) --> MgH2(solid) + 2B(solid) + 4H2(gas). However, experiments show that hydrogen release only occurs at temperatures above 300 °C, which severely limits applications in mobile storage. Using density-functional theory calculations, we systematically study bulk diffusion of defects in the reactant Mg(BH4)2 and products MgB12H12 and MgH2 during the first step of the solid-state dehydrogenation reaction. The defect concentrations and concentration gradients are calculated for a variety of defects, including charged vacancies and interstitials. We find that neutral [BH3] vacancies have the highest bulk concentration and concentration gradient in Mg(BH4)2. The diffusion mechanism of [BH3] vacancy in Mg(BH4)2 is studied using the nudged elastic band method. Our results shows that the calculated diffusion barrier for [BH3] vacancies is ~ . 2 eV, suggesting that slow mass transport limits the kinetics of hydrogen desorption.

  2. Sand sources and transport pathways for the San Francisco Bay coastal system, based on X-ray diffraction mineralogy

    Science.gov (United States)

    Hein, James R.; Mizell, Kira; Barnard, Patrick L.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    The mineralogical compositions of 119 samples collected from throughout the San Francisco Bay coastal system, including bayfloor and seafloor, area beaches, cliff outcrops, and major drainages, were determined using X-ray diffraction (XRD). Comparison of the mineral concentrations and application of statistical cluster analysis of XRD spectra allowed for the determination of provenances and transport pathways. The use of XRD mineral identifications provides semi-quantitative compositions needed for comparisons of beach and offshore sands with potential cliff and river sources, but the innovative cluster analysis of XRD diffraction spectra provides a unique visualization of how groups of samples within the San Francisco Bay coastal system are related so that sand-sized sediment transport pathways can be inferred. The main vector for sediment transport as defined by the XRD analysis is from San Francisco Bay to the outer coast, where the sand then accumulates on the ebb tidal delta and also moves alongshore. This mineralogical link defines a critical pathway because large volumes of sediment have been removed from the Bay over the last century via channel dredging, aggregate mining, and borrow pit mining, with comparable volumes of erosion from the ebb tidal delta over the same period, in addition to high rates of shoreline retreat along the adjacent, open-coast beaches. Therefore, while previously only a temporal relationship was established, the transport pathway defined by mineralogical and geochemical tracers support the link between anthropogenic activities in the Bay and widespread erosion outside the Bay. The XRD results also establish the regional and local importance of sediment derived from cliff erosion, as well as both proximal and distal fluvial sources. This research is an important contribution to a broader provenance study aimed at identifying the driving forces for widespread geomorphic change in a heavily urbanized coastal-estuarine system.

  3. Quantifying the effects of European beach grass on aeolian sand transport over the last century: Bodega Marine Reserve, California

    Science.gov (United States)

    Cesmat, R.; Werner, S.; Smith, M. E.; Riedel, T.; Best, R.; Olyarnik, S.

    2012-12-01

    Introduction of European beach grass (Ammophila arenaria) to coastal dune systems of western North America induced significant changes to the transport and storage of sediment, and consequently the nesting habitat of the western snowy plover (Charadrius alexandrinus nivosus). At the Bodega Marine Reserve and Sonoma Coast State Park, Ammophila was introduced within the ~0.5 km2 dune area in the 1920's to limit the flux of sand through Bodega Harbor and agricultural land. To assess the potential impact of restoration efforts (Ammophila removal) on aeolian sediment flux, we measured sediment flux as a function of wind speeds and ground cover, and used these measurements to parameterize a spatial model for historical sand deposition Fine- to coarse-grained lithic to sub-lithic sand is delivered to the Bodega dune system from Salmon Creek beach, the down-shore terminus of a littoral system fed by the 3846 km2 Russian River catchment, several small (Littoral sediment traverses the 1.8 km wide dune system from NW to SE via aeolian transport. Ammophila colonization occurred initially adjacent to the shoreface, inducing deposition of a ~10 meter-high foredune and has subsequently encroached the ~0.5 km2 region between the foredune and Bodega Harbor. Comparison of historical topographic maps via raster subtraction indicates rapid construction of both the foredune and a ~15 meter-high transverse dune (Gaffney ridge) at the edge of the planted region. An average accumulation rate of ~4,000 m3/yr is indicated within the study swath by the preserved sediment volumes. Within the modern dune system, unvegetated areas exhibit 2-3 meter wavelength, ~1/2 meter amplitude mega-ripples, and the uppermost 2-10 cm consists of coarse-sand to granule-sized armor layer. In contrast, grain-sizes in vegetated areas are largely vertically homogenous. Open areas are typically 2-8 meters lower than adjacent vegetated areas, and show evidence for net lowering of the land surface (i.e., exposed

  4. Chemical mass transport between fluid fine tailings and the overlying water cover of an oil sands end pit lake

    Science.gov (United States)

    Dompierre, Kathryn A.; Barbour, S. Lee; North, Rebecca L.; Carey, Sean K.; Lindsay, Matthew B. J.

    2017-06-01

    Fluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML)—the first full-scale demonstration oil sands end pit lake (EPL)—contains approximately 1.9 × 108 m3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m3 m-2 d-1, which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy.

  5. Assessment of existing sediment transport models for sand barrier dynamics under wave and currents

    Digital Repository Service at National Institute of Oceanography (India)

    Thuy, T.T.V.; Nghiem, L.T.; Jayakumar, S.; Nielsen, P.

    The paper summarizes morphology changes over rippled sand barriers under wave and wave combined current of 27 laboratorial experiments. Data of 4 wave conditions (H=10cm, T=1s; H=12cm, T=1s; H=12cm, T=1.5s; H=14cm, T=1.5s) and 6 currents (Q= 10, -10...

  6. Simulation of groundwater flow and chloride transport in the “1,200-foot” sand with scenarios to mitigate saltwater migration in the “2,000-foot” sand in the Baton Rouge area, Louisiana

    Science.gov (United States)

    Heywood, Charles E.; Lovelace, John K.; Griffith, Jason M.

    2015-07-16

    Groundwater withdrawals have caused saltwater to encroach into freshwater-bearing aquifers beneath Baton Rouge, Louisiana. The 10 aquifers beneath the Baton Rouge area, which includes East and West Baton Rouge Parishes, Pointe Coupee Parish, and East and West Feliciana Parishes, provided about 184.3 million gallons per day (Mgal/d) for public supply and industrial use in 2012. Groundwater withdrawals from the “1,200-foot” sand in East Baton Rouge Parish have caused water-level drawdown as large as 177 feet (ft) north of the Baton Rouge Fault and limited saltwater encroachment from south of the fault. The recently developed groundwater model for simulating transport in the “2,000-foot” sand was rediscretized to also enable transport simulation within the “1,200-foot” sand and was updated with groundwater withdrawal data through 2012. The model was recalibrated to water-level observation data through 2012 with the parameter-estimation code PEST and calibrated to observed chloride concentrations at observation wells within the “1,200-foot” sand and “2,000-foot” sand. The model is designed to evaluate strategies to control saltwater migration, including changes in the distribution of groundwater withdrawals and installation of scavenger wells to intercept saltwater before it reaches existing production wells.

  7. Tritium transport calculations for the IFMIF Tritium Release Test Module

    Energy Technology Data Exchange (ETDEWEB)

    Freund, Jana, E-mail: jana.freund@kit.edu; Arbeiter, Frederik; Abou-Sena, Ali; Franza, Fabrizio; Kondo, Keitaro

    2014-10-15

    Highlights: • Delivery of material data for the tritium balance in the IFMIF Tritium Release Test Module. • Description of the topological models in TMAP and the adapted fusion-devoted Tritium Permeation Code (FUS-TPC). • Computation of release of tritium from the breeder solid material into the purge gas. • Computation of the loss of tritium over the capsule wall, rig hull, container wall and purge gas return line. - Abstract: The IFMIF Tritium Release Test Module (TRTM) is projected to measure online the tritium release from breeder ceramics and beryllium pebble beds under high energy neutron irradiation. Tritium produced in the pebble bed of TRTM is swept out continuously by a purge gas flow, but can also permeate into the module's metal structures, and can be lost by permeation to the environment. According analyses on the tritium inventory are performed to support IFMIF plant safety studies, and to support the experiment planning. This paper describes the necessary elements for calculation of the tritium transport in the Tritium Release Test Module as follows: (i) applied equations for the tritium balance, (ii) material data from literature and (iii) the topological models and the computation of the five different cases; namely release of tritium from the breeder solid material into the purge gas, loss of tritium over the capsule wall, rig hull, container wall and purge gas return line in detail. The problem of tritium transport in the TRTM has been studied and analyzed by the Tritium Migration Analysis Program (TMAP) and the adapted fusion-devoted Tritium Permeation Code (FUS-TPC). TMAP has been developed at INEEL and now exists in Version 7. FUS-TPC Code was written in MATLAB with the original purpose to study the tritium transport in Helium Cooled Lead Lithium (HCLL) blanket and in a later version the Helium Cooled Pebble Bed (HCPB) blanket by [6] (Franza, 2012). This code has been further modified to be applicable to the TRTM. Results from the

  8. WIND TUNNEL EXPERIMENT OF SAND VELOCITY IN NATURE AEOLIAN SAND TRANSPORT USING PARTICLE IMAGE VELOCIMETRY%天然混合沙运动速度特征的风洞PIV实验

    Institute of Scientific and Technical Information of China (English)

    佟鼎; 黄宁

    2011-01-01

    Sand velocity in aeolian sand transport is measured using the PIV system(Particle Imaging Velocimetry) in a wind tunnel.The velocity probability distribution of ascending and descending particles,as well the influences of sand ripple on the sand particle motion are analyzed.The results show that velocity distributions of take-off particles and particles during sand movement accord with logarithm normal distribution.The mean incident velocity of sand particles is 1.005-1.4 times higher than take-off ones with different wind speed.It is found that sand ripples play an important role on the sand particles motion,which is a key factor that can not be neglected.%采用PIV(Particle Image Velocimetry)系统测量了天然混合沙风沙两相流中沙粒的速度分布特征,得到了沙粒入射以及起跳的速度分布情况,并且分析了沙波纹对风沙运动的影响。结果表明:沙粒运动过程中的速度分布与沙粒起跳速度的分布可以应用对数正态分布来表明;当有沙波纹存在时,沙粒总体速度分布与平坦沙床面差别很大,是不可忽略的重要因素;平坦沙床面沙粒平均入射速度是起跳平均速度的1.005倍~1.4倍,具体关系可以应用线性函数来拟合。

  9. Mimicking Retention and Transport of Rotavirus and Adenovirus in Sand Media Using DNA-labeled, Protein-coated Silica Nanoparticles

    Science.gov (United States)

    Pang, Liping; Farkas, Kata; Bennett, Grant; Varsani, Arvind; Easingwood, Richard; Tilley, Richard; Nowostawska, Urszula; Lin, Susan

    2014-05-01

    Rotavirus (RoV) and adenovirus (AdV) are important viral pathogens for the risk analysis of drinking water. Despite this, little is known about their retention and transport behaviors in porous media (e.g. sand filtered used for water treatment and groundwater aquifers due to a lack of representative surrogates. In this study, we developed RoV and AdV surrogates by covalently coating 70-nm sized silica nanoparticles with specific proteins and a DNA marker for sensitive detection. Filtration experiments using beach sand columns demonstrated the similarity of the surrogates' concentrations, attachment, and filtration efficiencies to the target viruses. The surrogates showed the same magnitude of concentration reduction as the viruses. Conversely, MS2 phage (a traditional virus model) over predicted concentrations of AdV and RoV by 1- and 2-orders of magnitude, respectively. The surrogates remained stable in size, surface charge and DNA concentration for at least one year. They can be easily and rapidly detected at concentrations down to one particle per PCR reaction and are readily detectable in natural waters and even in effluent. With up-scaling validation in pilot trials, the surrogates can be a useful cost-effective new tool for studying virus retention and transport in porous media, e.g. for assessing filter efficiency in water and wastewater treatment, tracking virus migration in groundwater after effluent land disposal, and establishing safe setback distances for groundwater protection.

  10. Considerations of beta and electron transport in internal dose calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bolch, W.E.; Poston, J.W. Sr.

    1990-12-01

    Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial transport of electron and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each case, preliminary results are very encouraging and plans for further research are detailed within this document.

  11. Humic acid facilitates the transport of ARS-labeled hydroxyapatite nanoparticles in iron oxyhydroxide-coated sand

    Science.gov (United States)

    Wang, Dengjun; Bradford, Scott A.; Harvey, Ronald W.; Gao, Bin; Cang, Long; Zhou, Dongmei

    2012-01-01

    Hydroxyapatite nanoparticles (nHAP) have been widely used to remediate soil and wastewater contaminated with metals and radionuclides. However, our understanding of nHAP transport and fate is limited in natural environments that exhibit significant variability in solid and solution chemistry. The transport and retention kinetics of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated packed columns that encompassed a range of humic acid concentrations (HA, 0–10 mg L–1), fractional surface coverage of iron oxyhydroxide coatings on sand grains (λ, 0–0.75), and pH (6.0–10.5). HA was found to have a marked effect on the electrokinetic properties of ARS-nHAP, and on the transport and retention of ARS-nHAP in granular media. The transport of ARS-nHAP was found to increase with increasing HA concentration because of enhanced colloidal stability and the reduced aggregate size. When HA = 10 mg L–1, greater ARS-nHAP attachment occurred with increasing λ because of increased electrostatic attraction between negatively charged nanoparticles and positively charged iron oxyhydroxides, although alkaline conditions (pH 8.0 and 10.5) reversed the surface charge of the iron oxyhydroxides and therefore decreased deposition. The retention profiles of ARS-nHAP exhibited a hyperexponential shape for all test conditions, suggesting some unfavorable attachment conditions. Retarded breakthrough curves occurred in sands with iron oxyhydroxide coatings because of time-dependent occupation of favorable deposition sites. Consideration of the above effects is necessary to improve remediation efficiency of nHAP for metals and actinides in soils and subsurface environments.

  12. Effect of Tube Length on Transport of Multi-Wall Nanotubes (MWNTs) in a Water-Saturated Quartz Sand

    Science.gov (United States)

    Wang, Y.; Baek, J.; Kim, J.; Pennell, K. D.

    2009-12-01

    With expanding commercial interests from various application areas, the production of carbon nanotubes (CNTs) in large scale is expected to grow rapidly. The inevitable release of CNTs into the environment and identification of the cytotoxicity of dispersed CNTs prompt the necessity of understanding their transport behavior in porous media. In this study, one-dimensional column experiments were conducted to assess the transport and retention of multi-wall nanotubes (MWNTs) in water-saturated 40-50 mesh Ottawa sand as a function of of tube length. In order to avoid damages to nanotube length by ultrasonication or superacids (e.g., HNO3), a chemical modification method involving a mild acid treatment was adopted to prepare suspensions of MWNTs with three different manufacture-reported (MR) lengths (0.5-2, 10-20, and 50 μm). For each experiment, a pulse (e.g., 5 pore volumes) of MWNT suspension was introduced into the column, followed by 3 pore volumes of MWNT-free solution elution. Measured concentrations of MWNTs in effluent and dissected solid samples were used to construct effluent breakthrough curves and retention profiles, respectively. For an input concentration of ca. 90 mg/L, MWNTs breakthrough concentrations decreased with the increasing MR length. Even with an MR length of 50 μm, MWNTs were readily transported through the packed bed, where ca. 80% of total injected nanotubes passed through the column. While the retention of MWNTs increased with MR length, concentrations of retained nanotubes decreased hyper-exponentially with distance from the column inlet. Further analysis of these findings suggests that clean-bed filtration theory alone is not sufficient to describe MWNT transport and retention behavior in a water-saturated quartz sand.

  13. Optimal array of sand fences.

    Science.gov (United States)

    Lima, Izael A; Araújo, Ascânio D; Parteli, Eric J R; Andrade, José S; Herrmann, Hans J

    2017-03-24

    Sand fences are widely applied to prevent soil erosion by wind in areas affected by desertification. Sand fences also provide a way to reduce the emission rate of dust particles, which is triggered mainly by the impacts of wind-blown sand grains onto the soil and affects the Earth's climate. Many different types of fence have been designed and their effects on the sediment transport dynamics studied since many years. However, the search for the optimal array of fences has remained largely an empirical task. In order to achieve maximal soil protection using the minimal amount of fence material, a quantitative understanding of the flow profile over the relief encompassing the area to be protected including all employed fences is required. Here we use Computational Fluid Dynamics to calculate the average turbulent airflow through an array of fences as a function of the porosity, spacing and height of the fences. Specifically, we investigate the factors controlling the fraction of soil area over which the basal average wind shear velocity drops below the threshold for sand transport when the fences are applied. We introduce a cost function, given by the amount of material necessary to construct the fences. We find that, for typical sand-moving wind velocities, the optimal fence height (which minimizes this cost function) is around 50 cm, while using fences of height around 1.25 m leads to maximal cost.

  14. Heterogeneity of Rapid Sand Filters and Its Effect on Contaminant Transport and Nitrification Performance

    DEFF Research Database (Denmark)

    Lopato, Laure Rose; Galaj, Zofia; Delpont, Sébastien

    2011-01-01

    dispersivity of more than 33% in the 116 h after the start of filtration with a constant pore-water velocity and a zero-order nitrification rate of 9 mgN=L=h. The full-scale experiments showed that the rapid sand filter was heterogeneous with pore-water velocities ranging from 2.2 to 3:3 m=h for the same inlet...... flow. A first-order nitrification reaction with spatially variable pore-water velocity could be interpreted as a zero-order reaction with a constant pore-water velocity. A model demonstrated that filter heterogeneity could result in higher filter outlet ammonium concentrations....

  15. Computer program for calculating thermodynamic and transport properties of fluids

    Science.gov (United States)

    Hendricks, R. C.; Braon, A. K.; Peller, I. C.

    1975-01-01

    Computer code has been developed to provide thermodynamic and transport properties of liquid argon, carbon dioxide, carbon monoxide, fluorine, helium, methane, neon, nitrogen, oxygen, and parahydrogen. Equation of state and transport coefficients are updated and other fluids added as new material becomes available.

  16. Computational Fluid Dynamics Simulation of Transport and Retention of Nanoparticle in Saturated Sand Filters

    Science.gov (United States)

    Experimental and computational investigation of the transport parameters of nano particles flowing through porous media has been made. The objective of this work was to develop a simulation capability applicable to the transport and retention of nanoparticles (NPs) in saturated p...

  17. Modeling and sensitivity analysis on the transport of aluminum oxide nanoparticles in saturated sand: effects of ionic strength, flow rate, and nanoparticle concentration.

    Science.gov (United States)

    Rahman, Tanzina; Millwater, Harry; Shipley, Heather J

    2014-11-15

    Aluminum oxide nanoparticles have been widely used in various consumer products and there are growing concerns regarding their exposure in the environment. This study deals with the modeling, sensitivity analysis and uncertainty quantification of one-dimensional transport of nano-sized (~82 nm) aluminum oxide particles in saturated sand. The transport of aluminum oxide nanoparticles was modeled using a two-kinetic-site model with a blocking function. The modeling was done at different ionic strengths, flow rates, and nanoparticle concentrations. The two sites representing fast and slow attachments along with a blocking term yielded good agreement with the experimental results from the column studies of aluminum oxide nanoparticles. The same model was used to simulate breakthrough curves under different conditions using experimental data and calculated 95% confidence bounds of the generated breakthroughs. The sensitivity analysis results showed that slow attachment was the most sensitive parameter for high influent concentrations (e.g. 150 mg/L Al2O3) and the maximum solid phase retention capacity (related to blocking function) was the most sensitive parameter for low concentrations (e.g. 50 mg/L Al2O3).

  18. Size- and concentration-dependent deposition of fluorescent silica colloids in saturated sand columns: transport experiments and modeling.

    Science.gov (United States)

    Vitorge, Elsa; Szenknect, Stéphanie; Martins, Jean M F; Gaudet, Jean-Paul

    2013-08-01

    This study investigates the size and concentration effects on the transport of silica colloids in columns of sandy aquifer material. Colloid transport experiments were performed with specifically developed fluorescent labeled silica colloids in columns of a repacked natural porous medium under hydro-geochemical conditions representative of sandy aquifers. Breakthrough curves and vertical deposition profiles of colloids were measured for various colloid concentrations and sizes. The results showed that for a given colloid concentration injected, deposition increased when increasing the size of the colloids. For a given colloid size, retention was also shown to be highly concentration-dependent with a non-monotonous pattern presenting low and high concentration specificities. Deposition increases when increasing both size and injected concentration, until a threshold concentration is reached, above which retention decreases, thus increasing colloid mobility. Results observed above the threshold concentration agree with a classical blocking mechanism typical of a high concentration regime. Results observed at lower colloid concentrations were not modeled with a classical blocking model and a depth- and time-dependent model with a second order kinetic law was necessary to correctly fit the experimental data in the entire range of colloid concentrations with a single set of parameters for each colloidal size. The colloid deposition mechanisms occuring at low concentrations were investigated through a pore structure analysis carried out with Mercury Intrusion Porosimetry and image analysis. The determined pore size distribution permitted estimation of the maximal retention capacity of the natural sand as well as some low flow zones. Altogether, these results stress the key role of the pore space geometry of the sand in controlling silica colloids deposition under hydro-geochemical conditions typical of sandy aquifers. Our results also showed originally that colloid

  19. Analytical calculation of the minimum wind speed required to sustain wind-blown sand on Earth and Mars

    CERN Document Server

    Kok, Jasper F

    2010-01-01

    The wind-driven hopping motion of sand grains, known as saltation, forms dunes and ripples and ejects fine dust particles into the atmosphere on both Earth and Mars. While the wind speed at which saltation is initiated, the fluid threshold, has been studied extensively, the wind speed at which it is halted, the impact threshold, has been poorly quantified for Mars conditions. We present an analytical model of the impact threshold, which we show to be in agreement with measurements and recent numerical simulations for Earth conditions. For Mars conditions, we find that the impact threshold is approximately an order of magnitude below the fluid threshold, in agreement with previous studies. Saltation on Mars can thus be sustained at wind speeds an order of magnitude less than required to initiate it, leading to the occurrence of hysteresis. These results confirm earlier simulations with a detailed numerical saltation model, and have important implications for the formation of sand dunes, ripples, and dust storm...

  20. Analysis of Wind-blown Sand Movement over Transverse Dunes

    Science.gov (United States)

    Jiang, Hong; Huang, Ning; Zhu, Yuanjian

    2014-12-01

    Wind-blown sand movement often occurs in a very complicated desert environment where sand dunes and ripples are the basic forms. However, most current studies on the theoretic and numerical models of wind-blown sand movement only consider ideal conditions such as steady wind velocity, flat sand surface, etc. In fact, the windward slope gradient plays a great role in the lift-off and sand particle saltation. In this paper, we propose a numerical model for the coupling effect between wind flow and saltating sand particles to simulate wind-blown sand movement over the slope surface and use the SIMPLE algorithm to calculate wind flow and simulate sands transport by tracking sand particle trajectories. We furthermore compare the result of numerical simulation with wind tunnel experiments. These results prove that sand particles have obvious effect on wind flow, especially that over the leeward slope. This study is a preliminary study on windblown sand movement in a complex terrain, and is of significance in the control of dust storms and land desertification.

  1. Field trial on the transport of Pseudomonas putida and Escherichia coli bacteria in the tertiary sand of Neuherberg test field; Gelaendeversuche zum Transport der Bakterien Pseudomonas putida und Escherichia coli im tertiaeren Sand des Versuchsfeldes Neuherberg

    Energy Technology Data Exchange (ETDEWEB)

    Mallen, G.; Engel, M.; Maloszewski, P.; Reichlmayr, E. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany). Inst. fuer Hydrologie

    2001-11-01

    The groundwater in the highly permeable, predominantly pebbly Quaternary structure of the Munich boulder plain is subject to considerable contamination and hazards. In the past this led some municipalities and large consumers (e.g. breweries) to draw groundwater from the underlying tertiary sands and coarse clay of the Upper Lacustrine Molasse. In spite of thick, barely permeable intermediate layers anthropogenic influences are gradually progressing further into the deep, compelling those concerned to draw groundwater from deeper and deeper aquifer layers. Formerly restricted to Quaternary aquifers, studies on the input, transport and fate of various pollutants must therefore now be extended to include Tertiary formations. [German] Das Grundwasser im hochdurchlaessigen, ueberwiegend kiesigen Quartaer der Muenchener Schotterebene ist erheblichen Belastungen und Gefaehrdungen ausgesetzt. Daher erschlossen einige Gemeinden und Grossverbraucher (z.B. Brauereien) in der Vergangenheit das GW aus den darunterliegenden tertiaeren Sanden und Schluffen der Oberen Suesswassermolasse. Trotz maechtiger, sehr geringdurchlaessiger stauender Zwischenschichten schreitet auch hier die anthropogene Beeinflussung von oben nach unten fort und erzwingt gleichzeitig die Erschliessung von GW-Vorkommen aus zunehmend tieferen Aquiferschichten. Bisher meist in quartaeren Aquiferen durchgefuehrte Untersuchungen zum Eintrag, Transport und Verbleib verschiedener Schadstoffe muessen daher auch auf das Tertiaer ausgedehnt werden. (orig.)

  2. Modeling and Calculator Tools for State and Local Transportation Resources

    Science.gov (United States)

    Air quality models, calculators, guidance and strategies are offered for estimating and projecting vehicle air pollution, including ozone or smog-forming pollutants, particulate matter and other emissions that pose public health and air quality concerns.

  3. Conceptual Model for Flow and Transport through Unsaturated Silty Loams and Sands in North Mississippi

    Science.gov (United States)

    Coleman, S. H.; Corley, D. S.; van Volkenburg, G. J.; Wildman, J. C.; Holt, R. M.

    2008-05-01

    We conducted a five-day ponded infiltration test at the University of Mississippi (UM) Soil Moisture Observatory (SMO). The 5 acre SMO is located in a former agricultural field at the UM Field Station, a 740 acre tract of land with restricted access located 11 miles from the UM campus in Oxford, Mississippi. At the infiltration site, the near surface soils consist of about infiltration test, the soil surface was leveled and a 2.0 m diameter infiltration ring was installed. Six neutron access tubes were installed to a depth of 2.5 m around the infiltration ring. A constant ponding depth of 13 cm was maintained throughout the duration of the experiment. Blue dye was added to the water to enable mapping of infiltration paths. During the experiment, moisture content profiles were periodically measured at each neutron access tube. Neutron probe data suggested that infiltration was dominated by capillary forces. However, later mapping of a trench through the infiltration site revealed that infiltration in the upper silt loam was dominated by macropore flow along roots and microfractures in the soil. In the sand, gravity driven fingers formed below the root-zone, where deep roots focused flow.

  4. Direct method for calculating temperature-dependent transport properties

    NARCIS (Netherlands)

    Liu, Y.; Yuan, Z.; Wesselink, R.J.H.; Starikov, A.A.; Schilfgaarde, van M.; Kelly, P.J.

    2015-01-01

    We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calcula

  5. Transport of microbial tracers in clean and organically contaminated silica sand in laboratory columns compared with their transport in the field

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, Louise, E-mail: louise.weaver@esr.cri.nz; Sinton, Lester W.; Pang, Liping; Dann, Rod; Close, Murray

    2013-01-15

    Waste disposal on land and the consequent transport of bacterial and viral pathogens in soils and aquifers are of major concern worldwide. Pathogen transport can be enhanced in the presence of organic matter due to occupation of attachment sites in the aquifer materials thus preventing pathogen attachment leading to their faster transport for longer distances. Laboratory column studies were carried out to investigate the effect of organic matter, in the form of dissolved organic carbon (DOC), on the transport of Escherichia coli and MS2 phage in saturated clean silica sand. Transport rates of these microbial tracers were also studied in a contaminated field site. Laboratory column studies showed that low concentrations (0.17 mg L{sup −1}) of DOC had little effect on E. coli J6-2 removal and slightly reduced the attachment of MS2 phage. After progressive conditioning of the column with DOC (1.7 mg L{sup −1} and 17 mg L{sup −1}), neither E. coli J6-2 nor MS2 phage showed any attachment and recovery rates increased dramatically (up to 100%). The results suggest that DOC can affect the transport rates of microbial contaminants. For E. coli J6-2 the predominant effect appeared to be an increase in the secondary energy minimum leading to an increase in E. coli attachment initially. However, after 17 mg L{sup −1} DOC conditioning of the silica sand no attachment of E. coli was observed as the DOC took up attachment sites in the porous media. MS2 phage appeared to be affected predominantly by out-competition of binding sites in the clean silica sand and a steady reduction in attachment was observed as the DOC conditioning increased. Field study showed a high removal of both E. coli and MS2 phage, although E. coli was removed at a lower rate than MS2 phage. In the field it is likely that a combination of effects are seen as the aquifer material will be heterogeneous in its surface nanoscale properties, demonstrated by the differing removal of E. coli and MS2 phage

  6. Particle size distribution, concentration, and magnetic attraction affect transport of polymer-modified Fe(0) nanoparticles in sand columns.

    Science.gov (United States)

    Phenrat, Tanapon; Kim, Hye-Jin; Fagerlund, Fritjof; Illangasekare, Tissa; Tilton, Robert D; Lowry, Gregory V

    2009-07-01

    The effect of particle concentration, size distribution (polydispersity) and magnetic attractive forces (Fe(0) content) on agglomeration and transport of poly(styrene sulfonate) (PSS) modified NZVI was studied in water-saturated sand (d(p) = 300 microm) columns. Particle concentrations ranged from 0.03 to 6 g/L in 5 mM NaCl/5 mM NaHCO3 at a pore water velocity of 3.2 x 10(-4) m/s. Three NZVI dispersions with different intrinsic particle size distributions obtained from sequential sedimentation are compared. The influence of magnetic attraction (Fe(0) content) on NZVI agglomeration and deposition in porous media is assessed by comparing the deposition behavior of PSS-modified NZVI (magnetic) having different Fe(0) contents with PSS-modified hematite (nonmagnetic) with the same surface modifier. At low particle concentration (30 mg/L) all particles were mobile in sand columns regardless of size or magnetic attractive forces. At high concentration (1 to 6 g/L), deposition of the relatively monodisperse dispersion containing PSS-modified NZVI (hydrodynamic radius (R(H)) = 24 nm) with the lowest Fe(0) content (4 wt%) is low (attachment efficiency (alpha) = 2.5 x 10(-3)), insensitive to particle concentration, and similar to PSS-modified hematite. At 1 to 6 g/L, the attachment efficiency of polydisperse dispersions containing both primary particles and sintered aggregates (R(H) from 15 to 260 nm) of PSS-modified NZVI with a range of Fe(0) content (10-60%) is greater (alpha = 1.2 x 10(-2) to 7.2 x 10(-2) and is sensitive to particle size distribution. The greater attachment for larger, more polydisperse Fe(0) nanoparticles with higher Fe(0) content is a result of their agglomeration during transport in porous media because the magnetic attractive force between particles increases with the sixth power of particle/agglomerate radius. A filtration model that considers agglomeration in porous media and subsequent deposition explains the observed transport of polydisperse PSS

  7. Transport properties of boron nanotubes investigated by ab initio calculation

    Institute of Scientific and Technical Information of China (English)

    Guo Wei; Hu Yi-Bin; Zhang Yu-Yang; Du Shi-Xuan; Gao Hong-Jun

    2009-01-01

    We investigate atomic and electronic structures of boron nanotubes (BNTs) by using the density functional theory(DFT). The transport properties of BNTs with different diameters and chiralities are studied by the Keldysh nonequi-librium Green function (NEGF) method. It is found that the cohesive energies and conductances of BNTs decrease as their diameters decrease. It is more difficult to form (N, 0) tubes than (M, M) tubes when the diameters of the two kinds of tubes are comparable. However, the (N, 0) tubes have a higher conductance than the (M, M) tubes. When the BNTs are connected to gold electrodes, the coupling between the BNTs and the electrodes will affect the transport properties of tubes significantly.

  8. Molecular-dynamics calculation of the vacancy heat of transport

    Energy Technology Data Exchange (ETDEWEB)

    Schelling, Patrick K.; Ernotte, Jacques; Shokeen, Lalit; Tucker, William C. [Advanced Material Processing and Analysis Center and Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816 (United States); Woods Halley, J. [Department of Physics, University of Minnesota, 116 Church Street SE, Minneapolis, Minnesota 555455 (United States)

    2014-07-14

    We apply the recently developed constrained-dynamics method to elucidate the thermodiffusion of vacancies in a single-component material. The derivation and assumptions used in the method are clearly explained. Next, the method is applied to compute the reduced heat of transport Q{sub v}{sup *}−h{sub fv} for vacancies in a single-component material. Results from simulations using three different Morse potentials, with one providing an approximate description of Au, and an embedded-atom model potential for Ni are presented. It is found that the reduced heat of transport Q{sub v}{sup *}−h{sub fv} may take either positive or negative values depending on the potential parameters and exhibits some dependence on temperature. It is also found that Q{sub v}{sup *}−h{sub fv} may be correlated with the activation entropy. The results are discussed in comparison with experimental and previous simulation results.

  9. Two-site kinetic modeling of bacteriophages transport through columns of saturated dune sand.

    Science.gov (United States)

    Schijven, Jack F; Hassanizadeh, S Majid; de Bruin, Ria H A M

    2002-08-01

    Breakthrough curves, on a semi-log scale, from tests in porous media with block-input of viruses, bacteria, protozoa and colloidal particles often exhibit a typical skewness: a rather slowly rising limb and a smooth transition of a declining limb to a very long tail. One-site kinetic models fail to fit the rising and declining limbs together with the tail satisfactorily. Inclusion of an equilibrium adsorption site does not seem to improve simulation results. This was encountered in the simulation of breakthrough curves from a recent field study on the removal of bacteriophages MS2 and PRD1 by passage through dune sand. In the present study, results of laboratory experiments for the study of this issue are presented. Breakthrough curves of salt and bacteriophages MS2, PRDI, and phiX174 in 1 D column experiments have been measured. One- and two-site kinetic models have been applied to fit and predict breakthrough curves from column experiments. The two-site model fitted all breakthrough curves very satisfactorily, accounting for the skewness of the rising limb as well as for the smooth transition of the declining limb to the tail of the breakthrough curve. The one-site model does not follow the curvature of the breakthrough tail, leading to an overestimation of the inactivation rate coefficient for attached viruses. Interaction with kinetic site 1 is characterized by relatively fast attachment and slow detachment, whereas attachment to and detachment from kinetic site 2 is fast. Inactivation of viruses and interaction with kinetic site 2 provide only a minor contribution to removal. Virus removal is mainly determined by the attachment to site 1. Bacteriophage phiX174 attached more than MS2 and PRD1, which can be explained by the greater electrostatic repulsion that MS2 and PRD1 experience compared to the less negatively charged phiX174.

  10. The calculation of transport phenomena in electromagnetically levitated metal droplets

    Science.gov (United States)

    El-Kaddah, N.; Szekely, J.

    1982-01-01

    A mathematical representation has been developed for the electromagnetic force field, fluid flow field, and solute concentration field of levitation-melted metal specimens. The governing equations consist of the conventional transport equations combined with the appropriate expressions for the electromagnetic force field. The predictions obtained by solving the governing equations numerically on a digital computer are in good agreement with lifting force and average temperature measurements reported in the literature.

  11. Development of Monte Carlo decay gamma-ray transport calculation system

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Satoshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Kawasaki, Nobuo [Fujitsu Ltd., Tokyo (Japan); Kume, Etsuo [Japan Atomic Energy Research Inst., Center for Promotion of Computational Science and Engineering, Tokai, Ibaraki (Japan)

    2001-06-01

    In the DT fusion reactor, it is critical concern to evaluate the decay gamma-ray biological dose rates after the reactor shutdown exactly. In order to evaluate the decay gamma-ray biological dose rates exactly, three dimensional Monte Carlo decay gamma-ray transport calculation system have been developed by connecting the three dimensional Monte Carlo particle transport calculation code and the induced activity calculation code. The developed calculation system consists of the following four functions. (1) The operational neutron flux distribution is calculated by the three dimensional Monte Carlo particle transport calculation code. (2) The induced activities are calculated by the induced activity calculation code. (3) The decay gamma-ray source distribution is obtained from the induced activities. (4) The decay gamma-rays are generated by using the decay gamma-ray source distribution, and the decay gamma-ray transport calculation is conducted by the three dimensional Monte Carlo particle transport calculation code. In order to reduce the calculation time drastically, a biasing system for the decay gamma-ray source distribution has been developed, and the function is also included in the present system. In this paper, the outline and the detail of the system, and the execution example are reported. The evaluation for the effect of the biasing system is also reported. (author)

  12. Development of Library Processing System for Neutron Transport Calculation

    Energy Technology Data Exchange (ETDEWEB)

    Song, J. S.; Park, S. Y.; Kim, H. Y. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)] (and others)

    2008-12-15

    A system for library generation was developed for the lattice neutron transport program for pressurized water reactor core analysis. The system extracts multi energy group nuclear data for requested nuclides from ENDF/B whose data are based on continuous energy, generates hydrogen equivalent factor and resonance integral table as functions of temperature and background cross section for resonance nuclides, generates subgroup data for the lattice program to treat resonance exactly as possible, and generates multi-group neutron library file including nuclide depletion data for use of the lattice program.

  13. An improved filtered spherical harmonic method for transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Ahrens, C. [Department of Applied Mathematics and Statistics, Colorado School of Mines, Golden, CO 80401 (United States); Merton, S. [Computational Physics Group, AWE Aldermaston, Berkshire (United Kingdom)

    2013-07-01

    Motivated by the work of R. G. McClarren, C. D. Hauck, and R. B. Lowrie on a filtered spherical harmonic method, we present a new filter for such numerical approximations to the multi-dimensional transport equation. In several test problems, we demonstrate that the new filter produces results with significantly less Gibbs phenomena than the filter used by McClarren, Hauck and Lowrie. This reduction in Gibbs phenomena translates into propagation speeds that more closely match the correct propagation speed and solutions that have fewer regions where the scalar flux is negative. (authors)

  14. AN ALTERNATE METHOD TO PREVENT SAND ABRASIVE EROSION IN PIPELINES FOR TRANSPORTING HIGH-SPEED NATURAL GAS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper presents an alternate method to re-move the sand carried by natural gas in the upstream pipelinestherefore preventing sand abrasive erosion in pipelines used intransporting high-speed natural gas. Conventionally, most ex-perts pay much attention to improving the anti-erosion charac-teristics of the pipeline materials to solve the problem of seri-ous abrasive erosion, but without significant success. Basedon the theory of multiphase flow and analysis of the character-istics of sandy jets, a new equipment named "Sand Catcher" isintroduced in this article. Experimental results show that theSand Catcher effectively removes most of the sand in the natu-ral gas and significantly reduces the abrasive erosion of thepipelines. The Sand Catcher can be widely applied in practicein the near future.

  15. The Suppression of Energy Discretization Errors in Multigroup Transport Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, Edward [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Nuclear Engineering and Radiological Sciences

    2013-06-17

    The Objective of this project is to develop, implement, and test new deterministric methods to solve, as efficiently as possible, multigroup neutron transport problems having an extremely large number of groups. Our approach was to (i) use the standard CMFD method to "coarsen" the space-angle grid, yielding a multigroup diffusion equation, and (ii) use a new multigrid-in-space-and-energy technique to efficiently solve the multigroup diffusion problem. The overall strategy of (i) how to coarsen the spatial an energy grids, and (ii) how to navigate through the various grids, has the goal of minimizing the overall computational effort. This approach yields not only the fine-grid solution, but also coarse-group flux-weighted cross sections that can be used for other related problems.

  16. Efficient algorithms for large-scale quantum transport calculations

    Science.gov (United States)

    Brück, Sascha; Calderara, Mauro; Bani-Hashemian, Mohammad Hossein; VandeVondele, Joost; Luisier, Mathieu

    2017-08-01

    Massively parallel algorithms are presented in this paper to reduce the computational burden associated with quantum transport simulations from first-principles. The power of modern hybrid computer architectures is harvested in order to determine the open boundary conditions that connect the simulation domain with its environment and to solve the resulting Schrödinger equation. While the former operation takes the form of an eigenvalue problem that is solved by a contour integration technique on the available central processing units (CPUs), the latter can be cast into a linear system of equations that is simultaneously processed by SplitSolve, a two-step algorithm, on general-purpose graphics processing units (GPUs). A significant decrease of the computational time by up to two orders of magnitude is obtained as compared to standard solution methods.

  17. Evaluation of dose equivalent rate distribution in JCO critical accident by radiation transport calculation

    CERN Document Server

    Sakamoto, Y

    2002-01-01

    In the prevention of nuclear disaster, there needs the information on the dose equivalent rate distribution inside and outside the site, and energy spectra. The three dimensional radiation transport calculation code is a useful tool for the site specific detailed analysis with the consideration of facility structures. It is important in the prediction of individual doses in the future countermeasure that the reliability of the evaluation methods of dose equivalent rate distribution and energy spectra by using of Monte Carlo radiation transport calculation code, and the factors which influence the dose equivalent rate distribution outside the site are confirmed. The reliability of radiation transport calculation code and the influence factors of dose equivalent rate distribution were examined through the analyses of critical accident at JCO's uranium processing plant occurred on September 30, 1999. The radiation transport calculations including the burn-up calculations were done by using of the structural info...

  18. Effect of Low Energy Waves on the Accumulation and Transport of Fecal Indicator Bacteria in Sand and Pore Water at Freshwater Beaches.

    Science.gov (United States)

    Wu, Ming Zhi; O'Carroll, Denis M; Vogel, Laura J; Robinson, Clare E

    2017-02-24

    Elevated fecal indicator bacteria (FIB) in beach sand and pore water represent an important nonpoint source of contamination to surface waters. This study examines the physical processes governing the accumulation and distribution of FIB in a beach aquifer. Field data indicate E. coli and enterococci can be transported 1 and 2 m, respectively, below the water table. Data were used to calibrate a numerical model whereby FIB are delivered to a beach aquifer by wave-induced infiltration across the beach face. Simulations indicate FIB rapidly accumulate in a beach aquifer with FIB primarily associated with sand rather than freely residing in the pore water. Simulated transport of E. coli in a beach aquifer is complex and does not correlate with conservative tracer transport. Beaches with higher wave-induced infiltration rate and vertical infiltration velocity (i.e., beaches with higher beach slope and wave height, and lower terrestrial groundwater discharge) had greater E. coli accumulation and E. coli was transported deeper below the beach face. For certain beach conditions, the amount of FIB accumulated in sand over 5-6 days was found to be sufficient to trigger a beach advisory if eroded to surface water.

  19. Applying Advanced Neutron Transport Calculations for Improving Fuel Performance Codes

    Energy Technology Data Exchange (ETDEWEB)

    Botazzoli, P.; Luzzi, L. [Politecnico di Milano, Department of Energy, Nuclear Engineering Division - CeSNEF, Milano (Italy); Schubert, A.; Van Uffelen, P. [European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe (Germany); Haeck, W. [Institute de Radioprotection et de Surete Nucleaire, Fontenay-aux-Roses (France)

    2009-06-15

    TRANSURANUS is a computer code for the thermal and mechanical analysis of fuel rods in nuclear reactors. As part of the code, the TUBRNP model calculates the local concentration of the actinides (U, Pu, Am, Cm), the main fission products (Xe, Kr, Cs and Nd) and {sup 4}He produced during the irradiation as a function of the radial position across a fuel pellet (radial profiles). These local quantities are required for the determination of the local power density, the local burn-up, and the source term of fission products and other inert gases. In previous works the neutronic code ALEPH has been used to validate the models for the actinides and fission products concentrations in UO{sub 2} fuels. A similar approach has been adopted in the present work for verifying the Helium production. The present paper focuses on the modelling of the Helium production in PWR oxide fuels (MOX and UO{sub 2}). A reliable prediction of the Helium production and release in LWR oxide fuels is of great interest in case of increasing burn-up, linear heat generation rates and Plutonium content. The contribution of the Helium released plays a fundamental role in the gap pressure and subsequently in the mechanical behaviour of the fuel rod, in particular during the storage of the high burn-up spent fuel. Helium is produced in oxide fuels by three main paths: (i) alpha decay of the actinides (the main contribution is due to {sup 242}Cm, {sup 238}Pu and {sup 244}Cm); (ii) (n,{alpha}) reactions; and (iii) ternary fission. In the present work, the contributions due to ternary fission and the (n,{alpha}) reaction on {sup 16}O as well as some refinements in the {sup 241}Am burn-up chain have been included in TUBRNP. The VESTA neutronic code has been used for the validation of the He production model. The generic VESTA Monte Carlo depletion interface developed at IRSN allows us to couple different Monte Carlo codes with a depletion module. It currently allows for combining the ORIGEN 2.2 isotope

  20. FORTRAN 4 computer program for calculation of thermodynamic and transport properties of complex chemical systems

    Science.gov (United States)

    Svehla, R. A.; Mcbride, B. J.

    1973-01-01

    A FORTRAN IV computer program for the calculation of the thermodynamic and transport properties of complex mixtures is described. The program has the capability of performing calculations such as:(1) chemical equilibrium for assigned thermodynamic states, (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. Condensed species, as well as gaseous species, are considered in the thermodynamic calculation; but only the gaseous species are considered in the transport calculations.

  1. ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS

    Energy Technology Data Exchange (ETDEWEB)

    BAKER, ZACHARY K. [Los Alamos National Laboratory; GOKHALE, MAYA B. [Los Alamos National Laboratory

    2007-01-08

    Shortest path algorithms are a key element of many graph problems. They are used in such applications as online direction finding and navigation, as well as modeling of traffic for large scale simulations of major metropolitan areas. As the shortest path algorithms are an execution bottleneck, it is beneficial to move their execution to parallel hardware such as Field-Programmable Gate Arrays (FPGAs). Hardware implementation is accomplished through the use of a small A core replicated on the order of 20 times on an FPGA device. The objective is to maximize the use of on-board random-access memory bandwidth through the use of multi-threaded latency tolerance. Each shortest path core is responsible for one shortest path calculation, and when it is finished it outputs its result and requests the next source from a queue. One of the innovations of this approach is the use of a small bubble sort core to produce the extract-min function. While bubble sort is not usually considered an appropriate algorithm for any non-trivial usage, it is appropriate in this case as it can produce a single minimum out of the list in O(n) cycles, whwere n is the number of elements in the vertext list. The cost of this min operation does not impact the running time of the architecture, because the queue depth for fetching the next set of edges from memory is roughly equivalent to the number of cores in the system. Additionally, this work provides a collection of simulation results that model the behavior of the node queue in hardware. The results show that a hardware queue, implementing a small bubble-type minimum function, need only be on the order of 16 elements to provide both correct and optimal paths. Because the graph database size is measured in the hundreds of megabytes, the Cray SRAM memory is insufficient. In addition to the A* cores, they have developed a memory management system allowing round-robin servicing of the nodes as well as virtual memory managed over the Hypertransport

  2. Development of a database system for the calculation of indicators of environmental pressure caused by transport

    DEFF Research Database (Denmark)

    Giannouli, Myrsini; Samaras, Zissis; Keller, Mario

    2006-01-01

    The scope of this paper is to summarise a methodology developed for TRENDS (TRansport and ENvironment Database System-TRENDS). The main objective of TRENDS was the calculation of environmental pressure indicators caused by transport. The environmental pressures considered are associated with air...

  3. Transport of bacteriophage PRD1 through saturated clean sand columns as a function of pH and ionic strength

    Science.gov (United States)

    Sadeghi, G.; Schijven, J. F.; Hassanizadeh, S. M.; Behrends, T.; Gerritse, J.

    2010-12-01

    Groundwater is a major source for drinking water, because of its good microbial quality in its natural state as compared with fresh surface water. Nevertheless, it may be contaminated with pathogenic microorganisms, especially viruses, and that may hamper drinking water production. The two most significant processes controlling virus mobility in the subsurface environment are virus attachment and inactivation. Based on previous studies, many factors have been identified that impact these processes, among them, pH and ionic strength (IS) seem to have the largest influence on virus removal. The objective of this work was to investigate the effects of pH and IS on virus removal in saturated porous media. In addition, it was the objective to determine quantitative relations for these effects. In order to do so, a systematic study was conducted in columns with clean sand under saturated conditions at various pH and IS values within the range of field conditions using bacteriophage PRD1 as a model virus. These experiments were conducted in a 50-cm column with clean quartz sand under saturated conditions and various combinations of pH and ionic strength. Values of pH were 5, 6, 7 and 8 and ionic strength values were 1, 10 and 20 mM. Bacteriophage PRD1 was used as a conservative model virus for virus removal. Attachment, detachment and inactivation rate coefficients were determined from fitting the breakthrough curves. Attachment rate coefficients were found to increase with decreasing pH and increasing ionic strength. Results were used to calculate sticking efficiency values and an empirical formula for it as a function of pH and ionic strength was developed. The applicability of this empirical formula at field scale requires further investigation. Effects of pH and ionic strength on the values of the detachment rate coefficients as well as on inactivation rate coefficients of attached virus particles were also determined but required higher certainty to obtain

  4. Value of gallbladder-preserving partial cholecystectomy in treatment of abnormal gallbladder morphology complicated by sand-like calculous cholecystitis: a reports of 18 cases

    Directory of Open Access Journals (Sweden)

    LIANG Fasheng

    2016-10-01

    Full Text Available Objective To investigate the value of laparoscopic gallbladder-preserving partial cholecystectomy in the treatment of abnormal gallbladder morphology complicated by sand-like calculous cholecystitis. Methods A total of 18 patients with abnormal gallbladder morphology complicated by sand-like calculous cholecystitis who underwent laparoscopic and choledochoscopic partial cholecystectomy in Dalian Friendship Hospital from July 2010 to January 2014 were enrolled. All the patients had abnormal gallbladder morphology manifested as folded gallbladder or adenomyosis, and the lesions were located in the distal end of the gallbladder. Before the surgery, gallbladder contraction test was performed for the diseased part and the normal part of the gallbladder to be preserved. During the surgery, choledochoscopy showed an unobstructed cystic duct and good elasticity in the gallbladder wall, and there was no marked chronic inflammation. After the diseased part of the gallbladder was removed, 4-0 absorbable suture was used for two-layer consecutive suture of the gallbladder. The t-test was used for comparison of continuous data between groups. Results All the patients underwent the surgery successfully. The mean time of operation was 98.0±9.0 minutes, and the mean time to first flatus was 22.8±2.5 hours. The patients were able to get out of the bed and drink water at 6 hours after surgery and to have meals at 24 hours after surgery. They fully recovered and were discharged at 5-7 days after surgery, and no patient experienced the complications such as bile leakage. The patients were followed up for 6-80 months; the patients′ preoperative clinical symptoms disappeared, and there was no recurrence of calculi. At 6-12 months after surgery, the patients experienced compensated cholecystectasis, and there was a significant increase in the mean volume of the gallbladder after surgery (30.29±4.23 cm3 vs 21.72±4.34 cm3, t=-13.00, P<0.001. There was a

  5. Time-dependent diffusion and transport calculations using a finite-element-spherical harmonics method

    Science.gov (United States)

    Aydin, E. D.; Katsimichas, S.; de Oliveira, C. R. E.

    2005-10-01

    In this paper, the finite-element-spherical harmonics (FE-PN) method is applied to the solution of transient Boltzmann transport equation. Firstly, transport and diffusion calculations are obtained for homogeneous and inhomogeneous circular regions. Results are compared in order to show the effects of different absorption coefficient values on the propagation of photons. Significant differences between two theories are shown to occur especially in cases when the absorption is increased. Secondly, to validate the FE-PN method, results from this method are compared with Monte Carlo calculations for different cases. Comparisons show good agreements between FE-transport and Monte Carlo solutions and demonstrate the correctness of the results obtained.

  6. Continuous Energy, Multi-Dimensional Transport Calculations for Problem Dependent Resonance Self-Shielding

    Energy Technology Data Exchange (ETDEWEB)

    T. Downar

    2009-03-31

    The overall objective of the work here has been to eliminate the approximations used in current resonance treatments by developing continuous energy multi-dimensional transport calculations for problem dependent self-shielding calculations. The work here builds on the existing resonance treatment capabilities in the ORNL SCALE code system.

  7. Modeling the simultaneous transport of silver nanoparticles and dissolved silver ions in water-saturated sand columns

    Science.gov (United States)

    Taghavy, A.; Wang, Y.; Mittelman, A.; Becker, M. D.; Pennell, K. D.; Abriola, L. M.

    2011-12-01

    Concerns over the potential adverse impacts of nanosilver particles (nAg) on human health and the environment have arisen based upon their widespread use in various commercial and biomedical products. In addition, in situ dissolution of deposited nAg could enhance its environmental impact through the formation of dissolved silver ion (Ag+) plumes. A hybrid mathematical model is presented that simulates the simultaneous reactive transport of nAg/Ag+ in porous media. The simulator couples a Lagrangian Random Walk-based Particle Tracking (RWPT) method for nAg transport with a conventional Eulerian Finite Differencing (FD) scheme for the reactive transport of dissolved solutes. In the absence of oxidants other than dissolved oxygen (DO), nAg is assumed to dissolve via a cooperative oxidation reaction with DO and proton ions (H+), and dissolution is modeled by a first-order kinetic expression. An existing empirical correlation is implemented for evaluation of the dissolution rate constant from physiochemical characteristics of the system and nanoparticles, including solution pH, particle specific surface area (SSA), and temperature. The hybrid modeling approach enables the consideration of different particle size classes and the associated particle-specific dissolution rates. The utility of simulator is demonstrated by modeling results obtained from nAg/ Ag+ transport studies performed in ca. 10.8-cm long borosilicate glass columns with an inside diameter of 2.5 cm. Three column experiments were performed at a constant flow rate, yielding a particle approach velocity of 7.68±0.04 m/day, at dissolved oxygen concentrations ranging from 1.65 mg/L to 8.99 mg/L. A 3 pore volume pulse of nAg suspension, containing 3.17±0.07 mg/L total Ag and 10mM NaNO3 at pH 7.07, was injected into water-saturated columns packed with washed 40-50 mesh Ottawa sand. Following nAg injection, the columns were flushed with nAg-free background solution for an additional 3 pore volumes, which

  8. Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Ratio of wave- and current-induced shear stress to critical values for oil-sand ball and sediment mobilization

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates...

  9. Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Surf-zone integrated alongshore potential flux for oil-sand balls of varying sizes weighted by probability of wave scenario occurrence

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates...

  10. Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Ratio of wave- and current-induced shear stress to critical values for oil-sand ball and sediment mobilization

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates...

  11. Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Surf-zone integrated alongshore potential flux for oil-sand balls of varying sizes weighted by probability of wave scenario occurrence

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates...

  12. Calculation of transport coefficient profiles in modulation experiments as an inverse problem

    CERN Document Server

    Escande, D F

    2011-01-01

    The calculation of transport profiles from experimental measurements belongs in the category of inverse problems which are known to come with issues of ill-conditioning or singularity. A reformulation of the calculation, the matricial approach, is proposed for periodically modulated experiments, within the context of the standard advection-diffusion model where these issues are related to the vanishing of the determinant of a 2x2 matrix. This sheds light on the accuracy of calculations with transport codes, and provides a path for a more precise assessment of the profiles and of the related uncertainty.

  13. Consequences of light absorptance in calculating electron transport rate of desert and succulent plants

    OpenAIRE

    Stemke, JA; Santiago, LS

    2011-01-01

    The proportional light absorptance by photosynthetic tissue (α) is used with chlorophyll (Chl) fluorescence methods to calculate electron transport rate (ETR). Although a value of α of 0.84 is often used as a standard for calculating ETR, many succulent plant species and species with crassulacean acid metabolism (CAM) have photosynthetic tissues that vary greatly in color or are highly reflective, and could have values of α that differ from 0.84, thus affecting the calculation of ETR. We meas...

  14. Performing three-dimensional neutral particle transport calculations on tera scale computers

    Energy Technology Data Exchange (ETDEWEB)

    Woodward, C S; Brown, P N; Chang, B; Dorr, M R; Hanebutte, U R

    1999-01-12

    A scalable, parallel code system to perform neutral particle transport calculations in three dimensions is presented. To utilize the hyper-cluster architecture of emerging tera scale computers, the parallel code successfully combines the MPI message passing and paradigms. The code's capabilities are demonstrated by a shielding calculation containing over 14 billion unknowns. This calculation was accomplished on the IBM SP ''ASCI-Blue-Pacific computer located at Lawrence Livermore National Laboratory (LLNL).

  15. Effect of adsorbed metals ions on the transport of Zn- and Ni-EDTA complexes in a sand and gravel aquifer

    Science.gov (United States)

    Kent, D.B.; Davis, J.A.; Anderson, L.C.D.; Rea, B.A.; Coston, J.A.

    2002-01-01

    Adsorption, complexation, and dissolution reactions strongly influenced the transport of metal ions complexed with ethylenediaminetetraacetic acid (EDTA) in a predominantly quartz-sand aquifer during two tracer tests conducted under mildly reducing conditions at pH 5.8 to 6.1. In tracer test M89, EDTA complexes of zinc (Zn) and nickel (Ni), along with excess free EDTA, were injected such that the lower portion of the tracer cloud traveled through a region with adsorbed manganese (Mn) and the upper portion of the tracer cloud traveled through a region with adsorbed Zn. In tracer test S89, Ni- and Zn-EDTA complexes, along with excess EDTA complexed with calcium (Ca), were injected into a region with adsorbed Mn. The only discernable chemical reaction between Ni-EDTA and the sediments was a small degree of reversible adsorption leading to minor retardation. In the absence of adsorbed Zn, the injected Zn was displaced from EDTA complexes by iron(III) [Fe(III)] dissolved from the sediments. Displacement of Zn by Fe(III) on EDTA became increasingly thermodynamically favorable with decreasing total EDTA concentration. The reaction was slow compared to the time-scale of transport. Free EDTA rapidly dissolved aluminum (Al) from the sediments, which was subsequently displaced slowly by Fe. In the portion of tracer cloud M89 that traveled through the region contaminated with adsorbed Zn, little displacement of Zn complexed with EDTA was observed, and Al was rapidly displaced from EDTA by Zn desorbed from the sediments, in agreement with equilibrium calculations. In tracer test S89, desorption of Mn dominated over the more thermodynamically favorable dissolution of Al oxyhydroxides. Comparison with results from M89 suggests that dissolution of Al oxyhydroxides in coatings on these sediment grains by Ca-EDTA was rate-limited whereas that by free EDTA reached equilibrium on the time-scale of transport. Rates of desorption are much faster than rates of dissolution of Fe

  16. Shielding calculation and criticality safety analysis of spent fuel transportation cask in research reactors.

    Science.gov (United States)

    Mohammadi, A; Hassanzadeh, M; Gharib, M

    2016-02-01

    In this study, shielding calculation and criticality safety analysis were carried out for general material testing reactor (MTR) research reactors interim storage and relevant transportation cask. During these processes, three major terms were considered: source term, shielding, and criticality calculations. The Monte Carlo transport code MCNP5 was used for shielding calculation and criticality safety analysis and ORIGEN2.1 code for source term calculation. According to the results obtained, a cylindrical cask with body, top, and bottom thicknesses of 18, 13, and 13 cm, respectively, was accepted as the dual-purpose cask. Furthermore, it is shown that the total dose rates are below the normal transport criteria that meet the standards specified.

  17. COMET-PE: an incident fluence response expansion transport method for radiotherapy calculations

    Science.gov (United States)

    Hayward, Robert M.; Rahnema, Farzad

    2013-05-01

    Accurate dose calculation is a central component of radiotherapy treatment planning. A new method of dose calculation has been developed based on transport theory and validated by comparison to Monte Carlo methods. The coarse mesh transport method has been extended to allow coupled photon-electron transport in 3D. The method combines stochastic pre-computation with a deterministic solver to achieve high accuracy and precision. To enhance the method for radiotherapy calculations, a new angular basis was derived, and an analytical source treatment was developed. Validation was performed by comparison to DOSXYZnrc using a heterogeneous interface phantom composed of water, aluminum, and lung. Calculations of both kinetic energy released per unit mass and dose were compared. Good agreement was found with a maximum error and root mean square relative error of less than 1.5% for all cases. The results show that the new method achieves an accuracy comparable to Monte Carlo.

  18. Calculation of transport coefficients of air-water vapor mixtures thermal plasmas used in circuit breakers

    Directory of Open Access Journals (Sweden)

    KOHIO Niéssan

    2014-12-01

    Full Text Available In this paper we calculate the transport coefficients of plasmas formed by air and water vapor mixtures. The calculation, which assume local thermodynamic equilibrium (LTE are performed in the temperature range from 500 to 12000 K. We use the Gibbs free energy minimization method to determine the equilibrium composition of the plasmas, which is necessary to calculate the transport coefficients. We use the Chapman-Enskog method to calculate the transport coefficients. The results are presented and discussed according to the rate of water vapor. The results of the total thermal conductivity and electrical conductivity show in particular that the increasing of the rate of water vapor in air can be interesting for power cut. This could be improve the performance of plasma during current breaking in air contaminate by the water vapor.

  19. Provenance, transport and composition of Dendê Coast beach sands in Bahia, central coast of Brazil

    Directory of Open Access Journals (Sweden)

    Renata Cardia Rebouças

    2011-12-01

    Full Text Available The great physiographic diversity of the Dendê Coast favors the production of different beach sediment types, including bioclastic components. In this study 74 beach samples collected at 2 km intervals were used to evaluate beach sediment composition. For each sample, 300 grains were identified for each grain size class coarser than 0.125 mm, using a binocular microscope. The beach sediments of the Dendê Coast are essentially siliciclastic (80-100%. Quartz is the major component (70-100%. Only at the Tinharé and Boipeba islands bioclasts are major components of beach sands reaching up to 80-100%. These sediments are made up essentially of fragments of Halimeda, reaching percentages up to 70%. Coralline algae and mollusks also contribute significantly to these sediments (up to 30%. The results obtained show that the spatial distribution of the bioclastic components provide important information on the environmental conditions present at the shoreline (energy levels, availability of hard substrates and protected areas, pattern of sediment dispersion and on the sediment sources as well. The composition of the beach sediments on the Dendê Coast reflects the present day environmental conditions and show that these sediments do not experience significant lateral transport. This situation is favored by an impeded longshore transport that characterizes most of the region. Although, in general, the rivers that discharge on the Dendê Coast appear to transport few sediments to the coastal zone, the presence of heavy minerals, micas and feldspars suggests river contributions to the beach sediments. On the other hand, the coral and coralline algae reefs, besides offering a natural protection to the shoreline, also represent an important source of beach sands.A grande diversidade fisiográfica da Costa do Dendê favorece a deposição de diferentes tipos de sedimentos em suas praias, inclusive sedimentos ricos em carbonato de cálcio. Neste estudo 86

  20. Simple stochastic cellular automaton model for starved beds and implications about formation of sand topographic features in terms of sand flux

    Science.gov (United States)

    Endo, Noritaka

    2016-12-01

    A simple stochastic cellular automaton model is proposed for simulating bedload transport, especially for cases with a low transport rate and where available sediments are very sparse on substrates in a subaqueous system. Numerical simulations show that the bed type changes from sheet flow through sand patches to ripples as the amount of sand increases; this is consistent with observations in flume experiments and in the field. Without changes in external conditions, the sand flux calculated for a given amount of sand decreases over time as bedforms develop from a flat bed. This appears to be inconsistent with the general understanding that sand flux remains unchanged under the constant-fluid condition, but it is consistent with the previous experimental data. For areas of low sand abundance, the sand flux versus sand amount (flux-density relation) in the simulation shows a single peak with an abrupt decrease, followed by a long tail; this is very similar to the flux-density relation seen in automobile traffic flow. This pattern (the relation between segments of the curve and the corresponding bed states) suggests that sand sheets, sand patches, and sand ripples correspond respectively to the free-flow phase, congested phase, and jam phase of traffic flows. This implies that sand topographic features on starved beds are determined by the degree of interference between sand particles. Although the present study deals with simple cases only, this can provide a simplified but effective modeling of the more complicated sediment transport processes controlled by interference due to contact between grains, such as the pulsatory migration of grain-size bimodal mixtures with repetition of clustering and scattering.

  1. Effects of the mid-air collision on sand saltation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    As to the fact that the effects of saltating particles’ mid-air collision on the sand transport rate are often neglected in the current theoretical models describing sand saltation movement,expressions to calculate velocity diversity of saltating parti-cles after mid-air collision are presented through collision theory of hard ball in this paper. Then,the theoretical model of the wind blown sand movement at the steady state,taking account of coupled interaction between saltation particles and wind,is combined with the model of the mid-air collision probability to calculate the sal-tating particles’ mass flux at heights,the sand transport rate,and further,their changing rules. The comparison of the results with those when the mid-air collision is not considered suggests that the mass flux at heights and the sand transport rate in this paper are less,and much closer,respectively,to the corresponding experi-mental values. The difference between the sand mass fluxes without and with con-sideration of mid-air collision increases at first,and then decreases as the height increases,exhibiting the stratified characteristics.

  2. Fontainebleau Sand

    DEFF Research Database (Denmark)

    Leth, Caspar Thrane

    2006-01-01

    The report is a summary of results from laboratory tests in the geotechncial research group on Fontainebleau sand.......The report is a summary of results from laboratory tests in the geotechncial research group on Fontainebleau sand....

  3. Guideline of Monte Carlo calculation. Neutron/gamma ray transport simulation by Monte Carlo method

    CERN Document Server

    2002-01-01

    This report condenses basic theories and advanced applications of neutron/gamma ray transport calculations in many fields of nuclear energy research. Chapters 1 through 5 treat historical progress of Monte Carlo methods, general issues of variance reduction technique, cross section libraries used in continuous energy Monte Carlo codes. In chapter 6, the following issues are discussed: fusion benchmark experiments, design of ITER, experiment analyses of fast critical assembly, core analyses of JMTR, simulation of pulsed neutron experiment, core analyses of HTTR, duct streaming calculations, bulk shielding calculations, neutron/gamma ray transport calculations of the Hiroshima atomic bomb. Chapters 8 and 9 treat function enhancements of MCNP and MVP codes, and a parallel processing of Monte Carlo calculation, respectively. An important references are attached at the end of this report.

  4. Development of Waste Acceptance Criteria at 221-U Building: Initial Flow and Transport Scoping Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Freedman, Vicky L.; Zhang, Z. F.; Keller, Jason M.; Chen, Yousu

    2007-05-30

    This report documents numerical flow and transport simulations performed that establish initial waste acceptance criteria for the potential waste streams that may be safely sequestered in the 221-U Building and similar canyon structures. Specifically, simulations were executed to identify the maximum loading of contaminant mass (without respect to volume) that can be emplaced within the 221-U Building with no more than 1 pCi/m2 of contaminant migrating outside the structure within a 1,000 year time period. The initial scoping simulations were executed in one dimension to assess important processes, and then two dimensions to establish waste acceptance criteria. Two monolithic conditions were assessed: (1) a grouted canyon monolith; and (2) a canyon monolith filled with sand, both assuming no cracks or fissures were present to cause preferential transport. A three-staged approach was taken to account for different processes that may impact the amount of contaminant that can be safely sequestered in canyon structure. In the first stage, flow and transport simulations established waste acceptance criteria based on a linear (Kd) isotherm approach. In the second stage, impacts on thermal loading were examined and the differences in waste acceptance criteria quantified. In the third stage of modeling, precipitation/dissolution reactions were considered on the release and transport of the contaminants, and the subsequent impact on the maximum contaminant loading. The reactive transport modeling is considered a demonstration of the reactive transport capability, and shows the importance of its use for future performance predictions once site-specific data have been obtained.

  5. VVER-440 Ex-Core Neutron Transport Calculations by MCNP-5 Code and Comparison with Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Borodkin, Pavel; Khrennikov, Nikolay [Scientific and Engineering Centre for Nuclear and Radiation Safety (SEC NRS) Malaya Krasnoselskaya ul., 2/8, bld. 5, 107140 Moscow (Russian Federation)

    2008-07-01

    Ex-core neutron transport calculations are needed to evaluate radiation loading parameters (neutron fluence, fluence rate and spectra) on the in-vessel equipment, reactor pressure vessel (RPV) and support constructions of VVER type reactors. Due to these parameters are used for reactor equipment life-time assessment, neutron transport calculations should be carried out by precise and reliable calculation methods. In case of RPVs, especially, of first generation VVER-440s, the neutron fluence plays a key role in the prediction of RPV lifetime. Main part of VVER ex-core neutron transport calculations are performed by deterministic and Monte-Carlo methods. This paper deals with precise calculations of the Russian first generation VVER-440 by MCNP-5 code. The purpose of this work was an application of this code for expert calculations, verification of results by comparison with deterministic calculations and validation by neutron activation measured data. Deterministic discrete ordinates DORT code, widely used for RPV neutron dosimetry and many times tested by experiments, was used for comparison analyses. Ex-vessel neutron activation measurements at the VVER-440 NPP have provided space (in azimuth and height directions) and neutron energy (different activation reactions) distributions data for experimental (E) validation of calculated results. Calculational intercomparison (DORT vs. MCNP-5) and comparison with measured values (MCNP-5 and DORT vs. E) have shown agreement within 10-15% for different space points and reaction rates. The paper submits a discussion of results and makes conclusions about practice use of MCNP-5 code for ex-core neutron transport calculations in expert analysis. (authors)

  6. Efficient method for the calculation of dissipative quantum transport in quantum cascade lasers.

    Science.gov (United States)

    Greck, Peter; Birner, Stefan; Huber, Bernhard; Vogl, Peter

    2015-03-09

    We present a novel and very efficient method for calculating quantum transport in quantum cascade lasers (QCLs). It follows the nonequilibrium Green's function (NEGF) framework but sidesteps the calculation of lesser self-energies by replacing them by a quasi-equilibrium expression. This method generalizes the phenomenological Büttiker probe model by taking into account individual scattering mechanisms. It is orders of magnitude more efficient than a fully self-consistent NEGF calculation for realistic devices. We apply this method to a new THz QCL design which works up to 250 K - according to our calculations.

  7. CLEAR (Calculates Logical Evacuation And Response): A Generic Transportation Network Model for the Calculation of Evacuation Time Estimates

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, M. P.; Urbanik, II, T.; Desrosiers, A. E.

    1982-03-01

    This paper describes the methodology and application of the computer model CLEAR (Calculates Logical Evacuation And Response) which estimates the time required for a specific population density and distribution to evacuate an area using a specific transportation network. The CLEAR model simulates vehicle departure and movement on a transportation network according to the conditions and consequences of traffic flow. These include handling vehicles at intersecting road segments, calculating the velocity of travel on a road segment as a function of its vehicle density, and accounting for the delay of vehicles in traffic queues. The program also models the distribution of times required by individuals to prepare for an evacuation. In order to test its accuracy, the CLEAR model was used to estimate evacuatlon tlmes for the emergency planning zone surrounding the Beaver Valley Nuclear Power Plant. The Beaver Valley site was selected because evacuation time estimates had previously been prepared by the licensee, Duquesne Light, as well as by the Federal Emergency Management Agency and the Pennsylvania Emergency Management Agency. A lack of documentation prevented a detailed comparison of the estimates based on the CLEAR model and those obtained by Duquesne Light. However, the CLEAR model results compared favorably with the estimates prepared by the other two agencies.

  8. Boundary-projection acceleration: A new approach to synthetic acceleration of transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Adams, M.L.; Martin, W.R.

    1987-01-01

    We present a new class of synthetic acceleration methods which can be applied to transport calculations regardless of geometry, discretization scheme, or mesh shape. Unlike other synthetic acceleration methods which base their acceleration on P1 equations, these methods use acceleration equations obtained by projecting the transport solution onto a coarse angular mesh only on cell boundaries. We demonstrate, via Fourier analysis of a simple model problem as well as numerical calculations of various problems, that the simplest of these methods are unconditionally stable with spectral radius less than or equal toc/3 (c being the scattering ratio), for several different discretization schemes in slab geometry. 28 refs., 4 figs., 3 tabs.

  9. Metallic impurities induced electronic transport in WSe2: First-principle calculations

    Science.gov (United States)

    Li, Hongping; Liu, Shuai; Huang, Songlei; Zhang, Quan; Li, Changsheng; Liu, Xiaojuan; Meng, Jian; Tian, Yi

    2016-08-01

    Using density functional theory calculations, we have systematically explored the effect of V, Nb and Ta impurities on the electronic transport properties of 2H-WSe2. The formation energies elucidate dopants are preferred to substitute W atoms, and the incorporation of Nb into WSe2 is most thermodynamically favorable. The crystal structures almost hold the pristine WSe2 structure-type in spite of with slightly bond relaxation. More importantly, a pronounced electronic transport behavior has realized in all doped systems, which is mainly triggered by metal impurities. Our calculation suggests chemical doping is an effective way to precisely modulate WSe2 performance for target technological applications.

  10. Saltation of Non-Spherical Sand Particles

    Science.gov (United States)

    Wang, Zhengshi; Ren, Shan; Huang, Ning

    2014-01-01

    Saltation is an important geological process and the primary source of atmospheric mineral dust aerosols. Unfortunately, no studies to date have been able to precisely reproduce the saltation process because of the simplified theoretical models used. For example, sand particles in most of the existing wind sand movement models are considered to be spherical, the effects of the sand shape on the structure of the wind sand flow are rarely studied, and the effect of mid-air collision is usually neglected. In fact, sand grains are rarely round in natural environments. In this paper, we first analyzed the drag coefficients, drag forces, and starting friction wind speeds of sand grains with different shapes in the saltation process, then established a sand saltation model that considers the coupling effect between wind and the sand grains, the effect of the mid-air collision of sand grains, and the effect of the sand grain shape. Based on this model, the saltation process and sand transport rate of non-spherical sand particles were simulated. The results show that the sand shape has a significant impact on the saltation process; for the same wind speed, the sand transport rates varied for different shapes of sand grains by as much as several-fold. Therefore, sand shape is one of the important factors affecting wind-sand movement. PMID:25170614

  11. THE CALCULATION OF THE ENERGY RECOVERY ELECTRIFIED URBAN TRANSPORT DURING THE INSTALLATION DRIVE FOR TRACTION SUBSTATION

    Directory of Open Access Journals (Sweden)

    A. A. Sulim

    2014-01-01

    Full Text Available At present a great attention is paid to increasing of energy efficiency at operated electrified urban transport. Perspective direction for increasing energy efficiency at that type of transport is the application of regenerative braking. For additional increasing of energy efficiency there were suggested the use of capacitive drive on tires of traction substation. One of the main task is the analysis of energy recovery application  with drive and without it.These analysis demonstrated that the calculation algorithms don’t allow in the full volume to carry out calculations of amount and cost of energy recovery without drive and with it. That is why we see the current interest to this topic. The purpose of work is to create methods of algorithms calculation for definite amount and cost of consumed, redundant and recovery energy of electrified urban transport due to definite regime of motion on wayside. There is algorithm developed, which allow to calculate amount and cost of consumed, redundant and recovery energy of electrified urban transport on wayside during the installation capacitive drive at traction substation. On the basis of developed algorithm for the definite regime of wagon motion of subway there were fulfilled the example of energy recovery amount and its cost calculation, among them with limited energy intensity drive, when there are 4 trains on wayside simultaneously.

  12. Improved method for calculating neoclassical transport coefficients in the banana regime

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, M., E-mail: taguchi.masayoshi@nihon-u.ac.jp [College of Industrial Technology, Nihon University, Narashino 275-8576 (Japan)

    2014-05-15

    The conventional neoclassical moment method in the banana regime is improved by increasing the accuracy of approximation to the linearized Fokker-Planck collision operator. This improved method is formulated for a multiple ion plasma in general tokamak equilibria. The explicit computation in a model magnetic field shows that the neoclassical transport coefficients can be accurately calculated in the full range of aspect ratio by the improved method. The some neoclassical transport coefficients for the intermediate aspect ratio are found to appreciably deviate from those obtained by the conventional moment method. The differences between the transport coefficients with these two methods are up to about 20%.

  13. Microwave emulations and tight-binding calculations of transport in polyacetylene

    Science.gov (United States)

    Stegmann, Thomas; Franco-Villafañe, John A.; Ortiz, Yenni P.; Kuhl, Ulrich; Mortessagne, Fabrice; Seligman, Thomas H.

    2017-01-01

    A novel approach to investigate the electron transport of cis- and trans-polyacetylene chains in the single-electron approximation is presented by using microwave emulation measurements and tight-binding calculations. In the emulation we take into account the different electronic couplings due to the double bonds leading to coupled dimer chains. The relative coupling constants are adjusted by DFT calculations. For sufficiently long chains a transport band gap is observed if the double bonds are present, whereas for identical couplings no band gap opens. The band gap can be observed also in relatively short chains, if additional edge atoms are absent, which cause strong resonance peaks within the band gap. The experimental results are in agreement with our tight-binding calculations using the nonequilibrium Green's function method. The tight-binding calculations show that it is crucial to include third nearest neighbor couplings to obtain the gap in the cis-polyacetylene.

  14. Testing Shelter Index and a Simple Wind Speed Parameter to Characterize Vegetation Control of Sand Transport Threshold and Flux

    Science.gov (United States)

    Gillies, John; Nield, Joanna; Nickling, William; Furtak-Cole, Eden

    2013-04-01

    Wind erosion and dust emissions occur in the Chihuahuan Desert surrounding Las Cruces NM from a range of surfaces with different types and amounts of vegetation. Understanding how vegetation modulates these processes remains a research challenge. One important aspect of research is to develop a relationship between a descriptor of the surface roughness that can be used to provide an indication of how susceptible the sediment transport system is to activation by wind. Here we present results from a study that examines the relationship between an index of shelter (distance from a point to the nearest upwind vegetation/vegetation height), as originally proposed by Okin (2008), and particle threshold expressed as a ratio of wind measured at 0.45 times the plant height divided by the wind speed at 17 m, and saltation flux (g cm-2 s-1). Saltation flux was measured using sediment traps positioned 15 cm above the surface and nearby optical gate sensors (Wenglor® model YH03PCT8)measuring saltation activity also placed at a height of 15 cm. The results are used to evaluate shelter index as a parameter to characterize the local winds as influenced by the vegetation and sediment transport conditions (threshold and transport). Wind speed, wind direction, saltation activity and point saltation flux were measured at 35 locations in defined test areas (~13,000 m2) in three vegetation communities: mature mesquite covered nebkha dunes, incipient nebkha dunes dominated by low mesquite plants, and a mature creosote bush area. Measurement positions represent the most open areas, and hence those places most susceptible to wind erosion among the vegetation elements. Shelter index was calculated for each measurement position for each approximately 10 degree wind direction bin using digital elevation models for each site acquired using terrestrial laser scanning.

  15. Calculation of thermodynamic and transport properties of thermal plasmas based on the Cantera software toolkit

    Science.gov (United States)

    Doiron, Charles; Hencken, Kai

    2013-09-01

    Computational fluid-dynamic simulations nowadays play a central role in the development of new gas circuit breakers. For these simulations to be reliable, a good knowledge of the pressure and temperature-dependence of the thermodynamic and transport properties of ionized gases is required. A key ingredient in the calculation of thermodynamic properties of thermal plasmas is the calculation of the chemical equilibrium composition of the gas. The general-purpose, open-source software toolkit Cantera provides most functionality required to carry out such thermodynamic calculations. In this contribution, we explain how we tailored Cantera specifically to calculate material properties of plasmas. The highly modular architecture of this framework made it possible to add support for Debye-Hückel non-ideality corrections in the calculation of the chemical equilibrium mixture, as well as to enable the calculation of the key transport parameters needed in CFD-based electric arc simulations: electrical and thermal conductivity, viscosity, and diffusion coefficients. As an example, we discuss the thermodynamic and transport properties of mixtures of carbon dioxide and copper vapor.

  16. Modeling the transport of shigella in silty and fine sand in shallow aquifers in Caostal area of bonny Niger delta; rivers state of Nigeria

    Directory of Open Access Journals (Sweden)

    Solomon Ndubuisi Eluozo

    2012-11-01

    Full Text Available Modeling the transport of shigella in silty and fine sand formation in shallow aquifer has been developed, the model were generated to monitor the transport of shigella in coastal area of bonny, as coastal environment  there are lots of  influence in the soil formation, the major variable were considered in the development of the theoretical model, this condition were assessed and were integrated , this variables were  considered and it  develop a system that generated the model equation since the microbes are  found to be in exponential phase ,because of high degree of porosity and permeability of the soil formation, the mathematical equation  were found to  consider  these variables to ensure it predict the rate of deposition of shigella in  silty and fine sand formation, the model developed predict the transport of shigella in the coastal area of bonny, Niger Delta area of Nigeria, the model will be one of the baseline to reduce high rate of shigella  in the study area, the study has also provide a design benchmark for practicing  engineers and scientist to ensure that thorough ground are provide by application of the these design model.  

  17. Applicability of the wide-band limit in DFT-based molecular transport calculations

    NARCIS (Netherlands)

    Verzijl, C.J.O.; Seldenthuis, J.S.; Thijssen, J.M.

    2013-01-01

    Transport properties of molecular junctions are notoriously expensive to calculate with ab initio methods, primarily due to the semi-infinite electrodes. This has led to the introduction of different approximation schemes for the electrodes. For the most popular metals used in experiments, such as g

  18. Computer program for calculation of thermodynamic and transport properties of complex chemical systems

    Science.gov (United States)

    Svehla, R. A.; Mcbride, B. J.

    1973-01-01

    Program performs calculations such as chemical equilibrium for assigned thermodynamic states, theoretical rocket performance for both equilibrium and frozen compositions during expansion, incident and reflected shock properties, and Chapman-Jouget detonation properties. Features include simplicity of input and storage of all thermodynamic and transport property data on master tape.

  19. Modeling of the Electro-Mechanical Response of Carbon Nanotubes: Molecular Dynamics and Transport Calculations

    Science.gov (United States)

    Svizhenko, Alexel; Anantram, M. P.; Maiti, Amitesh

    2003-01-01

    This paper presents viewgraphs on the modeling of the electromechanical response of carbon nanotubes, utilizing molecular dynamics and transport calculations. The topics include: 1) Simulations of the experiment; 2) Effect of diameter, length and temperature; and 3) Study of sp3 coordination-"The Table experiment".

  20. Neutron transport calculation for Activation Evaluation for Decommissioning of PET cyclotron Facility

    Science.gov (United States)

    Nobuhara, Fumiyoshi; Kuroyanagi, Makoto; Masumoto, Kazuyoshi; Nakamura, Hajime; Toyoda, Akihiro; Takahashi, Katsuhiko

    2017-09-01

    In order to evaluate the state of activation in a cyclotron facility used for the radioisotope production of PET diagnostics, we measured the neutron flux by using gold foils and TLDs. Then, the spatial distribution of neutrons and induced activity inside the cyclotron vault were simulated with the Monte Calro calculation code for neutron transport and DCHAIN-SP for activation calculation. The calculated results are in good agreement with measured values within factor 3. Therefore, the adaption of the advanced evaluation procedure for activation level is proved to be important for the planning of decommissioning of these facilities.

  1. Microwave emulations and tight-binding calculations of transport in polyacetylene

    Energy Technology Data Exchange (ETDEWEB)

    Stegmann, Thomas, E-mail: stegmann@icf.unam.mx [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Avenida Universidad s/n, 62210 Cuernavaca (Mexico); Franco-Villafañe, John A., E-mail: jofravil@fis.unam.mx [Instituto de Física, Benemérita Universidad Autónoma de Puebla, Apartado Postal J-48, 72570 Puebla (Mexico); Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Avenida Universidad s/n, 62210 Cuernavaca (Mexico); Ortiz, Yenni P. [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Avenida Universidad s/n, 62210 Cuernavaca (Mexico); Kuhl, Ulrich [Université de Nice – Sophia Antipolis, Laboratoire de la Physique de la Matière Condensée, CNRS, Parc Valrose, 06108 Nice (France); Mortessagne, Fabrice, E-mail: fabrice.mortessagne@unice.fr [Université de Nice – Sophia Antipolis, Laboratoire de la Physique de la Matière Condensée, CNRS, Parc Valrose, 06108 Nice (France); Seligman, Thomas H. [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Avenida Universidad s/n, 62210 Cuernavaca (Mexico); Centro Internacional de Ciencias, 62210 Cuernavaca (Mexico)

    2017-01-05

    A novel approach to investigate the electron transport of cis- and trans-polyacetylene chains in the single-electron approximation is presented by using microwave emulation measurements and tight-binding calculations. In the emulation we take into account the different electronic couplings due to the double bonds leading to coupled dimer chains. The relative coupling constants are adjusted by DFT calculations. For sufficiently long chains a transport band gap is observed if the double bonds are present, whereas for identical couplings no band gap opens. The band gap can be observed also in relatively short chains, if additional edge atoms are absent, which cause strong resonance peaks within the band gap. The experimental results are in agreement with our tight-binding calculations using the nonequilibrium Green's function method. The tight-binding calculations show that it is crucial to include third nearest neighbor couplings to obtain the gap in the cis-polyacetylene. - Highlights: • Electronic transport in individual polyacetylene chains is studied. • Microwave emulation experiments and tight-binding calculations agree well. • In long chains a band-gap opens due the dimerization of the chain. • In short chains edge atoms cause strong resonance peaks in the center of the band-gap.

  2. A new approach to calculate the transport matrix in RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Eidelman, Yu.; /Novosibirsk, IYF; Mokhov, N.; Nagaitsev, S.; Solyak, N.; /Fermilab

    2011-03-01

    A realistic approach to calculate the transport matrix in RF cavities is developed. It is based on joint solution of equations of longitudinal and transverse motion of a charged particle in an electromagnetic field of the linac. This field is a given by distribution (measured or calculated) of the component of the longitudinal electric field on the axis of the linac. New approach is compared with other matrix methods to solve the same problem. The comparison with code ASTRA has been carried out. Complete agreement for tracking results for a TESLA-type cavity is achieved. A corresponding algorithm will be implemented into the MARS15 code. A realistic approach to calculate the transport matrix in RF cavities is developed. Complete agreement for tracking results with existed code ASTRA is achieved. New algorithm will be implemented into MARS15 code.

  3. Numerical methods for spin-dependent transport calculations and spin bound states analysis in Rashba waveguides

    CERN Document Server

    Xie, Hang; Sha, Wei E I

    2015-01-01

    Numerical methods are developed in the quantum transport calculations for electron in the waveguides with spin-orbital (Rashba) interaction. The methods are based on a hybrid mode-matching scheme in which the wavefunctions are expressed as the superposition of eigenmodes in the lead regions and in the device region the wavefunction is expressed on the discrete basis. Two versions are presented for the lead without and with the Rashba interaction. In the latter case the eigenmodes are obtained from a quadratic eigenproblem calculation. These methods are suitable for the systems with variable geometries or arbitrary potential profiles. The computation can be effectively accelerated by the sparse matrix technique. We also investigate the Fano-Rashba bound states in the Rashba waveguides by some nonlinear eigenstate calculation. This calculation is based on a mode-matching method and self-consistent results are obtained in our calculations.

  4. A computational approach to calculate the heat of transport of aqueous solutions

    Science.gov (United States)

    Di Lecce, Silvia; Albrecht, Tim; Bresme, Fernando

    2017-01-01

    Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question both theoretically and experimentally. Here we discuss a computational approach to calculate heats of transport of aqueous solutions at finite concentrations, and apply our method to study lithium chloride solutions at concentrations >0.5 M. The heats of transport are significantly different for Li+ and Cl− ions, unlike what is expected at infinite dilution. We find theoretical evidence for the existence of minima in the Soret coefficient of LiCl, where the magnitude of the heat of transport is maximized. The Seebeck coefficient obtained from the ionic heats of transport varies significantly with temperature and concentration. We identify thermodynamic conditions leading to a maximization of the thermoelectric response of aqueous solutions.

  5. Characterization of physical mass transport through oil sands fluid fine tailings in an end pit lake: a multi-tracer study

    Science.gov (United States)

    Dompierre, Kathryn A.; Barbour, S. Lee

    2016-06-01

    Soft tailings pose substantial challenges for mine reclamation due to their high void ratios and low shear strengths, particularly for conventional terrestrial reclamation practices. Oil sands mine operators have proposed the development of end pit lakes to contain the soft tailings, called fluid fine tailings (FFT), generated when bitumen is removed from oil sands ore. End pit lakes would be constructed within mined-out pits with FFT placed below the lake water. However, the feasibility of isolating the underlying FFT has yet to be fully evaluated. Chemical constituents of interest may move from the FFT into the lake water via two key processes: (1) advective-diffusive mass transport with upward pore water flow caused by settling of the FFT; and (2) mixing created by wind events or unstable density profiles through the lake water and upper portion of the FFT. In 2013 and 2014, temperature and stable isotopes of water profiles were measured through the FFT and lake water in the first end pit lake developed by Syncrude Canada Ltd. Numerical modelling was undertaken to simulate these profiles to identify the key mechanisms controlling conservative mass transport in the FFT. Shallow mixing of the upper 1.1 m of FFT with lake water was required to explain the observed temperature and isotopic profiles. Following mixing, the re-establishment of both the temperature and isotope profiles required an upward advective flux of approximately 1.5 m/year, consistent with average FFT settling rates measured at the study site. These findings provide important insight on the ability to sequester soft tailings in an end pit lake, and offer a foundation for future research on the development of end pit lakes as an oil sands reclamation strategy.

  6. Sand supply to beaches

    Science.gov (United States)

    Aagaard, Troels

    2017-04-01

    In most cases, beaches and dunes are built by sand that has been transported onshore from the shoreface. While this has been known for a long time, we are still not able to quantitatively predict onshore sediment transport and sand supply to beaches. Sediment transport processes operating during brief, high-energy stormy conditions - when beaches erode and sand moves offshore - are fairly well known and they can be modelled with a reasonable degree of confidence. However, the slower onshore sand transport leading to beach recovery under low-to-moderate energy conditions - and the reason why beaches and dunes exist in the first place - is not yet well understood. This severely limits our capability to understand and predict coastal behaviour on long time scales, for example in response to changing sea level or wave conditions. This paper will discuss issues and recent developments in sediment transport measurement and prediction on the lower and upper shoreface and into the swash zone. The focus will be on the integration and upscaling of small-scale deterministic process measurements into parametric models that may increase modelling capabilities of coastal behaviour on larger temporal and spatial scales.

  7. Effects of microscopic transport coefficients on fission observables calculated by the Langevin equation

    Science.gov (United States)

    Usang, M. D.; Ivanyuk, F. A.; Ishizuka, C.; Chiba, S.

    2016-10-01

    Nuclear fission is treated by using the Langevin dynamical description with macroscopic and microscopic transport coefficients (mass and friction tensors), and it is elucidated how the microscopic (shell and pairing) effects in the transport coefficients, especially their dependence on temperature, affects various fission observables. We found that the microscopic transport coefficients, calculated by linear response theory, change drastically as a function of temperature: in general, the friction increases with growing temperature while the mass tensor decreases. This temperature dependence brings a noticeable change in the mass distribution and kinetic energies of fission fragments from nuclei around 236U at an excitation energy of 20 MeV. The prescission kinetic energy decreases from 25 MeV at low temperature to about 2.5 MeV at high temperature. In contrast, the Coulomb kinetic energy increases as the temperature increases. Interpolating the microscopic transport coefficients among the various temperatures enabled our Langevin equation to use the microscopic transport coefficients at a deformation-dependent local temperature of the dynamical evolution. This allowed us to compare directly the fission observables of both macroscopic and microscopic calculations, and we found almost identical results under the conditions considered in this work.

  8. Thermally driven hopping and electron transport in amorphous materials from density functional calculations

    Energy Technology Data Exchange (ETDEWEB)

    Abtew, Tesfaye A; Drabold, D A [Department of Physics and Astronomy, Ohio University, Athens, OH 45701-2979 (United States)

    2004-11-10

    In this paper we study electron dynamics and transport in models of amorphous silicon and amorphous silicon hydride. By integrating the time-dependent Kohn-Sham equation, we compute the time evolution of electron states near the gap, and study the spatial and spectral diffusion of these states due to lattice motion. We perform these calculations with a view to developing ab initio hopping transport methods. The techniques are implemented with the ab initio local basis code SIESTA, and may be applicable to molecular, biomolecular and other condensed matter systems.

  9. Coarse mesh methods for the transport calculation in the CRONOS reactor code

    Energy Technology Data Exchange (ETDEWEB)

    Fedon-Magnaud, C.; Lautard, J.J.; Akherraz, B.; Wu, G.J. [Commissariat a l`Energie Atomique, Gif sur Yvette (France)

    1995-12-31

    Homogeneous transport methods have been recently implemented in the kinetic code CRONOS dedicated mainly to PWR calculations. Two different methods are presented. The first one is based on the even parity flux formalism and uses finite element spatial discretization and a discrete ordinates angular approximation; the treatment of the anisotropic scattering is described in detail. The second method uses the odd flux as the main unknown, it is closely connected to nodal methods. This method is used to solve two different problems, the simplified PN equations and the exact transport equation using an angular PN expansion. Numerical results are presented for some standard benchmarks and the methods are compared.

  10. Coarse mesh methods for the transport calculation in the Cronos reactor code

    Energy Technology Data Exchange (ETDEWEB)

    Fedon-Magnaud, C.; Lautard, J.J.; Akherraz, B.; Wu, G.J.

    1995-12-31

    Homogeneous transports methods have been recently implemented in the kinetic code CRONOS dedicated mainly to PWR calculations. Two different methods are presented. The first one is based on the even parity flux formalism and uses finite element spatial discretization and a discrete ordinates angular approximation; the treatment of the anisotropic scattering is described in detail. The second method uses the odd flux as the main unknown, it is closely to nodal methods. This method is used to solve different problems, the simplified PN equations and the exact transport equation using an angular PN expansion. Numerical results are presented for some standard benchmarks and the method are compared. (authors). 18 refs., 3 tabs.

  11. The effect of gamma-ray transport on afterheat calculations for accident analysis

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, S.; Latkowski, J.F.; Sanz, J.

    2000-05-01

    Radioactive afterheat is an important source term for the release of radionuclides in fusion systems under accident conditions. Heat transfer calculations are used to determine time-temperature histories in regions of interest, but the true source term needs to be the effective afterheat, which considers the transport of penetrating gamma rays. Without consideration of photon transport, accident temperatures may be overestimated in others. The importance of this effect is demonstrated for a simple, one-dimensional problem. The significance of this effect depends strongly on the accident scenario being analyzed.

  12. Redox transformations and transport of cesium and iodine (-1, 0, +5) in oxidizing and reducing zones of a sand and gravel aquifer

    Science.gov (United States)

    Fox, P.M.; Kent, D.B.; Davis, J.A.

    2010-01-01

    Tracer tests were performed in distinct biogeochemical zones of a sand and gravel aquifer in Cape Cod, MA, to study the redox chemistry (I) and transport (Cs, I) of cesium and iodine in a field setting. Injection of iodide (I -) into an oxic zone of the aquifer resulted in oxidation of I - to molecular iodine (I2) and iodate (IO3-) over transport distances of several meters. Oxidation is attributed to Mn-oxides present in the sediment. Transport of injected IO 3- and Cs+ was retarded in the mildly acidic oxic zone, with retardation factors of 1.6-1.8 for IO3- and 2.3-4.4for Cs. Cs retardation was likely due to cation exchange reactions. Injection of IO3- into a Fe-reducing zone of the aquifer resulted in rapid and complete reduction to I- within 3 m of transport. The nonconservative behavior of Cs and I observed during the tracer tests underscores the necessity of taking the redox chemistry of I as well as sorption properties of I species and Cs into account when predicting transport of radionuclides (e.g., 129I and 137Cs) in the environment.

  13. Thermal transport across metal silicide-silicon interfaces: First-principles calculations and Green's function transport simulations

    Science.gov (United States)

    Sadasivam, Sridhar; Ye, Ning; Feser, Joseph P.; Charles, James; Miao, Kai; Kubis, Tillmann; Fisher, Timothy S.

    2017-02-01

    Heat transfer across metal-semiconductor interfaces involves multiple fundamental transport mechanisms such as elastic and inelastic phonon scattering, and electron-phonon coupling within the metal and across the interface. The relative contributions of these different transport mechanisms to the interface conductance remains unclear in the current literature. In this work, we use a combination of first-principles calculations under the density functional theory framework and heat transport simulations using the atomistic Green's function (AGF) method to quantitatively predict the contribution of the different scattering mechanisms to the thermal interface conductance of epitaxial CoSi2-Si interfaces. An important development in the present work is the direct computation of interfacial bonding from density functional perturbation theory (DFPT) and hence the avoidance of commonly used "mixing rules" to obtain the cross-interface force constants from bulk material force constants. Another important algorithmic development is the integration of the recursive Green's function (RGF) method with Büttiker probe scattering that enables computationally efficient simulations of inelastic phonon scattering and its contribution to the thermal interface conductance. First-principles calculations of electron-phonon coupling reveal that cross-interface energy transfer between metal electrons and atomic vibrations in the semiconductor is mediated by delocalized acoustic phonon modes that extend on both sides of the interface, and phonon modes that are localized inside the semiconductor region of the interface exhibit negligible coupling with electrons in the metal. We also provide a direct comparison between simulation predictions and experimental measurements of thermal interface conductance of epitaxial CoSi2-Si interfaces using the time-domain thermoreflectance technique. Importantly, the experimental results, performed across a wide temperature range, only agree well with

  14. Parametric HECTR calculations of hydrogen transport and combustion at N Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Payne, A.C. Jr.; Camp, A.L.

    1987-06-01

    This report describes a limited number of parametric calculations of hydrogen transport and combustion in the N Reactor confinement for selected accident sequences. The calculations are performed using the HECTR computer code, which is a lumped-parameter code developed specifically for evaluating hydrogen behavior in reactor containments. A number of parameters are evaluated in this study, including hydrogen source rate, spray effects, and source location. The calculations indicate that mixing within major compartments tends to occur fairly rapidly, but that mixing between compartments can be inhibited in certain situations, resulting in the formation of flammable mixtures. These results are being compared to calculations performed with other computer codes, including a code that uses finite-difference models. United Nuclear Corporation will present the results of these code comparisons in future reports.

  15. One-hundred-nm-scale electronic structure and transport calculations of organic polymers on the K computer

    Science.gov (United States)

    Imachi, Hiroto; Yokoyama, Seiya; Kaji, Takami; Abe, Yukiya; Tada, Tomofumi; Hoshi, Takeo

    2016-12-01

    One-hundred-nm-scale electronic structure calculations were carried out on the K supercomputer by our original simulation code ELSES (http://www.elses.jp/) The present paper reports preliminary results of transport calculations for condensed organic polymers. Large-scale calculations are realized by novel massively parallel order-N algorithms. The transport calculations were carried out as a theoretical extension for the quantum wavepacket dynamics simulation. The method was applied to a single polymer chain and condensed polymers.

  16. Calculation of a plasma HgDyI{sub 3} transport coefficients

    Energy Technology Data Exchange (ETDEWEB)

    Hajji, S.; HadjSalah, S.; Benhalima, A.; Charrada, K. [IPEIM, Unité d' Etude des Milieux Ionisés et Réactifs, 5019 route de Kairouan Monastir (Tunisia); Zissis, G. [Laboratoire Plasma et Conversion d' Énergie, 118 rte Narbonne, Bât3R2, 31062 Toulouse (France)

    2015-05-15

    This work is devoted to the calculation of the chemical composition and transport coefficients of HgDyI{sub 3} plasmas in thermal equilibrium. These calculations are performed for pressures equal to 2MP and for temperatures varying from 1000 to 10 000 K. The thermal and electrical conductivity as well as viscosity have been computed as a function of temperature at different atomic ratios. The computational method proposed by Devoto from the classical formalism described by Hirschfelder et al. [Molecular Theory of Gases and Liquids (John Wiley and Sons, New York, 1954)] is used.

  17. PyTransport: A Python package for the calculation of inflationary correlation functions

    CERN Document Server

    Mulryne, David J

    2016-01-01

    PyTransport constitutes a straightforward code written in C++ together with Python scripts which automatically edit, compile and run the C++ code as a Python module. It has been written for Unix-like systems (OS X and Linux). Primarily the module employs the transport approach to inflationary cosmology to calculate the tree-level power-spectrum and bispectrum of user specified models of multi-field inflation, accounting for all sub and super-horizon effects. The transport method we utilise means only coupled differential equations need to be solved, and the implementation presented here combines the speed of C++ with the functionality and convenience of Python. At present the code is restricted to canonical models. This document details the code and illustrates how to use it with a worked example.

  18. Electronic Transport in Monolayer Graphene with Extreme Physical Deformation: ab Initio Density Functional Calculation

    CERN Document Server

    Gao, Haiyuan; Li, Meijiao; Guo, Zhendong; Chen, Hongshen; Jin, Zhonghe; Yu, Bin

    2011-01-01

    Electronic transport properties of monolayer graphene with extreme physical bending up to 90o angle are studied using ab Initio first-principle calculations. The importance of key structural parameters including step height, curvature radius and bending angle are discussed how they modify the transport properties of the deformed graphene sheet comparing to the corresponding flat ones. The local density of state reveals that energy state modification caused by the physical bending is highly localized. It is observed that the transport properties of bent graphene with a wide range of geometrical configurations are insensitive to the structural deformation in the low-energy transmission spectra, even in the extreme case of bending. The results support that graphene, with its superb electromechanical robustness, could serve as a viable material platform in a spectrum of applications such as photovoltaics, flexible electronics, OLED, and 3D electronic chips.

  19. Ab initio transport calculations of molecular wires with electron-phonon couplings

    Science.gov (United States)

    Hirose, Kenji; Kobayashi, Nobuhiko

    2009-03-01

    Understanding of electron transport through nanostructures becomes important with the advancement of fabrication process to construct atomic-scale devices. Due to the drastic change of transport properties by contact conditions to electrodes in local electric fields, first-principles calculation approaches are indispensable to understand and characterize the transport properties of nanometer-scale molecular devices. Here we study the transport properties of molecular wires between metallic electrodes, especially focusing on the effects of contacts to electrodes and of the electron-phonon interactions. We use an ab initio calculation method based on the scattering waves, which are obtained by the recursion-transfer-matrix (RTM) method, combined with non-equilibrium Green's function (NEGF) method including the electron-phonon scatterings. We find that conductance shows exponential behaviors as a function of the length of molecular wires due to tunneling process determined by the HOMO-LUMO energy gap. From the voltage drop behaviors inside the molecular wires, we show that the contact resistances are dominant source for the bias drop and thus are related to local heating. We will present the electron-phonon coupling effects at contact on the inelastic scattering and discuss on the local heating and local temperature, comparing them with those of metallic atomic wires.

  20. Transport and Retention of CdSe/ZnS Quantum Dots in Saturated Sand: Effects of Organic Ligands, pH and Ionic Strength

    Science.gov (United States)

    Li, Chunyan; Snee, Preston; Darnault, Christophe

    2016-04-01

    The presence of nanomaterials in soil, water, and air systems following their life cycle or accidents and their effects on the environment and public health are inevitable. Ability to forecast the public health and ecological impacts of these nanomaterials encountered in the environment is limited. Therefore, it is critical to be able to predict the fate and transport on nanomaterials in the environment, in particular the subsurface, in order to conduct risk assessments. To assess the transport and retention of nanomaterials in the subsurface environment, we selected quantum dots (QDs). QDs are metal and semiconductor based nanomaterials that are essential to nanoscience and nanotechnology. Understanding the parameters that effect the transport and retention of QDs in the soil water environment is critical. Natural organic ligands are commonly found in soils and impact the soil physico-chemical processes through multifaceted reactions with metal ions present in soil solution and ligand exchange reactions on soil surfaces. Therefore, ligands may modify the surface properties of QDs and effect their stability, transport and retention in the subsurface environment. In this research, size, surface charge, and stability of CdSe/ZnS QDs in water solutions are monitored in batch experiments. The influence of organic ligands (acetate, oxalate, and citrate) on the stability of QDs at different pHs (1.5, 3.5, 5, 7 and 9) and ionic strengths (0.05 and 0.1 M) conditions were examined. The stability and aggregation phenomena of QDs were studied using UV-vis and DLS methods. Parameters from batch studies were selected to establish chemical conditions to be used in transport experiments to produce breakthrough curves and retention profiles in order to characterize the fate and transport of QDs in saturated sand. These transport experiments are essential to understand the mobility and retention processes in porous media where QD interactions with surfaces of heterogeneous

  1. Shelter Index and a simple wind speed parameter to characterize vegetation control of sand transport threshold and Flu

    Science.gov (United States)

    Gillies, J. A.; Nield, J. M.; Nickling, W. G.; Furtak-Cole, E.

    2014-12-01

    Wind erosion and dust emissions occur in many dryland environments from a range of surfaces with different types and amounts of vegetation. Understanding how vegetation modulates these processes remains a research challenge. Here we present results from a study that examines the relationship between an index of shelter (SI=distance from a point to the nearest upwind vegetation/vegetation height) and particle threshold expressed as the ratio of wind speed measured at 0.45 times the mean plant height divided by the wind speed at 17 m when saltation commences, and saltation flux. The results are used to evaluate SI as a parameter to characterize the influence of vegetation on local winds and sediment transport conditions. Wind speed, wind direction, saltation activity and point saltation flux were measured at 35 locations in defined test areas (~13,000 m2) in two vegetation communities: mature streets of mesquite covered nebkhas and incipient nebkhas dominated by low mesquite plants. Measurement positions represent the most open areas, and hence those places most susceptible to wind erosion among the vegetation elements. Shelter index was calculated for each measurement position for each 10° wind direction bin using digital elevation models for each site acquired using terrestrial laser scanning. SI can show the susceptibility to wind erosion at different time scales, i.e., event, seasonal, or annual, but in a supply-limited system it can fail to define actual flux amounts due to a lack of knowledge of the distribution of sediment across the surface of interest with respect to the patterns of SI.

  2. Calculation of the transport and relaxation properties of dilute water vapor

    Science.gov (United States)

    Hellmann, Robert; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa

    2009-07-01

    Transport properties of dilute water vapor have been calculated in the rigid-rotor approximation using four different potential energy hypersurfaces and the classical-trajectory method. Results are reported for shear viscosity, self-diffusion, thermal conductivity, and volume viscosity in the dilute-gas limit for the temperature range of 250-2500 K. Of these four surfaces the CC-pol surface of Bukowski et al. [J. Chem. Phys. 128, 094314 (2008)] is in best accord with the available measurements. Very good agreement is found with the most accurate results for viscosity in the whole temperature range of the experiments. For thermal conductivity the deviations of the calculated values from the experimental data increase systematically with increasing temperature to around 5% at 1100 K. For both self-diffusion and volume viscosity, the much more limited number of available measurements are generally consistent with the calculated values, apart from the lower temperature isotopically labeled diffusion measurements.

  3. Reference neutron transport calculation note for Korea nuclear power plants with 3-loop PWR reactors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung Cheol; Chang, Ki Oak

    1997-05-01

    Reactor pressure vessel (RPV) steels are subjected to neutron irradiation at a temperature of about 290 deg C. This radiation exposure alters the mechanical properties, leading to a shift of the brittle-to-ductile transition temperature toward higher temperatures and to a diminution of the rupture energy as determined by Charpy V-notch tests. This radiation embrittlement is one of the important aging factors of nuclear power plants. U.S. NRC recommended the basic requirements for the determination of the pressure vessel fluence by regulatory guide DG-1025 in order to reduce the uncertainty in the determination of neutron fluence calculation and measurements. The determination of the pressure vessel fluence is based on both calculations and measurements. The fluence prediction is made with a calculation and the measurements are used to qualify the calculational methodology. Because of the importance and the difficulty of these calculations, the method`s qualification by comparison to measurement must be made to ensure a reliable and accurate vessel fluence determination. This reference calculation note is to provide a series of forward and adjoint neutron transport calculations for use in the evaluation of neutron dosimetry from surveillance capsule irradiations at 3-loop PWR reactor as well as for use in the determination of the neutron exposure of the reactor vessel wall in accordance with U.S Regulatory Guide DG-1025 requirements. The calculations of the pressure vessel fluence consist of the following steps; (1) Determination of the geometrical and material input data, (2) Determination of the core neutron source, and (3) Propagation of the neutron fluence from the core to the vessel and into the cavity. (author). 12 tabs., 3 figs., 7 refs.

  4. First principles calculations of solid-state thermionic transport in layered van der Waals heterostructures

    Science.gov (United States)

    Wang, Xiaoming; Zebarjadi, Mona; Esfarjani, Keivan

    2016-08-01

    This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the transport. By adding more phosphorene layers, one can switch from tunneling-dominated transport to thermionic-dominated transport, resulting in transporting more heat per charge carrier, thus, enhancing the cooling coefficient of performance. The use of layered van der Waals heterostructures has two advantages: (a) thermionic transport barriers can be tuned by changing the number of layers, and (b) thermal conductance across these non-covalent structures is very weak. The phonon thermal conductance of the present van der Waals heterostructure is found to be 4.1 MW m-2 K-1 which is one order of magnitude lower than the lowest value for that of covalently-bonded interfaces. The thermionic coefficient of performance for the proposed device is 18.5 at 600 K corresponding to an equivalent ZT of 0.13, which is significant for nanoscale devices. This study shows that layered van der Waals structures have great potential to be used as solid-state energy-conversion devices.This work aims at understanding solid-state energy conversion and transport in layered (van der Waals) heterostructures in contact with metallic electrodes via a first-principles approach. As an illustration, a graphene/phosphorene/graphene heterostructure in contact with gold electrodes is studied by using density functional theory (DFT)-based first principles calculations combined with real space Green's function (GF) formalism. We show that for a monolayer phosphorene, quantum tunneling dominates the

  5. Considerations of beta and electron transport in internal dose calculations. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Bolch, W.E.

    1994-11-01

    The goal of this particular task is to consider, for the first time, the explicit transport of beta particles and photon-generated electrons in the series of six phantoms developed by Cristy and Eckerman (1987) at the Oak Ridge National Laboratory. In their report, ORNL/TM-8381, specific absorbed fractions of energy are reported for phantoms representing the newborn (3.4 kg), the one-year-old (9.8 kg), the five-year-old (19 kg), the ten-year-old (32 kg), the fifteen-year-old/adult female (55-58 kg), and the adult male (70 kg). Radiation transport calculations were performed with the Monte Carlo code ALGAMP which allows photon transport only. In subsequent calculations of radionuclide S values as is done in the MIRDOSE2 computer program, electron absorbed fractions are thus considered to be either unity or zero depending upon whether the source region does or does not equal the target region, respectively.

  6. Critical comparison of electrode models in density functional theory based quantum transport calculations.

    Science.gov (United States)

    Jacob, D; Palacios, J J

    2011-01-28

    We study the performance of two different electrode models in quantum transport calculations based on density functional theory: parametrized Bethe lattices and quasi-one-dimensional wires or nanowires. A detailed account of implementation details in both the cases is given. From the systematic study of nanocontacts made of representative metallic elements, we can conclude that the parametrized electrode models represent an excellent compromise between computational cost and electronic structure definition as long as the aim is to compare with experiments where the precise atomic structure of the electrodes is not relevant or defined with precision. The results obtained using parametrized Bethe lattices are essentially similar to the ones obtained with quasi-one-dimensional electrodes for large enough cross-sections of these, adding a natural smearing to the transmission curves that mimics the true nature of polycrystalline electrodes. The latter are more demanding from the computational point of view, but present the advantage of expanding the range of applicability of transport calculations to situations where the electrodes have a well-defined atomic structure, as is the case for carbon nanotubes, graphene nanoribbons, or semiconducting nanowires. All the analysis is done with the help of codes developed by the authors which can be found in the quantum transport toolbox ALACANT and are publicly available.

  7. Calculation of effective transport properties of partially saturated gas diffusion layers

    Science.gov (United States)

    Bednarek, Tomasz; Tsotridis, Georgios

    2017-02-01

    A large number of currently available Computational Fluid Dynamics numerical models of Polymer Electrolyte Membrane Fuel Cells (PEMFC) are based on the assumption that porous structures are mainly considered as thin and homogenous layers, hence the mass transport equations in structures such as Gas Diffusion Layers (GDL) are usually modelled according to the Darcy assumptions. Application of homogenous models implies that the effects of porous structures are taken into consideration via the effective transport properties of porosity, tortuosity, permeability (or flow resistance), diffusivity, electric and thermal conductivity. Therefore, reliable values of those effective properties of GDL play a significant role for PEMFC modelling when employing Computational Fluid Dynamics, since these parameters are required as input values for performing the numerical calculations. The objective of the current study is to calculate the effective transport properties of GDL, namely gas permeability, diffusivity and thermal conductivity, as a function of liquid water saturation by using the Lattice-Boltzmann approach. The study proposes a method of uniform water impregnation of the GDL based on the "Fine-Mist" assumption by taking into account the surface tension of water droplets and the actual shape of GDL pores.

  8. Computational methods for multiphase equilibrium and kinetics calculations for geochemical and reactive transport applications

    Science.gov (United States)

    Leal, Allan; Saar, Martin

    2016-04-01

    Computational methods for geochemical and reactive transport modeling are essential for the understanding of many natural and industrial processes. Most of these processes involve several phases and components, and quite often requires chemical equilibrium and kinetics calculations. We present an overview of novel methods for multiphase equilibrium calculations, based on both the Gibbs energy minimization (GEM) approach and on the solution of the law of mass-action (LMA) equations. We also employ kinetics calculations, assuming partial equilibrium (e.g., fluid species in equilibrium while minerals are in disequilibrium) using automatic time stepping to improve simulation efficiency and robustness. These methods are developed specifically for applications that are computationally expensive, such as reactive transport simulations. We show how efficient the new methods are, compared to other algorithms, and how easy it is to use them for geochemical modeling via a simple script language. All methods are available in Reaktoro, a unified open-source framework for modeling chemically reactive systems, which we also briefly describe.

  9. Comparison of atmospheric transport calculations over complex terrain using a mobile profiling system and rawinsondes

    Science.gov (United States)

    Cox, Robert M.; Cogan, James; Sontowski, John; Dougherty, Catherine M.; Fry, Richard N., Jr.; Smith, Thomas J.

    2000-12-01

    A comparison of atmospheric transport and dispersion calculations over complex terrain was investigated using a mobile profiling system (MPS) versus standard meteorological balloons. Meteorological and sulfur hexafluoride (SF6) concentration data were collected and used to evaluate the performance of a transport and diffusion model coupled with a mass consistency wind field model. Meteorological data were collected throughout April 1995, and parts of August 1995. Both meteorological and concentration data were measured in December 1995. Once the models were validated, the comparison of performance with different upper-air data were accomplished. The models used included the SCIPUFF (Second-order Closure Integrated Puff) transport and diffusion model and the MINERVE mass consistency wind model. Evaluation of the models was focused primarily on their effectiveness as a short-term (one to four hours) predictive tool. These studies showed how the combination of weather and transport models could be used to help direct emergency response following a hazardous material release. The models were used in tandem to direct the deployment of mobile sensors intended to intercept and measure tracer clouds. The MINERVE model was validated for the specific terrain of interest using April 1995 data. The capability of SCIPUFF driven by realistic three-dimensional wind fields generated by MINERVE is demonstrated using data collected in December 1995.

  10. Equilibrium Limit of Boundary Scattering in Carbon Nanostructures: Molecular Dynamics Calculations of Thermal Transport

    Science.gov (United States)

    Haskins, Justin; Kinaci, Alper; Sevik, Cem; Cagin, Tahir

    2012-01-01

    It is widely known that graphene and many of its derivative nanostructures have exceedingly high reported thermal conductivities (up to 4000 W/mK at 300 K). Such attractive thermal properties beg the use of these structures in practical devices; however, to implement these materials while preserving transport quality, the influence of structure on thermal conductivity should be thoroughly understood. For graphene nanostructures, having average phonon mean free paths on the order of one micron, a primary concern is how size influences the potential for heat conduction. To investigate this, we employ a novel technique to evaluate the lattice thermal conductivity from the Green-Kubo relations and equilibrium molecular dynamics in systems where phonon-boundary scattering dominates heat flow. Specifically, the thermal conductivities of graphene nanoribbons and carbon nanotubes are calculated in sizes up to 3 microns, and the relative influence of boundary scattering on thermal transport is determined to be dominant at sizes less than 1 micron, after which the thermal transport largely depends on the quality of the nanostructure interface. The method is also extended to carbon nanostructures (fullerenes) where phonon confinement, as opposed to boundary scattering, dominates, and general trends related to the influence of curvature on thermal transport in these materials are discussed.

  11. A Wind Tunnel Investigation of the Shear Stress with A Blowing Sand Cloud

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In a blowing sand system,the wind provides the driving forces for the particle movement while the moving particles exert the opposite forces to the wind by extracting its momentum.The wind-sand interaction that can be characterized by shear stress and force exerted on the wind by moving particles results in the modification of wind profiles.Detailed wind pro-files re-adapted to blown sand movement are measured in a wind tunnel for different grain size populations and at differ-ent free-stream wind velocities.The shear stress with a blowing sand cloud and force exerted on the wind by moving par-ticles are calculated from the measured wind velocity profiles.The results suggest that the wind profiles with presence of blowing sand cloud assume convex-upward curves on the u(z)-ln(z) plot compared with the straight lines characterizing the velocity profiles of clean wind,and they can be better fitted by power function than log-linear function.The exponent of the power function ranging from 0.1 to 0.17 tends to increase with an increase in wind velocity but decrease with an increase in particle size.The force per unit volume exerted on the wind by blown sand drift that is calculated based on the empirical power functions for the wind velocity profiles is found to decrease with height.The particle-induced force makes the total shear stress with blowing sand cloud partitioned into air-borne stress that results from the wind velocity gradient and grain-borne stress that results from the upward or downward movement of particles.The air-borne stress in-creases with an increase in height,while the grain-borne stress decreases with an increase in height.The air-borne shear stress at the top of sand cloud layer increases with both wind velocity and grain size,implying that it increases with sand transport rate for a given grain size.The shear stress with a blowing sand cloud is also closely related to the sand transport rate.Both the total shear stress and grain-borne stress on

  12. CppTransport: a platform to automate calculation of inflationary correlation functions

    CERN Document Server

    Seery, David

    2016-01-01

    CppTransport is a numerical platform that can automatically generate and solve the evolution equations for the 2- and 3-point correlation functions (in field space and for the curvature perturbation) for any inflationary model with canonical kinetic terms. It makes no approximations beyond the applicability of tree-level perturbation theory. Given an input Lagrangian, CppTransport performs symbolic calculations to determine the 'Feynman rules' of the model and generates efficient C++ to integrate the correlation functions of interest. It includes a visualization suite that automates extraction of observable quantities from the raw n-point functions and generates high quality plots with minimal manual intervention. It is intended to be used as a collaborative platform, promoting the rapid investigation of models and systematizing their comparison with observation. This guide describes how to install and use the system, and illustrates its use through some simple examples.

  13. Mixed first- and second-order transport method using domain decomposition techniques for reactor core calculations

    Energy Technology Data Exchange (ETDEWEB)

    Girardi, E.; Ruggieri, J.M. [CEA Cadarache, CEA/DEN/CAD/DER/SPRC/LEPH, 13 - Saint-Paul Lez Durance (France)

    2003-07-01

    The aim of this paper is to present the last developments made on a domain decomposition method applied to reactor core calculations. In this method, two kind of balance equation with two different numerical methods dealing with two different unknowns are coupled. In the first part the two balance transport equations (first order and second order one) are presented with the corresponding following numerical methods: Variational Nodal Method and Discrete Ordinate Nodal Method. In the second part, the Multi-Method/Multi-Domain algorithm is introduced by applying the Schwarz domain decomposition to the multigroup eigenvalue problem of the transport equation. The resulting algorithm is then provided. The projection operators used to coupled the two methods are detailed in the last part of the paper. Finally some preliminary numerical applications on benchmarks are given showing encouraging results. (authors)

  14. An approximate framework for quantum transport calculation with model order reduction

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Quan, E-mail: quanchen@eee.hku.hk [Department of Electrical and Electronic Engineering, The University of Hong Kong (Hong Kong); Li, Jun [Department of Chemistry, The University of Hong Kong (Hong Kong); Yam, Chiyung [Beijing Computational Science Research Center (China); Zhang, Yu [Department of Chemistry, The University of Hong Kong (Hong Kong); Wong, Ngai [Department of Electrical and Electronic Engineering, The University of Hong Kong (Hong Kong); Chen, Guanhua [Department of Chemistry, The University of Hong Kong (Hong Kong)

    2015-04-01

    A new approximate computational framework is proposed for computing the non-equilibrium charge density in the context of the non-equilibrium Green's function (NEGF) method for quantum mechanical transport problems. The framework consists of a new formulation, called the X-formulation, for single-energy density calculation based on the solution of sparse linear systems, and a projection-based nonlinear model order reduction (MOR) approach to address the large number of energy points required for large applied biases. The advantages of the new methods are confirmed by numerical experiments.

  15. A calculation program for harvesting and transportation costs of energy wood; Energiapuun korjuun ja kuljetuksen kustannuslaskentaohjelmisto

    Energy Technology Data Exchange (ETDEWEB)

    Kuitto, P.J.

    1996-12-31

    VTT Energy is compiling a large and versatile calculation program for harvesting and transportation costs of energy wood. The work has been designed and will be carried out in cooperation with Metsaeteho and Finntech Ltd. The program has been realised in Windows surroundings using SQLWindows graphical database application development system, using the SQLBase relational database management system. The objective of the research is to intensify and create new possibilities for comparison of the utilization costs and the profitability of integrated energy wood production chains with each other inside the chains

  16. Electronic transport properties of fullerene functionalized carbon nanotubes: Ab initio and tight-binding calculations

    DEFF Research Database (Denmark)

    Fürst, Joachim Alexander; Hashemi, J.; Markussen, Troels

    2009-01-01

    techniques and tight-binding calculations to illustrate these materials' transmission properties and give physical arguments to interpret the numerical results. Specifically, above the Fermi energy we find a strong reduction in electron transmission due to localized states in certain regions of the structure......Fullerene functionalized carbon nanotubes-NanoBuds-form a novel class of hybrid carbon materials, which possesses many advantageous properties as compared to the pristine components. Here, we report a theoretical study of the electronic transport properties of these compounds. We use both ab initio...

  17. An Approximate Framework for Quantum Transport Calculation with Model Order Reduction

    CERN Document Server

    Chen, Quan; Yam, Chiyung; Zhang, Yu; Wong, Ngai; Chen, Guanhua

    2014-01-01

    A new approximate computational framework is proposed for computing the non-equilibrium charge density in the context of the non-equilibrium Green's function (NEGF) method for quantum mechanical transport problems. The framework consists of a new formulation, called the X-formulation, for single-energy density calculation based on the solution of sparse linear systems, and a projection-based nonlinear model order reduction (MOR) approach to address the large number of energy points required for large applied biases. The advantages of the new methods are confirmed by numerical experiments.

  18. Modelling of turbulent impurity transport in fusion edge plasmas using measured and calculated ionization cross sections

    CERN Document Server

    Kendl, Alexander

    2014-01-01

    Turbulent transport of trace impurities impurities in the edge and scrape-off-layer of tokamak fusion plasmas is modelled by three dimensional electromagnetic gyrofluid computations including evolution of plasma profile gradients. The source function of impurity ions is dynamically computed from pre-determined measured and calculated electron impact ionization cross section data. The simulations describe the generation and further passive turbulent E-cross-B advection of the impurities by intermittent fluctuations and coherent filamentary structures (blobs) across the scrape-off-layer.

  19. Assessment model validity document. NAMMU: A program for calculating groundwater flow and transport through porous media

    Energy Technology Data Exchange (ETDEWEB)

    Cliffe, K.A.; Morris, S.T.; Porter, J.D. [AEA Technology, Harwell (United Kingdom)

    1998-05-01

    NAMMU is a computer program for modelling groundwater flow and transport through porous media. This document provides an overview of the use of the program for geosphere modelling in performance assessment calculations and gives a detailed description of the program itself. The aim of the document is to give an indication of the grounds for having confidence in NAMMU as a performance assessment tool. In order to achieve this the following topics are discussed. The basic premises of the assessment approach and the purpose of and nature of the calculations that can be undertaken using NAMMU are outlined. The concepts of the validation of models and the considerations that can lead to increased confidence in models are described. The physical processes that can be modelled using NAMMU and the mathematical models and numerical techniques that are used to represent them are discussed in some detail. Finally, the grounds that would lead one to have confidence that NAMMU is fit for purpose are summarised.

  20. Calculation of the transport properties of carbon dioxide. II. Thermal conductivity and thermomagnetic effects

    Science.gov (United States)

    Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa

    2004-05-01

    The transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory method. Results are reported in the dilute-gas limit for thermal conductivity and thermomagnetic coefficients for temperatures ranging from 200 K to 1000 K. Three recent carbon dioxide potential energy hypersurfaces have been investigated. Since thermal conductivity is influenced by vibrational degrees of freedom, not included in the rigid-rotor classical trajectory calculation, a correction for vibration has also been employed. The calculations indicate that the second-order thermal conductivity corrections due to the angular momentum polarization (Bukowski et al. (1999) are in good agreement with the available experimental data. They underestimate the best experimental data at room temperature by 1% and in the range up to 470 K by 1%-3%, depending on the data source. Outside this range the calculated values, we believe, may be more reliable than the currently available experimental data. Our results are consistent with measurements of the thermomagnetic effect at 300 K only when the vibrational degrees of freedom are considered fully. This excellent agreement for these properties indicates that particularly the potential surface of Bukowski et al. provides a realistic description of the anisotropy of the surface.

  1. Hydrodynamic calculation of a filter sand bed type used in the containment venting systems; Calculo hidrodinamico de un filtro tipo lecho de arena usado en los sistemas de venteo de la contencion

    Energy Technology Data Exchange (ETDEWEB)

    Cuevas V, D.; Sainz M, E.; Ortiz V, J., E-mail: delfy.cu@gmail.com [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2015-09-15

    The filtered venting of the containment has been adopted in European countries to mitigate the consequences of excess pressure containment during a severe accident. When venting has taken place, the fission products are released directly into the environment, unless a filter on the same path is placed, so that various types of filters are used to trap the fission products. The venting filters of the containment currently installed use different filtration technologies that involve more than one medium. Those using water as the first stage of filtration are called wet systems and are equipped with additional steps to remove water drops and fine aerosols emissions. And even they may also be equipped with an element containing certain absorption means for the filtration of gaseous iodine species. Other designs based on filtration of deep bed as the primary retention step; called dry filters, use filtration media of metal fiber, ceramic or sand to trap aerosols. This paper evaluates the hydraulic characteristics of the filter sand bed type designed by EDF as a candidate to be installed in the containment of BWR Mark II (type of primary containment of the nuclear power plant of Laguna Verde). The evaluation of filter sand bed type was performed using the software package of open source OpenFOAM. Models of each zone of the filtered device were generated and through a series of parametric calculations of computational fluid mechanics relevant hydrodynamic characteristics of the device were obtained, such as pressure drops against mass flow rate and pressure fields and speed at different operating conditions. On the other hand, the model validation of the sand bed filter when comparing the results of experimental tests on a sand column of PITEAS program (1985-1986) against OpenFOAM simulation was realized. The results are very close to those obtained experimentally. (Author)

  2. Effects of the Magnus and Saffman forces on the saltation trajectories of sand grain

    Science.gov (United States)

    Zou, Xue-Yong; Cheng, Hong; Zhang, Chun-Lai; Zhao, Yan-Zhi

    2007-10-01

    Saltating sand grains are the primary component of airborne sand and account for 75% of all sand transport flux. The saltation height and horizontal distance traveled by sand grains are key factors in sand-control engineering. In addition to gravity and aerodynamic drag, the Magnus and Saffman forces also play important roles in saltation. To quantify the magnitudes of these forces in saltation we used high-speed multi-flash photography to observe the movement of saltating sand grains in a wind tunnel; this proved to be an efficient technique for determining the movement and rotational velocities of grains of natural sand with grain sizes ranging from 0.2 to 0.3 mm and shear velocities ( u*) of 0.67, 0.83, and 0.87 m s - 1 . The rotational speed of saltating sand grains varied between 200 and 800 rev s - 1 ; mean clockwise and anticlockwise rotational speeds were nearly identical, and both increased with increasing saltation height. With saltation heights divided into 1 cm intervals, the rotational speeds followed a Lorentzian distribution. Calculations based on a saltation model showed that the maximum increases in saltation height and in horizontal distance due to the Magnus force were 10.2 and 24.9%, respectively. The rate of increase of both parameters increased with increasing lift-off angle. The maximum increases in saltation height and horizontal distance of sand grains caused by the Saffman force were only 4.6% and 3.7%, respectively.

  3. Proper orthogonal decomposition and wavelet methods for noise reduction in particle-based transport calculations

    Science.gov (United States)

    Nguyen van Ye, Romain; Del-Castillo-Negrete, Diego; Spong, D.; Hirshman, S.; Farge, M.

    2008-11-01

    A limitation of particle-based transport calculations is the noise due to limited statistical sampling. Thus, a key element for the success of these calculations is the development of efficient denoising methods. Here we discuss denoising techniques based on Proper Orthogonal Decomposition (POD) and Wavelet Decomposition (WD). The goal is the reconstruction of smooth (denoised) particle distribution functions from discrete particle data obtained from Monte Carlo simulations. In 2-D, the POD method is based on low rank truncations of the singular value decomposition of the data. For 3-D we propose the use of a generalized low rank approximation of matrices technique. The WD denoising is based on the thresholding of empirical wavelet coefficients [Donoho et al., 1996]. The methods are illustrated and tested with Monte-Carlo particle simulation data of plasma collisional relaxation including pitch angle and energy scattering. As an application we consider guiding-center transport with collisions in a magnetically confined plasma in toroidal geometry. The proposed noise reduction methods allow to achieve high levels of smoothness in the particle distribution function using significantly less particles in the computations.

  4. Comparison between Measured and Calculated Sediment Transport Rates in North Fork Caspar Creek, California

    Science.gov (United States)

    Kim, T. W.; Yarnell, S. M.; Yager, E.; Leidman, S. Z.

    2015-12-01

    Caspar Creek is a gravel-bedded stream located in the Jackson Demonstration State Forest in the coast range of California. The Caspar Creek Experimental Watershed has been actively monitored and studied by the Pacific Southwest Research Station and California Department of Forestry and Fire Protection for over five decades. Although total annual sediment yield has been monitored through time, sediment transport during individual storm events is less certain. At a study site on North Fork Caspar Creek, cross-section averaged sediment flux was collected throughout two storm events in December 2014 and February 2015 to determine if two commonly used sediment transport equations—Meyer-Peter-Müller and Wilcock—approximated observed bedload transport. Cross-section averaged bedload samples were collected approximately every hour during each storm event using a Helley-Smith bedload sampler. Five-minute composite samples were collected at five equally spaced locations along a cross-section and then sieved to half-phi sizes to determine the grain size distribution. The measured sediment flux values varied widely throughout the storm hydrographs and were consistently less than two orders of magnitude in value in comparison to the calculated values. Armored bed conditions, changing hydraulic conditions during each storm and variable sediment supply may have contributed to the observed differences.

  5. OECD/NEA benchmark for time-dependent neutron transport calculations without spatial homogenization

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Jason, E-mail: jason.hou@ncsu.edu [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Ivanov, Kostadin N. [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Boyarinov, Victor F.; Fomichenko, Peter A. [National Research Centre “Kurchatov Institute”, Kurchatov Sq. 1, Moscow (Russian Federation)

    2017-06-15

    Highlights: • A time-dependent homogenization-free neutron transport benchmark was created. • The first phase, known as the kinetics phase, was described in this work. • Preliminary results for selected 2-D transient exercises were presented. - Abstract: A Nuclear Energy Agency (NEA), Organization for Economic Co-operation and Development (OECD) benchmark for the time-dependent neutron transport calculations without spatial homogenization has been established in order to facilitate the development and assessment of numerical methods for solving the space-time neutron kinetics equations. The benchmark has been named the OECD/NEA C5G7-TD benchmark, and later extended with three consecutive phases each corresponding to one modelling stage of the multi-physics transient analysis of the nuclear reactor core. This paper provides a detailed introduction of the benchmark specification of Phase I, known as the “kinetics phase”, including the geometry description, supporting neutron transport data, transient scenarios in both two-dimensional (2-D) and three-dimensional (3-D) configurations, as well as the expected output parameters from the participants. Also presented are the preliminary results for the initial state 2-D core and selected transient exercises that have been obtained using the Monte Carlo method and the Surface Harmonic Method (SHM), respectively.

  6. Preliminary study on CAD-based method of characteristics for neutron transport calculation

    CERN Document Server

    Chen, Zhen-Ping; Sun, Guang-Yao; Song, Jing; Hao, Li-Juan; Hu, Li-Qin; Wu, Yi-Can

    2013-01-01

    The method of characteristics (MOC) is widely used for neutron transport calculation in recent decades. However, the key problem determining whether MOC can be applied in highly heterogeneous geometry is how to combine an effective geometry modeling method with it. Most of the existing MOC codes conventionally describe the geometry model just by lines and arcs with extensive input data. Thus they have difficulty in geometry modeling and ray tracing for complicated geometries. In this study, a new method making use of a CAD-based automatic modeling tool MCAM which is a CAD/Image-based Automatic Modeling Program for Neutronics and Radiation Transport developed by FDS Team in China was introduced for geometry modeling and ray tracing of particle transport to remove those limitations. The diamond -difference scheme was applied to MOC to reduce the spatial discretization errors of the flat flux approximation. Based on MCAM and MOC, a new MOC code was developed and integrated into SuperMC system, whic h is a Super ...

  7. A GPU-based Monte Carlo dose calculation code for photon transport in a voxel phantom

    Energy Technology Data Exchange (ETDEWEB)

    Bellezzo, M.; Do Nascimento, E.; Yoriyaz, H., E-mail: mbellezzo@gmail.br [Instituto de Pesquisas Energeticas e Nucleares / CNEN, Av. Lineu Prestes 2242, Cidade Universitaria, 05508-000 Sao Paulo (Brazil)

    2014-08-15

    As the most accurate method to estimate absorbed dose in radiotherapy, Monte Carlo method has been widely used in radiotherapy treatment planning. Nevertheless, its efficiency can be improved for clinical routine applications. In this paper, we present the CUBMC code, a GPU-based Mc photon transport algorithm for dose calculation under the Compute Unified Device Architecture platform. The simulation of physical events is based on the algorithm used in Penelope, and the cross section table used is the one generated by the Material routine, als present in Penelope code. Photons are transported in voxel-based geometries with different compositions. To demonstrate the capabilities of the algorithm developed in the present work four 128 x 128 x 128 voxel phantoms have been considered. One of them is composed by a homogeneous water-based media, the second is composed by bone, the third is composed by lung and the fourth is composed by a heterogeneous bone and vacuum geometry. Simulations were done considering a 6 MeV monoenergetic photon point source. There are two distinct approaches that were used for transport simulation. The first of them forces the photon to stop at every voxel frontier, the second one is the Woodcock method, where the photon stop in the frontier will be considered depending on the material changing across the photon travel line. Dose calculations using these methods are compared for validation with Penelope and MCNP5 codes. Speed-up factors are compared using a NVidia GTX 560-Ti GPU card against a 2.27 GHz Intel Xeon CPU processor. (Author)

  8. Effects of kaolinite colloids on Cd²⁺ transport through saturated sand under varying ionic strength conditions: Column experiments and modeling approaches.

    Science.gov (United States)

    Wikiniyadhanee, Rakkreat; Chotpantarat, Srilert; Ong, Say Kee

    2015-11-01

    Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L(-1) of Cd(2+) without kaolinite colloids and 10 mg L(-1) Cd(2+) mixed with 100 mg L(-1) kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd(2+) transport and Cd(2+) co-transported with kaolinite colloids better than the equilibrium model (CD(eq)) (R(2)=0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd(2+) and Cd(2+) mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd(2+) from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd(2+) from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (K(f)) were estimated from HYDRUS-1D of TSM for Cd(2+) transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. K(f) values of Cd(2+) transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd(2+) transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd(2+) in porous media for higher ionic strengths. Furthermore, retardation factors and K(f) values of both Cd(2+) transport and Cd(2+) co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd(2+) sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength. Copyright

  9. Toolkit for high performance Monte Carlo radiation transport and activation calculations for shielding applications in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Serikov, A.; Fischer, U.; Grosse, D.; Leichtle, D.; Majerle, M., E-mail: arkady.serikov@kit.edu [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany)

    2011-07-01

    The Monte Carlo (MC) method is the most suitable computational technique of radiation transport for shielding applications in fusion neutronics. This paper is intended for sharing the results of long term experience of the fusion neutronics group at Karlsruhe Institute of Technology (KIT) in radiation shielding calculations with the MCNP5 code for the ITER fusion reactor with emphasizing on the use of several ITER project-driven computer programs developed at KIT. Two of them, McCad and R2S, seem to be the most useful in radiation shielding analyses. The McCad computer graphical tool allows to perform automatic conversion of the MCNP models from the underlying CAD (CATIA) data files, while the R2S activation interface couples the MCNP radiation transport with the FISPACT activation allowing to estimate nuclear responses such as dose rate and nuclear heating after the ITER reactor shutdown. The cell-based R2S scheme was applied in shutdown photon dose analysis for the designing of the In-Vessel Viewing System (IVVS) and the Glow Discharge Cleaning (GDC) unit in ITER. Newly developed at KIT mesh-based R2S feature was successfully tested on the shutdown dose rate calculations for the upper port in the Neutral Beam (NB) cell of ITER. The merits of McCad graphical program were broadly acknowledged by the neutronic analysts and its continuous improvement at KIT has introduced its stable and more convenient run with its Graphical User Interface. Detailed 3D ITER neutronic modeling with the MCNP Monte Carlo method requires a lot of computation resources, inevitably leading to parallel calculations on clusters. Performance assessments of the MCNP5 parallel runs on the JUROPA/HPC-FF supercomputer cluster permitted to find the optimal number of processors for ITER-type runs. (author)

  10. Volume Transport Stream Function Calculated from World Ocean Atlas 2013 (WOA13-VTSF) and Climatological Wind (NCEI Accession 0138646)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset consists of calculated annual and monthly mean ocean volume transport stream function on 1 degree resolution using the WOA13 (T, S) and corresponding...

  11. Comparison of two numerical modelling codes for hydraulic and transport calculations in the near-field

    Energy Technology Data Exchange (ETDEWEB)

    Kalin, J., E-mail: jan.kalin@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Petkovsek, B., E-mail: borut.petkovsek@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Montarnal, Ph., E-mail: philippe.montarnal@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Genty, A., E-mail: alain.genty@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Deville, E., E-mail: estelle.deville@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Krivic, J., E-mail: jure.krivic@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia); Ratej, J., E-mail: joze.ratej@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia)

    2011-04-15

    In the past years the Slovenian Performance Analysis/Safety Assessment team has performed many generic studies for the future Slovenian low and intermediate level waste repository, most recently a Special Safety Analysis for the Krsko site. The modelling approach was to split the problem into three parts: near-field (detailed model of the repository), far-field (i.e., geosphere) and biosphere. In the Special Safety Analysis the code used to perform the near-field calculations was Hydrus2D. Recently the team has begun a cooperation with the French Commisariat al'Energie Atomique/Saclay (CEA/Saclay) and, as a part of this cooperation, began investigations into using the Alliances numerical platform for near-field calculations in order to compare the overall approach and calculated results. The article presents the comparison between these two codes for a silo-type repository that was considered in the Special Safety Analysis. The physical layout and characteristics of the repository are presented and a hydraulic and transport model of the repository is developed and implemented in Alliances. Some analysis of sensitivity to mesh fineness and to simulation timestep has been preformed and is also presented. The compared quantity is the output flux of radionuclides on the boundary of the model. Finally the results from Hydrus2D and Alliances are compared and the differences and similarities are commented.

  12. Transport calculation of thermal and cold neutrons using NMTC/JAERI-MCNP4A code system

    Energy Technology Data Exchange (ETDEWEB)

    Iga, Kiminori [Kyushu Univ., Fukuoka (Japan); Takada, Hiroshi; Nagao, Tadashi

    1998-01-01

    In order to investigate the applicability of the NMTC/JAERI-MCNP4A code system to the neutronics design study in the neutron science research project of JAERI, transport calculations of thermal and cold neutrons are performed with the code system on a spallation neutron source composed of light water cooled tantalum target with a moderator and a reflector system. The following neutronic characteristics are studied in the calculation : the variation of the intensity of neutrons emitted from a light water moderator or a liquid hydrogen with/without the B{sub 4}C decoupler, which are installed to produce sharp pulse, and that dependent on the position of external source neutrons in the tantalum target. The calculated neutron energy spectra are reproduced well by the semi-empirical formula with the parameter values reliable in physical meanings. It is found to be necessary to employ proper importance sampling technique in the statistics. It is confirmed from this work that the NMTC/JAERI-MCNP4A code system is applicable to the neutronics design study of spallation neutron sources proposed for the neutron science research project. (author)

  13. Criticality coefficient calculation for a small PWR using Monte Carlo Transport Code

    Energy Technology Data Exchange (ETDEWEB)

    Trombetta, Debora M.; Su, Jian, E-mail: dtrombetta@nuclear.ufrj.br, E-mail: sujian@nuclear.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Chirayath, Sunil S., E-mail: sunilsc@tamu.edu [Department of Nuclear Engineering and Nuclear Security Science and Policy Institute, Texas A and M University, TX (United States)

    2015-07-01

    Computational models of reactors are increasingly used to predict nuclear reactor physics parameters responsible for reactivity changes which could lead to accidents and losses. In this work, preliminary results for criticality coefficient calculation using the Monte Carlo transport code MCNPX were presented for a small PWR. The computational modeling developed consists of the core with fuel elements, radial reflectors, and control rods inside a pressure vessel. Three different geometries were simulated, a single fuel pin, a fuel assembly and the core, with the aim to compare the criticality coefficients among themselves.The criticality coefficients calculated were: Doppler Temperature Coefficient, Coolant Temperature Coefficient, Coolant Void Coefficient, Power Coefficient, and Control Rod Worth. The coefficient values calculated by the MCNP code were compared with literature results, showing good agreement with reference data, which validate the computational model developed and allow it to be used to perform more complex studies. Criticality Coefficient values for the three simulations done had little discrepancy for almost all coefficients investigated, the only exception was the Power Coefficient. Preliminary results presented show that simple modelling as a fuel assembly can describe changes at almost all the criticality coefficients, avoiding the need of a complex core simulation. (author)

  14. Towards quantitative accuracy in first-principles transport calculations: The GW method applied to alkane/gold junctions

    DEFF Research Database (Denmark)

    Strange, Mikkel; Thygesen, Kristian Sommer

    2011-01-01

    The calculation of the electronic conductance of nanoscale junctions from first principles is a long-standing problem in the field of charge transport. Here we demonstrate excellent agreement with experiments for the transport properties of the gold/alkanediamine benchmark system when electron-el...

  15. Suspended sediment transport response to upstream wash-load supply in the sand-bed reach of the Upper Yellow River, China

    Science.gov (United States)

    Ta, Wanquan; Wang, Haibin; Jia, Xiaopeng

    2015-09-01

    Wash load is a major component of suspended sediment transport in the sand-bed reach of the Upper Yellow River, China. This wash load sediment originates from the Loess region, with the high runoff mainly originating from the rock mountains of its upstream basin. These characteristics result in a mismatch between water and sediment sources and a low probability of high runoffs meeting high suspended sediment concentration (SSC) flows. As a result, higher runoff with lower SSC levels (HR-LS) and lower runoff with higher SSC values (HS) occur, whose SSCs do not follow the typical power form for flow discharges, Ci = αQβ, where Ci and Q are SSC and flow discharge, respectively. Here, we modify the traditional power form with an upstream wash-load supply function C1-β to satisfy the relation between the water and wash load sediment concentrations in water-sediment mismatched cases, Ci = αQβC1-β, where C is an input flow's SSC. Using the daily flow discharges and SSCs of nine typical HR-LS flows and 18 HS flows in our study reach from 1960 to 2012, we find that β changes in response to input flow conditions and downstream transport distances. When the downstream transport distance is between 360 and 663.5 km, β varies between 0.3 and 0.6 in a HS input flow condition, while in the HR-LS input flow case, β tends to be greater than 0.6 (between 0.74 and 0.65). The entrainment rate of an HR-LS flow and the deposition rate of an HS flow appear to be asymmetrically balanced, establishing a primary mechanism for channel aggradation and upward fining of floodplains in our study reach.

  16. Calculation of electrical transport properties and electron entanglement in inhomogeneous quantum wires

    Directory of Open Access Journals (Sweden)

    A A Shokri

    2013-10-01

    Full Text Available In this paper, we have investigated the spin-dependent transport properties and electron entanglement in a mesoscopic system, which consists of two semi-infinite leads (as source and drain separated by a typical quantum wire with a given potential. The properties studied include current-voltage characteristic, electrical conductivity, Fano factor and shot noise, and concurrence. The calculations are based on the transfer matrix method within the effective mass approximation. Using the Landauer formalism and transmission coefficient, the dependence of the considered quantities on type of potential well, length and width of potential well, energy of transmitted electron, temperature and the voltage have been theoretically studied. Also, the effect of the above-mentioned factors has been investigated in the nanostructure. The application of the present results may be useful in designing spintronice devices.

  17. A Transport Equation Approach to Green Functions and Self-force Calculations

    CERN Document Server

    Wardell, Barry

    2010-01-01

    In a recent work, we presented the first application of the Poisson-Wiseman-Anderson method of `matched expansions' to compute the self-force acting on a point particle moving in a curved spacetime. The method employs two expansions for the Green function which are respectively valid in the `quasilocal' and `distant past' regimes, and which may be matched together within the normal neighbourhood. In this article, we introduce the method of matched expansions and discuss transport equation methods for the calculation of the Green function in the quasilocal region. These methods allow the Green function to be evaluated throughout the normal neighborhood and are also relevant to a broad range of problems from radiation reaction to quantum field theory in curved spacetime and quantum gravity.

  18. SR97. Data and data uncertainties. Compilation of data and data uncertainties for radionuclide transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Johan [Golder Grundteknik KB (Sweden)

    1999-10-01

    This report concerns integration of data and data uncertainties in the radionuclide transport calculations within the SR 97 project. More specifically the present report: establishes a framework for handling data uncertainty within SR 97, explores uncertainties in the different underlying analyses and information such as inventory, canister life time, solubilities, K{sub d}-values, or different flow related migration parameters, which provide input to the radionuclide release and transport models used, suggests and motivates 'reasonable' input values, and 'pessimistic' input values representing conditions at Aaberg (Aespoe), Beberg (Finnsjoen) and Ceberg (Gideaa) when applicable, for the different models used, suggests 'probabilistic' parameter distributions when underlying data support any distribution. The intention of presenting 'reasonable' estimates is one of illustration - to obtain a view on how the repository system would operate without making overly optimistic or pessimistic assumptions. A pessimistic input datum implies a selection of a parameter value (and conceptual model) within the uncertainty range, which maximises the consequence.

  19. First-principles calculation method for electron transport based on the grid Lippmann-Schwinger equation.

    Science.gov (United States)

    Egami, Yoshiyuki; Iwase, Shigeru; Tsukamoto, Shigeru; Ono, Tomoya; Hirose, Kikuji

    2015-09-01

    We develop a first-principles electron-transport simulator based on the Lippmann-Schwinger (LS) equation within the framework of the real-space finite-difference scheme. In our fully real-space-based LS (grid LS) method, the ratio expression technique for the scattering wave functions and the Green's function elements of the reference system is employed to avoid numerical collapse. Furthermore, we present analytical expressions and/or prominent calculation procedures for the retarded Green's function, which are utilized in the grid LS approach. In order to demonstrate the performance of the grid LS method, we simulate the electron-transport properties of the semiconductor-oxide interfaces sandwiched between semi-infinite jellium electrodes. The results confirm that the leakage current through the (001)Si-SiO_{2} model becomes much larger when the dangling-bond state is induced by a defect in the oxygen layer, while that through the (001)Ge-GeO_{2} model is insensitive to the dangling bond state.

  20. Facilitated transport of titanium dioxide nanoparticles via hydrochars in the presence of ammonium in saturated sands: Effects of pH, ionic strength, and ionic composition.

    Science.gov (United States)

    Xu, Nan; Cheng, Xueying; Zhou, Kairong; Xu, Xiaoting; Li, Zuling; Chen, Jianping; Wang, Dongtian; Li, Duo

    2017-09-08

    The widespread use of nanoparticles (NPs) has led to their inevitable introduction into environmental systems. How the existence of hydrochars in crop soils will affect the mobility of nanoparticle titanium dioxide (nTiO2), especially in the presence of ammonium (NH4(+)), remains unknown. Research is needed to study the effects of hydrochars on the transport and retention of nTiO2 and to uncover the mechanisms of these effects on nTiO2 transport. Column experiments with nTiO2 and hydrochars were performed in various electrolyte (NaCl, NH4Cl, and CaCl2) solutions under a controlled pH (6.0 and 8.0). Additionally, the size distributions and scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the NPs were observed. The experimental results suggested that the mobility of the hydrochars was much better than that of nTiO2. Thus, the mobility of nTiO2 was improved upon their attachment to the hydrochars. The facilitated transport of nTiO2 in the presence of hydrochars was stronger at pH8.0 than at pH6.0, and facilitated transport was nearly independent of the electrolyte cation at pH8.0. However, at pH6.0, the facilitated transport in various electrolytes had the following order: NaCl>NH4Cl>CaCl2. The conversion from a completely reversible to a partially irreversible deposition of nTiO2 in sand was induced by the partially irreversible retention of hydrochars, and this phenomenon was more pronounced in the presence of NH4(+) than in the presence of Na(+). In particular, the irreversible deposition of nTiO2-hydrochars was enhanced as the cation concentration increased. The increased irreversible retention of nTiO2 was related to the greater k2 value (irreversible attachment coefficients) on site 2 for hydrochars based on two-site kinetic retention modeling. Thus, there is a potential risk of contaminating crops, soil, and underground water when nTiO2 exists in a hydrochar-amended environment, especially when associated with NH4-N

  1. Towards precise calculation of transport coefficients in the hadron gas. The shear and the bulk viscosities

    CERN Document Server

    Moroz, Oleg N

    2011-01-01

    The shear and the bulk viscosities of the hadron gas at low temperatures are studied in the model with constant elastic cross sections being relativistic generalization of the hard spheres model. One effective radius ${r=0.4 fm}$ is chosen for all elastic collisions. Only elastic collisions are considered which are supposed to be dominant at temperatures ${T\\leq 120-140 MeV}$. The calculations are done in the framework of the Boltzmann equation with the Boltzmann statistics distribution functions and the ideal gas equation of state. The applicability of these approximations is discussed. It's found that the bulk viscosity of the hadron gas is much larger than the bulk viscosity of the pion gas while the shear viscosity is found to be less sensitive to the mass spectrum of hadrons. The constant cross sections and the Boltzmann statistics approximation allows one not only to conduct precise numerical calculations of transport coefficients in the hadron gas but also to obtain some relatively simple relativistic ...

  2. Thermal transport in van der Waals solids from first-principles calculations

    Science.gov (United States)

    Lindroth, Daniel O.; Erhart, Paul

    2016-09-01

    The lattice thermal expansion and conductivity in bulk Mo and W-based transition metal dichalcogenides are investigated by means of density functional and Boltzmann transport theory calculations. To this end, a recent van der Waals density functional (vdW-DF-CX) is employed, which is shown to yield excellent agreement with reference data for the structural parameters. The calculated in-plane thermal conductivity compares well with experimental room-temperature values, when phonon-phonon and isotopic scattering are included. To explain the behavior over the entire available temperature range one must, however, include additional (temperature independent) scattering mechanisms that limit the mean free path. Generally, the primary heat carrying modes have mean free paths of 1 μ m or more, which makes these materials very susceptible to structural defects. The conductivity of Mo- and W-based transition metal dichalcogenides is primarily determined by the chalcogenide species and increases in the order Te-Se-S. While for the tellurides and selenides the transition metal element has a negligible effect, the conductivity of WS2 is notably higher than for MoS2, which may be traced to the much larger phonon band gap of the former. Overall, the present study provides a consistent set of thermal conductivities that reveal chemical trends and constitute the basis for future investigations of van der Waals solids.

  3. A simplified model for calculating atmospheric radionuclide transport and early health effects from nuclear reactor accidents

    Energy Technology Data Exchange (ETDEWEB)

    Madni, I.K. [Brookhaven National Lab., Upton, NY (United States); Cazzoli, E.G.; Khatib-Rahbar, M. [Energy Research, Inc., Rockville, MD (United States)

    1995-11-01

    During certain hypothetical severe accidents in a nuclear power plant, radionuclides could be released to the environment as a plume. Prediction of the atmospheric dispersion and transport of these radionuclides is important for assessment of the risk to the public from such accidents. A simplified PC-based model was developed that predicts time-integrated air concentration of each radionuclide at any location from release as a function of time integrated source strength using the Gaussian plume model. The solution procedure involves direct analytic integration of air concentration equations over time and position, using simplified meteorology. The formulation allows for dry and wet deposition, radioactive decay and daughter buildup, reactor building wake effects, the inversion lid effect, plume rise due to buoyancy or momentum, release duration, and grass height. Based on air and ground concentrations of the radionuclides, the early dose to an individual is calculated via cloudshine, groundshine, and inhalation. The model also calculates early health effects based on the doses. This paper presents aspects of the model that would be of interest to the prediction of environmental flows and their public consequences.

  4. Determination of the solid consumption in the transport of sands in sea beds with gold 198; Determinacion del gasto solido en el transporte de arenas en lechos marinos con oro 198

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez A, G

    1983-07-01

    The study of the movement of sediments in sea beds, is necessary when one plans to build a port. Among the techniques used for this studies, it is the radiotracer balance that gives an useful estimation of the quantity of sediment that it moves per day and by meter (perpendicular to the displacement). The main objectives of this work are: to) to present the characteristics of the obtaining of the used radiotracer, describing details those used safety measures, b) to describe the handling of the radiotracer and it radiological safety, during the transport and injection in the sea bottom, c) description of the detection way and the used equipment, d) to describe the information processing obtained in the field and finally, e) the estimate of the solid consumption and the determination of the direction and speed of displacement of those sediments in the sea bottom, in front of the Tabasco coast, to be used jointly with the information obtained by means of other techniques so that one can make a good planning of the operations of dredging during the construction and later on the maintenance of the Dos Bocas marine terminal. The first step is to obtain the radiotracer that in this case was sand of uniform grain metric, marked superficially with Gold-198. The second step is to transport the sand to the place of interest, to place it in the injection equipment and to deposit it in the sea bottom. The third step is to detect the radiotracer in the sea bed, from a craft that drags a sled, which takes mounted a scintillation detector of sodium iodide activated with thallium NaI(Tl) (probe). The fourth step is to process the field information and to obtain the corresponding results. (Author)

  5. Fluvial Transport Model from Spatial Distribution Analysis of Libyan Desert Glass Mass on the Great Sand Sea (Southwest Egypt: Clues to Primary Glass Distribution

    Directory of Open Access Journals (Sweden)

    Nancy Jimenez-Martinez

    2015-04-01

    Full Text Available Libyan Desert Glass (LDG is a natural silica-rich melted rock found as pieces scattered over the sand and bedrock of the Western Desert of Egypt, northeast of the Gilf Kebir. In this work, a population mixture analysis serves to relate the present spatial distribution of LDG mass density with the Late Oligocene–Early Miocene fluvial dynamics in the Western Desert of Egypt. This was verified from a spatial distribution model that was predicted from the log-normal kriging method using the LDG–mass-dependent transformed variable, Y(x. Both low- and high-density normal populations (–9.2 < Y(x < –3.5 and –3.8 < Y(x < 2.1, respectively were identified. The low-density population was the result of an ordinary fluvial LDG transport/deposition sequence that was active from the time of the melting process, and which lasted until the end of activity of the Gilf River. The surface distribution of the high-density population allowed us to restrict the source area of the melting process. We demonstrate the importance of this geostatistical study in unveiling the probable location of the point where the melting of surficial material occurred and the role of the Gilf River in the configuration of the observed strewn field.

  6. Patch behaviour and predictability properties of modelled finite-amplitude sand ridges on the inner shelf

    NARCIS (Netherlands)

    Vis-star, N.C.; de Swart, H.E.; Calvete, D.

    2008-01-01

    The long-term evolution of shoreface-connected sand ridges is investigated with a nonlinear spectral model which governs the dynamics of waves, currents, sediment transport and the bed level on the inner shelf. Wave variables are calculated with a shoaling-refraction model instead of using a paramet

  7. 3D Monte-Carlo transport calculations of whole slab reactor cores: validation of deterministic neutronic calculation routes

    Energy Technology Data Exchange (ETDEWEB)

    Palau, J.M. [CEA Cadarache, Service de Physique des Reacteurs et du Cycle, Lab. de Projets Nucleaires, 13 - Saint-Paul-lez-Durance (France)

    2005-07-01

    This paper presents how Monte-Carlo calculations (French TRIPOLI4 poly-kinetic code with an appropriate pre-processing and post-processing software called OVNI) are used in the case of 3-dimensional heterogeneous benchmarks (slab reactor cores) to reduce model biases and enable a thorough and detailed analysis of the performances of deterministic methods and their associated data libraries with respect to key neutron parameters (reactivity, local power). Outstanding examples of application of these tools are presented regarding the new numerical methods implemented in the French lattice code APOLLO2 (advanced self-shielding models, new IDT characteristics method implemented within the discrete-ordinates flux solver model) and the JEFF3.1 nuclear data library (checked against JEF2.2 previous file). In particular we have pointed out, by performing multigroup/point-wise TRIPOLI4 (assembly and core) calculations, the efficiency (in terms of accuracy and computation time) of the new IDT method developed in APOLLO2. In addition, by performing 3-dimensional TRIPOLI4 calculations of the whole slab core (few millions of elementary volumes), the high quality of the new JEFF3.1 nuclear data files and revised evaluations (U{sup 235}, U{sup 238}, Hf) for reactivity prediction of slab cores critical experiments has been stressed. As a feedback of the whole validation process, improvements in terms of nuclear data (mainly Hf capture cross-sections) and numerical methods (advanced quadrature formulas accounting validation results, validation of new self-shielding models, parallelization) are suggested to improve even more the APOLLO2-CRONOS2 standard calculation route. (author)

  8. Sand deposit-detecting method and its application in model test of sand flow

    Institute of Scientific and Technical Information of China (English)

    黎伟; 房营光; 莫海鸿; 谷任国; 陈俊生

    2013-01-01

    Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale model test of sand-flow method. The real-time data of sand-deposit height and radius were obtained by the self-developed sand-deposit detectors. The test results show that the detecting method is simple and has high precision. In the use of sand-flow method, the sand-carrying capability of fluid is limited, and sand particles are all transported to the sand-deposit periphery through crater, gap and chutes after the sand deposit formed. The diffusion range of the particles outside the sand-deposit does not exceed 2.0 m. Severe sorting of sand particles is not observed because of the unique oblique-layered depositing process. The temporal and spatial distributions of gap and chutes directly affect the sand-deposit expansion, and the expansion trend of the average sand-deposit radius accords with quadratic time-history curve.

  9. The Relationship Between Shoreline Change and Surf Zone Sand Thickness

    Science.gov (United States)

    Miselis, J. L.; McNinch, J. E.

    2002-12-01

    There is a lack of information concerning surf zone geologic processes and their relationship to shoreline behavior despite the consensus that the two are intimately linked. Variations in sand thickness over a highly irregular migration surface close to the shoreline may influence wave dynamics and sediment transport and thus may be connected to hotspot formation. A nearshore survey, spanning 40km from north of the USACE-FRF pier in Duck, NC to just north of Oregon Inlet, was conducted using an interferometric swath bathymetry system and a chirp sub-bottom profiler. The study was conducted within 1km of the shore (in the surf zone) to investigate the processes that may be responsible for the behavior of shoreline hotspots in the area. The topmost reflector and the seafloor of the seismic profile were digitized and the depth difference between them was calculated. Though no ground truths were done in the survey area, cores collected from just north of the site suggest that the topmost reflector is a pre-modern ravinement surface (cohesive muds with layers of sand and gravel) upon which the Holocene sands migrate. An isopach map was generated and shows that the layer of sand above the first sub-bottom reflector is very thin and in some places, exposed. There are many variables that may influence hotspot behavior, including bar position and wave conditions, however, the purpose of this study is to determine if there is a spatial correlation between a thin or absent (exposed reflector) nearshore sand layer and the presence of a shoreline hotspot. In an area associated with a hotspot approximately 14km south of the USACE-FRF pier in Duck, the maximum thickness of Holocene sands was less than 2.5m. The average thickness was less than 1m (0.705m). Thicknesses that were less than 0.2m were classified as areas where the reflector was exposed and accounted for 5 percent of those calculated. It seems the thin layer of sand may represent a deficient nearshore sand source

  10. Effects of two Asian sand dusts transported from the dust source regions of Inner Mongolia and northeast China on murine lung eosinophilia

    Energy Technology Data Exchange (ETDEWEB)

    He, Miao, E-mail: hemiao.cmu@gmail.com [Environment and Chronic Non-communicable Disease Research Center, College of Public Health, China Medical University, 11001 Shenyang (China); Department of Health Sciences, Oita University of Nursing and Health Sciences, 870-1201 Oita (Japan); Ichinose, Takamichi, E-mail: ichinose@oita-nhs.ac.jp [Department of Health Sciences, Oita University of Nursing and Health Sciences, 870-1201 Oita (Japan); Song, Yuan, E-mail: freude@med.uoeh-u.ac.jp [Department of Immunology and Parasitology, School of Medicine, University of Occupational and Environmental Health, Iseigaoka, Yahata-nishi-ku, Kitakyushu, 807-8555 Fukuoka (Japan); Yoshida, Yasuhiro, E-mail: songyuan1107@163.com [Department of Immunology and Parasitology, School of Medicine, University of Occupational and Environmental Health, Iseigaoka, Yahata-nishi-ku, Kitakyushu, 807-8555 Fukuoka (Japan); Arashidani, Keiichi, E-mail: arashi@snow.ocn.ne.jp [Department of Immunology and Parasitology, School of Medicine, University of Occupational and Environmental Health, Iseigaoka, Yahata-nishi-ku, Kitakyushu, 807-8555 Fukuoka (Japan); Yoshida, Seiichi, E-mail: syoshida@oita-nhs.ac.jp [Department of Health Sciences, Oita University of Nursing and Health Sciences, 870-1201 Oita (Japan); Liu, Boying, E-mail: boyingliu321@gmail.com [Environment and Chronic Non-communicable Disease Research Center, College of Public Health, China Medical University, 11001 Shenyang (China); Department of Health Sciences, Oita University of Nursing and Health Sciences, 870-1201 Oita (Japan); Nishikawa, Masataka, E-mail: mnishi@nies.go.jp [Environmental Chemistry Division, National Institute for Environmental Studies, 305-8506 Tsukuba, Ibaraki (Japan); Takano, Hirohisa, E-mail: htakano@health.env.kyoto-u.ac.jp [Environmental Health Division, Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, Kyoto daigaku-Katsura, Nishikyo-ku, Kyoto 615-8530 (Japan); and others

    2013-11-01

    The quality and quantity of toxic materials adsorbed onto Asian sand dust (ASD) are different based on dust source regions and passage routes. The aggravating effects of two ASDs (ASD1 and ASD2) transported from the source regions of Inner Mongolia and northeast China on lung eosinophilia were compared to clarify the role of toxic materials in ASD. The ASDs contained different amounts of lipopolysaccharides (LPS) and β-glucan (ASD1 < ASD2) and SiO{sub 2} (ASD1 > ASD2). CD-1 mice were instilled intratracheally with ASD1, ASD2 and/or ovalbumin (OVA) four times at 2-week intervals. ASD1 and ASD2 enhanced eosinophil recruitment induced by OVA in the submucosa of the airway, with goblet cell proliferation in the bronchial epithelium. ASD1 and ASD2 synergistically increased OVA-induced eosinophil-relevant cytokines interleukin-5 (IL-5), IL-13 (ASD1 < ASD2) and chemokine eotaxin (ASD1 > ASD2) in bronchoalveolar lavage fluid. ASD2 aggravating effects on lung eosinophilia were greater than ASD1. The role of LPS and β-glucan in ASD2 on the production of pro-inflammatory mediators was assessed using in vitro bone marrow-derived macrophages (BMDMs) from wild type, Toll-like receptor 2-deficient (TLR2 −/−), TLR4 −/−, and MyD88 −/− mice (on Balb/c background). ASD2-stimulated TLR2 −/− BMDMs enhanced IL-6, IL-12, TNF-α, MCP-1 and MIP-1α secretion compared with ASD2-stimulated TLR4 −/− BMDMs. Protein expression from ASD2-stimulated MyD88 −/− BMDM were very low or undetectable. The in vitro results indicate that lung eosinophilia caused by ASD is TLR4 dependent. Therefore, the aggravation of OVA-related lung eosinophilia by ASD may be dependent on toxic substances derived from microbes, such as LPS, rather than SiO{sub 2}. - Highlights: • Asian sand dust (ASD) from the deserts of China causes serious respiratory problems. • The aggravating effects of two ASDs on lung eosinophilia were compared. • The ASDs contained different LPS and β-glucan (ASD1

  11. Transport timescale calculations of sawteeth and helical structures in non-circular tokamak plasmas

    Science.gov (United States)

    Jardin, Stephen; Ferraro, Nate; Breslau, Josh; Chen, Jin

    2012-10-01

    We present results of using the implicit 3D MHD code M3D-C^1 [1,2] to perform 3D nonlinear magnetohydrodynamics calculations of the internal dynamics of a shaped cross-section tokamak plasma that span the timescales associated with ideal and resistive stability as well as parallel and perpendicular transport. We specify the transport coefficients and apply a ``current controller'' that adjusts the boundary loop-voltage to keep the total plasma current fixed. The 3D 2-fluid plasma model advances the magnetic field, velocities, electron and ion temperatures, and plasma density. We find that the plasma either reaches a stationary quasi-helical state in which the central safety factor is approximately unity, or it periodically undergoes either simple or compound sawtooth oscillations [3] with a period that approaches a constant value. By comparing a dee-shaped cross section with an elliptical shaped cross section, it is shown that the plasma shape has a large effect on determining the sawtooth behavior and the associated mode activity. Application to ITER shaped tokamak plasmas predict the magnitude of the 3D boundary deformation as a result of a stationary quasi-helical state forming in the interior. [4pt] [1] J. Breslau, N. Ferraro, S.C. Jardin, Physics of Plasmas 16 092503 (2009) [0pt] [2] S. C. Jardin, N. Ferraro, J. Breslau, J. Chen, Computational Science and Discovery 5 014002 (2012) [0pt] [3] X. von Goeler, W. Stodiek, and N. Sauthoff, Phys. Rev. Lett. 33, 1201 (1974)

  12. Analytical calculations of neutron slowing down and transport in the constant-cross-section problem

    Energy Technology Data Exchange (ETDEWEB)

    Cacuci, D.G.

    1978-04-01

    Aspects of the problem of neutron slowing down and transport in an infinite medium consisting of a single nuclide that scatters elastically and isotropically and has energy-independent cross sections were investigated. The method of singular eigenfunctions was applied to the Boltzmann Equation governing the Laplace transform (with respect to the lethargy variable) of the neutron flux. A new sufficient condition for the convergence of the coefficients of the expansion of the scattering kernel in Legendre polynomials was rigorously derived for this energy-dependent problem. Formulas were obtained for the lethargy-dependent spatial moments of the scalar flux that are valid for medium to large lethargies. Use was made of the well-known connection between the spatial moments of the Laplace-transformed scalar flux and the moments of the flux in the ''eigenvalue space.'' The calculations were aided by the construction of a closed general expression for these ''eigenvalue space'' moments. Extensive use was also made of the methods of combinatorial analysis and of computer evaluation of complicated sequences of manipulations. For the case of no absorption it was possible to obtain for materials of any atomic weight explicit corrections to the age-theory formulas for the spatial moments M/sub 2n/(u) of the scalar flux that are valid through terms of the order of u/sup -5/. The evaluation of the coefficients of the powers of n, as explicit functions of the nuclear mass, represent one of the end products of this investigation. In addition, an exact expression for the second spatial moment, M/sub 2/(u), valid for arbitrary (constant) absorption, was derived. It is now possible to calculate analytically and rigorously the ''age'' for the constant-cross-section problem for arbitrary (constant) absorption and nuclear mass. 5 figures, 1 table.

  13. An approximate calculation of advective gas-phase transport of 14C at Yucca Mountain, Nevada

    Science.gov (United States)

    Knapp, R. B.

    1990-01-01

    A quasilinear partial differential equation, which describes gas-phase transport of a 14C kinematic wave through a porous medium, is derived, its sensitivity to system variables is analyzed and it is applied to one possible release scenarion at the porposed Yucca Mountain, Nevada high-level radioactive waste repository. Advection, isotope exchange between CO 2 in a flowing gas phase and HCO 3- in a static aqueous phase, and radioactive decay are incorporated. The governing equation is solved analytically by the method of characteristics. The mass fraction of 14C in the gas phase,X 14g, is controlled by radioactive decay. The relatively long half-line of 14C, about 5720 years, and the relatively shallow proposed burial depth of the radioactive waste, about 350m, requires significant retardation of the 14C wave velocity for significant reduction in X 14g. 14C wave velocity is most sensitive to temperature and pH which control the distribution of total carbon between gas and liquid phase; the greater the partitioning of carbon into the liquid phase, the greater the retardation of the 14C wave velocity and the greater the ultimate reduction in X 14g from initial conditions. Partitioning of total carbon into the liquid phase is greatest at low temperatures, 8. Increasing water saturation also tends to retard 14C wave velocity but to a lesser extent. The governing equation has been applied using conditions that may possibly occur at the proposed Yucca Mountain repository. Calculations indicate that the 14C wave takes about 5900 years to reach the surface with a X 14g equal to 25 ppm. Diffusion and dispersion are not of major importance for these conditions. These calculations are approximate due to the number of assumptions involved. Discharge of 14C into the gas before the selected time would accelerate wave arrival and increase the amount of 14C reaching the surface.

  14. Sands styrke

    DEFF Research Database (Denmark)

    Jacobsen, H. Moust; Jørgensen, Mogens B.; Poulsen, H. Serup

    1975-01-01

    På grundlag af triaxialforsøg med D=7 og 20 cm og varierende højde på løse og faste lejringer af Blokhussand kan effekten af varierende højde-breddeforhold og spændingsniveau samt skalaeffekten bestemmes. Ved sammenligning med pladeforsøg med overfladelast op til 8 t/m2 kan den almindelige fremga...... fremgangsmåde ved bæreevneberegninger på sand undersøges....

  15. State Representation Approach for Atomistic Time-Dependent Transport Calculations in Molecular Junctions.

    Science.gov (United States)

    Zelovich, Tamar; Kronik, Leeor; Hod, Oded

    2014-08-12

    We propose a new method for simulating electron dynamics in open quantum systems out of equilibrium, using a finite atomistic model. The proposed method is motivated by the intuitive and practical nature of the driven Liouville-von-Neumann equation approach of Sánchez et al. [J. Chem. Phys. 2006, 124, 214708] and Subotnik et al. [J. Chem. Phys. 2009, 130, 144105]. A key ingredient of our approach is a transformation of the Hamiltonian matrix from an atomistic to a state representation of the molecular junction. This allows us to uniquely define the bias voltage across the system while maintaining a proper thermal electronic distribution within the finite lead models. Furthermore, it allows us to investigate complex molecular junctions, including multilead configurations. A heuristic derivation of our working equation leads to explicit expressions for the damping and driving terms, which serve as appropriate electron sources and sinks that effectively "open" the finite model system. Although the method does not forbid it, in practice we find neither violation of Pauli's exclusion principles nor deviation from density matrix positivity throughout our numerical simulations of various tight-binding model systems. We believe that the new approach offers a practical and physically sound route for performing atomistic time-dependent transport calculations in realistic molecular junction models.

  16. Colloid facilitated transport of humic substances in soil: laboratory experiment and modeling calculation.

    Science.gov (United States)

    Dinu, Marina; Moiseenko, Tatyana

    2016-04-01

    An understanding of ability to predict the fate and transport of colloids in soil systems are of great importance in many environmental and industrial applications. Especially, in the case study sizes and zeta potentials of lignin and humus components (as a parameter reflecting the mobility and tread of organic substances). The objects of investigation were water extracts of gleepodzolic soil of European territory of Russia and Western Siberia, as well as humus substances extracted from this soil. In this study, evaluation of size, molecular weight distribution and zeta potential were used to predict the mobility of the organic component fractions of the soil. Fractionation was performed using multistage filtration plant (100 Da) and measuring physic-chemical parameters measured with the Malvern Zetasizer Nano ZSP. Significant differences in the distribution of organic matter on the molecular weight, charge (sign) of the zeta potential and the size of the sample of European Russia in comparison with samples of Western Siberia have been found. Also, laboratory studies have demonstrated of any differences in physicochemical parameters as infrared spectra, ultraviolet spectra, complexing ability of samples of the same soil type but different areas of Russia. The results can be used in the prediction of the migration ability of fractions humus substances and their stability at change physic-chemical conditions (the coefficient of mobility of the organic components by calculated in MathCad). This work was supported by the grant № 14-17-00460 RSF from 07.11.2014

  17. Observations of several characteristics of aeolian sand movement in the Taklimakan Desert

    Institute of Scientific and Technical Information of China (English)

    HAN; Zhiwen; DONG; Zhibao; WANG; Tao; CHEN; Guangting; YAN

    2004-01-01

    With both sides of the Taklimakan Desert highway line as the study area, three typical aeolian sand landforms, i.e. complex dune ridge, barchan dune and flat sand land, were selected as sand beds for the observation, analysis and research of the characteristics of aeolian sand movement such as aeolian sand stream structure, sand transport intensity, etc. in the Taklimakan Desert. The results show that there is a linear relation between the height and the log of sand transport rate over transverse dune chain, longitudinal dune ridge and flat sand land, i.e. the sand transport percentage decreases exponentially with increasing height. Sand transport rate within the 10 cm height above the bed surface accounts for 80%-95% of the total sand transport rate of the observed height (40 cm), while the sand transport rate in 20 cm occupies 98% of the total amount. Sand transport rate (g·cm-1·min-1) differs greatly with respect to different landform types and different topographic positions. Based on the investigation and analysis on aeolian sand landform origin, morphological type and distribution feature, the two typical landform assemblages, complex transverse dune chain-alluvial plain and huge longitudinal dune ridge-interridge lowland in the Taklimakan Desert were divided into several characteristic zones of aeolian sand movement states. From this one can qualitatively judge the types and severities of sand disasters at various topographic positions in the engineering installation region and further put forward concrete schemes and measures to control sand damages.

  18. Development of the Gran Desierto sand sea, northwestern Mexico

    Science.gov (United States)

    Blount, Grady; Lancaster, Nicholas

    1990-08-01

    Three major eolian sand populations can be recognized in the Gran Desierto sand sea of northwestern Mexico by using spectral data from the Landsat thematic mapper in conjunction with textural and mineralogical studies of surface sands. Each sand population has distinct textural, mineralogic, and spectral properties that can be related to sand-dune morphology and position with reference to source areas and transport paths of the sands. The oldest eolian sediment in the sand sea was derived from the early to middle Pleistocene Colorado River that flowed through the area of the western Gran Desierto. Subsequent inputs of eolian sands came from the area of the present Colorado River valley and the coast south of the sand sea. The spatial and temporal pattern of eolian deposition in the region has been controlled by Quaternary tectonic and climatic changes, resulting in the episodic input and deposition of sand.

  19. Tar sand

    Energy Technology Data Exchange (ETDEWEB)

    McLendon, T.R.; Bartke, T.C.

    1990-01-01

    Research on tar sand is briefly discussed. The research program supported by the US Department of Energy (DOE) includes a variety of surface extraction schemes. The University of Utah has process development units (PDU) employing fluidized bed, hot, water-assisted, and fluidized-bed/heat-pipe, coupled combustor technology. Considerable process variable test data have been gathered on these systems: (1) a rotary kiln unit has been built recently; (2) solvent extraction processing is being examined; and (3) an advanced hydrogenation upgrading scheme (hydropyrolysis) has been developed. The University of Arkansas, in collaboration with Diversified Petroleum, Inc., has been working on a fatty acid, solvent extraction process. Oleic acid is the solvent/surfactant. Solvent is recovered by adjusting processing fluid concentrations to separate without expensive operations. Western Research Institute has a PDU-scale scheme called the Recycle Oil Pyrolysis and Extraction (ROPE) process, which combines solvent (hot recycle bitumen) and pyrolytic extraction. 14 refs., 19 figs.

  20. Density functional theory calculations of charge transport properties of ‘plate-like’ coronene topological structures

    Indian Academy of Sciences (India)

    ZIRAN CHEN; ZHANRONG HE; YOUHUI XU; WENHAO YU

    2017-09-01

    Charge transport rate is one of the key parameters determining the performance of organic electronic devices. In this paper, we used density functional theory (DFT) at the M06-2X/6−31+G(d) level to compute the charge transport rates of nine coronene topological structures. The results show that the energy gap of these nine coronene derivatives is in the range 2.90–3.30 eV, falling into the organic semiconductor category. The size of the conjugate ring has a large influence on the charge transport properties. Incorporation of methyl groupson the rigid core of tetrabenzocoronene and hexabenzocoronene is more conducive to the hole transport of the molecule than incorporating methoxyl groups. The derivatisation of a ‘long plate-like’ coronene with methoxylgroups facilitates both hole and electron transport. This class of molecules can thus be used in the design of ambipolar transport semiconductor materials.

  1. It's in the sand

    OpenAIRE

    Mitchell, Clive

    2016-01-01

    Sand is sand isn’t it? Sand gets everywhere but rather than a nuisance it is a valuable, high-purity raw material. Clive Mitchell, Industrial Minerals Specialist at the British Geological Survey (BGS), talks us through what sand is, what it can be used for and how to find it. His exploration of sand takes us from the deserts of Arabia to the damp sand pits of Mansfield!

  2. Improvements in practical applicability of NSHEX: nodal transport calculation code for three-dimensional hexagonal-Z geometry

    Energy Technology Data Exchange (ETDEWEB)

    Sugino, Kazuteru [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1998-07-01

    As a tool to perform a fast reactor core calculations with high accuracy, NSHEX the nodal transport calculation code for three-dimensional hexagonal-Z geometry is under development. To improve the practical applicability of NSHEX, for instance, in its application to safety analysis and commercial reactor core design studies, we investigated the basic theory used in it, improved the program performance, and evaluated its applicability to the analysis of commercial reactor cores. The current studies show the following: (1) An improvement in the treatment of radial leakage in the radial nodal coupling equation bettered calculational convergence for safety analysis calculation, so the applicability of NSHEX to safety analysis was improved. (2) As a result of comparison of results from NSHEX and the standard core calculation code, it was confirmed that there was consistency between them. (3) According to the evaluation of the effect due to the difference of calculational condition, it was found that the calculation under appropriate nodal expansion orders and Sn orders correspond to the one under most detailed condition. However further investigation is required to reduce the uncertainty in calculational results due to the treatment of high order flux moments. (4) A whole core version of NSHEX enabling calculation for any FBR core geometry has been developed, this improved general applicability of NSHEX. (5) An investigation of the applicability of the rebalance method to acceleration clarified that this improved calculational convergence and it was effective. (J.P.N.)

  3. Study of Black Sand Particles from Sand Dunes in Badr, Saudi Arabia Using Electron Microscopy

    Directory of Open Access Journals (Sweden)

    Haider Abbas Khwaja

    2015-08-01

    Full Text Available Particulate air pollution is a health concern. This study determines the microscopic make-up of different varieties of sand particles collected at a sand dune site in Badr, Saudi Arabia in 2012. Three categories of sand were studied: black sand, white sand, and volcanic sand. The study used multiple high resolution electron microscopies to study the morphologies, emission source types, size, and elemental composition of the particles, and to evaluate the presence of surface “coatings or contaminants” deposited or transported by the black sand particles. White sand was comprised of natural coarse particles linked to wind-blown releases from crustal surfaces, weathering of igneous/metamorphic rock sources, and volcanic activities. Black sand particles exhibited different morphologies and microstructures (surface roughness compared with the white sand and volcanic sand. Morphological Scanning Electron Microscopy (SEM and Laser Scanning Microscopy (LSM analyses revealed that the black sand contained fine and ultrafine particles (50 to 500 nm ranges and was strongly magnetic, indicating the mineral magnetite or elemental iron. Aqueous extracts of black sands were acidic (pH = 5.0. Fe, C, O, Ti, Si, V, and S dominated the composition of black sand. Results suggest that carbon and other contaminant fine particles were produced by fossil-fuel combustion and industrial emissions in heavily industrialized areas of Haifa and Yanbu, and transported as cloud condensation nuclei to Douf Mountain. The suite of techniques used in this study has yielded an in-depth characterization of sand particles. Such information will be needed in future environmental, toxicological, epidemiological, and source apportionment studies.

  4. Numerical solver for first-principles transport calculation based on real-space finite-difference method.

    Science.gov (United States)

    Iwase, Shigeru; Hoshi, Takeo; Ono, Tomoya

    2015-06-01

    We propose an efficient procedure to obtain Green's functions by combining the shifted conjugate orthogonal conjugate gradient (shifted COCG) method with the nonequilibrium Green's function (NEGF) method based on a real-space finite-difference (RSFD) approach. The bottleneck of the computation in the NEGF scheme is matrix inversion of the Hamiltonian including the self-energy terms of electrodes to obtain the perturbed Green's function in the transition region. This procedure first computes unperturbed Green's functions and calculates perturbed Green's functions from the unperturbed ones using a mathematically strict relation. Since the matrices to be inverted to obtain the unperturbed Green's functions are sparse, complex-symmetric, and shifted for a given set of sampling energy points, we can use the shifted COCG method, in which once the Green's function for a reference energy point has been calculated the Green's functions for the other energy points can be obtained with a moderate computational cost. We calculate the transport properties of a C(60)@(10,10) carbon nanotube (CNT) peapod suspended by (10,10)CNTs as an example of a large-scale transport calculation. The proposed scheme opens the possibility of performing large-scale RSFD-NEGF transport calculations using massively parallel computers without the loss of accuracy originating from the incompleteness of the localized basis set.

  5. Efficient Ab-Initio Electron Transport Calculations for Heterostructures by the Nonequilibrium Green’s Function Method

    Directory of Open Access Journals (Sweden)

    Hirokazu Takaki

    2014-01-01

    Full Text Available We present an efficient computation technique for ab-initio electron transport calculations based on density functional theory and the nonequilibrium Green’s function formalism for application to heterostructures with two-dimensional (2D interfaces. The computational load for constructing the Green’s functions, which depends not only on the energy but also on the 2D Bloch wave vector along the interfaces and is thus catastrophically heavy, is circumvented by parallel computational techniques with the message passing interface, which divides the calculations of the Green’s functions with respect to energy and wave vectors. To demonstrate the computational efficiency of the present code, we perform ab-initio electron transport calculations of Al(100-Si(100-Al(100 heterostructures, one of the most typical metal-semiconductor-metal systems, and show their transmission spectra, density of states (DOSs, and dependence on the thickness of the Si layers.

  6. Ecological hydraulic radius model to calculate instream flow requirements for transporting sediment in the western water transfer region

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Transporting sediment is a natural function of the river. To maintain the normal evolution of the river certain amount of water flow is required, which is called the instream flow requirements for transporting sediment (IFRTS). We defined the permitting flow velocity by the conception of IFRTS, and also put forward the ecological hydraulic radius model (EHRM) to estimate IFRTS. The calculating process of EHRM is explained by the example of Daofu Hydrological Station on Xianshui branch of Yalong River in the west line first-stage construction of South-North Water Transfer Project. The result shows that the IFRTS occupied 29.7%―59.5% of annual mean discharge in flood season, the average of IFRTS was about 100.2 m3/s during 1966―1987, it is close to the IFRTS 90 m3/s calculated by IFRTS conception. Hence, it is feasible to use EHRM to calculate IFRTS.

  7. EXPERIMENTAL STUDY AND NUMERICAL SIMULATION OF FLUORIDE IN SAND

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-mei; SU Bao-yu

    2006-01-01

    The transport and transformation of fluoride in sand were studied by using soil tank test under the condition of saturated water in this article. Based on the analysis of the laboratory experiments, the rules of fluorine transportation and transformation were simulated in sand by solving the advection-diffusion equation. Through comparison between computed results and observed data , it is shown that the established model and determined parameters could be used to simulate the fluoride transport in sand.

  8. Origins of late- Pleistocene coastal dune sheets, Magdalena and Guerrero Negro, from continental shelf low-stand supply (70-20 ka), under conditions of southeast littoral- and eolian-sand transport, in Baja California Sur, Mexico

    Science.gov (United States)

    Peterson, Curt D.; Murillo-Jiménez, Janette M.; Stock, Errol; Price, David M.; Hostetler, Steve W.; Percy, David

    2017-10-01

    Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km2) and Guerrero Negro (8000 km2) dune sheets, from the Pacific Ocean side of Baja California Sur, Mexico, have been analyzed for dune deposit age. The shallow morpho-stratigraphic sections (∼2-10 m depth) include 11 new TL and 14C ages, and paleosol chronosequences, that differentiate cemented late Pleistocene dune deposits (20.7 ± 2.1 to 99.8 ± 9.4 ka) from uncemented Holocene dune deposits (0.7 ± 0.05 to at least 3.2 ± 0.3 ka). Large linear dune ridges (5-10 m in height) in the dune sheet interiors trend southeast and are generally of late Pleistocene age (∼70-20 ka). The late Pleistocene dune deposits reflect eolian transport of marine sand across the emerged continental shelf (30-50 km southeast distance) from low-stand paleo-shorelines (-100 ± 25 m elevation), which were locally oriented nearly orthogonal to modeled deep-water wave directions (∼300° TN). During the Holocene marine transgression, onshore and alongshore wave transport delivered remobilized shelf-sand deposits to the nearshore areas of the large dune sheets, building extensive barrier islands and sand spits. Submerged back-barrier lagoons generally precluded marine sand supply to dune sheet interiors in middle to late Holocene time, though exceptions occur along some ocean and lagoon shorelines. Reactivation of the late Pleistocene dune deposits in the dune sheet interiors lead to generally thin (1-3 m thickness), but widespread, covers of Holocene dune deposits (0.41 ± 0.05 to 10.5 ± 1.6 ka). Mechanical drilling will be required to penetrate indurated subsoil caliche layers to reach basal Pleistocene dune deposits.

  9. QmeQ 1.0: An open-source Python package for calculations of transport through quantum dot devices

    DEFF Research Database (Denmark)

    Kiršanskas, Gediminas; Pedersen, Jonas Nyvold; Karlström, Olov

    2017-01-01

    QmeQ is an open-source Python package for numerical modeling of transport through quantum dot devices with strong electron–electron interactions using various approximate master equation approaches. The package provides a framework for calculating stationary particle or energy currents driven...... by differences in chemical potentials or temperatures between the leads which are tunnel coupled to the quantum dots. The electronic structures of the quantum dots are described by their single-particle states and the Coulomb matrix elements between the states. When transport is treated perturbatively to lowest...

  10. THE IMPROVEMENT OF FINANCIAL RESPONSIBILITY IN THE CALCULATIONS FOR INTERNATIONAL FREIGHT TRANSPORT

    Directory of Open Access Journals (Sweden)

    S. N. Vnukova

    2010-01-01

    Full Text Available It is suggested to bring in changes into the Rules of Complex Payments applied by the states-participants of the Commonwealth of Independent States and the Baltic States in payments for international freight transportations.

  11. Industrial sand and gravel

    Science.gov (United States)

    Dolley, T.P.

    2013-01-01

    Domestic production of industrial sand and gravel in 2012 was about 49.5 Mt (55 million st), increasing 13 percent compared with that of 2011. Some important end uses for industrial sand and gravel include abrasives, filtration, foundry, glassmaking, hydraulic fracturing sand (frac sand) and silicon metal applications.

  12. Transport theory calculation for a heterogeneous multi-assembly problem by characteristics method with direct neutron path linking technique

    Energy Technology Data Exchange (ETDEWEB)

    Kosaka, Shinya; Saji, Etsuro [In-Core Fuel Management System Department, Toden Software, Inc., Tokyo (Japan)

    2000-12-01

    A characteristics transport theory code, CHAPLET, has been developed for the purpose of making it practical to perform a whole LWR core calculation with the same level of calculational model and accuracy as that of an ordinary single assembly calculation. The characteristics routine employs the CACTUS algorithm for drawing ray tracing lines, which assists the two key features of the flux solution in the CHAPLET code. One is the direct neutron path linking (DNPL) technique which strictly connects angular fluxes at each assembly interface in the flux solution separated between assemblies. Another is to reduce the required memory storage by sharing the data related to ray tracing among assemblies with the same configuration. For faster computation, the coarse mesh rebalance (CMR) method and the Aitken method were incorporated in the code and the combined use of both methods showed the most promising acceleration performance among the trials. In addition, the parallelization of the flux solution was attempted, resulting in a significant reduction in the wall-clock time of the calculation. By all these efforts, coupled with the results of many verification studies, a whole LWR core heterogeneous transport theory calculation finally became practical. CHAPLET is thought to be a useful tool which can produce the reference solutions for analyses of an LWR (author)

  13. A new approach to calculate charge carrier transport mobility in organic molecular crystals from imaginary time path integral simulations.

    Science.gov (United States)

    Song, Linze; Shi, Qiang

    2015-05-07

    We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated.

  14. Computer codes in nuclear safety, radiation transport and dosimetry; Les codes de calcul en radioprotection, radiophysique et dosimetrie

    Energy Technology Data Exchange (ETDEWEB)

    Bordy, J.M.; Kodeli, I.; Menard, St.; Bouchet, J.L.; Renard, F.; Martin, E.; Blazy, L.; Voros, S.; Bochud, F.; Laedermann, J.P.; Beaugelin, K.; Makovicka, L.; Quiot, A.; Vermeersch, F.; Roche, H.; Perrin, M.C.; Laye, F.; Bardies, M.; Struelens, L.; Vanhavere, F.; Gschwind, R.; Fernandez, F.; Quesne, B.; Fritsch, P.; Lamart, St.; Crovisier, Ph.; Leservot, A.; Antoni, R.; Huet, Ch.; Thiam, Ch.; Donadille, L.; Monfort, M.; Diop, Ch.; Ricard, M

    2006-07-01

    The purpose of this conference was to describe the present state of computer codes dedicated to radiation transport or radiation source assessment or dosimetry. The presentations have been parted into 2 sessions: 1) methodology and 2) uses in industrial or medical or research domains. It appears that 2 different calculation strategies are prevailing, both are based on preliminary Monte-Carlo calculations with data storage. First, quick simulations made from a database of particle histories built though a previous Monte-Carlo simulation and secondly, a neuronal approach involving a learning platform generated through a previous Monte-Carlo simulation. This document gathers the slides of the presentations.

  15. "Multiscale Capabilities for Exploring Transport Phenomena in Batteries": Ab Initio Calculations on Defective LiFePO4

    Energy Technology Data Exchange (ETDEWEB)

    Kanai, Yosuke [Univ. of North Carolina, Chapel Hill, NC (United States); Tang, M [Univ. of North Carolina, Chapel Hill, NC (United States); Wood, B C [Univ. of North Carolina, Chapel Hill, NC (United States)

    2013-10-25

    We have began the project “Multiscale Capability for Exploring Transport Phenomena in Battery”, which is sponsored by Laboratory Directed Research and Development Program at Lawrence Livermore National Laboratory in February 2012 as the subcontract was approved. We have been performing first-principles quantum-mechanical calculations to first establish the general modeling framework. It was found that it is essential to employ advanced Density Functional Theory (DFT) calculations with Hubbard U correction, in order to describe the battery material, in particular, LiFePO4 (Figure 1). The presence of localized d-electrons at Fe ion sites requires the better treatment of non-local correlation beyond that of standard DFT. As our aim was to first identify and investigate key transport/reaction mechanisms affecting the performance of Lithium-ion based batteries, we have began out work by characterizing the standard structures and how the defects influence the important electronic structure.

  16. Accurate dose assessment system for an exposed person utilising radiation transport calculation codes in emergency response to a radiological accident.

    Science.gov (United States)

    Takahashi, F; Shigemori, Y; Seki, A

    2009-01-01

    A system has been developed to assess radiation dose distribution inside the body of exposed persons in a radiological accident by utilising radiation transport calculation codes-MCNP and MCNPX. The system consists mainly of two parts, pre-processor and post-processor of the radiation transport calculation. Programs for the pre-processor are used to set up a 'problem-dependent' input file, which defines the accident condition and dosimetric quantities to be estimated. The program developed for the post-processor part can effectively indicate dose information based upon the output file of the code. All of the programs in the dosimetry system can be executed with a generally used personal computer and accurately give the dose profile to an exposed person in a radiological accident without complicated procedures. An experiment using a physical phantom was carried out to verify the availability of the dosimetry system with the developed programs in a gamma ray irradiation field.

  17. DEPTH-AVERAGED 2-D CALCULATION OF FLOW AND SEDIMENT TRANSPORT IN CURVED CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Weiming WU; Sam S. Y. WANG

    2004-01-01

    The helical flow significantly affects the flow, sediment transport and morphological evolution in curved channels. A semi-empirical formula is proposed to determine the cross-stream distribution of the helical flow intensity in the developed regions of a channel bend. It is then used to evaluate the dispersion terms in the depth-averaged 2-D momentum equations and suspended-load transport equation as well as the bed-load transport angle, thus enhancing the depth-averaged 2-D model to account for the effect of helical flow. The tests in several experimental and field cases show that the enhanced depth-averaged 2-D model can much more reasonably predict the shifting of main flow from inner bank to outer bank, the erosion along outer bank and deposition along inner bank than the depth-averaged 2-D model without considering this effect.

  18. MULTISPECIES REACTIVE TRACER TEST IN A SAND AND GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS: PART 1: EXPERIMENTAL DESIGN AND TRANSPORT OF BROMIDE AND NICKEL-EDTA TRACERS

    Science.gov (United States)

    In this report, we summarize a portion of the results of a large-scale tracer test conducted at the U. S. Geological Survey research site on Cape Cod, Massachusetts. The site is located on a large sand and gravel glacial outwash plain in an unconfined aquifer. In April 1993, ab...

  19. Non-Equilibrium Green's Function Calculation for Electron Transport through Magnetic Tunnel Junction

    Directory of Open Access Journals (Sweden)

    Sara Nobakht

    2014-06-01

    Full Text Available In this paper non-equilibrium Green's function method –dependent electron transport through non magnetic layer (insulator has been studied in one dimension .electron transport in multi-layer (magnetic/non magnetic/ magneticlayers is studied as quantum .the result show increasing the binding strength of the electrical insulator transition probability density case , the electron density , broad levels of disruption increases. Broad band connection increases the levels of disruption to electrical insulation and show non- conductive insulating state to semiconductor stat and even conductor

  20. Transport coefficients of normal liquid helium-4 calculated by path integral centroid molecular dynamics simulation

    Science.gov (United States)

    Imaoka, Haruna; Kinugawa, Kenichi

    2017-03-01

    Thermal conductivity, shear viscosity, and bulk viscosity of normal liquid 4He at 1.7-4.0 K are calculated using path integral centroid molecular dynamics (CMD) simulations. The calculated thermal conductivity and shear viscosity above lambda transition temperature are on the same order of magnitude as experimental values, while the agreement of shear viscosity is better. Above 2.3 K the CMD well reproduces the temperature dependences of isochoric shear viscosity and of the time integral of the energy current and off-diagonal stress tensor correlation functions. The calculated bulk viscosity, not known in experiments, is several times larger than shear viscosity.

  1. Inelastic Transport through Molecules: Comparing First-Principles Calculations to Experiments

    DEFF Research Database (Denmark)

    Paulsson, Magnus; Frederiksen, Thomas; Brandbyge, Mads

    2006-01-01

    We present calculations of the elastic and inelastic conductance through three different hydrocarbon molecules connected to gold electrodes. Our method is based on a combination of the nonequilibrium Green's function method with density functional theory. Vibrational effects in these molecular...

  2. The use of symbolic computation in radiative, energy, and neutron transport calculations. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Frankel, J.I.

    1997-09-01

    This investigation used sysmbolic manipulation in developing analytical methods and general computational strategies for solving both linear and nonlinear, regular and singular integral and integro-differential equations which appear in radiative and mixed-mode energy transport. Contained in this report are seven papers which present the technical results as individual modules.

  3. Krylov subspace method for evaluating the self-energy matrices in electron transport calculations

    DEFF Research Database (Denmark)

    Sørensen, Hans Henrik Brandenborg; Hansen, Per Christian; Petersen, D. E.;

    2008-01-01

    We present a Krylov subspace method for evaluating the self-energy matrices used in the Green's function formulation of electron transport in nanoscale devices. A procedure based on the Arnoldi method is employed to obtain solutions of the quadratic eigenvalue problem associated with the infinite...

  4. Charge transport calculations of organic semiconductors by the time-dependent wave-packet diffusion method

    Science.gov (United States)

    Ishii, Hiroyuki; Kobayashi, Nobuhiko; Hirose, Kenji

    2012-02-01

    Organic materials form crystals by relatively weak Van der Waals attraction between molecules, and thus differ fundamentally from covalently bonded semiconductors. Carriers in the organic semiconductors induce the drastic lattice deformation, which is called as polaron state. The polaron effect on the transport is a serious problem. Exactly what conduction mechanism applies to organic semiconductors has not been established. Therefore, we have investigated the transport properties using the Time-Dependent Wave-Packet Diffusion (TD-WPD) method [1]. To consider the polaron effect on the transport, in the methodology, we combine the wave-packet dynamics based on the quantum mechanics theory with the molecular dynamics. As the results, we can describe the electron motion modified by (electron-phonon mediated) time-dependent structural change. We investigate the transport property from an atomistic viewpoint and evaluate the mobility of organic semiconductors. We clarify the temperature dependence of mobility from the thermal activated behavior to the power law behavior. I will talk about these results in my presentation. [1] H. Ishii, N. Kobayashi, K. Hirose, Phys. Rev. B, 82 085435 (2010).

  5. MCNP - transport calculations in ducts using multigroup albedo coefficients; Calculos de transporte em dutos utilizando coeficientes de albedo multigrupo no codigo MCNP

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Shizuca; Vieira, Wilson J.; Garcia, Roberto D.M. [Centro Tecnico Aeroespacial (CTA-IEAv), Sao Jose dos Campos, SP (Brazil). Inst. de Estudos Avancados

    2000-07-01

    In this work, the use of multigroup albedo coefficients in Monte Carlo calculations of particle reflection and transmission by ducts is investigated. The procedure consists in modifying the MCNP code so that an albedo matrix computed previously by deterministic methods or Monte Carlo is introduced into the program to describe particle reflection by a surface. This way it becomes possible to avoid the need of considering particle transport in the duct wall explicitly, changing the problem to a problem of transport in the duct interior only and reducing significantly the difficulty of the real problem. The probability of particle reflection at the duct wall is given, for each group, as the sum of the albedo coefficients over the final groups. The calculation is started by sampling a source particle and simulating its reflection on the duct wall by sampling a group for the emerging particle. The particle weight is then reduced by the reflection probability. Next, a new direction and trajectory for the particle is selected. Numerical results obtained for the model are compared with results from a discrete ordinates code and results from Monte Carlo simulations that take particle transport in the wall into account. (author)

  6. Electronic and thermoelectric properties of InN studied using ab initio density functional theory and Boltzmann transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Borges, P. D., E-mail: pdborges@gmail.com, E-mail: lscolfaro@txstate.edu; Scolfaro, L., E-mail: pdborges@gmail.com, E-mail: lscolfaro@txstate.edu [Department of Physics, Texas State University, San Marcos, Texas 78666 (United States)

    2014-12-14

    The thermoelectric properties of indium nitride in the most stable wurtzite phase (w-InN) as a function of electron and hole concentrations and temperature were studied by solving the semiclassical Boltzmann transport equations in conjunction with ab initio electronic structure calculations, within Density Functional Theory. Based on maximally localized Wannier function basis set and the ab initio band energies, results for the Seebeck coefficient are presented and compared with available experimental data for n-type as well as p-type systems. Also, theoretical results for electric conductivity and power factor are presented. Most cases showed good agreement between the calculated properties and experimental data for w-InN unintentionally and p-type doped with magnesium. Our predictions for temperature and concentration dependences of electrical conductivity and power factor revealed a promising use of InN for intermediate and high temperature thermoelectric applications. The rigid band approach and constant scattering time approximation were utilized in the calculations.

  7. Calculation of the transport properties of carbon dioxide. I. Shear viscosity, viscomagnetic effects, and self-diffusion

    Science.gov (United States)

    Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa

    2002-08-01

    Transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory approach. Results are reported for shear viscosity, viscomagnetic coefficients, and self-diffusion in the dilute-gas limit and in the temperature range of 200-1500 K for the three recently proposed carbon dioxide potential energy hypersurfaces. Agreement with the measurements is, in general, within the experimental error. The calculations indicate that the corrections in the second-order approximation and those due to the angular-momentum polarization for the viscosity are small, Bukowski [et al.] potential energy hypersurface (1999) with the experimental viscosity data is consistent with the rigid-rotor assumption made in the calculations being reasonable for the three properties considered.

  8. Eastern Scheldt Sand, Baskarp Sand No. 15

    DEFF Research Database (Denmark)

    Andersen, A. T; Madsen, E. B.; Schaarup-Jensen, A. L.

    The present data report contains data from 13 drained triaxial tests, performed on two different sand types in the Soil Mechanics Laboratory at Aalborg University in March, 1997. Two tests have been performed on Baskarp Sand No. 15, which has already ken extensively tested in the Soil Mechanics...... Laboratory. The remaining 11 triaxial tests have ben performed on Eastern Scheldt Sand, which is a material not yet investigated at the Soil Mechanics Laboratory. In the first pari of this data report, the characteristics of the two sand types in question will be presented. Next, a description...

  9. Testing of the ABBN-RF multigroup data library in photon transport calculations

    Directory of Open Access Journals (Sweden)

    Koscheev Vladimir

    2017-01-01

    Full Text Available Gamma radiation is produced via both of nuclear fuel and shield materials. Photon interaction is known with appropriate accuracy, but secondary gamma ray production known much less. The purpose of this work is studying secondary gamma ray production data from neutron induced reactions in iron and lead by using MCNP code and modern nuclear data as ROSFOND, ENDF/B-7.1, JEFF-3.2 and JENDL-4.0. Results of calculations show that all of these nuclear data have different photon production data from neutron induced reactions and have poor agreement with evaluated benchmark experiment. The ABBN-RF multigroup cross-section library is based on the ROSFOND data. It presented in two forms of micro cross sections: ABBN and MATXS formats. Comparison of group-wise calculations using both ABBN and MATXS data to point-wise calculations with the ROSFOND library shows a good agreement. The discrepancies between calculation and experimental C/E results in neutron spectra are in the limit of experimental errors. For the photon spectrum they are out of experimental errors. Results of calculations using group-wise and point-wise representation of cross sections show a good agreement both for photon and neutron spectra.

  10. Testing of the ABBN-RF multigroup data library in photon transport calculations

    Science.gov (United States)

    Koscheev, Vladimir; Lomakov, Gleb; Manturov, Gennady; Tsiboulia, Anatoly

    2017-09-01

    Gamma radiation is produced via both of nuclear fuel and shield materials. Photon interaction is known with appropriate accuracy, but secondary gamma ray production known much less. The purpose of this work is studying secondary gamma ray production data from neutron induced reactions in iron and lead by using MCNP code and modern nuclear data as ROSFOND, ENDF/B-7.1, JEFF-3.2 and JENDL-4.0. Results of calculations show that all of these nuclear data have different photon production data from neutron induced reactions and have poor agreement with evaluated benchmark experiment. The ABBN-RF multigroup cross-section library is based on the ROSFOND data. It presented in two forms of micro cross sections: ABBN and MATXS formats. Comparison of group-wise calculations using both ABBN and MATXS data to point-wise calculations with the ROSFOND library shows a good agreement. The discrepancies between calculation and experimental C/E results in neutron spectra are in the limit of experimental errors. For the photon spectrum they are out of experimental errors. Results of calculations using group-wise and point-wise representation of cross sections show a good agreement both for photon and neutron spectra.

  11. Spatially resolved transport data for electrons in gases: Definition, interpretation and calculation

    Energy Technology Data Exchange (ETDEWEB)

    Dujko, S., E-mail: sasa.dujko@ipb.ac.rs [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); ARC Centre for Antimatter-Matter Studies, School of Engineering and Physical Sciences, James Cook University, Townsville 4810 (Australia); Centrum Wiskunde and Informatica (CWI), P.O. Box 94079, 1090 GB, Amsterdam (Netherlands); White, R.D. [ARC Centre for Antimatter-Matter Studies, School of Engineering and Physical Sciences, James Cook University, Townsville 4810 (Australia); Raspopovic, Z.M.; Petrovic, Z.Lj. [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia)

    2012-05-15

    The spatiotemporal evolution of electron swarms in the presence of electric and magnetic fields is investigated to facilitate understanding temporal and spatial non-locality in low-temperature plasmas. Using two independent techniques, a multi-term solution of Boltzmann's equation and a Monte Carlo simulation technique, the synergism of an applied magnetic field and non-conservative collisions (ionization and/or electron attachment) is demonstrated as a means to control the non-locality of relaxation processes. In particular, oscillatory features in the spatial and temporal profiles are demonstrated, and shown to be enhanced or suppressed through the magnetic field strength, the angle between the electric and magnetic fields, and the degree of ionization. Finally we discuss the impact of field configurations and strengths on the transport properties, highlighting the distinctions in the measured transport properties between various experimental configurations when non-conservative processes are present.

  12. Determination of uncertainties in the calculation of dose rates at transport and storage casks; Unsicherheiten bei der Berechnung von Dosisleistungen an Transport- und Lagerbehaeltern

    Energy Technology Data Exchange (ETDEWEB)

    Schloemer, Luc Laurent Alexander

    2014-12-17

    The compliance with the dose rate limits for transport and storage casks (TLB) for spent nuclear fuel from pressurised water reactors can be proved by calculation. This includes the determination of the radioactive sources and the shielding-capability of the cask. In this thesis the entire computational chain, which extends from the determination of the source terms to the final Monte-Carlo-transport-calculation is analysed and the arising uncertainties are quantified not only by benchmarks but also by variational calculi. The background of these analyses is that the comparison with measured dose rates at different TLBs shows an overestimation by the values calculated. Regarding the studies performed, the overestimation can be mainly explained by the detector characteristics for the measurement of the neutron dose rate and additionally in case of the gamma dose rates by the energy group structure, which the calculation is based on. It turns out that the consideration of the uncertainties occurring along the computational chain can lead to even greater overestimation. Concerning the dose rate calculation at cask loadings with spent uranium fuel assemblies an uncertainty of (({sup +21}{sub -28}) ±2) % (rel.) for the total gamma dose rate and of ({sup +28±23}{sub -55±4}) % (rel.) for the total neutron dose rate are estimated. For mixed-loadings with spent uranium and MOX fuel assemblies an uncertainty of ({sup +24±3}{sub -27±2}) % (rel.) for the total gamma dose rate and of ({sup +28±23}{sub -55±4}) % (rel.) for the total neutron dose rate are quantified. The results show that the computational chain has not to be modified, because the calculations performed lead to conservative dose rate predictions, even if high uncertainties at neutron dose rate measurements arise. Thus at first the uncertainties of the neutron dose rate measurement have to be decreased to enable a reduction of the overestimation of the calculated dose rate afterwards. In the present thesis

  13. Global sand trade is paving the way for a tragedy of the sand commons

    Science.gov (United States)

    Torres, A.; Brandt, J.; Lear, K.; Liu, J.

    2016-12-01

    In the first 40 years of the 21st century, planet Earth is highly likely to experience more urban land expansion than in all of history, an increase in transportation infrastructure by more than a third, and a great variety of land reclamation projects. While scientists are beginning to quantify the deep imprint of human infrastructure on biodiversity at large scales, its off-site impacts and linkages to sand mining and trade have been largely ignored. Sand is the most widely used building material in the world. With an ever-increasing demand for this resource, sand is being extracted at rates that far exceed its replenishment, and is becoming increasingly scarce. This has already led to conflicts around the world and will likely lead to a "tragedy of the sand commons" if sustainable sand mining and trade cannot be achieved. We investigate the environmental and socioeconomic interactions over large distances (telecouplings) of infrastructure development and sand mining and trade across diverse systems through transdisciplinary research and the recently proposed telecoupling framework. Our research is generating a thorough understanding of the telecouplings driven by an increasing demand for sand. In particular, we address three main research questions: 1) Where are the conflicts related to sand mining occurring?; 2) What are the major "sending" and "receiving" systems of sand?; and 3) What are the main components (e.g. causes, effects, agents, etc.) of telecoupled systems involving sand mining and trade? Our results highlight the role of global sand trade as a driver of environmental degradation that threatens the integrity of natural systems and their capacity to deliver key ecosystem services. In addition, infrastructure development and sand mining and trade have important implications for other sustainability challenges such as over-fishing and global warming. This knowledge will help to identify opportunities and tools to better promote a more sustainable use

  14. Self-consistent GW calculations of electronic transport in thiol- and amine-linked molecular junctions

    DEFF Research Database (Denmark)

    Strange, M.; Rostgaard, Carsten; Hakkinen, H.

    2011-01-01

    The electronic conductance of a benzene molecule connected to gold electrodes via thiol, thiolate, or amino anchoring groups is calculated using nonequilibrium Green functions in combination with the fully self-consistent GW approximation for exchange and correlation. The calculated conductance...... suggest that more complex gold-thiolate structures where the thiolate anchors are chemically passivated by Au adatoms are responsible for the measured conductance. Analysis of the energy level alignment obtained with DFT, Hartree-Fock, and GW reveals the importance of self-interaction corrections...

  15. Tuning the Transport Properties of Layered Materials for Thermoelectric Applications using First-Principles Calculations

    KAUST Repository

    Saeed, Yasir

    2014-05-11

    Thermoelectric materials can convert waste heat into electric power and thus provide a way to reduce the dependence on fossil fuels. Our aim is to model the underlying materials properties and, in particular, the transport as controlled by electrons and lattice vibrations. The goal is to develop an understanding of the thermoelectric properties of selected materials at a fundamental level. The structural, electronic, optical, and phononic properties are studied in order to tune the transport, focusing on KxRhO2, NaxRhO2, PtSb2 and Bi2Se3. The investigations are based on density functional theory as implemented in the all electron linearized augmented plane wave plus local orbitals WIEN2k and pseudo potential Quantum-ESPRESSO codes. The thermoelectric properties are derived from Boltzmann transport theory under the constant relaxation time approximation, using the BoltzTraP code. We will discuss first the changes in the electronic band structure under variation of the cation concentration in layered KxRhO2 in the 2H phase and NaxRhO2 in the 3R phase. We will also study the hydrated phase. The deformations of the RhO6 octahedra turn out to govern the thermoelectric properties, where the high Seebeck coefficient results from ”pudding mold" bands. We investigate the thermoelectric properties of electron and hole doped PtSb2, which is not a layered material but shares “pudding mold" bands. PtSb2 has a high Seebeck coefficient at room temperature, which increases significantly under As alloying by bandgap opening and reduction of the lattice thermal conductivity. Bi2Se3 (bulk and thin film) has a larger bandgap then the well-known thermoelectric material Bi2Te3, which is important at high temperature. The structural stability, electronic structure, and transport properties of one to six quintuple layers of Bi2Se3 will be discussed. We also address the effect of strain on a single quintuple layer by phonon band structures. We will analyze the electronic and transport

  16. Efficient calculation of inelastic vibration signals in electron transport: Beyond the wide-band approximation

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Christensen, Rasmus Bjerregaard; Foti, Giuseppe;

    2014-01-01

    We extend the simple and efficient lowest order expansion (LOE) for inelastic electron tunneling spectroscopy (IETS) to include variations in the electronic structure on the scale of the vibration energies. This enables first-principles calculations of IETS line shapes for molecular junctions clo...

  17. Renormalization-group calculations of ground-state and transport properties of ultrasmall tunnel junctions

    DEFF Research Database (Denmark)

    Frota, H.O.; Flensberg, Karsten

    1992-01-01

    We have done a numerical renormalization-group calculation for a Hamiltonian modeling charging effect in ultrasmall tunnel junctions. We find that the conductance is enhanced by the quantum charge fluctuations allowing tunneling below the charging energy gap. However, in all cases the conductance...

  18. Analysis of simulation methodology for calculation of the heat of transport for vacancy thermodiffusion

    Energy Technology Data Exchange (ETDEWEB)

    Tucker, William C.; Schelling, Patrick K., E-mail: patrick.schelling@ucf.edu [Advanced Material Processing and Analysis Center and Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816 (United States)

    2014-07-14

    Computation of the heat of transport Q{sub a}{sup *} in monatomic crystalline solids is investigated using the methodology first developed by Gillan [J. Phys. C: Solid State Phys. 11, 4469 (1978)] and further developed by Grout and coworkers [Philos. Mag. Lett. 74, 217 (1996)], referred to as the Grout-Gillan method. In the case of pair potentials, the hopping of a vacancy results in a heat wave that persists for up to 10 ps, consistent with previous studies. This leads to generally positive values for Q{sub a}{sup *} which can be quite large and are strongly dependent on the specific details of the pair potential. By contrast, when the interactions are described using the embedded atom model, there is no evidence of a heat wave, and Q{sub a}{sup *} is found to be negative. This demonstrates that the dynamics of vacancy hopping depends strongly on the details of the empirical potential. However, the results obtained here are in strong disagreement with experiment. Arguments are presented which demonstrate that there is a fundamental error made in the Grout-Gillan method due to the fact that the ensemble of states only includes successful atom hops and hence does not represent an equilibrium ensemble. This places the interpretation of the quantity computed in the Grout-Gillan method as the heat of transport in doubt. It is demonstrated that trajectories which do not yield hopping events are nevertheless relevant to computation of the heat of transport Q{sub a}{sup *}.

  19. An OpenCL-based Monte Carlo dose calculation engine (oclMC) for coupled photon-electron transport

    CERN Document Server

    Tian, Zhen; Folkerts, Michael; Qin, Nan; Jiang, Steve B; Jia, Xun

    2015-01-01

    Monte Carlo (MC) method has been recognized the most accurate dose calculation method for radiotherapy. However, its extremely long computation time impedes clinical applications. Recently, a lot of efforts have been made to realize fast MC dose calculation on GPUs. Nonetheless, most of the GPU-based MC dose engines were developed in NVidia CUDA environment. This limits the code portability to other platforms, hindering the introduction of GPU-based MC simulations to clinical practice. The objective of this paper is to develop a fast cross-platform MC dose engine oclMC using OpenCL environment for external beam photon and electron radiotherapy in MeV energy range. Coupled photon-electron MC simulation was implemented with analogue simulations for photon transports and a Class II condensed history scheme for electron transports. To test the accuracy and efficiency of our dose engine oclMC, we compared dose calculation results of oclMC and gDPM, our previously developed GPU-based MC code, for a 15 MeV electron ...

  20. Application of GEANT4 radiation transport toolkit to dose calculations in anthropomorphic phantoms

    CERN Document Server

    Rodrigues, P; Peralta, L; Alves, C; Chaves, A; Lopes, M C

    2003-01-01

    In this paper we present the implementation of a dose calculation application, based on the GEANT4 Monte Carlo toolkit. Validation studies were performed with an homogeneous water phantom and an Alderson--Rando anthropomorphic phantom both irradiated with high--energy photon beams produced by a clinical linear accelerator. As input, this tool requires computer tomography images for automatic codification of voxel based geometries and phase space distributions to characterize the incident radiation field. Simulation results were compared with ionization chamber, thermoluminescent dosimetry data and commercial treatment planning system calculations. In homogeneous water phantom, overall agreement with measurements were within 1--2%. For anthropomorphic simulated setups (thorax and head irradiation) mean differences between GEANT4 and TLD measurements were less than 2%. Significant differences between GEANT4 and a semi--analytical algorithm implemented in the treatment planning system, were found in low density ...

  1. Electron transport in a Pt-CO-Pt nanocontact: Density functional theory calculations

    DEFF Research Database (Denmark)

    Strange, Mikkel; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel

    2006-01-01

    We have performed first-principles calculations for the mechanic and electric properties of pure Pt nanocontacts and a Pt contact with a single CO molecule adsorbed. For the pure Pt contacts we see a clear difference between point contacts and short chains in good agreement with experiments. We i...... of the transmission function for the Pt-CO-Pt contact, and show that the conductance is largely determined by the local d band at the Pt apex atoms....

  2. Phonon transport properties of two-dimensional group-IV materials from ab initio calculations

    Science.gov (United States)

    Peng, Bo; Zhang, Hao; Shao, Hezhu; Xu, Yuanfeng; Ni, Gang; Zhang, Rongjun; Zhu, Heyuan

    2016-12-01

    It has been argued that stanene has lowest lattice thermal conductivity among two-dimensional (2D) group-IV materials because of its largest atomic mass, weakest interatomic bonding, and enhanced ZA phonon scattering due to the breaking of an out-of-plane symmetry selection rule. However, we show that, although the lattice thermal conductivity κ for graphene, silicene, and germanene decreases monotonically with decreasing Debye temperature, unexpected higher κ is observed in stanene. By enforcing all the invariance conditions in 2D materials and including Ge 3 d and Sn 4 d electrons as valence electrons for germanene and stanene, respectively, the lattice dynamics in these materials are accurately described. A large acoustic-optical gap and the bunching of the acoustic-phonon branches significantly reduce phonon scattering in stanene, leading to higher thermal conductivity than germanene. The vibrational origin of the acoustic-optical gap can be attributed to the buckled structure. Interestingly, a buckled system has two competing influences on phonon transport: the breaking of the symmetry selection rule leads to reduced thermal conductivity, and the enlarging of the acoustic-optical gap results in enhanced thermal conductivity. The size dependence of thermal conductivity is investigated as well. In nanoribbons, the κ of silicene, germanene, and stanene is much less sensitive to size effect due to their short intrinsic phonon mean-free paths. This work sheds light on the nature of phonon transport in buckled 2D materials.

  3. Calculation models for prediction of Liquefied Natural Gas (LNG) ageing during ship transportation

    Energy Technology Data Exchange (ETDEWEB)

    Miana, Mario; Hoyo, Rafael del; Rodrigalvarez, Vega; Valdes, Jose Ramon [Instituto Tecnologico de Aragon, Area de Investigacion, Desarrollo y Servicios Tecnologicos, Maria de Luna 7, 50018 Zaragoza (Spain); Llorens, Raul [ENAGAS SA, Direccion de Ingenieria y Tecnologia del Gas, Autovia A - 2, km. 306.4, 50012 Zaragoza (Spain)

    2010-05-15

    A group of European gas transportation companies within the European Gas Research Group launched in 2007 the 'MOLAS' Project to provide a software program for the analysis of the Liquefied Natural Gas (LNG) ageing process during ship transportation. This program contains two different modeling approaches: a physical algorithm and an 'intelligent' model. Both models are fed with the same input data, which is composed of the ship characteristics (BOR and capacity), voyage duration, LNG composition, temperature, pressure, and volume occupied by liquid phase at the port of origin, together with pressure at the port of destination. The results obtained are the LNG composition, temperature and liquid volume at the port of destination. Furthermore, the physical model obtains the evolution over time of such variables en route as it is based on unsteady mass balances over the system, while the i-model applies neural networks to obtain regression coefficients from historical data composed only of origin and destination measurements. This paper describes both models and validates them from previous published models and experimental data measured in ENAGAS LNG regasification plants. (author)

  4. Large-scale quantum transport calculations for electronic devices with over ten thousand atoms

    Science.gov (United States)

    Lu, Wenchang; Lu, Yan; Xiao, Zhongcan; Hodak, Miro; Briggs, Emil; Bernholc, Jerry

    The non-equilibrium Green's function method (NEGF) has been implemented in our massively parallel DFT software, the real space multigrid (RMG) code suite. Our implementation employs multi-level parallelization strategies and fully utilizes both multi-core CPUs and GPU accelerators. Since the cost of the calculations increases dramatically with the number of orbitals, an optimal basis set is crucial for including a large number of atoms in the ``active device'' part of the simulations. In our implementation, the localized orbitals are separately optimized for each principal layer of the device region, in order to obtain an accurate and optimal basis set. As a large example, we calculated the transmission characteristics of a Si nanowire p-n junction. The nanowire is along (110) direction in order to minimize the number dangling bonds that are saturated by H atoms. Its diameter is 3 nm. The length of 24 nm is necessary because of the long-range screening length in Si. Our calculations clearly show the I-V characteristics of a diode, i.e., the current increases exponentially with forward bias and is near zero with backward bias. Other examples will also be presented, including three-terminal transistors and large sensor structures.

  5. Voxel2MCNP: software for handling voxel models for Monte Carlo radiation transport calculations.

    Science.gov (United States)

    Hegenbart, Lars; Pölz, Stefan; Benzler, Andreas; Urban, Manfred

    2012-02-01

    Voxel2MCNP is a program that sets up radiation protection scenarios with voxel models and generates corresponding input files for the Monte Carlo code MCNPX. Its technology is based on object-oriented programming, and the development is platform-independent. It has a user-friendly graphical interface including a two- and three-dimensional viewer. A row of equipment models is implemented in the program. Various voxel model file formats are supported. Applications include calculation of counting efficiency of in vivo measurement scenarios and calculation of dose coefficients for internal and external radiation scenarios. Moreover, anthropometric parameters of voxel models, for instance chest wall thickness, can be determined. Voxel2MCNP offers several methods for voxel model manipulations including image registration techniques. The authors demonstrate the validity of the program results and provide references for previous successful implementations. The authors illustrate the reliability of calculated dose conversion factors and specific absorbed fractions. Voxel2MCNP is used on a regular basis to generate virtual radiation protection scenarios at Karlsruhe Institute of Technology while further improvements and developments are ongoing.

  6. RISKIND: A computer program for calculating radiological consequences and health risks from transportation of spent nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Y.C. [Square Y, Orchard Park, NY (United States); Chen, S.Y.; LePoire, D.J. [Argonne National Lab., IL (United States). Environmental Assessment and Information Sciences Div.; Rothman, R. [USDOE Idaho Field Office, Idaho Falls, ID (United States)

    1993-02-01

    This report presents the technical details of RISIUND, a computer code designed to estimate potential radiological consequences and health risks to individuals and the collective population from exposures associated with the transportation of spent nuclear fuel. RISKIND is a user-friendly, semiinteractive program that can be run on an IBM or equivalent personal computer. The program language is FORTRAN-77. Several models are included in RISKIND that have been tailored to calculate the exposure to individuals under various incident-free and accident conditions. The incidentfree models assess exposures from both gamma and neutron radiation and can account for different cask designs. The accident models include accidental release, atmospheric transport, and the environmental pathways of radionuclides from spent fuels; these models also assess health risks to individuals and the collective population. The models are supported by databases that are specific to spent nuclear fuels and include a radionudide inventory and dose conversion factors.

  7. Sands at Gusev Crater, Mars

    Science.gov (United States)

    Cabrol, Nathalie A.; Herkenhoff, Kenneth E.; Knoll, Andrew H.; Farmer, Jack D.; Arvidson, Raymond E.; Grin, E.A.; Li, Ron; Fenton, Lori; Cohen, B.; Bell, J.F.; Yingst, R. Aileen

    2014-01-01

    Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine-to-medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).

  8. Calculative activation analysis of the transport rack for CASTOR {sup registered} casks; Berechnung der Aktivierung eines Transportgestells fuer CASTOR {sup registered} -Behaelter

    Energy Technology Data Exchange (ETDEWEB)

    Tittelbach, S. [Wissenschaftlich-Technische Ingenieurberatung GmbH (WTI), Juelich (Germany); Biedermann, R. [GNS Gesellschaft fuer Nuklear-Service mbH, Essen (Germany); Schmidt-Wohlfarth, Y.; Louia, A. [EnBW Kernkraft GmbH, Philippsburg (Germany)

    2011-07-01

    The transport rack for the internal transport of loaded CASTOR {sup registered} casks before the storage in the intermediate storage facility at the site of the NPP Philippsburg is exposed to neutron irradiation from the cask inventory. Using the Monte Carlo code MCNP the activation rates of the transport rack materials are calculated for typical storage times of the casks in the rack. The long-term activation was also calculated for the continuous use of the transport rack over 10 years. Further topics were the dose rate in the near surrounding of the transport rack after long-term activation and finally the disposability of rack components according to the legal regulations. The maximum contact dose rate was calculated to be below 1 micro Sv/h after 10 years of application. The transport rack can be disposed with large safety margins to the radiation protection limits.

  9. Influence green sand system by core sand additions

    OpenAIRE

    N. Špirutová; J. Beňo; V. Bednářová; J. Kříž; M. Kandrnál

    2012-01-01

    Today, about two thirds of iron alloys casting (especially for graphitizing alloys of iron) are produced into green sand systems with usually organically bonded cores. Separation of core sands from the green sand mixture is very difficult, after pouring. The core sand concentration increase due to circulation of green sand mixture in a closed circulation system. Furthermore in some foundries, core sands have been adding to green sand systems as a replacement for new sands. The goal of this co...

  10. Baskarp Sand No. 15

    DEFF Research Database (Denmark)

    Borup, Marianne; Hedegaard, Jette

    The Soil Mechanics Laboratory has started performing tests with a new sand, Baskarp No 15. Baskarp No 15 is a graded sand from Sweden. The shapes of the largest grains are round, while the small grains have sharp edges. The main part of of Baskarp No 15 is quarts, but it also contains feldspar...... and biotit. Mainly the sand will be used for tests concerning the development og the theory of building up pore pressure in sand, L. B. Ibsen 1993....

  11. Electron transport calculations in warm dense matter using scattering cross sections

    CERN Document Server

    Burrill, D J; Charest, M R J; Starrett, C E

    2015-01-01

    The Ziman formulation of electrical conductivity is tested in warm and hot dense matter using the pseudo-atom molecular dynamics method. Several implementation options that have been widely used in the literature are systematically tested through a comparison to accurate but expensive Kohn-Sham density functional theory molecular dynamics (KS-DFT-MD) calculations. The comparison is made for several elements and mixtures and for a wide range of temperatures and densities, and reveals a preferred method that generally gives very good agreement with the KSDFT-MD results, but at a fraction of the computational cost.

  12. A FIRST APPROXIMATION CALCULATION OF AIR CUSHION CHASSIS WEIGHT OF TRANSPORT AIRPLANE

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available This article describes a first approximation of a weighted estimate of air cushion chassis. The algorithm for calculating the weight of air cushion chassis allows not only to estimate the mass of the chassis to a first approximation, but also to conduct a preliminary analysis of the influence of various parameters of the aircraft and the chassis on the weight of the aircraft at the stage of before designing. The algorithm can be expanded to include additional design decisions, such as the transformation of the fuselage, increasing the air cushion chassis canopy due to extensions, center of gravity, etc.

  13. Lund Sand No 0

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Jakobsen, Finn Rosendal

    During the last 15 years the Geotechnical Engineering Group (GEG) at Aalborg University has performed triaxial tests with a sand called Lund No 0. Lund No 0 is a graded sand from a gravel pit near Horsens in Denmark. For the classification of the sand the following tests have been performed: Sieve...

  14. A probability-conserving cross-section biasing mechanism for variance reduction in Monte Carlo particle transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Mendenhall, Marcus H., E-mail: marcus.h.mendenhall@vanderbilt.edu [Vanderbilt University, Department of Electrical Engineering, P.O. Box 351824B, Nashville, TN 37235 (United States); Weller, Robert A., E-mail: robert.a.weller@vanderbilt.edu [Vanderbilt University, Department of Electrical Engineering, P.O. Box 351824B, Nashville, TN 37235 (United States)

    2012-03-01

    In Monte Carlo particle transport codes, it is often important to adjust reaction cross-sections to reduce the variance of calculations of relatively rare events, in a technique known as non-analog Monte Carlo. We present the theory and sample code for a Geant4 process which allows the cross-section of a G4VDiscreteProcess to be scaled, while adjusting track weights so as to mitigate the effects of altered primary beam depletion induced by the cross-section change. This makes it possible to increase the cross-section of nuclear reactions by factors exceeding 10{sup 4} (in appropriate cases), without distorting the results of energy deposition calculations or coincidence rates. The procedure is also valid for bias factors less than unity, which is useful in problems that involve the computation of particle penetration deep into a target (e.g. atmospheric showers or shielding studies).

  15. Response to Oil Sands Products Assessment

    Science.gov (United States)

    2015-09-01

    Tailings ponds are an operating facility common to all types of surface mining. For oil sands, tailings consisting of water , sand, clay, and residual ...oil, are pumped to these basins—or ponds— where settling occurs and water is recycled for reuse in the process. When the ponds are no longer required...of crude oil transported by tank vessel in Washington waters . In a 2013 Bloomburg Business news article , Dan Murtaugh states, “The dock probably

  16. Transport calculation of neutrons leaked to the surroundings of the facilities by the JCO criticality accident in Tokai-mura.

    Science.gov (United States)

    Imanaka, T

    2001-09-01

    A transport calculation of the neutrons leaked to the environment by the JCO criticality accident was carried out based on three-dimensional geometrical models of the buildings within the JCO territory. Our work started from an initial step to simulate the leakage process of neutrons from the precipitation tank, and proceeded to a step to calculate the neutron propagation throughout the JCO facilities. The total fission number during the accident in the precipitation tank was evaluated to be 2.5 x 10(18) by comparing the calculated neutron-induced activities per 235U fission with the measured values in a stainless-steel net sample taken 2 m from the precipitation tank. Shield effects by various structures within the JCO facilities were evaluated by comparing the present results with a previous calculation using two-dimensional models which suppose a point source of the fission spectrum in the air above the ground without any shield structures. The shield effect by the precipitation tank, itself, was obtained to be a factor of 3. The shield factor by the conversion building varied between 1.1 and 2, depending on the direction from the building. The shield effect by the surrounding buildings within the JCO territory was between I and 5, also depending on the direction.

  17. Real-Time Simulation of Aeolian Sand Movement and Sand Ripple Evolution: A Method Based on the Physics of Blown Sand

    Institute of Scientific and Technical Information of China (English)

    Ning Wang; Bao-Gang Hu

    2012-01-01

    Simulation and visualization of aeolian sand movement and sand ripple evolution are a challenging subject.In this paper,we propose a physically based modeling and simulating method that can be used to synthesize sandy terrain in various patterns.Our method is based on the mechanical behavior of individual sand grains,which are widely studied in the physics of blown sand.We accounted significant mechanisms of sand transportation into the sand model,such as saltation,successive saltation and collapsing,while simplified the vegetation model and wind field model to make the simulation feasible and affordable.We implemented the proposed method on the programming graphics processing unit (GPU) to get real-time simulation and rendering.Finally,we proved that our method can reflect many characteristics of sand ripple evolution through several demonstrations.We also gave several synthesized desert scenes made from the simulated height field to display its significance on application.

  18. 砂土中吸力式沉箱基础的最大承载力计算方法%Calculation method for maximum bearing capacity of suction caisson foundation in sand

    Institute of Scientific and Technical Information of China (English)

    黎冰; 高玉峰; 沙成明; 童小东

    2012-01-01

    To accurately determine the maximum pull-out loading capacity of suction caisson foundation in sand, the limit equilibrium method is applied. Based on the mechanical characteristics of suction caisson foundation with horizontal translation, a method for three-dimensional limit equilibrium analysis of maximum pull-out loading capacity of suction caisson foundation in sand is proposed. In the proposed method, the development process of earth pressure and shear resistance with displacement, and the characteristics of different earth pressure and side shear resistance over the caisson cross-section are considered. The earth pressure acting on the caisson is assumed to obey the Winkler model and is not in excess of the limiting earth pressure. The shear resistance between caisson and soil is assumed to be linearly proportional to the relative displacement between them before reaching its ultimate value. Fifteen model tests of suction caisson foundation under horizontal loading in sand are conducted to investigate its pull-out behaviors, and the load-displacement curves are obtained. The calculation results by the proposed method agree well with the experimental results, indicating that the proposed method is accurate and effective. Key w%为了准确确定砂土中吸力式沉箱基础的最大承载力,应用极限平衡法对其进行分析.基于吸力式沉箱基础平动时的受力特点,充分考虑土压力和摩擦力的发挥过程以及沉箱横截面上各点土压力大小的不同,提出了一种计算砂土中吸力式沉箱基础最大承载力的三维极限平衡方法.方法中假定沉箱侧壁土压力满足Winkler模型,但其值不超过水平极限土压力值;假定沉箱侧壁与地基土之间的摩擦力在达到最大值之前与两者之间的相对位移成线性正比关系.开展了15组水平荷载作用下吸力式沉箱基础的模型试验,得到了吸力式沉箱基础的荷载-位移曲线.利用所提方法得到的计

  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. A new, coupled transport-diffusion method for radiative transfer calculations

    Energy Technology Data Exchange (ETDEWEB)

    Wollaber, A. B.; Warsa, J. S. [Los Alamos National Laboratory, MS D409, P.O. Box 1663, Los Alamos NM, 87545 (United States)

    2013-07-01

    We derive and present a new frequency- and angle-integrated low-order system of equations designed to enhance the accuracy of a coupled, high-order (transport) solution of the thermal radiative transfer equations. In particular, our new low-order system is designed to use intensity-weighted opacities and anisotropic diffusion coefficients generated by a solution of the Implicit Monte Carlo (IMC) equations in order to predict the spatial dependence of the material temperature and radiation energies in the ensuing time cycle. The predicted temperature solution can then be exploited to generate appropriately time-centered opacities, specific heats, and Planck emission spectra for the upcoming IMC solution. Additionally, the relatively inexpensive solution of the low-order system can be iteratively solved to recommend an adaptive time step size before the IMC solution is computed. A test implementation has been implemented using existing software available from the Jayenne and Capsaicin projects at Los Alamos National Laboratory. We present initial results from a new driver code that has integrated these stochastic and deterministic software packages. (authors)

  1. First-principles calculation of transport property in nano-devices under an external magnetic field

    Institute of Scientific and Technical Information of China (English)

    Chen Jing-Zhe; Zhang Jin; Han Ru-Shan

    2008-01-01

    The mesoscopic quantum interference phenomenon (QIP) can be observed and behaves as the oscillation of conductance in nano-devices when the external magnetic field changes. Excluding the factor of impurities or defects, specific QIP is determined by the sample geometry. We have improved a first-principles method based on the matrix Green's function and the density functional theory to simulate the transport behaviour of such systems under a magnetic field. We have studied two kinds of QIP: universal conductance fluctuation (UCF) and Aharonov-Bohm effect (A-B effect). We find that the amplitude of UCF is much smaller than the previous theoretical prediction. We have discussed the origin of difference and concluded that due to the failure of ergodic hypothesis, the ensemble statistics is not applicable, and the conductance fluctuation is determined by the flux-dependent density of states (DOSs). We have also studied the relation between the UCF and the structure of sample. For a specific structure, an atomic circle, the A-B effect is observed and the origin of the oscillation is also discussed.

  2. Sweepless time-dependent transport calculations using the staggered block Jacobi method

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, G [Los Alamos National Laboratory; Larsen, E W [Los Alamos National Laboratory

    2009-01-01

    The Staggered-Block Jacobi (SBJ) method is a new numerical SN transport method for solving time-dependent problems without sweeps or low-order acceleration. Because it is a Jacobian method, it is trivial to parallelize and will scale linearly with the number of processors, It is highly accurate in thick-diffusive problems and unconditionally stable when combined with the lumped linear discontinuous finite element spatial discretization. In this way, the SBJ method is complementary to sweep-based methods, which are accurate and efficient in thin, streaming regions but inefficient in thick, diffusive problems without acceleration. We have extended previous work by demonstrating how sweep-based methods and the SBJ method may be combined to produce a method which is accurate and efficient without acceleration in all optical thicknesses while still retaining good parallel efficiency. Furthermore, iterations may also be added to the SBJ method. This is particularly useful for improving the accuracy of the SBJ method in intermediate-thickness problems.

  3. Criticality Calculations of Fresh LEU and MOX Assemblies for Transport and Storage at the Balakovo Nuclear Power Plant

    Energy Technology Data Exchange (ETDEWEB)

    Goluoglu, S.

    2001-01-11

    Transportation of low-enriched uranium (LEU) and mixed-oxide (MOX) assemblies to and within the VVER-1000-type Balakovo Nuclear Power Plant is investigated. Effective multiplication factors for fresh fuel assemblies on the railroad platform, fresh fuel assemblies in the fuel transportation vehicle, and fresh fuel assemblies in the spent fuel storage pool are calculated. If there is no absorber between the units, the configurations with all MOX assemblies result in higher effective multiplication factors than the configurations with all LEU assemblies when the system is dry. When the system is flooded, the configurations with all LEU assemblies result in higher effective multiplication factors. For normal operating conditions, effective multiplication factors for all configurations are below the presumed upper subcritical limit of 0.95. For an accident condition of a fully loaded fuel transportation vehicle that is flooded with low-density water (possibly from a fire suppression system), the presumed upper subcritical limit is exceeded by configurations containing LEU assemblies.

  4. DEPTH-AVERAGED 2-D CALCULATION OF TIDAL FLOW,SALINITY AND COHESIVE SEDIMENT TRANSPORT IN ESTUARIES

    Institute of Scientific and Technical Information of China (English)

    Weiming WU; Sam S.Y. WANG

    2004-01-01

    A depth-averaged 2-D numerical model for unsteady flow, salinity and cohesive sediment transport in estuaries is established using the finite volume method on the non-staggered, curvilinear grid. The convection terms are discretized by upwind schemes, the diffusion terms are by the central difference scheme, and the time derivative terms are by the three-time-level implicit scheme. The coupling of flow velocity and water level in the 2-D shallow water equations is achieved by the SIMPLEC algorithm with the Rhie and Chow's momentum interpolation method. The sediment model calculates the settling, deposition, erosion and transport of cohesive sediment, taking into account the influence of sediment size, sediment concentration, salinity and turbulence intensity on the flocculation of cohesive sediment. The flow model is first tested against the measurement data in the Tokyo Bay and San Francisco Bay, showing good agreements. And then, the entire model of flow, salinity and sediment transport is verified in the Gironde Estuary. The water elevation, flow velocity, salinity and sediment concentration are well predicted.

  5. A study of K variability and its effect on solute transport in subsurface-flow sand filters by measurement and modelling.

    Science.gov (United States)

    Kløve, Bjørn; Xu, Shulan; Lindahl, Anna; Wörman, Anders; Søvik, Anne-Kristine

    2005-01-01

    Hydraulics of subsurface flow filters (SSF) was studied by measurement of soil hydraulic conductivity (K) variation and performing tracer tests in two SSF filters consisting of 1-4 mm Ca rich sand (shell sand). Soil samples were carefully taken at several locations in Filter I. A tracer experiment was conducted in the undisturbed Filter II using KI. The measured K variability in Filer I was used to analyze the variations in tracer breakthrough. The spatially distribution of K was obtained by fitting a variogram to observed data and interpolation using Kriging. The tracer residence probability density function (PDF) was determined by modelling the tracer movement with a 3-D groundwater model. The observed and simulated tracer arrival was compared for cases with constant K, constant K and dispersion (D), and for spatially variable K and dispersion. The results show that groundwater models were well suited to simulate solute movement in the SSF system studied. An almost perfect fit to observed tracer PDF was obtained when variable K and dispersion was included in the model. This indicates that information on K variability and dispersion is important for studying solute movement in SSF constructed wetlands.

  6. Development and Implementation of Photonuclear Cross-Section Data for Mutually Coupled Neutron-Photon Transport Calculations in the Monte Carlo N-Particle (MCNP) Radiation Transport Code

    Energy Technology Data Exchange (ETDEWEB)

    White, Morgan C. [Univ. of Florida, Gainesville, FL (United States)

    2000-07-01

    The fundamental motivation for the research presented in this dissertation was the need to development a more accurate prediction method for characterization of mixed radiation fields around medical electron accelerators (MEAs). Specifically, a model is developed for simulation of neutron and other particle production from photonuclear reactions and incorporated in the Monte Carlo N-Particle (MCNP) radiation transport code. This extension of the capability within the MCNP code provides for the more accurate assessment of the mixed radiation fields. The Nuclear Theory and Applications group of the Los Alamos National Laboratory has recently provided first-of-a-kind evaluated photonuclear data for a select group of isotopes. These data provide the reaction probabilities as functions of incident photon energy with angular and energy distribution information for all reaction products. The availability of these data is the cornerstone of the new methodology for state-of-the-art mutually coupled photon-neutron transport simulations. The dissertation includes details of the model development and implementation necessary to use the new photonuclear data within MCNP simulations. A new data format has been developed to include tabular photonuclear data. Data are processed from the Evaluated Nuclear Data Format (ENDF) to the new class ''u'' A Compact ENDF (ACE) format using a standalone processing code. MCNP modifications have been completed to enable Monte Carlo sampling of photonuclear reactions. Note that both neutron and gamma production are included in the present model. The new capability has been subjected to extensive verification and validation (V&V) testing. Verification testing has established the expected basic functionality. Two validation projects were undertaken. First, comparisons were made to benchmark data from literature. These calculations demonstrate the accuracy of the new data and transport routines to better than 25 percent. Second

  7. RISKIND: A computer program for calculating radiological consequences and health risks from transportation of spent nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Y.C. [Square Y Consultants, Orchard Park, NY (US); Chen, S.Y.; Biwer, B.M.; LePoire, D.J. [Argonne National Lab., IL (US)

    1995-11-01

    This report presents the technical details of RISKIND, a computer code designed to estimate potential radiological consequences and health risks to individuals and the collective population from exposures associated with the transportation of spent nuclear fuel. RISKIND is a user-friendly, interactive program that can be run on an IBM or equivalent personal computer under the Windows{trademark} environment. Several models are included in RISKIND that have been tailored to calculate the exposure to individuals under various incident-free and accident conditions. The incident-free models assess exposures from both gamma and neutron radiation and can account for different cask designs. The accident models include accidental release, atmospheric transport, and the environmental pathways of radionuclides from spent fuels; these models also assess health risks to individuals and the collective population. The models are supported by databases that are specific to spent nuclear fuels and include a radionuclide inventory and dose conversion factors. In addition, the flexibility of the models allows them to be used for assessing any accidental release involving radioactive materials. The RISKIND code allows for user-specified accident scenarios as well as receptor locations under various exposure conditions, thereby facilitating the estimation of radiological consequences and health risks for individuals. Median (50% probability) and typical worst-case (less than 5% probability of being exceeded) doses and health consequences from potential accidental releases can be calculated by constructing a cumulative dose/probability distribution curve for a complete matrix of site joint-wind-frequency data. These consequence results, together with the estimated probability of the entire spectrum of potential accidents, form a comprehensive, probabilistic risk assessment of a spent nuclear fuel transportation accident.

  8. A calculation program for harvesting and transportation costs of energy and industrial wood; Energiapuun korjuun ja kuljetuksen kustannuslaskentaohjelmisto

    Energy Technology Data Exchange (ETDEWEB)

    Ranta, T. [VTT Energy, Jyvaeskylae (Finland)

    1997-12-01

    A computer based model has been developed for calculating the production costs of industrial wood and wood fuel. Several calculation situations, which might be useful for decision-making in energy wood supply, are included into this software. The model will be easy to use for practical purposes and flexible so that different new model and changes in the basis of calculations are easy to implement. Model will offer open interfaces for importing and exporting information. Model includes selected wood delivery chains and open interfaces for adding data from different procurement sources. The cost analysis model is built on Windows-based software, SQLWindows, using different sources of data (ODBC). With the model it is possible to manage these SQLBase databases with SQL-queries. The data included in the databases origins from various energy wood sources (local communities or part of them, forestry boards planning areas or even stands ready for cutting). By knowing the planned share of first thinnings, final cuttings and other harvesting operations it is possible to estimate the potential amount of wood fuel from each area. Also databases from energy wood users, forest and transportation machinery and distances are available in the system. Using the information it is possible to find out the fuel demand of power and heating plants in each moment (e.g., amount and quality), costs of various machines (harvesters, forwarders, trucks) as well as distances between energy wood sources and users. (orig.)

  9. Recommendations for computer code selection of a flow and transport code to be used in undisturbed vadose zone calculations for TWRS immobilized environmental analyses

    Energy Technology Data Exchange (ETDEWEB)

    VOOGD, J.A.

    1999-04-19

    An analysis of three software proposals is performed to recommend a computer code for immobilized low activity waste flow and transport modeling. The document uses criteria restablished in HNF-1839, ''Computer Code Selection Criteria for Flow and Transport Codes to be Used in Undisturbed Vadose Zone Calculation for TWRS Environmental Analyses'' as the basis for this analysis.

  10. GTNEUT: A code for the calculation of neutral particle transport in plasmas based on the Transmission and Escape Probability method

    Science.gov (United States)

    Mandrekas, John

    2004-08-01

    GTNEUT is a two-dimensional code for the calculation of the transport of neutral particles in fusion plasmas. It is based on the Transmission and Escape Probabilities (TEP) method and can be considered a computationally efficient alternative to traditional Monte Carlo methods. The code has been benchmarked extensively against Monte Carlo and has been used to model the distribution of neutrals in fusion experiments. Program summaryTitle of program: GTNEUT Catalogue identifier: ADTX Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTX Computer for which the program is designed and others on which it has been tested: The program was developed on a SUN Ultra 10 workstation and has been tested on other Unix workstations and PCs. Operating systems or monitors under which the program has been tested: Solaris 8, 9, HP-UX 11i, Linux Red Hat v8.0, Windows NT/2000/XP. Programming language used: Fortran 77 Memory required to execute with typical data: 6 219 388 bytes No. of bits in a word: 32 No. of processors used: 1 Has the code been vectorized or parallelized?: No No. of bytes in distributed program, including test data, etc.: 300 709 No. of lines in distributed program, including test data, etc.: 17 365 Distribution format: compressed tar gzip file Keywords: Neutral transport in plasmas, Escape probability methods Nature of physical problem: This code calculates the transport of neutral particles in thermonuclear plasmas in two-dimensional geometric configurations. Method of solution: The code is based on the Transmission and Escape Probability (TEP) methodology [1], which is part of the family of integral transport methods for neutral particles and neutrons. The resulting linear system of equations is solved by standard direct linear system solvers (sparse and non-sparse versions are included). Restrictions on the complexity of the problem: The current version of the code can

  11. An experiment to restore coastal sand dunes at Miramar beach, Goa: An appraisal

    Digital Repository Service at National Institute of Oceanography (India)

    Mascarenhas, A.

    . Loss of vegetation is attributed to continuous trampling by humans, resulting in the creation of loose free sand that gets transported landwards. During windy days, large quantities of beach sand are blown from the beach and subsequently accumulate...

  12. Model calculation of the characteristic mass for convective and diffusive vapor transport in graphite furnace atomic absorption spectrometry

    Science.gov (United States)

    Bencs, László; Laczai, Nikoletta; Ajtony, Zsolt

    2015-07-01

    A combination of former convective-diffusive vapor-transport models is described to extend the calculation scheme for sensitivity (characteristic mass - m0) in graphite furnace atomic absorption spectrometry (GFAAS). This approach encompasses the influence of forced convection of the internal furnace gas (mini-flow) combined with concentration diffusion of the analyte atoms on the residence time in a spatially isothermal furnace, i.e., the standard design of the transversely heated graphite atomizer (THGA). A couple of relationships for the diffusional and convectional residence times were studied and compared, including in factors accounting for the effects of the sample/platform dimension and the dosing hole. These model approaches were subsequently applied for the particular cases of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn analytes. For the verification of the accuracy of the calculations, the experimental m0 values were determined with the application of a standard THGA furnace, operating either under stopped, or mini-flow (50 cm3 min- 1) of the internal sheath gas during atomization. The theoretical and experimental ratios of m0(mini-flow)-to-m0(stop-flow) were closely similar for each study analyte. Likewise, the calculated m0 data gave a fairly good agreement with the corresponding experimental m0 values for stopped and mini-flow conditions, i.e., it ranged between 0.62 and 1.8 with an average of 1.05 ± 0.27. This indicates the usability of the current model calculations for checking the operation of a given GFAAS instrument and the applied methodology.

  13. Model calculation of the characteristic mass for convective and diffusive vapor transport in graphite furnace atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Bencs, László, E-mail: bencs.laszlo@wigner.mta.hu [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Laczai, Nikoletta [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Ajtony, Zsolt [Institute of Food Science, University of West Hungary, H-9200 Mosonmagyaróvár, Lucsony utca 15–17 (Hungary)

    2015-07-01

    A combination of former convective–diffusive vapor-transport models is described to extend the calculation scheme for sensitivity (characteristic mass — m{sub 0}) in graphite furnace atomic absorption spectrometry (GFAAS). This approach encompasses the influence of forced convection of the internal furnace gas (mini-flow) combined with concentration diffusion of the analyte atoms on the residence time in a spatially isothermal furnace, i.e., the standard design of the transversely heated graphite atomizer (THGA). A couple of relationships for the diffusional and convectional residence times were studied and compared, including in factors accounting for the effects of the sample/platform dimension and the dosing hole. These model approaches were subsequently applied for the particular cases of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn analytes. For the verification of the accuracy of the calculations, the experimental m{sub 0} values were determined with the application of a standard THGA furnace, operating either under stopped, or mini-flow (50 cm{sup 3} min{sup −1}) of the internal sheath gas during atomization. The theoretical and experimental ratios of m{sub 0}(mini-flow)-to-m{sub 0}(stop-flow) were closely similar for each study analyte. Likewise, the calculated m{sub 0} data gave a fairly good agreement with the corresponding experimental m{sub 0} values for stopped and mini-flow conditions, i.e., it ranged between 0.62 and 1.8 with an average of 1.05 ± 0.27. This indicates the usability of the current model calculations for checking the operation of a given GFAAS instrument and the applied methodology. - Highlights: • A calculation scheme for convective–diffusive vapor loss in GFAAS is described. • Residence time (τ) formulas were compared for sensitivity (m{sub 0}) in a THGA furnace. • Effects of the sample/platform dimension and dosing hole on τ were assessed. • Theoretical m{sub 0} of 18 analytes were

  14. Structural variations of sand-bearing airflow over dune at southeastern fringe of Tengger Desert

    Institute of Scientific and Technical Information of China (English)

    Hasi Eerdum

    2004-01-01

    From the analytical results of observed data on sand transport rates at different positions of dune surface at southeastern fringe of Tengger Desert, it has been found that the vertical distribution of blown sand flux exhibits a noticeable variation when sand grains move upslope and downslope of dune surface under the action of wind force. Within the height of 20 cm above the sand surface, the vertical distribution of mass flux at different positions from toe to dune crest of stoss slope of sand dunes coincides with a single exponentially decaying law; while the vertical distribution of mass flux over the lee slope occurs as two variable zones, with the height of 8—12 cm as the dividing line, the sand transport rate below this height exponentially decreases with increasing height, but above this height decreases in a power function law. On the stoss slope, the relative sand transport rate in the upper layer of sand flow tends to decrease with the increasing wind velocity and the total sand transport rate towards the dune crest due to the shortened trajectory length of saltation sand grains moving upslope. On the lee slope, the increase in lift-off height and trajectory length of saltation sand grains moving downslope leads to the increase in relative sand transport rate in the upper layer of sand flow.

  15. Development and application of neutron transport methods and uncertainty analyses for reactor core calculations. Technical report; Entwicklung und Einsatz von Neutronentransportmethoden und Unsicherheitsanalysen fuer Reaktorkernberechnungen. Technischer Bericht

    Energy Technology Data Exchange (ETDEWEB)

    Zwermann, W.; Aures, A.; Bernnat, W.; and others

    2013-06-15

    This report documents the status of the research and development goals reached within the reactor safety research project RS1503 ''Development and Application of Neutron Transport Methods and Uncertainty Analyses for Reactor Core Calculations'' as of the 1{sup st} quarter of 2013. The superordinate goal of the project is the development, validation, and application of neutron transport methods and uncertainty analyses for reactor core calculations. These calculation methods will mainly be applied to problems related to the core behaviour of light water reactors and innovative reactor concepts. The contributions of this project towards achieving this goal are the further development, validation, and application of deterministic and stochastic calculation programmes and of methods for uncertainty and sensitivity analyses, as well as the assessment of artificial neutral networks, for providing a complete nuclear calculation chain. This comprises processing nuclear basis data, creating multi-group data for diffusion and transport codes, obtaining reference solutions for stationary states with Monte Carlo codes, performing coupled 3D full core analyses in diffusion approximation and with other deterministic and also Monte Carlo transport codes, and implementing uncertainty and sensitivity analyses with the aim of propagating uncertainties through the whole calculation chain from fuel assembly, spectral and depletion calculations to coupled transient analyses. This calculation chain shall be applicable to light water reactors and also to innovative reactor concepts, and therefore has to be extensively validated with the help of benchmarks and critical experiments.

  16. Electric conductivity for laboratory and field monitoring of induced partial saturation (IPS) in sands

    Science.gov (United States)

    Kazemiroodsari, Hadi

    Liquefaction is loss of shear strength in fully saturated loose sands caused by build-up of excess pore water pressure, during moderate to large earthquakes, leading to catastrophic failures of structures. Currently used liquefaction mitigation measures are often costly and cannot be applied at sites with existing structures. An innovative, practical, and cost effective liquefaction mitigation technique titled "Induced Partial Saturation" (IPS) was developed by researchers at Northeastern University. The IPS technique is based on injection of sodium percarbonate solution into fully saturated liquefaction susceptible sand. Sodium percarbonate dissolves in water and breaks down into sodium and carbonate ions and hydrogen peroxide which generates oxygen gas bubbles. Oxygen gas bubbles become trapped in sand pores and therefore decrease the degree of saturation of the sand, increase the compressibility of the soil, thus reduce its potential for liquefaction. The implementation of IPS required the development and validation of a monitoring and evaluation technique that would help ensure that the sands are indeed partially saturated. This dissertation focuses on this aspect of the IPS research. The monitoring system developed was based on using electric conductivity fundamentals and probes to detect the transport of chemical solution, calculate degree of saturation of sand, and determine the final zone of partial saturation created by IPS. To understand the fundamentals of electric conductivity, laboratory bench-top tests were conducted using electric conductivity probes and small specimens of Ottawa sand. Bench-top tests were used to study rate of generation of gas bubbles due to reaction of sodium percarbonate solution in sand, and to confirm a theory based on which degree of saturation were calculated. In addition to bench-top tests, electric conductivity probes were used in a relatively large sand specimen prepared in a specially manufactured glass tank. IPS was

  17. Transport and optical properties of warm dense aluminum in the two-temperature regime: Ab initio calculation and semiempirical approximation

    CERN Document Server

    Knyazev, D V

    2014-01-01

    This work is devoted to the investigation of transport and optical properties of liquid aluminum in the two-temperature case. At first optical properties, static electrical and thermal conductivities were obtained in the \\textit{ab initio} calculation. The \\textit{ab initio} calculation is based on the quantum molecular dynamics, density functional theory and the Kubo-Greenwood formula. The semiempirical approximation was constructed based on the results of the \\textit{ab initio} caculation. The approximation yields the dependences $\\sigma_{1_\\mathrm{DC}}\\propto1/T_i^{0.25}$ and $K\\propto T_e/T_i^{0.25}$ for the static electrical conductivity and thermal conductivity, respectively. The approximation is valid for liquid aluminum at $\\rho=2.70$~g/cm$^3$, 3~kK~$\\leq T_i\\leq T_e\\leq20$~kK. Our results are well described by the Drude model with the effective relaxation time $\\tau\\propto T_i^{-0.25}$. We have compared our results with a number of other models. They are all reduced in the low-temperature limit to th...

  18. Adsorption of dyes on Sahara desert sand.

    Science.gov (United States)

    Varlikli, Canan; Bekiari, Vlasoula; Kus, Mahmut; Boduroglu, Numan; Oner, Ilker; Lianos, Panagiotis; Lyberatos, Gerasimos; Icli, Siddik

    2009-10-15

    Sahara desert sand (SaDeS) was employed as a mineral sorbent for retaining organic dyes from aqueous solutions. Natural sand has demonstrated a strong affinity for organic dyes but significantly lost its adsorption capacity when it was washed with water. Therefore, characterization of both natural and water washed sand was performed by XRD, BET, SEM and FTIR techniques. It was found that water-soluble kyanite, which is detected in natural sand, is the dominant factor affecting adsorbance of cationic dyes. The sand adsorbs over 75% of cationic dyes but less than 21% for anionic ones. Among the dyes studied, Methylene Blue (MB) demonstrated the strongest affinity for Sahara desert sand (Q(e)=11.98 mg/g, for initial dye solution concentration 3.5 x 10(-5)mol/L). The effects of initial dye concentration, the amount of the adsorbent, the temperature and the pH of the solution on adsorption capacity were tested by using Methylene Blue as model dye. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied. It was concluded that adsorption of Methylene Blue on Sahara desert sand followed pseudo-second order kinetics. Gibbs free energy, enthalpy change and entropy change were calculated and found -6411 J/mol, -30360 J/mol and -76.58 J/mol K, respectively. These values indicate that the adsorption is an exothermic process and has a spontaneous nature at low temperatures.

  19. Influence green sand system by core sand additions

    Directory of Open Access Journals (Sweden)

    N. Špirutová

    2012-01-01

    Full Text Available Today, about two thirds of iron alloys casting (especially for graphitizing alloys of iron are produced into green sand systems with usually organically bonded cores. Separation of core sands from the green sand mixture is very difficult, after pouring. The core sand concentration increase due to circulation of green sand mixture in a closed circulation system. Furthermore in some foundries, core sands have been adding to green sand systems as a replacement for new sands. The goal of this contribution is: “How the green sand systems are influenced by core sands?”This effect is considered by determination of selected technological properties and degree of green sand system re-bonding. From the studies, which have been published yet, there is not consistent opinion on influence of core sand dilution on green sand system properties. In order to simulation of the effect of core sands on the technological properties of green sands, there were applied the most common used technologies of cores production, which are based on bonding with phenolic resin. Core sand concentration added to green sand system, was up to 50 %. Influence of core sand dilution on basic properties of green sand systems was determined by evaluation of basic industrial properties: moisture, green compression strength and splitting strength, wet tensile strength, mixture stability against staling and physical-chemistry properties (pH, conductivity, and loss of ignition. Ratio of active betonite by Methylene blue test was also determined.

  20. Application of the Stefan-Maxwell Equations to determine limitations of Fick's law when modeling organic vapor transport in sand columns

    Science.gov (United States)

    Baehr, Arthur L.; Bruell, Clifford J.

    1990-01-01

    The organic component of the vapor phase of a porous medium contaminated by an immiscible organic liquid can be significant enough to violate the condition of a dilute species diffusing in a bulk phase assumed by Fick's law. The Stefan-Maxwell equations provide a more comprehensive model for quantifying steady state transport for a vapor phase composed of arbitrary proportions of its constituents. The application of both types of models to the analysis of column experiments demonstrates that use of a Fickian-based transport model can lead to significant overestimates of soil tortuosity constants. Further, the physical displacement of naturally occurring gases (e.g., O2), predicted by the Stefan-Maxwell model but not by application of Fick's Law, can be attributed improperly to a sink term such as microbial degradation in a Fickian-based transport model.

  1. Sands cykliske styrke

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    1992-01-01

    Sands cykliske styrke kan beskrives ved Cyclic Liquefaction, Mobilisering, Stabilization og Instant Stabilization. I artiklen beskrives hvorfor Stabilization og Instant Stabilization ikke observeres, når sands udrænede styrke undersøges i triaxial celler, der anvender prøver med dobbelt prøvehøjde....

  2. Baskarp Sand No. 15

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Bødker, Lars Bødker

    The Soil Mechanics Laboratory has started performing tests with a new sand, Baskarp No 15. Baskarp No 15 is a graded sand from Sweden. The shapes of the largest grains are round, while the small grains have sharp edges. The main part of of Baskarp No 15 is quarts, but it also contains feldspar...

  3. Opposite hysteresis of sand and gravel transport upstream and downstream of a bifurcation during a flood in the River Rhine, the Netherlands

    NARCIS (Netherlands)

    Kleinhans, M.G.; Wilbers, A.W.E.; Brinke, W.B.M. ten

    2007-01-01

    At river bifurcations water and sediment is divided among the downstream branches. Prediction of the sediment transport rate and divisionthereof at bifurcations is of utmost importance for understanding the evolution of the bifurcates for short-term management purposes and forlong-term fluvial plain

  4. MULTISPECIES REACTIVE TRACER TEST IN A SAND AND GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS: PART 2: TRANSPORT OF CHROMIUM (VI) AND LEAD-, COPPER-, AND ZINC-EDTA TRACERS

    Science.gov (United States)

    This report discusses the transport of a group of reactive tracers over the course of a large-scale, natural gradient tracer test conducted at the USGS Cape Cod Toxic Substances Hydrology Research site, near Falmouth, Massachusetts. The overall objectives of the experiment were ...

  5. Electronic structure calculations of atomic transport properties in uranium dioxide: influence of strong correlations; Etude des proprietes de transport atomique dans le dioxyde d'uranium par le calcul de structure electronique: influence des fortes correlations

    Energy Technology Data Exchange (ETDEWEB)

    Dorado, B.

    2010-09-15

    Uranium dioxide UO{sub 2} is the standard nuclear fuel used in pressurized water reactors. During in-reactor operation, the fission of uranium atoms yields a wide variety of fission products (FP) which create numerous point defects while slowing down in the material. Point defects and FP govern in turn the evolution of the fuel physical properties under irradiation. In this study, we use electronic structure calculations in order to better understand the fuel behavior under irradiation. In particular, we investigate point defect behavior, as well as the stability of three volatile FP: iodine, krypton and xenon. In order to take into account the strong correlations of uranium 5f electrons in UO{sub 2}, we use the DFT+U approximation, based on the density functional theory. This approximation, however, creates numerous metastable states which trap the system and induce discrepancies in the results reported in the literature. To solve this issue and to ensure the ground state is systematically approached as much as possible, we use a method based on electronic occupancy control of the correlated orbitals. We show that the DFT+U approximation, when used with electronic occupancy control, can describe accurately point defect and fission product behavior in UO{sub 2} and provide quantitative information regarding point defect transport properties in the oxide fuel. (author)

  6. Production of lightning NOx and its vertical distribution calculated from three-dimensional cloud-scale chemical transport model simulations

    KAUST Repository

    Ott, Lesley E.

    2010-02-18

    A three-dimensional (3-D) cloud-scale chemical transport model that includes a parameterized source of lightning NOx on the basis of observed flash rates has been used to simulate six midlatitude and subtropical thunderstorms observed during four field projects. Production per intracloud (PIC) and cloud-to-ground (PCG) flash is estimated by assuming various values of PIC and PCG for each storm and determining which production scenario yields NOx mixing ratios that compare most favorably with in-cloud aircraft observations. We obtain a mean PCG value of 500 moles NO (7 kg N) per flash. The results of this analysis also suggest that on average, PIC may be nearly equal to PCG, which is contrary to the common assumption that intracloud flashes are significantly less productive of NO than are cloud-to-ground flashes. This study also presents vertical profiles of the mass of lightning NOx after convection based on 3-D cloud-scale model simulations. The results suggest that following convection, a large percentage of lightning NOx remains in the middle and upper troposphere where it originated, while only a small percentage is found near the surface. The results of this work differ from profiles calculated from 2-D cloud-scale model simulations with a simpler lightning parameterization that were peaked near the surface and in the upper troposphere (referred to as a “C-shaped” profile). The new model results (a backward C-shaped profile) suggest that chemical transport models that assume a C-shaped vertical profile of lightning NOx mass may place too much mass near the surface and too little in the middle troposphere.

  7. Probability of rebound and eject of sand particles in wind-blown sand movement

    Institute of Scientific and Technical Information of China (English)

    Li Xie; Xiaojing Zheng

    2007-01-01

    When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the postcollision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, theimpact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as random variables, and calculate the rebound and eject velocities,angles and coefficients (ratio of rebound and eject velocity to incident velocity). Numerical results are found in accordance with current experimental results. The rebound and eject lift-off probabilities versus the incident and creeping velocities are predicted.

  8. Modification of a new potential model used for calculation of the second virial coefficient and zero density transport properties

    Science.gov (United States)

    Parsafar, G. A.; Shokouhi, M.

    A new hard-core potential model was recently used to calculate thermodynamic properties of some model fluids, including equilibrium properties, such as compressibility factor and internal energy. A Lennard-Jones (LJ) like potential has been used to modify the repulsive part of the potential. The modified potential contains five parameters, namely, α, R, ɛ, σ, and σHS. The parameter α is the tail of the attractive branch whose value changes from zero to one. In this work, we have chosen α = 1 to make the potential continuous at separation r = Rσ, where the parameter R is the well width. R lies in the range 1.2 to 2.5, and R = 1.3 was found to be the best value for all real gases studied. The parameter ɛ is the well depth of potential function, and σ is the separation at which the potential function is zero. σHS is the effective hard sphere diameter, which depends on temperature and an additional parameter. Using statistical mechanics along with the Boltzmann factor criterion (BFC) for the effective hard sphere diameter, an analytical expression has been derived for the reduced second virial coefficient in terms of the reduced temperature. Fitting experimental data to expression derived for the second virial coefficient, the potential parameters ɛ and σ are obtained. Since this potential is spherical (depending only on distance), three types of species are chosen, namely Ar and He (monoatomic), N2and O2 (diatomic), and methane (spherical molecule), to show how appropriate this potential model is for them. This model predicts an inversion temperature for the second virial coefficient (temperature at which the second virial coefficient pass through a maximum) at ILM0001, where T1 is the inversion temperature, and TB is the Boyle temperature. The predicted value is better than that of the L-J model (for which ILM0002). The maximum percentage deviation of the second virial coefficient is about 2%, except around the Boyle temperature. Then the transport

  9. Galveston Island, Texas, Sand Management Strategies

    Science.gov (United States)

    2016-07-01

    68 Figure 28. Jetty segment used for computation of aeolian sand transport. Background photograph 22 May 2012...113 Figure 68 . Total shoreline change after 50 years for 500,000 yd3 placed every 2 years in different locations...The berm at Ft. Myers, FL, was constructed with dredged material from Matanzas Pass. The dredged material contained greater than 10% fines, which

  10. Bedrock K{sub d} data and uncertainty assessment for application in SR-Site geosphere transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, James (Kemakta Konsult AB, Stockholm (Sweden))

    2010-12-15

    The safety assessment SR-Site is undertaken to assess the safety of a potential geologic repository for spent nuclear fuel at the Forsmark and Laxemar sites. The present report is one of several reports that form the data input to SR-Site and contains a compilation of recommended K{sub d} data (i.e. linear partitioning coefficients) for safety assessment modelling of geosphere radionuclide transport. The data are derived for rock types and groundwater compositions distinctive of the site investigation areas at Forsmark and Laxemar. Data have been derived for all elements and redox states considered of importance for far-field dose estimates as described in /SKB 2010d/. The K{sub d} data are given in the form of lognormal distributions characterised by a mean (mu) and standard deviation (sigma). Upper and lower limits for the uncertainty range of the recommended data are defined by the 2.5% and 97.5% percentiles of the empirical data sets. The best estimate K{sub d} value for use in deterministic calculations is given as the median of the K{sub d} distribution

  11. Numerical modeling of wind-blown sand on Mars.

    Science.gov (United States)

    Huang, HaoJie; Bo, TianLi; Zheng, XiaoJing

    2014-09-01

    Recent observation results show that sand ripples and dunes are movable like those on Earth under current Martian climate. And the aeolian process on Mars therefore is re-attracting the eyes of scientific researchers in different fields. In this paper, the spatial and temporal evolution of wind-blown sand on Mars is simulated by the large-eddy simulation method. The simulations are conducted under the conditions of both friction wind speed higher and lower than the "fluid threshold", respectively. The fluid entrainment of the sand particles, the processes among saltation sand particles and sand bed, and the negative feedback of sand movement to flow field are considered. Our results show that the "overshoot" phenomenon also exists in the evolution of wind-blown sand on Mars both temporally and spatially; impact entrainment affects the sand transport rate on Mars when the wind speed is smaller or larger than the fluid threshold; and both the average saltation length and height are one order of magnitudes larger than those on Earth. Eventually, the formulas describing the sand transport rate, average saltation length and height on Mars are given, respectively.

  12. Adaptation to life in aeolian sand: how the sandfish lizard, Scincus scincus, prevents sand particles from entering its lungs

    OpenAIRE

    Stadler, Anna T.; Vihar, Boštjan; Günther, Mathias; Huemer, Michaela; Riedl, Martin; Shamiyeh, Stephanie; Mayrhofer, Bernhard; Böhme, Wolfgang; Baumgartner, Werner

    2016-01-01

    ABSTRACT The sandfish lizard, Scincus scincus (Squamata: Scincidae), spends nearly its whole life in aeolian sand and only comes to the surface for foraging, defecating and mating. It is not yet understood how the animal can respire without sand particles entering its respiratory organs when buried under thick layers of sand. In this work, we integrated biological studies, computational calculations and physical experiments to understand this phenomenon. We present a 3D model of the upper res...

  13. Calculation of 2-temperature plasma thermo-physical properties considering condensed phases: application to CO2-CH4 plasma: part 2. Transport coefficients

    Science.gov (United States)

    Niu, Chunping; Chen, Zhexin; Rong, Mingzhe; Wang, Chunlin; Wu, Yi; Yang, Fei; Wang, Xiaohua; Pang, Qingping

    2016-10-01

    The transport coefficients, namely thermal conductivity, viscosity and electrical conductivity, of CO2-CH4 mixture in and out of LTE are calculated in this paper. The calculation was based on local chemical equilibrium (LCE) and local phase equilibrium assumption. The 2-temperature composition results obtained with consideration of condensed phase in the previous paper (Part I) of this series were used in this calculation. The transport coefficients were calculated by classical Chapman-Enskog method simplified by Devoto. The results are presented for different temperatures (300-30 000 K), pressures (0.1-10 atm), non-equilibrium degrees (1-5), and CH4 molar proportions (0-100%). The influence of condensed graphite, non-LTE effect, mixture ratio and pressure on the composition and thermodynamic properties has been discussed. The results will serve as reliable reference data for computational simulation of CO2-CH4 plasmas.

  14. On the Size Distribution of Sand

    DEFF Research Database (Denmark)

    Sørensen, Michael

    2016-01-01

    -distribution, by taking into account that individual grains do not have the same travel time from the source to the deposit. The travel time is assumed to be random so that the wear on the individual grains vary randomly. The model provides an interpretation of the parameters of the NIG-distribution, and relates the mean......A model is presented of the development of the size distribution of sand while it is transported from a source to a deposit. The model provides a possible explanation of the log-hyperbolic shape that is frequently found in unimodal grain size distributions in natural sand deposits, as pointed out...

  15. Sand and Gravel Deposits

    Data.gov (United States)

    Vermont Center for Geographic Information — This dataset is a statewide polygon coverage of sand, gravel, and stone resources. This database includes the best data available from the VT Agency of Natural...

  16. Sand and Gravel Operations

    Data.gov (United States)

    Department of Homeland Security — This map layer includes sand and gravel operations in the United States. These data were obtained from information reported voluntarily to the USGS by the aggregate...

  17. A methodology for calculating transport emissions in cities with limited traffic data: Case study of diesel particulates and black carbon emissions in Murmansk.

    Science.gov (United States)

    Kholod, N; Evans, M; Gusev, E; Yu, S; Malyshev, V; Tretyakova, S; Barinov, A

    2016-03-15

    This paper presents a methodology for calculating exhaust emissions from on-road transport in cities with low-quality traffic data and outdated vehicle registries. The methodology consists of data collection approaches and emission calculation methods. For data collection, the paper suggests using video survey and parking lot survey methods developed for the International Vehicular Emissions model. Additional sources of information include data from the largest transportation companies, vehicle inspection stations, and official vehicle registries. The paper suggests using the European Computer Programme to Calculate Emissions from Road Transport (COPERT) 4 model to calculate emissions, especially in countries that implemented European emissions standards. If available, the local emission factors should be used instead of the default COPERT emission factors. The paper also suggests additional steps in the methodology to calculate emissions only from diesel vehicles. We applied this methodology to calculate black carbon emissions from diesel on-road vehicles in Murmansk, Russia. The results from Murmansk show that diesel vehicles emitted 11.7 tons of black carbon in 2014. The main factors determining the level of emissions are the structure of the vehicle fleet and the level of vehicle emission controls. Vehicles without controls emit about 55% of black carbon emissions. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. OPTIMIZATION OF GRANULOMETRIC COMPOSITION OF DRY FRIABLE SAND BLENDS

    Directory of Open Access Journals (Sweden)

    V. S. Doroshenko

    2014-01-01

    Full Text Available A method for optimizing the composition of the grain loose sand mixtures by placing the binder particles into the pores of the frame sand compaction of these mixtures. An example of calculation of grain composition of such a mixture.

  19. Vestled - Hvide Sande

    DEFF Research Database (Denmark)

    Juel-Christiansen, Carsten; Hesselbjerg, Marianne; Schønherr, Torben

    2009-01-01

    Værket Vestled i Hvide Sande præsenteret i sammenhæng af 1000 nutidige landskabsarkitektoniske arbejder fra hele verden, hvor hvert værk vises på én side......Værket Vestled i Hvide Sande præsenteret i sammenhæng af 1000 nutidige landskabsarkitektoniske arbejder fra hele verden, hvor hvert værk vises på én side...

  20. Experiments on the Evolution of Sand Bed Forms for Varying Degrees of Supply Limitation

    Science.gov (United States)

    Langendoen, E. J.; Wren, D. G.; Kuhnle, R. A.

    2011-12-01

    The advanced age and impending decommissioning of many dams have brought increased attention to the fate of sediments stored in reservoirs. In many cases, fine sediments are reintroduced to coarse substrates that have large volumes of pore space available for storage after having sediments removed by years of sediment-starved flow. Recent research has found that the fine sediment elevation relative to the coarse substrate significantly alters bed surface roughness, turbulence characteristics, the mobility of the fine sediment, and consequently sediment transport rates and sediment bed forms that move over and through these coarse substrates. The roughness of the bed surface is an important parameter for the prediction of bulk flow and sediment transport rates. In order to calculate sediment transport rates, bed shear stresses are typically adjusted for drag exerted by the flow on macro roughness elements, which are related here to the protrusion of coarse substrate particles and sediment bed forms. Also, the partial mobility (or supply limitation) of sediment yields bed forms that differ from those observed for uniform bed material. Hence, a proper understanding of the interactions between near-bed flow structure, sediment transport rates, and bed surface elevation is needed to adequately determine the downstream impact of fine sediment releases from reservoirs. Recent experiments at the USDA-ARS-National Sedimentation Laboratory in a sediment-recirculating flume (15 m long, 0.36 m wide, and 0.45 m deep) were carried out to elucidate turbulence and sand transport over and through coarse gravel substrates. The median diameter of the sand was 0.3 mm, and that of the gravel was 35 mm. This paper presents results on the change in bed form types with increasing sand elevation relative to the coarse gravel substrate and for Froude numbers ranging from about 0.1 to 0.6. The mean sand elevation was varied between 5 cm below the top of the gravel and the top of the gravel

  1. MECHANICAL REGENERATION OF SAND WASTE

    Directory of Open Access Journals (Sweden)

    D. I. Gnir

    2005-01-01

    Full Text Available The experimental activation of the sand regenerator of the firm SINTO is carried out at ОАО “MZOO". It is shown that sand grains are cleared from films of binding agents, that allows to use the treated sand for preparation of agglutinant and core sands.

  2. 人工掘进顶管穿越沙基公路总顶力确定和施工风险规避%The Total Jacking Force to Calculate and Construction Risk Averse For Manual Pipe Jacking Through Sand Layers Road

    Institute of Scientific and Technical Information of China (English)

    李国明; 任哲; 杨帆

    2016-01-01

    人工掘进顶管穿越沙基公路施工易出现总顶力计算错误、后背墙倾斜、工作面坍塌等问题,从而造成顶管施工失败,应结合工程实例,探讨适于人工掘进顶管穿越沙基公路的总顶力计算公式,对于后背墙倾斜、工作面坍塌等施工难点提出具体的工程措施。通过理论计算与工程实例得出结论,国家标准总顶力计算公式适于人工掘进顶管总顶力计算;人工掘进顶管穿越沙基公路的穿越长度不宜大于26 m;后背墙、工具管的设计对于人工掘进顶管穿越沙基公路施工成败至关重要。%The total jacking force calculation error, backwall tilted, working face landslide and so on which caused by the manual pipe jacking through sand layers road construction fail-ure. Combined with construction, to discuss the calculation formula of the total jacking force which is suitable for construction of manual pipe jacking through sand layers road;En-gineering difficulties such as backwall tilted, working face landslide and so on, engineering measures is provided, and it can be referred to engineering practices. According to analysis, the calculation formula of the total jacking force which is adopted by the national standard is suitable for construction of manual pipe jacking through sand layers road;The total length should be less than 26 m while manual pipe jacking through sand layers road;Design of back-wall and tool pipe for manual pipe jacking through sand layers road are crucial to Success of engineering construction.

  3. Global standardization of the calculation of CO2 emissions along transport chains-gaps, approaches, perspectives of the global alignment process

    NARCIS (Netherlands)

    Ehrler, V.; Engel, A. van den; Davydenko, I.; Diekmann, D.; Kiel, J.; Lewis, A.; Seidel, S.

    2015-01-01

    The transport industry, consumers, shippers and political bodies are all pressing for a global standard for the calculation of emissions along supply chains. Comparability of the chains’ efficiency, reduction of energy consumption, transparency of the carbon footprint of products and identification

  4. Count rate balance method of measuring sediment transport of sand beds by radioactive tracers; Methode du bilan des taux de comptage d'indicateurs radioactifs pour la determination du debit de charriage des lits sableux

    Energy Technology Data Exchange (ETDEWEB)

    Sauzay, G. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

    1967-11-01

    Radioactive tracers are applied to the direct measurement of the sediment transport rate of sand beds. The theoretical measurement formula is derived: the variation of the count rate balance is inverse of that of the transport thickness. Simultaneously the representativeness of the tracer is critically studied. The minimum quantity of tracer which has to be injected in order to obtain a correct statistical definition of count rate given by a low number of grains 'seen' by the detector is then studied. A field experiment was made and has let to study the technological conditions for applying this method: only the treatment of results is new, the experiment itself is carried out with conventional techniques applied with great care. (author) [French] Les indicateurs radioactifs sont appliques a la mesure directe du debit de charriage des lits sableux. On etablit la formule theorique de mesure: le bilan des taux de comptage varie en sens inverse de l'epaisseur de charriage. Parallelement on fait une etude critique de la representativite de l'indicateur, puis on determine la quantite minimale de traceur qu'il faut immerger pour que les taux de comptage fournis pour un faible nombre de grains 'vus' par le detecteur aient une definition statistique correcte. Une experience de terrain a permis d'etudier les conditions technologiques de cette methode: seul le depouillement des resultats est nouveau. L'experimentation in-situ se fait suivant les procedes classiques avec un tres grand soin. (auteur)

  5. TECHNIQUES ABOUT DIRECT OPTIMIZING CONTROL OF GREEN SAND QUALITY*

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Green sand casting is still a main method in the world at present and it is very significant to develop the technology of controlling green sand quality. A new concept, from contents test to contents control, is advanced. In order to realize the new idea, a new method to on-line test active clay and moisture of green sand - double powers energizing alternately (DPEA) method is put forwards. The principle of the new method is to energize standard sand sample with AC and DC powers and to test the electric parameters, and then, to calculate active clay and moisture of green sand by using artificial neural network (ANN). Based on this new method, a direct optimizing system for controlling green sand quality is developed. Techniques about testing and controlling methods, hardware and software are discussed.

  6. Trajectory Calculation as Forecasting Support Tool for Dust Storms

    Directory of Open Access Journals (Sweden)

    Sultan Al-Yahyai

    2014-01-01

    Full Text Available In arid and semiarid regions, dust storms are common during windy seasons. Strong wind can blow loose sand from the dry surface. The rising sand and dust is then transported to other places depending on the wind conditions (speed and direction at different levels of the atmosphere. Considering dust as a moving object in space and time, trajectory calculation then can be used to determine the path it will follow. Trajectory calculation is used as a forecast supporting tool for both operational and research activities. Predefined dust sources can be identified and the trajectories can be precalculated from the Numerical Weather Prediction (NWP forecast. In case of long distance transported dust, the tool should allow the operational forecaster to perform online trajectory calculation. This paper presents a case study for using trajectory calculation based on NWP models as a forecast supporting tool in Oman Meteorological Service during some dust storm events. Case study validation results showed a good agreement between the calculated trajectories and the real transport path of the dust storms and hence trajectory calculation can be used at operational centers for warning purposes.

  7. Patch behaviour and predictability properties of modelled finite-amplitude sand ridges on the inner shelf

    Directory of Open Access Journals (Sweden)

    N. C. Vis-Star

    2008-12-01

    Full Text Available The long-term evolution of shoreface-connected sand ridges is investigated with a nonlinear spectral model which governs the dynamics of waves, currents, sediment transport and the bed level on the inner shelf. Wave variables are calculated with a shoaling-refraction model instead of using a parameterisation. The spectral model describes the time evolution of amplitudes of known eigenmodes of the linearised system. Bottom pattern formation occurs if the transverse bottom slope of the inner shelf, β, exceeds a critical value βc. For fixed model parameters the sensitivity of the properties of modelled sand ridges to changes in the number (N−1 of resolved subharmonics (of the initially fastest growing mode is investigated. For any N the model shows the growth and subsequent saturation of the height of the sand ridges. The saturation time scale is several thousands of years, which suggests that observed sand ridges have not reached their saturated stage yet. The migration speed of the ridges and the average longshore spacing between successive crests in the saturated state differ from those in the initial state. Analysis of the potential energy balance of the ridges reveals that bed slope-induced sediment transport is crucial for the saturation process. In the transient stage the shoreface-connected ridges occur in patches. The overall characteristics of the bedforms (saturation time, final maximum height, average longshore spacing, migration speed hardly vary with N. However, individual time series of modal amplitudes and bottom patterns strongly depend on N, thereby implying that the detailed evolution of sand ridges can only be predicted over a limited time interval. Additional experiments show that the critical bed slope βc increases with larger offshore angles of wave incidence, larger offshore wave heights and longer wave periods, and that the corresponding maximum height of the ridges

  8. Microbes in Beach Sands: Integrating Environment, Ecology and Public Health.

    Science.gov (United States)

    Whitman, Richard; Harwood, Valerie J; Edge, Thomas A; Nevers, Meredith; Byappanahalli, Muruleedhara; Vijayavel, Kannappan; Brandão, João; Sadowsky, Michael J; Alm, Elizabeth Wheeler; Crowe, Allan; Ferguson, Donna; Ge, Zhongfu; Halliday, Elizabeth; Kinzelman, Julie; Kleinheinz, Greg; Przybyla-Kelly, Kasia; Staley, Christopher; Staley, Zachery; Solo-Gabriele, Helena M

    2014-09-01

    Beach sand is a habitat that supports many microbes, including viruses, bacteria, fungi and protozoa (micropsammon). The apparently inhospitable conditions of beach sand environments belie the thriving communities found there. Physical factors, such as water availability and protection from insolation; biological factors, such as competition, predation, and biofilm formation; and nutrient availability all contribute to the characteristics of the micropsammon. Sand microbial communities include autochthonous species/phylotypes indigenous to the environment. Allochthonous microbes, including fecal indicator bacteria (FIB) and waterborne pathogens, are deposited via waves, runoff, air, or animals. The fate of these microbes ranges from death, to transient persistence and/or replication, to establishment of thriving populations (naturalization) and integration in the autochthonous community. Transport of the micropsammon within the habitat occurs both horizontally across the beach, and vertically from the sand surface and ground water table, as well as at various scales including interstitial flow within sand pores, sediment transport for particle-associated microbes, and the large-scale processes of wave action and terrestrial runoff. The concept of beach sand as a microbial habitat and reservoir of FIB and pathogens has begun to influence our thinking about human health effects associated with sand exposure and recreational water use. A variety of pathogens have been reported from beach sands, and recent epidemiology studies have found some evidence of health risks associated with sand exposure. Persistent or replicating populations of FIB and enteric pathogens have consequences for watershed/beach management strategies and regulatory standards for safe beaches. This review summarizes our understanding of the community structure, ecology, fate, transport, and public health implications of microbes in beach sand. It concludes with recommendations for future work in

  9. Bituminous sands : tax issues

    Energy Technology Data Exchange (ETDEWEB)

    Patel, B. [PricewaterhouseCoopers LLP, Calgary, AB (Canada)

    2004-07-01

    This paper examined some of the tax issues associated with the production of bitumen or synthetic crude oil from oil sands. The oil sands deposits in Alberta are gaining more attention as the supplies of conventional oil in Canada decline. The oil sands reserves located in the Athabasca, Cold Lake and Peace River areas contain about 2.5 trillion barrels of highly viscous hydrocarbons called bitumen, of which nearly 315 billion barrels are recoverable with current technology. The extraction method varies for each geographic area, and even within zones and reservoirs. The two most common extraction methods are surface mining and in-situ extraction such as cyclic steam stimulation (CSS); low pressure steam flood; pressure cycle steam drive; steam assisted gravity drainage (SAGD); hot water flooding; and, fire flood. This paper also discussed the following general tax issues: bituminous sands definition; bituminous sands leases and Canadian development expense versus Canadian oil and gas property expense (COGPE); Canadian exploration expense (CEE) for surface mining versus in-situ methods; additional capital cost allowance; and, scientific research and experimental development (SR and ED). 15 refs.

  10. Provenance of coastal dune sands along Red Sea, Egypt

    Indian Academy of Sciences (India)

    Samir M Zaid

    2017-06-01

    Texture, mineralogy, and major and trace element geochemistry of 26 coastal dune sand samples were studied to determine the provenance and tectonic environment of two dune fields close to the beaches of Safaga (SF) and Quseir (QS) at the Egyptian Red Sea coast. Onshore winds generate fine, moderate, moderately-well to well-sorted, coarse-skewed to near-symmetrical dune sands with mesokurtic distributions. Winds pick up and transport grains from nearby beach sands and alluvial deposits into a wide Red Sea coastal plain at the border of the beach. The mineralogical (Qt–Ft–Lt) and geochemical composition of the sands, indicate that SF and QS coastal dune sands are mature and influenced by quartz-rich sands. The average CIA values in SF and QS coastal dune sands are low relative to the range of the PAAS, suggesting an arid climate and a low intensity of chemical weathering. The SF and QS coastal dune sand samples are plotted in the recycled orogen and partly in craton interior fields suggesting recycled older sedimentary and partly metamorphic-plutonic sources. The high content of quartz with shell debris and carbonates in coastal dune sands support the recycled sedimentary beach and alluvial sand sources. The dominance of heavy minerals like amphiboles (hornblende) and biotite in the coastal dune sands also supports the effect of metamorphic-plutonic source rocks. The new tectonic discriminant-function diagrams suggest that the coastal dune sands were deposited in a passive margin of a synrift basin. The results provide a good evidence for the extension in the Red Sea rift system during Oligocene-post Pliocene, which is consistent with the general geology of Egypt.

  11. Optical and radiocarbon ages of stacked paleosols and dune sands in the Nebraska Sand Hills, USA

    Science.gov (United States)

    Goble, R. J.; Mason, Joseph A.; Loope, David B.; Swinehart, James B.

    2004-05-01

    Optical ages for eolian sands from the Nebraska Sand Hills indicate periods of extensive eolian activity at ca 115±25, 840±70, 2300±240, and 3560±340 a. Activity was also noted at single sampling locations at ca 6180±370, 8430±510 and 13110±800 a. Many of these ages are similar to those noted by earlier authors. Optical ages from samples collected within paleosols indicate shorter and possibly less extensive periods of eolian activity at approximately 1220±150, 1590±110, and possibly 1950±150 a, during which the paleosol sands accumulated. What was originally interpreted as a single 1.2 m thick paleosol is shown by optical dating to consist of three or more welded soils developed within eolian sands with optical ages of ca 3800±240, 2740±240, 1560±110, and possibly 1930±140 a, each of which match eolian pulses recognized elsewhere. Scatter in some optical ages is attributable to intersection of sand-filled rodent burrows extending in outcrop 1.5 m below the contact between paleosol and overlying topset beds. A 5310±360 a optical age for one probable intersected burrow provides evidence for upward or lateral transport of older sands.

  12. Lund Sand No 0

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Jakobsen, Finn Rosendal

    During the last 15 years the Geotechnical Engineering Group (GEG) at Aalborg University has performed triaxial tests with a sand called Lund No 0. Lund No 0 is a graded sand from a gravel pit near Horsens in Denmark. For the classification of the sand the following tests have been performed: Sieve...... test, Grain density, ds, Maximum, emax, and minimum, emin, void ratio. The strength parameters of Lund No 0 are detennined by some drained and undrained triaxial tests in the Danish Triaxial Cell. The Danish Triaxial Cell prescribes smooth pressure heads and specimens with equal height and diameter....... Four series with Id equal to 0.92, 0.87 0.76 and 0.55 have been performed....

  13. Sand dynamic in the Mekong River channel and export to the coastal ocean

    Science.gov (United States)

    Stephens, J. D.; Allison, M. A.; Di Leonardo, D. R.; Weathers, H. D.; Ogston, A. S.; McLachlan, R. L.; Xing, F.; Meselhe, E. A.

    2017-09-01

    Two field campaigns were conducted in the tidal and estuarine reach of the Sông Hậu distributary of the Mekong River to explore the dynamics of sand transport and export to the coastal ocean. This study examines variations in suspended sand concentration and net flux of suspended and bedload sand with respect to changes in discharge between the October 2014 high discharge and March 2015 low discharge season. Isokinetic measurements of suspended sand were used to calibrate a larger dataset of LISST profiles to report suspended sand mass concentrations. During the high discharge season, ebb and flood currents are a primary control on suspended sand concentrations. Ebb tidal flows are more capable of sand transport than flooding flows, due to river discharge augmenting tidal currents. Sand in suspension is primarily derived locally from bed material sand. Bedform transport estimates were limited, but suggest that bedload sand transport is less than 10% of net suspended sand flux. Very low concentrations of suspended sand sediment are found during the low discharge season. These low concentrations are likely caused by (1) a reduction in maximum ebb tide shear stresses associated with less freshwater input, and (2) mud mantling in the bed associated with upstream migration of estuarine circulation, that inhibits local sourcing (resuspension) of bed sand. Results of the observational study were used to calibrate a numerical model of annual sand flux to the ocean from all distributaries of the Mekong River. Annual sand export is estimated at 6.5 ± 1.6 Mt yr-1. The Định An subdistributary accounts for 32% of this total while the smaller Trần Đề subdistributary accounts for only 9%.

  14. UK Frac Sand Resources

    OpenAIRE

    Mitchell, C J

    2015-01-01

    Although still just a glimmer in the gas man’s eye, the prospect of shale hydrocarbon (oil and gas) development in the UK has many companies thinking about the industrial minerals it will require. Chief amongst these is silica sand which is used as a ‘proppant’ in the hydraulic fracturing, or ‘fracking’, of shales to help release the gas. The UK has large resources of sand and sandstone, of which only a small proportion have the necessary technical properties that classify them as ‘silica san...

  15. Bedform dynamics in a large sand-bedded river using multibeam echo sounding

    Science.gov (United States)

    Elliott, C. M.; Jacobson, R. B.; Erwin, S.; Eric, A. B.; DeLonay, A. J.

    2014-12-01

    High-resolution repeat multibeam Echo Sounder (MBES) surveys of the Lower Missouri River in Missouri, USA demonstrate sand bedform movement at a variety of scales over a range of discharges. Understanding dune transport rates and the temporal and spatial variability in sizes across the channel has implications for how sediment transport measurements are made and for understanding the dynamics of habitats utilized by benthic organisms over a range of life stages. Nearly 800 miles of the Lower Missouri River has been altered through channelization and bank stabilization that began in the early 1900's for navigation purposes. Channelization of the Lower Missouri River has created a self-scouring navigation channel with large dunes that migrate downstream over a wide range of discharges. Until the use of MBES surveys on the Missouri River the spatial variability of dune forms in the Missouri River navigation channel was poorly understood. MBES surveys allow for visualization of a range of sand bedforms and repeat measurements demonstrate that dunes are moving over a wide range of discharges on the river. Understanding the spatial variability of dunes and dune movement across the channel and in different channel settings (bends, channel cross-overs, near channel structures) will inform emerging methods in sediment transport measurement that use bedform differencing calculations and provide context for physical bedload sediment sampling on large sand-bedded rivers. Multiple benthic fish species of interest including the endangered pallid sturgeon utilize Missouri River dune fields and adjacent regions for migration, feeding, spawning, early development and dispersal. Surveys using MBES and other hydroacoustic tools provide fisheries biologists with broad new insights into the functionality of bedforms as habitat for critical life stages of large river fish species in the Missouri River, and similar sand-bedded systems.

  16. Sedimentation process of saturated sand under impact loading

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Junfeng; MENG; Xiangyue

    2005-01-01

    The initial small inhomogeneity of saturated sand could be amplified during the sedimentation process after liquefaction, and cracks could be observed in the sand column. Layers of fine sand could also be found at the exact place where cracks developed and disappeared. The phenomena and the whole process were experimentally shown by X-rays images. To account for the phenomena, a linearized stability analysis of the sedimentation of saturated sand was conducted; however, it did not produce a satisfactory result. A three-phase flow model describing the transportation of fine sand is presented in this paper. It is shown that such a kind of erosion/deposition model was qualitatively in good agreement with the experimental observation.

  17. A New Way to Calculate the Critical Pressure Gradient of Sand Production%计算砂岩出砂临界压力梯度的新方法

    Institute of Scientific and Technical Information of China (English)

    聂向荣; 杨胜来; 丁景辰; 李芳芳; 章星

    2013-01-01

    A capillary-tube model is proposed which could transform the porous medium solid liquid coupling problems to duct flow problems,and the dynamic mechanism of sand production is studied according to the fluid mechanics as well as skin effect considered.The critical pressure gradient formula is as a quantifying characterization for the sand production.Based on sensitivity analysis,the critical pressure gradient rises with its thickness increasing.With the sand particle radius increasing,the critical pressure gradient also rises.In order to validate the effectiveness of the formula,a physical simulation experiment is designed.The formulae has a good agreement with experimental,and the average error is only 16%.%将毛管束模型引入到出砂问题的研究中,同时考虑了表皮效应,建立了出砂毛管束物理模型,该模型能够将复杂的多孔介质固液耦合问题转化为宏观的管流流动问题,通过分析砂岩颗粒在毛管束中的受力和运动,建立了砂岩出砂数学模型,分析了出砂过程动态机理,推导了出砂临界压力梯度公式,该公式从理论上对出砂问题进行了定量表征.敏感性分析表明:随着表皮厚度的增大,临界压力梯度增大;随着砂粒半径的增大,临界压力梯度也随之增大.为了验证公式的有效性,设计了砂岩出砂物理模拟实验,结果表明平均误差为16%,和实验符合较好.

  18. Large-scale, low-amplitude bedforms (chevrons) in the selima sand sheet, egypt.

    Science.gov (United States)

    Maxwell, T A; Haynes, C V

    1989-03-03

    Landsat images of the Selima sand sheet in southwestern Egypt display alternating light and dark chevron-shaped patterns that occur downwind from low scarps and major dune fields. Images acquired between 1972 and 1988 indicate that these features move as discrete bedforms at a rate of up to 500 meters per year. Extremely long-wavelength (130 to 1200 meters), low-amplitude (10 to 30 centimeters) bedforms were measured in the field; the light chevrons seen in the orbital data may be thin accumulations of active sand sheet deposits in the lee of these bedforms. Dark chevrons contain an admixture of coarse-granule lag deposits that are continually winnowed by aeolian erosion on the windward sides of the large bedforms. Sediment transport budgets derived from orbital and field analyses suggest net movement of up to 83,000 cubic meters per year for a single light chevron; such measurements can be used as a check on similar calculations from dunes and other smaller scale features to determine sand transport budgets for large areas of the eastern Sahara.

  19. A new low-cost method of reclaiming mixed foundry waste sand based on wet-thermal composite reclamation

    Institute of Scientific and Technical Information of China (English)

    Fan Zitian; Liu Fuchu; Long Wei; Li Guona

    2014-01-01

    A lot of mixed clay-resin waste sand from large-scale iron foundries is discharged every day; so mixed waste sand reclamation in low cost and high quality has a great realistic significance. In the study to investigate the possibility of reusing two types of waste foundry sands, resin bonded sand and clay bonded sand which came from a Chinese casting factory, a new low-cost reclamation method of the mixed foundry waste sand based on the wet-thermal composite reclamation was proposed. The waste resin bonded sand was first reclaimed by a thermal method and the waste clay bonded sand was reclaimed by a wet method. Then, hot thermal reclaimed sand and the dehydrated wet reclaimed sand were mixed in certain proportions so that the hot thermal reclaimed sand dried the wet reclaimed sand leaving some water. The thermal reclamation efficiency of the waste resin bonded sand was researched at different heat levels. The optimized wet reclamation process of the waste clay bonded sand was achieved by investigating the effects of wet reclamation times, sand-water ratio and pH value on the reclaimed sand characteristics. The composite reclamation cost also was calculated. The research results showed that the properties of the mixed reclaimed sand can satisfy the application requirements of foundries; in which the temperature of the thermal reclamation waste resin bonded sand needs to be about 800 ºC, the number of cycles of wet reclamation waste clay bonded sand should reach four to five, the optimal sand-water ratio of wet reclamation is around 1:1.5, and the pH value should be adjusted by adding acid. The mass ratio of hot thermal reclaimed sand to dehydrated wet reclaimed sand is about 1:2.5, and the composite reclaimed sand cost is around 100 yuan RMB per ton.

  20. A new low-cost method of reclaiming mixed foundry waste sand based on wet-thermal composite reclamation

    Directory of Open Access Journals (Sweden)

    Fan Zitian

    2014-09-01

    Full Text Available A lot of mixed clay-resin waste sand from large-scale iron foundries is discharged every day; so mixed waste sand reclamation in low cost and high quality has a great realistic significance. In the study to investigate the possibility of reusing two types of waste foundry sands, resin bonded sand and clay bonded sand which came from a Chinese casting factory, a new low-cost reclamation method of the mixed foundry waste sand based on the wet-thermal composite reclamation was proposed. The waste resin bonded sand was first reclaimed by a thermal method and the waste clay bonded sand was reclaimed by a wet method. Then, hot thermal reclaimed sand and the dehydrated wet reclaimed sand were mixed in certain proportions so that the hot thermal reclaimed sand dried the wet reclaimed sand leaving some water. The thermal reclamation efficiency of the waste resin bonded sand was researched at different heat levels. The optimized wet reclamation process of the waste clay bonded sand was achieved by investigating the effects of wet reclamation times, sand-water ratio and pH value on the reclaimed sand characteristics. The composite reclamation cost also was calculated. The research results showed that the properties of the mixed reclaimed sand can satisfy the application requirements of foundries; in which the temperature of the thermal reclamation waste resin bonded sand needs to be about 800 篊, the number of cycles of wet reclamation waste clay bonded sand should reach four to five, the optimal sand-water ratio of wet reclamation is around 1:1.5, and the pH value should be adjusted by adding acid. The mass ratio of hot thermal reclaimed sand to dehydrated wet reclaimed sand is about 1:2.5, and the composite reclaimed sand cost is around 100 yuan RMB per ton.

  1. Building with Sand

    Science.gov (United States)

    Ashbrook, Peggy

    2010-01-01

    Children playing in damp sand invariably try to make a tower or a tunnel. By providing experiences with a variety of materials, alone and together, teachers set up the conditions for children to learn through their senses and ensure that a class approaches a topic with a common set of experiences to build on. Learning about the properties of…

  2. Faraday, Jets, and Sand

    NARCIS (Netherlands)

    Sandtke, M.; van der Meer, Roger M.; Versluis, Andreas Michel; Lohse, Detlef

    2003-01-01

    When a 6-mm layer of fine sand with an average grain size of 40 µm is poured into a cylindrical container and shaken vertically, thin jets are seen to emerge from an airy cloud of grains, almost like protuberances from the corona of the sun. A quasi two-dimensional setup reveals the jet-formation

  3. Building with Sand

    Science.gov (United States)

    Ashbrook, Peggy

    2010-01-01

    Children playing in damp sand invariably try to make a tower or a tunnel. By providing experiences with a variety of materials, alone and together, teachers set up the conditions for children to learn through their senses and ensure that a class approaches a topic with a common set of experiences to build on. Learning about the properties of…

  4. Speleothems and Sand Castles

    Science.gov (United States)

    Hance, Trevor; Befus, Kevin

    2015-01-01

    The idea of building sand castles evokes images of lazy summer days at the beach, listening to waves crash, enjoying salty breezes, and just unplugging for a while to let our inner child explore the wonderful natural toys beneath our feet. The idea of exploring caves might evoke feelings and images of claustrophobia or pioneers and Native…

  5. Virksomhedens sande ansigt

    DEFF Research Database (Denmark)

    Lundholt, Marianne Wolff

    2017-01-01

    Er modhistorier en byrde eller en styrke i forandringsprocesser? Hvad stiller vi op, når adgangen til organisationens sande identitet går gennem medarbejdernes modhistorier? Når vi sammenholder denne erkendelse med vores viden om, at medarbejdere helt naturligt afholder sig fra at videregive disse...

  6. Sand (CSW4)

    CSIR Research Space (South Africa)

    Estuarine and Coastal Research Unit

    1982-12-01

    Full Text Available This report is one of a series on Cape Estuaries being published under the general title "The Estuaries of the Cape, Part 2". The report provides information on sand estuary: historical background, abiotic and biotic characteristics. It is pointed...

  7. Parametric fits to 1-D neutron transport calculations for lithium-vanadium fusion power plant blankets in cylindrical and spherical geometries

    Energy Technology Data Exchange (ETDEWEB)

    Petzoldt, R.W.; Perkins, L.J.

    1995-06-16

    The authors performed 1-D coupled, neutron-gamma transport calculations for lithium-vanadium blankets and lithium-sodium cauldron pot blankets in cylindrical and spherical geometries. Parametric fits to the data are supplied for subsequent use in systems code models. Scaling relationships are given for various neutronics parameters of interest, including: tritium breeding ratio, neutron energy multiplication, magnet dose rates, magnet heating rates, and integrated magnet fluence.

  8. Erosion phenomena in sand moulds

    Directory of Open Access Journals (Sweden)

    A. Chojecki

    2008-03-01

    Full Text Available Authors studicd the erosion phcnorncna in sand moulds pured with cast iron. Thc study comprises an evaluation of erosionresistance of thc three sands: grccn sand. sand bondcd with inorganic or organic bindcr. It was concluded that thc most resistant is [heclassic green sand with thc addition of 5 B coal dust. Resistance of the sand with organic binder is generally weak and dcvnds onkind of used raisin. Spccinl nztcntion was paid to the sands with no organic bindcr watcr glass and phospha~c. It was Sound that thcirrcsistance depends on dehydratation conditions. When the mould is stored in law humidity of atmosphcrc the very strong crosion canbe expected. It rcsul ts hrn thc micro fractures in the bridges of binders, joining the grains of the sable. This phcnomcna facilitates thetearing away of fragments of sand [tom the surface

  9. Water management in the oil sands industry

    Energy Technology Data Exchange (ETDEWEB)

    Pauls, R. [Syncrude Canada Ltd., Fort McMurray, AB (Canada)

    2004-07-01

    Water management issues at Alberta's 4 oil sand deposits were discussed. The 4 deposits include the Peace River, Athabasca, Wabasca and Cold Lake deposits, with the Athabasca deposit being the largest and the only surface-mineable deposit. Large quantities of water are needed to extract bitumen from oil sands. This paper addressed water volume withdrawal from the Athabasca River, the primary source of water for the surface-mining oil sands industry. It also addressed Muskeg River watershed integrity, quality of water withdrawn from reclaimed landscapes, groundwater contamination, and ecological viability of end-pit lakes. Currently, half of Syncrude's oil sand is transported from mine to extraction plant by conveyor belts. The other half is pipelined as a warm water slurry. By 2005, all transport will be by pipeline. The oil sand is mixed with hot water, steam and surfactants to condition it for extraction. Seventy-nine per cent of the water used by Syncrude is recycled water and the remainder comes from the Athabasca River. Syncrude diverts 2.5 to 3 barrels of water from the Athabasca River for every barrel of oil produced. This paper discussed the in-stream flow needs of the Athabasca River based on protection of aquatic ecosystems. Flow needs are addressed by the Cumulative Effects Management Association (CEMA). The paper states that the proportion of annual flow withdrawn from the Athabasca River is too low to have a significant impact on aquatic systems, but the main concern lies in water use during low flow periods, typically during the winter months. Developers will likely come under pressure to develop off-site reservoirs to store water for use during these low-flow periods. tabs., figs.

  10. Incipient Motion of Sand and Oil Agglomerates

    Science.gov (United States)

    Nelson, T. R.; Dalyander, S.; Jenkins, R. L., III; Penko, A.; Long, J.; Frank, D. P.; Braithwaite, E. F., III; Calantoni, J.

    2016-12-01

    Weathered oil mixed with sediment in the surf zone in the northern Gulf of Mexico after the 2010 Deepwater Horizon oil spill, forming large mats of sand and oil. Wave action fragmented the mats into sand and oil agglomerates (SOAs) with diameters of about 1 to 10 cm. These SOAs were transported by waves and currents along the Gulf Coast, and have been observed on beaches for years following the spill. SOAs are composed of 70%-95% sand by mass, with an approximate density of 2107 kg/m³. To measure the incipient motion of SOAs, experiments using artificial SOAs were conducted in the Small-Oscillatory Flow Tunnel at the U.S. Naval Research Laboratory under a range of hydrodynamic forcing. Spherical and ellipsoidal SOAs ranging in size from 0.5 to 10 cm were deployed on a fixed flat bed, a fixed rippled bed, and a movable sand bed. In the case of the movable sand bed, SOAs were placed both proud and partially buried. Motion was tracked with high-definition video and with inertial measurement units embedded in some of the SOAs. Shear stress and horizontal pressure gradients, estimated from velocity measurements made with a Nortek Vectrino Profiler, were compared with observed mobility to assess formulations for incipient motion. For SOAs smaller than 1 cm in diameter, incipient motion of spherical and ellipsoidal SOAs was consistent with predicted critical stress values. The measured shear stress at incipient motion of larger, spherical SOAs was lower than predicted, indicating an increased dependence on the horizontal pressure gradient. In contrast, the measured shear stress required to move ellipsoidal SOAs was higher than predicted, even compared to values modified for larger particles in mixed-grain riverine environments. The laboratory observations will be used to improve the prediction of incipient motion, transport, and seafloor interaction of SOAs.

  11. On Pluvial Compaction of Sand

    DEFF Research Database (Denmark)

    Jacobsen, Moust

    At the Institute of Civil Engineering in Aalborg model tests on dry sand specimens have been carried out during the last five years. To reduce deviations in test results, the sand laying technique has been carefully studied, and the sand mass spreader constructed. Preliminary results have been...

  12. Off-line algorithm for calculation of vertical tracer transport in the troposphere due to deep convection

    NARCIS (Netherlands)

    Belikov, D.A.; Maksyutov, S.; Krol, M.C.; Fraser, A.; Rigby, M.; Bian, H.; Agusti-Panareda, A.; Bergmann, D.; Bousquet, P.; Cameron-Smith, P.; Chipperfield, M.P.; Fortems-Cheiney, A.; Gloor, E.; Haynes, K.; Hess, P.; Houweling, S.; Kawa, S.R.; Law, R.M.; Loh, Z.; Meng, L.; Palmer, P.I.; Patra, P.K.; Prinn, R.G.; Saito, R.; Wilson, C.

    2013-01-01

    A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical

  13. Off-line algorithm for calculation of vertical tracer transport in the troposphere due to deep convection

    Directory of Open Access Journals (Sweden)

    D. A. Belikov

    2012-08-01

    Full Text Available A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical transport within the scheme includes entrainment and detrainment processes in convective updrafts and downdrafts. Output from the proposed parametrisation scheme is employed in the National Institute for Environmental Studies (NIES global chemical transport model driven by JRA-25/JCDAS reanalysis. The simulated convective precipitation rate and mass fluxes are compared with observations and reanalysis data. A simulation of the short-lived tracer 222Rn is used to further evaluate the performance of the cumulus convection scheme. Simulated distributions of 222Rn are validated against observations at the surface and in the free troposphere, and compared with output from models that participated in the TransCom-CH4 Transport Model Intercomparison. From this comparison, we demonstrate that the proposed convective scheme can successfully reproduce deep cloud convection.

  14. Off-line algorithm for calculation of vertical tracer transport in the troposphere due to deep convection

    Directory of Open Access Journals (Sweden)

    D. A. Belikov

    2013-02-01

    Full Text Available A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical transport within the scheme includes entrainment and detrainment processes in convective updrafts and downdrafts. Output from the proposed parametrisation scheme is employed in the National Institute for Environmental Studies (NIES global chemical transport model driven by JRA-25/JCDAS reanalysis. The simulated convective precipitation rate and mass fluxes are compared with observations and reanalysis data. A simulation of the short-lived tracer 222Rn is used to further evaluate the performance of the cumulus convection scheme. Simulated distributions of 222Rn are evaluated against observations at the surface and in the free troposphere, and compared with output from models that participated in the TransCom-CH4 Transport Model Intercomparison. From this comparison, we demonstrate that the proposed convective scheme in general is consistent with observed and modeled results.

  15. Off-line algorithm for calculation of vertical tracer transport in the troposphere due to deep convection

    NARCIS (Netherlands)

    Belikov, D.A.; Maksyutov, S.; Krol, M.C.; Fraser, A.; Rigby, M.; Bian, H.; Agusti-Panareda, A.; Bergmann, D.; Bousquet, P.; Cameron-Smith, P.; Chipperfield, M.P.; Fortems-Cheiney, A.; Gloor, E.; Haynes, K.; Hess, P.; Houweling, S.; Kawa, S.R.; Law, R.M.; Loh, Z.; Meng, L.; Palmer, P.I.; Patra, P.K.; Prinn, R.G.; Saito, R.; Wilson, C.

    2013-01-01

    A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical transpo

  16. Geologic and paleoecologic studies of the Nebraska Sand Hills

    Science.gov (United States)

    Ahlbrandt, Thomas S.; Fryberger, S.G.; Hanley, John H.; Bradbury, J. Platt

    1980-01-01

    PART A: The Nebraska Sand Hills are an inactive, late Quaternary, most probably Holocene, dune field (covering 57,000 km 2 ) that have been eroded along streams and in blowouts, resulting in excellent lateral and vertical exposures of the stratification of dune and interdune sediments. This paper presents new data on the geometry, primary sedimentary structures, modification of sedimentary structures, direction of sand movement, and petrography of these eolian deposits. Eolian deposits of the Sand Hills occur as relatively thin (9-24 m) 'blanket' sands, composed of a complex of dune and discontinuous, diachronous interdune deposits unconformably overlying fluviolacustrine sediments. The internal stratification of large dunes in the Sand Hills (as high as 100 m), is similar to the internal stratification of smaller dunes of the same type in the Sand Hills, differing only in scale. Studies of laminae orientation in the Sand Hills indicate that transverse, barchan, and blowout dunes can be differentiated in rocks of eolian origin using both the mean dip angle of laminae and the mean angular deviation of dip direction. A variety of secondary structures modify or replace primary eolian stratification in the Sand Hills, the more common of which are dissipation structures and bioturbation. Dissipation structures in the Sand Hills may develop when infiltrating water deposits clay adjacent to less permeable layers in the sand, or along the upper margins of frozen layers that form in the sands during winter. Cross-bed measurements from dunes of the Nebraska Sand Hills necessitate a new interpretation of the past sand transport directions. The data from these measurements indicate a general northwest-to-southeast drift of sand, with a more southerly drift in the southeast part of the Sand Hills. A large area of small dunes Sand Hills was interpreted by him on the basis of morphology only. We interpret these as transverse-ridge dunes that were generally moving to the south

  17. Modeling of radionuclide transport through rock formations and the resulting radiation exposure of reference persons. Calculations using Asse II parameters; Modellierung des Transports von Radionukliden durch Gesteinsschichten und der resultierenden Strahlenexposition von Referenzpersonen. Berechnungen mit Parametern der Asse II

    Energy Technology Data Exchange (ETDEWEB)

    Kueppers, Christian; Ustohalova, Veronika; Steinhoff, Mathias

    2012-05-21

    The long-term release of radioactivity into the ground water path cannot be excluded for the radioactive waste repository Asse II. The possible radiological consequences were analyzed using a radio-ecological scenario developed by GRS. A second scenario was developed considering the solubility of radionuclides in salt saturated solutions and retarding/retention effects during the radionuclide transport through the cap rock layers. The modeling of possible radiation exposure was based on the lifestyle habits of reference persons. In Germany the calculation procedure for the prediction of radionuclide release from final repositories is not defined by national standards, the used procedures are based on analogue methods from other radiation protection calculations.

  18. Sand hazards on tourist beaches.

    Science.gov (United States)

    Heggie, Travis W

    2013-01-01

    Visiting the beach is a popular tourist activity worldwide. Unfortunately, the beach environment is abundant with hazards and potential danger to the unsuspecting tourist. While the traditional focus of beach safety has been water safety oriented, there is growing concern about the risks posed by the sand environment on beaches. This study reports on the death and near death experience of eight tourists in the collapse of sand holes, sand dunes, and sand tunnels. Each incident occurred suddenly and the complete burial in sand directly contributed to the victims injury or death in each case report.

  19. FW-CADIS Method for Global and Semi-Global Variance Reduction of Monte Carlo Radiation Transport Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, John C [ORNL; Peplow, Douglas E. [ORNL; Mosher, Scott W [ORNL

    2014-01-01

    This paper presents a new hybrid (Monte Carlo/deterministic) method for increasing the efficiency of Monte Carlo calculations of distributions, such as flux or dose rate distributions (e.g., mesh tallies), as well as responses at multiple localized detectors and spectra. This method, referred to as Forward-Weighted CADIS (FW-CADIS), is an extension of the Consistent Adjoint Driven Importance Sampling (CADIS) method, which has been used for more than a decade to very effectively improve the efficiency of Monte Carlo calculations of localized quantities, e.g., flux, dose, or reaction rate at a specific location. The basis of this method is the development of an importance function that represents the importance of particles to the objective of uniform Monte Carlo particle density in the desired tally regions. Implementation of this method utilizes the results from a forward deterministic calculation to develop a forward-weighted source for a deterministic adjoint calculation. The resulting adjoint function is then used to generate consistent space- and energy-dependent source biasing parameters and weight windows that are used in a forward Monte Carlo calculation to obtain more uniform statistical uncertainties in the desired tally regions. The FW-CADIS method has been implemented and demonstrated within the MAVRIC sequence of SCALE and the ADVANTG/MCNP framework. Application of the method to representative, real-world problems, including calculation of dose rate and energy dependent flux throughout the problem space, dose rates in specific areas, and energy spectra at multiple detectors, is presented and discussed. Results of the FW-CADIS method and other recently developed global variance reduction approaches are also compared, and the FW-CADIS method outperformed the other methods in all cases considered.

  20. PROCESSING OF MONAZITE SAND

    Science.gov (United States)

    Calkins, G.D.; Bohlmann, E.G.

    1957-12-01

    A process for the recovery of thorium, uranium, and rare earths from monazite sands is presented. The sands are first digested and dissolved in concentrated NaOH, and the solution is then diluted causing precipitation of uranium, thorium and rare earth hydroxides. The precipitate is collected and dissolved in HCl, and the pH of this solution is adjusted to about 6, precipitating the hydroxides of thorium and uranium but leaving the rare earths in solution. The rare earths are then separated from the solution by precipitation at a still higher pH. The thorium and uranium containing precipitate is redissolved in HNO/sub 3/ and the two elements are separated by extraction into tributyl phosphate and back extraction with a weakly acidic solution to remove the thorium.

  1. Moving sand dunes

    CERN Document Server

    Sparavigna, Amelia Carolina

    2011-01-01

    In several desert areas, the slow motion of sand dunes can be a challenge for modern human activities and a threat for the survival of ancient places or archaeological sites. However, several methods exist for surveying the dune fields and estimate their migration rate. Among these methods, the use of satellite images, in particular of those freely available on the World Wide Web, is a convenient resource for the planning of future human settlements and activities.

  2. OECD/NEA burnup credit criticality benchmarks phase IIIA: Criticality calculations of BWR spent fuel assemblies in storage and transport

    Energy Technology Data Exchange (ETDEWEB)

    Okuno, Hiroshi; Naito, Yoshitaka [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Ando, Yoshihira [Toshiba Corp., Kawasaki, Kanagawa (Japan)

    2000-09-01

    The report describes the final results of Phase IIIA Benchmarks conducted by the Burnup Credit Criticality Calculation Working Group under the auspices of the Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD/NEA). The benchmarks are intended to confirm the predictive capability of the current computer code and data library combinations for the neutron multiplication factor (k{sub eff}) of a layer of irradiated BWR fuel assembly array model. In total 22 benchmark problems are proposed for calculations of k{sub eff}. The effects of following parameters are investigated: cooling time, inclusion/exclusion of FP nuclides and axial burnup profile, and inclusion of axial profile of void fraction or constant void fractions during burnup. Axial profiles of fractional fission rates are further requested for five cases out of the 22 problems. Twenty-one sets of results are presented, contributed by 17 institutes from 9 countries. The relative dispersion of k{sub eff} values calculated by the participants from the mean value is almost within the band of {+-}1%{delta}k/k. The deviations from the averaged calculated fission rate profiles are found to be within {+-}5% for most cases. (author)

  3. Development And Implementation Of Photonuclear Cross-section Data For Mutually Coupled Neutron-photon Transport Calculations In The Monte Carlo N-particle (mcnp) Radiation Transport Code

    CERN Document Server

    White, M C

    2000-01-01

    The fundamental motivation for the research presented in this dissertation was the need to development a more accurate prediction method for characterization of mixed radiation fields around medical electron accelerators (MEAs). Specifically, a model is developed for simulation of neutron and other particle production from photonuclear reactions and incorporated in the Monte Carlo N-Particle (MCNP) radiation transport code. This extension of the capability within the MCNP code provides for the more accurate assessment of the mixed radiation fields. The Nuclear Theory and Applications group of the Los Alamos National Laboratory has recently provided first-of-a-kind evaluated photonuclear data for a select group of isotopes. These data provide the reaction probabilities as functions of incident photon energy with angular and energy distribution information for all reaction products. The availability of these data is the cornerstone of the new methodology for state-of-the-art mutually coupled photon-neutron tran...

  4. Model test study of evaporation mechanism of sand under constant atmospheric condition

    OpenAIRE

    Cui, Yu Jun; Ding, Wenqi; SONG, Weikang

    2014-01-01

    The evaporation mechanism of Fontainebleau sand using a large-scale model chamber is studied. First, the evaporation test on a layer of water above sand surface is performed under various atmospheric conditions, validating the performance of the chamber and the calculation method of actual evaporation rate by comparing the calculated and measured cumulative evaporations. Second,the evaporation test on sand without water layer is conducted under constant atmospheric condition. Both the evoluti...

  5. Analytical and Experimental Studieson Fracture Behaviour of Foundry Sand Concrete

    Directory of Open Access Journals (Sweden)

    Sasikumar.A

    2016-04-01

    Full Text Available Concrete is a widely used as vital material in the construction world. We can do partial substitution of industrial waste such as foundry sand like material in sand. Foundry sand is not only the economical material also improves the properties of the concrete. Foundry sand has emerged as construction material in its own right. This type of concrete normally contains around (30%, 40% by mass of total sand materials. It improves the workability, minimizes cracking due to thermal and drying shrinkage, and enhances durability to reinforcement corrosion, sulphateattack, and alkali-silica expansion. Fracture mechanics is the field of mechanics concerned with the study of the formation of cracks in materials. It uses methods of analytical Solid mechanics to calculate the driving force on a crack and those of experimental Solid mechanics to characterize the material's resistance to fracture. J-integral and critical stress intensity factor is the fracture parameter. The fracture parameters calculated in our study are stress intensity factor, Critical j-integral. Three point bending test is used to find the fracture parameter. The study is carried out on beams of grade M20 with 0%, 30%, & 40% foundry sand. The test is conducted for normal beams and pre-cracked beams of having a notch to depth ratio (A/W of 0.2. This study concludes that the critical j-integral and stress intensity factors increases by comparing the 0%, 30%, 40% foundry sand concrete

  6. Booming Sand Dunes

    Science.gov (United States)

    Vriend, Nathalie

    "Booming" sand dunes are able to produce low-frequency sound that resembles a pure note from a music instrument. The sound has a dominant audible frequency (70-105 Hz) and several higher harmonics and may be heard from far distances away. A natural or induced avalanche from a slip face of the booming dune triggers the emission that may last for several minutes. There are various references in travel literature to the phenomenon, but to date no scientific explanation covered all field observations. This thesis introduces a new physical model that describes the phenomenon of booming dunes. The waveguide model explains the selection of the booming frequency and the amplification of the sound in terms of constructive interference in a confined geometry. The frequency of the booming is a direct function of the dimensions and velocities in the waveguide. The higher harmonics are related to the higher modes of propagation in the waveguide. The experimental validation includes quantitative field research at the booming dunes of the Mojave Desert and Death Valley National Park. Microphone and geophone recordings of the acoustic and seismic emission show a variation of booming frequency in space and time. The analysis of the sensor data quantifies wave propagation characteristics such as speed, dispersion, and nonlinear effects and allows the distinction between the source mechanism of the booming and the booming itself. The migration of sand dunes results from a complicated interplay between dune building, wind regime, and precipitation. The morphological and morphodynamical characteristics of two field locations are analyzed with various geophysical techniques. Ground-penetrating radar images the subsurface structure of the dunes and reveal a natural, internal layering that is directly related to the history of dune migration. The seismic velocity increases abruptly with depth and gradually increases with downhill position due to compaction. Sand sampling shows local

  7. Nonequilibrium generalised Langevin equation for the calculation of heat transport properties in model 1D atomic chains coupled to two 3D thermal baths.

    Science.gov (United States)

    Ness, H; Stella, L; Lorenz, C D; Kantorovich, L

    2017-04-28

    We use a generalised Langevin equation scheme to study the thermal transport of low dimensional systems. In this approach, the central classical region is connected to two realistic thermal baths kept at two different temperatures [H. Ness et al., Phys. Rev. B 93, 174303 (2016)]. We consider model Al systems, i.e., one-dimensional atomic chains connected to three-dimensional baths. The thermal transport properties are studied as a function of the chain length N and the temperature difference ΔT between the baths. We calculate the transport properties both in the linear response regime and in the non-linear regime. Two different laws are obtained for the linear conductance versus the length of the chains. For large temperatures (T≳500 K) and temperature differences (ΔT≳500 K), the chains, with N>18 atoms, present a diffusive transport regime with the presence of a temperature gradient across the system. For lower temperatures (T≲500 K) and temperature differences (ΔT≲400 K), a regime similar to the ballistic regime is observed. Such a ballistic-like regime is also obtained for shorter chains (N≤15). Our detailed analysis suggests that the behaviour at higher temperatures and temperature differences is mainly due to anharmonic effects within the long chains.

  8. Calculation and validation of wetting depth of infiltration in aeolian sand in arid areas based on particle model%基于颗粒模型的风积砂层降雨入渗深度计算及验证

    Institute of Scientific and Technical Information of China (English)

    黄德文; 陈建生; 詹泸成

    2016-01-01

    为了研究沙漠干旱区降雨对砂层非饱和带水分的贡献,该文对风积砂层水分入渗过程中的水分存在形式和运移机理进行了理论和力学分析。通过以触点水为主要储水单元的立方布局颗粒模型推导出水分入渗过程中湿润深度的解析表达式,并进行验证。物理和力学分析表明,砂颗粒表面很难形成较厚的薄膜水,砂层非饱和带水分大部分以触点水的形式存在。模型计算结果表明,水分入渗的湿润深度与入渗水量和触点水湿润角有关。模型验证表明,水分入渗湿润深度的解析表达式在风积砂层入渗深度计算中具有一定的适用性,但触点水湿润角与砂颗粒粒径的函数关系还有待进一步研究当设定触点水湿润角为π/4时,比例常数为11.5。该研究可为干旱区农业规划提供依据。%In Badain Jaran Desert, an extremely arid region with annual precipitation of 100 mm and annual evaporation of 3 000 mm, the sand underneath a dry surface layer of about 20 cm is relatively wet. Even at the top of the giant dunes, which is about 300 m high, the moisture content at the depth of 2 m is more than 3% in a volumetric fraction. The provenance of soil water in the wet sand layer has always been in dispute over decades. In order to give a better understanding of the contribution of local rainfall to the soil water in unsaturated sand layers, the theoretical analysis and model calculation was conducted. The physical and mechanical mechanisms of moisture movement in the process of water infiltration were analyzed, and the states of moisture in unsaturated sand layers were taken into consideration. Focusing on the microscopic physical model, by the assumptions of spherical particles, the descriptions for the formation mechanism on pendular water and water retention attributed by pendular water in particle materials were presented. And the analytical expressions for rainfall infiltration

  9. GPU-Accelerated Monte Carlo Electron Transport Methods: Development and Application for Radiation Dose Calculations Using Six GPU cards

    Science.gov (United States)

    Su, Lin; Du, Xining; Liu, Tianyu; Xu, X. George

    2014-06-01

    An electron-photon coupled Monte Carlo code ARCHER - Accelerated Radiation-transport Computations in Heterogeneous EnviRonments - is being developed at Rensselaer Polytechnic Institute as a software testbed for emerging heterogeneous high performance computers that utilize accelerators such as GPUs. This paper presents the preliminary code development and the testing involving radiation dose related problems. In particular, the paper discusses the electron transport simulations using the class-II condensed history method. The considered electron energy ranges from a few hundreds of keV to 30 MeV. For photon part, photoelectric effect, Compton scattering and pair production were modeled. Voxelized geometry was supported. A serial CPU code was first written in C++. The code was then transplanted to the GPU using the CUDA C 5.0 standards. The hardware involved a desktop PC with an Intel Xeon X5660 CPU and six NVIDIA Tesla™ M2090 GPUs. The code was tested for a case of 20 MeV electron beam incident perpendicularly on a water-aluminum-water phantom. The depth and later dose profiles were found to agree with results obtained from well tested MC codes. Using six GPU cards, 6x106 electron histories were simulated within 2 seconds. In comparison, the same case running the EGSnrc and MCNPX codes required 1645 seconds and 9213 seconds, respectively. On-going work continues to test the code for different medical applications such as radiotherapy and brachytherapy.

  10. Bidirectional effect of magnetic field on electronic thermal transport of metals from all-electron first-principles calculations

    Science.gov (United States)

    Yang, Jia-Yue; Yue, Sheng-Ying; Hu, Ming

    2016-12-01

    Considerable discussions have occurred about the critical role played by free electrons in the transport of heat in pure metals. In principle, any environment that can influence the dynamical behaviors of electrons would have impact on electronic thermal conductivity (κel) of metals. Over the past decades, significant progress and comprehensive understanding have been gained from theoretical, as well as experimental, investigations by taking into account the effects of various conditions, typically temperature, impurities, strain, dimensionality, interface, etc. However, the effect of external magnetic field has received less attention. In this paper, the magnetic-field dependence of electron-phonon scattering, the electron's lifetime, and κel of representative metals (Al, Ni, and Nb) are investigated within the framework of all-electron spin-density functional theory. For Al and Ni, the induced magnetization vector field and difference in electron density under external magnetic-field aggregate toward the center of unit cell, leading to the enhanced electron-phonon scattering, the damped electron's lifetime, and thus the reduced κel. On the contrary, for Nb with strong intrinsic electron-phonon interaction, the electron's lifetime and κel slightly increase as external magnetic field is enhanced. This is mainly attributed to the separately distributed magnetization vector field and difference in electron density along the corner of unit cell. This paper sheds light on the origin of influence of external magnetic field on κel for pure metals and offers a new route for robust manipulation of electronic thermal transport via applying external magnetic field.

  11. Sediment mathematical model for sand ridges and sand waves

    Institute of Scientific and Technical Information of China (English)

    LI Daming; WANG Xiao; WANG Xin; LI Yangyang

    2016-01-01

    A new theoretical model is formulated to describe internal movement mechanisms of the sand ridges and sand waves based on the momentum equation of a solid-liquid two-phase flow under a shear flow. Coupling this equation with two-dimensional shallow water equations and wave reflection-diffraction equation of mild slope, a two-dimensional coupling model is established and a validation is carried out by observed hydrogeology, tides, waves and sediment. The numerical results are compared with available observations. Satisfactory agreements are achieved. This coupling model is then applied to the Dongfang 1-1 Gas Field area to quantitatively predict the movement and evolution of submarine sand ridges and sand waves. As a result, it is found that the sand ridges and sand waves movement distance increases year by year, but the development trend is stable.

  12. Parallel computing for homogeneous diffusion and transport equations in neutronics; Calcul parallele pour les equations de diffusion et de transport homogenes en neutronique

    Energy Technology Data Exchange (ETDEWEB)

    Pinchedez, K

    1999-06-01

    Parallel computing meets the ever-increasing requirements for neutronic computer code speed and accuracy. In this work, two different approaches have been considered. We first parallelized the sequential algorithm used by the neutronics code CRONOS developed at the French Atomic Energy Commission. The algorithm computes the dominant eigenvalue associated with PN simplified transport equations by a mixed finite element method. Several parallel algorithms have been developed on distributed memory machines. The performances of the parallel algorithms have been studied experimentally by implementation on a T3D Cray and theoretically by complexity models. A comparison of various parallel algorithms has confirmed the chosen implementations. We next applied a domain sub-division technique to the two-group diffusion Eigen problem. In the modal synthesis-based method, the global spectrum is determined from the partial spectra associated with sub-domains. Then the Eigen problem is expanded on a family composed, on the one hand, from eigenfunctions associated with the sub-domains and, on the other hand, from functions corresponding to the contribution from the interface between the sub-domains. For a 2-D homogeneous core, this modal method has been validated and its accuracy has been measured. (author)

  13. Density-functional calculations of transport properties in the nondegenerate limit and the role of electron-electron scattering

    Science.gov (United States)

    Desjarlais, Michael P.; Scullard, Christian R.; Benedict, Lorin X.; Whitley, Heather D.; Redmer, Ronald

    2017-03-01

    We compute electrical and thermal conductivities of hydrogen plasmas in the nondegenerate regime using Kohn-Sham density functional theory (DFT) and an application of the Kubo-Greenwood response formula, and demonstrate that for thermal conductivity, the mean-field treatment of the electron-electron (e-e) interaction therein is insufficient to reproduce the weak-coupling limit obtained by plasma kinetic theories. An explicit e-e scattering correction to the DFT is posited by appealing to Matthiessen's Rule and the results of our computations of conductivities with the quantum Lenard-Balescu (QLB) equation. Further motivation of our correction is provided by an argument arising from the Zubarev quantum kinetic theory approach. Significant emphasis is placed on our efforts to produce properly converged results for plasma transport using Kohn-Sham DFT, so that an accurate assessment of the importance and efficacy of our e-e scattering corrections to the thermal conductivity can be made.

  14. Dark grains of sand: a geological storytelling

    Science.gov (United States)

    Gallo Maresca, Magda

    2017-04-01

    In the secondary Italian school the Earth science learning begins at first year, in synergy with other natural science subjects such as Astronomy, Chemistry and Biology. Italian teachers have to focus on the landscape geomorphological aspects and often Earth processes are difficult to display since they are related to certain phenomena happened during the past and often far from the involved country. In order to better understand the environment surrounding us, very simple and poor materials, like sands, allow the teachers to create attractive lab experiences. According to the IBSE (Inquiry Based Science Education) approach, a learning unit has been implemented starting from a walking along the light carbonate beaches of the Adriatic sea: a smart look to the sands ("engage step"), stroke the students fantasy pushing them to explore some strange black grains on the sands. Dirty sands? Or rock landscape, soil degradation and Ofanto river and coastal processes (erosion, transportation and deposition)? This was the teaching challenge. Due to the youngest age, a third level, guided inquiry, was adopted so the teacher is the "guide of inquiry" encouraging the students using the research question ("Why is the sand dark?", "Do all sands look the same?", "Where does it come from?") and driving the students around their investigation plans ("How can I measure grain size?"). A procedure to answer the above questions and validate the results and explanations has been implemented to allow the students to be proactive in their study. During the learning activities will be the students to ask for field trip to elaborate their new knowledge, verify and visualize the speculated processes. The teaching skills allow to address several geosciences domains such as mineralogy, petrology, regional geology and geodynamics as well as other scientific disciplines such as mathematics (more specifically statistics), forensic science and even life sciences (the presence of bioclasts might

  15. Fresh groundwater resources in a large sand replenishment

    Science.gov (United States)

    Huizer, Sebastian; Oude Essink, Gualbert H. P.; Bierkens, Marc F. P.

    2016-08-01

    The anticipation of sea-level rise and increases in extreme weather conditions has led to the initiation of an innovative coastal management project called the Sand Engine. In this pilot project a large volume of sand (21.5 million m3) - also called sand replenishment or nourishment - was placed on the Dutch coast. The intention is that the sand is redistributed by wind, current, and tide, reinforcing local coastal defence structures and leading to a unique, dynamic environment. In this study we investigated the potential effect of the long-term morphological evolution of the large sand replenishment and climate change on fresh groundwater resources. The potential effects on the local groundwater system were quantified with a calibrated three-dimensional (3-D) groundwater model, in which both variable-density groundwater flow and salt transport were simulated. Model simulations showed that the long-term morphological evolution of the Sand Engine results in a substantial growth of fresh groundwater resources, in all adopted climate change scenarios. Thus, the application of a local sand replenishment could provide coastal areas the opportunity to combine coastal protection with an increase of the local fresh groundwater availability.

  16. The extraction of bitumen from western oil sands. Quarterly report, April--June 1993

    Energy Technology Data Exchange (ETDEWEB)

    Oblad, A.G.; Bunger, J.W.; Deo, M.D.; Fletcher, J.V.; Hanson, F.V.; Miller, J.D.; Seader, J.D.

    1993-07-01

    Accomplishments are briefly described for the following tasks: environmental impact statement; coupled fluidized bed bitumen recovery and coked sand combustion; water-based recovery of bitumen; rotary kiln process for recovery of bitumen and combustion of coke sand; recovery of bitumen from oil sands using fluidized bed reactors and combustion of spent sands in transport reactors; recovery of bitumen from oil sand and upgrading of bitumen by solvent extraction; catalytic and thermal upgrading of bitumens and bitumen-derived liquids; evaluation of Utah`s major oil sand deposits for the production of asphalt, high energy jet fuels and other specialty products; development of mathematical models for bitumen recovery and processing; completion of the cost examination study of the pilot plant restoration; development studies of equipment for three-product gravity separation of bitumen and sand; determine thickener requirements; and environmental studies of the North Salt Lake pilot plant rehabilitation and eventual operation and those environmental problems associated with eventual commercial products.

  17. Report of the Inland Waterway Transport (IWT) Mission, 5 February-20 April 1985. Appendices

    Science.gov (United States)

    1985-06-01

    Province would be coal, urea and moutai. It is proposed to build 6 dams along the river. Cargo volume could increase from 600,000 tons to 3.0 millions tons...between Tha Rua (Pasak River) and Bangkok for cement, maize and gravel transport, or on the lower Chao Phraya for sand transport. 115...given in Table 1 below. Traffic From surveys carried out in 1984, duplicated annual traffic through lock was calculated to be: Rice, paddy, maize 2.5

  18. Extension and validation of ARTM (atmospheric radionuclide transportation model) for the application as dispersion calculation model in AVV (general administrative provision) and SBG (incident calculation bases); Erweiterung und Validierung von ARTM fuer den Einsatz als Ausbreitungsmodell in AVV und SBG

    Energy Technology Data Exchange (ETDEWEB)

    Martens, Reinhard; Bruecher, Wenzel; Richter, Cornelia; Sentuc, Florence; Sogalla, Martin; Thielen, Harald

    2012-02-15

    In the medium-term time scale the Gaussian plume model used so far for atmospheric dispersion calculations in the General Administrative Provision (AVV) relating to Section 47 of the Radiation Protection Ordinance (StrISchV) as well as in the Incident Calculation Bases (SGB) relating to Section 49 StrISchV is to be replaced by a Lagrangian particle model. Meanwhile the Atmospheric Radionuclide Transportation Model (ARTM) is available, which allows the simulation of the atmospheric dispersion of operational releases from nuclear installations. ARTM is based on the program package AUSTAL2000 which is designed for the simulation of atmospheric dispersion of nonradioactive operational releases from industrial plants and was adapted to the application of airborne radioactive releases. In the context of the research project 3608S05005 possibilities for an upgrade of ARTM were investigated and implemented as far as possible to the program system. The work program comprises the validation and evaluation of ARTM, the implementation of technical-scientific extensions of the model system and the continuation of experience exchange between developers and users. In particular, the suitability of the model approach for simulations of radiological consequences according to the German SBG and the representation of the influence of buildings typical for nuclear power stations have been validated and further evaluated. Moreover, post-processing modules for calculation of dose-relevant decay products and for dose calculations have been developed and implemented. In order to continue the experience feedback and exchange, a web page has been established and maintained. Questions by users and other feedback have been dealt with and a common workshop has been held. The continued development and validation of ARTM has strengthened the basis for applications of this model system in line with the German regulations AVV and SBG. Further activity in this field can contribute to maintain and

  19. Compressive behavior of fine sand.

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Bradley E. (Air Force Research Laboratory, Eglin, FL); Kabir, Md. E. (Purdue University, West Lafayette, IN); Song, Bo; Chen, Wayne (Purdue University, West Lafayette, IN)

    2010-04-01

    The compressive mechanical response of fine sand is experimentally investigated. The strain rate, initial density, stress state, and moisture level are systematically varied. A Kolsky bar was modified to obtain uniaxial and triaxial compressive response at high strain rates. A controlled loading pulse allows the specimen to acquire stress equilibrium and constant strain-rates. The results show that the compressive response of the fine sand is not sensitive to strain rate under the loading conditions in this study, but significantly dependent on the moisture content, initial density and lateral confinement. Partially saturated sand is more compliant than dry sand. Similar trends were reported in the quasi-static regime for experiments conducted at comparable specimen conditions. The sand becomes stiffer as initial density and/or confinement pressure increases. The sand particle size become smaller after hydrostatic pressure and further smaller after dynamic axial loading.

  20. Features of Sand-dust Deposits in Harbin City, China

    Institute of Scientific and Technical Information of China (English)

    XIE Yuanyun; ZHANG Yan; HE Kui; ZHOU Jia; KANG Chunguo

    2006-01-01

    From the sedimentologic view, this paper analyses the grain-size distribution and the chemical composition of the deposits from sand-dust storm, occurring in Harbin on March 20, 2002. The result indicates that there exist plentiful coarse matters in the sand-dust deposits in Harbin, and the sand-dust composition presents obvious three peak distribution characteristics, indicating that the sand-dust in Harbin is composed of multi-origin components. The grain-size composition consists of silt (4-8Φ), accounting for 71.18% of the total, sand (>4Φ), 21.70%, and clay (<8Φ), only 7.13%. The average grain size (Mz) is 5.14Φ. The chemical elements of the deposits are mainly SiO2 and Al2O3 and Fe2O3, totally occupying 77.8%. The enrichment factors (EF) of Mg, K, Si, Fe, Mn, P, Ti, Co, Ni and V elements are all about 1, which mainly come from lithosphere source, while parts ofCu, Pb, Zn, Cr and Se elements are from pollution sources out of lithosphere source, and As, Cd and Sb elements are mainly from pollution sources. Based on the comprehensive analysis of grain-size, chemical composition, enrichment factor (EF), discriminant function (DF) and matter source index (PI), this paper points out that the grain-size distribution and element composition of the sand-dust deposits in Harbin are evidently different from the loess and sand-dust in Lanzhou, and that matter source of the sand-dust in Harbin is different from the loess in Northwest China and the sand-dust in Lanzhou. The sand-dust deposits in Harbin are an admixture of coarse grains transmitted in short distance and fine grains transported in long distance. The plentiful coarse grains of the sand-dust deposits in Harbin origin from sand of local spot, and are the near-source deposits transported by low altitude airflow.

  1. Sand dollar sites orogenesis

    Science.gov (United States)

    Amos, Dee

    2013-04-01

    The determinology of the humble sand dollars habitat changing from inception to the drastic evolution of the zone to that of present day. Into the cauldron along the southern Californian 'ring of fire' lithosphere are evidence of geosynclinals areas, metasedimentary rock formations and hydrothermal activity. The explanation begins with 'Theia' and the Moon's formation, battles with cometary impacts, glacial ages, epochs with evolutionary bottlenecks and plate tectonics. Fully illustrated the lecture includes localised diagrams and figures with actual subject photographic examples of plutonic, granitic, jade and peridodite. Finally, the origins of the materials used in the lecture are revealed for prosecution by future students and the enjoyment of interested parties in general.

  2. Sand Storms Trigger Alarm

    Institute of Scientific and Technical Information of China (English)

    LI LI

    2010-01-01

    @@ After an unusually humid winter with at least 10 snowfalls in Beijing, a severe andstorm blown by strong winds bringing with it thousands of tons of desert sand took many residents of the city by surprise.On the morning of March 20, Beijingers woke up to see clouds of yellow dust in the air and a sky that was an ominous orange in color.The loose soil and dust that had traveled htmdreds of miles from deserts in Mongolia and China's northwest blanketed Beijing's streets, covering parked vehicles, bikes, roofs and even plant life,as well as making its way into people's homes.

  3. Fortune Cookie Sand Dunes

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-432, 25 July 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of small barchan sand dunes in the north polar region near 71.7oN, 51.3oW. Some of them are shaped like fortune cookies. The message these dunes provide: winds blow through this region from the lower right toward the upper left. The steep slip face slopes of these dunes, which point toward the upper left, indicate the wind direction. The scene is illuminated by sunlight from the upper right. The image is 3 km (1.9 mi) wide.

  4. Benchmark experiment to verify radiation transport calculations for dosimetry in radiation therapy; Benchmark-Experiment zur Verifikation von Strahlungstransportrechnungen fuer die Dosimetrie in der Strahlentherapie

    Energy Technology Data Exchange (ETDEWEB)

    Renner, Franziska [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)

    2016-11-01

    Monte Carlo simulations are regarded as the most accurate method of solving complex problems in the field of dosimetry and radiation transport. In (external) radiation therapy they are increasingly used for the calculation of dose distributions during treatment planning. In comparison to other algorithms for the calculation of dose distributions, Monte Carlo methods have the capability of improving the accuracy of dose calculations - especially under complex circumstances (e.g. consideration of inhomogeneities). However, there is a lack of knowledge of how accurate the results of Monte Carlo calculations are on an absolute basis. A practical verification of the calculations can be performed by direct comparison with the results of a benchmark experiment. This work presents such a benchmark experiment and compares its results (with detailed consideration of measurement uncertainty) with the results of Monte Carlo calculations using the well-established Monte Carlo code EGSnrc. The experiment was designed to have parallels to external beam radiation therapy with respect to the type and energy of the radiation, the materials used and the kind of dose measurement. Because the properties of the beam have to be well known in order to compare the results of the experiment and the simulation on an absolute basis, the benchmark experiment was performed using the research electron accelerator of the Physikalisch-Technische Bundesanstalt (PTB), whose beam was accurately characterized in advance. The benchmark experiment and the corresponding Monte Carlo simulations were carried out for two different types of ionization chambers and the results were compared. Considering the uncertainty, which is about 0.7 % for the experimental values and about 1.0 % for the Monte Carlo simulation, the results of the simulation and the experiment coincide.

  5. A family of sand automata

    CERN Document Server

    Faulkner, Nicholas

    2012-01-01

    We study some dynamical properties of a family of two-dimensional cellular automata: those that arise from an underlying one dimensional sand automaton whose local rule is obtained using a latin square. We identify a simple sand automaton G whose local rule is algebraic, and classify this automaton as having equicontinuity points, but not being equicontinuous. We also show it is not surjective. We generalise some of these results to a wider class of sand automata.

  6. Dilatometric Characterization of Foundry Sands

    Directory of Open Access Journals (Sweden)

    M. Břuska

    2012-04-01

    Full Text Available The goal of this contribution is summary of physical – chemistry properties of usually used foundry silica and no – silica sands in Czech foundries. With the help of dilatometry analysis theoretical assumptions of influence of grain shape and size on dilatation value of sands were confirmed. Determined was the possibility of dilatometry analysis employment for preparing special (hybrid sands with lower and/or more linear character of dilatation.

  7. Large-scale patterns of eolian sediment transport on Venus - Predictions for Magellan

    Science.gov (United States)

    Saunders, R. S.; Wall, Stephen D.; Dobrovolskis, Anthony R.; Greeley, Ronald

    1990-01-01

    The atmosphere of Venus is likely to exert a major influence on the surface. Arecibo and Venera 15/16 observations of the population of impact craters with bright halos give direct evidence of surface modification, on the scale of centimeters, to smooth the surface on time scales of 50 - 250 my. Both chemical and mechanical modifications probably occur. Diurnal winds in the planetary boundary layer can transport particles. Using boundary layer theory, including the effects of topography, surface stresses and resulting transport and deposition of sand-size particles are calculated. Regional slopes are sites of largest surface stresses. Sand will be generally transported downhill, although there is a preferential net transport from east to west, in the same direction as the atmospheric superrotation. It is predicted here that streaks may be seen in the Magellan radar images which will indicate directions of net eolian transport on the surface of Venus.

  8. Monitoring sand particle concentration in multiphase flow using acoustic emission technology

    OpenAIRE

    El-Alej, Mohamed Essid

    2014-01-01

    Multiphase flow is the simultaneous flow of two or several phases through a system such as a pipe. This common phenomenon can be found in the petroleum and chemical engineering industrial fields. Transport of sand particles in multiphase production has attracted considerable attention given sand production is a common problem especially to the oil and gas industry. The sand production causes loss of pipe wall thickness which can lead to expensive failures and loss of product...

  9. Description of input and examples for PHREEQC version 3: a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations

    Science.gov (United States)

    Parkhurst, David L.; Appelo, C.A.J.

    2013-01-01

    PHREEQC version 3 is a computer program written in the C and C++ programming languages that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC implements several types of aqueous models: two ion-association aqueous models (the Lawrence Livermore National Laboratory model and WATEQ4F), a Pitzer specific-ion-interaction aqueous model, and the SIT (Specific ion Interaction Theory) aqueous model. Using any of these aqueous models, PHREEQC has capabilities for (1) speciation and saturation-index calculations; (2) batch-reaction and one-dimensional (1D) transport calculations with reversible and irreversible reactions, which include aqueous, mineral, gas, solid-solution, surface-complexation, and ion-exchange equilibria, and specified mole transfers of reactants, kinetically controlled reactions, mixing of solutions, and pressure and temperature changes; and (3) inverse modeling, which finds sets of mineral and gas mole transfers that account for differences in composition between waters within specified compositional uncertainty limits. Many new modeling features were added to PHREEQC version 3 relative to version 2. The Pitzer aqueous model (pitzer.dat database, with keyword PITZER) can be used for high-salinity waters that are beyond the range of application for the Debye-Hückel theory. The Peng-Robinson equation of state has been implemented for calculating the solubility of gases at high pressure. Specific volumes of aqueous species are calculated as a function of the dielectric properties of water and the ionic strength of the solution, which allows calculation of pressure effects on chemical reactions and the density of a solution. The specific conductance and the density of a solution are calculated and printed in the output file. In addition to Runge-Kutta integration, a stiff ordinary differential equation solver (CVODE) has been included for kinetic calculations with multiple rates that occur at widely different time scales

  10. Explicit formulation of a nodal transport method for discrete ordinates calculations in two-dimensional fixed-source problems

    Energy Technology Data Exchange (ETDEWEB)

    Tres, Anderson [Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Matematica Aplicada; Becker Picoloto, Camila [Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica; Prolo Filho, Joao Francisco [Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil). Inst de Matematica, Estatistica e Fisica; Dias da Cunha, Rudnei; Basso Barichello, Liliane [Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil). Inst de Matematica

    2014-04-15

    In this work a study of two-dimensional fixed-source neutron transport problems, in Cartesian geometry, is reported. The approach reduces the complexity of the multidimensional problem using a combination of nodal schemes and the Analytical Discrete Ordinates Method (ADO). The unknown leakage terms on the boundaries that appear from the use of the derivation of the nodal scheme are incorporated to the problem source term, such as to couple the one-dimensional integrated solutions, made explicit in terms of the x and y spatial variables. The formulation leads to a considerable reduction of the order of the associated eigenvalue problems when combined with the usual symmetric quadratures, thereby providing solutions that have a higher degree of computational efficiency. Reflective-type boundary conditions are introduced to represent the domain on a simpler form than that previously considered in connection with the ADO method. Numerical results obtained with the technique are provided and compared to those present in the literature. (orig.)

  11. Triaxial tests in Fontainebleau sand

    DEFF Research Database (Denmark)

    Latini, Chiara; Zania, Varvara

    2016-01-01

    The purpose of this internal report is to examine the influence of relative density on the strength and deformation characteristics of Fontainebleau sand. Compression triaxial tests were performed on saturated sand samples with different densities and initial confining pressure. Note that the tes......The purpose of this internal report is to examine the influence of relative density on the strength and deformation characteristics of Fontainebleau sand. Compression triaxial tests were performed on saturated sand samples with different densities and initial confining pressure. Note...... that the testing procedure and the data processing were carried out according to the specifications of ETCS-F1.97....

  12. Modeling spatial variability of sand-lenses in clay till settings using transition probability and multiple-point geostatistics

    DEFF Research Database (Denmark)

    Kessler, Timo Christian; Nilsson, Bertel; Klint, Knud Erik;

    2010-01-01

    the geology of e.g. a contaminated site, it is not always possible to gather enough information to build a representative geological model. Mapping in analogue geological settings and applying geostatistical tools to simulate spatial variability of heterogeneities can improve ordinary geological models...... that are predicated only on vertical borehole information. This study documents methods to map geological heterogeneity in clay till and ways to calibrate geostatistical models with field observations. A well-exposed cross-section in an excavation pit was used to measure and illustrate the occurrence and distribution...... of sand-lenses in clay till. Sand-lenses mainly account for horizontal transport and are prioritised in this study. Based on field observations, the distribution has been modeled using two different geostatistical approaches. One method uses a Markov chain model calculating the transition probabilities...

  13. Comparison of Atmospheric Travel Distances of Several PAHs Calculated by Two Fate and Transport Models (The Tool and ELPOS with Experimental Values Derived from a Peat Bog Transect

    Directory of Open Access Journals (Sweden)

    Sabine Thuens

    2014-05-01

    Full Text Available Multimedia fate and transport models are used to evaluate the long range transport potential (LRTP of organic pollutants, often by calculating their characteristic travel distance (CTD. We calculated the CTD of several polycyclic aromatic hydrocarbons (PAHs and metals using two models: the OECD POV& LRTP Screening Tool (The Tool, and ELPOS. The absolute CTDs of PAHs estimated with the two models agree reasonably well for predominantly particle-bound congeners, while discrepancies are observed for more volatile congeners. We test the performance of the models by comparing the relative ranking of CTDs with the one of experimentally determined travel distances (ETDs. ETDs were estimated from historical deposition rates of pollutants to peat bogs in Eastern Canada. CTDs and ETDs of PAHs indicate a low LRTP. To eliminate the high influence on specific model assumptions and to emphasize the difference between the travel distances of single PAHs, ETDs and CTDs were analyzed relative to the travel distances of particle-bound compounds. The ETDs determined for PAHs, Cu, and Zn ranged from 173 to 321 km with relative uncertainties between 26% and 46%. The ETDs of two metals were shorter than those of the PAHs. For particle-bound PAHs the relative ETDs and CTDs were similar, while they differed for Chrysene.

  14. 重庆市交通运输投资乘数的测算及分析%Calculation and Analysis of Transportation Investment Multiplier of Chongqing

    Institute of Scientific and Technical Information of China (English)

    郭建国; 陈正伟

    2012-01-01

    Based on Chongqing input-output table in 2007, this paper uses input-output model to quantitatively calculate the size of output multiplier and investment multiplier of Chongqing transportation investment, measures economic growth driving coefficient of Chongqing transportation investment and its contribution rate to GDP during 2005-2009 and,based on this,further analyzes the contribution of transportation investment to economic growth of Chongqing.%以重庆市2007年投入产出表为基础,运用投入产出模型定量测算出了重庆市交通运输投资的产出乘数与投资乘数的大小,测算出了2005—2009年交通运输投资对重庆市经济增长的拉动系数与GDP总量贡献率,并依此进一步分析了交通运输投资对重庆市经济增长的贡献。

  15. A research on the energy efficiency operational indicator EEOI calculation tool on M/V NSU JUSTICE of VINIC transportation company, Vietnam

    Directory of Open Access Journals (Sweden)

    Tien Anh Tran

    2017-03-01

    Full Text Available Nowadays, the development of science and technology brings the innovations and resolutions in aims with increasing the benefits and incomes for companies and producers. Additionally, the development of nation's economic associates with environmental protection. In the field of shipping transportation, the increasing in a number of ships operates then International Maritime Organization IMO's regulations become gradually more tightly about the environmental protection. EEOI – Energy Efficiency Operational Indicator is an operational measure tool for assessing the ship energy efficiency and CO2 emission to the environment. Furthermore, the research status is about ships energy efficiency management also has the optimistic trends and more effective. In the world, there are a lot of ships energy efficiency researches in aim with enhancing the energy efficiency and environmental protection. For instance, the voyage optimization, increasing the propulsion efficiency of ships, reducing the resistances, etc. However, in Vietnam, there are a lot of shipping transportation companies with different types of ship but the number of research about ships energy efficiency management also restrict. Since this research was carried out and applied the energy efficiency measure tool of International Maritime Organization (IMO for assessing all ships in Vietnam. The above workings were conducted by EEOI calculation tool for a certain ship with name M/V NSU JUSTICE 250,000 DWT of the VINIC Shipping Transportation Company, Vietnam.

  16. Computational methods for reactive transport modeling: An extended law of mass-action, xLMA, method for multiphase equilibrium calculations

    Science.gov (United States)

    Leal, Allan M. M.; Kulik, Dmitrii A.; Kosakowski, Georg; Saar, Martin O.

    2016-10-01

    We present an extended law of mass-action (xLMA) method for multiphase equilibrium calculations and apply it in the context of reactive transport modeling. This extended LMA formulation differs from its conventional counterpart in that (i) it is directly derived from the Gibbs energy minimization (GEM) problem (i.e., the fundamental problem that describes the state of equilibrium of a chemical system under constant temperature and pressure); and (ii) it extends the conventional mass-action equations with Lagrange multipliers from the Gibbs energy minimization problem, which can be interpreted as stability indices of the chemical species. Accounting for these multipliers enables the method to determine all stable phases without presuming their types (e.g., aqueous, gaseous) or their presence in the equilibrium state. Therefore, the here proposed xLMA method inherits traits of Gibbs energy minimization algorithms that allow it to naturally detect the phases present in equilibrium, which can be single-component phases (e.g., pure solids or liquids) or non-ideal multi-component phases (e.g., aqueous, melts, gaseous, solid solutions, adsorption, or ion exchange). Moreover, our xLMA method requires no technique that tentatively adds or removes reactions based on phase stability indices (e.g., saturation indices for minerals), since the extended mass-action equations are valid even when their corresponding reactions involve unstable species. We successfully apply the proposed method to a reactive transport modeling problem in which we use PHREEQC and GEMS as alternative backends for the calculation of thermodynamic properties such as equilibrium constants of reactions, standard chemical potentials of species, and activity coefficients. Our tests show that our algorithm is efficient and robust for demanding applications, such as reactive transport modeling, where it converges within 1-3 iterations in most cases. The proposed xLMA method is implemented in Reaktoro, a

  17. Comparison of Two Accelerators for Monte Carlo Radiation Transport Calculations, NVIDIA Tesla M2090 GPU and Intel Xeon Phi 5110p Coprocessor: A Case Study for X-ray CT Imaging Dose Calculation

    Science.gov (United States)

    Liu, Tianyu; Xu, X. George; Carothers, Christopher D.

    2014-06-01

    Hardware accelerators are currently becoming increasingly important in boosting high performance computing sys- tems. In this study, we tested the performance of two accelerator models, NVIDIA Tesla M2090 GPU and Intel Xeon Phi 5110p coprocessor, using a new Monte Carlo photon transport package called ARCHER-CT we have developed for fast CT imaging dose calculation. The package contains three code variants, ARCHER - CTCPU, ARCHER - CTGPU and ARCHER - CTCOP to run in parallel on the multi-core CPU, GPU and coprocessor architectures respectively. A detailed GE LightSpeed Multi-Detector Computed Tomography (MDCT) scanner model and a family of voxel patient phantoms were included in the code to calculate absorbed dose to radiosensitive organs under specified scan protocols. The results from ARCHER agreed well with those from the production code Monte Carlo N-Particle eXtended (MCNPX). It was found that all the code variants were significantly faster than the parallel MCNPX running on 12 MPI processes, and that the GPU and coprocessor performed equally well, being 2.89~4.49 and 3.01~3.23 times faster than the parallel ARCHER - CTCPU running with 12 hyperthreads.

  18. An object-oriented 3D nodal finite element solver for neutron transport calculations in the Descartes project

    Energy Technology Data Exchange (ETDEWEB)

    Akherraz, B.; Lautard, J.J. [CEA Saclay, Dept. Modelisation de Systemes et Structures, Serv. d' Etudes des Reacteurs et de Modelisation Avancee (DMSS/SERMA), 91 - Gif sur Yvette (France); Erhard, P. [Electricite de France (EDF), Dir. de Recherche et Developpement, Dept. Sinetics, 92 - Clamart (France)

    2003-07-01

    In this paper we present two applications of the Nodal finite elements developed by Hennart and del Valle, first to three-dimensional Cartesian meshes and then to two-dimensional Hexagonal meshes. This work has been achieved within the framework of the DESCARTES project, which is a co-development effort by the 'Commissariat a l'Energie Atomique' (CEA) and 'Electricite de France' (EDF) for the development of a toolbox for reactor core calculations based on object oriented programming. The general structure of this project is based on the object oriented method. By using a mapping technique proposed in Schneider's thesis and del Valle, Mund, we show how this structuration allows us an easy implementation of the hexagonal case from the Cartesian case. The main attractiveness of this methodology is the possibility of a pin-by-pin representation by division of each lozenge into smaller ones. Furthermore, we will explore the use of non structured quadrangles to treat the circular geometry within a hexagon. It remains nevertheless, in the hexagonal case, the implementation of the acceleration of the internal iterations by the DSA (Diffusion Synthetic Acceleration) or the TSA. (authors)

  19. Comparison of SERPENT and SCALE methodology for LWRs transport calculations and additionally uncertainty analysis for cross-section perturbation with SAMPLER module

    Directory of Open Access Journals (Sweden)

    Labarile Antonella

    2016-01-01

    Full Text Available In nuclear safety research, the quality of the results of simulation codes is widely determined by the reactor design and safe operation, and the description of neutron transport in the reactor core is a feature of particular importance. Moreover, for the long effort that is made, there remain uncertainties in simulation results due to the neutronic data and input specification that need a huge effort to be eliminated. A realistic estimation of these uncertainties is required for finding out the reliability of the results. This explains the increasing demand in recent years for calculations in the nuclear fields with best-estimate codes that proved confidence bounds of simulation results. All this has lead to the Benchmark for Uncertainty Analysis in Modelling (UAM for Design, Operation and Safety Analysis of LWRs of the NEA. The UAM-Benchmark coupling multi-physics and multi-scale analysis using as a basis complete sets of input specifications of boiling water reactors (BWR and pressurized water reactors (PWR. In this study, the results of the transport calculations carried out using the SCALE-6.2 program (TRITON/NEWT and TRITON/KENO modules as well as Monte Carlo SERPENT code, are presented. Additionally, they have been made uncertainties calculation for a PWR 15 × 15 and a BWR 7 × 7 fuel elements, in two different configurations (with and without control rod, and two different states, Hot Full Power (HFP and Hot Zero Power (HZP, using the TSUNAMI module, which uses the Generalized Perturbation Theory (GPT, and SAMPLER, which uses stochastic sampling techniques for cross-sections perturbations. The results obtained and validated are compared with references results and similar studies presented in the exercise I-2 (Lattice Physics of UAM-Benchmark.

  20. JMA's regional atmospheric transport model calculations for the WMO technical task team on meteorological analyses for Fukushima Daiichi Nuclear Power Plant accident.

    Science.gov (United States)

    Saito, Kazuo; Shimbori, Toshiki; Draxler, Roland

    2015-01-01

    The World Meteorological Organization (WMO) convened a small technical task team of experts to produce a set of meteorological analyses to drive atmospheric transport, dispersion and deposition models (ATDMs) for the United Nations Scientific Committee on the Effects of Atomic Radiation's assessment of the Fukushima Daiichi Nuclear Power Plant (DNPP) accident. The Japan Meteorological Agency (JMA) collaborated with the WMO task team as the regional specialized meteorological center of the country where the accident occurred, and provided its operational 5-km resolution mesoscale (MESO) analysis and its 1-km resolution radar/rain gauge-analyzed precipitation (RAP) data. The JMA's mesoscale tracer transport model was modified to a regional ATDM for radionuclides (RATM), which included newly implemented algorithms for dry deposition, wet scavenging, and gravitational settling of radionuclide aerosol particles. Preliminary and revised calculations of the JMA-RATM were conducted according to the task team's protocol. Verification against Cesium 137 ((137)Cs) deposition measurements and observed air concentration time series showed that the performance of RATM with MESO data was significantly improved by the revisions to the model. The use of RAP data improved the (137)Cs deposition pattern but not the time series of air concentrations at Tokai-mura compared with calculations just using the MESO data. Sensitivity tests of some of the more uncertain parameters were conducted to determine their impacts on ATDM calculations, and the dispersion and deposition of radionuclides on 15 March 2011, the period of some of the largest emissions and deposition to the land areas of Japan. The area with high deposition in the northwest of Fukushima DNPP and the hotspot in the central part of Fukushima prefecture were primarily formed by wet scavenging influenced by the orographic effect of the mountainous area in the west of the Fukushima prefecture.

  1. Simultaneous PIV and PTV measurements of wind and sand particle velocities

    Science.gov (United States)

    Zhang, Wei; Wang, Yuan; Lee, Sang Joon

    2008-08-01

    Wind-blown sand is a typical example of two-phase particle-laden flows. Owing to lack of simultaneous measured data of the wind and wind-blown sand, interactions between them have not yet been fully understood. In this study, natural sand of 100-125 μm taken from Taklimakan Desert was tested at the freestream wind speed of 8.3 m/s in an atmospheric boundary layer wind tunnel. The captured flow images containing both saltating sand and small wind tracer particles, were separated by using a digital phase mask technique. The 2-D PIV (particle imaging velocimetry) and PTV (particle tracking velocimetry) techniques were employed to extract simultaneously the wind velocity field and the velocity field of dispersed sand particles, respectively. Comparison of the mean streamwise wind velocity profile and the turbulence statistics with and without sand transportation reveal a significant influence of sand movement on the wind field, especially in the dense saltating sand layer ( y/ δ < 0.1). The ensemble-averaged streamwise velocity profile of sand particles was also evaluated to investigate the velocity lag between the sand and the wind. This study would be helpful in improving the understanding of interactions between the wind and the wind-blown sand.

  2. Effects of Polytypism on the Thermoelectric Properties of Group-IV Semiconductor Nanowires: A Combination of Density Functional Theory and Boltzmann Transport Calculations

    Science.gov (United States)

    Akiyama, Toru; Komoda, Takato; Nakamura, Kohji; Ito, Tomonori

    2017-08-01

    The effects of polytypism on thermoelectric properties of Si and Ge nanowires (NWs) are systematically investigated by using a combination of density functional theory and Boltzmann transport calculations. The calculations for NWs with various polytypes demonstrate that the thermoelectric figure of merit Z T of Si and Ge NWs can be tuned by changing different stacking sequences along the growth direction. In particular, the Z T values of n -type Si and Ge NWs with hexagonal (2 H ) structure at 300 K are significantly larger than Z T of Si and Ge NWs with a cubic (3 C ) structure. The underlying mechanism for the enhanced Z T value in Si NWs with a 2 H structure compared with a 3 C structure is attributed by the different Seebeck coefficient depending on the structure, while that in Ge NWs is due to the difference in both the Seebeck coefficient and electrical conductivity. The calculated results offer a way to design high-performance thermoelectric materials by controlling the polytype of NWs.

  3. The dimensions of sand ripples in full-scale oscillatory flows

    NARCIS (Netherlands)

    O'Donoghue, T.; Doucette, J.C.; Werf, van der J.J.; Ribberink, J.S.

    2006-01-01

    New large-scale experiments have been carried out in two oscillatory flow tunnels to study ripple regime sand suspension and net sand transport processes in full-scale oscillatory flows. The paper focuses on ripple dimensions and the new data are combined with existing data to make a large dataset o

  4. Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand

    NARCIS (Netherlands)

    Nolet, Corjan; Poortinga, Ate; Roosjen, Peter; Bartholomeus, Harm; Ruessink, Gerben

    2014-01-01

    Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure

  5. Dendrogeomorphology - a new tool to study drift-sand dynamics Netherlands Journal of Geosciences

    NARCIS (Netherlands)

    Ouden, den J.; Sass-Klaassen, U.; Copini, P.

    2007-01-01

    dendrogeomorphological approach is presented, using wood characteristics of native oak (Quercus robur L.) to infer dynamics of aeolian sediment transport in drift-sand areas. Wood samples, taken from oaks in two drift-sand areas, were analysed to study changes in tree-ring pattern and wood anatomy a

  6. Modeling fine-scale geological heterogeneity-examples of sand lenses in tills

    DEFF Research Database (Denmark)

    Kessler, Timo Christian; Comunian, Alessandro; Oriani, Fabio;

    2013-01-01

    Sand lenses at various spatial scales are recognized to add heterogeneity to glacial sediments. They have high hydraulic conductivities relative to the surrounding till matrix and may affect the advective transport of water and contaminants in clayey till settings. Sand lenses were investigated o...

  7. A sand wave simulation model

    NARCIS (Netherlands)

    Nemeth, A.A.; Hulscher, S.J.M.H.; Damme, van R.M.J.

    2003-01-01

    Sand waves form a prominent regular pattern in the offshore seabeds of sandy shallow seas. A two dimensional vertical (2DV) flow and morphological numerical model describing the behaviour of these sand waves has been developed. The model contains the 2DV shallow water equations, with a free water su

  8. Regeneration of dredged sand waves

    NARCIS (Netherlands)

    Hulscher, Suzanne J.M.H.; Knaapen, Michiel; Scholl, Olaf; Scholl, O.; Trenteseaux., A.; Garlan, T.

    2000-01-01

    Sand waves form a wavy pattern in the offshore sandy seabed. Since their crests reduce the navigability, it is important to know their evolution. A simple model is presented to estimate the recovery of sand wave amplitudes. This model is partially based on the similarity with sea ripples and

  9. Namibia : triaxial test on sand

    DEFF Research Database (Denmark)

    Steenfelt, Jørgen S.; Jacobsen, Kim P.

    In connection with a harbour project the friction angle of a fine sand is required. On Friday 13 March 1998 the Danish Geotechnical Institute (DGI) delivered app. 2.5 kg sand for testing at the Geotechnical Engineering Laboratory, Aalborg University. The present Data Report summarises the results...

  10. The sedimentary structure of linear sand dunes

    Science.gov (United States)

    Bristow; Bailey; Lancaster

    2000-07-06

    Linear sand dunes--dunes that extend parallel to each other rather than in star-like or crescentic forms--are the most abundant type of desert sand dune. But because their development and their internal structure are poorly understood, they are rarely recognized in the rock record. Models of linear dune development have not been able to take into account the sub-surface structure of existing dunes, but have relied instead either on the extrapolation of short-term measurements of winds and sediment transport or on observations of near-surface internal sedimentary structures. From such studies, it has not been clear if linear dunes can migrate laterally. Here we present images produced by ground penetrating radar showing the three-dimensional sedimentary structure of a linear dune in the Namib sand sea, where some of the world's largest linear dunes are situated. These profiles show clear evidence for lateral migration in a linear dune. Moreover, the migration of a sinuous crest-line along the dune produces divergent sets of cross-stratification, which can become stacked as the dune height increases, and large linear dunes can support superimposed dunes that produce stacked sets of trough cross-stratification. These clear structural signatures of linear dunes should facilitate their recognition in geological records.

  11. Sand swimming lizard: sandfish

    CERN Document Server

    Maladen, Ryan D; Kamor, Adam; Goldman, Daniel I

    2009-01-01

    We use high-speed x-ray imaging to reveal how a small (~10cm) desert dwelling lizard, the sandfish (Scincus scincus), swims within a granular medium [1]. On the surface, the lizard uses a standard diagonal gait, but once below the surface, the organism no longer uses limbs for propulsion. Instead it propagates a large amplitude single period sinusoidal traveling wave down its body and tail to propel itself at speeds up to ~1.5 body-length/sec. Motivated by these experiments we study a numerical model of the sandfish as it swims within a validated soft sphere Molecular Dynamics granular media simulation. We use this model as a tool to understand dynamics like flow fields and forces generated as the animal swims within the granular media. [1] Maladen, R.D. and Ding, Y. and Li, C. and Goldman, D.I., Undulatory Swimming in Sand: Subsurface Locomotion of the Sandfish Lizard, Science, 325, 314, 2009

  12. 2010 oil sands performance report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    With the depletion of traditional energy resources and the rising demand for energy, oil sands have become an important energy resource for meeting energy needs. Oil sands are a mixture of water, sand, clay and bitumen which is recovered either through open pit mining or in situ drilling techniques. The bitumen is then converted into syncrude or sold to refineries for the production of gasoline, diesel or other products. Shell has oil sands operations in Alberta and the aim of this report is to present its 2010 performance in terms of CO2, water, tailings, land, and reclamation and engagement. This document covers several of Shell's operations in the Muskeg River and Jackpine mines, Scotford upgrader, Peace River, Orion, Seal, Cliffdale and Chipmunk. It provides useful information on Shell's oil sands performance to governments, environmental groups, First Nations, local communities and the public.

  13. Sand harm in taklimakan Desert highway and sand control

    Institute of Scientific and Technical Information of China (English)

    HANZhiwen; WANGTao; SUNQingwei; DONGZhibao; WANGXunming

    2003-01-01

    Reputed as a wonderful achievement of the world’s highway construction history,the Taklimakan Desert highway is nor facing serious sand drift encroachment problems due to its 447-km-long passage of sand sea consisting of crescent dunes,barchan chains,compound transverse dune ridges and complex megadunes.To solve some technical problems in the protection of the highway from sang drift encroachment,desert experts have been conducting the theoretical and applied studies on sand movement laws;causes,severities and time-space differentiation of sand drift damages;and control ways including mechanical,chemical and biological measures.In this paper the authors give an overall summry on the research contents and recent progress in the control of sand drift damages in China and hold that the theoretical researc results and practices in the prevention of sand drift encroachment on the cross-desert highway represnt a breakthrough and has an cpoch-making significance.Since the construction of protective forest along the cross-desert highway requires large amount of ground water,what will be its environmental consequence and whether it can effectively halt sand drift encroachment on the highway forever are the questions to be studied urgently.

  14. Watching Faults Grow in Sand

    Science.gov (United States)

    Cooke, M. L.

    2015-12-01

    Accretionary sandbox experiments provide a rich environment for investigating the processes of fault development. These experiments engage students because 1) they enable direct observation of fault growth, which is impossible in the crust (type 1 physical model), 2) they are not only representational but can also be manipulated (type 2 physical model), 3) they can be used to test hypotheses (type 3 physical model) and 4) they resemble experiments performed by structural geology researchers around the world. The structural geology courses at UMass Amherst utilize a series of accretionary sandboxes experiments where students first watch a video of an experiment and then perform a group experiment. The experiments motivate discussions of what conditions they would change and what outcomes they would expect from these changes; hypothesis development. These discussions inevitably lead to calculations of the scaling relationships between model and crustal fault growth and provide insight into the crustal processes represented within the dry sand. Sketching of the experiments has been shown to be a very effective assessment method as the students reveal which features they are analyzing. Another approach used at UMass is to set up a forensic experiment. The experiment is set up with spatially varying basal friction before the meeting and students must figure out what the basal conditions are through the experiment. This experiment leads to discussions of equilibrium and force balance within the accretionary wedge. Displacement fields can be captured throughout the experiment using inexpensive digital image correlation techniques to foster quantitative analysis of the experiments.

  15. Optimization of deterministic transport parameters for the calculation of the dose distribution around a high dose-rate 192Ir brachytherapy source.

    Science.gov (United States)

    Gifford, Kent A; Price, Michael J; Horton, John L; Wareing, Todd A; Mourtada, Firas

    2008-06-01

    The goal of this work was to calculate the dose distribution around a high dose-rate 192Ir brachytherapy source using a multi-group discrete ordinates code and then to compare the results with a Monte Carlo calculated dose distribution. The unstructured tetrahedral mesh discrete ordinates code Attila version 6.1.1 was used to calculate the photon kerma rate distribution in water around the Nucletron microSelectron mHDRv2 source. MCNPX 2.5.c was used to compute the Monte Carlo water photon kerma rate distribution. Two hundred million histories were simulated, resulting in standard errors of the mean of less than 3% overall. The number of energy groups, S(n) (angular order), P(n) (scattering order), and mesh elements were varied in addition to the method of analytic ray tracing to assess their effects on the deterministic solution. Water photon kerma rate matrices were exported from both codes into an in-house data analysis software. This software quantified the percent dose difference distribution, the number of points within +/- 3% and +/- 5%, and the mean percent difference between the two codes. The data demonstrated that a 5 energy-group cross-section set calculated results to within 0.5% of a 15 group cross-section set. S12 was sufficient to resolve the solution in angle. P2 expansion of the scattering cross-section was necessary to compute accurate distributions. A computational mesh with 55 064 tetrahedral elements in a 30 cm diameter phantom resolved the solution spatially. An efficiency factor of 110 with the above parameters was realized in comparison to MC methods. The Attila code provided an accurate and efficient solution of the Boltzmann transport equation for the mHDRv2 source.

  16. Aeolian sediment flux derived from a natural sand trap

    NARCIS (Netherlands)

    Weerd, van der A.J.; Wijnberg, K.M.

    2016-01-01

    In 2011, a mega-nourishment (the ‘Sand Motor’) was constructed along the Dutch Coast. Since it is a pilot project, its evolution is closely monitored. This paper presents first results on the temporal variation in aeolian sediment transport across the nourishment, based on (a) the rate of infill ove

  17. Silica Sand Identification using ALOS PALSAR Full Polarimetry on The Northern Coastline of Rupat Island, Indonesia

    Directory of Open Access Journals (Sweden)

    Husnul Kausarian

    2016-10-01

    Full Text Available Silica sand is one of the minerals which relatively abundant in Indonesia. One of the areas with abundant of silica sand distribution is the northern coastline of Rupat Island, Bengkalis district, Riau province, Indonesia. The distribution of silica sand in this island identified only on the northern coastline in this island. Some selected sample of silica sand was measured to get the percentage of silica sand mineral’s content using X-Ray Fluorescence (XRF. Two adjacent scenes of ALOS PALSAR full-polarimetry were used. The physical properties of silica sand sample such as dielectric constant were measured using dielectric probe kit in the frequency range from 0.3 to 3.0 GHz and used for calculating the backscattering coefficient and the difference characteristics of silica sand with another object. Freeman-Durdeen and Yamaguchi techniques were used to get the scattering decomposition of physical scattering from the incoherent object model based. Surface scattering is the clearest of Scattering decomposition to show silica sand identification compares with other decompositions. From surface scattering, the backscattering coefficient value of silica sand was calculated starting from -59 dB until -52 dB. These values were given by the surface roughness condition, where the roughness is slightly rough planar. The flat condition supported by the grain size of silica sand particles that have almost the same size and shape, that were conducted by using microscopic photograph testing.

  18. Numerical analysis of biological clogging in two-dimensional sand box experiments

    DEFF Research Database (Denmark)

    Kildsgaard, J.; Engesgaard, Peter Knudegaard

    2001-01-01

    Two-dimensional models for biological clogging and sorptive tracer transport were used to study the progress of clogging in a sand box experiment. The sand box had been inoculated with a strip of bacteria and exposed to a continuous injection of nitrate and acetate. Brilliant Blue was regularly...... with the assumed linear constant Kd behaviour. It is demonstrated that the dimensionality of sand box experiments in comparison to column experiments results in a much lower reduction in hydraulic conductivity Žfactor of 100. and that the bulk hydraulic conductivity of the sand box decreased only slightly. However...

  19. Technology assessment: environmental, health, and safety impacts associated with oil recovery from US tar-sand deposits

    Energy Technology Data Exchange (ETDEWEB)

    Daniels, J.I.; Anspaugh, L.R.; Ricker, Y.E.

    1981-10-13

    The tar-sand resources of the US have the potential to yield as much as 36 billion barrels (bbls) of oil. The tar-sand petroleum-extraction technologies now being considered for commercialization in the United States include both surface (above ground) systems and in situ (underground) procedures. The surface systems currently receiving the most attention include: (1) thermal decomposition processes (retorting); (2) suspension methods (solvent extraction); and (3) washing techniques (water separation). Underground bitumen extraction techniques now being field tested are: (1) in situ combustion; and (2) in situ steam-injection procedures. At this time, any commercial tar-sand facility in the US will have to comply with at least 7 major federal regulations in addition to state regulations; building, electrical, and fire codes; and petroleum-industry construction standards. Pollution-control methods needed by tar-sand technologies to comply with regulatory standards and to protect air, land, and water quality will probably be similar to those already proposed for commercial oil-shale systems. The costs of these systems could range from about $1.20 to $2.45 per barrel of oil produced. Estimates of potential pollution-emisson levels affecting land, air, and water were calculated from available data related to current surface and in situ tar-sand field experiments in the US. These data were then extrapolated to determine pollutant levels expected from conceptual commercial surface and in situ facilities producing 20,000 bbl/d. The likelihood-of-occurrence of these impacts was then assessed. Experience from other industries, including information concerning health and ecosystem damage from air pollutants, measurements of ground-water transport of organic pollutants, and the effectiveness of environmental-control technologies was used to make this assessment.

  20. Technology assessment: environmental, health, and safety impacts associated with oil recovery from US tar-sand deposits

    Energy Technology Data Exchange (ETDEWEB)

    Daniels, J.I.; Anspaugh, L.R.; Ricker, Y.E.

    1981-10-13

    The tar-sand resources of the US have the potential to yield as much as 36 billion barrels (bbls) of oil. The tar-sand petroleum-extraction technologies now being considered for commercialization in the United States include both surface (above ground) systems and in situ (underground) procedures. The surface systems currently receiving the most attention include: (1) thermal decomposition processes (retorting); (2) suspension methods (solvent extraction); and (3) washing techniques (water separation). Underground bitumen extraction techniques now being field tested are: (1) in situ combustion; and (2) in situ steam-injection procedures. At this time, any commercial tar-sand facility in the US will have to comply with at least 7 major federal regulations in addition to state regulations; building, electrical, and fire codes; and petroleum-industry construction standards. Pollution-control methods needed by tar-sand technologies to comply with regulatory standards and to protect air, land, and water quality will probably be similar to those already proposed for commercial oil-shale systems. The costs of these systems could range from about $1.20 to $2.45 per barrel of oil produced. Estimates of potential pollution-emisson levels affecting land, air, and water were calculated from available data related to current surface and in situ tar-sand field experiments in the US. These data were then extrapolated to determine pollutant levels expected from conceptual commercial surface and in situ facilities producing 20,000 bbl/d. The likelihood-of-occurrence of these impacts was then assessed. Experience from other industries, including information concerning health and ecosystem damage from air pollutants, measurements of ground-water transport of organic pollutants, and the effectiveness of environmental-control technologies was used to make this assessment.