WorldWideScience

Sample records for surface flux-transport simulations

  1. Parameter optimization for surface flux transport models

    Science.gov (United States)

    Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.; Petrie, G. J. D.

    2017-11-01

    Accurate prediction of solar activity calls for precise calibration of solar cycle models. Consequently we aim to find optimal parameters for models which describe the physical processes on the solar surface, which in turn act as proxies for what occurs in the interior and provide source terms for coronal models. We use a genetic algorithm to optimize surface flux transport models using National Solar Observatory (NSO) magnetogram data for Solar Cycle 23. This is applied to both a 1D model that inserts new magnetic flux in the form of idealized bipolar magnetic regions, and also to a 2D model that assimilates specific shapes of real active regions. The genetic algorithm searches for parameter sets (meridional flow speed and profile, supergranular diffusivity, initial magnetic field, and radial decay time) that produce the best fit between observed and simulated butterfly diagrams, weighted by a latitude-dependent error structure which reflects uncertainty in observations. Due to the easily adaptable nature of the 2D model, the optimization process is repeated for Cycles 21, 22, and 24 in order to analyse cycle-to-cycle variation of the optimal solution. We find that the ranges and optimal solutions for the various regimes are in reasonable agreement with results from the literature, both theoretical and observational. The optimal meridional flow profiles for each regime are almost entirely within observational bounds determined by magnetic feature tracking, with the 2D model being able to accommodate the mean observed profile more successfully. Differences between models appear to be important in deciding values for the diffusive and decay terms. In like fashion, differences in the behaviours of different solar cycles lead to contrasts in parameters defining the meridional flow and initial field strength.

  2. Surface flux transport simulations: Effect of inflows toward active regions and random velocities on the evolution of the Sun's large-scale magnetic field

    Science.gov (United States)

    Martin-Belda, D.; Cameron, R. H.

    2016-02-01

    Aims: We aim to determine the effect of converging flows on the evolution of a bipolar magnetic region (BMR), and to investigate the role of these inflows in the generation of poloidal flux. We also discuss whether the flux dispersal due to turbulent flows can be described as a diffusion process. Methods: We developed a simple surface flux transport model based on point-like magnetic concentrations. We tracked the tilt angle, the magnetic flux and the axial dipole moment of a BMR in simulations with and without inflows and compared the results. To test the diffusion approximation, simulations of random walk dispersal of magnetic features were compared against the predictions of the diffusion treatment. Results: We confirm the validity of the diffusion approximation to describe flux dispersal on large scales. We find that the inflows enhance flux cancellation, but at the same time affect the latitudinal separation of the polarities of the bipolar region. In most cases the latitudinal separation is limited by the inflows, resulting in a reduction of the axial dipole moment of the BMR. However, when the initial tilt angle of the BMR is small, the inflows produce an increase in latitudinal separation that leads to an increase in the axial dipole moment in spite of the enhanced flux destruction. This can give rise to a tilt of the BMR even when the BMR was originally aligned parallel to the equator.

  3. Reconstructing solar magnetic fields from historical observations. II. Testing the surface flux transport model

    Science.gov (United States)

    Virtanen, I. O. I.; Virtanen, I. I.; Pevtsov, A. A.; Yeates, A.; Mursula, K.

    2017-07-01

    Aims: We aim to use the surface flux transport model to simulate the long-term evolution of the photospheric magnetic field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. Methods: We tested the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and studied how the flux distribution inside active regions and the initial magnetic field affected the simulation. We compared the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion, and input data. We also compared the simulated magnetic field with observations. Results: We find that there is generally good agreement between simulations and observations. Although the model is not capable of replicating fine details of the magnetic field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, which often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are somewhat minor or temporary, lasting typically one solar cycle.

  4. Reconstructing solar magnetic fields from historical observations: Testing the surface flux transport model

    Science.gov (United States)

    Virtanen, Iiro; Virtanen, Ilpo; Pevtsov, Alexei; Yeates, Anthony; Mursula, Kalevi

    2017-04-01

    We aim to use the surface flux transport model to simulate the long-term evolution of the photospheric magnetic field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. We test the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and study how the flux distribution inside active regions and the initial magnetic field affect the simulation. We compare the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion and input data. We also compare the simulated magnetic field with observations. We find that there is generally good agreement between simulations and observations. While the model is not capable of replicating fine details of the magnetic field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, that often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are rather minor or temporary, lasting typically one solar cycle.

  5. The Large-scale Coronal Structure of the 2017 August 21 Great American Eclipse: An Assessment of Solar Surface Flux Transport Model Enabled Predictions and Observations

    Science.gov (United States)

    Nandy, Dibyendu; Bhowmik, Prantika; Yeates, Anthony R.; Panda, Suman; Tarafder, Rajashik; Dash, Soumyaranjan

    2018-01-01

    On 2017 August 21, a total solar eclipse swept across the contiguous United States, providing excellent opportunities for diagnostics of the Sun’s corona. The Sun’s coronal structure is notoriously difficult to observe except during solar eclipses; thus, theoretical models must be relied upon for inferring the underlying magnetic structure of the Sun’s outer atmosphere. These models are necessary for understanding the role of magnetic fields in the heating of the corona to a million degrees and the generation of severe space weather. Here we present a methodology for predicting the structure of the coronal field based on model forward runs of a solar surface flux transport model, whose predicted surface field is utilized to extrapolate future coronal magnetic field structures. This prescription was applied to the 2017 August 21 solar eclipse. A post-eclipse analysis shows good agreement between model simulated and observed coronal structures and their locations on the limb. We demonstrate that slow changes in the Sun’s surface magnetic field distribution driven by long-term flux emergence and its evolution governs large-scale coronal structures with a (plausibly cycle-phase dependent) dynamical memory timescale on the order of a few solar rotations, opening up the possibility for large-scale, global corona predictions at least a month in advance.

  6. Intercomparison of the finite difference and nodal discrete ordinates and surface flux transport methods for a LWR pool-reactor benchmark problem in X-Y geometry

    International Nuclear Information System (INIS)

    O'Dell, R.D.; Stepanek, J.; Wagner, M.R.

    1983-01-01

    The aim of the present work is to compare and discuss the three of the most advanced two dimensional transport methods, the finite difference and nodal discrete ordinates and surface flux method, incorporated into the transport codes TWODANT, TWOTRAN-NODAL, MULTIMEDIUM and SURCU. For intercomparison the eigenvalue and the neutron flux distribution are calculated using these codes in the LWR pool reactor benchmark problem. Additionally the results are compared with some results obtained by French collision probability transport codes MARSYAS and TRIDENT. Because the transport solution of this benchmark problem is close to its diffusion solution some results obtained by the finite element diffusion code FINELM and the finite difference diffusion code DIFF-2D are included

  7. MAGNETIC FLUX TRANSPORT AND THE LONG-TERM EVOLUTION OF SOLAR ACTIVE REGIONS

    International Nuclear Information System (INIS)

    Ugarte-Urra, Ignacio; Upton, Lisa; Warren, Harry P.; Hathaway, David H.

    2015-01-01

    With multiple vantage points around the Sun, Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory imaging observations provide a unique opportunity to view the solar surface continuously. We use He ii 304 Å data from these observatories to isolate and track ten active regions and study their long-term evolution. We find that active regions typically follow a standard pattern of emergence over several days followed by a slower decay that is proportional in time to the peak intensity in the region. Since STEREO does not make direct observations of the magnetic field, we employ a flux-luminosity relationship to infer the total unsigned magnetic flux evolution. To investigate this magnetic flux decay over several rotations we use a surface flux transport model, the Advective Flux Transport model, that simulates convective flows using a time-varying velocity field and find that the model provides realistic predictions when information about the active region's magnetic field strength and distribution at peak flux is available. Finally, we illustrate how 304 Å images can be used as a proxy for magnetic flux measurements when magnetic field data is not accessible

  8. Total solar irradiance reconstruction since 1700 using a flux transport model

    Science.gov (United States)

    Dasi Espuig, Maria; Krivova, Natalie; Solanki, Sami K.; Jiang, Jie

    Reconstructions of solar irradiance into the past are crucial for studies of solar influence on climate. Models based on the assumption that irradiance changes are caused by the evolution of the photospheric magnetic fields have been most successful in reproducing the measured irradiance variations. Daily magnetograms, such as those from MDI and HMI, provide the most detailed information on the changing distribution of the photospheric magnetic fields. Since such magnetograms are only available from 1974, we used a surface flux transport model to describe the evolution of the magnetic fields on the solar surface due to the effects of differential rotation, meridional circulation, and turbulent diffusivity, before 1974. In this model, the sources of magnetic flux are the active regions, which are introduced based on sunspot group areas, positions, and tilt angles. The RGO record is, however, only available since 1874. Here we present a model of solar irradiance since 1700, which is based on a semi-synthetic sunspot record. The semi-synthetic record was obtained using statistical relationships between sunspot group properties (areas, positions, tilt angles) derived from the RGO record on one hand, and the cycle strength and phase derived from the sunspot group number (Rg) on the other. These relationships were employed to produce daily records of sunspot group positions, areas, and tilt angles before 1874. The semi-synthetic records were fed into the surface flux transport model to simulate daily magnetograms since 1700. By combining the simulated magnetograms with a SATIRE-type model, we then reconstructed total solar irradiance since 1700.

  9. Modelling total solar irradiance using a flux transport model

    Science.gov (United States)

    Dasi Espuig, Maria; Jiang, Jie; Krivova, Natalie; Solanki, Sami

    2014-05-01

    Reconstructions of solar irradiance into the past are of considerable interest for studies of solar influence on climate. Models based on the assumption that irradiance changes are caused by the evolution of the photospheric magnetic field have been the most successful in reproducing the measured irradiance variations. Our SATIRE-S model is one of these. It uses solar full-disc magnetograms as an input, and these are available for less than four decades. Thus, to reconstruct the irradiance back to times when no observed magnetograms are available, we combine the SATIRE-S model with synthetic magnetograms, produced using a surface flux transport model. The model is fed with daily, observed or modelled statistically, records of sunspot positions, areas, and tilt angles. To describe the secular change in the irradiance, we used the concept of overlapping ephemeral region cycles. With this technique TSI can be reconstructed back to 1700.

  10. A reconstruction of solar irradiance using a flux transport model

    Science.gov (United States)

    Dasi Espuig, Maria; Jiang, Jie; Krivova, Natalie; Solanki, Sami

    2013-04-01

    Reconstructions of solar irradiance into the past are of considerable interest for studies of solar influence on climate. Models based on the assumption that irradiance changes are caused by the evolution of the photospheric magnetic field have been the most successful in reproducing the measured irradiance variations. Our SATIRE-S model is one of these. It uses solar full-disc magnetograms as an input, and these are available for less than four decades. Thus, to reconstruct the irradiance back to times when no observed magnetograms are available, we combine the SATIRE-S model with synthetic magnetograms, produced using a surface flux transport model. The model is fed with daily, observed or modelled statistically, records of sunspot positions, areas, and tilt angles. To describe the secular change in the irradiance, we used the concept of overlapping ephemeral region cycles. With this technique TSI can be reconstructed back to 1610.

  11. Meridional Flow Observations: Implications for the current Flux Transport Models

    International Nuclear Information System (INIS)

    Gonzalez Hernandez, Irene; Komm, Rudolf; Kholikov, Shukur; Howe, Rachel; Hill, Frank

    2011-01-01

    Meridional circulation has become a key element in the solar dynamo flux transport models. Available helioseismic observations from several instruments, Taiwan Oscillation Network (TON), Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI), have made possible a continuous monitoring of the solar meridional flow in the subphotospheric layers for the last solar cycle, including the recent extended minimum. Here we review some of the meridional circulation observations using local helioseismology techniques and relate them to magnetic flux transport models.

  12. Non-kinematic Flux-transport Dynamos Including the Effects of Diffusivity Quenching

    Energy Technology Data Exchange (ETDEWEB)

    Ichimura, Chiaki; Yokoyama, Takaaki [Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2017-04-10

    Turbulent magnetic diffusivity is quenched when strong magnetic fields suppress turbulent motion in a phenomenon known as diffusivity quenching. Diffusivity quenching can provide a mechanism for amplifying magnetic field and influencing global velocity fields through Lorentz force feedback. To investigate this effect, we conducted mean field flux-transport dynamo simulations that included the effects of diffusivity quenching in a non-kinematic regime. We found that toroidal magnetic field strength is amplified by up to approximately 1.5 times in the convection zone as a result of diffusivity quenching. This amplification is much weaker than that in kinematic cases as a result of Lorentz force feedback on the system’s differential rotation. While amplified toroidal fields lead to the suppression of equatorward meridional flow locally near the base of the convection zone, large-scale equatorward transport of magnetic flux via meridional flow, which is the essential process of the flux-transport dynamo, is sustainable in our calculations.

  13. The Nature of Grand Minima and Maxima from Fully Nonlinear Flux Transport Dynamos

    Energy Technology Data Exchange (ETDEWEB)

    Inceoglu, Fadil; Arlt, Rainer [Leibniz-Institute for Astrophysics Potsdam, An der Sternwarte 16, D-14482, Potsdam (Germany); Rempel, Matthias, E-mail: finceoglu@aip.de [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

    2017-10-20

    We aim to investigate the nature and occurrence characteristics of grand solar minimum and maximum periods, which are observed in the solar proxy records such as {sup 10}Be and {sup 14}C, using a fully nonlinear Babcock–Leighton type flux transport dynamo including momentum and entropy equations. The differential rotation and meridional circulation are generated from the effect of turbulent Reynolds stress and are subjected to back-reaction from the magnetic field. To generate grand minimum- and maximum-like periods in our simulations, we used random fluctuations in the angular momentum transport process, namely the Λ-mechanism, and in the Babcock–Leighton mechanism. To characterize the nature and occurrences of the identified grand minima and maxima in our simulations, we used the waiting time distribution analyses, which reflect whether the underlying distribution arises from a random or a memory-bearing process. The results show that, in the majority of the cases, the distributions of grand minima and maxima reveal that the nature of these events originates from memoryless processes. We also found that in our simulations the meridional circulation speed tends to be smaller during grand maximum, while it is faster during grand minimum periods. The radial differential rotation tends to be larger during grand maxima, while it is smaller during grand minima. The latitudinal differential rotation, on the other hand, is found to be larger during grand minima.

  14. Incorporation of a Generalized Data Assimilation Module within a Global Photospheric Flux Transport Model

    Science.gov (United States)

    2016-03-31

    Table of Contents 1. INTRODUCTION...Traditional Photospheric Magnetic Flux Synoptic Maps .........................................................1 2.2 Photospheric Flux Transport Models...4 3. WH model evolved synoptic map (latitude vs. longitude

  15. Simulation of Gas-Surface Dynamical Interactions

    Science.gov (United States)

    2007-07-01

    surface. The substrate with lattice constant a is represented in a simple ball and spring picture. on the particular problem. Time-independent...παvwell , (26) Simulation of Gas-Surface Dynamical Interactions 4 - 10 RTO-EN-AVT-142 g E ad v mvc ∆ v’well vc cM Figure 4

  16. Modelling and simulation of surface water waves

    NARCIS (Netherlands)

    van Groesen, Embrecht W.C.; Westhuis, J.H.

    2002-01-01

    The evolution of waves on the surface of a layer of fluid is governed by non-linear effects from surface deformations and dispersive effects from the interaction with the interior fluid motion. Several simulation tools are described in this paper and compared with real life experiments in large

  17. Simulation Tool for GNSS Ocean Surface Reflections

    DEFF Research Database (Denmark)

    Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

    2015-01-01

    . This impedance concept gives an accurate lower boundary condition in the determination of the electromagnetic field, and makes itpossible to simulate reflections and the effects of transitions between different mediums. A semi-isotropic Philipsspectrum is used to represent the air-sea interaction.Simulated GPS...... on the solution of the parabolic equation. The parabolic equation in our simulator is solvedusing the split-step sine transformation. The Earth’s surface is modeled with the use of an impedance model. The value of the Earth impedance is given as a function of the range along the surface of the Earth...

  18. Building Airport Surface HITL Simulation Capability

    Science.gov (United States)

    Chinn, Fay Cherie

    2016-01-01

    FutureFlight Central is a high fidelity, real-time simulator designed to study surface operations and automation. As an air traffic control tower simulator, FFC allows stakeholders such as the FAA, controllers, pilots, airports, and airlines to develop and test advanced surface and terminal area concepts and automation including NextGen and beyond automation concepts and tools. These technologies will improve the safety, capacity and environmental issues facing the National Airspace system. FFC also has extensive video streaming capabilities, which combined with the 3-D database capability makes the facility ideal for any research needing an immersive virtual and or video environment. FutureFlight Central allows human in the loop testing which accommodates human interactions and errors giving a more complete picture than fast time simulations. This presentation describes FFCs capabilities and the components necessary to build an airport surface human in the loop simulation capability.

  19. Molecular Dynamics Simulations for Predicting Surface Wetting

    Directory of Open Access Journals (Sweden)

    Jing Chen

    2014-06-01

    Full Text Available The investigation of wetting of a solid surface by a liquid provides important insights; the contact angle of a liquid droplet on a surface provides a quantitative measurement of this interaction and the degree of attraction or repulsion of that liquid type by the solid surface. Molecular dynamics (MD simulations are a useful way to examine the behavior of liquids on solid surfaces on a nanometer scale. Thus, we surveyed the state of this field, beginning with the fundamentals of wetting calculations to an examination of the different MD methodologies used. We highlighted some of the advantages and disadvantages of the simulations, and look to the future of computer modeling to understand wetting and other liquid-solid interaction phenomena.

  20. Airborne Lidar Surface Topography (LIST) Simulator

    Science.gov (United States)

    Yu, Anthony W.; Krainak, Michael A.; Harding, David J.; Abshire, James B.; Sun, Xiaoli; Cavanaugh, John; Valett, Susan; Ramos-Izquierdo, Luis; Winkert, Tom; Plants, Michael; hide

    2011-01-01

    In this paper we will discuss our development effort of an airborne instrument as a pathfinder for the Lidar Surface Technology (LIST) mission. This paper will discuss the system approach, enabling technologies, instrument concept and performance of the Airborne LIST Simulator (A-LISTS).

  1. Numerical simulation of electromagnetic surface treatment

    Science.gov (United States)

    Sonde, Emmanuel; Chaise, Thibaut; Nelias, Daniel; Robin, Vincent

    2018-01-01

    Surface treatment methods, such as shot peening or laser shock peening, are generally used to introduce superficial compressive residual stresses in mechanical parts. These processes are carried out during the manufacturing steps or for the purpose of repairing. The compressive residual stresses prevent the initiation and growth of cracks and thus improve the fatigue life of mechanical components. Electromagnetic pulse peening (EMP) is an innovative process that could be used to introduce compressive residual stresses in conductive materials. It acts by generating a high transient electromagnetic field near the working surface. In this paper, the EMP process is presented and a sequentially coupled electromagnetic and mechanical model is developed for its simulation. This 2D axisymmetric model is set up with the commercial finite element software SYSWELD. After description and validation, the numerical model is used to simulate a case of introducing residual stresses of compression in a nickel-based alloy 690 thick sample, by the means of electromagnetic pulses. The results are presented in terms of effective plastic strain and residual mean stress. The influence of the process parameters, such as current intensity and frequency, on the results is analyzed. Finally, the predictability of the process is shown by several correlation studies.

  2. Computer simulation of surface and film processes

    Science.gov (United States)

    Tiller, W. A.; Halicioglu, M. T.

    1984-01-01

    All the investigations which were performed employed in one way or another a computer simulation technique based on atomistic level considerations. In general, three types of simulation methods were used for modeling systems with discrete particles that interact via well defined potential functions: molecular dynamics (a general method for solving the classical equations of motion of a model system); Monte Carlo (the use of Markov chain ensemble averaging technique to model equilibrium properties of a system); and molecular statics (provides properties of a system at T = 0 K). The effects of three-body forces on the vibrational frequencies of triatomic cluster were investigated. The multilayer relaxation phenomena for low index planes of an fcc crystal was analyzed also as a function of the three-body interactions. Various surface properties for Si and SiC system were calculated. Results obtained from static simulation calculations for slip formation were presented. The more elaborate molecular dynamics calculations on the propagation of cracks in two-dimensional systems were outlined.

  3. Computer simulation, nuclear techniques and surface analysis

    Directory of Open Access Journals (Sweden)

    Reis, A. D.

    2010-02-01

    Full Text Available This article is about computer simulation and surface analysis by nuclear techniques, which are non-destructive. The “energy method of analysis” for nuclear reactions is used. Energy spectra are computer simulated and compared with experimental data, giving target composition and concentration profile information. Details of prediction stages are given for thick flat target yields. Predictions are made for non-flat targets having asymmetric triangular surface contours. The method is successfully applied to depth profiling of 12C and 18O nuclei in thick targets, by deuteron (d,p and proton (p,α induced reactions, respectively.

    Este artículo trata de simulación por ordenador y del análisis de superficies mediante técnicas nucleares, que son no destructivas. Se usa el “método de análisis en energía” para reacciones nucleares. Se simulan en ordenador espectros en energía que se comparan con datos experimentales, de lo que resulta la obtención de información sobre la composición y los perfiles de concentración de la muestra. Se dan detalles de las etapas de las predicciones de espectros para muestras espesas y planas. Se hacen predicciones para muestras no planas que tienen contornos superficiales triangulares asimétricos. Este método se aplica con éxito en el cálculo de perfiles en profundidad de núcleos de 12C y de 18O en muestras espesas a través de reacciones (d,p y (p,α inducidas por deuterones y protones, respectivamente.

  4. Astronaut Neil Armstrong participates in simulation of moon's surface

    Science.gov (United States)

    1969-01-01

    Astronaut Neil A. Armstrong, wearing an Extravehicular Mobility Unit, deploys a lunar surface television camera during lunar surface simulation training in bldg 9, Manned Spacecraft Center. Armstrong is the prime crew commander of the Apollo 11 lunar landing mission.

  5. Monte Carlo Simulation of Protein Adsorption on Energetically Heterogeneous Surfaces

    OpenAIRE

    Danwanichakul, Panu

    2014-01-01

    The modified triangular-well potential model was applied to incorporate the effect of surface energy on the adsorption of particles or proteins on energetically heterogeneous surfaces. The method is convenient in simulating the adsorption on heterogeneous surface of which different region possesses different free energy. Spherical particles with attractive forces were added on the surface and underwent surface diffusion before they were quenched in place. It was seen that the ratio of surface...

  6. Simulation of surface evolution during ion bombardment

    International Nuclear Information System (INIS)

    Katardjiev, I.V.

    1988-01-01

    Some theoretical aspects of surface topography evolution during ion beam erosion are discussed. In particular, the theory of characteristics is considered in some detail and its limitations pointed out. Further theoretical development based on the Huygens principle of wave propagation is discussed also with respect to numerical evaluation of surface evolution. A new numerical algorithm based on the contemporary theoretical concepts of surface and edge propagation is proposed and compared with existing numerical models and theoretical expectations

  7. Modeling and Simulating Airport Surface Operations with Gate Conflicts

    Science.gov (United States)

    Zelinski, Shannon; Windhorst, Robert

    2017-01-01

    The Surface Operations Simulator and Scheduler (SOSS) is a fast-time simulation platform used to develop and test future surface scheduling concepts such as NASAs Air Traffic Demonstration 2 of time-based surface metering at Charlotte Douglas International Airport (CLT). Challenges associated with CLT surface operations have driven much of SOSS development. Recently, SOSS functionality for modeling hardstand operations was developed to address gate conflicts, which occur when an arrival and departure wish to occupy the same gate at the same time. Because surface metering concepts such as ATD2 have the potential to increase gates conflicts as departure are held at their gates, it is important to study the interaction between surface metering and gate conflict management. Several approaches to managing gate conflicts with and without the use of hardstands were simulated and their effects on surface operations and scheduler performance compared.

  8. Simulation Tool for GNSS Ocean Surface Reflections

    OpenAIRE

    Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

    2015-01-01

    GNSS coherent and incoherent reflected signals have the potential of deriving large scale parameters of ocean surfaces, as barotropic variability, eddy currents and fronts, Rossby waves, coastal upwelling, mean ocean surfaceheights, and patterns of the general ocean circulation. In the reflection zone the measurements may deriveparameters as sea surface roughness, winds, waves, heights and tilts from the spectral measurements. Previous measurements from the top of mountains and airplanes have...

  9. Local grid refinement for free-surface flow simulations

    NARCIS (Netherlands)

    van der Plas, Peter

    2017-01-01

    The principal goal of the current study is to explore and investigate the potential of local grid refinement for increasing the numerical efficiency of free-surface flow simulations in a practical context. In this thesis we propose a method for local grid refinement in the free-surface flow model

  10. Simulation of Solar Radiation Incident on Horizontal and Inclined Surfaces

    Directory of Open Access Journals (Sweden)

    MA Basunia

    2012-12-01

    Full Text Available A computer model was developed to simulate the hourly, daily and monthly average of daily solar radiation on horizontal and inclined surfaces. The measured hourly and daily solar radiation was compared with simulated radiation, and favourable agreement was observed for the measured and predicted values on clear days. The measured and simulated monthly averages of total (diffuse and beam daily solar radiation were compared and a reasonable agreement was observed for a number of stations in Japan. The simulation showed that during the rice harvesting season, September to October, there is a daily average of 14.7 MJ/m2 of solar irradiation on a horizontal surface in Matsuyama, Japan. There is a similar amount of solar radiation on a horizontal surface during the major rice harvesting season, November to December, in Bangladesh. This radiation can be effectively utilized for drying rough rice and other farm crops.

  11. Simple model of surface roughness for binary collision sputtering simulations

    International Nuclear Information System (INIS)

    Lindsey, Sloan J.; Hobler, Gerhard; Maciążek, Dawid; Postawa, Zbigniew

    2017-01-01

    Highlights: • A simple model of surface roughness is proposed. • Its key feature is a linearly varying target density at the surface. • The model can be used in 1D/2D/3D Monte Carlo binary collision simulations. • The model fits well experimental glancing incidence sputtering yield data. - Abstract: It has been shown that surface roughness can strongly influence the sputtering yield – especially at glancing incidence angles where the inclusion of surface roughness leads to an increase in sputtering yields. In this work, we propose a simple one-parameter model (the “density gradient model”) which imitates surface roughness effects. In the model, the target’s atomic density is assumed to vary linearly between the actual material density and zero. The layer width is the sole model parameter. The model has been implemented in the binary collision simulator IMSIL and has been evaluated against various geometric surface models for 5 keV Ga ions impinging an amorphous Si target. To aid the construction of a realistic rough surface topography, we have performed MD simulations of sequential 5 keV Ga impacts on an initially crystalline Si target. We show that our new model effectively reproduces the sputtering yield, with only minor variations in the energy and angular distributions of sputtered particles. The success of the density gradient model is attributed to a reduction of the reflection coefficient – leading to increased sputtering yields, similar in effect to surface roughness.

  12. Molecular dynamics simulation of annealed ZnO surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Min, Tjun Kit; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    The effect of thermally annealing a slab of wurtzite ZnO, terminated by two surfaces, (0001) (which is oxygen-terminated) and (0001{sup ¯}) (which is Zn-terminated), is investigated via molecular dynamics simulation by using reactive force field (ReaxFF). We found that upon heating beyond a threshold temperature of ∼700 K, surface oxygen atoms begin to sublimate from the (0001) surface. The ratio of oxygen leaving the surface at a given temperature increases as the heating temperature increases. A range of phenomena occurring at the atomic level on the (0001) surface has also been explored, such as formation of oxygen dimers on the surface and evolution of partial charge distribution in the slab during the annealing process. It was found that the partial charge distribution as a function of the depth from the surface undergoes a qualitative change when the annealing temperature is above the threshold temperature.

  13. Superhydrophobic surfaces: From nature to biomimetic through VOF simulation.

    Science.gov (United States)

    Liu, Chunbao; Zhu, Ling; Bu, Weiyang; Liang, Yunhong

    2018-04-01

    The contact angle, surface structure and chemical compositions of Canna leaves were investigated. According to the surface structure of Canna leaves which observed by Scanning Electron Microscopy(SEM), the CFD (Computational Fluid Dynamics)model was established and the method of volume of fluid (VOF) was used to simulate the process of droplet impacting on the surface and established a smooth surface for comparison to verify that the surface structure was an important factor of the superhydrophobic properties. Based on the study of Canna leaf and VOF simulation of its surface structure, the superhydrophobic samples were processed successfully and showed a good superhydrophobic property with a contact angle of 156 ± 1 degrees. A high-speed camera (5000 frames per second) was used to assess droplet movement and determine the contact time of the samples. The contact time for the sample was 13.1 ms. The results displayed that the artificial superhydrophobic surface is perfect for the performance of superhydrophobic properties. The VOF simulation method was efficient, accurate and low cost before machining artificial superhydrophobic samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Microprocessor-based simulator of surface ECG signals

    International Nuclear Information System (INIS)

    MartInez, A E; Rossi, E; Siri, L Nicola

    2007-01-01

    In this work, a simulator of surface electrocardiogram recorded signals (ECG) is presented. The device, based on a microcontroller and commanded by a personal computer, produces an analog signal resembling actual ECGs, not only in time course and voltage levels, but also in source impedance. The simulator is a useful tool for electrocardiograph calibration and monitoring, to incorporate as well in educational tasks and in clinical environments for early detection of faulty behaviour

  15. Multiscale simulation of ion beam impacts on a graphene surface

    International Nuclear Information System (INIS)

    Dybyspayeva, K B; Zhuldassov, A; Ainabayev, A; Insepov, Z; Vyatkin, A F; Alekseev, K

    2016-01-01

    Multiscale study of single and multilayer graphene irradiation is presented in this paper. Ab-initio density-functional theory (DFT) was used to study point defects, and a large scale parallel molecular-dynamics (MD) simulations were used for studying formation of gas cluster ion impacts. Moreover, Raman spectra of pure and defect graphene samples were studied from DFT calculations. Threshold energies for creating craters on the surface of graphene were obtained from MD and compared with published papers. The results of simulations were also compared with experimental craters and surface shape. (paper)

  16. Numerical simulations of viscoelastic flows with free surfaces

    DEFF Research Database (Denmark)

    Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri

    2013-01-01

    We present a new methodology to simulate viscoelastic flows with free-surfaces. These simulations are motivated by the modelling of polymers manufacturing techniques, such as extrusion and injection moulding. One of the consequences of viscoelasticity is that polymeric materials have a “memory......” of their past deformations. This generates some numerical difficulties which are addressed with the log-conformation transformation. The main novelty of this work lies on the use of the volume-of-fluid method to track the free surfaces of the viscoelastic flows. We present some preliminary results of test case...

  17. Simulation of Langmuir-Blodgett film surface STM images

    International Nuclear Information System (INIS)

    Agabekov, V.E.; Zhavnerko, G.K.; Bar, G.; Cantov, H.J.

    1998-01-01

    The simulation of the STM image of a hydrocarbon tail of the fatty acid was carried out and compared to the experimental results. The simulation procedure includes calculations of the distribution of an isolated molecule electronic density by the extended Huckel-Hoffman method. An agreement between the calculated and experimental STM images of closely packed Langmuir-Blodgett film of cobalt behenate on the graphite surface and the adsorbed molecules constituting bi- and multilayer Langmuir-Blodgett films can be neglected in simulations of STM images. (author)

  18. Simulation of secondary electron emission from rough surfaces

    International Nuclear Information System (INIS)

    Kawata, J.; Ohya, K.; Nishimura, K.

    1995-01-01

    The effect of surface roughness on the secondary electron emission from a beryllium surface under low-energy (≤1 keV) electron bombardment is investigated using a Monte Carlo simulation combined with the model of bowl-structured surface. With increasing aspect ratio H/W of the bowl structure, the secondary electron yield becomes greater than that for a flat surface, whereas for large H/W the yield is smaller; where H and W are the depth and width of the bowl structure, respectively. The former is due to emission of electrons, which cannot escape from the flat surface, from an inclined plane; it increases the low-energy component in the energy distribution. The latter is due to re-entrance of once-emitted electrons into the next part of the topographic surface; it decreases the number of electrons emitted with oblique angles. ((orig.))

  19. Simulations of surface stress effects in nanoscale single crystals

    Science.gov (United States)

    Zadin, V.; Veske, M.; Vigonski, S.; Jansson, V.; Muszinsky, J.; Parviainen, S.; Aabloo, A.; Djurabekova, F.

    2018-04-01

    Onset of vacuum arcing near a metal surface is often associated with nanoscale asperities, which may dynamically appear due to different processes ongoing in the surface and subsurface layers in the presence of high electric fields. Thermally activated processes, as well as plastic deformation caused by tensile stress due to an applied electric field, are usually not accessible by atomistic simulations because of the long time needed for these processes to occur. On the other hand, finite element methods, able to describe the process of plastic deformations in materials at realistic stresses, do not include surface properties. The latter are particularly important for the problems where the surface plays crucial role in the studied process, as for instance, in the case of plastic deformations at a nanovoid. In the current study by means of molecular dynamics (MD) and finite element simulations we analyse the stress distribution in single crystal copper containing a nanovoid buried deep under the surface. We have developed a methodology to incorporate the surface effects into the solid mechanics framework by utilizing elastic properties of crystals, pre-calculated using MD simulations. The method leads to computationally efficient stress calculations and can be easily implemented in commercially available finite element software, making it an attractive analysis tool.

  20. Moving least squares simulation of free surface flows

    DEFF Research Database (Denmark)

    Felter, C. L.; Walther, Jens Honore; Henriksen, Christian

    2014-01-01

    In this paper a Moving Least Squares method (MLS) for the simulation of 2D free surface flows is presented. The emphasis is on the governing equations, the boundary conditions, and the numerical implementation. The compressible viscous isothermal Navier–Stokes equations are taken as the starting ...

  1. Astronaut Neil Armstrong participates in lunar surface simulation training

    Science.gov (United States)

    1969-01-01

    Astronaut Neil A. Armstrong, wearing an Extravehicular Mobility Unit (EMU), participates in lunar surface simulation training on April 18, 1969 in bldg 9, Manned Spacecraft Center. Armstrong is the prime crew commander of the Apollo 11 lunar landing mission. Here, he is standing on Lunar Module mockup foot pad preparing to ascend steps.

  2. Manufacture of Cryoshroud Surfaces for Space Simulation Chambers

    Science.gov (United States)

    Ash, Gary S.

    2008-01-01

    Environmental test chambers for space applications use internal shrouds to simulate temperature conditions encountered in space. Shroud temperatures may range from +150 C to -253 C (20 K), and internal surfaces are coated with special high emissivity/absorptivity paints. To obtain temperature uniformity over large areas, detailed thermal design is required for placement of tubing for gaseous or liquid nitrogen and helium and other exotic heat exchange fluids. The recent increase in space simulation activity related to the James Webb Space Telescope has led to the design of new cryogenic shrouds to meet critical needs in instrument package testing. This paper will review the design and manufacturing of shroud surfaces for several of these programs, including fabrication methods and the selection and application of paints for simulation chambers.

  3. Simulating condensation on microstructured surfaces using Lattice Boltzmann Method

    Science.gov (United States)

    Alexeev, Alexander; Vasyliv, Yaroslav

    2017-11-01

    We simulate a single component fluid condensing on 2D structured surfaces with different wettability. To simulate the two phase fluid, we use the athermal Lattice Boltzmann Method (LBM) driven by a pseudopotential force. The pseudopotential force results in a non-ideal equation of state (EOS) which permits liquid-vapor phase change. To account for thermal effects, the athermal LBM is coupled to a finite volume discretization of the temperature evolution equation obtained using a thermal energy rate balance for the specific internal energy. We use the developed model to probe the effect of surface structure and surface wettability on the condensation rate in order to identify microstructure topographies promoting condensation. Financial support is acknowledged from Kimberly-Clark.

  4. Finite element simulations of surface effect on Rayleigh waves

    Science.gov (United States)

    He, Jin; Zhao, Jinling

    2018-03-01

    Rayleigh waves influenced by surface effect are investigated by using finite element methods, in which eigenfrequency analysis are performed on a model composed of a half-space covered by the surface effect dominated domain. For a given wavelength, the frequency of the Rayleigh wave is obtained as the eigenfrequency of the model satisfying Floquet periodic boundary conditions. The thickness of the surface effect can be set to be infinitely small or a finite value in the finite element methods. The curvature-dependent out-of-plane force induced by surface tension as described by the generalized Young-Laplace equation is realized through geometric nonlinear analysis. The finite element simulations show that the assumptions of small curvature and infinitely small thickness of the surface effect widely used in theoretical approaches become invalid when Rayleigh waves are highly influenced by the surface effect. This work gives a more accurate insight into the surface effect on Rayleigh waves and provides a potential method for measuring the thickness of the surface effect from the dispersion curves of surface effect influenced Rayleigh wave velocities.

  5. Simple model of surface roughness for binary collision sputtering simulations

    Science.gov (United States)

    Lindsey, Sloan J.; Hobler, Gerhard; Maciążek, Dawid; Postawa, Zbigniew

    2017-02-01

    It has been shown that surface roughness can strongly influence the sputtering yield - especially at glancing incidence angles where the inclusion of surface roughness leads to an increase in sputtering yields. In this work, we propose a simple one-parameter model (the "density gradient model") which imitates surface roughness effects. In the model, the target's atomic density is assumed to vary linearly between the actual material density and zero. The layer width is the sole model parameter. The model has been implemented in the binary collision simulator IMSIL and has been evaluated against various geometric surface models for 5 keV Ga ions impinging an amorphous Si target. To aid the construction of a realistic rough surface topography, we have performed MD simulations of sequential 5 keV Ga impacts on an initially crystalline Si target. We show that our new model effectively reproduces the sputtering yield, with only minor variations in the energy and angular distributions of sputtered particles. The success of the density gradient model is attributed to a reduction of the reflection coefficient - leading to increased sputtering yields, similar in effect to surface roughness.

  6. Molecular Dynamics Simulations of Slip on Curved Surfaces

    Directory of Open Access Journals (Sweden)

    Ross D.A.

    2016-07-01

    Full Text Available We present Molecular Dynamics (MD simulations of liquid water confined within nanoscale geometries, including slit-like and cylindrical graphitic pores. These equilibrium results are used for calculating friction coefficients, which in turn can be used to calculate slip lengths. The slip length is a material property independent of the fluid flow rate. It is therefore a better quantity for study than the fluid velocity at the wall, also known as the slip velocity. Once the slip length has been found as a function of surface curvature, it can be used to parameterise Lattice Boltzmann (LB simulations. These larger scale simulations are able to tell us about how fluid transport is affected by slip in complex geometries; not just limited to single pores. Applications include flow and transport in nano-porous engine valve deposits and gas shales. The friction coefficient is found to be a function of curvature and is higher for fluid on convex surfaces and lower for concave surfaces. Both concave and convex surfaces approach the same value of the friction coefficient, which is constant above some critical radius of curvature, here found to be 7.4 ± 2.9 nm. The constant value of the friction coefficient is 10,000 ± 600 kg m−2 s−1, which is equivalent to a slip length of approximately 67 ± 4 nm.

  7. Real-time High-fidelity Surface Flow Simulation.

    Science.gov (United States)

    Ren, Bo; Yuan, Tailing; Li, Chenfeng; Xu, Kun; Hu, Shi-Min

    2017-06-30

    Surface flow phenomena, such as rain water flowing down a tree trunk and progressive water front in a shower room, are common in real life. However, compared with the 3D spatial fluid flow, these surface flow problems have been much less studied in the graphics community. To tackle this research gap, we present an efficient, robust and high-fidelity simulation approach based on the shallow-water equations. Specifically, the standard shallow-water flow model is extended to general triangle meshes with a feature-based bottom friction model, and a series of coherent mathematical formulations are derived to represent the full range of physical effects that are important for real-world surface flow phenomena. In addition, by achieving compatibility with existing 3D fluid simulators and by supporting physically realistic interactions with multiple fluids and solid surfaces, the new model is flexible and readily extensible for coupled phenomena. A wide range of simulation examples are presented to demonstrate the performance of the new approach.

  8. Modelling and simulation of surface morphology driven by ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Yewande, E.O.

    2006-05-02

    Non-equilibrium surfaces, at nanometer length scales, externally driven via bombardment with energetic particles are known to exhibit well ordered patterns with a variety of applications in nano-technology. These patterns emerge at time scales on the order of minutes. Continuum theory has been quite successful in giving a general picture of the processes that interplay to give the observed patterns, as well as how such competition might determine the properties of the nanostructures. However, continuum theoretical descriptions are ideal only in the asymptotic limit. The only other theoretical alternative, which happens to be more suitable for the characteristic length-and time-scales of pattern formation, is Monte Carlo simulation. In this thesis, surface morphology is studied using discrete solid-on-solid Monte Carlo models of sputtering and surface diffusion. The simulations are performed in the context of the continuum theories and experiments. In agreement with the experiments, the ripples coarsen with time and the ripple velocity exhibits a power-law behaviour with the ripple wavelength, in addition, the exponent was found to depend on the simulation temperature, which suggests future experimental studies of flux dependence. Moreover, a detailed exploration of possible topographies, for different sputtering conditions, corresponding to different materials, was performed. And different surface topographies e.g. holes, ripples, and dots, were found at oblique incidence, without sample rotation. With sample rotation no new topography was found, its only role being to destroy any inherent anisotropy in the system. (orig.)

  9. Modelling and simulation of surface morphology driven by ion bombardment

    International Nuclear Information System (INIS)

    Yewande, E.O.

    2006-01-01

    Non-equilibrium surfaces, at nanometer length scales, externally driven via bombardment with energetic particles are known to exhibit well ordered patterns with a variety of applications in nano-technology. These patterns emerge at time scales on the order of minutes. Continuum theory has been quite successful in giving a general picture of the processes that interplay to give the observed patterns, as well as how such competition might determine the properties of the nanostructures. However, continuum theoretical descriptions are ideal only in the asymptotic limit. The only other theoretical alternative, which happens to be more suitable for the characteristic length-and time-scales of pattern formation, is Monte Carlo simulation. In this thesis, surface morphology is studied using discrete solid-on-solid Monte Carlo models of sputtering and surface diffusion. The simulations are performed in the context of the continuum theories and experiments. In agreement with the experiments, the ripples coarsen with time and the ripple velocity exhibits a power-law behaviour with the ripple wavelength, in addition, the exponent was found to depend on the simulation temperature, which suggests future experimental studies of flux dependence. Moreover, a detailed exploration of possible topographies, for different sputtering conditions, corresponding to different materials, was performed. And different surface topographies e.g. holes, ripples, and dots, were found at oblique incidence, without sample rotation. With sample rotation no new topography was found, its only role being to destroy any inherent anisotropy in the system. (orig.)

  10. Sputtering of rough surfaces: a 3D simulation study

    Science.gov (United States)

    von Toussaint, U.; Mutzke, A.; Manhard, A.

    2017-12-01

    The lifetime of plasma-facing components is critical for future magnetic confinement fusion power plants. A key process limiting the lifetime of the first-wall is sputtering by energetic ions. To provide a consistent modeling of the sputtering process of realistic geometries, the SDTrimSP-code has been extended to enable the processing of analytic as well as measured arbitrary 3D surface morphologies. The code has been applied to study the effect of varying the impact angle of ions on rough surfaces on the sputter yield as well as the influence of the aspect ratio of surface structures on the 2D distribution of the local sputtering yields. Depending on the surface morphologies reductions of the effective sputter yields to less than 25% have been observed in the simulation results.

  11. Surface Ship Shock Modeling and Simulation: Two-Dimensional Analysis

    Directory of Open Access Journals (Sweden)

    Young S. Shin

    1998-01-01

    Full Text Available The modeling and simulation of the response of a surface ship system to underwater explosion requires an understanding of many different subject areas. These include the process of underwater explosion events, shock wave propagation, explosion gas bubble behavior and bubble-pulse loading, bulk and local cavitation, free surface effect, fluid-structure interaction, and structural dynamics. This paper investigates the effects of fluid-structure interaction and cavitation on the response of a surface ship using USA-NASTRAN-CFA code. First, the one-dimensional Bleich-Sandler model is used to validate the approach, and second, the underwater shock response of a two-dimensional mid-section model of a surface ship is predicted with a surrounding fluid model using a constitutive equation of a bilinear fluid which does not allow transmission of negative pressures.

  12. Scattering from objects and surfaces in room acoustical simulations

    DEFF Research Database (Denmark)

    Marbjerg, Gerd Høy; Brunskog, Jonas; Jeong, Cheol-Ho

    2016-01-01

    In room acoustical simulations, scattering objects are often modeled as impenetrable boxes with high scattering coefficients assigned to the surfaces. In some cases, a cluster of objects is modeled as a virtual impenetrable box, such that no sound propagation can take place between the objects....... Thus, the scattering only takes place on the boundary surfaces of the box and the acoustic volume of the room is reduced. Another challenge with representing scattering objects by reflecting surfaces is that it increases the number of surfaces, which greatly increases the calculation complexity...... for methods such as the image source method. In this paper a modeling method where the scattering from objects takes place in certain parts of the room volume is proposed. In this method, sound can still travel through scattering objects, but be partly scattered. This volume scattering method has at present...

  13. A simulation of laser energy absorption by nanowired surface

    International Nuclear Information System (INIS)

    Vasconcelos, Miguel F.S.; Ramos, Alexandre F.

    2017-01-01

    Despite recent advances on research about laser inertial fusion energy, to increase the portion of energy absorbed by the target's surface from lasers remains as an important challenge. The plasma formed during the initial instants of laser arrival shields the target and prevents the absorption of laser energy by the deeper layers of the material. One strategy to circumvent that effect is the construction of targets whose surfaces are populated with nanowires. The nanowired surfaces have increased absorption of laser energy and constitutes a promising pathway for enhancing laser-matter coupling. In our work we present the results of simulations aiming to investigate how target's geometrical properties might contribute for maximizing laser energy absorption by material. Simulations have been carried out using the software FLASH, a multi-physics platform developed by researchers from the University of Chicago, written in FORTRAN 90 and Python. Different tools for generating target's geometry and analysis of results were developed using Python. Our results show that a nanowired surfaces has an increased energy absorption when compared with non wired surface. The software for visualization developed in this work also allowed an analysis of the spatial dynamics of the target's temperature, electron density, ionization levels and temperature of the radiation emitted by it. (author)

  14. Simulations of atomic trajectories near a dielectric surface

    Energy Technology Data Exchange (ETDEWEB)

    Stern, N P; Alton, D J; Kimble, H J, E-mail: hjkimble@caltech.edu [Norman Bridge Laboratory of Physics 12-33, California Institute of Technology, Pasadena, CA 91125 (United States)

    2011-08-15

    We present a semiclassical model of an atom moving in the evanescent field of a microtoroidal resonator. Atoms falling through whispering-gallery modes can achieve strong, coherent coupling with the cavity at distances of approximately 100 nm from the surface; in this regime, surface-induced Casmir-Polder level shifts become significant for atomic motion and detection. Atomic transit events detected in recent experiments are analyzed with our simulation, which is extended to consider atom trapping in the evanescent field of a microtoroid.

  15. Computer simulation of RBS spectra from samples with surface roughness

    Czech Academy of Sciences Publication Activity Database

    Malinský, Petr; Hnatowicz, Vladimír; Macková, Anna

    2016-01-01

    Roč. 371, MAR (2016), s. 101-105 ISSN 0168-583X. [22nd International conference on Ion Beam Analysis (IBA). Opatija, 14.06.2015-19.06.2015] R&D Projects: GA MŠk(CZ) LM2011019; GA ČR GA15-01602S Institutional support: RVO:61389005 Keywords : computer simulation * Rutherford backscattering * surface roughness Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.109, year: 2016

  16. Two dimensional simulation of high power laser-surface interaction

    International Nuclear Information System (INIS)

    Goldman, S.R.; Wilke, M.D.; Green, R.E.L.; Johnson, R.P.; Busch, G.E.

    1998-01-01

    For laser intensities in the range of 10 8 --10 9 W/cm 2 , and pulse lengths of order 10 microsec or longer, the authors have modified the inertial confinement fusion code Lasnex to simulate gaseous and some dense material aspects of the laser-matter interaction. The unique aspect of their treatment consists of an ablation model which defines a dense material-vapor interface and then calculates the mass flow across this interface. The model treats the dense material as a rigid two-dimensional mass and heat reservoir suppressing all hydrodynamic motion in the dense material. The computer simulations and additional post-processors provide predictions for measurements including impulse given to the target, pressures at the target interface, electron temperatures and densities in the vapor-plasma plume region, and emission of radiation from the target. The authors will present an analysis of some relatively well diagnosed experiments which have been useful in developing their modeling. The simulations match experimentally obtained target impulses, pressures at the target surface inside the laser spot, and radiation emission from the target to within about 20%. Hence their simulational technique appears to form a useful basis for further investigation of laser-surface interaction in this intensity, pulse-width range. This work is useful in many technical areas such as materials processing

  17. Simulating Sediment Sorting of Streambed Surfaces - It's the Supply, Stupid

    Science.gov (United States)

    Wilcock, P. R.

    2014-12-01

    The grain size of the streambed surface is an integral part of the transport system because it represents the grains immediately available for transport. If the rate and size of grains entrained from the bed surface differ from that delivered to the bed surface, the bed surface grain size will change. Although this balance is intuitively clear, its implications can surprise. The relative mobility of different sizes in a mixture change as transport rates increase. At small transport rates, smaller sizes are more mobile. As transport rate increases, the transport grain size approaches that of the bed. This presents a dilemma when using flumes to simulate surface sorting and transport. When sediment is fed into a flume, the same sediment is typically used regardless of feed rate. The transport grain size remains constant at all rates, which does not match the pattern observed in the field. This operational constraint means that sediment supply is coarser than transport capacity in feed flumes, increasingly so as transport rates diminish. This imbalance drives a coarsening of the stream bed as less mobile coarse grains concentrate on the surface as the system approaches steady-state. If sediment is recirculated in a flume, sediment supply and entrainment are perfectly matched. Surface coarsening is not imposed, but does occur via kinematic sieving. The coarsening of the transport (and supply) accommodates the rate-dependent change in mobility such that the bed surface grain size does not change with transport rate. Streambed armoring depends on both the rate and grain size of sediment supply - their implications do not seem to be fully appreciated. A coarsened bed surface does not indicate sorting of the bed surface during waning flows - it can persist with active sediment supply and transport. Neither sediment feed nor sediment recirculating flumes accurately mimic natural conditions but instead represent end members that bracket the dynamics of natural streams

  18. Improved simulation of groundwater - surface water interaction in catchment models

    Science.gov (United States)

    teklesadik, aklilu; van Griensven, Ann; Anibas, Christian; Huysmans, Marijke

    2016-04-01

    Groundwater storage can have a significant contribution to stream flow, therefore a thorough understanding of the groundwater surface water interaction is of prime important when doing catchment modeling. The aim of this study is to improve the simulation of groundwater - surface water interaction in a catchment model of the upper Zenne River basin located in Belgium. To achieve this objective we used the "Groundwater-Surface water Flow" (GSFLOW) modeling software, which is an integration of the surface water modeling tool "Precipitation and Runoff Modeling system" (PRMS) and the groundwater modeling tool MODFLOW. For this case study, the PRMS model and MODFLOW model were built and calibrated independently. The PRMS upper Zenne River basin model is divided into 84 hydrological response units (HRUs) and is calibrated with flow data at the Tubize gauging station. The spatial discretization of the MODFLOW upper Zenne groundwater flow model consists of 100m grids. Natural groundwater divides and the Brussels-Charleroi canal are used as boundary conditions for the MODFLOW model. The model is calibrated using piezometric data. The GSFLOW results were evaluated against a SWAT model application and field observations of groundwater-surface water interactions along a cross section of the Zenne River and riparian zone. The field observations confirm that there is no exchange of groundwater beyond the Brussel-Charleroi canal and that the interaction at the river bed is relatively low. The results show that there is a significant difference in the groundwater simulations when using GSFLOW versus SWAT. This indicates that the groundwater component representation in the SWAT model could be improved and that a more realistic implementation of the interactions between groundwater and surface water is advisable. This could be achieved by integrating SWAT and MODFLOW.

  19. Exposing earth surface process model simulations to a large audience

    Science.gov (United States)

    Overeem, I.; Kettner, A. J.; Borkowski, L.; Russell, E. L.; Peddicord, H.

    2015-12-01

    The Community Surface Dynamics Modeling System (CSDMS) represents a diverse group of >1300 scientists who develop and apply numerical models to better understand the Earth's surface. CSDMS has a mandate to make the public more aware of model capabilities and therefore started sharing state-of-the-art surface process modeling results with large audiences. One platform to reach audiences outside the science community is through museum displays on 'Science on a Sphere' (SOS). Developed by NOAA, SOS is a giant globe, linked with computers and multiple projectors and can display data and animations on a sphere. CSDMS has developed and contributed model simulation datasets for the SOS system since 2014, including hydrological processes, coastal processes, and human interactions with the environment. Model simulations of a hydrological and sediment transport model (WBM-SED) illustrate global river discharge patterns. WAVEWATCH III simulations have been specifically processed to show the impacts of hurricanes on ocean waves, with focus on hurricane Katrina and super storm Sandy. A large world dataset of dams built over the last two centuries gives an impression of the profound influence of humans on water management. Given the exposure of SOS, CSDMS aims to contribute at least 2 model datasets a year, and will soon provide displays of global river sediment fluxes and changes of the sea ice free season along the Arctic coast. Over 100 facilities worldwide show these numerical model displays to an estimated 33 million people every year. Datasets storyboards, and teacher follow-up materials associated with the simulations, are developed to address common core science K-12 standards. CSDMS dataset documentation aims to make people aware of the fact that they look at numerical model results, that underlying models have inherent assumptions and simplifications, and that limitations are known. CSDMS contributions aim to familiarize large audiences with the use of numerical

  20. Noble Gas Surface Flux Simulations And Atmospheric Transport

    Energy Technology Data Exchange (ETDEWEB)

    Carrigan, Charles R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sun, Yunwei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Simpson, Matthew D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-09-30

    Signatures from underground nuclear explosions or UNEs are strongly influenced by the containment regime surrounding them. The degree of gas leakage from the detonation cavity to the surface obviously affects the magnitude of surface fluxes of radioxenon that might be detected during the course of a Comprehensive Test Ban Treaty On-Site Inspection. In turn, the magnitude of surface fluxes will influence the downwind detectability of the radioxenon atmospheric signature from the event. Less obvious is the influence that leakage rates have on the evolution of radioxenon isotopes in the cavity or the downwind radioisotopic measurements that might be made. The objective of this letter report is to summarize our attempt to better understand how containment conditions affect both the detection and interpretation of radioxenon signatures obtained from sampling at the ground surface near an event as well as at greater distances in the atmosphere. In the discussion that follows, we make no attempt to consider other sources of radioactive noble gases such as natural backgrounds or atmospheric contamination and, for simplicity, only focus on detonation-produced radioxenon gases. Summarizing our simulations, they show that the decay of radioxenon isotopes (e.g., Xe-133, Xe-131m, Xe-133m and Xe-135) and their migration to the surface following a UNE means that the possibility of detecting these gases exists within a window of opportunity. In some cases, seeps or venting of detonation gases may allow significant quantities to reach the surface and be released into the atmosphere immediately following a UNE. In other release scenarios – the ones we consider here – hours to days may be required for gases to reach the surface at detectable levels. These release models are most likely more characteristic of “fully contained” events that lack prompt venting, but which still leak gas slowly across the surface for periods of months.

  1. Molecular dynamics simulation of uranium compound adsorption on solid surface

    International Nuclear Information System (INIS)

    Omori, Yuki; Takizawa, Yuji; Okamoto, Tsuyoshi

    2010-01-01

    Particles mixed in the UF6 gas have the property of accumulating on the inside of piping or units. This type of accumulation will cause material unaccounted for (MUF) in the UF6 gas processing facilities. Development of a calculation model for estimating the accumulation rate of uranium compounds has been expected. And predicting possible part of the units where uranium compounds adsorb will contribute to design an effective detection system. The purpose of this study is to take the basic knowledge of the particle's adsorption mechanism from the microscopic point of view. In simulation analysis, UF5 model particle is produced, then two types of solid surfaces are prepared; one is a solid surface at rest and the other is a moving solid surface. The result obtained by the code 'PABS' showed that when the solid surface moves at a lower velocity, the particle's adsorption process dominates over the particle's breakup one. Besides the velocity of the solid surface, other principal factors affecting an adsorption ratio were also discussed. (author)

  2. Solvent accessible surface area (ASA) of simulated phospholipid membranes

    DEFF Research Database (Denmark)

    Tuchsen, E.; Jensen, Morten Østergaard; Westh, P.

    2003-01-01

    The membrane-solvent interface has been investigated through calculations of the solvent accessible surface area (ASA) for simulated membranes of DPPC and POPE. For DPPC at 52 degreesC we found an ASA of 126 +/- 8 Angstrom(2) per lipid molecule, equivalent to twice the projected lateral area......, even the most exposed parts of the PC head-group show average ASAs of less than half of its maximal or 'fully hydrated' value. The average ASA of a simulated POPE membrane was 96 +/- 7 Angstrom(2) per lipid. The smaller value than for DPPC reflects much lower ASA of the ammonium ion, which is partially...... compensated by increased exposure of the ethylene and phosphate moieties. The ASA of the polar moieties Of (PO4, NH3 and COO) constitutes 65% of the total accessible area for POPE, making this interface more polar than that of DPPC. It is suggested that ASA information can be valuable in attempts...

  3. View-Dependent Tessellation and Simulation of Ocean Surfaces

    Directory of Open Access Journals (Sweden)

    Anna Puig-Centelles

    2014-01-01

    Full Text Available Modeling and rendering realistic ocean scenes have been thoroughly investigated for many years. Its appearance has been studied and it is possible to find very detailed simulations where a high degree of realism is achieved. Nevertheless, among the solutions to ocean rendering, real-time management of the huge heightmaps that are necessary for rendering an ocean scene is still not solved. We propose a new technique for simulating the ocean surface on GPU. This technique is capable of offering view-dependent approximations of the mesh while maintaining coherence among the extracted approximations. This feature is very important as most solutions previously presented must retessellate from the initial mesh. Our solution is able to use the latest extracted approximation when refining or coarsening the mesh.

  4. Simulation of gas compressible flow by free surface water flow

    International Nuclear Information System (INIS)

    Altafini, C.R.; Silva Ferreira, R.T. da

    1981-01-01

    The analogy between the water flow with a free surface and the compressible fluid flow, commonly called hydraulic analogy, is analyzed and its limitations are identified. The water table is the equipment used for this simulation, which allows the quatitative analysis of subsonic and supersonic flow with a low cost apparatus. The hydraulic analogy is applied to subsonic flow around circular cylinders and supersonic flow around cones. The results are compared with available theoretical and experimental data and a good agreement is achieved. (Author) [pt

  5. Simulation of actuated synthetic cilia expelling microorganisms from a surface

    Science.gov (United States)

    Shum, Henry; Tripathi, Anurag; Yeomans, Julia; Balazs, Anna

    2013-11-01

    The continual motion of cilia provides a defense against biofouling for a variety of marine organisms. Inspired by this natural solution, we perform numerical simulations to study the interactions between actuated, biomimetic cilia and model microswimmers that are hydrodynamically attracted to bare surfaces and therefore behave similarly to fouling organisms. The 3-dimensional fluid flow is coupled to the motion of the cilia and swimmers using an integrated lattice Boltzmann and immersed boundary method. We show that a sparse array of actuated cilia, through which the organisms are able to swim, is able to robustly expel swimmers. The average residence time of the swimmers in the ciliary layer is reduced if the motion of the cilia generates a net fluid flow, but for relatively fast swimmers, the steric interaction with the moving cilia alone is sufficient to ``knock'' the organisms away from the surface. As the demonstrated mechanisms for antifouling do not rely on specific chemical or physical properties of the surface or swimmer, actuated cilia can potentially protect microfluidic devices, filtration membranes or ship hulls from a wide range of fouling species.

  6. Applications of granular-dynamics numerical simulations to asteroid surfaces

    Science.gov (United States)

    Richardson, D. C.; Michel, P.; Schwartz, S. R.; Yu, Y.; Ballouz, R.-L.; Matsumura, S.

    2014-07-01

    Spacecraft images and indirect observations including thermal inertia measurements indicate most small bodies have surface regolith. Evidence of granular flow is also apparent in the images. This material motion occurs in very low gravity, therefore in a totally different gravitational environment than on the Earth. Upcoming sample-return missions to small bodies, and possible future manned missions, will involve interaction with the surface regolith, so it is important to develop tools to predict the surface response. We have added new capabilities to the N-body gravity tree code pkdgrav [1,2] that permit the simulation of granular dynamics, including multi-contact physics and friction forces, using the soft-sphere discrete-element method [3]. The numerical approach has been validated through comparison with laboratory experiments (e.g., [3,4]). (1) We carried out impacts into granular materials using different projectile shapes under Earth's gravity [5] and compared the results to laboratory experiments [6] in support of JAXA's Hayabusa 2 asteroid sample-return mission. We tested different projectile shapes and confirmed that the 90-degree cone was the most efficient at excavating mass when impacting 5-mm-diameter glass beads. Results are sensitive to the normal coefficient of restitution and the coefficient of static friction. Preliminary experiments in micro-gravity for similar impact conditions show both the amount of ejected mass and the timescale of the impact process increase, as expected. (2) It has been found (e.g., [7,8]) that ''fresh'' (unreddened) Q-class asteroids have a high probability of recent planetary encounters (˜1 Myr; also see [9]), suggesting that surface refreshening may have occurred due to tidal effects. As an application of the potential effect of tidal interactions, we carried out simulations of Apophis' predicted 2029 encounter with the Earth to see whether regolith motion might occur, using a range of plausible material parameters

  7. Simulation and Optimization of Silicon Solar Cell Back Surface Field

    Directory of Open Access Journals (Sweden)

    Souad TOBBECHE

    2015-11-01

    Full Text Available In this paper, TCAD Silvaco (Technology Computer Aided Design software has been used to study the Back Surface Field (BSF effect of a p+ silicon layer for a n+pp+ silicon solar cell. To study this effect, the J-V characteristics and the external quantum efficiency (EQE are simulated under AM 1.5 illumination for two types of cells. The first solar cell is without BSF (n+p structure while the second one is with BSF (n+pp+ structure. The creation of the BSF on the rear face of the cell results in efficiency h of up to 16.06% with a short-circuit current density Jsc = 30.54 mA/cm2, an open-circuit voltage Voc = 0.631 V, a fill factor FF = 0.832 and a clear improvement of the spectral response obtained in the long wavelengths range. An electric field and a barrier of potential are created by the BSF and located at the junction p+/p with a maximum of 5800 V/cm and 0.15 V, respectively. The optimization of the BSF layer shows that the cell performance improves with the p+ thickness between 0.35 – 0.39 µm, the p+ doping dose is about 2 × 1014 cm-2, the maximum efficiency up to 16.19 %. The cell efficiency is more sensitive to the value of the back surface recombination velocity above a value of 103 cm/s in n+p than n+pp+ solar cell.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9565

  8. A facile method for simulating randomly rough membrane surface associated with interface behaviors

    Science.gov (United States)

    Qu, Xiaolu; Cai, Xiang; Zhang, Meijia; Lin, Hongjun; Leihong, Zhao; Liao, Bao-Qiang

    2018-01-01

    Modeling rough surfaces has emerged as a distinct discipline of considerable research interest in interface behaviors including membrane fouling. In this paper, a facile method was proposed to simulate rough membrane surface morphology. Natural membrane surface was found to be randomly rough, and its height distribution obeys Gaussian distribution. A new method which combines spectrum method, Gaussian distribution and Fourier transform technique was deduced. Simulation of the rough membrane surface showed high similarity in terms of statistical roughness and height distribution between the simulated surface and the real membrane surface, indicating feasibility of the new method. It was found that, correlation length (l) and the number of superposed ridges (N) are key parameters affecting the simulated membrane surface morphology. This new method has evident advantages over conventional modeling methods The proposed method for randomly rough membrane surface modeling could be potentially used to quantify the interfacial interactions between two rough surfaces, giving implications for membrane fouling mitigation.

  9. Three-Dimensional Model of a Muscle and Simulation of its Surface EMG

    National Research Council Canada - National Science Library

    Schnetzer, M

    2001-01-01

    ...) and a simulation of its surface EMG. The simulations are part of a larger model including in addition the input system to the motoneuronal pool, the motoneuronal pool itself and the force generating mechanism...

  10. Reliable low precision simulations in land surface models

    Science.gov (United States)

    Dawson, Andrew; Düben, Peter D.; MacLeod, David A.; Palmer, Tim N.

    2017-12-01

    Weather and climate models must continue to increase in both resolution and complexity in order that forecasts become more accurate and reliable. Moving to lower numerical precision may be an essential tool for coping with the demand for ever increasing model complexity in addition to increasing computing resources. However, there have been some concerns in the weather and climate modelling community over the suitability of lower precision for climate models, particularly for representing processes that change very slowly over long time-scales. These processes are difficult to represent using low precision due to time increments being systematically rounded to zero. Idealised simulations are used to demonstrate that a model of deep soil heat diffusion that fails when run in single precision can be modified to work correctly using low precision, by splitting up the model into a small higher precision part and a low precision part. This strategy retains the computational benefits of reduced precision whilst preserving accuracy. This same technique is also applied to a full complexity land surface model, resulting in rounding errors that are significantly smaller than initial condition and parameter uncertainties. Although lower precision will present some problems for the weather and climate modelling community, many of the problems can likely be overcome using a straightforward and physically motivated application of reduced precision.

  11. Numerical Simulation of Floating Bodies in Extreme Free Surface Waves

    Science.gov (United States)

    Hu, Zheng Zheng; Causon, Derek; Mingham, Clive; Qiang, Ling

    2010-05-01

    and efficient. Firstly, extreme design wave conditions are generated in an empty NWT and compared with physical experiments as a precursor to calculations to investigate the survivability of the Bobber device operating in a challenging wave climate. Secondly, we consider a bench-mark test case involving in a first order regular wave maker acting on a fixed cylinder and Pelamis. Finally, a floating Bobber has been simulated under extreme wave conditions. These results will be reported at the meeting. Causon D.M., Ingram D.M., Mingham C.G., Yang G. Pearson R.V. (2000). Calculation of shallow water flows using a Cartesian cut cell approach. Advances in Water resources, 23: 545-562. Causon D.M., Ingram D.M., Mingham C.G. (2000). A Cartesian cut cell method for shallow water flows with moving boundaries. Advances in Water resources, 24: 899-911. Dalzell J.F. 1999 A note on finite depth second-order wave-wave interactions. Appl. Ocean Res. 21, 105-111. Ning D.Z., Zang J., Liu S.X. Eatock Taylor R. Teng B. & Taylor P.H. 2009 Free surface and wave kinematics for nonlinear focused wave groups. J. Ocean Engineering. Accepted. Hu Z.Z., Causon D.M., Mingham C.M. and Qian L.(2009). Numerical wave tank study of a wave energy converter in heave. Proceedlings 19th ISOPE conference, Osaka, Japan Qian L., Causon D.M. & Mingham C.G., Ingram D.M. 2006 A free-surface capturing method for two fluid flows with moving bodies. Proc. Roy. Soc. London, Vol. A 462 21-42.

  12. A multi-surface plasticity model for ductile fracture simulations

    Science.gov (United States)

    Keralavarma, Shyam M.

    2017-06-01

    The growth and coalescence of micro-voids in a material undergoing ductile fracture depends strongly on the loading path. Void growth occurs by diffuse plasticity in the material and is sensitive to the hydrostatic stress, while void coalescence occurs by the localization of plastic deformation in the inter-void ligaments under a combination of normal and shear stresses on the localization plane. In this paper, a micromechanics-based plasticity model is developed for an isotropic porous material, accounting for both diffuse and localized modes of plasticity at the micro-scale. A multi-surface approach is adopted, and two existing plasticity models that separately account for the two modes of yielding, above, are synthesized to propose an effective isotropic yield criterion and associated state evolution equations. The yield criterion is validated by comparison with quasi-exact numerical yield loci computed using a finite elements based limit analysis procedure. It is shown that the new criterion is in better agreement with the numerical loci than the Gurson model, particularly for large values of the porosity for which the loading path dependence of the yield stress is well predicted by the new model. Even at small porosities, it is shown that the new model predicts marginally lower yield stresses under low triaxiality shear dominated loadings compared to the Gurson model, in agreement with the numerical limit analysis data. Predictions for the strains to the onset of coalescence under proportional loading, obtained by numerically integrating the model, indicate that void coalescence tends to occur at relatively small plastic strain and porosity levels under shear dominated loadings. Implications on the prediction of ductility using the new model in fracture simulations are discussed.

  13. Simulation of surface dynamics during dissolution as a function of the surface orientation: Implications for non-constant dissolution rates

    Science.gov (United States)

    Godinho, J. R. A.; Piazolo, S.; Evans, L.

    2014-12-01

    An important problem in geochemistry is the understanding of how changes occurring on a surface during dissolution affect the variability of measured dissolution rates. In this study a new approach to study the effect of surface dynamics on dissolution rates is tested by coupling experimental data with a numerical model that simulates the retreat of surface profiles during dissolution. We present specific results from the simulation of dissolution of fluorite surfaces. The equations that determine the retreat of a surface are based on experimentally obtained equations that relate the retreat rate of a surface to a single variable, the crystallographic orientation of the surface. Our results show that depending on the starting orientation, different types of topography are developed, similar to those observed experimentally. During the initial dissolution phase, changes of topography are rapid and associated with fast dissolution rates. The progressively slower dissolution rates are coupled with the development of surface segments with orientations that dissolve at a slower rate. Consequently, the overall retreat rate of a profile decreases during the simulation, and tends to a near-constant value. The results show a close relationship between dissolution rates, surface orientation and surface dynamics, which suggests that the dissolution rate of a specific mineral phase is not constant but varies with dissolution time and surface structure. This variability needs to be considered in the evaluation of experimentally derived dissolution rates, future dissolution experiments, and predictive kinetic models of dissolution.

  14. Simulation of a Lunar Surface Base Power Distribution Network for the Constellation Lunar Surface Systems

    Science.gov (United States)

    Mintz, Toby; Maslowski, Edward A.; Colozza, Anthony; McFarland, Willard; Prokopius, Kevin P.; George, Patrick J.; Hussey, Sam W.

    2010-01-01

    The Lunar Surface Power Distribution Network Study team worked to define, breadboard, build and test an electrical power distribution system consistent with NASA's goal of providing electrical power to sustain life and power equipment used to explore the lunar surface. A testbed was set up to simulate the connection of different power sources and loads together to form a mini-grid and gain an understanding of how the power systems would interact. Within the power distribution scheme, each power source contributes to the grid in an independent manner without communication among the power sources and without a master-slave scenario. The grid consisted of four separate power sources and the accompanying power conditioning equipment. Overall system design and testing was performed. The tests were performed to observe the output and interaction of the different power sources as some sources are added and others are removed from the grid connection. The loads on the system were also varied from no load to maximum load to observe the power source interactions.

  15. Wintertime land surface characteristics in climatic simulations over ...

    Indian Academy of Sciences (India)

    eastward moving low-pressure synoptic weather systems, called Western Disturbances (WDs). (Pisharoty and Desai .... Land surface processes are controlled by surface roughness and albedo. Different land surfaces will have different roughness length and albedo. Table 1 illustrates vegetation types and their correspond-.

  16. Effect of Simulant Type on the Absorptance and Emittance of Dusted Thermal Control Surfaces in a Simulated Lunar Environment

    Science.gov (United States)

    Gaier, James R.

    2010-01-01

    During the Apollo program the effects of lunar dust on thermal control surfaces was found to be more significant than anticipated, with several systems overheating due to deposition of dust on them. In an effort to reduce risk to future missions, a series of tests has been initiated to characterize the effects of dust on these surfaces, and then to develop technologies to mitigate that risk. Given the variations in albedo across the lunar surface, one variable that may be important is the darkness of the lunar dust, and this study was undertaken to address that concern. Three thermal control surfaces, AZ-93 white paint and AgFEP and AlFEP second surface mirrors were dusted with three different lunar dust simulants in a simulated lunar environment, and their integrated solar absorptance ( ) and thermal emittance ( ) values determined experimentally. The three simulants included JSC-1AF, a darker mare simulant, NU-LHT-1D, a light highlands simulant, and 1:1 mixture of the two. The response of AZ-93 was found to be slightly more pronounced than that of AgFEP. The increased with fractional dust coverage in both types of samples by a factor of 1.7 to 3.3, depending on the type of thermal control surface and the type of dust. The of the AZ-93 decreased by about 10 percent when fully covered by dust, while that of AgFEP increased by about 10 percent. It was found that / varied by more than a factor of two depending on the thermal control surface and the darkness of the dust. Given that the darkest simulant used in this study may be lighter than the darkest dust that could be encountered on the lunar surface, it becomes apparent that the performance degradation of thermal control surfaces due to dust on the Moon will be strongly dependent on the and of the dust in the specific locality

  17. Virtual simulation of maneuvering captive tests for a surface vessel

    Directory of Open Access Journals (Sweden)

    Ahmad Hajivand

    2015-09-01

    Full Text Available Hydrodynamic derivatives or coefficients are required to predict the maneuvering characteristics of a marine vehicle. These derivatives are obtained numerically for a DTMB 5512 model ship by virtual simulating of captive model tests in a CFD environment. The computed coefficients are applied to predict the turning circle and zigzag maneuvers of the model ship. The comparison of the simulated results with the available experimental data shows a very good agreement among them. The simulations show that the CFD is precise and affordable tool at the preliminary design stage to obtain maneuverability performance of a marine vehicles.

  18. Simulations for Surface Evolvement and Footing Effect in ICP DRIE Fabrications

    International Nuclear Information System (INIS)

    Zhang Jian; Huang Qingan; Li Weihua

    2006-01-01

    Simulations of surface evolvement are performed using an ICP DRIE model, in which a new method is adopted for the material identification. The simulation and experimental results are shown in this paper, which indicate that the veracity provided by this modified model is satisfied. The high-efficiency of this model over other former ones are due to the ability of identification of different material by uniform algorithm, and accordingly, it has much shorter executing time. Further more, an approximate model is presented to simulate the footing effect in DRIE fabrications, with the simulation results of the surface affected by footing effect in accordance to the experiments

  19. Wintertime land surface characteristics in climatic simulations over ...

    Indian Academy of Sciences (India)

    culture and tourism. To assess such interplay, we conducted and analyzed two sets of model runs: a control run (CONT), in which the fine scale BATS scheme is not used and therefore the land sur- face has the same resolution as the ..... Higher precipitation events are well simulated by both the experiments in two.

  20. Characterization of photosynthetic gas exchange in leaves under simulated adaxial and abaxial surfaces alternant irradiation.

    Science.gov (United States)

    Zhang, Zi-Shan; Li, Yu-Ting; Gao, Hui-Yuan; Yang, Cheng; Meng, Qing-Wei

    2016-07-05

    Previous investigations on photosynthesis have been performed on leaves irradiated from the adaxial surface. However, leaves usually sway because of wind. This action results in the alternating exposure of both the adaxial and abaxial surfaces to bright sunlight. To simulate adaxial and abaxial surfaces alternant irradiation (ad-ab-alt irradiation), the adaxial or abaxial surface of leaves were exposed to light regimes that fluctuated between 100 and 1,000 μmol m(-2) s(-1). Compared with constant adaxial irradiation, simulated ad-ab-alt irradiation suppressed net photosynthetic rate (Pn) and transpiration (E) but not water use efficiency. These suppressions were aggravated by an increase in alternant frequency of the light intensity. When leaves were transferred from constant light to simulated ad-ab-alt irradiation, the maximum Pn and E during the high light period decreased, but the rate of photosynthetic induction during this period remained constant. The sensitivity of photosynthetic gas exchange to simulated ad-ab-alt irradiation was lower on abaxial surface than adaxial surface. Under simulated ad-ab-alt irradiation, higher Pn and E were measured on abaxial surface compared with adaxial surface. Therefore, bifacial leaves can fix more carbon than leaves with two "sun-leaf-like" surfaces under ad-ab-alt irradiation. Photosynthetic research should be conducted under dynamic conditions that better mimic nature.

  1. Long-term Surface Temperature (LoST) Database as a Complement for GCM Preindustrial Simulations

    Science.gov (United States)

    Cuesta-Valero, F. J.; García-García, A.; Beltrami, H.; Zorita, E.

    2017-12-01

    Control climate simulations aim to provide a stationary state to General Circulation Models (GCMs) under constant preindustrial conditions (piControl simulations). This stationary state is then used as initial conditions in GCM simulations to provide a stable and realistic climatology, reducing the potential bias in such simulations. However, it is difficult to provide a reference to assess the climatology of piControl simulations due to the lack of long-term preindustrial observations. We explore the use of long-term ground surface temperature estimates from borehole temperature profiles as an additional reference that may be useful for the initialization procedure of GCM simulations. We compare five last millennium simulations and five preindustrial control simulations from the third phase of the Palaeoclimate Modelling Intercomparison Project (PMIP3) and the fifth phase of the Coupled Model Intercomparison Project (CMIP5) archives against estimates of long-term preindustrial ground surface temperatures from 514 borehole temperature profiles over North America. These long-term surface temperatures are retrieved from the quasi-equilibrium state of the subsurface thermal regime in each temperature profile, which is estimated from the deepest section of the profile. That is, the equilibrium state is recovered from the least affected part of the temperature profile by the recent changes in the surface energy balance. The subsurface temperatures at the bottom part of each profile depend linearly on depth, and the extrapolation of this linear behavior to the surface is interpreted as the long-term surface temperature (T0 temperature) at each borehole site. Our results suggest that the ground surface temperature estimates from borehole data could be employed as a reference within piControl simulations to enhance the quality of the initial conditions in GCM climate simulations.

  2. High intensity surface plasma waves, theory and PIC simulations

    Science.gov (United States)

    Raynaud, M.; Héron, A.; Adam, J.-C.

    2018-01-01

    With the development of intense (>1019 W cm‑2) short pulses (≤25 fs) laser with very high contrast, surface plasma wave (SPW) can be explored in the relativistic regime. As the SPW propagates with a phase velocity close to the speed of light it may results in a strong acceleration of electron bunches along the surface permitting them to reach relativistic energies. This may be important e.g. for applications in the field of plasma-based accelerators. We investigate in this work the excitation of SPWs on grating preformed over-dense plasmas for laser intensities ranging from 1019 up to 1021 W cm‑2. We discuss the nature of the interaction with respect to the solid case in which surface plasmon can be resonantly excited with weak laser intensity. In particular, we show the importance of the pulse duration and focalization of the laser beam on the amplitude of the SPW.

  3. Airborne Lidar Simulator for the Lidar Surface Topography (LIST) Mission

    Science.gov (United States)

    Yu, Anthony W.; Krainak, Michael A.; Abshire, James B.; Cavanaugh, John; Valett, Susan; Ramos-Izquierdo, Luis

    2010-01-01

    In 2007, the National Research Council (NRC) completed its first decadal survey for Earth science at the request of NASA, NOAA, and USGS. The Lidar Surface Topography (LIST) mission is one of fifteen missions recommended by NRC, whose primary objectives are to map global topography and vegetation structure at 5 m spatial resolution, and to acquire global surface height mapping within a few years. NASA Goddard conducted an initial mission concept study for the LIST mission in 2007, and developed the initial measurement requirements for the mission.

  4. Molecular dynamics simulations study of nano bubble attachment at hydrophobic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Jiaqi; Dang, Liem X.; Miller, Jan D.

    2018-01-01

    Bubble attachment phenomena are examined using Molecular Dynamics Simulations (MDS) for the first time. The simulation involves a nitrogen nano bubble containing 906 nitrogen molecules in a water phase with 74,000 water molecules at molybdenite surfaces. During a simulation period of 1 ns, film rupture and displacement occurs. The attached nanobubble at the hydrophobic molybdenite face surface results in a contact angle of about 90º. This spontaneous attachment is due to a “water exclusion zone” at the molybdenite face surface and can be explained by a van der Waals (vdW) attractive force, as discussed in the literature. In contrast, the film is stable at the hydrophilic quartz (001) surface and the bubble does not attach. Contact angles determined from MD simulations are reported, and these results agree well with experimental and MDS sessile drop results. In this way, film stability and bubble attachment are described with respect to interfacial water structure for surfaces of different polarity. Interfacial water molecules at the hydrophobic molybdenite face surface have relatively weak interactions with the surface when compared to the hydrophilic quartz (001) surface, as revealed by the presence of a 3 Å “water exclusion zone” at the molybdenite/water interface. The molybdenite armchair-edge and zigzag-edge surfaces show a comparably slow process for film rupture and displacement when compared to the molybdenite face surface, which is consistent with their relatively weak hydrophobic character.

  5. Simulating Supercapacitors: Can We Model Electrodes As Constant Charge Surfaces?

    Science.gov (United States)

    Merlet, Céline; Péan, Clarisse; Rotenberg, Benjamin; Madden, Paul A; Simon, Patrice; Salanne, Mathieu

    2013-01-17

    Supercapacitors based on an ionic liquid electrolyte and graphite or nanoporous carbon electrodes are simulated using molecular dynamics. We compare a simplified electrode model in which a constant, uniform charge is assigned to each carbon atom with a realistic model in which a constant potential is applied between the electrodes (the carbon charges are allowed to fluctuate). We show that the simulations performed with the simplified model do not provide a correct description of the properties of the system. First, the structure of the adsorbed electrolyte is partly modified. Second, dramatic differences are observed for the dynamics of the system during transient regimes. In particular, upon application of a constant applied potential difference, the increase in the temperature, due to the Joule effect, associated with the creation of an electric current across the cell follows Ohm's law, while unphysically high temperatures are rapidly observed when constant charges are assigned to each carbon atom.

  6. Simulation of triple junction motion with arbitrary surface tensions

    Czech Academy of Sciences Publication Activity Database

    Shofianah, N.; Muhammad, R. Z.; Švadlenka, Karel

    2015-01-01

    Roč. 45, č. 3 (2015), s. 235-244 ISSN 1992-9978 Institutional support: RVO:67985840 Keywords : triple junction motion * mean curvature flow * surface tension Subject RIV: BA - General Mathematics http://www.iaeng.org/IJAM/issues_v45/issue_3/IJAM_45_3_09.pdf

  7. Numerical simulation of floating bodies in extreme free surface waves

    Directory of Open Access Journals (Sweden)

    Z. Z. Hu

    2011-02-01

    Full Text Available In this paper, we use the in-house Computational Fluid Dynamics (CFD flow code AMAZON-SC as a numerical wave tank (NWT to study wave loading on a wave energy converter (WEC device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water. The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.

  8. Radiation exchange between persons and surfaces for building energy simulations

    DEFF Research Database (Denmark)

    Vorre, Mette Havgaard; Jensen, Rasmus Lund; Dreau, Jerome Le

    2015-01-01

    Thermal radiation within buildings is a significant component of thermal comfort. Typically the methods applied for calculating view factors between a person and its building surfaces requires great computational time. This research developed a view factor calculation method suitable for building...

  9. Wintertime land surface characteristics in climatic simulations over ...

    Indian Academy of Sciences (India)

    Most of the surface characteristics show that major interplay between topography and western disturbances (WDs) takes place along the foothills rather than over the higher peaks of the western Himalayas. ... Present address: Hydrospheric Atmospheric Research Center (HyARC), Nagoya University, Nagoya, Japan.

  10. Modeling and simulation of the deformation process of PTFE flexiblestamps for nanoimprint lithography on curved surfaces

    DEFF Research Database (Denmark)

    Sonne, Mads Rostgaard; Smistrup, K.; Hannibal, Morten

    2015-01-01

    In the presented work, simulations of the deformation process of flexible stamps used for nanoimprint lithographron curved surfaces are presented. The material used for the flexible stamps was polytetrafluoroethylene (PTFE) whose material behavior was found to be viscoelastic-viscoplastic. This b......In the presented work, simulations of the deformation process of flexible stamps used for nanoimprint lithographron curved surfaces are presented. The material used for the flexible stamps was polytetrafluoroethylene (PTFE) whose material behavior was found to be viscoelastic...

  11. Design and simulation of the surface shape control system for membrane mirror

    Science.gov (United States)

    Zhang, Gengsheng; Tang, Minxue

    2009-11-01

    The surface shape control is one of the key technologies for the manufacture of membrane mirror. This paper presents a design of membrane mirror's surface shape control system on the basis of fuzzy logic control. The system contains such function modules as surface shape design, surface shape control, surface shape analysis, and etc. The system functions are realized by using hybrid programming technology of Visual C# and MATLAB. The finite element method is adopted to simulate the surface shape control of membrane mirror. The finite element analysis model is established through ANSYS Parametric Design Language (APDL). ANSYS software kernel is called by the system in background running mode when doing the simulation. The controller is designed by means of controlling the sag of the mirror's central crosssection. The surface shape of the membrane mirror and its optical aberration are obtained by applying Zernike polynomial fitting. The analysis of surface shape control and the simulation of disturbance response are performed for a membrane mirror with 300mm aperture and F/2.7. The result of the simulation shows that by using the designed control system, the RMS wavefront error of the mirror can reach to 142λ (λ=632.8nm), which is consistent to the surface accuracy of the membrane mirror obtained by the large deformation theory of membrane under the same condition.

  12. Molecular dynamics simulations on surface properties of silicon dioxide melts

    CERN Document Server

    Röder, A

    2000-01-01

    In the present thesis the surface properties of a silicon dioxide melt were studied. As first systems drops (i.e. sytems without periodic boundary conditions) of N=432, 1536, as well as 4608 atoms were considered. The second analyzed geometry corresponds to that of a thin film, i. e. periodic boundary conditions in x- and y-direction were present, while in z-direction one had a free surface. In this case a system of N=1152 atoms was considered. As model potential the two-body potential proposed by Beest, Kramer, and van Santen was applied. For both geometries five temperatures were considered, which lied in the range of 3000 K

  13. How do uncertainties in NCEP R2 and CFSR surface fluxes impact tropical ocean simulations?

    Science.gov (United States)

    Wen, Caihong; Xue, Yan; Kumar, Arun; Behringer, David; Yu, Lisan

    2017-11-01

    NCEP/DOE reanalysis (R2) and Climate Forecast System Reanalysis (CFSR) surface fluxes are widely used by the research community to understand surface flux climate variability, and to drive ocean models as surface forcings. However, large discrepancies exist between these two products, including (1) stronger trade winds in CFSR than in R2 over the tropical Pacific prior 2000; (2) excessive net surface heat fluxes into ocean in CFSR than in R2 with an increase in difference after 2000. The goals of this study are to examine the sensitivity of ocean simulations to discrepancies between CFSR and R2 surface fluxes, and to assess the fidelity of the two products. A set of experiments, where an ocean model was driven by a combination of surface flux components from R2 and CFSR, were carried out. The model simulations were contrasted to identify sensitivity to different component of the surface fluxes in R2 and CFSR. The accuracy of the model simulations was validated against the tropical moorings data, altimetry SSH and SST reanalysis products. Sensitivity of ocean simulations showed that temperature bias difference in the upper 100 m is mostly sensitive to the differences in surface heat fluxes, while depth of 20 °C (D20) bias difference is mainly determined by the discrepancies in momentum fluxes. D20 simulations with CFSR winds agree with observation well in the western equatorial Pacific prior 2000, but have large negative bias similar to those with R2 winds after 2000, partly because easterly winds over the central Pacific were underestimated in both CFSR and R2. On the other hand, the observed temperature variability is well reproduced in the tropical Pacific by simulations with both R2 and CFSR fluxes. Relative to the R2 fluxes, the CFSR fluxes improve simulation of interannual variability in all three tropical oceans to a varying degree. The improvement in the tropical Atlantic is most significant and is largely attributed to differences in surface winds.

  14. Modelling, simulating and optimizing boiler heating surfaces and evaporator circuits

    DEFF Research Database (Denmark)

    Sørensen, K.; Condra, T.; Houbak, Niels

    2003-01-01

    developed as a Differential-Algebraic-Equation system (DAE) and MATLAB has been applied for the integration of the models. In general MATLAB has proved to be very stable for these DAE systems. Experimental verification has been carried out at a full scale plant equipped with instrumentation to verify heat....... The dynamic model has been developed for the purpose of determining boiler material temperatures and heat transfer from the flue gas side to the water-/steam side in order to simulate the circulation in the evaporator circuit and hereby the water level fluctuations in the drum. The dynamic model has been...

  15. Visual simulation: a planning and design tool for surface mining

    International Nuclear Information System (INIS)

    Scott, R.D.

    1984-01-01

    Due to the controversial nature of the high level nuclear waste repository project proposed near Canyonlands National Park, public reaction has been considerable, particularly on visual impacts. Canyonlands is a primitive park; its appeal is solitude and pristine landscape. The Bureau of Land Management (BLM), the lead review agency, strongly recommended that the DOE employ visual simulation for displaying effects of visual change for the exploratory shaft, railroad access routes, and repository. As a result this study was conducted to address the concern for scenic values and the potential visual change within and surrounding the lands of Canyonlands National Park

  16. Mixture and method for simulating soiling and weathering of surfaces

    Science.gov (United States)

    Sleiman, Mohamad; Kirchstetter, Thomas; Destaillats, Hugo; Levinson, Ronnen; Berdahl, Paul; Akbari, Hashem

    2018-01-02

    This disclosure provides systems, methods, and apparatus related to simulated soiling and weathering of materials. In one aspect, a soiling mixture may include an aqueous suspension of various amounts of salt, soot, dust, and humic acid. In another aspect, a method may include weathering a sample of material in a first exposure of the sample to ultraviolet light, water vapor, and elevated temperatures, depositing a soiling mixture on the sample, and weathering the sample in a second exposure of the sample to ultraviolet light, water vapor, and elevated temperatures.

  17. Modelling total solar irradiance since 1878 from simulated magnetograms

    Science.gov (United States)

    Dasi-Espuig, M.; Jiang, J.; Krivova, N. A.; Solanki, S. K.

    2014-10-01

    Aims: We present a new model of total solar irradiance (TSI) based on magnetograms simulated with a surface flux transport model (SFTM) and the Spectral And Total Irradiance REconstructions (SATIRE) model. Our model provides daily maps of the distribution of the photospheric field and the TSI starting from 1878. Methods: The modelling is done in two main steps. We first calculate the magnetic flux on the solar surface emerging in active and ephemeral regions. The evolution of the magnetic flux in active regions (sunspots and faculae) is computed using a surface flux transport model fed with the observed record of sunspot group areas and positions. The magnetic flux in ephemeral regions is treated separately using the concept of overlapping cycles. We then use a version of the SATIRE model to compute the TSI. The area coverage and the distribution of different magnetic features as a function of time, which are required by SATIRE, are extracted from the simulated magnetograms and the modelled ephemeral region magnetic flux. Previously computed intensity spectra of the various types of magnetic features are employed. Results: Our model reproduces the PMOD composite of TSI measurements starting from 1978 at daily and rotational timescales more accurately than the previous version of the SATIRE model computing TSI over this period of time. The simulated magnetograms provide a more realistic representation of the evolution of the magnetic field on the photosphere and also allow us to make use of information on the spatial distribution of the magnetic fields before the times when observed magnetograms were available. We find that the secular increase in TSI since 1878 is fairly stable to modifications of the treatment of the ephemeral region magnetic flux.

  18. Simulation of Surface Erosion on a Logging Road in the Jackson Demonstration State Forest

    Science.gov (United States)

    Teresa Ish; David Tomberlin

    2007-01-01

    In constructing management models for the control of sediment delivery to streams, we have used a simulation model of road surface erosion known as the Watershed Erosion Prediction Project (WEPP) model, developed by the USDA Forest Service. This model predicts discharge, erosion, and sediment delivery at the road segment level, based on a stochastic climate simulator...

  19. Initialization of high resolution surface wind simulations using NWS gridded data

    Science.gov (United States)

    J. Forthofer; K. Shannon; Bret Butler

    2010-01-01

    WindNinja is a standalone computer model designed to provide the user with simulations of surface wind flow. It is deterministic and steady state. It is currently being modified to allow the user to initialize the flow calculation using National Digital Forecast Database. It essentially allows the user to downscale the coarse scale simulations from meso-scale models to...

  20. Numerical investigation of turbomolecular pumps using the direct simulation Monte Carlo method with moving surfaces

    NARCIS (Netherlands)

    Versluis, R.; Dorsman, R.; Thielen, L.; Roos, M.E.

    2009-01-01

    A new approach for performing numerical direct simulation Monte Carlo (DSMC) simulations on turbomolecular pumps in the free molecular and transitional flow regimes is described. The chosen approach is to use surfaces that move relative to the grid to model the effect of rotors and stators on a gas

  1. Simulation and Measurement of Angle Resolved Reflectance from Black Si Surfaces

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Wu, Kaiyu; Schmidt, Michael Stenbæk

    2015-01-01

    In this work angle-resolved reflectance from nanostructured Si surfaces realized by maskless RIE texturing has been simulated and measured. The simulation and experimental measurement data show the same trend. Experimentally a total reflectance below 1% for incident angles below 30o and specular...

  2. Simultaneous calibration of surface flow and baseflow simulations: A revisit of the SWAT model calibration framework

    Science.gov (United States)

    Accurate analysis of water flow pathways from rainfall to streams is critical for simulating water use, climate change impact, and contaminant transport. In this study, we developed a new scheme to simultaneously calibrate surface flow (SF) and baseflow (BF) simulations of Soil and Water Assessment ...

  3. Surface Wave Simulation and Processing with MatSeis

    Energy Technology Data Exchange (ETDEWEB)

    THOMPSON,BEVERLY D.; CHAEL,ERIC P.; YOUNG,CHRISTOPHER J.; WALTER,WILLIAM R.; PASYANOS,MICHAEL E.

    2000-08-07

    In order to exploit the information on surface wave propagation that is stored in large seismic event datasets, Sandia and Lawrence Livermore National Laboratories have developed a MatSeis interface for performing phase-matched filtering of Rayleigh arrivals. MatSeis is a Matlab-based seismic processing toolkit which provides graphical tools for analyzing seismic data from a network of stations. Tools are available for spectral and polarization measurements, as well as beam forming and f-k analysis with array data, to name just a few. Additionally, one has full access to the Matlab environment and any functions available there. Previously the authors reported the development of new MatSeis tools for calculating regional discrimination measurements. The first of these performs Lg coda analysis as developed by Mayeda and coworkers at Lawrence Livermore National Laboratory. A second tool measures regional phase amplitude ratios for an event and compares the results to ratios from known earthquakes and explosions. Release 1.5 of MatSeis includes the new interface for the analysis of surface wave arrivals. This effort involves the use of regionalized dispersion models from a repository of surface wave data and the construction of phase-matched filters to improve surface wave identification, detection, and magnitude calculation. The tool works as follows. First, a ray is traced from source to receiver through a user-defined grid containing different group velocity versus period values to determine the composite group velocity curve for the path. This curve is shown along with the upper and lower group velocity bounds for reference. Next, the curve is used to create a phase-matched filter, apply the filter, and show the resultant waveform. The application of the filter allows obscured Rayleigh arrivals to be more easily identified. Finally, after screening information outside the range of the phase-matched filter, an inverse version of the filter is applied to obtain a

  4. Improving precipitation simulation from updated surface characteristics in South America

    Science.gov (United States)

    Pereira, Gabriel; Silva, Maria Elisa Siqueira; Moraes, Elisabete Caria; Chiquetto, Júlio Barboza; da Silva Cardozo, Francielle

    2017-07-01

    Land use and land cover maps and their physical-chemical and biological properties are important variables in the numerical modeling of Earth systems. In this context, the main objective of this study is to analyze the improvements resulting from the land use and land cover map update in numerical simulations performed using the Regional Climate Model system version 4 (RegCM4), as well as the seasonal variations of physical parameters used by the Biosphere Atmosphere Transfer Scheme (BATS). In general, the update of the South America 2007 land use and land cover map, used by the BATS, improved the simulation of precipitation by 10 %, increasing the mean temporal correlation coefficient, compared to observed data, from 0.84 to 0.92 (significant at p Amazon deforestation arc; (2) around the Brazil-Bolivia border (in the Brazilian Pantanal wetlands); (3) in the Northeast region of Brazil; (4) in northwestern Paraguay; and (5) in the River Plate Basin, in Argentina. Moreover, the main precipitation differences between sensitivity and control experiments occurred during the rainy months in central-north South America (October to March). These were associated with a displacement in the South Atlantic convergence zone (SACZ) positioning, presenting a spatial pattern of alternated areas with higher and lower precipitation rates. These important differences occur due to the replacement of tropical rainforest for pasture and agriculture and the replacement of agricultural areas for pasture, scrubland, and deciduous forest.

  5. Characterization, modeling and simulation of fused deposition modeling fabricated part surfaces

    Science.gov (United States)

    Taufik, Mohammad; Jain, Prashant K.

    2017-12-01

    Surface roughness is generally used for characterization, modeling and simulation of fused deposition modeling (FDM) fabricated part surfaces. But the average surface roughness is not able to provide the insight of surface characteristics with sharp peaks and deep valleys. It deals in the average sense for all types of surfaces, including FDM fabricated surfaces with distinct surface profile features. The present research work shows that kurtosis and skewness can be used for characterization, modeling and simulation of FDM surfaces because these roughness parameters have the ability to characterize a surface with sharp peaks and deep valleys. It can be critical in certain application areas in tribology and biomedicine, where the surface profile plays an important role. Thus, in this study along with surface roughness, skewness and kurtosis are considered to show a novel strategy to provide new transferable knowledge about FDM fabricated part surfaces. The results suggest that the surface roughness, skewness and kurtosis are significantly different at 0° and in the range (0°, 30°], [30°, 90°] of build orientation.

  6. Coupling of surface relaxation and polarization in PbTiO{sub 3} from atomistic simulation

    Energy Technology Data Exchange (ETDEWEB)

    Behera, R K; Sinnott, S B; Phillpot, S R [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Hinojosa, B B; Asthagiri, A [Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 (United States)], E-mail: sphil@mse.ufl.edu

    2008-10-01

    Molecular dynamics simulations are used to characterize ferroelectricity on the (001) surfaces of PbTiO{sub 3} (PT), one of the most widely studied ferroelectric materials. Two different empirical interatomic shell model potentials are used. Both PbO and TiO{sub 2} surface terminations in PT under open circuit electrical boundary conditions are characterized. The results are found to be in good agreement with the results of density functional theory calculations. The atomic relaxations, interlayer spacings and surface rumplings of each of the four possible surface terminations are analyzed. The deviation of the polarization from the bulk value is observed to be larger when the polarization points out of the surface than when it points into the surface. Analysis of the surface energies for free-standing films shows that polarization parallel to the surface is energetically more favorable than the polarization normal to the surfaces.

  7. Airborne Instrument Simulator for the Lidar Surface Topography (LIST) Mission

    Science.gov (United States)

    Yu, Anthony W.; Krainak, Michael A.; Harding, David J.; Abshire, James B.; Sun, Xiaoli; Cavanaugh, John; Valett, Susan; Ramos-Izquierdo, Luis

    2010-01-01

    In 2007, the National Research Council (NRC) completed its first decadal survey for Earth science at the request of NASA, NOAA, and USGS. The Lidar Surface Topography (LIST) mission is one of fifteen missions recommended by NRC, whose primary objectives are to map global topography and vegetation structure at 5 m spatial resolution, and to acquire global coverage with a few years. NASA Goddard conducted an initial mission concept study for the LIST mission 2007, and developed the initial measurement requirements for the mission.

  8. Simulation of an oil film at the sea surface and its radiometric properties in the SWIR

    Science.gov (United States)

    Schwenger, Frédéric; Van Eijk, Alexander M. J.

    2017-10-01

    The knowledge of the optical contrast of an oil layer on the sea under various surface roughness conditions is of great interest for oil slick monitoring techniques. This paper presents a 3D simulation of a dynamic sea surface contaminated by a floating oil film. The simulation considers the damping influence of oil on the ocean waves and its physical properties. It calculates the radiance contrast of the sea surface polluted by the oil film in relation to a clean sea surface for the SWIR spectral band. Our computer simulation combines the 3D simulation of a maritime scene (open clear sea/clear sky) with an oil film at the sea surface. The basic geometry of a clean sea surface is modeled by a composition of smooth wind driven gravity waves. Oil on the sea surface attenuates the capillary and short gravity waves modulating the wave power density spectrum of these waves. The radiance of the maritime scene is calculated in the SWIR spectral band with the emitted sea surface radiance and the specularly reflected sky radiance as components. Wave hiding and shadowing, especially occurring at low viewing angles, are considered. The specular reflection of the sky radiance at the clean sea surface is modeled by an analytical statistical bidirectional reflectance distribution function (BRDF) of the sea surface. For oil at the sea surface, a specific BRDF is used influenced by the reduced surface roughness, i.e., the modulated wave density spectrum. The radiance contrast of an oil film in relation to the clean sea surface is calculated for different viewing angles, wind speeds, and oil types characterized by their specific physical properties.

  9. Boundary Slip and Surface Interaction: A Lattice Boltzmann Simulation

    International Nuclear Information System (INIS)

    Yan-Yan, Chen; Hua-Bing, Li; Hou-Hui, Yi

    2008-01-01

    The factors affecting slip length in Couette geometry flows are analysed by means of a two-phase mesoscopic lattice Boltzmann model including non-ideal fluid-fluid and fluid-wall interactions. The main factors influencing the boundary slip are the strength of interactions between fluid-fluid and fluid-wall particles. Other factors, such as fluid viscosity, bulk pressure may also change the slip length. We find that boundary slip only occurs under a certain density (bulk pressure). If the density is large enough, the slip length will tend to zero. In our simulations, a low density layer near the wall does not need to be postulated a priori but emerges naturally from the underlying non-ideal mesoscopic dynamics. It is the low density layer that induces the boundary slip. The results may be helpful to understand recent experimental observations on the slippage of micro flows

  10. Simulating the Near-Surface Environments of Solar System Bodies in the Laboratory

    Science.gov (United States)

    Donaldson Hanna, K. L.; Bowles, N. E.; Greenhagen, B. T.

    2016-12-01

    Thermal infrared (TIR) emissivity measurements are sensitive to a planetary body's near-surface (upper hundreds of microns) environment, porosity and particle size, which make the interpretation of thermal infrared remote sensing observations of planetary surfaces challenging. Thus, well-constrained laboratory TIR measurements of analogue samples for a range of particle sizes, porosities and near-surface environments are needed. Near-surface environments and porosities for a range of solar system bodies can be simulated using facilities within University of Oxford's Planetary Spectroscopy Facility (PSF). The Simulated Lunar Environment Chamber (SLEC) within Oxford's PSF is a vacuum chamber capable of simulating near-surface conditions for a range of solar system bodies by varying atmospheric pressure and incident solar irradiation. By varying the near-surface environment, the thermal gradient in the upper hundreds of microns of the sample is varied, which can affect the position and contrast of diagnostic features in TIR spectra. The atmospheric pressure inside the chamber is varied between 1000, 5 and < 10-4 mbar to simulate Earth, Mars and airless bodies (e.g. the Moon, Mars' moons and asteroids) conditions. The solar-like irradiation is varied by adjusting the power of the halogen lamp until the brightness temperature of the sample is similar to the brightness temperature of the simulated planetary body. Varying the sample packing in the sample cup simulates a range of near-surface porosities. Here we present laboratory emissivity spectra of a suite of well-characterized rock, soil and mineral samples (< 25 mm in particle size) measured under a range of simulated planetary conditions including Earth, Mars, Moon and asteroids. These well-controlled laboratory measurements enable the interpretation of remote sensing observations, which help in determining a planet's surface composition as well as the consolidated nature of its regolith.

  11. Simulating Near-Surface Environments of Solar System Bodies in the Laboratory

    Science.gov (United States)

    Donaldson Hanna, Kerri; Bowles, Neil

    2017-04-01

    Thermal infrared (TIR) emissivity measurements are sensitive to a planetary body's near-surface (upper hundreds of microns) environment, porosity and particle size, which make the interpretation of thermal infrared remote sensing observations of planetary surfaces challenging. Thus, well-constrained laboratory TIR measurements of analogue samples for a range of particle sizes, porosities and near-surface environments are needed. Near-surface environments and porosities for a range of solar system bodies can be simulated using facilities within University of Oxford's Planetary Spectroscopy Facility (PSF). The Simulated Lunar Environment Chamber (SLEC) within Oxford's PSF is a vacuum chamber capable of simulating near-surface conditions for a range of solar system bodies by varying atmospheric pressure and incident solar irradiation. By varying the near-surface environment, the thermal gradient in the upper hundreds of microns of the sample is varied, which can affect the position and contrast of diagnostic features in TIR spectra. The atmospheric pressure inside the chamber is varied between 1000, 5 and < 10-4 mbar to simulate Earth, Mars and airless bodies (e.g. the Moon, Mars' moons and asteroids) conditions. The solar-like irradiation is varied by adjusting the power of the halogen lamp until the brightness temperature of the sample is similar to the brightness temperature of the simulated planetary body. Varying the sample packing in the sample cup simulates a range of near-surface porosities. Here we present laboratory emissivity spectra of a suite of well-characterized rock, soil and mineral samples (< 25 microns in particle size) measured under a range of simulated planetary conditions including Earth, Mars, Moon and asteroids. These well-controlled laboratory measurements enable the interpretation of remote sensing observations, which help in determining a planet's surface composition as well as the consolidated nature of its regolith.

  12. Molecular dynamics simulation of temperature effects on CF3+ etching of Si surface

    NARCIS (Netherlands)

    Ning, J. P.; Lu, X. D.; Zhao, C. L.; Qin, Y. M.; He, P. N.; Bogaerts, A.; Gou, F. J.

    2010-01-01

    Molecular dynamics method was employed to investigate the effects of the reaction layer formed near the surface region on CF3+ etching of Si at different temperatures. The simulation results show that the coverages of F and C are sensitive to the surface temperature. With increasing temperature, the

  13. External surface adsorption on silicalite-1 zeolite studied by molecular simulation

    NARCIS (Netherlands)

    Garcia-Perez, E.; Schnell, S.K.; Castillo, J.M.; Calero, S.; Kjelstrup, S.; Dubbeldam, D.; Vlugt, T.J.H.

    2011-01-01

    We have studied the adsorption of ethane, propane, and their mixtures on the external surface of silicalite-1 zeolite by molecular simulation using a classical force field. The ideal adsorbed solution theory (IAST) was successfully used to describe mixture adsorption, both on the external surface

  14. Reproducing the Photospheric Magnetic Field Evolution during the Rise of Cycle 24 with Flux Transport by Supergranules

    Science.gov (United States)

    Hathaway, David; Upton, Lisa

    2012-01-01

    We simulate the transport of magnetic flux in the Sun s photosphere by an evolving pattern of cellular horizontal flows (supergranules). Characteristics of the simulated flow pattern can match observed characteristics including the velocity power spectrum, cell lifetimes, and cell motions in longitude and latitude. Simulations using an average, and north-south symmetric, meridional motion of the cellular pattern produce polar magnetic fields that are too weak in the North and too strong in the South. Simulations using cellular patterns with meridional motions that evolve with the observed changes in strength and north-south asymmetry will be analyzed to see if they reproduce the polar field evolution observed during the rise of Cycle 24.

  15. Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations Part I: Surface fluxes

    Directory of Open Access Journals (Sweden)

    P. Josse

    1999-04-01

    Full Text Available A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer

  16. Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations Part I: Surface fluxes

    Directory of Open Access Journals (Sweden)

    H. Giordani

    Full Text Available A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer

  17. Molecular Dynamics Simulations of Water Nanodroplets on Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    and DNA microarrays technologies.4,5,6,7,8 Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water,2,9-16 at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle...... computations of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems.3,16,17,18 For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence...... of air. Hence, nanobubles have been observed and proposed as the origin of long range ``hydrophobic'' forces19-30 even for hydrophilic silica-water interfaces unusual phenomena related to nanobubbles have been observed.31-33 In this work we study the role of air on the wetting of amorphous silica...

  18. Molecular Dynamics Simulations of Water Droplets On Hydrophilic Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems. For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence of air. Hence......Wetting is essential and ubiquitous in a variety of natural and technological processes. Silicon dioxides-water systems are abundant in nature and play fundamental roles in a vast variety of novel science and engineering activities such as silicon based devices, nanoscale lab on a chip systems...... and DNA microarrays technologies.Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water, at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle computations...

  19. Molecular dynamics simulations of water on a hydrophilic silica surface at high air pressures

    DEFF Research Database (Denmark)

    Zambrano, H.A.; Walther, Jens Honore; Jaffe, R.L.

    2014-01-01

    of air in water at different pressures. Using the calibrated force field, we conduct MD simulations to study the interface between a hydrophilic silica substrate and water surrounded by air at different pressures. We find that the static water contact angle is independent of the air pressure imposed......Wepresent a force field forMolecular Dynamics (MD) simulations ofwater and air in contactwith an amorphous silica surface. We calibrate the interactions of each species present in the systemusing dedicated criteria such as the contact angle of a water droplet on a silica surface, and the solubility...... on the system. Our simulations reveal the presence of a nanometer thick layer of gas at the water–silica interface. We believe that this gas layer could promote nucleation and stabilization of surface nanobubbles at amorphous silica surfaces. © 2014 Elsevier B.V. All rights reserved....

  20. Chemical stability and surface stoichiometry of vanadium oxide phases studied by reactive molecular dynamics simulations

    Science.gov (United States)

    Jeon, Byoungseon; Ko, Changhyun; van Duin, Adri C. T.; Ramanathan, Shriram

    2012-02-01

    Compositional stability of various vanadium oxides and oxide growth on vanadium surfaces have been studied using reactive molecular dynamics simulation methods. Vanadium dioxide (VO2), sesquioxide (V2O3), pentoxide (V2O5), and hexavanadium tridecaoxide (V6O13) are studied in bulk crystalline and thin film structures, investigating charge distribution and pair distribution functions of particle interactions. The stability is estimated to be pentoxide, hexavanadium tridecaoxide, sesquioxide, and dioxide respectively in decreasing order in thin film structures. We then analyze oxide growth kinetics on vanadium (100) and (110) surfaces. The oxidation rate, stoichiometry, charge distribution, and the effect of surface orientation on kinetic phenomena are noted. In the early stages of surface oxidation of our simulation configurations, sesquioxide is found to be the dominant component. The modeling and simulation results are compared with experiments where available.

  1. Snow specific surface area simulation using the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS

    Directory of Open Access Journals (Sweden)

    A. Roy

    2013-06-01

    Full Text Available Snow grain size is a key parameter for modeling microwave snow emission properties and the surface energy balance because of its influence on the snow albedo, thermal conductivity and diffusivity. A model of the specific surface area (SSA of snow was implemented in the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS version 3.4. This offline multilayer model (CLASS-SSA simulates the decrease of SSA based on snow age, snow temperature and the temperature gradient under dry snow conditions, while it considers the liquid water content of the snowpack for wet snow metamorphism. We compare the model with ground-based measurements from several sites (alpine, arctic and subarctic with different types of snow. The model provides simulated SSA in good agreement with measurements with an overall point-to-point comparison RMSE of 8.0 m2 kg–1, and a root mean square error (RMSE of 5.1 m2 kg–1 for the snowpack average SSA. The model, however, is limited under wet conditions due to the single-layer nature of the CLASS model, leading to a single liquid water content value for the whole snowpack. The SSA simulations are of great interest for satellite passive microwave brightness temperature assimilations, snow mass balance retrievals and surface energy balance calculations with associated climate feedbacks.

  2. The Numerical Simulation Application for Fire-Tube Boiler Heating Surface Safety Evaluation

    Directory of Open Access Journals (Sweden)

    Khaustov Sergei A.

    2016-01-01

    Full Text Available The numerical simulation is applied for fire-tube boiler heating surface safety estimation. Thermal processes in an inflatable fire-tube furnace during its emergency operation were simulated using the finite volume method with Euler approximation and the implicit pressure based algorithm. Study results reproduce failures connected with increasing of impasse aerodynamic resistance. The method of these failures prediction is suggested. Simulation has shown that entering the amount of coolant into combustion volume results in burner fan incapability to overcome the impasse resistance of the furnace. The simulation results are visually confirmed during the inspection of emergency boilers.

  3. The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

    DEFF Research Database (Denmark)

    Jensen, Morten Østergaard; Mouritsen, Ole G.; Peters, Günther H.J.

    2004-01-01

    Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C36H74 or n-alcohol C35H71OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding...... at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time......-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together...

  4. Numerical simulation of viscous flow and hydrodynamic noise in surface ship

    Directory of Open Access Journals (Sweden)

    YU Han

    2017-12-01

    Full Text Available [Objectives] The problem of noise caused by an unsteady flow field around a surface ship is a difficulty facing the stealth design of ship hulls, in which the existence of the free surface makes it different from submarine hydrodynamic noise calculation. To solve this problem,[Methods] the Volume of Fluid(VOF method and SST k-ω turbulence model are combined to simulate the unsteady flow field of the hull, and the free surface is given an air acoustic impedance to simulate the absorption boundary. The pulsating pressure of the hull surface is used as the source of the noise, and the underwater radiation noise of the surface ship is calculated with the acoustic finite element method.[Results] The results show high agreement with the experimental results and previous simulation results. The noise sources are mainly concentrated at the bow of the hull.[Conclusions] The results show that this calculation method can accurately simulate the flow field and sound field of a surface ship, and it can provides valuable reference for the acoustic stealth design of surface ships.

  5. Polarimetric infrared imaging simulation of a synthetic sea surface with Mie scattering.

    Science.gov (United States)

    He, Si; Wang, Xia; Xia, Runqiu; Jin, Weiqi; Liang, Jian'an

    2018-03-01

    A novel method to simulate the polarimetric infrared imaging of a synthetic sea surface with atmospheric Mie scattering effects is presented. The infrared emission, multiple reflections, and infrared polarization of the sea surface and the Mie scattering of aerosols are all included for the first time. At first, a new approach to retrieving the radiative characteristics of a wind-roughened sea surface is introduced. A two-scale method of sea surface realization and the inverse ray tracing of light transfer calculation are combined and executed simultaneously, decreasing the consumption of time and memory dramatically. Then the scattering process that the infrared light emits from the sea surface and propagates in the aerosol particles is simulated with a polarized light Monte Carlo model. Transformations of the polarization state of the light are calculated with the Mie theory. Finally, the polarimetric infrared images of the sea surface of different environmental conditions and detection parameters are generated based on the scattered light detected by the infrared imaging polarimeter. The results of simulation examples show that our polarimetric infrared imaging simulation can be applied to predict the infrared polarization characteristics of the sea surface, model the oceanic scene, and guide the detection in the oceanic environment.

  6. Numerical simulation of directivity for angle probe and surface defect

    International Nuclear Information System (INIS)

    Nam, Young Hyun

    1995-01-01

    An ultrasonic testing uses the directivity of the ultrasonic wave which propagates in one direction. The directivity is expressed as the relationship between the propagate direction and i ts sound pressure. This paper studied the directivity of shear waves emitted from angle probes and scattered from surface defects by using visualization method. These experimental results were compared with the theory which was based on the continuous wave. The applicability of continuous wave theory was discussed in terms of the parameter d/λ where d is transducer or defect size and λ is the wavelength. In the case of angle probes, the experimental results show good agreement with theoretical directivity on the principal lobe. When defect size was smaller than the wavelengths, clear directivity in the reflected wave was observed. In the case of the same ratio of defect size to wavelength, the directivity of reflected waves from the defect show almost the same directivity in spite of frequency differences. When the d/λ is greater than 1.5, measured directivities almost agreed with the theoretical one.

  7. Density-matrix simulation of small surface codes under current and projected experimental noise

    Science.gov (United States)

    O'Brien, T. E.; Tarasinski, B.; DiCarlo, L.

    2017-09-01

    We present a density-matrix simulation of the quantum memory and computing performance of the distance-3 logical qubit Surface-17, following a recently proposed quantum circuit and using experimental error parameters for transmon qubits in a planar circuit QED architecture. We use this simulation to optimize components of the QEC scheme (e.g., trading off stabilizer measurement infidelity for reduced cycle time) and to investigate the benefits of feedback harnessing the fundamental asymmetry of relaxation-dominated error in the constituent transmons. A lower-order approximate calculation extends these predictions to the distance-5 Surface-49. These results clearly indicate error rates below the fault-tolerance threshold of the surface code, and the potential for Surface-17 to perform beyond the break-even point of quantum memory. However, Surface-49 is required to surpass the break-even point of computation at state-of-the-art qubit relaxation times and readout speeds.

  8. Adsorption mechanism of ribosomal protein L2 onto a silica surface: a molecular dynamics simulation study.

    Science.gov (United States)

    Tosaka, Ryo; Yamamoto, Hideaki; Ohdomari, Iwao; Watanabe, Takanobu

    2010-06-15

    A large-scale molecular dynamics simulation was carried out in order to investigate the adsorption mechanism of ribosomal protein L2 (RPL2) onto a silica surface at various pH values. RPL2 is a constituent protein of the 50S large ribosomal subunit, and a recent experimental report showed that it adsorbs strongly to silica surfaces and that it can be used to immobilize proteins on silica surfaces. The simulation results show that RPL2, especially domains 1 (residues 1-60) and 3 (residues 203-273), adsorbed more tightly to the silica surface above pH 7. We found that a major driving force for the adsorption of RPL2 onto the silica surface is the electrostatic interaction and that the structural flexibility of domains 1 and 3 may further contribute to the high affinity.

  9. Finite element simulation of surface defects in the automobile door outer panel

    International Nuclear Information System (INIS)

    Fukumura, Masaru; Yamasaki, Yuji; Inage, Daisuke; Fujita, Takashi

    2004-01-01

    Recently, a sheet metal forming simulation has become an indispensable tool for developing a new model of an automobile part within a limited short period. In these days, the utilization of a springback calculation of the formed part has been increasing. However, only a few papers on the prediction of surface defects have been reported in spite of serious needs.In this paper, surface defects in the door outer panel, especially those around the door handle embossment, have been investigated. Applying an explicit solver to the forming simulation, and an implicit solver to the springback calculation, we have tried to evaluate surface defects in the panel. In order to improve the accuracy of the simulation, numerical tools have been modeled including the precise shape of the draw beads so that the draw bead effects on both the material flow and the restraint on the springback deformation have been considered. Compared with the actual panel shape, which shows apparent surface defects, the simulated result has closely predicted the above defects around the embossment.To demonstrate the applicability of our simulation, a few sensitivity analyses have been carried out, modifying forming conditions such as blank holder force. Each result has shown slight but distinctive differences in the cross section profile of the panel. As a result, it has been realized that the influence of each considered factor on surface defects is qualitatively consistent with our practical knowledge

  10. Impact of dynamic vegetation phenology on the simulated pan-Arctic land surface state

    Science.gov (United States)

    Teufel, Bernardo; Sushama, Laxmi; Arora, Vivek K.; Verseghy, Diana

    2018-03-01

    The pan-Arctic land surface is undergoing rapid changes in a warming climate, with near-surface permafrost projected to degrade significantly during the twenty-first century. Vegetation-related feedbacks have the potential to influence the rate of degradation of permafrost. In this study, the impact of dynamic phenology on the pan-Arctic land surface state, particularly near-surface permafrost, for the 1961-2100 period, is assessed by comparing two simulations of the Canadian Land Surface Scheme (CLASS)—one with dynamic phenology, modelled using the Canadian Terrestrial Ecosystem Model (CTEM), and the other with prescribed phenology. These simulations are forced by atmospheric data from a transient climate change simulation of the 5th generation Canadian Regional Climate Model (CRCM5) for the Representative Concentration Pathway 8.5 (RCP8.5). Comparison of the CLASS coupled to CTEM simulation to available observational estimates of plant area index, spatial distribution of permafrost and active layer thickness suggests that the model captures reasonably well the overall distribution of vegetation and permafrost. It is shown that the most important impact of dynamic phenology on the land surface occurs through albedo and it is demonstrated for the first time that vegetation control on albedo during late spring and early summer has the highest potential to impact the degradation of permafrost. While both simulations show extensive near-surface permafrost degradation by the end of the twenty-first century, the strong projected response of vegetation to climate warming and increasing CO2 concentrations in the coupled simulation results in accelerated permafrost degradation in the northernmost continuous permafrost regions.

  11. Numerial simulation and experimental study of non-newtonian mixing flow with a free surface

    Directory of Open Access Journals (Sweden)

    M. Dular

    2006-12-01

    Full Text Available The object of this work was to evaluate the capability of numerical simulation to predict different features of non-Newtonian fluid mixing process. A relatively simple impeller (six bladed vane rotor was used for the mixing of carboxymethyl cellulose. A LDA method was used to measure the tangential velocity at two points inside the mixing vessel. Using visualization, a significant vortex above the impeller was observed. The shape of the free surface was determined by a geometrical reconstruction of the images of the illuminated section. Torque on the impeller shaft was measured to determine the characteristics of the fluid. Fluent program package was used for the simulation. The problem is challenging since the effects of non-Newtonian fluid, mixing process and free surface have to be included in the simulation. The comparison between the experimental and numerical results confirms the accuracy of the simulations.

  12. An Approach for the Simulation of Ground and Honed Technical Surfaces for Training Classifiers

    Directory of Open Access Journals (Sweden)

    Sebastian Rief

    2017-10-01

    Full Text Available Training of neural networks requires large amounts of data. Simulated data sets can be helpful if the data required for the training is not available. However, the applicability of simulated data sets for training neuronal networks depends on the quality of the simulation model used. A simple and fast approach for the simulation of ground and honed surfaces with predefined properties is being presented. The approach is used to generate a diverse data set. This set is then applied to train a neural convolution network for surface type recognition. The resulting classifier is validated on the basis of a series of real measurement data and a classification rate of >85% is achieved. A possible field of application of the presented procedure is the support of measurement technicians in the standard-compliant evaluation of measurement data by suggestion of specific data processing steps, depending on the recognized type of manufacturing process.

  13. Original Research. Surface Roughness Changes of Different Restoration Materials after Tooth Brushing Simulation Using Different Toothpastes

    Directory of Open Access Journals (Sweden)

    Dudás Csaba

    2017-03-01

    Full Text Available Background: The need for the whitening effects of toothpastes became primary for most users. Changes in the surface roughness of restoration materials after tooth brushing are inevitable, and the abrasion is known to increase the possibility of dental plaque accumulation. Aim of the study: To evaluate in vitro surface roughness changes of different dental restorative materials after tooth brushing simulation. Material and methods: Fifty specimens of two composite materials (Evicrol, Super-Cor, two glass ionomer materials (Glassfill, Kavitan Cem and a silicate cement (Fritex were prepared according to the manufacturer’s instructions. Each group of specimens was divided in three subgroups for tooth brushing simulation: using two different types of toothpaste and without toothpaste. Before and after 153 hours of tooth brushing simulation with a custom-made device, the surface roughness was measured with a surface roughness tester. Statistical analysis was performed after collecting the data. Results: All materials exhibited changes in surface roughness after the use of both toothpastes. The self-curing composite showed the less change and glass ionomer materials showed the greatest changes in surface roughness. Conclusions: The surface changes of dental materials depended on their composition and the cleaning procedure. Although self-curing composite was the most resistant to surface changes, its surface roughness values were high. Light-curing composite presented the lowest surface roughness values, even after brushing with toothpastes. The “medium” labeled toothbrush caused significant changes without toothpaste on the surface of light-curing composite, glass ionomer and silicate cement materials.

  14. CFD simulation of rotor aerodynamic performance when using additional surface structure array

    Science.gov (United States)

    Wang, Bing; Kong, Deyi

    2017-10-01

    The present work analyses the aerodynamic performance of the rotor with additional surface structure array in an attempt to maximize its performance in hover flight. The unstructured grids and the Reynolds Average Navier-Stokes equations were used to calculate the performance of the prototype rotor and the rotor with additional surface structure array in the air. The computational fluid dynamics software FLUENT was used to simulate the thrust of the rotors. The results of the calculations are in reasonable agreement with experimental data, which shows that the calculation model used in this work is useful in simulating the performance of the rotor with additional surface structure array. With this theoretical calculation model, the thrusts of the rotors with arrays of surface structure in three different shapes were calculated. According to the simulation results and the experimental data, the rotor with triangle surface structure array has better aerodynamic performance than the other rotors. In contrast with the prototype rotor, the thrust of the rotor with triangle surface structure array increases by 5.2% at the operating rotating speed of 3000r/min, and the additional triangle surface structure array has almost no influence on the efficiency of the rotor.

  15. Parallel tempering Monte Carlo simulations of lysozyme orientation on charged surfaces

    Science.gov (United States)

    Xie, Yun; Zhou, Jian; Jiang, Shaoyi

    2010-02-01

    In this work, the parallel tempering Monte Carlo (PTMC) algorithm is applied to accurately and efficiently identify the global-minimum-energy orientation of a protein adsorbed on a surface in a single simulation. When applying the PTMC method to simulate lysozyme orientation on charged surfaces, it is found that lysozyme could easily be adsorbed on negatively charged surfaces with "side-on" and "back-on" orientations. When driven by dominant electrostatic interactions, lysozyme tends to be adsorbed on negatively charged surfaces with the side-on orientation for which the active site of lysozyme faces sideways. The side-on orientation agrees well with the experimental results where the adsorbed orientation of lysozyme is determined by electrostatic interactions. As the contribution from van der Waals interactions gradually dominates, the back-on orientation becomes the preferred one. For this orientation, the active site of lysozyme faces outward, which conforms to the experimental results where the orientation of adsorbed lysozyme is co-determined by electrostatic interactions and van der Waals interactions. It is also found that despite of its net positive charge, lysozyme could be adsorbed on positively charged surfaces with both "end-on" and back-on orientations owing to the nonuniform charge distribution over lysozyme surface and the screening effect from ions in solution. The PTMC simulation method provides a way to determine the preferred orientation of proteins on surfaces for biosensor and biomaterial applications.

  16. Surface signature of Mediterranean water eddies in a long-term high-resolution simulation

    Science.gov (United States)

    Ciani, D.; Carton, X.; Barbosa Aguiar, A. C.; Peliz, A.; Bashmachnikov, I.; Ienna, F.; Chapron, B.; Santoleri, R.

    2017-12-01

    We study the surface signatures of Mediterranean water eddies (Meddies) in the context of a regional, primitive equations model simulation (using the Regional Oceanic Modeling System, ROMS). This model simulation was previously performed to study the mean characteristics and pathways of Meddies during their evolution in the Atlantic Ocean. The advantage of our approach is to take into account different physical mechanisms acting on the evolution of Meddies and their surface signature, having full information on the 3D distribution of all physical variables of interest. The evolution of around 90 long-lived Meddies (whose lifetimes exceeded one year) was investigated. In particular, their surface signature was determined in sea-surface height, temperature and salinity. The Meddy-induced anomalies were studied as a function of the Meddy structure and of the oceanic background. We show that the Meddies can generate positive anomalies in the elevation of the oceanic free-surface and that these anomalies are principally related to the Meddies potential vorticity structure at depth (around 1000 m below the sea-surface). On the contrary, the Meddies thermohaline surface signatures proved to be mostly dominated by local surface conditions and little correlated to the Meddy structure at depth. This work essentially points out that satellite altimetry is the most suitable approach to track subsurface vortices from observations of the sea-surface.

  17. Effects of playing surface on physiological responses and performance variables in a controlled football simulation.

    Science.gov (United States)

    Hughes, Michael G; Birdsey, Laurence; Meyers, Rob; Newcombe, Daniel; Oliver, Jon Lee; Smith, Paul M; Stembridge, Michael; Stone, Keeron; Kerwin, David George

    2013-01-01

    In spite of the increased acceptance of artificial turf in football, few studies have investigated if matches are altered by the type of surface used and no research has compared physiological responses to football activity on artificial and natural surfaces. In the present study, participants performed a football match simulation on high-quality artificial and natural surfaces. Neither mean heart rate (171 ± 9 beats · min(-1) vs. 171 ± 9 beats · min(-1); P > 0.05) nor blood lactate (4.8 ± 1.6 mM vs. 5.3 ± 1.8 mM; P > 0.05) differed between the artificial and natural surface, respectively. Measures of sprint, jumping and agility performance declined through the match simulation but surface type did not affect the decrease in performance. For example, the fatigue index of repeated sprints did not differ (P > 0.05) between the artificial, (6.9 ± 2.1%) and natural surface (7.4 ± 2.4%). The ability to turn after sprinting was affected by surface type but this difference was dependent on the type of turn. Although there were small differences in the ability to perform certain movements between artificial and natural surfaces, the results suggest that fatigue and physiological responses to football activity do not differ markedly between surface-type using the high-quality pitches of the present study.

  18. A Coupled Groundwater-Surface Water Modeling Framework for Simulating Transition Zone Processes.

    Science.gov (United States)

    Mugunthan, Pradeep; Russell, Kevin T; Gong, Binglei; Riley, Michael J; Chin, Arthur; McDonald, Blair G; Eastcott, Linda J

    2017-05-01

    There is an identified need for fully representing groundwater-surface water transition zone (i.e., the sediment zone that connects groundwater and surface water) processes in modeling fate and transport of contaminants to assist with management of contaminated sediments. Most existing groundwater and surface water fate and transport models are not dynamically linked and do not consider transition zone processes such as bioturbation and deposition and erosion of sediments. An interface module is developed herein to holistically simulate the fate and transport by coupling two commonly used models, Environmental Fluid Dynamics Code (EFDC) and SEAWAT, to simulate surface water and groundwater hydrodynamics, while providing an enhanced representation of the processes in the transition zone. Transition zone and surface water contaminant processes were represented through an enhanced version of the EFDC model, AQFATE. AQFATE also includes SEDZLJ, a state-of-the-science surface water sediment transport model. The modeling framework was tested on a published test problem and applied to evaluate field-scale two- and three-dimensional contaminant transport. The model accurately simulated concentrations of salinity from a published test case. For the field-scale applications, the model showed excellent mass balance closure for the transition zone and provided accurate simulations of all transition zone processes represented in the modeling framework. The model predictions for the two-dimensional field case were consistent with site-specific observations of contaminant migration. This modeling framework represents advancement in the simulation of transition zone processes and can help inform risk assessment at sites where contaminant sources from upland areas have the potential to impact sediments and surface water. © 2016, National Ground Water Association.

  19. Estimation of Nanodiamond Surface Charge Density from Zeta Potential and Molecular Dynamics Simulations.

    Science.gov (United States)

    Ge, Zhenpeng; Wang, Yi

    2017-04-20

    Molecular dynamics simulations of nanoparticles (NPs) are increasingly used to study their interactions with various biological macromolecules. Such simulations generally require detailed knowledge of the surface composition of the NP under investigation. Even for some well-characterized nanoparticles, however, this knowledge is not always available. An example is nanodiamond, a nanoscale diamond particle with surface dominated by oxygen-containing functional groups. In this work, we explore using the harmonic restraint method developed by Venable et al., to estimate the surface charge density (σ) of nanodiamonds. Based on the Gouy-Chapman theory, we convert the experimentally determined zeta potential of a nanodiamond to an effective charge density (σ eff ), and then use the latter to estimate σ via molecular dynamics simulations. Through scanning a series of nanodiamond models, we show that the above method provides a straightforward protocol to determine the surface charge density of relatively large (> ∼100 nm) NPs. Overall, our results suggest that despite certain limitation, the above protocol can be readily employed to guide the model construction for MD simulations, which is particularly useful when only limited experimental information on the NP surface composition is available to a modeler.

  20. Experimental demonstration of Martian soil simulant removal from a surface using a pulsed plasma jet

    Science.gov (United States)

    Ticoş, C. M.; Scurtu, A.; Toader, D.; Banu, N.

    2015-03-01

    A plasma jet produced in a small coaxial plasma gun operated at voltages up to 2 kV and working in pure carbon dioxide (CO2) at a few Torr is used to remove Martian soil simulant from a surface. A capacitor with 0.5 mF is charged up from a high voltage source and supplies the power to the coaxial electrodes. The muzzle of the coaxial plasma gun is placed at a few millimeters near the dusty surface and the jet is fired parallel with the surface. Removal of dust is imaged in real time with a high speed camera. Mars regolith simulant JSC-Mars-1A with particle sizes up to 5 mm is used on different types of surfaces made of aluminium, cotton fabric, polyethylene, cardboard, and phenolic.

  1. Semi-implicit surface tension formulation with a Lagrangian surface mesh on an Eulerian simulation grid

    KAUST Repository

    Schroeder, Craig

    2012-02-01

    We present a method for applying semi-implicit forces on a Lagrangian mesh to an Eulerian discretization of the Navier Stokes equations in a way that produces a sparse symmetric positive definite system. The resulting method has semi-implicit and fully-coupled viscosity, pressure, and Lagrangian forces. We apply our new framework for forces on a Lagrangian mesh to the case of a surface tension force, which when treated explicitly leads to a tight time step restriction. By applying surface tension as a semi-implicit Lagrangian force, the resulting method benefits from improved stability and the ability to take larger time steps. The resulting discretization is also able to maintain parasitic currents at low levels. © 2011.

  2. High-Accuracy Near-Surface Large-Eddy Simulation with Planar Topography

    Science.gov (United States)

    2015-08-03

    Planar Topography ” The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued as an official...Simulation with Planar Topography ” Report Title Large-eddy simulation (LES) has been plagued by an inability to predict the law-of-the-wall (LOTW) in mean...Report July 2015 HIGH-ACCURACY NEAR-SURFACE LARGE-EDDY SIMULATION WITH PLANAR TOPOGRAPHY ARO Grant W911NF-04-1-0205 PI: James G. Brasseur

  3. Evaluation of Surface Runoff Generation Processes Using a Rainfall Simulator: A Small Scale Laboratory Experiment

    Science.gov (United States)

    Danáčová, Michaela; Valent, Peter; Výleta, Roman

    2017-12-01

    Nowadays, rainfall simulators are being used by many researchers in field or laboratory experiments. The main objective of most of these experiments is to better understand the underlying runoff generation processes, and to use the results in the process of calibration and validation of hydrological models. Many research groups have assembled their own rainfall simulators, which comply with their understanding of rainfall processes, and the requirements of their experiments. Most often, the existing rainfall simulators differ mainly in the size of the irrigated area, and the way they generate rain drops. They can be characterized by the accuracy, with which they produce a rainfall of a given intensity, the size of the irrigated area, and the rain drop generating mechanism. Rainfall simulation experiments can provide valuable information about the genesis of surface runoff, infiltration of water into soil and rainfall erodibility. Apart from the impact of physical properties of soil, its moisture and compaction on the generation of surface runoff and the amount of eroded particles, some studies also investigate the impact of vegetation cover of the whole area of interest. In this study, the rainfall simulator was used to simulate the impact of the slope gradient of the irrigated area on the amount of generated runoff and sediment yield. In order to eliminate the impact of external factors and to improve the reproducibility of the initial conditions, the experiments were conducted in laboratory conditions. The laboratory experiments were carried out using a commercial rainfall simulator, which was connected to an external peristaltic pump. The pump maintained a constant and adjustable inflow of water, which enabled to overcome the maximum volume of simulated precipitation of 2.3 l, given by the construction of the rainfall simulator, while maintaining constant characteristics of the simulated precipitation. In this study a 12-minute rainfall with a constant intensity

  4. Local-Scale Simulations of Nucleate Boiling on Micrometer-Featured Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sitaraman, Hariswaran [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Moreno, Gilberto [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dede, Ercan M. [Toyota Research Institute of North America; Joshi, Shailesh N. [Toyota Research Institute of North America; Zhou, Feng [Toyota Research Institute of North America

    2017-07-12

    A high-fidelity computational fluid dynamics (CFD)-based model for bubble nucleation of the refrigerant HFE7100 on micrometer-featured surfaces is presented in this work. The single-fluid incompressible Navier-Stokes equations, along with energy transport and natural convection effects are solved on a featured surface resolved grid. An a priori cavity detection method is employed to convert raw profilometer data of a surface into well-defined cavities. The cavity information and surface morphology are represented in the CFD model by geometric mesh deformations. Surface morphology is observed to initiate buoyancy-driven convection in the liquid phase, which in turn results in faster nucleation of cavities. Simulations pertaining to a generic rough surface show a trend where smaller size cavities nucleate with higher wall superheat. This local-scale model will serve as a self-consistent connection to larger device scale continuum models where local feature representation is not possible.

  5. Local-Scale Simulations of Nucleate Boiling on Micrometer Featured Surfaces: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sitaraman, Hariswaran [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Moreno, Gilberto [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dede, Ercan M. [Toyota Research Institute of North America; Joshi, Shailesh N. [Toyota Research Institute of North America; Zhou, Feng [Toyota Research Institute of North America

    2017-08-03

    A high-fidelity computational fluid dynamics (CFD)-based model for bubble nucleation of the refrigerant HFE7100 on micrometer-featured surfaces is presented in this work. The single-fluid incompressible Navier-Stokes equations, along with energy transport and natural convection effects are solved on a featured surface resolved grid. An a priori cavity detection method is employed to convert raw profilometer data of a surface into well-defined cavities. The cavity information and surface morphology are represented in the CFD model by geometric mesh deformations. Surface morphology is observed to initiate buoyancy-driven convection in the liquid phase, which in turn results in faster nucleation of cavities. Simulations pertaining to a generic rough surface show a trend where smaller size cavities nucleate with higher wall superheat. This local-scale model will serve as a self-consistent connection to larger device scale continuum models where local feature representation is not possible.

  6. Generating Inviscid and Viscous Fluid Flow Simulations over a Surface Using a Quasi-simultaneous Technique

    Science.gov (United States)

    Sturdza, Peter (Inventor); Martins-Rivas, Herve (Inventor); Suzuki, Yoshifumi (Inventor)

    2014-01-01

    A fluid-flow simulation over a computer-generated surface is generated using a quasi-simultaneous technique. The simulation includes a fluid-flow mesh of inviscid and boundary-layer fluid cells. An initial fluid property for an inviscid fluid cell is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. An initial boundary-layer fluid property a boundary-layer fluid cell is determined using the initial fluid property and a viscous fluid simulation that simulates fluid viscous effects. An updated boundary-layer fluid property is determined for the boundary-layer fluid cell using the initial fluid property, initial boundary-layer fluid property, and an interaction law. The interaction law approximates the inviscid fluid simulation using a matrix of aerodynamic influence coefficients computed using a two-dimensional surface panel technique and a fluid-property vector. An updated fluid property is determined for the inviscid fluid cell using the updated boundary-layer fluid property.

  7. MONTE CARLO SIMULATIONS OF THE ADSORPTION OF DIMERS ON STRUCTURED HETEROGENEOUS SURFACES

    Directory of Open Access Journals (Sweden)

    Abreu C.R.A.

    2001-01-01

    Full Text Available The effect of surface topography upon the adsorption of dimer molecules is analyzed by means of grand canonical ensemble Monte Carlo simulations. Heterogeneous surfaces were assumed to consist of a square lattice containing active sites with two different energies. These were distributed in three different configurations: a random distribution of isolated sites; a random distribution of grains with four high-energy sites; and a random distribution of grains with nine high-energy sites. For the random distribution of isolated sites, the results are in good agreement with the molecular simulations performed by Nitta et al. (1997. In general, the comparison with theoretical models shows that the Nitta et al. (1984 isotherm presents good predictions of dimer adsorption both on homogeneous and heterogeneous surfaces with sites having small differences in characteristic energies. The molecular simulation results also show that the energy topology of the solid surfaces plays an important role in the adsorption of dimers on solids with large differences in site energies. For these cases, the Nitta et al. model does not describe well the data on dimer adsorption on random heterogeneous surfaces (grains with one acid site, but does describe reasonably well the adsorption of dimers on more patchwise heterogeneous surfaces (grains with nine acid sites.

  8. Role of sea surface temperature responses in simulation of the climatic effect of mineral dust aerosol

    Directory of Open Access Journals (Sweden)

    X. Yue

    2011-06-01

    Full Text Available Mineral dust aerosol can be transported over the nearby oceans and influence the energy balance at the sea surface. The role of dust-induced sea surface temperature (SST responses in simulations of the climatic effect of dust is examined by using a general circulation model with online simulation of mineral dust and a coupled mixed-layer ocean model. Both the longwave and shortwave radiative effects of mineral dust aerosol are considered in climate simulations. The SST responses are found to be very influential on simulated dust-induced climate change, especially when climate simulations consider the two-way dust-climate coupling to account for the feedbacks. With prescribed SSTs and dust concentrations, we obtain an increase of 0.02 K in the global and annual mean surface air temperature (SAT in response to dust radiative effects. In contrast, when SSTs are allowed to respond to radiative forcing of dust in the presence of the dust cycle-climate interactions, we obtain a global and annual mean cooling of 0.09 K in SAT by dust. The extra cooling simulated with the SST responses can be attributed to the following two factors: (1 The negative net (shortwave plus longwave radiative forcing of dust at the surface reduces SST, which decreases latent heat fluxes and upward transport of water vapor, resulting in less warming in the atmosphere; (2 The positive feedback between SST responses and dust cycle. The dust-induced reductions in SST lead to reductions in precipitation (or wet deposition of dust and hence increase the global burden of small dust particles. These small particles have strong scattering effects, which enhance the dust cooling at the surface and further reduce SSTs.

  9. Stable water isotope simulation by current land-surface schemes:Results of IPILPS phase 1

    Energy Technology Data Exchange (ETDEWEB)

    Henderson-Sellers, A.; Fischer, M.; Aleinov, I.; McGuffie, K.; Riley, W.J.; Schmidt, G.A.; Sturm, K.; Yoshimura, K.; Irannejad, P.

    2005-10-31

    Phase 1 of isotopes in the Project for Intercomparison of Land-surface Parameterization Schemes (iPILPS) compares the simulation of two stable water isotopologues ({sup 1}H{sub 2} {sup 18}O and {sup 1}H{sup 2}H{sup 16}O) at the land-atmosphere interface. The simulations are off-line, with forcing from an isotopically enabled regional model for three locations selected to offer contrasting climates and ecotypes: an evergreen tropical forest, a sclerophyll eucalypt forest and a mixed deciduous wood. Here we report on the experimental framework, the quality control undertaken on the simulation results and the method of intercomparisons employed. The small number of available isotopically-enabled land-surface schemes (ILSSs) limits the drawing of strong conclusions but, despite this, there is shown to be benefit in undertaking this type of isotopic intercomparison. Although validation of isotopic simulations at the land surface must await more, and much more complete, observational campaigns, we find that the empirically-based Craig-Gordon parameterization (of isotopic fractionation during evaporation) gives adequately realistic isotopic simulations when incorporated in a wide range of land-surface codes. By introducing two new tools for understanding isotopic variability from the land surface, the Isotope Transfer Function and the iPILPS plot, we show that different hydrological parameterizations cause very different isotopic responses. We show that ILSS-simulated isotopic equilibrium is independent of the total water and energy budget (with respect to both equilibration time and state), but interestingly the partitioning of available energy and water is a function of the models' complexity.

  10. Numerical simulation of sloshing with large deforming free surface by MPS-LES method

    Science.gov (United States)

    Pan, Xu-jie; Zhang, Huai-xin; Sun, Xue-yao

    2012-12-01

    Moving particle semi-implicit (MPS) method is a fully Lagrangian particle method which can easily solve problems with violent free surface. Although it has demonstrated its advantage in ocean engineering applications, it still has some defects to be improved. In this paper, MPS method is extended to the large eddy simulation (LES) by coupling with a sub-particle-scale (SPS) turbulence model. The SPS turbulence model turns into the Reynolds stress terms in the filtered momentum equation, and the Smagorinsky model is introduced to describe the Reynolds stress terms. Although MPS method has the advantage in the simulation of the free surface flow, a lot of non-free surface particles are treated as free surface particles in the original MPS model. In this paper, we use a new free surface tracing method and the key point is "neighbor particle". In this new method, the zone around each particle is divided into eight parts, and the particle will be treated as a free surface particle as long as there are no "neighbor particles" in any two parts of the zone. As the number density parameter judging method has a high efficiency for the free surface particles tracing, we combine it with the neighbor detected method. First, we select out the particles which may be mistreated with high probabilities by using the number density parameter judging method. And then we deal with these particles with the neighbor detected method. By doing this, the new mixed free surface tracing method can reduce the mistreatment problem efficiently. The serious pressure fluctuation is an obvious defect in MPS method, and therefore an area-time average technique is used in this paper to remove the pressure fluctuation with a quite good result. With these improvements, the modified MPS-LES method is applied to simulate liquid sloshing problems with large deforming free surface. Results show that the modified MPS-LES method can simulate the large deforming free surface easily. It can not only capture

  11. Study on Applicability of Numerical Simulation to Evaluation of Gas Entrainment From Free Surface

    International Nuclear Information System (INIS)

    Kei Ito; Takaaki Sakai; Hiroyuki Ohshima

    2006-01-01

    An onset condition of gas entrainment (GE) due to free surface vortex has been studied to establish a design of fast breeder reactor with higher coolant velocity than conventional designs, because the GE might cause the reactor operation instability and therefore should be avoided. The onset condition of the GE has been investigated experimentally and theoretically, however, dependency of the vortex type GE on local geometry configuration of each experimental system and local velocity distribution has prevented researchers from formulating the universal onset condition of the vortex type GE. A real scale test is considered as an accurate method to evaluate the occurrence of the vortex type GE, but the real scale test is generally expensive and not useful in the design study of large and complicated FBR systems, because frequent displacement of inner equipments accompanied by the design change is difficult in the real scale test. Numerical simulation seems to be promising method as an alternative to the real scale test. In this research, to evaluate the applicability of the numerical simulation to the design work, numerical simulations were conducted on the basic experimental system of the vortex type GE. This basic experiment consisted of rectangular flow channel and two important equipments for vortex type GE in the channel, i.e. vortex generation and suction equipments. Generated vortex grew rapidly interacting with the suction flow and the grown vortex formed a free surface dent (gas core). When the tip of the gas core or the bubbles detached from the tip of the gas core reached the suction mouth, the gas was entrained to the suction tube. The results of numerical simulation under the experimental conditions were compared to the experiment in terms of velocity distributions and free surface shape. As a result, the numerical simulation showed qualitatively good agreement with experimental data. The numerical simulation results were similar to the experimental

  12. Water adsorption on amorphous silica surfaces: a Car-Parrinello simulation study

    International Nuclear Information System (INIS)

    Mischler, Claus; Horbach, Juergen; Kob, Walter; Binder, Kurt

    2005-01-01

    A combination of classical molecular dynamics (MD) and ab initio Car-Parrinello molecular dynamics (CPMD) simulations is used to investigate the adsorption of water on a free amorphous silica surface. From the classical MD, SiO 2 configurations with a free surface are generated which are then used as starting configurations for the CPMD. We study the reaction of a water molecule with a two-membered ring at the temperature T = 300 K. We show that the result of this reaction is the formation of two silanol groups on the surface. The activation energy of the reaction is estimated and it is shown that the reaction is exothermic

  13. SIMULATION OF THE Ku-BAND RADAR ALTIMETER SEA ICE EFFECTIVE SCATTERING SURFACE

    DEFF Research Database (Denmark)

    Tonboe, Rasmus; Andersen, Søren; Pedersen, Leif Toudal

    2006-01-01

    A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model...... is initialised with in situ data collected during the May 2004 GreenIce ice camp in the Lincoln Sea (73ºW; 85ºN). Our results show that the snow cover is important for the effective scattering surface depth in sea ice and thus for the range measurement, ice freeboard and ice thickness estimation....

  14. SIPSON--simulation of interaction between pipe flow and surface overland flow in networks.

    Science.gov (United States)

    Djordjević, S; Prodanović, D; Maksimović, C; Ivetić, M; Savić, D

    2005-01-01

    The new simulation model, named SIPSON, based on the Preissmann finite difference method and the conjugate gradient method, is presented in the paper. This model simulates conditions when the hydraulic capacity of a sewer system is exceeded, pipe flow is pressurized, the water flows out from the piped system to the streets, and the inlets cannot capture all the runoff. In the mathematical model, buried structures and pipelines, together with surface channels, make a horizontally and vertically looped network involving a complex interaction of flows. In this paper, special internal boundary conditions related to equivalent inlets are discussed. Procedures are described for the simulation of manhole cover loss, basement flooding, the representation of street geometry, and the distribution of runoff hydrographs between surface and underground networks. All these procedures are built into the simulation model. Relevant issues are illustrated on a set of examples, focusing on specific parameters and comparison with field measurements of flooding of the Motilal ki Chal catchment (Indore, India). Satisfactory agreement of observed and simulated hydrographs and maximum surface flooding levels is obtained. It is concluded that the presented approach is an improvement compared to the standard "virtual reservoir" approach commonly applied in most of the models.

  15. Simulation of free surfaces in 3-D with the arbitrary Lagrange-Euler method

    DEFF Research Database (Denmark)

    Szabo, Peter; Hassager, Ole

    1995-01-01

    The arbitrary Lagrange-Euler (ALE) kinematic description has been implemented in a 3-D transient finite element program so as to simulate multiple fluid flows with Surfaces and interfaces of general shapes. The description of fluid interfaces includes continuity of velocity and a discontinuous...

  16. Primary biodegradation of veterinary antibiotics in aerobic and anaerobic surface water simulation systems

    DEFF Research Database (Denmark)

    Ingerslev, Flemming; Toräng, Lars; Loke, M.-L.

    2001-01-01

    The primary aerobic and anaerobic biodegradability at intermediate concentrations (50-5000 mug/l) of the antibiotics olaquindox (OLA), metronidazole (MET), tylosin (TYL) and oxytetracycline (OTC) was studied in a simple shake flask system simulating the conditions in surface waters. The purpose...

  17. Simulation of an Underwater Acoustic Communication Channel Characterized by Wind-Generated Surface Waves and Bubbles

    NARCIS (Netherlands)

    Dol, H.S.; Colin, M.E.G.D.; Ainslie, M.A.; Walree, P.A. van; Janmaat, J.

    2013-01-01

    Abstract—Sea-surface scattering by wind-generated waves and bubbles is regarded to be the main nonplatform related cause of the time variability of shallow acoustic communication channels. Simulations for predicting the quality of acoustic communication links in such channels thus require adequate

  18. Simulation of an Underwater Acoustic Communication Channel Characterized by Wind-Generated Surface Waves and Bubbles

    NARCIS (Netherlands)

    Dol, H.S.; Ainslie, M.A.; Colin, M.E.G.D.; Janmaat, J.

    2012-01-01

    Sea surface scattering by wind-generated waves and bubbles is regarded to be the main nonplatform-related cause of the time variability of shallow acoustic communication channels. Simulations for predicting the quality of acoustic communication links in such channels thus require adequate modelling

  19. Surface Wind Regionalization over Complex Terrain: Evaluation and Analysis of a High-Resolution WRF Simulation

    NARCIS (Netherlands)

    Jiménez, P.A.; González-Rouco, J.F.; García-Bustamante, E.; Navarro, J.; Montávez, J.P.; Vilà-Guerau de Arellano, J.; Dudhia, J.; Muñoz-Roldan, A.

    2010-01-01

    This study analyzes the daily-mean surface wind variability over an area characterized by complex topography through comparing observations and a 2-km-spatial-resolution simulation performed with the Weather Research and Forecasting (WRF) model for the period 1992–2005. The evaluation focuses on the

  20. A quantum-classical simulation of a multi-surface multi-mode ...

    Indian Academy of Sciences (India)

    J. Chem. Sci. Vol. 124, No. 1, January 2012, pp. 51–58. c Indian Academy of Sciences. A quantum-classical simulation of a multi-surface multi-mode nuclear dynamics on C6H. +. 6 incorporating degeneracy among electronic states. #. SUBHANKAR SARDAR and SATRAJIT ADHIKARI. ∗. Department of Physical Chemistry, ...

  1. Thermal simulation of surface micromachined polysilicon hot plates of low power consumption

    NARCIS (Netherlands)

    Dumitrescu, Marius; Cobianu, Cornel; Lungu, Dan; Pascu, Adrian; Kolev, Spas; van den Berg, Albert

    1999-01-01

    A simple, IC compatible, surface micromachined polysilicon membrane was technologically designed and thermally simulated by 3D finite element ‘COSMOS' program in order to investigate its capability to work as a micro hot plate for a gas sensing test structure of low power consumption. For an

  2. Impact of Urban Surface Roughness Length Parameterization Scheme on Urban Atmospheric Environment Simulation

    Directory of Open Access Journals (Sweden)

    Meichun Cao

    2014-01-01

    Full Text Available In this paper, the impact of urban surface roughness length z0 parameterization scheme on the atmospheric environment simulation over Beijing has been investigated through two sets of numerical experiments using the Weather Research and Forecasting model coupled with the Urban Canopy Model. For the control experiment (CTL, the urban surface z0 parameterization scheme used in UCM is the model default one. For another experiment (EXP, a newly developed urban surface z0 parameterization scheme is adopted, which takes into account the comprehensive effects of urban morphology. The comparison of the two sets of simulation results shows that all the roughness parameters computed from the EXP run are larger than those in the CTL run. The increased roughness parameters in the EXP run result in strengthened drag and blocking effects exerted by buildings, which lead to enhanced friction velocity, weakened wind speed in daytime, and boosted turbulent kinetic energy after sunset. Thermal variables (sensible heat flux and temperature are much less sensitive to z0 variations. In contrast with the CTL run, the EXP run reasonably simulates the observed nocturnal low-level jet. Besides, the EXP run-simulated land surface-atmosphere momentum and heat exchanges are also in better agreement with the observation.

  3. Two-component injection moulding simulation of ABS-POM micro structured surfaces

    DEFF Research Database (Denmark)

    Tosello, Guido; Hansen, Hans Nørgaard; Islam, Aminul

    2013-01-01

    a pair of thermoplastic materials (ABS and POM) were conducted. Three dimensional process simulations based on the finite element method have been performed to explore the capability of predicting filling pattern shape at component-level and surface micro feature-level in a polymer/polymer overmoulding...

  4. Liquid flow in surface-nanostructured channels studied by molecular dynamics simulation

    Science.gov (United States)

    Cao, Bing-Yang; Chen, Min; Guo, Zeng-Yuan

    2006-12-01

    Molecular dynamics simulations have been carried out to investigate the fluid wetting and flow in nanochannels whose surfaces are structured by an array of nanoscale triangular modules. We find that the surface nanostructures have a dual effect on the boundary slip and friction of the liquid nanoflow. On the one hand, the nanostructures can enhance the surface hydrophilicity for a hydrophilic liquid-solid interaction, and can increase the hydrophobicity for a hydrophobic interaction due to a nanoscale lotus effect. In particular, the nanostructured surface may show superhydrophobicity and lead to the large velocity slip of the liquid flow. On the other hand, simultaneously, the nanostructures distort the nanoscale streamlines of the liquid flow near the channel surfaces and block the nanoflow directly, which decreases the apparent slip length equivalently. The dual effect of the nanostructures on the surface wettability and the hydrodynamic disturbance results in a nonmonotonic dependence of the slip length on the nanostructure size. The simulations imply that the surface nanostructures can be applied to control the friction of liquid micro- and nanoflows.

  5. Simulation of Specular Surface Imaging Based on Computer Graphics: Application on a Vision Inspection System

    Directory of Open Access Journals (Sweden)

    Seulin Ralph

    2002-01-01

    Full Text Available This work aims at detecting surface defects on reflecting industrial parts. A machine vision system, performing the detection of geometric aspect surface defects, is completely described. The revealing of defects is realized by a particular lighting device. It has been carefully designed to ensure the imaging of defects. The lighting system simplifies a lot the image processing for defect segmentation and so a real-time inspection of reflective products is possible. To bring help in the conception of imaging conditions, a complete simulation is proposed. The simulation, based on computer graphics, enables the rendering of realistic images. Simulation provides here a very efficient way to perform tests compared to the numerous attempts of manual experiments.

  6. Two-dimensional simulation research of secondary electron emission avalanche discharge on vacuum insulator surface

    Science.gov (United States)

    Cai, Libing; Wang, Jianguo; Zhu, Xiangqin; Wang, Yue; Zhang, Dianhui

    2015-01-01

    Based on the secondary electron emission avalanche (SEEA) model, the SEEA discharge on the vacuum insulator surface is simulated by using a 2D PIC-MCC code developed by ourselves. The evolutions of the number of discharge electrons, insulator surface charge, current, and 2D particle distribution are obtained. The effects of the strength of the applied electric field, secondary electron yield coefficient, rise time of the pulse, length of the insulator on the discharge are investigated. The results show that the number of the SEEA electrons presents a quadratic dependence upon the applied field strength. The SEEA current, which is on the order of Ampere, is directly proportional to the field strength and secondary electron yield coefficient. Finally, the electron-stimulated outgassing is included in the simulation code, and a three-phase discharge curve is presented by the simulation, which agrees with the experimental data.

  7. Two-dimensional simulation research of secondary electron emission avalanche discharge on vacuum insulator surface

    International Nuclear Information System (INIS)

    Cai, Libing; Wang, Jianguo; Zhu, Xiangqin; Wang, Yue; Zhang, Dianhui

    2015-01-01

    Based on the secondary electron emission avalanche (SEEA) model, the SEEA discharge on the vacuum insulator surface is simulated by using a 2D PIC-MCC code developed by ourselves. The evolutions of the number of discharge electrons, insulator surface charge, current, and 2D particle distribution are obtained. The effects of the strength of the applied electric field, secondary electron yield coefficient, rise time of the pulse, length of the insulator on the discharge are investigated. The results show that the number of the SEEA electrons presents a quadratic dependence upon the applied field strength. The SEEA current, which is on the order of Ampere, is directly proportional to the field strength and secondary electron yield coefficient. Finally, the electron-stimulated outgassing is included in the simulation code, and a three-phase discharge curve is presented by the simulation, which agrees with the experimental data

  8. Electrochemical deposition on surface nanometric defects: Thermodynamics and grand canonical Monte Carlo simulations

    International Nuclear Information System (INIS)

    Luque, Noelia B.; Reinaudi, Luis; Serra, Pablo; Leiva, Ezequiel P.M.

    2009-01-01

    A thermodynamic analysis is performed on electrochemical metal deposition in the cavity of a foreign substrate. In particular, the deposition of Cu and Ag in nanometer-sized holes on Au(1 1 1) is studied by means of off-lattice atomistic Grand Canonical Monte Carlo simulations, using embedded atom method potentials. The present simulation conditions emulate experiments of electrochemical metal deposition in nanocavities, as performed in the literature. Depending on the system, remarkable differences are found in the way in which the defects are decorated, as well as in their energetics. When the interaction of the adsorbate atoms with the substrate is less favorable than the bulk interaction of the adsorbate, clusters are found that grow stepwise over the level of the surface. In the opposite case, the filling of the cavity occurs stepwise, without the occurrence of cluster growth above the surface level. The results of the simulations present a good qualitative agreement with experimental results from the literature

  9. A Method to Simulate the Observed Surface Properties of Proton Irradiated Silicon Strip Sensors

    CERN Document Server

    INSPIRE-00335524; Bhardwaj, A.; Dalal, R.; Eber, R.; Eichhorn, T.; Lalwani, K.; Messineo, A.; Printz, M.; Ranjan, K.

    2015-04-23

    During the scheduled high luminosity upgrade of LHC, the world's largest particle physics accelerator at CERN, the position sensitive silicon detectors installed in the vertex and tracking part of the CMS experiment will face more intense radiation environment than the present system was designed for. To upgrade the tracker to required performance level, extensive measurements and simulations studies have already been carried out. A defect model of Synopsys Sentaurus TCAD simulation package for the bulk properties of proton irradiated devices has been producing simulations closely matching with measurements of silicon strip detectors. However, the model does not provide expected behavior due to the fluence increased surface damage. The solution requires an approach that does not affect the accurate bulk properties produced by the proton model, but only adds to it the required radiation induced properties close to the surface. These include the observed position dependency of the strip detector's charge collec...

  10. Spatial Variability of Soil Properties and its Impact on Simulated Surface Soil Moisture Patterns

    Science.gov (United States)

    Korres, W.; Bothe, T.; Reichenau, T. G.; Schneider, K.

    2015-12-01

    The spatial variability of soil properties (particle size distribution, PSD, and bulk density, BD) has large effects on the spatial variability of soil moisture and therefore on plant growth and surface exchange processes. In model studies, soil properties from soil maps are considered homogeneous over mapping units, which neglects the small scale variability of soil properties and leads to underestimated small scale variability of simulated soil moisture. This study focuses on the validation of spatial variability of simulated surface soil moisture (SSM) in a winter wheat field in Western Germany using the eco-hydrological simulation system DANUBIA. SSM measurements were conducted at 20 different sampling points and nine different dates in 2008. Frequency distributions of BD and PSD were derived from an independent dataset (n = 486) of soil physical properties from Germany and the USA. In the simulations, BD and PSD were parameterized according to these frequency distributions. Mean values, coefficients of variation and frequency distributions of simulated SSM were compared to the field measurements. Using the heterogeneous model parameterization, up to 76 % of the frequency distribution of the measured SSM can be explained. Furthermore, the results show that BD has a larger impact on the variability of SSM than PSD. The introduced approach can be used for simulating mean SSM and SSM variability more accurately and can form the basis for a spatially heterogeneous parameterization of soil properties in mesoscale models.

  11. Surface Roughness of Composite Resins after Simulated Toothbrushing with Different Dentifrices

    Science.gov (United States)

    Monteiro, Bruna; Spohr, Ana Maria

    2015-01-01

    Background: The aim of the study was to evaluate, in vitro, the surface roughness of two composite resins submitted to simulated toothbrushing with three different dentifrices. Materials and Methods: Totally, 36 samples of Z350XT and 36 samples of Empress Direct were built and randomly divided into three groups (n = 12) according to the dentifrice used (Oral-B Pro-Health Whitening [OBW], Colgate Sensitive Pro-Relief [CS], Colgate Total Clean Mint 12 [CT12]). The samples were submitted to 5,000, 10,000 or 20,000 cycles of simulated toothbrushing. After each simulated period, the surface roughness of the samples was measured using a roughness tester. Results: According to three-way analysis of variance, dentifrice (P = 0.044) and brushing time (P = 0.000) were significant. The composite resin was not significant (P = 0.381) and the interaction among the factors was not significant (P > 0.05). The mean values of the surface roughness (µm) followed by the same letter represent no statistical difference by Tukey's post-hoc test (P toothbrushing. The higher the brushing time, the higher the surface roughness of composite resins. The dentifrice OBW caused a higher surface roughness in both composite resins. PMID:26229362

  12. [Surface roughness and gloss of novel flowable composites after polishing and simulated brushing wear].

    Science.gov (United States)

    Wang, R L; Yuan, C Y; Pan, Y X; Tian, F C; Wang, Z H; Wang, X Y

    2017-04-09

    Objective: To investigate surface properties of novel flowable composites after polishing and simulated brushing wear, compared to their pasty counterpart. Methods: Composites employed in this study were: three flowable composites (A1: Clearfil Majesty ES Flow; B1: Beautifil Flow Plus F00; C1: Filtek Bulk Fill) and three paste composites (A2: Clearfil Majesty; B2: Beautifil; C2: Filtek Z350. Eleven disk-shaped specimens were made for each material. The specimens were cured, then subjected to sandpaper finishing for 20 s, one-step polishing for 30 s, finally subjected to simulated brushing for 10 000 cycles. Surface roughness and glossiness were measured before finishing, after finishing, after polishing, after 5 000 brushing cycles and after 10 000 brushing cycles, respectively. Data obtained were analyzed using two-way ANOVA method. Scanning electron microscope was employed to examine the microscopic appearance of each material. Results: Surface roughness (0.11~0.22 μm) and glossiness (74.25~86.48 GU) of each material were similar after one-step polishing. After brushing simulation, roughness increased significantly and glossiness decreased significantly for each material ( Pcomposites of group A1 and B1 tested in the present setup showed better surface properties compared to their pasty counterpart (group A2 and B2). Conclusions: Within the limit of this study, flowable composites tested in the present research can obtain similar surface polish or even better than the paste composite counterpart.

  13. Simulating the Effect of Modulated Tool-Path Chip Breaking On Surface Texture and Chip Length

    Energy Technology Data Exchange (ETDEWEB)

    Smith, K.S.; McFarland, J.T.; Tursky, D. A.; Assaid, T. S.; Barkman, W. E.; Babelay, Jr., E. F.

    2010-04-30

    One method for creating broken chips in turning processes involves oscillating the cutting tool in the feed direction utilizing the CNC machine axes. The University of North Carolina at Charlotte and the Y-12 National Security Complex have developed and are refining a method to reliably control surface finish and chip length based on a particular machine's dynamic performance. Using computer simulations it is possible to combine the motion of the machine axes with the geometry of the cutting tool to predict the surface characteristics and map the surface texture for a wide range of oscillation parameters. These data allow the selection of oscillation parameters to simultaneously ensure broken chips and acceptable surface characteristics. This paper describes the machine dynamic testing and characterization activities as well as the computational method used for evaluating and predicting chip length and surface texture.

  14. Generating a Simulated Fluid Flow Over an Aircraft Surface Using Anisotropic Diffusion

    Science.gov (United States)

    Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

    2013-01-01

    A fluid-flow simulation over a computer-generated aircraft surface is generated using a diffusion technique. The surface is comprised of a surface mesh of polygons. A boundary-layer fluid property is obtained for a subset of the polygons of the surface mesh. A pressure-gradient vector is determined for a selected polygon, the selected polygon belonging to the surface mesh but not one of the subset of polygons. A maximum and minimum diffusion rate is determined along directions determined using a pressure gradient vector corresponding to the selected polygon. A diffusion-path vector is defined between a point in the selected polygon and a neighboring point in a neighboring polygon. An updated fluid property is determined for the selected polygon using a variable diffusion rate, the variable diffusion rate based on the minimum diffusion rate, maximum diffusion rate, and angular difference between the diffusion-path vector and the pressure-gradient vector.

  15. Generating a Simulated Fluid Flow over a Surface Using Anisotropic Diffusion

    Science.gov (United States)

    Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

    2016-01-01

    A fluid-flow simulation over a computer-generated surface is generated using a diffusion technique. The surface is comprised of a surface mesh of polygons. A boundary-layer fluid property is obtained for a subset of the polygons of the surface mesh. A gradient vector is determined for a selected polygon, the selected polygon belonging to the surface mesh but not one of the subset of polygons. A maximum and minimum diffusion rate is determined along directions determined using the gradient vector corresponding to the selected polygon. A diffusion-path vector is defined between a point in the selected polygon and a neighboring point in a neighboring polygon. An updated fluid property is determined for the selected polygon using a variable diffusion rate, the variable diffusion rate based on the minimum diffusion rate, maximum diffusion rate, and the gradient vector.

  16. Simulated Fizeau ring fringes in transmission through spherical and plane reflected surfaces

    Science.gov (United States)

    Ramadan, W. A.; Wahba, H. H.

    2018-01-01

    In this paper, we present simulated Fizeau ring fringes. These fringes are constructed due to multiple reflection between highly reflected partially transmitted spherical and plane surfaces. The real paths of rays and consequently their amplitudes and phases have been determined when they reached the image plane. This plane is located at a certain distance above the interferometer. In these calculations, the impact of the image plane position, the radius of the spherical surface and the distance between the two surfaces on the fringe intensity distribution are investigated. A quite interesting result of our calculation is that the number of the interfered rays is varied and could be only two, even for a highly reflected surfaces. Three different estimated visualizations are included to give an overview imagination of the impact of the different parameter variation. These could be helpful for researchers for testing of spherical surfaces using interference-based methods.

  17. An algorithm for three-dimensional Monte-Carlo simulation of charge distribution at biofunctionalized surfaces

    KAUST Repository

    Bulyha, Alena

    2011-01-01

    In this work, a Monte-Carlo algorithm in the constant-voltage ensemble for the calculation of 3d charge concentrations at charged surfaces functionalized with biomolecules is presented. The motivation for this work is the theoretical understanding of biofunctionalized surfaces in nanowire field-effect biosensors (BioFETs). This work provides the simulation capability for the boundary layer that is crucial in the detection mechanism of these sensors; slight changes in the charge concentration in the boundary layer upon binding of analyte molecules modulate the conductance of nanowire transducers. The simulation of biofunctionalized surfaces poses special requirements on the Monte-Carlo simulations and these are addressed by the algorithm. The constant-voltage ensemble enables us to include the right boundary conditions; the dna strands can be rotated with respect to the surface; and several molecules can be placed in a single simulation box to achieve good statistics in the case of low ionic concentrations relevant in experiments. Simulation results are presented for the leading example of surfaces functionalized with pna and with single- and double-stranded dna in a sodium-chloride electrolyte. These quantitative results make it possible to quantify the screening of the biomolecule charge due to the counter-ions around the biomolecules and the electrical double layer. The resulting concentration profiles show a three-layer structure and non-trivial interactions between the electric double layer and the counter-ions. The numerical results are also important as a reference for the development of simpler screening models. © 2011 The Royal Society of Chemistry.

  18. Numerical simulation of binary collisions using a modified surface tension model with particle method

    International Nuclear Information System (INIS)

    Sun Zhongguo; Xi Guang; Chen Xi

    2009-01-01

    The binary collision of liquid droplets is of both practical importance and fundamental value in computational fluid mechanics. We present a modified surface tension model within the moving particle semi-implicit (MPS) method, and carry out two-dimensional simulations to investigate the mechanisms of coalescence and separation of the droplets during binary collision. The modified surface tension model improves accuracy and convergence. A mechanism map is established for various possible deformation pathways encountered during binary collision, as the impact speed is varied; a new pathway is reported when the collision speed is critical. In addition, eccentric collisions are simulated and the effect of the rotation of coalesced particle is explored. The results qualitatively agree with experiments and the numerical protocol may find applications in studying free surface flows and interface deformation

  19. Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field

    International Nuclear Information System (INIS)

    Cortes-Maldonado, R.; Perez-Rodrigues, F.; Espinosa-Rosales, J.E.; Carballo-Sanchez, A.F.

    2011-01-01

    The magnetic response of irreversible type-II superconductor slabs subjected to in-plane rotating magnetic field is investigated by applying the circular, elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state models. Specifically, the models have been applied to explain experiments on a PbBi rotating disk in a fixed magnetic field Ha, parallel to the flat surfaces. Here, we have exploited the equivalency of the experimental situation with that of a fixed disk under the action of a parallel magnetic field, rotating in the opposite sense. The effect of both the magnitude H a of the applied magnetic field and its angle of rotation α s upon the magnetization of the superconductor sample is analyzed. When H a is smaller than the penetration field H p , the magnetization components, parallel and perpendicular to H a , oscillate with increasing the rotation angle. On the other hand, if the magnitude of the applied field, H a , is larger than H p , both magnetization components become constant functions of αs at large rotation angles. The evolution of the magnetic induction profiles inside the superconductor is also studied.

  20. Modifying a dynamic global vegetation model for simulating large spatial scale land surface water balances

    Directory of Open Access Journals (Sweden)

    G. Tang

    2012-08-01

    Full Text Available Satellite-based data, such as vegetation type and fractional vegetation cover, are widely used in hydrologic models to prescribe the vegetation state in a study region. Dynamic global vegetation models (DGVM simulate land surface hydrology. Incorporation of satellite-based data into a DGVM may enhance a model's ability to simulate land surface hydrology by reducing the task of model parameterization and providing distributed information on land characteristics. The objectives of this study are to (i modify a DGVM for simulating land surface water balances; (ii evaluate the modified model in simulating actual evapotranspiration (ET, soil moisture, and surface runoff at regional or watershed scales; and (iii gain insight into the ability of both the original and modified model to simulate large spatial scale land surface hydrology. To achieve these objectives, we introduce the "LPJ-hydrology" (LH model which incorporates satellite-based data into the Lund-Potsdam-Jena (LPJ DGVM. To evaluate the model we ran LH using historical (1981–2006 climate data and satellite-based land covers at 2.5 arc-min grid cells for the conterminous US and for the entire world using coarser climate and land cover data. We evaluated the simulated ET, soil moisture, and surface runoff using a set of observed or simulated data at different spatial scales. Our results demonstrate that spatial patterns of LH-simulated annual ET and surface runoff are in accordance with previously published data for the US; LH-modeled monthly stream flow for 12 major rivers in the US was consistent with observed values respectively during the years 1981–2006 (R2 > 0.46, p < 0.01; Nash-Sutcliffe Coefficient > 0.52. The modeled mean annual discharges for 10 major rivers worldwide also agreed well (differences < 15% with observed values for these rivers. Compared to a degree-day method for snowmelt computation, the addition of the solar radiation effect on snowmelt

  1. A Numerical Simulation for Prediction of Infrared Radiation Emitted from Plain Surfaces with Different Geometries

    Directory of Open Access Journals (Sweden)

    Vakilabadi K.A.

    2017-08-01

    Full Text Available In this paper, infrared radiation exiting plain surfaces with different geometries is numerically simulated. Surfaces under consideration are assumed to have steady uniform heat generation inside. Moreover, the boundaries of the surfaces are considered to be at the surroundings temperature. Infrared radiation is calculated based on the temperature profile determined for the surface. The temperature profile of the surface is determined assuming the two dimensional heat conduction equations to govern the problem. The physical domain is transformed into the appropriate computational domain and the governing equation is mapped into the suitable forms in the new coordinate system of variables. After that the temperature profile of the surface is computed, the infrared radiation distribution of the surface is evaluated based on the equations given in the manuscript. The temperature profile as well as the IR images are given in the results section. It is concluded that the maximum value of infrared radiation of the surface occurs at the center. Moreover, it is concluded that among surfaces with equal areas, the one having the largest perimeter has the least value of IR at its center.

  2. Durability of simulated waste glass: effects of pressure and formation of surface layers

    International Nuclear Information System (INIS)

    Wicks, G.G.; Mosley, W.C.; Whitkop, P.G.; Saturday, K.A.

    1981-01-01

    The leaching behavior of simulated Savannah River Plant (SRP) waste glass was studied at elevated pressures and anticipated storage temperatures. An integrated approach, which combined leachate solution analyses with both bulk and surface studies, was used to study the corrosion process. Compositions of leachates were evaluated by colorimetry and atomic absorption. Used in the bulk and surface analyses were optical microscopy, scanning electron microscopy, x-ray energy spectroscopy, wide-angle x-ray, diffraction, electron microprobe analysis, infrared reflectance spectroscopy, electron spectroscopy for chemical analysis, and Auger electron spectroscopy. Results from this study show that there is no significant adverse effect of pressure, up to 1500 psi and 90 0 C, on the chemical durability of simulated SPR waste glass leached for one month in deionized water. In addition, the leached glass surface layer was characterized by an adsorbed film rich in minor constituents from the glass. This film remained on the glass surface even after leaching in relatively alkaline solutions at elevated pressures at 90 0 C for one month. The sample surface area to volume of leachant ratios (SA/V) was 10:1 cm -1 and 1:10 cm -1 . The corrosion mechanisms and surface and subsurface layers produced will be discussed along with the potential importance of these results to repository storage

  3. Model-simulated trend of surface carbon monoxide for the 2001–2010 decade

    Science.gov (United States)

    Yoon, Jongmin; Pozzer, Andrea

    2015-04-01

    We present decadal trend estimates of surface carbon monoxide (CO) simulated using the atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy for Atmospheric Chemistry) based on the emission scenarios Representative Concentration Pathways (RCP) 8.5 for anthropogenic activity and Global Fire Emissions Database (GFED) v3.1 for biomass burning from 2001 through 2010. The spatial distribution of the modeled surface CO is evaluated with monthly data from the Measurements Of Pollution In The Troposphere (MOPITT) thermal infrared product. The global means of correlation coefficient and relative bias for the decade 2001-2010 are 0.95 and -4.29 %, respectively. We also find a reasonable correlation (R =0.78) between the trends of EMAC surface CO and full 10-year monthly records from ground-based observation (World Data Centre for Greenhouse Gases, WDCGG). Over western Europe, eastern USA, and northern Australia, the significant decreases in EMAC surface CO are estimated at -35.5±5.8, -59.6±9.1, and -13.7±9.5 ppbv per decade, respectively. In contrast, the surface CO increases by +8.9±4.8 ppbv per decade over southern Asia. A high correlation (R =0.92) between the changes in EMAC-simulated surface CO and total emission flux shows that the significant regional trends are attributed to the changes in primary and direct emissions from both anthropogenic activity and biomass burning.

  4. Patterned gradient surface for spontaneous droplet transportation and water collection: simulation and experiment

    International Nuclear Information System (INIS)

    Tan, Xianhua; Zhu, Yiying; Shi, Tielin; Tang, Zirong; Liao, Guanglan

    2016-01-01

    We demonstrate spontaneous droplet transportation and water collection on wedge-shaped gradient surfaces consisting of alternating hydrophilic and hydrophobic regions. Droplets on the surfaces are modeled and simulated to analyze the Gibbs free energy and free energy gradient distributions. Big half-apex angle and great wettability difference result in considerable free energy gradient, corresponding to large driving force for spontaneous droplet transportation, thus causing the droplets to move towards the open end of the wedge-shaped hydrophilic regions, where the Gibbs free energy is low. Gradient surfaces are then fabricated and tested. Filmwise condensation begins on the hydrophilic regions, forming wedge-shaped tracks for water collection. Dropwise condensation occurs on the hydrophobic regions, where the droplet size distribution and departure diameters are controlled by the width of the regions. Condensate water from both the hydrophilic and hydrophobic regions are collected directionally to the open end of the wedge-shaped hydrophilic regions, agreeing with the simulations. Directional droplet transport and controllable departure diameters make the branched gradient surfaces more efficient than smooth surfaces for water collection, which proves that gradient surfaces are potential in water collection, microfluidic devices, anti-fogging and self-cleaning. (paper)

  5. COMPUTER SIMULATIONS OF SPRAY RETENTION BY A 3D BARLEY PLANT: EFFECT OF FORMULATION SURFACE TENSION.

    Science.gov (United States)

    Massinon, M; De Cock, N; Salah, S Ouled Taleb; Lebeau, F

    2015-01-01

    A spray retention model was used in this study to explore theoretically the effect of a range of mixture surface tension on the spray retention and the variability of deposits. The spray retention model was based on an algorithm that tested whether droplets from a virtual nozzle intercepted a 3D plant model. If so, the algorithm determined the contribution of the droplet to the overall retention depending on the droplet impact behaviour on the leaf; adhesion, rebound or splashing. The impact outcome probabilities, function of droplet impact energy, were measured using high-speed imaging on an excised indoor grown barley leaf (BBCH12) both for pure water (surface tension of 0.072 N/m) and a non-ionic super spreader (static surface tension of 0.021 N/m) depending on the surface orientation. The modification of spray mixture properties in the simulations was performed by gradually changing the spray the droplet impact probabilities between pure water and a solution with non-ionic surfactant exhibiting super spreading properties. The plant architecture was measured using a structured light scanner. The final retention was expressed as the volume of liquid retained by the whole plant relative to the projected leaf surface area in the main spray direction. One hundred simulations were performed at different volumes per hectare and flat-fan nozzles for each formulation surface tension. The coefficient of variation was used as indicator of variability of deposits. The model was able to discriminate between mixture surface tension. The spray retention increased as the mixture surface tension decreased. The variability of deposits also decreased as the surface tension decreased. The proposed modelling approach provides a suited tool for sensitivity analysis: nozzle kind, pressure, volume per hectare applied, spray mixture physicochemical properties, plant species, growth stage could be screened to determine the best spraying characteristics maximizing the retention. The

  6. Numerical Simulation of Turbulent Half-corrugated Channel Flow by Hydrophilic and Hydrophobic Surfaces

    Directory of Open Access Journals (Sweden)

    M. R. Rastan

    2018-03-01

    Full Text Available In the first part of the present study, a two dimensional half-corrugated channel flow is simulated at Reynolds number of 104, in no-slip condition (hydrophilic surfaces( using various low Reynolds turbulence models as well as standard k-ε model; and an appropriate turbulence model (k-ω 1998 model( is proposed. Then, in order to evaluate the proposed solution method in simulation of flow adjacent to hydrophobic surfaces, turbulent flow is simulated in simple channel and the results are compared with the literature. Finally, two dimensional half-corrugated channel flow at Reynolds number of 104 is simulated again in vicinity of hydrophobic surfaces for varoius slip lengths. The results show that this method is capable of drag reduction in such a way that an increase of 200 μm in slip length leads to a massive drag reduction up to 38%. In addition, to access a significant drag reduction in turbulent flows, the non-dimensionalized slip length should be larger than the minimum.

  7. Auger neutralization of He{sup +} on Cu surfaces: Simulation of azimuthal scans

    Energy Technology Data Exchange (ETDEWEB)

    Goebl, D., E-mail: dominik.goebl@jku.at [Institut für Experimentalphysik, Abteilung für Atom- und Oberflächenphysik, Johannes Kepler Universität Linz, 4040 Linz (Austria); Primetzhofer, D. [Institutionen för Fysik och Astronomi, Uppsala Universitet, Box 516, S-751 20 Uppsala (Sweden); Abad, E. [Departamento de Física Teórica de la Materia Condensada C5, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Monreal, R.C. [Departamento de Física Teórica de la Materia Condensada C5, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Centro de Investigación de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Bauer, P. [Institut für Experimentalphysik, Abteilung für Atom- und Oberflächenphysik, Johannes Kepler Universität Linz, 4040 Linz (Austria)

    2013-12-15

    Charge exchange by Auger neutralization (AN) plays an important role in surface analysis techniques such as low energy ion scattering (LEIS). Recent advances in the theoretical description of AN have included a model based on a linear combination of atomic orbitals (LCAO) approach, which is able to calculate accurate neutralization probabilities of He{sup +} due to AN in LEIS. Previous investigations have shown that the neutralization probability is strongly influenced by the distance dependent shift of the He 1s level. In this study simulations of He{sup +} scattered from Cu(1 0 0) and Cu(1 1 0) surfaces at fixed azimuth angles are presented. Additionally, the azimuth dependence of ion- and neutral-yield for He{sup +} scattered from Cu(1 0 0) is simulated and compared to experimental data. Calculations were performed using the LCAO model in combination with molecular dynamics simulations. The excellent agreement between simulation and experiment provides evidence that the obtained values for the level shift are a characteristic property of the surface.

  8. Ion beam processing of surfaces and interfaces. Modeling and atomistic simulations

    International Nuclear Information System (INIS)

    Liedke, Bartosz

    2011-01-01

    Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund's sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called TRIDER (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as 'cleanest' possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In general

  9. Ion beam processing of surfaces and interfaces. Modeling and atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Liedke, Bartosz

    2011-03-24

    Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund's sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called TRIDER (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as 'cleanest' possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In

  10. Surface Roughness of Composite Resins after Simulated Toothbrushing with Different Dentifrices.

    Science.gov (United States)

    Monteiro, Bruna; Spohr, Ana Maria

    2015-07-01

    The aim of the study was to evaluate, in vitro, the surface roughness of two composite resins submitted to simulated toothbrushing with three different dentifrices. Totally, 36 samples of Z350XT and 36 samples of Empress Direct were built and randomly divided into three groups (n = 12) according to the dentifrice used (Oral-B Pro-Health Whitening [OBW], Colgate Sensitive Pro-Relief [CS], Colgate Total Clean Mint 12 [CT12]). The samples were submitted to 5,000, 10,000 or 20,000 cycles of simulated toothbrushing. After each simulated period, the surface roughness of the samples was measured using a roughness tester. According to three-way analysis of variance, dentifrice (P = 0.044) and brushing time (P = 0.000) were significant. The composite resin was not significant (P = 0.381) and the interaction among the factors was not significant (P > 0.05). The mean values of the surface roughness (µm) followed by the same letter represent no statistical difference by Tukey's post-hoc test (P composite resins. The dentifrice OBW caused a higher surface roughness in both composite resins.

  11. Atomistic simulations of surface segregation of defects in solid oxide electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hark B., E-mail: hblee@stanford.edu [Department of Mechanical Engineering, Stanford University, CA 94305-4040 (United States); Prinz, Friedrich B., E-mail: fprinz@stanford.edu [Department of Mechanical Engineering, Stanford University, CA 94305-4040 (United States); Cai, Wei, E-mail: caiwei@stanford.edu [Department of Mechanical Engineering, Stanford University, CA 94305-4040 (United States)

    2010-04-15

    We performed atomistic simulations of yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) to study the segregation of point defects near (1 0 0) surfaces. A hybrid Monte Carlo-molecular dynamics algorithm was developed to sample the equilibrium distributions of dopant cations and oxygen vacancies. The simulations predict an increase of dopant concentration near the surface, which is consistent with experimental observations. Oxygen vacancies are also found to segregate in the first anion layer beneath the surface and to be depleted in the subsequent anion layers. While the ionic size mismatch between dopant and host cations has been considered as a driving force for dopant segregation to the surface, our simulations show that the correlation between individual point defects plays a dominant role in determining their equilibrium distributions. This correlation effect leads to more pronounced dopant segregation in GDC than in YSZ, even though the size mismatch between dopant and host cations is much greater in YSZ than in GDC.

  12. Monte Carlo simulations of temperature-programmed and isothermal desorption from single-crystal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lombardo, S.J. (California Inst. of Tech., Pasadena, CA (USA). Dept. of Chemical Engineering Lawrence Berkeley Lab., CA (USA))

    1990-08-01

    The kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H{sub 2} on Mo(100); and H{sub 2} on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H{sub 2} coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H{sub 2} coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.

  13. Simulation insight into the cytochrome c adsorption on graphene and graphene oxide surfaces

    Science.gov (United States)

    Zhao, Daohui; Li, Libo; Zhou, Jian

    2018-01-01

    Graphene-based materials might serve as an ideal platform for the regulation and promotion of metalloprotein electron transfer (ET); however, the underpinning mechanism at the molecular level has not yet been fully revealed. The orientation of cytochrome c (Cyt c) on surfaces is vital for ET. In this work, the orientation of Cyt c on graphene and graphene oxide (GO) surfaces, as well as the dominant driving forces, the conformational change and the ET pathways were investigated by molecular dynamics simulations. The results show that Cyt c is adsorbed onto the GO surface mainly through lysine residues; whereas hydrophobic interaction contributes to the Cyt c adsorption on graphene surface. There is no significant conformational change of Cyt c upon adsorption. The heme plane of Cyt c tends to be horizontally oriented and far away from the graphene surface, which is not conducive to ET. On the GO surface, the heme plane is slightly deviated from the normal direction to the surface and the axial ligand Met80 is much closer to the surface, which facilitates the ET. These findings shed some light on the ET mechanism of Cyt c on graphene-based materials and provide guidance for the development of bionic electronic devices.

  14. Theory and Monte-Carlo simulation of adsorbates on corrugated surfaces

    DEFF Research Database (Denmark)

    Vives, E.; Lindgård, P.-A.

    1993-01-01

    -phase between the commensurate and incommensurate phase stabilized by defects. Special attention has been given to the study of the epitaxial rotation angles of the different phases. Available experimental data is in agreement with the simulations and with a general theory for the epitaxial rotation which takes......Phase transitions in systems of adsorbed molecules on corrugated surfaces are studied by means of Monte Carlo simulation. Particularly, we have studied the phase diagram of D2 on graphite as a function of coverage and temperature. We have demonstrated the existence of an intermediate gamma...

  15. Pulsed melting of silicon (111) and (100) surfaces simulated by molecular dynamics

    International Nuclear Information System (INIS)

    Abraham, F.F.; Broughton, J.Q.

    1986-01-01

    The pulsed heating of Si (100) and (111) surfaces has been simulated by molecular dynamics. The (111) crystal-melt interface propagates by layer-by-layer growth whereas the (100) interface grows in a continuous fashion. The equilibrium crystal-melt interface is sharp for the (111) orientation and broad for the (100) orientation. These simulations are the first use of nonpairwise potentials to study interfaces between condensed phases, and the results support models of interfaces which heretofore had to be deduced from indirect experimental information

  16. Simulation of self-assembled nanopatterns in binary alloys on the fcc(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Sebastian

    2008-07-01

    In this PhD thesis, we study the heteroepitaxial crystal growth by means of Monte Carlo simulations. Of particular interest in this work is the influence of the lattice mismatch of the adsorbates relative to the substrate on surface structures. In the framework of an off-lattice model, we consider one monolayer of adsorbate and investigate the emerging nanopatterns in equilibrium and their formation during growth. In chapter 1, a brief introduction is given, which describes the role of computer simulations in the field of the physics of condensed matter. Chapter 2 is devoted to some technical basics of experimental methods of molecular beam epitaxy and the theoretical description. Before a model for the simulation can be designed, it is necessary to make some considerations of the single processes which occur during epitaxial growth. For that purpose we look at an experimental setup and extract the main microscopic processes. Afterwards a brief overview of different theoretical concepts describing that physical procedures is given. In chapter 3, the model used in the simulations is presented. The aim is to investigate the growth of an fcc crystal in the [111] direction. In order to keep the simulation times within a feasible limit a simple pair potential, the Lennard-Jones potential, with continuous particle positions is used, which are necessary to describe effects resulting from the atomic mismatch in the crystal. Furthermore the detailed algorithm is introduced which is based on the idea to calculate the barrier of each diffusion event and to use the barriers in a rejection-free method. Chapter 4 is attended to the simulation of equilibrium. The influence of different parameters on the emerging structures in the first monolayer upon the surface, which is completely covered with two adsorbate materials, is studied. Especially the competition between binding energy and strain leads to very interesting pattern formations like islands or stripes. In chapter 5 the

  17. Nonequilibrium Molecular Simulations of New Ionic Lubricants at Metallic Surfaces: Prediction of the Friction.

    Science.gov (United States)

    Mendonça, Ana C F; Pádua, Agílio A H; Malfreyt, Patrice

    2013-03-12

    We report nonequilibrium molecular dynamics of ionic liquids interacting with metallic surfaces. A specific set of interaction parameters for ionic liquids composed of alkylammonium cations and alkylsulfonate anions with an iron surface, which has been previously developed (J. Chem. Theory Comput.2012, 8, 3348) is used here. We develop a procedure for a quantitative prediction of the friction coefficient at different loads and shear rates. The simulated friction coefficient agrees very well with the available experimental ones. The dependence of friction on the load, shear velocity, surface topology, and length of alkyl side chains in the ionic liquid is also investigated. The changes in the frictional forces are explained in terms of the specific arrangements and orientations of groups forming the ionic liquid at the vicinity of the surface.

  18. Dust generation mechanisms under powerful plasma impacts to the tungsten surfaces in ITER ELM simulation experiments

    International Nuclear Information System (INIS)

    Makhlaj, V.A.; Garkusha, I.E.; Aksenov, N.N.; Chuvilo, A.A.; Chebotarev, V.V.; Landman, I.; Malykhin, S.V.; Pestchanyi, S.; Pugachov, A.T.

    2013-01-01

    In recent tokamak simulation experiments with the QSPA Kh-50 facility several mechanisms of dust generation from tungsten surfaces under ITER ELM-like energy loads have been identified. Here cracking and melting are reported. The brittle destruction dominates after a few transient impacts when a network of major cracks forms on the surface. Bifurcation of major cracks results in ejection of dust particles with sizes up to ∼30 μm. Dust generation occurs also after surface melting and following resolidification when fine crack networks along the grain boundaries develop. In this process the destruction is accompanied by bridge formation due to capillary tension across the fine cracks. Next impacts (even weak melt-free ones) can destroy those bridges, which produces considerable amounts of dust particles of nm-size dust. Surface modification after the repetitive plasma pulses also results in creation of nm-size dust

  19. Eco-hydrological process simulations within an integrated surface water-groundwater model

    DEFF Research Database (Denmark)

    Butts, Michael; Loinaz, Maria Christina; Bauer-Gottwein, Peter

    2014-01-01

    Integrated water resources management requires tools that can quantify changes in groundwater, surface water, water quality and ecosystem health, as a result of changes in catchment management. To address these requirements we have developed an integrated eco-hydrological modelling framework...... that allows hydrologists and ecologists to represent the complex and dynamic interactions occurring between surface water, ground water, water quality and freshwater ecosystems within a catchment. We demonstrate here the practical application of this tool to two case studies where the interaction of surface...... water and ground water are important for the ecosystem. In the first, simulations are performed to understand the importance of surface water-groundwater interactions for a restored riparian wetland on the Odense River in Denmark as part of a larger investigation of water quality and nitrate retention...

  20. An Efficient Surface Algorithm for Random-Particle Simulation of Vorticity and Heat Transport

    Science.gov (United States)

    Smith, P. A.; Stansby, P. K.

    1989-04-01

    A new surface algorithm has been incorporated into the random-vortex method for the simulation of 2-dimensional laminar flow, in which vortex particles are deleted rather than reflected as they cross a solid surface. This involves a modification to the strength and random walk of newly created vortex particles. Computations of the early stages of symmetric, impulsively started flow around a circular cylinder for a wide range of Reynolds numbers demonstrate that the number of vortices required for convergence is substantially reduced. The method has been further extended to accommodate forced convective heat transfer where temperature particles are created at a surface to satisfy the condition of constant surface temperature. Vortex and temperature particles are handled together throughout each time step. For long runs, in which a steady state is reached, comparison is made with some time-averaged experimental heat transfer data for Reynolds numbers up to a few hundred. A Karman vortex street occurs at the higher Reynolds numbers.

  1. Molecular simulation insights on the in vacuo adsorption of amino acids on graphene oxide surfaces with varying surface oxygen densities

    Energy Technology Data Exchange (ETDEWEB)

    Rahmani, Farzin; Nouranian, Sasan, E-mail: sasan@olemiss.edu; Mahdavi, Mina [University of Mississippi, Department of Chemical Engineering (United States); Al-Ostaz, Ahmed [University of Mississippi, Department of Civil Engineering (United States)

    2016-11-15

    In this fundamental study, a series of molecular dynamics simulations were performed in vacuo to investigate the energetics and select geometries of 20 standard amino acids (AAs) on pristine graphene (PG) and graphene oxide (GO) surfaces as a function of graphene surface oxygen density. These interactions are of key interest to graphene/biomolecular systems. Our results indicate that aromatic AAs exhibit the strongest total interactions with the PG surfaces due to π-π stacking. Tryptophan (Trp) has the highest aromaticity due to its indole side chain and, hence, has the strongest interaction among all AAs (−16.66 kcal/mol). Aliphatic, polar, and charged AAs show various levels of affinity to the PG sheets depending on the strength of their side chain hydrophobic interactions. For example, arginine (Arg) with its guanidinium side chain exhibits the strongest interaction with the PG sheets (−13.81 kcal/mol) following aromatic AAs. Also, glycine (Gly; a polar AA) has the weakest interaction with the PG sheets (−7.29 kcal/mol). When oxygen-containing functional groups are added to the graphene sheets, the π-π stacking in aromatic AAs becomes disrupted and perfect parallelism of the aromatic rings is lost. Moreover, hydrogen bonding and/or electrostatic interactions become more pronounced. Charged AAs exhibit the strongest interactions with the GO surfaces. In general, the AA-GO interactions increase with increasing surface oxygen density, and the effect is more pronounced at higher O/C ratios. This study provides a quantitative measure of AA-graphene interactions for the design and tuning of biomolecular systems suitable for biosensing, drug delivery, and gene delivery applications.

  2. Free surface simulation of a two-layer fluid by boundary element method

    Directory of Open Access Journals (Sweden)

    Weoncheol Koo

    2010-09-01

    Full Text Available A two-layer fluid with free surface is simulated in the time domain by a two-dimensional potential-based Numerical Wave Tank (NWT. The developed NWT is based on the boundary element method and a leap-frog time integration scheme. A whole domain scheme including interaction terms between two layers is applied to solve the boundary integral equation. The time histories of surface elevations on both fluid layers in the respective wave modes are verified with analytic results. The amplitude ratios of upper to lower elevation for various density ratios and water depths are also compared.

  3. Mars Mission Surface Operation Simulation Testing of Lithium-Ion Batteries

    Science.gov (United States)

    Smart, M. C.; Bugga, R.; Whitcanack, L. D.; Chin, K. B.; Davies, E. D.; Surampudi, S.

    2003-01-01

    The objectives of this program are to 1) Assess viability of using lithium-ion technology for future NASA applications, with emphasis upon Mars landers and rovers which will operate on the planetary surface; 2) Support the JPL 2003 Mars Exploration Rover program to assist in the delivery and testing of a 8 AHr Lithium-Ion battery (Lithion/Yardney) which will power the rover; 3) Demonstrate applicability of using lithium-ion technologyfor future Mars applications: Mars 09 Science Laboratory (Smart Lander) and Future Mars Surface Operations (General). Mission simulation testing was carried out for cells and batteries on the Mars Surveyor 2001 Lander and the 2003 Mars Exploration Rover.

  4. MD simulation: determination of the physical properties and surface vaporization analysis of beryllium armours

    International Nuclear Information System (INIS)

    Prinzio, M. Di; Aquaro, D.

    2006-01-01

    The erosion of the divertor and of the first wall determined on the base of the anticipated operating conditions, is a critical issue that could affect the performance and the operating schedule of the nuclear fusion reactor ITER. This paper deals with the analysis of beryllium thermal properties by means of MD simulations, in order to better predict thermal behaviour of beryllium armoured PFCs in fusion devices. The importance of this analysis is clearly connected to thermal response evaluation of PFCs to high heat flux exposure, during off-normal events and Edge Localized Modes. The ensuing strong over-heating, in fact, produces material ablation through vaporization of surface material layers and possible loss of melting material. The overall PFCs erosion has bearings on plasma contamination, due to eroded material transport, and components lifetime, due to armour thickness reduction. An important feature of beryllium is its high vapour pressure. During thermal transients the strong vaporization keeps surface temperature relatively low but eroded thickness results high as well. Small changes in beryllium vapour pressure produce not negligible differences in thermal analyses results. On the basis of available force fields, classical Molecular Dynamics simulations have been carried out in order to better understand surface vaporization in tokamak conditions and to evaluate the effect of beryllium oxides formation. This effect has been successfully modelled by MD simulation, carried out with Moldy code. Morse stretching and bending potential for Be-O bond simulation have been used, and partial charges method, accounting for molecular polarity, has been employed. Since during short thermal transients, such as ELMs, only a few microns of Be armour will be overheated and reach melting threshold, the effective thermal conductivity is very important in determining the temperature evolution of surface layers and the ensuing erosion. Thermal conductivity can be evaluated

  5. Using an In-Class Simulation in the First Accounting Class: Moving from Surface to Deep Learning

    Science.gov (United States)

    Phillips, Mary E.; Graeff, Timothy R.

    2014-01-01

    As students often find the first accounting class to be abstract and difficult to understand, the authors designed an in-class simulation as an intervention to move students toward deep learning and away from surface learning. The simulation consists of buying and selling merchandise and accounting for transactions. The simulation is an effective…

  6. Investigating surface and subsurface physical properties of small bodies from light scattering observations and simulations

    Science.gov (United States)

    Levasseur-Regourd, A. C.; Hadamcik, E.; Lasue, J.; Renard, J. B.

    Investigating surface and subsurface physical properties of small bodies from light scattering observations and simulations A.C. Levasseur-Regourd (1), E. Hadamcik (1), J. Lasue (1), J.B. Renard (2) (1) Université Pierre et Marie Curie-Paris6, UMR 7620, Aéronomie, BP-3, Verrières, 91371 France, (2) LPCE-CNRS, 3A av. Recherche Scientifique, Orléans, F-45071 France Investigating surface and subsurface physical properties of asteroids and comet nuclei is of major interest to i) assess future space missions and ii) constrain formation and evolution models. Our purpose is to infer such properties from the properties of solar light scattered by such media. We will first summarize recent remote polarimetric observations of small bodies, which confirm the main characteristics of the variation of the linear polarization of solar scattered light in the visible domain with the scattering geometry and the wavelength (1). To interpret such characteristics in terms of physical properties of the regoliths (e.g. albedo, size distribution, complex refractive index, porosity), experimental and numerical simulations on various types of particles and aggregates are mandatory, together with some comparisons between experimental and numerical simulations (2,3). We will thus present recent results of such simulations (for dust around bright comets, for core-mantle particles, for loose deposited transparent and dark materials), and point out the trends already suggested by this approach. Finally, we will mention future key observations and elaborate simulations, which could solve open questions about surface and subsurface properties of small bodies. References 1. Levasseur-Regourd et al., ASR 37, 161, 2006. 2. Hadamcik et al., JQSRT 100, 143, 2006. 3. Lasue et al., JQSRT 100, 220, 2006.

  7. Surface roughness effect on ultracold neutron interaction with a wall and implications for computer simulations

    OpenAIRE

    Steyerl, A.; Malik, S. S.; Desai, A. M.; Kaufman, C.

    2009-01-01

    We review the diffuse scattering and the loss coefficient in ultracold neutron reflection from slightly rough surfaces, report a surprising reduction in loss coefficient due to roughness, and discuss the possibility of transition from quantum treatment to ray optics. The results are used in a computer simulation of neutron storage in a recent neutron lifetime experiment that re-ported a large discrepancy of neutron lifetime with the current particle data value. Our partial re-analysis suggest...

  8. Simulating measures of wood density through the surface by Compton scattering

    International Nuclear Information System (INIS)

    Penna, Rodrigo; Oliveira, Arno H.; Braga, Mario R.M.S.S.; Vasconcelos, Danilo C.; Carneiro, Clemente J.G.; Penna, Ariane G.C.

    2009-01-01

    Monte Carlo code (MCNP-4C) was used to simulate a nuclear densimeter for measuring wood densities nondestructively. An Americium source (E = 60 keV) and a NaI (Tl) detector were placed on a wood block surface. Results from MCNP shown that scattered photon fluxes may be used to determining wood densities. Linear regressions between scattered photons fluxes and wood density were calculated and shown correlation coefficients near unity. (author)

  9. Measurements and TCAD Simulations of Bulk and Surface Radiation Damage Effects

    CERN Document Server

    F. Moscatelli; G. M. Bilei; A. Morozzi; G.-F. Dalla Betta; R. Mendicino; M. Boscardin; N. Zorzi; L. Servoli; P. Maccagnani

    2016-01-01

    In this work we propose the application of a radiation damage model based on the introduction of deep level traps/recombination centers suitable for device level numerical simulation of radiation detectors at very high fluences (e.g. 1÷2×1016 1-MeV equivalent neutrons per square centimeter) combined with a surface damage model developed by using experimental parameters extracted from measurements from gamma irradiated p-type dedicated test structures.

  10. Simulation of RBS spectra with known 3D sample surface roughness

    Czech Academy of Sciences Publication Activity Database

    Malinský, Petr; Siegel, J.; Hnatowicz, Vladimír; Macková, Anna; Švorčík, V.

    2017-01-01

    Roč. 406, SEP (2017), s. 99-103 ISSN 0168-583X R&D Projects: GA MŠk LM2015056; GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:61389005 Keywords : computer simulation * surface roughness * AFM Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders OBOR OECD: Nuclear physics Impact factor: 1.109, year: 2016

  11. Simulation of Bridging at the Static Surface Filtration by CFD-DEM Coupling

    Science.gov (United States)

    Hund, David; Antonyuk, Sergiy; Ripperger, Siegfried

    2017-06-01

    To achieve a better understanding of the bridging mechanism at the static surface filtration, simulations of particle deposition at a three-dimensional pore model of a filter were performed. The simulations are used to investigate the total filter resistance, which results from interferences between filter medium, particles and fluid. Thereby a CFD (Computational Fluid Dynamics) method for flow simulation was coupled with a Discrete Element Method (DEM) which calculates the particle interactions. The results show that a built particle bridge influences the flow through an unclosed pore. It was concluded that bridging of open pores is hindered at high velocities of approach caused by increasing percentage of closed pores. Moreover, it could be shown, that the total filter resistance depends on the approaching velocity and shape of particles.

  12. Simulation of Bridging at the Static Surface Filtration by CFD-DEM Coupling

    Directory of Open Access Journals (Sweden)

    Hund David

    2017-01-01

    Full Text Available To achieve a better understanding of the bridging mechanism at the static surface filtration, simulations of particle deposition at a three-dimensional pore model of a filter were performed. The simulations are used to investigate the total filter resistance, which results from interferences between filter medium, particles and fluid. Thereby a CFD (Computational Fluid Dynamics method for flow simulation was coupled with a Discrete Element Method (DEM which calculates the particle interactions. The results show that a built particle bridge influences the flow through an unclosed pore. It was concluded that bridging of open pores is hindered at high velocities of approach caused by increasing percentage of closed pores. Moreover, it could be shown, that the total filter resistance depends on the approaching velocity and shape of particles.

  13. Role of land surface processes and diffuse/direct radiation partitioning in simulating the European climate

    Directory of Open Access Journals (Sweden)

    E. L. Davin

    2012-05-01

    Full Text Available The influence of land processes and in particular of diffuse/direct radiation partitioning on surface fluxes and associated regional-scale climate feedbacks is investigated using ERA-40 driven simulations over Europe performed with the COSMO-CLM2 Regional Climate Model (RCM. Two alternative Land Surface Models (LSMs, a 2nd generation LSM (TERRA_ML and a more advanced 3rd generation LSM (Community Land Model version 3.5, and two versions of the atmospheric component are tested, as well as a revised coupling procedure allowing for variations in diffuse/direct light partitioning at the surface, and their accounting by the land surface component.

    Overall, the RCM performance for various variables (e.g., surface fluxes, temperature and precipitation is improved when using the more advanced 3rd generation LSM. These improvements are of the same order of magnitude as those arising from a new version of the atmospheric component, demonstrating the benefit of using a realistic representation of land surface processes for regional climate simulations. Taking into account the variability in diffuse/direct light partitioning at the surface further improves the model performance in terms of summer temperature variability at the monthly and daily time scales. Comparisons with observations show that the RCM realistically captures temporal variations in diffuse/direct light partitioning as well as the evapotranspiration sensitivity to these variations. Our results suggest that a modest but consistent fraction (up to 3 % of the overall variability in summer temperature can be explained by variations in the diffuse to direct ratio.

  14. A New Method for Urban Storm Flood Inundation Simulation with Fine CD-TIN Surface

    Directory of Open Access Journals (Sweden)

    Zhifeng Li

    2014-05-01

    Full Text Available Urban storm inundation, which frequently has dramatic impacts on city safety and social life, is an emergent and difficult issue. Due to the complexity of urban surfaces and the variety of spatial modeling elements, the lack of detailed hydrological data and accurate urban surface models compromise the study and implementation of urban storm inundation simulations. This paper introduces a Constrained Delaunay Triangular Irregular Network (CD-TIN to model fine urban surfaces (based on detailed ground sampling data and subsequently employs a depression division method that refers to Fine Constrained Features (FCFs to construct computational urban water depressions. Storm-runoff yield is placed through mass conservation to calculate the volume of rainfall, runoff and drainage. The water confluences between neighboring depressions are provided when the water level exceeds the outlet of a certain depression. Numerical solutions achieved through a dichotomy are introduced to obtain the water level. Therefore, the continuous inundation process can be divided into different time intervals to obtain a series of inundation scenarios. The main campus of Beijing Normal University (BNU was used as a case study to simulate the “7.21” storm inundation event to validate the usability and suitability of the proposed methods. In comparing the simulation results with in-situ observations, the proposed method is accurate and effective, with significantly lower drainage data requirements being obtained. The proposed methods will also be useful for urban drainage design and city inundation emergency preparations.

  15. Simulated studies of wear and friction in total hip prosthesis components with various ball sizes and surface finishes

    Science.gov (United States)

    Swikert, M. A.; Johnson, R. L.

    1976-01-01

    Experiments were conducted on a newly designed total hip joint simulator. The apparatus closely simulates the complex motions and loads of the human hip in normal walking. The wear and friction of presently used appliance configurations and materials were determined. A surface treatment of the metal femoral ball specimens was applied to influence wear. The results of the investigation indicate that wear can be reduced by mechanical treatment of metal femoral ball surfaces. A metallographic examination and surface roughness measurements were made.

  16. Simulations of The Extreme Precipitation Event Enhanced by Sea Surface Temperature Anomaly over the Black Sea

    Science.gov (United States)

    Hakan Doǧan, Onur; Önol, Barış

    2016-04-01

    Istanbul Technical University, Aeronautics and Astronautics Faculty, Meteorological Engineering, Istanbul, Turkey In this study, we examined the extreme precipitation case over the Eastern Black Sea region of Turkey by using regional climate model, RegCM4. The flood caused by excessive rain in August 26, 2010 killed 12 people and the landslides in Rize province have damaged many buildings. The station based two days total precipitation exceeds 200 mm. One of the usual suspects for this extreme event is positive anomaly of sea surface temperature (SST) over the Black Sea where the significant warming trend is clear in the last three decades. In August 2010, the monthly mean SST is higher than 3 °C with respect to the period of 1981-2010. We designed three sensitivity simulations with RegCM4 to define the effects of the Black Sea as a moisture source. The simulation domain with 10-km horizontal resolution covers all the countries bordering the Black Sea and simulation period is defined for entire August 2010. It is also noted that the spatial variability of the precipitation produced by the reference simulation (Sim-0) is consistent with the TRMM data. In terms of analysis of the sensitivity to SST, we forced the simulations by subtracting 1 °C (Sim-1), 2 °C (Sim-2) and 3 °C (Sim-3) from the ERA-Interim 6-hourly SST data (considering only the Black Sea). The sensitivity simulations indicate that daily total precipitation for all these simulations gradually decreased based on the reference simulation (Sim-0). 3-hourly maximum precipitation rates for Sim-0, Sim-1, Sim-2 and Sim-3 are 32, 25, 13 and 10.5 mm respectively over the hotspot region. Despite the fact that the simulations signal points out the same direction, degradation of the precipitation intensity does not indicate the same magnitude for all simulations. It is revealed that 2 °C (Sim-2) threshold is critical for SST sensitivity. We also calculated the humidity differences from the simulation and these

  17. Simulating transport of nitrogen and phosphorus in a Cambisol after natural and simulated intense rainfall.

    Science.gov (United States)

    Kaufmann, Vander; Pinheiro, Adilson; Castro, Nilza Maria dos Reis

    2014-05-01

    Intense rainfall adversely affects agricultural areas, causing transport of pollutants. Physically-based hydrological models to simulate flows of water and chemical substances can be used to help decision-makers adopt measures which reduce such problems. The purpose of this paper is to evaluate the performance of SWAP and ANIMO models for simulating transport of water, nitrate and phosphorus nutrients, during intense rainfall events generated by a simulator, and during natural rainfall, on a volumetric drainage lysimeter. The models were calibrated and verified using daily time series and simulated rainfall measured at 10-minute intervals. For daily time-intervals, the Nash-Sutcliffe coefficient was 0.865 for the calibration period and 0.805 for verification. Under simulated rainfall, these coefficients were greater than 0.56. The pattern of both nitrate and phosphate concentrations in daily drainage flow under simulated rainfall was acceptably reproduced by the ANIMO model. In the simulated rainfall, loads of nitrate transported in surface runoff varied between 0.08 and 8.46 kg ha(-1), and in drainage form the lysimeter, between 2.44 and 112.57 kg ha(-1). In the case of phosphate, the loads transported in surface runoff varied between 0.002 and 0.504 kg ha(-1), and in drainage, between 0.005 and 1.107 kg ha(-1). The use of the two models SWAP and ANIMO shows the magnitudes of nitrogen and phosphorus fluxes transported by natural and simulated intense rainfall in an agricultural area with different soil management procedures, as required by decision makers. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Simulation calculations of physical sputtering and reflection coefficient of plasma-irradiated carbon surface

    International Nuclear Information System (INIS)

    Kawamura, T.; Ono, T.; Yamamura, Y.

    1994-08-01

    Physical sputtering yields from the carbon surface irradiated by the boundary plasma are obtained with the use of a Monte Carlo simulation code ACAT. The yields are calculated for many random initial energy and angle values of incident protons or deuterons with a Maxwellian velocity distribution, and then averaged. Here the temperature of the boundary plasma, the sheath potential and the angle δ between the magnetic field line and the surface normal are taken into account. A new fitting formula for an arrangement of the numerical data of sputtering yield is introduced, in which six fitting parameters are determined from the numerical results and listed. These results provide a way to estimate the erosion of carbon materials irradiated by boundary plasma. The particle reflection coefficients for deuterons and their neutrals from a carbon surface are also calculated by the same code and presented together with, for comparison, that for the case of monoenergetic normal incidence. (author)

  19. Coalbed Methane Production System Simulation and Deliverability Forecasting: Coupled Surface Network/Wellbore/Reservoir Calculation

    Directory of Open Access Journals (Sweden)

    Jun Zhou

    2017-01-01

    Full Text Available As an unconventional energy, coalbed methane (CBM mainly exists in coal bed with adsorption, whose productivity is different from conventional gas reservoir. This paper explains the wellbore pressure drop, surface pipeline network simulation, and reservoir calculation model of CBM. A coupled surface/wellbore/reservoir calculation architecture was presented, to coordinate the gas production in each calculation period until the balance of surface/wellbore/reservoir. This coupled calculation method was applied to a CBM field for predicting production. The daily gas production increased year by year at the first time and then decreased gradually after several years, while the daily water production was reduced all the time with the successive decline of the formation pressure. The production of gas and water in each well is almost the same when the structure is a star. When system structure is a dendritic surface system, the daily gas production ranked highest at the well which is the nearest to the surface system collection point and lowest at the well which is the farthest to the surface system collection point. This coupled calculation method could be used to predict the water production, gas production, and formation pressure of a CBM field during a period of time.

  20. Degradation of unglazed rough graphite-aluminium solar absorber surfaces in simulated acid and neutral rain

    International Nuclear Information System (INIS)

    Konttinen, P.; Lund, P.D.; Salo, T.

    2005-01-01

    Degradation mechanisms of unglazed solar absorber surfaces based on aluminium substrate were studied. Rough graphite-aluminium surfaces were total-immersion subjected to aerated and de-aerated simulated neutral and acid rain. Test conditions were based on calculated absorber stagnation temperature and global rain acidity measurements. Changes in optical properties, elemental composition and sample mass were examined by spectrometry, energy dispersive X-ray spectrometry and thermogravimetry, respectively. The absorbers exhibited almost no degradation at pH value of 3.5. At pH 5.5 alumina on the surface hydrated significantly degrading the optical properties of the surfaces severely in most cases. Therefore these absorber surfaces can not be recommended to be used in non-glazed applications if they are exposed to rain with pH exceeding ∼ 3.5-4.5. The total-immersion test needs to be developed further as the test results exhibited poor temperature and time dependency thus preventing accurate service lifetime estimates. Still, these tests were useful in determining favourable and non-favourable operating conditions for the absorber surfaces based on aluminium substrate. (author)

  1. Sub-discretized surface model with application to contact mechanics in multi-body simulation

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, S; Williams, J

    2008-02-28

    The mechanics of contact between rough and imperfectly spherical adhesive powder grains are often complicated by a variety of factors, including several which vary over sub-grain length scales. These include several traction factors that vary spatially over the surface of the individual grains, including high energy electron and acceptor sites (electrostatic), hydrophobic and hydrophilic sites (electrostatic and capillary), surface energy (general adhesion), geometry (van der Waals and mechanical), and elasto-plastic deformation (mechanical). For mechanical deformation and reaction, coupled motions, such as twisting with bending and sliding, as well as surface roughness add an asymmetry to the contact force which invalidates assumptions for popular models of contact, such as the Hertzian and its derivatives, for the non-adhesive case, and the JKR and DMT models for adhesive contacts. Though several contact laws have been offered to ameliorate these drawbacks, they are often constrained to particular loading paths (most often normal loading) and are relatively complicated for computational implementation. This paper offers a simple and general computational method for augmenting contact law predictions in multi-body simulations through characterization of the contact surfaces using a hierarchically-defined surface sub-discretization. For the case of adhesive contact between powder grains in low stress regimes, this technique can allow a variety of existing contact laws to be resolved across scales, allowing for moments and torques about the contact area as well as normal and tangential tractions to be resolved. This is especially useful for multi-body simulation applications where the modeler desires statistical distributions and calibration for parameters in contact laws commonly used for resolving near-surface contact mechanics. The approach is verified against analytical results for the case of rough, elastic spheres.

  2. Clinical application of synthesized brain surface imaging for preoperative simulation of brain biopsy under local anesthesia

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Yuko; Katada, Kazuhiro; Imai, Fumihiro; Fujisawa, Kazuhisa; Takeshita, Gen; Kanno, Tetsuo; Koga, Sukehiko (Fujita Health Univ., Toyoake, Aichi (Japan))

    1994-06-01

    Surface anatomy scanning (SAS) is the technique which permits the direct visualization of brain surface structures, including cortical sulci, guri, subcortical lesions as well as skin markings for craniotomy. A synthesized brain surface image is a technique that combines MR angiography (MRA) with SAS, and it proposed by us for detecting cerebral superficial veins with these surface structures on the same image. The purpose of this report is to present the result of applying the synthesized brain surface image to the preoperative simulation of biopsy under local anesthesia in 2 cases of multiple metastatic brain tumors. The parameters for SAS were TR/TE=50/40 msec, flip angle=60deg by the fast T[sub 2] technique using refocused FID in steady-state (STERF technique). SAS images were processed by gray scale reversal. The MRA data were acquired with two-dimensional time of flight (TOF) sequence after intravenous administration of Gd-DTPA. Before imaging, the water-filled plastic tubes were placed on the patients scalp as markings for craniotomy. Their positions were planned by the neurosurgeons. On SAS, the markings for burr-hole appeared located above the tumors. However on the synthesized brain surface images, the positions of burr-hole were considered to be inadequate, since superficial cerebral vein and sinus were also visualized in the area of the markings. From these results, the positions of burr-hole were reset to avoid the venous structures, and so as to include the lesions in operations. The biopsies were performed successfully and safely because the venous structure could be excluded from the operative field. By this technique it was easy to confirm the relationships among lesions, skin markings and venous structures. The technique described appears to be a useful method for preoperative simulation of biopsies for multiple metastatic brain tumors under local anesthesia. (author).

  3. Simulation and Theory of Antibody Binding to Crowded Antigen-Covered Surfaces.

    Directory of Open Access Journals (Sweden)

    Cristiano De Michele

    2016-03-01

    Full Text Available In this paper we introduce a fully flexible coarse-grained model of immunoglobulin G (IgG antibodies parametrized directly on cryo-EM data and simulate the binding dynamics of many IgGs to antigens adsorbed on a surface at increasing densities. Moreover, we work out a theoretical model that allows to explain all the features observed in the simulations. Our combined computational and theoretical framework is in excellent agreement with surface-plasmon resonance data and allows us to establish a number of important results. (i Internal flexibility is key to maximize bivalent binding, flexible IgGs being able to explore the surface with their second arm in search for an available hapten. This is made clear by the strongly reduced ability to bind with both arms displayed by artificial IgGs designed to rigidly keep a prescribed shape. (ii The large size of IgGs is instrumental to keep neighboring molecules at a certain distance (surface repulsion, which essentially makes antigens within reach of the second Fab always unoccupied on average. (iii One needs to account independently for the thermodynamic and geometric factors that regulate the binding equilibrium. The key geometrical parameters, besides excluded-volume repulsion, describe the screening of free haptens by neighboring bound antibodies. We prove that the thermodynamic parameters govern the low-antigen-concentration regime, while the surface screening and repulsion only affect the binding at high hapten densities. Importantly, we prove that screening effects are concealed in relative measures, such as the fraction of bivalently bound antibodies. Overall, our model provides a valuable, accurate theoretical paradigm beyond existing frameworks to interpret experimental profiles of antibodies binding to multi-valent surfaces of different sorts in many contexts.

  4. EFFECT OF SOIL TILLAGE AND PLANT RESIDUE ON SURFACE ROUGHNESS OF AN OXISOL UNDER SIMULATED RAIN

    Directory of Open Access Journals (Sweden)

    Elói Panachuki

    2015-02-01

    Full Text Available Surface roughness of the soil is formed by mechanical tillage and is also influenced by the kind and amount of plant residue, among other factors. Its persistence over time mainly depends on the fundamental characteristics of rain and soil type. However, few studies have been developed to evaluate these factors in Latossolos (Oxisols. In this study, we evaluated the effect of soil tillage and of amounts of plant residue on surface roughness of an Oxisol under simulated rain. Treatments consisted of the combination of the tillage systems of no-tillage (NT, conventional tillage (CT, and minimum tillage (MT with rates of plant residue of 0, 1, and 2 Mg ha-1 of oats (Avena strigosa Schreb and 0, 3, and 6 Mg ha-1 of maize (Zea mays L.. Seven simulated rains were applied on each experimental plot, with intensity of 60±2 mm h-1 and duration of 1 h at weekly intervals. The values of the random roughness index ranged from 2.94 to 17.71 mm in oats, and from 5.91 to 20.37 mm in maize, showing that CT and MT are effective in increasing soil surface roughness. It was seen that soil tillage operations carried out with the chisel plow and the leveling disk harrow are more effective in increasing soil roughness than those carried out with the heavy disk harrow and leveling disk harrow. The roughness index of the soil surface decreases exponentially with the increase in the rainfall volume applied under conditions of no tillage without soil cover, conventional tillage, and minimum tillage. The oat and maize crop residue present on the soil surface is effective in maintaining the roughness of the soil surface under no-tillage.

  5. Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model

    Directory of Open Access Journals (Sweden)

    H. W. Ter Maat

    2010-08-01

    Full Text Available This paper is a case study to investigate what the main controlling factors are that determine atmospheric carbon dioxide content for a region in the centre of The Netherlands. We use the Regional Atmospheric Modelling System (RAMS, coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C, and including also submodels for urban and marine fluxes, which in principle should include the dominant mechanisms and should be able to capture the relevant dynamics of the system. To validate the model, observations are used that were taken during an intensive observational campaign in central Netherlands in summer 2002. These include flux-tower observations and aircraft observations of vertical profiles and spatial fluxes of various variables.

    The simulations performed with the coupled regional model (RAMS-SWAPS-C are in good qualitative agreement with the observations. The station validation of the model demonstrates that the incoming shortwave radiation and surface fluxes of water and CO2 are well simulated. The comparison against aircraft data shows that the regional meteorology (i.e. wind, temperature is captured well by the model. Comparing spatially explicitly simulated fluxes with aircraft observed fluxes we conclude that in general latent heat fluxes are underestimated by the model compared to the observations but that the latter exhibit large variability within all flights. Sensitivity experiments demonstrate the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same tests also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations.

  6. Sensitivity of simulated South America climate to the land surface schemes in RegCM4

    Science.gov (United States)

    Llopart, Marta; da Rocha, Rosmeri P.; Reboita, Michelle; Cuadra, Santiago

    2017-12-01

    This work evaluates the impact of two land surface parameterizations on the simulated climate and its variability over South America (SA). Two numerical experiments using RegCM4 coupled with the Biosphere-Atmosphere Transfer Scheme (RegBATS) and the Community Land Model version 3.5 (RegCLM) land surface schemes are compared. For the period 1979-2008, RegCM4 simulations used 50 km horizontal grid spacing and the ERA-Interim reanalysis as initial and boundary conditions. For the period studied, both simulations represent the main observed spatial patterns of rainfall, air temperature and low level circulation over SA. However, with regard to the precipitation intensity, RegCLM values are closer to the observations than RegBATS (it is wetter in general) over most of SA. RegCLM also produces smaller biases for air temperature. Over the Amazon basin, the amplitudes of the annual cycles of the soil moisture, evapotranspiration and sensible heat flux are higher in RegBATS than in RegCLM. This indicates that RegBATS provides large amounts of water vapor to the atmosphere and has more available energy to increase the boundary layer thickness and cause it to reach the level of free convection (higher sensible heat flux values) resulting in higher precipitation rates and a large wet bias. RegCLM is closer to the observations than RegBATS, presenting smaller wet and warm biases over the Amazon basin. On an interannual scale, the magnitudes of the anomalies of the precipitation and air temperature simulated by RegCLM are closer to the observations. In general, RegBATS simulates higher magnitude for the interannual variability signal.

  7. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    KAUST Repository

    Cai, Mick Y.

    2015-04-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10. m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (~1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  8. Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators

    Science.gov (United States)

    Subramaniam, Vivek; Raja, Laxminarayan L.

    2017-06-01

    Recent experiments by Loebner et al. [IEEE Trans. Plasma Sci. 44, 1534 (2016)] studied the effect of a hypervelocity jet emanating from a coaxial plasma accelerator incident on target surfaces in an effort to mimic the transient loading created during edge localized mode disruption events in fusion plasmas. In this paper, we present a magnetohydrodynamic (MHD) numerical model to simulate plasma jet formation and plasma-surface contact in this coaxial plasma accelerator experiment. The MHD system of equations is spatially discretized using a cell-centered finite volume formulation. The temporal discretization is performed using a fully implicit backward Euler scheme and the resultant stiff system of nonlinear equations is solved using the Newton method. The numerical model is employed to obtain some key insights into the physical processes responsible for the generation of extreme stagnation conditions on the target surfaces. Simulations of the plume (without the target plate) are performed to isolate and study phenomena such as the magnetic pinch effect that is responsible for launching pressure pulses into the jet free stream. The simulations also yield insights into the incipient conditions responsible for producing the pinch, such as the formation of conductive channels. The jet-target impact studies indicate the existence of two distinct stages involved in the plasma-surface interaction. A fast transient stage characterized by a thin normal shock transitions into a pseudo-steady stage that exhibits an extended oblique shock structure. A quadratic scaling of the pinch and stagnation conditions with the total current discharged between the electrodes is in qualitative agreement with the results obtained in the experiments. This also illustrates the dominant contribution of the magnetic pressure term in determining the magnitude of the quantities of interest.

  9. Parallel Simulation of Three-Dimensional Free Surface Fluid Flow Problems

    International Nuclear Information System (INIS)

    BAER, THOMAS A.; SACKINGER, PHILIP A.; SUBIA, SAMUEL R.

    1999-01-01

    Simulation of viscous three-dimensional fluid flow typically involves a large number of unknowns. When free surfaces are included, the number of unknowns increases dramatically. Consequently, this class of problem is an obvious application of parallel high performance computing. We describe parallel computation of viscous, incompressible, free surface, Newtonian fluid flow problems that include dynamic contact fines. The Galerkin finite element method was used to discretize the fully-coupled governing conservation equations and a ''pseudo-solid'' mesh mapping approach was used to determine the shape of the free surface. In this approach, the finite element mesh is allowed to deform to satisfy quasi-static solid mechanics equations subject to geometric or kinematic constraints on the boundaries. As a result, nodal displacements must be included in the set of unknowns. Other issues discussed are the proper constraints appearing along the dynamic contact line in three dimensions. Issues affecting efficient parallel simulations include problem decomposition to equally distribute computational work among a SPMD computer and determination of robust, scalable preconditioners for the distributed matrix systems that must be solved. Solution continuation strategies important for serial simulations have an enhanced relevance in a parallel coquting environment due to the difficulty of solving large scale systems. Parallel computations will be demonstrated on an example taken from the coating flow industry: flow in the vicinity of a slot coater edge. This is a three dimensional free surface problem possessing a contact line that advances at the web speed in one region but transitions to static behavior in another region. As such, a significant fraction of the computational time is devoted to processing boundary data. Discussion focuses on parallel speed ups for fixed problem size, a class of problems of immediate practical importance

  10. Large-eddy simulation of open channel flow with surface cooling

    International Nuclear Information System (INIS)

    Walker, R.; Tejada-Martínez, A.E.; Martinat, G.; Grosch, C.E.

    2014-01-01

    Highlights: • Open channel flow comparable to a shallow tidal ocean flow is simulated using LES. • Unstable stratification is imposed by a constant surface cooling flux. • Full-depth, convection-driven, rotating supercells develop when cooling is applied. • Strengthening of cells occurs corresponding to an increasing of the Rayleigh number. - Abstract: Results are presented from large-eddy simulations of an unstably stratified open channel flow, driven by a uniform pressure gradient and with zero surface shear stress and a no-slip lower boundary. The unstable stratification is applied by a constant cooling flux at the surface and an adiabatic bottom wall, with a constant source term present to ensure the temperature reaches a statistically steady state. The structure of the turbulence and the turbulence statistics are analyzed with respect to the Rayleigh number (Ra τ ) representative of the surface buoyancy relative to shear. The impact of the surface cooling-induced buoyancy on mean and root mean square of velocity and temperature, budgets of turbulent kinetic energy (and components), Reynolds shear stress and vertical turbulent heat flux will be investigated. Additionally, colormaps of velocity fluctuations will aid the visualization of turbulent structures on both vertical and horizontal planes in the flow. Under neutrally stratified conditions the flow is characterized by weak, full-depth, streamwise cells similar to but less coherent than Couette cells in plane Couette flow. Increased Ra τ and thus increased buoyancy effects due to surface cooling lead to full-depth convection cells of significantly greater spanwise size and coherence, thus termed convective supercells. Full-depth convective cell structures of this magnitude are seen for the first time in this open channel domain, and may have important implications for turbulence analysis in a comparable tidally-driven ocean boundary layer. As such, these results motivate further study of the

  11. Revealing Surface Waters on an Antifreeze Protein by Fusion Protein Crystallography Combined with Molecular Dynamic Simulations.

    Science.gov (United States)

    Sun, Tianjun; Gauthier, Sherry Y; Campbell, Robert L; Davies, Peter L

    2015-10-08

    Antifreeze proteins (AFPs) adsorb to ice through an extensive, flat, relatively hydrophobic surface. It has been suggested that this ice-binding site (IBS) organizes surface waters into an ice-like clathrate arrangement that matches and fuses to the quasi-liquid layer on the ice surface. On cooling, these waters join the ice lattice and freeze the AFP to its ligand. Evidence for the generality of this binding mechanism is limited because AFPs tend to crystallize with their IBS as a preferred protein-protein contact surface, which displaces some bound waters. Type III AFP is a 7 kDa globular protein with an IBS made up two adjacent surfaces. In the crystal structure of the most active isoform (QAE1), the part of the IBS that docks to the primary prism plane of ice is partially exposed to solvent and has clathrate waters present that match this plane of ice. The adjacent IBS, which matches the pyramidal plane of ice, is involved in protein-protein crystal contacts with few surface waters. Here we have changed the protein-protein contacts in the ice-binding region by crystallizing a fusion of QAE1 to maltose-binding protein. In this 1.9 Å structure, the IBS that fits the pyramidal plane of ice is exposed to solvent. By combining crystallography data with MD simulations, the surface waters on both sides of the IBS were revealed and match well with the target ice planes. The waters on the pyramidal plane IBS were loosely constrained, which might explain why other isoforms of type III AFP that lack the prism plane IBS are less active than QAE1. The AFP fusion crystallization method can potentially be used to force the exposure to solvent of the IBS on other AFPs to reveal the locations of key surface waters.

  12. Ab initio STM and STS simulations on magnetic and nonmagnetic metallic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dick, Alexey

    2008-04-14

    The aim of this work was to provide an in-depth understanding of a new generation of scan- ning tunneling microscopy experiments, performed employing different regimes of the STM: the spectroscopy-mode (the so-called Fourier Transformed STM, FT-STM), and the spin-sensitive mode (the so-called spin-polarized STM, SP-STM). In the present thesis ab initio tools are proposed that are based on DFT calculations to theoretically predict and analyze such types of the STM. The first part of this thesis focusses on the simulation of FT-STM, the mode that allows to probe local dispersion properties of the electrons at the surface. In order to provide the theoretical counterpart of the experimental FT-STM spectra we have introduced a new implicit approach that is derived from Tersoff-Hamann theory of the STM. The importance of an accurate description of surface wavefunctions at 5-15 A above the surface as well as the spurious quantum- size effects have been discussed in detail together with approaches to obtain converged FT-STM images. We applied our method to FT-STM experiments performed on Ag(110) surfaces. In the second part of the thesis we discuss the modeling of the spin-resolved STM, the mode that allows to characterize the magnetic structure of a surface. As a case system we studied here the magnetically-ordered transition-metal nitride surface Mn{sub 3}N{sub 2}(010). Because SP-STM experiments did not allow a conclusive understanding of the surface structure, we have first employed ab initio thermodynamics to figure out the most stable magnetic and atomic configuration of the surface that are consistent with experiments. To simulate SP-STM images on the most stable Mn{sub 3}N{sub 2}(010) surface we have employed the spin-generalized transfer-Hamiltonian formalism, assuming that the tip wavefunctions have dominant radial symmetry (s-like tip). (orig.)

  13. A new design of the LAPS land surface scheme for use over and through heterogeneous and non-heterogeneous surfaces: Numerical simulations and tests

    Science.gov (United States)

    Mihailovic, Dragutin T.; Lazic, Jelena; Leśny, Jacek; Olejnik, Janusz; Lalic, Branislava; Kapor, Darko; Cirisan, Ana

    2010-05-01

    Numerical simulations and tests with the recently redesigned land-air parameterization scheme (LAPS) are presented. In all experiments, supported either by one-point micrometeorological, 1D or 3D simulations, the attention has been directed to: (1) comparison of simulation outputs, expressing the energy transfer over and through heterogeneous and non-heterogeneous surfaces, versus observations and (2) analysis of uncertainties occurring in the solution of the energy balance equation at the land-air interface. To check the proposed method for aggregation of albedo, "propagating hole" sensitivity tests with LAPS over a sandstone rock grid cell have been performed with the forcing meteorological data for July 17, 1999 in Baxter site, Philadelphia (USA). Micrometeorological and biophysical measurements from the surface experiments conducted over crops and apple orchard in Serbia, Poland, Austria and France were used to test the operation of LAPS in calculating surface fluxes and canopy environment temperatures within and above plant covers of different densities. In addition, sensitivity tests with single canopy covers over the Central Europe region and comparison against the observations taken from SYNOP data using 3D simulations were made. Validation of LAPS performances over a solid surface has been done by comparison of 2 m air temperature observations against 5-day simulations over the Sahara Desert rocky ground using 3D model. To examine how realistically the LAPS simulates surface processes over a heterogeneous surface, we compared the air temperature measured at 2 m and that predicted by the 1D model with the LAPS as the surface scheme. Finally, the scheme behaviour over urban surface was tested by runs over different parts of a hypothetical urban area. The corresponding 1D simulations were carried out with an imposed meteorological dataset collected during HAPEX-MOBILHY experiment at Caumont (France). The quantities predicted by the LAPS compare well with the

  14. Reinitialised versus continuous regional climate simulations using ALARO-0 coupled to the land surface model SURFEXv5

    Science.gov (United States)

    Berckmans, Julie; Giot, Olivier; De Troch, Rozemien; Hamdi, Rafiq; Ceulemans, Reinhart; Termonia, Piet

    2017-01-01

    Dynamical downscaling in a continuous approach using initial and boundary conditions from a reanalysis or a global climate model is a common method for simulating the regional climate. The simulation potential can be improved by applying an alternative approach of reinitialising the atmosphere, combined with either a daily reinitialised or a continuous land surface. We evaluated the dependence of the simulation potential on the running mode of the regional climate model ALARO coupled to the land surface model Météo-France SURFace EXternalisée (SURFEX), and driven by the ERA-Interim reanalysis. Three types of downscaling simulations were carried out for a 10-year period from 1991 to 2000, over a western European domain at 20 km horizontal resolution: (1) a continuous simulation of both the atmosphere and the land surface, (2) a simulation with daily reinitialisations for both the atmosphere and the land surface and (3) a simulation with daily reinitialisations of the atmosphere while the land surface is kept continuous. The results showed that the daily reinitialisation of the atmosphere improved the simulation of the 2 m temperature for all seasons. It revealed a neutral impact on the daily precipitation totals during winter, but the results were improved for the summer when the land surface was kept continuous. The behaviour of the three model configurations varied among different climatic regimes. Their seasonal cycle for the 2 m temperature and daily precipitation totals was very similar for a Mediterranean climate, but more variable for temperate and continental climate regimes. Commonly, the summer climate is characterised by strong interactions between the atmosphere and the land surface. The results for summer demonstrated that the use of a daily reinitialised atmosphere improved the representation of the partitioning of the surface energy fluxes. Therefore, we recommend using the alternative approach of the daily reinitialisation of the atmosphere for

  15. Simulation of bubble expansion and collapse in the vicinity of a free surface

    Energy Technology Data Exchange (ETDEWEB)

    Koukouvinis, P., E-mail: foivos.koukouvinis.1@city.ac.uk; Gavaises, M. [City University London, Northampton Square, London EC1V 0HB (United Kingdom); Supponen, O.; Farhat, M. [EPFL-LMH, Avenue de Cour 33 Bis, CH-1007, Lausanne (Switzerland)

    2016-05-15

    The present paper focuses on the numerical simulation of the interaction of laser-generated bubbles with a free surface, including comparison of the results with instances from high-speed videos of the experiment. The Volume Of Fluid method was employed for tracking liquid and gas phases while compressibility effects were introduced with appropriate equations of state for each phase. Initial conditions of the bubble pressure were estimated through the traditional Rayleigh Plesset equation. The simulated bubble expands in a non-spherically symmetric way due to the interference of the free surface, obtaining an oval shape at the maximum size. During collapse, a jet with mushroom cap is formed at the axis of symmetry with the same direction as the gravity vector, which splits the initial bubble to an agglomeration of toroidal structures. Overall, the simulation results are in agreement with the experimental images, both quantitatively and qualitatively, while pressure waves are predicted both during the expansion and the collapse of the bubble. Minor discrepancies in the jet velocity and collapse rate are found and are attributed to the thermodynamic closure of the gas inside the bubble.

  16. Monte Carlo simulation of stress corrosion cracking on smooth surface under non-uniform stress condition

    International Nuclear Information System (INIS)

    Suzuki, Hiromitsu; Tohgo, Keiichiro; Shimamura, Yoshinobu; Nakayama, Guen; Hirano, Takashi

    2008-01-01

    A Monte Carlo simulation model for the process of stress corrosion cracking (SCC) in structural metal materials under non-uniform stress condition has been proposed. The possible number of crack initiations is set for given space and initiation times for all cracks are assigned random numbers based on exponential distributions depending on stress level. Sites and lengths of the cracks are assigned by random numbers based on uniform distribution and normal distribution, respectively. Coalescence of cracks and subcritical crack growth are determined based on the fracture mechanics concept. Through the SCC process in the model, the influence of semi-elliptical surface cracks is taken into consideration. SCC simulations were carried out on a smooth surface under two kinds of non-uniform stress conditions such as residual stress distribution around a weld line. Multiple parallel cracks and multiple cracks along narrow high stress region were obtained depending on the stress distributions, respectively. Simulation results exhibit the applicability of the model to describe the SCC behavior observed in real structures. (author)

  17. Simulating Exposure Concentrations of Engineered Nanomaterials in Surface Water Systems: Release of WASP8

    Science.gov (United States)

    Knightes, C. D.; Bouchard, D.; Zepp, R. G.; Henderson, W. M.; Han, Y.; Hsieh, H. S.; Avant, B. K.; Acrey, B.; Spear, J.

    2017-12-01

    The unique properties of engineered nanomaterials led to their increased production and potential release into the environment. Currently available environmental fate models developed for traditional contaminants are limited in their ability to simulate nanomaterials' environmental behavior. This is due to an incomplete understanding and representation of the processes governing nanomaterial distribution in the environment and by scarce empirical data quantifying the interaction of nanomaterials with environmental surfaces. The well-known Water Quality Analysis Simulation Program (WASP) was updated to incorporate nanomaterial-specific processes, specifically hetero-aggregation with particulate matter. In parallel with this effort, laboratory studies were used to quantify parameter values parameters necessary for governing processes in surface waters. This presentation will discuss the recent developments in the new architecture for WASP8 and the newly constructed Advanced Toxicant Module. The module includes advanced algorithms for increased numbers of state variables: chemicals, solids, dissolved organic matter, pathogens, temperature, and salinity. This presentation will focus specifically on the incorporation of nanomaterials, with the applications of the fate and transport of hypothetical releases of Multi-Walled Carbon Nanotubes (MWCNT) and Graphene Oxide (GO) into the headwaters of a southeastern US coastal plains river. While this presentation focuses on nanomaterials, the advanced toxicant module can also simulate metals and organic contaminants.

  18. Surface Defects in Sheet Metal Forming: a Simulative Laboratory Device and Comparison with FE Analysis

    Science.gov (United States)

    Thuillier, Sandrine; Le Port, Alban; Manach, Pierre-Yves

    2011-08-01

    Surface defects are small concave imperfections that can develop during forming on outer convex panels of automotive parts like doors. They occur during springback steps, after drawing in the vicinity of bending over a curved line and flanging/hemming in the vicinity of the upper corner of a door. They can alter significantly the final quality of the automobile and it is of primary importance to deal with them as early as possible in the design of the forming tools. The aim of this work is to reproduce at the laboratory scale such a defect, in the case of the flanging along a curved edge, made of two orthogonal straight part of length 50 mm and joint by a curved line. A dedicated device has been designed and steel samples were tested. Each sample was measured initially (after laser cutting) and after flanging, with a 3D measuring machine. 2D profiles were extracted and the curvature was calculated. Surface defects were defined between points where the curvature sign changed. Isovalues of surface defect depth could then be plotted, thus displaying also the spatial geometry on the part surface. An experimental database has been created on the influence of process parameters like the flanging height and the flanging radius. Numerical simulations have been performed with the finite element code Abaqus to predict the occurrence of such surface defects and to analyze stress and strain distribution within the defect area.

  19. Numerical simulation of the double pits stress concentration in a curved casing inner surface

    Directory of Open Access Journals (Sweden)

    Wei Yan

    2016-12-01

    Full Text Available Sour or sweet oil fields development is common in recent years. Casing and tubing are usually subjected to pitting corrosion because of exposure to the strong corrosion species, such as CO2, H2S, and saline water. When the corrosion pits formed in the casing inner surface, localized stress concentration will occur and the casing strength will be degraded. Thus, it is essential to evaluate the degree of stress concentration factor accurately. This article performed a numerical simulation on double pits stress concentration factor in a curved inner surface using the finite element software ABAQUS. The results show that the stress concentration factor of double pits mainly depends on the ratio of two pits distance to the pit radius (L/R. It should not be only assessed by the absolute distance between the two pits. When the two pits are close and tangent, the maximum stress concentration factor will appear on the inner tangential edges. Stress concentration increased by double pits in a curved casing inner surface is more serious than that in a flat surface. A correction factor of 1.9 was recommended in the curved inner surface double pits stress concentration factor predict model.

  20. Atomic-Level Simulation Study of n-Hexane Pyrolysis on Silicon Carbide Surfaces.

    Science.gov (United States)

    Sajib, Md Symon Jahan; Samieegohar, Mohammadreza; Wei, Tao; Shing, Katherine

    2017-10-24

    Ethylene production plays a key role in the petrochemical industry. The severe operation conditions of ethylene thermal cracking, such as high-temperature and coke-formation, pose challenges for the development of new corrosion-resistant and coking-resistant materials for ethylene reactor radiant coils tubes (RCTs). We investigated the performance of ceramic materials such as silicon carbide (SiC) in severe pyrolysis conditions by using reactive force field molecular dynamics (ReaxFF MD) simulation method. Our results indicate that β-SiC surface remains fully stable at 1500 K, whereas increased temperature results in melted interface. At 2500 K, fully grown cross-linked-graphene-like polycyclic aromatic hydrocarbon coking structure on SiC surfaces was observed. Such coking was particularly severe in the carbon-side of the surface slab. The coking structures were mainly derived from surface atoms at the initial 3.0 ns, as a result of the loss of interfacial hydroxyl layer and further hydrothermal corrosion. The SiC substrate surface enhances the ethylene cracking rate and also leads to different intermediate-state compounds. Our fundamental research will have significant and broad impact on both petrochemical industry and academic research in materials science, petrochemistry, and combustion chemistry.

  1. Path planning and kinematics simulation of surfacing cladding for hot forging die

    Directory of Open Access Journals (Sweden)

    Wang Huajun

    2015-01-01

    Full Text Available During the course of their work, a variety of damage and failure of hot forging die occurs and seriously affect the service life. Multi-layer metal hot forging die with functionally graded material structure can effectively extend the service life. In this paper, According to the needs of strengthening forging cavity, the CAD model of surfacing forming center was designed. Based on technological requirements of surface cladding for die cavity, the coupled movement equation of weld torch was established, and the trajectory of welding positioner and Cartesian robot kinematics was solved. The weld torch path was planned, according to the typical methods used in plane welding, and the surfacing path data was extracted by the secondary development of UG/OPEN. Then the kinematics solver program, which can output the control function of motion simulation, was written in MATLAB to solve the kinematics equation. Finally, in UG NX7.5, the kinematics simulation model was built to verify the correctness of mathematical model and the rationality of welding path planning. The above studies can provide a technical support for the die repair and manufacturing of a multilayer metal forging die.

  2. Molecular dynamics simulations of ejecta production from sinusoidal tin surfaces under supported and unsupported shocks

    Science.gov (United States)

    Wu, Bao; Wu, FengChao; Zhu, YinBo; Wang, Pei; He, AnMin; Wu, HengAn

    2018-04-01

    Micro-ejecta, an instability growth process, occurs at metal/vacuum or metal/gas interface when compressed shock wave releases from the free surface that contains surface defects. We present molecular dynamics (MD) simulations to investigate the ejecta production from tin surface shocked by supported and unsupported waves with pressures ranging from 8.5 to 60.8 GPa. It is found that the loading waveforms have little effect on spike velocity while remarkably affect the bubble velocity. The bubble velocity of unsupported shock loading remains nonzero constant value at late time as observed in experiments. Besides, the time evolution of ejected mass in the simulations is compared with the recently developed ejecta source model, indicating the suppressed ejection of unmelted or partial melted materials. Moreover, different reference positions are chosen to characterize the amount of ejecta under different loading waveforms. Compared with supported shock case, the ejected mass of unsupported shock case saturates at lower pressure. Through the analysis on unloading path, we find that the temperature of tin sample increases quickly from tensile stress state to zero pressure state, resulting in the melting of bulk tin under decaying shock. Thus, the unsupported wave loading exhibits a lower threshold pressure causing the solid-liquid phase transition on shock release than the supported shock loading.

  3. Monte Carlo simulation of light reflection from cosmetic powder particles near the human skin surface.

    Science.gov (United States)

    Okamoto, Takashi; Kumagawa, Tatsuya; Motoda, Masafumi; Igarashi, Takanori; Nakao, Keisuke

    2013-06-01

    The reflection and scattering properties of light incident on human skin covered with powder particles have been investigated. A three-layer skin structure with a pigmented area is modeled, and the propagation of light in the skin's layers and in a layer of particles near the skin's surface is simulated using the Monte Carlo method. Assuming that only single scattering of light occurs in the powder layer, the simulation results show that the reflection spectra of light from the skin change with the size of powder particles. The color difference between normal and discolored skin is found to decrease considerably when powder particles with a diameter of approximately 0.25 μm are present near the skin's surface. The effects of the medium surrounding the particles, and the influence of the distribution of particle size (polydispersity), are also examined. It is shown that a surrounding medium with a refractive index close to that of the skin substantially suppresses the extreme spectral changes caused by the powder particles covering the skin surface.

  4. Numerical Simulation of the Effects of Water Surface in Building Environment

    Science.gov (United States)

    Li, Guangyao; Pan, Yuqing; Yang, Li

    2018-03-01

    Water body could affect the thermal environment and airflow field in the building districts, because of its special thermal characteristics, evaporation and flat surface. The thermal influence of water body in Tongji University Jiading Campus front area was evaluated. First, a suitable evaporation model was selected and then was applied to calculate the boundary conditions of the water surface in the Fluent software. Next, the computational fluid dynamics (CFD) simulations were conducted on the models both with and without water, following the CFD practices guidelines. Finally, the outputs of the two simulations were compared with each other. Results showed that the effect of evaporative cooling from water surface strongly depends on the wind direction and temperature decrease was about 2∼5°C. The relative humidity within the enclosing area was affected by both the building arrangement and surrounding water. An increase of about 0.1∼0.2m/s of wind speed induced by the water evaporation was observed in the open space.

  5. Coupling a groundwater model with a land surface model to improve water and energy cycle simulation

    Directory of Open Access Journals (Sweden)

    W. Tian

    2012-12-01

    Full Text Available Water and energy cycles interact, making these two processes closely related. Land surface models (LSMs can describe the water and energy cycles on the land surface, but their description of the subsurface water processes is oversimplified, and lateral groundwater flow is ignored. Groundwater models (GWMs describe the dynamic movement of the subsurface water well, but they cannot depict the physical mechanisms of the evapotranspiration (ET process in detail. In this study, a coupled model of groundwater flow with a simple biosphere (GWSiB is developed based on the full coupling of a typical land surface model (SiB2 and a 3-D variably saturated groundwater model (AquiferFlow. In this coupled model, the infiltration, ET and energy transfer are simulated by SiB2 using the soil moisture results from the groundwater flow model. The infiltration and ET results are applied iteratively to drive the groundwater flow model. After the coupled model is built, a sensitivity test is first performed, and the effect of the groundwater depth and the hydraulic conductivity parameters on the ET are analyzed. The coupled model is then validated using measurements from two stations located in shallow and deep groundwater depth zones. Finally, the coupled model is applied to data from the middle reach of the Heihe River basin in the northwest of China to test the regional simulation capabilities of the model.

  6. Simulation of imperfections in plastic lenses - transferring local refractive index changes into surface shape modifications

    Science.gov (United States)

    Arasa, Josep; Pizarro, Carles; Blanco, Patricia

    2016-06-01

    Injection molded plastic lenses have continuously improved their performance regarding optical quality and nowadays are as usual as glass lenses in image forming devices. However, during the manufacturing process unavoidable fluctuations in material density occur, resulting in local changes in the distribution of refractive index, which degrade the imaging properties of the polymer lens. Such material density fluctuations correlate to phase delays, which opens a path for their mapping. However, it is difficult to transfer the measured variations in refractive index into conventional optical simulation tool. Thus, we propose a method to convert the local variations in refractive index into local changes of one surface of the lens, which can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method was tested on a commercial gradient index (GRIN) lens for a set of six different object positions, using the MTF sagittal and tangential cuts to compare the differences between the real lens and a lens with homogenous refractive index, and the last surface converted into a free-form shape containing the internal refractive index changes. The same procedure was used to reproduce the local refractive index changes of an injected plastic lens with local index changes measured using an in-house built polariscopic arrangement, showing the capability of the method to provide successful results.

  7. Supersonic flow over a pitching delta wing using surface pressure measurements and numerical simulations

    Directory of Open Access Journals (Sweden)

    Mostafa HADIDOOLABI

    2018-01-01

    Full Text Available Experimental and numerical methods were applied to investigating high subsonic and supersonic flows over a 60° swept delta wing in fixed state and pitching oscillation. Static pressure coefficient distributions over the wing leeward surface and the hysteresis loops of pressure coefficient versus angle of attack at the sensor locations were obtained by wind tunnel tests. Similar results were obtained by numerical simulations which agreed well with the experiments. Flow structure around the wing was also demonstrated by the numerical simulation. Effects of Mach number and angle of attack on pressure distribution curves in static tests were investigated. Effects of various oscillation parameters including Mach number, mean angle of attack, pitching amplitude and frequency on hysteresis loops were investigated in dynamic tests and the associated physical mechanisms were discussed. Vortex breakdown phenomenon over the wing was identified at high angles of attack using the pressure coefficient curves and hysteresis loops, and its effects on the flow features were discussed.

  8. The simulation of thermal characteristics of 980 nm vertical cavity surface emitting lasers

    Science.gov (United States)

    Fang, Tianxiao; Cui, Bifeng; Hao, Shuai; Wang, Yang

    2018-02-01

    In order to design a single mode 980 nm vertical cavity surface emitting laser (VCSEL), a 2 μm output aperture is designed to guarantee the single mode output. The effects of different mesa sizes on the lattice temperature, the output power and the voltage are simulated under the condition of continuous working at room temperature, to obtain the optimum process parameters of mesa. It is obtained by results of the crosslight simulation software that the sizes of mesa radius are between 9.5 to 12.5 μm, which cannot only obtain the maximum output power, but also improve the heat dissipation of the device. Project supported by the Beijing Municipal Eduaction Commission (No. PXM2016_014204_500018) and the Construction of Scientific and Technological Innovation Service Ability in 2017 (No. PXM2017_014204_500034).

  9. Simulation of groundwater and surface-water flow in the upper Deschutes Basin, Oregon

    Science.gov (United States)

    Gannett, Marshall W.; Lite, Kenneth E.; Risley, John C.; Pischel, Esther M.; La Marche, Jonathan L.

    2017-10-20

    This report describes a hydrologic model for the upper Deschutes Basin in central Oregon developed using the U.S. Geological Survey (USGS) integrated Groundwater and Surface-Water Flow model (GSFLOW). The upper Deschutes Basin, which drains much of the eastern side of the Cascade Range in Oregon, is underlain by large areas of permeable volcanic rock. That permeability, in combination with the large annual precipitation at high elevations, results in a substantial regional aquifer system and a stream system that is heavily groundwater dominated.The upper Deschutes Basin is also an area of expanding population and increasing water demand for public supply and agriculture. Surface water was largely developed for agricultural use by the mid-20th century, and is closed to additional appropriations. Consequently, water users look to groundwater to satisfy the growing demand. The well‑documented connection between groundwater and the stream system, and the institutional and legal restrictions on streamflow depletion by wells, resulted in the Oregon Water Resources Department (OWRD) instituting a process whereby additional groundwater pumping can be permitted only if the effects to streams are mitigated, for example, by reducing permitted surface-water diversions. Implementing such a program requires understanding of the spatial and temporal distribution of effects to streams from groundwater pumping. A groundwater model developed in the early 2000s by the USGS and OWRD has been used to provide insights into the distribution of streamflow depletion by wells, but lacks spatial resolution in sensitive headwaters and spring areas.The integrated model developed for this project, based largely on the earlier model, has a much finer grid spacing allowing resolution of sensitive headwater streams and important spring areas, and simulates a more complete set of surface processes as well as runoff and groundwater flow. In addition, the integrated model includes improved

  10. Coupled DEM-LBM method for the free-surface simulation of heterogeneous suspensions

    Science.gov (United States)

    Leonardi, Alessandro; Wittel, Falk K.; Mendoza, Miller; Herrmann, Hans J.

    2014-05-01

    The complexity of the interactions between the constituent granular and liquid phases of a suspension requires an adequate treatment of the constituents themselves. A promising way for numerical simulations of such systems is given by hybrid computational frameworks. This is naturally done, when the Lagrangian description of particle dynamics of the granular phase finds a correspondence in the fluid description. In this work we employ extensions of the Lattice-Boltzmann Method for non-Newtonian rheology, free surfaces, and moving boundaries. The models allows for a full coupling of the phases, but in a simplified way. An experimental validation is given by an example of gravity driven flow of a particle suspension.

  11. IrPd nanoalloys: simulations, from surface segregation to local electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Andriamiharintsoa, T. H. [Institut de Physique et Chimie des Matériaux de Strasbourg CNRS-UDS UMR 7504 (France); Rakotomahevitra, A. [Institut pour la Maîtrise de l’Énergie, Faculté des sciences d’Antananarivo (Madagascar); Piccolo, L. [Institut de Recherches sur la Catalyse et l’Environnement de Lyon IRCELYON, UMR 5256 CNRS and Université Lyon 1 (France); Goyhenex, C., E-mail: christine.goyhenex@ipcms.unistra.fr [Institut de Physique et Chimie des Matériaux de Strasbourg CNRS-UDS UMR 7504 (France)

    2015-05-15

    Using semi-empirical modeling, namely tight-binding at different levels of accuracy, the chemical, crystallographic, and electronic structures of bimetallic IrPd nanoparticles are characterized. For the purpose, model cuboctahedral particles containing 561 atoms are considered. Atomistic simulations show that core–shell nanoparticles are highly stable, with a strong surface segregation of Pd, at least for one atomic shell thickness. Within self-consistent tight-binding calculations founded on the density functional theory, an accurate insight is given into the electronic structure of these materials which have a high potential as catalysts.

  12. The assessment of muscle strain with surface electromyograms during simulated mushroom picking

    DEFF Research Database (Denmark)

    Ohashi, Jun-Ya; Blangsted, Anne Katrine; Kofoed Nielsen, Pernille B.

    2008-01-01

    Muscle strain was assessed with surface EMG during simulated mushroom picking. Nine female subjects performed five periods of work (W1-W5). The duration of each period was about 20 min. W1, W2 and W3 were separated by a short break of several minutes. W3, W4 and W5 were separated by a rest period...... in the trapezius was interpreted as spare capacity for the work. The infraspinatus and deltoid were assessed to be more fatigued than the trapezius. The fatigue level of the erector spinae was low....

  13. Surface roughness effect on ultracold neutron interaction with a wall and implications for computer simulations

    International Nuclear Information System (INIS)

    Steyerl, A.; Malik, S. S.; Desai, A. M.; Kaufman, C.

    2010-01-01

    We review the diffuse scattering and the loss coefficient in ultracold neutron reflection from slightly rough surfaces, report a surprising reduction in loss coefficient due to roughness, and discuss the possibility of transition from quantum treatment to ray optics. The results are used in a computer simulation of neutron storage in a recent neutron lifetime experiment that reported a large discrepancy of neutron lifetime with the current particle data value. Our partial reanalysis suggests the possibility of systematic effects that were not included in this publication.

  14. The computer simulation of the structure of transition metal surface alloys

    International Nuclear Information System (INIS)

    Bilic, A.; King, B.V.; O'Connor, D.J.

    1999-01-01

    In recent years interest has arisen in connection with the thin alloy films of Al and Pd. Such films are created by deposition of ≥ 0.5 ML of Al onto Pd(001) and annealing to 750-950 K. The structure has been investigated using low-energy ion scattering (LEIS) and shows a p(2x2)-p4g clock reconstruction. A structure was proposed consisting of a clock-rotated Pd top layer over a c(2x2) Al-Pd underlayer. This paper presents a simulation study of the structure and energetics of Al dissolution into the Pd(001) surface using the embedded atom method (EAM)

  15. Soil and glass surface photodegradation of etofenprox under simulated california rice growing conditions.

    Science.gov (United States)

    Vasquez, Martice; Cahill, Thomas; Tjeerdema, Ronald

    2011-07-27

    Photolysis is an important degradation process to consider when evaluating a pesticide's persistence in a rice field environment. To simulate both nonflooded and flooded California rice field conditions, the photolytic degradation of etofenprox, an ether pyrethroid, was characterized on an air-dried rice soil and a flooded rice soil surface by determination of its half-life (t(1/2)), dissipation rate constant (k) and identification and quantitation of degradation products using LC/MS/MS. Photodegradation was also characterized on a glass surface alone to rule out confounding soil factors. Measured photolytic dissipation rates were used as input parameters into a multimedia environmental fate model to predict etofenprox persistence in a rice field environment. Photolytic degradation proceeded at a faster rate (0.23/day, t(1/2) = 3.0 days) on the flooded soil surface compared to the air-dried surface (0.039/day, t(1/2) = 18 days). Etofenprox degradation occurred relatively quickly on the glass surface (3.1/day, t(1/2) = 0.23 days or 5.5 h) compared to both flooded and air-dried soil layers. Oxidation of the ether moiety to the ester was the major product on all surfaces (max % yield range = 0.2 ± 0.1% to 9.3 ± 2.3%). The hydroxylation product at the 4' position of the phenoxy phenyl ring was detected on all surfaces (max % yield range = 0.2 ± 0.1% to 4.1 ± 1.0%). The air-dried soil surface did not contain detectable residues of the ester cleavage product, whereas it was quantitated on the flooded soil (max % yield = 0.6 ± 0.3%) and glass surface (max % yield = 3.6 ± 0.6%). Dissipation of the insecticide in dark controls was significantly different (p < 0.05) compared to the light-exposed surfaces indicating that degradation was by photolysis. Laboratory studies and fate model predictions suggest photolysis will be an important process in the overall degradation of etofenprox in a rice field environment.

  16. Modeling and simulation for fewer-axis grinding of complex surface

    Science.gov (United States)

    Li, Zhengjian; Peng, Xiaoqiang; Song, Ci

    2017-10-01

    As the basis of fewer-axis grinding of complex surface, the grinding mathematical model is of great importance. A mathematical model of the grinding wheel was established, and then coordinate and normal vector of the wheel profile could be calculated. Through normal vector matching at the cutter contact point and the coordinate system transformation, the grinding mathematical model was established to work out the coordinate of the cutter location point. Based on the model, interference analysis was simulated to find out the right position and posture of workpiece for grinding. Then positioning errors of the workpiece including the translation positioning error and the rotation positioning error were analyzed respectively, and the main locating datum was obtained. According to the analysis results, the grinding tool path was planned and generated to grind the complex surface, and good form accuracy was obtained. The grinding mathematical model is simple, feasible and can be widely applied.

  17. Molecular Dynamics Simulation of Water Nanodroplets on Silica Surfaces at High Air Pressures

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Jaffe, Richard Lawrence; Walther, Jens Honore

    2010-01-01

    e.g., nanobubbles. In the present work we study the role of air on the wetting of hydrophilic systems. We conduct molecular dynamics simulations of a water nanodroplet on an amorphous silica surface at different air pressures. The interaction potentials describing the silica, water, and air...... are obtained from the literature. The silica surface is modeled by a large 32 ⨯ 32 ⨯ 2 nm amorphous SiO2 structure consisting of 180000 atoms. The water consists of 18000 water molecules surrounded by N2 and O2 air molecules corresponding to air pressures of 0 bar (vacuum), 50 bar, 100 bar and 200 bar. We...... the effect of air and find a consistent increase in the water contact angle reaching 53º at 200 bar air pressure. These results are important for the creation and stability of nanobubbles at hydrophilic interfaces....

  18. An Electric Field Volume Integral Equation Approach to Simulate Surface Plasmon Polaritons

    Directory of Open Access Journals (Sweden)

    R. Remis

    2013-02-01

    Full Text Available In this paper we present an electric field volume integral equation approach to simulate surface plasmon propagation along metal/dielectric interfaces. Metallic objects embedded in homogeneous dielectric media are considered. Starting point is a so-called weak-form of the electric field integral equation. This form is discretized on a uniform tensor-product grid resulting in a system matrix whose action on a vector can be computed via the fast Fourier transform. The GMRES iterative solver is used to solve the discretized set of equations and numerical examples, illustrating surface plasmon propagation, are presented. The convergence rate of GMRES is discussed in terms of the spectrum of the system matrix and through numerical experiments we show how the eigenvalues of the discretized volume scattering operator are related to plasmon propagation and the medium parameters of a metallic object.

  19. Recent Advancements in the Numerical Simulation of Surface Irradiance for Solar Energy Applications: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Yu; Sengupta, Manajit; Deline, Chris

    2017-06-27

    This paper briefly reviews the National Renewable Energy Laboratory's recent efforts on developing all-sky solar irradiance models for solar energy applications. The Fast All-sky Radiation Model for Solar applications (FARMS) utilizes the simulation of clear-sky transmittance and reflectance and a parameterization of cloud transmittance and reflectance to rapidly compute broadband irradiances on horizontal surfaces. FARMS delivers accuracy that is comparable to the two-stream approximation, but it is approximately 1,000 times faster. A FARMS-Narrowband Irradiance over Tilted surfaces (FARMS-NIT) has been developed to compute spectral irradiances on photovoltaic (PV) panels in 2002 wavelength bands. Further, FARMS-NIT has been extended for bifacial PV panels.

  20. A New Approach to Simulate the Kinetics of Metal Desorption from Mineral Surfaces

    Science.gov (United States)

    Tinnacher, R. M.; Powell, B. A.; Kersting, A. B.; Zavarin, M.

    2010-12-01

    The relevance of colloid-facilitated metal transport is largely dependent on metal sorption/desorption kinetics and the degree of reversibility of metal surface binding. Thus, transport predictions need to incorporate modeling concepts that can simulate time- and history-dependent surface processes on the microscale. In this study, we characterized the sorption and desorption kinetics of neptunium(V) reactions on goethite in a flow-cell experiment. Modeling was used to evaluate differences between sorption and desorption kinetics in terms of aging, hysteresis, and ‘irreversible’ sorption. First, aging represents a series of surface-chemical processes on the microscale that lead to changes in contaminant surface speciation over time. Second, hysteresis effects indicate fundamental, chemical differences in the microscopic pathways of reactions for net sorption and desorption processes. Both phenomena may result in a sorbed contaminant fraction that is not readily available for exchange with the solution phase (apparent irreversible sorption). Most currently available kinetic sorption/desorption models incorporate fundamental changes in adsorption and desorption behavior indirectly, e.g., by postulating surface sites with different kinetic rates or ‘irreversible’ sorption behavior. We propose a new approach that allows for the specific incorporation of changes in overall reaction pathways for (ad)sorption and desorption processes. Based on experimental results, observed rates for Np(V) desorption from goethite are substantially slower than for (ad)sorption processes. Differences in metal sorption and desorption kinetics can be simulated with a minimum number of fitting parameters by combining isotherm-based sorption rate laws with a modeling concept related to transition state theory (TST). This concept is based on the assumption that changes in reaction pathways for (ad)sorption and desorption processes lead to differences in overall driving forces and

  1. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations.

    Science.gov (United States)

    Wang, Tao; Peng, Shushi; Krinner, Gerhard; Ryder, James; Li, Yue; Dantec-Nédélec, Sarah; Ottlé, Catherine

    2015-01-01

    Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation) into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms) and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique) improve the simulation accuracy of mean seasonal (October throughout May) snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the magnitude of

  2. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations.

    Directory of Open Access Journals (Sweden)

    Tao Wang

    Full Text Available Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique improve the simulation accuracy of mean seasonal (October throughout May snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the

  3. Simulation of the Impact of New Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Black, Peter; Chen, Shuyi; Hood, Robbie; Johnson, James; Jones, Linwood; Ruf, Chris; Uhlhorn, Eric

    2008-01-01

    The H*Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of surface wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa.gov/hrd/data sub/wind.html. The Hurricane Imaging Radiometer (HIRAD) is a new passive microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRAD is being designed to enhance the current real-time airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft using the operational airbome Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath (approximately 3 x the aircraft altitude, or approximately 2 km from space). The instrument is described in a separate paper presented at this conference. The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a numerical model from the University of Miami, and those results are used to construct H*Wind analyses. Evaluations will be presented on the relative impact of HIRAD and other instruments on H*Wind analyses, including the use of HIRAD from 2 aircraft altitudes and from a space-based platform.

  4. Surface properties of monolithic zirconia after dental adjustment treatments and in vitro wear simulation.

    Science.gov (United States)

    Preis, Verena; Schmalzbauer, Michael; Bougeard, Dominique; Schneider-Feyrer, Sibylle; Rosentritt, Martin

    2015-01-01

    To investigate the surface properties (roughness, composition, phase transformation) of monolithic zirconia specimens after dental adjustment procedures (grinding, polishing) and wear simulation. Zirconia specimens (Cercon base, Cercon ht, DeguDent, G; n=10/material) were successively sintered, ground, and polished with an intraoral polishing kit in a three-step procedure. Sintered zirconia specimens with high surface roughness served as a reference. For each treatment step, wear simulations with steatite plates (d=10 mm) as antagonists were conducted as well as surface roughness tests (Ra), EDX analysis, and X-ray diffraction (XRD) measurements. SEM pictures were taken, and data were statistically analyzed (one-way ANOVA, post hoc Bonferroni, α=0.05). Grinding significantly (p=0.000) increased the roughness of sintered zirconia up to values of 1.36±0.11 μm (Ra). Polishing significantly (p=0.000) reduced Ra. The lowest roughness value after the final polishing step was 0.20±0.03 μm. Wear testing resulted in a further slight decrease of Ra. After the grinding procedure, SEM pictures showed deep grooves that were progressively smoothed by polishing. The EDX spectra showed that magnesium was transferred from steatite antagonists to zirconia by wear. In the XRD-patterns, monoclinic (m) peaks were observed after grinding and polishing. The maximum intensity ratio between the m (11-1) peak and the tetragonal t (111) peak decreased after the completion of all polishing steps. Wear did not induce phase transformation. Adequate polishing reduced the roughness of ground zirconia. Wear had little influence on roughness and no influence on phase transformation. Careful polishing is recommended to keep surface roughness and phase transformation low. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Extended survival of several organisms and amino acids under simulated martian surface conditions

    Science.gov (United States)

    Johnson, A. P.; Pratt, L. M.; Vishnivetskaya, T.; Pfiffner, S.; Bryan, R. A.; Dadachova, E.; Whyte, L.; Radtke, K.; Chan, E.; Tronick, S.; Borgonie, G.; Mancinelli, R. L.; Rothschild, L. J.; Rogoff, D. A.; Horikawa, D. D.; Onstott, T. C.

    2011-02-01

    Recent orbital and landed missions have provided substantial evidence for ancient liquid water on the martian surface as well as evidence of more recent sedimentary deposits formed by water and/or ice. These observations raise serious questions regarding an independent origin and evolution of life on Mars. Future missions seek to identify signs of extinct martian biota in the form of biomarkers or morphological characteristics, but the inherent danger of spacecraft-borne terrestrial life makes the possibility of forward contamination a serious threat not only to the life detection experiments, but also to any extant martian ecosystem. A variety of cold and desiccation-tolerant organisms were exposed to 40 days of simulated martian surface conditions while embedded within several centimeters of regolith simulant in order to ascertain the plausibility of such organisms' survival as a function of environmental parameters and burial depth. Relevant amino acid biomarkers associated with terrestrial life were also analyzed in order to understand the feasibility of detecting chemical evidence for previous biological activity. Results indicate that stresses due to desiccation and oxidation were the primary deterrent to organism survival, and that the effects of UV-associated damage, diurnal temperature variations, and reactive atmospheric species were minimal. Organisms with resistance to desiccation and radiation environments showed increased levels of survival after the experiment compared to organisms characterized as psychrotolerant. Amino acid analysis indicated the presence of an oxidation mechanism that migrated downward through the samples during the course of the experiment and likely represents the formation of various oxidizing species at mineral surfaces as water vapor diffused through the regolith. Current sterilization protocols may specifically select for organisms best adapted to survival at the martian surface, namely species that show tolerance to radical

  6. Modeling and Simulation of Long-Term Performance of Near-Surface Barriers

    International Nuclear Information System (INIS)

    Piet, S. J.; Jacobson, J. J.; Martian, P.; Martineau, R.; Soto, R.

    2003-01-01

    INEEL started a new project on long-term barrier integrity in April 2002 that aims to catalyze a Barrier Improvement Cycle (iterative learning and application) and thus enable Remediation System Performance Management (doing the right maintenance neither too early nor too late, prior to system-level failure). This paper describes our computer simulation approach for better understanding the relationships and dynamics between the various components and management decisions in a cap. The simulation is designed to clarify the complex relationships between the various components within the cap system and the various management practices that affect the barrier performance. We have also conceptualized a time-dependent 3-D simulation with rigorous solution to unsaturated flow physics with complex surface boundary conditions

  7. Modeling and Simulation of Long-Term Performance of Near-Surface Barriers

    Energy Technology Data Exchange (ETDEWEB)

    Piet, S. J.; Jacobson, J. J.; Martian, P.; Martineau, R.; Soto, R.

    2003-02-25

    . Thus, the INEEL started a new project on long-term barrier integrity in April 2002 that aims to catalyze a Barrier Improvement Cycle (iterative learning and application) and thus enable Remediation System Performance Management (doing the right maintenance neither too early nor too late, prior to system-level failure). This paper describes our computer simulation approach for better understanding the relationships and dynamics between the various components and management decisions in a cap. The simulation is designed to clarify the complex relationships between the various components within the cap system and the various management practices that affect the barrier performance. We have also conceptualized a time-dependent 3-D simulation with rigorous solution to unsaturated flow physics with complex surface boundary conditions.

  8. Modeling and Simulation of Long-Term Performance of Near-Surface Barriers

    Energy Technology Data Exchange (ETDEWEB)

    Piet, Steven James; Jacobson, Jacob Jordan; Soto, Rafael; Martian, Pete; Martineau, Richard Charles

    2003-02-01

    , the INEEL started a new project on long-term barrier integrity in April 2002 that aims to catalyze a Barrier Improvement Cycle (iterative learning and application) and thus enable Remediation System Performance Management (doing the right maintenance neither too early nor too late, prior to system-level failure). This paper describes our computer simulation approach for better understanding the relationships and dynamics between the various components and management decisions in a cap. The simulation is designed to clarify the complex relationships between the various components within the cap system and the various management practices that affect the barrier performance. We have also conceptualized a time-dependent 3-D simulation with rigorous solution to unsaturated flow physics with complex surface boundary conditions.

  9. Balancing an accurate representation of the molecular surface in generalized Born formalisms with integrator stability in molecular dynamics simulations

    Czech Academy of Sciences Publication Activity Database

    Chocholoušová, Jana; Feig, M.

    2006-01-01

    Roč. 27, č. 6 (2006), s. 719-729 ISSN 0192-8651 Keywords : molecular surface * generalized Born formalisms * molecular dynamic simulations Subject RIV: CC - Organic Chemistry Impact factor: 4.893, year: 2006

  10. Hydromechanical Simulations of Surface Uplift due to CO2 Injection at In Salah (Invited)

    Science.gov (United States)

    Morris, J. P.; Hao, Y.; Foxall, W.; McNab, W. W.

    2009-12-01

    We present recent simulations of the hydromechanical response of the reservoir and overburden associated with CO2 injection at In Salah. Using the best available field data for the reservoir and fault network properties, we are able to demonstrate excellent agreement between simulation and observation. These results are providing new insight into the fate of the CO2 about one of the injectors where intriguing morphology was observed in surface uplift. Additionally, this work is helping to better establish the advantages and limitations of interpreting surface displacements to guide our understanding of fluid fate. The In Salah Project (a joint venture of BP, StatoilHydro and Sonatrach) includes a CO2 sequestration effort that has successfully injected millions of tons of CO2 into a deep saline formation close to a producing gas field in Algeria. We have been funded by the Joint Industry Project (A consortium consisting of BP, StatoilHydro and Sonatrach, hereafter the JIP) and the U.S. Department of Energy to investigate the role of injection induced mechanical deformation and geochemical alteration at the In Salah CO2 storage project. Here we focus upon the hydromechanical portion of the study. We have performed detailed simulations of the hydromechanical response in the vicinity of the KB-502 CO2 injector specifically because the morphology of the observed surface deformation differed from that above the other injectors at the field. First we performed a geomechanical analysis to predict which faults are flow conduits and which are flow barriers. NUFT simulations were performed based upon this information using permeability fields for the reservoir provided by the JIP. These results indicate that the presence of faults in the vicinity of the KB-502 injector may be responsible for the early breakthrough of CO2 observed at a nearby well, KB-5. We have simulated the mm-scale uplift of the overburden and compared the results with observed deformation using InSAR data

  11. Development of Advanced Wear and Corrosion Resistant Systems Through Laser Surface Alloying and Materials Simulations

    Energy Technology Data Exchange (ETDEWEB)

    R. P. Martukanitz and S. Babu

    2007-05-03

    Laser surfacing in the form of cladding, alloying, and modifications are gaining widespread use because of its ability to provide high deposition rates, low thermal distortion, and refined microstructure due to high solidification rates. Because of these advantages, laser surface alloying is considered a prime candidate for producing ultra-hard coatings through the establishment or in situ formation of composite structures. Therefore, a program was conducted by the Applied Research Laboratory, Pennsylvania State University and Oak Ridge National Laboratory to develop the scientific and engineering basis for performing laser-based surface modifications involving the addition of hard particles, such as carbides, borides, and nitrides, within a metallic matrix for improved wear, fatigue, creep, and corrosion resistance. This has involved the development of advanced laser processing and simulation techniques, along with the refinement and application of these techniques for predicting and selecting materials and processing parameters for the creation of new surfaces having improved properties over current coating technologies. This program has also resulted in the formulation of process and material simulation tools capable of examining the potential for the formation and retention of composite coatings and deposits produced using laser processing techniques, as well as positive laboratory demonstrations in producing these coatings. In conjunction with the process simulation techniques, the application of computational thermodynamic and kinetic models to design laser surface alloying materials was demonstrated and resulted in a vast improvement in the formulation of materials used for producing composite coatings. The methodology was used to identify materials and to selectively modify microstructures for increasing hardness of deposits produced by the laser surface alloying process. Computational thermodynamic calculations indicated that it was possible to induce the

  12. Generating Inviscid and Viscous Fluid-Flow Simulations over an Aircraft Surface Using a Fluid-Flow Mesh

    Science.gov (United States)

    Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

    2013-01-01

    Fluid-flow simulation over a computer-generated aircraft surface is generated using inviscid and viscous simulations. A fluid-flow mesh of fluid cells is obtained. At least one inviscid fluid property for the fluid cells is determined using an inviscid fluid simulation that does not simulate fluid viscous effects. A set of intersecting fluid cells that intersects the aircraft surface are identified. One surface mesh polygon of the surface mesh is identified for each intersecting fluid cell. A boundary-layer prediction point for each identified surface mesh polygon is determined. At least one boundary-layer fluid property for each boundary-layer prediction point is determined using the at least one inviscid fluid property of the corresponding intersecting fluid cell and a boundary-layer simulation that simulates fluid viscous effects. At least one updated fluid property for at least one fluid cell is determined using the at least one boundary-layer fluid property and the inviscid fluid simulation.

  13. Molecular dynamics simulations of the DNA interaction with metallic nanoparticles and TiO2 surfaces

    International Nuclear Information System (INIS)

    Kholmurodov, Kh.T.; Krasavin, E.A.; Dushanov, E.B.; Hassan, H.K.; Galal, A.; ElHabashy, H.A.; Sweilam, N.H.; Yasuoka, K.

    2013-01-01

    The understanding of the mechanism of DNA interactions and binding with metallic nanoparticles (NPs) and surfaces represents a great interest in today's medicine applications due to diagnostic and treatment of oncology diseases. Recent experimental and simulation studies involve the DNA interaction with highly localized proton beams or metallic NPs (such as Ag, Au, etc.), aimed at targeted cancer therapy through the injection of metal micro- or nanoparticles into the tumor tissue with consequent local microwave or laser heating. The effects of mutational structure changes in DNA and protein structures could result in destroying of native chemical (hydrogen) bonds or, on the contrary, creating of new bonds that do not normally exist there. The cause of such changes might be the alteration of one or several nucleotides (in DNA) or the substitution of specific amino acid residues (in proteins) that can lead to the essential structural destabilization or unfolding. At the atomic or molecular level, the replacement of one nucleotide by another (in DNA double helices) or replacement of one amino acid residue by another (in proteins) cause essential modifications of the molecular force fields of the environment that break locally important hydrogen bonds underlying the structural stability of the biological molecules. In this work, the molecular dynamics(MD) simulations were performed for four DNA models and the flexibilities of the purine and pyrimidine nucleotides during the interaction process with the metallic NPs and TiO 2 surface were clarified

  14. Full Coupling Between the Atmosphere, Surface, and Subsurface for Integrated Hydrologic Simulation

    Science.gov (United States)

    Davison, Jason Hamilton; Hwang, Hyoun-Tae; Sudicky, Edward A.; Mallia, Derek V.; Lin, John C.

    2018-01-01

    An ever increasing community of earth system modelers is incorporating new physical processes into numerical models. This trend is facilitated by advancements in computational resources, improvements in simulation skill, and the desire to build numerical simulators that represent the water cycle with greater fidelity. In this quest to develop a state-of-the-art water cycle model, we coupled HydroGeoSphere (HGS), a 3-D control-volume finite element surface and variably saturated subsurface flow model that includes evapotranspiration processes, to the Weather Research and Forecasting (WRF) Model, a 3-D finite difference nonhydrostatic mesoscale atmospheric model. The two-way coupled model, referred to as HGS-WRF, exchanges the actual evapotranspiration fluxes and soil saturations calculated by HGS to WRF; conversely, the potential evapotranspiration and precipitation fluxes from WRF are passed to HGS. The flexible HGS-WRF coupling method allows for unique meshes used by each model, while maintaining mass and energy conservation between the domains. Furthermore, the HGS-WRF coupling implements a subtime stepping algorithm to minimize computational expense. As a demonstration of HGS-WRF's capabilities, we applied it to the California Basin and found a strong connection between the depth to the groundwater table and the latent heat fluxes across the land surface.

  15. Competitive adsorption and ordered packing of counterions near highly charged surfaces: From mean-field theory to Monte Carlo simulations.

    Science.gov (United States)

    Wen, Jiayi; Zhou, Shenggao; Xu, Zhenli; Li, Bo

    2012-04-01

    Competitive adsorption of counterions of multiple species to charged surfaces is studied by a size-effect-included mean-field theory and Monte Carlo (MC) simulations. The mean-field electrostatic free-energy functional of ionic concentrations, constrained by Poisson's equation, is numerically minimized by an augmented Lagrangian multiplier method. Unrestricted primitive models and canonical ensemble MC simulations with the Metropolis criterion are used to predict the ionic distributions around a charged surface. It is found that, for a low surface charge density, the adsorption of ions with a higher valence is preferable, agreeing with existing studies. For a highly charged surface, both the mean-field theory and the MC simulations demonstrate that the counterions bind tightly around the charged surface, resulting in a stratification of counterions of different species. The competition between mixed entropy and electrostatic energetics leads to a compromise that the ionic species with a higher valence-to-volume ratio has a larger probability to form the first layer of stratification. In particular, the MC simulations confirm the crucial role of ionic valence-to-volume ratios in the competitive adsorption to charged surfaces that had been previously predicted by the mean-field theory. The charge inversion for ionic systems with salt is predicted by the MC simulations but not by the mean-field theory. This work provides a better understanding of competitive adsorption of counterions to charged surfaces and calls for further studies on the ionic size effect with application to large-scale biomolecular modeling.

  16. The Separation of Blood Components Using Standing Surface Acoustic Waves (SSAWs Microfluidic Devices: Analysis and Simulation

    Directory of Open Access Journals (Sweden)

    Ahmed M. Soliman

    2017-03-01

    Full Text Available The separation of blood components (WBCs, RBCs, and platelets is important for medical applications. Recently, standing surface acoustic wave (SSAW microfluidic devices are used for the separation of particles. In this paper, the design analysis of SSAW microfluidics is presented. Also, the analysis of SSAW force with Rayleigh angle effect and its attenuation in liquid-loaded substrate, viscous drag force, hydrodynamic force, and diffusion force are explained and analyzed. The analyses are provided for selecting the piezoelectric material, width of the main microchannel, working area of SAW, wavelength, minimum input power required for the separation process, and widths of outlet collecting microchannels. The design analysis of SSAW microfluidics is provided for determining the minimum input power required for the separation process with appropriated the displacement contrast of the particles.The analyses are applied for simulation the separation of blood components. The piezoelectric material, width of the main microchannel, working area of SAW, wavelength, and minimum input power required for the separation process are selected as LiNbO3, 120 μm, 1.08 mm2, 300 μm, 371 mW. The results are compared to other published results. The results of these simulations achieve minimum power consumption, less complicated setup, and high collecting efficiency. All simulation programs are built by MATLAB.

  17. Transfer of spatio-temporal multifractal properties of rainfall to simulated surface runoff

    Science.gov (United States)

    Gires, Auguste; Giangola-Murzyn, Agathe; Richard, Julien; Abbes, Jean-Baptiste; Tchiguirinskaia, Ioulia; Schertzer, Daniel; Willinger, Bernard; Cardinal, Hervé; Thouvenot, Thomas

    2014-05-01

    In this paper we suggest to use scaling laws and more specifically Universal Multifractals (UM) to analyse in a spatio-temporal framework both the radar rainfall and the simulated surface runoff. Such tools have been extensively used to analyse and simulate geophysical fields extremely variable over wide range of spatio-temporal scales such as rainfall, but have not often if ever been applied to surface runoff. Such novel combined analysis helps to improve the understanding of the rainfall-runoff relationship. Two catchments of the chair "Hydrology for resilient cities" sponsored by Véolia, and of the European Interreg IV RainGain project are used. They are both located in the Paris area: a 144 ha flat urban area in the Seine-Saint-Denis County, and a 250 ha urban area with a significant portion of forest located on a steep hillside of the Bièvre River. A fully distributed urban hydrological model currently under development called Multi-Hydro is implemented to represent the catchments response. It consists in an interacting core between open source software packages, each of them representing a portion of the water cycle in urban environment. The fully distributed model is tested with pixels of size 5, 10 and 20 m. In a first step the model is validated for three rainfall events that occurred in 2010 and 2011, for which the Météo-France radar mosaic with a resolution of 1 km in space and 5 min in time is available. These events generated significant surface runoff and some local flooding. The sensitivity of the model to the rainfall resolution is briefly checked by stochastically generating an ensemble of realistic downscaled rainfall fields (obtained by continuing the underlying cascade process which is observed on the available range of scales) and inputting them into the model. The impact is significant on both the simulated sewer flow and surface runoff. Then rainfall fields are generated with the help of discrete multifractal cascades and inputted in the

  18. Simulation of time-dependent free-surface Navier-Stokes flows

    International Nuclear Information System (INIS)

    Muldowney, G.P.

    1989-01-01

    Two numerical methods for simulation of time-dependent free-surface Navier-Stokes flows are developed. Both techniques are based on semi-implicit time advancement of the momentum equations, integral formulation of the spatial problem at each timestep, and spectral-element discretization to solve the resulting integral equation. Central to each algorithm is a boundary-specific solution step which permits the spatial treatment in two dimensions to be performed in O(N 3 ) operations per timestep despite the presence of deforming geometry. The first approach is a domain-integral formulation involving integrals over the entire flow domain of kernel functions which arise in time-differencing the Navier-Stokes equations. The second is a particular-solution formulation which replaces domain integration with an iterative scheme to generate particular velocity and pressure fields on individual elements, followed by a patching step to produce a particular solution continuous over the full domain. Two of the most difficult aspects of viscous free-surface flow simulations, namely time-dependent geometry and nontrivial boundary conditions, are well accommodated by these integral equation techniques. In addition the methods offer spectral accuracy in space and admit arbitrarily high-order discretization in time. For large-scale computations and/or long-term time advancement the domain-integral algorithm must be executed on a supercomputer to deliver results in reasonable processing time. A detailed simulation of gas liquid flow with full resolution of the free phase boundary requires approximately five CPU hours at 80 megaflops

  19. Greenland ice sheet surface mass balance: evaluating simulations and making projections with regional climate models

    Directory of Open Access Journals (Sweden)

    J. G. L. Rae

    2012-11-01

    Full Text Available Four high-resolution regional climate models (RCMs have been set up for the area of Greenland, with the aim of providing future projections of Greenland ice sheet surface mass balance (SMB, and its contribution to sea level rise, with greater accuracy than is possible from coarser-resolution general circulation models (GCMs. This is the first time an intercomparison has been carried out of RCM results for Greenland climate and SMB. Output from RCM simulations for the recent past with the four RCMs is evaluated against available observations. The evaluation highlights the importance of using a detailed snow physics scheme, especially regarding the representations of albedo and meltwater refreezing. Simulations with three of the RCMs for the 21st century using SRES scenario A1B from two GCMs produce trends of between −5.5 and −1.1 Gt yr−2 in SMB (equivalent to +0.015 and +0.003 mm sea level equivalent yr−2, with trends of smaller magnitude for scenario E1, in which emissions are mitigated. Results from one of the RCMs whose present-day simulation is most realistic indicate that an annual mean near-surface air temperature increase over Greenland of ~ 2°C would be required for the mass loss to increase such that it exceeds accumulation, thereby causing the SMB to become negative, which has been suggested as a threshold beyond which the ice sheet would eventually be eliminated.

  20. Water formation at low temperatures by surface O2 hydrogenation III: Monte Carlo simulation.

    Science.gov (United States)

    Lamberts, Thanja; Cuppen, Herma M; Ioppolo, Sergio; Linnartz, Harold

    2013-06-07

    Water is the most abundant molecule found in interstellar icy mantles. In space it is thought to be efficiently formed on the surfaces of dust grains through successive hydrogenation of O, O2 and O3. The underlying physico-chemical mechanisms have been studied experimentally in the past decade and in this paper we extend this work theoretically, using Continuous-Time Random-Walk Monte Carlo simulations to disentangle the different processes at play during hydrogenation of molecular oxygen. CTRW-MC offers a kinetic approach to compare simulated surface abundances of different species to the experimental values. For this purpose, the results of four key experiments-sequential hydrogenation as well as co-deposition experiments at 15 and 25 K-are selected that serve as a reference throughout the modeling stage. The aim is to reproduce all four experiments with a single set of parameters. Input for the simulations consists of binding energies as well as reaction barriers (activation energies). In order to understand the influence of the parameters separately, we vary a single process rate at a time. Our main findings are: (i) The key reactions for the hydrogenation route starting from O2 are H + O2, H + HO2, OH + OH, H + H2O2, H + OH. (ii) The relatively high experimental abundance of H2O2 is due to its slow destruction. (iii) The large consumption of O2 at a temperature of 25 K is due to a high hydrogen diffusion rate. (iv) The diffusion of radicals plays an important role in the full reaction network. The resulting set of 'best fit' parameters is presented and discussed for use in future astrochemical modeling.

  1. Three-Body Abrasion Testing Using Lunar Dust Simulants to Evaluate Surface System Materials

    Science.gov (United States)

    Kobrick, Ryan L.; Budinski, Kenneth G.; Street, Kenneth W., Jr.; Klaus, David M.

    2010-01-01

    Numerous unexpected operational issues relating to the abrasive nature of lunar dust, such as scratched visors and spacesuit pressure seal leaks, were encountered during the Apollo missions. To avoid reoccurrence of these unexpected detrimental equipment problems on future missions to the Moon, a series of two- and three-body abrasion tests were developed and conducted in order to begin rigorously characterizing the effect of lunar dust abrasiveness on candidate surface system materials. Two-body scratch tests were initially performed to examine fundamental interactions of a single particle on a flat surface. These simple and robust tests were used to establish standardized measurement techniques for quantifying controlled volumetric wear. Subsequent efforts described in the paper involved three-body abrasion testing designed to be more representative of actual lunar interactions. For these tests, a new tribotester was developed to expose samples to a variety of industrial abrasives and lunar simulants. The work discussed in this paper describes the three-body hardware setup consisting of a rotating rubber wheel that applies a load on a specimen as a loose abrasive is fed into the system. The test methodology is based on ASTM International (ASTM) B611, except it does not mix water with the abrasive. All tests were run under identical conditions. Abraded material specimens included poly(methyl methacrylate) (PMMA), hardened 1045 steel, 6061-T6 aluminum (Al) and 1018 steel. Abrasives included lunar mare simulant JSC- 1A-F (nominal size distribution), sieved JSC-1A-F (sieved version of the simulant. The lunar dust displayed abrasivity to all of the test materials, which are likely to be used in lunar landing equipment. Based on this test experience and pilot results obtained, recommendations are made for systematic abrasion testing of candidate materials intended for use in lunar exploration systems and in other environments with similar dust challenges.

  2. Confronting the surface temperature cold bias in AGCMs over the Tibetan Plateau and improving climate simulations

    Science.gov (United States)

    Wu, G. X.; Liu, Y.; Bao, Q.; Chen, X.; Li, J.

    2017-12-01

    One of the mid-term progresses of the NSFC- Key Research Program "Land-air Coupling over the Tibetan Plateau and Its Climate Impact " is presented. The elevated heating in summer and cooling in winter of the Tibetan Plateau significantly regulate the seasonal change of the atmospheric circulation and exert remarkable impacts on world climate. Recent studies have demonstrated that the majority of the Phase-5 Coupled Model Inter-comparison Project (CMIP5) models underestimate annual and seasonal mean surface air temperatures (Ta) over the Tibetan Plateau (TP). In addition, more than half of the models underestimate annual and seasonal mean surface temperatures (Ts) over the TP. These cold biases are larger over the western TP. By decomposing the Ts bias using the surface energy budget equation, it was demonstrated that this TP's cold bias can be attributed to various factors, in which the stronger bias in surface albedo (a-) and the weaker bias in clear-sky downward Longwave radiation (DLR) play the most significant roles. Since a- and DLR are respectively affected by snow coverage fraction at the ground surface and water vapor content in the atmosphere, these results then imply that the cold bias over the TP is caused by too large snow coverage fraction and too less water vapor content over the TP in the models. The FAMIL AGCM model developed at LASG also suffers from the similar cold bias over the TP. By introducing the 3D- Radiative Transfer Parameterization Over Mountains/Snow (Liou, 2013) into the model, the total solar radiation reaching the ground surface is increased during the daytime, resulting in more snowmelt and less snow coverage. Accordingly, surface albedo is decreased on the sunny side of the mountains, and the surface cold bias over mountain areas is decreased. It is shown that the improvement is sensitive to the model resolution: increased the horizontal resolution of Community Land Model version 4.0 (CLM 4.0) from nearly 200km (1.9o×2.5o) to

  3. Impact of improved Greenland ice sheet surface representation in the NASA GISS ModelE2 GCM on simulated surface mass balance and regional climate

    Science.gov (United States)

    Alexander, P. M.; LeGrande, A. N.; Fischer, E.; Tedesco, M.; Kelley, M.; Schmidt, G. A.; Fettweis, X.

    2017-12-01

    Towards achieving coupled simulations between the NASA Goddard Institute for Space Studies (GISS) ModelE2 general circulation model (GCM) and ice sheet models (ISMs), improvements have been made to the representation of the ice sheet surface in ModelE2. These include a sub-grid-scale elevation class scheme, a multi-layer snow model, a time-variable surface albedo scheme, and adjustments to parameterization of sublimation/evaporation. These changes improve the spatial resolution and physical representation of the ice sheet surface such that the surface is represented at a level of detail closer to that of Regional Climate Models (RCMs). We assess the impact of these changes on simulated Greenland Ice Sheet (GrIS) surface mass balance (SMB). We also compare ModelE2 simulations in which winds have been nudged to match the European Center for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis with simulations from the Modèle Atmosphérique Régionale (MAR) RCM forced by the same reanalysis. Adding surface elevation classes results in a much higher spatial resolution representation of the surface necessary for coupling with ISMs, but has a negligible impact on overall SMB. Implementing a variable surface albedo scheme increases melt by 100%, bringing it closer to melt simulated by MAR. Adjustments made to the representation of topography-influenced surface roughness length in ModelE2 reduce a positive bias in evaporation relative to MAR. We also examine the impact of changes to the GrIS surface on regional atmospheric and oceanic climate in coupled ocean-atmosphere simulations with ModelE2, finding a general warming of the Arctic due to a warmer GrIS, and a cooler North Atlantic in scenarios with doubled atmospheric CO2 relative to pre-industrial levels. The substantial influence of changes to the GrIS surface on the oceans and atmosphere highlight the importance of including these processes in the GCM, in view of potential feedbacks between the ice sheet

  4. Ion-nanostructure interaction. Comparing simulation and experiment towards surface structuring using nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Holland-Moritz, Henry

    2016-10-18

    Nanotechnology is a buzzword in context of the proceeding miniaturization of devices and their components. Nanoparticles (NPs) can nowadays easily be synthesized from different material compositions by different chemical and physical processes. However, most of these techniques work close to or at the thermal equilibrium. One subsequent approach to tune materials beyond equilibrium conditions is ion beam irradiation. An important effect of this approach is sputtering. Sputtering is enhanced in NPs compared to their bulk counterparts due to their large surface-to-volume ratio, especially when the ion range matches the NP size. In this work, the sputtering effects of Ar{sup +} and Ga{sup +} ion irradiated Au nanoparticles are investigated in detail by Monte Carlo (MC) and molecular dynamics (MD) simulations and a variety of experiments. The sputtering of Ar{sup +} and Ga{sup +} irradiated Au NPs was investigated as a function of ion energy, NP size and impact parameter by the MC code iradina and MD code parcas. The simulation results are directly compared to experiments using high resolution scanning electron microscopy (SEM) of Au NPs on top of Si, whereat the sputter yields are significantly enhanced compared to the MC simulations. Additionally, the interaction of NPs and substrate were investigated by Rutherford backscatter spectrometry (RBS), atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). A new MC code was developed to study the redeposition of sputtered atoms of Ga{sup +} irradiated Au NP arrays on neighboring NPs. The redeposition can lead to growth of NPs with diameters of 1 nm in vicinity of ∝50 nm NP. These simulations are directly compared to an in situ experiment. Nanostructures, spherical NPs as well as nanowires (NWs) are used as irradiation masks to structure lithium niobate (LNO) using the ion beam enhanced etching (IBEE) technique. The aspect ratio of the obtained structures can be enhanced by a second IBEE step

  5. Finite Element Simulation of Dynamic Stability of Plane Free-Surface of a Liquid under Vertical Excitation

    Directory of Open Access Journals (Sweden)

    Siva Srinivas Kolukula

    2013-01-01

    Full Text Available When partially filled liquid containers are excited vertically, the plane free-surface of the liquid can be stable or unstable depending on the amplitude and frequency of the external excitation. For some combinations of amplitude and frequency, the free-surface undergoes unbounded motion leading to instability called parametric instability or parametric resonance, and, for few other combinations, the free-surface undergoes bounded stable motion. In parametric resonance, a small initial perturbation on the free-surface can build up unboundedly even for small external excitation, if the excitation acts on the tank for sufficiently long time. In this paper, the stability of the plane free-surface is investigated by numerical simulation. Stability chart for the governing Mathieu equation is plotted analytically using linear equations. Applying fully nonlinear finite element method based on nonlinear potential theory, the response of the plane free-surface is simulated for various cases.

  6. NUMERICAL MODELING AND DYNAMIC SIMULATIONS OF NONLINEAR AEROTHERMOELASTIC OF A DOUBLE-WEDGE LIFTING SURFACE

    Directory of Open Access Journals (Sweden)

    ARIF A. EBRAHEEM AL-QASSAR

    2008-12-01

    Full Text Available The design of the re-entry space vehicles and high-speed aircrafts requires special attention to the nonlinear thermoelastic and aerodynamic instabilities of their structural components. The thermal effects are important since temperature environment influences significantly the static and dynamic behaviors of flight structures in supersonic/hypersonic regimes. To contribute to the understanding of dynamic behavior of these “hot” structures, a double-wedge lifting surface with combined freeplay and cubic stiffening structural nonlinearities in both plunging and pitching degrees-of-freedom operating in supersonic/hypersonic flight speed regimes has been analyzed. A third order Piston Theory Aerodynamics is used to evaluate the applied nonlinear unsteady aerodynamic loads. The loss of torsional stiffness that may be incurred by lifting surfaces subjected to axial stresses induced by aerodynamic heating is also considered. The aerodynamic heating effect is estimated based on the adiabatic wall temperature due to high speed airstreams. Modelling issues as well as simulation results have been presented and pertinent conclusions outlined. It is highlighted that a serious loss of torsional stiffness may induce the dynamic instability of the lifting surfaces. The influence of various parameters such as flight condition, thickness ratio, freeplays and pitching stiffness nonlinearity are also discussed.

  7. Mathematical simulation of sediment and contaminant transport in surface waters. Annual report, October 1977--September 1978

    International Nuclear Information System (INIS)

    Onishi, Y.; Arnold, E.M.; Serne, R.J.; Cowan, C.E.; Thompson, F.L.; Mayer, D.W.

    1979-01-01

    Various pathways exist for exposure of humans and biota to radioactive materials released from nuclear facilities. Hydrologic transport (liquid pathway) is one element in the evaluation of the total radiation dose to man. Mathematical models supported by well-planned field data collection programs can be useful tools in assessing the hydrologic transport and ultimate fate of radionuclides. Radionuclides with high distribution coefficients or radionuclides in surface waters with high suspended sediment concentrations are, to a great extent, adsorbed by river and marine sediments. Thus, otherwise dilute contaminants are concentrated. Contaminated sediments may be deposited on the river and ocean beds creating a significant pathway to man. Contaminated bed sediment in turn may become a long-term source of pollution through desorption and resuspension. In order to assess migration and accumulation of radionuclides in surface waters, mathematical models must correctly simulate essential mechanisms of radionuclide transport. The objectives of this study were: (1) to conduct a critical review of (a) radionuclide transport models as well as sediment transport and representative water quality models in rivers, estuaries, oceans, lakes, and reservoirs, and (b) adsorption and desorption mechanisms of radionuclides with sediments in surface waters; (2) to synthesize a mathematical model capable of predicting short- and long-term transport and accumulation of radionuclides in marine environments

  8. Analyzing the Molecular Kinetics of Water Spreading on Hydrophobic Surfaces via Molecular Dynamics Simulation.

    Science.gov (United States)

    Zhao, Lei; Cheng, Jiangtao

    2017-09-07

    In this paper, we report molecular kinetic analyses of water spreading on hydrophobic surfaces via molecular dynamics simulation. The hydrophobic surfaces are composed of amorphous polytetrafluoroethylene (PTFE) with a static contact angle of ~112.4° for water. On the basis of the molecular kinetic theory (MKT), the influences of both viscous damping and solid-liquid retarding were analyzed in evaluating contact line friction, which characterizes the frictional force on the contact line. The unit displacement length on PTFE was estimated to be ~0.621 nm and is ~4 times as long as the bond length of C-C backbone. The static friction coefficient was found to be ~[Formula: see text] Pa·s, which is on the same order of magnitude as the dynamic viscosity of water, and increases with the droplet size. A nondimensional number defined by the ratio of the standard deviation of wetting velocity to the characteristic wetting velocity was put forward to signify the strength of the inherent contact line fluctuation and unveil the mechanism of enhanced energy dissipation in nanoscale, whereas such effect would become insignificant in macroscale. Moreover, regarding a liquid droplet on hydrophobic or superhydrophobic surfaces, an approximate solution to the base radius development was derived by an asymptotic expansion approach.

  9. Effect of Nonsmooth Nose Surface of the Projectile on Penetration Using DEM Simulation

    Directory of Open Access Journals (Sweden)

    Jing Han

    2017-01-01

    Full Text Available The nonsmooth body surface of the reptile in nature plays an important role in reduction of resistance and friction when it lives in a soil environment. To consider whether it was feasible for improving the performance of penetrating projectile we investigated the influence of the convex as one of nonsmooth surfaces for the nose of projectile. A numerical simulation study of the projectile against the concrete target was developed based on the discrete element method (DEM. The results show that the convex nose surface of the projectile is beneficial for reducing the penetration resistance greatly, which is also validated by the experiments. Compared to the traditional smooth nose structure, the main reason of difference is due to the local contact normal pressure, which increases dramatically due to the abrupt change of curvature caused by the convex at the same condition. Accordingly, the broken particles of the concrete target obtain more kinetic energy and their average radial flow velocities will drastically increase simultaneously, which is in favor of decreasing the interface friction and the compaction density of concrete target around the nose of projectile.

  10. Surface Interaction of Nanoscale Water Film with SDS from Computational Simulation and Film Thermodynamics

    Directory of Open Access Journals (Sweden)

    Tiefeng Peng

    2017-11-01

    Full Text Available Foam systems have been attracting extensive attention due to their importance in a variety of applications, e.g., in the cleaning industry, and in bubble flotation. In the context of flotation chemistry, flotation performance is strongly affected by bubble coalescence, which in turn relies significantly on the surface forces upon the liquid film between bubbles. Conventionally, unusual short-range strongly repulsive surface interactions for Newton black films (NBF between two interfaces with thickness of less than 5 nm were not able to be incorporated into the available classical Derjaguin, Landau, Verwey, and Overbeek (DLVO theory. The non-DLVO interaction would increase exponentially with the decrease of film thickness, as it plays a crucial role in determining liquid film stability. However, its mechanism and origin are still unclear. In the present work, we investigate the surface interaction of free-standing sodium dodecyl-sulfate (SDS nanoscale black films in terms of disjoining pressure using the molecular simulation method. The aqueous nanoscale film, consisting of a water coating with SDS surfactants, and with disjoining pressure and film tension of SDS-NBF as a function of film thickness, were quantitatively determined by a post-processing technique derived from film thermodynamics.

  11. Efficient uncertainty quantification in fully-integrated surface and subsurface hydrologic simulations

    Science.gov (United States)

    Miller, K. L.; Berg, S. J.; Davison, J. H.; Sudicky, E. A.; Forsyth, P. A.

    2018-01-01

    Although high performance computers and advanced numerical methods have made the application of fully-integrated surface and subsurface flow and transport models such as HydroGeoSphere common place, run times for large complex basin models can still be on the order of days to weeks, thus, limiting the usefulness of traditional workhorse algorithms for uncertainty quantification (UQ) such as Latin Hypercube simulation (LHS) or Monte Carlo simulation (MCS), which generally require thousands of simulations to achieve an acceptable level of accuracy. In this paper we investigate non-intrusive polynomial chaos for uncertainty quantification, which in contrast to random sampling methods (e.g., LHS and MCS), represents a model response of interest as a weighted sum of polynomials over the random inputs. Once a chaos expansion has been constructed, approximating the mean, covariance, probability density function, cumulative distribution function, and other common statistics as well as local and global sensitivity measures is straightforward and computationally inexpensive, thus making PCE an attractive UQ method for hydrologic models with long run times. Our polynomial chaos implementation was validated through comparison with analytical solutions as well as solutions obtained via LHS for simple numerical problems. It was then used to quantify parametric uncertainty in a series of numerical problems with increasing complexity, including a two-dimensional fully-saturated, steady flow and transient transport problem with six uncertain parameters and one quantity of interest; a one-dimensional variably-saturated column test involving transient flow and transport, four uncertain parameters, and two quantities of interest at 101 spatial locations and five different times each (1010 total); and a three-dimensional fully-integrated surface and subsurface flow and transport problem for a small test catchment involving seven uncertain parameters and three quantities of interest at

  12. A contribution to the electron-beam surface-melting process of metallic materials. Numerical simulation and experimental verification

    International Nuclear Information System (INIS)

    Bruckner, A.

    1996-08-01

    For the optimization of the surface melting process it is necessary to make many different experiments. Therefore, the simulation of the surface melting process becomes a major role for the optimization. Most of the simulations, developed for the laser surface melting process, are not usable for the electron-beam surface melting process, because of the different energy input and the possibility of high frequent movement of the electron-beam. In this thesis, a calculation model for electron-beam surface melting is presented. For this numerical simulation a variable volume source is used, which moves in axial direction with the same velocity as the vapor cavity into the material. With this calculation model also the high frequent movement of the electron-beam may be taken into account. The electron-beam diameter is measured with a method of drilling holes with short electron-beam pulses in thin foils. The diameter of the holes depends on the pulse length and reaches a maximal value, which is used for the diameter of the volume source in the calculation. The crack-formation, seen in many treated surfaces, is examined with the Acoustic-Emission Testing. The possibilities of the electron-beam surface melting process are shown with some experiments for different requirements of the treated surfaces, like increasing the hardness, reducing the porosity of a sintered material and the alloying of tin in an aluminium-silicon surface. (author)

  13. Effects of whitening dentifrice on yttria-stabilized tetragonal zirconia polycrystal surfaces after simulating brushing.

    Science.gov (United States)

    Pinelli, Lígia Antunes Pereira; Gimenes Olbera, Amanda Caroline; Candido, Lucas Miguel; Miotto, Larissa Natiele; Antonio, Selma Gutierrez; Fais, Laiza Maria Grassi

    2017-01-01

    The changes that occur after brushing yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) are unknown. These changes may favor the retention of microorganisms and chemisorption of water, impairing its longevity. The purpose of this in vitro study was to evaluate the effects of a whitening dentifrice on Y-TZP surfaces after simulating 10 years of brushing. Seventy-two bar-shaped specimens (20×4×1.2 mm) were divided into 4 groups: storage in distilled water (SW, control), brushing with distilled water (BW), brushing with dentifrice (BD), and brushing with whitening dentifrice (BWD). Brushing was conducted using a linear brushing machine (878400 cycles, 0.98 N, soft toothbrush). The mean roughness (Ra) was analyzed with a profilometer and the superficial topography with scanning electron microscopy (SEM) at baseline and after treatment. Crystalline phases were characterized using x-ray diffraction. Baseline and posttreatment Ra were analyzed using the 1-way ANOVA and Tukey HSD multiple comparison test; the paired t test was used for intragroup comparison (all α=.05). The Ra (μm) means (before/after treatment) were SW 0.28/0.28; BW 0.32/0.31; BD 0.28/0.36; BWD 0.30/0.20. No statistically significant difference was found for Ra at baseline (P=.108) than for posttreatment results (P<.001); the BD group had higher Ra values when compared with baseline (P=.019); the BWD group had the lowest values (P<.001). The BD surfaces showed pronounced scratches and detachment of the surface, while BWD showed smoother surfaces; similar crystallographic results among groups were observed. Brushing Y-TZP with conventional dentifrice increased roughness, while brushing with whitening dentifrice reduced roughness. Neither dentifrice changed the crystallographic phases after brushing. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  14. Performance of surface on ultrafine grained Ti-0.2Pd in simulated body fluid

    Science.gov (United States)

    Wang, Xiu-Lai; Zhou, Qing; Yang, Kai; Zou, Cheng-Hong; Wang, Lei

    2018-03-01

    Ti-0.2 wt% Pd (Ti-0.2Pd) which has high crevice corrosion resistance is highlighted for implant applications. In this work, Ti-0.2Pd alloy is subjected to equal channel angular pressing (ECAP) for grain refinement. The effect of the microstructure on the surface performance of Ti-0.2Pd in a simulated body fluid (SBF) adding bovine serum albumin is investigated. Heat-treated specimens including furnace cooled (FC) and water quenched (WQ) specimens are also prepared for comparison. The corrosion resistance is evaluated by the tests of potentiodynamic polarization and the measurement of electrochemical impedance spectroscopy (EIS). The composition and morphology of the surface after exposing to SBF 60 days were examined by X-ray photoelectronic spectroscopy (XPS), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show an ultrafine grained microstructure with average grain size of 3.6 μm is obtained after ECAP. The ultrafine grained Ti-0.2Pd has higher corrosion resistance than AR(as-received), WQ and FC specimens. The quantitative analysis of the surface shows larger numbers of precipitations formed on ECAPed Ti-0.2Pd than those formed on heat-treated. The precipitation contains more oxygen, calcium and phosphorus on ECAPed specimen than those on other specimens. The Ca:P ratio is ranged from 1:0.7 to 1:4.4, no dependent on the specimen type. A larger Warburg resistance is obtained on WQ specimen indicating a denser layer formation on WQ specimen. The precipitation formed on WQ specimens is the least among three kinds of specimens. Palladium is not found on the surfaces after exposure to SBF.

  15. Simulations

    CERN Document Server

    Ngada, Narcisse

    2015-06-15

    The complexity and cost of building and running high-power electrical systems make the use of simulations unavoidable. The simulations available today provide great understanding about how systems really operate. This paper helps the reader to gain an insight into simulation in the field of power converters for particle accelerators. Starting with the definition and basic principles of simulation, two simulation types, as well as their leading tools, are presented: analog and numerical simulations. Some practical applications of each simulation type are also considered. The final conclusion then summarizes the main important items to keep in mind before opting for a simulation tool or before performing a simulation.

  16. Combined quantum chemistry and Monte Carlo simulation of competitive adsorption of O{sub 2} and OH on Pt surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Li, Rui, E-mail: ruililcu@gmail.com [Department of Chemistry, Liaocheng University, Liaocheng 252059 (China); Li, Haibo; Xu, Shuling [Department of Chemistry, Liaocheng University, Liaocheng 252059 (China); Liu, Jifeng, E-mail: liujifeng111@gmail.com [Key Laboratory of Food Nutrition and Safety, Ministry of Education of China, Tianjin University of Science and Technology, Tianjin 300457 (China)

    2017-07-15

    Highlights: • Competitive adsorption of O{sub 2} and OH on different Pt surfaces was theoretically studied. • The adsorption energies of O{sub 2} and OH depend on the Pt surfaces and the adsorption sites. • The order of O{sub 2} adsorption efficiency was characterized. - Abstract: To obtain a microscopic explanation on the difference of oxygen reduction reaction activity on different Pt low index surfaces, we simulated competitive adsorptions of O{sub 2} and OH on four Pt low index surfaces. Firstly, all possible chemical adsorption configurations of the O{sub 2} and OH molecules on the three surfaces were acquired through density functional theory. The distribution of these configurations on the different surfaces was collected from Monte Carlo simulations. Our results demonstrated that the adsorption energy order of O{sub 2} on different surfaces was (110)(1 × 2) > (110) > (100) > (111) and that the adsorption energy order of the OH molecules on Pt surfaces was the same. Considering the competitive adsorption of O{sub 2} and OH on Pt surfaces, the final O{sub 2} adsorption efficiencies order of three surfaces was (111) > (110) > (100) > (110)(1 × 2), which was consistent with the experimental activities of oxygen reduction. Our study provided theoretical references for previous experimental studies and had important significance for the understanding of oxygen adsorption on Pt surfaces.

  17. Mesopelagic Prokaryotes Alter Surface Phytoplankton Production during Simulated Deep Mixing Experiments in Eastern Mediterranean Sea Waters

    Directory of Open Access Journals (Sweden)

    Or Hazan

    2018-01-01

    Full Text Available Mesopelagic prokaryotes (archaea and bacteria, which are transported together with nutrient-rich intermediate-water to the surface layer by deep convection in the oceans (e.g., winter mixing, upwelling systems, can interact with surface microbial populations. This interaction can potentially affect production rates and biomass of surface microbial populations, and thus play an important role in the marine carbon cycle and oceanic carbon sequestration. The Eastern Mediterranean Sea (EMS is one of the most oligotrophic and warm systems in the world's oceans, with usually very shallow winter mixing (<200 m and lack of large-size spring algal blooms. In this study, we collected seawater (0–1,500 m in 9 different cruises at the open EMS during both the stratified and the mixed seasons. We show that the EMS is a highly oligotrophic regime, resulting in low autotrophic biomass and primary productivity and relatively high heterotrophic prokaryotic biomass and production. Further, we simulated deep water mixing in on-board microcosms using Levantine surface (LSW, ~0.5 m and intermediate (LIW, ~400 m waters at a 9:1 ratio, respectively and examined the responses of the microbial populations to such a scenario. We hypothesized that the LIW, being nutrient-rich (e.g., N, P and a “hot-spot” for microbial activity (due to the warm conditions that prevail in these depths, may supply the LSW with not only key-limiting nutrients but also with viable and active heterotrophic prokaryotes that can interact with the ambient surface microbial population. Indeed, we show that LIW heterotrophic prokaryotes negatively affected the surface phytoplankton populations, resulting in lower chlorophyll-a levels and primary production rates. This may be due to out-competition of phytoplankton by LIW populations for resources and/or by a phytoplankton cell lysis via viral infection. Our results suggest that phytoplankton in the EMS may not likely form blooms, even after

  18. WRF Simulation over the Eastern Africa by use of Land Surface Initialization

    Science.gov (United States)

    Sakwa, V. N.; Case, J.; Limaye, A. S.; Zavodsky, B.; Kabuchanga, E. S.; Mungai, J.

    2014-12-01

    to quantify possible improvements in simulated temperature, moisture and precipitation resulting from the experimental land surface initialization. These MET tools enable KMS to monitor model forecast accuracy in near real time. This study highlights verification results of WRF runs over East Africa using the LIS land surface initialization.

  19. Detection analysis of surface hydroxyl active sites and simulation calculation of the surface dissociation constants of aqueous diatomite suspensions

    Science.gov (United States)

    Ma, Shu-Cui; Wang, Zhi-Gang; Zhang, Ji-Lin; Sun, De-Hui; Liu, Gui-Xia

    2015-02-01

    The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation-deprotonation behavior was determined by continuous acid-base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m2/g and large numbers of surface hydroxyl functional groups (i.e. tbnd Si-OH, tbnd Fe-OH, and tbnd Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K1, log K2) and surface site concentrations (log C)) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation-deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent.

  20. Experimental simulations of oxidizing conditions and organic decomposition on the surface of Mars

    International Nuclear Information System (INIS)

    Stoker, C.R.; Mancinelli, R.L.; Mckay, C.P.

    1988-01-01

    One important scientific objective of a Mars Rover Sample Return mission would be to look for traces of living and extinct life on Mars. An instrument to search for organic carbon may be the simplest instrument that could screen samples which are interesting from a biological point of view. An experimental program is described which would help to understand the nature of the oxidizing soil on Mars and the mechanism responsible for organic degradation on the Martian surface. This is approached by lab simulations of the actual conditions that occur on Mars, particularly the oxidant production by atmospheric photochemistry, and the combined effects of UV light and oxidants in decomposing organic compounds. The results will be used to formulate models of the photochemistry of the atmospheric, the atmosphere-soil interaction, and the diffusion of reactive compounds into the soils. This information will provide insights and constraints on the design of a sampling strategy to search for organic compounds on Mars

  1. Analysis of surface insulation resistance related failures in electronics by circuit simulation

    DEFF Research Database (Denmark)

    Verdingovas, Vadimas; Joshy, Salil; Jellesen, Morten Stendahl

    2017-01-01

    of the circuits using a range of empirical leakage resistance values combined with the knowledge of the humidity and contamination profile of the electronics can be used for the robust design of a device, which is also important for electronic products relying on low current consumption for long battery lifetime......Purpose-The purpose of this study is to show that the humidity levels for surface insulation resistance (SIR)-related failures are dependent on the type of activators used in no-clean flux systems and to demonstrate the possibility of simulating the effects of humidity and contamination on printed...... conduction medium. Findings-This paper provides a summary of the effects of contamination with various weak organic acids representing the active components in no-clean solder flux residue, and demonstrates the effect of humidity and contamination on the possible malfunctions and errors in electronic...

  2. Magnetotransport properties of lateral-surface superlattices by molecular-dynamics Monte Carlo simulation

    Science.gov (United States)

    Yamada, Toshishige; Ferry, D. K.

    1993-01-01

    The magnetotransport properties of a lateral-surface superlattice, a two-dimensional (2D) electron system in a 2D periodic potential, are studied with use of a Monte Carlo technique, where the effect of the magnetic field is included through a Lorentz force and the interparticle Coulomb interaction is included with a molecular-dynamics method. Excellent numerical energy conservation is achieved by adopting a predictor-corrector algorithm to integrate the equations of motion. The simulation shows that the diffusion constant, as a function of the magnetic field, is not a simple monotone function but has a structure with multiple minima. This structure is attributed to the correlated circular electron motion, and this is reminiscent of classical pinning orbits in a 2D antidot array, even in the presence of the Coulomb interaction. The radial-distribution function shows no significant dependence upon the magnetic field up to ten flux quanta per unit cell.

  3. Experimental rig to estimate the coefficient of friction between tire and surface in airplane touchdown simulations.

    Science.gov (United States)

    Li, Chengwei; Zhan, Liwei

    2015-08-01

    To estimate the coefficient of friction between tire and runway surface during airplane touchdowns, we designed an experimental rig to simulate such events and to record the impact and friction forces being executed. Because of noise in the measured signals, we developed a filtering method that is based on the ensemble empirical mode decomposition and the bandwidth of probability density function of each intrinsic mode function to extract friction and impact force signals. We can quantify the coefficient of friction by calculating the maximum values of the filtered force signals. Signal measurements are recorded for different drop heights and tire rotational speeds, and the corresponding coefficient of friction is calculated. The result shows that the values of the coefficient of friction change only slightly. The random noise and experimental artifact are the major reason of the change.

  4. Diagnosing Model Errors in Simulations of Solar Radiation on Inclined Surfaces: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Yu; Sengupta, Manajit

    2016-06-01

    Transposition models have been widely used in the solar energy industry to simulate solar radiation on inclined PV panels. Following numerous studies comparing the performance of transposition models, this paper aims to understand the quantitative uncertainty in the state-of-the-art transposition models and the sources leading to the uncertainty. Our results suggest that an isotropic transposition model developed by Badescu substantially underestimates diffuse plane-of-array (POA) irradiances when diffuse radiation is perfectly isotropic. In the empirical transposition models, the selection of empirical coefficients and land surface albedo can both result in uncertainty in the output. This study can be used as a guide for future development of physics-based transposition models.

  5. Multimodel simulations of Arctic Ocean sea surface height variability in the period 1970-2009

    DEFF Research Database (Denmark)

    Koldunov, Nikolay V.; Serra, Nuno; Koehl, Armin

    2014-01-01

    is in reasonable agreement with available measurements. Focusing on results from one of the models for a detailed analysis, it is shown that the decadal-scale SSH variability over shelf areas and deep parts of the Arctic Ocean have pronounced differences that are determined mostly by salinity variations. A further......The performance of several numerical ocean models is assessed with respect to their simulation of sea surface height (SSH) in the Arctic Ocean, and the main patterns of SSH variability and their causes over the past 40 years (1970-2009) are analyzed. In comparison to observations, all tested models...... of low-salinity shelf water. Overall, we show that present-day models can be used for investigating the reasons for low-frequency SSH variability in the region....

  6. Simulation of Gravity Wave Propagation in Free Surface Flows by an Incompressible SPH Algorithm

    International Nuclear Information System (INIS)

    Amanifard, N.; Mahnama, S. M.; Neshaei, S. A. L.; Mehrdad, M. A.; Farahani, M. H.

    2012-01-01

    This paper presents an incompressible smoothed particle hydrodynamics model to simulate wave propagation in a free surface flow. The Navier-Stokes equations are solved in a Lagrangian framework using a three-step fractional method. In the first step, a temporary velocity field is provided according to the relevant body forces. This velocity field is renewed in the second step to include the viscosity effects. A Poisson equation is employed in the third step as an alternative for the equation of state in order to evaluate pressure. This Poisson equation considers a trade-off between density and pressure which is utilized in the third step to impose the incompressibility effect. The computations are compared with the experimental as well as numerical data and a good agreement is observed. In order to validate proposed algorithm, a dam-break problem is solved as a benchmark solution and the computational results are compared with the previous numerical ones.

  7. Detection analysis of surface hydroxyl active sites and simulation calculation of the surface dissociation constants of aqueous diatomite suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Shu-Cui [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province, Changchun University of Science and Technology, Changchun 130022 (China); Wang, Zhi-Gang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhang, Ji-Lin, E-mail: zjl@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Sun, De-Hui [Changchun Institute Technology, Changchun 130012 (China); Liu, Gui-Xia, E-mail: liuguixia22@163.com [Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province, Changchun University of Science and Technology, Changchun 130022 (China)

    2015-02-01

    Highlights: • To examine surface hydroxyl functional groups of the calcined diatomite by TGA-DSC, FTIR, and XPS. • To calculate the optimized log K{sub 1}, log K{sub 2} and log C values and the surface species distribution of each surface reactive site using ProtoFit and PHREEQC, respectively. - Abstract: The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation–deprotonation behavior was determined by continuous acid–base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m{sup 2}/g and large numbers of surface hydroxyl functional groups (i.e. ≡Si-OH, ≡Fe-OH, and ≡Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K{sub 1}, log K{sub 2}) and surface site concentrations (log C)) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation–deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent.

  8. Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Lin, E-mail: lz@njust.edu.cn [School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Zheng, Song [School of Mathematics and Statistics, Zhejiang University of Finance and Economics, Hangzhou 310018 (China); Zhai, Qinglan [School of Economics Management and Law, Chaohu University, Chaohu 238000 (China)

    2016-02-05

    In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.

  9. Direct molecular simulation of nitrogen dissociation based on an ab initio potential energy surface

    International Nuclear Information System (INIS)

    Valentini, Paolo; Schwartzentruber, Thomas E.; Bender, Jason D.; Nompelis, Ioannis; Candler, Graham V.

    2015-01-01

    The direct molecular simulation (DMS) approach is used to predict the internal energy relaxation and dissociation dynamics of high-temperature nitrogen. An ab initio potential energy surface (PES) is used to calculate the dynamics of two interacting nitrogen molecules by providing forces between the four atoms. In the near-equilibrium limit, it is shown that DMS reproduces the results obtained from well-established quasiclassical trajectory (QCT) analysis, verifying the validity of the approach. DMS is used to predict the vibrational relaxation time constant for N 2 –N 2 collisions and its temperature dependence, which are in close agreement with existing experiments and theory. Using both QCT and DMS with the same PES, we find that dissociation significantly depletes the upper vibrational energy levels. As a result, across a wide temperature range, the dissociation rate is found to be approximately 4–5 times lower compared to the rates computed using QCT with Boltzmann energy distributions. DMS calculations predict a quasi-steady-state distribution of rotational and vibrational energies in which the rate of depletion of high-energy states due to dissociation is balanced by their rate of repopulation due to collisional processes. The DMS approach simulates the evolution of internal energy distributions and their coupling to dissociation without the need to precompute rates or cross sections for all possible energy transitions. These benchmark results could be used to develop new computational fluid dynamics models for high-enthalpy flow applications

  10. Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow

    International Nuclear Information System (INIS)

    Zheng, Lin; Zheng, Song; Zhai, Qinglan

    2016-01-01

    In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.

  11. Cloud-enabled large-scale land surface model simulations with the NASA Land Information System

    Science.gov (United States)

    Duffy, D.; Vaughan, G.; Clark, M. P.; Peters-Lidard, C. D.; Nijssen, B.; Nearing, G. S.; Rheingrover, S.; Kumar, S.; Geiger, J. V.

    2017-12-01

    Developed by the Hydrological Sciences Laboratory at NASA Goddard Space Flight Center (GSFC), the Land Information System (LIS) is a high-performance software framework for terrestrial hydrology modeling and data assimilation. LIS provides the ability to integrate satellite and ground-based observational products and advanced modeling algorithms to extract land surface states and fluxes. Through a partnership with the National Center for Atmospheric Research (NCAR) and the University of Washington, the LIS model is currently being extended to include the Structure for Unifying Multiple Modeling Alternatives (SUMMA). With the addition of SUMMA in LIS, meaningful simulations containing a large multi-model ensemble will be enabled and can provide advanced probabilistic continental-domain modeling capabilities at spatial scales relevant for water managers. The resulting LIS/SUMMA application framework is difficult for non-experts to install due to the large amount of dependencies on specific versions of operating systems, libraries, and compilers. This has created a significant barrier to entry for domain scientists that are interested in using the software on their own systems or in the cloud. In addition, the requirement to support multiple run time environments across the LIS community has created a significant burden on the NASA team. To overcome these challenges, LIS/SUMMA has been deployed using Linux containers, which allows for an entire software package along with all dependences to be installed within a working runtime environment, and Kubernetes, which orchestrates the deployment of a cluster of containers. Within a cloud environment, users can now easily create a cluster of virtual machines and run large-scale LIS/SUMMA simulations. Installations that have taken weeks and months can now be performed in minutes of time. This presentation will discuss the steps required to create a cloud-enabled large-scale simulation, present examples of its use, and

  12. The effect of GCM biases on global runoff simulations of a land surface model

    Science.gov (United States)

    Papadimitriou, Lamprini V.; Koutroulis, Aristeidis G.; Grillakis, Manolis G.; Tsanis, Ioannis K.

    2017-09-01

    Global climate model (GCM) outputs feature systematic biases that render them unsuitable for direct use by impact models, especially for hydrological studies. To deal with this issue, many bias correction techniques have been developed to adjust the modelled variables against observations, focusing mainly on precipitation and temperature. However, most state-of-the-art hydrological models require more forcing variables, in addition to precipitation and temperature, such as radiation, humidity, air pressure, and wind speed. The biases in these additional variables can hinder hydrological simulations, but the effect of the bias of each variable is unexplored. Here we examine the effect of GCM biases on historical runoff simulations for each forcing variable individually, using the JULES land surface model set up at the global scale. Based on the quantified effect, we assess which variables should be included in bias correction procedures. To this end, a partial correction bias assessment experiment is conducted, to test the effect of the biases of six climate variables from a set of three GCMs. The effect of the bias of each climate variable individually is quantified by comparing the changes in simulated runoff that correspond to the bias of each tested variable. A methodology for the classification of the effect of biases in four effect categories (ECs), based on the magnitude and sensitivity of runoff changes, is developed and applied. Our results show that, while globally the largest changes in modelled runoff are caused by precipitation and temperature biases, there are regions where runoff is substantially affected by and/or more sensitive to radiation and humidity. Global maps of bias ECs reveal the regions mostly affected by the bias of each variable. Based on our findings, for global-scale applications, bias correction of radiation and humidity, in addition to that of precipitation and temperature, is advised. Finer spatial-scale information is also provided

  13. Surface drag effects on simulated wind fields in high-resolution atmospheric forecast model

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Kyo Sun; Lim, Jong Myoung; Ji, Young Yong [Environmental Radioactivity Assessment Team,Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Shin, Hye Yum [NOAA/Geophysical Fluid Dynamics Laboratory, Princeton (United States); Hong, Jin Kyu [Yonsei University, Seoul (Korea, Republic of)

    2017-04-15

    It has been reported that the Weather Research and Forecasting (WRF) model generally shows a substantial over prediction bias at low to moderate wind speeds and winds are too geostrophic (Cheng and Steenburgh 2005), which limits the application of WRF model in the area that requires the accurate surface wind estimation such as wind-energy application, air-quality studies, and radioactive-pollutants dispersion studies. The surface drag generated by the subgrid-scale orography is represented by introducing a sink term in the momentum equation in their studies. The purpose of our study is to evaluate the simulated meteorological fields in the high-resolution WRF framework, that includes the parameterization of subgrid-scale orography developed by Mass and Ovens (2010), and enhance the forecast skill of low-level wind fields, which plays an important role in transport and dispersion of air pollutants including radioactive pollutants. The positive bias in 10-m wind speed is significantly alleviated by implementing the subgrid-scale orography parameterization, while other meteorological fields including 10-m wind direction are not changed. Increased variance of subgrid- scale orography enhances the sink of momentum and further reduces the bias in 10-m wind speed.

  14. Simulated Response of a Tissue-equivalent Proportional Counter on the Surface of Mars.

    Science.gov (United States)

    Northum, Jeremy D; Guetersloh, Stephen B; Braby, Leslie A; Ford, John R

    2015-10-01

    Uncertainties persist regarding the assessment of the carcinogenic risk associated with galactic cosmic ray (GCR) exposure during a mission to Mars. The GCR spectrum peaks in the range of 300(-1) MeV n to 700 MeV n(-1) and is comprised of elemental ions from H to Ni. While Fe ions represent only 0.03% of the GCR spectrum in terms of particle abundance, they are responsible for nearly 30% of the dose equivalent in free space. Because of this, radiation biology studies focusing on understanding the biological effects of GCR exposure generally use Fe ions. Acting as a thin shield, the Martian atmosphere alters the GCR spectrum in a manner that significantly reduces the importance of Fe ions. Additionally, albedo particles emanating from the regolith complicate the radiation environment. The present study uses the Monte Carlo code FLUKA to simulate the response of a tissue-equivalent proportional counter on the surface of Mars to produce dosimetry quantities and microdosimetry distributions. The dose equivalent rate on the surface of Mars was found to be 0.18 Sv y(-1) with an average quality factor of 2.9 and a dose mean lineal energy of 18.4 keV μm(-1). Additionally, albedo neutrons were found to account for 25% of the dose equivalent. It is anticipated that these data will provide relevant starting points for use in future risk assessment and mission planning studies.

  15. AC surface flashover strength and barrier effect of LN 2 for HTS transformer with simulated electrode

    Science.gov (United States)

    Joung, Jong-Man; Baek, Seung-Myeong; Kim, Hae-Jong; Kim, Sang-Hyun

    2003-10-01

    In the response to an increasing demand for electrical energy, much effort aimed to develop and commercialise HTS power equipments is going on around the world. For the development, it is necessary to establish the dielectric technology in LN 2. Hence many types of dielectric tests should be carried out to understand the dielectric phenomena at cryogenic temperature and to gather various dielectric data. Among the many types dielectric tests, the characteristic of surface flashover and the barrier effect were conducted with the simulated electrode after analysing the insulating configuration of the pancake-coil-type HTS transformer. The influence of a barrier on the dielectric strength was measured according to the size of the barrier, the position of the barrier and the effect of the back-electrode. It was shown that the effectiveness, namely the ratio of the breakdown voltage in presence of barrier to the voltage without barrier, is highest when the barrier is placed at the needle electrode side. The effect increased up to 1.8 times when collar length is 10 mm. The flashover characteristic with back-electrode was remarkably lower than the characteristic without one in the case the electrodes located at the same surface of dielectric plate. On the contrary, in the case the barrier was placed between the electrodes, the characteristic was even improved slightly.

  16. Observations and simulations of microplastic marine debris in the ocean surface boundary layer

    Science.gov (United States)

    Kukulka, T.; Brunner, K.; Proskurowski, G. K.; Lavender Law, K. L.

    2016-02-01

    Motivated by observations of buoyant microplastic marine debris (MPMD) in the ocean surface boundary layer (OSBL), this study applies a large eddy simulation model and a parametric one-dimensional column model to examine vertical distributions of MPMD. MPMD is widely distributed in vast regions of the subtropical gyres and has emerged as a major open ocean pollutant whose distribution is subject to upper ocean turbulence. The models capture wind-driven turbulence, Langmuir turbulence (LT), and enhanced turbulent kinetic energy input due to breaking waves (BW). Model results are only consistent with MPMD observations if LT effects are included. Neither BW nor shear-driven turbulence is capable of deeply submerging MPMD, suggesting that the observed vertical MPMD distributions are a characteristic signature of wave-driven LT. Thus, this study demonstrates that LT substantially increases turbulent transport in the OSBL, resulting in deep submergence of buoyant tracers. The parametric model is applied to eleven years of observations in the North Atlantic and North Pacific subtropical gyres to show that surface measurements substantially underestimate MPMD concentrations by a factor of three to thirteen.

  17. Orbiter BLT Flight Experiment Wind Tunnel Simulations: Nearfield Flowfield Imaging and Surface Thermography

    Science.gov (United States)

    Danehy, Paul M.; Ivey, Christoper B.; Barthel, Brett F.; Inman, Jennifer A.; Jones, Stephen B.; Watkins, Anthony N.; Goodman, Kyle Z.; McCrea, Andrew C.; Leighty, Bradley D.; Lipford, William K.; hide

    2010-01-01

    This paper reports a series of wind tunnel tests simulating the near-field behavior of the Space Shuttle Orbiter Boundary Layer Transition Detailed Test Objective (BLT DTO) flight experiment. Hypersonic flow over a flat plate with an attached BLT DTO-shaped trip was tested in a Mach 10 wind tunnel. The sharp-leading-edge flat plate was oriented at an angle of 20 degrees with respect to the freestream flow, resulting in post-shock edge Mach number of approximately 4. The flowfield was visualized using nitric oxide (NO) planar laser-induced fluorescence (PLIF). Flow visualizations were performed at 10 Hz using a wide-field of view and high-resolution NO PLIF system. A lower spatial resolution and smaller field of view NO PLIF system visualized the flow at 500 kHz, which was fast enough to resolve unsteady flow features. At the lowest Reynolds number studied, the flow was observed to be laminar and mostly steady. At the highest Reynolds number, flow visualizations showed streak instabilities generated immediately downstream of the trip. These instabilities transitioned to unsteady periodic and spatially irregular structures downstream. Quantitative surface heating imagery was obtained using the Temperature Sensitive Paint (TSP) technique. Comparisons between the PLIF flow visualizations and TSP heating measurements show a strong correlation between flow patterns and surface heating trends.

  18. Simulation Study of Near-Surface Coupling of Nuclear Devices vs. Equivalent High-Explosive Charges

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, Kevin B [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Walton, Otis R [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Benjamin, Russ [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dunlop, William H [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-09-29

    A computational study was performed to examine the differences in near-surface ground-waves and air-blast waves generated by high-explosive energy sources and those generated by much higher energy - density low - yield nuclear sources. The study examined the effect of explosive-source emplacement (i.e., height-of-burst, HOB, or depth-of-burial, DOB) over a range from depths of -35m to heights of 20m, for explosions with an explosive yield of 1-kt . The chemical explosive was modeled by a JWL equation-of-state model for a ~14m diameter sphere of ANFO (~1,200,000kg – 1 k t equivalent yield ), and the high-energy-density source was modeled as a one tonne (1000 kg) plasma of ‘Iron-gas’ (utilizing LLNL’s tabular equation-of-state database, LEOS) in a 2m diameter sphere, with a total internal-energy content equivalent to 1 k t . A consistent equivalent-yield coupling-factor approach was developed to compare the behavior of the two sources. The results indicate that the equivalent-yield coupling-factor for air-blasts from 1 k t ANFO explosions varies monotonically and continuously from a nearly perfec t reflected wave off of the ground surface for a HOB ≈ 20m, to a coupling factor of nearly zero at DOB ≈ -25m. The nuclear air - blast coupling curve, on the other hand, remained nearly equal to a perfectly reflected wave all the way down to HOB’s very near zero, and then quickly dropped to a value near zero for explosions with a DOB ≈ -10m. The near - surface ground - wave traveling horizontally out from the explosive source region to distances of 100’s of meters exhibited equivalent - yield coupling - factors t hat varied nearly linearly with HOB/DOB for the simulated ANFO explosive source, going from a value near zero at HOB ≈ 5m to nearly one at DOB ≈ -25m. The nuclear-source generated near-surface ground wave coupling-factor remained near zero for almost all HOB’s greater than zero, and then appeared to vary nearly - linearly with depth

  19. Simulation of Missing Pellet Surface thermal behavior with 3D dynamic gap element

    International Nuclear Information System (INIS)

    Kim, Hyo Chan; Yang, Yong Sik; Koo, Yang Hyun; Kang, Chang Hak; Lee Sung Uk; Yang, Dong Yol

    2014-01-01

    Most of the fuel performance codes that are able to simulate a multidimensional analysis are used to calculate the radial temperature distribution and perform a multidimensional mechanical analysis based on a one-dimensional (1D) temperature result. The FRAPCON-FRAPTRAN code system incorporates a 1D thermal module and two-dimensional (2D) mechanical module when FEM option is activated. In this method, the multidimensional gap conductance model is not required because one-dimensional thermal analysis is carried out. On the other hand, a gap conductance model for a multi-dimension should be developed in the code to perform a multidimensional thermal analysis. ALCYONE developed by CEA introduces an equivalent heat convection coefficient that represents the multidimensional gap conductance. However, the code does not employ dynamic gap conductance which is a function of gap thickness and gap characteristics in direct. The BISON code, which has been developed by INL (Idaho National Laboratory), employed a thermo-mechanical contact method that is specifically designed for tightly-coupled implicit solutions that employ Jacobian-free solution methods. Owing to tightly-coupled implicit solutions, the BISON code solves gap conductance and gap thickness simultaneously with given boundary conditions. In this paper, 3D dynamic gap element has been proposed to resolve convergence issue and nonlinear characteristic of multidimensional gap conductance. To evaluate 3D dynamic gap element module, 3D thermomechanical module using FORTRAN77 has been implemented incorporating 3D dynamic gap element. To demonstrate effect of 3D dynamic gap element, thermal behavior of missing pellet surface (MPS) has been simulated by the developed module. LWR fuel performance codes should incorporate thermo-mechanical loop to solve gap conductance problem, iteratively. However, gap conductance in multidimensional model is difficult issue owing to its nonlinearity and convergence characteristics. In

  20. Evaluation of surface roughness of microhybrid and nanofilled composites after pH-cycling and simulated toothbrushing.

    Science.gov (United States)

    Penteado, Roberta Alves Pinto Moura; Tonholo, Josealdo; Júnior, José Ginaldo; Silva, Milton Fernando de Andrade; Queiroz, Celso da Silva; Cavalli, Vanessa; Rego, Marcos Augusto do; Liporoni, Priscila Christiane Suzy

    2010-12-01

    This study evaluated the surface roughness patterns of two resin-based composite restorative materials, a microhybrid (Filtek Z250, 3M ESPE) and a nanofilled (Filtek Supreme, 3M ESPE), subjected to a regimen that simulated dynamic pH-cycling and toothbrushing. Twelve standardized cylindrical specimens of each resin-based composite material were prepared, finished, and mechanically polished. The experimental units were submitted to a pH-cycling regimen followed by 50,000 toothbrushing cycles, after which the surface roughness was measured using an atomic force microscope (AFM). AFM surface roughness was evaluated at three intervals: (1) immediately after specimen preparation (baseline), (2) after pH-cycling, and (3) after simulated toothbrushing. The results were then analyzed using a split-plot design and followed by linear regression and a Tukey's test at a significance level of ptoothbrushing provoked a remarkable increase in surface roughness for both types of composite resins tested (p=0.0031). However, pH-cycling did not alter the surface of the composite under the conditions of this experiment. Based on the results obtained, it was concluded that simulated toothbrushing was capable of increasing the surface roughness of the microhybrid (Filtek Z250) and the nanofilled (Filtek Supreme) composites tested. Surface roughness of nanofilled and microhybrid composites is significantly increased after toothbrushing, although pH-cycling, as tested in this study, does not appear to affect the morphology of either composite material.

  1. Contact angle and surface free energy of experimental resin-based dental restorative materials after chewing simulation.

    Science.gov (United States)

    Rüttermann, Stefan; Beikler, Thomas; Janda, Ralf

    2014-06-01

    To investigate contact angle and surface free energy of experimental dental resin composites containing novel delivery systems of polymeric hollow beads and low-surface tension agents after chewing simulation test. A delivery system of novel polymeric hollow beads differently loaded with two low-surface tension agents was used in different amounts to modify commonly formulated experimental dental resin composites. The non-modified resin was used as standard. Surface roughness Ra, contact angle Θ, total surface free energy γS, its apolar γS(LW), polar γS(AB), Lewis acid γS(+) and base γS(-) terms were determined and the results prior to and after chewing simulation test were compared. Significance was phollow beads highly loaded with low-surface tension agents were found to significantly increase contact angle and thus to reduce surface free energy of experimental dental resin composites prior to and after chewing simulation test. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Evaluation of air-soil temperature relationships simulated by land surface models during winter across the permafrost region

    Science.gov (United States)

    Wang, Wenli; Rinke, Annette; Moore, John C.; Ji, Duoying; Cui, Xuefeng; Peng, Shushi; Lawrence, David M.; McGuire, A. David; Burke, Eleanor J.; Chen, Xiaodong; Delire, Christine; Koven, Charles; MacDougall, Andrew; Saito, Kazuyuki; Zhang, Wenxin; Alkama, Ramdane; Bohn, Theodore J.; Ciais, Philippe; Decharme, Bertrand; Gouttevin, Isabelle; Hajima, Tomohiro; Krinner, Gerhard; Lettenmaier, Dennis P.; Miller, Paul A.; Smith, Benjamin; Sueyoshi, Tetsuo

    2016-01-01

     A realistic simulation of snow cover and its thermal properties are important for accurate modelling of permafrost. We analyze simulated relationships between air and near-surface (20 cm) soil temperatures in the Northern Hemisphere permafrost region during winter, with a particular focus on snow insulation effects in nine land surface models and compare them with observations from 268 Russian stations. There are large across-model differences as expressed by simulated differences between near-surface soil and air temperatures, (ΔT), of 3 to 14 K, in the gradients between soil and air temperatures (0.13 to 0.96°C/°C), and in the relationship between ΔT and snow depth. The observed relationship between ΔT and snow depth can be used as a metric to evaluate the effects of each model's representation of snow insulation, and hence guide improvements to the model’s conceptual structure and process parameterizations. Models with better performance apply multi-layer snow schemes and consider complex snow processes. Some models show poor performance in representing snow insulation due to underestimation of snow depth and/or overestimation of snow conductivity. Generally, models identified as most acceptable with respect to snow insulation simulate reasonable areas of near-surface permafrost (12–16 million km2). However, there is not a simple relationship between the quality of the snow insulation in the acceptable models and the simulated area of Northern Hemisphere near-surface permafrost, likely because several other factors such as differences in the treatment of soil organic matter, soil hydrology, surface energy calculations, and vegetation also provide important controls on simulated permafrost distribution.

  3. Stimulated Raman signals at conical intersections: Ab initio surface hopping simulation protocol with direct propagation of the nuclear wave function

    Energy Technology Data Exchange (ETDEWEB)

    Kowalewski, Markus, E-mail: mkowalew@uci.edu; Mukamel, Shaul, E-mail: smukamel@uci.edu [Department of Chemistry, University of California, Irvine, California 92697-2025 (United States)

    2015-07-28

    Femtosecond Stimulated Raman Spectroscopy (FSRS) signals that monitor the excited state conical intersections dynamics of acrolein are simulated. An effective time dependent Hamiltonian for two C—H vibrational marker bands is constructed on the fly using a local mode expansion combined with a semi-classical surface hopping simulation protocol. The signals are obtained by a direct forward and backward propagation of the vibrational wave function on a numerical grid. Earlier work is extended to fully incorporate the anharmonicities and intermode couplings.

  4. Stimulated Raman signals at conical intersections: Ab initio surface hopping simulation protocol with direct propagation of the nuclear wave function

    International Nuclear Information System (INIS)

    Kowalewski, Markus; Mukamel, Shaul

    2015-01-01

    Femtosecond Stimulated Raman Spectroscopy (FSRS) signals that monitor the excited state conical intersections dynamics of acrolein are simulated. An effective time dependent Hamiltonian for two C—H vibrational marker bands is constructed on the fly using a local mode expansion combined with a semi-classical surface hopping simulation protocol. The signals are obtained by a direct forward and backward propagation of the vibrational wave function on a numerical grid. Earlier work is extended to fully incorporate the anharmonicities and intermode couplings

  5. CFD simulation of direct contact condensation with ANSYS CFX using surface renewal theory based heat transfer coefficients

    Energy Technology Data Exchange (ETDEWEB)

    Wanninger, Andreas; Ceuca, Sabin Cristian; Macian-Juan, Rafael [Technische Univ. Muenchen, Garching (Germany). Dept. of Nuclear Engineering

    2013-07-01

    Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)

  6. Molecular dynamics simulation of temperature effects on low energy near-surface cascades and surface damage in Cu

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Guo; Sun, Jiangping; Guo, Xiongxiong; Zou, Xixi; Zhang, Libin; Gan, Zhiyin, E-mail: ganzhiyin@126.com

    2017-06-15

    The temperature effects on near-surface cascades and surface damage in Cu(0 0 1) surface under 500 eV argon ion bombardment were studied using molecular dynamics (MD) method. In present MD model, substrate system was fully relaxed for 1 ns and a read-restart scheme was introduced to save total computation time. The temperature dependence of damage production was calculated. The evolution of near-surface cascades and spatial distribution of adatoms at varying temperature were analyzed and compared. It was found that near-surface vacancies increased with temperature, which was mainly due to the fact that more atoms initially located in top two layers became adatoms with the decrease of surface binding energy. Moreover, with the increase of temperature, displacement cascades altered from channeling-like structure to branching structure, and the length of collision sequence decreased gradually, because a larger portion of energy of primary knock-on atom (PKA) was scattered out of focused chain. Furthermore, increasing temperature reduced the anisotropy of distribution of adatoms, which can be ascribed to that regular registry of surface lattice atoms was changed with the increase of thermal vibration amplitude of surface atoms.

  7. Molecular dynamics simulation of temperature effects on low energy near-surface cascades and surface damage in Cu

    Science.gov (United States)

    Zhu, Guo; Sun, Jiangping; Guo, Xiongxiong; Zou, Xixi; Zhang, Libin; Gan, Zhiyin

    2017-06-01

    The temperature effects on near-surface cascades and surface damage in Cu(0 0 1) surface under 500 eV argon ion bombardment were studied using molecular dynamics (MD) method. In present MD model, substrate system was fully relaxed for 1 ns and a read-restart scheme was introduced to save total computation time. The temperature dependence of damage production was calculated. The evolution of near-surface cascades and spatial distribution of adatoms at varying temperature were analyzed and compared. It was found that near-surface vacancies increased with temperature, which was mainly due to the fact that more atoms initially located in top two layers became adatoms with the decrease of surface binding energy. Moreover, with the increase of temperature, displacement cascades altered from channeling-like structure to branching structure, and the length of collision sequence decreased gradually, because a larger portion of energy of primary knock-on atom (PKA) was scattered out of focused chain. Furthermore, increasing temperature reduced the anisotropy of distribution of adatoms, which can be ascribed to that regular registry of surface lattice atoms was changed with the increase of thermal vibration amplitude of surface atoms.

  8. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface

    NARCIS (Netherlands)

    Wolthers, M.; Di Tommaso, D.; Du, Z.; de Leeuw, N.H.

    2012-01-01

    Calcite–water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity.

  9. Size-effects on the surface tension near the critical point: Monte Carlo simulations of the Lennard-Jones fluid

    Science.gov (United States)

    Goujon, Florent; Ghoufi, Aziz; Malfreyt, Patrice

    2018-02-01

    We report Monte Carlo (MC) simulations of the Lennard-Jones (LJ) fluid at the liquid-vapor interface in the critical region. A slab-based tail method is associated with the MC simulations to approach as close as possible the critical point (T∗ = 0.98 TC∗) . We investigate then the impact of system-sizes on the surface tension and coexisting densities by considering very large box dimensions for which the surface tension is independent of system-sizes at low temperatures.

  10. Simulation of Intra- or transboundary surface-water-rights hierarchies using the farm process for MODFLOW-2000

    Science.gov (United States)

    Schmid, W.; Hanson, R.T.

    2007-01-01

    Water-rights driven surface-water allocations for irrigated agriculture can be simulated using the farm process for MODFLOW-2000. This paper describes and develops a model, which simulates routed surface-water deliveries to farms limited by streamflow, equal-appropriation allotments, or a ranked prior-appropriation system. Simulated diversions account for deliveries to all farms along a canal according to their water-rights ranking and for conveyance losses and gains. Simulated minimum streamflow requirements on diversions help guarantee supplies to senior farms located on downstream diverting canals. Prior appropriation can be applied to individual farms or to groups of farms modeled as "virtual farms" representing irrigation districts, irrigated regions in transboundary settings, or natural vegetation habitats. The integrated approach of jointly simulating canal diversions, surface-water deliveries subject to water-rights constraints, and groundwater allocations is verified on numerical experiments based on a realistic, but hypothetical, system of ranked virtual farms. Results are discussed in light of transboundary water appropriation and demonstrate the approach's suitability for simulating effects of water-rights hierarchies represented by international treaties, interstate stream compacts, intrastate water rights, or ecological requirements. ?? 2007 ASCE.

  11. Trend of surface solar radiation over Asia simulated by aerosol transport-climate model

    Science.gov (United States)

    Takemura, T.; Ohmura, A.

    2009-12-01

    . Continuous hindcast simulation during the last several decades is done to compare with surface radiation measurements. Cause of the global dimming and brightening is separated into the aerosol direct and indirect effects from the simulation. Acknowledgments. The simulation in this study was performed on the NIES supercomputer system (NEC SX-8R). This study is partly supported by the Global Environment Research Fund (RF-091) by the Ministry of the Environment of Japan, Grant-in-Aid for Young Scientist (21681001) by the Ministry of Education, Culture, Sports, Science, and Technology of Japan, and Mitsui & Co., Ltd. Environment Fund (R08-D035). References Ohmura, A. (2009), J. Geophys. Res., 114, doi:10.1029/2008JD011290. Takemura, T., et al. (2000), J. Geophys. Res., 105, 17853-17873. Takemura, T., et al. (2002), J. Climate, 15, 333-352. Takemura, T., et al. (2005), J. Geophys. Res., 110, doi:10.1029/2004JD005029. Takemura, T., et al. (2009), Atmos. Chem. Phys., 9, 3061-3073. Wild, M. (2009), J. Geophys. Res., 114, doi:10.1029/2008JD011470.

  12. Study of Near-Surface Models in Large-Eddy Simulations of a Neutrally Stratified Atmospheric Boundary Layer

    Science.gov (United States)

    Senocak, I.; Ackerman, A. S.; Kirkpatrick, M. P.; Stevens, D. E.; Mansour, N. N.

    2004-01-01

    Large-eddy simulation (LES) is a widely used technique in armospheric modeling research. In LES, large, unsteady, three dimensional structures are resolved and small structures that are not resolved on the computational grid are modeled. A filtering operation is applied to distinguish between resolved and unresolved scales. We present two near-surface models that have found use in atmospheric modeling. We also suggest a simpler eddy viscosity model that adopts Prandtl's mixing length model (Prandtl 1925) in the vicinity of the surface and blends with the dynamic Smagotinsky model (Germano et al, 1991) away from the surface. We evaluate the performance of these surface models by simulating a neutraly stratified atmospheric boundary layer.

  13. Applications of computer simulation, nuclear reactions and elastic scattering to surface analysis of materials

    Directory of Open Access Journals (Sweden)

    Pacheco de Carvalho, J. A.

    2008-08-01

    Full Text Available This article involves computer simulation and surface analysis by nuclear techniques, which are non-destructive. Both the “energy method of analysis” for nuclear reactions and elastic scattering are used. Energy spectra are computer simulated and compared with experimental data, giving target composition and concentration profile information. The method is successfully applied to thick flat targets of graphite, quartz and sapphire and targets containing thin films of aluminium oxide. Depth profiles of 12C and 16O nuclei are determined using (d,p and (d,α deuteron induced reactions. Rutherford and resonance elastic scattering of (4He+ ions are also used.

    Este artículo trata de simulación por ordenador y del análisis de superficies mediante técnicas nucleares, que son no destructivas. Se usa el “método de análisis en energia” para reacciones nucleares, así como el de difusión elástica. Se simulan en ordenador espectros en energía que se comparan com datos experimentales, de lo que resulta la obención de información sobre la composición y los perfiles de concentración de la muestra. Este método se aplica con éxito em muestras espesas y planas de grafito, cuarzo y zafiro y muestras conteniendo películas finas de óxido de aluminio. Se calculan perfiles en profundidad de núcleos de 12C y de 16O a través de reacciones (d,p y (d,α inducidas por deuterones. Se utiliza también la difusión elástica de iones (4He+, tanto a Rutherford como resonante.

  14. The Role of Surface Energy Exchange for Simulating Wind Inflow: An Evaluation of Multiple Land Surface Models in WRF for the Southern Great Plains Site Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Wharton, Sonia [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Simpson, Matthew [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Osuna, Jessica [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Newman, Jennifer [National Renewable Energy Lab. (NREL), Golden, CO (United States); Biraud, Sebastien [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2016-05-01

    The Weather Research and Forecasting (WRF) model is used to investigate choice of land surface model (LSM) on the near-surface wind profile, including heights reached by multi-megawatt wind turbines. Simulations of wind profiles and surface energy fluxes were made using five LSMs of varying degrees of sophistication in dealing with soil-plant-atmosphere feedbacks for the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Southern Great Plains (SGP) Central Facility in Oklahoma. Surface-flux and wind-profile measurements were available for validation. The WRF model was run for three two-week periods during which varying canopy and meteorological conditions existed. The LSMs predicted a wide range of energy-flux and wind-shear magnitudes even during the cool autumn period when we expected less variability. Simulations of energy fluxes varied in accuracy by model sophistication, whereby LSMs with very simple or no soil-plant-atmosphere feedbacks were the least accurate; however, the most complex models did not consistently produce more accurate results. Errors in wind shear also were sensitive to LSM choice and were partially related to the accuracy of energy flux data. The variability of LSM performance was relatively high, suggesting that LSM representation of energy fluxes in the WRF model remains a significant source of uncertainty for simulating wind turbine inflow conditions.

  15. High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Pogorelko, Victor V., E-mail: vik_ko83@mail.ru [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation); Mayer, Alexander E., E-mail: mayer@csu.ru [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation); Krasnikov, Vasiliy S., E-mail: vas.krasnikov@gmail.com [Chelyabinsk State University, Bratiev Kashirinykh 129, 454001 Chelyabinsk (Russian Federation); South Ural State University (National Research University), Lenin Prospect 76, 454080 Chelyabinsk (Russian Federation)

    2016-12-30

    Highlights: • High-speed nanoparticle impact induces shock waves and intensive plastic deformation. • Lattice orientation strongly influences on the deformation degree. • Plastic deformation goes through nucleation, growth and separation of semi-loops. • Medium impact energy and elevated temperature are optimal for high-quality coating. • High impact velocity and room temperature lead to plastic deformation and coating. - Abstract: We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2–22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the

  16. Peri-Elastodynamic Simulations of Guided Ultrasonic Waves in Plate-Like Structure with Surface Mounted PZT

    Directory of Open Access Journals (Sweden)

    Subir Patra

    2018-01-01

    Full Text Available Peridynamic based elastodynamic computation tool named Peri-elastodynamics is proposed herein to simulate the three-dimensional (3D Lamb wave modes in materials for the first time. Peri-elastodynamics is a nonlocal meshless approach which is a scale-independent generalized technique to visualize the acoustic and ultrasonic waves in plate-like structure, micro-electro-mechanical systems (MEMS and nanodevices for their respective characterization. In this article, the characteristics of the fundamental Lamb wave modes are simulated in a sample plate-like structure. Lamb wave modes are generated using a surface mounted piezoelectric (PZT transducer which is actuated from the top surface. The proposed generalized Peri-elastodynamics method is not only capable of simulating two dimensional (2D in plane wave under plane strain condition formulated previously but also capable of accurately simulating the out of plane Symmetric and Antisymmetric Lamb wave modes in plate like structures in 3D. For structural health monitoring (SHM of plate-like structures and nondestructive evaluation (NDE of MEMS devices, it is necessary to simulate the 3D wave-damage interaction scenarios and visualize the different wave features due to damages. Hence, in addition, to simulating the guided ultrasonic wave modes in pristine material, Lamb waves were also simulated in a damaged plate. The accuracy of the proposed technique is verified by comparing the modes generated in the plate and the mode shapes across the thickness of the plate with theoretical wave analysis.

  17. Measurements of Regolith Simulant Thermal Conductivity Under Asteroid and Mars Surface Conditions

    Science.gov (United States)

    Ryan, A. J.; Christensen, P. R.

    2017-12-01

    Laboratory measurements have been necessary to interpret thermal data of planetary surfaces for decades. We present a novel radiometric laboratory method to determine temperature-dependent thermal conductivity of complex regolith simulants under rough to high vacuum and across a wide range of temperatures. This method relies on radiometric temperature measurements instead of contact measurements, eliminating the need to disturb the sample with thermal probes. We intend to determine the conductivity of grains that are up to 2 cm in diameter and to parameterize the effects of angularity, sorting, layering, composition, and eventually cementation. We present the experimental data and model results for a suite of samples that were selected to isolate and address regolith physical parameters that affect bulk conductivity. Spherical glass beads of various sizes were used to measure the effect of size frequency distribution. Spherical beads of polypropylene and well-rounded quartz sand have respectively lower and higher solid phase thermal conductivities than the glass beads and thus provide the opportunity to test the sensitivity of bulk conductivity to differences in solid phase conductivity. Gas pressure in our asteroid experimental chambers is held at 10^-6 torr, which is sufficient to negate gas thermal conduction in even our coarsest of samples. On Mars, the atmospheric pressure is such that the mean free path of the gas molecules is comparable to the pore size for many regolith particulates. Thus, subtle variations in pore size and/or atmospheric pressure can produce large changes in bulk regolith conductivity. For each sample measured in our martian environmental chamber, we repeat thermal measurement runs at multiple pressures to observe this behavior. Finally, we present conductivity measurements of angular basaltic simulant that is physically analogous to sand and gravel that may be present on Bennu. This simulant was used for OSIRIS-REx TAGSAM Sample Return

  18. SUNYA Regional Climate Model Simulations of East Asia Summer Monsoon: Effects of Cloud Vertical Structure on the Surface Energy Balance

    Directory of Open Access Journals (Sweden)

    Wei Gong and Wei-Chyung Wang

    2007-01-01

    Full Text Available We used the State University of New York at Albany (SUNYA regional climate model to study the effect of cloud vertical distribution in affecting the surface energy balance of the East Asia summer monsoon (EASM. Simulations were conducted for the summers of 1988 and 1989, during which large contrast in the intra-seasonal cloud radiative forcing (CRF was observed at the top of the atmosphere. The model results indicate that both the high and low clouds are persistent throughout the summer months in both years. Because of large cloud water, low clouds significantly reduce the solar radiation flux reaching the surface, which nevertheless still dominate the surface energy balance, accounting for more than 50% of the surface heating. The low clouds also contribute significantly the downward longwave radiation to the surface with values strongly dependent on the cloud base temperature. The presence of low clouds effectively decreases the temperature and moisture gradients near surface, resulting in a substantial decrease in the sensible and latent heat fluxes from surface, which partially compensate the decrease of the net radiative cooling of the surface. For example, in the two days, May 8 and July 11 of 1988, the total cloud cover of 80% is simulated, but the respective low cloud cover (water was 63% (114 gm-2 and 22% (21 gm-2. As a result, the downward solar radiation is smaller by 161 Wm-2 in May 8. On the other hand, the cloud temperature was _ lower, yielding 56 Wm-2 smaller downward longwave radiation. The near surface temperature and gradient is more than _ smaller (and moisture gradient, leading to 21 and 81 Wm-2 smaller sensible heat and latent heat fluxes. It is also demonstrated that the model is capable to reproduce the intraseasonal variation of shortwave CRF, and catches the relationship between total cloud cover and SW CRF. The model results show the dominance of high cloud on the regional mean longwave CRF and low cloud on the intra

  19. Coupling a three-dimensional subsurface flow model with a land surface model to simulate stream-aquifer-land interactions

    Science.gov (United States)

    Huang, M.; Bisht, G.; Zhou, T.; Chen, X.; Dai, H.; Hammond, G. E.; Riley, W. J.; Downs, J.; Liu, Y.; Zachara, J. M.

    2016-12-01

    A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively-parallel multi-physics reactive tranport model (PFLOTRAN). The coupled model (CLM-PFLOTRAN) is applied to a 400m×400m study domain instrumented with groundwater monitoring wells in the Hanford 300 Area along the Columbia River. CLM-PFLOTRAN simulations are performed at three different spatial resolutions over the period 2011-2015 to evaluate the impact of spatial resolution on simulated variables. To demonstrate the difference in model simulations with and without lateral subsurface flow, a vertical-only CLM-PFLOTRAN simulation is also conducted for comparison. Results show that the coupled model is skillful in simulating stream-aquifer interactions, and the land-surface energy partitioning can be strongly modulated by groundwater-river water interactions in high water years due to increased soil moisture availability caused by elevated groundwater table. In addition, spatial resolution does not seem to impact the land surface energy flux simulations, although it is a key factor for accurately estimating the mass exchange rates at the boundaries and associated biogeochemical reactions in the aquifer. The coupled model developed in this study establishes a solid foundation for understanding co-evolution of hydrology and biogeochemistry along the river corridors under historical and future hydro-climate changes.

  20. Impacts of Ocean Waves on the Atmospheric Surface Layer: Simulations and Observations

    National Research Council Canada - National Science Library

    Sullivan, Peter P; McWilliams, James C; Melville, W. K

    2008-01-01

    ... planetary boundary layers (PBL). Efforts were focused on the effects of surface gravity waves on the near-surface dynamics, surface fluxes, and coupling between the atmospheric and oceanic PBLs...

  1. Density functional theory calculations and molecular dynamics simulations of the adsorption of biomolecules on graphene surfaces.

    Science.gov (United States)

    Qin, Wu; Li, Xin; Bian, Wen-Wen; Fan, Xiu-Juan; Qi, Jing-Yao

    2010-02-01

    There is increasing attention in the unique biological and medical properties of graphene, and it is expected that biomaterials incorporating graphene will be developed for the graphene-based drug delivery systems and biomedical devices. Despite the importance of biomolecules-graphene interactions, a detailed understanding of the adsorption mechanism and features of biomolecules onto the surfaces of graphene is lacking. To address this, we have performed density functional theory (DFT) and molecular dynamics (MD) methods exploring the adsorption geometries, adsorption energies, electronic band structures, adsorption isotherms, and adsorption dynamics of l-leucine (model biomolecule)/graphene composite system. DFT calculations confirmed the energetic stability of adsorption model and revealed that electronic structure of graphene can be controlled by the adsorption direction of l-leucine. MD simulations further investigate the potential energy and van der Waals energy for the interaction processes of l-leucine/graphene system at different temperatures and pressures. We find that the van der Waals interaction between the l-leucine and the graphene play a dominant role in the adsorption process under a certain range of temperature and pressure, and the l-leucine molecule could be adsorbed onto graphene spontaneously in aqueous solution.

  2. MD simulation analysis of resin filling into nano-sized pore formed on metal surface

    Science.gov (United States)

    Mori, Hodaka; Matubayasi, Nobuyuki

    2018-01-01

    All-atom MD simulation was conducted for the filling of epoxy resin into a nano-sized pore formed on aluminum surface. The resin species examined were polyphenol mixed with polyglycidylether of o-cresol formaldehyde novolac and their oligomers formed through ring-opening reactions. The degree of oligomerization was varied from 0.5 to 2.5 nm in terms of the radius of gyration, and the radius of the cylindrical pore was fixed at 2.5 nm. It was observed that a small resin penetrates into the pore along the wall, while larger resins move rather uniformly in the pore. The maximum density in the pore achieved with pushing was then seen to be larger when the resin is smaller. It was found that when the radius of gyration of resin is larger than half the pore radius, the resin density in the pore does not reach half the bulk density of the resin. This implies that the resin-resin interaction inhibits the filling of the nano-sized pore.

  3. Ion-surface interaction: simulation of plasma-wall interaction (ITER)

    International Nuclear Information System (INIS)

    Salou, Pierre

    2013-01-01

    The wall materials of magnetic confinement in fusion machines are exposed to an aggressive environment; the reactor blanket is bombarded with a high flux of particles extracted from the plasma, leading to the sputtering of surface material. This sputtering causes wall erosion as well as plasma contamination problems. In order to control fusion reactions in complex reactors, it is thus imperative to well understand the plasma-wall interactions. This work proposes the study of the sputtering of fusion relevant materials. We propose to simulate the charged particles influx by few keV single-charged ion beams. This study is based on the catcher method; to avoid any problem of pollution (especially in the case of carbon) we designed a new setup allowing an in situ Auger electron spectroscopy analysis. The results provide the evolution of the angular distribution of the sputtering yield as a function of the ion mass (from helium to xenon) and its energy (from 3 keV to 9 keV). (author) [fr

  4. Reproducing kernel potential energy surfaces in biomolecular simulations: Nitric oxide binding to myoglobin

    International Nuclear Information System (INIS)

    Soloviov, Maksym; Meuwly, Markus

    2015-01-01

    Multidimensional potential energy surfaces based on reproducing kernel-interpolation are employed to explore the energetics and dynamics of free and bound nitric oxide in myoglobin (Mb). Combining a force field description for the majority of degrees of freedom and the higher-accuracy representation for the NO ligand and the Fe out-of-plane motion allows for a simulation approach akin to a mixed quantum mechanics/molecular mechanics treatment. However, the kernel-representation can be evaluated at conventional force-field speed. With the explicit inclusion of the Fe-out-of-plane (Fe-oop) coordinate, the dynamics and structural equilibrium after photodissociation of the ligand are correctly described compared to experiment. Experimentally, the Fe-oop coordinate plays an important role for the ligand dynamics. This is also found here where the isomerization dynamics between the Fe–ON and Fe–NO state is significantly affected whether or not this co-ordinate is explicitly included. Although the Fe–ON conformation is metastable when considering only the bound 2 A state, it may disappear once the 4 A state is included. This explains the absence of the Fe–ON state in previous experimental investigations of MbNO

  5. Do climate simulations from models forced by averaged sea surface temperatures represent actual dynamics?

    Directory of Open Access Journals (Sweden)

    P. J. Roebber

    1997-01-01

    Full Text Available Recently atmospheric general circulation models (AGCMs forced by observed sea surface temperatures (SSTs have offered the possibility of studying climate variability over periods ranging from years to decades. Such models represent and alternative to fully coupled asynchronous atmosphere ocean models whose long term integration remains problematic. Here, the degree of the approximation represented by this approach is investigated from a conceptual point of view by comparing the dynamical properties of a low order coupled atmosphere-ocean model to those of the atmospheric component of the same model when forced with monthly values of SST derived from the fully coupled simulation. The low order modelling approach is undertaken with the expectation that it may reveal general principles concerning the dynamical behaviour of the forced versus coupled systems; it is not expected that such an approach will determine the details of these differences, for which higher order modelling studies will be required. We discover that even though attractor (global averages may be similar, local dynamics and the resultant variability and predictability characteristics differ substantially. These results suggest that conclusions concerning regional climatic variability (in time as well as space drawn from forced modelling approaches may be contaminated by an inherently unquantifiable error. It is therefore recommended that this possibility be carefully investigated using state-of-the-art coupled AGCMs.

  6. Evaporation Flux Distribution of Drops on a Hydrophilic or Hydrophobic Flat Surface by Molecular Simulations.

    Science.gov (United States)

    Xie, Chiyu; Liu, Guangzhi; Wang, Moran

    2016-08-16

    The evaporation flux distribution of sessile drops is investigated by molecular dynamic simulations. Three evaporating modes are classified, including the diffusion dominant mode, the substrate heating mode, and the environment heating mode. Both hydrophilic and hydrophobic drop-substrate interactions are considered. To count the evaporation flux distribution, which is position dependent, we proposed an azimuthal-angle-based division method under the assumption of spherical crown shape of drops. The modeling results show that the edge evaporation, i.e., near the contact line, is enhanced for hydrophilic drops in all the three modes. The surface diffusion of liquid molecular absorbed on solid substrate for hydrophilic cases plays an important role as well as the space diffusion on the enhanced evaporation rate at the edge. For hydrophobic drops, the edge evaporation flux is higher for the substrate heating mode, but lower than elsewhere of the drop for the diffusion dominant mode; however, a nearly uniform distribution is found for the environment heating mode. The evidence shows that the temperature distribution inside drops plays a key role in the position-dependent evaporation flux.

  7. 3-D numerical simulation on the vibration of liquid sodium's free surface in sodium pool of FBR

    International Nuclear Information System (INIS)

    Han Biao; Yao Zhaohui; Ye Hongkai; Wang Xuefang

    1997-01-01

    This paper succeeds in simulating three-dimensional incompressible flows with free surface, complicated in-flow and out-flow boundary conditions and internal obstacles, and also can treat these fluid flows in arbitrary shape vessel using a partial cell. According to all kinds of the element influencing the free surface's vibration in sodium pool it may give the various wave's form, the highest and lowest position, and the amount of the vibration. This paper introduces the brief principle of VOF numerical method, develops the computational program based on NASA-VOF3D, provides some results about the free surface's vibration in sodium pool of FBR

  8. Prediction of residual stress distributions due to surface machining and welding and crack growth simulation under residual stress distribution

    International Nuclear Information System (INIS)

    Ihara, Ryohei; Katsuyama, JInya; Onizawa, Kunio; Hashimoto, Tadafumi; Mikami, Yoshiki; Mochizuki, Masahito

    2011-01-01

    Research highlights: → Residual stress distributions due to welding and machining are evaluated by XRD and FEM. → Residual stress due to machining shows higher tensile stress than welding near the surface. → Crack growth analysis is performed using calculated residual stress. → Crack growth result is affected machining rather than welding. → Machining is an important factor for crack growth. - Abstract: In nuclear power plants, stress corrosion cracking (SCC) has been observed near the weld zone of the core shroud and primary loop recirculation (PLR) pipes made of low-carbon austenitic stainless steel Type 316L. The joining process of pipes usually includes surface machining and welding. Both processes induce residual stresses, and residual stresses are thus important factors in the occurrence and propagation of SCC. In this study, the finite element method (FEM) was used to estimate residual stress distributions generated by butt welding and surface machining. The thermoelastic-plastic analysis was performed for the welding simulation, and the thermo-mechanical coupled analysis based on the Johnson-Cook material model was performed for the surface machining simulation. In addition, a crack growth analysis based on the stress intensity factor (SIF) calculation was performed using the calculated residual stress distributions that are generated by welding and surface machining. The surface machining analysis showed that tensile residual stress due to surface machining only exists approximately 0.2 mm from the machined surface, and the surface residual stress increases with cutting speed. The crack growth analysis showed that the crack depth is affected by both surface machining and welding, and the crack length is more affected by surface machining than by welding.

  9. A Regional Model for Malaria Vector Developmental Habitats Evaluated Using Explicit, Pond-Resolving Surface Hydrology Simulations.

    Science.gov (United States)

    Asare, Ernest Ohene; Tompkins, Adrian Mark; Bomblies, Arne

    2016-01-01

    Dynamical malaria models can relate precipitation to the availability of vector breeding sites using simple models of surface hydrology. Here, a revised scheme is developed for the VECTRI malaria model, which is evaluated alongside the default scheme using a two year simulation by HYDREMATS, a 10 metre resolution, village-scale model that explicitly simulates individual ponds. Despite the simplicity of the two VECTRI surface hydrology parametrization schemes, they can reproduce the sub-seasonal evolution of fractional water coverage. Calibration of the model parameters is required to simulate the mean pond fraction correctly. The default VECTRI model tended to overestimate water fraction in periods subject to light rainfall events and underestimate it during periods of intense rainfall. This systematic error was improved in the revised scheme by including the a parametrization for surface run-off, such that light rainfall below the initial abstraction threshold does not contribute to ponds. After calibration of the pond model, the VECTRI model was able to simulate vector densities that compared well to the detailed agent based model contained in HYDREMATS without further parameter adjustment. Substituting local rain-gauge data with satellite-retrieved precipitation gave a reasonable approximation, raising the prospects for regional malaria simulations even in data sparse regions. However, further improvements could be made if a method can be derived to calibrate the key hydrology parameters of the pond model in each grid cell location, possibly also incorporating slope and soil texture.

  10. Simulation of trace metals and PAH atmospheric pollution over Greater Paris: Concentrations and deposition on urban surfaces

    Science.gov (United States)

    Thouron, L.; Seigneur, C.; Kim, Y.; Legorgeu, C.; Roustan, Y.; Bruge, B.

    2017-10-01

    Urban areas can be subject not only to poor air quality, but also to contamination of other environmental media by air pollutants. Here, we address the potential transfer of selected air pollutants (two metals and three PAH) to urban surfaces. To that end, we simulate meteorology and air pollution from Europe to a Paris suburban neighborhood, using a four-level one-way nesting approach. The meteorological and air quality simulations use urban canopy sub-models in order to better represent the effect of the urban morphology on the air flow, atmospheric dispersion, and deposition of air pollutants to urban surfaces. This modeling approach allows us to distinguish air pollutant deposition among various urban surfaces (roofs, roads, and walls). Meteorological model performance is satisfactory, showing improved results compared to earlier simulations, although precipitation amounts are underestimated. Concentration simulation results are also satisfactory for both metals, with a fractional bias air pollutants to other environmental media. Dry deposition fluxes to various urban surfaces are mostly uniform for PAH, which are entirely present in fine particles. However, there is significantly less wall deposition compared to deposition to roofs and roads for trace metals, due to their coarse fraction. Meteorology, particle size distribution, and urban morphology are all important factors affecting air pollutant deposition. Future work should focus on the collection of data suitable to evaluate the performance of atmospheric models for both wet and dry deposition with fine spatial resolution.

  11. Variations in calcite growth kinetics with surface topography: molecular dynamics simulations and process-based growth kinetics modelling

    NARCIS (Netherlands)

    Wolthers, M.; Di Tommaso, D.; Du, Zhimei; de Leeuw, Nora H.

    2013-01-01

    It is generally accepted that cation dehydration is the rate-limiting step to crystal growth from aqueous solution. Here we employ classical molecular dynamics simulations to show that the water exchange frequency at structurally distinct calcium sites in the calcite surface varies by about two

  12. Simulation of Sentinel-3 images by four stream surface atmosphere radiative transfer modeling in the optical and thermal domains

    NARCIS (Netherlands)

    Verhoef, W.; Bach, H.

    2012-01-01

    Simulation of future satellite images can be applied in order to validate the general mission concept and to test the performance of advanced multi-sensor algorithms for the retrieval of surface parameters. This paper describes the radiative transfer modeling part of a so-called Land Scene Generator

  13. A non-linear and stochastic response surface method for Bayesian estimation of uncertainty in soil moisture simulation from a land surface model

    Directory of Open Access Journals (Sweden)

    F. Hossain

    2004-01-01

    Full Text Available This study presents a simple and efficient scheme for Bayesian estimation of uncertainty in soil moisture simulation by a Land Surface Model (LSM. The scheme is assessed within a Monte Carlo (MC simulation framework based on the Generalized Likelihood Uncertainty Estimation (GLUE methodology. A primary limitation of using the GLUE method is the prohibitive computational burden imposed by uniform random sampling of the model's parameter distributions. Sampling is improved in the proposed scheme by stochastic modeling of the parameters' response surface that recognizes the non-linear deterministic behavior between soil moisture and land surface parameters. Uncertainty in soil moisture simulation (model output is approximated through a Hermite polynomial chaos expansion of normal random variables that represent the model's parameter (model input uncertainty. The unknown coefficients of the polynomial are calculated using limited number of model simulation runs. The calibrated polynomial is then used as a fast-running proxy to the slower-running LSM to predict the degree of representativeness of a randomly sampled model parameter set. An evaluation of the scheme's efficiency in sampling is made through comparison with the fully random MC sampling (the norm for GLUE and the nearest-neighborhood sampling technique. The scheme was able to reduce computational burden of random MC sampling for GLUE in the ranges of 10%-70%. The scheme was also found to be about 10% more efficient than the nearest-neighborhood sampling method in predicting a sampled parameter set's degree of representativeness. The GLUE based on the proposed sampling scheme did not alter the essential features of the uncertainty structure in soil moisture simulation. The scheme can potentially make GLUE uncertainty estimation for any LSM more efficient as it does not impose any additional structural or distributional assumptions.

  14. Toward prethreshold gate-based quantum simulation of chemical dynamics: using potential energy surfaces to simulate few-channel molecular collisions

    Science.gov (United States)

    Sornborger, Andrew T.; Stancil, Phillip; Geller, Michael R.

    2018-05-01

    One of the most promising applications of an error-corrected universal quantum computer is the efficient simulation of complex quantum systems such as large molecular systems. In this application, one is interested in both the electronic structure such as the ground state energy and dynamical properties such as the scattering cross section and chemical reaction rates. However, most theoretical work and experimental demonstrations have focused on the quantum computation of energies and energy surfaces. In this work, we attempt to make the prethreshold (not error-corrected) quantum simulation of dynamical properties practical as well. We show that the use of precomputed potential energy surfaces and couplings enables the gate-based simulation of few-channel but otherwise realistic molecular collisions. Our approach is based on the widely used Born-Oppenheimer approximation for the structure problem coupled with a semiclassical method for the dynamics. In the latter the electrons are treated quantum mechanically but the nuclei are classical, which restricts the collisions to high energy or temperature (typically above ≈ 10 eV). By using operator splitting techniques optimized for the resulting time-dependent Hamiltonian simulation problem, we give several physically realistic collision examples, with 3-8 channels and circuit depths < 1000.

  15. Effects of microwave electric fields on the translational diffusion of dipolar molecules in surface potential: A simulation study

    Science.gov (United States)

    Kapranov, Sergey V.; Kouzaev, Guennadi A.

    2018-01-01

    Variations of effective diffusion coefficient of polar molecules exposed to microwave electric fields in a surface potential are studied by solving coupled stochastic differential equations of motion with a deterministic component of the surface force. Being an essential tool for the simulation interpretation, a theoretical approach to effective diffusion in surface potential is first developed. The effective diffusion coefficient is represented as the product of the normal diffusion coefficient and potential-dependent correction function, whose temperature dependence is close to the Arrhenius form. The analytically found zero-diffusion condition defines the state of thermal equilibrium at the surface. The diffusion of a water-like dipole molecule in the potential of graphite surface is simulated in the field-free conditions and in the presence of the alternating electric fields of various magnitude intensities and frequencies. Temperature dependence of the correction function exhibits field-induced variations of the effective Lennard-Jones energy parameter. It demonstrates maximum departure from the zero-field value at certain frequencies and intensities, which is associated with variations in the rotational dynamics. A concept of the amplitude-frequency resonance put forward to interpret the simulation results is explained using a heuristic reasoning and is corroborated by semi-quantitative considerations in terms of the Dissado-Hill cluster theory of dielectric relaxation.

  16. 21st century changes in the surface mass balance of the Greenland ice sheet simulated with the global model CESM

    Science.gov (United States)

    Vizcaíno, M.; Lipscomb, W. H.; Van den Broeke, M.

    2012-04-01

    We present here the first projections of 21st century surface mass balance change of the Greenland ice sheet simulated with the Community Earth System Model (CESM). CESM is a fully-coupled, global climate model developed at many research centers and universities, primarily in the U.S. The model calculates the surface mass balance in the land component (the Community Land Model, CLM), at the same resolution as the atmosphere (1 degree), with an energy-balance scheme. The snow physics included in CLM for non-glaciated surfaces (SNiCAR model, Flanner and Zender, 2005) are used over the ice sheet. The surface mass balance is calculated for 10 elevation classes, and then downscaled to the grid of the ice sheet model (5 km in this case) via vertical linear interpolation between elevation classes combined with horizontal bilinear interpolation. The ice sheet topography is fixed at present-day values for the simulations presented here. The use of elevation classes reduces computational costs while giving results that reproduce well the mass balance gradients at the steep margins of the ice sheet. The simulated present-day surface mass balance agrees well with results from regional models. We focus on the regional model RACMO (Ettema et al. 2009) to compare the results on 20th-century surface mass balance evolution and two-dimensional patterns. The surface mass balance of the ice sheet under RCP8.5. forcing becomes negative in the last decades of the 21st century. The equilibrium line becomes ~500 m higher on average. Accumulation changes are positive in the accumulation zone. We examine changes in refreezing, accumulation, albedo, surface fluxes, and the timing of the melt season.

  17. Atomistic simulation of the coupled adsorption and unfolding of protein GB1 on the polystyrenes nanoparticle surface

    Science.gov (United States)

    Xiao, HuiFang; Huang, Bin; Yao, Ge; Kang, WenBin; Gong, Sheng; Pan, Hai; Cao, Yi; Wang, Jun; Zhang, Jian; Wang, Wei

    2018-03-01

    Understanding the processes of protein adsorption/desorption on nanoparticles' surfaces is important for the development of new nanotechnology involving biomaterials; however, an atomistic resolution picture for these processes and for the simultaneous protein conformational change is missing. Here, we report the adsorption of protein GB1 on a polystyrene nanoparticle surface using atomistic molecular dynamic simulations. Enabled by metadynamics, we explored the relevant phase space and identified three protein states, each involving both the adsorbed and desorbed modes. We also studied the change of the secondary and tertiary structures of GB1 during adsorption and the dominant interactions between the protein and surface in different adsorption stages. The results we obtained from simulation were found to be more adequate and complete than the previous one. We believe the model presented in this paper, in comparison with the previous ones, is a better theoretical model to understand and explain the experimental results.

  18. Dynamics of epiretinal membrane removal off the retinal surface: a computer simulation project.

    Science.gov (United States)

    Dogramaci, Mahmut; Williamson, Tom H

    2013-09-01

    To use a computer simulation to discern the safest angle at which to peel epiretinal membranes. We used ANSYS V.14.1 software to analyse the dynamics involved in membrane removal off the retinal surface. The geometrical values were taken from optical coherence tomography of 30 eyes with epiretinal membranes. A range of Young's modulus values of 0.03, 0.01 and 0.09 MPa were assigned to the epiretinal membrane and to the retina separately. The ratio of maximum shear stress (MSS) recorded at the attachment pegs over that recorded at the membrane (P/E ratio) was determined at nine displacement angles (DA). Mean MSS values recorded at the attachment pegs, epiretinal membrane and retina were significantly different at 0.8668, 0.6091 and 0.0017 Pa consecutively (p<0.05). There was a significant negative linear correlation between DA and MSS recorded at the epiretinal membrane when the Young's modulus for the epiretinal membrane was higher than or equal to that for the attachment pegs and the retina. Nevertheless, there was a significant positive linear correlation between DA and P/E ratio when the Young's modulus for the epiretinal membrane was equal to or lower than that for the attachment pegs and the retina. Attachment pegs appear to be the most likely part to fail (tear) during removal procedures. Changing the direction at which the edge of the membrane is pulled can relocate the MSS within in the tissue complex. Safer and effective removal could be achieved by pulling epiretinal membranes onto themselves at 165° DA.

  19. Application of the extended boundary condition method to Monte Carlo simulations of scattering of waves by two-dimensional random rough surfaces

    Science.gov (United States)

    Tsang, L.; Lou, S. H.; Chan, C. H.

    1991-01-01

    The extended boundary condition method is applied to Monte Carlo simulations of two-dimensional random rough surface scattering. The numerical results are compared with one-dimensional random rough surfaces obtained from the finite-element method. It is found that the mean scattered intensity from two-dimensional rough surfaces differs from that of one dimension for rough surfaces with large slopes.

  20. Flood Simulations and Uncertainty Analysis for the Pearl River Basin Using the Coupled Land Surface and Hydrological Model System

    Directory of Open Access Journals (Sweden)

    Yongnan Zhu

    2017-06-01

    Full Text Available The performances of hydrological simulations for the Pearl River Basin in China were analysed using the Coupled Land Surface and Hydrological Model System (CLHMS. Three datasets, including East Asia (EA, high-resolution gauge satellite-merged China Merged Precipitation Analysis (CMPA-Daily, and the Asian Precipitation Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE daily precipitation were used to drive the CLHMS model to simulate daily hydrological processes from 1998 to 2006. The results indicate that the precipitation data was the most important source of uncertainty in the hydrological simulation. The simulated streamflow driven by the CMPA-Daily agreed well with observations, with a Pearson correlation coefficient (PMC greater than 0.70 and an index of agreement (IOA similarity coefficient greater than 0.82 at Liuzhou, Shijiao, and Wuzhou Stations. Comparison of the Nash-Sutcliffe efficiency coefficient (NSE shows that the peak flow simulation ability of CLHMS driven with the CMPA-Daily rainfall is relatively superior to that with the EA and APHRODITE datasets. The simulation results for the high-flow periods in 1998 and 2005 indicate that the CLHMS is promising for its future application in the flood simulation and prediction.

  1. Simulation of the Impact of New Aircraft- and Satellite-based Ocean Surface Wind Measurements on Estimates of Hurricane Intensity

    Science.gov (United States)

    Uhlhorn, Eric; Atlas, Robert; Black, Peter; Buckley, Courtney; Chen, Shuyi; El-Nimri, Salem; Hood, Robbie; Johnson, James; Jones, Linwood; Miller, Timothy; hide

    2009-01-01

    The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave remote sensor currently under development to enhance real-time hurricane ocean surface wind observations. HIRAD builds on the capabilities of the Stepped Frequency Microwave Radiometer (SFMR), which now operates on NOAA P-3, G-4, and AFRC C-130 aircraft. Unlike the SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath (approximately 3 times the aircraft altitude). To demonstrate potential improvement in the measurement of peak hurricane winds, we present a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing platforms (air, surface, and space-based) are simulated from the output of a high-resolution (approximately 1.7 km) numerical model. Simulated retrieval errors due to both instrument noise as well as model function accuracy are considered over the expected range of incidence angles, wind speeds and rain rates. Based on numerous simulated flight patterns and data source combinations, statistics are developed to describe relationships between the observed and true (from the model s perspective) peak wind speed. These results have implications for improving the estimation of hurricane intensity (as defined by the peak sustained wind anywhere in the storm), which may often go un-observed due to sampling limitations.

  2. Influences of Two Land-Surface Schemes on RegCM4 Precipitation Simulations over the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Xuejia Wang

    2015-01-01

    Full Text Available The effects of different RegCM4 land-surface schemes on Tibetan Plateau (TP precipitation simulations were investigated. Two groups of ten-year (1992–2001 simulation experiments (hereafter referred to as BATS and CLM were performed based on two land-surface schemes (BATS and CLM3.5, resp. and were compared with observed data using the same domain, initial, and lateral boundary conditions, cumulus convective scheme, and spatial resolution. The results showed that the CLM monthly precipitation more closely matched the observed data compared with BATS. BATS and CLM both overestimated summer precipitation in the northern TP but underestimated summer precipitation in the southern TP. However, CLM, because of its detailed land-surface process descriptions, reduced the overestimated precipitation areas and magnitudes of BATS. Compared to CN05, the regional average summer precipitation in BATS and CLM was overestimated by 34.7% and underestimated by 24.7%, respectively. Higher soil moisture, evapotranspiration, and heating effects in the BATS experiment triggered changes in atmospheric circulation patterns over the TP. Moreover, BATS simulated the lower atmosphere as warmer and more humid and the upper atmosphere (~150 hPa as colder than the CLM simulations; these characteristics likely increased the instability for moist convection and produced more summer precipitation.

  3. Role of Surface Energy Exchange for Simulating Wind Turbine Inflow: A Case Study in the Southern Great Plains, USA

    Directory of Open Access Journals (Sweden)

    Sonia Wharton

    2014-12-01

    Full Text Available The Weather Research and Forecasting (WRF model is used to investigate choice of land surface model (LSM on the near surface wind profile, including heights reached by multi-megawatt (MW wind turbines. Simulations of wind profiles and surface energy fluxes were made using five LSMs of varying degrees of sophistication in dealing with soil–plant–atmosphere feedbacks for the Department of Energy (DOE Southern Great Plains (SGP Atmospheric Radiation Measurement Program (ARM Central Facility in Oklahoma, USA. Surface flux and wind profile measurements were available for validation. WRF was run for three, two-week periods covering varying canopy and meteorological conditions. The LSMs predicted a wide range of energy flux and wind shear magnitudes even during the cool autumn period when we expected less variability. Simulations of energy fluxes varied in accuracy by model sophistication, whereby LSMs with very simple or no soil–plant–atmosphere feedbacks were the least accurate; however, the most complex models did not consistently produce more accurate results. Errors in wind shear were also sensitive to LSM choice and were partially related to energy flux accuracy. The variability of LSM performance was relatively high suggesting that LSM representation of energy fluxes in WRF remains a large source of model uncertainty for simulating wind turbine inflow conditions.

  4. Can we use remotely sensed land surface temperatures to evaluate and improve model simulations of the urban heat island?

    Science.gov (United States)

    Hu, L.; Monaghan, A. J.; Brunsell, N. A.; Barlage, M. J.; Feddema, J. J.; Wilhelmi, O.

    2013-12-01

    Extreme heat events are the leading cause of weather-related human mortality in the United States and in many countries world-wide, and the development of highly accurate urban climate models to predict heat waves and extreme heat events is critical. However, the heterogeneous urban surface with myriad energy and moisture fluxes increases model complexity and uncertainty. Remotely sensed land surface temperature (LST) offers advantages such as comparable spatial scale, global coverage, steady periodicity, and long-term observations, which can be applied to assess model simulations. This research proposes a sampling technique to select and compare MODIS LST and model-simulated radiative temperature for eight configurations of the High Resolution Land Data Assimilation System (HRLDAS) during 2003-2012 summers (JJA) for Houston, TX. The objective is to decrease comparison biases between MODIS and HRLDAS caused by clouds, view angles, and the LST retrieval algorithm, and to understand which urban surface properties are critical for accurate UHI simulations. The results show that the accurate description of urban fraction can effectively decrease more than 25% of RMSE for HRLDAS LST for both daytime and nighttime comparisons. Assuming irrigated vegetation in the urban area largely improved the RMSE by about 2K during the daytime, while there was no significant difference for the nighttime periods. In the most realistic scenario HRLDAS performed quite well at night, both temporally and spatially. HRLDAS daytime LST simulations are warmer than MODIS observations by approximately 5K but with relatively strong correlations. In summary, remotely sensed LST can be a good observational source for the assessment of UHI simulations, but requires careful pre-processing beforehand to avoid unrepresentative comparisons. The proposed sampling method is practical and effective for validation of long-term urban-scale model simulations.

  5. Searching for stable Si(n)C(n) clusters: combination of stochastic potential surface search and pseudopotential plane-wave Car-Parinello simulated annealing simulations.

    Science.gov (United States)

    Duan, Xiaofeng F; Burggraf, Larry W; Huang, Lingyu

    2013-07-22

    To find low energy Si(n)C(n) structures out of hundreds to thousands of isomers we have developed a general method to search for stable isomeric structures that combines Stochastic Potential Surface Search and Pseudopotential Plane-Wave Density Functional Theory Car-Parinello Molecular Dynamics simulated annealing (PSPW-CPMD-SA). We enhanced the Sunders stochastic search method to generate random cluster structures used as seed structures for PSPW-CPMD-SA simulations. This method ensures that each SA simulation samples a different potential surface region to find the regional minimum structure. By iterations of this automated, parallel process on a high performance computer we located hundreds to more than a thousand stable isomers for each Si(n)C(n) cluster. Among these, five to 10 of the lowest energy isomers were further optimized using B3LYP/cc-pVTZ method. We applied this method to Si(n)C(n) (n = 4-12) clusters and found the lowest energy structures, most not previously reported. By analyzing the bonding patterns of low energy structures of each Si(n)C(n) cluster, we observed that carbon segregations tend to form condensed conjugated rings while Si connects to unsaturated bonds at the periphery of the carbon segregation as single atoms or clusters when n is small and when n is large a silicon network spans over the carbon segregation region.

  6. Searching for Stable SinCn Clusters: Combination of Stochastic Potential Surface Search and Pseudopotential Plane-Wave Car-Parinello Simulated Annealing Simulations

    Directory of Open Access Journals (Sweden)

    Larry W. Burggraf

    2013-07-01

    Full Text Available To find low energy SinCn structures out of hundreds to thousands of isomers we have developed a general method to search for stable isomeric structures that combines Stochastic Potential Surface Search and Pseudopotential Plane-Wave Density Functional Theory Car-Parinello Molecular Dynamics simulated annealing (PSPW-CPMD-SA. We enhanced the Sunders stochastic search method to generate random cluster structures used as seed structures for PSPW-CPMD-SA simulations. This method ensures that each SA simulation samples a different potential surface region to find the regional minimum structure. By iterations of this automated, parallel process on a high performance computer we located hundreds to more than a thousand stable isomers for each SinCn cluster. Among these, five to 10 of the lowest energy isomers were further optimized using B3LYP/cc-pVTZ method. We applied this method to SinCn (n = 4–12 clusters and found the lowest energy structures, most not previously reported. By analyzing the bonding patterns of low energy structures of each SinCn cluster, we observed that carbon segregations tend to form condensed conjugated rings while Si connects to unsaturated bonds at the periphery of the carbon segregation as single atoms or clusters when n is small and when n is large a silicon network spans over the carbon segregation region.

  7. Direct numerical simulation of the transition to turbulence in a supersonic boundary layer on smooth and rough surfaces

    Science.gov (United States)

    Khotyanovsky, D. V.; Kudryavtsev, A. N.

    2017-09-01

    Direct numerical simulations of instability development and transition to turbulence in a supersonic boundary layer on a flat plate are performed. The computations are carried out for moderate supersonic (free-stream Mach number M = 2) and hypersonic (M = 6) velocities. The boundary layer development is simulated, which includes the stages of linear growth of disturbances, their nonlinear interaction, stochastization, and turbulent flow formation. A laminar-turbulent transition initiated by distributed roughness of the plate surface at the Mach number M = 2 is also considered.

  8. A biogeochemical transport model to simulate the attenuation of chlorinated hydrocarbon contaminant fluxes across the groundwater-surface water interface

    DEFF Research Database (Denmark)

    Malaguerra, Flavio; Binning, Philip John; Albrechtsen, Hans-Jørgen

    2009-01-01

    Chlorinated hydrocarbons originating from point sources are amongst the most prevalent contaminants of ground water and surface water resources. Riparian zones may play an important role in the attenuation of contaminant concentrations when contaminant plumes flow from groundwater to surface water...... because of the occurrence of redox gradients, strongly reductive conditions and high biological activity. In order to meet the expectations of the EU Water Framework Directive, an evaluation of the impact of such plumes on surface water is needed. The aim of this work is to develop a groundwater transport...... number of geochemical processes, allows the simulation of soil geochemical transformations when microbial by-products are released to surface water, and the consideration of non-linear feedbacks on bacterial growth and pollutant transformations. Sensitivity analysis is performed through Monte Carlo...

  9. Vibrational Analysis of Brucite Surfaces and the Development of an Improved Force Field for Molecular Simulation of Interfaces.

    Science.gov (United States)

    Zeitler, Todd R; Greathouse, Jeffery A; Gale, Julian D; Cygan, Randall T

    2014-04-17

    We introduce a nonbonded three-body harmonic potential energy term for Mg-O-H interactions for improved edge surface stability in molecular simulations. The new potential term is compatible with the Clayff force field and is applied here to brucite, a layered magnesium hydroxide mineral. Comparisons of normal mode frequencies from classical and density functional theory calculations are used to verify a suitable spring constant ( k parameter) for the Mg-O-H bending motion. Vibrational analysis of hydroxyl librations at two brucite surfaces indicates that surface Mg-O-H modes are shifted to frequencies lower than the corresponding bulk modes. A comparison of DFT and classical normal modes validates this new potential term. The methodology for parameter development can be applied to other clay mineral components (e.g., Al, Si) to improve the modeling of edge surface stability, resulting in expanded applicability to clay mineral applications.

  10. Linear and non-linear simulation of joints contact surface using ...

    African Journals Online (AJOL)

    The joint modelling including non-linear effects needs accurate and precise study of their behaviors. When joints are under the dynamic loading, micro, macro- slip happens in contact surface which is non-linear reason of the joint contact surface. The non-linear effects of joint contact surface on total behavior of structure are ...

  11. Surface Roughness effects on Runoff and Soil Erosion Rates Under Simulated Rainfall

    Science.gov (United States)

    Soil surface roughness is identified as one of the controlling factors governing runoff and soil loss yet, most studies pay little attention to soil surface roughness. In this study, we analyzed the influence of random soil surface roughness on runoff and soil erosion rates. Bulk samples of a silt l...

  12. Laboratory investigation and direct numerical simulation of wind effect on steep surface waves

    Science.gov (United States)

    Troitskaya, Yuliya; Sergeev, Daniil; Druzhinin, Oleg; Ermakova, Olga

    2015-04-01

    particles 20 μm in diameter were injected into the airflow. The images of the illuminated particles were photographed with a digital CCD video camera at a rate of 1000 frames per second. For the each given parameters of wind and waves, a statistical ensemble of 30 movies with duration from 200 to 600 ms was obtained. Individual flow realizations manifested the typical features of flow separation, while the average vector velocity fields obtained by the phase averaging of the individual vector fields were smooth and slightly asymmetrical, with the minimum of the horizontal velocity near the water surface shifted to the leeward side of the wave profile, but do not demonstrate the features of flow separation. The wave-induced pressure perturbations, averaged over the turbulent fluctuations, were retrieved from the measured velocity fields, using the Reynolds equations. It ensures sufficient accuracy for study of the dependence of the wave increment on the wave amplitude. The dependences of the wave growth rate on the wave steepness are weakly decreasing, serving as indirect proof of the non-separated character of flow over waves. Also direct numerical simulation of the airflow over finite amplitude periodic surface wave was performed. In the experiments the primitive 3-dimensional fluid mechanics equations were solved in the airflow over curved water boundary for the following parameters: the Reynolds number Re=15000, the wave steepness ka=0-0.2, the parameter c/u*=0-10 (where u* is the friction velocity and c is the wave celerity). Similar to the physical experiment the instant realizations of the velocity field demonstrate flow separation at the crests of the waves, but the ensemble averaged velocity fields had typical structures similar to those excising in shear flows near critical levels, where the phase velocity of the disturbance coincides with the flow velocity. The wind growth rate determined by the ensemble averaged wave-induced pressure component in phase of the

  13. The SURFEXv7.2 land and ocean surface platform for coupled or offline simulation of earth surface variables and fluxes

    Science.gov (United States)

    Masson, V.; Le Moigne, P.; Martin, E.; Faroux, S.; Alias, A.; Alkama, R.; Belamari, S.; Barbu, A.; Boone, A.; Bouyssel, F.; Brousseau, P.; Brun, E.; Calvet, J.-C.; Carrer, D.; Decharme, B.; Delire, C.; Donier, S.; Essaouini, K.; Gibelin, A.-L.; Giordani, H.; Habets, F.; Jidane, M.; Kerdraon, G.; Kourzeneva, E.; Lafaysse, M.; Lafont, S.; Lebeaupin Brossier, C.; Lemonsu, A.; Mahfouf, J.-F.; Marguinaud, P.; Mokhtari, M.; Morin, S.; Pigeon, G.; Salgado, R.; Seity, Y.; Taillefer, F.; Tanguy, G.; Tulet, P.; Vincendon, B.; Vionnet, V.; Voldoire, A.

    2013-07-01

    SURFEX is a new externalized land and ocean surface platform that describes the surface fluxes and the evolution of four types of surfaces: nature, town, inland water and ocean. It is mostly based on pre-existing, well-validated scientific models that are continuously improved. The motivation for the building of SURFEX is to use strictly identical scientific models in a high range of applications in order to mutualise the research and development efforts. SURFEX can be run in offline mode (0-D or 2-D runs) or in coupled mode (from mesoscale models to numerical weather prediction and climate models). An assimilation mode is included for numerical weather prediction and monitoring. In addition to momentum, heat and water fluxes, SURFEX is able to simulate fluxes of carbon dioxide, chemical species, continental aerosols, sea salt and snow particles. The main principles of the organisation of the surface are described first. Then, a survey is made of the scientific module (including the coupling strategy). Finally, the main applications of the code are summarised. The validation work undertaken shows that replacing the pre-existing surface models by SURFEX in these applications is usually associated with improved skill, as the numerous scientific developments contained in this community code are used to good advantage.

  14. The SURFEXv7.2 land and ocean surface platform for coupled or offline simulation of earth surface variables and fluxes

    Directory of Open Access Journals (Sweden)

    V. Masson

    2013-07-01

    Full Text Available SURFEX is a new externalized land and ocean surface platform that describes the surface fluxes and the evolution of four types of surfaces: nature, town, inland water and ocean. It is mostly based on pre-existing, well-validated scientific models that are continuously improved. The motivation for the building of SURFEX is to use strictly identical scientific models in a high range of applications in order to mutualise the research and development efforts. SURFEX can be run in offline mode (0-D or 2-D runs or in coupled mode (from mesoscale models to numerical weather prediction and climate models. An assimilation mode is included for numerical weather prediction and monitoring. In addition to momentum, heat and water fluxes, SURFEX is able to simulate fluxes of carbon dioxide, chemical species, continental aerosols, sea salt and snow particles. The main principles of the organisation of the surface are described first. Then, a survey is made of the scientific module (including the coupling strategy. Finally, the main applications of the code are summarised. The validation work undertaken shows that replacing the pre-existing surface models by SURFEX in these applications is usually associated with improved skill, as the numerous scientific developments contained in this community code are used to good advantage.

  15. Improved meteorology and ozone air quality simulations using MODIS land surface parameters in the Yangtze River Delta urban cluster, China

    Science.gov (United States)

    Li, Mengmeng; Wang, Tijian; Xie, Min; Zhuang, Bingliang; Li, Shu; Han, Yong; Song, Yu; Cheng, Nianliang

    2017-03-01

    Land surface parameters play an important role in the land-atmosphere coupling and thus are critical to the weather and dispersion of pollutants in the atmosphere. This work aims at improving the meteorology and air quality simulations for a high-ozone (O3) event in the Yangtze River Delta urban cluster of China, through incorporation of satellite-derived land surface parameters. Using Moderate Resolution Imaging Spectroradiometer (MODIS) input to specify the land cover type, green vegetation fraction, leaf area index, albedo, emissivity, and deep soil temperature provides a more realistic representation of surface characteristics. Preliminary evaluations reveal clearly improved meteorological simulation with MODIS input compared with that using default parameters, particularly for temperature (from -2.5 to -1.7°C for mean bias) and humidity (from 9.7% to 4.3% for mean bias). The improved meteorology propagates through the air quality system, which results in better estimates for surface NO2 (from 11.5 to 8.0 ppb for mean bias) and nocturnal O3 low-end concentration values (from -18.8 to -13.6 ppb for mean bias). Modifications of the urban land surface parameters are the main reason for model improvement. The deeper urban boundary layer and intense updraft induced by the urban heat island are favorable for pollutant dilution, thus contributing to lower NO2 and elevated nocturnal O3. Furthermore, the intensified sea-land breeze circulation may exacerbate O3 pollution at coastal cities through pollutant recirculation. Improvement of mesoscale meteorology and air quality simulations with satellite-derived land surface parameters will be useful for air pollution monitoring and forecasting in urban areas.

  16. Static force fields simulations of reduced CeO2 (110) surface: Structure and adsorption of H2O molecule

    Science.gov (United States)

    Vives, Serge; Meunier, Cathy

    2018-02-01

    The CeO2(110) surface properties are largely involved in the catalysis, energy and biological phenomenon. The Static Force Fields simulations are able to describe large atomic systems surface even if no information on the electronic structure can be obtained. We employ those simulations to study the formation of the neutral 2 CeCe‧ VO•• cluster. We focus on seven different cluster configurations and find that the defect formation energy is the lower for the 1N-2N configurations. Two geometries are possible, as it is the case for the ab initio studies, the in plane and the more stable bridging one. We evidence the modifications of the surface energy and the Potential Energy Surface due to the presence of the 2 CeCe‧ VO•• defect. The physical adsorption of a water molecule is calculated and the geometry described for all the cluster configurations. The H2O molecule physisorption stabilizes the Ce(110) surface and the presence of the 2 CeCe‧ VO•• defect increases this effect.

  17. A modified Lattice Boltzmann model for pore-scale simulation of desorption process at surface water-groundwater interface

    Science.gov (United States)

    Zhang, Pei; Galindo Torres, Sergio; Tang, Hongwu; Scheuermann, Alexander; Jin, Guangqiu; Li, Ling

    2017-04-01

    A pore-scale numerical model is introduced to simulate the desorption process at surface water-groundwater interface. The Navier-Stokes equations for fluid and Advection-Diffusion equation for scalar transport are solved by Lattice Boltzmann Method (LBM). In previous studies, the macroscopic desorption kinetic equations are usually applied as a boundary condition. However, it may be problematic for pore-scale simulation since most desorption kinetic equations are fitted from macroscopic global variables. We avoid this problem by discretizing the particle surface into a large number of adsorption sites to mimic the microscopic desorption process. The state of each adsorption site follows the Langmuir's theory. Furthermore, benefiting from the mesoscopic inherent of the LBM, the total number of adsorbate which really contacted with the particle surface can be calculated rather than the local concentration. The predicted desorption Isotherm and concentration profile match well with theoretical solutions and experimental data. By using presented model, we find that the desorption process at surface water-groundwater interface shows a complex response to surface water flow.

  18. Evaluation of surface contamination with cyclophosphamide following simulated hazardous drug preparation activities using two closed-system products.

    Science.gov (United States)

    Zock, Matthew D; Soefje, Scott; Rickabaugh, Keith

    2011-03-01

    A preliminary investigation was conducted to evaluate and compare the effectiveness of two closed-system products in preventing contamination of typical pharmacy workplace surfaces with cyclophosphamide during simulated hazardous drug preparation activities in a controlled laboratory setting. Two separate trials simulating hazardous drug compounding using cyclophosphamide were performed with two different closed-system products. Prior to each trial, work area surfaces of the biological safety cabinet (BSC) workbench, the BSC airfoil and front grill, and the floor below the BSC were cleaned, and wipe samples were collected and analyzed to determine, if present, levels of cyclophosphamide. Following each trial, wipe samples were collected from the work area surfaces to determine the hazardous drug containment effectiveness of each closed-system product. Cyclophosphamide was not detected on work area surfaces prior to each trial. Low levels were detected on the BSC workbench surface following both trials. Based on the limited number of samples obtained during this preliminary study and the determination of the presence of the chemical of interest on the drug vials, no statistical evaluation was performed to compare the relative effectiveness of the two systems tested. Work practices and procedures regarding product operation may affect hazardous drug containment and worker safety. Further study and statistical analyses are needed.

  19. Evaluation of surface roughness of a nanofill resin composite after simulated brushing and immersion in mouthrinses, alcohol and water

    Directory of Open Access Journals (Sweden)

    Ana Carolina de Carvalho Rocha

    2010-03-01

    Full Text Available This study investigated the alteration of surface roughness of the nanofill composite Filtek Z350 3M/ESPE®, caused by simulated brushing associated with the use of mouthrinses with or without alcohol. Sixty specimens were prepared and distributed into six groups: distilled water, ethylic alcohol, Listerine® Vanilla Mint, Plax® without alcohol, Oral B® without alcohol and a control group. Each group was submitted to two intercalary 5,000 simulated brushing cycles. At the end of each cycle, the specimens were washed in tap water and immersed for two cycles of six hours equivalent to one year of daily use of the solution for 2 minutes. It was possible to verify significant alteration in surface roughness of the composite influenced by ethylic alcohol. It was not significant for distilled water and the mouthrinses.

  20. Simulation and Analysis for Wide-band Scattering Characteristics of 2-D Linear and Nonlinear Sea Surfaces

    Directory of Open Access Journals (Sweden)

    Wang Jia-ning

    2015-06-01

    Full Text Available In this paper, the wideband backscattering fields of two-Dimensional (2-D linear and nonlinear sea surfaces are numerically simulated employing the Weighted Curvature Approximation (WCA method. A large number of Monte Carlo trials are performed to investigate the statistical characteristics of the rang-resolved sea clutter, especially for the sea spike phenomenon. Simulation results demonstrate that the long tail of the sea clutter intensity Probability Density Function (PDF tends to be more evident with finer radar resolution, higher wind speed, and when the radar sight changes from the crosswind direction to the upwind direction. Meanwhile, it is found that the nonlinear sea surfaces are more likely to have sea spikes. In addition, the Pareto distribution is demonstrated to describe the statistics of the sea clutter intensities better than the Kdistribution and Weibull distribution at low grazing angles.

  1. Simulating the Effects of Surface Roughness on Reinforced Concrete T Beam Bridge under Single and Multiple Vehicles

    Directory of Open Access Journals (Sweden)

    Rahul Kalyankar

    2016-01-01

    Full Text Available This research focuses on the application of the spatial system of finite element modeling for the vehicle-bridge interaction on reinforced concrete US Girder Bridge in order to obtain the effect of surface roughness. Single vehicle and multiple vehicles on reinforced concrete T beam bridge were studied with variable surface roughness profiles. The effects of six different surface roughness profiles (very good, good, measured, average, poor, and very poor were investigated for vehicle-bridge interaction. The values of the Dynamic Amplification Factor (DAF were obtained for single and multiple vehicles on T Beam Bridge for different surface roughness profiles, along with the distances between the axles of heavy vehicle. It was observed that when the bridge has very good, good, measured, and average surface roughness, the DAF values for the single vehicle over the bridge were observed to be within acceptable limits specified by AASHTO. However, for the bridge with multiple vehicles only very good and measured surface roughness profiles showed a DAF and vehicle axle distances within the acceptable limits. From the current studies, it was observed that the spatial system showed reliable responses for predicting the behavior of the bridge under variable road surface roughness conditions and was reliable in vehicle axle detection, and therefore, it has a potential to be use for realistic simulations.

  2. Simulation

    DEFF Research Database (Denmark)

    Gould, Derek A; Chalmers, Nicholas; Johnson, Sheena J

    2012-01-01

    Recognition of the many limitations of traditional apprenticeship training is driving new approaches to learning medical procedural skills. Among simulation technologies and methods available today, computer-based systems are topical and bring the benefits of automated, repeatable, and reliable...... performance assessments. Human factors research is central to simulator model development that is relevant to real-world imaging-guided interventional tasks and to the credentialing programs in which it would be used....

  3. SUNYA Regional Climate Model Simulations of East Asia Summer Monsoon: Effects of Cloud Vertical Structure on the Surface Energy Balance

    Directory of Open Access Journals (Sweden)

    Wei Gong Wei-Chyung Wang

    2007-01-01

    Full Text Available We used the State University of New York at Albany (SUNYA regional climate model to study the effect of cloud vertical distribution in affecting the surface energy balance of the East Asia summer monsoon (EASM. Simulations were conducted for the summers of 1988 and 1989, during which large contrast in the intra-seasonal cloud radiative forcing (CRF was observed at the top of the atmosphere.

  4. Simulation of mirror surfaces for virtual estimation of visibility lines for 3D motor vehicle collision reconstruction.

    Science.gov (United States)

    Leipner, Anja; Dobler, Erika; Braun, Marcel; Sieberth, Till; Ebert, Lars

    2017-10-01

    3D reconstructions of motor vehicle collisions are used to identify the causes of these events and to identify potential violations of traffic regulations. Thus far, the reconstruction of mirrors has been a problem since they are often based on approximations or inaccurate data. Our aim with this paper was to confirm that structured light scans of a mirror improve the accuracy of simulating the field of view of mirrors. We analyzed the performances of virtual mirror surfaces based on structured light scans using real mirror surfaces and their reflections as references. We used an ATOS GOM III scanner to scan the mirrors and processed the 3D data using Geomagic Wrap. For scene reconstruction and to generate virtual images, we used 3ds Max. We compared the simulated virtual images and photographs of real scenes using Adobe Photoshop. Our results showed that we achieved clear and even mirror results and that the mirrors behaved as expected. The greatest measured deviation between an original photo and the corresponding virtual image was 20 pixels in the transverse direction for an image width of 4256 pixels. We discussed the influences of data processing and alignment of the 3D models on the results. The study was limited to a distance of 1.6m, and the method was not able to simulate an interior mirror. In conclusion, structured light scans of mirror surfaces can be used to simulate virtual mirror surfaces with regard to 3D motor vehicle collision reconstruction. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. The Effects of Surface Gravity Waves on Coastal Currents: Implementation, Phenomenological Explanation, and Realistic Simulation with ROMS

    Science.gov (United States)

    2008-05-30

    is a dynamical component of sea surface elevation and h is a local resting depth. The primary-wave-averaged effects, which we call WEC (wave effects on...empirical parameters related to wave breaking, and Hrm, is R.M.S. wave height. A comparative simulation with DUCK 94. The barotropic ROMS with WEC and the...driven by obliquely incident waves to beaches. The barotropic ROMS with WEC and CEW is used to carried out an experiment for reproducing shear waves

  6. Monte Carlo simulation taking account of surface crack effect for stress corrosion cracking in a stainless steel SUS 304

    International Nuclear Information System (INIS)

    Tohgo, Keiichiro; Suzuki, Hiromitsu; Shimamura, Yoshinobu; Nakayama, Guen; Hirano, Takashi

    2008-01-01

    Stress corrosion cracking (SCC) in structural metal materials occurs by initiation and coalescence of micro cracks, subcritical crack propagation and multiple large crack formation or final failure under the combination of materials, stress and corrosive environment. In this paper, a Monte Carlo simulation for the process of SCC has been proposed based on the stochastic properties of micro crack initiation and fracture mechanics concept for crack coalescence and propagation. The emphasis in the model is put on the influence of semi-elliptical surface cracks. Numerical simulations are carried out based on CBB (creviced bent beam) test results of a sensitized stainless steel SUS 304 and the influence of micro crack initiation rate and coalescence condition on the simulation results is discussed. The numerical examples indicate the applicability of the present model to a prediction of the SCC behavior in real structures. (author)

  7. A software tool for simulation of surfaces generated by ball nose end milling

    DEFF Research Database (Denmark)

    Bissacco, Giuliano

    2004-01-01

    mathematical relationships relating surface parameters to cutting conditions are available. Basic models of kinematical roughness, determined by the tool profile and the pattern of relative motions of tool and workpiece, have been so far not reliable. The actual roughness may be more than five times higher due...... readable by a surface processor software (SPIP [2]), for calculation of a number of surface roughness parameters. In the next paragraph a description of the basic features of ball nose end milled surfaces is given, while in paragraph 3 the model is described.......The number of models available for prediction of surface topography is very limited. The main reason is that these models cannot be based on engineering principles like those for elastic deformations. Most knowledge about surface roughness and integrity is empirical and up to now very few...

  8. Simulation of extreme rainfall event of November 2009 over Jeddah, Saudi Arabia: the explicit role of topography and surface heating

    Science.gov (United States)

    Almazroui, Mansour; Raju, P. V. S.; Yusef, A.; Hussein, M. A. A.; Omar, M.

    2018-04-01

    In this paper, a nonhydrostatic Weather Research and Forecasting (WRF) model has been used to simulate the extreme precipitation event of 25 November 2009, over Jeddah, Saudi Arabia. The model is integrated in three nested (27, 9, and 3 km) domains with the initial and boundary forcing derived from the NCEP reanalysis datasets. As a control experiment, the model integrated for 48 h initiated at 0000 UTC on 24 November 2009. The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results indicate that a strong low-level (850 hPa) wind over Jeddah and surrounding regions enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the mesoscale system. The influences of topography and heat exchange process in the atmosphere were investigated on the development of extreme precipitation event; two sensitivity experiments are carried out: one without topography and another without exchange of surface heating to the atmosphere. The results depict that both surface heating and topography played crucial role in determining the spatial distribution and intensity of the extreme rainfall over Jeddah. The topography favored enhanced uplift motion that further strengthened the low-level jet and hence the rainfall over Jeddah and adjacent areas. On the other hand, the absence of surface heating considerably reduced the simulated rainfall by 30% as compared to the observations.

  9. Sensitivity Analysis of the Surface Runoff Coefficient of HiPIMS in Simulating Flood Processes in a Large Basin

    Directory of Open Access Journals (Sweden)

    Yueling Wang

    2018-03-01

    Full Text Available To simulate flood processes at the basin level, the GPU-based High-Performance Integrated Hydrodynamic Modelling System (HiPIMS is gaining interest as computational capability increases. However, the difficulty of coping with rainfall input to HiPIMS reduces the possibility of acquiring a satisfactory simulation accuracy. The objective of this study is to test the sensitivity of the surface runoff coefficient in the HiPIMS source term in the Misai basin with an area of 797 km2 in south China. To achieve this, the basin was divided into 909,824 grid cells, to each of which a Manning coefficient was assigned based on its land use type interpreted from remote sensing data. A sensitivity analysis was conducted for three typical flood processes under four types of surface runoff coefficients, assumed a priori, upon three error functions. The results demonstrate the crucial role of the surface runoff coefficient in achieving better simulation accuracy and reveal that this coefficient varies with flood scale and is unevenly distributed over the basin.

  10. Efficient Monte Carlo Simulation of Scattering from Rough Sea Surfaces with Objects via Transformation Electromagne

    OpenAIRE

    Özgün, Özlem

    2013-01-01

    Statistical properties of scattered fields (or radar cross section values) in electromagnetic scattering from objects (such as ship- and decoy-like objects) on or above random rough sea surfaces are predicted by using transformation electromagnetics, finite element method (FEM) and Monte Carlo technique. The rough sea surface is modeled as a random process and is randomly generated by using the Pierson-Moskowitz spectrum. For each realization of the sea surface, scattered fields and the radar...

  11. Generalized Temporal Acceleration Scheme for Kinetic Monte Carlo Simulations of Surface Catalytic Processes by Scaling the Rates of Fast Reactions.

    Science.gov (United States)

    Dybeck, Eric C; Plaisance, Craig P; Neurock, Matthew

    2017-04-11

    A novel algorithm is presented that achieves temporal acceleration during kinetic Monte Carlo (KMC) simulations of surface catalytic processes. This algorithm allows for the direct simulation of reaction networks containing kinetic processes occurring on vastly disparate time scales which computationally overburden standard KMC methods. Previously developed methods for temporal acceleration in KMC were designed for specific systems and often require a priori information from the user such as identifying the fast and slow processes. In the approach presented herein, quasi-equilibrated processes are identified automatically based on previous executions of the forward and reverse reactions. Temporal acceleration is achieved by automatically scaling the intrinsic rate constants of the quasi-equilibrated processes, bringing their rates closer to the time scales of the slow kinetically relevant nonequilibrated processes. All reactions are still simulated directly, although with modified rate constants. Abrupt changes in the underlying dynamics of the reaction network are identified during the simulation, and the reaction rate constants are rescaled accordingly. The algorithm was utilized here to model the Fischer-Tropsch synthesis reaction over ruthenium nanoparticles. This reaction network has multiple time-scale-disparate processes which would be intractable to simulate without the aid of temporal acceleration. The accelerated simulations are found to give reaction rates and selectivities indistinguishable from those calculated by an equivalent mean-field kinetic model. The computational savings of the algorithm can span many orders of magnitude in realistic systems, and the computational cost is not limited by the magnitude of the time scale disparity in the system processes. Furthermore, the algorithm has been designed in a generic fashion and can easily be applied to other surface catalytic processes of interest.

  12. Inferring past land use-induced changes in surface albedo from satellite observations: a useful tool to evaluate model simulations

    Directory of Open Access Journals (Sweden)

    J. P. Boisier

    2013-03-01

    Full Text Available Regional cooling resulting from increases in surface albedo has been identified in several studies as the main biogeophysical effect of past land use-induced land cover changes (LCC on climate. However, the amplitude of this effect remains quite uncertain due to, among other factors, (a uncertainties in the extent of historical LCC and, (b differences in the way various models simulate surface albedo and more specifically its dependency on vegetation type and snow cover. We derived monthly albedo climatologies for croplands and four other land cover types from the Moderate Resolution Imaging Spectroradiometer (MODIS satellite observations. We then reconstructed the changes in surface albedo between preindustrial times and present-day by combining these climatologies with the land cover maps of 1870 and 1992 used by seven land surface models (LSMs in the context of the LUCID ("Land Use and Climate: identification of robust Impacts" intercomparison project. These reconstructions show surface albedo increases larger than 10% (absolute in winter, and larger than 2% in summer between 1870 and 1992 over areas that experienced intense deforestation in the northern temperate regions. The historical surface albedo changes estimated with MODIS data were then compared to those simulated by the various climate models participating in LUCID. The inter-model mean albedo response to LCC shows a similar spatial and seasonal pattern to the one resulting from the MODIS-based reconstructions, that is, larger albedo increases in winter than in summer, driven by the presence of snow. However, individual models show significant differences between the simulated albedo changes and the corresponding reconstructions, despite the fact that land cover change maps are the same. Our analyses suggest that the primary reason for those discrepancies is how LSMs parameterize albedo. Another reason, of secondary importance, results from differences in their simulated snow extent

  13. Impact of high-resolution sea surface temperature, emission spikes and wind on simulated surface ozone in Houston, Texas during a high ozone episode

    Science.gov (United States)

    Pan, Shuai; Choi, Yunsoo; Jeon, Wonbae; Roy, Anirban; Westenbarger, David A.; Kim, Hyun Cheol

    2017-03-01

    Model-measurement comparisons for surface ozone often show significant error, which could be attributed to problems in meteorology and emissions fields. A WRF-SMOKE-CMAQ air quality modeling system was used to investigate the contributions of these inputs. In this space, a base WRF run (BASE) and a WRF run initializing with NOAA GOES satellite sea surface temperature (SST) (SENS) were performed to clarify the impact of high-resolution SST on simulated surface ozone (O3) over the Greater Houston area during 25 September 2013, corresponding to the high O3 episode during the NASA DISCOVER-AQ Texas campaign. The SENS case showed reduced land-sea thermal contrast during early morning hours due to 1-2 °C lower SST over water bodies. The lowered SST reduced the model wind speed and slowed the dilution rate. These changes led to a simulated downwind O3 change of ∼5 ppb near the area over land with peak simulated afternoon O3. However, the SENS case still under-predicted surface O3 in urban and industrial areas. Episodic flare emissions, dry sunny postfrontal stagnated conditions, and land-bay/sea breeze transitions could be the potential causes of the high O3. In order to investigate the additional sources of error, three sensitivity simulations were performed for the high ozone time period. These involved adjusted emissions, adjusted wind fields, and both adjusted emissions and winds. These scenarios were superimposed on the updated SST (SENS) case. Adjusting NOx and VOC emissions using simulated/observed ratios improved correlation and index of agreement (IOA) for NOx from 0.48 and 0.55 to 0.81 and 0.88 respectively, but still reported spatial misalignment of afternoon O3 hotspots. Adjusting wind fields to represent morning weak westerly winds and afternoon converging zone significantly mitigated under-estimation of the observed O3 peak. For example, simulations with adjusted wind fields and adjusted (emissions + wind fields) reduced under-estimation of the peak

  14. Aggregate strength for bituminous surfacings for low volume roads: a heavy vehicle simulator experience

    CSIR Research Space (South Africa)

    Paige-Green, P

    2004-09-01

    Full Text Available This paper discusses an investigation using the CSIR Transportek Heavy Vehicle Simulator (HVS) to determine the impact of using aggregates softer than specified in chip seals and to propose possible relaxations in the currently specified strength...

  15. Towards Global Simulation of Irrigation in a Land Surface Model: Multiple Cropping and Rice Paddy in Southeast Asia

    Science.gov (United States)

    Beaudoing, Hiroko Kato; Rodell, Matthew; Ozdogan, Mutlu

    2010-01-01

    Agricultural land use significantly influences the surface water and energy balances. Effects of irrigation on land surface states and fluxes include repartitioning of latent and sensible heat fluxes, an increase in net radiation, and an increase in soil moisture and runoff. We are working on representing irrigation practices in continental- to global-scale land surface simulation in NASA's Global Land Data Assimilation System (GLDAS). Because agricultural practices across the nations are diverse, and complex, we are attempting to capture the first-order reality of the regional practices before achieving a global implementation. This study focuses on two issues in Southeast Asia: multiple cropping and rice paddy irrigation systems. We first characterize agricultural practices in the region (i.e., crop types, growing seasons, and irrigation) using the Global data set of monthly irrigated and rainfed crop areas around the year 2000 (MIRCA2000) dataset. Rice paddy extent is identified using remote sensing products. Whether irrigated or rainfed, flooded fields need to be represented and treated explicitly. By incorporating these properties and processes into a physically based land surface model, we are able to quantify the impacts on the simulated states and fluxes.

  16. VolRoverN: enhancing surface and volumetric reconstruction for realistic dynamical simulation of cellular and subcellular function.

    Science.gov (United States)

    Edwards, John; Daniel, Eric; Kinney, Justin; Bartol, Tom; Sejnowski, Terrence; Johnston, Daniel; Harris, Kristen; Bajaj, Chandrajit

    2014-04-01

    Establishing meaningful relationships between cellular structure and function requires accurate morphological reconstructions. In particular, there is an unmet need for high quality surface reconstructions to model subcellular and synaptic interactions among neurons and glia at nanometer resolution. We address this need with VolRoverN, a software package that produces accurate, efficient, and automated 3D surface reconstructions from stacked 2D contour tracings. While many techniques and tools have been developed in the past for 3D visualization of cellular structure, the reconstructions from VolRoverN meet specific quality criteria that are important for dynamical simulations. These criteria include manifoldness, water-tightness, lack of self- and object-object-intersections, and geometric accuracy. These enhanced surface reconstructions are readily extensible to any cell type and are used here on spiny dendrites with complex morphology and axons from mature rat hippocampal area CA1. Both spatially realistic surface reconstructions and reduced skeletonizations are produced and formatted by VolRoverN for easy input into analysis software packages for neurophysiological simulations at multiple spatial and temporal scales ranging from ion electro-diffusion to electrical cable models.

  17. Simulation study and guidelines to generate Laser-induced Surface Acoustic Waves for human skin feature detection

    Science.gov (United States)

    Li, Tingting; Fu, Xing; Chen, Kun; Dorantes-Gonzalez, Dante J.; Li, Yanning; Wu, Sen; Hu, Xiaotang

    2015-12-01

    Despite the seriously increasing number of people contracting skin cancer every year, limited attention has been given to the investigation of human skin tissues. To this regard, Laser-induced Surface Acoustic Wave (LSAW) technology, with its accurate, non-invasive and rapid testing characteristics, has recently shown promising results in biological and biomedical tissues. In order to improve the measurement accuracy and efficiency of detecting important features in highly opaque and soft surfaces such as human skin, this paper identifies the most important parameters of a pulse laser source, as well as provides practical guidelines to recommended proper ranges to generate Surface Acoustic Waves (SAWs) for characterization purposes. Considering that melanoma is a serious type of skin cancer, we conducted a finite element simulation-based research on the generation and propagation of surface waves in human skin containing a melanoma-like feature, determine best pulse laser parameter ranges of variation, simulation mesh size and time step, working bandwidth, and minimal size of detectable melanoma.

  18. Simulation of near-surface proton-stimulated diffusion of boron in silicon

    International Nuclear Information System (INIS)

    Aleksandrov, O. V.; Kozlovski, V. V.

    2008-01-01

    A quantitative model for near-surface redistribution of doping impurity in silicon in the course of proton-stimulated diffusion is developed for the first time. According to the model, the near-surface peak of the impurity concentration is caused by migration of neutral impurity-self-interstitial pairs to the surface with subsequent decomposition of these pairs and accumulation of the impurity at the silicon surface within a thin layer (referred to as δ-doped layer). The depletion and enhancement regions that are found deeper than the near-surface concentration peak are caused by expulsion of ionized impurity by an electric field from the near-surface region of the field penetration. The field appears due to the charge formed in the natural-oxide film at the silicon surface as a result of irradiation with protons. The diffusion-kinetic equations for the impurity, self-interstitials, vacancies, and impurity-self-interstitial pairs were solved numerically simultaneously with the Poisson equation. It is shown that the results of calculations are in quantitative agreement with experimental data on the proton-stimulated diffusion of boron impurity in the near-surface region of silicon

  19. Kinetic Monte Carlo simulation of surface segregation in Pd–Cu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Feng [Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University (China); He, Xiang [Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008 (China); Chen, Zhao-Xu, E-mail: zxchen@nju.edu.cn [Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University (China); Huang, Yu-Gai [Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University (China); JiangSu Second Normal University, Nanjing (China)

    2015-11-05

    The knowledge of surface composition and atomic arrangement is prerequisite for understanding of catalytic properties of an alloy catalyst. Gaining such knowledge is rather difficult, especially for those possessing surface segregation. Pd–Cu alloy is used in many fields and possesses surface segregation. In this paper kinetic Monte Carlo method is used to explore the surface composition and structure and to examine the effects of bulk composition and temperature on the surface segregation of Pd–Cu alloys. It is shown that the segregation basically completes within 900 s at 500 K. Below 900 K and within 20 min the enriched surface Cu atoms mainly come from the top five layers. For the first time we demonstrate that there exists a “bulk-inside flocking” or clustering phenomenon (the same component element congregates in bulk) in Pd–Cu alloys. Our results indicate that for alloys with higher Cu content there are small Pd ensembles like monomers, dimers and trimers with contiguous subsurface Pd atoms. - Highlights: • Kinetic Monte Carlo was first used to study surface segregation of Pd–Cu alloys. • Bulk-inside flocking (the same component element congregates in bulk) was observed. • Small Pd ensembles with contiguous subsurface Pd exist on surfaces of Cu-rich alloys.

  20. Kinetic Monte Carlo simulation of surface segregation in Pd–Cu alloys

    International Nuclear Information System (INIS)

    Cheng, Feng; He, Xiang; Chen, Zhao-Xu; Huang, Yu-Gai

    2015-01-01

    The knowledge of surface composition and atomic arrangement is prerequisite for understanding of catalytic properties of an alloy catalyst. Gaining such knowledge is rather difficult, especially for those possessing surface segregation. Pd–Cu alloy is used in many fields and possesses surface segregation. In this paper kinetic Monte Carlo method is used to explore the surface composition and structure and to examine the effects of bulk composition and temperature on the surface segregation of Pd–Cu alloys. It is shown that the segregation basically completes within 900 s at 500 K. Below 900 K and within 20 min the enriched surface Cu atoms mainly come from the top five layers. For the first time we demonstrate that there exists a “bulk-inside flocking” or clustering phenomenon (the same component element congregates in bulk) in Pd–Cu alloys. Our results indicate that for alloys with higher Cu content there are small Pd ensembles like monomers, dimers and trimers with contiguous subsurface Pd atoms. - Highlights: • Kinetic Monte Carlo was first used to study surface segregation of Pd–Cu alloys. • Bulk-inside flocking (the same component element congregates in bulk) was observed. • Small Pd ensembles with contiguous subsurface Pd exist on surfaces of Cu-rich alloys

  1. Free surface entropic lattice Boltzmann simulations of film condensation on vertical hydrophilic plates

    DEFF Research Database (Denmark)

    Hygum, Morten Arnfeldt; Karlin, Iliya; Popok, Vladimir

    2015-01-01

    A model for vapor condensation on vertical hydrophilic surfaces is developed using the entropic lattice Boltzmann method extended with a free surface formulation of the evaporation–condensation problem. The model is validated with the steady liquid film formation on a flat vertical wall. It is sh...

  2. Plasma-surface interaction and mechanisms of dust production in ITER ELM simulation experiments with QSPA Kh-50

    International Nuclear Information System (INIS)

    Makhlaj, V.A.; Garkusha, I.E.; Aksenov, N.N.; Byrka, O.V.; Lebedev, S.I.; Shevchuk, P.B.; Landman, I.

    2012-01-01

    Experimental simulations of ITER transient events with relevant surface heat load parameters (energy density and the pulse duration) were carried out with a quasi-stationary plasma accelerator QSPA Kh-50. The several mechanisms of dust generation from tungsten surfaces were identified. The major cracks development and it bifurcation led to generation dust particles with sizes up to tens μ. Melting of surface and development of fine meshes of cracks along the grain boundaries are accompanied by resolidified bridges formation through the fine cracks. Such bridges produce nm-size dust. Appearance of sub-micron and nanometer-size cellular structures under plasma irradiation can leads to the intensification of the dust formation.

  3. Chemical Modification: an Effective Way of Avoiding the Collapse of SWNTs on Al Surface Revealed by Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Xie, J.; Xue, Q. Z.; Yan, K. Y.

    2009-01-01

    The rapid collapse of intrinsic single-walled carbon nanotube (SWNT) on the aluminum surface is observed using molecular dynamics simulation. The collapsing threshold is similar to 10 angstrom, and the length has no influence on its collapse. Furthermore, we report that the structural stability...... of cylindrical SWNTs oil the aluminum surface can be improved through the surface modification method. The stability of SWNTs call be enhanced by increasing the modification coverage. When the modification coverage exceeds 3.3% and 3.8% coverage, respectively, both amidogen- and carboxyl-modified SWNTs can...... basically maintain the cylindrical structure in our described systems. The results also show that, to avoid SWNTs collapse by chemical modification, the longer and larger SWNTs are, the more modification coverage SWNTs require. and vice versa. Our method allows potentially used modified SWNTs...

  4. Immobilization of simulated reducing agent at the surface of SiO2 fillers in dental composite resins.

    Science.gov (United States)

    Shibata, Satoki; Hirata, Isao; Nomura, Yuji; Shirai, Kenichi; Fujitani, Morioki; Shintani, Hideaki; Okazaki, Masayuki

    2007-07-01

    To reduce the leachability of reducing agents from composite resins, immobilization of a simulated reducing agent at the surface of SiO2 fillers was examined. SiO2 plates were immersed in 2% 3-aminopropyltriethoxy silane/ethanol solution, and then immersed in dimethyl sulfoxide with 0.25 wt% 4-dimethyl amino benzoic acid (DMABA), 2.0 wt% 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, and 0.5 wt% N-hydroxysuccinimide. Wide-scan spectrum of X-ray photoelectron spectroscopy did not detect carbon contamination. However, narrow scan detected an O=C-N peak at 399.8 eV, suggesting that DMABA could be immobilized on silane-coupled SiO2 plates. Further, surface plasmon resonance analysis indicated the adsorption of MMA at the surface of reducing agent-immobilized plate.

  5. A new boundary scheme for simulation of gas flow in kerogen pores with considering surface diffusion effect

    Science.gov (United States)

    Wang, Lingquan; Zeng, Zhong; Zhang, Liangqi; Qiao, Long; Zhang, Yi; Lu, Yiyu

    2018-04-01

    Navier-Stokes (NS) equations with no-slip boundary conditions fail to realistically describe micro-flows with considering nanoscale phenomena. Particularly, in kerogen pores, slip-flow and surface diffusion are important. In this study, we propose a new slip boundary scheme for the lattice Boltzmann (LB) method through the non-equilibrium extrapolation scheme to simulate the slip-flow considering surface diffusion effect. Meanwhile, the second-order slip velocity can be taken into account. The predicted characteristics in a two-dimensional micro-flow, including slip-velocity, velocity distribution along the flow direction with/without surface diffusion are present. The results in this study are compared with available analytical and reference results, and good agreements are achieved.

  6. Enhanced Dynamics of Hydrated tRNA on Nanodiamond Surfaces: A Combined Neutron Scattering and MD Simulation Study.

    Science.gov (United States)

    Dhindsa, Gurpreet K; Bhowmik, Debsindhu; Goswami, Monojoy; O'Neill, Hugh; Mamontov, Eugene; Sumpter, Bobby G; Hong, Liang; Ganesh, Panchapakesan; Chu, Xiang-Qiang

    2016-09-14

    Nontoxic, biocompatible nanodiamonds (ND) have recently been implemented in rational, systematic design of optimal therapeutic use in nanomedicines. However, hydrophilicity of the ND surface strongly influences structure and dynamics of biomolecules that restrict in situ applications of ND. Therefore, fundamental understanding of the impact of hydrophilic ND surface on biomolecules at the molecular level is essential. For tRNA, we observe an enhancement of dynamical behavior in the presence of ND contrary to generally observed slow motion at strongly interacting interfaces. We took advantage of neutron scattering experiments and computer simulations to demonstrate this atypical faster dynamics of tRNA on ND surface. The strong attractive interactions between ND, tRNA, and water give rise to unlike dynamical behavior and structural changes of tRNA in front of ND compared to without ND. Our new findings may provide new design principles for safer, improved drug delivery platforms.

  7. Finite Element Simulation of Shot Peening: Prediction of Residual Stresses and Surface Roughness

    Science.gov (United States)

    Gariépy, Alexandre; Perron, Claude; Bocher, Philippe; Lévesque, Martin

    Shot peening is a surface treatment that consists of bombarding a ductile surface with numerous small and hard particles. Each impact creates localized plastic strains that permanently stretch the surface. Since the underlying material constrains this stretching, compressive residual stresses are generated near the surface. This process is commonly used in the automotive and aerospace industries to improve fatigue life. Finite element analyses can be used to predict residual stress profiles and surface roughness created by shot peening. This study investigates further the parameters and capabilities of a random impact model by evaluating the representative volume element and the calculated stress distribution. Using an isotropic-kinematic hardening constitutive law to describe the behaviour of AA2024-T351 aluminium alloy, promising results were achieved in terms of residual stresses.

  8. Electromigration-Induced Surface Drift and Slit Propagation in Polycrystalline Interconnects: Insights from Phase-Field Simulations

    Science.gov (United States)

    Mukherjee, Arnab; Ankit, Kumar; Selzer, Michael; Nestler, Britta

    2018-04-01

    We employ the phase-field method to assess electromigration (EM) damage in wide polycrystalline interconnects due to grain-boundary grooving. An interplay of surface and grain-boundary diffusion is shown to drastically influence the mode of progressive EM damage. Rapid atomic transport along the surface leads to shape-preserving surface drift reminiscent of Blech drift-velocity experiments. On the other hand, a comparatively faster grain-boundary transport localizes the damage, resulting in the proliferation of intergranular slits with a shape-preserving tip. At steady state, the two regimes exhibit exponents of 1 and 3 /2 , respectively, in Black's law. While surface drift obeys an inverse scaling with grain size, slits exhibit a direct relationship at small sizes, with the dependence becoming weaker at larger ones. Furthermore, we explain the influence of curvature- or EM-mediated healing fluxes running along the surface on groove replenishment. Insights derived from phase-field simulations of EM in bicrystals are extended to investigate the multiphysics of mixed-mode damage of a polycrystalline interconnect line that is characterized by a drift of small grain surfaces, slit propagation, and coarsening. The triple and quadruple junctions are identified as prominent sites of failure.

  9. Can Any Surface Species On Meteoritic Nanodiamonds Survive The Extraction Procedure: Simulation Study

    Science.gov (United States)

    Koscheev, A. P.; Serzhantov, A. E.; Merchel, S.; Ott, U.; Guillois, O.; Reynaud, C.

    Information on the surface chemistry of interstellar diamond nanograins found in me- teorites is important for at least two reasons: 1) Diamond surface species may be responsible for some of the IR features observed in emission spectra of some circum- stellar objects; 2) Some surface chemical features acquired during the long journey of the diamonds from the stellar source region to the laboratory may have survived and carry a signature of chemical processes in the interstellar medium. It is well known that the severe acidic treatment used to extract nanodiamonds from meteorites modi- fies some of their surface IR active chemical features. However, some relation between the surface chemistry of nanodiamonds before and after treatment (memory effect) could not be excluded. The existence of such a relation hardly can be established using meteoritic diamond grains because of their uncertain initial properties. To overcome this problem we used ultradispersed detonation diamonds (UDD) with different initial surface chemistry as analogs of meteoritic ones. Five different samples of UDD were treated by the same chemical procedure used to separate meteoritic diamonds. The surface species both before and after treatment were studied by complementary meth- ods of IR spectroscopy and thermodesorption mass spectrometry. Our results strongly indicate that, even though the chemical extraction procedure affects the surface chem- istry of UDD, some surface features can either survive partially (CHx-groups) or vary in a manner controlled by the initial state (CO-groups). If this is also true in the case of meteoritic nanodiamonds, our observations may open a way to reproduce to some extent the real surface chemistry of presolar diamonds from data on chemically sepa- rated meteoritic diamonds. The work was supported in part by Russian Foundation for Basic Research (Grant #01-05-65416), DFG and the Department of Foreign Affairs of France.

  10. Using sea surface temperatures to improve performance of single dynamical downscaling model in flood simulation under climate change

    Science.gov (United States)

    Chao, Y.; Cheng, C. T.; Hsiao, Y. H.; Hsu, C. T.; Yeh, K. C.; Liu, P. L.

    2017-12-01

    There are 5.3 typhoons hit Taiwan per year on average in last decade. Typhoon Morakot in 2009, the most severe typhoon, causes huge damage in Taiwan, including 677 casualties and roughly NT 110 billion (3.3 billion USD) in economic loss. Some researches documented that typhoon frequency will decrease but increase in intensity in western North Pacific region. It is usually preferred to use high resolution dynamical model to get better projection of extreme events; because coarse resolution models cannot simulate intense extreme events. Under that consideration, dynamical downscaling climate data was chosen to describe typhoon satisfactorily, this research used the simulation data from AGCM of Meteorological Research Institute (MRI-AGCM). Considering dynamical downscaling methods consume massive computing power, and typhoon number is very limited in a single model simulation, using dynamical downscaling data could cause uncertainty in disaster risk assessment. In order to improve the problem, this research used four sea surfaces temperatures (SSTs) to increase the climate change scenarios under RCP 8.5. In this way, MRI-AGCMs project 191 extreme typhoons in Taiwan (when typhoon center touches 300 km sea area of Taiwan) in late 21th century. SOBEK, a two dimensions flood simulation model, was used to assess the flood risk under four SSTs climate change scenarios in Tainan, Taiwan. The results show the uncertainty of future flood risk assessment is significantly decreased in Tainan, Taiwan in late 21th century. Four SSTs could efficiently improve the problems of limited typhoon numbers in single model simulation.

  11. Experimental and Numerical Simulation of the Dynamic Frictional Contact between an Aircraft Tire Rubber and a Rough Surface

    Directory of Open Access Journals (Sweden)

    Iulian Rosu

    2016-08-01

    Full Text Available This paper presents a numerical simulation of an aircraft tire in contact with a rough surface using a variable friction coefficient dependent on temperature and contact pressure. A sliding facility was used in order to evaluate this dependence of the friction coefficient. The temperature diffusion throughout the tire cross-section was measured by means of thermocouples. Both frictional heating and temperature diffusion were compared to numerical two- and three- dimensional simulations. An adequate temperature prediction could be obtained. In future simulations, wear should be taken into account in order to have a more accurate simulation especially in the case of high pressures and slipping velocities. A 3D finite element model for a rolling tire at a velocity of 37.79 knots (19.44 m/s and in a cornering phase was investigated using a variable friction coefficient dependent on temperature and pressure. The numerical simulation tended to predict the temperature of the tire tread after a few seconds of rolling in skidding position, the temperature of the contact zone increases to 140 °C. Further investigations must be carried out in order to obtain the evolution of the temperature observed experimentally. The authors would like to point out that for confidentiality reasons, certain numerical data could not be revealed.

  12. Evaluation of land surface model simulations of evapotranspiration over a 12 year crop succession: impact of the soil hydraulic properties

    Science.gov (United States)

    Garrigues, S.; Olioso, A.; Calvet, J.-C.; Martin, E.; Lafont, S.; Moulin, S.; Chanzy, A.; Marloie, O.; Desfonds, V.; Bertrand, N.; Renard, D.

    2014-10-01

    Evapotranspiration has been recognized as one of the most uncertain term in the surface water balance simulated by land surface models. In this study, the SURFEX/ISBA-A-gs simulations of evapotranspiration are assessed at local scale over a 12 year Mediterranean crop succession. The model is evaluated in its standard implementation which relies on the use of the ISBA pedotransfer estimates of the soil properties. The originality of this work consists in explicitly representing the succession of crop cycles and inter-crop bare soil periods in the simulations and assessing its impact on the dynamic of simulated and measured evapotranspiration over a long period of time. The analysis focuses on key soil parameters which drive the simulation of evapotranspiration, namely the rooting depth, the soil moisture at saturation, the soil moisture at field capacity and the soil moisture at wilting point. The simulations achieved with the standard values of these parameters are compared to those achieved with the in situ values. The portability of the ISBA pedotransfer functions is evaluated over a typical Mediterranean crop site. Various in situ estimates of the soil parameters are considered and distinct parametrization strategies are tested to represent the evapotranspiration dynamic over the crop succession. This work shows that evapotranspiration mainly results from the soil evaporation when it is continuously simulated over a Mediterranean crop succession. The evapotranspiration simulated with the standard surface and soil parameters of the model is largely underestimated. The deficit in cumulative evapotranspiration amounts to 24% over 12 years. The bias in daily daytime evapotranspiration is -0.24 mm day-1. The ISBA pedotransfer estimates of the soil moisture at saturation and at wilting point are overestimated which explains most of the evapotranspiration underestimation. The overestimation of the soil moisture at wilting point causes the underestimation of

  13. Simulation

    CERN Document Server

    Ross, Sheldon

    2006-01-01

    Ross's Simulation, Fourth Edition introduces aspiring and practicing actuaries, engineers, computer scientists and others to the practical aspects of constructing computerized simulation studies to analyze and interpret real phenomena. Readers learn to apply results of these analyses to problems in a wide variety of fields to obtain effective, accurate solutions and make predictions about future outcomes. This text explains how a computer can be used to generate random numbers, and how to use these random numbers to generate the behavior of a stochastic model over time. It presents the statist

  14. Quantifying soil surface photolysis under conditions simulating water movement in the field: a new laboratory test design.

    Science.gov (United States)

    Hand, Laurence H; Nichols, Carol; Kuet, Sui F; Oliver, Robin G; Harbourt, Christopher M; El-Naggar, Essam M

    2015-10-01

    Soil surface photolysis can be a significant dissipation pathway for agrochemicals under field conditions, although it is assumed that such degradation ceases once the agrochemical is transported away from the surface following rainfall or irrigation and subsequent drainage of soil porewater. However, as both downward and upward water movements occur under field conditions, relatively mobile compounds may return to the surface, prolonging exposure to ultraviolet light and increasing the potential for degradation by photolysis. To test this hypothesis, a novel experimental system was used to quantify the contribution of photolysis to the overall dissipation of a new herbicide, bicyclopyrone, under conditions that mimicked field studies more closely than the standard laboratory test guidance. Soil cores were taken from 3 US field study sites, and the surfaces were treated with [(14) C]-bicyclopyrone. The radioactivity was redistributed throughout the cores using a simulated rainfall event, following which the cores were incubated under a xenon-arc lamp with continuous provision of moisture from below and a wind simulator to induce evaporation. After only 2 d, most of the test compound had returned to the soil surface. Significantly more degradation was observed in the irradiated samples than in a parallel dark control sample. Degradation rates were very similar to those observed in both the thin layer photolysis study and the field dissipation studies and significantly faster than in the soil metabolism studies conducted in the dark. Thus, for highly soluble, mobile agrochemicals, such as bicyclopyrone, photolysis is not terminated permanently by rainfall or irrigation but can resume following transport to the surface in evaporating water. © 2015 SETAC.

  15. Observed and simulated effect of plant physiology and structure on land surface energy fluxes and soil conditions

    Science.gov (United States)

    Lu, Yen-Sen; Rihani, Jehan; Langensiepen, Matthias; Simmer, Clemens

    2016-04-01

    The parameterization of stomatal conductance and leaf area index (LAI) in land surface models largely influence simulated terrestrial system states. While stomatal conductance mainly controls transpiration, latent heat flux, and root-water-uptake, LAI impacts additionally the radiative energy exchange. Thus both affect canopy evaporation and transpiration and land surface energy and water fluxes as a whole. Common parameterizations of stomatal conductance follow either semi-mechanistic forms based on photosynthesis (Ball-Berry Type (BB)) or forms which consider environmental factors such as impact of light, temperature, humidity and soil moisture (Jarvis-Stewart Type (JS)). Both approaches differ also in the interpretation of humidity effects and light-use efficiency. While soil moisture plays an important role for root-water-uptake there is no clear conclusion yet about how soil moisture interacts with stomata activity. Values for LAI can be obtained from field measurements, satellite estimates or modelling and are used as an essential model input. While field measurements are very time consuming and only represent single points, satellite estimates may have biases caused by variable albedo and sensor limitations. Representing LAI within land surface models requires complex schemes in order to represent all processes contributing to plant growth. We use the Terrestrial System Modelling Platform (TerrSysMP) over the Rur watershed in Germany for studying the influence of plant physiology and structure on the state of the terrestrial system. The Transregional Collaborative Research Center 32 (TR32) extensively monitors this catchment for almost a decade. The land surface (CLM3.5) and the subsurface (ParFlow) modules of TerrSysMP are conditioned based on satellite-retrieved land cover and the soil map from FAO and forced with a high-resolution reanalysis by DWD. For studying the effect of plant physiology, the Ball-Berry-Leuning, and Jarvis-Stewart stomatal

  16. SPATKIN: a simulator for rule-based modeling of biomolecular site dynamics on surfaces.

    Science.gov (United States)

    Kochanczyk, Marek; Hlavacek, William S; Lipniacki, Tomasz

    2017-11-15

    Rule-based modeling is a powerful approach for studying biomolecular site dynamics. Here, we present SPATKIN, a general-purpose simulator for rule-based modeling in two spatial dimensions. The simulation algorithm is a lattice-based method that tracks Brownian motion of individual molecules and the stochastic firing of rule-defined reaction events. Because rules are used as event generators, the algorithm is network-free, meaning that it does not require to generate the complete reaction network implied by rules prior to simulation. In a simulation, each molecule (or complex of molecules) is taken to occupy a single lattice site that cannot be shared with another molecule (or complex). SPATKIN is capable of simulating a wide array of membrane-associated processes, including adsorption, desorption and crowding. Models are specified using an extension of the BioNetGen language, which allows to account for spatial features of the simulated process. The C ++ source code for SPATKIN is distributed freely under the terms of the GNU GPLv3 license. The source code can be compiled for execution on popular platforms (Windows, Mac and Linux). An installer for 64-bit Windows and a macOS app are available. The source code and precompiled binaries are available at the SPATKIN Web site (http://pmbm.ippt.pan.pl/software/spatkin). spatkin.simulator@gmail.com. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

  17. Fast, Statistical Model of Surface Roughness for Ion-Solid Interaction Simulations and Efficient Code Coupling

    Science.gov (United States)

    Drobny, Jon; Curreli, Davide; Ruzic, David; Lasa, Ane; Green, David; Canik, John; Younkin, Tim; Blondel, Sophie; Wirth, Brian

    2017-10-01

    Surface roughness greatly impacts material erosion, and thus plays an important role in Plasma-Surface Interactions. Developing strategies for efficiently introducing rough surfaces into ion-solid interaction codes will be an important step towards whole-device modeling of plasma devices and future fusion reactors such as ITER. Fractal TRIDYN (F-TRIDYN) is an upgraded version of the Monte Carlo, BCA program TRIDYN developed for this purpose that includes an explicit fractal model of surface roughness and extended input and output options for file-based code coupling. Code coupling with both plasma and material codes has been achieved and allows for multi-scale, whole-device modeling of plasma experiments. These code coupling results will be presented. F-TRIDYN has been further upgraded with an alternative, statistical model of surface roughness. The statistical model is significantly faster than and compares favorably to the fractal model. Additionally, the statistical model compares well to alternative computational surface roughness models and experiments. Theoretical links between the fractal and statistical models are made, and further connections to experimental measurements of surface roughness are explored. This work was supported by the PSI-SciDAC Project funded by the U.S. Department of Energy through contract DOE-DE-SC0008658.

  18. Effect of Non-Equilibrium Surface Thermochemistry in Simulation of Carbon Based Ablators

    Science.gov (United States)

    Chen, Yih-Kanq; Gokcen, Tahir

    2012-01-01

    This study demonstrates that coupling of a material thermal response code and a flow solver using non-equilibrium gas/surface interaction model provides time-accurate solutions for the multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and AblatioN Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas mass conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between the material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of nonequilibrium gas/surface interaction chemistry between air and the carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

  19. Mass and heat transfer between evaporation and condensation surfaces: Atomistic simulation and solution of Boltzmann kinetic equation.

    Science.gov (United States)

    Zhakhovsky, Vasily V; Kryukov, Alexei P; Levashov, Vladimir Yu; Shishkova, Irina N; Anisimov, Sergey I

    2018-04-16

    Boundary conditions required for numerical solution of the Boltzmann kinetic equation (BKE) for mass/heat transfer between evaporation and condensation surfaces are analyzed by comparison of BKE results with molecular dynamics (MD) simulations. Lennard-Jones potential with parameters corresponding to solid argon is used to simulate evaporation from the hot side, nonequilibrium vapor flow with a Knudsen number of about 0.02, and condensation on the cold side of the condensed phase. The equilibrium density of vapor obtained in MD simulation of phase coexistence is used in BKE calculations for consistency of BKE results with MD data. The collision cross-section is also adjusted to provide a thermal flux in vapor identical to that in MD. Our MD simulations of evaporation toward a nonreflective absorbing boundary show that the velocity distribution function (VDF) of evaporated atoms has the nearly semi-Maxwellian shape because the binding energy of atoms evaporated from the interphase layer between bulk phase and vapor is much smaller than the cohesive energy in the condensed phase. Indeed, the calculated temperature and density profiles within the interphase layer indicate that the averaged kinetic energy of atoms remains near-constant with decreasing density almost until the interphase edge. Using consistent BKE and MD methods, the profiles of gas density, mass velocity, and temperatures together with VDFs in a gap of many mean free paths between the evaporation and condensation surfaces are obtained and compared. We demonstrate that the best fit of BKE results with MD simulations can be achieved with the evaporation and condensation coefficients both close to unity.

  20. Surface gravity wave effects in the oceanic boundary layer: large-eddy simulation with vortex force and stochastic breakers

    Science.gov (United States)

    Sullivan, Peter P.; McWilliams, James C.; Melville, W. Kendall

    The wind-driven stably stratified mid-latitude oceanic surface turbulent boundary layer is computationally simulated in the presence of a specified surface gravity-wave field. The gravity waves have broad wavenumber and frequency spectra typical of measured conditions in near-equilibrium with the mean wind speed. The simulation model is based on (i) an asymptotic theory for the conservative dynamical effects of waves on the wave-averaged boundary-layer currents and (ii) a boundary-layer forcing by a stochastic representation of the impulses and energy fluxes in a field of breaking waves. The wave influences are shown to be profound on both the mean current profile and turbulent statistics compared to a simulation without these wave influences and forced by an equivalent mean surface stress. As expected from previous studies with partial combinations of these wave influences, Langmuir circulations due to the wave-averaged vortex force make vertical eddy fluxes of momentum and material concentration much more efficient and non-local (i.e. with negative eddy viscosity near the surface), and they combine with the breakers to increase the turbulent energy and dissipation rate. They also combine in an unexpected positive feedback in which breaker-generated vorticity seeds the creation of a new Langmuir circulation and instigates a deep strong intermittent downwelling jet that penetrates through the boundary layer and increases the material entrainment rate at the base of the layer. These wave effects on the boundary layer are greater for smaller wave ages and higher mean wind speeds.

  1. Flux-surface closure during resistive-MHD simulations of Coaxial Helicity Injection (CHI) in NSTX

    Science.gov (United States)

    Hooper, E. B.; Sovinec, C. R.; Raman, R.; Ebrahimi, Fatima; Menard, J. E.

    2012-10-01

    CHI in STs offers considerable promise for generating startup plasmas, with NSTX experiments demonstrating coupling to Ohmic drive with magnetic flux savings.footnotetextR. Raman et al., Phys. Rev. Letters 104, 095003 (2010). Success in these experiments depends in part on the achievement of flux closure following CHI voltage crowbarring. Flux closure is demonstrated here in whole-device, resistive MHD simulations using the NIMROD code. In axisymmetric plasmas significant closure due to resistive effects requires the injection slot to be narrow (e.g. 4 cm vs. 11 cm) in agreement with experiment. In simulations reduction of the applied injector flux following the crowbar forms an X-point close to the bottom of NSTX that significantly enlarges the closed volume; closure is not seen if the flux is held constant. The physics of closure will be discussed and applied to maximizing the volume. Effects of a background plasma in simulations of flux formation and closure will also be described.

  2. GSFLOW model simulations used to evaluate the impact of irrigated agriculture on surface water - groundwater interaction

    Data.gov (United States)

    Department of the Interior — Watershed-scale coupled surface water (SW) – groundwater (GW) flow modeling was used to examine changes in streamflow and SW – GW interaction resulting from...

  3. Impacts of Ocean Waves on the Atmospheric Surface Layer: Simulations and Observations

    Science.gov (United States)

    2008-06-06

    than about 5 m s −1 (Makin, Kudryavtsev & Mastenbroek 1995; Banner & Peirson 1998). Ocean boundary layers with vortex force and stochastic breaking...amplitude. Proc. Roy. Soc. Lond. A 342, 157–174. Makin, V. K., Kudryavtsev , V. N. & Mastenbroek, C. 1995 Drag of the sea surface. Boundary- Layer Met. 73...to study some of the impacts of fast-moving waves on marine surface layers (e.g., Gent and Taylor 1976; Gent 1977; Li 1995; Kudryavtsev and Makin 2004

  4. Simulation of surface displacement and strain field of the 2011 Japan Mw9.0 earthquake

    Directory of Open Access Journals (Sweden)

    Chen Shujun

    2011-11-01

    Full Text Available Based on dislocation theory of Okada, we adopted a finite-element fault model inverted by Gavin Hayes from seismic data for the 2011 Japan Mw9.0 earthquake, and obtained the corresponding surface displacement and strain fields. The calculated displacement field is consistent with the observed GPS results in the trend of changes. Also the surface displacement and strain fields both show large variations in space.

  5. Monte Carlo simulation of the surface magnetic phase transition in chromium

    International Nuclear Information System (INIS)

    Mata, G.J.; Valera, M.

    1995-03-01

    Antiferromagnetic chromium is known to have a surface magnetic phase transition at a temperature T s = 780K, which is well above its bulk Neel temperature, T N = 311K. Electronic structure calculations predict an enhancement of the magnetic moment at the surface, due to changes in the local electronic environment. In order to ascertain the role of such an enhancement in the surface magnetic transition, we have modelled the surface by means of a classical Heisenberg model in which: a) the magnitude of a given spin is equal to the value of the corresponding magnetic moment predicted by band structure calculations, b) the exchange interaction J between spins is the same throughout the system, and c) the exchange interaction is chosen so as to reproduce the bulk transition temperature. We find a ratio of surface to bulk transition temperature of T S /T N = 2.5, which is an excellent agreement with the experimental result. Our results suggest that the surface magnetic transition in chromium is driven by fluctuations in the orientation of the magnetic moments and that quantum fluctuations play a minor role. (author). 18 refs, 5 figs

  6. The Fast Simulation of Scattering Characteristics from a Simplified Time Varying Sea Surface

    Directory of Open Access Journals (Sweden)

    Yiwen Wei

    2015-01-01

    Full Text Available This paper aims at applying a simplified sea surface model into the physical optics (PO method to accelerate the scattering calculation from 1D time varying sea surface. To reduce the number of the segments and make further improvement on the efficiency of PO method, a simplified sea surface is proposed. In this simplified sea surface, the geometry of long waves is locally approximated by tilted facets that are much longer than the electromagnetic wavelength. The capillary waves are considered to be sinusoidal line superimposing on the long waves. The wavenumber of the sinusoidal waves is supposed to satisfy the resonant condition of Bragg waves which is dominant in all the scattered short wave components. Since the capillary wave is periodical within one facet, an analytical integration of the PO term can be performed. The backscattering coefficient obtained from a simplified sea surface model agrees well with that obtained from a realistic sea surface. The Doppler shifts and width also agree well with the realistic model since the capillary waves are taken into consideration. The good agreements indicate that the simplified model is reasonable and valid in predicting both the scattering coefficients and the Doppler spectra.

  7. Simulated Effects of Land Cover Conversion on the Surface Energy Budget in the Southwest of China

    Directory of Open Access Journals (Sweden)

    Jiangbo Gao

    2014-03-01

    Full Text Available In this paper, the coupled WRF/SSiB model, accompanied by a Karst Rocky Desertification (KRD map of the Guizhou Karst Plateau (GKP of China, was applied to detect how the changed vegetation and soil characteristics over the GKP modify the energy balance at the land surface. The results indicated that land degradation led to reduced net radiation by inducing more upward shortwave and longwave radiation, which were associated with increasing surface albedo and temperature, respectively. The KRD also resulted in changed surface energy partitioning into sensible and latent heat fluxes. The latent heat flux at land surface was reduced substantially due to the higher surface albedo and stomatal resistance, the lower Leaf Area Index (LAI and roughness length in the degradation experiment, while the sensible heat flux increased, mainly because of the higher surface temperature. Furthermore, the moisture flux convergence was reduced, owing to the lower atmospheric heating and the relative subsidence. However, compared with the reduced evaporation, the decrease in moisture flux convergence contributed much less to the reduced precipitation. Precipitation strongly affects soil moisture, vegetation growth and phenology, and thus evaporation and convective latent heating, so when precipitation was changed, a feedback loop was created.

  8. Simulation of the Impact of New Aircraft and Satellite-Based Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, TImothy L.; Atlas, R. M.; Black, P. G.; Case, J. L.; Chen, S. S.; Hood, R. E.; Johnson, J. W.; Jones, L.; Ruf, C. S.; Uhlborn, E. W.

    2008-01-01

    Accurate observations of surface ocean vector winds (OVW) with high spatial and temporal resolution are required for understanding and predicting tropical cyclones. As NASA's QuikSCAT and Navy's WindSat operate beyond their design life, many members of the weather and climate science communities recognize the importance of developing new observational technologies and strategies to meet the essential need for OVW information to improve hurricane intensity and location forecasts. The Hurricane Imaging Radiometer (HIRAD) is an innovative technology development which offers new and unique remotely sensed satellite observations of both extreme oceanic wind events and strong precipitation. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR), which is the only proven remote sensing technique for observing tropical cyclone (TC) ocean surface wind speeds and rain rates. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer (STAR) technology. This sensor will operate over 4-7 GHz (C-band frequencies) where the required TC remote sensing physics has been validated by both SFMR and WindSat radiometers. The instrument is described in more detail in a paper by Jones et al. presented to the Tropical Meteorology Special Symposium at this AMS Annual Meeting. Simulated HIRAD passes through a simulation of hurricane Frances are being developed to demonstrate HIRAD estimation of surface wind speed over a wide swath in the presence of heavy rain. These are currently being used in "quick" OSSEs (Observing System Simulation Experiments) with H'Wind analyses as the discriminating tool. The H'Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic , Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of wind

  9. Chemical Dynamics Simulations of Thermal Desorption of Protonated Dialanine from a Perfluorinated Self-Assembled Monolayer Surface.

    Science.gov (United States)

    Kohale, Swapnil C; Pratihar, Subha; Hase, William L

    2018-04-05

    Classical chemical dynamics simulation results are presented for the thermal desorption kinetics and energetics of protonated dialanine ions (ala 2 -H + ) physisorbed on/in a perfluorinated self-assembled monolayer (F-SAM) surface. Previously developed analytic potentials were used for the F-SAM and the ala 2 -H + /F-SAM intermolecular interaction, and the AMBER valence force field was used for ala 2 -H + . The activation energy, E a = 13.2 kcal/mol, determined from the simulations is consistent with previous simulations of the ala 2 -H + /F-SAM binding energy. The A-factor, 7.8 × 10 11 s -1 , is about an order of magnitude lower than those representative of small molecule desorption from metal and semiconductor surfaces. This finding is consistent with the decreased entropies of ala 2 -H + and the F-SAM upon desorption. Using the Arrhenius parameters for ala 2 -H + desorption from the F-SAM, the lifetime of ala 2 -H + adsorbed on the F-SAM at 300 K is 5 × 10 -3 s. Larger peptide ions are expected to have longer adsorption lifetimes.

  10. QM/MM and classical molecular dynamics simulation of histidine-tagged peptide immobilization on nickel surface

    Energy Technology Data Exchange (ETDEWEB)

    Yang Zhenyu [State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080(China); Zhao Yapu [State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080 (China)]. E-mail: yzhao@lnm.imech.ac.cn

    2006-05-15

    The hybrid quantum mechanics (QM) and molecular mechanics (MM) method is employed to simulate the His-tagged peptide adsorption to ionized region of nickel surface. Based on the previous experiments, the peptide interaction with one Ni ion is considered. In the QM/MM calculation, the imidazoles on the side chain of the peptide and the metal ion with several neighboring water molecules are treated as QM part calculated by 'GAMESS', and the rest atoms are treated as MM part calculated by 'TINKER'. The integrated molecular orbital/molecular mechanics (IMOMM) method is used to deal with the QM part with the transitional metal. By using the QM/MM method, we optimize the structure of the synthetic peptide chelating with a Ni ion. Different chelate structures are considered. The geometry parameters of the QM subsystem we obtained by QM/MM calculation are consistent with the available experimental results. We also perform a classical molecular dynamics (MD) simulation with the experimental parameters for the synthetic peptide adsorption on a neutral Ni(1 0 0) surface. We find that half of the His-tags are almost parallel with the substrate, which enhance the binding strength. Peeling of the peptide from the Ni substrate is simulated in the aqueous solvent and in vacuum, respectively. The critical peeling forces in the two environments are obtained. The results show that the imidazole rings are attached to the substrate more tightly than other bases in this peptide.

  11. Role of surface on the size-dependent mechanical properties of copper nanowire under tensile load: A molecular dynamics simulation

    International Nuclear Information System (INIS)

    Liu, Wei-Ting; Hsiao, Chun-I.; Hsu, Wen-Dung

    2014-01-01

    In this study we have used atomistic simulations to investigate the role of surface on the size-dependent mechanical properties of nanowires. In particular, we have performed computational investigation on single crystal face-centered cubic copper nano-wires with diameters ranging from 2 to 20 nm. The wire axis for all the nanowires are considered along the [0 0 1] direction. Characterization of the initial optimized structures revealed clear differences in interatomic spacing, stress, and potential energy in all the nanowires. The mechanical properties with respect to wire diameter are evaluated by applying tension along the [0 0 1] direction until yielding. We have discussed the stress–strain relationships, Young's modulus, and the variation in potential energy from surface to the center of the wire for all the cases. Our results indicate that the mechanical response (including yield strain, Young's modulus, and resilience) is directly related to the proportion of surface to bulk type atoms present in each nanowire. Thus the size-dependent mechanical properties of single crystal copper nanowire within elastic region are attributed to the surface to volume ratio (surface effect). Using the calculated response, we have formulated a mathematical relationship, which predicts the nonlinear correlation between the mechanical properties and the diameter of the wire.

  12. Simulation of dissolution in porous media in three dimensions with lattice Boltzmann, finite-volume, and surface-rescaling methods

    Science.gov (United States)

    Gray, F.; Cen, J.; Boek, E. S.

    2016-10-01

    We present a pore-scale dissolution model for the simulation of reactive transport in complex porous media such as those encountered in carbon-storage injection processes. We couple a lattice Boltzmann model for flow calculation with a finite-volume method for solving chemical transport equations, and allow the computational grid to change as mineral surfaces are dissolved according to first-order reaction kinetics. We appraise this scheme for use with high Péclet number flows in three-dimensional geometries and show how the popular first-order convection scheme is affected by severe numerical diffusion when grid Péclet numbers exceed unity, and confirm that this can be overcome relatively easily by using a second-order method in conjunction with a flux-limiter function. We then propose a surface rescaling method which uses parabolic elements to counteract errors in surface area exposed by the Cartesian grid and avoid the use of more complex embedded surface methods when surface reaction kinetics are incorporated. Finally, we compute dissolution in an image of a real porous limestone rock sample injected with HCl for different Péclet numbers and obtain dissolution patterns in concordance with theory and experimental observation. A low injection flow rate was shown to lead to erosion of the pore space concentrated at the face of the rock, whereas a high flow rate leads to wormhole formation.

  13. Effect of nontronite smectite clay on the chemical evolution of several organic molecules under simulated martian surface ultraviolet radiation conditions.

    Science.gov (United States)

    Poch, Olivier; Jaber, Maguy; Stalport, Fabien; Nowak, Sophie; Georgelin, Thomas; Lambert, Jean-François; Szopa, Cyril; Coll, Patrice

    2015-03-01

    Most of the phyllosilicates detected at the surface of Mars today are probably remnants of ancient environments that sustained long-term bodies of liquid water at the surface or subsurface and were possibly favorable for the emergence of life. Consequently, phyllosilicates have become the main mineral target in the search for organics on Mars. But are phyllosilicates efficient at preserving organic molecules under current environmental conditions at the surface of Mars? We monitored the qualitative and quantitative evolutions of glycine, urea, and adenine in interaction with the Fe(3+)-smectite clay nontronite, one of the most abundant phyllosilicates present at the surface of Mars, under simulated martian surface ultraviolet light (190-400 nm), mean temperature (218 ± 2 K), and pressure (6 ± 1 mbar) in a laboratory simulation setup. We tested organic-rich samples that were representative of the evaporation of a small, warm pond of liquid water containing a high concentration of organics. For each molecule, we observed how the nontronite influences its quantum efficiency of photodecomposition and the nature of its solid evolution products. The results reveal a pronounced photoprotective effect of nontronite on the evolution of glycine and adenine; their efficiencies of photodecomposition were reduced by a factor of 5 when mixed at a concentration of 2.6 × 10(-2) mol of molecules per gram of nontronite. Moreover, when the amount of nontronite in the sample of glycine was increased by a factor of 2, the gain of photoprotection was multiplied by a factor of 5. This indicates that the photoprotection provided by the nontronite is not a purely mechanical shielding effect but is also due to stabilizing interactions. No new evolution product was firmly identified, but the results obtained with urea suggest a particular reactivity in the presence of nontronite, leading to an increase of its dissociation rate.

  14. A multi - layer land surface energy budget model for implicit coupling with global atmospheric simulations

    NARCIS (Netherlands)

    Ryder, J.; Polcher, J.; Peylin, P.; Ottlé, C.; Chen, Y; van Gorsel, E.; Haverd, V.; McGrath, M.J.; Naudts, K.; Otto, J.; Valade, A; Luyssaert, S

    2014-01-01

    See, stats, and : https : / / www . researchgate . net / publication / 276534648 A - layer for simulations Article DOI : 10 . 5194 / gmdd - 7 - 8649 - 2014 CITATIONS 9 READS 155 12 , including : Some : land Master Jan French 193 , 481 SEE Eva Australian 98 , 225 SEE Vanessa The 85 SEE Juliane

  15. Simulated microgravity activates MAPK pathways in fibroblasts cultured on microgrooved surface topography

    NARCIS (Netherlands)

    Loesberg, W.A.; Walboomers, X.F.; van Loon, J.J.W.A.; Jansen, J.A.

    2008-01-01

    This study evaluated in vitro the differences in morphological behaviour between fibroblast cultured on smooth and microgrooved substrata (groove depth: 0.5 mu m, width: I pm), which were subjected to simulated microgravity. The aim of the study was to clarify which of these parameters was more

  16. Simulated microgravity activates MAPK pathways in fibroblasts cultured on microgrooved surface topography.

    NARCIS (Netherlands)

    Loesberg, W.A.; Walboomers, X.F.; Loon, J.J.W.A. van; Jansen, J.A.

    2008-01-01

    This study evaluated in vitro the differences in morphological behaviour between fibroblast cultured on smooth and microgrooved substrata (groove depth: 0.5 mum, width: 1 mum), which were subjected to simulated microgravity. The aim of the study was to clarify which of these parameters was more

  17. Dental ceramics coated with bioactive glass: Surface changes after exposure in a simulated body fluid under static and dynamic conditions

    Science.gov (United States)

    Papadopoulou, L.; Kontonasaki, E.; Zorba, T.; Chatzistavrou, X.; Pavlidou, E.; Paraskevopoulos, K.; Sklavounos, S.; Koidis, P.

    2003-07-01

    Bioactive materials develop a strong bond with living tissues through a carbonate-containing hydroxyapatite layer, similar to that of bone. The fabrication of a thin bioactive glass coating on dental ceramics used in metal-ceramic restorations, could provide a bioactive surface, which in combination with a tissue regenerative technique could lead to periodontal tissues attachment. The aim of this study was the in vitro investigation of the surface structure changes of dental ceramics used in metal-ceramic restorations, coated with a bioactive glass heat-treated at 950 °C, after exposure in a simulated body fluid (SBF) under two different soaking conditions. Coating of dental ceramics with a bioactive glass resulted in the formation of a stable and well bonded with the ceramic substrate thin layer. The growth of a well-attached carbonate apatite layer on their surface after immersion in a simulated body fluid is well evidenced under both experimental conditions, although in static environment the rate of apatite growth is constant and the grown layers seem to be more dense and compact compared with the respective layers observed on specimens under dynamic conditions.

  18. Weight loss and changes in surface roughness of denture base and reline materials after simulated toothbrushing in vitro.

    Science.gov (United States)

    Machado, Ana Lucia; Giampaolo, Eunice Teresinha; Vergani, Carlos Eduardo; Pavarina, Ana Cláudia; Salles, Débora da Silva Lopes; Jorge, Janaina Habib

    2012-06-01

    To evaluate the weight loss and the surface roughness of acrylic resins after simulated brushing tests. Ten specimens of each material (Tokuyama Rebase II-TR, New Truliner-NT, Ufi Gel Hard-UH and Lucitone 550-L) were made. The wear loss (mg) by weight and the surface roughness (Ra μm) of each specimen was determined before and after brushing. The specimens were placed on the brushing machine and a total of 20,000 brushing cycles was performed. The results of weight loss and roughness values were submitted to the anova followed by the Tukey's test (p = 0.05). The mean weight loss of material L was statistically higher (p 0.05). Only for L, toothbrushing increased the surface roughness. After toothbrushing, there was no significant difference between the roughness values of materials L and NT. The highest mean weight loss during the simulated toothbrushing tests was observed for L. Before the toothbrushing tests, the NT exhibited the highest mean roughness. Brushing resulted in increase in roughness only for resin L. © 2011 The Gerodontology Society and John Wiley & Sons A/S.

  19. Uncertainties of Large-Scale Forcing Caused by Surface Turbulence Flux Measurements and the Impacts on Cloud Simulations at the ARM SGP Site

    Science.gov (United States)

    Tang, S.; Xie, S.; Tang, Q.; Zhang, Y.

    2017-12-01

    Two types of instruments, the eddy correlation flux measurement system (ECOR) and the energy balance Bowen ratio system (EBBR), are used at the Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) site to measure surface latent and sensible fluxes. ECOR and EBBR typically sample different land surface types, and the domain-mean surface fluxes derived from ECOR and EBBR are not always consistent. The uncertainties of the surface fluxes will have impacts on the derived large-scale forcing data and further affect the simulations of single-column models (SCM), cloud-resolving models (CRM) and large-eddy simulation models (LES), especially for the shallow-cumulus clouds which are mainly driven by surface forcing. This study aims to quantify the uncertainties of the large-scale forcing caused by surface turbulence flux measurements and investigate the impacts on cloud simulations using long-term observations from the ARM SGP site.

  20. The influence of mouthrinses and simulated toothbrushing on the surface roughness of a nanofilled composite resin

    Directory of Open Access Journals (Sweden)

    Keico Graciela Sano Trauth

    2012-06-01

    Full Text Available The aim of this study was to determine the influence of mouthrinses on the surface roughness of a nanofilled composite resin after toothbrushing. One hundred nanofilled composite resin specimens were prepared and randomly distributed into two groups-brushed and non-brushed-and then assigned to five subgroups, according to the mouthrinse solutions (n = 10: Colgate Plax Fresh Mint, Oral B, Cepacol, Colgate Plax, and artificial saliva. Each sample was immersed in 20 mL of the mouthrinses for 1 minute, 5 days per week, twice a day, for a 3-week period. The control group used in the study was one in which the specimens were not subjected to brushing and remained only in artificial saliva. Toothbrushing was performed once a week for 1 minute, for 3 weeks. Surface roughness measurements (Ra were performed after the immersion period and toothbrushing, by means of a profilometer. Data were analyzed by two-way ANOVA and Tukey's test. Analysis revealed that the association between toothbrushing and Colgate Plax Fresh Mint produced the lowest surface roughness (p < 0.05. All other groups tested (Oral B, Cepacol, Colgate Plax, artificial saliva exhibited no statistically significant differences between surfaces, whether subjected to toothbrushing or not (p < 0.05. It was concluded that the surface roughness of the nanofilled composite resin tested can be influenced by the mouthrinse associated with toothbrushing.

  1. Copper(II) adsorption on the kaolinite(001) surface: Insights from first-principles calculations and molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Xiang-Ping, E-mail: kxp2004@163.com; Wang, Juan, E-mail: juaner80@163.com

    2016-12-15

    Highlights: • Several issues about Cu(II) adsorption on the kaolinite (0 0 1) surface were solved. • Complexation of water molecules with Cu(II) was considered for adsorption complex. • Charge transfer and bonding mechanism of Cu–O{sub s} (surface oxygen) were explored. - Abstract: The adsorption behavior of Cu(II) on the basal hydroxylated kaolinite(001) surface in aqueous environment was investigated by first-principles calculations and molecular dynamics simulations. Structures of possible monodentate and bidentate inner-sphere adsorption complexes of Cu(II) were examined, and the charge transfer and bonding mechanism were analyzed. Combining the binding energy of complex, the radial distribution function of Cu(II) with oxygen and the extended X-ray absorption fine structure data, monodentate complex on site of surface oxygen with “upright” hydrogen and bidentate complex on site of two oxygens (one with “upright” hydrogen and one with “lying” hydrogen) of single Al center have been found to be the major adsorption species of Cu(II). Both adsorption species are four-coordinated with a square planar geometry. The distribution of surface hydroxyls with “lying” hydrogen around Cu(II) plays a key role in the structure and stability of adsorption complex. Upon the Mulliken population analysis and partial density of states, charge transfer occurs with Cu(II) accepting some electrons from both surface oxygens and aqua oxygens, and the bonding Cu 3d-O 2p state filling is primarily responsible for the strong covalent interaction of Cu(II) with surface oxygen.

  2. Simulated effects of surface coal mining and agriculture on dissolved solids in the Redwater River, east-central Montana

    Science.gov (United States)

    Ferreira, R.F.; Lambing, J.H.

    1985-01-01

    Dissolved solids concentrations in five reaches of the Redwater River in east-central Montana were simulated to evaluate the effects of surface coal mining and agriculture. A mass-balance model of streamflow and dissolved solids load developed for the Tongue River in southeastern Montana was modified and applied to the Redwater River. Mined acreages, dissolved solids concentrations in mined spoils, and irrigated acreage can be varied in the model to study relative changes in the dissolved solids concentration in consecutive reaches of the river. Because of extreme variability and a limited amount of data, the model was not consecutively validated. Simulated mean and median monthly mean streamflows and consistently larger than those calculated from streamflow records. Simulated mean and median monthly mean dissolved solids loads also are consistently larger than regression-derived values. These discrepancies probably result from extremely variable streamflow, overestimates of streamflow from ungaged tributaries, and weak correlations between streamflow and dissolved solids concentrations. The largest increases in simulated dissolved solids concentrations from mining and agriculture occur from September through January because of smaller streamflows and dissolved solids loads. Different combinations of agriculture and mining under mean flow conditions resulted in cumulative percentage increases of dissolved solids concentrations of less than 5% for mining and less than 2% for agriculture. (USGS)

  3. A stable high-order perturbation of surfaces method for numerical simulation of diffraction problems in triply layered media

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Youngjoon, E-mail: hongy@uic.edu; Nicholls, David P., E-mail: davidn@uic.edu

    2017-02-01

    The accurate numerical simulation of linear waves interacting with periodic layered media is a crucial capability in engineering applications. In this contribution we study the stable and high-order accurate numerical simulation of the interaction of linear, time-harmonic waves with a periodic, triply layered medium with irregular interfaces. In contrast with volumetric approaches, High-Order Perturbation of Surfaces (HOPS) algorithms are inexpensive interfacial methods which rapidly and recursively estimate scattering returns by perturbation of the interface shape. In comparison with Boundary Integral/Element Methods, the stable HOPS algorithm we describe here does not require specialized quadrature rules, periodization strategies, or the solution of dense non-symmetric positive definite linear systems. In addition, the algorithm is provably stable as opposed to other classical HOPS approaches. With numerical experiments we show the remarkable efficiency, fidelity, and accuracy one can achieve with an implementation of this algorithm.

  4. Transport properties of water molecules confined between hydroxyapaptite surfaces: A Molecular dynamics simulation approach

    Science.gov (United States)

    Prakash, Muthuramalingam; Lemaire, Thibault; Di Tommaso, Devis; de Leeuw, Nora; Lewerenz, Marius; Caruel, Matthieu; Naili, Salah

    2017-10-01

    Water diffusion in the vicinity of hydroxyapatite (HAP) crystals is a key issue to describe biomineralization process. In this study, a configuration of parallel HAP platelets mimicking bone nanopores is proposed to characterize the nanoscopic transport properties of water molecules at HAP-water surface and interfaces using various potential models such as combination of the Core-Shell (CS) model, Lennard-Jones (LJ) potentials with SPC or SPC/E water models. When comparing all these potentials models, it appears that the core-shell potential for HAP together with the SPC/E water model more accurately predicts the diffusion properties of water near HAP surface. Moreover, we have been able to put into relief the possibility of observing hydroxyl (OH-) ion dissociation that modifies the water structure near the HAP surface.

  5. Runoff of pyrethroid insecticides from concrete surfaces following simulated and natural rainfalls.

    Science.gov (United States)

    Jiang, Weiying; Haver, Darren; Rust, Michael; Gan, Jay

    2012-03-01

    Intensive residential use of insecticides has resulted in their ubiquitous presence as contaminants in urban surface streams. For pest eradication, urban hard surfaces such as concrete are often directly treated with pesticides, and wind/water can also carry pesticides onto hard surfaces from surrounding areas. This study expanded on previous bench-scale studies by considering pesticide runoff caused by irrigation under dry weather conditions and rain during the wet season, and evaluated the effects of pesticide residence time on concrete, single versus recurring precipitations, precipitation intensity, and concrete surface conditions, on pesticide transferability to runoff water. Runoff from concrete 1 d after pesticide treatment contained high levels of bifenthrin (82 μg/L) and permethrin (5143 μg/L for cis and 5518 μg/L for trans), indicating the importance of preventing water contact on concrete after pesticide treatments. Although the runoff transferability quickly decreased as the pesticide residence time on concrete increased, detectable residues were still found in runoff water after 3 months (89 d) exposure to hot and dry summer conditions. ANOVA analysis showed that precipitation intensities and concrete surface conditions (i.e., acid wash, silicone seal, stamping, and addition of microsilica) did not significantly affect the pesticide transferability to runoff. For concrete slabs subjected to natural rainfalls during the winter wet season, pesticide levels in the runoff decreased as the time interval between pesticide application and the rain event increased. However, bifenthrin and permethrin were still detected at 0.15-0.17 and 0.75-1.15 μg/L in the rain runoff after 7 months (221 d) from the initial treatment. In addition, pesticide concentrations showed no decrease between the two rainfall events, suggesting that concrete surfaces contaminated by pesticides may act as a reservoir for pesticide residues, leading to sustained urban runoff

  6. Simulation and Analysis of Topographic Effect on Land Surface Albedo over Mountainous Areas

    Science.gov (United States)

    Hao, D.; Wen, J.; Xiao, Q.

    2017-12-01

    Land surface albedo is one of the significant geophysical variables affecting the Earth's climate and controlling the surface radiation budget. Topography leads to the formation of shadows and the redistribution of incident radiation, which complicates the modeling and estimation of the land surface albedo. Some studies show that neglecting the topography effect may lead to significant bias in estimating the land surface albedo for the sloping terrain. However, for the composite sloping terrain, the topographic effects on the albedo remain unclear. Accurately estimating the sub-topographic effect on the land surface albedo over the composite sloping terrain presents a challenge for remote sensing modeling and applications. In our study, we focus on the development of a simplified estimation method for land surface albedo including black-sky albedo (BSA) and white-sky albedo (WSA) of the composite sloping terrain at a kilometer scale based on the fine scale DEM (30m) and quantitatively investigate and understand the topographic effects on the albedo. The albedo is affected by various factors such as solar zenith angle (SZA), solar azimuth angle (SAA), shadows, terrain occlusion, and slope and aspect distribution of the micro-slopes. When SZA is 30°, the absolute and relative deviations between the BSA of flat terrain and that of rugged terrain reaches 0.12 and 50%, respectively. When the mean slope of the terrain is 30.63° and SZA=30°, the absolute deviation of BSA caused by SAA can reach 0.04. The maximal relative and relative deviation between the WSA of flat terrain and that of rugged terrain reaches 0.08 and 50%. These results demonstrate that the topographic effect has to be taken into account in the albedo estimation.

  7. An adaptive finite element method for simulating surface tension with the gradient theory of fluid interfaces

    KAUST Repository

    Kou, Jisheng

    2014-01-01

    The gradient theory for the surface tension of simple fluids and mixtures is rigorously analyzed based on mathematical theory. The finite element approximation of surface tension is developed and analyzed, and moreover, an adaptive finite element method based on a physical-based estimator is proposed and it can be coupled efficiently with Newton\\'s method as well. The numerical tests are carried out both to verify the proposed theory and to demonstrate the efficiency of the proposed method. © 2013 Elsevier B.V. All rights reserved.

  8. Simulated plasma facing component measurements for an in situ surface diagnostic on Alcator C-Moda)

    Science.gov (United States)

    Hartwig, Z. S.; Whyte, D. G.

    2010-10-01

    The ideal in situ plasma facing component (PFC) diagnostic for magnetic fusion devices would perform surface element and isotope composition measurements on a shot-to-shot (˜10 min) time scale with ˜1 μm depth and ˜1 cm spatial resolution over large areas of PFCs. To this end, the experimental adaptation of the customary laboratory surface diagnostic—nuclear scattering of MeV ions—to the Alcator C-Mod tokamak is being guided by ACRONYM, a Geant4 synthetic diagnostic. The diagnostic technique and ACRONYM are described, and synthetic measurements of film thickness for boron-coated PFCs are presented.

  9. Application of FTLOADDS to Simulate Flow, Salinity, and Surface-Water Stage in the Southern Everglades, Florida

    Science.gov (United States)

    Wang, John D.; Swain, Eric D.; Wolfert, Melinda A.; Langevin, Christian D.; James, Dawn E.; Telis, Pamela A.

    2007-01-01

    The Comprehensive Everglades Restoration Plan requires numerical modeling to achieve a sufficient understanding of coastal freshwater flows, nutrient sources, and the evaluation of management alternatives to restore the ecosystem of southern Florida. Numerical models include a regional water-management model to represent restoration changes to the hydrology of southern Florida and a hydrodynamic model to represent the southern and western offshore waters. The coastal interface between these two systems, however, has complex surface-water/ground-water and freshwater/saltwater interactions and requires a specialized modeling effort. The Flow and Transport in a Linked Overland/Aquifer Density Dependent System (FTLOADDS) code was developed to represent connected surface- and ground-water systems with variable-density flow. The first use of FTLOADDS is the Southern Inland and Coastal Systems (SICS) application to the southeastern part of the Everglades/Florida Bay coastal region. The need to (1) expand the domain of the numerical modeling into most of Everglades National Park and the western coastal area, and (2) better represent the effect of water-delivery control structures, led to the application of the FTLOADDS code to the Tides and Inflows in the Mangroves of the Everglades (TIME) domain. This application allows the model to address a broader range of hydrologic issues and incorporate new code modifications. The surface-water hydrology is of primary interest to water managers, and is the main focus of this study. The coupling to ground water, however, was necessary to accurately represent leakage exchange between the surface water and ground water, which transfers substantial volumes of water and salt. Initial calibration and analysis of the TIME application produced simulated results that compare well statistically with field-measured values. A comparison of TIME simulation results to previous SICS results shows improved capabilities, particularly in the

  10. Simulation of surface energy fluxes and stratification of a small boreal lake by a set of one-dimensional models

    Directory of Open Access Journals (Sweden)

    Victor Stepanenko

    2014-01-01

    Full Text Available Five one-dimensional (1D lake models were run for the open water season in 2006 for Lake Valkea-Kotinen (Finland using on-lake measured meteorological forcing. The model results were validated using measurements of water temperature and of eddy covariance (EC fluxes. The surface temperature is satisfactorily simulated by all models showing slight overestimation (by 0.1–1.1°C. Both sensible and latent heat fluxes are positively biased in respect to EC data, consistent with earlier studies. However, correlation coefficients between EC-fluxes and those simulated are relatively high ranging from 0.55 to 0.74. The skill to simulate vertical temperature profiles by different models is assessed as well. It is found that the lake models underestimate the EC-derived surface drag coefficient, however providing realistic temperature profiles. It is argued that the real momentum flux from the atmosphere is larger than simulated, however it is split up between the wave development and the acceleration of lake currents. Adopting the simple parameterisation for momentum flux partitioning in one of the models showed that this mechanism can be significant. Finally, the effect of including the lake bathymetry data in k-ɛ models was the drastic overheating of water below the thermocline. This is likely to be caused by omitting the heat flux at the lake margins. Thus, the parameterisation of heat flux at the lake's margins should be included in the models; otherwise it is recommended to neglect bathymetry effects for such small water bodies as the Lake Valkea-Kotinen.

  11. Comparing atmosphere-land surface feedbacks from models within the tropics (CALM). Part 1: Evaluation of CMIP5 GCMs to simulate the land surface-atmosphere feedback

    Science.gov (United States)

    Williams, C.; Allan, R.; Kniveton, D.

    2012-04-01

    Man-made transformations to the environment, and in particular the land surface, are having a large impact on the distribution (in both time and space) of rainfall, upon which all life is reliant. From global changes in the composition of the atmosphere, through the emission of greenhouse gases and aerosols, to more localised land use and land cover changes due to an expanding population with an increasing ecological footprint, human activity has a considerable impact on the processes controlling rainfall. This is of particular importance for environmentally vulnerable regions such as many of those in the tropics. Here, widespread poverty, an extensive disease burden and pockets of political instability has resulted in a low resilience and limited adaptative capacity to climate related shocks and stresses. Recently, the 5th Climate Modelling Intercomparison Project (CMIP5) has run a number of state-of-the-art climate models using various present-day and future emission scenarios of greenhouse gases, and therefore provides an unprecedented amount of simulated model data. This paper presents the results of the first stage of a larger project, aiming to further our understanding of how the interactions between tropical rainfall and the land surface are represented in some of the latest climate model simulations. Focusing on precipitation, soil moisture and near-surface temperature, this paper compares the data from all of these models, as well as blended observational-satellite data, to see how the interactions between rainfall and the land surface differs (or agrees) between the models and reality. Firstly, in an analysis of the processes from the "observed" data, the results suggest a strong positive relationship between precipitation and soil moisture at both daily and seasonal timescales. There is a weaker and negative relationship between precipitation and temperature, and likewise between soil moisture and temperature. For all variables, the correlations are

  12. Numerical simulations of conjugate convection combined with surface thermal radiation using an Immersed-Boundary Method

    International Nuclear Information System (INIS)

    Favre, F.; Colomer, G.; Lehmkuhl, O.; Oliva, A.

    2016-01-01

    Dynamic and thermal interaction problems involving fluids and solids were studied through a finite volume-based Navier-Stokes solver, combined with immersed-boundary techniques and the net radiation method. Source terms were included in the momentum and energy equations to enforce the non-slip condition and the conjugate boundary condition including the radiative heat exchange. Code validation was performed through the simulation of two cases from the literature: conjugate natural convection in a square cavity with a conducting side wall; and a cubical cavity with conducting walls and a heat source. The accuracy of the methodology and the validation of the inclusion of moving bodies into the simulation was performed via a theoretical case (paper)

  13. Monte Carlo simulation of an in-situ search of water on the Martian surface by using neutron spectroscopy

    CERN Document Server

    Vincke, H H; Müller, H; Bruckner, J

    2003-01-01

    In this paper the concept for in-situ search of water in the Martian soil by applying neutron spectroscopy is examined. Monte-Carlo simulations were carried out to determine homogeneous water concentrations in the Martian surface. In addition, the effect of an ice layer with a thickness of 10 cm, buried in the soil, was investigated. Furthermore, a method is presented that provides the ability to distinguish between the effects caused by a homogeneous water distribution and an ice layer located at different depths.

  14. Integrating satellite retrieved leaf chlorophyll into land surface models for constraining simulations of water and carbon fluxes

    KAUST Repository

    Houborg, Rasmus

    2013-07-01

    In terrestrial biosphere models, key biochemical controls on carbon uptake by vegetation canopies are typically assigned fixed literature-based values for broad categories of vegetation types although in reality significant spatial and temporal variability exists. Satellite remote sensing can support modeling efforts by offering distributed information on important land surface characteristics, which would be very difficult to obtain otherwise. This study investigates the utility of satellite based retrievals of leaf chlorophyll for estimating leaf photosynthetic capacity and for constraining model simulations of water and carbon fluxes. © 2013 IEEE.

  15. Shallow to Deep Convection Transition over a Heterogeneous Land Surface Using the Land Model Coupled Large-Eddy Simulation

    Science.gov (United States)

    Lee, J.; Zhang, Y.; Klein, S. A.

    2017-12-01

    The triggering of the land breeze, and hence the development of deep convection over heterogeneous land should be understood as a consequence of the complex processes involving various factors from land surface and atmosphere simultaneously. That is a sub-grid scale process that many large-scale models have difficulty incorporating it into the parameterization scheme partly due to lack of our understanding. Thus, it is imperative that we approach the problem using a high-resolution modeling framework. In this study, we use SAM-SLM (Lee and Khairoutdinov, 2015), a large-eddy simulation model coupled to a land model, to explore the cloud effect such as cold pool, the cloud shading and the soil moisture memory on the land breeze structure and the further development of cloud and precipitation over a heterogeneous land surface. The atmospheric large scale forcing and the initial sounding are taken from the new composite case study of the fair-weather, non-precipitating shallow cumuli at ARM SGP (Zhang et al., 2017). We model the land surface as a chess board pattern with alternating leaf area index (LAI). The patch contrast of the LAI is adjusted to encompass the weak to strong heterogeneity amplitude. The surface sensible- and latent heat fluxes are computed according to the given LAI representing the differential surface heating over a heterogeneous land surface. Separate from the surface forcing imposed from the originally modeled surface, the cases that transition into the moist convection can induce another layer of the surface heterogeneity from the 1) radiation shading by clouds, 2) adjusted soil moisture pattern by the rain, 3) spreading cold pool. First, we assess and quantifies the individual cloud effect on the land breeze and the moist convection under the weak wind to simplify the feedback processes. And then, the same set of experiments is repeated under sheared background wind with low level jet, a typical summer time wind pattern at ARM SGP site, to

  16. Modeling and simulation of the free electron laser and railgun on an electric Naval surface platform

    OpenAIRE

    Bowlin, Oscar E.

    2006-01-01

    The Free Electron Laser (FEL) and Rail Gun are electric weapons which will require a significant amount of stored energy for operation. These types of weapons are ideal for use onboard an all-electric ship. An investigation is made of the effects these weapons will have on a proposed electrical system architecture using simulation modeling. Specifically, this thesis identifies possible design weaknesses and shows where further research and modeling is needed in order to ensure the proper inte...

  17. Simulations of absorbed dose on the phantom surface of MATROSHKA-R experiment at the ISS

    Czech Academy of Sciences Publication Activity Database

    Kolísková, Zlata; Sihver, L.; Ambrožová, Iva; Sato, T.; Spurný, František; Shurshakov, V. A.

    2012-01-01

    Roč. 49, č. 2 (2012), s. 230-236 ISSN 0273-1177 R&D Projects: GA ČR GA205/09/0171; GA AV ČR KJB100480901; GA ČR GD202/09/H086 Institutional research plan: CEZ:AV0Z10480505 Keywords : MATROSHKA-R * PHITS * Simulations * Space radiation * Dose estimation Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.183, year: 2012

  18. A simulation tool for integrating climate change and Canadian surface transport : towards assessing impacts and adaptations

    International Nuclear Information System (INIS)

    Kanaroglou, P.; Maoh, H.; Woudsma, C.; Marshall, S.

    2008-01-01

    Extreme weather events resulting from climate change will have a significant impact of the performance of the Canadian transportation system. This presentation described a simulation tool designed to investigate the potential ramifications of future climate change on transportation and the economy. The CLIMATE-C tool was designed to simulate future weather scenarios for the years 2020 and 2050 using weather parameters obtained from a global general circulation model. The model accounted for linkages between weather, transportation, and economic systems. A random utility-based multi-regional input-output model was used to predict inter-regional trade flows by truck and rail in Canada. Simulated weather scenarios were used to describe predicted changes in demographic, social, economic, technological and environmental developments to 2100. Various changes in population and economic growth were considered. Six additional scenarios were formulated to consider moderate and high rainfall events, moderate, high and extreme snowfall, and cold temperatures. Results of the preliminary analysis indicated that the model is sensitive to changes in weather events. Future research is needed to evaluate future weather scenarios and analyze weather-transport data in order to quantify travel speed reduction parameters. tabs., figs.

  19. On the sensitivity of numerical weather prediction to remotely sensed marine surface wind data - A simulation study

    Science.gov (United States)

    Cane, M. A.; Cardone, V. J.; Halem, M.; Halberstam, I.

    1981-01-01

    The reported investigation has the objective to assess the potential impact on numerical weather prediction (NWP) of remotely sensed surface wind data. Other investigations conducted with similar objectives have not been satisfactory in connection with a use of procedures providing an unrealistic distribution of initial errors. In the current study, care has been taken to duplicate the actual distribution of information in the conventional observing system, thus shifting the emphasis from accuracy of the data to the data coverage. It is pointed out that this is an important consideration in assessing satellite observing systems since experience with sounder data has shown that improvements in forecasts due to satellite-derived information is due less to a general error reduction than to the ability to fill data-sparse regions. The reported study concentrates on the evaluation of the observing system simulation experimental design and on the assessment of the potential of remotely sensed marine surface wind data.

  20. Combined Bulk and Surface Radiation Damage Effects at Very High Fluences in Silicon Detectors: Measurements and TCAD Simulations

    CERN Document Server

    Moscatelli, F; Morozzi, A; Mendicino, R; Dalla Betta, G F; Bilei, G M

    2016-01-01

    In this work we propose a new combined TCAD radiation damage modelling scheme, featuring both bulk and surface radiation damage effects, for the analysis of silicon detectors aimed at the High Luminosity LHC. In particular, a surface damage model has been developed by introducing the relevant parameters (NOX, NIT) extracted from experimental measurements carried out on p-type substrate test structures after gamma irradiations at doses in the range 10-500 Mrad(Si). An extended bulk model, by considering impact ionization and deep-level cross-sections variation, was included as well. The model has been validated through the comparison of the simulation findings with experimental measurements carried out at very high fluences (2×1016 1 MeV equivalent n/cm2) thus fostering the application of this TCAD approach for the design and optimization of the new generation of silicon detectors to be used in future HEP experiments.

  1. Simulated solar light phototransformation of organophosphorus azinphos methyl at the surface of clays and goethite.

    Science.gov (United States)

    Menager, Matthieu; Sarakha, Mohamed

    2013-01-15

    The photochemical behavior of the pesticide azinphos methyl at the surface of clays (kaolinite, bentonite) and goethite was studied using Suntest setup (λ > 300 nm). The quantum yield on the clays was found to be roughly three times lower than that in aqueous solution. However, the photochemical efficiency was much higher at the surface of goethite owing to its photocatalytic activity through the hydroxyl radical production. The added humic substances on kaolonite show an inhibition of azinphos methyl degradation while the incorporation of iron(III) aquacomplexes leads to an important increase of the disappearance together with the formation of iron(II). Hydroxyl radical species were found to be formed either by excitation of goethite or clays. The goethite support acts as a more efficient catalyst for the formation of these reactive oxygen species. The photodecomposition reactions observed were (i) hydrolysis process leading to the formation of benzotriazone and the oxidation of the P = S bond giving rise to the formation of the oxon derivative, and (ii) homolytic cleavage of the N-C and C-S bonds of the organophosphorus bridge leading to the formation of dimers that appear to be specific to the irradiation at the surface of solid supports since they were not observed when the irradiation was performed in aqueous media: a statement that is related to the presence of aggregates at the surface of solid supports.

  2. Simulation of surface-directed phase separation in a solution-processed polymer/PCBM blend

    NARCIS (Netherlands)

    Michels, J.J.; Moons, E.

    2013-01-01

    The formation of the surface-induced stratified lamellar composition profile experimentally evidenced in spincoated layers of the photovoltaic donor-acceptor blend consisting of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5- (4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole]/ phenyl-C61-butyric acid

  3. Coupled slow and fast surface dynamics in an electrocatalytic oscillator: Model and simulations

    International Nuclear Information System (INIS)

    Nascimento, Melke A.; Nagao, Raphael; Eiswirth, Markus; Varela, Hamilton

    2014-01-01

    The co-existence of disparate time scales is pervasive in many systems. In particular for surface reactions, it has been shown that the long-term evolution of the core oscillator is decisively influenced by slow surface changes, such as progressing deactivation. Here we present an in-depth numerical investigation of the coupled slow and fast surface dynamics in an electrocatalytic oscillator. The model consists of four nonlinear coupled ordinary differential equations, investigated over a wide parameter range. Besides the conventional bifurcation analysis, the system was studied by means of high-resolution period and Lyapunov diagrams. It was observed that the bifurcation diagram changes considerably as the irreversible surface poisoning evolves, and the oscillatory region shrinks. The qualitative dynamics changes accordingly and the chaotic oscillations are dramatically suppressed. Nevertheless, periodic cascades are preserved in a confined region of the resistance vs. voltage diagram. Numerical results are compared to experiments published earlier and the latter reinterpreted. Finally, the comprehensive description of the time-evolution in the period and Lyapunov diagrams suggests further experimental studies correlating the evolution of the system's dynamics with changes of the catalyst structure

  4. Excess electrons at anatase TiO2 surfaces and interfaces: insights from first principles simulations

    Science.gov (United States)

    Selçuk, Sencer; Selloni, Annabella

    2017-07-01

    TiO2 is an important technological material with widespread applications in photocatalysis, photovoltaics and self-cleaning surfaces. Excess electrons from intrinsic defects, dopants and photoexcitation play a key role in the properties of TiO2 that are relevant to its energy-related applications. The picture of excess and photoexcited electrons in TiO2 is based on the polaron model, where the electron forms a localized state that is stabilized by an accompanying lattice distortion. Here, we focus on excess and photoexcited electrons in anatase, the TiO2 polymorph most relevant to photocatalysis and solar energy conversion. For anatase, evidence of both small and large electron polarons has been reported in the literature. In addition, several studies have revealed a remarkable dependence of the photocatalytic activity of anatase on the crystal surface. After an overview of experimental studies, we briefly discuss recent progress in the theoretical description of polaronic states in TiO2, and finally present a more detailed account of our computational studies on the trapping and dynamics of excess electrons near the most common anatase surfaces and aqueous interfaces. The results of these studies provide a bridge between surface science experiments under vacuum conditions and observations of crystal-face-dependent photocatalysis on anatase, and support the idea that optimization of the ratio between different anatase facets can help enhance the photocatalytic activity of this material.

  5. Coupled slow and fast surface dynamics in an electrocatalytic oscillator: Model and simulations

    Science.gov (United States)

    Nascimento, Melke A.; Nagao, Raphael; Eiswirth, Markus; Varela, Hamilton

    2014-12-01

    The co-existence of disparate time scales is pervasive in many systems. In particular for surface reactions, it has been shown that the long-term evolution of the core oscillator is decisively influenced by slow surface changes, such as progressing deactivation. Here we present an in-depth numerical investigation of the coupled slow and fast surface dynamics in an electrocatalytic oscillator. The model consists of four nonlinear coupled ordinary differential equations, investigated over a wide parameter range. Besides the conventional bifurcation analysis, the system was studied by means of high-resolution period and Lyapunov diagrams. It was observed that the bifurcation diagram changes considerably as the irreversible surface poisoning evolves, and the oscillatory region shrinks. The qualitative dynamics changes accordingly and the chaotic oscillations are dramatically suppressed. Nevertheless, periodic cascades are preserved in a confined region of the resistance vs. voltage diagram. Numerical results are compared to experiments published earlier and the latter reinterpreted. Finally, the comprehensive description of the time-evolution in the period and Lyapunov diagrams suggests further experimental studies correlating the evolution of the system's dynamics with changes of the catalyst structure.

  6. Greenland ice sheet surface mass balance: evaluating simulations and making projections with regional climate models

    NARCIS (Netherlands)

    Rae, J.G.L.; Aðalgeirsdóttir, G.; Edwards, T.L.; Fettweis, X.; Gregory, J.M.; Hewitt, H.T.; Lowe, J.A.; Lucas-Picher, P.; Mottram, R.H.; Payne, A.J.; Ridley, J.K.; Shannon, S.R.; van de Berg, W.J.|info:eu-repo/dai/nl/304831611; van de Wal, R.S.W.|info:eu-repo/dai/nl/101899556; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643

    2012-01-01

    Four high-resolution regional climate models (RCMs) have been set up for the area of Greenland, with the aim of providing future projections of Greenland ice sheet surface mass balance (SMB), and its contribution to sea level rise, with greater accuracy than is possible from coarser-resolution

  7. A Simulation Model of Focus and Radial Servos in Compact Disc Players with Disc Surface Defects

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Stoustrup, Jakob; Andersen, Palle

    2004-01-01

    Compact Disc players have been on the market in more than two decades.As a consequence most of the control servo problems have been solved. A large remaining problem to solve is the handling of Compact Discs with severe surface defects like scratches and fingerprints. This paper introduces a method...

  8. Air Abrasive Disinfection of Implant Surfaces in a Simulated Model of Peri-Implantitis

    Science.gov (United States)

    2016-06-01

    Introduction: Dental implant technology has evolved into a predictable treatment option for the restoration of edentulous sites. However, peri... implantitis is an emerging complication leading to increased morbidity or mortality of osseointegrated implants . The prevalence of peri- implant ... implant surface. The aim of this in vitro study was to evaluate the ability of air-powder abrasion to mechanically decontaminate dental implants in a

  9. Effect of nontronite smectite clay on the chemical evolution of several organic molecules under simulated Mars surface UV radiation conditions

    Science.gov (United States)

    Poch, Olivier; Dequaire, Tristan; Stalport, Fabien; Jaber, Maguy; Lambert, Jean-François; Szopa, Cyril; Coll, Patrice

    2015-04-01

    The search for organic carbon-containing molecules at the surface of Mars, as clues of past habitability or remnants of life, is a major scientific goal for Mars exploration. Several lines of evidence, including the detection of phyllosilicates, suggest that early Mars offered favorable conditions for long-term sustaining of water. As a consequence, we can assume that in those days, endogenous chemical processes, or even primitive life, may have produced organic matter on Mars. Moreover, exogenous delivery from small bodies or dust particles is likely to have brought fresh organic molecules to the surface of Mars up today. Organic matter is therefore expected to be present at the surface/subsurface of the planet. But the current environmental conditions at the surface - UV radiation, oxidants and energetic particles - generate physico-chemical processes that may affect organic molecules. On the other hand, on Earth, phyllosilicates are known to accumulate and preserve organic matter. But are phyllosilicates efficient at preserving organic molecules under the current environmental conditions at the surface of Mars? We have monitored the qualitative and quantitative evolutions of glycine, urea and adenine interacting with the Fe3+-smectite clay nontronite, one of the most abundant phyllosilicates present at the surface of Mars, under simulated Martian surface ultraviolet light (190-400 nm), mean temperature (218 ± 2 K) and pressure (6 ± 1 mbar) in a laboratory simulation setup. We have tested organic-rich samples which may be representative of the evaporation of a warm little pond of liquid water having concentrated organics on Mars. For each molecule, we have observed how the nontronite influences the quantum efficiency of its photodecomposition and the nature of its solid evolution products. The results reveal a pronounced photoprotective effect of nontronite on the evolution of glycine and adenine: their efficiencies of photodecomposition are reduced by a factor

  10. Simulation of groundwater flow and interaction of groundwater and surface water on the Lac du Flambeau Reservation, Wisconsin

    Science.gov (United States)

    Juckem, Paul F.; Fienen, Michael N.; Hunt, Randall J.

    2014-01-01

    The Lac du Flambeau Band of Lake Superior Chippewa and Indian Health Service are interested in improving the understanding of groundwater flow and groundwater/surface-water interaction on the Lac du Flambeau Reservation (Reservation) in southwest Vilas County and southeast Iron County, Wisconsin, with particular interest in an understanding of the potential for contamination of groundwater supply wells and the fate of wastewater that is infiltrated from treatment lagoons on the Reservation. This report describes the construction, calibration, and application of a regional groundwater flow model used to simulate the shallow groundwater flow system of the Reservation and water-quality results for groundwater and surface-water samples collected near a system of waste-water-treatment lagoons. Groundwater flows through a permeable glacial aquifer that ranges in thickness from 60 to more than 200 feet (ft). Seepage and drainage lakes are common in the area and influence groundwater flow patterns on the Reservation. A two-dimensional, steady-state analytic element groundwater flow model was constructed using the program GFLOW. The model was calibrated by matching target water levels and stream base flows through the use of the parameter-estimation program, PEST. Simulated results illustrate that groundwater flow within most of the Reservation is toward the Bear River and the chain of lakes that feed the Bear River. Results of analyses of groundwater and surface-water samples collected downgradient from the wastewater infiltration lagoons show elevated levels of ammonia and dissolved phosphorus. In addition, wastewater indicator chemicals detected in three downgradient wells and a small downgradient stream indicate that infiltrated wastewater is moving southwest of the lagoons toward Moss Lake. Potential effects of extended wet and dry periods (within historical ranges) were evaluated by adjusting precipitation and groundwater recharge in the model and comparing the

  11. Surface Energy Balance in Jakarta and Neighboring Regions As Simulated Using Fifth Mesoscale Model (MM5

    Directory of Open Access Journals (Sweden)

    Yopi Ilhamsyah

    2014-04-01

    Full Text Available The objective of the present research was to assess the surface energy balance particularly in terms of the computed surface energy and radiation balance and the development of boundary layer over Jakarta and Neighboring Regions (JNR by means of numerical model of fifth generation of Mesoscale Model (MM5. The MM5 with four domains of 9 kilometers in spatial resolution presenting the outermost and the innermost of JNR is utilized. The research focuses on the third and fourth domains covering the entire JNR. The description between radiation and energy balance at the surface is obtained from the model. The result showed that energy balance is higher in the city area during daytime. Meanwhile, energy components, e.g., surface sensible and latent heat flux showed that at the sea and in the city areas were higher than other areas. Moreover, ground flux showed eastern region was higher than others. In general, radiation and energy balance was higher in the daytime and lower in the nighttime for all regions. The calculation of Bowen Ratio, the ratio of surface sensible and latent heat fluxes, was also higher in the city area, reflecting the dominations of urban and built-up land in the region. Meanwhile, Bowen Ratio in the rural area dominated by irrigated cropland was lower. It is consistent with changes of land cover properties, e.g. albedo, soil moisture, and thermal characteristics. In addition, the boundary layer is also higher in the city. Meanwhile western region dominated by suburban showed higher boundary layer instead of eastern region.

  12. Numerical simulation and experimental study on farmland nitrogen loss to surface runoff in a raindrop driven process

    Science.gov (United States)

    Li, Jiayun; Tong, Juxiu; Xia, Chuanan; Hu, Bill X.; Zhu, Hao; Yang, Rui; Wei, Wenshuo

    2017-06-01

    It has been widely recognized that surface runoff from agricultural field is an important non-point pollution source, which however, the chemical transfer amount in the process is very difficult to be quantified in field since some variables and natural factors are hard to control, such as rainfall intensity, temperature, wind speeds and soil spatial heterogeneity, which may significantly affect the field experimental results. Therefore, a physically based nitrogen transport model was developed and tested with the so called semi-field experiments (i.e., artificial rainfall was used instead of natural rainfall, but other conditions were natural) in this paper. Our model integrated the raindrop driven process and diffusion effect with the simplified nitrogen chain reactions. In this model, chemicals in the soil surface layer, or the 'exchange layer', were transformed into the surface runoff layer due to raindrop impact. The raindrops also have a significant role on the diffusion process between the exchange layer and the underlying soil. The established mathematical model was solved numerically through the modified Hydrus-1d source code, and the model simulations agreed well with the experimental data. The modeling results indicate that the depth of the exchange layer and raindrop induced water transfer rate are two important parameters for the simulation results. Variation of the water transfer rate, er, can strongly influence the peak values of the NO-3-N and NH+4-N concentration breakthrough curves. The concentration of NO-3-N is more sensitive to the exchange layer depth, de, than NH+4-N. In general, the developed model well describes the nitrogen loss into surface runoff in a raindrop driven process. Since the raindrop splash erosion process may aggravate the loss of chemical fertilizer, choosing an appropriate fertilization time and application method is very important to prevent the pollution.

  13. MOD_FreeSurf2D: a Surface Fluid Flow Simulation Model for Rivers, Streams, and Shallow Estuaries

    Science.gov (United States)

    Martin, N.; Gorelick, S. M.

    2003-12-01

    The MOD_FreeSurf2D, Modular Free Surface Flow in Two-Dimensions, computer model simulates free surface fluid flow in streams, rivers, and shallow estuaries under the assumptions of a well-mixed water column, a small water depth to width ratio, and a hydrostatic pressure distribution. The dependent variables in the model are free surface elevation, which provides total water depth, and fluid velocity. Primary advantages of MOD_FreeSurf2D relative to other two-dimensional models are a stable and computationally efficient numerical representation and a transparent representation of wetting and drying of the simulation domain. MOD_FreeSurf2D approximates the depth-averaged, shallow water equations with a finite volume, semi-implicit, semi-Lagrangian numerical representation similar to the TRIM method (Casulli, 1990; Casulli and Cheng, 1992; Casulli, 1999). The semi-implicit, semi-Lagrangian approach is computationally efficient because time steps can exceed the Courant-Friedrich-Lewy (CFL) stability criterion without significant accuracy degradation (Robert, 1982; Casulli, 1990). The rectangular, Arakawa C-grid, finite-volume layout allows flooding and drying in response to changing flow conditions without prior channel specification or closed boundary specification. Open boundary conditions available in MOD_FreeSurf2D are specified flux, specified total water depth, specified velocity, radiation free surface, and radiation velocity. MOD_FreeSurf2D requires initial topography, undisturbed water depth, and Manning's roughness coefficient. MOD_FreeSurf2D simulated results are shown to converge to the semi-empirical solution for a simple straight channel case. Two applications demonstrate the accuracy of MOD_FreeSurf2D. The first application is the evolution of water depth in the dambreak-style flume experiment of Bellos et al. (1992). In this case, MOD_FreeSurf2D accurately simulates the changing water depth in the flume during the experiment and models the wetting of

  14. Atomistic simulation of charge effects: From tunable thin film growth to isolation of surface states with spin-orbit coupling

    Science.gov (United States)

    Ming, Wenmei

    This dissertation revitalizes the importance of surface charge effects in semiconductor nanostructures, in particular in the context of thin film growth and exotic electronic structures under delicate spin-orbit coupling. A combination of simulation techniques, including density functional theory calculation, kinetic Monte Carlo method, nonequilibrium Green's function method, and tight binding method, were employed to reveal the underlying physical mechanisms of four topics: (1) Effects of Li doping on H-diffusion in MgH 2 for hydrogen storage. It addresses both the effect of Fermi level tuning by charged dopant and the effect of dopant-defect interaction, and the latter was largely neglected in previous works; (2) Tuning nucleation density of the metal island with charge doping of the graphene substrate. It is the first time that the surface charge doping effect is proposed and studied as an effective approach to tune the kinetics of island nucleation at the early stage of thin film growth; (3) Complete isolation of Rashba surface states on the saturated semiconductor surface. It shows that the naturally saturated semiconductor surface of InSe(0001) with Au single layer film provides a mechanism for the formation of Rashba states with large spin splitting; it opens up an innovative route to obtaining ideal Rashba states without the overwhelming bulk spin-degenerate carriers in spin-dependent transport; (4) Formation of large band gap quantum spin Hall state on Si surface. This study reveals the importance of atomic orbital composition in the formation of a topological insulator, and shows promisingly the possible integration of topological insulator technology into Si-based modern electronic devices.

  15. Reversible redox reaction and water configuration on a positively charged platinum surface: first principles molecular dynamics simulation.

    Science.gov (United States)

    Ikeshoji, Tamio; Otani, Minoru; Hamada, Ikutaro; Okamoto, Yasuharu

    2011-12-07

    The water dissociation reaction and water molecule configuration on a positively charged platinum (111) surface were investigated by means of first principles molecular dynamics under periodic boundary conditions. Water molecules on the Pt surface were mostly in the O-down orientation but some H-down structures were also found. OH(-) ion, generated by removing H from H(2)O in the bulk region, moved to the Pt surface, on which a positive charge is induced, by a Grotthuss-like proton-relay mechanism and adsorbed on it as OH(Pt). Hydrogen atom exchange between OH(Pt) and a near-by water molecule frequently occurred on the Pt surface and had a low activation energy of the same order as room temperature energy. When a positive charge (7 μC cm(-2)) was added to the Pt surface, H(3)O(+) and OH(Pt) were generated from 2H(2)O on the Pt. This may be coupled with an electron transfer to the Pt electrode [2H(2)O → H(3)O(+) + OH(Pt) + e(-)]. The opposite reaction was also observed on the same charged surface during a simulation of duration about 10 ps; it is a reversible redox reaction. When further positive charge (14 μC cm(-2)) was added, the reaction shifted to the right hand side completely. Thus, this one-electron transfer reaction, which is a part of the oxygen electrode reaction in fuel cells and water electrolysis, was confirmed to be a low activation energy process.

  16. Simulation of Effective Slip and Drag in Pressure-Driven Flow on Superhydrophobic Surfaces

    Directory of Open Access Journals (Sweden)

    Yuanding Huang

    2016-01-01

    Full Text Available The flow on superhydrophobic surfaces was investigated using finite element modeling (FEM. Surfaces with different textures like grooves, square pillars, and cylinders immersed in liquid forming Cassie state were modeled. Nonslip boundary condition was assumed at solid-liquid interface while slip boundary condition was supposed at gas-liquid interface. It was found that the flow rate can be affected by the shape of the texture, the fraction of the gas-liquid area, the height of the channel, and the driving pressure gradient. By extracting the effective boundary slip from the flow rate based on a model, it was found that the shape of the textures and the fraction of the gas-liquid area affect the effective slip significantly while the height of the channel and the driving pressure gradient have no obvious effect on effective slip.

  17. Numerical Simulation and Monitoring of Surface Environment Influence of Waterless Sand Layer Shield Tunneling

    Science.gov (United States)

    Shang, Yanliang; Han, Tongyin; Shi, Wenjun; Du, Shouji; Qin, Zhichao

    2017-10-01

    The development of urban subway is becoming more and more rapid and plays an increasingly important role. The shield tunneling method has become the first choice for the construction of urban subway tunnel in the construction of urban subway. The paper takes the interval of Shijiazhuang Metro Line 3 Administrative Center Station and Garden Park Station as the engineering background. The establishment of double shield finite difference model by considering the thickness of covering soil, tunnel excavation and excavation at the same time, distance and other factors, the surface deformation, and soil thickness. The ground deformation law is obtained, the surface settlement is inversely proportional to the overburden thickness and the double line spacing, and the gradual excavation is smaller than the synchronous excavation.

  18. A quantum-classical simulation of a multi-surface multi-mode ...

    Indian Academy of Sciences (India)

    states. The X-B-C Hamiltonian29 comprises of three electronic surfaces and eight vibrational modes, namely ν1, ν2, νef f and ν16 - ν20, which in view of doubly degeneracy of the X2E1g and B2E2g state shows thir- teen DOFs with five electronic states. These vibrational modes can be classified as: ν1 + ν2 the totally symmet ...

  19. Two-component injection moulding simulation of ABS-POM micro structured surfaces

    DEFF Research Database (Denmark)

    Tosello, Guido; Hansen, Hans Nørgaard; Islam, Aminul

    2013-01-01

    Multi-component micro injection moulding (μIM) processes such as two-component (2k) μIM are the key technologies for the mass fabrication of multi-material micro products. 2k-μIM experiments involving a miniaturized test component with micro features in the sub-mm dimensional range and moulding a...... process. Flow front predictions are compared with experimental results using the short shots technique over the whole miniaturized component and within the surface micro structures....

  20. Numerical simulation of near surface rail cracks subject to thermal contact stress

    OpenAIRE

    Fletcher, D.I.

    2014-01-01

    Boundary element modelling was conducted to investigate rail cracks subject to combined thermal and contact loading such as occurs in 'stud' or 'squat type' defects in which white etching layer lies above shallow cracks formed without evidence of plastic flow. An embedded crack at 0.5. mm below the rail surface was modelled, revealing a thermal mechanism of crack opening. Stress intensity values for a range of contact temperatures were calculated. © 2013 Elsevier B.V.

  1. Force field and a surface model database for silica to simulate interfacial properties in atomic resolution

    OpenAIRE

    Emami, FS; Puddu, V; Berry, RJ; Varshney, V; Patwardhan, SV; Perry, CC; Heinz, H

    2014-01-01

    Silica nanostructures find applications in drug delivery, catalysis, and composites, however, understanding of the surface chemistry, aqueous interfaces, and biomolecule recognition remain difficult using current imaging techniques and spectroscopy. A silica force field is introduced that resolves numerous shortcomings of prior silica force fields over the last thirty years and reduces uncertainties in computed interfacial properties relative to experiment from several 100% to less than 5%. I...

  2. Simulation and modeling of the powder diffraction pattern from nanoparticles: Studying the influence of surface strain

    Science.gov (United States)

    Beyerlein, Kenneth Roy

    Nanostructured materials are currently at the forefront of nearly every emerging industry, as they offer promising solutions to problems ranging from those facing energy technologies, to those concerning the structural integrity of materials. With all of these future applications, it is crucial that methods are developed which can offer accurate, and statistically reliable characterization of these materials in a reasonable amount of time. X-ray diffraction is one such method which is already widely available, and can offer further insight into the atomic structure, as well as, microstructure of nanomaterials. This thesis work is then focused on investigating how different structural features of nanoparticles influence the line profiles of the x-ray powder diffraction pattern. Due to their extremely small size, the contribution from crystallite size broadening becomes the dominating feature in an observed diffraction peak. Therefore, the theory of size broadening was critically reviewed concerning the considerations necessary when the crystallite size approaches a few nanometers. Furthermore, the analysis of synthesized shape controlled platinum nanoparticles was carried out using a developed line profile analysis routine, based on the Debye function analysis (DFA) approach, to determine the distribution of particle size and shape in the sample. The DFA method is based on the use of atomistic models to simulate the features in the powder diffraction pattern. The atomistic descriptions of molecular dynamics simulations was coupled with this approach, allowing for the further understanding of the pattern from nanoparticles. The techniques were developed to study how lattice dynamics, and the resulting thermal diffuse scattering, are affected by the small crystallite domains. Furthermore, the relaxation of structural models for nanoparticles by MD simulations allowed for the assessment of features which are a present in the powder pattern as a result of a strain

  3. Simulation of erosion and deposition processes of many-component surface layers in fusion devices; Simulation von Erosion- und Depositionsprozessen mehrkomponentiger Oberflaechenschichten in Fusionsanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Droste, S.

    2007-02-15

    The present choice of first wall materials in ITER will unavoidably lead to the formation of mixed carbon, tungsten and beryllium layers. Predictive modelling of erosion processes, impurity transport and deposition processes is important. For this the 3D Monte-Carlo code ERO can be used. In this thesis ERO has been coupled to the existing Monte-Carlo code SDTrimSP to describe material mixing processes in wall components correctly. SDTrimSP describes the surface by calculating the transport of ions in solids. It keeps track of the depth dependent material concentration caused by the implantation of projectiles in the solid. The calculation of movements of the recoil atoms within the solid gives reflection coefficients and sputtering yields. Since SDTrimSP does not consider chemical processes a new method has been developed to implement chemical erosion of carbon by the impact of hydrogen projectiles. The new code ERO-SDTrimSP was compared to TEXTOR experiments which were carried out to study the formation of mixed surface layers. In these experiments methane CH4 was injected through drillings in graphite and tungsten spherical limiters into the plasma. A pronounced substrate dependence was observed. The deposition efficiency, i.e. the ratio of the locally deposited to the injected amount of carbon, was 4% for graphite and 0.3% for tungsten. The deposition-dominated area on the graphite limiter covers a five times larger area than on the tungsten limiter. Modelling of this experiment with ERO-SDTrimSP also showed a clear substrate dependence with 2% deposition efficiency for graphite and less than 0.5% for tungsten. An important result of the comparison between experiment and simulation was that the effective sticking of hydrocarbon radicals hitting the surface must be negligible. Furthermore, it was shown that local re-deposited carbon layers are 10 times more effectively eroded than ordinary graphite. Simulation of the impurity transport in the plasma was checked

  4. The influence of mouthrinses and simulated toothbrushing on the surface roughness of a nanofilled composite resin.

    Science.gov (United States)

    Trauth, Keico Graciela Sano; Godoi, Ana Paula Terossi de; Colucci, Vivian; Corona, Silmara Aparecida Milori; Catirse, Alma Blásida Concepción Elizaur Benitez

    2012-01-01

    The aim of this study was to determine the influence of mouthrinses on the surface roughness of a nanofilled composite resin after toothbrushing. One hundred nanofilled composite resin specimens were prepared and randomly distributed into two groups-brushed and non-brushed-and then assigned to five subgroups, according to the mouthrinse solutions (n = 10): Colgate Plax Fresh Mint, Oral B, Cepacol, Colgate Plax, and artificial saliva. Each sample was immersed in 20 mL of the mouthrinses for 1 minute, 5 days per week, twice a day, for a 3-week period. The control group used in the study was one in which the specimens were not subjected to brushing and remained only in artificial saliva. Toothbrushing was performed once a week for 1 minute, for 3 weeks. Surface roughness measurements (Ra) were performed after the immersion period and toothbrushing, by means of a profilometer. Data were analyzed by two-way ANOVA and Tukey's test. Analysis revealed that the association between toothbrushing and Colgate Plax Fresh Mint produced the lowest surface roughness (p toothbrushing or not (p toothbrushing.

  5. Analysis of the free-energy surface of proteins from reversible folding simulations.

    Directory of Open Access Journals (Sweden)

    Lucy R Allen

    2009-07-01

    Full Text Available Computer generated trajectories can, in principle, reveal the folding pathways of a protein at atomic resolution and possibly suggest general and simple rules for predicting the folded structure of a given sequence. While such reversible folding trajectories can only be determined ab initio using all-atom transferable force-fields for a few small proteins, they can be determined for a large number of proteins using coarse-grained and structure-based force-fields, in which a known folded structure is by construction the absolute energy and free-energy minimum. Here we use a model of the fast folding helical lambda-repressor protein to generate trajectories in which native and non-native states are in equilibrium and transitions are accurately sampled. Yet, representation of the free-energy surface, which underlies the thermodynamic and dynamic properties of the protein model, from such a trajectory remains a challenge. Projections over one or a small number of arbitrarily chosen progress variables often hide the most important features of such surfaces. The results unequivocally show that an unprojected representation of the free-energy surface provides important and unbiased information and allows a simple and meaningful description of many-dimensional, heterogeneous trajectories, providing new insight into the possible mechanisms of fast-folding proteins.

  6. Loss of fibrinogen receptors from the platelet surface during simulated extracorporeal circulation

    Energy Technology Data Exchange (ETDEWEB)

    Musial, J.; Niewiarowski, S.; Hershock, D.; Morinelli, T.A.; Colman, R.W.; Edmunds, L.H. Jr.

    1985-04-01

    In vitro recirculation of fresh human heparinized blood in an extracorporeal circuit with a membrane oxygenator decreased fibrinogen- induced platelet aggregation and diminished the number of fibrinogen receptors and glycoprotein IIb/IIIa (GPIIb/GPIIIa) antigenic sites on the platelet surface. In seven experiments, the mean +/- SD Km value for fibrinogen (i.e., molar concentration of fibrinogen required to cause 50% of the maximal rate of aggregation) was 1.58 x 10(-7) mo